Novel Fe-containing Sn–1Ag–0.5Cu lead-free solder alloy with further enhanced elastic compliance and plastic energy dissipation ability for mobile products

This work investigates the effects of small additions (0.1 and 0.3 wt.%) of Fe on the microstructure, mechanical, and thermal properties of the Sn–1Ag–0.5Cu (SAC105) solder alloy. The addition of Fe leads to the formation of large FeSn2 intermetallic compound (IMC) particles located in the eutectic regions besides the small Ag3Sn and Cu6Sn5 IMC particles. Fe-bearing solders have also been shown to form large primary β-Sn grains. The formation of large FeSn2 IMC particles, together with the presence of large primary β-Sn grains have resulted in a significant reduction on the elastic modulus and yield strength. Moreover, the presence of large primary β-Sn grains causes the Fe-bearing solders to maintain the total elongation at the SAC105 level. This effect can increase the elastic compliance and plastic energy dissipation ability of the bulk solder, which play an important role in drop impact performance enhancement. The addition of Fe did not produce any significant effect on the melting behavior. As a result, the use conditions of the Fe-bearing solders are consistent with the conditions for conventional Sn–Ag–Cu solder alloys.

► This work investigates the effect of Fe addition on the SAC105 bulk solder.
► The addition of Fe leads to the formation of large FeSn2 IMC particles.
► The addition of Fe also leads to the formation of large primary β-Sn grains.
► This effect leads to significantly reduce the elastic modulus and yield strength.
► The presence of large β-Sn grains maintains the total elongation at the SAC105 level.