Fabrication of RF Circuit Structures on a PCB Material Using Inkjet Printing-Electroless Plating and the Substrate Preparation for the Same

Abstract

This paper describes the optimisation of the surface characteristics of a high-frequency substrate material widely used in the PCB (printed circuit board) industry by means of CF 4 /O 2 plasma etching, in order to make it suitable for the fabrication of RF (radio frequency) circuit structures by a combination of inkjet printing and electroless plating. A statistical DoE (design of experiments) based on a CCRD (central composite rotatable design) was used to systematically vary the plasma etching parameters and explore the characteristics of the etching process. This experimental design yielded 31 substrates, all of which were assessed in terms of surface energy, surface roughness and adhesion. Out of these sub-strates, 5 were identified as having the most favourable surface characteristics. Finally, RF circuit structures in the form of S-band filters were fabricated on these substrates using an inkjet printing-electroless plating combination, and the RF performance of these structures was characterised and compared.