Modification of adhesive joints resistance with current pulses

Strips of electrically conductive adhesive were printed on a test PCB. Strips were processed by a standard curing process and then aged at the temperature of 125
^o
C. One group of samples was aged in an oven; the second group was heated with current pulses of high intensity. Ageing was carried out 150 hours. The frequency, amplitude and pulse duty cycle were changed. The strip resistance was measured by the four-terminal method, the resistance of the contact between strips and pads using the three-terminal method. It was found that the resistance of the strip heated in an oven slowly grew with the time of ageing. The resistance of the samples heated with current pulses first decreased and then started to growth rapidly. The course depended on parameters of the pulses. The reasons of the resistance changes were discussed.