Characterization and Comparison of Lead Free Eutectic Sn-Based Solder Alloys and the Effect of Addition of Ni in Eutectic Sn-0.7Cu Solder Alloy

Abstract

Until recently, lead-containing alloys were used widely in electronic and automotive industry. However, with the implementation of European union environmental directives, the use of such alloys has become prohibited. In this work we have studied various eutectic system like Sn-8.8 wt. % Zn, Sn-3.5 wt. % Ag and Sn-43 wt. % Bi and Sn-0.7 Cu to find best alternative of Sn-Pb solder alloy. Further we have studied the effect of Ni addition on the properties of Sn-0.7Cu solder alloy. The characterization of microstructure was done by optical as well as SEM. Energy Dispersive X- ray spectroscopy was done in order to find the various component present in the solder alloy. In order to find the melting point Differential scanning calorimetry was done. X- ray diffraction was done in order to find different phase present in solder alloy. It has been found that Sn-3.5 Ag eutectic solder alloy have highest melting point of 243.28 oC and lowest electrical resistivity of 1.91 µΩ-cm. Sn-43 Bi eutectic solder has lowest melting point of 141.60 oC and have highest electrical resistivity of 14.17 µΩ-cm. The lowest hardness was observed in the case of Sn-0.7 Cu eutectic solder alloy at 82.2 MPa whereas the highest hardness of 193.7 MPa was found in Sn-57Bi eutectic alloy. The results of the various solder alloys were also compared with the properties reported for the Sn-38.1 Pb eutectic solder alloy. The results suggest that Sn-Ag and Sn-Cu eutectic alloys are the best possible substitute for the Sn-Pb solder alloy as they have electrical resisitivities less than that of the Sn-Pb solder alloy although and their melting points are slightly higher than that of the commercial Sn-Pb solder alloy. Furthermore, the effect of Ni addition suggests that when the Ni concentration was increased the melting point and electrical resistivity increase and the hardness decreases. The results were observed to have positive effect of the Ni in enhancing the performance of the Sn-0.7Cu solder alloy.