Solid electrolytic capacitor

Abstract

The solid electrolytic capacitor includes a capacitor element and a cathode lead-out layer. The capacitor element is provided with a film-like valve-action metal substrate, a dielectric layer, and a solid electrolyte layer containing a conductive polymer. The solid electrolyte layer contains inorganic particles. The capacitor element and the cathode lead-out layer are laminated in a state in which the solid electrolyte layer and the cathode lead-out layer are in contact with each other. The concentration of the inorganic particles in the solid electrolyte layer decreases in a direction from a contact surface between the solid electrolyte layer and the cathode lead-out layer toward the valve action metal substrate. The concentration of the inorganic particles contained in the solid electrolyte layer is the highest on the surface where the solid electrolyte layer and the cathode are in contact.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor having a structure in which a capacitor element having a dielectric layer and a solid electrolyte layer formed on a valve-acting metal body and a cathode film are laminated. Background Art

[0002] The solid electrolytic capacitor of Patent Document 1 includes an anode containing a valve-acting metal (valve metal), a dielectric layer containing an oxide layer of the valve-acting metal, and a cathode containing a conductive polymer layer formed on the dielectric layer. At this time, the bonding area between the cathode current collector and the cathode is increased by roughening the surface of the cathode current collector connected to the cathode, or embedding carbon particles in the surface, or forming a carbon thin film layer on the surface.

[0003] In addition, the solid electrolytic capacitor of Patent Document 2 includes an anode body, a dielectric layer formed on the surface of the anode body, and a solid electrolyte layer covering a part of the dielectric layer. The solid electrolyte layer includes a conductive polymer, a binder, and conductive inorganic particles. With this structure, the film strength of the solid electrolyte layer is improved, and the increase in resistance in the solid electrolyte layer is reduced, suppressing the increase in the ESR of the solid electrolytic capacitor.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 11-219861

[0007] Patent Document 2: Japanese Patent Laid-Open No. 2019-87558 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, the conductive polymer in the structure of Patent Document 1 softens at the mounting temperature of the solid electrolytic capacitor (for example, exceeding 200°C). That is, the conductive polymer flows, and even if the bonding area between the cathode current collector and the cathode is increased, the anode, the conductive polymer, and the cathode current collector may not achieve good adhesion.

[0010] In addition, in the structure of Patent Document 2, although a structure in which the solid electrolyte layer contains conductive inorganic particles is shown, the position of the inorganic particles is not clearly defined. That is, even if the inorganic particles are included on the solid electrolyte layer side, as in Patent Document 1, depending on the position where the inorganic particles are included, the solid electrolyte layer softens and flows. Therefore, the anode, the solid electrolyte layer, and the cathode layer may not achieve good adhesion.

[0011] Therefore, an object of the present invention is to provide a solid electrolytic capacitor that suppresses internal peeling insulation and suppresses an increase in ESR.

[0012] Technical solution for solving the problem

[0013] The solid electrolytic capacitor of the present invention includes a capacitor element and a cathode lead-out layer. The capacitor element includes a film-like valve-acting metal substrate, a dielectric layer, and a solid electrolyte layer containing a conductive polymer. The solid electrolyte layer contains inorganic particles. The capacitor element and the cathode lead-out layer are laminated in a state where the solid electrolyte layer and the cathode lead-out layer are in contact. In the direction from the contact surface of the solid electrolyte layer and the cathode lead-out layer toward the valve-acting metal substrate, the concentration of inorganic particles in the solid electrolyte layer decreases. At the surface where the solid electrolyte layer abuts against the cathode, the concentration of inorganic particles contained in the solid electrolyte layer is the highest.

[0014] In this structure, the solid electrolyte layer in the region where the solid electrolyte layer and the cathode are in contact contains inorganic particles. There is a difference in the coefficient of thermal expansion between the conductive polymer and the inorganic particles in the solid electrolyte layer. Therefore, by changing the concentration of the inorganic particles stepwise, the coefficient of thermal expansion is changed stepwise. That is, even when thermal strain occurs when the solid electrolytic capacitor is heated and pressurized, a sharp change caused by the thermal strain can be suppressed. That is, through this stepwise change in thermal strain, the adhesion strength between the solid electrolyte layer and the cathode is improved. In other words, the close contact between the capacitor element and the cathode is improved, and an increase in ESR can be suppressed.

[0015] Advantages of the invention

[0016] According to the present invention, it is possible to provide a solid electrolytic capacitor that suppresses internal peeling insulation and suppresses an increase in ESR. Description of the drawings

[0017] Figure 1 is an external perspective view of a solid electrolytic capacitor according to the first embodiment.

[0018] Figure 2 is a side cross-sectional view showing the structure of a solid electrolytic capacitor according to the first embodiment.

[0019] Figure 3 (A) is a top view of the capacitor element, Figure 3 (B) is a side cross-sectional view of the capacitor element.

[0020] Figure 4 (A), Figure 4 (B) is a cross-sectional view showing the structure of the outer layer CP.

[0021] Figure 5It is a flowchart showing an example of a schematic process of a method for manufacturing a solid electrolytic capacitor according to this embodiment.

[0022] Figure 6 (A) of is a perspective external view of a capacitor element sheet, Figure 6 and (B) of is a perspective external view of a cathode sheet.

[0023] Figure 7 It is a perspective external view of a laminate of a capacitor element sheet and a cathode sheet (sheet-type capacitor laminate).

[0024] Figure 8 (A) of is a side cross-sectional view showing the structure of an outer-layer CP and a cathode film according to the second embodiment, Figure 8 and (B) of is a side cross-sectional view showing the shape of a recess formed in the cathode film. Detailed embodiments

[0025] [First Embodiment]

[0026] Regarding the solid electrolytic capacitor according to the first embodiment of the present invention and the method for manufacturing the solid electrolytic capacitor, it will be described with reference to the drawings.

[0027] (Explanation of the structure of the solid electrolytic capacitor 10)

[0028] Figure 1 It is a perspective external view of the solid electrolytic capacitor according to the embodiment of the present invention. Figure 2 It is a side cross-sectional view showing the structure of the solid electrolytic capacitor according to the embodiment of the present invention. Figure 2 It is a cross-sectional view based on a plane orthogonal to the top surface, bottom surface, and end surfaces of the body of the solid electrolytic capacitor. In addition, in Figure 2 , for easy understanding of the structure, the dimensions in each direction are appropriately emphasized, and in particular, the dimension in the height direction (the z-axis direction in the figure) is emphasized.

[0029] As Figure 1 , Figure 2 shown, the solid electrolytic capacitor 10 includes a body 11, resin electrodes 71, resin electrodes 72, external electrodes 81, and external electrodes 82.

[0030] The body 11 has a rectangular parallelepiped shape and has a top surface, a bottom surface, end surfaces 111, end surfaces 112, and two side surfaces. The body 11 includes a plurality of capacitor elements 20, a plurality of cathode films 30, an insulating resin 50, and an insulator layer 500. The cathode film 30 corresponds to the "cathode lead-out layer" of the present invention.

[0031] (Capacitor element 20)

[0032] Figure 3(A) is a top view of the capacitor element, Figure 3 (B) is a side cross-sectional view of the capacitor element. Figure 3 (B) is a cross-sectional view based on a plane orthogonal to the flat film surface and the end surface of the capacitor element.

[0033] As Figure 3 shown in (A), Figure 3 (B) of, the capacitor element 20 includes an anode electrode 21, an inner layer CP22, and an outer layer CP23. The solid electrolyte layer 25 is formed by the inner layer CP22 and the outer layer CP23.

[0034] The anode electrode 21 is in the form of a flat film and has end surfaces 211, 212, flat film surfaces 213, 214. In Figure 3 (A), Figure 3 (B), the illustration of the detailed structure is omitted, but the anode electrode 21 has many holes recessed from the flat film surfaces 213, 214. In other words, a portion of a given thickness near the flat film surfaces 213, 214 in the anode electrode 21 is a porous body in a porous state. The thickness ratio of the porous body and the core part on one side of the anode electrode 21 to the porous body on the other side is about 1:1:1. The dielectric layer 210 covers the outer surface of the anode electrode 21. In Figure 3 (B), the illustration of the detailed structure of the anode electrode 21 is omitted, so the dielectric layer 210 is schematically illustrated as covering the macroscopic surface (flat film surfaces 213, 214) of the anode electrode 21. However, in reality, the dielectric layer 210 not only covers the macroscopic surface (flat film surfaces 213, 214) of the anode electrode 21, but also covers the inner surfaces of many holes of the anode electrode 21.

[0035] The anode electrode 21 includes, for example, metal monomers such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, silicon, or alloys containing these metals. In addition, the anode electrode 21 is preferably aluminum or an aluminum alloy. The anode electrode 21 only needs to be a valve action metal body (valve action metal matrix) that exhibits a so-called valve action.

[0036] The inner layer CP22 covers the surface of the dielectric layer 210. The inner layer CP22 contains a conductive polymer. The inner layer CP22 fills the fine recesses of the porous part.

[0037] The outer layer CP23 covers the surface of the inner layer CP22. In other words, for example, the outer layer CP23 is formed as a layer covering the entire dielectric layer 210 after the inner layer CP22 in which fine recesses for filling the porous part are formed. The outer layer CP23 contains the same material as the inner layer CP22 and contains inorganic particles. In addition, the outer layer CP23 may be a material (including composition) different from that of the inner layer CP22. At this time, as will be described later, for example, the inner layer CP22 can be formed of poly-PEDOT [(3,4-ethylenedioxythiophene): PSS (polystyrene sulfonic acid)], and the outer layer CP23 can be formed of polypyrrole. The detailed structure of the outer layer CP23 will be described later.

[0038] The insulator layer 500 is formed near the end faces 211 and 212 of the flat film surfaces 213 and 214 of the anode electrode 21. The insulator layer 500 is a frame that limits the formation regions of the inner layer CP22 and the outer layer CP23. Thereby, for example, the inner layer CP22 and the outer layer CP23 do not reach the end face 211 in the anode electrode 21.

[0039] With such a structure, the anode electrode 21 and the solid electrolyte layer (the laminate of the inner layer CP22 and the outer layer CP23) face each other with the dielectric layer 210 interposed therebetween, and the capacitor element 20 functions as a capacitor having a given electrostatic capacitance.

[0040] (Cathode film 30)

[0041] The cathode film 30 is a flat film-like metal film. For example, the cathode film 30 is formed of, for example, aluminum, titanium, copper, silver, or the like.

[0042] (Laminated structure of a plurality of capacitor elements 20 and a plurality of cathode films 30)

[0043] A plurality of capacitor elements 20 and a plurality of cathode films 30 are arranged such that their flat film surfaces are substantially parallel to the top surface and the bottom surface of the main body 11. The plurality of capacitor elements 20 and the plurality of cathode films 30 are alternately laminated in the direction orthogonal to the top surface and the bottom surface (the height direction of the main body 11 (the z-axis direction in the figure)). In addition, in Figure 2 , the number of the plurality of capacitor elements 20 is 3, and the number of the plurality of cathode films 30 is 4, but it is not limited thereto.

[0044] At this time, the capacitor element 20 and the cathode film 30 adjacent to each other in the lamination direction are in contact. More specifically, the flat film surface of the cathode film 30 is in contact with the outer surface 230 of the outer layer CP23 of the capacitor element 20.

[0045] (Structure of the main body 11)

[0046] Such a laminate of a plurality of capacitor elements 20 and a plurality of cathode films 30 is covered with an insulating resin 50. Thereby, the main body 11 is formed.

[0047] End surfaces 211 of the capacitor elements 20 are exposed from the end surface 111 of the body 11 to the outside of the body 11. In addition, end surfaces 311 of the cathode films 30 are exposed from the end surface 112 of the body 11 to the outside of the body 11.

[0048] (Structure of terminal conductor)

[0049] Resin electrode 71 contacts and covers end surface 111 of body 11. Thus, resin electrode 71 is connected to end surfaces 211 of multiple capacitor elements 20. External electrode 81 is a laminated structure consisting of electrode film 811 and electrode film 812. Electrode film 811 covers the outer surface of resin electrode 71. Electrode film 812 covers the outer surface of electrode film 811. Resin electrode 71 and external electrode 81 constitute a first terminal conductor.

[0050] The resin electrode 72 contacts and covers the end surface 112 of the body 11. This connects the resin electrode 72 to the end surfaces 311 of the plurality of cathode films 30. The external electrode 82 comprises a laminated structure of an electrode film 821 and an electrode film 822. The electrode film 821 covers the outer surface of the resin electrode 72. The electrode film 822 covers the outer surface of the electrode film 821. The resin electrode 72 and the external electrode 82 constitute a second terminal conductor.

[0051] With the above structure, the solid electrolytic capacitor 10 can be realized.

[0052] (Outer layer CP23)

[0053] Figure 4 (A) Figure 4 (B) is a cross-sectional view showing the structure of the outer layer CP23. Figure 4 (A) Figure 4 The outer layer CP23 shown in (B) comprises multiple conductive polymers (hereinafter referred to as conductive polymer layers 231, 232, 233, 234, and 235). For convenience, the outer layer CP23 is described as being composed of multiple conductive polymer layers 231, 232, 233, 234, and 235. However, in reality, the outer layer CP23 is formed from a single layer. Furthermore, the dashed lines separating the conductive polymer layers 231, 232, 233, 234, and 235 are shown hypothetically to illustrate the concentration distribution of the inorganic particles contained in the conductive polymer layers. The structure of the outer layer CP23 will be described in more detail later.

[0054] (Connection structure of outer layer CP23 and cathode film 30)

[0055] In the above structure, the contact portion between the outer layer CP23 and the cathode film 30 has the following structure.

[0056] As shown in Figure 4 (A) of FIG. Figure 4 , the conductive polymer layers 231-235 include a plurality of inorganic particles 250. As the material of the inorganic particles 250, metals such as silicon (Si), cobalt (Co), chromium (Cr), zinc (Zn), molybdenum (Mo), etc., their oxides or their complexes, or compounds containing them are preferably used.

[0057] The conductive polymer layer 235 is the layer in contact with the cathode film 30, and the conductive polymer layer 231 is the layer in contact with the inner layer CP22 (refer to Figure 4 (B) of FIG. Figure 4 ). The surface of the conductive polymer layer 231 in contact with the inner layer CP22 corresponds to the "contact surface" of the present invention.

[0058] In Figure 4 (A) of FIG. Figure 4 and Figure 4 (B) of FIG. Figure 4 , in the structure of the outer layer CP23, the concentration of the inorganic particles 250 contained in the plurality of conductive polymer layers 231-235 changes stepwise. For example, regarding the concentration of the inorganic particles 250, the conductive polymer layer 234 is lower than the conductive polymer layer 235, and the conductive polymer layer 233 is lower than the conductive polymer layer 234. And, regarding the concentration of the inorganic particles 250, the conductive polymer layer 232 is lower than the conductive polymer layer 233, and the conductive polymer layer 231 is lower than the conductive polymer layer 232. The structure in which the concentration of the inorganic particles 250 contained in the plurality of conductive polymer layers 231-235 changes stepwise is achieved by separately coating the conductive polymer layers 231-235 with different concentrations of the inorganic particles 250 in multiple stages.

[0059] In this way, in the conductive polymer layers 231, 232, 233, 234, 235 constituting the outer layer CP23, the concentration of the inorganic particles is lowered in proportion to the distance from the cathode film 30. In other words, in the outer layer CP23, the inorganic particles 250 are biased toward the surface side in contact with the cathode film 30.

[0060] At this time, the thermal expansion coefficients of the conductive polymer layers 231, 232, 233, 234, 235 forming the outer layer CP23 and the inorganic particles 250 contained in the outer layer CP23 are different. More specifically, the thermal expansion coefficient of the conductive polymer in the outer layer CP23 is high. On the other hand, the thermal expansion coefficient of the inorganic particles 250 in the outer layer CP23 is low. That is, by heating and pressurizing the solid electrolytic capacitor 10, a thermal expansion difference is generated between the conductive polymer layers 231, 232, 233, 234, 235 and the inorganic particles 250. Therefore, different thermal strains are generated in each of the conductive polymer layers of the conductive polymer layers 231, 232, 233, 234, 235.

[0061] By having such a difference in thermal strain, a sharp change in thermal strain is not generated, and accordingly, the bonding strength between the outer layer CP23 and the cathode film 30 is increased. That is, it is possible to increase the bonding strength of the surface where the outer layer CP23 and the cathode film 30, which are most likely to peel off inside during heating and pressurizing of the solid electrolytic capacitor 10, are in contact with each other.

[0062] Moreover, as described above, from the conductive polymer layer 235 to the conductive polymer layer 231, the concentration of the inorganic particles 250 contained therein gradually (gradually) decreases. Therefore, the concentration of the inorganic particles 250 in the interior of the outer layer CP23 (for example, the conductive polymer layer 233) is lower than that in the conductive polymer layer 235. Therefore, the flexibility is higher inside the outer layer CP23. The structure in which the concentration of the particles 237 facing the inside of the outer layer CP23 is low also functions as a stress relaxation region for deformation accompanying an increase in shear and internal pressure caused by the difference in thermal expansion coefficient. Therefore, peeling inside the solid electrolytic capacitor 10 can be more effectively suppressed.

[0063] In addition, a plurality of cathode films 30 are connected to the resin electrode 72. In this structure, both the cathode film 30 and the resin electrode 72 contain a resin component. Thereby, the difference in physical properties between the cathode film 30 and the resin electrode 72 is reduced, and peeling insulation between the cathode film 30 and the resin electrode 72 can be suppressed.

[0064] (Manufacturing method of the solid electrolytic capacitor 10)

[0065] The solid electrolytic capacitor 10 including the above structure is manufactured, for example, as follows. Figure 5 is a flowchart showing an example of the schematic process of the manufacturing method of the solid electrolytic capacitor according to the present embodiment. Figure 6 In (A), it is a perspective view of the appearance of the capacitor element sheet, Figure 6 In (B), it is a perspective view of the appearance of the cathode sheet. Figure 7 is a perspective view of the appearance of a laminate (sheet-type capacitor laminate) of the capacitor element sheet and the cathode sheet.

[0066] Form a capacitor element sheet 20M (S11). As Figure 6 shown in (A), the capacitor element sheet 20M is a sheet in which a plurality of capacitor elements 20 are two-dimensionally arranged. The specific structure of the plurality of capacitor elements 20 is as described above, including an anode electrode 21, a dielectric layer 210, an inner layer CP22, and an outer layer CP23, and an insulator layer 500 for the inner layer CP22 and the outer layer CP23 is formed.

[0067] Form a cathode sheet 30M (S12). As Figure 6As shown in (B) thereof, the cathode sheet 30M is a sheet in which a plurality of cathode films 30 are two-dimensionally arranged. The arrangement pitch of the plurality of cathode films 30 is the same as the arrangement pitch of the plurality of capacitor elements 20.

[0068] The plurality of capacitor element sheets 20M and the plurality of cathode sheets 30M are sequentially laminated and heat-pressed (S13). More specifically, the plurality of capacitor element sheets 20M and the plurality of cathode sheets 30M are laminated such that the outer surfaces 230 of the plurality of outer layers CP23 of the capacitor element sheets 20M adjacent in the lamination direction face and abut against the portions of the cathode films 30 of the cathode sheet 30M. Thereby, a sheet-type capacitor laminate is formed. Then, the sheet-type capacitor laminate is heated and pressurized. By this heating and pressurization, the difference in the coefficient of thermal expansion in the surfaces where the outer layer CP23 and the cathode film 30 abut shows a stepwise change and does not change abruptly. Thereby, the difference in thermal strain is suppressed, and the bonding strength between the outer layer CP23 and the cathode film 30 is increased.

[0069] The sheet-type capacitor laminate is cut along the Figure 7 cutting lines CL1 and CL2 as shown to be made into individual pieces (S14). At this time, since the cathode sheet 30M (cathode film 30) is resin-based, burrs generated on the cut surface can be suppressed. Thereby, an unwanted short circuit or the like can be suppressed.

[0070] The individual-piece capacitor laminate is coated with an insulating resin 50 (S15). At this time, the insulating resin 50 is heated and pressurized. Thereby, the insulating resin 50 is cured to form the main body 11 of the solid electrolytic capacitor 10.

[0071] Terminal conductors are formed on the end surfaces 111 and 112 of the main body 11 (S16). More specifically, a resin electrode 71 is formed on the end surface 111 of the main body 11, and electrode films 811 and 812 are formed on the surface of the resin electrode 71. A resin electrode 72 is formed on the end surface 112 of the main body 11, and electrode films 821 and 822 are formed on the surface of the resin electrode 72.

[0072] By using the manufacturing method as described above, the solid electrolytic capacitor 10 can be manufactured without using a conductive adhesive between the outer layer CP23 and the cathode film 30. Moreover, the solid electrolytic capacitor 10 with a strong bonding strength between the outer layer CP23 and the cathode film 30 and suppressing peeling insulation can be manufactured easily and more reliably.

[0073] [Second Embodiment]

[0074] Next, the solid electrolytic capacitor according to the second embodiment will be described with reference to the drawings. Figure 8 (A) is a side cross-sectional view showing the structure of the outer layer CP and the cathode film according to the second embodiment, Figure 8Figure (B) is a side cross-sectional view showing the shape of the recess formed in the cathode film.

[0075] As Figure 8 shown in Figure (A), Figure 8 As shown in Figure (B), the solid electrolytic capacitor 10A according to the second embodiment is different in the structure of the cathode film 30A from the solid electrolytic capacitor 10 according to the first embodiment. The other structures of the solid electrolytic capacitor 10A are the same as those of the solid electrolytic capacitor 10, and the description of the same parts is omitted.

[0076] As Figure 8 shown in Figure (A), the cathode film 30A has recesses 35. The recesses 35 are formed on the surface that abuts against the outer layer CP23 (conductive polymer layer 235). When the cathode film 30A is viewed from above, the recesses 35 may be formed in a regular arrangement or at random positions. In other words, the recesses 35 may be formed at positions, with sizes, depths (Rz), and numbers that do not impair the function of the cathode film 30A. Preferably, the recesses 35 may be uniformly formed in the cathode film 30A.

[0077] As Figure 8 shown in Figure (B), at least one inorganic particle 250 enters the recess 35. That is, the inorganic particle 250 may be offset at least by the depth (Rz) of the recess 35 in the cathode film 30A. In this case, for example, as Figure 8 shown in Figure (B), the depth of the recess 35 may be on the order of the thickness Rz of the conductive polymer layer 235.

[0078] By having such a structure, a plurality of inorganic particles 250 can easily enter the recesses 35. That is, it is easy to make the inorganic particles 250 be more concentrated near the joint portion between the outer layer CP23 and the cathode film 30A, and the bonding strength between the outer layer CP23 and the cathode film 30A is further improved.

[0079] (Description of an example of the specific material, etc. of each component of the solid electrolytic capacitor 10)

[0080] (Capacitor element)

[0081] The capacitor element 20 can be realized, for example, with the following materials and thicknesses.

[0082] The anode electrode 21 includes, for example, metal monomers such as aluminum, tantalum, niobium, titanium, zirconium, magnesium, copper, or alloys containing these metals. In addition, the anode electrode 21 is preferably aluminum or an aluminum alloy. The anode electrode 21 only needs to be a valve action metal that exhibits a so-called valve action.

[0083] The anode electrode 21 is preferably plate-shaped, and the thickness of the core part of the anode electrode 21 (the central part where the pores of the porous body do not reach) is preferably 5 μm or more and 100 μm or less. The thickness of the porous part (the part where the pores of the porous body are formed) (the thickness on one side) is preferably 5 μm or more and 200 μm or less.

[0084] The dielectric layer 210 preferably includes an oxide film of the anode electrode 21. For example, when the anode electrode 21 is made of aluminum foil, the dielectric layer 210 is formed by oxidizing it in an aqueous solution containing boric acid, phosphoric acid, adipic acid, or their sodium salts, ammonium salts, etc. The thickness of the dielectric layer 12 is preferably 1 nm or more and 100 nm or less.

[0085] The inner layer CP22 can also be realized, for example, by a conductive polymer having a skeleton such as pyrrole, thiophene, aniline, etc., or PEDOT [poly(3,4-ethylenedioxythiophene)] which is a conductive polymer having a thiophene skeleton, and is a layer of PEDOT:PSS in which it is compounded with polystyrene sulfonic acid (PSS) as a dopant. The inner layer CP22 is formed, for example, by a method of forming a polymer film such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric layer 210 using a treatment liquid containing monomers such as 3,4-ethylenedioxythiophene, or a method of coating a dispersion liquid of a polymer such as poly(3,4-ethylenedioxythiophene) on the surface of the dielectric part and drying it.

[0086] The thickness of the outer layer CP23 is preferably 2 μm or more and 20 μm or less. The material of the outer layer CP23 is the same as that of the inner layer CP22. In addition, as described above, the material of the outer layer CP23 can also be different from that of the inner layer CP22. In this case, for example, the inner layer CP22 can be formed of PEDOT:PSS, and the outer layer CP23 can be formed of polypyrrole.

[0087] The insulating resin 50 may also contain a filler. As the resin, for example, epoxy resin, phenolic resin, polyimide resin, silicone resin, polyamide resin, liquid crystal polymer, etc. are preferred. As the filler, for example, insulating oxide particles such as silica particles, alumina particles, titanium dioxide particles, zirconia particles, etc. are preferred. The maximum diameter of the filler is, for example, desirably 10 μm or more and 50 μm or less. For example, a material containing silica particles in a solid epoxy resin and phenolic resin is more preferred.

[0088] In the above structure, as the solid electrolytic capacitor 10, a chip capacitor having electrodes at both ends is shown as an example. However, even a capacitor structure in which a lead frame is used as a terminal electrode and led out to both ends can achieve the same effect.

[0089] Description of Reference Numerals

[0090] CL1... Cutting line

[0091] 10, 10A... Solid electrolytic capacitor

[0092] 11... Body

[0093] 20... Capacitor element

[0094] 20M... Capacitor element sheet

[0095] 21... Anode electrode

[0096] 22... Inner layer CP

[0097] 23... Outer layer CP

[0098] 25... Solid electrolyte layer

[0099] 30, 30A... Cathode film

[0100] 30M... Cathode sheet

[0101] 35... Recess

[0102] 50... Insulating resin

[0103] 71, 72... Resin electrode

[0104] 81, 82... External electrode

[0105] 111, 112, 211, 212, 311... End face

[0106] 210... Dielectric layer

[0107] 213, 214... Flat film surface

[0108] 230... Outer surface

[0109] 231, 232, 233, 234, 235... Conductive polymer layer

[0110] 250... Inorganic particles

[0111] 500... Insulator layer

[0112] 811, 812, 821, 822... Electrode film.

Claims

1. A solid electrolytic capacitor comprising: a capacitor element including a film-like valve action metal substrate, a dielectric layer, and a solid electrolyte layer containing a conductive polymer; and a cathode lead-out layer, wherein the solid electrolyte layer contains inorganic particles, the capacitor element and the cathode lead-out layer are laminated in a state where the solid electrolyte layer and the cathode lead-out layer are in contact with each other, in a direction from the contact surface of the solid electrolyte layer and the cathode lead-out layer toward the valve action metal substrate, the concentration of the inorganic particles in the solid electrolyte layer decreases, at the surface where the solid electrolyte layer abuts against the cathode, the concentration of the inorganic particles contained in the solid electrolyte layer is the highest.

2. The solid electrolytic capacitor according to claim 1, wherein the cathode has a recess at least on the surface where the solid electrolyte layer abuts against the cathode.

3. The solid electrolytic capacitor according to claim 2, wherein the volume of the inorganic particles in the solid electrolyte layer is smaller than the volume of the recess.

4. The solid electrolytic capacitor according to claim 3, wherein at least one of the plurality of inorganic particles enters the recess.

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