JP2013056793A - Aluminum oxide sintered body, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum oxide sintered body producible comparatively inexpensively, having a low dielectric loss tangent, and excellent in processability, and to provide a method for producing the same.SOLUTION: In this aluminum oxide sintered body in which the purity of aluminum oxide is ≥99.0 wt.%, titanium oxide and silicon dioxide are contained in as much as ≥0.2 wt.% to ≤0.8 wt.% in total, and the average particle size in the lengthy direction of aluminum oxide particles is ≥20 μm. Thus, since titanium oxide is contained, aluminum oxide particles are coarsened, and the grain boundary between each aluminum oxide particle is reduced, thus lowering the dielectric loss tangent. On the other hand, since silicon oxide is contained, the dielectric loss tangent can be lowered stably. Further, since the particles are coarsened, processability can be improved. Furthermore, cost can be reduced, because an extremely high purity of aluminum oxide is unnecessary.

Description

  The present invention relates to an aluminum oxide sintered body having a purity of aluminum oxide of 99.0% by weight or more and a method for producing the same.

The Al ₂ O ₃ sintered body is excellent in mechanical strength, heat resistance, corrosion resistance, etc., and uses a microwave or particularly high frequency like a semiconductor manufacturing apparatus, and uses a corrosive gas such as Cl or F. It is used in devices that are placed in difficult environments. Since Al ₂ O ₃ has high corrosion resistance against corrosion gases such as Cl and F and is inexpensive, it is often used for the above-described members.

However, it is preferable to use a low tan δ material in an environment where high frequency is used. In order to suppress the dielectric loss tangent of the Al ₂ O ₃ sintered body to a low level, a method using a low-alkali high-purity raw material, a method of adding an alkaline earth metal compound, and the like can be given. For example, the dielectric ceramic composition described in Patent Document 1 attempts to reduce variations in dielectric constant by adding a Ca compound and silicon dioxide to produce an aluminum oxide sintered body. Moreover, the alumina sintered body described in Patent Document 2 attempts to reduce the dielectric loss tangent by adding an alkaline earth metal to produce an aluminum oxide sintered body.

JP 2006-124217 A JP 2009-203088 A

  However, the method using a low-purity, high-purity raw material is not preferable because it has a high purity and is expensive. In addition, the method of adding an alkaline earth metal compound is not necessarily preferable because alkaline earth metals having a large ionic radius are strongly avoided due to recent refinement of semiconductor design rules.

Furthermore, the Al ₂ O ₃ sintered body is generally difficult to process, and a large amount of processing is necessary when aiming at a large shape or a complicated shape with many processed parts, and as a result, the processing cost tends to increase.

  The present invention has been made in view of such circumstances, and provides an aluminum oxide sintered body that can be manufactured at a relatively low cost, has a low electrostatic tangent, and is excellent in workability, and a method for manufacturing the same. For the purpose.

  (1) In order to achieve the above object, the aluminum oxide sintered body of the present invention is an aluminum oxide sintered body having a purity of aluminum oxide of 99.0% by weight or more, and titanium oxide and silicon dioxide in total. The aluminum oxide particles are contained in an amount of 0.2 wt% or more and 0.8 wt% or less, and the average particle size in the longitudinal direction of the aluminum oxide particles is 20 μm or more.

  Thus, by containing titanium oxide, the aluminum oxide particles are coarsened and the grain boundaries between the aluminum oxide particles are reduced, so that the dielectric loss tangent can be lowered. On the other hand, since silicon dioxide is contained, the dielectric loss tangent can be stably reduced. Moreover, workability can be improved by coarsening the particles. In addition, the extremely high purity of aluminum oxide is unnecessary, and the cost can be reduced.

  (2) Moreover, in the aluminum oxide sintered body of the present invention, the titanium oxide and silicon dioxide contained in the titanium oxide each have a titanium oxide content of 0.1 wt% or more and 0.4 wt% or less, and a silicon dioxide content of 0. It is characterized by being contained in an amount of 1 to 0.5% by weight. As a result, the sinterability is improved and, for example, even a thick sintered body is sintered to the inside of the sintered body, so that the dielectric loss tangent tan δ can be uniformly lowered throughout the aluminum oxide sintered body.

(3) The aluminum oxide sintered body of the present invention is characterized in that the dielectric loss tangent tan δ is smaller than 1 × 10 ⁻³ . Thereby, high-frequency electrical energy loss can be reduced. As a result, the aluminum oxide sintered body can be effectively used for parts used in an environment where high frequency is used.

  (4) Further, the aluminum oxide sintered body of the present invention is characterized in that the grinding resistance is 17 kgf or less. Thus, the aluminum oxide sintered body of the present invention has low grinding resistance and excellent workability, so it can be effectively applied to large-sized products and products with complex shapes with many processed parts, and also reduces processing costs. It becomes possible.

  (5) Moreover, the manufacturing method of the aluminum oxide sintered compact of this invention is a manufacturing method of the aluminum oxide sintered compact whose purity of aluminum oxide is 99.0 weight% or more, Comprising: The purity of aluminum oxide is 99.8. Mixing titanium oxide and silicon dioxide in a total amount of 0.2% by weight or more and 0.8% by weight or less with aluminum oxide powder of weight% or more, forming raw material powder, forming the raw powder, and forming And a step of firing the molded body obtained at 1400 ° C. or more for 3 hours or more. Thereby, about the manufactured aluminum oxide sintered compact, a dielectric loss tangent can be reduced stably and workability can be improved.

  According to the present invention, the aluminum oxide particles are coarsened, the grain boundaries between the aluminum oxide particles are reduced, and the dielectric loss tangent can be stably reduced. Moreover, workability can be improved by coarsening the particles. In addition, the extremely high purity of aluminum oxide is unnecessary, and the cost can be reduced.

It is a figure which shows content of the titanium oxide and silicon dioxide suitable for the aluminum oxide sintered compact of this invention.

  Next, embodiments of the present invention will be described with reference to the drawings.

[Configuration of sintered aluminum oxide]
In the aluminum oxide sintered body of the present invention, the purity of aluminum oxide (Al ₂ O ₃ ) is 99.0% by weight or more. On the other hand, titanium oxide (TiO ₂ ) and silicon dioxide (SiO ₂ ) are contained in a total of 0.2 wt% to 0.8 wt%. By containing titanium oxide, the aluminum oxide particles are coarsened and the grain boundaries between the aluminum oxide particles are reduced, so that the dielectric loss tangent can be lowered. Further, since silicon dioxide is contained, the dielectric loss tangent can be stably reduced. Moreover, workability can be improved by coarsening the particles. In addition, since the sinterability is improved by the effect of containing titanium oxide and silicon dioxide, even a thick sintered body is sintered to the inside of the sintered body, and a uniform low tan δ value throughout the sintered body Can be obtained.

FIG. 1 is a view showing the contents of titanium oxide and silicon dioxide suitable for the aluminum oxide sintered body of the present invention. As shown in FIG. 1, when the content of titanium oxide is represented by x wt% and the content of silicon dioxide is represented by y wt%, it is preferable that the following relationships (a) to (c) are satisfied. As a result, the sinterability is improved and, for example, even a thick sintered body is sintered to the inside of the sintered body, so that the dielectric loss tangent tan δ can be uniformly lowered throughout the aluminum oxide sintered body.
(A) 0.1 ≦ x ≦ 0.4
(B) 0.1 ≦ y ≦ 0.5
(C) x + 3y ≦ 1.6
Moreover, it is preferable that the dielectric loss tangent tanδ is smaller than 1 × 10 ^{−3 in the} aluminum oxide sintered body due to the configuration in which the particles are coarsened as described above. Thereby, high-frequency electrical energy loss can be reduced. As a result, the aluminum oxide sintered body can be effectively used for parts used in an environment where high frequency is used.

  Moreover, it is preferable that the aluminum oxide particle which comprises an aluminum oxide sintered compact has an average particle diameter of a longitudinal direction of 20 micrometers or more. Thus, the processability of the aluminum oxide sintered body is improved by the coarsening of the particles particularly in the longitudinal direction. Grinding is processed by hitting the workpiece with a grindstone when viewed microscopically, and when the direction of contact with the grindstone is perpendicular to the long direction, the processing is likely to proceed.

  As a result of having the above configuration, the aluminum oxide sintered body preferably has a grinding resistance of 17 kgf or less. In this way, since the grinding resistance is small and the workability is excellent, the aluminum oxide sintered body can be effectively applied to large-sized products and products with complex shapes with many processed parts, and the processing cost can be reduced. .

[Method for producing aluminum oxide sintered body]
First, aluminum oxide powder is prepared. Aluminum oxide is not necessarily high-purity and can be inexpensive. However, in order to reduce the dielectric loss tangent and improve the workability, it is desirable to use high-purity aluminum oxide powder. The purity is preferably 99.8% by weight or more, more preferably 99.9% by weight or more. An extremely high purity of aluminum oxide is not necessary, and the cost can be reduced. The average particle size of the aluminum oxide powder is preferably 0.5 μm or less. A more preferable range of the particle diameter is 0.1 μm or more and 0.5 μm or less.

  To the aluminum oxide powder, titanium oxide and silicon dioxide are added in a total amount of 0.2 wt% or more and 0.8 wt% or less. It is preferable to add 0.1 to 0.4% by weight of titanium oxide and 0.1 to 0.5% by weight of silicon dioxide. Examples of silicon dioxide to be added include silicon dioxide powder, silica sol, silica gel, silicon halide or silicon alkoxide, and water glass. When added as a powder, it is preferable to use one having an average particle size of 1.0 μm or less, and more preferably 0.5 μm or less.

  Titanium oxide is preferably added as a powder, but is not limited to this, and may be added in various forms such as chlorides and organic titanium compounds that generate oxides after sintering in the atmosphere. good. By using such a titanium oxide powder, an aluminum oxide sintered body excellent in workability can be obtained.

  The total amount of impurities such as alkaline earth metal oxides such as MgO and CaO that cannot be removed in the raw material is preferably 0.2% by weight or less. Impurities include not only alkaline earth metal oxides but also alkali metals, alkali metal oxides, alkaline earth metals, and the like.

  Mixing of the aluminum oxide powder, silicon dioxide powder and titanium oxide powder can be performed by a known method such as ball mill mixing. In that case, a dispersing agent, a binder, etc. are added suitably. In this way, the raw material powder is produced.

  Next, the raw material powder is formed. The raw material powder can be molded by various molding methods such as uniaxial press molding, CIP molding, wet molding, pressure casting and waste mud casting. When mixing the powder, it is preferable to ensure sufficient time for mixing. For example, the mixing time can be 18 hours or longer. By sufficiently mixing in this way, a slurry with uniform dispersion can be obtained.

  The molded body thus obtained is fired in the air at 1400 ° C. or higher for 3 hours or longer. In addition, it is preferable to bake at 1500 degreeC or more for 3 hours or more, and it is more preferable to bake at 1500 degreeC or more for 5 hours or more. Moreover, it is preferable that this temperature increase rate is 300 degrees C / h or less. If the heating rate is too high, a temperature difference between the surface and the interior tends to occur, and the difference in workability due to the difference in microstructure causes the production of a sintered body with uneven workability. It is for preventing. In particular, in order to fire a sintered material having a thickness of 10 mm or more, it is preferable to fire under the above-described raw material conditions and firing conditions.

[Examples and Comparative Examples]
(Sample preparation)
As raw materials, aluminum oxide powder with a purity of 99.8% by weight, titanium oxide powder with a purity of 99.9% by weight or more and a particle size of 0.4 μm or less and a rutile ratio of 80% or more, a purity of 99.9% by weight, a particle size of 0 The one added with 5 μm silica sol was used. In such an aluminum oxide powder, a solvent, an organic binder, and a dispersant were added in an appropriate formulation and mill mixed. The mixture thus obtained was granulated with a spray dryer. And the granule was CIP-molded and the plate-shaped molded object of 150x150x20 mm was produced. Furthermore, this was baked at 1400 degreeC or more for 3 hours.

(Evaluation method)
Various measurements were performed on the obtained aluminum oxide sintered body. The respective contents of titanium oxide and silicon dioxide were measured by ICP-MS. The average particle size was evaluated by performing SEM observation after the surface of the sintered body was mirror-polished, the polished surface was thermally corroded, and crystal grain boundaries were precipitated. The dielectric loss tangent was measured using a Q meter manufactured by Meguro Radio Co., Ltd. The workability was evaluated by measuring the surface grinding resistance. Table 1 shows specific conditions of the surface grinding process. Grinding resistance was measured when the cutting depth of the grindstone during surface grinding plunge processing was 60 μm. Grinding resistance is evaluated by attaching a tool dynamometer (AFT-ZM type, manufactured by Keyence) to the table surface of a precision surface grinder (SGC-104PCNC manufactured by Nagase), fixing the work material to the dynamometer, and performing plunge grinding did.

Table 2 shows the composition, particle size, dielectric loss tangent measurement result, and grinding resistance of each sample. As shown in Table 2, Samples 1 to 8 are examples, and Samples 9 to 14 are comparative examples. In the list of dielectric loss tangent tan δ, ◯ is described when the dielectric tangent tan δ is smaller than 1 × 10 ^{−3, and} × when the dielectric loss tangent tan δ is 1 × 10 ⁻³ or more.

As shown in Table 2, the purity of aluminum oxide is 99.0% by weight or more for Samples 1 to 8, and the total content of titanium oxide and silicon dioxide is 0.2% by weight or more and 0.8% by weight. % Or less. The dielectric loss tangent tan δ is smaller than 1 × 10 ⁻³ for both 1 MHz and 10 MHz, and the grinding resistance is 17 kgf at the largest.

On the other hand, for samples 9, 11, and 14, the purity of aluminum oxide is 99.0% by weight or more, but the total content of titanium oxide and silicon dioxide is less than 0.2% by weight. Therefore, the dielectric loss tangent tan δ is 1 × 10 ⁻³ or more in any measurement of 1 MHz and 10 MHz. For sample 12, the purity of aluminum oxide is 99.0% by weight or more, and the total content of titanium oxide and silicon dioxide is in the range of 0.2% by weight to 0.8% by weight. The dielectric loss tangent tan δ is smaller than 1 × 10 ⁻³ for both 1 MHz and 10 MHz. However, the particle size is 20 μm or less, and the grinding resistance exceeds 20 kgf. For samples 10 and 13, the purity of aluminum oxide is less than 99.0% by weight, and the dielectric loss tangent tan δ is smaller than 1 × 10 ⁻³ and satisfies the standard, but the grinding resistance exceeds 18 kgf. .

  Thus, since the dielectric loss tangent tan δ is too large or the grinding resistance is too large, the comparative example is not suitable for a member for a semiconductor manufacturing apparatus, for example. On the other hand, it was demonstrated that the aluminum oxide sintered body of the example has a low electrostatic tangent and is excellent in workability.

Claims (5)

An aluminum oxide sintered body having an aluminum oxide purity of 99.0% by weight or more,
An aluminum oxide sintered body characterized in that titanium oxide and silicon dioxide are contained in a total amount of 0.2% by weight or more and 0.8% by weight or less, and the average particle size in the longitudinal direction of the aluminum oxide particles is 20 μm or more.   The titanium oxide and silicon dioxide contained are each contained in a titanium oxide content of 0.1 wt% to 0.4 wt% and a silicon dioxide content of 0.1 wt% to 0.5 wt%. The aluminum oxide sintered body according to claim 1. 3. The aluminum oxide sintered body according to claim 1, wherein the dielectric loss tangent tan δ is smaller than 1 × 10 ⁻³ .   The aluminum oxide sintered body according to any one of claims 1 to 3, wherein a grinding resistance is 17 kgf or less. A method for producing an aluminum oxide sintered body having a purity of aluminum oxide of 99.0% by weight or more,
A step of mixing a total of 0.2 wt% and 0.8 wt% of titanium oxide and silicon dioxide with aluminum oxide powder having an aluminum oxide purity of 99.8 wt% or more, and generating raw material powder;
Forming the raw material powder;
And a step of firing the molded body obtained by the molding at 1400 ° C. or higher for 3 hours or longer.

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