Solid electrolytic capacitor element and solid electrolytic capacitor

Abstract

A solid electrolytic capacitor element includes: an anode body provided with a porous portion, a dielectric layer, and a cathode portion. The cathode portion includes a solid electrolyte layer covering the dielectric layer. The anode body includes a first anode body portion in which the solid electrolyte layer is formed, and a second anode body portion in which the solid electrolyte layer is not formed. The solid electrolyte layer includes a first solid electrolyte layer disposed in the porous portion, and a second solid electrolyte layer disposed outside the porous portion. When a length of a long side direction of the first anode body portion is set as a length L, a layer thickness of the second solid electrolyte layer in a first region between an interface of the first anode body portion and the second anode body portion and a position at which a length from the interface is 0.05L is 1 μm or more.

Description

Technical Field

[0001] This invention relates to solid electrolytic capacitor elements and solid electrolytic capacitors. Background Technology

[0002] A solid electrolytic capacitor comprises: a solid electrolytic capacitor element having a solid electrolyte layer, lead terminals electrically connected to the solid electrolytic capacitor element, and an outer casing sealing the solid electrolytic capacitor element. The solid electrolytic capacitor element, for example, comprises: an anode body having porous portions on its surface, a dielectric layer formed on at least a portion of the surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode lead layer covering at least a portion of the solid electrolyte layer.

[0003] Patent Document 1 (International Publication No. 2013 / 080486) discloses "a capacitor characterized in that it comprises: a substrate including a valve metal and having opposing first and second surfaces; a first roughening layer formed by vapor deposition of the valve metal on the first surface and having an outer surface and internal voids; a first conductive polymer inner layer formed in the voids of the first roughening layer; a first conductive polymer outer layer formed on the outer surface of the first roughening layer; a second roughening layer formed by vapor deposition of the valve metal on the second surface and having an outer surface and internal voids; a second conductive polymer inner layer formed in the voids of the second roughening layer; a second conductive polymer outer layer formed on the outer surface of the second roughening layer; and a dielectric film formed on the surfaces of the first and second roughening layers, wherein the surface area of ​​the second roughening layer is smaller than that of the first roughening layer, and the second conductive polymer outer layer is thicker than the first conductive polymer outer layer."

[0004] Patent document 2 (Japanese Patent Application Publication No. 11-87177) discloses "a solid electrolytic capacitor, characterized in that, in a solid electrolytic capacitor in which a conductive polymer compound formed by chemical oxidation polymerization is used as a solid electrolyte, the thickness of the conductive polymer compound layer at the center of the capacitor element is at least 0.02 μm."

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2013 / 080486

[0008] Patent Document 2: Japanese Patent Application Publication No. 11-87177 Summary of the Invention

[0009] One aspect of the present invention relates to a solid electrolytic capacitor element. The solid electrolytic capacitor element includes: an anode body having a porous surface, a dielectric layer covering at least a portion of the anode body, and a cathode portion covering at least a portion of the dielectric layer. The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer. The anode body includes a first anode body portion having the solid electrolyte layer formed thereon and a second anode body portion not having the solid electrolyte layer formed thereon. The solid electrolyte layer includes a first solid electrolyte layer disposed within the porous surface and a second solid electrolyte layer disposed outside the porous surface. When the length of the long side of the first anode body portion is defined as length L, in a first region between the interface of the first anode body portion and the second anode body portion and a position where the distance from the interface to the first anode body portion is 0.05L, the thickness of the second solid electrolyte layer is 1 μm or more.

[0010] Another aspect of the invention relates to an electrolytic capacitor. This electrolytic capacitor comprises the solid electrolytic capacitor element of the present invention.

[0011] According to the present invention, the reduction of capacitance of solid electrolytic capacitors can be suppressed. Attached Figure Description

[0012] Figure 1 A cross-sectional view illustrating an example of a capacitor element in Embodiment 1 of the present invention.

[0013] Figure 2 for Figure 1 An enlarged view of a portion of the cross-section of the capacitor element shown.

[0014] Figure 3 A cross-sectional view illustrating another example of the capacitor element in Embodiment 1.

[0015] Figure 4 A cross-sectional view illustrating an example of the electrolytic capacitor of Embodiment 2.

[0016] Figure 5 A cross-sectional view illustrating another example of the electrolytic capacitor of Embodiment 2. Detailed Implementation

[0017] Before describing the implementation methods, the issues in the prior art are briefly shown below.

[0018] In solid electrolytic capacitors, oxygen from the external air can sometimes penetrate into the capacitor element. If this intruding oxygen comes into contact with the solid electrolyte layer within the capacitor element, the solid electrolyte deteriorates, leading to a decrease in the capacitance of the solid electrolytic capacitor. The decrease in capacitance caused by oxygen intrusion becomes significant at high temperatures.

[0019] In view of the above-mentioned problems, the present invention provides a solid electrolytic capacitor element and a solid electrolytic capacitor capable of suppressing the reduction of capacitance of a solid electrolytic capacitor.

[0020] Hereinafter, examples of embodiments of the present invention will be described. It should be noted that the embodiments of the present invention are illustrated by examples in the following description, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials are illustrated, but other numerical values ​​and materials can be applied as long as the effects of the present invention are achieved. In this specification, when referred to as the "range of numerical value A to numerical value B," this range includes both numerical value A and numerical value B.

[0021] (Solid electrolytic capacitor element)

[0022] The solid electrolytic capacitor element of this embodiment includes: an anode body having a porous surface, a dielectric layer covering at least a portion of the anode body, and a cathode portion covering at least a portion of the dielectric layer. The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer. The anode body includes a first anode body portion having a solid electrolyte layer formed thereon and a second anode body portion not having a solid electrolyte layer formed thereon. The solid electrolyte layer includes a first solid electrolyte layer disposed within the porous surface and a second solid electrolyte layer disposed outside the porous surface. When the length of the long side of the first anode body portion is defined as length L, in a first region between the interface of the first anode body portion and the second anode body portion and a position of the first anode body portion at a distance of 0.05L from the interface, the thickness of the second solid electrolyte layer is 1 μm or more. Hereinafter, the interface between the first anode body portion and the second anode body portion may be referred to as "interface (B)". Furthermore, the solid electrolytic capacitor element of this embodiment may be referred to as "capacitor element (CE)". Furthermore, there is a case where the region between the interface (B) and the first anode body, at a distance of 0.05L from the interface (B), is referred to as "region (R1)".

[0023] As a result of their research, the inventors discovered that because the second solid electrolyte layer is thinner near its ends, oxygen can penetrate from this thinner portion, leading to a decrease in electrostatic capacitance. This invention is based on this new insight.

[0024] In the capacitor element (CE), the thickness of the end (region (R1)) of the second solid electrolyte layer is 1 μm or more. Therefore, oxygen intrusion from this end is suppressed. As a result, the reduction in characteristics (e.g., capacitance) caused by oxygen intrusion is suppressed in the capacitor element (CE) and the solid electrolytic capacitor using the capacitor element (CE).

[0025] The thickness of the second solid electrolyte layer in region (R1) can be greater than 2 μm or greater than 5 μm. There is no specific upper limit to the thickness of the second solid electrolyte layer in region (R1), and it can be less than 30 μm. As long as these lower and upper limits do not contradict each other, they can be combined arbitrarily.

[0026] The minimum thickness of the second solid electrolyte layer in the region between the interface (B) and the first anode body at a distance of 0.05L from the interface (B) is defined as layer thickness T1. The thickness of the second solid electrolyte layer at a distance of 0.5L from the interface (B) of the first anode body is defined as layer thickness T2. In this case, layer thickness T1 can be greater than 0.5 times (e.g., 0.7 times) of layer thickness T2. Layer thickness T1 can be less than 3 times (e.g., less than 1.5 times) of layer thickness T2. For example, layer thicknesses T1 and T2 can satisfy 0.7T2 < T1 < 1.5T2. By satisfying 0.7T2 < T1, oxygen intrusion can be particularly suppressed. By satisfying T1 < 1.5T2, the parallelism of the component can be improved during welding of the stacked anode body, and defects such as exposure can be reduced.

[0027] The average thickness of the first solid electrolyte layer can be 30 nm or more (e.g., 50 nm or more). This configuration allows for the full utilization of the initial electrical characteristics of the solid electrolytic capacitor, and is therefore preferred. Here, the average layer thickness is obtained by measuring the thickness of the first solid electrolyte layer at any five points and averaging the five measurements. The thickness of the first solid electrolyte layer at any point can be measured, for example, using a cross-sectional scanning electron microscope (SEM) image.

[0028] On the surface of the first anode body, an adhesive comprising at least one element selected from C, N, O, and Si may be present. In this case, the amount of adhesive in the region between the interface (B) and the position of the first anode body at a distance of 0.03L from the interface (B) is preferably less than the amount of adhesive in the region between the position of the first anode body at a distance of 0.03L from the interface (B) and the position of the first anode body at a distance of L from the interface (B). With this configuration, thinning of the end of the second solid electrolyte layer can be prevented.

[0029] In the region between the interface (B) and the first anode portion at a distance of 0.03L from the interface (B), a binder comprising at least one element selected from C, N, O, and Si may be present. In this case, it is preferable that no binder is present in the region between the position of the first anode portion at a distance of 0.03L from the interface (B) and the position of the first anode portion at a distance of L from the interface (B). With this configuration, thinning of the end of the second solid electrolyte layer can be prevented. The binder can be analyzed, for example, by elemental analysis.

[0030] In the manufacture of solid electrolytic capacitor elements, adhesives are sometimes used in the first anode portion. For example, adhesives are sometimes used to bond wiring for the electrolytic polymer solid electrolyte layer, or to bond insulating tape. The inventors have recently discovered that these adhesives diffuse to the vicinity of the end of the second solid electrolyte layer, resulting in thinning of the end of the second solid electrolyte layer. By reducing the amount of adhesive remaining near the end of the second solid electrolyte layer, thinning of the end of the second solid electrolyte layer can be prevented.

[0031] Examples of the above-mentioned adhesives containing at least one element selected from C, N, O and Si include acrylic adhesives, silicone adhesives, etc.

[0032] In a capacitor element (CE), it is preferable to prevent oxygen from penetrating from the second anode body portion into the solid electrolyte layer. Therefore, it is preferable that the surface of the portion of the second anode body portion adjacent to the first anode body portion contains a material with high oxygen barrier properties. Examples of such materials include insulating resins, compositions containing insulating resins, insulating tapes, and metals that are substantially free of voids. For example, the oxygen barrier properties of this portion can be improved by removing or compressing the porous portion present on the surface of the portion of the second anode body portion adjacent to the first anode body portion. Alternatively, the porous portion present on the surface of the portion of the second anode body portion adjacent to the first anode body portion can be coated with insulating resin (or a composition containing insulating resin), or an insulating tape can be disposed on the porous portion.

[0033] The second anode body may include an anode end and a separation portion disposed between the anode end and the first anode body. In this case, a first insulating resin may be disposed in at least a portion of the separation portion. With this configuration, short circuits between the anode end and the cathode portion can be suppressed. Furthermore, with this configuration, oxygen intrusion from the separation portion can be suppressed. When the separation portion has porous portions on its surface, the first insulating resin may be disposed in the pores of the porous portions.

[0034] Examples of the first insulating resin include insulating tapes (such as photoresist tapes) and films containing the first insulating resin. That is, a resin composition containing the first insulating resin can be disposed in at least a portion of the separation section.

[0035] The first insulating resin can be a thermoplastic resin or a curable resin. The first insulating resin may contain one or more types of insulating resin. Examples of thermoplastic resins include polyolefins, polyesters, polyamides, and thermoplastic polyimides. The curable resin can be a thermosetting resin or a photocurable resin. Examples of photocurable resins include resins cured by ultraviolet or visible light. Examples of thermosetting resins include epoxy resins, phenolic resins, unsaturated polyester resins, thermosetting polyurethane resins, thermosetting polyimides, and photoresists. The resin composition containing the first insulating resin may also contain components other than the first insulating resin (e.g., curing agents, curing accelerators, catalysts, additives, etc.).

[0036] When the second anode body includes an anode end and a separation portion, the second anode body may have a recess formed in the separation portion. The aforementioned first insulating resin may be disposed in this recess. For example, an insulating tape (resist tape, etc.) containing the first insulating resin may be disposed in this recess.

[0037] The capacitor element (CE) may include a second insulating resin disposed on the outer surface of the portion of the second solid electrolyte layer adjacent to the interface (B). With this configuration, short circuits between the anode and cathode portions can be suppressed. Furthermore, with this configuration, oxygen intrusion via the second solid electrolyte layer can be particularly suppressed.

[0038] The second insulating resin can be a thermoplastic resin or a curing resin. The second insulating resin can contain one or more types of insulating resin. The first insulating resin and the second insulating resin can be the same or different.

[0039] Examples of thermoplastic resins used as the second insulating resin include at least one selected from vinyl resins (e.g., vinyl chloride, vinyl acetate, aromatic vinyl resins), polyolefins (e.g., polyethylene, polypropylene), acrylic resins, polyamides, polycarbonates, thermoplastic polyimides, and polyamide-imides. Examples of aromatic vinyl resins include polystyrene and acrylonitrile-butadiene-styrene copolymer (ABS resin). Those exemplified in the second insulating resin can also be used as the curing resin for use as the second insulating resin.

[0040] The second insulating resin can be configured on the second solid electrolyte layer, for example, by applying a coating liquid or resin composition containing the second insulating resin onto the second solid electrolyte layer and allowing it to dry or cure.

[0041] (Examples of the components that make up a capacitor element (CE))

[0042] Examples of constituent components for a capacitor element (CE) are described below. For constituent components other than the characteristic portions of this invention, known constituent components may be used.

[0043] (Anode)

[0044] As described above, the anode body comprises a first anode body portion having a solid electrolyte layer formed thereon, and a second anode body portion not having a solid electrolyte layer formed thereon. The anode body may contain a valve-acting metal, an alloy containing a valve-acting metal, or a compound containing a valve-acting metal. These materials may be used individually or in combination of two or more. For example, aluminum, tantalum, niobium, and titanium are preferred as valve-acting metals. An anode body with porous surfaces can be obtained, for example, by roughening the surface of a metal foil containing a valve-acting metal. Roughening can be performed by electrolytic etching or the like. The anode body as a whole can be porous. However, from a strength point of view, the anode body preferably includes porous portions disposed on two main surfaces and a core portion disposed between these porous portions. The porosity of the core portion is lower than the porosity of the porous portions. Porous portions are regions having a large number of fine pores. The core portion is, for example, a region that has not been electrolytically etched.

[0045] (Dielectric layer)

[0046] The dielectric layer is an insulating layer that functions as a dielectric. It is formed by anodizing a valve-operated metal on the surface of an anode (e.g., a metal foil). The dielectric layer only needs to be formed in a manner that covers at least a portion of the anode. The dielectric layer is typically formed on the surface of the anode. Because it is formed on the porous surface of the anode, the dielectric layer forms along the inner walls of the pores and recesses (also called pits) on the surface of the anode.

[0047] A typical dielectric layer contains an oxide of the valve-acting metal. For example, a typical dielectric layer using tantalum as the valve-acting metal contains Ta₂O₅, and a typical dielectric layer using aluminum as the valve-acting metal contains Al₂O₃. It should be noted that the dielectric layer is not limited to these types; it only needs to function as a dielectric.

[0048] (Cathode section)

[0049] The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer, and may further include a cathode lead-out layer covering at least a portion of the solid electrolyte layer. The solid electrolyte layer and the cathode lead-out layer will be described below.

[0050] (Solid electrolyte layer)

[0051] As described above, the solid electrolyte layer includes a first solid electrolyte layer disposed within the porous portion of the anode body (more specifically, the void portion of the porous portion) and a second solid electrolyte layer disposed outside the porous portion.

[0052] The solid electrolyte layer comprises a conductive polymer. If desired, the solid electrolyte layer may further comprise at least one selected from dopants and other additives. Examples of dopants include, but are not limited to, p-toluenesulfonic acid, naphthalenesulfonic acid, and polystyrenesulfonic acid (PSS).

[0053] As conductive polymers, π-conjugated polymers can be used, for example. Examples of conductive polymers include those with polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylidene, polyphenylene oxide, and polythiophene vinylidene as their basic backbone. These polymers also include homopolymers, copolymers of two or more monomers, and their derivatives (substitutes with substituents, etc.). For example, polythiophene includes poly(3,4-ethylenedioxythiophene). However, these are merely examples, and conductive polymers are not limited to these examples.

[0054] The solid electrolyte layer only needs to be formed in a manner that covers at least a portion of the dielectric layer. The solid electrolyte layer can be formed directly on the dielectric layer or via a conductive pre-coating. The pre-coating can be formed, for example, from a conductive material (conductive polymer, inorganic conductive material, etc.). There are no particular limitations on the conductive material constituting the pre-coating; for example, those known to be used can be employed.

[0055] (Cathode lead-out layer)

[0056] The cathode lead-out layer may have at least a first layer that contacts and covers at least a portion of the solid electrolyte layer, or it may have a first layer and a second layer covering the first layer. Examples of the first layer include a layer containing conductive particles, a metal foil, etc. Examples of conductive particles include at least one selected from conductive carbon and metal powder. For example, a layer containing conductive carbon (hereinafter referred to as a "carbon layer") may be used as the first layer, and a layer containing metal powder or a metal foil may be used as the second layer, and these two layers may be used to form the cathode lead-out layer. When a metal foil is used as the first layer, the cathode lead-out layer may be formed using this metal foil. Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0057] When using a layer containing metal powder as the second layer, the second layer can be formed by laminating a composition containing metal powder onto the surface of the first layer. Examples of such a second layer include a metal paste layer formed using a composition containing metal powder such as silver particles and a resin (binder resin). Thermoplastic resins can also be used as the resin, but thermosetting resins such as imide resins and epoxy resins are preferred.

[0058] When using metal foil as the first layer, the type of metal is not particularly limited, but valve-acting metals such as aluminum, tantalum, and niobium, or alloys containing valve-acting metals, are preferred. The surface of the metal foil can be roughened as needed. A chemical conversion coating or a coating of a different metal (dissimilar metal) or non-metal can be applied to the surface of the metal foil. Examples of dissimilar metals or non-metals include metals such as titanium and non-metals such as carbon (conductive carbon, etc.).

[0059] The aforementioned dissimilar metal or non-metal (e.g., conductive carbon) coating can be used as the first layer, and the aforementioned metal foil can be used as the second layer.

[0060] (Solid electrolytic capacitor)

[0061] The solid electrolytic capacitor of this embodiment includes at least one solid electrolytic capacitor element. This solid electrolytic capacitor element is the aforementioned capacitor element (CE). It should be noted that the solid electrolytic capacitor may include solid electrolytic capacitor elements other than capacitor elements (CE). In a preferred embodiment, all solid electrolytic capacitor elements included in the solid electrolytic capacitor are capacitor elements (CE). The number of solid electrolytic capacitor elements included in the solid electrolytic capacitor can be in the range of 1 to 20 (e.g., 2 to 20).

[0062] In electrolytic capacitors comprising multiple capacitor elements (CEs), these capacitor elements (CEs) can be stacked. Typically, the second anode bodies (e.g., anode ends) of the stacked capacitor elements (CEs) are electrically connected to each other. For example, these second anode bodies can be joined by welding. Multiple second anode bodies can also be welded after being riveted to anode lead terminals. Anode lead terminals can be joined to at least one second anode body.

[0063] Typically, the cathode lead layers of stacked capacitor elements are electrically connected to each other. Cathode lead terminals can be joined to the cathode lead layer of at least one capacitor element. The cathode lead terminals can be joined to the cathode lead layer via a conductive adhesive or solder. Alternatively, the cathode lead terminals can also be joined to the cathode lead layer by welding (resistance welding, laser welding, etc.). The conductive adhesive is, for example, a mixture of a curable resin and carbon or metal particles.

[0064] The solid electrolytic capacitor may further include an outer casing and / or a housing that seals the at least one solid electrolytic capacitor element. The housing may include a container such as a bottom casing and a sealing body that seals the opening of the container. Examples of materials constituting the container and the sealing body include, for example, metallic materials and resin materials.

[0065] The outer casing preferably comprises a cured product containing a curable resin composition, but may also contain a thermoplastic resin or a composition containing the same. The curable resin composition may include a curable resin and a filler. A thermosetting resin is preferred as the curable resin. Examples of resin materials constituting the casing include thermoplastic resins or compositions containing the same. Examples of metal materials constituting the casing include metals such as aluminum, copper, and iron, or their alloys (including stainless steel and brass).

[0066] One end of the anode lead terminal and one end of the cathode lead terminal are exposed outside the outer casing or housing. These ends are used for solder connection to the substrate on which the solid electrolytic capacitor is mounted, etc.

[0067] (Solid electrolytic capacitor elements and manufacturing methods of solid electrolytic capacitors)

[0068] The manufacturing method of the capacitor element (CE) and solid electrolytic capacitor in this embodiment is not particularly limited. In these manufacturing methods, apart from controlling the thickness of the second solid electrolyte layer, known manufacturing methods can be applied, or a portion of a known manufacturing method can be modified.

[0069] The following describes an example of the manufacturing method of the capacitor element (CE) and solid electrolytic capacitor according to this embodiment. However, the capacitor element (CE) and solid electrolytic capacitor of this embodiment can also be manufactured using methods other than those described below. The matters described for the capacitor element (CE) and solid electrolytic capacitor can also be applied to the manufacturing method described below, therefore, there are instances where repeated descriptions are omitted. Furthermore, the matters described for the manufacturing method described below can be applied to the capacitor element (CE) and solid electrolytic capacitor of this embodiment.

[0070] An example of a method for manufacturing a solid electrolytic capacitor includes: a process of fabricating a capacitor element, a process of electrically connecting lead terminals to the capacitor element, and a process of covering a portion of the capacitor element and lead terminals with an outer casing. Examples of these processes are described below.

[0071] (The process of manufacturing capacitor components)

[0072] The capacitor element is manufactured in the following order. The steps for manufacturing the capacitor element include: forming an anode body with porous portions, forming a dielectric layer on the surface of the anode body, forming a solid electrolyte layer, and forming a cathode lead-out layer. The manufacturing method of a solid electrolytic capacitor may further include a step of forming a separation portion before the step of forming the solid electrolyte layer.

[0073] (1) Process of forming an anode with porous portion

[0074] As the raw material for the anode, a metal foil containing a valve-acting metal can be used, for example. The porous portion can be formed, for example, by roughening the surface of the metal foil containing the valve-acting metal. By roughening the surface, a porous portion is formed on the surface of the anode (metal foil). Inside the metal foil, an unroughened substrate portion can exist. Roughening can be performed, for example, by etching (e.g., electrolytic etching) the surface of the metal foil.

[0075] (2) Process of forming dielectric layer

[0076] In this process, a dielectric layer is formed on the anode body. The dielectric layer can be formed by anodizing the surface of the metal foil that becomes the anode body. Anodizing can be performed by known methods, such as chemical conversion treatment. Chemical conversion treatment can be performed by applying a voltage between the anode body (anode) immersed in a chemical conversion solution and the cathode immersed in the chemical conversion solution. For example, an aqueous solution of phosphoric acid is preferably used as the chemical conversion solution.

[0077] It should be noted that the process of forming the dielectric can be carried out in one stage or in multiple stages. For example, the process of forming the dielectric layer can be carried out again after forming the dielectric layer and then carrying out other processes.

[0078] When forming a separation section on the anode body, the anode body (metal foil) before or after forming the dielectric layer is divided into an anode end, a separation section, and a first anode body section. For example, the separation section can be formed by making a portion of the anode body a thin-walled section. The thin-walled section can be formed by compressing or removing the porous portion of the region that becomes the separation section. Compression can be performed by pressing or the like. Removal of the porous portion can be performed by cutting, laser processing, or the like.

[0079] Separation members can be disposed on the surface of the separation section. The process of disposing of the separation members is performed before the process of forming the solid electrolyte layer, thereby preventing the formation of conductive polymers on the anode end side during the formation of the solid electrolyte layer. When the separation members are bonded with an adhesive, there is a possibility that heating can be used to increase the adhesive strength of the separation members. If the heating temperature is increased, the adhesive easily diffuses to the second anode body. At the locations where the adhesive diffuses, the second solid electrolyte layer may become thinner. Therefore, it is preferable not to heat the separation members during bonding, or to set the heating temperature to a low level (e.g., below 70°C).

[0080] (3) Process of forming solid electrolyte layer

[0081] A solid electrolyte layer can be formed, for example, by using a treatment solution containing a precursor of a conductive polymer and polymerizing the precursor on a dielectric layer. The polymerization can be carried out by at least one of chemical polymerization and electrolytic polymerization. In the case of electrolytic polymerization, a conductive pre-coating can be formed prior to the electrolytic polymerization. Examples of precursors for the conductive polymer include at least one selected from monomers, oligomers, and prepolymers.

[0082] A solid electrolyte layer can be formed by drying after adhering a treatment liquid (e.g., a dispersion or solution) containing a conductive polymer to the dielectric layer. Examples of dispersion media (or solvents) include water, organic solvents, or mixtures thereof. The treatment liquid may further contain other components (selected from at least one of dopants and additives).

[0083] A portion of the solid electrolyte layer is formed within the porous portion (more specifically, the void portion of the porous portion), while the remaining portion is formed outside the porous portion. As a result, a first solid electrolyte layer disposed within the porous portion and a second solid electrolyte layer disposed outside the porous portion are formed.

[0084] When a solid electrolyte layer is formed by electrolytic polymerization, there are cases where the conductive strip used to supply electricity is placed near the second anode body during electrolytic polymerization. In this case, the adhesive used to fix the conductive strip may diffuse into the second anode body. At the sites of adhesive diffusion, the second solid electrolyte layer may become thinner. Therefore, when the conductive strip is placed near the second anode body, it is preferable to set a certain distance between the second anode body and the conductive strip. This can suppress deviations in the thickness of the second solid electrolyte layer and prevent localized thinning of the second solid electrolyte layer.

[0085] The case of forming a solid electrolyte layer by electrolytic polymerization after forming a pre-coating was investigated. In this case, if the formation of the pre-coating near interface B is insufficient, the second solid electrolyte layer near interface B becomes thinner. Therefore, it is important to form the pre-coating sufficiently up to the vicinity of interface B. For example, when forming a pre-coating, it is preferable to also form the pre-coating in the region between interface B and the first anode body at a distance of 0.05L from interface B.

[0086] (4) Process of forming cathode lead-out layer

[0087] In this process, a cathode lead-out layer is formed on the surface of the solid electrolyte layer. The cathode lead-out layer can be formed, for example, by sequentially coating the solid electrolyte layer with carbon paste and silver paste. In this way, a capacitor element (CE) is formed.

[0088] (5) Manufacturing of solid electrolytic capacitors

[0089] Next, using capacitor elements (CE), a solid electrolytic capacitor is manufactured using the following method. An example of a method for manufacturing a solid electrolytic capacitor comprising multiple capacitor elements (CE) will be described below.

[0090] First, a laminate is fabricated by stacking multiple capacitor elements (CE). The anode ends of the multiple capacitor elements are joined together to form an electrical connection, such as by welding and / or riveting. Adjacent cathode lead layers can be connected using a metal paste or the like. If necessary, anode lead terminals are connected to anode terminal sections, and cathode lead terminals are connected to cathode lead layers.

[0091] As described above, a laminate of multiple capacitor elements (CE) is obtained. Next, the obtained laminate and a portion of the lead terminals are sealed using an outer casing. Sealing can be performed using known molding techniques (injection molding, insert molding, compression molding, etc.). For example, a predetermined mold can be used, and the material (resin composition) of the outer casing can be configured to cover a portion of the laminated solid electrolytic capacitor elements and lead terminals, followed by heating. In this way, the outer casing is formed.

[0092] Examples of embodiments of the present invention will be specifically described below with reference to the accompanying drawings. The constituent elements described above can be applied to the constituent elements of the examples described below. Furthermore, the examples described below can be modified based on the above description. Additionally, the matters described below can also be applied to the above embodiments. Furthermore, in the embodiments described below, non-essential constituent elements of the solid electrolytic capacitor element and solid electrolytic capacitor of the present invention can be omitted. The solid electrolytic capacitor element and solid electrolytic capacitor described below can be manufactured by the above method. It should be noted that the following figures are schematic and may differ from actual configurations.

[0093] (Implementation Method 1)

[0094] Figure 1 This is a schematic cross-sectional view of the solid electrolytic capacitor element of Embodiment 1. Figure 1 The capacitor element 100 shown includes an anode body 110, a dielectric layer 113 covering at least a portion of the anode body 110, and a cathode portion 130 covering at least a portion of the dielectric layer 113. The cathode portion 130 includes a solid electrolyte layer 120 covering at least a portion of the dielectric layer 113, and a cathode lead-out layer 131 covering at least a portion of the solid electrolyte layer 120. The cathode lead-out layer 131 includes a carbon layer 131a disposed on the solid electrolyte layer 120, and a metal paste layer 131b disposed on the carbon layer 131a. On the surface of the anode body 110, the main surface on which the solid electrolyte layer 120 is formed is roughened to form a porous portion (see reference). Figure 2 ).

[0095] The anode body 110 includes a first anode body portion 111 and a second anode body portion 112. A solid electrolyte layer 120 is disposed on the first anode body portion 111. No solid electrolyte layer is disposed on the second anode body portion 112. The second anode body portion 112 includes an anode end 112a and a separation portion 112b. The separation portion 112b is disposed between the anode end 112a and the first anode body portion 111.

[0096] exist Figure 1 In the diagram, for ease of understanding, the interface B between the first anode body and the second anode body is represented by a dashed line. Additionally, the interface between the anode end 112a and the separation portion 112b is also represented by a dashed line. The separation portion 112b is thinner than the other parts of the anode body 110. A separation member 140 is disposed on the separation portion 112b. The separation member 140 is insulating. The separation member 140 may contain the aforementioned first insulating resin.

[0097] Let the length of the long side of the first anode body 111 be L. Figure 1 The interface B between the first anode body and the second anode body is shown. Furthermore, in... Figure 1 The region R1 is shown between interface B and the first anode body 111 at a distance of 0.05L from interface B. Furthermore, in Figure 1 The region R2 is shown between interface B and the first anode body 111 at a distance of 0.03L from interface B. It should be noted that lengths 0.03L and 0.05L are lengths along the long side of the first anode body 111.

[0098] exist Figure 2 This schematically shows an enlarged cross-section of the solid electrolyte layer 120 formed on the first anode body 111. (See diagram below.) Figure 2 As shown, the first anode body portion 111 has a porous portion 111a on its surface. The solid electrolyte layer 120 includes a first solid electrolyte layer 121 disposed within the porous portion 111a and a second solid electrolyte layer 122 disposed outside the porous portion 111a. In other words, the second solid electrolyte layer 122 is disposed outside the first anode body portion 111. The first solid electrolyte layer 121 and the second solid electrolyte layer 122 are connected and constitute the solid electrolyte layer 120.

[0099] exist Figure 2 The thickness ta of the first solid electrolyte layer 121 and the thickness tb of the second solid electrolyte layer 122 at a certain point P are shown. Unevenness exists at the boundary between the porous portion 111a and other portions. However, since the unevenness is minute relative to the thickness of the solid electrolyte layer, the boundary between the porous portion 111a and other portions can be considered as a plane when measuring the thickness of the solid electrolyte layer.

[0100] As described above, in the region R1 between the interface B between the first anode body 111 and the second anode body 112 and a position 0.05L away from the interface B, the thickness of the second solid electrolyte layer 122 is 1 μm or more. With this configuration, it is possible to suppress oxygen from penetrating into the portion of the first solid electrolyte layer 121 through the thinner portion of the second solid electrolyte layer 122. Therefore, it is possible to suppress the degradation of device characteristics caused by oxygen.

[0101] The minimum thickness of the second solid electrolyte layer 122 in the region between interface B and the first anode body 111 at a distance of 0.05L from interface B is defined as layer thickness T1. The thickness of the second solid electrolyte layer 122 at a position where the first anode body 111 is 0.5L from interface B is defined as layer thickness T2. Layer thickness T1 and layer thickness T2 can satisfy the above relationship. Furthermore, the average thickness of the first solid electrolyte layer can be within the above range.

[0102] When an adhesive containing at least one element selected from C, N, O and Si is present on the surface of the first anode body portion 111, the amount of adhesive may be the amount described above.

[0103] On the outer surface of the portion of the second solid electrolyte layer 122 adjacent to interface B, a layer comprising the aforementioned second insulating resin may be formed. Figure 3 The diagram schematically shows a cross-sectional view of a capacitor element 100 including such a layer 142. Layer 142 is formed such that it covers the portion of the second solid electrolyte layer 122 adjacent to interface B. The area near interface B in the second solid electrolyte layer 122 tends to be thinned. According to... Figure 3The configuration shown reduces the amount of oxygen passing through the easily thinned second solid electrolyte layer 122.

[0104] (Implementation Method 2)

[0105] Figure 4 This is a schematic cross-sectional view of the solid electrolytic capacitor of Embodiment 2. Figure 4 The electrolytic capacitor 200 shown includes a capacitor element 100, an anode lead terminal 211, a cathode lead terminal 212, and an outer casing 230.

[0106] Anode lead terminal 211 is connected to anode end 112a. Cathode lead terminal 212 is connected to cathode lead layer 131 via conductive member 213 such as metal paste. A portion of anode lead terminal 211 and a portion of cathode lead terminal 212 are exposed from outer casing 230. The exposed portions function as terminals. Outer casing 230 is configured to cover the entire capacitor element 100.

[0107] Electrolytic capacitor 200 uses capacitor element 100. Therefore, according to electrolytic capacitor 200, it is possible to suppress the decrease in capacitance caused by oxygen.

[0108] It should be noted that the solid electrolytic capacitor of the present invention may comprise multiple capacitor elements. Figure 5 This schematically illustrates an example of a solid electrolytic capacitor comprising multiple capacitor elements 100. Figure 5 The electrolytic capacitor 200 comprises a plurality of capacitor elements 100 stacked and connected in parallel. The plurality of capacitor elements 100 are covered by an outer casing 230.

[0109] Example

[0110] The solid electrolytic capacitor element and solid electrolytic capacitor of the present invention will be described in more detail through embodiments.

[0111] [Preparation and Evaluation of Electrolytic Capacitor A1]

[0112] A solid electrolytic capacitor (electrolytic capacitor A1) is manufactured using the method described below. Electrolytic capacitor A1 comprises seven capacitor elements stacked and connected in parallel. Each capacitor element has a structure similar to that of capacitor element 100 described in Embodiment 1.

[0113] (1) Fabrication of capacitor components

[0114] First, the surface of an aluminum foil (100 μm thick) is etched to obtain an anode foil (anode body) containing porous portions disposed on the surface. This anode foil is then immersed in a 0.3% by mass phosphoric acid solution (at 70°C) and a DC voltage of 70 V is applied for 20 minutes. This voltage application forms a dielectric layer containing aluminum oxide (Al₂O₃) on the surface of the anode foil.

[0115] Next, the portion of the anode foil that becomes the separation section is compressed by pressing to create a recess. Then, an insulating resist tape (separation member) is attached to the recess. At this point, the separation member is firmly bonded to the recess by heat treatment. The heat treatment is performed at 70°C for 24 hours. Thus, a separation section with the separation member is formed.

[0116] Next, a pre-coating is formed on the anode foil by immersing it in a liquid composition containing a conductive material. The pre-coating is formed in the region where the solid electrolyte layer is formed. Next, a polymerization solution containing pyrrole (a monomer of a conductive polymer), naphthalenesulfonic acid (a dopant), and water is prepared. The anode foil with the pre-coated layer is impregnated in the obtained polymerization solution. While the anode foil is immersed in the polymerization solution, electrolytic polymerization is performed by applying a voltage of 3V to form a solid electrolyte layer. Through this process, a first solid electrolyte layer disposed within the porous portion of the anode foil and a second solid electrolyte layer disposed outside the porous portion are formed.

[0117] Next, a dispersion of graphite particles in water is coated onto the solid electrolyte layer and then dried. This forms a carbon layer on the surface of the solid electrolyte layer. Then, a silver paste containing silver particles and a binder resin (epoxy resin) is coated onto the surface of the carbon layer and heated to cure the binder resin. This forms a metal paste layer (silver paste layer). Thus, a cathode lead-out layer consisting of the carbon layer and the silver paste layer is formed. As described above, a cathode portion consisting of the solid electrolyte layer and the cathode lead-out layer is formed.

[0118] (2) Assembly of electrolytic capacitor A1

[0119] Seven capacitor elements were fabricated using the method described above. A laminate was then formed by stacking the seven capacitor elements. The anode terminals were connected to each other, and the silver paste layers were connected to each other using a conductive adhesive. Furthermore, anode lead terminals were connected to the anode terminals, and cathode lead terminals were connected to the cathode lead layer. The resulting laminate was then sealed with resin. As described above, an electrolytic capacitor A1 comprising seven stacked and parallel-connected capacitor elements, and an outer casing covering them, was obtained.

[0120] (3) Determination of the thickness of the second solid electrolyte layer

[0121] For electrolytic capacitor A1, the region between interface B and the first anode body at a distance of 0.05L from interface B is measured. Figure 1 The thickness of the second solid electrolyte layer in region R1). Here, interface B is the interface between the first anode body portion with a solid electrolyte layer formed and the second anode body portion without a solid electrolyte layer formed. The thickness of the second solid electrolyte layer is measured by the following method. First, for example... Figure 1 The cross-section of the component shown was ground to expose a section near the center of the component. This cross-section was observed using an optical microscope (1000x magnification) to determine the thickness of the second solid electrolyte layer. Specifically, the thickness was measured at... Figure 1 The thickness T1 of the thinnest part of the second solid electrolyte layer in region R1 is measured. Additionally, the thickness T2 of the second solid electrolyte layer at a position 0.5L from interface B in the first anode body is measured.

[0122] In addition, for electrolytic capacitor A1, the presence of adhesive in region R2 is evaluated using the method described above.

[0123] (4) Determination of the rate of change of capacitance caused by high temperature exposure

[0124] The initial capacitance F0 of electrolytic capacitor A1 was measured using a 4-terminal LCR meter at 20°C. Then, electrolytic capacitor A1 was placed in an atmosphere at 165°C for 200 hours (high-temperature storage). Afterward, the capacitance F1 of electrolytic capacitor A1 after high-temperature storage was measured using the same method as for the initial capacitance F0. Then, the rate of change of capacitance was calculated according to the following formula.

[0125] Capacitance change rate (%) = (F1 - F0) / F0 × 100

[0126] [Preparation and evaluation of electrolytic capacitors A2-A4 and C1]

[0127] Except for some changes to the manufacturing conditions, electrolytic capacitors A2 to A4 and C1 are manufactured using the same conditions and methods as electrolytic capacitor A1. Specifically, the conditions (temperature and / or time) of the heat treatment when bonding the separation member to the recess are changed. The lower the temperature of this heat treatment, the less adhesive is present in region R2, and the thicker the second solid electrolyte layer in region R1 tends to be. Furthermore, the shorter the heat treatment time, the less adhesive is present in region R2, and the thicker the second solid electrolyte layer in region R1 tends to be. Specifically, the heat treatment conditions are changed as follows.

[0128] Electrolytic capacitor A2: 60℃ for 24 hours

[0129] Electrolytic capacitor A3: 50℃ for 24 hours

[0130] Electrolytic capacitor A4: 70℃ for 48 hours

[0131] Electrolytic capacitor C1: 100℃ for 24 hours

[0132] The manufactured electrolytic capacitors were evaluated using the same method as electrolytic capacitor A1. The evaluation results are shown in Table 1. A capacitance change rate of less than -20% is considered defective.

[0133] [Table 1]

[0134]

[0135] As shown in Table 1, electrolytic capacitors A1 to A4, whose second solid electrolyte layer in region R1 has a thickness of 1 μm or more, maintain high capacitance even after being placed at high temperatures. This is believed to be due to the suppression of oxygen intrusion from region R1. When the thickness of the second solid electrolyte layer in region R1 is 5 μm or more (e.g., 6 μm or more), the capacitance after being placed at high temperatures is particularly high. On the other hand, in electrolytic capacitor C1, where the second solid electrolyte layer in region R1 is thin, the capacitance after being placed at high temperatures decreases significantly.

[0136] Industrial availability

[0137] This invention can be used in solid electrolytic capacitor elements and solid electrolytic capacitors.

[0138] Explanation of reference numerals in the attached figures

[0139] 100: Capacitor element

[0140] 110: Anode

[0141] 111: First anode body section

[0142] 111a: Porous portion

[0143] 112: Second anode body

[0144] 112a: Anode end

[0145] 112b: Separation section

[0146] 113: Dielectric layer

[0147] 120: Solid electrolyte layer

[0148] 121: First solid electrolyte layer

[0149] 122: Second solid electrolyte layer

[0150] 130: Cathode section

[0151] 200: Electrolytic capacitor

[0152] B: Interface

Claims

1. A solid electrolytic capacitor element, comprising: Anode bodies with porous surfaces A dielectric layer covering at least a portion of the anode body, and The cathode portion covering at least a portion of the dielectric layer, The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer. The anode body includes a first anode body portion having the solid electrolyte layer formed thereon, and a second anode body portion not having the solid electrolyte layer formed thereon. The solid electrolyte layer includes a first solid electrolyte layer disposed within the porous portion and a second solid electrolyte layer disposed outside the porous portion. When the length of the long side of the first anode body is defined as length L, In a first region between the interface between the first anode body and the second anode body, and at a position 0.05L away from the interface of the first anode body, the thickness of the second solid electrolyte layer is 1 μm or more. On the surface of the first anode body, there is an adhesive containing at least one element selected from C, N, O, and Si. The amount of adhesive in the second region between the interface and the position of the first anode body at a distance of 0.03L from the interface is less than the amount of adhesive in the third region between the position of the first anode body at a distance of 0.03L from the interface and the position of the first anode body at a distance of L from the interface.

2. A solid electrolytic capacitor element, comprising: Anode bodies with porous surfaces A dielectric layer covering at least a portion of the anode body, and The cathode portion covering at least a portion of the dielectric layer, The cathode portion includes a solid electrolyte layer covering at least a portion of the dielectric layer. The anode body includes a first anode body portion having the solid electrolyte layer formed thereon, and a second anode body portion not having the solid electrolyte layer formed thereon. The solid electrolyte layer includes a first solid electrolyte layer disposed within the porous portion and a second solid electrolyte layer disposed outside the porous portion. When the length of the long side of the first anode body is defined as length L, In a first region between the interface between the first anode body and the second anode body, and at a position 0.05L away from the interface of the first anode body, the thickness of the second solid electrolyte layer is 1 μm or more. In a second region between the interface and the first anode body at a distance of 0.03L from the interface, there exists an adhesive containing at least one element selected from C, N, O, and Si. In the third region between the position of the first anode body at a distance of 0.03L from the interface and the position of the first anode body at a distance of L from the interface, the adhesive is not present.

3. The solid electrolytic capacitor element according to claim 1 or 2, wherein, The minimum thickness T1 of the second solid electrolyte layer in the first region and the thickness T2 of the second solid electrolyte layer at a position 0.5L away from the interface of the first anode body satisfy 0.7T2 < T1 < 1.5T2.

4. The solid electrolytic capacitor element according to claim 1 or 2, wherein, The average thickness of the first solid electrolyte layer is 30 nm or more.

5. The solid electrolytic capacitor element according to claim 1 or 2, wherein, The second anode body includes an anode end and a separation portion disposed between the anode end and the first anode body. At least a portion of the separation section is provided with a first insulating resin.

6. The solid electrolytic capacitor element according to claim 5, wherein, The second anode body portion has a recess formed in the separation portion.

7. The solid electrolytic capacitor element according to claim 1 or 2, comprising a second insulating resin disposed on the outer surface of the portion of the second solid electrolyte layer adjacent to the interface.

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

9. The solid electrolytic capacitor of claim 8, comprising a plurality of said solid electrolytic capacitor elements stacked together.

Images