Photonic Sintering of Inkjet Printed Copper Oxide Layer

Abstract

Recently, printing technologies have been adapted for the manufacturing of flexible electronic devices such as RFID antennas, capacitors, rectifiers, organic thin film transistors, photovoltaics, etc. In contrast to traditional production of electronics, printing technologies can enable low cost, high throughput, and large-area processing on flexible polymer materials. Photolithographical processes can be substituted by direct printing, e.g. of metal nanoparticles (NPs) or organic inks on flexible polymer foils. After the deposition of the materials by printing, curing, drying and/or sintering is required to remove solvents and additives, and to develop a functional layer. The operating temperatures of these post-printing processes are usually higher than the tolerable temperature of the polymer foils, which results in plastic thermal deformations of the foils. Photonic sintering is considered as one of the promising technology, especially for R2R processing, to prevent the thermal deformation of the substrate. It allows processing in ambient conditions without damaging the polymer foils due to energy exposure in microseconds-scale.In this paper, the effect of photonic sintering conditions on inkjet printed copper oxide (CuO) layers was investigated. We found that the conductivity is proportional to the exposure energy. However, excessive energy will lead to "over-sintering" and thus destroys the copper layer. Optimized photonic sintering parameters were proposed to obtain inkjet-printed copper layers with high conductivity and no layer ablation.