Component Identification

Through hole vs Surface mount

• there are two primary types of components, the difference being how they are attached to the circuit board.

• One group is called through hole

• The other type is called surface mount

Through holeThrough hole components have leads that are inserted through mounting holes in the circuit board

Surface MountSurface mount components are designed so they are placed directly onto lands that serve as mounting points on the surface of the board

Through hole leads

Axial Leads = Arms

Axial leaded components have two leads — with one lead extending from each side of the component, like arms Axial components need to have their leads bent so they can be inserted through the holes of a circuit board

Radial Leads = LegsRadial leaded components have two or more leads extending from the bottom of the component, like legs

PackagesSingle In-line Packagesor SIPs, are through hole components that have a row of leads in a single, straight line

Dual In-line Packagesor DIPs, are components that have two rows of leads in parallel straight lines

Pin Grid Arraysor PGAs, are ICs that have several rows of round pins extending from the bottom of the component

Surface mount LeadlessLeadless means there are no metal leads sticking out of the component body These types of components are attached to a circuit board using some type of metalized termination

This QFN has terminals

Chips & MELFs use terminations on opposite ends

of the component’s body

Ball Grid Arrays, or BGAs, consist of rows of tiny balls of solder on the bottom of the component These solder balls are connected to matching rows of lands on the circuit board

Castellations are half round metalized recesses in the side of a component that are filled with solder when connected to the

circuit board

Surface mount LeadedGull Wing Lead: The gull wing lead is a metal lead that bends down and away — similar to a

seagull’s wing J-Lead: The J-lead is a metal lead that bends down and underneath a component

in the shape of the letter J

L-Lead: The L-lead is inward

formed underneath a component Flat Lead: The flat lead protrudes directly out from the body of a component.

I-Lead: The I-lead, or butt lead, is actually a through hole lead that has been cut short for surface mounting. Because the connection is not very strong or stable, the I-lead is not considered suitable for high reliability assemblies.

Lead PitchAn important characteristic of some leaded surface mount components is lead pitch. Pitch is the distance between the center or one lead to the center of the next When a component has fine pitch it means the leads are

spaced very close together (less than 25 mils) Lead pitch

Component Packaging

• Component packaging refers to the way component manufacturers package their product for use by electronics assemblers

• Through hole and surface mount components are packaged in one of four ways: on tape and reel, in tubes, in waffle trays or in static-safe bags

• The packaging method depends on the component type and whether the component will be assembled onto the circuit board by machine or by hand

• • most component packages are made to protect the components

from electrostatic discharge, or ESD, which could damage them .

Tape and ReelsTape and ReelTape reels are used for axial leaded through hole components and the smaller surface mount components. Automatic insertion machines cut through hole components off tape reels and insert them into the board. Surface mount assembly machines, called “pick and place”, pick surface mount

components from tape reels and place them onto the board

TubesTubes are used to keep components straight and ready to drop into auto-insertion or auto-placement machines

Waffle TraysWaffle trays are used for many of the larger surface mount components They are stackable on pick and place machines Trays also provide protection for fragile leads during storage and handling

Static-Safe BagsSome components are simply packaged loose in static-safe bags These components are usually simple through hole axial and radial devices

that are too large or unusually shaped to be inserted by machine

Identifying ComponentsEvery component has a manufacturer’s part number This number is either marked on the component itself, or on the packaging

Every assembly to be manufactured has a works order raised.The works order will list the part number of the product, a description, the WO number, start and required dates and Qty.The sequence of operations is listed and the proposed time it should take.

Build of Materials

The second part of the works order lists a Build of materials, or BOM. This includes CIL’s part number, a description of the part, where the part is kept in stores and the sequence the part appears on the customers parts list.

Sub assemblies

The part number of the product will state which type of assembly it isIt could be a sub assembly ie;-

• A surface mount assembly• A conventional assembly• A cable assembly

Or it could be a final product

SMT Assemblies

A works order for a surfaceMount assembly willInclude all of the parts to beFitted at the surface mountStage.A surface mount part isIdentifiable by its part numberAnd its description.

Surface mount partsSurface Mount chip resistors

Surface Mount chip capacitors

A chip’s size, in inches or millimeters, is described by a 4-digit code:

The first 2 digits are the length The second 2 digits are the width.This is the same for Resistors or Capacitors

Chip Sizes

Size Codes (inches)0402 04" x 02"0603 06" x 03"0805 08" x 05"1005 10" x 05"1206 12" x 06"1210 12" x 10"1812 18" x 12"2225 22" x 25"

Size Codes (metric)1005 1 0 x 0 5 mm1508 1 5 x 0 8 mm2012 2 0 x 1 2 mm2512 2 5 x 1 2 mm3225 3 2 x 2 5 mm4532 4 5 x 3 2 mm5664 5 6 x 6 4 mm

CIL’s Part numbersUsually follow theImperial system (inches)

Resistor Values

• Resistance value is designated in units called the "Ohm." A 1000 Ohm resistor is typically shown as 1K-Ohm ( kilo Ohm, 1KΩ ), and 1000 K-Ohms is written as 1M-Ohm ( Megohm, 1MΩ)

Markings

• For surface mount resistors, a numerical code is used.

• For 0805 or larger, 5%,10% tolerance resistors, 3 numbers are used

• For 0805 or larger, 1% resistors, 4 digits are used.

Values

• the first two or three digits are the significant digits,

• the last digit is the multiplier (expressed as an exponent of 10).

• This is easy to remember as "the first digits then as many zeros as the last digit after it" ohms.

Examples

• 205 = 20 and 105 or 2,000,000Ω, or 2 MegΩ or 2MΩ

• Resistances less than 100 ohms are written: 100, 220, 470. The final zero represents ten to the power zero

• 100= 10x1 or 10Ω, 220 = 22x1 or 22Ω

Small Values

• For small resistance values an R is used in place of the decimal

• 2R0 = 2Ω

• 3R24=3.24Ω

Tolerance

• The tolerance of a resistor denotes how close it is to the actual rated resistance value.

• For example, a ±5% tolerance would indicate a resistor that is within ±5% of the specified resistance value