Microstructure, mechanical, and thermal properties of the Sn-1Ag-0.5Cu solder alloy bearing Fe for electronics applications

This work investigates the effect of Fe addition on the microstructural, mechanical, and thermal properties of the Sn-1Ag-0.5Cu (SAC105) solder alloy. The addition of Fe leads to the formation of large circular FeSn2 intermetallic compound (IMC) particles, which produce a weak interface with the β-Sn matrix. The addition of Fe also leads to the inclusion of Fe in the Ag3Sn and Cu6Sn5 IMC particles. Moreover, Fe-bearing solders have been shown to form large primary β-Sn grains. The weak interface between the large FeSn2 IMC particles and the β-Sn matrix together with the presence of the large primary β-Sn grains results in a significant reduction on the elastic modulus and yield strength of the Fe-bearing solders. Moreover, the improved plasticity of the large primary β-Sn grains causes the Fe-bearing solders to exhibit large total elongation. The addition of Fe also significantly reduces the effect of aging. After aging at 100 °C and 180 °C, it has been observed that the Fe-bearing solders significantly suppress the coarsening of the Ag3Sn IMC particles; consequently, they exhibit stable mechanical properties. This effect can be attributed to the inclusion of Fe in the Ag3Sn IMC particles. In addition, fracture surface analysis indicates that the addition of Fe to the SAC105 solder alloy does not affect the mode of fracture, and all tested solders exhibited large ductile-dimples on the fracture surface. Moreover, 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.