Abstract
The correlations between grain structures and shear strength of 300μm SAC305/Cu and SAC305-0.1Ni/Cu solder joints before and after aging were explored in this study. The grain structure of SAC305 solder revealed to be beach ball-like grain, while SAC305-0.1Ni solder exhibited multiple grain with interlaced sections in both aging conditions. Ni spread in solder acted as nucleation sites for the IMC precipitates and thus affected the growth of β-tin. With the aid of XYZtec bonding test, no matter before or after aging, the higher peak force of Ni-doped solder joints was detected due to the inhibition of dislocation suggested by Hall-Petch and dispersion strengthening mechanism. Thus, it is demonstrated that the mechanical reliability of SAC305-0.1Ni/Cu solder joint is superior to that of SAC305/Cu solder joint regardless of aging conditions.