Effects of Sb on SnAgCu lead-free solder

This research work investigates the effect of 0.5 wt%, 1.0 wt% and 1.5 wt% Sb addition in 96.8 wt% Sn 2.5 wt% Ag 0.7 wt% Cu. Addition of Sb has shown significant effect on metallography, wettability (using ZnCl2 as flux), thermal properties as well as mechanical properties of the SnAgCu solder. The wettability test has been carried out using Cu as substrate by varying the solder temperature. A good wettability profile has been obtained at 280°C. Differential scanning calorimetry and thermogravimetric analysis have been performed on the solders to determine the melting temperature, melting behaviour and thermal stability of the solders. Results show that Sb addition has not reduced the melting temperature of SnAgCu. The solders show no significant weight loss after heating up to 300°C. Tensile and shear tests have been carried out on soldered copper substrates and all of the solders tested show a ductile fracture mode. The strength of the solder joint is actually a competition in between the ductility of the solder and also the percentage of voids formed in the joint.