Sensitivity of Resistance, Noise and Nonlinearity of Conductive Adhesive Joints to Changes in Adhesive

Conductive adhesive joints were formed by adhesive assembly of resistors with "zero" resistance on Cu pads. Adhesive with bis-phenol epoxy matrix filled by silver flakes in concentration 75 % b.w. was used for experiments. The test samples were aged at the temperature of 125 degrees C and the relative humidity of 64 %, in an environment with 95 % relative humidity at the temperature of 24 degrees C and in an environment having the temperature 85 degrees C and the relative humidity 85 %. Changes of basic electrical parameters of the joints, the resistance, noise and nonlinearity of the current-voltage characteristic, were examined. It was found that changes of noise and nonlinearity are significantly higher in comparison with the changes of the joint resistance. It is assumed that the reason is that the junction resistance is a result of all the mechanisms of conductivity in adhesive and in the contacts between the adhesive, component and a pad, whereas nonlinearity and noise examine the nonlinear mechanisms only, especially tunneling.