JP7186930B1 - Ceramic sintered plate and method for manufacturing ceramic sintered plate - Google Patents

Abstract

One aspect of the present disclosure is a sintered ceramic having a maximum dielectric loss ε″ of 1×10 or less when an AC voltage of 1 V is applied while continuously changing the frequency between 800 Hz and 1 MHz. provide a body.

Description

The present disclosure relates to a ceramic sintered body and a method for manufacturing a ceramic sintered body.

Power modules that control large currents are used in fields such as automobiles, electric railways, industrial equipment, and power generation. An insulating ceramic plate is used for the circuit board mounted on the power module. As a method for manufacturing a ceramic plate, for example, the following manufacturing method described in Patent Document 1 is known. That is, a step of mixing and kneading ceramic powder with a sintering aid or the like and then extrusion molding into a continuous sheet shape, a step of punching the continuous sheet into a desired shape to form a green sheet, and a green sheet A ceramic substrate is manufactured by performing the step of firing. In the green sheet firing process, the green sheets are fired in a state in which a required number of green sheets of about 10 to 20 are stacked.

In addition, in the case of applications such as power modules that are exposed to thermal changes during use, the amount of deformation of each member differs due to the difference in coefficient of thermal expansion of the members that make up the power module. In order to withstand such deformation, the ceramic plate is required to have excellent bending strength. For example, Patent Document 2 discloses a silicon nitride sintered body prepared using a specific boride as a sintering aid.

JP-A-3-060469 JP-A-7-172925

An object of the present disclosure is to provide a ceramic sintered body having excellent bending strength. Another object of the present disclosure is to provide a method of manufacturing a ceramic sintered body as described above.

If there are voids, defects, uneven portions of the structure, etc. in the ceramic sintered body, it is considered that the bending strength of the ceramic sintered body is affected. When a high-frequency AC voltage is applied to a ceramic sintered body, a slight discharge occurs and the dielectric loss ε” increases. Furthermore, the dielectric loss in a specific frequency band corresponds well to the bending strength. The present disclosure has been made based on the above findings.

One aspect of the present disclosure is a ceramic having a maximum value of dielectric loss ε″ that occurs when an alternating voltage of 1 V is applied while continuously changing the frequency between 800 Hz and 1 MHz is 1×10 ⁻² or less A sintered body is provided.

The ceramic sintered body has a dielectric loss within the above range in a specific frequency band when an AC voltage is applied, and can exhibit excellent bending strength.

The ceramic sintered body described above may be composed of silicon nitride. Since the silicon nitride sintered body has both heat resistance and high strength, it is superior to the ceramic sintered body in bending strength.

One aspect of the present disclosure includes a degreasing step of heating and degreasing a laminate of green sheets containing a ceramic, a sintering aid, a binder, and a dispersant, and heating the degreased laminate at a predetermined firing temperature. a firing step of obtaining a heat-treated product; and a temperature-lowering step of cooling the heat-treated product from the firing temperature to room temperature to obtain a ceramic sintered body. A method for producing a ceramic sintered body is provided, comprising a first step of holding for 5 to 2.0 hours and a second step of holding at a temperature of 1400 to 1600° C. for 1.5 to 4.0 hours.

Since the above method for producing a ceramic sintered body includes the temperature lowering step as described above, it is possible to produce a ceramic sintered body having excellent bending strength.

According to the present disclosure, a ceramic sintered body having excellent bending strength can be provided. The present disclosure can also provide a method of manufacturing a ceramic sintered body as described above.

FIG. 1 is a schematic diagram for explaining a method for measuring dielectric loss ε″.

Embodiments of the present disclosure will be described below. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

The materials exemplified in this specification can be used singly or in combination of two or more unless otherwise specified. The content of each component in the composition means the total amount of the multiple substances present in the composition unless otherwise specified when there are multiple substances corresponding to each component in the composition. .

In one embodiment of the ceramic sintered body, the maximum value of dielectric loss ε″ that occurs when an alternating voltage of 1 V is applied while continuously changing the frequency between 800 Hz and 1 MHz is 1×10 ⁻² or less. A ceramic sintered body having a dielectric loss within the above range in a high frequency band has few defects such as voids and can exhibit excellent bending strength.

The maximum value of the dielectric loss ε″ mentioned above may be, for example, 1×10 ⁻² or less, 9×10 ⁻³ or less, 8×10 ⁻³ or less, or 6×10 ⁻³ or less. The maximum value of ε″ is generally 1×10 ⁻³ or more, or 2×10 ⁻³ or more. The maximum value of the dielectric loss ε″ described above may be adjusted within the ranges described above, for example, 1×10 ⁻³ to 1×10 ⁻² , 1×10 ⁻³ to 9×10 ⁻³ , or 1×10 ⁻³ to 6×10 ⁻³ .

The dielectric loss ε″ in this specification means a value measured by the following method. The frequency is continuously changed from 50 Hz to 1 MHz, the dielectric constant ε and tan δ are measured between 800 Hz and 1 MHz, and the measured values are used to calculate the dielectric loss ε” based on the following formula (1). be able to. Measurements are made at 25°C. For the above measurement, for example, an LCR meter manufactured by Hewlett-Packard (product name: 4284A Precision LCR meter) can be used. For reference, FIG. 1 shows a schematic diagram of an evaluation sample for measuring the dielectric loss ε″. FIG. ) is a cross-sectional view along the line 1b-1b' As shown in FIG. A guard electrode 20 is provided so as to surround the main electrode 10 , and a counter electrode 30 is provided on the other main surface of the ceramic sintered body 100 .
Dielectric loss ε″=27.3×f/C×ε×tan δ Equation (1)
In equation (1), f means the measurement frequency, and C means the speed of light (299792458 ms ^-1 ).

The ceramic sintered body may be composed of silicon nitride. Even when the ceramic sintered body is composed of silicon nitride, it may contain other components within the scope of the present disclosure. For example, it may contain a crystal phase, a glass phase, etc. derived from a sintering aid used when producing a ceramic sintered body.

The density of the ceramic sintered body may be, for example, 3.24 g/cm ³ or higher, 3.25 g/cm ³ or higher, or 3.26 g/cm ³ or higher. The upper limit of the density of the ceramic sintered body is usually 3.35 g/cm ³ or less, and may be 3.30 g/cm ³ or less, or 3.28 g/cm ³ or less. The density of the ceramic sintered body may be adjusted within the range described above, and may be, for example, 3.24-3.35 g/cm ³ , or 3.25-3.28 g/cm ³ . The density of the ceramic sintered body means a value measured based on the Archimedes method.

The surface roughness Ra of the main surface of the ceramic sintered body may be, for example, 0.28 μm or less, 0.27 μm or less, or 0.25 μm or less. The lower limit of the surface roughness Ra on the main surface of the ceramic sintered body may be, for example, 0.10 μm or more, 0.13 μm or more, 0.18 μm or more, 0.20 μm or more, or 0.22 μm or more. The surface roughness Ra of the main surface of the ceramic sintered body may be adjusted within the range described above, and may be, for example, 0.10-0.28 μm, or 0.22-0.27 μm. The surface roughness Ra in this specification is measured according to the method described in JIS B 0601: 2013 "Product Geometric Characteristic Specification (GPS)-Surface Texture: Contour Curve Method-Terms, Definitions and Surface Texture Parameters". means the arithmetic mean roughness.

The shape of the ceramic sintered body may be plate-like, for example. That is, the ceramic sintered body may be a ceramic sintered plate. The thickness of the plate-shaped ceramic sintered body may be, for example, 0.20 mm or more, or 0.25 mm or more. The upper limit of the thickness of the plate-shaped ceramic sintered body may be, for example, 0.50 mm or less, 0.40 mm or less, or 0.35 mm or less. The thickness of the ceramic sintered plate may be adjusted within the ranges mentioned above, and may be, for example, 0.20-0.50 mm, 0.25-0.40 mm, or 0.25-0.35 mm.

The ceramic sintered body described above has excellent bending strength. The bending strength of the ceramic sintered body can be 780 MPa or more, 800 MPa or more, 810 MPa or more, 820 MPa or more, or 830 MPa or more. The bending strength of a ceramic sintered body means a value measured by a three-point bending test in accordance with the description of JIS R 1601:2008 "Room temperature bending strength test method for fine ceramics".

The ceramic sintered body described above can exhibit excellent thermal conductivity. The thermal conductivity of the ceramic sintered body can be, for example, 89 W/m·K or more, or 90 W/m·K or more. The thermal conductivity of a ceramic sintered body can be measured by a laser flash method.

One embodiment of the method for producing a ceramic sintered body includes the steps of preparing a green sheet containing a ceramic, a sintering aid, a binder and a dispersant, a degreasing step of heating and degreasing the laminate of the green sheets, A firing step of heating the degreased laminate at a predetermined firing temperature to obtain a heat-treated product, and a cooling step of cooling the heat-treated product from the firing temperature to room temperature to obtain a ceramic sintered body. The temperature lowering step includes a first step (hereinafter also referred to as a first holding step) of holding at a temperature of 900 to 1200° C. for 0.5 to 2.0 hours, and a temperature of 1400 to 1600° C. for 1.5 to 4 hours. and a second step of holding for 0 hours (hereinafter also referred to as a second holding step).

A green sheet is produced, for example, by the following procedures. First, a raw material slurry containing a ceramic, a sintering aid, a binder and a dispersant is prepared. Ceramics are not particularly limited, and include, for example, nitrides, oxides and carbides. The ceramic may specifically be silicon nitride, silicon carbide, alumina, aluminum nitride, boron nitride and the like, preferably silicon nitride. Binders include those containing organic components. The binder may be, for example, an acrylic copolymer. Dispersants can be, for example, unsaturated fatty acids.

Examples of sintering aids include oxides of alkaline earth metals such as magnesium oxide and calcium oxide, rare earth oxides such as yttrium oxide, aluminum oxide, silicon dioxide, and complex oxides such as spinel. A plurality of sintering aids are preferably used in combination. The sintering aid preferably contains at least one selected from the group consisting of yttrium oxide, magnesium oxide, and silicon dioxide.

The composition of the sintering aid is based on the total amount of the ceramic and sintering aid, for example, 1 to 10% by weight of yttrium oxide, 0.5 to 7% by weight of magnesium oxide, and 5% by weight or less of dioxide. may contain silicon, may contain 2-7% by weight yttrium oxide, 0.5-5% by weight magnesium oxide, and up to 3% by weight silicon dioxide, 5-7% by weight yttrium oxide; It may contain 5-2% by weight of magnesium oxide and 0.5-2% by weight or less of silicon dioxide.

The raw material slurry described above is applied to a release film in a predetermined thickness by, for example, a doctor blade method, a calendar method, or an extrusion method. After that, the applied raw material slurry is dried and peeled off from the release film to obtain a green sheet. The green sheet may be processed into a desired shape by, for example, cutting. The material and shape of the plurality of green sheets may be the same or different.

A green sheet may have a flat plate shape. The size of the green sheet is not particularly limited, but may be, for example, 170 to 300 mm or 170 to 200 mm in diagonal length. The thickness of the green sheet may be, for example, 0.2-2 mm, 0.2-1 mm, 0.2-0.5 mm, or 0.2-0.4 mm.

In the degreasing step, a laminate obtained by laminating a plurality of green sheets prepared as described above is heated to reduce the content of the binder component in each green sheet. The number of green sheets constituting the laminate may be, for example, 20 to 150 or 50 to 100. When the number of green sheets constituting the laminate is within the above range, deformation of the green sheets themselves due to the weight of the green sheets can be further suppressed, and productivity can be improved.

The laminate may be one in which a plurality of green sheets are laminated such that the main surfaces thereof are in contact with each other. In order to prevent the green sheets from adhering to each other, a release material is provided on the main surface of each green sheet. may be applied. The release material may be, for example, ceramic powder such as boron nitride, graphite powder, and the like.

In the degreasing step, the laminate is placed in a degreasing furnace and heated to 300° C. to 700° C., for example. As a result, the binder and dispersant contained in the green sheet volatilize, and the content of organic components in the green sheet is reduced.

In the firing step, the degreased laminate of green sheets is placed in a firing furnace and heated at a predetermined firing temperature. In the firing step, the green sheet is fired to obtain a flat ceramic sintered body. The degreasing furnace used for degreasing and the firing furnace used for firing may be the same furnace or may be different furnaces. The firing temperature may be, for example, 1600°C to 2000°C.

The heating time in the firing step may be, for example, 8 to 20 hours, or 8 to 12 hours. The heating time means the time during which the temperature inside the furnace reaches a predetermined firing temperature and is maintained within the firing temperature. Unless otherwise specified, the predetermined firing temperature means the maximum attainable temperature within the firing temperature range.

The baking step may include a plurality of steps with different heating temperatures. By performing the heat treatment in a plurality of steps, the structure of the ceramic sintered body can be further homogenized. The firing step includes, for example, a first firing step in which heat treatment is performed at a temperature of 1600 ° C. or higher and lower than 1800 ° C., and a and a second firing step in which heat treatment is performed at a temperature of ) below.

Of the heating time in the firing step, it is desirable to secure a longer time (eg, several hours) for heat treatment at a temperature of 1600° C. or more and less than 1800° C. (for example, the time for heat treatment in the first firing step). Therefore, the time for holding the temperature in the furnace at 1600 ° C. or more and less than 1800 ° C. may be, for example, 4 hours or more, 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, or 9 hours or more. hours or less, or 12 hours or less. The time for which the temperature inside the furnace is maintained at 1600° C. or more and less than 1800° C. may be, for example, 4 to 15 hours, or 5 to 8 hours. In the temperature range of 1600° C. or more and less than 1800° C., the sintering aid forms a liquid phase, so by securing a sufficient time to hold at this temperature, the environment for grain growth of the ceramic can be made more homogeneous. The bending strength of the ceramic sintered body can be further improved.

In addition, it is preferable to secure a longer time for heat treatment at a temperature of 1800 ° C. or higher, and the time for holding the temperature in the furnace at a temperature of 1800 to 2000 ° C. (for example, the time for heat treatment in the second firing step) is, for example, It may be 3 hours or more, or 4 hours or more, and may be 7 hours or less, or 6 hours. The time for which the temperature in the furnace is maintained at a temperature of 1800-2000° C. may be, for example, 3-7 hours or 4-6 hours. In the temperature range of 1800 to 2000 ° C., the ceramic powder dissolves in the liquid phase derived from the sintering aid, and the growth of a thermodynamically more stable crystal phase is promoted, so the time to hold at this temperature is secured. This promotes the grain growth of the ceramic and improves the thermal conductivity of the obtained ceramic sintered body. In addition, by setting the time for holding at a temperature of 1800 to 2000° C. within the above range, decomposition of the ceramic and the sintering aid can be suppressed, and inhibition of densification of the ceramic sintered body can be suppressed more sufficiently. .

More specifically, the firing step includes, for example, a first firing step of performing heat treatment at a temperature of 1600 ° C. or higher and lower than 1800 ° C. for 1 to 2 hours, and a 1800 ° C. or higher and 2000 ° C. or lower (preferably 1800 ° C. or higher and 1850 ° C. or lower , more preferably 1800° C. or higher and 1830° C. or lower) for 4 to 5 hours.

The temperature lowering step includes a first step (hereinafter also referred to as a first holding step) in which the temperature is lower than the firing temperature and is held at a temperature of 900 to 1200 ° C. for 0.5 to 2.0 hours, and a temperature of 1400 to 1600 ° C. and a second step of holding for 5 to 4.0 hours (hereinafter also referred to as a second holding step). The second holding step is a step subsequent to the first holding step, preferably a step performed immediately after the first holding step. By providing at least two stages of holding steps with different temperatures as a temperature-lowering step and cooling the fired body to room temperature, the sintering aid is decomposed in the firing process and escapes from the surface layer of the fired body, thereby sintering the ceramic. It is possible to suppress the occurrence of defects and the like on the surface layer of the body.

The temperature (first temperature) at which the fired body is held in the first holding step may be, for example, 1200° C. or lower, or 1100° C. or lower. By setting the first temperature within the above range, the solidification of the sintering aid can be promoted, and the removal of the sintering aid from the surface layer can be further suppressed. Although the lower limit of the first temperature is not particularly limited, it may be, for example, 900° C. or higher, or 1000° C. or higher. By setting the lower limit of the first temperature within the above range, the productivity of the ceramic sintered body can be further improved. The first temperature may be adjusted within the ranges described above, eg, 900-1200°C, or 1000-1200°C.

In the first holding step, the time for holding at the first temperature (holding time) may be, for example, 0.5 to 2.0 hours. The holding time in the first holding step may be, for example, 0.8 hours or longer, 0.9 hours or longer, or 1.0 hours or longer. The holding time of the first holding step may be, for example, 1.8 hours or less, or 1.6 hours or less.

In the temperature lowering step, the heat-treated material is cooled from the firing temperature to room temperature to obtain a ceramic sintered body. Around the firing temperature, the sintering aid in the surface layer of the ceramic sintered body tends to decompose and the concentration of the aid tends to decrease. can occur. When quenching is started immediately after the firing process, the crystalline phase or glass phase derived from the sintering aid is distributed on the surface and inside of the ceramic sintered body, and the spread of the distribution increases the bending strength. can decline. Furthermore, since the solidification temperature differs depending on the sintering aid, when using multiple sintering aids together, each sintering aid forms a crystal phase or glass phase, promoting the formation of grain boundaries. Therefore, the bending strength can be further reduced. Therefore, it is desirable to adjust the temperature drop rate in the temperature drop step. By slowing down the temperature drop rate, the occurrence of defects in the surface layer of the ceramic sintered body due to the removal of the sintering aid as described above can be further suppressed, and the crystal phase and glass in the surface layer and inside of the ceramic sintered body can be suppressed. It is possible to suppress the distribution of phases and the formation of grain boundaries in the crystal phase and the glass phase, thereby producing a ceramic sintered body with superior bending strength. The rate of temperature drop from the firing temperature to the first temperature may be, for example, 8° C./min or less, 7° C./min or less, or 6° C./min or less.

The temperature (second temperature) at which the fired body is held in the second holding step is set higher than the first temperature. By setting the second temperature to a temperature higher than the first temperature, the sintering aid held in the fired body is suppressed by suppressing the escape of the sintering aid in the first holding step, and then slightly heated. By making the agent melt again, defects in the surface layer can be repaired, the smoothness can be further improved, and the bending strength can be further improved.

The second temperature in the second holding step may be, for example, 1600°C or lower, or 1550°C or lower. By setting the second temperature within the above range, the further decomposition of the sintering aid can be sufficiently suppressed, and the occurrence of defects in the ceramic sintered body can be further suppressed. The lower limit of the second temperature may be, for example, 1400° C. or higher, or 1450° C. or higher. By setting the lower limit of the second temperature within the above range, it is possible to promote the formation of the liquid phase by melting the sintering aid and improve the dispersibility of the liquid phase. Smoothness can be further enhanced. The second temperature in the second holding step may be adjusted within the ranges described above, and may be, for example, 1400-1600°C, or 1450-1550°C.

In the second holding step, the holding time at the second temperature (holding time) may be, for example, 1.5 to 4.0 hours. The holding time in the second holding step may be, for example, 1.8 hours or longer, 1.9 hours or longer, or 2.0 hours or longer. The holding time in the second holding step may be, for example, 3.5 hours or less, 3.0 hours or less, or 2.5 hours or less.

The rate of temperature drop from the second temperature to room temperature is not particularly limited, but may be, for example, 10° C./min or more, or 20° C./min or more.

Although several embodiments have been described above, the mutual descriptions can be applied to common configurations. Moreover, the present disclosure is not limited to the above embodiments.

The contents of the present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

(Example 1)
<Production of ceramic plate>
Silicon nitride powder and yttrium oxide powder, magnesium oxide powder and silicon dioxide as sintering aids were prepared. These were blended in Si ₃ N ₄ :Y ₂ O ₃ :MgO:SiO ₂ =91:5:2:2 (mass ratio) to obtain raw material powder. A binder, a dispersant, and a dispersion medium were added to this raw material powder to prepare a raw material slurry. Next, the raw material slurry was applied onto a release film by a doctor blade method, and the coating thickness was adjusted to 0.4 mm to produce a green sheet.

The produced ceramic green sheet was cut into a length of 250 mm×width of 180 mm, and 70 sheets were laminated to prepare a laminate. The laminate was placed in an electric furnace equipped with a carbon heater and heated in the air at 500° C. for 20 hours for degreasing to obtain a degreased body.

Next, the pressure in the firing furnace was reduced to 100 Pa or less, the temperature was raised to 900° C., and the degreased body was heat-treated under vacuum. After that, nitrogen gas was introduced into the firing furnace, the temperature was raised to 1500 ° C. under a pressure of about 0.9 MPa, the above degreased body was heated, and it was held at 1500 ° C. for 4 hours in order to soak the heat (first firing process) . After holding, the temperature was raised at 1830°C over 3.5 hours to heat the degreased body, and the temperature was increased to 1830°C for 5 hours . A sintered body was obtained by holding for 5 hours (second sintering step) .

The sintered body described above was finally cooled by the following temperature-lowering step to prepare a ceramic sintered body. That is, regarding the temperature of the firing furnace in the cooling step, it was cooled from 1830° C. to 1100° C. over 120 minutes and held at a temperature of 1100° C. (first temperature) for 2 hours. Then, it was heated to 1500° C. over 240 minutes and held at 1500° C. (second temperature) for 2 hours. After further cooling to 1100° C. over 80 minutes, the heater power source of the kiln was turned off and allowed to cool naturally.

(Example 2)
A ceramic plate was obtained in the same manner as in Example 1, except that the second temperature was changed to 1600°C.

(Example 3)
A ceramic plate was obtained in the same manner as in Example 1, except that the first temperature was changed to 1200°C.

(Example 4)
A ceramic plate was obtained in the same manner as in Example 1, except that the thickness of the ceramic green sheet was adjusted to be 23% thinner. The thickness of the obtained ceramic plate was 0.25 mm.

(Example 5)
A ceramic plate was obtained in the same manner as in Example 1, except that the amount of the sintering aid was changed as shown in Table 1.

(Comparative example 1)
A ceramic plate was obtained in the same manner as in Example 1, except that the heating time at 1830° C. in the firing step was changed to 10.0 hours.

(Comparative example 2)
A ceramic plate was obtained in the same manner as in Example 1, except that the temperature lowering step was changed to natural cooling and the first holding step and the second holding step were not provided.

(Comparative Example 3)
In the same manner as in Example 1, except that the temperature lowering step was cooled to 1500° C. at 6° C./min, held at 1500° C. for 2 hours, and then naturally cooled (the holding step in the temperature lowering step was changed to one step). , to obtain a ceramic plate.

<Evaluation of ceramic plate>
The thickness, dielectric loss, density, surface roughness, thermal conductivity and bending strength of the ceramic plates prepared in Examples 1-5 and Comparative Examples 1-3 were measured. Dielectric loss, density, surface roughness, thermal conductivity and bending strength were measured by the method described later using a sample obtained by processing the above ceramic plate into a size of 50 mm×50 mm. Table 1 shows the results.

[Measurement of dielectric loss of ceramic plate]
A circular electrode is formed on a ceramic plate, and an alternating voltage with an effective value of 1 V is applied at 25 ° C., and the frequency of the alternating voltage is continuously changed from 50 Hz to 1 MHz to change the dielectric constant between 800 Hz and 1 MHz. ε and tan δ were measured to calculate the dielectric loss ε″. For the measurement, an LCR meter manufactured by Hewlett-Packard (product name: 4284A Precision LCR meter) was used.

[Measurement of Density of Ceramic Plate]
The density of the ceramic plate was measured based on the Archimedes method.

[Measurement of surface roughness (arithmetic mean roughness) of ceramic plate]
The surface roughness Ra was measured in accordance with the method described in JIS B 0601:2013 "Product Geometric Characteristic Specification (GPS)-Surface Texture: Contour Curve Method-Terms, Definitions and Surface Texture Parameters".

[Measurement of thermal conductivity of ceramic plate]
The thermal conductivity of the ceramic plate was measured by the laser flash method.

[Measurement of bending strength of ceramic plate]
For each of the ceramic plates prepared in Examples 1 to 5 and Comparative Examples 1 to 3, transverse bending was performed by a three-point bending test in accordance with the description of JIS R 1601:2008 "Testing method for room temperature bending strength of fine ceramics". Strength was measured.

According to the present disclosure, a ceramic sintered body having excellent bending strength can be provided. The present disclosure can also provide a method of manufacturing a ceramic sintered body as described above.

DESCRIPTION OF SYMBOLS 10... Main electrode, 20... Guard electrode, 30... Counter electrode, 100... Ceramic sintered body.

Claims (2)

Composed of silicon nitride, Density 3.24-3.35g/cm ³ and
The surface roughness Ra on the main surface is 0.28 μm or less,
The maximum value of dielectric loss ε” that occurs when an AC voltage of 1 V is applied while continuously changing the frequency between 800 Hz and 1 MHz is 1 × 10^-2Ceramic sintered, which is belowboard. silicon nitride , a degreasing step of heating and degreasing a laminate of green sheets containing a sintering aid, a binder and a dispersant;
a firing step of heating the degreased laminate at a predetermined firing temperature to obtain a heat-treated product;
a cooling step of cooling the heat-treated product from the firing temperature to room temperature to obtain a ceramic sintered body,
The firing step includes
A first firing step of performing heat treatment at a temperature of 1600 ° C. or more and less than 1800 ° C.;
A second firing step of performing heat treatment at a temperature of 1800 ° C. or higher and 2000 ° C. or lower for 3 to 7 hours;
including
The temperature lowering step includes
A first step of holding at a temperature of 900 to 1200 ° C. for 0.5 to 2.0 hours;
a second step of holding at a temperature of 1400 to 1600° C. for 1.5 to 4.0 hours;
ceramic sintering, includingboardmanufacturing method.

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