Topic:

Glossary: C

Here you are going to find explications of important terms in plasma technology:

I,J

P,Q

X,Y,Z

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carbon fibre: Carbon fibres are industrially produced fibres with a very high stiffness and stability, but low ultimate strain. A carbon fibre has a diameter of about 5-8 micrometers. 1,000 to 24,000 of these filaments are commonly bundled to a roving. These rovings are then spooled onto bobbins.
The further treatment e.g. to textile structures is done by weaving machines. As short cut fibres, they can be admixed with polymers and worked into plastic components via extruders and injection moulding machines. Beside this low filament types, there are so-called heavy-two types with 120,000 to 200,000 filaments that are worked into short cut fibres mainly, or also into textile clutches. It is as well possible to manufacture such heavy-tows with sub-tows e.g. in the form 7 x 60,000 single filaments.
Carbon fibres are made from organic educts. Basically, such compounds come into question that can be converted into an infusible and fire-proof interstage and then be carbonised, conserving the form. In this carbonisation treatment (pyrolysis), all elements except for the main component carbon are demerged. The carbon content grows with increasing carbonisation temperature.
Usual carbonisation temperatures lie in the range of 1300-1500°C, which makes the carbon content go up to 96-98 % by weight. Above 180°C, the term „graphitisation“ comes into play. Here, the graphite carbon layers are perfected more and more. The fibres‘ structural multitude with a large band width of properties results from the anisotropy of the graphite layers, determined by the production parameters. In order to be able to use the fibres‘ mechanical properties, they are worked into fibre composites.
Carbon fibres are still relatively expensive in comparison to glass fibres. Therefore, their main use is in aerospace and high-performance sports.
case hardening: Alloying up and hardening; leads to harder border zones with a soft centre at the same time. The residual stresses change massively.
caustic agent: Corrosive substance (see "etching").
cauterisation: see "etching"
cauterization: see "etching"
CF4: Tetrafluormethane, Freon 14, source material for plasma treatment using low-pressure methods. Because of their high toxicity, such layers are not applied under atmosphere.
changing a Teflon surface: see „etching Teflon"
changing the state of the surface: see “surface treatment”
chemical adsorption: see ”chemisorption“
chemical etching: Etching process where the removal of material is due to chemical reactions with the substrate. Galvano-caustic, thus galvanic etching, is done by putting the prepared metal plate into highly diluted nitric acid and connecting it with the positive pole of a galvanic battery; as a result, the non-protected parts of the metal are dissolved very fast.
chemisorption: Chemisorption is a special form of adsorption where, in contrast to physical adsorption, the adsorbate molecule is bound to the substrate by stronger chemical bounds.
chemosorption: see ”chemisorption“
chip packaging: „Packaging“ an electronic chip in a circuit casing. A final cleaning is done by applying plasma, which can e.g. reduce the energy of the bonding process; misbonding is avoided.
chromosulphuric acid: Chromosulphuric acid is a brownish viscous mixture with the formula H2SO4 / CrO3, consisting mainly of concentrated sulphuric acid and about 5% chromate of potassium.
It is classified a fire hazardous substance. The compound was employed for surface treatment due to its strong oxidizing effect. Nowadays it is not used any more because of its containing the extremely toxic and carcinogenic chromium(VI) oxide and the environmental pollution.
circuit board: A circuit board (or printed circuit board, PCB, or printed wiring board, PWB) serves to connect electronic components without using conventional cables.
cleaning: Through the effect of plasma, adsorbates are defragmented and thus turned into short molecules (plasma cleaning). When the molecules are sufficiently short, they can leave the surface permanently. Chemically active gases like oxygen support this very efficiently. Components that can not be defragmented can not be cleaned off (salts, refractory components).
cleaning copper: see „copper“. In hydrogen plasma copper oxides can be decomposed.
cleaning plastics: see „pre-treatment of plastics”
coating facility: see “coating techniques”
coating installation: see “coating techniques”
coating methods: see "coating technologies"
coating plastics: Plastics can be coated by varnishing, low-pressure, or electroplating techniques. In many cases, the low adhesion of a coating on the plastic surface causes a problem. For this reason, the adhesion is improved through a pre-treatment process, like flame impingement, corona, coating with an adhesive agent, or plasma.
coating PTFE: Coating PTFE via plasma polymerisation.
coating techniques: Different coating techniques, atmospheric and in vacuo, are available for the deposit or precipitation of functional layers. The atmospheric plasma polymerization deposits thin layers from the gas phase of an evaporated precursor that was brought into the plasma by a carrier gas. Sputtering is a coating technique for which the material to be applied (e.g. titanium, tungsten carbide...) is embedded in the plasma chamber.
Through application of a high electric potential ions are accelerated so much that they are carried out of the plasma. They hit the sputtering material so hard that atoms are ejected from it, which then fly over to the work piece to be coated and settle on it as a thin layer.
Coating with reactive plasma: besides the process gas, other gases (e.g. methane, ethine, nitrogen) can be admitted. In the low pressure plasma, the electrons have such a high energy level, that chemical reactions are possible. In this case the plasma is called reactive plasma, since the reaction products precipitate on the work piece.
Reactive plasmas can be (and are) combined with sputtering methods (reactive sputtering). The deposited layers are applied in many areas, e.g. optics (anti-reflection layers), product refinement (titan nitride as substitute for gold), armourings, electronics…
coating technology: see "coating technologies"
coatings: Openair®-plasma made it possible for the first time to deposit functional layers on surfaces. This technique is known from vacuum plasma. With plasma polymeric layers, materials obtain new properties, in many cases their operative range is largely extended. Plastics get gasproof, e.g., conductive layers preclude electrostatic charge, hydrophobic layers prevent dirt deposit or facilitate ejection from the mould. Plasma coatings can be either hydrophobic or hydrophilic, depending on the process environment.
colour of the plasma: Photons, emitted through relaxation to less energetic states, indicate typical plasma states. Atmospheric plasmas are yellow, almost independent of the power density.
components of the system: Plasma nozzle; high voltage unit; plasma generator.
composite material: A composite material is a construction material that consists of two or more different materials; the goal is hereby to combine the various advantages of the single materials in the resulting material, and to eliminate their disadvantages. The products can be materials in which one or more components are integrated into a matrix (fibres, metal or ceramic particles…), or materials made up of different layers (compound films, multi-layer plates…) in order to obtain high stability at low weight. Composite materials play a big role with regard to economy of weight.
composite materials: see “composite material”
contact angle: Molecules in a liquid interact with their neighbouring atoms through van der Waals forces, amongst others. Since there are no counterbalanced interactions with other substances in all directions at the interface, there is a net force, the so-called surface tension. If a drop is put onto a solid body, it wettens the surface, if the liquid‘s surface tension is equal to or less than the surface tension of the solid body, or the drop does not wetten the surface if the liquid‘s surface tension is larger than the one of the body. At the contact point of all three phases, the drop forms an angle between body and liquid.
contamination: Contaminations are impurities.
copper: Copper is a good electrical and thermal conductor. Therefore it is the fundamental material for the electric industry. The limited corrosion resistance makes it necessary to provide copper with protective layers. In order to provide for an optimal solderability, certain fluxing agents for lead-free soldering have to be applied.
corrosion: Corrosion is the (chemical) decomposition of materials of high valency through (electro-)galvanic influences caused by the environment and wear.
cross-cut test: After varnishing, the varnish layer on a plastic substrate is carved with grid-shaped cuts. Now the adhesion can be tested by definedly pushing adhesive tape onto the grid structure and removing it in one fell swoop. If varnish rests stick at the tape, then the test was negative and the adhesion insufficient. This so-called cross-cut test is a measure of adhesiveness of varnish layers on plastics.
CVD coating: Chemical vapour deposition: on the heated surface of substrate, a solid component is deposited from the gas phase due to a chemical reaction. This requires that there are volatile compounds of the layer components which deposit a solid layer at a certain reaction temperature. The CVD process is distinguished by at least one reaction on the surface of the work piece to be coated. There must be at least two gaseous reactants and minimally two end-products in this reaction, of which at least one has to be gaseous and one solid.
In order to favour the surface reaction above competing reactions in the gas phase and such to avoid the formation of solid particles, CVD processes are mostly executed with reduced pressure (0,01-10 hPa, typically).
A specific characteristic of the CVD method is the conformable layer deposition. In contrast to physical processes, the chemical vapour deposition allows coating of complex three-dimensionally shaped surfaces as well. This way e.g. finest cavities in wafers or even hollow parts on their inside can be coated uniformly.
Besides the designation PACVD, in the English literature the term PE-CVD, plasma enhanced CVD, exists as well.