Influence of Current Pulses on Resistance of Conductive Adhesive Joints

Abstract

Conductive adhesive joints were created from two types of electrically conductive adhesives with isotropic electrical conductivity by the adhesive mounting of resistors with “zero” resistance on the test board with copper pads. Both adhesives were from the same manufacturer, one was one-component and the other two-component. Joints were loaded first climatically, and then by current pulses. Climatic loading was carried out for one group of joints at normal temperature and 99 % relative humidity, for the other group of joints in an environment with a temperature of 85 °C and relative humidity of 85 %. The exposure time was always 300 hours. Then the joints were loaded with current pulses with a frequency of 50 Hz for 20, 50, and 100 minutes. The amplitudes of the current pulses were 5, 15, and 40 A, respectively. The semi-wide pulse was 2 μ.s The resistance of joins was measured in the four-point arrangement. Climatic loading of joints made of two-component glue caused, in the case of both types of loading, only small changes in the resistance of the joints. With one-component adhesive, the changes were greater. The same applies to current pulse loading. It was found, regardless of the type of adhesive, that for joints climatic aged in an environment with normal temperature and high RH, the application of current pulses provokes a decrease in the resistance of the joints. This can be justified by the heat loss that is generated in the joint due to the application of current pulses. This heat causes additional hardening of the adhesive, reducing its volume and improving the contact between the filler particles.