Effect of heating on the electrical resistivity of conductive adhesive and soldered joints

Thermal cycling from room temperature to 60°C was found to cause the contact resistivity of a silver-epoxy conductive adhesive joint to decrease irreversibly, due to an irreversible decrease of the thickness of the joint. This effect was much smaller for a soldered joint cycled to 40°C. An extended period of current on-off cycling caused a slight irreversible increase in the contact resistivity of the adhesive and soldered joints, but thermal cycling using a heater did not. Within each thermal cycle, the contact resistivity increased reversibly with increasing temperature, due to the increase in volume resistivity of the solder or adhesive. Temperature variation caused fractional changes in contact resistivity up to 48% and 6% for adhesive and soldered joints, respectively.