Always employed as a final manufacturing step, functional testing provides a go or no-go decision on finished PCBs.
There are several PCB test strategies to choose from, including functional, in-circuit, boundary-scan and manufacturing defects analyzers. In-circuit testing has been a consistently popular test strategy. In-circuit testers evaluate individual components after they’ve been soldered to the PCB. In-circuit testing harkens back to a simpler time, when PCBs were one-sided, and a bed of nails could contact the board on the opposite side. The theory behind in-circuit testing is that if a PCB is designed and built correctly, it will perform correctly. "The in-circuit guy says, ‘Look. If the design is right, which has been validated, and the parts coming in are good, all I really want to do is make sure that I’ve put them together correctly," says Ken Hallmen, marketing manager for CheckSum (Arlington WA).