JP2009238776A - Method of manufacturing solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a solid electrolytic capacitor improved in adhesiveness between layers, and reduced in ESR, in a capacitor element of the solid electrolytic capacitor having a solid electrolyte. <P>SOLUTION: The method of manufacturing a solid electrolytic capacitor includes a process of manufacturing a capacitor element having a positive electrode body having a positive electrode extraction part, and composed by sequentially forming, on a circumferential surface of the positive electrode body excluding the positive electrode extraction part, a dielectric coating layer, a negative electrode layer and a negative electrode extraction part. The process of manufacturing the capacitor element includes step of: forming the positive electrode body having the positive electrode extraction part; forming the dielectric coating layer; forming the negative electrode layer; forming the negative electrode extraction part; and carrying out a surface treatment by ultraviolet irradiation or plasma irradiation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor having a capacitor element in which a dielectric film layer, a cathode layer, and a cathode lead portion are sequentially formed on the peripheral surface of an anode body.

  Conventionally, a solid electrolytic capacitor using a conductive polymer as a solid electrolyte for forming a cathode layer has been known for the purpose of lowering ESR. As these conductive polymers, polythiophene, polypyrrole, polyaniline, or the like can be used.

  By the way, in recent years, electronic information devices have been digitized, and the driving voltage has been reduced and the driving current has been increased with the increase in driving frequency. In particular, the speed of the microprocessor, which is the heart of a personal computer, has been remarkably increased, and the driving voltage has been steadily reduced. As a circuit for supplying high-precision power to such a microprocessor, a DC-DC converter called a voltage control module (VRM) is widely used.

  By the way, as the voltage of the microprocessor is lowered, the voltage range for guaranteeing the operation of the microprocessor is becoming narrower. The demand current of the microprocessor changes very fast depending on the situation imposed on the microprocessor. Therefore, the DC-DC converter alone cannot cope with the change, and a load capacitor is connected to the output side to cope with the load fluctuation of the microprocessor. is doing.

The function required for such a load capacitor is that ESR (Equivalent Series Resistance) is small in order to reduce loss. Therefore, further reduction in ESR is also demanded for solid electrolytic capacitors used for such load capacitors. As an attempt to reduce the ESR of such a solid electrolytic capacitor, there is a method disclosed in Patent Document 1.
Japanese Patent Application Laid-Open No. 11-135377.

  However, as described in Patent Document 1, in a solid electrolytic capacitor in which a conductive film layer in which some organic compounds are contained in metal fine particles having a particle diameter of 10 to 500 mm is formed, silver particles are fine on the surface of the solid electrolyte layer. Although the contact resistance can be reduced by entering the irregularities and expanding the contact area between the silver paste layer and the solid electrolyte layer as a whole, when the binder component is removed when the silver paste is sintered, A microcrack will arise in a silver paste layer, and the contact frequency between silver particles will fall. As a result, the low efficiency of the silver paste layer was increased, and the ESR characteristics of the solid electrolytic capacitor could not be reduced as expected.

  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 further reducing ESR and a method for manufacturing the same. .

  In view of the above problems, the present invention includes an anode body having an anode lead portion, and a dielectric film layer, a cathode layer, and a cathode lead portion are sequentially formed on the peripheral surface of the anode body excluding the anode lead portion. In the method of manufacturing a solid electrolytic capacitor including a step of manufacturing a capacitor element, the step of manufacturing the capacitor element includes a step of forming the anode body having the anode lead portion, and a step of forming the dielectric coating layer. And a step of forming the cathode layer, a step of forming the cathode lead-out portion, and a step of performing a surface treatment by irradiating with ultraviolet rays or plasma. The surface treatment step may be performed after the step of forming the cathode lead portion, after the step of forming the cathode layer, or after the step of forming the dielectric coating layer. Alternatively, it may be performed after the step of forming the anode body.

  By irradiating the surface of each layer with ultraviolet light or plasma, polar carboxyl groups and hydroxyl groups are generated on the surface of each layer. The presence of the carboxyl group or hydroxyl group causes the surface of each layer to become rough, thereby improving the surface tension and wettability and improving the adhesion between the layers, so that the ESR of the capacitor can be reduced.

  The best mode for carrying out the present invention will be described below.

FIG. 1 is a sectional view of a solid electrolytic capacitor of the present invention, and FIG. 2 is a sectional view of a capacitor element. The solid electrolytic capacitor of the present invention includes a capacitor element 1 from which an anode lead portion 21 protrudes, an anode lead frame 61 connected to the anode section 21, a cathode lead frame 62 connected to the capacitor element 1, and a capacitor element. 1 and an exterior resin 7 covering 1.
Here, the capacitor element 1 specifically has a structure shown in FIG. That is, it has a structure in which the dielectric coating layer 3, the cathode layer 4, and the cathode lead portion 5 are sequentially formed on the peripheral surface of the anode body 22 where the anode lead portion 21 is planted. Such a solid electrolytic capacitor is manufactured as follows.
(1. Formation process of each layer of capacitor element)
First, an anode wire is disposed so as to protrude from the mold as the anode lead-out portion 21, and the mold is filled with powder of a valve metal such as tantalum or niobium, pressure-molded, sintered, and sintered. Form. Next, the dielectric coating layer 3 is formed on the peripheral surface of the anode body 22. Specifically, the anode body 22 from which the cathode lead portion 21 protrudes is immersed in an acid solution such as sulfuric acid, nitric acid, or adipic acid, and the dielectric coating layer 3 is formed by an anodic oxidation reaction.

  Next, the cathode layer 4 is formed. The cathode layer 4 is composed of a solid electrolyte layer, may be composed of a single layer, or may be composed of a plurality of layers. Solid electrolytes that form the solid electrolyte layer include inorganic semiconductors such as manganese dioxide, organic semiconductors such as TCNQ (7,7,8,8-tetracyanoquinodimethane) complex salts, and conductive materials such as polypyrrole, polythiophene, polyfuran, and polyaniline. A cationic polymer can be employed, and the cathode layer 4 may be formed by a combination thereof. The solid electrolyte that can be used as the cathode layer 4 exemplified above can be formed by a conventionally known method. In the present embodiment, the cathode layer 4 using a conductive polymer as the solid electrolyte is formed.

  As a method for forming a conductive polymer, a chemical polymerization method, an electrolytic polymerization method, and the like are known. The chemical polymerization method is a method for forming a conductive polymer by subjecting a monomer to an oxidation reaction using an oxidizing agent. As the monomer, one or more kinds can be arbitrarily selected and used from pyrrole, thiophene, furan, aniline, and derivatives thereof. As the oxidizing agent, conventionally known ones such as hydrogen peroxide, potassium permanganate, iron (III) oxide, and potassium dichromate can be used. The chemical polymerization method is performed, for example, by immersing the anode body 22 having the dielectric film layer 3 formed on the surface thereof in a solution containing the monomer and the oxidizing agent. Alternatively, a solution containing a monomer and a solution containing an oxidizing agent may be prepared, and the anode body 22 may be immersed in each solution. Furthermore, the solution used for the chemical polymerization may contain an additive such as a surfactant. In order to improve the conductivity of the conductive polymer, a dopant is preferably included. As the dopant, organic sulfonic acid, iron (III) chloride, or the like can be used. Moreover, when an oxidizing agent and a dopant are contained in the solution, a substance that serves as an oxidizing agent and a dopant may be included. Examples of such materials include ferric salts such as iron (III) benzenesulfonate, iron (III) p-toluenesulfonate, and iron (III) naphthalenesulfonate.

  In the electrolytic polymerization method, anode body 22 is immersed in a solution containing a monomer and a dopant, anode body 22 is used as an anode electrode, and a current is passed between the anode electrode and a cathode electrode disposed in the solution. In this method, an electrooxidation reaction is generated to form a conductive polymer. As the monomer and dopant, the same materials as those used in the chemical polymerization method can be used.

  After the cathode layer 4 is formed by the above method, the cathode lead-out portion 5 is formed. The cathode lead-out portion 5 can adopt a single layer structure including only a silver paste layer in addition to a laminate of the conductive carbon layer 51 and the silver paste layer 52 as shown in FIG. The conductive carbon layer 51 is formed by immersing the anode body 22 having the cathode layer 4 formed on the surface thereof in a solution containing a conductive carbon material such as graphite, carbon black, or carbon nanotube, and a binder. The silver paste layer 52 is formed by immersing the anode body 22 in a solution containing silver particles and a binder. Here, as the conductive carbon material and the binder, various conventionally known materials can be adopted, and the solvent used for the solution for forming the conductive carbon layer 51 and the solution for forming the silver paste layer 52 are used. As for, it is possible to use a conventionally known material such as water or an organic solvent. For example, methyl cellulose, polyacrylonitrile, methyl methacrylate, phenol resin, polyester resin, acrylic resin, epoxy resin, or the like can be used as the binder. Moreover, butyl acetate, alcohols, ketones, etc. can be used as said solvent.

As described above, each layer of the capacitor element 1 is formed.
(2. Surface treatment process)
Next, the surface treatment process of the capacitor element 1 will be described. The surface treatment of the present invention is performed in order to improve the wettability by roughening the surface of the layer, and examples thereof include ultraviolet irradiation and plasma irradiation. The wavelength of ultraviolet light used for ultraviolet irradiation is preferably within a range where ozone is generated by ultraviolet irradiation in an oxygen atmosphere. In the case of using plasma treatment, the output, irradiation time, and the like can be changed as appropriate, and the values should not be particularly limited.
The surface treatment is performed after the anode body 22 is formed, the dielectric coating layer 3 is formed, the cathode layer 4 is formed, and the cathode lead portion 5 is formed in the step of manufacturing the capacitor element 1 described above. However, it is preferably performed at least for the silver paste layer 52 described above. When the silver paste layer 52 is irradiated with ultraviolet rays or plasma, polar carboxyl groups or hydroxyl groups are generated on the surface of the silver paste layer 52. Due to the presence of the carboxyl group and the hydroxyl group, the surface of the silver paste layer 52 is roughened and the surface tension is increased, thereby improving the adhesion with the cathode lead frame 62 functioning as a terminal described later, and thus the ESR of the solid electrolytic capacitor. Is reduced.
Moreover, it is preferable to perform surface treatment after forming the cathode layer 4. Although the surface of the cathode layer 4 formed of a solid electrolyte layer made of a conductive polymer as in the present invention is relatively smooth, the surface of the cathode layer 4 is roughened by surface treatment. Thereby, since the contact area with the cathode lead part 5 having a relatively rough surface is increased and the adhesion is improved, ESR of the solid electrolytic capacitor can be reduced. When the cathode layer 4 is composed of a stack of a large number of solid electrolyte layers, the surface treatment may be performed on each solid electrolyte layer. The presence or absence of surface treatment for the electrolyte layer is not particularly limited. For example, when a conductive polymer layer formed by a chemical polymerization method and a conductive polymer layer formed by an electropolymerization method are included, the surface treatment of the present invention can be applied to each conductive polymer layer. Although it may be performed on the layer or only one of them, it is preferably performed on at least the layer of the conductive polymer formed by the chemical polymerization method. When surface treatment is performed on the conductive polymer layer formed by the chemical polymerization method, the surface of the conductive polymer layer formed by the chemical polymerization method is activated, and carboxyl groups and hydroxyl groups are formed on the surface. A functional group having the same polarity is generated. This improves wettability and improves the adhesion between the conductive polymer layer formed by the chemical polymerization method and the conductive polymer layer formed by the electrolytic polymerization method, thus reducing the ESR of the solid electrolytic capacitor. can do.
(3. Production of solid electrolytic capacitors)
First, an anode lead frame 61 and a cathode lead frame 62 are prepared. On the capacitor element 1 produced from the above 1 and 2, the anode lead portion 21 and the anode lead frame 61 are in contact with each other, and the cathode lead portion 5 The cathode lead frame 62 is placed in contact with each other and connected to each other. The anode lead frame 61 and the cathode lead frame 62 are preferably made of a metal member, and the surfaces thereof are preferably plated. The anode lead portion 21 and the anode lead frame 61 can be connected to the cathode lead portion 5 and the cathode lead frame 62 through a conductive paste, for example, by resistance welding or the like, and the method is not particularly limited. . Next, the capacitor element 1 is covered with a mold die while leaving a part of the anode lead frame 61 and the cathode lead frame 62, and the exterior resin 7 is filled in the die and pressure-molded. Thereafter, the anode lead frame 61 and the cathode lead frame 62 protruding from the exterior resin 7 are bent in the same direction along the peripheral surface of the exterior resin 7 to produce a solid electrolytic capacitor. The anode lead frame 61 and the cathode lead frame 62 exposed from the exterior resin 7 each have a surface connected to the mounting substrate, and the surfaces connected to the mounting substrate function as an anode terminal and a cathode terminal, respectively.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
The anode wire 21 made of tantalum is disposed so as to protrude from the mold, and the mold is filled with a material made of tantalum powder, pressure-molded and sintered, and the anode body 22 in which the anode wire 21 is planted is formed. Obtained. Next, an acid aqueous solution was prepared, and the anode body 22 was immersed in the acid aqueous solution, and the dielectric coating layer 3 was formed on the peripheral surface of the anode body 22 by an anodic oxidation reaction. Next, the anode body 22 having the dielectric film layer 3 formed on the surface thereof is immersed in a solution containing pyrrole as a monomer and sodium naphthalene sulfonate as a dopant, and then dried to form a conductive polymer layer by a chemical polymerization method. After that, a solution containing pyrrole as a monomer and sodium naphthalene sulfonate as a dopant is put into a polymerization tank in which electrodes are arranged in advance, and a conductive polymer layer is formed on the surface by a chemical polymerization method. The anode body 22 was immersed. By conducting electricity between the anode body 22 and the electrode in the solution, a conductive polymer layer was formed by electrolytic polymerization. The conductive polymer layer formed by the chemical polymerization method and the conductive polymer layer formed by the electrolytic polymerization method are collectively referred to as a cathode layer 4.

  Next, the anode body 22 having the cathode layer 4 formed on the surface thereof is immersed in a solution containing conductive carbon and a binder and dried to form the conductive carbon layer 51, and then the anode carbon is added to the solution containing silver particles and the binder. The body 22 was immersed to form a silver paste layer 52 on the surface of the conductive carbon layer 51.

  Next, the surface of the silver paste layer 52 was irradiated with ultraviolet rays of 184.9 nm and 253.7 nm for 30 seconds to 10 minutes using an ultraviolet irradiation device (ultraviolet cleaning reforming device: manufactured by Sen Special Light Source Co., Ltd.).

Thereafter, the capacitor element 1 is placed on the anode lead frame 61 and the cathode lead frame 62 so that the anode lead frame 61 and the anode wire 21 and the cathode lead frame 62 and the silver paste layer 52 are in contact with each other. The anode lead frame 62 and the silver paste layer 52 were connected to each other via a conductive paste by resistance welding of the anode wire 21 and the anode wire 21. Thereafter, the capacitor element 1 is covered with a molding die so as to leave a part of the anode lead frame 61 and the cathode lead frame 62, the exterior mold 7 is filled in the molding die, and pressure molding is performed. 1 was coated with the exterior resin 7, and then the anode lead frame 61 and the cathode lead frame 62 protruding from the exterior resin 7 were bent in the same direction along the peripheral surface of the exterior resin 7 to produce a solid electrolytic capacitor.
(Example 2)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the ultraviolet irradiation was not performed after the silver paste layer 52 was formed, but after the conductive polymer layer was formed by chemical polymerization.
(Example 3)
A solid electrolytic capacitor was produced in the same manner as in Example 1, except that the ultraviolet irradiation was not performed after the silver paste layer 52 was formed, but after the conductive polymer layer was formed by the electrolytic polymerization method.
Example 4
A solid electrolytic capacitor was fabricated in the same manner as in Example 1 except that the ultraviolet irradiation was not performed after the silver paste layer 52 was formed, but was performed on the anode body 22 after the anode body 22 was formed.
(Example 5)
A solid electrolytic capacitor was fabricated in the same manner as in Example 1 except that the ultraviolet irradiation was not performed after the silver paste layer 52 was formed, but after the dielectric coating layer 3 was formed.
(Example 6)
A solid electrolytic capacitor was fabricated in the same manner as in Example 1 except that the ultraviolet irradiation was not performed after the formation of the silver paste layer 52 but was performed after the formation of the conductive carbon layer 51.
(Example 7)
After forming the anode body 22, forming the dielectric coating layer 3, forming the conductive polymer layer by chemical polymerization, and forming the conductive polymer layer by electrolytic polymerization. A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the conductive carbon layer 51 was formed and then the silver paste layer 52 was formed.
(Comparative Example 1)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that ultraviolet irradiation by an ultraviolet irradiation device was not performed.

  For the solid electrolytic capacitors of Examples 1 to 7 and Comparative Example 1, ESR at 100 kHz was measured. The results are shown in Table 1.

From Table 1, it can be seen that the example of the present invention subjected to the surface treatment has a lower ESR of the solid electrolytic capacitor than the comparative example 1 in which the surface treatment is not performed at all. This is because the surface treatment activates the surface of the layer to generate polar carboxyl groups and hydroxyl groups on the surface of the layer, and the presence of these functional groups improves the adhesion to the adjacent layer or cathode lead frame. Because.
The above embodiments are merely illustrative of the present invention and should not be construed as limiting the invention described in the claims. The present invention can be freely modified within the scope of the claims and the scope of equivalent meanings. For example, in the embodiments of the present invention, the anode wire is used as the anode lead-out portion, but the present invention is not limited to this, and a part of a valve action metal foil such as aluminum can be used as the anode lead-out portion. The structure of the solid electrolytic capacitor of the present invention is not limited to that shown in FIG. 1, and a conventionally known solid electrolytic capacitor structure can be arbitrarily adopted.

It is sectional drawing of the solid electrolytic capacitor of this invention. It is sectional drawing of the capacitor | condenser element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 21 Anode extraction part 22 Anode body 3 Dielectric film layer 4 Cathode layer 5 Cathode extraction part 51 Conductive carbon layer 52 Silver paste layer 61 Anode lead frame 62 Cathode lead frame 7 Exterior resin

Claims (5)

A solid having a process for producing a capacitor element having an anode body having an anode lead portion and sequentially forming a dielectric film layer, a cathode layer, and a cathode lead portion on the peripheral surface of the anode body excluding the anode lead portion In the method of manufacturing an electrolytic capacitor,
The step of producing the capacitor element includes the step of forming the anode body having the anode lead portion, the step of forming the dielectric coating layer, the step of forming the cathode layer, and the cathode lead portion. And a solid electrolytic capacitor manufacturing method comprising a step of performing surface treatment by ultraviolet irradiation or plasma irradiation.   The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the surface treatment step is performed after the step of forming the cathode lead portion.   The method for producing a solid electrolytic capacitor according to claim 1, wherein the surface treatment step is performed after the step of forming the cathode layer.   The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the surface treatment step is performed after the step of forming the dielectric coating layer.   The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the surface treatment step is performed after the step of forming the anode body.

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