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 .

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) .