Spring-Loaded GaN Packaging for Cryogenic Thermal Cycling

Cryogenic power module packaging brings additional challenges for lack of low-temperature soft potting material and flexible electrical connections. Thermal expansion mismatches among different rigid layers of the package can cause the die failure. This paper develops and demonstrates a cryogenically cooled GaN packaging for a 750V/100A solid-state circuit breaker (SSCB) module. The proposed printed circuit boards (PCB)/direct bonded copper (DBC) hybrid module, clamped by spacers and springs to form a spring-loaded structure, can survive thermal cycling down to cryogenic temperatures. Experimental results of thermal cycling and interrupting a 10X fault current (1kA) by the proposed module are provided to show the effectiveness of the proposed packaging method operated with cryogenic cooling.