Crystallographic, microstructure, electrical, and hardness characterization of advanced Sn-9Zn-0.5ZrO2 and Sn-9Zn-xNi lead-free solder alloys

Abstract The eutectic Sn-9Zn solder alloys reinforced with ZrO 2 nanoparticles, or Ni synthesized by the vacuum melting process. The crystal structure and morphology features revealed that adding ZrO 2 to Sn-9Zn reduced unit cell volume of β-Sn with a contraction in lattice parameters, which refined the crystallite size and reduced β-Sn grain size. But Ni additions do not affect the cell symmetry whereas the crystallite size and grain size were refined due to formation of Ni 5 Zn 21 and Sn 3 Ni 4 Zn 3 IMCs with homogenous distribution. The electrical resistivity (ρ) and thermal conductivity was determined in relation to alloy composition at different temperatures. The temperature coefficient of resistivity (α) for Sn-9Zn was around 4.19 × 10 –4 K −1 lower than the traditional Sn–Pb solders and reaching 2.35 × 10 –4 K −1 for Sn-9Zn-0.3Ni, which indicated that the resistivity for Sn-9Zn is less temperature-sensitive. The hardness for Sn-9Zn was enhanced with incorporating of ZrO 2 or Ni elements. The results obtained for the stress exponent suggesting dispersion with strengthening mechanisms.