Rapid low temperature sintering in air of copper submicron particles with synergistic surface-activation and anti-oxidative protection

The technology to sinter copper inks in air is beneficial for the applications in flexible printed electronics. However, copper based ink could hardly produce conductive copper patterns when sintered in air, because copper is easily oxidized. In this study, a convenient fabrication process for conductive copper films with a simple heat treatment on hotplate in air was successfully developed. The ink was prepared by mixing copper submicron particles with formic acid and an amino-alcohol. The copper oxide on the surface of untreated copper submicron particles was converted to decomposable copper formate. More importantly, the copper submicron particles could be activated by the chemisorbed HCOOH to sinter at low temperatures. 3-Dimethylamino-1,2-propanediol (DMAPD) was introduced to protect copper from oxidation when sintered in air. In addition, DMAPD could promote the decomposition of copper formate by forming copper-amine complex. A resistivity of 54 +/- 2 mu Omega cm was obtained after sintered at 200 degrees C for 50s (63 +/- 4 mu Omega cm for only 10s). This simple, convenient and rapid sintering of submicron copper inks in air provides an alternative fabrication method of copper patterns in printed electronics.