Interfacial microstructure, wettability and material properties of nickel (Ni) nanoparticle doped tin–bismuth–silver (Sn–Bi–Ag) solder on copper (Cu) substrate

Abstract

This paper investigates the influence of adding nickel (Ni) nanoparticles on the microstructure, wettability and material properties of Sn–35Bi–1Ag (wt%) based solders. Material properties such as elastic and shear moduli, stress/strain behavior and electrical resistivity of bulk composite solder were improved significantly in comparison to the corresponding properties of reference solder alloy. The elastic and shear moduli of composite solder increased about 16.8 and 19 % respectively, while the electrical resistivity at room temperature was improved from 23.7 to 25.1 μΩ cm. On the other hand, in solder joint on Cu substrate, an island-shaped Cu6Sn5 IMC layer was clearly observed at interface for the plain solder/substrate system. Further a prolong reaction, a very thin Cu3Sn IMC layer was also formed at the substrate surface. However, in the case of the composite solder/substrate system, a scallop-shaped ternary (Cu, Ni)–Sn IMC layer was observed to be adhered at the interface without formation of Cu3Sn IMC layer for the composite solder/substrate system. Moreover, the composite solder/substrate system hindered the growth behavior of IMC layer as well as refined the microstructure which can influence life-span of electronic devices. Additionally, the overall micro-hardness values of composite solder joints exhibited higher values as compare to the plain solder joints due to the second phase strengthening mechanism.