A Computational Model of a Molten Solder Droplet Spreading on Orthogonal Pads

A dynamic model based on energy balance method for describing the solder profile evolution on orthogonal pads is proposed. This model combines the fluid mechanics and the surface physics and accounts for the inertial, viscous and gravitational forces, the interfacial tensions and the equilibrium contact angle of the spreading system. A corresponding computational scheme is developed without invoking the spherical cap assumption. In order to verify the model predictions, the high speed videography technique is used to capture the instantaneous solder profile. The results show that the model prediction is in good agreement with the experimental spreading process. The characteristic of this model is that it can predict not only the equilibrium shape of solder joint but also the instantaneous shape during the spreading process.