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, oils, waxes, 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) .