JP2532617B2 - Green sheet for laminated porcelain capacitors - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a green sheet used for manufacturing a laminated ceramic capacitor.

2. Description of the Related Art In recent years, with the development of ultra-small, thin, and lightweight electronic devices such as radios, microcassette recorders, electronic tuners, and video cameras, there is a strong demand for miniaturization and large capacity of capacitors used as circuit elements. It's coming. A multilayer ceramic capacitor is known as a component satisfying these requirements.

As a method of manufacturing a laminated ceramic capacitor, first, a slurry composed of a dielectric powder, a binder, a plasticizer and an organic solvent is used to form a dielectric layer having a thickness of several tens of μm on a base film by a doctor blade method to obtain a green sheet. To make.

Next, a plurality of sheets with the internal electrodes printed thereon are stacked on this green sheet, and thereafter, a laminated molded body is manufactured by pressure bonding, and thereafter, it is cut into chips and baked, and then external electrodes are formed. ("Insulation Dielectric Ceramics" CM
On the other hand, it is desirable to make the dielectric layer thinner in order to achieve higher capacity, but the doctor blade method has a limit to the thickness of the dielectric layer. The amount is increased from the conventional value, the slurry viscosity is made smaller, and a thin sheet of 10 μm or less is produced by the reverse roll method. Utilizing the large amount of binder, the dielectric layer is formed by thermocompression bonding from the green sheet base film. Recently, a method of laminating dielectric layers by a so-called hot stamping method, which transfers the image, has been proposed.

The manufacturing process of the laminated ceramic capacitor by the hot stamp method will be briefly described with reference to FIG.

First, by using a slurry prepared by mixing a dielectric powder with a binder, a plasticizer, a solvent, etc., an extremely thin dielectric layer 30 having a thickness of several μm to several tens of μm is formed by a reverse roll method or the like. It is formed on 31 and hot stamp sheet 32 is produced. Next, a portion of the dielectric layer 30a that does not directly contribute to electrical characteristics is formed on the base film 31a so that it can withstand warping during sintering and handling, and then the above-mentioned hot stamp sheet 32 is laminated. afterwards,
By simultaneously applying heat and pressure from the surface side of the base film 31 with a heat roller 33 or the like, the dielectric layer 30 of the hot stamp sheet 32 is transferred to the dielectric layer 30a. Next, the base film 31 of the hot stamp sheet 32 is peeled off. The electrode paste containing Pd as a main component is applied to the peeled surface by a screen printing method or the like so as to have a predetermined shape.
To form. After that, the dielectric layer 30b of another hot stamp sheet 32b, after superposed on the hot stamp sheet described above, by applying heat and pressure from the base film surface 31b at the same time by a heat roller 33 or the like, the hot stamp sheet 32b The base film 31b is peeled off. After repeating another hot stamp sheet stacking, transfer by thermocompression bonding, peeling of the base film, and electrode formation, a dielectric layer portion that does not directly relate to electrical characteristics is produced on the uppermost layer, and then, Cut and fire. After that, the external electrodes 35 are formed to produce a laminated ceramic capacitor.

However, the hot stamp type green sheet uses an electrode paste mainly composed of Pd powder or the like because the amount of the binder is larger than that of the conventional green sheet so that the thermal transfer can be performed. When the internal electrode 34 is formed on the sheet by a screen printing method or the like, the organic solvent, which is the main component of the electrode paste, partially dissolves the binder of the dielectric layer of the green sheet, and as shown in FIG. Since the internal electrodes 34 that contact each other come into contact with each other, the internal electrodes are
There was a problem that the 34 parts were short-circuited with each other and did not function as a laminated ceramic capacitor.

In FIG. 4, reference numeral 30 is a dielectric layer, 42 is a dielectric powder, 43 is a binder and a plasticizer, 46 is an electrode paste which has reached the internal electrode 34 facing the internal electrode paste when printed with the binder, 31 Is a base film.

In view of the above-mentioned problems, the present invention, even after forming an electrode by a screen printing method or the like using an electrode paste mainly composed of Pd powder on a green sheet formed of a thin dielectric layer, after sintering, An object of the present invention is to provide a green sheet for a laminated ceramic capacitor that does not cause a short circuit phenomenon.

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 multi-layered structure has a structure using a binder that is insoluble or hardly soluble in the organic solvent of the internal electrode paste.

Action An example of the green sheet of the laminated ceramic capacitor of the present invention is shown in FIG. The green sheet shown in FIG. 1 has a two-layer structure in which different kinds of binders are used. 11 is a base film, 12 is a dielectric layer using a binder capable of thermal transfer, 13 is insoluble in an organic solvent, or It is a dielectric layer that uses a binder that does not melt easily. 14a, 14b
Is a dielectric powder, and 15a and 15b are a binder and a plasticizer. Also, the composition of the dielectric layer 12 must contain a binder amount that enables a hot stamp system.

It is assumed that a laminated ceramic capacitor is manufactured by using the hot stamp sheet having such a multilayer structure according to the same manufacturing process as the conventional method shown in FIG. As shown in FIG. 2, after the dielectric layer 12 of the sheet according to the present invention is heat-transferred by a heat roller or the like onto the dielectric layer 24 which is not directly involved in the electric characteristics on the base film 25, the base film 11 is peeled off. Then, the internal electrode 21 is formed on the surface by the screen printing method. Then, after superimposing another sheet according to the present invention,
The dielectric layer 12 is transferred with a heat roller, and a laminated molded body is manufactured while again forming the internal electrodes 21 on the surface from which the base film 11 has been peeled off by the screen method.

In the case of a conventional hot stamp sheet, since a large amount of binder is required in the dielectric layer 30 to enable thermal transfer, the organic solvent of the electrode paste invades the binder 43 and short-circuits between the opposing internal electrodes 34. .

However, in the sheet of the present invention, since at least one layer 13 or more of the dielectric layers uses a binder that is insoluble or hardly soluble in an organic solvent, the internal electrodes 21 are formed by an electrode paste by a screen printing method. Even
Dissolution of the binder by the organic solvent of the electrode paste is significantly suppressed, and there is no invasion of the electrode paste into the dielectric layer 12 or it is extremely small, if any, and does not reach the opposing internal electrode 21. . Therefore, the short circuit phenomenon between the internal electrodes 21 is eliminated, and the productivity is remarkably improved.

EXAMPLES Specific examples of the present invention will be described in detail.

First, 25 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl phthalate were mixed with 100 parts by weight of a dielectric powder containing BaTiO ₃ as a main component, and the mixture was kneaded in a ball mill for 20 hours using tetrahydrofuran as a solvent. A slurry with a viscosity of ~ 15 cps was prepared. After defoaming the slurry, a dielectric layer having a thickness of 8 μm was formed on a polyester film having a thickness of 50 μm by a reverse roll method to obtain a hot stamping sheet. This hot stamp sheet is a dielectric layer 12 which has the same composition as a conventional hot stamp sheet and is capable of thermal transfer. Then BaTiO ₃
After mixing 10 parts by weight of an acrylic resin emulsion and 8 parts by weight of polyethylene glycol with 100 parts by weight of a dielectric powder containing as a main component, kneading was carried out for 20 hours in a ball mill using distilled water as a solvent, and then 20 to 25 cps. A slurry having a viscosity was prepared. This slurry was used in exactly the same manner as above to form a dielectric layer 13 having a thickness of 8 μm on a polyester film to prepare a hot stamp sheet insoluble in an organic solvent.
Dielectric layers of sheets with different types of these two binders
After facing each other so that 12 and 13 overlap each other, from the base film side of the hot stamp sheet using polyvinyl butyral resin as a binder, pressure 50 kg with a heat roll
Under the thermocompression bonding conditions of / cm ³ and a temperature of 190 ° C, two sheets having different types of binder were integrated. After that, the base film of the hot stamp sheet using polyvinyl butyral resin as a binder was peeled off to prepare a green sheet of the present invention as shown in FIG.

Next, a dielectric layer 24 of a green sheet, in which a 200 μm dielectric layer 24 made of polyvinyl butyral resin and powder particles containing BaTiO ₃ as a main component is formed on a polyester film having a thickness of 50 μm by a doctor blade method,
After the dielectric layers 12 and 13 of the hot stamp sheet having the above-mentioned two-layer structure are superposed so as to face each other, the hot stamp sheet of the present invention is heated from the base film surface side by a heat roller at a temperature of 185 ° C. and pressure. Dielectric layer 12,1 of hot stamping sheet by thermocompression bonding for 2 seconds under 50kg / cm ² condition
Transcribed 3. After that, the base film surface of the hot stamp sheet is peeled off, and a commercially available Pd paste [trade name ML = 3724 manufactured by Shoei Chemical Co., Ltd.] is used on the peeled surface to form a 3.5 × 1.0 mm internal shape by screen printing. electrode
21 formed. Next, another hot stamp sheet according to the present invention is overlaid thereon, and the dielectric layers 12 and 13 of the hot stamp sheet are bonded by thermocompression bonding under the same conditions as described above.
After transferring, the base film was peeled off, and the same internal electrodes 21 as described above were printed on the surface of the base film. The overlapping portion of the internal electrodes 21, that is, the electrode area effectively acting as a multilayer capacitor was laminated and molded so as to be 1.4 × 1.0 mm. After repeating this step 10 times, the above-mentioned green sheets having a thickness of 200 μm and manufactured by the doctor blade method were stacked. Next, this laminated body was further pressure-bonded using a die press at 80 ° C. under the condition of 500 kg / cm ² . Then, after cutting into a chip shape of 2.4 × 1.6 mm, while sprinkling the chip molded body into ZrO ₂ powder, 13
It was baked at 00 ° C for 1 hr. The rate of temperature increase / decrease is 200 ℃ / hr.
Then, in order to remove the binder on the way, it was held at 375 ° C. for 10 hours and at 420 ° C. The electric capacity of the thus-fabricated porcelain capacitor was measured using an LCR meter and the presence or absence of a short circuit was confirmed. The number of samples measured is 100. Table 1 shows the average value of the electric capacities of the non-short-circuited samples and the number of short-circuited samples. As a result of observing the fine structure of the sample produced using the green sheet according to the present invention with a scanning electron microscope, the sintered body was extremely dense, and no particularly large difference from the conventional sample was observed.

Next, a hot stamp sheet by a conventional method was prepared for comparison. That is, a dielectric powder mainly composed of BaTiO ₃
After blending 25 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl phthalate with 100 parts by weight, tetrahydrofuran was used as a solvent and kneaded for 20 hours in a ball mill to prepare a slurry having a viscosity of 10 to 15 cps. After defoaming this slurry, a 16 μm-thick dielectric layer 30 was formed on a 50 μm-thick polyester film by a reverse roll method to obtain a conventional hot stamp sheet. Using this hot stamp sheet, a laminated porcelain capacitor was manufactured under the same conditions as described above, and the electric capacity of the laminated porcelain capacitor was measured using an LCR meter and the presence or absence of a short circuit was confirmed. The number of samples measured is 100. Table 1 shows the average value of the electric capacities of the non-short-circuited samples and the number of short-circuited samples. As shown in Table 1, the laminated porcelain capacitor using the green sheet according to the present invention has the same electrical characteristics as the conventional product, and the short-circuit phenomenon, which has been a problem in the related art, is not recognized at all. The yield can be significantly improved.

In this example, the derivative layers having different types of binders are used.
Although 12 and 13 are green sheets consisting of two layers, a hot stamp sheet having a multi-layer structure consisting of three or more types of dielectric layers having different kinds of binders is further produced, and using this, a laminated ceramic capacitor is produced. However, the same effect can be obtained.

EFFECTS OF THE INVENTION As described above, the green sheet for a laminated ceramic capacitor according to the present invention comprises a dielectric layer composed of a dielectric powder, a binder and a plasticizer and a base film, and the dielectric layer comprises two or more layers having different kinds of binders. Hot stamp sheet having a dielectric layer thickness of 10 μm or less because at least one of a plurality of dielectric layers uses a binder that is insoluble or hardly soluble in the organic solvent of the internal electrode paste. Even if a laminated porcelain capacitor is manufactured by using, the internal electrode short circuit phenomenon does not occur, and the production yield at the time of manufacturing can be greatly improved, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a green sheet for a laminated ceramic capacitor according to the present invention, FIG. 2 is an enlarged sectional view around an internal electrode of a laminated molding using the green sheet according to the present invention, and FIG. 3 is a hot stamp system. FIG. 4 is a diagram showing the manufacturing process of the laminated ceramic capacitor, and FIG. 4 is an enlarged cross-sectional view in the vicinity of the internal electrodes of the laminated molded body using the conventional hot stamp sheet. 11 ... Base film, 12 ... Dielectric layer consisting of binder and amount of binder that enables thermal transfer, 13 ... Dielectric layer consisting of binder that is insoluble or hardly soluble in organic solvent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideyuki Okinaka 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References Japanese Patent Publication No. 46-13224 (JP, B1)

Claims (1)

(57) [Claims] 1. A peelable base film is provided with a dielectric layer having a multilayer structure of two or more layers having different kinds of binders to enable thermal transfer, and at least one or more of the plurality of dielectric layers are provided. A green sheet for a laminated ceramic capacitor, which contains a binder that is insoluble or hardly soluble in an organic solvent of the internal electrode paste.