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.
