JP2003243258A - Manufacturing method of solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid electrolytic capacitor, which can improve the efficiency and the quality of the manufactured products in the methods of manufacturing solid electrolytic capacitors having solid electrolytic layers formed in the cells of the porous sintered material. <P>SOLUTION: This manufacturing method includes a step to immerse a porous sintered material 2 in a solution to impregnate and form a solid electrolytic layer 5, and a step to adhere the solid electrolytic layer 5 into the porous sintered material 2. The impregnation step includes a first immersion treatment to immerse a part of the porous sintered material 2 in the solution for a certain time and a second immersion treatment to immerse the whole porous sintered material 2 in the solution. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor in which a solid electrolyte layer is formed in each hole of a porous body.

[0002]

2. Description of the Related Art Conventionally, capacitors have been widely used in electronic circuits. Among capacitors, solid electrolytic capacitors are often used in power supply circuits and the like because of their relatively small size and large capacity.

As a solid electrolytic capacitor, there is one having a structure as shown in FIG. 1, for example. In this solid electrolytic capacitor 1, for example, a dielectric layer 4 made of Ta ₂ O ₅ and MnO 2 are provided in each hole 3 of a porous sintered body 2 obtained by sintering a compression molded body made of metal powder such as tantalum. _A solid electrolyte layer 5 composed of ₂ is formed. In the porous sintered body 2, one end portion of the metal wire 6 as an anode is embedded or integrated by welding to form the porous sintered body 2
The surface of the substrate has a buffer layer 7 and a metal layer 8 as a cathode.
Are formed.

The solid electrolyte layer 5 of such a solid electrolytic capacitor 1 is usually formed by impregnating the porous sintered body 2 on which the dielectric layer 4 is formed with a manganese nitrate solution and then performing a thermal decomposition treatment. To be done.

[0005]

To impregnate the porous sintered body 2 with the manganese nitrate solution, as shown in FIG. 2, the porous sintered body is immersed in the manganese nitrate solution L held in the container C. This is done by immersing the whole of 2. However, when the entire porous sintered body 2 is immersed in the manganese nitrate solution L, bubbles may be generated in each hole 3 in the porous sintered body 2 due to the surface tension of the manganese nitrate solution. Is less likely to be impregnated to the inside of each hole 3.

Therefore, there is a method of using a manganese nitrate solution having a low viscosity in order to almost completely impregnate the manganese nitrate solution, but in this method, it is necessary to repeat the immersion treatment and the thermal decomposition treatment several tens of times. However, there is a problem that the workability is poor and the work takes a long time. Also,
When the porous sintered body 2 is not sufficiently impregnated with the manganese nitrate solution, the dielectric layer 4 formed around the porous sintered body 2 may be damaged, and the characteristics of the solid electrolytic capacitor 1 such as impedance and The leakage current increases,
Inconveniences such as not being able to obtain an appropriate insulating property or being unable to obtain a desired electrostatic capacitance occur.

The present invention was conceived under the above circumstances, and it is an object of the present invention to provide a method of manufacturing a solid electrolytic capacitor which can improve the efficiency and quality of manufacturing work. It is an issue.

[0008]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention takes the following technical means.

The method for producing a solid electrolytic capacitor provided by the present invention comprises an impregnating step of impregnating a porous body with an impregnating solution for forming a solid electrolyte layer, and fixing the solid electrolyte layer to the porous body. A method for manufacturing a solid electrolytic capacitor, comprising: a first dipping treatment in which a part of the porous body is held in the impregnating solution for a certain period of time and dipped; A second step of immersing the entire porous body in the impregnation solution after the first impregnation treatment.
Immersion treatment is included.

Usually, in the impregnation step for forming the solid electrolyte layer, the entire porous body is immersed in an impregnating solution for forming the solid electrolyte layer, for example, a manganese nitrate solution, and each pore in the porous body is immersed. The inside is impregnated with a manganese nitrate solution. On the other hand, according to the production method of the present invention, before the entire porous body is immersed in the manganese nitrate solution, preliminary,
A part of the porous body is immersed in a manganese nitrate solution for a certain period of time. Thereby, the manganese nitrate solution infiltrates into each pore in the porous body from a part of the porous body,
Wetting the surface in each hole by capillarity. for that reason,
After that, when the entire porous body is immersed in the manganese nitrate solution, the manganese nitrate solution is easily impregnated into the porous body, and the possibility that bubbles are generated is reduced. As a result, according to the invention of the present application, it has been repeated several times that the dipping treatment and the thermal decomposition treatment as the fixing step were repeatedly performed so that the pores in the porous body were almost completely filled. Can be reduced to. Therefore, the manufacturing time can be shortened and the efficiency of the manufacturing work can be improved.
Moreover, since the pores in the porous body are almost completely filled with the solid electrolyte layer by the first and second dipping treatments, damage to the dielectric layer formed around the porous body can be suppressed, and the solid electrolytic capacitor can be suppressed. It is possible to prevent the impedance and the leakage current from increasing in the characteristic of (3) and improve the quality.

The second immersion treatment may be performed a plurality of times, and the first immersion treatment may be performed every time the second immersion treatment is performed. This makes it easier for the manganese nitrate solution to penetrate into the details in the porous body in the first immersion treatment, and to further promote the impregnation of the porous body with the manganese nitrate solution during the second immersion treatment.

In the first dipping treatment, it is desirable that less than half of the outer surface of the porous body is dipped in the impregnating solution. This is because if more than half of the outer surface of the porous body is immersed, the manganese nitrate solution will easily be impregnated into each pore of the porous body, and the effect of being able to reduce the possibility of producing bubbles will be diminished. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 shows a cross-sectional view of a solid electrolytic capacitor according to the present invention and an enlarged view of a main part thereof (portion circled in the figure). In the solid electrolytic capacitor 1 shown in FIG. 1, a dielectric layer 4 and a solid electrolyte layer 5 are formed around the porous sintered body 2 or in each hole 3 of the porous sintered body 2. In the porous sintered body 2, one end of the metal wire 6 is embedded or integrated by welding, and a buffer layer 7 and a metal layer 8 are formed on a part of the surface of the porous sintered body 2. ing.

The porous sintered body 2 is formed by compression-molding powder of valve-acting metal such as tantalum, aluminum or niobium into a substantially rectangular parallelepiped shape and sintering it in a high vacuum state.

The dielectric layer 4 is made of a metal oxide, such as Ta ₂ O ₅ , that constitutes the porous sintered body 2, and functions as a dielectric. The capacitance of the solid electrolytic capacitor 1 is determined by the total area and thickness of this dielectric layer 4. Such a dielectric layer 4 can be formed by, for example, anodic oxidation (chemical conversion) treatment. More specifically, for example, in a state where a phosphoric acid solution or the like is held in a metal container that functions as a cathode and the porous sintered body 2 is immersed in this solution, the porous sintered body 2 and the metal container are The dielectric layer 4 is formed by energizing the gap.

The solid electrolyte layer 5 is provided, for example, by forming a manganese oxide layer (MnO ₂ ) in the cavity of the remaining porous sintered body 2 after forming the dielectric layer 4. There is. Usually, the solid electrolyte layer 5 is obtained by immersing the porous sintered body 2 in an impregnating solution containing manganese nitrate,
It is formed by performing an impregnation step of impregnating each manganese nitrate solution into each hole 3 of the porous sintered body 2 and a heating (pyrolysis) step performed thereafter. Details of the impregnation step and the thermal decomposition step will be described later. The solid electrolyte layer 5 can also be formed of a conductive polymer.

The metal wire 6 functions as an anode, and is made of, for example, the same kind of metal as the metal forming the porous sintered body 2. Such metal wire 6
Is embedded or welded at the same time when the porous sintered body 2 is compression-molded, or after the porous sintered body 2 is compression-molded in the porous sintered body 2, By embedding the part, it is integrated with the porous sintered body 2. The metal wire 6 is a Teflon (registered trademark) ring (or a Teflon tower) from the base end 2b of the porous sintered body 2.
A part is covered with 9 and extends to a predetermined length.

The buffer layer 7 is made of graphite or the like, and is provided between the solid electrolyte layer 5 and the metal layer 8 for the purpose of reducing the resistance when the contact resistance between them is large. For example, if the solid electrolyte layer 5 is MnO ₂
And the buffer layer 7 is provided when the metal layer 8 is made of silver or the like. Therefore, the buffer layer 7 is an optional layer provided as necessary.

The metal layer 8 functions as a cathode and is provided, for example, by applying a coating treatment to form a conductor layer of silver or the like.

Here, the step of forming the solid electrolyte layer 5 will be described. In the impregnation step of impregnating the porous sintered body 2 with the impregnation solution, first, before performing a normal immersion treatment (second immersion treatment). A preliminary dipping treatment (first dipping treatment) is performed.
That is, as shown in FIG. 3, the manganese nitrate solution L held in the container C is held for a certain period of time (for example, 0.01 to several hours) while the tip 2a of the porous sintered body 2 is immersed. .

After the completion of the first immersion treatment, the porous sintered body 2 is not pulled up once, but the second immersion treatment is continuously performed. That is, as shown in FIG. 2, the entire porous sintered body 2 is immersed in the manganese nitrate solution L, and the pores 3 in the porous sintered body 2 are impregnated with the manganese nitrate solution.

After that, the solid electrolyte layer 5 is formed on the porous sintered body 2.
Then, a fixing step for fixing and forming is performed. Specifically, the solid electrolyte layer 5 is fixedly formed by subjecting manganese nitrate to a heat treatment to generate MnO ₂ on the surface of the dielectric layer 4, for example, by performing a thermal decomposition treatment.
The thermal decomposition treatment is performed at 150 ° C. or higher for several tens of minutes.

The first immersion treatment, the second immersion treatment and the thermal decomposition treatment are carried out as a set, and the porous sintered body 2 is used.
A plurality of sets are performed until the inside of each hole 3 in is completely filled.

As described above, when the first immersion treatment is performed, the manganese nitrate solution L becomes the tip portion 2a of the porous sintered body 2.
From the inside into each hole 3 in the porous sintered body 2 (see arrow A in FIG. 3), and travels through each hole 3 by a capillary phenomenon.
Wet the surface of the dielectric layer 4. Therefore, after that, the second
When the dipping treatment is performed, the manganese nitrate solution is easily impregnated into each hole 3 of the porous sintered body 2 and the possibility that bubbles are generated is reduced. As a result, the work in which the dipping process and the thermal decomposition process are conventionally repeated a plurality of times, for example, about 15 times can be reduced to about 7 or 8 times by performing the first dipping process as described above. . Therefore, the manufacturing time can be shortened and the efficiency of the manufacturing work can be improved. In addition, by performing the first and second dipping treatments, the manganese nitrate solution is impregnated into the pores 3 of the porous sintered body 2 evenly, so that damage to the dielectric layer 4 can be suppressed. Therefore, it is possible to prevent the impedance and the wetting current from increasing in the characteristics of the solid electrolytic capacitor 1, and it is possible to provide the solid electrolytic capacitor 1 having excellent quality.

As described above, it is desirable that the first immersion treatment be performed each time the second immersion treatment and the thermal decomposition treatment are performed. By doing this, the second
Porous sintered body of manganese nitrate solution during immersion treatment 2
Impregnation can be further promoted. Further, the first immersion treatment may be performed every time the second immersion treatment and the thermal decomposition treatment are performed multiple times.

Further, as described above, the tip portion 2a is more preferable for the portion of the porous sintered body 2 that is dipped in the manganese nitrate solution in the first dipping treatment. With the tip portion 2a, it is possible to easily immerse the porous sintered body 2 in the manganese nitrate solution simply by moving it up and down. The portion to be dipped in the manganese nitrate solution is not limited to the tip portion 2a, but other outer surface portions may be dipped, but half or less of the outer surface of the porous sintered body 2 is dipped. It is desirable to be done. When more than half of the outer surface of the porous sintered body 2 is immersed, the manganese nitrate solution is easily impregnated in each hole 3 of the porous sintered body 2 and the possibility of generating bubbles can be reduced. This is because the effect of being able to do so will fade.

The solvent in the manganese nitrate solution is
Appropriate concentrations of water or low molecular weight alcohols are desirable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a solid electrolytic capacitor.

FIG. 2 is a diagram for explaining a conventional immersion treatment in manufacturing a solid electrolytic capacitor.

FIG. 3 is a diagram for explaining a first immersion treatment in manufacturing a solid electrolytic capacitor.

[Explanation of symbols]

1 Solid electrolytic capacitor 2 Porous sintered body 3 holes (of porous sintered body) 5 Solid electrolyte layer

Claims (3)

[Claims] 1. A solid electrolytic capacitor comprising: an impregnating step of impregnating a porous body with an impregnating solution for forming a solid electrolyte layer; and a fixing step for fixing and forming the solid electrolyte layer on the porous body. A manufacturing method, wherein the impregnating step includes a first immersion treatment in which a part of the porous body is immersed in the impregnating solution for a certain period of time, and a whole of the porous body after the first impregnation treatment. A second dipping treatment of immersing the above in the impregnating solution, and a method for producing a solid electrolytic capacitor, comprising: 2. The solid electrolytic capacitor according to claim 1, wherein the second immersion treatment is performed a plurality of times, and the first immersion treatment is performed each time the second immersion treatment is performed. Production method. 3. The method for producing a solid electrolytic capacitor according to claim 1, wherein in the first immersion treatment, half or less of the outer surface of the porous body is immersed in the impregnating solution.