Electrolytic capacitor

Abstract

The electrolytic capacitor includes: a capacitor element including an anode portion and a cathode portion; an exterior body for sealing the capacitor element; a metal foil electrically connected to the cathode part; a first external electrode electrically connected to the metal foil; and a conductive adhesive layer. The metal foil has a through hole penetrating in the thickness direction. The conductive adhesive layer includes a first layer interposed between the cathode portion and the main surface of the metal foil, and a second layer filling the through hole, and the first layer and the second layer are integrated. The metal foil has a first end surface exposed from the exterior body, and the first end surface is electrically connected to the first external electrode.

Description

Technical Field

[0001] The present disclosure relates to an electrolytic capacitor. Background Art

[0002] An electrolytic capacitor includes a capacitor element, an outer package that seals the capacitor element, and an external electrode electrically connected to the capacitor element. The capacitor element includes an anode portion and a cathode portion. The cathode portion is bonded to a metal foil by a conductive adhesive layer. The metal foil has an end face exposed from the outer package, and this end face is electrically connected to the external electrode on the cathode side.

[0003] Patent Document 1 discloses "a solid electrolytic capacitor in which a plurality of units are laminated, each unit having a valve-acting metal substrate having a porous layer on its surface, a dielectric layer formed on the surface of the porous layer, and a solid electrolyte layer provided on the dielectric layer, and the solid electrolytic capacitor is characterized in that a conductor layer is present between the laminated units, at least one of the conductor layers contains a metal foil, the units and the conductor layer are sealed with an outer resin, the anode portion side end face of the valve-acting metal substrate is directly connected to an anode external electrode formed on the surface of the outer resin at one end face of the solid electrolytic capacitor, and the metal foil is directly connected to a cathode external electrode formed on the surface of the outer resin at the other end face of the solid electrolytic capacitor".

[0004] In addition, Patent Document 1 discloses that "the conductor layer containing the metal foil is composed of a carbon layer provided on the solid electrolyte layer, a conductive adhesive layer provided on the carbon layer, and a metal foil provided on the conductive adhesive layer".

[0005] Prior art documents

[0006] Patent documents

[0007] Patent Document 1: Pamphlet of International Publication No. 2018 / 074408 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The bonding strength achieved by the conductive adhesive layer between the metal foil and the capacitor element (cathode portion) is low. Therefore, peeling between the metal foil and the capacitor element (hereinafter also referred to as "lamination peeling") is likely to occur, increasing the contact resistance. In addition, displacement between the capacitor element and the metal foil (hereinafter also referred to as "lamination displacement") is likely to occur when sealing the capacitor element. As a result, the reliability of the electrolytic capacitor decreases.

[0010] Solutions to the Problems

[0011] One technical solution of the present disclosure relates to an electrolytic capacitor, which includes: a capacitor element including an anode portion and a cathode portion; an outer package for sealing the capacitor element; a metal foil electrically connected to the cathode portion; a first external electrode electrically connected to the metal foil; and a conductive adhesive layer.

[0012] The metal foil has a through-hole penetrating in the thickness direction. The conductive adhesive layer includes a first layer sandwiched between the main surface of the cathode portion and the metal foil and a second layer filled in the through-hole. The first layer and the second layer are integrated. The metal foil has a first end face exposed from the outer package, and the first end face is electrically connected to the first external electrode.

[0013] Effects of the Invention

[0014] According to the present disclosure, a decrease in the reliability of the electrolytic capacitor can be suppressed.

[0015] The new features of the present invention are described in the appended claims. However, the present invention relates to both the structure and the content. Together with other objects and features of the present invention, it should be better understood through the following detailed description with reference to the accompanying drawings. Description of the Drawings

[0016] Figure 1 It is a cross-sectional view schematically showing an example of an electrolytic capacitor according to an embodiment of the present disclosure.

[0017] Figure 2 It is enlarged at Figure 1 A cross-sectional schematic view of a main part near the metal foil disposed between adjacent capacitor elements of the element laminate of the electrolytic capacitor shown.

[0018] Figure 3 It is enlarged at Figure 1 A cross-sectional schematic view of a main part near the metal foil disposed at one end of the element laminate of the electrolytic capacitor shown.

[0019] Figure 4 It is a top view schematically showing an example of a metal foil having a through-hole with a circular cross-section.

[0020] Figure 5 It is a top view schematically showing an example of a metal foil having two through-holes with circular cross-sections.

[0021] Figure 6 It is a top view schematically showing an example of a metal foil having five through-holes with circular cross-sections.

[0022] Figure 7It is a top view schematically showing an example of a metal foil having three through-holes with a linear cross-section.

[0023] Figure 8 It is a top view schematically showing an example of a metal foil having five through-holes with a linear cross-section.

[0024] Figure 9 It is a top view schematically showing an example of a metal foil having seven through-holes with a linear cross-section.

[0025] Figure 10 It is a top view schematically showing an example of a metal foil having nine through-holes with a linear cross-section.

[0026] Figure 11 It is a top view schematically showing an example of a metal foil having eleven through-holes with a linear cross-section. Detailed implementation manners

[0027] Hereinafter, embodiments of the present disclosure will be illustrated by way of examples, but the present disclosure is not limited to the examples described below. In the following description, there are cases where specific numerical values and materials are exemplified, but as long as the effects of the present disclosure can be obtained, other numerical values and materials can also be applied. In this specification, a description such as "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be replaced with "not less than numerical value A and not more than numerical value B". In the following description, when the lower limit and the upper limit of a numerical value related to a specific physical property, condition, etc. are exemplified, any one of the exemplified lower limits and any one of the exemplified upper limits can be arbitrarily combined as long as the lower limit does not become greater than the upper limit. When multiple materials are exemplified, either one can be selected and used alone, or two or more can be combined and used.

[0028] In addition, the present disclosure includes combinations of matters described in two or more claims arbitrarily selected from the multiple claims described in the appended claims. That is, as long as there is no technical contradiction, the matters described in two or more claims arbitrarily selected from the multiple claims described in the appended claims can be combined together.

[0029] An electrolytic capacitor according to an embodiment of the present disclosure includes: a capacitor element including an anode portion and a cathode portion; an outer package that seals the capacitor element; a metal foil electrically connected to the cathode portion; a first external electrode electrically connected to the metal foil; and a conductive adhesive layer. The metal foil has a first end face exposed from the outer package, and the first end face is electrically connected to the first external electrode. The metal foil has a through hole penetrating in the thickness direction. The conductive adhesive layer includes a first layer interposed between the main surface of the cathode portion and the metal foil and a second layer filled in the through hole. The first layer and the second layer are integrated. The electrolytic capacitor may include one capacitor element or a plurality of capacitor elements. The first layer is formed on the main surface of the metal foil and the second layer filled in the through hole.

[0030] The bonding effect and the anchoring effect of the second layer filled in the through hole cooperate, and the adhesion strength between the metal foil and the cathode portion and the adhesive layer (first layer) is improved. Thereby, a decrease in the bonding strength between the metal foil and the cathode portion can be suppressed, an increase in the contact resistance can be suppressed, laminate peeling and laminate shift can be suppressed, and a decrease in the reliability of the electrolytic capacitor caused by the laminate peeling and the laminate shift can be suppressed. The decrease in reliability includes a decrease in performance, an increase in performance fluctuations, and the like.

[0031] Desirably, the second layer fills the entire through hole, but a portion (void) where the second layer is not filled locally in the through hole may be included within a range that does not impair the effect of the second layer. The filling rate of the second layer into the through hole may be 55% or more, or may be 75% or more. The filling rate of the second layer into the through hole is the ratio of the area of the region occupied by the second layer to the area of the region occupied by the through hole in a cross section in the thickness direction of the metal foil (a cross section having the through hole), that is, in the above cross section, when the area of the region occupied by the through hole is set to S0 and the area of the region occupied by the second layer is set to S1, it is obtained according to (S1 / S0)×100. When the second layer is filled in a plurality of through holes respectively, desirably, in 60% or more (preferably 80% or more) of the total number of through holes, the filling rate of the second layer is 90% or more.

[0032] Alternatively, the electrolytic capacitor may include an element laminate formed by laminating a plurality of capacitor elements. In this case, the metal foil is disposed in at least one of the plurality of capacitor elements. In this case, preferably, the metal foil is disposed between adjacent capacitor elements. That is, preferably, one metal foil is shared between adjacent capacitor elements. In this case, the first layer is formed on both main surfaces of the metal foil. That is, the first layer includes: a first A layer sandwiched between the cathode portion of one of the adjacent capacitor elements and one main surface of the metal foil; and a first B layer sandwiched between the cathode portion of the other of the adjacent capacitor elements and the other main surface of the metal foil. The first A layer and the first B layer are integrated with the second layer.

[0033] When the metal foil is disposed between adjacent capacitor elements, a region sandwiching the first A layer, the second layer, and the first B layer is formed between the adjacent capacitor elements. The first A layer and the first B layer are integrated by means of the second layer. As a result, the adhesion strength between the capacitor elements is further improved. The anchoring effect of the second layer can be efficiently exerted on both the first A layer and the first B layer.

[0034] In addition, when the metal foil is disposed between adjacent capacitor elements, the gas generated in the element laminate is discharged through the through-holes of the metal foil, which can suppress the expansion in the stacking direction of the electrolytic capacitor caused by an increase in the amount of gas generated, and can suppress the deterioration of performance (such as an increase in ESR) and the fluctuation of performance caused by this expansion. The gas particularly easily moves in the region (void) where the second layer is not filled in the through-holes. This gas is likely to be generated when the electrolytic capacitor is exposed to a high temperature due to a curing process by heating during the formation of the conductive adhesive layer, a reflow soldering process, or the like.

[0035] (Through-hole)

[0036] The metal foil has one or more through-holes penetrating in the thickness direction. The number of through-holes is, for example, from 1 to 500. The maximum diameter of the through-hole is, for example, 0.01 mm or more and 2 mm or less. The cross-sectional area of the through-hole is, for example, 78 μm 2 or more and 3.14 mm 2 or less. A plurality of through-holes may be provided regularly. The plurality of through-holes may be arranged in a lattice pattern (such as a staggered lattice pattern, a square lattice pattern).

[0037] From the viewpoints of achieving an increase in adhesive strength by forming the second layer, ensuring a bonding region with the cathode portion using the first layer, and ensuring the strength of the metal foil, etc., when observing the metal foil from the normal direction of the main surface of the metal foil, the proportion of the area occupied by the through-holes in the metal foil (the region bonded to the cathode portion) is preferably 0.04% or more and 15% or less, more preferably 0.1% or more and 10% or less. The region bonded to the cathode portion can also be said to be the region where the first layer is formed. In the case of having a plurality of through-holes, the area of the through-holes is the total area of the plurality of through-holes.

[0038] When the proportion of the area of the through-holes is 0.04% or more (or 0.1% or more), it is easy to obtain the effect achieved by the second layer. When the proportion of the area of the through-holes is 15% or less (or 10% or less), the conductivity of the metal foil can be sufficiently ensured.

[0039] When observing the metal foil from the normal direction of the main surface of the metal foil, the shape of the through-holes can be a circular shape, an elliptical shape, a polygonal shape, or a linear shape. Depending on the shape, the through-holes can be formed by punching. The linear through-holes are shapes with a slender width formed using a cutter or the like. The linear shape can be either straight or curved. As the polygonal shape, a triangular shape, a quadrilateral shape, etc. can be cited. As the metal foil having through-holes, for example, Figures 4 to 11 the metal foil 20 having the through-holes 20b as shown. Additionally, Figures 4 to 11 the shaded portion in

[0040] is the region bonded to the cathode portion. According to the formation method of the through-holes, sometimes the roughness of the main surface of the metal foil may increase. For example, in the case of forming linear through-holes using a cutter or the like, convex portions may be formed at the peripheral portion of the through-holes. The surface roughness Sa of the main surface of the metal foil having through-holes is, for example, 10 μm or more and 200 μm or less. Additionally, "surface roughness Sa" is one of the three-dimensional surface characteristic parameters specified in Japanese Industrial Standard JIS B 0681-2:2018, representing the arithmetic mean height.

[0041] (metal foil)

[0042] From the viewpoints of ease of formation, strength, conductivity, etc. of the through-holes, the metal foil preferably contains aluminum, aluminum alloy, copper, or copper alloy. The main surface of the metal foil can also be roughened by etching treatment or the like. The metal foil can also have a coating layer on the main surface. The coating layer can be formed on one main surface of the metal foil or on both main surfaces. The coating layer contains, for example, a material different from the metal foil (metal, metal compound, non-metal, etc.).

[0043] Examples of the material constituting the coating layer include metals (such as titanium and nickel), metal compounds such as titanium compounds (nitrides, carbides, carbonitrides, oxides, etc.), and carbonaceous materials. The metal oxide can be formed by chemical conversion treatment. The coating layer can contain one of the above materials or two or more thereof. The coating layer can be a single-layer structure or a multi-layer structure.

[0044] The coating layer is preferably composed of at least one selected from the group consisting of a titanium layer, a nickel layer, a titanium nitride layer, a titanium carbide layer, a titanium carbonitride layer, a titanium oxide layer, and a carbon layer. In this case, it is easy to suppress the deterioration of performance (such as the increase in ESR), and it is easy to reduce the performance fluctuation.

[0045] Depending on the material, the coating layer can be formed by a vapor deposition method, a firing method, etc. The material constituting the coating layer is directly fixed to the metal foil, and high conductivity can be obtained. Examples of the vapor deposition method include evaporation (vacuum evaporation, electron beam evaporation, arc plasma evaporation, etc.), sputtering method, CVD method, etc.

[0046] The thickness of the metal foil can be from 0.1 μm to 100 μm, or can be from 1 μm to 50 μm. On the main surface on one side of the metal foil, the thickness of the coating layer can be from 0.5 μm to 10 μm, or can be from 1 μm to 5 μm.

[0047] (Conductive adhesive layer)

[0048] Preferably, the conductive adhesive layer contains conductive particles and a resin (binder resin). Preferably, the conductive particles contain at least one selected from the group consisting of carbon particles and metal particles. Examples of the metal particles include silver particles, copper particles, etc. The resin can also contain at least one of a thermoplastic resin and a cured product of a solid resin.

[0049] The conductive adhesive used for forming the conductive adhesive layer contains, for example, conductive particles and at least one resin material of a thermoplastic resin and a solid resin. Examples of the resin material used for the conductive adhesive include epoxy resin, acrylic resin, polyimide resin, polyamide resin, polyurethane resin, polyester resin, fluororesin, vinyl resin, polyolefin resin, phenoxy resin, rubber-like materials, etc. As the epoxy resin, bisphenol F type epoxy resin, bisphenol A type epoxy resin, or a resin obtained by mixing bisphenol F type epoxy resin and bisphenol A type epoxy resin can be used. In addition, the epoxy resin can also contain a polyfunctional epoxy resin. As the polyfunctional epoxy resin, tetrahydroxy phenylethane type resin can be used. The conductive adhesive can also contain other materials such as a curing agent and a polymerization initiator. The conductive adhesive can also contain a solvent.

[0050] The conductive adhesive layer can be formed, for example, by applying a conductive adhesive to one major surface of the metal foil (the region in close contact with the cathode portion), disposing a capacitor element (cathode portion) thereon, and then filling the through-hole with the conductive adhesive from the opening of the through-hole on the other major surface side of the metal foil. Thereafter, when a capacitor element (cathode portion) is additionally disposed on the other major surface of the metal foil, it may be that a conductive adhesive is further applied onto the other major surface of the metal foil and the conductive adhesive filled in the through-hole, and a capacitor element (cathode portion) is disposed thereon.

[0051] In addition, the conductive adhesive can be applied to the cathode portion on one major surface side of the capacitor element, a metal foil can be disposed thereon, and then the conductive adhesive can be applied to the cathode portion on the other major surface side of the capacitor element, and another metal foil can be disposed thereon. Thereafter, a load is applied to the capacitor element from above the metal foil, so that a part of the conductive adhesive applied to the cathode portion enters the through-hole. In this way, the conductive adhesive layer can also be formed.

[0052] Hereinafter, the electrolytic capacitor will be described in detail.

[0053] The capacitor element includes an anode portion and a cathode portion. The anode portion is, for example, an anode body including a first portion and a second portion. The above-mentioned first portion includes one end portion of the anode body (also referred to as the first end portion), and the above-mentioned second portion includes the other end portion (also referred to as the second end portion) on the side opposite to one end portion of the anode body. The cathode portion is formed on the second portion of the anode body. The anode body has a dielectric layer at least on the surface of the second portion.

[0054] (Anode body)

[0055] The anode body can include, for example, a valve-acting metal, an alloy containing a valve-acting metal, and a compound containing a valve-acting metal (intermetallic compound, etc.). The above-mentioned materials can be used alone or in combination of two or more. Examples of the valve-acting metal include aluminum, tantalum, niobium, titanium, etc. The anode body can be a foil (anode foil) of a valve-acting metal, an alloy containing a valve-acting metal, or a compound containing a valve-acting metal, or a formed body (porous formed body) of particles of a valve-acting metal, an alloy containing a valve-acting metal, or a compound containing a valve-acting metal, or a sintered body (porous sintered body) thereof.

[0056] When using an anode foil as the anode body, generally, in order to increase the surface area, a porous portion is formed on the surface of at least the second portion of the anode foil. Such an anode foil has a core portion and a porous portion formed on the surface of the core portion. For example, the porous portion is formed by forming unevenness on the surface of the anode foil. For example, the surface of at least the second portion of the anode foil can also be roughened by etching (such as electrolytic etching) to form an anode foil with a porous portion. The roughening treatment such as etching can also be performed after disposing a predetermined mask member on the surface of the first portion. On the other hand, the entire surface of the anode foil can be roughened by an etching treatment or the like. In the former case, an anode foil having no porous portion on the surface of the first portion but having a porous portion on the surface of the second portion can be obtained. In the latter case, in addition to the surface of the second portion, a porous portion is also formed on the surface of the first portion. As the etching treatment, a known method can be used, and for example, electrolytic etching can be cited. The mask member is not particularly limited and can be a conductor containing a conductive material, but is preferably an insulator such as resin. The mask member is removed before forming the solid electrolyte layer.

[0057] When the entire surface of the anode foil is roughened, a porous portion is present on the surface of the first portion. In this case, from the viewpoint of suppressing air from entering the inside of the solid electrolytic capacitor through the contact portion between the porous portion and the exterior body, at least a part of the porous portion formed on the first portion can be removed in advance or the pores of the porous portion can be compressed and flattened by compressing this part. Thereby, a decrease in the reliability of the electrolytic capacitor due to the entry of air can be suppressed.

[0058] When stacking a plurality of capacitor elements, the first ends of the anode bodies of the capacitor elements can be bundled and connected to a lead wire to be electrically connected to an external electrode. However, instead of bundling, the end faces of the plurality of first ends can be exposed from the outer surface of the exterior body and electrically connected to the external electrode.

[0059] In addition, the outer surface of the exterior body refers to the surface forming the outer shape of the exterior body. For example, when the sealed object in which the capacitor element and the substrate are sealed together by the exterior body has a shape such as a rectangular parallelepiped or a cube, sometimes one surface (such as the bottom surface) corresponds to the surface of the substrate, and the remaining five surfaces (such as the side surfaces, the top surface, etc.) other than the surface of the substrate correspond to the outer surface of the exterior body.

[0060] (Dielectric layer)

[0061] For example, anodic oxidation is performed on the valve-acting metal on the surface of at least the second part of the anode body through chemical conversion treatment or the like, thereby forming a dielectric layer. The dielectric layer contains an oxide of the valve-acting metal. For example, when aluminum is used as the valve-acting metal, the dielectric layer contains aluminum oxide. The dielectric layer is formed at least along the surface of the second part where the porous portion is formed (including the inner wall surface of the pores of the porous portion). In addition, the method for forming the dielectric layer is not limited thereto, and it is only necessary to form an insulating layer that functions as a dielectric on the surface of the second part. The dielectric layer may also be formed on the surface of the first part (for example, the porous portion on the surface of the first part).

[0062] For example, by immersing the anode body in a chemical conversion solution, infiltrating the chemical conversion solution into the surface of the anode body, and applying a voltage between the anode body as the anode and the cathode immersed in the chemical conversion solution, the chemical conversion treatment can be performed. When there is a porous portion on the surface of the anode body, the dielectric layer is formed along the uneven shape of the surface of the porous portion.

[0063] (Cathode part)

[0064] The cathode part is formed on the second part of the anode body having the dielectric layer. There is also a case where the cathode part covers the surface on the second part side of the separation layer.

[0065] The cathode part may include a solid electrolyte layer that covers at least a part of the dielectric layer and a cathode lead layer that covers at least a part of the solid electrolyte layer. In this case, the metal foil is bonded to the cathode lead layer using a conductive adhesive. That is, a conductive adhesive layer is interposed between the cathode lead layer and the metal foil. The cathode part is formed by forming a solid electrolyte in a manner that covers at least a part of the dielectric layer and forming a cathode lead layer in a manner that covers at least a part of the solid electrolyte layer. A capacitor element is obtained by forming the cathode part locally on the anode body having the dielectric layer.

[0066] (Solid electrolyte layer)

[0067] The solid electrolyte layer contains, for example, a conductive polymer (conjugated polymer, dopant, etc.). As the conjugated polymer, for example, a π-conjugated polymer (polypyrrole, polythiophene, polyaniline, and their derivatives, etc.) can be used. For example, poly(3,4-ethylenedioxythiophene) (PEDOT) etc. are included in the polythiophene derivatives. As the dopant, polystyrene sulfonic acid (PSS) etc. can be used, and naphthalene sulfonic acid, toluene sulfonic acid, etc. can also be used. For example, by polymerizing a precursor (monomer, oligomer, etc.) of the conjugated polymer and a dopant (naphthalene sulfonic acid, toluene sulfonic acid, etc.) on the dielectric layer using at least one of chemical polymerization and electrolytic polymerization, the solid electrolyte layer can be formed. Alternatively, the solid electrolyte layer can also be formed by attaching a solution in which a conjugated polymer and a dopant are dissolved or a dispersion in which a conjugated polymer and a dopant are dispersed to the dielectric layer and drying. As the dispersion medium (solvent), for example, water, an organic solvent, or a mixture thereof can be cited. The solid electrolyte layer can also contain a manganese compound.

[0068] (Cathode lead-out layer)

[0069] The cathode lead-out layer can have a layer containing conductive carbon (also referred to as a carbon layer) that covers at least a part of the solid electrolyte layer. In this case, the metal foil is bonded to the carbon layer using a conductive adhesive. That is, a conductive adhesive layer can also be interposed between the carbon layer and the metal foil. As the conductive carbon contained in the carbon layer, for example, graphite (artificial graphite, natural graphite, etc.) can be cited.

[0070] The cathode lead-out layer can also further have a metal-containing layer that covers at least a part of the carbon layer. In this case, the metal foil is bonded to the metal-containing layer. And a conductive adhesive layer can be interposed between the metal-containing layer and the metal foil. The metal-containing layer contains, for example, metal particles and a resin. As the metal particles, silver particles etc. can be cited. As the resin (binder resin) used for forming the metal-containing layer, a thermoplastic resin can be used, and a thermosetting resin such as an imide-based resin or an epoxy resin is preferred.

[0071] (Separation layer)

[0072] In order to electrically separate the anode part and the cathode part, an insulating separation layer can be provided. The separation layer is formed before the cathode part is formed. The separation layer can be provided in a manner that covers at least a part of the surface of the first part and approaches the cathode part. From the viewpoint of suppressing air from entering the solid electrolytic capacitor, the separation layer can also be bonded to the first part and the outer package. The separation layer can also be disposed above the first part with a dielectric layer therebetween. Such a separation layer is formed after the dielectric layer is formed. However, it is not limited to this case, and according to need, it can also be formed before the dielectric layer is formed.

[0073] The separation layer contains, for example, a resin and can use the materials exemplified for the outer package described later. It is also possible to make the dielectric layer formed in the porous portion of the first part dense by compression to have insulating properties.

[0074] For example, the separation layer can also be provided by pasting a sheet-like insulating member (such as a resin tape) on the first part. When using an anode foil having a porous portion on the surface, it is also possible to make the insulating member adhere to the first part after removing or compressing at least a part of the porous portion of the first part for flattening. Preferably, the sheet-like insulating member has an adhesive layer on the surface on the side pasted to the first part.

[0075] In addition, a liquid resin can be applied or infiltrated into at least a part of the first part to form an insulating member that adheres to the first part. In the method using a liquid resin, the insulating member can be formed to fill the unevenness on at least the surface layer of the porous portion of the first part. In this case, the liquid resin easily enters the concave portions on the surface layer of the porous portion, and an insulating member can be easily formed even in the concave portions. In this case, since the porous portion on the surface layer of the anode body is protected by the insulating member, when the end portion of the anode body and the outer package are partially removed together to form the outer surface of the outer package and the end surface of the anode body is exposed from the outer surface of the outer package, the collapse of the porous portion of the anode body can be suppressed. Since the surface layer of the porous portion of the anode body and the insulating member are firmly adhered, when the end portion of the anode body and the outer package are partially removed together, the peeling of the insulating member from the surface of the porous portion of the anode body can be suppressed.

[0076] As the liquid resin, for example, a curable resin composition exemplified for the outer package described later can be used, or a solution in which a resin is dissolved in a solvent can also be used. In addition, the liquid resin can be applied or infiltrated, and a sheet-like insulating member can be used.

[0077] (Substrate)

[0078] The electrolytic capacitor can also include a substrate that supports one capacitor element or a laminate having a plurality of capacitor elements. The substrate is, for example, an insulating substrate. When it is possible to electrically separate between the first external electrode and the second external electrode, the substrate can also be a metal substrate or a printed circuit board with a wiring pattern applied.

[0079] When the substrate is an insulating substrate, one capacitor element or a laminate having a plurality of capacitor elements can be placed on the substrate using an adhesive (such as an epoxy-based adhesive).

[0080] When the substrate is a metal substrate or the like, a metal foil can be disposed between the cathode portion of one capacitor element and the substrate, or a metal foil can be disposed between the cathode portion of the capacitor element closest to the substrate in the element laminate and the substrate. In this case, the metal foil can also be bonded to the cathode portion and the substrate using a conductive adhesive. In this case, a conductive adhesive layer is formed not only between the metal foil and the cathode portion but also between the metal foil and the substrate. That is, the conductive adhesive layer includes a first layer sandwiched between the main surface on the cathode portion side of the metal foil and the cathode portion, a third layer sandwiched between the main surface on the substrate side of the metal foil and the substrate, and a second layer filled in the through holes of the metal foil and integrally formed with the first layer and the third layer. By the presence of the second layer, the bonding strength between the substrate and the metal foil is also improved together with the bonding strength between the cathode portion and the metal foil.

[0081] Examples of the insulating substrate include glass epoxy substrates, paper phenol substrates, glass polyimide substrates, fluorine substrates, etc. The thickness of the insulating substrate is, for example, 500 μm or less, and can also be 250 μm or less, and can also be 200 μm or less or 150 μm or less. In addition, the thickness of the insulating substrate can also be, for example, 50 μm or more.

[0082] The substrate can also have a coating film covering at least one main surface of the insulating substrate. The coating film can include at least one of a cured product of a solid resin (such as an epoxy resin) and a thermoplastic resin (such as a fluororesin). Epoxy resins can use the resins exemplified above. Examples of fluororesins include polytetrafluoroethylene, perfluoroalkoxy alkane, perfluoroethylene propylene copolymer, perfluoroethylene propylene copolymer, polyvinylidene fluoride, and vinylidene fluoride copolymer.

[0083] The resin material for forming the coating film can be either a thermoplastic resin or a solid resin. The resin material (resin composition) for forming the coating film can also include additives such as catalysts, curing agents, crosslinking agents, polymerization initiators, and curing accelerators. The coating film is formed by applying a coating agent containing the resin material to the main surface of the insulating substrate and drying or heating it. The coating agent can also contain a solvent. Examples of the solvent include water and organic solvents.

[0084] The coating film can also include fillers. Examples of fillers include insulating particles and insulating fibers. Examples of the insulating materials constituting the fillers include insulating compounds (oxides, etc.) such as silica and alumina, glass, and mineral materials (talc, mica, clay, etc.).

[0085] The thickness of the coating film is, for example, 0.3 μm or more, and can also be 1 μm or more or 3 μm or more, and can also be 10 μm or more or 30 μm or more. In addition, the thickness of the coating film can also be, for example, 100 μm or less.

[0086] (Outer package)

[0087] The capacitor element (or a plurality of stacked capacitor elements) is sealed by being covered with the outer package. The capacitor element can be sealed in such a way that at least one end face of the anode portion and the cathode portion is exposed from the outer surface of the outer package, or the outer surface can be formed by locally removing the outer package after sealing, and at least one end face of the anode portion and the cathode portion is exposed from the outer surface. It is also possible to seal with the outer package in such a way that the other end of the lead wire electrically connected to one of the anode portion and the cathode portion is in a state of being led out from the outer package, and connect the other end of the lead wire and the external electrode. In addition, the electrical connection between the capacitor element and the lead terminal can be made by pasting a plate-shaped external lead terminal bent into a predetermined shape to the surface of the cathode portion exposed in the capacitor element (or the lowermost or uppermost layer of a plurality of stacked capacitor elements) by means of a conductive paste or the like.

[0088] The outer package preferably contains, for example, a cured product of a curable resin composition, and may also contain a thermoplastic resin or a composition containing the thermoplastic resin.

[0089] The outer package can also be formed, for example, by using a forming technique such as injection molding. The outer package can also be formed, for example, by filling a predetermined portion with a curable resin composition or a thermoplastic resin (composition) in such a way as to cover the capacitor element supported on the substrate by using a predetermined mold.

[0090] The curable resin composition may contain at least one selected from fillers, curing agents, polymerization initiators, catalysts, etc. in addition to the curable resin. As the curable resin, a thermosetting resin can be exemplified. The curing agent, polymerization initiator, catalyst, etc. are appropriately selected according to the type of the curable resin.

[0091] Examples of the curable resin include epoxy resin, phenolic resin, urea resin, polyimide, polyamideimide, polyurethane, diallyl phthalate, unsaturated polyester, etc. Examples of the thermoplastic resin include polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), etc. A thermoplastic resin composition containing a thermoplastic resin and a filler can also be used.

[0092] From the viewpoint of improving the strength of the outer package, etc., the outer package preferably contains a filler. As the filler, it can also be selected from the fillers described for the coating film. The outer package can contain either one filler or a combination of two or more.

[0093] (Contact layer)

[0094] Alternatively, at least one of the end faces of the anode portion and the cathode portion exposed from the outer package body is connected to the external electrode via a contact layer. The contact layer can be formed, for example, by an electroless Ni plating layer, or can be formed by an electroless Ni plating layer and an electroless Ag plating layer covering the electroless Ni plating layer. When the contact layer is provided, the electrical connection between the end face of the anode portion or the cathode portion and the external electrode can be made more reliable by the contact layer, which is advantageous in terms of improving the reliability of the solid electrolytic capacitor.

[0095] Alternatively, the contact layer is not formed so as to cover the surface of the outer package body as much as possible, but is selectively formed so as to cover only the end face of the anode portion or the cathode portion exposed from the outer package body. It is also possible to perform a zincate treatment before forming the electroless Ni plating layer in such a manner that the electroless Ni plating layer is selectively formed on the end face of the anode portion or the cathode portion.

[0096] (External electrode)

[0097] The external electrode generally includes a first external electrode connected to the cathode portion and a second external electrode connected to the anode portion. When the anode portion includes an anode body having a dielectric layer, it is also possible that the anode body (second portion) has a second end face exposed from the outer package body, and the second end face is electrically connected to the second external electrode. Each external electrode can also include a metal layer. The metal layer is, for example, a plating layer. The metal layer includes, for example, at least one selected from the group consisting of nickel (Ni), copper (Cu), zinc (Zn), tin (Sn), silver (Ag), and gold (Au). The formation of the metal layer can be performed, for example, using film-forming techniques such as electrolytic plating, electroless plating, sputtering, vacuum evaporation, chemical vapor deposition (CVD), cold spraying, and spraying.

[0098] Each external electrode can also include, for example, a laminated structure of a Ni layer and a Sn layer. Each external electrode is preferably a metal having excellent wettability with solder. Examples of such a metal include Sn, Au, Ag, Pd, etc.

[0099] Each external electrode can also include, for example, a laminated structure of a conductive paste layer and a plating layer. In terms of excellent wettability with solder, as the plating layer, a plating layer having the above-mentioned laminated structure of a Ni layer and a Sn layer (Ni / Sn plating layer, etc.) can be used.

[0100] (Conductive paste layer)

[0101] The conductive paste layer can be formed to cover at least one of the end faces of the anode portion and the cathode portion of the capacitor element or a plurality of capacitor elements. At this time, the conductive paste layer can also be formed in such a manner as to cover the end face with the contact layer interposed therebetween. In addition, the conductive paste layer can also be formed in such a manner as to cover not only the end face of the anode portion or the cathode portion but also the surface (such as the side surface) of the outer package body exposing the end face. In this way, the anode portion or the cathode portion of the capacitor element is electrically connected to the conductive paste layer.

[0102] The conductive paste layer can be formed by applying a conductive paste containing conductive particles and a resin material to the surface of the outer package body exposing the end face of the anode portion or the cathode portion and drying it. Therefore, the conductive paste layer can also be referred to as a conductive resin layer containing conductive particles. The resin material is suitable for bonding with the outer package body and the contact layer, and the bonding strength can be improved through chemical bonding (such as hydrogen bonding). As the conductive particles, for example, metal particles such as silver and copper, and particles of conductive inorganic materials such as carbon can be used.

[0103] The conductive paste layer can also cover not only the surface (such as the side surface) of the outer package body exposing the end face of the anode portion or the cathode portion of the capacitor element but also a part of the surface (such as the upper surface or the bottom surface) intersecting with the surface. In addition, when a part of the outer surface of the capacitor element is formed on the surface of the substrate, a part of the surface of the substrate can also be covered.

[0104] In the case of using a laminated substrate including an insulating substrate as the insulating substrate, an external electrode (such as a first external electrode electrically connected to the cathode portion) can also be formed in advance on the side of the laminated substrate opposite to the side on which the element laminate is placed. Through placement, the external electrode (such as the first external electrode) can be electrically connected to the anode portion or the cathode portion (usually the cathode portion) of the capacitor element by means of the wiring pattern formed on the laminated substrate and the through hole connecting the wiring pattern on the front side and the wiring pattern on the back side. In this case, the first external electrode is electrically connected to the cathode portion of each capacitor element by means of the substrate. According to the wiring pattern on the back side, the first external electrode (cathode) can be arbitrarily arranged in the central region of the bottom surface of the electrolytic capacitor. For example, the first external electrode can also be arranged close to the second external electrode.

[0105] Figure 1 is a cross-sectional view schematically showing an example of an electrolytic capacitor according to an embodiment of the present disclosure. Figure 2 is an enlarged Figure 1 cross-sectional schematic view of the main part near the metal foil disposed between adjacent capacitor elements of the element laminate of the electrolytic capacitor shown. Figure 3 is an enlarged Figure 1 cross-sectional schematic view of the main part near the metal foil disposed at the end of the element laminate of the electrolytic capacitor shown. In addition, Figure 1The electrolytic capacitor 100 has Figure 2 and Figure 3 the through-hole 20b and the conductive adhesive layer 30 shown, but in Figure 1 for convenience, the through-hole 20b and the conductive adhesive layer 30 are not shown and are omitted.

[0106] As Figure 1 shown, the electrolytic capacitor 100 includes a plurality of stacked capacitor elements 10, an outer package 14 that seals the capacitor elements 10, a first external electrode 22, and a second external electrode 21. In the illustrated example, the plurality of stacked capacitor elements 10 are supported on a substrate 17. The substrate 17 includes an insulating substrate 17a and a coating film 17b that covers one main surface of the insulating substrate 17a.

[0107] Each capacitor element 10 includes a cathode portion 6 and an anode body 3 that constitutes an anode portion. The anode body 3 is, for example, an anode foil. The anode body 3 has a core portion 4 and a porous portion 5 formed on the surface of the core portion 4 (the surface layer of the anode body 3). A dielectric layer (not shown) is formed on at least a part of the surface of the porous portion 5. The cathode portion 6 covers at least a part of the dielectric layer. The cathode portion 6 includes a solid electrolyte layer 7 and a cathode lead-out layer.

[0108] At one end (the first end) of the capacitor element 10, the anode body 3 is exposed without being covered by the cathode portion 6. The other end (the second end) of the capacitor element 10 is covered by the cathode portion 6. The portion of the anode body 3 covered by the cathode portion 6 (particularly the solid electrolyte layer 7) is referred to as the second portion 2, and the other portion of the anode body 3 is referred to as the first portion 1. The first portion 1 is the portion of the anode body 3 not covered by the cathode portion 6. The end of the first portion 1 is the first end, and the end of the second portion 2 is the second end.

[0109] In the illustrated example, the second portion 2 has a core portion 4 and a porous portion 5 formed on the surface of the core portion 4. In the first portion 1, the surface may or may not have a porous portion 5. The dielectric layer is formed at least along the surface of the porous portion 5 formed in the second portion 2. At least a part of the dielectric layer covers the inner wall surface of the pores of the porous portion 5 and is formed along the inner wall surface.

[0110] The cathode portion 6 includes a solid electrolyte layer 7 that covers at least a part of the dielectric layer and a cathode lead-out layer that covers at least a part of the solid electrolyte layer 7. An uneven shape corresponding to the shape of the surface of the anode body 3 is formed on the surface of the dielectric layer. The solid electrolyte layer 7 is formed, for example, to fill such unevenness of the dielectric layer. The cathode lead-out layer includes a carbon layer 8 that covers at least a part of the solid electrolyte layer 7.

[0111] The electrolytic capacitor 10 includes a metal foil 20 electrically connected to the cathode portion 6 ( Figure 2 ,Figure 3 )。The metal foil 20 has at least one through hole 20b penetrating in the thickness direction. The metal foil 20 is bonded to the cathode lead layer (carbon layer 8) of the cathode portion 6 by the conductive adhesive layer 30. The conductive adhesive layer 30 includes a first layer 31 interposed between the main surfaces of the cathode portion 6 and the metal foil 20 and a second layer 32 filled in the through hole 20b. The first layer 31 is formed on the main surface of the metal foil 20 and the second layer 32 filled in the through hole 20b and is integrated with the second layer 32.

[0112] Figure 2 The metal foil 20 shown is disposed between capacitor elements 10 adjacent to each other in the stacking direction. In this case, the first layer 31 is formed on both main surfaces of the metal foil 20. That is, the first layer 31 includes a first A layer 31A interposed between the cathode portion 6 of one capacitor element 10 among the capacitor elements 10 adjacent to each other and one main surface of the metal foil 20 and a first B layer 31B interposed between the cathode portion 6 of the other capacitor element 10 among the capacitor elements 10 adjacent to each other and the other main surface of the metal foil 20. The first A layer 31A and the first B layer 31B are integrated with the second layer 32. The first A layer 31A and the first B layer 31B are integrated with each other by the second layer 32.

[0113] Figure 3 The metal foil 20 shown is disposed on the capacitor element 10 at the end in the stacking direction. In this case, the first layer 31 is formed on one main surface (capacitor element 10 side) of the metal foil 20. The first layer 31 and the second layer 32 are integrated.

[0114] An insulating separation layer (or insulating member) 12 may be formed in a region of the anode body 3 that does not face the cathode portion 6 and at least in a portion adjacent to the cathode portion 6 so as to cover the surface of the anode body 3. Thereby, contact between the cathode portion 6 and the exposed portion (first portion 1) of the anode body 3 can be restricted. The separation layer 12 is, for example, an insulating resin layer.

[0115] The exterior body 14 has a substantially rectangular parallelepiped shape, and the electrolytic capacitor 100 also has a substantially rectangular parallelepiped shape. In the illustrated example, the exterior body 14 has a first outer surface 14a and a second outer surface 14b on the side opposite to the first outer surface 14a. The end surface 1a of the first end portion of the anode body 3, which is the anode portion of each capacitor element 10, is exposed in the first outer surface 14a. In addition, the end surface 20a of the metal foil 20 is exposed from the exterior body in the second outer surface 14b.

[0116] The end faces 20a of the metal foil 20 exposed from the outer package 14 and the second outer surface 14b are covered by the first external electrode 22. The contact layer 15 is formed on the end faces 20a so as to cover the end faces 20a of the metal foil 20. The first external electrode 22 is electrically connected to the end faces 20a of the metal foil 20 through the contact layer 15.

[0117] In the electrolytic capacitor 100, the end faces 1a of the first ends of the plurality of anode bodies 3 exposed from the outer package 14 and the first outer surface 14a are covered by the second external electrode 21. The contact layer 15 is formed on the end faces 1a so as to cover the end faces 1a of the anode bodies 3. In the illustrated example, the end face of the separation layer 12 is also exposed from the first outer surface 14a of the outer package 14, and the exposed end face is also covered by the second external electrode 21. The second external electrode 21 is electrically connected to the end faces 1a of the anode bodies 3 through the contact layer 15.

[0118] The second external electrode 21 includes, for example, a conductive paste layer 21A such as a silver paste layer and a Ni / Sn plating layer 21B covering the conductive paste layer 21A. Similarly, the first external electrode 22 includes, for example, a conductive paste layer 22A such as a silver paste layer and a Ni / Sn plating layer 22B covering the conductive paste layer 22A.

[0119] The second external electrode 21 covers the entire first outer surface 14a of the outer package 14, and also covers a part of the third outer surface perpendicular to the first outer surface 14a and the first outer surface 14a side of the substrate 17 respectively. The first external electrode 22 also similarly covers the entire second outer surface 14b, and also covers a part of the third outer surface 14c perpendicular to the second outer surface 14b and the second outer surface 14b side of the substrate 17 respectively. According to such a structure, the adhesion can be further improved between the second external electrode 21 and the first outer surface 14a and between the first external electrode 22 and the second outer surface 14b. The first external electrode 22 and the second external electrode 21 covering a part of the substrate 17 are exposed at the bottom surface of the electrolytic capacitor 100 respectively. The above exposed portions constitute the anode terminal and the cathode terminal of the electrolytic capacitor 100 respectively.

[0120] <Supplementary Note>

[0121] Based on the description of the above embodiments, the following technologies are disclosed.

[0122] (Technology 1)

[0123] An electrolytic capacitor, wherein,

[0124] This electrolytic capacitor includes:

[0125] A capacitor element including an anode portion and a cathode portion;

[0126] An outer package for sealing the capacitor element;

[0127] A metal foil electrically connected to the cathode portion;

[0128] A first external electrode electrically connected to the metal foil; and

[0129] A conductive adhesive layer,

[0130] The metal foil has a through-hole penetrating in the thickness direction,

[0131] The conductive adhesive layer includes a first layer sandwiched between the main surfaces of the cathode portion and the metal foil and a second layer filled in the through-hole,

[0132] The first layer and the second layer are integrated,

[0133] The metal foil has a first end face exposed from the outer package,

[0134] The first end face is electrically connected to the first external electrode.

[0135] (Technology 2)

[0136] The electrolytic capacitor according to Technology 1, wherein,

[0137] The electrolytic capacitor includes an element laminate in which a plurality of the capacitor elements are laminated.

[0138] (Technology 3)

[0139] The electrolytic capacitor according to Technology 2, wherein,

[0140] In the element laminate, the metal foil is disposed between adjacent capacitor elements.

[0141] The first layer includes: a first A layer sandwiched between the cathode portion of one of the adjacent capacitor elements and one main surface of the metal foil; and a first B layer sandwiched between the cathode portion of the other of the adjacent capacitor elements and the other main surface of the metal foil,

[0142] The first A layer and the first B layer are integrated with the second layer.

[0143] (Technology 4)

[0144] The electrolytic capacitor according to any one of Technologies 1 to 3, wherein,

[0145] The cathode portion includes a solid electrolyte layer covering at least a part of the surface of the dielectric layer and a cathode lead-out layer covering the solid electrolyte layer,

[0146] A conductive adhesive layer is interposed between the cathode lead-out layer and the metal foil.

[0147] (Technology 5)

[0148] The electrolytic capacitor according to Technology 4, wherein

[0149] the cathode lead-out layer includes a carbon layer covering the surface of the solid electrolyte layer,

[0150] a conductive adhesive layer is interposed between the carbon layer and the metal foil.

[0151] (Technology 6)

[0152] The electrolytic capacitor according to Technology 4, wherein

[0153] the cathode lead-out layer includes a carbon layer covering the surface of the solid electrolyte layer and a metal-containing layer covering the surface of the carbon layer,

[0154] the metal-containing layer contains metal particles and a resin,

[0155] a conductive adhesive layer is interposed between the metal-containing layer and the metal foil.

[0156] (Technology 7)

[0157] The electrolytic capacitor according to any one of Technologies 1 to 6, wherein

[0158] the electrolytic capacitor includes a second external electrode electrically connected to the anode portion.

[0159] (Technology 8)

[0160] The electrolytic capacitor according to Technology 7, wherein

[0161] the anode portion includes an anode body having a dielectric layer on its surface,

[0162] the anode body has a second end face exposed from the outer package,

[0163] the second end face is electrically connected to the second external electrode.

[0164] (Technology 9)

[0165] The electrolytic capacitor according to any one of Technologies 1 to 8, wherein

[0166] When the metal foil is observed from the normal direction of the main surface of the metal foil, the proportion of the area occupied by the through hole in the region of the metal foil that is in close contact with the cathode portion is 0.04% or more and 15% or less.

[0167] (Technology 10)

[0168] The electrolytic capacitor according to any one of Technologies 1 to 9, wherein,

[0169] When the metal foil is observed in the normal direction of the main surface of the metal foil, the shape of the through hole is a circular shape, an elliptical shape, a polygonal shape, or a linear shape.

[0170] (Technology 11)

[0171] The electrolytic capacitor according to any one of Technologies 1 to 10, wherein,

[0172] The plurality of through holes are arranged regularly.

[0173] (Technology 12)

[0174] The electrolytic capacitor according to Technology 11, wherein,

[0175] The plurality of through holes are arranged in a lattice pattern.

[0176] (Technology 13)

[0177] The electrolytic capacitor according to any one of Technologies 1 to 12, wherein,

[0178] The metal foil contains aluminum, aluminum alloy, copper, or copper alloy.

[0179] (Technology 14)

[0180] The electrolytic capacitor according to any one of Technologies 1 to 13, wherein,

[0181] The metal foil has a coating layer on the main surface,

[0182] The coating layer is composed of at least one selected from the group consisting of a titanium layer, a nickel layer, a titanium nitride layer, a titanium carbide layer, a titanium carbonitride layer, a titanium oxide layer, and a carbon layer.

[0183] (Technology 15)

[0184] The electrolytic capacitor according to Technology 2, wherein,

[0185] The electrolytic capacitor includes a substrate that supports the element laminate.

[0186] (Technology 16)

[0187] The electrolytic capacitor according to any one of Technologies 1 to 15, wherein,

[0188] The conductive adhesive layer contains conductive particles and a resin,

[0189] The conductive particles include at least one selected from the group consisting of carbon particles and metal particles.

[0190] [Examples]

[0191] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0192] "Electrolytic Capacitors A1 to A8 and B1"

[0193] Manufacture was carried out according to the following procedure Figure 1 The solid electrolytic capacitor shown, which includes a plurality of stacked capacitor elements 10, was evaluated for its characteristics.

[0194] (Manufacture of Capacitor Element 10)

[0195] Etching treatment was performed on both sides of an aluminum foil (thickness: 100 μm) to produce an anode body 3. A dielectric layer (layer of aluminum oxide) was formed on the surface of the second portion 2 of the anode body 3 by chemical conversion treatment. After a separation layer 12 was formed on the first end portion 1 of the anode body 3, a solid electrolyte layer 7 containing a conductive polymer was formed so as to cover the second portion 2 of the anode body 3 having a dielectric layer on its surface.

[0196] The anode body 3 having a dielectric layer and a solid electrolyte layer on its surface was immersed in a dispersion liquid in which graphite particles were dispersed in water, and after being taken out of the dispersion liquid, it was heated and dried, so that a carbon layer 8 was formed at least on the surface of the solid electrolyte layer 7. In this way, a cathode lead-out layer composed of the carbon layer 8 was formed on the surface of the solid electrolyte layer 7, and the capacitor element 10 was obtained.

[0197] (Manufacture of Metal Foil 20)

[0198] As the metal foil 20 used for manufacturing the element laminate, an aluminum foil with a thickness of 20 μm was prepared. Through holes 20b having the shapes and numbers shown in Table 1 were provided at predetermined positions on the metal foil 20 ( Figures 4 to 7 ). The size of the through holes was adjusted so that the area ratio occupied by the through holes in the metal foil (the shaded portion of the region in contact with the cathode portion: Figures 4 to 7 ) became the value shown in Table 1. Circular through holes were provided by punching. Linear through holes were formed using a cutter.

[0199] (Lamination of Capacitor Elements 10)

[0200] A plurality of capacitor elements 10 are stacked in such a manner that the first parts 1 overlap each other to fabricate an element laminate. At this time, metal foils 20 (aluminum foils, thickness 20 μm) are disposed between adjacent capacitor elements 10. Also, metal foils 20 are disposed on the capacitor elements 10 at the ends in the stacking direction (the ends on the side opposite to the substrate 17).

[0201] The metal foils 20 are bonded to the capacitor elements 10 (carbon layer 8) using a conductive adhesive. As the conductive adhesive, a conductive paste containing conductive carbon particles and a resin material is used. Specifically, the conductive adhesive is applied to the main surface of the metal foil and filled into the through-holes of the metal foil to form a conductive adhesive layer 30. As the conductive adhesive layer 30, a first layer 31 and a second layer 32 are integrally formed. The first layer 31 is formed between the cathode lead-out layer of the capacitor element 10 and the main surface of the metal foil 20. The second layer is formed inside the through-hole 20b. The filling rate of the second layer into the through-hole 20b is 75% or more.

[0202] (Arrangement of the substrate 17)

[0203] The element laminate is placed on the substrate 17 using an epoxy-based adhesive. The substrate 17 is composed only of an insulating substrate 17a. As the insulating substrate 17a, a material obtained by heating and drying a glass epoxy substrate with an average thickness of 100 μm is used.

[0204] (Sealing by the outer package 14)

[0205] By molding, an outer package 14 made of an insulating resin is formed around the capacitor element 10.

[0206] The side portion of the outer package 14 is cut off by cutting to form a first outer surface 14a and a second outer surface 14b. At this time, the outer package 14 is cut in such a manner that the end surface 1a of the anode body 3 of each capacitor element 10 is exposed from the first outer surface 14a and the end surface 20a of the metal foil 20 is exposed from the second outer surface 14b. In this way, a precursor in a state where the end surface 1a of the anode body 3 is exposed from the first outer surface 14a and the end surface 20a of the metal foil 20 constituting the cathode portion 6 is exposed from the second outer surface 14b is obtained. The first outer surface 14a and the second outer surface 14b of the outer package 14 and the end surface of the separation layer 12 exposed from the first outer surface 14a are subjected to a cleaning process and a hydrophilic treatment.

[0207] (Formation of the contact layer 15)

[0208] Using the precursor obtained as described above, an electroless Ni plating layer is formed so as to cover the end face 1a of the anode body 3 exposed from the first outer surface 14a, and then an electroless Ag plating layer is formed on the electroless Ni plating layer. In this way, a contact layer 15 composed of an electroless Ni plating layer and an electroless Ag plating layer is formed. A contact layer 15 covering the end face 20a of the metal foil 20 exposed from the second outer surface 14b is formed in the same manner as described above.

[0209] (Formation of the first external electrode 22 and the second external electrode 21)

[0210] The first external electrode 22 and the second external electrode 21 are respectively formed so as to cover the contact layer 15 formed as described above and the first outer surface 14a and the contact layer 15 and the second outer surface 14b.

[0211] More specifically, by applying a conductive paste containing silver particles and resin to the contact layer 15 and the outer surface of the package and heating and drying, conductive paste layers 21A and 22A are respectively formed. Then, an electrolytic Ni plating layer and an electrolytic Sn plating layer are formed so as to cover the conductive paste layers 21A and 22A respectively. In this way, Ni / Sn plating layers 21B and 22B are respectively formed. By washing the surface of the plating layer with water and drying it, an electrolytic capacitor having the first external electrode 22 and the second external electrode 21 is obtained.

[0212] 《Electrolytic capacitor B1》

[0213] An electrolytic capacitor B1 is obtained in the same manner as the electrolytic capacitor A1 except that through holes are not provided in the metal foil.

[0214] The following evaluations 1 to 2 are performed on the obtained electrolytic capacitor.

[0215] [Evaluation 1: Initial capacitance, ESR, height dimension]

[0216] The initial capacitance (μF) at a frequency of 120 Hz and the initial ESR (mΩ) at a frequency of 100 kHz are measured for the electrolytic capacitor using a 4-terminal measuring LCR tester in an environment of 20°C.

[0217] In addition, the initial height dimension (mm) of the electrolytic capacitor is measured. The height dimension of the electrolytic capacitor is set as the height dimension of the electrolytic capacitor in the stacking direction of the component stack (from Figure 1 the length in the stacking direction from the upper surface of the package 14 shown to the lower surface of the substrate 17 exposed).

[0218] Set the number of tests for initially measuring the capacitance, ESR, and height dimension of the electrolytic capacitor to 10. Calculate the standard deviation of the 10 measured values for the initial capacitance and ESR respectively. In addition, for ESR and height dimension, calculate the average of the 10 measured values as the initial ESR (X0) and height dimension (H0).

[0219] [Evaluation 2: ΔESR and Δ dimension (expansion) after reflow soldering treatment]

[0220] First, place the electrolytic capacitor in a constant temperature bath at 155°C for 24 hours (baking treatment). Then, place the electrolytic capacitor in a constant temperature and humidity chamber at 30°C and 60% RH for 192 hours (moisture absorption treatment). After that, take out the electrolytic capacitor from the constant temperature and humidity chamber and cool it to 25°C.

[0221] Next, perform reflow soldering treatment on the electrolytic capacitor in accordance with IPC / JEDEC J-STD-020D. Specifically, preheat the electrolytic capacitor under the conditions of maintaining the temperature: 150°C to 200°C and maintaining the time: within 180 seconds. Heat the preheated solid electrolytic capacitor at a temperature above 255°C (maximum temperature 260°C) for 30 seconds. The heating at the maximum temperature of 260°C at this time is set to within 10 seconds.

[0222] Find the ESR (X1) and height dimension (H1) of the electrolytic capacitor after reflow soldering treatment by the same method as in Evaluation 1.

[0223] Use the obtained X0 and X1 and calculate ΔESR (%) (the change rate of ESR after reflow soldering treatment) according to the following formula (1).

[0224] ΔESR = (X1 - X0) / X0 × 100 ···· (1)

[0225] Use the obtained H0 and H1 and calculate Δ dimension (expansion) (%) (the change rate of height after reflow soldering treatment) according to the following formula (2).

[0226] Δ dimension (expansion) = (H1 - H0) / H0 × 100 ···· (2)

[0227] Present the evaluation results in Table 1. In Table 1, A1 to A8 are examples, and B1 is a comparative example. In addition, the standard deviations σ of the initial capacitance and initial ESR in Table 1 are expressed as relative values when the standard deviation σ of the initial capacitance and initial ESR of the electrolytic capacitor B1 is set to 100. Moreover, ΔESR and Δ dimension (expansion) in Table 1 are expressed as relative values when the ΔESR and Δ dimension (expansion) of the electrolytic capacitor B1 are set to 100.

[0228]

Table 1

[0229]

[0230] Among electrolytic capacitors A1 to A8, compared with electrolytic capacitor B1, the standard deviation σ of the initial capacitance is smaller, the fluctuation is reduced, and the reliability is improved. In addition, among electrolytic capacitors A1 to A8, the ΔESR and Δ size after reflow soldering treatment are smaller, and the heat resistance is also improved. In particular, among electrolytic capacitors A1 to A7 in the range where the area ratio of the through holes is 0.04% or more and 15% or less, the standard deviation of the initial ESR is also smaller, the fluctuation is reduced, and the reliability is further improved.

[0231] "Electrolytic Capacitors A9 to A12"

[0232] Use a cutter to set 5, 7, 9, or 11 wire-shaped through holes at a predetermined position on the metal foil ( Figures 8 to 11 ). Adjust the size of the through holes so that the area ratio occupied by the through holes in the metal foil (the shaded part of the area in contact with the cathode part: Figures 8 to 11 ) becomes the value shown in Table 2. Except for the above, electrolytic capacitors A9 to A12 are manufactured in the same manner as electrolytic capacitor A1. The ΔESR and Δ size (expansion) after reflow soldering treatment are obtained in the same manner as above.

[0233] The evaluation results are shown in Table 2. The results of electrolytic capacitor B1 are also shown in Table 2. In Table 2, A9 to A12 are examples. The ΔESR and Δ size (expansion) in Table 2 are represented by relative values when the ΔESR and Δ size (expansion) of electrolytic capacitor B1 are set to 100.

[0234]

Table 2

[0235]

[0236] Among electrolytic capacitors A9 to A12, compared with electrolytic capacitor B1, the ΔESR and Δ size (expansion) after reflow soldering treatment are smaller.

[0237] Hereinafter, the adhesion between the metal foil and the capacitor element is evaluated.

[0238] [Evaluation 3: Adhesion Strength between Metal Foil and Capacitor Element]

[0239] The metal foil uses an aluminum foil with a thickness of 20 μm. One circular through hole ( Figure 4 ) is provided near the center of the area of the metal foil in contact with the cathode part. The diameter of the through hole is set to 0.5 mm, 1 mm, 1.5 mm, or 2 mm. The through hole in the metal foil (the area in contact with the cathode part: Figure 4The area ratio occupied in the shaded part) is the value shown in Table 3. The conductive adhesive is applied to one main surface of the metal foil and filled into the through holes, and the capacitor element is disposed on one main surface of the metal foil, and the metal foil is bonded to the capacitor element (cathode portion). In this way, a conductive adhesive layer including the first layer and the second layer is formed, and laminated samples a1 to a4 are produced. The capacitor element and the conductive adhesive used are the same capacitor element and conductive adhesive as those used in the electrolytic capacitor A1. In addition, except that through holes are not provided in the metal foil (the second layer is not formed), the laminated sample b1 is produced in the same manner as the laminated sample a1.

[0240] A tensile test is performed on each laminated sample, and a load is applied until fracture, and the maximum load at the time of fracture (when the metal foil is peeled off from the capacitor element) (hereinafter referred to as "fracture load") is obtained. As the measuring device, a tensile testing machine in accordance with Japanese Industrial Standard JIS B 7721 is used. Specifically, a load testing machine HIT-M and a load cell JLC-M50N manufactured by Nihon Keisoku System Co., Ltd. are used. Ten pieces of each of the laminated samples a1 to a4 and the laminated sample b1 are produced, and the average value of the ten measured values is obtained.

[0241] The evaluation results are shown in Table 3. The fracture load in Table 3 is expressed as a relative value when the fracture load of the laminated sample b1 is set to 100.

[0242]

Table 3

[0243]

[0244] In the laminated samples a1 to a4, the fracture load is larger than that of the laminated sample b1, and the bonding strength is improved. In particular, in the laminated samples a1 to a3 in which the ratio of the through holes is 15% or less, excellent bonding strength can be obtained.

[0245] Industrial Applicability

[0246] The electrolytic capacitor of the present disclosure can be used for various applications that require high reliability.

[0247] The present invention has been described by the current preferred embodiments, but such a disclosure should not be construed in a limiting manner. Various modifications and changes will be obvious to those skilled in the art in the technical field to which the present invention pertains by reading the above disclosure. Therefore, the appended claims should be construed to include all modifications and changes without departing from the true spirit and scope of the present invention.

[0248] Explanation of Reference Numerals

[0249] 1: Part 1 (anode lead-out part), 1a: End face of the first end, 2: Part 2 (cathode forming part), 3: Anode body, 4: Core part, 5: Porous part, 6: Cathode part, 7: Solid electrolyte layer, 8: Carbon layer, 10: Capacitor element, 12: Separation layer (insulating member), 14: Outer package, 14a: First outer surface of the outer package, 14b: Second outer surface of the outer package, 15: Contact layer, 17: Substrate, 17a: Insulating substrate, 17b: Coating film, 20: Gold electrode foil, 20a: End face of the metal foil, 20b: Through hole of the metal foil, 21: Second external electrode, 21A: Silver paste layer, 21B: Ni / Sn coating, 22: First external electrode, 22A: Silver paste layer, 22B: Ni / Sn coating, 30: Conductive adhesive layer, 31: First layer, 31A: First A layer, 31B: First B layer, 32: Second layer, 100: Electrolytic capacitor.

Claims

1. An electrolytic capacitor, wherein, the electrolytic capacitor includes: a capacitor element including an anode portion and a cathode portion; an outer package for sealing the capacitor element; a metal foil electrically connected to the cathode portion; a first external electrode electrically connected to the metal foil; and a conductive adhesive layer, the metal foil has a through-hole penetrating in the thickness direction, the conductive adhesive layer includes a first layer sandwiched between the main surface of the cathode portion and the metal foil and a second layer filled in the through-hole, the first layer and the second layer are integrated, the metal foil has a first end face exposed from the outer package, the first end face is electrically connected to the first external electrode.

2. The electrolytic capacitor according to claim 1, wherein, the electrolytic capacitor includes an element laminate formed by laminating a plurality of the capacitor elements.

3. The electrolytic capacitor according to claim 2, wherein, in the element laminate, the metal foil is disposed between adjacent capacitor elements, the first layer includes: a first A layer sandwiched between the cathode portion of one of the adjacent capacitor elements and one main surface of the metal foil; and a first B layer sandwiched between the cathode portion of the other of the adjacent capacitor elements and the other main surface of the metal foil, the first A layer and the first B layer are integrated with the second layer.

4. The electrolytic capacitor according to claim 1, wherein, the cathode portion includes a solid electrolyte layer covering at least a part of the surface of the dielectric layer and a cathode lead-out layer covering the solid electrolyte layer, the conductive adhesive layer is sandwiched between the cathode lead-out layer and the metal foil.

5. The electrolytic capacitor according to claim 4, wherein, the cathode lead-out layer includes a carbon layer covering the surface of the solid electrolyte layer, the conductive adhesive layer is sandwiched between the carbon layer and the metal foil.

6. The electrolytic capacitor according to claim 4, wherein, the cathode lead-out layer includes a carbon layer covering the surface of the solid electrolyte layer and a metal-containing layer covering the surface of the carbon layer, the metal-containing layer includes metal particles and a resin, the conductive adhesive layer is sandwiched between the metal-containing layer and the metal foil.

7. The electrolytic capacitor according to claim 1, wherein, the electrolytic capacitor includes a second external electrode electrically connected to the anode portion.

8. The electrolytic capacitor according to claim 7, wherein, the anode portion includes an anode body having a dielectric layer on the surface, the anode body has a second end face exposed from the outer package, the second end face is electrically connected to the second external electrode.

9. The electrolytic capacitor according to claim 1, wherein, when the metal foil is observed from the normal direction of the main surface of the metal foil, the ratio of the area occupied by the through-hole in the region of the metal foil in close contact with the cathode portion is 0.04% or more and 15% or less.

10. The electrolytic capacitor according to claim 1, wherein, When observing the metal foil in the normal direction of the main surface of the metal foil, the shape of the through hole is a circular shape, an elliptical shape, a polygonal shape, or a linear shape.

11. The electrolytic capacitor according to claim 1, wherein a plurality of the through holes are regularly arranged.

12. The electrolytic capacitor according to claim 11, wherein a plurality of the through holes are arranged in a lattice pattern.

13. The electrolytic capacitor according to claim 1, wherein the metal foil contains aluminum, an aluminum alloy, copper, or a copper alloy.

14. The electrolytic capacitor according to claim 1, wherein the metal foil has a coating layer on the main surface, the coating layer is composed of at least one selected from the group consisting of a titanium layer, a nickel layer, a titanium nitride layer, a titanium carbide layer, a titanium carbonitride layer, a titanium oxide layer, and a carbon layer.

15. The electrolytic capacitor according to claim 2, wherein the electrolytic capacitor includes a substrate that supports the element laminate.

16. The electrolytic capacitor according to claim 1, wherein the conductive adhesive layer contains conductive particles and a resin, the conductive particles contain at least one selected from the group consisting of carbon particles and metal particles.

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