Double-Side Cooled SiC MOSFET Power Modules With Sintered-Silver Interposers for a 100-kW/L Traction Inverter

Abstract

Low-profile double-side cooled power modules are emerging in electric-drive inverters to achieve higher power density and efficiency. However, the rigid interconnection between the devices and two substrates raises the thermo-mechanical reliability issue of double-side cooled modules. In the prior work, we proposed the use of porous sintered-silver (Ag) interposers in the double-side cooled modules, resulting in reduced thermo-mechanical stresses, better heat extraction, and lower package parasitic inductance. To further improve the power density and demonstrate the benefits of using the sintered-Ag interposers, we proposed a revised half-bridge module layout that further reduced the power-loop parasitic inductance by 23%, improved the power handling capability by 44%, and retained a similar thermo-mechanical stress reduction. After carefully selecting high-temperature packaging materials, we fabricated the improved module layout with a reasonably high yield due to the deformable feature of sintered-Ag interposers. The thermal testing showed that the module had excellent power handling capability with a junction-to-fluid thermal resistance of 0.76°C/W due to the double-sided cooling. The electrical characterization at elevated temperatures up to 250°C and the switching characterization validated the functionalities of the power modules with SiC devices aimed for high-temperature and fast switching. Six of the double-side cooled power modules with sintered-Ag interposers were assembled into a segmented traction inverter, demonstrating a high power density of over 100 kW/L.