Success Story: CORNET project Metaplast

The project METAPLAST was dedicated to investigate innovative, environment friendly plasma based technologies for deposition of metallic layers on polymer and composite surfaces at atmospheric pressure and ambient temperature.

Polycarbonate substrate after local plasma based infection with catalytic palladium nanoparticles and electroless nickel plating. © Fraunhofer IFAM

Currently, the polymer metallization is a complex procedure requiring several wet-chemical baths for the surface pretreatment and the electro‐ or electroless plating. Thereby, the surface pretreatment is often based on toxic, environmentally critical chemical compounds, e.g. Cr(VI), severely restricted by the EU regulations. Consequently, the industry is highly interested in a suitable alternative processing.

New approaches- the environment friendly atmospheric pressure plasma process

Two technical approaches have been investigated in the framework of METAPLAST to replace the wet-chemical bath pretreatment of the polymer surfaces before their metallization by a dry, environment friendly atmospheric pressure plasma process. Both technologies based on compact, commercially available atmospheric pressure plasma sources, differing in the plasma discharge type. In the first approach, a metallic wire (e.g. palladium) was placed into an arc-like plasma discharge, acting simultaneously as a grounded electrode extension and a source of metallic nanoparticles, that were deposited onto polymer surfaces as catalytic centers for the following electroless plating (e.g. nickel). In the other approach, metal powders (e.g. copper or zinc) were fed directly into an atmospheric plasma torch, where they are melted and then deposited onto polymer substrates as a structured metal layer. The employed plasma sources and process parameters were iteratively adjusted to enable and improve the metallization of various thermosensitive polymers and composites.

The advantages of the atmospheric pressure plasma process

The pulsed arc-like atmospheric pressure plasma process enables a technically simple, cost-efficient infection of polymer surfaces with catalytic palladium nanoparticles prior to the electroless plating. This one-step atmospheric pressure plasma process is dry, inline-capable and thus offers a feasible alternative to the conventional multi-step wet-chemical pretreatments. In addition, the studied technical approach enables a local metallization of different types of polymers, according to technical and design requirements for the target products. The plasma torch based process achieves the metal layers directly from the metal powders with a low melting point (e.g. copper, tin, zinc). Depending on the application, it can be a final coating or a base for further metallization (e.g. by means of electroplating).

Round polymer tube after plasma based infection with catalytic palladium nanoparticles and electroless nickel plating. © Fraunhofer IFAM

Economic benefits – realization of the use of the standard typical polymers

From the economic point of view, both technical approaches represent a feasible alternative to the conventional, wet-chemical pretreatment processing prior to the further metallization, as well to special applications, where polymer components have to be metallized locally and the process and/or raw material costs are relatively high. One example is the Laser Direct Structuring (LDS), in which relatively expensive polymer systems with metalorganic additives are used. Due to the investigated technical approaches, the use of standard technical polymers could be realized.

Project duration: 01.07.2017 – 31.12.2019

Contact person:

David Hoffmann, DFO e.V.
E-Mail: hoffmann@dfo-online.de
Phone: +4921314081112

Participants from Germany

Fraunhofer IFAM – The Fraunhofer Institute for Manufacturing Technology and Advanced Materials, Bremen (research partner)

DFO e.V. – The German Research Association for Surface Treatment, Neuss (project coordination)

Participant from Belgium

MATERIA Nova – The Materials Research Center & Engineering, Mons (research partner)

The research project was carried out in the framework of the Collective Research Networking (IGF / CORNET no. 197 EN). It was supported by the Federal Ministry for Economic Affairs and Energy (BMWi) through the AiF (German Federation of Industrial Research Associations e.V.) based on a decision taken by the German Bundestag.