Characteristics of 600 V / 450 A IGBT module assembled by Ag sintering technology

Up to now, more than 180 countries including China, Japan, EU and others have signed the Kyoto Protocol, then “Energy-saving and Carbon reduction” becomes a popular slogan and an important mission to protect the environment and to pursue the national sustainability. Taiwanese government is pushing the R&D institutes like ITRI to develop the renewable energies and smart grid technologies, and is also making many environmental policies as well for driving the people to purchase the eco-products like electric car, hybrid car and household appliances to reach the goal of Carbon reduction, and the industries are also actively involved in the mass production of the key components such as high power IGBT modules for EV / HEV, intelligent power module (IPM) for air-conditioner, and MOSFET SiP modules for the power management of consumer electronics and hand-held machine tools. ITRI has already achieved a 600 V / 450 A IGBT module composed of IGBTs and freewheel diodes (FWD) for EV / HEV applications. Previously, a Pb-free solder perform with a thickness of 100 μm was adopted to attach 2 IGBTs and 2 FWDs on one Al₂O₃ direct bonded copper (DBC) substrate in a vacuum reflow oven, and 3 DBCs were then soldered on a Cu baseplate by a solder perform as well, by this structure, the junction temperature of the IGBT device is very close to 150°C and may deteriorate the long-term reliability. Therefore, a Ag paste sintering method was used to replace the conventional soldering process to improve the thermal dissipation and to lower the junction temperature. With an optimized process condition, a voidless die attaching joint was gained, and the die shear strength was as high as 27 MPa. Furthermore, a reduction of 22% of thermal resistance was measured by using Ag sintering, and the electrical performance of the newly developed power module was fully reported in this study.