A L P H A

ExactalloySolder preforms

for product and process improvement

™ExactalloySolder preforms

for product and process improvement

™

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There is anExactalloy™

preform inthe rightshape andsize toimproveyour assemblyoperation,product reliabilityand quality.

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C O O K S O N E L E C T R O N I C S

Exactalloy™ solder preformsare the ideal solution to high-volume, precision-solderingprocesses in electronic assem-blies, sealed lighting, filteredconnectors, multiple leadedconnectors, component manu-facturing and the plumbingindustry.

What are preforms?

Preforms are precisely formedpieces of solder, produced inlarge quantities with very tighttolerances. There are almostunlimited combinations of different preform shapes,sizes, combinations of solderalloys and flux delivery systems.

Preforms are commonly formedin 63/37 tin/lead solder. Bothlower melting point and highermelting point alloys are alsoavailable. See the Soft SolderAlloys table on page 10 for alist of the most common alloysused to produce Exactalloy™

preforms. Some solder alloyscannot be used to producesome preform shapes. Highbismuth alloys, for example,can be very brittle, and cannotwithstand rolling and stamp-ing processes required to formsome shapes.

A wide range ofdesign choices

Exactalloy™ preforms are avail-able in sizes from 0.020" to2.00" (squares, discs or washerOD). Thickness can range from.004" to 0.25". Generally, fluxadd-on represents .5% to 2.5%by weight of the preform.

Improved qualityand performance

Cookson Electronics AssemblyMaterials’ experienced repre-sentatives are ready to workdirectly with your designers to recommend solder preformsto provide maximum assemblyefficiency, product quality, andimprove your manufacturingprocesses.

We can furnish Exactalloy™

preforms in discs, rectangles,squares, rings, washers, sleevesand washer arrays (linked preforms). Your CooksonElectronics technical repre-sentative can help you specifythe size and shape to achievethe maximum benefit for yoursoldering process.

Custom shapes can also beproduced to match specificapplications. Tooling chargesmay apply to custom shapesand sizes.

Both X-ray diffraction and wet analysis methods are

used to assure that every lot of Exactalloy™ preforms

meets or exceeds the metallurgical requirements of the

IPC and the customer.

Opposite: Exactalloy™ preforms can

be produced in thousands of shapes

and sizes, solving even the most

difficult soldering design challenge.

Each batch of Exactalloy™ preforms

is carefully examined under

magnification to assure compliance

with dimensional requirements.

Cookson Electronics' uniqueflux coating process offers twodistinct advantages over fluxfilled preforms: a flux-coatedExactalloy™ preform deliversflux to the area to be solderedwhen it is needed most — justbefore the solder is melted, andflux-coated solder is protectedfrom oxidation. Oxide-free solder yields better wettingand joint strength, and caneliminate the formation ofcold solder joints that canhave a severe impact on prod-uct reliability. Flux coating islimited to preforms at least.007" (0.18 mm) thick. Thinnerpreforms may lose their shapein the fluxing process. Seechart for available flux options.

Available Flux TypesFLUX TYPE INTERNAL EXTERNAL

RMA (ROL1) yes yes

RA (ROM1) no yes

NC (ROL0) yes yes

RSA (ROH1) no yes

WS (ORL0) yes no

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Precise control of foil thickness is a critical

step in providing the exact volume of solder

required. Here, linked arrays are used to

eliminate hand soldering on multiple-row

connector sets. Preforms also provide

more solder volume, eliminating

inefficient paste-in thru-hole processes.

There are numerous exampleswhere the use of Exactalloy™

preforms can optimize one or both of the common mass soldering techniques.

Eliminate hand soldering

The use of preforms can pro-vide a more consistent qualityalternative to repetitive handsoldering applications. If corewire is being used to hand solder multiple leaded connec-tors, or to solder a non-planararea in a circuit assembly, preforms often offer a bettersolution.

Exactalloy™ preforms deliverthe exact volume of solderrequired. They can be placedexactly where needed, andmultiple solder joints can bereflowed simultaneously usinga heat gun, or a reflow oven.Low melting temperature preforms are commonly usedto eliminate disturbance ofother solder joints alreadyformed on the assembly.

High-temperature preforms canbe used if the hand solderingassembly is being performedbefore conventional SMT orwave soldering processes.10/88/2 (Tin/Lead/Silver) or96/4 (Tin/Silver) are commonchoices for this application.See the Soft Solder Alloystable on page 10.

Paste-in thru-hole

Problem: In an attempt toeliminate wave soldering,many assembly processes usesolder paste to solder thru-holecomponents. The goal is toeliminate wave soldering, andsubsequent thermal stressresulting from multiple solderreflow cycles.

Solder paste is very difficult tostencil over an open hole, anddispensing adequate volumesof paste can be just as chal-lenging. Thick, multiple layerboards also make paste inthru-hole processes moredifficult. Per IPC Standard B610, at least 75% of the spacebetween the lead pin and thehole must be filled with solder.

Solution: The use of Exactalloy™

washers or linked washerarrays eliminates the inherentproblems of delivering enoughsolder to meet the IPC standard.The design of the preformbegins with the inner diameterof the washer. It should be 0.002" to 0.005" larger thanthe OD of the lead pin. The

next consideration is thediameter of the thru-hole orvia. The OD of the Exactalloy™

washer must be at least .005"greater than the diameter ofthe hole. The limit of the ODis usually the diameter of thepad surrounding the platedthru-hole.

Given the ID and the OD,Cookson Electronics can man-ufacture the washer to anythickness from .004" to a limitof 110% of the ID. Using thistechnique, Exactalloy™ preformscan be engineered to meet orexceed the IPC standard.

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Exactalloy™ preform solutions provide a wide range ofadvantages in electronic circuit assembly applications.

Above left: Cladded discs provide

a simple method of soldering very

large components from the opposite

side of the board.

Top right: Cookson Electronics can

package preforms on tape and reel

for use with common pick and

place equipment.

Left: Our extensive engineering

capabilities can turn your ideas into

high-production reality. Bimetallic

solder sleeves are but one example

of Cookson Electronics’ ability to

engineer solder fabrication.

Step stenciling

Problem: In some SMT assem-blies, larger volumes of solderare required on one or moresurface mount pads. Traditionalco-planar paste stenciling willnot yield the solder volumerequired. In this case, theprocess engineer has twochoices, neither of which maybe acceptable: stencil morepaste onto the required padsor use a second dispensingprocess. The dispensing optionis often impossible in finepitch applications.

Solution: Place an Exactalloy™

solder preform segment(square or rectangle) into thestenciled paste. Exactalloy™

preforms are available in tapeand reel packaging. The pre-form is sequenced in yourpick and place process to bepositioned prior to placementof the SMT component desig-nated for that pad.

Simply sequence the preformplacement prior to the compo-nent requiring the additionalsolder volume.

C O O K S O N E L E C T R O N I C S

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Reduce or eliminatewave soldering

Problem: The primary assemblyprocess used is SMT. Thereare still one or more thru-holecomponents on the assemblywhere the board must be runthrough the wave to assure a complete solder joint. The second thermal cycle maydamage some of the paste joints.Eliminating wave solderingwill reduce the cycle time ofeach assembly.

Solution: After the paste hasbeen stenciled, and all of theSMT components have beenplaced, use a semi-automatictechnique to position flux-coated preform solder washerson the thru-hole componentleads. This completely elimi-nates the wave soldering step,increasing the production rateand reducing rejects. (See theconnector jig schematic, onopposite page.)

Sealed beam lighting

As the leader in lead (Pb) freesoldering, Cookson Electronicshas developed several alloysthat exceed today’s require-ments for the elimination oflead, which is the trend in thisindustry. Both flux-coatedwashers and flux-cored seg-ments are used to automatethe placement of solder insealed beam lighting.

Flux-filled and flux-coated lead-free

solder preforms are used by the

major automobile lighting producers

to deliver the exact amount of solder,

in exactly the right shape, exactly

where it is needed.

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Exactalloy™ preforms deliverexactly the right amount ofsolder, in the exact alloy, everytime. Consistent, reproduciblesoldering is the real benefit tothe lighting industry.

Connectors

Filtered and ShieldedConnectorsExactalloy™ preform washersare made in both a single alloy,and in laminated layers of abase metal and solder. A typicalapplication is attaching a ferriteEMI shield to a connector pin.The pin is suspended in themiddle of the ferrite tube bythe unmelted base metal. Thesolder layers on either side ofthe base metal form the solderjoint. Similar technology isused to produce RFI shieldedconnector leads. CooksonElectronics’ lead-free alloysand flux-coating processes

See how Exactalloy™ preforms are providing innovativesolutions in actual applications.

Component manufacturing

CapacitorsPreforms are used in both surface mount and thru-holecomponent manufacturing.Both axial and radial leadedcapacitors are manufacturedusing solder preforms. A hightemperature alloy (Sn 95/Ag 5,Sn 10/Pb 88/Ag2, Sn 5/Pb 85/Sb 10) is typical, to eliminatesolder reflow when the capaci-tor is soldered to the final circuit assembly. High temper-ature alloys allow for the useof thermal curing encapsulentsas well.

Soldering lead frames toceramic capacitor bodies withflux-coated Exactalloy™ pre-forms can eliminate problemsassociated with the use of solder paste. Preforms alsooffer the additional advantagesof delivering reproducible volume, eliminating fluxresidue, increasing productionspeed and producing fasterreflow cycle times.

provide an unlimited numberof beneficial solutions for theconnector manufacturer.

Pre-Soldered ConnectorsExactalloy™ preforms can beautomatically placed on con-nector leads, and the resultingconnector requires no addi-tional paste or thru-hole sol-dering by the connector user.Your Cookson Electronicstechnical representative canshow you several methods ofapplying preforms to multiplepin connectors.

Attaching Coaxial ConnectorsHand soldering can be elimi-nated as a high volume methodof soldering coaxial connectorsto cable ends. Several uniquesolutions have been developedby Cookson Electronics forattaching solder sleeves to barewire ends. Coaxial connectorscan be slid over the preformring, followed by inductionreflow of the solder. Flux-coated sleeves make thisprocess highly efficient andreproducible.

Hundreds of solder washers can

be placed automatically by using

fixtures. Your Cookson Electronics

technical representative can help

you design a fixture for rapid place-

ment of flux-coated washers on

multiple-pin assemblies.

C O O K S O N E L E C T R O N I C S

Automatic placement of preforms

is often the key in reaping the

efficiency offered by automatic

soldering. In this application, a

bowl feeder dispenses flux-coated

washers for subsequent placement

and reflow.

TOP VIEWOF FIXTURE

CROSS SECTIONOF FIXTUREØ Hole = Ø Washer+0.15mmLength hole = Washerthickness +25%

Preform washers aredropped into fixture.

Connector is placed in fixture allowing preformsto attach to connectorpins.

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Using a solder preform to coatthe surface mount contactswith solder in chip scalecapacitors eliminates dippingheat-sensitive ceramics intohigh melting point solder baths.

ThyristorsExactalloy™ preforms are theideal metal to metal, and metalto diode joining material. Hightemperature alloys are used toeliminate solder reflow duringthe coating and curing of epoxyencapsulents. Flux-coatedExactalloy™ preforms (discs,rectangles or squares) are ideal for this application.

RectifiersDiode attachment with thesuitable preform alloy choicemakes high volume productionpossible.

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Optoelectronics

Indium-based alloys affordexcellent ductility, gold scav-enging resistance, and lowtemperature soldering (whereneeded) in this rapidly evolv-ing market. Indium’s ductilityallows for soldering materialwith large differences in theircoefficient of thermal expansion.Cookson Electronics’ technicalservice personnel will helpyou specify the best alloy andpreform to improve yourapplication.

Hybrid Circuits

Solder based fuses are used to protect high temperaturecircuits. Tin/lead and

Precise solder shapes can be used

as counterweights in analog

instruments.

Connector manufacturers can attach

Exactalloy™ preform sets, providing

customers with ready-to-solder

assemblies.

tin/lead/silver alloys, stampedinto horseshoe-shaped pre-forms, are used in automotiverheostats and other hybrid circuits to prevent catastrophicfailures from excess heat.

Plumbing

Lead-free Exactalloy™ preformrings and washers are used tosolder internal plumbing joints,and to automate the joining of brass, copper, bronze andtin plate materials. CooksonElectronics has several IAPMOcertified alloys for use in theseapplications. Washers up to 2" in diameter are available.Larger rings can also be pro-duced flux-coated, flux-filledor plain.

C O O K S O N E L E C T R O N I C S

Total Quality Management is the driving force in thedesign and manufacture ofCookson Electronics precisionExactalloy™ preforms. CooksonElectronics has earned ISO9001 certification for itsExactalloy™ production facili-ties. Comprehensive qualitycontrols include SPC (statisti-cal process control), non-destructive tests and randomsample analysis.

All incoming metals are exam-ined by spectrographic analysisand all alloy materials are analyzed for content and purityprior to in-house molten stateprocessing. Cookson Electronicsunique post-alloying batchanalysis is used to identifypreforms by date, time, andmaterials used in manufactur-ing. All materials, includingfluxes, are examined usingemission spectrography, X-raydefraction, gas chromatography,atomic absorption and classicalwet chemistry techniques.

The physical characteristics ofprecision preforms, includingdimensions, weight and uni-formity, are checked meticu-lously to ensure conformancewith customer specificationsand Cookson Electronics’ rigidin-house standards.

Our ISO 9001

certifiedquality program,along withextensivetool makingcapabilitieshave madeCooksonElectronicsthe firstchoice ofsolder preformusers.

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Standard Dimensional Tolerances

DIMENSION TOLERANCE

Diameter ±0.002” (±0.051mm)

Length and Width ±0.005” (±0.127mm)

ThicknessUp to 0.005” (0.127mm) ±0.0005 in (±0.0127mm) 0.006 to 0.010” (0.152 to 0.254mm) ±10% of thicknessGreater than 0.010” (0.254mm) ±15% of thickness

Thickness (flux-filled)Up to 0.010” (0.254mm) ±0.0015” (0.0381mm) 0.011 to 0.030” (0.279 to 0.762mm) ±15% of thicknessGreater than 0.030” (0.762mm) ±10% of thickness but

not less than 0.0045” (0.1143mm)

Horizontal Burr 0.005” (0.127mm) maximum

Vertical BurrUp to 0.010” (0.254mm) 0.003” (0.0762mm) maximumGreater than 0.010” (0.254mm) 3% but not to exceed

0.005” (0.127mm)

Tin/Lead Phase Diagram

RECOMMENDED ALLOY TEMPERATURE DURING WETTING

Soft Solder AlloysALLOY MELTING TEMPERATURE RANGE

°F °C

TIN/LEAD

63Sn/37Pb 361 183

60Sn/40Pb 361-379 183-190

50Sn/50Pb 361-421 183-216

40Sn/60Pb 361-460 183-238

10Sn/90Pb 514-576 268-299

5Sn/95Pb 581-594 305-312

SILVER BEARING

62Sn/36Pb/2Ag 355 179

96.5Sn/3.5Ag 430 221

95Sn/5Ag 430-473 221-245

10Sn/88Pb/2Ag 514-517 268-299

5Sn/92.5Pb/2.5Ag 549-565 287-296

92.5Pb/2.5Ag/5 In 572 300

97.5Pb/2.5Ag 579 304

1Sn/97.5Pb/1.5Ag 588 309

SAC 305

96.5Sn/3Ag/.5Cu 422 217

TIN/ANTIMONY

100Sn 450 232

95Sn/5Sb 450-464 232-240

99Sn/1Sb 453 234

LOW-TEMPERATURE

16Sn/32Pb/52Bi 204 96

48Sn/52In 244 118

50Sn/40Pb/10Bi 248-332 120-167

43Sn/43Pb/14Bi 291-32 144-163

37.5Sn/37.5Pb/25In 274-358 134-181

50Sn/32Pb/18Cd 293 145

3Ag/97In 295 146

15Pb/5Ag/80In 298-300 148-149

GOLD BEARING

20Sn/80Au 536 280

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C O O K S O N E L E C T R O N I C S

Use these drawingsto help specifyExactalloy™ solderpreforms

The size ranges indicated on these drawings representthe dimensions in whichExactalloy™ solder preformsare available. For informationon preforms outside of thesedimensions to meet yourspecific application needs,please contact your CooksonElectronics Sales Representativeat 1-800-289-3797. You may also fax drawings to us at: 1-814-944-8094, or contact us on our web site at:www.alphametals.com

Cookson ElectronicsAssembly Materialsis a member ofCookson Electronics.The power behindthe process.

As a member of CooksonElectronics, Cookson ElectronicsAssembly Materials sharesCookson’s goal: To create totalprocess solutions that willpower our customers to greaterproductivity. We are committedto optimizing every element of our customers’ productioncapabilities by providingadvanced process development,comprehensive consulting and world-class training. Ourpeople aim to deliver realresults. To share their know-ledge in ways that improveperformance and productivity,and help our customers achievetheir goals. Cookson Electronics.The Power Behind The Process.

ODMin = .020” (0.508mm)Max = 3.00” (76.2mm)

IDMin = .008” (0.203mm)Max = OD – .010” (0.254mm)

T (Thickness)Min = .002” (0.0508mm)Max = .110” (2.794mm)

S (Side)Min = .020” (0.508mm)Max = 2.30” (58.42mm)

T (Thickness)Min = .002” (0.0508mm)Max = .200” (5.08mm)

D (Diameter)Min = .020” (0.508mm)Max = 2.10” (53.34mm)

T (Thickness)Min = .001” (0.0254mm)Max = .200” (5.08mm)

ODMin = .057” (1.4478mm)Max = 1.05” (26.67mm)

IDMin = .049” (1.2446mm)Max = 1.024” (26.01mm)

H (Height)Min = .024” (0.61mm)Max = .472” (11.99mm)

Cookson Electronics Assembly MaterialsEnergiestraat 211411 AR NaardenTelephone +31 35 695-5411Fax +31 35 694-8451www.alphametals.com

©2002 Cookson Electronics Assembly Materials

Cookson Electronics Assembly Materials4100 Sixth AvenueAltoona, PA 16602 USAOrder Hotline 800-289-3797 ext. 1685Technical Services Hotline 814-941-1690www.alphametals.com

The Power Behind The Process