Abstract
The thermomechanical behavior of soldered joints have received much attention, due to the importance of thermal fatigue and creep as causes of degradation and failure. Previous work in this area mainly involved optical methods, diffraction, mechanical testing and modeling. The experimental techniques were commonly applied before and after a certain number of cycles of temperature and/or stress variation, so the observations were limited to effects that were irreversible. However, an effect may be partly reversible. In order to observe the reversible part of a phenomenon, observation must be conducted in real time using a nondestructive technique. Measurement of the DC electrical resistivity was found to be effective for monitoring in real time the effects of stress and thermal cycling on a soldered joint. The solder was eutectic tin-lead. The adjoining materials were copper. The resistivity was that of the overall sandwich. Both reversible and irreversible effects were observed.
