Role of Advanced Polishing Techniques in Enhancing Al–Cu Diffusion Bonding: Eliminating Impurities and Voids for High-Performance Conductive Joints

The demand for lightweight, high-efficiency components in electric vehicles (EVs) highlights the critical need for reliable Al-Cu joints with superior electrical and thermal conductivity. While diffusion bonding has emerged as a promising approach, interfacial impurities and voids often degrade joint quality and conductivity. In this work, we introduce a novel integration of electropolishing pretreatment with ultra-thin copper foil (<50 µm) assisted diffusion bonding to achieve cleaner, void-free interfaces. Electropolishing effectively removes surface contaminants and oxides, enabling intimate atomic contact during bonding and minimizing the formation of brittle intermetallic phases. A systematic investigation of bonding parameters temperature, pressure, and time was conducted using a custom-designed graphite clamping system. Microstructural analyses reveal that polishing plays a pivotal role in producing uniform, impurity-free interfaces, resulting in reduced intermetallic thickness, improved bonding strength, and enhanced current-carrying capability. This study establishes the significance of advanced polishing in diffusion bonding and demonstrates a scalable pathway to manufacture high-performance conductive joints for next-generation EV motor and power distribution systems.