How does the plasma cleaning of metals work?

Some treatment goods are with fats, oils, waxes, silicones (not LABS-free)  and other organic and inorganic contaminants (also oxide layers) covered.

Some treatment goods are with fats, oilswaxes, silicones (not LABS-free and other organic and inorganic contaminants (also oxide layers) covered .

For certain applications it may be necessary to achieve absolutely clean and oxide-free surfaces e.g. B.

  • before  sputtering
  • before  painting
  • before  gluing
  • before  printing
  • before PVD and CVD coating
  • for  special medical applications
  • with analytical sensors
  • before bonding
  • before soldering circuit boards
  • for switches etc.

The plasma cleaning works in two different ways:

1. It removes organic layers

  • These are e.g. B. chemically  attacked by  oxygen  and air  .
  • Due to the negative pressure and the superficial heating of the low-pressure plasma  ,  some of the contaminants evaporate . In the case of atmospheric pressure plasma, these are blown away from the surface by the excess pressure.
  • Due to the high-energy particles in the plasma, the impurities are converted into  smaller, stable molecules  and can be sucked away / transported away.
  • Also,  UV radiation  can destroy the contamination and cause its detachment from the surface.

The impurities may only be  a few micrometers  thick, since the plasma is only able to remove a few nm / s.

Fats contain e.g. B. lithium compounds. Only the  organic components can be  removed from them. The same is true for  fingerprints , so that is  wearing  of  gloves  is recommended.

2. Reduction of oxides

  • The metal oxide reacts  chemically  with the process gas. Pure hydrogen or a mixture with argon or nitrogen is used as the process gas.

With low-pressure plasma, it is also possible to run the processes in  two  stages. For example, the items to be treated are only oxidized with oxygen for 5 minutes  ; then they  are  reduced for 5 minutes with argon-hydrogen (e.g. mixture of 90% argon and 10% hydrogen) .