JPS63188926A - Manufacture of laminated porcelain capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a multilayer ceramic capacitor.

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, there has been a strong demand for smaller and larger capacity capacitors used as circuit elements. It has become. A multilayer ceramic capacitor is known as a component that satisfies these requirements.

As is well known, the capacitance C (pF) of a capacitor consisting of n layers of ceramic dielectric and n pairs of electrodes is expressed by the following equation.

However, S is the electrode area (mdi), ε1 is the relative dielectric constant,
t is the thickness of the dielectric, and n is the number of layers.

Here, n-1 is a single-plate capacitor, and n≧2 is a multilayer ceramic capacitor.

The thickness of one dielectric layer of a multilayer ceramic capacitor is
It is designed to have a thickness of about several tens of micrometers, which is equivalent to a thickness of less than 100 micrometers compared to the several hundred micrometers of conventional single-plate capacitors.

In addition, as shown in the above formula, the capacitance is inversely proportional to the thickness and proportional to the total number of laminated dielectrics, so the thinner the thickness of one dielectric layer, the greater the capacitance. Then, the number of dielectric layers can also be increased. Therefore, compared to a single-plate capacitor, a multilayer ceramic capacitor can have a larger capacity with the same volume, and can be made smaller with the same capacity.

FIG. 2 shows the entire general manufacturing process of a conventional multilayer ceramic capacitor. First, a dielectric layer 2 having a predetermined thickness is placed on an organic film 1 made of polyester or the like using a doctor blade method using a slurry prepared by adding a binder, a plasticizer, an organic solvent, etc. to dielectric powder. A green sheet 3 on which is formed is prepared. Next, this green sheet 3 is peeled off from the organic film 1 and punched out to a predetermined size, and then electrodes are applied in a predetermined pattern onto the punched dielectric layer 2 by screen printing.

By drying, the internal electrode 4 is formed. Next, the number of dielectric layers 2 on which the internal electrodes 4 are formed are placed into the metal die 5, and the layers are laminated while applying heat and pressure. At this time, dielectric layers 2a on which no electrodes are printed are placed on the upper and lower parts of the laminate, and are designed to withstand warping during sintering and stress during handling. Thereafter, it is cut into chips and fired, after which external electrodes 6 are formed to produce a capacitor. ([Insulating/Dielectric Ceramics J, Published by CMC, 1960, Supervised by Tadashi Shiozaki, P, 211-227)
Problems to be Solved by the Invention With the miniaturization of electronic circuits and electronic equipment, there is a strong desire for multilayer ceramic capacitors to be smaller and larger in capacity. For this purpose, it is essential to further reduce the thickness of the dielectric layer, and specifically, it is necessary to reduce the current thickness of the dielectric layer from several tens of micrometers to several tens of micrometers. When using such ultra-thin sheets and laminating them according to the manufacturing process shown in Figure 2, the dielectric sheet with electrodes printed on it is peeled off from the organic film and is evenly stuffed into a metal die without wrinkles and crimped. Doing so is an extremely difficult task. In addition, when wrinkles occur, air remains inside the molded body, which causes separation between the dielectric and the electrode after sintering.

It also causes so-called delamination, which poses many problems in terms of workability and process yield.

In view of the above-mentioned problems, the present invention aims to provide a method for manufacturing a multilayer ceramic capacitor, which allows even extremely thin dielectric sheets to be stacked uniformly and with good adhesion.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a multilayer ceramic capacitor of the present invention is as follows.

In other words, when heat and pressure are applied from the base film side of a green sheet consisting of a dielectric layer and a base film,
After forming a predetermined electrode on the dielectric layer of a green sheet that can transfer the dielectric layer from the base film to the object, this green sheet is placed on the dielectric layer of another green sheet on which no electrode is formed. After stacking the dielectric layers so that they face each other, the green sheet on which the electrodes are formed is bonded by thermocompression from the base film side, so that all the dielectric layers of the sheet are bonded to the green sheet on which the electrodes are not formed. After being transferred to the dielectric layer, the base film of the green sheet on which the electrodes are formed is peeled off, and another green sheet on which the electrodes are formed is used to overlay the transferred dielectric layer. , transfer by thermocompression,
The base film is repeatedly peeled off, and the dielectric layers and electrode layers are all alternately laminated.

Function The focus of the method for manufacturing a multilayer ceramic capacitor according to the present invention is to use a green sheet (hereinafter referred to as a hot stamp sheet) that enables the so-called hot stamping method, in which the dielectric layer is transferred to the object with good adhesion when heat and pressure are applied. ).

The slurry viscosity when producing this hot stamp sheet can be designed to be extremely small, at several tens of cps, compared to the slurry viscosity of 2,000 to 30 oCpS when using the conventional doctor blade method. Therefore, hot-stamped sheets can be easily produced using the reverse roll method or the like even with ultra-thin dielectric layers up to several micrometers, which was considered impossible using conventional methods. In addition, when laminating ultra-thin dielectric layers from a few μm to over 10 μm, they can be stacked together with the base film, making it possible to layer the dielectric layers evenly and uniformly without wrinkles. It becomes possible.

In addition, unlike the conventional method in which many printed dielectric layers are packed into a mold die during lamination and then pressurized, in the present invention, hot stamp sheets are pressed one by one using a hot roller or the like. , transcription.

The dielectrics to be transferred and the electrodes or the binders contained in the dielectrics are once softened and then fixed to each other. Therefore, adhesion is significantly improved compared to the conventional method. Furthermore, since the dielectric layer is brought into close contact with the dielectric layer while pushing out air when it is heated and pressed with a roller, it is difficult for air to remain in the laminate molded body, and it is possible to significantly suppress the occurrence of delamination.

EXAMPLE The basic manufacturing process of a multilayer ceramic capacitor according to the present invention will be explained below using FIG. First, a slurry prepared by adding binder, plasticizer, organic solvent, etc. to dielectric powder is used, and by reverse roll method etc.
An extremely thin dielectric layer 7 with a thickness of several μm to more than ten μm is formed on a base film 8 to produce a hot stamp sheet 9.

In this case, the type and amount of the binder must be carefully considered depending on the object so that the hot stamping system can be used. Note that, in order to facilitate the peeling of the dielectric layer 7 during thermocompression bonding, the hot stamp sheet 9 may be formed by forming a peeling layer on the base film 8 in advance, and then forming the dielectric layer 7 thereon. Next, after forming internal electrodes 10 in a predetermined shape on the dielectric layer 7,
Dielectric layer 1 of green sheet 11 on which no electrode is formed
2, a hot stamp sheet 9 on which electrodes 1o are formed is superimposed so that the dielectric layers 7 and 12 face each other, and heat and pressure are simultaneously applied from the base film 8 side using a heat roller 13 or the like. After transferring the dielectric layer 7 of the hot stamp sheet 9 to the dielectric layer 12 on the green sheet 11 on which no electrodes are printed, the base film 8 of the hot stamp sheet 9 is peeled off. Here, 14 is a base film constituting the green sheet 11. Next, the above-mentioned another electrode was printed again on the above-mentioned transferred surface, and the dielectric layer was transferred by hot stamp sheet lamination and thermocompression bonding.

After repeating the peeling of the base film a necessary number of times and alternately laminating dielectric layers and electrode layers, it is cut into chips and fired, and then external electrodes 16 are formed to produce a capacitor.

Next, specific embodiments of the present invention will be described in detail.

First, 22 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl phthalate were mixed with 100 parts by weight of dielectric powder mainly composed of BaTiO3, and then kneaded for 20 hours in a ball mill using tetrahydrofuran as a solvent.
0~15 Cp! A slurry having a viscosity of E was prepared. After degassing this slurry, a 15 μm thick film was applied onto a 60 μm thick polyester film using the reverse roll method.
A hot stamp sheet was produced by forming a dielectric layer of . Commercially available Pd paste [
An electrode having a size of 3.5 m x 1.0 m was formed by screen printing using ML-3724 (trade name, manufactured by Shoei Kagaku Co., Ltd.).

Next, on a polyester film with a thickness of 60 μm, powder particles mainly composed of BaTiO3 prepared by a doctor blade method and a thickness of 2
On a green sheet on which a dielectric layer of 00 μm was formed,
After stacking the hot stamp sheets printed with the electrodes described above, the base film side of the hot stamp sheets is heated with a heated roller at a temperature of 130°C and a pressure of 50 kg/c.
The dielectric layer of the hot stamp sheet was transferred to the dielectric layer of the dielectric green sheet by heat-pressing for 3 seconds under Al conditions.

After that, the base film of the hot stamp sheet was peeled off. Next, another hot stamp sheet on which electrodes were printed on the transferred dielectric layer was hot-pressed using a hot roller under the same conditions as before, and then the base film was peeled off. Note that the overlapping portion of the internal electrodes, that is, the area of the electrodes that effectively function as a multilayer capacitor, is 1.4 x 1. o,,
It was laminated and molded so that After repeating this process 10 times, the dielectric green sheets fabricated by the doctor blade method having a thickness of 20,011 m described above were superimposed. Next, this laminate was further heated to 500 k at 80°C using a mold press.
The pressure bonding was carried out under the conditions of g/ad. After tightening, 2.4X1,6
After cutting into chicken chip shapes, the chip molded bodies were baked at 1300° C. for 1 hour while being sprinkled with ZrO2 powder. In addition,
The temperature raising and cooling rate Fi was set to 200°C/hr, and the temperature was maintained at 380°C for 1 ohr to remove the binder during the process, fC.

The capacitance of the capacitor thus produced was measured using a conventional method, and the fine structure of the sintered body was observed using a scanning electron microscope to measure the thickness of the dielectric layer and confirm the presence or absence of delamination. The number of measurement samples was 10.
It was set to 0. Table 1 below shows the average capacitance, dielectric layer thickness of the sintered body, and delamination occurrence rate for n=100. In addition, for comparison, as a conventional method, a green sheet with a thickness of 40 μm made of a dielectric layer powder containing BaTiO3 as the main component and having exactly the same composition as described above was prepared using a doctor blade method, and a second Table 1 also shows the capacitance, dielectric layer thickness, and delamination occurrence rate of the multilayer capacitor manufactured according to the manufacturing process shown in the figure. Here, the type and shape of the electrodes, the number of laminated sheets, firing conditions, etc. were all set to the same conditions.

As is clear from the above results, the laminated ceramic capacitor manufactured according to the present invention can be laminated evenly with good adhesion by using the hot stamping method, making it possible to laminate sheets made of ultra-thin dielectric material uniformly with good adhesion. The occurrence of lamination can be suppressed. Furthermore, since the dielectric layer of the sintered body is thin, the capacitance is greatly improved compared to the conventional method, and miniaturization is also possible.

In addition, in the example, BaTi0. 1/IJE, SrTiO3 system, MgTi0. −
CaTiO.

There is no problem in using a ceramic powder having any dielectric properties such as a ceramic powder. Furthermore, although a heated roller was used to transfer the dielectric layer, it goes without saying that the same effect can be obtained by moving a heating plate with a built-in heater up and down for thermocompression bonding.0 Invention Effects As described above, the present invention utilizes a system in which a dielectric layer can be transferred to an object when a green sheet consisting of a dielectric layer and a base film is thermocompression bonded from the base film side, the so-called hot stamping method. The manufacturing method for multilayer ceramic capacitors includes a process of laminating layers using green sheets designed to make it possible to achieve good adhesion and uniformity even with green sheets made of ultra-thin dielectric layers, which was previously considered impossible. It is compact because it can be stacked on top of other parts.

In addition to achieving a large capacity, it is also possible to suppress the occurrence of delamination, making it possible to improve productivity, and its industrial value is extremely high.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a manufacturing process of a multilayer ceramic capacitor according to the present invention, and FIG. 2 is a diagram illustrating a manufacturing process according to a conventional method. 7... Dielectric layer, 8, 14... Base film, 9... Hot stamp sheet, 10
...Internal electrode, 11... Green sheet on which no electrode is formed, 12... Dielectric layer on which no electrode is formed, 13... Heat Laura, 15
...External electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
- One-of-a-kind film 4 ~ = internal electricity supply

Claims (1)

[Claims] When heat and pressure are applied from the base film side of a green sheet consisting of a dielectric layer and a base film, the dielectric layer can be transferred from the base film to the object on the dielectric layer of the green sheet. , after forming a predetermined electrode, the green sheet was superimposed on the dielectric layer of another green sheet on which no electrode was formed so that the dielectric layers faced each other, and then the electrode was formed. The dielectric layer of the green sheet is transferred to the dielectric layer of the green sheet on which the electrodes are not formed by thermocompression bonding from the side of the base film of the green sheet, and then the green sheet on which the electrodes are formed is transferred. After peeling off the base film, using another green sheet on which electrodes are formed, overlaying the transferred dielectric layer, transfer by thermocompression bonding, and peeling off the base film are repeated, and then the dielectric layer is removed. A method for manufacturing a multilayer ceramic capacitor, characterized by alternately stacking electrode layers.