On the Thermal Performance of Si3N4-Based Ceramic Multilayer Substrates

Ceramic multilayer substrates represent efficient platforms for liquid cooled, compact, and low inductive power modules with fast switching semiconductors. This work shows how their thermal performance can be optimized. It is demonstrated with simulations and measurements that a thick copper layer in the middle of the layer stack serves as a heat spreader and thermal buffer. Integrating a cooler at the back of the substrate allows for omitting thermally unfavorable solder layers, while reducing the overall package size. Thus, additional ceramic layers can be compensated for. In combination with a customized cooling jacket, the introduced multilayer substrate shows improved thermal performance of up to ~25 % compared to state-of-the-art solutions.