Mechanical Design Considerations for Electric Vehicle Power Electronics

Designing power electronics to operate in harsh vehicle environments while meeting packaging requirements such as mass, volume, and power density, creates several challenges for their mechanical design. In this work, we concentrate on the power inverter module (PIM) which converts high voltage (HV) DC voltage power from the HV battery to AC power to drive the motor. The PIM main components are the power module, gate drive and the bulk capacitor. The sizing and selection of the bulk capacitor and power module depend on performance criteria and drive profiles in addition to operating temperatures. In this work, we share the main challenges of packaging components within the inverter. We then discuss best practices to ensure a robust mechanical design which meets inverter durability and reliability targets for an electric vehicle application. The main challenges discussed are bulk capacitor thermals, sealing, and Silicon Carbide (SiC) packaging. The bulk capacitor offers a low impedance path to current ripple generated and reduces the leakage of the power module. Current ripple causes significant heat rise, so proper thermal management is key to ensure lifetime targets. Sealing the inverter enclosure and coolant channel prove to be one of the greatest challenges in packaging. The final topic discussed is SiC packaging and the different methods used to design a power module containing SiC dies such as sintering for die-attach. Power module substrate cooling is also addressed.