Properties of Ag-Au-Ge medium temperature solder

Two eutectic alloys, AAG1 and AAG2, were selected as solder according to the Ag-Au-Ge ternary phase diagram. The solder alloys were prepared by vacuum melting. The melting point, wettability, microstructure of the solder alloys and the interface between solder and Al-SiC/Ni/Au substrate were investigated. The results show that these two solder alloys have large temperature gap between solidus and liquidus. The temperature of solidus and liquidus are 410.0℃; and 449.8℃ for AAG1 and 401.1℃ and 441.0℃ for AAG2, respectively. The alloy AAG1 has good wettability to the substrate. Both two solder alloys have good adhesion with the substrate. No intermetallic phase was found at the interface. It is concluded that the alloy AAG1 could be possibly used as the solder for 400-500℃.