Numerical Simulation of Reflow Soldering

Abstract

To guarantee a high level of solder joint durability for soft solder die attach, a uniform bond line thickness is crucial. In addition, for high electrical performance, a low void concentration is desirable. However, these goals are difficult to achieve during reflow soldering. The die tilt and the formation of voids are mainly controlled by fluid forces. We develop a fluid dynamical model to better understand these mechanisms. The model is validated using experimental data. In order to use the model for design improvement, the simulation model is coupled with a genetic optimization algorithm. This arrangement can help to develop designs which lead to (a) uniform bond line thickness and (b) minimal void concentration. Furthermore, advanced search strategies act as an enabler for the generation of innovative design features. They may in turn foster the formulation of new intellectual property. To illustrate the spectrum of possible application scenarios, we show three industrial use cases.