JP2001284174A - Solid electrolytic capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solid electrolytic capacitor with which short circuits between terminals can be prevented and an LC (leakage current) failure reduced. SOLUTION: At least a round bar part as a measure for leading an electrode on anode side among the flat plate part and round bar part for leading an electrode is immerged in advance in an ammonium dihydrogenphosphate aqueous solution of 0.05-0.5 wt.%, and a voltage of 5-150 V is applied for 1 sec to 5 min, and then a chemical cover film is formed at least on the surface of the round bar part as a means for leading out an electrode on the anode side and means is connected with both electrode foils, and furthermore, it is wound around together with a separator to form a capacitor element. Then, the capacitor element is immerged in an ammonium dihydrogenphosphate aqueous solution, and a voltage is applies thereto for 5 to 120 min for chemical repairing treatment. In addition, the capacitor is immersed in an EDT or an EDT solution and dipped in a butanol solution, containing a para-toluene sulphonic secondary iron of 30-60% and is heated at 20-180 deg.C for 30 min or longer, thereby chemically polymerizing a conductive polymer in the capacitor element. Thereafter, it is housed in a casing together with a sealing body, to finish a solid electrolytic capacitor.

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 method for manufacturing the same, and more particularly, to a method in which a solid electrolyte is formed between round rod portions of an electrode lead means when a solid electrolyte is polymerized. The present invention relates to a solid electrolytic capacitor improved to prevent occurrence of short circuit between terminals and to reduce LC (leakage current) failure, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In an electrolytic capacitor using a metal having a valve action such as tantalum or aluminum, a valve action metal as an anode-side counter electrode is formed into a shape of a sintered body or an etching foil to expand a dielectric material. By using such a structure, it is possible to obtain a large capacity with a small size. In particular, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has characteristics that it is small, large-capacity, low equivalent series resistance, easy to chip, and suitable for surface mounting. It is indispensable for miniaturization, high performance, and low cost of electronic devices.

In this type of solid electrolytic capacitor, for small size and large capacity applications, generally, an anode foil and a cathode foil made of valve metal such as aluminum are wound with a separator interposed therebetween to form a capacitor element. The capacitor element is impregnated with a driving electrolyte, and the capacitor element is housed in a metal case such as aluminum or a synthetic resin case, and has a sealed structure. Note that as the anode material, aluminum, tantalum, niobium, titanium, or the like is used, and as the cathode material, the same kind of metal as the anode material is used.

As a solid electrolyte used for a solid electrolytic capacitor, manganese dioxide, 7, 7, 8, 8-
A tetracyanoquinodimethane (TCNQ) complex is known, but recently, polyethylenedioxythiophene (hereinafter, referred to as PEDT), which has a slow reaction rate and excellent adhesion to an oxide film layer of an anode electrode, has been developed. There is a technique (Japanese Patent Laid-Open No. 2-15611) that has been focused on.

[0005] Such a wound-type capacitor element is made of PE.
A solid electrolytic capacitor of the type forming a solid electrolyte layer made of DT is manufactured, for example, as follows.
First, the surface of the anode foil made of a valve metal such as aluminum is roughened by electrochemical etching treatment in a chloride aqueous solution to form a large number of etching pits, and then, in an aqueous solution such as ammonium borate. A voltage is applied to form an oxide film layer serving as a dielectric (chemical formation). Like the anode foil, the cathode foil is made of a valve metal such as aluminum, but its surface is only subjected to etching.

As shown in FIGS. 2 and 3, the anode foil 1 and the cathode foil 2 are connected to external lead-out means 4 and 5 for connecting the respective electrodes to the outside. 3 and the capacitor element 10 is formed. The external drawing means 4 and 5 are composed of a flat plate portion 11 connected to the electrode foil, a round bar portion 12 for penetrating the sealing means, and an external connection portion (lead wire) 13.
The flat plate 11 and the round bar 12 are made of aluminum. Further, the round bar portion 12 and the lead wire 13 are connected by welding. Hereinafter, this welded portion is referred to as a welded portion 14.

After forming the capacitor element 10 in this manner, a repair formation is performed. In the repair formation, the electrode foil is subjected to mechanical stress in the winding step, and when the oxide film is damaged due to cracks caused by the mechanical stress, the electrode foil is formed again in a chemical conversion solution, An oxide film is formed on the cracked portion to repair the damage.

Subsequently, the restoration-formed capacitor element 10 is replaced with 3,4-ethylenedioxythiophene (hereinafter referred to as E
This polymer solution is impregnated in the capacitor element 10 by immersion in a mixed solution (polymer solution) of an oxidant and an oxidizing agent. Alternatively, the capacitor element 10 is alternately immersed in the EDT and the oxidizing agent solution for impregnation. In either case,
After impregnating the capacitor element 10 with EDT and an oxidizing agent, a polymerization reaction is performed to generate a solid electrolyte layer made of PEDT. Thereafter, as shown in FIG.
Is stored in the outer case 15 together with the sealing body 16 to produce a solid electrolytic capacitor.

In the above manufacturing method, a dipping method is used as a method for impregnating the capacitor element with EDT and an oxidizing agent. However, a method of injecting the EDT and the oxidizing agent at room temperature by a syringe or the like (injection method) Can also be used.
In such a wound-type electrolytic capacitor using PEDT as a solid electrolyte, a solid electrolytic capacitor having excellent characteristics can be obtained since the formability between PEDT electrode foils is good.

[0010]

By the way, in a solid electrolytic capacitor using PEDT manufactured by the above-described method, when the capacitor element is immersed in EDT or an oxidizing agent solution, external drawing means 4, 5 The EDT and the oxidizing agent solution creep up and adhere to the surface of the round bar portion 12 due to the surface tension, and the PEDT is formed on the surface of the round bar portions 12 on both sides because of the good formability of PEDT after polymerization. Also, there is a problem that the PEDT inside the capacitor element is pushed out of the element and adheres to the surface of the round bar portion, thereby increasing LC and causing a short circuit. Further, even when PEDT adheres to one of the round bars, there is a problem that LC increase and short-circuit occur similarly.

In order to solve such a problem, it is necessary to form an oxide film layer on the surface of the round bar by chemical conversion to insulate the round bar from the PEDT. At the time of chemical conversion, a method of forming an oxide film layer on the surface of the round bar portion can be used. That is, in the repair formation of the capacitor element, the wound part of the electrode foil of the capacitor element and the separator (the “A” part in FIG. 3) is usually immersed in the chemical conversion solution. Since the oxide film is formed on the flat portion of the electrode drawing means and the portion where the oxide film is not formed, such as the joint portion between the flat portion and the electrode foil, the insulation between the electrodes is maintained. In these portions, it is possible to prevent LC failure and short circuit from occurring.

However, at the time of repair formation of the capacitor element, if the formation is carried out by immersing the round bar portion 12 (portion "B" in FIG. 3) in the formation solution, the formation solution is formed up to the welding portion 14 with the lead wire 13. There is a danger of immersion. If the welding portion 14 with the lead wire is immersed in the chemical conversion solution as described above, the current will flow, and there is a limit to forming the round bar portion 12 during the repair formation of the capacitor element.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and an object of the present invention is to form a solid electrolyte between round bars when a solid electrolyte is polymerized. It is an object of the present invention to provide a solid electrolytic capacitor capable of preventing occurrence of a short circuit between terminals due to the above and reducing LC (leakage current) failure and a method of manufacturing the same.

[0014]

Means for Solving the Problems In order to solve the above problems, the present inventors have developed a solid electrolytic capacitor and a solid electrolytic capacitor which can prevent the solid electrolyte from being formed between the round bars when the solid electrolyte is polymerized. As a result of intensive studies on the manufacturing method,
The present invention has been completed. That is, FIG.
As shown in (2), an oxide film 20 is formed in advance on at least the round bar portion 12 of the electrode drawing means on the anode side of the flat plate portion 11 and the round bar portion 12 of the electrode drawing means, and then wound together with the electrode foil. To form a capacitor element. Then, only the wound portion of the electrode foil and the separator of the capacitor element was immersed in a chemical conversion solution to perform repair formation, and thereafter, good results were obtained by polymerizing PEDT in the capacitor element. It is.

[1. Manufacturing method of electrolytic capacitor]
The method for manufacturing the solid electrolytic capacitor of the present invention will be described. That is, in the solid electrolytic capacitor according to the present invention, among the flat plate portion and the round bar portion of the electrode lead means, at least the round bar portion of the electrode lead means on the anode side is 0.05 to
Immersed in a 0.5 wt% aqueous solution of ammonium dihydrogen phosphate, and applied with a voltage of 5 to 150 V for 1 second to 5 minutes to form a chemical conversion film on at least the surface of the round bar portion of the electrode drawing means on the anode side; This electrode lead means is connected to both electrode foils and wound together with the separator to form a capacitor element. Thereafter, this capacitor element is immersed in an aqueous solution of ammonium dihydrogen phosphate, and a voltage is applied to perform repair formation for 5 to 120 minutes.

Subsequently, the capacitor element is impregnated with EDT or an EDT solution, and further impregnated with a 30 to 60% ferric paratoluenesulfonate butanol solution to give
By heating at 180 ° C. for 30 minutes or more, the conductive polymer is chemically polymerized in the capacitor element. Thereafter, the solid electrolytic capacitor is housed in an outer case together with the sealing body to produce a solid electrolytic capacitor. In addition, as a method of impregnating the capacitor element with EDT and an oxidizing agent, an injection method in which a fixed amount is injected with a syringe or the like at room temperature or an immersion method can be used.

[2. Method for forming an oxide film on a round bar or the like] In an aqueous solution (concentration: 0.05 to 0.5 wt%) of ammonium borate, ammonium phosphate, ammonium dihydrogen phosphate, ammonium adipate, etc. 50
A voltage of 0 V is applied for 1 second to 5 minutes to perform anodic oxidation treatment (a so-called chemical conversion treatment), and at least to the round bar portion of the electrode drawing means on the anode side among the flat plate portion and the round bar portion of the electrode drawing means. An oxide film is formed.

The formation voltage at this time is only required to form an insulating oxide film, and is usually 5 to 150 V.
The time for forming the oxide film may be any time before winding the capacitor element, and may be after the lead wire is welded to the round bar portion, but it is more preferable before the lead wire is welded to the round bar portion.

In the present invention, an oxide film is formed on at least the round bar portion of the electrode lead-out means on the anode side.
This is considered to be due to the following behavior. That is, the cathode foil wound as the capacitor element is obtained by cutting aluminum foil. Therefore,
At least there is no conversion coating on the surface of the cut portion, and then repair conversion is performed.However, since this is performed only on the anode foil, conversion of the cathode foil is not performed, and a conversion coating is formed on the cut portion of the cathode foil. It has not been done. Therefore,
When the PEDT adheres to the round bar portion of the electrode drawing means on the anode side, and when the PEDT is conducting with the conducting portion of the cathode foil such as the cut portion of the cathode foil, the insulation between the anode and the cathode of the capacitor is made. Is reduced.

Therefore, if an oxide film is formed on the round bar of the electrode extraction means on the anode side as in the present invention, even if PEDT adheres to this round bar, the oxide film becomes an insulating portion and becomes an insulating portion. There is no decrease in sex. Also, if an oxide film is also formed on the round bar portion of the electrode extraction means on the cathode side,
This is more preferable because a new effect that the withstand voltage of the entire cathode is improved and the withstand voltage of the capacitor is improved can be obtained.

[3. Restoration formation] As the formation solution of the restoration formation, there are phosphoric acid-based formation solutions such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate, boric acid-based formation solutions such as ammonium borate, and adipic acid such as ammonium adipate. Although a chemical conversion solution of a system can be used, it is particularly preferable to use ammonium dihydrogen phosphate. Also,
The time for immersing the capacitor element in a chemical conversion solution and applying a voltage to perform repair formation is preferably 5 to 120 minutes. The applied voltage for the repair formation is preferably 0.5 to 1.1 times the formation voltage of the anode foil.

[4. EDT, Oxidizing Agent] As the EDT to be impregnated into the capacitor element, an EDT monomer can be used.
A monomer solution mixed at a volume ratio of 1: 3 can also be used. Examples of the volatile solvent include hydrocarbons such as pentane, ethers such as tetrahydrofuran, esters such as ethyl formate, ketones such as acetone, alcohols such as methanol, and nitrogen compounds such as acetonitrile. However, among them, methanol, ethanol, acetone and the like are preferable.

As the oxidizing agent, ferric paratoluenesulfonate dissolved in butanol is used. In this case, the ratio between butanol and ferric paratoluenesulfonate may be arbitrary, but in the present invention, a 30 to 60% solution is used. The mixing ratio of EDT and oxidizing agent is 1: 1 to 1
A range of 1: 6 is preferred.

[5. Function / Effect] According to the manufacturing method of the present invention as described above, when the capacitor element is immersed in the monomer solution and the oxidant solution, the solution adheres to the round bar portion of the electrode lead-out means, and this portion also Even when a conductive polymer is formed, at least the round bar portion of the electrode lead-out means on the anode side has an oxide film formed in advance, so that short-circuiting between terminals and an increase in LC are prevented. Can be.

[0025]

The present invention will be described more specifically with reference to the following examples. (Example 1) In forming an electrode lead means on the anode side, an electrode tab (a flat plate portion and a round bar portion) before connecting a lead wire was immersed in a 0.2 wt% ammonium dihydrogen phosphate aqueous solution, A voltage of 130 V was applied for 2 minutes to form a chemical conversion film on the surface of the electrode tab. A lead wire is connected to the round bar portion of the electrode tab on which the chemical conversion film has been formed in this way to form an electrode lead-out means.
It was connected to an anode foil having an oxide film layer formed on the surface to form an electrode lead-out means on the anode side.

On the other hand, the electrode lead means on the cathode side is formed by connecting a lead wire to a round bar portion of an electrode tab on which a chemical conversion film is not formed to form an electrode lead means. Side electrode lead means was formed. The anode foil and the cathode foil were wound via a separator to form a capacitor element. Then, the capacitor element was immersed in an aqueous solution of ammonium dihydrogen phosphate, and a voltage was applied to perform repair formation for 40 minutes.

Subsequently, this capacitor element was impregnated with an EDT monomer solution, further impregnated with a 45% ferric paratoluenesulfonate butanol solution as an oxidizing agent solution, and heated at 100 ° C. for 1 hour. A solid electrolyte layer made of PEDT was formed. Thereafter, the solid electrolytic capacitor was housed in an outer case together with the sealing body to obtain a solid electrolytic capacitor.

The solid electrolyte layer made of PEDT is
It was formed such that the round bar portions of both poles were connected. Also,
This solid electrolytic capacitor has a shape of φ4 × 8 L, a rated voltage of 6.3 V, and a rated capacity of 33 μF.

(Example 2) Only the round bar portion of the electrode tab before the lead wire was connected was immersed in an aqueous solution of ammonium dihydrogen phosphate. A chemical conversion film was formed on the surface of the round bar portion. Other steps were the same as in Example 1 to produce a solid electrolytic capacitor.

(Comparative Example 1) A lead wire was connected to an electrode tab without forming a chemical conversion film, and this electrode lead-out means was connected to an anode foil and a cathode foil having an oxide film layer formed on the surface. The foil and the cathode foil were wound via a separator to form a capacitor element. Other steps are described in Example 1 above.
A solid electrolytic capacitor was produced in the same manner as described above.

[Comparative Results] The electrical characteristics of Example 1 and Comparative Example 1 were examined. The results shown in Table 1 were obtained.

[Table 1]

As is apparent from Table 1, in Example 1 in which the chemical conversion film was formed on both the round bar portion and the flat plate portion of the electrode drawing means on the anode side, the maximum value of the leakage current was 3 μA, and Comparative Example 1 in which no conversion coating was formed (400 μm
Compared with A), it was about 0.008 times. In Comparative Example 1, two out of ten short-circuits occurred, but in Example 1, no short-circuit occurred.

Further, in Example 2 in which the chemical conversion film was formed only on the round bar portion of the electrode drawing means on the anode side, the maximum value of the leakage current was 4 μA, and Comparative Example 1 in which no chemical conversion film was formed on the electrode tabs ( 400 μA), which is about 0.01 times, and a result equivalent to that of Example 1 was obtained. Also, in Example 2, no short circuit occurred. In Example 2 in which the chemical conversion film was formed only on the round bar portion of the electrode drawing means on the anode side, the same result as in Example 1 was obtained even if the chemical conversion film was not formed on the flat plate portion. It is considered that the flat portion is formed during the repair formation.

As described above, when an oxide film is previously formed on at least the round bar portion of the electrode drawing means on the anode side,
It has been found that the leakage current can be significantly reduced, and the occurrence of a short circuit can be prevented. In addition, it was found that when an oxide film was formed in advance on both the round bar portion and the flat plate portion, not only the occurrence of a short circuit but also the leakage current could be almost completely prevented.

[0035]

As described above, according to the present invention, when a solid electrolyte is polymerized, a short circuit between terminals due to formation of a solid electrolyte between round rod portions is prevented, and LC ( It is possible to provide a solid electrolytic capacitor capable of reducing defects (leakage current) and a method of manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an electrode tab on which a chemical conversion film is formed by a production method of the present invention.

FIG. 2 is a perspective view showing a winding state of a capacitor element.

FIG. 3 is an exploded perspective view showing an example of a capacitor element.

FIG. 4 is a sectional view showing an example of a solid electrolytic capacitor obtained by a conventional manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anode foil 2 ... Cathode foil 3 ... Separator 4, 5 ... Electrode lead-out means 10 ... Capacitor element 11 ... Flat plate part 12 ... Round bar part 13 ... Lead wire 14 ... Welded part 15 ... Metal case 16 ... Sealing body 20 ... Oxidation Film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01G 9/24 BC (72) Inventor Hidehiko Ito 1-1167 Higashi-Ome, Ome-shi, Tokyo 1 Nippon Chemi-Con Co., Ltd. F-term (reference) 4J032 BA04 BB01 BC03 CG01

Claims (4)

[Claims] 1. An electrode lead means comprising: a flat plate portion connected to an electrode foil; a round bar portion for sealing means penetrating; and an external connection portion connected to the round bar portion via a welded portion. In the solid electrolytic capacitor formed by winding the two electrode foils wound through a separator to form a capacitor element and forming a solid electrolyte layer made of polyethylene dioxythiophene between the two electrode foils, Among the flat plate portion and the round bar portion, at least an oxide film is formed in advance on the round bar portion of the electrode drawing means on the anode side, and thereafter an external connection portion is connected to the round bar portion. Capacitors. 2. An electrode lead means comprising a flat plate portion connected to the electrode foil, a round bar portion for penetrating the sealing means, and an external connection portion connected to the round bar portion via a welded portion is connected. The two electrode foils are wound through a separator to form a capacitor element, and a solid electrolytic capacitor formed by forming a solid electrolyte layer made of polyethylene dioxythiophene between the two electrode foils. A solid electrolytic capacitor characterized in that an oxide film is previously formed on at least the round bar portion of the electrode drawing means on the anode side, out of the flat plate portion and the round bar portion, before winding the capacitor element. 3. The flat plate of the electrode drawing means comprising a flat plate portion connected to the electrode foil, a round bar portion for penetrating the sealing means, and an external connection portion connected to the round bar portion via a welded portion. Of the part and the round bar part, at least an oxide film is formed in advance on the round bar part of the electrode lead means on the anode side, and then the external connection part is connected to the round rod part to form the electrode lead means, Connecting the electrode lead means to both electrode foils, winding the capacitor together with the separator to form a capacitor element, and then impregnating the capacitor element with a monomer solution and an oxidizing agent solution to form a solid electrolyte layer Manufacturing method of electrolytic capacitor. 4. An electrode lead-out means comprising: a flat plate portion connected to an electrode foil; a round bar portion for sealing means penetration; and an external connection portion connected to the round bar portion via a welded portion. Of the flat plate portion and the round bar portion, an oxide film is formed in advance on at least the round bar portion of the electrode drawing means on the anode side, and then the electrode drawing means is connected to both electrode foils and wound together with the separator to form a capacitor element. Forming a solid electrolyte layer by impregnating the capacitor element with a monomer solution and an oxidizing agent solution.