SPRT for Weibull distributed integrated circuit failures

In this paper, we propose a sequential probability ratio test (SPRT) based on a two parameter Weibull distribution for IC failures. The shape parameter of the Weibull distribution characterizes the decreasing, constant and the increasing failure rate regions in the bath tub model for ICs. The algorithm detects the operating region of the IC based on the observed failure times. Unlike the fixed-length tests, the proposed algorithm due to its sequential nature uses the minimum average number of devices for the test for fixed error tolerances in the detection procedure. We find that the proposed test is on an average 96% more efficient than the fixed-length test. Our algorithm is shown to be highly robust to the variations in the model parameters unlike other existing sequential tests. Further, extensive simulations are used to validate the analytic results of the sequential test.