Date of Graduation

8-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Mantooth, H. Alan

Committee Member

Chen, Zhong

Second Committee Member

Zhao, Yue

Third Committee Member

Huitink, David

Keywords

Double-sided cooling; Integrated power module; Power module packaging

Abstract

Double-sided cooled (DSC) power modules in conjunction with Silicon Carbide (SiC) power devices are expected to significantly elevate the performance of the next-generation electric vehicle power inverters. The double-sided cooling enables maximum heat dissipation, resulting in higher power density. SiC power devices, with their fast-switching speeds, reduce the power losses for higher efficiency. A half-bridge power module consisting of 13 mΩ 1.2 kV SiC devices is used for this work. A baseline DSC power module was designed, fabricated, and tested. This unique design uses truncated rectangular copper connection blocks for better heat dissipation from the device top side compared to conventional cubical connection blocks. Another important design feature includes a low temperature co-fired ceramic interposer, which is placed in between the top and bottom power substrates, for electrical isolation and mechanical strength. The power substrates underpin the SiC devices, providing both heat dissipation path and electrical connection to form the half-bridge topology. The placement of the temperature sensors on power substrates help to monitor the junction temperature of the SiC devices accurately. A novel three-part housing is designed to integrate the gate driver boards in the power module to increase the integration level of the design, ultimately leading to a high-power density system. The integration of the gate driver boards in the module housing will protect the control circuitry from environmental disturbances as well. Key electrical and thermal parameters are discussed and compared with the state-of-the- art. Pre-fabrication and fabrication process flows are developed and conducted in-house. Notably, pressure-less sinter technology is adopted for several attachments. Bond shear tests are conducted to prove good bond strengths for all the attachment surfaces according to the defined military standards. Static and dynamic electrical characterization of the module was performed. Building on the baseline module but to further improve the electrical performance of the module, the next generation of the module is designed with more integrated features. Decoupling capacitors were integrated in the power module. This resulted in a reduction of the power loop inductance value, as compared with the baseline, by 82% to 1.76 nH. Consequently, a 72% reduction in the voltage overshoots across the power devices was noted experimentally when switched at 800 V DC link and 164 A load current. Further integration features include silicon on insulator (SOI)-based gate drivers instead of the Texas Instruments (TI) gate drivers used in the baseline module, incorporating safety features like active miller clamping, over-current detection, and under-voltage lockout circuits. With novel design feature such as a printed circuit board (PCB)-based AC power terminal, current sensor can be integrated into this module design. All these integrations lead to a conceptual high power density inverter with a volumetric power density of 100 kW/L.

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