Cluster effects on electrical conductance of isotropically conductive adhesive

We have studied the DC electric conductance of isotropically conductive adhesive (ICA). It was demonstrated theoretically that assuming completely random distribution of the metal fillers in the ICA, the volume percentage of the metal fillers can be significantly reduced by adding nano-size fillers into the system originally containing only micro-size fillers. It is however shown experimentally that due to the surface tension nanofillers tend to gather around microfillers as well as form clusters themselves so that the resistivity of the ICA increases following the increase of the nanofillers' volume percentage. In the present work we try to study theoretically these cluster effects by simulating the detailed random walkings of the nanofillers and microfillers in the system. It has been concluded eventually that the cluster effects of the nanofillers deteriorate the electric conductivity of the ICA by separating the microfillers from each other so that electric conduction path becomes more difficult to form in the electric conducting network of the ICA.