Effects of TiO2 nanoparticles on mechanical and corrosion properties of Cu/SAC305–xTiO2/Cu solder joints: experiments and theoretical calculations

In this study, the shear strength and corrosion resistance of Cu/Sn–3.0Ag–0.5Cu–xTiO₂/Cu solder joints were systematically investigated to determine the mechanism by which various mass fractions of TiO₂ nanoparticle doping affect them. The experiment was designed with four sets of TiO₂ doping concentrations (x = 0, 0.3, 0.6, 0.9 wt%). The corrosion and mechanical properties of the soldered joints were characterized at various periods of corrosion. The joints were subjected to immersion corrosion testing in a 3.5 wt% NaCl solution for a maximum of 28 days. The experimental results indicate that the corrosion resistance of the soldered joints firstly increases and then decreases as the TiO₂ doping content increases. Under uncorroded conditions, the shear strength shows a monotonically increasing pattern. The shear strength of the solder joints containing 0.9 wt% TiO₂ decreased significantly more than that of the other groups after 28 days of corrosion. Based on first-principles calculations, the corrosion resistance of the solder joints can be enhanced by the formation of stable TiO₂–Sn interface chemical bonds, which have a binding energy of 2.04 eV, within the Sn matrix through the incorporation of TiO₂ nanoparticles. However, the agglomeration effect of TiO₂ nanoparticles results in a substantial decrease in the effective bonding area between the Sn substrate and TiO₂ nanoparticles when the doping concentration surpasses the critical threshold. Consequently, the corrosion protection performance is substantially diminished.