Modeling and Adapting Production Environmental Stress Testing

This study describes the production sampling environmental stress test (PSEST) process and the offline analysis conducted. Some of the key characteristics and parameters of the test are outlined. The analytical process is based on two types of regression model, each of which links a dependent variable (the log of time to failure in each dwell, or the log of the number failed in each dwell) to independent variables such as temperature and age. These two types of regression are known as Weibull regression1 and Poisson regression.2 Using the estimated regression coefficients, expressions for the probability distribution of a unit under test can be written and used to optimize the test duration.