JPH0297008A - Solid electrolytic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To achieve smaller size and smaller volume and a uniform electrically conductive polymer film to obtain improved capacitor characteristics by causing film forming metal foil, on which a dielectric oxide film is formed, and a spacer to comprise at least a chemical oxidation polymerized film, an electrolytic oxidation polymerized film, and an electrically conductive film, which are successively formed. CONSTITUTION:A capacitor element, wherein film forming metal foil 1, on which a dielectric oxide film is formed, and a spacer 4 are wound: said film forming metal foil 1 and said spacer 4 constitute at least a chemical oxidation polymerized film and an electrolytic oxidation polymerized film, and an electrode leader terminal is led out from said film forming metal foil 1 and said electrically conductive film. For example, a polypyrrole film 3 is formed on anode foil 1, consisting of high purity aluminum foil on which a dielectric oxide film is formed and to which an anode lead 2 is mounted, through chemical oxidative polymerization. Then, a separator paper sheet 4 is superposed on the anode foil 1, and these are wound in a spiral form to fabricate the capacitor element 5, and thereafter a polypyrrole film is formed by chemical oxidative polymerization, and further a polypyrrole film and an electrically conductive film are formed by electrolytic oxidative polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a solid electrolytic capacitor in which a solid electrolyte is formed on the surface of a dielectric oxide film, and a method for manufacturing the same.

(Conventional technology) Solid electrolytic capacitors are usually aluminum.

A dielectric oxide film is formed on the surface of a film-forming metal such as tantalum, and manganese dioxide, TCN, etc. are formed on the oxide film.
It is constructed by sequentially forming a solid electrolyte layer such as a Q complex and a conductor layer.

Capacitors using manganese dioxide as a solid electrolyte have drawbacks such as easy damage to the electrolyte oxide film during the manufacturing process, while capacitors using TCNQ complexes have drawbacks such as poor thermal stability.

In addition, a capacitor has been proposed in which a polymer of a heterocyclic compound such as virol is formed by electrolytic polymerization on a dielectric oxide film and used as a solid electrolyte, but since the dielectric oxide film is an insulator, It is very difficult to form an electrolytically polymerized film on the surface, and a uniform film cannot be formed. Particularly in an element having a structure in which anode foil is wound, it is impossible to form a uniform electrolytic polymer film between the foils stacked closely in a spiral manner.

In addition, conductive polymer l11 (I) is chemically polymerized using an oxidizing agent on the anodic oxide film, and is wound together with separator paper and cathode foil to form an element. II) A solid electrolytic capacitor having a structure has been proposed. This capacitor has large capacitance and good temperature and frequency characteristics, but electrolytic polymerization occurs from both the surface of the chemically polymerized conductive polymer film and the surface of the cathode foil, so the conductive polymer film is This resulted in non-uniformity, and when assembled into a capacitor, there remained issues to be improved, such as a large leakage Ml flow and a large loss angle tangent (tan δ).

(Problems to be Solved by the Invention) An object of the present invention is to provide a solid electrolytic capacitor having a structure in which a 39W1 polymer film is formed as a solid electrolyte on the surface of a dielectric oxide film, and a method for manufacturing the same. An object of the present invention is to provide a solid electrolytic capacitor that can be increased in volume, has a uniform conductive polymer film formed thereon, and has excellent capacitor characteristics.

Structure of the Invention] (Means for Solving the Problems) As a result of intensive research, the present inventors came to invent a solid electrolytic capacitor that can achieve the above object.

That is, a spirally wound film-forming metal foil has a dielectric oxide film formed on its surface, a conductive polymer film (I) formed by chemical polymerization, and a conductive polymer film formed by electrolytic polymerization. This solid electrolytic capacitor is characterized in that it has a molecular film (II), and a carbon layer and a conductive coating film are formed on the conductive polymer film (It) formed by electrolytic polymerization.

Aluminum, tantalum, niobium, etc. are used as the film-forming metal, and aluminum foil is usually used as the wound type. When aluminum foil is used, the surface is roughened by electrochemical etching. Further, electrolytic oxidation is performed in an aqueous solution of ammonium borate or the like to form a dielectric oxide film on the surface to obtain an anode. This anode foil is cut into a predetermined size, and a lead wire for leading out the anode is connected to a portion thereof by caulking or high-frequency bonding. Next, after uniformly dispersing a solution containing at least 0.01 mol/l of a conductive polymer monomer on the oxide film, an oxidizing agent of 0.001 mol/j! ~
2 mol/J), or conversely, after uniformly dispersing the oxidizing agent, contacting with a conductive polymer film Zimmer solution to form a conductive polymer film (I) that is chemically oxidized and polymerized. to make the surface conductive. As the conductive polymer, polypyrrole, polythiophene, and polyfuran are used, and polypyrrole is particularly preferably used.

The oxidizing agent used in chemical oxidative polymerization is iodine.

Halogens such as bromine and bromine iodide, arsenic pentafluoride, antimony pentafluoride, silicon tetrafluoride, phosphorus pentachloride, phosphorus pentafluoride, and aluminum chloride.

Metal halides such as molybdenum chloride, sulfuric acid.

Nitric acid, fluorosulfuric acid, trifluoromethane sulfuric acid.

Protonic acids such as chlorosulfuric acid, sulfur trioxide.

These include oxygen-containing compounds such as nitrogen dioxide, persulfates such as sodium persulfate and ammonium persulfate, and peroxides such as hydrogen peroxide and peracetic acid.

The anode foil thus obtained is spirally wound together with a spacer such as capacitor paper, and the number of turns per turn, diameter per turn, pitch, etc. is determined by each individual's wishes.
There are no particular restrictions.

Thereafter, a conductive polymer film is formed by chemical oxidation polymerization on the entire element, that is, on the spacer and the dielectric oxide film.

Further, it is also possible to form an sN polymer film on the spacer paper in advance by chemical oxidation polymerization in a separate process, and then wind it with an anode foil on which a conductive polymer film has been formed by the chemical oxidation polymerization. After that, supporting electrolyte 0.01 mof/J ~
2 n+ol/j! and conductive polymer monomer 0.01
mol/j! When electrolytic oxidative polymerization is carried out in an electrolytic solution containing ~5 mol/J, a chemically oxidatively polymerized conductive polymer film (I
) A uniform electrolytically polymerized conductive polymer film (II) is formed on the top.

The supporting electrolyte used in the electrolytic oxidative polymerization of the present invention includes anion such as a halide anion such as hexafluoroline, hexafluoroarsenic, or tetrafluoroborine, a halogen anion such as iodine, bromine, or chlorine, a perchlorate anion, or a benzenesulfonic acid anion. , a sulfonic acid anion such as alkylbenzenesulfonic acid, and the cation is an alkali metal cation such as lithium, potassium, or sodium,
It is a quaternary ammonium cation such as ammonium or tetraalkylammonium. LIPF as a compound
, LiAsF6. LicIo, LiBF,
K.I.

Examples include NaPF , NaCl0 +F'sodium toluenesulfonate, and tetrabutylammonium toluenesulfonate.

Thereafter, this element is immersed in colloidal carbon to form a carbon layer on the surface. At this time, if an element with separator paper interposed is used, a composite layer in which carbon is dispersed in the separator paper is formed. Further, a y4 conductive coating film is formed using 1ffi paste on top of the coating, and a lead wire for drawing out the cathode is connected to a part of the coating film. As the conductive paste, silver paste, copper paste, aluminum paste, etc. can be used.

The capacitor element configured as described above is packaged in a resin mold, a resin case, or a metal case to provide the solid electrolytic capacitor of the present invention.

After winding the aluminum foil with the dielectric oxide film and the spacer, conductive polymer # (I
), and then electrolytic oxidative polymerization to form a conductive polymer film (II
), and thereafter the capacitor may be constructed by similar steps.

(Function) In the solid electrolytic capacitor and the manufacturing method thereof according to the present invention, the conductive polymer film acts as a cathode, so a cathode foil is not required, and the spacer is also formed with a conductive polymer film, and the electrode foil is not required. Since electrolytic oxidation polymerization is carried out including the conductive polymer film formed by chemical oxidation polymerization above, a sufficient cathode layer is formed as a whole, so the capacitor element volume is small and the electrical characteristics are stable and good. becomes.

(Example) Example 1 As shown in Fig. 1, an anode lead 2 was attached by caulking to a high-purity aluminum foil having a dielectric oxide film formed thereon and having a thickness of 40 μm and a width of 3 m+, and then cut into 50 pieces. Anode foil 1 was obtained. The anode foil 1 is 2 mol/j pyrol/
After immersing in the ethanol solution for 5 minutes, an additional 0.5 mo
The film was then immersed in an aqueous ammonium persulfate solution for 5 minutes to form a polypyrrole film 3 by chemical oxidative polymerization.

Next, a separator paper 4 is layered on this anode foil 1 and wound into a spiral to form an element 5! After 1I, the dielectric oxide film was repaired by re-formation. Furthermore, this element was added at 2 mol/
J) After immersing in virol/ethanol solution for 5 minutes, further soaking in 0.5 a+ol/ρ ammonium persulfate solution
A separator paper 6 having a polypyrrole film formed thereon as shown in FIG. 2 was obtained by immersion for 0 minutes and chemical oxidative polymerization. Furthermore, this element 5 was mixed with 1 mol of virol monomer, 1 mol, and 1 mol of sodium paratoluenesulfonate as a supporting electrolyte.
A polypyrrole chemically polymerized by immersing it in an acetonitrile solution containing mol/1 is used as an anode, and a constant current electrolytic oxidation polymerization (111^/ax 2.305in) is conducted between it and an external cathode.
A polypyrrole film was formed by electrolytic oxidative polymerization. This element 5 was immersed in colloidal carbon to form a carbon layer, and then silver paste was applied to form a conductive coating, and a cathode was taken out from a part of the coating.

This element is sealed in a case and the rated voltage is 25V.

A solid electrolytic capacitor with a nominal capacitance of 15 μF was completed.

As shown in Table 1, this capacitor has approximately two-thirds the volume compared to conventional capacitors, and has a dense cathode layer made of conductive polymer film, which improves leakage current and withstand voltage. Ta.

Example 2 2 ■of/J Beer/
After immersion in ethanol solution for 10 seconds, further 0.5 m
A polypyrrole film formed by chemical oxidation polymerization by immersion in OL/J ammonium persulfate aqueous solution for 1 minute and an anode foil formed with a conductive polymer film by chemical oxidation polymerization shown in Example 1 were stacked to form a spiral shape. A capacitor was completed in the same manner as in Example 1, except that the capacitor was wound to form an element.

This capacitor also has the characteristics shown in Table 1 compared to conventional capacitors.

Example 3 A capacitor element was constructed by winding an anode foil with the same dielectric oxide film as in Example 1 and separator paper, and produced a polypyrrole film by chemical oxidation polymerization, and polypyrrole by electrolytic oxidation polymerization using this polypyrrole film as an anode. A film was formed.

Thereafter, a capacitor was constructed using the same means as in Example 1.

Comparative example A dielectric oxide film is formed with a thickness of 40 μm.

An anode lead was attached to a high purity aluminum foil having a width of 3III#I by caulking and cut into 50 pieces to obtain an anode foil. After immersing the anode foil in a 2 a+ol/j virol/ethanol solution for 5 minutes, an additional 0.5 mol/j! It was immersed in an ammonium persulfate aqueous solution for 5 minutes to form a polypyrrole film by chemical oxidative polymerization. Next, this anode foil was stacked with a separator paper and a cathode foil and wound spirally to produce an element, and then a capacitor was produced according to the method of Example 1. This capacitor has a separator paper and a cathode foil, and its volume is equivalent to that of a conventional capacitor.

Data of the examples of the present invention are shown in Table 1 along with comparative examples. Note that the volume ratios in Table 1 are volume ratios calculated assuming that the size of the capacitor obtained in the comparative example is 100.

Table 1 [Effects of the Invention] The solid electrolytic capacitor and manufacturing method thereof according to the present invention are as follows:
Compared to conventional capacitors using cathode foil, the volume ratio can be significantly reduced, and a conductive polymer film can be formed uniformly and densely on the dielectric oxide film, reducing tanδ and leakage current. is small, and excellent characteristics can be obtained.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a perspective view showing a wound state, and FIG. 2 is a perspective view showing a state in which a chemical oxidation polymer film is formed on a spacer. 1... Anode foil 2... Anode lead 3... Polypyrrole film 4... Separator paper 5... Capacitor element 6... ...Patent application for separator paper with polypyrrole film formed Marcon Electronics Co., Ltd. Nippon Carlit Co., Ltd.

Claims (4)

[Claims] (1) A capacitor element in which a film-forming metal foil with a dielectric oxide film formed thereon and a spacer are wound, and a chemical oxidation polymer film, an electrolytic oxidation polymer film, in which the film-forming metal foil and the spacer are formed at least sequentially, A solid electrolytic capacitor comprising a conductive coating film, and having an electrode lead terminal drawn out from the film-forming metal foil and the conductive coating film. (2) After forming a capacitor element by winding the film-forming metal foil with a chemically oxidized polymeric film formed on the dielectric oxide film and a spacer, the capacitor element is sequentially coated with at least a chemically oxidized polymeric film, an electrolytic oxidized polymeric film, and a spacer. A method for manufacturing a solid electrolytic capacitor that forms a conductive coating. (3) After forming a capacitor element by winding a film-forming metal foil with a chemical oxidation polymer film formed on a dielectric oxide film and a spacer with a chemical oxidation polymer film formed thereon, the capacitor element is sequentially coated with at least electrolytic film. A method for manufacturing solid electrolytic capacitors that forms oxidized polymer films and conductive coatings. (4) After forming a capacitor element by winding the film-forming metal foil on which the dielectric oxide film has been formed and the spacer,
A method for manufacturing a solid electrolytic capacitor, comprising sequentially forming at least a chemical oxidation polymer film, an electrolytic oxidation polymer film, and a conductive coating film on the capacitor element.