JP2011046562A - Setter for firing ceramic green sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive setter for firing a ceramic green sheet without including a process such as scattering or removal of powder on the surface of the setter in every firing of the ceramic green sheet and without causing breaking, strain, warpage or the deterioration in characteristics. <P>SOLUTION: An NiZn-based spinel ferrite layer 3 having thickness of 10-50 μm is formed on a ferrite sheet placing surface 2 having surface roughness wherein the center line average roughness of the setter 1 is 2-10 μm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a setter used for firing a ceramic green sheet used for manufacturing an electronic component, particularly a ferrite green sheet.

  In recent years, demands for smaller, lighter, and lower cost electronic components such as inductors, capacitors, and impedance elements are increasing. Especially when obtaining elements using ceramic materials, they are suitable for thinning elements. As a technique to do this, various ceramic green sheets are fired.

  A ceramic green sheet is a slurry obtained by uniformly stirring and mixing an organic binder, ceramic raw material powder, and a volatile dispersion medium on a carrier sheet typified by polyethylene terephthalate, and then drying it. It can be obtained by removing the volatile dispersion medium.

  In this manufacturing process, the volume occupied by the dispersion medium in the slurry is gradually reduced with drying. As a result, at the end of drying, the binder and the ceramic raw material powder are bonded to each other, and a uniform and dense ceramic green sheet is obtained.

  The ceramic green sheet is cut or divided into a desired shape, placed on a setter that is a stage on which the ceramic green sheet is placed during firing, and fired to obtain a ceramic sheet. Since the ceramic green sheet has homogeneity and density reflecting the uniformity of the slurry, the ceramic sheet obtained by firing can obtain a homogeneous structure.

  Ceramic sheets obtained by firing ceramic green sheets are various, depending on their use, such as thin films and thick films, all of which are free from defects such as cracks, cracks, warpage, and internal voids. Quality is required.

  However, since the thickness of the ceramic green sheet is as thin as several μm to 500 μm, the components of the ceramic green sheet are lost by diffusing to the setter surface, or the components of the setter enter the ceramic green sheet. As a result, the ceramic sheet may be cracked, distorted, warped or deteriorated in characteristics after firing.

  In particular, for example, Zn among the components contained in the ceramic green sheet has a great influence on the sintering temperature. The diffusion of Zn into the setter results in differences in the sintering shrinkage at each part of the ceramic green sheet, and the occurrence of cracks, distortions, and warpage may become more prominent.

Of the setter-containing components, for example, SiO ₂ has a great influence on the sintering temperature of the ceramic green sheet. Due to the diffusion of SiO _{2 into} the ceramic green sheet, the occurrence of cracks, distortions, and warping may be noticeable.

  Therefore, in order to stabilize the quality of the ceramic sheet, a ceramic green sheet using a setter with a surface layer formed of a surface powder of components contained in the ceramic green sheet or a setter with a surface formed with a zirconia coating layer is used. A technique for preventing the reaction between the setter and the ceramic green sheet by firing the ceramic is disclosed.

  Patent Document 1 discloses a method for preventing a reaction between a setter and a ceramic green sheet by using a setter in which a floor powder having almost the same composition as that of a material to be fired is placed in a groove provided on the setter surface. Yes.

  In Patent Document 2, a slurry containing a spread powder component is formed on a carrier sheet, a ceramic green sheet is formed and dried, and the ceramic green sheet peeled off from the carrier sheet is placed on a setter and fired. Discloses a method for preventing the reaction between the setter and the ceramic green sheet using a setter having a spreader layer formed on the setter surface.

  In Patent Document 3, after spraying zirconia on the setter surface, by firing, using a setter in which a zirconia coating layer having a predetermined centerline average roughness (Ra) and a predetermined porosity is formed, A method for preventing the reaction between the setter and the ceramic green sheet is disclosed.

  In Patent Document 4, a setter and a ceramic are formed by spraying zirconia on a setter surface to form a zirconia coating layer having a predetermined centerline average roughness (Ra) and a predetermined thickness. A method for reducing green sheet reaction is disclosed.

JP-A-4-331774 JP-A-4-42865 JP 2002-60277 A Japanese Patent No. 4024544

  As in the method disclosed in Patent Document 1, when firing is performed on a setter in which a bed powder having almost the same composition as the ceramic green sheet is pressed on the surface, the baking of the pressed bed powder proceeds. Phenomenon of falling off the floor powder occurs. Therefore, it is necessary to periodically remove and re-form the bed layer. In order to stabilize the quality of the ceramic sheet, there has been a problem that the process of spraying and removing the powder on the setter is required every time the ceramic ceramic green sheet is fired, and the work process becomes complicated.

  Next, in the method disclosed in Patent Document 2, after forming a ceramic green sheet containing a spread powder, the ceramic green sheet and the setter that form the spread powder layer are placed on the setter and fired. There has been a problem in that a bonding powder layer in which a coating powder is applied evenly on the setter surface after firing cannot be formed without sufficient bonding strength. In addition, repeated firing using this setter has a problem in that a phenomenon that the bed powder falls off occurs. Therefore, there is a problem that a ceramic sheet having a stable quality cannot be manufactured.

  Also, in the method of forming a zirconia coating layer on the setter surface by spraying zirconia on the setter surface disclosed in Patent Document 3, depending on the average roughness of the setter surface, a stable zirconia coating on the setter surface There was a problem that a layer was not obtained. Accordingly, there is a problem that zirconia is peeled off or dropped out even by repeated firing using this setter.

  Further, in the method of forming a zirconia coating layer by spraying on the setter surface disclosed in Patent Document 4, the durability can be improved by preventing the zirconia from peeling off or dropping off, but the production cost is reduced by performing the spraying. There was a problem of becoming higher.

  The present invention solves the above-mentioned problems and does not include a process of spreading and removing the spreader on the setter surface every time the ceramic green sheet is fired, causing cracks, distortion, warpage, and deterioration of characteristics. It is an object of the present invention to provide an inexpensive ceramic green sheet firing setter which can be fired without any trouble and can produce a ceramic sheet having a stable quality even after repeated firing.

  The present invention provides a sintered ceramic green sheet characterized in that a NiZn-based spinel ferrite layer having a thickness of 10 μm or more and 50 μm or less is provided on a surface having a center line average roughness (Ra) of 2 μm or more and 10 μm or less. It is a setter.

In the present invention, the NiZn-based spinel ferrite layer contains 0.02 to 1.5% by mass of Bi ₂ O _{3 in} the ceramic green sheet firing setter described above, It is.

  When firing a ceramic green sheet, particularly a ferrite green sheet, after forming a ferrite layer on the setter surface in order to prevent the reaction between the ferrite green sheet and the setter, or the mutual diffusion of component elements between the two, Alumina or zirconia powder was uniformly spread on the setter, and a ferrite green sheet was placed on the setter and fired. According to the present invention, the alumina and zirconia powder was spread on the setter each time the fired. This eliminates the need for a process to be performed and a process to be removed, thereby solving the problem that the work process becomes complicated.

  By providing a ferrite layer on the surface of the ceramic green sheet firing setter of the present invention, the reaction between the setter and the ferrite green sheet can be suppressed, so there is no difference in shrinkage due to fluctuations in the components of each part, It is possible to suppress cracking, distortion, warpage, and deterioration of characteristics in the ferrite sheet due to firing.

  By setting the thickness of the ferrite layer of the setter for firing a ceramic green sheet of the present invention to 10 μm or more and 50 μm or less, mutual diffusion of components between the setter and the ceramic green sheet can be sufficiently reduced, and the ferrite layer is thick. It is possible to prevent the ferrite layer from peeling off or falling off when it is too high.

  Like the ceramic green sheet firing setter of the present invention, by setting the surface roughness to a center line average roughness (Ra) of 2 μm or more and 10 μm or less, the fixing force between the setter surface and the ferrite layer is increased, and the setter of the ferrite layer is increased. Can be prevented from peeling or falling off, and the surface after firing is sufficiently smooth, and a ferrite sheet having a small surface warpage can be obtained.

  Further, it can be manufactured by an inexpensive method without using a high-cost thermal spraying technique as in the case of forming a zirconia coating layer on the setter surface.

By providing a ferrite layer having a Bi ₂ O ₃ content of 0.2% by mass or more and 1.5% by mass or less on the surface of the setter, an effect of promoting the sintering by Bi ₂ O ₃ occurs, The effect of eliminating the difference in shrinkage rate is obtained. That is, when a proper amount of Bi ₂ O ₃ component is diffused from the setter surface to the ferrite sheet side when the green sheet is fired, the surface of the fired ferrite sheet is warped, and an excellent fired ferrite sheet with little warpage is obtained.

  By firing the ferrite green sheet using the ceramic green sheet firing setter of the present invention, it becomes possible to prevent the reaction between the ferrite green sheet and the setter surface, or the mutual diffusion of the component elements between the two, cracking and A ferrite sheet with little distortion and warpage, high flatness and little characteristic variation can be obtained.

It is explanatory drawing of the setter for ceramic green sheet baking by this invention, FIG. 1 (a) is explanatory drawing of the setter surface. FIG. 1B is an explanatory diagram of the ferrite layer. It is explanatory drawing of the form which mounted the ferrite green sheet on the setter for ceramic green sheet baking by this invention.

  An embodiment for carrying out the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of a setter for firing ceramic green sheets according to the present invention, and FIG. 1 (a) is an explanatory view of a setter surface. FIG. 1B is an explanatory diagram of the ferrite layer.

  As shown in FIG. 1 (a), the setter 1 of the setter for firing ceramic green sheets of the present invention is manufactured by molding a 96% purity alumina mold. The ceramic green sheet mounting surface 2 is processed so that the surface roughness satisfies a center line average roughness (Ra) of 2 μm or more and 10 μm or less. By molding using a mold subjected to sandblasting, it has a fine surface roughness.

  As shown in FIG. 1B, the ceramic green sheet firing setter of the present invention has a ferrite layer 3 formed on the ceramic green sheet placement surface 2 of the setter 1. The ferrite layer 3 and the sintered ferrite green sheet desirably have the same components and composition, but need not necessarily be the same.

  The ferrite layer 3 is formed by applying a slurry obtained by uniformly stirring and mixing ferrite powder, a binder, and a volatile dispersion medium to the ferrite green sheet placement surface 2. The ferrite layer 3 is formed by heat treatment at a temperature of 800 ° C. or higher after slurry application. Printing, drying, and heat treatment are performed so that the thickness of the ferrite layer 3 is 10 μm or more and 50 μm or less after firing. The method for applying the ferrite layer is not limited to screen printing, and any method that can satisfy a thickness of 10 μm or more and 50 μm or less, such as dipping or spraying, may be used.

  FIG. 2 is an explanatory diagram of a form in which a ferrite green sheet is placed on a ceramic green sheet firing setter according to the present invention. A ferrite green sheet 4 is placed on the ferrite layer 3. The ferrite green sheet 4 is fired in this form to obtain a ferrite sheet.

  Here, the ferrite green sheet 4 is manufactured using a green sheet manufacturing apparatus. The slurry is obtained by determining the weight of the ferrite raw material powder, which is the main raw material, and then mixing and stirring the binder, the volatile dispersion, and the medium additive in a mixer.

  The ferrite green sheet is prepared by adjusting the height of the opening of the slurry discharge port of the green sheet manufacturing apparatus so as to obtain a desired coating film thickness, and applying it on the carry sheet. Such a slurry coating method is called a die slot method.

  Next, the ferrite green sheet is transported and dried at a constant speed in the drying zone of the green sheet manufacturing apparatus maintained at 60 ° C. and 80% relative humidity. The dried ferrite green sheet is peeled off from the carry sheet and cut. The ferrite green sheet that has been dried and cut is placed on the previously prepared ceramic green sheet firing alumina setter and fired to obtain a ferrite sheet.

  Ferrite green sheet firing setter is produced by providing a ferrite layer on an alumina setter having a different surface roughness by molding using a mold subjected to sandblasting, and then firing the ferrite green sheet, The warpage of the ferrite sheet after falling off and after firing was measured.

First, a ferrite slurry was prepared. 5 weight of polyvinyl butyral as an organic binder is added to the powder of Ni—Cu—Zn based ferrite having the chemical formula 27.5 (Ni _0.9 Cu _0.1 ) O-23.0ZnO-49.5Fe ₂ O ₃ In addition, 35 parts by weight of ethanol as a volatile dispersant, a small amount of a plasticizer and a thickener were added, and the mixture was mixed by a ball mill for 20 hours.

  Next, the setter was formed into a square having a thickness of 4 mm and a side of 200 mm using alumina having a purity of 96% using a molding die whose surface was sandblasted. The average surface roughness was Ra = 0.5, 2, 6, 10, 20 μm.

  As shown in FIG. 1 (a), a ferrite slurry is applied to each setter by screen printing on the ferrite green sheet mounting surface 2, and heat treatment is performed in the atmosphere at 900 ° C. for a holding time of 3 hours. A setter for firing a ferrite green sheet on which the ferrite layer 3 as shown in FIG. The average thickness of the ferrite layer after firing was six types of 5, 10, 30, 50, 60, and 100 μm.

  Next, the ferrite green sheet for mounting on these alumina green setters for baking and baking it was produced. The above-described ferrite slurry is discharged onto a polyethylene terephthalate film (hereinafter referred to as PET film) from a slurry discharge port having an opening width of 200 mm and an opening height of 0.8 mm of a die slot type green sheet manufacturing apparatus. A ferrite green sheet was produced by transporting and drying the inside of a drying zone maintained at a relative humidity of 80% at a constant speed.

  Next, as shown in FIG. 2, a ferrite green sheet 4 cut to a 40 mm square was placed on a ferrite green sheet placing surface 2 on various setters and fired. Firing conditions were as follows: a box-type electric furnace was used, and the temperature in the atmosphere was ascending rate 100 ° C./hour, holding temperature 1000 ° C., holding time 4 hours, and cooling rate 150 ° C./hour. The thickness of the sintered ferrite sheet was 0.4 mm.

  For the ferrite sheet, a total of 40 ferrite green sheets were fired for each setter and evaluated for cracking and flatness. The flatness was evaluated by detecting the maximum height when the ferrite sheet was allowed to stand on a surface plate with a laser displacement meter (Keyence Corporation KS-1100).

  The surface roughness of the setter before forming the ferrite layer was measured with a laser displacement meter. The thickness of the ferrite layer formed on the setter is the difference between the setter thickness before forming the ferrite layer and the setter thickness after the ferrite layer is formed on the setter surface and the ferrite layer forming surface is polished with a vertical polishing machine. did.

  As Example 1, a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 30 μm was provided on a setter having a center line average surface roughness (Ra) of 2 μm. As Example 2, a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 30 μm was provided on a setter having a center line average surface roughness (Ra) of 10 μm. In Example 3, a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 10 μm was provided on a setter having a center line average surface roughness (Ra) of 6 μm. Example 4 was a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 50 μm was provided on a setter having a center line average surface roughness (Ra) of 6 μm.

  Next, a comparative example will be described. As Comparative Example 1, a ferrite sheet fired with a setter in which a ferrite layer was not provided on a setter having a center line average surface roughness (Ra) of 0.5 μm. As Comparative Example 2, a ferrite sheet fired with a setter in which a ferrite layer was not provided on a setter having a center line average surface roughness (Ra) of 6 μm. As Comparative Example 3, a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 30 μm was provided on a setter having a center line average surface roughness (Ra) of 0.5 μm.

  As Comparative Example 4, a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 30 μm was provided on a setter having a center line average surface roughness (Ra) of 20 μm. As Comparative Example 5, a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 5 μm was provided on a setter having a center line average surface roughness (Ra) of 6 μm. As Comparative Example 6, a ferrite sheet fired with a setter having a thickness of 60 μm on a setter having an average surface roughness (Ra) of 6 μm. As Comparative Example 7, a ferrite sheet fired with a setter in which a ferrite layer having a thickness of 100 μm was provided on an alumina setter having a center line average surface roughness (Ra) of 6 μm.

  Table 1 shows the number of occurrences of peeling or dropping of the ferrite layers of various setters, and the average value of the maximum height of the ferrite sheets placed on the various setters and fired. The number of occurrences of peeling or dropping of the ferrite layer of various setters is the number of peeling or dropping of the ferrite layer after using 10 setters for 10 times firing. The measurement result of the average value of the maximum height in the ferrite sheet is the average value of the maximum height of 40 ferrite sheets, and represents the magnitude of warpage of the ferrite sheet.

  In Examples 1 and 2, no peeling off occurred in the ferrite layer of the setter. The maximum height was 0.6 mm or less, and an excellent ferrite sheet with small warpage of the ferrite sheet was obtained. By setting the center line average surface roughness (Ra) of the setter to 2 and 10 μm and the ferrite layer to 30 μm, the ferrite layer was stably formed on the setter, and a ferrite sheet with small warpage could be manufactured.

  In Examples 3 and 4, no peeling off occurred in the ferrite layer of the setter. The maximum height of the ferrite sheet was 0.6 mm or less, and an excellent ferrite sheet with small warpage of the ferrite sheet was obtained. By setting the center line average surface roughness (Ra) of the setter to 6 μm and the ferrite layer to 10, 50 μm, the ferrite layer was stably formed on the setter, and a ferrite sheet with small warpage could be produced.

  In Comparative Examples 1 and 2, since the ferrite layer is not provided on the setter, the ferrite layer is not peeled off, but the maximum height of the ferrite sheet is 1.2 mm, and the most warped of the produced ferrite sheets. It became bigger.

  In Comparative Example 3, the ferrite layer 30 μm was formed on a setter having a center line average surface roughness (Ra) of 0.5 μm, but peeling and dropping occurred in all of the 10 setters. This is probably because the alumina setter having a center line average surface roughness (Ra) of 0.5 μm has a surface that is too smooth and the ferrite layer has not been stably formed.

  In Comparative Example 4, a ferrite layer of 30 μm was formed on a setter having a center line average surface roughness (Ra) of 20 μm. However, since the surface roughness of the setter is too large, a ferrite layer with a uniform thickness cannot be formed on the setter surface. Did not.

  In Comparative Example 5, a ferrite layer of 5 μm was formed on a setter having a center line average surface roughness (Ra) of 6 μm. The ferrite layer was not peeled off, but the maximum height of the ferrite sheet was 1.1 mm, and the warpage of the ferrite sheet was increased. Since the thickness of the ferrite layer on the setter surface is too thin, there is no effect of providing a ferrite layer, and mutual diffusion of components occurs between the setter and the ferrite green sheet, and it is considered that the warpage of the ferrite sheet is increased.

  In Comparative Examples 6 and 7, ferrite layers 60 and 100 μm were formed on a setter having a center line average surface roughness (Ra) of 6 μm. Since the average thickness of the ferrite layer on the setter was too thick, the ferrite layer was cracked. In Comparative Example 6, one out of 10 ferrite layers and in Comparative Example 7 eight out of 10 ferrite layers were dropped.

  As described above, according to the setter having the ferrite layer having the thickness range of the present invention in the setter having the range of the center line average surface roughness (Ra) of the present invention, an excellent ferrite sheet was obtained.

Next, using a setter content of Bi ₂ O ₃ was coated with different ferrite slurry, to prepare a ferrite sheet. The center line average surface roughness (Ra) of the setter surface was 6 μm, and the thickness of the ferrite layer was 30 μm. As Example 5, a setter having a ferrite layer formed of a ferrite slurry having a Bi ₂ O ₃ content of 0.2% by mass was produced. As Example 6, a setter having a ferrite layer formed of a ferrite slurry having a Bi ₂ O ₃ content of 0.5% by mass was produced. As Example 7, a setter having a ferrite layer formed of a ferrite slurry having a Bi ₂ O ₃ content of 1.0 mass% was produced. As Example 8, a setter having a ferrite layer formed of a ferrite slurry having a Bi ₂ O ₃ content of 1.5% by mass was produced. As Comparative Example 8, a setter having a ferrite layer formed of a ferrite slurry having a Bi ₂ O ₃ content of 0% by mass was produced. As Comparative Example 9, a setter having a ferrite layer formed of a ferrite slurry having a Bi ₂ O ₃ content of 1.5% by mass was produced.

  Table 2 shows the number of occurrences of peeling or dropping of the ferrite layer of various setters and the average value of the maximum height of the ferrite sheet placed on the various setters and fired. The method for measuring the number of occurrences of peeling or dropping of the ferrite layers of various setters and the average value of the maximum height of the ferrite sheet is the same as described above.

  From the evaluation results shown in Table 2, the ferrite layers were not peeled off or dropped off in all the setters of Examples 5, 6, 7 and Comparative Examples 8 and 9. This is because the ferrite layer on the setter is optimized when the average thickness of the ferrite layer is 30 μm and the average surface roughness Ra of the setter surface is 6 μm.

However, paying attention to the measurement result of the average value of the maximum height in the fired ferrite sheet, in Examples 5, 6, and 7, an excellent fired ferrite sheet having a warp of 0.1 mm or less was obtained. Also in Example 8, it was 0.6 mm. In Comparative Example 8, it was 0.5 mm, but in Comparative Example 9, it was 0.9 mm. From these results, when the content of Bi ₂ O _{3 in} the ferrite layer formed on the setter surface was 0.2% by mass or more and 1.5% by mass or less, an excellent fired ferrite sheet with small warpage was obtained.

1 Setter 2 Ceramic green sheet placement surface 3 Ferrite layer 4 Ferrite green sheet

Claims (2)

  A setter for firing a ceramic green sheet, wherein a NiZn spinel ferrite layer having a thickness of 10 μm or more and 50 μm or less is provided on a surface having a surface roughness with a center line average roughness of 2 μm or more and 10 μm or less. Wherein the NiZn spinel ferrite layer, a ceramic green sheet for firing setter according to claim 1, characterized in that the _Bi 2 _{O 3} of 1.5 wt% or less than 0.02 mass% is contained.

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