Electrolytic capacitor

Abstract

The electrolytic capacitor (1) of the present application includes: a resin molded body (9) including a laminate (30) including a capacitor element (20) and a sealing resin (8) sealing the periphery of the laminate (30); and an anode external electrode (11) and a cathode external electrode (13) provided on an outer surface (9a, 9b) of the resin molded body (9), the capacitor element (20) including: a valve action metal base (4) having a core portion (4a) and a porous portion (4b) formed along the surface thereof, the end portion of which is exposed on the outer surface (9a) of the resin molded body (9); a dielectric layer (5) formed on the porous portion (4b); a solid electrolyte layer (7a) formed on the dielectric layer (5); and a conductive layer (7b) formed on the solid electrolyte layer (7a), the cathode external electrode (13) being electrically connected to the conductive layer (7b), the anode external electrode (11) including a first electrode layer (11a) directly connected to the core portion (4a) of the valve action metal base (4), the first electrode layer (11a) including flat particles (15) having an aspect ratio of 2 or more in a cross section including the outer surface (9a) of the resin molded body (9) and a main surface of the valve action metal base (4) exposed on the outer surface (9a) and being orthogonal to each other, the flat particles (15) having a long axis direction in the direction along the outer surface (9a).

Description

Technical Field

[0001] This invention relates to electrolytic capacitors. Background Technology

[0002] An electrolytic capacitor is disclosed in Patent Document 1.

[0003] Patent Document 1 describes the following: As a method for setting external electrodes in a capacitor element, methods such as plating, cold spraying, and spraying are mentioned, in which metal is attached to the end face of the anode foil exposed from the outer casing.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2019 / 065870 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The technology described in Patent Document 1 can prevent air from entering the interior of the electrolytic capacitor, prevent the deterioration of the solid electrolyte layer contained in the cathode, and improve the reliability of the electrolytic capacitor.

[0009] However, in the above structure, the following problem sometimes occurs: especially on the end face of the anode side, the adhesion between the exposed part of the internal electrode and the metal layer formed by plating or the like weakens.

[0010] Therefore, the object of the present invention is to provide an electrolytic capacitor in which the exposed portion of the internal electrode and the external electrode have a high adhesion force.

[0011] means for solving problems

[0012] The electrolytic capacitor of the present invention comprises: a resin molded body having 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 disposed on the outer surface of the resin molded body. The capacitor element comprises: a valve-acting metal substrate having a core and a porous portion formed along the surface of the core, the end of the valve-acting metal substrate being 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 is electrically connected to the conductive layer. The anode external electrode includes a first electrode layer directly contacting the core of the valve-acting metal substrate. In a cross-section of the first electrode layer that is orthogonal to the outer surface of the valve-acting metal substrate exposed on the outer surface of the resin molded body and the main surface of the valve-acting metal substrate, and including the first electrode layer, the first electrode layer includes flattened particles with an aspect ratio of 2 or more in the direction along the outer surface of the resin molded body, where the long axis direction is along the outer surface.

[0013] Invention Effects

[0014] According to the present invention, an electrolytic capacitor is provided that provides a high adhesion force between the exposed portion of the internal electrode and the external electrode. Attached Figure Description

[0015] Figure 1 This is a perspective view schematically illustrating an example of the electrolytic capacitor of the present invention.

[0016] Figure 2 yes Figure 1 The electrolytic capacitor shown is a cross-sectional view along line AA.

[0017] Figure 3 This is a schematic cross-sectional view showing the vibratory metal matrix near the first end face of the resin molded body.

[0018] Figure 4 It is shown schematically. Figure 3 An enlarged cross-sectional view of the region of the first electrode layer surrounded by dashed lines.

[0019] Figure 5 This is a schematic cross-sectional view showing the vicinity of the cathode lead-out layer at the second end face of the resin molded body.

[0020] Figure 6 This is a cross-sectional view schematically illustrating another example of the electrolytic capacitor of the present invention.

[0021] Figure 7 This is a schematic cross-sectional view illustrating an example of a resin molded body.

[0022] Figure 8This is a schematic diagram illustrating the process of forming the first electrode layer by aerosol deposition.

[0023] Figure 9 This is an electron microscope image of the first electrode layer on the first end face side of the electrolytic capacitor in Example 2. Detailed Implementation

[0024] The electrolytic capacitor of the present invention will now be described.

[0025] However, the present invention is not limited to the following structures, and can be applied by appropriate modifications without changing the spirit of the invention. It should be noted that structures obtained by combining two or more preferred structures of the various embodiments of the present invention described below also belong to the present invention.

[0026] Figure 1 This is a perspective view schematically illustrating an example of the electrolytic capacitor of the present invention.

[0027] Figure 1 The resin molded body 9 constituting the electrolytic capacitor 1 is shown in the figure.

[0028] 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 cuboid. However, cuboid does not mean that it is a perfect cuboid; it can also be a cone shape where the face forming the resin molded body is not orthogonal to the other faces, or it can be a chamfered shape.

[0029] Figure 1 The image 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).

[0030] The resin molded body 9 has a first end face 9a and a second end face 9b facing each other in the length direction as its outer surface. 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.

[0031] The resin molded body 9 has a bottom surface 9c and an upper surface 9d facing each other in the thickness direction as its outer surface.

[0032] In addition, the resin molded body 9 has a first side surface 9e and a second side surface 9f facing each other in the width direction as its outer surface.

[0033] It should be noted that, in this specification, the surface of the electrolytic capacitor or resin molded body along the length direction (L direction) and thickness direction (T direction) 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.

[0034] Furthermore, in the following description, the surface of the resin molded body on which the anode external electrode is provided is designated as the first end face, and the surface on which the cathode external electrode is provided is designated as the second end face. It should be noted that the anode external electrode and the cathode external electrode may also be provided on the same surface of the resin molded body.

[0035] Figure 2 yes Figure 1 The electrolytic capacitor shown is a cross-sectional view along line AA.

[0036] The capacitor element 20 includes an anode 3 having a dielectric layer 5 on its surface and a cathode 7 opposite to the anode 3.

[0037] Multiple capacitor elements 20 are stacked to form a laminate 30, and the laminate 30 is sealed with sealing resin 8 to form a resin molded body 9. Within the laminate 30, the stacked capacitor elements 20 can also be bonded to each other using a conductive adhesive (not shown). The laminate 30 may also contain only one capacitor element 20.

[0038] An external anode electrode 11 is formed on the first end face 9a of the resin molded body 9, and the external anode electrode 11 is electrically connected to the anode 3 exposed from the first end face 9a.

[0039] An external cathode electrode 13 is formed on the second end face 9b of the resin molded body 9, and the external cathode electrode 13 is electrically connected to the cathode 7 exposed from the second end face 9b.

[0040] The end of the valve-acting metal substrate 4 constituting the capacitor element 20 on the second end face 9b side is sealed with sealing resin 8, and the valve-acting metal substrate 4 is not in direct contact with the solid electrolyte layer 7a or the conductive layer 7b. On the other hand, when the end of the valve-acting metal substrate 4 on the second end face 9b side is insulated by being covered by the dielectric layer 5 or the like, the end of the valve-acting metal substrate 4 on the second end face 9b side can also be covered by the solid electrolyte layer 7a and the conductive layer 7b.

[0041] Figure 3 This is a schematic cross-sectional view showing the vibratory metal matrix near the first end face of the resin molded body.

[0042] Figure 3 It is also shown schematically. Figure 2 A cross-sectional view of the lower left portion of the area enclosed by dashed lines.

[0043] The valve-acting metal substrate 4 has a core 4a and a porous portion 4b formed along the surface of the core 4a. The end of the valve-acting metal substrate 4 is exposed at the first end face 9a of the resin molded body 9.

[0044] A dielectric layer 5 is formed on the surface of the porous part 4b.

[0045] Valve-acting metals that form the valve-acting metal matrix include, for example, individual metals such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, and silicon, or alloys comprising these metals. Among these, aluminum or aluminum alloys are preferred.

[0046] The shape of the valve-acting metal substrate is not particularly limited, but it is preferably flat, and more preferably foil-shaped. Furthermore, the porous portion is preferably an etched layer that has undergone etching treatment using hydrochloric acid or the like.

[0047] The thickness of the valve-acting metal substrate before etching is preferably 60 μm or more, and more preferably 180 μm or less. Furthermore, the thickness of the valve-acting metal substrate (core) that has not been etched after the etching process is preferably 10 μm or more, and more preferably 70 μm or less. Regarding the thickness of the porous portion, it is designed to match the voltage withstand capability and electrostatic capacitance required for electrolytic capacitors, but it is preferable that the combined thickness of the porous portions on both sides of the valve-acting metal substrate is 10 μm or more, and more preferably 120 μm or less.

[0048] The dielectric layer preferably comprises the oxide film of the valve-acting metal described above. For example, when aluminum foil is used as the valve-acting metal substrate, the oxide film that forms the dielectric layer can be formed by anodizing in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium or ammonium salts.

[0049] Fine pores (recesses) are formed by forming a dielectric layer along the surface of the porous portion. The thickness of the dielectric layer is designed to match the voltage withstand and electrostatic capacitance required by the electrolytic capacitor, but is preferably 3 nm or more and more preferably 200 nm or less.

[0050] An external anode electrode 11 is disposed on the first end face 9a of the resin molded body 9.

[0051] The anode external electrode 11 includes a first electrode layer 11a that is directly connected to the core 4a of the valve-acting metal substrate 4.

[0052] In a cross-section that is orthogonal to the first end face 9a of the resin molded body 9 and the main surface of the valve-acting metal substrate 4 and includes the first electrode layer 11a, flattened particles with an aspect ratio of 2 or more along the direction of the long axis along the first end face 9a of the resin molded body 9 are included. That is, the metal particles constituting the first electrode layer include flattened particles.

[0053] Please refer to the attached diagram for further explanation.

[0054] Figure 4 It is shown schematically. Figure 3 An enlarged cross-sectional view of the region of the first electrode layer surrounded by dashed lines.

[0055] Figure 4 The cross-section shown is orthogonal to the first end face 9a of the resin molded body 9 and the main face of the valve-acting metal substrate 4, and includes the first electrode layer 11a. However, this figure is also... Figure 2 The cross-sectional view shown is after the LT plane has been cut off.

[0056] This figure is a schematic diagram of an image obtained by taking a cross-section including the first electrode layer using an electron microscope.

[0057] The first electrode layer 11a is an electrode layer with multiple particles stacked on top of each other. The first electrode layer 11a includes flat particles 15 with an aspect ratio of 2 or higher.

[0058] The flattened particle 15 is a particle whose long axis is oriented along the first end face 9a of the resin molded body 9.

[0059] Flattened particles can take the form of plates, ribbons, rods, etc. In other words, any particle that conforms to the above definition, regardless of its shape, is acceptable.

[0060] The dimensions of the particles contained in the first electrode layer are 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, "in the direction along the first end face of the resin molded body" does not mean a direction that is completely parallel to the first end face of the resin molded body; it is also permissible to have an inclined direction from the direction parallel to the first end face of the resin molded body. For example, it can be inclined at about 45° from the first end face, which is generally about the direction along the first end face.

[0061] The longest dimension in that direction is set as the dimension along the major axis of the particle. Figure 4 The dimension indicated by the double arrow La in the diagram). Then, take the longest dimension in the direction orthogonal to the major axis, and set this dimension as the dimension in the direction of the minor axis of the particle ( Figure 4 (The dimensions indicated by the double arrow Lb in the diagram).

[0062] Then, the ratio of the dimension along the major axis to the dimension along the minor axis is taken as the aspect ratio. If the dimension along the major axis is more than twice the dimension along the minor axis, it is considered a flat particle with an aspect ratio of 2 or higher.

[0063] Furthermore, regarding the selection of the major axis, in the case of particles with an arc shape, it is determined to be the longest line passing through the particle, rather than a straight line. In the case of particles with an arc shape, the line along the arc shape is set as the major axis. Figure 4 Lc is used to indicate the long axis along the arc shape.

[0064] In a first electrode layer containing flattened particles with an aspect ratio of 2 or more along the direction of the long axis oriented along the first end face of the resin molded body, the flattened particles are stacked from the first end face of the resin molded body to form the first electrode layer. In this type of first electrode layer, compared to a layer of stacked spherical particles, the contact area between the particles constituting the first electrode layer is large, thus the bonding strength between the particles is stronger. Furthermore, the contact area between the core of the valve-acting metal substrate, which serves as the inner electrode, and the flattened particles is also large, thus the bonding strength between the first electrode layer, the core of the valve-acting metal substrate, and the first electrode layer is also stronger. Therefore, the connection strength between the inner electrode's exposed electrode portion and the first electrode layer is high. When a second electrode layer is formed on the first electrode layer to form the anode external electrode, the anchoring effect of the first electrode layer is increased, resulting in an electrolytic capacitor with high adhesion between the inner electrode's exposed electrode portion and the external electrode.

[0065] The particles constituting the first electrode layer do not necessarily have to be all flat particles. The particles constituting the first electrode layer can also include both flat particles and non-flat particles. Figure 4 The image also schematically shows particle 16, which is not a flat particle.

[0066] In this case, the first electrode layer preferably includes flat particles in a proportion of 30% or more. When the first electrode layer includes flat particles in a proportion of 30% or more, the adhesion between the exposed portion of the inner electrode and the outer electrode can be further improved.

[0067] like Figure 4 As shown, by determining the outline of the particles contained in a specified observation area in the first electrode layer, each particle can be classified into flat particles and non-flat particles, and the proportion of flat particles relative to all particles can be calculated, thereby calculating the proportion of flat particles contained in the first electrode layer.

[0068] The average size of the flattened particles in the long axis direction can be 0.3 μm or more, or 1.0 μm or more. Alternatively, the upper limit of the average size of the flattened particles in the long axis direction can be 5.0 μm.

[0069] In addition, the aspect ratio (average value) of the flattened particles is preferably 2 or more and 10 or less.

[0070] It is possible to calculate the size and aspect ratio of flat particles by extracting only the flat particles present in the observation area and taking the average of the size of the major axis and the size of the minor axis of each flat particle.

[0071] It should be noted that it is preferable to set the number of flat particles used to obtain their average value to be 30 or more.

[0072] The thickness of the first electrode layer formed in the core of the valve-acting metal substrate is preferably 0.2 μm or more and 30 μm or less.

[0073] The thickness of the first electrode layer formed in the core of the valve-acting metal substrate is determined to be the thickness at the thickest part of the first electrode layer formed in the core. Figure 3 In the diagram, the thickness of the first electrode layer 11a formed on the core 4a of the valve-acting metal substrate 4 is indicated by a double arrow T1.

[0074] 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 on the first electrode layer can be improved.

[0075] In a cross-section that is orthogonal to the outer surface of the exposed valve-acting metal substrate (the first end face of the resin molded body) and the main surface of the valve-acting metal substrate, and includes the first electrode layer, the cross-sectional shape of the first electrode layer is preferably wedge-shaped. Figure 3 The cross-sectional shape of the first electrode layer 11a is shown to be wedge-shaped.

[0076] When the cross-sectional shape of the first electrode layer is wedge-shaped, the adhesion force between the first electrode layer and the second electrode layer formed on the first electrode layer is increased under the effect of anchoring, thus improving the terminal bonding strength.

[0077] In this specification, a wedge shape refers to the following: in the cross-sectional shape described above, it has a bottom that is in contact with the valve-acting metal substrate, and its width gradually narrows along a direction orthogonal to the bottom (height direction). The shape of the wedge's apex is not particularly limited; it can be sharp, rounded, or flat. Furthermore, the apex of the wedge can appear generally smooth or, in a microscopic manner, have irregularities.

[0078] like Figure 3 As shown, the first electrode layer 11a can also be connected to the sealing resin 8.

[0079] The first electrode layer 11a is preferably an electrode layer comprising at least one selected from the group consisting of Cu, Ni, Sn, Ag, Zn, and Au. In particular, an electrode layer comprising at least one of Cu and Ni is preferred.

[0080] The first electrode layer 11a is preferably an electrode layer formed on the outer surface of the resin molded body 9, i.e., the first end face 9a, by aerosol deposition. The method for forming the first electrode layer by aerosol deposition will be described below.

[0081] The anode external electrode 11 preferably further includes a second electrode layer 11b formed on the first electrode layer 11a.

[0082] The second electrode layer 11b is preferably a conductive resin electrode layer comprising conductive components and resin components.

[0083] As conductive components, Ag, Cu, Ni, Sn, etc. are preferred as main components; as resin components, epoxy resin, phenolic resin, etc. are preferred as main components.

[0084] In particular, it is preferable that the second electrode layer is a conductive resin electrode layer comprising Ag. When the electrode layer is a conductive resin electrode layer comprising Ag, the ESR can be reduced because Ag has a low resistivity.

[0085] In addition, the second electrode layer is preferably a printed resin electrode layer formed by screen printing of an electrode paste.

[0086] When the second electrode layer is a printed resin electrode layer, the external electrode can be made flatter compared to the case where an electrode paste is formed by impregnation. That is, the uniformity of the film thickness of the external electrode is improved.

[0087] Electrode pastes may also include organic solvents, with ethylene glycol ether-based solvents being preferred. Examples include diethylene glycol monobutyl ether and diethylene glycol monophenyl ether.

[0088] Additionally, additives may be used as needed. Additives are useful for adjusting the rheological properties, especially the thixotropic properties, of the electrode paste. The additive content is preferably less than 5% by weight relative to the electrode paste.

[0089] An outer coating layer can also be formed on the surface of the second electrode layer. Figure 2 The image shows the outer plating layer, namely the third electrode layer 11c, disposed on the surface of the second electrode layer 11b.

[0090] The third electrode layer is preferably a Ni-plated layer or a Sn-plated layer.

[0091] In the case where the third electrode layer has two layers, the third electrode layer may also have a first outer plating layer formed on the surface of the second electrode layer and a second outer plating layer formed on the surface of the first outer plating layer.

[0092] The first outer coating layer is preferably a Ni coating layer, and the second outer coating layer is preferably a Sn coating layer.

[0093] This concludes the explanation of the structure associated with anode 3. Next, refer to... Figure 2 This will be used to explain the structure associated with the cathode 7 and other structures that constitute the resin molded body.

[0094] The cathode 7 constituting the capacitor element 20 is formed by stacking 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 lead-out layer 7c formed on the conductive layer 7b.

[0095] An electrolytic capacitor that has a solid electrolyte layer as part of the cathode can be called a solid electrolytic capacitor.

[0096] Materials constituting the solid electrolyte layer include conductive polymers with pyrrole, thiophene, and aniline backbones. Examples of conductive polymers with thiophene backbones include PEDOT [poly(3,4-ethylenedioxythiophene)], or PEDOT:PSS composited with polystyrene sulfonic acid (PSS) as a dopant.

[0097] The solid electrolyte layer is formed, for example, by methods such as: forming a polymer film of poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer using a treatment solution including monomers such as 3,4-ethylenedioxythiophene; or applying a dispersion of polymers such as poly(3,4-ethylenedioxythiophene) to the surface of the dielectric layer and allowing it to dry. It should be noted that, preferably, after forming an inner solid electrolyte layer that fills the pores (recesses), an outer solid electrolyte layer covering the entire dielectric layer is formed.

[0098] The solid electrolyte layer can be formed in a specified area by applying the aforementioned treatment liquid or dispersion onto the dielectric layer through methods such as sponge transfer, screen printing, spray coating, dispensing, or inkjet printing. The thickness of the solid electrolyte layer is preferably 2 μm or more, and more preferably 20 μm or less.

[0099] The conductive layer is provided for electrical and mechanical connection between the solid electrolyte layer and the cathode lead-out layer. For example, it is preferably a carbon layer, graphene layer, silver layer, copper layer, or nickel layer formed by applying a conductive paste such as a carbon paste, graphene paste, silver paste, copper paste, or nickel paste. Alternatively, it may be a composite layer with a silver layer, copper layer, or nickel layer disposed on a carbon layer or graphene layer, or a mixed layer formed by applying a mixed paste obtained by mixing a carbon paste, graphene paste, silver paste, copper paste, or nickel paste.

[0100] The conductive layer can be formed by applying a conductive paste, such as carbon paste, to a solid electrolyte layer through methods such as sponge transfer, screen printing, spray coating, dispensing, or inkjet printing. It should be noted that the cathode lead-out layer for the next process is preferably laminated while the conductive layer is still viscous before drying. The thickness of the conductive layer is preferably 2 μm or more, and more preferably 20 μm or less.

[0101] The cathode lead-out layer can be formed from metal foil.

[0102] In the case of a metal foil, it is preferable to include at least one metal selected from the group consisting of Al, Cu, Ag, and alloys with these metals as the main components. When the metal foil includes the aforementioned metal, the resistivity of the metal foil can be reduced, and the ESR can be lowered.

[0103] Alternatively, metal foils obtained by film formation methods such as sputtering or vapor deposition, in which carbon or titanium coatings are applied to the surface, can also be used. Al foil with a carbon coating is more preferred. The thickness of the metal foil is not particularly limited, but from the viewpoints of operability, miniaturization, and reduction of ESR in the manufacturing process, it is preferable to be 20 μm or more, and more preferably 50 μm or less.

[0104] Figure 5 This is a schematic cross-sectional view showing the vicinity of the cathode lead-out layer at the second end face of the resin molded body.

[0105] Figure 5 It is also shown schematically. Figure 2 A cross-sectional view of the area in the lower right corner surrounded by dashed lines.

[0106] The cathode lead-out layer 7c, which serves as a metal foil, is exposed at the second end face 9b of the resin molded body 9.

[0107] The external cathode electrode 13 is disposed on the outer surface of the resin molded body 9, namely the second end face 9b.

[0108] The external cathode electrode 13 may also include a first electrode layer 13a that is directly connected to the cathode lead-out layer 7c. As this first electrode layer 13a, an electrode layer with the same structure as the first electrode layer 11a formed on the first end face 9a of the resin molded body 9 can be used.

[0109] In a cross-section that is orthogonal to the outer surface of the exposed cathode lead-out layer (the second end face of the resin molded body) and the main surface of the cathode lead-out layer, and includes the first electrode layer, the cross-sectional shape of the first electrode layer is preferably wedge-shaped. Figure 5 The cross-sectional shape of the first electrode layer 13a is shown to be wedge-shaped.

[0110] In addition, with Figure 4 Similarly, when observing the enlarged cross-sectional view of the first electrode layer 13a, the first electrode layer preferably includes flat particles with an aspect ratio of 2 or more in the direction of the long axis along the outer surface of the resin molded body, i.e., the second end face of the resin molded body.

[0111] The cathode external electrode 13, like the anode external electrode 11, may also include a second electrode layer 13b formed on the first electrode layer 13a, and may also include a third electrode layer 13c.

[0112] The structures of the second electrode layer 13b and the third electrode layer 13c can also use the same structures as those of the second electrode layer 11b and the third electrode layer 11c in the anode external electrode 11.

[0113] The sealing resin 8 constituting the resin molded body 9 includes at least a resin, and preferably includes both a resin and a filler. As the resin, insulating resins such as epoxy resin, phenolic resin, polyimide resin, silicone resin, polyamide resin, and liquid crystal polymer are preferred. Furthermore, the resin molded body 9 may also be composed of two or more insulating resins. The sealing resin 8 can be either a solid resin or a liquid resin. As the filler, inorganic particles such as silica particles, alumina particles, and metal particles are preferred. Materials that include silica particles in solid epoxy resin and phenolic resin are more preferably used.

[0114] As a molding method for resin molded articles, when using solid sealing materials, resin molding such as compression molding or transfer molding is preferred, and compression molding is more preferred. Furthermore, when using liquid sealing materials, molding methods such as dispensing or printing are preferred. Preferably, in compression molding, the resin molded article 9 is formed by sealing the laminate 30 of the capacitor element 20, including the anode 3, dielectric layer 5, and cathode 7, with sealing resin 8.

[0115] Figure 6 This is a cross-sectional view schematically illustrating another example of the electrolytic capacitor of the present invention.

[0116] exist Figure 6 In the electrolytic capacitor 2 shown, the cathode lead-out layer 7c and the cathode lead-out portion 7d are formed by electrode paste rather than metal foil.

[0117] In this case, the electrode paste can be applied to the conductive layer by methods such as sponge transfer, screen printing, spray coating, dispensing, and inkjet printing to form a cathode lead-out layer in a specified area. As the electrode paste, an electrode paste with Ag, Cu, or Ni as its main components is preferred. When the cathode lead-out layer is formed from the electrode paste, the thickness of the cathode lead-out layer can be reduced compared to using metal foil; in the case of screen printing, a thickness of 2 μm or more and 20 μm or less can be used.

[0118] When the cathode lead-out layer 7c and cathode lead-out portion 7d are formed by electrode paste, the second electrode layer 13b can be formed by screen printing of the electrode paste without providing the first electrode layer on the cathode side.

[0119] The cathode lead-out layers 7c of each capacitor element 20 converge near the second end face 9b to form a cathode lead-out portion 7d and are exposed on the second end face 9b.

[0120] The cathode lead-out portion 7d can also be formed of the same electrode paste as the cathode lead-out layer 7c. Alternatively, the electrode pastes constituting the cathode lead-out portion 7d and the cathode lead-out layer 7c can have different compositions.

[0121] When the cathode lead-out layer 7c and the cathode lead-out portion 7d are formed by electrode paste, the adhesion to the second electrode layer 13b formed by screen printing through the electrode paste becomes good.

[0122] In addition, although Figure 6 It is not explicitly stated, but an insulating mask may also be present on the anode side. In this case, the insulating mask may also be disposed on the surface of the dielectric layer.

[0123] It should be noted that, in Figure 6 In another example of the electrolytic capacitor of the present invention, the aforementioned treatment liquid or dispersion can also be applied to the dielectric layer by impregnation, thereby forming a solid electrolyte layer in a defined area. Alternatively, a conductive layer can also be formed by impregnation of a conductive paste, such as a carbon paste, onto the solid electrolyte layer.

[0124] Next, an example of a method for manufacturing the electrolytic capacitor of the present invention will be described.

[0125] In 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 or vapor phase deposition. In particular, it is preferable to form the first electrode layer on the outer surface of the resin molded body by aerosol deposition.

[0126] The following describes a method for manufacturing an electrolytic capacitor, including the following steps: a first electrode layer is formed on the outer surface, i.e., the first end face, of a resin molded body using an aerosol deposition method. The step of forming the first electrode layer is referred to as the first electrode layer forming step.

[0127] First, prepare a resin molded body that exposes the valve-acting metal matrix from the first end face.

[0128] Figure 7 This is a schematic cross-sectional view illustrating an example of a resin molded body.

[0129] In the first electrode layer formation process, metal particles are sprayed onto the first end face of the resin molded body under a pressure lower than atmospheric pressure, and then collided with it to form the first electrode layer.

[0130] When the first electrode layer is formed through this process, the external electrode can be formed without using a plating process that easily causes corrosion of the internal electrode. Therefore, leakage current (LC) defects caused by the plating solution can be suppressed.

[0131] Figure 8This is a schematic diagram illustrating the process of forming the first electrode layer by aerosol deposition.

[0132] exist Figure 8 The diagram shows an aerosol deposition apparatus 51. The aerosol deposition apparatus 51 includes a gas storage bottle containing a carrier gas 52, an aerosol generator 54 that generates aerosol by introducing the carrier gas 52 and metal particles 53, a chamber 55 into which aerosol is introduced, and a stage 57 on which resin molded bodies 9 are fixed and arranged with their first end face 9a facing upward.

[0133] In the aerosol deposition method, metal particles 53 are ejected from a nozzle 56 located at the front end of the aerosol generator 54. The metal particles 53 become the first electrode layer by colliding with the first end face 9a of the resin molded body 9.

[0134] In aerosol deposition, aerosolized metal particles collide with the first end face of a resin molded body. When other metal particles collide with each other, the metal particles are broken up. As the metal particles repeatedly collide, they extend and expand along the direction of the first end face of the resin molded body. As a result, the metal particles become flattened particles.

[0135] Furthermore, when the first electrode layer is formed by aerosol deposition, the thickness of the first electrode layer can be reduced, and the adhesion between the resin molded body and the first electrode layer can be enhanced. In addition, the aerosol deposition method can slow down the film formation rate and lower the temperature for film formation, thus reducing damage to the resin molded body.

[0136] The first electrode layer formation process is performed under conditions below atmospheric pressure. This pressure is achieved by vacuuming the chamber. Preferably, the pressure inside the chamber is set to 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. Increasing the gas flow rate to, for example, 100 Pa or more, accelerates the film formation process, thereby reducing film formation costs.

[0137] The first electrode layer formation process is preferably carried out at a temperature below 100°C, and more preferably at room temperature. Since there is no need to increase the temperature, damage to the resin molded body can be reduced, and by carrying it out at room temperature, the apparatus can also be simplified.

[0138] The ambient temperature is acceptable, but it can be between 10°C and 30°C.

[0139] The preferred metal particles are those selected from the group consisting of at least one of Cu, Ni, Sn, Ag, Zn and Au, and more preferably particles including at least one of Cu and Ni.

[0140] By varying the particle size of the metal particles, the scanning speed of the nozzle, and the amount of metal particles ejected per unit time, the proportion of flat particles with an aspect ratio of 2 or higher in the first electrode layer can be adjusted. Furthermore, the aspect ratio can be controlled by the duration of metal particle ejection. By extending the ejection time, i.e., by repeated ejection or by performing prolonged ejection, the aspect ratio can be increased.

[0141] From the viewpoint that it is easy to form flat particles, the particle size of metal microparticles is preferably D50 less than 5 μm, and more preferably D50 less than 3 μm.

[0142] The D50 of metal particles is the median particle size of the volume distribution baseline determined by laser diffraction / scattering.

[0143] For example, the MT3300 manufactured by Macchique Bayer Co., Ltd. can be used as a measuring device for the D50 of metal particles.

[0144] Alternatively, after forming the first electrode layer, a second electrode layer forming process can be performed to form a second electrode layer comprising conductive and resin components on the first electrode layer.

[0145] In the second electrode layer formation process, it is preferable to screen print the electrode paste to form a printed resin electrode layer as the second electrode layer.

[0146] When the second electrode layer is formed by screen printing of the electrode paste, the outer electrode can be made flatter compared to the case where the electrode paste is formed by impregnation. That is, the uniformity of the film thickness of the outer electrode is improved.

[0147] Alternatively, after forming the second electrode layer, a third electrode layer forming process can be performed on the second electrode layer by plating to form the third electrode layer.

[0148] Alternatively, a third electrode layer forming process can be performed on the first electrode layer by plating to form a third electrode layer, without forming a second electrode layer.

[0149] When the first electrode layer is pre-formed on the resin molded body, even if a third electrode layer based on plating is subsequently formed, LC defects are less likely to occur.

[0150] For the second end face of the resin molded body, the same first electrode layer forming process can be performed as for the first end face of the resin molded body to form the first electrode layer on the second end face.

[0151] Through this process, it is possible to Figure 5 The first electrode layer 13a shown is formed on the second end face 9b of the resin molded body.

[0152] Subsequently, a second electrode layer 13b and a third electrode layer 13c can be formed in the same manner as the first end face side of the resin molded body.

[0153] Especially when the cathode lead-out layer is a metal foil, when the first electrode layer is set through the first electrode layer forming process, the adhesion between the metal foil and the first electrode layer can be improved, and therefore it is effective.

[0154] Example

[0155] The following examples illustrate the relationship between the number ratio of flattened particles and the adhesion force in relation to the electrolytic capacitor of the present invention. It should be noted that the present invention is not limited to these examples.

[0156] (Examples 1-7)

[0157] Using a sealing resin that includes epoxy resin and silica particles to Figure 1 and Figure 2 The laminated structure shown is sealed to obtain a resin molded body.

[0158] A first electrode layer was formed on the first end face of the resin molded body using aerosol deposition (AD method). Cu particles with a D50 of 1 μm were used as the metal microparticles, and the proportion of flat particles in the first electrode layer was changed by altering the film formation conditions in the aerosol deposition method.

[0159] A first electrode layer is also formed on the second end face of the resin molded body, similar to the first end face.

[0160] Subsequently, an electrode paste comprising Ag is applied to the end faces (first and second end faces) of the resin molded body by screen printing and then thermosetting to form a second electrode layer. Furthermore, a Ni plating layer and a Sn plating layer are formed on the surface of the second electrode layer as a third electrode layer to fabricate an electrolytic capacitor.

[0161] (Comparative Example 1)

[0162] The first and second end faces of the resin molded body were etched using an acid with nitric acid as the main component to form a Zn coating, thereby performing zincate treatment. Ni and Ag plating were then performed to form the first electrode layer.

[0163] The second and third electrode layers are formed in the same manner as in Example 1 to produce an electrolytic capacitor.

[0164] [Determination of the proportion of flattened particles]

[0165] The LT surface of the electrolytic capacitor was cross-sectionally ground, and the cross-section was observed using SEM / EDS (JEOL Ltd. JSM-7100F) to determine the ratio of flattened particles to Cu particles in the first electrode layer on the first end face side of the electrolytic capacitor. Table 1 shows the results.

[0166] [Evaluation of Adhesion]

[0167] For the aluminum plate that mimics the function of a valve, a metal film mimicking the first electrode layer was formed by aerosol deposition or plating, using the same method as in the embodiments and comparative examples.

[0168] The adhesion between the aluminum plate and the metal film was measured using a tensile testing machine.

[0169] Using an adhesive, the tensile terminal is bonded to the metal film within a 2.5mm × 5mm area, and the peel strength measured by lifting vertically is set as the adhesion force.

[0170] For the evaluation criteria of the adhesion force, 20N and above is set as ◎ (excellent), 15N and above is set as ○ (good), and less than 15N is set as △ (no practical problems). Table 1 shows the results.

[0171] [Table 1]

[0172]

[0173] Figure 9 This is an electron microscope image of the first electrode layer on the first end face side of the electrolytic capacitor in Example 2. The proportion of flattened particles obtained from this image is 84%. Figure 9 As illustrated, the first electrode layer formed by aerosol deposition becomes a first electrode layer comprising flattened particles.

[0174] In various embodiments, the first electrode layer includes flattened particles, forming a first electrode layer with high adhesion relative to the aluminum plate.

[0175] In contrast, in Comparative Example 1, a first electrode layer was formed by plating, and no flat particles were present in the first electrode layer. Furthermore, the adhesion of the first electrode layer to the aluminum plate was lower.

[0176] Explanation of reference numerals in the attached figures

[0177] 1. Electrolytic capacitors;

[0178] 3 anodes;

[0179] 4. Valve action on metal substrate;

[0180] 4a core;

[0181] 4b Porous portion;

[0182] 5. Dielectric layer;

[0183] 7. Cathode;

[0184] 7a Solid electrolyte layer;

[0185] 7b conductive layer;

[0186] 7c cathode lead-out layer;

[0187] 7d cathode lead-out section;

[0188] 8. Sealing resin;

[0189] 9. Resin molded body;

[0190] The first end face (outer surface of the resin molded body) of 9a resin molded body;

[0191] 9b The second end face of the resin molded body (outer surface of the resin molded body);

[0192] The bottom surface of the 9c resin molded body (the outer surface of the resin molded body);

[0193] The upper surface (outer surface) of the 9d resin molded body;

[0194] The first side surface of the 9e resin molded body (outer surface of the resin molded body);

[0195] 9f The second side surface of the resin molded body (outer surface of the resin molded body);

[0196] 11. External anode electrode;

[0197] 11a, 13a First electrode layers;

[0198] 11b, 13b second electrode layers;

[0199] 11c, 13c third electrode layer;

[0200] 13. External cathode electrode;

[0201] 15 flattened particles;

[0202] 16 is not a flat particle;

[0203] 20 capacitor elements;

[0204] 30-layer stack;

[0205] 51 Aerosol Deposition Device;

[0206] 52 carrier gases;

[0207] 53. Metal particles;

[0208] 54 Aerosol Generator;

[0209] 55 chambers;

[0210] 56 nozzles;

[0211] 57 units.

Claims

1. An electrolytic capacitor, comprising: A resin molded article comprising a laminate including capacitor elements and a sealing resin sealing the periphery of the laminate; and The anode external electrode and the cathode external electrode are disposed on the outer surface of the resin molded body. Its features are, The capacitor element includes: A valve-acting metal matrix having a core and a porous portion formed along the surface of the core, the end of the valve-acting metal matrix being exposed on the outer surface of the resin molded body; A dielectric layer is formed on the porous portion; A solid electrolyte layer is formed on the dielectric layer; and A conductive layer is formed on the solid electrolyte layer. The external cathode electrode is electrically connected to the conductive layer. The external anode electrode includes a first electrode layer that is directly connected to the core of the valve-acting metal substrate and does not include a glass phase. The first electrode layer includes flattened particles with an aspect ratio of 2 or more in the cross section of the outer surface of the valve-acting metal substrate exposed in the outer surface of the resin molded body and the main surface of the valve-acting metal substrate, which are respectively orthogonal to the outer surface of the first electrode layer.

2. The electrolytic capacitor according to claim 1, wherein, The first electrode layer comprises at least 30% of the flattened particles.

3. The electrolytic capacitor according to claim 1 or 2, wherein, The thickness of the first electrode layer formed in the core of the valve-acting metal substrate is 0.2 μm or more and 30 μm or less.

4. The electrolytic capacitor according to any one of claims 1 to 3, wherein, In a cross-section that is orthogonal to the outer surface of the exposed valve-acting metal substrate and the main surface of the valve-acting metal substrate and includes the first electrode layer, the cross-sectional shape of the first electrode layer is wedge-shaped.

5. The electrolytic capacitor according to any one of claims 1 to 4, wherein, The first electrode layer is an electrode layer comprising at least one selected from the group consisting of Cu, Ni, Sn, Ag, Zn and Au.

6. The electrolytic capacitor according to any one of claims 1 to 5, wherein, The external anode 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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