Volume-shrinkage-driven curling behavior of dual-composition Al/Ni multilayer thin films for bonding applications

Abstract Dual-composition Al/Ni multilayer thin films with various architectural designs were fabricated to investigate curling motion driven by volume shrinkage and to assess their potential to enhance the direct bonding of Al busbars. The reacted films exhibited pronounced, composition-dependent curling deformation, with a higher Al fraction yielding a smaller radius. In contrast, total film thickness and bilayer period had only a minor influence. A theoretical curvature analysis was conducted to compare predicted deformation with experimental results, and to estimate the mismatch strain and the bending-generated energy. Bonding between two Al busbars was demonstrated. Larger curvature led to increased cracking in the reacted layer, which is expected to facilitate easier removal of the reacted interlayer after bonding. These results demonstrate that tailoring the Al/Ni film’s multilayer architecture provides effective control of curvature after reaction, offering a promising pathway for reactive bonding systems that require simple post-bonding removal of the reacted NiAl film or reduced mechanical damage.