Fabrication and investigation of a new copper-doped screen-printable carbon paste's conductive mechanism by AFM

This paper presents a new low-cost water-based carbon/copper screen printing conductive paste, with commercial micron-grade graphite, nanometer acetylene black and synthesized copper submicron particles of about 226 nm in diameter as the mixed conducting fillers. The relationship between micromorphology and conductivity of the screen-printed line patterns made by the paste was monitored by atomic force microscopy. There are several different packing modes of conducting fillers relating the conductivity of screen-printed line patterns. Variations in the copper content, sintering temperature and time can remarkably affect the packing density and conductivity. The addition of copper submicron particles to the paste further improved the particle osculation by filling the interstices among the micron-grade graphite layers and arranging themselves densely with the smaller acetylene black particles. The optimized paste reached a film resistivity of 33.3 m Omega cm using screen printing and annealing at 260 degrees C.