Effect of Ag content and the minor alloying element Fe on the electrical resistivity of Sn–Ag–Cu solder alloy

• The electrical resistivity of Sn–Ag–Cu solder is affected by the content of Fe and Ag.
• The electrical resistivity increases with decreasing the Ag content.
• Adding 0.1 wt.% Fe to the SAC105 solder reduces the electrical resistivity.
• Fe-added SAC105 solder exhibits comparable electrical performance to support mechanical performance.

In this paper, we investigated the electrical resistivity of the high-Ag-content Sn–3Ag–0.5Cu, the low-Ag-content Sn–1Ag–0.5Cu solder alloy, and the three quaternary solder alloys Sn–1Ag–0.5Cu–0.1Fe, Sn–1Ag–0.5Cu–0.3Fe, and Sn–1Ag–0.5Cu–0.5Fe. The electrical resistivity was characterized by the four-point probe technique. The results show that both the Ag content and the addition of Fe significantly affected the electrical resistivity. The electrical resistivity was found to increase with a reduction in the Ag content in the solder alloy. The electrical resistivity of Fe-modified Sn–1Ag–0.5Cu solder alloys decreased initially with the addition of 0.1 wt.% Fe, and then gradually increased with 0.3 wt.% and 0.5 wt.% Fe addition. Microstructural changes resulting from the content of Ag and the addition of Fe have been correlated to the electrical resistivity change.