Solid electrolytic capacitors

Abstract

To provide a solid electrolytic capacitor with excellent capacitance and voltage resistance. [Solution] The solid electrolytic capacitor according to the present disclosure includes at least one capacitor element comprising an anode body having a porous portion on at least its surface, a dielectric layer covering the surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, wherein the solid electrolyte layer has a first portion filled in the voids of the porous portion in the anode body having the dielectric layer, and a second portion disposed on the outer surface of the anode body having the dielectric layer, the first portion comprising a self-doped conductive polymer, and the second portion comprising a non-self-doped conductive polymer.

Description

[Technical Field]

[0001] This disclosure relates to solid electrolytic capacitors. [Background technology]

[0002] A solid electrolytic capacitor comprises, for example, a capacitor element and an outer casing that encloses the capacitor element. The capacitor element comprises, for example, an anode, a dielectric layer formed on the surface of the anode, and a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolyte layer is formed, for example, by chemical polymerization or electrolytic polymerization, or by using a processing solution containing a conductive polymer. As the conductive polymer, for example, self-doped conductive polymers or non-self-doped conductive polymers are used.

[0003] Patent Document 1 proposes a "solid electrolytic capacitor comprising a capacitor element comprising a tantalum-containing anode; a dielectric disposed on the anode; and a solid electrolyte disposed on the dielectric, wherein the solid electrolyte comprises an intrinsically conductive polymer containing repeating thiophene units, the capacitor exhibits a dielectric strength of about 0.6 volts / nanometer or more, and further, the capacitor exhibits a charge-discharge capacitance after being subjected to a surge voltage for 3,000 cycles, and an initial capacitance before being subjected to said surge voltage, with the ratio of said charge-discharge capacitance to said initial capacitance being about 0.75 to 1." [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-506716 [Overview of the project] [Problems that the invention aims to solve]

[0005] Patent Document 1 discloses that various capacitor characteristics can be improved depending on the material type of the solid electrolyte layer and the state of the dielectric. However, there is a market demand for further improvements in various capacitor characteristics. In particular, there is no mention of the material of the solid electrolyte inside the anode, the pores formed inside the anode, the solid electrolyte formed inside these pores, or the details of the solid electrolyte on the outer surface of the anode. [Means for solving the problem]

[0006] One aspect of the present disclosure relates to a solid electrolytic capacitor comprising at least one capacitor element including an anode body having a porous portion on at least its surface, a dielectric layer covering the surface of the anode body, and a solid electrolyte layer covering at least a portion of the dielectric layer, wherein the solid electrolyte layer has a first portion filled in the voids of the porous portion in the anode body having the dielectric layer, and a second portion disposed on the outer surface of the anode body having the dielectric layer, the first portion comprising a self-doped conductive polymer, and the second portion comprising a non-self-doped conductive polymer. [Effects of the Invention]

[0007] The present disclosure aims to provide a solid electrolytic capacitor with excellent capacitance and voltage resistance. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view of a solid electrolytic capacitor according to one embodiment of the present disclosure. [Figure 2] This is a schematic cross-sectional enlargement view showing region II in Figure 1. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values, materials, etc. may be given as examples, but other numerical values, materials, etc. may be applied as long as the effects of this disclosure are obtained. In addition, components other than those characteristic of this disclosure may be replaced with components of known capacitors. In this specification, when "range of numerical value A to numerical value B" is used, that range includes numerical values ​​A and B. When multiple materials are given as examples, one of them may be selected and used alone, or two or more may be used in combination.

[0010] Furthermore, this disclosure encompasses any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims. In other words, any combination of matters described in two or more claims, which may be arbitrarily selected from the multiple claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0011] An electrolytic capacitor according to one embodiment of the present disclosure comprises a capacitor element. The form of the capacitor element is not particularly limited. The capacitor element comprises an anode portion and a cathode portion. The capacitor element comprises an anode body having a porous portion in at least its surface layer, a dielectric layer covering at least a portion of the surface of the anode body, and a solid electrolyte layer covering at least a portion of the dielectric layer. The anode body constitutes the anode portion. The solid electrolyte layer constitutes the cathode portion. The cathode portion may include a cathode extraction layer.

[0012] The solid electrolyte layer has a first portion and a second portion. The first portion is a part that fills the voids in the porous portion of the anode body, at least a part of which is a dielectric layer. The second portion, on the other hand, is a part that is located on the outer surface of the anode body having a dielectric layer (in other words, a part that extends beyond the main surface of the anode body).

[0013] A part of the first portion may not be filled into the voids of the porous part having the dielectric layer, and may protrude from the main surface of the porous part having the dielectric layer. That is, the first portion may have an inner layer filled into the voids of the porous part having the dielectric layer, and an outer layer protruding from the main surface of the porous part having the dielectric layer.

[0014] The second portion may be formed in a skin-like shape covering the anode body having the dielectric layer. A part of the second portion can be filled into the surface layer portion of the anode body (on the main surface side of the porous part) among the voids in the porous part having the dielectric layer.

[0015] At least the first portion contains a self-doped conductive polymer. The self-doped conductive polymer has a small particle size and is easily impregnated into the porous part, so that it can penetrate deep into the pores of the dielectric layer and cover a wider surface of the dielectric layer. Thereby, the capacitance can be extracted from the dielectric layer formed on the anode body. In addition, since the solid electrolyte layer in the voids of the porous part is made of the self-doped conductive polymer, high voltage resistance of the solid electrolytic capacitor can be achieved.

[0016] The porous part may contain a non-self-doped conductive polymer. In that case, the solid electrolyte constituting the first portion filled in the porous part has a larger amount of the self-doped conductive polymer than the non-self-doped conductive polymer. Thereby, high voltage resistance of the solid electrolytic capacitor can be achieved.

[0017] The ratio of the volume of the voids filled in the porous part to the volume of the solid electrolyte is preferably 1.0 or more, whereby high voltage resistance of the solid electrolytic capacitor can be achieved.

[0018] The thickness of the solid electrolyte layer in the second portion is preferably 1 μm or more and 200 μm or less.

[0019] As preferred embodiments of the solid electrolyte layer according to the present disclosure, the following embodiments can be exemplified. (First Embodiment) An anode body including a porous portion at least in a surface layer, a dielectric layer covering a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the solid electrolytic capacitor comprising at least one capacitor element including the above, wherein the solid electrolyte layer has a first portion filled in voids of the porous portion in the anode body having the dielectric layer, and a second portion disposed on an outer surface of the anode body having the dielectric layer, the first portion contains a self-doped conductive polymer, and the second portion contains a non-self-doped conductive polymer, solid electrolytic capacitor. (Second aspect) An anode body including a porous portion at least in a surface layer, a dielectric layer covering a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the solid electrolytic capacitor comprising at least one capacitor element including the above, wherein the solid electrolyte layer has a first portion filled in voids of the porous portion in the anode body having the dielectric layer, and a second portion disposed on an outer surface of the anode body having the dielectric layer, the first portion contains a self-doped conductive polymer, the second portion contains a non-self-doped conductive polymer, and a ratio of a volume of the voids in the porous portion to a volume of the solid electrolyte is 1.0 or more, the solid electrolytic capacitor according to any one of the preceding clauses. (Third aspect) An anode body including a porous portion at least in a surface layer, a dielectric layer covering a surface of the anode body, and a solid electrolyte layer covering at least a part of the dielectric layer, the solid electrolytic capacitor comprising at least one capacitor element including the above, wherein the solid electrolyte layer has a first portion filled in voids of the porous portion in the anode body having the dielectric layer, and a second portion disposed on an outer surface of the anode body having the dielectric layer, the first portion contains a self-doped conductive polymer, and the second portion contains a non-self-doped conductive polymer, The thickness of the solid electrolyte layer in the second part is between 1 μm and 200 μm. Solid electrolytic capacitor. (Fourth aspect) an anode body having a porous portion in at least its surface, A dielectric layer covering the surface of the anode, A capacitor element comprising a solid electrolyte layer covering at least a portion of a dielectric layer, The solid electrolyte layer is The anode body having a dielectric layer comprises a first portion filled in the voids of the porous portion and a second portion disposed on the outer surface of the anode body having a dielectric layer, The first part comprises a self-doped conductive polymer, and the second part comprises a non-self-doped conductive polymer. The second part further comprises the self-doped conductive polymer, the self-doped conductive polymer in the second part being disposed between the dielectric layer and the non-self-doped conductive polymer. Solid electrolytic capacitor.

[0020] The configuration of an example of an electrolytic capacitor related to this disclosure will be described in more detail below. [Solid electrolytic capacitors] A capacitor element included in a solid electrolytic capacitor includes an anode portion and a cathode portion. The cathode portion includes a solid electrolyte layer. Since the solid electrolytic capacitor and capacitor element according to this disclosure are mainly characterized by the solid electrolyte layer, there are no particular limitations on other components. Components used in known solid electrolytic capacitors may be applied to each component.

[0021] (Capacitor element) The anode portion of the capacitor element includes an anode body. A dielectric layer is formed on at least a portion of the surface of the anode body. A cathode portion is formed on at least a portion of the surface of the dielectric layer.

[0022] (Anode) The anode body is made of a conductive material. The anode body may be a sheet-like anode foil, or it may be a molded or sintered body of metal particles.

[0023] The conductive material constituting the anode may include valve metals, alloys containing valve metals, compounds containing valve metals, etc. The anode may contain one of these materials, or a combination of two or more. As valve metals, aluminum, tantalum, niobium, and titanium are preferred, for example.

[0024] The anode body has a porous region at least on its surface. The anode body has numerous fine voids in the porous region. Due to this porous region, the anode body has a fine, uneven surface.

[0025] An anode body having a porous portion on its surface can be obtained, for example, by roughening the surface of a substrate containing a valve-acting metal (such as a sheet-like substrate (e.g., foil-like or plate-like substrate)). Surface roughening may be performed, for example, by etching (electrolytic etching, chemical etching, etc.). Such an anode body (anode foil) has, for example, a core portion and porous portions formed integrally with the core portion on the surfaces of both the core portion and the core portion.

[0026] The anode body may be a sintered or molded body of particles containing a valve metal. The molded and sintered bodies are porous and may have a rectangular parallelepiped, cubic, or similar shape. As a sintered body, for example, it may be a sintered body of particles containing tantalum.

[0027] The anode body may have an electrode lead portion (also referred to as the anode lead portion) including a first end, and a cathode forming portion including a second end opposite to the first end. A cathode portion including a solid electrolyte layer is formed on the surface of the cathode forming portion of the anode body. The anode lead portion is used, for example, for electrical connection to an external electrode on the anode side. An anode lead terminal may be connected to the anode lead portion.

[0028] (Anode wire) If the anode body is a porous sintered or molded body, the anode portion may include an anode wire. The anode wire may be a metal wire. Examples of materials for the anode wire include the valve metals, copper, or copper alloys mentioned above. A portion of the anode wire is embedded in the anode body, and the remaining portion protrudes outward from the end face of the anode body. The outwardly protruding end of the anode wire corresponds to the first end, and the end of the anode body opposite the first end corresponds to the second end.

[0029] (Dielectric layer) The dielectric layer is formed to cover at least a portion of the surface of the anode or porous portion. The dielectric layer can be formed by known methods. The dielectric layer may also be formed by oxidizing the valve metal on the surface of the anode or porous portion by chemical conversion treatment or the like. The dielectric layer has a fine uneven surface shape that conforms to the surface shape of the porous portion.

[0030] The dielectric layer contains an oxide of the valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains tantalum oxide such as Ta2O5, and when aluminum is used as the valve metal, the dielectric layer contains aluminum oxide such as Al2O3. Note that the dielectric layer is not limited to these examples; any material that functions as a dielectric is acceptable.

[0031] (Cathode part) The cathode portion includes at least a solid electrolyte layer covering at least a portion of the dielectric layer. The solid electrolyte layer is formed via the dielectric layer in the portion on the second end side of the anode body (in other words, the cathode formation portion). The cathode portion typically includes a solid electrolyte layer covering at least a portion of the dielectric layer and a cathode extraction layer covering at least a portion of the solid electrolyte layer.

[0032] (Solid electrolyte layer) In a capacitor element, the solid electrolyte layer is formed to cover at least a portion of the dielectric layer. The solid electrolyte layer has a first portion that fills the voids in the porous part of the anode body having the dielectric layer, and a second portion that extends beyond the main surface of the anode body having the dielectric layer. The first portion contains a self-doped conductive polymer and an antioxidant, as described above. The first portion may further contain a non-self-doped conductive polymer.

[0033] (Self-doped conductive polymer) Self-doped conductive polymers, for example, have a conjugated polymer skeleton and functional groups (such as anionic groups) that function as dopants, directly or indirectly bonded to this skeleton by covalent bonds.

[0034] Examples of anionic groups include sulfo groups, carboxyl groups, phosphate groups, and phosphonic acid groups. Self-doped conductive polymers may contain one type of anionic group, or two or more types. From the viewpoint of easily ensuring higher conductivity of self-doped conductive polymers, self-doped conductive polymers may contain at least a sulfo group.

[0035] The anionic groups of a self-doped conductive polymer may be present in any form, such as anions, acids, esters, and salts, and may be present in a form that interacts with or is complexed with components contained in the solid electrolyte layer. In this specification, all of these forms are simply referred to as anionic groups.

[0036] Examples of conjugated polymers that constitute the backbone of self-doped conductive polymers include polymers with a π-conjugated polymer (such as polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene) as the basic backbone. The above polymers only need to contain at least one monomer unit that constitutes the basic backbone. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (such as substituted products having substituents). For example, polythiophene includes poly(3,4-ethylenedioxythiophene). Self-doped conductive polymers have anionic groups in the backbone of these conjugated polymers. The anionic groups may be directly introduced into the backbone of the conjugated polymer or introduced via linking groups. Preferred linking groups include polyvalent groups (divalent groups) containing alkylene groups. Examples of linking groups include aliphatic polyvalent groups (divalent groups, etc.) such as alkylene groups, -R 1 -XR 2 - group (X is an oxygen element or a sulfur element, R 1 and R 2 These are identical or different alkylene groups. The number of carbon atoms in each alkylene group included in the linking group is, for example, 1 to 10, or 1 to 6. The alkylene group may be linear or branched. The linking group may contain, for example, at least an alkylene group with 2 or more carbon atoms. The number of carbon atoms in such an alkylene group may be 2 to 10 (or 3 to 10), or 2 to 6 (or 3 to 6). For example, R 1 is an alkylene group having 1 to 6 carbon atoms, and R 2 The linking group may be an alkylene group having 2 or more (or 3 or more) and 10 or less carbon atoms. However, the linking group is not limited to these.

[0037] The conjugated polymer constituting the skeleton of the self-doping conductive polymer may be polypyrrole, polythiophene or polyaniline. From the viewpoint of easily obtaining high conductivity and the like, the self-doping conductive polymer is preferably a polymer having a conjugated polymer skeleton containing a repeating structure of monomer units corresponding to a thiophene compound, and an anionic group introduced into this skeleton.

[0038] Examples of the thiophene compound include compounds having a thiophene ring and capable of forming a repeating structure of the corresponding monomer units. The thiophene compound can be linked at the 2-position and 5-position of the thiophene ring to form a repeating structure of monomer units.

[0039] The thiophene compound may have a substituent at, for example, at least one of the 3-position and 4-position of the thiophene ring. The substituent at the 3-position and the substituent at the 4-position may be linked to form a ring fused to the thiophene ring. Examples of the thiophene compound include thiophene which may have a substituent at at least one of the 3-position and 4-position, and alkylenedioxythiophene compounds (C such as ethylenedioxythiophene compounds 2-4 alkylenedioxythiophene compounds, etc.). The alkylenedioxythiophene compounds also include compounds having a substituent on the alkylene group moiety.

[0040] Examples of the substituent include alkyl groups (C such as methyl group, ethyl group 1-4 alkyl group, etc.), alkoxy groups (C such as methoxy group, ethoxy group 1-4 alkoxy group, etc.), hydroxy groups, and hydroxyalkyl groups (hydroxy C such as hydroxymethyl group 1-4 alkyl group, etc.) are preferred, but not limited thereto. When the thiophene compound has two or more substituents, each substituent may be the same or different. The thiophene ring (in the case of an alkylenedioxythiophene ring, at least one of the thiophene ring and the alkylene group) may have, as a substituent, the aforementioned anionic group or a group containing an anionic group (for example, a sulfoalkyl group, etc.).

[0041] The self-doped conductive polymer may have a conjugated polymer backbone (such as PEDOT) containing a repeating structure of monomer units corresponding to at least a 3,4-ethylenedioxythiophene compound (such as 3,4-ethylenedioxythiophene (EDOT)). The conjugated polymer backbone containing a repeating structure of monomer units corresponding to at least EDOT may contain only monomer units corresponding to EDOT, or it may contain monomer units corresponding to thiophene compounds other than EDOT in addition to those monomer units.

[0042] An example of monomer units for self-doped conductive polymers is shown below.

[0043] [ka]

[0044] The weight-average molecular weight (Mw) of the self-doped conductive polymer may be between 1,000 and 1,000,000, or between 1,000 and 50,000.

[0045] In this specification, the weight-average molecular weight (Mw) is the polystyrene-converted value measured by gel permeation chromatography (GPC). GPC is typically measured using a polystyrene gel column and water / methanol (volume ratio 8 / 2) as the mobile phase.

[0046] (Non-self-doped conductive polymer) The non-self-doped conductive polymer includes, for example, a non-self-doped conjugated polymer (e.g., a conjugated polymer without anionic groups) and a dopant.

[0047] Examples of conjugated polymers include those exemplified as conjugated polymers constituting the backbone of self-doped conductive polymers (such as π-conjugated polymers). Conjugated polymers may be used individually or in combination of two or more types. From the viewpoint of easily ensuring high initial capacity and voltage resistance, as well as high heat resistance, unself-doped conjugated polymers containing repeating structures of monomer units of thiophene compounds may be used. Examples of thiophene compounds corresponding to the monomer units of unself-doped conjugated polymers include the thiophene compounds described for self-doped conductive polymers. Unself-doped conjugated polymers may include conjugated polymers (such as PEDOT) containing repeating structures of monomer units corresponding to at least 3,4-ethylenedioxythiophene compounds (such as EDOT). Conjugated polymers containing repeating structures of monomer units corresponding to at least EDOT may contain only the monomer units corresponding to EDOT, or they may contain monomer units corresponding to thiophene compounds other than EDOT in addition to the monomer units.

[0048] The dopant can be at least one selected from the group consisting of anions and polyanions (polymer anions, etc.). Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions. Examples of dopants that generate sulfonate ions include p-toluenesulfonic acid and naphthalenesulfonic acid. Polymer anions may be used from the viewpoint of easily obtaining higher heat resistance and reliability, as well as higher dielectric strength. Examples of polymer anions having a sulfo group include high molecular weight polysulfonic acid. Specific examples of polymer anions include polyvinylsulfonic acid, polystyrenesulfonic acid (PSS (including copolymers and substituted products having substituents)), polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylatesulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, polyestersulfonic acid (aromatic polyestersulfonic acid, etc.), and phenolsulfonic acid novolac resin. However, Dopants are not limited to these specific examples. A single Dopant may be used alone, or two or more may be used in combination.

[0049] In a non-self-doped conductive polymer, the amount of dopant may be 10 to 1000 parts by mass, or 20 to 500 parts by mass, per 100 parts by mass of the conjugated polymer.

[0050] (Method for forming a solid electrolyte layer) The process of forming a solid electrolyte layer so as to cover at least a portion of the dielectric layer includes, for example, a first step of forming a first portion and a second step of forming a second portion. The process may further include any processing between the first and second steps.

[0051] (First step in forming the first part) The first step involves forming a first layer containing a self-doped conductive polymer.

[0052] (Process for forming the first layer) In the step of forming the first layer, for example, the first layer may be formed using a processing solution (first processing solution) containing a self-doped conductive polymer. More specifically, the first processing solution containing a self-doped conductive polymer is applied to the dielectric layer to form the first layer. The dielectric layer may be dried after the first processing solution is applied. If necessary, the application of the first processing solution to the dielectric layer and drying may be repeated two or more times.

[0053] The first processing solution includes, for example, a self-doped conductive polymer and a liquid medium. The first processing solution may contain one type of self-doped conductive polymer, or two or more types. The liquid medium is, for example, a medium that is liquid at room temperature (e.g., 20°C to 35°C). Examples of liquid media include water, organic solvents, or mixtures thereof. Water is preferred among these.

[0054] The first treatment solution may be a dispersion in which particles of self-doped conductive polymer are dispersed in a liquid medium, or it may be a solution in which the self-doped conductive polymer is dissolved in a liquid medium. Self-doped conductive polymers have relatively flexible polymer chains, and the positions of functional groups such as anionic groups are random. In addition, self-doped conductive polymers have low orientation of polymer chains and low crystallinity. Therefore, compared to non-self-doped conductive polymers, they are easier to dissolve in a liquid medium or dispersed in particulate form. As a result, the viscosity of the first treatment solution is relatively low, and it is easy to impregnate the voids in the porous part with high permeability.

[0055] The concentration of the self-doped conductive polymer in the first processing solution may be 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less.

[0056] (Process for forming the second layer) In the step of forming the second layer, for example, the second layer may be formed using a treatment solution (second treatment solution) containing a non-self-doped conductive polymer. More specifically, the second treatment solution containing a non-self-doped conductive polymer is applied to the dielectric layer to form the second layer. The dielectric layer may be dried after the second treatment solution is applied. If necessary, the application of the second treatment solution to the dielectric layer and drying may be repeated two or more times.

[0057] The second treatment solution includes, for example, a non-self-doped conductive polymer and a liquid medium. The second treatment solution may be a dispersion in which particles of the non-self-doped conductive polymer are dispersed in the liquid medium. Examples of the liquid medium include water, an organic solvent, or a mixture thereof. Water is preferred among these.

[0058] The concentration of the non-self-doped conductive polymer in the second processing solution may be 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less.

[0059] Furthermore, in the step of forming the second layer, the second layer may be formed using a processing solution (second processing solution) containing a monomer of a non-self-doped conductive polymer, an oxidizing agent / dopant, and a liquid solvent. More specifically, the capacitor element may be immersed in the second processing solution and then dried. If necessary, the application of the second processing solution to the dielectric layer and drying may be repeated two or more times.

[0060] (Second step in forming the second part) The second step involves forming a second portion, which covers at least a part of the first portion, using a processing solution (second processing solution) containing a non-self-doped conductive polymer, so as to extend beyond the main surface of the anode body having a dielectric layer. More specifically, the second processing solution containing the non-self-doped conductive polymer is applied to the dielectric layer to form the second portion. The first portion may be dried after the second processing solution has been applied.

[0061] The second treatment solution includes, for example, a non-self-doped conductive polymer and a liquid medium. The second treatment solution may contain one or more self-doped conductive polymers in addition to the non-self-doped conductive polymer. Examples of the liquid medium include water, an organic solvent, or a mixture thereof. Water is preferred among these.

[0062] The concentration of the non-self-doped conductive polymer in the second processing solution may be 0.5% by mass or more and 5% by mass or less, or 1% by mass or more and 3% by mass or less. Large particle sizes of the non-self-doped conductive polymer are less likely to fill the pores inside the porous part of the anode body, and tend to form a skin-like film of the non-self-doped conductive polymer on the outside of the porous part.

[0063] Furthermore, this second step may involve using a processing solution (second processing solution) containing monomers of a non-self-doped conductive polymer, an oxidizing agent / dopant, and a liquid solvent to form a second portion that covers at least a part of the first portion, extending beyond the main surface of the anode body having a dielectric layer. More specifically, the capacitor element may be immersed in the second processing solution and then dried. If necessary, the application of the second processing solution to the dielectric layer and drying may be repeated two or more times. By increasing the viscosity of the second processing solution, the non-self-doped conductive polymer is less likely to fill the pores of the porous portion of the anode body, and a film of the non-self-doped conductive polymer is more likely to form on the outside of the porous portion in a skin-like manner.

[0064] (Cathode extraction layer) The cathode extraction layer may include, for example, a first extraction layer that is in contact with the solid electrolyte layer and covers at least a portion of the solid electrolyte layer. The cathode extraction layer may also include a first extraction layer and a second extraction layer that covers at least a portion of the first extraction layer.

[0065] Examples of the first extraction layer include a layer containing conductive particles and a metal foil. Examples of conductive particles include at least one selected from conductive carbon and metal powder. The cathode portion (more specifically the cathode extraction layer) may include a layer containing metal powder (such as a metal particle-containing layer). The cathode extraction layer may consist, for example, a layer containing conductive carbon as the first extraction layer (carbon layer) and a layer containing metal powder (such as a metal particle-containing layer) or a metal foil as the second extraction layer.

[0066] If the cathode extraction layer includes a metal foil or a metal particle-containing layer, the entire cathode extraction layer may be composed of the metal foil or metal particle-containing layer. Alternatively, at least one of the first and second extraction layers may be composed of the metal particle-containing layer.

[0067] Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).

[0068] A layer containing metal powder, which serves as a second extraction layer, can be formed, for example, by laminating a composition containing metal powder onto the surface of the first extraction layer. An example of such a second extraction layer is a metal particle-containing layer formed using a paste containing metal powder and a resin binder. While thermoplastic resins can be used as the resin binder, thermosetting resins such as imide resins and epoxy resins are preferred. From the viewpoint of easily obtaining high conductivity in the second extraction layer, silver-containing particles may be used as the metal powder. Examples of silver-containing particles include silver particles and silver alloy particles. The second extraction layer may contain one type of silver-containing particle, or a combination of two or more types. The silver particles may contain small amounts of impurities.

[0069] When a metal foil is used as the first lead layer, the type of metal is not particularly limited. Preferably, the metal foil is a valve metal (such as aluminum, tantalum, or niobium) or an alloy containing a valve metal. The surface of the metal foil may be roughened as needed. The surface of the metal foil may be coated with a chemical conversion film, or a coating of a metal different from the metal constituting the metal foil (a dissimilar metal) or a nonmetal. Examples of dissimilar metals or nonmetals include metals such as titanium or nonmetals such as carbon (such as conductive carbon).

[0070] The above-mentioned dissimilar metal or nonmetal (for example, conductive carbon) coating may be used as the first draw-out layer, and the above-mentioned metal foil may be used as the second draw-out layer.

[0071] The cathode extraction layer is formed by known methods depending on its layer configuration. For example, if the cathode extraction layer includes a metal foil as a first or second extraction layer, the first or second extraction layer is formed by laminating the metal foil so as to cover at least a portion of the solid electrolyte layer or the first extraction layer. The first extraction layer containing conductive particles is formed, for example, by applying a conductive paste or liquid dispersion containing conductive particles and optionally a resin binder (water-soluble resin, curable resin, etc.) to the surface of the solid electrolyte layer. The second extraction layer containing metal powder is formed, for example, by applying a paste containing metal powder and a resin binder to the surface of the first extraction layer. During the process of forming the cathode extraction layer, drying treatment, heat treatment, etc., may be performed as needed.

[0072] The capacitor element is sealed using a resin casing. For example, the capacitor element and the resin material for the casing (e.g., uncured thermosetting resin and filler) may be placed in a mold, and the capacitor element may be sealed with the resin casing by a transfer molding method, compression molding method, or the like. In this case, the other ends of the anode lead terminal and cathode lead terminal connected to the anode lead drawn out from the capacitor element are exposed from the mold. The leads may be wire-shaped or frame-shaped (e.g., lead frame).

[0073] Figure 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to one embodiment of the present disclosure. The solid electrolytic capacitor 20 includes a capacitor element 10 including an anode portion 6 and a cathode portion 7, an outer casing 11 that encloses the capacitor element 10, an anode lead frame 13 electrically connected to the anode portion 6, and a cathode lead frame 14 electrically connected to the cathode portion 7.

[0074] The anode section 6 comprises an anode body 1 and an anode wire 2. A portion of the anode wire 2 is embedded within the anode body 1, while the remaining portion protrudes outward from the outer surface of the anode body 1. A portion of the first part of the anode lead frame 13 is joined to this protruding portion of the anode wire 2 by welding or other means, and is electrically connected to it.

[0075] A dielectric layer 3 is formed on the surface of the anode 1. The cathode 7 has a solid electrolyte layer 4 that covers at least a portion of the dielectric layer 3 and a cathode extraction layer 5 that covers at least a portion of the surface of the solid electrolyte layer 4. The cathode extraction layer 5 has a carbon layer formed to cover at least a portion of the surface of the solid electrolyte layer 4 and a metal particle-containing layer formed to cover at least a portion of the carbon layer. A portion of the first part of the cathode lead frame 14 is bonded to and electrically connected to the cathode extraction layer 5 via a conductive adhesive layer 8.

[0076] Figure 2 is a schematic cross-sectional enlargement view showing region II of Figure 1. A dielectric layer 3 is formed on the surface of the anode 1. The solid electrolyte layer consists of a first portion 41 filled in the voids of the porous portion and a second portion 42 placed on the outer surface of the anode 1. The first portion 41 is formed between the dielectric layer 3 and the second portion 42 on the outer surface of the anode 1. A carbon layer 51 is placed on the upper surface of the second portion 42, and a silver paste layer 52 is placed on the upper surface of the carbon layer 51.

[0077] Although the present invention has been described in relation to preferred embodiments at present, such disclosures should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosures. [Industrial applicability]

[0078] The solid electrolytic capacitors relating to this disclosure can be used in applications where excellent capacitance and voltage resistance are required. [Explanation of Symbols]

[0079] 20: Solid electrolytic capacitors 10: Capacitor element 1: Anode 2: Anode wire 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode extraction layer 6: Anode section 7: Cathode 8: Conductive adhesive layer 11: Exterior 13: Anode lead frame 14: Cathode lead frame 41: Part 1 42:Second part 51: Carbon layer 52: Silver paste layer

Claims

1. an anode body having a porous portion in at least its surface, A dielectric layer covering the surface of the anode body, The capacitor element includes at least one capacitor element comprising a solid electrolyte layer covering at least a portion of the dielectric layer, The solid electrolyte layer is The anode body having the dielectric layer comprises a first portion filled in the voids of the porous portion and a second portion disposed on the outer surface of the anode body having the dielectric layer, The first portion comprises a self-doped conductive polymer, and the second portion comprises a non-self-doped conductive polymer. Solid electrolytic capacitor.

2. The ratio of the volume of the voids within the porous portion to the volume of the solid electrolyte is 1.0 or greater. The solid electrolytic capacitor according to claim 1.

3. The thickness of the solid electrolyte layer in the second portion is 1 μm or more and 200 μm or less. The solid electrolytic capacitor according to claim 2.

4. The second portion further comprises the self-doped conductive polymer, wherein the self-doped conductive polymer in the second portion is disposed between the dielectric layer and the unself-doped conductive polymer. The solid electrolytic capacitor according to claim 3.

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