Influence of Ag, Cu and additive Bi elements on the thermal property of low-Ag SAC solder alloys

This paper investigated the influence of Ag, Cu, and additive Bi elements on the thermal property of low-Ag SAC solder alloys. The results indicate that the solidus is barely influenced by the content of Ag in the solders. But the liquidus and melting range decrease evidently due to the increase of Ag content; When the content of Cu increase from 0.3wt% to 0.7wt%, the liquidus of the solders decrease from 228.05° down to 225.77°C. When the content of Cu increases to 1.0wt%, the liquidus increases to 226.66°C; The addition of Bi significantly decreases both solidus and liquids of the low-Ag SAC solders. Compare with liquidus, the influence of Bi on solidus is more effective. As a result, when the content of Bi increased from 2.0wt% to 4.0wt%, the melting range of the solders increased from 16.7° to 20.94°C.