Wetting Dynamics Study of Sn-Ag Solder during Reflow

At present, solder joints are widely used to bond chips to their substrates for electronic connection and packaging. Good wettability is an essential requirement to form electronic interconnects. In this paper, an image acquisition system was used to observe time-dependent contact angle variation of 96.5Sn-3.5Ag lead-free BGA solder ball on Cu substrate. The wetting dynamics of the solder materials were investigated on Cu substrate, with two flux systems, at different heating temperatures. The results showed that an increase in temperature accelerated the wetting rate of solder significantly. The kind of flux had a large effect on the dynamics of solder wetting. The Suk's model was discussed to validate the experiment results