Laser micro-welding of Cu-Al dissimilar metals

Abstract

To study laser micro-welding technology of dissimilar metals, experimental research has been conducted on laser micro-welding of a fine copper wire to an Al pin of an integrated circuit chip. The results show that a Nd:YAG pulse laser welding system with a maximum output power of 300 W can successfully join a fine copper wire of 0.25-mm diameter with an Al pin. The process parameters include a single pulse energy of 3.3 J, a defocusing amount of −0.5 mm, and a peak power of 0.7 kW. During the laser micro-welding process, the laser beam illuminates the surface of the fine copper wire, which has high melting temperature and good fluidity, melting it so that the Al pin becomes submerged in the copper melt, attaining common defects such as blowholes and cracks and exhibiting poor fluidity and high oxidability. Solution-diffusion welding is conducted, and good metallurgical bonding is obtained between the fine copper wires and the Al pins with the decrease of their temperature.