Photonic sintering of inkjet printable molecular base copper ink at ambient conditions

Abstract

Copper (Cu)-based inks provide an efficient and cost-effective solution for creating conductive pathways in electronic devices. However, one of the major challenges regarding Cu ink processing reflects Cu’s high chemical reactivity and oxidation sensitivity, which can compromise its electrical performance following thermal sinter processing. To address this challenge, Cu sintering is typically performed with precise control of ambient conditions through use of an inert or reducing atmosphere to prevent oxidation and ensure electrical conductivity. To overcome these processing requirements, we report on the synthesis of an inkjet printable, thermally reducible molecular base copper ink that demonstrates compatibility with photonic pulse sinter processing technologies, permitting thermal sintering for copper film deposition without requirement for environmental conditioning. Following inkjet print substrate patterning, molecular base copper inks were sintered via photonic pulse under atmospheric conditions, resulting in the deposition of conductive copper traces on glass and polyimide (Kapton®), polycarbonate (PC), and polyetherimide (PEI) polymer substrates. Dark-field microscopy, scanning electron microscopy, X-ray diffraction spectroscopy, and four-point probe electrical testing, coupled with stylus profilometry, permitted macrostructural, microstructural, spectral, and electrical characterization of Cu films, identifying Cu deposition without contamination of copper oxides and minimum sheet resistance values of 0.235 Ohm. This study unlocks the potential for widespread use of copper in electronics with low-temperature substrates and large-scale printed circuits without the need for costly environmental controls during production.