Copper Ion Inks Capable of Screen Printing and Intense Pulsed-Light Sintering on PET Substrates

A copper ion ink capable of screen printing and intense pulsed-light (IPL) sintering on poly(ethylene terephthalate) (PET) substrates was developed. Using copper nitrate trihydrate as a copper precursor, we prepared this ink with 2-butoxyethanol solvent and an ethyl cellulose additive to ensure excellent wettability with PET substrates and screen printability. After screen printing on PET substrates with this transparent ion ink, the printed ink patterns dry quickly at a low temperature of 100 °C, and an excellent electrical resistivity of 5 μΩ·cm was obtained by short IPL sintering of 20 ms. Because of the high boiling point of 2-butoxyethanol used as a solvent, this ink has a very low evaporation rate at room temperature, so it is suitable for screen printing without clogging of the screen mesh. With this ion ink, it was possible to screen-print copper patterns with a line width of 200 μm. We compared screen-printing properties using this copper ion ink with those of silver and copper nanoparticle inks. Nanoparticle inks showed significant spread in the printed patterns during the screen printing, whereas this copper ion ink showed the lowest spread to enable the formation of fine patterns. In addition, it was confirmed that this ion ink had the least damage to the PET substrate during the IPL sintering process compared to other nanoparticle inks. This ink also has a long storage stability over 4 weeks without precipitation or phase separation. The optimal ink composition and process conditions for securing such excellent copper pattern printing characteristics were suggested in this study.