Graphene-covered copper substrates for soldering applications: Experimental and atomistic insights into interfacial reactions and wetting with SAC305

The effect of a graphene interlayer on wetting behavior and interfacial reactions during the soldering of SAC305 alloy to copper was investigated through a combined experimental and computational approach. Sessile drop tests at 250 °C demonstrated that graphene significantly alters spreading dynamics and suppresses the formation of intermetallic compounds (IMCs). SEM and in-situ TEM analyses revealed that Sn atoms penetrate beneath the graphene layer via structural defects, initiating localized interfacial reactions and leading to crater formation and the development of a thin, continuous IMC layer in its vicinity. A Raman spectroscopy investigation confirmed the presence of graphene after wetting test and indicated its partial degradation at the interface. Molecular dynamics simulations provided atom level insight into early stages of wetting mechanism, confirming that Sn diffuses through graphene discontinuities, which are essential for reactive wetting to occur. Based on these observations, a wetting model was proposed to explain the role of graphene discontinuities and surface diffusion in the evolution of the interfacial structure. These findings suggest that graphene can be engineered as a functional interlayer in soldering technology to control diffusion, suppress excessive IMC growth, and tune joint morphology. The study provides a foundation for optimizing processing conditions and interfacial design in advanced materials joining applications. • Graphene suppresses the diffusion between liquid SAC305 solder and copper substrate. • Initially, the diffusion occurs only around discontinuity in the graphene structure. • Sn limited atomic movement beneath the graphene may favour Cu 3 Sn IMC formation. • Graphene may detach from the interface and migrate toward the droplet during reflow.