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 substrates, 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.

Ink-jet printing technology enables self-aligned mould patterning for electroplating in a single step

“…For certain high frequency frequency applications, these ripples may lead to losses. However, to investigate these ripples in respect to losses, one could make a reference comparison as performed by Sridhar [8,26]. Further investigation is beyond the scope of this paper.…”

Surface Treatments for Inkjet Printing onto a PTFE-Based Substrate for High Frequency Applications

“…However, the focus of their work in modifying the substrate surface characteristics was to improve the adhesion between the metal traces and the substrate. 20 Consequently substrate surfaces which were sufficiently rough, with sufficiently high surface energies were preferable. 20 In contrast, the aim of this paper is to achieve lower surface roughness for a typical high frequency laminate intended for the inkjet printing process, with the goal of improving the interconnect losses at higher frequencies.…”

“…20 Consequently substrate surfaces which were sufficiently rough, with sufficiently high surface energies were preferable. 20 In contrast, the aim of this paper is to achieve lower surface roughness for a typical high frequency laminate intended for the inkjet printing process, with the goal of improving the interconnect losses at higher frequencies. Specifically, this paper seeks to investigate suitable surface modification techniques to achieve the aim.…”

“…Sridhar et al also considered a plasma etching process to modify the surface of a high frequency substrate, through a design of experiment (DoE) approach to vary the plasma etching parameters. However, the focus of their work in modifying the substrate surface characteristics was to improve the adhesion between the metal traces and the substrate . Consequently substrate surfaces which were sufficiently rough, with sufficiently high surface energies were preferable .…”