Laser Curing of the Silver/Copper Nanoparticle Ink via Optical Property Measurement and Calculation

Abstract

The spectral optical properties of the silver/copper nanoparticle ink at visible and near-infrared wavelength were measured by ellipsometry. The purpose of the measurement of the optical properties is to select the optimal process parameters such as working wavelength and laser incidence angle by finding the maximum absorption wavelength. The reflectance and absorptivity of the nano-ink including silver/copper nanoparticles were calculated from the experimentally obtained refractive indices. The absorptivity has been maximized at the green wavelength for the normal incident angle to the target at the initial stage of the curing. Therefore, a continuous wave green laser at the wavelength of 532nm is chosen for the laser curing. For the laser curing process, the inkjet-printed silver/copper nano-ink samples on the glass and poly(ethylene terephthalate) (PET) substrates are adopted to find the effect of the substrate materials on laser curing process. The used laser energy is 31.62 and 177.27W/cm(2) to analyze the effect of the laser intensity on laser curing process. The nano-ink on the PET substrate has lower specific resistance than that on the glass substrate with the identical laser irradiation time. The higher laser intensity is recommended to obtain the lower specific resistance with same laser irradiation. Compared with the 30-min furnace curing process at the temperature of 250 degrees C, a few seconds laser curing process can be effectively adopted with appropriate scanning system to shorten the curing time.