A compliant lead-free solder alloy

The effects of 0.5 wt.% Fe addition on the microstructural and mechanical properties of the Sn-1Ag-0.5Cu (SAC105) solder alloy were investigated. 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. The addition of Fe also leads to enlarge the primary β-Sn grains and diminish the eutectic regions. The formation of large FeSn₂ IMC particles together with the presence of large primary β-Sn grains leads to significantly lower elastic modulus and yield strength values for Fe-bearing SAC105 solder alloy. Moreover, the presence of large primary β-Sn grains causes the Fe-bearing solder alloy to maintain the total elongation at the level of SAC105 solder alloy. This effect can increase the bulk compliance and plastic energy dissipation ability of the solder joint, which play an important role in drop impact performance enhancement.