Silver nanocluster formation using UV radiation for direct metal patterning on polyimide

This article presents progress towards the direct metallisation of polyimide via silver ion exchange and nanocluster formation. The aim of this research is to develop a more cost-effective process for the large-scale manufacturing of polymer based electronics. The benefits of this additive approach are the reduced number of fabrication steps and volume of waste materials compared to existing manufacturing processes. The metallization can be achieved by exposure to UV light from either a standard arc lamp or a laser of appropriate wavelength and power intensity. Presented here are results from exposure to a UV arc lamp. The chosen polyimide, Kapton (PMDA-ODA), was treated by a chemical process previously documented by the group to incorporate silver ions in the polymer chain matrix. To initiate the growth of silver nanoparticles from the nested ions, the sample was then exposed to UV light using a photomask to selectively pattern the substrate and annealed at 300°C. Optimal conditions were found for fabrication of a micro-patterned seed-layer suitable for subsequent electroless plating. Also observed was a harmful effect of the process onto the underlying substrate. The durations of both the light exposure and annealing times were varied and their effects measured using FEGSEM imaging to observe the nanoparticle growth. Zygo white light interferometry and optical microscopy were used for surface profiling and imaging. Reflectivity measurements were taken with a HeNe class 2 laser and silicon photodetector.