Effect of Ni-CNTs on microstructure, thermodynamic characteristic and mechanical properties of Sn58Bi-0.1Er based lead-free solder

Sn-Bi solder alloys have been widely used in electronic devices due to its low melting point, low thermal expansion coefficient and good mechanical properties. However, due to the brittleness of Bi element in SnBi solder, Bi phase is easy to be vulgar at high temperature, which leads to poor plasticity and ductility of solder joint, which affects the reliability of solder joint in high temperature service. The results show that the wettability, tensile strength and ductility of Sn58Bi solder can be improved when the content of Er is 0.1%. In this paper, Sn58Bi-0.1Er was used as the base metal, and the effects of Ni-CNTs particle reinforced phase on the melting characteristics, mechanical properties, microstructure and composition of the solder were discussed. The results of XRD shows that with the addition of Ni-CNTs, Ni element reacts with Sn to form Ni3Sn4 intermetallic compound, while carbon nanotubes still exist in the form of carbon element. The increase of Ni-CNTs particles can reduce the dendrite structure and refine the microstructure of the composite solder. The addition of Ni-CNTs increased the melting temperature of the composite solder. The tensile test results shows that with the increase of Ni-CNTs particles, the tensile strength and elongation of the composite solder increase first and then decrease. When the content of Ni-CNTs particles is 0.03%, the elongation of composite solder is 82.06%, which is 43% higher than that of Sn58Bi-0.1Er.