Electrolytic capacitor and its manufacturing method

Abstract

This method for producing an electrolytic capacitor comprises a first connection step, a second connection step, a first insertion step, an accommodation step, and a sealing step. In the first connection step, a foil-shaped first internal lead is connected to a first electrode foil. In the second connection step, after the first connection step, a rod-shaped first external lead is connected to the first internal lead, and a first electrode is obtained. In the first insertion step, after the second connection step, the first external lead is inserted into an insertion opening in a sealing plate. In the accommodation step, after the first insertion step, the first electrode is accommodated in a container. In the sealing step, after the accommodation step, the opening of the container is closed using the sealing plate.

Description

[Technical Field]

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

[0002] An electrolytic capacitor typically comprises a capacitor element, leads connected to the capacitor element, a container that houses these components, and a sealing plate that closes the opening of the container. The leads are routed to the outside through the sealing plate. Patent Document 1 teaches connecting multiple leads to each of the anode foil and the cathode foil. Patent Document 2 teaches a method of routing the electrodes to the outside by placing conductive rivets on the sealing plate and connecting multiple leads to the conductive rivets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-503668 [Patent Document 2] Japanese Patent Application Publication No. 10-229032 Summary of the Invention

[0004] A manufacturing method for an electrolytic capacitor according to a first aspect of the present disclosure is a manufacturing method for an electrolytic capacitor having a first electrode and a second electrode, and includes a first connecting step, a second connecting step, a first inserting step, an accommodating step, and a sealing step. In the first connecting step, a foil-shaped first internal lead is connected to a first electrode foil. In the second connecting step, after the first connecting step, a rod-shaped first external lead is connected to the first internal lead to obtain a first electrode. In the first inserting step, after the second connecting step, the first external lead is inserted into an insertion opening of a sealing plate. In the accommodating step, after the first inserting step, the first electrode and the second electrode are accommodated in a container. In the sealing step, after the accommodating step, the opening of the container is closed with the sealing plate.

[0005] An electrolytic capacitor according to a second aspect of the present disclosure includes a first electrode including a first electrode foil, a foil-shaped first internal lead connected to the first electrode foil, and a rod-shaped first external lead connected to the first internal lead, a second electrode, a container accommodating the first electrode and the second electrode, and a sealing plate closing an opening of the container. The first external lead is inserted through an insertion opening in the sealing plate and extends to the outside of the container. The length of a first drawn-out portion of the first internal lead, from an end face of the first electrode foil to a contact portion with the first external lead, is equal to or less than the maximum diameter of the container.

[0006] An electrolytic capacitor according to a third aspect of the present disclosure includes a first electrode including a first electrode foil, a foil-shaped first internal lead connected to the first electrode foil, and a rod-shaped first external lead connected to the first internal lead; a second electrode; a container that houses the first electrode and the second electrode; and a sealing plate that closes an opening of the container. The first external lead is inserted through an insertion opening in the sealing plate and extends to the outside of the container. The sealing plate includes a rubber member. The international rubber hardness of the rubber member is 99 or less.

[0007] According to the present disclosure, the ESR of an electrolytic capacitor can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a flowchart illustrating a manufacturing method according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view schematically showing the electrode foil after first and third connection steps according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a perspective view schematically illustrating an example of a laminate obtained by a lamination step according to an embodiment of the present disclosure. [Figure 4] FIG. 10 is a perspective view illustrating second and fourth connecting steps of a manufacturing method according to an embodiment of the present disclosure. [Figure 5] 10A and 10B are side views schematically showing the laminate and the external leads in second and fourth connecting steps according to an embodiment of the present disclosure. [Figure 6]FIG. 6 is a side view illustrating the operation following FIG. 5. [Figure 7] FIG. 2 is a side view schematically showing a laminated body after first and second insertion steps according to an embodiment of the present disclosure. [Figure 8] FIG. 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor obtained by a manufacturing method according to an embodiment of the present disclosure. [Figure 9A] FIG. 1 is a cross-sectional view schematically illustrating an example of a sealing plate according to an embodiment of the present disclosure. [Figure 9B] FIG. 10 is a cross-sectional view schematically illustrating another example of a sealing plate according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] The methods of Patent Documents 1 and 2 cannot sufficiently reduce the ESR of the electrolytic capacitor.

[0010] Foil leads lack rigidity. Therefore, foil internal leads are usually connected to rigid and conductive external terminals. The electrodes are drawn to the outside through these external terminals. As shown in Patent Document 2, these external terminals are usually attached to a sealing plate. The foil leads are joined to the external terminals attached to the sealing plate by crimping or welding. At this time, the internal leads must be drawn out sufficiently from the electrode foil to prevent interference between the sealing plate and the jig of the joining device.

[0011] The inter-electrode resistance of capacitor elements is becoming smaller through the use of conductive polymers and the extension of multiple leads from one electrode. As a result, the length of the internal leads has a greater impact on the increase in the resistance of the capacitor element. For example, as mentioned above, the resistance of the capacitor element increases due to the internal leads being extended long to connect to the external terminals. As a result, the ESR of the electrolytic capacitor also increases.

[0012] In this embodiment, when an electrode is drawn to the outside through a foil-like internal lead, instead of using a member in which the sealing plate and external terminal are integrated, the lead and external terminal are connected and then the external terminal is inserted into the sealing plate. This eliminates the need to draw out a long internal lead to prevent interference between the sealing plate and a jig or the like of a bonding device, and makes it possible to suppress an increase in resistance due to the internal lead.

[0013] [Manufacturing method] The method for manufacturing an electrolytic capacitor according to this embodiment includes a first connecting step, a second connecting step, a first inserting step, a housing step, and a sealing step. In the first connecting step, a foil-shaped first internal lead is connected to a first electrode foil. In the second connecting step, after the first connecting step, a rod-shaped first external lead is connected to the first internal lead to obtain a first electrode. In the first inserting step, after the second connecting step, the first external lead is inserted into an insertion opening of a sealing plate. In the housing step, after the first inserting step, the first electrode and the second electrode are housed in a container. In the sealing step, after the housing step, the opening of the container is closed with a sealing plate.

[0014] When a foil-shaped internal lead is connected to the second electrode foil, the second electrode may be fabricated in the same manner as the first electrode. That is, the manufacturing method according to this embodiment may include a third connecting step of connecting a foil-shaped second internal lead to the second electrode foil, a fourth connecting step of connecting a rod-shaped second external lead to the second internal lead to obtain a second electrode after the third connecting step, and a second inserting step of inserting the second external lead into another insertion hole in the sealing plate after the fourth connecting step. This facilitates further reduction of the ESR of the electrolytic capacitor.

[0015] Hereinafter, this embodiment will be specifically described using an example in which the first electrode and the second electrode are fabricated by the same method and are stacked together. However, this embodiment is not limited to this. Figure 1 is a flowchart showing a manufacturing method according to this embodiment.

[0016] (1) First and third connection steps (S1) A foil-shaped first internal lead is connected to the first electrode foil. It is preferable that multiple first internal leads are connected to the first electrode foil. This is because the distance that electric charges travel is shortened, thereby reducing electrical resistance. The connection method is not particularly limited, and examples include welding methods such as laser welding and resistance welding.

[0017] Similarly, a foil-shaped second internal lead is connected to the second electrode foil. From the same viewpoint, it is preferable that a plurality of second internal leads are connected to the second electrode foil.

[0018] The connection positions of the first and second internal leads (hereinafter sometimes referred to collectively as internal leads) are not particularly limited and may be set appropriately taking into consideration the shapes of the first and second electrode foils (hereinafter sometimes referred to collectively as electrode foils) and the electrolytic capacitor, etc. When the electrode foil is wound, the internal leads are connected so that the longitudinal direction of the internal leads is aligned with the winding axis direction.

[0019] The size of the internal lead is not particularly limited. The longitudinal length of the internal lead may be set appropriately taking into consideration the size of the electrode foil, the size of the container, the size of the separator, etc. According to this embodiment, it is not necessary to make the longitudinal length of the internal lead excessively long.

[0020] (2) Lamination process (S2) After the first and third connecting steps, the first electrode foil and the second electrode foil are laminated together. The first electrode foil and the second electrode foil are laminated, for example, via a separator. The laminate may be further wound. In this case, the laminate is wound so that the internal lead extends along the winding axis. The laminating step is performed before the sealing step. In terms of simplifying the manufacturing process, the laminating step may be performed before the second and fourth connecting steps.

[0021] (3) Second and fourth connection steps (S3) A rod-shaped first external lead is connected to the first internal lead, and a rod-shaped second external lead is connected to the second internal lead, thereby obtaining a first electrode and a second electrode.

[0022] When multiple internal leads are connected to an electrode foil, it is preferable that the multiple internal leads connected to electrode foils of the same polarity are connected together to one first external lead or one second external lead (hereinafter sometimes collectively referred to as external leads).

[0023] There are no particular limitations on the method of connecting the internal lead and the external lead. At this time, the sealing plate has not yet been attached to the external lead, so there is no need to consider interference between the sealing plate and the joining jig. Therefore, there are no limitations on the connection method. The connection method may be welding or pressing. Since there is no need to consider interference between the sealing plate and the jig, there is no need to excessively extend the internal lead.

[0024] Among these, it is preferable to connect the internal lead and the external lead by pressing, since the equipment required is simple. In the case of pressing, for example, a through hole is formed in the internal lead, and the external lead is inserted through this through hole. At this time, the internal lead extends in a first direction (e.g., the winding axis direction), and the external lead extends in a second direction intersecting the first direction. Then, both main surfaces of the internal lead are pressed to crush one end of the external lead. The crushed portion of the external lead acts as a stopper, preventing the external lead from coming out of the through hole of the internal lead. In this way, the external lead is locked to the internal lead, and the two are electrically connected.

[0025] The external lead includes, for example, a lead body portion, a first portion that closes at least a portion of the insertion opening in the sealing plate, and a second portion that is closer to the connection portion with the internal lead than the first portion and has a larger diameter than the insertion opening. The second portion makes it easier to position the external lead relative to the sealing plate and makes it easier to prevent the external lead from coming off the sealing plate. The materials of the lead body portion, the first portion, and the second portion may be the same or different.

[0026] (4) First and second insertion process (S4) The external lead connected to the internal lead is inserted through the insertion opening of the sealing plate. This integrates the laminate and the sealing plate. If the sealing plate includes a rubber member, the first portion of the external lead may be press-fitted into the rubber member. This further facilitates preventing the external lead from coming loose.

[0027] When an internal lead extending in a first direction and an external lead extending in a second direction are connected as described above, the internal lead is bent so that the connection portion of the internal lead with the external lead is aligned along the second direction, and the external lead is positioned so that the extension direction of the external lead is aligned along the first direction. Then, the external lead is inserted into the sealing plate.

[0028] (5) Conductive polymer adhesion process (S5) Before the sealing process, a conductive polymer may be attached to the electrode foil as needed. The conductive polymer reduces the inter-electrode resistance of the capacitor element. According to this embodiment, the drawn-out portion of the internal lead can be shortened, which makes it easier for the conductive polymer to exert its effect of reducing the inter-electrode resistance.

[0029] The step of adhering the conductive polymer may be carried out at any time before the sealing step, but from the viewpoint of ease of handling, the step of adhering the conductive polymer is preferably carried out on the laminate integrated with the sealing plate after the first and second insertion steps.

[0030] The conductive polymer can be attached to the electrode foil by chemical polymerization and / or electrolytic polymerization of raw material monomers in the presence of the electrode foil. The conductive polymer may also be attached to the electrode foil by impregnating the electrode foil with a conductive polymer dispersion or solution containing the conductive polymer and a dispersion medium.

[0031] (6) Accommodation process (S6) After the first and second insertion steps, the laminate integrated with the sealing plate is housed in a container so that the external leads are led out from the opening of the container and the sealing plate can close the opening of the container.

[0032] (7) Liquid component impregnation step (S7) Before the sealing step, the laminate may be impregnated with a liquid component as needed. The impregnation step is performed, for example, after the accommodation step. The liquid component facilitates improving the self-repairing performance of the dielectric layer. Furthermore, since the liquid component essentially functions as a cathode material, it is expected to have the effect of increasing the electrostatic capacitance. The impregnation method is not particularly limited.

[0033] (8) Sealing process (S8) The resulting laminate is sealed with a container and a sealing plate, completing the electrolytic capacitor. After that, an aging treatment may be performed while applying a rated voltage.

[0034] When the sealing plate includes a rubber member, the sealing plate may be placed on the open end of the container, and the open end of the container may be bent inward. The sealing plate including the rubber member may be crimped by the open end without being damaged. This fixes the sealing plate to the container and seals the container. Furthermore, the container may be recessed inward to compress the rubber member. For example, an annular groove may be formed in the portion of the container facing the rubber member. This makes it easier to prevent the sealing plate from coming off even when the rubber member is reduced in diameter and the internal pressure increases.

[0035] The manufacturing method according to this embodiment will be specifically described below with reference to the drawings, taking as an example a case in which first and second electrode foils are stacked and wound, although this embodiment is not limited thereto.

[0036] FIG. 2 is a plan view schematically illustrating the electrode foil after the first and third connection steps according to this embodiment. For convenience, the first electrode foil, the second electrode foil, and the first and second lead portions (described later) are shown hatched in FIG. 2. For convenience, the first electrode foil, the second electrode foil, and the separator are shown shifted in position in FIG. 2. The first electrode foil and the second electrode foil are stacked so that most of them overlap. The separator is disposed between the first electrode foil and the second electrode foil to prevent them from contacting each other.

[0037] A plurality of foil-shaped first internal leads 15A are connected to the first electrode foil 11A. A plurality of foil-shaped second internal leads 15B are connected to the second electrode foil 11B. A through-hole 15a is formed at one end of each internal lead. Each internal lead is connected so that its longitudinal direction is along the winding axis direction of the electrode foil (direction indicated by A in the figure). The internal leads are preferably connected so that, when the laminate is wound, multiple internal leads connected to electrode foils of the same polarity are positioned close to each other. The internal leads are preferably connected so that, when the laminate is wound, the first internal lead 15A and the second internal lead 15B are positioned symmetrically with respect to the center of the wound body 10.

[0038] Thereafter, first electrode foil 11A, second electrode foil 11B and separator 13 are layered and wound. Separator 13 is also placed on the outermost periphery of the wound body, and the end of the winding is secured with stop tape 14.

[0039] Fig. 3 is a perspective view showing a typical example of a laminate (wound body) obtained by the lamination process according to this embodiment. For convenience, separators are omitted from Fig. 3. First and second internal leads 15A and 15B extend along the winding axis direction of wound body 10 (direction indicated by A in the figure).

[0040] 4 is a perspective view illustrating the second and fourth connecting steps of the manufacturing method according to this embodiment. Fig. 4 shows how the first outer lead is connected to the first inner lead. The second outer lead is connected to the second inner lead in a similar manner.

[0041] The first external lead 17A has a lead body portion 171, a first portion 172, and a second portion 173. The first portion 172 is a portion that is engaged with the sealing plate and blocks at least a part of the insertion opening in the sealing plate. The second portion 173 is located closer to the connection portion with the first internal lead 15A than the first portion 172, and has a diameter larger than the through-hole 15a formed in the first internal lead 15A and the insertion opening in the sealing plate.

[0042] The lead body portion 171 is inserted into the through-hole 15a of the first internal lead 15A. At this time, the lead body portion 171 is inserted into the through-holes 15a of the multiple first internal leads 15A at once. A washer 18 is placed on the opposite side of the second portion 173, and the lead body portion 171 is Washer 18 In this way, the first internal lead 15A is sandwiched between the second portion 173 and the washer 18. The washer 18 is used as needed. If the washer 18 is not used, the lead body portion 171 is sufficiently crushed in the next pressing step.

[0043] FIG. 5 is a side view schematically illustrating the wound body and external leads in the second and fourth connecting steps according to this embodiment. A first external lead 17A is inserted through the through holes of the first internal leads 15A, and a second external lead 17B is inserted through the through holes of the second internal leads 15B. At this time, each internal lead extends in the winding axis direction (first direction: direction indicated by A in the figure), and each external lead extends in a second direction (direction indicated by B in the figure) that intersects with the first internal lead. In this state, each internal lead is pressed from both main surfaces to crush the end of each external lead on the washer 18 side. This causes the first external lead 17A to be locked and connected to the first internal leads 15A. Similarly, the second external lead 17B is locked and connected to the second internal leads 15B.

[0044] Figure 6 is a side view illustrating the process following Figure 5. After the internal lead and external lead are connected, the external lead extending in the second direction (the direction indicated by B in the figure) is rotated so that its extension direction is aligned with the first direction (the direction indicated by A in the figure). At this time, internal leads 15A and 15B are bent, and the vicinity of the contact portion between the internal lead and external lead is positioned along the second direction.

[0045] 7 is a side view schematically showing the wound body after the first and second insertion steps according to this embodiment. The sealing plate 20 is brought close to the external leads extending in a first direction (the direction indicated by A in the figure) along the first direction. Then, the external leads 17A and 17B are inserted into insertion openings (not shown) provided in the sealing plate 20. At this time, each external lead is locked to the sealing plate 20 by the first portion 172. Each external lead is positioned by the second portion 173. In this way, the wound body 10 and the sealing plate 20 are integrated.

[0046] Subsequently, if necessary, a conductive polymer may be attached to the electrode foil.

[0047] 8 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor obtained by the manufacturing method according to this embodiment, in which the first lead portion and the second lead portion are also shown hatched for convenience.

[0048] The wound body 10 integrated with the sealing plate 20 is housed in a container 60. The internal leads are bent, but the drawn-out portions 15Aa and 15Ba are short and are equal to or smaller than the maximum diameter of the container 60 (the diameter indicated by R in the drawing).

[0049] Thereafter, if necessary, the wound body may be impregnated with a liquid component.

[0050] Finally, the wound body 10 is sealed with the container 60 and the sealing plate 20. This completes the electrolytic capacitor 100. Thereafter, an aging treatment may be performed while applying the rated voltage.

[0051] When sealing, the sealing plate 20 is placed on the opening edge of the container 60, and the opening edge of the container 60 is bent inward. This causes the opening edge to be crimped to the sealing plate 20. Because the sealing plate 20 includes a rubber member, it is fixed to the opening edge without being damaged. Furthermore, the vicinity of the opening of the container 60 is recessed inward so as to reduce the diameter of the rubber member of the sealing plate 20. This makes it easier to prevent the sealing plate 20 from coming loose.

[0052] Although the method for manufacturing an electrolytic capacitor according to this embodiment has been described above using a wound electrolytic capacitor as an example, the configuration of the electrolytic capacitor is not limited to this. This embodiment can be applied to, for example, a stacked electrolytic capacitor including a capacitor element including an anode foil and a cathode extraction layer covering the anode foil.

[0053] [Electrolytic capacitor] The electrolytic capacitor according to this embodiment includes a first electrode including a first electrode foil, a foil-shaped first internal lead connected to the first electrode foil, and a rod-shaped first external lead connected to the first internal lead, a second electrode, a container that houses the first electrode and the second electrode, and a sealing plate that closes an opening of the container. The first external lead is inserted through an insertion opening in the sealing plate and led out of the container.

[0054] The length of the first drawn-out portion from the end face of the first electrode foil of the first internal lead to the contact point with the first external lead is equal to or less than the maximum diameter of the container. Because the internal lead is short, an increase in resistance due to the lead is suppressed. Such an electrolytic capacitor is manufactured by the manufacturing method of an electrolytic capacitor according to the present embodiment described above.

[0055] The second electrode preferably has a similar configuration to the first electrode, since this facilitates further reduction in ESR. That is, the second electrode includes a second electrode foil, a foil-shaped second internal lead connected to the second electrode foil, and a rod-shaped second external lead connected to the second internal lead, and the length of the second lead-out portion from the end face of the second electrode foil of the second internal lead to the contact portion with the second external lead is preferably equal to or less than the maximum diameter of the container.

[0056] The first and second lead-out portions (hereinafter sometimes collectively referred to as the lead-out portions) are the portions of the internal lead that protrude from the electrode foil to which the internal lead is connected and that are not in contact with the external lead (see 15Aa and 15Ba in Figures 2 and 8). The length L of the lead-out portion is measured by straightening the internal lead. The length L of the lead-out portion is the length of the line segment connecting the midpoints of the two longitudinal ends of the lead-out portion.

[0057] The maximum diameter R of the container is, for example, the maximum diameter of the bottom surface inside the container (see FIG. 8).

[0058] The length of the drawn-out portion is preferably 50% or less of the maximum diameter R of the container.

[0059] It is preferable that multiple internal leads are connected to one electrode foil, which shortens the distance that charges must travel and further reduces electrical resistance. In this case, it is preferable that internal leads with the same polarity are connected together to one external lead.

[0060] The internal lead and the external lead may be connected by press working as described above. For example, a through hole may be formed in the internal lead, and the external lead may be inserted through this through hole with one end thereof crushed. In this way, the external lead may be locked to the internal lead and electrically connected.

[0061] As described above, the external lead may include a lead body portion, a first portion that blocks at least a portion of the insertion opening in the sealing plate, and a second portion that is closer to the connection portion with the first internal lead than the first portion and has a larger diameter than the insertion opening. This makes it easier to position the external lead relative to the sealing plate and to prevent the external lead from coming off the sealing plate. Furthermore, if the sealing plate includes a rubber member, the first portion of the external lead can be press-fitted. This further reduces the likelihood of the external lead coming off. The materials of the lead body portion, the first portion, and the second portion may be the same or different.

[0062] The lead-out portion of the internal lead may have a bent portion that bends from a direction toward the opening of the container to a direction that intersects with the opening. Because the lead-out portion is short, an increase in resistance is suppressed even if the lead-out portion has a bent portion.

[0063] The first electrode and the second electrode are laminated, for example, with a separator interposed therebetween. After being laminated, the first electrode and the second electrode may be further wound. A conductive polymer may be attached to the first electrode and / or the second electrode. The first electrode and / or the second electrode may be impregnated with a liquid component.

[0064] The sealing plate may include a rubber material. The rubber material has elasticity, making it easy to secure the sealing plate to the container without damage and to seal the container. With the sealing plate placed on the open end of the container, the open end may be bent inward. This causes the open end to be crimped to the sealing plate, thereby securing the sealing plate. Furthermore, the container may be recessed inward to reduce the diameter of the rubber material. This makes it easier to prevent the sealing plate from coming loose even when the internal pressure increases.

[0065] The components of the electrolytic capacitor according to this embodiment will be specifically described below, although this embodiment is not limited thereto.

[0066] (1st electrode foil) The first electrode foil functions as, for example, an anode. In this case, the first electrode foil is a metal foil containing at least one valve metal such as titanium, tantalum, aluminum, or niobium. The first electrode foil may contain the valve metal in the form of an alloy containing the valve metal or a compound containing the valve metal. The thickness of the first electrode foil is not particularly limited and is, for example, 15 μm or more and 300 μm or less. The thickness is the average value at any five points (the same applies hereinafter).

[0067] The surface of the first electrode foil may be roughened by etching or the like. A dielectric layer may be formed on the surface of the first electrode foil. The dielectric layer may be formed, for example, by chemically treating the first electrode foil. In this case, the dielectric layer may contain an oxide of a valve metal. However, the dielectric layer is not limited to this, and may be any layer that functions as a dielectric.

[0068] (Second electrode foil) The second electrode foil functions as, for example, a cathode. The second electrode foil may be a metal foil. The type of metal is not particularly limited, and like the first electrode foil, it may be a valve metal or an alloy containing a valve metal, or it may be a metal other than a valve metal such as iron (Fe) or copper (Cu). The thickness of the second electrode foil is not particularly limited, and is, for example, 15 μm or more and 300 μm or less.

[0069] The surface of the second electrode foil may be roughened or subjected to a chemical conversion treatment as necessary, and may also be provided with an inorganic layer containing carbon, nickel, titanium, or oxides or nitrides thereof.

[0070] (1st and 2nd internal leads) The internal lead is in the form of a foil. Specifically, the internal lead is a conductive member having a thickness of 15 μm to 300 μm. The material thereof is not particularly limited as long as it is conductive, and examples thereof include aluminum, titanium, nickel, copper, iron, tantalum, niobium, and alloys thereof.

[0071] (separator) The separator is not particularly limited as long as it is porous. Examples of the separator include a cellulose fiber nonwoven fabric, a glass fiber nonwoven fabric, and a polyolefin microporous membrane, woven fabric, or nonwoven fabric. The thickness of the separator is not particularly limited, and is, for example, 10 μm or more and 500 μm or less. When a conductive polymer having a sufficient thickness is disposed between the first electrode foil and the second electrode foil, the separator may be omitted.

[0072] (1st and 2nd external leads) The external lead is a conductive member used to extend the electrode to the outside. The external lead is rod-shaped and has enough rigidity to be inserted into the sealing plate. The material for the external lead is not particularly limited as long as it is conductive, and examples thereof include aluminum, titanium, nickel, copper, iron, tantalum, niobium, and alloys thereof.

[0073] (Sealing board) The sealing plate closes the opening of the container.

[0074] The sealing plate may be made of any insulating material. In particular, the sealing plate preferably includes a rubber material. The rubber material has elasticity. Therefore, when the external leads are inserted into the sealing plate, damage to both the external leads and the sealing plate is more easily suppressed. Furthermore, even when the internal pressure increases, the rubber material deforms, suppressing cracking of the sealing plate and suppressing damage to the internal leads.

[0075] In particular, the International Rubber Hardness Degrees (IRHD) of the rubber member is preferably 99 or less, more preferably 95 or less. The IRHD of the rubber member is preferably 70 or more, more preferably 80 or more. Examples of elastic polymers that constitute such rubber members include silicone rubber, fluorine-containing rubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber (such as Hypalon rubber), butyl rubber, isoprene rubber, and isobutyl-isoprene rubber. Of these, fluorine-containing rubber is preferred from the viewpoint of heat resistance. One type of elastic polymer may be used alone, or two or more types may be used in combination.

[0076] A hindered phenol compound may be added to the rubber component. The hindered phenol compound has a first hindered group and a second hindered group at two substitution positions (first substitution position and second substitution position) adjacent to the phenolic hydroxy group in the phenol skeleton, respectively. These hindered groups each contain at least one tertiary carbon, and one of the tertiary carbons in each hindered group is bonded to the substitution position, resulting in a quaternary carbon in the hindered phenol compound. Specifically, one of the tertiary carbons in the first and second hindered groups is directly bonded to the first substitution position and the second substitution position, respectively. Hindered phenol compounds with this structure have higher heat resistance, are less susceptible to decomposition even at high temperatures (e.g., 155°C), and experience almost no change in mass compared to compounds in which a hydrogen atom or a primary or secondary carbon of a substituent is bonded to the first substitution position or the second substitution position. Therefore, even in a high-temperature environment, the hindered phenol compound remains in the rubber member and exhibits a radical scavenging function, thereby making it possible to suppress thermal degradation of the rubber member.

[0077] Examples of hindered phenol compounds include pentaerythritol tetrakis[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate], 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate, 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene, 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 2,2'-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. One type of hindered phenol compound may be used alone, or two or more types may be used in combination.

[0078] The amount of the hindered phenol compound added to the rubber member is preferably 0.5 to 6.0 parts by mass, more preferably 0.5 to 4.0 parts by mass, per 100 parts by mass of the elastic polymer.

[0079] The rubber member may further contain a filler. Examples of the filler include talc, mica, silica, kaolin, titania, and / or alumina. The amount of the filler contained in the rubber member is, for example, preferably 10 parts by mass or more, and more preferably 50 parts by mass or more, per 100 parts by mass of the elastic polymer.

[0080] Furthermore, the rubber member may contain additives (reinforcing agents (carbon black, etc.), crosslinking agents, crosslinking accelerators, dispersing aids, modifiers, vulcanizing agents, vulcanization aids, antioxidants, and / or processing aids, etc.) as needed.

[0081] The sealing plate may include a resin layer in addition to the rubber member. The IRHD of the thermosetting resin is usually 100 or more. The resin layer is preferably arranged so as not to inhibit the elasticity of the rubber member. For example, the resin layer may be formed on the outer surface of the sealing plate. The resin layer preferably occupies 10% by volume or less of the entire sealing plate. It is particularly preferable that the entire sealing plate be made of a rubber member.

[0082] The sealing plate has one or more insertion openings for inserting the external leads. The positions of the insertion openings are set appropriately depending on the positions of the external leads. The number of insertion openings is set appropriately depending on the number of external leads.

[0083] A recess for accommodating at least a part of the second portion of the external lead may be formed on the main surface of the sealing plate facing the bottom surface of the container. This makes it easier to position the external lead. In addition, it makes it easier to ensure a distance between the external lead and the electrode foil of the opposite polarity, making it easier to prevent short circuits between them.

[0084] The sealing plate may have a protrusion protruding toward the bottom surface on its main surface facing the bottom surface of the container. This protrusion helps ensure a distance between the external lead and the electrode foil of opposite polarity, making it easier to prevent short circuits between them. One protrusion or two or more protrusions may be provided.

[0085] To prevent short-circuiting between the external lead and the electrode foil having the opposite polarity, the amount of separator that protrudes from the electrode foil and is disposed in the space between the wound body and the sealing plate may be increased.

[0086] 9A and 9B are side views schematically illustrating an example of a sealing plate according to this embodiment. As shown in FIG. 9A, a recess 20a that accommodates at least a part of the second portion 173 of the external lead may be formed on the main surface of the sealing plate 20 facing the bottom surface of the container. This makes it even easier to position the external lead. Furthermore, it becomes easier to ensure a distance between the external lead and the electrode foil of the opposite polarity, making it easier to prevent short circuits between them.

[0087] 9B, a protrusion 21 that protrudes toward the bottom surface of the container may be provided on the main surface of sealing plate 20 that faces the bottom surface of the container. This protrusion makes it easier to ensure a distance between the external lead and the electrode foil of opposite polarity, making it easier to prevent a short circuit between them.

[0088] (container) The container has an opening. The container has, for example, a cylindrical portion and a bottom surface that closes one end of the cylindrical portion. The other end (open end) of the cylindrical portion is closed with a sealing plate. The outer shape of the container is, for example, cylindrical or approximately cylindrical.

[0089] The material of the container is not particularly limited, and examples thereof include metals such as aluminum, aluminum alloy, stainless steel, copper, iron, brass, etc. A surface layer (e.g., an oxide layer, a resin layer, etc.) having a desired function may be formed on the outer surface of the container.

[0090] (conductive polymer) Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polythiophene vinylene, etc. These may be used alone or in combination of two or more kinds, or may be copolymers of two or more kinds of monomers.

[0091] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene).

[0092] The conductive polymer is dispersed in a dispersion medium, for example, in the form of particles. The average particle size of the conductive polymer particles is not particularly limited and can be adjusted appropriately depending on the polymerization conditions, dispersion conditions, etc. For example, the average particle size of the conductive polymer particles may be 0.01 μm or more and 0.5 μm or less. Here, the average particle size is the median diameter in the volume particle size distribution measured using a particle size analyzer by dynamic light scattering.

[0093] The weight average molecular weight of the conductive polymer may be, for example, 1,000 or more and 200,000 or less, or 50,000 or more and 150,000 or less.

[0094] The conductive polymer may be dispersed in a dispersion medium together with a dopant.

[0095] The dopant may be a monomolecular anion or a polymeric anion. Specific examples of monomolecular anions include paratoluenesulfonic acid and naphthalenesulfonic acid. Specific examples of polymeric anions include polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyacrylicsulfonic acid, polymethacrylicsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, and polyacrylic acid. These may be used alone or in combination of two or more. Furthermore, these may be polymers of a single monomer or copolymers of two or more monomers. Among these, polymeric anions derived from polystyrenesulfonic acid are preferred.

[0096] The dispersion medium is not particularly limited and may be water, a non-aqueous solvent, or a mixture thereof. The non-aqueous solvent is a general term for liquids other than water, and includes organic solvents and ionic liquids. Among these, the dispersion medium may be water from the viewpoint of ease of handling and dispersibility of the conductive polymer. Water may account for 50% by mass or more of the dispersion medium, 70% by mass or more, or 90% by mass or more. Examples of non-aqueous solvents used together with water include polar solvents (protic solvents and / or aprotic solvents).

[0097] A dispersion liquid containing a conductive polymer can be obtained, for example, by a method of dispersing conductive polymer particles in a dispersion medium, or by a method of polymerizing a precursor monomer of the conductive polymer in a dispersion medium to generate conductive polymer particles in the dispersion medium.

[0098] In the dispersion containing the conductive polymer, the content of the conductive polymer may be, for example, 0.5% by mass or more and less than 5% by mass. The viscosity of the conductive polymer dispersion measured at room temperature (20°C) using a vibration viscometer is preferably, for example, less than 100 mPa s.

[0099] (liquid component) The liquid component includes a solvent.

[0100] Examples of solvents include sulfone compounds, lactone compounds, carbonate compounds, polyhydric alcohols, etc. Examples of sulfone compounds include sulfolane, dimethyl sulfoxide, and diethyl sulfoxide. Examples of lactone compounds include γ-butyrolactone and γ-valerolactone. Examples of carbonate compounds include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC). Examples of polyhydric alcohols include glycol compounds such as ethylene glycol (EG), diethylene glycol, triethylene glycol, propylene glycol, and polyethylene glycol (PEG); glycerin, etc. These may be used alone or in combination.

[0101] In particular, the solvent may contain a compound having two or more hydroxy groups. Examples of such compounds include polyhydric alcohols. The content of the compound having two or more hydroxy groups may be 50% by mass or more, 60% by mass or more, or 70% by mass or more of the total solvent.

[0102] The liquid component may further contain an acid component. When a conductive polymer and a dopant are attached to the electrolytic capacitor, the acid component in the liquid component suppresses the dopant de-doping phenomenon and stabilizes the conductivity of the conductive polymer. Even if the dopant is de-doped from the conductive polymer, the acid component in the liquid component re-dops the sites left by the de-doping, making it easier to maintain a low ESR.

[0103] It is desirable that the acid component in the liquid component does not excessively increase the viscosity of the liquid component, but rather generates anions that dissociate easily in the liquid component and move easily in the solvent. Examples of such acid components include aliphatic sulfonic acids having 1 to 30 carbon atoms and aromatic sulfonic acids having 6 to 30 carbon atoms. Among aliphatic sulfonic acids, monovalent saturated aliphatic sulfonic acids (e.g., hexanesulfonic acid) are preferred. Among aromatic sulfonic acids, aromatic sulfonic acids having a hydroxy group or a carboxy group in addition to a sulfo group are preferred, specifically, oxyaromatic sulfonic acids (e.g., phenol-2-sulfonic acid) and sulfoaromatic carboxylic acids (e.g., p-sulfobenzoic acid, 3-sulfophthalic acid, 5-sulfosalicylic acid) are preferred.

[0104] Examples of other acid components include carboxylic acids. The carboxylic acid preferably includes an aromatic carboxylic acid (aromatic dicarboxylic acid) having two or more carboxyl groups. Examples of aromatic carboxylic acids include phthalic acid (ortho-isomer), isophthalic acid (meta-isomer), terephthalic acid (para-isomer), maleic acid, benzoic acid, salicylic acid, trimellitic acid, and pyromellitic acid. Among these, aromatic dicarboxylic acids such as phthalic acid (ortho-isomer) and maleic acid are more preferred. The carboxyl groups of aromatic dicarboxylic acids are stable and do not easily cause side reactions. Therefore, they exhibit the effect of stabilizing the conductive polymer over a long period of time, which is advantageous for extending the life of the electrolytic capacitor. The carboxylic acid may also be an aliphatic carboxylic acid such as adipic acid.

[0105] The acid component may contain a complex compound of an organic acid and an inorganic acid from the viewpoint of thermal stability. Examples of the complex compound of an organic acid and an inorganic acid include borodisalicylic acid, borodioxalic acid, and borodiglycolic acid, which have high heat resistance.

[0106] The acid component may include inorganic acids such as boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and phosphonic acid.

[0107] In order to enhance the effect of suppressing the undoping phenomenon, the concentration of the acid component may be 5% by mass or more and 50% by mass or less, or 15% by mass or more and 35% by mass or less.

[0108] The liquid component may contain a base component together with an acid component. The base component neutralizes at least a portion of the acid component. Therefore, corrosion of the electrode caused by the acid component can be suppressed while increasing the concentration of the acid component. From the viewpoint of effectively suppressing dedoping, it is preferable that the acid component is in excess of the base component in terms of equivalent ratio. For example, the equivalent ratio of the acid component to the base component may be 1 or more and 30 or less. The concentration of the base component contained in the liquid component may be 0.1 mass % or more and 20 mass % or less, or 3 mass % or more and 10 mass % or less.

[0109] The base component is not particularly limited. Examples of the base component include ammonia, primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and amidinium compounds. Examples of the amines include aliphatic amines, aromatic amines, and heterocyclic amines.

[0110] The pH of the liquid component is preferably 4 or less, more preferably 3.8 or less, and even more preferably 3.6 or less. By adjusting the pH of the liquid component to 4 or less, deterioration of the conductive polymer is further suppressed. The pH is preferably 2.0 or more.

[0111] (Variation) When the internal pressure of an electrolytic capacitor increases, outward stress is applied to the sealing plate. If the sealing plate is rigid, this stress can cause it to crack or other damage. When the sealing plate cracks, the internal leads joined to the external terminals may be pulled outward and damaged. Foil-like internal leads are particularly susceptible to damage.

[0112] An electrolytic capacitor according to a modification of this embodiment includes a first electrode including a first electrode foil, a foil-shaped first internal lead connected to the first electrode foil, and a rod-shaped first external lead connected to the first internal lead, a second electrode, a container accommodating the first and second electrodes, and a sealing plate closing an opening of the container. The first external lead is inserted through an insertion opening in the sealing plate and led out of the container.

[0113] In a modification of this embodiment, a sealing plate including a rubber member is used. The rubber member has an International Rubber Hardness Degrees (IRHD) of 99 or less. Such a rubber member has appropriate elasticity. Therefore, the rubber member deforms as the internal pressure increases, relieving the above-mentioned stress. This prevents damage to the sealing plate and also to the internal leads. Furthermore, when the external leads are inserted into the sealing plate, damage to both the external leads and the sealing plate is more likely to be prevented.

[0114] The electrolytic capacitor according to this modification has the same configuration as the above-described embodiment, except that the rubber member included in the sealing plate has an international rubber hardness of 99 or less. The electrolytic capacitor according to this modification can be manufactured using the same manufacturing method as the electrolytic capacitor described in the above-described embodiment. The following mainly describes the configuration of the sealing plate of the electrolytic capacitor according to this modification.

[0115] (Sealing board) The IRHD of the rubber member is 99 or less. The IRHD of the rubber member is preferably 95 or less. The IRHD of the rubber member is preferably 70 or more, and more preferably 80 or more. The materials described in the above embodiments can be used as the elastic polymer that constitutes such a rubber member.

[0116] The sealing plate is placed on the open end of the container. At this time, the open end may be bent inward. The sealing plate, including the rubber member, is crimped by the open end without being damaged. This fixes the sealing plate to the container and seals the container. Furthermore, the container may be recessed inward so as to compress the rubber member. For example, an annular groove may be formed in a portion of the container facing the rubber member. This makes it easier to prevent the sealing plate from coming off even when the rubber member is reduced in diameter and the internal pressure increases.

[0117] A sealing plate including a rubber member is particularly useful when an electrolytic capacitor is produced by connecting a foil-shaped internal lead and a rod-shaped external lead and then inserting the external lead into the sealing plate. When the external lead is inserted into the sealing plate, the internal lead is already connected to the external lead. As described above, the foil-shaped internal lead is easily damaged. Therefore, when inserting the external lead into the sealing plate, it is necessary to avoid applying a load to the internal lead. If the sealing plate is elastic, it becomes easy to insert the external lead into the sealing plate by deforming the sealing plate while minimizing the load on the external lead and, in turn, the internal lead.

[0118] The method of connecting a foil-shaped internal lead and an external lead and then inserting the external lead into the sealing plate is preferable because it can suppress the ESR of the electrolytic capacitor. When using a component in which the sealing plate and external lead are integrated and the internal lead is joined to this, as in Patent Document 2, the internal lead needs to be sufficiently extended from the electrode foil to prevent interference between the sealing plate and the jig of the joining device. An extended internal lead increases the resistance of the capacitor element, resulting in an increase in the ESR of the electrolytic capacitor. On the other hand, when connecting the internal lead and the external lead and then inserting the external lead into the sealing plate, it is not necessary to extend the internal lead long enough to prevent interference between the sealing plate and the jig of the joining device. This suppresses an increase in resistance due to the internal lead.

[0119] The length of the first drawn-out portion from the end surface of the first electrode foil of the first internal lead to the contact portion with the first external lead is, for example, equal to or less than the maximum diameter R of the container. The length of the first drawn-out portion is preferably equal to or less than 50% of the maximum diameter R of the container. As described above, suppressing damage to the sealing plate also suppresses the internal lead from being pulled outward. Therefore, even when the internal lead is short like this, damage to the internal lead is suppressed.

[0120] The second electrode preferably has a similar configuration to the first electrode, since this facilitates further reduction in ESR. That is, the second electrode preferably includes a second electrode foil, a foil-shaped second internal lead connected to the second electrode foil, and a rod-shaped second external lead connected to the second internal lead. In this case, the length of the second lead portion from the end face of the second electrode foil of the second internal lead to the contact portion with the second external lead can be set to be equal to or less than the maximum diameter R of the container. The length of the second lead portion is preferably equal to or less than 50% of the maximum diameter R of the container. [Explanation of symbols]

[0121] 100 electrolytic capacitors 10. Wound body 11A 1st electrode foil 11B 2nd electrode foil 13 Separator 14 Winding tape 15A First Internal Lead 15Aa 1st drawer part 15B Second internal lead 15Ba 2nd drawer part 15a through hole 17A First External Lead 17B Second external lead 171 Lead body 172 Part 1 173 Part 2 18 Washer 20 Sealing plate 20a Recess 21 Protrusion 60 containers

Claims

1. A method for manufacturing an electrolytic capacitor having a first electrode and a second electrode, comprising: a first connecting step of connecting a plurality of first foil-shaped internal leads to the first electrode foil; a second connecting step of connecting the plurality of first internal leads together to a rod-shaped first external lead to obtain the first electrode after the first connecting step; a first insertion step of inserting the first external lead into an insertion opening of a sealing plate after the second connecting step; a housing step of housing the first electrode and the second electrode in a container after the first insertion step; a sealing step of closing the opening of the container with the sealing plate after the containing step, the first inner lead has a through hole; In the second connection step, after the first external lead is inserted into the through hole, both main surfaces of the first internal lead are pressed to crush one end of the first external lead, thereby engaging the first external lead with the first internal lead.

2. In the second connecting step, the first internal lead extending in a first direction is connected to the first external lead extending in a second direction intersecting the first direction, 2. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the first insertion step, the first internal lead is bent so that a connection portion of the first internal lead with the first external lead is aligned along the second direction, and the first external lead is positioned so that an extension direction of the first external lead is aligned along the first direction, and then the first external lead is inserted into the sealing plate.

3. a third connecting step of connecting a foil-shaped second internal lead to the second electrode foil; 3. The method for manufacturing an electrolytic capacitor according to claim 1, further comprising a lamination step of laminating the first electrode foil and the second electrode foil after the first connecting step and the third connecting step and before the second connecting step.

4. a fourth connecting step of connecting a rod-shaped second external lead to the second internal lead after the third connecting step to obtain the second electrode; 4. The method for manufacturing an electrolytic capacitor according to claim 3, further comprising: a second insertion step of inserting the second outer lead into another insertion hole of the sealing plate after the fourth connecting step.

5. In the third connecting step, a plurality of second internal leads including the second internal lead are connected to the second electrode foil, 5. The method for manufacturing an electrolytic capacitor according to claim 4, wherein in the fourth connecting step, the plurality of second internal leads are collectively connected to the second external lead.

6. the sealing plate includes a rubber member, 6. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the sealing step, the sealing plate is placed at an open end of the container, the open end of the container is bent inward, and the container is recessed inward so as to compress the rubber member.

7. The method for manufacturing an electrolytic capacitor according to claim 1 , further comprising, before the sealing step, a step of adhering a conductive polymer to the first electrode foil.

8. The method for manufacturing an electrolytic capacitor according to claim 1 , further comprising, before the sealing step, a step of impregnating the first electrode foil with a liquid component.

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