Solid electrolytic capacitor

Abstract

To provide a solid electrolytic capacitor formed of a capacitor element excellent in the shape stability of an insulating layer and excellent in heat resistance.SOLUTION: A solid electrolytic capacitor includes a capacitor element including an anode part, a cathode part and an intermediate part. The anode part, the intermediate part and the cathode part are arranged along one anode body having a dielectric oxide coating layer formed in a porous area and on the surface of the porous area on the side of the main surface; the anode part has a first portion of the anode body; the intermediate part includes a first insulating layer having an insulating resin charged into the porous area of a second portion of the anode body and the holes of the dielectric oxide coating layer and a second insulating layer covering the first insulating layer and including the insulating resin; the cathode part includes a third portion of the anode body, a solid electrolyte layer covering a third dielectric oxide coating layer and a cathode lead-out layer covering the solid electrolyte layer; and the insulating resin includes a compound including a thioether structure obtained by reacting a maleimide group and an epoxy group with a thiol group.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electrolytic capacitor and a method for manufacturing the same, and more particularly to improving heat resistance reliability. Related.

Background Art

[0002] Electrolytic capacitors are mounted on various electronic devices because they have a small equivalent series resistance (ESR) and excellent frequency characteristics. The capacitor element used in an electrolytic capacitor includes a foil containing a valve metal such as titanium, tantalum, aluminum, or niobium as an anode body. For example, a capacitor element having a configuration in which one anode body having an oxide film formed on its surface is divided into an anode part and a cathode part is known. In such a capacitor element, a solid electrolyte layer and a cathode lead-out layer are formed on the surface of the anode body on the cathode part side.

[0003] In such a capacitor element, an insulating material may be disposed between the anode part and the cathode part for the purpose of surely insulating the anode part and the cathode part. For example, in Patent Document 1, in order to surely insulate the anode part and the cathode part and suppress the movement of oxygen from the anode part to the cathode part, a masking material is disposed in the boundary region between the anode part and the cathode part. More specifically, a material having a core region and a porous region disposed around the core region as an anode body is prepared, and a part of the porous region is reduced by laser processing. Then, a polyimide varnish is applied to the region with a width of 0.8 mm and thermally cured at 180° C. for 30 minutes to provide a masking material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method described in Patent Document 1, when applying the masking material, heat curing at 100°C or higher is required, and it is difficult to control the shape of the masking material. In the temperature range where the curing reaction of the polyimide varnish starts, or in the temperature range where the solvent in the polyimide varnish volatilizes, the polyimide has a lower viscosity. Therefore, in the method as in Patent Document 1, the polyimide cures while spreading not only in the thickness direction but also in the width direction of the porous region.

[0006] As a result, near the interface between the core region and the porous region inside the anode body, that is, inside the anode body, the impregnation rate of the masking material tends to be low. As a result, oxygen that has entered from the anode part may reach the cathode part side through the porous region inside the anode body, and the movement of oxygen may not be sufficiently suppressed. Then, the solid electrolyte layer may be oxidized and deteriorated, and the heat resistance reliability may decrease.

[0007] The present disclosure has been made to solve the conventional problems. Specifically, an object is to provide a solid electrolytic capacitor having excellent heat resistance, including a capacitor element with excellent shape stability of an insulating layer.

Means for Solving the Problems

[0008] In order to solve the above problems, the solid electrolytic capacitor of the present disclosure includes a capacitor element including an anode part, a cathode part, and an intermediate part interposed therebetween. The anode part, the intermediate part, and the cathode part are arranged along one anode body having a porous region on the main surface side and a dielectric oxide film layer formed on the surface of the porous region. The anode part has a first part of the anode body. The intermediate part has a first insulating layer in which the pores of the porous region and the dielectric oxide film layer of the second part of the anode body are filled with an insulating resin, and a second insulating layer covering the first insulating layer and including the insulating resin. The cathode part has a third part of the anode body, a solid electrolyte layer covering the dielectric oxide film layer of the third part, and a cathode lead-out layer covering the solid electrolyte layer. The insulating resin includes a compound including a thioether structure in which a maleimide group and an epoxy group react with a thiol group, and is a solid electrolytic capacitor. [Advantages of the Invention]

[0009] According to the present disclosure, a solid electrolytic capacitor with excellent shape stability of the insulating layer of the capacitor element and excellent heat resistance is provided. [Brief Description of the Drawings]

[0010]

Figure 1

Figure 2

Figure 3

[0011] [Solid Electrolytic Capacitor] (Overall Configuration) The overall configuration of a solid electrolytic capacitor according to an embodiment of the present disclosure will be described. The solid electrolytic capacitor according to this embodiment includes a capacitor element including an anode portion, a cathode portion, and an intermediate portion interposed therebetween. In the capacitor element, the anode portion, the intermediate portion, and the cathode portion are arranged in this order along one anode body having a porous region on the main surface side and a dielectric oxide film layer formed on the surface of the porous region. The anode portion of the capacitor element is composed of a first portion that is a part of the anode body having a porous region. The intermediate portion includes a second portion adjacent to the first portion of the anode body, and includes a first insulating layer in which the pores of the porous region and the dielectric oxide film layer of the second portion are filled with an insulating resin, and a second insulating layer covering the first insulating layer and containing an insulating resin. The cathode portion is other than the first portion and the second portion of the anode body, and includes a third portion adjacent to the second portion, a solid electrolyte layer covering the dielectric oxide film layer of the third portion, and a cathode lead-out layer covering the solid electrolyte layer.

[0012] In addition, the insulating resin that constitutes the first insulating layer and the second insulating layer in the intermediate portion contains a compound including a thioether structure in which a maleimide group and an epoxy group react with a thiol group. The compound including the thioether structure can be filled into the porous region of the anode body and the dielectric oxide film layer without using a solvent. Furthermore, since the viscosity of the compound before curing is appropriate, it can be sufficiently filled into the porous region of the anode body and the dielectric oxide film layer. That is, since the intermediate portion includes the first insulating layer made of such an insulating resin, it becomes possible to block 90% or more of a plurality of pores existing in the porous region of the anode body in the intermediate portion with the insulating resin. Therefore, the diffusion of oxygen that has entered the solid electrolytic capacitor from the anode portion side to the cathode portion side through the intermediate portion is suppressed. Thus, the deterioration of the solid electrolyte layer is suppressed and the heat resistance reliability is improved.

[0013] In addition, the intermediate portion of the capacitor element of the present embodiment includes, in addition to the first insulating layer, a second insulating layer that covers the first insulating layer. Therefore, the anode portion and the cathode portion are surely insulated from each other.

[0014] In view of the object of the present disclosure, when the capacitor element has a flat plate shape, it is preferable that the first insulating layer and the second insulating layer are arranged on both surfaces of the capacitor element.

[0015] In this specification, the direction connecting the anode portion, the intermediate portion, and the cathode portion of the capacitor element is defined as the first direction. Also, the end portion on the anode portion side of the capacitor element in the first direction is defined as the first end portion, and the end portion on the cathode portion side is defined as the second end portion. The boundary between the anode portion and the intermediate portion and the boundary between the intermediate portion and the cathode portion can be determined from an arbitrary cross section (hereinafter, also referred to as the "first cross section") obtained by cutting the capacitor element parallel to the first direction with the main surface. The boundary between the anode portion and the intermediate portion can be set at a position passing through the point closest to the first end portion of the insulating resin filled in the porous region on the first surface. On the other hand, the boundary between the intermediate portion and the cathode portion can be set at a position passing through the end portion closest to the first end portion among the end portions of the solid electrolyte layer on the main surface of the capacitor element. Note that the intermediate portion is a region between the boundary between the anode portion and the intermediate portion determined as described above and the boundary between the intermediate portion and the cathode portion.

[0016] Hereinafter, the capacitor element in the electrolytic capacitor will be specifically described with reference to the drawings. However, the present embodiment is not limited thereto.

[0017] FIG. 1 is a cross-sectional view schematically showing the capacitor element according to the present embodiment. Note that, in the drawings, the dimensions of each component of the electrolytic capacitor are shown as relative ones in order to clarify the shape or characteristics thereof, and are not necessarily represented at the same scale ratio.

[0018] FIG. 1 is a cross-sectional view obtained by cutting the main surfaces 110X and 110Y of the capacitor element in parallel with the first direction connecting the first end portion 110T1 on the anode portion side and the second end portion 110T2 on the cathode portion side of the capacitor element 110.

[0019] The capacitor element 110 has, for example, a flat plate shape. The anode portion 110a, the intermediate portion 110b, and the cathode portion 110c are arranged in this order in the first direction along one anode body 11. The anode body 11 has a core region 11Y, porous regions 11X disposed on both surfaces of the core region 11Y, and dielectric oxide film layers (a first dielectric oxide film layer 12a, a second dielectric oxide film layer 12b, and a third dielectric oxide film layer 12c) disposed on the surfaces of the porous regions 11X.

[0020] The anode portion 110a includes a first portion 11a that is a part of the anode body 11. That is, the anode portion 110a includes the core region 11Y, the porous regions 11X disposed on both surfaces of the core region 11Y, and the first dielectric oxide film layer 12a covering the surfaces of the porous regions 11X.

[0021] The intermediate portion 110b includes the second portion 11b of the anode body 11. However, in the intermediate portion 110b, the pores of the porous region 11X of the anode body 11 and the second dielectric oxide film layer 12b are filled with an insulating resin. In this specification, the region in which the pores of the porous region 11X and the second dielectric oxide film layer 12b are filled with an insulating resin is referred to as the first insulating layer 21. The intermediate portion 110b further includes a second insulating layer 22 on the first insulating layer 21. In other words, the intermediate portion 110b has a core region 11Y, a first insulating layer 21 disposed in the region of the core region 11Y, and a second insulating layer 22 covering the first insulating layer 21.

[0022] The cathode portion 110c includes a third portion 11c of the anode body 11, a solid electrolyte layer 13 covering the third portion 11c, and a cathode lead-out layer 14 covering the solid electrolyte layer 13. That is, it includes a core region 11Y, porous regions 11X disposed on both surfaces of the core region 11Y, a third dielectric oxide film layer 12c covering the surface of the porous region 11X, a solid electrolyte layer 13 covering the third dielectric oxide film layer 12c, and a cathode lead-out layer 14 covering the solid electrolyte layer 13.

[0023] In the capacitor element 110, an insulating resin containing a thioether structure in which a maleimide group and an epoxy group react with a thiol group is disposed in a plurality of pores of the porous region 11X and the second dielectric oxide film layer 12b of the intermediate portion 110b. Thereby, the pores of the porous region 11X and the second dielectric oxide film layer 12b are sufficiently blocked, and the diffusion of oxygen from the anode portion 110a side to the cathode portion 110c side is suppressed. By having the second insulating layer 22 covering the first insulating layer 21, the insulating property as the intermediate portion is further enhanced.

[0024] (Anode portion) As described above, the anode portion 110a of the capacitor element 110 includes the first portion 11a of the anode body 11. Here, the anode body 11 may have a porous region 11X and a dielectric oxide film layer formed on its surface (in the anode portion 110a, it is the first dielectric oxide film layer 12a), but from the viewpoint of strength, it is preferable to provide a core region 11Y having a lower porosity at the center.

[0025] The anode body 11 is obtained by subjecting a foil (metal foil) containing a valve-acting metal to roughening treatment and forming treatment, for example, by electrolytic etching. Specifically, a porous region 11X is formed by roughening the foil or the like. At this time, the region that has not been roughened becomes the core region 11Y. Then, a dielectric oxide film layer (in the anode portion 110a, the first dielectric oxide film layer 12a) is formed by further subjecting the roughened foil to forming treatment or the like. The porous region 11X, the core region 11Y, and the first dielectric oxide film layer 12a can be distinguished from the first cross-section of the capacitor element 110.

[0026] Examples of the valve-acting metal include titanium, tantalum, aluminum, and niobium. The valve-acting metal may be an alloy or an intermetallic compound. The thickness of the anode body 11 varies depending on the purpose of use, but is generally about 40 to 150 μm. Also, the size and shape of the anode body 11 vary depending on the application, but when it is in a flat plate shape, a rectangular shape with a width of about 1 to 50 mm and a length of about 1 to 50 mm is preferable, and a rectangular shape with a width of about 2 to 20 mm and a length of about 2 to 20 mm is more preferable.

[0027] The thickness of the porous region 11X in the anode body 11 is not particularly limited. From the viewpoint of capacitance, the thickness of the porous region 11X disposed on one main surface side of the anode body 11 is preferably 20% or more of the thickness of the foil before roughening. On the other hand, from the viewpoint of strength, the thickness of the porous region 11X is preferably 40% or less of the thickness of the foil before roughening. The thickness of the porous region 11X in the anode portion 110a is the average value when three points are measured from the boundary between the first dielectric oxide film 12a and the porous region 11X to the boundary between the porous region 11X and the core region 11Y in the first cross-section of the capacitor element 110.

[0028] On the other hand, the dielectric oxide film layer (the first dielectric oxide film layer 12a) is a layer formed along the main surface (surface) of the anode body 11 and is a layer formed along the inner wall of the pores in the porous region. Therefore, the dielectric oxide film layer also has a plurality of fine pores.

[0029] The dielectric oxide film layer may be formed on the entire surface of the anode body 11, or may be formed only on a part thereof. The dielectric oxide film layer is formed by anodizing the surface of the porous region 11X or the like. Therefore, the dielectric oxide film layer may contain an oxide of the valve metal. For example, when aluminum is used as the valve metal, the dielectric oxide film layer may contain aluminum oxide. However, the dielectric oxide film layer is not limited thereto, and any layer that functions as a dielectric may be used.

[0030] (Intermediate part) The intermediate part 110b includes the core region 11Y of the anode body 11, a first insulating layer 21 filled with an insulating resin in the porous region 11X of the anode body 11 and the second dielectric oxide film layer 12b, and a second insulating layer 22 covering the first insulating layer 21. Note that the core region 11Y, the porous region 11X, and the dielectric oxide film layer (in the intermediate part 110b, the second dielectric oxide film layer 12b) of the anode body 11 have the same configuration as that included in the anode part 110a described above, and thus detailed description thereof is omitted here.

[0031] The first insulating layer 21 is a layer in which an insulating resin is disposed in a plurality of pores of the porous region 11X and the second dielectric oxide film layer 12b. When viewing the first cross section of the capacitor element 110, the arrangement ratio of the insulating resin, that is, the filling rate of the insulating resin, with respect to the plurality of pores of the porous region 11X and the second dielectric oxide film layer 12b is preferably 90% or more. When it is less than 90%, oxygen that has invaded from the anode part 110a side may reach the cathode part 110c side through the porous region 11X inside the anode body 11. Therefore, the solid electrolyte layer 13 of the cathode part 110c may be oxidized and deteriorated, and the heat resistance reliability may be reduced. On the other hand, when the above filling rate is greater than 90%, diffusion of oxygen is suppressed regardless of the temperature, so that the heat resistance reliability is improved.

[0032] As a method for confirming the filling rate, the first cross section of the capacitor element 110 is observed with a scanning electron microscope (SEM), and the area of a plurality of pores in the porous region 11X and the area of the insulating resin filled in the pores are calculated from the observation photograph. Then, it is obtained from the ratio of these [(area of insulating resin / area of pores) × 100].

[0033] Further, the second insulating layer 22 is a layer containing an insulating resin, which is disposed so as to cover the first insulating layer 21. The second insulating layer 22 may be a layer formed of an insulating material that protruded without being filled in the porous region 11X or the second dielectric oxide film layer 12b when, for example, the porous region 11X was filled with an insulating resin to form the first insulating layer 21. Alternatively, it may be a layer formed by separately applying an insulating resin onto the first insulating layer 21 after the formation of the first insulating layer 21.

[0034] Since the intermediate portion 110b has not only the first insulating layer 21 but also the second insulating layer 22 that covers the first insulating layer 21, the insulation property of the intermediate portion 110b is further enhanced.

[0035] The thickness of the second insulating layer 22 is preferably normally 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 35 μm or less. When the thickness of the second insulating layer 22 is within this range, the insulation property of the intermediate portion 110b is more likely to be enhanced.

[0036] Here, the insulating resin contained in the first insulating layer 21 and the second insulating layer 22 contains a compound including a thioether structure in which a maleimide group and an epoxy group react with a thiol group.

[0037] A compound including a thioether structure in which a maleimide group and an epoxy group react with a thiol group is obtained by curing a composition including a maleimide-based compound including a maleimide group, an epoxy-based compound including an epoxy group, and a thiol-based compound including a thiol group. For example, curing may be promoted by a photo-base generator. Further, when applying the above composition to the porous region 11X or the second dielectric oxide film layer 12b, a solvent may be used as necessary.

[0038] In order to improve the heat resistance reliability of the solid electrolytic capacitor 100, it is required that the insulating resin present in each pore of the porous region 11X does not cause peeling at the interface between the pore and the insulating resin or deterioration of the insulation property due to thermal decomposition of the insulating resin even when exposed to a high temperature environment for a long time.

[0039] Generally, maleimide compounds and epoxy compounds are excellent in heat resistance but brittle. Therefore, when these compounds are reacted with thiol compounds for crosslinking, a thioether structure is formed, and flexibility is exhibited. Therefore, the insulating resin containing the compound is excellent in heat resistance and difficult to peel at the interface with pores.

[0040] Furthermore, when trying to fill pores such as the porous region 11X only with maleimide compounds and epoxy compounds, heat treatment at 150°C or higher is required during curing. On the other hand, when a thiol compound is combined with maleimide compounds and epoxy compounds, curing at a low temperature becomes possible. Furthermore, when a photo-base generator or the like is further combined, photocuring at room temperature becomes possible. In this case, after applying (filling) the composition into a plurality of pores in the porous region 11X and the second dielectric oxide film layer 12b, curing can be immediately performed by light irradiation. That is, by using a compound containing a thioether structure in which a maleimide group and an epoxy group react with a thiol group, the first insulating layer 21 and the second insulating layer 22 excellent in shape stability can be formed.

[0041] Here, the maleimide compound may be a compound having one or more maleimide groups in the molecule, but a compound having two or more maleimide groups is more preferable from the viewpoint of easily increasing the crosslinking density. Specific examples of maleimide compounds include maleimides having a phenylene skeleton, a cyclohexane skeleton, an aliphatic skeleton, etc., and among these, bismaleimide having a phenylene skeleton is preferable.

[0042] In addition, the epoxy compound may be any compound having one or more epoxy groups in the molecule, but a compound having two or more epoxy groups is more preferable from the viewpoint of easily increasing the crosslinking density. Specific examples of the epoxy compound include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, etc., and among these, bisphenol A type epoxy compounds are preferable. Further, the amount of the epoxy compound when forming the insulating resin is preferably 100 to 500 parts by mass, and more preferably 100 to 300 parts by mass, based on 100 parts by mass of the maleimide compound.

[0043] The thiol compound may be any compound having one or more thiol groups in the molecule, but a compound having two or more thiol groups is more preferable from the viewpoint of easily increasing the crosslinking density. Examples of the thiol compound include tetrafunctional thiols having a glycoluril skeleton as the mother skeleton, secondary polyfunctional thiols, etc., and among these, tetrafunctional thiols having a glycoluril skeleton as the mother skeleton are preferable. Further, the amount of the thiol compound when forming the insulating resin is preferably 100 to 450 parts by mass, and more preferably 100 to 300 parts by mass, based on 100 parts by mass of the maleimide compound.

[0044] In addition, the photo-base generator that can be combined with the above compound can be a known photo-base generator, such as carboxylate, salts containing borate anions, quaternary ammonium salts, and carbamates. Among these, o-nitrobenzyl type photo-base generators, (8E)-8-ethylidene-4-methoxy-5,6,7,8-tetrahydronaphthalene-1-carboxylic acid 1,8-diazabicyclo[5,4,0]undec-7-ene, 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate, 1,2-dicyclohexyl-4,4,5,5-tetramethyldiguanidium n-butyltriphenylborate, (2-(9-oxoxanthen-2-yl)propionic acid 1,5,7-triazabicyclo[4,4,0]dec-5-ene) are preferred. Also, the amount of the photo-base generator when forming the insulating resin is preferably 0.5 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the amounts of the maleimide-based compound and the epoxy-based compound.

[0045] From the viewpoint of heat resistance reliability, the glass transition temperature of the insulating resin is desirably 150°C or higher. The glass transition point is a value measured by the dynamic viscoelasticity measurement (DMA) method under the measurement conditions of a heating rate of 5°C / min and a frequency of 10 Hz. When the glass transition temperature of the insulating resin is 150°C or higher, it is difficult to thermally decompose even when exposed to a high-temperature environment for a long time. Therefore, the insulation property can be maintained over a long period, and the heat resistance reliability is likely to be high.

[0046] The oxygen transmission coefficient of the insulating resin is -10 cc·cm / (cm 2 ·sec·cmHg) or less is desirable. The oxygen transmission coefficient is a value measured by the electrolytic sensor method in accordance with JIS K7176-1. When the oxygen transmission coefficient of the insulating resin is -10 cc·cm / (cm 2 ·sec·cmHg) or less, the oxygen that has entered from the anode part 110a can be sufficiently suppressed from moving to the cathode part 110c side through the porous region 11X inside the anode body 11.

[0047] Here, the ratio of the length of the intermediate portion 110b in the first direction to the length of the cathode portion 110c in the first direction (length of intermediate portion 110b / length of cathode portion 110c) is desirably 0.04 or more and 0.1 or less. For example, assuming the length of the cathode portion 110c in the first direction is 5.5 mm, the length of the intermediate portion 110b in the first direction is preferably 0.20 mm to 0.55 mm. When the above ratio is 0.04 or more, insulation and oxygen barrier properties are good, and heat resistance reliability is likely to increase. Also, when the above ratio is 0.1 or less, it is difficult to affect the capacitance, which is a basic characteristic of the capacitor.

[0048] (Cathode portion) As described above, the cathode portion 110c includes the third portion 11c of the anode body 11, a solid electrolyte layer 13 covering the third portion 11c, and a cathode lead-out layer 14 covering the solid electrolyte layer 13. Since the anode body 11 is the same as the anode body 11 included in the above-described anode portion 110a, a detailed description thereof is omitted here.

[0049] The solid electrolyte layer 13 may be formed so as to cover at least a part of the third dielectric oxide film layer 12c of the anode body 11, or may be formed so as to cover the entire surface of the dielectric oxide film layer 12c. The solid electrolyte layer 13 is composed of a conductive polymer material such as polypyrrole, polythiophene, polyfuran, or polyaniline, for example.

[0050] The cathode lead-out layer 14 may be formed so as to cover at least a part of the solid electrolyte layer 13, or may be formed so as to cover the entire surface of the solid electrolyte layer 13. The cathode lead-out layer 14 is, for example, a laminate in which a carbon layer and a metal (e.g., silver) paste layer formed on the surface of the carbon layer are sequentially laminated. Note that the configuration of the cathode lead-out layer 14 is not limited to this, and any configuration having a current collecting function may be used.

[0051] (Solid electrolytic capacitor) FIG. 2 is a cross-sectional view schematically showing an electrolytic capacitor according to an embodiment. The solid electrolytic capacitor 100 of this embodiment includes one or more capacitor elements 110, an anode lead terminal 120A joined to the anode portion 110a of the capacitor element 110, a cathode lead terminal 120B joined to the cathode portion 110c, and a sealing resin 130 for sealing the capacitor element 110.

[0052] The solid electrolytic capacitor 100 may include a plurality of capacitor elements 110. When a plurality of capacitor elements 110 are included, they are laminated. The number of laminated capacitor elements 110 is not particularly limited, and is, for example, 2 or more and 10 or less. The anode portions 110a of the laminated capacitor elements 110 are joined together by welding, caulking, or the like, and are electrically connected.

[0053] Also, an anode lead terminal 120A is joined to the anode portion 110a of the capacitor element 110. The anode portion 110a and the anode lead terminal 120A may be joined by laser welding or the like, or may be joined by resistance welding or the like.

[0054] Also, the cathode portions 110c of the laminated capacitor elements 110 are also electrically connected. And a cathode lead terminal 120B is joined to the cathode portion 110c of the capacitor element 110. The cathode lead terminal 120B is joined to the cathode portion 110c via, for example, a conductive adhesive or solder. The conductive adhesive can be, for example, a mixture of a curable resin and carbon particles or metal particles.

[0055] Also, the capacitor element 110 joined to each of the lead terminals 120A and 120B is sealed with a sealing resin 130 such that at least a part of the anode lead terminal 120A and the cathode lead terminal 120B is exposed. Examples of the sealing resin include phenol resin, urea resin, melamine resin, epoxy resin, and the like.

[0056] [Method for manufacturing an electrolytic capacitor] The electrolytic capacitor according to this embodiment can be manufactured by the following method.

[0057] The manufacturing method of the solid electrolytic capacitor according to this embodiment includes, for example, as shown in the flowchart of FIG. 3, a preparation step of preparing an anode body having a porous region, a dielectric oxide film layer forming step of forming a dielectric oxide film layer on the surface of the porous region, and filling the pores of the porous region and the dielectric oxide film layer at a position corresponding to the middle part of the anode body having the dielectric oxide film layer formed on the surface with an insulating resin to form a first insulating layer, a first insulating layer forming step, arranging the insulating resin so as to cover the first insulating layer, a second insulating layer forming step of forming a second insulating layer covering the first insulating layer, and a cathode part forming step of forming a solid electrolyte layer on the dielectric oxide film layer at a position corresponding to the cathode part of the anode body and further forming a cathode lead-out layer on the solid electrolyte layer. After forming the capacitor element by this method, a lead terminal connection step or a sealing step may be performed as necessary. However, this embodiment is not limited thereto.

[0058] (Preparation step) In this step, an anode body having a porous region is prepared. For example, a commercially available anode body may be prepared. On the other hand, at least one main surface of a metal foil containing a valve action metal may be roughened to prepare an anode body having a porous region. Examples of the method for roughening the metal foil include electrolytic etching, etc., but the conditions are not particularly limited and are appropriately set according to the depth of the porous region, the type of valve action metal, etc.

[0059] (Dielectric oxide film layer forming step) In this step, a dielectric oxide film layer is formed on the surface of the anode body prepared in the above preparation step. The method for forming the dielectric oxide film layer is not particularly limited. The dielectric oxide film layer can be formed, for example, by subjecting the anode body to a forming treatment. When performing the forming treatment, for example, the above anode body can be immersed in a forming solution such as an ammonium adipate solution and heat-treated. Also, the dielectric oxide film layer may be formed by immersing the above anode body in a forming solution and applying a voltage.

[0060] Note that the dielectric oxide film layer may be formed on the entire surface of the porous region or only on a partial region.

[0061] (First insulating layer forming step) In this step, an insulating resin is filled into the pores of the porous region and the dielectric oxide film layer at the position corresponding to the middle part of the anode body having the dielectric oxide film layer formed on its surface, and the first insulating layer is formed.

[0062] As a method of filling the pores with the insulating resin, a composition containing a maleimide compound, an epoxy compound, and a thiol compound is applied in a sufficient amount onto the porous region and the dielectric oxide film layer by various printing methods, coating by a dispenser, transfer method, etc., and after impregnation, these are reacted and cured. The above curing may be thermal curing, but photo-curing is more preferable because the insulating resin can be cured before spreading outside the position corresponding to the middle part.

[0063] Note that in order to sufficiently impregnate the above composition into the pores of the porous region and the dielectric oxide film layer, the above composition may contain a solvent. Also, when a photo-base generator or the like is applied together with the above maleimide compound, epoxy compound, and thiol compound, it becomes possible to quickly photo-cure.

[0064] (Second insulating layer forming step) After the first insulating layer forming step, a second insulating layer is disposed so as to cover the surface of the first insulating layer. Similar to the first insulating layer, the second insulating layer is formed by applying a liquid agent in which a raw material of an insulating resin is blended in the middle part by a printing method, a method using a dispenser, a transfer method, etc., and then curing by light irradiation so as to cover the surface of the first insulating layer.

[0065] (Cathode part forming step) In this process, a solid electrolyte layer and a cathode lead-out layer are formed on the surface of the dielectric oxide film layer at the position corresponding to the cathode portion. The solid electrolyte layer can be formed by chemically polymerizing or electrolytically polymerizing a raw material monomer or oligomer in the presence of an anode body. The solid electrolyte layer may also be formed by applying a solution in which a conductive polymer is dissolved or a dispersion in which a conductive polymer is dispersed to the dielectric oxide film layer. The application method of the dispersion is not particularly limited and can be the same as known methods.

[0066] Next, on the surface of the solid electrolyte layer, for example, carbon paste and silver paste are sequentially applied to form a cathode lead-out layer. The application method of the carbon paste or silver paste is not particularly limited and can be the same as known methods.

[0067] (Lead terminal connection process) In the lead terminal connection process, an anode lead terminal is electrically connected to the anode body, and a cathode lead terminal is electrically connected to the cathode lead-out layer. The electrical connection between the anode body and the anode lead terminal is performed, for example, by welding them. Also, the electrical connection between the cathode lead-out layer and the cathode lead terminal is performed, for example, by adhering the cathode lead-out layer and the cathode lead terminal via a conductive adhesive.

[0068] (Sealing process) A part of the capacitor element and the lead terminal may be sealed with a sealing resin. The sealing is performed using molding techniques such as injection molding, insert molding, and compression molding. For example, using a predetermined mold, a composition containing a curable resin or a thermoplastic resin is filled so as to cover one end portion of the capacitor element and the lead terminal, and then heating or the like is performed.

Examples

[0069] Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples. It is not limited to the following examples.

[0070] (Preparation of raw materials) As the material of the insulating layer, the following compounds were prepared. (1) Maleimide-based compound BMI: Bismaleimide, manufactured by Kayaku Co., Ltd., maleimide group equivalent 179 PIDBM: High solubility bismaleimide, manufactured by Kawaguchi Chemical Industry Co., Ltd., maleimide group equivalent 213 (2) Epoxy-based compound jER828: Bisphenol A type epoxy compound, manufactured by Mitsubishi Chemical Corporation, epoxy group equivalent 190 BATG: Tetrafunctional epoxy compound, manufactured by Showa Denko K.K., epoxy group equivalent 128 (3) Thiol-based compound TS-G: Tetrafunctional thiol having a glycoluril skeleton as the main skeleton, manufactured by Shikoku Chemicals Corporation, thiol group equivalent 96 C3TS-G: Tetrafunctional thiol having a glycoluril skeleton as the main skeleton, manufactured by Shikoku Chemicals Corporation, thiol group equivalent 110 (4) Photo base generator O-nitrobenzyl type photo base generator represented by the following general formula

Chemical formula

[0071] (Example 1) (1) Preparation of the anode body An aluminum foil with a thickness of 115 μm was subjected to electrolytic etching treatment to prepare an anode body having porous regions on both of its main surfaces. The thickness of the porous regions formed on each main surface of the anode body was 40 μm. Also, the length of the anode body in the first direction was 6.5 cm.

[0072] (2) Formation of the dielectric oxide film layer The above anode body was subjected to chemical conversion treatment to form a dielectric layer covering both of its main surfaces.

[0073] (3) Formation of the first insulating layer 4.00 parts by mass of a maleimide compound "BMI" and 4.00 parts by mass of an epoxy compound "jER828" were mixed. To enhance solubility, the mixture was heated in a thermostat at 50 - 70 °C for 10 minutes and then cooled to room temperature. Then, 3.0 parts by mass of acetone was added. Subsequently, 2.02 parts by mass of a thiol compound "TS-G", 2.46 parts by mass of a thiol compound "C3TS-G", and 1.20 parts by mass of a photo-base generator were further added, and the mixture was thoroughly kneaded using a planetary kneader. Subsequently, the mixture was linearly applied to the region corresponding to the middle part of the anode body by a dispenser. Immediately after application, it was irradiated with ultraviolet rays at an integrated light quantity of 20000 mJ / cm 2 Thereby, a first insulating layer in which the pores of the porous region were filled with an insulating resin was formed.

[0074] (4) Formation of the second insulating layer During the formation of the first insulating layer in the above (3), the mixture remaining on the anode body without completely entering the pores of the porous region and the dielectric oxide film was cured to form the second insulating layer.

[0075] (5) Formation of the solid electrolyte layer An aniline aqueous solution containing aniline and sulfuric acid was prepared. A tape-shaped electrode was attached onto the formed second insulating layer above. Subsequently, the region corresponding to the cathode part of this anode body and the counter electrode were immersed in the aniline aqueous solution, and electrolytic polymerization was performed at a current density of 10 mA / cm 2 for 20 minutes. Thereby, a solid electrolyte layer was formed in the cathode part.

[0076] (6) Formation of the cathode lead-out layer Carbon paste and silver paste were sequentially applied onto the solid electrolyte layer and dried. Thereby, a cathode lead-out layer was formed, and a capacitor element was obtained.

[0077] (Examples 2 - 5, and Comparative Examples 1 - 2) As shown in Table 1, capacitor elements were fabricated in the same manner as in Example 1 except that the raw material mixing ratio of the insulating resin was changed.

[0078] (Evaluation) · Heat resistance of insulating resin: Glass transition temperature The glass transition temperature of the insulating resin produced in the above procedure (3) was measured by the dynamic viscoelastic measurement (DMA) method. Specifically, it was measured under the measurement conditions of a heating rate of 5°C / min and a frequency of 10 Hz. When the glass transition temperature was 150°C or higher, it was marked as "〇", and when it was less than 150°C, it was marked as "×".

[0079] · Oxygen barrier property of insulating resin: Oxygen permeability coefficient The oxygen permeability coefficient of the insulating resin produced in the above procedure (3) was measured by the electrolytic sensor method in accordance with JIS K7176-1. When the oxygen permeability coefficient was 1.0×10 -10 cc·cm / (cm 2 · sec·cmHg) or less, it was marked as "〇", and when it was greater than 1.0×10 -10 cc·cm / (cm 2 · sec·cmHg), it was marked as "×".

[0080] · Heat resistance reliability evaluation of capacitor element The capacitance of the capacitor element obtained above before and after heat treatment was measured, and the change rate was calculated. The heating was performed at 145°C for 250 hours. The change rate was obtained by {(capacitance before heat treatment - capacitance after heat treatment) / capacitance before heat treatment}. When the change rate was 40% or less, it was marked as "〇", when it was greater than 40% and 70% or less, it was marked as "△", and when it was greater than 70%, it was marked as "×".

[0081] · Resin filling property of the middle part of capacitor element Also, the filling rate of the insulating resin of the capacitor element obtained as described above was measured. Specifically, the first cross-section of the capacitor element was observed by SEM. Then, from the observation photograph, the areas of a plurality of pores in the porous region of the middle part and the area of the insulating resin were obtained, and the ratio [(area of insulating resin / area of pores)×100] was obtained as the filling rate. When the filling rate was 90% or more, it was marked as "〇", and when it was less than 90%, it was marked as "×".

[0082] · Comprehensive judgment In each of the above evaluations, when all the judgments were "○", the comprehensive judgment was "〇". When there was a "△" in the four judgments, the comprehensive judgment was "△". When there was an "×" in any of the four judgments, the comprehensive judgment was determined as "×". △ or above is within the range where there are no practical problems.

[0083]

Table 1

[0084] Regarding the heat resistance of the insulating resin, in Examples 1 to 5, all were evaluated as "〇" or "△", while in Comparative Example 1 and Comparative Example 2, they were evaluated as "×". This is because in Comparative Example 1 and Comparative Example 2, the compound contains a thioether structure in which the epoxy group reacts only with the thiol group, and it is considered that the crosslinking density of the cured product is small and the glass transition temperature is less than 150 °C. Therefore, it is considered that resin deterioration due to heat occurred in the heat resistance reliability test, and the capacitance change rate also increased. From this, it became clear that it is preferable for the insulating resin to contain a compound containing a thioether structure in which a maleimide group and an epoxy group react with a thiol group, and the glass transition temperature is 150 °C or higher.

[0085] Regarding the oxygen barrier property of the insulating resin, in Examples 1 to 5, all were evaluated as "〇", while in Comparative Example 1 and 2, they were evaluated as "×". This is because in Comparative Example 1, for the same reason as above, the crosslinking density of the cured product is small, so the oxygen permeability coefficient is considered to be 1.0×10 -10 cc·cm / (cm 2 ·sec·cmHg) or more. Therefore, it is considered that oxygen that invaded from the anode part from the initial stage of the test in the heat resistance reliability test could not be sufficiently suppressed from moving to the cathode part through the porous region inside the anode body, and the capacitance change rate also deteriorated. From this, it became clear that it is preferable for the insulating resin to be 1.0×10 -10 cc·cm / (cm 2 ·sec·cmHg) or less.

[0086] Regarding the size of the intermediate part, in Examples 1 to 4 and Comparative Example 1, the ratio of the length of the intermediate part in the first direction to the length of the cathode part was 0.04 or more, whereas in Example 5 it was 0.03. When the length of the intermediate part is short as in Example 5, the inhibitory effect on the movement of oxygen that has invaded from the anode part through the porous region inside the anode body to the cathode part is slightly reduced. Therefore, it is considered that the capacitance change rate has decreased compared with Examples 1 to 4. From this, it has become clear that the ratio of the length of the intermediate part in the first direction to the length of the cathode part is preferably 0.04 or more and 0.1 or less. However, when Example 5 is compared with Comparative Examples 1 and 2, the capacitance change rate has decreased to some extent, and it can be said that the embodiment of Example 5 also has a certain effect.

[0087] Regarding the resin filling rate, all of Examples 1 to 5 were evaluated as ○, whereas in Comparative Example 1 it was evaluated as ×. This is because in Comparative Example 1, the insulating resin formed by the reaction of an epoxy compound, a thiol compound, and a photo-base generator, that is, a compound containing a thioether structure in which an epoxy group has reacted only with a thiol group, has poor reactivity with only light irradiation, and the mixed solution spreads on the surface of the intermediate part, making it impossible to control the shape of the first insulating layer, and it is considered that the resin filling rate has become small. Therefore, it is considered that oxygen that has invaded from the anode part from the initial stage of the test in the heat resistance reliability test cannot be sufficiently suppressed from moving through the porous region inside the anode body to the cathode part, and the capacitance change rate has also deteriorated. From this, the filling rate of the insulating resin is preferably 90% or more. Note that in Comparative Example 2, although the resin filling rate was evaluated as ○, as described above, the oxygen permeability was high and the heat resistance reliability was evaluated as ×.

Industrial Applicability

[0088] Since the solid electrolytic capacitor of the present disclosure is excellent in heat resistance reliability, it can be used for various applications.

Explanation of Signs

[0089] 11 Anode body 11X Porous region 11Y Core region 11a First part Part 2 of 11b Part 3 of 11c First dielectric oxide film layer of 12a Second dielectric oxide film layer of 12b Third dielectric oxide film layer of 12c Solid electrolyte layer of 13 Cathode lead-out layer of 14 First insulating layer of 21 Second insulating layer of 22 Electrolytic capacitor of 100 Capacitor element of 110 Anode part of 110a Intermediate part of 110b Cathode part of 110c First end of 110T1 Second end of 110T2 Main surfaces of 110X, 110Y Anode lead terminal of 120A Cathode lead terminal of 120B Sealing resin of 130

Claims

1. A capacitor element comprising an anode portion, a cathode portion, and an intermediate portion interposed therebetween, wherein the anode portion, the intermediate portion, and the cathode portion are arranged along a single anode body having a porous region on the main surface side and a dielectric oxide film layer formed on the surface of the porous region, the anode portion has a first portion of the anode body, the intermediate portion has a first insulating layer in which the pores of the porous region and the dielectric oxide film layer of the second portion of the anode body are filled with an insulating resin, and a second insulating layer covering the first insulating layer and containing the insulating resin, the cathode portion has a third portion of the anode body, a solid electrolyte layer covering the dielectric oxide film layer of the third portion, and a cathode lead-out layer covering the solid electrolyte layer, the insulating resin contains a compound containing a thioether structure in which a maleimide group and an epoxy group react with a thiol group, Solid electrolytic capacitor.

2. In the first insulating layer, the filling rate of the insulating resin with respect to a plurality of the pores is 90% or more, The solid electrolytic capacitor according to claim 1.

3. The ratio of the length of the intermediate portion to the length of the cathode portion in the direction connecting the anode portion, the intermediate portion, and the cathode portion is 0.04 or more and 0.1 or less, The solid electrolytic capacitor according to claim 1 or 2.

4. The glass transition temperature of the insulating resin is 150°C or higher, The solid electrolytic capacitor according to any one of claims 1 to 3.

5. The oxygen permeability coefficient of the insulating resin is 1.0×10 －１０ cc·cm / (cm ２ ·sec·cmHg) or less. The solid electrolytic capacitor according to any one of claims 1 to 4.

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