Surface Modifications of PCB-Based Plasma Sources Induced by Atmospheric Plasma: A Comparative Study of Dielectric and Electrode Materials

TL;DR

This study compares how different dielectric and electrode materials in plasma sources resist atmospheric plasma exposure, revealing that Al2O3 and silver are most resistant, while FR-4 and copper degrade more rapidly.

Contribution

It provides a comparative analysis of material resistance to atmospheric plasma, highlighting the importance of material selection for plasma device durability.

Findings

Al2O3 shows highest resistance with minimal surface changes

PTFE undergoes oxidation, forming new chemical groups

Silver electrodes are most resilient to plasma exposure

Abstract

The study investigated the effects of atmospheric plasma on various dielectric materials (FR-4, PTFE, Al$_2$O$_3$) and electrode materials (copper, silver, gold-plated copper) used in surface micro-discharge plasma sources. XPS and laser microscopy were used to analyze changes in surface properties and chemical composition after 10 hours of plasma exposure. Al$_2$O$_3$ showed the highest resistance, with no significant changes in Al/O ratio or oxidation state. PTFE underwent oxidation, with fluorine substituted by oxygen, forming carbonyl, hydroxyl and aldehyde groups. FR-4 showed the most substantial changes, with etching of the epoxy matrix exposing glass fibers. This was in line with the XPS results, which show a higher O/C-ratio, less epoxy groups and higher nitrogen signals. Silver electrodes were most resilient, with sintered particles redistributed across the Al$_2$O$_3$ surface. Copper and gold-plated copper electrodes were more susceptible to oxidation and degradation, especially in areas exposed to plasma filaments. The results highlight the importance of carefully selecting materials based on resistance to plasma exposure and compatibility with the application.