Size effect on thermal transport performance of inserted Cu/Cu₃Sn bilayer

Cu-Sn bonding is widely used in integrated circuits packaging due to the excellent stability and electrical performance, whose thermal transport mechanism is essential to be understood. Here, the size effect on thermal transport performance of Cu/Cu₃Sn bilayer inserted between the diamond/carbon nanotube interface was comprehensively investigated. The thermal conductivities of phonon component and electron component were studied by non-equilibrium molecular dynamics simulation and thermal-electrical analogy, respectively. The thermal-electrical analogy was verified to be a promising way to predict the size effect of electron thermal conductivity. In view of interfacial thermal resistance (R_K) is determined by phonon-phonon resistance, electron-phonon resistance, and electron-interface resistance, these three components were researched separately. At atomic level, the phenomenon of cross-layer effect and structural disorder were elaborated to reveal the mechanism of phonon heat transfer. The electron effects on R_K were also well incorporated, to make our prediction approaching to real-world metal-dielectric interfacial heat transfer. Based on the above results, the total thermal resistance of the inserted Cu/Cu₃Sn bilayer was calculated in the last section, revealing the dominant role of R_K in micro/nano scale bonding. This work provides a comprehensive understanding of the thermal transport performance of multilayer metal bonding.