JP7185099B2 - Ceramic plate manufacturing method, setter manufacturing method, and setter recycling method - Google Patents

Description

The present disclosure relates to a ceramic plate manufacturing method, a setter manufacturing method, and a setter recycling method.

Power modules that control large currents are used in fields such as automobiles, electric railways, industrial equipment, and power generation. A circuit board mounted on the power module has an insulating ceramic plate. As a method for manufacturing a ceramic plate, the following manufacturing method described in Patent Document 1, for example, is known. That is, a step of mixing ceramic powder with a sintering aid or the like and then extruding into a sheet shape, a step of stamping to form a ceramic green sheet, and a step of firing the ceramic green sheet are performed. to produce a ceramic plate. In the ceramic green sheet firing process, the ceramic green sheets are fired in a state in which about 10 to 20 ceramic green sheets are laminated on the setter.

JP-A-3-60469

From the viewpoint of effective utilization of resources, the setter used in the firing process of the ceramic green sheets is preferably recycled and reused after use. Therefore, the present disclosure provides a method of manufacturing a ceramic plate capable of improving the production efficiency of the ceramic plate by regenerating the setter. In addition, the present invention provides a setter manufacturing method and a setter recycling method that enable effective use of resources.

When the setter is repeatedly used for firing the ceramic green sheets, even if the facing surface of the setter before firing is smooth, the surface of the ceramic plate may become uneven. According to the investigations of the present inventors, fine foreign matter caused by the components contained in the ceramic green sheet or ceramic plate adhered to the setter grows by firing to become coarse particles, and the shape of the coarse particles is transferred. It was found that the surface of the ceramic plate was uneven due to the heat treatment.

Therefore, a method for manufacturing a ceramic plate according to one aspect of the present disclosure includes a first firing step to obtain a ceramic plate by stacking and firing the setter and the first ceramic green sheet so that they are in contact with each other; a heating step of heating the setter with at least part of the contact surface of the setter exposed, and the setter and the second ceramic green sheet are laminated and fired so that they are in contact with each other at least part of the contact surface. and a second firing step of obtaining a ceramic plate.

In the manufacturing method described above, the setter is heated in a state in which at least a portion of the contact surface of the setter, which was in contact with the first ceramic green sheets, is exposed. By heating the setter in this manner, minute foreign matter originating from the first ceramic green sheet is reduced, and the occurrence of unevenness in the ceramic plate obtained in the second firing step can be suppressed. In this way, even if the setter is used repeatedly, the yield of the ceramic plates can be maintained, so that the production efficiency of the ceramic plates can be improved.

In the heating step, the contact surface may be heated to a temperature higher than the temperature at which foreign substances containing components different from those contained in the setter are decomposed. As a result, it is possible to sufficiently reduce the amount of foreign matter adhering to the contact surface and to sufficiently reduce the unevenness generated on the surface of the ceramic plate. Therefore, the yield of ceramic plates can be further improved. In the present disclosure, the "components contained in the setter" refer to components originally contained in the setter before being used in the method of manufacturing the ceramic plate. That is, it is a component (constituent component) contained in the unused setter. For example, the component contained in a setter made of a boron nitride sintered body is boron nitride.

In the first firing step, the plurality of setters including the setters and the plurality of first ceramic green sheets including the first ceramic green sheets may be stacked and fired such that they are in contact with each other. At this time, in the heating step, the plurality of setters may be heated while the contact surfaces of the plurality of setters that have been in contact with the first ceramic green sheets are separated from each other. This allows multiple setters to be heated together for regeneration. Therefore, it is possible to further improve the production efficiency of the ceramic plate.

The first ceramic green sheet contains silicon nitride, and in the heating step, the setter may be heated at 1450-2000° C. in an inert gas atmosphere. As a result, the decomposition of the silicon nitride contained in the foreign matter proceeds smoothly, and the time required for the heating process can be shortened. In addition, foreign matter on the contact surface of the setter can be sufficiently reduced, and unevenness generated on the surface of the ceramic plate obtained in the second firing step can be further reduced.

In a method for manufacturing a setter according to one aspect of the present disclosure, a first setter and a ceramic green sheet are laminated so as to be in contact with each other and fired, and the contact surface with the ceramic green sheet has a component different from that of the first setter. and a heating step of heating the second setter with at least a portion of the contact surface exposed to reduce the amount of foreign matter on the contact surface. .

The above-described manufacturing method includes a heating step of heating the second setter in which the foreign matter adheres to the contact surface with the ceramic green sheet in the firing step. In the heating step, the second setter is heated with at least a portion of the contact surface exposed to reduce foreign matter on the contact surface. The setter (third setter) obtained by reducing foreign matters can be laminated and fired so as to be in contact with the ceramic green sheets again. As described above, in the method for manufacturing a setter, by manufacturing a setter (third setter) with reduced foreign matter from the second setter to which foreign matter is adhered, it is possible to reduce the waste amount of the setter and effectively utilize resources. can.

In the heating step, the foreign matter may be heated to a temperature higher than the decomposition temperature. As a result, it is possible to sufficiently and smoothly reduce the foreign matter adhering to the contact surface. Therefore, the setter can be manufactured efficiently.

In the firing step, a plurality of first setters including the first setters and a plurality of ceramic green sheets including the ceramic green sheets are stacked and fired so as to be in contact with each other, and a plurality of second setters including the second setters are stacked. You may get a 2 setter. At this time, in the heating step, the plurality of second setters may be heated while the contact surfaces of the plurality of second setters that have been in contact with the ceramic green sheets are separated from each other. This allows multiple second setters to be heated together to produce multiple setters simultaneously. Therefore, it is possible to improve the production efficiency of the setter.

The ceramic green sheet contains silicon nitride, and in the heating step, the second setter may be heated at 1450 to 2000° C. in an inert gas atmosphere. As a result, the decomposition of the silicon nitride contained in the foreign matter proceeds smoothly, and the time required for the heating process can be shortened. Also, a setter with sufficiently reduced foreign matter can be obtained.

A method for regenerating a setter according to one aspect of the present disclosure includes stacking and firing a first setter and a ceramic green sheet so that they are in contact with each other, and the contact surface with the ceramic green sheet has a component different from that of the first setter. A baking step of obtaining a second setter to which foreign matter containing the component is adhered, and a heating step of heating the second setter in a state where at least a part of the contact surface is exposed to reduce foreign matter on the contact surface.

The above-described recycling method includes a heating step of heating the second setter to which the foreign matter adheres to the contact surface with the ceramic green sheet in the firing step. In the heating step, the second setter is heated with at least a portion of the contact surface exposed to reduce foreign matter on the contact surface. The setter (third setter) obtained by reducing foreign matters can be laminated and fired so as to be in contact with the ceramic green sheets again. As described above, in the above setter recycling method, by recycling the setter (third setter) to which the foreign matter is reduced from the second setter to which the foreign matter is adhered, it is possible to reduce the waste amount of the setter and effectively utilize resources. can.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a ceramic plate manufacturing method capable of improving the production efficiency of ceramic plates by regenerating the setter. In addition, it is possible to provide a setter manufacturing method and a setter recycling method that enable effective use of resources.

It is a figure explaining an example of the baking process of a laminated body. 4 is a SEM photograph showing an example of foreign matter (boron nitride particles) adhering to the contact surface of a setter made of a sintered boron nitride. It is a figure which shows an example of a heating process. 4 is a SEM photograph showing the main surface (before firing) of the setter used in Example 1. FIG. 5 is an SEM photograph showing the main surface of FIG. 4, taken at a higher magnification than FIG. 4; 4 is an SEM photograph showing the contact surface of the setter after the first firing step in Example 1. FIG. 7 is an SEM photograph showing the contact surface of FIG. 6, taken at a higher magnification than FIG. 6; 4 is a SEM photograph showing the contact surface of the setter after the heating process in Example 1. FIG. 9 is an SEM photograph showing the contact surface of FIG. 8, taken at a higher magnification than FIG. 8; 4 is an SEM photograph showing the contact surface of the setter after the heating process in Comparative Example 1. FIG. 12 is an SEM photograph showing the contact surface of FIG. 10, taken at a higher magnification than FIG. 11; 4 is a photograph showing an example of protrusions on the surface of a silicon nitride plate.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents. In the explanation, the same reference numerals are given to the same elements or elements having the same function, and duplicate explanations are omitted. In addition, the positional relationships such as up, down, left, and right used in the description are based on the positional relationships shown in the drawings unless otherwise specified.

A method for manufacturing a ceramic plate according to one aspect of the present disclosure includes firing a laminate (first laminate) in which a setter and a ceramic green sheet (first ceramic green sheet) are in contact with each other, and firing a ceramic plate. and a heating step of separating the first laminate into a setter and a ceramic plate, and heating the setter in a state where at least part of the contact surface of the setter in contact with the ceramic green sheet is exposed. and a second firing for obtaining a ceramic plate by firing the laminate (second laminate) laminated such that the setter and the ceramic green sheet (second ceramic green sheet) are in contact with each other at least part of the contact surface. and

The first ceramic green sheet and the second ceramic green sheet are ceramic green sheets laminated so as to be in contact with the setter. The first ceramic green sheet and the second ceramic green sheet that are laminated so as to contact the setter in the first firing step and the second firing step are manufactured, for example, by the following procedure. First, a raw slurry containing ceramic powder, a sintering aid and a binder is formed. Ceramics are not particularly limited, and examples thereof include carbides, oxides and nitrides. Specific examples include silicon carbide, alumina, silicon nitride, aluminum nitride and boron nitride. Binders include those containing organic components.

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

For the setter, for example, a commercially available ceramic sintered body may be purchased, or it may be manufactured by a known method. Examples of setters include those containing at least one selected from the group consisting of boron nitride, silicon carbide, alumina, zirconia, graphite, and silicon nitride. Among these, a setter made of boron nitride is preferably used because it has both heat resistance and good machinability. From the viewpoint of suppressing adhesion between the setter and the ceramic plate after firing, the material of the setter may be different from the material of the ceramic plate.

When a boron nitride sintered body is used as the setter, it can be produced by the following procedure. First, a compact is produced using hexagonal boron nitride powder as a raw material. If necessary, a sintering aid may be added to the hexagonal boron nitride powder before molding. Sintering aids include alkaline earth oxides such as magnesium oxide and calcium oxide, rare earth oxides such as aluminum oxide, silicon oxide and yttrium oxide, and complex oxides such as spinel. For molding, uniaxial pressure molding and CIP molding may be performed. Uniaxial pressing may be performed at 3-20 MPa. CIP molding may be performed at 50-300 MPa.

The obtained compact is fired to obtain a boron nitride sintered body. Firing may be carried out in a non-oxidizing atmosphere at a rate of temperature increase of 150° C./hr or less, a maximum temperature of 1800 to 2200° C., and a holding time in this temperature range of 5 hours or more. Examples of the non-oxidizing atmosphere include nitriding gas atmospheres such as nitrogen and ammonia. The density of the boron nitride sintered body may be 1600 kg/m ³ or more. The method for producing the boron nitride sintered body is not limited to the method described above. For example, it may be produced by a hot press method. A ceramic sintered body other than the boron nitride sintered body can be produced by a known method.

The setter thus obtained and the first ceramic green sheet are laminated so as to be in contact with each other to produce a laminate. There are no particular restrictions on the number of setters and ceramic green sheets that constitute the laminate. In the laminate, for example, a plurality of (eg, 50 to 100) ceramic green sheets including the first ceramic green sheets may be sandwiched between a pair of setters. Also, one setter and a plurality of ceramic green sheets including the first ceramic green sheets may be alternately arranged. By firing a plurality of ceramic green sheets in the first firing step in this manner, a plurality of ceramic plates can be manufactured simultaneously.

The material and shape of the ceramic green sheets laminated together with the first ceramic green sheets may be the same as or different from those of the first ceramic green sheets. A release agent may be applied to the main surface of the ceramic green sheet (first ceramic green sheet) in order to prevent adjacent ceramic green sheets from adhering to each other during firing. A release agent may also be applied to the surface of the setter facing the main surface of the first ceramic green sheet. Examples of components contained in the release agent include ceramic powder such as boron nitride, graphite powder, binder, and the like.

FIG. 1 is a diagram for explaining an example of the first firing step of a laminate. A laminate 50 includes three setters 10 and a plurality of ceramic green sheets 30 . The plurality of ceramic green sheets 30 includes four first ceramic green sheets 30 a adjacent to three setters 10 . A pair of setters 10A and 10B of the three setters 10 are stacked on the bottom and top of the laminate 50 . Therefore, in the setters 10A and 10B, one main surface is in contact with the first ceramic green sheet 30a. The rest of the setters 10C are stacked in the central portion of the stack 50. As shown in FIG. Therefore, both main surfaces of the setter 10C are in contact with the first ceramic green sheets 30a. Thus, the contact surface of the setter 10 where the first ceramic green sheet 30a and the setter 10 are in contact is included in one or both main surfaces.

As shown in FIG. 1, the laminate 50 is placed in the degreasing furnace 20 and heated to 300.degree. C. to 700.degree. As a result, the binder contained in the ceramic green sheets 30 is removed. Subsequently, the degreased laminate 50 is placed in the firing furnace 25 and heated to 1600.degree. C. to 2000.degree. Thereby, the ceramic green sheets are fired to obtain a ceramic plate. The degreasing furnace 20 used for degreasing and the firing furnace 25 used for firing may be the same furnace or may be different furnaces. Also, the heating temperature, time and atmosphere may be appropriately adjusted according to the composition of the ceramic green sheet.

In the heating step, the laminate (first laminate) fired in the first firing step is separated into a ceramic plate and a setter. The obtained ceramic plate may be processed as necessary to form, for example, a circuit board. The contact surface of the separated setter that was in contact with the first ceramic green sheet 30a (ceramic plate) has adhered granular foreign matter containing components different from those contained in the setter. Components contained in the foreign matter include, for example, components contained in the ceramic green sheet or ceramic plate, and reaction products of these components and components contained in the setter. The particle size of the foreign matter may be larger than the particles that make up the setter. That is, the foreign matter may be coarse particles.

FIG. 2 is a SEM photograph showing an example of foreign matter (boron nitride particles) adhering to the contact surface of a setter composed of a boron nitride sintered body. The composition of foreign matter can be measured by EDS analysis. When the setter is composed of a boron nitride sintered body and the foreign matter is silicon nitride particles, it is difficult to detect the foreign matter with the naked eye because the colors of the two are similar. In such a case, as shown in FIG. 2, the presence or absence of foreign matter can be determined by performing SEM observation at a high magnification (for example, 500 times or more).

A setter with such a foreign matter adhering to the contact surface is heated with the contact surface exposed. This makes it possible to volatilize or decompose and reduce foreign matter adhering to the contact surface. Heating may be performed in an inert gas atmosphere. Examples of inert gases include nitrogen gas and argon gas. The heating temperature in the heating step may be higher than the sintering temperature in the first sintering step, and may be a temperature at which the foreign matter is decomposed or higher.

A specific heating temperature may be, for example, 1450° C. or higher, 1600° C. or higher, or 1700° C. or higher. By increasing the heating temperature, it is possible to promote the decomposition of foreign matter and obtain a setter having a main surface (contact surface) with sufficiently reduced foreign matter. With such a heating temperature, silicon nitride particles adhering as foreign matter to the contact surface of the setter can be sufficiently reduced when manufacturing a silicon nitride plate as a ceramic plate. The heating temperature may be, for example, 2000° C. or lower, 1950° C. or lower, or 1900° C. or lower. As a result, it is possible to suppress excessive heating, reduce damage to the setter, and improve energy efficiency. The heating time at the above heating temperature may be, for example, 0.5 to 10 hours, or may be 1 to 5 hours.

FIG. 3 is a diagram explaining an example of the heating process. A plurality of setters 11 are stacked on a bottom plate 13 in the heating furnace 28 . A spacer 12 is arranged between the setters 11 adjacent to each other in the vertical direction. Thereby, the contact surfaces of adjacent setters 11 are arranged so as to be separated from each other by a predetermined interval. As a result, part or all of the contact surface included in the main surface of the setter 11 is heated in the heating furnace 28 in an exposed state. The heating furnace 28 may be the same as the firing furnace 25 in FIG. 1, or may be different. By simultaneously heating a plurality of setters 11 in the heating furnace 28, a plurality of setters 11 can be regenerated at the same time.

It is not essential to heat a plurality of setters 11 simultaneously as shown in FIG. 3, and the setters 11 may be heated one by one. Moreover, it is not essential to use the spacer 12, and it is sufficient if the contact surface of each setter 11 can be heated in an exposed state. For example, a frame having a support portion for supporting the setters 11 may be used, and a plurality of setters may be heated while being arranged horizontally or vertically so that their contact surfaces are separated from each other.

In the second firing step, the setter and the second ceramic green sheet are laminated so that the setter and the second ceramic green sheet are in contact with at least a part of the contact surface of the setter from which foreign matter has been reduced in the heating step. 2 laminate). This second laminate is heated in a degreasing furnace and a firing furnace to obtain a ceramic plate. The degreasing furnace and the firing furnace may be the same as or different from those used in the first firing step. The second laminate may have the same laminate structure as the first laminate 50 produced in the first firing step, or may have a different laminate structure. In the second firing process, degreasing and firing are sequentially performed in the same manner as in the first firing process to obtain a ceramic plate.

In the second laminate, the setter contacts the second ceramic green sheet at the contact surface with reduced foreign matter. Therefore, the amount of foreign matter on the contact surface between the second ceramic green sheet and the setter is reduced. Therefore, it is possible to suppress the occurrence of irregularities in the ceramic plate obtained in the second firing step. Thus, even if the setter used in the first firing step is reused, the yield of ceramic plates can be maintained. Therefore, it is possible to improve the production efficiency of the ceramic plate.

After the second firing step, the heating step and the second firing step may be repeated. The number of repetitions may be one or more. The setter may be heated in a state where the contact surface with the second ceramic green sheet is exposed each time the laminate is fired once, or the production of the laminate, the firing of the laminate, and the bonding of the ceramic plate and the setter may be performed. The heating step may be performed after the fractionation is repeated multiple times. The frequency of the heating process may be adjusted according to the presence or amount of foreign matter on the contact surface. In any case, by repeatedly regenerating and using the setter, it is possible to effectively utilize resources and reduce the manufacturing cost of the ceramic plate.

The ceramic plates obtained in the first firing step and the second firing step of the manufacturing method described above have the same surface quality. Therefore, it can be used for similar purposes. The ceramic plate may be used as a circuit board, for example, by forming an electric circuit composed of a metal layer on one or both main surfaces.

A setter manufacturing method (recycling method) according to one embodiment includes firing a laminate in which a first setter and a ceramic green sheet are laminated so as to be in contact with each other, and then firing the first setter on the contact surface with the ceramic green sheet. A firing step (first firing step) of obtaining a second setter to which a foreign substance containing a component different from the contained component adheres, and separating the laminate into a second setter and a ceramic plate, wherein at least a part of the contact surface is and heating the second setter in an exposed state to reduce foreign matter on the contact surface.

The firing process can be performed in the same manner as the first firing process described above. That is, the first setter may be purchased from a commercially available ceramic sintered body, or may be manufactured by a known method. Examples of the setter include those composed of at least one selected from the group consisting of boron nitride, silicon carbide, alumina, zirconia, graphite, and silicon nitride. The manufacturing procedure when using the boron nitride sintered body as the first setter may be as described above. In the firing step, the laminate as shown in FIG. 1 may be placed in a firing furnace 25 and heated. In the present embodiment, the setter before being fired in the firing process (first firing process) is referred to as the "first setter", and the setter that has been fired in the firing process and has foreign matter adhering to the contact surface is referred to as the "second setter". there is

In the heating step, the laminate obtained in the firing step is separated into a ceramic plate and a second setter, and the second setter is placed in a state where at least part of the contact surface with the ceramic green sheet (ceramic plate) of the second setter is exposed. Heat the setter. As a result, the foreign matter adhering to the contact surface is volatilized or decomposed, and the foreign matter can be reduced. The setter in which the foreign matters are reduced by the heating process in this way is sometimes called a "third setter".

The heating conditions in the heating step may be the same as in the heating step in the embodiment of the ceramic plate manufacturing method described above. Foreign matter adhering to the surface of the setter (third setter) obtained by the heating process is sufficiently reduced. This setter (third setter) may, for example, have the same surface quality as the first setter. The setter (third setter) thus obtained through the heating process may be used in the firing process (second firing process) in place of the first setter. As a result, the ceramic plate as well as the second setter with the foreign matter adhering to the contact surface are obtained again. After this, the heating step may be performed again.

As described above, according to the setter manufacturing method (recycling method) of the present embodiment, the used second setter can be recycled as the third setter, and the amount of waste of the second setter can be reduced. As a result, effective use of resources can be achieved. The second baking step and the heating step may be repeated multiple times. In this case, the reproduction of the second setter to the third setter and the production of ceramic plates using the third setter (the production of the second setter) are repeated. Therefore, it is possible to further improve the effective utilization of resources.

In addition, in the setter manufacturing method of the present embodiment, the used second setter used in the firing process is heated to newly create a setter (third setter) with reduced foreign matter on the surface. corresponds to the manufacturing method of From another point of view, since the used setter is surface-treated and the used setter is recycled, it can also be called a setter surface treatment method or a setter recycling method.

Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment. For example, the ceramic plates, ceramic green sheets and setters may have shapes other than rectangular parallelepiped shapes. These may be chamfered at the corners. Alternatively, the setter may be arranged only below the laminate.

[Manufacturing of ceramic plates and recycling of setters]
(Example 1)
<First firing step>
Raw material powders containing silicon nitride powder and sintering aids (magnesium oxide powder, yttrium oxide powder and silicon dioxide powder) were uniaxially pressure molded to produce a compact (sheet material). This sheet material was punched out using a cutting device to form 68 rectangular parallelepiped ceramic green sheets. Separately, three setters made of boron nitride having a rectangular parallelepiped shape (manufactured by Denka Co., Ltd., trade name: NB-1000) were prepared. FIG. 4 is an SEM photograph (100 times) of the main surface of the setter (before firing). FIG. 5 is a SEM photograph (500×) of the main surface of the setter (before firing) taken at a higher magnification than FIG. As shown in FIGS. 4 and 5, no foreign matter was detected on the main surface of the setter (first setter) before firing. In the following, a laminate was produced such that the main surface and the ceramic green sheet were in contact with each other.

A laminate in which 68 ceramic green sheets are vertically sandwiched between a pair of setters, and the setter is placed in the center to laminate 3 setters (3 first setters) and 68 ceramic green sheets. got In this laminate, 34 ceramic green sheets were stacked between the lower setter and the central setter and between the central setter and the upper setter. In producing the laminate, the contact surface of the setter with the ceramic green sheets and one main surface of each ceramic green sheet were coated with a release slurry. Using a degreasing furnace and a firing furnace, the produced laminate was degreased and fired. The degreasing temperature was 500° C., and the degreasing time was 30 hours. Also, the firing temperature was 1800° C., and the firing time was 30 hours. After firing, the laminate was taken out from the firing furnace, the ceramic plates were removed from the laminate, and a pair of setters was recovered.

The contact surface of the setter with the ceramic green sheet (main surface facing the ceramic green sheet) was observed with a scanning electron microscope (SEM). FIG. 6 is an SEM photograph (100 times) of the contact surface of the setter recovered from the laminate. FIG. 7 is an SEM photograph (500×) of the contact surface of the setter taken at a higher magnification than FIG. Although the presence of foreign matter could not be visually confirmed, when the contact surface was observed at a high magnification (approximately 500 times) using an SEM as shown in FIG. 7, it was confirmed that foreign matter 40 had adhered. EDS analysis of this foreign matter detected Si and N. From this, it was confirmed that the silicon nitride particles contained in the ceramic green sheet (ceramic plate) were present as foreign matter on the contact surface of the setter.

<Heating process>
As shown in FIG. 3, the three setters (three second setters) whose contact surfaces were confirmed to have foreign matter were stacked via spacers and placed in a firing furnace. The portion of the contact surface to which the foreign matter adhered was exposed to the space inside the firing furnace without contacting the spacer. Using a firing furnace, three setters were heated at 1850° C. for 2 hours in a nitrogen gas atmosphere.

FIG. 8 is an SEM photograph (100 times) of the contact surface of the setter after heating in the heating step. FIG. 9 is an SEM photograph (500×) of the contact surface of the setter taken at a higher magnification than FIG. FIG. 9 shows the contact surface of the setter enlarged with the same magnification as FIG. As shown in FIG. 9, the heating process sufficiently reduced the amount of foreign matter adhering to the contact surface.

(Comparative example 1)
The baking process was carried out in the same manner as in Example 1 to obtain three setters (three second setters) with foreign matters adhering to their contact surfaces. The heating step was performed in the same manner as in Example 1, except that the three setters were stacked so that their contact surfaces were in contact with each other and heated in a kiln. That is, the three setters were fired so that the contact surfaces of the three setters were not exposed to the space in the firing furnace.

FIG. 10 is an SEM photograph (100 times) of the contact surface of the setter after heating in the heating step. FIG. 11 is an SEM photograph (500×) of the contact surface of the setter taken at a higher magnification than FIG. As shown in FIGS. 10 and 11, the contact surface of the setter had foreign matter 42 which had grown coarse during the heating process.

[Reuse of Setter and Evaluation of Ceramic Plate]
(Example 1 and Comparative Example 1)
<Second firing step>
Using the setters (third setters) obtained in the above heating steps of Example 1 and Comparative Example 1, the second firing step was performed. The laminate production procedure and firing conditions in the second firing step were the same as those in the first firing step. The presence or absence of unevenness on the surface of each ceramic plate (silicon nitride plate) obtained in the second firing step was evaluated. FIG. 12 is a photograph showing an example of protrusions on the surface of the silicon nitride plate obtained in the second firing step. FIG. 12 shows a convex portion 60 formed in the central portion of the main surface of the silicon nitride plate.

Each silicon nitride plate obtained in the second firing step of Example 1 and Comparative Example 1 was evaluated for quality. Specifically, the main surface of the silicon nitride plate was observed with a one-shot 3D shape measuring machine (model: VR-3000) manufactured by KEYENCE CORPORATION to examine the size of surface unevenness. A product having a convex portion with a height of 11 μm or more or a concave portion with a depth of 11 μm or more was determined to be defective. As a result, in Example 1, the ratio of defective products was able to be reduced to 1/3 or less compared to Comparative Example 1.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a ceramic plate manufacturing method capable of improving the production efficiency of ceramic plates by regenerating the setter. Moreover, it is possible to provide a setter manufacturing method that enables effective use of resources.

DESCRIPTION OF SYMBOLS 10, 10A, 10B, 10C, 11... Setter, 12... Spacer, 13... Bottom plate, 20... Degreasing furnace, 25... Firing furnace, 28... Heating furnace, 30... Ceramic green sheet, 30a... First ceramic green sheet, 40 , 42... Foreign matter, 50... Laminated body, 60... Convex part.

Claims (9)

a first firing step in which the setter and the first ceramic green sheet containing silicon nitride are stacked such that they are in contact with each other and fired to obtain a ceramic plate;
In an inert gas atmosphere, in a state where at least a part of the contact surface of the setter with the first ceramic green sheet is exposed, the contact surface contains silicon and nitrogen, which are components different from the components contained in the setter. a heating step of heating the setter to which the granular foreign matter is attached;
a second firing step for obtaining a ceramic plate by stacking and firing the setter and the second ceramic green sheet so that they are in contact with each other on at least a part of the contact surface;
The method for manufacturing a ceramic plate, wherein in the heating step, the setter is heated to 1600 to 2000° C. to reduce the foreign matter on the contact surface . 2. The method of manufacturing a ceramic plate according to claim 1, wherein in the heating step, the setter is heated to a temperature at which the foreign matter is decomposed or higher. 3. The method of manufacturing a ceramic plate according to claim 1, wherein the heating temperature of said setter in said heating step is higher than the firing temperature in said first firing step. In the first firing step, the plurality of setters and the plurality of first ceramic green sheets are stacked and fired so that they are in contact with each other,
4. The setter according to any one of claims 1 to 3, wherein in the heating step, the plurality of setters are heated while the contact surfaces of the plurality of setters that were in contact with the first ceramic green sheets are separated from each other. A method for producing the ceramic plate described. The first setter and a ceramic green sheet containing silicon nitride are stacked and fired so that they are in contact with each other, and the contact surface with the ceramic green sheet contains silicon and nitrogen, which are different from the components contained in the first setter. A baking step of obtaining a second setter to which granular foreign matter containing
a heating step of heating the second setter in an inert gas atmosphere with at least a portion of the contact surface exposed;
The method for manufacturing a setter, wherein in the heating step, the second setter is heated to 1600 to 2000° C. to reduce the foreign matter on the contact surface . The setter manufacturing method according to claim 5, wherein in the heating step, the foreign matter is heated to a temperature at which the foreign matter is decomposed or higher. The setter manufacturing method according to claim 5 or 6, wherein the heating temperature of the second setter in the heating step is higher than the firing temperature in the firing step. In the firing step, the plurality of first setters and the plurality of ceramic green sheets are stacked so as to be in contact with each other and fired to obtain a plurality of second setters,
8. The plurality of second setters according to any one of claims 5 to 7, wherein in the heating step, the plurality of second setters are heated while the contact surfaces of the plurality of second setters that were in contact with the ceramic green sheets are separated from each other. A method for manufacturing the setter according to the above item. The first setter and a ceramic green sheet containing silicon nitride are stacked and fired so that they are in contact with each other, and the contact surface with the ceramic green sheet contains silicon and nitrogen, which are different from the components contained in the first setter. A baking step of obtaining a second setter to which granular foreign matter containing
a heating step of heating the second setter in an inert gas atmosphere with at least a portion of the contact surface exposed;
The setter regeneration method, wherein in the heating step, the second setter is heated to 1600 to 2000° C. to reduce the foreign matter on the contact surface .

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