JP2001302339A - Member for precise measuring instrument and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for precise measuring instrument which has low thermal expansion property, high Young' s modulus and high specific rigid ity and is capable of satisfying the recent requirement for high precision, and the manufacturing method. SOLUTION: The member for precise measuring instrument is constituted of a composite ceramic consisting practically of eucryptite and silicon nitride and/or silicon carbide and has <=2×10-6/ deg.C coefficient of thermal expansion at 10-40 deg.C, >=1300 Pa Young's modulus at room temperature and >=50 GPa specific rigidity (Young's modulus/specific gravity).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for precision measuring equipment such as an air slide, a surface plate, a square, a stage and the like, and a method of manufacturing the same.

Conventionally, jigs and tools for precision measuring instruments such as air slides, surface plates, squares and stages, various stages such as XY stages combining them, and various inspection equipment parts such as length measuring machines (hereinafter collectively referred to as these) High precision Young's modulus (rigidity), high specific rigidity (Young's modulus / specific gravity), high accuracy, excellent surface roughness and flatness, thermal expansion coefficient Small,
Characteristics such as excellent wear resistance are required.

[0003] For example, in the case of an air slide or a surface plate, if the Young's modulus is low, the deflection due to its own weight increases because the basic structure is a beam structure. A problem arises that it is not possible

[0004] Even if the Young's modulus is high, the specific stiffness is reduced if the specific gravity (= weight) of the material itself is large.
Again, the deflection due to its own weight increases. The inconvenience due to the low specific rigidity can be avoided to some extent by reducing the weight by designing such as a rib structure, but it goes without saying that not only high Young's modulus but also high specific rigidity is desirable.

[0005] When the coefficient of thermal expansion is large, there is not much problem if the precision of the product is relatively low. Even if the temperature of was controlled,
A material having a large coefficient of thermal expansion cannot be used for such a member for a precision measuring device because the expansion and contraction of the member due to a slight temperature difference causes a decrease in product accuracy. In particular, in the flow of ultra-miniaturization and refinement typified by semiconductor products, the importance of the coefficient of thermal expansion has become extremely large.

As described above, there are many requirements required for members for precision measuring instruments, but materials conventionally applied to members for precision measuring instruments do not always satisfy these requirements.

In many cases, metals, natural stones, and ceramics are generally used as these members. Although cast iron is widely used as a metal, its dimensional change due to a slight temperature difference is large because its coefficient of thermal expansion is as large as 11 × 10 ⁻⁶ / ° C. Although the Young's modulus is relatively large at 110 GPa, the specific gravity is also large at 7.8, and as a result, the specific rigidity is as small as 14 GPa, and the deformation due to bending is large. Therefore, it is difficult to apply the present invention to members for precision measuring instruments of high precision that have recently been required.

On the other hand, those made of natural stones have problems such as anisotropy and joints (a kind of crack) peculiar to natural stones, so that when they are processed into a desired shape, the shape and size are limited. Although it is not impossible to process a large member, it is inevitably extremely expensive due to a problem of yield and the like. Stone, contrary to metal, has a specific gravity as small as about 2.5 to 3.0, but also has a Young's modulus of 2 to 3.0.
5 to 70 GPa, small and specific rigidity at most 10 to 30
It is difficult to apply to a member having a small GPa and also requiring high accuracy.

Alumina is known as a ceramic, and is superior to the above materials in all aspects such as specific rigidity, wear resistance, accuracy, and dimensional stability. However, the coefficient of thermal expansion of alumina near room temperature is 4.5.
It is up to 5.0 × 10 ⁻⁶ / ° C., and although it has not been a problem in the past, it cannot be said that the precision is sufficient under recent demands for ultra-precision.

[0010]

As described above, the conventional materials have a characteristic problem in terms of any one of the thermal expansion coefficient, the Young's modulus, and the specific rigidity with respect to recently required high-precision members. However, it is insufficient as a member for precision measuring instruments.

The present invention has been made in view of the above circumstances, and has a low thermal expansion property, a high Young's modulus and a high specific rigidity, and is a precision measuring instrument capable of satisfying recent demands for high precision. It is an object to provide a member for use and a method for manufacturing the same.

[0012]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a low thermal expansion eucryptite is combined with silicon nitride and / or silicon carbide having a high Young's modulus. It has been found that the Young's modulus can be significantly increased while maintaining excellent low thermal expansion characteristics, and that high specific rigidity can be obtained, and a member for precision measurement equipment having excellent characteristics can be obtained, and the present invention has been completed. .

That is, the present invention firstly comprises a composite ceramic consisting essentially of eucryptite and silicon nitride and / or silicon carbide at 10 to 40 ° C.
Coefficient of thermal expansion is 2 × 10 ⁻⁶ / ° C. or less, Young's modulus at room temperature is 130 GPa or more, specific rigidity (Young's modulus / specific gravity)
Is not less than 50 GPa.

A second aspect of the present invention is a precision measuring instrument, which is substantially composed of 5 to 90% by weight of eucryptite and 10 to 95% by weight of silicon nitride and / or silicon carbide in the first aspect. A member for use is provided.

[0015] Third, the present invention relates to eucryptite 5
90% by weight, silicon nitride and / or silicon carbide 10
A method for producing a member for a precision measuring instrument, characterized in that a molded body substantially consisting of ９５95% by weight is fired at a temperature of 1100 to 1700 ° C. in a vacuum or an inert gas atmosphere.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The member for a precision measurement device of the present invention is composed of a composite ceramic substantially consisting of eucryptite and silicon nitride and / or silicon carbide, and has a coefficient of thermal expansion at 10 to 40 ° C. of 2 × 10 ⁻⁶ / ° C. or less. The Young's modulus at room temperature is 130 GPa or more and the specific rigidity (Young's modulus / specific gravity) is 5
0 GPa or more.

When the coefficient of thermal expansion exceeds 2 × 10 ⁻⁶ / ° C.,
Even a slight temperature difference makes it impossible for the expansion amount and the contraction amount to satisfy the requirements. More preferably, 1.5 × 10 ⁻⁶ /
° C, more preferably 1 × 10 ^-6 / ° C.

If the Young's modulus is less than 130 GPa, even if the specific rigidity is high, the bending deformation due to its own weight increases,
It becomes difficult to satisfy the required accuracy, and the advantage of using ceramics is lost. More preferably 150G
Pa or more, more preferably 170 GPa or more.

If the specific stiffness is less than 50 GPa, even if the Young's modulus satisfies the above range, the bending deformation is still large, which is not preferable. A more preferable range of the specific rigidity is 60 GPa or more, and further preferably 70 GPa or more.

Eucryptite has the general formula Li ₂ O · A
l ₂ O ₃ · 2SiO ₂ and is an important component for lowering the thermal expansion of the sintered body. Silicon nitride and silicon carbide are:
Since it is a component that improves the rigidity (Young's modulus) of the sintered body, by compounding them, the Young's modulus can be significantly increased while maintaining excellent low thermal expansion characteristics, and the specific rigidity is increased. .

It is preferable that the member for a precision measuring instrument of the present invention is substantially composed of 5 to 90% by weight of eucryptite and 10 to 95% by weight of silicon nitride and / or silicon carbide.

When the amount of eucryptite for lowering the thermal expansion of the sintered body is less than 5% by weight, the thermal expansion coefficient increases, and when the amount of eucryptite exceeds 90% by weight, the Young's modulus decreases, which is not preferable. A more preferable range of the amount of eucryptite is 25 to 80% by weight, and further preferably 45 to 75% by weight.

Further, silicon nitride and silicon carbide are components for improving the rigidity (Young's modulus) of the sintered body. Is difficult to obtain. On the other hand, when the amount of silicon nitride and / or silicon carbide increases, the coefficient of thermal expansion increases, and when the amount exceeds 95% by weight, it becomes difficult to obtain a coefficient of thermal expansion in the above range. As described above, since the thermal expansion coefficient of silicon nitride at 10 to 40 ° C. is about 1.5 × 10 ⁻⁶ / ° C., even silicon nitride alone is 2 × 10 ⁻⁶ / ° C. or less. The invention is directed to composite ceramics and does not include silicon nitride alone. Further, since the thermal expansion coefficient of silicon carbide is about 2.5 × 10 ⁻⁶ / ° C.,
The amount at which the coefficient of thermal expansion at 40 ° C. is in the range of 2 × 10 ⁻⁶ / ° C. or less is different from that of silicon nitride, and when silicon carbide alone is added, the amount exceeds 2% by weight. A value of × 10 ⁻⁶ / ° C. or less becomes difficult.

In the composite ceramics constituting the member for precision measuring equipment of the present invention, the interface between eucryptite particles and silicon nitride particles and / or the interface between eucryptite particles and silicon carbide particles may have a glass phase or a crystalline phase. May exist as a grain boundary phase. However, when the amount of such a grain boundary phase is too large, the coefficient of thermal expansion of the sintered body increases, and the excellent low thermal expansion characteristics of eucryptite cannot be exhibited, which is not preferable.

In order to manufacture the composite ceramic of the present embodiment, the eucryptite powder is added in an amount of 10 to 90% by weight.
And silicon nitride and / or silicon carbide powder in 10 to
It is weighed and blended at a ratio of 90% by weight. After blending the respective powders in such a ratio, they are sufficiently mixed by a ball mill or the like and formed into a desired shape by a desired molding means, for example, a die press,
After being formed into an arbitrary shape by cold isostatic pressing, extrusion molding or the like, firing is performed.

The calcination is carried out in a vacuum or in an atmosphere of an inert gas such as Ar or N _{2 at} a temperature of 1100 to 1700 ° C., preferably 1200 to 1500 ° C., for about 1 to 10 hours. By sintering in this way, the sintered body can be densified. If the firing temperature is lower than 1100 ° C., densification cannot be achieved, and if it exceeds 1700 ° C., the molded article may be melted. In addition, when firing in an oxidizing atmosphere such as air, silicon nitride and / or silicon carbide is oxidized, and the effect of increasing the Young's modulus is not exhibited. The appropriate firing temperature varies depending on the composition, and increases as the amount of silicon nitride and / or silicon carbide increases.

[0027]

Embodiments of the present invention will be described below. First, a commercially available eucryptite powder was molded and fired at 1350 ° C. to obtain a sintered body having a diameter of 50 mm and a plate thickness of 4 mm as shown in Table 1. 3 × 4 from this ceramic
A sample of × 15 mm was taken out, and the coefficient of thermal expansion was measured in the range of −40 to 100 ° C. (measuring device: RIX-1 manufactured by Vacuum Riko Co., Ltd.). As shown in Table 1, the thermal expansion coefficient of this sample at 10 to 40 ° C. was −0.53 × 10 ⁻⁶ / ° C., and its crystal phase was β-eucryptite. In addition, when the Young's modulus at room temperature was measured by the ultrasonic pulse method, the Young's modulus was 100 GPa as shown in Table 1 and the rigidity was low (Sample No. 1).

Using the respective powders of silicon nitride and silicon carbide, the compact was fired under the conditions shown in Table 1 to obtain a similar sintered body. The thermal expansion coefficient and the Young's modulus were measured in the same manner. As shown in Table 1, although the Young's modulus was large as shown in Table 1, the thermal expansion coefficient was 1.5 × 10 ⁻⁶ / ° C. for silicon nitride and 2 for silicon carbide. 0.5 × 10 ⁻⁶ / ° C. (Sample N
o. 2, 3).

Next, sample no. Sample No. 1 was added to the eucryptite powder of No. 1. No. 2 silicon nitride powder or sample no.
3 or both were added at the ratios shown in Table 1 and mixed for 24 hours in a ball mill.
Molding was performed at a pressure of nf / cm ² . Then, the molded body was fired under the conditions shown in Table 1, and the coefficient of thermal expansion at 10 to 40 ° C. and the Young's modulus at room temperature were measured to further determine the specific rigidity. Table 1 shows the results.

A 630 × 400 × 150 mm platen was formed of the ceramic having the composition of the sample described above, the four corners at the lower part of the platen were supported at four points, and a 30 kg weight was loaded at the center of the upper surface. The amount of deflection was measured. The results are also shown in Table 1.

As is clear from the results shown in Table 1, the sample No. containing 5 to 90% by weight of eucryptite and 95 to 10% by weight of silicon nitride. 4-15, eucryptite 20-
Sample N having 90% by weight and 80 to 10% by weight of silicon carbide
o. 17 to 24, 20 to 90% by weight of eucryptite
In the same amount of silicon nitride and silicon carbide are each 40 ~
5% by weight of sample no. 26 to 33 are all 10 to 4
The coefficient of thermal expansion at 0 ° C. was 2 × 10 ⁻⁶ / ° C. or less, the Young's modulus at room temperature was 130 GPa or more, the specific rigidity was 50 GPa or more, and the amount of deflection of the surface plate was small. On the other hand, those deviating from the composition of the present invention had a large coefficient of thermal expansion and large expansion and contraction, or had a low Young's modulus and specific rigidity and a large amount of deflection.

Next, a molded body obtained by adding 45% by weight of silicon nitride and 45% by weight of silicon carbide to 55% by weight of eucryptite powder was used at 1300 ° C., 1050 ° C. and 1750 ° C.
(Sample Nos. 34 to 39). Table 2 shows the results.
Shown in

As shown in Table 2, Sample No. baked at 1300 ° C. Samples Nos. 34 and 35 exhibited characteristics suitable as members for precision measuring instruments. Three
6, 37 could not be densified and had a low Young's modulus. On the other hand, No. 1 fired at 1750 ° C. 38,39
The molded product was found to have melted, and the thermal expansion coefficient and the Young's modulus could not be measured.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

As described in detail above, according to the present invention, by combining low thermal expansion eucryptite with silicon nitride and / or silicon carbide having high Young's modulus, excellent low thermal expansion characteristics and high Young's modulus are obtained. And high specific rigidity,
It is possible to obtain a member for a precision measuring instrument that can satisfy the recent demand for higher precision.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 35/58 102Y F-term (Reference) 4G001 BA22 BA32 BA65 BB22 BB32 BB65 BC52 BD05 BD13 4G030 AA02 AA36 AA37 AA47 AA52 BA20 BA24 GA24 GA27 HA25

Claims (3)

[Claims] 1. A method according to claim 1, wherein the eucryptite and silicon nitride and / or
Or a composite ceramic substantially consisting of silicon carbide and having a coefficient of thermal expansion of 2 × 1 at 10 to 40 ° C.
0 ⁻⁶ / ° C. or less, Young's modulus at room temperature is 130 GPa or more,
A member for precision measuring equipment, wherein the specific rigidity (Young's modulus / specific gravity) is 50 GPa or more. 2. The member for a precision measuring instrument according to claim 1, wherein the member substantially consists of 5 to 90% by weight of eucryptite and 10 to 95% by weight of silicon nitride and / or silicon carbide. 3. A molded body consisting essentially of 5 to 90% by weight of eucryptite, 10 to 95% by weight of silicon nitride and / or silicon carbide, at a temperature of 1100 to 1700 ° C. in a vacuum or inert gas atmosphere. A method for producing a member for precision measuring equipment, characterized by firing.