Weibull analysis of component failure data from accelerated testing

The Weibull distribution is commonly used to describe the failure rate parameters of electronic components and has the advantage of presenting an ‘easy-to-understand’ picture of component failure modes with respect to time. This allows conclusions to be drawn on whether an increasing, decreasing or constant failure rate is present which is undoubtedly a key factor in making any reliability statements.

This paper describes in detail how a transistor problem on a colour video display unit (VDU) was screened out and the time-to-fail data plotted on Weibull paper to allow conclusions to be drawn. Two different transistors were evaluated in the same application to determine from their respective Weibull plots, the reliability characteristics of each type. As the product under discussion was in its early production stage, the Weibull plots were not used to predict field fallout from the test data, but to understand the failure mechanism.

The paper also describes the way in which weak component failure distributions can be isolated in Weibull plots by using a form of the Bayesian statistical approach. Isolating the weak distribution in this manner allows a more exact calculation of the required burn-in duration which may often have a marked effect on improving product reliability.