Metallic conductivity via CoCu filler-Co nanocatalyst bridge for a novel thermoset paste

Silver printable conductors on resin substrates and silver conductive adhesives for low-temperature assembly of electronic components have been developed to meet the requirements of mobile electronic devices. However, silver has the disadvantages of high environmental load and short circuiting easily in harsh conditions owing to its low migration resistance. Here, we report a copper-carbon paste composed of copper-carbon microfillers and nano-cobalt, which has huge potential as a thermoset paste that does not require sintering and melting of fillers. The film paste curable at 150 °C in air shows metallic temperature variation and has electrical resistivity of 0.23 mΩcm at room temperature, similar to 0.11 mΩcm for thermoset silver flake paste. We propose an extraordinary mechanism that goes beyond the conventional mechanism: electron transport between the host alloy and the catalyst cobalt. These findings highlight resource strategies for realizing a sustainable society.