JPH02117113A - Green sheet for laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To obtain a green sheet for laminated ceramic capacitor which enables electrodes to be formed by the screen printing process without causing short circuit after sintering by using a binder unsoluble or hardly soluble in an organic solvent for at least one of multiple dielectric layers. CONSTITUTION:In the drawing, 11 indicates a base film, 12 indicates a dielectric layer containing a binder which can be transferred thermally and 13 indicates a dielectric layer containing a binder which is unsoluble or hardly soluble in an organic solvent. Since at least one (13 in this case) of the dielectric layers contains the binder which is unsoluble or hardly soluble in an organic solvent, when inner electrodes 21 are formed from an electrode paste by the screen printing process, the binder is not substantially solved in the organic solvent of the electrode paste. Therefore, no or very little electrode paste is allowed to penetrate into the dielectric layer 12 and no electrode paste is allowed to reach an opposing inner electrode. Consequently, short circuit between the inner electrodes 21 can be prevented and productivity is improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to green sheets used in the manufacture of multilayer ceramic capacitors.

Background of the Invention In recent years, with the development of ultra-compact, thin, and lightweight electronic devices such as radios, microcassette recorders, electronic tuners, and video cameras, capacitors used as circuit elements have become smaller and smaller.
There is a strong demand for larger capacity. A multilayer ceramic capacitor is known as a component that satisfies these requirements.

The method for manufacturing a multilayer ceramic capacitor is to first form a dielectric layer several tens of micrometers thick on a base film using a doctor blade method using a slurry consisting of dielectric powder, binder, plasticizer, and organic solvent. Create a green sheet.

Next, multiple green sheets with internal electrodes printed on them are stacked up, and then a laminate is created by pressure bonding, and then cut into chips.

After firing, external electrodes are formed and manufactured. (“Insulating Dielectric Ceramics Published by JOMC, supervised by Tadashi Shiozaki, p211
~227 Published in 1960) On the other hand, in order to achieve even higher capacity, it is desirable to make the dielectric layer thinner, but since there is a limit to the thickness of the dielectric layer in the doctor blade method, the amount of binder must be increased compared to the conventional method. Then, the slurry viscosity is further reduced to produce a thin sheet of 10 μm or less using the reverse roll method, and by utilizing the large amount of binder, the dielectric layer is transferred from the base film of the green sheet by thermocompression bonding. A method of stacking dielectric layers using the Stang method has also been recently proposed.

The manufacturing process of a laminated ceramic capacitor using the hot stamping method will be briefly explained using FIG.

First, using a slurry prepared by adding a binder, a plasticizer, a solvent, etc. to dielectric powder, and using a reverse roll method etc., an ultra-thin dielectric layer 3o with a thickness of several μm to more than 10 μm is formed. It is formed on a base film 31 to produce a hot stamp sheet 32. Next, in order to withstand warpage during sintering and handling, a dielectric layer 301L portion that does not directly affect electrical properties is formed on the base film 311L, and then the hot stamp sheet 32 described above is laminated thereon. Thereafter, the dielectric layer 30 of the hot stamp sheet 32 is transferred to the dielectric layer 3oa by simultaneously applying heat and pressure from the side of the base film 31 using a heat roller 33 or the like. Next, the base film 31 of the hot stamp sheet 32 is peeled off. On this peeled surface, an electrode paste containing P(i as a main component) is applied to a predetermined shape by a screen printing method or the like to form an internal electrode 34. Thereafter, a dielectric layer 30b of another hot stamp sheet 32b is formed.
is superimposed on the above-mentioned hot stamp sheet, and then heat and pressure are applied to the base film surface 31 using heat roller 233 or the like.
The base film 31b of the hot stamp sheet 32b is peeled off by applying the hot stamp sheet 32b at the same time. After repeating the stacking of another hot stamp sheet, transfer by thermocompression bonding, peeling off the base film, and forming electrodes, a dielectric layer portion that does not directly affect electrical properties is created on the top layer in the same manner as described above, and then, Perform cutting and firing. Thereafter, external electrodes 36 are formed to produce a multilayer ceramic capacitor.

Problems to be Solved by the Invention However, in order to enable thermal transfer, hot-stamped green sheets require a larger amount of binder than conventional green sheets, so an electrode paste mainly made of Pd powder is used. When the internal electrodes 34 are formed on the sheet by screen printing or the like, the organic solvent that is the main component of the electrode paste partially dissolves the binder in the dielectric layer of the green sheet and forms the opposite side as shown in FIG. Since the internal electrodes 34 contact each other, when a molded body obtained by laminating and molding sheets on which these electrodes are formed is sintered, the internal electrodes 34 are short-circuited and the capacitor does not function as a multilayer ceramic capacitor. Was.

In FIG. 4, 3o is a dielectric layer, 42 is a dielectric powder, 43 is a binder, a plasticizer, and 46 is an internal electrode 3 that faces the inner electrode 3 after the binder has been disturbed during printing of the internal electrode paste.
The electrode paste reached up to 4, and 31 is the base film.

In view of the above-mentioned problems, the present invention has been developed to form a stain electrode on a green sheet consisting of a thin dielectric layer by a screen printing method or the like using an electrode paste mainly composed of Pd powder as in the past. It is an object of the present invention to provide a green sheet for a multilayer ceramic capacitor that does not cause a short circuit phenomenon after bonding.

Means for Solving the Problems The sheet of the present invention for solving the above problems is as follows. That is, at least one of the dielectric layers having a multilayer structure uses a binder that is insoluble or hardly soluble in organic solvents.

Operation An example of the green sheet of the multilayer ceramic capacitor of the present invention is shown in FIG. The green sheet shown in Figure 1 has a two-layer structure with different types of binders. 11 is a base film, 12 is a dielectric layer using a binder that can be thermally transferred, and 13 is a layer that is insoluble in organic solvents or This dielectric layer uses a binder that is difficult to melt. Note 14
a.

14b is a dielectric powder, and 16a and 1sb are a binder and a plasticizer. Also, the composition of the dielectric layer 12 must contain a binder amount such that a hot stamping system is possible.

It is assumed that a multilayer ceramic capacitor is manufactured using a hot-stamped sheet having such a multilayer structure and following the same manufacturing process as the conventional method shown in FIG.

As shown in FIG. 2, the dielectric layer 12 of the sheet according to the present invention is heated and transferred onto the dielectric layer 24 that does not directly affect the electrical properties on the base film 26 using a heated roller, and then the base film 26 is heated and transferred. 11 is peeled off, and internal electrodes 21 are formed on that surface by screen printing. Next, after overlapping another sheet according to the present invention, the dielectric layer 12 is
is transferred, and the internal electrodes 21 are formed on the surface from which the base film 11 has been peeled off again by the screen method to produce a laminate molded body.

In the case of conventional hot stamp sheets, a large amount of binder is required in the dielectric layer 3o to enable thermal transfer, so the organic solvent of the electrode paste corrodes the binder 43 and shorts occur between the opposing internal electrodes 34. .

However, in the sheet of the present invention, at least one layer 13 of the dielectric layers uses a binder that is insoluble or hardly soluble in organic solvents, so the internal electrodes 21 are formed using electrode paste by screen printing. However, the dissolution of the binder by the organic solvent of the electrode paste is significantly suppressed, and the electrode paste does not penetrate into the dielectric layer 12, or even if it does, it is extremely small.
It does not reach the internal electrodes 21 facing each other.

Therefore, there is no short-circuit phenomenon between the internal electrodes 21, and productivity is significantly improved.

Example Specific embodiments of the present invention will be described in detail.

First, dielectric powder 10 containing BaTiOs as a main component
0 parts by weight, 25 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl 7-talate were blended, and then kneaded for 2Q hours in a ball mill using tetrahydrofuran as a solvent to prepare a slurry having a viscosity of 10 to 15 Cps. . After defoaming, this slurry was applied to a 50 μm thick polyester film using a reverse roll method to a thickness of 8 μm.
A dielectric layer of m was formed to prepare a sheet for hot stamping. Note that this hot stamp sheet has the same composition as the conventional host stamp sheet, and has a dielectric layer 12 that can be thermally transferred. Next, 1Q parts by weight of acrylic resin emulsion and 8 parts by weight of polyethylene glycol were blended with 100 parts by weight of dielectric powder containing BaTiO3 as the main component, and then kneaded for 2 hours in a ball mill using distilled water as a solvent. , a slurry having a viscosity of 20 to 25 Cps was prepared. Using this slurry, a dielectric layer 13 having a thickness of 8 μm was formed on a polyester film in exactly the same manner as described above to produce a hot stamp sheet insoluble in organic solvents. After the dielectrics 11112.13 of these two sheets with different types of binders are placed facing each other so as to overlap each other, pressure is applied with a hot roll from the base film side of the hot stamp sheet using polyvinyl butyral resin as the binder. kg/ar! Two sheets with different types of binders were combined under thermocompression bonding conditions at a temperature of 190'C. Thereafter, the base film of the host stamp sheet using polyvinyl butyral resin as a binder was peeled off to produce a green sheet of the present invention as shown in FIG. 1.

Next, on a polyester film with a thickness of 6 μm, powder particles mainly composed of Ba Ti O 5 prepared by a doctor blade method and 2 made of polyvinyl butyral resin were coated.
After the dielectric layer 24 of the green sheet on which the dielectric layer 24 of 00 μm is formed and the dielectric layers 12 and 13 of the hot stamp sheet having the above-mentioned two-layer structure are stacked so as to face each other, the present invention The temperature of the hot stamp sheet is 185℃ using a hot roller from the base film side.

The dielectric layer 12.13 of the hot stamp sheet was transferred by thermocompression bonding for 2 seconds under a pressure of 50 ktq/(:RF.Then, the base film surface of the hot stamp sheet was peeled off, and a commercially available An internal electrode 21 having a shape of 35 x 10 mm was formed by screen printing using Pd paste (manufactured by Shoei Kagaku Co., Ltd., trade name ML = 3724).Next, another host stamp sheet according to the present invention was placed thereon. 7) After transferring the dielectric layers 12 and 13 of the stamp sheet by thermocompression bonding under exactly the same conditions as described above, the base film was peeled off, and the same internal electrodes 21 as described above were printed on the surface. Note that the overlapping portion of the internal electrodes 21, that is, the area of the electrodes that effectively function as a multilayer capacitor, is 1.4 x 1. Lamination molding was performed so that the thickness was 0 mm. After repeating this process 10 times,
The green sheets prepared by the doctor blade method with a thickness of 200 μm as described above were stacked on top of each other. Next, this laminate was further pressure-bonded using a die press at 80° C. under the condition of so kg/at. Thereafter, after cutting into a chip shape of 24 x 16 mm, the chip molded body was baked at 1300'C for 1 hour while being sprinkled in ZrO2 powder. The temperature increase and decrease rate was 200℃/hr, and the temperature was increased at 3℃ to remove the binder during the
It was held at 76°C for 1 ohr and 420°C. The capacitance of the multilayer ceramic capacitor thus produced was measured using an LCR meter, and the presence or absence of short circuits was confirmed. Note that the number of samples measured was 100. Table 1 shows the average capacitance of samples that were not short-circuited and the number of samples that were short-circuited.

The microstructure of the sample prepared using the green sheet of the present invention was observed using a scanning electron microscope, and the results showed that the sintered body was extremely dense and no major differences were observed from conventional samples. Next, for comparison, a hot stamp sheet was produced using a conventional method. That is, after blending 26 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl phthalate with 100 parts by weight of dielectric powder whose main component is BILTi (h), 20 parts by weight of dielectric powder containing BILTi (h) as a main component was mixed, and then 20 parts by weight of dielectric powder was mixed with 26 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl phthalate.
The mixture was kneaded for hours to prepare a slurry having a viscosity of 10 to 15 Cps. After degassing this slurry, a dielectric layer 30 having a thickness of 16 μm was formed on a polyester film having a thickness of 60 μm using a reverse roll method to obtain a hot stamp sheet using a conventional method. Using this hot stamp sheet, a multilayer ceramic capacitor was produced under exactly the same conditions as described above, and the capacitance of the multilayer ceramic capacitor was measured using an LCR meter, and the presence or absence of short circuits was confirmed. Note that the number of samples measured was 100. Table 1 shows the average capacitance of samples that were not short-circuited and the number of samples that were short-circuited.

As shown in Table 1, the multilayer ceramic capacitor using the green sheet according to the present invention is no different from conventional products in terms of electrical characteristics, and the short circuit phenomenon that was a problem in the past was not observed at all. It is possible to significantly improve yield.

Note that in this example, dielectric layers 1 with different types of binders are used.
2. In addition to the green sheet made of two layers in 2.13, we also made a hot-stamped sheet with a multilayer structure made of three or more dielectric layers with different types of binders, and used this to make a multilayer ceramic capacitor. A similar effect can also be obtained.

Effects of the Invention As described above, the green sheet for a multilayer ceramic capacitor according to the present invention consists of a dielectric layer and a base film made of dielectric powder, a binder, and a plasticizer, and the dielectric layer is composed of two or more layers containing different types of binders. It has a multilayer structure, and at least one of the multiple dielectric layers uses a binder that is insoluble or difficult to dissolve in organic solvents.
Even if a laminated ceramic capacitor is manufactured using a hot-stamped sheet with the following dielectric layer thickness, there will be no short-circuit phenomenon of the internal electrodes, and the production yield during manufacturing can be greatly improved. The value is extremely large.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the structure of the green sheet for laminated ceramic capacitors of the present invention, Figure 2 is an enlarged cross-sectional view of the vicinity of the internal electrodes of the laminated molded product using the green sheet of the present invention, and Figure 3 is hot stamping. FIG. 4 is an enlarged cross-sectional view of the vicinity of the internal electrodes of a laminated molded body using a conventional hot stamp sheet. 11... Base film, 12. Mountain... Dielectric layer consisting of the type and amount of binder that enables thermal transfer, 13... Consisting of a binder that is insoluble or hardly soluble in organic solvents. dielectric layer. ＋＋−−Baize film +2−? 13 - Boarding house in Tsukishagata, or 1 year old; Vine 9, which is difficult to store, is a body layer.

Claims (1)

[Claims] A dielectric layer is provided on the green sheet, and this dielectric layer has a multilayer structure of two or more layers using different types of binders, and at least one of these multiple dielectric layers is insoluble in organic solvents or Green sheet for laminated ceramic capacitors using a hard-to-melt binder.