Effect of Field Stress Variance on Test to Field Correlation in Accelerated Reliability Demonstration Testing

This paper discusses the effect of field stress variance on the value of demonstrated reliability. In many cases, the acceleration factor for a reliability demonstration test is calculated based on a high percentile field stress level, typically corresponding to severe user or environmental conditions. In those cases, the actual field reliability for the population will be higher than that demonstrated by the test. This paper presents a mathematical approach to estimating ‘true’ field reliability based on the acceleration model and stress variable distribution over the product field population. This method is illustrated by an example of automotive electronics reliability demonstration testing and has a wide range of practical applications.