Direct Microjoining of Copper Materials Using Laser Beams ∗

Direct microjoining using Yttrium-Aluminium-Garnet (YAG) laser beams of copper wire and a plate or substrate board was carried out. The control of the behavior of the molten wire was extremely important to prevent joining defects such as evaporation or constriction of the wire. Both the contact angle between the wire and the plate and the distance from the tip of the wire to the laser irradiation point affected the improvement of the defect. Controlling the input heat by pulse waveform adjustment was also effective in controlling the melt behavior of the wire. Therefore, for plates 100 and 200μm thick, high peeling strength of 4N with little dispersion was obtained. However, for copper foil 70 μm thick, the strength was poor and the dispersion was high. Because of the low heat capacity of the foil, the thermal condition of the wire extremely severe. Therefore, more details on input heat control are required.