Lectures on TCM. Work order

Hello, friends.

So, the story began a little earlier, when we got a vacuum chamber. Her path to us was not close and can be described in a separate story, but this, as they say, is "a completely different story." I can only say that even earlier it brought people some benefit in one of the laboratories of the University of Göttingen.

The first thing we started to use the vacuum chamber with was to try out the method of thermal deposition of metals on substrates. The method is simple and as old as the world. The target of the sputtered metal, for example, silver, is placed in the molybdenum crucible. Placed around it a heating element. We used tungsten-rhenium alloy wire, which was wound in a spiral.

The complete thermal spray device looks like in the following way:

Tooling for thermal spraying of metals. a. Assembled (protective screen and valve removed). Designations: 1 – crucible, 2 – heating element, 3 – steam line, 4 – current lead, 5 – thermocouple, 6 – sample frame.

After the current is passed (it goes into the vacuum chamber through the pressure seals), the spiral heats up, heats the boat, in which the target material also heats up and evaporates. A cloud of metal vapor rises along the steam pipeline and envelops the body, on which it is necessary to deposit a metal film.

The method itself is simple and good, but there are also disadvantages: high energy consumption, it is difficult to place surfaces (bodies) in the vapor cloud on which the film needs to be deposited. Adhesion is also not the best. applied to different materials, including for metals, glass, plastic, etc. Basically - for research purposes, since we only mastered vacuum equipment.

Now it's time to talk about the vacuum system. The experiments were carried out in a vacuum chamber equipped with a vacuum system consisting of a rotary fore-vacuum and turbomolecular pump and providing a residual pressure of 9.5 10 -6 - 1.2 10 -5 mm Hg.
If at first glance it seems that it is not difficult, then in fact it is not. First, the chamber itself must have the tightness necessary to maintain a high vacuum. This is achieved by sealing all functional flanges and openings. The upper and lower flanges-covers have the same, in principle, rubber seals, as well as the smallest holes designed for installing windows, sensors, devices, pressure seals and other flange covers, only with a much larger diameter. For example, for reliable sealing of such a hole

Requires flange, gasket and fasteners as shown in this photo.

This sensor measures the vacuum in the chamber, the signal from it goes to the device, which shows the level of high vacuum.

Vacuum required level(eg 10-5 mmHg) is achieved as follows. First, a low vacuum is pumped out by a fore-vacuum pump to a level of 10-2. Upon reaching this level, a high-vacuum pump (turbomolecular) is switched on, the rotor of which can rotate at a speed of 40,000 rpm. At the same time, the foreline pump continues to work - it pumps out pressure from the turbomolecular pump itself. The latter is a rather capricious unit and its “thin” device played a certain role in this story. We use Japanese Osaka vacuum turbomolecular pump.

The air pumped out from the chamber with oil vapors is recommended to be discharged into the atmosphere, since fine droplets of oil can “splatter” the entire room.

Having dealt with the vacuum system and worked out the thermal deposition, we decided to try another method of film deposition - magnetron. We had a long experience of communicating with one large laboratory, which applied functional nanocoatings to us for some of our developments using the magnetron sputtering method. In addition, we have fairly close ties with some departments of MEPhI, Moscow Higher Technical School and other universities, which also helped us to master this technology.

But over time, we wanted to use more of the possibilities that the vacuum chamber provides.

Soon we had a small magnetron, which we decided to adapt for film deposition.

It is the magnetron vacuum method of deposition of thin metal and ceramic films that is considered one of the most productive, economical and easy to operate among all physical deposition methods: thermal evaporation, magnetron, ion, laser, electron beam. The magnetron is installed in one of the flanges, which is convenient for use. However, this is still not enough for deposition, since it requires a certain voltage, cooling water, and gases to be supplied to ensure plasma ignition.

Theoretical excursion

Simplistically, the magnetron is arranged as follows. On the base, which also serves as a magnetic circuit, strong magnets are placed, which form a strong magnetic field. On the other hand, the magnets are covered with a metal plate, which serves as a source of the sputtered material and is called the target. Potential is applied to the magnetron, and earth is applied to the body of the vacuum chamber. The potential difference formed between the magnetron and the chamber body in a rarefied atmosphere and magnetic field leads to the following. An atom of the plasma-forming argon gas falls into the action of magnetic and electric field and ionized under their action. The ejected electron is attracted to the chamber body. A positive ion is attracted to the magnetron target and, having accelerated under the action of magnetic field lines, hits the target, knocking out a particle from it. It flies out at an angle opposite to the angle at which the ion of the argon atom hit the target. A metal particle flies away from the target towards a substrate located opposite it, which can be made of any material.

Our university friends made a DC power supply with a power of about 500 W for this magnetron.

We also built a gas supply system for the plasma-forming argon gas.

To accommodate the objects on which the films will be sprayed, we have built the following device. There are technological holes in the cover of the chamber, in which various devices can be installed: electrical power feedthroughs, traffic pressure feedthroughs, transparent windows, sensors, and so on. In one of these holes, we installed a pressure seal of a rotating shaft. Outside the chamber, we brought rotation to this shaft from a small electric motor. By setting the speed of rotation of the drum on the order of 2-5 hertz, we have achieved good uniformity in the application of films around the circumference of the drum.

From below, i.e. inside the chamber, we mounted a light metal basket on the shaft, on which objects can be hung. In a stationery store, such a standard drum is sold as a waste basket and costs about 100 rubles.

Now we had in stock almost everything needed for film deposition. We used the following metals as targets: copper, titanium, stainless steel, aluminum, copper-chromium alloy.

And they started to dust. Through the transparent windows into the chamber, one could observe the plasma glow on the surface of the magnetron target. In this way, we controlled “by eye” the moment of plasma ignition and the deposition intensity.

The way to control the thickness of the spraying came up with a fairly simple one. The same piece of foil with the measured surface area was placed on the drum, and its mass was measured before and after the spraying session. Knowing the density of the deposited metal, the thickness of the deposited coating was easily calculated. The coating thickness was controlled either by changing the deposition time or by adjusting the voltage at the magnetron power source. This photo shows a precision balance that allows you to measure the mass of samples with an accuracy of ten-thousandths of a gram.

We put on various materials: wood, metals, foil, plastics, paper, polyethylene films, fabrics, in short, everything that could be placed in the chamber and attached to the drum. Basically, we focused on obtaining decorative effects - changing the color or tactile perception of the surface. On these samples of organic and inorganic origin, you can see the difference in color before and after applying different metal films.

Even more clearly the difference in color before and after spraying is visible on fabrics and films. Here is the right piece of the usual polyethylene film- not sprayed, but the left one is covered with a layer of copper.

Another effect that can be used for various needs is the conductivity of thin films on substrates. This photo shows the resistance of a piece of paper (in ohms) with a thin layer of titanium just over a micron thick.

For further development, we have chosen several directions. One of them is to improve the efficiency of film deposition by magnetrons. We are going to "swing" at our own development and manufacture of a more powerful magnetron with a height of a camera and a power 2 times greater than that shown in this essay. We also want to test the technology of reactive deposition, when, together with the plasma-forming gas argon, oxygen or nitrogen are fed into the chamber, and during the deposition of films on the surface of the substrate, not pure metal films are formed, but oxides or nitrides, which have a different range of properties than pure ones. metal films.

To change the basic properties of metal, plastic, ceramic or other materials, a metallization process can be carried out. Vacuum plating is one of the most common methods of metal deposition, due to which a protective surface is formed with certain properties that are unusual for the substrate. Let us consider the features of vacuum metallization technology in more detail.

Technological process of vacuum metallization

The considered method of processing parts has been used for a long time. Vacuum metallization is a process based on the evaporation and deposition of material condensate onto a substrate. Among the features of this process, the following points should be noted:

1. The versatility and high efficiency of the method determines its wide distribution. In the future, more extensive use of the process of metallization of polymeric and other materials is expected. The development of the processing method under consideration is associated with the improvement of the equipment used. So modern vacuum plants allow you to automate the procedure for metallization of parts, improve the quality of the surfaces obtained, and reduce the cost of the products obtained. The only obstacle to the development of this industry is high price modern equipment and the difficulties encountered in its installation, use and maintenance.
2. The technological process of vacuum metallization is quite complicated, the result reflects the condition of each stage. When the material that is to become the future coating is heated, it undergoes a large number of changes. An example is that the coating initially evaporates, then adsorption occurs, after which condensation occurs and crystallization to fix the layer on the surface.
3. The quality of the result obtained is affected by a sufficiently large number of factors, among which we note the physicochemical qualities of the substrate, the conditions of metallization that can be maintained.
4. The formation of a deposited coating during metallization occurs in two main stages: the transfer of energy and mass from the source to the surface and their distribution over the entire substrate.

Vacuum metallization plant

Vacuum plating technology is suitable for processing the most various parts. An example is roll materials made of plastic or plastic.

Typical technology consists of several main stages:

1. Preparation of the part for the ongoing process. Among the requirements that apply to the part, it is possible to note the absence of sharp edges and hidden areas from the direct ingress of condensate. Vacuum plating of plastics or other materials is possible only if the shape of the workpiece is not complex.
2. Degreasing and drying. Some materials may contain a large amount of adsorbed moisture, such as polymers. Drying is carried out at a temperature of about 80 degrees Celsius, the holding time is 3 hours. Degreasing is already carried out in a vacuum chamber at preparatory stage. The degreasing technology provides for unwinding the roll and exposure to a glow discharge. As the results of the conducted studies show, annealing at the stage of polymer preparation favorably affects the structure of the material under consideration, since the index of internal stress is significantly reduced. Vacuum roll plating should be carried out with the exception of the possibility of wrinkling at the stage of preparation of the workpiece, since they can be called defects.
3. The stage of activation surface treatment. Vacuum metallization of plastic and other materials involves surface activation. In this case, the most various methods activations, the choice of which depends on the qualities of the material itself. This process designed to increase the adhesion index of the surface.
4. Applying a substance to a surface. In most cases vacuum metallization aluminum or other alloy passes using the resistive evaporation method under the condition of exposure to temperature. Tungsten evaporation technology is used much less frequently, as it involves heating the medium to a low temperature, as a result of which the evaporator is destroyed in the shortest possible time.
5. The final stage concerns the quality control of metallization. If the applied layer is decorative, then in most cases quality control consists in recording optical properties. In addition, attention is paid to the uniformity of spraying, the strength of the connection of the surface layer and structure.

The result of vacuum metallization

The technology of vacuum metallization of plastics and other materials is complex; in order to obtain a high-quality surface, all processing conditions must be observed.

Scope of vacuum metallization

When considering the scope of this technology, we note that it can be used to coat the following materials:

1. plastic;
2. aluminum;
3. various polymers;
4. glass;
5. ceramics;
6. metals.

The most widespread is the metallization of plastic products. This is due to the fact that in this way a product made of cheap plastic acquires more attractive appearance.

If you need to save on production, but at the same time ensure high decorative qualities, aluminum or other metals are sprayed.

An example is the manufacture of car parts that are used in interior decoration. Chinese and Japanese automakers have long begun to use the technology in question to reduce the cost of their cars. At the same time, the use of vacuum metallization is carried out not only in decorative purposes, due to the higher strength of the surface layer, the parts last longer, the degree of friction is reduced. However, metallization does not improve the strength of the entire polymer product.

This technology is also used in the production of various things used in everyday life, inexpensive jewelry. The wide distribution is due to the fact that the surface layer does not wear out over a long period of operation. Previously used spraying technologies did not provide for the creation of high adhesion between the substrate and the decorative coating.

Advantages of vacuum plating

This technology has a fairly large number of advantages:

1. Ability to automate the process. As previously noted, the equipment being installed makes it possible to automate the process under consideration as much as possible, thereby reducing the likelihood of defects due to human error.
2. The resulting surface will be uniform, which provides an attractive appearance and high performance details. As a rule, after metallization, the surface of polymers resembles polished metal.
3. If the spraying technology is followed, the surface layer can last for many years. The quality control stage makes it possible to eliminate the possibility of chipping off the surface sprayed layer or its rapid abrasion.
4. In this way, it is possible to give the product a variety of qualities: corrosion resistance, electrical conductivity, reduce the degree of friction, increase the surface hardness. In most cases, vacuum metallization is used to decorate parts.
5. The main performance properties of the substrate remain virtually unchanged. During the drying stage, the material is heated to a temperature that will not lead to a restructuring of its structure.
6. The technology can be applied at the final stage of part manufacturing. At correct execution it is not necessary to carry out the finalization of the machined parts at all stages.

If we consider the disadvantages, then it should be noted the complexity of the process of transition of the sprayed substance from one state to another. It is possible to ensure the required conditions only during installation special equipment. Therefore, with your own hands, carry out vacuum metallization with the provision High Quality surface is almost impossible.

In conclusion, we note that even a small thickness of the metal layer on polymer coating It is able to give polymers a metallic sheen and electrical conductivity, protect the structure from exposure to sunlight and atmospheric aging. In this case, the created layer can have a thickness of only a few fractions of a millimeter, due to which the weight of the product remains practically unchanged. In addition, vacuum metallization makes it possible to obtain completely unique material, which will have flexibility and lightness, as well as the properties that are inherent in metals.

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Process vacuum deposition consists of a group of methods of deposition of coatings (the thinnest films) in a vacuum sphere, in which compensation comes out by the action of direct condensation of the vapor caused by the element.

There are the following stages of vacuum deposition:

• Production of gases (steam) from components that produce compensation;
• Vapor transport to the substrate;
• Accumulation of vapors in the substrate and the creation of sputtering;

The list of vacuum deposition methods includes the following scientific and technical movements, and in addition, fast types of these operations.

List of thermal spray methods:

• Evaporation with a galvanic beam;
• Evaporation with a laser beam.

Vacuum arc evaporation:

• The raw material is evaporated in the cathode spot, an electric arc is responsible for this;
• Epitaxy using a molecular beam.

Ion scattering:

• The original raw materials are sputtered by ion beam bombardment and impact on the substrate.

Application

Vacuum compensation is used to develop in-plane components, devices and mechanisms of operational coatings - conductors, insulators, wear-resistant, corrosion-stable, erosion-resistant, anti-friction, anti-seize, barrier and others. These manipulations are used to apply decorative coatings, for example, when assembling watch movements with a gilded surface and coating spectacle frames. One of the main operations of microelectronics, where it is used for the purpose of applying conductive layers (metallization). Vacuum compensation is used to extract optical coatings: antireflection, reflective, filtering.

A chemically active gas, for example, acetylene (for the purpose of coatings that introduce carbon), non-metal, air space, can be introduced into the scientific and technical field. Chem. the response in the plane of the substrates is triggered by heating, or by ionization and dissociation of gases in one of the configurations of the gas system.

Thanks to the use of vacuum deposition methods, a coating is obtained, the thickness of which can be several angstroms or reach many microns, as a rule, as a result of deposition, the surface does not require additional processing.

Vacuum deposition methods

The fate of each of the grains of the sprayed component upon impact with the surface, the constituents, depends on its energy, plane temperature and chemical. affinities of film elements and constituents. Atoms or molecules that have reached the plane have every opportunity either to be reflected from it, or to be adsorbed and, after a specific period of time, to leave it (desorption), or to be adsorbed and create a condensate in the plane (sealant). At high grain energies, high temperature plane and insignificant chem. affinity, the element is reflected by the surface. The temperature of the plane of the part, above which all particles are reflected from it and the layer is not formed, is called the serious vacuum deposition temperature, its significance depends on the nature of the elements of the film and the plane of the components, and on the state of the plane. At extremely low flows of evaporable elements, including the case when these particles are adsorbed in the plane, but rarely occur with other similar particles, they are desorbed and cannot create nuclei, that is, the layer does not grow at all. The serious frequency of the flow of evaporative components for a given temperature of the plane is the lowest density at which the particles condense and form a cover.

Vacuum plasma spraying

According to this method, thin films with a thickness of 0.02-0.11 μm are obtained as a result of heating, volatilization and deposition of the component on the substrate in a separated chamber under compressed gas pressure in it. In the chamber, with the help of a vacuum pump, the greatest effect of residual gases is created, approximately 1.2x10-3 Pa.

The working chamber consists of a metal or glass hood with an external water cooling concept. The chamber is located in the central plate and creates a vacuum-protected connection with it. The substrate in which the deposition is carried out is fixed on the holder. A heater is adjacent to the substrate, which heats the substrate up to 2400-4400 °C in order to improve the adhesion of the deposited film. The capacitor includes a heater and a source of the sprayed component. The transition damper closes the vapor flow from the evaporator to the substrate. The compensation lasts for the duration of the time the shutter is not slammed.

To heat the sprayed component, 2 types of evaporators are mainly used:

• Direct-heated multiwire or two-ribbon heat exchanger made from tungsten or molybdenum;
• Electron-radial evaporators with heating of the evaporated component by galvanic bombardment.

Explosive volatilization is used to deposit films from multicomponent elements. In this case, the condenser is heated up to 15000 ° C and sprinkled with powder from a mixture of evaporable elements. By a similar method, it is possible to acquire composite coatings.

Some popular plating elements (for example, gold) have poor adhesion to silicon and other semiconductor elements. In the case of low-quality adhesion of the evaporative element to the substrate, evaporation is laid in 2 layers. First, a layer of an alloy is applied over the substrate, which has excellent adhesion to the semiconductor substrate. Then the main layer is sprayed, in which the adherence to the sublayer was previously excellent.

Ion-vacuum deposition

This method consists in sputtering the element of the causative component present in front of the negative potential due to the bombardment by ions of an inactive gas that occur during the excitation of a glow discharge inside the vacuum deposition installation.

The material of a negatively charged electrode is sprayed under the influence of ionized atoms of an inactive gas hitting it. These sputtered transition atoms are deposited on top of the substrate. The main advantage of the ion-vacuum deposition method is the absence of the need to heat the evaporator up to a high temperature.

Mechanism of occurrence of the overflowing discharge. The decaying discharge is monitored in chambers with low gas pressure between 2 metal electrodes, to which high voltage is applied up to 1-3 kW. In this case, the negative electrode is usually grounded. The cathode is a target with a sputtered element. The air space is preliminarily evacuated from the chamber, then gas is started up to a pressure of 0.6 Pa.

The glow discharge got its name due to the presence of the so-called glow glow in the target (cathode). This radiance is due to the large drop in capacity in the tight reservoir of space charge near the cathode. Adjacent to the TC zone is the area of ​​the Faraday dark spot, which passes into the positive column, which is an independent part of the discharge, completely unsuitable from other layers of the discharge.

Near the anode, in addition, there is a small layer of space charge, called the anode layer. Another element of the interelectrode gap is captured by the plasma quasi-neutral. In a similar way, a raster glow from alternating dark and light stripes is tracked in the camera.

For the passage of current between the electrodes, a stable emission of cathode electrons is necessary. This emission can be induced under duress by heating the cathode, or by irradiating it with ultraviolet light. This kind of discharge is non-self-sustaining.

Vacuum coating of aluminum

In some cases, especially when spraying plastic, aluminum plating is used, and this metal is a fairly light raw material and not wear-resistant in any way, in this case certain special scientific and technical methods are needed. The user needs to understand that similar components are best protected from contamination immediately after stamping, and in addition, it is undesirable to use various lubricating powders and powders in molds.

Vacuum deposition of metals

Metals that can only evaporate at a temperature below their melting zone are allowed to be heated by direct current, silver and gold arrangements are evaporated in shuttle baths with tantalum or tungsten. Compensation is required to be carried out in a chamber at a pressure of less than 10-3 mm Hg. Art.

Vacuum ion-plasma spraying

For the occurrence of an independent glow discharge, it is necessary to cause the emission of electrons from the cathode by applying a high voltage of 2-4 kW between the electrodes. If the applied voltage exceeds the ionization capacity of the gas in the chamber (usually Ar), in this case, as a result of collisions of electrons with Ar molecules, the gas is ionized to form positively charged Ar+ ions. As a result, a small visual discharge and, consequently, a strong electric field appear in the region of the cathode black space.

The Ar+ ions, acquiring energy in the provided zone, knock out the atoms of the cathode element, at the same time, provoking the emission of side electrons from the cathode. It is this emission that preserves the independent glow discharge. Transition atoms from the cathode element reach the substrate and are deposited on its plane.

Vacuum spraying unit UVN

The design is armed with a significant complex modern appliances and devices that guarantee the deposition of coatings of metals of their syntheses and alloys with established features, excellent adhesion and high uniformity according to the part of the area.

The complex of devices and devices that are included in the structure of the device:

• Semi-automatic vacuum system control source;
• Magnetron sputtering theory in a stable current;
• Heating concept (with control and maintenance of the set temperature);
• The concept of cleaning the sprayed goods in the area of ​​the overflow discharge;
• The concept of moving products in the vacuum sphere;
• Numerical vacuum gauge;
• The concept of controlling the counteraction of growing films;
• Inverter power supply for magnetrons.

Vacuum systems are a complex of interrelated elements that ensure the creation and maintenance of a given vacuum in a certain volume. All vacuum systems are divided according to the degree of rarefaction into systems of low, high and ultra-high vacuum.

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In addition, vacuum systems

Main components of vacuum systems:

vacuum pump or installation providing pumping out of the gaseous medium;

pipelines connecting the components of vacuum systems;

container, vessel or other closed volume in which a vacuum is created;

various shut-off valves and safety devices;

a system of sensors that transmit data on the state of the system;

a controller that manages the entire system based on the information received from the sensors.

Some of the items listed above may be missing, it all depends on the specific requirements for the system. In addition, some or even all of the elements may be duplicated, ensuring continuous maintenance of a given vacuum. A fully automatic vacuum system is able to independently connect additional modules to work, control valves and constantly maintain the required degree of vacuum in given volumes.

Drawings of vacuum systems in each case are developed taking into account the requirements of customers and must comply with the requirements of the NTD. They are an integral part of any project, take into account all variables and are developed by trained specialists.

An example is medical vacuum systems, the shutdown of which can be fatal during a surgical operation. Each sensor of this type of vacuum system is necessarily duplicated, full redundancy of the system and autonomous power supply are often used. The automatic vacuum system maintains the required vacuum by turning on and off the pumps that pump out air according to the readings of the sensors.

Vacuum systems are mainly used for:

creating conditions chemical reactions in the chemical oil industry and research laboratories;

production of lenses in optics;

vacuum packaging of products in the food industry;

degassing of melts in metallurgical melting furnaces;

processing of electrical circuit boards in electronics;

ensuring the operation of blood-sucking devices and the production of certain drugs in medicine;

deposition of different in structure and immiscible materials in the automotive industry;

creating a vacuum in the milking machines of agricultural enterprises.

Valves for vacuum systems are divided into shut-off, safety and control valves. Some types of control valves can replace shut-off valves if necessary. To shutoff valves applies to most vacuum and check valves, having 2 positions and providing only cutting off (passage) of the working medium, regulating and safety devices.

working layout vacuum plant used to teach students:

Vacuum installation (sputtering)

Vacuum plants used for spraying are batch, semi-continuous and continuous. For mass and serial processing of parts, continuous vacuum units are used. Batch and semi-continuous installations may have several loaded working chambers or one loaded with several positions. The spraying process can be divided into several operations:

• loading parts and sealing the working chamber;
• creating the necessary vacuum;
• evaporation or spraying of the sprayed material;
• thermal treatment of spraying;

Vacuum deposition has been used in the manufacture of various electronic boards, applying tinting on car windows and metallizing some plastics. Typically, vacuum spraying installations have the following elements in their design:

• sealed enclosed space (working chamber);
• source of evaporation or spraying of sprayed materials;
• a system that creates a vacuum, which includes a pump and pipelines with all shut-off, control and safety valves;
• sensors connected to the process control system;
• conveyor or other feeding device;
• additional devices (filters, manipulators, drives, filter units).
• Vacuum spraying can be carried out using:
• cathode sputtering materials ( electricity is fed to the sputtered cathode, and since the part acts as an anode, the sputtered material is deposited onto it);
• magnetron sputtering;
• ion-plasma sputtering of cathodes;

Since with an increase in the surface temperature of the workpiece, the applied particles are rejected, therefore, properly organized cooling is very important. Depending on the equipment used to create a vacuum, the entire installation is named. For example, a water ring vacuum installation means the use of liquid ring pumps when pumping gases from the working chamber.

There are many vacuum plants that differ in the principle of spraying, the type of vacuum pumps used, the degree of automation, volume and other elements. Vacuum units UV-24S, UV-947, Bulat-3T, UVN-15, Magna 2M, Oratoriya-9 and many others based on them can be cited as an example.

Scheme of a vacuum installation for magnetron sputtering of metals:

Vacuum system equipment (fittings, flanges, sensors)

The most common mistake in the design of vacuum systems is the complexity of the project and the presence of many unnecessary elements. It can be like extra valves that lead to additional places for sealing, sensors located in uncomfortable places and constantly destroyed, flanges installed where a one-piece structure could be dispensed with.

Manufacturers of vacuum equipment in most cases produce equipment that meets customer requirements for performance, maximum possible vacuum and pumping speed. On high-performance systems, the installation of extra elements can cause them to depressurize and not ensure operation. safety devices. Therefore, it should be taken into account that an unprofessional vacuum system can be not only unsatisfactory for the operating conditions, but also dangerous for the operating personnel.

All fittings used in the installation of vacuum systems must fully comply with the operating conditions and be manufactured using appropriate technologies. The production of vacuum equipment should be the main focus of the enterprise that supplies all the elements of the system.

High vacuum sensor:

Vacuum technology (technology for creating and maintaining a vacuum)

Vacuum and compressor technology have many similar properties. Quite often, manufacturers of compressor equipment produce vacuum systems and their elements. The production of vacuum equipment is based on additional methods of processing equipment, achieving maximum sealing of systems.

The technologies for creating and maintaining a vacuum have improved over time. On the this moment vacuum science and technology make it possible to create a rarefaction corresponding to the deep vacuum of space.

Vertical and horizontal vacuum pumps:

Vacuum pumps (types and applications)

There are several types of vacuum pumps in use. Each of them has its own advantages and disadvantages, which provides its scope of application.

The water ring pump got its name from the fact that the vacuum in vacuum system created using a permanent ring of water in the working plane. The pump shaft is offset, so that on one side of the pump the blades pass close to the housing (without touching it), and on the opposite side there is a significant distance to the wall.

When rotating, the impeller blades capture the liquid (water), twisting it in the form of a ring. The friction forces acting in this case cause the liquid to heat up, so the water in the ring is constantly replaced with fresh water. Since gas is sucked off with the help of a water ring, most of the abrasive contaminants of the pumped medium are filtered out and pure gas comes out.

Such pumps are very easy to maintain, produce fast pumping of gases, are undemanding to their composition, but cannot create a deep vacuum, which limits their use in industry.

Scheme of operation of a water ring pump:

Where point H shows the place of the highest compression of the pumped gas (connection of the outlet pipe), B is the inlet to the pump, K is the water ring.

The rotary vane pump pumps out gases due to the shaft located eccentrically with respect to the housing. On the shaft there are special holes in which the springs are installed. Under the action of the springs, the blades are constantly pressed against the body, forming sealed chambers with respect to each other. When the rotor rotates, each chamber changes its volume from the minimum (in this case, the maximum compression of the gases in it occurs) to the maximum (creating a rarefaction). In order to reduce the friction of the plates against the body, a special oil is used.

The scope of application is limited, since a filtering device is required to guarantee the absence of abrasive particles in the pumped gases and oil vapors are present in the outgoing gases.

Scheme of operation of rotary vane pumps:

The foreline pump can be various types, for example, rotary vane, water ring, spool. The main task of such pumps is to create a fore vacuum (preliminary vacuum) as quickly as possible to ensure the operation of pumps that provide high vacuum. This is due to the fact that some models of pumps have a low pumping speed at normal atmospheric pressure and they require the highest possible vacuum to create a deep vacuum.

Turbomolecular, steam-oil diffuse and other types of pumps are used as the second stage in fore-vacuum pumps.

Roots pumps pump out gas mixtures due to the presence of two synchronously rotating rotors. One of the rotors receives rotational movement from the engine, and the other is driven by a gear transmission, which ensures rotation synchronism. The design allows you to create even a high vacuum, but requires mandatory cleaning of the incoming working chamber gas.

Scheme of operation of 2-cam (pos. "a") and 3-cam (pos. "b") Roots pumps.

 Vacuum deposition is based on the creation of a directed flow of particles (atoms, molecules, clusters) of the applied material onto the surface of products and their condensation.
The process includes several stages: the transition of the sprayed substance or material from the condensed phase to the gas phase, the transfer of gas phase molecules to the surface of the product, their condensation on the surface, the formation and growth of nuclei, and the formation of a film.
  Vacuum coating- the transfer of particles of the sprayed substance from the source (the place of its transfer into the gas phase) to the surface of the part is carried out along rectilinear trajectories at a vacuum of 10 -2 Pa and below (vacuum evaporation) and by diffusion and convective transfer in plasma at pressures of 1 Pa (cathode sputtering) and 10 -1 -10 -2 Pa (magnetron and ion-plasma sputtering). The fate of each of the particles of the sprayed substance upon impact with the surface of the part depends on its energy, the surface temperature, and the chemical affinity of the materials of the film and the part. Atoms or molecules that have reached the surface can either be reflected from it, or adsorbed and leave it after some time (desorption), or adsorbed and form a condensate on the surface (condensation). At high particle energies, high surface temperature, and low chemical affinity, the particle is reflected by the surface.
 The surface temperature of the part, above which all particles are reflected from it and the film is not formed, is called the critical temperature of vacuum deposition; its value depends on the nature of the film materials and the surface of the part, and on the state of the surface. At very low fluxes of evaporating particles, even if these particles are adsorbed on the surface, but rarely occur with other similar particles, they are desorbed and cannot form nuclei; film does not grow. critical density the flux of evaporated particles for a given surface temperature is the lowest density at which the particles condense and form a film.
 The structure of the deposited films depends on the properties of the material, the state and temperature of the surface, and the deposition rate. The films can be amorphous (glassy, ​​eg oxides, Si), polycrystalline (metals, alloys, Si), or single crystalline (eg, semiconductor films obtained by molecular beam epitaxy). To streamline the structure and reduce internal mechanical stress films, increasing the stability of their properties and improving adhesion to the surface of products immediately after deposition without violating the vacuum, the films are annealed at temperatures slightly higher than the surface temperature during deposition. Often, by means of vacuum deposition, multilayer film structures are created from various materials.
  Vacuum spraying used in the planar technology of semiconductor microcircuits, in the production of thin-film hybrid circuits, products of piezotechnics, acoustoelectronics, etc. (deposition of conductive, dielectric, protective layers, masks, etc.), in optics (applying antireflection, reflective, and other coatings), to a limited extent - when metallizing the surface of plastic and glass products, car window tinting. Metals (Al, Au, Cu, Cr, Ni, V, Ti, etc.), alloys (for example, NiCr, CrNiSi), chemical compounds (silicides, oxides, borides, carbides, etc.) are applied by vacuum deposition.

 
Rice. P2.1.

 For vacuum deposition use technological equipment intermittent, semi-continuous and continuous action. Installations of periodic action carry out one cycle of film deposition with a given number of loaded products. Continuous installations are used for serial and mass production. They are of two types: multi-chamber and multi-position single-chamber. The former consist of sequentially arranged deposition modules, in each of which the deposition of films of certain materials or their heat treatment and control is carried out. The modules are interconnected by lock chambers and a transport conveyor device. Multi-position single-chamber installations contain several sputtering posts (located in one vacuum chamber) connected by a transport device of a conveyor or rotary type. The main components and systems of installations for vacuum deposition are independent devices, performing the specified functions:
  creating a vacuum;
  evaporation or spraying of film material;
  Transportation and coating deposition;
  Control of vacuum deposition modes and film properties;
  power supply.

  Vacuum coating plants

 DV-502B series vacuum resistive spraying machine (Fig. A2.2.) ( this installation is desktop)

Rice. P2.2.

 Installation VATT1600-4DK (Fig. P2.4.) is designed for applying a combined coating, which may consist of a metal layer, a layer of this metal compound (oxide, nitride, carbide) and a layer of SiOx.

Rice. P2.3.

 Applying various connections titanium can be obtained various shades gold, blue, green, black and some other colors (Fig. A2.4.). Coatings can be applied to sheets of stainless steel with any surface treatment: mirror, sanded, decorative textured or plain matte. The dimensions of the vacuum unit allow spraying sheets of 1500x3000 mm in size. Sheets after spraying can be covered with a self-adhesive protective film. The cost of spraying - from 700 rubles / sq.m.

 

Rice. P2.4. The use of vacuum deposition.

Stainless steel:

 Stainless steel substrate is used for vacuum deposition with titanium nitride.
  elegance and grace in decoration;
  Corrosion resistance, weather resistance;
  match the most stringent hygiene requirements;
  ease of care and durability;
  heat resistance and fire safety;
  great combination with others finishing materials(glass, plastic, wood, stone).

Specifications:

  Substrate material - stainless steel, 08X18H10 (AISI 304);
  Substrate thickness 0.5mm - 1.5mm;
  Titanium nitride coating, thickness 0.2-6 microns;
  Coating color - various shades of gold;
  Light scattering - from mirror to matte;
  · Mechanical properties - allows repeated bending and cold stamping;
 · Weather resistance - not less than 50 years.

Material Receiving Method

 Coating on stainless steel TIN, TiO2 and TiON obtained by ion-plasma spraying in a vacuum chamber.
 Stainless steel sheets, after pre-treatment, which provides a high reflectivity of the coating, are placed in a sealed vacuum chamber. During the spraying process, a deep vacuum is created in the chamber, which ensures the desired color and durability of the coatings.
 In ion-plasma spraying, high-energy plasma ions knock out titanium atoms from the surface of a titanium sheet, which, in turn, passing through a highly rarefied cloud of nitrogen or oxygen, oxidizing, are introduced into the substrate material.
 This process provides good adhesive and decorative properties coatings.
 Vacuum deposition technologies are extremely energy intensive and are becoming a niche product in many countries. Many companies are replacing vacuum deposition with more productive and less expensive atmospheric plasma deposition.
  Qualities and properties of the material:
 High weather and corrosion resistance decorative coating confirmed by the certificate of conformity GOST No.СХ02.1.3,0040 dated 18.09.96. and is 50 years in an urban atmosphere;
 Any color can be achieved, but technological process debugged for three primary colors: imitating the color of gold - TiN coating, blue - TiO2 coating, imitating the color of fresh copper - TiON coating;
 Reflective ability of a covering - 60-70%;

Areas of use:

  Roofing of domes of churches and roofs of buildings;
  Outdoor advertising (plates, three-dimensional and flat letters made of stainless steel);
  Decorative design of buildings and interiors;
  Restoration of cultural monuments;
 ·Production of fragments of souvenirs and accessories.
 Vacuum deposition is used for products made of both ferrous metal and other metals, various deposition is used, including those for gold, silver (Fig. P2.5.).

 

Rice. P2.5. The use of vacuum deposition.

  Coating materials:
  TiN- titanium nitride (golden-bronze, increased wear resistance);
  TiOx1Cx2Nx3- titanium carbonide
  Gr- chrome (white);
  TiOx- titanium oxide (blue, multicolor, mother-of-pearl);
  Nigr- nichrome (light gray);
  ZrN- zirconium nitride (light golden);
  also aluminum, copper, etc., at the request of the customer.
 Color, hardness and other parameters of the coating may vary in a wide range of materials and shades.
 Important characteristics of microcircuits are speed, electrical contacts, matrix format, etc. To enhance one of the most important parameter- speed - it is required to increase the conductivity of electrical contacts. Most in a simple way to do this is to vacuum deposition the elements through loose masks. Gold has a very good conductivity, which makes it possible to increase the speed of information passing.

PRAM-memory chip from Intel (Fig. A2.6.)

 Material: Gold(silver).

 
Rice. P2.6. Intel PRAM chip

Plain bearings centrifugal pumps(Fig. A2.6.)

 Yourself main characteristic bearing is its resource. To increase it, plain bearings have developed special technology detonation spraying with application of nanopowders. In the process of detonation spraying, nanostructured coatings with a monocarbide content of 62% were obtained. Tests of such coatings for friction and wear in water have shown that they have a reduced coefficient of friction, a high galling load compared to a conventional ceramic powder coating.
 Technologies: vacuum deposition
 Industry: Electronics and Electrical Engineering
 Material: fast-hardened BZMP magnetic powders of the Nd-Fe-B system.

Rice. P2.6. Plain bearing

High Speed ​​Spray

 High-speed flame spraying is considered to be the most modern spraying technology. Carbide coatings applied by high-speed spraying, in all respects superior to galvanized coatings, the process of creation of which is recognized extremely carcinogenic.
 At the beginning of the 1980s, high-speed sputtering installations appeared, which were simpler in design and based on classical scheme LRE, with a gas flow rate of more than 2000 m/s. Coating density reaches 99%. Powders of carbides, metal carbides, alloys based on Ni, Cu, etc. are used as the applied material. Laval nozzle. On Fig. P2.7. the scheme of the sprayer of the VSN system is presented.

Rice. P2.6. Diagram of high speed powder sprayer:
1 - powder supply (axial); 2 - oxygen supply; 3 - fuel supply;
4 - powder supply (radial); 5 - trunk.