JP3121701B2 - Rolling bearings for semiconductor manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing used in semiconductor manufacturing equipment.

[0002]

2. Description of the Related Art Grease is widely used as a lubricant for rolling bearings. The grease is a thickening agent for keeping the lubricating base oil in a semi-solid state, and
Vacuum grease, which is a mixture of additives for improving the properties of oil, is particularly known for use under a sealed vacuum represented by semiconductor manufacturing equipment. As a vacuum grease, for example, PF having a low vapor pressure is used.
There is a mixture in which PE (perfluoropolyether) is used as a base oil and PTFE (polytetrafluoroethylene), which is a fluorine compound, is used as a thickener. Vacuum grease is superior in terms of lubricity but low in dust generation compared to solid lubricants such as gold, silver, molybdenum disulfide and PTFE, which are generally used as lubricants for bearings for vacuum equipment. Is inferior. Therefore, the bearing in which the vacuum grease is sealed shows good durability but generates a large amount of dust.

[0003]

In recent years, in the field of semiconductor manufacturing, the line width of circuit patterns has become finer as the degree of integration of semiconductors has increased.
When the tickle adheres to the pattern, various adverse effects may be caused. Therefore, particularly low dust generation is required as a characteristic of the bearing. On the other hand,
In semiconductor manufacturing equipment, a truly high degree of cleanliness is required in the vicinity of the wafer and in a portion away from the wafer (for example, in the case of a wafer transfer robot, a rotary shaft portion corresponds to a wafer hand). In this case, the standard of cleanliness tends to be slightly relaxed as compared with the vicinity of the wafer. So, to put it another way,
Bearings used in such an environment do not necessarily need to have as high a low dust generation property as bearings used in the vicinity of the wafer, and rather, if durability becomes one of the important characteristics. I can say. Of course, higher low dust generation is required as compared with commonly used bearings.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rolling bearing having relatively good low dust generation and excellent durability, and is mainly used in a semiconductor manufacturing facility at a portion remote from a wafer. It seeks to achieve optimal use.

[0005]

A rolling bearing for semiconductor manufacturing equipment according to the present invention has a lubricating film made of polytetrafluoroethylene formed on at least a surface of a rolling bearing that generates rolling friction or sliding friction, Further, fluorine-based vacuum grease is sealed in the bearing.

[0006]

The presence of the PTFE lubricating coating suppresses the breakage of the thickener mixed in the vacuum grease. In addition, since the thickener is a fluorine-based compound and can be expected to have an affinity for the lubricating film, it is difficult to discharge broken powder generated by breaking of the thickener to the outside.

[0007]

Embodiments of the present invention will be described below.

FIG. 1 shows an embodiment in which the present invention is applied to a sealed deep groove ball bearing. This bearing is mounted on the inner ring 1, the outer ring 2, the plurality of balls 3 interposed between the inner and outer rings 1, 2, the retainer 4 for holding the balls 3 at equal circumferential intervals, and the inner diameter portions at both ends of the outer ring 2. For example, it is constituted by a bearing component such as a shield plate 5 made of SUS304. The lubricating coating 1 made of PTFE, for example, PTFE having an average molecular weight of 5000 or less (hereinafter, referred to as “low molecular weight PTFE” for simplicity) is formed on the rolling surfaces of the inner and outer rings 1 and 2 and the surface of the ball 3.
a, 2a and 3a are formed, and fluorine-based vacuum grease 6 is sealed in the bearing.

The lubricating coatings 1a, 2a and 3a have a low molecular weight P
TFE (for example, ARC7 manufactured by Acheson Japan)
This is sprayed and adhered to the film-forming surface from a distance of m. Here, low-molecular-weight PTFE is briefly described (for details, see Japanese Patent Application No. 3-190150 filed by the present applicant). Conventionally, PTFE generally used as a solid lubricant for bearings is: The average molecular weight is 1 × 10 ⁵ or more, mainly 1 × 10 ⁶ to 1 × 10 ^7.
The shear strength is remarkably low and the transferability is excellent. Therefore, low-molecular-weight PTFE itself has excellent lubricity and low dust generation.

As PTFE, in addition to the above-mentioned ARC7, Vidax AR, Vidax 1000 (all manufactured by DuPont), MP1200, MP1300 (all manufactured by Mitsui Fluorochemicals), Lubron D-1 (made by Daikin Industries) Etc. Although the average thickness of the coating is about 0.6 μm, this is considerably exaggerated in FIG. Also, in FIG. 1, the lubricating coatings 1a, 2a are not formed on the fitting surfaces and the like of the outer surfaces of the inner and outer rings 1, 2, but this is not subjected to coating treatment by masking or is a final product. Removed earlier.

FIG. 2 schematically shows the rolling surface of the inner ring 1 as an example (the same applies to the rolling surface of the outer ring 2 and the surface of the ball 3). The lubricating film 1a is formed in an island shape on the rolling surface. As a coating method of low molecular weight PTFE, there is an immersion method and the like in addition to the spray method described above. According to the spray method, a low molecular weight PTFE dispersion is sprayed and sprayed on a film forming surface.
a tends to have an island distribution as shown in FIG. Lubricant coating 1
a is covered with the vacuum grease 6 sealed in the bearing.

The vacuum grease 6 is a fluorine-based vacuum grease. For example, PFPE (perfluoropolyether) having a low vapor pressure is used as a base oil 6a, and PTFE (polytetrafluoroethylene) as a fluorine-based compound is added thereto. It was mixed as thickener 6b. As a fluorine-based vacuum grease, Blecoat 601 (Castrol)
Etc. It should be noted that P, which is a thickening agent for fluorine-based vacuum grease,
TFE has a larger average molecular weight than PTFE used as a thickener for fluorine-based grease.

FIG. 3 shows the results of a durability test performed on the rolling bearing (vacuum grease + PTFE lubricating coating: bearing A) having the above configuration and a conventional product (vacuum grease only: bearing B). In the durability test, the two test bearings with the shafts supported were rotated under the conditions of room temperature, a degree of vacuum of 10 ⁻⁶ Torr or less, a thrust load of 10 N, and a rotation speed of 2500 rpm, and the friction torque of the two test bearings was reduced. The sum is 1
The time when it reached 0 ^-2 Nm was defined as the life. As shown in the figure, the bearing A showed about 1.1 times or more the durability of the bearing B.

FIG. 4 shows the results of a dust generation test performed on bearings A and B. In the dust test, the number of rotations: 50r
pm, thrust load: 10N, degree of vacuum: 10 ^-6 Torr
Hereinafter, the test bearing was rotated under the condition of temperature: room temperature, and the amount of dust generated was measured by a dust detector disposed immediately below the test bearing. As shown in FIG.
The bearing A significantly reduced to less than 1/0, and the bearing A showed extremely low dust generation compared to the bearing B.

In the bearing A of the present embodiment, the following reason can be considered as the reason why the low dust generation is greatly improved. Referring to FIG. 5 (Bearing A) and FIG. 6 (Bearing B), first, a large amount of dust is generated in the bearing B because the thickener 6b contained in the vacuum grease 6 3 is broken by the shearing force between the rolling surface 3 and the rolling surface to become minute broken powder 6b1.
This is because most of 1 are discharged out of the bearing as it is. On the other hand, in bearing A,

(1) Since the lubricating film 1a is interposed between the ball 3 and the rolling surface, it acts as a buffer,
Suppress the breaking of thickener 6b,

(2) Since the lubricating film 1a is distributed in an island shape, the broken powder 6b1 of the thickener 6b enters the concave portion between the islands 1a2 and 1a2, and is hardly discharged to the outside. In other words, the broken powder 6b1 is divided into the islands 1a2 and 1a2.
Is trapped by the concave portion between and becomes difficult to be discharged outside,

(3) Since the PTFE as the thickener 6b and the low-molecular-weight PTFE as the material for forming the lubricating film 1a are of the same type as the fluorine-based compound, an affinity between them can be expected, and the thickener 6b is broken. The powder 6b1 is easily transferred onto the lubricating coating 1a, and is easily transferred to the concave portion together with the lubricating powder 1a1 of the lubricating coating 1a.

Therefore, it is considered that the amount of dust generation was significantly reduced. And, among the above-mentioned reasons, it is considered that the effect due to the island-shaped distribution of the lubricating coating 1a is the greatest.

It is considered that the slightly improved durability of the bearing A is due to the synergistic effect of the good lubricity of the vacuum grease 6 and the good lubricity of the low molecular weight PTFE.

The lubricating coatings 1a, 2a, 3a are not limited to the island distribution, but may be a continuous island distribution (in which islands and islands are continuous with thin coating portions) or a uniform distribution. Further, as the material for forming the lubricating coatings 1a, 2a, and 3a, generally used PTFE can be used in addition to the low-molecular-weight PTFE described above. Even in such a case, a considerable effect can be expected. Further, the bearing type is not limited to the deep groove ball bearing shown in FIG. 1, but can be widely applied to rolling bearings in general.

[0022]

As described above, in the rolling bearing for semiconductor manufacturing equipment of the present invention, a lubricating film made of polytetrafluoroethylene is formed on at least a surface of the rolling bearing which generates rolling friction or sliding friction. In addition, since it has a configuration in which fluorine-based vacuum grease is sealed in the bearing, it has durability equal to or higher than that of conventional vacuum grease only, and has extremely good low dust generation. Has the property. Therefore, according to the present invention, in a semiconductor manufacturing facility, for example, it is used for a part where relatively good low dust generation and high durability are required at the same time, such as a rotating shaft part in a wafer transfer robot. The most suitable rolling bearing can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sealed deep groove ball bearing according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view schematically showing a rolling surface portion of an inner race in FIG.

FIG. 3 is a diagram showing the results of a durability test.

FIG. 4 is a diagram showing the results of a dust test.

FIG. 5 is an enlarged sectional view schematically showing a rolling surface portion of an inner race in FIG.

FIG. 6 is an enlarged cross-sectional view schematically showing a rolling surface portion of an inner race in a conventional product.

[Explanation of symbols]

 Reference Signs List 1 inner ring 1a lubricating coating 2 outer ring 2a lubricating coating 3 ball 3a lubricating coating 6 vacuum grease

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16C 33/30-33/66

Claims (1)

(57) [Claims] A lubricating film made of polytetrafluoroethylene is formed on at least a surface of a rolling bearing that generates rolling friction or sliding friction, and
A rolling bearing for semiconductor manufacturing equipment, wherein fluorine-based vacuum grease is sealed in the bearing.