Development of Sn-Pb-Bi solder materials for fine pitch package

This paper describes a new solder which is less likely to result in solder bridging. In this research, it was clarified that the bridging was related with surface tension and temperature difference of solidus and liquidus at a solder composition. We have selected 53Sn-2Bi-45Pb solder from results of experiment. Bridging occurrence rate of this solder is less than 1/10 of 63Sn-37Pb solder in cases of 0.5 mm and 0.3 mm pitch QFPs soldering.