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Printed Circuit Applications




Typical applications for Printed Circuits are as follows:

Class 1 - General Electronics Products -

Class 2 - Dedicated Service Electronics -

Class 3 – High Reliability Electronics -

See if you can classify the following product categories:

Consumer Electronics – Digital Wrist Watch, CD Player, Am/FM/Radio/Alarm Clock, Television, Calculator, Digital Coffee Pot, Microwave Oven, Home Alarm Systems, Cellular Telephone, Home Computer, Home Theater/Stereo Surround Sound System, Cable Television Converter Box, Hand Held Video Games, Remote control electronic toys… LOJACK auto recovery system…etc.

Telecommunications – Point to Point Microwave Transceivers, Police/ Fire/ Rescue Radios, Digital Network Equipment, SatCom transceivers, Commercial and Private Aircraft Radios and Instrumentation, Cell Telephone Relay Stations, CB Radio/2 Way Walkie Talkies, etc…

Industrial Electronics and Instrumentation – Weather Radar and Weather related Telemetry, Oscilloscopes, Network Analyzers, Ohm Meters, Temperature meters, Strain Gauges, Environmental Chambers and Ovens, Spectrum Analyzers, Solar Photovoltaic Power Cogeneration equipment, DC to AC Power Inverters, Switcher Power Supplies, CCD Telescopes…

Military Electronics – IFF transponders, IR detectors, Night Vision Goggles, Military grade Computers with encryption, Fire Control circuits, Satellite Navigation instrumentation, Encrypted Frequency Hopping VHF Radios, Direction Finding Equipment, Missile Guidance Systems, FLIR Pod Test equipment, etc…

Aerospace Electronics – Satellite systems, Space Shuttle controls and system, Aircraft communications and controls, etc…

Automotive Electronics – Automotive Ignition Controls, Emission monitoring and controls, Fuel Air Mixture, Fuel Injection, Climate controls, Dash Instrumentation, Radio/TV entertainment accessories, etc…

Medical Electronics – Heart Monitors, Automated Medicine dispensing equipment, Breathing machine, Dialysis machine, Laser assisted tooth whitening machine, Laser optical corrective surgery machine LASIX, X-ray or CAT Scan equipment, MRI Imaging equipment, etc…

According to IPC-2221 1.6 Printed board assemblies are classified by intended end item use. The Performance Classes are listed as follows:

Class 1 - General Electronics Products - Includes consumer products, some computer and computer peripherals, as well as general military hardware suitable for applications where cosmetic defects are not as important, and the major requirement of the board is its functionality.

Class 2 - Dedicated Service Electronics – Includes Communication Equipment, sophisticated business machines, instruments and military equipment where high performance and extended life are required, and for which uninterrupted service is desired but not critical. Certain Cosmetic imperfections are allowed.

Class 3 – High Reliability Electronics – Includes Military and Commercial equipment where continued performance or performance on demand is critical. Equipment failure or down time is not tolerated and must function when required in the case of life support systems, or critical weapons systems. For applications where high levels of assurance are required and service is essential.

Producibility Levels:

Level A – General Design Complexity - preferred

Level B – Moderate Design Complexity - standard

Level C – High Design Complexity – reduced producibility.

Board Type:

Type 1 – Single Sided PCB

Type 2 – Double sided PCB

Type 3 – Multilayer without Blind or Buried vias

Type 4 – Multilayer With Blind and/or Buried vias

Type 5 – Multilayer Metal Core board without blind and/or buried vias

Type 6 – MultiLayer Metal Core board with blind and/or buried vias






A. Component Placement and Spacing:

Avoid components to be placed in random orientation.
Keep thru-hole components on one side, SMD on other side.
Hole to hole spacing for most adjacent components (end-end, side-end and end-side) should be 0.1" or more if permitted by body size.

Hole to hole spacing between socket and other component should be 0.175" or more.
Keep edges of the board clear from pads, holes, traces and components for at least 0.025"

B. Component Lead Spacing (Span) and Hole Sizes:

Radial component lead spacing should be 0.2". It's not recommended to use 0.1" span.
Axial component lead spacing should be 0.3" to 0.8" with max. body size 0.28"D x 0.66"L. We recommend to use the following span for widely used components:
a) 1/4w resistor and diode: 0.5"
b) Bypass axial cap and small axial cap: 0.375" (fits all axial equipment)
c) Small axial type die. cap: 0.7" to 0.8" with body less than 0.5"L.
Min. distance from center of hole to end of body: 0.07" to 0.120" depends on lead size, for 0.02"D leads, we recommend a min. distance of 0.08".
Min. hole size should be Lead diameter + 0.010" + Tol. (0.006). We recommend the following hole size for widely used components:
a) 1/4w resistor and small caps: 0.042", while 0.038" should be the absolute min.
b) IC pins and similar pin size: 0.039", while 0.037" should be the absolute min.
c) IC socket pins: 0.042", while 0.040" should be the absolute min.

C. Selection of Components:

Use same technology components instead of mixing technology components (SMD and through holes)

D. Layout Consideration:

For SMD layout, place 3 pads (0.04" and up) as fiducial marks (free of mask) at approximately 0.5" from corner of the PCB panel. If PCB panel has more than one unit, do the same for all sub-panels.
For SMD with fine pitch components (less than 0.035"), place 1 pad (0.04" and up) as local fiducial mark at the center location of that components.
For through hole components, keep pad size 0.014" lager than hole sizes.
For BGA devices, do not place via at the pads, unless blind vias are used at a higher board cost.









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