An organic silver complex conductive ink using both decomposition and self-reduction mechanisms in film formation

Flexible electronics is of considerable interest for many applications due to the distinctive features of low-cost, flexibility and light weight capabilities. However, in translating the technology from research to practical applications one faces many challenges. One of them is to formulate suitable ink materials where the selection of functional components, for example in the case of organic silver ink, the silver precursor, complexing agent and volatile organic solvent, are very critical because these constituents determine the final properties of the ink. In this paper, a new type of silver organic ink with decomposition and self-reduction mechanisms (10 wt% silver content) was formulated. It is shown that the ink is capable of producing silver films with good uniformity and conductivity on a polyimide substrate after sintering at 155 °C. The effect of solvent on the thermal property of the formulated ink have been investigated by differential scanning calorimetry (DSC) and UV–Vis spectrscopy, where the active roles of the solvents and the underlying chemical reactions in the ink during heating were studied. The reaction mechanism between the complexing agent and the silver precursor was confirmed by FT-IR measurements. The effects of sintering temperature and time on the microstructure and electrical properties of the silver ink films have been studied in detail using XRD, SEM/EDX and 4-probe based techniques. The defects such as voids and cracks as well as the coffee rings, which are often associated with films produced from organic silver inks, were reduced significantly by using both decomposition and self-reduction mechanisms in film formation.