Molecular Dynamics Analysis of Impact of Alloyed Interlayers in Ni–Al Reactive Multilayer Nanofoils

Reactive multilayer nanofoils (RMNFs), comprised of alternating layers of metals such as nickel and aluminum, have emerged as a focal point of interest owing to their distinctive properties and versatile applications across semiconductor and micro-electromechanical systems.This nanoengineered material undergoes a self-contained exothermic reaction, initiated by a small external trigger delivering localized heat up to 1500 ℃ in fractions of a second.It can be a heat source material primarily used to make a bond between electric components by melting solders.However, the volume shrinkage during reaction causes void formation and microcracking in the reaction product, and it reduces the reliability of the bonding.In this study, we systematically investigate 11 different Ni-Al RMNFs, including multilayers with 0, 10, 30, 50, 70, and 90% alloyed regions (polycrystalline B2-NiAl or amorphous-NiAl) using molecular dynamic simulations.We found that samples with alloyed interlayers exhibit reduced reaction temperatures and volume shrinkage after the reaction.By controlling the thickness of the alloyed interlayers and structures, we can reduce the damage caused by volume shrinkage during the reaction while obtaining a sufficient reaction temperature.