The Simulation of Shape Evolution of Solder Joints during Reflow Process and Its Experimental Validation

A three-dimensional computer aided analysis system has been developed in this study based on fluid dynamics to simulate the shape evolution of solder joints during the reflow process. The solution of velocity and pressure fields is based on SOLA (SOLution Algorithm) scheme, and the method to construct the interface and the transportation of volume fractions of liquid in the cells are coupled with PLIC (Piecewise Linear Interface Calculation) and VOF (Volume of Fluid) technologies. In order to consider the effect of surface tension on a fluid surface, the CSF (Continuum Surface Force) model is employed. The simulated results are compared with experimental measurements and good consistency is observed. Furthermore, the simulated results can reveal the evolution of the molten solder from its initial state to the equilibrium state. It is also capable of analyzing the overflow conditions when the amount of solder deposit is too much to be constrained in the solder pad, which is not achievable by the energy-based technique such as Surface Evolver.