Soldering electronic components to circuit boards involves usingenvironmentally harmful cleaning agents and toxic heavy metals like lead.Solder joints can be unreliable in high shock environments because ofnon-uniform adhesion. This program will develop an entirely new method forwelding such joints. In this novel method, 50-500 nm diam monodispersedroplets of high temperature filler metal are generated remotely and thendeposited at the joint to be welded. Almost any metal can be a filler,including the same metal as the those being joined. Droplet size andtemperature are controlled so that the depth of the weld and therefore, itsreliability is also controlled. No flux or cleaning solvent is used in thisprocess. Toxic heavy metal solder is replaced by benign filler metal. Sincethere is no contact of the energy source with the weld site, thermal orelectrical damage to components is eliminated. In Phase I, copper,aluminum, and nichrome wires will be welded to copper foil on a circuitboard (copper or aluminum filler). Weld strengths will be measured andcorrelated with the experimental parameters, droplet metal identity, size,and temperature. In Phase II more detailed evaluations will be made toautomate and scale-up the method in Phase III follow-on work.
