Mechanical shock-induced self-propagating exothermic reaction in Ti/Si multilayer nanofilms for low-power reactive bonding

In this study, we describe the development of a new solder bonding technique using a Ti/Si multilayer film, which can be conducted by mechanical shock only. A Ti/Si multilayer film is a self-propagating exothermic reactive material that can be ignited by applying both mechanical and electrical shocks (e.g. a spark in the latter case). The influence of bilayer thickness on film ignition was investigated by means of mechanical impact testing. The threshold energy for the exothermic reaction gradually decreased with decreasing bilayer thickness. We demonstrate the effectiveness of reactive solder bonding for a Si wafer by applying mechanical shock to a 25 nm bilayer thick Ti/Si film using an anisotropic wet-etched Si pyramid. (c) 2020 The Japan Society of Applied Physics