JP2005175015A - Method of manufacturing electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrolytic capacitor which enables manufacture of an electrolytic capacitor, as easily and stably as possible. <P>SOLUTION: As a solution to dipping an anode 11 in, to form a dielectric layer 12 and a solid-state electrolyte layer 13 on the anode 11, a formation solution containing a surfactant is used. In a single process using the formation solution, chemical conversion treatment (formation of dielectric layer portions 12C and 12D) and surface treatment (fixing surfactant to the surface of the dielectric layer 12) are conducted in batch on the anode 11. Compared with the case where the chemical conversion treatment and the surface treatment are conducted as individual processes (that is, two processes) other than conducted as a single process, smaller man-hours are required for manufacturing the electrolytic capacitor. Moreover, since the single process, using the formation solution, requires no complicated works, there is no seriously large difference in the performances of the chemical conversion treatments and the surface treatments conducted on the anode 11 among individual operators. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an electrolytic capacitor having a solid electrolyte layer.

  In recent years, electrolytic capacitors are mounted on various electronic devices as one of electronic components suitable for high-frequency applications. With regard to this electrolytic capacitor, for example, in a situation where the digitization, downsizing and speeding up of electronic devices are accelerating, there is a demand for large capacity and low impedance, as well as operational stability and operation. There is also a demand for ensuring reliability and extending the service life.

  An electrolytic capacitor has, for example, an anode made of a valve metal, a dielectric layer made of an oxide film formed by anodizing the surface layer of the anode, an electrolyte layer, and a cathode in this order. Have a structure.

  This electrolytic capacitor is mainly divided into two types according to the type of the electrolyte layer. That is, a liquid electrolytic capacitor having an electrolyte layer (electrolytic solution) made of a liquid material and having conductive characteristics mainly using ionic conductivity, and an electrolyte layer made of a solid material such as a complex salt or a conductive polymer This is a solid electrolytic capacitor having a (solid electrolyte layer) and having conductive characteristics mainly utilizing electronic conductivity. When these two types of electrolytic capacitors are compared in terms of stability of operating characteristics, for example, in liquid electrolytic capacitors, the operating characteristics may deteriorate over time due to leakage or evaporation of the electrolytic solution. As the electrolytic capacitors that can become the mainstream in the future are recently being actively researched and developed for solid electrolytic capacitors instead of liquid electrolytic capacitors, the deterioration of the operating characteristics due to leakage and evaporation of the liquid cannot occur with solid electrolytic capacitors. ing. In the research process for this solid electrolytic capacitor, for example, considering a series of operating characteristics such as leakage current characteristics, impedance characteristics, and heat resistance characteristics, the main part of the solid electrolyte layer is made of manganese dioxide or a complex salt from electron donating or electron It is rapidly shifting to a conjugated conductive polymer containing (doped) an attractive substance (dopant).

  When forming a solid electrolyte layer containing a conductive polymer doped with this dopant, for example, after preparing an anode on which a dielectric layer is formed, a monomer, a dopant and an oxidizing agent are used. A conductive polymer containing a dopant is produced by oxidative polymerization of a monomer using an oxidant on a dielectric layer, and several methods for forming this type of solid electrolyte layer have already been proposed. Techniques are known.

Specifically, for example, a method of generating a conductive polymer using a single solution containing all of a monomer, a dopant, and an oxidizing agent (so-called one-component method; see, for example, Patent Document 1) or , A method of generating a conductive polymer using a plurality of solutions separately containing any combination of a monomer, a dopant, and an oxidizing agent (so-called two-component method; see, for example, Patent Documents 2 and 3). Proposed. In this two-component method, in particular, a conductive polymer is produced by using a solution containing a monomer and a solution containing an oxidizing agent (each solution contains a dopant if necessary) (for example, patents) Reference 2)), a conductive polymer is generated by using a solution containing a monomer and a mobile dopant and a solution containing a fixed dopant (for example, see Patent Document 3).
Japanese Patent No. 3040113 Japanese Patent No. 3273761 Japanese Patent Publication No. 06-068926

  By the way, in a solid electrolytic capacitor, in general, for the purpose of realizing a high capacity, the anode is subjected to surface enlargement (or roughening) treatment, and the anode has a fine surface uneven structure. Yes. Accordingly, the dielectric layer formed on the surface layer of the anode similarly has a fine uneven structure, and a solid electrolyte layer is provided so as to cover the dielectric layer having the uneven structure. Therefore, in view of the structural characteristics between the dielectric layer and the solid electrolyte layer, in order to stably improve the capacity characteristics of the solid electrolytic capacitor, the fixability of the solid electrolyte layer to the dielectric layer, More specifically, it is necessary to improve as much as possible the fixability of the dopant, which has a great influence on the conductive properties of the solid electrolyte layer. In this case, in particular, in consideration of mass production of solid electrolytic capacitors, establishment of a manufacturing technique capable of improving the fixability of dopants while manufacturing the solid electrolytic capacitors as easily and stably as possible. Is desired.

  However, in the conventional method for manufacturing a solid electrolytic capacitor described above, since the fixability of the dopant to the dielectric layer needs to be improved as much as possible, the fixability of the dopant is not sufficient. There has been a problem that it is difficult to stably improve the capacity characteristics. In addition, if the relationship between the manufacturing method of the conventional solid electrolytic capacitor and the fixability of the dopant to the dielectric layer is described in detail, the fixability of the dopant can be improved in the two-component method than the one-component method, The fixability of the dopant is still not sufficient even in the conventional two-component method. Moreover, considering the fixability of the entire dopant in the solid electrolyte layer, in order to improve the fixability of the dopant as much as possible, not only the fixability to the dielectric layer but also the fixability to the conductive polymer, That is, it is important to improve the ease of entry of the dopant into the network structure of the conductive polymer.

  The present invention has been made in view of such problems, and a first object thereof is to produce an electrolytic capacitor capable of stably improving the capacity characteristics by improving the fixability of the dopant as much as possible. It is to provide a method.

  The second object of the present invention is to provide an electrolytic capacitor manufacturing method capable of manufacturing an electrolytic capacitor as easily and stably as possible.

  An electrolytic capacitor manufacturing method according to the present invention is a method for manufacturing an electrolytic capacitor having a laminated structure in which an electrode, a dielectric layer, and a solid electrolyte layer are laminated in this order. The step of forming comprises immersing the electrode in a first solution containing at least one of a surfactant and a dopant, and oxidizing the surface layer of the electrode using the first solution to form the dielectric layer A step of immersing the electrode on which the dielectric layer is formed in a second solution containing a monomer and a dopant, and polymerizing the monomer in the second solution to form a conductive polymer Forming a solid electrolyte layer containing a dopant together with the conductive polymer so as to cover the dielectric layer.

  In the method for producing an electrolytic capacitor according to the present invention, the electrode is immersed in a first solution containing at least one of a surfactant and a dopant, and the dielectric layer is formed by oxidizing the surface layer of the electrode. Both (chemical conversion treatment) and treatment (surface treatment) for fixing at least one of a surfactant and a dopant on the surface of the dielectric layer are collectively applied to the electrodes in a single step. As a result, the number of steps required to manufacture the electrolytic capacitor is reduced as compared with the case where the chemical conversion treatment and the surface treatment are not performed in a single step but are performed in separate steps (that is, two steps). In addition, since the single process using the first solution does not require complicated work, it does not cause a significant individual difference for each worker in the results of chemical conversion treatment or surface treatment.

  Further, in the method for manufacturing an electrolytic capacitor according to the present invention, by performing surface treatment on the electrode using the first solution, for example, among the hydroxyl group present on the surface of the dielectric layer, the surfactant, and the dopant It becomes easy to bond with at least one, and at least one of the surfactant and the dopant easily enters the pores constituted by the dielectric layer. In this case, the dopant itself easily binds to the hydroxyl groups of the dielectric layer and easily enters the pores. Of course, the surfactant easily binds to the hydroxyl groups of the dielectric layer and enters the pores. Even in the case where it becomes easy, the dopant in the second solution becomes easy to bond to the dielectric layer via the surfactant, so that in any case, the fixability of the dopant to the dielectric layer is improved as a result, that is, doping is performed. The rate improves stably. Moreover, in this case, based on the improvement of the fixability of the dopant to the dielectric layer, the dopant easily enters the network structure of the conductive polymer, that is, the fixability of the dopant to the conductive polymer is also improved. In this respect, the doping rate is stably improved.

  In the method for producing an electrolytic capacitor according to the present invention, as long as it is possible to apply both the chemical conversion treatment and the surface treatment to the electrode using the first solution, the surfactant is used as the first solution. A solution containing only a dopant, a solution containing only a dopant, or a solution containing both a surfactant and a dopant may be used. In particular, when a solution containing only a surfactant is used as the first solution, a solution that also serves as a dopant may be used as the surfactant.

  According to the method for producing an electrolytic capacitor according to the present invention, in a single step of immersing the electrode in the first solution containing at least one of the surfactant and the dopant, both the chemical conversion treatment and the surface treatment are performed together. Electrolytic capacitors are possible because the number of manufacturing processes for electrolytic capacitors is reduced based on the manufacturing characteristics applied to the electrodes, and there are no significant individual differences among workers in the results of chemical conversion treatment or surface treatment. It can be manufactured as easily and stably as possible. In addition, by performing surface treatment on the electrode, the doping rate is stably improved based on the improvement of the fixability of the dopant, so that the capacitance characteristics of the electrolytic capacitor can be stably improved.

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

[First Embodiment]
First, with reference to FIG. 1 and FIG. 2, the structure of the electrolytic capacitor manufactured using the manufacturing method of the electrolytic capacitor based on the 1st Embodiment of this invention is demonstrated easily. 1 and 2 show the configuration of the main part (capacitor element 10) of the electrolytic capacitor, FIG. 1 shows the external configuration, and FIG. 2 is an enlarged cross-sectional configuration along the line II-II shown in FIG. As shown.

  In the electrolytic capacitor manufactured in this embodiment, an anode lead and a cathode lead (both not shown) are connected to capacitor element 10 shown in FIGS. 1 and 2, and both of these anode lead and cathode lead are The capacitor element 10 has a structure in which the periphery is covered with a mold resin (not shown) so as to be partially exposed. The capacitor element 10 generates an electrical reaction as a main part of the electrolytic capacitor. For example, as shown in FIGS. 1 and 2, the anode 11 and the periphery (one end) of the anode 11 are partially provided. A dielectric layer 12 provided to cover the dielectric layer 12, a solid electrolyte layer 13 provided to cover the periphery of the dielectric layer 12, and a cathode 14 provided to cover the periphery of the solid electrolyte layer 13. In other words, the anode 11, the dielectric layer 12, the solid electrolyte layer 13 and the cathode 14 are laminated in this order.

  The anode 11 is an electrode having an enlarged (or roughened) surface structure, and is made of, for example, a valve metal such as aluminum (Al), titanium (Ti), tantalum (Ta), or niobium (Nb). It is configured. Specifically, the anode 11 is, for example, a metal foil such as aluminum or titanium, or a sintered body such as tantalum or niobium. Note that the surface uneven structure of the anode 11 whose surface has been enlarged will be described later (see FIG. 3).

The dielectric layer 12 is an oxide film formed by, for example, anodizing the surface layer of the anode 11 made of a valve metal. For example, when the anode 11 is made of aluminum, the dielectric layer 12 is made of aluminum oxide (Al ₂ O ₃ ; hereinafter simply referred to as “alumina”).

  The solid electrolyte layer 13 includes a conductive polymer and a dopant, that is, is formed of a conductive polymer doped with a dopant. The conductive polymer constitutes a main part of the solid electrolyte layer 13, and is composed of, for example, at least one selected from the group including polyaniline, polypyrrole, polythiophene, polyfuran, and derivatives thereof. Examples of the “derivative” include polyethylenedioxythiophene which is a derivative of polythiophene. The dopant is for increasing the conductivity of the conductive polymer. For example, alkylbenzene sulfonic acid and its salt (for example, iron iron paratoluene sulfonate), alkyl naphthalene sulfonic acid and its salt (for example, iron isopropyl naphthalene sulfonate) Etc.), and at least one of the group containing phosphoric acid. The capacitor element 10 provided with the solid electrolyte layer 13 is a so-called solid electrolytic capacitor element.

  The cathode 14 has, for example, a laminated structure in which a carbon (graphite) layer 14A and a silver (Ag) layer 14B are laminated.

  For reference, both the anode lead and the cathode lead are, for example, a metal such as iron (Fe) or copper (Cu), or a plating treatment (for example, tin (Sn) plating or tin lead (SnPb)) on these metals. It is made of a plated metal subjected to plating, and is connected to the anode 11 and the cathode 14 of the capacitor element 10, respectively. The mold resin is made of an insulating resin such as an epoxy resin, for example.

  Next, a detailed configuration of the capacitor element 10 will be described with reference to FIG. FIG. 3 is a partially enlarged cross-sectional view of the capacitor element 10 shown in FIG.

  In the capacitor element 10, for example, as shown in FIG. 3, a dielectric layer 12, a solid electrolyte layer 13, and a cathode 14 (carbon layer 14A, silver layer 14B) are laminated in this order so as to cover the anode 11. In the capacitor element 10, as described above, in order to realize a high capacity by increasing the surface area of the anode 11, the anode 11 is subjected to a surface enlargement process (or a surface roughening process). That is, the anode 11 has a fine surface uneven structure. Accordingly, the dielectric layer 12 formed so as to cover the anode 11 has a fine uneven structure, and a solid electrolyte layer 13 is provided so as to cover the dielectric layer 12 having this uneven structure. Yes. In particular, the dielectric layer 12 forms a plurality of pores 12H as recesses in the concavo-convex structure, and the solid electrolyte layer 13 partially enters the pores 12H of the dielectric layer 12.

  Next, a method for manufacturing an electrolytic capacitor including the capacitor element 10 shown in FIGS. 1 to 3 will be described with reference to FIGS. FIG. 4 is for explaining the flow of the electrolytic capacitor manufacturing process, and FIG. 5 is for explaining the composition of the solution (chemical conversion solution, monomer solution) used in the electrolytic capacitor manufacturing process. is there. FIG. 6 shows a cross-sectional configuration of the anode 11 before the chemical conversion treatment, and FIG. 7 shows a cross-sectional configuration of the anode 11 after the chemical conversion treatment. These FIGS. 6 and 7 correspond to FIG. Yes.

  When manufacturing an electrolytic capacitor, first, the capacitor element 10 which is the main part of the electrolytic capacitor is formed. That is, first, as shown in FIG. 6, for example, as shown in FIG. 6, the anode 11 made of a valve metal foil (for example, aluminum foil or titanium foil) has been subjected to a surface enlargement process (see FIG. 3). First, a layer in which a part of the dielectric layer 12 is partially formed is prepared. In the anode 11 shown in FIG. 6, for example, four surfaces constituting a rectangular cross section, that is, one set of surfaces PA, PB, PC, and PD facing each other are preliminarily formed on one surface PA, PB. Dielectric layer portions 12A and 12B constituting part of the dielectric layer 12 are formed, respectively, and the other set of surfaces PC and PD are both exposed. For example, as shown in FIG. 3, these dielectric layer portions 12A and 12B have a concavo-convex structure corresponding to the surface concavo-convex structure of the anode 11, and a plurality of pores 12H are formed as concave portions in the concavo-convex structure. In addition, when the material for forming the anode 11 is an aluminum surface-enlarging foil, it is made of alumina. The anode 11 is, for example, a wide anode 11 having dielectric layers 12A and 12B formed in advance on the surfaces PA and PB and cut into strips on the surfaces PC and PD. In addition, as a constituent material of the anode 11, for example, a sintered body of a valve metal such as tantalum or niobium can be used instead of the above-described valve metal foil.

  After preparing the anode 11 in which the dielectric layer portions 12A and 12B are formed in advance, for example, as shown in FIG. 5, as a chemical conversion solution (first solution) containing at least one of a surfactant and a dopant. Then, a solution containing only the surfactant is prepared, and the anode 11 is immersed in this chemical conversion solution (step S101).

  In preparing the chemical conversion solution, for example, the following materials are used as a surfactant and a solvent. That is, as the surfactant, for example, (1) anionic surfactant, (2) cationic surfactant, (3) amphoteric surfactant, or (4) nonionic surfactant (ether type, ether) (1) Among the surfactants belonging to the anionic surfactant, the function as a surfactant as well as the function as a dopant is used. Use a compound that doubles as well. Examples of this type of compound include sodium alkylbenzene sulfonate and sodium alkyl naphthalene sulfonate. In addition, as a solvent, water etc. are used, for example.

  Subsequently, using the chemical conversion solution, both the chemical conversion treatment (step S102) and the surface treatment (step S103) are collectively performed on the electrode 11. Specifically, as the chemical conversion treatment, the anode 11 in which the dielectric layer portions 12A and 12B are formed in advance is immersed in the chemical conversion solution, and then a voltage is applied while being immersed in the chemical conversion solution to expose the surface layer of the anode 11 (exposure). By partially anodizing the surfaces PC and PD), dielectric layer portions 12C and 12D made of an oxide film are partially formed so as to cover the exposed surfaces PC and PD of the anode 11. By this chemical conversion treatment, the dielectric layer 12 constituted by a series of dielectric layer portions 12A to 12D is formed. Further, as a surface treatment, a surfactant is fixed on the surface of the dielectric layer 12 by attaching a chemical conversion solution to the surface of the dielectric layer 12 (dielectric layer portions 12A to 12D). By this surface treatment, for example, the surfactant easily binds to a hydroxyl group present on the surface of the dielectric layer 12, and the surfactant easily enters the pores 12 </ b> H of the dielectric layer 12. The voltage applied to the anode 11 when performing the chemical conversion treatment can be freely set within a range of several volts to several hundred volts, for example, depending on the formation thickness of the dielectric layer portions 12C and 12D. In particular, after chemical conversion treatment is performed on the anode 11 using a chemical conversion solution, it is preferable to wash the anode 11 after chemical conversion treatment with water as necessary, for example, in order to wash away the used surfactant.

  Subsequently, as shown in FIG. 5, a monomer solution (second solution) containing an oxidant together with the monomer and the dopant was prepared, and the dielectric layer 12 was formed in this monomer solution. The anode 11 is immersed (step S104).

  In preparing the monomer solution, for example, the following materials are used as a monomer, a dopant, an oxidizing agent, and a solvent. That is, as the monomer, for example, at least one of aniline, pyrrole, thiophene, furan and derivatives thereof is used. Thereby, at least 1 sort (s) of polyaniline, polypyrrole, polythiophene, polyfuran, and these derivatives is produced | generated as a conductive polymer, for example. Further, as a dopant, for example, at least one selected from the group comprising alkylbenzenesulfonic acid and a salt thereof (for example, iron paratoluenesulfonate), alkylnaphthalenesulfonic acid and a salt thereof (for example, iron isopropylnaphthalenesulfonate), and phosphoric acid. 1 type is used, and as an oxidizing agent, for example, halide (for example, iodine or bromine), metal halide (for example, silicon pentafluoride), protonic acid (for example, sulfuric acid), oxygen compound (for example, sulfur trioxide) ), Sulfate (eg, cerium sulfate, etc.), persulfate (eg, sodium persulfate, etc.), peroxide (eg, hydrogen peroxide), or iron salt (eg, iron alkylbenzene sulfonate or iron alkylnaphthalene sulfonate) Is used. In addition, as a solvent, water, butanol, etc. are used, for example.

  Subsequently, the solid electrolyte layer 13 is formed so as to cover the periphery of the dielectric layer 12 (dielectric layer portions 12A to 12D) by polymerizing the monomer in the monomer solution (step S105). Specifically, the anode 11 on which the dielectric layer 12 is formed is immersed in the monomer solution, and then the anode 11 is pulled up from the monomer solution and heated, and the monomer is removed using an oxidizing agent. Conductive polymer is generated by oxidative polymerization. Thereby, the solid electrolyte 13 which has a structure which contains the dopant with the conductive polymer, that is, the dopant is doped in the conductive polymer is formed. At this time, the dopant is firmly fixed on the dielectric layer 12 by utilizing an anchor action based on the surfactant fixed on the surface of the dielectric layer 12 during the chemical conversion treatment. After the solid electrolyte layer 13 is formed, the solid electrolyte layer 13 is washed with water as necessary. For example, the unreacted monomer contained in the conductive polymer or the conductive polymer is not doped. Wash away excess dopant, used oxidant, etc. Note that the combination process of “immersing the anode 11 in the monomer solution (step S104)” and “forming the solid electrolyte layer 13 (step S105)” is not necessarily performed once, for example. Further, it may be repeated a plurality of times depending on the formation thickness of the solid electrolyte layer 13.

  After forming the solid electrolyte layer 13 through the above procedure, the cathode 14 is formed so as to cover the periphery of the solid electrolyte layer 13 (step S106). When the cathode 14 is formed, for example, a carbon paste is applied around the solid electrolyte layer 13 and dried to form the carbon layer 14A, and then a silver paste is further applied onto the carbon layer 14A. The silver layer 14B is formed by drying, and a laminated structure of the carbon layer 14A and the silver layer 14B is formed. Thereby, the capacitor element 10 having a laminated structure in which the anode 11, the dielectric layer 12, the solid electrolyte layer 13, and the cathode 14 are laminated in this order is completed (see FIGS. 1 to 3).

  After the capacitor element 10 is formed, an electrolytic capacitor is assembled using the capacitor element 10. That is, for example, after connecting the anode lead to the anode 11 of the capacitor element 10 and connecting the cathode lead to the cathode 14 (step S107), both the anode lead and the cathode lead are partially exposed. The periphery of the capacitor element 10 is covered with a mold resin (step S108). As a result, the anode lead and the cathode lead are connected to the capacitor element 10, and an electrolytic capacitor having a structure in which the capacitor element 10 is covered with the mold resin so as to partially expose the anode lead and the cathode lead is completed. To do. In addition, when connecting the anode lead and the cathode lead to the capacitor element 10, for example, the capacitor element 10 may be directly connected using a welding process or a caulking process, or a conductive adhesive or the like is used. And may be indirectly connected.

  In the electrolytic capacitor manufacturing method according to the present embodiment, when forming the dielectric layer 12 and the solid electrolyte layer 13 on the anode 11, a chemical conversion solution containing a surfactant is used as a solution for immersing the anode 11. Since the anode 11 is subjected to both chemical conversion treatment and surface treatment in the chemical conversion solution, the dielectric layer portions 12C and 12D are formed by forming the dielectric layer portions 12C and 12D in a single process using the chemical conversion solution. Both the chemical conversion treatment for forming the body layer 12 (dielectric layer portions 12A to 12D) and the surface treatment for fixing the surfactant on the surface of the dielectric layer 12 (dielectric layer portions 12A to 12D) are performed together. Applied to the electrode 11. In this case, the number of steps required to manufacture the electrolytic capacitor is reduced as compared with the case where the chemical conversion treatment and the surface treatment are not performed in a single step but are performed in separate steps (that is, two steps). . In addition, a single process using the chemical conversion solution does not require a complicated operation, and only a simple operation of applying a voltage as necessary while immersing the anode 11 in the chemical conversion solution is required. The results of the chemical conversion treatment and the surface treatment to be made do not cause a serious difference between workers. Therefore, in the present embodiment, the electrolytic capacitor can be manufactured as easily and stably as possible.

  In particular, in the present embodiment, the surface treatment is performed on the anode 11 using the chemical conversion solution, so that the surfactant is easily bonded to the hydroxyl groups present on the surface of the dielectric layer 12 as described above. As a result of being easy to enter the hole 12H and improving the fixability of the surfactant to the dielectric layer 12, the fixability of the dopant in the monomer solution to the dielectric layer 12 using the anchor action based on the surfactant. Therefore, the doping rate is stably improved. In addition, in this case, based on the improvement of the fixability of the dopant to the dielectric layer 12, the dopant easily enters the network structure of the conductive polymer, that is, the fixability of the dopant to the conductive polymer is also improved. Therefore, also from this viewpoint, the doping rate is stably improved. Therefore, in the present embodiment, the capacitance characteristics of the electrolytic capacitor can be stably improved.

  Further, in the present embodiment, by using a surfactant that also functions as a dopant as the surfactant contained in the chemical conversion solution, a monomer is present when the anode 11 is immersed in the chemical conversion solution. In the absence of the dopant, the dopant alone contacts the dielectric layer 12. In this case, as compared with the case where the dopant is in contact with the dielectric layer 12 in the state where the monomer is present in the monomer solution, the dielectric layer 12 is as much as the monomer is not present. The contact area between the dopant and the dopant is increased, and the wettability of the dielectric layer 12 with respect to the dopant is improved, so that the dopant is more likely to be bonded than the hydroxyl group present on the surface of the dielectric layer 12 and more easily enters the pores 12H. Become. Therefore, in this embodiment, both the fixability of the dopant to the dielectric layer 12 and the fixability of the dopant to the conductive polymer are further improved, so that the capacitance characteristics of the electrolytic capacitor can be improved more stably. .

  In the present embodiment, as the surfactant contained in the chemical conversion solution, a surfactant that also functions as a dopant is used. However, the surfactant is not necessarily limited to this, and for example, also functions as a dopant. No surfactant may be used. As this type of surfactant, for example, a series of surfactants listed in the above embodiment, namely (1) anionic surfactant, (2) cationic surfactant, and (3) amphoteric surfactant. Or (4) A series of materials obtained by removing a metal salt that can function as a dopant from nonionic surfactants. Also in this case, by fixing the surfactant on the surface of the dielectric layer 12 using the chemical conversion solution, the anchoring action based on the surfactant is used to fix the dopant in the monomer solution. Since it can be improved, it is possible to obtain substantially the same effect as the above embodiment.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  FIG. 8 is for explaining the composition of the solution (chemical conversion solution, monomer solution) used in the manufacturing process of the electrolytic capacitor according to the present embodiment, and corresponds to FIG. The electrolytic capacitor manufacturing method according to the present embodiment uses the same manufacturing procedure as that of the first embodiment except that the composition of the chemical conversion solution used for forming the dielectric layer 12 is different. It is.

  In this embodiment, as the chemical conversion solution, for example, as shown in FIG. 8, unlike the first embodiment (see FIG. 5) using a solution containing a surfactant that can function as a dopant, Instead of the surfactant, a solution containing a dopant (a dopant that cannot function as a surfactant) is used. As this dopant, it is possible to use, for example, iron paratoluenesulfonate. In addition, as a monomer solution, the solution containing an oxidizing agent with a monomer and a dopant is used similarly to the said 1st Embodiment, for example.

  In the present embodiment, the solution (chemical conversion solution, monomer solution) shown in FIG. 8 is used, and the dielectric layer 12 is subjected to the same steps as the manufacturing steps shown in FIG. 4 in the first embodiment. By forming the solid electrolyte layer 13, it is possible to manufacture the electrolytic capacitor shown in FIGS. 1 to 3. In the surface treatment using this chemical conversion solution, the dopant is fixed on the surface of the dielectric layer 12 (dielectric layers 12A to 12D) formed through the chemical conversion treatment.

  In the manufacturing method of the electrolytic capacitor according to the present embodiment, since the chemical conversion solution containing the dopant is used to perform the chemical conversion treatment on the anode 11, even in this case, a single process using the chemical conversion solution is used. In FIG. 5, both the chemical conversion treatment and the surface treatment are performed on the anode 11 at once. Therefore, the number of steps required to manufacture an electrolytic capacitor is reduced by the same operation as that of the first embodiment, and the result of chemical conversion treatment and surface treatment applied to the anode 11 in the single step is achieved. Since an individual difference for each worker does not occur to a serious degree, the electrolytic capacitor can be manufactured as easily and stably as possible. In this case, unlike the first embodiment in which a solution containing a surfactant is used as the chemical conversion solution, it is not necessary to wash away the used surfactant after the chemical conversion treatment is performed on the anode 11. Therefore, the manufacturing process of the electrolytic capacitor can be further simplified by the amount that the water washing process becomes unnecessary.

  In particular, in the present embodiment, the use of a chemical conversion solution containing a dopant improves the fixability of the dopant to the dielectric layer 12 as in the first embodiment. As a result, the dopant for the conductive polymer is increased. The fixing rate is also improved, so that the doping rate is stably improved. Therefore, it is possible to stably improve the capacity characteristics of the electrolytic capacitor.

  In addition, the manufacturing procedures, operations, and effects other than those described above relating to the method for manufacturing the electrolytic capacitor according to the present embodiment are the same as those in the first embodiment.

  Next, specific examples of the present invention will be described.

  An electrolytic capacitor was manufactured using the method for manufacturing an electrolytic capacitor described in each of the above embodiments. That is, first, after preparing a chemical conversion solution together with an aluminum foil (15 mm × 30 mm; see FIG. 6) that has been pre-treated as the anode 11 (surface-expanded and dielectric layer portions 12A and 12B have been formed) Aluminum foil was immersed in the chemical conversion solution. Subsequently, a voltage (= 23 V) was applied to the aluminum foil in the chemical conversion solution to advance the anodic oxidation reaction, thereby forming dielectric layer portions 12C and 12D made of an aluminum oxide film (see FIG. 7). As a result, the dielectric layer 12 (dielectric layer portions 12A to 12D) was formed so as to cover the periphery of the anode 11. Subsequently, a monomer solution containing an oxidizing agent together with the monomer and the dopant is prepared, and the anode 11 on which the dielectric layer 12 is formed is immersed in the monomer solution for 30 seconds. After the monomer solution was attached to the layer 12, the anode 11 was pulled up at 0.5 mm / second and dried at room temperature. Subsequently, the anode 11 immersed in the monomer solution is put into a dryer (temperature = 95 ° C.) and heated, and the monomer is oxidized using the oxidizing agent contained in the monomer solution. A conductive polymer was produced by polymerization. As a result of this oxidative polymerization reaction, a solid electrolyte layer 13 made of a conductive polymer doped with a dopant was formed so as to cover the dielectric layer 12. When the solid electrolyte layer 13 is formed, the above-described procedure for forming the solid electrolyte layer 13 is repeated three times. In particular, the solid electrolyte layer 13 is washed with distilled water or ethanol every time the oxidative polymerization reaction is completed. Unreacted monomers, excess dopant, and oxidizing agent were removed as needed. Subsequently, a carbon paste 14A is formed by applying a carbon paste around the solid electrolyte layer 13 to a thickness of 5 μm to 10 μm and drying, and then a silver paste is formed on the carbon layer 14A by 20 μm to 50 μm. The silver layer 14B was formed by applying and drying so as to have a thickness of 5 mm, and the cathode 14 was formed so as to have a laminated structure of the carbon layer 14A and the silver layer 14B. Thereby, capacitor element 10 having a laminated structure in which anode 11, dielectric layer 12, solid electrolyte layer 13 and cathode 14 were laminated in this order was formed (see FIGS. 1 to 3). Finally, after connecting the anode lead and cathode lead made of copper to the capacitor element 10, the periphery of the capacitor element 10 is covered with epoxy resin as a mold resin so that the anode lead and cathode lead are partially exposed. The capacitor is complete.

  With respect to this electrolytic capacitor, the operating characteristics were examined after setting the composition of the chemical conversion solution and the monomer solution as follows. When examining the operating characteristics of the electrolytic capacitor, the capacitor element 10 is used as the simplified electrolytic capacitor shown in FIG. 9 in place of the finished electrolytic capacitor in order to investigate the operating characteristics in a simple and highly accurate manner. Then, an operating characteristic test was conducted. In the capacitor element 10 shown in FIG. 9, test leads 15 and 16 for testing are connected to the anode 11 and the cathode 14, respectively, instead of the anode lead and the cathode lead, and the anode 11 and the cathode 14 are insulated from each other. Therefore, it has the same structure as the capacitor element 10 shown in FIGS. 1 to 3 except that the anode 11 is provided with an insulating layer 17 (for example, silicon resin).

(Example 1)
The electrolytic capacitor manufacturing method described in the first embodiment was used. That is, as the chemical conversion solution, a solution containing sodium alkylnaphthalene sulfonate as a surfactant also serving as a dopant was used, and specifically, a 1.6% aqueous solution of sodium alkyl naphthalene sulfonate was used. In addition, as a monomer solution, a solution containing 3,4-ethylenedioxythiophene as a monomer and iron paratoluenesulfonate as a dopant and oxidant is used. Baytron M (trade name) manufactured by company was used, and 40% butanol solution of iron paratoluenesulfonate (Baytron C (trade name) manufactured by Bayer Co., Ltd.) was used as a dopant and oxidizing agent. In preparing this monomer solution, the monomer (3,4-ethylenedioxythiophene) and the dopant / oxidizer (40% butanol solution of iron paratoluenesulfonate) were sufficiently cooled with ice water, Next, 0.867 g and 13.0 g of the monomer and the dopant / oxidant were weighed and mixed, and the mixture was stirred with a magnetic stirrer while being cooled with ice water.

(Example 2)
The electrolytic capacitor manufacturing method described in the second embodiment was used. That is, as the chemical solution, a solution containing iron paratoluenesulfonate as a dopant was used, and specifically, a 1.6% butanol solution of iron paratoluenesulfonate (Baytron C (trade name) manufactured by Bayer Co., Ltd.) was used. . Moreover, the solution similar to Example 1 was used as a monomer solution.

(Comparative example)
When investigating the operating characteristics of the electrolytic capacitors of the present invention (Examples 1 and 2), in order to compare and evaluate the performance, in place of the chemical conversion solution of the present invention, either a surfactant or a dopant is used. Examine the operating characteristics of the electrolytic capacitor of the comparative example manufactured through the same procedure as in Examples 1 and 2 except that a chemical conversion treatment was performed using a solution containing a non-applicable electrolyte (7% aqueous solution of ammonium adipate). It was.

  As the operating characteristic of the electrolytic capacitor, first, the impedance characteristic was examined, and the result shown in FIG. 10 was obtained. FIG. 10 represents the impedance change of the electrolytic capacitor. The “horizontal axis” represents elapsed time (hours), and the “vertical axis” represents the impedance change rate (%). When examining the impedance change of the electrolytic capacitor, the operating frequency is set to 100 kHz, and the impedance change when the electrolytic capacitor is put in a high temperature environment (temperature = 125 ° C.) in order to accelerate the impedance change is examined. Tracked. Note that “10A, 10B, and 10C” shown in FIG. 10 represent the results regarding Example 1, Example 2, and Comparative Example, respectively.

  As can be seen from the results shown in FIG. 10, the impedance change rate gradually increased in the positive direction as the elapsed time passed in all of Examples 1 and 2 and the comparative example. However, comparing the behavior of the impedance change rate between Examples 1 and 2 and the comparative example, the impedance change rate in Examples 1 and 2 was smaller than that in the comparative example, that is, the impedance was less likely to change. In particular, when the impedance change rate was compared between Examples 1 and 2, the impedance change rate in Example 1 was significantly smaller than that in Example 2. More specifically, the rate of change in impedance after the test (after about 900 hours) was about 57%, about 167%, and about 214% in Examples 1 and 2 and Comparative Example, respectively.

  Subsequently, when the capacitance characteristics of the electrolytic capacitor were examined, the result shown in FIG. 11 was obtained. FIG. 11 shows the capacitance change of the electrolytic capacitor, where the “horizontal axis” indicates elapsed time (hours) and the “vertical axis” indicates the rate of change in capacitance (%). When examining the capacitance change of the electrolytic capacitor, two types of operating frequencies (120 Hz, 10 kHz) are set for any of Examples 1 and 2 and the comparative example, and the electrolytic capacitor is set in the same manner as when the impedance change is examined. The change in capacity at the time of charging in a high temperature environment (temperature = 125 ° C.) was traced. In addition, “11A, 11B, 11C, 11D, 11E, and 11F” shown in FIG. 11 are respectively Example 1 (120 Hz), Example 2 (120 Hz), Comparative Example (120 Hz), Example 1 (10 kHz), and Example. The result regarding Example 2 (10 kHz) and a comparative example (10 kHz) is represented.

  As can be seen from the results shown in FIG. 11, regardless of the difference in operating frequency (120 Hz, 10 kHz), the capacity change rate gradually decreased as the elapsed time passed for all of Examples 1 and 2 and the comparative example. Became larger in the direction of. However, comparing the capacity change rate between Examples 1 and 2 and the comparative example, the capacity change rate in Examples 1 and 2 was smaller than that in the comparative example, that is, the capacity was less likely to change. In particular, when the capacity change rate was compared between Examples 1 and 2, the capacity change rate was significantly smaller in Example 1 than in Example 2. More specifically, the rate of change in capacity after the test (after about 880 hours) is as follows: Example 1 (120 Hz), Example 2 (120 Hz), Comparative Example (120 Hz), Example 1 (10 kHz), Example 2 (10 kHz) and Comparative Example (10 kHz) were about −5.7%, about −6.7%, about −7.6, about −9.5%, about −18%, and about −23%, respectively. It was.

  When the results shown in FIG. 10 and FIG. 11 are summarized, the electrolytic capacitors of Examples 1 and 2 are less likely to change impedance than the electrolytic capacitor of Comparative Example, and accordingly, the capacitance is less likely to change. It was confirmed that the capacity characteristics can be improved stably.

  The present invention has been described above with reference to some embodiments and examples. However, the present invention is not limited to these embodiments and examples, and various modifications can be made.

  Specifically, in each of the above-described embodiments and examples, in the electrolytic capacitor manufacturing process, as shown in FIG. 6, the dielectric layer portion 12A is previously formed on the surfaces PA and PB of the four surfaces PA to PD. , 12B are formed, and the anode 11 having a structure in which the remaining surfaces PC, PD are exposed is used. However, the present invention is not limited to this, and in the manufacturing process of the electrolytic capacitor The structure of the anode 11 to be used can be freely set. For example, instead of the anode 11 having the structure shown in FIG. 6, as shown in FIG. 12, no dielectric layer portion is formed in advance on any of the four surfaces PA to PD, that is, all surfaces The anode 11 having a structure in which PA to PD are exposed may be used. In this case, the surface layers (surfaces PA to PD) of the anode 11 are entirely anodized using the chemical conversion solution, for example, as shown in FIG. 13, the four surfaces PA to PD of the anode 11. The dielectric layer 12 (dielectric layer portions 12A to 12D) can be collectively formed so as to cover the surface. Also in this case, the same effects as those of the above embodiments and examples can be obtained.

  Further, in each of the above embodiments and examples, in the electrolytic capacitor manufacturing process, the valve action metal foil that has been subjected to the surface enlargement process in advance is used as the anode 11, but is not necessarily limited thereto. For example, using untreated valve action metal foil that has not been subjected to surface enlargement treatment in advance, and using chemical or electrochemical etching in the manufacturing process of electrolytic capacitors, surface enlargement to valve action metal foil Processing may be performed separately. Also in this case, the same effects as those of the above embodiments and examples can be obtained.

  In each of the above embodiments and examples, as the chemical conversion solution, a solution containing only a surfactant that can function as a dopant in the first embodiment is used, and only the dopant is used in the second embodiment. However, the present invention is not necessarily limited to this. As long as it is possible to perform both the chemical conversion treatment and the surface treatment on the anode 11 using the chemical conversion solution, the chemical conversion solution The composition can be changed freely. Specifically, for example, a solution containing both a surfactant that can function as a dopant and a dopant may be used as the chemical conversion solution. Also in this case, the same effects as those of the above embodiments and examples can be obtained.

  The method for manufacturing an electrolytic capacitor according to the present invention can be applied to a manufacturing process of an electrolytic capacitor in which a main part that generates an electrical reaction is composed of a solid material (conductive polymer).

It is an external view showing the external appearance structure of the principal part (capacitor element) of the electrolytic capacitor manufactured using the manufacturing method of the electrolytic capacitor which concerns on the 1st Embodiment of this invention. It is sectional drawing which expands and represents the cross-sectional structure along the II-II line of the capacitor | condenser element shown in FIG. FIG. 3 is a cross-sectional view illustrating a partially enlarged cross-sectional configuration of the capacitor element illustrated in FIG. 2. It is a flowchart for demonstrating the flow of the manufacturing process in the manufacturing method of an electrolytic capacitor. It is a figure for demonstrating the composition of the solution (chemical conversion solution, monomer solution) used in the manufacturing method of an electrolytic capacitor. It is sectional drawing showing the cross-sectional structure of the anode before chemical conversion treatment used in the manufacturing method of the electrolytic capacitor which concerns on the 1st Embodiment of this invention. It is sectional drawing showing the cross-sectional structure of the anode after chemical conversion treatment. It is a figure for demonstrating the composition of the solution (chemical conversion solution, monomer solution) used in the manufacturing method of the electrolytic capacitor which concerns on the 2nd Embodiment of this invention. It is an external view showing the external appearance structure of the electrolytic capacitor (capacitor element) for a test. It is a figure showing the impedance change of an electrolytic capacitor. It is a figure showing the capacity | capacitance change of an electrolytic capacitor. It is sectional drawing for demonstrating the modification regarding the structure of the anode before chemical conversion treatment used in the manufacturing method of the electrolytic capacitor of this invention. It is sectional drawing showing the cross-sectional structure after the chemical conversion treatment of the anode shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Capacitor element, 11 ... Anode, 12 ... Dielectric layer, 12A-12D ... Dielectric layer part, 13 ... Solid electrolyte layer, 14 ... Cathode, 14A ... Carbon layer, 14B ... Silver layer, 15, 16 ... Test lead 17 ... Insulating layer, PA-PD ... surface.

Claims (11)

A method for producing an electrolytic capacitor having a laminated structure in which an electrode, a dielectric layer, and a solid electrolyte layer are laminated in this order,
Forming the dielectric layer and the solid electrolyte layer;
Immersing the electrode in a first solution containing at least one of a surfactant and a dopant;
Forming a dielectric layer by oxidizing the surface layer of the electrode using the first solution;
Immersing the electrode on which the dielectric layer is formed in a second solution containing a monomer and a dopant;
Forming a solid electrolyte layer containing the dopant together with the conductive polymer so as to cover the dielectric layer by polymerizing the monomer in the second solution to form a conductive polymer; A method for manufacturing an electrolytic capacitor, comprising: The at least one of the surfactant and the dopant is fixed on the surface of the dielectric layer by forming the dielectric layer using the first solution. Manufacturing method of the electrolytic capacitor. The method for producing an electrolytic capacitor according to claim 1 or 2, wherein a solution containing only the surfactant is used as the first solution. The method for producing an electrolytic capacitor according to claim 3, wherein the surfactant also serves as the dopant. The method for producing an electrolytic capacitor according to claim 1, wherein a solution containing only the dopant is used as the first solution. The method for producing an electrolytic capacitor according to claim 1 or 2, wherein a solution containing both the surfactant and the dopant is used as the first solution. Using the second solution containing an oxidant together with the monomer and the dopant,
The method for producing an electrolytic capacitor according to any one of claims 1 to 6, wherein the conductive polymer is produced by oxidative polymerization of the monomer. As the electrode, using a part of the dielectric layer that is not partially formed in advance,
The method for manufacturing an electrolytic capacitor according to any one of claims 1 to 7, wherein the dielectric layer is formed by totally oxidizing a surface layer of the electrode. As the electrode, a part of the dielectric layer that is partially formed in advance is used,
The method for manufacturing an electrolytic capacitor according to any one of claims 1 to 7, wherein the dielectric layer is formed by partially oxidizing a surface layer of the electrode layer. The said conductive polymer produces | generates at least 1 sort (s) of the group containing polyaniline, polypyrrole, polythiophene, polyfuran, and these derivatives. The one of Claim 1 thru | or 9 characterized by the above-mentioned. Manufacturing method of electrolytic capacitor. 11. The method according to claim 1, wherein at least one member selected from the group comprising alkylbenzene sulfonic acid and a salt thereof, alkyl naphthalene sulfonic acid and a salt thereof, and phosphoric acid is used as the dopant. The manufacturing method of the electrolytic capacitor of description.

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