Numerical computation of wetting angles of Sn–(3−x)Ag–0.5Cu−x(Bi,In) quaternary Pb-free solder alloy systems on Cu substrate

This paper was aimed to study of the wetting angle (Θ) of Sn–Ag–Cu, Sn–(3−x)Ag–0.5Cu–(x)Bi and Sn–(3−x)Ag–0.5Cu–(x)In (x=0.5, 1 and 2 in wt.%) Pb-free solder alloy systems at various temperatures (250, 280 and 310∘C) on Cu substrate in Ar atmosphere. The new Sn–(3−x)Ag–0.5Cu–xBi and Sn–(3−x)Ag–0.5Cu−(x) In systems, low Ag content quaternary Pb-free solder alloys, were produced by adding 0.5%, 1% and 2% Bi and In separately to the near-eutectic Sn-3wt.%Ag–0.5wt.%Cu (SAC305) alloy. The wetting angles of new alloys, Sn−2.5wt.%Ag−0.5wt.%Cu−0.5wt.%Bi (SAC-0.5Bi), Sn−2wt.%Ag−0.5wt.%Cu−1wt.%Bi(SAC-1Bi), Sn−1wt.%Ag−0.5wt.%Cu−2wt.%Bi(SAC-2Bi), Sn−2.5wt.%Ag−0.5wt.%Cu−0.5wt.%In (SAC-0.5In), Sn−2wt.%Ag−0.5wt.%Cu−1wt.%In (SAC-1In) and Sn−1wt.%Ag−0.5wt%.Cu−2wt.%In (SAC-2In) were measured by sessile drop method. Experimental results showed that additions of Bi and In separately to SAC305 resulted in a continuous decrease in the Θ up to 1wt.% above which the Θ value was increased and it is appeared that a correlation among the Θ, alloys compositions and the test temperatures exists which recommended an empirical model to estimate the Θ at a given Bi and In content and temperature for a given alloy systems. The numerical model estimates the Θ understandably well with the present work.