Printed circuit board assemblies (PCBA) are the core of nearly every electronic product.
PCBAs are complex and sensitive, and even the smallest manufacturing error can render a PCBA unusable. Every PCBA must be tested to guarantee functionality before it can be integrated into a final product. Experienced electronics and hardware engineers design PCBAs to facilitate the testing process, and “test points” are a part of any design. Test Points are places where we can make electrical contact to apply power or transmit and receive digital and analog signals, confirming functionality.
Even a small PCBA can incorporate dozens of test points. Since they are small and closely spaced, “touching” all of them requires exquisite precision and a well-thought-out strategy for alignment and indexing.
Designing for PCB Testing
The optimum design for a PCB Text Fixture is a function of many variables. The number, size, and spacing of the test points is critical. Functional complexity and manufacturing volumes must also be considered when devising the general architecture and specific features.
The most common arrangement for testing PCBAs is called a “bed of nails” fixture. A PCBA is placed on top of an array of Pogo Pins. The board travels just enough to compress, but not over compress, each carefully-positioned pin.
The smallest amount of sideways motion or force will damage these delicate test pins, so it is necessary to engineer a fixture that guarantees pure downward motion. Here is an example of a complete PCB Test Fixture designed by Porticos.
Notice that the test fixture itself includes a PCBA, whose job it is to apply power, provide a signal, measure response, log the results, and inform the test operator of the outcome.
PCB Test Fixture Extras
Depending on the complexity of the board and the test, the fixture may be designed to incorporate other useful features and functionality:
- Automated loading/unloading of a test piece.
- Mechanical latching to hold the PCBA in place during a longer manual test.
- Lighted or alphanumeric indicators to communicate the status and/or outcome (pass/fail) to a technician.
- Data logging to facilitate Continuous Quality Improvement.
- Two-sided testing, in which pogo-pin connections are made to both sides of the PCBA simultaneously.
- The loading of firmware onto a board that has been tested and judged good (also known as “flashing”).
PCB Testing in Production
Test fixtures can also be integrated into the production process. A test fixture built into the manufacturing line can allow errors to be caught immediately, allowing fast corrections and continuous improvement.
With Porticos, you have an engineering team with experience. Check out our projects that have utilized PCB Layouts and learn how our product development process takes design and testing into consideration.