Microhardness and shear performance of Fe/Bi-bearing SAC105 solder alloys under high temperature aging

In this study, the microhardness and shear performance of the new Fe/Bi-bearing Sn–1Ag–0.5Cu (SAC105) solder alloys has been extensively studied under high temperature aging at 200 °C for 100, 200 and 300 h. Vickers hardness tests were done using a load of 245.2 mN and 10 s load dwell time. Hardness was increased from 10.5 to 22.6 HV with the addition of Fe/Bi to SAC105, increasing by over 100 %. Shear tests were carried out using a shear speed of 0.25 mm/min. Shear strength increased from 17.8 to 34.3 MPa with the addition of Fe/Bi to SAC105, increasing by about 100 %. Microstructure study revealed that Bi refines the IMCs particles (Ag3Sn and Cu6Sn5) as well as the β-Sn grains and strengthens the alloy by its solid solution strengthening mechanism. These modifications in the microstructure improve the hardness and shear strength of the Fe/Bi added SAC105 solder alloy. Under high temperature aging, the microstructure of Fe/Bi added SAC105 solders remained more stable than the base alloy SAC105, due to the presence of both Fe and Bi in the alloy, which contributed to the stability in their mechanical properties, like hardness and shear strength, during aging.