Effect of binder chemistry on the electrical conductivity of air-cured epoxy-based electrically conductive adhesives containing copper filler

An epoxy-based electrically conductive adhesive containing Cu microrods as a filler was prepared using an amine-based hardener. This adhesive can exhibit a low electrical resistivity of 10^-4 Ωcm after curing in air. The development of electrical conduction paths in the adhesive was dynamically analyzed by viscoelastic characterization combined with electrical resistance monitoring. Conduction paths developed through two elementary steps: microstructure formation of a filler network and evolution of the electrical conductivity between filler particles. In the Cu-loaded adhesive, a Cu-amine complex that formed in the paste during initial heating was suggested to be reduced in the same temperature range as where the conduction paths developed during curing. Therefore, control of the interfacial reaction between binder and fillers will be useful to help develop advanced Cu-loaded conductive adhesives.