PRINCIPLE ----------------------------------------------------------------------------------------------------

Plasma technology involves placing the materials to be treated into a vacuum chamber, into which a process gas such as argon or oxygen is injected at low pressure (between 0.01 and 1 mbar). Supplying energy in the form of an electric field with a frequency varying between continuous and microwave frequencies causes the gas to decompose partially, resulting in the state of plasma. The species resulting from this decomposition are composed of ions, electrons and various radicals.

The radicals thus created are extremely reactive. They may react with each other and with the surrounding surfaces, including the surface of the material that is being treated. They have thus a finite lifetime after which they are recombined or fall once again into their fundamental energy state. Surface reactions then occur that lead to a functional modification of the surface. Naturally, these reactions depend on the type of process gas used.

Among the species generated by the plasma are metastables, which have long lifetimes and therefore have a very wide range of action. Parts with complex forms and large parts can thus be treated.

This technique can be used to treat surfaces either inside or outside the plasma. This is known as post-discharge treatment.

The exposure time can vary from a few seconds to a few minutes depending on the process. Very little gas is used during these processes.

APPLICATIONS -------------------------------------------------------------------------------------------------

The main interactions between the species generated by the plasma and the surface can be classed into 3 categories:

Surface activation and modification :
New specific chemical functions are created on the surface through the rupture of polymer chains, ejection of certain types of atoms and the grafting of certain atoms known for their particular properties. These functions also confer new properties on the surface: oxidation, fluorination, etc. The surface energy is thus completely modified.

The main applications are : Surface activation: (surface energy > 65 mJ/m²) increasing adhesion (polymers, ceramics, metals, etc.) prior to bonding, over moulding, painting. Hydrophobic treatment: surface energy <15 mJ/m².

Etching and cleaning:
The plasma species may react with impurities on the surface and transform them into volatile compounds. Depending on the nature of the process gas used, it is possible to etch a considerable number of materials.

The main applications are:
Etching of substrates in the microelectronics industry
Cleaning of polymer, metal, inorganic part finishes, etc.

The film deposition:
Certain plasma radicals condense on the surface of the product to form an amorphous thin film. Depending on the process gas used, the film obtained may have special properties: gas diffusion barrier, hardness, hydrophilic qualities, etc.…

Many sectors benefit from these applications:
Packaging, optics, automobile industry, aeronautics, electronics, etc.