Study on electrical contact of a solid–liquid interface between a copper-based electrode and liquid metal

Abstract

Copper-based electrodes are widely used for electrical connections due to their excellent electrical and thermal conductivity. However, efficient electrical connectivity is often hindered by high interfacial contact resistance and reliability issues inherent in conventional solid–solid contacts. Gallium-based liquid metals (GLMs) offer a solution through their unique liquid-state compliant contact and reactive interface. This study systematically investigates the reactive wetting behavior and electrical contact stability of GLM in contact with four common copper-based electrode types: pure copper (T2), brass (H62), bronze (QSn6.5-0.1), and alumina-dispersed copper (C15760). Contact resistance at the solid–liquid interface was measured quantitatively using the transmission line model method. The results demonstrate that contact resistance undergoes a progressive reduction and reaches a quasi-steady state after 20 days of continuous contact. This is primarily due to enhanced interfacial wettability and the consequent increase in the effective contact area. Notably, the T2 and H62 interfaces achieved a stable contact resistivity of approximately 10⁻⁶ Ω cm². Microstructural analysis (XRD and SEM) confirms the formation of a CuGa₂ intermetallic compound layer through reactive wetting. This intermetallic compound layer significantly enables a transition from discrete physical contact to a stable, metallic bond wetting, thereby effectively reducing solid–liquid contact resistance. These findings demonstrate the great potential of gallium-based liquid metal for forming reliable and efficient solid–liquid electrical contacts with copper-based electrodes via reactive wetting. This opens broad prospects for advanced electrical interface applications.