Electrolytic capacitor

Abstract

An electrolytic capacitor 1 according to the present invention is provided with: a resin molded body 9 which is provided with a multilayer body 30 that comprises a capacitor element 20 and a sealing resin 8 that seals the periphery of the multilayer body 30; and a positive external electrode 11 and a negative external electrode 13, which are provided on outer surfaces 9a, 9b of the resin molded body 9. The capacitor element 20 comprises: a valve-acting metal substrate 4 which has a core part 4a and a porous part 4b that is formed along the surface of the core part, and an end of which is exposed in the outer surface 9a of the resin molded body 9; a dielectric layer 5 which is formed on the porous part 4b; a solid electrolyte layer 7a which is formed on the dielectric layer 5; and a conductive layer 7b which is formed on the solid electrolyte layer 7a. The negative external electrode 13 is electrically connected to the conductive layer 7b. The positive external electrode 11 comprises a first electrode layer 11a which is in direct contact with the core part 4a of the valve-acting metal substrate 4. The first electrode layer 11a contains flattened particles 15, each of which has an aspect ratio of 2 or more, and the major axis direction of which is along the outer surface 9a in a cross-section that contains the first electrode layer 11a, while being perpendicular to the main surface of the valve-acting metal substrate 4 and to the outer surface 9a, in which the valve-acting metal substrate 4 is exposed, among the outer surfaces of the resin molded body 9.

Description

[Technical field]

[0001] The present invention relates to an electrolytic capacitor. [Background technology]

[0002] Patent Document 1 discloses an electrolytic capacitor. Patent Document 1 lists methods such as plating, cold spraying, and thermal spraying as methods for providing an external electrode on a capacitor element, and describes using these methods to attach metal to the end face of the anode foil exposed from the outer casing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 065870 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in Patent Document 1 is said to be able to prevent air from entering the inside of the electrolytic capacitor, prevent deterioration of the solid electrolyte layer contained in the cathode portion, and increase the reliability of the electrolytic capacitor.

[0005] However, with the above-mentioned configuration, there has been a problem in that the adhesive strength between the exposed electrode portion of the internal electrode and the metal layer formed by plating or the like is weakened, particularly at the end face on the anode side.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an electrolytic capacitor having a high adhesion between the exposed electrode portions of the internal electrodes and the external electrodes. [Means for solving the problem]

[0007] The electrolytic capacitor of the present invention is an electrolytic capacitor comprising: a resin molded body comprising a laminate including a capacitor element and a sealing resin sealing the periphery of the laminate; and an anode external electrode and a cathode external electrode provided on the outer surface of the resin molded body, wherein the capacitor element comprises a valve metal base having a core portion and a porous portion formed along the core portion and the porous portion, an end portion of which is exposed on the outer surface of the resin molded body, a dielectric layer formed on the porous portion, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer, the cathode external electrode being electrically connected to the conductive layer, the anode external electrode comprising a first electrode layer in direct contact with the core portion of the valve metal base, the first electrode layer being orthogonal to the outer surface of the resin molded body where the valve metal base is exposed and to a main surface of the valve metal base, and comprising flat particles having an aspect ratio of 2 or more whose major axis direction is along the outer surface in a cross section including the first electrode layer. Effect of the Invention

[0008] According to the present invention, it is possible to provide an electrolytic capacitor having high adhesion between the exposed electrode portions of the internal electrodes and the external electrodes. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view illustrating an example of an electrolytic capacitor of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the electrolytic capacitor shown in FIG. 1 taken along line AA. [Diagram 3] FIG. 3 is a cross-sectional view that typically shows the vicinity of the valve metal base on the first end surface of the resin molded body. [Figure 4] FIG. 4 is an enlarged cross-sectional view illustrating a schematic view of a region surrounded by a dotted line in the first electrode layer illustrated in FIG. [Diagram 5] FIG. 5 is a cross-sectional view that illustrates a schematic view of the vicinity of the cathode lead layer on the second end face of the resin molded body. [Figure 6] FIG. 6 is a cross-sectional view illustrating a schematic diagram of another example of the electrolytic capacitor of the present invention. [Figure 7] FIG. 7 is a cross-sectional view that illustrates an example of a resin molded body. [Figure 8] FIG. 8 is a schematic diagram showing a process of forming a first electrode layer by an aerosol deposition method. [Figure 9] FIG. 9 is an electron microscope photograph of the first electrode layer on the first end face side of the electrolytic capacitor of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The electrolytic capacitor of the present invention will now be described. However, the present invention is not limited to the following configurations, and can be modified and applied as appropriate within the scope of the present invention. Note that the present invention also includes a combination of two or more of the preferred configurations of each embodiment of the present invention described below.

[0011] FIG. 1 is a perspective view illustrating an example of an electrolytic capacitor of the present invention. FIG. 1 shows a resin molded body 9 that constitutes the electrolytic capacitor 1. The shape of the resin molded body constituting the electrolytic capacitor of the present invention is not particularly limited, and any three-dimensional shape can be adopted. The shape of the resin molded body is preferably a rectangular parallelepiped. Moreover, the term "rectangular parallelepiped" does not mean a perfect rectangular parallelepiped, and the surface forming the resin molded body may be tapered and not perpendicular to other surfaces, and the corners may be chamfered.

[0012] FIG. 1 shows a rectangular parallelepiped resin molded body 9, which has a length direction (L direction), a width direction (W direction), and a thickness direction (T direction). The resin molded body 9 has, as its outer surfaces, a first end face 9a and a second end face 9b facing each other in the longitudinal direction. An anode external electrode 11 is formed on the first end face 9a, and a cathode external electrode 13 is formed on the second end face 9b. The resin molded body 9 has, as its outer surfaces, a bottom surface 9c and a top surface 9d which face each other in the thickness direction. Moreover, the resin molded body 9 has, as its outer surfaces, a first side surface 9e and a second side surface 9f which face each other in the width direction.

[0013] In this specification, the surface along the length direction (L direction) and thickness direction (T direction) of the electrolytic capacitor or resin molding is referred to as the LT surface, the surface along the length direction (L direction) and width direction (W direction) is referred to as the LW surface, and the surface along the width direction (W direction) and thickness direction (T direction) is referred to as the WT surface. In the following description, the surface of the outer surface of the resin molded body on which the anode external electrode is provided will be referred to as a first end surface, and the surface on which the cathode external electrode is provided will be referred to as a second end surface. Note that the anode external electrode and the cathode external electrode may be provided on the same surface of the outer surface of the resin molded body.

[0014] FIG. 2 is a cross-sectional view of the electrolytic capacitor shown in FIG. 1 taken along line AA. Capacitor element 20 includes an anode 3 having a dielectric layer 5 on its surface, and a cathode 7 facing anode 3 . A plurality of capacitor elements 20 are stacked to form a laminate 30, and the periphery of the laminate 30 is sealed with a sealing resin 8 to form a resin molded body 9. In the laminate 30, the stacked capacitor elements 20 may be bonded to each other via a conductive adhesive (not shown). The laminate 30 may include only one capacitor element 20. An anode external electrode 11 is formed on a first end surface 9a of the resin molded body 9, and the anode external electrode 11 is electrically connected to the anode 3 exposed from the first end surface 9a. A cathode external electrode 13 is formed on the second end surface 9b of the resin molded body 9, and the cathode external electrode 13 is electrically connected to the cathode 7 exposed from the second end surface 9b. The end of the valve metal base 4 constituting the capacitor element 20 on the side of the second end face 9b is sealed with a sealing resin 8, and the valve metal base 4 is not in direct contact with the solid electrolyte layer 7a or the conductive layer 7b. On the other hand, if the end of the valve metal base 4 on the side of the second end face 9b is covered with a dielectric layer 5 or otherwise insulated, the end of the valve metal base 4 on the side of the second end face 9b may be covered with the solid electrolyte layer 7a and the conductive layer 7b.

[0015] FIG. 3 is a cross-sectional view that typically shows the vicinity of the valve metal base on the first end surface of the resin molded body. FIG. 3 is also a cross-sectional view that diagrammatically illustrates the area surrounded by the dotted line in the lower left portion of FIG. The valve metal substrate 4 has a core portion 4a and a porous portion 4b formed along the surface of the core portion 4a. An end portion of the valve metal substrate 4 is exposed at a first end surface 9a of the resin molded body 9. A dielectric layer 5 is formed on the surface of the porous portion 4b.

[0016] Examples of the valve metal constituting the valve metal substrate include simple metals such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, silicon, etc., and alloys containing these metals. Among these, aluminum or an aluminum alloy is preferred.

[0017] The shape of the valve metal substrate is not particularly limited, but is preferably a flat plate, more preferably a foil, and the porous portion is preferably an etching layer that has been etched with hydrochloric acid or the like. The thickness of the valve metal base before etching is preferably 60 μm or more and preferably 180 μm or less. Furthermore, the thickness of the valve metal base (core portion) that is not etched after etching is preferably 10 μm or more and preferably 70 μm or less. The thickness of the porous portion is designed according to the withstand voltage and electrostatic capacitance required for the electrolytic capacitor, and the combined thickness of the porous portions on both sides of the valve metal base is preferably 10 μm or more and preferably 120 μm or less.

[0018] The dielectric layer is preferably made of an oxide film of the valve metal. For example, when an aluminum foil is used as the valve metal substrate, an oxide film serving as the dielectric layer can be formed by anodizing in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or a sodium salt or ammonium salt thereof. The dielectric layer is formed along the surface of the porous portion to form pores (recesses). The thickness of the dielectric layer is designed according to the withstand voltage and capacitance required for the electrolytic capacitor, but is preferably 3 nm or more and 200 nm or less.

[0019] The anode external electrode 11 is provided on a first end surface 9a of the resin molded body 9. The anode external electrode 11 includes a first electrode layer 11 a in direct contact with the core portion 4 a of the valve metal substrate 4 . The first electrode layer 11a is orthogonal to the first end face 9a of the resin molded body 9 and the main surface of the valve metal base 4, and contains flat particles with an aspect ratio of 2 or more whose major axis direction is aligned along the first end face 9a of the resin molded body 9 in a cross section including the first electrode layer 11a. That is, the metal particles constituting the first electrode layer contain flat particles. This will be described with reference to the drawings.

[0020] FIG. 4 is an enlarged cross-sectional view illustrating a schematic view of a region surrounded by a dotted line in the first electrode layer illustrated in FIG. The cross section shown in Figure 4 is perpendicular to the first end face 9a of the resin molding 9 and the main surface of the valve metal base 4, and includes the first electrode layer 11a, and is a cross section cut along the LT plane also shown in Figure 2. This figure is a schematic diagram showing an image of a cross section including the first electrode layer taken by an electron microscope. The first electrode layer 11a is an electrode layer in which a plurality of particles are laminated, and the first electrode layer 11a includes flat particles 15 with an aspect ratio of 2 or more. The flat particle 15 is a particle whose major axis direction is along the first end face 9 a of the resin molded body 9 . The shape of the flat particles includes plate-like, strip-like, rod-like, etc. In other words, regardless of the shape, it is sufficient that the shape meets the above definition.

[0021] The aspect ratio of the particles contained in the first electrode layer is determined as follows. First, for each particle, the longest dimension is taken in the direction along the first end face of the resin molded body. Here, "the direction along the first end face of the resin molded body" does not mean a direction completely parallel to the first end face of the resin molded body, but means that a direction inclined from the direction parallel to the first end face of the resin molded body is also allowed. For example, it may be inclined at about 45° from the first end face, and it is sufficient that the direction is generally along the first end face when viewed macroscopically. The longest dimension in that direction is taken as the dimension in the long axis direction of the particle (the dimension indicated by the double-headed arrow La in FIG. 4).Then, the longest dimension in the direction perpendicular to the long axis is taken as the dimension in the short axis direction of the particle (the dimension indicated by the double-headed arrow Lb in FIG. 4). The aspect ratio is calculated by dividing the major axis dimension by the minor axis dimension. If the major axis dimension is twice or more the minor axis dimension, the particle is deemed to have an aspect ratio of 2 or more. Furthermore, when the particle has a bow-like shape, the major axis is not taken as a straight line, but as the longest line passing only through the particle. When the particle has a bow-like shape, the major axis is the line that follows the bow shape. In Figure 4, the major axis that follows the bow shape is shown as Lc.

[0022] In the first electrode layer having flat particles with an aspect ratio of 2 or more whose long axis direction is along the first end face of the resin molded body, the flat particles are stacked from the first end face of the resin molded body to form the first electrode layer. In the first electrode layer having such a shape, the contact area between the particles constituting the first electrode layer is larger than that of a form in which spherical particles are stacked, so the bond strength between the particles is stronger. In addition, the contact area between the core of the valve metal base, which is the electrode exposed portion of the internal electrode, and the flat particles is also larger, so the bond strength between the first electrode layer, the core of the valve metal base, and the first electrode layer is also stronger. Therefore, when the connection strength between the electrode exposed portion of the internal electrode and the first electrode layer is high and a second electrode layer is formed on the first electrode layer to form an anode external electrode, the anchor effect of the first electrode layer is large, resulting in an electrolytic capacitor with high adhesion between the electrode exposed portion of the internal electrode and the external electrode.

[0023] The particles constituting the first electrode layer do not all need to be flat particles. The particles constituting the first electrode layer may contain both flat particles and non-flat particles. Figure 4 also shows a schematic diagram of a particle 16 that is not a flat particle. In this case, the first electrode layer preferably contains 30% or more flat particles by number. When the first electrode layer contains 30% or more flat particles by number, the adhesive strength between the exposed electrode portion of the internal electrode and the external electrode can be further increased. The proportion of flat particles contained in the first electrode layer can be calculated by determining the outline of the particles contained within a specified observation area on the first electrode layer as shown in Figure 4, classifying each particle into flat particles and non-flat particles, and determining the proportion of flat particles to all particles.

[0024] The major axis dimension (average dimension) of the flat particles contained in the first electrode layer may be 0.3 μm or more, or 1.0 μm or more, and the upper limit of the major axis dimension (average dimension) of the flat particles may be 5.0 μm. The aspect ratio (average value) of the flat particles is preferably 2 or more and 10 or less. These dimensions and aspect ratios can be calculated by extracting only the flat particles present within the observation area and averaging the dimensions in the major axis direction and the minor axis direction of each flat particle. It is preferable to use 30 or more flat particles to obtain these average values.

[0025] The thickness of the first electrode layer formed on the core of the valve metal base is preferably 0.2 μm or more and 30 μm or less. The thickness of the first electrode layer formed on the core of the valve metal substrate is defined as the thickness at the thickest point of the first electrode layer formed on the core. In FIG. 3, the thickness of the first electrode layer 11a formed on the core 4a of the valve metal substrate 4 is indicated by a double-headed arrow T 1 As shown in Fig. When the thickness of the first electrode layer is within the above range, the ESR (equivalent series resistance) can be reduced, and the adhesion between the first electrode layer and the second electrode layer formed thereon can be increased.

[0026] In a cross section including the first electrode layer, which is perpendicular to the outer surface of the resin molded body where the valve metal base is exposed (the first end face of the resin molded body) and the main surface of the valve metal base, the cross section of the first electrode layer is preferably wedge-shaped. Fig. 3 shows the cross section of the first electrode layer 11a being wedge-shaped. When the cross-sectional shape of the first electrode layer is wedge-shaped, the adhesive strength with the second electrode layer formed on the first electrode layer is improved due to the anchor effect, thereby improving the terminal fixing strength. In this specification, the wedge shape means a shape having a bottom that contacts the valve metal base in the above-mentioned cross-sectional shape, and a width perpendicular to the direction away from the bottom (height direction) that gradually narrows. The shape of the top of the wedge is not particularly limited, and may be pointed, rounded, or flat. In addition, the top of the wedge may appear roughly smooth, but may have irregularities when viewed microscopically.

[0027] As shown in FIG. 3, the first electrode layer 11a may be in contact with the sealing resin 8.

[0028] The first electrode layer 11a is preferably an electrode layer containing at least one selected from the group consisting of Cu, Ni, Sn, Ag, Zn, and Au, and is particularly preferably an electrode layer containing at least one of Cu and Ni.

[0029] The first electrode layer 11a is preferably an electrode layer formed by an aerosol deposition method on the first end face 9a, which is the outer surface of the resin molded body 9. The method of forming the first electrode layer by an aerosol deposition method will be described later.

[0030] The anode external electrode 11 preferably further includes a second electrode layer 11b formed on the first electrode layer 11a. The second electrode layer 11b is preferably a conductive resin electrode layer containing a conductive component and a resin component. The conductive component preferably contains Ag, Cu, Ni, Sn or the like as a main component, and the resin component preferably contains epoxy resin, phenol resin or the like as a main component. In particular, it is preferable that the second electrode layer is a conductive resin electrode layer containing Ag. When the conductive resin electrode layer contains Ag, the specific resistance of Ag is small, and therefore the ESR can be reduced.

[0031] Moreover, the second electrode layer is preferably a printed resin electrode layer formed by screen printing an electrode paste. When the second electrode layer is a printed resin electrode layer, the external electrodes can be made flatter than when an electrode paste is formed by dipping, which improves the uniformity of the film thickness of the external electrodes.

[0032] The electrode paste may contain an organic solvent, and as the organic solvent, it is preferable to use a glycol ether-based solvent, such as diethylene glycol monobutyl ether or diethylene glycol monophenyl ether. If necessary, additives may be used. The additives are useful for adjusting the rheology of the electrode paste, particularly the thixotropy. The content of the additives is preferably less than 5% by weight based on the weight of the electrode paste.

[0033] An outer plating layer may be provided on the surface of the second electrode layer 11b. Fig. 2 shows a third electrode layer 11c which is an outer plating layer provided on the surface of the second electrode layer 11b. The third electrode layer is preferably a Ni-plated layer or a Sn-plated layer. When the third electrode layer has two layers, the third electrode layer may have a first outer layer plating layer formed on the surface of the second electrode layer, and a second outer layer plating layer formed on the surface of the first outer layer plating layer. The first outer plating layer is preferably a Ni plating layer, and the second outer plating layer is preferably a Sn plating layer.

[0034] Up to this point, the configuration related to the anode 3 has been described. Next, the configuration related to the cathode 7 and other components constituting the resin molded body will be described with reference to FIG.

[0035] The cathode 7 constituting the capacitor element 20 is formed by laminating a solid electrolyte layer 7a formed on the dielectric layer 5, a conductive layer 7b formed on the solid electrolyte layer 7a, and a cathode extraction layer 7c formed on the conductive layer 7b. An electrolytic capacitor in which a solid electrolyte layer is provided as part of the cathode can be said to be a solid electrolytic capacitor.

[0036] Examples of materials constituting the solid electrolyte layer include conductive polymers having a skeleton of pyrroles, thiophenes, anilines, etc. Examples of conductive polymers having a skeleton of thiophenes include PEDOT [poly(3,4-ethylenedioxythiophene)], which may be PEDOT:PSS complexed with polystyrene sulfonic acid (PSS) as a dopant.

[0037] The solid electrolyte layer is formed, for example, by a method of forming a polymerized film of poly(3,4-ethylenedioxythiophene) or the like on the surface of the dielectric layer using a treatment liquid containing a monomer such as 3,4-ethylenedioxythiophene, or a method of applying a dispersion liquid of a polymer such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric layer and drying it, etc. Note that it is preferable to form a solid electrolyte layer for an outer layer that covers the entire dielectric layer after forming a solid electrolyte layer for an inner layer that fills the pores (recesses). The solid electrolyte layer can be formed in a predetermined region by applying the above-mentioned treatment liquid or dispersion onto the dielectric layer by sponge transfer, screen printing, spray application, dispenser, inkjet printing, etc. The thickness of the solid electrolyte layer is preferably 2 μm or more and 20 μm or less.

[0038] The conductive layer is provided to electrically and mechanically connect the solid electrolyte layer and the cathode lead layer. For example, it is preferably a carbon layer, a graphene layer, a silver layer, a copper layer, a nickel layer, or the like formed by applying a conductive paste such as carbon paste, graphene paste, silver paste, copper paste, nickel paste, or the like. It may also be, for example, a composite layer in which a silver layer, a copper layer, or a nickel layer is provided on a carbon layer or a graphene layer, or a mixed layer formed by applying a mixed paste in which a carbon paste or a graphene paste is mixed with a silver paste, a copper paste, or a nickel paste.

[0039] The conductive layer can be formed by applying a conductive paste such as carbon paste to the solid electrolyte layer by sponge transfer, screen printing, spray coating, dispenser, inkjet printing, or the like. It is preferable to laminate the cathode lead layer in the next step while the conductive layer is still in a viscous state before drying. The thickness of the conductive layer is preferably 2 μm or more and 20 μm or less.

[0040] The cathode extraction layer can be formed of a metal foil. In the case of a metal foil, it is preferable that the metal foil is made of at least one metal selected from the group consisting of Al, Cu, Ag, and alloys mainly composed of these metals. When the metal foil is made of the above metals, the resistance value of the metal foil can be reduced, and the ESR can be reduced. The metal foil may be a metal foil having a carbon or titanium coating on the surface by a film forming method such as sputtering or vapor deposition. It is more preferable to use a carbon-coated Al foil. The thickness of the metal foil is not particularly limited, but from the viewpoints of handling in the manufacturing process, miniaturization, and reducing ESR, it is preferably 20 μm or more and 50 μm or less.

[0041] FIG. 5 is a cross-sectional view that illustrates a schematic view of the vicinity of the cathode lead layer on the second end face of the resin molded body. FIG. 5 is also a cross-sectional view that diagrammatically illustrates the area surrounded by the dotted line in the lower right portion of FIG. Cathode extraction layer 7c, which is a metal foil, is exposed at second end surface 9b of resin molded body 9.

[0042] The cathode external electrode 13 is provided on the second end face 9b which is the outer surface of the resin molded body 9. The cathode external electrode 13 may include a first electrode layer 13a in direct contact with the cathode lead layer 7c. The first electrode layer 13a may have a similar configuration to the first electrode layer 11a formed on the first end surface 9a of the resin molded body 9. In a cross section including the first electrode layer, which is perpendicular to the outer surface of the resin molded body where the cathode extraction layer is exposed (the second end face of the resin molded body) and the main surface of the cathode extraction layer, the cross section of the first electrode layer is preferably wedge-shaped. Fig. 5 shows a cross section of first electrode layer 13a that is wedge-shaped. Furthermore, when observing an enlarged cross-sectional view of the first electrode layer 13a as in Figure 4, it is preferable that the first electrode layer contains flat particles with an aspect ratio of 2 or more whose major axis direction is along the second end face of the resin molding, which is the outer surface of the resin molding.

[0043] Similar to the anode external electrode 11, the cathode external electrode 13 may include a second electrode layer 13b formed on a first electrode layer 13a, and may also include a third electrode layer 13c. The second electrode layer 13b and the third electrode layer 13c may have the same configuration as the second electrode layer 11b and the third electrode layer 11c in the anode external electrode 11.

[0044] The sealing resin 8 constituting the resin molded body 9 contains at least a resin, and preferably contains a resin and a filler. As the resin, it is preferable to use an insulating resin such as an epoxy resin, a phenol resin, a polyimide resin, a silicone resin, a polyamide resin, or a liquid crystal polymer. The resin molded body 9 may be composed of two or more kinds of insulating resins. The sealing resin 8 may be in the form of either a solid resin or a liquid resin. As the filler, it is preferable to use inorganic particles such as silica particles, alumina particles, or metal particles. It is more preferable to use a material containing silica particles in a solid epoxy resin and a phenol resin. As a molding method of the resin molded body, when a solid sealing material is used, it is preferable to use a resin mold such as a compression mold or a transfer mold, and it is more preferable to use a compression mold. When a liquid sealing material is used, it is preferable to use a molding method such as a dispensing method or a printing method. It is preferable to seal a laminate 30 of a capacitor element 20 consisting of an anode 3, a dielectric layer 5, and a cathode 7 with a sealing resin 8 by compression molding to form a resin molded body 9.

[0045] FIG. 6 is a cross-sectional view illustrating a schematic diagram of another example of the electrolytic capacitor of the present invention. In the electrolytic capacitor 2 shown in FIG. 6, the cathode lead layer 7c and the cathode lead portion 7d are formed from an electrode paste rather than a metal foil. In this case, the electrode paste is applied onto the conductive layer by sponge transfer, screen printing, spray coating, dispenser, inkjet printing, or the like to form the cathode lead layer in a predetermined region. As the electrode paste, an electrode paste containing Ag, Cu, or Ni as a main component is preferable. When the cathode lead layer is formed by the electrode paste, the thickness of the cathode lead layer can be made thinner than when a metal foil is used, and in the case of screen printing, the thickness can be made 2 μm or more and 20 μm or less.

[0046] When cathode lead layer 7c and cathode lead portion 7d are formed using electrode paste, second electrode layer 13b can be formed by screen printing of the electrode paste without providing a first electrode layer on the cathode side.

[0047] Cathode lead layers 7c of capacitor elements 20 are gathered together in the vicinity of second end face 9b as cathode lead portion 7d and exposed to second end face 9b. Cathode lead portion 7d may be formed from the same electrode paste as cathode lead layer 7c, or the electrode pastes constituting cathode lead portion 7d and cathode lead layer 7c may have different compositions. When cathode lead layer 7c and cathode lead portion 7d are formed from electrode paste, they have good adhesion to second electrode layer 13b formed by screen printing of the electrode paste.

[0048] Further, although not shown in Fig. 6, an insulating mask may be provided on the anode side. In that case, the insulating mask may be provided on the surface of the dielectric layer.

[0049] In another example of the electrolytic capacitor of the present invention shown in Fig. 6, the above-mentioned treatment liquid or dispersion liquid may be applied to the dielectric layer by dipping to form a solid electrolyte layer in a predetermined region. Similarly, a conductive paste such as a carbon paste may be applied to the solid electrolyte layer by dipping to form a conductive layer.

[0050] Next, an example of a method for producing the electrolytic capacitor of the present invention will be described. When manufacturing the electrolytic capacitor of the present invention, it is preferable to form the first electrode layer on the outer surface of the resin molded body by aerosol deposition method, gas deposition method, etc. It is particularly preferable to form the first electrode layer on the outer surface of the resin molded body by aerosol deposition method. Hereinafter, a method for manufacturing an electrolytic capacitor will be described, which includes a step of forming a first electrode layer on a first end face, which is an outer surface of a resin molded body, by an aerosol deposition method. The step of forming the first electrode layer will be referred to as a first electrode layer forming step.

[0051] First, a resin molded body is prepared in which the valve metal substrate is exposed from a first end surface. FIG. 7 is a cross-sectional view that illustrates an example of a resin molded body. In the first electrode layer forming step, metal particles are sprayed onto the first end face of the resin molded body under a pressure lower than atmospheric pressure, and are caused to collide with the first end face to form the first electrode layer. By forming the first electrode layer through this process, the external electrodes can be formed without using a plating process that is prone to causing corrosion to the internal electrodes, thereby suppressing leakage current (LC) defects caused by the plating solution.

[0052] FIG. 8 is a schematic diagram showing a process of forming a first electrode layer by an aerosol deposition method. 8 shows an aerosol deposition apparatus 51. The aerosol deposition apparatus 51 has a cylinder containing a carrier gas 52, an aerosol generator 54 into which the carrier gas 52 and metal fine particles 53 are introduced to generate an aerosol, a chamber 55 into which the aerosol is introduced, and a stage 57 on which the resin molded bodies 9 are fixed and arranged with their first end faces 9a facing up. In the aerosol deposition method, metal particles 53 are sprayed from a nozzle 56 provided at the tip of an aerosol generator 54, and collide with the first end face 9a of the resin molded body 9 to form the first electrode layer.

[0053] In the aerosol deposition method, aerosolized metal particles are collided with the first end face of the resin molded body. When a metal particle collides with another metal particle, the metal particle crushes the metal particle. When the metal particles collide repeatedly, the particles stretch and spread in the direction along the first end face of the resin molded body. As a result, the shape of the metal particles becomes flat.

[0054] In addition, when the first electrode layer is formed by the aerosol deposition method, the thickness of the first electrode layer can be reduced and the adhesive strength between the resin molded body and the first electrode layer can be strengthened. Furthermore, the aerosol deposition method allows the film to be formed at a slow film formation speed and a low temperature, so that damage to the resin molded body can be reduced.

[0055] The first electrode layer forming process is carried out under a pressure lower than atmospheric pressure. The pressure inside the chamber can be made lower than atmospheric pressure by evacuating the chamber. The pressure inside the chamber is preferably 10 Pa or more and 1000 Pa or less. The pressure inside the chamber can be adjusted by increasing or decreasing the gas flow rate. When the gas flow rate is increased so that the pressure inside the chamber becomes, for example, 100 Pa or more, the film formation speed can be increased, and as a result, the film formation cost can be reduced.

[0056] The first electrode layer forming step is preferably carried out at 100° C. or less, and more preferably at room temperature. Since there is no need to raise the temperature, damage to the resin molded body can be reduced, and carrying out the step at room temperature allows the device to be simplified. The normal temperature may be the temperature of the working environment, and may be, for example, 10°C or higher and 30°C or lower.

[0057] The metal fine particles are preferably fine particles containing at least one selected from the group consisting of Cu, Ni, Sn, Ag, Zn and Au, and more preferably fine particles containing at least one of Cu and Ni. The proportion of flat particles with an aspect ratio of 2 or more contained in the first electrode layer can be adjusted by changing the particle size of the metal particles, the nozzle scanning speed, and the amount of metal particles ejected per unit time. The aspect ratio can also be controlled by the time for which the metal particles are ejected. The aspect ratio can be increased by extending the ejection time, i.e., by ejecting repeatedly or for a long period of time. From the viewpoint of facilitating the formation of flat particles, the particle size of the metal fine particles is preferably D50 less than 5 μm, and more preferably D50 less than 3 μm. D50 of metal particles is the volume distribution based median diameter measured by laser diffraction / scattering method. As a measuring device for D50 of metal particles, for example, MT3300 manufactured by Microtrack Bell Corporation can be used.

[0058] After the first electrode layer is formed, a second electrode layer forming step may be performed in which a second electrode layer containing a conductive component and a resin component is formed on the first electrode layer. In the second electrode layer forming step, it is preferable to perform screen printing of an electrode paste to form a printed resin electrode layer as the second electrode layer. When the second electrode layer is formed by screen printing of the electrode paste, the external electrodes can be made flatter than when the electrode paste is formed by dipping, which improves the uniformity of the film thickness of the external electrodes.

[0059] After the second electrode layer is formed, a third electrode layer forming step may be performed in which a third electrode layer is formed on the second electrode layer by plating.

[0060] Alternatively, a third electrode layer forming step may be performed in which a third electrode layer is formed by plating on the first electrode layer without forming a second electrode layer. If the first electrode layer is formed in advance on the resin molded body, LC defects are less likely to occur even if the third electrode layer is subsequently formed by plating.

[0061] The second end face of the resin molded body may also be subjected to the first electrode layer forming step in the same manner as the first end face of the resin molded body, to form the first electrode layer on the second end face. By this step, a first electrode layer 13a as shown in FIG. 5 can be formed on the second end surface 9b of the resin molded body. Thereafter, the second electrode layer 13b and the third electrode layer 13c can be formed in the same manner as on the first end face side of the resin molded body. In particular, when the cathode extraction layer is a metal foil, providing the first electrode layer in the first electrode layer formation step is effective because it can improve the adhesive strength between the metal foil and the first electrode layer. EXAMPLES

[0062] Hereinafter, examples will be shown in which the relationship between the number ratio of flat particles and the adhesive strength of the electrolytic capacitor of the present invention is evaluated, but the present invention is not limited to these examples.

[0063] (Examples 1 to 7) The laminate having the structure shown in FIG. 1 and FIG. 2 was sealed with a sealing resin containing an epoxy resin and silica particles to obtain a resin molded body. A first electrode layer was formed on a first end surface of the resin molded body by the aerosol deposition method (AD method). Cu particles with a D50 of 1 μm were used as the metal fine particles, and the film formation conditions in the aerosol deposition method were changed to change the number ratio of flat particles in the first electrode layer. A first electrode layer was formed on a second end surface of the resin molded body in the same manner as on the first end surface.

[0064] Then, an electrode paste containing Ag was applied to the end faces (first end face and second end face) of the resin molded body by screen printing and thermally cured to form a second electrode layer. Furthermore, a Ni plating layer and a Sn plating layer, which are the third electrode layer, were formed on the surface of the second electrode layer to produce an electrolytic capacitor.

[0065] Comparative Example 1 The first and second end faces of the resin molded body were etched with an acid mainly composed of nitric acid, and a zincate treatment was performed by forming a Zn coating. The first electrode layer was formed by Ni plating and Ag plating. The second electrode layer and the third electrode layer were formed in the same manner as in Example 1 to prepare an electrolytic capacitor.

[0066] [Measurement of the number of flat particles] The LT surface of the electrolytic capacitor was cross-sectionally polished and observed using SEM / EDS (JEOL Ltd. JSM-7100F) to determine the ratio of the number of flat particles to the number of Cu particles contained in the first electrode layer on the first end face side of the electrolytic capacitor. The results are shown in Table 1.

[0067] [Adhesion evaluation] A metal film simulating the first electrode layer was formed on an aluminum plate simulating a valve metal substrate by the same aerosol deposition method or plating as in each of the examples and comparative examples. The adhesion strength between the aluminum plate and the metal film was measured using a tensile tester. A tensile terminal was attached to the metal film over an area of ​​2.5 mm x 5 mm using an adhesive, and the peel strength measured by pulling it up vertically was taken as the adhesion strength. The evaluation criteria for adhesion were 20 N or more: ⊚ (particularly good), 15 N or more: ○ (good), and less than 15 N: △ (acceptable for practical use). The results are shown in Table 1.

[0068] [Table 1]

[0069] Fig. 9 is an electron microscope photograph of the first electrode layer on the first end face side of the electrolytic capacitor of Example 2. The number ratio of flat particles obtained from this photograph is 84%. As illustrated in Fig. 9, the first electrode layer formed by the aerosol deposition method is a first electrode layer containing flat particles. In each example, the first electrode layer contained flat particles, and the first electrode layer had high adhesion to the aluminum plate.

[0070] In contrast, in Comparative Example 1, the first electrode layer was formed by plating, and no flat particles were present in the first electrode layer. Also, the adhesion of the first electrode layer to the aluminum plate was low. [Explanation of symbols]

[0071] 1, 2 Electrolytic capacitor 3 Anode 4 Valve metal substrate 4a Core 4b Porous part 5 Dielectric Layer 7 Cathode 7a Solid electrolyte layer 7b Conductive layer 7c Cathode extraction layer 7d Cathode lead-out section 8 Sealing resin 9. Resin molding 9a: First end surface of resin molded body (outer surface of resin molded body) 9b: second end surface of resin molded body (outer surface of resin molded body) 9c Bottom surface of resin molded body (outer surface of resin molded body) 9d Upper surface of resin molded body (outer surface of resin molded body) 9e First side surface of resin molded body (outer surface of resin molded body) 9f: second side surface of the resin molded body (outer surface of the resin molded body) 11 Anode external electrode 11a, 13a 1st electrode layer 11b, 13b second electrode layer 11c, 13c 3rd electrode layer 13 Cathode external electrode 15 Flat particles 16 Non-flat particles 20 Capacitor element 30 Laminate 51 Aerosol Deposition Device 52 Carrier Gas 53 Metal fine particles 54 Aerosol Generator 55 Chamber 56 Nozzle 57 Stages

Claims

1. a resin molded body including a laminate including a capacitor element and a sealing resin that seals the periphery of the laminate; an electrolytic capacitor comprising an anode external electrode and a cathode external electrode provided on an outer surface of the resin molded body, The capacitor element is a valve metal base having a core and a porous portion formed along the surface of the core, the end of which is exposed on the outer surface of the resin molded body; a dielectric layer formed on the porous portion; a solid electrolyte layer formed on the dielectric layer; a conductive layer formed on the solid electrolyte layer, the valve metal substrate is aluminum or an aluminum alloy; the cathode external electrode is electrically connected to the conductive layer, the anode external electrode includes a first electrode layer in direct contact with the core portion, the porous portion, and the sealing resin of the valve metal base, The first electrode layer is formed for each valve metal base of the capacitor element, and is perpendicular to the outer surface of the resin molded body where the valve metal base is exposed and to the main surface of the valve metal base, and is characterized in that it contains flat particles with an aspect ratio of 2 or more whose major axis direction is along the outer surface in a cross section including the first electrode layer.

2. 2. The electrolytic capacitor according to claim 1, wherein the first electrode layer contains 30% or more of the flat particles by number.

3. 3. The electrolytic capacitor according to claim 1, wherein the first electrode layer formed on the core portion of the valve metal substrate has a thickness of 0.2 [mu]m or more and 30 [mu]m or less.

4. 4. The electrolytic capacitor according to claim 1, wherein in a cross section including the first electrode layer, which is perpendicular to the outer surface of the resin molded body where the valve action metal base is exposed and to the main surface of the valve action metal base, the cross section of the first electrode layer is wedge-shaped.

5. 5. The electrolytic capacitor according to claim 1, wherein the first electrode layer is an electrode layer containing at least one selected from the group consisting of Cu, Ni, Sn, Ag, Zn and Au.

6. 6. The electrolytic capacitor according to claim 1, wherein the anode external electrode further includes a second electrode layer formed on the first electrode layer.

7. The electrolytic capacitor according to claim 6 , wherein the second electrode layer is a conductive resin electrode layer containing Ag.

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