Effects of Bi content on thermal, microstructure and mechanical properties of Sn-Bi-In-Zn solder alloy systems

In the present study, various amounts of Bi were added to two groups of Sn-In-Zn lead-free solder alloy systems (Sn-[x] Bi-2In-9Zn (x = 4,14,24) and Sn-[x]Bi-5In-9Zn (x = 1,6,10) to investigate the Bi effect on microstructural, mechanical and thermal properties to obtain optimal lead-free alternative solder alloy system. In order to observe microstructure of the systems and to determine the composition of the phases in the structures, Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis were used, respectively. Melting temperatures, the enthalpy of fusion and the specific heat exchange between liquid and solid phases were determined by Differential Scanning Calorimetry. The results showed that increasing amount of Bi, decreased the melting temperature. Additionally, tensile strength and microhardness measurements were performed and it was seen that, microhardness and tensile strength values increased with increasing Bi amount.