WO2017043115A1 - Grossite ceramics, kiln equipment using same, and method for manufacturing grossite ceramics - Google Patents

Abstract

In this grossite ceramics, the value of I_B/I_A is 0.05 or less, I_B/I_A being the ratio of the integrated intensity I_B of the peak at 2θ=30.07º which is the main peak originating from CaAl₂O₄ in X-ray diffraction with respect to the integrated intensity I_A of the peak at 2θ=25.47º which is the main peak originating from CaAl₄O₇ in X-ray diffraction, and measured under an air atmosphere, the coefficient of thermal expansion from 27ºC to 300ºC is 2.0×10^-6/K or less. In a thermomechanical analysis when this grossite ceramic is heated under an air atmosphere, it is preferred that, in a size versus temperature graph obtained, either a temperature region in which size decreases are observed or a plateau temperature region in which size does not substantially change is observed.

Description

Glossite ceramics, kiln tool using the same, and method for producing globite ceramics

The present invention relates to a grosite ceramic, a kiln tool using the same, and a method for producing the grosite ceramic.

In recent years, electronic components such as capacitors have become extremely miniaturized. For this reason, in the firing process of electronic components, the process of putting the electronic components to be fired together with the firing kiln tools into a furnace from room temperature to a very high temperature for a short time and taking out from the furnace to complete firing is becoming mainstream. Along with this, even when the firing kiln tool is exposed to a more rapid thermal shock than before, the mounting portion deflection or cracking of the object to be fired due to the thermal shock, and further on the surface of the mounting portion There is a demand for a material that does not peel off.

By the way, the grosite is a compound composed of an oxide of Ca and Al, and its chemical formula is usually represented by CaAl ₄ O ₇ and may be expressed as CaO · 2Al ₂ O ₃ or CA _2. . For example, Non-Patent Document 1 discloses a ceramic containing glocyte having a thermal expansion coefficient α of 3.9 × 10 ⁻⁶ / K when heated from 20 ° C. to 800 ° C. (Table 3). . Patent Document 1 includes calcium aluminate containing a main phase of CaAl ₄ O ₇ and a subphase of CaAl ₂ O ₄ , and has a temperature range of about 25 × 10 ⁻⁷ / 8 over a temperature range of about 27 ° C. to about 800 ° C. A ceramic product is described which exhibits a thermal expansion of less than 0C. Patent Document 2 discloses low melting points such as ZrO ₂ , K ₂ O, Li ₂ O, B ₂ O ₃ , CaF ₂ , MgO, TiO ₂ , ZnO, SnO, SrO, Y ₂ O ₃ , Fe ₂ O ₃ , and BaO. It is described that the thermal expansion of ceramics containing grosite is reduced by adding an additive for crystallization.

US2003 / 232713A1 US6689707B1

Non-patent document 1 describes a ceramic containing grosite (hereinafter also referred to as “glossite ceramic”), which has a high thermal expansion coefficient and insufficient spalling resistance. In addition, the gloccite ceramics composed of calcium aluminate containing a CaAl ₄ O ₇ main phase and a CaAl ₂ O ₄ subphase described in Patent Document 1 has CaAl ₂ O ₄ less CaAl ₄ O ₇ than CaAl ₄ O _7. Since it is stable and weak against deflection due to high temperature, it was difficult to repeatedly use it at high temperature. In addition, as described in Patent Document 2, the grosite ceramics having a low thermal expansion coefficient with an additive for forming a low-melting-point composition has a low creep property at high temperatures and is easily bent or softened. There was concern about a decrease in high-temperature strength, and it was not suitable for practical use as a kiln tool for firing electronic components.

Therefore, an object of the present invention is to provide a grosite ceramic that can eliminate the various disadvantages of the above-described prior art, a kiln tool using the same, and a method for producing the grosite ceramic.

The present invention relates to 2θ which is the main peak derived from CaAl ₂ O ₄ in the X-ray diffraction with respect to the integrated intensity I _A of 2θ = 25.47 degrees which is the main peak derived from CaAl ₄ O ₇ in the X-ray diffraction. = the value of 30.07 which is the ratio of the integrated intensity _{I B} of a peak of the degree _I B / _{I a} is 0.05 or less,
The present invention provides a grosite ceramic having a coefficient of thermal expansion of not more than 2.0 × 10 ⁻⁶ / K measured from 27 ° C. to 300 ° C. in an air atmosphere.

Also, the present invention provides a kiln tool using the above-mentioned grosite ceramics.

Further, the present invention is a preferred method for producing the above-mentioned grosite ceramics,
A mixed powder of alumina particles having a volume cumulative particle size D ₅₀ of 5 μm or less and a calcium carbonate particle having a volume cumulative particle size D ₅₀ of 25 μm or less measured by a laser diffraction / scattering particle size distribution measurement method. The present invention provides a method for producing a glossite ceramic, comprising a step of molding and firing the obtained molded body at a temperature of 1450 ° C. or higher.

The glossite ceramic of the present invention has a low degree of thermal expansion at a high temperature and has a high spalling resistance. Such a glossite ceramic of the present invention can withstand repeated thermal cycles with severe temperature rise and cooling conditions and can be used in the firing process of electronic components for a long period of time. Therefore, according to the kiln tool of the present invention using the glossite ceramic of the present invention, the running cost can be reduced and the yield of electronic parts can be improved. Moreover, the manufacturing method of the glocytic ceramics of this invention can manufacture said glocytic ceramics efficiently.

FIG. 1 is an X-ray diffraction chart of the glossite ceramic obtained in Example 1. FIG. 2 is a dimension-temperature graph obtained by thermomechanical analysis of the globite ceramic obtained in Example 1. FIG. 3 is a photomicrograph of the cross section of the glossite ceramic obtained in Example 1, and is a photo used to measure the number and length of microcracks. FIG. 4 is a photomicrograph of the cross section of the grosite ceramic obtained in Example 1, and is a photograph used for measuring the crystal grain size. FIG. 5 is a dimension-temperature graph obtained by thermomechanical analysis of the globite ceramics obtained in Example 3. FIG. 6 is a schematic diagram illustrating a method for measuring spalling resistance.

Hereinafter, the present invention will be described based on preferred embodiments thereof. The composition of calcium aluminate in the glossite ceramic of the present invention is substantially a CaAl ₄ O ₇ single phase. CaAl ₄ O ₇ is more stable than CaAl ₂ O ₄ , is resistant to high temperature deflection, and can be used repeatedly at high temperatures. As described above, by using calcium aluminate substantially composed of a CaAl ₄ O ₇ single phase, the grosite ceramic of the present invention is repeatedly used at a higher temperature than when CaAl ₂ O ₄ is contained as a subphase. It can use suitably for uses, such as a kiln tool. Moreover, not using CaAl ₂ O ₄ having high solubility in water can make the grosite ceramic of the present invention easy to handle in various other applications.

The globite ceramic of the present invention is a main peak derived from CaAl ₂ O ₄ with respect to an integrated intensity I _A of 2θ = 25.47 degrees which is a main peak derived from CaAl ₄ O ₇ in X-ray diffraction. the value of the ratio of the integrated intensity _{I B} of 2 [Theta] = 30.07 ° of the peak _I B / _{I a} is 0.05 or less. Thus, it is understood that the glow site ceramics of the present invention is substantially free of CaAl ₂ O _4. As X-ray diffraction, powder X-ray diffraction measurement is usually performed. The value of _I B / _{I A} in Gros site ceramic of the present invention, the smaller well, preferably 0.01 or less, more preferably 0.005 or less, 0.001 or less Is most preferred. It is preferable from the standpoint of ease of quality control As the lower limit of _I B / _{I A} to 0.0004 or more.

Gro site ceramics value of I B _/ I _A is equal to or less than the upper limit described above, in the manufacturing method of Gros sites ceramic to be described later, by adjusting the ratio of the alumina particles and calcium carbonate particles and the firing conditions of the mixed powder It can be obtained by adjusting or the like.

Note that, when the X-ray powder diffraction measurement was performed on the grosite ceramic of the present invention using a Cu source as a radiation source, the peak having the maximum intensity in the range of 2θ = 10 degrees to 70 degrees is usually CaAl ₄ O _7. It is preferable that it is a peak at 2θ = 25.47 degrees which is a main peak derived from.

One characteristic of the glossite ceramics of the present invention is that the degree of thermal expansion when heated from room temperature to a relatively low specific temperature is low. The present inventors examined the relationship between the grosite ceramics in which calcium aluminate is composed of a CaAl ₄ O ₇ single phase and thermal expansion at a high temperature (eg, 800 ° C. or higher). As a result, it has been found that a low degree of thermal expansion to a relatively low temperature is important for reducing the degree of thermal expansion at a high temperature.

Specifically, the glossite ceramic of the present invention has a coefficient of thermal expansion from 27 ° C. to 300 ° C. of 2.0 × 10 ⁻⁶ / K or less as measured in an air atmosphere. Thereby, the glow site ceramics of the present invention can reduce the thermal expansion coefficient at high temperature, and become high in spalling resistance. From this viewpoint, the coefficient of thermal expansion from 27 ° C. to 300 ° C. measured in the atmospheric atmosphere of the grosite ceramic is preferably 1.5 × 10 ⁻⁶ / K or less, and more preferably 1.0 × 10 ⁻⁶ / K or less, particularly preferably 0.5 × 10 ⁻⁶ / K or less.
Further, the lower limit of the thermal expansion coefficient is preferably −10.0 × 10 ⁻⁶ / K or more from the viewpoint of fracture strength. This thermal expansion coefficient is a linear expansion coefficient, and can be measured by the method described in Examples described later.

As described above, in connection with the low coefficient of thermal expansion up to 300 ° C of the grosite ceramic of the present invention, the grosite ceramic of the present invention has a specific dimension-temperature graph obtained by thermomechanical analysis (TMA). It has the shape of Specifically, in the grosite ceramic of the present invention, in a thermomechanical analysis when heated in an air atmosphere, a temperature region in which the size decreases is observed in the shape of the obtained size-temperature graph, Alternatively, a plateau temperature region where the dimensions do not change substantially is observed. Thereby, the thermal expansion coefficient at a high temperature of the glossite ceramic can be more reliably lowered, and the spalling resistance can be improved. Such a temperature range is more preferably observed in a thermomechanical analysis when the grosite ceramic is heated from 27 ° C. to 600 ° C. in an air atmosphere, and a thermomechanical machine when heated from 27 ° C. to 300 ° C. It is particularly preferred to be observed in the analysis.

More specifically, in the dimension-temperature graph, the temperature range where the dimension decreases is the area where the slope of the graph has decreased with respect to the dimension before the test, and a plateau temperature range where the dimension does not change substantially. The term “region” refers to a region in which the dimensional variation due to temperature variation is smaller than the pre-test size. Specifically, the dimension-temperature graph shows, for example, a test of a dimensional difference ΔL (= L−L ′) between the dimension L before the test and the dimension L ′ at a certain temperature with the temperature T as the horizontal axis. The ratio to the previous dimension L (ΔL / L, unit:%) is the vertical axis. For example, the temperature region in which the dimension decreases refers to a region where a dimensional decrease of more than 0.05% is observed with respect to the dimension L before the test. The plateau temperature range in which the dimensions do not substantially change is that the thermal expansion amount (absolute amount of elongation or shrinkage | ΔL |) is 0.05% or less (preferably 0) with respect to the dimension L before the test. .01% or less).

For example, in a graph with ΔL / L on the vertical axis and temperature T on the horizontal axis, the difference between the lowest temperature T _L and the highest temperature T _H (T _H -T _L ) is preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. The upper limit of the temperature difference (T _H −T _L ) may be 500 ° C. or less from the viewpoint of the availability of the grosite ceramics.

Further, the difference (T ′ _H −T ′ _L ) between the lowest temperature T ′ _L and the highest temperature T ′ _H in one “plateau temperature region in which the dimensions do not substantially change” is the coefficient of thermal expansion. From the viewpoint of further reducing the temperature, it is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. As the upper limit of this temperature difference (T ′ _H −T ′ _L ), 500 ° C. or less can be mentioned from the viewpoint of availability of grosite ceramics.

In particular, in the grosite ceramic of the present invention, in a thermomechanical analysis when heated from 27 ° C. to 600 ° C. in an air atmosphere, the obtained dimension-temperature graph shows a convex curve toward the direction in which the dimension decreases. Preferably, it has a plateau temperature range in which the dimension does not substantially change and a temperature range in which the subsequent dimension increases. Thereby, the thermal expansion coefficient at a high temperature of the glossite ceramics can be further reliably reduced, and the spalling resistance can be improved.

As described above, the dimension-temperature graph of the grosite ceramic of the present invention is a convex curve toward the direction in which the dimension decreases in the thermomechanical analysis when heated from 27 ° C. to 600 ° C., or It has a plateau temperature region in which the dimension does not substantially change and a temperature region in which the subsequent dimension increases. In the former case, in the dimension-temperature graph, after a dimensional decrease of more than 0.05% with respect to the pre-test dimension L is observed, the dimensional increase with respect to the pre-test dimension L is less than 0.05%. Observed. In the former case, the temperature at which the dimension decreases most in the range of 27 to 600 ° C. is also called the inflection point. The dimension reduction at the inflection point is preferably 0.06% or more with respect to the dimension L before the test from the viewpoint of enhancing the effect of the present invention, and is preferably 1% or less from the viewpoint of the ease of manufacturing of the grosite ceramics. Further, the inflection point in this case is preferably observed within a range of 100 ° C. or higher and 600 ° C. or lower, and more preferably observed within a range of 150 ° C. or higher and 500 ° C. or lower.
In the latter case, a region where the thermal expansion amount (absolute amount of elongation or shrinkage | ΔL |) is 0.05% or less (preferably 0.01% or less) with respect to the dimension L before the test, And a region where the increase in dimension is higher than 0.05% with respect to the dimension L before the test. In this case, the temperature at which the transition from the region where the thermal expansion amount is 0.05% or less to the region where it exceeds 0.05% occurs is preferably 250 ° C. or more and 600 ° C. or less, and 300 ° C. or more and 450 ° C. The following is more preferable.

The reason why the dimension-temperature graph has a specific shape in thermomechanical analysis is not clear, but the inventors of the present invention have one of the reasons that the grosite ceramic of the present invention has microcracks as described later. I guess it is. That is, it is considered that when the grosite ceramic of the present invention has microcracks, the microcracks absorb and absorb the expansion due to heating when the grosite ceramic is heated, and apparently absorb the thermal expansion. Although Patent Document 1 describes “a network structure of microcracks”, there is no description or suggestion that a glaucite ceramic substantially composed of a CaAl ₄ O ₇ single phase has microcracks.

In order to obtain a grosite ceramic having a specific shape in the dimension-temperature graph by thermomechanical analysis as described above, and a grosite ceramic having a thermal expansion coefficient from 27 ° C. to 300 ° C. in a desired range, What is necessary is just to manufacture the glossite ceramics of this invention with the manufacturing method mentioned later.

Furthermore, in the grosite ceramics of the present invention, hysteresis is observed in the obtained dimension-temperature graph in the thermomechanical analysis when heated from 27 ° C. to 800 ° C. in the atmosphere and then cooled in this temperature range. It is preferable. This hysteresis means that the TMA curve during temperature rise does not match the TMA curve during cooling. As described above, the inventors of the present invention show that the glossite ceramic of the present invention in which hysteresis is observed in the dimension-temperature graph can further reduce the thermal expansion when heated to a high temperature and has high spalling resistance. Found out. In other words, in the above-described thermomechanical analysis, it is preferable that the difference in dimensions at the same temperature is observed during the heating and the subsequent cooling.

The reason why the hysteresis is observed in this way is unclear, but the present inventors believe that there is a possibility that the characteristics of the microcrack in the glossite ceramic of the present invention are related. That is, it is presumed that microcracks closed by heating may not open during cooling, or the temperature at which microcracks close during heating may differ from the temperature that opens during cooling. In order to make the above-mentioned hysteresis observed in the grosite ceramics of the present invention, the grosite ceramics of the present invention may be produced by the production method described later and the raw material type, firing temperature, etc. may be adjusted.

From the viewpoint of more effectively lowering the thermal expansion coefficient when heated to a high temperature of the glossite ceramics of the present invention, the difference between the dimension at the time of temperature rise and the dimension at the time of cooling caused by the hysteresis is the same. The maximum value is preferably 0.02% or more, more preferably 0.025% or more, and particularly preferably 0.03% or more with respect to the dimension before the test. The dimensional difference here is an absolute value of the dimensional difference. Further, from the viewpoint of preventing dimensional fluctuations when the grosite ceramic of the present invention is repeatedly heated, this maximum value is preferably 0.1% or less, and 0.08% or less with respect to the dimensions before the test. It is more preferable that it is 0.06% or less.

Furthermore, from the viewpoint of further effectively reducing the coefficient of thermal expansion when the grosite ceramic is heated to a high temperature, the grosite ceramic of the present invention has a dimensional difference between heating and cooling in the thermomechanical analysis ( The temperature range in which the absolute value) is 0.01% or more with respect to the dimension before the test is preferably 60% or more, more preferably 80% or more of the range from 27 ° C to 800 ° C. . When there are multiple temperature regions in the range from 27 ° C to 800 ° C where the dimensional difference between heating and cooling is 0.01% or more with respect to the size before the test, the temperature range here Is the sum of the ratios of the plurality of temperature regions.

The degree of thermal expansion at a high temperature is excellent in the glossite ceramic of the present invention. Specifically, it is preferable that the coefficient of thermal expansion from 27 ° C. to 800 ° C. is 3.4 × 10 ⁻⁶ / K or less for the glossite ceramics measured in an air atmosphere. Such a glossite ceramic of the present invention has high spalling resistance suitable for a kiln tool for rapid firing of electronic parts. From this viewpoint, the coefficient of thermal expansion from 27 ° C. to 800 ° C. measured in the atmospheric atmosphere of the grosite ceramics is preferably 3.0 × 10 ⁻⁶ / K or less, more preferably 2.5 ×. 10 ⁻⁶ / K or less, particularly preferably 2.0 × 10 ⁻⁶ / K or less. The lower limit of the thermal expansion coefficient is preferably −2.0 × 10 ⁻⁶ / K or more from the viewpoint of fracture strength. As described above, in order to obtain a grosite ceramic having a desired coefficient of thermal expansion up to 800 ° C. by thermomechanical analysis, the grosite ceramic of the present invention may be produced by the production method described later.

In the glossite ceramic of the present invention, as described above, it is preferable that microcracks are observed in a microscopic image with the cross section enlarged 150 times from the viewpoint of more reliably reducing the degree of thermal expansion. The microcrack usually has a shape having a width direction and a longitudinal direction longer than the width direction. From the viewpoint of reducing the degree of thermal expansion, the microcrack of the present invention has a microscopic image in which the cross section is magnified 150 times. One or more observations per one field of view of 0.84 mm × 0.59 mm are preferable, three or more observations are more preferable, and ten or more observations are particularly preferable. Microscopic observation can be performed using a scanning electron microscope (SEM) as a microscope, for example, by a method of an example described later. A microcrack is observed as a white elongated image on the cross-section of the grosite ceramic under the condition that the acceleration voltage is 15 kV using a scanning electron microscope (SEM). The number of the microcracks in the glossite ceramic of the present invention can be represented by, for example, an average value for 10 different visual fields in a microscopic image. One or more micro cracks having a specific length or more are observed per field of view in the gloucite ceramics. When ten different fields are observed under the above observation conditions, one or more micro cracks are observed in each field of view. That's fine.

The shape of the microcracks may be, for example, a linear shape such as a curved line, a straight line, or an intermittent line, may be a band, may or may not have a bent portion, Or may be discontinuous. The length along the longitudinal direction is the length of the path from the end to the end of the microcrack along the bend when the microcrack has a bent portion or the like and is not a straight line.

From the viewpoint of further reducing the degree of thermal expansion of the glossite ceramics of the present invention, in the microscopic image, the total length per one visual field of the microcracks having a length along the longitudinal direction of 50 μm or more is: It is preferably 500 μm or more, more preferably 1000 μm or more, and even more preferably 1500 μm or more. The total length here is the total length along the longitudinal direction of the microcracks observed per one visual field. From the viewpoint of breaking strength, the total length per field of view is preferably 7000 μm or less, more preferably 5000 μm or less, and particularly preferably 4500 μm or less. The total length of the microcracks in the glossite ceramic of the present invention can be represented by, for example, an average value for 10 different visual fields in a microscopic image. As described above, it is preferable that one or more microcracks having a length along the longitudinal direction of 50 μm or more in each visual field are observed in each of the visual fields when observed for 10 different visual fields.

Furthermore, the glossite ceramic of the present invention has a cross-section so that the grain boundary can be properly recognized according to the crystal grain size from the viewpoint of being suitable for thermal expansion and spalling resistance for obtaining a microcrack structure. Is preferably 5 μm or more on average in a microscopic image obtained by magnifying the film from 150 to 1500 times. The crystal grain size is obtained by polishing the cross-section of the globite ceramics obtained as follows, then firing in the air at 1400 ° C. (keep time 0 minutes), and thermal etching. Next, the etched surface is photographed using a scanning electron microscope (SEM) under the condition of an acceleration voltage of 15 kV to obtain an image. The cord length of the obtained image is measured by the intercept method, and the crystal grain size is calculated. Usually, in an image, a crystal grain is a region surrounded by a crystal grain boundary that looks dark and has a mesh shape (see FIG. 4). Ten line segments are measured in one visual field, and this measurement is performed in 10 different arbitrary visual fields, and the average value of all crystal grain sizes observed for each visual field is used. From the above viewpoint, the average grain size obtained by the above method is more preferably 5 μm or more, and particularly preferably 10 μm or more. In addition, the crystal grain size is preferably 300 μm or less in terms of the average value from the viewpoint of ease of production of the grosite ceramics and fracture strength.
In order to make the number and length of the microcracks and the crystal grain size of the glossite ceramics of the present invention within the above ranges, the glossite ceramics of the present invention are produced by the production method described later, The firing temperature and the like may be adjusted.

Furthermore, it is preferable that the glowing ceramic of the present invention has a spalling resistance ΔT of 600 ° C. or higher. The spalling resistance is measured, for example, by the method described in the following examples. Grositic ceramics having a spalling resistance equal to or higher than the above lower limit can be obtained by a production method described later. From the viewpoint of further facilitating repeated use of the glossite ceramic of the present invention at a high temperature, the spalling resistance ΔT is more preferably 600 ° C. or higher, and even more preferably 700 ° C. or higher. It is particularly preferable that the temperature is 800 ° C. or higher. In order to make the spalling resistance ΔT within the above range, the grossite ceramic of the present invention is produced by the production method described later, and the particle size of the raw material, the production method and type of the raw material, and the firing temperature are adjusted. Good.

The glossite ceramic of the present invention may contain a compound other than CaAl ₄ O _{7 as} long as the effects of the present invention are not impaired. For example, the glossite ceramic of the present invention may contain a compound for lowering the melting point of CaAl ₄ O ₇ to lower the thermal expansion. ZrO ₂ , K ₂ O, Li ₂ O described in Patent Document 2 , B ₂ O ₃ , CaF ₂ , MgO, TiO ₂ , ZnO, SnO, SrO, Y ₂ O ₃ , Fe ₂ O ₃ , BaO and the like may be contained. However, it is preferable that the glossite ceramic of the present invention does not contain these compounds as much as possible because it is easy to prevent deterioration of high temperature characteristics such as high temperature creep characteristics when used as a kiln tool for firing electronic parts.
From this viewpoint, the content of elements other than Ca, O, and Al in the glossite ceramic of the present invention, specifically, Zr, K, Li, B, F, Mg, Ti, Zn, Sn, Sr, Y, The total content of elements of Fe, BaSi, Ni, and Na is preferably 10,000 ppm or less, more preferably 7000 ppm or less, and particularly preferably 5000 ppm or less in the grossite ceramic. The upper limit of the total is preferably 1000 ppm or more from the viewpoint of ease of production of the grosite ceramics.

The bulk specific gravity of the glossite ceramic of the present invention is preferably 1.8 or more, and more preferably 2.0 or more. There exists an advantage that intensity | strength can be ensured by making a bulk specific gravity more than the said lower limit. The glossite ceramic preferably has a bulk specific gravity of 2.88 or less, and more preferably 2.85 or less. There exists an advantage that it can reduce in weight by making bulk specific gravity below the said upper limit. Further, the apparent porosity (hereinafter, also simply referred to as “porosity”) of the glossite ceramic of the present invention is preferably 0% or more, and more preferably 1% or more. There exists an advantage that it can reduce in weight by making a porosity more than the said lower limit. The porosity is preferably 37% or less, and more preferably 31% or less. There exists an advantage that intensity | strength can be ensured by making a porosity into below the said upper limit. The bulk specific gravity is calculated, for example, by measuring the mass of the grosite ceramic (or kiln tool) and dividing this by the volume obtained from the measurement of the size of the grosite ceramic (or kiln tool). The porosity can be calculated from a formula of (1−bulk specific gravity / apparent specific gravity) × 100. Here, the apparent specific gravity is a value obtained by dividing the mass of the grosite ceramics (or kiln tool) by the mass of water at 4 ° C. having the same volume as the apparent volume (JIS R2001), and is measured by the Archimedes method. The The bulk density and porosity are adjusted by adjusting the particle size of the raw material, the manufacturing method and type of the raw material, and the firing temperature in the method for producing the grosite ceramic of the present invention. It can be adjusted by adopting an appropriate method corresponding to the required bulk specific gravity and porosity, such as molding.

The glossite ceramic of the present invention preferably has a bending strength of 8 MPa or more, and more preferably 10 MPa or more. By making bending strength more than the said lower limit, there exists an advantage that it has intensity | strength sufficient for handling as a baking tool. The glossite ceramic preferably has a bending strength of 200 MPa or less, and more preferably 150 MPa or less. By setting the bending strength to be equal to or less than the above upper limit value, there is an advantage that microcracks are substantially introduced and a reduction in the thermal expansion coefficient can be expected. The bending strength here is a room temperature bending strength measured according to JIS R2619. The bending strength within this range is an appropriate method for adjusting the particle size of the raw material, the manufacturing method and type of the raw material, and the firing temperature in the method for producing the grosite ceramics of the present invention, as well as the method for forming the molded body subjected to firing. It can be adjusted by adopting.

Hereinafter, the suitable manufacturing method of the glossite ceramics of this invention is demonstrated. This production method comprises alumina particles having a volume cumulative particle size D ₅₀ of 5 μm or less at a cumulative volume of 50 vol% by a laser diffraction scattering type particle size distribution measurement method, and calcium carbonate particles having a volume cumulative particle size D ₅₀ of 25 μm or less. And baking the mixed powder at a temperature of 1450 ° C. or higher.

In this production method, the particle sizes of the alumina particles and the calcium carbonate particles are important. In this production method, when the alumina particles or the calcium carbonate particles do not satisfy the above particle diameter, it is difficult to generate the number of microcracks required for sufficiently reducing the degree of thermal expansion. From the viewpoint of sufficiently reducing the degree of thermal expansion, the volume cumulative particle diameter D ₅₀ of the alumina particles is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less. Further, the lower limit of the volume cumulative particle diameter D ₅₀ of the alumina particles is preferably 0.01 μm or more, for example, from the viewpoint of the availability of alumina particles and the homogeneity of mixing due to aggregation.

The volume cumulative particle diameter D ₅₀ of the calcium carbonate particles is preferably 25 μm or less, more preferably 24 μm or less, and even more preferably 23 μm or less. Further, the lower limit of the volume cumulative particle diameter D ₅₀ of calcium carbonate is preferably 0.01 μm or more, for example, from the viewpoint of availability of calcium carbonate particles and homogeneity of mixing due to aggregation.

In order to make the D ₅₀ of the alumina particles within the above range, a method of pulverizing with a ball mill or a vibration mill or a method of classifying with a sieve or the like can be mentioned. In order to make the D ₅₀ of the calcium carbonate particles within the above range, a method of pulverizing with a ball mill or a vibration mill or a method of classifying with a sieve or the like can be mentioned.

D ₅₀ can be measured, for example, by Microtrack HRA and Microtrack 3000 series (for example, MT-3000II series such as MT3200II, MT3300EXII, MT3300II, etc.) manufactured by Nikkiso Co., Ltd. (or manufactured by Microtrack Bell Co., Ltd.). Specifically, when the microtrack HRA is used, the following is performed.

<Method of measuring the D _50>
An amount containing about 0.4 g of alumina particles or calcium carbonate particles is put into a 100 mL glass beaker, and then pure water is added as a dispersion medium up to the 100 mL line of the beaker to obtain a slurry for measurement. This measurement slurry is dropped into a chamber of a sample circulator of Microtrack HRA manufactured by Nikkiso Co., Ltd. containing pure water until the apparatus determines that the concentration is appropriate, and D ₅₀ is determined.

The crystal structure of the alumina particles may be any of α, γ, θ, η, δ, and the like.

Examples of the calcium carbonate particles include heavy calcium carbonate particles and light calcium carbonate particles. Heavy calcium carbonate particles are obtained by mechanically pulverizing and processing natural chalk (chalk), limestone, marble, and the like. On the other hand, light calcium carbonate is a synthetic calcium carbonate chemically produced from limestone as a raw material. In this production method, it is preferable to use heavy calcium carbonate particles in order to make the grosite ceramics more difficult to thermally expand.

It is also preferable to use a calcium carbonate particle that has not been subjected to a surface treatment with an organic compound in order to obtain a grosite ceramic that is more difficult to thermally expand. Examples of the organic compound include fatty acids, fatty acid esters, and fatty acid salts.

The blending ratio of the alumina particles and the calcium carbonate particles is important in order to make the calcium aluminate constituting the obtained gloucite ceramics consist of a CaAl ₄ O ₇ single phase. The mixing ratio of the alumina particles to the calcium carbonate particles is preferably (calcium carbonate / alumina) = 1.99: 1 or more and 2.01: 1 or less in terms of molar ratio, and is 1.995: 1 or more and 2.005: 1. More preferably, it is as follows.

The mixed powder of the raw material may contain only alumina particles and calcium carbonate particles, or may contain other minerals in addition to the alumina particles and calcium carbonate particles. A binder may also be added. Examples of the binder include glass and silica.

Various molding methods such as hydraulic molding and cast molding can be used to obtain a molded body that is a precursor of the grosite ceramics using the mixed powder of raw materials. In the case of using hydraulic molding, 25 to 100% by mass of water is added to the mixed powder to form a hydrous fluid, and the hydrous fluid is filled in a cavity of a mold to perform pressure molding. For the pressure molding, for example, biaxial pressing can be employed. The applied pressure is preferably set to 100 to 1000 kg / cm ² . By adjusting the applied pressure, the bulk specific gravity, porosity, and bending strength of the resulting grosite ceramics can be adjusted. The molded body thus obtained is dried to remove moisture and fired.

On the other hand, when cast molding is performed, preferably 25 to 100% by mass of water and preferably 0.5 to 3.0% by mass of a dispersant are added to the mixed powder to form a slurry. As the dispersant, for example, a polycarboxylic acid-based dispersant can be used. Next, the obtained slurry is poured into a plaster mold and solidified. After demolding from the gypsum mold, the molded body from which moisture has been removed by drying is fired.

The molded article obtained by various molding methods is fired under a firing temperature condition of 1450 ° C. or higher in an oxygen-containing atmosphere such as the air, thereby obtaining the target grosite ceramics. In this production method, both the particle size of the raw material and the firing temperature condition of 1450 ° C. or higher must be satisfied. If either requirement is not met, and Gros sites ceramics value of I B _/ I _A exceeds the upper limit of the thermal expansion coefficient of up to 300 ° C. resulting in glow sites ceramics has exceeded the upper limit of the above obtained . In order to make it easy to obtain a grosite ceramic that is difficult to thermally expand, the lower limit of the firing temperature is preferably 1450 ° C. or higher, and more preferably 1500 ° C. or higher. Moreover, as an upper limit of baking temperature, it is preferable from a viewpoint of melting | fusing point (1760 degreeC) of material, for example that it is 1750 degrees C or less, and it is more preferable that it is 1730 degrees C or less. The maximum temperature holding time is preferably 1 to 10 hours when the firing temperature is within this range.

The thus obtained glossite ceramic of the present invention has low thermal expansion and spalling resistance during high-temperature heating, so that it can be suitably used for various applications such as molten aluminum members in addition to kiln tools. Can do. As a kiln tool, it can be used suitably for a kiln tool for rapid firing of electronic parts and a kiln tool for powder metallurgy.

The kiln tool of the present invention uses the glossite ceramic of the present invention. Examples of kiln tools include trays, pods, mortars, and containers. As a kiln tool, the rectangular or circular plate-like thing mounted on the hearth of a baking furnace is mentioned. Alternatively, the kiln tool has a rectangular or circular bottom surface that is placed on the hearth of the firing furnace and a closed wall surface that rises from the periphery of the bottom surface, and has an open top. May be. Moreover, the kiln tool may be used like a container by combining a frame and a plate.

The kiln tool of the present invention is particularly preferably used as a kiln tool for rapid firing of electronic parts. When a kiln tool for rapid firing of electronic parts is used as the kiln tool of the present invention, an electronic part obtained by firing the kiln tool includes, for example, a multilayer ceramic capacitor (hereinafter referred to as MLCC). ) And other ceramic electronic components. MLCC is, for example, an internal electrode material such as nickel powder, a dielectric material such as BaTiO ₃ , kneaded with a binder or the like, processed into a paste, and alternately laminated in a manner such as screen printing to form a sheet After cutting to a predetermined size, an external electrode is attached and sintered. Firing for an electronic component such as MLCC is performed by putting it in a furnace in a high temperature range of, for example, 1200 ° C. or higher and 1450 ° C. or lower. The firing atmosphere can be a weak reducing atmosphere or an inert atmosphere using nitrogen and hydrogen. Moreover, as the temperature increase rate in the rapid firing, for example, the average temperature increase rate from the normal temperature in the furnace to the maximum holding temperature is 20 ° C./min or more, particularly 50 ° C./min or more. The cooling rate is 20 ° C./min or more, particularly 50 ° C./min or more, as an average cooling rate from the maximum holding temperature in the furnace to room temperature. The kiln tool of the present invention uses a grosite ceramic that has an excellent and low degree of thermal expansion and a high spalling resistance. As a result, running costs can be reduced and the yield of electronic components can be improved. In addition, when using a kiln tool for the rapid baking of an electronic component, in order to prevent reaction with an electronic component still more reliably, the surface may be coated with zirconia etc.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”. “Part” means “part by mass”.

[Example 1]
67.1 parts of alumina particles having a D ₅₀ of 0.4 μm, 32.9 parts of calcium carbonate particles having a D ₅₀ of 2 μm (heavy, no surface treatment), a 20% PVA aqueous solution, and a polycarboxylic acid dispersant (manufactured by Kao) 1 part of Poise 532A) was mixed to obtain a slurry. The PVA aqueous solution was added so that the amount of the PVA in the slurry was 1%. This slurry was dried at 90 ° C., and the dried product was granulated with a sieve (aperture 250 μm) to obtain granules. The granules were filled in a mold and molded by uniaxial pressing. The applied pressure was 700 kg / cm ² . The obtained molded body was fired by holding it at 1600 ° C. for 3 hours in an air atmosphere furnace to obtain a target grosite ceramic. The glossite ceramic was a plate having a width of 110 mm, a height of 110 mm, and a height of 4 mm.

The bulk specific gravity, the porosity (%), and the bending strength (MPa) of the obtained grosite ceramics were measured by the above methods. The results are shown in Table 1.

Further, the glow sites ceramics obtained, subjected to powder X-ray diffraction measurement under the following conditions to obtain the integrated intensity I _B and I _A of the peak of interest was calculated I B _/ I _A. The results are shown in Table 2. A chart obtained by powder X-ray diffraction measurement is shown in FIG.

Further, the obtained grosite ceramics is subjected to thermomechanical analysis under the following conditions, and the thermal expansion coefficient (/ K) from 27 ° C. to 300 ° C. and the thermal expansion coefficient (/ K) from 27 ° C. to 800 ° C. And a dimension-temperature graph was obtained, and the shape of the curve of this graph was confirmed. The results are shown in Table 2. The obtained graph is shown in FIG. As shown in FIG. 2, hysteresis was observed in the graph. Based on the graph, the ratio (%) of the maximum value of the difference at the same temperature between the dimension at the time of heating and the dimension at the time of cooling to the dimension before the test was measured. The results are shown in Table 2.

Further, the obtained glossite ceramics was observed under a microscope under the following conditions, and the number of microcracks per field of view, the total length of microcracks per field of view in the longitudinal direction (μm), crystals The particle size (μm) was determined. The results are shown in Table 2. Moreover, the photograph of the cross section obtained at the time of microcrack observation is shown in FIG. 3, and the photograph of the cross section obtained at the time of crystal grain diameter observation is shown in FIG. 4, respectively.

Furthermore, the spalling resistance ΔT was determined for the obtained grosite ceramics under the following conditions. Moreover, the amount of deflection (mm) was determined under the following conditions for the obtained glocyceramics. The results are shown in Table 2.

[Examples 2-7, Comparative Examples 1-2]
In the same manner as in Example 1, except that the particle size of alumina, the type of calcium carbonate, the presence or absence of surface treatment, the particle size, the molar ratio of alumina and calcium carbonate, and the firing temperature were changed as shown in Table 1 below, Obtained site ceramics. The same evaluation as Example 1 was performed about the obtained glocyceramics. The results are shown in Tables 1 and 2. Among these, FIG. 5 shows a graph of dimension-temperature at the time of temperature increase obtained by thermomechanical analysis of the globite ceramic obtained in Example 3.
In addition, the surface treatment of calcium carbonate used in Example 7 used a fatty acid as a surface treatment agent. In Table 1, “heavy” of calcium carbonate indicates “heavy”, and “light” indicates “light”.

〔Evaluation methods〕
<Powder X-ray diffraction measurement>
・ Device: Mini Flex600 (manufactured by Rigaku Corporation)
-Radiation source: Cu wire-Tube voltage: 40 kV
・ Tube current: 15 mA
・ Scanning speed: 20 degrees / min
・ Step: 0.01 degrees ・ Scanning range: 2θ = 10 degrees to 70 degrees

<Thermomechanical analysis>
A 5 × 5 × 20 mm test piece made of the grosite ceramic of the present invention was set in a differential thermomechanical analysis (TMA) apparatus of Thermoplus TMA8310 manufactured by Rigaku Corporation. The temperature was increased from 27 ° C. to 300 ° C. or from 27 ° C. to 800 ° C. at a rate of temperature increase of 5 ° C./min. The load was 0.5N. As a reference, alumina having the same size as the test piece was set in a thermomechanical analysis (TMA) apparatus, and the temperature was similarly raised, and the dimensional difference ΔLa between the alumina and the test piece was measured. As the alumina elongation ΔLb during this period, the thermal expansion coefficient was calculated by the following equation.
Thermal expansion coefficient (/ K) = (ΔLa + ΔLb) / (L × Δt) (In the above formula, L = length of test piece before test, Δt = temperature difference measured for elongation)

Further, the test piece was heated from 27 ° C. to 800 ° C. at a rate of 5 ° C./min by the above-described thermomechanical analysis (TMA) apparatus, and subsequently cooled at this rate within this temperature range. During this time, the length of the test piece is measured every 5 seconds, and the difference between the length of the test piece at each measurement point minus the test piece before the test, that is, the elongation ΔL of the test piece is obtained. I got the graph. The temperature holding time at 800 ° C. until the temperature was changed to cooling after the temperature increase was 5 minutes.

<Microscopic observation of cross section>
A cross-section obtained by cutting the grosite ceramics with a diamond cutter was polished with SiC polishing paper and diamond slurry. The sample was observed with a scanning electron microscope (SEM, JSM-6380A manufactured by JEOL Ltd.) under an acceleration voltage of 15 kV, and a 150-fold photograph was taken. In the obtained photograph, the number of microcracks having a length along the longitudinal direction of 50 μm or more per one visual field of the actual size 0.84 mm × 0.59 mm in the grosite ceramics was counted for 10 visual fields, and the average value was calculated. Asked. In the SEM photograph shown in FIG. 3, the microcracks are shown as a long and thin white image. Further, in the grosite ceramics of each example, one or more micro cracks having a length along the longitudinal direction of 50 μm or more were observed in all the 10 visual fields.

Furthermore, in the above-mentioned microscopic observation, the total length (μm) per one visual field of microcracks having a length along the longitudinal direction of 50 μm or more was counted for 10 visual fields, and the average value was obtained.

Further, after polishing the cross section of the grosite ceramics, the polished surface was air baked (keep at 1400 ° C. × 0 min) in a baking furnace and thermally etched. Next, the etched surface was observed and photographed at a magnification of 1500 using a scanning electron microscope (SEM) under the condition that the acceleration voltage was 15 kV, and an image was obtained. The cord length of the obtained image was measured by the intercept method, and the crystal grain size was calculated. In one field of view, 10 line segments parallel to the direction along the long side of the rectangular image were measured. This measurement was performed in 10 different fields of view, and the average value of the crystal grain sizes observed for each field of view was calculated. An image used for the measurement of the crystal grain size is shown in FIG. In FIG. 4, examples of crystal grain boundaries are indicated by arrows.

<Spalling resistance △ T>
Test specimens of grosite ceramics in each Example and Comparative Example that were processed into a length of 100 mm, a width of 100 mm, and a height of 2 mm were prepared. Separately from this, an alumina brick column having a length of 15 mm, a width of 8 mm and a height of 7 mm was prepared. Four struts were placed on the base plate at positions facing the four corners of the test specimen, and one specimen was placed thereon. On the test body, an alumina brick plate having a length of 68 mm, a width of 68 mm, and a height of 16 mm, which was assumed to be an electronic component to be fired, was placed. The above arrangement state is shown in FIG. In FIG. 6, the test body is denoted by reference symbol S, the support column is denoted by reference symbol P, and the plate assuming an electronic component is denoted by reference symbol M. After raising the temperature of the electric furnace to a predetermined temperature (temperature raising rate: 200 ° C./hr) and holding it for 30 minutes, the test specimen in the state of FIG. 6 was placed in the furnace together with the base plate. After holding at that temperature for 60 minutes, the specimen was removed from the furnace together with the base plate and allowed to cool in the atmosphere (temperature T ₁ ). It was visually confirmed whether or not the specimen was cracked or broken. The above operation was carried out by increasing the temperature from 400 ° C. to 50 ° C., the upper limit T ₂ of the temperature at which cracking did not occur was measured, and the value obtained by subtracting T ₁ from T ₂ was defined as the spalling resistance ΔT.

<Deflection test>
A sample of grosite ceramics processed to 100 mm x 30 mm x 3 mm is separated into two square members 90 mm apart as a span (the length in the longitudinal direction parallel to the longitudinal direction of the grosite ceramic is 20 mm, the length in the transverse direction is 200 mm, Place the refractory of 10 mm x 10 mm x 30 mm in the center of the sample, and adjust the weight on the refractory so that 4 kg / cm ² load is applied. And loaded. Heating was performed at 1200 ° C. (temperature increase rate: 200 ° C./hr, keeping 3 hours) in an air firing furnace, and the amount of warpage before and after firing was measured.
As the amount of warping, a hole is made in the center of an aluminum bar (200 mm × 50 mm × 50 mm) without warping as a reference, and the portion of the aluminum bar warped with grosite ceramics is projected in an upward direction, A measuring portion of a digimatic indicator was inserted into this hole from below, and the distance between the aluminum bar and the grosite ceramics was measured.

　

As shown in Table _2, the value of I B / _{I A} is 0.05 or less, as measured in an air atmosphere, the thermal expansion coefficient of up to 300 ° C. from 27 ° C. is, 2.0 × ^{10 -6} / K or less The glossite ceramics of the examples having a low thermal expansion coefficient from 27 ° C. to 800 ° C., high spoke resistance, little deflection at high temperature, and difficult to soften at high temperature. On the other hand, the grosite ceramic of Comparative Example 1 having a thermal expansion coefficient from 27 ° C. to 300 ° C. ^exceeding 2.0 × 10 ⁻⁶ / K has a high thermal expansion coefficient from 27 ° C. to 800 ° C. resistance spokes ring resistance is low, Gros site ceramics of Comparative example 2 the value of I B _/ I _a is 0.05 greater, the amount of deflection is large, it becomes easily softened at a high temperature.
From the above, the glossite ceramic of the present invention has high spalling resistance and can be used in a high-temperature firing process of electronic parts for a long period of time. It turns out that it is suitable.

S Specimen P Prop M Plate assuming electronic parts

Claims (12)

1. To the integral intensity _{I A} of the peak of 2 [Theta] = 25.47 degrees, which is the main peak derived from CaAl ₄ O ₇ in the X-ray diffraction, the main peak derived from CaAl ₂ O ₄ in an X-ray diffraction 2 [Theta] = 30.07 the value of the ratio of the integrated intensity _{I B} of a peak of the time _I B / _{I a} is 0.05 or less,
   Grositic ceramics having a thermal expansion coefficient of 2.0 × 10 ⁻⁶ / K or less measured in an air atmosphere from 27 ° C. to 300 ° C.
2. In thermo-mechanical analysis when heated in an air atmosphere, a temperature range where the size decreases or a plateau temperature range where the size does not change substantially is observed in the obtained dimension-temperature graph. The glossite ceramic according to claim 1.
3. In thermomechanical analysis when heated from 27 ° C to 600 ° C in an air atmosphere, the resulting dimension-temperature graph becomes a convex curve in the direction of decreasing dimension, or the dimension changes substantially The glossite ceramic according to claim 1 or 2, which has a plateau temperature range that does not occur and a temperature range in which a subsequent dimension increases.
4. The hysteresis is observed in the obtained dimension-temperature graph in the thermomechanical analysis when heated from 27 ° C. to 800 ° C. in the atmosphere and subsequently cooled in this temperature range. The glossite ceramics according to Item.
5. The maximum value of the difference at the same temperature between the dimension at the time of temperature rise and the dimension at the time of cooling caused by the hysteresis is 0.02% or more with respect to the dimension of the grosite ceramic before thermomechanical analysis. The glossite ceramic described.
6. 6. The grosite ceramic according to any one of claims 1 to 5, which has a coefficient of thermal expansion of not more than 3.4 × 10 ⁻⁶ / K measured from 27 ° C. to 800 ° C. in an air atmosphere.
7. Microcracks are observed in the microscopic image of the cross section magnified 150 times,
   The micro crack has a shape having a width direction and a longitudinal direction longer than the width direction,
   7. The microcrack having a length along the longitudinal direction of 50 μm or more is observed one or more per field of view of 0.84 mm × 0.59 mm at the magnification. 8. Grosite ceramics.
8. The grossite ceramics according to claim 7, wherein the total length per one visual field of the microcracks having a length along the longitudinal direction of 50 µm or more is 1000 µm or more.
9. 9. The glossite ceramic according to claim 1, wherein an average crystal grain size of the cross-section observed in a microscopic image is 5 μm or more.
10. The globite ceramic according to any one of claims 1 to 9, wherein the spalling resistance ΔT is 600 ° C or higher.
11. A kiln tool using the globite ceramic according to any one of claims 1 to 10.
12. A method for producing a grosite ceramic according to any one of claims 1 to 10,
    A mixed powder of alumina particles having a volume cumulative particle size D ₅₀ of 5 μm or less and a calcium carbonate particle having a volume cumulative particle size D ₅₀ of 25 μm or less measured by a laser diffraction / scattering particle size distribution measurement method. A method for producing a grosite ceramic, comprising a step of molding and firing the obtained molded body at a temperature of 1450 ° C. or higher.

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