Capacitor and production method for same

Abstract

The purpose of the present disclosure is to make it possible to maintain the strength and performance of a capacitor by, for example, suppressing the cracking of an electrode foil when a lead-out terminal is connected to the electrode foil.　A capacitor (2) comprises a terminal member (4) and an electrode foil (6) that comprises a broadened layer (8). The terminal member and the electrode foil are connected by connection parts (14-1, 14-2, 14-3). In regions (24-1, 24-2) that are between the connection parts and ends of the electrode foil, the broadened layer has strengthened parts (26-1, 26-2) that have been strengthened more than other portions of the broadened layer.

Description

Capacitor and Method for Manufacturing the Same

[0001] The present disclosure relates to a capacitor and a method for manufacturing the same.

[0002] A capacitor includes electrode foils such as an anode foil and a cathode foil. The electrode foils are connected to lead-out terminals and are connected to other components or a circuit board via the lead-out terminals. For the connection between the lead-out terminals and the electrode foils, connection methods such as a stitch connection method or a cold pressure welding connection method are used (for example, Patent Document 1). In the stitch connection method, a needle is pierced from the lead-out terminal side into the stacked electrode foils and the lead-out terminal, a terminal piece of the lead-out terminal is formed on the electrode foil side, and the lead-out terminal is connected to the electrode foil by pressing the terminal piece toward the electrode foil side. In the cold pressure welding connection, the stacked lead-out terminals and electrode foils are pressed from the electrode foil side by a pressure welding die, and the lead-out terminal is connected to the electrode foil by cold pressure welding.

[0003] Japanese Patent Laid-Open No. 2-277217

[0004] By the way, when the surface area of the electrode foil is increased for increasing the capacitance of the capacitor, the electrode foil becomes fragile as the surface area increases. An oxide film harder than the metal portion of the electrode foil may be formed on the surface of the electrode foil. When the surface area of the electrode foil is increased for increasing the capacitance of the capacitor, the amount of the hard oxide film per unit volume of the electrode foil increases as the surface area increases. Therefore, the flexibility of the electrode foil decreases and the electrode foil becomes fragile.

[0005] In connection methods such as the stitch connection method or the cold pressure welding connection method, when the terminal piece is pressed, or when the electrode foil and the lead-out terminal are pressed, the electrode foil and the lead-out terminal tend to extend in all directions from the pressing point of the electrode foil and the lead-out terminal.As the electrode foil with an oxide film formed on the enlarged surface area has a different elongation ease from that of the lead-out terminal made of simple aluminum or the like. Therefore, for example, the electrode foil cannot follow the elongation of the lead-out terminal. When the electrode foil becomes fragile due to an increase in the capacitance (expansion of the surface area) of the electrode foil, the electrode foil that cannot follow the elongation of the lead-out terminal is likely to crack in the region of the foil end of the electrode foil from the connection portion with the lead-out terminal. The cracking of the electrode foil may be a factor for reducing the connectivity with the lead-out terminal.

[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 purpose of this disclosure is to suppress cracking of the electrode foil during the process of connecting lead terminals to the electrode foil, thereby maintaining the strength and performance of the capacitor.

[0008] According to a first aspect of the present disclosure, the capacitor comprises a terminal member and an electrode foil having an expanding layer, the terminal member and the electrode foil being connected by a connection portion, and the expanding layer having a reinforced portion in the region between the connection portion and the foil edge of the electrode foil which is reinforced compared to the rest of the expanding layer.

[0009] In the above-described capacitor, the widened surface layer of the reinforced portion may have a smaller porosity or a higher density than the widened surface layer of the other portion.

[0010] In the capacitor described above, the reinforced portion may be arranged to a length corresponding to at least the connection portion in the width direction of the terminal member.

[0011] In the capacitor described above, the electrode foil and the terminal member may be connected by a cold pressure welding method or a stitch connection method.

[0012] In the above capacitor, the widened surface layer of the reinforced portion may be thinner than the widened surface layer of the other portions.

[0013] According to a second aspect of this disclosure, a method for manufacturing a capacitor includes the steps of laminating an electrode foil including an expanding layer and a terminal member, forming a reinforced portion in the region of the electrode foil between the portion intended to be connected to the terminal member and the foil edge of the electrode foil, and connecting the terminal member to the electrode foil by a pressing process.

[0014] In the above method for manufacturing a capacitor, the reinforced portion may be formed by reducing the porosity of the widened surface layer or by increasing its density.

[0015] In the above method for manufacturing the capacitor, the connection between the electrode foil and the terminal member may be made by cold pressure welding or stitching.

[0016] In the capacitor manufacturing method described above, the void ratio of the expanded surface layer may be reduced or the density may be increased by pressing the electrode foil and the terminal member in the stacking direction of the electrode foil and the terminal member.

[0017] According to this disclosure, the following effects can be obtained.

[0018] (1) The reinforced portion formed on the electrode foil can suppress the propagation of stress from the connection between the terminal member and the electrode foil to the foil edge, for example, during connection, thereby suppressing cracking of the electrode foil.

[0019] (2) By suppressing cracking of the electrode foil, the strength and performance of the capacitor are maintained, and the reliability of the capacitor is improved.

[0020] (3) While suppressing cracking of the electrode foil, the surface area of ​​the electrode foil can be increased, and the capacitance of the capacitor can be increased.

[0021] This figure shows an example of electrode foil and terminal member of a capacitor according to an embodiment. This is a schematic diagram showing an example of a cross-section along line II-II in Figure 1. Figures 3A and 3B show an example of the process of forming a reinforced part, and Figure 3C is an enlarged view of part IIIC shown in Figure 3B. Figures 4A and 4B show an example of the process of connecting terminal member to electrode foil. This figure shows an example of criteria for determining foil cracking.

[0022] Figure 1 shows an example of electrode foil and terminal member of a capacitor according to an embodiment. In Figure 1, the dashed line represents the outer shape of the terminal member 4 located on the back surface of the electrode foil 6, and the area enclosed by the dashed line and the foil end 22-1 represents the area where the terminal member 4 and the electrode foil 6 overlap. In Figure 1, the dashed line represents a straight line L with length Lw and width. Figure 2 is a schematic diagram showing an example of a cross-section along line II-II in Figure 1, schematically showing the cross-sections of the reinforced parts 26-1 and 26-2 and their surrounding areas. The configurations shown in Figures 1 and 2 are examples, and the technology of this disclosure is not limited to such configurations.

[0023] Capacitor 2 is an example of an electronic component, such as an electrolytic capacitor. Capacitor 2 includes, for example, a capacitor element, a terminal member 4, an electrolyte, a sealing member, and an outer casing.

[0024] A capacitor element includes multiple electrode foils 6, such as cathode foil and anode foil, and a separator. The electrode foils 6 and the separator are stacked and wound together so that the separator is placed between the electrode foils 6, forming a wound element. This wound element forms the capacitor element.

[0025] The electrode foil 6 is, for example, a strip-shaped foil, and is a valve-acting metal foil such as aluminum foil, tantalum foil, niobium foil, titanium foil, hafnium foil, zirconium foil, zinc foil, tungsten foil, bismuth foil, or antimony foil. The electrode foil 6 has a surface expansion layer 8 on its surface and a base metal 10 in the center in the thickness direction (Figure 2). The surface expansion layer 8 has a plurality of holes, and these holes give it, for example, a porous structure. The surface expansion layer 8 increases the surface area of ​​the electrode foil 6 compared to the surface area of ​​a flat foil. The plurality of holes are formed, for example, by etching, and may include etching pits such as tunnel-shaped etching pits or sponge-like etching pits. The surface expansion layer 8 formed by etching is, for example, called an etching layer. The surface expansion layer 8 may also be a particle surface expansion layer formed by metal particles. The particle surface expansion layer may be formed on the base foil by depositing or sintering metal particles onto the base foil instead of etching, or it may be formed on the base foil by depositing or sintering metal particles onto the base foil after etching. Multiple electrode foils 6 are used as cathode foils or anode foils. The cathode foils constitute the cathode side electrode of the capacitor 2, and the anode foils constitute the anode side electrode of the capacitor 2.

[0026] The surface of the anode foil includes the surface-expanding layer 8 described above, as well as a dielectric oxide film formed, for example, by a chemical conversion treatment. The anode foil contacts the electrolyte via the dielectric oxide film with an expanded surface area.

[0027] A separator is placed between the anode foil and the cathode foil to prevent a short circuit between them. 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.

[0028] The terminal member 4 is made of a conductive metal such as aluminum. The terminal member 4 is, for example, a tab terminal or a lead terminal. The lead terminal is, for example, a lead terminal having a tab 12 and a lead wire 13 (for example, A in Figure 3), which protrudes from one end face of the capacitor element. The tab 12 and the lead wire 13 are connected by arc welding or the like. The tab 12 is made of a conductive metal such as aluminum and includes a flat portion. The flat portion of the tab 12 of the terminal member 4 and the electrode foil 6 are connected at connection points 14-1, 14-2, and 14-3, for example, by a stitch connection method. Alternatively, the terminal member 4 may be a tab terminal instead of a lead terminal. The tab terminal is, for example, a thin metal plate or a metal tab, and has a strip shape. The flat portion is superimposed on the electrode foil and connected to the electrode foil by cold pressure welding at multiple connection points, for example.

[0029] In the stitch connection method, a stitch needle 50 (A in Figure 4) is inserted from the terminal member 4 side into the tabs 12 of the terminal members 4 and the electrode foil 6 which are stacked on top of each other, forming terminal pieces 16 and foil pieces 18 (A in Figure 4) on the terminal member 4 and electrode foil 6, respectively. The formed terminal pieces 16 and foil pieces 18 are bent and pressed or compressed against the electrode foil 6. Therefore, each connection portion 14-1, 14-2, and 14-3 is formed in the portion where the terminal piece 16 is located. In the stitch connection method, through holes may be provided in advance in the portion of the electrode foil 6 into which the stitch needle 50 is inserted. That is, the terminal member 4 is positioned so as to cover the through holes provided in the electrode foil 6, and the stitch needle 50 is inserted into the terminal member 4 so as to be inserted into the through holes in the electrode foil 6. Since the stitch needle 50 does not pierce the electrode foil 6, terminal pieces 16 are formed, but foil pieces 18 are not formed. Alternatively, in the stitch connection method in which through holes are pre-formed in the electrode foil 6, the stitch needle 50 may slightly pierce the electrode foil 6 to form small foil pieces. In this case, the formed terminal pieces 16 are bent and pressed or pressure-bonded to the electrode foil 6. Furthermore, the method of connecting the terminal member 4 and the electrode foil 6 is not limited to the stitch connection method, but may also be other connection methods such as cold pressure welding with pressing.

[0030] The widening layer 8 of the electrode foil 6 has reinforcing portions 26-1 and 26-2. Reinforcing portion 26-1 is located, for example, at the non-end of region 24-1 between the connecting portion 14-1 and the foil edge 22-1 of the electrode foil 6. Reinforcing portion 26-2 is located, for example, at the non-end of region 24-2 between the connecting portion 14-2 and the foil edge 22-2 of the electrode foil 6. Connecting portion 14-1 is located closest to the foil edge 22-1 among the connecting portions 14-1, 14-2, and 14-3, and connecting portion 14-2 is located closest to the foil edge 22-2 among the connecting portions 14-1, 14-2, and 14-3. The non-end is defined as the portion of region 24-1 or region 24-2 other than the edge, for example, the central portion or the peripheral portion of the central portion. When the region between the end of the connecting portion 14-1 on the foil end 22-1 side and the end of the connecting portion 14-2 on the foil end 22-2 side is defined as the connecting region 28, region 24-1 is defined as the region between the connecting region 28 and the foil end 22-1, and region 24-2 is defined as the region between the connecting region 28 and the foil end 22-2. The reinforcing portion 26-1 located at the non-end is separated from the connecting portion 14-1 and the foil end 22-1, and the reinforcing portion 26-2 located at the non-end is separated from the connecting portion 14-2 and the foil end 22-2.

[0031] The reinforcing portions 26-1 and 26-2 have, for example, a linear or strip shape, extend in the width direction (Figure 1) of the terminal member 4, and are arranged over the entire width direction of the region where the terminal member 4 and the electrode foil 6 overlap. The reinforcing portions 26-1 and 26-2 may have a length Lw corresponding to at least the connection portion 14-1 or connection portion 14-2 in the width direction of the terminal member 4, or they may be arranged within a wide straight line L passing through the connection portions 14-1, 14-2, and 14-3 and having a width corresponding to the length Lw. The electrode foil 6 having the reinforcing portions 26-1 and 26-2 may be an anode foil or a cathode foil.

[0032] As shown in Figure 2, in the reinforced sections 26-1 and 26-2, the electrode foil 6 has a recess 30, and the expanded surface layer 8 in the reinforced sections 26-1 and 26-2 is thinner than the expanded surface layer 8 in the other section (hereinafter referred to as "general section 32"). Such reinforced sections 26-1 and 26-2 are formed, for example, by pressing the electrode foil 6, and the expanded surface layer 8 is compressed in the reinforced sections 26-1 and 26-2. As a result, the voids in the expanded surface layer 8 become smaller or less due to the deformation of the pits contained in the expanded surface layer 8 (for example, reduction in length or width). In other words, the expanded surface layer 8 in the reinforced sections 26-1 and 26-2 has a smaller porosity and a higher density than the expanded surface layer 8 in the general section 32. Due to the smaller porosity and higher density, the reinforced sections 26-1 and 26-2 are stronger than the general section 32. The decrease in porosity increases the density. Since there is a correlation between porosity and density, if either a small porosity or a high density is confirmed, the other is also confirmed, and it is not necessary to confirm both. The reinforced sections 26-1 and 26-2 may be formed from either of the widening layers 8, or from both of the widening layers 8.

[0033] The general portion 32 is the portion other than the reinforced portions 26-1 and 26-2, and includes the surrounding portions of the reinforced portions 26-1 and 26-2. The general portion 32 is defined as the portion that has not been subjected to the same or similar treatment as the treatment (e.g., pressing as described above) applied to the reinforced portions 26-1 and 26-2.

[0034] The recess 30 forms, for example, a curved surface on the exposed surface of the electrode foil 6, providing a height difference to the reinforced portions 26-1 and 26-2. The exposed surface of the electrode foil 6 is defined as the surface opposite to the surface on the terminal member 4 side (i.e., the surface on which the terminal piece 16 is placed) and not covered by the terminal member 4. In the cross section shown in Figure 2 (cross section along line II-II in Figure 1), the expanding layer 8 has a thickness Te at the ends of the reinforced portions 26-1 and 26-2, and a thickness Tc in the central part of the reinforced portions 26-1 and 26-2. The thickness of the expanding layer 8 gradually decreases from the ends to the central part of the reinforced portions 26-1 and 26-2. Therefore, from the ends to the central part of the reinforced portions 26-1 and 26-2, for example, the porosity gradually decreases and the density gradually increases.

[0035] When forming a curved surface, the pressing force on the ends of the reinforced sections 26-1 and 26-2 is reduced. Therefore, the pressing force is reduced compared to when the entire reinforced sections 26-1 and 26-2 are pressed evenly. In addition, when forming a curved surface, abrupt changes in porosity and density are suppressed, and the load on the electrode foil 6 is reduced.

[0036] The electrolyte contains at least an electrolyte solution and fills the voids and separators within the capacitor element.

[0037] When a lead terminal is used as the terminal member 4, the sealing member is made of, for example, insulating rubber. The sealing member has an insertion hole at a position corresponding to the terminal member 4. The terminal member 4 penetrates the insertion hole of the sealing member and is exposed to the outside of the capacitor 2. Alternatively, when a tab terminal is used as the terminal member 4, the sealing member may be, for example, a phenolic laminate with an external terminal attached. The phenolic laminate is made by layering rubber material on paper phenolic resin and heat-pressing it, and is molded to correspond to the opening shape of the outer case. This sealing member is fixed by passing a rivet-shaped external terminal through it. The external terminal attached to the phenolic laminate is connected to one end of the tab terminal protruding from the capacitor element.

[0038] The outer casing is, for example, a bottomed cylindrical aluminum case. The capacitor element and a portion of the terminal member 4 are inserted into 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 a portion of the terminal member 4 are sealed inside the outer casing. The terminal member 4 passes through a through-hole in the sealing member and protrudes from the sealing member. [Capacitor Manufacturing Process]

[0039] The manufacturing process for the capacitor 2 is an example of a method for manufacturing the capacitor of the present disclosure, and includes, for example, a step of manufacturing an electrode foil 6, a step of manufacturing a separator, a step of laminating the electrode foil 6 and the terminal member 4, a step of forming reinforcement parts 26-1 and 26-2, a step of connecting the terminal member 4 to the electrode foil 6 (hereinafter referred to as the "connection step of the terminal member 4"), a step of manufacturing a capacitor element, and a step of encapsulating the capacitor element.

[0040] In the process of manufacturing the electrode foil 6, the surface of the valve-acting metal foil described above is etched, for example, to form a surface expansion layer 8 on the surface of the valve-acting metal foil. The valve-acting metal foil is etched, for example, by applying an electric current to a valve-acting metal foil immersed in a chloride aqueous solution such as hydrochloric acid or sodium chloride. The applied current may be direct current or alternating current. The etched valve-acting metal foil is cut to produce the electrode foil. Alternatively, instead of etching, metal particles may be deposited or sintered onto the base foil, or metal particles may be deposited or sintered onto the base foil that has undergone etching to form a surface expansion layer 8 (particle surface expansion layer) on the base foil.

[0041] When the electrode foil 6 is the anode foil, the valve metal foil is subjected to a chemical conversion treatment after etching to form a dielectric oxide film on the surface of the valve metal foil. In the chemical conversion treatment of the valve metal foil, a voltage is applied to the valve metal foil immersed in an electrolyte solution containing, for example, ammonium borate, ammonium phosphate, or ammonium adipate. The converted valve metal foil is then cut to produce the anode foil.

[0042] In the separator manufacturing process, the separator components described above are cut to produce the separators.

[0043] In the process of laminating the electrode foil 6 and the terminal member 4, the terminal member 4 is placed on top of the electrode foil 6, so that the electrode foil 6 and the terminal member 4 are laminated together.

[0044] In the process of forming the reinforced parts 26-1 and 26-2, the reinforced parts 26-1 and 26-2 described above are formed. For example, a pressing device is used to form the reinforced parts 26-1 and 26-2. As shown in Figures 3A and 3B, the pressing device includes a first mold 42 and second molds 44-1 and 44-2. The first mold 42 is a fixed mold having a flat surface on the side of the second molds 44-1 and 44-2. The second molds 44-1 and 44-2 are movable molds that can move to change the distance from the first mold 42. The second molds 44-1 and 44-2 include a pressing part 46. The pressing part 46 has, for example, a semicylindrical-shaped tip facing the first mold 42. The pressing part 46 applies a pressing force to the terminal member 4 and electrode foil 6 using elastic force or mechanical methods.

[0045] As shown in A of FIG. 3, the laminated electrode foil 6 and the terminal member 4 are disposed between the first mold 42 and the second molds 44-1 and 44-2. The second molds 44-1 and 44-2 are moved toward the first mold 42. Then, as shown in B of FIG. 3, in the lamination direction of the electrode foil 6 and the terminal member 4, the tip portions of the pressing portions 46 of the second molds 44-1 and 44-2 press the electrode foil 6 and the terminal member 4, and press the electrode foil 6 and the terminal member 4 against the first mold 42. As shown in C of FIG. 3 (an enlarged view of the IIIC portion shown in B of FIG. 3), depressions 30 are formed in the regions 24-1 and 24-2 of the electrode foil 6 by the pressing of the pressing portion 46, and reinforcing portions 26-1 and 26-2 are formed. At the stage when the reinforcing portions 26-1 and 26-2 are formed, the regions 24-1 and 24-2 are defined as the regions between the planned connection portions with the terminal member 4 and the foil ends 22-1 and 22-2 of the electrode foil 6.

[0046] The pressing force applied to the electrode foil 6 and the terminal member 4 in the step of forming the reinforcing portions 26-1 and 26-2 may be of such a magnitude that, for example, depressions 30 are formed on the exposed surface of the electrode foil 6, and is smaller than the pressing force applied to the electrode foil 6 and the terminal member 4 in the connection step of the terminal member 4. Therefore, cracking of the electrode foil 6 in the step of forming the reinforcing portions 26-1 and 26-2 is suppressed.

[0047] The magnitude of the pressing force itself may be adjusted so that the depressions 30 are formed, or the contact area of the pressing portion 46 with respect to the electrode foil 6 may be adjusted. When the contact area becomes smaller, the pressing force per unit area becomes larger. That is, the depressions 30 may be formed by reducing the contact area without changing the magnitude of the pressing force itself.

[0048] In the connection step of the terminal member 4, the terminal member 4 is connected to the electrode foil 6 by a connection method such as a cold pressure welding connection method or a stitch connection method. In the stitch connection method, a stitch connection device is used. As shown in A and B of FIG. 4, the stitch connection device includes holding means (for example, the first mold 42 and the second molds 44-1 and 44-2), a stitch needle 50, and a forming mold 52. The holding means may be a member other than the first mold 42 and the second molds 44-1 and 44-2, or the first mold 42 and the second molds 44-1 and 44-2 of the pressing device may also serve as the holding means.

[0049] As shown in A of FIG. 4, the terminal member 4 and the electrode foil 6 held by the holding means are pierced from the side of the terminal member 4 with a stitch needle 50 to form terminal pieces 16 and foil pieces 18 on the terminal member 4 and the electrode foil 6, respectively. After the formation of the terminal piece 16 and the foil piece 18, the stitch needle 50 is removed from the terminal member 4 and the electrode foil 6.

[0050] As shown in B of FIG. 4, for example, the molding die 52 is moved to the side of the holding means (for example, the first mold 42), and the terminal member 4, the electrode foil 6, particularly the terminal piece 16 and the foil piece 18 are pressed from the side of the electrode foil 6 with the molding die 52. By the pressing process with the molding die 52, the terminal piece 16 and the foil piece 18 are folded back, and the terminal member 4 is connected to the electrode foil 6.

[0051] In the manufacturing process of the capacitor element, a separator is disposed between electrode foils (an anode foil and a cathode foil), and the electrode foils and the separator are wound to manufacture the capacitor element.

[0052] In the encapsulation process of the capacitor element, the capacitor element impregnated with an electrolyte such as an electrolytic solution is inserted into the interior of the exterior case, and then a sealing member is attached to the opening of the exterior case to manufacture the capacitor 2. [Evaluation of Examples and Comparative Examples]

[0053] The states of the electrode foil 6 and the terminal member 4 according to the example and the electrode foil 106 and the terminal member 4 according to the comparative example were confirmed. The electrode foil 6 according to the example is the electrode foil 6 according to the embodiment, and is the same as the anode foil having sponge-like etching pits on the surface portion as the roughened layer 8. Further, the terminal member 4 according to the example is the same as the lead terminal according to the embodiment. The electrode foil 106 and the terminal member 4 according to the comparative example are the same as the electrode foil 6 and the terminal member 4 according to the example except for the reinforcing portions 26-1 and 26-2.

[0054] The electrode foil 6 and the terminal member 4 according to the example were created based on the manufacturing process described above in the embodiment. The electrode foil 106 and the terminal member 4 according to the comparative example were created based on the manufacturing process described above in the embodiment except for the process of forming the reinforcing portions 26-1 and 26-2. For the connection of the terminal member 4, the stitch connection method was used.

[0055] A cross-sectional view of the electrode foil 6 along line II-II (Figure 1) was taken using an electron microscope to confirm the thickness of the widened surface layer 8 and the base metal 10 in the reinforced sections 26-1 and 26-2 and their surrounding areas. Table 1 below shows the results of the thickness confirmation. The compression ratio is expressed by the following formula, where "thickness of the reinforced section" is the thickness at the center of the reinforced section (i.e., the previously described thickness Tc). Compression ratio = 1 - (thickness of the reinforced section / thickness of the surrounding area)

[0056] Compression of the expanded surface layer 8 on the terminal member 4 side was confirmed. In the reinforced sections 26-1 and 26-2, the expanded surface layer 8 on the terminal member 4 side was compressed, resulting in improved density and reduced porosity.

[0057] A cross-sectional view of electrode foil 106 in the comparative example was taken using an electron microscope to confirm the thickness of the expanded layer 8 and the base metal 10. In electrode foil 106 in the comparative example, no depression 30 was observed, and no compression of the expanded layer 8 was confirmed.

[0058] Foil cracks 100 were confirmed in the electrode foil 6 according to the embodiment and the electrode foil 106 according to the comparative example. The foil cracks 100 occur from the foil ends 22-1 and 22-2 when stress F generated during the connection process of the terminal member 4 is transmitted to the foil ends 22-1 and 22-2. The stress F is generated in the connection parts 14-1, 14-2, 14-3, etc., for example, by the hole punching process with the stitching needle 50, the folding process of the terminal piece 16 and foil piece 18, or the pressing process in cold pressure welding connection.

[0059] The criteria for determining foil cracks 100 were set as shown in Figure 5, for example, as follows: Evaluation A: No cracks. Evaluation B: There are cracks that do not reach the connection area 28. Evaluation C: There are cracks that reach the connection area 28.

[0060] The results of the inspection for foil cracks 100 in electrode foil 6 according to the example and electrode foil 106 according to the comparative example were as follows: Electrode foil 6 according to the example: Evaluation A…100% Evaluation B…0% Evaluation C…0% Electrode foil 106 according to the comparative example: Evaluation A…86% Evaluation B…6% Evaluation C…8%

[0061] From the results of the foil cracking 100 inspection, it was confirmed that the electrode foil 6 having reinforced portions 26-1 and 26-2 is superior to the electrode foil 106 without reinforced portions 26-1 and 26-2 in suppressing foil cracking 100. It was confirmed that foil cracking 100 is suppressed when the difference in thickness of the expanding layer 8 (the difference in thickness between the surrounding portion and the reinforced portion) is 2.8 μm (i.e., 46.9 μm - 44.1 μm). Furthermore, even if the difference in thickness of the expanding layer 8 is 0.2 μm (i.e., 45.4 μm - 45.2 μm), there is a possibility that foil cracking 100 will be suppressed. In other words, there is a possibility that the foil cracking 100 suppression effect can be obtained when the difference in thickness of the expanding layer 8 is 0.2 μm or more, and considering the compression of the base metal, it is preferable that the difference in thickness of the expanding layer 8 is, for example, 0.2 μm or more and 3.5 μm or less. If the difference in thickness of the widening layer 8 is replaced with a compression ratio, a compression ratio of 0.4% or more may provide an effect of suppressing foil cracking 100, and it is preferable that the compression ratio is, for example, 0.4% or more and 7.5% or less.

[0062] Furthermore, even if the reinforced portions 26-1 and 26-2 are formed on only one of the widened surface layers 8, the electrode foil 6 is considered to be superior to the electrode foil 106 in suppressing foil cracking 100.

[0063] According to this embodiment, for example, the following effects can be obtained.

[0064] (1) The electrode foil 6 can be partially reinforced, and unique parts can be formed on the electrode foil 6, such as those that can suppress the propagation of stress F.

[0065] (2) The reinforced portions 26-1 and 26-2 of the electrode foil 6 suppress the propagation of stress F to the foil edges 22-1 and 22-2, for example, and thus suppress cracking of the electrode foil 6.

[0066] (3) By suppressing cracking of the electrode foil 6, the strength and performance of the capacitor 2 are maintained, and the reliability of the capacitor 2 is improved.

[0067] (4) While suppressing cracking of the electrode foil 6, the surface area of ​​the electrode foil 6 can be increased, and the capacitance of the capacitor 2 can be increased.

[0068] (5) The reinforced sections 26-1 and 26-2 are separated from the connecting sections 14-1 and 14-2, respectively. The stress F generated during the formation of the connecting sections 14-1 and 14-2 does not directly act on any part of the reinforced sections 26-1 and 26-2. Because the stress F acts on the reinforced sections 26-1 and 26-2 in a somewhat leveled manner, the concentration of stress F on any part of the reinforced sections 26-1 and 26-2 can be suppressed.

[0069] (6) The reinforced portions 26-1 and 26-2 are separated from the foil ends 22-1 and 22-2, respectively. The stress generated during the formation of the reinforced portions 26-1 and 26-2 does not directly act on the foil ends 22-1 and 22-2, and the stress acting on the foil ends 22-1 and 22-2 is suppressed. [Modified form]

[0070] The features and variations of the embodiments described above are listed below.

[0071] (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 electrode foils 6 and a separator are stacked.

[0072] (2) The materials of the electrode 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 terminal members 4 led out from the capacitor element may be connected to the external terminals of the sealing member, or the capacitor element and sealing member may be inserted into the outer case and sealed with the sealing member.

[0073] (3) The reinforced portions 26-1 and 26-2 may be formed on the cathode foil, on the anode foil, or on both the cathode foil and the anode foil.

[0074] (4) In the above embodiment, the capacitor 2 includes three connection parts 14-1, 14-2, and 14-3. However, the number of connection parts 14-1, 14-2, and 14-3 is not limited to three, and may be one, two, or four or more.

[0075] (5) In the above embodiment, the reinforced portions 26-1 and 26-2 are thinner than the general portion 32 in the expanding layer 8 on the terminal member 4 side. However, in an expanding layer 8 other than the expanding layer 8 on the terminal member 4 side (the expanding layer 8 on the non-terminal member side), the reinforced portions 26-1 and 26-2 may be thinner than the general portion 32, and in multiple expanding layers 8, the reinforced portions 26-1 and 26-2 may be thinner than the general portion 32.

[0076] (6) In the above embodiment, the recess 30 in the electrode foil 6 forms a curved surface. However, the recess 30 may form a flat inclined surface to provide a height difference to the reinforced portions 26-1 and 26-2. For example, the cross-sectional shape of the recess 30 in the cross-section shown in Figure 2 may be an inverted trapezoid or a V-shape. A recess 30 having an inverted trapezoidal cross-section can be formed by making the cross-sectional shape of the tip of the second mold 44-1 and 44-2 a trapezoid, and a recess 30 having a V-shaped cross-section can be formed by making the cross-sectional shape of the tip triangular. Also, the cross-sectional shape of the recess 30 in the cross-section shown in Figure 2 may be a U-shape or the like, and a uniform or nearly uniform height may be provided to the reinforced portions 26-1 and 26-2. The shape of the recess 30, the difference in thickness of the expanding layer 8 (difference in thickness between the surrounding part and the reinforced part), and the compression ratio may be appropriately changed considering the thickness of the expanding layer 8 and the fragility of the electrode foil 6.

[0077] (7) In the above embodiment, the manufacturing process of the capacitor 2 includes the manufacturing process of the electrode foil 6 and the manufacturing process of the separator, and the electrode foil 6 and separator are manufactured before the reinforcement parts 26-1 and 26-2 are formed. However, the electrode foil 6 and separator may be prepared by purchase, for example.

[0078] (8) In the above embodiment, the first mold 42 is a fixed type, and the second molds 44-1 and 44-2 are movable types. Therefore, the reinforced part 26-1 can be adjusted by adjusting the second mold 44-1, and the reinforced part 26-2 can be adjusted by adjusting the second mold 44-2, and the reinforced parts 26-1 and 26-2 can be adjusted separately. However, the first mold 42 may also be a movable type, and the second molds 44-1 and 44-2 may be fixed types. Also, the arrangement of the first mold 42 and the second molds 44-1 and 44-2 may be reversed.

[0079] (9) In the above embodiment, the terminal member 4 is connected to the electrode foil 6 by a stitch connection method. However, the terminal member 4 may also be connected to the electrode foil 6 by a connection method that includes a pressing process, such as a cold pressure welding connection method.

[0080] (10) In the above embodiment, the terminal piece 16 and the foil piece 18 are folded back while both the electrode foil 6 and the terminal member 4 are held in place by the holding means. However, the holding by the holding means may be released after the terminal piece 16 and the foil piece 18 have been formed while the electrode foil 6 and the terminal member 4 are held by the holding means, or the terminal piece 16 and the foil piece 18 may be folded back without being held by the holding means.

[0081] As described above, the most preferred embodiments of this disclosure have been explained. The technology of this disclosure is not limited to the above description. Various modifications and changes are possible for those skilled in the art based on the gist of the invention as described in the claims or disclosed in the specification. It goes without saying that such modifications and changes are within the scope of this disclosure.

[0082] The technology of this disclosure can be used in and is useful in capacitors that include electrode foils having a surface expansion layer.

[0083] 2 Capacitor 4 Terminal members 6, 106 Electrode foil 8 Expanding layer 10 Base metal 12 Tab 13 Lead wire 14-1, 14-2, 14-3 Connection part 16 Terminal piece 18 Foil piece 22-1, 22-2 Foil end 24-1, 24-2 Area 26-1, 26-2 Reinforcement part 28 Connection area 30 Recess 32 General part 42 First mold 44-1, 44-2 Second mold 46 Pressing part 50 Stitching needle 52 Molding mold 100 Foil crack

Claims

1. A capacitor comprising a terminal member and an electrode foil having an expanding layer, wherein the terminal member and the electrode foil are connected by a connection portion, and the expanding layer has a reinforced portion in the region between the connection portion and the foil edge of the electrode foil that is stronger than the rest of the expanding layer.

2. The capacitor according to claim 1, wherein the widened surface layer of the reinforced portion has a smaller void ratio or a higher density than the widened surface layer of the other portion.

3. The capacitor according to claim 1 or claim 2, wherein the reinforcement portion is arranged to have a length corresponding to at least the connection portion in the width direction of the terminal member.

4. The capacitor according to claim 1 or claim 2, wherein the electrode foil and the terminal member are connected by a cold pressure welding method or a stitch connection method.

5. The capacitor according to claim 1 or claim 2, wherein the widening layer of the reinforced portion is thinner than the widening layer of the other portion.

6. A method for manufacturing a capacitor, comprising: a step of laminating an electrode foil including an expanded layer and a terminal member; a step of forming a reinforced portion in the region of the electrode foil between the portion of the electrode foil intended to be connected to the terminal member and the foil edge of the electrode foil; and a step of connecting the terminal member to the electrode foil by a pressing process.

7. The method for manufacturing a capacitor according to claim 6, wherein the reinforced portion is formed by reducing the porosity of the widened surface layer or by increasing its density.

8. The method for manufacturing a capacitor according to claim 6 or claim 7, wherein the connection between the electrode foil and the terminal member is made by a cold pressure welding method or a stitch connection method.

9. The method for manufacturing a capacitor according to claim 7, wherein the void ratio of the expanded surface layer is reduced or the density is increased by pressing the electrode foil and the terminal member in the lamination direction of the electrode foil and the terminal member.

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