Phase Field Simulation of Solidification Behavior and Microstructure Evolution of Sn-58Bi/Cu Solder Interconnect During Reflow Soldering Process

Among the lead-free solders used in the electronic industry, Sn-Bi based alloys have been largely considered for low temperature soldering applications due to low melting-point feature and good wettability resulting from Bi addition which can reduce the surface tension of liquid solders and lower the reaction speed between Sn and Cu. In this paper, the phase field simulation method was adopted to study the solidification process of Sn-58Bi/Cu solder joint during reflow soldering, the focus was placed on characterizing the effect of the undercooling and interfacial anisotropy as well as the disturbation parameter on the dendritic morphology and solid phase volume fraction in the joint. The simulation results show that the disturbance mainly affect the growth of dendrite side arms while having no obvious influence on the main arm. Decreasing the interfacial anisotropy would reduce the growth rate of dendrites and result in smooth main arms with absence of side arms. It is also observed that the increase of undercooling would not only accelerate the growth rate of the dendrite, but also coarsen the dendrite arm.