Packaging of integrated solid-state power assembly cells: a thermomechanics-based approach

The design of integrated solid-state power assemblies presents unique challenges originating from the high current, voltage, and temperature levels at which they operate. Specifically, they are subject to high levels of internal mechanical stress owing to the dissimilar materials from which they are fabricated coupled with the higher temperatures and currents that develop within the modules during their operation. However, as future demands grow for compact power assemblies with ever-increasing controlled-power density coupled with low cost and straightforward manufacturability, the necessity for a predictive capability for their reliability is greater than ever. Surprisingly, despite the lack of a widely accepted methodology for such designs, much of the basic knowledge is in place. Therefore, the goal of this article is to summarize the main modes of failure in power assemblies, the corresponding material degradation mechanisms and driving forces, and the material properties that are required to help stimulate further developments in this area. A vital component of the approach presented here is to base the understanding on a rigorous knowledge of the physics involved in failure.