Effect of alloying elements on microstructural and electrical property in Sn–Cu–Bi lead-free solder alloys

Abstract

Sn–0.7Cu eutectic alloy is a low-cost alloy with moderate melting point and wetting that appears to be adequate for some applications. Lead-free Sn–0.7Cu joint solders on copper substrate were investigated in this study. To enhance the performance of the alloy, many previous studies verified the importance of adding bismuth to the eutectic alloy. (84.3Sn–0.7Cu–15Bi) ternary alloy is regarded as a potential substitute for hazardous Sn–Pb solders, possessing a melting point of 206 °C. The effects of incorporating selenium, zinc, or indium on the electrical characteristics, crystal structure and microstructure of the tin copper-bismuth alloy were examined. Phase identification of the base solder and various newly developed alloys was performed by X-ray diffraction tests and an LCR meter was used to measure the electrical resistance of the prepared samples. The unit cell volume, and lattice parameters of the tetragonal Sn base were altered, along with the electrical characteristics of the base solder alloy. According to the test results, the best addition was by indium since it reduced the grain size of the base solder alloy. Smaller grain size improves the mechanical properties of the solder. Furthermore, indium addition increased the electrical conductivity of the base solder alloy compared to other alloying additions.