A Comparative Study of the Sn-Ag, Sn-Zn, Sn-Cu, Sn-Bi Lead Free Solder Alloys with the Commercially Available Sn-Pb Solder Alloy

Abstract

As soldering controls the effective usage and processing of electronic components in applications and devices. Solders are used as interconnect materials in microelectronic packaging. Traditionally Pb-Sn eutectic alloys have been used due to its low melting point and good wettability. However, due to the toxic nature of lead (Pb) and it harmful effect on environment and health the usage of Pb in solder should be avoided. This is why there is a need to develop environmentally benign Pb-free solders (LFS).In this research work four different lead free solder alloys, Sn-Cu, Sn-Ag , Sn-Bi , Sn-Zn, and Sn-Pb are developed and characterized. Eutectic Sn-0.7 wt. % Cu, Sn-3.5 wt. % Ag, Sn-57 wt. % Bi, Sn-8.8 wt. % Zn and Sn-37 wt % Pb solder alloys have been developed by melting and casting route. A comparative study of all the five alloys was done based on their microstructure and various properties like electrical resistivity, hardness, fractography and wettability on Cu substrate. Their microstructure of the alloys was analyzed using optical microscopy and scanning electron microscopy (SEM). The various phases in the alloys were analyzed using energy dispersive x-ray spectroscopy (EDS) attached to the SEM. The nature of fracture in the alloys was analyzed using SEM. The melting point of the alloys was determined using differential scanning calorimeter (DSC). Hardness of the alloys was determined using a Vicker‟s microhard ness tester. The wettability of the solder alloys on Cu substrate was analyzed using SEM. Electrical resistivity of all the alloys were determined using a four point electrical probe. The objective of this study is to find out the solder alloy among the four eutectic solder alloys chosen here which could replace the traditional Sn-Pb solder alloy.