Computer-aided Design of Multimodal Non-spherical Cu Pastes and Their Low-temperature Sintering Behaviors

doi:10.3901/JME.260119

Abstract

Abstract: Low-temperature Cu sinter-joining technology, with excellent thermodynamic stability and packaging reliability, is regarded as one of the core potential technologies for high-reliability and heat-resistant interconnections in wide-bandgap semiconductor devices. However, the porous structure of sintered-joints reduces its electrical and thermal conductivity due to porosity issues, restricting the improvement of joints performance. Compared with unimodal Cu particle pastes, multimodal Cu particle pastes can significantly improve the density of joints, but they face challenges in terms of development efficiency and ratio optimization. How to quickly determine the optimal ratio of multimodal particles to achieve maximum packing density and reduce the porosity of joints has become the key to promoting the practical application of this technology. For this purpose, a random packing algorithm for multimodal particles was designed based on the Monte Carlo model, which is used to simulate the packing process of spherical and non-spherical (elliptical flakes) particles of different sizes and calculate the packing density, in order to obtain the optimal particle ratio at a specific size. The results show that the random packing density of the unimodal sphere is stable at around 0.61; for the bimodal spheres system, under fixed conditions, the larger the particle size difference, the higher the packing density, and within a specific range, the peak of packing density always appears when the proportion of small particles is 30%; for the mixed system of spheres and elliptical flakes with specific sizes, the packing density reaches the optimal when the proportion of spheres is 70%~80%. The relevant sintering experiments further verified the practicality and reliability of the algorithm, providing support for assisting in the design of multimodal non-spherical Cu particle pastes, accelerating the development of high-performance pastes, and facilitating the breakthrough of multimodal Cu pastes technology.

Key words: Cu sinter-joining technology, computer-aided design, Monte Carlo model, random packing, non-spherical particle

CLC Number:

TG425

ZHU Zhihong, MIU Junwei, WANG Yujian, LI Wanli. Computer-aided Design of Multimodal Non-spherical Cu Pastes and Their Low-temperature Sintering Behaviors[J]. Journal of Mechanical Engineering, 2026, 62(4): 215-223.

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