WO2022054684A1

WO2022054684A1 - Ceramic plate and manufacturing method therefor, plate spring, setter, and method for manufacturing ceramic sintered body

Info

Publication number: WO2022054684A1
Application number: PCT/JP2021/032285
Authority: WO
Inventors: 利貴山縣; 里樹東
Original assignee: デンカ株式会社
Priority date: 2020-09-10
Filing date: 2021-09-02
Publication date: 2022-03-17
Also published as: JPWO2022054684A1; JP7126035B2

Abstract

Provided is a ceramic plate having a convexly curved first main surface and a concavely curved second main surface on the reverse side from the first main surface, with a warpage amount W of 1 mm or more. Also provided is a method for manufacturing the ceramic plate comprising a step for overlapping and heating a setter having a convex or concave curved surface and a ceramic green sheet so that the main surface of the ceramic green sheet is along the curved surface, to obtain a ceramic plate with a warpage amount of 1 mm or more.

Description

Ceramic plate and its manufacturing method, leaf spring, setter, and ceramic sintered body manufacturing method

The present disclosure relates to a ceramic plate and a method for manufacturing the same, a leaf spring, a setter, 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. The circuit board mounted on the power module has an insulating ceramic plate. The ceramic plate has, for example, a step of mixing ceramic powder, a sintering aid, an organic binder, a dispersant, etc. and then extruding into a sheet, a step of punching to form a ceramic green sheet, and a ceramic green sheet. Is manufactured by sequentially performing the steps of firing. At the time of firing, in order to improve productivity, it has been attempted to simultaneously produce a plurality of ceramic plates by placing a laminate containing a plurality of ceramic green sheets on a setter and heating the laminate.

By the way, since the ceramic green sheet contains a binder, a dispersant, etc., these components evaporate from the inside and shrink with heating. Patent Document 1 proposes to reduce the influence of strain generated in such a shrinkage process by providing a dividing groove in the ceramic green sheet in advance.

Japanese Unexamined Patent Publication No. 2014-51409

When the components contained in the ceramic green sheet volatilize and shrink, there is a concern that the positions of the plurality of ceramic green sheets laminated due to the volatilization and shrinkage may shift from each other, affecting the quality. Therefore, the present disclosure discloses a leaf spring having excellent heat resistance and capable of suppressing the displacement of a plurality of laminated ceramic green sheets from each other, and a ceramic plate preferably used as the leaf spring and manufacturing thereof. Provide a method. Further, the present disclosure provides a setter capable of easily manufacturing such a ceramic plate. Further, the present disclosure provides a manufacturing method capable of stably manufacturing a ceramic sintered body having high quality by suppressing the positions of a plurality of laminated ceramic green sheets from being displaced from each other.

The present disclosure has a first main surface that is curved convexly on one side surface and a second main surface that is curved concavely on the opposite side of the first main surface, and the amount of warpage W is large. Provided is a ceramic plate having a size of 1 mm or more. Since such a ceramic plate is made of ceramic, it has excellent heat resistance. Further, since it has a convex first main surface and a concave second main surface and has a large warp amount W, it can be suitably used as a leaf spring utilizing the restoring force generated by elastic deformation. However, its use is not limited to leaf springs. The warp amount W of the ceramic plate in the present disclosure is measured as the maximum height of the second main surface from the measuring table when the ceramic plate is placed on the measuring table with the first main surface side facing upward. ..

The thickness of the ceramic plate may be 2 mm or less, and the radius of curvature of the first main surface and the second main surface may be 100 to 1000 mm. As a result, when used as a leaf spring, it is possible to sufficiently increase the deflection while suppressing damage due to deformation.

The ratio of the warp amount W to the average value of the areas of the first main surface and the second main surface may be 1 × 10 ^-5 / mm or more. As a result, the deflection per unit area of the main surface can be increased, so that the spring can be more preferably used as a leaf spring.

The ceramic plate may be made of a silicon nitride sintered body. The silicon nitride sintered body has both heat resistance and high strength, and can increase the deflection when used as a spring. Therefore, as a leaf spring, it can be particularly suitably used for applications that require a large restoring force (repulsive force) and a large deflection.

The present disclosure provides, in one aspect, a leaf spring composed of any of the ceramic plates described above. Since such a leaf spring has excellent heat resistance, it can sufficiently exert its function as a spring even at the heating temperature of the ceramic green sheet. Therefore, by holding the laminated body by using such a leaf spring, it is possible to prevent the positions of the plurality of green sheets included in the laminated body from being displaced from each other.

In the present disclosure, a setter having a convex or concave curved surface and a ceramic green sheet on one side surface are superposed and heated so that the main surface of the ceramic green sheet is along the curved surface, and the amount of warpage W Provided is a method for manufacturing a ceramic plate, which comprises a step of obtaining a ceramic plate having a size of 1 mm or more.

In the above manufacturing method, a ceramic plate having a warp amount W of 1 mm or more is obtained by using a setter having a convex or concave curved surface. As described above, a ceramic plate suitably used as a leaf spring utilizing the restoring force can be obtained by a simple manufacturing method. Therefore, the above-mentioned method for manufacturing a ceramic plate can also be said to be a method for manufacturing a leaf spring. However, the use of the ceramic plate obtained by the above-mentioned manufacturing method is not limited to the leaf spring.

The present disclosure provides a setter having a convex or concave curved surface on one side surface, and the height difference of the portion on the curved surface on which the ceramic green sheet is placed is 1 mm or more. By using such a setter, a ceramic plate suitably used as a leaf spring, for example, can be easily manufactured. The setter may heat a ceramic green sheet placed so as to cover the portion of the curved surface to form a ceramic plate having a warp amount W of 1 mm or more.

The present disclosure has, in one aspect, a degreasing step of heating and degreasing a laminate containing a plurality of ceramic green sheets, and a firing step of calcining the degreased laminate to obtain a ceramic plate, and degreasing. In one or both of the steps and the firing step, the laminate provides a method for producing a ceramic sintered body, which is held by the restoring force generated by the elastic deformation of any of the ceramic plates described above.

When the laminated body is heated to produce a ceramic sintered body, if the positions of the plurality of laminated ceramic green sheets are displaced from each other, the heated state changes between the exposed surface and the unexposed surface. It causes the quality such as color and properties to vary. Further, if the positions of the plurality of ceramic green sheets are displaced from each other, it may cause warpage. However, in the above manufacturing method, the laminated body is held by the restoring force generated by the elastic deformation of the ceramic plate. Therefore, it is possible to prevent the positions of the plurality of laminated ceramic green sheets from shifting from each other. Therefore, it is possible to stably produce a ceramic sintered body having high quality.

In one or both of the degreasing step and the firing step of the above-mentioned manufacturing method, the ceramic plate is arranged in an elastically deformed state between the fixing member provided above the laminated body and the laminated body, and accompanies the shrinkage of the laminated body. The amount of warpage W of the ceramic plate may be increased. As a result, the laminated body can be stably held, and the positions of the plurality of laminated ceramic green sheets can be sufficiently suppressed from being displaced from each other.

It is possible to provide a leaf spring having excellent heat resistance and capable of suppressing the displacement of a plurality of laminated ceramic green sheets from each other, and a ceramic plate preferably used as the leaf spring and a method for manufacturing the same. can. Further, it is possible to provide a setter capable of easily manufacturing such a ceramic plate. Further, by suppressing the positions of the plurality of laminated ceramic green sheets from being displaced from each other, it is possible to provide a manufacturing method capable of stably manufacturing a ceramic sintered body having high quality.

FIG. 1 is a perspective view of a ceramic plate according to an embodiment. FIG. 2 is a side view of the ceramic plate according to the embodiment. FIG. 3 is a perspective view of a ceramic plate according to another embodiment. FIG. 4 is a perspective view of the setter according to the embodiment. FIG. 5 is a side view of the setter of FIG. FIG. 6 is a perspective view of the setter according to another embodiment. FIG. 7 is a side view of the setter of FIG. FIG. 8 is a perspective view showing an example of a laminated body used in a method for manufacturing a ceramic plate. FIG. 9 is a perspective view showing another example of the laminated body used in the method for manufacturing a ceramic plate. FIG. 10 is a side view showing an example of a laminated body and a holding body used in the method for manufacturing a ceramic sintered body of the present embodiment. FIG. 11 is a side view showing an example of the laminated body and the holding body after the degreasing step. FIG. 12 is a graph showing the measurement result of the amount of deflection of Reference Example 1. FIG. 13 is a graph showing the measurement result of the amount of deflection of Reference Example 2.

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 description, the same elements or elements having the same function are designated by the same reference numerals, and duplicate description will be omitted. In addition, the positional relationship such as up, down, left, and right used in the explanation shall be based on the positional relationship shown in the drawings unless otherwise specified.

FIG. 1 is a perspective view of a ceramic plate according to an embodiment. The ceramic plate 100 has a first main surface 100A that is curved in an arch shape and is curved in a convex shape, and a second main surface 100B that is curved in a concave shape on the opposite side of the first main surface 100A. Of the four side surfaces of the ceramic plate 100, the pair of side surfaces 11 arranged facing each other is rectangular, while the other pair of side surfaces 13 arranged facing each other is curved in an arch shape.

FIG. 2 is a side view of the ceramic plate 100 of FIG. The ceramic plate 100 is placed on a measuring table 150 having a horizontal flat surface. The ceramic plate 100 is curved in an arch shape. Therefore, of the second main surface 100B of the ceramic plate 100, only the side 12 on the side of the pair of side surfaces 11 comes into contact with the measuring table 150, and between the other part of the second main surface 100B and the measuring table 150. There is a gap. The amount of warpage W of the ceramic plate 100 is defined as the maximum height of the second main surface 100B from the measuring table 150 when the ceramic plate 100 is placed on the measuring table 150 with the first main surface 100A side facing upward. Be measured. The warp amount W is a value in a state where no external force is applied to the ceramic plate 100 and the ceramic plate 100 is not elastically deformed. Since the warp amount W is 1 mm or more, the deflection until the second main surface 100B and the measuring table 150 become parallel can be sufficiently increased. Therefore, it can be suitably used as a leaf spring that utilizes the restoring force. The warp amount Z of the ceramic plate 100 is the maximum value of the height difference of the first main surface 100A which is curved in a convex shape. The amount of warpage Z may also be 1 mm or more.

In the side view as shown in FIG. 2, the radius of curvature of the first main surface 100A and the second main surface 100B may be 100 to 1000 mm, 150 to 800 mm, or 200 to 500 mm. As a result, the deflection can be sufficiently increased while suppressing the damage. Therefore, the function as a leaf spring can be fully exhibited. The radii of curvature of the first main surface 100A and the second main surface 100B may be the same or different. Further, the radius of curvature of the first main surface 100A does not have to be uniform and may differ depending on the position. In this case as well, the radius of curvature at each position may be within the above range. The radius of curvature of the second main surface 100B does not have to be uniform and may differ depending on the position. In this case as well, the radius of curvature at each position may be within the above range.

From the viewpoint of further increasing the amount of deformation until the second main surface 100B and the measuring table 150 are parallel to each other, the warp amount W (warp amount Z) may be 1.2 mm or more, and may be 1.4 mm or more. You may. On the other hand, if the amount of deformation is too large, the ceramic plate 100 tends to be easily damaged. Therefore, from the viewpoint of sufficiently increasing the durability of the ceramic plate 100, the warp amount W (warp amount Z) may be 5 mm or less, 4 mm or less, or 3 mm or less. The ratio of the warp amount Z to the warp amount W may be 0.9 to 1.1, or may be 0.95 to 1.05.

The thickness of the ceramic plate 100 (distance between the first main surface 100A and the second main surface 100B) may be 2 mm or less, 1.5 mm or less, and 1 mm or less from the viewpoint of sufficiently increasing the deflection. May be. The thickness of the ceramic plate 100 may be 0.1 mm or more, or 0.2 mm or more, from the viewpoint of sufficiently increasing the restoring force when the ceramic plate 100 is used as a leaf spring. An example of the thickness of the ceramic plate 100 may be 0.1 to 2 mm.

The ratio of the amount of warpage W to the thickness of the ceramic plate 100 may be 1 or more, and may be 2 or more, from the viewpoint of sufficiently increasing the deflection until the second main surface 100B and the measuring table 150 are parallel to each other. May be good. The ratio of the warp amount W to the thickness of the ceramic plate 100 may be 15 or less, or 10 or less, from the viewpoint of sufficiently increasing the durability as a leaf spring. An example of the ratio of the warp amount W to the thickness of the ceramic plate 100 may be 1 to 15.

The area of the first main surface 100A and the second main surface 100B may be 100 to 10000 mm ² or 500 to 5000 mm ² . The areas of the first main surface 100A and the second main surface 100B may be the same or different. The ratio of the warp amount W to the average value of the areas of the first main surface 100A and the second main surface 100B may be 1 × 10 ^-5 / mm or more from the viewpoint of sufficiently enhancing the usefulness as a leaf spring. It may be 5 × 10 ^-5 / mm or more, and may be 1 × 10 ^-4 / mm or more. From the same viewpoint, the ratio of the warp amount W to the average value of the areas of the first main surface 100A and the second main surface 100B may be 2 × 10 − ² / mm or less, and may be 1 × 10 − ² / mm or less. It may be 5 × 10 ^-3 / mm or less.

The ceramic plate 100 may be composed of a nitride sintered body, a carbide sintered body, or an oxide sintered body. When the ceramic plate 100 is used as a leaf spring, it may be composed of a silicon nitride sintered body. A leaf spring composed of a silicon nitride sintered body can sufficiently increase the deflection. Further, since the silicon nitride sintered body has high bending strength, it is also excellent in durability.

The bending strength of the ceramic plate 100 may be 500 MPa or more, or 600 MPa or more, from the viewpoint of improving durability. The bending strength of the ceramic plate 100 may be, for example, 1000 MPa or less, or 900 MPa. An example of the bending strength of the ceramic plate 100 is 500 to 1000 MPa. The bending strength in the present disclosure is a three-point bending strength, and is measured using a commercially available bending strength meter (manufactured by Shimadzu Corporation, device name: AG-2000) in accordance with JIS R 1601: 2008. ..

Since the ceramic plate 100 is made of ceramic, it has excellent heat resistance. Therefore, the leaf spring composed of the ceramic plate 100 can be suitably used in various environments. For example, it is suitable for applications that require restoring force due to elastic deformation in a high temperature environment.

FIG. 3 is a perspective view of a ceramic plate according to another embodiment. In the ceramic plate 102, all four side surfaces 24 are curved so as to be arched, and the first main surface 102A is curved in a convex shape and the ceramic plate 102 is curved in a concave shape on the opposite side of the first main surface 102A. It has a second main surface 102B. The central portion of the first main surface 102A projects upward from the end portion. The central portion of the second main surface 102B is recessed from the end portion. The arch shapes of the four side surfaces 24 may be the same or different from each other.

When the ceramic plate 102 is placed on the measuring table 150 with the first main surface 102A facing upward as in FIG. 2, only the four tops 20 of the second main surface 102B of the ceramic plate 102 are measured. Contact the table 150. There is a gap between the other part of the second main surface 102B and the measuring table 150. The warp amount W of the ceramic plate 102 is also the maximum height of the second main surface 102B from the measuring table 150 when the ceramic plate 102 is placed on the measuring table 150 with the first main surface 102A side facing upward. Measured as. The warp amount Z of the ceramic plate 102 is also measured as the maximum value of the height difference of the first main surface 102A which is curved in a convex shape.

The numerical range such as the warp amount W, the warp amount Z, the thickness, and the ratio of the warp amount W to the thickness of the ceramic plate 102, and the material may be the same as those of the ceramic plate 100. The numerical range such as the radius of curvature and the area of the first main surface 102A and the second main surface 102B may be the same as that of the first main surface 100A and the second main surface 100B. The ceramic plate 102 can also be suitably used as a leaf spring under various environments.

FIG. 4 is a perspective view of the setter according to the embodiment. The setter 50 has a substantially semi-cylindrical shape. That is, the setter 50 has a shape in which one surface is bulged in an arch shape, and has a curved surface 50A that is curved in a convex shape and a flat surface 50B on the opposite side of the curved surface 50A. The pair of side edges 54 facing each other on the curved surface 50A are curved, and the other pair of side edges 52 facing each other extend linearly. A ceramic green sheet is placed so as to cover at least a part of the curved surface 50A of the setter 50. When the ceramic green sheet is placed on the curved surface 50A, the ceramic green sheet is curved along the curved surface 50A. By heating the curved ceramic green sheet, as shown in FIG. 1, the first main surface 100A, which is curved in an arch shape and is curved in a convex shape, and the first main surface 100A are curved in a concave shape on the opposite side of the first main surface 100A. It is possible to form a ceramic plate 100 having a second main surface 100B and having a warp amount W (warp amount Z) of 1 mm or more.

In the side view as shown in FIG. 5, the radius of curvature of the curved surface 50A of the setter 50 may be 100 to 1000 mm, 150 to 800 mm, or 200 to 500 mm. This makes it possible to easily manufacture a ceramic plate suitable as a leaf spring. The height difference H1 between the top of the curved surface 50A at the center and the side edge 52 at the lower end of the curved surface may be 1 mm or more from the viewpoint of manufacturing a sufficiently flexible leaf spring (ceramic plate 100). It may be 2 mm or more, and may be 1.4 mm or more. From the viewpoint of producing a ceramic plate having excellent durability against repeated elastic deformation, the height difference H1 may be 5 mm or less, 4 mm or less, or 3 mm or less.

FIG. 6 is a perspective view of the setter according to another embodiment. The setter 60 has a curved surface 60A curved in a concave shape and a flat surface 60B on the opposite side of the curved surface 60A. The four side edges 64 that form the contour of the curved surface 60A are all curved and are curved so as to be convex downward. The recessed portion 61 in the central portion of the curved surface 60A is a portion of the curved surface 60A closest to the plane 60B. The curved surface 60A is curved so as to move away from the plane 60B toward the side edge 64 of the curved surface 60A from the central portion. The tops 65 at the four corners of the curved surface 60A are the portions of the curved surface 60A that are farthest from the plane 60B.

A ceramic green sheet is placed so as to cover at least a part of the curved surface 60A of the setter 60. When the ceramic green sheet is placed on the curved surface 60A, the ceramic green sheet is curved along the curved surface 60A. By heating the curved ceramic green sheet, the first main surface 102A which is curved convexly and the second main surface 102A which is concavely curved on the opposite side of the first main surface 102A as shown in FIG. It is possible to manufacture a ceramic plate 102 having a surface 102B and having an arch shape on four side surfaces.

In the side view as shown in FIG. 7, the radius of curvature of the curved surface 60A of the setter 60 may be 100 to 1000 mm, 150 to 800 mm, or 200 to 500 mm. This makes it possible to easily manufacture a ceramic plate suitable as a leaf spring. The height difference H2 between the recess 61 at the center of the curved surface 60A and the top 65 of the curved surface may be 1 mm or more, and 1.2 mm or more, from the viewpoint of manufacturing a sufficiently flexible leaf spring (ceramic plate 100). It may be 1.4 mm or more. From the viewpoint of improving durability against repeated elastic deformation, the height difference H2 may be 5 mm or less, 4 mm or less, or 3 mm or less.

The method for manufacturing the ceramic plate 100 (102) is to use a setter 50 (60) having a convex curved surface 50A (concave curved surface 60A) and a ceramic green sheet, and the main surface of the ceramic green sheet is a curved surface 50A ( It has a step of superimposing and heating along 60A) to obtain a ceramic plate 100 (102) having a warp amount W (warp amount Z) of 1 mm or more. In the above manufacturing method, a ceramic plate having a warp amount W (warp amount Z) of 1 mm or more can be obtained by using a setter 50 or a setter 60 having a convex or concave curved surface. As described above, a ceramic plate suitably used as a leaf spring utilizing the restoring force can be obtained by a simple manufacturing method. The use of the ceramic plate is not limited to the leaf spring.

The setter used for manufacturing the ceramic plate is not limited to the shapes shown in FIGS. 4, 5, 6 and 7, and may be appropriately changed according to the shape of the ceramic plate. For example, in the modified example, instead of the setter 50 in FIG. 4, a setter having a curved surface curved in a concave shape may be used. In this case, the pair of curved side edges 54 of the curved surface may be bent so as to project downward, contrary to FIG. Further, in another modification, a setter having a curved surface curved in a convex shape may be used instead of the setter 60 in FIG. In this case, the four curved side edges 64 of the curved surface may be bent so as to project upward as opposed to FIG. A ceramic plate manufactured using such a setter has a sufficient amount of warpage. Therefore, it is suitable as a leaf spring used in the method for manufacturing a ceramic sintered body described below.

FIG. 8 is a perspective view showing an example of a setter used in a method for manufacturing a ceramic plate and a laminated body in which a ceramic green sheet is laminated. In the laminated body 200 of FIG. 8, the setter 50 shown in FIG. 4 is arranged at the lowermost portion, and three ceramic green sheets 110 are laminated on the curved surface 50A of the setter 50. A setter 70 is arranged on the setter 70, and three ceramic green sheets 110 are laminated on one surface (upper surface) of the setter 70. A setter 80 is arranged on the setter 80.

The curved shape of the curved surface 50A is transferred to the three ceramic green sheets 110 arranged on the curved surface 50A of the setter 50. The other surface (lower surface) of the setter 70 is a concave curved surface complementary to the convex curved surface 50A. Therefore, the curved shape of the curved surface 50A and the lower surface of the setter 70 is sufficiently transferred to the three ceramic green sheets 110 sandwiched between the setter 70 and the setter 50. As a result, one main surface of the ceramic green sheet 110 is curved in a convex shape, and the other main surface is curved in a concave shape.

The upper surface of the setter 70 is curved in a convex shape like the curved surface 50A of the setter 50. The lower surface of the setter 80 is a concave curved surface complementary to the upper surface of the convex setter 70. Therefore, the curved shape of the upper surface of the setter 70 and the curved shape of the lower surface of the setter 80 are sufficiently transferred to the three ceramic green sheets 110 placed on the upper surface of the setter 70. As a result, one main surface of the ceramic green sheet 110 is curved in a convex shape, and the other main surface is curved in a concave shape. By heating such a laminated body 200, a plurality of ceramic green sheets 110 can be degreased and fired at the same time, and the ceramic plate 100 shown in FIG. 1 can be mass-produced.

The laminate 200 has a plurality of ceramic green sheets 110 sandwiched between a pair of

setters

50 and 80 from above and below. Since the main surfaces of the pair of

setters

50 and 80 in contact with the ceramic green sheets 110 are curved in a convex and concave shape and have complementary shapes to each other, the warpage amount W and the warp amount Z of the plurality of ceramic plates 100 The variation can be sufficiently reduced. Further, a setter 70 sandwiched between a pair of

setters

50 and 80 by a ceramic green sheet 110 is used. The contact surface of the setter 70 with the ceramic green sheet 110 is curved in the same manner as the curved surface of the

setters

50 and 80. By using such a setter 70, the number of laminated ceramic green sheets 110 can be increased. As a result, a large number of ceramic plates 100 can be manufactured at the same time. However, the laminated body may be formed without using the setter 70. Further, a plurality of setters 70 may be individually arranged at arbitrary positions between the pair of

setters

50 and 80.

FIG. 9 is a perspective view showing another example of a setter used in a method for manufacturing a ceramic plate and a laminated body in which ceramic green sheets are laminated. In the laminated body 210 of FIG. 9, the setter 82 is arranged at the lowermost portion, and three ceramic green sheets 111 are laminated on the curved surface of the setter 82. A setter 72 is arranged on the setter 72, and three ceramic green sheets 111 are laminated on one surface (upper surface) of the setter 72. On it, the setter 60 of FIG. 6 is arranged so that the plane 60B faces upward.

The curved shape of the curved surface is transferred to the ceramic green sheet 111 arranged on the curved surface of the setter 82. The curved surface of the setter 82 is a convex curved surface complementary to the curved surface 60A of the concave setter 60. The other surface (lower surface) of the setter 72 is a curved surface having the same shape as the curved surface 60A of the setter 60. Therefore, in the ceramic green sheet 111 sandwiched between the setter 72 and the setter 82, the curved shape of the upper surface of the setter 82 and the curved shape of the lower surface of the setter 72 are sufficiently transferred. As a result, one main surface of the ceramic green sheet 111 is curved in a convex shape, and the other main surface is curved in a concave shape.

The upper surface of the setter 72 is a convex curved surface complementary to the curved surface 60A of the concave setter 60. Therefore, the curved shape of the upper surface of the setter 72 and the curved shape of the curved surface 60A of the setter 60 are sufficiently transferred to the ceramic green sheet 110 placed on the upper surface of the setter 72. Therefore, one main surface of the ceramic green sheet 110 sandwiched between the upper surface of the setter 72 and the curved surface 60A of the setter 60 is curved in a convex shape, and the other main surface is curved in a concave shape. By heating such a laminated body 210, a plurality of ceramic green sheets 111 can be degreased and fired at the same time, and the ceramic plate 102 shown in FIG. 3 can be mass-produced.

The laminate 210 has a plurality of ceramic green sheets 111 sandwiched between a pair of

setters

60 and 82 from above and below. Since the main surfaces of the pair of

setters

60 and 82 in contact with the ceramic green sheets 111 are curved in a convex and concave shape and have complementary shapes to each other, the warpage amount W and the warp amount Z of the plurality of ceramic plates 102 The variation can be sufficiently reduced. Further, the setter 72 is arranged between the pair of

setters

60 and 82 so as to be sandwiched between the ceramic green sheets 111. The contact surface of the setter 72 with the ceramic green sheet 111 is curved in the same manner as the curved surface of the

setters

60 and 82. By using such a setter 72, the number of laminated ceramic green sheets 111 can be increased. As a result, a large number of ceramic plates 102 can be manufactured at the same time. However, the laminated body may be formed without using the setter 72. Further, a plurality of setters 72 may be individually arranged at arbitrary positions between the pair of

setters

60 and 82.

The

setters

50, 60, 70, 72, 80, 82 may be made of ceramic. For example, those composed of at least one selected from the group consisting of boron nitride, silicon carbide, alumina, zirconia, graphite, and silicon nitride can be mentioned. Of these, a setter made of boron nitride is preferably used because it has both heat resistance and good machinability. The material of the setter may be different from the material of the ceramic plate from the viewpoint of suppressing the adhesion between the setter and the ceramic plate during firing.

The

setters

50, 60, 70, 72, 80, 82 may be made of boron nitride (BN) from the viewpoint of heat resistance. The boron nitride setter can be manufactured by the following procedure. First, a molded product 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. Examples of the sintering aid include oxides of alkaline earth metals such as magnesium oxide and calcium oxide, rare earth oxides such as aluminum oxide, silicon oxide and yttrium oxide, and composite oxides such as spinel. The molding may be performed by uniaxial pressure molding and CIP molding. Uniaxial pressure molding may be performed at 3 to 20 MPa. CIP molding may be performed at 50 to 300 MPa.

The obtained molded product is calcined to obtain a setter made of boron nitride. The firing may be carried out under the conditions of a non-oxidizing atmosphere, a heating rate of 150 ° C./hr or less, a maximum temperature of 1800 to 2200 ° C., and a holding time of 5 hours or more in this temperature range. Examples of the non-oxidizing atmosphere include a nitride gas atmosphere such as nitrogen and ammonia. The density of the boron nitride setter may be 1600 kg / m ³ or more. The method for manufacturing the setter is not limited to the above method. For example, it may be manufactured by a hot press method. Further, degreasing may be performed before firing. The degreasing may be performed by heating the molded product in air or in a non-oxidizing atmosphere such as nitrogen to 300 to 700 ° C. The heating time may be, for example, 1 to 10 hours.

In the method for manufacturing a ceramic sintered body according to one embodiment, a ceramic plate having a warp amount W of 1 mm or more is used. The manufacturing method includes a laminating step of laminating a plurality of ceramic green sheets to obtain a laminated body, a degreasing step of heating and degreasing the laminated body, and a firing step of firing the degreased laminated body to obtain a ceramic plate. And have. Details will be described below.

A ceramic green sheet is produced, for example, by the following procedure. Prepare a raw material slurry containing ceramic powder, sintering aid, binder and dispersant. The ceramic is not particularly limited, and examples thereof include nitrides, oxides, and carbides. Specific examples thereof include silicon nitride, silicon carbide, alumina, aluminum nitride and boron nitride. Binders include those containing organic components. The binder may be an acrylic copolymer. The dispersant may be unsaturated fatty acids.

Apply the raw material slurry to a predetermined thickness on the release film by the doctor blade method, calendar method, extrusion method, etc. Then, the applied raw material slurry is dried and peeled off from the release film to obtain a ceramic green sheet. The ceramic green sheet may be processed into a desired shape by, for example, cutting. The materials and shapes of the plurality of ceramic green sheets may be the same as each other or may be different from each other.

As the setter used in the method for producing the ceramic sintered body, for example, a commercially available setter may be purchased or may be produced 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. Of these, a setter made of boron nitride is preferably used because it has both heat resistance and good machinability. The material of the setter may be different from the material of the ceramic sintered body from the viewpoint of suppressing the adhesion between the setter after firing and the ceramic sintered body manufactured by this manufacturing method.

A plurality of ceramic green sheets are layered on the setter prepared in this way to obtain a laminated body. A plurality of ceramic green sheets may be laminated so that the main surfaces of the ceramic green sheets are in contact with each other, and another setter may be placed on the laminated body to prepare a laminated body. That is, a plurality of laminated ceramic green sheets may be sandwiched between a pair of setters arranged so as to face each other in the stacking direction to prepare a laminated body. A ceramic plate having a warp amount of 1.5 mm or more is arranged outside the pair of setters in the produced laminate, and the laminate is pressed along the lamination direction to prepare a holding body.

FIG. 10 is a side view showing an example of a laminated body and a holding body used in the method for manufacturing a ceramic sintered body of the present embodiment. The holding body 350 of FIG. 10 includes a laminated body 300, a fixing member 37 provided above the laminated body 300 and fixing the laminated body 300, and a ceramic plate 100a between the fixing member 37 and the laminated body 300. .. The laminate 300 is placed on the support 400, and the setter 92, the plurality of ceramic green sheets 41, the setter 94, the plurality of ceramic green sheets 41, and the setter 96 are arranged in this order from the support 400 side. It is laminated. Both these setters and ceramic green sheets have a flat plate shape. The ceramic plate 100a exhibits an arch shape with a warp amount W as shown as the ceramic plate 100 in FIG. 2 in a state where no external force is applied.

In the holding body 350 of FIG. 10, the ceramic plate 100a arranged so as to face the upper surface of the setter 96 is pressed toward the laminated body 300 by the fixing member 37. Therefore, it is elastically deformed so that the amount of warpage becomes small, and becomes a flat plate shape. The setter 96 on the lower side of the ceramic plate 100a is urged downward by the restoring force of the ceramic plate 100a as a leaf spring. In this way, the holding body 350 restrains the laminated body 300 by sandwiching the laminated body 300 between the support 400 and the ceramic plate 100a in the laminating direction.

In the degreasing step, the holding body 350 provided with the laminated body 300 is housed in a degreasing furnace and heated to, for example, 300 ° C. to 700 ° C. As a result, the binder and the dispersant contained in the ceramic green sheet 41 are volatilized, and the ceramic green sheet 41 shrinks.

FIG. 11 is a side view showing the ceramic green sheet 42, the laminated body 301, and the holding body 351 obtained by degreasing the ceramic green sheet 41. The ceramic green sheet 42 is thinner due to shrinkage than the ceramic green sheet 41 before degreasing. Therefore, the position of the setter 96 in the laminated body 301 after degreasing is closer to the support 400 than in the setter 96 in the laminated body 300 before degreasing. At this time, since the positional relationship between the support 400 and the fixing member 37 does not change before and after degreasing, the distance between the setter 96 and the fixing member 37 becomes large. Along with this, the elastically deformed ceramic plate 100a is restored, and the warp amount W1 becomes large. That is, the warp amount W1 increases with the passage of the heating time. The warp amount W1 of the ceramic plate 100b is smaller than the warp amount W of the ceramic plate 100 when no external force is applied. Therefore, the ceramic plate 100b can continue to restrain the laminated body 300 by the restoring force as a leaf spring.

Since the holding body 351 includes a ceramic plate 100 (100b) that functions as a leaf spring, even if the ceramic green sheet 42 shrinks during the degreasing step, the restoring force of the elastically deformed ceramic plate 100 acts. As a result, the laminated body 301 can be continuously restrained. Therefore, it is possible to prevent the ceramic

green sheets

41 and 42 from being displaced from each other, resulting in uneven baking or warpage. Therefore, it is possible to stably produce a ceramic sintered body having high quality.

The number of ceramic plates 100 used in the holder 350 (351) is not limited to one, and a plurality of ceramic plates 100 may be stacked in the vertical direction. As a result, the restoring force of the leaf spring can be increased, and the

laminated bodies

300 and 301 can be restrained more firmly. Further, the arrangement of the ceramic plate 100 is not limited to between the setter 96 and the fixing member 37, and may be between the setter 92 and the support 400, or between the pair of ceramic green sheets 41 (42). There may be. A plurality of ceramic plates 100 may be arranged at different positions from each other. The ceramic plate 102 may be used instead of the ceramic plate 100. Further, a ceramic plate having a shape different from these may be used as long as it functions as a leaf spring.

There is no particular limitation on the number of

setters

92, 94, 96 and the ceramic green sheet 41 (42) constituting the

laminated body

300, 301. The materials and thicknesses of the plurality of ceramic green sheets 41 (42) may be the same or different from each other. A mold release agent may be applied to the main surface of the ceramic green sheet 41 (42) in order to prevent the adjacent ceramic green sheets from adhering to each other during firing. Further, the mold release agent may be applied to the surface of the

setters

92, 94, 96 facing the main surface of the ceramic green sheet 41 (42). Examples of the component contained in the release agent include ceramic powder such as boron nitride, graphite powder, and binder.

In the firing step, the degreased ceramic green sheet 42 is housed in a firing furnace and heated to 1600 ° C to 2000 ° C. As a result, the ceramic green sheet is fired and a ceramic plate is obtained. The degreasing furnace used for degreasing and the firing furnace used for firing may be the same furnace or different furnaces. Further, the heating temperature, time and atmosphere may be appropriately adjusted according to the composition of the ceramic green sheet.

In the firing step, the holding body 351 of FIG. 11 may be housed in a firing furnace to fire the ceramic green sheet 42, or the holding body 351 may be disassembled and the ceramic green sheet 42 may be held and fired by another setter. You may. Also in the firing step, the ceramic green sheet 42 may further shrink due to factors such as the progress of grain growth and the volatilization of the remaining binder and the dispersant. Therefore, similarly to the degreasing step, the position shift of the ceramic green sheet 42 can be suppressed by urging and restraining the laminated body 301 by the restoring force of the ceramic plate 100.

In the modified example, the holding body provided with the ceramic plate 100 may be used only in the firing step. In this case as well, it is possible to prevent the positions of the plurality of ceramic green sheets from being displaced from each other after degreasing. This makes it possible to stably produce a ceramic sintered body having high quality.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. For example, the thickness of the ceramic plate is not uniform and may be different. In this case, the average thickness of the ceramic plate can be obtained as the average value of the thickest portion and the thinnest portion. This average thickness may be within the numerical range of the above-mentioned thickness.

Ceramic plates may be used for different purposes than leaf springs. For example, the ceramic plate may be used as a member of the filter. In this case, for example, two ceramic plates 100 (102) are arranged so that the first main surface 100A (102A) and the second main surface 100B (102B) face each other to form a curved flow path between the two ceramic plates. , The liquid content or the solid content contained in the gas flowing through the flow path may be removed. The medium flowing through the flow path is not limited to gas, and may be mist or liquid. The filter may be configured by arranging three or more ceramic plates 100 (102) side by side so that the main surfaces face each other. The flow path in the filter may be formed by arranging a ceramic plate having a flat main surface and a ceramic plate 100 (102) side by side.

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

(Example 1)
<Ceramic plate production>
Silicon nitride powder, magnesium oxide powder, and yttrium oxide powder were prepared as sintering aids. These were blended at Si ₃ N ₄ : Y ₂ O ₃ : MgO = 94.0: 3.0: 3.0 (mass ratio) to obtain a raw material powder. This raw material powder was uniaxially pressure-molded to prepare a plurality of ceramic green sheets. The produced ceramic green sheet and a setter made of boron nitride were superposed to obtain a laminate as shown in FIG. The radius of curvature of the curved surface of each of the three setters was 290 mm. This is placed in an electric furnace equipped with a carbon heater, heated in air at 500 ° C. for 5 hours to degreas, and then fired at 1800 ° C. for 12 hours in a nitrogen gas atmosphere to form a silicon nitride sintered body. A ceramic plate to be composed was obtained.

<Evaluation of the shape of the ceramic plate>
As shown in FIGS. 1 and 2, the ceramic plate is curved in an arch shape, and has a first main surface that is curved in a convex shape and a first main surface that is curved in a concave shape on the opposite side of the first main surface. It had two main surfaces. The vertical length (arc length) measured along the longitudinal direction of the first main surface and the second main surface was 68 mm. The lateral length (width) measured along the lateral direction of the first main surface and the second main surface was 35.4 mm. The areas of the first main surface and the second main surface were both 68 × 35.4 = 2407.2 mm ² . The thickness (the shortest distance between the first main surface and the second main surface) measured along the direction orthogonal to the first main surface and the second main surface was 0.635 mm.

As shown in FIG. 2, the obtained ceramic plate was placed on a measuring table having a horizontal flat surface, and the amount of warpage W was measured. A one-shot 3D shape measuring machine (trade name: VR-3050) manufactured by KEYENCE CORPORATION was used for the measurement. The measurement results of the warp amount W of the three ceramic plates are as shown in Table 1. As shown in FIG. 2, the warp amount W is the maximum height of the second main surface curved in a concave shape from the measuring table. The warpage amount Z of the three ceramic plates measured using the same measuring instrument is as shown in Table 1. As shown in FIG. 2, the warp amount Z is the maximum value of the height difference of the first main surface that is curved in a convex shape.

As shown in Table 1, the warpage amount W of the three ceramic plates was almost the same. Further, the warp amount W and the warp amount Z did not change significantly. The radius of curvature of the first main surface and the second main surface was the same as the radius of curvature of the curved surface of the setter. Table 1 shows the area and thickness of the main surface, the ratio of the warp amount W to the area of the main surface, and the ratio of the warp amount W to the thickness.

Three ceramic plates of Examples 1-1, 1-2, 1-3 were superposed to prepare a holding body similar to the holding body 350 of FIG. In FIG. 10, only one ceramic plate 100a is shown, but in this embodiment, three ceramic plates are used in an overlapping manner so that the directions of the first main surface and the second main surface are aligned. 60 ceramic green sheets were prepared in the same manner as in the above-mentioned "Ceramic plate preparation". As the setters, commercially available ones made of boron nitride were used. Thirty ceramic green sheets, setters (second setter), and 30 ceramic green sheets and setters (third setter) were laminated on the lower setter (first setter) in this order to obtain a laminated body. Three ceramic plates were placed on the upper setter (third setter). The laminated body was restrained by pressing downward with a fixing member arranged on the upper side of the three ceramic plates to prepare a holding body as shown in FIG. The laminate was urged downward by the restoring force associated with the elastic deformation of the three ceramic plates.

The holding body provided with such a laminated body was housed in a degreasing furnace and heated in air at 500 ° C. for 5 hours to perform a degreasing step. In the degreasing step, the positions of the plurality of ceramic green sheets did not shift from each other. Then, the ceramic green sheet was taken out from the holding body and placed on another boron nitride setter to perform a firing step. In the firing step, the degreased ceramic green sheet was heated at 1800 ° C. for 12 hours in a firing furnace under a nitrogen atmosphere. The quality variation of the obtained silicon nitride sintered body was sufficiently reduced.

(Reference example 1)
A ceramic green sheet was produced by the same procedure as in Example 1. A ceramic green sheet was placed on a flat plate-shaped setter, and a degreasing step and a firing step were performed under the same heating conditions as in Example 1 to obtain a flat plate-shaped ceramic plate composed of a silicon nitride sintered body. The size of the ceramic plate was length × width × thickness = 68 mm × 35.4 mm × 0.635 mm.

N pieces of the above-mentioned ceramic plates were prepared, and the amount of deflection was measured by the following procedure. The amount of deflection was measured by performing a three-point bending test at a distance between fulcrums of 30 mm using a tensile compression tester (model: SDT-503NB-50R1T) manufactured by Imada Seisakusho Co., Ltd. FIG. 12 shows the measurement results of n ceramic plates side by side.

(Reference example 2)
A flat plate-shaped ceramic plate composed of a silicon nitride sintered body was obtained in the same manner as in Reference Example 1 except that the thickness of the ceramic plate was changed. The size of the ceramic plate was length × width × thickness = 68 mm × 35.4 mm × 0.32 mm. N ceramic plates were prepared, and the amount of deflection was measured by the same procedure as in Reference Example 1. The measurement results are as shown in FIG. From the results of FIGS. 12 and 13, it was confirmed that the amount of deflection can be adjusted by changing the thickness of the ceramic plate.

According to the present disclosure, a leaf spring having excellent heat resistance and capable of suppressing the position of a plurality of laminated ceramic green sheets from shifting from each other, and a ceramic plate preferably used as the leaf spring and manufacturing thereof. A method can be provided. Further, it is possible to provide a setter capable of easily manufacturing such a ceramic plate. Further, by suppressing the positions of the plurality of laminated ceramic green sheets from being displaced from each other, it is possible to provide a manufacturing method capable of stably manufacturing a ceramic sintered body having high quality.

11,13,24 ... Side, 20,65 ... Top, 37 ... Fixing member, 41,42,110 ... Ceramic green sheet, 50,60,70,72,80,82,92,94,96 ... Setter, 50A , 60A ... Curved surface, 50B, 60B ... Flat surface, 52, 54 ... Side edge, 61 ... Recess, 64 ... Side edge, 400 ... Support, 100, 100a, 100b, 102 ... Ceramic plate, 100A, 102A ... 1 main surface, 100B, 102B ... second main surface, 150 ... measuring table, 200, 210, 300, 301 ... laminated body, 350, 351 ... holding body.

Claims

A ceramic plate having a first main surface that is curved in a convex shape and a second main surface that is curved in a concave shape on the opposite side of the first main surface, and has a warp amount W of 1 mm or more.
The ceramic plate according to claim 1, wherein the thickness is 2 mm or less, and the radius of curvature of the first main surface and the second main surface is 100 to 1000 mm.
The ceramic plate according to claim 1 or 2, wherein the ratio of the warp amount W to the average value of the areas of the first main surface and the second main surface is 1 × 10 -5 / mm or more.
The ceramic plate according to any one of claims 1 to 3, which is composed of a silicon nitride sintered body.
A leaf spring composed of the ceramic plate according to any one of claims 1 to 4.
A setter having a convex or concave curved surface and a ceramic green sheet are superposed and heated so that the main surface of the ceramic green sheet is along the curved surface to obtain a ceramic plate having a warp amount W of 1 mm or more. A method for manufacturing a ceramic plate having a process.
A setter that has a convex or concave curved surface, and the height difference of the portion on the curved surface on which the ceramic green sheet is placed is 1 mm or more.
The setter according to claim 7, wherein the ceramic green sheet placed so as to cover the portion of the curved surface is heated to form a ceramic plate having a warp amount W of 1 mm or more.
A degreasing process that heats and degreases a laminate containing multiple ceramic green sheets,
It has a firing step of firing the degreased laminate to obtain a ceramic plate.
In one or both of the degreasing step and the firing step, the laminated body is held by the restoring force generated by the elastic deformation of the ceramic plate according to any one of claims 1 to 4. Production method.
In one or both of the degreasing step and the firing step, the ceramic plate is arranged in a state of being elastically deformed between the fixing member provided above the laminated body and the laminated body, and shrinkage of the laminated body. The method for producing a ceramic sintered body according to claim 9, wherein the amount of warpage W of the ceramic plate increases accordingly.