<p>Stricter specifications have been set on the characteristics of Sn-Zn-Cu-Ni lead-free solders due to the advancement of microelectronic packaging and the growing need for solder joints to have specialized service environments. Therefore, nanoparticles have been widely used to enhance the properties of such solders. This study aimed to investigate the effect of TiO₂ and ZrO₂ nanoparticles on characterizations for Sn-6.5Zn-0.5Cu-0.2Ni lead-free solder. Thermal properties such as the melting temperature, solidus, and liquidus temperatures, as well as the pasty range and heat of fusion of Sn-Zn-Cu-Ni, Sn-Zn-Cu-Ni-TiO₂, and Sn-Zn-Cu-Ni-ZrO₂ solders, were investigated by the Differential Temperature Analysis (DTA) technique. Also, the electrical resistivity, electrical conductivity, thermal conductivity, and the temperature coefficient of resistance were measured at different testing temperatures. From microstructure analysis, the lattice parameters, unit cell volume, and crystal size of the β-Sn matrix are improved by adding TiO₂ or ZrO₂ nanoparticles. Also, the grain size of the β-Sn is decreased with a&#xa0;uniform distribution of intermetallic compounds upon adding TiO₂ or ZrO₂ nanoparticles. The internal friction, thermal diffusivity, and Young’s modulus were enhanced with the addition of TiO₂ or ZrO₂ nanoparticles, and the best effect is for ZrO₂ nanoparticles.</p>