Pressureless Silver Sintering of Silicon-Carbide Power Modules for Electric Vehicles

Pressureless silver (Ag) sintering was optimized at 250 degrees C in vacuum and nitrogen gas atmosphere with silicon carbide (SiC) chips, and silicon nitride active metal-brazed substrates (AMB). A 1200-V/200-A power module was developed using a pressureless Ag-sintered live SiC metal-oxide-semiconductor field-effect transistor (MOSFET) device and a Si3N4 AMB substrate module, and diverse reliability tests were performed. The void content and the bonding layer thickness of the Ag sinter joints were 1.2-3.4% and 68.5 mu m. The bonding strength of the Ag sinter joints after thermal cycling testing (TCT) were slightly decreased due to the crack generation. In contrast, high-temperature storage testing (HTST) was carried out for a long time at high temperature, the sintering process occurred continuously, and the shear strength increased by 31% after HTST. The drain-source on-resistance (R-DS(ON)) of a SiC MOSFET power module before and after the TCT and power cycle test was similar to the as-sintered state without change.