IPC-2615
Printed Board Dimensions
and Tolerances
ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES
2215 Sanders Road, Northbrook, IL 60062-6135Tel. 847.509.9700 Fax 847.509.9798
www.ipc.org
IPC-2615July 2000 A standard developed by IPC
The Principles ofStandardization
In May 1995 the IPC’s Technical Activities Executive Committee adopted Principles ofStandardization as a guiding principle of IPC’s standardization efforts.
Standards Should:• Show relationship to Design for Manufacturability
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problems for future improvement
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IPC-2615
Printed Board Dimensions
and Tolerances
Developed by the Dimensioning and Tolerancing Task Group (1-10a) ofthe Printed Board Design Committee (1-10)
Users of this standard are encouraged to participate in thedevelopment of future revisions.
Contact:
IPC2215 Sanders RoadNorthbrook, Illinois60062-6135Tel 847 509.9700Fax 847 509.9798
ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES
AcknowledgmentAny Standard involving a complex technology draws material from a vast number of sources. While the principal membersof the Dimensioning and Tolerancing Task Group (1-10a) of the Printed Board Design Committee (1-10) are shown below,it is not possible to include all of those who assisted in the evolution of this standard. To each of them, the members of theIPC extend their gratitude.
Printed Board DesignCommittee
Dimensioning andTolerancing Task Group
Technical Liaisons of theIPC Board of Directors
ChairmanRick HartleyApplied Innovation
ChairmanJohn A. Sabo. C.I.D.Rockwell Automation/Allen Bradley
Stan PlzakPensar Corp.
Peter BigelowBeaver BrookCircuits Inc.
Dimensioning and Tolerancing Task Group
Leon Cohen
C. Don Dupriest, Lockheed MartinCorporation
Will J Edwards, Lucent TechnologiesInc.
Joe Fjelstad, Pacific Consultants LLC
Pierre Gadoua, Bae Systems Canada,Inc.
John H. Morton, C.I.D., LockheedMartin Corporation
Deepak K. Pai, C.I.D., GeneralDynamics Information Sys. Inc.
John A. Sabo, C.I.D., RockwellAutomation/Allen-Bradley
Margaret Terpening, Boeing PhantomWorks
Wally Younger, Nelco Technology,Inc.
IPC-2615 July 2000
ii
Table of Contents
1 PURPOSE ................................................................. 1
1.1 Scope .................................................................... 1
1.2 General ................................................................. 1
1.2.1 Units ..................................................................... 1
1.2.2 Reference to This Standard ................................. 1
1.2.3 Figures .................................................................. 1
1.2.4 Notes .................................................................... 1
1.2.5 Reference to Gauging .......................................... 1
1.3 References ............................................................ 1
1.3.1 IPC Specifications ................................................ 1
1.3.2 ANSI Standards ................................................... 1
2 TERMS AND DEFINITIONS ..................................... 1
2.1 Actual Size ........................................................... 1
2.2 Basic Dimension .................................................. 1
2.3 Bilateral Tolerance ............................................... 1
2.4 Cumulative Tolerances ........................................ 1
2.5 Datum ................................................................... 2
2.6 Datum Feature ..................................................... 2
2.7 Datum Axis .......................................................... 2
2.8 Datum Target ....................................................... 2
2.9 Dependent of Size ............................................... 2
2.10 Dimension ............................................................ 2
2.11 End Product (End Item) ...................................... 2
2.12 Fabrication Allowance ......................................... 2
2.13 Feature .................................................................. 2
2.14 Feature of Size ..................................................... 2
2.15 Fiducial ................................................................. 2
2.16 Geometric Tolerance ............................................ 2
2.17 Limits of Size ...................................................... 2
2.18 Least Material Condition (LMC) ........................ 2
2.19 Maximum Material Condition (MMC) ............... 2
2.20 Positional Tolerance ............................................. 2
2.21 Reference Dimension ........................................... 2
2.22 Regardless of Feature Size (RFS) ....................... 2
2.23 Simulated Datum ................................................. 2
2.24 Tolerance .............................................................. 2
2.25 Tolerance, Statistical ............................................ 2
2.26 Toleranced Dimension ......................................... 3
2.27 True Position ........................................................ 3
2.28 Undimensioned Drawing ..................................... 3
2.29 Unilateral Tolerance ............................................. 3
2.30 Virtual Condition ................................................. 3
3 GEOMETRIC CHARACTERS AND SYMBOLS ...... 3
3.1 General ................................................................. 3
3.2 Use of Notes to Supplement Symbols ................ 3
3.3 Symbol Construction ........................................... 3
3.3.1 Geometric Characteristic Symbols ...................... 3
3.3.2 Datum Feature Symbol ........................................ 3
3.3.3 Basic Dimension Symbol
3.3.4 Material Condition Symbols ............................... 4
3.3.5 Diameter and Radius Symbols ............................ 4
3.3.6 Reference Symbol ................................................ 4
3.4 Geometric Tolerance Symbols ............................ 4
3.4.1 Feature Control Frame ......................................... 4
3.4.2 Feature Control Frame Incorporating DatumReferences ............................................................ 4
3.4.3 Combined Feature Control Frame and DatumFeature Symbol .................................................... 5
3.5 Feature Control Frame Placement ....................... 6
4 GENERAL RULES .................................................... 7
4.1 Maximum Material Condition Principle(MMC) Effect of MMC. ...................................... 7
4.2 Regardless of Feature Size .................................. 7
4.3 Least Material Condition Principle ..................... 7
4.4 Limits of Size ...................................................... 7
4.4.1 Individual Feature of Size (Rule #1) .................. 7
4.4.2 Relationship Between Individual Features ......... 9
4.5 Applicability of MMC, RFS, and LMC ............. 9
5 DATUM REFERENCING .......................................... 9
5.1 General ................................................................. 9
5.1.1 Application ........................................................... 9
5.1.2 Datum Reference Frame .................................... 10
5.2 Datum Features .................................................. 10
5.2.1 Datum Feature Symbols .................................... 10
5.2.2 Datum Feature Control ...................................... 10
5.2.3 Specifying Datums in Order of Precedence ..... 11
5.3 Establishing Datums .......................................... 12
5.3.1 Primary Datum Feature ..................................... 12
5.3.2 Secondary and Tertiary Datum Features NotSubject to Size Variations .................................. 12
5.3.3 Secondary and Tertiary Datum FeaturesSubject to Size Variations .................................. 12
5.3.4 Specifying Datum Features RFS ....................... 12
5.3.5 Specifying Datum Features at MMC ................ 13
5.3.6 Cylindrical Datum Features ............................... 13
5.3.7 Angular Orientation ........................................... 16
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5.3.8 Pattern of Features to Establish a SecondaryDatum ................................................................. 16
5.3.9 Multiple Datum Reference Frames ................... 16
5.4 Datum Targets .................................................... 18
5.4.1 Datum Target Symbols ...................................... 18
5.4.2 Datum Target Dimensions ................................. 19
5.4.3 Datum Planes ..................................................... 19
6 TOLERANCES OF LOCATION .............................. 21
6.1 General ............................................................... 21
6.2 Positional Tolerancing ....................................... 21
6.2.1 Feature Locations Given by Basic Dimensions...... 21
6.2.2 Feature Control Frame ....................................... 21
6.2.3 Establish Datums for Dimensions LocatingTrue Positions .................................................... 21
6.2.4 Application to Base Line and ChainDimensioning ..................................................... 21
6.3 Fundamental Explanation of PositionalTolerancing ......................................................... 21
6.3.1 Material Condition Basis ................................... 21
6.3.2 MMC as Related to Positional Tolerancing ...... 21
6.3.3 LMC as Related to Positional Tolerancing ....... 24
6.3.4 Multiple Patterns of Features Located byBasic Dimensions Relative to CommonDatums ............................................................... 24
6.4 Feature Pattern Location ................................... 26
6.4.1 Composite Positional Tolerancing ..................... 26
6.5 Bi-directional Positional Tolerancing of Features.... 26
6.6 Position of Non-Circular Features .................... 26
6.6.1 Non-circular Features at MMC ......................... 27
6.7 Undimensioned Drawings (Artwork) ................ 27
7 TOLERANCES OF FORM, ORIENTATION,PROFILE ................................................................. 38
7.1 General ............................................................... 38
7.2 Form and Orientation Control ........................... 38
7.3 Specifying Form and Orientation Tolerances ... 38
7.3.1 Form and Orientation Tolerance Zones ............ 38
7.4 Profile Control ................................................... 38
7.4.1 Profile Tolerancing ............................................. 39
7.4.2 Controlled Radius Tolerance ............................. 39
7.4.3 Angular Surfaces ............................................... 39
Appendix A: FUNDAMENTAL DIMENSIONING ANDTOLERANCING RULES ........................ 45
Appendix B: GENERAL TOLERANCING ANDRELATED PRINCIPLES ........................ 56
Appendix C: DIMENSIONING FOR COMPUTER-AIDED DESIGN ANDMANUFACTURING ................................ 58
Figures
Figure 3-1 Datum Feature Symbol .................................... 4
Figure 3-2 Examples of Datum Identification ..................... 5
Figure 3-3 Basic Dimension Symbol .................................. 5
Figure 3-4 Feature Control Frame ..................................... 6
Figure 3-5 Feature Control Frame Incorporating DatumReport ............................................................... 6
Figure 3-6 Order of Precedence of Datum Reference ...... 6
Figure 3-7 Multiple Feature Control Frames ...................... 7
Figure 3-8 Symbol for All Around ....................................... 7
Figure 3-9 Combined Feature Control Frame and DatumFeature Symbol ................................................ 7
Figure 3-10 Feature Control Frame Placement ................... 7
Figure 4-1 Positional Tolerancing at MMC ......................... 8
Figure 4-2 Variations of Form Allowed By SizeTolerance .......................................................... 9
Figure 5-1 Datum Reference Frame ................................ 10
Figure 5-2 Datum Reference Frame to Printed BoardRelationships .................................................. 11
Figure 5-3 Datum Reference Using Printed BoardEdges .............................................................. 12
Figure 5-4 Hole and Slot Establishing Secondary andTertiary Datums .............................................. 12
Figure 5-5 Additional Datum Example ............................. 13
Figure 5-6 Datum Feature Identification and Reference . 14
Figure 5-7 Secondary Datum Established By InternalFeature ........................................................... 14
Figure 5-8 Datum Feature and Simulated Datum ........... 15
Figure 5-9 Virtual Condition of Datum Feature ................ 15
Figure 5-10 Part With Cylindrical Datum Features(a) primary datum feature K, whichestablishes a datum plane; and(b) secondary datum feature M, whichestablishes a datum axis. ............................... 16
Figure 5-11 Cylindrical Internal Datum Features ............... 17
Figure 5-12 Development of a Datum Reference Frame .. 17
Figure 5-13 Pattern of Feature to Establish SecondaryDatum ............................................................. 18
Figure 5-14 Multiple Datum Reference Conditions(Rigid/Flex) Examples .................................... 18
Figure 5-15 Referencing Datums in Feature ControlFrames ............................................................ 19
Figure 5-16 Datum Target Symbol ..................................... 19
Figure 5-17 Datum Target Point ......................................... 20
Figure 5-18 Dimensioning Datum Targets ......................... 20
Figure 5-19 Primary Datum Plane Established ................. 21
Figure 6-1 Identifying Basic Dimensions ......................... 22
Figure 6-2 Positional Tolerances With DatumReference ....................................................... 23
Figure 6-3 Positional Tolerancing ..................................... 23
Figure 6-4 Establishing Datums for True PositionLocation .......................................................... 24
Figure 6-5 Basic Dimensioning Using Chain orBaseline Format ............................................. 25
IPC-2615 July 2000
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Figure 6-6 Boundary for Surface of Hole at MMC ........... 26
Figure 6-7 Hole Axes in Relation to PositionalTolerance Zones ............................................. 27
Figure 6-8 Increase in Positional Tolerance WhereHole is Not at MMC ........................................ 28
Figure 6-9 Conventional Positional Tolerancingat MMC ........................................................... 29
Figure 6-10 Regardless of Feature Size Applied toA Feature and A Datum .................................. 29
Figure 6-11 Increase in Positional Tolerance WhereHole is not at LMC ......................................... 30
Figure 6-12 LMC Applied to A Pattern of Mounting Pins ... 31
Figure 6-13 Multiple Patterns of Features ......................... 32
Figure 6-14 Tolerance Zones for Patterns Shown inFigure 6-13 ..................................................... 33
Figure 6-15 Multiple Patterns of Features, SeparateRequirement ................................................... 34
Figure 6-16 Hole Patterns Located By CompositePositional Tolerancing ..................................... 35
Figure 6-17 Tolerance Zone for Three-Hole HolePatterns Shown in Figure 6-16. ..................... 36
Figure 6-18 Bi-Directional Positional Tolerancing,Rectangular Coordinate Method .................... 37
Figure 6-19 Keying Slot Detail ........................................... 37
Figure 6-20 ‘‘V’’ Groove ..................................................... 37
Figure 6-21 Keying Slot Detail ........................................... 38
Figure 7-1 Application of A Profile of A Surface to AContour ........................................................... 40
Figure 7-2 Specifying Profile of A Surface All Around ..... 41
Figure 7-3 Specifying Different Profile Tolerance ............ 42
Figure 7-4 Profile Implementation .................................... 42
Figure 7-5 Specifying A Controlled Radius ...................... 43
Figure 7-6 Tolerancing An Angular Surface Using ACombination of Linear and AngularDimensions ..................................................... 43
Figure 7-7 Interpreting Angularity Tolerances .................. 44
Figure 7-8 45 Degree Chamfer ........................................ 44
Figure A-1 Angular Units .................................................. 46
Figure A-2 Millimeter Dimensioning ................................. 46
Figure A-3 Decimal Inch Dimensioning ............................ 46
Figure A-4 Application of Dimensions .............................. 47
Figure A-5 Grouping of Dimensions ................................. 47
Figure A-6 Spacing of Dimensions ................................... 47
Figure A-7 Staggered Dimensions ................................... 47
Figure A-8 Dimension Line/Extension Line ...................... 47
Figure A-9 Oblique Extension Lines ................................. 48
Figure A-10 Breaks In Extension Lines .............................. 48
Figure A-11 Point Location ................................................. 48
Figure A-12 Limited Length or Area Indication .................. 48
Figure A-13 Leader-Directed Dimension ............................ 48
Figure A-14 Minimizing Leaders ......................................... 49
Figure A-15 Leader Directed to Circle ............................... 49
Figure A-16 Reading Direction ........................................... 49
Figure A-17 Intermediate Reference Dimension ................ 49
Figure A-18 Radii ................................................................ 50
Figure A-19 Radius With Locating Center ......................... 50
Figure A-20 Radii With Unlocated Center .......................... 50
Figure A-21 Dimensioning Chords, Arcs, and Angles ........ 50
Figure A-22 Fully Rounded Ends ....................................... 51
Figure A-23 Partially Rounded Ends .................................. 51
Figure A-24 Rounded Corners ........................................... 51
Figure A-25 Circular Arc Outline ........................................ 51
Figure A-26 Coordinate or Offset Outline ........................... 51
Figure A-27 Tabulated Outline ............................................ 51
Figure A-28 Round Holes ................................................... 52
Figure A-29 Slotted Holes .................................................. 52
Figure A-30 Equalized Chamfers ....................................... 52
Figure A-31 Chamfers at Other Than 90°° ........................ 53
Figure A-32 Edge Card Connector ..................................... 53
Figure A-33 Rectangular Coordinate Dimension ............... 54
Figure A-34 Rectangular Coordinate DimensionsWithout Dimension Lines ................................ 54
Figure A-35 Polar Coordinate Dimensions ......................... 54
Figure A-36 Repetitive Features and Dimensions ............. 55
Figure A-37 Equal Spacing of Feature ............................... 55
Figure B-1 Limit Dimensions ............................................ 56
Figure B-2 Plus or Minus Tolerances ............................... 57
Figure C-1 Mathematical Quadrants ................................ 58
Figure C-2 Locating A Circuit Pattern Using FiducialsRelative to Plated-Through Holes .................. 59
TablesTable 3-1 General Geometric Characteristic Symbols ........ 3
Table 3-2 Special Application Symbols ............................... 3
Table 3-3 Modifying Symbols .............................................. 6
Table 4-1 Maximum Material Condition Range ................... 8
Table 4-2 Regardless of Feature Size Range .................... 8
Table 4-3 Least Material Condition Range ......................... 9
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IPC-2615 July 2000
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July 2000 IPC-2615
Printed Board Dimensions and Tolerances
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1 PURPOSE
The purpose of this Standard is to establish acceptaprincipals and practices for dimensioning and tolerancused to define end-product requirements for printed boaand printed board assemblies.
1.1 Scope This Standard covers dimensioning and toleancing of electronic packaging as it relates to printboards and the assembly of printed boards. The concdefined in this Standard are derived from ASME Y14.5M1994. Printed boards have such wide applications that thmay be times where this standard does not address acific case. In those cases, the user is referred to ASY14.5M 1994 for use of additional dimensioning and toerancing concepts.
1.2 General This Standard covers dimensioning, toleancing, and related practices for use on printed board drings and in related documents. Uniform practices for sing and interpreting these requirements are establisherein.
1.2.1 Units The International System of Units (Sl) is featured in this Standard.
1.2.2 Reference to This Standard Where drawings arebased on this Standard, this fact shall be noted ondrawings or in a document referenced on the drawinReferences to this Standard shall state ‘‘IPC-2615 orIPC-2615.’’
1.2.3 Figures The figures in this Standard are intendonly as illustrations to aid the user in understandingprinciples and methods of dimensioning and tolerancdescribed in the text. The absence of a figure illustratthe desired application is neither reason to assume inapcability nor basis for drawing rejection. In some instancfigures show added detail for emphasis, in other instanfigures are incomplete by intent. Numerical valuesdimensions and tolerances are illustrative only.
1.2.4 Notes Notes herein in capital letters are intendedappear on finished drawings. Notes in lower case lettersexplanatory only and are not intended to appear on drings.
1.2.5 Reference to Gauging This document is notintended as a gauging standard. Any reference to gauis included for explanatory purposes only.
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1.3 References
1.3.1 IPC Specifications1
IPC-T-50 Terms and Definitions
IPC-D-310 Guidelines for Phototool and Artwork Generation
IPC-D-325 Documentation for Printed Boards and PrinteBoard Assemblies
IPC-D-330 Design Guide for Printed Boards and PrinteBoard Assemblies
IPC-2220 Design Standard Series for Printed Boards
IPC-6010 Performance Specification Series for PrinteBoards
1.3.2 ANSI Standards2 When the following AmericanNational Standards referred to in this Standard are supseded by a revision approved by the American NationStandards Institute, Inc., the latest revision shall apply.
ANSI Y14.1-1980, Drawing Sheet Size and FormatANSI Y14.2M-1979, Line Conventions and LetteringASME Y14.5M-1994, Geometric Dimensioning and TolerancingANSI Z210.1-1976, Metric Practice
2 TERMS AND DEFINITIONS
The definition of terms shall be in accordance with IPCT-50 and the following.
2.1 Actual Size The measured size.
2.2 Basic Dimension A numerical value used to describethe theoretically exact size, profile, orientation, or locatioof a feature or datum target. It is the basis from which pemissible variations are established by tolerances on otdimensions, in notes, or in feature control frames (s3.4.1).
2.3 Bilateral Tolerance A tolerance in which variation ispermitted in both directions from the specified dimensio
2.4 Cumulative Tolerances The summation of all toler-ances permitted between functionally related features:
1. IPC, 2215 Sanders Road, Northbrook, IL 600622. ANSI, 655 15th Street N.W., Suite 300, Washington, DC 20005-5794
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IPC-2615 July 2000
a) Chain Dimensioning The maximum variationbetween two features is equal to the sum of the tolances on the intermediate distances; this results ingreatest tolerance accumulation.
b) Base Line Dimensioning The maximum variationbetween two features is equal to the sum of the tolances on the two dimensions from their origin to thfeatures; this results in a reduction of tolerance acmulation.
c) Basic Dimensioning The maximum variationbetween two features is controlled by the positiontolerance on the two features; this results in zero tolance accumulation.
2.5 Datum A theoretically exact point, axis, or planderived from the true geometric counterpart of a specifidatum feature. A datum is the origin from which the loction or geometric characteristics of features of a printboard are established.
2.6 Datum Feature An actual feature of a printed boarthat is used to establish a datum.
2.7 Datum Axis The theoretical axis derived from thtrue geometric counterpart of a specified feature (i.e., toing hole, fiducial) as established by the extremities of cotacting points of the actual datum feature.
2.8 Datum Target A specified point or area on a printeboard used to establish a datum.
2.9 Dependent of Size The concept that permits tolerances of form or position to vary in proportion to, andependent on, the size of the feature.
2.10 Dimension A numerical value expressed in appropriate units of measure and indicated on a drawing andother documents along with lines, symbols and notesdefine the size, location or geometric characteristic oprinted board or printed board feature.
2.11 End Product (End Item) An end product is the indi-vidual printed board or assembly in its final or completstate.
2.12 Fabrication Allowance An amount added to aprinted board feature, e.g., the diameter of a land, whichan accumulation of manufacturing variation. The fabriction allowance is intended to assure that manufacturvariation does not allow certain performance characteristo be exceeded, such as minimum annular ring.
2.13 Feature The general term applied to a physical potion of a printed board or printed board assembly, sucha surface, hole, slot, or surface mount land.
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2.14 Feature of Size One cylindrical surface or a set otwo plane parallel surfaces, each of which is associawith a size dimension.
2.15 Fiducial A printed board artwork feature (or features) that is created in the same process as the priboard conductive pattern and that provides a common msurable point for component mounting with respect toland pattern or land patterns.
2.16 Geometric Tolerance The general term applied tothe category of tolerances used to control form, profiorientation, and location.
2.17 Limits of Size The specified maximum and minimum sizes.
2.18 Least Material Condition (LMC) The condition inwhich a feature of size contains the least amount of marial within the stated limits of size - for example, maximuhole diameter, or minimum printed board size.
2.19 Maximum Material Condition (MMC) The conditionin which a feature of size contains the maximum amountmaterial within the stated limits of size; for example, minmum hole diameter, maximum printed board size.
2.20 Positional Tolerance The amount that a feature ipermitted to vary from the location of true position.
2.21 Reference Dimension A dimension, usually with-out tolerance, used for information purposes only. It is cosidered auxiliary information and does not govern prodution or inspection operations. A reference dimension isrepeat of a dimension or is derived from other valushown on the drawing or on related drawings.
2.22 Regardless of Feature Size (RFS) The term used toindicate that a geometric tolerance or datum referenapplies at any increment of size of the feature withinsize tolerance. Regardless of feature size permits no ational positional, form, or orientation tolerance other ththat stated in the applicable feature control frame. RFSonly be applied to features of size.
2.23 Simulated Datum A point, axis, or plane established by processing or inspection equipment.
2.24 Tolerance The total amount by which a specifidimension is permitted to vary. The tolerance is the diffeence between the maximum and minimum limits.
2.25 Tolerance, Statistical A tolerance that is based ostatistical models, usually combining a variety of specitolerances i.e., Root Mean Square (RMS) value.
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2.26 Toleranced Dimension A dimension with a directlyapplied tolerance as opposed to a basic dimensionspecifies the exact size or location of a feature.
2.27 True Position The theoretically exact location of afeature established by basic dimensions.
2.28 Undimensioned Drawing An undimensioned draw-ing depicts to a precise scale on environmentally stamaterial a template or a pattern for which dimensiondetail drawings would be impractical.
2.29 Unilateral Tolerance A tolerance in which varia-tion is permitted in one direction from the specified dimesion.
2.30 Virtual Condition The boundary generated by thcollective effects of the specified MMC or LMC limit ofsize of a feature and any applicable geometric toleranc
3 GEOMETRIC CHARACTERS AND SYMBOLS
3.1 General This Section establishes the symbols fospecifying geometric characteristics and other dimensiorequirements typically used on PCB engineering drawin
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Symbols should be of sufficient clarity to meet the legibility and reproducibility requirements of ANSI Y14.2M. Forsymbols not described in the following, refer to ASMEY14.5M-1994.
3.2 Use of Notes to Supplement Symbols Situationsmay arise where the desired geometric requirement canbe completely conveyed by symbology. In such cases,note may be used to describe the requirement, either serately or supplementing a geometric tolerance. See 6.3.5
3.3 Symbol Construction Information related to the con-struction, form, and proportion of individual symbolsdescribed herein is contained in ASME Y14.5M-199Appendix C.
3.3.1 Geometric Characteristic Symbols The symbolsdenoting central geometric characteristics are shownTable 3-1. Table 3-2 shows other symbols used in specapplications.
3.3.2 Datum Feature Symbol The datum feature symbolconsists of a capital letter enclosed in a square frame wa leader line extending from the frame to the concernefeature, terminating with a triangle (see Figure 3-1). Th
CHARACTERISTIC SYMBOL TYPE OF TOLERANCE USES
POSITION LOCATION HOLE AND LAND LOCATION
PROFILE OF SURFACE PROFILE BOARD EDGES
FLATNESS FORM BOW & TWIST
IPC-2615-t3-01
Table 3-1 General Geometric Characteristic Symbols
CHARACTERISTIC SYMBOL TYPE OF TOLERANCE USES
STRAIGHTNESS FORM BONDING OF HEATSINK
CIRCULARITY FORM ROUND PRINTED BOARD, TIGHT FITTING CASE
ANGULARITY ORIENTATION SPECIAL SLOT OF FEATURE CONTROL
PERPENDICULARITY ORIENTATION HOLE TO THICK BOARD RELATIONSHIP
PARALLELISM ORIENTATION EDGES TO TIGHT FITTING CASE
CONCENTRICITY LOCATION METAL CORE BOARD HOLES, TEST FEATURE
IPC-2615-t3-02
Table 3-2 Special Application Symbols
3
IPC-2615 July 2000
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A
OR
DATUM FEATURETRIANGLE MAY BEFILLED OR NOT FILLED
ø
M0.2
IPC-2615-3-01
Figure 3-1 Datum Feature Symbol
-e
ae
rse
ab
te
is
fnrd
thna
in
awu
-lot,
gnisa-beastalture
-3.ler-
(or
let-trol
ree
cere-ial
am
ce
triangle may be filled or not filled. The datum feature symbol is applied to the concerned feature surface outlinextension line, dimension line, or feature control frameshown in Figure 3-2. The symbol frame is related to thdatum feature by one of the methods prescribed in 3.5.
3.3.2.1 Letters of the Alphabet Letters of the alphabet(except I, O, and Q) are used as datum identifying letteEach datum feature requiring identification shall bassigned a different letter.
3.3.2.2 Repeated Datum Feature Symbols Where thesame datum feature symbol is repeated to identify thsame feature in other locations on a drawing, it need notidentified as a reference.
3.3.3 Basic Dimension Symbol A basic dimension statesonly half of the requirement; a tolerance must be associawith the feature to complete the requirement.
The symbolic means of indicating a basic dimensionshown in Figure 3-3.
3.3.4 Material Condition Symbols The symbols used toindicate ‘‘at maximum material condition,’’ ‘‘regardless ofeature size,’’ and ‘‘at least material condition’’ are showin Table 3-3. The use of these symbols in local and genenotes is prohibited. When no material modifier is useRFS is assumed.
The use of MMC permits greater possible tolerance aspart feature deviates from its maximum material conditioIt also assures interchangeability and permits functiongauging techniques. The maximum material condition prciple is normally valid only when both of the followingconditions exist.
Two or more features are interrelated with respect to loction or orientation (e.g., a hole and an edge or surface, tholes, etc.). At least one of the related features is a feat
4
,s
.
te
d
al,
e.l-
-ore
of size. The feature (or features) to which the MMC principle is to apply must be a feature of size (e.g., a hole, sconductor, etc.) with an axis or center plane.
Least material condition applies when special desirequirements will not accommodate MMC or when RFStoo strict. It can be used to maintain critical center loctions of features for which the positional tolerance canincreased as the size of the feature departs from its lematerial condition. The amount of increase in positiontolerance permissible is equal to the feature size deparfrom LMC.
3.3.5 Diameter and Radius Symbols The symbols usedto indicate diameter and radius are shown in Table 3These symbols precede the value of a dimension or toance given as a diameter or radius, as applicable.
3.3.6 Reference Symbol A reference dimension (or ref-erence data) is identified by enclosing the dimensiondata) within parentheses. See Table 3-3.
3.4 Geometric Tolerance Symbols Geometric character-istic symbols, the tolerance value, and datum referenceters, where applicable, are combined in a feature conframe to express a geometric tolerance.
3.4.1 Feature Control Frame A geometric tolerance foran individual feature is specified by means of a featucontrol frame divided into compartments containing thgeometric characteristic symbol followed by the toleran(see Figure 3-4). Where applicable, the tolerance is pceded by the diameter symbol and followed by a matercondition symbol.
3.4.2 Feature Control Frame Incorporating Datum Ref-erences Where a geometric tolerance is related todatum, this relationship is indicated by entering the datureference letter in a compartment following the toleran
July 2000 IPC-2615
B CA
90˚ IMPLIED
DATUM LINES WITHIN BOARD(MOUNTING HOLES MAY BE USED)
B
C
X
Y
Y
X
Y
X
A
+
+
+
+
+
+
+
+
EDGE OF BOARD DATUM(BOARD EDGE IS
CRITICAL TO MOUNTING)
Y
X
B C
X
Y
Y
X A
+
+
+
+
+
+
+
+
+
DATUM LINES OUTSIDEOF BOARD
(VERY SMALL BOARD)
IPC-2615-3-02
Figure 3-2 Examples of Datum Identification
nc
ole)rdmth
lerf
ts.et-d
3-7
esc-g-
-ea-ol
mea-mre
(see Figure 3-5). Where applicable, the datum refereletter is followed by a material condition symbol.
3.4.2.1 Multiple Datum Requirements Where more thanone datum is required, the datum reference letters (flowed by a material condition symbol, where applicablare entered in separate compartments in the desired oof precedence, from left to right (see Figure 3-6). Datureference letters need not be in alphabetical order infeature control frame.
3.4.2.2 Composite Feature Control Frame A compositefeature control frame is used where more than one toance is specified for the same geometric characteristic o
25
IPC-2615-3-03
Figure 3-3 Basic Dimension Symbol
e
-
er
e
-a
feature or features having different datum requiremenThe composite frame contains a single entry of the geomric characteristic symbol followed by each tolerance andatum requirement, one above the other (see Figureand 6.4.1).
3.4.2.3 Common Profile Tolerance Symbol The symbolused to indicate that a profile tolerance applies to surfacall around the printed board is a circle located at the juntion of the leader from the feature control frame (see Fiure 3-8).
3.4.3 Combined Feature Control Frame and Datum Fea-
ture Symbol Where a feature or pattern of features controlled by a geometric tolerance also serves as a datum fture, the feature control frame and datum feature symbare combined (see Figure 3-9).
3.4.3.1 Control Frame and Datum Feature Symbol Com-
binations Wherever a feature control frame and datufeature symbol are combined, datums referenced in the fture control frame are not considered part of the datufeature symbol. In the positional tolerance example, Figu
5
IPC-2615 July 2000
TERM SYMBOL
MAXIMUM MATERIAL CONDITION
LEAST MATERIAL CONDITION
DIAMETER
RADIUS
REFERENCE
ARC LENGTH
STATISTICAL TOLERANCE
BETWEEN
REGARDLESS OF FEATURE SIZE
M
L
S
R
ST
( )
IPC-2615-t3-03
Table 3-3 Modifying Symbols
oer
fer-
the
tohe
0.08
0.14
Geometriccharacteristicsymbol
Tolerance
Diameter symbol Material conditionsymbol
M
IPC-2615-3-04
Figure 3-4 Feature Control Frame
C0.05
Geometriccharacteristicsymbol Tolerance
Datum referenceletterDiameter symbol
Material conditionsymbol
M
IPC-2615-3-05
Figure 3-5 Feature Control Frame Incorporating DatumReport
6
3-9, a feature is controlled for position in relation tdatums A and B, and identified as datum C. Whenevdatum C is referenced elsewhere on the drawing, the reence applies to datum C not to datums A and B.
3.5 Feature Control Frame Placement The feature con-trol frame is related to the considered feature by one offollowing methods as depicted in Figure 3-10.
a) locating the feature control frame below or attacheda leader-directed callout or dimension pertaining to tfeature;
(a) Onedatumreference
(b) Twodatumreferences
(a) Threedatumreferences
Multiple datumprimary
Primary
Secondary
Primary
SecondaryTertiary
0.05
0.25
0.4
MM
M
A-D
A
A B C
B
IPC-2615-3-06
Figure 3-6 Order of Precedence of Datum Reference
ion
ion
n
anon
itedC
asistal
ris-reanstheasitsthe
nceThetheumt itstual
edred
theeant ofionr-tumit.rtedn-see
sia-hisas
di-its
July 2000 IPC-2615
b) running a leader from the frame to the feature;
c) attaching a side or an end of the frame to an extensline from the feature, provided it is a plane surface;
d) attaching a side or an end of the frame to an extensof the dimension line pertaining to a feature of size.
0.8 M B C D0.25 M B
0.8 M B C D0.25 M B
(a) Composite
(b) Two single segmentsIPC-2615-3-07
Figure 3-7 Multiple Feature Control Frames
0.3 A
Symbol for all around
IPC-2615-3-08
Figure 3-8 Symbol for All Around
0.2 M A B
C
M
IPC-2615-3-09
Figure 3-9 Combined Feature Control Frame and DatumFeature Symbol
0.14
0.20
8x 7.9 – 8.1M A
A
C Ma
b
IPC-2615-3-10
Figure 3-10 Feature Control Frame Placement
4 GENERAL RULES
The following rules apply to the use of material conditiomodifiers.
4.1 Maximum Material Condition Principle (MMC) Effectof MMC. Where a geometric tolerance is applied onMMC basis, the specified tolerance is interdependentthe size of the considered feature. The tolerance is limto the specified value if the feature is produced at its MMlimit of size. Where the actual size of the feature hdeparted from MMC, an increase in the toleranceallowed equal to the amount of such departure. The topermissible variation in the specific geometric charactetic is maximum when the feature is at LMC (see Figu4-1). Referencing a datum feature on an MMC basis methe datum is the axis or center plane of the feature atMMC limit. Where the actual size of the datum feature hdeparted from MMC, a deviation is allowed betweenaxis or center plane and the axis or center plane ofdatum (see Table 4-1).
4.2 Regardless of Feature Size Where a geometric tol-erance is applied on an RFS basis, the specified tolerais independent of the size of the considered feature.tolerance is limited to the specified value regardless ofactual size of the feature. Likewise, referencing a datfeature on an RFS basis means that a centering abouaxis or center plane is necessary, regardless of the acsize of the feature (see Table 4-2).
4.3 Least Material Condition Principle Where a posi-tional tolerance is applied on an LMC basis, the specifitolerance is interdependent on the size of the considefeature. The tolerance is limited to the specified value iffeature is produced at its LMC limit of size. Where thactual size of the feature has departed from LMC,increase in the tolerance is allowed equal to the amounsuch departure. The total permissible variation in positis maximum when the feature is at MMC. Likewise, refeencing a datum feature on an LMC basis means the dais the axis or center plane of the feature at the LMC limWhere the actual size of the datum feature has depafrom LMC, a deviation is allowed between its axis or ceter plane and the axis or center plane of the datum (Table 4-3).
4.4 Limits of Size Unless otherwise specified, the limitof size of a feature prescribe the extent within which vartions of geometric form, as well as size, are allowed. Tcontrol applies solely to individual features of sizedefined in 2.14.
4.4.1 Individual Feature of Size (Rule #1) Where only atolerance of size is specified, the limits of size of an invidual feature prescribe the extent to which variations ingeometric form, as well as size, are allowed.
7
IPC-2615 July 2000
▼
▼
▼
▼0.2
5
[0.01
0]
0.18
[0.00
7]
True Position of Hole Center
0.06[0.0025]
0.13[0.005]
▼
▼ ▼
▼ ▼
Bilateral Tolerance ZoneThe shaded square represents thetolerance zone of a hole with a positionedtolerance of 0.13 ± [0.005].
Positional Tolerance ZoneBy using the positional tolerance shown inDetail A, a 0.18 [0.007] diameter tolerancezone is established. The tolerance zone isincreased 57%.
Bonus Tolerance Based onMaximum Material ConceptBy modifying the positional tolerance to apply at maximum material condition, as shown in detail B, the tolerance zoneincreases as the measured hole size deviatesfrom its minimum size (maximum material condition). In this example, the tolerancezone can increase to 0.25 [.010].
Ø .18 [0.007]
3.66 - 3.73[0.144 - 0.147]
Detail A
Detail B
3.66 - 3.73[0.144 - 0.147]
Ø .25 [0.010] MIPC-2615-4-01
Figure 4-1 Positional Tolerancing at MMC
ci
f
hs
ndat
4.4.1.1 Variations of Size The actual size of an indi-vidual feature at any cross section shall be within the spefied tolerance of size.
4.4.1.2 Variations of Form (Envelope Principle) Theform of an individual feature is controlled by its limits o
.01
.78
.85
LMC
MMC
M
size tolerance.85 .07.84 .06.83 .05.82 .04.80 .03.79 .02.78 .01
IPC-2615-t4-01
Table 4-1 Maximum Material Condition Range
8
-size to the extent prescribed in the following paragrapand illustrated in Figure 4-2.
a) The surface or surfaces of a feature shall not extebeyond a boundary (envelope) of perfect formMMC. This boundary is the true geometric form
.01
.78
.85
LMC
MMC
S
size tolerance.85 .01.84 .01.83 .01.82 .01.80 .01.79 .01.78 .01
IPC-2615-t4-02
Table 4-2 Regardless of Feature Size Range
isf
om
mfi-m
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July 2000 IPC-2615
represented by the drawing. No variation in formpermitted if the feature is produced at its MMC limit osize.
b) Where the actual size of a feature has departed frMMC toward LMC, a variation in form is allowedequal to the amount of such departure.
c) There is no requirement for a boundary of perfect forat LMC. Thus, a feature produced at its LMC limit osize is permitted to vary from true form to the maxmum variation allowed by the boundary of perfect forat MMC.
4.4.2 Relationship Between Individual Features Thelimits of size do not control the orientation or locatiorelationship between individual features. Features shoperpendicular, coaxial, or symmetrical to each other mbe controlled for location or orientation to avoid incomplete drawing requirements.
4.5 Applicability of MMC, RFS, and LMC Applicabilityof RFS, MMC, and LMC is limited to features subject t
.01
.78
.85
LMC
MMC
L
size tolerance.85 .01.84 .02.83 .03.82 .04.80 .05.79 .06.78 .07
IPC-2615-t4-03
Table 4-3 Least Material Condition Range
nt
variations in size. They may be datum features or othfeatures whose axes or center planes are controlled by gmetric tolerances. In such cases, the following practicapply.
a) Tolerances of Position (Rule #2 ) RFS, MMC or LMCmust be specified on the drawing with respect to tindividual tolerance, datum reference, or both, as appcable.*
* Retained for explanation purposes on older drawings. PASME Y14.5M-1994, RFS is assumed unless otherwindicated
b) All Other Geometric Tolerances (Rule #3). RFapplies, with respect to the individual tolerance, datureference, or both, where no modifying symbolspecified. MMC must be specified on the drawinwhere it is required.
5 DATUM REFERENCING
5.1 General This section establishes the principle odatum referencing used to relate features of a printed boto an appropriate datum or datum reference frame. It ctains the criteria for selecting, designating, and using fetures of a printed board as the basis for dimensional dnition. A datum indicates the origin of a dimensionarelationship between a toleranced feature and a designfeature or features on a printed board. The designatedture serves as a datum feature, whereas its true geomcounterpart establishes the datum.
5.1.1 Application Because a datum is theoretical, mesurements cannot be made from a true geometric counpart. A datum is assumed to exist in and be simulatedthe associated processing equipment. For exampmachine tables and surface plates, though not true plaare of such quality that they are used to simulate tdatums from which measurements are taken and dimsions verified. The flat surfaces of manufactured print
20.220.1
20.1 (MMC)
20.2 (LMC)
MMC Perfectform boundary
20.2 (LMC)
20.2 (LMC)
20.1 (MMC)
IPC-2615-4-02
Figure 4-2 Variations of Form Allowed By Size Tolerance
9
cirt ism
tediontlyisisettehetetoe
o-nsosacssthoterte
, adi-erof
d atachfer-ofef-er-tab-
eureperfea-ture
ibleibleumpi-ec-w-
ntedter-ec-
thes
-heurere
of
IPC-2615 July 2000
board are seen to have irregularities due to both thecuitry and the variation in the laminate surface. Contacmade with a datum plane at a number of surface extreties or high points.
5.1.2 Datum Reference Frame Sufficient datum fea-tures, those most important to the design of a prinboard, are chosen to position the printed board in relatto a set of three mutually perpendicular planes, joincalled a datum reference frame. This reference frame exin theory only and not on the printed board. Therefore, itnecessary to establish a method for simulating the theorcal reference frame from the actual features of the prinboard. This simulation is accomplished by positioning tprinted board on appropriate datum features to adequarelate the printed board to the reference frame andrestrict motion of the printed board in relation to it (seFigure 5-1).
5.1.2.1 Plane Simulation Relationship These planes aresimulated in a mutually perpendicular relationship to prvide direction as well as the origin for related dimensioand measurements. Thus, when the printed board is ptioned on the datum reference frame (by physical contbetween each datum feature and its counterpart in the aciated processing equipment), dimensions related todatum reference frame by a feature control frame or nare thereby mutually perpendicular. This theoretical refence frame constitutes the three plane dimensioning sysused for datum referencing.
5.1.2.2 Datum Options In the case of a printed boardprofile or a secondary datum feature of size positionsingle datum reference frame will suffice. In others, adtional datum reference frames may be necessary whphysical separation or the functional relationship
10
-
i-
ts
i-d
ly
i-to-ee-m
e
features require that datum reference frames be appliespecific locations on the printed board. In such cases, efeature control frame must contain the datum feature reences that are applicable. Any difference in the orderprecedence or in the material condition of any datums rerenced in multiple feature control frames requires diffent datum simulation methods and, consequently, eslishes a different datum reference frame. See 5.3.9.
5.2 Datum Features A datum feature is selected on thbasis of its geometric relationship to the toleranced featand the requirements of the design. To ensure proprinted board interface and assembly, correspondingtures of mating parts are also selected as a datum feawhere practical. Datum features must be readily discernon the printed board. A datum feature should be accesson the printed board. For printed boards, the primary datfeatures will normally be the plane of the board, and tycally the mounting (nonplated-through) holes used as sondary and tertiary datum features (see Figure 5-2). Hoever, there may be occasions when the edges of the priboard, slots, or fiducials may serve as secondary andtiary datum features (see Figures 5-3, 5-4, and 5-5, resptively). Using fiducials as datum features means thatprofile is controlled in relation to the circuit pattern aopposed to the hole pattern, as is normally the case.
5.2.1 Datum Feature Symbols Datum features are identified on the drawing by means of symbols (see 3.3.2). Tdatum feature symbol is applied to the concerned featsurface outline, extension line, dimension line or featucontrol frame.
5.2.2 Datum Feature Control Measurements made froma datum plane do not take into account any variations
90˚
90˚
90˚
Mutually perpendicularplanes
Direction ofMeasurements
IPC-2615-5-01
Figure 5-1 Datum Reference Frame
July 2000 IPC-2615
LAYER ONE
A
B
A
B
A
C
LAYER ONE
LAYER ONE
(A) With the view oriented with Layer One facingup, Datum A becomes the last layer of theprinted board.
(B) Datum B defines two planes at right angles to each other, but free to rotate around the centerof the hole.
(C) Datum C completes the datum reference frame byfixing the rotation of the datum axis of datum B.
IPC-2615-5-02
Figure 5-2 Datum Reference Frame to Printed Board Relationships
en-mot
edr-acarle
ce
nceedon-of
tumrolasC.
nc-ri-ely,e.
ntion
the datum surface from the datum plane. This can happwith a warped printed board lying on a surface plate. Cosideration shall be given to the desired accuracy of datufeatures relative to design requirements and the degreecontrol necessary for the toleranced features relatedthem. If not sufficiently accurate, datum features may neto be controlled by specifying appropriate geometric toleances. Where control of the entire feature becomes imprtical, use of datum targets may be considered. Datum tgets are used for assemblies only; not for unassembprinted wiring boards. See 5.4.
5.2.3 Specifying Datums in Order of Precedence Toproperly position a printed board on the datum referen
n
fo
--d
frame, datums must be specified in an order of precedein the feature control frame. Figure 5-6 illustrates a printboard where the datum features follow the preferred cvention for noncircular printed boards. The desired orderprecedence is indicated by entering the appropriate dareference letters, from left to right, in the feature contframe. In Figure 5-6, the datum features are identifiedsurface A, and features (nonplated-through holes) B, andThese features are most important to the design and fution of the printed board. Features A, B, and C are the pmary, secondary, and tertiary datum features, respectivsince they appear in that order in the feature control framTypically, the printed board is oriented with the componeside or the designated Layer 1 facing up. This orientat
11
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IPC-2615 July 2000
establishes the opposite side of the printed board asprimary datum feature. The other two datum planesestablished by either two holes, etched features or edgethe printed board. Coordinate zero for measurement shooriginate at the secondary datum feature. All datum fetures should either be located on grid or establish gridterion. All datum features shall be located within the boaprofile or on the board profile itself.
5.2.3.1 Positioning Part on Datum Reference FrameFigure 5-2 illustrated the typical sequence for positionithe printed board shown in Figure 5-6 on a datum refereframe as simulated by the processing equipment. Themary datum feature relates the printed board to the dareference frame by bringing a minimum of three pointsthe surface into contact with the first datum plane (see Fure 5-2a). The printed board is further related to the fraby bringing at least two points of the secondary datum fture into contact with the second datum plane as simulaby a pin in a drill press (see Figure 5-2b and Figure 5-The relationship is completed by bringing at least one poof the tertiary datum feature into contact with the thidatum plane (see Figure 5-2c). As measurements are m
C
A
B
IPC-2615-5-03
Figure 5-3 Datum Reference Using Printed Board Edges
B
C A
IPC-2615-5-04
Figure 5-4 Hole and Slot Establishing Secondary andTertiary Datums
12
eeofld--
ei-m
-e-d.t
de
from datum planes, positioning of the printed board ondatum reference frame in this manner ensures a commbasis for measurements.
5.3 Establishing Datums The following paragraphsdefine the criteria for establishing datums from datum fetures.
5.3.1 Primary Datum Feature The primary datum fea-ture for a printed board will usually be the plane surfacethe board and may be either the first or last layer of tprinted board. Most often, it will be the surface opposiLayer 1, but there may be cases where Layer 1 is an apppriate choice for the primary datum. The primary datumsimulated by a plane contacting the high points of that sface (see Figure 5-8). If irregularities on the surface ofprimary or secondary datum feature are such thatprinted board is unstable (that is, it wobbles) when brouginto contact with the corresponding surface of a fixture, tprinted board may be adjusted to an optimum position,necessary, to simulate the datum. Unless otherwise spfied on the drawing, it is understood that the contact poincould be circuitry or the base laminate, depending on tflatness of the printed board.
5.3.2 Secondary and Tertiary Datum Features Not Sub-ject to Size Variations The sequence for establishing thdatum reference frame is illustrated in Figure 5-3 when tedges of a printed board are specified as secondary andtiary datum features. The primary datum feature relatespart to the datum reference frame by bringing a minimuof three points on the surface into contact with the firdatum plane. The secondary datum is established by briing at least two points of the secondary datum feature incontact with the second datum plane. The relationshipcompleted by bringing at least one point of the tertiadatum into contact with the third datum plane. Measurments on the printed board are made from the datuplanes. This method of establishing a datum referenframe is recommended when the edges are the most ccal locating features of the printed board.
5.3.3 Secondary and Tertiary Datum Features Subject
to Size Variations Datum features such as diameters awidths (e.g., slots) are subject to variations in size as was form. Because variations are allowed by the size dimsion, it becomes necessary to determine whether RFSMMC applies in each case (see 4.1, 4.2, and 4.3). Fotolerance of position, the datum reference letter is alwafollowed by the appropriate modifying symbol in the feature control frame. For all geometric tolerances, RFSimplied unless otherwise specified.
5.3.4 Specifying Datum Features RFS Where a datumfeature of size is applied on an RFS basis, the datumestablished by physical contact between the feature surf
July 2000 IPC-2615
A
D
C
NOTE: ALL DIMENSIONS ARE BASIC.XX
.XX
.XX
.yy
0.05
0.5
FIDUCIAL 1.0 ± .03
A
CA B
B
B
0.05FIDUCIAL 1.0 ± .03
A
IPC-2615-5-05
Figure 5-5 Additional Datum Example
tioizeareture
) ised,ofthein-yl-ry
e.
) islleor-ea-twoactingthe
ineich
truethe
ise
rmit
theifiedchdi-pleeci-
pedo-ht
or surfaces and surfaces of the processing or inspecequipment. Machine elements which are variable in s(such as tooling pins, surface plates, or guide rails)used to simulate a true geometric counterpart of the feaand to establish the datum.
a) Secondary Datum Feature – DiameterFor an externalfeature, the secondary datum (axis or center planeestablished by the axis of the smallest circumscribperfect cylinder which contacts the profile surfacethe printed board. For an internal feature (a hole),datum is the axis of the largest inscribed, perfect cylder which contacts the hole surface. The contacting cinder must be oriented perpendicular to the primadatum. Datum B in Figure 5-7 illustrates this principl
b) Secondary Datum Feature – WidthFor an externalfeature, the secondary datum (axis or center planeestablished by the center plane between two paraplanes which, at minimum separation, contact the cresponding surfaces of the feature. For an internal fture (a slot), the datum is the center plane betweenparallel planes which at maximum separation contthe corresponding surfaces of the slot. The contactparallel planes must be oriented perpendicular toprimary datum.
n
l
5.3.5 Specifying Datum Features at MMC Where adatum feature of size is applied on an MMC basis, machand gauging elements in the processing equipment, whremain constant in size, may be used to simulate ageometric counterpart of the feature and to establishdatum. In each case, the size of the simulated datumdetermined by the specified MMC limit of size of thdatum feature or its virtual condition, where applicable.
5.3.5.1 Datum Feature Size Control Where a datumfeature of size is controlled by a specified tolerance of fo(profile), the size of the simulated datum is the MMC limof size.
5.3.5.2 Secondary or Tertiary Datum Features of SizeWhere secondary or tertiary datum features of size insame datum reference frame are controlled by a spectolerance of location or orientation with respect to eaother, the size of the simulated datum is the virtual contion of the datum feature (see Figure 5-9). This examillustrates both secondary and tertiary datum features spfied at MMC but simulated at virtual condition.
5.3.6 Cylindrical Datum Features Cylindrical datumfeatures can be holes or the profile of a circular shaprinted board. A cylindrical datum feature is always assciated with two theoretical planes intersecting at rig
13
IPC-2615 July 2000
C
BA
XXX A B CIPC-2615-5-06
Figure 5-6 Datum Feature Identification and Reference
A
A
B
2.602.50
of Drill Press
2.5 Pin which represents B
IPC-2615-5-07
Figure 5-7 Secondary Datum Established By Internal Feature
14
July 2000 IPC-2615
A
Datum Feature (3 Point Contact withSimulated Datum)
Simulated Datum(Surface Plate)
IPC-2615-5-08
Figure 5-8 Datum Feature and Simulated Datum
0.2
8.1 – 8.2
CBAM M
0.2 BA
A
M M C M
4x 7.7 – 7.8
B
This on the drawing:
Means this:
Simulated SecondaryDatum Center
Plane B
Simulated PrimaryDatum Plane A
Simulated DatumB Virtual Condition–WidthPerpendicularto Plane A
Printed Board
Simulated Datum C Virtual Condition–Hole Perpendicular to Plane A
90˚
IPC-2615-5-09
Figure 5-9 Virtual Condition of Datum Feature
15
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ain. Inef-ec-
IPC-2615 July 2000
angles on the datum axis. These planes indicate the dirtion of measurements made from the datum axis. Tdatum established by a cylindrical surface is the axis oftrue cylinder simulated by the processing equipment (s5.3.4 and 5.3.5). Since most printed boards use tooliholes for mounting or positioning, the use of cylindricadatum features, that is, holes, for the secondary and tertidatum is the common method for establishing the datureference frame.
5.3.6.1 Cylindrical External Datum Features Figure5-10 illustrates a printed board having an external cylindrcal datum feature. Primary datum feature K relates tprinted board to the first datum plane. Since secondadatum feature M is cylindrical, it is associated with two
50
M
K50
50
50
0.2 MKM M
4x 3.5 – 3.6
80.480.2
(a)
(b)
Thirddatumplane
Firstdatumplane
Seconddatumplane
Datum axis
IPC-2615-5-10
Figure 5-10 Part With Cylindrical Datum Features (a)primary datum feature K, which establishes a datumplane; and (b) secondary datum feature M, whichestablishes a datum axis.
16
-
y
theoretical planes – the second and third in a three-plarelationship. These two theoretical planes are represenon a drawing by centerlines crossing at right angles, asFigure 5-10, part (a). The intersection of these planes cocides with the datum axis (see Figure 5-10(b)). Once estlished, the datum axis becomes the origin for relatdimensions while the two planes (X and Y) indicate thdirection of measurements. In this example, angular orietation of planes X and Y is immaterial, as rotation of thpattern of holes about the datum axis has no effect onfunction of the printed board. In such cases, only twdatum features are referenced in the feature control fram
5.3.6.2 Cylindrical Internal Datum Features Figure5-11 illustrates a hole used as an internal cylindrical datufeature. It is associated with two theoretical planes – tsecond and third in a three-plane relationship. The interstion of these planes coincides with the datum axis. Onestablished, the datum axis becomes the origin for reladimensions while the two planes (X and Y) indicate thdirection of measurements.
5.3.7 Angular Orientation When using a circular datumfeature to establish the secondary datum plane, a tertdatum feature must be specified to establish angular oritation. To establish angular orientation of two planes abothe datum axis, a third or tertiary datum feature is refeenced in the feature control frame. The feature can behole, or a slot (see Figures 5-4 and 5-9). In this exampangular orientation of the two planes intersecting throughis established by the center plane of slot C, the tertiadatum feature. Figure 5-12 illustrates the developmentthe theoretical datum reference frame for the positional terance applied in Figure 5-4.
5.3.8 Pattern of Features to Establish a SecondaryDatum Multiple features of size, such as a patternholes at MMC, may be used as a group to establishdatum when part function dictates (see Figure 5-13). In tcase, individual datum axes are established at the true ption of each hole. These are the axes of true cylindewhich simulate the virtual condition of the holes. When thprinted board is mounted on the primary datum surface arotated about the centroid of the secondary pattern of hoa central datum axis (axis of rotation) is generated festablishing the datum reference frame.
5.3.9 Multiple Datum Reference Frames More than onedatum reference frame may be established for certprinted boards, depending upon functional requirementsFigure 5-14, datums A, B, and C constitute one datum rerence frame, while datums A, D, and E constitute a sond datum reference frame.
July 2000 IPC-2615
0.2 M MA B
C
45˚
0.1 M A 12
0.7 M B M MCA
4X 7.7 – 7.8
Datum axis B
Simulated datum B – largest inscribedcylinder perpendicular to datum plane A
True geometric counterpart ofdatum feature A
THIS ON THE DRAWING MEANS THISPrinted Board Simulated datum C–
parallel planes atmaximum separationperpendicular todatum plane A.Center planealigned withdatum axis B.
Datum center plane C
Printed board
Datum plane A90˚
8.2 - 8.5
B
A
4.1 - 4.3
IPC-2615-5-11
Figure 5-11 Cylindrical Internal Datum Features
Datum Axis B
Datum CenterPlane C
DatumPlane A
DatumReferenceFrame
IPC-2615-5-12
Figure 5-12 Development of a Datum Reference Frame
17
IPC-2615 July 2000
4x ∅ 2.5-2.6
∅ 0.08 M A
C
A
B
IPC-2615-5-13
Figure 5-13 Pattern of Feature to Establish SecondaryDatum
Y
Y
Y
Y
X
X
0.5 A B C
B C
Y
Y
X
X
D E
AIPC-2615-5-14
Figure 5-14 Multiple Datum Reference Conditions (Rigid/Flex) Examples
beeoonvelyr a
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holelane,onne.
nns ofl isial
5.3.9.1 Referencing Datums in Feature ControlFrames Only the required number of datums shouldreferenced in a feature control frame when specifying gmetric tolerances. An understanding of the geometric ctrol provided by these tolerances is necessary to effectidetermine the number of datum references required fogiven application. Additionally, functional requirementsthe design should be the basis for selecting the relatedtures to be referenced as datums. Figure 5-15 illustratprinted board where three geometric tolerances are spfied, each having the required number of datum referenAlthough common datum identifying letters appear in eaframe, each combination is a different and independrequirement.
5.4 Datum Targets Datum targets designate specifipoints, lines, or areas of contact on a printed board thatused in establishing a datum reference frame. Becaus
18
--
-ai-.
t
ef
inherent irregularities, the entire surface of some featcannot be effectively used to establish a datum. Examare nonplanar or uneven surfaces produced by moldingthin section surfaces subject to bowing, warping, or oinherent or induced distortions. The use of datum tarcan be beneficial when the bottom layer of an assemprinted board is specified as a primary datum; the existeof solder-side components and leads from the through-components elevating the printed board to an uneven pit is difficult to determine the datum plane for inspectipurposes. Datum targets simplify locating the datum plaSee 5.4.1 through 5.4.2 for additional information.
5.4.1 Datum Target Symbols Points, lines, and areas odatum features are designated on the drawing by meaa datum target symbol (see Figure 5-16). The symboplaced outside the printed board outline with a rad
July 2000 IPC-2615
▼
▼
▼
▼
▼
▼ ▼▼ ▼
A
AA
▼ ▼
3.61 - 3.71[0.142 - 0.146]
AM
MM
0.38 [0.015] B C
Symbol Quantity Diameter Location
3 3.61 - 3.71[0.142 - 0.146]
3.61 - 3.71[0.142 - 0.146]
A
0.01 [0.004]
B C▼
▼ A
M
BB M
M
0.15 [0.006]
IPC-2615-5-15
Figure 5-15 Referencing Datums in Feature Control Frames
iaa
nura
noja-
,hersicd toum. Intab-re,
-n aaryrget
(leader) line directed to the target. The use of a solid rad(leader) line indicates that the datum target is on the ne(visible) surface. The use of a dashed radial (leader) liindicates that the datum target is on the far (hidden) sface. The datum feature itself is identified in the usumanner with a datum feature symbol.
A16
6
A1
Datumidentifyingletter
Datumidentifyingletter
Target area size, where applicable
Target number
Targetnumber
or
IPC-2615-5-16
Figure 5-16 Datum Target Symbol
lr
e-l
5.4.1.1 Datum Target Points A datum target point isindicated by the symbol ‘‘X,’’ which is dimensionallylocated on a direct view of the surface. Where there isdirect view, the point location is dimensioned on two adcent views (see Figure 5-17).
5.4.2 Datum Target Dimensions The location and sizewhere applicable, of datum targets are defined with eitbasic or toleranced dimensions. If defined with badimensions, tooling or gaging tolerances are assumeapply. Figure 5-18 illustrates a printed board where dattarget points are located by means of basic dimensionsthis example, three mutually perpendicular planes areeslished by three target points on the primary datum featutwo on the secondary, and one on the tertiary.
5.4.3 Datum Planes A primary datum plane is established by at least three target points or areas not ostraight line (see Figure 5-19). Secondary and tertidatum planes are usually established by two and one tapoints or areas, respectively.
19
IPC-2615 July 2000
P 2
P 2
AB C
Bottom Surfaceof Printed Board
P 2
OR
IPC-2615-5-17
Figure 5-17 Datum Target Point
A 3
A 2
A 1
B 1B 2
C 111.2
10.0
5.0
20.0
20.0
40.0 A
C
B
IPC-2615-5-18
Figure 5-18 Dimensioning Datum Targets
20
July 2000 IPC-2615
A 2A 1∅ 15
A 3∅ 15
THIS ON THE DRAWING
▼
▼
▼
▼ ▼ ▼
▼
▼
A
32
∅ 15
9016
45
16
MEANS THIS
A
SimulatedDatum(Surface Plate)
Area Contact A1, A2, A3
IPC-2615-5-19
Figure 5-19 Primary Datum Plane Established
o
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6 TOLERANCES OF LOCATION
6.1 General
This Section establishes the principles of toleranceslocation used to control the following relationships:
a) center distance between such features as holes, sand tabs;
b) location of features as a group from datum featursuch as plane;
c) features with center distances equally disposed abodatum axis or plane.
6.2 Positional Tolerancing A positional tolerancedefines a zone within which the center, axis, or center plof a feature of size is permitted to vary from true (theorecally exact) position. Basic dimensions establish the tposition from specified datum features and between inrelated features. A positional tolerance is indicated byposition symbol, a tolerance, and appropriate datum reences placed in a feature control frame.
6.2.1 Feature Locations Given by Basic DimensionsThe location of each feature (hole, slot, etc.) is givenbasic dimensions. Many drawings are based on a scheof general tolerances, usually provided near the drawtitle block. See ANSI Y14.1. Dimensions locating truposition must be excluded from the general toleranceone of the following ways:
a) applying the basic dimension symbol to each of tbasic dimensions [see Figure 6-1, parts (a) and (b)]
b) specifying on the drawing (or in a document referencon the drawing) the general note: UNTOLERANCEDIMENSIONS LOCATING TRUE POSITION AREBASIC [see Figure 6-1), part (c)]
f
ts,
,
a
e
-
-
le
6.2.2 Feature Control Frame A feature control frame isadded to the note used to specify the size and numbefeatures (see Figures 6-2 and 6-3). These figures showferent types of feature pattern dimensioning.
6.2.3 Establish Datums for Dimensions Locating TruePositions It is necessary to identify features on printeboard to establish datums for dimensions locating trpositions. On printed boards, this is generally accoplished by using nonplated-through holes as in Figuresand 5-2. The intended datum features are identified wdatum feature symbols and the applicable datum referenare included in the feature control frame. For informatioon specifying datums in an order of precedence, see 5.see Figure 6-4
6.2.4 Application to Base Line and Chain Dimension-ing True position dimensioning can be applied as baline dimensioning or as chain dimensioning. For positiontolerancing, unlike plus and minus tolerancing as shownFigure 6-5, basic dimensions are used to establish theposition of features. Assuming identical positional toleances are specified, the resultant tolerance between anyholes will be the same for chain dimensioning as for baline dimensioning. This also applies to angular dimensiowhether base line or chain type.
6.3 Fundamental Explanation of Positional Tolerancing
6.3.1 Material Condition Basis Positional tolerancing isapplied on an MMC, RFS, or LMC basis. The appropriasymbol follows the specified tolerance and applicabdatum reference in the feature control frame (see 4.5).
6.3.2 MMC as Related to Positional Tolerancing Thepositional tolerance and maximum material conditionmating features are considered in relation to each oth
21
IPC-2615 July 2000
4 X 45°
∅ 160.02
▼
▼
▼
▼
(a) Basic dimensionsin polar coordinates
(b) Basic dimensionsin rectangular coordinates
▼▼
▼
▼
▼▼ ▼▼
50
50
5050
▼
▼▼
▼
50
50
50 50▼▼▼▼
NOTE: UNTOLERANCED DIMENSIONS LOCATING TRUE POSITION ARE BASIC
(c) Basic dimensions identified by a note IPC-2615-6-01
Figure 6-1 Identifying Basic Dimensions
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inof
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at
uesi-(b).inmiss.
MMC by itself means a feature of a finished product cotains the maximum amount of material permitted by ttoleranced size dimension for that feature. Thus, for hoslots, and other internal features, maximum material iscondition where these features are at their minimum alloable sizes. For lands, surface mount features, tabs,other external features, maximum material is the conditwhere these features are at their maximum allowable si
6.3.2.1 Positional Tolerance Applied at MMC A posi-tional tolerance applied at MMC may be explainedeither of the following ways. (a) In Terms of the Surface
22
,
-d
s.
a Hole. While maintaining the specified size limits of thhole, no element of the hole surface shall be inside a thretical boundary located at true position (see Figure 6-(b) In Terms of the Axis of a Hole. Where a hole isMMC (minimum diameter), its axis must fall within acylindrical tolerance zone whose axis is located at trposition. The diameter of this zone is equal to the potional tolerance as shown in Figure 6-7, parts (a) andThis tolerance zone also defines the limits of variationthe attitude of the axis of the hole in relation to the datusurface (see Figure 6-7 (c)). It is only when the featureat MMC that the specified positional tolerance applie
July 2000 IPC-2615
NOTE : UNTOLERANCED DIMENSIONS LOCATING TRUE POSITION ARE BASIC
∅ 0.3 M A B M
∅6X3.323.30
6.64
6
12
10.4
8 10
(∅24)
8.95
8.95
∅ 19.018.8
8 6
10.4
∅ 33.233.0
1.5
A
▼▼
▼
▼
▼▼
▼
▼
▼
▼
▼
▼
▼▼ ▼▼
▼▼
▼
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▼
▼
▼
▼ ▼▼ ▼
C
B
IPC-2615-6-02
Figure 6-2 Positional Tolerances With Datum Reference
∅ 0.25 M MA B MC
360-0.5
∅ 22 +0.40
1.5360-0.5
24
C
B
24
∅ 0.25 M MA B MC
4X ∅ 4+0.250
▼▼
▼▼
▼
▼
▼
▼▼
▼
▼
▼
A
IPC-2615-6-03
Figure 6-3 Positional Tolerancing
23
IPC-2615 July 2000
∅14+0.8 0
4x ∅4+0.25 0
∅ 0.25 M A B C
∅ 0.25 M A B C
B
C A
IPC-2615-6-04
Figure 6-4 Establishing Datums for True Position Location
Chicee
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Fhaua
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th
ureli-
ardce)ycesent
si-astn-astareorleateal
ch
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ig-
ons
Where the actual size of the feature is larger than MMadditional positional tolerance results (see Figure 6-8). Tincrease of positional tolerance is equal to the differenbetween the specified maximum material limit of siz(MMC) and the actual size of the feature.
6.3.2.2 RFS as Related to Positional Tolerancing Incertain cases, the design or function of a part may requthe positional tolerance or datum reference, or both, tomaintained regardless of actual feature sizes. RFS, whapplied to the positional tolerance, requires the axis of efeature to be located within the specified positional tolance regardless of the size of the feature. This requiremimposes a closer control of the features involved and intduces complexities in verification.
6.3.2.3 Positional Location Example In Figure 6-10, thesix holes may vary in size from 6.30 to 6.40 diameter. Eahole must be located within the specified positional tolance regardless of the size of that hole. A hole at LM(6.40 diameter) is as accurately located as a hole at M(6.30 diameter). This positional control is more restrictithan the MMC principle.
6.3.2.4 Functional Requirements Variations The func-tional requirements of some designs may require that Rbe applied to both the hole pattern and datum feature. Tis, it may be necessary to require the axis of an actdatum feature (such as datum diameter B in Figure 6-10be the datum axis for the holes in the pattern regardlesthe datum feature’s size. The RFS application does not pmit any shift between the axis of the datum feature and
24
,s
eereh
nt-
Stlof
r-e
pattern of features, as a group, where the datum featdeparts from MMC. This may become necessary in appcations such as rigid mounting features on a printed bowhere mating chassis features have a tight (or interferenfit in order to function properly. It typically is not necessarfor component mounting holes because sufficient toleranare in place to allow a clearance fit between componleads and holes.
6.3.3 LMC as Related to Positional Tolerancing Wherepositional tolerancing at LMC is specified, the stated potional tolerance applies when the feature contains the leamount of material permitted by its toleranced size dimesion. Thus for holes, slots, and other internal features, lematerial condition is the condition where these featuresat their maximum allowable sizes. For profile featuresother external features, LMC is the minimum allowabsize. Specification of LMC further requires perfect formLMC. Perfect form at MMC is not required. Where thfeature departs from its LMC size, an increase in positiontolerance is allowed, which is equal to the amount of sudeparture.
Specifying LMC is limited to positional tolerancing applications where MMC does not provide the desired contand RFS is too restrictive (see Figure 6-11). LMC is usto maintain a desired relationship between the surface ofeature and its true position at tolerance extremes. Conserations critical to the design are usually involved (see Fure 6-12).
6.3.4 Multiple Patterns of Features Located by BasicDimensions Relative to Common Datums Where two ormore patterns of features are located by basic dimensi
July 2000 IPC-2615
40 40 40
THIS ON THE DRAWING
MEANS THE SAME AS THIS
A B C
4 X ∅ 3.20 .05 NPTH+-
∅ 20
120
80
40
A B C
4 X ∅ 3.20 .05 NPTH+-
∅ 20
▼ ▼ ▼ ▼ ▼ ▼▼
▼
▼▼
▼
▼
▼
▼
AC
AB
B
C
IPC-2615-6-05
Figure 6-5 Basic Dimensioning Using Chain or Baseline Format
m
te
re-ca-doralles
relative to common datum features referenced in the saorder of precedence, the following apply.
6.3.4.1 Multiple Patterns of Features Example One InFigure 6-13, each pattern of features is located relativecommon datum features not subject to size toleranc
e
os.
Since all locating dimensions are basic and all measuments are from a common datum reference frame, verifition of positional tolerance requirements for the printeboard can be collectively accomplished in a single setupgage as illustrated by Figure 6-14. The actual centers ofholes must lie on or within their respective tolerance zon
25
e-a
nslernmmds.p
emee
ur-sildtote
nethac
ofosi-
ori-ern-ce
pli-nce.
on-chip)t of
edthere
a-theofne
onaloth
6-12lyol-thencenesce
onevio-
rese inasive.
onebeare-
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er-to
elon-nce
allelts abol19
IPC-2615 July 2000
when measured from datums A, B, and C.Note: Theexplanation given in Figure 6-14 still applies where indpendent verification of pattern locations becomes necessdue to size or complexity of the printed board.
6.3.4.2 Multiple Patterns of Features Example TwoMultiple patterns of features, located by basic dimensiofrom common datum features that are subject to size toances, are also considered a single composite pattertheir respective feature control frames contain the sadatums in the same order of precedence with the samodifying symbols. If such interrelationship is not requirebetween one pattern and any other pattern or patternnotation such as SEP REQT is placed beneath each apcable feature control frame (see Figure 6-15).
This allows each feature pattern, as a group, to shift indpendently of each other relative to the axis of the datufeature and denotes an independent relationship betwthe patterns.
6.4 Feature Pattern Location Where design require-ments permit the location of a pattern of features as a groto vary within a larger tolerance than the positional toleance assigned to each feature in the pattern, compopositional tolerancing is used. For example, this wouapply to a set of mounting holes to allow the patternfloat while maintaining a tighter tolerance center to cenamong the pattern.
6.4.1 Composite Positional Tolerancing Compositeapplication of positional tolerancing provides for locatioof feature patterns as well as the interrelation of featurwithin these patterns. Requirements are annotated byuse of a composite feature control frame. See 3.4.2.2. E
▼
Hole position may varybut no point on its surfaceshall be inside theoreticalboundary.
True position
Theoretical boundary-minimum diameter ofhole (MMC) minus thepositional tolerance.
84
84 ▼
▼ ▼
▼▼
IPC-2615-6-06
Figure 6-6 Boundary for Surface of Hole at MMC
26
ry
-ifee
ali-
-
n
p
te
r
seh
complete horizontal entry in the feature control frameFigure 6-16 constitutes a separate requirement. The ption symbol is entered once and is applicable to both hzontal entries. The upper entry is referred to as the pattlocating control. It specifies the larger positional toleranfor the location of the pattern of features as a group. Apcable datums are specified in a desired order of precedeThe lower entry is referred to as the feature-relating ctrol. It specifies the smaller positional tolerance for eafeature within the pattern (feature-to-feature relationshand repeats the primary datum (same as upper parframe).
6.4.1.1 Pattern of Features Located from SpecifiedDatums Each pattern of features is located from specifidatums by basic dimensions. Figure 6-17 providesexplanation and interpretation of the illustration in Figu6-16. The lower entry, in addition to providing interreltionship control of the features in each pattern, controlsextent of attitude variation (perpendicularity in the caseFigure 6-16) of each feature axis in relation to the plaestablished by datum A. As can be seen from the sectiview of the tolerance zones in Figure 6-17, the axes of bthe large and small zones are parallel. The axes of theholes may vary obliquely (out of perpendicular) onwithin the confines of the respective smaller positional terance zones. The axes of the holes must lie withinlarger tolerance zones and also within the smaller tolerazones. In certain instances, a portion of the smaller zomay fall beyond the peripheries of the larger toleranzones. However, this portion of the smaller tolerance zis not usable because the axis of the feature must notlate the larger tolerance zone.Note: The zones in Figure6-17 are shown as they exist at MMC of the featudepicted in Figure 6-16. The large zones would increassize by the amount the features depart from MMC,would the smaller zones; the two zones are not cumulat
6.5 Bi-directional Positional Tolerancing of FeaturesWhere it is desired to specify a greater tolerance indirection than another, bi-directional tolerancing mayapplied. Bi-directional positional tolerancing results innoncircular tolerance zone for locating round holes; thefore, the diameter symbol is omitted from the feature ctrol frame in these applications (see Figure 6-18).
6.6 Position of Non-Circular Features The basic prin-ciples of true position dimensioning and positional tolancing for circular features, such as holes, apply alsononcircular features, such as open end slots, tabs, andgated holes. For such features of size, a positional tolerais used to locate the center plane established by parsurfaces of the feature. The tolerance value represendistance between two parallel planes. The diameter symis omitted from the feature control frame (see Figures 6-and 6-20).
July 2000 IPC-2615
Cylindrical tolerance zone (equal to positional tolerance)
Axis of hole at true position
Extreme positional variation
Extreme attitude variation
Primary datum
Axis of hole
True position axisAxis of hole
Axis of hole iscoincident withtrue position axis
Axis of hole is locatedat extreme position to the left of true positionaxis (but within toler-ance zone)
Axis of hole is inclinedto extreme attitudewithin tolerance zone
(a) (b) (c)
Note: The length of the tolerance zone is equal to the thickness of the printed board.
90° 90° 90°
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Minimum hole diameter
IPC-2615-6-07
Figure 6-7 Hole Axes in Relation to Positional Tolerance Zones
t -
heeby
ionin
toalfea-arere-heat-en-
6.6.1 Non-circular Features at MMC Where a positionaltolerance of a noncircular feature - for example, a sloapplies at MMC, the following apply.
In Terms of the Surfaces of a Slot. While maintaining tspecified width limits of the slot, no element of its sidsurfaces shall be inside a theoretical boundary definedtwo parallel planes equally disposed about true positand separated by a distance equal to that shown for WFigure 6-21.
6.7 Undimensioned Drawings (Artwork) An undimen-sioned drawing, as referenced in IPC-D-325 and appliedprinted board artwork actually is dimensioned in digitdatabase without tolerances. Positional tolerances fortures such as circular lands for plated-through holesdefined by minimum annular ring and registration requiments in combination with the hole position tolerance. Tterm ‘‘undimensioned’’ comes from the standpoint of a ptern that is used as supplied, without reference to dimsions, except for location.
27
IPC-2615 July 2000
▼Tolerance zone increased by anamount equal to departure from MMC(larger than minimum diameter)
Tolerance zone when hole is at MMC(minimum diameter)
True positionHole at MMC(minimum diameter)
Actual hole(larger than minimum diameter)_
▼
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▼
▼
▼
IPC-2615-6-08
Figure 6-8 Increase in Positional Tolerance Where Hole is Not at MMC
28
July 2000 IPC-2615
4x ∅ 4.25
∅ 0.2 M A B C
AB
+0.05-0.0
C
104.3
8.6
8.352.7
IPC-2615-6-09
Figure 6-9 Conventional Positional Tolerancing at MMC
▼
▼
▼
▼
▼
▼
6 X 60
75 ± .08
B
R30
6 X Ø6.35 ± .05 NPTH
Ø.20 S A B SA
C
75 ± .08
Note: If no material modifier is noted in thefeature control frame such as or ,RFS is assumed.
M L
IPC-2615-6-10
Figure 6-10 Regardless of Feature Size Applied to A Feature and A Datum
29
IPC-2615 July 2000
▼
Tolerance zone increased by anamount equal to departure from LMC(smaller than maximum diameter)
Tolerance zone when hole is at LMC( maximum diameter)
True position Actual hole smaller than(maximum diameter)
Hole at LMC(maximum diameter)
▼
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▼
IPC-2615-6-11
Figure 6-11 Increase in Positional Tolerance Where Hole is not at LMC
30
July 2000 IPC-2615
∅ .20 L A B C
THIS ON THE DRAWING
MEANS:
AT 2.55∅, OR LMC, THERE IS A .20 DIAMETER TOLERANCE ZONE FOR POSITIONAT 2.50∅, THERE IS A .25 DIAMETER TOLERANCE ZONE FOR POSITIONAT 2.45∅, OR MMC, THERE IS A .30 DIAMETER TOLERANCE ZONE FOR POSITION
(BONUS TOLERANCE IS ADDED AS THE PIN GETS SMALLER WHEN LMC IS APPLIED)
4 X ∅ 2.50 ± .05
AB
C
NNN
NNN
NNNNNN
IPC-2615-6-12
Figure 6-12 LMC Applied to A Pattern of Mounting Pins
31
IPC-2615 July 2000
∅ 0.5 M A B C
∅ 0.1 M A B C
32 16
24
90
6X 60°
∅ 3225
25
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▼
▼
6X ∅ 6 -0.20
4X ∅ 8 -0.30
C
B
A
IPC-2615-6-13
Figure 6-13 Multiple Patterns of Features
32
July 2000 IPC-2615
∅ 0.8 tolerance zoneat LMC of 4 holes
∅ 0.5 tolerance zoneat MMC of 4 holes
∅ 0.3 tolerance zoneat LMC of 6 holes
∅ 0.1 tolerance zoneat MMC of 6 holes
Datum plane B
Datum plane C
24
90
60°
32 16
25
25 ∅ 32
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IPC-2615-6-14
Figure 6-14 Tolerance Zones for Patterns Shown in Figure 6-13
33
IPC-2615 July 2000
14
∅ 0.7 M MA B MC
0-0.4
C
∅ 64
▼▼
▼▼
▼▼
▼
▼
∅ 35
0-0.2
B
A
2X ∅ 6+0.10- 0.05
2X ∅ 10+0.10- 0.05
∅ 0.5 M MA B MC
SEP REQT
SEP REQT
IPC-2615-6-15
Figure 6-15 Multiple Patterns of Features, Separate Requirement
34
July 2000 IPC-2615
∅ 0.8 M A B C
A
76
25
20
6.4
20
50
∅ 50
125
38
12.5
10
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6X 60°
6X ∅ 10+0.25 0
∅ 0.25 M
∅ 0.8 M A B C
A
4X ∅ 6 +0.14 0
∅ 0.25 M
∅ 0.8 A B C
A
3X ∅ 3 +0.14 0
C
∅ 0.25 M
M
B A
IPC-2615-6-16
Figure 6-16 Hole Patterns Located By Composite Positional Tolerancing
35
IPC-2615 July 2000
∅ 0.8 M A B C
▼
First part of callout means:
Axes of holes must lie within ∅ 0.8 pattern-locating tolerance zones, thezones being basically located in relation to the specified datum reference frame.
6.4 fromdatum B
Pattern-locatingtolerance zone
True positionrelated to datumreference frame
76 fromdatum C
▼▼
▼
▼▼ ▼▼ ▼
Axes of holes must lie within ∅ 0.25 feature-relating tolerance zones,the zones being basically related to each other and basically orientedto datum plane A.
76 fromdatum C
▼
∅ 0.25 M A
Second part of callout means: Actual hole
axis withinboth zones
Feature relatingtolerance zone
20 20
2020
▼▼
▼
▼▼ ▼
▼
Pattern-locating tolerance zoneshown with hole nearing itsmaximum positional shift.
∅ 0.8 pattern-locating tolerancezoneDatum plane A
▼▼
90°▼
▼ ▼
∅ 0.25 pattern-locatingtolerance zone
Datum plane A
▼ ▼
▼
▼
90°
Feature-relating tolerance zoneshown with hole at its maximuminclination in relation to datum plane A.
∅ 0.8
∅ 0.25
IPC-2615-6-17
Figure 6-17 Tolerance Zone for Three-Hole Hole Patterns Shown in Figure 6-16.
36
July 2000 IPC-2615
▼
0.4 M A B C 0.2 A B C
THIS ON THE DRAWING
+0.2-03X 1.6
3X 3X
60
20
B
6060
▼
▼
▼ ▼▼ ▼▼ ▼
▼▼
▼
▼
MEANS THIS
0.4 Wide tolerancezone at MMC
True positionrelated to datum reference frame
Axes of holes must lie within the 0.4 X 0.2 rectangular tolerancezone basically located in relation to the specified datum reference frame.
0.2 wide tolerancezone at MMC20 from
datum B
60 fromdatum C
▼▼ ▼▼ ▼
▼
▼
▼
▼▼
▼
A
C
M
IPC-2615-6-18
Figure 6-18 Bi-Directional Positional Tolerancing, Rectangular Coordinate Method
0.02 S A B C1.25 + 0.2- 0.0
12.5 + 0.0- 0.6
(R 0.625)
IPC-2615-6-19
Figure 6-19 Keying Slot Detail
0.25 S SA B C
120˚ ± 5˚
2X 1.375 ± 0.25
IPC-2615-6-20
Figure 6-20 ‘‘V’’ Groove
37
IPC-2615 July 2000
Side surface of slot mayvary in attitude, providedW is not violated and slotwidth is within limits of size.
Slot position may vary asshown, but no point on eitherside shall be inside of W.
W
A A
1/2 W
3 Views ofSection A-A
IPC-2615-6-21
Figure 6-21 Keying Slot Detail
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7 TOLERANCES OF FORM, ORIENTATION, PROFILE
7.1 General This Section establishes the principles amethods of dimensioning and tolerancing to control forprofile, and orientation of various geometrical shapes afree state variations.
7.2 Form and Orientation Control Form tolerances con-trol straightness, flatness and circularity. Orientation tolances control angularity, parallelism and perpendicularA profile tolerance may control form, orientation, and sizdepending on how it is applied. Since, to a certain degrthe limits of size control form and parallelism, and toleances of location control orientation, the extent of this cotrol should be considered before specifying form and oentation tolerances.
7.3 Specifying Form and Orientation Tolerances Formand orientation tolerances critical to function and intechangeability are specified where the tolerances of sizelocation do not provide sufficient control. A tolerance o
38
,
d
form or orientation may be specified where no tolerancesize is given; for example, the control of flatness aftassembly of the printed board.
7.3.1 Form and Orientation Tolerance Zones A form ororientation tolerance specifies a zone within which the cosidered feature, its axis, or its center plane must be ctained. The tolerance value represents a total linear distabetween two geometric boundaries.
7.3.1.1 Tolerance Control Over a Limited Area Certaindesigns require control over a limited area or length of tsurface, rather than control of the total surface. In theinstances, the area, or length, and its location are indicaby a heavy chain line drawn adjacent to the surface wappropriate dimensioning. Where so indicated, the spefied tolerance applies within these limits instead of to ttotal surface.
7.4 Profile Control A profile can be the outline of aprinted board or the outline of a land or land pattern. Telements of a profile are straight lines, arcs, and oth
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curved lines. If the drawing specifies individual tolerancfor segments of a profile, these segments must be indivially verified. With profile tolerancing, the true profile mabe defined by basic radii, basic angular dimensions, bacoordinate dimensions, and formulas or undimensiondrawings (artwork).
7.4.1 Profile Tolerancing The profile tolerance specifiesa uniform boundary along the true profile within which thelements of the surface must lie. It is used to control foror combinations of size, form, and orientation. Profile toerances are specified as a tolerance divided bilaterallyboth sides of the true profile or applied unilaterallyeither side of the true profile. Where an equally disposbilateral tolerance is intended, it is necessary to show othe feature control frame with a leader directed to the sface.
For an unequally disposed or a unilateral tolerance, phtom lines are drawn parallel to the true profile to indicathe tolerance zone boundary. One end of a dimensionis extended to the feature control frame. The phantom lneed extend only a sufficient distance to make its applition clear (see Figure 7-1).
Where a profile tolerance applies all around the profile oprinted board, the symbol used to designate ‘‘all around’’placed on the leader from the feature control frame (sFigure 7-2). Where segments of a profile have different terances, the extent of each profile tolerance is indicatedthe use of reference letters to identify the extremitieslimits of each requirement (see Figure 7-3).
7.4.1.1 Profile Tolerance Implementation The tolerancevalue represents the distance between two boundariesposed about the true profile or entirely disposed on oside of the true profile. Profile tolerances apply norm(perpendicular) to the true profile at all points along thprofile. The boundaries of the tolerance zone follow tgeometric shape of the true profile. The actual surface mlie within the specified tolerance zone and all variatiofrom the true profile must blend. Where a profile toleranencompasses a sharp corner, the tolerance zone extenthe intersection of the boundary lines (see Figure 7-Since the intersecting surfaces may lie anywhere withthis converging zone, the actual printed board contocould conceivably be rounded. If this is undesirable, t
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drawing must indicate the design requirements, such asspecifying the maximum radius (see Figure 7-5).
7.4.1.2 Application of Datums In most cases, profile ofa surface tolerance requires reference to datums in ordeprovide proper orientation of the profile.
7.4.2 Controlled Radius Tolerance A controlled toler-anced radius symbol CR creates a tolerance zone defiby two arcs (the minimum and maximum radii) that atangent to the adjacent surfaces (see Figure 7-5). Tprinted board contour within the crescent-shaped tolerazone must be a faired curve without reversals. Additionaradii taken at all points on the printed board contour shneither be smaller than the specified minimum limit nlarger than the maximum limit.
7.4.3 Angular Surfaces Where an angular surface, sucas the chamfer on an edge connector is defined by a cbination of a linear dimension and an angle, the surfamust lie within a tolerance zone represented by two noparallel planes (see Figure 7-6). The tolerance zone willwider as the distance from the apex of the angle increasWhere a tolerance zone with parallel boundaries is desira basic angle may be specified as in Figure 7-7.
7.4.3.1 Angularity Tolerance Angularity is an orienta-tion tolerance applicable to related features. This tolerancontrols the orientation of features to one another. Angulity is the condition of a surface or axis at a specified ang(other than 90°) from a datum plane or axis. An angulartolerance specifies a tolerance zone defined by two paraplanes at the specified basic angle from a datum planeaxis, within which the surface of the considered featumust lie.
7.4.3.2 Implied 90° Angle By convention, where centerlines and surfaces of features of a part are depictedengineering drawings intersection at right angles, a 9angle is not specified. Implied 90° angles are understoodapply.
7.4.3.3 Chamfers Specified By Note A note may beused to specify 45° chamfers as in Figure 7-8. This methis used only with 45° chamfers as the linear value applin either direction.
39
IPC-2615 July 2000
▼
▼
A
0.8 A
0.8 A
0.8 A
0.8 wide tolerance zone equally dispositioned about the true profile (0.4 each side)
True profile relative to Datum A
Actual profile
▼▼ ▼
0.8 wide tolerance zone entirely disposed on one side of the true profile, as indicated
True profile relative to Datum A
Actual profile
▼▼ ▼
0.8 wide tolerance zone entirely disposed on one side of the true profile, as indicated
True profile relative to Datum A
Actual profile
▼ ▼▼
(a) Bilateral tolerance
▼
▼
(b) Unilateral tolerance (inside)
(c) Unilateral tolerance (outside)
THIS ON THE DRAWING MEANS THIS
(a)
(b)
(c)
▼
A
A A
A A
IPC-2615-7-01
Figure 7-1 Application of A Profile of A Surface to A Contour
40
July 2000 IPC-2615
▼
0.8 A
THIS ON THE DRAWING
▼
MEANS THIS
0.8 wide tolerance zone
▼
90°
A
AIPC-2615-7-02
Figure 7-2 Specifying Profile of A Surface All Around
41
IPC-2615 July 2000
▼
0.12 A
▼
0.1 A
Between Y & Z
Between Z & W
Between W & X
▼
0.1 A
0.12 A
Between X & Y
▼
▼
Y X
WZ
A
IPC-2615-7-03
Figure 7-3 Specifying Different Profile Tolerance
0.25 A0.125
0.25
0.25
D E
ED
BilateralProfileB C
0.25 A
D E
B C Unilateral Profile
IPC-2615-7-04
Figure 7-4 Profile Implementation
42
July 2000 IPC-2615
Minimum radius 2.1
Maximum radius 2.7
Part contour
CR2.4±0.3
THIS ON THE DRAWING MEANS THIS
IPC-2615-7-05
Figure 7-5 Specifying A Controlled Radius
30˚ ± 0˚ 30'
30˚30'
29˚30'10 ± 0.5
9.5
10.5
THIS ON THE DRAWING MEANS THIS
Indicated origin plane
The surface controlled by the angular dimensionmay be anywhere within the tolerance zonewith one restriction: its angle must not be lessthan 29˚30' nor more than 30˚30'. IPC-2615-7-06
Figure 7-6 Tolerancing An Angular Surface Using A Combination of Linear and Angular Dimensions
43
IPC-2615 July 2000
0.4 A
30
▼
▼
▼
THIS ON THE DRAWING
MEANS THIS
30 ▼
▼
▼
Datum plane B
▼
0.4 wide tolerance zone
Possible orientationof the actual surface
▼
The surface must lie between two parallel planes 0.4 apartwhich are inclined at 30 to datum plane A. Additionally,the surface must be within the specified limits of size.
B
▼
IPC-2615-7-07
Figure 7-7 Interpreting Angularity Tolerances
44
2.54 x 45˚OR
2.54 x 2.54IPC-2615-7-08
Figure 7-8 45 Degree Chamfer
July 2000 IPC-2615
Appendix A: FUNDAMENTAL DIMENSIONING AND TOLERANCING RULES
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A1.0 Dimensioning and Tolerancing Fundamentals
Dimensioning and tolerancing shall clearly define engineing intent and shall conform to the following.
a) Each dimension shall have a tolerance, except for thdimensions specifically identified as reference, mamum, minimum, or stock (commercial stock size). Thtolerance may be applied directly to the dimension (indirectly in the case of basic dimensions), indicateda general note, or located in a supplementary blockthe drawing format (see ANSI Y14.1).
b) Dimensions for size, form, and location of featureshall be complete to the extent that there is full undestanding of the characteristics of each feature. Neithscaling (measuring the size of a feature directly fromengineering drawing) nor assumption of a distancesize is permitted.Note: Undimensioned drawings, suchas printed board artwork prepared on stable materare excluded, provided the necessary control dimesions are specified.
c) Each necessary dimension of an end product shallshown. No more dimensions than those necessarycomplete definition shall be given. The use of referendimensions on a drawing should be minimized.
d) Dimensions shall be selected and arranged to suitfunction and mating relationship of a printed board ashall not be subject to more than one interpretation.
e) The drawing should define a printed board withospecifying manufacturing methods. Thus, only the fiished diameter of a hole is given without indicatinwhether it is to be drilled, punched, or made by another operation. However, in those instances whemanufacturing, processing, quality assurance, or enronmental information is essential to the definitionengineering requirements, it shall be specified on tdrawing or in a document referenced on the drawii.e., drilled hole considerations used to determine lasize.
f) It is permissible to identify as nonmandatory certaprocessing dimensions that provide for finish allowance, shrink allowance, and other requirements, pvided the final dimensions are given on the drawinNonmandatory processing dimensions shall be idenfied by an appropriate note, such as NONMANDATORY (MFG DATA).
g) Dimensions should be arranged to provide requirinformation for optimum readability. Dimensionsshould be shown in true profile views and refer to viible outlines.
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h) Wires, cables, laminate sheets, rods, and other matals manufactured to gauge or code numbers shallspecified by linear dimensions indicating the diametor thickness. Gauge or code numbers may be shownparentheses following the dimension.
i) A 90° angle is implied where center lines and linedepicting features are shown on a drawing at rigangles and no angle is specified.
j) A 90° BASIC angle applies where center lines of features in a pattern or surfaces shown at right anglesthe drawing are located or defined by basic dimensioand no angle is specified.
k) Unless otherwise specified, all dimensions are appcable at 25°C (68°F). Compensation may be mademeasurements made at other temperatures.
A1.2 Units of Measurement For uniformity, all dimen-sions in this Standard are given in SI units. However, tunit of measurement selected should be in accordance wthe policy of the user.
A1.2.1 SI Metric Linear Units The commonly used SIlinear unit used on engineering drawings is the millimete
A1.2.2 U.S. Customary Linear Units Historically, thecommon U.S. customary linear unit used on engineeridrawings was the decimal inch. However, for electronithe dominate and preferred system is now the metric stem.
A1.2.3 Identification of Linear Units On drawingswhere all dimensions are either in millimeters or incheindividual identification of linear units is not requiredHowever, the drawing shall contain a note stating UNLESOTHERWISE SPECIFIED, ALL DIMENSIONS ARE INMILLIMETERS (or IN INCHES, as applicable).
A1.2.3.1 Unit Abbreviations Where some inch dimen-sions are shown on a millimeter-dimensioned drawing, tabbreviation IN. shall follow the inch values. Where sommillimeter dimensions are shown on an inch-dimensiondrawing, the symbol mm shall follow the millimeter val-ues.
A1.2.3.2 Angular Units Angular dimensions areexpressed in either degrees and decimal parts of a degor in degrees, minutes, and seconds. These latter dimsions are expressed by symbols: for degrees °, for minu’, and for seconds.’’ Where degrees are indicated alone,numerical value shall be followed by the symbol °. Wher
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IPC-2615 July 2000
only minutes or seconds are specified, the number of mutes or seconds shall be preceded by ‘‘0’ or ‘‘00,’’ as appcable (see Figure A-1).
A1.3 Types of Dimensioning Decimal dimensioningshall be used on drawings.
A1.3.1 Millimeter Dimensioning The following shall beobserved when specifying millimeter dimensions on draings.
a) Where the dimension is less than one millimeter, a zeprecedes the decimal point (see Figure A-2).
b) Where the dimension is a whole number, neither tdecimal point nor a zero is shown (see Figure A-2).
c) Where the dimension exceeds a whole number bydecimal fraction of one millimeter, the last digit to thright of the decimal point is not followed by a zero (seFigure A-2). Note: This practice differs for tolerancesexpressed bilaterally or as limits (see B1.3).
d) Neither commas nor spaces shall be used to sepadigits into groups in specifying millimeter dimensionon drawings.
A1.3.2 Decimal Inch Dimensioning The decimal inchsystem is explained in ANSI B87.1. The following shall bobserved when specifying decimal inch dimensionsdrawings.
a) A zero is not used before the decimal point for valuless than one inch.
b) A dimension is expressed to the same number of demal places as its tolerance. Zeros are added to the rof the decimal point where necessary (see Figure Aand B1.3).
25° 15'
25° 30' 45"
25.6°
0°0' 45"
▼
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▼
▼
▼
▼
▼
▼
IPC-2615-a-01
Figure A-1 Angular Units
in
46
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A1.3.3 Decimal Points Decimal points must be uniformdense, and large enough to be clearly visible and meetreproduction requirements of ANSI Y14.2M. Decimapoints are placed in line with the bottom of the associadigits.
A1.3.4 Conversion and Rounding of Linear Units Forconversion and rounding of linear units, see appendixB1.5.2.
A1.4 Application of Dimensions Dimensions are appliedby means of dimension lines, extension lines, chain linor a leader from a dimension, note, or specification directo the appropriate feature (see Figure A-4). General noare used to convey additional information. For furthinformation on dimension lines, extension lines, chalines, and leaders. see ANSI Y14.2M.
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19.3
12
15
0.9
∅16.4
38
1.7
11.5
IPC-2615-a-02
Figure A-2 Millimeter Dimensioning
▼
.750
.418.50
.215
.50.750
.312
1.25
∅.745
▼ ▼
▼ ▼
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▼
▼
▼▼
▼▼
▼▼
▼
IPC-2615-a-03
Figure A-3 Decimal Inch Dimensioning
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July 2000 IPC-2615
A1.4.1 Dimension Lines A dimension line, with itsarrowheads, shows the direction and extent of a dimensNumerals indicate the number of units of a measuremePreferably, dimension lines should be broken for insertiof numerals as shown in Figure A-4. Where horizontdimension lines are not broken, numerals are placed aband parallel to the dimension lines.
A1.4.1.1 Dimension Lines Alignment Dimension linesshall be aligned if practical and grouped for uniformappearance (see Figure A-5).
A1.4.1.2 Orientation of Dimension Lines to MeasuredFeature Dimension lines are drawn parallel to the diretion of measurement. The space between the first dimsion line and the printed board outline should be not lethan 10 mm; the space between succeeding parallel dimsion lines should be not less than 6 mm (see Figure A-
Note: These spacings are intended as guides only. Ifdrawing meets the reproduction requirements of taccepted industry or military reproduction specificationon conformance to these spacing requirements is nobasis for rejection of the drawing.
Where there are several parallel dimension lines, tnumerals should be staggered for easier reading (see FiA-7).
40
20
14
28
20
30°∅12
▼ ▼▼▼
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▼
▼
IPC-2615-a-04
Figure A-4 Application of Dimensions
60
20 20 ▼▼▼▼
▼▼
IPC-2615-a-05
Figure A-5 Grouping of Dimensions
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A1.4.1.3 The following shall not be used as a dimensioline:
- a center line,- an extension line,- a phantom line,- a line that is part of the outline of the object, or- a continuation of any of these lines.
A dimension line is not used as an extension line, excwhere a simplified method of coordinate dimensioningused to define curved outlines (see Figure A-8).
6Min
10Min
40
20
8
16
∅6
▼▼
▼ ▼
▼
▼
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▼
▼
▼
{{
Visiblegap
IPC-2615-a-06
Figure A-6 Spacing of Dimensions
54
48
42
54
32
24
14
▼▼
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IPC-2615-a-07
Figure A-7 Staggered Dimensions
60
35
17
7.358.3
IPC-2615-a-08
Figure A-8 Dimension Line/Extension Line
47
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IPC-2615 July 2000
A1.4.1.4 Dimension Line of an Angle The dimensionline of an angle is an arc drawn with its center at the apof the angle. The arrowheads terminate at the extensionthe two sides (see Figures A-1 and A-4).
A1.4.1.5 Crossing Dimension Lines Crossing dimensionlines should be avoided. Where unavoidable, the dimenslines are unbroken.
A1.4.2 Extension (Projection) Lines Extension lines areused to indicate the extension of a surface or point tolocation outside the printed board outline. Normally, extesion lines start with a short visible gap from the outlinethe printed board and extend beyond the outermost reladimension line (see Figure A-6). Extension lines are ually drawn perpendicular to dimension lines. Where spais limited, extension lines may be drawn at an obliqangle to clearly illustrate where they apply. Where obliqlines are used, the dimension lines are shown in the dirtion in which they apply (see Figure A-9).
A1.4.2.1 Crossing Extension Lines Wherever practical,extension lines should neither cross one another nor cdimension lines. To minimize such crossings, the shortdimension line is shown nearest the outline of the obj(see Figure A-7). Where extension lines must cross otextension lines, dimension lines, or lines depicting featurthey are not broken. Where extension lines cross arroheads or dimension lines close to arrowheads, a breathe extension line is advisable (see Figure A-10).
A1.4.2.2 Point Location by Extension Lines Where apoint is located by extension lines only, the extension linfrom surfaces should pass through the point (see FigA-11).
A1.4.3 Limited Length or Area Indication Where it isdesired to indicate that a limited length or area of a surfais to receive additional treatment or consideration withlimits specified on the drawing, the extent of these lim
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15
45
60
16
IPC-2615-a-09
Figure A-9 Oblique Extension Lines
48
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may be indicated by use of a chain line. Where the desirarea is shown on a direct view of the surface, the areasection lined within the chain line boundary and approprately dimensioned (see Figure A-12).
A1.4.4 Leaders (Leader Lines) A leader is used to directa dimension, note, or symbol to the intended place on tdrawing (see Figure A-13).
▼▼
▼▼ ▼
▼
IPC-2615-a-10
Figure A-10 Breaks In Extension Lines
▼▼
IPC-2615-a-11
Figure A-11 Point Location
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▼▼▼IPC-2615-a-12
Figure A-12 Limited Length or Area Indication
▼
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R4
R3
IPC-2615-a-13
Figure A-13 Leader-Directed Dimension
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July 2000 IPC-2615
A1.4.4.1 Leader-Directed Dimensions Leader-directeddimensions are specified individually to avoid complicatleaders. If too many leaders would impair the legibilitythe drawing, letters or symbols should be used to idenfeatures (see Figure A-14).
A1.4.4.2 Leaders Directed to Circles or Arcs Where theleader is directed to a circle or an arc, its direction shobe radial (see Figure A-15).
A1.4.5 Reading Direction Dimensions and notes shoulbe placed to be read from the bottom of the drawing wregard to orientation of the drawing format (see FiguA-16).
A1.4.6 Reference Dimensions The method for identify-ing a reference dimension (or reference data) on drawiis to enclose the dimension (or data) within parenthese
A1.4.7 Overall Dimensions Where an overall dimensionis specified, one intermediate dimension is omitted or idtified as a reference dimension. Where the intermeddimensions are more important than the overall dimensthe overall dimension, if used, is identified as a referendimension (see Figure A-17).
A1.4.8 Dimensioning Within the Outline of a ViewDimensions are usually placed outside the outline oview. Where directness of application makes it desirable
▼
▼Y
Y
Y
Ø 8.8 3 HolesIndicated Y
Ø 8.63 Holes
IPC-2615-a-14
Figure A-14 Minimizing Leaders
▼
IPC-2615-a-15
Figure A-15 Leader Directed to Circle
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-te,
e
ar
where extension lines or leader lines would be excessivlong, dimensions may be placed within the outline ofview
A1.4.9 Dimensions Not to Scale Where it is necessaryor desirable to indicate that a particular feature is notscale, the dimension should be underlined with a straithick line.
A1.5 Dimensioning Features Various characteristics andfeatures of printed board require unique methods of dimsioning.
A1.5.1 Diameters The diameter symbol precedes all diametrical values. Where the diameters of a number of cocentric cylindrical features are specified, such diametshould be dimensioned in a longitudinal view if practica
A1.5.2 Radii Each radius value is preceded by the apprpriate radius symbol. A radius dimension line uses oarrowhead, at the arc end. An arrowhead is never usethe radius center. Where location of the center is importand space permits, a dimension line is drawn from tradius center with the arrowhead touching the arc, anddimension is placed between the arrowhead and the cenWhere space is limited, the dimension line is extend
60
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
36
24
40
45
20 ▼▼
IPC-2615-a-16
Figure A-16 Reading Direction
▼▼ 60
▼▼ 20 ▼▼ 20 ▼▼ (20)
IPC-2615-a-17
Figure A-17 Intermediate Reference Dimension
49
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dig-s,
,(see
IPC-2615 July 2000
through the radius center. Where it is inconvenient to plathe arrowhead between the radius center and the arc, itbe placed outside the arc with a leader. Where the centea radius is not dimensionally located, the center shallbe indicated (see Figure A-18).
A1.5.2.1 Dimensions Given to the Center of a RadiusWhere a dimension is given to the center of a radiussmall cross is drawn at the center. Extension lines adimension lines are used to locate the center (see FigA-19). Where location of the center is unimportant, thdrawing must clearly show that the arc location is cotrolled by other dimensioned features such as tangentfaces (see Figure A-20).
A1.5.2.2 Center of a Radius Outside or Interfering withthe Drawing Where the center of a radius is outside thdrawing or interferes with another view, the radius dimesion line may be foreshortened (see Figure A-20). Tportion of the dimension line extending from the arrowhead is radial relative to the arc. Where the radius dimsion line is foreshortened and the center located by coonate dimensions, the dimension line locating the centealso foreshortened.
+
R 14
R3
▼
R3▼
R3
▼
▼
R 130
▼
IPC-2615-a-18
Figure A-18 Radii
14
28
R 8
IPC-2615-a-19
Figure A-19 Radius With Locating Center
50
yf
t
dre
r-
t
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A1.5.2.3 Multiple Radii of the Same Dimension Wherea printed board has a number of radii of the same dimesion, a note may be used instead of dimensioning earadius separately.
A1.5.3 Chords, Arcs, and Angles The dimensioning ofchords, arcs, and angles shall be as shown in Figure A-
A1.5.4 Rounded Ends Overall dimensions are used forprinted boards having rounded ends. For fully roundeends, the radii are indicated but not dimensioned (see Fure A-22). For printed board with partially rounded endthe radii are dimensioned (see Figure A-23).
A1.5.5 Rounded Corner Where corners are roundeddimensions define the edges and the arcs are tangentFigure A-24).
R 10
R 5
R 10
20
30
40
1224
IPC-2615-a-20
Figure A-20 Radii With Unlocated Center
53
Chord
Arc
30°
Angle
(
▼
56
▼▼
▼▼
▼
IPC-2615-a-21
Figure A-21 Dimensioning Chords, Arcs, and Angles
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July 2000 IPC-2615
A1.5.6 Outlines Consisting of Arcs A curved outlinecomposed of two or more arcs is dimensioned by givithe radii of all arcs and locating the necessary centers wcoordinate dimensions. Other radii are located on the bof their points of tangency (see Figure A-25).
R2 PLACES
46
12
▼▼
▼
▼▼
IPC-2615-a-22
Figure A-22 Fully Rounded Ends
R 102 PLACES
14
70
▼
▼
▼ ▼
▼
IPC-2615-a-23
Figure A-23 Partially Rounded Ends
▼▼
▼
▼
▼
50
14
R 10IPC-2615-a-24
Figure A-24 Rounded Corners
R 18
R 40R 80
R 10
30 40 ▼▼▼▼
▼
▼▼
▼
Note use of foreshortened radii.IPC-2615-a-25
Figure A-25 Circular Arc Outline
this
A1.5.7 Irregular Outlines Irregular outlines may bedimensioned as shown in Figures A-26 and A-27.
A1.5.7.1 Circular or Non-Circular Outlines Circular ornoncircular outlines may be dimensioned by the rectanlar coordinate or offset method (see Figure A-26). Coonates are dimensioned from base lines. Where many cdinates are required to define an outline, the verticalhorizontal coordinate dimensions may be tabulated, aFigure A-27.
A1.5.7.2 Curved Patterns Curved patterns may bdefined by a grid system with numbered grid lines.
A1.5.8 Round Holes Round holes are dimensionedshown in Figure A-28. Where it is not clear that a hole gothrough, the abbreviation THRU follows a dimension. Tdepth dimension of a blind hole is the depth of the fdiameter from the surface of the printed board. Wherblind hole is also counterbored or counterdrilled, the dedimension applies from the outer surface. For clarity, irecommended that a fully dimensioned, side view detaiprovided.
▼
▼
24.4
19.315 8.2
4.3
2
5
15
27
55
Base lines
▼▼
▼
▼▼
▼▼
▼
▼
▼▼
▼
▼▼
▼ ▼
▼
IPC-2615-a-26
Figure A-26 Coordinate or Offset Outline
▼
Y
1
2
3
45
Baselines
X
Station 1 2 3 4 5
X 2 5 15 27 55
Y 4.3 8.2 15 19.3 24.4
▼
▼▼
IPC-2615-a-27
Figure A-27 Tabulated Outline
51
IPC-2615 July 2000
Ø 816 DEEP
Ø 12
Ø 12THRU
Ø 816 DEEP
Ø 8
16
IPC-2615-a-28
Figure A-28 Round Holes
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A1.5.9 Slotted Holes Slotted holes are dimensionedshown in Figure A-29. The end radii are indicated but ndimensioned.
A1.5.12 Chamfers Chamfers are dimensioned by aangle and a linear dimension, or by two linear dimensio(see Figure A-30). Where an angle and a linear dimensare specified, the linear dimension is the distance fromindicated surface of the printed board to the start ofchamfer. A note may be used to specify 45° chamfers. Tmethod is used only with 45° chamfers, as the linear vaapplies in either the longitudinal or radial direction. Whechamfers are required for surfaces intersecting at otherright angles, the methods shown in Figure A-31 are us
A1.5.13 Edge Card Connector Dimensions Edge cardconnectors are dimensioned by length, width, and locato the critical mating feature (see Figure A-32). Toleranfor card edges and keying slots shall be such that keyslots do not cut into or damage contact finger.
A1.5.14 Surface Texture Methods of specifying surfacetexture requirements are covered in ANSI Y14.36. Fadditional information, see ANSI B46.1.
A1.2 Location of Features Rectangular coordinate opolar coordinate dimensions locate features with respecone another and, as a group or individually, from a dator an origin. The features that establish this datum orgin must be identified. See 6.2.3. Round holes or othertures of symmetrical contour are located by giving dtances or distances and directions to the features’ cen(see Figures A-33 through A-35).
A1.2.1 Rectangular Coordinate Dimensioning Whererectangular coordinate dimensioning is used to locatetures, linear dimensions specify distances in coordin
52
ne
s
n.
g
o
--
rs
-
10
14 R2 PLACES
10
10 X 24 R2 PLACES
R2 PLACES
10
(a)
(b)
(c)IPC-2615-a-29
Figure A-29 Slotted Holes
2
45°
2
45° x 2or 2 x 2
IPC-2615-a-30
Figure A-30 Equalized Chamfers
esrlyes
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chtedin-th
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earxedlly
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see
inghe
July 2000 IPC-2615
directions from two or three mutually perpendicular plan(see Figure A-33). Coordinate dimensioning must cleaindicate which features of the printed board establish thplanes.
A1.2.2 Rectangular Coordinate Dimensioning WithoutDimension Lines Dimensions may be shown on extesion lines without the use of dimension lines or arroheads. The base lines are indicated as zero coordinatethey may be labelled as X, Y, and occasionally Z (see Fure A-34).
A1.2.3 Tabular Dimensioning Tabular dimensioning is atype of rectangular coordinate dimensioning in whidimensions from mutually perpendicular planes are lisin a table on the drawing rather than on the pictorial deleation. This method is used on drawings that require
2
2 2
60°
IPC-2615-a-31
Figure A-31 Chamfers at Other Than 90°
e
or-
e
location of a large number of similarly shaped featurTables are prepared in any suitable manner that adequlocates the features.
A1.2.4 Polar Coordinate Dimensioning Where polarcoordinate dimensioning is used to locate features, a linand an angular dimension specify a distance from a fipoint at an angular direction from two or three mutuaperpendicular planes. The fixed point is the intersectionthese planes. Components shall not be located on pgrids because of manufacturing equipment incompatib(see Figure A-35).
A1.2.5 Repetitive Features or Dimensions Repetitivefeatures or dimensions may be specified by the use o‘‘X’’ in conjunction with a numeral to indicate the ‘‘number of times’’ or ‘‘places’’ required.
A1.2.5.1 Repeated Features Features, such as holes aslots which are repeated in a series or pattern, mayspecified by giving the required number of features and‘‘X,’’ followed by the size dimension of the feature. Aspace is used between the ‘‘X’’ and the dimension (Figure A-36).
A1.2.5.2 Equal Spacing of Features Equal spacing offeatures in a series or pattern may be specified by givthe required number of spaces and an ‘‘X,’’ followed by t
▼
▼ ▼
T
Tolerance applied tothis feature mustcorrelate with thetolerance applied tothe conductor pattern location
▼▼–D–
0.25 [0.010] L A D S
1.14 - 1.40[0.045 - 0.055]
▼▼
▼
▼
IPC-2615-a-32
Figure A-32 Edge Card Connector
53
IPC-2615 July 2000
IPC-2615-a-33
Figure A-33 Rectangular Coordinate Dimension
A A A
A A A
B
B
B
B
B
40
30
20
15
10
5
0
0 15 30 60
Qty.
6
5
Hole List
Symbol
A
B
Dia.
.20 – .25
.10 – .15
IPC-2615-a-34
Figure A-34 Rectangular Coordinate Dimensions Without Dimension Lines
X’’ltof
efer-
he
IPC-2615-a-35
Figure A-35 Polar Coordinate Dimensions
54
applicable dimension. A space is used between the ‘‘and the dimension (see Figure A-37). Where it is difficuto distinguish between the dimension and the numberspaces, one space is dimensioned and identified as rence.
A1.2.6 Use of ‘‘X’’ to Indicate ‘‘BY’’ ‘‘X’’ may be used toindicate ‘‘BY’’ between coordinate dimensions. In succases, the ‘‘X’’ shall be preceded and followed by oncharacter space.
July 2000 IPC-2615
18X Ø7
17X 18 (=306)
(18)
15
7
8X Ø8
IPC-2615-a-36
Figure A-36 Repetitive Features and Dimensions
6X Ø7
5X 10° (=50°)IPC-2615-a-37
Figure A-37 Equal Spacing of Feature
55
IPC-2615 July 2000
56
Appendix B: GENERAL TOLERANCING AND RELATED PRINCIPLES
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B1 General This Section establishes practices fexpressing tolerances on linear and angular dimensiapplicability for material condition modifiers, and interprtations governing limits and tolerances.
B1.2 Application of Tolerances Tolerances may beexpressed as follows:
a) as direct limits or as tolerance values applied directlya dimension;
b) as a geometric tolerance,
c) in a note referring to specific dimensions;
d) as specified in other documents referenced on the ding for specific features or processes;
e) in a general tolerance block referring to all dimensioon a drawing for which tolerances are not otherwspecified; see ANSI Y14.1.
B1.2.1 Tolerances on Feature Location Tolerances ondimensions that locate features of size may be appdirectly to the locating dimensions or specified by the potional tolerancing method described in (Section 5).
B1.2.2 Angular Tolerances Within General ToleranceNotes Unless otherwise specified, where a general toler-ance note on the drawing includes angular tolerances, itapplies to features shown at specified angles and atimplied 90°angles.
B1.3 Direct Tolerancing Methods Limits and directlyapplied tolerance values are specified as follows.
a) Limit Dimensioning. The high limit (maximum valueis placed above the low limit (minimum value). Wheexpressed in a single line, the low limit precedeshigh limit and a dash separates the two values (seeure B-1).
b) Plus and Minus Tolerancing. The dimension is givfirst and is followed by a plus and minus expressiontolerance (see Figure B-2).
B1.4 Tolerance Expression The conventions pertainingto the number of decimal places carried in the tolerashown in the following paragraphs shall be observed.
B1.4.1 Millimeter Tolerances Where millimeter dimen-sions are used on the drawings, the following applies.
a) Where unilateral tolerancing is used and either the por minus value is nil, a single zero is shown withouplus or minus sign.
s,
-
d-
-
f
e
s
EXAMPLE:
0 +0.0232 or 32
-0.02 0
b) Where bilateral tolerancing is used, both the plus aminus values have the same number of decimal placusing zeros where necessary.
EXAMPLE:
+0.25 +0.2532 not
-0.10 -0.1
22.522.0
▼
▼▼
7.57.4∅ 7.6
7.5∅
▼
▼▼
▼
7.5 - 7.6∅
▼
25.2°25.1°
▼
▼
▼
25°30'45"25°30'15"
IPC-2615-b-01
Figure B-1 Limit Dimensions
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July 2000 IPC-2615
c) Where limit dimensioning is used and either the mamum or minimum value has digits following a decimpoint, the other value has zeros added for uniformit
EXAMPLE:
25.45 25.45not
25.00 25
B1.4.2 Inch Tolerances Where inch dimensions are useon the drawing, both limit dimensions or the plus aminus tolerance and its dimension shall be expressedthe same number of decimal places.
EXAMPLES:
.750 .75not
.748 .748
B1.5 Interpretation of Limits
B1.5.1 Acceptability When Limiting Values Are Speci-fied Specified limiting values of 63.5 mm [2.5 in.] maxmum, 63.50 mm [2.50 in.] maximum, 63.500 mm [2.5
(a) Unilateral tolerancing
▼
▼
25.6° 0 -0.2
22 ± 0.2
22 +0.1 -0.2
▼▼
▼▼
▼▼
(b) Bilateral tolerancing
25° 15' ± 0°5'
▼
▼
▼▼
22 0 -0.3
12 +0.1 0
IPC-2615-b-02
Figure B-2 Plus or Minus Tolerances
-
th
in.] maximum are taken to mean that, for the purposesdetermining conformance to this specification, an observvalue shall be rounded off to the nearest .1 mm [0.1 in0.01 mm [0.01 in] and .001 mm [0.001 in], respectiveland then compared to the specified limiting value. (SASTM E29-67).
B1.5.2 Rounding Convention When measurements armade to greater precision than is required by this specifition, it becomes necessary to round results in orderdetermine conformance. The following rounding convetion shall be used (See ANSI Z25.1 - 1940):
B1.5.2.1 Rules for Not Changing Last Place Figure Thefigure in the last place to be retained shall be keunchanged when the figure in the next place
- is less than 5; or- is 5 followed by no other figures or only by zeroes an
the next figure in the next place is even.
B1.5.2.2 Rules for Increasing by One the Last Place Fig-ure The figure in the last place to be retained shallincreased by 1 when the figure in the next place
- is less than 5; or- is followed by no other figure or only by zeroes, and th
figure in the last place to be retained is odd; or- is 5 followed by any figure or figures other than zero.
B1.5.2.3 Rounding the Last Figure The final roundedfigure shall be obtained from the most precise value avable and not from a series of successive roundings.
B1.6 Dimensions for Plated or Coated Printed BoardsWhen the printed board is to be plated or coated, the draing or referenced document shall specify whether tdimensions are before or after plating. Typical examplesnotes are the following:
a) DIMENSIONAL LIMITS APPLY AFTER PLATING.
b) DIMENSIONAL LIMITS APPLY BEFORE PLAT-ING.
c) (For coatings other than plating, substitute the appropate term.)
B1.7 Single Limits MIN or MAX is placed after adimension where other elements of the design definitdetermine the other unspecified limit. Features suchdepth of holes, corner radii, chamfers, etc., may be limitin this way. Single limits are used where the intent will bclear, and the unspecified limit can be zero or approainfinity and will not result in a condition detrimental to thdesign.
57
IPC-2615 July 2000
58
Appendix C: DIMENSIONING FOR COMPUTER-AIDEDDESIGN AND MANUFACTURING
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C1 General. Industry Acceptance of CAD and CAMGeneral. Industry acceptance of Computer-Aided Des(CAD) and Computer-Aided Manufacturing (CAM) systems for use in component design and fabrication is rapiaccelerating. Collectively, these highly sophisticated stems can be used to describe the desired part as a georic model, interactively interject manufacturing data, adeliver this information to a designated machine tool fexecution of the finished part. Although computer-aidsystems continue to require dimensions and tolerancesprinted board definition, in many cases the dimensioningaccomplished by means of algorithms which emulamanual dimensioning practices. In view of the changistate-of-the-art, it is important that the designer understwhere certain practices can be employed for expressdimensional requirements most effectively. The purposethis Appendix is to contribute to that understanding by fiiterating the standard coordinate system and then providguidelines applicable to the CAD/CAM (data base) moas well as the manual (conventional drawing) mode. Tinformation will assist the designer in developing dimesioning and tolerancing practices common to these mod
C2 Coordinate System The coordinate system is thsame for both the geometric model created by CAD athe graphic definition found on conventional drawings. Itthe standard system of rectangular or Cartesian coordinwherein a point is located by its distance from each of twor three mutually perpendicular intersecting planes. Twdimensional coordinates (in X and Y directions) locapoints on a plane, while three-dimensional coordinatesX, Y, and Z directions) locate points in space. Once a gmetric model is defined, it is the basis for interactive prgramming of commands for the machine tool to executhe required relative motion between cutting tool and wopiece. For CAM usage, dimensional coordinates transinto point locations relative to coordinate axes since lineand rotary motion is involved.
C3 Reference Planes For CAD, three mutually perpendicular planes are established from which a geomemodel of the desired printed board can be constructThese planes normally coincide with the exterior outlineprinted boards having surfaces at right angles. Whereprinted board is circular, two of these planes intersect alothe axis of the cylinder and the third is perpendicular toWhen viewed from above, as in the top view of Figure Cthese planes are oriented in accordance with the followi
a) The first plane lies in the plane of projection. It is thplane from which coordinate distances are specifiedthe Z direction.
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b) The second plane is horizontal and perpendicular to tfirst. It is the plane from which coordinate distances arspecified in the Y direction.
c) The third plane is vertical and perpendicular to thother two. It is the plane from which coordinate distances are specified in the X direction.
C4 Reference Axes For CAM, three mutually perpen-dicular axes are established along which linear and rotamotions occur in the machine tool used for producing thdesired printed board. Generally, these axes are designaas the basic coordinate axes of the equipment. Addition(secondary) axes may also be designated, dependingmachine capability and printed board configuration. Thbasic axes, when viewed from above, or the top/primaside. are oriented in accordance with the following.
a) The first axis is horizontal in the plane of projection. Iis the X axis of motion.
b) The second axis is vertical in the plane of projectioand perpendicular to the X axis. It is the Y axis omotion.
c) The third axis is perpendicular to the plane of projection and perpendicular to the X and Y axes. It is the Zaxis of motion.
C5 Mathematical Quadrants The intersection of the Xaxis and Y axis forms quadrants described in Figure C-These axes are normally aligned or coincident with apprpriate surfaces or features on the desired printed boaWhen programming commands for the machine tool, thworkpiece should be positioned in a quadrant in suchway that a maximum of positive values will result. Forexample, if the workpiece is positioned in Quadrant 1
QUAD. II
X value = –Y value = +
QUAD. III
X value = –Y value = –
QUAD. I
X value = +Y value = +
QUAD. IV
X value = +Y value = –
X X
Y
YIPC-2615-c-01
Figure C-1 Mathematical Quadrants
positive values will result. If the workpiece is positioned intwo or more quadrants, positive and negative values willresult, and the potential for error is greater. This precautionis generally not necessary when programming on the com-puter, but helpful when programming without computerassistance. The considerations described above also applyto quadrants formed by intersections of the X-Z and Y-Zaxes.
C6 Dimensioning and Tolerancing
C6.1 Locating and Tolerancing of Patterns Produced inA Common Fabrication Operation To maximize produc-ibility, a good practice is to separately locate and toleranceas patterns those features that are produced in the samefabrication operations. Applicable patterns are as follows:
a) Unplated-Through Hole PatternsTwo or more ofthese holes are typically used as datum features.
b) Plated-Through Hole PatternsThe plated-throughhole pattern is generally the first drilling operation andas such is the first operation to define the printed board.The holes are typically located on a basic grid. Thehole location tolerance is specified either on the holelist, by drawing note, or in a separate specification. Thebasic grid must be located in relation to the datum ref-erence frame.
c) Conductor Pattern The conductor pattern does notneed a separate datum reference frame provided a mini-mum annular ring is specified. The fabrication allow-ance in essence becomes the location tolerance for theconductor pattern. Fiducials may also be used to locatethe conductor pattern. The centerlines of two orthogo-nal conductors may also be used to locate the conduc-tor pattern (see Figure C-2).
July 2000 IPC-2615
.XXX
.YYY
.YYY
.YYY
.XXX
.XXX.XXX
.YYY
.YYY
NOTE: ALL DIMENTIONS ARE BASIC UNLESS OTHERWISE SPECIFIED.
.XXX
.YYY
.YYY
.XXX
▼
▼
▼
▼▼
PLATED THRU HOLEGRID ORIGIN
FIDUCIAL MARK2x .040 DIA. MIN.
Ø .006
Ø .006 S
Ø .006 M A
.006
Ø .006 M A
CB
A
M M MA B C
M MA B C
M MA B C
IPC-2615-c-02
Figure C-2 Locating A Circuit Pattern Using Fiducials Relative to Plated-Through Holes
59
d) Printed Board Profile The printed board profile,including cutouts and slots, require a minimum of onedatum reference to the primary datum. The use of threedatum references maximizes producibility and allowsuse of hard tool gauging.
e) Solder Resist CoatingsThe solder resist coating maybe located by specifying a minimum land clearance ortargets may be provided which serve the same functionas fiducials do for the conductor pattern. A minimumland clearance serves the same function as a minimumannular ring requirement in that it tolerances the solder-mask pattern location with respect to the conductor pat-tern.
C6.2 Recommended Guidelines for Dimensioning andTolerancing PCBs Recommended guidelines for dimen-sioning and tolerancing practices for use in defining printedboard for the CAD/CAM mode are as follows.
a) Major features of a printed board are used to establishthe basic coordinate system for initial printed boarddefinition. These features may or may not be subse-quently identified as datum features.
b) For final printed board definition, any number of sub-coordinate systems may be used to locate and orientfeatures of a printed board. These systems, however,must be geometrically related to the basic coordinatesystem of the given printed board.
c) Define printed board features in relation to three mutu-ally perpendicular reference planes. Establish theseplanes along features that parallel the axes and motionsof CAM equipment, wherever possible.
d) The assignment of datum features is based primarily onthe functional requirements of the printed board.
e) Dimension the printed board so that its geometric shapeis completely defined and mathematically precise.
f) Regular geometric profiles such as ellipses, parabolas,hyperbolas, etc., may be defined on the drawing bymathematical formulas. CAM equipment can be pro-grammed to generate these profiles by linear interpola-tion, that is, a series of short straight lines whose endpoints are spaced close enough to approximate thedesired profile within the specified profile tolerance.
g) A printed board surface whose profile is defined on thedrawing by a mathematical formula should not be coor-dinately dimensioned unless specific dimensions arerequired for inspection or identified as reference infor-mation.
h) For arbitrary profiles, the drawing should specifyappropriate points on the profile by coordinate dimen-sions. or provide a table of coordinates. When deter-mining the number of points needed to define the pro-file. keep in mind that the tighter the tolerance or thesmaller the radius of curvature, the closer together thepoints should be. Terms such as ‘‘blend smoothly’’ and‘‘faired curve’’ are not specified.
i) Profiles may also be defined by other coordinate sys-tems, such as polar or cylindrical, as applicable. How-ever, it is desirable to use the same coordinate systemon a given drawing.
j) Any change in profile (points of inflection or tangency)should be clearly defined, with prime considerationgiven to design intent. Precise continuity of the profileis necessary for CAD.
k) A circular pattern of holes may be defined by polarcoordinate dimensions. Location and orientation of thepattern must be clearly shown.
l) Where possible, express angular dimensions in degreesand decimal parts of a degree.
m) Where plus and minus tolerancing is used, the toleranceshould be bilateral and not unilateral. Equal plus andminus values are preferred. Positional tolerancing isrecommended for locating features of size.
n) Geometric tolerances are specified in all cases wherethe control of specific geometric characteristics ofprinted board features is required. Where applicable,identifying datum features on the drawing and referenc-ing them in an order of precedence will clearly indicatetheir usage for CAM.
o) Tolerances should be specified on the basis of actualdesign requirements. The accuracy capability of CAMequipment is not a basis for specifying more restrictivetolerances than are functionally required.
IPC-2615 July 2000
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ANSI/IPC-T-50 Terms and Definitions forInterconnecting and Packaging Electronic CircuitsDefinition Submission/Approval Sheet
The purpose of this form is to keepcurrent with terms routinely used inthe industry and their definitions.Individuals or companies areinvited to comment. Pleasecomplete this form and return to:
IPC2215 Sanders RoadNorthbrook, IL 60062-6135Fax: 847 509.9798
SUBMITTOR INFORMATION:
Name:
Company:
City:
State/Zip:
Telephone:
Date:
❑ This is a NEW term and definition being submitted.❑ This is an ADDITION to an existing term and definition(s).❑ This is a CHANGE to an existing definition.
Term Definition
If space not adequate, use reverse side or attach additional sheet(s).
Artwork: ❑ Not Applicable ❑ Required ❑ To be supplied
❑ Included: Electronic File Name:
Document(s) to which this term applies:
Committees affected by this term:
Office UseIPC Office Committee 2-30
Date Received:Comments Collated:Returned for Action:Revision Inclusion:
Date of Initial Review:Comment Resolution:Committee Action: ❑ Accepted ❑ Rejected
❑ Accept Modify
IEC ClassificationClassification Code • Serial Number
Terms and Definition Committee Final Approval Authorization:Committee 2-30 has approved the above term for release in the next revision.
Name: Committee: Date:IPC 2-30
ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES
This Page Intentionally Left Blank
Technical QuestionsThe IPC staff will research your technical question and attempt to find an appropriate specificationinterpretation or technical response. Please send your technical query to the technical department via:
tel 847/509-9700 fax 847/509-9798 www.ipc.org e-mail: [email protected]
IPC World Wide Web Page www.ipc.orgOur home page provides access to information about upcoming events, publications and videos, membership, andindustry activities and services. Visit soon and often.
IPC Technical ForumsIPC technical forums are opportunities to network on the Internet. It’s the best way to get the help you need today!Over 2,500 people are already taking advantage of the excellent peer networking available through e-mail forumsprovided by IPC. Members use them to get timely, relevant answers to their technical questions.
[email protected] forum is for discussion of technical help, comments or questions on IPC specifications, or othertechnical inquiries. IPC also uses TechNet to announce meetings, important technical issues, surveys, etc.
[email protected] forum is for discussion of flip chip and related chip scale semiconductor packaging technologies. It iscosponsored by the National Electronics Manufacturing Initiative (NEMI).
[email protected] forum covers environmental, safety and related regulations or issues.
[email protected] Council forum covers information on upcoming IPC Designers Council activities as well as information,comment, and feedback on current design issues, local chapter meetings, new chapters forming,and other design topics.
[email protected] IPC Roadmap forum is the communication vehicle used by members of the Technical Working Groups (TWGs)who develop the IPC National Technology Roadmap for Electronic Interconnections.
[email protected] forum acts as a peer interaction resource for staying on top of lead elimination activities worldwide and withinIPC.
ADMINISTERING YOUR SUBSCRIPTION STATUS:All commands (such as subscribe and signoff) must be sent to [email protected]. Please DO NOT send any command tothe mail list address, (i.e.<mail list> @ipc.org), as it would be distributed to all the subscribers.
Example for subscribing: Example for signing off:To: [email protected] To: [email protected]: Subject:Message: subscribe TechNet Joseph H. Smith Message: sign off DesignerCouncil
Please note you must send messages to the mail list address ONLY from the e-mail address to which you wantto apply changes. In other words, if you want to sign off the mail list, you must send the signoff command from theaddress that you want removed from the mail list. Many participants find it helpful to signoff a list when travelling oron vacation and to resubscribe when back in the office.
How to post to a forum:To send a message to all the people currently subscribed to the list, just send to <mail list>@ipc.org. Please note, use themail list address that you want to reach in place of the <mail list> string in the above instructions.
Example:To: [email protected]: <your subject>Message: <your message>
The associated e-mail message text will be distributed to everyone on the list, including the sender. Further informationon how to access previous messages sent to the forums will be provided upon subscribing.For more information, contact Hugo Scaramuzzatel 847/790-5312 fax 847/509-9798e-mail: [email protected] www.ipc.org/html/forum.htm
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Education and TrainingIPC conducts local educational workshops and national conferences to help you better understand emergingtechnologies. National conferences have covered Ball Grid Array and Flip Chip/Chip Scale Packaging. Some workshoptopics include:
Printed Wiring Board Fundamentals High Speed DesignTroubleshooting the PWB Manufacturing Process Design for ManufacturabilityChoosing the Right Base Material Laminate Design for AssemblyAcceptability of Printed Boards Designers Certification PreparationNew Design Standards
IPC-A-610 Training and Certification Program“The Acceptability of Electronic Assemblies” (ANSI/IPC-A-610) is the most widely used specification for the PWBassembly industry. An industry consensus Training and Certification program based on the IPC-A-610 is available toyour company.For more information on programs, contact John Rileytel 847/790-5308 fax 847/509-9798e-mail: [email protected] www.ipc.org
IPC Video Tapes and CD-ROMsIPC video tapes and CD-ROMs can increase your industry know-how and on the job effectiveness.
For more information on IPC Video/CD Training, contact Mark Pritchardtel 505/758-7937 ext. 202 fax 505/758-7938e-mail: [email protected] www.ipc.orgwww.ipc.org
IPC Printed Circuits ExpoSM
IPC Printed Circuits Expo is the largest trade exhibition in North America devoted to the PWB industry. Over 90technical presentations make up this superior technical conference.
Exhibitor information: Registration information:Contact: Jeff Naccarato tel 847/790-5361tel 630/434-7779 fax 847/509-9798
e-mail: [email protected]
APEXSM / IPC SMEMA CouncilElectronics Assembly Process Exhibition & ConferenceAPEX is the premier technical conference and exhibition dedicated entirely to the PWB assembly industry.
Exhibitor information: Registration information:Contact: Mary MacKinnon APEX Hotline: tel 877/472-4724tel 847/790-5386 fax 847/790-5361
e-mail: [email protected]
How to Get InvolvedThe first step is to join IPC. An application for membership can be found in the back of this publication. Once youbecome a member, the opportunities to enhance your competitiveness are vast. Join a technical committee and learnfrom our industry’s best while you help develop the standards for our industry. Participate in market research programswhich forecast the future of our industry. Participate in Capitol Hill Day and lobby your Congressmen and Senators forbetter industry support. Pick from a wide variety of educational opportunities: workshops, tutorials, and conferences.More up-to-date details on IPC opportunities can be found on our web page: www.ipc.org.
For information on how to get involved, contact:Jeanette Ferdman, Membership Managertel 847/790-5309 fax 847/509-9798e-mail: [email protected] www.ipc.org
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April 4-6, 2000San Diego, California
April 3-5, 2001Anaheim, California
March 26-28, 2002Long Beach, California
March 14-16, 2000Long Beach, California
January 16-18, 2001San Diego, California
Spring 2002TBA
for SiteMembershipApplication
Our facility purchases, uses and/or manufactures printed wiring boards or other electronic interconnectionproducts for our own use in a final product. Also known as original equipment manufacturers (OEM).
We are representatives of a government agency, university, college, technical institute who are directlyconcerned with design, research, and utilization of electronic interconnection devices. (Must be a non-profit or not-for-profit organization.)
■■ One-sided and two-sided rigidprinted boards
■■ Multilayer printed boards
■■ Flexible printed boards■■ Flat cable■■ Hybrid circuits
■■ Discrete wiring devices■■ Other interconnections
IS YOUR INTEREST IN:
■■ purchasing/manufacture of printed circuit boards
■■ purchasing/manufacturing printed circuit assemblies
What is your company’s main product line?
_________________________________________________________________________________
WHAT PRODUCTS DO YOU
MAKE FOR SALE?
■■ Turnkey■■ SMT■■ Chip Scale Technology
■■ Through-hole■■ Mixed Technology
■■ Consignment■■ BGA
Our facility assembles printed wiring boards on a contract basis and/or offers other electronic interconnection products for sale.
Our facility supplies raw materials, machinery, equipment or services used in the manufacture orassembly of electronic interconnection products.
Thank you for your decision to join IPC. IPC Membership is site specific, whichmeans that IPC member benefits are available to all individuals employed at the site designated on the other side of this application.
To help IPC serve your member site in the most efficient manner possible, pleasetell us what your facility does by choosing the most appropriate member category.
Our facility manufactures and sells to other companies, printed wiring boards or other electronic interconnection products on the merchant market.
Name of Chief ExecutiveOfficer/President___________________________________________________________________
Please be sure to complete both pages of application.
PLEASE CHECK
APPROPRIATE
CATEGORY
■
INDEPENDENT
PRINTED
BOARD
MANUFACTURERS
■
INDEPENDENT
PRINTED BOARD
ASSEMBLERS
EMSI COMPANIES
■
OEM –
MANUFACTURERS
OF ANY END
PRODUCT USING
PCB/PCAS
OR CAPTIVE
MANUFACTURERS
OF PCBS/PCAS
■
INDUSTRY
SUPPLIERS
■
GOVERNMENT
AGENCIES/
ACADEMIC
TECHNICAL
LIAISONS
ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES
Name of Chief ExecutiveOfficer/President___________________________________________________________________
What products do you supply?
_________________________________________________________________________________
ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES
SiteMembership
Applicationfor
PLEASE ATTACH BUSINESS CARD
OF OFFICIAL REPRESENTATIVE HERE
Please check one:
❏ $1,000.00 Annual dues for Primary Site Membership (Twelve months of IPC membership beginsfrom the time the application and payment are received)
❏ $800.00 Annual dues for Additional Facility Membership: Additional membership for a site withinan organization where another site is considered to be the primary IPC member.
❏ $600.00** Annual dues for an independent PCB/PWA fabricator or independent EMSI provider withannual sales of less than $1,000,000.00. **Please provide proof of annual sales.
❏ $250.00 Annual dues for Government Agency/University/not-for-profit organization
TMRC Membership ❏ Please send me information on Membership in the Technology MarketingResearch Council (TMRC)
AMRC Membership ❏ Please send me information for Membership in the Assembly MarketingResearch Council (AMRC)
Mail application with
check or money order to:
IPCDept. 851-0117WP.O. Box 94020Palatine, IL 60094-4020
Fax/Mail application with
credit card payment to:
IPC2215 Sanders RoadNorthbrook, IL 60062-6135Tel: 847 509.9700Fax: 847 509.9798
Payment Information
Enclosed is our check for $
Please bill my credit card: (circle one) MC AMEX VISA DINERS
Card No. Exp date _______________
Authorized Signature
Company Name
Street Address
City State Zip Country
Main Phone No. Fax
Primary Contact Name
Title Mail Stop
Phone Fax e-mail
Senior Management Contact
Title Mail Stop
Phone Fax e-mail
Standard Improvement Form IPC-2615The purpose of this form is to provide theTechnical Committee of IPC with inputfrom the industry regarding usage ofthe subject standard.
Individuals or companies are invited tosubmit comments to IPC. All commentswill be collected and dispersed to theappropriate committee(s).
If you can provide input, please completethis form and return to:
IPC2215 Sanders RoadNorthbrook, IL 60062-6135Fax 847 [email protected]
1. I recommend changes to the following:
Requirement, paragraph number
Test Method number , paragraph number
The referenced paragraph number has proven to be:
Unclear Too Rigid In Error
Other
2. Recommendations for correction:
3. Other suggestions for document improvement:
Submitted by:
Name Telephone
Company E-mail
Address
City/State/Zip Date
ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES
ASSOCIATION CONNECTINGELECTRONICS INDUSTRIES
2215 Sanders Road, Northbrook, IL 60062-6135Tel. 847.509.9700 Fax 847.509.9798
www.ipc.org
ISBN #1-580982-49-2
