Development and Characterization of Sn-Zn-Bi Lead Free Solder

Sn-Zn based lead free solder is a promising candidate to replace the Sn-Pb eutectic solder due to its low cost and melting temperature (198 A degrees C) near to the Sn-Pb eutectic solder (183 A degrees C). So far eutectic or near eutectic Sn-Pb alloys have been used as solder material but due to harmful effect on environment and human health Pb has to be eliminated from solder and prevent our environment from being polluted. Here the near eutectic composition of Sn-8 wt% Zn has been chosen. Apart from Sn-8 wt% Zn four different alloys containing different wt% of Bi were considered. They are Sn-8Zn-3Bi, Sn-8Zn-6Bi, Sn-8Zn-8Bi and Sn-8Zn-10Bi. The results of the differential scanning colorimetry (DSC) analysis show that addition of Bi to the near eutectic composition of Sn-8 wt% Zn lowers the melting temperature. The microstructure of the alloys were investigated using a scanning electron microscope and energy dispersive x-ray spectroscopy analysis. Tensile test shows that both tensile strength and elongation of the alloys reduce on addition of high wt% Bi to the Sn-8Zn solder alloy.