JP2005195252A - Heating furnace wall, microwave firing furnace and ceramic electronic component manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating furnace wall 22 to be suitably used for microwave firing of ceramic compacts, having construction easily adaptable to different materials for fired objects W while holding uniform temperature distribution in a firing chamber 20 of a microwave firing furnace 1. <P>SOLUTION: The heating furnace wall 22 is detachably provided on the in-furnace surface of the firing chamber 20 of the microwave firing furnace. The heating furnace wall 22 comprises a heating element 24 having microwave absorbing property and a plate 23 for holding the heating element 24. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a microwave firing furnace that fires an object to be fired by microwaves, a heating furnace wall that constitutes the furnace inner surface of the firing chamber, and a method of manufacturing a ceramic electronic component using the microwave firing furnace.

  Conventionally, in a firing furnace such as an electric furnace or a gas furnace, it is necessary to gradually increase the temperature in the furnace so that there is no difference in the heating temperature between the surface and the inside of the body to be fired. It takes a long time to complete.

  In view of this, a microwave baking furnace has been proposed that heat-treats the body to be fired using microwaves so that the heating temperature does not differ between the surface and the inside of the body to be fired. In this microwave baking furnace, microwaves are uniformly absorbed regardless of the surface and inside of the body to be fired, so that there may be a difference in heating temperature between the surface and inside of the body to be fired during heat treatment. Few. As a result, the furnace temperature can be raised quickly rather than gradually, so that the time required for the heat treatment of the object to be fired can be shortened and uniform heat treatment can be performed.

  In such a microwave firing furnace, conventionally, the fired body is pseudo-completely surrounded by surrounding the fired body with a furnace wall having microwave absorption characteristics equivalent to the fired body. As a state of a proper heat insulating structure, a technique has been proposed in which a thermal gradient is prevented from being generated in a fired body by radiation cooling (see Patent Document 1).

  FIG. 11 shows an example of such a microwave baking furnace 1. Referring to FIG. 11, reference numeral 10 denotes a chamber, 11 and 11 denote chambers 10, respectively, and the microwave is transmitted to the inside of the chamber 10 on the lower surface of the figure via the respective waveguides 12 and 12. A microwave transmitter is shown.

  Reference numerals 13 and 13 denote stir mechanisms that are respectively attached to the left and right sides of the chamber 10 facing each other and that stir the both microwaves that have entered the chamber 10.

  The agitating mechanisms 13 and 13 include drive motors 14 and 14, rotary shafts 15 and 15 rotated by the drive motors 14 and 14, and fans 16 and 16 attached to the tips of the rotary shafts 15 and 15, respectively. It is comprised by.

Reference numeral 50 denotes a firing chamber that is placed between the fans 16 and 16 of the stirring mechanisms 13 and 13 in the chamber 10 and accommodates the body W to be fired. In the firing chamber 50, a layer 52 is configured by directly coating the inner surface of the ceramic heat insulating board 51 with a slurry made of the same material (mainly mullite-based material) as the body W to be fired.
JP 2002-130960 A

  The firing chamber 50 in the conventional microwave firing furnace shown in FIG. 12 is mainly used for firing mullite materials such as ceramics by microwave heating, and the slurry is directly coated on a commercially available alumina-silica heat insulation board 51. Thus, since the layer 52 can be formed, there is an advantage that it is easy to manufacture, but it is difficult to apply it to firing of the ceramic molded body.

  The reason will be described in detail. When the body to be fired W is a ceramic molded body, it is required to ensure a temperature environment state in which the internal temperature of the entire firing chamber 50 is precisely controlled. In order to ensure such a temperature environment state, it is conceivable to make the layer 52 thick.

  However, the thickening of the layer 52 is limited by the coating technique. Further, even if the layer 52 can be coated thickly, there is a great possibility that cracks or peeling will occur on the surface of the layer 52 or in the inside thereof, which will be impractical. Further, when the layer 52 is peeled off, heat generation unevenness occurs in the furnace wall of the firing chamber 50, and there is a problem that the temperature in the furnace cannot be maintained in the above temperature environment state.

  The thickness of the coating in layer 52 will be described. The coating thickness of the layer 52 was set to about 1 mm, and the temperature inside the firing chamber 50 was measured by a temperature sensor provided in the firing chamber 50. In this measurement result, the temperature variation in the firing chamber 50 was as large as 20 to 40 ° C. For this reason, the characteristics of ceramic molded bodies such as electronic parts fired in the firing chamber 50 having such temperature variations did not fall within practical standards.

  In addition, since there are many types of ceramic molded bodies, it is necessary to change the material type of the layer 52 to be coated on the heat insulating board 51 corresponding to the type of ceramic molded body.

  However, since the layer 52 is coated directly on the insulating board 51, the layer 52 alone cannot be replaced, and the entire insulating board 51 including the layer 52 needs to be replaced. Such replacement work is costly.

  The heating furnace wall according to the present invention includes a heating element having microwave absorption characteristics and a holding body for holding the heating element, and has a configuration that can be detachably attached to the furnace inner surface of the firing chamber of the microwave firing furnace. It is characterized by having.

  The holding body preferably includes a pair of plates as a configuration that can be detachably attached, and is configured by sandwiching a heating element between the pair of plates. And this holding body can be fitted into a groove or the like formed on the inner surface of the heat insulating board constituting the firing chamber, or it can be fixed to the inner surface of the heat insulating board with a fastener or the like. It can be made detachable with respect to the furnace inner surface of the firing chamber.

  In the present invention, the detachable structure of the holding body with respect to the furnace inner surface of the baking chamber is not limited to the above, and includes other detachable structures.

  The holding body is preferably composed of a plate having a void portion on the surface thereof, and the void portion of the plate is filled with a substance (slurry) having a microwave absorption characteristic equivalent to the fired body to form a heating element.

  In addition to using the same material as the material to be fired as a material for the heating element equivalent to the material to be fired, a micro-material having almost the same microwave absorption property as the material to be fired is used. Any material may be used as long as the material has wave absorption characteristics.

  A microwave baking furnace according to the present invention is a microwave baking furnace provided with a baking chamber for storing an object to be fired, wherein the heating furnace wall is provided on the furnace inner surface of the baking chamber. is there.

  A method for producing a ceramic electronic component according to the present invention is a method for producing a ceramic electronic component using the above-mentioned microwave firing furnace, wherein a ceramic molded body is stored as a body to be fired in a firing chamber of the microwave firing furnace. And firing the ceramic molded body by irradiating microwaves into the firing chamber.

  As a to-be-fired body, various ceramic molded bodies other than ceramics are mentioned. In addition, examples of a material for a heating element having a microwave absorption characteristic equivalent to a fired body include a mullite type, a silicon nitride type, and an alumina type.

  According to the method for manufacturing a heating furnace wall, a firing furnace, and a ceramic electronic component of the present invention, the heating furnace wall is detachably provided on the furnace inner surface of the firing chamber of the firing furnace, and the microwave absorption equivalent to the body to be fired is provided. It can be easily replaced with a heating furnace wall provided with a heating element having characteristics, and is suitable for microwave firing of a ceramic molded body having a large number of materials.

  In addition, the heating furnace wall is formed by holding a heating element having microwave absorption characteristics with a holding body, and the thickness of the heating element can be made sufficiently thick, so that cracks and peeling do not occur, and uneven heating is generated on the furnace wall. It does not occur, and the temperature distribution in the furnace can be made uniform.

  According to the heating furnace wall and firing furnace of the present invention, the temperature distribution in the furnace can be kept uniform, and the microwave absorption equivalent to the fired body can be easily accommodated to the difference in the material of the fired body. An object to be fired can be surrounded by a furnace wall having characteristics, and an effect of being suitable for microwave firing of a ceramic molded body can be obtained. In addition, according to the method for manufacturing a ceramic electronic component of the present invention, a good product with no variation in characteristics can be obtained.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as Example 1) will be described in detail with reference to the drawings.

  1 to 4 relate to Embodiment 1 of the present invention, FIG. 1 is a sectional view showing a schematic structure of a microwave baking furnace, and FIG. 2 is an enlarged view of a baking chamber disposed in the microwave baking furnace of FIG. 3 is an exploded perspective view showing a heating furnace wall constituting the firing chamber of FIG. 2, and FIG. 4 is a sectional view showing a sectional structure of the heating furnace wall of FIG.

With reference to FIG. 1, 1 shows the whole microwave baking furnace.
Reference numeral 10 denotes a chamber, and two microwave transmitters 11 and 11 are attached to the lower surface of the chamber 10 via the corresponding waveguides 12 and 12, respectively. On both the left and right side surfaces of the chamber 10 in the drawing, stirring mechanisms 13 and 13 for stirring the microwaves that have entered the chamber 10 from the microwave transmitters 11 and 11 are provided. A firing chamber 20 that houses the object to be fired W is disposed in the center of the chamber 10.

  The chamber 10 has a structure in which at least an inner surface reflects microwaves. Examples of the material that reflects the microwave include stainless steel, and the material can be appropriately selected.

  Both the microwave transmitters 11 and 11 transmit microwaves, respectively, and the frequency of the transmitted microwaves is, for example, about 0.9 to 100 GHz. The microwave transmitters 11 and 11 are disposed on the both sides of the lower surface of the chamber 10 via the waveguides 12 and 12 at a predetermined distance from each other on the drawing.

  The agitation mechanisms 13 and 13 are configured by drive motors 14 and 14, rotary shafts 15 and 15 thereof, and fans 16 and 16 attached to the tips of the rotary shafts 15 and 15, respectively.

  The firing chamber 20 includes a heat insulating board 21 having a hollow rectangular parallelepiped shape. A plurality of heating furnace walls 22 are provided on the inner surface of the heat insulating board 21. In addition, these heat generating furnace walls 22 are shown with the same code | symbol irrespective of the arrangement position with respect to the heat insulation board 21, for easy understanding of illustration.

  Each heating furnace wall 22 is shown only on the bottom surface, top surface, and left and right side surfaces, but is also provided on the front side and the back side. Therefore, although the front side and the back side in the firing chamber 20 are not shown in the figure, all these heating furnace walls are simply referred to as heating furnace walls 22. Although not shown in the drawing, the baking chamber 20 is preferably provided with an auxiliary heat insulating wall surrounding the baking chamber 20.

  The heat insulation board 21 is made of a material having heat insulation properties and microwave transmission properties, such as alumina fiber and foamed alumina. In the figure of the heat insulation board 21, the front side is a fitting door for taking in and out the body W to be fired. The door is not shown for simplicity of illustration.

  Thus, the heating furnace wall 22 is installed on all the furnace inner surfaces of the heat insulation board 21. The heating furnace wall 22 is attached to the furnace inner surface of the heat insulating board 21 by being fitted into a groove formed on the inner surface of the heat insulating board 21 so that the heat generating furnace wall 22 can be easily detached from the heat insulating board 21. Or it fixes with the fastener etc. which can be attached or detached easily.

  The structure of the baking chamber 20 will be described in detail with reference to FIGS.

  Each heating furnace wall 22 includes a pair of rectangular plates 23 and 23 facing each other as a holding body, a plate-like heating element 24 made of a heating material sandwiched between the plates 23 and 23, a plate 23, 23, a pair of outer frames 25 and 25 are joined together in a state in which a heat generating body 24 is included. Both outer frames 25, 25 are made of the same material as the plates 23, 23, for example. An alumina adhesive is used for bonding the plates 23 and 23 to the outer frames 25 and 25.

  In each heating furnace wall 22, both plates 23, 23 are formed of a material inferior in microwave absorption characteristics as compared with the body to be fired W. For example, both plates 23 and 23 are formed of alumina, zirconia, or the like.

  In each heating furnace wall 22, the plates 23, 23 are formed in a mesh shape. This is so that microwaves can easily pass from the outside of the baking chamber 20 to the inside of the baking chamber 20, and the heat of the heating element 24 can be quickly and easily transferred into the furnace by absorption of the microwaves. It is to do. The plate 23 may be a perforated plate or the like other than the mesh shape, or may be a simple flat plate having no holes or the like as long as microwaves and heat pass sufficiently.

Further, the heating element 24 is made of a material having a microwave absorption characteristic equivalent to that of the object to be fired W. For example, the same material as the body to be fired W is used as the material constituting the heating element 24. That is, when the ceramic molded body to be fired W to be fired by microwaves is made of, for example, a dielectric resonator (Zr, Sn) TiO ₄ based material, the (Zr, Sn) TiO ₄ based material generates heat. A heating element 24 is obtained by forming into a plate shape by using as a substance and further baking. In addition, you may form the heat generating body 24 using the material which is a different material from a ceramic molded body, and has a substantially the same microwave absorption characteristic.

  The heating element 24 is formed in such a size that a slight gap is formed between the plates 23 and 23 and the outer frames 25 and 25 in the housed state. This is to prevent the heat generating element 24 from coming into contact with the plates 23 and 23 and the outer frames 25 and 25 when the heat generating element 24 is thermally expanded during firing.

  Next, firing of the body to be fired W made of a ceramic molded body will be described.

  As for the to-be-fired body W, ceramic powder is press-molded in disk shape and degreased beforehand, for example. A large number of objects to be fired W are stored in the firing chamber 20. In this stored state, the motors 14 and 14 of the stirring mechanisms 13 and 13 are driven to rotate the fans 16 and 16. On the other hand, the microwave transmitters 11 and 11 are operated to introduce the microwave into the chamber 10. The microwave passes through the heat insulating board 21 in the baking chamber 20 and is absorbed by the heating element 24 and the object to be fired W. The microwave absorbed in this way is converted into thermal energy, and the temperature of the heating element 24 and the body to be fired W is raised.

  Temperature control in the furnace of the baking chamber 20 is performed by controlling the microwave output of the microwave transmitter 11 according to the temperature measurement value of the to-be-fired body W obtained using a radiation thermometer, for example. In the case of Example 1, specifically, the temperature in the furnace of the baking chamber 20 was set to 1350 ° C., and the temperature state was maintained for 2 hours for baking. Thereafter, the characteristics of the ceramic molded body thus produced were evaluated.

  According to the method of manufacturing a heating furnace wall, a firing furnace and a ceramic electronic component configured as described above, the heating furnace wall 22 is detachable from the furnace inner surface of the firing chamber 20 of the firing furnace 1, so Can be easily replaced in a short time with a heating furnace wall 22 having a heating element 24 made of a material having a microwave absorption characteristic equivalent to that of the object to be fired W. It becomes suitable for the microwave firing of the ceramic molded body containing the material.

  Further, the heating furnace wall 22 holds a heating element 24 made of a material having a microwave absorption characteristic equivalent to the body to be fired W by a plate 23, so that the thickness of the heating element 24 can be sufficiently increased. Cracks and peeling do not occur in the furnace wall 22, and heat generation unevenness does not occur in the heating furnace wall 22, and the furnace temperature distribution in the firing chamber 20 can be maintained uniformly.

  Specifically, when the thickness of the heating element 24 was about 3 mm, the temperature variation in the furnace due to the temperature sensor remained in the range of 5 to 10 ° C. This is because unevenness of heat generation is less likely to occur because the plate-like heating element 24 that does not cause the peeling phenomenon generates heat. Further, the fact that it is thicker than the coating and the calorific value is increased also has a positive effect on the uniform temperature distribution. As a result, the variation in the resonator characteristics after firing was small, and the effect of being within the standard was obtained.

  The heating furnace wall 22 is formed by sandwiching a heating element 24 between a pair of rectangular plates 23 and 23 serving as a holding body, and joining the plates 23 and 23 with an outer frame 25, thereby facilitating manufacture.

  Other embodiments will be described below.

  A second embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is a sectional view of the firing chamber of the firing furnace, FIG. 6 is a manufacturing process diagram of the heating furnace wall, and FIG. 7 is a perspective view of the heating furnace wall.

  The second embodiment is characterized by the heating furnace wall 32, and the overall structure of the firing furnace, the firing method of the body W to be fired, and the like are the same as the example described in the first embodiment.

  The production of the heating furnace wall 32 will be described.

As shown in FIG. 6, an alumina mesh plate 33 serving as a holding body was immersed in a slurry 34 made of a (Zr, Sn) TiO ₄ material serving as a heating element, followed by drying and degreasing steps. As a result, the slurry 34 was sintered and filled between the meshes serving as the voids, and a heating furnace wall 32 close to a state where the entire mesh plate 33 was made of a heating material was obtained.

  Similarly to the first embodiment, the heating furnace wall 32 configured in this way is detachably installed on the four sides of the heat insulating board 31 and the top and bottom surfaces in total. As a result of accommodating the object to be fired W in the firing chamber 30 and performing microwave firing, the same effects as in Example 1 were obtained.

  A heating furnace wall 32 formed by filling and firing slurry 34 serving as a heating element in the mesh plate 33 is sandwiched between the plates 23 instead of the heating element 24 of the heating furnace wall 22 shown in the first embodiment, and the heating furnace is provided. It may be a wall.

  In addition, the holding body is not limited to the mesh plate 33, and may be formed of a plate having a void portion including a concave portion whose surface is filled with the slurry 34, for example.

  Next, a third embodiment of the present invention will be described with reference to FIGS.

  FIG. 8 is a sectional view of the firing chamber of the firing furnace, FIG. 9 is an exploded perspective view of the heating furnace wall, and FIG. 10 is a sectional view of the heating furnace wall.

  The third embodiment is characterized by the heating furnace wall 42, and the overall structure of the firing furnace, the firing method of the body W to be fired, and the like are the same as the example described in the first embodiment.

  The production of the heating furnace wall 42 will be described.

  The heating element 26 is made of a material having microwave absorption characteristics equivalent to the body to be fired W. In this embodiment, for example, a PTC thermistor material mainly composed of barium titanate is used as the heating element 26. As the shape sandwiched between the mesh-like plates 23, a disc-like PTC thermistor after firing produced as a product was used as it was. Thereby, like Example 1, the effort which shape | molds in plate shape can be abbreviate | omitted and cost reduction can be achieved.

  The heating furnace wall 42 is formed by sandwiching a plurality of heating elements 26 between a pair of rectangular plates 23 and 23 serving as a holding body, and joining the plates 23 and 23 with outer frames 25 and 25.

  Similarly to the first embodiment, the heat generating furnace wall 42 configured in this manner is detachably installed on the four sides of the heat insulation board 41 and the top and bottom surfaces in total.

  And as a result of accommodating the to-be-fired body W in the baking chamber 40 and carrying out microwave baking, the same effect as Example 1 was acquired.

In each of the above embodiments, the ceramic electronic component is a dielectric resonator, and the ceramic molded body to be fired W is made of (Zr, Sn) TiO ₄ based material, or the ceramic electronic component is a PTC thermistor. However, the ceramic molded body to be fired W is exemplified by a barium titanate material. However, the present invention is not limited thereto, and the heating element is a material having microwave absorption characteristics equivalent to that of the fired W. Can be used as appropriate.

  The present invention relates to a firing furnace for firing a ceramic molded body constituting a ceramic electronic component such as a dielectric resonator or a PTC thermistor by microwaves, a heating furnace wall of the firing chamber, and a method for producing a ceramic electronic component using the firing furnace. Useful as.

Schematic cross-sectional view of a microwave baking furnace according to Example 1 of the present invention Sectional drawing of the baking chamber of the microwave baking furnace which concerns on the same Example 1 The exploded perspective view of the heating furnace wall of the microwave baking furnace which concerns on the same Example 1 Sectional drawing of the heating furnace wall of the microwave baking furnace which concerns on the Example 1 Sectional drawing of the baking chamber of the microwave baking furnace which concerns on Example 2 of this invention Manufacturing process diagram of heating furnace wall of microwave firing furnace according to Example 2 The perspective view of the heating furnace wall of the microwave baking furnace which concerns on the same Example 2 Sectional drawing of the baking chamber of the microwave baking furnace which concerns on Example 3 of this invention. The exploded perspective view of the heating furnace wall of the microwave baking furnace which concerns on the same Example 3 Sectional drawing of the heating furnace wall of the microwave baking furnace which concerns on the same Example 3 Schematic cross-sectional view of a conventional firing furnace Sectional view of the firing chamber of a conventional firing furnace

Explanation of symbols

1 Microwave firing furnace 20, 30, 40 Firing chamber 22, 32, 42 Heating furnace wall 23 Plate (holding body)
24, 26 Heating element 33 Mesh plate (holding body)
34 Slurry (heating element)
W To-be-fired body (ceramic molded body)

Claims (5)

A heating element having microwave absorption characteristics;
A holding body for holding the heating element,
A heating furnace wall characterized by having a structure that can be detachably attached to a furnace inner surface of a firing chamber of a microwave firing furnace.   The heating furnace wall according to claim 1, wherein the holding body is composed of at least a pair of plates, and the heating element is sandwiched between the pair of plates.   The heating element according to claim 1, wherein the holding body is made of a plate having a gap portion on a surface thereof, and the gap portion of the plate is filled with a substance having microwave absorption characteristics to form the heating element. Furnace wall. A microwave firing furnace having a firing chamber for storing a body to be fired,
4. A microwave firing furnace characterized in that the heating furnace wall according to any one of claims 1 to 3 is provided on a furnace inner surface of the firing chamber. A method for producing a ceramic electronic component using the microwave firing furnace according to claim 4,
In the firing chamber of the microwave firing furnace, a step of storing a ceramic molded body as a fired body,
And a step of irradiating microwaves into the firing chamber to fire the ceramic molded body.

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