Fabrication of high-resolution conductive patterns on a thermally imprinted polyetherimide film by the capillary flow of conductive ink

We developed herein a simple and economical high-resolution wiring process on a plastic substrate. High-resolution conductive patterns on the PEI film was fabricated by utilizing the thermal imprint technology and the capillary flow of the conductive ink. An amorphous thermoplastic polyetherimide (PEI) film was thermally imprinted with a metal mold having line (8 mu m)/space (12 mu m) structures. The effects of the imprint temperature, melting time, and imprint pressure on the PEI film transferability were investigated. A higher replication ratio was obtained when the molding temperature was higher, the melting time was longer, the imprint pressure was higher, and the mold structure height was lower. The mold structures were almost perfectly transferred on the PEI film surface at a molding temperature of 285 degrees C, a melting time of 3.0 min, and a molding pressure of 1.0 MPa. Two different wiring processes, namely, spin coating and capillary flowing of Ag ink onto the imprinted PEI film, were conducted. For the spin-coating wiring process, the Ag ink existed not only inside the grooves but also on the convex area as the residual layer, regardless of rotational speed and time. For the capillary flowing wiring process, when the Ag ink contacted the edge of the imprinted pattern on the PEI film, it spontaneously flowed toward the wiring direction. Only the concave grooves were selectively filled with Ag ink, and the residual layer was not observed. The fabricated wiring conformed to Ohm's law, with an electric resistivity of 42 x 10(-8) omega m.