JP2000205181A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat releasing property and corrosion resistance by subjecting at least the base material surface of the rotor of a vacuum pump to a coating treatment consisting of a metal plating layer and a ceramics dispersed metal plating layer, and specifying the thickness of the ceramics dispersed metal plating layer. SOLUTION: A turbo molecular pump A comprises a rotor 1 rotated at high speed within a stator 2 by a motor part within a motor housing 12. The rotor 1 comprises a rotor body 16 having a plurality of rotor blades 15 protruded on the outside surface, and the stator 2 comprises a plurality of stackable annular split bodies 21 having stator blades 22 protruded on the inside surface. The surface of the aluminum alloy base material 3 of the rotor 1 and the stator 2 is coated with a metal plating layer 4 and a ceramic dispersed metal plating layer having ceramic particles dispersed in a metal. The thickness of the ceramics dispersed plating layer is set to about 0.9-2.0X to the average diameter X of the ceramic particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial vacuum apparatus widely used in the field of thin film industry such as semiconductor manufacturing.

[0002]

2. Description of the Related Art Conventionally, various molecular pumps have been used to evacuate a film forming reaction chamber (chamber) of a semiconductor manufacturing apparatus or the like.
A thread groove molecular pump, a compound molecular pump in which these are combined, and the like are known. Both have the same main configuration, that is, a casing having an intake port at one end and an exhaust port at the other end, a stator fixed inside the casing, and a high-speed rotatable inside the casing. The pump performs a pumping operation by high-speed rotation of the rotor, and exhausts a film-forming reaction chamber connected to an intake port.

[0003]

However, in recent years, CVD (Chemical Vapor Deposition) and RIE, which are often used in recent years, have been proposed.
In the process of (reactive ion etching equipment), highly corrosive process gases such as HF and HCl are used, and corrosive reaction products such as AlCl3 are also sucked into the vacuum pump and rapidly corrode inside the pump. The serious problem of doing so has begun. In particular, rotors of vacuum pumps are often made of aluminum alloy from the viewpoint of weight reduction, workability, and superiority in specific strength.
Corrosion was a more serious problem.

[0004] In order to prevent corrosion of the components, various devices such as Ni plating have been conventionally devised. In addition, some ceramic pumps have been applied to achieve both heat dissipation and corrosion resistance for suppressing a rise in temperature of a rotor or the like, which is another important issue of a molecular pump. For example, alumite treatment or electrodeposition treatment of the surface of an aluminum alloy is performed. However, pores are always formed on such a treated surface, and corrosive Cl ions and the like may enter through the pores on the plating surface and corrode the aluminum substrate. Further, when a coating was applied with a fluororesin such as PTFE (polytetrafluoroethylene), a large amount of gas was emitted from the treated surface, and it could not be said that this was suitable as a surface treatment method for a vacuum pump.

The present invention solves these problems, improves the heat dissipation and corrosion resistance of components of a vacuum pump such as a rotor, and has a complicated shape such as a rotor of a turbo molecular pump. It is an object of the present invention to provide a vacuum pump provided with a coating capable of treating even the above components.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, a vacuum pump according to the present invention has a casing having an intake port at one end and an exhaust port at the other end, and a casing inside the casing. A vacuum pump that includes a fixed stator and a rotor configured to be rotatable in the casing, and performs a pumping operation by rotation of the rotor,
At least the rotor has a metal plating layer that is directly coated on the base material surface of the rotor, and a ceramic dispersion metal plating layer that is further provided on the metal plating layer and that contains ceramic particles dispersed therein. The ceramic coating metal coating layer is formed so that the film thickness of the ceramic dispersed metal plating layer is about 0.9 to 2.0X with respect to the average particle diameter X of the dispersed ceramic particles.

As the metal plating layer, for example, a Ni-based metal plating layer having high corrosion resistance such as Ni-P is desirable. As the ceramic particles dispersed in the metal plating layer, for example, Al
An oxide ceramic such as 2O3, a nitride ceramic such as AlN, a carbide ceramic such as SiC, or a mixture thereof is used.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a vacuum pump according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a turbo molecular pump. The figure shows the internal structure of the turbo molecular pump A, in which a stator 2 and a cylindrical casing 1 are shown.
0 and the base frame 11 supporting this casing 10
A motor housing 12 in the casing 10 and fixed to the base frame 11; and a pair of bearings 13 disposed on the motor housing 12 and the base frame 11, respectively.
A shaft 14 supported near both shaft ends by the shaft and a rotor 1 fixed to the shaft 14 so as to be integrally rotatable and containing a motor housing 12 on the inner periphery.

The rotor 1 has a rotor body 16 and a plurality of rotor blades 15 protruding from the outer peripheral surface of the rotor body 16. The stator 2 includes a plurality of stackable annular divided bodies 21 and a plurality of stator blades 22 protruding from the inner peripheral surface thereof. And this rotor wing
15 and the stator blades 22 are arranged alternately, and the intake port 17
The gas sucked in from the base frame is sent downward by the interaction between the rotor 15 and the stator
It is configured to be able to forcibly exhaust air from an exhaust port 18 provided in 11.

In the turbo-molecular pump A having such a configuration, the rotor 1 and the stator 2 of the present embodiment are formed by plating a surface of a base material 3 made of an aluminum alloy with a metal plating, as schematically shown in partial cross section in FIG. Coated with layer 4. In the present embodiment, the metal plating layer 4 is made of Ni or Ni-P, which has better corrosion resistance and heat radiation property than aluminum alloy. Cr-based metals can be used, but Ni is not suitable for corrosion resistance.
The system is better. Either electrolytic plating or electroless plating may be used as the plating method, but electroless plating is preferable in terms of film uniformity. The film thickness is set to an arbitrary film thickness of 3 to 20 μm that can exhibit the effects of corrosion resistance and heat radiation.

Further, the surface of the metal plating layer 4 is coated with a ceramic dispersed metal plating layer 40 in which ceramic particles 42 are dispersed in a metal 41. In this embodiment, the metal 41 constituting the dispersion plating layer 40 is Ni or Ni-P
It consists of. As described above, these materials have excellent corrosion resistance and heat radiation properties, and also have the advantage that they cover the metal plating layer 4 well and are difficult to peel off. Further, as the ceramic particles 42 to be dispersed, for example, Al2O3 is used. Al2
In addition to oxide ceramics such as O3, nitride ceramics such as AlN, carbide ceramics such as SiC, or a mixture thereof can be used. It is the most desirable material because it is not affected by gas and has excellent heat radiation.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a description will be given of a coating process for a rotor of a vacuum pump according to the present invention.

First, the aluminum alloy rotor is degreased and washed with an alkali, and then acid washed with hydrofluoric acid. By this acid cleaning, the adhesion of the plating film can be further improved. Thereafter, the rotor was zinc-substituted, and electroless Ni-P plating with a film thickness of 10 μm was performed by a known method. Further, activation treatment was performed on the rotor, and dispersed Ni-P plating containing Al2O3 particles dispersed therein was performed. At this time, the plating solution is constantly stirred to prevent precipitation and non-uniformity of Al2O3 particles. Al2
Since O3 particles of 4.7 μm were used, the thickness of the dispersion plating was set to 5 μm. Thereafter, the rotor was washed with water and dried with a blower to obtain a desired two-layer coating. Stator, etc.
Similar processing is performed when processing is performed on members other than the rotor.

The plating layer obtained by such a coating process has the structure shown in FIG. A Ni-P plating layer 4 is formed on the surface of a rotor substrate 3 made of an aluminum alloy, and a ceramic dispersed metal plating layer 40 in which ceramic particles 42 are dispersed in a metal 41 is formed on the surface.
As a result of intensive studies, the present inventors have derived an optimal relationship between the average particle diameter X of the ceramic particles 42 and the thickness of the dispersion plating layer 40 at this time. That is, the dispersed metal plating layer
It was clarified from the following test data that good film performance can be exhibited by adjusting the film thickness of 40 to be about 0.9 to 2.0X with respect to the average particle diameter X of the ceramic particles 42 dispersed therein.

FIG. 4 shows experimental results showing the relationship between the film thickness Y of the ceramic-dispersed metal plating layer and the thermal emissivity.
FIG. 5 shows the experimental results showing the relationship between the film thickness Y of the ceramic-dispersed metal plating layer and the thermal emissivity when ultrasonic cleaning was performed on the experimental sample after plating. FIG. 6 is an experimental result showing the relationship between the thickness Y of the ceramic-dispersed metal plating layer and the weight loss (g) when the ultrasonic cleaning is performed on the experimental sample after plating. In each of the experiments, Al2O3 ceramic particles having an average particle diameter of X = 4.7 μm were used, and the thermal emissivity was measured with infrared rays having a wavelength of 5 μm.

Referring to FIG. 4, the thermal emissivity is highest when the thickness Y of the ceramic dispersed metal plating layer is about 0.6X to 2.0X with respect to the average particle diameter X of the ceramic particles. However, when this is ultrasonically cleaned, as shown in FIG.
Below about 0.9X, the thermal emissivity decreases. On the other hand, in FIG.
= Weight reduction is observed in the range of about 0.9X or less.

To infer from the above experimental results, first,
The reason why the thermal emissivity is low in the range of the film thickness Y = about 0.6X or less is that the film thickness is small with respect to the particle diameter of the ceramic particles dispersed in the plating layer. It is considered that the ceramic particles could not be held in the plating layer. Similarly, when the film thickness Y is less than about 0.9X, it is considered that the dispersion particles are not sufficiently fixed, and the particles have fallen off by the ultrasonic cleaning. Conversely, the thermal emissivity decreases when the film thickness Y is about 2.0X or more, because of the characteristics of dispersion plating, as the film thickness increases after plating starts, the amount of dispersed particles taken in decreases, and the plating metal This is because the occupancy ratio increases and the thermal emissivity decreases.

From the above experimental results, the best thermal emissivity can be obtained when the thickness Y of the ceramic dispersed metal plating layer 40 is in the range of about 0.9 to 2.0X with respect to the average particle diameter X of the dispersed particles. found. If the film thickness Y is less than this range, the dispersed ceramic particles are likely to be desorbed, and overheating of the rotor, the stator, and the like due to air friction in the initial stage of the exhaust is likely to occur. On the other hand, when the film thickness Y is more than this range, the high heat radiation property and corrosion resistance of the ceramic particles cannot be effectively utilized, and the coating effect cannot be sufficiently exhibited.

The results of evaluation tests on the corrosion resistance and heat radiation of the rotor coated as described above are shown. When both the rotor coated with the present embodiment and the conventional product were immersed in 20% HCl for 20 minutes, the conventional product was
While it reacted violently with HCl and turned black, and eventually dissolved, no change was seen in the rotor of this example.
In addition, when the heat radiation coefficients of both of them were examined, the heat radiation coefficient of the conventional product was 0.1, and the heat radiation coefficient of the rotor of this embodiment was 0.9, which was very good.

The present invention is not limited to the configuration of the embodiment described above. For example, the type of vacuum pump is not limited to a turbo-molecular pump, but is also applicable to other vacuum pumps such as other scroll pumps and mechanical booster pumps.

As a matter of course, the pump substrate to be coated may be made of a material other than aluminum alloy, such as stainless steel.

The location where the coating treatment is performed is not limited to the rotor, and may be adopted in a location where corrosion resistance and heat dissipation should be improved, such as a motor housing and a stator. Since it is less necessary to provide heat radiation to the stator side than to the rotor side where overheating occurs, only the rotor side is subjected to the coating treatment of the present invention, and the stator side is coated with another material having only corrosion resistance. Can be performed.

The metal plating layer 4 can be arbitrarily selected from Ni, Ni-P, Cr-based metals, and the like. Also, the plating method is not limited to electroless plating, and another plating method such as electrolytic plating may be adopted.

The type of the ceramic particles 42 dispersed in the dispersion plating layer 40 is not limited to Al2O3. In addition to oxide ceramics such as Al2O3, nitride ceramics such as AlN, SiC
And the like, or a mixture thereof can be arbitrarily selected and used. The metal 41 serving as the base material of the dispersion plating is not limited to Ni, and various selections are possible as with the metal plating layer 4, but by selecting the same metal type for the metal plating layer 4 and the metal 41. Thus, an overlying layer having good adhesion between both layers and hardly peeling off even with thermal expansion or the like can be obtained.

[0026]

As described above, according to the vacuum pump of the present invention, the base material surface of the pump is coated with at least two layers of a metal plating layer having excellent corrosion resistance and a ceramic-dispersed metal plating layer. Therefore, the method can be used sufficiently for evacuation of highly corrosive process gas such as HF and HCl.

Further, the thickness of the ceramic-dispersed metal plating layer is configured to be about 0.9 to 2.0X with respect to the average particle diameter X of the dispersed ceramic particles, so that the ceramic particles can be made of Ni or Ni-P. Blocks the pores formed on the plating surface, prevents erosion that progresses from the pores toward the substrate to reach the pump substrate, and can exhibit high corrosion resistance in cooperation with corrosion-resistant metals . In addition, the ceramics particles can effectively exhibit the high heat radiation property of the ceramics itself, and at the same time, can hold the ceramic particles well without dropping off from the coating surface.

By such a coating treatment, overheating of the pump member such as the rotor and the like and dulling thereof can be prevented.
It is possible to maintain the pump operating state satisfactorily for a long period of time, for example, to prevent corrosion of the pump base material, peeling of the coating film, or prevention of galling of the rotor, and to provide a high-performance vacuum pump.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a turbo-molecular pump showing one embodiment of the present invention.

FIG. 2 is a partial schematic diagram showing a schematic cross section of the rotor of the embodiment.

FIG. 3 is a partially enlarged view showing a schematic cross section of the rotor of the embodiment.

FIG. 4 is an experimental result showing the relationship between the film thickness Y of the ceramic dispersed metal plating layer and the thermal emissivity.

FIG. 5 is an experimental result showing a relationship between a film thickness Y of a ceramics-dispersed metal plating layer and a thermal emissivity when an ultrasonic cleaning is performed on an experimental sample after plating.

FIG. 6 is an experimental result showing the relationship between the thickness Y of the ceramic-dispersed metal plating layer and the weight loss (g) when an ultrasonic cleaning is performed on the experimental sample after plating.

[Explanation of symbols]

 A: Turbo molecular pump 1: Rotor 15: Rotor blade 16: Rotor body 2: Stator 22: Stator blade 3: Base material 4: Metal plating layer 40: Ceramics dispersed metal plating layer 41: Metal layer 42: Ceramic particles 10: Casing 11: Base frame 12: Motor housing 13: Bearing 14: Shaft 17: Inlet 18: Exhaust

Continued on the front page (72) Inventor Katsuhiko Kada 1 Kuwabaracho, Nishinokyo, Nakagyo-ku, Kyoto F-term in Shimadzu Corporation (reference) 3H031 DA00 DA02 EA00 EA01 EA09 FA01 FA03 FA34 3H033 AA02 AA04 BB01 BB08 BB19 CC06 DD26 EE19 EE02 EE19

Claims (1)

[Claims] 1. A casing having an intake port at one end and an exhaust port at the other end, a stator fixed in the casing, and a rotor rotatable in the casing. A vacuum pump that performs a pumping operation by rotation of the rotor, wherein at least the rotor has a metal plating layer directly coated on the surface of the base material of the rotor, and is further provided on the metal plating layer. A coating treatment comprising at least two layers with a ceramic-dispersed metal plating layer containing dispersed ceramic particles is performed, and the film thickness of the ceramic-dispersed metal plating layer is about the average particle diameter X of the dispersed ceramic particles. A vacuum pump characterized in that the pressure is 0.9 to 2.0X.