Fault simulation and test generation for clock delay faults

In this paper, we investigate the effects of delay faults on clock lines under launch-on-capture test strategy. In this fault model we assume that scan-in and scan-out operations, being relatively slow, can perform correctly even in the presence of a fault. However, a flip-flop may fail to capture a value at correct timing during system clock operation, thus requiring the use of launch-on-capture test strategy to detect such a fault. In the paper, we first show simulation results providing a relation between the duration of the delay and difficulty of detecting such faults in the launch-on-capture test. Next, we propose test generation methods to detect such clock delay faults, and show some experimental results to establish the effectiveness of our methods.