JPH02155211A - Green sheet for laminated porcelain capacitor - Google Patents

Abstract

PURPOSE:To prevent even the generation of a short-circuit phenomenon at the time of the formation of an internal electrode, and to improve the yield of production at the time of manufacture largely by forming a dielectric layer in multilayer constitution composed of a composition, in which the quantities of a binder differ to those of the same dielectric powder quantity. CONSTITUTION:A green sheet consists of the two layer structure of dielectric layers 12, 13, the quantities of a binder respectively differ to the same dielectric powder quantity, and the dielectric layers are made up of dielectric powder 14, the binder and a plasticizer 15. The dielectric layers 12, 13 of a hot stamp sheet are heated and transferred onto the dielectric layers not related to electrical characteristics direct]y by a heated roller, etc., a base film 11 is peeled, and an internal electrode is shaped onto the surface of the base film through a screen printing method by electrode paste. The quantity of the binder is reduced in the dielectric layer 13 and the layer 13 is filled densely with dielectric layer powder, and electrode paste, in which the dissolution of the binder is inhibited by the organic solvent of the electrode paste, is not intruded to the dielectric layer 13, and does not reach an adjacent internal electrode 26. A short-circuit phenomenon between the internal electrodes 26 is also removed, thus improving productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to dielectric 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 manufacturing method for multilayer ceramic capacitors includes dielectric powder,
A ceramic dielectric green sheet with a thickness of several tens of micrometers is produced on an organic film by a doctor blade method using a slurry consisting of a binder, a plasticizer, and an organic solvent.

After stacking a plurality of sheets with internal electrodes printed on them, a laminated molded body is produced by pressure bonding, and then cut into chips, and after firing, external electrodes are formed.

([Insulating Dielectric Ceramics 4 CMC, supervised by Tadashi Shiozaki, p. 211-227, published in 1960) On the other hand, in order to achieve even higher capacitance, it is desirable to make the dielectric layer thinner, but with the doctor blade method, there is a limit to the dielectric layer thickness. Therefore, by increasing the amount of binder than before and further reducing the viscosity of the slurry, we created a thin sheet of 10 μm or less using the reverse roll method. Recently, a method has also been proposed in which dielectric layers are laminated by a so-called hot stamping method in which dielectric layers are transferred by thermocompression bonding.

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

First, using Sujiri, which is prepared by adding a binder, a plasticizer, a solvent, etc. to dielectric powder and mixing it, an ultra-thin dielectric layer 30 with a thickness of several μm to more than 10 μm is applied to a base film using a reverse roll method or the like. 31 to produce a hot stamp sheet 32.

Next, in order to withstand warping during sintering and handling,
After a dielectric layer 301L that does not directly affect electrical properties is produced on the base film 31a, the hot stamp sheet 32 described above is superimposed. Thereafter, the dielectric layer 30 of the hot stamp sheet 32 is transferred to the dielectric layer 30 & by simultaneously applying heat and pressure from the base film 31 side using a heat roller 33 or the like, and then the base film of the hot stamp sheet 32 is 31 is peeled off. On this peeled surface, an electrode paste containing P(1 as a main component) is applied by a screen printing method or the like so as to have a predetermined shape, thereby forming an internal electrode 34. After that, another hot stamp sheet 3 is applied.
After overlapping the dielectric layers 30b of the hot stamp sheet 2b so that the dielectric layers of the hot stamp sheet face each other, heat and pressure are applied to the base film surface 31 using a heat roller 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 a sheet by screen printing or the like, the organic solvent, which is the main component of the electrode paste, partially dissolves the binder and inder of the dielectric layer of the green sheet, resulting in the formation of internal electrodes as shown in FIG. Since adjacent internal electrodes 44 come into contact with each other, when a molded body obtained by laminating and molding the sheets forming these internal electrodes 44 is sintered, the internal electrodes 44 will short-circuit and will not function as a multilayer ceramic capacitor. There was a problem.

In FIG. 4, 41 is a dielectric layer, 42 is a dielectric powder, 43 is a binder, a plasticizer, 44 is an internal electrode, and 4 is a dielectric layer.
6 is an electrode paste in which the binder was disturbed during printing of the internal electrode paste and the adjacent internal electrodes 46 were dripped;
7 is a base film.

In view of the above-mentioned problems, the present invention has been developed to form internal electrodes 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 PC1 powder as in the past. The object of the present invention is to provide a green sheet for a laminated ceramic capacitor that does not cause a short circuit phenomenon after bonding.

Means for Solving the Problems The sheet of the present invention that solves the above problems is as follows. In other words, in a green sheet consisting of a dielectric layer consisting of dielectric powder, a binder, and a plasticizer, and a base film, the dielectric layer has a multilayer structure consisting of a composition with different amounts of binder for the same amount of dielectric powder. be.

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 Fig. 1 has a two-layer structure in which the amount of binder is different for the same amount of dielectric powder, 11 is a base film, 12 is a dielectric layer with a larger amount of binder, and 13 is a layer with more binder than the dielectric layer 12. The dielectric layer has a small amount of dielectric powder 14 and a binder.

It consists of plasticizer 16. Note that the composition of the dielectric layer No. 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.

After heat-transferring the dielectric layers 12 and 13 of the hot stamp sheet according to the present invention onto the dielectric layer that does not directly affect electrical properties using a hot roller or the like, the base film 11 is peeled off, and an electrode paste is screened onto that surface. Internal electrodes are formed using a printing method. Next, after superimposing another hot stamp sheet according to the present invention, a dielectric layer is transferred using a heat roller, and an electrode is formed on the surface from which the base film has been peeled off again by a screen method to produce a laminate molded body. .

FIG. 2 shows an enlarged view of the vicinity of the electrodes of the laminate molded product thus produced. In the case of conventional hot stamp sheets, a large amount of binder is required in the dielectric layer to enable thermal transfer, so the organic solvent in the electrode paste corrodes the binder and causes shorts between adjacent electrodes.

However, if the green sheet of the present invention is used,
As shown in FIG. 2, the surface 23 on which the internal electrodes 26 are printed does not particularly require a hot stamping stem, that is, a thermal transfer function, so there is no particular problem even if the surface 23 is a dielectric layer that does not require a large amount of binder. . Therefore, if this dielectric layer 13 has a small amount of binder, in other words, if the dielectric layer powder is densely packed, dissolution of the binder by the organic solvent of the electrode paste will be significantly suppressed, so the electrode paste There is no penetration into the dielectric layer 13, or even if there is, it is extremely small and does not reach the adjacent internal electrode 26. Therefore, the phenomenon of short circuit between the internal electrodes 26 is also eliminated, and productivity is significantly improved. In FIG. 2, 24 is a dielectric layer that does not directly affect electrical characteristics, and 26 is a base film.

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

First, 1oO dielectric powder containing BaTi0s as the main component
25 parts by weight of polyvinyl butyral resin based on parts by weight,
After blending 2 parts by weight of dioctyl phthalate, the mixture was kneaded in a ball mill for 20 hours using tetrahydrofuran as a solvent.
A slurry having a viscosity of 10 to 15 CpS was prepared.

After degassing this slurry, a dielectric layer with a thickness of 8 μm was formed on a polyester film with a thickness of 50 μm by a reverse roll method, and a hot stamp sheet was prepared. This hot stamp sheet has the same composition as the conventional hot stamp sheet, and has a dielectric layer 1 that can be thermally transferred.
It is 2. Next, 8 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl phthalate were blended with 100 parts by weight of dielectric powder containing mario 5 as the main component, and then kneaded for 20 hours in a ball mill using tetrahydrofuran as a solvent. A slurry having a viscosity of ~1519S was prepared. A dielectric layer 13 having a thickness of 8 μm was formed on a polyester film using this slurry in exactly the same manner as described above,
A hot stamp sheet with a small amount of binder was created. Dielectric layer 12.1 of these two types of sheets with different amounts of binder
After the three comrades face each other so as to overlap, from the base film side of the dielectric layer 12 of the sheet with a large amount of binder,
Pressure 5oKg/cd with heat roller.

After combining the two dielectric layers 12 and 13 with different amounts of binder under thermocompression bonding conditions at a temperature of 190° C., the base film of the dielectric layer 12 with a large amount of binder was peeled off, and as shown in the first factor, A green sheet of the present invention was produced.

Next, on a polyester film with a thickness of 50 μm, powder particles mainly composed of BaTiO3 prepared by a doctor blade method and 200 μm made of polyvinyl butyral resin were placed.
After the dielectric layer of the green sheet on which the dielectric layer of μm is formed and the dielectric layers of the hot stamp sheet having the above-mentioned two-layer structure are stacked so as to face each other, the pot stamp sheet of the present invention is prepared. The dielectric layers 12 and 13 of the hot stamp sheet were transferred by thermocompression bonding on the 11th side of the base film for 2 seconds at a temperature of 186° C. and a pressure of 6 oKp/i using the heated roller. After that, the base film 11 of the hot stamp sheet was peeled 11i'flL, and a reprinted Pd paste was applied to this peeled surface [product name ML manufactured by Shoei Chemical Co., Ltd.]
= 3,5 by screen printing method using 37241
An internal electrode 26 having a shape of X 1 and Oas was formed. Next, another hot stamp sheet according to the present invention is superimposed on top of the hot stamp sheet, and after transferring the dielectric layers 12 and 13 of the hot stamp sheet by thermocompression bonding under exactly the same conditions as described above, the base film 11 is peeled off. Internal electrodes 26 were printed in a predetermined shape using the same electrode base as described above. Note that the overlapping portion of the internal electrode 26, that is, the area of the electrode that effectively functions as a multilayer capacitor, is 1.4×1.
．． Lamination molding was performed to obtain Oa+. After repeating this process 10 times, the green sheets prepared by the doctor blade method and having a thickness of 200 μm described above were stacked on top of each other. Next, this laminate was further heated to 600 9/l using a mold press at 80°C.
Crimp bonding was carried out under the conditions of d.

After that, after cutting into a chip shape of 2.4 x 1.6 layers,
1300 while sprinkling the chip molded body in ZrO2 powder
It was baked at ℃ for 1 hour. In addition, the temperature increase and decrease rate is 200'
(, /llr) and held at 400°C for 10 hours to remove the binder during the process. 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. The number is 100. Table 1 shows the average value of capacitance of samples that are not short-circuited and the number of samples that are short-circuited.

Table 1 Next, a hot stamp sheet was prepared using a conventional method for comparison. That is, for 100 parts by weight of dielectric powder mainly composed of BaTi05, 2 parts by weight of polyvinyl butyral resin.
After blending 6 parts by weight and 2 parts by weight of dioctyl phthalate,
Tetrahydrofuran was added to a solvent and the mixture was kneaded in a ball mill for 20 hours to prepare a slurry having a viscosity of 10 to 15 cps. After degassing this slurry, a dielectric layer with a thickness of 16 μm was formed on a polyester film with a thickness of 60 μm by 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 embodiment, the dielectric layers 12.
No. 13 uses a green sheet consisting of two layers, but even if a hot-stamped sheet with a multilayer structure consisting of three or more types of dielectric layers with different amounts of binder is created and a multilayer ceramic capacitor is manufactured using this, Needless to say, similar effects can be obtained.

Effects of the Invention As described above, the green sheet for a multilayer ceramic capacitor according to the present invention is composed of a dielectric layer consisting of dielectric powder, a binder, and a plasticizer, and a base film, in which the dielectric layer has the same amount of dielectric powder. On the other hand, the multi-layer structure with different compositions of binders eliminates the occurrence of short circuits during the formation of internal electrodes, greatly improving the production yield during manufacturing, and its industrial value is extremely high. There is something big.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the structure of the green sheet for laminated ceramic capacitors of the present invention, Fig. 2 is a cross-sectional view of the vicinity of the internal electrodes of a laminated molded product using the green sheet of the present invention, and Fig. 3 is a hot stamping system. FIG. 4 is a cross-sectional view of the vicinity of the internal electrodes of a laminated molded body using a hot stamp sheet according to the conventional method. 11...Base film, 12...Dielectric layer with a large amount of binder, 13...Dielectric layer with a small amount of binder, 14...Dielectric powder , 15
...Binder. plasticizer. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (1)

[Claims] Green for laminated ceramic capacitors consists of a dielectric layer consisting of dielectric powder, a binder, and a plasticizer, and a base film, and the dielectric layer has a multilayer structure consisting of a composition with different amounts of binder for the same amount of dielectric powder. sheet.