Influence of Nanoscaled Surface Modification on the Reaction of Al/Ni Multilayers

Sputtered reactive multilayers applied as a heat source in electronic joining processes are an emerging technology. It promises low-stress assembly of components while improving the thermal contact and thus thermal resistance. The use of nanostructures can significantly enhance the adhesion and reliability of joints between different materials. This work presents a phenomenological proof of the hypothesis. Reactive multilayers of nickel and aluminum directly deposited on nanostructured surfaces of silicon wafers and reference samples with flat surface are compared. The investigation of the self-propagating reaction shows a clear influence of the layer thickness, dependent on the multilayer thickness and nanostructure morphology. Rapid thermal annealing results in the formation of Al_1.1Ni_0.9 phase. The necessary annealing temperature is much higher than this applied for nanofoils, sputtered multilayer or particles. The nanostructured interface seems to hinder the full transformation of the present nickel. On the other hand, the surfaces modification improves adhesion of the formed alloy on silicon surfaces and can thus reduce the strength of joints based on reactive aluminum/nickel multilayer . The use of nanostructured surface modifications is thus a promising approach to realized reliable multi-material joints in complex systems.