Comparative Study on Thermal Generation and Weld Performances of Two Types of Micro-Resistance Welding Between Thick Multi-Strand Cu Wire and Kovar Interconnector with Different Electrode Systems

The joining quality of welds between Kovar interconnectors and multi-strand copper wires is crucial for the energy efficiency and operating life of solar arrays in space orbits. High-power solar arrays demand reduced circuit resistance by increasing the thickness of copper wires. However, it is challenging to obtain satisfied joining between the interconnector and thick wires with a core diameter above 200 μm by traditional single-side double spot welding (SDSW). In this case, single-side single spot welding (SSSW) with a redesigned electrode system is introduced to match different welding conditions and achieve better welding quality. In this research, the difference between the two welding processes is systemically compared experimentally and numerically. The over-heated electrode/wire interface and under-heated wire/interconnector interface found in the SDSW joints are significantly reduced in the SSSW joints. Attributing to the rebuilt welding current path, more Joule heat generates at the wire–interconnector interface, which reduces the thermal gap between the upper surface and the interface of weld and hence achieved enhanced weld interface and lowered thermal damage. The SSSW also improves the temperature within the cores, which improves the bonding quality between the wire filaments by filling the gaps between wire filaments with Ag-Cu eutectics and solid solutions.