真空金屬鍍膜 |超硬鍍膜 |光學鍍膜 |Plasma treatment |Vacuum Components
Plasma treatment
  • Pre-treatment of plastic materials before lacquering
  • Cleaning and/or activation of the substrate surface prior to coating
  • Surface cleaning
Design and size of plasma systems depend on specific applications. They work time-controlled and are usually incorporated in phased production lines.

Their purpose is an environmentally compatible surface activation, ultra-fine cleaning or surface modification of substrates, in particular in the automotive industry.

A major application is plasma pretreatment of plastic substrates before they are coated to increase the paint film's adherence.

Plasma is generated between two large-surface electrodes by a high-power AC glow discharge. This is realised by applying a high voltage up to 4kV.

Major components of plasma systems include:

  • Vacuum chamber upper part, supported by a frame;
  • Vacuum generation by means of a combination from two Roots vacuum pumps and a slide vane rotary vacuum pump;
  • Vacuum chamber lower part, mounted on a lifting unit, with
    • plasma electrodes,roller conveyor
    • rails with substrate carrier locks;
  • Control and power cabinet (automatic, manual and service operation).

Plasma treatment is aiming for various goals as for example:

  • Improved adhesion
  • Removal of the "water skin"
  • Activation of the substrate surface
  • Modification of the substrate surface
  • Cleaning of substrate surfaces

Plasma surface treatment is part of the most applied technologies at VTD. However, it is also used separately prior to lacquering or for cleaning purposes. Cleaning procedures with plasma at low pressure enable microscopically thorough, non-aggressive and mechanically non-destructive removal of absorbed dirt such as oxide layers, organic impurities (oil, wax, lacquer) and micro-organisms (sterilisation) on surfaces and hydrophilising or activation respectively, of plastic surfaces.

Generally speaking, after the evacuation to a processing pressure of approx. 5 x 10e-2 to 9 x 10e-1 mbar, a plasma is ignited. Preferably a glow discharge plasma is used, which can be maintained from a DC as well as an AC source. Processing gases are often air, nitrogen, Argon, oxygen, or combinations of these. The ions and electrons formed in the plasma now impact on the substrate surface. This leads to interaction on the surface, or areas near the surface respectively, between the particles of the plasma and those of the substrates. Result of this interaction can be the removal of particles adsorbed on the surface (e. g. H2O), the activation of surface atoms, the breaking of connections on the substrate surface, modification of the substrate surface through chemical reaction or many other events. Choice of suitable process parameters (type of plasma, pressure, process gas, voltage, current) will decide which of these processes take place preferentially.

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