Production PCB Assembly
The OEM mindset for production PCB assembly involves a number of considerations. Those include Design-for-Test (DFT) and Design-for-Manufacturability (DFM), updated documentation, written diagnostic tests and macros, tester limitations, and written troubleshooting guidelines, among others.
In terms of DFM, if circuit board fabrication is involved, panel size utilization for maximum yields is an important issue, especially if the circuit board is odd shaped. SMT as well as wave solder fixtures are needed to run multiple boards in one panel that goes through a pick and place line, wave solder, washer, and then through a tester. To start with, panel size must be used efficiently so fabrication panel waste is prevented. Plus, there should be the right and final balance between the number of boards placed on a panel and the amount of time required to perform pick and place or test.
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.