Effect of Cu addition on wettability and mechanical properties of Sn-58Bi lead-free solder

摘要

In this study, Cu nanoparticles were dispersed into Sn-58Bi solder paste to prepare Sn-58Bi-xCu solders in order to inhibit the disadvantages of undesirable Bi segregation and microstructure coarsening of Sn-58Bi solder in electronic industry. The content of Cu ranged from 0 to 2.0wt.% in the solders. The effects of Cu nanoparticles on microstructure, hardness and ball shear strength of Sn-Bi lead-free solder were investigated. The results indicated that small amount of Cu addition in Sn-58Bi solder enhanced not only the shear strength but also to some extent the hardness of the composite solder, which may be attributed to the uniform distribution of the formed Cu_6Sn_5 IMCs and the refined microstructure of composite solder. However, further increase of Cu additions decreased the shear strength, which may be attribute to the relatively more primary β-Sn grains, the gathered Cu_6Sn_5 IMCs and the coarse eutectic structure. The Cu nanoparticles addition of 1.0% in Sn-58Bi is the optimal addition ratio to get well dispersed microstructure.