JP2010278200A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor with a protecting function against an overcurrent occurring on a circuit while maintaining low ESR characteristics. <P>SOLUTION: The solid electrolytic capacitor has a capacitive element 4. The capacitive element includes an anode foil 1 having an anodic oxide film 1a formed on a surface, a resin film 3 having a conductor material formed on a surface, and a separator 2 arranged between the anode foil and the resin film. The capacitive element is formed by winding the anode foil and the resin film together with the separator. Furthermore, the capacitive element holds a solid-state electrolyte 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor.

  Conventionally, valve action metals such as aluminum, tantalum and niobium have been used as anode electrodes for electrolytic capacitors. In this anode electrode, etching pits and fine holes are formed. An oxide film layer serving as a dielectric is formed on the surface of the anode electrode, and an electrolyte layer is formed on the oxide film layer. An electrolytic capacitor is formed by extracting the electrode from the electrode.

  The true cathode of the electrolytic capacitor is the above-described electrolyte layer, and since this electrolyte layer has a great influence on the electrical characteristics of the electrolytic capacitor, a number of formation methods have been proposed.

  Further, in the non-solid electrolytic capacitor, an electrolytic solution made of a liquid electrolyte is used. Since this liquid electrolyte is ion-conductive, the impedance characteristics of the non-solid electrolytic capacitor deteriorate in the high frequency region. On the other hand, in the solid electrolytic capacitor, a solid electrolyte having electron conductivity is used instead of the liquid electrolyte. Among these, it is known to use a 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex as a solid electrolyte. The TCNQ complex is melted by heat and dipped in an anode electrode and applied to form a solid electrolyte (see, for example, Patent Document 1).

  Further, as another technique, attempts have been made to use a conductive polymer such as polyethylenedioxythiophene (PEDOT) as a solid electrolyte (see, for example, Patent Document 2).

  In addition, a capacitor with a built-in fuse or PTC has been proposed for the purpose of disconnecting the electrolytic capacitor from the circuit before the electrolytic capacitor is short-circuited due to overcurrent or the like on the circuit. For this reason, many techniques for incorporating a fuse or a PTC in a capacitor or in a lead terminal portion have been studied (for example, see Patent Documents 3 to 5).

JP 58-191414 A JP-A-2-15611 Japanese Patent Laid-Open No. 2004-200422 Japanese Patent Application Laid-Open No. 2004-273511 JP 2006-93337 A

  Since the equivalent series resistance of a solid electrolytic capacitor using the above-described conductive polymer such as PEDOT as a solid electrolyte is low (hereinafter referred to as a low ESR characteristic), such a solid electrolytic capacitor is used in various circuits. . However, in order to disconnect the electrolytic capacitor from the circuit before the electrolytic capacitor is short-circuited due to overcurrent or the like on the circuit, when a fuse or PTC is provided in the lead terminal portion in the electrolytic capacitor, the resistance of the fuse or PTC Since this affects the equivalent series resistance, the low ESR characteristic cannot be obtained as a capacitor.

  Accordingly, the inventors of the present invention have developed a solid electrolytic capacitor using a conductive polymer such as PEDOT as a solid electrolyte layer, and has a protection function against overcurrent while maintaining the original low ESR characteristic of the solid electrolyte. Propose.

  The specific invention based on this idea is as follows.

  In the present invention, an anode foil having an anodized film formed on the surface and a resin film having a conductor material formed on the surface are wound through a separator, and the capacitor element holds the solid electrolyte. It is a feature.

  Thus, by using a resin film for the capacitor element and holding the solid electrolyte, while maintaining low ESR characteristics and before the electrolytic capacitor is short-circuited due to overcurrent on the circuit, The electrolytic capacitor can be disconnected from the circuit.

  Further, the above-described resin film has a solubility that dissolves at a predetermined temperature, a solid electrolyte is held between the separator and the anode foil, and a solid electrolyte is held between the separator and the resin film. preferable.

  Since the resin film has a solubility that dissolves at a predetermined temperature, the electrolytic capacitor can be separated from the circuit before being melted by heat generation due to overcurrent and short-circuiting the electrolytic capacitor.

  The resin film is preferably one of polyethylene, polypropylene, nylon 6, nylon 66, polyethylene terephthalate, and polytetrafluoroethylene.

  Since these resin films have different melting points, it is possible to appropriately provide a solid electrolytic capacitor adapted to a required guaranteed temperature by selecting a resin film to be used according to each thermal characteristic.

  The conductor material is preferably one of metal, metal nitride, metal carbide, and carbon.

  By using these conductor materials, it is possible to appropriately provide a solid electrolytic capacitor adapted to the required guaranteed temperature while maintaining the electrical characteristics of the solid electrolytic capacitor.

  The conductive polymer constituting the solid electrolyte is preferably any of polyaniline, polypyrrole, polythiophene and polyethylenedioxythiophene.

  In addition, a solid electrolytic capacitor adapted to the required guaranteed temperature can be provided by appropriately selecting the conductor material according to the thermal characteristics such as the melting point of each of these conductive polymers.

  In the present invention, a solid electrolyte is held by a capacitor element in which an anode foil having an anodized film formed on the surface and a resin film having a conductive material formed on the surface are wound through a separator, thereby allowing a conventional solid While maintaining the low ESR characteristic of the electrolytic capacitor, the electrolytic capacitor can be disconnected from the circuit before the electrolytic capacitor is short-circuited due to an overcurrent or the like generated on the circuit.

It is a disassembled perspective view of the capacitor | condenser element 4 by this invention. It is sectional drawing which shows roughly the laminated structure of the solid electrolytic capacitor by this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing a schematic configuration of a capacitor element of a solid electrolytic capacitor according to an embodiment of the present invention.

  Referring to FIG. 1, the solid electrolytic capacitor according to the present embodiment is one in which a conductive polymer is held in capacitor element 4. The capacitor element 4 is formed by winding the anode foil 1 and the resin film 3 through the separator 2. That is, the separator 2 is disposed between the anode foil 1 and the resin film 3 so as to be sandwiched between the anode foil 1 and the resin film 3. The capacitor element 4 can be formed by winding the anode foil 1, the resin film 3, and the separator 2 while the separator 2 is sandwiched between the anode foil 1 and the resin film 3. An anode lead wire 5 is connected to the anode foil 1. A cathode lead wire 6 is connected to the resin film 3.

  The anode foil 1 is made of a valve metal such as aluminum. As shown in FIG. 2, the surface of the anode foil 1 is roughened (etching pit formation) by an etching process, and an anodized film 1 a is formed on the surface of the anode foil 1 by anodic oxidation (chemical conversion).

  The resin film 3 is made of polyethylene, polypropylene, nylon 6, nylon 66, polyethylene terephthalate, polytetrafluoroethylene, or the like. Further, the resin film 3 may be formed of polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polystyrene or the like. As shown in FIG. 2, a conductive material layer 3 a such as metal, metal nitride, metal carbide, or carbon is formed on the surface of the resin film 3.

  A solid electrolyte 7 made of a conductive polymer is held on both surfaces of the separator 2. That is, the solid electrolyte 7 is sandwiched between the anode foil 1 and the separator 2 and between the resin film 3 and the separator 2. As the conductive polymer constituting the solid electrolyte 7, polyaniline, polypyrrole, polyethylenedioxythiophene (PEDOT) or the like can be used, and these are generated by chemical polymerization or electrolytic polymerization of monomers. As a method for retaining the solid electrolyte, there are a method in which a capacitor element is impregnated and polymerized by chemical polymerization or electrolytic polymerization, and a method in which the capacitor element is impregnated in a polymer state.

  The protection mechanism when an overcurrent flows through the solid electrolytic capacitor produced by the above method is as follows. That is, when an overcurrent flows through the solid electrolytic capacitor, the solid electrolytic capacitor generates heat according to the magnitude of the current. Due to the heat generated by the solid electrolytic capacitor, the resin film 3 (see FIG. 2) used as the cathode material is dissolved, so that the lead tab portion of the cathode lead wire and the conductive material are insulated. be able to.

  Specific examples will be described below.

[Example]
(Capacitor element manufacturing process)
The surface of anode foil 1 made of a valve metal such as aluminum was roughened by etching, and an oxide film layer was formed on the surface of anode foil 1. On the other hand, an aluminum film was formed on the surface of the polyethylene terephthalate film 3 as the resin film 3 by vapor deposition, and then a carbon layer was formed. The carbon layer was formed by immersing the resin film 3 in a solution in which carbon powder was dissolved in a suspension, and then lifting and drying. Thereafter, the anode lead wire 5 is connected to the anode foil 1, the cathode lead wire 6 is connected to the polyethylene terephthalate film 3, and the anode foil 1 and the polyethylene terephthalate film 3 are wound via the separator 2, thereby Element 4 was produced.

(Element formation / heat treatment process)
In the aqueous solution of diammonium adipate, a voltage was applied to the capacitor element 4 to perform element formation, and the element element that had been formed was heat-treated to pre-polymerize the capacitor element 4.

(Solid electrolyte formation process)
The above-described pre-polymerized capacitor element 4 is dipped in a solution prepared by mixing a p-toluenesulfonic acid iron solution and a monomer (3,4-ethylenedioxythiophene) and then pulled up and heated at 100 ° C. for 60 minutes. Impregnated with PEDOT by chemical polymerization.

(Assembly process)
The capacitor element 4 after forming the solid electrolyte was housed in a bottomed cylindrical outer case, and the opening was sealed with rubber packing or the like.

(Aging process)
The assembled capacitor element 4 was aged at 125 ° C. to produce a solid electrolytic capacitor with a rating of 4V-560 μF.

[Conventional example]
As a capacitor element manufacturing process, an anode foil 1 made of a valve metal such as aluminum having a roughened surface by etching and an oxide film layer formed on the surface, and an aluminum foil 9 having a carbon layer formed on the surface were prepared. Thereafter, the anode lead wire 5 is connected to the anode foil 1, the cathode lead wire 6 is connected to the aluminum foil 9, and the anode foil 1 and the aluminum foil 9 are wound via the separator 2, thereby forming a capacitor. Element 4 ′ was produced. A solid electrolytic capacitor as a conventional example was manufactured by the same process as that of the above-described example except for the process of manufacturing the capacitor element 4 ′.

  The electrical characteristics (capacitance, ESR and leakage current) of the solid electrolytic capacitors according to the above-described examples and conventional examples, and an overcurrent of 6 A were passed, and the maximum temperature at the top of the solid electrolytic capacitor was measured. In addition, the short rate and open rate were confirmed. The results are shown in Table 1.

  As is clear from Table 1, the solid electrolytic capacitor according to the example is more stable than the solid electrolytic capacitor according to the conventional example, even if the solid electrolytic capacitor generates heat due to overcurrent while maintaining the conventional ESR characteristics. It can be seen that the capacitor can be opened and disconnected from the circuit without rising above the temperature. Moreover, it turns out that the solid electrolytic capacitor which concerns on an Example can be made into an open state safely, without raise | generating a short circuit compared with a prior art example.

  In addition, this invention is not limited to the said Example.

  For example, in the above embodiment, a polyethylene terephthalate film is used as the resin film. However, the present invention is not limited to this, but polyethylene, polypropylene, nylon 6, nylon 66, polytetrafluoroethylene, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, The same effect can be obtained by using polystyrene or the like.

  Since each of these resin films has a unique thermal characteristic, the resin film can be appropriately selected according to the required guaranteed temperature.

  In addition, a carbon layer is formed on the conductor layer formed on the surface of the resin film. However, the present invention is not limited to this. The same effect can be obtained by using the above.

  Moreover, in the said Example, although PEDOT was used for the solid electrolyte, the same effect is acquired even if it uses a well-known conductive polymer (polyaniline, polypyrrole).

  Furthermore, as a method of impregnating the capacitor element with the solution, a method of impregnating the capacitor element with the oxidizing agent and the monomer separately, a method of impregnating the capacitor element with a solution prepared by mixing and mixing the oxidizing agent and the monomer in advance, and a polymer solution with the capacitor The same effect can be obtained by any method of impregnating the element.

  It goes without saying that various design changes and modifications within the scope of the claims can be made.

  By using the present invention, a solid electrolytic capacitor having a protection function against overcurrent can be obtained.

DESCRIPTION OF SYMBOLS 1 Anode foil 1a Anodized film 2 Separator 3 Resin film, polyethylene terephthalate film 3a Conductive material layer 4 Capacitor element 5 Anode lead wire 6 Cathode lead wire 7 Solid electrolyte

Claims (5)

A solid electrolytic capacitor having a capacitor element,
The capacitor element is
An anode foil having an anodized film formed on the surface;
A resin film with a conductive material formed on the surface;
A separator disposed between the anode foil and the resin film,
The capacitor element is formed by winding the anode foil and the resin film together with the separator,
A solid electrolytic capacitor characterized in that a solid electrolyte is held in the capacitor element. The resin film has a solubility that dissolves at a predetermined temperature,
The solid electrolyte is held between the separator and the anode foil,
The solid electrolytic capacitor according to claim 1, wherein the solid electrolyte is held between the separator and the resin film.   The solid electrolytic capacitor according to claim 1, wherein the resin film is one of polyethylene, polypropylene, nylon 6, nylon 66, polyethylene terephthalate, and polytetrafluoroethylene.   4. The solid electrolytic capacitor according to claim 1, wherein the conductor material is a metal, a metal nitride, a metal carbide, or carbon. 5.   5. The solid electrolytic capacitor according to claim 1, wherein the conductive polymer constituting the solid electrolyte is any one of polyaniline, polypyrrole, polythiophene, and polyethylenedioxythiophene. .

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