JPH058847B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a cylindrical capacitor, and particularly to a method for forming outer electrodes thereof.

Conventional technology As shown in FIG. 2, a conventional cylindrical capacitor is manufactured by forming an inner electrode b and an outer electrode c on the inner and outer surfaces of a cylindrical ceramic element a, respectively. It is constructed so that capacitance is taken at the opposing portions of both electrodes b and c, as shown in the figure.
This outer electrode c often extends to one end surface of the porcelain body a, and the inner electrode b is extended to the lead electrode part d.
In order to form a porcelain body a, the porcelain body a is usually extended from the other end surface to the outer surface.

In such a cylindrical capacitor, the outer electrode c
is formed by inserting a rotating pin coated with a metal paste such as Ag or Ag-Pd into the inner surface of the porcelain element a.
After forming the metal coating film for the inner surface electrode, as shown in FIG.
Accordingly, a common method is to form a metal coating h on the outer surface of the porcelain body a, dry it, and bake it.

At this time, the metal paste e is also applied to a portion of the inner surface electrode b corresponding to the extraction electrode portion d, thereby forming a metal coating film i. In this way, metal paste e
goes around to both end faces of the porcelain body a, and a coating film of the metal paste e is formed on both end faces as well.
Furthermore, there are cases where, for example, brush painting or spatula painting is performed without using the transfer roller g.

Problems to be Solved by the Invention However, the method for forming a metal coating film for an external electrode as described above has the following problems. That is, when applying the metal paste e to the outer surface of the porcelain element body using the transfer roller g, if there is variation in the amount of metal paste deposited on the transfer roller g, the thickness of the metal coating films h and i on the outer surface of the porcelain element a will increase. The metal coatings h, i often become uneven, the metal coatings h, i become blurred, and the edges of the metal coatings h, i often become wavy, as shown by the dashed lines in FIG.
It is difficult to form an external electrode with a predetermined area and thickness.

When applying the metal paste e to the outer surface of the porcelain body a using the transfer roller g as described above, the transfer roller g must be constantly checked to ensure that the amount of metal paste adhering to the transfer roller g does not fluctuate. It is necessary to frequently stop and clean the transfer roller g, and these adjustment operations take time and effort, resulting in a decrease in the operating rate.

In the metal paste application method using the transfer roller g, it is extremely difficult to perform multi-processing in which the metal paste e is applied to the outer surfaces of a large number of porcelain bodies a at once, and an improvement in manufacturing efficiency cannot be expected.

The metal paste application method using the transfer roller g is difficult to apply to rectangular cylindrical shapes other than cylindrical porcelain bodies.

Mass production cannot be expected with metal paste application methods such as brush painting or spatula painting.

There were other problems.

The present invention solves these conventional problems, and
The purpose of the present invention is to provide a method for manufacturing cylindrical capacitors that improves quality and is highly mass-producible.

Means for Solving the Problems In order to achieve the above object, the manufacturing method of the present invention provides a metal paste bath in a pressure-adjustable processing tank, and in this processing tank, a cylinder having openings at both ends is provided. With the opening at one end of the molded porcelain element sealed, the other end of the porcelain element is placed in contact with the bath surface of the metal paste, and the pressure inside the treatment tank is adjusted to be lower than the internal pressure of the porcelain element. Then, the porcelain element is immersed in a bath of metal paste to form a metal coating film for an external electrode on the outer surface of the porcelain element.

Effect According to the above manufacturing method, the opening of one end of the porcelain element is sealed in the processing tank, and the other end of the porcelain element is placed in contact with the bath surface of the metal paste, and the pressure inside the processing tank is When the porcelain element is immersed in a bath of metal paste after the pressure is lower than the atmospheric pressure inside the porcelain element, the metal paste is prevented from penetrating into the interior of the porcelain element because the air pressure inside the porcelain element is high. Therefore, no metal coating film is formed on the inner surface of the porcelain element, and a metal coating can be formed by adhering the metal paste only to one end surface and the outer surface of the porcelain element. The area on which the metal paste is adhered to the outer surface of the porcelain body is determined by the depth of immersion of the porcelain body into the metal paste bath.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

1A to 1H are explanatory diagrams sequentially explaining one embodiment of the manufacturing method of the present invention (external electrode forming method), and FIG. 1A shows a cylindrical porcelain body 1 formed with both ends open .

The porcelain body 1 is held on a holding plate 2 with the opening 1b at one end facing downward as shown in FIG.
It is placed on a bath of metal paste 4 such as Ag-Pd type. The number of porcelain bodies 1 held on the holding plate 2 is
In reality, there are hundreds to thousands of them, but only one is shown in this figure for ease of understanding.

Next, as shown in FIG. 1C, the porcelain element 1 is
The opening 1b is arranged so as to be in contact with the bath surface of the metal paste 4. Then, the inside of the processing tank 3 is evacuated using a vacuum pump (not shown) or the like to reduce the pressure to a predetermined pressure, and the air pressure outside the porcelain element 1 is made lower than the air pressure inside the porcelain element 1.

Next, while maintaining this pressure difference, the porcelain body 1 is immersed in a bath of metal paste 4 as shown in FIG. 1D. The depth of this immersion may be determined according to the required dimensions of the external electrode. When the porcelain element 1 is immersed in the immersion with a pressure difference, the pressure inside the porcelain element 1 is high, which prevents the metal paste 4 from penetrating into the porcelain element 1. Paste 4 will adhere. Therefore, the first
As shown in FIG.
is formed.

The metal coating film 5 for the external electrode formed in this way has the metal paste 4 sufficiently adhered evenly over the entire circumference of the immersed part of the outer surface of the porcelain element 1, so that
No blurring occurs, and the film thickness remains almost constant. Moreover, the area of the metal coating film 5 is determined by the depth of immersion, so it is always constant, and the upper edge does not wave unevenly, so the inner surface electrode b
A clear clearance can be formed between the lead electrode portion d and the lead electrode portion d (see FIG. 2).

Further, although not shown in the drawings, the metal coating film for the inner surface electrode may be formed by any method such as a rotating pin.

After the predetermined metal coating film 5 is formed on the inner and outer surfaces of the porcelain body 1 as described above, dry baking is then performed to complete the manufacture of the cylindrical capacitor. The manufactured cylindrical capacitor is as shown in FIG.

It goes without saying that the present invention is not limited to the embodiments described above. For example, in the state shown in FIG.
After the porcelain body 1 is placed in contact with the bath surface, even if the air in the treatment tank 3 is released to return it to atmospheric pressure, a pressure difference will occur between the inside and outside of the porcelain body 1, and the main The purpose of the invention can be achieved. still,
In this case, the degree of pressurization is sufficient as long as the metal paste 4 does not penetrate into the inside of the porcelain body when the porcelain body 1 is immersed in the bath of metal paste 4. Specifically, the pressure is 100 mmHg higher than atmospheric pressure. It is preferable to pressurize to a relatively high pressure.

Effects of the Invention As detailed above, according to the method of manufacturing a cylindrical capacitor of the present invention, it is possible to prevent the metal coating film for the external electrode from becoming blurred or the edges of the metal coating film becoming unevenly wavy. Since the area, shape, dimensions, etc. of the metal coating film are always constant, there may be defects in capacity due to variations in the area, etc. of the outer electrode formed by the metal coating film, or there may be problems with the pull-out of the outer electrode and inner electrode. There are almost no defective products due to short circuits with the electrode parts, and production yields are improved by about 10 to 20%.

In addition, since a transfer roller is not used as in the past, there is no need to check or clean it, and the operating rate is greatly improved.

Furthermore, since the dipping method is employed, it is possible to form a metal coating film having an even and uniform thickness not only on a cylindrical porcelain element but also on a rectangular cylindrical porcelain element.

Furthermore, according to the manufacturing method of the present invention, it is possible to perform multi-processing in which metal coatings are formed on hundreds to thousands of porcelain bodies at once, so productivity is several tens to hundreds of times higher than conventional methods. You can get remarkable effects such as a dramatic improvement of twice as much.

Furthermore, in the present invention, a treatment tank whose pressure can be freely adjusted is used, and a coating method is adopted within the tank, so that delicate coating dimensions can be set stably. That is, for example, the metal paste bath is opened to atmospheric pressure without using a treatment tank, and the inside of the porcelain body is connected to a nozzle or the like that can adjust the air pressure so that the pressure can be adjusted. The height can also be controlled, but in that case, if the atmospheric pressure fluctuates, the pressure difference between the inside and outside of the porcelain body cannot be kept constant, resulting in variations in coating dimensions.

In contrast, in the present invention, a metal paste bath is provided in the processing tank, and the application dimensions are set by adjusting the internal pressure of the tank, so that highly accurate application is possible.

[Brief explanation of the drawing]

1A to 1H are explanatory diagrams sequentially explaining a method for manufacturing a cylindrical capacitor according to an embodiment of the present invention;
The figure is a cross-sectional view of a cylindrical capacitor, and FIG. 3 is a cross-sectional view of essential parts explaining an example of a conventional manufacturing method. 1...Porcelain body, 4...Metal paste, 5...
Metal coating.

Claims (1)

[Scope of Claims] 1. A metal paste bath is provided in a treatment tank whose pressure can be freely adjusted, and in this treatment tank, the porcelain is treated with one end opening of a cylindrical porcelain body formed with openings at both ends sealed. The other end of the element is placed in contact with the metal paste bath surface, the pressure inside the treatment tank is adjusted to be lower than the internal pressure of the porcelain element, and then the porcelain element is immersed in the metal paste bath. A method for manufacturing a cylindrical capacitor, characterized in that a metal coating film for an outer electrode is formed on the outer surface of the porcelain body. 2. The cylindrical type according to claim 1, wherein the pressure inside the treatment tank is adjusted to atmospheric pressure, and the pressure inside the porcelain body is set higher than atmospheric pressure to form the metal coating film. Method of manufacturing capacitors. 3. The tube according to claim 1, wherein the metal coating film is formed by adjusting the pressure inside the porcelain body to atmospheric pressure and adjusting the pressure inside the processing tank to a pressure lower than atmospheric pressure. Method of manufacturing type capacitors.