by ADL Technology ADL Technology

Testing your printed circuit board assembly is a balancing act.  You want to maximize the coverage of the test without making it cost prohibitive and bogging down the production process.  Having a good understanding of your PCB assembly and common failure modes is key to developing a test that is both thorough and cost-effective.  At ADL, we are constantly working with our customers to develop and improve their test requirements.

Here are 9 tips that we’ve learned over the years:

  1. Don’t rely solely on a visual inspection.  Even if your PCB assembly is simple, it can have problems that are invisible to the eye.  And if you have to return a failed unit to the manufacturer for repair, they have no way of troubleshooting it.
  2. A simple power-up test is a vast improvement over visual inspection.  It can help to ensure proper operation of all voltage rails, detect power-to-ground shorts, and identify polarized components that are incorrectly oriented.
  3. Design your board for ease of testing whenever possible.
    • Add test points to as many nets as possible.
    • Include a serial port for interacting with the PCBA and providing diagnostic data.
    • Provide ready access to all nets, pins and headers that are needed as part of the test.
  4. Provide your manufacturer with a “golden board” that can be used to validate the test procedure and test fixture.  A golden board is a perfectly functioning PCB assembly used as the gold standard for testing and production.
  5. Provide documentation that is as detailed as it needs to be – but no more so.  Underspecifying can lead to incorrect assumptions being made by technicians; over specifying can lengthen test time unnecessarily.
  6. As you learn more about failure modes of your product, update your test procedure accordingly.  Your contract manufacturer should be willing to work with you to change their test in order to help you weed out any recurring failures that are making it through to your shelves.
  7. It’s worth investing in your test fixture.
    • A custom test PC board or assembly can be designed and built for very low cost.
    • Consider an intermediate board for a connector that will be mated many times over its life.  When the connector starts to wear down, throw away the intermediate board and replace it with a new one rather than halting production while reworking the fixture.
    • Purchase the programmer recommended by the chip manufacturer for production applications rather than the lower-cost “lite” or “dev board” version that will wear out quickly.
  8. Consider incorporating LabVIEW or Python into your test procedure.  These tools are great for testing assemblies that are highly complex, for test procedures that are lengthy or easily automated, or for implementing record collection to ensure product traceability.  LabVIEW is also a very good way to translate a difficult-to-check reading into an easy pass/fail.  (Would you rather use a multimeter to verify a thousand times that 17 different test points are all between 3.768V and 3.876V, or look at a screen that tells you with a PASS or a FAIL?)
  9. Work with your manufacturer to optimize your test procedure.  They should be happy to provide feedback to you on where they commonly see failures, what steps slow them down, and how the overall efficiency and efficacy of the test can be improved.  Ultimately, this collaborative dialogue can be used to improve your design.

At ADL, we perform a full functional test of every PCB assembly that we build, and we work with our customers to develop test procedures that are thorough and efficient.  If you’re looking for a contract manufacturer who will partner with you to ensure your PCB assembly is built correctly, on time, and cost-effectively, contact us today!