Investigation on microstructures and properties of low Ag content lead-free solder alloy

The microstructure, the wettability and dissolution behavior of Sn0.8Ag0.5Cu2.0Bi0.05Ni (SACBN) and Sn3.0Ag0.5Cu (SAC305) lead-free solder alloys were comparatively investigated. The results show that the microstructure of SACBN solder alloy contains β-Sn and eutectic phase, and that the eutectic phase is made of β-Sn, well-ditributed needlelike Ag3Sn, granular (Cu, Ni)6Sn5 and minor granular Bi. The max wetting force of SACBN was higher, and the wetting time was shorter than SAC305 while the wetting angle is bigger and the spreading area is smaller under same temperature. The dissolution quantity of Cu substrate linearly increases with increasing immersion time in the two solder alloys. The dissolution rate of SACBN solder alloy is lower than SAC305 at 250°Cand 275°C, and is higher at 300°C.