Reactive wetting and dewetting of liquid SnPb solder on the butterfly pattern

The sputter-deposited Cu thin film, coated with a thinner gold layer, was prepared into the butterfly pattern with alternating zones beween Cu thin film and Si. The eutectic SnPb solder balls with different sizes were reflowed on the butterfly pattern. As a result, the liquid solder would be selectively retained on the Au/Cu film zones. At the same time, under the energy minimization control, the liquid solder would dewet from the unwettable Si zones. Especially, for a fixed size pattern, the different reactive wetting and dewetting behavior would happen with the solder ball size changing.