Reaction of Al/Ni Multilayers

Sputtered reactive multilayers applied as a heat source in electronic joining processes are 11 an emerging technology. It promises low-stress assembly of components while improving the 12 thermal contact and thus thermal resistance. The use of nanostructures can significantly enhance 13 the adhesion and reliability of joints between different materials. This work presents a 14 phenomenological proof of the hypothesis. Reactive multilayers of nickel and aluminum directly 15 deposited on nanostructured surfaces of silicon wafers and reference samples with flat surface are 16 compared. The investigation of the self-propagating reaction shows a clear influence of the layer 17 thickness, dependent on the multilayer thickness and nanostructure morphology. Rapid thermal 18 annealing results in the formation of Al1.1Ni0.9 phase. The necessary annealing temperature is much 19 higher than this applied for nanofoils, sputtered multilayer or particles. The nanostructured 20 interface seems to hinder the full transformation of the present nickel. On the other hand, the 21 surfaces modification improves adhesion of the formed alloy on silicon surfaces and can thus 22 increase the reliability of joints based on reactive aluminum/nickel multilayer. The use of 23 nanostructured surface modifications is thus a promising approach to realized reliable multi24 material joints in complex systems. 25