Optimal Stress Screening strategies formulti‐component systems sold under warranty:The case of phase‐type lifetimes

Environmental Stress Screening (ESS) is employed to reduce, if not eliminate, the occurrenceof early field failures. This paper examines the necessary trade‐offs between thereduction in warranty costs and the increase in manufacturing costs associated with optimalstress screening strategies. A multi‐level ESS model is presented for a multi‐componentelectronic system. Screening can be performed at component, unit, and system levels. Componentsand connections are assumed to come from good and substandard populations andtheir time‐to‐failure distributions are modeled by mixed distributions. The majority of ESSmodels found in the literature assume that the time‐to‐failure distributions are exponential.The exponential distribution is used primarily to take advantage of its mathematical tractability.This paper generalizes previous work by modeling component and connection lifetimes withphase-type distributions. Phase‐type distributions offer the advantage of mathematical tractabilityas well as versatility in the family of distributions they can represent. To date thereis no significant research into the impact that the selection of a lifetime distributions formodeling the failure process has on ESS decisions. In this paper, we evaluate screeningstrategies for several lifetime distributions. Numerical examples are provided to illustratethe effect of various model parameters on the optimal stress screening strategy. Copyright Kluwer Academic Publishers 1999