Capacitor and method for manufacturing the same

Abstract

To provide a stitch connection structure suitable for example for cathode foils containing a carbon layer.SOLUTION: A cathode foil (6) includes a base foil (12) and a carbon layer (14) formed on the base foil. A pull-out terminal (4) includes a terminal portion (18) and a terminal piece (20) extending from the terminal portion, and a stitch connection portion (10) is connected to the cathode foil by sandwiching the cathode foil between the terminal portion and the terminal piece. The pull-out terminal includes a metal surface portion (28) and a hardened surface portion (30) that is harder than the metal surface portion, the metal surface portion is in contact with the substrate foil in a first region (36) of the stitch connection portion, and the hardened surface portion is laminated to the carbon layer in a second region (38) of the stitch connection portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a capacitor including a cathode foil containing a carbon layer and a method for manufacturing the same.

Background Art

[0002] A capacitor includes an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil, and can store electricity. Regarding such a capacitor, a basic capacitor including a cathode foil composed only of an aluminum foil is known. In recent years, a capacitor including a cathode foil including an aluminum foil and a carbon layer formed on the aluminum foil has also been known (for example, Patent Document 1). The carbon layer has an effect of increasing, for example, the capacitance of the cathode foil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Electrode foils such as an anode foil and a cathode foil are connected to a lead-out terminal by connection means such as a stitch connection. In a stitch connection process for forming a stitch connection, a stitch needle is inserted from the lead-out terminal side into the lead-out terminal and the electrode foil that are overlapped with each other, a terminal hole and a terminal piece are formed in the lead-out terminal, and a through hole and a foil piece are formed in the electrode foil. The terminal piece protrudes from the back surface of the electrode foil through the through hole of the electrode foil. The terminal piece and the foil piece are pressed and overlapped on the back surface of the electrode foil. As a result, a stitch connection is formed and the electrode foil is connected to the lead-out terminal.

[0005] Incidentally, the carbon layer has a lower coefficient of static friction than metal foils such as aluminum foil and their oxides (i.e., oxide films), and cathode foil containing a carbon layer is more slippery than cathode foil consisting only of metal foil or oxidized metal foil. Therefore, when connecting a terminal piece to the cathode foil, more specifically, when the terminal piece and foil piece press against the cathode foil, the foil piece moves from its base towards its tip. As a result, the pressing force of the terminal piece and foil piece is distributed in the direction of pressing and the direction of foil piece movement, so the pressing force required to press the terminal piece against the cathode foil is reduced in cathode foil containing a carbon layer compared to cathode foil consisting only of metal foil or oxidized metal foil. Due to the reduced pressing force, there is a problem in that the cathode foil is difficult to fix with the terminal piece.

[0006] Furthermore, there is a problem in that the connection force of the carbon layer to the terminal piece is lower both electrically and physically compared to the connection force of the metal foil or oxidized metal foil to the terminal piece.

[0007] Therefore, the present disclosure aims to provide a stitch connection structure suitable for cathode foil including, for example, a carbon layer. [Means for solving the problem]

[0008] According to a first aspect of this disclosure, a capacitor comprises a cathode foil and a lead terminal. The cathode foil includes a base foil and a carbon layer formed on the base foil. The lead terminal includes a terminal portion and a terminal piece extending from the terminal portion, and is connected to the cathode foil at a stitch connection portion by sandwiching the cathode foil between the terminal portion and the terminal piece. The lead terminal has a metal surface portion and a hardened surface portion that is harder than the metal surface portion. Formed exposed between the separated hardened surface portions The aforementioned metal surface portion is Formed exposed between the separated carbon layers Contacting the aforementioned substrate foil and includes the first region formed in the stitch connection portion. The hardened surface portion ,before Laminated in the carbon layer The second region is formed in the stitch connection portion.

[0009] In the capacitor described above, the cathode foil may include a foil piece that contacts the terminal piece.

[0010] In the above capacitor, the non-folded cathode foil may be placed in the stitch connection portion.

[0011] In the capacitor described above, the carbon layer may include carbon that has been coated and pressed onto the base foil.

[0012] In the capacitor described above, the first region and the second region may be formed in both the first contact portion where the terminal piece contacts the cathode foil and the second contact portion where the terminal portion contacts the cathode foil.

[0013] To achieve the above objective, according to a second aspect of this disclosure, a method for manufacturing a capacitor comprises the steps of: arranging a lead terminal having a terminal portion and a hardened surface portion on a cathode foil comprising a base foil and a carbon layer formed on the base foil; piercing the lead terminal from the lead terminal side with a stitching needle to form a terminal piece extending from the terminal portion; and pressing the terminal piece against the cathode foil and connecting the lead terminal to the cathode foil at a stitching connection portion by sandwiching the cathode foil between the terminal portion and the terminal piece, wherein in one or more steps of the steps of manufacturing the lead terminal, forming the terminal piece, and connecting the lead terminal to the cathode foil, a metal surface portion is formed on the lead terminal, the hardened surface portion is harder than the metal surface portion, and in the step of connecting the lead terminal to the cathode foil, Formed between the hardened surface portions that have separated due to the deformation of the aforementioned lead terminals. The aforementioned metal surface portion is Formed exposed between the separated carbon layers Contacting the aforementioned substrate foil and includes the first region formed in the stitch connection portion. The hardened surface portion ,before Laminated in the carbon layer The second region is formed in the stitch connection portion. [Effects of the Invention]

[0014] According to the above aspects of this disclosure, for example, one of the following effects can be obtained:

[0015] (1) Since the metal surface of the lead terminal comes into contact with the base foil of the cathode foil, the connection of the lead terminal to the cathode foil is physically and electrically stable due to the contact between metallic materials.

[0016] (2) The hardened surface portion of the lead-out terminal penetrates into the carbon layer of the cathode foil, suppressing the slippage or relative movement of the cathode foil with respect to the lead-out terminal. The decrease in the pressing force is suppressed, and the ease of connection between the lead-out terminal and the cathode foil can be enhanced.

[0017] (3) When the lead-out terminal is connected, the metal surface portion extends or expands. Since the hardened surface portion suppresses the slippage or relative movement of the cathode foil, the portion of the cathode foil in contact with the metal surface portion extends or expands to expose the base material foil, and the metal surface portion can be brought into contact with the base material foil. That is, by utilizing the difference in hardness on the surface of the lead-out terminal, a first region where the metal surface portion contacts the base material foil can be formed.

[0018] (4) A stitch connection suitable for the properties of the cathode foil can be realized.

[0019] (5) The stability or reliability of a capacitor provided with a cathode foil including a carbon layer can be enhanced.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram showing an example of a terminal connection portion of a capacitor according to the first embodiment. [Figure 2] It is a diagram showing an example of an end face of a cathode foil. [Figure 3] It is a diagram showing a separated terminal piece and a cathode foil. [Figure 4] It is a diagram for explaining a contact surface between a lead-out terminal and a cathode foil. [Figure 5] It is a diagram showing an example of a connection process of a lead-out terminal to an electrode foil. [Figure 6] It is a diagram for explaining the connection of a lead-out terminal to a cathode foil. [Figure 7] It is a diagram showing an example of a terminal connection portion of a capacitor according to the second embodiment.

Modes for Carrying Out the Invention

[0021] Figure 1 shows an example of a terminal connection portion of a capacitor according to the first embodiment. Figure 2 shows an example of an end face of a cathode foil. The configurations shown in Figures 1 and 2 are examples, and the technology of this disclosure is not limited to such configurations. The terminal connection portion includes the connection location where the lead terminal 4 is connected to the cathode foil 6 by a stitch connection, i.e., the stitch connection portion 10 and its surrounding portion. The stitch connection portion 10 is the region in which the terminal piece 20 is overlapped with at least the terminal portion 18 and the cathode foil 6, and is the shaded portion in Figure 1A. Figure 1B shows a cross-section of the IB-IB line in Figure 1A, and Figure 1C shows an enlarged cross-section of the IC portion shown in Figure 1B.

[0022] Capacitor 2 is an example of an electronic component, such as an electrolytic capacitor. Capacitor 2 includes, for example, a capacitor element, lead terminals 4, an electrolyte, a sealing member such as insulating rubber, and an outer casing such as an aluminum case. The capacitor element filled with electrolyte and a portion of the lead terminals 4 are inserted into the outer casing, and the sealing member is installed in the opening of the outer casing. The lead terminals 4 penetrate the sealing member and protrude from the sealing member.

[0023] A capacitor element includes a cathode foil 6, an anode foil, and a separator. The cathode foil 6, anode foil, and separator are stacked and wound together so that the separator is positioned between the cathode foil 6 and the anode foil, forming a wound element. This wound element forms a capacitor element.

[0024] The cathode foil 6 constitutes the cathode of the capacitor 2. The cathode foil 6 is, for example, a strip-shaped foil and includes a base foil 12 and a carbon layer 14. The base foil 12 is, for example, a valve-acting metal foil such as aluminum foil, tantalum foil, niobium foil, titanium foil, hafnium foil, zirconium foil, zinc foil, tungsten foil, bismuth foil, or antimony foil. The surface of the base foil 12 has irregularities 16 formed, for example by etching, as shown in Figure 2, and the surface area of ​​the base foil 12 is increased. The surface of the base foil 12 may include, for example, tunnel-shaped or spongy etching pits, and these tunnel-shaped or spongy etching pits may form the irregularities 16.

[0025] The carbon layer 14 is arranged on both sides of the base foil 12, for example. The carbon layer 14 may be arranged on only one side of the base foil 12. The carbon layer 14 partially penetrates into the interior of the irregularities 16, as shown in Figure 2, and therefore adheres closely to and engages with the irregularities 16 of the base foil 12. In other words, the carbon layer 14 has a surface shape that engages with the irregularities 16. The carbon layer 14 is arranged on the outside of the base foil 12, and the cathode foil 6 has a two-layer structure consisting of the base foil 12 and the carbon layer 14, or a three-layer structure in which the carbon layer 14 is arranged on both sides of the base foil 12. The carbon layer 14 contains a carbon material as the main material, and further contains a binder and a dispersant as additives.

[0026] Carbon materials include activated carbon, carbon black, carbon nanohorns, amorphous carbon, natural graphite, artificial graphite, graphitized Ketjenblack, mesoporous carbon, and fibrous carbon. Activated carbon is produced from raw materials such as natural plant tissues like coconut shells, synthetic resins like phenol, coal, coke, or pitch. Carbon black includes Ketjenblack, acetylene black, channel black, or thermal black. Fibrous carbon includes carbon nanotubes and carbon nanofibers. Carbon nanotubes can be single-walled carbon nanotubes with a single layer of graphene sheet, or multi-walled carbon nanotubes (MWCNTs) with two or more layers of graphene sheet coiled coaxially, forming a multi-layered tube wall.

[0027] The carbon material is preferably spherical carbon, specifically carbon black. By using spherical carbon black with an average primary particle diameter of 100 nanometers or less, the carbon layer 14 becomes dense. Furthermore, by using carbon black with a particle size smaller than the opening diameter of the irregularities 16 formed on the surface of the cathode foil 6 by etching, the carbon black can easily penetrate deeper into the irregularities 16, the carbon layer 14 adheres closely to the base foil 12 of the cathode foil 6, and the interfacial resistance between the carbon layer 14 and the base foil 12 tends to decrease. The carbon material is preferably a mixture containing spherical carbon and graphite. The graphite may be, for example, natural graphite, artificial graphite, or graphitized Ketjenblack, and may have shapes such as flakes, scales, lumps, soil-like, spherical, or flaky. The graphite is preferably flake or flaky, and the aspect ratio of the short axis to the long axis of the graphite is preferably in the range of 1:5 to 1:100. The flaky or thin-layered graphite having the aspect ratio described above can, for example, press spherical carbon into irregularities 16 such as etching pits, allowing a portion of the carbon layer 14 to form inside the etching pits. As a result, the carbon layer 14 can adhere firmly to the base foil 12 due to the anchoring effect.

[0028] When the carbon material is a mixture of graphite and spherical carbon, in order to obtain the combined effect of graphite and spherical carbon, the mass ratio of graphite to the mixture of graphite and spherical carbon [mass of graphite / (mass of graphite + mass of spherical carbon)] is, for example, in the range of 25% to 90%.

[0029] The binder is a resin-based binder such as styrene-butadiene rubber, polyvinylidene fluoride, or polytetrafluoroethylene, which binds the carbon material. The dispersant is, for example, sodium carboxymethylcellulose.

[0030] The anode foil constitutes the anode of capacitor 2. The anode foil is, for example, a valve-acting metal foil as described above, and is in the form of a strip. The surface of the anode foil has an expanded surface area having a porous structure. The porous structure consists of, for example, tunnel-shaped pits, spongy pits, or voids between densely packed powder particles formed by etching. The surface of the expanded surface area includes a dielectric oxide film formed by chemical conversion treatment. The anode foil is connected to the anode-side lead terminal by stitch connection or other connection means.

[0031] The separator is placed between the anode foil and the cathode foil 6 to prevent short circuits between the anode foil and the cathode foil 6. The separator is an insulating material and may include kraft as a separator member, and may also include other separator members such as Manila hemp, esparto, hemp, rayon, cellulose, or mixtures thereof.

[0032] The lead terminal 4 is formed of a conductive metal such as aluminum. The lead terminal 4 is a lead terminal that includes, for example, a lead wire, a terminal portion 18, and a terminal piece 20. The lead wire is connected to the terminal portion 18 by, for example, arc welding. The terminal portion 18 is superimposed on the cathode foil 6 and includes a flat portion and a terminal hole 22 formed in the flat portion. The terminal piece 20 extends from the edge of the terminal hole 22 of the terminal portion 18, wraps around to the opposite side of the cathode foil 6, and is pressed against the opposite side of the cathode foil 6.

[0033] The lead terminal 4 is connected to the cathode foil 6 at the stitch connection section 10 by sandwiching the cathode foil 6 between the terminal portion 18 and the terminal piece 20. At the stitch connection section 10, the contact surface 24 (Figure 3) of the terminal piece 20 of the lead terminal 4 contacts the contact surface 26 (Figure 3) of the cathode foil 6, and the contact surface of the terminal portion 18 of the lead terminal 4 contacts the other contact surfaces of the cathode foil 6.

[0034] Figure 4A is a diagram illustrating the contact surface of the lead terminal, showing the contact surface 24 in the direction of the arrow labeled "IVA" in Figure 3. Figure 4B is a diagram illustrating the contact surface of the cathode foil, showing the contact surface 26 in the direction of the arrow labeled "IVB" in Figure 3. Figures 4A and 4B are diagrams illustrating images or outlines of the contact surfaces 24 and 26, and the art of this disclosure is not limited by the images or outlines shown in Figures 4A and 4B. The contact surfaces 24 and 26 can be exposed, for example, by pulling the terminal piece 20 away from the cathode foil 6 and the terminal portion 18, as shown in Figure 3.

[0035] The lead terminal 4 has a metal surface portion 28 and a hardened surface portion 30 on its contact surface 24. The metal surface portion 28 mainly contains the non-oxidized conductive metal contained in the lead terminal 4, and may contain a small amount of oxide of the conductive metal contained in the lead terminal 4. The proportion of oxide in the metal surface portion 28 is suppressed so that the metal surface portion 28 has the same or nearly the same properties as the non-oxidized conductive metal. The metal surface portion 28 may include a metal surface portion 28-1 and a metal surface portion 28-2. The metal surface portion 28-1 is formed between slightly separated hardened surface portions 30 and has an elongated surface shape. The metal surface portion 28-2 is formed in areas of low surface density of the hardened surface portion 30 and has a sheet-like surface shape. The metal surface portion 28 may be of a size that is not directly visible but can be confirmed by an optical microscope or electron microscope. The metal surface portion 28 can be distinguished from the hardened surface portion 30, for example, by its metallic luster.

[0036] The hardened surface portion 30 is harder than the metal surface portion 28 and is an oxide surface portion containing, for example, an oxide of the conductive metal contained in the lead terminal 4. The oxide surface portion is formed on the surface of the lead terminal 4 to suppress leakage current from the lead terminal 4 and has the same or substantially the same properties as the oxide of the conductive metal contained in the lead terminal 4. On the contact surface 24, the hardened surface portion 30 forms, for example, spots (i.e., dots sparsely dispersed on the surface) or dots that exist in a striped pattern. The hardened surface portion 30 may be unevenly scattered or uniformly arranged. The hardened surface portion 30 may be partially formed when it is formed, or it may be broken by deformation of the lead terminal 4 during the stitch connection process to form hardened surface portions 30-1 and 30-2. When the hardened surface portions 30-1 and 30-2 separate, the conductive metal of the lead terminal 4, i.e., the base metal, is exposed between the hardened surface portions 30-1 and 30-2, forming, for example, the metal surface portion 28-1. The hardened surface portion 30 protrudes, for example, from the metal surface portion 28. The hardened surface portion 30 does not have to protrude partially from the metal surface portion 28.

[0037] The properties of the metal surface portion 28 and the hardened surface portion 30 can be described, for example, as follows: (1) The hardened surface portion 30 is harder than the metal surface portion 28. (2) The metal surface portion 28 is more deformable than the hardened surface portion 30. (3) The metal surface portion 28 has a higher mechanical and electrical connection force with other metals, especially non-oxidizing metals, than the hardened surface portion 30.

[0038] On the contact surface 26 of the cathode foil 6, the carbon layer 14 forms, for example, spots. The carbon layer 14 may be unevenly distributed and scattered. In areas where the carbon layer 14 is not observed, for example, the base foil 12 is exposed. Parts of the carbon layer 14 are similar in position and shape to parts of the hardened surface portion 30 on the contact surface 24. Therefore, it is considered that such carbon layers 14 are formed by the pressing of the hardened surface portion 30. In other words, in the stitch connection portion 10, as shown in C of Figure 1, the metal surface portion 28 contacts the base foil 12 to form a first region 36, and the hardened surface portion 30 is laminated on the carbon layer 14 to form a second region 38. In the first region 36, an electrically and physically stable connection is obtained by metal-to-metal contact, pressure bonding, or compression bonding. In the second region 38, the insertion of the hardened surface portion 30 into the carbon layer 14 suppresses the sliding or relative movement of the cathode foil 6 with respect to the terminal piece 20. The locations of the first region 36 and the second region 38 can be confirmed by comparing the position of the metal surface portion 28 or hardened surface portion 30 on the contact surface 24 with the position of the base foil 12 or carbon layer 14 on the contact surface 26.

[0039] Areas other than the first area 36 and the second area 38 may be formed in the stitch connection area 10. For example, a part of the metal surface area 28 may be in contact with the carbon layer 14, and a part of the hardened surface area 30 may be in contact with the base foil 12.

[0040] The carbon layer 14 may stretch, extend, tear, or separate due to deformation of the cathode foil 6, for example, during the stitching process. The stretching or extension of the carbon layer 14 may result in the formation of a carbon layer thinner than the carbon layer 14 before the stitching process.

[0041] The base foil 12 of the cathode foil 6, i.e., the base metal, may be exposed due to rupture or separation of the carbon layer 14. The exposed base foil 12 may include an exposed portion 13. The exposed portion 13 is formed between slightly separated carbon layers 14, as shown in Figure 4B, and has an elongated surface shape. The exposed base foil 12 may be too large to be directly visible but can be confirmed by an optical or electron microscope. The carbon layer 14 can be distinguished from the base foil 12 by its color, such as black.

[0042] The electrolyte can be an electrolyte solution, a gel electrolyte, or a solid electrolyte containing a conductive polymer. A so-called hybrid electrolytic capacitor may be formed by comprising an electrolyte solution or gel electrolyte and a solid electrolyte containing a conductive polymer.

[0043] In the electrolyte of an electrolytic capacitor, a solute is dissolved in a solvent, and additives are added as needed. The solvent may be either a protic polar solvent or an aprotic polar solvent. Examples of protic polar solvents include monohydric alcohols, polyhydric alcohols, oxyalcohol compounds, and water. Examples of aprotic polar solvents include sulfones, amides, lactones, cyclic amides, nitriles, and oxides. The solute contains anionic and cationic components and is typically an organic acid or its salt, an inorganic acid or its salt, or a complex compound of an organic acid and an inorganic acid or an ionically dissociable salt thereof, and is used alone or in combination of two or more. The anionic acid and the cationic base may be added separately to the electrolyte as solute components.

[0044] When a solid electrolyte is used, for example, a conductive polymer is contained in the electrolyte layer. The conductive polymer is a conjugated polymer or a doped conjugated polymer. Any known conjugated polymer can be used without particular limitation. Examples of conjugated polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene, with poly(3,4-ethylenedioxythiophene) being preferred. The conjugated polymer may be used alone, in combination of two or more types, or as a copolymer of two or more monomers.

[0045] Figure 5 shows an example of the process of connecting lead terminals to electrode foils in the manufacturing process of a capacitor. Figure 6 is a diagram illustrating the connection of lead terminals to cathode foils. The configuration shown in Figure 5 is an example, and Figure 6 is a diagram representing an image or overview of the connection of lead terminals 4 to cathode foil 6. The technology of this disclosure is not limited by the configuration shown in Figure 5 or the image or overview shown in Figure 6.

[0046] The manufacturing process for capacitor 2 is an example of a method for manufacturing a capacitor according to the present disclosure, and includes, for example, a process for manufacturing an anode foil, a process for manufacturing a cathode foil 6, a process for manufacturing a separator, a process for manufacturing lead terminals 4, a process for connecting lead terminals 4 to electrode foils, a process for manufacturing a capacitor element, and a process for encapsulating the capacitor element.

[0047] In the process of manufacturing the anode foil, for example, a porous expanded surface is formed on the surface of the valve metal foil described above, and a dielectric oxide film is formed on the surface of the valve metal foil on which the expanded surface is formed by a chemical conversion treatment. The expanded surface is formed by DC etching, AC etching, or by deposition or sintering of metal particles onto the valve metal foil. In DC etching or AC etching, a DC current or AC current is typically applied to the valve metal foil immersed in an acidic aqueous solution containing halogen ions, such as hydrochloric acid. The anode foil is manufactured by cutting the valve metal foil on which the dielectric oxide film has been formed.

[0048] In the process of manufacturing the cathode foil 6, for example, the base foil 12 is manufactured by etching to form irregularities 16 on the surface of the valve-acting metal foil described above. The etching of the cathode foil 6 may be the same as or different from the etching of the anode foil. A carbon layer 14 is formed on the base foil 12, and the base foil 12 on which the carbon layer 14 is formed is cut to manufacture the cathode foil 6.

[0049] The carbon layer 14 is prepared as follows: The carbon material, binder, and dispersant described above are added to a diluent and mixed by a dispersion treatment such as a mixer, jet mixing, ultracentrifugation, or ultrasonic treatment to form a slurry. The diluent is, for example, an alcohol, a hydrocarbon solvent, an aromatic solvent, an amide solvent, water, or a mixture thereof. Examples of alcohols are methanol, ethanol, or 2-propanol. Examples of amide solvents are N-methyl-2-pyrrolidone (NMP) or N,N-dimethylformamide (DMF).

[0050] A slurry is applied to the base foil 12, the solvent is evaporated to form a carbon layer 14, and the carbon layer 14 is pressed. Pressing allows the carbon material to be pushed into the pores of the uneven surface 16, and the carbon material to be deformed along the uneven surface 16, improving, for example, the adhesion and fixation between the carbon layer 14 and the base foil 12. If the carbon material contains graphite, pressing aligns the graphite and deforms the graphite to conform to the uneven surface 16 of the base foil 12. When the graphite is pressed against the uneven surface 16, the pressing pushes spherical carbon into the interior of the uneven surface 16, causing the slurry to adhere to the base foil 12, and as a result, the carbon layer 14 adheres to the base foil 12. If the carbon material consists only of spherical carbon, for example, spherical carbon with an average primary particle size of 100 nanometers or less can penetrate the uneven surface 16, reducing the interfacial resistance between the carbon layer 14 and the base foil 12. Furthermore, if the carbon material consists solely of spherical carbon, the static friction coefficient of the surface of the carbon layer 14 is improved, making it less likely for the terminal piece 20 to slip when pressed against the cathode foil 6, resulting in a stitch connection with stable connectivity.

[0051] In the separator manufacturing process, the separator components described above are cut to produce the separators.

[0052] In the manufacturing process of the lead terminal 4, the terminal portion 18 is manufactured by pressing, for example, the conductive metal described above. The lead wires are connected to the terminal portion 18 by arc welding or the like. An oxide film is formed on the terminal portion 18 by chemical conversion treatment to manufacture the lead terminal 4 before stitch connection.

[0053] In the process of connecting the lead terminals 4 to the electrode foil, the lead terminals 4 are connected to the cathode foil 6 and the anode foil, respectively.

[0054] As shown in Figure 5A, the cathode foil 6 before stitch connection is placed on a first mold 42 such as a lower mold, and the lead terminal 4 (specifically the terminal portion 18) before stitch connection is superimposed on the upper surface of the cathode foil 6, i.e., the terminal placement surface. A second mold 44 such as an upper mold is placed on the upper surface of the lead terminal 4. As a result, the cathode foil 6 and the lead terminal 4 are sandwiched between the first mold 42 and the second mold 44 and held by the first mold 42 and the second mold 44.

[0055] The first type 42 has a through hole 50, and the second type 44 has a through hole 52. The through hole 52 is smaller than the through hole 50 and is positioned directly above the through hole 50. The stitching needle 46 has, for example, a cylindrical shaft with an acute-angled, pyramidal tip and is positioned above the through hole 52.

[0056] The stitching needle 46 is lowered in the direction of the block arrow shown in Figure 5A, and as shown in Figure 5B, the stitching needle 46 is inserted through the lead terminal 4 and the cathode foil 6 from the lead terminal 4 side. The insertion of the stitching needle 46 forms a through hole 32 and a foil piece 34 in the cathode foil 6, and a terminal hole 22 and a terminal piece 20 in the lead terminal 4. The lowered stitching needle 46 is raised, and the stitching needle 46 is removed from the lead terminal 4 and the cathode foil 6.

[0057] The mold 48 has, for example, a flat pressing surface on its upper side and is positioned below the through-hole 50. The mold 48 is raised in the direction of the block arrow shown in Figure 5B, and the pressing surface presses the lead terminal 4 and the cathode foil 6, in particular the terminal piece 20 and foil piece 34, from the cathode foil 6 side. As shown in Figure 5C, the terminal piece 20 and foil piece 34 are sandwiched between the second mold 44 and the mold 48. The terminal piece 20 and foil piece 34 are folded back by the pressure, and the lead terminal 4 is connected to the cathode foil 6.

[0058] As shown in Figure 6A, before pressing, the terminal piece 20 of the lead terminal 4 has, for example, a metal surface portion 28 and a hardened surface portion 30 on its surface, and the cathode foil 6 (specifically the foil piece 34) has a carbon layer 14 covering the base foil 12. The terminal piece 20 may have only the hardened surface portion 30 on its surface, and the cathode foil 6 may have a carbon layer 14 partially on its surface.

[0059] When the terminal piece 20 is pressed against the cathode foil 6 in the direction of the block arrow in Figure 6B, the pressing force generates tension in the lead terminal 4 and the cathode foil 6 in the direction of the dashed arrow. The hardened surface portion 30 bites into, for example, the carbon layer 14, forming a second region 38 as shown in Figure 6C. In the second region 38, sliding or relative movement between the terminal piece 20 and the cathode foil 6 is suppressed, for example, by a spike effect. The tension stretches or extends the lead terminal 4 and the cathode foil 6 along the contact surfaces 24 and 26. In the terminal piece 20, for example, the metal surface portion 28, which has higher deformability than the hardened surface portion 30, stretches or extends, and in the cathode foil 6, for example, the portion in contact with the metal surface portion 28 stretches or extends in accordance with the stretching or extending of the metal surface portion 28. The stretching or extension of the cathode foil 6 causes, for example, the carbon layer 14 to rupture and separate, exposing the base foil 12 between the ruptured carbon layer 14. The metal surface portion 28 comes into contact with the exposed base foil 12, forming the first region 36 as shown in Figure 6C.

[0060] When the carbon layer 14 overlapping the hardened surface portion 30 ruptures and separates, the hardened surface portion 30 may rupture and separate in accordance with the rupture and separation of the carbon layer 14, thereby forming hardened surface portions 30-1, 30-2 and metal surface portion 28-1. The hardened surface portions 30-1 and 30-2 are laminated on the carbon layer 14 to form a second region 38, and the metal surface portion 28-1 contacts, for example, the exposed portion 13 between the ruptured carbon layer 14 to form a first region 36.

[0061] As shown in Figure 6C, the metal surface portion 28 may come into contact with the carbon layer 14 to form a third region 58. If the carbon layer 14 overlapping the hardened surface portion 30 ruptures and separates, the hardened surface portion 30 may come into contact with the exposed portion 13 that has emerged between the ruptured carbon layer 14 to form a fourth region 60.

[0062] The process of connecting the lead terminals 4 to the anode foil may be the same as or different from the process of connecting the lead terminals 4 to the cathode foil 6.

[0063] In the capacitor element fabrication process, a first separator is placed between the anode foil and the cathode foil 6, and a second separator is placed outside either the anode foil or the cathode foil 6. The anode foil, cathode foil 6, and the first and second separators are wound together to fabricate the capacitor element.

[0064] In the capacitor element encapsulation process, capacitor elements impregnated with an electrolyte such as an electrolyte solution are inserted into the outer casing, and then a sealing member is attached to the opening of the outer casing to manufacture capacitor 2.

[0065] According to the first embodiment, for example, the following effects can be obtained.

[0066] (1) The metal surface portion 28 of the lead terminal 4 comes into contact with the base foil 12 of the cathode foil 6. The connection of the lead terminal 4 to the cathode foil 6 is stabilized physically and electrically by the contact between metallic materials.

[0067] (2) The hardened surface portion 30, which is harder than the metal surface portion 28, bites into the carbon layer 14, suppressing the sliding or relative movement of the cathode foil 6 with respect to the lead terminal 4. This suppresses the reduction in pressing force and improves the ease of connecting the lead terminal 4 and the cathode foil 6.

[0068] (3) When the lead terminal 4 is connected, the metal surface portion 28 stretches or extends. Because the hardened surface portion 30 suppresses the sliding or relative movement of the cathode foil 6, the portion of the cathode foil 6 in contact with the metal surface portion 28 stretches or extends, exposing the base foil 12, and allowing the metal surface portion 28 to come into contact with the base foil 12.

[0069] (4) A stitch connection suitable for the properties of the cathode foil 6 including the carbon layer 14 can be achieved, and the stability or reliability of the capacitor 2 having the cathode foil 6 including the carbon layer 14 can be improved.

[0070] (5) At the stitch connection portion 10, the foil piece 34 is folded over the cathode foil 6. In other words, the carbon layers 14 overlap, making the cathode foil 6 slippery. Also, since the carbon is pressed during the formation process of the carbon layer 14, the surface roughness of the carbon layer 14 is reduced, making the cathode foil 6 slippery. The hardened surface portion 30 can effectively penetrate such a slippery cathode foil 6. Second Embodiment

[0071] Figure 7 shows an example of a capacitor terminal connection according to the second embodiment. In Figure 7, the same parts as in Figure 1 are denoted by the same reference numerals. The configuration shown in Figure 7 is an example, and the technology of this disclosure is not limited to such a configuration.

[0072] In the capacitor 2 according to the first embodiment, the cathode foil 6 includes foil strips 34, and these foil strips 34 are in contact with the terminal strips 20. The cathode foil 6 is folded at the stitch connection portion 10. In the capacitor 72 according to the second embodiment, as shown in Figure 7, the cathode foil 6 does not include foil strips 34, and an unfolded cathode foil 6 is placed at the stitch connection portion 10. In the capacitor 72, a single layer of cathode foil 6 is sandwiched between the terminal portion 18 and the terminal strips 20. Except for not including foil strips 34, the capacitor 72 is the same as the capacitor 2, and its description will be omitted.

[0073] The manufacturing process for capacitor 72 is the same as that for capacitor 2 described in the first embodiment, except for the manufacturing process for cathode foil 6 and the process for connecting lead terminals 4 to the electrode foil. Therefore, a description of the same process will be omitted.

[0074] The process for manufacturing the cathode foil 6 includes, for example, the process for manufacturing the cathode foil 6 described in the first embodiment. In the process for manufacturing the cathode foil 6 in the second embodiment, a through hole 32 having a shape larger than the cross-sectional shape of the stitching needle 46 is formed in the cathode foil 6 in advance.

[0075] The process of connecting the lead terminals 4 to the electrode foil is the same as the process of connecting the lead terminals 4 to the electrode foil described in the first embodiment, except for the differences shown below, and therefore the explanation of the same process will be omitted. Differences: The cathode foil 6 is installed such that the pre-formed through-holes 32 in the cathode foil 6 are positioned in the path of the stitching needle 46. Therefore, the stitching needle 46 passes through the inside of the through-holes 32. No foil piece 34 is formed, and the terminal piece 20 is folded back by pressure and connected to the unfolded cathode foil 6.

[0076] According to the second embodiment, for example, the following effects can be obtained.

[0077] (1) The same effects as in the first embodiment can be obtained.

[0078] (2) The carbon layers 14 do not come into contact with each other, which can suppress sliding or relative movement of the cathode foil 6. This further suppresses the reduction in pressing force and improves the connectivity of the lead terminals 4 to the cathode foil 6.

[0079] The features and variations of the first and second embodiments are listed below.

[0080] (1) The capacitor element, lead terminals 4, outer casing, sealing member, electrolyte, etc. are not limited to those described in the first embodiment. These materials may be other materials used in aluminum electrolytic capacitors or similar capacitors. For example, the lead terminals 4 may be tab terminals, and the sealing member may be a phenolic laminate with external terminals attached. After impregnating the capacitor element with electrolyte, the lead terminals 4 led out from the capacitor element may be connected to the external terminals of the sealing member, or the capacitor element and sealing member may be inserted into an outer casing and sealed with the sealing member. The capacitor element may be, for example, a laminated element in which a plurality of flat anode foils, cathode foils 6 and separators are laminated. The material of the carbon layer 14 is not limited to those described in the first embodiment. The material forming the carbon layer 14 may be any conductive member containing carbon. Furthermore, the adhesion or engagement state of the carbon layer 14 to the base foil 12 is not limited to those described in the first embodiment.

[0081] (2) In the first and second embodiments, the lead terminal 4 is positioned on the cathode foil 6, the stitching needle 46 pierces the lead terminal 4 and cathode foil 6 from above, and the mold 48 presses the lead terminal 4 and cathode foil 6 from below. The lead terminal 4, cathode foil 6, stitching needle 46 and mold 48 may be positioned upside down or rotated by any angle relative to these arrangements described in the first embodiment, for example.

[0082] (3) In the first and second embodiments, the stitching needle 46 was inserted through the lead terminal 4 and the cathode foil 6 and the cathode foil 6 while both the cathode foil 6 and the lead terminal 4 were held between the first mold 42 and the second mold 44, and the terminal piece 20 was pressed to form the stitching connection portion 10. However, the embodiment is not limited to this. For example, after inserting the stitching needle 46 through the lead terminal 4 and the cathode foil 6 while both the cathode foil 6 and the lead terminal 4 are held between the first mold 42 and the second mold 44, the holding by the first mold 42 and the second mold 44 is released, and with at least the terminal piece 20 formed, the cathode foil 6 and the lead terminal 4 are sent to the next step, and the stitching connection portion 10 may be formed by pressing them with a mold having a flat pressing surface that sandwiches at least the side with the terminal piece 20 formed and the side with the lead terminal 4.

[0083] (4) In the first embodiment, the cathode foil 6 includes foil pieces 34, while in the second embodiment, the cathode foil 6 does not include foil pieces 34. The cathode foil 6 may include foil pieces smaller than the foil pieces 34 shown in the first embodiment. In the manufacturing process of the cathode foil 6, through holes 32 having a shape smaller than the cross-sectional shape of the stitching needle 46 may be formed in the cathode foil 6 in advance, and the stitching needle 46 may pass through the inside of the through holes 32 to form small foil pieces 34. As the foil pieces 34 become smaller, the area of ​​the laminated portion of the cathode foil 6 and foil pieces 34 becomes smaller than the area of ​​the laminated portion of the cathode foil 6 and foil pieces 34 at the stitch connection portion 10 between the lead terminal 4 and the cathode foil 6 by the manufacturing method that forms the through holes 32, thereby suppressing sliding or relative movement of the cathode foil 6. As a result, the reduction in pressing force is further suppressed, and the connectivity of the lead terminal 4 to the cathode foil 6 can be improved.

[0084] (5) As described in the first embodiment, the first to fourth regions 36 to 60 may be formed on the contact surfaces 24 and 26 (i.e., the first contact portion where the terminal piece 20 contacts the cathode foil 6). However, the first to fourth regions 36 to 60 may also be formed on the contact surface between the terminal portion 18 and the cathode foil 6 (i.e., the second contact portion where the terminal portion 18 contacts the cathode foil 6). The first to fourth regions 36 to 60 may be formed on both the first and second contact portions. Regardless of the position of the contact portion, the effects described above can be obtained by the first region 36 and the second region 38. Furthermore, if the first region 36 and the second region 38 are formed on both the first and second contact portions, the fixing of the lead terminal 4 to the cathode foil 6 becomes stronger by the two contact portions, and connectivity is improved.

[0085] As explained above, the most preferred embodiments of this disclosure have been described, but this disclosure is not limited to the above description, and it goes without saying that various modifications and changes can be made by those skilled in the art based on the gist of the invention described in the claims or disclosed in the specification, and such modifications and changes are included in the scope of this disclosure. [Industrial applicability]

[0086] The technology disclosed herein can be used in connections between cathode foil containing a carbon layer and lead terminals, and in capacitors including these, and is useful. [Explanation of symbols]

[0087] 2.72 Capacitors 4. Outlet terminals 6 Cathode foil 10 Stitch connection 12 Base foil 13 Exposed section 14 Carbon layer 16 Unevenness 18 Terminal section 20 terminal strip 22 Terminal hole 24, 26 contact surface 28, 28-1, 28-2 Metal surface part 30, 30-1, 30-2 Hardened surface portion 32 Through holes 34 foil sheets 36 First Domain 38 Second Domain 46 ステッチneedle 58 Third Field 60 The Fourth Domain

Claims

1. A cathode foil comprising a base foil and a carbon layer formed on the base foil, A lead terminal comprising a terminal portion and a terminal piece extending from the terminal portion, wherein the cathode foil is sandwiched between the terminal portion and the terminal piece, and the lead terminal is connected to the cathode foil at the stitch connection portion. Equipped with, The aforementioned lead terminal has a metal surface portion and a hardened surface portion that is harder than the metal surface portion. The metal surface portion formed exposed between the separated hardened surface portions is in contact with the base foil formed exposed between the separated carbon layers, and includes a first region formed in the stitch connection portion. The hardened surface portion includes a second region formed in the stitch connection portion by lamination on the carbon layer. A characteristic capacitor.

2. The capacitor according to claim 1, characterized in that the cathode foil includes a foil piece that contacts the terminal piece.

3. The capacitor according to claim 1, characterized in that the non-folded cathode foil is arranged at the stitch connection portion.

4. The capacitor according to any one of claims 1 to 3, characterized in that the carbon layer includes carbon that has been coated and pressed onto the base foil.

5. The capacitor according to any one of claims 1 to 3, characterized in that the first region and the second region are formed in both the first contact portion where the terminal piece contacts the cathode foil and the second contact portion where the terminal portion contacts the cathode foil.

6. A step of arranging a lead terminal having a terminal portion and a hardened surface portion on a cathode foil which includes a base foil and a carbon layer formed on the base foil, The process involves inserting a stitching needle into the pull-out terminal from the pull-out terminal side to form a terminal piece extending from the terminal portion, The process involves pressing the terminal piece against the cathode foil and sandwiching the cathode foil between the terminal portion and the terminal piece to connect the lead terminal to the cathode foil at the stitch connection portion. Equipped with, In one or more steps of the process of manufacturing the lead terminal, forming the terminal piece, and connecting the lead terminal to the cathode foil, a metal surface portion is formed on the lead terminal, and the hardened surface portion is harder than the metal surface portion. A method for manufacturing a capacitor, characterized in that, in the step of connecting the lead terminal to the cathode foil, the metal surface portion that is exposed and formed between the hardened surface portions separated by deformation of the lead terminal contacts the base foil that is exposed and formed between the separated carbon layers, and includes a first region formed in the stitch connection portion, and the hardened surface portion is laminated on the carbon layer and includes a second region formed in the stitch connection portion.

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