Vacuum arc deposition by using a Venetian blind particle filter
Vacuum arc deposition is a commonly used technology for the deposition of hard coatings and all kinds of metals. The vacuum arc discharge is a simple source of highly ionized metal plasma. Films with a very dense structure and an excellent adhesion can be produced because of the high ion energy inside the vacuum arc plasma. But also a certain number of macroparticles is emitted and deposited. That is why a great number of particle filters was developed in the past, but no one of them has larger industrial usage. A very simple but effective filter design is the Venetian blind filter. The macroparticles are shielded from the substrate but the plasma is guided through the filter by means of magnetic and electric fields. With this type of filter, films with a dramatically reduced number of droplets can be produced. A plasma transmission through the filter of approximately 20% could be reached. Micrographs of the film surfaces were analyzed by a certa in method to investigate the droplet distribution in number and size for different materials. A reduction of the droplet number down to 10%1% of the unfiltered case could be determined. A filter unit for using at the most common vacuum arc deposition machines was developed and tested and is now available. The filter does not reduce the deposition area, so the standard deposition processes can be used furthermore. The filter is in use for metal deposition. A process for the production of hard coatings as metal nitride films is under development. Such particle reduced coatings are especially appropriate for the surface protection of tools with high demands of surface smoothness and precision, for example forming tools for high precision parts. The fields of application of the vacuum arc technology can be enlarged by means of this type of plasma filter. The advantages of this filter are the good handling properties and the possibility of retrofitting existing arc coaters.