Effect of Sb and In additives on thermal and electrical properties of Sn–9Zn–4Bi alternative lead-free solder alloy

Due to the threats of lead to human and environmental health with Tin (Sn)- lead (Pb) solder alloys, efforts to develop lead-free solders continue. To adapt to different soldering areas, especially electronics, the search for alloys that can replace Sn–Pb has increased. The better the solders are in terms of thermal and electrical properties at the junctions, the better the performance of the circuit. In this study, changes in thermal conductivity, electrical conductivity, and melting behavior of 0.5–2 mass percent (wt.%) antimony (Sb) and 0.5–1.5 mass percent (wt.%) indium (In) addition to Sn–9Zn–4Bi alloy were investigated. Measurements of thermal and electrical conductivity with temperature were made by linear heat flow and four-point probe methods, respectively. The melting temperatures (peak temperature) of the alloys produced vary between 477.70 and 484 K (K). When the transition temperature, which is important in solders, is compared to Sn–9Zn–4Bi-[x]Sb (x = 0.5–2 wt%) and Sn–9Zn–4Bi-yIn (y = 0.5–1.5 wt%) alloys, it is the alloy with the lowest value with 13.80 K and the addition of 1 wt% Sb. The thermal and electrical conductivity values increased with the contribution of Sb and In. In addition, temperature coefficients for thermal and electrical conductivity were calculated. Electron and phonon contributions to the thermal conductivity were determined from the Wiedemann-Franz law. It was determined that electron contribution was higher for each alloy.