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What is the so-called resistance evaporation source evaporation method in the evaporation coationg machine?

What is the so-called resistance evaporation source evaporation method in the evaporation coationg machine?

2021-03-28

What is the so-called resistance evaporation source evaporation method in the evaporation coationg machine?

In the evaporation coationg machine, the so-called resistance evaporation source evaporation method is to use high melting point metals such as tantalum, molybdenum, tungsten, etc., to make an evaporation source of appropriate shape, load the material to be evaporated on it, and let the air flow through to directly evaporate the material. Heat evaporation, or put the material to be evaporated into alumina, beryllium oxide and other crucibles for indirect heating and evaporation. This is the resistance heating evaporation method.






For my country's ion plating, it is a new development of vacuum coating technology. In ordinary vacuum coating (also called vacuum evaporation), the workpiece is clamped in a vacuum hood. When the high-temperature evaporation source is energized and heated, the material to be plated, that is, the evaporation material, melts and evaporates.


As the temperature rises, the evaporated material particles obtain a certain ion plating kinetic energy, then slowly rise along the line of sight, and finally adhere to the surface of the workpiece to form a film. The coating formed by this process does not have a strong chemical bond with the surface of the part, and there is no diffusion connection. Adhesion is poor. Sometimes, it's like dust falling on the table, which will be wiped off by hand.


However, the ion plating process is different. Although it is also carried out in a vacuum hood, the coating process is realized in the form of charge transfer. That is to say, the particles of the evaporated material act as positively charged high-energy ions, which are injected into the surface of the workpiece at a high speed under the attraction of the high-voltage cathode (ie, the workpiece). It is equivalent to a high-speed bullet, which can penetrate deeply into the substrate and form a solidly adhered diffusion coating on the workpiece. The technological process of ion plating is as follows: the evaporation source is connected with the anode, and the workpiece is connected with the cathode. When a high voltage direct current of 3 to 5 kilovolts is applied, an arc discharge is generated between the evaporation source and the workpiece.


Since the vacuum cover is filled with inert argon, part of the argon is ionized under the action of the discharge electric field, thereby forming a plasma dark zone around the cathode workpiece. The positively charged argon ions are attracted by the negative high voltage of the cathode and violently bombard the surface of the workpiece, causing particles and dirt on the surface of the workpiece to splash out, so that the surface of the workpiece to be plated can be fully cleaned by ion bombardment. Then, the AC power supply of the evaporation source is connected, and the evaporation material particles melt and evaporate, and enter the glow discharge area for ionization. Under the attraction of the cathode, the positively charged evaporation material ions and argon ions rush toward the workpiece. When the number of evaporating material ions on the surface of the workpiece exceeds the number of splashing ions, they will gradually accumulate to form a coating firmly attached to the surface of the workpiece. This is a simple process of ion plating.



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