Using step stress to explore the kinetics of failure

In this paper a case study is presented illustrating a new step stress experiment design and associated graphical techniques for analysing failure data. The design and analysis procedures probe the process causing failure and suggest models for the kinetic processes underlying failure. The resulting kinetic models can be used to extrapolate the high stress behaviour to operating conditions. This case study concerns a failure mode observed at accelerated stresses in epoxy glass printed wiring boards. This failure mode has been found to be impossible to analyse using simple acceleration factors. The procedure described here quickly reveals this fact and indicates what kind of kinetic model is consistent with the observed data. The resulting qualitative model agrees with the results of independent physical experiments, and field experience.