Low temperature sintering of metallacyclic stabilized copper nanoparticles and adhesion enhancement of conductive copper film to a polyimide substrate
We report that both low electric resistivity and strong adhesion to polyimide film were attained for a conductive Cu film prepared by low temperature sintering of 2 amino 1 butanol protected Cu nanoparticles (AB Cu NPs) with an average size of 4.4 nm. The sintering temperature of 60 degC for the AB Cu NPs is the lowest ever reported for Cu NPs. A nanoink comprising these AB Cu NPs ~35 wt% Cu) produced a conductive Cu film with resistivity of 52 mO cm after heating at 150 degC under a nitrogen flow. The adhesion to a polyimide film was compared for films prepared from nanoinks consisting of three different types of alkanol amine based Cu NPs: AB Cu NPs, 1 amino 2 propanol Cu NPs, and 3 amino 1 propanol Cu NPs. Only the Cu film prepared from the AB Cu nanoink established strong adhesion to the substrate without decreasing the electrical conductivity. The adhesiveness is attributed to residual oxidation products after thermal sintering of the Cu nanoinks.
Journal of Materials Science: Materials in Electronics