Microstructure refinement, thermodynamic characteristic, wettability and shear strength of Bi-added rapid solidification SAC305 solder.

SAC305-XBi (X = 0, 2) solder ribbons were prepared by two-roll rapid solidification technology. The microstructure, phase composition, melting characteristics, wettability and Cu/Solder/Cu joint interface microstructure, shear strength, and fracture morphology of the solder were investigated in this work. The experimental results show that the addition of 2.0 wt% Bi to the rapidly solidified SAC305 solder, the β-Sn were fine equiaxed crystal and the (Ag₃Sn + Cu₆Sn₅) intermetallic compounds were uniformly distributed as tiny granules on the β-Sn matrix. The microstructure was refined and the compositions were evenly distributed. Rapid solidification increases the limit of Bi solid solution. The addition of Bi reduced critical nucleation radius, critical nucleation energy, and the nucleation undercooling of structure, which promoted nucleation. Ultimately, compared to the rapidly solidified SAC305 solder, the melting temperature was lower, the spreading areas enhanced about 40.0%, and the wettability was improved. The thickness of the IMC layer of the joint interface decreased approximately 21.6%, and the shear strength increased. [ABSTRACT FROM AUTHOR]