Mechanical Bonding Properties of SAC-SB Mixed Solder Containing Sn-58Bi Eutectic Solder

In this study, a SAC-SB mixed solder was developed by incorporating Sn-58Bi (SB) eutectic solder to enhance the mechanical bonding properties of Sn-3Ag-0.5Cu (SAC) solder. To evaluate the mechanical bonding properties of SAC-SB mixed solder according to the addition of SB eutectic solder, two types of mixed solder with and without SB solder (mixing ratio between SAC and SB (vol%): 100:0 and 90:10) were prepared. Ball shear and microhardness tests were conducted to investigate the influence of the SB solder on the mechanical properties of SAC-SB mixed solder, and microstructure and fracture surface analyses were performed to elucidate the underlying mechanisms responsible for the observed changes in mechanical properties according to the addition of SB solder. The results revealed that the SAC-SB mixed solder containing SB solder exhibited a 71% increase in shear strength and an 81% increase in microhardness compared to that of SAC-SB mixed solder without SB solder. These improvements were attributed to the precipitation hardening and dispersion strengthening effects induced by the fine Bi phase and Ag3Sn, Cu?Sn? intermetallic compound (IMC) particles precipitated within the SAC-SB mixed solder joint.