Molecular dynamics simulations were used to analyze diffusion bonding at Cu/Al interfaces. The results indicated that the thickness of the interfacial layer was temperature-dependent, with higher temperatures yielding greater thicknesses. Below 750K, the interface thickness was found to increase in a step-wise manner as a function of time. Above 750K, the thickness increased rapidly and smoothly. When surface roughness was present, the bonding process consisted of 3 stages. In the first stage, surfaces deformed under stress, resulting in increased contact area. The second stage involved significant plastic deformation at the interface as the temperature increased; resulting in the disappearance of interstices and full contact of the surface pair. The final stage involved the diffusion of atoms at constant temperature.

Atomistic Investigation of the Effects of Temperature and Surface Roughness on Diffusion Bonding between Cu and Al. S.Chen, F.Ke, M.Zhou, Y.Bai: Acta Materialia, 2007, 55[9], 3169-75