A new copper ink with low sintering temperature for flexible substrates

The metal organic decomposition ink, one of the frequently-used conductive ink, has attracted more and more attentions. However, a serious drawback of the metal organic decomposition inks is that the sintering temperature is too high for the fabrication of printed electronic devices on a flexible organic substrate, such as PET film. Thus, the metal decomposition ink with low sintering temperature below 200 °C is required. It has been reported that the octylamine can effectively reduce the decomposition temperature of copper formate for metal organic decomposition ink. In this paper, we present the development of a new copper ink, which is composed of copper formate and isopropanolamine. The ink can decompose at 120 °C under nitrogen and form a conductive film. The copper organic decomposition ink was characterized by UV, FTIR and TGA. Copper film was obtained by coating the ink onto the glass and PET substrate followed by sintering at a relatively low temperature. The copper film showed a low resistance of 32.3 µΩ·cm when sintered at 135 °C, measured with a four-point probe method. The structure of copper film was characterized by XRD which consisted of pure copper. SEM showed the differences in the morphology of the copper film at various temperature.