Development of high speed laser soldering process for lead-free solder with diode-laser

The compactness of electronic equipments is leading the narrow pitch assembly of components on,P board or film by soldering. Diode-laser soldering system had already been realized as a high-density assembly process; however, the soldering quality became unstable when the system targeted to achieve short time, such as sub second, soldering, i.e. high productivity. A high speed soldering process for lead-free solder with diode-laser was developed. By measuring soldering temperature profiles of chips on film, it was found that the time period for soldering temperature reaching melting point at both sides of chip, which was over 0.6 sec, determined the soldering quality. According to SEM observation and EDS analysis, diffusion and inter-metalic layers, which were determined by plated materials of land, formed near the boundary of solder and land.