Understanding the Types and Applications of Printed Circuit Boards

printed circuit boardThe invention of the printed circuit board has contributed to the advancement of the world of electronics. This small, simple, unassuming board has opened up the manufacture of an array of electronic products that made life better. Typically, there are 3 main classes of PCB applications. The classifications were based on the intended end use of the PCB, according to the IPC- 2221 1.6. Performance classes include Class 1 general electronics products, Class 2 dedicated service electronics and Class 3 high reliability electronics.

Class 1 Application – General Electronics Products

PCBs classified under Class 1 are boards that were manufactured with the intended end use for the production of general electronics products. Most often, these are things considered as consumer electronic products, which are mostly for home, office or personal use. These boards are also used in non-special service computers and its peripherals (e.g., printers, scanners, etc). Also, general military hardware is also included under this category. Basically, a printed circuit board under Class 1 category has an end use for electronics that are not very sensitive. These are used in equipment and gadgets where cosmetic defect are acceptable because the function of the electronic product is not that sensitive (i.e., life and limb does not depend on its function, does not require point-accurate readings or data, etc). Also, products that value functionality over everything else use Class 1 printed circuit board.

Examples of end products with Class 1 boards include:

• Digital wrist watches
• FM/AM radios (with or without alarm clocks)
• Digital alarm clocks
• Calculators
• Televisions
• Coffee pots (digital type)
• Home alarm systems
• Microwave ovens
• Slow cookers
• Automatic grinders
• Blenders and food processors
• Juicers
• Cellular phones
• Hand-held video games
• Home theater systems
• Stereo surround sound systems
• Home or personal computers
• Cable TV converter box
• LOJACK auto recovery system
• Remote controlled electronic toys (e.g., toy robots, RC cars, planes, etc)

Class 2 Application – Dedicated Service Electronics

A printed circuit board classified under Class 2 is one that will be used in the manufacture of machinery and equipment that are used for businesses, instruments and in some military equipment. Equipment and instruments for communications also uses Class 2 PCBs.

These PCBs are used in electronic products that require high performance. Long life with reliable function and uninterrupted service are also factors for this type of application. However, the services required of the electronics products are not that critical, which can also accommodate minimal cosmetic defects.

Examples include equipment used in telecommunication such as the following:

• Fire/Rescue/Police radios
• Point-to-point microwave transceivers
• CB radios (2-way walkie talkies)
• Private and commercial aircraft instrumentation and radio systems
• SatCom transceivers
• Digital network equipment
• Cellphone relay stations
Industrial Instrumentations and Electronics also use Class 2 PCBs such as the following:
• Oscilloscopes
• Weather radar
• Weather-related telemetry
• Network analyzers
• DC to AC power inverters
• Environmental chamber oven
• Ohm meters
• Strain gauges
• Temperature meters
• Equipment for solar photovoltaic power cogeneration
• Supplies for switcher power
• CCD telescopes
Some military electronics that use PCBs under this category include:
• IR detectors
• IFF transponders
• Night vision goggles
• Encrypted frequency hopping VHF radios
• Equipment for finding directions

Automotive electronics also require top grade performance and reliability to reduce road accidents that may endanger lives. This would include the use of Class 2 PCB in fuel air mixture, automotive ignition controls, fuel injection climate controls and dash instruments.

Class 3 Application – High Reliability Electronics

Printed circuit board for electronics that require top quality performance and reliability-on-demand are classified under Class 3. These electronic product need to perform continuously and provide accurate function each time. Any down time is not tolerated from these types of equipment. These include instruments and equipment used in life support systems and critical weapons systems of the military.

Military electronics that use Class 3 PCBs include:

• Military grade computers that use encryption software
• Satellite navigation systems
• Forward-looking infra-red (FLIR) Pod Test equipment
• Missile guidance systems
• Fire control circuits

Aerospace electronics also require the top function and reliability of Class 3 printed circuit board, such as in satellite systems, aircraft controls and communications and space shuttle systems and controls, among many others.

Medical electronic equipment also requires top performance such as in the following:

• Heart monitors
• Assistive breathing machines
• LASIX for laser corrective eye surgeries
• CAT scans and X-ray equipment
• MRIs
• Dialysis machines