Optimal laser condition for laser soldering in cream and ring solder

This study describes fundamental melting phenomena of ring and cream solder and an evaluation of heat loss in laser soldering. Laser soldering is attractive from the viewpoint of minimum thermal impact on surrounding devices. However, detecting an appropriate laser irradiation condition is difficult since the heat loss is affected by several factors. Therefore, detecting an appropriate laser irradiation condition is important for more efficient laser soldering. In this study, to observe the fundamental melting phenomena of ring and cream solder, the movie of the melting phenomena were taken by highspeed camera. Then, laser irradiation time and solder type dependence of energy loss (heat loss) from solder to surrounding parts was discussed. The results indicated that contact surface of melted cream solder becomes larger than that of ring solder during laser irradiation. Due to larger contact surface, the minimum required laser power for complete melt of cream solder is larger than that of ring solder. Further, it was investigated the energy loss per second of each solder becomes constant.