JP4720076B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid electrolytic capacitor capable of improving capacitance and a method for manufacturing the same.

  An electrolytic capacitor using a metal having a valve action such as tantalum or aluminum is obtained by expanding the dielectric by making the valve action metal as the anode-side counter electrode into the shape of a sintered body or an etching foil. Since it is small and a large capacity can be obtained, it is widely used. In particular, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has features such as small size, large capacity, low equivalent series resistance, easy to chip, and suitable for surface mounting. It is indispensable for miniaturization, high functionality and low cost of electronic equipment.

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

  As solid electrolytes used for solid electrolytic capacitors, manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complexes are known. There is a technique (see Patent Document 1) that focuses on a conductive polymer such as polyethylenedioxythiophene (hereinafter referred to as PEDT) having excellent adhesion to an oxide film layer of an electrode.

  A solid electrolytic capacitor of a type in which a solid electrolyte layer made of a conductive polymer such as PEDT is formed on such a wound capacitor element is produced as follows. First, the surface of the anode foil made of valve action metal such as aluminum is roughened by electrochemical etching treatment in an aqueous chloride solution to form many 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 conversion). Like the anode foil, the cathode foil is made of a valve action metal such as aluminum, but the surface is only subjected to etching treatment.

Thus, the anode foil having the oxide film layer formed on the surface and the cathode foil having only the etching pits are wound through a separator to form a capacitor element. Subsequently, a polymerizable monomer such as 3,4-ethylenedioxythiophene (hereinafter referred to as EDT) and an oxidizer solution are respectively discharged into the capacitor element subjected to restoration conversion, or immersed in a mixture of both. The polymerization reaction is promoted in the capacitor element, and a solid electrolyte layer made of a conductive polymer such as PEDT is generated. Thereafter, the capacitor element is housed in a bottomed cylindrical outer case, and the opening of the case is sealed with a sealing rubber to produce a solid electrolytic capacitor.
JP-A-2-15611

  Incidentally, in recent years, electronic information devices have been digitized, and further, the driving frequency of a microprocessor (MPU), which is the heart of these electronic information devices, has been increased. Along with this, the power consumption has been increasing and the problem of reliability due to heat generation has become obvious. Therefore, the drive voltage has been reduced as a countermeasure.

  In order to reduce the drive voltage, a DC-DC converter called a voltage control module is widely used as a circuit for supplying highly accurate power to the microprocessor, and the output side capacitor is used to prevent a voltage drop. Many capacitors with low ESR are used. As the capacitor having such a low ESR characteristic, the solid electrolytic capacitor as described above has been put into practical use and widely used.

However, the increase in the driving frequency of the microprocessor is remarkable, and accordingly, the power consumption further increases. In order to cope with this, further increase in the power supplied from the capacitor to prevent the voltage drop is required. That is, a large amount of power must be able to be supplied in a short time. For this reason, solid electrolytic capacitors are required to have higher ESR characteristics as well as larger capacity, smaller size, and lower voltage.
Such a problem occurs not only when EDT is used as the polymerizable monomer but also when other thiophene derivatives, pyrrole, aniline, and the like are used.

  The present invention has been proposed to solve the above-described problems of the prior art, and an object of the present invention is to provide a solid electrolytic capacitor capable of improving capacitance and a method for manufacturing the same. is there.

  As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, it has been found that the capacitance of a solid electrolytic capacitor can be increased by forming a polymer layer composed of an organometallic polymer block and an organic resin block between a dielectric oxide film and a conductive polymer. It is.

  In addition, as a method of forming a polymer layer composed of an organometallic polymer block and an organic resin block, a repaired capacitor element is formed by using a polymer composed of an organometallic polymer block and an organic resin block in a predetermined organic solvent at 2 wt% or less. It has been found that a method of immersing in a solution dissolved at a concentration is preferable.

(Method for manufacturing solid electrolytic capacitor)
The manufacturing method of the solid electrolytic capacitor according to the present invention is as follows. That is, an anode foil and a cathode foil having an oxide film layer formed on the surface thereof are wound through a separator to form a capacitor element, and this capacitor element is subjected to restoration conversion. Thereafter, the capacitor element is dipped in a solution in which a polymer composed of an organometallic polymer block and an organic resin block is dissolved in a predetermined organic solvent at a concentration of 2 wt% or less, pulled up, and then the solvent is evaporated at 40 to 100 ° C. Then, heat treatment is performed at 150 to 200 ° C.
Subsequently, the capacitor element is immersed in a mixed solution of a polymerizable monomer and an oxidizing agent to cause a polymerization reaction of the conductive polymer in the capacitor element, thereby forming a solid electrolyte layer. And this capacitor | condenser element is accommodated in an exterior case, an opening edge part is sealed with sealing rubber | gum, and a solid electrolytic capacitor is formed.

  The capacitor element is impregnated with a polymerizable monomer and an oxidizing agent. The capacitor element is immersed in a mixed solution of the monomer and the oxidizing agent. The capacitor element is immersed in the monomer solution and then immersed in the oxidizing agent solution. A method of discharging the oxidant solution after discharging the monomer solution to the capacitor element can be used.

(Organic metal polymer)
An organometallic polymer is a polymer in which the main chain is composed of a metal element such as Si, Ti, or B and a non-metal element such as O or N, and an organic group such as a methyl group or a phenyl group is bonded to the side chain. Yes, for example, polysiloxane, polypolosiloxane, polytitanosiloxane, polycarbosilane, polysilastyrene, polysilazane, polytitanocarbosilane and the like can be mentioned.

(Organic resin)
Organic resins include polyimide resins, polyvinyl resins, fluorocarbon resins such as polytetrafluoroethylene resins, benzocyclobutene resins, fluorinated polyallyl ether resins, polyolefin resins such as polyethylene resins, other polyarylate resins, polycarbonate resins, polyamides Examples thereof include resins, polysulfone resins, polyether ketone resins, polyether nitrile resins, polystyrene resins, and ABS resins.

(Polymer composed of organometallic polymer block and organic resin block)
As the polymer composed of the organometallic polymer block and the organic resin block, a silicone-modified organic resin composed of any of the above organic resins and polysiloxane is preferable, and more preferably, a polyimide silicone resin composed of a polyimide resin block and a polysiloxane block is used. .

(Polyimide silicone)
When the polymer composed of the organometallic polymer block and the organic resin block is polyimide silicone, the solvent is preferably a ketone solvent having good solubility of polyimide silicone, and cyclohexanone, acetone, methyl ethyl ketone, or the like can be used.
The concentration of polyimide silicone is preferably 0.05 to 2 wt%. If the concentration is less than this range, the withstand voltage is not sufficient, and if it exceeds this range, the insulation of the polyimide silicone layer increases and the capacitance decreases.

The reason why the capacitance increases when the concentration of the polyimide silicone is within this range is considered as follows. That is, both polyimide and the conductive polymer such as PEDT constituting polyimide silicone are organic compounds, so the adhesion is good. Also, both Si and the dielectric oxide film (Al ₂ O ₃ ) in polyimide silicone are inorganic compounds, so they are adhesive. Therefore, as a result, it is considered that the adhesion between the conductive polymer and the dielectric oxide film is improved through the polyimide silicone layer, and the capacitance is increased.

(EDT and oxidizing agent)
When EDT is used as the polymerizable monomer, EDT monomer can be used as EDT impregnated in the capacitor element, but a monomer solution in which EDT and a volatile solvent are mixed at a volume ratio of 1: 0 to 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, nitrogen compounds such as acetonitrile, and the like. Of these, methanol, ethanol, acetone and the like are preferable.

  Further, as the oxidizing agent, an aqueous solution of ferric paratoluenesulfonate, periodic acid or iodic acid dissolved in ethanol can be used, and the concentration of the oxidizing agent with respect to the solvent is preferably 40 to 65 wt%, and 45 to 57 wt%. % Is more preferable. The higher the oxidant concentration in the solvent, the lower the ESR. As the oxidant solvent, the volatile solvent used in the monomer solution can be used, and ethanol is particularly preferable. Ethanol is suitable as the oxidant solvent because it is easy to evaporate due to its low vapor pressure and the remaining amount is small.

(Chemical solution for restoration conversion)
As the chemical solution for restoration chemical conversion, phosphoric acid type chemicals such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate, boric acid type chemicals such as ammonium borate, and adipic acid type chemicals such as ammonium adipate, etc. Although a liquid can be used, it is preferable to use ammonium dihydrogen phosphate. The immersion time is preferably 5 to 120 minutes.

(Other polymerizable monomers)
The polymerizable monomer used in the present invention includes, in addition to the above EDT, a thiophene derivative other than EDT, aniline, pyrrole, furan, acetylene or a derivative thereof, which is oxidatively polymerized with a predetermined oxidizing agent, and is a conductive polymer. As long as it forms, it can be applied. As the thiophene derivative, one having the following structural formula can be used.

(Action / Effect)
The reason why the capacitance of the solid electrolytic capacitor can be increased with the configuration of the present invention is considered as follows.
That is, the organometallic polymer block has a good bondability with an inorganic dielectric oxide film, and the organic resin block has a good bondability with a conductive polymer, and therefore consists of an organometallic polymer block and an organic resin block. Since the polymer layer acts as an adhesive layer between the dielectric oxide film and the conductive polymer, it is considered that the capacitance and ESR are improved.

  ADVANTAGE OF THE INVENTION According to this invention, the solid electrolytic capacitor which enabled the improvement of an electrostatic capacitance, and its manufacturing method can be provided.

  Subsequently, the present invention will be described in more detail based on Examples and Comparative Examples manufactured as follows.

Example 1
An electrode lead means was connected to the anode foil and the cathode foil having an oxide film layer formed on the surface, and both electrode foils were wound through a separator to form a capacitor element. And this capacitor | condenser element was immersed in ammonium dihydrogen phosphate aqueous solution for 40 minutes, and restoration | restoration conversion was performed. Thereafter, the capacitor element was immersed in a 0.5 wt% cyclohexanone solution of polyimide silicone, pulled up, and then heat treated at 170 ° C. for 1 hour.
Subsequently, a 45 wt% butanol solution of EDT and ferric p-toluenesulfonate is poured into a predetermined container so that the molar ratio is 6: 1 to prepare a mixed solution, and the capacitor element is mixed as described above. The capacitor element was impregnated with EDT and an oxidizing agent by dipping in the solution for 10 seconds. Then, this capacitor element was left in a constant temperature bath at 120 ° C. for 1 hour to cause a polymerization reaction of PEDT in the capacitor element, thereby forming a solid electrolyte layer. Then, this capacitor | condenser element was accommodated in the bottomed cylindrical aluminum case, and it sealed with sealing rubber | gum, and formed the solid electrolytic capacitor. This solid electrolytic capacitor has a rated voltage of 25 WV and a rated capacity of 10 μF.

(Example 2)
The concentration of the polyimide silicone cyclohexanone solution was 1.5 wt%. Otherwise, a solid electrolytic capacitor was prepared under the same conditions and steps as in Example 1.
(Example 3)
Instead of polyimide silicone, silicone-modified polyvinyl alcohol was used. Otherwise, a solid electrolytic capacitor was prepared under the same conditions and steps as in Example 1.

(Comparative example)
A solid electrolytic capacitor was prepared in the same manner as in Example 1 except that the polyimide silicone treatment was not performed.

[Comparison result]
When the electrostatic capacity was investigated about the Example and comparative example which were obtained by said method, the result as shown in Table 1 was obtained.

  As is clear from Table 1, in each of Example 1 and Example 2 in which a polyimide silicone layer was formed, and Example 3 in which a silicone-modified polyvinyl alcohol layer was formed, compared with a comparative example in which polyimide silicone treatment was not performed. The capacitance was improved.

Claims (7)

A solid electrolyte layer made of a conductive polymer is formed by impregnating a polymerizable monomer and an oxidizing agent on a capacitor element in which an anode foil and a cathode foil each having a dielectric oxide film formed thereon are wound through a separator. In the solid electrolytic capacitor
By immersing the capacitor element in a solution in which a polymer composed of an organometallic polymer block and an organic resin block is dissolved in a predetermined organic solvent at a concentration of 0.05 to 2 wt% or less, the dielectric oxide film and the conductive polymer A solid electrolytic capacitor characterized in that a polymer layer composed of an organometallic polymer block and an organic resin block is formed therebetween. The solid electrolytic capacitor according to claim 1, wherein the organometallic polymer block is polysiloxane. The solid electrolytic capacitor according to claim 1, wherein the organic resin block is polyimide. Solid that forms a solid electrolyte layer made of a conductive polymer by impregnating a polymerizable monomer and an oxidizing agent into a capacitor element in which an anode foil and a cathode foil each having a dielectric oxide film formed thereon are wound through a separator. In the method of manufacturing an electrolytic capacitor,
The capacitor element is immersed in a solution in which a polymer composed of an organometallic polymer block and an organic resin block is dissolved in a predetermined organic solvent at a concentration of 0.05 to 2 wt%, and the dielectric oxide film and the conductive polymer are immersed in the capacitor element. A method for producing a solid electrolytic capacitor, wherein a polymer layer comprising an organometallic polymer block and an organic resin block is formed therebetween.   The method for producing a solid electrolytic capacitor according to claim 4, wherein the polymer composed of the organometallic polymer block and the organic resin block is polyimide silicone.   The method for producing a solid electrolytic capacitor according to claim 4, wherein the polymerizable monomer is a thiophene derivative.   The method for producing a solid electrolytic capacitor according to claim 6, wherein the thiophene derivative is 3,4-ethylenedioxythiophene.