Gas plasma process

Following treatments are possible in one and the same equipment:

• Surface activation
• Surface cleaning
• Micro etching
• Plasma polymerisation

The formed reactive particles react in a direct way with the surface without damaging the bulk properties of the treated part. In fact the surface modification is limited to the outermost 10 to 1000A of the substrate. Following process mechanisms are possible on polymer, fluoropolymer and other plastic surfaces:

Surface activation

Is the replacement of weak bondings by high reactive carbonyl, carboxyl and hydroxyl groups. The surface is super active after treatment which is not the case for an untreated polymer surface. Activation can also be performed with amino groups or other functional groups.

Cleaning

Is the removal of the organic contaminants at the surface. Non visible oil films, rest contamination layers, Sicontamination and even partially absorbed contaminations can be removed by plasma cleaning. Particles or anorganic contamination are not removed by plasma, because there is no mechanical interaction. Also visible oil films will not be removed economically by this technique. Therefore it is called super-fine cleaning.

Micro-Etching

Is the process to break down the weak covalent bondings at the surface. The outer most molecular layers are affected by this as is also present contaminant layers which are of the same type of weak C-H bondings. In this way the surface is cleaned, oil films and possible plastic injection moulding additives or weak bondings at the surface are removed to result in a uniform active polymer surface.

Deposition

Is the process where out of gases a thin polymer coating is formed at the surface. By choosing the gas and process parameters these thin coatings can be deposited with various properties or acting as barrier layer.

Cross linking

Is the result of an inert gas action to cross link the polymer surface. A stronger and harder micro surface is formed. In some occasions it leads to more wear or chemical resistance of the polymer.

Through gas selection and parameter setting it can be determined which of these physical processes will be the main one.

For metals and ceramics plasma treatment is mainly a matter of cleaning and deposition as can be understand from the physics described above.