Microstructural evolution of laser-brazed joint of Mg2Si and HMS on DBC substrate for thermoelectric generator

Abstract Joints properties of high temperature thermoelectric (TE) modules, which are composed of n-type Mg 2 Si and p-type higher manganese silicide (HMS), were investigated using the laser brazing process. In this process, the direct-bonded copper (DBC) and the TE materials were bonded using the Ag Cu based brazing filler metal. Heating and cooling rates were controlled by changing laser power and irradiation time gradually for preventing from thermal shock damage. The properties of joints were investigated by die shear test and microstructural analysis. As a result, improved joints of TE modules were fabricated through the laser brazing. Suitable heat input condition was deducted to optimize inter-diffusion between the filler metal and TE materials for obtaining reliable bond strength. In order to evaluate the high temperature stability, heat treatments were performed with TE modules using the furnace. As the heat treatment time increased, voids was formed at the joint but the diffusion distance of Cu and Ag did not increase.