Wettabilities of Cu Nanoparticle Reinforced Sn-Pb Matrix Composite Solders

This paper summarizes a study of nanoparticle reinforced composite solder pastes’ spreading over Cu substrates. The nano reinforcements included Cu and non-Cu particles. Solder matrix were lead and lead-free systems (including binder and flux). This report focuses in particular on Cu reinforced Sn-Pb materials and indicates some differences vs. lead free systems. Wettability of the composite over Cu substrates was investigated using a real-time in-situ visualization of the triple line movement as well as the equilibrium contact angle measurements. It was established that the addition of Cu nanoparticles hampers spreading of the eutectic Sn-Pb solder paste during its melting. The melting temperature of a nano composite is suppressed with an increase of nanoparticle content, but does not significantly change the spreading time, the final spread domain and the equilibrium contact angle, if the content of nano particle is less than 2.5 %. Further increase of nano-particle content up to 5% indicates a decrease in the final spreading domain and increase in the equilibrium contact angle.