Design-for-test or DFT takes into account several major and minor considerations at the design layout stage. In this limited webpage space, the key ones are described. However, the overall DFT success for 90 percent plus test coverage relies heavily on implementing all these critical design considerations.
Initially, the PCB design engineer should lay out all test points on one side of the board. Another consideration is maintaining minimum test point distance from one test point to another. There should be a minimum distance of 100 ml., accounting for about 2.54 millimeters so that probes can perform their job properly.
Test point distribution is important, as well. A high density of test points or clusters should be avoided. Test points should be uniformly distributed throughout the board, making it easier to test with multiple probes and not having to rely on a specific area for all the probes to concentrate on. Moreover, there should be a free zone or a safe zone designated as a keep out area.