Enhancing the ductility and mechanical behavior of Sn-1.0Ag-0.5Cu lead-free solder by adding trace amount of elements Ni and Sb

Abstract

The present paper investigates the microstructural and mechanical properties of Sn-1.0Ag-0.5Cu (SAC105) solder alloy with 0.06 wt% Ni and 0.5 wt% Sb additions. The study revealed that the microstructure properties and elastic moduli of such solder alloy improved. Results indicated that Ni element diffused from the molten solder matrix into the IMC particles to form the Ni3Sn4 IMC phase during solidification. Thus, Ni improved the solder microstructure and increased the drop lifetime of the electronic assembly. Meanwhile, by adding Sb element, no new IMCs formed due to the high solubility of Sb in Sn, but provide solid solution strengthening. In terms of tensile behavior, the SAC105–0.5Sb exhibited the highest strength and largest ductility. As well, all examined alloys exhibited higher mechanical properties with increasing strain rate and/or decreasing testing temperature. Moreover, notable improvements of 31.25% and 101.1% in elongation were obtained with addition of Ni and Sb elements, respectively. Consequently, ductility was enhanced by Ni or Sb additions. Furthermore, the average activation energy (Q) for SAC105, SAC105-0.06Ni, and SAC105-0.5Sb solders were 49, 57 and 63.5 kJ/mol, respectively, which is close to that of pipe-diffusion mechanism in Sn-based solder matrix.