WO2025052903A1 - Solid electrolytic capacitor element, solid electrolytic capacitor, and method for manufacturing solid electrolytic capacitor element - Google Patents

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

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

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 then a metal foil is laminated on top of the carbon layer to form a cathode foil.

JP 2019-79866 A

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 may leak, which causes a problem in productivity. In addition, due to the presence of interface resistance between the solid electrolyte layer and the carbon layer, and between the carbon layer and the cathode foil, the resistance value of the solid electrolytic capacitor element increases as the number of layers increases.
Under 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.

The conductive polymers used in the solid electrolyte layer are often mixed with dopants to improve conductivity. Because a strongly acidic material is used as the dopant, the materials that make up the solid electrolyte layer as a whole exhibit a strongly acidic nature.

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 is not denatured and no problem occurs. However, when the solid electrolyte layer is in direct contact with the cathode foil, a problem occurs in that the cathode foil is corroded and dissolved due to contact with the strongly acidic material.
If the metal foil melts, a void will be created, resulting in complete insulation and the capacitor may stop functioning.

The present invention has been made to solve the above problems, and aims 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 caused by contact between the solid electrolyte layer and the cathode foil is prevented.

The solid electrolytic capacitor element of the present invention comprises a valve metal substrate having a dielectric layer on at least one of its main surfaces, 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 the copper foil, the passivation coating having a thickness of 1 nm or more and 1 μm or less.

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, the anode 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.

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 substrate having a dielectric layer on at least one of its main surfaces, and arranging the cathode foil so that it is in contact with the solid electrolyte layer.

The present invention provides a solid electrolytic capacitor element in which the resistance is low due to the 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.

FIG. 1 is a perspective view illustrating a schematic 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 AA. FIG. 2B is a cross-sectional view of another example of a solid electrolytic capacitor. FIG. 3 is a cross-sectional view illustrating a schematic example of a solid electrolytic capacitor element. FIG. 4 is a cross-sectional view illustrating a schematic diagram of another example of a solid electrolytic capacitor. FIG. 5 is a cross-sectional view illustrating a schematic diagram of another example of a solid electrolytic capacitor element.

The solid electrolytic capacitor element, the solid electrolytic capacitor, and the method for producing the 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 modified and applied as appropriate within the scope of the present invention. Note that the present invention also includes a combination of two or more of the preferred configurations of each embodiment of the present invention described below.

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, the anode 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.

FIG. 1 is a perspective view illustrating a schematic 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 constituting 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. Moreover, the term "rectangular parallelepiped" does not mean a perfect rectangular parallelepiped, and the surface forming the resin molded body may be tapered and not perpendicular to other surfaces, and the corners may be chamfered.

FIG. 1 shows a resin molded body 9 in the shape of a rectangular parallelepiped.
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 surface, a first end face 9a and a second end face 9b facing 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 surface 9c and a top surface 9d which face each other in the thickness direction.
Further, the resin molded body 9 has, as its outer surfaces, a first side surface 9e and a second side surface 9f which face each other in the width direction.

In this specification, the surface 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 along the length direction (L direction) and width direction (W direction) is referred to as the LW surface, and the surface along the width direction (W direction) and thickness direction (T direction) is referred to as the WT surface.

FIG. 2A is a cross-sectional view of the solid electrolytic capacitor shown in FIG. 1 taken along line AA.
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.

The anode 3 comprises a valve metal substrate 4, which has 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 .

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 is made of a copper foil 7c having a passivation film 7d on the surface thereof.
Cathode foil 7 e is connected to cathode external electrode 13 formed on second end surface 9 b (surface of exterior resin) of resin molded body 9 at the cathode side end surface of solid electrolytic capacitor element 20 .

The end of the valve metal substrate 4 on the second end surface 9b side that constitutes the solid electrolytic capacitor element 20 is sealed with an 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 second end surface 9b side is covered with a dielectric layer 5 or otherwise insulated, the end of the valve metal substrate 4 on the second end surface 9b side may be covered with the solid electrolyte layer 7a.

The exterior resin 8 constituting the resin molded body 9 includes at least a resin, and preferably includes a resin and a filler. As the resin, it is preferable to use an insulating resin such as an epoxy resin, a phenol resin, a polyimide resin, a silicone resin, a polyamide resin, or a liquid crystal polymer. The resin molded body 9 may be composed of two or more types of insulating resin. The exterior resin 8 may be in the form of either a solid resin or a liquid resin. As the filler, it is preferable to use inorganic particles such as silica particles, alumina particles, or metal particles. It is more preferable to use a material containing silica particles in a solid epoxy resin and a phenol resin.
As a molding method of the resin molded body, when a solid sealing material is used, it is preferable to use a resin mold such as a compression mold or a transfer mold, and it is more preferable to use a compression mold. When a liquid sealing material is used, it is preferable to use a molding method such as a dispensing method or a printing method. It is preferable to seal a laminate 30 of solid electrolytic capacitor elements 20 consisting of an anode 3, a dielectric layer 5, and a cathode 7 with an exterior resin 8 by compression molding to form a resin molded body 9.

An example of the anode external electrode 11 is one having 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.

An example of the cathode external electrode 13 is one having 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.

FIG. 2B is a cross-sectional view of another example of a solid electrolytic capacitor.
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 is in contact with the solid electrolyte layer 7a. However, the surface of the copper foil 7c does not have the passivation coating 7d in the vicinity of the cathode side end face of the solid electrolytic capacitor element 20 where the cathode foil 7e is not in contact with the solid electrolyte layer 7a. Since the effect of the copper foil having a passivation coating is exerted in the portion where the copper foil is in contact with 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.

The solid electrolytic capacitor element of the present invention comprises a valve metal substrate having a dielectric layer on at least one of its main surfaces, 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 the copper foil, the passivation coating having a thickness of 1 nm or more and 1 μm or less.

Fig. 3 is a cross-sectional view showing a schematic diagram of an example of a solid electrolytic capacitor element 20. The solid electrolytic capacitor element 20 shown in Fig. 3 constitutes a part of the solid electrolytic capacitor 1 shown in Fig. 2A.
A solid electrolytic capacitor element 20 shown in FIG. 3 includes a valve metal base 4 having a dielectric layer 5 on at least one principal surface, 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.

The valve metal constituting the valve metal substrate may be, for example, a single metal such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, silicon, or an alloy containing these metals. Among these, aluminum or an aluminum alloy is preferred.

The shape of the valve metal substrate is not particularly limited, but is preferably a flat plate, more preferably a foil, and the porous portion is preferably an etching layer that has been etched with hydrochloric acid or the like.
The thickness of the valve metal base before etching is preferably 60 μm or more and 180 μm or less. Also, the thickness of the valve metal base (core portion) that is not etched 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 electrostatic capacitance required for the electrolytic capacitor, and the thickness of the porous portions on both sides of the valve metal base combined is preferably 10 μm or more and 120 μm or less.

The dielectric layer is preferably made of an oxide film of the valve metal. For example, when an aluminum foil is used as the valve metal substrate, an oxide film serving 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 to form 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.

Examples of materials constituting the solid electrolyte layer include conductive polymers having a skeleton of pyrroles, thiophenes, anilines, etc. Examples of conductive polymers having 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 a dopant, the material constituting the solid electrolyte layer exhibits strong acidity. In addition, when a dopant exhibiting acidity is added 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.

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

The cathode foil is a metal foil for extending the cathode to a position where it is connected to an external cathode electrode, and has a passivation coating on the surface of the copper foil.
When the metal foil constituting the cathode foil is a 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 film 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 50 μm or less.

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

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

In addition, copper has the lowest redox potential of all metals that form natural oxide films. In other words, it is a desirable metal material that also has the function of preventing corrosion through a passive film. Metal materials with higher redox potentials than copper (gold, platinum, etc.) are chemically very stable, but are expensive, making it difficult to apply them to industrial products in reality.

By providing a passivation coating on the surface of the copper foil, the copper foil is made corrosion-resistant, so that even if the solid electrolyte layer is made of a strongly acidic material and the cathode foil is placed in direct contact with the solid electrolyte layer, the copper foil is prevented from corroding.

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 thickness of the passivation film is 1 nm or more, the function of preventing corrosion of the cathode foil is suitably exhibited, and when the thickness of the passivation film is 1 μm or less, an increase in resistance due to the passivation film can be prevented.
Furthermore, in solid electrolytic capacitors, a relatively high voltage (e.g., 5 V or more, several tens of V or more, or several hundred V) is applied, and applying a high voltage causes a tunneling current to flow through the passivation film. Therefore, even if a passivation film exists, conduction is possible through the passivation film. To improve conduction by the tunneling current, it is better for the passivation film to be thin, and from that perspective, the thickness of the passivation film is set to 1 μm or less.

Regarding the position where the passivation film is provided on the copper foil, the passivation film is preferably provided on the entire main surface of the copper foil, and is preferably 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.
It is also preferable that no passivation film is provided on the end of the copper foil, which is the portion where the end of the copper foil is connected to the external cathode electrode.

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 by only the steps of applying the silane coupling agent to the copper foil and reacting the silane coupling agent, which is a simple process.
The silane coupling agent film is a glass-based film, and therefore has high mechanical strength and chemical stability, making it an excellent passivation film for preventing corrosion of the copper foil.
The silane coupling agent film itself is a film with low electronic conductivity, so it is preferable that the thickness is thin, for example, 20 nm or less. The silane coupling agent film is a highly stable film, so the strength and shape of the film itself can be maintained even if the thickness is reduced.
When the passive film contains a silane coupling agent film, the passive film may consist of only a silane coupling agent film, or the passive film may contain a native copper oxide film and a silane coupling agent film.

By applying a relatively high voltage (e.g., 5 V or more, several tens of V or more, or even several hundred V) to the silane coupling agent coating, electron conduction by tunneling current is possible, making it possible for electrical conduction to occur through the passive coating.

As the copper foil having a silane coupling agent as a passivation coating, a commercially available product can be used.
Specific examples of the silane coupling agent include water-based silane coupling agents, radically polymerizable silane coupling agents, and rubber-modified silane coupling agents.

The passive film preferably includes a chromate film. When the passive film includes a chromate film, the passive film can be formed by subjecting the copper foil to a chromate plating treatment. This process is more complicated and difficult to control than when a silane coupling agent film is formed as the passive film.
Since a chromate coating has higher electronic conductivity than a silane coupling agent coating, the resistance is less likely to become high even if the coating is made thicker than the silane coupling agent coating.
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 thickness too thin.
From this viewpoint, when the passive film is a chromate film, the thickness of the chromate film is preferably 5 nm or more and 1 μm or less.
When the passive film contains a chromate film, the passive film may consist of only a chromate film, or the passive film may contain a natural copper oxide film and a chromate film.

As the copper foil having a chromate coating as a passive coating, a commercially available product can be used.
Specific examples of the chromate coating include a hexavalent chromium chemical conversion coating and a trivalent chromium chemical conversion coating.

The resistance value of the cathode foil is preferably 0.5 Ω or less.
The resistance value of the cathode foil is the resistance value 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.

In addition, as shown in FIG. 2B, the solid electrolytic capacitor element of the present invention does not need to have a passivation coating on the surface of the copper foil near the cathode end face of the solid electrolytic capacitor element.

Next, an example of a method for producing a solid electrolytic capacitor element of the present invention will be described.
The method for producing 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 having a thickness of 1 nm or more and 1 μm or less on its surface; 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.

The cathode foil is prepared by forming a passivation coating having a thickness of 1 nm to 1 μm on the surface of the 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 with the silane coupling agent (for example, hydrolysis reaction by drying or condensation reaction).
Furthermore, a passivation film, which is a chromate film, can be formed by subjecting the copper foil to a chromate plating treatment.
The thickness of the passive film can be adjusted by adjusting the conditions for forming the passive film (for example, adjusting the amount of silane coupling agent applied, adjusting the chromate treatment time).
The cathode foil may also be prepared by commercially purchasing copper foil having a passivation coating.

The solid electrolytic capacitor element can be manufactured by preparing a first sheet having a valve metal substrate with a dielectric layer formed on its surface and a solid electrolyte layer provided on the dielectric layer, and a second sheet which is a cathode foil, and arranging the second sheet which is a cathode foil so that it is in contact with the solid electrolyte layer of the first sheet. When using a cathode foil in which a passivation film is formed on part of the surface of the copper foil, the part on which the passivation film is formed is arranged so that it is in contact with the solid electrolyte layer.

A solid electrolytic capacitor element is obtained by laminating the first sheet and the second sheet.
When manufacturing a solid electrolytic capacitor having a plurality of solid electrolytic capacitor elements stacked together, the first sheet and the second sheet are alternately stacked together to form a laminate, which is then 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.

Other embodiments of the solid electrolytic capacitor element and the solid electrolytic capacitor will be described below.
FIG. 4 is a cross-sectional view showing a schematic diagram of another example of a solid electrolytic capacitor, and FIG. 5 is a cross-sectional view showing a schematic diagram of 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 from each other to prevent them from being short-circuited.
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 (tetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinylether copolymer, etc.), a composition of soluble polyimidesiloxane and epoxy resin, polyimide resin, polyamideimide resin, and derivatives or precursors thereof.

The cathode side end face of the valve metal substrate 4 is covered with a dielectric layer 5 and a solid electrolyte layer 7a.
Other configurations may be similar to those of the solid electrolytic capacitor shown in FIG. 2A and the solid electrolytic capacitor element shown in FIG.

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 a plurality of the solid electrolytic capacitor elements, sealing them with an exterior resin, and forming external electrodes, but the manner of use is not limited to the above-mentioned manner.
For example, it may be used as an element for realizing a capacitor element that is embedded in a substrate that also embeds a capacitor element.
The method for extracting the anode and cathode is not limited to the method using external electrodes formed on the surface of the exterior resin, but may be a method using a lead frame. The anode and cathode can be extracted by connecting the valve metal base to the lead frame at the anode end face and connecting the cathode foil to the lead frame at the cathode end face.

The following is disclosed in this specification:

The present disclosure (1) is a solid electrolytic capacitor element comprising a valve metal substrate having a dielectric layer on at least one of its main surfaces, 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 the copper foil, the passivation coating having a thickness of 1 nm or more and 1 μm or less.

The present disclosure (2) is a solid electrolytic capacitor element according to the present disclosure (1), in which the passive film includes a natural oxide film of copper.

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

The present disclosure (4) is a solid electrolytic capacitor element according to the present disclosure (1) or (2), in which the passive film includes a chromate film.

The present disclosure (5) is a solid electrolytic capacitor element according to the present disclosure (4), in which the thickness of the chromate coating is 5 nm or more.

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

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 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.

The present disclosure (8) is a method for manufacturing a solid electrolytic capacitor element, which 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 of its main surfaces, and arranging the cathode foil so as to be in contact with the solid electrolyte layer.

Reference Signs List 1, 1', 2 Solid electrolytic capacitor 3 Anode 4 Valve 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 9b of resin molded body Second end face 9c of resin molded body Bottom face 9d of resin molded body Top face 9e of resin molded body First side face 9f of resin molded body Second side face 11 of resin molded body Anode external electrode 11b Conductive resin electrode layer 11c Outer plating layer 13 Cathode external electrode 13b Conductive resin electrode layer 13c Outer plating layer 17 Insulating layers 20, 22 Solid electrolytic capacitor element 30 Laminate

Claims (8)

a valve metal substrate having a dielectric layer on at least one of its principal surfaces;
a solid electrolyte layer provided on the dielectric layer;
a cathode foil in direct contact with the solid electrolyte layer;
The cathode foil has a passivation coating on a surface of a copper foil,
A solid electrolytic capacitor element, wherein the thickness of the passivation film is 1 nm or more and 1 μm or less. The solid electrolytic capacitor element according to claim 1, wherein the passive film includes a natural oxide film of copper. The solid electrolytic capacitor element according to claim 1 or 2, wherein the passive coating includes a silane coupling agent coating. The solid electrolytic capacitor element according to claim 1 or 2, wherein the passive film includes a chromate film. The solid electrolytic capacitor element according to claim 4, wherein the thickness of the chromate coating is 5 nm or more. A solid electrolytic capacitor element according to any one of claims 1 to 5, in which the resistance value of the cathode foil is 0.5 Ω or less. A plurality of solid electrolytic capacitor elements according to any one of claims 1 to 6 are stacked and sealed with an exterior resin,
an 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 an anode side end face of the solid electrolytic capacitor element,
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; preparing a cathode foil which is a copper foil having a passivation film 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 at least one main surface thereof;
and placing the cathode foil so as to be in contact with the solid electrolyte layer.

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