Maskless Metal Patterning on Polyimide Substrate Using Laser-Enhanced Electroless Nickel Plating.

Abstract

We studied how polyimide substrate etching and argon laser irradiation conditions affected the deposition of nickel line patterns. Polyimide substrates were etched in NaOH solutions at room temperature, followed by measurement of contact angles, AFM diagrams, and FT-IR spectra to determine optimum NaOH concentration and etching duration ensuring good deposition. After etching at concentrations exceeding 10wt% and at durations exceeding 30s, the etched substrate surface consisted of polar molecules and had a low contact angle, resulting in good nickel pattern deposition. Excess etching caused macroscopic roughening of the substrate surface. Although a certain degree of laser power density was needed to ensure deposition, too high a power caused plating solution to boil and substrates to be thermally damaged. When laser beam was scanned at more than 50μm/s, no deposition was obtained because substrates were not heated enough. Optimum deposition was at 300-800W/cm2 and scanning slower than 25μm/s for a substrate 50μm thick and a beam diameter of 100μm. Nickel lines about 100μm wide and 0.3-0.4μm thick were obtained, although their width increased with increasing power density.