JP2005263538A - Method for manufacturing composite ceramic sheet and method for manufacturing ceramic electronic parts using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a large decrease in yield of electronic parts due to short circuit failure caused by a metallic component having seeped into a ceramic sheet. <P>SOLUTION: A composite ceramic sheet having high strength and high density is prepared by filling a vehicle containing at least an organic substance into the void parts of and on the surface of a ceramic sheet which contains a ceramic powder and a polyolefin and has voids at the inside. By using the composite ceramic sheet, a ceramic electronic part with little short circuit failure can be provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a composite ceramic sheet used for producing a multilayer ceramic capacitor, for example, and a method for producing a ceramic electronic component using the same.

  FIG. 2 is a partial cross-sectional perspective view of a general multilayer ceramic capacitor 11, in which ceramic dielectric layers 12 and internal electrodes 13 are alternately stacked to form a multilayer body, and the internal electrode 13 has a multilayer body at its end surface. Are stacked so as to be alternately exposed at both opposite end faces, and are alternately connected to a pair of external electrodes 14 formed on both end faces of the laminate.

  A conventional method for manufacturing a multilayer ceramic capacitor will be described below.

  First, a ceramic sheet formed by adding polyethylene to dielectric powder mainly composed of barium titanate to be the ceramic dielectric layer 12 is prepared, and a metal paste to be the conductor layer 13 is formed thereon by a printing method. Print in the shape of. Next, a plurality of ceramic sheets on which the conductor layer 13 is produced are laminated so that the conductor layers 13 are alternately opposed to each other with the ceramic sheet interposed therebetween to obtain a laminate.

  Then, this laminated body was baked, and the external electrode 14 was formed on both end faces where the conductor layer 13 was exposed.

For example, Patent Document 1 is known as prior art document information relating to a method of directly producing a green sheet from a raw material without using a carrier sheet in relation to the invention of this application.
JP 55-19562 A

  When a ceramic sheet is formed using polyethylene as a binder as described above, the carrier is compared with a raw sheet obtained by coating (casting) a ceramic slurry on a carrier sheet such as a commonly used polyester film. While there is an advantage that the sheet is unnecessary and the thickness is 10 μm or less, the ceramic sheet is strong enough to be handled alone, while the ratio of voids present in the ceramic sheet tends to be large, When the metal paste is printed directly on the ceramic sheet, the metal component penetrates into the ceramic sheet. Further, since the binder is polyethylene, the adhesive strength of the ceramic sheet is low, and there is a problem that internal structural defects are likely to occur unless the heating and pressurizing conditions during lamination are precisely controlled.

  In recent years, in order to achieve higher capacity of multilayer ceramic capacitors, the ceramic sheet has been made thinner, and it is necessary to thoroughly suppress the intrusion of metal components in addition to high strength. This is because there is a problem that the conductor layers are short-circuited by the metal component infiltrated into the ceramic sheet to cause a short circuit failure of the multilayer ceramic capacitor.

  Accordingly, an object of the present invention is to provide a composite ceramic sheet with few short-circuit defects after lamination, a manufacturing method thereof, and a ceramic electronic component using the same even if the sheet is thinned.

  In order to achieve this object, the present invention has the following configuration.

  The invention according to claim 1 of the present invention includes a first step of preparing a ceramic sheet containing ceramic powder and polyolefin and having voids therein, and a second step of preparing a vehicle solution containing at least an organic substance, A method of manufacturing a composite ceramic sheet comprising a void portion of the ceramic sheet and a third step of filling the vehicle solution on the surface, and the metal component is ceramic even if a metal paste is printed on the obtained ceramic sheet. It is possible to provide a composite ceramic sheet that can suppress intrusion into the sheet and significantly reduce short-circuit defects in a ceramic electronic component using the composite ceramic sheet.

  The invention according to claim 2 is a first step of preparing a ceramic sheet containing ceramic powder and polyolefin and having voids therein, a second step of preparing a vehicle solution containing at least an organic substance, and the ceramic sheet A third step of applying the vehicle solution thereon, a fourth step of forming a conductor layer on the composite ceramic sheet obtained by the third step, and the conductor layer sandwiching the composite ceramic sheet. A ceramic electronic component manufacturing method comprising a fifth step of stacking a plurality of sheets so as to face each other to obtain a laminate and a sixth step of firing the laminate, and providing a ceramic electronic component with few short-circuit defects can do.

  The invention described in claims 3 and 4 is characterized in that the organic substance contains at least a polyvinyl butyral resin, can provide a method for producing a high-strength and high-density composite ceramic sheet, and has few short-circuit defects. A ceramic electronic component can be provided.

  The invention according to claims 5 and 6 is characterized in that the organic substance does not dissolve a ceramic sheet containing ceramic powder and polyolefin and having voids therein, and is a composite ceramic sheet having high strength and high density. A manufacturing method can be provided, and a ceramic electronic component with few short-circuit defects can be provided.

  Invention of Claim 7 provides the process of heating and pressurizing the composite ceramic sheet obtained at a 1st process and reducing a space | gap before the 2nd process of preparing the vehicle to apply | coat. This is a method for producing a composite ceramic sheet. A ceramic sheet containing polyolefin has a void of about 60% by volume. After coating the vehicle, the ceramic sheet is heated and pressurized to form a void of 15% to 35% by volume. % Can be reduced. As a result, a high-strength, high-density ceramic sheet can be produced.

  According to an eighth aspect of the present invention, in the step of heating and pressurizing the composite ceramic sheet obtained in the first step before the second step of preparing the vehicle to be coated to reduce the voids, two composite ceramic sheets are provided. A method for producing a composite ceramic sheet according to claim 7, wherein the composite ceramic sheet is heated and pressed by being sandwiched between rolls, and the composite ceramic sheet can be continuously heated and pressed. A sheet can be produced.

  The invention according to claim 9 is a step of reducing the voids by heating and pressurizing the composite ceramic sheet obtained in the first step between two rolls before the second step of preparing the vehicle to be applied. 9. The method for producing a composite ceramic sheet according to claim 8, wherein one of the two rolls has a temperature equal to or higher than a softening point of the polyolefin and a temperature of the other roll equal to or lower than the softening point of the polyolefin. In addition, since the composite ceramic sheet can be continuously heated and pressed at a high temperature without being cut, a high-strength and high-precision ceramic sheet can be produced with high mass productivity.

  Invention of Claim 10 provides the process of heating and pressurizing the composite ceramic sheet obtained at a 1st process and reducing a space | gap before the 2nd process of preparing the vehicle to apply | coat. This is a method for producing a ceramic electronic component, which can produce a high-strength, high-density ceramic sheet and can provide a ceramic electronic component with few short-circuit defects.

  According to the eleventh aspect of the present invention, in the step of heating and pressurizing the composite ceramic sheet obtained in the first step before the second step of preparing the vehicle to be coated to reduce the voids, two composite ceramic sheets are provided. A method for producing a ceramic electronic component according to claim 10, wherein the ceramic electronic component is heated and pressurized by being sandwiched between rolls, and a ceramic sheet having a high strength and a high density can be produced with high mass productivity, and the short-circuit defect is small. Can be provided with high productivity.

  The invention according to claim 12 is a step of reducing the gap by heating and pressurizing the composite ceramic sheet obtained in the first step between two rolls before the second step of preparing the vehicle to be applied. The temperature of one of the two rolls is not less than the temperature of the softening point of the polyolefin, and the temperature of the other roll is not more than the temperature of the softening point of the polyolefin. This is a manufacturing method that can be continuously heated and pressed at a high temperature without cutting the composite ceramic sheet, so that it is possible to produce a high-strength, high-density ceramic sheet with high mass productivity, and there are few short circuit defects. Parts can be provided with high productivity.

  The invention according to any one of claims 13 to 14 includes a method for producing a composite ceramic sheet according to claim 1 and a ceramic electronic component according to claim 2, wherein the polyolefin has a network structure and the polyolefin and the ceramic powder are present in layers. Provided is a method for manufacturing a composite ceramic sheet, which is a manufacturing method, has high sheet strength and is easy to handle, and facilitates uniform distribution of ceramic slurry, and can further reduce short-circuit defects when laminated using this sheet. It is also possible to provide a ceramic electronic component with few short-circuit defects.

  The composite ceramic sheet of the present invention contains ceramic powder and polyolefin, and has a high strength but a ceramic sheet surface having voids inside, and is filled with a vehicle containing organic matter, so that a high strength and high density ceramic sheet is produced. It is possible to suppress the intrusion of metal components into the ceramic sheet even if a metal paste is printed on this, so that it is possible to suppress short-circuit defects and greatly improve the yield of electronic components. Is what it brings. Further, the filling of the highly adhesive vehicle can remarkably improve the adhesive strength of the ceramic sheet, and therefore can suppress the occurrence of internal structural defects such as delamination.

(Embodiment)
Hereinafter, the invention according to the first to fourteenth aspects of the present invention will be described using an embodiment as an example of a multilayer ceramic capacitor.

  FIG. 1 is a cross-sectional view showing a production process of a ceramic sheet according to an embodiment of the present invention. The construction is such that the surface of a ceramic sheet 1 mainly composed of barium titanate powder and polyethylene is heated and a pressure roller 2 is used. After reducing the voids in the ceramic sheet by treating with the above, the vehicle solution 3 composed of a binder resin, a plasticizer, and a solvent is applied by the transfer roller 4 and the organic material composed of the above-mentioned vehicle solution on the surface of the ceramic sheet. The composite ceramic sheet 7 having a small amount of voids and high strength is obtained by filling 5 and drying with a dryer 6.

  First, a ceramic sheet 1 having a thickness of 3 μm is prepared using a polyethylene resin having a weight average molecular weight of 400,000 and a ceramic raw material powder mainly composed of barium titanate having an average particle diameter of 0.5 μm. This ceramic sheet 1 is a void having a porosity of 65%, 80% or more of the voids having a diameter of 0.1 μm or more, and an ultra-high molecular weight polyolefin resin is oriented in a network structure to serve as a polyethylene resin and a filler. The ceramic powder has a high strength because it has a so-called matrix structure in which the ceramic powder is present in layers. Furthermore, because of the structure in which the resin and ceramic powder are present in layers, defects such as pinholes found in general ceramic sheets obtained by coating ceramic slurry on a support film even when the sheet thickness is reduced Less is.

  The ceramic sheet is heated and pressed from both sides using the pressure roller 2 to reduce the porosity of the ceramic sheet to 25%.

  The temperature of the upper roller of the heating and pressure roller is 130 to 150 ° C, and the temperature of the lower roller is 80 to 120 ° C.

  When the temperature of the heating and pressure roller is higher than the softening temperature of polyethylene of 130 ° C, the porosity tends to decrease, but the ceramic sheet is likely to be cut by pressurization, so the temperature of the lower roller is made lower than the softening temperature of polyethylene. The ceramic sheet can be made difficult to cut.

  The pressure applied to the ceramic sheet by the heating and pressure roller is in the range of 100 to 300 kg / cm per roller length.

  Pressurization may increase the density of the ceramic sheet and cause elongation in the width direction, but there is no problem as long as thickness variation does not occur. However, if the pressure is too high, the sheet will be damaged, and 100 to 200 kg / cm is more preferable.

  On the other hand, a vehicle solution 3 made of a solvent such as polyvinyl butyral resin, phthalate ester, or butyl acetate is prepared. Since polyvinyl butyral resin tends to be agglomerated, it is preferable to filter the vehicle in advance using a filter having a diameter of 1 μm or less to remove the agglomerated resin.

  The solvent in the vehicle solution 3 does not dissolve the polyethylene resin, and it is important to mix at least one organic component in the vehicle solution 3 that softens at a lower temperature than the polyethylene resin.

  By setting it as this structure, the ceramic sheet | seat which maintains the property of a ceramic sheet | seat uniformly and is excellent in the adhesiveness of the sheet | seat at the time of lamination | stacking can be produced.

  Next, this vehicle solution is roller-transferred onto the ceramic sheet 1 using the transfer roller 4 and coated, and the organic substance 5 made of the vehicle liquid is filled in the gaps and surfaces of the surface portions of both surfaces and dried. At this time, the filling amount of the organic substance 5 can be controlled by the vehicle concentration, viscosity, roller peripheral speed and the relative speed of the ceramic sheet, and the organic substance 5 with respect to 100% by weight of the ceramic sheet can be selected by selecting the above conditions. 4% by weight.

  Further, if the solvent remains in the composite ceramic sheet 7 after drying, the sheet is stretched at the time of lamination. Therefore, the drying must be performed so that the residual solvent in the entire ceramic sheet is 1% by weight or less. .

  The porosity of the ceramic sheet after drying can be reduced to about 2% to 10%. A nickel paste to be a conductor layer is printed on the sheet in a pattern and dried. In addition to nickel powder, the nickel paste contains a resin component such as polyvinyl butyral and acrylic and a solvent component such as butyl acetate.

  The particle size of the nickel powder is in the range of 0.1 μm to 0.4 μm.

  Further, as a comparative example by a conventional method without using the method of the present invention, a ceramic sheet having a porosity of 65% was similarly printed with a nickel paste in a pattern.

  The two types of ceramic sheets printed with the nickel paste are prepared, and each of the 150 sheets is stacked and stacked under the conditions of 100 ° C. and 10 MPa. The temperature at the time of lamination | stacking can be performed above the temperature which the organic substance 5 softens, and below decomposition temperature.

  Furthermore, this pressurization is performed in the range of 90 ° C. to 150 ° C. and 10 MPa to 60 MPa. It is important that the temperature at this time is higher than the softening point of the organic substance 5 and within a temperature range not exceeding 20 ° C. higher than the softening point of the polyethylene resin. Moreover, as a method of this pressurization, an isostatic press is preferable.

  Next, the two types of laminates are cut into 3.2 mm × 1.6 mm, fired at 1300 ° C. using nitrogen and hydrogen, and copper external electrodes, nickel plating treatment, and tin plating treatment on both end faces of the sintered body. To obtain a multilayer ceramic capacitor sample.

  When the thickness of the ceramic layer after firing was measured, all the samples were 2.5 μm.

For the above two types of multilayer ceramic capacitors, use an insulation resistance meter to determine that the measured voltage is 10V and the resistance value is 10 ⁶ Ω or less. The comparison of the short-circuit rate is shown in (Table 1).

  (Table 1) shows that the short-circuit rate is sufficiently reduced in the present invention. In addition, when analyzing the short-circuited portion generated in the conventional method, it is confirmed that nickel penetrates the ceramic layer, and the reduction of the short-circuit rate in the present invention is due to the suppression of such nickel penetration. It was confirmed that there was. Further, in the sample according to the embodiment of the present invention, no defects such as delamination were observed inside the sintered body, but in the sample of the comparative example obtained by the conventional method, 15 of 100 delaminations were observed. It was.

  In this embodiment, the thickness of the fired ceramic is 2.5 μm. However, when the thickness after firing is 3 μm or less and particularly 2 μm or less, the effect of reducing the short-circuit rate is remarkably exhibited. is there.

  In the present embodiment, both surfaces of the ceramic sheet 1 are filled with the organic material 5 made of the vehicle liquid. However, the same effect can be obtained even when the organic material 5 is formed on one side of the front or back surface of the ceramic sheet 1. Furthermore, when the vehicle liquid is impregnated in the vehicle liquid and then the vehicle liquid on the surface is wiped off, and the organic material consisting of the vehicle liquid is filled only inside the ceramic sheet, or the organic material is applied only to the surface of the ceramic sheet using the transfer method. The same effect as described above can be obtained even when the is filled.

  As the vehicle solution, an organic material is used, but the vehicle may contain ceramic powder.

  Moreover, although embodiment using polyethylene resin as polyolefin was described, it is not limited to polyethylene resin, For example, the same effect is acquired even when polyolefin resin, such as a polypropylene, is used.

  Further, the multilayer ceramic capacitor has been described as an example, but the same effect can be obtained in a ceramic electronic component such as a varistor, thermistor, multilayer board, or filter.

  The composite ceramic sheet according to the present invention can produce a high-strength and high-density ceramic sheet, and even if a metal paste is printed thereon, the metal component is prevented from entering the ceramic sheet. Therefore, it has the effect of suppressing short-circuit defects and is useful for electronic parts having a laminated structure.

Sectional drawing which shows the production process of the ceramic sheet in Embodiment 1 of this invention Partial sectional perspective view of multilayer ceramic capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramic sheet 2 Heating and pressure roller 3 Vehicle solution 4 Transfer roller 5 Organic substance 6 Dryer 7 Composite ceramic sheet 11 Multilayer ceramic capacitor 12 Ceramic dielectric layer 13 Conductor layer 14 External electrode

Claims (14)

A first step of preparing a ceramic sheet containing at least ceramic powder and polyolefin and having voids therein; a second step of preparing a vehicle solution containing at least a binder and a plasticizer; And a third step of applying the vehicle solution to the surface of the ceramic sheet. A first step of preparing a ceramic sheet containing at least ceramic powder and polyolefin and having voids therein; a second step of preparing a vehicle solution containing at least a binder and a plasticizer; A third step of applying a vehicle solution to the surface of the ceramic sheet; a fourth step of forming a conductor layer on the composite ceramic sheet obtained by the third step; and the conductor layer sandwiches the composite ceramic sheet. A method of manufacturing a ceramic electronic component comprising a fifth step of stacking a plurality of sheets so as to face each other and obtaining a laminate, and a sixth step of firing the laminate. The method for producing a composite ceramic sheet according to claim 1, wherein the binder contains at least a polyvinyl butyral resin. The method for producing a ceramic electronic component according to claim 2, wherein the binder contains at least a polyvinyl butyral resin. The method for producing a composite ceramic sheet according to claim 1, wherein the vehicle does not dissolve a ceramic sheet containing ceramic powder and polyolefin and having voids therein. 3. The method of manufacturing a ceramic electronic component according to claim 2, wherein the organic substance does not dissolve a ceramic sheet containing ceramic powder and polyolefin and having voids therein. The method for producing a composite ceramic sheet according to claim 1, wherein a step of reducing the voids by heating and pressurizing the composite ceramic sheet obtained in the first step is provided before the second step. The step of heating and pressing the composite ceramic sheet obtained in the first step before the second step to reduce the gap is a method of heating and pressing the composite ceramic sheet between two rolls. The manufacturing method of the composite ceramic sheet | seat of description. In the step of heating and pressing the composite ceramic sheet obtained in the first step before the second step to reduce the voids, the temperature of one of the two rolls is equal to or higher than the softening point of the polyolefin. The method for producing a composite ceramic sheet according to claim 8, wherein the temperature of the other roll is equal to or lower than the temperature of the softening point of the polyolefin. The method of manufacturing a ceramic electronic component according to claim 2, wherein a step of reducing the voids by heating and pressurizing the composite ceramic sheet obtained in the first step is provided before the second step. The step of heating and pressurizing the composite ceramic sheet obtained in the first step before the second step to reduce the gap is a method of heating and pressing the composite ceramic sheet between two rolls. The manufacturing method of the composite ceramic sheet | seat of description. In the step of heating and pressing the composite ceramic sheet obtained in the first step before the second step to reduce the voids, the temperature of one of the two rolls is equal to or higher than the softening point of the polyolefin. The method for producing a composite ceramic sheet according to claim 11, wherein the temperature of the other roll is equal to or lower than the temperature of the softening point of the polyolefin. The method for producing a composite ceramic sheet according to claim 1, wherein the polyolefin has a network structure, and the polyolefin and the ceramic powder are present in layers. The method for producing a ceramic electronic component according to claim 2, wherein the polyolefin has a network structure and the polyolefin and the ceramic powder are present in layers.

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