Numerical analysis of the formation of coined solder bumps

In this study, two solder materials, Sn-37Pb and Sn-3.5Ag, were tested and numerically analyzed for the solder bumps coining process. This process has an object that equal coined height could be achieved and the flatness of the coined surface should be guaranteed. Before the coining process, the original solder bumps height is about 85 μm. The final desired coined height is around 25 μm. To get the desired coined height, we must study the effects of process variables such as process time (coining rate) and temperature. Two solder materials were developed to form the area-array type solder bumps and were tested under 4 coining rates and 4 process temperatures. To get the basis for optimal experiments, we performed numerical analyses considering the rate and temperature dependent material behaviors. These important factors of the coining process could be applied by adopting the published references. From the results of numerical analysis and experiment, as the process temperature increased, coining load was reduced. And as the coining rate increased, higher coining load was required. But the effect of coining rate is less than that of temperature variation