Capacitor and method for manufacturing the same

Abstract

To provide a stitch connection structure suitable for a cathode foil including, for example, a carbon layer.SOLUTION: A capacitor (2) includes a cathode foil (6) including a carbon layer formed on a surface of a base material foil, and a lead-out terminal (4) connected to the cathode foil by stitch connection. The lead-out terminal includes a metal wire (17) and a flat portion (18) connected to the cathode foil. A press mark end (32) formed on a metal wire side of the flat portion by the stitch connection protrudes from a foil end (30) of the cathode foil, or coincides with the foil end, or overlaps with the cathode foil at an interval of 0.1 millimeter or less from the foil end.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 capacitor including a cathode foil made of aluminum foil is known. In recent years, a capacitor including a cathode foil containing a carbon layer has also become known (for example, Patent Document 1). The carbon layer has an effect of increasing the capacitance of the cathode foil, for example.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An electrode foil is connected to a lead-out terminal by a connecting means such as a stitch connection. In a stitch connection process for forming a stitch connection, a stitch needle is inserted through the overlapped lead-out terminal and electrode foil from the lead-out terminal side, 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 is formed, for example, by applying a slurry mainly composed of carbon particles and a binder to the surface of aluminum foil, and bonding the carbon particles together with the binder. In cathode foil containing a carbon layer, the binder contained in the carbon layer generates an outward stress from the pressed area in response to the pressure applied to the carbon layer, making cathode foil containing a carbon layer more stretchable than cathode foil made only of metal foil such as aluminum foil. In the stitch connection process of cathode foil with a carbon layer, the carbon layer stretches when the terminal piece and foil piece are pressed, and the base material of the cathode foil stretches in accordance with the carbon layer. In other words, cathode foil with a carbon layer has the problem of being more stretchable than cathode foil without a carbon layer in the stitch connection process. Furthermore, when cathode foil with a carbon layer stretches, there is the problem that the strength of the cathode foil decreases.

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

[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] To achieve the above objective, according to a first aspect of this disclosure, a capacitor includes a cathode foil having a carbon layer formed on the surface of a substrate foil, and a lead terminal connected to the cathode foil by a stitch connection. The lead terminal has a metal wire and a flat portion that connects to the cathode foil, and the press mark end formed on the metal wire side of the flat portion by the stitch connection is the foil of the cathode foil. At the edge It coincides with, or overlaps with, the cathode foil at a distance of 0.1 millimeters or less from the edge of the foil.

[0009] In the capacitor described above, the terminal end of the lead terminal may protrude from the other end of the cathode foil, or it may coincide with the other end of the foil, or it may overlap the cathode foil with a gap of 0.1 mm or less or 0.5 mm or more from the other end of the foil.

[0010] To achieve the above objective, according to a second aspect of this disclosure, a method for manufacturing a capacitor includes the steps of: manufacturing a lead terminal including a metal wire and a flat portion; manufacturing a cathode foil including a carbon layer formed on the surface of a base foil; and placing the flat portion of the lead terminal on the cathode foil, and forming a press mark on the metal wire side of the flat portion by pressing a mold. At the edge The process includes the step of pressing the lead terminal with the die so that it matches, or so that the pressed edge overlaps the cathode foil at a distance of 0.1 millimeters or less from the foil edge, thereby connecting the lead terminal to the cathode foil by a stitch connection.

[0011] In the step of connecting the lead terminal to the cathode foil, the lead terminal may be connected to the cathode foil such that the terminal end of the lead terminal protrudes from the other end of the cathode foil, or in the step of connecting the lead terminal to the cathode foil, the lead terminal may be connected to the cathode foil such that the terminal end coincides with the other end of the foil or overlaps the cathode foil at a distance of 0.1 mm or less or 0.5 mm or more from the other end of the foil.

[0012] To achieve the above objective, according to a third aspect of this disclosure, the cathode foil including the carbon layer Prepare The method for manufacturing a capacitor involves the steps of creating a lead terminal including a metal wire and a flat portion, and the press mark end formed on the metal wire side of the flat portion by pressing a mold, which is the foil of the cathode foil. At the edge The process includes: adjusting the stitch connection device so that it matches or so that the pressed edge overlaps the cathode foil at a distance of 0.1 millimeters or less from the foil edge; and connecting the lead terminal to the cathode foil by stitch connection using the adjusted stitch connection device, thereby forming the pressed edge at the adjusted position.

[0013] In the step of adjusting the stitch connecting device, the stitch connecting device may be adjusted such that the terminal end of the lead-out terminal protrudes from the other foil end of the cathode foil. Alternatively, in the step of adjusting the stitch connecting device, the stitch connecting device may be adjusted such that the terminal end coincides with the other foil end or overlaps the cathode foil at an interval of 0.1 millimeter or less or 0.5 millimeter or more from the other foil end.

Advantages of the Invention

[0014] According to the above aspect of the present disclosure, for example, any of the following effects can be obtained.

[0015] (1) Foil cracking caused by the cathode foil including a carbon layer is suppressed. Therefore, the connection between the lead-out terminal and the cathode foil can be stabilized.

[0016] (2) A stitch connection suitable for the properties of the cathode foil can be realized.

[0017] (3) The stability or reliability of a capacitor including a cathode foil including a carbon layer can be enhanced.

Brief Description of the Drawings

[0018] [Figure 1] It is a diagram showing an example of a lead-out terminal and a cathode foil of a capacitor according to an embodiment. [Figure 2] It is a diagram showing a first experimental result. [Figure 3] It is a diagram for explaining an estimated mechanism of foil cracking suppression. [Figure 4] It is a diagram for explaining an estimated mechanism of foil cracking. [Figure 5] It is a diagram showing a second experimental result. [Figure 6] It is a diagram for explaining an estimated mechanism of foil cracking suppression. [Figure 7]It is a diagram for explaining a mechanism for suppressing foil breakage or estimating foil breakage. [Figure 8] It is a diagram showing an example of a process of connecting a lead terminal to an electrode foil. [Figure 9] It is a diagram showing a modified example.

Mode for Carrying Out the Invention

[0019] FIG. 1 shows an example of a lead terminal and a cathode foil of a capacitor according to an embodiment. The configuration shown in FIG. 1 is an example, and the technology of the present disclosure is not limited to such a configuration.

[0020] The capacitor 2 is an example of an electronic component, for example, an electrolytic capacitor. The capacitor 2 includes, for example, a capacitor element (not shown), a lead terminal 4, an electrolyte (not shown), a sealing member, and an outer case.

[0021] 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 overlapped and wound so that the separator is disposed between the cathode foil 6 and the anode foil, and a wound element is formed. This wound element forms the capacitor element.

[0022] The cathode foil 6 constitutes the cathode-side electrode of the capacitor 2. The cathode foil 6 is, for example, a strip-shaped foil and includes a base material foil and a carbon layer. The base material foil 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, antimony foil, etc. On the surface of the base material foil, for example, a roughened layer having irregularities, that is, depressions and protrusions, formed by etching is formed, and the surface area of the base material foil is enlarged. The surface of the base material foil may include, for example, tunnel-shaped or sponge-shaped etching pits, and these tunnel-shaped or sponge-shaped etching pits may form depressions and protrusions.

[0023] The carbon layer is arranged on both sides of the base foil, for example. The carbon layer may be arranged on only one side of the base foil. The carbon layer partially penetrates into the depressions of the uneven surface, and thus adheres closely to and engages with the uneven surface of the base foil. The carbon layer is arranged on the outside of the base foil, and the cathode foil 6 has a two-layer structure consisting of the base foil and the carbon layer, or a three-layer structure in which carbon layers are arranged on both sides of the base foil. The carbon layer contains a carbon material as the main material, and further contains a binder and a dispersant as additives.

[0024] 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.

[0025] The carbon material is preferably spherical carbon, specifically carbon black. By using spherical carbon black with an average primary particle size of 100 nanometers or less, the carbon layer becomes denser and adheres more easily to the expansion layer, thus reducing the interfacial resistance between the carbon layer and the substrate foil. The carbon material is also 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 flake, scale-like, lumpy, earthy, spherical, or flaky. The graphite is preferably flake-like 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. With flake-like or flaky graphite having the aforementioned aspect ratio, spherical carbon can be pressed into depressions in uneven surfaces such as etching pits, and a portion of the carbon layer can be formed inside the etching pits. Therefore, due to the anchoring effect, the carbon layer can adhere firmly to the substrate foil.

[0026] 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. The carbon layer 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.

[0027] The anode foil constitutes the anode electrode of capacitor 2. The anode foil is a valve-acting metal foil, such as tantalum foil or aluminum foil, and is, for example, in the form of a strip. The surface of the anode foil has irregularities formed, for example, by etching, and also contains a dielectric oxide film formed, for example, by chemical conversion treatment. The irregularities formed by etching have, for example, a porous structure.

[0028] 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 well as other separator materials such as Manila hemp, esparto, hemp, rayon, cellulose, or mixtures thereof.

[0029] The cathode foil 6 is connected to the lead terminal 4 by stitch connection. The anode foil is connected to other lead terminals (hereinafter referred to as "lead terminal 4" for convenience) by stitch connection or other connection means. The lead terminal 4 protrudes from one end face of the capacitor element. The lead terminal 4 is made of a conductive metal, such as aluminum. The lead terminal 4 is composed of, for example, an aluminum wire and a metal wire 17, and the aluminum wire and the metal wire 17 are connected by arc welding or the like. The aluminum wire has a roughly cylindrical round bar portion and a flat portion 18 formed by press working or the like on the round bar portion, and the round bar portion has an inclined portion on the flat portion 18 side where the thickness decreases linearly to the thickness of the flat portion 18. The flat portion 18 is superimposed on the cathode foil 6 and connected to the cathode foil 6 by stitch connection, forming a stitch connection portion. The stitch connection area is the region where the terminal piece 24 (Figure 8) is located, and the flat portion 18 is connected to the cathode foil 6 by stitch connection at the stitch connection area.

[0030] The electrolyte, for example, includes an electrolyte solution and fills the voids and separators within the capacitor element. A solid electrolyte may be used instead of an electrolyte solution, or a solid electrolyte layer may be used in combination with the electrolyte solution. When a solid electrolyte layer is used, the electrolyte solution is impregnated into the capacitor element on which the solid electrolyte layer is formed. The solid electrolyte layer includes a conductive polymer, which is a conjugated polymer or a doped conjugated polymer. Any known conjugated polymer can be used without particular limitation.

[0031] The sealing member is made of, for example, insulating rubber. The sealing member has an insertion hole at a position corresponding to the lead terminal 4. The lead terminal 4 passes through the insertion hole of the sealing member and is exposed to the outside of the capacitor 2.

[0032] The outer casing is, for example, a bottomed cylindrical aluminum case. The capacitor element and part of the lead terminals 4 are inserted into the inside of the outer casing along with the electrolyte. A sealing member is installed at the opening of the outer casing to seal the inside of the outer casing. In other words, the capacitor element and part of the lead terminals 4 are sealed inside the outer casing. The lead terminals 4 pass through the through-holes in the sealing member and protrude from the sealing member.

[0033] As previously described, the flat portion 18 is connected to the cathode foil 6 by a stitch connection, forming a stitch connection portion. The flat portion 18 includes terminal holes 22 and terminal pieces 24 (Figure 8), and the cathode foil 6 includes through holes and foil pieces 28 (Figure 8). The terminal holes 22, terminal pieces 24, through holes, and foil pieces 28 are formed by inserting a stitch needle 46 (Figure 8) from the lead terminal 4 side. The terminal holes 22 are positioned to overlap the through holes. The terminal pieces 24 and foil pieces 28 are folded back by pressure from the cathode foil 6 side and pressed against the back surface of the cathode foil 6, that is, the surface opposite the terminal arrangement surface.

[0034] The positions of the press marks 32 and terminal ends 34 of the lead terminal 4 are adjusted or controlled relative to the foil ends 30 and 31 of the cathode foil 6, respectively, to suppress foil cracking of the cathode foil 6. Press marks are traces formed on the lead terminal 4, particularly the flat portion 18, by the pressing of a die such as the second die 44 and the molding die 48 (B in Figure 3), and the press mark end 32 is a trace formed on the flat portion 18 of the lead terminal 4 by the pressing of the die end 45 (B in Figure 3) of the second die 44. In other words, the press mark end 32 represents the boundary of the pressed area. The press mark end 32 is formed, for example, on the metal wire 17 side of the flat portion 18.

[0035] The pressed end 32 of the lead terminal 4 is recessed, for example, from the foil end 30 of the cathode foil 6, and the distance Z1 (in mm) between the pressed end 32 and the foil end 30 is adjusted or controlled to 0.1 or less. The distance Z1 may be 0.0, and the pressed end 32 may coincide with the foil end 30. In other words, the distance Z1 is adjusted or controlled to a range represented, for example, by the following formula (1). 0.0 ≤ Z1 ≤ 0.1 ···(1)

[0036] Furthermore, the press-marked end 32 may protrude from the foil edge 30. If the press-marked end 32 is adjusted or controlled to protrude from the foil edge 30, foil cracking of the cathode foil 6 is suppressed.

[0037] The terminal end 34 of the lead terminal 4 is recessed, for example, from the foil end 31 of the cathode foil 6, and the distance Y1 (in mm) between the terminal end 34 and the foil end 31 is preferably 0.1 or less, or 0.5 or more. The distance Y1 may be 0.0, and the terminal end 34 may coincide with the foil end 31. In other words, the distance Y1 is adjusted or controlled to a range represented, for example, by the following formula (2). 0.0 ≤ Y1 ≤ 0.1, or 0.5 ≤ Y1 ···(2)

[0038] When the distance Y1 is 0.5 or greater, it is expected that foil cracking of the cathode foil 6 will be suppressed as the distance Y1 increases. Therefore, the maximum value of the distance Y1 should be set from the standpoint of the structure or performance of the capacitor 2. In addition, the lead terminal 4 may protrude from the foil end 31. The protruding lead terminal 4 suppresses foil cracking of the cathode foil 6.

[0039] Figure 2 shows the results of the first experiment, illustrating the occurrence of foil cracks at distances Z1 or Z2 (hereinafter referred to as "distances Z1 and Z2"). Foil cracking is defined as a crack extending from the foil edge 30 of the cathode foil 6 to the terminal piece 24 of the stitch connection. Foil cracking can occur, for example, when the lead terminal 4 is connected to the cathode foil 6 by a stitch connection, due to the pressure on the lead terminal 4 and the cathode foil 6. In the first experiment, cracks that do not meet the definition described above, such as cracks that do not reach the terminal piece 24, are not treated as foil cracks. Distance Z2 (unit: mm) is defined as the distance between the press mark end 32 of the lead terminal 4 protruding from the foil edge 30 of the cathode foil 6 and the foil edge 30. The first experiment is an experiment to confirm the presence or absence of foil cracking when the distances Z1 and Z2 between the press mark end 32 and the foil edge 30 are changed as conditions for stitch connection of the lead terminal 4 to the cathode foil 6 containing the carbon layer.

[0040] When the pressed edge 32 protruded from the foil edge 30, no foil cracking occurred. Also, when the pressed edge 32 coincided with the foil edge 30 or was recessed from the foil edge 30, no foil cracking occurred within the range of distance Z1 represented by the above formula (1). When the distance Z1 was 0.2 millimeters (hereinafter referred to as "mm") or 0.3 mm, experimental pieces with foil cracking were observed. In the first experiment, it was found that capacitors 2 that met the following conditions (1) or (2) were less likely to develop foil cracking compared to capacitors 2 that did not meet conditions (1) or (2). Condition (1): The pressed edge 32 protrudes from the foil edge 30. Condition (2): The distance Z1 is within the range of the above formula (1). That is, the press mark edge 32 coincides with the foil edge 30, or overlaps with the cathode foil 6 at a distance of 0.1 mm or less from the foil edge 30.

[0041] As shown in Figure 3A, when the press mark end 32 protrudes from the foil end 30, the area pressed by the lead terminal 4 overlaps with the foil end 30 of the cathode foil 6. When the lead terminal 4 is connected to the cathode foil 6 by stitch connection, as shown in Figure 3B, the foil end 30 of the cathode foil 6 is sandwiched and fixed between the second die 44 and the molding die 48 via the lead terminal 4. As already mentioned, the cathode foil 6 containing a carbon layer is more prone to stretching than the cathode foil without a carbon layer. However, when the cathode foil 6 and the lead terminal 4 are sandwiched between the second die 44 and the molding die 48 such that the press mark end 32 is formed outside the foil end 30, it is presumed that the stretching of the foil end 30 is suppressed by the fixing of the foil end 30, and thus foil cracking of the cathode foil 6 is suppressed. When the pressed edge 32 coincides with the foil edge 30, and when the pressed edge 32 is slightly recessed (for example, 0.1 mm) from the foil edge 30, it is presumed that fixing the foil edge 30 or its vicinity will suppress the elongation of the foil edge 30, and thus suppress the cracking of the cathode foil 6.

[0042] As shown in Figures 4A and 4B, when the press mark edge 32 is recessed by 0.2 mm or 0.3 mm from the foil edge 30, the cathode foil 6 protrudes from the area pressed by the lead terminal 4, leaving the foil edge 30 and its vicinity free. Stress from the mold 48 and the lead terminal 4 propagates to the foil edge 30 and its vicinity of the cathode foil 6. Therefore, it is presumed that the foil edge 30 and its vicinity of the cathode foil 6, which contains the carbon layer, deforms, and that the cathode foil 6 cracks.

[0043] There may be conditions under which foil cracking of the cathode foil 6 is suppressed at a distance Z1 of 0.4 mm or more. The first experimental result does not suggest that the same results will be obtained at a distance Z1 of 0.4 mm or more as at 0.2 mm and 0.3 mm.

[0044] Figure 5 shows the results of the second experiment, illustrating the occurrence of foil cracks at distances Y1 or Y2 (hereinafter referred to as "distances Y1, Y2"). The definition of foil cracking is the same as in the first experiment, except that the foil edge 30 is changed to the foil edge 31. In the second experiment, cracks that do not meet the definition described above, such as cracks that do not reach the terminal piece 24, are not treated as foil cracks. Distance Y2 (unit: mm) is defined as the distance between the terminal end 34 of the lead terminal 4 protruding from the foil edge 31 of the cathode foil 6 and the foil edge 31. The second experiment is conducted to confirm the presence or absence of foil cracking when the distances Y1 and Y2 between the terminal end 34 and the foil edge 31 are changed as conditions for stitch connection of the lead terminal 4 to the cathode foil 6 containing the carbon layer.

[0045] When the terminal end 34 protruded from the foil end 31, no foil cracking occurred. Also, when the terminal end 34 coincided with the foil end 31 or was recessed from the foil end 31, no foil cracking occurred within the range of distance Y1 represented by the above equation (2). When the distance Y1 was 0.2 mm, 0.3 mm, or 0.4 mm, experimental pieces with foil cracking were observed. In the second experiment, it was found that capacitors 2 that satisfy the following conditions (3) or (4) are less likely to develop foil cracking compared to capacitors 2 that do not meet conditions (3) or (4). Condition (3): The terminal end 34 protrudes from the foil end 31. Condition (4): The distance Y1 is within the range of equation (2) above. That is, the terminal end 34 coincides with the foil end 31, or overlaps with the cathode foil 6 at a distance of 0.1 mm or less or 0.5 mm or more from the foil end 31.

[0046] As shown in Figure 6A, when the terminal end 34 protrudes from the foil end 31, the lead terminal 4 overlaps with the foil end 31 of the cathode foil 6. Therefore, when the lead terminal 4 is connected to the cathode foil 6 by stitch connection, as shown in Figure 6B, the foil end 31 of the cathode foil 6 is sandwiched and fixed between the second mold 44 and the molding die 48 via the lead terminal 4. As already mentioned, the cathode foil 6 containing a carbon layer is more prone to stretching than the cathode foil without a carbon layer. However, when the terminal end 34 protrudes from the foil end 31, it is presumed that the stretching of the foil end 31 is suppressed by fixing the foil end 31, and thus foil cracking of the cathode foil 6 is suppressed. When the terminal end 34 coincides with the foil end 31, and when the terminal end 34 is slightly recessed (for example, 0.1 mm) from the foil end 31, it is presumed that fixing the foil end 31 or the vicinity of the foil end 31 will suppress the elongation of the foil end 31, and thus suppress the cracking of the cathode foil 6.

[0047] As shown in Figure 7A, when the terminal end 34 is recessed from the foil end 31, the cathode foil 6 protrudes from the lead terminal 4, forming a protruding foil end 36. When the lead terminal 4 is connected to the cathode foil 6 by stitch connection, as shown in Figures 7B and 7C, the protruding foil end 36 is not sandwiched between the second mold 44 and the molding die 48 via the lead terminal 4, and remains free. When the distance of the protruding foil end 36, i.e., distance Y1, is, for example, 0.5 mm or more, and the area of ​​the protruding foil end 36 is large, it is estimated that the stress propagating from the molding die 48 and the lead terminal 4 to the cathode foil 6 is distributed to the buffer region 38 including the protruding foil end 36 and its surrounding area, and it is estimated that foil cracking of the cathode foil 6 is suppressed. Note that the arrows in Figures 7A and 7C represent the stress propagating to the cathode foil 6.

[0048] Even if the terminal end 34 is recessed from the foil end 31, if the distance Y1 of the protruding foil end 36 is, for example, 0.2 mm or more and 0.4 mm or less, and the area of ​​the protruding foil end 36 is narrow, it is presumed that the stress propagating from the mold 48 and lead terminal 4 to the cathode foil 6 will propagate to the protruding foil end 36, and the elongation of the cathode foil 6 due to this stress will increase. Therefore, it is presumed that foil cracking will occur in the cathode foil 6.

[0049] Cracks in the cathode foil 6 do not affect the performance or vibration resistance of the capacitor 2. However, if the metal wire 17 of the capacitor 2 is subjected to vibrations greater than expected, and these vibrations propagate to the connection between the lead terminal 4 and the cathode foil 6, it will affect the vibration resistance of the capacitor 2, for example. Therefore, the vibration resistance of the capacitor 2 can be improved by adjusting or controlling the distances Z1 and Z2 between the press mark end 32 and the foil end 30 to satisfy condition (1) or condition (2), and the vibration resistance of the capacitor 2 can be improved by adjusting or controlling the distances Y1 and Y2 between the terminal end 34 and the foil end 31 to satisfy condition (3) or condition (4). Even when used in environments where vibrations are applied, the equivalent series resistance of the capacitor 2 can be maintained for a long period of time, for example. [Capacitor manufacturing process]

[0050] The manufacturing process for capacitor 2 is an example of the manufacturing method for 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 adjusting a stitch connection device 40 (A in Figure 8), a process for connecting lead terminals 4 to electrode foils (hereinafter referred to as the "lead terminal connection process"), a process for manufacturing capacitor elements, and a process for encapsulating capacitor elements.

[0051] In the anode foil manufacturing process, the surface of valve metal foil, such as tantalum foil or aluminum foil, is etched to form an expanded surface layer consisting of irregularities on the surface of the valve metal foil. After etching, the valve metal foil is subjected to a chemical conversion treatment to form a dielectric oxide film on the surface of the valve metal foil. The converted valve metal foil is then cut to produce the anode foil.

[0052] In the process of manufacturing the cathode foil 6, the surface of valve-acting metal foils such as aluminum foil, tantalum foil, niobium foil, titanium foil, hafnium foil, zirconium foil, zinc foil, tungsten foil, bismuth foil, and antimony foil is etched to create irregularities on the surface of the valve-acting metal foil, thereby manufacturing the base foil. After the etching process, a carbon layer is formed on the valve-acting metal foil, i.e., the base foil, and the base foil with the carbon layer is cut to manufacture the cathode foil 6.

[0053] The carbon layer is prepared as follows: The carbon material, binder, and dispersant described above are added to a diluent and mixed using a dispersion treatment such as a mixer, jet mixing, ultracentrifugation, or ultrasonic treatment to form a slurry. The binder is added in the amount necessary for bonding the carbon material, for example, and the dispersant is added in the amount necessary for dispersing the carbon material, for example.

[0054] Diluents include, for example, alcohols, hydrocarbon solvents, aromatic solvents, amide solvents, water, and mixtures thereof. Alcohols include, for example, methanol, ethanol, or 2-propanol. Amide solvents include, for example, N-methyl-2-pyrrolidone (NMP) or N,N-dimethylformamide (DMF).

[0055] The slurry is applied to the valve metal foil, i.e., the base foil, after etching. The slurry is dried to evaporate the solvent and form a carbon layer. Then the carbon layer is pressed to push the carbon material into the pores of the uneven surface and deform the carbon material along the uneven surface.

[0056] In the separator manufacturing process, the separator components described above are cut to produce the separators.

[0057] In the adjustment process of the stitch connection device 40, adjustment processes are performed for distances Y1, Y2 and Z1, Z2. In the adjustment process for distances Y1, Y2, the position of the lead terminals 4 relative to the cathode foil 6 is adjusted, for example, so as to satisfy the above condition (3) or condition (4). In the adjustment process for distances Z1, Z2, the position of the second die 44 relative to the cathode foil 6, particularly the position of the die end 45, is adjusted, for example, so as to satisfy the above condition (1) or condition (2) so as to the press marks 32 that will be formed on the lead terminals 4 by the pressing of the die after the lead terminal connection process. The adjustment of distances Y1, Y2 and distances Z1, Z2 is performed, for example, by adjusting the position of the alignment device for the lead terminals 4 or the cathode foil 6, by adjusting the position of the second die 44 or the molding die 48, or by multiple such position adjustments. For example, when the cathode foil 6 is fixed in a reference position, distances Y1, Y2 are adjusted by adjusting the position of the lead terminals 4. When the positions of the cathode foil 6 and the lead terminals 4 are fixed, the distances Z1 and Z2 are adjusted by adjusting the position of the second mold 44, particularly the position of the mold end 45. Distances Y1 and Y2 and distances Z1 and Z2 basically coincide before and after the lead terminal connection process. Therefore, conditions (1) to (4) in the capacitor 2 can be used in the adjustment process of the stitch connection device 40.

[0058] In the lead terminal connection process, the lead terminals 4 are connected to the cathode foil 6 and the anode foil, respectively. A stitch connection device 40 is used in the process of connecting the lead terminals 4 to the cathode foil 6. The stitch connection device 40 includes, for example, a first mold 42, a second mold 44, a stitching needle 46, and a molding die 48. In the process of connecting the lead terminals 4 to the cathode foil 6, the lead terminals 4 are connected to the cathode foil 6 after the distances Y1, Y2 and Z1, Z2 have been adjusted.

[0059] As shown in Figure 8A, the cathode foil 6 is placed on a first mold 42, such as a lower mold, and the lead terminals 4 are 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 terminals 4. Therefore, the cathode foil 6 and the lead terminals 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. The cathode foil 6 placed on the first mold 42 is the cathode foil 6 before the through holes and foil pieces 28 are formed, and the lead terminals 4 superimposed on the cathode foil 6 are the lead terminals 4 before the terminal holes 22 and terminal pieces 24 are formed.

[0060] The first mold 42 has a through-hole 50, and the second mold 44 has a through-hole 52. The through-hole 50 has a hole shape that is slightly larger than the cross-sectional shape of the molding die 48. The through-hole 52 has a hole shape that is slightly larger than the cross-sectional shape of the stitching needle 46. 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.

[0061] The stitching needle 46 is lowered in the direction of the arrow shown in Figure 8A, and as shown in Figure 8B, 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 and a foil piece 28 in the cathode foil 6, and a terminal hole 22 and a terminal piece 24 in the lead terminal 4. The lowered stitching needle 46 is raised and removed from the lead terminal 4 and the cathode foil 6.

[0062] The molding die 48 has, for example, a flat pressing surface on its upper side and is positioned below the through-hole 50. The molding die 48 is raised in the direction of the arrow shown in Figure 8B, and the pressing surface presses the lead terminal 4 and the cathode foil 6, in particular the terminal piece 24 and the foil piece 28, from the cathode foil 6 side. As shown in Figure 8C, the terminal piece 24 and the foil piece 28 are sandwiched between the second die 44 and the molding die 48. The terminal piece 24 and the foil piece 28 are folded back by the pressure, and the lead terminal 4 is connected to the cathode foil 6. When the pressing surface presses the lead terminal 4 and the cathode foil 6 from the cathode foil 6 side, the pressure of the second die 44 forms a press mark on the lead terminal 4, and a press mark end 32 is formed at the contact position of the die end 45.

[0063] 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. Since the anode foil does not have a carbon layer formed on its surface, it is less likely to stretch due to stress caused by mold pressing, unlike the cathode foil 6 which is a carbon layer-containing foil.

[0064] 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.

[0065] 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.

[0066] According to this embodiment, for example, the following effects can be obtained.

[0067] (1) By adjusting the protrusion, alignment, or recess of the press mark end 32 or terminal end 34 of the lead terminal 4, or by adjusting the distances Y1, Y2 or Z1, Z2, foil cracking of the cathode foil 6 can be suppressed, and for example, the connection between the lead terminal 4 and the cathode foil 6 can be stabilized.

[0068] (2) By adjusting the protrusion, alignment, or recess of the press mark end 32 or terminal end 34, or by adjusting the distances Y1, Y2 or Z1, Z2, the foil ends 30, 31 are fixed when stress is generated in the cathode foil 6, or the generated stress is widely distributed. To strengthen the connection of the easily stretchable cathode foil 6, even if the stress generated in the cathode foil 6 is greater than the stress of the cathode foil without the carbon layer described above, foil cracking can be suppressed by fixing the foil ends 30, 31 or distributing the stress. For example, the connection between the lead terminal 4 and the cathode foil 6 can be stabilized.

[0069] (3) By suppressing foil cracking, the risk of crack expansion due to vibration can be reduced, and the vibration resistance of capacitor 2 can be improved.

[0070] (4) By suppressing foil cracking, the reliability of capacitor 2 can be improved.

[0071] (5) A stitch connection suitable for the properties of the cathode foil 6 containing a carbon layer can be achieved, thereby improving the stability or reliability of the capacitor 2 equipped with the cathode foil 6 containing a carbon layer.

[0072] (6) By sandwiching the periphery of the cathode foil 6, which is pressed by the molding die 48, between the first die 42 and the second die 44, the cathode foil 6 is restrained, thereby suppressing stress directed outward from the carbon layer and improving stability or reliability. Furthermore, as shown in Figure 8, by sandwiching the corners of the lead terminals 4 between the first die 42 and the second die 44, it is possible to prevent the stress from being transmitted to the contact area between the cathode foil 6 and the corners of the lead terminals 4 during pressing by the molding die 48. As a result, cracks are less likely to occur at the contact area between the cathode foil 6 and the corners of the lead terminals 4.

[0073] The features and variations of the embodiments described above are listed below.

[0074] (1) In the above embodiment, the capacitor element is a wound element. However, the capacitor element may also be a laminated element in which a plurality of flat anode foils, cathode foils 6 and separators are stacked.

[0075] (2) The materials of the anode foil, cathode foil 6, separator, outer case, sealing member 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 with external terminals attached may be used as the sealing member, or the capacitor elements may be impregnated with the electrolyte and then the lead terminals led out from the capacitor elements may be connected to the external terminals of the sealing member, or the capacitor elements and sealing member may be inserted into an outer case and sealed with the sealing member.

[0076] (3) The material of the carbon layer is not limited to those described in the above embodiments. The material forming the carbon layer may be any conductive member containing carbon. Furthermore, the adhesion or engagement state of the carbon layer to the base foil is not limited to those described in the above embodiments.

[0077] (4) In the above embodiment, distances Y1, Y2 and distances Z1, Z2 are adjusted. However, only distances Z1 and Z2 may be adjusted. By adjusting distances Z1 and Z2, foil cracking on the foil edge 30 side can be suppressed.

[0078] (5) In the above embodiment, the shapes of the foil edges 30, 31 and terminal edges 34 remain almost unchanged except for the parts where cracks occur. However, the shapes of the foil edges 30, 31 and terminal edges 34 may change due to the pressing during the lead terminal connection process. Due to the pressing during the lead terminal connection process, the foil edges 31 and terminal edges 34 may bulge outwards, for example, as shown in Figure 9. Even if the foil edges 31 and terminal edges 34 bulge outwards, the position of the corner 54 of the terminal edge 34 and the position of the foil edge 31 near the corner 54 remain almost unchanged. In other words, if the minimum distance between the corner 54 and the foil edge 31 is measured as distances Y1 and Y2, the distances Y1 and Y2 before and after the lead terminal connection process can be basically made to match. Also, due to the pressing during the lead terminal connection process, the foil edges 30 and press marks 32 may bulge outwards, for example. Even if the foil edge 30 and the pressed edge 32 bulge outwards, the position of the corner of the pressed edge 32 and the position of the foil edge 30 near the corner remain almost unchanged. In other words, by measuring the minimum distance between the corner of the pressed edge 32 and the foil edge 30 as distances Z1 and Z2, the distances Z1 and Z2 before and after the connection process of the lead terminals can be basically made to match.

[0079] (6) In the above embodiment, the positions of both ends of the second mold 44 coincide with the positions of both ends of the molding die 48 in the longitudinal direction of the lead terminal 4. However, the positions of both ends or one end of the second mold 44 may differ from the positions of both ends or one end of the molding die 48, and it is expected that results similar to the first and second experimental results will be obtained.

[0080] (7) In the above embodiment, the distances Y1, Y2 and Z1, Z2 are adjusted by adjusting the stitch connection device 40. However, the foil width of the cathode foil 6 or the length of the flat portion 18 of the lead terminal 4 may be further adjusted in order to adjust the distances Y1, Y2 or Z1, Z2. Increasing the number of adjustment items increases the degree of adjustment flexibility.

[0081] (8) In the above embodiment, 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 molding die 48 presses the lead terminal 4 and cathode foil 6 from below. However, it is sufficient if the relative arrangement of the lead terminal 4, cathode foil 6, stitching needle 46 and molding die 48 is the same or similar. The lead terminal 4, cathode foil 6, stitching needle 46 and molding die 48 may be positioned, for example, upside down or rotated by any angle relative to their arrangement in the embodiment.

[0082] (9) In the above embodiment, the process of forming the foil piece 28 and the terminal piece 24 by inserting the stitching needle 46 through the terminal piece 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, and the process of forming the stitching connection portion by pressing the foil piece 28 and the terminal piece 24 with the molding die 48 is performed, but the embodiment is not limited to this. For example, while holding both the cathode foil 6 and the lead terminal 4 between the first mold 42 and the second mold 44, a stitching needle 46 is inserted through the lead terminal 4 and the cathode foil 6 to form the foil piece 28 and the terminal piece 24. After this process, the holding by the first mold 42 and the second mold 44 is released, and with the foil piece 28 and the terminal piece 24 formed, the cathode foil 6 and the lead terminal 4 are sent to the next step. A mold with a flat pressing surface is used to press the sides of the cathode foil 6 with the foil piece 28 and the terminal piece 24 formed on them, and the sides of the lead terminal 4, so as to sandwich them, in order to form the stitch connection portion.

[0083] (10) In the above embodiment, the stitching needle 46 was inserted through the lead terminal 4 and the cathode foil 6 while both the cathode foil 6 and the lead terminal 4 were sandwiched and held by the first mold 42 and the second mold 44 to form the foil piece 28 and the terminal piece 24. However, the invention is not limited to this. For example, a through hole may be formed in advance at the location where the stitching needle 46 will form the through hole in the cathode foil 6. The lead terminal 4 may then be placed on top of the cathode foil 6 so as to cover the through hole. With both the cathode foil 6 and the lead terminal 4 sandwiched and held by the first mold 42 and the second mold 44, the stitching needle 46 may be inserted through the lead terminal 4 so as to form a terminal hole 22 at a position that coincides with the through hole previously formed in the cathode foil 6. Therefore, when the terminal piece 24 is pressed by the mold 48, the foil piece 28 is not present between the terminal piece 24 and the cathode foil 6, as in the embodiment described above. As already mentioned, when a carbon layer is formed on the surface, the cathode foil 6 becomes more stretchable. By not having the easily stretchable foil piece 28 between the terminal piece 24 and the cathode foil 6, the stretching of the cathode foil 6 due to pressing on the foil piece 28 is suppressed, and the connection between the lead terminal 4 and the cathode foil 6 can be made more stable. In this case, the stitch connection portion is the area where the terminal piece 24 is located, and refers to the area including the terminal hole 22, the lead terminal 4, the cathode foil 6, and the terminal piece 24 are laminated together.

[0084] 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]

[0085] 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]

[0086] 2 Capacitors 4. Outlet terminals 6 Cathode foil 17 Metal wire 18 Flat area 22 Terminal hole 24 Terminal strip 28 Foil piece 30, 31 Foil edge 32 Press mark edge 34 Terminal end 36 Protruding foil end 38 Buffer area 40 Stitching Connection Device 42 First type 44. Second type 45 type end 46 stitching needles 48 Molding mold 50, 52 Through-holes 54 corners

Claims

1. A cathode foil containing a carbon layer formed on the surface of a base foil, The lead terminal connected to the cathode foil by stitch connection, Equipped with, The lead terminal has a metal wire and a flat portion that connects to the cathode foil. The press mark end formed on the metal wire side of the flat portion by the stitch connection, Coinciding with the edge of the cathode foil, or A capacitor characterized in that it overlaps the cathode foil at a distance of 0.1 millimeters or less from the foil edge.

2. The terminal end of the aforementioned lead terminal is The cathode foil protrudes from the other foil end, or Coinciding with the other foil edge, or Overlapping the cathode foil at a distance of 0.1 mm or less or 0.5 mm or more from the other foil edge. The capacitor according to feature 1.

3. A process for manufacturing a lead terminal including a metal wire and a flat portion, A process for producing a cathode foil containing a carbon layer formed on the surface of a base foil, The process involves placing the flat portion of the lead terminal on the cathode foil, pressing the lead terminal with the die so that the press mark end formed on the metal wire side of the flat portion by the die pressing coincides with the foil edge of the cathode foil, or so that the press mark end overlaps the cathode foil at a distance of 0.1 mm or less from the foil edge, thereby connecting the lead terminal to the cathode foil by stitch connection. A method for manufacturing a capacitor, characterized by comprising the following features.

4. In the step of connecting the lead terminal to the cathode foil, the lead terminal is connected to the cathode foil such that the terminal end of the lead terminal protrudes from the other end of the cathode foil, or In the step of connecting the lead terminal to the cathode foil, the lead terminal is connected to the cathode foil such that the terminal end coincides with the other foil end or overlaps the cathode foil by a distance of 0.1 mm or less or 0.5 mm or more from the other foil end. The method for manufacturing a capacitor according to claim 3.

5. A method for manufacturing a capacitor comprising a cathode foil containing a carbon layer, A process for manufacturing a lead terminal including a metal wire and a flat portion, A step of adjusting the stitching connection device so that the press mark end formed on the metal wire side of the flat portion by the pressing of the mold coincides with the foil edge of the cathode foil, or so that the press mark end overlaps the cathode foil at a distance of 0.1 mm or less from the foil edge, The process involves connecting the lead terminal to the cathode foil by stitch connection using the adjusted stitch connection device, and forming the pressed end at the adjusted position. A method for manufacturing a capacitor, characterized by comprising the following features.

6. In the step of adjusting the stitching connection device, the stitching connection device is adjusted so that the terminal end of the lead terminal protrudes from the other end of the cathode foil, or In the step of adjusting the stitching connection device, the stitching connection device is adjusted so that the terminal end coincides with the other foil end or overlaps the cathode foil by a distance of 0.1 mm or less or 0.5 mm or more from the other foil end. The method for manufacturing a capacitor according to claim 5.

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