Double-sided treatment device, double-sided treatment method, and method for producing sintered body

Abstract

A double-sided treatment device according to an embodiment causes a release agent to adhere to both surfaces of a ceramic green sheet. The double-sided treatment device comprises a first conveyance mechanism, a first treatment unit, a first roller unit, a second roller unit, a second conveyance mechanism, and a second treatment unit. The first conveyance mechanism moves the ceramic green sheet in a first direction. The first treatment unit causes a release agent to adhere to a first surface of the ceramic green sheet conveyed by the first conveyance mechanism. The first roller unit is provided at an end part of the first conveyance mechanism in the first direction, and changes the movement direction of the ceramic green sheet to a second direction that intersects the first direction. The second roller unit changes the movement direction of the ceramic green sheet that has moved in the second direction in a direction opposite to the first direction. The second conveyance mechanism moves the ceramic green sheet in the opposite direction. The second treatment unit causes a release agent to adhere to a second surface of the ceramic green sheet conveyed by the second conveyance mechanism.

Description

Double-sided processing apparatus, double-sided processing method, and method for manufacturing sintered body

[0001] The embodiments relate to a double-sided processing apparatus and a double-sided processing method for applying a release agent to both sides of a ceramic green sheet, and a method for producing a sintered body.

[0002] Patent Document 1 describes a method for manufacturing a ceramic substrate. In this manufacturing method, multiple green sheets are stacked with a separating material interposed therebetween and sintered. Then, multiple sintered bodies are separated to manufacture multiple ceramic substrates. In the invention described in Patent Document 1, after the green sheet is cut, a separating material made of boron nitride powder is attached to one or both sides of the green sheet. Then, multiple green sheets are stacked and sintered, and then separated to obtain multiple silicon nitride sintered bodies.

[0003] Patent Document 2 discloses an apparatus for applying paint to both sides of a sheet. According to the invention described in Patent Document 2, paint is applied to one side of a sheet using a coater and dried, and then paint is applied to the other side using another coater and dried. In this apparatus, a mechanism for turning the sheet upside down is provided between the first dryer and the second coater.

[0004] Patent Document 3 discloses an apparatus for applying active material to both sides of an electrode foil. According to the invention described in Patent Document 3, in applying active material to an electrode foil for a battery, a front surface coating sprayer, a back surface coating sprayer, a front surface hot air sprayer, and a back surface hot air sprayer are installed, so that active material can be applied without changing the front and back surfaces of the electrode foil.

[0005] Patent No. 5339214 JP 62-279865 A Utility Model No. 3019021 A

[0006] Ceramic substrate green sheets are manufactured by mixing ceramic powder with an organic binder and then drying the mixture. These ceramic green sheets lack the strength of resin films or metal foils and are easily damaged by tension. Conventionally, to reduce waste, ceramic green sheets have been cut to a predetermined shape and then coated with a release agent on both sides. However, as ceramic substrates have become thinner in recent years, ceramic green sheets have also become thinner. Handling thin, soft ceramic green sheets without damaging them is challenging and time-consuming. Therefore, a technology is needed that can apply a release agent to both sides of ceramic green sheets while minimizing damage.

[0007] A double-side processing apparatus according to an embodiment applies a release agent to both sides of a ceramic green sheet. The double-side processing apparatus includes a first conveying mechanism, a first processing section, a first roller unit, a second roller unit, a second conveying mechanism, and a second processing section. The first conveying mechanism moves the ceramic green sheet in a first direction. The first processing section applies a release agent to the first side of the ceramic green sheet conveyed by the first conveying mechanism. The first roller unit is provided at an end of the first conveying mechanism in the first direction and changes the movement direction of the ceramic green sheet to a second direction intersecting the first direction. The second roller unit changes the movement direction of the ceramic green sheet moved in the second direction to the direction opposite to the first direction. The second conveying mechanism moves the ceramic green sheet in the opposite direction. The second processing section applies a release agent to a second surface of the ceramic green sheet transported by the second transport mechanism.

[0008] FIG. 1 is a plan view of a double-sided processing apparatus according to an embodiment; FIG. 2 is a cross-sectional view of a double-sided processing apparatus according to an embodiment; FIG. 3 is a plan view of another double-sided processing apparatus according to an embodiment; FIG. 4 is a cross-sectional view of another double-sided processing apparatus according to an embodiment; FIG. 5 is a schematic view showing an example of a spray; FIG. 6 is a schematic view showing another example of a spray; FIG. 7 is a flowchart showing a method for manufacturing a sintered body according to an embodiment; and FIG. 8 is a cross-sectional view showing a manufacturing process of a sintered body according to an embodiment.

[0009] A double-side processing apparatus according to an embodiment applies a release agent to both sides of a ceramic green sheet. The double-side processing apparatus includes a first conveying mechanism, a first processing section, a first roller unit, a second roller unit, a second conveying mechanism, and a second processing section. The first conveying mechanism moves the ceramic green sheet in a first direction. The first processing section applies a release agent to the first side of the ceramic green sheet conveyed by the first conveying mechanism. The first roller unit is provided at an end of the first conveying mechanism in the first direction and changes the movement direction of the ceramic green sheet to a second direction intersecting the first direction. The second roller unit changes the movement direction of the ceramic green sheet moved in the second direction to the direction opposite to the first direction. The second conveying mechanism moves the ceramic green sheet in the opposite direction. The second processing section applies a release agent to a second surface of the ceramic green sheet transported by the second transport mechanism.

[0010] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those already described are designated by the same reference numerals, and detailed description will be omitted as appropriate.

[0011] Ceramic green sheets are thin ceramic sintered bodies such as ceramic substrates in their pre-sintered state. They consist of ceramic raw material powder, sintering aid powder, and organic materials. Ceramic raw material powder is the main component of ceramic substrates. Sintering aid powder is added to sinter the ceramic raw materials. Organic materials, such as resin, are used to form the powder into a sheet. Ceramic green sheets are produced by mixing the powder and organic material in a solvent, forming the mixture into a sheet, and drying the formed body. Ceramic green sheets are soft and can be easily cut with a cutter or other blade, but they lack strength and are easily damaged when subjected to tensile or other forces.

[0012] The ceramic substrate manufactured with a release agent applied to both sides is preferably one selected from aluminum nitride substrates, aluminum oxide substrates, and silicon nitride substrates. An Argil substrate is one type of aluminum oxide substrate. Argil is a sintered body consisting of 20 to 80 wt% aluminum oxide and the remainder zirconium oxide. The three-point bending strength of an aluminum nitride substrate or aluminum oxide substrate is approximately 300 to 450 MPa. The strength of an Argil substrate is approximately 550 MPa. The thermal conductivity of aluminum nitride is 170 W / (m·K) or more, and can be further increased to 200 W / (m·K) or more. The thermal conductivity of aluminum oxide is 20 W / (m·K). The thickness of aluminum nitride and aluminum oxide is preferably 0.8 mm or less, and more preferably 0.635 mm or less. The three-point bending strength of a silicon nitride substrate is 600 MPa or more, and can be further increased to 700 MPa or more. The thermal conductivity of silicon nitride substrates is 50 W / (m·K) or more, and can even be increased to 80 W / (m·K) or more. In particular, in recent years, silicon nitride substrates have been developed that combine both high strength and high thermal conductivity. Because silicon nitride substrates have high strength, they can be made thin, enabling improved heat dissipation. For this reason, the thickness of the silicon nitride substrate is preferably 0.635 mm or less, and more preferably 0.3 mm or less. There is no specific lower limit for the thickness, but it is preferably 0.1 mm or more. This is to ensure the electrical insulation of each ceramic substrate. The thickness here refers to the dimension in the direction connecting the upper surface of the ceramic substrate and the lower surface of the ceramic substrate.

[0013] The thickness of the ceramic green sheet processed by the double-side processing apparatus according to the embodiment is preferably 1 mm or less. A thick ceramic green sheet improves its strength. However, if a release agent is applied to a thick ceramic green sheet and the sheet is dried, cracks are likely to occur on the surface due to bending forces. The thickness of the ceramic green sheet is preferably 0.8 mm or less, and more preferably 0.6 mm or less.

[0014] When a ceramic green sheet is thin, the strength of the ceramic green sheet is weak and the ceramic green sheet is easily damaged. Therefore, the ceramic green sheet is not easy to handle. According to an embodiment of the present invention, a release agent can be attached to such a thin ceramic green sheet while suppressing damage to the ceramic green sheet.

[0015] To obtain multiple ceramic substrates by stacking and sintering ceramic green sheets, it is preferable that the release agent attached to the ceramic green sheets is a substance that is stable even at high temperatures during sintering and does not easily react with the ceramic substrate. A typical release agent attached to ceramic green sheets is boron nitride (BN). Boron nitride can be attached by dispersing boron nitride powder in water or an organic solvent.

[0016] A double-side processing apparatus according to an embodiment will be described with reference to the accompanying drawings.

[0017] FIG. 1 is a plan view of a double-sided processing apparatus 1 according to an embodiment. FIG. 2 is a cross-sectional view of the double-sided processing apparatus 1 according to the embodiment shown in FIG. 1. In FIGS. 1 and 2, reference numeral 2 denotes a ceramic green sheet. In the example shown in FIGS. 1 and 2, the ceramic green sheet 2 is carried in horizontally from one side of the double-sided processing apparatus 1 and carried out horizontally to the same side. This allows a sheet feeder, a sheet storage device, and the like to be connected to one side of the double-sided processing apparatus 1. The sheet feeder, the double-sided processing apparatus 1, and the sheet storage device can be efficiently arranged together.

[0018] 1 and 2, the double-side processing apparatus 1 includes a first roller unit 6, a second roller unit 7, and roller units 11a to 11g. These roller units are rotatable by power from a motor or the like, and convey the ceramic green sheet 2 by rotation. The double-side processing apparatus 1 also includes nip rollers 12a to 12d. The nip rollers 12a to 12d are driven wheels that are not capable of rotating by power.

[0019] For example, a ceramic green sheet 2 is continuously supplied to the double-side processing apparatus 1 from a sheet forming machine (not shown). The ceramic green sheet 2 supplied to the double-side processing apparatus 1 comes into contact with the roller units 11a to 11e in sequence. Specifically, the roller unit 11a changes the moving direction of the ceramic green sheet 2 from horizontal to downward. The roller unit 11b changes the moving direction from downward to horizontal. The roller unit 11c feeds the ceramic green sheet 2 horizontally. The nip roller 12a is provided near the roller unit 11c and faces the roller unit 11c. The nip roller 12a sandwiches the ceramic green sheet 2 between itself and the roller unit 11c and applies an appropriate pressure to the ceramic green sheet 2. Then, the roller unit 11d changes the moving direction of the ceramic green sheet 2 from horizontal to upward, and the roller unit 11e changes the moving direction from upward to horizontal. The nip roller 12b is provided near the roller portion 11e and faces the roller portion 11e. The nip roller 12b sandwiches the ceramic green sheet 2 between itself and the roller portion 11e, and applies an appropriate pressure to the ceramic green sheet 2.

[0020] The ceramic green sheet 2 supplied to the double-side processing apparatus 1 is transported horizontally by the first transport mechanism 5 with the first surface 2a facing upward. At this time, the upward-facing side of the ceramic green sheet is the same as the side facing upward when transported to the double-side processing apparatus 1. By changing the positions of the roller units and nip rollers, the side facing downward when transported to the double-side processing apparatus 1 can be made to face upward when transported to the first transport mechanism 5. The number of roller units can also be reduced to four or less. For simplicity, the ceramic green sheet 2 can be transported to the first transport mechanism 5 using one roller unit or a combination of one roller unit and a nip roller. Conversely, six or more roller units may be installed to adjust the transport function.

[0021] In the illustrated example, the ceramic green sheet 2 is transported to the right of the page (an example of a first direction). The first transport mechanism 5 is a roller conveyor including a plurality of guide rollers 5a. The first transport mechanism 5 may include a belt conveyor instead of guide rollers. Each guide roller 5a is a driven wheel that does not have the function of rotating with power, and rotates following the movement of the ceramic green sheet 2. While being transported by the first transport mechanism 5, the ceramic green sheet 2 enters the first processing section 3.

[0022] The first processing unit 3 includes a spray 3a and an envelope 3b. The spray 3a sprays a liquid in which a release agent is dispersed. The envelope 3b is provided to prevent the sprayed release agent from diffusing to the surroundings, and the spray 3a is disposed inside the envelope 3b. An opening for carrying in and an opening for carrying out the ceramic green sheet 2 are provided at the bottom of the envelope 3b. The spray 3a sprays the release agent toward the ceramic green sheet 2 carried in through the opening. The ceramic green sheet 2, wet with the liquid, is carried out through another opening.

[0023] The ceramic green sheet 2 with the release agent attached thereto is transferred to the first drying section 4 and dried. The first drying section 4 includes a blower 4a and an envelope 4b. The blower 4a blows air toward the ceramic green sheet 2. The blower 4a may have a function of heating air and blow warm air toward the ceramic green sheet 2. A heater that irradiates the ceramic green sheet 2 with infrared rays or the like may be provided instead of the blower 4a. The envelope 4b has openings at its bottom for loading and unloading the ceramic green sheet 2. The ceramic green sheet 2 that has become wet due to the treatment in the first processing section 3 is loaded into the opening of the envelope 4b and dried by the blower 4a. The dried ceramic green sheet 2 is unloaded from another opening.

[0024] The dried ceramic green sheet 2 comes into contact with the first roller unit 6. The first roller unit 6 changes the moving direction of the ceramic green sheet 2 from horizontal to upward (an example of a second direction). The ceramic green sheet 2 that has moved upward comes into contact with the second roller unit 7. The second roller unit 7 changes the moving direction of the ceramic green sheet 2 from upward to horizontal (toward the left on the paper). At this time, the moving direction of the ceramic green sheet 2 after being changed by the second roller unit 7 is opposite to the moving direction of the ceramic green sheet 2 before being changed by the first roller unit 6, and the second surface 2b of the ceramic green sheet 2 faces upward. In other words, the first surface 2a and the second surface 2b of the ceramic green sheet 2 are inverted upside down by the first roller unit 6 and the second roller unit 7. The nip roller 12c is provided near the second roller unit 7 and faces the second roller unit 7. The nip roller 12 c sandwiches the ceramic green sheet 2 between itself and the second roller portion 7 , and applies an appropriate pressure to the ceramic green sheet 2 .

[0025] The ceramic green sheet 2 sent horizontally by the second roller unit 7 is then continued to be transported horizontally by a second transport mechanism 8. The second transport mechanism 8 is a roller conveyor including a plurality of guide rollers 8a. Each guide roller 8a is a driven wheel that is not equipped with the function of rotating by power, and rotates following the movement of the ceramic green sheet 2. While being transported by the second transport mechanism 8, the ceramic green sheet 2 enters a second processing section 9.

[0026] The second processing section 9 includes a spray 9a and an envelope 9b, similar to the first processing section 3. The spray 9a sprays a liquid in which a release agent is dispersed. The spray 9a sprays the release agent toward the ceramic green sheet 2 carried in through an opening in the envelope 9b. The ceramic green sheet 2 wet with the liquid is carried out through another opening in the envelope 9b. The ceramic green sheet 2 with the release agent attached is moved to the second drying section 10 and dried. The second drying section 10 includes a blower 10a and an envelope 10b, similar to the first drying section 4. The blower 10a blows air toward the ceramic green sheet 2 to dry it. The ceramic green sheet 2 wetted by the processing in the second processing section 9 is carried in through an opening in the envelope 10b and dried by the blower 10a. The dried ceramic green sheet 2 is carried out through another opening in the envelope 10b.

[0027] The dried ceramic green sheet 2 is discharged from the double-side processing apparatus 1. The moving direction of the discharged ceramic green sheet 2 is changed from horizontal to downward by the roller unit 11f. The ceramic green sheet 2 then moves diagonally downward by the sheet guide 14. The ceramic green sheet 2 that has moved downward is then moved diagonally upward by the guide roller 13a. The ceramic green sheet 2 is then fed horizontally by the nip roller 12d and the roller unit 11g.

[0028] The above-described components of the double-sided processing device 1 are attached directly or indirectly to a frame 16. The frame 16 is a member that forms the outer casing of the double-sided processing device 1 and serves to support the structure of the entire device.

[0029] In the double-side processing device 1, the number of roller units, nip rollers, guide rollers, sheet guides, etc. other than the first roller unit 6 and the second roller unit 7 does not need to be as shown in the figure, and may be added or omitted as appropriate. At least some of the plurality of guide rollers 5a or at least some of the plurality of guide rollers 8a may be replaced with roller units equipped with motors, etc.

[0030] In the above-described example, the release agent is applied to the ceramic green sheet 2 by spraying in the first processing unit 3 and the second processing unit 9. However, the present invention is not limited to this example, and the release agent may be applied to the surface of the ceramic green sheet 2 by a roll coater or a brush. However, spraying is most preferable in order to apply the release agent more uniformly while suppressing the amount of the release agent applied.

[0031] Furthermore, if the ceramic green sheet 2 can be sufficiently dried without the first drying section 4 and the second drying section 10, the first drying section 4 and the second drying section 10 may be omitted. For example, if dry air is circulating in the space through which the ceramic green sheet 2 is transported, the ceramic green sheet 2 can be dried even without the first drying section 4 and the second drying section 10. However, the inventors' studies have revealed that the shorter the time from when the release agent is applied to the ceramic green sheet 2 until it dries, the more effectively the ceramic green sheet can be prevented from warping or undulating. Therefore, in order to prevent the ceramic green sheet from warping or undulating, it is preferable to provide the first drying section 4 and the second drying section 10 and shorten the time the ceramic green sheet 2 is wet.

[0032] In the example shown in FIG. 2 , the ceramic green sheet 2 is carried in horizontally at the bottom of the double-side processing apparatus 1 and carried out horizontally at the top of the double-side processing apparatus 1. The configuration of the double-side processing apparatus 1 according to the embodiment is not limited to this example. For example, the ceramic green sheet 2 may be carried in horizontally at the top of the double-side processing apparatus 1 and carried out horizontally at the bottom of the double-side processing apparatus 1. In this case, the positions of the processing section and the drying section may be reversed from the example shown in FIG. 2 , the conveying direction of the ceramic green sheet 2 may be reversed from the example shown in FIG. 2 , or the arrangement or number of roller units may be changed. Alternatively, the ceramic green sheet 2 may be carried in or out vertically relative to the double-side processing apparatus 1. In this case, the configuration can be accommodated by changing the position or number of roller units. The ceramic green sheet 2 may be carried in either the horizontal or vertical direction and carried out either the horizontal or vertical direction.

[0033] 3 and 4 show another double-sided processing apparatus according to an embodiment. Fig. 3 is a plan view of another double-sided processing apparatus 1a according to an embodiment. Fig. 4 is a cross-sectional view of the double-sided processing apparatus 1a according to the embodiment shown in Fig. 3. In the double-sided processing apparatus 1a, the ceramic green sheet 2 is carried in horizontally from one side and carried out horizontally from the other side. This allows the sheet feeder, double-sided processing apparatus 1a, sheet storage apparatus, etc. to be arranged linearly.

[0034] In the double-side processing apparatus 1a shown in Figures 3 and 4, a ceramic green sheet 2 is continuously supplied from a sheet forming machine (not shown) or the like. The supplied ceramic green sheet 2 is fed horizontally by guide rollers 13b and 13c. The ceramic green sheet 2 moving horizontally comes into contact with roller unit 11a, and the direction of movement of the ceramic green sheet 2 changes to downward. The direction of movement of the ceramic green sheet 2 is then changed to horizontal by roller unit 11b. The ceramic green sheet 2 moving horizontally passes between roller unit 11h and nip roller 12e and is transported to the third transport mechanism 15 of the double-side processing apparatus 1a.

[0035] The third conveying mechanism 15 is a roller conveyor including a plurality of guide rollers 15a. The third conveying mechanism 15 conveys the ceramic green sheet 2 horizontally (toward the left on the paper). A roller unit 11i (third roller unit) is disposed at the end of the third conveying mechanism 15. The ceramic green sheet 2 conveyed by the third conveying mechanism 15 is moved upward by the roller unit 11i. The ceramic green sheet 2 then passes between the roller unit 11j (fourth roller unit) and the nip roller 12b and is conveyed to the first conveying mechanism 5. The first conveying mechanism 5 conveys the ceramic green sheet 2 horizontally (toward the right on the paper). That is, the moving direction of the ceramic green sheet 2 is reversed by the roller unit 11i, the roller unit 11j, and the nip roller 12b.

[0036] The configuration and processing of the first conveying mechanism 5 and subsequent steps in the double-side processing apparatus 1a may be the same as the configuration and processing of the first conveying mechanism 5 and subsequent steps in the double-side processing apparatus 1. That is, the first conveying mechanism 5 is a roller conveyor including a plurality of guide rollers 5a. The ceramic green sheet 2 is conveyed with its first surface 2a facing upward. During conveyance, the ceramic green sheet 2 enters the first processing section 3, where a release agent is applied to the first surface 2a by a spray 3a. The ceramic green sheet 2 with the release agent applied thereto is dried in the first drying section 4.

[0037] The ceramic green sheet 2 coated with the release agent is moved upward by the first roller unit 6 and then moved horizontally (to the left on the paper) by the second roller unit 7. The second roller unit 7 is provided with a nip roller 12c for pressing the ceramic green sheet.

[0038] The ceramic green sheet 2 sent horizontally by the second roller unit 7 is then transported by a second transport mechanism 8 with the second surface 2b facing upward. The second transport mechanism 8 is a roller conveyor including a plurality of guide rollers 8a. During transport, the ceramic green sheet 2 enters a second processing unit 9, where a release agent is applied to the second surface 2b by a spray 9a. The ceramic green sheet 2 with the release agent applied thereto is dried in a second drying unit 10.

[0039] The ceramic green sheet 2 with the release agent attached on both sides thereof is conveyed downward by the roller unit 11f. The ceramic green sheet 2 that has been moved downward is then moved diagonally downward by the sheet guide 14. Thereafter, the ceramic green sheet 2 passes between the roller unit 11g and the nip roller 12d and is fed horizontally.

[0040] In the double-side processing device 1a, the number of roller units, nip rollers, guide rollers, sheet guides, etc. other than the first roller unit 6 and the second roller unit 7 does not need to be as shown in the figure, and may be added or omitted as appropriate. At least some of the plurality of guide rollers 5a, at least some of the plurality of guide rollers 8a, or at least some of the plurality of guide rollers 15a may be replaced with roller units equipped with motors, etc.

[0041] In the example shown in FIG. 4 , the ceramic green sheet 2 is horizontally loaded from the right side at the bottom of the double-side processing apparatus 1 and then horizontally unloaded to the left side at the top of the double-side processing apparatus 1. The configuration of the double-side processing apparatus 1a according to the embodiment is not limited to this example. For example, the ceramic green sheet 2 may be loaded horizontally from one of the right and left sides at the top of the double-side processing apparatus 1 and then unloaded horizontally to the other of the right and left sides at the bottom of the double-side processing apparatus 1. Alternatively, the ceramic green sheet 2 may be loaded and unloaded vertically relative to the double-side processing apparatus 1. In this case, the configuration can be accommodated by changing the position or number of the roller units. The ceramic green sheet 2 may be loaded in one of the horizontal and vertical directions and unloaded in the other of the horizontal and vertical directions.

[0042] 4, the third conveying mechanism 15 conveys the ceramic green sheet 2 before the release agent is attached thereto. This example is not limiting, and the third conveying mechanism 15 may convey the ceramic green sheet 2 after the release agent is attached thereto. In this case, the third conveying mechanism 15 may be disposed above the second conveying mechanism 8. In this case, the configuration can be adapted by changing the position or number of the roller units. In addition to the third conveying mechanism 15, another conveying mechanism may be added for the purpose of turning the ceramic green sheet 2 upside down or changing the moving direction.

[0043] As another example other than those shown in FIGS. 1 to 4 , the first conveying mechanism 5 may convey the ceramic green sheet 2 upward (an example of a first direction), and the second conveying mechanism 8 may convey the ceramic green sheet 2 downward. In this case, the first processing unit 3 sprays a release agent onto the first surface 2 a of the ceramic green sheet 2 moving upward, and the first drying unit 4 dries the ceramic green sheet 2. The second processing unit 9 sprays a release agent onto the second surface 2 b of the ceramic green sheet 2 moving downward, and the second drying unit 10 dries the ceramic green sheet 2. In a double-side processing apparatus, if the ceramic green sheet 2 moves vertically, the installation area of ​​the double-side processing apparatus can be further reduced. Therefore, to reduce the installation area, it is effective to convey the ceramic green sheet 2 vertically. On the other hand, when processing the ceramic green sheet 2 during vertical transport, the release agent sprayed on the surface of the ceramic green sheet 2 may move downward. The liquids may aggregate, causing uneven adhesion of the release agent to the surface of the ceramic green sheet 2. Therefore, in order to more uniformly adhere the release agent to the ceramic green sheet 2, it is effective to transport the ceramic green sheet 2 in the horizontal direction.

[0044] FIG. 5 is a schematic diagram showing an example of a spray. As shown in FIG. 5, the spray 3a and the spray 9a include a spray gun 18 and a spray gun moving unit 19. In the example shown in FIG. 5, the ceramic green sheet 2 is transported toward the depth of the page. The spray gun 18 performs a swinging motion (swing) from side to side as indicated by the arrow. At this time, the rotation axis of the spray gun 18 is parallel to the transport direction of the ceramic green sheet 2. The spray gun 18 performs a swinging motion around the transport direction. In the example shown in FIG. 5, the spray gun 18 swings approximately 90 degrees. As a result, the release agent is sprayed widely within the area surrounded by the dotted line. The release agent sprayed from the spray gun 18 adheres to the surface of the ceramic green sheet 2.

[0045] The spray gun moving unit 19 moves the spray gun 18 left and right on the paper (an example of a third direction). For example, the spray gun moving unit 19 includes an actuator such as a motor or an air cylinder, and moves the spray gun 18 left and right by the power thereof. In the example shown in FIG. 5 , the spray gun moving unit 19 moves the spray gun 18 back and forth left and right from center to right to center to left. The spray gun 18 oscillates while oscillating left and right. By moving left and right and oscillating the spray gun 18, the release agent can be uniformly applied to the edge of the ceramic green sheet 2.

[0046] Figure 6 is a schematic diagram showing another example of spraying. In the example shown in Figure 6, the ceramic green sheet 2 is transported toward the depth of the page. The spray gun 18 is moved left and right by a spray gun moving unit 19, reciprocating from center to right to center to left. The orientation of the spray gun 18 is fixed vertically, and it does not perform the oscillating motion shown in Figure 5. The release agent sprayed from the spray gun adheres to the surface of the ceramic green sheet 2. By fixing the spray gun, it is possible to reduce the amount of release agent that does not adhere to the ceramic green sheet 2.

[0047] The double-side processing apparatus according to the embodiment can suitably process the ceramic green sheet 2. For example, in the past, after cutting the ceramic green sheet 2, the ceramic green sheet 2 was turned over by hand while a release agent was applied to both sides of the ceramic green sheet 2. In contrast, the double-side processing apparatus according to the embodiment can apply a release agent to both sides of the ceramic green sheet 2 while turning over the ceramic green sheet 2 using the first conveying mechanism 5, the first roller unit 6, the second roller unit 7, and the second conveying mechanism 8.

[0048] Furthermore, in recent years, as ceramic substrates have become thinner, the ceramic green sheet 2 has also tended to be formed thinner. When the ceramic green sheet 2 is thin, it is prone to warping and wrinkling. To prevent this, it is desirable to apply tension to the ceramic green sheet 2. However, because the ceramic green sheet 2 has low strength, the ceramic green sheet 2 easily breaks when a large tension is applied to it. In the double-side processing apparatus according to the embodiment, nip rollers are provided for at least some of the roller units to apply an appropriate tension to the ceramic green sheet 2 and prevent warping, wrinkling, and the like. By providing the nip rollers and sandwiching the ceramic green sheet 2 between the roller units and the nip rollers, warping, wrinkling, and the like can be suppressed without applying excessive tension to the ceramic green sheet 2.

[0049] A specific example of a process for applying a release agent to a ceramic green sheet using the double-side processing apparatus according to the embodiment will be described below. Here, an example of applying boron nitride powder to a green sheet made of silicon nitride will be described.

[0050] A silicon nitride green sheet is supplied to the double-side processing apparatus shown in FIGS. 1 and 2 from a supplying device (not shown), such as a sheet forming machine or a sheet supplying machine.

[0051] The silicon nitride green sheet is conveyed toward the roller portion 11a by the guide roller. The number of guide rollers may be one or three or more depending on the configuration of the device to be connected. Multiple guide rollers may be arranged below the silicon nitride green sheet so that the silicon nitride green sheet is placed on top.

[0052] The silicon nitride green sheet is fed downward by roller unit 11a, and then fed horizontally by roller unit 11b. Next, the silicon nitride green sheet is pulled in while pressure is applied to the silicon nitride green sheet by nip roller 12a and roller unit 11c. The silicon nitride green sheet is fed upward by roller unit 11d. Next, the silicon nitride green sheet is pulled in while pressure is applied to the silicon nitride green sheet by nip roller 12b and roller unit 11e. The silicon nitride green sheet is fed horizontally and transported to first transport mechanism 5.

[0053] During transport by the first transport mechanism 5, the silicon nitride green sheet passes through the first processing section 3. The double-side processing device 1 applies a release agent to the surface of the silicon nitride green sheet. The release agent is a boron nitride liquid prepared by dispersing boron nitride in water. For example, the boron nitride liquid is produced by dispersing 20 to 30 weight percent boron nitride in water. The boron nitride liquid is supplied to the spray 3a via a hose (not shown). The spray 3a sprays the boron nitride liquid downward to deposit it on the upper surface (front surface) of the silicon nitride green sheet. The spray 3a sprays the boron nitride liquid while reciprocating in a direction perpendicular to the transport direction and horizontally, thereby uniformly depositing the boron nitride liquid on the surface of the silicon nitride green sheet. Note that the direction of reciprocation of the spray 3a does not need to be strictly perpendicular to the transport direction; for example, the spray 3a may reciprocate in a direction oblique to the transport direction and horizontal direction.

[0054] The reciprocating speed of the spray 3a is adjusted depending on the transport speed of the silicon nitride green sheet, the concentration of the boron nitride liquid, and the like. When the double-side processing device is connected to a sheet forming machine, the transport speed changes depending on the forming speed of the silicon nitride green sheet. That is, when the silicon nitride green sheet is thin, it can be formed quickly, so the transport speed is fast. When the silicon nitride green sheet is thick, it can be formed slowly, so the transport speed is slow. When the transport speed is fast, it is preferable that the reciprocating speed of the spray 3a be fast. When the transport speed is slow, it is preferable that the reciprocating speed of the spray 3a be slow. The transport speed may be set depending on the concentration of the boron nitride liquid. For example, when the concentration of the boron nitride liquid is low within the above-mentioned concentration range, it is preferable that the reciprocating speed of the spray 3a be slow. When the concentration of the boron nitride liquid is high within the above-mentioned concentration range, it is preferable that the reciprocating speed of the spray 3a be fast. The above adjustments are made when the amount sprayed from the spray 3a is constant. When the spray 3a has a function of adjusting the amount of spray, the amount of spray may be adjusted according to the conveying speed or the concentration of the liquid without changing the reciprocating speed.

[0055] The silicon nitride green sheet with the boron nitride liquid attached is transported to the first drying section 4. In the first transport mechanism 5, natural drying or heat drying is performed. In natural drying, dry air is sent into the first drying section 4 and sucked through a duct or the like. This evaporates the moisture, causing the sheet to dry, leaving boron nitride powder attached to the surface of the silicon nitride green sheet. In heat drying, heated air is sent in or the moisture is evaporated by heating with a heater installed inside the envelope 4b. Natural drying can reduce costs, but the time required for drying is longer. This requires the first drying section 4 to be longer in the transport direction of the silicon nitride green sheet. In contrast, heat drying incurs heating costs but shortens the time required for drying.

[0056] The silicon nitride green sheet carried out from the first drying section 4 is sent upward by the first roller section 6 at the terminal end of the first conveying mechanism 5. The silicon nitride green sheet is then sent horizontally by the second roller section 7 and nip roller 12c. At this time, the surface opposite to the surface with the boron nitride attached (the back surface) becomes the upper surface. The silicon nitride green sheet is then conveyed by the second conveying mechanism 8 in the opposite direction to the first conveying mechanism 5.

[0057] The silicon nitride green sheet is sprayed with boron nitride liquid and dried, as with the first conveying mechanism 5. The silicon nitride green sheet with boron nitride attached is conveyed to the end of the second conveying mechanism 8 and sent in a substantially downward direction by roller unit 11f. It is then separated from the end of the second conveying mechanism 8 by sheet guide 14 and carried out by roller unit 11g and nip roller 12d.

[0058] As long as the release agent can be applied to both sides of the ceramic green sheet 2, the amount and thickness of the release agent applied by the first processing unit 3 and the amount and thickness of the release agent applied by the second processing unit 9 can be appropriately set. Preferably, the thickness of the release agent applied to the first surface 2a by the first processing unit 3 is greater than the thickness of the release agent applied to the second surface 2b by the second processing unit 9. The release agent applied by the first processing unit 3 is dried not only by the first drying unit 4 but also by the second drying unit 10. Therefore, even if a thicker layer of release agent is applied to the first surface 2a than to the second surface 2b, the release agent on the first surface 2a can be sufficiently dried. Furthermore, by thinning the thickness of the release agent applied to the second surface 2b, the time required to dry the release agent can be shortened. As a result, the time required to process the ceramic green sheet 2 can be shortened, and the production efficiency of the ceramic green sheet 2 can be improved.

[0059] For example, after cutting the ceramic green sheets 2, a plurality of the ceramic green sheets 2 are stacked and sintered. At this time, the plurality of ceramic green sheets 2 are stacked so that the first surface 2a, to which the release agent is adhered relatively thickly, comes into contact with the second surface 2b, to which the release agent is adhered relatively thinly. This allows the ceramic green sheets 2 to be more easily separated from each other after sintering.

[0060] Here, the case where a boron nitride liquid is applied to a silicon nitride green sheet has been described. However, the embodiment of the present invention is not limited to this example and can also be applied to the case where a release agent is applied to other ceramic green sheets.

[0061] FIG. 7 is a flowchart showing a method for manufacturing a sintered body according to an embodiment. FIGS. 8(a) to 8(e) are cross-sectional views showing the manufacturing process of a sintered body according to an embodiment. The double-sided processing apparatus according to an embodiment is suitable for manufacturing a sintered body made of ceramic. First, ceramic raw material powder and a sintering aid are mixed. The sintering aid may be an oxide of a rare earth element, magnesium, titanium, hafnium, or the like. An organic binder is added to the mixed raw materials, and the mixture is degassed to produce a raw material slurry (Step S1). As shown in FIG. 8(a), the raw material slurry is molded to produce a ceramic green sheet 2 (Step S2). A doctor blade method is preferably used for sheet molding. The doctor blade method allows for the production of thin, large green sheets, improving mass productivity.

[0062] As shown in Fig. 8(b), a release agent 20 is applied to each of the first surface 2a and the second surface 2b of the ceramic green sheet 2 (step S3). The double-side processing apparatus according to the embodiment is used to apply the release agent 20. As shown in Fig. 8(c), the ceramic green sheet to which the release agent 20 has been applied is cut to a predetermined size using a cutter or the like (step S4).

[0063] As shown in Fig. 8(d), the cut ceramic green sheets 2 are stacked in a sintering container 21 (step S5). The sintering container 21 is made of boron nitride or the like and is composed of, for example, a setter 22 and a setter 23. The setter 22 is arranged horizontally, and the setter 23 is arranged vertically. The setters 22 and 23 are arranged in a space surrounded by them.

[0064] The stacked ceramic green sheets are heated at a temperature of 1000°C or less to produce a degreased body (Step S6). The atmosphere for the degreasing process is preferably an inert atmosphere such as nitrogen gas or argon gas. An oxygen-containing atmosphere, in which oxygen is added to an inert atmosphere, may also be used. The degreased body is sintered at a temperature of 1600°C or more and 2000°C or less (Step S7). A pressurized atmosphere is preferably used inside the sintering furnace. Degreasing and sintering may be performed consecutively in the same sintering vessel. The stacked sintered bodies are separated, and the release agent is removed by honing or the like (Step S8). A sintered body is produced through the above steps. In the example shown in Figure 8(e), a ceramic substrate 2C is produced as a sintered body.

[0065] When the ceramic substrate 2C is manufactured as a sintered body, the surface of the sintered body is subjected to surface treatment such as polishing, if necessary. When the ceramic substrate 2C is used as a circuit board, a step of bonding a metal plate or the like to the ceramic substrate 2C may be further performed.

[0066] Embodiments of the present invention include the following features: (Feature 1) A double-side processing apparatus for applying a release agent to both sides of a ceramic green sheet, comprising: a first conveying mechanism for moving the ceramic green sheet in a first direction, a first processing unit for applying a release agent to the first side of the ceramic green sheet conveyed by the first conveying mechanism, a first roller unit provided at an end of the first conveying mechanism in the first direction and for changing the moving direction of the ceramic green sheet to a second direction intersecting the first direction, a second roller unit for changing the moving direction of the ceramic green sheet moved in the second direction to a direction opposite to the first direction, a second conveying mechanism for moving the ceramic green sheet in the opposite direction, and a second processing unit for applying a release agent to the second side of the ceramic green sheet conveyed by the second conveying mechanism. (Feature 2) The double-sided processing apparatus according to Feature 1, further comprising: a first drying unit that dries the release agent adhered to the first surface; and a second drying unit that dries the release agent adhered to the second surface. (Feature 3) The double-sided processing apparatus according to Feature 1 or Feature 2, wherein the second roller unit has a rotation axis perpendicular to the first direction and the second direction, rotates about the rotation axis, and further comprises a nip roller that faces the second roller unit and presses the ceramic green sheet. (Feature 4) The double-sided processing apparatus according to any of Features 1 to 3, wherein the first processing unit adheres the release agent to the first surface while reciprocating in a third direction perpendicular to the first direction and the second direction or while swinging around the first direction, and the second processing unit adheres the release agent to the second surface while reciprocating in the third direction or while swinging around the opposite direction.(Feature 5) The double-sided processing apparatus according to any one of Features 1 to 4, further comprising: a third conveying mechanism that moves the ceramic green sheet in the opposite direction, a third roller unit that is provided at an end of the third conveying mechanism in the opposite direction and that changes the moving direction of the ceramic green sheet from the opposite direction to the second direction, and a fourth roller unit that changes the moving direction of the ceramic green sheet that has moved in the second direction to the first direction toward the first conveying mechanism. (Feature 6) The double-sided processing apparatus according to any one of Features 1 to 5, wherein the first processing unit sprays the release agent toward the first surface, and the second processing unit sprays the release agent toward the second surface. (Feature 7) A double-sided processing method using the double-sided processing apparatus according to Feature 1, comprising: carrying the ceramic green sheet into the first conveying mechanism; adhering the release agent to the first surface by the first processing section; adhering the release agent to the second surface by the second processing section; and carrying the ceramic green sheet out from the second conveying mechanism. (Feature 8) The double-sided processing method according to Feature 7, wherein the thickness of the release agent adhered to the first surface by the first processing section is greater than the thickness of the release agent adhered to the second surface by the second processing section. (Feature 9) The double-sided processing method according to Feature 7 or Feature 8, wherein the ceramic green sheet contains silicon nitride, aluminum nitride, or aluminum oxide. (Feature 10) The double-sided processing method according to any one of Feature 7 to Feature 9, wherein the ceramic green sheet has a thickness of 1 mm or less. (Feature 11) A method for producing a sintered body, comprising: carrying out the double-side processing method according to any one of Features 7 to 10; cutting the ceramic green sheet having the release agent attached to the first surface and the second surface; and stacking and sintering the cut ceramic green sheets.

[0067] Although several embodiments of the present invention have been illustrated, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. Modifications of these embodiments are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other.

[0068] DESCRIPTION OF SYMBOLS 1...Double-sided processing device 2...Ceramic green sheet 2a...First side of ceramic green sheet 2b...Second side of ceramic green sheet 3...First processing section 3a...Spray 3b...Enclosure 4...First drying section 4a...Air blowing section 4b...Enclosure 5...First conveying mechanism 5a...Guide roller 6...First roller section 7...Second roller section 8...Second conveying mechanism 8a...Guide roller 9...Second processing section 9a...Spray 9b...Enclosure 10...Second drying section 10a...Air blowing section 10b...Enclosure 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h...Roller section 12a, 12b, 12c, 12d, 12e...Nip rollers 13a, 13b, 13c...Guide roller 14...Sheet guide 15... Third conveying mechanism 15a... Guide roller 16... Frame 18... Spray gun 19... Spray gun moving section 20... Mold release agent 21... Sintering container 22, 23... Setter

Claims

1. A double-sided processing apparatus for applying a release agent to both sides of a ceramic green sheet, comprising: a first conveying mechanism for moving the ceramic green sheet in a first direction; a first processing unit for applying a release agent to the first side of the ceramic green sheet conveyed by the first conveying mechanism; a first roller unit provided at an end of the first conveying mechanism in the first direction for changing the moving direction of the ceramic green sheet to a second direction intersecting the first direction; a second roller unit for changing the moving direction of the ceramic green sheet moved in the second direction to a direction opposite to the first direction; a second conveying mechanism for moving the ceramic green sheet in the opposite direction; and a second processing unit for applying a release agent to the second side of the ceramic green sheet conveyed by the second conveying mechanism.

2. The double-sided processing apparatus according to claim 1, further comprising: a first drying section that dries the release agent adhered to the first surface; and a second drying section that dries the release agent adhered to the second surface.

3. A double-sided processing device as described in either claim 1 or claim 2, wherein the second roller unit has a rotation axis perpendicular to the first direction and the second direction, rotates around the rotation axis, and faces the second roller unit and further includes a nip roller for pressing the ceramic green sheet.

4. A double-sided processing apparatus as described in claim 1 or claim 2, wherein the first processing unit applies the release agent to the first surface while moving back and forth in a third direction perpendicular to the first direction and the second direction, or while oscillating around the first direction, and the second processing unit applies the release agent to the second surface while moving back and forth in the third direction or while oscillating around the opposite direction.

5. A double-sided processing apparatus as described in claim 1 or claim 2, further comprising: a third conveying mechanism that moves the ceramic green sheet in the opposite direction; a third roller unit provided at an end of the third conveying mechanism in the opposite direction and that changes the moving direction of the ceramic green sheet from the opposite direction to the second direction; and a fourth roller unit that changes the moving direction of the ceramic green sheet that has moved in the second direction to the first direction toward the first conveying mechanism.

6. A double-sided processing apparatus as described in claim 1 or claim 2, wherein the first processing section sprays the release agent toward the first surface, and the second processing section sprays the release agent toward the second surface.

7. A double-sided processing method using the double-sided processing apparatus of claim 1, comprising the steps of: feeding the ceramic green sheet into the first conveying mechanism; adhering the release agent to the first side by the first processing section; adhering the release agent to the second side by the second processing section; and transporting the ceramic green sheet out of the second conveying mechanism.

8. The double-sided processing method according to claim 7, wherein the thickness of the release agent applied to the first surface by the first processing section is greater than the thickness of the release agent applied to the second surface by the second processing section.

9. The double-sided processing method according to claim 7 or 8, wherein the ceramic green sheet contains silicon nitride, aluminum nitride, or aluminum oxide.

10. The double-side processing method according to claim 7 or 8, wherein the ceramic green sheet has a thickness of 1 mm or less.

11. A method for producing a sintered body, comprising carrying out the double-sided processing method according to claim 7, cutting the ceramic green sheet having the release agent applied to the first and second surfaces thereof, and stacking and sintering the cut ceramic green sheets.

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