Analysis on wettability and dissolution behavior of low Ag SnAgCuBiNi lead-free solder alloys

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 composed of β-Sn, well-distributed 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 was bigger and the spreading area was smaller with 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℃ and 275℃, and is higher at 300℃.