Capacitor and manufacturing method thereof

Abstract

To provide a structure to suppress electrolyte penetration into an electrical connection part between a cathode foil, including a carbon layer, and a lead-out terminal.SOLUTION: A capacitor 2 has a cathode foil 6 which includes: a carbon layer 14 disposed on a surface of substrate foil 12; an open hole 32; and a foil strip 34 extending from an edge of the open hole and folded back at the edge. A lead-out terminal 4 includes: a terminal body 26 having a terminal hole 22 located on a terminal placement surface of the cathode foil and overlapping the open hole; and a terminal piece 24 extending from an edge 28 of the terminal hole through the open hole and is arranged on a back face of the cathode foil. A base part 24-1 of the terminal piece directly connects to the terminal body to form a connection part 30 between the terminal piece and the terminal body. At an edge 36 of the open hole in the cathode foil, a folding-back part 40 is placed, formed by folding back the foil strip. The cathode foil connects to the terminal body to form a connection part 38 between the cathode foil and the terminal body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A capacitor includes an anode foil, a cathode foil, and a separator disposed between the anode foil and the cathode foil, and is capable of storing electricity. Among such capacitors, a basic capacitor including a cathode foil made only of aluminum foil is known. Recently, a capacitor including a cathode foil including a carbon layer has also become known (see, for example, Patent Document 1). The carbon layer has the effect of increasing the capacitance of the cathode foil, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-80111 Summary of the Invention [Problem to be solved by the invention]

[0004] The electrode foil is connected to the lead terminal by a connection method such as stitch connection. In stitch connection, a stitch needle is inserted through the overlapping lead terminal and electrode foil from the lead terminal side, forming a terminal hole and terminal piece in the lead terminal and a through hole and foil piece in the electrode foil. The terminal piece passes through the through hole in the electrode foil and is overlapped on the back surface of the electrode foil. As a result, the electrode foil is connected to the lead terminal.

[0005] However, if electrolyte penetrates the electrical connection between the lead terminal and the electrode foil, the surface of the lead terminal or electrode foil may oxidize, potentially completely or partially disrupting the electrical connection. Capacitor users have long recognized that basic capacitors containing cathode foils made solely of aluminum foil do not experience connection problems that would impede their use, except in special cases such as manufacturing defects. Therefore, capacitor users can use basic capacitors with confidence. However, the stitched connection between the cathode foil containing a carbon layer and the lead terminal has not been proven for many years, and capacitors with cathode foils containing a carbon layer still need to gain credibility.

[0006] Patent Document 1 does not disclose or suggest such a problem, and the configuration disclosed in Patent Document 1 cannot solve such a problem.

[0007] Therefore, an object of the present disclosure is to provide a stitch connection structure for suppressing the intrusion of an electrolyte into an electrical connection between a cathode foil including a carbon layer and a lead terminal, for example. [Means for solving the problem]

[0008] To achieve the above object, according to an aspect of the present disclosure, a capacitor includes a cathode foil and a lead terminal. The cathode foil is disposed on the surface of a base foil and includes a carbon layer containing a resin-based binder, and has a through hole and a foil piece extending from the edge of the through hole and folded back at the edge. The lead terminal includes a terminal body disposed on the terminal arrangement surface of the cathode foil and having a terminal hole at a position overlapping the through hole, and a terminal piece extending from the edge of the terminal hole and passing through the through hole and disposed on the back surface of the cathode foil. A base of the terminal piece is directly connected to the terminal body to form a connection between the terminal piece and the terminal body. A folded portion formed by folding back the foil piece is disposed at the edge of the through hole in the cathode foil, and the cathode foil is connected to the terminal body to form a connection between the cathode foil and the terminal body. and is formed. Formed outside the connection portion are a laminated structure in which the terminal piece, the foil piece, the cathode foil, and the terminal body are laminated, a first structure in which the foil piece, the cathode foil, and the terminal body are laminated, and a second structure in which the cathode foil and the terminal body are laminated.

[0009] In the above capacitor, the connection portion between the terminal piece and the terminal body may be in contact with or in close contact with the folded portion of the cathode foil.

[0011] In the above capacitor, the substrate foil may have an uneven surface, and the carbon layer may have a surface shape that engages with the uneven surface of the substrate foil.

[0012] In the capacitor, the foil piece is overlapped with the cathode foil and the terminal piece, The aforementioned A laminated structure may be formed. The thickness of the foil piece at the middle part of the laminated structure may be thinner than the thickness of the foil piece at the periphery of the laminated structure.

[0013] The capacitor may be an electrolytic capacitor containing an electrolyte.

[0014] To achieve the above object, according to one aspect of the present disclosure, a method for manufacturing a capacitor includes the steps of: preparing a cathode foil including a carbon layer disposed on a surface of a base foil and containing a resin-based binder; arranging a drawer terminal on a terminal arrangement surface of the cathode foil and inserting a stitching needle through the drawer terminal and the cathode foil from the drawer terminal side to form a through hole and a foil piece in the cathode foil, and forming a terminal hole and a terminal piece in the drawer terminal that extends from an edge of the terminal hole through the through hole; and pressing the terminal piece to place the terminal piece together with the foil piece on a back surface of the cathode foil and connect the cathode foil to a terminal body of the drawer terminal at the edge of the through hole in the cathode foil to form a connection between the cathode foil and the terminal body. In the step of pressing the terminal piece, the cathode foil separates from the base of the terminal piece, and the base of the terminal piece directly connects to the terminal body, thereby forming a connection between the terminal piece and the terminal body. At the same time, a laminated structure in which the terminal piece, the foil piece, the cathode foil, and the terminal body are laminated, a first structure in which the foil piece, the cathode foil, and the terminal body are laminated, and a second structure in which the cathode foil and the terminal body are laminated are formed outside the connection portion. .

[0015] In the method for manufacturing a capacitor, in the step of pressing the terminal piece, the connection portion between the terminal piece and the terminal body may be in contact with or in close contact with a folded portion formed by folding back the foil piece of the cathode foil. [Effects of the Invention]

[0016] According to the above-described aspects of the present disclosure, for example, any of the following effects can be obtained.

[0017] (1) The structure having the connection between the terminal piece and the terminal body can serve as a measure to prevent the electrolyte from entering the connection between the cathode foil and the terminal body, for example.

[0018] (2) When the connection portion between the terminal piece and the terminal body is in contact with or in close contact with the folded portion of the cathode foil, the structure in which this connection portion is in contact with or in close contact with the folded portion can provide, for example, an additional measure to prevent electrolyte from penetrating into the connection portion between the cathode foil and the terminal body.

[0019] (3) Users can safely use capacitors having a structure including a connection between a terminal piece and a terminal body, and further capacitors having a structure in which the connection between the terminal piece and the terminal body is in contact with or in close contact with the folded portion.

[0020] (4) For example, it provides a basis for building up a track record of capacitor use. [Brief explanation of the drawings]

[0021] [Figure 1] 1A and 1B are diagrams illustrating an example of a terminal connection portion of a capacitor according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an example of an end surface of a cathode foil. [Figure 3] 10A to 10C are diagrams showing an example of a process for connecting a lead terminal to an electrode foil. [Figure 4] 10A and 10B are diagrams showing an example of changes in shape of a lead terminal and a cathode foil due to pressing. [Figure 5] FIG. 10 is a diagram for explaining the effect. DETAILED DESCRIPTION OF THE INVENTION

[0022] Fig. 1 shows an example of a terminal connection portion of a capacitor according to an embodiment. Fig. 2 shows an example of an end face of a cathode foil. The configurations shown in Figs. 1 and 2 are merely examples, and the technology of the present disclosure is not limited to such configurations. In this embodiment, terminal connection portion 10 is the portion where cathode foil 6 is connected to lead-out terminal 4, and includes, for example, the portion where terminal piece 24 and foil piece 34 are arranged and the surrounding area.

[0023] The capacitor 2 is an example of an electronic component, such as an electrolytic capacitor, and includes, for example, a capacitor element (not shown), a lead terminal 4, an electrolyte, a sealing member, and an exterior case (not shown).

[0024] The capacitor element includes a cathode foil 6, an anode foil, and a separator. The cathode foil 6, the anode foil, and the separator are stacked and wound together to form a wound element, with the separator disposed between the cathode foil 6 and the anode foil. The wound element forms the capacitor element.

[0025] The cathode foil 6 constitutes the cathode electrode 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 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. As shown in FIG. 2 , the surface of the base foil 12 has irregularities 16 formed, for example, by etching, that is, depressions 16-1 and protrusions 16-2, thereby increasing the surface area of ​​the base foil 12. The surface of the base foil 12 may include, for example, tunnel-shaped or spongy etching pits, which may form the depressions 16-1 and protrusions 16-2.

[0026] The carbon layer 14 is disposed, for example, on both sides of the base foil 12. The carbon layer 14 may also be disposed on only one side of the base foil 12. As shown in FIG. 2 , the carbon layer 14 partially penetrates into the depressions 16-1 of the asperities 16, and therefore is in close contact with and engages with the asperities 16 of the base foil 12. In other words, the carbon layer 14 has a surface shape that engages with the asperities 16. The carbon layer 14 is disposed 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 layers 14 are disposed on both sides of the base foil 12. The carbon layer 14 contains a carbon material as a main material, and further contains a binder and a dispersant as additives.

[0027] Carbon materials include activated carbon, carbon black, carbon nanohorns, amorphous carbon, natural graphite, artificial graphite, graphitized ketjen black, mesoporous carbon, and fibrous carbon. Activated carbon is produced from natural plant tissues such as coconut husks, synthetic resins such as phenols, and fossil fuel-derived materials such as coal, coke, and pitch. Carbon black includes ketjen black, acetylene black, channel black, and thermal black. Fibrous carbon includes carbon nanotubes and carbon nanofibers. Carbon nanotubes may be single-walled carbon nanotubes, which have a single graphene sheet, or multi-walled carbon nanotubes (MWCNTs), which have two or more graphene sheets rolled coaxially to form multiple tube walls.

[0028] The carbon material is preferably carbon black, which is spherical carbon. By using spherical carbon black with an average primary particle diameter of 100 nm or less, the carbon layer 14 becomes dense and is more likely to adhere to the surface-expanding layer, thereby reducing interfacial resistance. A mixture containing spherical carbon and graphite is also preferred as the carbon material. Graphite, such as natural graphite, artificial graphite, or graphitized ketjen black, can be in the form of flakes, scales, chunks, clay, spheres, or flakes. The graphite is preferably flake-shaped or flake-shaped, and the aspect ratio of the minor axis to the major axis of the graphite is preferably in the range of 1:5 to 1:100. With flake-shaped or flake-shaped graphite having the above-mentioned aspect ratio, the spherical carbon can be pressed into the depressions 16-1 of the irregularities 16, such as etching pits, so that part of the carbon layer 14 extends into the etching pits. Therefore, the carbon layer 14 can be firmly adhered to the base foil 12 due to the anchor effect.

[0029] When the average particle size of the graphite is 6 μm or more and 10 μm or less, it is possible to obtain effects such as suppressing the decrease in capacitance due to high-temperature environmental load. Furthermore, when the average particle size of the graphite is 6 μm or less, it is possible to increase the capacitance of the capacitor 2 while suppressing the decrease in capacitance due to high-temperature environmental load. Furthermore, when the average particle size of the graphite is 6 μm or less, it is easier to retain the graphite within the carbon layer 14, and the amount of binder added can be reduced. Reducing the amount of binder added increases the proportion of carbon material. Therefore, it is possible to reduce the electrical resistance of the cathode foil 6 and the equivalent series resistance (ESR) of the capacitor 2. Note that the aforementioned average particle size values ​​are values ​​based on the median diameter, or so-called D50.

[0030] When the carbon material is a mixture of graphite and spherical carbon, in order to obtain the effect of the combined use 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% or more and 90% or less.

[0031] 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 carboxymethyl cellulose. The carbon layer 14 is made from, for example, an aqueous solution in which spherical carbon is dispersed. The dispersant can disperse the carbon material in the aqueous solution.

[0032] The anode foil constitutes the anode electrode of the capacitor 2. The anode foil is, for example, a valve metal foil such as tantalum foil or aluminum foil, and is, for example, a strip-shaped foil. The surface of the anode foil has irregularities formed, for example, by etching, and includes a dielectric oxide film formed, for example, by chemical conversion treatment. The irregularities formed by etching have, for example, a porous structure.

[0033] The separator is disposed 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, and may also include other separator materials such as manila hemp, esparto, hemp, rayon, cellulose, and mixtures thereof.

[0034] The cathode foil 6 is connected to the lead terminal 4 by stitch connection. The anode foil is connected to another lead terminal (not shown, hereinafter referred to as "lead terminal 4" for convenience) by stitch connection or other connection means. The lead terminal 4 is made of a conductive metal such as aluminum, for example, with good conductivity. The lead terminal 4 is composed of, for example, an aluminum wire and a metal wire, and the aluminum wire and the metal wire are connected by arc welding or the like. The aluminum wire has a roughly cylindrical round bar portion and a flat plate portion formed by pressing the round bar portion or the like, and the round bar portion has a sloped portion on the flat plate portion side whose thickness linearly decreases to the thickness of the flat plate portion. A flat plate portion is arranged on the cathode foil 6. The lead terminal 4 protrudes from one end face of the capacitor element.

[0035] The electrolyte contains at least an electrolytic solution, and fills the voids in the capacitor element and the separator.

[0036] The sealing member is made of, for example, insulating rubber. The sealing member has an insertion hole at a position corresponding to the lead-out terminal 4. The lead-out terminal 4 passes through the insertion hole of the sealing member and is exposed to the outside of the capacitor 2.

[0037] The outer case is, for example, a cylindrical aluminum case with a bottom. The capacitor element and part of the lead-out terminal 4 are inserted into the inside of the outer case together with the electrolyte. A sealing material is installed at the opening of the outer case to seal the inside of the outer case. In other words, the capacitor element and part of the lead-out terminal 4 are sealed inside the outer case. The lead-out terminal 4 passes through a through-hole in the sealing material and protrudes from the sealing material.

[0038] As described above, the cathode foil 6 is connected to the lead terminal 4 by stitch connection. The lead terminal 4 is placed on the terminal arrangement surface of the cathode foil 6, and a stitch needle 50 (A in FIG. 3) is inserted through the lead terminal 4 and the cathode foil 6 from the lead terminal 4 side. As shown in FIGS. 1A and 1B, the insertion of the stitch needle 50 forms a terminal hole 22 and a terminal piece 24 in the lead terminal 4, and a through hole 32 and a foil piece 34 in the cathode foil 6. The terminal hole 22 is positioned so as to overlap the through hole 32. The terminal piece 24 and the foil piece 34 are pressed from the cathode foil 6 side and placed on the back surface of the cathode foil 6, i.e., on the surface opposite the terminal arrangement surface.

[0039] The terminal hole 22 is formed in a terminal body 26 of the lead terminal 4. The terminal strip 24 extends from an edge 28 of the terminal hole 22, passes through a through hole 32, and is disposed on the back surface of the cathode foil 6. In this embodiment, the edge 28 is defined as a region that connects the terminal strip 24 to the terminal body 26 during the process of forming the terminal hole 22 and the terminal strip 24. The edge 28 is to be distinguished from a connection portion 30 that is formed when the terminal strip 24 connects to the terminal body 26 when pressed.

[0040] The through hole 32 is larger than the terminal hole 22. Therefore, as shown in FIG. 1A, the terminal body 26 is exposed to the rear side through the through hole 32. For example, in the cross section shown in FIG. 1B, the edge 36 of the through hole 32 is separated from the edge 28 of the terminal hole 22 by a distance S. Therefore, the base 24-1 of the terminal piece 24 is directly connected to the terminal body 26, forming a connection 30 between the terminal piece 24 and the terminal body 26. Electrical connection is not necessarily required at the connection 30; it is sufficient that the terminal piece 24 and the terminal body 26 are structurally connected.

[0041] 1B, the foil piece 34 extends from an edge 36 of the cathode foil 6 and is folded back at the edge 36 to form a folded back portion 40. The foil piece 34 partially overlaps the tip portion 24-2 of the terminal strip 24, and is also folded back to overlap the cathode foil 6 itself. As a result, a laminated structure 37 of the cathode foil 6, the foil piece 34, and the terminal strip 24 is formed.

[0042] At and near edge 36, cathode foil 6 is connected to terminal body 26, forming connection 38 between cathode foil 6 and terminal body 26. At connection 38, terminal body 26 is crimped to cathode foil 6, and terminal body 26 is electrically connected to cathode foil 6.

[0043] 1B, connection portion 30 between terminal piece 24 and terminal body 26 is in contact with or in close contact with folded portion 40 of cathode foil 6. Therefore, connection portion 38 is isolated from the outside of lead terminal 4 and cathode foil 6 and is protected from the formation of an oxide film due to contact with the electrolyte.

[0044] Capacitor 2 further has the following structures (1) to (3) that are not included in a basic capacitor that includes a cathode foil made only of aluminum foil.

[0045] Structure (1): The arrangement range of foil pieces 34 in capacitor 2 is relatively wider than the arrangement range of foil pieces in the basic capacitor. For example, the amount of protrusion P of foil pieces 34 from terminal pieces 24 in capacitor 2 is larger than the amount of protrusion of foil pieces from terminal pieces in the basic capacitor.

[0046] Structure (2): The thickness T of the tip of the foil piece 34 in the capacitor 2 is relatively thicker than the thickness T of the tip of the foil piece in the basic capacitor.

[0047] Structure (3): The thickness M of the foil pieces 34 in the middle of the laminated structure 37 of the capacitor 2 is relatively thinner than the thickness of the foil pieces in the middle of the laminated structure of the basic capacitor. Also, the thickness M of the foil pieces 34 of the capacitor 2 is thinner than the thickness of the foil pieces 34 in the peripheral parts of the laminated structure 37.

[0048] From structures (1), (2), and (3), it can be seen that, in comparison with the basic capacitor, foil piece 34 of capacitor 2 is relatively moved from laminated structure portion 37 to the outside of terminal piece 24. Furthermore, because thickness M of foil piece 34 is thinner than the surrounding area, foil piece 34 within laminated structure portion 37 has undulations, and these undulations function to prevent cathode foil 6 from slipping relative to lead-out terminal 4. [Capacitor manufacturing process]

[0049] The manufacturing process of capacitor 2 is an example of a method for manufacturing a capacitor of the present disclosure, and includes, for example, a step of making an anode foil, a step of making a cathode foil 6, a step of making a separator, a step of connecting lead terminals 4 to the electrode foils, a step of making a capacitor element, and a step of encapsulating the capacitor element.

[0050] In the anode foil production process, the surface of a valve metal foil such as a tantalum foil or an aluminum foil is etched to form irregularities on the surface of the valve metal foil. The etched valve metal foil is then subjected to a chemical conversion treatment to form a dielectric oxide film on the surface of the valve metal foil. The valve metal foil is etched by applying a current to the valve metal foil immersed in an aqueous chloride solution such as hydrochloric acid or salt. The applied current may be either direct current or alternating current. The valve metal foil is then chemically converted by applying a voltage to the valve metal foil immersed in an electrolyte solution containing a solution of ammonium borate, ammonium borate, ammonium phosphate, ammonium adipate, or the like. The chemically converted valve metal foil is then cut to produce anode foils.

[0051] In the process of producing the cathode foil 6, the surface of a valve 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 is etched to form irregularities 16 on the surface of the valve metal foil, thereby producing the base foil 12. The etching on the cathode foil 6 side may be the same as or different from the etching on the anode foil side. A carbon layer 14 is formed on the etched valve metal foil, i.e., the base foil 12, and the valve metal foil with the carbon layer 14 formed thereon is cut to produce the cathode foil 6.

[0052] The carbon layer 14 is produced as follows: The carbon material, binder, and dispersant described above are added to a dilution liquid and mixed by a dispersion process such as a mixer, jet mixing (jet collision), ultracentrifugation, or ultrasonic treatment to form a slurry. The binder is added, for example, in an amount necessary to bind the carbon material, and the dispersant is added, for example, in an amount necessary to disperse the carbon material. Therefore, the amounts of binder and dispersant added are smaller than the amount of carbon material added. When graphite is used as the carbon material, the graphite may be pulverized using a pulverizer such as a bead mill or ball mill to adjust the average particle size of the graphite before adding it to the dilution liquid.

[0053] The diluent may be, for example, an alcohol, a hydrocarbon solvent, an aromatic solvent, an amide solvent, water, or a mixture thereof. The alcohol may be, for example, methanol, ethanol, or 2-propanol. The amide solvent may be, for example, N-methyl-2-pyrrolidone (NMP) or N,N-dimethylformamide (DMF).

[0054] The slurry is applied to the etched valve metal foil, i.e., the base foil 12. Because the base foil 12 has an asperity 16, the carbon material penetrates into the asperity 16, improving adhesion. The slurry is dried to volatilize the solvent, forming a carbon layer 14, and then the carbon layer 14 is pressed. Adding a pressing process to the formation of the asperity 16 allows the carbon material to be forced into the pores of the asperity 16 and to deform along the asperity surface of the asperity 16, further improving adhesion and fixation between the carbon layer 14 and the base foil 12. If the carbon material contains graphite, the graphite is aligned and deformed to conform to the asperity 16 of the base foil 12 by pressing. Furthermore, when the graphite is pressed against the asperity 16, the spherical carbon is pressed into the recesses 16-1, such as the pores, of the base foil 12. This allows the slurry to adhere to the base foil 12, resulting in a carbon layer 14 that adheres to the base foil 12.

[0055] In the separator manufacturing process, the separator member described above is cut to manufacture the separator.

[0056] In the step of connecting the lead terminals 4 to the electrode foils, the lead terminals 4 are connected to the cathode foil 6 and the anode foil, respectively.

[0057] 3A, the cathode foil 6 is placed on a first mold 42, such as a lower mold, and the lead terminal 4 is placed 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. Therefore, the cathode foil 6 and the lead terminal 4 are sandwiched between and held by the first mold 42 and the second mold 44. The cathode foil 6 placed on the first mold 42 is the cathode foil 6 before the through hole 32 and the foil piece 34 are formed, and the lead terminal 4 placed on the cathode foil 6 is the lead terminal 4 before the terminal hole 22 and the terminal piece 24 are formed.

[0058] The first die 42 has a through hole 46, and the second die 44 has a through hole 48. The through hole 46 has a hole shape that is slightly larger than the cross-sectional shape of the forming die 52 (FIG. 3B). The through hole 48 has a hole shape that is slightly larger than the cross-sectional shape of the stitching needle 50. The through hole 48 is smaller than the through hole 46 and is positioned directly above the through hole 46. The stitching needle 50 has, for example, a cylindrical shaft with an acute, pyramidal tip, and is positioned above the through hole 48.

[0059] The stitching needle 50 is lowered in the direction of the arrow shown in Fig. 3A, and as shown in Fig. 3B, the stitching needle 50 is inserted into the lead-out terminal 4 and the cathode foil 6 from the lead-out terminal 4 side. By inserting the stitching needle 50, the through-hole 32 and the foil piece 34 are formed in the cathode foil 6, and the terminal hole 22 and the terminal piece 24 are formed in the lead-out terminal 4. The lowered stitching needle 50 is then raised, and the stitching needle 50 is removed from the lead-out terminal 4 and the cathode foil 6.

[0060] Forming die 52 has, for example, a flat pressing surface on its upper side and is positioned below through-hole 46. Forming die 52 is raised in the direction of the arrow shown in FIG. 3B, and the pressing surface presses lead terminal 4 and cathode foil 6, particularly terminal strip 24 and foil piece 34, from the cathode foil 6 side. As shown in FIG. 3C, terminal strip 24 and foil piece 34 are sandwiched between second die 44 and forming die 52. Terminal strip 24 and foil piece 34 are folded back by the pressure, and lead terminal 4 is connected to cathode foil 6.

[0061] The process of connecting the lead terminal 4 to the anode foil may be the same as or different from the process of connecting the lead terminal 4 to the cathode foil 6.

[0062] FIG. 4 shows an example of the shape change of the drawer terminal 4 and the cathode foil 6 due to pressing. FIG. 4A shows the shape of the drawer terminal 4 and the cathode foil 6 after the stitching needle 50 is inserted and before pressing by the forming die 52. FIG. 4B, FIG. 4C, and FIG. 4D show the shapes of the drawer terminal 4 and the cathode foil 6 at the early, middle, and late stages of pressing by the forming die 52, respectively. FIG. 4E shows the shape of the drawer terminal 4 and the cathode foil 6 after pressing by the forming die 52. The shape change shown in FIG. 4 is an example, and the technology of the present disclosure is not limited to such shape change. In FIGS. 4A to 4E, the arrangement of the drawer terminal 4 and the cathode foil 6 is shown upside down relative to the arrangement of the drawer terminal 4 and the cathode foil 6 shown in FIGS. 3A to 3C.

[0063] As shown in FIG. 4A, after the stitching needle 50 is inserted, the terminal body 26 has an inclined surface 54 on the edge 28. The inclined surface 54 is pressed and ultimately positioned on an extension of the surface of the terminal body 26, as shown in FIG. 4E. The pressed portions of the pull-out terminal 4 and the cathode foil 6 become thinner and elongate in a direction perpendicular to the direction of pressure, for example, horizontally. As a result, the cathode foil 6 at the edge 36 and the laminated structure 37 is inclined by the pressure and sinks into the pull-out terminal 4. The edge 28 of the pull-out terminal 4 is subjected to a first pressing force toward the terminal hole 22, and the cathode foil 6 at the edge 36 and the laminated structure 37 is subjected to a second pressing force in the opposite direction to the first pressing force.

[0064] As shown in A of Fig. 4, after the stitching needle 50 is inserted, the foil piece 34 of the cathode foil 6 is in contact or nearly in contact with the base portion 24-1 of the terminal piece 24 of the lead terminal 4. However, as shown in A of Fig. 1, the terminal body 26 is exposed on the rear side via the through hole 32. In other words, it is considered that, for example, at a middle stage or later of pressing by the forming die 52, the cathode foil 6 separates from the base portion 24-1 of the terminal piece 24, and the connection portion 30 is formed.

[0065] The cathode foil 6 includes a carbon layer 14 on its surface, which contains a binder, such as a resin-based binder. The binder has higher fracture strength and elongation than the valve action metal foil forming the base foil 12. Therefore, when subjected to the second pressing force, the carbon layer 14 of the foil piece 34 moves toward the outside of the terminal piece 24. As shown in FIG. 2 , the carbon layer 14 partially penetrates into the depression 16-1 of the asperity 16 and is in close contact with and engaged with the base foil 12 of the cathode foil 6. Therefore, when the forming die 52 presses the terminal piece 24 and the foil piece 34, the base foil 12 moves toward the outside of the terminal piece 24 along with the carbon layer 14. In other words, the amount of movement of the cathode foil 6 with the carbon layer 14 due to pressing is greater than the amount of movement of a cathode foil made of only aluminum foil due to pressing. Therefore, the movement of the cathode foil 6 allows the base portion 24-1 of the terminal piece 24 to directly connect to the terminal body 26, forming the connection portion 30. Furthermore, the structure (3) is formed from the structure (1) already described.

[0066] At the connection portion 30, the base portion 24-1 of the terminal piece 24 is pressed against the terminal body 26. This prevents the terminal piece 24 from returning to its original shape, i.e., from peeling off from the terminal body 26, and allows the connection portion 30 and its vicinity to come into contact with or be in close contact with the folded portion 40 of the cathode foil 6.

[0067] In the process of manufacturing the capacitor element, a first separator is placed between the anode foil and the cathode foil 6, and a second separator is placed on the outside of the anode foil or the cathode foil 6. The anode foil, the cathode foil 6, and the first and second separators are wound together to manufacture the capacitor element.

[0068] In the capacitor element encapsulation process, the capacitor element impregnated with an electrolyte such as an electrolytic solution is inserted into the exterior case, and then a sealing member is attached to the opening of the exterior case, thereby producing the capacitor 2.

[0069] According to the above embodiment, for example, the following effects can be obtained.

[0070] (1) Capacitor 2 has connecting portion 30, which prevents terminal piece 24 from returning to its original shape, that is, from peeling off terminal body 26. Connecting portion 30 and its vicinity can contact or be in close contact with folded portion 40 of cathode foil 6.

[0071] (2) As mentioned above, the stitch connection between the cathode foil 6 including the carbon layer 14 and the lead terminal 4 has not been used for many years, and the reliability of the capacitor 2 including the cathode foil 6 including the carbon layer 14 needs to be established in the future. Even if the thickness of the terminal connection portion 10 after pressing by the forming die 52 is constant, if the thickness M of the foil piece 34 at the middle portion of the laminated structure 37 is relatively thinner than the thickness of the foil piece at the middle portion of the laminated structure of the basic capacitor, the adhesion between the terminal piece 24 and the foil piece 34 may be weaker than the adhesion between the terminal piece and the foil piece in the basic capacitor. As a result, electrolyte may penetrate along the path indicated by the arrow in Figure 5. Because the capacitor 2 has the connection portion 30, the connection portion 30 and its vicinity can contact or be in close contact with the folded portion 40 of the cathode foil 6. This contact or intimate contact structure prevents electrolyte from penetrating the connection portion 38, reassuring users and providing a basis for building a proven track record.

[0072] The following are some characteristics and modifications of the embodiment described above.

[0073] (1) In the above embodiment, the capacitor element is a wound element. However, the capacitor element may be a laminated element in which, for example, a plurality of flat anode foils, cathode foils 6, and separators are laminated.

[0074] (2) The materials for the anode foil, cathode foil 6, separator, outer case, sealing material, and electrolyte are not limited to those described in the above embodiment. These materials may be other materials used in aluminum electrolytic capacitors or similar capacitors. For example, a phenolic laminate plate with external terminals attached may be used as the sealing material. After the capacitor element is impregnated with an electrolyte, the lead terminals from the capacitor element may be connected to the external terminals of the sealing material. Alternatively, the capacitor element and sealing material may be inserted into an outer case and sealed with the sealing material.

[0075] (3) The material of the carbon layer 14 is not limited to those described in the above embodiment. The material forming the carbon layer 14 may be any conductive material containing carbon. Furthermore, the state of adhesion or engagement of the carbon layer 14 with the base foil 12 is not limited to those described in the above embodiment.

[0076] (4) In the above embodiment, the connection portion 30 between the terminal piece 24 and the terminal body 26 is in contact with or in close contact with the folded portion 40 of the cathode foil 6. However, it is sufficient that the connection portion 30 is positioned relative to the folded portion 40 so as to prevent the intrusion of the electrolyte. The connection portion 30 does not have to be in contact with or in close contact with the folded portion 40.

[0077] (5) In the above embodiment, the capacitor 2 has the above-described structures (1) to (3). However, the structures (1) to (3) are optional structures, and the capacitor 2 does not necessarily have to include the structures (1) to (3).

[0078] (6) In the above embodiment, the draw terminal 4 is placed on the cathode foil 6, the stitching needle 50 pierces the draw terminal 4 and the cathode foil 6 from above, and the forming die 52 presses the draw terminal 4 and the cathode foil 6 from below. However, it is sufficient if the relative arrangements of the draw terminal 4, the cathode foil 6, the stitching needle 50, and the forming die 52 are the same or similar. The draw terminal 4, the cathode foil 6, the stitching needle 50, and the forming die 52 may be arranged upside down or rotated by any angle relative to the arrangement in the embodiment, for example.

[0079] As explained above, the most preferred embodiment of the present disclosure has been described, but the present disclosure is not limited to the above description, and it goes without saying that various modifications and changes are possible for those skilled in the art based on the gist of the invention as described in the claims or disclosed in the specification, and such modifications and changes are naturally included in the scope of the present disclosure. [Industrial Applicability]

[0080] The technology of the present disclosure is useful for connecting a cathode foil including a carbon layer to a lead terminal and for use in a capacitor including these. [Explanation of symbols]

[0081] 2 capacitors 4 Lead terminal 6 cathode foil 10 Terminal connection 12 Base foil 14 carbon layer 16 Unevenness 16-1 Depression 16-2 Protrusion 22 Terminal hole 24 Terminal strip 24-1 Base 24-2 Tip 26 Terminal body 28, 36 Edge 30 Connection 32 Through hole 34 Foil piece 37 Laminated structure section 38 Connection 40 Turned part 42 First Type 44 Second Type 46, 48 Through holes 50 stitch needles 52 Molding mold 54 Slope

Claims

1. a cathode foil including a carbon layer disposed on a surface of a base foil and including a resin-based binder, the cathode foil having a through hole and a foil piece extending from an edge of the through hole and folded back at the edge; a lead-out terminal including: a terminal body disposed on a terminal arrangement surface of the cathode foil and having a terminal hole at a position overlapping the through hole; and a terminal piece extending from an edge of the terminal hole, passing through the through hole, and disposed on a back surface of the cathode foil; Equipped with The base of the terminal piece is directly connected to the terminal body to form a connection between the terminal piece and the terminal body, a folded portion formed by folding back the foil piece is disposed at an edge of the through hole of the cathode foil, and the cathode foil is connected to the terminal body to form a connection portion between the cathode foil and the terminal body, and a laminated structure in which the terminal piece, the foil piece, the cathode foil, and the terminal body are laminated, a first structure in which the foil piece, the cathode foil, and the terminal body are laminated, and a second structure in which the cathode foil and the terminal body are laminated are formed outside the connection portion.

2. 2. The capacitor according to claim 1, wherein the connection portion between the terminal piece and the terminal body is in contact with or in close contact with the folded portion of the cathode foil.

3. The substrate foil has an uneven surface, 3. The capacitor according to claim 1, wherein the carbon layer has a surface shape that engages with the irregularities of the base foil.

4. the foil piece is overlaid on the cathode foil and the terminal piece to form the laminated structure; 4. The capacitor according to claim 1, wherein the thickness of the foil piece in the middle of the laminated structure is thinner than the thickness of the foil piece in the periphery of the laminated structure.

5. 5. The capacitor according to claim 1, wherein the capacitor is an electrolytic capacitor containing an electrolytic solution.

6. preparing a cathode foil including a carbon layer disposed on a surface of a substrate foil and including a resin-based binder; a step of arranging a lead terminal on a terminal arrangement surface of the cathode foil, and inserting a stitch needle from the lead terminal side into the lead terminal and the cathode foil to form a through hole and a foil piece in the cathode foil, and also forming a terminal hole in the lead terminal and a terminal piece extending from an edge of the terminal hole through the through hole; pressing the terminal piece to place the terminal piece together with the foil piece on the back surface of the cathode foil, and connecting the cathode foil to the terminal body of the lead terminal at the edge of the through hole of the cathode foil to form a connection between the cathode foil and the terminal body; Equipped with a step of pressing the terminal piece, wherein the cathode foil separates from the base of the terminal piece and the base of the terminal piece directly connects to the terminal body to form a connection between the terminal piece and the terminal body, and further wherein a laminated structure in which the terminal piece, the foil piece, the cathode foil, and the terminal body are laminated, a first structure in which the foil piece, the cathode foil, and the terminal body are laminated, and a second structure in which the cathode foil and the terminal body are laminated are formed outside the connection.

7. 7. The method for manufacturing a capacitor according to claim 6, wherein in the step of pressing the terminal piece, the connection portion between the terminal piece and the terminal body is brought into contact with or in close contact with a folded portion formed by folding back the foil piece of the cathode foil.

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