JP2004231463A - Firing furnace and method for producing non-oxide ceramic sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a firing furnace which requires only a small maintenance work and in which a dewaxing process and a sintering process can be performed for producing a sintered compact having a constant quality, and to provide a production method thereof using the firing furnace. <P>SOLUTION: The firing furnace has a chamber which can be closed, a heating chamber which is provided in the chamber and has a heater, a first exhaust tube connected to the chamber, a first vacuum pump connected to the first exhaust tube, a second exhaust tube directly connected to the heating chamber, and a collecting apparatus for collecting binder components in the exhaust gas and a second vacuum pump which are connected to the second exhaust tube. The method for producing the non-oxide ceramic sintered compact comprises a process for continuously performing the dewaxing process and the sintering process by using the firing furnace. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a firing furnace for sintering ceramics and the like, and more particularly to a firing furnace capable of performing both a degreasing step and a sintering step, and a method for producing a non-oxide ceramic sintered body using the sintering furnace. .
[0002]
[Prior art]
In general, when producing a non-oxide ceramic sintered body, a ceramic raw material powder or a sintering aid is mixed with a binder, and a molded body is produced using various molding methods. It is placed in a firing furnace and heated in the air to perform a degreasing treatment. Thereafter, the green body after the degreasing treatment from which the binder has been removed is transferred to a firing furnace for sintering, where the green body is fired at a high temperature in an inert gas or in a vacuum to obtain a sintered body. As described above, conventionally, the degreasing step and the sintering step having different firing atmospheres and firing temperatures have been performed using separate firing furnaces.
[0003]
Therefore, two facilities, a degreasing baking furnace and a sintering baking furnace, are required, which imposes a burden on equipment costs, and the work of loading and unloading materials into and out of each baking furnace, as well as the temperature for raising and lowering the temperature. The time required for management was a burden on manufacturing costs.
[0004]
On the other hand, in a baking furnace for MIM (Metal Injection Molding), a vacuum degreasing baking furnace capable of performing a degreasing step and a sintering step in one furnace for the purpose of reducing such equipment costs and shortening the process. It has been proposed (Patent Document 1) that the use of a firing furnace that can perform the degreasing step and the sintering step in one furnace is also desired for the same purpose in a firing furnace for non-oxide ceramics.
[0005]
[Patent Document 1]
Japanese Patent Publication No. 6-41610. FIG.
[0006]
[Patent Document 2]
JP-A-9-48668.
[0007]
[Problems to be solved by the invention]
For example, in an electrostatic chuck used as a means for fixing a substrate in a semiconductor manufacturing apparatus, a non-oxide ceramic sintered body such as silicon nitride or aluminum nitride is used as a base material. The substrate resistivity of the electrostatic chuck is greatly influenced by the volume resistivity of the ceramic substrate. The volume resistivity is affected by the type and content of impurities in the ceramic substrate. It is necessary to adjust with high precision. Therefore, if a binder component is mixed in the sintered body or the concentration of these impurities is not uniform in some places, the product performance is impaired.
[0008]
Also, in a ceramic heater used as a substrate heating means in a semiconductor manufacturing apparatus, non-oxide ceramics such as silicon nitride and aluminum nitride are used as a ceramic base material. It has been proposed to use a blackened ceramic base material for the purpose of providing an aesthetic appearance that meets the taste of the Japanese Patent Application Laid-Open No. H10-157,086 (Patent Document 2). Patent Literature 2 discloses a method for adding 500 ppm to 5000 ppm of carbon to an aluminum nitride sintered body as a blackening method.
[0009]
As described above, in the method for producing a non-oxide ceramic sintered body, it is desirable to use a firing furnace capable of continuously performing the degreasing step and the sintering step for the purpose of reducing equipment costs and shortening the steps. On the other hand, it is necessary to use a firing furnace capable of adjusting the content of impurities in the non-oxide ceramics sintered body with high accuracy depending on the application.
[0010]
However, in the configuration of the vacuum degreasing firing furnace as disclosed in Patent Document 1, the binder component easily adheres to the exhaust pipe. In addition, since the pipe for exhausting the gas containing the binder component and the exhaust pipe for evacuating the inside of the firing furnace are common, if the binder component attached to the exhaust pipe increases, the influence of the gas from these deposits can be ignored. In addition, since it is difficult to obtain a desired degree of vacuum in the firing furnace, it is necessary to frequently overhaul the piping. Furthermore, since the binder component is easily mixed into the firing atmosphere, the firing conditions are not stable, and it is difficult to adjust the impurity content with high precision as described above, and a sintered body having a predetermined impurity content is reproduced. It is also difficult to manufacture well.
[0011]
SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to perform a degreasing step and a sintering step continuously, reduce the maintenance burden, and produce a sintered body having predetermined characteristics with good reproducibility. Is to provide a furnace.
[0012]
Another object of the present invention is to provide a method for producing a non-oxide ceramic in which the carbon content in a sintered body can be adjusted with good reproducibility.
[0013]
[Means for Solving the Problems]
The features of the firing furnace of the present invention include a sealable chamber, a heating chamber provided in the chamber and having a heater, a first exhaust pipe connected to the chamber or the heating chamber, and a first exhaust pipe. A first vacuum pump connected thereto, a second exhaust pipe directly connected to the heating chamber, a collector connected to the second exhaust pipe for collecting a binder component in the exhaust gas, and a collector. And a second vacuum pump connected to the second exhaust pipe via the device.
[0014]
According to the characteristics of the firing furnace of the present invention, apart from the first exhaust pipe connected to the chamber, the second exhaust pipe directly connected to the heating chamber and the binder component in the exhaust gas connected to the second exhaust pipe are connected to the second exhaust pipe. Since a trapping device for trapping is provided, exhaust gas containing a binder component discharged in the degreasing step is exhausted by a second exhaust pipe directly connected to the heating chamber, and the binder component contained in the exhaust gas is exhausted. The exhaust pipe can be selectively used so that the exhaust gas is collected by the collecting device and exhausted in other steps is exhausted by the first exhaust pipe. Therefore, both the degreasing step and the sintering step can be performed continuously in one baking furnace, and the first exhaust pipe can be maintained in a clean state without adhesion of a binder component. In addition, since the second exhaust pipe is directly connected to the heating chamber, the binder component can be efficiently exhausted without leaking to the outside of the heating chamber, and the adhesion of the binder component to the inner wall of the chamber can be prevented. In addition, since the binder component trapping device is provided before the second vacuum pump, contamination by the binder component in the second vacuum pump can be suppressed. Therefore, in the baking process after the degreasing process, the stable baking atmosphere can be secured with good reproducibility without being affected by degassing from the pipe or the binder adhering to the inner wall of the chamber. Can be reduced.
[0015]
In the firing furnace having the above characteristics of the present invention, further, a gas supply pipe connected to the chamber and supplying an inert gas into the chamber or the heating chamber, a pressure gauge monitoring the pressure in the chamber, and a pressure gauge in the chamber. A gas flow controller for adjusting the supply amount of the inert gas into the chamber may be provided accordingly. In this case, an inert gas atmosphere at a predetermined pressure can be maintained in the chamber. Therefore, it is suitable for producing a sintered body of non-oxide ceramics or metal, and the degree of degreasing of the binder can be adjusted by adjusting the pressure in the chamber.
[0016]
The baking furnace having the above features of the present invention may further include a CO concentration meter for monitoring the CO concentration in the chamber. In this case, by monitoring the CO concentration in the chamber that changes with the progress of the binder removal, the binder removal processing conditions such as the processing time can be accurately adjusted.
[0017]
It is preferable that the firing furnace having the above feature of the present invention further include a heating unit that heats the second exhaust pipe between the heating chamber and the collection device. By heating the second exhaust pipe, condensation of the binder component can be prevented, and the second exhaust pipe can be kept clean. Therefore, in the firing step, a clean firing atmosphere can be obtained without being affected by the gas generated from the binder component attached to the second exhaust pipe.
[0018]
The firing furnace having the above characteristics of the present invention may further include a combustion device connected to the second exhaust pipe via the collection device and the second vacuum pump to burn organic components in the exhaust gas. Good. In this case, since the binder component that could not be collected by the collection device can be reliably decomposed by the combustion device, the organic odor remaining in the exhaust gas can be removed.
[0019]
In the firing furnace having the above characteristics of the present invention, the first vacuum pump and the second vacuum pump may be a single common rotary pump. In this case, the apparatus cost can be reduced.
[0020]
In the firing furnace having the above characteristics of the present invention, a third vacuum pump for a higher vacuum than the first vacuum pump may be interposed between the first exhaust pipe and the first vacuum pump. The inside of the chamber can be made in a higher vacuum state.
[0021]
The sintering furnace having the above characteristics of the present invention may further include a pressing mechanism for pressing the sintering material placed in the heating chamber in a uniaxial direction. Hot press sintering becomes possible by adding a pressing mechanism.
[0022]
In the firing furnace having the above characteristics of the present invention, a graphite heater may be used as a heater. In this case, sintering of non-oxide ceramics that requires high-temperature firing becomes possible.
[0023]
The method for producing a non-oxide ceramics sintered body of the present invention is characterized in that the degreasing step and the sintering step are continuously performed using the above-described firing furnace of the present invention.
[0024]
According to the method for producing a non-oxide ceramic sintered body of the present invention, since the degreasing step and the sintering step are performed continuously using the above-described firing furnace of the present invention, the time required for raising and lowering the temperature is saved. As a result, the manufacturing process can be shortened, and a sintered product of stable quality can be provided with good reproducibility by a firing atmosphere free from the influence of contamination by a binder component.
[0025]
The method for producing a non-oxide ceramic sintered body of the present invention, using the firing furnace,
A degreasing step in which the non-oxide ceramic molded body is heated to a temperature required for thermal decomposition of the binder in an inert gas atmosphere, and a non-oxidation after degreasing under a pressure condition higher than the atmospheric pressure in the inert gas atmosphere. Sintering step of heating the ceramic body to the sintering temperature required for sintering, and sintering the non-oxide ceramics at the above sintering temperature under the pressurized condition higher than the atmospheric pressure of the inert gas atmosphere May be provided.
[0026]
In this case, in the temperature raising step and the firing step after the degreasing step, in order to maintain a high pressurized state, gasification of the binder component remaining in the compact during the degreasing step is suppressed, and carbon is contained in the sintered body. Can be left. As a result, due to the high dispersibility of the binder, it is possible to obtain a sintered body of non-oxide ceramics uniformly containing a predetermined amount of carbon.
[0027]
The method for producing a non-oxide ceramic sintered body of the present invention, using the firing furnace,
A degreasing step in which the non-oxide ceramic body is heated to a temperature required for thermal decomposition of the binder in an inert gas atmosphere, and a step of sintering the degreased ceramic body under reduced pressure in an inert gas atmosphere. Even if it has a sintering step of firing the non-oxide ceramics at the firing temperature under a pressurizing condition higher than the atmospheric pressure of the inert gas atmosphere, and a heating step of heating to the required firing temperature. Good.
[0028]
In this case, a high vacuum state is set in the temperature raising step after the degreasing step, and the gasification of the binder component remaining in the compact during the degreasing step is promoted, so that the residual binder component in the sintered body can be suppressed. As a result, it is possible to obtain a non-oxide ceramic sintered body that does not leave carbon due to the binder component.
[0029]
In the method for producing a non-oxide ceramic sintered body of the present invention, in the degreasing step, the gas in the chamber is exhausted through the second exhaust pipe, and in the steps other than the degreasing step, the first exhaust is performed. It is desirable to exhaust the gas in the chamber through a tube.
[0030]
Further, the non-oxide ceramic is a non-oxide ceramic selected from the group consisting of silicon nitride, aluminum nitride, silicon carbide, and sialon, or a composite material of at least two or more non-oxide ceramics selected from the group. It may be.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
The firing furnace according to the present embodiment is a firing furnace capable of continuously performing the degreasing step and the sintering step, and is a firing furnace including an exhaust pipe for exhaust gas containing a binder component and an exhaust pipe for vacuum exhaust. . Hereinafter, the configuration of the firing furnace according to the present embodiment will be described with reference to FIG. Here, an example of a firing furnace for hot press sintering will be described, but the type of the firing furnace is not limited, and a firing furnace for normal pressure sintering without a pressing mechanism may be used.
[0032]
As shown in FIG. 1, the firing furnace according to the present embodiment has a chamber 10 that can be hermetically sealed and a heating chamber 12 installed in the chamber 10. The heating chamber 12 is surrounded by a heat insulating material such as a carbon fiber mat covered with a carbon composite plate, and a heater 14 such as graphite capable of heating at, for example, 2000 ° C. or higher is disposed inside the heating chamber 12. Note that the heating chamber 12 is not in a completely closed state, and the atmospheric pressure shows a value equal to that of the chamber 10. A cooling water pipe is provided on the outer wall of the chamber 10 and is cooled by circulation of the cooling water.
[0033]
A pressurizing mechanism 18 capable of pressurizing in an up-down uniaxial direction is fixed to a gantry 16 installed outside the chamber 10, and an upper ram 18 a connected to this pressurizing mechanism is provided at the center of the heating chamber 12. And the lower ram 18b. A ceramic molded body including a binder which is a non-sintered material is set in a mold 40 and mounted on a base of the lower ram 18b.
[0034]
A vacuum exhaust pipe (first exhaust pipe) 20 for vacuum exhaust is connected to the chamber 10, and the vacuum exhaust pipe 20 further includes one or more exhaust pumps such as a mechanical booster pump 22 and a rotary pump 24. Connected to pump. The inside of the chamber 10 including the heating chamber 12 can be made to have a high vacuum atmosphere by a rotary pump 24 and a mechanical booster pump 22 which is a pump for higher vacuum. The type and number of exhaust pumps to be used are not particularly limited, and it is also possible to use only a rotary pump. In addition, a diffusion pump or the like can be used instead of the mechanical booster pump 22. The evacuation pipe 20 may be connected to the heating chamber 12 instead of the chamber 10.
[0035]
On the other hand, the chamber 10 is provided with a pressure sensor 54 for monitoring the pressure in the chamber. Further, an inert gas introduction pipe is connected to the chamber 10 and, for example, nitrogen (N ₂ Inert gas such as gas is introduced into the chamber via the mass flow controller 50.
[0036]
Introducing the inert gas into the chamber is performed by uniformly arranging a plurality of inert gas inlet pipes in the circumferential direction at a position from the center to the lower part in the longitudinal direction of the chamber, and supplying an equal amount of inert gas from each inlet pipe. Preferably, it is introduced. By doing so, the binder can be uniformly removed from the molded body. Note that the inert gas introduction pipe may be connected to the heating chamber 12 instead of the chamber 10. Also in this case, in order to perform the binder removal uniformly, it is preferable to dispose a plurality of inert gas introduction pipes evenly in the circumferential direction below the heating chamber.
[0037]
The flow rate value of the mass flow controller is adjusted by a controller 52 having an automatic control circuit so that the pressure in the chamber 10 becomes constant in accordance with the value monitored by the pressure sensor 54.
[0038]
Further, a CO concentration meter 56 is installed in the chamber 10. According to the CO concentration meter 56, since the CO concentration in the chamber can be monitored, a change in the CO concentration accompanying the debinding process in the degreasing step can be monitored. Therefore, it is possible to accurately adjust the binder removal processing time for obtaining a desired binder removal state. In order to monitor the CO concentration, it is preferable to use a CO concentration meter 56 capable of measuring a CO concentration of several percent or less.
[0039]
The firing furnace according to the present embodiment further includes a degreasing exhaust pipe 30 (first exhaust pipe 30) which is a dedicated exhaust pipe for exhaust gas containing a binder component, which is directly connected to the inside of the heating chamber 12, separately from the above-described vacuum exhaust pipe 20. 2 exhaust pipes). The degreasing exhaust pipe 30 is connected to a cold trap 32 for collecting a binder component, and further connected to the rotary pump 24 downstream of the cold trap 32. The vacuum exhaust pipe 20 and the degassing exhaust pipe 30 are provided with electromagnetic on-off valves 21 and 33, respectively. In the degreasing step, the electromagnetic on-off valve 21 is closed, the electromagnetic on-off valve 33 is opened, and the degreasing exhaust pipe 30 is opened. In other steps, the electromagnetic on-off valve 21 is opened, the electromagnetic on-off valve 33 is closed, and the air is exhausted through the vacuum exhaust pipe 20.
[0040]
In addition, a heating means such as a band heater 31 is provided around the degreasing exhaust pipe 30 from the heating chamber 12 to the cold trap 32 to maintain the inside of the pipe at a high temperature to prevent the binder component from condensing. .
[0041]
In the cold trap 32, the liquid cooled by the chiller 34 circulates, cools the exhaust gas passing through the cold trap 32, liquefies and collects a binder component contained in the exhaust gas.
[0042]
The cold trap 32 is connected to the rotary pump 24 via an exhaust pipe 30a. Since most of the binder components in the exhaust gas are collected by the cold trap 32, contamination of the oil of the rotary pump 24 by mixing of the binder components hardly occurs.
[0043]
An exhaust pipe of the rotary pump 24 is connected to an exhaust gas combustion device 38 via an oil mist trap 36 that collects oil mist discharged from the rotary pump 24. A small amount of the binder component that cannot be collected by the cold trap 32 and remains in the exhaust gas is combusted by the exhaust gas combustion device 38 by a reaction with the air supplied from outside. Thus, the exhaust gas is exhausted to the outside after completely removing the organic odor.
[0044]
The degassing exhaust system including the degassing exhaust pipe 30 and the vacuum evacuation system including the vacuum exhaust pipe 20 may be completely independent, and each may be provided with a separate rotary pump, as shown in FIG. In addition, the rotary pump 24 and the exhaust system downstream thereof can be made common, which is preferable from the viewpoint of reducing equipment costs.
[0045]
According to the baking furnace according to the present embodiment described above, during the degreasing step, since the evacuation is performed using the degreasing exhaust pipe 30 directly connected to the heating chamber 12, the vacuum exhaust pipe 20, the mechanical booster 22, and the like are used. Can be prevented from being contaminated by the binder component.
[0046]
Further, the exhaust gas containing the binder component exhausted through the exhaust pipe 30 for degreasing passes through the rotary pump 24 after collecting the binder component by the cold trap 32, so that the contamination of the oil of the rotary pump can be prevented. Furthermore, since the exhaust pipe 30 for degreasing from the heating chamber 12 to the cold trap 32 is heated, the adhesion of the binder component to the exhaust pipe 30 for degreasing can be prevented. Therefore, according to the firing furnace according to the present embodiment, the contamination of the piping and the pump by the binder component is small, and the frequency of overhaul can be greatly reduced, so that the maintenance cost can be suppressed.
[0047]
On the other hand, since the binder component hardly adheres to the vacuum exhaust pipe 20 and the inner wall of the chamber 10, the firing atmosphere is not contaminated by the binder component, and a fired body of a constant quality can be manufactured with good reproducibility.
[0048]
The exhaust pipe 30 for degreasing is more preferably provided with a slope for the purpose of preventing the stagnation of the binder. Further, it is more preferable that the connection point of the degreasing exhaust pipe 30 to the heating chamber 12 is equally connected at two or more locations at the center when the heating chamber 12 is viewed in the vertical direction and at two or more places in the circumferential direction. By adopting such a configuration, the binder removal process from the molded body can proceed uniformly and evenly, which is effective as a measure against color unevenness of the sintered body.
[0049]
Although not shown, an auxiliary evacuation pipe may be provided between the chamber 10 and the mechanical booster 22 separately from the evacuation pipe 20. For example, by making the pipe diameter of the auxiliary evacuation pipe smaller than the evacuation pipe 20, the evacuation speed can be reduced. Therefore, when the object to be heated is powdery, slowly exhaust the evacuation with the auxiliary evacuation pipe. Thereby, scattering of powder due to rapid exhaustion can be prevented.
[0050]
Next, a method for manufacturing a non-oxide ceramics sintered body using the above-described firing furnace according to the present embodiment will be described. Here, taking aluminum nitride as an example, first, a method for producing a black aluminum nitride sintered body in which a trace amount of a binder component is left will be described.
[0051]
The aluminum nitride powder, the sintering aid yttria and the binder are mixed to prepare a slurry or a mixed powder, and various molding methods such as uniaxial pressure molding, CIP, slip casting, extrusion molding, and injection molding are used. Thus, a molded body containing a binder is produced. Although the shape of the molded body is not limited, for example, a disk-shaped molded body having a diameter of 200 mm to 350 mm and a thickness of about 10 mm is produced. The type of the binder is not limited. For example, an acrylic binder such as polyalkyl methacrylate is used.
[0052]
Next, the aluminum nitride molded body including the binder is set in the mold 40, and is placed on the pedestal of the lower ram 18b in the heating chamber 12 shown in FIG. An unillustrated upper punch, lower punch, sleeve, spacer, and the like are attached to the mold, and a plurality of molded bodies can be set. In order to efficiently and uniformly remove the binder from the compact, gas grooves may be provided on the side surfaces of the upper punch and the lower punch, or a porous carbon material such as C cloth may be used at the interface between the compact and the sleeve.
[0053]
The chamber 10 is sealed, and the inside of the chamber 10 is depressurized using an evacuation system for evacuation. That is, the electromagnetic on-off valve 33 of the exhaust pipe 30 for degreasing is closed, the electromagnetic on-off valve 21 of the vacuum exhaust pipe 20 is opened, and the inside of the chamber 10 is first pre-evacuated using the rotary pump 24. When the evacuation state is stabilized, evacuation by the mechanical booster pump 22 is started, and the inside of the chamber 10 is evacuated by the two pumps, the mechanical booster pump 22 and the rotary pump 24. Thus, the pressure inside the chamber 10 and the heating chamber 12 is reduced to about 0.06 Torr (8 Pa). By this decompression operation, moisture and oxygen adhering to the chamber 10 and the heating chamber 12 are gasified and exhausted, and at the same time, moisture and the like remaining in the compact are partially evaporated and exhausted.
[0054]
Next, nitrogen gas is supplied into the chamber 10 via the mass flow controller 50, and the pressure in the chamber 10 is set to about 15 Torr (2 × 10 ³ Adjust to Pa). The pressure in the chamber 10 is adjusted by monitoring the pressure in the chamber with the pressure sensor 54 and controlling the nitrogen flow set value of the mass flow controller 50 by the controller 52 having a control function based on this value. When the pressure in the chamber 10 is about 15 Torr (2 × 10 ³ When it is stabilized to about Pa), the degreasing step is started.
[0055]
In the degreasing step, the temperature of the molded body in the heating chamber 12 is raised to 500 ° C. to 600 ° C. in accordance with the decomposition temperature of the binder in the molded body, and the inside of the chamber 10 is heated to about 15 Torr (2 × 10 ³ The binder removal processing is performed while maintaining the nitrogen atmosphere of Pa). The decomposition product (binder component) of the binder decomposed and gasified during this time is exhausted by the rotary pump 24 via the degreasing exhaust pipe 30 directly connected to the heating chamber 12. Most of the exhausted binder component is liquefied in the cold trap 32 and collected.
[0056]
FIG. 2 is a graph showing an example of data of a vapor pressure curve of a binder component. For example, when polyalkyl methacrylate is used as a binder, a binder component gas such as n-butyl methacrylate or i-butyl methacrylate is generated by thermal decomposition. In order for these binder components not to condense in the exhaust pipe 30 for degreasing and to be efficiently collected by the cold trap 32, the temperature of the cold trap 32 must be determined by referring to the vapor pressure curve of each component shown in FIG. And the heating temperature of the exhaust pipe 30 for degreasing is determined. For example, referring to the graph of FIG. 2, the pressure in the exhaust pipe 20 for degreasing is 15 Torr (2 × 10 ³ In the case of Pa), it is preferable to set the temperature in the degreasing exhaust pipe 30 to about 60 ° C. or more in order not to condense any of the binder components described above. On the other hand, in order to collect these binder components by the cold trap 32, the binder components are cooled to a temperature at which the vapor pressure of these binder components can be reduced as much as possible, for example, 15 ° C. or lower, more preferably to the temperature of liquid nitrogen.
[0057]
Note that the remaining binder components that are not collected by the cold trap 32 are burned by the exhaust gas combustion device 38, so that the odor due to the organic components does not remain in the gas finally discharged to the outside.
[0058]
The binder removal processing time is shorter than usual and ranges from one hour to several hours. Accurate adjustment of the processing time is performed using the CO concentration meter 56 installed in the chamber 10. With the start of the binder removal processing, the CO concentration in the chamber 10 increases due to the decomposition of the binder, and the CO concentration eventually saturates. As the process proceeds further, the CO concentration decreases, and the binder removal ends. Therefore, by monitoring the CO concentration in the chamber 10 with the CO concentration meter 56, the progress of the binder removal can be accurately grasped. For example, when the concentration reaches a slightly higher concentration, for example, 0.01 to 1% by volume than the CO concentration at the time when the binder removal is completed, the binder removal processing is completed. That is, the process of maintaining the temperature of the heating chamber at 500 to 600 ° C., which is the binder removal condition, ends, and the process shifts to the temperature rising process to 1,600 to 1,900 ° C., which is the firing temperature. In this way, it is possible to accurately adjust the binder removal processing time required for allowing a fixed amount of the binder component to remain in the molded body.
[0059]
When the degreasing step is completed, the exhaust line is switched to a high vacuum line as required. That is, the electromagnetic on-off valve 33 of the degreasing exhaust pipe 30 is closed, and thereafter, the electromagnetic on-off valve 21 of the vacuum exhaust pipe 20 is opened and closed as required.
[0060]
In the case of automatically operating the firing furnace, an electric signal output from the CO concentration meter 56 is transferred to an automatic control device (not shown), where the CO concentration is monitored, and a preset CO concentration, for example, in this case, When the temperature reaches 0.01 to 1 vol%, the output of the heater 14 is automatically increased, and a transition operation is performed from a holding process at 500 ° C. to 600 ° C. to a heating process at a firing process at 1600 ° C. to 1900 ° C. To do. In addition, it is preferable to set such that the switching of the exhaust line and the pressure adjustment operation in the chamber, which will be described later, are simultaneously performed in conjunction with the shift operation.
[0061]
Subsequently, a nitrogen gas is introduced into the chamber 10 to evacuate the chamber to 1.5 atm (1.52 × 10 ⁵ The pressure is adjusted to Pa). While maintaining this pressurized state, the inside of the heating chamber 12 is heated to 1600 ° C. to 1900 ° C., which is a firing temperature required for sintering aluminum nitride. By maintaining the pressure in the chamber 10 at a high pressure of 1.5 atm in this way, the progress of gasification of the binder remaining in the aluminum nitride in a trace amount is suppressed, and carbon as a binder component is contained in the sintered body. Can be left.
[0062]
When the temperature of the heating chamber 12 reaches 1600 ° C. to 1900 ° C., the upper ram 18a and the lower ram 18b of the pressurizing mechanism 18 are operated, and the formed body placed in the mold 40 in the upper and lower uniaxial directions is, for example, 200 to 300 kg. / Cm ² And pressurize. Thus, 1600 ° C to 1900 ° C, 200 to 300 kg / cm ² Hot press sintering is carried out under the conditions described above for about 1 to 3 hours.
[0063]
When the sintering is completed, the pressurization by the upper ram 18a and the lower ram 18b is released, the inside of the heating chamber 12 is cooled, the inside of the chamber 10 is returned to the atmospheric pressure, and the sintered body is taken out.
[0064]
According to the above-described manufacturing method, in the degreasing step, the CO concentration meter 56 is used to accurately monitor the CO concentration in the chamber so that a predetermined amount of the binder remains in the molded body so that the binder removal processing time is reduced. In addition to the adjustment, after the degreasing step, the inside of the chamber 10 is maintained in a pressurized state, the temperature is raised to the sintering temperature, and the sintering is performed so that the amount of carbon in the aluminum nitride sintered body is, for example, about 800 ppm. Aluminum nitride can be obtained.
[0065]
As a method for producing a black aluminum nitride sintered body, there is a method of adding a metal powder or a carbon powder, and the like. Is uniformly mixed in the aluminum nitride molded body, so that even in the aluminum nitride sintered body obtained after sintering, carbon as a residual component of the binder can be uniformly left in the sintered body. Therefore, it is possible to manufacture aluminum nitride, which is a good black sintered body without color tone unevenness depending on places.
[0066]
Since the black aluminum nitride sintered body thus obtained has the effect of increasing the amount of radiant heat, it can be used as a base material of a ceramic heater or various ceramic base materials that provide an external aesthetic appearance that meets customer's preference. .
[0067]
Further, according to the above-described firing furnace shown in FIG. 1, the binder component does not adhere to the degreasing exhaust pipe 30 or the chamber 10. Therefore, unlike the related art, there is no problem such as contamination of the firing atmosphere due to the binder component attached to the exhaust pipe or the chamber, and a sintered body of aluminum nitride with good reproducibility can be manufactured.
[0068]
Next, a method for manufacturing another aluminum nitride sintered body will be described. Here, a method for producing a white or off-white aluminum nitride sintered body that does not leave a binder component in the sintered body, that is, contains almost no carbon will be described.
[0069]
As in the case of the above-described method for producing a black sintered body, the aluminum nitride molded body containing the binder is set in the mold 40, and the inside of the chamber 10 is evacuated to about 0.06 Torr (evacuation pipe 20). The pressure is reduced until the pressure reaches about 8 Pa). Thereafter, the exhaust line is switched from the vacuum exhaust pipe 20 to the exhaust pipe 30 for degreasing, and the degreasing step is started.
[0070]
In the degreasing step, the temperature of the compact in the heating chamber 12 is raised to 500 ° C. to 600 ° C. in accordance with the decomposition temperature of the binder in the compact, and the inside of the chamber 10 is adjusted to about 0.6 Torr (80 Pa). The binder removal treatment is performed for about 3 hours or more, which is sufficiently longer than the production conditions of the black sintered body. Specifically, the CO concentration in the chamber 10 during the binder removal process is monitored by the CO concentration meter 56, and the binder removal process is performed until the CO concentration reaches, for example, 0.1 vol% or less.
[0071]
During this time, the decomposed and gasified binder component is exhausted by the rotary pump 24 via the exhaust pipe 30 for degreasing. The exhausted binder component is collected by the cold trap 32, and the exhaust gas passing through the cold trap 32 is further exhausted to the outside via the rotary pump 24. The binder component remaining in the exhaust gas without being collected by the cold trap 32 is burned by the exhaust gas combustion device 38.
[0072]
When the degreasing step is completed, the exhaust system line is switched to a high vacuum line. That is, the electromagnetic on-off valve 33 of the exhaust pipe 30 for degreasing is closed, the electromagnetic on-off valve 21 of the vacuum exhaust pipe 20 is opened, and the mechanical booster pump 22 and the Evacuation is performed using the rotary pump 24. While maintaining this degree of vacuum, the inside of the heating chamber 12 is heated to 1600 ° C. to 1900 ° C., which is the firing temperature for sintering aluminum nitride. As described above, by keeping the inside of the chamber under reduced pressure after the degreasing step and raising the temperature to the firing temperature, a small amount of the binder component remaining in the molded body in the degreasing step is almost completely gasified.
[0073]
When the temperature of the heating chamber 12 reaches 1600 ° C. to 1900 ° C., nitrogen is introduced into the chamber 10 and 1.5 atm (1.52 × 10 ⁵ Pa). The upper ram 18a and the lower ram 18b of the pressing mechanism 18 are operated, and the compact placed in the mold 40 is, for example, 200 to 300 kg / cm. ² And hot press firing is performed for about 1 to 3 hours. When the sintering is completed, the pressurization by the upper ram 18a and the lower ram 18b is released, the inside of the heating chamber 12 is cooled, the inside of the chamber is returned to the atmospheric pressure, and the sintered body is taken out.
[0074]
Thus, it is possible to obtain an aluminum nitride sintered body in which almost no residual component of the binder remains. As in the above-described method for producing a black sintered body, according to the firing furnace shown in FIG. 1 described above, the exhaust pipe 30 for degreasing and the vacuum exhaust pipe 20 are separately provided, and the exhaust pipe for degreasing is further provided. No condensation of the binder component occurs in the chamber 30 or the chamber 10. Therefore, unlike the related art, there is no problem such as contamination of the firing atmosphere due to the binder component attached to the exhaust pipe, and a white or off-white aluminum nitride sintered body having good reproducibility can be manufactured.
[0075]
When a ceramic heater is manufactured using the above-described manufacturing method, a high heat-resistant metal wire such as molybdenum (Mo) is embedded as a resistance heating element in an aluminum nitride compact. When an electrostatic chuck is manufactured, a mesh-shaped Mo electrode may be embedded as an electrode in the aluminum nitride molded body.
[0076]
When burying a metal body in a ceramic sintered body such as a ceramic heater or an electrostatic chuck, once the metal body is buried in the molded body, removing the binder in the atmosphere causes oxidation of the metal. Not preferred. However, according to the above-described manufacturing method using the firing furnace shown in FIG. 1, since the process proceeds from the degreasing step to the firing step in an inert atmosphere, oxidation of the electrode can be prevented.
[0077]
The method of manufacturing an aluminum nitride sintered body using the firing furnace shown in FIG. 1 has been described above. However, the above-described firing furnace is made of silicon nitride, silicon carbide, sialon, or a composite of these non-oxide ceramics. It can be used as a firing furnace for sintering various non-oxide ceramics.
[0078]
For example, when producing a silicon nitride sintered body, silicon nitride powder and MgO, Al ₂ O ₃ And CeO ₂ Sintering aid powders are mixed, and a molded body containing a binder is produced using various molding methods. Thereafter, the compact including the binder is placed in the heating chamber 12 in the firing furnace shown in FIG. 1, and degreasing and sintering are performed in the same procedure as the above-described method. The sintering temperature and the sintering time in the sintering step are preferably 1700 ° C. to 1800 ° C., about 1 hour to several hours.
[0079]
In the case of producing a sintered body of Sialon, powders of silicon nitride, aluminum nitride, alumina or silicon dioxide and a binder are added, and a molded body is produced using various methods. Sintering is performed using firing conditions.
[0080]
Further, when producing a sintered body of silicon carbide, the sintering aid B ₄ A molded body containing a binder is produced using C, and then the molded body containing the binder is placed in the heating chamber 12 in the firing furnace shown in FIG. 1 and subjected to degreasing and firing in the same procedure as described above. Do. The sintering temperature and sintering time are 2,000 ° C. to 2200 ° C. for about 1 hour to 5 hours.
[0081]
The firing furnace for sintering non-oxide ceramics and the method for manufacturing a non-oxide ceramics sintered body according to the present invention have been described above in accordance with the embodiments and examples. It is not limited to the description of the examples. It will be apparent to those skilled in the art that various modifications and changes can be made.
[0082]
In the above-described example, the molded body is degreased and sintered. However, the present invention is not limited to the molded body, and the firing furnace of the present invention can be used for degreasing and sintering a granular body including a binder. Further, the firing furnace of the present invention can be used for sintering metal powders and metal molded bodies. If an acid-resistant material is used as a heat insulating material for the heater and the heating chamber of the firing furnace, it can be used for producing a sintered body of oxide ceramics.
[0083]
【The invention's effect】
As described above, according to the firing furnace of the present invention, the degreasing step and the sintering step of the compact can be performed in one firing furnace, so that the equipment cost can be reduced. Further, since the degreasing step and the sintering step can be performed consecutively, the manufacturing step can be shortened. Further, according to the firing furnace of the present invention, since the exhaust pipe for degreasing and the exhaust pipe for vacuum exhaust are independently provided, the inside of the high vacuum pipe can be kept clean. Therefore, the number of overhauls of the piping and the pump can be reduced, and the maintenance cost can be significantly reduced.
[0084]
Further, according to the method for manufacturing a ceramic sintered body of the present invention, since the degreasing step and the sintering step can be performed continuously, the manufacturing cost can be significantly reduced, and a clean firing atmosphere can be reproduced. The amount of carbon, which is a residual component of the binder, can be accurately adjusted, and a sintered body of stable quality can be produced with good reproducibility.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a firing furnace according to an embodiment of the present invention.
FIG. 2 is a graph showing a vapor pressure curve of a binder component.
[Explanation of symbols]
10 chambers
12 heating room
14 heater
16 base
18 Pressure mechanism
18a Upper ram
18b Lower ram
20 vacuum exhaust pipe
21 Solenoid on-off valve
22 Mechanical booster pump
24 Rotary pump
31, 31a Exhaust pipe for degreasing
32 cold trap
34 Chiller
36 Oil mist trap
38 Exhaust gas combustion device
40 mold
50 Mass flow controller
52 Controller
54 pressure sensor

Claims (14)

A sealable chamber;
A heating chamber provided in the chamber and having a heater;
A first exhaust pipe connected to the chamber or the heating chamber;
A first vacuum pump connected to the first exhaust pipe;
A second exhaust pipe directly connected to the heating chamber;
A collecting device connected to the second exhaust pipe, for collecting a binder component in the exhaust gas;
A second vacuum pump connected to the second exhaust pipe via the collection device. A gas supply pipe connected to the chamber or the heating chamber and supplying an inert gas into the chamber;
A pressure gauge or a pressure gauge for monitoring the pressure in the chamber;
The firing furnace according to claim 1, further comprising: a gas flow control device that adjusts a supply amount of the inert gas into the chamber according to a pressure in the chamber. The firing furnace according to claim 1, further comprising a CO concentration meter that monitors a CO concentration in the chamber or the heating chamber. The firing furnace according to any one of claims 1 to 3, further comprising a heating unit configured to heat the second exhaust pipe between the heating chamber and the collection device. 5. A combustion device connected to the second exhaust pipe via the trapping device and the second vacuum pump to burn an organic component in exhaust gas. Item 2. The firing furnace according to item 1. The said 1st vacuum pump and the said 2nd vacuum pump are one common rotary pump, The baking furnace of any one of Claims 1-5 characterized by the above-mentioned. The third vacuum pump for a higher vacuum than the first vacuum pump is interposed between the first exhaust pipe and the first vacuum pump. Item 2. The firing furnace according to item 1. The firing furnace according to any one of claims 1 to 7, further comprising a pressing mechanism configured to press a material to be sintered placed in the heating chamber in a uniaxial direction. The firing furnace according to any one of claims 1 to 8, wherein the heater is a graphite heater. A method for producing a non-oxide ceramics sintered body, wherein the degreasing step and the sintering step are performed continuously using the firing furnace according to claim 1. A degreasing step of heating the non-oxide ceramic molded body to a temperature required for thermal decomposition of the binder in an inert gas atmosphere;
A heating step of heating the degreased non-oxide ceramic molded body to a firing temperature required for sintering under a pressurized condition higher than the atmospheric pressure of an inert gas atmosphere,
The sintering step of firing the non-oxide ceramic at the firing temperature under a pressurized condition higher than the atmospheric pressure of an inert gas atmosphere, and a sintering step. The method of manufacturing the aggregate. A degreasing step of heating the non-oxide ceramic molded body to a temperature required for thermal decomposition of the binder in an inert gas atmosphere;
Under a reduced pressure condition of an inert gas atmosphere, the non-oxide ceramic body after degreasing is heated to a firing temperature required for sintering,
The sintering step of firing the non-oxide ceramic at the firing temperature under a pressurized condition higher than the atmospheric pressure of an inert gas atmosphere, and a sintering step. The method of manufacturing the aggregate. In the degreasing step, the gas in the chamber is exhausted through the second exhaust pipe,
The non-oxide ceramics sinter according to any one of claims 10 to 12, wherein in the steps other than the degreasing step, the gas in the chamber is exhausted through the first exhaust pipe. How to make the body. The non-oxide ceramic is one non-oxide ceramic selected from the group consisting of silicon nitride, aluminum nitride, silicon carbide, and sialon, or a composite material of at least two or more non-oxide ceramics selected from the group. A method for producing the non-oxide ceramic sintered body according to claim 10.

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