Solid electrolytic capacitor element and solid electrolytic capacitor

Abstract

A solid electrolytic capacitor element 1 includes: a valve action metal base 10 in which a porous part 12 having pores 11 is formed; a dielectric layer 20 formed on a surface of the valve action metal base 10; and a solid electrolyte layer 40 formed on the dielectric layer 20. The solid electrolyte layer 40 includes: a first layer 41 filled in the pores 11 of the porous part 12 and composed of an aggregate of conductive polymer particles 41a; a second layer 42 formed on the first layer 41; and a third layer 43 formed on the second layer 42 and composed of a film-shaped conductive polymer 43a. The second layer 42 includes both the aggregate of conductive polymer particles 41a constituting the first layer 41 and the film-shaped conductive polymer 43a constituting the third layer 43.

Description

Solid electrolytic capacitor element and solid electrolytic capacitor

[0001] The present invention relates to a solid electrolytic capacitor element and a solid electrolytic capacitor.

[0002] Patent Document 1 describes a method for manufacturing a solid electrolytic capacitor element, which includes a step of forming a solid electrolyte layer by immersing an aluminum foil in a solution of a monomer that will become the solid electrolyte and chemically polymerizing the monomer to form a solid electrolyte layer made of a conductive polymer. In Example 1, it is described that the solid electrolyte layer was formed by repeating the immersion and chemical polymerization process 25 times.

[0003] Patent No. 4623404

[0004] The surface of the valve metal substrate that constitutes the solid electrolytic capacitor has a porous structure with fine pores, and a dielectric layer is formed on the surface of the valve metal substrate. To create a high-capacity capacitor, it is necessary to cover as much of the surface of the dielectric layer as possible with a solid electrolyte layer (conductive polymer).

[0005] When the solid electrolyte layer is formed by the chemical polymerization method described in Patent Document 1, a monomer enters the pores, and polymerization occurs within the pores to form a conductive polymer, which has the advantage of covering the inside of the pores with a solid electrolyte layer, resulting in a high-capacity capacitor.

[0006] On the other hand, conductive polymers produced by chemical polymerization are particulate, and the solid electrolyte layer is an agglomeration of conductive polymer particles. The agglomeration of particles does not have a dense structure, but has many voids.

[0007] If the solid electrolyte layer has voids and the conductive paste that forms the cathode layer penetrates the voids in the solid electrolyte layer and comes into contact with the dielectric layer, a short circuit will occur, so it is necessary to prevent the solid electrolyte layer from having voids that the cathode layer can penetrate. For this reason, in the example shown in Patent Document 1, a thick solid electrolyte layer is formed by repeating immersion and chemical polymerization.

[0008] Furthermore, if voids exist in the solid electrolyte layer, there may arise a problem that the solid electrolyte layer may break starting from these voids.

[0009] The present invention has been made to solve the above problems, and aims to provide a solid electrolytic capacitor element that can be used as a high-capacity capacitor and that is prevented from short-circuiting defects and breakage of the solid electrolyte layer due to voids present in the solid electrolyte layer.

[0010] The solid electrolytic capacitor element of the present invention is a solid electrolytic capacitor element comprising a valve metal substrate having a porous portion with pores formed therein, a dielectric layer formed on the surface of the valve metal substrate, and a solid electrolyte layer formed on the dielectric layer, wherein the solid electrolyte layer has a first layer filled in the pores of the porous portion and consisting of an agglomerate of conductive polymer particles, a second layer formed on the first layer, and a third layer formed on the second layer and consisting of a film of conductive polymer, and the second layer contains both the agglomerate of conductive polymer particles that constitutes the first layer and the film of conductive polymer that constitutes the third layer.

[0011] The solid electrolytic capacitor of the present invention includes the solid electrolytic capacitor element of the present invention.

[0012] According to the present invention, it is possible to provide a solid electrolytic capacitor element that can be made into a high-capacity capacitor and that is prevented from short-circuiting defects and breakage of the solid electrolyte layer due to voids present in the solid electrolyte layer.

[0013] FIG. 1 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor element according to the present invention. FIG. 2 is a cross-sectional view schematically showing the structure of a solid electrolyte layer. FIG. 3 is a cross-sectional view schematically showing a solid electrolyte layer formed only from an aggregate of a conductive polymer. FIG. 4 is a cross-sectional view schematically showing a solid electrolyte layer formed only from a film-like conductive polymer. FIG. 5 is a perspective view schematically showing an example of a solid electrolytic capacitor according to the present invention. FIG. 6 is a cross-sectional view taken along line Z-Z of the solid electrolytic capacitor shown in FIG. 5. FIG. 7 is a cross-sectional view of an example of a solid electrolytic capacitor according to the present invention in which a lead frame is used as an external electrode.

[0014] The solid electrolytic capacitor element and solid electrolytic capacitor of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual desirable configurations described below also constitutes the present invention.

[0015] The solid electrolytic capacitor element of the present invention is a solid electrolytic capacitor element comprising a valve metal substrate having a porous portion with pores formed therein, a dielectric layer formed on the surface of the valve metal substrate, and a solid electrolyte layer formed on the dielectric layer, wherein the solid electrolyte layer has a first layer filled in the pores of the porous portion and consisting of an agglomerate of conductive polymer particles, a second layer formed on the first layer, and a third layer formed on the second layer and consisting of a film of conductive polymer, and the second layer contains both the agglomerate of conductive polymer particles that constitutes the first layer and the film of conductive polymer that constitutes the third layer.

[0016] Fig. 1 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor element according to the present invention. The solid electrolytic capacitor element 1 shown in Fig. 1 comprises a valve metal substrate 10 having a porous portion with pores formed therein, a dielectric layer 20 formed on the surface of the valve metal substrate 10, and a solid electrolyte layer 40 formed on the dielectric layer 20. Note that the dielectric layer 20 is shown schematically in Fig. 1, and its detailed structure is shown in Fig. 2.

[0017] The solid electrolytic capacitor element 1 further includes a carbon layer 50 provided on the solid electrolyte layer 40, and a metal layer 60 provided on the carbon layer 50. An insulating mask layer 30 of a predetermined width is provided around the dielectric layer 20. The insulating mask layer 30 is provided on both main surfaces and both side surfaces of the valve metal base 10 so as to extend along the short sides of the valve metal base 10. The insulating mask layer 30 separates the valve metal base 10 into an anode portion 31 and a cathode portion 32. In the solid electrolytic capacitor element of the present invention, the carbon layer, the metal layer, and the insulating mask layer are optional components.

[0018] 2 is a cross-sectional view schematically illustrating the structure of the solid electrolyte layer, showing the periphery of a porous portion having pores, and also showing the area A surrounded by the dotted line in FIG.

[0019] The valve metal substrate 10 is made of a valve metal, such as an elemental metal such as aluminum, tantalum, niobium, titanium, or zirconium, or an alloy containing at least one of these metals. A porous portion 12 having pores 11 is formed in the valve metal substrate 10. The porous portion 12 is provided on the main surface of the valve metal substrate, and may be formed by etching the surface of a metal foil, forming a porous fine powder sintered body on the surface of a metal foil, or the like, as appropriate.

[0020] A dielectric layer 20 is formed on the surface of the valve metal substrate 10. The dielectric layer 20 is preferably made of aluminum oxide. The aluminum oxide is formed by anodizing the surface of the valve metal substrate 10. The dielectric layer 20 is also formed on the inner surfaces of the pores 11, and also on the surface of the valve metal substrate 10 other than the pores 11 (the upper surface of the porous portion 12).

[0021] The solid electrolyte layer is formed on the dielectric layer. Here, "on the dielectric layer" means that the solid electrolyte layer is in contact with the dielectric layer, and does not indicate a top-bottom direction.

[0022] The solid electrolyte layer 40 includes a first layer 41 that is filled in the pores 11 of the porous portion 12 and is made of an aggregate of conductive polymer particles, a second layer 42 that is formed on the first layer 41, and a third layer 43 that is made of a film of conductive polymer and is formed on the second layer 42. These components will be described in detail below.

[0023] The first layer 41 is made of an aggregate of conductive polymer particles 41a. The portion where the aggregate of conductive polymer particles fills the pores of the porous portion is defined as the first layer. The conductive polymer particles are formed when a monomer that becomes the conductive polymer enters the pores, polymerizes within the pores, and grows into particles. By entering the pores as a pre-polymerized monomer, the narrow regions deep inside the pores can be filled. By filling the solid electrolyte layer deep into the pores, the contact area between the dielectric layer and the solid electrolyte layer increases, resulting in a high-capacity capacitor.

[0024] The shape of the conductive polymer particles is not particularly limited and may be scale-like, spindle-like, etc. Voids exist between the particles that make up the conductive polymer aggregates.

[0025] Fig. 3 is a diagram illustrating the voids between particles that constitute an aggregate of conductive polymer particles. Fig. 3 is a cross-sectional view that schematically shows a solid electrolyte layer formed only from an aggregate of conductive polymer particles. The configuration of this solid electrolyte layer is different from the configuration of the solid electrolyte layer of the solid electrolytic capacitor element of the present invention.

[0026] 3 shows a solid electrolyte layer 140 made only of conductive polymer particles 41a. Voids 41b exist between the conductive polymer particles 41a, and the presence of the voids 41b poses a problem of peeling starting from the voids 41b. Furthermore, the thickness of the solid electrolyte layer needs to be large enough to prevent the conductive paste for forming the carbon layer from penetrating the solid electrolyte layer, and a thicker solid electrolyte layer poses a problem of increased ESR.

[0027] The solid electrolytic capacitor element of the present invention has a configuration that can solve the problems that arise when a solid electrolyte layer is formed solely from an aggregate of conductive polymer particles.

[0028] Prior to describing the second layer, the third layer will be described. The third layer 43 is a layer made of a film-like conductive polymer 43a and is located at the top of the solid electrolyte layer 40 (the side farther from the surface of the valve metal substrate 10). The third layer 43 is the layer where the solid electrolyte layer 40 comes into contact with the carbon layer 50 (see FIG. 1).

[0029] The third layer is a layer in which a film-like conductive polymer is present but no conductive polymer particles are present. The film-like conductive polymer is a layer in which voids are substantially absent. The film-like conductive polymer is formed by applying a dispersion liquid containing the conductive polymer and drying it.

[0030] If a layer substantially free of voids is present at the portion where the solid electrolyte layer contacts the carbon layer, the conductive paste for forming the carbon layer is prevented from penetrating the solid electrolyte layer, and the occurrence of short-circuit defects due to the conductive paste contacting the dielectric layer is prevented. Note that, in this specification, "substantially free of voids" means that there are no voids large enough to allow the conductive paste in contact with the solid electrolyte layer to penetrate, and does not require a completely dense body.

[0031] Fig. 4 is a diagram illustrating a film-like conductive polymer. Fig. 4 is a cross-sectional view schematically showing a solid electrolyte layer formed only from a film-like conductive polymer. The configuration of this solid electrolyte layer is different from the configuration of the solid electrolyte layer of the solid electrolytic capacitor element of the present invention.

[0032] Figure 4 shows a solid electrolyte layer 240 consisting solely of a film-like conductive polymer 43a. Because the film-like conductive polymer 43a is substantially free of voids, it functions as a layer that prevents short-circuit defects. However, because the film-like conductive polymer is a material that is applied as a solid dispersion to form the solid electrolyte layer, it clogs the entrances of the pores 11 in the porous portion 12, as shown in Figure 4, making it difficult to fill the pores 11 to their depths. Therefore, if only a film-like conductive polymer is used, the contact area between the dielectric layer and the solid electrolyte layer cannot be increased, and the capacitance of the capacitor cannot be sufficiently increased. Furthermore, because the solid electrolyte layer cannot penetrate the pores of the porous portion, the anchoring effect between the porous portion and the solid electrolyte layer is difficult to achieve, making the solid electrolyte layer more susceptible to peeling.

[0033] The solid electrolytic capacitor element of the present invention has a configuration that can solve the problems that arise when the solid electrolyte layer is formed only from a film-like conductive polymer.

[0034] 2 again, the configuration of the solid electrolytic capacitor element of the present invention will be described. The second layer 42 is a layer that exists between the first layer 41 and the third layer 43. In terms of positional relationship, the second layer 42 is formed on the first layer 41, and the third layer 43 is formed on the second layer 42. The second layer 42 includes both the aggregates of conductive polymer particles 41a that make up the first layer 41 and the film-like conductive polymer 43a that makes up the third layer 43.

[0035] The second layer is a layer in which both conductive polymer particle aggregates and a film-like conductive polymer exist. When determining the boundaries between the first layer and the second layer and the second layer and the third layer, the layer in which both conductive polymer particle aggregates and a film-like conductive polymer exist is defined as the second layer, the layer in which conductive polymer particle aggregates exist but a film-like conductive polymer does not exist is defined as the first layer, and the layer in which a film-like conductive polymer exists but a film-like conductive polymer does not exist is defined as the third layer. By defining these layers in this way, the boundaries between the first layer, the second layer, and the third layer can be determined.

[0036] The first layer is a layer in which no film-like conductive polymer exists, but it is preferable that the first layer does not exist above the upper surface of the porous portion (a portion distant from the surface of the porous portion). This is because the effect of only having an aggregate of conductive polymer particles present above the upper surface of the porous portion is not exerted, and problems such as an increase in the resistance value due to an increase in the thickness of the solid electrolyte layer and an increased possibility of peeling off of the solid electrolyte layer are likely to occur.

[0037] A portion of the film-like conductive polymer may penetrate into the pores of the porous portion, and the portion where the film-like conductive polymer has penetrated into the pores of the porous portion constitutes the second layer. That is, a portion of the second layer may penetrate into the pores of the porous portion. In this case, it can be said that a structure is formed in which the agglomerates of conductive polymer particles filling the pores of the porous portion are connected to the film-like conductive polymer on the porous portion. With such a structure, the agglomerates of conductive polymer particles penetrate into the pores, creating an anchor effect, making peeling between the porous portion and the solid electrolyte layer less likely to occur. Furthermore, because the agglomerates of conductive polymer particles are connected by the film-like conductive polymer and the film-like conductive polymer has penetrated into the voids between the conductive polymer particles, peeling of the solid electrolyte layer is less likely to occur compared to when the solid electrolyte layer is formed only with the film-like conductive polymer.

[0038] In the second layer, the film-like conductive polymer may be in direct contact with the dielectric layer in some portions, or may be in direct contact with the dielectric layer in some portions on the surface of the valve metal substrate that is not a pore (the upper surface of the porous portion).

[0039] It is preferable that the second layer contains more conductive polymer particle aggregates than film-like conductive polymers, in which case the film-like conductive polymer can penetrate and fill the voids in the conductive polymer particle aggregates, thereby preventing the occurrence of a peeling mode in which the solid electrolyte layer breaks from the voids in the aggregates.

[0040] Whether the second layer contains more conductive polymer particles or film-like conductive polymer can be determined by observing cross-sectional photographs taken with an electron microscope (SEM).Conductive polymer particles and film-like conductive polymers have different shapes, so they can be distinguished in cross-sectional photographs taken with an electron microscope.

[0041] The thicknesses of the first, second, and third layers can be determined from cross-sectional electron microscope photographs. The boundaries between the first and second layers and the boundaries between the second and third layers can be determined, and the respective thicknesses can be determined. The thickness of the first layer is preferably 0.1 μm or more and 5 μm or less. The thickness of the second layer is preferably 0.1 μm or more and 3 μm or less. The thickness of the third layer is preferably 5 μm or more and 10 μm or less.

[0042] Furthermore, it is preferable that the thickness of the solid electrolyte layer located on the upper surface of the porous portion is 10 μm or less. The thickness of the solid electrolyte layer located on the upper surface of the porous portion (the thickness indicated by the double arrow t in FIG. 2) is the sum of the thickness of all or part of the second layer and the thickness of the third layer. When the boundary between the first and second layers coincides with the upper surface of the porous portion, the thickness of the solid electrolyte layer located on the upper surface of the porous portion is the sum of the thicknesses of the second layer and the third layer. The position of the upper surface of the porous portion is determined by visually drawing a line on the microscopic cross-sectional photograph.

[0043] The fact that the thickness of the solid electrolyte layer located on the upper surface of the porous portion is 10 μm or less means that the thickness of the entire solid electrolyte layer is thin. In particular, when forming a thick solid electrolyte layer as in the technology of Patent Document 1, a solid electrolyte layer of about 100 μm is required. However, in the configuration of the present invention, in which a film-like conductive polymer is used as the solid electrolyte layer located on the upper surface of the porous portion, the thickness of the solid electrolyte layer can be made thin because a short circuit does not occur even if the thickness of the solid electrolyte layer is made thin. By making the thickness of the solid electrolyte layer thin, the resistance of the solid electrolyte layer can be reduced.

[0044] In all of the first, second, and third layers, the material constituting the solid electrolyte layer is a conductive polymer. The same materials can be used for the particle-like conductive polymer and the film-like conductive polymer, and conductive polymers such as polypyrroles, polythiophenes, and polyanilines are used. Among these, polythiophenes are preferred, with poly(3,4-ethylenedioxythiophene) known as PEDOT being particularly preferred. Conductive polymers such as polypyrroles, polythiophenes, and polyanilines are used. Among these, polythiophenes are preferred, with poly(3,4-ethylenedioxythiophene) known as PEDOT being particularly preferred.

[0045] The conductive polymer preferably contains a dopant. The same dopant may be used in the conductive polymer particles and the conductive polymer film, or different dopants may be used. If different dopants are used in the conductive polymer particles and the conductive polymer film, it can be determined by chemical analysis that two types of materials are used to form the solid electrolyte layer, making it easier to estimate that a conductive polymer particles and a conductive polymer film are used.

[0046] Examples of the dopant include halogens such as iodine, bromine, and chlorine; halides such as hexafluorophosphorus, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, and perchloric acid; alkyl-substituted organic sulfonic acids such as methanesulfonic acid and dodecylsulfonic acid; cyclic sulfonic acids such as camphorsulfonic acid ion; alkyl-substituted or unsubstituted benzene mono- or disulfonic acids such as benzenesulfonic acid, paratoluenesulfonic acid, dodecylbenzenesulfonic acid, polystyrenesulfonic acid, and benzenedisulfonic acid; sulfonic acids such as 2-naphthalenesulfonic acid and 1,7-naphthalenedisulfonic acid; alkyl-substituted or unsubstituted naphthalenesulfonic acids such as naphthalenesulfonic acids substituted with 1 to 4 sulfonic acid groups, anthracenesulfonic acid, anthraquinonesulfonic acid, alkyl-substituted or unsubstituted biphenylsulfonic acids such as alkylbiphenylsulfonic acids and biphenyldisulfonic acids, polymeric sulfonic acids such as polystyrenesulfonic acid and naphthalenesulfonic acid-formaldehyde condensates, heteropolyacids such as molybdophosphoric acid, tungstophosphoric acid and tungstomolybdophosphoric acid, methoxybenzenesulfonic acid, ethoxybenzenesulfonic acid, xylenesulfonic acid, or ions thereof.

[0047] Among these, alkyl-substituted or unsubstituted biphenylsulfonic acids such as anthracenesulfonic acid, anthraquinonesulfonic acid, alkylbiphenylsulfonic acid, and biphenyldisulfonic acid are preferred as dopants contained in the conductive polymer particles, and anthraquinonesulfonic acid is particularly preferred.

[0048] As the dopant contained in the film-like conductive polymer, a polymeric sulfonic acid such as polystyrene sulfonic acid or a naphthalene sulfonic acid formalin condensate is preferred, with polystyrene sulfonic acid being particularly preferred.

[0049] It is preferable that chemical analysis of the solid electrolyte layer reveals that anthraquinone sulfonic acid is detected in the first layer portion, polystyrene sulfonic acid is detected in the third layer portion, and anthraquinone sulfonic acid and polystyrene sulfonic acid are detected in the second layer portion.

[0050] The carbon layer, metal layer, and insulating mask layer, which are optional elements in the solid electrolytic capacitor element of the present invention, are described below. The carbon layer can be formed by applying a carbon paste. The metal layer can be formed by applying a conductive paste such as a silver paste, and is preferably a silver layer. The insulating mask layer is formed by applying a mask material such as a composition containing an insulating resin. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc.), compositions consisting of soluble polyimidesiloxane and epoxy resin, polyimide resin, polyamideimide resin, and derivatives or precursors thereof.

[0051] An example of a solid electrolytic capacitor of the present invention including a solid electrolytic capacitor element of the present invention will be described below. The solid electrolytic capacitor element of the present invention may be included in a solid electrolytic capacitor having a different configuration. For example, a lead frame may be used as an external electrode. The solid electrolytic capacitor of the present invention may also include a solid electrolytic capacitor element other than the solid electrolytic capacitor element of the present invention.

[0052] Fig. 5 is a perspective view schematically showing an example of the solid electrolytic capacitor of the present invention, and Fig. 6 is a cross-sectional view taken along line ZZ of the solid electrolytic capacitor shown in Fig. 5.

[0053] 5 and 6, the length direction of solid electrolytic capacitor 100 and exterior body 110 is indicated by L, the width direction is indicated by W, and the height direction is indicated by T. Here, the length direction L, the width direction W, and the height direction T are perpendicular to each other.

[0054] 5 and 6 , the solid electrolytic capacitor 100 has a substantially rectangular parallelepiped outer shape. The solid electrolytic capacitor 100 includes an outer casing 110, a first external electrode 120, a second external electrode 130, and a plurality of solid electrolytic capacitor elements 1. The solid electrolytic capacitor elements 1 are an example of the solid electrolytic capacitor element of the present invention.

[0055] The exterior body 110 seals a plurality of solid electrolytic capacitor elements 1. That is, a plurality of solid electrolytic capacitor elements 1 are embedded in the exterior body 110. Note that the exterior body 110 may seal a single solid electrolytic capacitor element 1. That is, a single solid electrolytic capacitor element 1 may be embedded inside the exterior body 110.

[0056] The exterior body 110 has a substantially rectangular parallelepiped outer shape. The exterior body 110 has a first main surface 110a and a second main surface 110b that face each other in a height direction T, a first side surface 110c and a second side surface 110d that face each other in a width direction W, and a first end surface 110e and a second end surface 110f that face each other in a length direction L.

[0057] As described above, the exterior body 110 has a substantially rectangular parallelepiped outer shape, but the corners and ridges are preferably rounded. A corner is a portion where three surfaces of the exterior body 110 intersect, and a ridge is a portion where two surfaces of the exterior body 110 intersect.

[0058] The exterior body 110 is made of, for example, a sealing resin. The sealing resin contains at least a resin, and preferably contains a resin and a filler. The resin preferably includes an epoxy resin, a phenol resin, a polyimide resin, a silicone resin, a polyamide resin, a liquid crystal polymer, or the like. The filler preferably includes silica particles, alumina particles, metal particles, or the like.

[0059] The first external electrode 120 is provided on the first end surface 110e of the exterior body 110. The second external electrode 130 is provided on the second end surface 110f of the exterior body 110. The first external electrode 120 and the second external electrode 130 may be provided across the first main surface 110a, the second main surface 110b, the first side surface 110c, and the second side surface 110d, respectively.

[0060] The first external electrode 120 is electrically connected to the valve metal base 10 of the solid electrolytic capacitor element 1 exposed from the exterior body 110. The first external electrode 120 may be directly or indirectly connected to the valve metal base 10 at the first end surface 110e of the exterior body 110.

[0061] The second external electrode 130 is electrically connected to the metal layer 60 of the solid electrolytic capacitor element 1 exposed from the exterior body 110. The second external electrode 130 may be directly or indirectly connected to the metal layer 60 at the second end surface 110f of the exterior body 110.

[0062] The first external electrode 120 and the second external electrode 130 may be conductive layers having both or either a resin electrode layer containing a conductive component and a resin component and a plating layer, and their configuration is not particularly limited.

[0063] Fig. 7 is a cross-sectional view of an example of a solid electrolytic capacitor of the present invention, in which a lead frame is used as an external electrode. In the solid electrolytic capacitor 101 shown in Fig. 7, a plurality of solid electrolytic capacitor elements 1 are stacked, and the ends of the anode lead frame 61 and the valve metal substrate 10 are welded, and the cathode lead frame 62 and the metal layer 60 are connected with a conductive adhesive 70 such as adhesive silver. Furthermore, the anode lead frame 61 and the cathode lead frame 62 are sealed with an exterior body 110, except for the portions necessary for mounting them on a substrate.

[0064] An example of a method for manufacturing a solid electrolytic capacitor element of the present invention and a method for manufacturing a solid electrolytic capacitor of the present invention will be described below.

[0065] (Preparation of Valve Metal Substrate) A chemically formed aluminum foil having an etching layer on its surface is prepared as a valve metal substrate. The surface of the chemically formed aluminum foil is anodized by immersing it in an aqueous solution of ammonium adipate, thereby forming a dielectric layer on the cut surface of the chemically formed aluminum foil. This method results in a porous portion having pores, and an aluminum foil having a dielectric layer formed on its surface. It is also preferable to form an insulating mask layer in a predetermined position to separate the anode and cathode portions.

[0066] (Formation of a solid electrolyte layer (first layer) composed of an aggregate of conductive polymer particles) A ​​polymerization solution containing a monomer that will become a conductive polymer through a chemical polymerization reaction is prepared. Examples of the monomer include pyrrole, thiophene, and aniline. Of these, 3,4-ethylenedioxythiophene is more preferable. The polymerization solution preferably contains a dopant. An aluminum chemically formed foil is immersed in the polymerization solution, then removed and allowed to stand. Once the liquid has accumulated in the pores and the liquid outside the pores has almost dried, the foil is immersed in an oxidizing agent, removed in the same manner, and dried. This process is repeated approximately four times to form a first layer composed of an aggregate of conductive polymer particles within the pores of the porous portion. The foil is then washed to remove excess material. Examples of oxidizing agents include ammonium persulfate, iron p-toluenesulfonate (PTSA), and the like. When a strong acid such as a sulfonate is used as the oxidizing agent, washing is required to prevent corrosion of the aluminum foil. Since the aggregate of conductive polymer particles contains voids, which tend to leave oxidizing agents behind, careful washing is particularly important. If the number of times of immersion in the polymerization solution is large, the number of times of washing is also large, and the working efficiency is low, but if the number of times of immersion is small, the working efficiency can be improved.

[0067] (Formation of a solid electrolyte layer (part of the second layer) made of an aggregate of conductive polymer particles) A ​​solid electrolyte layer made of an aggregate of conductive polymer particles is formed on the first layer, even on the porous portion. This solid electrolyte layer becomes part of the second layer.

[0068] (Solid electrolyte layer made of a film-like conductive polymer (formation of part of the second layer and the third layer)) A water dispersion containing a conductive polymer dispersion and a dopant is applied to a solid electrolyte layer made of an aggregate of conductive polymer particles, and then dried to form a solid electrolyte layer made of a film-like conductive polymer. Thereafter, the solid electrolyte layer is washed to remove excess material.

[0069] The surface portion of the solid electrolyte layer where a film-like conductive polymer is present but no agglomerates of conductive polymer particles are present is the third layer, and the portion where the film-like conductive polymer fills the voids in the agglomerates of conductive polymer particles is the second layer. Because the solid electrolyte layer made of a film-like conductive polymer has no voids, the substance to be cleaned is less likely to remain, making cleaning easy.

[0070] (Formation of carbon layer and silver layer, formation of external electrodes) Carbon paste is applied to the surface of the solid electrolyte layer and dried to form a carbon layer. Silver paste is then applied and dried to form a silver layer. This process forms a carbon layer and a metal layer to produce a solid electrolytic capacitor element. The solid electrolytic capacitor elements are then stacked in the thickness direction, sealed with resin, and external electrodes are then formed to produce a solid electrolytic capacitor.

[0071] The present specification discloses the following:

[0072] The present disclosure (1) provides a solid electrolytic capacitor element comprising a valve metal substrate having a porous portion with pores formed therein, a dielectric layer formed on the surface of the valve metal substrate, and a solid electrolyte layer formed on the dielectric layer, wherein the solid electrolyte layer has a first layer filled in the pores of the porous portion and made of an agglomerate of conductive polymer particles, a second layer formed on the first layer, and a third layer formed on the second layer and made of a film of conductive polymer, and the second layer contains both the agglomerate of conductive polymer particles that constitutes the first layer and the film of conductive polymer that constitutes the third layer.

[0073] The present disclosure (2) is the solid electrolytic capacitor element according to the present disclosure (1), wherein the second layer contains more aggregates of conductive polymer particles than the film-like conductive polymer.

[0074] The present disclosure (3) is the solid electrolytic capacitor element according to the present disclosure (1) or (2), in which the thickness of the solid electrolyte layer located on the upper surface of the porous portion is 10 μm or less.

[0075] The present disclosure (4) is the solid electrolytic capacitor element according to any one of the present disclosures (1) to (3), wherein the conductive polymer particles contain alkyl-substituted or unsubstituted biphenyl sulfonic acid as a dopant.

[0076] The present disclosure (5) is the solid electrolytic capacitor element according to the present disclosure (4), in which the alkyl-substituted or unsubstituted biphenylsulfonic acid is anthraquinonesulfonic acid.

[0077] The present disclosure (6) is the solid electrolytic capacitor element according to any one of the present disclosures (1) to (5), wherein the film-like conductive polymer contains a polymeric sulfonic acid as a dopant.

[0078] The present disclosure (7) is the solid electrolytic capacitor element according to the present disclosure (6), in which the polymeric sulfonic acid is polystyrene sulfonic acid.

[0079] The present disclosure (8) is a solid electrolytic capacitor including the solid electrolytic capacitor element according to any one of the present disclosures (1) to (7).

[0080] REFERENCE SIGNS LIST 1 Solid electrolytic capacitor element 10 Valve action metal substrate 11 Pore 12 Porous portion 20 Dielectric layer 30 Insulating mask layer 31 Anode portion 32 Cathode portion 40, 140, 240 Solid electrolyte layer 41 First layer 41a Conductive polymer particles 41b Voids 42 Second layer 43 Third layer 43a Film-like conductive polymer 50 Carbon layer 60 Metal layer 61 Anode lead frame 62 Cathode lead frame 70 Conductive adhesive 100, 101 Solid electrolytic capacitor 110 Exterior body 110a First main surface 110b Second main surface 110c First side surface 110d Second side surface 110e First end surface 110f Second end surface 120 First external electrode 130 Second external electrode

Claims

1. A solid electrolytic capacitor element comprising a valve metal substrate having a porous portion having pores formed therein, a dielectric layer formed on the surface of the valve metal substrate, and a solid electrolyte layer formed on the dielectric layer, wherein the solid electrolyte layer has a first layer filled in the pores of the porous portion and consisting of an agglomerate of conductive polymer particles, a second layer formed on the first layer, and a third layer formed on the second layer and consisting of a film of conductive polymer, and the second layer contains both the agglomerate of conductive polymer particles that constitutes the first layer and the film of conductive polymer that constitutes the third layer.

2. The solid electrolytic capacitor element according to claim 1, wherein the second layer contains more agglomerates of conductive polymer particles than the film-like conductive polymer.

3. A solid electrolytic capacitor element according to claim 1 or 2, wherein the thickness of the solid electrolyte layer located on the upper surface of the porous portion is 10 μm or less.

4. The solid electrolytic capacitor element according to any one of claims 1 to 3, wherein the conductive polymer particles contain alkyl-substituted or unsubstituted biphenyl sulfonic acid as a dopant.

5. The solid electrolytic capacitor element according to claim 4, wherein the alkyl-substituted or unsubstituted biphenylsulfonic acid is anthraquinonesulfonic acid.

6. The solid electrolytic capacitor element according to any one of claims 1 to 5, wherein the film-like conductive polymer contains a polymeric sulfonic acid as a dopant.

7. The solid electrolytic capacitor element according to claim 6, wherein the polymeric sulfonic acid is polystyrene sulfonic acid.

8. A solid electrolytic capacitor comprising the solid electrolytic capacitor element according to any one of claims 1 to 7.

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