Thermal conductivity of isotropic conductive adhesives composed of an epoxy-based binder

The thermal conductivity of a practical isotropic conductive adhesive (ICA) comprising of an epoxy-based binder containing flake-shaped and spherical Ag particles has been studied. The specimens exhibit anisotropy in their thermal conductivities. In addition, their thermal conductivities apparently depend on their thermal history during the curing and subsequent annealing processes, even if they are fully cured. Analysis using the Wiedemann-Franz rule indicates that their thermal conductivities increase with increasing contribution from electrical conduction. Curing and annealing conditions that induce a large shrinkage of the adhesive binder lead to decreased electrical resistivity and increased thermal conductivity, because the contacts between the filler particles are enhanced, therefore causing a decrease any interfacial resistances. In order to analyze the thermal conductivity of advanced conductive adhesives, a novel analytical method that includes a reasonable definition of the state of the percolation networks that are formed by the filler particles needs to be developed.