JP2006093423A - Solid-state electrolytic capacitor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state electrolytic capacitor using 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) complex salt in a cathode layer, which has a high capacitance impregnation rate and a large electrostatic capacity, and is miniaturized and excellent in electric characteristic, and its manufacturing method. <P>SOLUTION: In the solid-state electrolytic capacitor, a cathode layer consisting of polyethylenedioxythiophene and 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) complex salt is formed on an anode foil of a capacitor element which is formed by winding the anode foil and a cathode foil opposite to the anode foil, wherein a dielectric oxide film is formed via a separator. The cathode layer is formed by impregnating ethylenedioxithiophene monomer with molten and liquified TCNQ complex salt after it is subjected to polymerization reaction by oxidant. Charge transfer complex salt or the like wherein N-n-buthylisoquinolinium is donor and TCNQ is acceptor is used as TCNQ complex salt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a small-sized and large-capacity solid electrolytic capacitor and a method for manufacturing the same, and more specifically, to a capacitor element in which an anode foil formed with a dielectric oxide film and a counter cathode foil are wound through a separator. , 7,7,8,8-tetracyanoquinodimethane (hereinafter abbreviated as “TCNQ”) complex salt and a method for producing the same.

  Conventionally, various solid electrolytic capacitors using an organic semiconductor TCNQ complex salt or a conductive polymer as a cathode layer have been proposed. These cathode layers are also referred to as solid electrolytes, and act as true cathodes as with the electrolytes of conventional electrolyte type capacitors.

  In Patent Document 1, a complex salt of N-alkyl-substituted isoquinolinium and TCNQ is melted and liquefied on an anode foil, and after impregnating the molten liquid into a capacitor element, it is cooled and solidified to form a cathode layer. A solid electrolytic capacitor is disclosed.

  In recent years, with the downsizing of electronic devices, the capacitor characteristics are required to be small and large in capacity. As a countermeasure, a solid electrolytic capacitor uses an anode foil whose surface has a high magnification.

  In general, in order to obtain a high-capacity solid electrolytic capacitor using an anode foil whose surface has a high magnification, it is necessary to sufficiently fill the solid electrolyte in fine pores on the surface. It is known that when the filling is insufficient, the capacity impregnation rate (percentage of the capacitance value when using the solid electrolyte with respect to the capacitance value when using the electrolytic solution) decreases.

  A conventional solid electrolytic capacitor using a TCNQ complex salt has excellent high frequency characteristics and a relatively simple manufacturing process compared to an electrolyte type capacitor, and an inexpensive capacitor can be obtained, but the capacity impregnation rate is still insufficient. Therefore, it is difficult to sufficiently draw out the characteristics of the anode foil whose surface has a high magnification, and there remains a problem to be improved in terms of electrical characteristics such as capacitance and dielectric loss.

JP 58-191414 A

  An object of the present invention is a solid electrolytic capacitor in which a TCNQ complex salt is formed in a cathode layer, a solid electrolytic capacitor having a high capacity impregnation rate, a small size, a large capacitance, and excellent electrical characteristics, and a method for manufacturing the same. Is to provide.

  As a result of intensive studies, the present inventors have found that a solid electrolytic capacitor in which a cathode layer made of polyethylene dioxythiophene (hereinafter abbreviated as “PEDOT”) and a TCNQ complex salt can solve the above problems. The present invention has been completed.

  That is, the present invention is a solid electrolytic capacitor in which a cathode layer made of PEDOT and a TCNQ complex salt is sequentially formed on an anode foil on which a dielectric oxide film is formed.

  Further, the present invention is characterized in that the TCNQ complex salt is a charge transfer complex salt (hereinafter abbreviated as “BIQ · TCNQ”) having Nn-butylisoquinolinium as a donor and TCNQ as an acceptor. It is a solid electrolytic capacitor.

  In the present invention, the TCNQ complex salt is a charge transfer complex salt having N, N′-octamethylene-di-3,5-lutidinium as a donor and TCNQ as an acceptor (hereinafter, abbreviated as “ODL · TCNQ”). Is a mixed charge transfer complex salt containing 1 to 50% by mass of the residue and the balance being BIQ · TCNQ.

  In the present invention, the TCNQ complex salt is 1 to 50% by mass of a charge transfer complex salt (hereinafter abbreviated as “OIQ · TCNQ”) having Nn-octylisoquinolinium as a donor and TCNQ as an acceptor. It is a solid electrolytic capacitor characterized in that it is a mixed charge transfer complex salt containing BIQ · TCNQ.

  Further, in the present invention, an ethylene dioxythiophene monomer (hereinafter, “EDOT”) is abbreviated as a capacitor element in which an anode foil having a dielectric oxide film formed thereon and a counter cathode foil are wound through a separator. ) Is polymerized with an oxidizing agent to form a PEDOT layer, and then the element is impregnated with a heated and melted TCNQ complex salt, and then cooled, whereby the cathode made of PEDOT and TCNQ complex salt is formed on the anode foil. A method of manufacturing a solid electrolytic capacitor characterized in that a layer is formed.

  The present invention is a solid electrolytic capacitor in which a cathode layer made of PEDOT and TCNQ complex salt is sequentially formed on an anode foil on which a dielectric oxide film is formed. The cathode layer formed according to the present invention has a high conductivity. By impregnating EDOT, which is a molecular monomer, and polymerizing with an oxidizing agent, the etching pores of the anode foil can be sufficiently filled with PEDOT. Further, the TCNQ complex salt is formed between the anode foil and the cathode foil. Since it is formed without a gap, a solid electrolytic capacitor having a high capacity impregnation rate, a small size, a large capacitance and excellent electrical characteristics can be obtained as compared with a conventional product using only the TCNQ complex salt as a cathode layer. Moreover, since PEDOT used for this invention has high decomposition temperature, the solid electrolytic capacitor excellent in heat resistance and durability is obtained.

  According to the method for producing a solid electrolytic capacitor of the present invention, a capacitor element in which an anode foil and a counter cathode foil on which a dielectric oxide film is formed is wound through a separator, and EDOT is polymerized by an oxidizing agent. After the PEDOT layer is formed, the element is impregnated with the heated and melted TCNQ complex salt, and then cooled to easily and efficiently produce a solid electrolytic capacitor having a cathode layer made of PEDOT and TCNQ complex salt. Can be manufactured automatically.

  The solid electrolytic capacitor of the present invention is obtained by sequentially forming a cathode layer made of PEDOT and a TCNQ complex salt on an anode foil on which a dielectric oxide film is formed.

  As the anode foil, a film-forming metal simple substance such as aluminum, tantalum, titanium, zirconium, niobium, or an alloy thereof is used.

  In the present invention, the PEDOT layer formed on the anode foil can form a PEDOT layer having a desired thickness by controlling the amount of EDOT and oxidant impregnated in the anode foil. The upper limit of the thickness is preferably 0.8 mm. If the thickness exceeds 0.8 mm, the capacitor characteristics may deteriorate and the cost may increase.

  The TCNQ complex salt used in the present invention is an isoquinolinium TCNQ complex salt (BIQ · TCNQ, OIQ · TCNQ) represented by the general formula [1] substituted at the N position and / or a lutidinium TCNQ complex salt represented by the general formula [2]. (ODL / TCNQ), specifically, a charge transfer complex of BIQ / TCNQ alone, a mixed charge transfer complex salt containing 1 to 50% by mass of ODL / TCNQ, and the balance consisting of BIQ / TCNQ, or OIQ A mixed charge transfer complex salt containing 1 to 50% by mass of TCNQ and the balance being BIQ · TCNQ is used. The content of ODL / TCNQ or OIQ / TCNQ in the mixed charge transfer complex salt is preferably 5 to 20% by mass, and if the content is less than 1% by mass or more than 50% by mass, the capacitor characteristics deteriorate. There is a case.

  In general formula [1], n represents a positive integer of 3 or 7.

  The solid electrolytic capacitor of the present invention comprises a PEDOT layer, which is a conductive polymer, and a cathode layer made of the TCNQ complex salt on an anode foil on which a dielectric oxide film is formed. The method of manufacturing the capacitor will be described in detail, taking as an example the case of using an aluminum foil as the anode foil and a mixed charge transfer complex salt of ODL / TCNQ and BIQ / TCNQ as the TCNQ complex salt.

  First, after the surface of the anode aluminum foil is roughened by etching, an anode lead is connected, and then a chemical conversion treatment is performed in an aqueous solution of diammonium adipate or the like to form a dielectric oxide film. In practicing the present invention, it is preferable to use a foil having a large etching magnification, whereby a capacitor having a large capacitance can be obtained.

  Separately, a separator such as manila paper is sandwiched between the facing cathode aluminum foil to which the cathode lead is connected and the anode aluminum foil, wound up in a cylindrical shape, and then carbonized by heat treatment, and the winding type capacitor. Prepare the device.

  Next, a cathode layer made of PEDOT and a TCNQ complex salt is formed on the anode foil of the capacitor element. As a method for forming PEDOT, a capacitor element is impregnated with EDOT, which is a conductive polymer monomer, by a method such as dipping, coating, or spraying, and then the impregnated EDOT is subjected to a polymerization reaction by contacting with an oxidizing agent. To form a PEDOT layer. In addition, the method of impregnating with an oxidizing agent first and then polymerizing by contacting EDOT and the method of polymerizing by impregnating EDOT and an oxidizing agent at a time can be applied, and are not particularly limited. Further, the chemical polymerization is performed in a gas phase or a liquid phase at a temperature of 0 to 150 ° C. Above this temperature, PEDOT may decompose and capacitor characteristics may deteriorate.

  As the oxidizing agent used in the present invention, halides such as iodine, bromine, bromine iodide, chlorine dioxide, iodic acid, periodic acid, chlorous acid, antimony pentafluoride, phosphorus pentachloride, phosphorus pentafluoride, Metal halides such as aluminum chloride, molybdenum chloride, or salts of high valence state metal ions such as permanganate, dichromate, chromic anhydride, ferric salt, cupric salt, sulfuric acid, nitric acid, Protonic acids such as trifluoromethanesulfuric acid, oxygen compounds such as sulfur trioxide and nitrogen dioxide, hydrogen peroxide, ammonium persulfate, peroxo acids and salts such as sodium perborate, molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid And the like. In addition, by using an oxidant containing an anionic component, the anionic component is incorporated into the conductive polymer after chemical polymerization and functions as a dopant, so that a conductive polymer with improved conductivity can be formed. Preferred anionic components include organic sulfonate ions, carboxylate ions, boron compound ions, phosphate compound ions, and the like.

  Using at least one of the above oxidizing agents, EDOT impregnated in the capacitor element and the oxidizing agent are brought into contact with each other, and then a polymerization reaction is performed at a temperature of 0 ° C. to 150 ° C. to first form a PEDOT layer.

  By the above process, a first cathode layer in which PEDOT is sufficiently filled in the fine etching holes of the anode aluminum foil is formed.

  Next, in a separately prepared cylindrical aluminum capacitor case with a bottom, 20% by mass of ODL / TCNQ is mixed thoroughly with a mixed charge transfer complex salt containing BIQ / TCNQ, and the required amount is packed. Heat to 250 to 320 ° C. to melt and liquefy the TCNQ complex salt in the capacitor case. Below this temperature, the formation of TCNQ complex salt on the capacitor element becomes insufficient, which is inconvenient.

  The capacitor element in which the PEDOT layer has been formed is immersed in the molten and liquefied TCNQ complex salt, and then immediately cooled and solidified to form a second cathode layer made of the TCNQ complex salt. When the capacitor element is immersed in the melted and liquefied TCNQ complex salt, the capacitor element is preheated to 150 ° C. or more and 350 ° C. or less, so that the TCNQ complex salt does not have a gap between the anode foil and the cathode foil of the capacitor element. It is formed.

  Next, an epoxy resin or the like is used to seal the capacitor case, and voltage is applied to perform aging to complete the solid electrolytic capacitor of the present invention.

  According to the method for producing a solid electrolytic capacitor of the present invention, the fine etching holes of the anode foil can be sufficiently filled with PEDOT, and further, there is no gap between the TCNQ complex salt between the anode foil and the cathode foil. Therefore, a solid electrolytic capacitor having a high capacity impregnation rate, a small size, a large capacitance, and excellent electrical characteristics can be obtained. The solid electrolytic capacitor of the present invention uses only a conventional TCNQ complex salt as a cathode. Compared to the capacitor used, it has a high capacity impregnation rate, a small size, a large capacity, and excellent electrical characteristics.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited at all by an Example. In Examples, “%” represents “% by mass”, capacitance (C) and dielectric loss (tan δ) were measured at a frequency of 120 Hz, and equivalent series resistance (ESR) was measured at a frequency of 100 kHz. The capacity impregnation rate was measured based on the capacitance in a 15% ammonium adipate aqueous solution.

Example 1
After the surface of the aluminum foil is etched and roughened, the anode lead is connected by caulking, followed by chemical conversion treatment at a voltage of 4 V in a 10% ammonium adipate aqueous solution to form a dielectric oxide film on the surface. Formed.

  Next, 50 μm thick Manila paper is sandwiched as a separator between the anode foil and the counter cathode aluminum foil to which the cathode lead is connected by resistance welding, and then wound into a cylindrical shape, and then at a temperature of 400 ° C. for 4 minutes. The capacitor element was prepared by heat treatment to carbonize the manila paper. The capacitance of the obtained capacitor element in a 15% ammonium adipate aqueous solution was 40 μF.

  Next, EDOT, which is a conductive polymer monomer, and 40% p-toluenesulfonic acid iron / n-butanol solution, which is an oxidizing agent, are mixed at a mass ratio of 1: 6 to obtain a polymerization liquid, and the liquid is prepared first. 70 μL was injected into the capacitor element, and then subjected to a polymerization reaction at 80 ° C. for 1 hour to form a PEDOT layer.

  Next, 60 mg of BIQ / TCNQ is packed in a bottomed cylindrical aluminum capacitor case (diameter 6 mmφ × height 7 mm), and the capacitor case is placed on a hot plate at a temperature of 300 ° C. The moving complex salt was melted and liquefied.

  In the molten and liquefied TCNQ complex salt, the capacitor element formed with the PEDOT layer previously heated at 300 ° C. is immersed, and then immediately cooled to solidify the TCNQ complex salt, and PEDOT is formed on the anode aluminum foil. And a cathode layer composed of a TCNQ complex salt.

  Next, the capacitor case was sealed with an epoxy resin, and aging was performed by applying a voltage of 4 V to both electrodes to complete a solid electrolytic capacitor.

  Table 1 shows the initial electrical characteristics, the capacity impregnation rate, and the electrical characteristics after high-temperature loading (held in an atmosphere at a temperature of 260 ° C. for 10 seconds) of the obtained solid electrolytic capacitor.

Example 2
In the same manner as in Example 1, a capacitor element was prepared, and 10 μL of EDOT, which is a conductive polymer monomer, was injected into the capacitor element, and then 60 μL of 40% p-toluenesulfonic acid iron / n-butanol solution was injected. The PEDOT layer was formed by heat treatment at 80 ° C. for 1 hour to cause a polymerization reaction.

  Next, a bottomed cylindrical aluminum capacitor case (diameter 6 mmφ × height 7 mm) is filled with 60 mg of a mixed charge transfer complex salt containing 10% of OIQ · TCNQ and the balance being BIQ · TCNQ. Was placed on a hot plate having a temperature of 300 ° C., and the charge transfer complex salt in the case was melted and liquefied.

  In the molten and liquefied TCNQ complex salt, the capacitor element formed with the PEDOT layer previously heated at 300 ° C. is immersed, and then immediately cooled to solidify the TCNQ complex salt, and PEDOT is formed on the anode aluminum foil. And a cathode layer composed of a TCNQ complex salt.

  Next, the capacitor case was sealed with an epoxy resin, and aging was performed by applying a voltage of 4 V to both electrodes to complete a solid electrolytic capacitor.

  Table 1 shows the initial electrical characteristics, the capacity impregnation rate, and the electrical characteristics after high-temperature loading (held in an atmosphere at a temperature of 260 ° C. for 10 seconds) of the obtained solid electrolytic capacitor.

Comparative Example A solid electrolytic capacitor was completed in the same manner as in Example 1, except that only the TCNQ complex salt was formed in the cathode layer without forming the PEDOT layer in the capacitor element.

  Table 1 shows the initial electrical characteristics, the capacity impregnation rate, and the electrical characteristics after high-temperature loading (held in an atmosphere at a temperature of 260 ° C. for 10 seconds) of the obtained solid electrolytic capacitor.

As shown in Table 1, the solid electrolytic capacitors (Example 1 and Example 2) of the present invention in which the cathode layer made of PEDOT and TCNQ complex salt is formed are comparative examples in which only the conventional TCNQ complex salt is formed in the cathode layer. It can be seen that the capacity impregnation rate is high, the capacitance is large, and the electrical characteristics are excellent as compared with the solid electrolytic capacitor. Moreover, according to the solid electrolytic capacitor of the present invention, by using PEDOT having excellent heat resistance, the electric characteristics are not deteriorated after high temperature load, and the heat resistance and durability are excellent.

Claims (10)

Polyethylenedioxythiophene (hereinafter abbreviated as “PEDOT”) and 7,7,8,8-tetracyanoquinodimethane (hereinafter “TCNQ”) are sequentially formed on the anode foil on which the dielectric oxide film is formed. A solid electrolytic capacitor in which a cathode layer made of a complex salt is formed. 2. The TCNQ complex salt is a charge transfer complex salt (hereinafter abbreviated as “BIQ · TCNQ”) using Nn-butylisoquinolinium as a donor and TCNQ as an acceptor. Solid electrolytic capacitor. The TCNQ complex salt is a charge transfer complex salt (hereinafter abbreviated as “ODL · TCNQ”) using N, N′-octamethylene-di-3,5-lutidinium as a donor and TCNQ as an acceptor. 2. The solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is contained in a mixed charge transfer complex salt containing BIQ · TCNQ. The TCNQ complex salt contains 1 to 50% by mass of a charge transfer complex salt (hereinafter abbreviated as “OIQ · TCNQ”) having Nn-octylisoquinolinium as a donor and TCNQ as an acceptor, and the remainder 2. The solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is a mixed charge transfer complex salt composed of BIQ and TCNQ. Ethylenedioxythiophene monomer (hereinafter abbreviated as “EDOT”) is polymerized with an oxidizing agent in a capacitor element in which an anode foil and a counter cathode foil on which a dielectric oxide film is formed are wound through a separator. After reacting to form a PEDOT layer, the element is impregnated with heated and melted TCNQ complex salt and then cooled to form a cathode layer made of PEDOT and TCNQ complex salt on the anode foil. A method for producing a solid electrolytic capacitor. A PEDOT layer having an upper limit of 0.8 mm in thickness is obtained by polymerizing the EDOT with an oxidizing agent to a capacitor element in which an anode foil and a counter cathode foil formed with a dielectric oxide film are wound through a separator. Then, the element is impregnated with a heated and melted TCNQ complex salt and then cooled to form a cathode layer made of PEDOT and TCNQ complex salt on the anode foil. Manufacturing method. A capacitor element in which an anode foil and a counter cathode foil on which a dielectric oxide film is formed is wound through a separator is subjected to a polymerization reaction of EDOT with an oxidizing agent to form a PEDOT layer, and then 150 ° C. or higher. The element heated to 350 ° C. or lower is impregnated with a TCNQ complex salt heated and melted to 250 ° C. or higher and 320 ° C. or lower and then cooled to form a cathode layer made of PEDOT and TCNQ complex salt on the anode foil. A method for producing a solid electrolytic capacitor characterized by the above. The method for producing a solid electrolytic capacitor according to claim 5, wherein the TCNQ complex salt is BIQ · TCNQ. 8. The TCNQ complex salt is a mixed charge transfer complex salt containing 1 to 50% by mass of ODL · TCNQ and the balance being BIQ · TCNQ. 9. A method for producing a solid electrolytic capacitor. 8. The TCNQ complex salt is a mixed charge transfer complex salt containing 1 to 50% by mass of OIQ · TCNQ, and the balance being BIQ · TCNQ. 9. A method for producing a solid electrolytic capacitor.