Solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing solid electrolytic capacitor element

Abstract

A solid electrolytic capacitor element 20 comprises: a valve-acting metal substrate 4 having a dielectric layer 5 on at least one main surface; a solid electrolyte layer 7a provided on the dielectric layer 5; and a cathode foil 7e which is in direct contact with the solid electrolyte layer 7a. The cathode foil 7e comprises a copper foil 7c having a passivation film 7d formed on a surface thereof, and the thickness of the passivation film 7d is 1 nm to 1 μm.

Description

Solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing solid electrolytic capacitor element

[0001] The present invention relates to a solid electrolytic capacitor element, a solid electrolytic capacitor, and a method for manufacturing a solid electrolytic capacitor element.

[0002] Patent Document 1 describes a method for manufacturing a solid electrolytic capacitor in which a carbon layer is provided as a conductive layer on a solid electrolyte layer, and a metal foil as a cathode foil is further laminated on top of the carbon layer.

[0003] Japanese Patent Application Laid-Open No. 2019-79866

[0004] In Patent Document 1, a carbon layer is provided on a solid electrolyte layer. The carbon layer is formed by applying a carbon paste, but when the paste is applied and pressed, the carbon layer can leak, posing a productivity issue. Furthermore, due to the presence of interfacial resistance between the solid electrolyte layer and the carbon layer, and between the carbon layer and the cathode foil, increasing the number of layers increases the resistance of the solid electrolytic capacitor element. Given these circumstances, it is hoped that a solid electrolytic capacitor element with reduced resistance can be obtained by directly contacting the solid electrolyte layer and the cathode foil without using a carbon layer, thereby reducing the number of interfaces.

[0005] Conductive polymers used in solid electrolyte layers are often blended with dopants to improve conductivity. Because strongly acidic materials are used as dopants, the materials constituting the solid electrolyte layer as a whole exhibit strong acidity.

[0006] In a configuration in which a carbon layer is in contact with a solid electrolyte layer, as in the technology described in Patent Document 1, the carbon layer is made of a material that is stable against acids, so even if the material constituting the solid electrolyte layer is strongly acidic, the carbon layer does not denature and no problems arise. However, when the solid electrolyte layer and the cathode foil are in direct contact with each other, the cathode foil may corrode or dissolve due to contact with the strongly acidic material. When the metal foil dissolves, a space is created, which can result in complete insulation and the capacitor may stop functioning.

[0007] The present invention has been made to solve the above problems, and has an object to provide a solid electrolytic capacitor element in which the solid electrolyte layer and the cathode foil are in direct contact with each other, thereby reducing the interfacial resistance and thus the resistance value, and in which corrosion of the cathode foil due to contact between the solid electrolyte layer and the cathode foil is prevented.

[0008] The solid electrolytic capacitor element of the present invention comprises a valve metal substrate having a dielectric layer on at least one main surface thereof, a solid electrolyte layer provided on the dielectric layer, and a cathode foil in direct contact with the solid electrolyte layer, the cathode foil having a passivation coating on the surface of copper foil, the passivation coating having a thickness of 1 nm or more and 1 μm or less.

[0009] The solid electrolytic capacitor of the present invention is formed by stacking a plurality of solid electrolytic capacitor elements of the present invention and sealing them with an exterior resin, and the anode portion side end face of the valve metal base is connected to an anode external electrode formed on the surface of the exterior resin at the anode side end face of the solid electrolytic capacitor element, and the cathode foil is connected to a cathode external electrode formed on the surface of the exterior resin at the cathode side end face of the solid electrolytic capacitor element.

[0010] The method for manufacturing a solid electrolytic capacitor element of the present invention includes the steps of: preparing a cathode foil, which is copper foil having a passivation coating on its surface with a thickness of 1 nm or more and 1 μm or less; providing a solid electrolyte layer on a dielectric layer of a valve metal base having a dielectric layer on at least one main surface of the base; and arranging the cathode foil so as to be in contact with the solid electrolyte layer.

[0011] According to the present invention, it is possible to provide a solid electrolytic capacitor element in which the resistance value is reduced due to direct contact between the solid electrolyte layer and the cathode foil, and corrosion of the cathode foil caused by contact between the solid electrolyte layer and the cathode foil is prevented.

[0012] FIG. 1 is a perspective view schematically showing an example of a solid electrolytic capacitor. FIG. 2A is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 1 taken along line A-A. FIG. 2B is a cross-sectional view of another example of a solid electrolytic capacitor. FIG. 3 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor element. FIG. 4 is a cross-sectional view schematically showing another example of a solid electrolytic capacitor. FIG. 5 is a cross-sectional view schematically showing another example of a solid electrolytic capacitor element.

[0013] The solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing a solid electrolytic capacitor element 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 preferred configurations of each embodiment of the present invention described below also constitutes the present invention.

[0014] The solid electrolytic capacitor of the present invention is formed by stacking a plurality of solid electrolytic capacitor elements of the present invention and sealing them with an exterior resin, and the anode portion side end face of the valve metal base is connected to an anode external electrode formed on the surface of the exterior resin at the anode side end face of the solid electrolytic capacitor element, and the cathode foil is connected to a cathode external electrode formed on the surface of the exterior resin at the cathode side end face of the solid electrolytic capacitor element.

[0015] FIG. 1 is a perspective view schematically illustrating an example of a solid electrolytic capacitor. FIG. 1 shows a resin molded body 9 that constitutes a solid electrolytic capacitor 1. The shape of the resin molded body that constitutes the solid electrolytic capacitor is not particularly limited, and any three-dimensional shape can be adopted. The shape of the resin molded body is preferably a rectangular parallelepiped. Furthermore, the term "rectangular parallelepiped" does not mean a perfect rectangular parallelepiped; the surfaces that form the resin molded body may be tapered and not perpendicular to other surfaces, and the shape may also have chamfered corners.

[0016] FIG. 1 shows a rectangular parallelepiped resin molded body 9. The resin molded body 9 has a length direction (L direction), a width direction (W direction), and a thickness direction (T direction). The resin molded body 9 has, as its outer surfaces, a first end face 9a and a second end face 9b that face each other in the length direction. An anode external electrode 11 is formed on the first end face 9a, and a cathode external electrode 13 is formed on the second end face 9b. The resin molded body 9 has, as its outer surfaces, a bottom face 9c and a top face 9d that face each other in the thickness direction. The resin molded body 9 also has, as its outer surfaces, a first side face 9e and a second side face 9f that face each other in the width direction.

[0017] In this specification, the surface extending along the length direction (L direction) and thickness direction (T direction) of the solid electrolytic capacitor or resin molding is referred to as the LT surface, the surface extending along the length direction (L direction) and width direction (W direction) is referred to as the LW surface, and the surface extending along the width direction (W direction) and thickness direction (T direction) is referred to as the WT surface.

[0018] 2A is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 1 taken along line A-A. The solid electrolytic capacitor element 20 includes an anode 3 having a dielectric layer 5 on its surface, and a cathode 7 facing the anode 3. A plurality of solid electrolytic capacitor elements 20 are stacked to form a laminate 30, and the periphery of the laminate 30 is sealed with an exterior resin 8 to form a resin molded body 9. In the laminate 30, the stacked solid electrolytic capacitor elements 20 may be bonded to each other via a conductive adhesive (not shown). The laminate 30 may include only one solid electrolytic capacitor element 20.

[0019] The anode 3 includes a valve metal substrate 4 having a core and a porous portion formed along the surface of the core. A dielectric layer 5 is formed on the surface of the porous portion. The anode-side end face of the valve metal substrate 4 is connected to an anode external electrode 11 formed on a first end face 9 a (surface of the exterior resin) of the resin molded body 9 at the anode-side end face of the solid electrolytic capacitor element 20.

[0020] The cathode 7 includes a solid electrolyte layer 7a formed on the dielectric layer 5 and a cathode foil 7e in direct contact with the solid electrolyte layer 7a. The cathode foil 7e has a passivation coating 7d on the surface of a copper foil 7c. The cathode foil 7e is connected to a cathode external electrode 13 formed on the second end surface 9b (surface of the exterior resin) of the resin molded body 9 at the cathode side end surface of the solid electrolytic capacitor element 20.

[0021] The end of the valve metal substrate 4 constituting the solid electrolytic capacitor element 20 on the side of the second end face 9b is sealed with the exterior resin 8, and the valve metal substrate 4 and the solid electrolyte layer 7a are not in direct contact with each other. On the other hand, if the end of the valve metal substrate 4 on the side of the second end face 9b is covered with an insulating treatment, such as by being covered with a dielectric layer 5, the end of the valve metal substrate 4 on the side of the second end face 9b may be covered with the solid electrolyte layer 7a.

[0022] The exterior resin 8 constituting the resin molded body 9 contains at least a resin, preferably a resin and a filler. Examples of the resin include, for example, insulating resins such as epoxy resin, phenolic resin, polyimide resin, silicone resin, polyamide resin, and liquid crystal polymer. The resin molded body 9 may also be composed of two or more types of insulating resins. The exterior resin 8 can be in the form of either a solid or liquid resin. Examples of the filler include, for example, inorganic particles such as silica particles, alumina particles, and metal particles. It is more preferable to use a material containing silica particles in a solid epoxy resin and a phenolic resin. When a solid encapsulant is used, resin molding such as compression molding or transfer molding is preferred, and compression molding is more preferred. When a liquid encapsulant is used, molding methods such as dispensing and printing are preferred. The resin molded body 9 is preferably produced by encapsulating a stack 30 of solid electrolytic capacitor elements 20, including an anode 3, a dielectric layer 5, and a cathode 7, with the exterior resin 8 using compression molding.

[0023] An example of the anode external electrode 11 is a configuration including a conductive resin electrode layer 11b containing a conductive component and a resin component, and an outer plating layer 11c. The outer plating layer 11c is preferably a Ni plating layer or a Sn plating layer.

[0024] An example of the cathode external electrode 13 is a configuration including a conductive resin electrode layer 13b containing a conductive component and a resin component, and an outer plating layer 13c. The outer plating layer 13c is preferably a Ni plating layer or a Sn plating layer.

[0025] 2B is a cross-sectional view of another example of a solid electrolytic capacitor. In the solid electrolytic capacitor 1′ shown in FIG. 2B , the cathode foil 7e has a passivation coating 7d on the surface of the copper foil 7c in a portion where the cathode foil 7e contacts the solid electrolyte layer 7a. However, the passivation coating 7d is not present on the surface of the copper foil 7c near the cathode end face of the solid electrolytic capacitor element 20, where the cathode foil 7e is not in contact with the solid electrolyte layer 7a. Because the effect of the copper foil having a passivation coating is exerted in the portion where the copper foil contacts the solid electrolyte layer, the cathode foil does not need to have a passivation coating in the portion where the copper foil is not in contact with the solid electrolyte layer.

[0026] The solid electrolytic capacitor element of the present invention comprises a valve metal substrate having a dielectric layer on at least one main surface thereof, a solid electrolyte layer provided on the dielectric layer, and a cathode foil in direct contact with the solid electrolyte layer, the cathode foil having a passivation coating on the surface of copper foil, the passivation coating having a thickness of 1 nm or more and 1 μm or less.

[0027] Fig. 3 is a cross-sectional view schematically showing an example of a solid electrolytic capacitor element. The solid electrolytic capacitor element 20 shown in Fig. 3 constitutes a part of the solid electrolytic capacitor 1 shown in Fig. 2A. The solid electrolytic capacitor element 20 shown in Fig. 3 includes a valve metal substrate 4 having a dielectric layer 5 on at least one main surface thereof, a solid electrolyte layer 7a provided on the dielectric layer 5, and a cathode foil 7e in direct contact with the solid electrolyte layer 7a, the cathode foil 7e having a passivation coating 7d on the surface of a copper foil 7c.

[0028] Examples of the valve metal constituting the valve metal substrate include simple metals such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, and silicon, as well as alloys containing these metals. Among these, aluminum and aluminum alloys are preferred.

[0029] The shape of the valve metal substrate is not particularly limited, but is preferably flat, and more preferably foil-like. The porous portion is preferably an etching layer obtained by etching with hydrochloric acid or the like. The thickness of the valve metal substrate before etching is preferably 60 μm or more and 180 μm or less. The thickness of the unetched valve metal substrate (core portion) after etching is preferably 10 μm or more and 70 μm or less. The thickness of the porous portion is designed according to the withstand voltage and capacitance required for the electrolytic capacitor, and the combined thickness of the porous portions on both sides of the valve metal substrate is preferably 10 μm or more and 120 μm or less.

[0030] The dielectric layer is preferably made of an oxide film of the valve metal. For example, when aluminum foil is used as the valve metal substrate, an oxide film that serves as the dielectric layer can be formed by anodizing in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium salts, ammonium salts, or the like. The dielectric layer is formed along the surface of the porous portion, thereby forming pores (recesses). The thickness of the dielectric layer is designed according to the withstand voltage and capacitance required for the electrolytic capacitor, but is preferably 3 nm or more and 200 nm or less.

[0031] Examples of materials constituting the solid electrolyte layer include conductive polymers with a skeleton of pyrroles, thiophenes, anilines, etc. Examples of conductive polymers with a skeleton of thiophenes include PEDOT [poly(3,4-ethylenedioxythiophene)], which may be PEDOT:PSS composited with polystyrene sulfonic acid (PSS) as a dopant. When a strongly acidic material such as polystyrene sulfonic acid is used as the dopant, the material constituting the solid electrolyte layer exhibits strong acidity. Furthermore, by adding an acidic dopant to the main skeleton of not only polystyrene sulfonic acid but also pyrroles, thiophenes, anilines, etc., the material constituting the solid electrolyte layer exhibits acidity.

[0032] The solid electrolyte layer can be formed, for example, by using a treatment liquid containing a monomer such as 3,4-ethylenedioxythiophene to form a polymer film such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer, or by applying a dispersion of a polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric layer and drying it. It is preferable to form an inner solid electrolyte layer that fills the pores (recesses) and then form an outer solid electrolyte layer that covers the entire dielectric layer. The solid electrolyte layer can be formed in a predetermined region by applying the treatment liquid or dispersion to the dielectric layer using sponge transfer, screen printing, spray coating, dispenser printing, inkjet printing, or the like. The thickness of the solid electrolyte layer is preferably 2 μm or more and 20 μm or less.

[0033] The cathode foil is a metal foil for extending the cathode to a position where it is connected to the cathode external electrode, and is made of copper foil having a passivation coating on its surface. When the metal foil constituting the cathode foil is copper foil, the resistance value of the cathode foil can be reduced, and the ESR can be reduced. The thickness of the copper foil excluding the passivation coating is not particularly limited, but from the viewpoints of handling in the manufacturing process, miniaturization, and reduced ESR, it is preferably 20 μm or more and preferably 50 μm or less.

[0034] The solid electrolytic capacitor element of the present invention uses copper foil having a passivation film on its surface as the cathode foil in direct contact with the solid electrolyte layer, and the thickness of the passivation film is 1 nm or more and 1 μm or less.

[0035] The passive film preferably includes a natural oxide film of copper. Copper has a higher redox potential and is less susceptible to oxidation than aluminum, which is typically used as the cathode foil material in solid electrolytic capacitor elements. Therefore, the thickness of the metal-derived passive film can be made thinner than when aluminum is used as the cathode foil material. Because the passive film itself functions as a film that inhibits conduction, it is preferable to make its thickness as thin as possible.

[0036] Furthermore, copper has the lowest redox potential among metals that form a natural oxide film. This means that it is a desirable metal material that can also provide corrosion protection through a passive film. Metals with higher redox potentials than copper (gold, platinum, etc.) are chemically very stable, but are expensive, making them difficult to use in industrial products.

[0037] By providing a passivation coating on the surface of the copper foil, corrosion resistance is imparted to the copper foil, and therefore, when the solid electrolyte layer is made of a strongly acidic material, the copper foil is prevented from corroding even if the cathode foil is brought into direct contact with the solid electrolyte layer.

[0038] In addition, in the solid electrolytic capacitor element of the present invention, the thickness of the passivation film is set to 1 nm or more and 1 μm or less. When the passivation film is 1 nm or more, the function of preventing corrosion of the cathode foil is suitably exhibited. Furthermore, when the passivation film is 1 μm or less, the resistance caused by the passivation film can be prevented from increasing. Furthermore, a relatively high voltage (e.g., 5 V or more, several tens of V, or even several hundred V) is applied to a solid electrolytic capacitor, and applying a high voltage causes a tunneling current to flow through the passivation film. Therefore, even if a passivation film is present, conduction through the passivation film is possible. To improve conduction by tunneling current, a thinner passivation film is preferable, and from that perspective, the thickness of the passivation film is set to 1 μm or less.

[0039] Regarding the location where the passivation film is provided on the copper foil, it is preferable that the passivation film be provided on the entire main surface of the copper foil. Furthermore, it is preferable that the passivation film be provided at least on the portion that is in direct contact with the solid electrolyte layer, but the passivation film does not have to be provided on the portion that is not in direct contact with the solid electrolyte layer. Furthermore, it is preferable that the passivation film not be provided on the end of the copper foil, where the end of the copper foil is connected to the cathode external electrode.

[0040] The passive film preferably includes a silane coupling agent film. When the passive film includes a silane coupling agent film, the passive film can be formed simply by applying a silane coupling agent to the copper foil and reacting with the silane coupling agent, making the process simple. Since the silane coupling agent film is a glass-based film, it has high mechanical strength and chemical stability, making it an excellent passive film for preventing corrosion of copper foil. Since the silane coupling agent film itself has low electronic conductivity, it is preferable that its thickness is thin, for example, 20 nm or less. Since the silane coupling agent film is a highly stable film, the strength and shape of the film itself can be maintained even when its thickness is thin. When the passive film includes a silane coupling agent film, the passive film may be only a silane coupling agent film, or the passive film may include a copper native oxide film and a silane coupling agent film.

[0041] Applying a relatively high voltage (for example, 5 V or more, several tens of V or more, or several hundred V) to a silane coupling agent coating allows electron conduction by tunneling current, so conduction through the passivation coating is possible.

[0042] The copper foil having a silane coupling agent as a passivation coating can be commercially available. Specific examples of the silane coupling agent include water-based silane coupling agents, radical-polymerizable silane coupling agents, and rubber-modified silane coupling agents.

[0043] The passive film preferably includes a chromate film. When the passive film includes a chromate film, it can be formed by chromate plating the copper foil. The process is more complicated and difficult to control than when a silane coupling agent film is formed as the passive film. Because a chromate film has higher electronic conductivity than a silane coupling agent film, even if the film is made thicker than a silane coupling agent film, the resistance is less likely to increase. On the other hand, since the chemical stability of the passive film is inferior to that of a silane coupling agent film, it is preferable not to make the film too thin. From this perspective, when the passive film is a chromate film, the thickness of the chromate film is preferably 5 nm or more. Furthermore, it is preferably 1 μm or less. When the passive film includes a chromate film, the passive film may consist of only a chromate film, or the passive film may include a natural copper oxide film and a chromate film.

[0044] Commercially available copper foils can be used as the copper foil having a chromate coating as a passive coating. Specific examples of the chromate coating include a hexavalent chromium chemical conversion coating and a trivalent chromium chemical conversion coating.

[0045] The resistance of the cathode foil is preferably 0.5 Ω or less. The resistance of the cathode foil is the resistance in the thickness direction of the metal foil including the copper foil and the passivation coating, and can be measured by measuring the resistance on both sides of the cathode foil using a four-terminal method.

[0046] As shown in FIG. 2B, the solid electrolytic capacitor element of the present invention may not have a passivation film on the surface of the copper foil in the vicinity of the cathode side end face of the solid electrolytic capacitor element.

[0047] Next, an example of a method for manufacturing a solid electrolytic capacitor element of the present invention will be described. The method for manufacturing a solid electrolytic capacitor element of the present invention includes the steps of preparing a cathode foil, which is a copper foil having a passivation coating on its surface with a thickness of 1 nm or more and 1 μm or less, providing a solid electrolyte layer on a dielectric layer of a valve metal substrate having a dielectric layer on at least one main surface of the dielectric layer, and arranging the cathode foil so as to be in contact with the solid electrolyte layer.

[0048] Cathode foil is prepared by forming a passivation coating having a thickness of 1 nm or more and 1 μm or less on the surface of copper foil. The passivation coating, which is a silane coupling agent coating, can be formed by applying a silane coupling agent to the copper foil and reacting the silane coupling agent (e.g., hydrolysis reaction by drying, condensation reaction). Alternatively, the passivation coating, which is a chromate coating, can be formed by chromate plating the copper foil. The thickness of the passivation coating can be adjusted by adjusting the conditions for forming the passivation coating (e.g., adjusting the amount of silane coupling agent applied, adjusting the chromate treatment time). Alternatively, the cathode foil can be prepared by purchasing a commercially available copper foil with a passivation coating.

[0049] A solid electrolytic capacitor element can be manufactured by preparing a first sheet including a valve metal substrate having a dielectric layer formed on its surface and a solid electrolyte layer provided on the dielectric layer, and a second sheet serving as a cathode foil, and then arranging the second sheet serving as the cathode foil so that it is in contact with the solid electrolyte layer of the first sheet. When a cathode foil having a passivation film formed on a portion of the surface of copper foil is used, the second sheet serving as the cathode foil is arranged so that the portion with the passivation film is in contact with the solid electrolyte layer.

[0050] A solid electrolytic capacitor element is obtained by laminating the first sheet and the second sheet. When manufacturing a solid electrolytic capacitor having multiple stacked solid electrolytic capacitor elements, the first sheet and the second sheet are alternately stacked, and the periphery of the stacked body is sealed with an exterior resin to obtain a resin molded body. Then, an anode external electrode and a cathode external electrode are formed on the end faces of the resin molded body. A solid electrolytic capacitor is obtained by the above process.

[0051] Other embodiments of solid electrolytic capacitor elements and solid electrolytic capacitors will be described below. FIG. 4 is a cross-sectional view schematically illustrating another example of a solid electrolytic capacitor, and FIG. 5 is a cross-sectional view schematically illustrating another example of a solid electrolytic capacitor element. In the solid electrolytic capacitor element 22 shown in FIGS. 4 and 5 , which constitutes the solid electrolytic capacitor 2 shown in FIG. 4 , an insulating layer 17 is provided on the dielectric layer 5, and the insulating layer 17 separates the anode 3 and the cathode 7 to prevent short-circuiting. The insulating layer 17 is formed by applying a resin solution called a mask material, such as a composition containing an insulating resin. Examples of insulating resins include polyphenylsulfone (PPS), polyethersulfone (PES), cyanate ester resin, fluororesin (e.g., tetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), a composition consisting of a soluble polyimidesiloxane and an epoxy resin, a polyimide resin, a polyamideimide resin, and derivatives or precursors thereof.

[0052] The cathode side end face of the valve metal substrate 4 is covered with the dielectric layer 5 and the solid electrolyte layer 7a. The other configurations can be the same as those of the solid electrolytic capacitor shown in FIG. 2A and the solid electrolytic capacitor element shown in FIG.

[0053] The solid electrolytic capacitor element of the present invention can be used as an element constituting the solid electrolytic capacitor of the present invention by stacking multiple elements, sealing them with an exterior resin, and forming external electrodes, but the use mode is not limited to this. For example, it can also be used as an element to realize a capacitor element built into a substrate that also incorporates a capacitor element. Furthermore, the method of extending the anode and cathode is not limited to the method using external electrodes formed on the surface of the exterior resin, but a method using a lead frame can also be used. The anode and cathode can be extended by connecting the valve metal substrate to the lead frame at the anode end face and connecting the cathode foil to the lead frame at the cathode end face.

[0054] The present specification discloses the following:

[0055] The present disclosure (1) is a solid electrolytic capacitor element comprising: a valve metal substrate having a dielectric layer on at least one main surface thereof; a solid electrolyte layer provided on the dielectric layer; and a cathode foil in direct contact with the solid electrolyte layer, wherein the cathode foil has a passivation coating on a surface of copper foil, and the passivation coating has a thickness of 1 nm or more and 1 μm or less.

[0056] The present disclosure (2) is the solid electrolytic capacitor element according to the present disclosure (1), wherein the passivation film includes a native oxide film of copper.

[0057] The present disclosure (3) is the solid electrolytic capacitor element according to the present disclosure (1) or (2), wherein the passivation coating includes a silane coupling agent coating.

[0058] The present disclosure (4) is the solid electrolytic capacitor element according to the present disclosure (1) or (2), wherein the passivation film includes a chromate film.

[0059] The present disclosure (5) is the solid electrolytic capacitor element according to the present disclosure (4), wherein the thickness of the chromate coating is 5 nm or more.

[0060] The present disclosure (6) is the solid electrolytic capacitor element according to any one of the present disclosures (1) to (5), wherein the resistance value of the cathode foil is 0.5 Ω or less.

[0061] The present disclosure (7) is a solid electrolytic capacitor in which a plurality of solid electrolytic capacitor elements according to any one of the present disclosures (1) to (6) are stacked and sealed with an exterior resin, the anode portion side end face of the valve metal base is connected to an anode external electrode formed on the surface of the exterior resin at the anode side end face of the solid electrolytic capacitor element, and the cathode foil is connected to a cathode external electrode formed on the surface of the exterior resin at the cathode side end face of the solid electrolytic capacitor element.

[0062] The present disclosure (8) is a method for manufacturing a solid electrolytic capacitor element, comprising the steps of: preparing a cathode foil, which is copper foil having a passivation coating on its surface with a thickness of 1 nm or more and 1 μm or less; providing a solid electrolyte layer on a dielectric layer of a valve metal base having a dielectric layer on at least one main surface of the base; and arranging the cathode foil so as to be in contact with the solid electrolyte layer.

[0063] DESCRIPTION OF SYMBOLS 1, 1', 2 Solid electrolytic capacitor 3 Anode 4 Valve action metal substrate 5 Dielectric layer 7 Cathode 7a Solid electrolyte layer 7c Copper foil 7d Passivation coating 7e Cathode foil 8 Exterior resin 9 Resin molded body 9a First end face of resin molded body 9b Second end face of resin molded body 9c Bottom face of resin molded body 9d Top face of resin molded body 9e First side face of resin molded body 9f Second side face of resin molded body 11 Anode external electrode 11b Conductive resin electrode layer 11c Outer layer plating layer 13 Cathode external electrode 13b Conductive resin electrode layer 13c Outer layer plating layer 17 Insulating layer 20, 22 Solid electrolytic capacitor element 30 Laminate

Claims

1. A solid electrolytic capacitor element comprising: a valve metal base having a dielectric layer on at least one principal surface thereof; a solid electrolyte layer provided on said dielectric layer; and a cathode foil in direct contact with said solid electrolyte layer, said cathode foil having a passivation coating on a surface of said copper foil, said passivation coating having a thickness of 1 nm or more and 1 μm or less.

2. The solid electrolytic capacitor element according to claim 1, wherein the passivation film includes a native copper oxide film.

3. A solid electrolytic capacitor element according to claim 1 or 2, wherein the passivation film includes a silane coupling agent film.

4. A solid electrolytic capacitor element according to claim 1 or 2, wherein the passive film includes a chromate film.

5. The solid electrolytic capacitor element according to claim 4, wherein the thickness of the chromate coating is 5 nm or more.

6. The solid electrolytic capacitor element according to any one of claims 1 to 5, wherein the resistance value of the cathode foil is 0.5 Ω or less.

7. A solid electrolytic capacitor comprising a plurality of solid electrolytic capacitor elements according to any one of claims 1 to 6 stacked together and sealed with an exterior resin, the anode side end face of the valve metal base being connected to an anode external electrode formed on the surface of the exterior resin at the anode side end face of the solid electrolytic capacitor element, and the cathode foil being connected to a cathode external electrode formed on the surface of the exterior resin at the cathode side end face of the solid electrolytic capacitor element.

8. A method for manufacturing a solid electrolytic capacitor element, comprising the steps of: preparing a cathode foil which is a copper foil having a passivation coating on its surface with a thickness of 1 nm or more and 1 μm or less; providing a solid electrolyte layer on a dielectric layer of a valve metal base having a dielectric layer on at least one main surface of the base; and positioning the cathode foil so as to be in contact with the solid electrolyte layer.

Images