This paper describes joining enabled by energetic thin films.  As demonstrated previously by Weihs and colleagues using Ni/Al, energetic films can be used to solder different materials.  Energetic films consist of two or more reactants, typically deposited as a heterostructure, that combust and give off heat.  The released heat can drive a self-propagating reaction and raise the temperature in neighboring solder layers to required levels.  Joining via exothermic thin films holds promise for reducing the heat load on temperature-sensitive piece parts/devices and minimizing the residual stress of an assembly, because significant temperature extremes are confined to the film, neighboring solder and the near-surface region of the parent materials.
In this presentation, we discuss energetic Co/Al and Ni/Ti multilayers and the ability to solder and braze with these materials.  Co/Al and Ni/Ti exhibit self-propagating reactions with maximum steady-state wavefront speeds equal to 10 m/s and 1m/s, respectively.  Co/Al is used to solder dissimilar materials when using a procedure similar to that described by Weihs, yet Ni/Ti is insufficiently energetic to maintain a self-propagating reaction when constrained.  Co/Al is also favored, because it forms a ductile B2 microstructure for all multilayer designs investigated.  Ni/Ti can form a B2 structure but is often compromised by the presence of a B19’ phase.  The mechanical properties of assemblies soldered by Co/Al energetic films are reasonable.
Both energetic thin film materials show promise for joining via low temperature braze processes.  For this we use braze alloys having melting temperatures ~500-750C and energetic films of thickness 50-100 microns.  We describe methods that preheat assemblies to a moderate temperature, ~200C, prior to film ignition.  A slight preheat, ~200-300C, is allowed since, for many activities, the coefficients of thermal expansion are reasonably matched over this range.