Effect of PVP-coated silver nanoparticles using laser direct patterning process by photothermal effect

Laser direct patterning of silver nanoparticles (AgNPs) conductive patterns on a polyimide substrate using photothermal effect of nanoparticles provides various advantages for applications in flexible electronics. Two PVP content AgNPs were used in this research. Since the thin and thick PVP-coated AgNPs have a strong optical absorption at 426 and 405 nm, respectively, a UV laser (405 nm and 60 mW) is used to trigger AgNPs to convert light into heat due to photothermal effect of nanoparticles. After UV laser beam irradiating on the AgNPs thin film, the AgNPs aggregate into larger conducting grains and improve the adhesion between AgNPs and the polyimide substrate at the same time. Then the desired AgNPs conductive lines (line width: 30 μm, line space: 70 μm) are formed after washing the unirradiated AgNPs. By this method, we have demonstrated a 5 μm width AgNPs conductive line. In the mean time, we also found out that the higher PVP content, the laser direct patterning of AgNPs conductive lines would have more straight and smooth boundaries. And the adhesion between the AgNPs conductive patterns and PI substrate would be better while using higher PVP content AgNPs.