Improving Definition of Screen-Printed Functional Materials for Sensing Application.

Screen printing is one of the most used techniques for developing printed electronics. It stands out for its simplicity, scalability, and effectivity. Specifically, the manufacturing of hybrid integrated circuits has promoted the development of the technique, and the photovoltaic industry has enhanced the printing process by developing high-performance metallization pastes and high-end screens. In recent years, fine lines of 50 µm or smaller are about to be adopted in mass production, and screen printing has to compete with digital printing techniques such as inkjet printing, which can reach narrower lines. In this sense, this work is focused on testing the printing resolution of a high-performance stainless-steel screen with commercial conductive inks and functional lab-made inks based on reduced graphene oxide using an interdigitated structure. We achieved electrically conductive functional patterns with a minimum printing resolution of 40 µm for all inks.

Photonic sintering of copper for rapid processing of thick film conducting circuits on FTO coated glass.

Copper potentially provides a cost-effective replacement for silver in printed electronic circuitry with diverse applications in healthcare, solar energy, IOT devices and automotive applications. The primary challenge facing copper is that it readily oxidizes to its non-conductive state during the sintering process. Photonic sintering offers a means of overcoming the oxidation by which rapid conversion from discrete nano-micro particles to fully or partially sintered products occurs. An experimental study of flash lamp sintering of mixed nano copper and mixed nano/ micro copper thick film screen printed structures on FTO coated glass was carried out. It shows that there may be multiple energy windows which can successfully sinter the thick film copper print preventing detrimental copper oxidation. Under optimum conditions, the conductivities achieved in under 1 s was (3.11-4.3 × 10-7 Ω m) matched those achieved in 90 min at 250 °C under reducing gas conditions, offering a significant improvement in productivity and reduced energy demand. Also present a good film stability of a 14% increase in line resistance of 100 N material, around 10% for the 50N50M ink and only around 2% for the 20N80M.