<p>In this work, low-temperature Sn-57.6wt%Bi-0.4wt%Ag (Sn-Bi-Ag) solder alloy was enhanced with SnO₂ nanoparticles (NPs, 0 to 0.7wt%) using low energy milling and melting process. The developed solders were reflowed to join Cu/Ni pad of 1608 mini-light emitting diode (LED) chips at 238&#xa0;°C. The morphology, melting temperature, thermal conductivity, and electrical properties of the developed alloys were evaluated. The findings revealed a depression in melting point of Sn-Bi-Ag/SnO₂ solder by 1.1&#xa0;°C compared to the pristine Sn-Bi-Ag alloy. Microstructural analysis indicated a refinement in the β-Sn and Bi-rich phase in Sn-Bi-Ag alloy after the addition of SnO₂ NPs (≈0.5wt%), accompanied by a decrease in β-Sn area fraction (0.49) with a mild increase in Bi-rich area (0.46). Additionally, the thermal diffusivity and conductivity were significantly enhanced, with the values of 13.2 mm²/s and 14.2&#xa0;J/K/g all of which outperformed the Sn -Bi -Ag alloy. The electrical resistivity of the developed samples was in the range of 5.0 × 10^–7 to 3 × 10^–7 Ω.cm. To further assess solder joint reliability, the SnO₂ NPs-modified solder was applied to a 1608 mini-LED chip and bonded onto the Cu/Ni pad of a fiber glass reinforced printed circuit board (FR4-PCB). The solder joint characteristics was evaluated by shear strength tests by examining the post fractured joint morphology of the specimens. The shear tests showed an increasing trend with the fraction of SnO₂ NPs in the Sn-Bi-Ag matrix. The shear strength was improved by ≈10–11%, respectively, over Sn-Bi-Ag alloy. The fracture morphology revealed a mixed ductile and brittle fracture at 0.5wt.%SnO₂ NPs in the matrix while brittle fracture dominates at a higher fraction of SnO₂ NPs (0.7wt.%) is added to the matrix alloy. It is inferred from this investigation that an optimum amount of 0.5wt.% is desired for realizing high thermal conductivity, low-melting, and reliable solder joints in future microelectronics mini-LED packaging.</p>