Effect of thermal contact heat transfer on solidification of Pb–Sn and Pb-free solders

The effect of thermal contact heat transfer on the solidification of spherical droplets of four solder alloys, namely, Sn–37Pb, Sn–9Zn, Sn–0.7Cu and Sn–3.5Ag, was studied using SOLIDCAST simulation package. A significant drop in the arrest time was observed for increase in heat transfer coefficient from 1000 to 2000 W/m2 K. Effect of contact conductance and thermal diffusivity of solder alloys on arrest time is quantified by the power relation, β = m(ϕ)n where β and ϕ are defined as arrest time and heat transfer parameters, respectively. Experiments were also carried out to investigate the effect of cooling rate on solidification behaviour of the solder alloys used in simulation. The results indicated the significant effect of mould material on interfacial heat flux and metallurgical microstructure.