In printed circuit board manufacturing, power electronics and other semiconductor processes, clean and functional metal surfaces are essential for soldering, contacting and bonding processes. To achieve resource-efficient production without the use of chemical etching agents or vacuum technology, manufacturers and suppliers of electronic components rely on plasma systems suitable for in-line integration.
Due to their high electrical conductivity, copper and silver in particular are used in the semiconductor industry. Oxidation under normal ambient conditions can lead to problems with soldering and electrical conductivity. Whilst the problematic oxide and sulphide layers can be removed using conventional methods, these are often technically complex: energy-intensive thermal reduction processes or low-pressure treatments involving the associated vacuum technology.
Our research partner, INNOVENT e.V., has carried out investigations using the TIGRES CAT system into the targeted reduction of sulphide and oxide layers on silver and copper surfaces. The standard plasma system used for this purpose was operated with a forming gas comprising 95 per cent nitrogen and 5 per cent hydrogen.
Forming gas is a commonly used process gas which is employed in industry, particularly as a shielding gas in the hot working of metals, and can easily be connected to our CAT and T-SPOT series plasma systems in place of standard compressed air.
The copper oxide and silver sulphide layers examined were effectively reduced by the plasma treatment. Not only was the removal of the dark oxide layer, revealing a shiny copper surface once more, visible to the naked eye, but the surface resistance also returned to a level close to that of the original metallic copper layer.
The sulphide layer was also significantly reduced in the silver layers. As with the oxide layers, a shiny surface was observed following plasma treatment. XPS analyses also confirmed the restoration of a functional silver surface.
Further details and information can be found in the original publication by INNOVENT e.V. Technologieentwicklung Jena:
A brief summary has been published in a press release on idw-Online.
The original publication appeared as a WOMag article entitled “Atmospheric pressure plasma for the reduction of metal oxide or metal sulphide-containing surfaces” [Raveena Pradeep, Oliver Beier, Klaus Vogelsang, Adrian Würzl and Andreas Pfuch, Jena] and can be found at https://www.wotech-technical-media.de/womag/ausgabe/2026/06/ 22_beier_plasma_06j2026/22_beier_plasma_06j2026.php
