Research Article Published online 25 November 2009 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/qre.1081 Stress Test Optimization Using an Integrated Production Test and Field Reliability Model Bahman Honari, a ∗ † John Donovan, b Toby Joyce, c Simon Wilson d and Eamonn Murphy a Numerous papers and texts have been written in the reliability literature regarding the determination of the optimum test duration for a production stress or a burn-in test. The techniques presented have largely been based on the identification of the change point at which infant mortality has largely been removed from the units. The time-on-test is typically the only factor that influences this decision. Few of these models have attempted to integrate the field performance or the influence of warranty costs into this decision. This paper proposes and validates a methodology that integrates the influence of the production test failures and the field performance including their respective costs into a single unified model. The objective is to identify a production test duration that minimizes the overall cost. A Weibull model is initially developed for the production test that incorporates the failure observations in different time segments of the test based on the ability to detect latent defects in the product. A separate Weibull model is then developed for the product’s performance in the field that includes the lifetime of the unit. This paper identifies how both these Weibull models can be combined into a single model including both test and field costs with the objective of minimizing the overall cost. The advantage of the proposed technique is that it does not require one to track individual units from production through to the field in order to develop an integrated test and field cost model. Copyright © 2009 John Wiley & Sons, Ltd. Keywords: Weibull model; environmental stress testing; test optimization 1. Introduction 1.1. Background E arly field failures of a product can reduce the customer satisfaction level and increase warranty and compensation costs. These failures are commonly caused by latent defects, which are supposed to be detected during the production and Environmental Stress Testing (EST). This test is typically performed before sending the units to the field in an effort to improve the product’s reliability. Temperature cycling during the EST is one of the most commonly used test procedures. As it is an expensive and energy- intensive procedure, it is desirable to reduce the test duration and optimize the test regime so as to reduce the overall test cost. A lengthy test is often initially recommended for a new product but is based on the product’s test performance or possible manufacturing process modifications; the expectation is that the test duration and regime may be reduced over time. Numerous papers and texts have been written in the reliability literature regarding the determination of the optimum test duration for a production stress or burn-in test. The techniques that are used to determine the optimum test duration have largely been based on the identification of the change point at which infant mortality has been removed from the units (see Jensen and Petersen 1 ). The time-on-test has typically been the only factor that influences this decision. Dalal and Mallows 2 have proposed several graphical procedures that are easy to implement. Readers are referred to Meeker and Escobar 3 for a good summary of the models used in the accelerated testing and to Block and Savits 4 for an extensive review on mixture models and cost models used in the determination of the optimum test time. a CTVR ‡ , Department of Mathematics and Statistics, University of Limerick, Ireland b School of Engineering, Institute of Technology Sligo, Ireland c Alcatel-Lucent Technologies, Blanchardstown, Dublin, Ireland d Department of Statistics, Trinity College Dublin, Ireland ∗ Correspondence to: Bahman Honari, CTVR, Department of Mathematics and Statistics, University of Limerick, Ireland. † E-mail: bahman.honari@ul.ie ‡ Center for Telecommunications Value-chain Research. Contract/grant sponsor: Science Foundation Ireland; contract/grant number: 03/CE3/1405 Copyright © 2009 John Wiley & Sons, Ltd. Qual. Reliab. Engng. Int. 2010, 26 579--592 579