JP7649211B2 - Insulation - Google Patents

Description

The present disclosure relates to an insulation body having a fitting.

Conventionally, shrink fitting has been used to fit ceramics together. For example, Patent Document 1 proposes a high-pressure discharge lamp in which end caps made of translucent alumina are hermetically joined to both ends of a cylindrical container body made of translucent alumina by shrink fitting, forming a discharge space inside.

JP2006-93046A

The high pressure discharge lamp proposed in Patent Document 1 is made of translucent alumina, a ceramic with high thermal conductivity, and is formed by shrink fitting without gaps. Translucent alumina is made of crystal grains with large diameters, and has a small proportion of grain boundary phases that hinder thermal conduction. In addition, because it is shrink fitted without gaps, the thermal conduction at the fitting part between the translucent alumina pieces is good. Therefore, there is a problem that translucent alumina fittings are not suitable for applications that require high thermal insulation.

An object of the present disclosure is to provide an insulator having a fitting with high thermal insulation properties.

A first heat insulator of the present disclosure for solving the above problems includes a base and a lid placed on the upper surface of the base, an internal space for maintaining a vacuum state is formed between the base and the lid, and a plurality of columnar bodies are arranged at predetermined intervals in the internal space. At least the tip portions of the columnar bodies are made of a first ceramic mainly composed of aluminum oxide, and the base is made of a second ceramic mainly composed of aluminum oxide and has a recess into which the tip portions are inserted. The tip portions are fitted into the recess, and there is a gap between the tip surface of the tip portion and the inner bottom surface of the recess.

The second heat insulator of the present disclosure comprises a base and a lid placed on the upper surface of the base, an internal space for maintaining a vacuum state is formed between the base and the lid, and a plurality of columnar bodies are arranged at predetermined intervals within the internal space. The columnar bodies have a protrusion made of a first ceramic mainly composed of aluminum oxide and a base supporting the protrusion, and the base is made of a second ceramic mainly composed of aluminum oxide and has a recess into which the protrusion is inserted. The protrusion is fitted into the recess, and there is a gap between the tip surface of the protrusion and the inner bottom surface of the recess.

In the first insulator of the present disclosure, both the columnar body and the base are formed from ceramics whose main component is aluminum oxide, which has low thermal conductivity, and the tip of the columnar body is fitted into a recess in the base, with a gap between the tip surface of the tip and the inner bottom surface of the recess, thereby improving insulation.
The second insulator of the present disclosure has a first member and a second member both formed from ceramics whose main component is aluminum oxide, which has low thermal conductivity, and further, the convex portion of the first member is fitted into the concave portion of the second member, and there is a gap between the tip surface of the convex portion and the inner bottom surface of the concave portion, thereby improving insulation properties.

FIG. 1 is a perspective view of an insulation body having a fitting according to an embodiment of the present disclosure. FIG. 2 is a partially enlarged cross-sectional view of FIG. 1 . FIG. 3 is an enlarged cross-sectional view of the fitting body shown in FIG. 2 . FIG. 13 is a cross-sectional view of an insulator according to another embodiment of the present disclosure.

An insulator according to an embodiment of the present disclosure will now be described. Fig. 1 shows a plate-shaped insulator 1 having a fitting according to an embodiment of the present disclosure.

As shown in FIG. 2, this insulator 1 comprises a base 2 having a rising portion 21 on its periphery, and a lid 3 disposed on the upper surface of the base 2. The lower peripheral edge of the lid 3 is bonded to the upper surface of the rising portion 21 of the base 2 via a first bonding layer 4, and an internal space 5 is formed between the base 2 and the lid 3. The internal space 5 is maintained in a vacuum state by vacuum heating treatment or the like, thereby imparting high thermal insulation properties to the insulator 1.

In the thermal insulator 1, a plurality of pillars 6 are arranged at predetermined intervals in the internal space 5 so as to be able to withstand reduced pressure. The pillars 6 are interposed between the base 2 and the lid 3, and serve to maintain a constant gap between the base 2 and the lid 3.
The internal space 5 functions as a heat insulating layer. The width W of the internal space 5 is preferably 10 mm or more and 60 mm or less. The thicknesses of the base body 2 and the lid body 3 are preferably 10 mm or more and 30 mm or less.

FIG. 3 shows an example of a fitting body in which a columnar body 6 is fitted into a recess 7. As shown in FIG. 3, a recess 7 is formed on the inner surface of the cover body 3, and the tip of the columnar body 6 is inserted into this recess 7. The columnar body 6 is fitted into the recess 7, and the insulator 1 has a gap 8 between the tip surface of the columnar body 6 and the inner bottom surface of the recess 7. This improves the thermal insulation. The width w of the gap 8 at the axis of the recess 7 is preferably 0.03 mm or more. This increases the space occupied by the gap 8, further improving the thermal insulation. It is more preferable that the width w is 1/2 or less of the depth of the recess 7. If the width w is 1/2 or less of the depth of the recess 7, the tip of the columnar body 6 inserted into the recess 7 can be fitted and fixed, and can sufficiently withstand vibration and pulling force.
On the other hand, the rear end of the column 6 is bonded to the inner surface of the lid 3 via a second bonding layer 9 .

In the present disclosure, at least the tip of the columnar body 6 is made of a first ceramic mainly composed of aluminum oxide, and the base body 2 is made of a second ceramic mainly composed of aluminum oxide.
The first ceramic and the second ceramic both have a thermal conductivity of 33 W/(m·K) or less, preferably 32 W/(m·K) or less at 20° C. In this way, since the tip of the columnar body 6 and the base body 2 are both made of ceramics with low thermal conductivity, heat insulation is ensured.
The thermal conductivity may be determined in accordance with JIS R 1611:2010.

The first ceramic forming the tip of the columnar body 6 preferably contains more aluminum oxide than the second ceramic of the base body 2. This results in a smaller amount of glass component (sintering aid) contained in the first ceramic than in the second ceramic, thereby improving mechanical properties such as three-point bending strength and rigidity of the tip of the columnar body 6. On the other hand, the glass component is easily eluted from the inner peripheral surface of the recess 7 facing the outer peripheral surface of the tip of the columnar body 6 during firing, which will be described later, thereby increasing the fitting strength and preventing the gap 8 from being blocked even when external pressure is applied from the rear end side of the columnar body 6.
The content of aluminum oxide in the second ceramic is 95% by mass or more, and preferably 96% by mass or more and 99% by mass or less.

The first ceramic and the second ceramic may contain aluminum oxide as a main component, and may also contain silicon, magnesium, and calcium. Specifically, the silicon may be contained in an amount of 0.01% by mass or more and 1% by mass or less in terms of oxide. The magnesium may be contained in an amount of 0.1% by mass or more and 0.4% by mass or less in terms of oxide. The calcium may be contained in an amount of 0.01% by mass or more and 1% by mass or less in terms of oxide.
The total content of silicon, magnesium, and calcium elements converted into oxides is preferably smaller in the first ceramic than in the second ceramic. This increases the high-temperature creep property of the first ceramic, so that the tip of the columnar body 6 can be used in a high-temperature environment for a long period of time even if it is elongated. In particular, the difference in the total content of the above elements converted into oxides is preferably 0.6% by mass or more and 1% by mass or less.

The total content of silicon, magnesium and calcium in the second ceramics calculated as oxides is preferably 1 mass % or less, which can increase the rigidity of the base 2 made of the first ceramics and the second ceramics.
Here, the total content of the above elements in the first ceramic calculated as oxides is, for example, 0.17 mass % or more and 0.57 mass % or less.
The main components in the first ceramic and the second ceramic refer to components that occupy 90% by mass or more of the 100% by mass of the components that constitute each ceramic, and each component may be identified by an X-ray diffraction apparatus using CuKα radiation. The content of the identified component may be calculated by calculating the content of the element using an ICP (Inductively Coupled Plasma) emission spectrometer or an X-ray fluorescence analyzer (XRF) and converting it into the identified component.

The first ceramic preferably has a smaller average circle-equivalent diameter of the aluminum oxide crystal grains than the second ceramic. This increases the mechanical properties of the tip, such as three-point bending strength and rigidity, and allows the tip and the protruding portion, which will be described later, to be longer. The circle-equivalent diameter can be determined according to the following procedure.
First, the cross sections of the substrate 2 and the tip portion of the columnar body 6 are polished to a mirror finish.
Specifically, the following first to third polishing steps are carried out in this order.
(1) First polishing: polishing with a diamond disk using diamond abrasive grains with an average particle size _D50 of 45 μm (2) Second polishing: polishing with a copper plate using diamond abrasive grains with an average particle size _D50 of 3 μm (3) Third polishing: polishing with a tin plate using diamond abrasive grains with an average particle size _D50 of 0.5 μm The polished surface obtained by the above-mentioned method is heat-treated at 1350 ° C., and the surface obtained is obtained by photographing it at a magnification of 400 times using a digital macroscope (VHX-500). Specifically, the measurement range is a range of an area of 7.2 × 10 ^-3 mm ² in the photographed image. The circle equivalent diameter of the crystal grains of aluminum oxide can be obtained by analyzing the above measurement range using image analysis software (for example, Win ROOF, manufactured by Mitani Shoji Co., Ltd.). In the analysis, the threshold value of the circle equivalent diameter is 0.2 μm, and circle equivalent diameters of 0.2 μm or less are not subject to calculation of the average value.

The average circle-equivalent diameters of the first ceramic and the second ceramic determined by this measurement method are both smaller than the average circle-equivalent diameter (31.6 μm to 53.6 μm) of translucent alumina (e.g., LUCALOX, a trademark of General Electric Co.). For example, the average circle-equivalent diameter of the first ceramic is 3 μm to 8 μm, and the average circle-equivalent diameter of the first ceramic is 10 μm to 30 μm. Both the first ceramic and the second ceramic do not transmit visible light, and have a relative density of 96% or more. The relative density of the first ceramic is the percentage of the apparent density of the first ceramic relative to the theoretical density, and the apparent density is determined in accordance with JIS R 1634:1998. The relative density of the second ceramic can also be determined by the same method.

Next, a method for manufacturing the thermal insulator 1 will be described.
First, a process for producing the base 2 will be described. Aluminum oxide powder (with a purity of 99.9% by mass or more), which is the main component of the second ceramic, and powders of silicon oxide, magnesium hydroxide, and calcium carbonate are charged into a grinding mill together with a solvent (ion-exchanged water) and ground until the average particle size ( _D50 ) of the powder becomes 1.5 μm or less, and then an organic binder and a dispersant for dispersing the aluminum oxide powder are added and mixed to obtain a slurry.

Here, the content of silicon oxide powder is 0.01 to 0.05 mass%, the content of magnesium hydroxide powder is 0.15 to 0.57 mass%, the content of calcium carbonate powder is 0.9 to 1.8 mass%, and the remainder is aluminum oxide powder and unavoidable impurities, out of a total of 100 mass% of the above powders.

Organic binders include acrylic emulsions, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, etc.

Next, the slurry is sprayed and granulated to obtain granules, which are then filled into a mold. Using a uniaxial press molding device or a cold isostatic pressurizing device, the granules filled into the mold are compressed at a molding pressure of 78 MPa to 128 MPa to obtain a rectangular plate-shaped molded body. Then, by cutting, a depression that will become the recess 7 after firing and an enclosed space that will become the internal space 5 after the lid 3 is joined are formed in the molded body 1. The enclosed space is a space that is open on one side in the thickness direction of the molded body and is surrounded on the outer edge. A carbon sheet (not shown) is laid on the inner bottom surface of the depression. The thickness of the carbon sheet may be the same as the width w of the gap 8 to be formed. In consideration of degreasing properties, the carbon sheet should be porous, and in particular, it is preferable that the porosity is 30% to 80%.

On the other hand, the columnar body 6 is obtained in the same manner as the base body 2. At this time, the silicon oxide powder content is 0.3 to 1 mass %, the magnesium hydroxide powder content is 0.15 to 0.57 mass %, the calcium carbonate powder content is 0.018 to 0.9 mass %, and the balance is aluminum oxide powder and unavoidable impurities, out of a total of 100 mass % of the raw material powders constituting the columnar body 6.

The produced columnar body 6 is fired to obtain a sintered body. The firing atmosphere is air, reduced pressure, or vacuum, the firing temperature is 1500°C to 1700°C, and the holding time is preferably 4 hours to 6 hours. With the tip of the columnar body 6, which is the sintered body, inserted into the recess, the rectangular plate-shaped body is fired under the same firing conditions as those described above. As a result, the tip of the columnar body 6 fits into the recess 7 due to firing shrinkage, the carbon sheet disappears, and a gap 8 is formed between the tip surface of the columnar body 6 and the inner bottom surface of the recess 7.

Next, the lid 3 is attached. If the lid 3 is made of ceramics (for example, ceramics whose main component is aluminum oxide, like the base 2), glass paste is applied to the other end face of the columnar body 6 and the end face of the rising portion 21 located on the periphery of the base 2 to form a glass bond, thereby obtaining the insulator 1.

On the other hand, if the lid 3 is made of metal (e.g., stainless steel such as SUS304 or SUS630, aluminum, etc.), the other end face of the columnar body 6 and the end face of the rising portion 21 located on the periphery of the base body 2 are each coated with brazing material (e.g., 63-70.5% by mass Ag, 27.5-35% by mass Cu, and 2% by mass Ti) and brazed to obtain the insulator 1.

Next, a heat insulator according to another embodiment of the present disclosure will be described with reference to Fig. 4. Note that the same components as those in the heat insulator 1 shown in Fig. 3 are denoted by the same reference numerals and description thereof will be omitted.
This embodiment includes a columnar body 11 ( first member ) having a protrusion 11b and a base 11a supporting the protrusion 11b, and a base body 12 ( second member ) having a recess 17 into which the protrusion 11b is inserted. The protrusion 11b is fitted into the recess 17, and there is a gap 8 between the tip surface of the protrusion 11b and the inner bottom surface of the recess 17.

Like the aforementioned columnar body 6, at least the protruding portion 11b of the columnar body 11 is made of a first ceramic mainly composed of aluminum oxide. Like the aforementioned base body 2, the base body 12 is made of a second ceramic mainly composed of aluminum oxide.
The protruding portion 11b can be formed by, for example, cutting processing.

The insulator 1 produced using the fitting shown in FIG. 3 or FIG. 4 can be used, for example, in semiconductor manufacturing equipment, plasma equipment, etc., but is not limited to these applications. Furthermore, the fitting shown in FIG. 3 or FIG. 4 can be used not only for the insulator 1, but also for various applications that require fitting.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications and improvements are possible within the scope of the present disclosure.

REFERENCE SIGNS LIST 1: Insulator 2: Base 21: Upright portion 3: Lid 4: First bonding layer 5: Internal space 7: Recess 8: Gap 9: Second bonding layer 11: Columnar body ( first member )
11a Base 11b Protrusion 12 Base ( second member )
17 Recess

Claims (10)

A substrate;
A lid body disposed on an upper surface of the base body ,
An internal space for maintaining a vacuum state is formed between the base body and the lid body,
A thermal insulator having a plurality of pillars arranged at predetermined intervals in the internal space,
At least a tip portion of the columnar body is made of a first ceramic mainly composed of aluminum oxide,
the base is made of a second ceramic containing aluminum oxide as a main component and having a recess into which the tip portion is inserted;
The tip portion is fitted into the recess, and a gap is provided between a tip surface of the tip portion and an inner bottom surface of the recess. A substrate;
A lid body disposed on an upper surface of the base body ,
An internal space for maintaining a vacuum state is formed between the base body and the lid body ,
A thermal insulator having a plurality of pillars arranged at predetermined intervals within the internal space,
The columnar body has a protrusion made of a first ceramic containing aluminum oxide as a main component and a base supporting the protrusion,
the base body is made of a second ceramic containing aluminum oxide as a main component and having a recess into which the protrusion is inserted;
The convex portion is fitted into the concave portion, and a gap is provided between a tip surface of the convex portion and an inner bottom surface of the concave portion. The insulator according to claim 1 or 2, wherein the width of the gap at the axis of the recess is 0.03 mm or more. The insulator according to any one of claims 1 to 3, wherein the first ceramic has a higher aluminum oxide content than the second ceramic. The heat insulator according to claim 4, wherein the content of aluminum oxide contained in the second ceramic is 95 mass% or more. The heat insulator according to any one of claims 1 to 5, wherein the first ceramic and the second ceramic contain silicon, magnesium, and calcium, and the total content of these elements converted into oxides is less in the first ceramic than in the second ceramic. The insulator according to claim 6, wherein the total content of silicon, magnesium, and calcium contained in the second ceramic, converted into oxides, is 1 mass% or less. The insulator according to any one of claims 1 to 7, wherein the first ceramic has a smaller average circle equivalent diameter of aluminum oxide crystal grains than the second ceramic. The insulator according to any one of claims 1 to 8, wherein the gap has a width w that is equal to or less than 1/2 the depth of the recess. The thermal insulator according to any one of claims 1 to 9, wherein the internal space has a width W of 10 mm or more and 60 mm or less.