Successful design-for-test depends on careful attention to factors related to the design layout stage. Having an understanding of the complete process and implementing the necessary design considerations are crucial to achieving a 90+ percent test coverage - a PCB testing environment that delivers optimal results. Some of important factors we consider in the PCB Design for Test stage include::
We follow best practice guidelines by laying out all test points on one side of the board with a minimum distance of 100 ml between points. This allows enough room for probes to function properly.
Balanced test point distribution with no high density clusters is ideal. When test points are distributed evenly on the board, it's easier to use multiple probes. If the design includes taller components, the board should include a free or safe zone where no test probes can go. This accommodation should occur at the design stage.
These modules are available for circuit board testing and using them is a good idea. It is important, however, to make sure they are laid out so they can be tested independently. You want to avoid situations where if there's a fault in one module and not others, you won't compromise the test. Another important consideration is whether there is access to bus, data and address lines. At the design stage, the engineer should determine if system level feedback loops can be de-controlled and insure that during testing, all the system and subsystem specs are available in case debugging by the test technician is required. It's also important to provide access to a least one test node, and there should be one or perhaps multiple test points for each individual node.