Selective Electrodeposition of Micro-Nano Cu Arrays for Ambient Air Compatible Low Temperature Cu-Cu Bonding with Gradient Nanocrystalline Structure

This study proposes a solid-phase bonding method using micro-nano engineered Cu arrays to improve the interfacial metallurgical quality and mechanical reliability in wide-bandgap semiconductor packaging. Micron-scale Cu arrays with nanoscale surface undulations are created through selective electrodeposition. Copper nanoparticles (CuNPs) are added to the Cu arrays, forming sintered joints that combine "nanoscale surface energy matching" and "microscale structural reinforcement." The nano undulations in the array utilize the Gibbs-Thomson effect to lower atomic migration barriers, which accelerates interfacial diffusion and forms a dense metallurgical layer. The three-dimensional Cu array structure forms mechanical interlocks with the sintered matrix through geometric anchoring, significantly increasing the shear strength of the joints through synergistic effects. The arrays and embedded nanoparticles form a gradient nanocrystalline structure with hierarchical coarse and nanosized grains. This structure balances strength and toughness by hindering dislocation motion and enabling plastic deformation, providing unique microstructural reinforcement. The cross-scale structural synergy approach overcomes the interfacial metallurgical kinetic mismatch bottleneck in traditional sintering techniques, offering a scalable solution for efficient and reliable packaging of high-power electronic devices.