JP7611537B2 - Electrolytic capacitors - Google Patents

Description

This disclosure relates to an electrolytic capacitor that includes a molded resin layer that covers a sealing member.

An electrolytic capacitor comprises a capacitor element including a pair of electrodes, an electrolyte interposed between the pair of electrodes, a case containing the capacitor element and the electrolyte and having an opening, a sealing member that seals the opening of the case, and a pair of leads that are electrically connected to the pair of electrodes and pass through the sealing member. Each lead comprises a tab portion, for example made mainly of aluminum, and a lead portion connected to one end of the tab portion. The tab portion is connected to the electrodes inside the case, and the lead portion is led out to the outside of the case.

The sealing material may deteriorate due to oxidation in a high-temperature environment, and deterioration of the sealing material reduces the sealing ability of the electrolytic capacitor. In addition, there is a tendency for electrolyte components to permeate the sealing material, evaporate, and gradually decrease. Therefore, in order to improve the airtightness inside the case, it has been proposed to cover the outer surface of the sealing material facing the open side of the case with a molded resin layer (Patent Document 1). The provision of the molded resin layer suppresses the evaporation of electrolyte components to the outside of the case.

Japanese Unexamined Patent Publication No. 60-245106

The electrolytic capacitor according to the first aspect of the present disclosure includes a capacitor element including a pair of electrodes, an electrolyte interposed between the pair of electrodes, a case that accommodates the capacitor element and the electrolyte, a sealing member, a pair of leads that penetrate the sealing member, and a molded resin layer. The case has an opening. The sealing member seals the opening of the case. The pair of leads are electrically connected to the pair of electrodes, respectively. The molded resin layer covers at least a portion of the outer surface of the sealing member facing the opening side. At least one of the pair of leads has a tab portion and an extension portion. The tab portion is connected to the electrode. The extension portion is connected to one end of the tab portion. One end of the tab portion protrudes from the outer surface of the sealing member.

According to the present disclosure, in an electrolytic capacitor having a molded resin layer that covers at least a portion of the outer surface of the sealing member facing the open side of the case, corrosion of the leads can be suppressed.

Also, an electrolytic capacitor according to a second aspect of the present disclosure includes a capacitor element including a pair of electrodes, an electrolyte interposed between the pair of electrodes, a case that accommodates the capacitor element and the electrolyte, a sealing member, a molded resin layer that covers the sealing member, and a pair of leads that penetrate the sealing member and the molded resin layer. The case has an opening. The sealing member seals the opening of the case. The pair of leads are electrically connected to the pair of electrodes, respectively. At least one of the pair of leads has an insulating region covered with an electrical insulating layer. The electrical insulating layer is provided between at least one of the pair of leads and at least one of the sealing member and the molded resin layer.

According to the present disclosure, it is possible to suppress corrosion of the leads of an electrolytic capacitor having a molded resin layer that covers a sealing material.

Furthermore, an electrolytic capacitor according to a third aspect of the present disclosure includes a capacitor element including a pair of electrodes, a case that houses the capacitor element, a sealing member, a molded resin layer that covers the sealing member, and a pair of leads that penetrate the sealing member and the molded resin layer. The case has an opening. The sealing member seals the opening of the case. The pair of leads are electrically connected to the pair of electrodes, respectively. A gap is provided between the sealing member and the molded resin layer.

According to the present disclosure, it is possible to suppress the deterioration of the sealing property of the electrolytic capacitor caused by the occurrence of cracks in the molded resin layer.

1 is a schematic cross-sectional view of an electrolytic capacitor according to a first embodiment of the present disclosure. FIG. 2 is a schematic diagram illustrating a configuration of an example of a capacitor element. FIG. 2 is a schematic cross-sectional view of an electrolytic capacitor according to a first modified example of the first embodiment of the present disclosure. FIG. 11 is a schematic cross-sectional view of an electrolytic capacitor according to a second modified example of the first embodiment of the present disclosure. 1 is a schematic cross-sectional view of an electrolytic capacitor according to a reference embodiment of the present disclosure. 6 is a cross-sectional view of a main part showing the vicinity of the boundary between the sealing material and the mold resin layer in FIG. 5 . FIG. 4 is a schematic cross-sectional view of an electrolytic capacitor according to a second embodiment of the present disclosure. FIG. 11 is a schematic cross-sectional view of an electrolytic capacitor according to a modified example of the second embodiment of the present disclosure. 1 is a cross-sectional view of a main portion of an electrolytic capacitor in which an electrical insulating layer is provided and then the rod-shaped portion is inserted into a sealing material so that the joint between the drawn portion and the rod-shaped portion is positioned within a hole in the sealing material. 1 is a cross-sectional view of a main portion of an electrolytic capacitor in which an electrical insulating layer is provided and then the rod-shaped portion is inserted into a sealing material so that the joint between the drawn portion and the rod-shaped portion is positioned outside the hole in the sealing material. 1 is a cross-sectional view of a main portion of an electrolytic capacitor in which an electrical insulating layer is provided after the rod-shaped portion is inserted into the sealing material so that the joint between the drawn portion and the rod-shaped portion is positioned within the hole of the sealing material. 13 is a cross-sectional view of a main portion of an electrolytic capacitor in which an electrical insulating layer is provided after the rod-shaped portion is inserted into the sealing material so that the joint between the drawn portion and the rod-shaped portion is positioned outside the hole of the sealing material. FIG. FIG. 11 is a schematic cross-sectional view of an electrolytic capacitor according to a third embodiment of the present disclosure. This is a cross-sectional view of a key portion of an electrolytic capacitor when a gap is formed while the rod-shaped portion is inserted into a hole in a sealing material so that the joint between the drawn-out portion and the rod-shaped portion is positioned within the hole in the sealing material. This is a cross-sectional view of a key portion of an electrolytic capacitor when a gap is formed when the rod-shaped portion is inserted into a hole in a sealing material so that the joint between the drawn-out portion and the rod-shaped portion is located outside the hole in the sealing material. FIG. 13 is a schematic cross-sectional view of an electrolytic capacitor according to a modified example of the third embodiment of the present disclosure.

Prior to describing the embodiments of the present disclosure, the problems in the prior art will be briefly described. A pair of leads penetrates the sealing member and the molded resin layer, and is drawn out from the mounting surface side of the molded resin layer. An electrolyte (e.g., a solvent) is relatively easy to permeate through a sealing member containing a rubber component, but is difficult to permeate through the molded resin layer. Therefore, when the outer surface of the sealing member is covered with a molded resin layer, the electrolyte may remain inside the sealing member or at the boundary between the sealing member and the molded resin layer. In such a case, the chlorine component (component containing chlorine) contained in the sealing member is likely to dissolve into the electrolyte. If the lead comes into contact with an electrolyte containing a chlorine component, corrosion of the lead may progress.

More specifically, the structure of an example of an electrolytic capacitor according to the embodiment of the present disclosure will be described with reference to Figures 5 and 6.

The electrolytic capacitor 1D comprises a capacitor element 10, an electrolyte (not shown), and a case 11 that contains the capacitor element 10 and the electrolyte. The opening of the case 11 is sealed with a sealing member 12. The outer surface of the sealing member 12 facing the opening of the case 11 (hereinafter also simply referred to as the outer surface of the sealing member 12) is covered with a molded resin layer 13. Leads 14A and 14B are connected to a pair of electrodes of the capacitor element 10, respectively.

The leads 14A and 14B have tab portions 16A and 16B connected to one and the other electrodes, respectively, and lead portions 15A and 15B connected to the tab portions 16A and 16B, respectively. The connection portions between the tab portions 16A and 16B and the lead portions 15A and 15B are hereinafter also referred to as the lead internal connection portions 175A and 175B.

One electrode is an anode and the other electrode is a cathode. The anode has a dielectric layer on a surface. The electrolytic capacitor may include a solid electrolyte layer covering at least a portion of the surface of the dielectric layer. One lead is an anode lead connected to the anode and the other lead is a cathode lead connected to the cathode.

In the illustrated example, the tab portions 16A and 16B have rod-shaped portions 17A and 17B and flat portions 18A and 18B, respectively. The flat portions 18A and 18B are connected to the anode and cathode, respectively. The rod-shaped portions 17A and 17B are connected to the lead-out portions 15A and 15B, respectively. At least a portion of the lead-out portions 15A and 15B is drawn out from the mounting surface 13S of the molded resin layer 13 and is housed in the groove portions 13A and 13B provided in the mounting surface 13S. It is preferable that the bottom surfaces 13a and 13b of the groove portions 13A and 13B have a predetermined inclination.

One end (hereinafter also referred to as the tip) of the rod-shaped portions 17A and 17B is located in a through hole provided in the sealing member 12. Electrolyte components tend to remain near the boundary between the sealing member 12 and the molded resin layer 13. When the tip of the rod-shaped portions 17A and 17B is located in the through hole of the sealing member 12, the electrolyte components remaining near the boundary between the sealing member 12 and the molded resin layer 13 tend to come into contact with the lead internal connection portions 175A and 175B and the draw-out portions 15A and 15B. At this time, the remaining electrolyte components corrode the lead internal connection portions 175A and 175B and the draw-out portions 15A and 15B. In addition, if the electrolyte penetrates into a wide area of the boundary between the sealing material 12 and the molded resin layer 13 and electrolyte components remain between the lead internal connections 175A, 175B and/or between the lead portions 15A, 15B of a pair of leads 14A, 14B, corrosion of the lead internal connections 175A, 175B and/or the lead portions 15A, 15B (especially the anode lead side) is accelerated when a voltage is applied between the leads. Furthermore, as shown in FIG. 6, when the tip of the rod-shaped portion 17A, 17B is located in the through hole of the sealing material, a gap is likely to occur between the leads 14A, 14B and the molded resin layer 13. Electrolyte components are likely to remain in such gaps, accelerating corrosion of the lead internal connections 175A, 175B and/or the lead portions 15A, 15B.

First Embodiment
The electrolytic capacitor according to the first embodiment of the present disclosure includes a capacitor element including a pair of electrodes, an electrolyte interposed between the pair of electrodes, a case for accommodating the capacitor element and the electrolyte, a sealing member, a pair of leads penetrating the sealing member, and a molded resin layer. The sealing member seals the opening of the case. The pair of leads are electrically connected to the pair of electrodes, respectively. The molded resin layer covers at least a portion of the outer surface of the sealing member. At least one of the pair of leads has a tab portion and an extended portion. The tab portion is connected to the electrode. The extended portion is connected to a tip portion of the tab portion. The tip portion of the tab portion protrudes from the outer surface of the sealing member. This prevents the retained electrolyte component from coming into contact with the connection portion between the tip portion of the rod-shaped portion and the extended portion. This makes it less likely that defects such as lead breakage will occur.

Among the leads, the tab portion (or the rod-shaped portion and the flat portion) is originally housed in the case, and is therefore made of a material (such as a valve metal) that is resistant to corrosion due to contact with the electrolyte. For example, the tab portion is covered with an oxide film, and therefore is resistant to corrosion. On the other hand, the connection portion between the tab portion and the draw-out portion (internal lead connection portion) and the subsequent draw-out portion contain materials that are prone to corrosion (transition metals such as Fe and Cu), such as CP wire and Cu wire. By protruding the end portion (or the tip portion of the rod-shaped portion) of the tab portion on the draw-out portion side from the sealing material, the internal lead connection portion and the subsequent draw-out portion can be separated from the boundary between the molded resin layer and the sealing material. This suppresses contact between the electrolyte components and the internal lead connection portion and the draw-out portion.

When a voltage is applied while both of the pair of leads are in contact with the stagnant electrolyte components, the lead components are electrolyzed, accelerating lead corrosion. Therefore, by preventing contact between at least one of the pair of leads and the electrolyte components, lead corrosion can be prevented. Of the anode and cathode leads, the anode lead is more susceptible to corrosion, so it is preferable to have at least the end of the anode lead on the pull-out side (or the tip of the rod-shaped part) protrude from the outer surface of the sealing member. However, in order to enhance the effect of preventing lead corrosion, it is desirable to prevent contact between both of the pair of leads and the electrolyte components.

The lead internal connection may be embedded in the molded resin layer. This forms an adhesive interface between the molded resin layer and the lead internal connection. Since the stagnant electrolyte components are less likely to penetrate into the adhesive interface, the effect of suppressing corrosion of the lead is enhanced. The lead internal connection usually has a weld mark between the tab portion and the pull-out portion. If at least a portion of the weld mark is covered with the molded resin layer, a corresponding corrosion suppression effect can be obtained.

The end of the tab portion on the pull-out side may have an exposed portion that is not covered with the molded resin layer. Since the exposed portion does not form an adhesive interface between the molded resin layer and the lead, electrolyte components do not creep up to the exposed portion due to capillary action. Since the exposed portion is constantly exposed to the outside air, it is unlikely to become wet with electrolyte components and is more likely to dry. This prevents the lead from coming into contact with electrolyte components.

The entire tab portion protruding from the outer surface of the sealing member may be exposed without being covered with the molded resin layer. In this case, a region without the molded resin layer is formed around the through hole through which the lead passes, surrounding the through hole. At this time, no boundary between the molded resin layer and the sealing member is formed around the tab portion protruding from the sealing member, and this portion is exposed to the outside. This further suppresses the retention of electrolyte components around the tab portion protruding from the sealing member.

On the other hand, the end of the tab portion on the pull-out side may be embedded in the molded resin layer so that the entire weld mark is covered with the molded resin layer. In this case, a part of the pull-out portion continuing from the end of the tab portion on the pull-out side may also be embedded in the molded resin layer.

The tab portion is preferably covered with an oxide film of the metal that constitutes the tab portion. This makes it less likely for corrosion to occur due to contact between the tab portion and electrolyte components. For example, if the tab portion contains a valve metal such as aluminum, the tab portion can be anodized to form an oxide film on the tab portion. It is sufficient to form the oxide film only on the anode lead, but an oxide film may also be formed on the cathode lead.

The lead-out portion is preferably a flexible linear member. The linear member preferably comprises a core material and a plating layer that covers the surface of the core material. The core material is preferably mainly composed of, for example, Cu, steel, or Fe, which has excellent electrical conductivity. The plating layer is preferably formed of a low-melting point metal. By providing the lead-out portion with a plating layer of a low-melting point metal, it becomes easy to connect the lead-out portion to a predetermined connected electrode. Specifically, CP wire, Cu wire, etc. can be used for the lead-out portion. A CP wire is a linear member whose core material is formed of steel or Fe, etc., and whose plating layer is formed of Sn, Cu, etc. A Cu wire is a linear member whose core material is formed of Cu, and whose plating layer is formed of Sn, etc.

If the drawer section contains a transition metal, the transition metal is likely to dissolve from the drawer section into the electrolyte components. By protruding the end of the tab section on the drawer section side from the outer surface of the sealing member, corrosion of the drawer section is significantly suppressed.

The evaporation of electrolyte components from the outer surface of the sealing member covered with the molded resin layer is suppressed. Therefore, the molded resin layer only needs to cover at least a portion of the outer surface of the sealing member. As already mentioned, an area of the outer surface of the sealing member that does not have the molded resin layer may be provided around the through hole for passing the lead, so as to surround the through hole. However, it is preferable that the area of the outer surface of the sealing member other than the area around the through hole is covered with the molded resin layer. In this case, it is preferable that 50% or more of the area of the outer surface of the sealing member is covered with the molded resin layer. The entire area (100%) of the outer surface of the sealing member may be covered with the molded resin layer.

It is preferable that the molded resin layer covers not only the outer surface of the sealing member, but also at least a portion of the side surface leading to the opening of the case. This can further improve the airtightness inside the case. It is preferable that the molded resin layer is in close contact with the case in the area facing the case. This can more firmly fix the molded resin layer to the sealing member.

The electrolytic capacitor according to the first embodiment of the present disclosure will be described in detail below with reference to the drawings, but the present disclosure is not limited thereto.

The electrolytic capacitor 1A shown in FIG. 1 comprises a capacitor element 10, an electrolyte (not shown), and a case 11 that contains these and has an opening. The case 11 is, for example, cylindrical with a bottom. The opening of the case 11 is sealed with a sealing member 12. The outer surface of the sealing member 12 facing the opening side of the case 11 is entirely covered with a molded resin layer 13. The molded resin layer 13 is provided so as to cover the opening of the case 11 together with the outer surface of the sealing member 12, and further covers at least a portion of the side surface of the case 11 that continues to the opening.

After accommodating the capacitor element 10, the opening of the case 11 is sealed with the sealing material 12 and the molded resin layer 13. The open end of the case 11 is drawn toward the sealing material 12 and crimped inward. This fixes the sealing material 12 to the opening of the case 11, and the case 11 is sealed by the sealing material 12. The molded resin layer 13 only needs to be partially bonded to the case 11 in the area facing the case 11, and there may be some areas that are not bonded.

The molded resin layer 13 preferably contains a cured product of a curable resin composition. The curable resin composition may contain, in addition to the curable resin, a filler, a curing agent, a polymerization initiator, and/or a catalyst. Examples of the curable resin include a photocurable resin and a thermosetting resin. The curing agent, polymerization initiator, catalyst, etc. are appropriately selected depending on the type of the curable resin.

As the curable resin, for example, a compound that cures or polymerizes by the action of heat (for example, a monomer, an oligomer, a prepolymer, etc.) is used. Examples of such compounds (or curable resins) include epoxy resins, phenolic resins, urea resins, polyimides, polyamideimides, polyurethanes, diallyl phthalates, unsaturated polyesters, etc. The curable resin composition may contain multiple curable resins.

As the filler, for example, insulating particles (inorganic, organic) and/or fibers are preferable. As the insulating material constituting the filler, for example, insulating compounds (oxides, etc.) such as silica and alumina, glass, mineral materials (talc, mica, clay, etc.) and the like can be mentioned. The molded resin layer may contain one type of these fillers or a combination of two or more types. The content ratio of the filler in the molded resin layer is, for example, 10 mass % or more and 90 mass % or less.

The molded resin layer 13 may contain a thermoplastic resin or a composition containing the thermoplastic resin. Examples of the thermoplastic resin that can be used include polyphenylene sulfide (PPS) and polybutylene terephthalate (PBT).

The molded resin layer 13 can be formed using a molding technique such as injection molding, insert molding, or compression molding. The molded resin layer 13 can be formed, for example, by using a predetermined mold and filling a predetermined portion of the mold with a curable resin composition or a thermoplastic resin (composition) so that it covers the opening of the case 11 together with the outer surface of the sealing member 12.

The capacitor element 10 shown in FIG. 2 is formed by winding an anode 21 and a cathode 22 with a separator 23 between them. An anode lead 14A and a cathode lead 14B are electrically connected to the anode 21 and the cathode 22, respectively. Each lead penetrates the sealing material 12 and is drawn out to the outside.

The anode lead 14A and the cathode lead 14B have tab portions 16A and 16B connected to the anode 21 and the cathode 22, respectively, and lead portions 15A and 15B connected to the tab portions 16A and 16B, respectively. The tab portions 16A and 16B include, for example, aluminum. The lead portions 15A and 15B are, for example, CP wires or Cu wires that include metals such as iron, copper, nickel, and tin. When the electrolytic capacitor 1A is mounted on a substrate, the connected electrodes on the substrate and the leads 14A and 14B of the capacitor element 10 are electrically connected via the lead portions 15A and 15B.

The tab portions 16A and 16B each have a rod-shaped portion 17A, 17B and a flat portion 18A, 18B. The rod-shaped portions 17A, 17B and the flat portions 18A, 18B only need to be electrically connected to each other, and may be integral. For example, the flat portion is formed by rolling a portion of the rod-shaped body. The area that is not rolled remains as a rod-shaped portion. This allows the tab portions 16A and 16B to be formed in which the flat portion and the rod-shaped portion are integrated.

The rod-shaped portions 17A and 17B each penetrate the sealing member 12. The shape of the rod-shaped portions 17A and 17B is not particularly limited, and may be a round rod (e.g., a rod with a circular or elliptical cross section) or a square rod (e.g., a rod with a polygonal cross section). The rod-shaped portions 17A and 17B are connected to the capacitor element 10 via the flat portions 18A and 18B, respectively. The flat portions 18A and 18B facilitate the connection of the leads 14A and 14B to the anode and cathode.

The lead-out portions 15A and 15B are connected to the tips of the rod-shaped portions 17A and 17B by welding or the like, and lead-internal connection portions 175A and 175B are formed at the boundaries between the lead-out portions 15A and 15B and the rod-shaped portions. At least a portion of the lead-out portions 15A and 15B passes through the molded resin layer 13 and is drawn out to the outside. The shape of the lead-out portions 15A and 15B is not particularly limited, and may be, for example, wire-shaped or ribbon-shaped.

The tips of the rod-shaped parts 17A and 17B protrude from the outer surface of the sealing member 12. The distance D between the lead internal connection parts 175A and 175B corresponding to the most distal ends of the rod-shaped parts 17A and 17B or the part of the weld mark closest to the lead-out part and the outer surface of the sealing member 12 is preferably as large as possible from the viewpoint of suppressing contact between the lead-out parts 15A and 15B or the lead internal connection parts 175A and 175B and the electrolyte solution components. The distance D is preferably 5% or more of the maximum thickness T of the molded resin layer 13. At this time, it is desirable that the tips of the rod-shaped parts 17A and 17B do not protrude from the mounting surface 13S of the molded resin layer 13. Here, the maximum thickness T of the molded resin layer 13 is the maximum vertical distance between the mounting surface 13S of the molded resin layer 13 and the outer surface of the sealing member 12. The vertical distance refers to the distance in the normal direction of the outer surface of the sealing member 12.

In the above configuration, the lead internal connection parts 175A, 175B are embedded in the molded resin layer 13. The tips of the rod-shaped parts 17A, 17B are entirely covered with the molded resin layer 13, and an adhesive interface between the molded resin layer 13 and the tips of the rod-shaped parts 17A, 17B is formed with a sufficiently large area. This adhesive interface significantly suppresses contact between the lead internal connection parts 175A, 175B or the lead-out parts 15A, 15B and the electrolyte solution components.

As shown in FIG. 1, the mounting surface 13S of the molded resin layer 13 has elongated grooves 13A and 13B. The pull-out portions 15A and 15B have portions that are pulled out from the mounting surface 13S to the outside. These portions are accommodated in the grooves 13A and 13B, and are positioned near the mounting surface 13S.

The bottom surfaces 13a, 13b are inclined so that the depth of the grooves 13A, 13B gradually increases from the point where the extensions 15A, 15B start to be extended from the molded resin layer 13 to the outside toward the outer periphery of the mounting surface 13S. When the extensions 15A, 15B are bent substantially parallel to the mounting surface 13S, a restoring force acts on the extensions 15A, 15B to return them to their original shape. Taking this restoring force into consideration, the bottom surfaces of the grooves 13A, 13B are inclined as described above. The inclination angle of the bottom surfaces 13a, 13b with respect to the mounting surface 13S is, for example, 3° or more and 30° or less. The depth of the grooves 13A, 13B may be constant without inclining the bottom surfaces 13a, 13b.

The sealing material 12 may be an insulating material. An elastic material is preferable as the insulating material. By using a sealing material 12 containing an elastic material such as rubber, high sealing performance can be ensured. From the viewpoint of easily obtaining high heat resistance, silicone rubber, fluororubber, ethylene propylene rubber, chlorosulfonated polyethylene rubber (Hypalon (trademark) rubber, etc.), butyl rubber, isoprene rubber, etc. are preferable.

The sealing member 12 has a shape (e.g., a disk shape such as a disc shape) that corresponds to the shape of the opening of the case 11. The sealing member 12 has through holes for passing the rod-shaped portions 17A and 17B. The shape and size of the through holes may be determined appropriately depending on the shape and size of the rod-shaped portions 17A and 17B.

The capacitor element 10 is described below.

The capacitor element 10 has a wound body as shown in FIG. 2, for example. The wound body has an anode 21 having a dielectric layer, a cathode 22, and a separator 23 interposed therebetween. In the capacitor element 10, a lead 14A is connected to the anode 21, and a lead 14B is connected to the cathode 22.

The anode 21 and cathode 22 are wound with a separator 23 in between. The outermost periphery of the wound body is fixed with a stop tape 24. Note that Figure 2 shows the outermost periphery of the wound body unfastened and partially unfolded.

As the anode 21, for example, a metal foil with a roughened surface is used. The type of metal constituting the metal foil is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal, because it is easy to form a dielectric layer.

The metal foil surface can be roughened by a known method. By roughening, multiple projections and recesses are formed on the surface of the metal foil. The roughening is preferably performed, for example, by etching the metal foil. The etching may be performed, for example, by direct current electrolysis or alternating current electrolysis.

The dielectric layer is formed on the surface of the anode 21. Specifically, the dielectric layer is formed on the surface of the roughened metal foil, so that it is formed along the inner wall surfaces of the holes and depressions (pits) on the surface of the anode 21.

The method for forming the dielectric layer is not particularly limited, but it can be formed by subjecting the metal foil to a chemical conversion treatment. The chemical conversion treatment may be performed, for example, by immersing the metal foil in a chemical conversion solution such as an ammonium adipate solution. In the chemical conversion treatment, if necessary, a voltage may be applied while the metal foil is immersed in the chemical conversion solution.

For example, a metal foil is used for the cathode 22. Although the type of metal is not particularly limited, it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal. The cathode 22 may be roughened and/or chemically treated as necessary. The roughening and chemical treatment can be performed, for example, by the method described for the anode 21.

The separator 23 is not particularly limited, and may be, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid).

The wound body can be produced by a known method. When forming the wound body, the leads may be wound while being wound, so that the leads 14A and 14B are planted from the wound body as shown in FIG. 2.

The capacitor element 10 includes an electrolyte. The electrolyte may be a non-aqueous solvent or a mixture of a non-aqueous solvent and an ionic substance (solute, for example, an organic salt) dissolved therein. The non-aqueous solvent may be an organic solvent or an ionic liquid. Examples of the non-aqueous solvent that can be used include ethylene glycol, propylene glycol, sulfolane, γ-butyrolactone, and N-methylacetamide. Examples of the organic salt include trimethylamine maleate, triethylamine borodisalicylate, triethylamine phthalate, ethyldimethylamine phthalate, mono 1,2,3,4-tetramethylimidazolinium phthalate, and mono 1,3-dimethyl-2-ethylimidazolinium phthalate.

The capacitor element 10 may include a solid electrolyte layer that covers at least a portion of the surface of the dielectric layer.

The solid electrolyte layer includes, for example, a manganese compound and a conductive polymer. Examples of the conductive polymer that can be used include polypyrrole, polythiophene, polyaniline, and derivatives thereof. The solid electrolyte layer can be formed, for example, by chemically polymerizing and/or electrolytically polymerizing raw material monomers on the dielectric layer. Alternatively, the solid electrolyte layer can be formed by applying a solution in which the conductive polymer is dissolved or a dispersion in which the conductive polymer is dispersed to the dielectric layer.

The case 11 is made of a material such as aluminum, stainless steel, copper, iron, brass, or an alloy of these metals.

(First Modification of the First Embodiment)
Electrolytic capacitor 1B shown in Fig. 3 has the same structure as that of the first embodiment, except that the tips of rod-shaped portions 17A, 17B of tab portions 16A, 16B are not embedded in molded resin layer 13. In this modification, lead internal connection portions 175A, 175B and subsequent drawn-out portions 15A, 15B can also be sufficiently spaced apart from the boundary between sealing material 12 and molded resin layer 13. In Fig. 3, the same reference numerals are used to designate the same components as those in the first embodiment shown in Fig. 1.

The molded resin layer 13 completely covers the outer surface of the sealing material 12. On the other hand, the tips of the rod-shaped portions 17A and 17B and the internal lead connections 175A and 175B are not embedded in the molded resin layer 13 and are exposed to the outside. In such exposed portions, capillary action that promotes the rise of electrolyte components does not occur. In addition, the exposed portions are constantly exposed to the outside air and are prone to drying. As a result, electrolyte components are further prevented from accumulating between the leads.

Again, the distance D is preferably 5% or more of the maximum thickness T of the molded resin layer 13. In this case, it is desirable to set the distance D so that the tips of the rod-shaped portions 17A and 17B do not protrude from the mounting surface 13S of the molded resin layer 13.

When providing elongated grooves 13A, 13B on mounting surface 13S of molded resin layer 13, it is preferable to increase the depth of grooves 13A, 13B where the tips of rod-shaped portions 17A, 17B protrude from molded resin layer 13. This allows lead internal connection portions 175A, 175B and the subsequent extension portions 15A, 15B to be housed in grooves 13A, 13B. This makes it possible to prevent extension portions 15A, 15B from protruding from mounting surface 13S.

(Second Modification of the First Embodiment)
In the electrolytic capacitor 1C shown in Fig. 4, the entire portions of the rod-shaped portions 17A, 17B that protrude from the outer surface of the sealing material 12 are exposed and not covered by the molded resin layer 13. Except for this, the electrolytic capacitor 1C has the same structure as the first embodiment. Again, the distance D is preferably 5% or more of the maximum thickness T of the molded resin layer 13. Note that in Fig. 4, the same reference numerals are used to designate the same components as those in the first embodiment shown in Fig. 1.

Around the through-hole of the sealing member 12 from which the rod-shaped parts 17A and 17B protrude, an area that is not covered by the molded resin layer 13 is formed so as to surround the through-hole. For example, a cylindrical through-hole is formed in the molded resin layer 13, through which a part of the rod-shaped parts 17A and 17B is inserted. In this case, the boundary between the molded resin layer 13 and the sealing member 12 is not formed at least in a part around the rod-shaped parts 17A and 17B protruding from the sealing member 12, and the outer surface of the sealing member 12 is slightly exposed. Therefore, around the rod-shaped parts 17A and 17B protruding from the sealing member 12, the boundary between the sealing member 12 and the molded resin layer 13 becomes discontinuous. In addition, the capillary phenomenon that promotes the creeping up of the electrolyte component does not occur in the rod-shaped parts 17A and 17B protruding from the sealing member 12, and the tip parts of the rod-shaped parts 17A and 17B are constantly exposed to the outside air and are easily dried. This further suppresses lead corrosion caused by electrolyte components.

If at least one of the anode lead and the cathode lead protrudes from the outer surface of the sealing member as shown in FIG. 1, FIG. 3, or FIG. 4, the lead is prevented from coming into contact with the electrolyte components. In addition, one of the anode lead and the cathode lead may have any of the configurations shown in FIG. 1, FIG. 3, or FIG. 4, and the other may have any of the other configurations shown in FIG. 1, FIG. 3, or FIG. 4.

Second Embodiment
The electrolytic capacitor according to the second embodiment of the present disclosure includes a capacitor element including a pair of electrodes, an electrolyte interposed between the pair of electrodes, a case for accommodating the capacitor element and the electrolyte, a sealing member, a molded resin layer covering the sealing member, and a pair of leads penetrating the sealing member and the molded resin layer. The case has an opening. The sealing member seals the opening of the case. The pair of leads are electrically connected to the pair of electrodes, respectively. At least one of the pair of leads has an insulating region covered with an electrical insulating layer. The electrical insulating layer is provided between at least one of the pair of leads and at least one of the sealing member and the molded resin layer. It is sufficient that the electrical insulating layer is formed in at least a portion of the region where the leads penetrate the sealing member and the molded resin layer.

One of the pair of electrodes is an anode and the other is a cathode. The anode has a dielectric layer on its surface. One of the pair of leads is an anode lead that electrically connects to the anode and the other is a cathode lead that electrically connects to the cathode.

By providing the insulating region (electrical insulating layer), even if the electrolyte accumulates inside the sealing member or at the boundary between the sealing member and the molded resin layer, contact between the lead and the electrolyte is suppressed. Therefore, even if the chlorine component contained in the sealing member dissolves into the electrolyte, corrosion of the lead can be suppressed. Note that electrolyte accumulation means that components contained in the electrolyte (e.g., a solvent or a solution in which an electrolyte salt is dissolved) accumulate.

The lead may come into contact with the stagnant electrolyte not only in the area where the lead penetrates the sealing member, but also in the area where the lead penetrates the molded resin layer. Therefore, if an electrical insulating layer is formed between the lead and the sealing member and/or the molded resin layer (at least in a part of the area where the lead penetrates the sealing member and the molded resin layer), the effect of suppressing corrosion of the lead can be obtained.

In particular, since the electrolyte is likely to remain at the boundary between the sealing member and the molded resin layer, it is preferable that the electrical insulation layer is provided so that at least one of the pair of leads does not come into contact with the boundary between the sealing member and the molded resin layer (i.e., the lead does not face the boundary). In this case, the effect of providing the insulating region can be further enhanced. Furthermore, it is more preferable that the electrical insulation layer is provided across the boundary between the sealing member and the molded resin layer.

In addition, if a voltage is applied to the electrolytic capacitor in a state where the pair of leads are in contact with the electrolyte remaining at the boundary between the sealing material and the molded resin layer, corrosion of the leads (particularly the anode lead) will progress. By providing an electrical insulating layer so that at least one of the pair of leads does not come into contact with the boundary between the sealing material and the molded resin layer, the progress of corrosion of such leads can be suppressed. In order to further enhance the effect of suppressing the progress of corrosion of such leads, it is preferable that an insulating region is provided on both of the pair of leads. In addition, in such a state, the metal (e.g., aluminum or tin) constituting the anode lead is likely to dissolve out of the anode lead. Therefore, an insulating region may be provided only on the anode lead.

It is preferable that the electrical insulating layer has excellent corrosion resistance against the electrolyte or a solvent containing a chlorine component. In this case, the effect of providing the insulating region can be maintained for a long period of time.

The electrolytic capacitor according to the second embodiment of the present disclosure will be described in detail below with reference to the drawings, but the present disclosure is not limited thereto.

The electrolytic capacitor 2A shown in FIG. 7 comprises a capacitor element 10 including an anode foil 21 (see FIG. 2) and a cathode foil 22 (see FIG. 2), an electrolyte (not shown) interposed between the anode foil 21 and the cathode foil 22, and a cylindrical case 11 with an opening and a bottom that contains the capacitor element 10 and the electrolyte. Examples of materials for the case 11 include metals such as aluminum, stainless steel, copper, iron, and brass, or alloys of these metals.

The electrolytic capacitor 2A includes a sealing member 12 that seals the opening of the case 11, and a molded resin layer 13 that covers the sealing member 12. The molded resin layer 13 is provided so as to cover the opening of the case 11 together with the main surface of the sealing member 12 that is disposed on the outside of the case 11. After the capacitor element 10 is accommodated, the opening of the case 11 is sealed with the sealing member 12 and the molded resin layer 13. The vicinity of the opening end of the case 11 is drawn toward the sealing member 12, and the opening end of the case 11 is crimped inward. As a result, the sealing member 12 is fixed to the opening of the case 11, and the case 11 is sealed with the sealing member 12. The provision of the molded resin layer 13 suppresses deterioration of the sealing member 12 due to oxidation, etc., and further improves the sealing property of the electrolytic capacitor 2A.

As shown in FIG. 7, it is preferable that the molded resin layer 13 further covers at least a portion of the side surface continuing to the opening of the case 11. This can further improve the sealing of the electrolytic capacitor. Note that in this embodiment, there may be some areas where the molded resin layer 13 is not partially bonded to the case 11 and the sealing material 12.

The molded resin layer 13 can be made of the same material and configuration as in the first embodiment.

The electrolytic capacitor 2A has a pair of leads 14A, 14B that are electrically connected to the anode foil 21 and cathode foil 22 included in the capacitor element 10, respectively, and that penetrate the sealing material 12 and the molded resin layer 13. When the electrolytic capacitor is mounted on a substrate, the capacitor element 10 is electrically connected to a terminal on the substrate via the leads 14A, 14B.

The leads 14A and 14B have tab portions 16A and 16B connected to the anode foil 21 and the cathode foil 22, respectively, and lead portions 15A and 15B connected to the tab portions 16A and 16B, respectively. The lead portions 15A and 15B and the tab portions 16A and 16B are connected by welding or the like. The lead portions 15A and 15B include a metal such as iron, copper, nickel, or tin. The tab portions 16A and 16B include aluminum, for example.

The tab portions 16A and 16B each have a rod-shaped portion 17A or 17B and a flat portion 18A or 18B. The rod-shaped portion 17A or 17B and the flat portion 18A or 18B may be integrated as long as they are electrically connected. For example, a flat portion is formed by rolling one end of a rod-shaped body, and the area that is not rolled remains as a rod-shaped portion, thereby forming a tab portion in which the flat portion and the rod-shaped portion are integrated.

In this embodiment, rod-shaped portions 17A and 17B each include a portion disposed within sealing material 12. Lead-out portions 15A and 15B extend from the tip of rod-shaped portions 17A and 17B, respectively. Rod-shaped portions 17A and 17B are connected to capacitor element 10 via flat portions 18A and 18B, respectively. Having flat portions 18A and 18B facilitates connection between leads 14A and 14B and the capacitor element.

The shape of the drawers 15A and 15B is not particularly limited, and may be, for example, wire-like or ribbon-like. The shape of the rod-shaped parts 17A and 17B is not particularly limited, and may be round rod-like (for example, rod-like with a circular or elliptical cross section) or square rod-like (for example, rod-like with a polygonal cross section).

The leads 14A and 14B have insulating regions covered with electrical insulating layers 19A and 19B. The electrical insulating layers 19A and 19B are provided between the leads 14A and 14B and the sealing material 12 and molded resin layer 13. By providing the electrical insulating layers 19A and 19B, corrosion of the leads can be suppressed even if the chlorine component contained in the sealing material 12 dissolves into the electrolyte that remains inside the sealing material 12 or at the boundary between the sealing material 12 and the molded resin layer 13.

As shown in FIG. 7, the electrical insulation layers 19A, 19B are preferably provided so that the leads 14A, 14B do not come into contact with the boundary between the sealing material 12 and the molded resin layer 13. By providing such electrical insulation layers 19A, 19B, it is possible to prevent the leads 14A, 14B from coming into contact with the electrolyte remaining at the boundary between the sealing material 12 and the molded resin layer 13. It is possible to prevent the progress of corrosion of the leads 14A, 14B (particularly the anode lead 14A) when a voltage is applied to the electrolytic capacitor with the leads 14A, 14B in contact with the electrolyte.

As shown in FIG. 7, it is more preferable that the electrical insulating layers 19A and 19B are provided across the boundary between the sealing material 12 and the molded resin layer 13. In this case, the effect of preventing the leads 14A and 14B from coming into contact with the electrolyte remaining at the boundary between the sealing material 12 and the molded resin layer 13 can be further enhanced.

It is preferable that the electrical insulating layers 19A and 19B have excellent corrosion resistance to electrolytes or solvents containing chlorine components. In this case, the effect of providing the insulating regions can be maintained for a long period of time.

The thickness of the electrical insulation layers 19A and 19B is, for example, 0.01 mm or more and 1.00 mm or less.

When the lead-out portions 15A, 15B contain a transition metal, the ends of the lead-out portions 15A, 15B and the rod-shaped portions 17A, 17B are fused together during welding of the lead-out portions 15A, 15B and the rod-shaped portions 17A, 17B, exposing the transition metal on the surface of the joint. Therefore, when the joint comes into contact with the electrolyte remaining at the boundary between the sealing material 12 and the molded resin layer 13, corrosion is likely to progress at the joint (especially the joint on the anode side), and the lead is likely to break at the joint. Therefore, as shown in FIG. 7, it is preferable that at least the joint between the tab portions 16A, 16B (rod-shaped portions 17A, 17B) and the lead-out portions 15A, 15B is covered with an electrical insulating layer 19A, 19B. In other words, it is preferable that the insulating region is provided in the region extending from the rod-shaped portions 17A, 17B of the leads 14A, 14B to the lead-out portions 15A, 15B. By covering the joint with an electrical insulating layer, the progression of corrosion at the joint and the associated breakage at the joint can be suppressed. As shown in Figure 1, if the joint is located near the above-mentioned boundary, it is likely to come into contact with the electrolyte remaining at the above-mentioned boundary, so the effect of covering the joint with electrical insulating layers 19A and 19B shown in Figure 7 is remarkable.

In this embodiment, as shown in FIG. 7, at least a portion of the joint between the tab portions 16A, 16B (rod-shaped portions 17A, 17B) and the lead portions 15A, 15B is located on the sealing material 12 side of the boundary between the sealing material 12 and the molded resin layer 13, but at least a portion of the joint may be located on the molded resin layer 13 side of the boundary.

It is preferable that the distances t1a and t1b of the insulating region extending from the boundary between the sealing material 12 and the molded resin layer 13 toward the molded resin layer 13 be 10% or more of the thickness T1 of the molded resin layer 13. In this case, the sealing performance of the electrolytic capacitor can be further improved.

In this embodiment, the distances t1a and t1b of the insulating regions are the distances that the electrical insulating layers 19A and 19B extend from the boundary surface between the sealing material 12 and the molded resin layer 13 toward the molded resin layer 13 in a direction perpendicular to the boundary surface. The thickness T1 of the molded resin layer 13 is the thickness in the axial direction of the case 11 (X direction in FIG. 1), and is the thickness of the region of the molded resin layer 13 where the grooves 13A and 13B described below are not provided.

It is preferable that the distances t2a and t2b of the insulating region extending from the boundary between the sealing material 12 and the molded resin layer 13 toward the sealing material 12 side are 10% or more of the thickness T2 of the sealing material 12. In this case, the sealing performance of the electrolytic capacitor can be further improved.

In this embodiment, the distances t2a and t2b of the insulating regions are the distances that the electrical insulating layers 19A and 19B extend from the boundary surface between the sealing material 12 and the molded resin layer 13 toward the sealing material 12 in a direction perpendicular to the boundary surface. The thickness T2 of the sealing material 12 is the thickness in the axial direction of the case 11 (the X direction in FIG. 1).

In this embodiment, an insulating region is provided on both lead 14A and lead 14B, but an insulating region may be provided on one of lead 14A and lead 14B.

(Modification of the second embodiment)
In the second embodiment, the electrical insulating layers 19A and 19B shown in Fig. 7 are provided, but the electrical insulating layers 29A and 29B shown in Fig. 8 may be provided. By providing the electrical insulating layers 29A and 29B, contact with the electrolyte can be suppressed over the entire region where the leads 14A and 14B penetrate the sealing material 12 and the molded resin layer 13.

One end of each of the electrical insulating layers 29A and 29B is exposed from the main surface of the sealing material 12 opposite the molded resin layer 13. In this case, the effect of providing the insulating region can be further enhanced.

The other ends of the electrical insulation layers 29A and 29B are exposed from the mounting surface 13S side of the molded resin layer 13. In this case, the effect of providing the insulating region can be further enhanced. However, in order to improve mountability, it is preferable that the electrical insulation layers 29A and 29B are not provided in the portion where the leads 14A and 14B are mounted.

It is preferable that the electrical insulating layers 19A, 19B, 29A, and 29B include at least one of an insulating resin layer and an insulating ceramic layer. In this case, an electrical insulating layer having excellent electrical insulation and corrosion resistance against the electrolyte (a solvent containing a chlorine component) is obtained.

The insulating resin layer preferably contains a cured product of a curable resin composition, a thermoplastic resin, or a composition containing the same. As the curable resin, for example, those exemplified as materials that can be used in the molded resin layer, such as a thermosetting resin, can be used. The curable resin composition may contain, in addition to the curable resin, a filler, a curing agent, etc.

As the thermosetting resin, for example, phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester, alkyd resin, polyurethane, thermosetting polyimide, etc. can be used. Among them, as the thermosetting resin, phenol resin, epoxy resin, and thermosetting polyimide are preferable.

As the thermoplastic resin, for example, fluororesin (e.g., polytetrafluoroethylene), polyamideimide, polyimide, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, ABS resin, AS resin, acrylic resin, etc. can be used. Among them, fluororesin, polyamideimide, and polyimide are preferable as the thermoplastic resin.

The insulating resin layer may be formed by applying a thermosetting resin composition to a predetermined location on the lead and then curing the composition, or by applying a thermoplastic resin (composition) to a predetermined location on the lead. The insulating resin layer may also be formed by applying an insulating resin tape to a predetermined location on the lead.

The insulating ceramic layer preferably contains silica, metal oxides, carbides, borides, and coupling agents. Examples of silica include natural crystalline silica, natural amorphous silica, synthetic crystalline silica, and synthetic amorphous silica. Of these, it is preferable that the silica contains synthetic amorphous silica. Examples of metal oxides include oxides containing aluminum, oxides containing titanium, and oxides containing tantalum. Examples of carbides include silicon carbide, titanium carbide, and boron carbide. Examples of borides include aluminum diboride and titanium diboride. Examples of coupling agents include silane coupling agents and titanate coupling agents.

The insulating ceramic layer is formed, for example, by attaching ceramics to a specified location on the lead using an aerosol deposition method, by applying a tape containing ceramics, or by applying a paint containing ceramics.

The electrical insulation layer may be formed before or after the leads are inserted into the sealing material.

Here, an example of an electrolytic capacitor in which the electrical insulation layer is formed before the leads are inserted into the sealing material is shown in Figures 9 and 10. Figures 9 and 10 are cross-sectional views of the main part of an electrolytic capacitor, showing the vicinity of the boundary between the sealing material and the molded resin layer.

In the case of the electrolytic capacitor shown in FIG. 9, for example, the electrical insulating layers 39A and 39B shown in FIG. 9 are provided. After that, the rod-shaped portions 17A and 17B are inserted into the sealing member 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are positioned within the holes of the sealing member 12, and then the molded resin layer 13 is formed.

In the case of the electrolytic capacitor shown in FIG. 10, for example, the electrical insulating layers 49A and 49B shown in FIG. 10 are provided. After that, the rod-shaped portions 17A and 17B are inserted into the sealing member 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are positioned outside the holes in the sealing member 12, and then the molded resin layer 13 is formed.

Figures 11 and 12 show an example of an electrolytic capacitor in which the electrical insulation layer is formed after the leads are inserted into the sealing material. Figures 11 and 12 are cross-sectional views of the main part of the electrolytic capacitor, showing the vicinity of the boundary between the sealing material and the molded resin layer.

In the case of the electrolytic capacitor shown in FIG. 11, for example, the rod-shaped portions 17A and 17B are inserted into the sealing member 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are positioned within the holes in the sealing member 12. Then, the electrical insulating layers 59A and 59B shown in FIG. 11 are provided, and then the molded resin layer 13 is formed.

In the case of the electrolytic capacitor shown in FIG. 12, for example, the rod-shaped portions 17A and 17B are inserted into the sealing material 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are positioned outside the holes in the sealing material 12. Then, the electrical insulating layers 69A and 69B shown in FIG. 12 are provided, and then the molded resin layer 13 is formed.

In this embodiment, the electrical insulation layer is not limited to the electrical insulation layer shown in Figures 9 to 12. In this embodiment, if the electrical insulation layer is provided between the lead and the sealing material and/or the molded resin layer, the effect of suppressing corrosion of the lead can be obtained. The electrical insulation layer may be provided between the lead and the sealing material and the molded resin layer (for example, across the boundary between the sealing material and the molded resin layer). In addition, the electrical insulation layer may be provided only between the lead and the sealing material (the area where the lead penetrates the sealing material) or only between the lead and the molded resin layer (the area where the lead penetrates the molded resin).

The extension sections 15A and 15B have portions that are extended from the mounting surface 13S side of the molded resin layer 13 to the outside, and these portions are arranged along the mounting surface 13S of the molded resin layer 13.

As shown in FIG. 7, elongated grooves 13A and 13B may be provided on the mounting surface 13S of the molded resin layer 13 to accommodate the portions of the leads 14A and 14B (drawing portions 15A and 15B) drawn out from the molded resin layer 13. By accommodating the drawing portions 15A and 15B in the grooves 13A and 13B, the drawing portions 15A and 15B can be stably fixed and positioned near the mounting surface 13S.

The bottom surfaces 13a and 13b of the grooves 13A and 13B are inclined so that the depth of the grooves 13A and 13B gradually increases from one end where the leads 14A and 14B of the grooves 13A and 13B are drawn out from the molded resin layer 13 to the other end. When the drawers 15A and 15B are bent so as to be approximately parallel to the mounting surface 13S, a force acts on the drawers 15A and 15B to return them to their original shape. By inclining the bottom surfaces of the grooves 13A and 13B in the above manner, the drawers 15A and 15B do not protrude excessively from the mounting surface 13S, and the drawers 15A and 15B can be accommodated within the grooves 13A and 13B. The inclination angle of the bottom surfaces of the grooves 13A and 13B with respect to the mounting surface 13S is, for example, 3° or more and 30° or less.

In this embodiment, the bottom surfaces of grooves 13A and 13B are inclined, but the depth of grooves 13A and 13B may be constant without inclining the bottom surfaces of grooves 13A and 13B.

The sealing member 12 can have the same structure and material as in the first embodiment.

The capacitor element 10 is similar to that of the first embodiment, so a description thereof will be omitted. Note that in this embodiment, the conductivity of the electrolyte may be low.

The electrolyte contained in the case may contain a solvent capable of dissolving the chlorine component contained in the sealing material. Therefore, even if the amount of electrolyte (solvent) in the case is small, there is a risk of the leads corroding. By providing an electrical insulating layer, it is possible to suppress such corrosion of the leads.

Third Embodiment
The molded resin layer is usually formed in close contact with the sealing material. However, the degree of expansion (linear expansion coefficient) of the molded resin layer and the sealing material when the temperature rises is significantly different. Therefore, stress is concentrated near the boundary between the molded resin layer and the sealing material, which may cause cracks in the molded resin layer and reduce the sealing performance of the electrolytic capacitor.

The electrolytic capacitor according to the third embodiment of the present disclosure includes a capacitor element including a pair of electrodes, a case that houses the capacitor element, a sealing member, a molded resin layer that covers the sealing member, and a pair of leads that penetrate the sealing member and the molded resin layer. The case has an opening. The sealing member seals the opening of the case. The pair of leads are electrically connected to the pair of electrodes, respectively. A gap is provided between the sealing member and the molded resin layer.

By providing the above gap, even if the degree of expansion (linear expansion coefficient) during temperature rise differs greatly between the molded resin layer and the sealing material, stress is less likely to concentrate near the boundary between the molded resin layer and the sealing material. By mitigating the concentration of stress, it is possible to prevent cracks from occurring in the molded resin layer. Therefore, it is possible to prevent a decrease in the sealing ability of the electrolytic capacitor due to cracks occurring in the molded resin layer.

It is preferable that the above gap is a very small gap formed by the molded resin layer not being in close contact (bonded) with the sealing material. Having a very small gap is advantageous for miniaturizing the electrolytic capacitor. In addition, the very small gap can be formed by the method described below.

It is preferable that the molded resin layer further covers at least a portion of the side surface continuing to the opening of the case. In this case, the sealing performance of the electrolytic capacitor can be further improved. It is preferable that the molded resin layer is in close contact with the case in the area facing the case. In this case, the molded resin layer covering the sealing member can be more firmly fixed.

When the electrolytic capacitor has an electrolyte, it is preferable that a film of a component contained in the electrolyte is formed on the surface (exposed surface) of the sealing member exposed to the gap. That is, it is preferable that at least a part of the exposed surface is covered with a film of a component contained in the electrolyte. By covering the exposed surface of the sealing member with a film of a component contained in the electrolyte, contact between the sealing member and oxygen is suppressed even when the molded resin layer contains a resin component that is relatively easy for oxygen to permeate. Therefore, even in a high-temperature environment, deterioration of the sealing member due to contact between the oxygen that has permeated the molded resin layer and the sealing member is suppressed.

When an electrolytic capacitor has an electrolyte solution interposed between a pair of electrodes and the electrolyte solution is contained in a case, a film of the components contained in the electrolyte solution may be formed by the components of the electrolyte solution contained in the case permeating the sealing member and remaining in the gap between the sealing member and the molded resin layer. When an electrolytic capacitor has an electrolyte solution interposed between a pair of electrodes and the electrolyte solution is contained in a case, the components (e.g., a solvent) contained in the electrolyte solution relatively easily permeate the sealing member, but are difficult to permeate the molded resin layer. Therefore, by providing a gap between the sealing member and the molded resin layer, the components of the electrolyte solution that have permeated the sealing member are more likely to remain in the gap between the sealing member and the molded resin layer. Therefore, a film of the components of the electrolyte solution can be efficiently formed on the exposed surface of the sealing member.

One of the pair of electrodes is an anode, and the other is a cathode. The anode has a dielectric layer on its surface. One of the pair of leads is an anode lead that is electrically connected to the anode, and the other is a cathode lead that is electrically connected to the cathode. The pair of leads that penetrate the sealing member and the molded resin layer are exposed to a gap provided between the sealing member and the molded resin layer. Therefore, it is preferable that at least one of the pair of leads has an insulating region covered with an electrically insulating layer. It is more preferable that the insulating region is provided at least across the gap. In other words, it is more preferable that the insulating region is provided so as to pass (straddle) the gap from the portion where the lead penetrates the sealing member to the portion where the lead penetrates the molded resin layer.

By providing the insulating region, even if a film of the components contained in the electrolyte is formed in the gap between the sealing material and the molded resin layer (the components contained in the electrolyte are retained), contact between the pair of leads and the components of the electrolyte is suppressed. If a voltage is applied to the electrolytic capacitor while the pair of leads are in contact with the components of the electrolyte, corrosion of the leads (particularly the anode lead) will progress. By providing the insulating region, the progress of such corrosion is suppressed.

Even if an insulating region is provided on only one of a pair of leads, it is possible to suppress the progression of corrosion as described above. However, to further enhance the effect of suppressing the progression of lead corrosion, it is preferable to provide an insulating region on both of the pair of leads.

It is preferable that the electrical insulation layer has excellent electrolyte resistance. In this case, the effect of providing the insulating region can be maintained for a long period of time. It is preferable that the electrical insulation layer includes, for example, at least one of an insulating resin layer and an insulating ceramic layer.

The electrolytic capacitor may include an electrolytic solution interposed between a pair of electrodes, and the electrolytic solution may be contained in a case. The electrolytic capacitor may include a solid electrolyte layer that covers at least a portion of the surface of the dielectric layer. The electrolytic capacitor may include both the electrolytic solution and the solid electrolyte layer.

The electrolytic capacitor according to the third embodiment of the present disclosure will be described in detail below with reference to the drawings, but the present disclosure is not limited thereto.

The electrolytic capacitor 3A shown in FIG. 13 includes a capacitor element 10 including an anode foil 21 (see FIG. 2) and a cathode foil 22 (see FIG. 2), an electrolyte (not shown) interposed between the anode foil 21 and the cathode foil 22, and a cylindrical case 11 with an opening and a bottom that contains the capacitor element 10 and the electrolyte. Examples of materials for the case 11 include metals such as aluminum, stainless steel, copper, iron, and brass, or alloys of these metals.

The electrolytic capacitor 3A includes a sealing member 12 that seals the opening of the case 11, and a molded resin layer 13 that covers the sealing member 12. The molded resin layer 13 is provided so as to cover the opening of the case 11 together with the main surface of the sealing member 12 that is disposed on the outside of the case 11. After the capacitor element 10 is accommodated in the opening of the case 11, the opening is sealed with the sealing member 12 and the molded resin layer 13. The vicinity of the opening end of the case 11 is drawn toward the sealing member 12, and the opening end of the case 11 is crimped inward. As a result, the sealing member 12 is fixed to the opening of the case 11, and the case 11 is sealed by the sealing member 12. By providing the molded resin layer 13, the sealing property of the electrolytic capacitor 3A is further improved.

The molded resin layer 13 is not bonded to the sealing member 12 in the area facing the sealing member 12, and a minute gap 20 is formed between the molded resin layer 13 and the sealing member 12. By providing the gap 20, stress is less likely to concentrate near the boundary between the molded resin layer 13 and the sealing member 12, even if the degree of expansion (linear expansion coefficient) during temperature rise differs greatly between the molded resin layer 13 and the sealing member 12. By mitigating the concentration of stress, it is possible to suppress the occurrence of cracks in the molded resin layer 13.

As shown in FIG. 13, it is preferable that the molded resin layer 13 further covers at least a portion of the side surface leading to the opening of the case 11. This can further improve the sealing performance of the electrolytic capacitor 3A.

The molded resin layer 13 is adhered to the case 11 in the area facing the case 11. This allows the molded resin layer 13 covering the sealing material 12 to be firmly fixed. In this embodiment, the molded resin layer 13 only needs to be partially adhered to the case 11 in the area facing the case 11, and there may be some areas where it is not adhered.

The molded resin layer 13 can be made of the same material and configuration as in the first embodiment.

One method for providing the gap 20 between the sealing member 12 and the molded resin layer 13 is, for example, to apply a release agent to a predetermined area of the sealing member 12 (the area covered by the molded resin layer 13) when forming the molded resin layer 13. This makes it possible to easily form a minute gap by preventing the molded resin layer 13 from adhering to the sealing member 12. For example, a silicone-based or fluorine-based release agent is used as the release agent.

It is preferable that a film (not shown) of the components contained in the electrolyte is formed on the surface (exposed surface) of the sealing member 12 exposed to the gap 20. For example, by allowing the components of the electrolyte that have permeated the sealing member 12 to remain in the gap 20, a film of the components contained in the electrolyte can be formed so as to cover at least a portion of the exposed surface of the sealing member 12.

By covering the exposed surface of the sealing member 12 with a film of components contained in the electrolyte, contact between the sealing member 12 and oxygen is suppressed even if external oxygen penetrates the molded resin layer 13 and reaches the gap 20. Therefore, even in a high-temperature environment, deterioration of the sealing member 12 due to contact between oxygen and the sealing member 12 is suppressed.

The electrolytic capacitor has a pair of leads 14A, 14B that are electrically connected to the anode foil 21 and cathode foil 22 included in the capacitor element 10, respectively, and that penetrate the sealing material 12 and the molded resin layer 13. When the electrolytic capacitor is mounted on a substrate, the capacitor element 10 is electrically connected to a terminal on the substrate via the leads 14A, 14B.

The leads 14A and 14B have tab portions 16A and 16B connected to the anode foil 21 and the cathode foil 22, respectively, and lead portions 15A and 15B connected to the tab portions 16A and 16B, respectively. The lead portions 15A and 15B and the tab portions 16A and 16B are connected by welding or the like. The lead portions 15A and 15B include a metal such as iron, copper, nickel, or tin. The tab portions 16A and 16B include aluminum, for example.

The tab portions 16A and 16B each have a rod-shaped portion 17A or 17B and a flat portion 18A or 18B. The rod-shaped portion 17A or 17B and the flat portion 18A or 18B may be integrated as long as they are electrically connected. For example, a flat portion is formed by rolling one end of a rod-shaped body, and the area that is not rolled remains as a rod-shaped portion, thereby forming a tab portion in which the flat portion and the rod-shaped portion are integrated.

The rod-shaped portions 17A and 17B each include a portion that penetrates the sealing material 12. The shape of the rod-shaped portions 17A and 17B is not particularly limited, and may be a round rod (e.g., a rod with a circular or elliptical cross section) or a square rod (e.g., a rod with a polygonal cross section). The rod-shaped portions 17A and 17B are connected to the capacitor element 10 via the flat portions 18A and 18B, respectively. The flat portions 18A and 18B facilitate the connection between the leads 14A and 14B and the capacitor element.

Each of the draw-out portions 15A and 15B includes a portion that penetrates the molded resin layer 13. The shape of the draw-out portions 15A and 15B is not particularly limited, and may be, for example, wire-shaped or ribbon-shaped. The draw-out portions 15A and 15B extend from the tips of the rod-shaped portions 17A and 17B, respectively.

Here, FIG. 14 shows an example of an electrolytic capacitor in which a gap is formed when the rod-shaped portion is inserted into the hole of the sealing member so that the joint between the drawn portion and the rod-shaped portion is located within the hole of the sealing member. FIG. 14 is a cross-sectional view of a main portion of an electrolytic capacitor showing the vicinity of the boundary between the sealing member and the molded resin layer.

As shown in FIG. 14, the rod-shaped portions 17A and 17B are inserted into the holes of the sealing material 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are located within the holes of the sealing material 12. The tips of the rod-shaped portions 17A and 17B are exposed from the sealing material 12 on the molded resin layer 13 side. A gap 30 is provided between the tips of the rod-shaped portions 17A and 17B and the sealing material 12, and the molded resin layer 13.

The gap 30 is formed, for example, by the following method. The rod-shaped portions 17A and 17B are inserted into the holes of the sealing material 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are positioned within the holes of the sealing material 12. Then, when molding the molded resin layer 13, a release agent is applied to the tips of the rod-shaped portions 17A and 17B and to a predetermined area of the sealing material 12 (the area covered by the molded resin layer 13).

Figure 15 shows an example of an electrolytic capacitor in which a gap is formed when the rod-shaped portion is inserted into the hole of the sealing member so that the joint between the drawn portion and the rod-shaped portion is located outside the hole of the sealing member. Figure 15 is a cross-sectional view of a main portion of an electrolytic capacitor showing the vicinity of the boundary between the sealing member and the molded resin layer.

As shown in FIG. 15, the rod-shaped portions 17A and 17B are inserted into the holes of the sealing material 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are located outside the holes of the sealing material 12. The tips of the rod-shaped portions 17A and 17B are exposed from the sealing material 12 on the molded resin layer 13 side. A gap 40 is provided between the tips of the rod-shaped portions 17A and 17B and the sealing material 12, and the molded resin layer 13.

The gap 40 is formed, for example, by the following method. The rod-shaped portions 17A and 17B are inserted into the holes of the sealing material 12 so that the joints between the lead portions 15A and 15B and the rod-shaped portions 17A and 17B are positioned within the holes of the sealing material 12. Then, when molding the molded resin layer 13, a release agent is applied to the tips of the rod-shaped portions 17A and 17B and to a predetermined area of the sealing material 12 (the area covered by the molded resin layer 13).

As shown in Figures 14 and 15, when the tip portions of the rod-shaped portions 17A and 17B are exposed from the sealing material 12 on the molded resin layer 13 side, a gap that is connected to the gap formed between the sealing material 12 and the molded resin layer 13 may be further formed between the tip portions of the rod-shaped portions 17A and 17B and the molded resin layer 13.

(Modification of the third embodiment)
A portion of the leads 14A, 14B is exposed in a gap 20 provided between the sealing material 12 and the molded resin layer 13. Therefore, as shown in Fig. 16, the leads 14A, 14B preferably have an insulating region covered with an electrical insulating layer 19A, 19B. The insulating region is preferably provided across at least the gap 20. In other words, the insulating region is preferably provided so as to pass through (straddle) the gap 20 from the portion where the leads 14A, 14B penetrate the sealing material 12 to the portion where the leads 14A, 14B penetrate the molded resin layer 13.

By providing an insulating region, even if a film of components contained in the electrolyte is formed on the surface of the sealing member 12 exposed to the gap 20 (if the components contained in the electrolyte remain in the gap 20), contact between the leads 14A and 14B and the components of the electrolyte is suppressed. This suppresses the progression of corrosion of the leads 14A and 14B (especially the lead 14A on the anode side).

In FIG. 16, an insulating region is provided on both lead 14A and lead 14B, but an insulating region may be provided on one of lead 14A and lead 14B.

When the lead-out portions 15A, 15B contain a transition metal, the ends of the lead-out portions 15A, 15B and the rod-shaped portions 17A, 17B are fused together during welding of the lead-out portions 15A, 15B and the rod-shaped portions 17A, 17B, exposing the transition metal on the surface of the joint. Therefore, when the joint comes into contact with the components of the electrolyte remaining in the gap 20, corrosion is likely to progress at the joint (especially the joint on the anode side), and the lead is likely to break at the joint. Therefore, as shown in FIG. 16, it is preferable that at least the joint between the tab portions 16A, 16B (rod-shaped portions 17A, 17B) and the lead-out portions 15A, 15B is covered with an electrical insulating layer 19A, 19B. In other words, it is preferable that the insulating region is provided in the region extending from the rod-shaped portions 17A, 17B of the leads 14A, 14B to the lead-out portions 15A, 15B. Covering the joint with an electrically insulating layer can suppress the progression of corrosion at the joint and the associated breakage at the joint. As shown in FIG. 16, when the joint is located near the gap 20, it is more likely to come into contact with the components of the electrolyte remaining in the gap 20, so the effect of covering the joint with the electrically insulating layers 19A and 19B is more pronounced.

The distances t1a and t1b that the insulating region extends from the boundary between the molded resin layer 13 and the gap 20 toward the molded resin layer 13 are preferably 10% or more of the thickness T1 of the molded resin layer 13. In this case, the effect of providing the insulating region can be further enhanced.

In this embodiment, the distances t1a and t1b of the insulating regions are the distances that the electrical insulating layers 19A and 19B extend from the boundary surface between the molded resin layer 13 and the gap 20 toward the molded resin layer 13 in a direction perpendicular to the boundary surface. The thickness T1 of the molded resin layer 13 is the thickness in the axial direction of the case 11 (X direction in FIG. 16), and is the thickness of the region of the molded resin layer 13 where the grooves 13A and 13B described below are not provided.

The distances t2a and t2b that the insulating region extends from the boundary between the sealing material 12 and the gap 20 toward the sealing material 12 are preferably 10% or more of the thickness T2 of the sealing material 12. In this case, the effect of providing the insulating region can be further enhanced.

In this embodiment, the distances t2a and t2b of the insulating regions are the distances that the electrical insulating layers 19A and 19B extend from the boundary surface between the sealing member 12 and the gap 20 toward the sealing member 12 in a direction perpendicular to the boundary surface. The thickness T2 of the sealing member 12 is the thickness in the axial direction of the case 11 (the X direction in FIG. 16).

From the viewpoint of maintaining the effect of providing an insulating region for a long period of time, it is preferable that the electrical insulating layers 19A, 19B include an insulating resin layer and/or an insulating ceramic layer that are excellent in resistance to electrolyte. The thickness of the electrical insulating layers 19A, 19B may be, for example, 0.01 mm or more and 1.00 mm or less.

The insulating resin layer and the insulating ceramic layer can be made of the same structure and materials as those in the second embodiment. The insulating ceramic layer can be formed, for example, by attaching ceramics to a predetermined location on the lead using an aerosol deposition method, by applying a tape containing ceramics, or by applying a paint containing ceramics.

In FIG. 13, the lead-out portions 15A and 15B have portions that are drawn out from the mounting surface 13S side of the molded resin layer 13. The portions are arranged along the mounting surface 13S of the molded resin layer 13. Here, as shown in FIG. 13, the mounting surface 13S of the molded resin layer 13 may be provided with elongated grooves 13A and 13B for accommodating the portions of the leads 14A and 14B that are drawn out from the molded resin layer 13 to the outside. By accommodating the lead-out portions 15A and 15B in the grooves 13A and 13B, the lead-out portions 15A and 15B can be stably fixed and positioned near the mounting surface 13S.

The bottom surfaces 13a, 13b of the grooves 13A, 13B are inclined so that the depth of the grooves 13A, 13B gradually increases from one end where the leads 14A, 14B of the grooves 13A, 13B are drawn out from the molded resin layer 13 to the other end. When the drawers 15A, 15B are bent so as to be approximately parallel to the mounting surface 13S, a force acts on the drawers 15A, 15B to return to their original shape. Taking this into consideration, by inclining the bottom surfaces of the grooves 13A, 13B as described above, the drawers 15A, 15B do not protrude excessively from the mounting surface 13S, and the drawers 15A, 15B can be accommodated in the grooves 13A, 13B. The inclination angle of the bottom surfaces 13a, 13b of the grooves 13A, 13B with respect to the mounting surface 13S is, for example, 3° or more and 30° or less.

In this embodiment, the bottom surfaces of grooves 13A and 13B are inclined, but the depth of grooves 13A and 13B may be constant without inclining the bottom surfaces of grooves 13A and 13B.

The sealing member 12 can have the same structure and material as in the first embodiment.

The capacitor element 10 is similar to that of the first embodiment, and therefore will not be described. The capacitor element 10 may include an electrolyte and a solid electrolyte layer.

This disclosure is useful for electrolytic capacitors that contain an electrolyte in a case and have a sealing material and a molded resin layer.

1A, 1B, 1C, 1D, 2A, 2B, 3A, 3B: electrolytic capacitor 10: capacitor element 11: case 12: sealing material 13: molded resin layer 13S: mounting surfaces 13A, 13B: grooves 13a, 13b: bottom surfaces 14A, 14B: leads 15A, 15B: lead-out portions 16A, 16B: tab portions 17A, 17B: rod-shaped portions 18A, 18B: flat portions 19A, 19B, 29A, 29B, 39A, 39B, 49A, 49B, 59A, 59B, 69A, 69B: electrical insulating layers 20, 30, 40: gaps 21: anode, anode foil 22: cathode, cathode foil 23: separator 24: stop tape 175A, 175B: lead internal connection portion

Claims (2)

A capacitor element including a pair of electrodes;
An electrolyte;
a case that accommodates the capacitor element and the electrolyte and has an opening;
a sealing member that seals the opening;
a mold resin layer covering the sealing member;
at least one pair of leads electrically connected to the pair of electrodes, respectively, and penetrating the sealing material and the mold resin layer;
A gap is provided between the sealing material and the mold resin layer ,
An electrolytic capacitor, wherein a component contained in the electrolytic solution is present in the gap . At least one of the pair of leads has an insulating region covered with an electrically insulating layer;
The electrolytic capacitor according to claim 1 , wherein the insulating region is provided across at least the gap.