Working principle of plasma cleaning machine
From: Author:Mark Hardy Publish time:2021-09-08 11:41 Clicks:0
1. Degreasing and cleaning the metal surface
There are often organic substances and oxide layers such as grease and oil on the metal surface. Before sputtering, painting, bonding, bonding, welding, brazing and PVD, CVD coating, plasma treatment is needed to get completely clean and non-oxidized. The surface of the layer. Plasma treatment in this case will produce the following effects:
1.1 Ashing surface organic layer
－The surface will be chemically bombarded (below)
－Partial evaporation of pollutants under vacuum and instantaneous high temperature conditions
－Pollutants are crushed under the impact of high-energy ions and taken out by vacuum
－Ultraviolet radiation destroys pollutants
Because plasma treatment can only penetrate a few nanometers in thickness per second, the contamination layer cannot be too thick. Fingerprints are also applicable.
1.2 Oxide removal
The metal oxide chemically reacts with the processing gas (picture below)
This treatment uses hydrogen or a mixture of hydrogen and argon. Sometimes a two-step process is also used. In the first step, oxygen is used to oxidize the surface for 5 minutes, and in the second step, a mixture of hydrogen and argon is used to remove the oxide layer. It can also be treated with several gases at the same time.
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Usually, printed circuit boards are treated with chemical flux before soldering. After the welding is completed, these chemicals must be removed by plasma method, otherwise it will cause corrosion and other problems.
Good bonding is often impaired by residues from electroplating, bonding, and soldering operations, which can be selectively removed by plasma methods. At the same time, the oxide layer is also harmful to the quality of the bonding, and plasma cleaning is also required.
2. Plasma etching
In the plasma etching process, through the action of the processing gas, the etched object will become a gas phase (for example, when fluorine gas is used to etch silicon, the figure below). The processing gas and matrix material are drawn out by the vacuum pump, and the surface is continuously covered by fresh processing gas. It is not desirable to use materials to cover the etched part (for example, the semiconductor industry uses chromium as a covering material).
The plasma method is also used to etch the plastic surface, and the filling mixture can be ashed by oxygen, and the distribution analysis can be obtained at the same time. The etching method is very important as a pretreatment method when printing and bonding plastics, such as POM, PPS and PTFE. Plasma treatment can greatly increase the bonding wetting area.
3. Etching and ashing
PTFE cannot be printed or glued without treatment. It is well known that the use of active alkaline metals can enhance the bonding ability, but this method is not easy to master, and the solution is toxic. Using plasma method not only protects the environment, but also achieves better results. (The following figure)
The plasma structure can maximize the surface while forming an active layer on the surface so that the plastic can be bonded and printed.
Etching of PTFE mixture
The etching of the PTFE mixture must be carried out very carefully to prevent the filler from being over-exposed, thereby weakening the adhesion.
The processing gas can be oxygen, hydrogen, and argon. It can be applied to PE, PTFE, TPE, POM, ABS and propylene.
4. Surface activation and cleaning of plastics, glass and ceramics
Plastic, glass, ceramics, like polypropylene and PTFE, are non-polar, so these materials must be processed before printing, bonding, and coating. At the same time, slight metal contamination on the surface of glass and ceramics can also be cleaned by plasma. Plasma treatment does not damage the sample compared to burning treatment. At the same time, the entire surface can be treated very uniformly, no toxic fumes will be generated, and hollow and gaped samples can also be processed.
· No need for solvent pretreatment
· All plastics can be applied
· Environmentally friendly
· Occupies a small work space
· low cost
The effect of plasma surface treatment can be verified simply with water, and the surface of the treated sample is completely wetted by water. Long-term plasma treatment (more than 15 minutes), the surface of the material is not only activated but also etched, and the etched surface has the maximum wetting ability. Commonly used processing gases are: air, oxygen, argon, argon-hydrogen mixed gas, CF4, etc.
Five, plasma coating
During coating, two gases enter the reaction chamber at the same time, and the gases converge in a plasma environment. This application is more stringent than activation and cleaning requirements. A typical application is the formation of a protective layer, which is applied to fuel containers, scratch-resistant surfaces, coatings similar to PTFE materials, and waterproof coatings. The coating layer is very thin, usually a few microns, and the affinity of the surface is very good at this time. There are 3 commonly used situations
· Waterproof coating—cyclohexyl
· Coating similar to PTFE material --- fluorine-containing treatment gas
· Hydrophilic coating---ethylene acetic acid
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