Novel developments in photonic sintering of inkjet printed functional inks

Inkjet printing of electrical tracks in roll-to-roll applications was hampered for a long time since nano-particle inks required thermal sintering at temperatures greater than 120 °C for several minutes. Among a large number of potential R2R compatible techniques, photonic sintering of inkjet-printed metal-based inks was shown to enable very fast sintering times and providing high quality of structural integrity and low electrical resistance [1]. While the above investigations were carried out with a low dutylow frequency irradiation source, novel developments allow for pulse shaping on the timescale of several microseconds and, therefore, the combination of drying and sintering pulses into a single piece of equipment. In this contribution the photonic sintering process was investigated numerically and experimentally for the case of inkjetprinted aqueous copper oxide ink and a Pulse Forge®3200 X2 tool, both implemented onto a NovaCentrix roll-to-roll machine. Our finding support the assumption, that pulse shaping and, therefore, energy tailoring as a function of time, is essential for efficient conversion of wet copper oxide deposits into conductive copper with no impact on the underlying substrate. The paper presents and discusses the resulting electrical resistances of features processed with a conventional hybrid solution using IRradiation for pre-drying as well as a single step drying and sintering using a single radiation source.