Brian A. Oistad

Current inverter technologies used in electric vehicles (EVs) are bulky, heavy, and expensive. The performance of the inverter is also limited by the traditional Si-based semiconductor and packaging technology. These constraints are responsible for extra weight and volume in the vehicle that reduces the driving range along with usable space within the vehicle. Moreover, operating temperature restrictions, and boundaries on the inverter location within the vehicle drastically reduces the inverter performance. Thus an improved inverter design is required for next generation electric vehicles. The objective of this project was to research, develop and demonstrate a highly integrated WBG power module targeting the next generation of plugin hybrid electric vehicles (PHEVs). This power module needed to be functionally and mechanically optimized for General Motors (GM) traction inverter architecture. General Motors was the prime contractor, led the project, and oversaw the design, build, and test of the integrated power module. Virginia Polytechnic Institute and State University (VT) performed modeling and simulation tasks as well as power module design support. Monolith Semiconductor, Inc provided SiC dies and consulted on devices for the inverter. Oak Ridge National Laboratory (ORNL) performed power module technology evaluations, design evaluations of interconnect options, and performed material analysis andmore » cross-sectioning of die activities. « less

This study uses three-point flexural testing to estimate the room-temperature apparent fracture toughness ( K _{Ic_app}) of a pressureless sintered-silver interconnect - a candidate material for use in power electronic devices. The K _{Ic_app} estimation occurs via work-of-fracture measurement of a chevron-shaped sintered-silver joint centrally located in an “interconnect bend test specimen”. The chevron-shape was stencil-printed on a silver (Ag)-plated direct bonded copper (DBC) substrate, mated to an Ag-plated DBC substrate, and then sintered. The chevron-shape, used for decades in fracture mechanics examinations and in standardized tests of monolithic materials, enables controlled stable crack initiation and propagation that are prerequisites for valid K _{Ic_app} estimation. The employed combination of an interconnect bend test specimen and bend test method is robust and simple, enables a means for interpreting the resistance to crack growth and delamination in an interconnect, provides a dependable way to judge the efficacies of sintered-silver processing conditions, and ultimately supports process optimization of sintered-silver interconnects.