KR19980052537A - Film formation method with excellent adhesion and surface properties - Google Patents

Abstract

Provided is a method for forming a film having excellent adhesion and surface properties on various small parts, and the method is characterized by forming an film by ion plating under high vacuum of 10 ^-4 Torr or less.

In this method, it is possible to economically form a coating having high coating efficiency, excellent adhesion and excellent corrosion resistance compared to the existing method.

Description

Film formation method with excellent adhesion and surface properties

The present invention relates to a film forming method used to manufacture metal or compound films on various small parts to improve the properties of the parts. Particularly, the present invention relates to sensors, speakers, recording media such as meters, shutters, as well as various electric motors. The present invention relates to a film forming method that can be evenly coated on the front surface of the part while excellent in adhesion and economical in coating mechanical parts such as permanent magnets and bolts widely used.

The so-called permanent magnets, which have a magnetic force and generate magnetic fields around them, are used in various ways around us. That is, various electric motors, as well as applications such as sensors, speakers, recording media, such as meters, shutters, etc. are difficult to understand, and most of them are closely related to our real life.

Permanent magnets include ferrite magnets, alnico magnets (alloys of aluminum, nickel and cobalt), samarium magnets (alloys of samarium and cobalt), and niodium magnets (alloys of nidium, iron and boron). The characteristic of nidium magnets is that the residual magnetic flux density and coercive force are two to three times higher than ferrite, and the maximum energy is more than five times higher than other magnets up to ten times higher.

However, despite these advantages of nidium magnets, there are some fatal drawbacks, one of which is that corrosion occurs very easily in the atmosphere. This is because the neodymium magnet is a compound made of rare earth element nidium and iron.

Surface treatment methods for preventing the corrosion of nidium magnets can be classified into four categories: nickel electroplating, electrodeposition coating, epoxy coating, aluminum coating. The most widely used method is nickel electroplating, and most of them are used for special purposes. Therefore, most magnet manufacturers use nickel electroplating. However, in the case of nickel plated products, products requiring high speed rotation or better characteristics are showing their limitations. As a means to solve this problem, the aluminum coating is gradually expanding its area.

Aluminum coating is beautiful in color and excellent in corrosion resistance, and is widely used in decorative coatings such as cosmetic cases and accessories, as well as in conductive films of semiconductors, protective films of magnetic materials and steel sheets.

In addition, aluminum has a wide variety of industrial applications due to its properties (low density, excellent workability, corrosion resistance and thermal conductivity). Recently, as the space development and the aviation industry are greatly developed, researches to improve the corrosion resistance and mechanical properties by coating aluminum on various materials are being actively conducted.

McDonald's Douglas, for example, uses aluminum as a coating for various parts used in airplanes as corrosion and wear resistant materials.

On the other hand, in Germany, aluminum is vacuum deposited on steel sheets and used in containers and home appliances. For this reason, products coated with aluminum appeared early, and have been used since 1983 for nidium magnets.

Aluminum is most commonly used for physical vapor deposition because its efficiency is low when it is coated with electroplating. Physical vapor deposition includes vacuum deposition, sputtering and ion plating. In order to improve corrosion resistance, ion plating is generally used. In particular, McDonnell Douglas and Sumitomo Special Metals manufacture and sell aluminum coated products known as AC coatings.

Aluminum coatings generally contain many holes in the coating layer and also have a disadvantage of poor adhesion to the substrate. To solve this problem, in order to solve the vacuum coating, the substrate must be heated to a high temperature and applied to the substrate in ion plating. It is necessary to introduce a larger amount of discharge gas in order to increase the voltage or increase the ionization rate.

However, when the substrate is heated to a high temperature, not only the substrate is damaged but also the adhesion amount decreases as the substrate becomes a high temperature, thereby reducing economic efficiency, and a method of applying a high voltage to the substrate also damages the substrate. When the amount of discharge gas is increased to increase the ionization rate, the discharge gas is mixed into the film, which damages the film, and scattering occurs between the discharge gas and the evaporated aluminum. In order to solve these problems, various methods of vacuum deposition, sputtering, ion plating apparatus or method (Japanese Patent Publication 61-059861, British Patent Publication 2141442, Japanese Patent Publication 57-09549, British Patent 2162205, Japanese Patent 7942676 ), It has the main characteristics such as uniformity of film and adhesion between film and substrate, stability of generated plasma, material and structure of evaporation source and high ionization rate.

On the other hand, in the case of coating aluminum on the neodymium magnet from McDonnell Douglas Corporation or Sumitomo special metal, a direct current ion plating method is used. However, this method requires a high voltage to be applied to the substrate for plasma discharge because the coating is performed at a low vacuum of 10 ^-3 Torr or more, and has a disadvantage in that economic efficiency is reduced due to a decrease in adhesion amount.

Accordingly, an object of the present invention is to provide an economical film formation method having excellent adhesion to a substrate and surface properties in consideration of the conventional problems as described above.

1 is a schematic arrangement of an apparatus for carrying out the method according to the invention.

* Description of the symbols for the main parts of the drawings *

1: vacuum chamber 2: evaporation source

3: ionization electrode 4: filament

5: shutter 6: thickness monitor

7: heating device 8: barrel

9: vacuum gauge 10: gas inlet

According to the present invention, in the method of forming a metal or compound film on various small parts, the method is characterized in that the film is formed on the surface of the part by generating plasma by ion plating in a high vacuum of 10 ^-4 Torr or less. Is provided.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The inventors of the present invention apply a high voltage to the substrate for plasma discharge because the conventional ion plating method forms a film at a low vacuum of 10 ^-3 Torr or more. It has been found that the adhesion amount is also reduced and the economical efficiency is lowered. As a result of continuing the research to form the film by using the ion plating method at a higher vacuum than this method, the present invention has been completed.

In the present invention, an ionization electrode and a filament were used as an ionizer in a conventional vacuum deposition apparatus, and a barrel for supporting and rotating the specimen was used to form a film evenly on the front surface of the material.

1 is an embodiment of an apparatus for practicing the method of the present invention.

In the vacuum chamber 1, first, an ionization electrode 3 and a filament 4 capable of ion plating were provided. In addition to the inside of the vacuum chamber 1, the evaporation source 2, the shutter 5, the thickness monitor 6, the heating device 7, the barrel 8 for holding and rotating the specimen, and the vacuum gauge for measuring the degree of vacuum 9 And a gas inlet 10 for injecting gas. The evaporation source 2 used an electron gun or a resistance heating evaporation source.

First, aluminum used as a coating material is charged in the evaporation source 2, the specimen is mounted in the barrel 8, the container is closed, and the vacuum is discharged to a desired degree of vacuum using a vacuum pump (not shown). When the vacuum is less than 10 ^-5 Torr, argon gas is injected to clean the specimen and a negative voltage is applied to the specimen to clean the specimen.

Cleaning the specimen is a very important step and includes removing not only impurities such as organic matter present in the specimen, but also naturally occurring oxide films.

If this oxide film is not removed sufficiently, it will affect the adhesion and should be sufficiently cleaned. The cleanliness of the specimens is usually conducted by inducing a glow discharge by applying a negative voltage of 400-1000V to the specimen in an argon gas atmosphere of approximately 10 ^-2 Torr.

In this way, argon ions present in the discharge region collide with the specimen to remove the oxide film present in the specimen. After cleaning the specimen, the vacuum is maintained at 10 ^-4 Torr or lower and then coated.

Thus, in the present invention, even if the film is formed under a vacuum of 10 ^-4 Torr or less, plasma can be generated by the ion plating method, thereby forming a film having a higher coating rate and excellent corrosion resistance than the prior art.

Hereinafter, the present invention will be described in more detail with reference to Examples.

In the present invention 1 is to produce an aluminum film to improve the corrosion resistance of the neodymium permanent magnet. First, aluminum which was a vapor deposition material was put in the electron beam evaporation source 2, and the ionization electrode 3 and the filament 4 were provided. Subsequently, 300 disk-shaped permanent magnets having a diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 1 mm were placed in the barrel 8, and then the vacuum vessel was closed and evacuated using a vacuum pump. The neodymium magnet was first removed from the oil present in the specimen by ultrasonic cleaning using an organic solvent before the barrel (8). When the vacuum degree was 10 ⁻⁵ Torr or less, 1.2 × 10 ⁻² Torr of argon gas was injected through the gas inlet 10 to clean the specimen, and secondary cleaning of the specimen by glow discharge was performed.

At this time, the voltage applied to the barrel was 500V, and the current was 400-800 kV, and cleaning was performed for 20 minutes while rotating the barrel. After the specimen has been cleaned, the vacuum is less than 10 ^-5 Torr.

In the example of the present invention, when necessary to stabilize the plasma more preferably, 2 × 10 ⁻⁴ Torr of argon gas was injected through the gas inlet 10. First, a stable plasma was generated by applying power to the electron beam evaporation source 2 and applying power to the ionization electrode 3 and the filament 4 while evaporating aluminum.

That is, an alumina crucible was used to improve the evaporation rate during electron beam evaporation, and the power of the electron beam was adjusted to 8 kV, 150 to 300 mW, and when the evaporation started to occur, the next step is to generate a plasma. At this time, the ionization electrode 3 and the filament 4 were used, respectively, and 60 V and 12 to 16 A flowed through the ionization electrode, and 40 to 50 A flowed through the filament 4. Argon gas of 2 × 10 ⁻⁴ Torr or less was injected. When the plasma was stabilized, a voltage of 200 V was applied to the substrate, and the shutter 5 was opened while the barrel 8 was rotated to deposit for 30 minutes. At this time, the thickness of the aluminum coated on the specimen was measured using a thickness monitor (6) and deposited an average thickness of 15㎛.

In order to explain the effects of the present invention, the following Examples and Tables are divided into coatings according to the Invention Examples and Comparative Examples, and then the characteristics of the coating rate, adhesion, and corrosion resistance are compared. The coating rate is a measure of the thickness of the front surface of the material and shows the ratio of the thickness of the thickest part to the thinnest part. The adhesiveness was divided into three stages through the measurement using the tape test and the scratch test, and the case where the adhesiveness was very excellent was indicated by ●, and the case where the adhesiveness was dropped into the tape by △. Corrosion resistance, on the other hand, is a comparison of the amount of red blue generated in the plating layer after elapse of 150 hours in a 5% NaCl solution. The comparison was divided into three stages, and marked as ● for the insignificant titration, △ if the titration incidence was less than 5% of the total area, and × for the titration incidence.

Inventive Example 2)

Same as Inventive Example 1, but using a pipe-shaped nidium magnet.

Inventive Example 3)

Same as Inventive Example 1, but using a bolt as a material and evaporation using a resistance heating evaporation source.

Inventive Example 4

Same as Inventive Example 1, but was deposited on the bolt using nickel as a deposition material.

Comparative example 1)

In order to compare with the invention example, the aluminum is deposited on the nidium magnet by the vacuum deposition method and the characteristics are compared.

Comparative example 2)

In order to compare with the invention example, nickel was deposited on nidium magnets by vacuum evaporation to compare characteristics.

TABLE 1

When the film is produced by the method of the present invention described above, it can be seen that it is possible to economically produce a film having a high coating rate, excellent adhesion and excellent corrosion resistance compared to the existing method.

Claims (2)

In a method of forming a metal or compound film on a material such as a small machine part or a magnet, A film forming method, characterized by forming a film on the entire surface of the material by generating a plasma in a high vacuum of less than 10 ^-4 Torr. The method of claim 1, wherein a barrel that rotates while supporting the material is used to uniformly form the material, and an electron beam or a resistive heating source is used as the evaporation source, and in the case of the electron beam, an alumina crucible is used to improve the evaporation rate. Film formation method.