Numerical simulation and multi objectives optimization of fillet height in reinforced SAC305 solder joints for ultrafine capacitor assemblies

Purpose This study aims to investigate the design configuration for a multi-objective optimum solder height of reinforced SAC305 solder joints in an ultrafine capacitor assembly. Design/methodology/approach A multiphase finite volume model was developed to simulate reflow soldering and determine the fillet height of reinforced SAC305 solder joints. Different solders – SAC305-x, SAC305-xNiO and SAC305-xTi – with varying nanoparticle weight percentages (x = 0, 0.01, 0.05, 0.10, 0.15 wt.%) were analyzed. The simulation results were validated via reflow experiments and high-resolution transmission electron microscope (HRTEM) imaging. Taguchi’s L20 Orthogonal Array (OA) and grey relational analysis were employed to optimize the fillet height. The optimal configuration was identified as SAC305 reinforced with 0.15 wt.% Ti nanoparticles. Findings A strong correlation was observed between HRTEM micrographs and simulated nanoparticle distributions. The predicted fillet height was in agreement with experiments, showing a maximum deviation of 5.43%. Ti nanoparticles, having the lowest density among the tested materials, exhibited the highest buoyancy effect in molten solder. Taguchi analysis revealed that nanoparticle material had a more significant influence than weight percentage on optimizing fillet height. The optimal configuration – SAC305 with 0.15 wt.% Ti – resulted in a 41.13% improvement over plain SAC305 solder. Practical implications The fillet height of solder joints significantly affects the reliability of ultrafine electronic packages. The findings provide guidance for optimizing solder design to improve long-term performance in capacitor assemblies. Originality/value This work provides a novel integration of multiphase finite volume method-discrete phase model modeling with experimental validation for optimizing solder fillet geometry, an underexplored reliability factor in miniaturized assemblies. Unlike prior studies focusing on mechanical or microstructural properties, this research emphasizes fillet height optimization using TiO2, NiO and Fe2O3 nanoparticles, offering valuable insights for advanced electronic packaging.