Optimization modeling of the cooling stage of reflow soldering process for ball grid array package using the gray-based Taguchi method

The current paper introduces an effective numerical technique for optimization of the cooling stage of reflow soldering process. The study aims to optimize the thermal stress of a solder joint and cooling rate of a ball grid array package using the gray-based Taguchi method. The current methodology comprised numerical techniques for computational fluid modeling of the internal flow in the reflow oven coupled with the structural heat modeling at the board and package levels. The Multi-physics Code Coupling Interface (MpCCI) was used as the coupling software. Various parameters, such as printed circuit board density, cooling temperature, inlet velocity, and conveyor speed, were considered. Nine simulated experiment runs based on Taguchi L9 orthogonal arrays were performed. The optimal parameter settings for multiple performance characteristics were determined and compared with the single performance characteristic. From the analysis of variance (ANOVA) result, the most influential factor for the multiple performance characteristics was found to be the inlet velocity. Simulated experiment results showed that the performance characteristics during the cooling stage in the reflow oven obviously improved. The new approach greatly helps in reducing soldering defects and enhances solutions to lead-free reliability issues.