Cutting-edge low-Ag solder rides high on reliability, strength
Until last year, solders have been seriously affected by the high cost of metal materials. At present, the SAC305 (Sn-3mass%Ag-0.5mass%Cu) is the mainstream lead-free solder. Its chemical composition contains 3 percent of silver (Ag), which is a precious metal. At one point, the price of silver had risen to ¥60,000/kg. This price increase has become an additional burden to soldering cost. Although metal prices dropped sharply for a while due to the recent economic recession, the cost of metal is on its way up again. Using large quantities of precious metal, which is a target of market speculations, is not helpful for the industrial sector. To respond to the high cost of metals, the Second-Generation Flow Solder Alloy Standardization Project of the Japan Electronics and Information Technology Industries Association (JEITA) has recommended several low-Ag solder compositions for flow soldering (Table 1). Such solders also pose lesser problems with regard to the reliability of joints. When flow soldering is performed, a very large quantity of solder must be put into a solder tank. This makes low-Ag solder, or solder containing less amount of Ag in its composition, very effective in reducing cost.