Low-pressure plasma offers a wide range of options for surface modification, for example fine-cleaning of contaminated components, plasma activation of plastic parts, etching of PTFE or silicon, and coating of plastic parts with PTFE-like layers. This means that low-pressure plasma is used in a great variety of industries when it comes to combining materials or changing the surface characteristics in a directly targeted manner.
What is the design and functionality of low-pressure plasma systems?
In the low-pressure plasma technology, gas is excited in a vacuum by supply of energy. This results in energetic ions and electrons, as well as other reactive particles which constitute the plasma. It can be used to effectively alter surfaces. Three plasma effects are differentiated:
The mode of operation of the plasma is changed by varying the process parameters such as pressure, power, process time, gas flow and gas composition. Thus, several effects can be achieved in a single process step.
Plasma removes release agents (also silicones and oils) from the surface. They are chemically attacked for example by oxygen and converted into volatile compounds. Under-pressure and surface heating cause the release agents or their residues to evaporate in part. The high-energy particles in the plasma disintegrate the molecules of the release agent into smaller molecule fragments which can now be extracted. Furthermore, a "micro-blasting effect" is generated on the atomic level. UV radiation can disintegrate release agents.
Usually, invisible deposits such as greases, oils, silicones, moisture or oxidation layers are found on freshly produced as well as stored products. To ensure perfect coating of these surfaces, they must be PWIS-free (PWIS = contaminated with Paint Wetting Impairment Substances), which can be achieved with plasma cleaning.
Example for a typical process parameter
Flow rate: 500 Watt, process chamber volume: 100 litre, process gas: air or oxygen, pressure: 0.2 - 0.6 mbar, duration: 1 – 5 minutes
A wide range of process gases (e.g. air, oxygen, argon, argon-hydrogen, tetrafluormethane-oxygen) and chemicals (e.g. hexamethyldisiloxane, vinyl acetate, acetone, fluorinated chemicals) are available.
However, there is the following basic rule: The process know-how is the decisive factor. The plasma must match the material so that all desired effects can be achieved in a directly targeted manner.
Component
Product carriers
vacuum chamber
vacuum valve
gas bottle
valve (needle valve (NV), mass flow controller (MFC))
electrode
venting valve
Vacuum pump
High-frequency generator
FAQ Frequently Asked Questions
Can the components be touched after treatment?
Yes, it is safe – we recommend handling it with care and wearing gloves to prevent contamination. This is because plasma removes organic, but not inorganic, contaminants. For example, the sweat from fingerprints contains salts (inorganic contaminants).
How should treated parts be stored?
Following plasma treatment, it is advisable not to store the parts in the open, as they attract dust, organic contamination and moisture.
Sealed parts have a significantly longer shelf life than those stored in the open.
Parts treated by us on a contract basis are packaged in close consultation with the customer, e.g. in certified silicone-free PE bags, ESD packaging or customer-specific packaging material provided to us.
How long can activated parts be stored before further processing?
The curing time of the components depends on the activation time and the material, and varies from a few minutes to several months. It is therefore often necessary to carry out tests on site.
Metals, ceramics, glass and elastomers: a few hours
; plastics (excluding elastomers): several days, weeks or months
Which monomers must not be used?
Due to their highly toxic nature, halogen-containing gases and monomers (F₂, Cl₂, Br₂, I) must not be used with atmospheric plasma!
Can you see through the sight glass?
Yes, depending on the material, it is possible to see inside the vacuum chamber.
Can the chamber door be opened whilst the machine is running?
Under normal circumstances, no – the negative pressure created by the vacuum pulls the door against the chamber housing.
What types of impurities can be removed?
All organic, film-like contaminants up to a size of approximately 1 micrometre can be removed using Diener electronic’s plasma systems.
Can metal chips or dust be removed from components?
Unfortunately, it is not possible to clean metal shavings or dust from the surfaces.
Is low-pressure or atmospheric-pressure plasma the better solution?
When it comes to surface treatment at Diener electronic, there is no such thing as ‘better or worse’, but rather ‘suitable or unsuitable for the application’.
Which vacuum chamber or generator is right for my application?
Depending on your requirements, Diener electronic offers the appropriate vacuum chamber or generator.
What sets your atmospheric and low-pressure plasma surface treatment equipment, units and systems apart from those of your competitors?
The equipment and systems for plasma surface treatment from Diener electronic stand out from those of their market competitors due to:
- over 20 years’ experience with AD and 30 years’ experience with ND in a variety of production environments at our customers’ sites, thanks to the reliability of the technology
- several thousand systems already installed
- compact design
- modern communication protocols are available on PC models, such as Profinet, EtherCAT, etc.
