Thermal characterization of DBC and MMC stacks for power modules

This paper presents the predicted thermal characterization of silicon carbide aluminum (SiC/Al) baseplates under high current applications. SiC/Al, or metal matrix composites (MMC) is a technology being evaluated for application in high current power modules. In an effort to improve module reliability, the Hybrid Power Module operation (HPM) chose to investigate the possibility of tailoring a material, such that the structural characteristics of a baseplate would match that of a ceramic isolation without compromising thermal performance. The result was SiC/Al MMC which are constructed by infiltrating a molten aluminum alloy into a molded or machined porous silicon carbide preform, such as a baseplate. Through controlling the volumetric fraction of the aluminum alloy during infiltration, various thermal-structural properties can be tailored to achieve desired values. The end result is a composite structure with superior structural properties than copper, however with thermal properties which warrant further investigation, hence the subject of this paper. Thermal characterization of SiC/Al (or MMC) began with defining various module configurations, whereby a direct comparison of copper baseplate technologies could be ascertained. To assist in expediting the design process for analytical and experimental evaluation a series of solid models were constructed which were then utilized for subsequent finite element analyses and the production of test specimens. This paper discusses the various methodologies employed for the development of MMC baseplate technology and the analytical and experimental simulation results.