Electrolytic capacitor and method for producing electrolytic capacitor

Abstract

A multilayer element in this electrolytic capacitor comprises: a capacitor element having an anode foil 22 including a metal section and a dielectric layer, and a cathode foil facing the anode foil 22 with a separator therebetween; and an anode lead 31 electrically connected with the anode foil 22. The anode foil 22 has an anode main section and an anode lead-out section 22b. The cathode foil faces the dielectric layer of the anode main section. A part of the anode lead 31 overlaps the anode lead-out section 22b. A plurality of joints J1 in which the anode lead 31 and the metal section are joined are formed in the overlapping region R1 of the anode lead-out section 22b and the anode lead 31. Two adjacent joints J1 among the plurality of joints J1 are connected via the metal section. In a portion of the overlapping region R1 other than the plurality of joints J1, the dielectric layer is interposed between the anode lead 31 and the metal section.

Description

Electrolytic capacitor and method for manufacturing the same CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2023-213289, filed on December 18, 2023, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to electrolytic capacitors and methods for manufacturing electrolytic capacitors.

[0003] Conventionally, a laminated electrolytic capacitor including a plurality of anode foils and a plurality of cathode foils stacked with separators interposed therebetween has been known (for example, Patent Document 1). In the electrolytic capacitor of Patent Document 1, anode foils and cathode foils each having an oxide coating layer are stacked in order with separators interposed therebetween. In one embodiment of the electrolytic capacitor, the protruding portion (lead portion) of the anode foil is formed from a single foil that is integral with the anode foil. After the oxide coating layer of the protruding portion is removed with a laser, the multiple protruding portions are connected to each other by friction stir welding or the like.

[0004] Japanese Patent Application Laid-Open No. 2005-45078

[0005] However, in the electrolytic capacitor of Patent Document 1, the welds are large, and the area required to connect multiple anode foils to each other is large, reducing the proportion of the area that contributes to the capacitance of the electrolytic capacitor (the area where the anode foils face each other). Furthermore, a process for removing the oxide film layer before welding is required, which may increase manufacturing costs. A separate process for connecting the anode lead to the anode foil for external connection is also required. In light of these circumstances, the present disclosure provides an electrolytic capacitor with a joint that can firmly and with low resistance join the anode foils to each other in a small area.

[0006] One aspect of the present disclosure relates to an electrolytic capacitor including a laminated element, the laminated element including at least one capacitor element having an anode foil including a metal portion and a dielectric layer formed on a surface of the metal portion, and a cathode foil facing the anode foil with a separator interposed therebetween, an anode lead electrically connected to the anode foil, and a cathode lead electrically connected to the cathode foil, the anode foil having an anode main portion and an anode lead portion, the cathode foil facing the dielectric layer formed on the anode main portion, a portion of the anode lead overlapping the anode lead, a plurality of joints formed in an overlapping area between the anode lead and the anode lead by joining the anode lead to the metal portion of the anode foil, two adjacent joints among the plurality of joints being connected via the metal portion of the anode foil, and the dielectric layer being interposed between the anode lead and the metal portion of the anode foil in a portion of the overlapping area other than the plurality of joints.

[0007] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor, the method including: a first step of preparing an anode foil having a metal portion and a dielectric layer formed on a surface of the metal portion; a second step of laminating a cathode foil onto at least a portion of the dielectric layer with a separator interposed therebetween to form at least one capacitor element; and a third step of overlapping an anode lead with an anode lead portion of the anode foil that does not face the cathode foil, and irradiating the anode lead with a laser to join the anode lead and the metal portion of the anode foil to form multiple joints.

[0008] According to the present disclosure, an electrolytic capacitor having low resistance and strong joints can be obtained. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0009] Fig. 2 is a perspective view schematically showing a multilayer element according to a first embodiment; Fig. 3 is a plan view of an electrolytic capacitor including the multilayer element of Fig. 1; Fig. 4 is a cross-sectional view of an anode lead and an anode extraction portion in a cross section passing through a plurality of joints (a cross section taken along line III-III in Fig. 2), with a portion enlarged and shown at the bottom left; Fig. 5 is a perspective view schematically showing an anode extraction portion and an anode lead of a multilayer element according to a second embodiment;

[0010] The following describes examples of embodiments of an electrolytic capacitor and a method for manufacturing an electrolytic capacitor according to the present disclosure. However, the present disclosure is not limited to the examples described below. While the following description may use specific numerical values ​​and materials, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0011] (Electrolytic Capacitor) The electrolytic capacitor according to the present disclosure is a laminated electrolytic capacitor including an anode foil and a cathode foil laminated with a separator interposed therebetween. The electrolytic capacitor according to the present disclosure includes a laminated element. The laminated element includes at least one capacitor element, an anode lead, and a cathode lead. The laminated element may include a plurality of capacitor elements. The laminated element and portions of the anode lead and cathode lead are housed in a case together with an electrolyte.

[0012] The capacitor element has an anode foil and a cathode foil. The anode foil includes a metal portion and a dielectric layer formed on the surface of the metal portion. The cathode foil faces the anode foil via a separator. A solid electrolyte may be disposed between the anode foil and the cathode foil. The separator may contain a solid electrolyte. A plurality of anode foils and cathode foils may be stacked alternately with the separator sandwiched therebetween.

[0013] The anode foil has an anode main portion and an anode lead portion. The anode foil may be formed in a sheet shape. The metal portion of the anode foil usually has a porous layer formed by roughening the surface by etching or the like, and a non-porous core portion. That is, the metal portion of the anode foil may have a core portion and a porous portion arranged outside the core. The dielectric layer is formed on the surface of the metal portion of the anode main portion and the anode lead portion. That is, the dielectric layer is formed along the surface of the porous portion of the metal portion. The dielectric layer is made of an oxide of the metal that constitutes the metal portion. Note that the dielectric layer may also be made of an oxide of a metal other than the metal that constitutes the metal portion. At least a portion of the dielectric layer is covered with a solid electrolyte.

[0014] The metal portion may be made of a valve metal, or an alloy or compound containing a valve metal, such as aluminum, tantalum, or niobium.

[0015] The dielectric layer may be formed by, for example, immersing a foil made of a metal portion in a chemical conversion solution such as an ammonium adipate solution and applying a voltage as needed to the foil, or by atomic layer deposition (ALD), chemical vapor deposition (CVD), or the like.

[0016] The solid electrolyte includes, for example, a manganese compound or a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and derivatives thereof. A solid electrolyte containing a conductive polymer can be formed, for example, by chemical polymerization and / or electrolytic polymerization of raw material monomers on a dielectric layer. Alternatively, the solid electrolyte can be formed, for example, by applying a solution in which a conductive polymer is dissolved or a dispersion in which a conductive polymer is dispersed to the dielectric layer.

[0017] The cathode foil faces a dielectric layer formed on the anode portion of the anode foil via a separator. The capacitance of the electrolytic capacitor can be realized in the region where the anode foil and the cathode foil face each other. The cathode foil may be made of a metal foil. The valve metals described above can be used as the material for the metal foil. The surface of the cathode foil may be roughened. An oxide film may be formed on the surface of the cathode foil as needed. A conductive layer such as a carbon layer may be formed on the surface of the cathode foil as needed.

[0018] The separator is interposed between the anode foil and the cathode foil. A nonwoven fabric can be used as the separator. Fiber materials that make up the nonwoven fabric include cellulose, polyethylene terephthalate, vinylon, and polyamides (aliphatic polyamides, aromatic polyamides, etc.). The separator may be impregnated with an electrolyte solution.

[0019] The electrolyte may be a mixture of a non-aqueous solvent and an ionic substance (solute, e.g., an organic salt) dissolved therein. The non-aqueous solvent may be an organic solvent or an ionic liquid. Examples of non-aqueous solvents that can be used include ethylene glycol, propylene glycol, sulfolane, γ-butyrolactone, and N-methylacetamide. Examples of organic salts that can be used include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate. The electrolyte may be a component that is liquid at room temperature (25°C) or at the temperature at which the electrolytic capacitor is used.

[0020] The anode lead is electrically connected to the anode foil. The anode lead is made of a metal (e.g., aluminum, aluminum alloy, gold, silver, platinum, etc.). A plating layer containing nickel, gold, copper, or tin may be formed on the surface of the anode lead. The anode lead and the cathode foil may be made of the same material. In this case, good electrical connection between the anode lead and the anode foil can be achieved. The anode lead functions as the first external terminal of the electrolytic capacitor.

[0021] The cathode lead is electrically connected to the cathode foil. The cathode lead is made of a metal (e.g., aluminum, aluminum alloy, gold, silver, copper, platinum, etc.). Alternatively, a plating layer containing nickel, gold, copper, or tin may be formed on the surface of the cathode lead. The cathode lead and the cathode foil may be made of the same material. In this case, good electrical connection between the cathode lead and the cathode foil can be achieved. The cathode lead functions as a second external terminal of the electrolytic capacitor.

[0022] A portion of the anode lead overlaps the anode lead portion of the anode foil. In the overlapping region between the anode lead portion and the anode lead (the region where the anode lead portion and the anode lead overlap each other as viewed from the stacking direction of the capacitor elements), multiple joints are formed by joining the anode lead to the metal portion of the anode foil. Each of the multiple joints may be formed in a spot shape as viewed from the stacking direction of the capacitor elements. The multiple joints may be arranged linearly or in a staggered pattern as viewed from the stacking direction. The multiple joints may also form a spot-bonded region where spot-shaped joints are aggregated, and multiple such spot-bonded regions may exist. Each of the multiple joints has a columnar shape that connects the upper surface of the anode lead to the lower surface of the anode foil (or the lower surface of the lowest anode foil when multiple anode foils are bonded). Two adjacent joints among the multiple joints are connected via the metal portion of the anode foil. In the overlapping region other than the plurality of joints, a dielectric layer is interposed between the anode lead and the metal portion of the anode foil.

[0023] Such multiple joints allow the size of each joint to be reduced and multiple joints to be arranged side by side, thereby narrowing the area that does not contribute to the capacitance of the electrolytic capacitor and providing a low-resistance, strong bond between the anode lead and the anode foil in the stacking direction of the capacitor element. The low-resistance bond is achieved primarily because the presence of multiple joints ensures a sufficient area for the current path in the stacking direction. Furthermore, in addition to the strong bond achieved by the presence of multiple joints, two adjacent joints among the multiple joints are connected via a metal portion of the anode foil. Therefore, a strong bond is also achieved in a direction perpendicular to the stacking direction (hereinafter simply referred to as the perpendicular direction). When viewed in a cross section passing through the multiple joints, this joint structure appears as a lattice-like joint structure (hereinafter simply referred to as a lattice structure) extending in both the stacking direction and the perpendicular direction. The lattice structure is stronger than a joint structure in which multiple joints are formed individually (i.e., a joint structure without perpendicular connections). As described above, the electrolytic capacitor according to the present disclosure has a low-resistance and strong joint (or joint structure).

[0024] The ratio (T1 / T2) of the total thickness T1 of the anode foil and anode lead at each of the multiple joints to the total thickness T2 of the anode foil and anode lead in the overlapping region other than the multiple joints may be 0.7 or greater and 1.2 or less. In this configuration, there is no significant difference in the total thickness of the anode foil and anode lead between the joint and its surrounding area. In other words, the thickness of the anode foil does not change significantly or deform significantly during the process of forming the joint. This reduces the likelihood of defects such as cracks occurring in the anode foil, thereby stabilizing the electrode structure achieved by the multiple joints. Each of the total thicknesses T1 and T2 can be calculated by measuring the total thickness at any number of locations within the corresponding region and averaging the results.

[0025] The metal portion of the anode foil may have a core portion and a porous portion disposed outside the core portion. The maximum width of each of the multiple joints may be greater than the thickness of the core portion of the metal portion of the anode foil. In this configuration, the path of current flowing through the multiple joints in the stacking direction (or the area of ​​each of the multiple joints) is large, thereby further reducing the electrical resistance at the joints. The maximum width of a joint refers to the maximum dimension of each joint in the perpendicular direction in a cross section passing through the multiple joints. The thickness of the core portion of the metal portion (i.e., the length dimension of the core portion of the metal portion in the stacking direction) can be determined by measuring the thickness of the core portion of the metal portion at any multiple locations and averaging the measurements. The maximum width of a joint and the thickness of the core portion of the metal portion can be determined, for example, based on a scanning electron microscope (SEM) image of a cross section passing through the multiple joints.

[0026] The shortest distance between two adjacent joints may be greater than 0 μm and less than 300 μm. By providing adjacent joints close to each other, a large number of joints can be formed in a given area, thereby reducing the connection resistance between the anode lead and the anode foil. The shortest distance may be greater than 0 μm and less than 200 μm, or may be greater than 50 μm and less than 150 μm.

[0027] The maximum width of each of the multiple joints may be 100 μm or less. In this configuration, by reducing the width of the joints, it is possible to narrow the area that does not contribute to the capacitance of the electrolytic capacitor. Furthermore, deformation of the anode foil (and anode lead) before and after forming the joints is suppressed, thereby stabilizing the electrode structure. The maximum width may be 90 μm or less, or 80 μm or less. The maximum width may also be greater than 0 μm.

[0028] In the overlapping region, there may be no through-holes that penetrate the anode foil in the thickness direction at positions where the anode foil contacts the multiple joints. The absence of through-holes can reduce wasted area for electrical connection between the anode lead and the anode foil.

[0029] The proportion of the insulating material constituting the dielectric layer at the multiple joints may be 0% by volume or more and 20% by volume or less. Because the proportion of the insulating material (e.g., an oxide of a valve metal contained in the metal portion) is small, the electrical resistance at each joint can be reduced, and therefore the equivalent series resistance (ESR) of the electrolytic capacitor can be reduced. The proportion may be 0% by volume or more and 10% by volume or less, or 0% by volume or more and 5% by volume or less.

[0030] At least one capacitor element may be composed of a plurality of capacitor elements, including a first capacitor element and a second capacitor element, stacked adjacent to each other. The anode lead portion of the anode foil of the first capacitor element and the anode lead portion of the anode foil of the second capacitor element are joined to each other at a plurality of joints, and preferably, in the vicinity of each of the plurality of joints, the distance between the anode lead portion of the anode foil of the first capacitor element and the anode lead portion of the anode foil of the second capacitor element is 0% to 20% of the thickness of the anode foil. This configuration ensures reliable joining of the anode foils of the plurality of capacitor elements. Note that the vicinity of each of the plurality of joints refers to an area that is 100 μm or less from the outline of the joint when viewed from the stacking direction.

[0031] (Method for Manufacturing Electrolytic Capacitor) The method for manufacturing an electrolytic capacitor according to the present disclosure can be used to manufacture, for example, the electrolytic capacitor described above, but can also be used to manufacture other electrolytic capacitors. The method for manufacturing an electrolytic capacitor according to the present disclosure includes a first step, a second step, and a third step.

[0032] In the first step, an anode foil having a metal portion and a dielectric layer formed on the surface of the metal portion is prepared. The preparation of the anode foil includes both newly fabricating the anode foil and obtaining a pre-finished anode foil.

[0033] In the second step, a cathode foil is laminated on at least a portion of the dielectric layer via a separator to form at least one capacitor element.

[0034] In the third step, an anode lead is placed over the anode lead portion of the anode foil that is not facing the cathode foil, and the anode lead is irradiated with a laser to bond the anode lead to the metal portion of the anode foil, forming multiple joints, which allows for low-resistance and strong joints to be achieved.

[0035] It is not necessary to drill holes in the anode foil at the joining portion before the second step, which saves time required for drilling holes and reduces the manufacturing cost of the electrolytic capacitor.

[0036] The dielectric layer at the position where the joint is to be formed may not need to be removed in advance before the third step. In this case, the anode lead may be irradiated with a laser in the third step so that the dielectric layer is removed at the joint and the anode lead and the metal portion of the anode foil are joined. Typically, when a laser is directly irradiated onto a stacked anode foil so that the dielectric layer is removed at the joint and the anode lead and the metal portion of the anode foil are joined, the laser power can melt the metal portion of the anode foil in the irradiated area, resulting in an unsuccessful joint. In contrast, in the present application, by irradiating the anode lead overlapping the anode foil with a laser, the molten metal of the anode lead can penetrate into the portion of the anode foil corresponding to the joint, thereby forming a joint without melting the metal portion of the anode foil. The laser may be irradiated multiple times at one location on the anode lead. The laser may be irradiated with each joint so that the output gradually decreases from the start of irradiation. The laser output increases in proportion to the number of anode foils stacked, and may be 30 W or more and 70 W or less per anode foil. The laser irradiation time may be 1 second or less per joint.

[0037] As described above, the present disclosure provides an electrolytic capacitor with a low-resistance, strong joint due to the lattice-like joint structure. Furthermore, the present disclosure enables such an electrolytic capacitor to be manufactured at low cost.

[0038] An example of an electrolytic capacitor and a method for manufacturing an electrolytic capacitor according to the present disclosure will be described in detail below with reference to the drawings. The components and steps described above can be applied to the components and steps of the example electrolytic capacitor and the method for manufacturing an electrolytic capacitor described below. The components and steps of the example electrolytic capacitor and the method for manufacturing an electrolytic capacitor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above-described embodiment. Among the components and steps of the example electrolytic capacitor and the method for manufacturing an electrolytic capacitor described below, components and steps that are not essential to the electrolytic capacitor and the method for manufacturing an electrolytic capacitor according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes or number of actual components. Furthermore, while terms indicating directions such as "up" and "down" may be used in the following description, these are used for convenience of explanation and do not limit the scope of the present disclosure in any way.

[0039] First Embodiment A first embodiment of the present disclosure will be described. As shown in FIGS. 1 to 3, an electrolytic capacitor 10 of this embodiment includes a multilayer element 20 and a case 40.

[0040] The laminated element 20 includes a plurality of capacitor elements 21, an anode lead 31, and a cathode lead 32. The plurality of capacitor elements 21 include a first capacitor element 21 and a second capacitor element 21 adjacent to each other.

[0041] Each capacitor element 21 includes an anode foil 22, a cathode foil 23, and a separator 24 interposed therebetween. The anode foil 22 and the cathode foil 23 are made of a valve metal or an alloy or compound containing a valve metal. The separator 24 is made of, for example, a nonwoven fabric. The separator 24 contains a solid electrolyte and is impregnated with an electrolytic solution (not shown).

[0042] The anode foil 22 is foil- or sheet-shaped and has a rectangular outer shape. The anode foil 22 includes a metal portion and a dielectric layer formed on the surface of the metal portion. The metal portion of the anode foil 22 has a roughened surface and includes a core portion 22c and a porous portion 22d disposed outside the core portion 22c (see FIG. 3 ). A dielectric layer is formed along the surface of the porous portion 22d. The anode foil 22 includes an anode main portion 22a and an anode lead portion 22b. The anode main portion 22a faces the cathode foil 23 via the separator, and the anode lead portion 22b is the portion of the anode foil 22 other than the anode main portion 22a. The porous portion 22d, including the dielectric layer, is formed on the surfaces of both the anode main portion 22a and the anode lead portion 22b. At least a portion of the dielectric layer is covered with a solid electrolyte.

[0043] Cathode foil 23 is foil- or sheet-shaped and has a rectangular outer shape. Cathode foil 23 has cathode main portion 23a and cathode lead portion 23b. Cathode main portion 23a faces anode foil 22 (more specifically, anode main portion 22a) across the separator. Cathode lead portion 23b is the portion of cathode foil 23 other than cathode main portion 23a. Cathode main portion 23a faces the dielectric layer formed on anode main portion 22a. Cathode main portion 23a is in contact with the solid electrolyte.

[0044] The anode lead 31 is electrically connected to the anode foil 22. A portion of the anode lead 31 overlaps the anode extension portion 22b of the anode foil 22. In the overlapping region R1 between the anode extension portion 22b and the anode lead 31, multiple joints J1 are formed, where the anode lead 31 and the metal portion of the anode foil 22 are joined. The multiple joints J1 are linearly aligned in the width direction of the anode foil 22 (the direction along the Y axis in FIG. 1 ). Each joint J1 is formed to penetrate the anode lead 31 and the multiple anode extension portions 22b in the stacking direction. Two adjacent joints J1 among the multiple joints J1 are connected via the core portion 22c of the metal portion of the anode foil 22. In the overlapping region R1 other than the multiple joints J1, a porous portion 22d including a dielectric layer is interposed between the anode lead 31 and the core portion 22c of the metal portion of the anode foil 22. As a result, the above-mentioned lattice structure is formed in the overlap region R1.

[0045] It is preferable that the ratio (T1 / T2) of the total thickness T1 of the anode foil 22 and the anode lead 31 at each of the multiple joints J1 to the total thickness T2 of the anode foil 22 and the anode lead 31 in the overlapping region R1 other than the multiple joints J1 be 0.7 or more and 1.2 or less.

[0046] The maximum width W of each of the plurality of joints J1 is preferably greater than the thickness T of the core portion 22c of the metal portion of the anode foil 22.

[0047] The shortest distance D between two adjacent joints J1 is preferably greater than 0 μm and equal to or less than 300 μm.

[0048] The maximum width W of each of the plurality of joints J1 is preferably 100 μm or less.

[0049] In the overlapping region R1, it is preferable that no through-holes penetrating the anode foil 22 in the thickness direction are present at positions in contact with the multiple joints J1.

[0050] The ratio of the insulating material (for example, an oxide of a valve metal) that constitutes the dielectric layer in the multiple joints J1 is preferably 0% by volume or more and 20% by volume or less.

[0051] Anode lead portion 22b of anode foil 22 of first capacitor element 21 and anode lead portion 22b of anode foil 22 of second capacitor element 21 adjacent to first capacitor element 21 are joined to each other at a plurality of joints J1. In the vicinity of each of the plurality of joints J1, the distance between anode lead portion 22b of anode foil 22 of first capacitor element 21 and anode lead portion 22b of anode foil 22 of second capacitor element 21 is preferably 0% or more and 20% or less of the thickness of anode foil 22.

[0052] Cathode lead 32 is electrically connected to cathode foil 23. A portion of cathode lead 32 overlaps cathode lead portion 23b of cathode foil 23. Similar to overlapping region R1, a plurality of joints J2 are preferably formed in overlapping region R2 between cathode lead portion 23b and cathode lead 32.

[0053] The case 40 houses the multilayer element 20. An anode lead 31 and a cathode lead 32 extend from one side (the bottom side in FIG. 2 ) of the case 40, spaced apart from each other. The multilayer element 20 may be housed in the case 40 together with an electrolytic solution. The case 40 in this embodiment is made of a laminate sheet having a metal barrier layer, but is not limited to this. For example, the case 40 may be made of an insulating material such as ceramics or a resin material, a metal such as aluminum, stainless steel, copper, iron, or brass, or an alloy of these.

[0054] (Method for Manufacturing Electrolytic Capacitor) A method for manufacturing the electrolytic capacitor of this embodiment will be described. The manufacturing method includes a first step, a second step, and a third step.

[0055] In the first step, an anode foil 22 is prepared, which has a metal portion and a dielectric layer formed on the surface of the metal portion.

[0056] In the second step, cathode foil 23 is laminated on at least a portion of the dielectric layer via a separator to form a plurality of capacitor elements 21. Here, before the second step, it is preferable not to perform drilling on the portion of anode foil 22 that will become joint J1 (in the third step).

[0057] In the third step, the anode lead 31 is placed on the anode extraction portion 22b of the anode foil 22 that is not opposed to the cathode foil 23, and a laser is irradiated onto the anode lead 31 to join the anode lead 31 and the metal portion of the anode foil 22, thereby forming multiple joints J1. In the third step, it is preferable to irradiate the anode lead 31 with a laser so that the dielectric layer is removed at the joints J1 and the anode lead 31 and the metal portion of the anode foil 22 are joined.

[0058] Second Embodiment A second embodiment of the present disclosure will be described. The electrolytic capacitor 10 of this embodiment differs from the first embodiment in the configuration of the anode lead 31. The following mainly describes the differences from the first embodiment.

[0059] 4, in this embodiment, a plurality of (three in this example) anode leads 31 (31A, 31B, 31C) are provided. The plurality of anode leads 31 include a first anode lead 31A, a second anode lead 31B, and a third anode lead 31C. Note that at least one of the second anode lead 31B and the third anode lead 31C may be omitted. Furthermore, the number of anode leads 31 is not limited to three and can be set arbitrarily.

[0060] The first anode lead 31A has a top wall 31a and a side wall 31b. The top wall 31a is placed on top of the anode foils 22 (specifically, the anode lead portions 22b) when viewed from the stacking direction (the direction along the Z axis in FIG. 4). The side wall 31b is formed integrally with the top wall 31a and extends in the stacking direction so as to cover the ends (the left ends in FIG. 4) of the anode foils 22. In other words, the first anode lead 31A is formed in a generally L-shape when viewed from the Y axis direction in FIG. 4. The side wall 31b can realize a so-called end-face current collection structure.

[0061] The second anode lead 31B is disposed between the multiple anode foils 22 (specifically, anode extraction portions 22b) so as to be spaced apart from the top wall portion 31a of the first anode lead 31A in the stacking direction, and is in contact with or close to the side wall portion 31b of the first anode lead 31A. The shape of the second anode lead 31B may be the same as or different from the shape of the top wall portion 31a of the first anode lead 31A. Note that while FIG. 4 depicts the second anode lead 31B and the anode foil 22 thereon as being spaced apart in the stacking direction, in reality, the second anode lead 31B and the anode foil 22 thereon are in contact with or electrically connected to each other at least at joint J1 (the same applies to the third anode lead 31C and the anode foil 22 thereon).

[0062] The third anode lead 31C is disposed between the multiple anode foils 22 (specifically, the anode extraction portions 22b) so as to be spaced apart from the second anode lead 31B in the stacking direction, and is in contact with or close to the side wall portion 31b of the first anode lead 31A. The shape of the third anode lead 31C may be the same as or different from the shape of the top wall portion 31a of the first anode lead 31A.

[0063] In an overlap region R1 between the anode lead portion 22b and the first to third anode leads 31A to 31C, a plurality of joints J1 are formed at which the first to third anode leads 31A to 31C are joined to the metal portions of the anode foil 22. Two adjacent joints J1 among the plurality of joints J1 are connected via the metal portions of the anode foil 22. In the portions of the overlap region R1 other than the plurality of joints J1, a dielectric layer is interposed between the first to third anode leads 31A to 31C and the metal portions of the anode foil 22.

[0064] These multiple joints J1 may be formed by irradiating the top wall 31a of the first anode lead 31A with a laser. During laser irradiation, in addition to forming a lattice structure similar to that in the first embodiment, the molten metal material (the constituent material of the first to third anode leads 31A to 31C and the metal portions of each anode foil 22) melts into and integrates with the side wall 31b of the first anode lead 31A. This can achieve an even stronger joint structure.

[0065] In this embodiment, the first anode lead 31A has the side wall 31b, but the present invention is not limited to this, and the first anode lead 31A may have only a portion corresponding to the top wall 31a. In this case, in the process of forming the multiple joints J1 by irradiating the end of the overlap region R1 (the left end in FIG. 4) with a laser, the constituent material of the first to third anode leads 31A to 31C may melt and form a structure corresponding to at least a part of the side wall 31b.

[0066] <<Supplementary Note>> The above description of the embodiment discloses the following techniques. anode lead electrically connected to the anode foil; and a cathode lead electrically connected to the cathode foil, wherein the anode foil has an anode main portion and an anode lead, the cathode foil faces the dielectric layer formed on the anode main portion, a portion of the anode lead overlaps the anode lead, a plurality of joints are formed in an overlapping region between the anode lead and the anode lead, where the anode lead and the metal portion of the anode foil are joined, and two adjacent joints of the plurality of joints are connected via the metal portion of the anode foil, and the dielectric layer is interposed between the anode lead and the metal portion of the anode foil in a portion of the overlapping region other than the plurality of joints. (Technology 2) The electrolytic capacitor according to Technology 1, wherein the ratio (T1 / T2) of the total thickness T1 of the anode foil and the anode lead at each of the plurality of joints to the total thickness T2 of the anode foil and the anode lead in the overlapping region other than the plurality of joints is 0.7 or more and 1.2 or less. (Technology 3) The electrolytic capacitor according to Technology 1 or 2, wherein the metal portion of the anode foil has a core and a porous portion disposed outside the core, and wherein the maximum width of each of the plurality of joints is greater than the thickness of the core of the metal portion of the anode foil. (Technology 4) The electrolytic capacitor according to any one of Technology 1 to 3, wherein the shortest distance between two adjacent joints is greater than 0 μm and 300 μm or less. (Technology 5) The electrolytic capacitor according to any one of Technology 1 to 4, wherein the maximum width of each of the plurality of joints is 100 μm or less. (Technology 6) The electrolytic capacitor according to any one of Technologies 1 to 5, wherein no through-holes penetrating the anode foil in the thickness direction are present in the overlapping region at positions contacting the plurality of joints.(Technology 7) The electrolytic capacitor according to any one of Technologies 1 to 6, wherein a ratio of the insulating material constituting the dielectric layer at the plurality of joints is 0% to 20% by volume. (Technology 8) The electrolytic capacitor according to any one of Technologies 1 to 7, wherein the at least one capacitor element is composed of a plurality of capacitor elements stacked on top of each other and including adjacent first and second capacitor elements, the anode lead portion of the anode foil of the first capacitor element and the anode lead portion of the anode foil of the second capacitor element are joined to each other at the plurality of joints, and a distance between the anode lead portion of the anode foil of the first capacitor element and the anode lead portion of the anode foil of the second capacitor element near each of the plurality of joints is 0% to 20% of the thickness of the anode foil. (Technology 9) A method for manufacturing an electrolytic capacitor, comprising: a first step of preparing an anode foil having a metal portion and a dielectric layer formed on the surface of the metal portion; a second step of laminating a cathode foil on at least a portion of the dielectric layer via a separator to form at least one capacitor element; and a third step of overlapping an anode lead with an anode lead portion of the anode foil that does not face the cathode foil, and irradiating the anode lead with a laser to join the anode lead and the metal portion of the anode foil to form a plurality of joints. (Technology 10) A method for manufacturing an electrolytic capacitor according to Technology 9, wherein, before the second step, no holes are drilled in the portions of the anode foil that will become the joints. (Technology 11) A method for manufacturing an electrolytic capacitor according to Technology 9 or 10, wherein, in the third step, the anode lead is irradiated with the laser so that the dielectric layer is excluded at the joints and the anode lead and the metal portion of the anode foil are joined.

[0067] The present disclosure can be used for an electrolytic capacitor and a method for manufacturing an electrolytic capacitor.

[0068] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0069] DESCRIPTION OF SYMBOLS 10: Electrolytic capacitor 20: Laminated element 21: Capacitor element 22: Anode foil 22a: Anode main part 22b: Anode lead part 22c: Core part 22d: Porous part 23: Cathode foil 23a: Cathode main part 23b: Cathode lead part 24: Separator 31: Anode lead 31A: First anode lead 31a: Top wall part 31b: Side wall part 31B: Second anode lead 31C: Third anode lead 32: Cathode lead 40: Case D: Shortest distance between joints J1: Joint part (anode side) J2: Joint part (cathode side) R1: Overlap area (anode side) R2: Overlap area (cathode side) T: Thickness of core part T1: Total thickness (joint part) T2: Total thickness (other than joint part) W: Maximum width of joint part

Claims

1. An electrolytic capacitor comprising: a laminated element, the laminated element comprising: at least one capacitor element having an anode foil including a metal portion and a dielectric layer formed on a surface of the metal portion, and a cathode foil facing the anode foil with a separator interposed therebetween; an anode lead electrically connected to the anode foil; and a cathode lead electrically connected to the cathode foil, the anode foil having an anode main portion and an anode lead, the cathode foil facing the dielectric layer formed on the anode main portion, a part of the anode lead overlapping the anode lead, a plurality of joints are formed in an overlapping area between the anode lead and the anode lead, where the anode lead and the metal portion of the anode foil are joined, and two adjacent joints of the plurality of joints are connected via the metal portion of the anode foil, and in a portion of the overlapping area other than the plurality of joints, the dielectric layer is interposed between the anode lead and the metal portion of the anode foil.

2. The electrolytic capacitor according to claim 1, wherein a ratio (T1 / T2) of a total thickness T1 of the anode foil and the anode lead at each of the plurality of joints to a total thickness T2 of the anode foil and the anode lead at a portion of the overlapping region other than the plurality of joints is 0.7 or more and 1.2 or less.

3. The electrolytic capacitor according to claim 1 or 2, wherein the metal portion of the anode foil has a core and a porous portion arranged on the outside of the core, and the maximum width of each of the plurality of joints is greater than the thickness of the core of the metal portion of the anode foil.

4. The electrolytic capacitor according to claim 1 or 2, wherein the shortest distance between two adjacent joints is greater than 0 μm and equal to or less than 300 μm.

5. The electrolytic capacitor according to claim 1 or 2, wherein the maximum width of each of the plurality of joints is 100 μm or less.

6. The electrolytic capacitor according to claim 1 or 2, wherein in the overlapping region, there is no through hole penetrating through the anode foil in the thickness direction at a position contacting the plurality of joints.

7. The electrolytic capacitor according to claim 1 or 2, wherein the ratio of the insulating material constituting the dielectric layer in the plurality of joints is equal to or greater than 0 volume % and equal to or less than 20 volume %.

8. The electrolytic capacitor according to claim 1 or 2, wherein the at least one capacitor element is constituted by a plurality of capacitor elements including a first capacitor element and a second capacitor element stacked on top of each other and adjacent to each other, the anode lead portion of the anode foil of the first capacitor element and the anode lead portion of the anode foil of the second capacitor element are joined to each other at the plurality of joints, and a distance between the anode lead portion of the anode foil of the first capacitor element and the anode lead portion of the anode foil of the second capacitor element in the vicinity of each of the plurality of joints is equal to or greater than 0% and equal to or less than 20% of a thickness of the anode foil.

9. A method for manufacturing an electrolytic capacitor, comprising: a first step of preparing an anode foil having a metal portion and a dielectric layer formed on a surface of the metal portion; a second step of laminating a cathode foil onto at least a portion of the dielectric layer via a separator to form at least one capacitor element; and a third step of overlapping an anode lead with an anode lead portion of the anode foil that does not face the cathode foil, and irradiating the anode lead with a laser to join the anode lead and the metal portion of the anode foil to form a plurality of joints.

10. The method for producing an electrolytic capacitor according to claim 9, wherein, prior to the second step, no hole is drilled in the portion of the anode foil that will become the joint.

11. A method for manufacturing an electrolytic capacitor as described in claim 9 or 10, wherein in the third step, the laser is irradiated to the anode lead so that the dielectric layer is rejected at the joint and the anode lead and the metal portion of the anode foil are joined.

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