Similarly, DFT needs to be incorporated into production PCB assembly. This involves, among other things spreading out test points evenly across the circuit board so that all areas are accessible by test probes. Maximum accessibility should be made available on the circuit board for debugging and testing. If it is a mature product, investment in a special jig or creating special equipment may be a wise thing to do to make the PCB production run smoothly and error free. As the product matures and has a long life cycle, an OEM can amortize the value of that special jig or fixture over the product’s lifetime. Fixtures are costly, however, OEMs realize major savings due to considerably reduced handling time fixtures provide versus manually handling one or two boards at a time.
When a product comprises multiple printed circuit boards (PCBs), a test mechanism should be implemented to test the full functional system, as well as individual boards. Unless boards can be tested individually, considerable time is incurred to run system testing to isolate a fault and debug it. Also, as part of the OEM mindset for production PCB assembly, a troubleshooting guideline should be produced for test technicians. Guidelines for production quantities should be clearly define, stated, and explained in easy to understand language.
Efficient production assembly also places considerable attention on testers and their limitations. Targeting the proper test strategy for a given product is crucial. For instance, flying probe may be sufficient for a board with a few components on it, for example 25-100. On the other hand, a board populated with 1,500 to 2,500 components demands proper In-Circuit Testing (ICT) with its fixtures in place. Troubleshooting guidelines, diagnostic tests, and associated documentation must also support ICT.
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