Traditional In-circuit test systems are used for the structural verification of printed wiring assemblies. The verification of component values, component orientations, detection of shorts and detection of opens with a guarded 2-wire or 4-wire measurement systems are the primary strengths of in-circuit test systems. In-circuit test systems rely on electrically connecting the printed wiring board to the test system with a custom fabricated bed-of-nails fixture which uses a large number of spring probes to make contact with every electrical net of the printed wiring board. Although bed-of-nails in-circuit programs execute quickly, the technique offers some significant limitations for some test scenarios. Bed-of-nails fixturing requires spring probe targets of a minimum size that may challenge the success of a printed wiring board layout and the spring probes generally cannot be placed closer than 1.27mm. Engineering changes which trigger a new the printed wiring board artwork can make an expensive bed-of-nails fixture obsolete and the fabrication time of a bed-of-nails fixture may also present challenges to the product release schedule as fixture fabrication can take weeks. The Flying Probe test systems, although slower in test execution, directly addresses most of the limitations of bed-of-nails testing solutions. The flying prober can reliably hit targets down to 150um. The most capable flying probe testers allow double sided moving probes with the ability to change the probe angle relative to the shape of the probing target and also possess the same measurement system as a bed-of-nails in-circuit tester. Flying probe testers are best used for prototype testing, testing of small volume products for which a bed-of-nails cost is not cost effective, testing of boards that have limited testability for probing targets or as a prescreen for technician troubleshooting of products that don't use in-line in-circuit testing in high first pass yield product assessment scenarios.
Accolade Engineering Solutions offers a variety of Electrical Testing Applications services. Contact us today to discuss your testing needs with someone who can provide you with the expert knowledge to determine the right testing solution for you.
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