RELIABILITY VERIFICATION OF PRINTED BOARD ASSEMBLIES: CRITICAL REVIEW OF TEST METHODS AND FUTURE TEST STRATEGY
Author: Per-Erik Tegehall Company: IVF Date Published: 8/23/1998
Surface Mount International
Abstract: The traditional way to ensure reliability of a product is to produce according to standards. Since the time standards were first developed, the approach has been to regulate quality requirements of materials used and how production should be performed. The instructions are based on long experience of products made with these materials and processes. However, during recent years, this approach has been questioned. People have become aware that experience with old technologies is not necessarily adequate for new technologies. Since the goal is to ensure the reliability of the end product, reliability requirements ought to be performance-based. Also, there is a need to more clearly specify who is responsible for the various stages in ascertaining the reliability of a product. For this reason many of the old military standards have been cancelled without replacement. Requirements will be specified in performance terms in all future military acquisitions. Also IPC has declared that their standards shall focus on end product performance. A performance-based approach for assuring the production of reliable printed board assemblies requires a capability for predicting those failure mechanisms that will be crucial to reliability and for adequately performing accelerated testing of these. A deep knowledge of the loading conditions during the product life cycle, materials and processes used for manufacturing and adequate quantified reliability requirements is a necessity for successful results. The rationale for abandoning the traditional type of standards and the implications of adopting a performance-based approach will be discussed in this paper. It will at depth describe some of the most important contamination-related failure mechanisms at board level and the various parameters of importance for these mechanisms. Thereafter, a discussion of various accelerated test methods for evaluating the impact of these failure mechanisms on reliability will be held. Test methods used today will be critically reviewed and alternative more relevant test methods will be proposed.