JP7126035B2 - Ceramic plate and manufacturing method thereof, plate spring, setter, and manufacturing method of ceramic sintered body - Google Patents

Description

The present disclosure relates to a ceramic plate and its manufacturing method, a plate spring, a setter, and a method of 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. A circuit board mounted on the power module has an insulating ceramic plate. The ceramic plate is produced by, for example, a step of mixing ceramic powder, a sintering aid, an organic binder, a dispersing agent, etc. and then extruding into a sheet shape, a step of punching to form a ceramic green sheet, and a step of forming a ceramic green sheet It is manufactured by sequentially performing the step of firing. At the time of firing, in order to improve productivity, an attempt has been made to simultaneously produce a plurality of ceramic plates by placing a laminate including 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, and the like, these components evaporate from the inside and shrink when heated. Patent Literature 1 proposes to reduce the influence of the strain that occurs in the shrinking process by previously providing dividing grooves in the ceramic green sheet.

JP 2014-51409 A

When the component contained in the ceramic green sheet volatilizes and shrinks, there is concern that the positions of the laminated ceramic green sheets may shift due to the volatilization and shrinkage, which may affect the quality. Accordingly, the present disclosure provides a leaf spring that has excellent heat resistance and is capable of suppressing a plurality of stacked ceramic green sheets from being displaced from each other, a ceramic plate suitably used as the leaf spring, and its manufacture. provide a way. The present disclosure also provides a setter that can easily produce such ceramic plates. In addition, the present disclosure provides a manufacturing method capable of stably manufacturing a high-quality ceramic sintered body by suppressing mutual displacement of a plurality of laminated ceramic green sheets.

In one aspect, the present disclosure has a convexly curved first principal surface and a concavely curved second principal surface on the opposite side of the first principal surface, and the amount of warpage W is A ceramic plate is provided, which is 1 mm or more. Since such a ceramic plate is made of ceramic, it is excellent in heat resistance. Moreover, since it has a convex first principal surface and a concave second principal surface, and has a large amount of warp W, it can be suitably used as a leaf spring that utilizes a restoring force generated by elastic deformation. However, its application 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 principal surface and the second principal 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.

A ratio of the amount of warpage 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, it is possible to increase the deflection per unit area of the main surface, so that it can be used more preferably as a leaf spring.

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

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

In one aspect of the present disclosure, a setter having a convex or concave curved surface and a ceramic green sheet are superimposed and heated such that the main surface of the ceramic green sheet is along the curved surface, and the warp amount W Provided is a method for manufacturing a ceramic plate, comprising a step of obtaining a ceramic plate having a diameter of 1 mm or more.

In the manufacturing method described above, 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. Thus, it is possible to obtain a ceramic plate suitable for use as a leaf spring utilizing a restoring force by a simple manufacturing method. Therefore, the above-described method for manufacturing a ceramic plate can also be called a method for manufacturing a leaf spring. However, the application of the ceramic plate obtained by the above manufacturing method is not limited to leaf springs.

In one aspect, the present disclosure provides a setter having a convex or concave curved surface, and a height difference of 1 mm or more in the curved surface where the ceramic green sheets are placed. By using such a setter, it is possible to easily manufacture a ceramic plate that is suitably used as a plate spring, for example. The setter may heat the 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.

In one aspect, the present disclosure includes a degreasing step of heating and degreasing a laminate including a plurality of ceramic green sheets, and a firing step of firing the degreased laminate to obtain a ceramic plate. Provided is a method for producing a ceramic sintered body, wherein the laminated body is held by a restoring force generated by elastic deformation of any of the ceramic plates described above in one or both of the process and the firing process.

When a laminated body is heated to produce a ceramic sintered body, if the positions of the laminated ceramic green sheets are shifted from each other, the heating state changes between the exposed surface and the non-exposed surface. This is a factor that causes variations in quality such as color and properties. Further, if the positions of the ceramic green sheets are shifted from each other, it may cause warpage. However, in the manufacturing method described above, the laminate is held by the restoring force generated by the elastic deformation of the ceramic plates. Therefore, it is possible to prevent the stacked ceramic green sheets from being displaced from each other. Therefore, a ceramic sintered body having high quality can be stably produced.

In one or both of the degreasing step and the firing step of the above manufacturing method, the ceramic plate is placed in an elastically deformed state between the fixing member provided above the laminate and the laminate, and the ceramic plate is elastically deformed as the laminate shrinks. Therefore, the amount of warp W of the ceramic plate may increase. As a result, the laminated body can be stably held, and it is possible to sufficiently prevent the positions of the laminated ceramic green sheets from being shifted from each other.

It is possible to provide a leaf spring that has excellent heat resistance and is capable of suppressing displacement of a plurality of laminated ceramic green sheets, a ceramic plate suitably used as the leaf spring, and a method for producing the same. can. Moreover, it is possible to provide a setter that can easily produce such a ceramic plate. Also, by suppressing the positional deviation of a plurality of laminated ceramic green sheets, it is possible to provide a manufacturing method capable of stably manufacturing a high-quality ceramic sintered body.

FIG. 1 is a perspective view of a ceramic plate according to one embodiment. FIG. 2 is a side view of a ceramic plate according to one embodiment. FIG. 3 is a perspective view of a ceramic plate according to another embodiment. FIG. 4 is a perspective view of a setter according to one embodiment. 5 is a side view of the setter of FIG. 4; FIG. FIG. 6 is a perspective view of a setter according to another embodiment. 7 is a side view of the setter of FIG. 6; FIG. FIG. 8 is a perspective view showing an example of a laminate used in the ceramic plate manufacturing method. FIG. 9 is a perspective view showing another example of the laminate used in the ceramic plate manufacturing method. FIG. 10 is a side view showing an example of a laminate and a holder used in the method for producing a ceramic sintered body according to this embodiment. FIG. 11 is a side view showing an example of the laminate and the holder after the degreasing process. 12 is a graph showing measurement results of the amount of deflection of Reference Example 1. FIG. 13 is a graph showing measurement results of the amount of deflection of Reference Example 2. FIG.

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.

FIG. 1 is a perspective view of a ceramic plate according to one embodiment. The ceramic plate 100 is arched and has a convexly curved first major surface 100A and a concavely curved second major surface 100B on the opposite side of the first major surface 100A. Of the four side surfaces of the ceramic plate 100, a pair of opposing side surfaces 11 are rectangular, while another pair of opposing side surfaces 13 are curved like an arch.

2 is a side view of the ceramic plate 100 of FIG. 1. FIG. The ceramic plate 100 is placed on a measuring table 150 having a horizontal plane. The ceramic plate 100 is curved like an arch. Therefore, of the second main surface 100B of the ceramic plate 100, only the sides 12 on the side of the pair of side surfaces 11 are in contact with the measuring platform 150, and there is no space between the other part of the second main surface 100B and the measuring platform 150. There is a gap. The warp amount 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 facing upward. measured. The amount of warp W is a value when the ceramic plate 100 is not subjected to external force and 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 a restoring force. The warp amount Z of the ceramic plate 100 is the maximum value of the height difference of the convexly curved first main surface 100A. The warp amount Z may also be 1 mm or more.

In a 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 100-1000 mm, 150-800 mm, or 200-500 mm. This makes it possible to sufficiently increase deflection while suppressing breakage. 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. Also, the radius of curvature of the first major surface 100A may not be uniform, and may vary depending on the position. Also in this case, the radius of curvature at each position should be within the above range. The radius of curvature of the second main surface 100B may not be uniform, and may vary depending on the position. Also in this case, the radius of curvature at each position should 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 become parallel, the amount of warp W (amount of warp Z) may be 1.2 mm or more, and may be 1.4 mm or more. 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. A ratio of the amount of warp Z to the amount of warp W may be 0.9 to 1.1, or may be 0.95 to 1.05.

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

The ratio of the warp amount W to the thickness of the ceramic plate 100 may be 1 or more, or 2 or more, from the viewpoint of sufficiently increasing the deflection until the second main surface 100B and the measuring table 150 become parallel. good too. The ratio of the amount of warpage 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 amount of warpage W to the thickness of the ceramic plate 100 may be 1-15.

The area of the first major surface 100A and the second major surface 100B may be 100-10000 mm ² and may be 500-5000 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 warpage 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 amount of warpage 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 1×10 ⁻² /mm or less. and 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 have a sufficiently large deflection. Moreover, 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 may be 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, and may be 900 MPa. An example of the bending strength of the ceramic plate 100 is 500-1000 MPa. The bending strength in the present disclosure is the three-point bending 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 a 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. The ceramic plate 102 is curved so that all four side surfaces 24 are arched, and the first main surface 102A is convexly curved and the concavely curved side is opposite to the first main surface 102A. and a second major surface 102B. The central portion of the first main surface 102A protrudes upward from the end portions. The central portion of the second main surface 102B is recessed more than the end portions. The arch shapes of the four sides 24 may be the same or different.

When the ceramic plate 102 is placed on the measuring table 150 with the first main surface 102A side facing upward in the same manner as in FIG. contact with platform 150; A gap is generated between the other portion of the second main surface 102B and the measurement table 150 . Similarly to FIG. 2, the warp amount W of the ceramic plate 102 is also determined by the maximum height of the second main surface 102B from the measuring table 150 when placed on the measuring table 150 with the first main surface 102A 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 convexly curved first main surface 102A.

The ceramic plate 102 may be the same as the ceramic plate 100 in terms of numerical ranges such as the amount of warp W, the amount of warp Z, the thickness, the ratio of the amount of warp W to the thickness, and the material. Numerical ranges such as the radius of curvature and the area of the first principal surface 102A and the second principal surface 102B may be the same as those of the first principal surface 100A and the second principal 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 a setter according to one embodiment. The setter 50 has a substantially kamaboko shape. That is, the setter 50 has one surface that bulges into an arch shape, and has a convex curved surface 50A and a flat surface 50B on the opposite side of the curved surface 50A. A 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 portion 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 curves along the curved surface 50A. By heating the curved ceramic green sheet, as shown in FIG. It is possible to form a ceramic plate 100 having a second main surface 100B that is curved and a warpage amount W (warpage amount Z) of 1 mm or more.

5, the radius of curvature of the curved surface 50A of the setter 50 may be 100-1000 mm, 150-800 mm, or 200-500 mm. This makes it possible to easily manufacture a ceramic plate suitable as a leaf spring. The height difference H1 between the apex at the center of the curved surface 50A 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, or 1.4 mm or more. From the viewpoint of manufacturing 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 a setter according to another embodiment. The setter 60 has a concavely curved curved surface 60A and a flat surface 60B on the opposite side of the curved surface 60A. All of the four side edges 64 forming the contour of the curved surface 60A are curved and curved downward to form a convex shape. A recessed portion 61 at the center of the curved surface 60A is a portion of the curved surface 60A that is closest to the flat surface 60B. The curved surface 60A curves away from the plane 60B as it goes from the center to the side edge 64 of the curved surface 60A. Apices 65 at the four corners of the curved surface 60A are parts 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 portion 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 curves along the curved surface 60A. By heating the curved ceramic green sheets, a convexly curved first major surface 102A and a concavely curved second major surface opposite to the first major surface 102A, as shown in FIG. A ceramic plate 102 can be manufactured having four arcuate sides with a surface 102B.

7, the radius of curvature of the curved surface 60A of the setter 60 may be 100-1000 mm, 150-800 mm, or 200-500 mm. This makes it possible to easily manufacture a ceramic plate suitable as a leaf spring. A height difference H2 between the depression 61 at the center of the curved surface 60A and the top 65 of the curved surface may be 1 mm or more, and may be 1.2 mm or more, from the viewpoint of manufacturing a leaf spring (ceramic plate 100) that is sufficiently flexible. and 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) includes a setter 50 (60) having a convex curved surface 50A (concave curved surface 60A), a ceramic green sheet, and a ceramic green sheet having a curved surface 50A ( 60A) and heating to obtain a ceramic plate 100 (102) having a warpage amount W (warpage amount Z) of 1 mm or more. In the above manufacturing method, by using the setter 50 or setter 60 having a convex or concave curved surface, a ceramic plate having a warpage amount W (warpage amount Z) of 1 mm or more can be obtained. Thus, it is possible to obtain a ceramic plate suitable for use as a leaf spring utilizing a restoring force by a simple manufacturing method. The application of the ceramic plate is not limited to leaf springs.

The shape of the setter used for manufacturing the ceramic plate is not limited to those shown in FIGS. 4, 5, 6 and 7, and may be changed according to the shape of the ceramic plate. For example, in a variation, the setter 50 of FIG. 4 may be replaced with a setter having a concave curved surface. A pair of curved side edges 54 of the curved surface in this case may be curved so as to protrude downward, contrary to FIG. Also, in another modification, the setter 60 of FIG. 6 may be replaced with a setter having a convexly curved curved surface. The four curvilinear side edges 64 of the curved surface in this case may be curved so as to protrude upward, contrary 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 of manufacturing a ceramic sintered body described below.

FIG. 8 is a perspective view showing an example of a setter used in the method of manufacturing a ceramic plate and a laminate in which ceramic green sheets are laminated. A laminate 200 shown in FIG. 8 has a setter 50 shown in FIG. A setter 70 is arranged thereon, and three ceramic green sheets 110 are laminated on one surface (upper surface) of the setter 70 . A setter 80 is arranged thereon.

The curved shape of the curved surface 50A is transferred to the three ceramic green sheets 110 placed 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 setters 70 and 50 . As a result, one main surface of the ceramic green sheet 110 is curved convexly, and the other main surface is curved concavely.

The upper surface of the setter 70 is convexly curved 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 convexly, and the other main surface is curved concavely. By heating such a laminate 200, a plurality of ceramic green sheets 110 are simultaneously degreased and sintered, 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. The main surfaces of the pair of setters 50 and 80 in contact with the ceramic green sheets 110 are curved convexly and concavely, respectively, and have mutually complementary shapes. Variation can be sufficiently reduced. Also, a setter 70 sandwiched by ceramic green sheets 110 is used between a pair of setters 50 and 80 . The contact surface of the setter 70 with the ceramic green sheet 110 is curved like the curved surfaces of the setters 50 and 80 . By using such a setter 70, the number of laminated ceramic green sheets 110 can be increased. Thereby, a large number of ceramic plates 100 can be manufactured at the same time. However, the laminate may be constructed without using the setter 70 . Moreover, you may arrange|position several setters 70 individually in the arbitrary positions between a pair of setters 50 and 80. FIG.

FIG. 9 is a perspective view showing another example of a setter used in the method of manufacturing a ceramic plate and a laminate in which ceramic green sheets are laminated. A laminate 210 in FIG. 9 has a setter 82 arranged at the bottom, and three ceramic green sheets 111 are laminated on the curved surface of the setter 82 . A setter 72 is arranged thereon, and three ceramic green sheets 111 are laminated on one surface (upper surface) of the setter 72 . The setter 60 of FIG. 6 is placed thereon with the plane 60B facing upward.

The curved shape of the curved surface is transferred to the ceramic green sheet 111 placed on the curved surface of the setter 82 . The curved surface of the setter 82 is a convex curved surface complementary to the concave curved surface 60A of the 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, 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 to the ceramic green sheet 111 sandwiched between the setters 72 and 82 . As a result, one main surface of the ceramic green sheet 111 is curved convexly, and the other main surface is curved concavely.

The upper surface of the setter 72 is a convex curved surface complementary to the concave curved surface 60A of the 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 as well. 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 convexly, and the other main surface is curved concavely. By heating such a laminate 210, a plurality of ceramic green sheets 111 are simultaneously degreased and sintered, 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. The main surfaces of the pair of setters 60 and 82 in contact with the ceramic green sheets 111 are curved convexly and concavely, respectively, and have mutually complementary shapes. Variation can be sufficiently reduced. A 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 like the curved surfaces of the setters 60 and 82 . By using such a setter 72, the number of laminated ceramic green sheets 111 can be increased. This allows a large number of ceramic plates 102 to be manufactured simultaneously. However, the laminate may be constructed without using the setter 72 . Also, a plurality of setters 72 may be individually arranged at arbitrary positions between the pair of setters 60 and 82 .

Setters 50, 60, 70, 72, 80, 82 may be made of ceramic. Examples thereof include those composed of 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 during firing, the material of the setter may be different from the material of the ceramic plate.

The setters 50, 60, 70, 72, 80, 82 may be made of boron nitride (BN) from the viewpoint of heat resistance. A setter made of boron nitride can be manufactured 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. Examples of sintering aids 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 complex oxides such as spinel. For molding, uniaxial pressure molding and CIP molding may be performed. Uniaxial pressing may be performed at 3 to 20 MPa. CIP molding may be performed at 50-300 MPa.

The obtained compact is fired to obtain a setter made of boron nitride. 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 setter made of boron nitride may have a density of 1600 kg/m ³ or higher. Note that the setter manufacturing method is not limited to the above method. For example, it may be produced by a hot press method. Moreover, you may degrease before baking. The degreasing may be performed by heating the compact to 300 to 700° C. in air or in a non-oxidizing atmosphere such as nitrogen. 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 warpage amount W of 1 mm or more is used. The manufacturing method includes a lamination step of laminating a plurality of ceramic green sheets to obtain a laminate, a degreasing step of heating and degreasing the laminate, and a firing step of firing the degreased laminate to obtain a ceramic plate. and have Details are described below.

A ceramic green sheet is produced, for example, by the following procedure. A raw slurry containing ceramic powder, sintering aid, binder and dispersant is prepared. Ceramics are not particularly limited, and include, for example, nitrides, oxides and carbides. Specific examples 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 an unsaturated fatty acid.

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. Thereafter, the coated raw material slurry is dried and peeled off from the release film to obtain a ceramic green sheet. The ceramic green sheets may be processed into a desired shape, for example by cutting. The materials and shapes of the plurality of ceramic green sheets may be the same or different.

The setter used in the method for producing a ceramic sintered body may be purchased commercially, 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. 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 after firing and the ceramic sintered body produced by this production method, the material of the setter may be different from the material of the ceramic sintered body.

A laminate is obtained by stacking a plurality of ceramic green sheets on the setter thus prepared. A plurality of ceramic green sheets may be laminated so that their main surfaces are in contact with each other, and another setter may be placed thereon to produce a laminate. That is, a laminate may be produced by sandwiching a plurality of laminated ceramic green sheets between a pair of setters arranged so as to face each other in the lamination direction. A ceramic plate having a warpage 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 produce a holder.

FIG. 10 is a side view showing an example of a laminate and a holder used in the method for producing a ceramic sintered body according to this embodiment. A holder 350 of FIG. 10 includes a laminate 300, a fixing member 37 provided above the laminate 300 and fixing the laminate 300, and a ceramic plate 100a between the fixing member 37 and the laminate 300. . The laminate 300 is placed on a support 400. From the support 400 side, a setter 92, a plurality of ceramic green sheets 41, a setter 94, a plurality of ceramic green sheets 41, and a setter 96 are arranged in this order. Laminated. Both of 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 indicated by the ceramic plate 100 in FIG. 2, when no external force is applied.

In the holding body 350 of FIG. 10, the ceramic plate 100a arranged to face the upper surface of the setter 96 is pressed toward the laminate 300 by the fixing member 37. As shown in FIG. Therefore, it is elastically deformed so as to reduce the amount of warp, and has a flat plate shape. The setter 96 below the ceramic plate 100a is biased downward by the restoring force of the ceramic plate 100a as a plate spring. In this manner, the holder 350 sandwiches and restrains the laminate 300 between the support 400 and the ceramic plate 100a in the laminate direction.

In the degreasing step, the holder 350 including the laminated body 300 is placed in a degreasing furnace and heated to 300° C. to 700° C., for example. As a result, the binder and dispersant contained in the ceramic green sheets 41 volatilize and the ceramic green sheets 41 shrink.

FIG. 11 is a side view showing the ceramic green sheet 42 obtained by degreasing the ceramic green sheet 41, the laminate 301, and the holder 351. FIG. The ceramic green sheet 42 is thinner than the ceramic green sheet 41 before degreasing due to shrinkage. Therefore, the position of the setter 96 in the laminate 301 after degreasing is closer to the support 400 than the setter 96 in the laminate 300 before degreasing. At this time, since the positional relationship between the support 400 and the fixing member 37 remains unchanged before and after the degreasing, the distance between the setter 96 and the fixing member 37 increases. Along with this, the elastically deformed ceramic plate 100a is restored, and the amount of warp W1 increases. 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 laminate 300 with a restoring force as a plate spring.

Since the holder 351 has the ceramic plate 100 (100b) functioning as a leaf spring, even if the ceramic green sheet 42 shrinks during the degreasing process, the restoring force of the elastically deformed ceramic plate 100 acts. Thus, the laminate 301 can be continuously restrained. Therefore, it is possible to prevent the ceramic green sheets 41 and 42 from being misaligned, resulting in variations in the degree of baking and occurrence of warping. Therefore, a ceramic sintered body having high quality can be stably produced.

The number of ceramic plates 100 used in the holder 350 (351) is not limited to one, and a plurality of plates may be stacked vertically. As a result, the restoring force of the plate spring can be increased, and the laminates 300 and 301 can be restrained more firmly. Also, the arrangement of the ceramic plate 100 is not limited to between the setter 96 and the fixing member 37, but 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. A ceramic plate 102 may be used instead of the ceramic plate 100 . Also, a ceramic plate having a shape different from these may be used as long as it functions as a plate spring.

The numbers of the setters 92, 94, 96 and the ceramic green sheets 41 (42) constituting the laminates 300, 301 are not particularly limited. The material and thickness of the plurality of ceramic green sheets 41 (42) may be the same or different. A release agent may be applied to the main surfaces of the ceramic green sheets 41 (42) in order to prevent adjacent ceramic green sheets from adhering to each other during firing. Also, the surfaces of the setters 92, 94, 96 facing the main surfaces of the ceramic green sheets 41 (42) may be coated with a release agent. Examples of components contained in the release agent include ceramic powder such as boron nitride, graphite powder, binder, and the like.

In the firing process, the degreased ceramic green sheets 42 are placed in a firing furnace and heated to 1600.degree. C. to 2000.degree. Thereby, the ceramic green sheets are fired to obtain a ceramic plate. The degreasing furnace used for degreasing and the firing furnace 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 firing step, the holding body 351 of FIG. 11 may be placed in a firing furnace and the ceramic green sheets 42 may be fired, or the holding body 351 may be dismantled and the ceramic green sheets 42 held and fired by another setter. may Also in the firing process, the ceramic green sheets 42 may further shrink due to factors such as progress of grain growth and volatilization of the remaining binder and dispersant. Therefore, as in the degreasing process, the restoring force of the ceramic plate 100 urges and constrains the laminate 301 , thereby suppressing the displacement of the ceramic green sheets 42 .

In a variant, the holder comprising the ceramic plate 100 may be used only in the firing process. Also in this case, it is possible to suppress the displacement of the plurality of ceramic green sheets after degreasing. Thereby, a ceramic sintered body having high quality can be stably produced.

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 may not be uniform and may vary. In this case, the average thickness of the ceramic plate can be determined as the average value of the thickest portion and the thinnest portion. This average thickness may be within the numerical range of thicknesses given above.

Ceramic plates may be used in applications other than leaf springs. For example, a 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 or solid content contained in the gas flowing through the channel may be removed. Note that 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) such that their main surfaces face each other. The channel in the filter may be formed by arranging a ceramic plate having a flat main surface and the ceramic plate 100 (102).

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

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

As shown in FIG. 2, the obtained ceramic plate was placed on a measuring table having a horizontal plane, and the amount of warpage W was measured. For the measurement, a one-shot 3D shape measuring machine (trade name: VR-3050) manufactured by Keyence Corporation was used. Table 1 shows the measurement results of the amount of warpage W of the three ceramic plates. The amount of warp W is the maximum height of the concavely curved second main surface from the measuring platform, as shown in FIG. Table 1 shows the amount of warpage Z of the three ceramic plates measured using the same measuring instrument. The amount of warp Z is the maximum value of the height difference of the convexly curved first main surface, as shown in FIG.

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

Three ceramic plates of Examples 1-1, 1-2, and 1-3 were superimposed to prepare a holder similar to the holder 350 in FIG. In FIG. 10, only one ceramic plate 100a is shown, but in this example, three ceramic plates were used so that the directions of the first main surface and the second main surface are aligned. 60 ceramic green sheets were produced in the same manner as in the above-mentioned "Preparation of ceramic plates". A commercially available setter made of boron nitride was used. A laminate was obtained by laminating 30 ceramic green sheets, a setter (second setter), and 30 ceramic green sheets and a setter (third setter) in this order on the lower setter (first setter). Three ceramic plates were placed on top of the upper setter (third setter). A fixing member arranged on the upper side of the three ceramic plates was pressed downward to constrain the laminate, and a holder as shown in FIG. 10 was produced. The laminate was urged downward by the restoring force associated with the elastic deformation of the three ceramic plates.

A holder having such a laminate was placed in a degreasing furnace and heated in the air at 500° C. for 5 hours to perform a degreasing step. In the degreasing process, the positions of the plurality of ceramic green sheets did not shift. After that, the ceramic green sheet was taken out from the holder, placed on another setter made of boron nitride, and fired. In the firing process, the degreased ceramic green sheets were heated at 1800° C. for 12 hours in a firing furnace under a nitrogen atmosphere. The obtained silicon nitride sintered body had sufficiently reduced quality variation.

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

n pieces of the above-mentioned ceramic plate were produced, and the amount of deflection was measured by the following procedure. The amount of deflection was measured by performing a three-point bending test with a distance between fulcrums of 30 mm using a tension/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 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 x width x thickness = 68 mm x 35.4 mm x 0.32 mm. Using the same procedure as in Reference Example 1, n ceramic plates were prepared and the amount of deflection was measured. The measurement results were as shown in FIG. From the results of FIGS. 12 and 13, it was confirmed that the deflection amount can be adjusted by changing the thickness of the ceramic plate.

ADVANTAGE OF THE INVENTION According to the present disclosure, a leaf spring having excellent heat resistance and capable of suppressing a plurality of laminated ceramic green sheets from being displaced from each other, a ceramic plate suitable for use as the leaf spring, and its manufacture can provide a method. Moreover, it is possible to provide a setter that can easily produce such a ceramic plate. Also, by suppressing the positional deviation of a plurality of laminated ceramic green sheets, it is possible to provide a manufacturing method capable of stably manufacturing a high-quality ceramic sintered body.

11, 13, 24... side surface, 20, 65... top part, 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... Plane surface 52, 54... Side edge 61... Hollow part 64... Side edge 400... Support body 100, 100a, 100b, 102... Ceramic plate 100A, 102A... Third 1 principal surface, 100B, 102B, second principal surface, 150, measuring table, 200, 210, 300, 301, laminate, 350, 351, holder.

Claims (10)

having a convexly curved first major surface, a concavely curved second major surface on the opposite side of the first major surface, and four arcuately curved side surfaces ;
A ceramic plate having an amount of warp W of 1 mm or more, which is measured as the maximum height of the second main surface from the horizontal surface when placed on a horizontal surface with the first main surface facing upward . 2. The ceramic plate according to claim 1, wherein the thickness is 2 mm or less, and the radius of curvature of said first main surface and said second main surface is 100-1000 mm. 3. The ceramic plate according to claim 1, wherein the ratio of the amount of warpage W to the average value of the areas of said first main surface and said second main surface is 1×10 ⁻⁵ /mm or more. 4. The ceramic plate according to any one of claims 1 to 3, which is composed of a silicon nitride sintered body. A leaf spring made 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 superimposed and heated such 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. having a process
The ceramic plate has a convexly curved first principal surface, a concavely curved second principal surface opposite to the first principal surface, and four arch-curved side surfaces. , has
The method of manufacturing a ceramic plate, wherein the amount of warp is measured as the maximum height of the second main surface from the horizontal surface when placed on a horizontal surface with the first main surface facing upward . having a convex or concave curved surface,
When the curved surface is concave, the apexes at the four corners of the curved surface are positioned at the top of the curved surface, and the four side edges forming the outline of the curved surface are convex downward. It is curved like
When the curved surface is convex, the apexes at the four corners of the curved surface are located at the lowest position of the curved surface, and the four side edges forming the outline of the curved surface are convex upward. It is bent so that
The setter, wherein the curved surface has a height difference of 1 mm or more where the ceramic green sheet is placed. 8. The setter according to claim 7, wherein said ceramic green sheet placed so as to cover said portion of said curved surface is heated to form a ceramic plate having an amount of warpage W of 1 mm or more. a degreasing step of heating and degreasing a laminate including a plurality of ceramic green sheets;
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 laminate is held by a restoring force generated by elastic deformation of the ceramic plate ,
The ceramic plate has a convexly curved first principal surface and a concavely curved second principal surface on the opposite side of the first principal surface, and has an amount of warp W of 1 mm or more. A method for producing a ceramic sintered body. In one or both of the degreasing step and the firing step, the ceramic plate is placed in an elastically deformed state between a fixing member provided above the laminate and the laminate, so that the laminate shrinks. 10. The method for producing a ceramic sintered body according to claim 9, wherein the amount of warp W of the ceramic plate increases with increasing.

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