No direct feedback about the PEM (plastic encapsulated microcircuit) model has ever been received from the authors of the Critique [1]. The Critique is based on misconceptions by its authors with respect to: 1) the merits of the various model approaches, and 2) the needs of the various segments of the reliability community. Its authors also misrepresent the facts concerning the development of the PEM model. The RAC (Reliability Analysis Center) position is that reliability professionals who perform assessments should decide what approaches are appropriate for their specific purposes. Having had experience with both deterministic & empirical modeling, the RAC is well qualified to provide the reliability community with an unbiased assessment of the issues surrounding the two approaches. RAC's purpose is to provide reliability practitioners with the tools & techniques necessary to perform reliability engineering tasks, and RAC is always interested in obtaining feedback on the models it develops. The RAC would welcome an unbiased comparison of reliability predictions performed: using its models, using the PoF (physics of failure) approach, Such a comparison, which must include the cost of obtaining the results, will be good for the reliability engineering community in understanding the merits of the two approaches. The RAC will continue to promote an open, unbiased dialogue of issues of concern to reliability practitioners. Hopefully, others involved in the discipline will embrace the same philosophy so that the users of the various approaches & techniques will be better served. I believe that criticism of statistical models because they are statistical, and to propose PoF models as the only viable alternative, demonstrates a profound lack of understanding of the broad sr. varied needs of practitioners who are credibly served by statistical models. The reality is that both types of models,are very important to the reliability community. The needs of all segments of the reliability engineering community must be recognized. The RAC model has been widely used and accepted by the reliability community. For example, the following companies are a small sample of those that have successfully applied the model by using it for its intended purpose: Lockheed Martin, RAC fully understands PoF approaches and strongly advocates their appropriate use. IITRI, the operating contractor of RAC for the past 30 years, in conjunction with the (then) Pome Air Development Center, established the 'Physics of Failure in Electronics' symposium in 1962. This symposium later became the 'International Reliability Physics Symposium (IRPS)'. Since that time, IITRI has and continues to perform many studies in this domain. It uses failure analysis, physical modeling, and accelerated testing when they are appropriate. However, to estimate field-failure rates of systems, a physics-based approach is neither practical nor cost-effective.
