Accelerated testing for demonstration of product lifetime reliability

A reliability test is designed to simulate product lifetime usage and expectations. With the assumptions that the product reliability, as demonstrated in test, is a multiple of its reliabilities regarding various operational and environmental stresses and of their undetermined interaction, a well designed reliability test accounts for all operational and environmental cumulative exposures to the stresses that the product will encounter in the actual field use. To determine levels and durations of each of the separate stress to be applied in test they are assumed to be independent. The stress independency assumption allows determination of duration and intensity of each applied environmental or operational stress to prove product lifetime reliability regarding all expected stresses, while the tests are accelerated to allow for reasonable and cost effective length of test in that environment. This cannot be accomplished without detail knowledge of product's usage profile, sequence of operation, and expected use environments. The synergism or the test sequence is not disregarded as it will be the factor possibly contributing to lower demonstrated reliability.