Effect of the $$\text {TiO}_2$$ Nanoparticles on the Growth Behavior of Intermetallics in Sn/Cu Solder Joints

In order to investigate the effect of \(\text {TiO}_{2}\) nanoparticles on growth behavior of interfacial \(\text {Cu}_6\text {Sn}_5\) intermetallics compounds (IMCs) in Pb-free Sn/Cu system, the solder joints are fabricated by using flux doped with different content (0.0–2.0 wt% of flux) and particle diameter (5 nm and 50 nm) of \(\text {TiO}_{2}\). In context of isothermal reflow soldering at 250 °C and subsequent air cooling, the increase in reflow duration from 10 to 120 s was characterized with an increment in IMC layer thickness and grain size, due to the enhancement of Cu flux contribution for Ostwald ripening during constant temperature reflow and precipitation kinetics during cooling. The increased proportion of \(\text {TiO}_{2}\) nanoparticles in flux was found to reduce the growth of IMC layer and grain size. The suppression effect on IMC was more pronounced for 5 nm particles as compared to the 50 nm \(\text {TiO}_{2}\). The \(\text {TiO}_{2}\) nanoparticles, adsorbed on IMC plane can retard the growth of the latter. Presence of sufficient amount of a given sized \(\text {TiO}_{2}\) nanoparticles among IMCs, by increasing the effective stress at the localized interfaces, and causing the breaking of brittle \(\text {Cu}_6\text {Sn}_5\) during growth stage; can help in the inhibition of IMC whisker formation. Particle diameter and mass proportion of \(\text {TiO}_{2}\) nanoparticles are important for soldering materials design.