In-circuit testing (ICT) is an example of white box testing where an electrical probe tests a populated printed circuit board (PCB), checking for shorts, opens, resistance, capacitance, and other basic quantities which will show whether the assembly was correctly fabricated. It may be performed with a "bed of nails" test fixture and specialist test equipment, or with a fixtureless in-circuit test setup. In-Circuit Test (ICT) is a widely used and cost-efficient method for testing medium to high volume electronic printed circuit board assemblies (PCBAs). It has maintained its popularity over the years due to its ability to diagnose component-level faults and its operational speed. Using In-Circuit Test fixtures is a very effective way of maintaining standards when carrying out tests. It can help to reduce production downtime by identifying faults early in the testing process, ensuring that defective products are removed from the production line and fixed.

Fixtures for in-circuit testing

A common form of in-circuit testing uses a bed-of-nails tester. This is a fixture that uses an array of spring-loaded pins known as "pogo pins". When a printed circuit board is aligned with and pressed down onto the bed-of-nails tester, the pins make electrical contact with locations on the circuit board, allowing them to be used as test points for in-circuit testing. Bed-of-nails testers have the advantage that many tests may be performed at a time, but have the disadvantage of placing substantial strain on the PCB. An alternative is the use of flying probes, which place less mechanical strain on the boards being tested. Their advantages and disadvantages are the opposite of bed-of-nails testers: the flying probes must be moved between tests, but they place much less strain on the PCB.

Example test sequence

While in-circuit testers are typically limited to testing the above devices, it is possible to add additional hardware to the test fixture to allow different solutions to be implemented. Such additional hardware includes:

Limitations

While in-circuit test is a very powerful tool for testing PCBs, it has these limitations:

Related technologies

The following are related technologies and are also used in electronic production to test for the correct operation of Electronics Printed Circuit boards: