Failure Evolution and Reliability Assessment of Epoxy Mold Compounds in Power Module Encapsulation

Abstract:
Driven by increased automotive requirements, high temperature encapsulation is a desired feature for next-generation silicon carbide power modules. Current reliability methods (pass or fail of 1000 hours or 1000 cycles of thermal tests) induce significant time and energy consumption, as well as valuable information loss about the failure formation and evolution and saturation during the reliability tests. In this study, we investigated the occurrence and evolution of encapsulant delamination failures over time / cycles by multiple intermediate inspections. The propagation of mold delamination across the different experiments can be well modelled by a logistic function. Parameter estimates are given for all mold compounds studied and experiments conducted. In addition, this study discovers a fast-evolving behavior of mold delamination at high temperature storage tests, and suggests a more efficient reliability approach combining short pre-screening (10-20 % of testing time) and long-term qualification for those materials passing the screen.