Effects of copper powder size and content on tin penetration and joint porosity in soldering: a molecular dynamics and experimental study

HB Li and H Jiang and YJ Guan and J Shen, JOURNAL OF MATERIALS SCIENCE- MATERIALS IN ELECTRONICS, 36, 1250 (2025).

DOI: 10.1007/s10854-025-15322-9

Copper renowned for its exceptional electrical and thermal conductivity is widely regarded as an optimal material for electronic packaging applications and plays a crucial role in enhancing the performance of solder joints. However, it may also influence the porosity of the joints. Despite its significance, limited research has been conducted on the penetration of tin into copper and its effect on joint porosity. This study employs both molecular dynamics simulations and experimental techniques to examine the influence of copper powder particle size and content on joint porosity, optimizing these factors in terms of the tin- to-copper particle size ratio and the average spacing between copper particles. The results indicate that tin penetration into copper occurs in two distinct stages. During the initial stage, rapid penetration induces substantial flux volatilization, which subsequently reduces joint porosity as the copper particle size decreases. At 40% copper content and a particle size of 500 nm, the joint porosity is minimized at 36.98%. Furthermore, a critical copper content threshold of 20% by mass (with a particle spacing of 10 & Aring;) is identified, below which changes in porosity become negligible. Specifically, at 500-nm particle size and 20% copper content, the porosity is reduced to 4.06%. These findings provide valuable theoretical insights for managing solder joint porosity.

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