Graphene as a diffusion barrier at the interface of Liquid–State low-melting Sn–58Bi alloy and copper foil

[Display omitted] •Interfacial reactions between Sn-58Bi/Graphene/Cu.•Graphene as a great diffusion barrier between liquid metal and solid metal.•Significant Suppression of the interfacial layer of Cu-Sn intermetallic compounds.•Activation energy (32.6 kJ/mol∙k) for Cu diffusion increased by graphene barrier. Graphene is widely used as a barrier at the solid–solid and gas–solid state interface. However, the use of graphene as a barrier at the liquid–solid interface has been rarely reported, particularly in the case of a liquid-state metal and a solid-state metal interface. Herein, a graphene layer is synthesized on a Cu foil, and single-layer and bilayer graphene is detected via Raman spectroscopy. The interfacial intermetallic compound between eutectic Sn–58Bi alloy with a melting temperature of 138 °C and Cu with a melting temperature of 1085 °C can be significantly suppressed by graphene using different reflow temperatures (180 °C and 300 °C) and reflow times (144–625 s). Cu diffusion through graphene is visible in the Sn–Cu intermetallic compound (IMC) formations in the SB58 solder and at the interface after the reflow processes. We found that the activation energy of Cu diffusion through graphene into the liquid-state graphene is ∼ 32.6 kJ/(mol∙k), which is higher than that attained without graphene. Therefore, the findings of this study show that graphene is a promising diffusion barrier for the liquid–solid interface.