Electrolytic capacitor

Abstract

This electrolytic capacitor includes two or more capacitor elements that are overlapped in the same direction. The capacitor elements each include a metal foil having a porous part, a core part that is continuous with the porous part, and a dielectric layer that is formed on the surface of the porous part. The metal foil has a first section that includes an anode lead-out part, a second section that is a cathode formation part, and a separation section between the first section and the second section. The first section has an adhesive component that is provided on the surface of the dielectric layer. The separation section has an insulating component that is provided on the surface of the dielectric layer. The second section has a cathode part that is formed on the surface of the dielectric layer.

Description

Electrolytic capacitor Cross-reference to related applications

[0001] This disclosure claims the benefit of priority of Japanese Patent Application No. 2024-190999, filed on October 30, 2024, with the Japan Patent Office, and the entire contents of the said patent application are incorporated herein by reference.

[0002] This disclosure relates to an electrolytic capacitor.

[0003] Patent Document 1 discloses a surface-mount thin capacitor using a metal foil composed of a metal core portion and etched portions covering both surfaces of the metal core portion as a base material, wherein both ends of the metal foil are used as anodes, a cathode is formed on the surface of the central portion of the metal foil, the surface-mount thin capacitor includes a resist resin formed at the boundary between the anode and the cathode, and a conductive polymer layer inside and on the surface of the etched portion in the central portion of the metal foil, and in the surface-mount capacitor in which the cathode is formed on the surface of the conductive polymer layer, an insulating resin covering both ends of the cathode and at least a part of the resist resin is provided.

[0004] Patent Document 1 describes that with the above configuration, "even if the anode portion and the cathode portion of the elements facing each other above and below the laminate are in contact due to displacement of the elements during the formation of the laminate, short-circuiting can be prevented."

[0005] Japanese Patent Application Laid-Open No. 2009-129936

[0006] In an electrolytic capacitor including two or more capacitor elements stacked in the same direction, displacement of the capacitor elements may occur during the manufacturing process, resulting in defects. Such displacement can occur when welding the anode leads of two or more capacitor elements, or when sealing the laminate of capacitor elements with an exterior resin.

[0007] Patent Document 1 aims to prevent short circuits when the element actually shifts, but it does not suppress the element shifting itself. Element shifting can cause various defects. Furthermore, if an insulating resin is provided to cover both ends of the cathode and at least a portion of the resist resin, the thickness of the element at both ends of the cathode increases, and the stress on the element increases.

[0008] One aspect of the present disclosure relates to an electrolytic capacitor comprising two or more capacitor elements stacked in the same direction, each capacitor element comprising a metal foil having a porous portion, a core portion continuous with the porous portion, and a dielectric layer formed on the surface of the porous portion, wherein the metal foil has a first portion including an anode lead portion, a second portion which is a cathode forming portion, and a separation portion between the first portion and the second portion, the first portion having an adhesive component provided on the surface of the dielectric layer, the separation portion having an insulating component provided on the surface of the dielectric layer, and the second portion having a cathode portion provided on the surface of the dielectric layer.

[0009] According to this disclosure, in an electrolytic capacitor including two or more capacitor elements stacked in the same direction, misalignment of the capacitor elements can be suppressed.

[0010] This is a schematic cross-sectional view of a capacitor element according to one embodiment of the present disclosure. This is a schematic plan view of a part of another capacitor element. This is a schematic plan view of a part of yet another capacitor element. This is a schematic cross-sectional view schematically showing an electrolytic capacitor according to one embodiment of the present disclosure. This is a schematic plan view of a capacitor element showing the area to be analyzed by EPMA.

[0011] Novel features of the present invention are described in the appended claims, but the present invention, both in terms of structure and content, and in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in conjunction with the drawings.

[0012] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits are given as examples for numerical values ​​of specific physical properties or conditions, either of the given lower limits and either of the given upper limits can be arbitrarily combined, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0013] This disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0014] In this disclosure, the type of electrolytic capacitor is not particularly limited. This disclosure includes two or more capacitor elements stacked in the same direction, each capacitor element including a metal foil having a porous portion, a core portion continuous with the porous portion, and a dielectric layer formed on the surface of the porous portion, and the metal foil is applicable to all electrolytic capacitors having a first portion including an anode lead portion, a second portion which is a cathode forming portion, and a separation portion. The electrolytic capacitor may also be a solid electrolytic capacitor.

[0015] An electrolytic capacitor according to one embodiment of the present disclosure (hereinafter also referred to as "electrolytic capacitor (C)") includes two or more capacitor elements stacked in the same direction. That is, the electrolytic capacitor (C) includes a laminate of capacitor elements. Each capacitor element includes a metal foil, and each metal foil has a porous portion, a core portion continuous with the porous portion, and a dielectric layer formed on the surface of the porous portion. The metal foil is divided into a first portion including an anode extraction portion, a second portion which is a cathode forming portion, and a separation portion between the first portion and the second portion. Thus, the laminate of capacitor elements has a laminated portion in which the first portion (anode extraction portion) is stacked, a laminated portion in which the separation portion is stacked, and a laminated portion in which the second portion (cathode portion) is stacked. In the laminated portion in which the first portion (anode extraction portion) is stacked, an adhesive component is interposed at least between adjacent first portions (anode extraction portions).

[0016] A metal foil having a porous portion, a core portion continuous with the porous portion, and a dielectric layer formed on the surface of the porous portion can be obtained, for example, by forming a dielectric layer on an etched foil with a roughened surface. Such a metal foil is also called an electrode foil. The material of the metal foil includes valve metals such as aluminum, tantalum, niobium, and titanium.

[0017] The separation portion is a region that insulates the anode extraction portion of the first portion from the cathode portion formed in the second portion. Insulation between the first portion and the second portion is ensured by an insulating component. The insulating component is applied to at least a portion of the surface or pores of the porous portion of the separation portion. As the insulating component, for example, insulating tape may be used, or a resist resin may be used. The insulating tape is attached to the surface of the porous portion of the separation portion. The resist resin is impregnated into at least a portion of the porous portion of the separation portion. The resist resin may be a thermosetting resist or a photoresist resin.

[0018] The first portion is located at one end of the metal foil and has an anode lead portion at that end. The anode leads of adjacent capacitor elements are overlapped and connected in parallel. Multiple capacitor elements are free from each other until the overlapped anode leads are fixed to each other by parallel connection. Therefore, misalignment of the capacitor elements can occur due to various factors. Such misalignment can be significantly suppressed by providing an adhesive component on the surface of the dielectric layer of the first portion. The adhesive component plays the role of fixing the overlapped anode leads to each other by adhesion until they are fixed to each other by parallel connection.

[0019] Furthermore, misalignment of capacitor elements can occur even after the stacked anode leads are connected in parallel and firmly fixed to each other. For example, when sealing a laminate of multiple capacitor elements with an outer resin, the laminate is subjected to pressure from the molten outer resin material, causing the outer resin material to flow into the gaps between adjacent capacitor elements, thus easily causing misalignment. Such misalignment can be significantly suppressed by providing an adhesive component on the surface of the dielectric layer of the anode leads. This is because the adhesive component improves the adhesion between capacitor elements, making it difficult for the outer resin material to flow into the gaps between them. In addition, by connecting the anode leads in parallel while they are bonded to each other, misalignment between capacitor elements in the laminate is suppressed, and the laminate maintains a balanced state, making it less susceptible to random pressure from the outer resin material.

[0020] A portion of the adhesive component may cover at least a portion of the insulating component. By providing the adhesive component not only on the surface of the dielectric layer of the first portion but also on the surface of the film formed by the insulating component, the coating area of ​​the adhesive component is increased, and the effect of suppressing displacement of the capacitor element is enhanced. Furthermore, since the adhesive component and the insulating component continuously cover the boundary between the separated portion and the first portion, the intrusion of air and moisture from the first portion into the cathode portion is suppressed. Therefore, an effect of suppressing the deterioration of the cathode portion is obtained.

[0021] The method for connecting the first parts (anode extraction portions) of two or more capacitor elements in parallel is not particularly limited, but welding may be performed using a method such as a laser. For example, the anode extraction portions of the capacitor elements can be electrically connected by irradiating the stacked portion of the anode extraction portion with a laser from one side in the stacking direction.

[0022] The first portions (anode lead portions) of two or more capacitor elements may be compressed in the stacking direction. For example, the stacked portion of the anode lead portion may be compressed by a lead terminal, which is a separate component from the capacitor element. Specifically, one end of the lead terminal may be bent into a hook shape, and the stacked portion of the anode lead portion may be sandwiched between them, and the hook-shaped portion may be crimped to the stacked portion of the anode lead portion.

[0023] The distance from the end of the first part to the end of the second part of the separation, i.e., the width of the separation, may be 0.5 mm or less. When the width of the separation is narrow in this way, the frictional force due to the insulating component becomes small. Therefore, without the adhesive component, displacement of the capacitor element is likely to occur. In contrast, the presence of the adhesive component significantly suppresses displacement of the capacitor element. Also, the narrower the width of the separation, the larger the width between the first and second parts becomes. Therefore, in the first part, the area to which the adhesive component can be applied becomes larger, and the application area of ​​the adhesive component becomes larger, thus increasing the effect of suppressing displacement of the capacitor element. In addition, the capacitance increases as the width of the second part increases.

[0024] The adhesive component can be any component that exhibits adhesive strength. Examples of adhesive components include acrylic adhesives, epoxy adhesives, and urethane adhesives. Among these, it is preferable that the adhesive component includes an acrylic adhesive. Acrylic adhesives contain acrylic resins that have excellent weather resistance and heat resistance, as well as low viscosity and are easy to apply. Examples of acrylic resins include poly(meth)acrylic acid, poly(meth)acrylic acid esters, copolymers of (meth)acrylic acid and (meth)acrylic acid esters such as acrylic acid-acrylic acid ester copolymers, and (meth)acrylamide resins such as poly(meth)acrylamide and modified poly(meth)acrylamide.

[0025] The amount of adhesive component on the surface of the dielectric layer of the first part can be evaluated by analyzing multiple minute regions in the central part of the first part, viewed from the thickness direction of the capacitor element, using an electron probe microanalyzer (EPMA). In the first part, the underlying component of the adhesive component is the dielectric layer, which is a metal oxide. On the other hand, the adhesive component is an organic substance. Therefore, with EPMA, the amount of adhesive component can be evaluated from the signal intensity of the carbon element (C) in the minute region. The carbon element (C) reflects the amount of the organic adhesive component present.

[0026] From the viewpoint of enhancing the effect of suppressing displacement of the capacitor elements, a larger amount of adhesive component is preferable on the surface of the dielectric layer of the first portion. However, the larger the amount of adhesive component, the greater the resistance component of the electrical connection between the first portions. Therefore, it is preferable to control the amount of adhesive component used so that the signal intensity of the carbon element (C) detected by EPMA does not become too large.

[0027] Furthermore, the greater the voltage rating Vw of an electrolytic capacitor, the greater the thickness of the dielectric layer. Therefore, for electrolytic capacitors with a high voltage rating Vw, it is preferable to reduce the amount of adhesive component used to limit the resistance component of the electrical connection between the first parts.

[0028] Based on the above, it is preferable to control the product (Sc × Vw) of the carbon element signal intensity Sc (unit: Count) detected on the surface of the first part by EPMA and the withstand voltage Vw (unit: V) of the electrolytic capacitor to 2100 or less. However, if the amount of adhesive component used is reduced, the effect of suppressing the displacement of the capacitor element will decrease, so it is more preferable to control it to 35 < Sc. The withstand voltage of the electrolytic capacitor is determined by a measurement method in accordance with JIS C 2110-1:2016. For example, the voltage is increased at 1 V / s in an atmosphere of 85°C and it is determined as the voltage at which dielectric breakdown occurs. The withstand voltage is the average value of the dielectric breakdown voltages of 10 or more electrolytic capacitors.

[0029] For EPMA analysis, a sample is prepared by removing a laminate of capacitor elements from an electrolytic capacitor, peeling off the cleanest capacitor elements possible, and separating them from adjacent capacitor elements. EPMA analysis is performed on a minute region in the central part of the first portion of the delamination surface formed by the delamination process.

[0030] For EPMA analysis, a platinum film with a thickness of 1 nm to 2 nm may be formed on the sample by sputtering platinum (Pt) onto the central part of the first portion of the delamination surface using a sputtering apparatus. Elemental mapping of a micro-region is performed based on the difference in wavelengths of characteristic X-rays detected by EPMA, and the Net intensity of carbon (C) present in the micro-region is measured as the signal intensity Sc (unit: Count). The Net intensity is the measured value of each element minus the background (noise). The signal intensity Sc of carbon (C) is determined in multiple regions (for example, five regions), and the average value is calculated. By performing a similar analysis with other elements, the relative abundance ratios of various elements can be understood.

[0031] The conditions for EPMA analysis are as follows: Equipment manufactured by Shimadzu Corporation: EPMA-8050G Acceleration voltage: 15.0 kV Beam current: 50.4 nA Beam size: MIN Integration time: 50.0 ms / point Spectroscopic crystals: CH1 RAP / LSA120, CH2 PbST / LSA70, CH3 LiF / PET, CH4 LiF / ADP, CH5 LSA80 / LSA200 Note that for the measurement of carbon (C), the spectroscopic crystal CH1 is set to LSA120 and the measurement is performed.

[0032] The following explanation will be given with reference to the drawings. However, the capacitor elements and electrolytic capacitors relating to this disclosure are not limited to the embodiments shown in the drawings. Each drawing is a schematic diagram, and the shape or characteristics of each component in each drawing do not necessarily reflect the actual dimensions, nor are they necessarily represented at the same scale.

[0033] Figure 1 is a schematic cross-sectional view of a capacitor element 110. The capacitor element 110 is formed on a base of a metal foil (electrode foil) 6 and generally has a sheet-like shape. The metal foil 6 has a porous portion 6b, a core portion 6a continuous with the porous portion 6b, and a dielectric layer formed on the surface of the porous portion 6b. The metal foil 6 is divided into a first portion 11a that functions as an anode extraction portion, a second portion 11b that is a cathode forming portion, and a separation portion 11c between the first portion 11a and the second portion 11b.

[0034] The first portion 11a includes one end IIe of the metal foil 6 and has an adhesive component 14 provided on the surface of the dielectric layer. The adhesive component 14 may cover a part of the surface of the first portion 11a, as shown in the illustrated example, or it may cover the entire surface of the first portion 11a. The adhesive component 14 may be provided only on the surface where adjacent capacitor elements 110 exist. As described above, the adhesive component 14 plays a role in bonding and fixing adjacent first portions 11a together when a plurality of capacitor elements 110 are stacked in the same direction. The separation portion 11c has an insulating component 13 provided on the surface of the dielectric layer. The second portion 11b includes the other end Ie of the metal foil 6 and has a cathode portion 8 formed on the surface of the dielectric layer. In the illustrated example, a recess is provided in the porous portion 6b of the separation portion 11c, but the recess is not required.

[0035] The cathode portion 8 comprises a solid electrolyte layer 9 covering at least a portion of the dielectric layer and a cathode extraction layer 10 covering at least a portion of the solid electrolyte layer 9. The cathode extraction layer 10 is formed, for example, by sequentially forming a carbon layer 11 and a metal paste layer 12.

[0036] The solid electrolyte layer 9 preferably contains a conductive polymer. Examples of conductive polymers include π-conjugated polymers. Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, and polyaniline. The conductive polymer may be used alone, in combination of two or more types, or as a copolymer of two or more monomers. The weight-average molecular weight of the conductive polymer is, for example, 1,000 to 100,000.

[0037] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc., refer to polymers that have polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc., may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene), etc.

[0038] The conductive polymer may be doped with a dopant. The solid electrolyte layer may contain a dopant along with the conductive polymer. Examples of dopants include polystyrene sulfonic acid.

[0039] Figure 2 is a schematic cross-sectional view of a part of another capacitor element. Here, a portion of the adhesive component 14 covers at least a portion of the surface of the film formed by the insulating component 13. That is, the adhesive component 14 is applied not only to the first portion 11a, but also beyond the boundary between the first portion 11a and the separated portion 11c to the separated portion 11c. In this case, the coating area of ​​the adhesive component 14 is increased, which enhances the effect of suppressing displacement of the capacitor element 110, and also suppresses the phenomenon of air and moisture penetrating from the first portion 11a and the separated portion 11c to the cathode side.

[0040] Figure 3 is a schematic cross-sectional view of a part of yet another capacitor element. In the illustrated example, there are no recesses in the porous portion 6b of the separation portion 11c, and the insulating component 13 is impregnated into the porous portion 6b of the separation portion 11c. For example, a liquid resist resin that has excellent weather resistance and heat resistance and is easy to apply due to its low viscosity is impregnated into the porous portion 6b of the separation portion 11c as the insulating component 13. The liquid resist resin includes, for example, a polyamide-imide resin.

[0041] The polyamideimide resin can be diluted with a solvent and its viscosity can be adjusted, so it is easy to apply, and the width of the separation part 11c in the direction from the first part 11a to the second part 11b (that is, the distance from the first part 11a to the second part 11b) can be made 0.5 mm or less. When the width of the separation part 11c is narrow in this way, the frictional force by the insulating component 13 becomes small, and if there is no adhesive component 14, the displacement of the capacitor element 110 is likely to occur. On the other hand, due to the presence of the adhesive component 14, the displacement of the capacitor element 110 is significantly suppressed. As the adhesive component 14, for example, an acrylic adhesive containing an acrylic resin is used.

[0042] FIG. 4 is a cross-sectional view schematically showing an electrolytic capacitor. The electrolytic capacitor 100 includes a laminate of a plurality of capacitor elements 110, an anode lead terminal 120A joined to the laminated portion of the first portion (anode lead-out portion) 11a of the capacitor element 110, a cathode lead terminal 120B joined to the cathode portion, and an exterior resin 130 for sealing the laminate of the capacitor elements 110. In the laminated portion of the first portion (anode lead-out portion) 11a, the first portions are connected in parallel by laser welding. One end portion of the anode lead terminal 120A is bent into a hook shape and sandwiches the laminated portion of the anode lead-out portion. The hook-shaped portion of the anode lead terminal 120A is caulked to the laminated portion of the anode lead-out portion and compresses the laminated portion in the lamination direction.

[0043] Note that FIG. 5 is a plan schematic view of the capacitor element 110. The minute region analyzed by EPMA is set in the first portion 11a, for example, within the region (central portion) surrounded by a broken line.

[0044] A method for manufacturing an electrolytic capacitor includes, for example, the steps of: preparing two or more capacitor elements and applying an adhesive component to the first portion of each capacitor element; stacking the two or more capacitor elements to form a laminate; connecting the stacked portions of the anode lead of the laminate in parallel and electrically connecting the anode lead terminals to the stacked portions of the anode lead of the laminate; electrically connecting the cathode lead terminals to the cathode portion of the laminate; and covering the laminate and a portion of each lead terminal with an outer resin. An example is described below, but the method for manufacturing an electrolytic capacitor is not limited to the example below.

[0045] The manufacturing method for an electrolytic capacitor specifically comprises, for example, (a-1) a step of roughening the surface of a raw material metal foil (plain foil) to form a porous portion, (a-2) a step of forming a dielectric layer in the porous portion, (a-3) a step of cutting out an assembly of anode bodies having a dielectric layer from the metal foil having a dielectric layer, (a-4) a step of applying an insulating component to the separated portion of the anode body having a dielectric layer, (a-5) a step of forming a capacitor element by forming a cathode portion in the second portion of the anode body having a dielectric layer, (a-6) a step of separating the capacitor elements into individual pieces and applying an adhesive component to the first portion of the capacitor elements to laminate them and form a laminate, (a-7) a step of connecting the anode lead portions of the first portion of the laminate in parallel and electrically connecting anode lead terminals to the laminated portion of the anode lead portion and electrically connecting cathode lead terminals to the cathode portion, and (a-8) a step of sealing the laminate with an outer resin.

[0046] The raw material metal foil is a metal foil containing valve-acting metal and does not have a porous portion. By roughening the surface of the raw material metal foil, a porous portion is formed and an electrode foil is obtained (a-1). When the surface of the raw material metal foil is etched (e.g., electrolytic etching), an etched foil is obtained.

[0047] The dielectric layer is formed, for example, by anodizing an electrode foil (etching foil) (a-2). Anodization can be performed by a known chemical conversion treatment or the like. The chemical conversion treatment can be performed by immersing the electrode foil in a chemical conversion solution and applying a voltage between the electrode foil as an anode and the cathode of the counter electrode. For example, an aqueous phosphoric acid solution can be used as the chemical conversion solution. Note that the dielectric layer can also be formed by other methods (for example, atomic layer deposition (ALD) method).

[0048] The electrode foil having a dielectric layer is usually in a wide and simple strip shape. From such an electrode foil, an aggregate of anode bodies having a dielectric layer is cut out by processing such as slitting or punching (a-3).

[0049] Each anode body having a dielectric layer has a first portion 11a including an anode lead portion, a second portion 11b that is a cathode forming portion, and a separation portion 11c between the first portion 11a and the second portion 11b.

[0050] At any timing, an insulating component is applied to the separation portion 11c (a-4). The application of the insulating component can be performed, for example, by a coating method or a dispensing method using various coaters or dispensers, dipping, transfer (such as roller transfer), or the like. When a liquid resist resin is used as the insulating component, it is possible to make the width of the separation portion 11c very small, and accordingly, the second portion for forming the cathode portion can be enlarged. Liquid photoresist resins and thermosetting resists have low viscosities and are suitable for microfabrication.

[0051] Next, a cathode portion is formed on the second portion (a-5). The step of forming the cathode portion includes, for example, a step of forming a solid electrolyte layer so as to cover at least a part of the dielectric layer, and a step of forming a cathode lead layer on the surface of the solid electrolyte layer.

[0052] The solid electrolyte layer may be formed, for example, by polymerizing a conductive polymer precursor on a dielectric layer using a processing solution containing the precursor (so-called "in-situ polymerization"). Polymerization may be carried out by either chemical polymerization or electrolytic polymerization. Alternatively, the solid electrolyte layer may be formed by attaching a dispersion or solution containing the conductive polymer to the dielectric layer and then drying it.

[0053] The cathode extraction layer includes, for example, the steps of forming a carbon layer containing conductive carbon and forming a metal paste layer containing metal powder. The carbon layer can be formed by immersing an anode body having a solid electrolyte layer formed on it in a dispersion containing conductive carbon, or by applying a paste containing conductive carbon to the surface of the solid electrolyte layer.

[0054] A metal paste layer can be formed by laminating a paste-like composition containing metal powder onto the surface of a carbon layer. The composition may include, for example, silver particles and a binder resin.

[0055] Next, at some point, the adhesive component 14 is applied to the first part 11a (a-6). The adhesive component (for example, a liquid acrylic adhesive) is applied to the first part 11a by, for example, a coating method or dispensing method using various coaters or dispensers, immersion, transfer (roller transfer, etc.).

[0056] Furthermore, at some point, the capacitor elements are separated into individual pieces and stacked to form a laminate (a-7). At this time, the adhesive component 14 applied to the first portion 11a has a remarkable effect in suppressing misalignment of the multiple capacitor elements.

[0057] Subsequently, the laminated portion of the anode lead section of the laminate is crimped by the anode lead terminal, and the electrical connection between the anode lead terminal and the anode lead section, as well as the parallel connection between the anode lead sections, are simultaneously performed, for example, by laser welding. Because the misalignment of the multiple capacitor elements is suppressed by the adhesive component 14, good welding is possible. The cathode lead terminal is electrically connected to the cathode section using a conductive adhesive (a-8).

[0058] Next, the laminate of capacitor elements and a portion of each lead terminal are sealed with an outer resin (a-9). The sealing process is carried out using molding techniques such as injection molding, insert molding, and compression molding. An electrolytic capacitor is obtained through the above process.

[0059] 《Note》 The above description of embodiments discloses the following technologies. (Technology 1) An electrolytic capacitor comprising two or more capacitor elements stacked in the same direction, wherein each capacitor element comprises a metal foil having a porous portion, a core portion continuous with the porous portion, and a dielectric layer formed on the surface of the porous portion, wherein the metal foil has a first portion including an anode lead portion, a second portion which is a cathode forming portion, and a separation portion between the first portion and the second portion, the first portion having an adhesive component provided on the surface of the dielectric layer, the separation portion having an insulating component provided on the surface of the dielectric layer, and the second portion having a cathode portion provided on the surface of the dielectric layer. (Technology 2) The electrolytic capacitor according to Technology 1, wherein the product (Sc × Vw) of the carbon element signal intensity Sc (unit: Count) detected on the surface of the first portion by an electron beam probe microanalyzer (EPMA) and the withstand voltage Vw (unit: V) of the electrolytic capacitor is 2100 or less. (Technology 3) An electrolytic capacitor according to any one of Technology 1 or 2, wherein a part of the adhesive component covers at least a part of the surface of the insulating component. (Technology 4) An electrolytic capacitor according to any one of Technology 1 to 3, wherein the adhesive component includes an acrylic resin. (Technology 5) An electrolytic capacitor according to any one of Technology 1 to 4, wherein the insulating component includes a resist resin. (Technology 6) An electrolytic capacitor according to any one of Technology 1 to 5, wherein the distance from the end of the separation portion on the first portion side to the end of the separation portion on the second portion side (width of the separation portion) is 0.5 mm or less. (Technology 7) An electrolytic capacitor according to any one of Technology 1 to 6, wherein the first portions of two or more capacitor elements are connected in parallel by welding. (Technology 8) An electrolytic capacitor according to any one of Technology 1 to 7, wherein the first portions of two or more capacitor elements are compressed in the stacking direction by lead terminals.

[0060] [Examples] The present disclosure will be described below in detail based on examples and comparative examples, but the present disclosure is not limited to the examples.

[0061] 《Example 1》 An electrolytic capacitor A1 was fabricated using the following procedure, comprising a laminate of seven capacitor elements having the voltage withstand voltage described in Table 1. (1) Fabrication of capacitor elements Aluminum foil (thickness 100 μm) was prepared as the raw material metal foil (plain foil), and the surface of the aluminum foil was etched (a-1) to form a porous portion (thickness 35 μm on one main surface side of the aluminum foil, and 35 μm on the other main surface side).

[0062] Next, the metal foil having a porous portion is immersed in a 0.3% by mass phosphoric acid solution (liquid temperature 70°C) and a predetermined DC voltage is applied for 20 minutes, thereby causing aluminum oxide (Al2O) to be applied to the surface of the porous portion. ３ A dielectric layer containing ) was formed to obtain an electrode foil (a-2).

[0063] An assembly of anode bodies having a dielectric layer was cut from the electrode foil (a-3), and the anode body was divided into an anode portion, a cathode forming portion, and a separation portion between them. Liquid resist resin was applied to the separation portion and cured (a-4). Specifically, at a predetermined position between the first and second portions of the anode foil on which the dielectric layer was formed, liquid resist resin was impregnated in a strip along the entire width direction of both surfaces of the electrode foil, and the resist resin was cured by heating at 200°C for 30 minutes. The resist resin hardens while filling the pores of the porous portion. The resist resin is a liquid composition containing a curable polyamide-imide resin (precursor), γ-butyrolactone (solvent), and bisphenol A type liquid epoxy resin.

[0064] Next, the anode body with the dielectric layer formed on it was immersed in a liquid composition containing a conductive material to form a pre-coat layer. Then, the anode body with the dielectric layer and pre-coat layer formed on it was immersed in a polymerization solution containing pyrrole (a monomer of a conductive polymer), naphthalene sulfonic acid (a dopant), and water, and electrolytic polymerization was carried out at an applied voltage of 3V to form a solid electrolyte layer.

[0065] Furthermore, a dispersion of graphite particles in water was applied to the solid electrolyte layer and then dried to form a carbon layer on the surface of the solid electrolyte layer.

[0066] Next, a silver paste containing silver particles and a binder resin (epoxy resin) was applied to the surface of the carbon layer, and then heated to harden the binder resin, forming a silver paste layer (15 μm thick). In this way, a cathode extraction layer composed of the carbon layer and the silver paste layer was formed, and an assembly of capacitor elements was obtained (a-5).

[0067] The obtained capacitor elements were separated into individual pieces, and an acrylic adhesive was applied as an adhesive component (tack) to the first portion of each capacitor element. The seven capacitor elements were then stacked to obtain a laminate (a-6).

[0068] Next, the laminated portion of the anode lead section of the laminate was crimped by clamping it with one end of a hook-shaped anode lead terminal, and the anode lead sections were connected in parallel with a laser and welded to the anode lead terminal. Meanwhile, one end of the cathode lead terminal was connected to the cathode section via a conductive adhesive (a-7).

[0069] Subsequently, the laminate was sealed with an outer resin so that the other ends of the anode and cathode lead terminals were exposed, completing the electrolytic capacitor (a-9).

[0070] <Comparative Example 1> An electrolytic capacitor B1 was manufactured in the same manner as in Example 1, except that no adhesive component was applied to the first portion of the capacitor element.

[0071] Examples 2-4: Electrolytic capacitors A2-A4 were manufactured in the same manner as in Example 1, except that the conversion voltage was changed when forming a dielectric layer on the surface of the porous portion of the metal foil to form capacitor elements with the dielectric strength described in Table 1. In addition, the amount of adhesive component applied to the first portion was changed.

[0072] <Comparative Example 2> An electrolytic capacitor B2 was manufactured in the same manner as in Example 2, except that no adhesive component was applied to the first portion of the capacitor element.

[0073] Thirty electrolytic capacitors were fabricated, and their dielectric loss tangent (tanδ) at 120 Hz was measured using a four-terminal LCR meter in a 20°C environment. Here, a tanδ of 0.01 or less was judged as excellent (◎), 0.02 or less as good (〇), and greater than 0.02 as poor (△).

[0074] Furthermore, using the method described above, the product (Sc × Vw) of the carbon element signal intensity Sc (unit: Count) detected on the surface of the first part and the withstand voltage Vw (unit: V) of the electrolytic capacitor was calculated. The results are shown in Table 1. In all examples, the condition 35 < Sc was satisfied.

[0075] After measuring the electrical characteristics, the dielectric breakdown voltage of the electrolytic capacitor was confirmed. Here, in accordance with JIS C2110-1:2016, the voltage applied to the electrolytic capacitor in an 85°C environment was boosted at a rate of 1 V / s, and the voltage at which dielectric breakdown occurred was defined as the dielectric breakdown voltage (i.e., withstand voltage).

[0076]

[0077] As shown in Table 1, electrolytic capacitors A1 to A4, in which an adhesive component was applied to the first portion of the capacitor element, showed a significant improvement in quality compared to electrolytic capacitors B1 and B2. Furthermore, the improvement in quality was even more pronounced when the product (Sc × Vw) was 2100 or less.

[0078] This disclosure is suitably applicable to electrolytic capacitors where high reliability is required.

[0079] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0080] 100 Electrolytic capacitor 110 Capacitor element 6 Anode 6a Core 6b Porous part 8 Cathode 9 Solid electrolyte layer 10 Cathode lead layer 11 Carbon layer 12 Metal paste layer 13 Insulating component 14 Adhesive component 120A: Anode lead terminal 120B: Cathode lead terminal 130: Outer resin

Claims

1. An electrolytic capacitor comprising two or more capacitor elements stacked in the same direction, wherein each capacitor element comprises a metal foil having a porous portion, a core portion continuous with the porous portion, and a dielectric layer formed on the surface of the porous portion, the metal foil having a first portion including an anode lead portion, a second portion which is a cathode forming portion, and a separation portion between the first portion and the second portion, the first portion having an adhesive component provided on the surface of the dielectric layer, the separation portion having an insulating component provided on the surface of the dielectric layer, and the second portion having a cathode portion provided on the surface of the dielectric layer.

2. The electrolytic capacitor according to claim 1, wherein the product (Sc × Vw) of the signal intensity of the carbon element Sc (unit: Count) detected on the surface of the first portion by an electron probe microanalyzer (EPMA) and the withstand voltage Vw (unit: V) of the electrolytic capacitor is 2100 or less.

3. The electrolytic capacitor according to claim 1, wherein a portion of the adhesive component covers at least a portion of the insulating component.

4. The electrolytic capacitor according to claim 1, wherein the adhesive component includes an acrylic resin.

5. The electrolytic capacitor according to claim 1, wherein the insulating component includes a resist resin.

6. The electrolytic capacitor according to claim 1, wherein the distance from the end of the separation portion on the first portion side to the end of the separation portion on the second portion side is 0.5 mm or less.

7. The electrolytic capacitor according to claim 1, wherein the first portions of two or more capacitor elements are connected in parallel by welding.

8. The electrolytic capacitor according to claim 1, further comprising lead terminals that compress the first portions of two or more capacitor elements in the stacking direction.

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