Method for inspecting amount of deposited powder and method for manufacturing ceramic substrate using same

Abstract

The invention provides an inspection method for inspecting the adhesion amount of powder on a ceramic molded body. Also provided is a method for manufacturing a ceramic substrate using the inspection method. A method for inspecting the adhesion amount of a powder according to an embodiment includes an adhesion step and an inspection step. In the adhesion step, the powder is adhered to the surface of the ceramic molded body. In the inspection step, reflected light or transmitted light of the surface is detected by using a photoelectric sensor or an image sensor, and the adhesion amount of the powder is inspected.

Description

Technical Field

[0001] The following embodiments generally relate to a method for inspecting the amount of applied powder and a method for manufacturing a ceramic substrate using the same. Background Art

[0002] A ceramic substrate is used as a circuit substrate for mounting semiconductor elements. Various substrates such as a silicon nitride substrate, an aluminum nitride substrate, an alumina substrate, a zirconia substrate, and an alumina-zirconia substrate are used for the ceramic substrate. An alumina-zirconia substrate is a substrate in which zirconia and alumina are mixed. Sometimes, the alumina-zirconia substrate is also referred to as an alumina zirconia substrate.

[0003] The manufacturing process of the ceramic substrate includes a raw material mixing process, a forming process, a debinding process, a sintering process, etc. In the raw material mixing process, raw material powder and an organic binder are mixed to prepare a raw material paste. In the forming process, a sheet-shaped green body is prepared from the raw material paste. In the debinding process, the binder is removed from the sheet-shaped green body. In the sintering process, the sheet-shaped green body after debinding is sintered. The sheet-shaped green body is cut into a specified size and then subjected to the debinding process and the sintering process. In the sintering process, in order to improve the manufacturing efficiency, the sheet-shaped green bodies are stacked. When stacking the green bodies, an applied powder is used. By using the applied powder, it is possible to prevent the sheet-shaped green bodies from adhering to each other.

[0004] For example, in Japanese Patent No. 5339214 (Patent Document 1), the particle size and the amount of adhesion of the applied powder are controlled. By controlling the amount of adhesion of the applied powder, etc., the unevenness on the surface of the ceramic substrate is reduced.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 5339214

[0008] Patent Document 2: Japanese Utility Model Laid-Open No. 10-84 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] By controlling the amount of powder coating adhered as in Patent Document 1, the unevenness on the surface of the ceramic substrate can be reduced. However, when the throughput (such as an increase in the production volume of ceramic substrates or an increase in the size of the sheets) increases, the phenomenon of reduced yield occurs. The reason was investigated, and as a result, it was found that the cause lies in the deviation of the amount of powder coating adhered to the ceramic green body. For example, in Patent Document 1, a sprayer is used to adhere the powder coating. In Japanese Utility Model Laid-Open No. 10-84 (Patent Document 2), a brush or a brush is used to adhere the powder coating. The powder coating is a small powder with an average particle size of 20 μm or less. In recent years, the size and length of the sheet-shaped green body before cutting have increased. In addition, in order to improve production efficiency, the powder coating is adhered while moving the sheet-shaped green body. As a result, there is a phenomenon of uneven adhesion of the powder coating. Even if uneven adhesion of the powder coating occurs, it is difficult to distinguish with the naked eye. If the sintering process is carried out in a state where uneven adhesion occurs, a ceramic substrate with large surface irregularities can be manufactured.

[0011] The embodiment is for solving such a problem and provides a method for inspecting the amount of powder coating adhered to a ceramic green body.

[0012] Means for Solving the Problem

[0013] The method for inspecting the amount of powder coating adhered in the embodiment includes an adhesion step and an inspection step. In the adhesion step, the powder coating is adhered to the surface of the ceramic green body. In the inspection step, the amount of the adhered powder coating is inspected by detecting the reflected light or transmitted light of the above surface using a photoelectric sensor or an image sensor. Description of the Drawings

[0014] Figure 1 It is a flowchart showing an example of the method for inspecting the amount of powder coating adhered in the embodiment.

[0015] Figure 2 It is a view showing an example of the ceramic green body in the embodiment.

[0016] Figure 3 It is a view showing an example of the method of adhering the powder coating using a spray method.

[0017] Figure 4 It is a view showing an example of the method for inspecting the amount of powder coating adhered.

[0018] Figure 5 It is a flowchart showing the manufacturing method of the ceramic substrate in the embodiment.

[0019] Figure 6 It is a view showing an example of the manufacturing method of the ceramic substrate in the embodiment. Detailed Embodiment

[0020] The inspection method for the amount of powder coating adhesion in the embodiment includes an adhesion process and an inspection process. In the adhesion process, the powder coating is made to adhere to the surface of the ceramic green body. In the inspection process, the amount of the powder coating adhesion is inspected by detecting the reflected light or transmitted light of the above surface using a photoelectric sensor or an image sensor.

[0021] Figure 1 It is a flowchart showing an example of the inspection method for the amount of powder coating adhesion in the embodiment. As Figure 1 shown, the inspection method M1 for the amount of powder coating adhesion in the embodiment includes an adhesion process P1 for making the powder coating adhere to the ceramic green body and an inspection process P2 for inspecting the amount of the powder coating adhesion.

[0022] Figure 2 It is a view showing an example of the ceramic green body in the embodiment. In Figure 2 it, reference numeral 1 is the ceramic green body, and reference numeral 2 is the surface of the ceramic green body 1. First, prepare Figure 2 the ceramic green body 1 shown. The ceramic green body 1 is a green body formed from ceramic powder. In the ceramic green body 1, an organic binder or the like may be added as needed. The shape of the ceramic green body 1 is not particularly limited and may be a sheet shape, a circular shape, a shape with unevenness, or the like. Hereinafter, the sheet-shaped ceramic green body 1 will be described as an example.

[0023] The ceramic green body 1 has, for example, one selected from silicon nitride, aluminum nitride, alumina, zirconia, and silicon carbide as a main component. The main component means the component with the largest amount among the components constituting the ceramic sintered body. For example, the ceramic green body 1 having silicon nitride as the main component becomes a silicon nitride sintered body after sintering. The ceramic green body 1 having alumina as the main component becomes an alumina sintered body after sintering.

[0024] When two or more selected from silicon nitride, aluminum nitride, alumina, zirconia, and silicon carbide are mixed, the component with the larger amount is used as the main component. For example, an alumina-zirconia sintered body is a sintered body in which alumina and zirconia are mixed. If alumina is the component with the largest amount in the alumina-zirconia sintered body, it becomes an alumina sintered body after sintering. In addition to the main component, the ceramic sintered body may contain a sintering aid.

[0025] The manufacturing method of the ceramic green body 1 uses a doctor blade method, die forming, cold isostatic pressing (CIP), an injection molding method, or the like. As will be described later, in the case of manufacturing a ceramic substrate, the doctor blade method is preferred. As needed, a debinding process is performed on the ceramic green body 1. In other words, the debound body on which the debinding process has been performed is also included in the ceramic green body 1. The debinding process may be performed before making the powder coating adhere to the ceramic green body 1 or after making the powder coating adhere to the ceramic green body 1.

[0026] Next, an attachment step P1 is performed to attach the powder to the surface 2 of the prepared ceramic green body 1. As a method of attaching the powder, there are a method using a sprayer, a method of passing the ceramic green body 1 through a solution in which the powder is dispersed, a method using a brush, a method using static electricity, a method using gravure printing, a method of dipping the ceramic green body 1 in a solution containing the powder, and the like. As will be described later, when the ceramic green body 1 is used for a ceramic substrate, the method using a sprayer is preferred. In the case of the spray method, the spraying amount of the powder can be stabilized. The spray method includes a method of spraying only the powder and a method of spraying a solution in which the powder is dispersed. As the spray method, a method of spraying a solution in which the powder is dispersed is more preferred. By previously dispersing the powder in the solution, agglomeration of the powder can be suppressed.

[0027] Figure 3 FIG. is an example of a method of attaching the powder using the spray method. Figure 3 In the figure, reference numeral 3 is a powder attachment layer, reference numeral 5 is a sprayer, and reference numeral 6 is the powder. Figure 3 An example is shown in which the sprayer 5 sprays the powder 6 from above the ceramic green body 1. As Figure 3 shown, the sprayer 5 can spray the powder 6 directly above the ceramic green body 1 or can spray the powder 6 obliquely above the ceramic green body 1. In addition, in Figure 3 the example shown, one sprayer 5 sprays the powder 6, but multiple sprayers 5 can also spray the powder 6 separately.

[0028] The powder 6 is one or more kinds of powders selected from boron nitride, zirconia, alumina, and aluminum nitride. By attaching the powder 6 to the surface 2 of the ceramic green body 1, a powder attachment layer 3 is formed. The powder attachment layer 3 has the function of preventing the ceramic sintered bodies from bonding to each other when a plurality of ceramic green bodies 1 are stacked and sintered. That is, the powder 6 is a powder that does not bond to the ceramic sintered body in the sintering process of the ceramic sintered body.

[0029] The powder 6 is preferably boron nitride powder. As will be described later, the ceramic green body 1 is sintered at 1600 to 2000 ° C. to manufacture a ceramic sintered body. Boron nitride is difficult to bond to the ceramic sintered body even in a high-temperature environment. The structure of boron nitride is various structures such as hexagonal crystal, cubic crystal, and rhombohedral crystal. Among them, hexagonal boron nitride is preferred. Hexagonal boron nitride is sometimes denoted as h-BN.

[0030] The average particle size of the dusting powder 6 is preferably 20 μm or less. By reducing the average particle size, it is easy to form a dusting powder adhesion layer 3 with a uniform film thickness on the surface 2 of the ceramic green body 1. When the average particle size is greater than 20 μm, the film thickness of the dusting powder adhesion layer 3 becomes uneven, which may have an adverse effect on the surface properties of the ceramic sintered body. Therefore, the average particle size of the dusting powder 6 is preferably 20 μm or less. The average particle size of the dusting powder is more preferably 10 μm or less, and further preferably 6 μm or less. The lower limit of the average particle size of the dusting powder 6 is not particularly limited, and is preferably 2 μm or more. If the average particle size is less than 2 μm, the operability may deteriorate.

[0031] Next, an inspection process P2 for inspecting the adhesion amount of the dusting powder 6 on the surface 2 of the ceramic green body 1 is performed. In the inspection process, the reflected light or transmitted light on the surface 2 is detected by a photoelectric sensor or an image sensor, thereby inspecting the adhesion amount of the dusting powder 6.

[0032] The photoelectric sensor includes a light projecting unit that emits light and a light receiving unit that receives light. The light emitted from the light projecting unit irradiates the ceramic green body 1 on which the dusting powder adhesion layer 3 is formed. When a reflection type photoelectric sensor is used, the light reflected on the surface 2 of the ceramic green body 1 on which the dusting powder adhesion layer 3 is formed is detected by the light receiving unit. In the case of using a transmission type photoelectric sensor, the light transmitted through the ceramic green body 1 on which the dusting powder adhesion layer 3 is formed is detected by the light receiving unit. The light of the light projecting unit uses infrared rays or laser light, etc. The wavelength of infrared rays is longer than that of visible light. The laser uses monochromatic visible light. When using a photoelectric sensor, it is preferable to irradiate light onto the dusting powder adhesion layer 3 and detect its reflected light.

[0033] The image sensor includes a camera and an image processing unit. The camera forms an image of the light incident from the object (the surface 2 of the ceramic green body 1 on which the dusting powder adhesion layer 3 is formed) on the light receiving surface of the image sensor (imaging element) through an optical system such as a lens, and converts it into an electrical signal. Thereby, image data is obtained. The image processing unit detects the feature amount of the object by performing image processing on the data output from the camera. When using an image sensor, light is irradiated onto the dusting powder adhesion layer 3 and its reflected light is detected.

[0034] The image sensor is preferably an infrared image sensor or a ultraviolet image sensor. The infrared image sensor is a sensor that detects infrared rays (wavelength 780 nm or more and 1000 μm or less). The ultraviolet image sensor is a sensor that detects ultraviolet rays (wavelength 10 nm or more and 400 nm or less). In the case of using a ultraviolet image sensor, a phosphor that emits light through ultraviolet rays can be mixed into the dusting powder. By mixing the phosphor, the detection accuracy of the reflected light can be improved.

[0035] The intensity of the light detected by the sensor depends not only on the amount of the powder coating 6 attached but also on the intensity of the light irradiated onto the ceramic green body 1. In order to reduce the influence of the deviation of the intensity of the irradiated light on the inspection result, in the inspection process, it is preferable to use a lighting device. The lighting device emits light with a preset intensity. In the case of using an infrared image sensor, the lighting device emits infrared light. In the case of using a ultraviolet image sensor, the lighting device emits ultraviolet light.

[0036] In the case of using an image sensor, the lighting device for irradiating light can be either a coaxial system or a reflection system. In the coaxial system, the light incident on the object and the light reflected from the object are on the same optical axis. In the reflection system, the direction of the light irradiated onto the surface of the object is different from the direction of the light reflected from the object.

[0037] Figure 4 It is a diagram showing an example of a method for inspecting the amount of the powder coating attached. In Figure 4 it, reference numeral 7 is the lighting device and reference numeral 8 is the sensor. In the example shown in Figure 4 the lighting device 7 irradiates light obliquely from above the surface 2. The sensor 8 detects the light reflected by the surface 2 from directly above. Not limited to the example shown in Figure 4 in order to irradiate each part of the surface 2 uniformly, a plurality of lighting devices 7 may be provided.

[0038] When comparing a photoelectric sensor and an image sensor, the image sensor is preferable. The image sensor can detect a wide range of light at one time. When comparing an infrared image sensor and a ultraviolet image sensor, the infrared image sensor is preferable. By using infrared rays, it is not easily affected by natural light and indoor light. In addition, by using infrared rays, it is difficult to be affected by the shadows of people, the shadows of objects, etc.

[0039] It is preferable to use edge detection for the image generated by detecting reflected light or transmitted light. Edge detection is a process for detecting edges from an image and is a kind of feature detection. An "edge" is a region where the gradient of pixel values (luminance) between adjacent pixels exceeds a threshold value. The pixel value depends on the luminance of the object (the intensity of reflected light or transmitted light). A point where the change in luminance changes significantly is considered to be a point where the shape or material of the object changes greatly. The color of the powder coating is brighter than the color of the ceramic green body 1. Therefore, as the amount of the powder coating attached increases, the luminance of the object increases. And if the powder coating of a specified amount or more is attached, the color of the ceramic green body 1 cannot be seen and the luminance of the object does not change.

[0040] For example, when the amount of powder coating adhered is small, a difference in brightness is generated on the surface of the ceramic formed body 1 between the portion with a large amount of powder coating adhered and the portion with a small amount of powder coating adhered. Therefore, the boundary between the portion with a large amount of powder coating adhered and the portion with a small amount of powder coating adhered is detected as an edge. When the overall amount of powder coating adhered to the surface of the ceramic formed body 1 is insufficient, more detected edges are obtained. When the amount of powder coating adhered increases, the number of detected edges in the entire ceramic formed body 1 decreases. When the overall amount of powder coating adhered to the surface of the ceramic formed body 1 is excessive, the proportion of the portion with a high brightness increases, and it becomes difficult to detect edges.

[0041] That is, when the adhered amount is appropriate, the corresponding brightness is detected. An appropriate brightness range is set, and edge detection is performed on the brightness outside the range. The brightness outside the range is detected as the number of edges. In other words, by adhering the powder coating to the ceramic formed body 1 in such a way that the brightness is within this range, the adhered amount of the powder coating can be kept within an appropriate range.

[0042] For example, if a target value of 90% or more of the yield rate is set, it is also effective to set the target value based on the data that results in a yield rate of 90% or more. This is a method of setting the target value as the brightness of the end portion of the ceramic formed body 1 with the powder coating adhered when the yield rate of 90% or more is obtained.

[0043] In addition, in the process of checking the adhered amount of the powder coating using the process of detecting reflected light, any criterion can be used to determine whether the adhered amount of the powder coating is qualified. If edge detection is used to check the adhered amount of the powder coating, edge pixels are detected. When the adhered amount of the powder coating is large, the edge pixels become larger, and when the adhered amount of the powder coating is small, the edge pixels become smaller. Utilizing this phenomenon, a range of edge pixels for determining qualification is set. The set range of edge pixels is arbitrary. If the edge pixels are set to a small value, the possibility of defective products being mixed into the products determined to be qualified becomes high. In addition, if the edge pixels are set to a large value, the possibility of qualified products being mixed into the products determined to be unqualified becomes high. Therefore, it is preferable to collect data on the edge pixels of qualified products and unqualified products and set the edge pixels for determining qualification. When the adhered amount of the powder coating is small, the edge pixels become small values relative to the target value. In addition, when the adhered amount of the powder coating is large, the edge pixels become large values relative to the target value. In addition, when the target value is set to 100, an example of the edge pixels for determining qualification is within the range of 100 ± 60. This means that the case where the edge pixels are within the range of 100 ± 60 is determined to be a qualified product. The positive and negative ranges can be changed arbitrarily. In addition, when determining qualification, it is also effective to use a machine learning method.

[0044] In the attaching step P1, the powder 6 can be attached while the ceramic green body 1 is stopped, or the powder 6 can be attached while the ceramic green body 1 is moving. It is more preferable to attach the powder 6 in a spraying manner while the ceramic green body 1 is moving. By attaching the powder 6 while the ceramic green body 1 is moving, mass productivity can be improved.

[0045] As described above, there are various methods for forming the ceramic green body 1, such as the doctor blade method and the die forming method. According to the doctor blade method, a wide and long-sized sheet-shaped green body can be produced. The powder 6 is attached to the long-sized sheet-shaped green body in a spraying manner. The long-sized sheet-shaped green body to which the powder 6 is attached is wound into a roll shape and used for the next process. By attaching the powder 6 while the ceramic green body 1 is moving, the processes of sheet forming, attachment of the powder 6, inspection of the attached amount of the powder 6, and winding the green body into a roll shape can be continuously performed.

[0046] In die forming, a sheet-shaped green body is produced using a die. According to die forming, a sheet-shaped green body corresponding to the die size can be formed. By attaching the powder 6 while conveying with a conveyor belt or the like, mass productivity can be improved.

[0047] In the inspection step P2, the attached amount can be inspected while the ceramic green body 1 is stopped, or the attached amount can be inspected while the ceramic green body 1 is moving. Regarding the inspection step P2, by performing it while the ceramic green body 1 is moving, mass productivity can be further improved. In addition, by using a photoelectric sensor or an image sensor, the attached amount of the powder 6 can be inspected even while the ceramic green body 1 is moving.

[0048] According to the inspection method of the attached amount of the powder as described above, the attached amount of the powder 6 can be effectively inspected. In addition, since the inspection can be performed while the ceramic green body 1 is moving, mass productivity can be improved. The inspection method of the attached amount of the powder in the embodiment can be used in the manufacturing method of the ceramic sintered body.

[0049] Figure 5 is a flowchart showing the manufacturing method of the ceramic substrate according to the embodiment. As Figure 5 shown, the manufacturing method M2 of the ceramic substrate according to the embodiment includes a step of executing the inspection method M1 (attaching step P1 and inspection step P2), a post-treatment step P3, and a sintering step P4. By the inspection method M1, it is determined whether the attached amount of the powder 6 is within a specified range. When it is determined that the attached amount of the powder 6 is more than the specified range, or when it is determined that the attached amount of the powder 6 is less than the specified range, the post-treatment step P3 is executed. When it is determined that the attached amount of the powder 6 is within the specified range, the post-treatment step P3 can be omitted.

[0050] For example, when it is determined by the inspection method of the amount of powder coating adhesion that the amount of powder coating adhesion is large, the process of reducing the adhesion amount of the powder coating 6 can be performed as the post-treatment process P3. By reducing the amount of the powder coating 6 that adheres in large quantities, defective products can be turned into qualified products. Thereby, the yield of the ceramic sintered body can be improved. In order to reduce the adhesion amount of the powder coating 6, methods such as using blowing air are performed. During blowing air, by blowing air onto the surface 2 of the ceramic green body 1, the remaining powder coating 6 is scattered, and the adhesion amount of the powder coating 6 is reduced. After performing the process of reducing the adhesion amount of the powder coating 6, if necessary, the inspection method of the powder coating adhesion amount of the embodiment can be carried out.

[0051] When it is determined by the inspection method of the amount of powder coating adhesion that the amount of powder coating adhesion is large, the process of removing the ceramic green body 1 with a large amount of the powder coating 6 adhering thereto can be performed as the post-treatment process P3. Regarding this removal process, in the case of manufacturing a long-sized sheet-shaped green body, it is only necessary to remove the part with a large amount of the powder coating 6 adhering thereto. In the case of manufacturing a plurality of sheet-shaped green bodies, it is only necessary to remove the green bodies with a large amount of the powder coating 6 adhering thereto.

[0052] When it is determined by the inspection method of the amount of powder coating adhesion that the amount of powder coating adhesion is small, the process of making the powder coating 6 adhere again can be performed as the post-treatment process P3. By making the powder coating 6 adhere again, defective products can be turned into qualified products. Thereby, the yield of the ceramic sintered body can be improved. In addition, after making the powder coating 6 adhere again, if necessary, the inspection method of the powder coating adhesion amount of the embodiment can be carried out.

[0053] When it is determined by the inspection method of the amount of powder coating adhesion that the amount of powder coating adhesion is small, the process of removing the ceramic green body 1 with a small amount of the powder coating 6 adhering thereto can be performed as the post-treatment process P3. Regarding this removal process, in the case of manufacturing a long-sized sheet-shaped green body, it is only necessary to remove the part with a small amount of the powder coating 6 adhering thereto. In the case of manufacturing a plurality of sheet-shaped green bodies, it is only necessary to remove the green bodies with a small amount of the powder coating 6 adhering thereto.

[0054] In the sintering process P4, the ceramic green body 1 with the powder coating adhesion amount controlled within a specified range is sintered to obtain a ceramic sintered body. In the case of making the powder coating 6 adhere to a long-sized sheet-shaped green body, the ceramic sintered body is cut into a required size. The sintering temperature in the sintering process P4 is preferably in the range of 1600 °C or higher and 2000 °C or lower. The pressure in the space where the sintering process P4 is performed can be any one of pressurization, normal pressure, and depressurization. In the sintering process P4, various atmospheres such as in the air, in an inert atmosphere, and in a vacuum can be applied.

[0055] Figure 6 is a diagram showing an example of the manufacturing method of the ceramic substrate of the embodiment. In Figure 6 it, the symbol 9 represents a backing plate. In the sintering process P4, as Figure 6As shown, a ceramic green body 1 provided with a powder coating layer 3 is disposed on a backing plate 9. The backing plate 9 is made of a boron nitride plate or the like. A plurality of ceramic green bodies 1 provided with the powder coating layer 3 are stacked. If necessary, other backing plates 9 may be disposed on the stacked plurality of ceramic green bodies 1. Further, another plurality of ceramic green bodies 1 provided with the powder coating layer 3 may be stacked on the backing plate 9.

[0056] Since the amount of powder coating adhered to the surface 2 of the ceramic green body 1 is controlled, even when the sintering process is performed in a state where a plurality of ceramic green bodies 1 provided with the powder coating layer 3 are stacked, generation of defective products can be suppressed. For example, it is possible to prevent the stacked ceramic sintered bodies from bonding to each other.

[0057] In addition, the stacked ceramic sintered bodies can be peeled from each other with a small stress. The small stress is, for example, the force of a person or the force of wind generated by blowing. If a large stress is required to peel the stacked ceramic sintered bodies from each other, the ceramic sintered bodies may be damaged during peeling. From this point of view, according to the embodiment, the yield can also be improved.

[0058] In addition, unevenness on the surface of the ceramic sintered body can be suppressed. The ceramic sintered body is preferably a ceramic substrate. Even when the thickness of the ceramic substrate is 3 mm or less, by controlling the amount of powder coating adhered within a specified range, unevenness on the surface 2 can be suppressed. Moreover, even when the thickness of the ceramic substrate is 1 mm or less, surface unevenness can be suppressed. In other words, the inspection method according to the embodiment is suitable for the manufacturing method of the ceramic substrate.

[0059] The ceramic substrate is preferably a silicon nitride substrate. Examples of the ceramic substrate include a silicon nitride substrate, an aluminum nitride substrate, an alumina substrate, a zirconia substrate, and a silicon carbide substrate. Among them, the silicon nitride substrate is expensive, so the effect of improving the yield is large.

[0060] (Example)

[0061] (Examples 1 to 8, Comparative Examples 1 to 2)

[0062] In Examples 1 to 6, a silicon nitride green body was prepared as the ceramic green body. As the silicon nitride green body, a long-sized sheet-shaped green body was produced by the doctor blade method. The width of the long-sized sheet-shaped green body was 1 m. The thickness of the sheet-shaped green body was set so that a silicon nitride substrate having a thickness of 0.32 mm could be obtained as a sintered body.

[0063] In Example 7, an aluminum nitride green body was prepared as the ceramic green body. As the aluminum nitride green body, a long-sized sheet-shaped green body was produced by the doctor blade method. The width of the long-sized sheet-shaped green body was 1 m. The thickness of the sheet-shaped green body was set so that an aluminum nitride substrate having a thickness of 0.635 mm could be obtained as a sintered body.

[0064] In Example 8, an alumina formed body was prepared as a ceramic formed body. As the alumina formed body, a long-sized sheet formed body was produced by the doctor blade method. The width of the long-sized sheet formed body was 1 m. The thickness of the sheet formed body was set such that an alumina substrate with a thickness of 0.635 mm could be obtained as a sintered body.

[0065] In the examples and comparative examples, an attachment step of attaching powder to the surface of the long-sized sheet formed body was performed. As the powder, boron nitride (BN) powder was used. The powder was attached to the ceramic formed body by a spraying method. An inspection step was performed on the ceramic formed body to which the powder was attached. The production conditions of the formed body, the conditions at the time of powder attachment, the conditions of the inspection step, etc. are shown in Table 1.

[0066] Table 1

[0067]

[0068] In the "presence or absence of movement" in Table 1, "yes" means that the powder was attached to the formed body while moving the sheet-shaped formed body. "No" means that the powder was attached to the formed body in a state where the sheet-shaped formed body was stopped. "Presence or absence of edge detection" indicates whether edge detection was performed on the obtained image. The "range of edge pixels set as acceptable products" was set based on data with a yield of 98% or more. In addition, in the examples, the region smaller than the edge pixels set as acceptable products was removed. That is, a sintering step was performed on the formed body determined to be acceptable by the inspection method of the powder attachment amount of the embodiment.

[0069] The sheet formed body to which the powder was attached was cut into 200 mm × 150 mm. The cut formed bodies were stacked and a sintering step was performed. The sintering step was performed in the range of 1700 to 1900°C. Through this sintering step, a ceramic substrate was produced. In the examples and comparative examples, 1000 ceramic substrates were produced respectively, and the yield and surface flatness were investigated.

[0070] Regarding the yield, the ceramic substrates peeled off by blowing air or human force were set as acceptable products. The ceramic substrates that could not be peeled off by blowing air or human force, or the ceramic substrates damaged during peeling were set as unacceptable products. The yield (%) is the ratio of acceptable products among 1000 pieces. Examples with a yield of 99% or more and 100% or less were set as "excellent", examples with 95% or more and less than 99% were set as "good", and examples with less than 95% were set as "bad".

[0071] Regarding the flatness of the surface, a ceramic substrate in which the difference between the maximum value of the convex portion and the maximum value of the concave portion of the surface is 50 μm or less is regarded as a qualified product. The difference between the maximum value of the convex portion and the maximum value of the concave portion is calculated by image analysis of the surface of the ceramic substrate. An example in which the ratio of the ceramic substrate with the difference between the maximum value of the convex portion and the maximum value of the concave portion being 50 μm or less is 98% or more and 100% or less is set as "excellent", an example in which it is 95% or more and less than 98% is set as "good", and an example in which it is less than 95% is set as "bad". The results are shown in Table 2.

[0072] Table 2

[0073] Yield Surface flatness Example 1 Excellent Excellent Example 2 Excellent Excellent Example 3 Excellent Excellent Example 4 Excellent Excellent Example 5 Excellent Excellent Example 6 Excellent Excellent Example 7 Excellent Excellent Example 8 Excellent Excellent Comparative Example 1 Good Good Comparative Example 2 Poor Poor

[0074] As can be seen from Table 2, the yield and surface flatness of the ceramic sintered body using the manufacturing method of the ceramic sintered body of the examples are improved. The best results were obtained in Example 2 that satisfied the preferred conditions. Therefore, it can be seen that even when attaching powder while moving the sheet-shaped compact, the inspection method functions effectively. On the other hand, in Comparative Example 1 and Comparative Example 2, the inspection method of the embodiment was not applied, so the yield and flatness were lower than those of the examples. This is because the uneven attachment of the powder cannot be grasped. In particular, as in Comparative Example 2, when attaching powder while moving the sheet-shaped compact, uneven attachment is likely to occur. Since the compact with uneven attachment is sintered, the yield and flatness are reduced.

[0075] Next, for the compacts determined to be unqualified by the powder attachment amount inspection method of Examples 1 to 8, a process for making them qualified is carried out. In the area where the powder attachment amount is determined to be large, a part of the powder is removed by blowing. Powder is reattached in the area where the powder attachment amount is determined to be small. Then, the sintering process is carried out in the same manner as in Examples 1 to 8. For the obtained ceramic substrate, the yield and surface flatness are investigated. The measurement conditions are the same as those in Examples 1 to 8. The results are shown in Table 3.

[0076] Table 3

[0077] Defective product Yield Surface flatness Example 1B Example 1 Excellent Excellent Example 2B Example 2 Excellent Excellent Example 3B Example 3 Excellent Excellent Example 4B Example 4 Excellent Excellent Example 5B Example 5 Excellent Excellent Example 6B Example 6 Excellent Excellent Example 7B Example 7 Excellent Excellent Example 8B Example 8 Excellent Excellent

[0078] In Table 3, in Example 1B, the powder attachment amount of the compact determined to be unqualified in Example 1 was controlled to an amount determined to be a qualified product. Similarly, in Examples 2B to 8B, the powder attachment amounts of the compacts determined to be unqualified in Examples 2 to 8 were respectively controlled to amounts determined to be qualified products.

[0079] As can be seen from Table 3, by re-controlling the amount of powder coating adhered to an appropriate amount, defective products can be made into qualified products. By using the discrimination method of the inspection method for the amount of powder coating according to the embodiment, it is possible to perform a process of improving only the formed bodies determined to be defective products into qualified products. Thus, the productivity can be improved. In addition, since the amount of the discarded formed bodies is reduced, the environmental performance can also be improved.

[0080] Embodiments of the present invention include the following features.

[0081] (Feature 1)

[0082] An inspection method for the amount of powder coating, which includes the following steps:

[0083] An adhesion step of adhering powder coating to the surface of a ceramic formed body; and

[0084] An inspection step of inspecting the amount of the adhered powder coating by detecting reflected light or transmitted light on the surface by using a photoelectric sensor or an image sensor.

[0085] (Feature 2)

[0086] The inspection method for the amount of powder coating according to Feature 1, wherein the image sensor is an infrared image sensor or an ultraviolet image sensor,

[0087] The reflected light on the surface is detected by using the infrared image sensor or the ultraviolet image sensor.

[0088] (Feature 3)

[0089] The inspection method for the amount of powder coating according to Feature 1 or Feature 2, wherein in the inspection step, edge detection is performed on the image obtained by detecting the reflected light or the transmitted light.

[0090] (Feature 4)

[0091] The inspection method for the amount of powder coating according to any one of Features 1 to 3, wherein the average particle size of the powder coating is 20 μm or less.

[0092] (Feature 5)

[0093] The inspection method for the amount of powder coating according to any one of Features 1 to 4, wherein the ceramic formed body is a silicon nitride formed body.

[0094] (Feature 6)

[0095] The inspection method for the amount of powder coating according to any one of Features 1 to 5, wherein the powder coating is boron nitride powder.

[0096] (Feature 7)

[0097] The inspection method for the amount of powder adhered according to any one of Features 1 to 6, wherein, in the adhesion step, while moving the ceramic green body, the powder is adhered to the surface by a spraying method.

[0098] (Feature 8)

[0099] A method for manufacturing a ceramic substrate, comprising the following steps:

[0100] A step of performing the inspection method for the amount of powder adhered according to any one of Features 1 to 7; and

[0101] A sintering step of sintering the ceramic green body determined to be a qualified product by the inspection method.

[0102] (Feature 9)

[0103] The method for manufacturing a ceramic substrate according to Feature 8, wherein the manufacturing method includes a step of reducing the adhesion amount in the case where the adhesion amount is determined to be large.

[0104] (Feature 10)

[0105] The method for manufacturing a ceramic substrate according to Feature 8, wherein the manufacturing method includes a step of removing the ceramic green body having a large amount of the powder adhered thereto in the case where the adhesion amount is determined to be large.

[0106] (Feature 11)

[0107] The method for manufacturing a ceramic substrate according to Feature 8, wherein the manufacturing method includes a step of re - adhering the powder in the case where the adhesion amount is determined to be small.

[0108] (Feature 12)

[0109] The method for manufacturing a ceramic substrate according to Feature 8, wherein the manufacturing method includes a step of removing the ceramic green body having a small amount of the powder adhered thereto in the case where the adhesion amount is determined to be small.

[0110] Above, several embodiments of the present invention are exemplified, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. These embodiments or their variations are included in the scope or gist of the invention and are included in the invention described in the claims and its equivalents. In addition, the above - mentioned embodiments can be implemented in combination with each other.

[0111] Symbol Explanation

[0112] 1…Ceramic formed body

[0113] 2…Surface part

[0114] 3…Powder coating layer

[0115] 4…Sensor

Claims

1. A method for inspecting the amount of powder adhering, comprising the following steps: An adhering step of causing powder to adhere to the surface of a ceramic green body; and An inspecting step of inspecting the amount of the adhering powder by detecting reflected light or transmitted light of the surface by using a photoelectric sensor or an image sensor.

2. The method for inspecting the amount of powder adhering according to claim 1, wherein The image sensor is an infrared image sensor or an ultraviolet image sensor. The reflected light of the surface is detected using the infrared image sensor or the ultraviolet image sensor.

3. The method for inspecting the amount of powder adhering according to claim 1 or 2, wherein In the inspection process, edge detection is performed on the image obtained by detecting the reflected light or the transmitted light.

4. The method for inspecting the amount of powder adhering according to claim 1 or 2, wherein The average particle size of the powder coating is 20 μm or less.

5. The method for inspecting the amount of powder adhering according to claim 3, wherein The average particle size of the powder coating is 20 μm or less.

6. The method for inspecting the amount of powder adhering according to claim 1 or 2, wherein The ceramic formed body is a silicon nitride formed body.

7. The method for inspecting the amount of powder adhering according to claim 5, wherein The ceramic formed body is a silicon nitride formed body.

8. The method for inspecting the amount of powder adhering according to claim 1 or 2, wherein The powder coating is boron nitride powder.

9. The method for inspecting the amount of powder adhering according to claim 6, wherein The powder coating is boron nitride powder.

10. The method for inspecting the amount of powder adhering according to claim 7, wherein The powder coating is boron nitride powder.

11. The method for inspecting the amount of powder adhering according to claim 1 or 2, wherein In the attachment process, while moving the ceramic formed body, the powder coating is attached to the surface by a spraying method.

12. The method for inspecting the amount of powder adhering according to claim 8, wherein In the attachment process, while moving the ceramic formed body, the powder coating is attached to the surface by a spraying method.

13. The method for inspecting the amount of powder adhering according to claim 10, wherein In the attachment process, while moving the ceramic formed body, the powder coating is attached to the surface by a spraying method.

14. A method for manufacturing a ceramic substrate, comprising the following steps: A step of performing the method for inspecting the amount of powder adhering according to claim 1 or 2; and A sintering step of sintering the ceramic green body determined to be a qualified product by the inspection method.

15. The method for manufacturing a ceramic substrate according to claim 14, wherein The manufacturing method includes a process of reducing the attachment amount when it is determined that the attachment amount is large.

16. The manufacturing method of the ceramic substrate according to claim 14, wherein, The manufacturing method includes a process of removing the ceramic formed body with a large amount of the powder coating attached when it is determined that the attachment amount is large.

17. The manufacturing method of the ceramic substrate according to claim 14, wherein, The manufacturing method includes a process of re-attaching the powder coating when it is determined that the attachment amount is small.

18. The manufacturing method of the ceramic substrate according to claim 14, wherein, The manufacturing method includes a process of removing the ceramic formed body with a small amount of the powder coating attached when it is determined that the attachment amount is small.

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