This article describes a method of forming a stacked hybrid metal structure and pattern to enhance radio-frequency identification antenna coil inductance. The essential strategies included the use of multilayer self-assembled polyelectrolytes to modify the surface property of substrates, an ink jet printing process for a Pd containing catalyst, and a stacked hybrid metal layer formed by electroless plating in subsequent processes. The results demonstrate that the minimum line width and line spacing can reach 100 μm/100 μm, and electrical performance is compared to prior research in employing different approaches. The method presented in this article enhances the capability by adapting to any substrate surface using the self-assembled polyelectrolyte technique. Therefore, results were verified on different substrates, such as PI, PET, and FR-4; satisfactory electric performance for application was obtained. In detail, the inductance of the antenna improved from 300 nH to 20 μH for a monolayer coil, and 600 nH to 50 μH for a double layer coil, depending on the metal thickness.
Chung-Wei Wang, Ming-Huan Yang, Yuh-Zheng Lee, Kevin Cheng, "Hybrid Stacked RFID Antenna Coil Fabricated by Ink Jet Printing of Catalyst with Self-assembled Polyelectrolytes and Electroless Plating" in Journal of Imaging Science and Technology, 2007, pp 452 - 455, https://doi.org/10.2352/J.ImagingSci.Technol.(2007)51:5(452)