Laser assisted eutectic-driven fabrication of thermally conductive Al/AlN composites substrate and joining mechanism

Direct bonded aluminium (DBA) substrates have been widely implemented in high-power electronic devices. However, the oxidation-prone nature of molten aluminum has been a long-term reliability issue. Herein, we have proposed a novel DBA fabrication process utilising laser-assisted electrochemical copper plating to prepare a metallic transition layer. Through the Al-Cu eutectic method, bonding between pure aluminium and aluminium nitride ceramic substrates has been achieved at sintering temperatures ranging from 610 to 650 ℃. The bonding mechanism of Al/AlN was elucidated, along with the influence of the CuAl₂ phase at the interface on joint fracture behaviour. Based on theoretical analysis of interfacial diffusion, the formation and growth of the eutectic phase at the Al/Cu interface were controlled, thereby enhancing the bonding strength and achieving an average shear strength of 55.1 MPa for the Al/AlN substrate. This eutectic process not only avoids the oxidation issues associated with liquid aluminium, but also forms a robust bond at the joint, thereby providing a new strategy for the development of high-performance DBA substrates.