Improvement of discharge system in cool plasma sintering method for copper fine traces.

As a wiring material for printed electronics (PE), copper is strongly needed instead of silver. For a sintering method of copper traces, we have developed the method using oxygen pump and atmospheric pressure plasma, and demonstrated the ink composed of nanoparticles can be sintered to bulk-like structure. In this study, we have improved the sintering system to make it effective especially for copper inks made of submicron particles. We have tried to increase the thickness of the sintered layer and decrease the resistivity by changing the power supply system of plasma discharge and increasing the plasma density. The improved system has successfully demonstrated that a copper trace at least 4 μ m thick can be sintered and that the resistivity decreases to approximately 3.3 μ Ω·cm. These results can lead to huge breakthroughs in PE based on copper. [ABSTRACT FROM AUTHOR]