Stress−strain analysis and morphological parameter optimization of CSP solder joints under coupled tensile and shear loading

Purpose This paper aims to construct a quantitative model using response surface methodology and optimize the structural parameters of Chip Scale Package (CSP) solder joints through genetic algorithms. This approach enhances the reliability of CSP solder joints under coupled tensile and shear loading, thereby improving the overall reliability of electronic products. Design/methodology/approach A finite element model for CSP solder joints was established using ANSYS software. Stress−strain finite element analysis was performed under coupled tensile and shear loading conditions. The resulting stress and strain distribution within the solder joints under this coupled loading was obtained. An experimental platform was constructed, and stress measurement experiments on CSP solder joints under coupled tensile and shear loading were conducted, thereby validating the accuracy of the simulation results. Taking solder joint diameter, solder joint height, pad diameter and pad thickness as design parameters, and the coupled tensile-shear stress value in the CSP solder joint as the objective, 27 sets of parameter level combinations were designed using the Response Surface Methodology. Corresponding finite element models for these 27 sets were established and subjected to simulation analysis under coupled tensile and shear loading. The relationship between the 27 sets of coupled stress values and the CSP solder joint morphological parameters was fitted using the response surface method, establishing a quantitative relationship equation. This equation was then subjected to optimization analysis using a genetic algorithm. Findings The results indicate that the location of maximum stress and strain is at the interface between the solder joint and the lower pad, which is identified as a potential failure site. The theoretically optimal combination of morphological parameters for the CSP solder joint, obtained via the genetic algorithm, is as follows: solder joint diameter of 0.3180 mm, solder joint height of 0.2302 mm, pad diameter of 0.2286 mm and pad thickness of 0.0168 mm. Simulation verification of this optimal parameter set demonstrated that the coupled tensile and shear stress value under the optimal combination is superior to those obtained from the 27 simulation experiments. This successfully achieves the morphological parameter optimization of CSP solder joints under coupled tensile and shear loading. Originality/value The relationship between the 27 sets of coupled stress values and the CSP solder joint morphological parameters was fitted using the response surface method, establishing a quantitative relationship equation. This equation was then subjected to optimization analysis using a genetic algorithm.