JPH0536575A - Solid electrolytic capacitor and its manufacture - Google Patents

Abstract

PURPOSE:To provide a solid electrolytic capacitor and its manufacturing method wherein an electrostatic-capacity characteristic, a leakage-current characteristic and the like are improved in the solid electrolytic capacitor which uses a conductive polymer as an electrolyte. CONSTITUTION:The following are wound via a separator 3: a metal anode foil 1 on which an oxide film has been formed and which is provided with a valve action; and a metal cathode foil 2 which is not provided with any oxide film. A conductive polymer film is formed by a chemical polymerization operation. Thereby, a capacitor element is manufactured. The cathode foil 2 for the capacitor element is used as an electricity-feeding electrode, and an electrolytic polymerization operation is executed. Thereby, the electrolytically polymerized film of a conductive polymer is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor and a manufacturing method thereof, and more particularly to a solid electrolytic capacitor using a conductive polymer as an electrolyte and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, JP-A-3-52218 (H
01G 9/02), in the method of manufacturing a solid electrolytic capacitor using a conductive polymer as an electrolyte, first, a valve action of aluminum, tantalum, niobium, etc., on which an oxide film (dielectric layer) is formed in advance, is applied. After immersing the metal foil having it in an oxidizing agent such as ammonium persulfate or dilute sulfuric acid, it chemically reacts in the vapor phase or liquid phase of pyrrole monomer, aniline monomer, etc. to form a chemically polymerized film of polypyrrole, polyaniline, etc. . The thus obtained anode foil and separator paper are wound to form a capacitor element, and this capacitor element is electrolyzed in an electrolytic solution such as a pyrrole / ethanol system or a pyrrole / sulfonic acid system as shown in FIG. By conducting the polymerization, an electrolytically polymerized film of polypyrrole, polyaniline or the like having higher heat resistance and higher molecular density is formed.

Thereafter, an external power supply electrode such as a nickel wire, a platinum wire or a stainless wire is brought into direct contact with the capacitor element to supply an electrolytic polymerization current to form an electrolytic polymerization film of polypyrrole, polyaniline or the like. Then, a cathode lead-out layer is provided on the electrolytic polymerized film to draw out the cathode terminal, and in the final step, the capacitor element is packaged to manufacture a solid electrolytic capacitor.

In another conventional example, an anode foil obtained by forming a chemically polymerized film of polypyrrole, polyaniline or the like is formed into a strip shape, and a solid electrolytic capacitor is formed through the same steps as those described above.

[0005]

However, in the method of manufacturing a wound-type solid electrolytic capacitor as described above, since the anode foil is already covered with the oxide film, the leads connected to this anode foil. Electrolytic polymerization current cannot be supplied through the terminals. Therefore, it is necessary to bring the external power supply electrode into direct contact with the capacitor element during electrolytic polymerization to supply electrolytic polymerization current. Therefore, it is necessary to remove this external power feeding electrode after completion of electrolytic polymerization, but since the capacitor element and the external power feeding electrode are covered and fixedly integrated by the electrolytic polymerization film, the anode foil is removed when removing the external power feeding electrode. Since the oxide film above and the polymer film of polypyrrole, polyaniline and the like are damaged, not only the leakage current is increased but also various characteristics are defective.

Further, in the case of a wound-type capacitor element, the external power supply electrode is brought into direct contact with the outermost shell of the capacitor element to supply an electrolytic polymerization current, so that an electrolytic polymerization film of polypyrrole, polyaniline or the like reaches the center of the capacitor element. Are difficult to form and the appearance rate of capacity is very poor. Further, in the case of the strip type capacitor element, it is difficult to increase the capacity because the electrode area is limited.

[0007]

According to the present invention, a metal anode foil having a valve action and having an oxide film on its surface and a cathode foil without an oxide film are wound around a separator to form a capacitor element, and a conductive element is formed. A solid electrolytic capacitor characterized by using a conductive polymer as an electrolyte.

Further, a metal anode foil having a valve action having an oxide film on the surface and a cathode foil having no oxide film are wound around a separator to form a capacitor element, and the cathode foil is used as a power supply electrode for electrolysis. A method for producing a solid electrolytic capacitor, characterized in that a conductive polymer is formed by polymerization.

At this time, it is preferable that a conductive polymer film is previously formed on the capacitor element by chemical polymerization.

[0010]

According to the present invention, since the conductive polymer is efficiently formed even in the central portion of the capacitor element, the capacitance characteristic can be improved.

Further, it is not necessary to additionally provide an external power feeding electrode, the manufacturing process can be reduced, and various characteristics such as leakage current characteristics are improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an essential part of a solid electrolytic capacitor element of the present invention.

An anode foil (etched aluminum foil) 1 of 60 to 90 [μm] having an oxide film and a cathode foil (stainless steel foil) 2 of 60 to 90 [μm] having no oxide film are interposed with a separator paper 3 in between. After winding, re-formation and heat treatment are performed. Next, hydrogen peroxide solution / sulfuric acid (20/3 [wt%])
After being immersed in an oxidant consisting of 5 to 10 minutes, a chemical reaction is carried out in the pyrrole monomer vapor phase or liquid phase for several minutes to form a polypyrrole chemically polymerized film 4 to form a capacitor element. The anode foil 1 and the cathode foil 2 have lead terminals 5 and 6, respectively.

(Example 1) As shown in FIG. 2, the capacitor element formed as described above was prepared by using pyrrole monomer 0.2 [m].
ol / l] and naphthalene sulfonic acid (dopant)
In a water-based electrolytic solution containing 0.06 [mol / l], the cathode foil 2 was used as a feeding electrode for electrolytic polymerization, and an electrolytic polymerization current from the lead-out terminal 6 of the cathode foil 2 was about 30 depending on the size of the capacitor. By supplying power for 120 minutes, an electrolytically polymerized film of polypyrrole is efficiently formed up to the center of the capacitor element. In the subsequent final step, the capacitor element is packaged to complete the solid electrolytic capacitor.

(Embodiment 2) As shown in FIG. 2, the capacitor element formed as described above has a pyrrole monomer content of 0.2 [m].
ol / l] and paratoluenesulfonic acid (dopant)
In an acetonitrile-based electrolytic solution containing 0.1 [mol / l], the cathode foil 2 is used as a power feeding electrode for electrolytic polymerization, and an electrolytic polymerization current from a lead-out terminal 6 of the cathode foil 2 is adjusted according to the size of the capacitor. By supplying power for 30 to 120 minutes, the electrolytically polymerized film of polypyrrole is efficiently formed up to the center of the capacitor element. In the subsequent final step, the capacitor element is packaged to complete the solid electrolytic capacitor.

Table 1 shows the characteristics of the solid electrolytic capacitor obtained in Example 1 and a solid electrolytic capacitor prepared by a conventional method as a comparative example.

[0017]

[Table 1]

Here, the comparative example has a thickness of 9 with an oxide film.
A 0 [μm] aluminum anode foil was wound with a separator paper to form a chemically polymerized film to form a capacitor element, and pyrrole monomer 0.2 [mol / l] and naphthalene sulfonic acid (dopant) 0.06 [mol]. / L]
In a water-based electrolytic solution containing the external power supply electrode (φ0.
3 [mm] stainless wire) 7 is brought into contact with the outer shell of the capacitor element, and an electrolytic polymerization current is supplied for about 30 to 120 minutes to form an electrolytic polymerization film (see FIG. 3), and then the external power supply electrode 7 is removed. After that, the cathode lead-out layer is provided, the cathode terminal is drawn out, and the exterior is completed to complete the solid electrolytic capacitor.

Although polypyrrole is used as the conductive polymer in this embodiment, it is not particularly limited, and for example, polyaniline, polythiophene, polyfuran, etc. can be used.

Further, although stainless is used as the material of the cathode foil (feed electrode foil), other conductive materials may be used as long as they do not have an oxide film, such as aluminum,
The same effect can be obtained by using nickel, platinum, copper, tin, brass or the like.

Further, in this embodiment, the chemically polymerized film is formed after winding, but the anode foil (on the oxide film) and the separator paper on which the chemically polymerized film is previously provided are wound to form the capacitor element. You may.

[0022]

According to the present invention, when a conductive polymer is formed on a capacitor element by electrolytic polymerization, the electrolytic polymer film is formed on the anode foil without damaging the oxide film and the chemically polymerized film of the conductive polymer. Since the central portion of the element can be formed, the capacitance characteristics can be dramatically improved as compared with the solid electrolytic capacitor manufactured by the conventional manufacturing method, and a large-capacity solid electrolytic capacitor can be realized.

Furthermore, since the cathode foil is used as a feeding electrode for electrolytic polymerization, it is not necessary to newly provide a cathode lead-out layer to draw out a terminal, the number of steps can be reduced, and leakage current characteristics and the like are improved. can do.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a capacitor element.

FIG. 2 is a schematic diagram of a power supply state during electrolytic polymerization.

FIG. 3 is a schematic diagram of a power supply state during conventional electrolytic polymerization.

[Explanation of symbols]

1 Anode foil 2 Cathode foil (feed electrode foil) 3 separator paper 4 Chemically polymerized film 5 Anode lead terminal 6 cathode lead-out terminal 7 External power supply electrode

Claims (3)

[Claims] 1. A metal anode foil having a valve action, which has an oxide film on its surface, and a cathode foil without an oxide film are wound around a separator to form a capacitor element, and a conductive polymer is used as an electrolyte. A solid electrolytic capacitor characterized by the above. 2. A metal anode foil having a valve action and having an oxide film on its surface and a cathode foil without an oxide film are wound around a separator to form a capacitor element, and the cathode foil is used as a feeding electrode for electrolysis. A method for producing a solid electrolytic capacitor, which comprises forming a conductive polymer by polymerization. 3. The method for manufacturing a solid electrolytic capacitor according to claim 2, wherein the capacitor element has a conductive polymer film formed in advance by chemical polymerization.