Copper(II) ethylene glycol carboxylates as precursors for inkjet printing of conductive copper patterns

Abstract Copper(II) ethylene glycol carboxylates were investigated as precursors for inkjet printing of conductive copper patterns. The compounds with the general formula Cu[O 2 CCRR′(OC 2 H 4 ) 2 OCH 3 ] 2 (R = R′ = H: 2a ; R = H, R′ = Me: 2b ; R = R′ = Me: 2c ; R = H, R′ = Ph: 2d , R/R′ = O: 2e ) show a high solubility in water and many organic solvents. By thermal decomposition the compounds yield pure copper as the only non-volatile product, as confirmed by X-ray powder diffraction and energy-dispersive X-ray spectroscopy. Depending on the substituents R and R′ the decomposition temperature varies between 175 and 220 °C. The mechanism of the thermal degradation was studied by thermogravimetry–mass spectrometry coupling experiments. For complex 2a , an aqueous 1.5 M solution (7.7 wt.% copper) exhibits rheological properties that are well-suited for inkjet printing. Thermal conversion of the as-printed structures under inert conditions yielded copper layers with only minor residues of carbon and oxygen. Electrical conductivities of 1.5 · 10 6  S·m − 1 on polyimide and 8.1 · 10 6  S·m − 1 on glass were found, which correspond to 2.6 and 14% of the bulk copper conductivity, respectively.