Fine-Pitch Copper Wiring Formed with Super-Inkjet and Oxygen Pump

We have successfully printed wires of 5 ?m line widths and spaces in copper nanoparticle ink with a super-inkjet printer. The wires show resistivity as low as 8.1 ???cm after sintering at 250 ?C in an extremely low oxygen atmosphere generated by an oxygen pump. To our knowledge, this is the first report of micron-scale copper wiring formed by a direct printing method without any masks or templates.