Electrolytic capacitor and its manufacturing method

Abstract

To provide an electrolytic capacitor in which the contact resistance between a lead member and an electrode foil is reduced.SOLUTION: An electrolytic capacitor includes an electrode foil having a first main surface and a second main surface on the opposite side of the first main surface, and a lead member connected to the electrode foil. The electrode foil and the lead member are connected by a fastening part in an overlapping part where the first main surface of the electrode foil and the lead member overlap each other. The fastening part has a penetration hole penetrating the electrode foil and the lead member. In the fastening part, the electrode foil has a first folding part that extends from a peripheral part of the penetration hole and that is folded onto the second main surface. The lead member includes a penetration part that forms an inner wall of the penetration hole and penetrates the electrode foil, and a second folding part that extends from an end part of the penetration part and is folded onto the second main surface. The second folding part incorporates the first folding part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to electrolytic capacitors and methods for manufacturing the same. [Background technology]

[0002] The electrolytic capacitor includes an electrode foil having a first main surface and a second main surface opposite the first main surface, and a lead member connected to the electrode foil. The electrode foil and the lead member are connected through steps (a) and (b). In step (a), the lead member is placed over the first main surface of the electrode foil, and a through hole is formed by perforating a predetermined position of the overlapping portion from the lead member side using a needle-shaped member. In step (b), the portion of the lead member that is extended from the periphery of the through hole to the second main surface of the electrode foil after perforation is folded back onto the second main surface and crimped.

[0003] Patent Document 1 proposes an electrolytic capacitor comprising a pair of electrode bodies connected to a lead-out terminal and an electrolyte interposed between the electrode bodies, wherein one or both of the electrode bodies are graphite-exposed electrode bodies and have a carbon layer containing graphite exposed on their outer surfaces, and the lead-out terminal and the graphite-exposed electrode body have a stitch connection structure, which has a through hole penetrating the graphite-exposed electrode body, a burr that occurs only in the lead-out terminal and is extended from the through hole to a back surface of the graphite-exposed electrode body, and a folded portion of the burr that is folded back toward the back surface of the graphite-exposed electrode body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-97163 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for a reduction in the contact resistance between the lead member and the electrode foil. [Means for solving the problem]

[0006] One aspect of the present disclosure relates to an electrolytic capacitor including: an electrode foil having a first main surface and a second main surface opposite the first main surface; and a lead member connected to the electrode foil; the electrode foil and the lead member are connected by a crimping portion at an overlapping portion where the first main surface of the electrode foil and the lead member overlap; the crimping portion has a through hole that penetrates the electrode foil and the lead member; at the crimping portion, the electrode foil extends from a peripheral portion of the through hole and has a first fold portion that is folded back onto the second main surface; and the lead member has a through portion that forms an inner wall of the through hole and penetrates the electrode foil, and a second fold portion that extends from an end of the through portion and is folded back onto the second main surface; and the second fold portion contains the first fold portion.

[0007] Another aspect of the present disclosure provides a method for manufacturing an electronic component, the method including: a first step of preparing an electrode foil having a first main surface and a second main surface opposite to the first main surface; and a lead member; and a second step of connecting the electrode foil and the lead member, The second step includes a 2A step of forming a preliminary through hole in the electrode foil and overlapping the lead member in a predetermined region of the first main surface including the preliminary through hole; and a 2B step of, after the 2A step, piercing a needle-like member from the lead member side at a position corresponding to the preliminary through hole to form a hole, drawing a peripheral portion of the hole in the lead member to the second main surface of the electrode foil, and passing the needle-like member through the preliminary through hole to expand the preliminary through hole, thereby causing the peripheral portion of the preliminary through hole in the electrode foil to protrude from the second main surface of the electrode foil. a second C process of folding back onto the second main surface a portion P2 of the lead member that has been drawn out to the second main surface together with a portion P1 that protrudes from the second main surface of the electrode foil, and crimping the folded-back portions of the portion P1 and the portion P2 onto the second main surface, The method relates to a method for manufacturing an electrolytic capacitor, wherein in step 2B, a diameter D1 of the preliminary through hole corresponding to a diameter D2 of the needle-like member when the needle-like member is passed through the preliminary through hole is smaller than the diameter D2 of the needle-like member, and in step 2C, the portion P2 is folded back on the second main surface so as to include the folded back portion of the portion P1. [Effects of the Invention]

[0008] According to the present disclosure, the contact resistance between the lead member and the electrode foil in an electrolytic capacitor can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a front view of the electrode foil and the main part of the lead member in the electrolytic capacitor according to the embodiment of the present disclosure, viewed from the lead member side. [Figure 2] FIG. 2 is a front view of the electrode foil and the main parts of the lead member in the electrolytic capacitor according to the embodiment of the present disclosure, viewed from the electrode foil side. [Figure 3] 3 is an enlarged front view of the first crimping portion of FIG. 2. FIG. [Figure 4] XX cross-sectional view of FIG. 2. [Figure 5] 2 is a cross-sectional view schematically showing a main part of an electrode foil and a lead member after step 2A (before drilling) in a manufacturing method for an electrolytic capacitor according to an embodiment of the present disclosure. FIG. [Figure 6] 4 is a cross-sectional view schematically showing the electrode foil and the main part of the lead member after step 2B (after drilling) in the method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure. FIG. [Figure 7] 1 is a cross-sectional view schematically illustrating an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 8] FIG. 2 is a perspective view schematically illustrating the configuration of a wound body included in the electrolytic capacitor according to the embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Electrolytic capacitor] An electrolytic capacitor according to an embodiment of the present disclosure includes an electrode foil having a first main surface and a second main surface opposite the first main surface, and a lead member connected to the electrode foil. The electrode foil and the lead member are connected by a crimping portion at an overlapping portion where the first main surface of the electrode foil and the lead member overlap.

[0011] The crimping portion has a through hole that penetrates the electrode foil and the lead member. In the crimping portion, the electrode foil extends from the peripheral edge of the through hole and has a first folded portion that is folded back onto the second main surface. The lead member has a penetrating portion that constitutes the inner wall of the through hole and penetrates the electrode foil, and a second folded portion that extends from the end of the through portion and is folded back onto the second main surface. The second folded portion contains the first folded portion.

[0012] The phrase "the second folded portion contains the first folded portion" means that the following conditions (i) and (ii) are met.

[0013] Condition (i): When the crimped portion is viewed from the normal direction of the second main surface of the electrode foil, the area S1 of the region where the second folded portion covers the first folded portion is smaller than the area S2 of the second folded portion.

[0014] Condition (ii): When the crimped portion is viewed from the normal direction of the second main surface of the electrode foil, the area S3a of the region where the first fold portion is covered by the second fold portion is larger than the area S3b of the region where the first fold portion is not covered by the second fold portion, or the entire first fold portion is covered by the second fold portion.

[0015] The ratio of area S1 to area S2: S1 / S2 may be, for example, 1 / 3 or more (or 1 / 2 or more) and less than 1, 1 / 3 or more (or 1 / 2 or more) and 9 / 10 or less, or 1 / 3 or more (or 1 / 2 or more) and 4 / 5 or less.

[0016] When the second folded portion is formed separately into multiple crimping pieces, it is sufficient that at least 1 / 2 of the multiple crimping pieces satisfy S1 / S2<1, and it is preferable that at least 3 / 4 (or all) of the multiple crimping pieces satisfy S1 / S2<1.

[0017] In the case of the crimping portion 710 shown in FIG. 3, the second folded portion 412 is separated into four crimping pieces (four triangular portions), and each of the four crimping pieces has an area covering the first folded portion 312 (four diagonally shaded portions in FIG. 3). In this case, the area S2 in (i) above is the area of ​​one crimping piece (one triangular portion). The area S1 is the area of ​​one diagonally shaded portion of one crimping piece. In the crimping portion 710 shown in FIG. 3, all four crimping pieces satisfy S1 / S2<1.

[0018] The ratio of the area S3b to the area S3a: S3b / S3a may be, for example, 0 or more and 1 / 3 or less (or 1 / 2 or less), or 0 or more and 1 / 4 or less.

[0019] In the case of the crimped portion 710 shown in Fig. 3, the area S3a in (ii) above is the area of ​​the region of the first folded portion 312 that is covered by the second folded portion 412 (four crimping pieces) (the area of ​​the four shaded areas in Fig. 3). The area S3b is the value obtained by subtracting the area S3a from the entire area of ​​the first folded portion 312. The crimped portion 710 shown in Fig. 3 satisfies S3b / S3a<1.

[0020] The crimped portion having the first folded portion and the second folded portion is formed by the manufacturing method described below. When the second folded portion is formed so as to enclose the first folded portion, the first folded portion is pressed together with the second folded portion while being wrapped by the second folded portion on the second main surface when the crimped portion is formed (when the overlapping portion is pressed). This allows the first folded portion and the second folded portion to be firmly attached to each other, ensuring a sufficient area for adhesion. As a result, the contact resistance between the lead member and the electrode foil is reduced. Furthermore, the connection strength between the lead member and the electrode foil is increased, and low contact resistance is maintained even when a load is applied to the connection portion (crimped portion) between the lead member and the electrode foil.

[0021] If the second folded portion does not contain the first folded portion, the first folded portion will not be easily fixed by the second folded portion during pressing and will be more likely to shift in a direction that protrudes from the second folded portion on the second main surface. As a result, sufficient adhesion between the first folded portion and the second folded portion will not be ensured, and the area where they are in close contact will also be smaller.

[0022] The electrode foil includes a metal foil containing a first metal, which includes a valve metal such as aluminum, tantalum, niobium, etc. The metal foil may be a plain foil or a metal foil whose surface has been roughened by etching or the like.

[0023] The metal foil having a roughened surface has a porous portion and a core portion continuous with the porous portion. The thickness of the porous portion (thickness per side) is, for example, 1 / 10 or more and 3 / 10 or less of the total thickness of the metal foil. The porous portion has a large number of pits (or pores) surrounded by metal portions. The pit diameter (or pore diameter) peak is, for example, 50 nm to 2000 nm (or 100 nm to 300 nm). The pit diameter (or pore diameter) peak is the most frequent pore diameter in the volume-based pore diameter distribution measured, for example, with a mercury porosimeter.

[0024] The surface of the metal foil is usually covered with a natural oxide film or a coating layer described below. When an electrode foil whose surface is covered with a coating layer (or natural oxide film) is used to form a crimped portion by the manufacturing method described below, the first folded portion may have a region on the surface covered by the second folded portion that is not covered with the coating layer (or natural oxide film), i.e., a region where the metal base of the electrode foil is exposed (region C described below). Even if the conductivity of the coating layer is low, the presence of region C can reduce the contact resistance between the lead member and the electrode foil. The metal base of the electrode foil can also be said to be the metal structure of the metal foil. However, in the case of a metal foil with a roughened surface, the metal base of the electrode foil refers to the metal structure of the core of the metal foil.

[0025] If the second folded portion does not include the first folded portion, the region C is likely to be covered by the edge of the second folded portion, which may result in poor adhesion between the region C and the second folded portion, or the region C may be exposed from the second folded portion.

[0026] The electrode foil may include a metal foil and a coating layer covering the surface of the metal foil. The coating layer is formed, for example, to improve the corrosion resistance and conductivity of the cathode foil. In this case, the coating layer may include at least one selected from the group consisting of a metal oxide layer, a metal nitride layer, a metal carbide layer, and a conductive layer. The coating layer may include a second metal. Examples of the second metal include titanium, nickel, tantalum, and niobium. The coating layer may include two or more second metals. The second metal may be the same as or different from the first metal. Furthermore, the coating layer may include carbon, and the conductive layer may be a carbon layer. When the surface of the metal foil is roughened, the electrode foil may include a coating layer covering the metal skeleton that constitutes the porous portion.

[0027] When the electrode foil is used as a cathode foil, the thickness of the electrode foil is, for example, 20 μm or more and 60 μm or less, and the thickness of the coating layer is, for example, 0.1 μm or more and 5 μm or less. In the case of a metal foil with a roughened surface, the thickness of the coating layer refers to the thickness of the coating layer that covers the outer surface of the porous portion.

[0028] The electrode foil may include a metal foil having a porous portion and a core portion continuous with the porous portion, and a metal oxide layer covering the metal skeleton constituting the porous portion. In this case, the electrode foil can be used as an anode foil. The metal oxide layer can function as a dielectric layer. The metal oxide layer may be a formation film (oxide layer of the first metal) formed by a formation treatment.

[0029] In the cross-section of the electrode foil in the thickness direction at the caulked portion, the length L1 in the plane direction of the electrode foil from the center of the through-hole to the end of the first folded portion is preferably smaller than the length L2 in the plane direction of the electrode foil from the center of the through-hole to the end of the second folded portion. L1 / L2 may be 0.9 or less, or may be 0.8 or less. Also, L1 / L2 is preferably larger than 1 / 2 times the diameter D2 of the needle-like member described later, and may be 0.4 or more, or may be 0.5 or more. L1 / L2 may be in a range (for example, more than D / 2 and less than 1) obtained by arbitrarily combining the above upper and lower limits. When L1 / L2 is within the above range, the first folded portion (region C) is easily covered by the second folded portion, and good adhesion between the first folded portion and the second folded portion is easily ensured.

[0030] Note that the "end of the second folded portion" described above is the point P farthest from the center of the through-hole in the second folded portion. L2 is the shortest distance from the center to point P. The "end of the first folded portion" described above is the point Q farthest from the center of the through-hole in the first folded portion in the cross-section (cross-section in the thickness direction of the electrode foil) including the point P of the caulked portion. L1 is the shortest distance from the center to point Q. When the second folded portion is divided into a plurality of caulked pieces, it is sufficient that the relationship L1 < L2 is satisfied in at least one caulked piece, and it is desirable that the relationship L1 < L2 is satisfied in 1 / 2 or more (or all) of the plurality of caulked pieces. When the shape of the through-hole is a regular polygon when the caulked portion is viewed from the normal direction of one main surface of the electrode foil, the center of the through-hole coincides with the center of the circumscribed circle of the regular polygon.

[0031] Here, Fig. 1 is a front view of the electrode foil and the main parts of the lead member in the electrolytic capacitor according to the embodiment of the present disclosure, as viewed from the lead member side. In Fig. 1, the overlapping portion 600 is viewed from the lead member 400 side (the first main surface S1 side of the electrode foil 300). Fig. 2 is a front view of the electrode foil and the main parts of the lead member in the electrolytic capacitor according to the embodiment of the present disclosure, as viewed from the electrode foil side. In Fig. 2, the overlapping portion 600 is viewed from the electrode foil 300 side (the second main surface S2 side). For convenience, the overlapping portion 600 is hatched in Figs. 1 and 2.

[0032] The electrode foil 300 has a first main surface S1 and a second main surface S2 opposite to the first main surface S1. The electrode foil 300 includes a metal foil 301, a first coating layer 302a covering one main surface of the metal foil 301 (on the first main surface S1 side), and a second coating layer 302b covering the other main surface of the metal foil 301 (on the second main surface S2 side). The metal foil 301 is a plain foil, and the coating layers 302a and 302b are formed on both sides of the plain foil. However, the metal foil is not limited to this, and may be a metal foil with a roughened surface. The metal foil may also have a first porous portion on the first main surface S1 side, a second porous portion on the second main surface S2 side, and a core portion continuous with the first porous portion and the second porous portion.

[0033] The lead member 400 includes a lead wire 427, a flat tab portion 425, and a lead wire connection portion 426 to which the lead wire 427 is connected. The lead member 400 is not particularly limited as long as it is a conductive member having the tab portion 425, the lead wire connection portion 426, and the lead wire 427, but can be prepared, for example, as follows: A metal rod-shaped member is prepared, and one end of the member is flattened by pressing or the like to form the tab portion 425. The other end remains rod-shaped and becomes the lead wire connection portion 426. The lead wire connection portion 426 and the lead wire 427 are connected by welding or the like.

[0034] An overlapping portion 600 is formed by overlapping the electrode foil 300 and the tab portion 425. The electrode foil 300 and the tab portion 425 of the lead member 400 are connected at the overlapping portion 600 by four crimping portions 700 (a first crimping portion 710, a second crimping portion 720, a third crimping portion 730, and a fourth crimping portion 740). The four crimping portions 700 are each formed by a manufacturing method described below.

[0035] Each of the multiple crimping portions 700 has one through hole 701 (first through hole 711, second through hole 721, third through hole 731, fourth through hole 741) that penetrates through the electrode foil 300 and the lead member 400. The inner wall of each through hole 701 is formed mainly by the lead member 400, a portion of which is extended toward the second main surface S2 of the electrode foil 300, but a portion of the through hole 701 may also be formed by exposing the electrode foil 300. The lead member 400 forms the inner wall of the through hole 701 and has a penetration portion that penetrates the electrode foil 300 from the first main surface S1 to the second main surface S2. When the crimping portion 700 is viewed from the normal direction of one main surface of the electrode foil 300, the region where neither the lead member 400 nor the electrode foil 300 is present is the through hole 701. The outer periphery of the through-hole 701 is a circular line formed by projecting the through-hole 701 onto one main surface of the electrode foil.

[0036] Each of the multiple crimping portions 700 has one crimping piece 702 (first crimping piece 712, second crimping piece 722, third crimping piece 732, fourth crimping piece 742) formed on the periphery of one through hole 701 (first through hole 711, second through hole 721, third through hole 731, fourth through hole 741).

[0037] Here, Fig. 3 is an enlarged front view of the first crimping portion 710 in Fig. 2. Fig. 4 is a cross-sectional view taken along line XX in Fig. 2, showing a cross section where the length of the crimping piece 712 (folded-back portion 312, 412) wrapping around to the second main surface S2 side (corresponding to lengths L1 and L2 described below) is at its maximum. Fig. 4 is a cross-sectional view schematically showing the first crimping portion 710. Note that the second crimping portion 720 to the fourth crimping portion 740 have the same configuration as the first crimping portion 710, and therefore their description will be omitted.

[0038] In the first crimping portion 710, the electrode foil 300 extends from the periphery of the first through-hole 711 and has a first folded portion 312 folded back onto the second main surface S2. The lead member 400 has a through portion 430 that constitutes the inner wall of the through-hole 711 and passes through the electrode foil 300, and a second folded portion 412 that extends from the end of the through portion 430 and is folded back onto the second main surface S2. The second folded portion 412 encloses the first folded portion 312 on the second main surface S2 side. The first crimping piece 712 is composed of the crimping pieces of the first folded portion 312 and the second folded portion 412. The second folded portion 412 is formed as four separate crimping pieces (triangular portions in FIG. 3 ). The first folded portion 312 is composed of one crimping piece, but may be formed as a plurality of (for example, four) separate crimping pieces. The lead member 400 (through portion 430) forms the inner wall of the first through hole 711. The surface of the first folded portion 312 covered with the second folded portion 412 has an area C where the metal structure of the metal foil 301 is exposed. The area C is located near the end of the first folded portion 312.

[0039] In a cross section (cross section XX in FIG. 2) in the thickness direction of electrode foil 300 at first crimping portion 710 shown in FIG. 4, L1 denotes the length in the plane direction of electrode foil 300 from the center of first through hole 711 to the end of first folded portion 312. L2 denotes the length in the plane direction of electrode foil 300 from the center of first through hole 711 to the end of second folded portion 412. In this case, it is preferable that L1 / L2 be within the above-mentioned range. In this case, the first folded portion is easily covered by the second folded portion, and good adhesion between the first folded portion and the second folded portion is easily ensured.

[0040] The cross-sectional shape of the crimping piece 712 varies depending on which cross section of the crimping portion 712 is viewed. The same is true for the cross-sectional shapes of the other crimping pieces. Figure 4 is a cross section taken along line XX in Figure 2, and shows the cross section at which the length of the crimping piece 712 (folded-back portion 312, 412) that wraps around to the second main surface S2 is at its maximum.

[0041] 1 and 2 show an example in which four through holes 701 are arranged in a row in the width direction of electrode foil 300, but the arrangement of the through holes is not limited to this. From the viewpoint of securing the crimped portion and connection strength, the four through holes may be spaced apart by, for example, 0.5 mm or more, or may be spaced apart by 0.5 mm or more and 3.0 mm or less.

[0042] The number of crimping portions 700 (through holes 701) formed in the overlapping portion in Figures 1 and 2 is four, but the number of crimping portions (through holes) is not limited to this and is usually two or more, and from the viewpoint of contact resistance and connection strength, for example, 2 to 4 (or 3 to 4) is preferable.

[0043] The size of the through hole 701 is not particularly limited, but a maximum diameter of 0.5 mm or more and 1.2 mm or less (or 0.7 mm or more and 1 mm or less) is preferable. If the maximum diameter of the through hole is 0.5 mm or more, electrical connection is likely to be reliable. If the maximum diameter of the through hole is 1.2 mm or less, the mechanical strength of the lead member and electrode foil is likely to be maintained. The sizes of the multiple through holes may be different from each other.

[0044] Some of the four crimping portions may have a structure other than that shown in Figure 4, but from the standpoint of reducing the contact resistance between the electrode foil and the lead member, it is preferable that all of the crimping portions have the structure shown in Figure 4.

[0045] [Manufacturing method of electrolytic capacitors] A method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure includes a first step of preparing an electrode foil having a first main surface and a second main surface opposite the first main surface, and a lead member, and a second step of connecting the electrode foil and the lead member. The second step includes steps 2A to 2C.

[0046] In step 2A, preliminary through holes are formed in the electrode foil, and the lead member is superimposed on a predetermined region of the first main surface where the preliminary through holes are formed. In step 2B, a needle-like member is inserted from the lead member side at a position corresponding to the preliminary through hole of the lead member to form a hole, and the peripheral portion of the hole in the lead member is drawn out to the second main surface of the electrode foil (i.e., the peripheral portion of the hole in the lead member is passed through the electrode foil and drawn out from the first main surface side to the second main surface side of the electrode foil), and the needle-like member is passed through the preliminary through hole to expand it, causing the peripheral portion of the preliminary through hole in the electrode foil to protrude from the second main surface of the electrode foil.

[0047] In step 2B, the diameter D1 of the preliminary through hole, which corresponds to the diameter D2 of the needle-like member when the needle-like member is passed through the preliminary through hole, is smaller than the diameter D2 of the needle-like member. When D1 / D2<1 is satisfied, a protrusion is likely to be formed along with the lead-out portion. A protrusion having region B described below can be formed. D1 / D2 may be 0.9 or less, or may be 0.8 or less. In step 2B, the needle-like member is passed through the preliminary through hole so that the diameter indicating the diameter D2 of the needle-like member and the diameter indicating the diameter D1 of the preliminary through hole coincide when viewed from the normal direction of the first main surface of the electrode foil.

[0048] The diameter D2 of the needle-shaped member refers to the length of any line segment that passes through the center of the cross section corresponding to the base of the pyramidal tip of the needle-shaped member (the axis of the needle-shaped member) and crosses the cross section, where the distance between at least one end of the line segment and the center is the shortest. If the shape of the cross section is a regular polygon, the diameter D2 can also be said to correspond to the height dimension when any one side of the regular polygon is used as the base. If the shape of the cross section is a regular rectangle, the diameter D2 corresponds to the length of one side of the regular rectangle. If the cross section is a regular polygon, the center of the cross section is the center of the circumscribing circle of the regular polygon.

[0049] In the 2C step, the portion P2 extended to the second main surface of the lead member together with the portion P1 protruding from the second main surface of the electrode foil are folded back onto the second main surface, and the folded portions of the portions P1 and P2 are crimped to the second main surface. A crimped portion is formed in the 2C step. In the 2C step, the overlapping portion of the electrode foil and the lead member is pressed in the thickness direction of the electrode foil and the lead member. Hereinafter, the portions P1 and P2 are also referred to as the "protruding portion" and the "extended portion," respectively. The folded portions of the portions P1 and P2 are also referred to as the "first folded portion" and the "second folded portion," respectively.

[0050] In step 2C, portion P2 is folded back on the second main surface so as to enclose the folded back portion of portion P1. In this case, when forming the crimped portion in step 2C (when pressing the overlapping portion), the first folded back portion is pressed on the second main surface while being wrapped by the second folded back portion. This ensures that the first folded back portion and the second folded back portion are firmly attached to each other, and a sufficient area for adhesion is secured. As a result, the contact resistance between the lead member and the electrode foil is reduced. In addition, the connection strength between the lead member and the electrode foil is improved, and low contact resistance is maintained even when a load is applied to the connection portion (crimped portion) between the lead member and the electrode foil.

[0051] In step 2A, as the preliminary through hole is formed, region A is formed on the inner wall surface of the preliminary through hole in the electrode foil, where the metal base of the electrode foil is exposed. In step 2B, as the protrusion is formed, region B, which originates from region A and where the metal base of the electrode foil is exposed, is formed on the upper end surface of the protrusion. In step 2C, as the first and second folded portions are formed and pressed, region C, which originates from region B and where the metal base of the electrode foil is exposed, is formed on the surface covered by the second folded portion of the first folded portion (the surface opposite the second main surface). This region C is formed near the tip of the first folded portion and is firmly attached to the second folded portion. Region A is stretched toward the second main surface when the protrusion is formed, and region B is pressed out when the first folded portion is formed, so region C is likely to be large. Region C and the second folded portion are likely to be in planar contact, and a metallic bond can be formed between region C (the first metal) and the second folded portion. As a result, the contact resistance between the lead member and the electrode foil can be reduced.

[0052] Even if region A is small, region C can be sufficiently formed, and the effect of reducing contact resistance can be significantly achieved even in the case of a thin cathode foil. The thickness of the cathode foil is, for example, 20 μm or more and 60 μm or less.

[0053] If the second folded portion is formed so as not to enclose the first folded portion, the first folded portion will be less likely to be fixed by the second folded portion during pressing and will be more likely to shift out of the second folded portion on the second main surface. As a result, sufficient adhesion between the first folded portion (region C) and the second folded portion will not be ensured, and the area of ​​adhesion will be smaller. In some cases, region C will not be covered by the second folded portion.

[0054] If the preliminary through-holes are not formed in step 2A, the first folded portion is unlikely to be enclosed by the second folded portion, and region C may not be covered by the second folded portion.

[0055] If 1≦D1 / D2, in step 2B, the periphery of the preliminary through hole is difficult to draw out, a protruding portion (region B) is difficult to form, and the first folded portion that tightly adheres to the second folded portion is difficult to form. This reduces the strength of the connection (crimped portion) between the lead member and the electrode foil, which can increase contact resistance when a load is applied to the connection. Furthermore, the protruding portion (region B) is difficult to form, and in step 2B, the through portion of the lead portion is formed to cover the inner wall surface of the preliminary through hole, and in step 2C, the overlapping portion is pressed with the through portion of the lead portion covering the inner wall surface of the preliminary through hole. In this case, the adhesion between region A and the through portion is low (the adhesion area is small), and the contact between the metal base of the electrode foil and the lead member at the crimped portion may be insufficient.

[0056] The height H1 (maximum height) from the second main surface of the portion P1 before being folded back onto the second main surface is preferably smaller than the height H2 (maximum height) from the second main surface of the portion P2 before being folded back onto the second main surface. H1 / H2 may be greater than 0 and less than 1, or may be 0.1 or greater and 0.9 or less, or 0.2 or greater (or 0.4 or greater) and 0.8 or less. In this case, a second folded portion that encapsulates the first folded portion is easily formed in step 2C.

[0057] It is preferable that the diameter D1 (mm) of the preliminary through-hole, the diameter D2 (mm) of the needle-like member, and the thickness T (mm) of the lead member (tab portion) satisfy the relationship of the following formula (1).

[0058] 0<(D2-D1) / T≦1 / 2 (1)

[0059] When formula (1) is satisfied, it is easy to adjust the height H1 to be smaller than the height H2, and it is easy to adjust H1 / H2 within the above range. It is easy to adjust the length L1 to be smaller than the length L2, and it is easy to adjust L1 / L2 within the above range. It is easy to form the second folded portion that includes the first folded portion in the 2C step.

[0060] An example of the second step in the manufacturing method of an electrolytic capacitor according to an embodiment of the present disclosure will be described below. Fig. 5 is a cross-sectional view schematically showing the electrode foil and the main part of the lead member after step 2A. Fig. 6 is a cross-sectional view schematically showing the electrode foil and the main part of the lead member after step 2B. Fig. 4 is a cross-sectional view schematically showing the electrode foil and the main part of the lead member after step 2C.

[0061] (2nd A process) A cylindrical preliminary through hole 330 is formed in the electrode foil 300 using a predetermined jig such as a punch. The electrode foil 300 has a region A where the metal structure of the metal foil 301 is exposed on the inner wall surface of the preliminary through hole 330. When the electrode foil 300 is viewed from the normal direction of its main surface, the preliminary through hole 330 has a circular shape. However, the shape of the preliminary through hole is not limited to this and may be a polygon or a star-shaped polygon. When the shape of the preliminary through hole is a (star-shaped) regular polygon, the center of the preliminary through hole is the center of the circumscribing circle of the (star-shaped) regular polygon.

[0062] By overlapping the lead member 400 in a predetermined region of the first main surface S1 of the electrode foil 300 that includes the preliminary through-hole 330, an overlapping portion 600 between the electrode foil 300 and the lead member 400 is formed.

[0063] (2nd B process) A predetermined position of the overlapping portion 600 is perforated using the needle-shaped member 500. Specifically, the needle-shaped member 500 is thrust into the overlapping portion 600 from the lead member 400 side at a position corresponding to the preliminary through-hole 330 of the lead member 400. At the position perforated by the needle-shaped member 500, a through-hole 711 is formed that passes through both the electrode foil 300 and the lead member 400.

[0064] As through hole 711 is formed, a portion of lead member 400 is drawn to second main surface S2 around through hole 711, and a portion of electrode foil 300 protrudes from second main surface S2. That is, as through hole 430 is formed, a portion of lead member 400 is drawn to second main surface S2 of electrode foil 300, and drawn-out portion 411 is formed. Furthermore, as needle-like member 500 passes through preliminary through hole 330, preliminary through hole 330 is expanded. At this time, the peripheral edge of preliminary through hole 330 in electrode foil 300 protrudes from second main surface S2 of electrode foil 300, and protrusion 311 is formed.

[0065] The tip of the needle-like member 500 has a quadrangular pyramid shape, and the cross section of the tip shape is quadrangular. The electrode foil 300 (around the preliminary through-hole 330) and the lead member 400 are broken through along the corners of the cross section of the tip of the needle-like member 500. As a result of the perforation by the needle-like member 500, the protruding portion 311 and the lead portion 411 that protrude from the second main surface S2 have a shape that is spread out like petals on all four sides. Note that the tip shape of the needle-like member is not limited to this, and may be a pyramid shape other than a quadrangular pyramid. In this case, the shapes of the through-hole and the protruding portion (lead portion) may differ from the examples in FIGS. 1 and 2.

[0066] 5 and 6, the diameter D1 of the preliminary through hole 330, which corresponds to the diameter D2 of the needle-like member 500 when the needle-like member 500 is passed through the preliminary through hole 330, is smaller than the diameter D2 of the needle-like member 500. The diameter D2 of the needle-like member 500 corresponds to the length of one side of the rectangle in the cross section corresponding to the base of the tip of the quadrangular pyramid, and can also be said to correspond to the length of the through hole 711 in the XX direction in Fig. 3. The end face of the protrusion 311 has a region B derived from region A, where the metal structure of the metal foil 301 is exposed.

[0067] As shown in FIG. 5, the diameter D1 (mm) of the preliminary through-hole 330, the diameter D2 (mm) of the needle-shaped member 500, and the thickness T (mm) of the lead member 400 (tab portion 425) preferably satisfy the relationship of the above-mentioned formula (1). When formula (1) is satisfied, H1 and H2 in FIG. 6 can be easily adjusted so that H1 / H2 is less than 1 (or 0.9 or less). Furthermore, L1 and L2 in FIG. 4 can be easily adjusted so that L1 / L2 is less than 1 (or 0.9 or less). In FIG. 5, H1 indicates the maximum height of the protruding portion 311 from the second main surface, and H2 indicates the maximum height of the drawn-out portion 411 from the second main surface. In FIG. 5, the heights of the protruding portion and the drawn-out portion are maximum at the same cross section of the overlapping portion, but they may be maximum at different cross sections of the overlapping portion.

[0068] (2nd C process) The overlapping portion 600, on which the protruding portion 311 and the leading portion 411 are formed, is pressed to form the crimped portion 710. The overlapping portion 600 is pressed, for example, at a pressure of 8 to 12 MPa. The pressing time is not particularly limited, but is, for example, about 0.3 to 1 second. By pressing the overlapping portion 600, the leading portion 411 is folded back onto the second main surface together with the protruding portion 311, forming the first folded portion 312 and the second folded portion 412. Furthermore, the overlapping portion 600 (the first folded portion 312 and the second folded portion 412) is pressed, and the first folded portion 312 and the second folded portion 412 are crimped to the second main surface.

[0069] The lead-out portion 411 is folded back on the second main surface S2 so as to enclose the first folded back portion 312. That is, the second folded back portion 412 enclosing the first folded back portion 312 is formed in the crimped portion 710. The surface of the first folded back portion 312 covered with the second folded back portion 412 (the surface opposite to the second main surface S2) has a region C derived from the region B where the metal structure of the metal foil 301 is exposed.

[0070] Overlapping portion 600 is pressed in the thickness direction of electrode foil 300, deforming through hole 711, electrode foil 300 around through hole 711, and lead member 400 together with protruding portion 311 and drawn-out portion 411. Due to the deformation of protruding portion 311 and drawn-out portion 411, crimping pieces 712 having first folded portions 312 and second folded portions 412 are formed on the outer periphery of through hole 711. Crimping pieces 712 are formed in a petal shape on all four sides from through hole 711. Electrode foil 300 is pressed firmly by crimping pieces 712 and is crimped to lead member 2. This crimping electrically connects electrode foil 300 and lead member 400.

[0071] Here, Fig. 7 is a cross-sectional view schematically illustrating an electrolytic capacitor according to an embodiment of the present disclosure. Fig. 7 shows an example of an electrolytic capacitor including a wound capacitor element. Fig. 8 is a perspective view schematically illustrating the configuration of the wound body of Fig. 7.

[0072] Electrolytic capacitor 200 includes a wound body 100. Wound body 100 is formed by winding anode foil 10 and cathode foil 20 with separator 30 interposed therebetween.

[0073] One end of lead tabs 50A and 50B is connected to anode foil 10 and cathode foil 20, respectively, and lead tabs 50A and 50B are wound to form wound body 100. Lead wires 60A and 60B are connected to the other end of lead tabs 50A and 50B, respectively.

[0074] The connection between the anode foil 10 and the lead tab 50A and / or the connection between the cathode foil 20 and the lead tab 50B is performed by the manufacturing method (second step) of an electrolytic capacitor according to the present disclosure. In particular, since the cathode foil 20 has a small thickness, the manufacturing method significantly reduces the contact resistance between the cathode foil and the lead tab 50B.

[0075] A stop tape 40 is disposed on the outer surface of the cathode foil 20 located in the outermost layer of the wound body 100, and the ends of the cathode foil 20 are fixed by the stop tape 40. When the anode foil 10 is prepared by cutting it from a large foil, the wound body 100 may be further subjected to a chemical conversion treatment in order to provide a dielectric layer on the cut surface.

[0076] The wound body 100 contains an electrolyte, and the electrolyte is interposed between the anode foil 10 (dielectric layer) and the cathode foil. The wound body 100 containing the electrolyte is formed, for example, by impregnating the wound body 100 with a treatment liquid containing a conductive polymer. The impregnation may be performed under reduced pressure, for example, in an atmosphere of 10 kPa to 100 kPa. The wound body 100 may further contain an electrolytic solution.

[0077] The wound body 100 is housed in the bottomed case 211 so that the lead wires 60A and 60B are located on the opening side of the bottomed case 211. The material of the bottomed case 211 can be a metal such as aluminum, stainless steel, copper, iron, brass, or an alloy of these metals.

[0078] A sealing member 212 is placed at the opening of a bottomed case 211 in which the wound body 100 is stored, the open end of the bottomed case 211 is crimped to the sealing member 212 and curled, and a seat plate 213 is placed at the curled portion, thereby sealing the wound body 100 within the bottomed case 211.

[0079] The separator 30 is not particularly limited, and may be made of, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (for example, aliphatic polyamide, aromatic polyamide such as aramid).

[0080] Sealing member 212 is formed so that lead wires 60A and 60B can pass through it. Sealing member 212 may be made of any insulating material, and is preferably made of an elastic material. Among these, highly heat-resistant materials such as silicone rubber, fluororubber, ethylene propylene rubber, hypalon rubber, butyl rubber, and isoprene rubber are preferred.

[0081] The electrolyte includes at least one of a solid electrolyte and an electrolytic solution. The electrolytic solution includes a non-aqueous solvent and a solute (e.g., an organic salt) dissolved therein. A non-aqueous solvent may be used together with the solid electrolyte. The solid electrolyte includes a conductive polymer such as polythiophene. The solid electrolyte may include a dopant such as polystyrene sulfonic acid together with the conductive polymer.

[0082] [Example] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples.

[0083] Example 1 The caulking portion shown in FIGS. 1 to 4 was formed to connect the cathode foil and the lead member. A cathode foil was prepared as the electrode foil, consisting of a 28 μm-thick aluminum foil (plain foil) with a titanium nitride layer (thickness: 1 μm) formed on both sides. The cathode foil was cut into a strip measuring 300 mm in length and 10 mm in width. Four cylindrical preliminary through-holes (diameter D1: 0.5 mm) were formed at predetermined positions in the cathode foil using a specified punch. The four preliminary through-holes were formed at regular intervals along the width direction of the cathode foil. A lead member (thickness T: 0.3 mm) was overlapped on the cathode foil at the positions where the preliminary through-holes were formed, forming an overlapping portion. A needle-shaped member (diameter D2: 0.6 mm) with a quadrangular pyramidal tip was used to drill holes in the overlapping portion at positions corresponding to the preliminary through-holes. The drilling was performed from the lead member side. Next, the cathode foil and lead member were connected by pressing at four crimped portions. In this way, Sample A, in which the lead member and electrode foil were connected, was obtained. In sample A, a second folded portion was formed that contained the first folded portion. L1 / L2 had the values ​​shown in Table 1.

[0084] [Evaluation 1: Contact resistance measurement] The contact resistance between the cathode foil and the lead member was measured using the four-terminal method. Fifteen samples of Sample A were prepared, and the average value of the contact resistances of the 15 samples was calculated.

[0085] [Evaluation 2: Measurement of contact resistance after loading] The cathode foil was fixed, and a load of 100 gf was applied in a direction parallel to the length of the cathode foil from the side edge near the overlapping portion of the lead member (2 mm from the end of the overlapping portion). The load was applied for 3 seconds. The contact resistance after the load was then measured using the same method as in Evaluation 1. Ten samples A were prepared, and the average contact resistance after the load was calculated.

[0086] Comparative Example 1 Except for not providing the preliminary through holes in the cathode foil, Sample B1 was obtained and evaluated in the same manner as in Example 1. In Sample B1, the first folded portion was not enclosed by the second folded portion.

[0087] Comparative Example 2 Except for setting the diameter D1 of the preliminary through-hole to 0.7 mm, sample B2 was obtained and evaluated in the same manner as in Example 1. In sample B2, the first folded portion was hardly formed.

[0088] The evaluation results are shown in Table 1. The contact resistances in Table 1 are expressed as relative values, with the contact resistance of Sample B1 obtained in Evaluation 1 being set at 100.

[0089] [Table 1]

[0090] Sample A had reduced contact resistance, high connection strength, and low contact resistance after loading. Sample B1 had high contact resistance, low connection strength, and increased contact resistance after loading. Sample B2 had low connection strength and increased contact resistance after loading. [Industrial Applicability]

[0091] The method for manufacturing an electrolytic capacitor according to the present disclosure can be suitably used to manufacture an electrolytic capacitor having low contact resistance between the lead member and the electrode foil. [Explanation of symbols]

[0092] 10: anode foil, 20: cathode foil, 30: separator, 40: winding tape, 60A, 60B: lead wire, 50A, 50B: lead tab, 100: wound body, 200: electrolytic capacitor, 211: bottomed case, 212: sealing member, 213: seat plate, 300: electrode foil, 301: metal foil, 302a: first covering layer, 302b: second covering layer, 311: protrusion, 312: first folded portion, 330: spare through hole, 400 lead member, 411: lead-out portion, 412: second folded portion, 4 25: tab portion, 426: lead wire connecting portion, 427: lead wire, 430: through portion, 500: needle-shaped member, 600: overlapping portion, 700: crimping portion, 710: first crimping portion, 720: second crimping portion, 730: third crimping portion, 740: fourth crimping portion, 701: through hole, 711: first through hole, 721: second through hole, 731: third through hole, 741: fourth through hole, 702 crimping piece, 712: first crimping piece, 722: second crimping piece, 732: third crimping piece, 742: fourth crimping piece

Claims

1. an electrode foil having a first main surface and a second main surface opposite to the first main surface; and a lead member connected to the electrode foil; the electrode foil and the lead member are connected by a crimping portion at an overlapping portion where the first main surface of the electrode foil and the lead member overlap, the crimping portion has a through hole that penetrates the electrode foil and the lead member, In the crimped portion, the electrode foil has a first folded portion that extends from a peripheral edge of the through hole and is folded onto the second main surface; the lead member has a through portion that forms an inner wall of the through hole and passes through the electrode foil, and a second folded portion that extends from an end of the through portion and is folded back onto the second main surface, the second folded portion includes the first folded portion, The electrode foil comprises a metal foil and a coating layer covering both main surfaces of the metal foil, the coating layer includes at least one layer selected from the group consisting of a metal oxide layer, a metal nitride layer, a metal carbide layer, and a conductive layer; the first folded portion has a region C in which the metal structure of the metal foil is exposed on a surface covered by the second folded portion, The thickness of the electrode foil is 20 μm or more and 60 μm or less.

2. 2. The electrolytic capacitor according to claim 1, wherein the coating layer has a thickness of 0.1 μm or more and 5 μm or less.

3. In a cross section in the thickness direction of the electrode foil at the crimped portion, 3. The electrolytic capacitor according to claim 1, wherein a length L1 of the electrode foil in a planar direction from the center of the through hole to the end of the first folded portion is smaller than a length L2 of the electrode foil in a planar direction from the center of the through hole to the end of the second folded portion.

4. An electrolytic capacitor described in any one of claims 1 to 3, wherein the ratio of the thickness of the electrode foil to the thickness of the lead member is 1 / 15 or more and 1 / 5 or less.

5. A first step of preparing an electrode foil having a first main surface and a second main surface opposite to the first main surface, and a lead member; a second step of connecting the electrode foil and the lead member, The second step comprises: a second A step of forming a preliminary through hole in the electrode foil and overlapping the lead member in a predetermined region on the first main surface including the preliminary through hole; a second B step after the second A step of inserting a needle-like member from the lead member side into a position corresponding to the preliminary through hole of the lead member to form a through hole, drawing a peripheral portion of the through hole of the lead member onto a second main surface of the electrode foil, and passing the needle-like member through the preliminary through hole to expand the preliminary through hole, thereby causing the peripheral portion of the preliminary through hole of the electrode foil to protrude from the second main surface of the electrode foil; a second C process in which a portion P2 of the lead member extended to the second main surface together with a portion P1 of the electrode foil protruding from the second main surface are folded back onto the second main surface, and the folded-back portions of the portion P1 and the portion P2 are crimped to the second main surface; Including, a diameter D1 of the preliminary through hole corresponding to a diameter D2 of the needle-like member when the needle-like member is passed through the preliminary through hole in the second B step is smaller than the diameter D2 of the needle-like member; In the second step C, the portion P2 is folded back on the second main surface so as to include the folded-back portion of the portion P1 therein; In the first step, the electrode foil is prepared, the electrode foil including a metal foil and a coating layer covering both main surfaces of the metal foil; the coating layer includes at least one layer selected from the group consisting of a metal oxide layer, a metal nitride layer, a metal carbide layer, and a conductive layer; an inner wall surface of the preliminary through hole provided in the second A step has a region A in which the metal structure of the metal foil is exposed; The portion P1 formed in the second B step has, on an upper end surface of the portion P1, a region B that originates from the region A and in which the metal structure of the metal foil is exposed, A method for manufacturing an electrolytic capacitor, wherein the folded portion of the portion P1 formed in the second C step has a region C on the surface covered by the folded portion of the portion P2, which region C originates from the region B and exposes the metal structure of the metal foil.

6. 6. The method for manufacturing an electrolytic capacitor according to claim 5, wherein a height H1 from the second main surface of the portion P1 before being folded back onto the second main surface is smaller than a height H2 from the second main surface of the portion P2 before being folded back onto the second main surface.

7. The diameter D1 of the preliminary through hole, the diameter D2 of the needle-like member, and the thickness T of the lead member are 0<(D2-D1) / T≦1 / 2 The method for manufacturing an electrolytic capacitor according to claim 5 or 6, wherein the following relationship is satisfied:

8. In the second step C, in a cross section in the thickness direction of the electrode foil at a crimped portion formed by crimping the folded portions of the portion P1 and the portion P2 to the second main surface, When the length in the surface direction of the electrode foil from the center of the through hole to the end of the folded-back portion of the portion P1 is L1, and the length in the surface direction of the electrode foil from the center of the through hole to the end of the folded-back portion of the portion P2 is L2, The diameter D2 of the needle-shaped member, the length L1, and the length L2 are The method for manufacturing an electrolytic capacitor according to any one of claims 5 to 7, wherein the relationship D2 / 2<L1 / L2<1 is satisfied.

9. 9. The method for manufacturing an electrolytic capacitor according to claim 5, wherein the tip of the needle-like member has a pyramidal shape.

10. 10. The method for manufacturing an electrolytic capacitor according to claim 5, wherein the preliminary through holes have a shape of a circle, a polygon, or a star-shaped polygon.

11. A method for manufacturing an electrolytic capacitor described in any one of claims 5 to 10, wherein the thickness of the electrode foil is 20 μm or more and 60 μm or less.

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