JPS6258646B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a method of manufacturing a ceramic multilayer capacitor, and particularly to a method of manufacturing a small-sized, large-capacity capacitor. Explanation of Prior Art When manufacturing ceramic multilayer capacitors, ceramic slurry is made into a thin film using a doctor blade, etc., and after drying, metal powder paste such as palladium or silver-palladium is printed as internal electrodes, and a large number of these are stacked. Crimp and integrate. This is fired at 1100°C to 1350°C to turn it into porcelain, and external electrodes are applied to obtain ceramic multilayer capacitor chips. A ceramic green sheet printed with internal electrodes obtained at an intermediate stage of the manufacturing process as described above is shown in FIG. In Figure 1, 1
is a ceramic green sheet, and 2 is an internal electrode. In the above-mentioned manufacturing process, the aspects of manufacturing the ceramic green sheet will be explained in detail as follows. A slurry, which is a mixture of dielectric powder, binder, dispersant, and solvent, is applied onto a mirrored stainless steel plate or plastic tape using a doctor blade, and then peeled off after drying.
Ceramic green sheets with a thickness of 35 to 60 μm were obtained. The capacitance per unit volume of a capacitor is determined by the dielectric constant of the ceramic dielectric, the total area of the internal electrodes, and the square of the thickness of each dielectric layer, but in order to obtain a small capacitor with large capacity, , it is necessary to reduce the thickness of the dielectric layer. However, for the following reasons, the thickness of ceramic green sheets has conventionally been limited to about 35 μm. In other words, if the ceramic green sheet is made thinner than this limit, (1) micro defects in the ceramic green sheet, such as pinholes, will develop into fatal defects such as shortening between the electrodes, and (2) the tensile strength of the ceramic green sheet will decrease. The ceramic green sheets become weak and difficult to handle, and it is not possible to automatically perform processes such as peeling off the ceramic green sheets, printing internal electrodes, and drying the ceramic green sheets in a continuous sheet form.
and (3) deformation of the ceramic green sheet due to penetration of the solvent into the internal electrode paste, causing inconvenience in subsequent processes. Purpose of the Invention Therefore, the purpose of the present invention is to improve the tensile strength when handling ceramic green sheets even when they are extremely thin, and to automate the printing of internal electrodes and the drying process of ceramic green sheets. enable. An object of the present invention is to provide a method for manufacturing a ceramic multilayer capacitor. Another object of the present invention is to provide a method for manufacturing a ceramic multilayer capacitor that can minimize the development of minute defects in ceramic green sheets into fatal defects. Still another object of the present invention is to provide a method for manufacturing a ceramic multilayer capacitor in which deformation of the internal electrodes after printing is prevented. Summary of the Invention In this invention, a ceramic multilayer capacitor can be obtained by following the steps below. First, a polyester film (FIG. 2...3), which has good adhesion to the binder in the ceramic slurry, is prepared. Although it is preferable for this resin film to be as thin as possible, its thickness is determined in relation to tensile strength. For example, in the case of a polyester resin film, one having a thickness of about 1.5 to 14 μm is used. A layer of ceramic slurry (FIG. 2...1) is formed on both surfaces of such a resin film to form a three-layer structure sheet (FIG. 2, 4). A layer of ceramic slurry can be formed by applying the doctor blade method to both sides of the resin film, but the pulling method, in which the resin film is passed through the ceramic slurry, can simultaneously apply the doctor blade method to both sides of the resin film. It is efficient in that a layer of ceramic slurry can be formed on the surface. This 3
The layered structure sheet 4 is dried as appropriate. Next, an internal electrode (FIG. 2...2) is formed on one side of such a three-layer structure sheet without peeling off the ceramic slurry layer from the resin film. The internal electrodes are preferably automatically printed and the printed internal electrodes are dried. Thereafter, as in the conventional case, a plurality of sheets having this three-layer structure are stacked so that the internal electrodes are alternately led out from different ends, and are integrated by pressure if necessary. By firing this, the resin film located in the middle of each three-layer structure sheet is burnt out. If the thickness of the resin film is less than a certain thickness, the layer in which it existed will be joined together with the upper and lower ceramics at the same time as the resin film burns out, and will not substantially remain as a gap layer. External electrodes electrically connected to internal electrodes are formed on the end faces of the laminated sintered body obtained as described above to obtain ceramic laminated capacitor chips. Effects of the Invention According to the present invention, since the mechanically weak thin ceramic green sheet can be handled as a three-layer structure sheet with a resin film interposed, the tensile strength can be increased. It is easier to handle, and it is also easier to automate the printing of internal electrodes and the drying process of ceramic green sheets. Further, due to such advantages in handling, it is naturally possible to reduce the thickness of the ceramic dielectric layer, and it becomes possible to manufacture a small-sized, large-capacity ceramic multilayer capacitor. For example, while the average tensile strength of conventional ceramic green sheets was 20 to 40 g/ ^mm2 , the three-layer structure sheet according to the present invention has a tensile strength of 10,000 to 20,000 g/mm2.
It has now become possible to increase it to g/mm ² . In addition, since the ceramic green sheet is formed in two layers with a resin film interposed between them, the probability that micro defects occurring in each two layers are aligned in the thickness direction is extremely rare, resulting in penetrating pinholes. The fatal defect of occurrence of this can be reduced to almost zero. DESCRIPTION OF EXAMPLE BaTiO ₃ 89% by weight, CaZrO ₃ 10% by weight, and
10% of an acrylic water-soluble binder as an organic binder and 0.1% of a dispersant were added to a high permittivity dielectric composition powder consisting of 1.0% by weight of MgTiO ₃ and wet-mixed for 12 hours using an equal weight of pure water. I did it. The obtained slurry was defoamed in a vacuum container and then transferred to a stainless steel container. Next, each thickness is in the range of 1.5 to 20 μm as shown in Table 1 later, and the width is 15 cm.
A polyester film was passed through the slurry in the stainless steel container described above and pulled up vertically at a constant speed to form a uniform layer of slurry on both sides of the polyester film. This slurry was heat-dried to obtain a three-layer structure sheet 4 in which the ceramic green sheets 1 were adhered to both sides of the polyester film 3 (FIG. 3). The thickness of the ceramic green sheet in this three-layer structure sheet is
Each is as shown in Table 1. These three-layer structure sheets 4 were punched into a rectangle of 7.0 x 10.0 cm using a mold, and palladium paste was printed on this using a screen printer to form internal electrodes 2 (Fig. 3). After drying, 410 printed three-layer structure sheets and 10 each of unprinted three-layer structure sheets 4a on top and bottom were stacked so that internal electrodes were alternately opposed (FIG. 4). This was put into a mold and crimped under conditions of 40 to 80°C and 0.5 to 2 ton/cm ² to integrate. From the integrated laminate,
For example, a single element of a capacitor is cut out with a blade along cutting line 5 in Fig. 4, and heated at 200 to 500°C.
After burning the binder under conditions of ~15 hours,
It was fired at 1340°C for 2 hours to form porcelain. After firing, a silver paste was applied to the chip 6 as an external electrode 7 (FIG. 5), and the chip 6 was fired at 800°C. The dimensions of this chip were 0.2 to 0.5 mm thick, 5.0 mm long, and 4.0 mm wide. The properties of each sample thus obtained are shown in Table 1. In Table 1, the thickness of the polyester film of each sample (μm), the total thickness of both sides of the ceramic green sheet (μm), the tensile strength per 1 cm width of the ceramic green sheet (Kg), and the through holes generated in the ceramic green sheet. Number of defects (per 15cm x 1m), number of layer defects (delamination) occurring in the laminate after firing (number of occurrences per 100 samples), thickness of one dielectric layer after firing (μm), average static Capacity is indicated. 100 samples were prepared for each sample, and the values in Table 1 represent the average values. As a comparative example, similar data were measured for several samples of ceramic multilayer capacitors produced by conventional manufacturing methods, and are shown in Table 2.

【table】

[Table] As is clear from the data shown in Table 1, the thinner the polyester film, the better. If the polyester film is thicker than 14 μm, layer defects (delamination) will occur in more than half of the sintered body, making it impossible to obtain the designed capacitance. Furthermore, as is clear from the comparison between Table 1 and Table 2, the strength of the ceramic green sheet produced by the conventional method is more than an order of magnitude weaker than the strength of the ceramic green sheet produced by the present invention. unsuitable for the process, and
Thin sheets of 30 μm or less have a large number of minute through-pinhole defects, and when they are made into finished products, shot defects occur frequently. In the description of the above embodiments, a polyester film was used as the resin film. This polyester film has high tensile strength and is superior to other resin films in terms of heat resistance. Therefore, for example, the ceramic slurry layer has excellent heat resistance during drying, and there is an advantage that the ceramic slurry layer can be made thin while maintaining dimensional stability. Therefore, the dielectric layer interposed between the internal electrodes can be made thinner, and as a result, a large capacity can be obtained. However, the resin film is not limited to such a polyester film, but may be a resin film made of other materials, such as a polyethylene film.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a ceramic green sheet on which internal electrodes, which are one component of a laminate of a ceramic multilayer capacitor, are formed by a conventional method. FIG. 2 is a perspective view showing a ceramic green sheet on which internal electrodes, which are one component of a ceramic multilayer capacitor, are formed according to the present invention. 3 to 5 sequentially show the steps for obtaining a ceramic multilayer capacitor according to the present invention, in which FIG. 3 is a sectional view of one ceramic green sheet provided with internal electrodes, and FIG. Figure 4 is a sectional view of a block made by stacking and integrating a plurality of these, and Figure 5 is a sectional view of a multilayer capacitor in which external electrodes are provided on a single chip cut and fired along cutting line 5 in Figure 4. . In the figure, 1 is a ceramic green sheet or a layer of slurry, 2 is an internal electrode, 3 is a resin film or polyester film, 4 is a three-layer structure sheet, 6 is a capacitor chip, and 7 is an external electrode.

Claims (1)

[Claims] 1. Prepare a resin film that has good adhesion to the binder in the ceramic slurry, form a layer of ceramic slurry on both sides of the resin film to form a three-layer structure sheet, and prepare a three-layer structure sheet. An internal electrode is formed on one side, and a three-layer structure sheet on which the internal electrode is formed,
A porcelain sintered body containing a plurality of internal electrodes is obtained by laminating a plurality of sheets to form a laminate so that the internal electrodes are alternately led out to different ends, and burning the resin film at the same time as firing the laminate. A method for manufacturing a ceramic multilayer capacitor, comprising: forming an external electrode electrically connected to the internal electrode on the outer surface of the fired multilayer body.