Test Point Insertion for Non-Feedback Bridging Faults

This paper studies pseudo-random pattern testing of bridging faults. Although bridging faults are generally more random pattern testable than stuck-at faults, examples are shown to illustrate that some bridging faults can be much less random pattern testable than stuck-at faults. A fast method for identifying these random-pattern-resistant bridging faults is described. It is shown that state-of-the-art test point insertion techniques, which are based on the stuck-at fault model, are inadequate. Data is presented which indicates that even after inserting test points that result in 100 % single stuck-at fault coverage, many bridging faults are still not detected. A test point insertion procedure that targets both single stuck-at faults and non-feedback bridging faults is presented. It is shown that by considering both types of faults when selecting the location for test points, higher fault coverage can be obtained with little or no increase in overhead. Thus, the test point insertion procedure described here is a lowcost way to improve the quality of built-in self-test. While this paper considers only non-feedback bridging faults, the techniques that are described can be applied to feedback bridging faults in a straightforward manner