Properties of Two New Medium Temperature Solders

The increasingly utilization of Al-matrix composites in electronics packaging raised demands of solder materials with melting temperature at 400-500degC. In the present work, four candidate solder alloys in Au-Ag-Ge and Ag-Cu-Sb system were studied, two Ag-Au-Ge alloys (AAGl and AAG2) and two Ag-Cu-Sb alloys (ACSl and ACS2). Melting points, wettabilities, microstructure of the solders and the interface between the solder and substrate were investigated. The results show that the ACS alloys have small temperature gaps between solidus and liquidus. The temperatures of solidus and liquidus are 422.9degC/429.2degC for ACSl and 483.3degC/488.1degC for ACS2 respectively. For two AAG alloys, the temperature of solidus and liquidus are 410.0degC/449.8degC and 401.1degC/441.0degC respectively. The wettability tests showed that two ACS and AAGl alloys have good wettability to the substrate. Except for ACS2 alloy, the other alloys have good adhesion with the substrate. No IMCS were found at the interface. It is concluded that the two ACS alloys and the AAGl alloy could be possibly used as the solder for 400-500degC.