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

Abstract

Sputtered reactive multilayers applied as a heat source in electronic joining processes are an emerging technology. Their use promises low-stress assembly of components while improving thermal contact and reducing thermal resistance. Nanostructured surface modifications can significantly enhance adhesion and reliability of joints between different materials. This work examines reactive multilayer of nickel and aluminum, directly sputtered on nanostructured black silicon surfaces and compares their phase transformation with reference samples deposited on pristine silicon surface. The investigation of the quenched self-propagating reaction reveals a clear influence of the nanostructured surface on the prolongation of the phase transition. Rapid thermal annealing tests result in the formation of Al 1.1 Ni 0.9 phase. The nanostructured interface seems to hinder the full transformation of the parent material. The surface modification improves the adhesion of the formed alloy on silicon surfaces and can possibly increase the reliability of joints based on reactive aluminum/nickel multilayer. The use of black silicon, a nanostructured surface modification, is thus a promising approach to realize reliable multi-material joints in complex systems.

Phase Transformation and Characterization of 3D Reactive Microstructures in Nanoscale Al/Ni Multilayers

“…Both 3D-RMS on silicon needles and standard RMS on flat silicon were treated by rapid thermal annealing at 550 • C. During the process the heat radiation was used to initiate the phase transformation by solid diffusion. The multilayers deposited on flat Si after RTA peeled off from the substrate; however, the 3D-RMS remained attached to the substrate, this effect was already observed in previous investigations demonstrating the improvement in the adhesion of multilayers on silicon needles [18]. In order to verify the influence of the structure on the phase transformation, XRD analysis was performed.…”

“…These studies were carried out using multilayer foils. However, it is also possible to produce reactive multilayer particles by using structured substrates such as nylon fibers or black Si [17,18]. Particles produced on nylon fibers were separated from the substrate and funneled into glass tubes in order to measure the propagation front velocity.…”

“…Nanostructured Si has interesting properties such as surface enlargement that can be exploited in chip assembly [20]. For this reason, it was used as a substrate during the deposition of Al/Ni RMS [18]. The needle-shaped topography of Si disturbs the morphology of the deposited multilayers, giving rise to a complex structure of 3D reactive multilayers (3D-RMS).…”

“…The needle-shaped topography of Si disturbs the morphology of the deposited multilayers, giving rise to a complex structure of 3D reactive multilayers (3D-RMS). Furthermore, the black Si surface enhanced the adhesion of the RMS on the substrate in comparison with a flat surface, even after heat treatment [18]. During rapid thermal annealing (RTA) at a maximum temperature of 550 • C, 3D-RMS on Si needles reacted only partially forming B2-AlNi leaving unreacted Ni residue, unlike RMS foils on flat Si which fully transform the precursor materials into the B2-AlNi phase.…”

Self-Powered Fast Brazing of Ti-6Al-4V Using Ni/Al Reactive Multilayer Films

“…Lastly, we assume, in the LAMPS © simulation, that the RMF is defect free and perfectly flat. However, defects present in the real RMF [3], which are possibly introduced through applied pressure, can decrease the propagation efficiency of the film [26].…”