New interconnection technologies based on Ni nano-particle and Ni micro-plating bonding with stress relaxation effect for high-temperature resistant power device packaging

There are high expectations for silicon carbide (SiC) devices as power device modules in electric vehicles (EV). The need for a new bonding method has been strongly anticipated in order to maximize the performance of SiC power devices, which can provide high-temperature thermal resistance that can replace solder bonding. We have proposed a new method of low-temperature nickel nano-particle sintering to form die bonding connections. We have confirmed that bonding at a temperature of 400°C or lower is possible. To increase deformability and reduce gas voids in the bond layer, we mixed Al micro-particles into the Ni nanoparticle paste. The reliability of the bond formed with Ni nano /Al micro particle composite was evaluated, and it was found that the bonds have excellent long-term high heat resistance. Using these newly developed methods, we implemented heat-resistant mounting of SiC Schottky barrier diodes on T0247-type packages and confirmed the I-V characteristics even after high-temperature storage at 250°C for 1000hrs without any significant degradation. We have also developed a new micro-plating interconnection technology called Nickel Micro Plating Bonding (NMPB), which allows for interconnection in a narrow space between electrodes and SiC devices via our new lead frame formed in a chevron shape. Regarding the bonding strength of NMPB, sufficient joint strength values have been confirmed through shear testing. Additionally, to minimize stress at the bonding interface caused by CTE mismatch between SiC and Ni or Cu, we deposited a layer of Fe-Ni alloy with an invar-alloy composition having a coefficient of thermal expansion (CTE) of approximately 4ppm/K, similar to that of Si or SiC.