Publication: Thermal fluid-structure interaction study on copper pillar solder bump during reflow soldering process
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Date
2023-07
Authors
Chong, Mun Xi
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Abstract
There are numerous interconnect technologies in the field of electronic packaging which help to enhance the reliability of the interconnection of the package. Copper pillar bump is a new interconnect technology introduced in the flip chip industry. The goal of this study was to investigate the effects of different copper pillar bump heights and soldering materials on temperature distributions, total deformation, and von-Mises stress during reflow soldering process. The reflow oven environment was simulated using the fluid domain of the oven model. A grid independence test was carried out on the fluid mesh to determine the optimal mesh model for the simulations. In addition, a reflow experiment was conducted based on the JEDEC Standard to verify the accuracy of the fluid analysis by comparing the obtained results with experimental data. A thermal fluid-structure interaction (FSI) approach was employed to couple the thermal results from the fluid analysis with the solid assembly for structural analysis. The five different copper pillar heights (0.07mm, 0.09mm, 0.11mm, 0.13mm, and 0.15mm) were simulated through FSI approach in ANSYS. The results of the coupling analysis revealed that copper pillar bumps with a height of 0.09 mm exhibited the lowest reflow temperature, minimal maximum total deformation, and von-Mises stress, indicating that it is the most potential height for forming a good interconnection. The study also examined the effects of three different soldering materials (SAC305, SAC405, and SnBi) on the copper pillar bump. The results show that there is no significant difference in the deformation and von-Mises stress behaviours of the copper pillar bumps between the soldering materials. The study also suggested SnBi solder material as a better solder material in terms of costing and technical performance. Overall, this study enables a comprehensive analysis of the thermal and mechanical performances of different copper pillar bump parameters during the reflow process.