Copper is one of the most frequently used materials for the current-carrying component of batteries, power modules, industrial motors, etc., due to its high electric conductivity and high formability. These products are required to have a high power density, high integration, low cost, etc., and these demands are particularly strong in the car electronics industry. To satisfy these demands, a thick bus bar, large welding area, and efficient welding process need to be developed.
Conventional welding methods for copper, such as arc welding, resistance welding, friction stir welding, and laser welding, have been extensively studied, but not many of them have actually been applied to copper welding because each method clashes in some way with various properties of the copper, such as the high thermal and electric conductivity and high reflectivity of 1-μm wavelength laser light. As shown in Table I, the electric conductivity of pure copper...
