Three-dimensional CFD simulation of the stencil printing performance of solder paste

The first step in the surface mount technology is the printing of the solder paste. The amount of solder placed on the cooper pad is important in guaranteeing an acceptable quality of soldering. Experimental works and studies for this process consume time and cost. There is a need for a cost-effective method to study this process. The simulation method has shown as a good alternative method for the solder paste printing process. Thus, this study presents a 3D computer simulation of stencil printing for the deposited volume prediction of solder paste. The volume of fluid (VOF) method integrated with the cross viscosity model was used for the numerical simulation. A widely used industry lead-free solder paste Sn/Ag/Cu (SAC305) of type 3 was utilized. The experimental and simulation results for filling volume of solder paste at different aperture sizes were compared. Results for different aperture sizes show a similar trend and agree well with the experimental results. This study was extended to investigate stencil printing at different squeegee speeds and aperture sizes. The squeegee speed of 35 mm/s provided the highest solder paste volume in the aperture with acceptable printing time.