Reliable Integration of Double-Sided Cooled Stacked Power Switches based on 70 micrometer Thin IGBTs and Diodes

A stacked assembly concept of substrate-chip-bump-chip-substrate has been developed for a bi-directional power switch based on the latest generation Infineon Technologies(R) 70 micrometer thin IGBTs and diodes, rated at 200A-600 V. Using solder joints as joining method, this paper mainly reports the thermo-mechanical simulation to optimize the design of such a stacked assembly with consideration of substrates and bump shapes for maximizing the thermal performance of the chips and minimizing stress and creep strain development in the solder joints.The simulated results reveal that the thickest AlN-based substrate offers the best thermal performance, while the thinnest Si3N4-based substrate leads to the lowest creep strain accumulation in the critical solder joints. The effect of the bump shapes on the thermal performance is negligible, while hollow cylinder bumps can reduce the creep strain accumulation in the critical solder joints when compared to the solid cylinder bumps. In addition, a preliminary experiment demonstrates that the stacked integration can achieve the electrical function of the bi-directional power switch.