JPH0426773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming internal electrodes in a cylindrical capacitor, particularly a semiconductor cylindrical capacitor such as a surface insulated type capacitor.

BACKGROUND ART As a method for forming internal electrodes of a so-called surface-insulated cylindrical capacitor whose surface is covered with an oxide film, a method called a reduced pressure method has been considered. This reduced-pressure construction method involves immersing the open end of a cylindrical porcelain body with one end blind in a bath of metal paste in a reduced-pressure atmosphere, then returning the pressure to atmospheric pressure and applying the metal paste inside the porcelain body. This is a method of forming a predetermined metal coating film for internal electrodes by filling the porcelain body with air, creating a reduced pressure atmosphere for a certain period of time, and sucking and scraping out the metal paste inside the porcelain body.

Incidentally, in a surface insulated semiconductor capacitor, the capacitance has a certain correlation with the film thickness of the electrode, so it is necessary to control the film thickness in order to obtain a desired capacitance. In this case, the film thickness of the internal electrodes was controlled by changing the viscosity and specific gravity of the metal paste used.

Problems to be Solved by the Present Invention However, with the method of changing the viscosity and specific gravity of metal paste as described above, various metal pastes must be prepared, resulting in poor workability and increased product cost. The dot was hot.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a method for manufacturing a cylindrical capacitor that can be manufactured at low cost with simple improvements.

Means for Solving the Problems In order to achieve the above object, the manufacturing method of the present invention includes immersing the open end of a cylindrical porcelain body with one end blind in a bath of metal paste, and then The outside air pressure of the cylindrical porcelain element is made higher than the internal air pressure, and the metal paste is filled inside the cylindrical porcelain element, and then the air pressure inside the cylindrical porcelain element is reduced. Along with forming a metal coating on the inner peripheral surface,
The gist is to control the film thickness of the metal coating film by varying the pressure reduction time at that time.

Effect According to the above manufacturing method, the open end of a cylindrical porcelain element whose one end is blind is immersed in a bath of metal paste, and the air pressure outside the porcelain element is made lower than the air pressure inside the porcelain element. When a high pressure is applied, the metal paste is pushed up into the interior of the porcelain body due to the pressure difference, and the metal paste is filled up to the pushed up portion. Next, when the air pressure inside the porcelain body is reduced, a portion of the filled metal paste is scraped out to form a metal coating film for internal electrodes. At this time, we made the decompression time variable, so if the decompression time is short, the amount scraped out will be smaller, producing a cylindrical capacitor with a thick internal electrode film, and if the decompression time is long, the amount scraped out will be smaller. As a result, cylindrical capacitors with thin internal electrodes are manufactured.

EXAMPLES Hereinafter, the present invention will be explained in detail based on illustrated examples.

FIG. 1 is an explanatory diagram for explaining the manufacturing method of the present invention. First, as shown in A, a cylindrical porcelain element 2 having a bottom 1 formed so as to be blind at one end can be press-adjusted. Ag contained in the treatment tank 3 or
It is placed on a bath of metal paste 4 such as Ag-Pd.
Then, the inside of the processing tank 3 is degassed by a vacuum pump (not shown) to reduce the pressure to a predetermined atmospheric pressure.

After the pressure reduction of the processing tank 3 is completed, the open end 5 of the porcelain body 2 is immersed in the bath of the metal paste 4, as shown in FIG.

Next, as shown in c, outside air is introduced into the processing tank 3 to return the inside of the processing tank 3 to atmospheric pressure, and the porcelain body 2 is heated.
The internal atmospheric pressure is made lower than the atmospheric pressure outside the porcelain body 2. In other words, a pressure difference is created between the inside and outside of the porcelain body 2. The metal paste 4 is pushed up into the porcelain body 2 by this pressure difference, and the metal paste 4 is pushed up into the porcelain body 2.
Filled inside. Since this pushing-up height H is determined by the above-mentioned pressure difference, in order to obtain the desired pushing-up height H, the initial pressure reduction value in the processing tank 3 may be appropriately set.

Next, as shown in d, the pressure inside the processing tank 3 is reduced again, the excess metal paste 4 filled inside the porcelain body 2 is scraped out, and a metal coating film 6 for the internal electrode is formed. Here, if the value reduced in the processing tank 3 (2) is the secondary reduced pressure value, and the value reduced in the processing tank 3 (A) is the primary reduced pressure value, then the secondary reduced pressure value is: Secondary reduced pressure value = Primary reduced pressure value It is desirable to set it to +10mmHg.

That is, by setting the secondary decompression value to be slightly larger than the primary decompression value, all of the metal paste 4 inside the porcelain body 2 is scraped out, so that no excess metal paste remains in the opening of the porcelain body. It is.

Therefore, in the above figure D, the present invention defines the time required for the pressure to be reduced from atmospheric pressure to the secondary pressure reduction value as the pressure reduction time S, and by variably controlling the pressure reduction time S, The thickness T of the metal coating film 6 is set to a desired thickness. In other words, if the depressurization time S is short, the amount of metal paste 4 scraped out is small, and therefore the film thickness T becomes thick. If the depressurization time S is long, the amount of metal paste 4 scraped out is increased, so the film thickness T It becomes thinner.
Incidentally, it is preferable that the pressure reduction time S is variably controlled between 10 seconds and 500 seconds. If the decompression time S is shorter than 10 seconds, the amount of scraping is small, so the film thickness T of the metal paste 4 becomes too thick, and the porcelain body 2
If the decompression time S is longer than 500 seconds, the scraping amount will be large, and the thickness T of the metal paste 4 will become too thin, and it will not function as an electrode. It is.

Next, as shown in E, the porcelain body 2 having such a metal coating film 6 formed on the inner peripheral surface is coated with a metal paste 4.
When the porcelain body 2 is lifted out of the bath, a metal coating 6 is formed from the open end 5 to the outer surface of the porcelain body 2, and after baking and drying, it becomes an internal electrode.

After forming the internal electrodes, external electrodes are formed to a predetermined thickness by a known method, baked, and dried to obtain a capacitor.

Figure 2 shows that when forming internal electrodes using the reduced pressure method, the primary reduced pressure value is 656 mmHg, and the secondary reduced pressure value is 656 mmHg.
This figure shows an example of the relationship between the atmospheric pressure D in the processing tank 3 and the depressurization time S when it is set to 666 mmHg, and as can be seen from the figure, the depressurization time S is 248 seconds. In addition, at this time, the viscosity of the metal paste is
The one used was 30000 cps, specific gravity 1.911, and paste temperature 24°C. FIG. 3 shows the relationship between the average film thickness T after dry baking and the pressure reduction time S. In the above example, when the pressure reduction time S is 248 seconds, the film thickness T is 6.43 μm. For example, decompression time is 180
In seconds, the average film thickness is 10 μm. From this figure, it was confirmed that in order to function effectively as an electrode, it is preferable to control the depressurization time S in the range of 10 seconds to 500 seconds.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that the design can be changed within the scope of the invention. In the present invention, it is sufficient that one end is made blind, and even in a cylindrical capacitor with both ends open, although not shown, one end of the porcelain body can be made blind with a retaining plate or the like. It goes without saying that if you do this, you can achieve the same effect.

Furthermore, in the above embodiment, the porcelain body 2 was immersed in the paste bath after the pressure inside the treatment tank 3 was reduced, but it was immersed at normal pressure, and then the inside of the treatment tank 3 was pressurized and re-pressurized. It is easy to understand that similar results can be obtained. In this case, the electrode film thickness is varied by controlling the pressure recovery time.

Effects of the Invention As detailed above, in the manufacturing method of the present invention, after immersing the open end of a cylindrical porcelain body with one end blind in a bath of metal paste, the cylindrical porcelain body is The metal paste is filled inside the cylindrical porcelain body by setting the external air pressure higher than the internal air pressure, and then the air pressure inside the cylindrical porcelain body is reduced to coat the inner peripheral surface with metal. In addition to forming a film, the thickness of the metal coating film can be controlled by freely changing the decompression time, so even if you want to obtain capacitors with different capacitances even if the ceramic body has the same size. This eliminates the need to prepare multiple types of metal pastes with different viscosities and specific gravity as in the past, improving productivity and significantly reducing costs. Furthermore, it can be applied to control sheet thickness in the production of laminated sheets, and is also promising for future industrial applications.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram sequentially explaining a manufacturing method according to an embodiment of the present invention, Figure 2 is a diagram showing the relationship between atmospheric pressure and depressurization time, and Figure 3 is a diagram showing the relationship between film thickness and depressurization time. It is a diagram. 2...Porcelain body, 4...Metal paste, 5...
Opening end, 6...Metal coating film, S...Decompression time, T...
...Film thickness.

Claims (1)

[Claims] 1. After immersing the open end of a cylindrical porcelain body with one end blind in a bath of metal paste, the pressure outside the cylindrical porcelain body is made higher than the pressure inside the cylindrical porcelain body. Filling the inside of the element body with the metal paste, and then reducing the air pressure inside the cylindrical porcelain element body to form a metal coating film on the inner peripheral surface thereof,
A method for manufacturing a cylindrical capacitor, characterized in that the thickness of the metal coating film is controlled by varying the pressure reduction time at that time.