JPH05101969A - Manufacture of monolithic ceramic capacitor - Google Patents

Abstract

PURPOSE:To suppress occurrence of a structural defect such as delamination in a method for manufacturing a monolithic ceramic capacitor to be used for various electronic apparatuses. CONSTITUTION:A screen printing is conducted by employing a block having regions which have two types of different meshes on the same surface and so disposing fine mesh parts 2 as to coincide with forming parts of inner electrodes 5 and rough mesh parts 3 as to coincide with nonforming parts of the electrodes 5 in a step of forming a dielectric layer by a screen printing method of the type of covering a base film 4 as a support with the electrodes 5. Thus, since the electrodes 5 are coated with thin dielectric layer and the other parts are covered with thick dielectric layer, the thicknesses of the electrodes 5 are cancelled to obtain a green sheet having a flat surface. A satisfactory lamination is conducted by a heat transferring method using the sheet to obtain a uniform laminated layer forming body, and hence occurrence of a structural defect such as delamination in an element after baking can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a monolithic ceramic capacitor used in various electronic devices such as video cameras.

[0002]

2. Description of the Related Art In recent years, the demand for monolithic ceramic capacitors has increased more and more with the miniaturization and higher frequency of electronic devices.

A method of manufacturing a general monolithic ceramic capacitor will be described below. First, a green sheet is produced by a doctor blade method using a slurry composed of a dielectric powder such as barium titanate and an organic binder, a plasticizer and an organic solvent. Next, an internal electrode is formed on the green sheet by a screen printing method or the like using a conductive paste containing a noble metal such as palladium or platinum as a main component.

Next, the green sheets on which the internal electrodes are formed are arranged so that the internal electrodes are alternately opposed to each other with the dielectric layer interposed therebetween, and are sequentially laminated, and the lamination is repeated up to a desired number of laminated layers.
The laminated molded body thus obtained is cut into chips of a desired size, the organic binder is degreased, and then 1200 ° C. to 14 ° C.
Bake at 00 ° C. Next, silver, silver-palladium or the like is applied to the internal electrodes appearing at both ends of the element obtained by firing so that these internal electrodes are electrically connected, and external electrodes are formed by baking, Manufactures monolithic ceramic capacitors.

On the other hand, it is necessary to reduce the thickness of the dielectric layer in order to increase the capacity of the capacitor, but the doctor blade method has a limit in reducing the thickness of the dielectric layer of the green sheet. Therefore, by increasing the amount of organic binder in the slurry and further decreasing the viscosity of the slurry, a thin sheet having a thickness of 10 μm or less is manufactured by a reverse roll method or the like, and heat and pressure are applied from above the base film by a heating press to prepare in advance. After thermally transferring the green sheet on the dielectric layer and peeling off the base film, print the internal electrodes on the film surface of the green sheet, and after drying, put another green sheet on the base film side. Recently, a manufacturing method (hereinafter referred to as a thermal transfer method) in which thermal transfer is performed in the same manner as described above and the layers are sequentially stacked up to a desired number of layers has been recently proposed.

[0006]

However, in the case of the thermal transfer method as described above, due to the thickness of the internal electrodes, as the lamination progresses to a higher order, the laminated molded body is remarkably formed in the portion including the internal electrodes and the peripheral portion thereof. Unevenness will occur. At this time, the peripheral portion not including the internal electrode becomes a recess and the pressure during lamination is not sufficiently applied, and structural defects such as cracks and delamination occur in this portion in the laminated molded body and the element after firing, This has been a major issue in the method of manufacturing a monolithic ceramic capacitor.

In view of the above problems, the present invention provides a method for producing a laminated ceramic capacitor using a green sheet having a flat surface which does not adversely affect the unevenness due to the thickness of the internal electrodes in the laminated body during lamination. It is the one we are trying to provide.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a dielectric material by screen printing in the form of a multilayer ceramic capacitor so as to cover the internal electrodes formed on a base film serving as a support. A step of forming a green sheet for forming a layer, and a step of laminating the green sheet directly on the base film by directly heat-pressing the dielectric layer including the internal electrodes to repeatedly laminate the layers sequentially, In addition, a plate having two kinds of regions having different mesh numbers in the same plane is used as a portion having a large mesh number, that is, a fine mesh portion is a portion having a small mesh number in an internal electrode formation portion, that is, a coarse mesh portion is an internal portion. The screen printing is performed by arranging the electrodes so as to match the non-formed portions of the electrodes.

[0009]

In general, in the screen printing method, when the number of meshes of the plate is changed under the same printing conditions, the coarser the mesh, the thicker the printed coating film becomes, and the finer the mesh, the thinner the printed coating film tends to become. is there. Therefore, the present invention is configured as described above, that is, by performing printing by arranging a portion having a large number of meshes in a portion where internal electrodes are formed and a portion having a small number of meshes in portions where internal electrodes are not formed, respectively. Since the dielectric layer is thin on the internal electrode formation portion and the dielectric layer is thick on the internal electrode non-formation portion, the dielectric layer cancels the surface irregularities due to the internal electrode thickness. Can be formed, and a green sheet with a flat surface can be obtained. Further, at the time of stacking, the green sheet is directly heat-pressed from the base film of the green sheet thus obtained, the base film is peeled off, and then the next green sheet having a flat surface is sequentially laminated on the peeled surface. Therefore, the laminated surface is always a flat surface, and uniform pressing is always possible, so that the above-mentioned defects due to the unevenness of the laminated molded body can be eliminated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 uses a plate 1 having two kinds of regions having different mesh numbers in the same plane in one embodiment of the present invention, and a fine portion 2 of the mesh is used as a portion where the internal electrode 5 is formed on the base film 4. FIG. 2 is a diagram illustrating a step of printing by arranging the rough portion 3 so as to match a portion where the internal electrode 5 is not formed. FIG. 2 shows a green sheet produced by printing the dielectric layer 6 using the plate 1. It is a partial cross section figure which shows a structure.

Next, the production of a laminated ceramic capacitor using the green sheet of the present invention will be described. First, a commercially available palladium paste was used on the surface of the base film 4 serving as a support to form the internal electrodes 5 having a desired pattern by a screen printing method. Further, 100 parts by weight of barium titanate powder, 25 parts by weight of polyvinyl butyral resin, 50 parts by weight of butyl carbitol, and 5 parts by weight of dioctyl phthalate were mixed and kneaded with a three-roll mill to prepare a paste for a dielectric layer. ..

Next, according to the pattern of the internal electrodes 5 formed as described above, a fine mesh portion 2 corresponding to the internal electrodes 5 has a 400 mesh portion, and a coarse mesh portion 3 corresponding to a portion where the internal electrodes 5 are not formed. A screen printing plate 1 having different mesh numbers in the same plane, such as 250 mesh, was prepared. On the base film 4 on which the internal electrode 5 produced above using this plate 1 is formed,
As shown in FIG. 1, the two layers are aligned so that their patterns match each other, and then the dielectric layer paste prepared above is used to form a dielectric layer 6 by a screen printing method so as to cover the internal electrodes 5. , A green sheet was prepared. The surface of the green sheet thus obtained was measured with a contact type surface roughness meter to calculate the surface step Δt ₁ (μm).

Next, the green sheet produced above is subjected to the first step of the laminating step of FIG. 3 (a) according to the above-mentioned thermal transfer method.
As shown in the step diagram, using a heating press, the surface temperature of the mold 7 having the heater built-in is 120 ° C., the pressure is 35 kg / cm ² , from above the base film 4 of the green sheet.
Under a thermocompression bonding condition of a pressurizing time of 5 seconds, thermal transfer is performed on the lower support layer 8 which does not contribute to the electric capacity of the capacitor previously produced on the stacking pallet 9, and then the second step of FIG. 3B. As shown in the figure, after peeling off the base film 4 of the transferred green sheet, the position of the next green sheet was shifted by a predetermined dimension to obtain the capacity, and thermal transfer was performed in the same manner as above. .. Thereafter, such stacking is repeated, and when stacking of 70 layers is completed, an upper support layer (not shown) having the same thickness as above is formed on the uppermost layer to prepare a multilayer molded body. This laminated compact was cut into a desired size, and the thickness of the portion including the internal electrode 5 and its peripheral portion was measured to obtain the thickness difference Δt ₂ (μm).

Next, the chip-shaped laminated molded body obtained above was left in the electric furnace at 350 ° C. for 5 hours for degreasing of the organic binder and then fired at 1300 ° C. for 2 hours. After firing, the appearance and the inside of the obtained device are observed, the occurrence rate of structural defects such as delamination is calculated for 1000 samples, and the result is obtained by a normal screen printing method, that is, a screen printing plate mesh. The results were compared with the case of the element after firing in which 100 layers were stacked by the same thermal transfer method as above using a 250 mesh plate without any change in the number. At this time, the difference in surface step of the green sheet and the thickness difference between the laminated molded bodies were measured by the same method as described above, and also compared. As described above, the surface difference Δt ₁ (μm) of the green sheet and the thickness difference Δt ₂ (μ
m) and the occurrence rate (%) of structural defects for 1000 elements after firing are summarized in (Table 1) below.

[0015]

[Table 1]

As is clear from this (Table 1), according to the present embodiment, the surface step of the green sheet is overwhelmingly reduced, and a uniform laminated molded body having no surface irregularity even after lamination is obtained. I understand. Further, occurrence of structural defects such as delamination of the device after firing could be almost completely suppressed.

In the above embodiments, the case where palladium is used as the internal electrode has been described, but the present invention is not limited to this, and one containing palladium such as palladium-silver as a main component, The present invention can be applied to the case where a base metal such as nickel is used.

[0018]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to produce a green sheet having a flat surface by printing a dielectric layer by using plates having different mesh numbers in the same plane. As a result, it is possible to realize a monolithic ceramic capacitor in which the occurrence of structural defects is almost completely suppressed, and in the manufacture thereof, an epoch-making effect is brought about in improving productivity.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a screen printing method according to an embodiment of the present invention.

FIG. 2 is a partial sectional view of a green sheet according to an embodiment of the present invention.

FIG. 3A is an explanatory view of a first step of a laminating process in an embodiment of the present invention, and FIG. 3B is an explanatory view of the second step.

[Explanation of symbols]

 1 plate 2 fine part 3 rough part 4 base film 5 internal electrode 6 dielectric layer 7 mold 8 lower support layer 9 stacking pallet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideyuki Okinaka 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A step of producing a green sheet in which a dielectric layer is formed by screen printing so as to cover the internal electrodes formed on a base film serving as a support, and the green sheet is directly heated from above the base film. Laminating step in which the dielectric layers including the internal electrodes are repeatedly thermally transferred by pressing and sequentially laminating, and a plate having two kinds of regions having different mesh numbers in the same plane has a large mesh number. A method for manufacturing a monolithic ceramic capacitor, comprising: arranging a portion having a small mesh number in a portion where the internal electrode is formed so as to match a portion where the internal electrode is not formed, and performing the screen printing.