In-Circuit test, or ICT, is the most common method of electrical test for an assembled PCB. It is the most comprehensive and accurate method to ensure that both the PWB and components are working to specification. Not all components however can be electrically measured, such as filter capacitors of certain values. This method isolates components from the circuit to measure their respective values to tolerance, and can also take measurements on a circuit net. Test access is obtained by a fixture, either mechanical press or via vacuum, to bring the PCBA into contact with the test pins. This is referred to as �fixed pin ICT�. Another method is by flying probe (pins) tester. In this system the probes move X-Y-Z to programmed positions on the board to perform the same test as a fixture would. Functional tests can also be done on an ICT machineOther than ICT, there are testers that do node impedance, boundary scan or circuit analyzers whereby a norm good �golden� board has its signature taken and is compared to subsequent boards. Also, many assemblers employ functional test.
To see equipment and get more info, please go to these sites:
www.teradyne.com/ict
www.seica.com
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