Solid-state bonding behavior between surface-nanostructured Cu and Au: a molecular dynamics simulation

In recent years, solid-state bonding has attracted attention for various electronic packaging applications as an alternative to conventional solders. Surface-nanostructured materials enable solid-state bonding without complex surface modifications and operate at a low bonding temperature and pressure. Therefore, in this study, molecular dynamics simulations were conducted to investigate the solid-state bonding behavior between surface-nanostructured Cu and Au, with a focus on diffusion phenomena. A periodic ligament-cavity nanostructured Cu (NS-Cu) model was prepared at the bonding interface between Cu and Au slabs. The simulation results indicated that the larger the specific surface area of NS-Cu, the faster the densification at the bonding interface. Atomic displacement analysis showed that rapid densification occurred via the displacement of Cu and Au atoms in the vicinity of NS-Cu. The preferential diffusion of atoms along NS-Cu cavities contributed to this phenomenon. At this stage of densification, the diffusion coefficients were higher than the surface diffusion coefficients estimated based on literature, which indicates that this behavior is specific to surface-nanostructured materials. The highly disordered atomic arrangement at the bonding interface enabled significant atomic diffusion. Therefore, this study confirmed that the use of surface-nanostructured materials would contribute to a promising bonding technology for application in electronics.

Automated summary

Solid-state bonding has gained attention as an alternative to conventional solders in electronic packaging applications. Surface-nanostructured materials enable bonding at low temperature and pressure without complex modifications. This study used molecular dynamics simulations to investigate the bonding behavior between surface-nanostructured Cu and Au, revealing that larger specific surface area leads to faster densification at the bonding interface. Atomic displacement analysis showed preferential diffusion along NS-Cu cavities, with diffusion coefficients higher than surface diffusion coefficients. The highly disordered atomic arrangement allowed significant atomic diffusion, confirming the potential of surface-nanostructured materials in bonding technology for electronics.