Design for Testability Recomendations
Assistance with Design for Testability is also a service from ACC, but it needs to happen long before the board layout is finalized. In fact, it really should occur before the board layout is started. We will provide your design engineer general guidelines for improving testablitiy. This is a critical issue when In-Circuit Testing is required. The challenge is to provide the tester access to every circuit that must be tested. The simple addition of a small pad and/or via may provide access to a connection that is made on an inner layer of a multi-layer printed circuit board.
We had experience with one board for which the in-circuit test design house could only provide about 65% coverage (access only about 65% of the circuitry). This made the value of in-circuit testing questionable. More recently, we were involved with a board for which the customer's design engineer provided 98% coverage! In the latter case, the test fixture and software are easier to design and the test results are far more reliable.