High Temperature SiC Power Module Packaging

Wide band gap semiconductors such as silicon carbide (SiC) provide the potential for significant advantages over traditional silicon alternatives including operation at high temperatures for extreme environments and applications, higher voltages reducing the number of devices required for high power applications, and higher switching frequencies to reduce the size of passive elements in the circuit and system. All of these attributes contribute to increased power density at the device and system levels, but the ability to exploit these properties requires complementary high temperature packaging techniques and materials to connect these semiconductors to the system around them. With increasing temperature, the balance of thermal, mechanical, and electrical properties for these packaging materials becomes critical to ensure low thermal impedance, high reliability, and minimal electrical losses. A primary requirement for module operation at high temperatures is a suitable high temperature attachment technology at both the device and module levels. This paper presents a transient liquid phase (TLP) attachment method implemented to provide lead-free bonding for a SiC half-bridge power module. This module was designed for continuous operation above 250 °C for use as a building block for multiple system level applications including hybrid electric vehicles, distributed energy resources, and multilevel converters. A silver-based TLP system was used to accommodate the device and substrate bond with a single TLP system compatible with the device metallurgy. A SiC power module was built using this system and electrically tested at a 250 °C continuous junction temperature. The TLP bonding process was demonstrated for multiple devices in parallel and large substrate bonding surfaces with traditional device and substrate metallization and no requirements for surface planarization or treatment. The results are presented in the paper.