Metal targets are widely used in vacuum coating industry
The method of vaporizing or sputtering metal, alloy or compound in vacuum to make it solidify and deposit on the coated object (called substrate, substrate or matrix) is called vacuum coating.For example, vacuum titanium plating, vacuum aluminum plating, vacuum chrome plating and so on.
Introduction of vacuum coating technology
Vacuum coating technology is generally divided into two categories,
Physical vapor deposition (PVD) technique
Chemical vapor deposition (CVD) technique
PVD physical vapor deposition technology refers to the method of vaporizing the plating material into atoms or molecules or ionizing them into ions under vacuum conditions and directly depositing them on the surface of the substrate by various physical methods.Most hard reaction films are prepared by physical vapor deposition method, which USES some physical processes, such as thermal evaporation of materials or sputtering of atoms on the surface of materials under ion bombardment, to realize the controllable transfer of atoms from source materials to thin films.Physical vapor deposition technology has the advantages of good film/substrate binding force, uniform and dense film, good film thickness controllability, wide application of target materials, wide sputtering range, thick film deposition, alloy film with stable composition and good repeatability. At the same time, physical vapor deposition technology due to its processing temperature can be controlled under 500 ℃, thus can be used as the final treatment process for high speed steel and carbide class film cutter.Because the physical vapor deposition process can greatly improve the cutting performance of cutting tools, people are racing to develop high performance and high reliability equipment at the same time, but also the application of the field of expansion, especially in the high-speed steel, hard alloy and ceramic tools in the application of a more in-depth study.
Chemical vapor deposition technology is the elemental gas containing a membrane element or compound supply base, with the aid of the gas phase or substrate on the surface of a chemical reaction, on the matrix method of making metal or compound film, mainly including atmospheric pressure chemical vapor deposition, low pressure chemical vapor deposition and has both features of CVD and PVD plasma chemical vapor deposition, etc.
Vacuum coating is an important aspect in the field of vacuum application. Based on vacuum technology, it USES physical or chemical methods and absorbs a series of new technologies, such as electron beam, molecular beam, ion beam, etc., radio frequency and magnetic control, to provide a new process for film preparation for scientific research and practical production.
As is known to all, the surface of some materials, as long as the coating of a thin film, can make the material has many new, good physical and chemical properties.In the 1970s, the main methods of coating on the surface of objects are electroplating and electroless plating.The former is through electrification, electrolyte electrolysis, electrolyte ion plating as another electrode on the surface of the substrate, so the condition of this coating, the substrate must be a good conductor of electricity, and the thickness of the film is difficult to control.The latter is the use of chemical reduction method, must be made up of membrane into a solution, and can quickly participate in the reduction reaction, this coating method is not only the bonding strength of the film is poor, and coating is neither uniform nor easy to control, but also produce a lot of waste liquid, causing serious pollution.Therefore, these two methods, which are called wet coating process, are very limited.
Vacuum coating is a new kind of coating technology developed relative to the wet coating method, which is usually called dry coating technology.
Compared with wet coating technology, vacuum coating technology has the following advantages:
(1) wide selection of film and matrix materials, film thickness can be controlled to prepare functional films with various functions.
(2) the film is prepared under the vacuum condition. The environment is clean and the film is not easy to be polluted. Therefore, the film with good compactness, high purity and uniform coating can be obtained.
(3) the film has good bonding strength with the matrix and the film is firm.
(4) dry coating neither produces waste liquid, nor environmental pollution.
Vacuum coating technology mainly includes vacuum evaporation plating, vacuum sputtering plating, vacuum ion plating, vacuum beam deposition, chemical vapor deposition and other methods.In addition to the CVD method, the other methods have the following common characteristics:
(1) all kinds of coating technologies need a specific vacuum environment to ensure that the movement of vapor molecules formed in the process of heated evaporation or sputtering of film-making materials will not be affected by the collision, blocking and interference of a large number of gas molecules in the atmosphere, and the adverse effects of impurities in the atmosphere will be eliminated.
(2) each coating technology requires an evaporating source or target to convert the evaporating film material into gas.Due to the continuous improvement of source or target, the selection range of membrane materials has been greatly expanded. Whether it is metal, metal alloy, intermetallic compound, ceramic or organic material, all kinds of metal films and dielectric films can be steamed. In addition, multi-layer films can be obtained by steaming different materials at the same time.
(3) vaporized or sputtered film-making materials can be accurately measured and controlled in the process of forming films with workpieces to be plated, so as to ensure the uniformity of film thickness.
(4) each kind of film can be precisely controlled by the fine-tuning valve coating chamber residual gas composition and mass fraction, so as to prevent the oxidation of evaporation materials, reduce the oxygen mass fraction to a minimum, but also filled with inert gas, etc., which is not possible for wet coating.
(5) due to the continuous improvement of coating equipment, coating process can achieve continuous, thus greatly increasing the output of products, and in the production process of no pollution to the environment.
(6) as the film is made under vacuum conditions, the film has high purity, good compactness and bright surface without the need for reprocessing, which makes the mechanical properties and chemical properties of the film better than electroplating film and chemical film.
Vacuum coating method.
(1) vacuum evaporation: the substrate to be coated is cleaned and placed in the coating chamber. After being evacuated, the membrane material is heated to a high temperature to make the vapor reach about 13.3pa and the vapor molecules fly to the surface of the substrate and coagulate to form a film.
(2) cathode sputtering: put need coating substrate opposite the cathode, access to the inert gas such as argon) has to indoor, to keep the pressure is about 1.33 ~ 13.3 Pa, the cathode can then be connected to 2000 v dc power supply, and stimulate the glow discharge, positively charged argon ion collision cathode, make its injection atomic, sputtering out of atoms by membrane is formed on the inert atmosphere to the substrate.
(3) chemical vapor deposition: the process of obtaining thin films by thermal decomposition of selected metal compounds or organic compounds.
(4) ion plating: actually, ion plating is an organic combination of vacuum evaporation and cathode sputtering, which has both technical characteristics.
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