Joining mechanism of connection between Ag-plated Kovar interconnector and stranded Ag-plated Cu wire produced via parallel gap resistance welding

A space solar array includes GaAs solar cell, interconnector, and stranded Cu wire. Due to the preferential high working efficiency, the assembly of solar array is mostly performed using parallel gap resistance welding (PGRW). Since strengthening of the PGRW joints is the key to further extend service life of solar array, it is necessary to elucidate joining mechanism of each connection. In the present research, to clarify the controversy over PGRW joining mechanism between Ag-plated Kovar interconnector and stranded Ag-plated Cu wire, various advanced material characterization methods are conducted to joining interfaces. Experimental results confirm that, in addition to the known Ag/Cu eutectic interface, solid evidence of metallurgy bonding is also found in Cu/ Cu interface. Such finding has significant implication for further enlarge the PGRW process window and produce stronger joints.