![]() ![]() Telcordia SR-332 was originally the Bell Laboratories Bellcore standard for the reliability prediction of commercial electronic components. What’s in Telcordia SR-332? The Telcordia Standard allows reliability predictions to be performed using three methods.Įricsson acquired Telcordia in 2012. Bellcore previously used MIL-HDBK-217 for their reliability predictions, but found that 217 gave pessimistic numbers for its commercial quality products. A few years ago (1985), Bellcore used 217 as a starting point, modified (and simplified) the models to better reflect their field experience, and developed the Bellcore reliability prediction procedure, which is applicable to commercial electronic products. Telcordia has continued the development of the reliability prediction procedure. Most commercial electronic product companies are now choosing to use the Telcordia SR-332 handbook for their reliability predictions. RelCalc V5.1-TELC3 implements the models of this Telcordia document: 'Reliability Prediction Procedure for Electronic Equipment' Document Number SR-332, Issue 3 You can order this document directly from Telcordia: Telcordia Customer Service Center (Piscataway, New Jersey) Phone: 1-84 (USA/Canada) Phone: 1-91 (All Others) E-mail: Please note: T-Cubed Systems, Inc. ![]() Has no connection or affiliation with Telcordia, and Telcordia does not review, approve, or support the RelCalc software in any way.MTBF stands for mean time between failure and predicts elapsed time between inherent failures of a mechanical or electronic system during normal system operations. ![]() MTBF uses an empirical failure rate calculation based on historical component data. This data is compiled independently in different handbooks, such as the Telcordia SR-332 and the MIL-HDBK-217. Over- and Under-predicting Product Failure There are a number of limitations that arise when engineers rely only on the handbook-based MTBF method for reliability testing: 1. One limitation of the handbook-based MTBF method is that it assumes that failures are random in nature and occur at a constant rate once the failure rate calculation is generated. However, assuming that failures are random and occur at a constant rate is not always accurate. ![]() Studies have shown that the failure rates generated in these handbooks can vary widely, both from handbook to handbook - between MIL handbook and Telcordia - and from handbook to actual field failure data. What is worse is they can vary in both directions, both over- and under- predicting failures. MTBF Doesn’t Account for all Design Decisions Learn more about MTBF failure rate calculations in the “Limitations of MTBF vs Reliability Physics” webinar. Potentially the biggest limitation of relying on an MTBF analysis is that it does not directly account for many global assembly effects. ![]()
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