JP2023147908A - Solid electrolytic capacitor and method for manufacturing the same - Google Patents

Abstract

To reduce increase in ESR when a solid electrolytic capacitor is exposed to an environment where stress is applied on components inside the solid electrolytic capacitor.SOLUTION: A solid electrolytic capacitor includes: a capacitor element including an anode part and a cathode part; a cathode lead frame including a first part and electrically connected to the cathode part; and an exterior body covering the capacitor element and the first part. The cathode part includes at least a cathode lead-out layer. The cathode lead-out layer is electrically connected to at least part of the first part via a conductive adhesive layer. The conductive adhesive layer includes a first stress buffer part. The cathode lead-out layer does not include a second stress buffer part, or includes the second buffer part. In a cross section A parallel to a thickness direction DT and a length direction DL of the conductive adhesive layer and the cathode lead-out layer, an area occupied by the first stress buffer part is greater than an area occupied by the second stress buffer part.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a solid electrolytic capacitor and a method of manufacturing the same.

A solid electrolytic capacitor includes, for example, a capacitor element including an anode part and a cathode part, and an exterior body that seals the capacitor element. One end of the lead is connected to the anode part or the cathode part, and the other end is drawn out of the exterior body and used for solder connection for mounting on a board or the like. The cathode section includes, for example, a solid electrolyte layer that covers at least a portion of the surface of an anode body constituting the anode section via a dielectric layer, and a cathode extraction layer that covers at least a portion of the solid electrolyte layer. For example, a lead frame may be used as the lead. For example, the cathode lead is connected to the surface of the cathode extraction layer via a conductive adhesive layer.

Patent Document 1 discloses a step of manufacturing a capacitor element by sequentially forming a dielectric film and a cathode layer on the surface of an anode body, and a step of connecting the cathode layer and a cathode terminal via a conductive adhesive. In the method for manufacturing a solid electrolytic capacitor, the conductive adhesive contains silver powder, a bisphenol F-type epoxy resin, and a diluent, and the content of the diluent is 0 to 15% by weight. We propose a method for manufacturing solid electrolytic capacitors characterized by the following.

Patent Document 2 includes at least an anode metal layer, a dielectric layer, a conductive polymer layer, and a cathode layer, the cathode layer includes at least a graphite film layer, and the graphite film layer includes the conductive polymer layer. The proposed electrolytic capacitor is formed in contact with a graphite film layer, and the apparent specific gravity of the graphite film layer is within the range of 0.4 to 1.8 g/cm ³ .

Patent Document 3 discloses a porous conductor forming step of forming a porous conductor, and a step of forming a conductor layer consisting of a plurality of layers including at least a solid electrolyte outer layer and a metal layer so as to cover at least the outer surface of the porous conductor. a conductor layer forming step, in which at least one layer of the plurality of layers is coated with a coating material containing conductive particles, a binder, and a solvent. A method for manufacturing a capacitor element is proposed, which is characterized in that the capacitor element is formed by evaporating the solvent after coating.

Japanese Patent Application Publication No. 2010-225606 Japanese Patent Application Publication No. 2007-234768 JP2003-324040A

Solid electrolytic capacitors are subjected to various stresses internally during manufacturing and product use, which can cause peeling of internal components. For example, when charging and discharging are repeated in a high-temperature environment, stress is applied to the constituent members due to expansion of moisture contained inside, which may cause peeling. Depending on the location where delamination occurs, the equivalent series resistance (ESR) may drop significantly.

A first aspect of the present disclosure provides a capacitor element including an anode part and a cathode part;
a cathode lead frame including a first portion and electrically connected to the cathode portion;
A solid electrolytic capacitor comprising: an exterior body covering the capacitor element and the first portion;
The cathode section includes at least a cathode extraction layer,
The cathode extraction layer is electrically connected to at least a portion of the first portion via a conductive adhesive layer,
The conductive adhesive layer includes a first stress buffer,
The cathode extraction layer does not include a second stress buffer or includes a second stress buffer,
In a cross section A parallel to the thickness direction _DT and length direction _DL of the conductive adhesive layer and the cathode extraction layer, the area occupied by the first stress buffer part is larger than the area occupied by the second stress buffer part. Regarding large, solid electrolytic capacitors.

A second aspect of the present disclosure includes a first step of preparing a capacitor element including an anode portion and a cathode portion including at least a cathode extraction layer;
A conductive adhesive layer is formed between the cathode extraction layer and at least a portion of the first portion of the cathode lead frame including the first portion, and the cathode extraction layer and the a second step of electrically connecting the cathode lead frame; and a third step of covering the capacitor element and the first portion of the cathode lead frame with an exterior body,
The second step relates to a method for manufacturing a solid electrolytic capacitor, including a substep of forming a first stress buffer within the conductive adhesive layer.

It is possible to reduce the increase in ESR when the components inside the solid electrolytic capacitor are exposed to an environment where stress is applied.

FIG. 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure.

The cathode portion of a solid electrolytic capacitor includes a solid electrolyte layer, a cathode extraction layer, and the like. A cathode lead frame is connected to the cathode extraction layer via a conductive adhesive layer. A solid electrolytic capacitor has a structure in which a plurality of constituent members are stacked in this manner on the cathode side. Therefore, when stress is applied to the internal components of a solid electrolytic capacitor, for example, between the solid electrolyte layer and the cathode extraction layer, inside the cathode extraction layer, between the cathode extraction layer and the conductive adhesive layer, the conductive Peeling is likely to occur inside the adhesive layer or between the conductive adhesive layer and the cathode lead frame. The cathode drawing layer includes, for example, a carbon layer containing conductive carbon and a resin binder or a cured product thereof, and a metal particle-containing layer containing metal particles and a resin binder or a cured product thereof. The conductive adhesive layer is, for example, a metal particle-containing layer containing metal particles and a resin binder or a cured product thereof. The metal particle-containing layer constituting the cathode extraction layer or the metal particle-containing layer constituting the conductive adhesive layer has extremely high conductivity compared to the solid electrolyte layer. Therefore, even if peeling occurs partially in the metal particle-containing layer, electricity flows relatively smoothly by bypassing the peeled portion, so that the increase in ESR is not so significant. On the other hand, the carbon layer constituting the cathode extraction layer has even lower conductivity than the solid electrolyte layer. Therefore, if peeling occurs between the carbon layer and a layer adjacent to the carbon layer (solid electrolyte layer, metal particle-containing layer, etc.), electricity will flow through a portion with high resistance when bypassing the peeled portion. Therefore, the loss of electricity due to resistance becomes significant, resulting in a large increase in ESR. Therefore, it is important to prevent delamination involving layers with relatively low conductivity, such as carbon layers or solid electrolyte layers.

In view of the above, in the present disclosure, the conductive adhesive layer includes a stress buffer section (first stress buffer section), and the cathode extraction layer does not include a stress buffer section (second stress buffer section), or the conductive adhesive layer includes a stress buffer section (second stress buffer section). section (second stress buffer section). In a cross section A parallel to the thickness direction _DT and the length direction _DL of the conductive adhesive layer and the cathode extraction layer, the area occupied by the first stress buffer part (S1) is the area occupied by the second stress buffer part. (S2) is larger. As described above, since the area S1 of the first stress buffering portion in the conductive adhesive layer having high conductivity is relatively large, most of the stress within the solid electrolytic capacitor can be alleviated by the conductive adhesive layer. It is possible to suppress peeling from occurring in other members. In particular, peeling involving layers with relatively low conductivity, such as carbon layers or solid electrolyte layers, is suppressed. Therefore, even in an environment where stress is applied to the components inside the solid electrolytic capacitor (for example, when the solid electrolytic capacitor is exposed to high temperatures during reflow treatment), it is possible to reduce the increase in ESR.

Note that the stress buffer in the conductive adhesive layer is referred to as a first stress buffer, and the stress buffer in the cathode extraction layer is referred to as a second stress buffer. The stress buffering portion is a portion that can buffer (or relax) stress applied to each layer. Therefore, the stress buffering portion usually has a certain size so as to be able to buffer or relieve stress.

Each of the first stress buffering section and the second stress buffering section may include at least one void. The voids constituting each stress buffering section are voids capable of buffering stress. The voids included in the conductive adhesive layer and capable of buffering stress are referred to as first voids, and the voids included in the cathode extraction layer capable of buffering stress are referred to as second voids. The voids are usually formed by forming air bubbles of a size that can relieve stress when forming each layer. Therefore, the voids often have a spherical shape, an elliptic spherical shape, a shape similar to these, or a shape in which these shapes are flattened. For example, in the case of delamination, the delamination occurs over a wide range, and the distance that electricity must detour becomes longer, which tends to increase ESR. However, in a gap having the above shape, since electricity flows along the periphery of the gap, the detour distance is shortened, and electricity tends to flow smoothly toward the cathode lead frame, making it easier to suppress an increase in ESR. Furthermore, since it is easier to control the size and position of the voids compared to unintentionally formed peeling, it is easier to suppress an increase in ESR.

The present disclosure also includes a method of manufacturing a solid electrolytic capacitor. A method for manufacturing a solid electrolytic capacitor includes, for example, a first step of preparing a capacitor element, a second step of electrically connecting a cathode lead layer of the capacitor element and a cathode lead frame via a conductive adhesive layer, and a second step of preparing a capacitor element. The method includes a third step of covering the element and a portion of the cathode lead frame with an exterior body. Here, the second step includes a substep of forming a first stress buffer within the conductive adhesive layer. The first stress buffer portion formed by such sub-steps can relieve much of the stress within the solid electrolytic capacitor, and can suppress peeling from occurring in other members. Therefore, an increase in ESR can be suppressed even in an environment where stress is applied to the structural members within the solid electrolytic capacitor.

In cross section A parallel to the thickness direction _DT and the length direction _DL of the conductive adhesive layer and cathode part (cathode extraction layer, etc.) of the solid electrolytic capacitor, from the outermost surface of the conductive adhesive layer to the surface of the dielectric layer Let the maximum value of the length of the space existing between the above thickness direction _DT (in other words, the thickness of the space) in the direction parallel to the above thickness direction DT be a, and the length in the direction parallel to the above length direction _DL Let b be the maximum value of the length (in other words, the length of the space). Then, in the cross section B parallel to the thickness direction _DT and the width direction _DW of the conductive adhesive layer and the cathode part (cathode extraction layer, etc.) of the solid electrolytic capacitor, the space parallel to the width direction _DW of the above space is Let c be the maximum value of the length in the direction (in other words, the width of the space). At this time, a large space that satisfies at least one of 20a≦b and 20a≦c hardly exists in the conductive adhesive layer and the cathode part before stress is applied, and is confirmed when stress is applied. Sometimes. Such a space corresponds to a space formed by peeling, and is distinguished from a "void" in this specification. On the other hand, a space that satisfies 20a>b and 20a>c is called a "void". For example, when the anode portion includes an anode wire, the direction in which the anode wire protrudes is parallel to the length direction _DL .

Hereinafter, the solid electrolytic capacitor of the present disclosure and its manufacturing method will be described in more detail.

[Solid electrolytic capacitor]
A capacitor element included in a solid electrolytic capacitor includes an anode portion and a cathode portion. A cathode lead frame is electrically connected to the cathode portion (more specifically, the cathode extraction layer) via a conductive adhesive layer. A solid electrolytic capacitor includes an exterior body that covers a capacitor element, a portion of a cathode lead frame, and the like. The solid electrolytic capacitor may have an anode lead frame electrically connected to the anode portion. In each lead frame of the cathode lead frame and the anode lead frame, a portion buried in the exterior body is referred to as a first portion, and a portion drawn out from the exterior body is referred to as a second portion.

In the solid electrolytic capacitor of the present disclosure, components other than the conductive adhesive layer and the cathode extraction layer are not particularly limited, and components used in known solid electrolytic capacitors may be applied. Furthermore, if necessary, components of cathode extraction layers used in known solid electrolytic capacitors may be applied to the cathode extraction layer.

(capacitor element)
The capacitor element includes an anode body, a dielectric layer formed on the surface of the anode body, and a cathode portion covering at least a portion of the dielectric layer. The anode body constitutes an anode section.

(capacitor element)
(Anode part)
The anode portion includes an anode body. The anode portion may include an anode body and an anode wire.

(Anode body)
The anode body may include a valve metal, an alloy containing a valve metal, a compound containing a valve metal, and the like. The anode body may contain one kind of these materials or a combination of two or more kinds. Preferred valve metals include, for example, aluminum, tantalum, niobium, and titanium.

The anode body has a porous portion at least in the surface layer. The anode body has many fine pores in the porous part. Due to such a porous portion, the anode body has a fine uneven shape.

An anode body having a porous portion on the surface layer can be obtained, for example, by roughening the surface of a base material (such as a sheet-like (for example, foil-like, plate-like) base material) containing a valve metal. The surface roughening may be performed by, for example, etching treatment (electrolytic etching, chemical etching, etc.). Such an anode body has, for example, a core portion and a porous portion formed integrally with the core portion on both surfaces of the core portion.

The anode body may be a porous molded body or a porous sintered body (such as a sintered body of a porous molded body) of particles containing a valve metal. Each of the molded body and the sintered body may have a sheet-like shape, a rectangular parallelepiped, a cube, or a shape similar to these. The porous sintered body may be, for example, a porous sintered body containing tantalum.

(Anode wire)
When the anode body is a porous sintered body or a porous molded body, the anode portion may include an anode wire. The anode wire may be a wire made of metal. Examples of materials for the anode wire include the valve metals mentioned above, copper, or copper alloys. 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.

(dielectric layer)
The dielectric layer is formed, for example, to cover at least a portion of the surface of the anode body (more specifically, the porous portion). The dielectric layer is an insulating layer that functions as a dielectric. The dielectric layer is formed by anodizing the valve metal on the surface of the anode body by chemical conversion treatment or the like. Since the dielectric layer is formed on the porous surface of the anode body, the surface of the dielectric layer has fine irregularities along the shape of the porous portion.

The dielectric layer includes an oxide of a valve metal. For example, the dielectric layer contains Ta ₂ O ₅ when tantalum is used as the valve metal, and the dielectric layer contains Al ₂ O ₃ when aluminum is used as the valve metal. Note that the dielectric layer is not limited to these examples, and may function as a dielectric.

(Cathode part)
The cathode portion is formed to cover at least a portion of the dielectric layer formed on the surface of the anode body. In the present disclosure, the cathode section includes at least a cathode extraction layer. The cathode portion (more specifically, the cathode extraction layer) is electrically connected to at least a portion of the first portion of the cathode lead frame via a conductive adhesive layer. The cathode portion of a solid electrolytic capacitor typically includes a solid electrolyte layer covering at least a portion of a dielectric layer. The cathode extraction layer covers at least a portion of the solid electrolyte layer.

(solid electrolyte layer)
The solid electrolyte layer includes, for example, a conductive polymer (a conjugated polymer, a dopant, etc.). As the conjugated polymer, for example, π-conjugated polymers (polypyrrole, polythiophene, polyaniline, derivatives thereof, etc.) may be used. For example, polythiophene derivatives include poly(3,4-ethylenedioxythiophene) (PEDOT) and the like. As the dopant, polystyrene sulfonic acid (PSS) or the like may be used, naphthalene sulfonic acid, toluene sulfonic acid, or the like.

The solid electrolyte layer is formed by, for example, using at least one of chemical polymerization and electrolytic polymerization of a conjugated polymer precursor (monomer, oligomer, etc.) and a dopant (naphthalene sulfonic acid, toluene sulfonic acid, etc.) on a dielectric layer. It can be formed by polymerization. Alternatively, a solid electrolyte layer may be formed by attaching a solution in which a conjugated polymer and a dopant are dissolved, or a dispersion in which a conjugated polymer and a dopant are dispersed, to a dielectric layer and drying. Examples of the dispersion medium (solvent) include water, organic solvents, and mixtures thereof.

The solid electrolyte layer may contain additives as necessary. Examples of the additive include known additives (for example, coupling agents, silane compounds) added to the solid electrolyte layer, and known conductive materials other than conductive polymers. The solid electrolyte layer or each solid electrolyte may contain one kind of these additives or a combination of two or more kinds. Examples of the conductive material as an additive include conductive inorganic materials such as manganese compounds (such as manganese dioxide) and at least one selected from the group consisting of TCNQ complex salts.

(Cathode extraction layer)
The cathode extraction layer includes, for example, a conductive layer that contacts the solid electrolyte layer and covers at least a portion of the solid electrolyte layer. The cathode drawing layer may include a metal particle-containing layer. In this case, usually at least a portion of the first portion of the cathode lead frame is electrically connected to the metal particle-containing layer via a conductive adhesive layer. The cathode extraction layer may include a first layer covering at least a portion of the solid electrolyte layer and a second layer covering at least a portion of the first layer. For example, the cathode extraction layer may include a layer containing conductive carbon (also referred to as a carbon layer) as a first layer and a layer containing metal particles as a second layer.

Examples of the conductive carbon contained in the carbon layer include graphite (artificial graphite, natural graphite, etc.). The carbon layer contains a conductive carbon material such as graphite and resin. The carbon layer is formed, for example, by applying a dispersion containing conductive carbon and a dispersion medium (such as an aqueous dispersion medium (water)) to the surface of the solid electrolyte layer and drying the dispersion. The dispersion liquid may contain a surfactant, a dispersant, a resin binder, etc., as necessary. The dispersion may be applied, for example, by immersing the portion of the anode body on which the solid electrolyte layer is formed in the dispersion, or by coating the surface of the solid electrolyte layer.

The conductivity of the carbon layer is about several hundred S/m, and the conductivity of the solid electrolyte layer is about several thousand to 10,000 S/m. The electrical conductivity of the metal particle-containing layer and the conductive adhesive layer is about several thousand to 10,000 times that of the carbon layer, and about 100 to 1000 times that of the solid electrolyte layer. The conductivity of the carbon layer and the solid electrolyte layer is lower than that of the metal particle-containing layer or the conductive adhesive layer. When peeling occurs between layers (second layer) due to the action of stress, the increase in resistance greatly affects the increase in ESR. In the present disclosure, a relatively large number of stress buffering parts (first stress buffering parts) are formed in the conductive adhesive layer, so even if stress is applied inside the solid electrolytic capacitor, most of the stress is alleviated by the conductive adhesive layer. This suppresses peeling at locations where the increase in supply as described above greatly affects the increase in ESR. Therefore, even when exposed to an environment where stress is applied, an increase in ESR can be reduced.

The second metal particle-containing layer includes, for example, metal particles (second metal particles) and a resin binder (second resin binder) or a cured product thereof. Examples of the second metal particles include silver particles, silver alloy particles, and copper particles. The second metal particles may be used alone or in combination of two or more. Although a thermoplastic resin may be used as the second resin binder, it is preferable to use a thermosetting resin. From the viewpoint of easily ensuring high adhesion and high heat resistance, among the curable resins, epoxy resins, polyamideimide resins, polyimide resins, phenol resins, etc. are preferable. The second resin binder may be used alone or in combination of two or more. The second resin binder may include additives (curing agent, curing accelerator, catalyst, etc.) that can constitute the thermosetting resin composition.

The metal particle-containing layer is formed, for example, by applying a metal paste containing second metal particles, a second resin binder, and optionally a dispersion medium to the surface of the first layer (carbon layer, etc.) and drying it. It is formed. When the resin binder is a thermosetting resin, the resin binder may be cured by heating the metal paste coating. By performing drying under heat, the dispersion medium may be vaporized and the resin binder may be cured. As the dispersion medium, for example, an organic dispersion medium is used. An organic dispersion medium and water may be used in combination. As the dispersion medium, a medium that dissolves the resin binder may be used. The metal paste may contain at least one selected from the group consisting of surfactants (cationic surfactants, etc.) and dispersants (fatty acids, etc.), if necessary.

The cathode extraction layer may include the second stress buffer, but preferably does not include the second stress buffer. In addition to the fact that the stress buffering portion basically has low conductivity, the carbon layer has relatively low conductivity as described above. Further, when stress is relaxed by the carbon layer, the stress that cannot be relaxed is applied to the carbon layer and the adjacent solid electrolyte layer, which may cause peeling. Therefore, from the viewpoint of ensuring a higher effect of suppressing peeling between the solid electrolyte layer, the carbon layer, between these layers, or between the carbon layer and the metal particle-containing layer (second layer), at least the carbon layer ( The first layer) preferably does not include the second stress buffer. In other words, when the cathode extraction layer includes the second stress buffer, the second stress buffer is preferably included in the metal particle-containing layer.

The second stress buffer portion may be composed of, for example, a dispersed phase of a rubber-like polymer, but is preferably composed of at least one void (second void).

In cross section A, when the average thickness of the metal particle-containing layer is t, the maximum value a of the length (thickness of the second void) in the direction parallel to the thickness direction _DT of the second void is, for example, It is 0.15t or more and t or less, may be 0.2t or more and t or less, or may be 0.3t or more and t or less. In these ranges, the upper limit of the maximum value a may be 0.7t or less. When the maximum length a of the second void is within such a range, when stress is applied inside the solid electrolytic capacitor, not only the conductive adhesive layer but also the cathode extraction layer (more specifically, the metal particles (containing layer) can also effectively relieve stress. In addition, it is preferable that the maximum value a of the thickness is within the above range for each second void.

In cross section A, the ratio of the total area of the second voids to the entire area of the metal particle-containing layer is, for example, 35% or less, may be 25% or less, or may be 20% or less. The ratio of the total area of the second voids to the entire area of the metal particle-containing layer may be, for example, 1% or more.

In cross section A, the ratio of the total area of metal particles to the entire area of the metal particle-containing layer is, for example, 60% or more, and may be 70% or more. The ratio of the total area of metal particles to the entire area of the metal particle-containing layer is, for example, 95% or less.

The cathode drawing layer (more specifically, the metal particle-containing layer) including the second stress buffering section is formed by using a rubber-like elastic body when forming a layer constituting the cathode drawing layer, such as the metal particle-containing layer. It can be formed by dispersing or forming second voids. In the case of a rubber-like elastic body, the stress relaxation property can be adjusted by adjusting the tan δ of the rubber-like elastic body or by adjusting the dispersion state (for example, adjusting the size of the dispersed phase). I can do it. For example, when forming the second void, when defoaming under reduced pressure after preparing the metal paste, at least one of the degree of decompression and the defoaming time may be adjusted, or an air dispenser may be used when applying the metal paste. By adjusting the amount of air mixed in using a metal paste, by using a relatively non-volatile dispersion medium in preparing the metal paste, by adjusting the drying time, and by adjusting the pressure during drying. It is possible to form two voids or adjust the size of the second void. Further, the second voids may be formed by introducing fine bubbles (microbubbles, nanobubbles, etc.) into the metal paste (for example, by blowing or bubbling) to incorporate air bubbles into the paste. In this case, the size of the second void may be adjusted by adjusting the amount of air bubbles taken in and the degree of mixing. Note that fine bubbles are bubbles with a diameter of 100 μm or less, microbubbles are bubbles with a diameter of 1 μm or more and 100 μm or less, and nanobubbles are bubbles with a diameter of less than 1 μm.

The average thickness t of the metal particle-containing layer may be, for example, 5 μm or more and 500 μm or less, 7 μm or more and 300 μm or less, or 10 μm or more and 200 μm or less.

In the present disclosure, it is sufficient that the first stress buffer portion is formed at least in the conductive adhesive layer. When the cathode extraction layer does not include the second stress buffer, the structure of the cathode extraction layer is not particularly limited, and may be any structure as long as it has a current collecting function.

Note that to measure the size (length, width, thickness, area) of the void in cross section A (or cross section B), a cross-sectional image taken by a scanning electron microscope (SEM) of the cross section is used. A sample for photographing cross section A can be produced, for example, by the following procedure. First, a solid electrolytic capacitor is embedded in a curable resin and the curable resin is cured. The cured product is wet-polished or dry-polished to obtain a cross section parallel to the thickness direction _DT and the length direction _DL of the conductive adhesive layer and the cathode extraction layer (the lamination state of each layer of the conductive adhesive layer and the cathode extraction layer). expose a verifiable cross section). By smoothing the exposed cross section using ion milling, a sample for imaging can be obtained. In the case of cross section B, a sample can also be formed by exposing a cross section parallel to the thickness direction _DT and the width direction _DW of the conductive adhesive layer and the cathode extraction layer, similarly to the case of cross section A. The exposed cross section is binarized and divided into voids and non-void portions (metal particles, resin binder, cured product thereof, etc.), and the size of the void portions is determined. However, in the cross-sectional image, the material scraped off by ion milling during ion milling may redeposit on the inner wall of the void. Since the redeposited matter is attached to a portion that is originally a void, the size of the void is measured while ignoring the redeposited matter. Note that in the SEM image, redeposited matter appears denser and whiter than the voids or surrounding layers, so it can be distinguished. During ion milling, cutting marks caused by ions may appear on the SEM image, making it impossible to accurately measure the size of the void. In this case, the size of the void is measured based on the image after cutting marks in the SEM image are removed using image processing software (specifically, Dragonfly manufactured by Object Research Systems). In addition, the area ratio (%) occupied by the total area of voids existing in each layer to the entire area of the conductive adhesive layer or cathode extraction layer in cross section A is the percentage of voids in the image subjected to the above binarization process. It is calculated from the area ratio occupied by each of the other parts.

The metal particle-containing layer constituting the cathode extraction layer has a lower ratio of resin binder (or its cured product) and a higher content of metal particles than the conductive adhesive layer. Therefore, from the SEM image of cross section A, the boundary between the metal particle-containing layer constituting the cathode drawing layer and the conductive adhesive layer is determined by the difference in the distribution state of the metal particles or resin binder (or its cured product) (for example, the above-mentioned (difference in area ratio). More specifically, in the SEM image using the above sample, the area ratio of metal particles is small (area ratio of the resin binder or its cured product) in parts other than voids (metal particles and resin binder or its cured product, etc.). The layer with a larger area ratio of metal particles corresponds to the conductive adhesive layer, and the layer with a larger area ratio of metal particles corresponds to the metal particle-containing layer of the cathode extraction layer.

The average thickness of the metal particle-containing layer is determined from the SEM image of cross section A using the above sample. More specifically, in the SEM image, the average thickness is determined by measuring the thicknesses at arbitrary multiple locations (for example, 10 locations) of the metal particle-containing layer and averaging them.

A method for manufacturing a solid electrolytic capacitor includes, for example, a first step of preparing a capacitor element including an anode portion and a cathode portion including at least a cathode extraction layer. When forming the second stress buffer in the cathode extraction layer, the first step may include a substep of forming the second stress buffer in the cathode extraction layer. At this time, the second stress buffer section is formed such that the area S1 occupied by the first stress buffer section in cross section A is larger than the area S2 occupied by the second stress buffer section. For example, the first step includes a step of preparing an anode section, a step of forming a dielectric layer on the surface of at least a portion of the anode section, and a step of forming a cathode section so as to cover at least a portion of the dielectric layer. It may also include. The step of forming the cathode part includes, for example, a step of forming a solid electrolyte layer to cover at least a portion of the dielectric layer, and a step of forming a cathode extraction layer to cover at least a portion of the solid electrolyte layer. May include. The step of forming the cathode extraction layer includes, for example, a step of forming a first layer (such as a carbon layer) that covers at least a portion of the solid electrolyte layer, and a second layer (such as a carbon layer containing metal particles) that covers at least a portion of the first layer. layer, etc.). The step of forming the second layer includes preparing a metal paste containing second metal particles, a second resin binder, and optionally a dispersion medium, and applying the metal paste to the surface of the first layer. It may also include a step of drying (or heating). In any step of forming the second layer, as described above, the dispersion state of the rubber-like elastic body is adjusted, air is introduced into the metal paste, and the degree of defoaming of the metal paste is adjusted. The second stress buffering portion can be formed by selecting the dispersion medium used in the metal paste, or by adjusting the drying or heating conditions when drying or heating the metal paste coating. In other words, the first step (more specifically, the step of forming the second layer) can include a substep of forming the second stress buffer. This substep may be included in either the step of preparing the metal paste and the step of drying or heating the coating of the metal paste, or it may be included in both steps (in other words, it may be included in both steps). , a second stress buffer may be formed). Note that regarding the first step, the above description regarding the capacitor element can be referred to.

(Conductive adhesive layer)
In the solid electrolytic capacitor, the conductive adhesive layer is interposed between the cathode extraction layer (more specifically, the second layer (metal particle-containing layer, etc.)) and at least a portion of the first portion of the cathode lead frame. .

The conductive adhesive layer includes a first stress buffer. In cross section A, the area S1 occupied by the first stress buffer is larger than the area S2 occupied by the second stress buffer. Since the conductive adhesive layer includes a relatively large number of first stress buffer parts, when stress is applied to the solid electrolytic capacitor, most of the stress is alleviated by the conductive adhesive layer, and the solid electrolyte layer has low conductivity. It is possible to suppress peeling at the interface between the carbon layer, the carbon layer, or an adjacent layer. Therefore, it is possible to reduce the increase in ESR when the solid electrolytic capacitor is exposed to an environment where stress is applied.

The first stress buffer portion may be composed of a dispersed phase of a rubber-like elastic body, but is preferably composed of at least one void (first void).

In cross section A, when the average thickness of the conductive adhesive layer is T, the maximum value a of the length (thickness of the first gap) in the direction parallel to the thickness direction _DT of the first gap is 0. It is preferably 4T or more and T or less, and may be 0.5T or more and T or less, and may be 0.7T or more and T or less. Since the thickness of the first gap is large in this way, when stress is applied inside the solid electrolytic capacitor, the effect of relieving stress can be further enhanced. It is preferable that the maximum thickness a of each first gap is within the above range.

The average thickness T of the conductive adhesive layer may be, for example, 5 μm or more and 1000 μm or less, 7 μm or more and 700 μm or less, or 10 μm or more and 500 μm or less.

In cross section A, the ratio of the total area of the first voids to the entire area of the conductive adhesive layer is, for example, 25% or more, and may be 30% or more (or 35% or more), or 35% or more ( or 40% or more). In the conductive adhesive layer, when the ratio of the total area of the first voids is within such a range, the effect of relieving stress can be further enhanced when stress is applied within the solid electrolytic capacitor. From the viewpoint of easily ensuring higher conductivity in the conductive adhesive layer, in cross section A, the ratio of the total area of the first voids to the entire area of the conductive adhesive layer is, for example, 75% or less, and 70%. It may be less than or equal to 65%. These lower limit values and upper limit values can be arbitrarily combined. For example, the ratio of the total area of the first voids may be 25% or more and 75% or less, or 35% or more and 70% or less. At least one of the lower limit value and upper limit value of these ranges may be changed to the above-mentioned numerical value.

The conductive adhesive layer includes, for example, metal particles (first metal particles) and a resin binder (first resin binder) or a cured product thereof. The first metal particles and the first resin binder are selected, for example, from the components described for the metal particle-containing layer of the cathode extraction layer. The first resin binder may include the additives described for the second resin binder.

The conductive adhesive layer applies a metal paste (also called a conductive adhesive) containing first metal particles, a first resin binder, and optionally a dispersion medium to one surface of the cathode extraction layer and the cathode lead frame. It is formed by coating one part of the metal paste, overlapping the other part, adhering it, and drying the coated film of metal paste. When the resin binder is a thermosetting resin, the resin binder may be cured by heating the metal paste coating. By performing drying under heat, the dispersion medium may be vaporized and the resin binder may be cured. As the dispersion medium, for example, an organic dispersion medium is used. An organic dispersion medium and water may be used in combination. As the dispersion medium, a medium that dissolves the resin binder may be used. The metal paste (conductive adhesive) may contain at least one selected from the group consisting of surfactants (cationic surfactants, etc.) and dispersants (fatty acids, etc.), if necessary.

In cross section A, the ratio of the total area of metal particles to the entire area of the conductive adhesive layer is, for example, 40% or more, and may be 50% or more. The ratio of the total area of metal particles to the entire area of the metal particle-containing layer is, for example, 75% or less.

The conductive adhesive layer including the first stress buffer can be formed in the same manner as the metal particle-containing layer including the second stress buffer.

The size (length, width, thickness, area) of the voids included in the conductive adhesive layer can be measured according to the procedure described for the cathode extraction layer. The average thickness of the conductive adhesive layer can also be determined according to the procedure described for the metal particle-containing layer.

The method for manufacturing a solid electrolytic capacitor includes a second step of forming a conductive adhesive layer between a cathode extraction layer included in the capacitor element and at least a portion of the first portion of the cathode lead frame including the first portion. . In the second step, the cathode extraction layer and the cathode lead frame are electrically connected via the conductive adhesive layer. The second step is performed after the first step.

The second step includes, for example, a step of preparing a metal paste (conductive adhesive) containing first metal particles, a first resin binder, and, if necessary, a dispersion medium; through a step of applying to a part of the surface of one of the cathode extraction layer (more specifically, the second layer (metal particle-containing layer)) and the first part of the cathode lead frame, and a coating film of metal paste. It may include the step of overlapping the other layer, and the step of drying (or heating) the coating film to form a conductive adhesive layer. In any of the second steps, as described above, the dispersion state of the rubber-like elastic body is adjusted, air is introduced into the metal paste, the degree of defoaming of the metal paste is adjusted, the metal paste is The first stress buffer portion can be formed by selecting the dispersion medium used for the first stress buffering portion or by adjusting the drying or heating conditions when drying or heating the metal paste coating. In other words, the second step can include a substep of forming a first stress buffer within the conductive adhesive layer. This substep may be included in either the process of preparing the metal paste, the process of drying or heating the coating film of the metal paste, or it may be included in both processes (in other words, , the first stress buffer may be formed by both steps). Formation of the first stress buffer part and adjustment of the size of the first stress buffer part can be performed in the same manner as in the case of the second stress buffer part. Regarding the second step, reference can be made to the above description regarding the conductive adhesive layer.

(Lead frame)
A portion (more specifically, an end) of the first portion of the anode lead frame is, for example, electrically connected to the anode wire. The material of the anode lead frame is not particularly limited as long as it is electrochemically and chemically stable and has conductivity. The anode lead frame may be made of metal such as copper, or may be made of non-metal. The anode lead frame may be, for example, a bent metal flat plate or metal sheet.

The ends of the anode lead frame may be joined to the protrusions of the anode wire by conductive adhesive or solder. Further, the end of the anode lead frame may be joined to the protrusion of the anode wire by resistance welding or laser welding. The second portion of the anode lead frame is exposed to the outside of the exterior body, and the end on the second portion side is arranged on the mounting surface of the solid electrolytic capacitor.

The cathode lead frame is electrically connected to the cathode extraction layer via a conductive adhesive layer. The material, shape, and thickness of the cathode lead frame may be the same as or different from those of the anode lead frame. The cathode lead frame may be, for example, a bent metal flat plate or metal sheet.

The thickness of the cathode lead frame (metal flat plate or metal sheet, etc.) (the distance between the main surfaces of the cathode lead frame) may be 25 μm or more and 200 μm or less, or 25 μm or more and 100 μm or less, from the viewpoint of reducing the height. It may be. The second portion of the cathode lead frame is exposed to the outside of the exterior body, and the end on the second portion side is arranged on the mounting surface of the solid electrolytic capacitor.

(exterior body)
The exterior body covers the capacitor element and the first portion of the cathode lead frame. The housing typically also covers the first portion of the anode lead frame. The exterior body is usually made of resin.

For example, a capacitor element is housed in a mold with the second portion of each lead frame pulled out, and a resin material for the exterior body (for example, an uncured thermosetting resin and a filler) is housed in the mold. The capacitor element is sealed in the exterior body by molding the resin by a transfer molding method, a compression molding method, or the like.

The solid electrolytic capacitor may further include a case disposed outside the resin exterior body, if necessary. The case is made of resin material, metal material, or the like. Examples of the resin material constituting the case include thermoplastic resins and compositions containing thermoplastic resins. Examples of the metal material constituting the case include metals such as aluminum, copper, and iron, or alloys thereof (including stainless steel, brass, etc.).

The method for manufacturing a solid electrolytic capacitor may include, for example, a third step of covering the capacitor element and the first portion of the cathode lead frame with an exterior body. In the third step, the first portion of the anode lead frame is also usually covered with an exterior body. The third step is usually performed after the second step. Regarding the third step, the above description regarding the exterior body can be referred to.

(others)
A solid electrolytic capacitor includes at least one capacitor element, and may include two or more capacitor elements. Two or more capacitor elements may be sealed with an exterior body while the second portion of each lead frame is pulled out.

FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present disclosure.
The solid electrolytic capacitor 20 includes a capacitor element 10 including an anode part 6 and a cathode part 7, an exterior body 11 that seals the capacitor element 10, an anode lead frame 13 electrically connected to the anode part 6, and a cathode part 7. and a cathode lead frame 14 electrically connected to the cathode lead frame 14 . The anode lead frame 13 and the cathode lead frame 14 each have a first portion buried in the exterior body 11 and a second portion exposed to the outside from the exterior body 11.

The anode section 6 includes an anode body 1 and an anode wire 2. A part of the anode wire 2 is buried in the anode body 1, and the remaining part protrudes outward from the outer surface of the anode body 1. A part of the first portion of the anode lead frame 13 is joined to the protruding portion of the anode wire 2 by welding or the like, and is electrically connected.

A dielectric layer 3 is formed on the surface of the anode body 1 . The cathode section 7 includes 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 includes 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 part of the first portion of the cathode lead frame 14 is adhered to and electrically connected to the cathode extraction layer 5 (more specifically, the metal particle-containing layer) via the conductive adhesive layer 8. There is. In the present disclosure, in a cross section A parallel to the thickness direction and length direction of the conductive adhesive layer 8 and the cathode extraction layer 5 (preferably metal particle-containing layer), the area (S1) occupied by the first stress buffer section is , is larger than the area (S2) occupied by the second stress buffer. Therefore, even if stress is applied inside the solid electrolytic capacitor 20, much of the stress can be alleviated by the conductive adhesive layer 8, and peeling of other members can be suppressed. Therefore, an increase in ESR can be suppressed even under an environment where stress is applied to the structural members within the solid electrolytic capacitor (for example, when the solid electrolytic capacitor is exposed to high temperatures during reflow treatment).

[Example]
EXAMPLES Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

《Examples 1 to 3 and Comparative Example 1》
A solid electrolytic capacitor was manufactured in the manner described below, and its characteristics were evaluated.

(1) Preparation of anode body having dielectric layer A tantalum sintered body (porous body) in which a part of the anode wire was embedded was prepared as the anode body. By anodizing the surface of this tantalum sintered body, a dielectric layer containing tantalum oxide was formed on the surface of the anode body.

(2) Formation of solid electrolyte layer After the tantalum sintered body was immersed in the liquid dispersion for about 30 to 60 seconds, the tantalum sintered body was pulled out of the liquid dispersion and heated at 140 to 180° C. for 10 to 20 minutes. Dipping in the liquid dispersion and heating were repeated multiple times. In this way, a solid electrolyte layer was formed. As the liquid dispersion, an aqueous dispersion containing PEDOT doped with PSS at a concentration of 1 to 4% by mass was used.

(3) Formation of cathode extraction layer The tantalum sintered body on which the solid electrolyte layer has been formed is immersed in a dispersion of graphite particles in water, taken out from the dispersion, and dried to form a solid electrolyte layer on the surface of the solid electrolyte layer. A carbon layer (first layer) was formed on. Drying was performed at 180° C. for 10 to 30 minutes.

Next, the silver paste containing silver particles and a resin binder (epoxy resin) was thoroughly defoamed under vacuum. The defoamed silver paste is applied to the surface of the carbon layer, dried at 60-80°C for 20-40 minutes, and then further heated at 180°C for 30-60 minutes to harden the resin binder and form metal particles. A containing layer (second layer) was formed.
In this way, a cathode extraction layer composed of a carbon layer and a metal particle-containing layer was formed, and a capacitor element including a cathode section composed of a solid electrolyte layer and a cathode extraction layer was produced.

(4) Connection of the cathode lead frame The cathode lead frame (more specifically, the layer containing metal particles) of the capacitor element obtained in (3) above is bonded to the cathode lead frame using a conductive adhesive. A conductive adhesive layer was formed by heating at 160° C. for 60 minutes. The conductive adhesive layer was formed to cover the entire opposing surfaces of the cathode extraction layer and the cathode lead frame. The conductive adhesive is made by mixing silver particles (average particle diameter D ₅₀ : 0.5 to 5 μm), liquid epoxy resin as a resin binder, cationic surfactant, and fatty acid as a dispersant, and then applying the mixture under reduced pressure. It was prepared by performing the defoaming treatment below. Examples include defoaming treatment conditions (higher pressure, shorter drying time, etc.), drying conditions (higher drying temperature, shorter drying time, drying under mild reduced pressure, etc.) or under atmospheric pressure) and mixing conditions (mixing using an air dispenser, mixing while introducing fine bubbles, etc.). A first void constituting a first stress buffering portion was formed, and its size was adjusted. In addition, in the example, the maximum value a of the length in the direction parallel to the thickness direction of the first gap is 0.4T with respect to the average thickness T of the conductive adhesive layer, which is determined by the procedure described above. The aspect ratio b/a and c/a of the first void were both less than 20.

In Comparative Example 1, the conductive adhesive was thoroughly defoamed under vacuum, and after the conductive adhesive was applied between the cathode extraction layer and the cathode lead frame, it was heated at 160°C in vacuum for 60°C. A conductive adhesive layer was formed by heating for a minute. In Comparative Example 1, almost no voids are observed in the conductive adhesive layer, and even when voids are observed, the maximum length of the voids in the direction parallel to the thickness direction of the conductive adhesive layer is 0. It was less than 4T (more specifically, about 0.1T to 0.4T), and was a size that could hardly be used to buffer stress.

(5) Connection of anode lead frame A part (more specifically, an end) of the first part of the anode lead frame was joined to a part of the anode wire protruding from the capacitor element by laser welding.

(6) Assembly of solid electrolytic capacitor A resin exterior body made of insulating resin was formed around the capacitor element by a transfer molding method. At this time, the first portion of the anode lead frame and the first portion of the cathode lead frame were in a state of being buried in the exterior body, and the second portion of each lead frame was in a state of being pulled out from the exterior body.
In this way, a total of 20 solid electrolytic capacitors were completed.

(7) Evaluation (a) Ratio of voids In cross section A, the ratio of the total area (S1) of the first voids (first stress buffer) to the entire area of the conductive adhesive layer and the metal particles The ratio of the total area (S2) of the second voids (second stress buffering portion) to the total area of the containing layer was determined.

(b) ESR
ESR was measured using a solid electrolytic capacitor according to the following procedure.
First, the initial ESR (mΩ) of the solid electrolytic capacitor at a frequency of 100 kHz was measured in an environment of 20° C. using a four-terminal LCR meter. Then, the average value of 20 solid electrolytic capacitors was determined.

Next, the solid electrolytic capacitor was subjected to reflow treatment in accordance with IPC/JEDEC J-STD-020D. Specifically, the solid electrolytic capacitor was preheated at a holding temperature of 150 to 200°C and a holding time of 180 seconds or less. The preheated solid electrolytic capacitor was heated for 30 seconds at a temperature of 255° C. or higher (maximum temperature 260° C.). Heating at the maximum temperature of 260° C. at this time was within 10 seconds. Next, it was cooled to 25° C. over 10 minutes, and this heating and cooling was repeated two more times (that is, three times in total).

An accelerated test was conducted by placing the reflow-treated solid electrolytic capacitor in a constant temperature bath in a 125° C. atmosphere and maintaining the rated voltage applied for 1000 hours. Thereafter, the ESR was measured in a 20° C. environment using the same procedure as the initial ESR, and the average value of the 20 solid electrolytic capacitors (ESR after the accelerated test) was determined. When the initial average ESR value was set to 100, the relative value of the average ESR value after the accelerated test was determined.

The evaluation results are shown in Table 1. In Table 1, E1 to E3 are Examples, and C1 is Comparative Example 1.

As shown in Table 1, in the comparative example, the ESR after the accelerated test increased significantly. When cross section A of the cathode section of the comparative example was observed with an SEM, peeling was observed in a wide range of regions between the carbon layer and the solid electrolyte layer. Further, peeling was also observed between the carbon layer and the metal particle-containing layer. As described above, in the comparative example, since peeling occurred in a portion with relatively low conductivity, it is considered that the ESR after the accelerated test increased significantly due to a large increase in resistance in the cathode portion.

On the other hand, in the examples, the increase in ESR after the accelerated test is suppressed to a lower level than in the comparative examples. When observing the SEM image of cross section A of the cathode part of the example, it was found that relatively large voids (first voids) were formed within the conductive adhesive layer, and the carbon layer and solid electrolyte layer as in the comparative example were found to be relatively large. No peeling was observed between the carbon layer and the metal particle-containing layer. Further, in Examples 1 and 2, peeling was observed between the conductive adhesive layer and the cathode extraction layer, but the increase in ESR was suppressed to a low level. In the example, even if stress is generated inside the solid electrolytic capacitor due to reflow treatment or accelerated testing, most of the stress is alleviated by the first void, and peeling is suppressed in the area where resistance increases, and the conductivity in the cathode part is improved. It is thought that the decrease in

In the solid electrolytic capacitor of the present disclosure, an increase in ESR is reduced when the solid electrolytic capacitor is exposed to an environment where internal components are subjected to stress, such as an environment where the solid electrolytic capacitor is exposed to high temperatures such as in a reflow process. Therefore, it is suitable for applications that require high reliability or high heat resistance. However, the uses of solid electrolytic capacitors are not limited to these only.

20: Electrolytic capacitor 10: Capacitor element 1: Anode body 2: Anode wire 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode extraction layer 6: Anode part 7: Cathode part 8: Conductive adhesive layer 11: Exterior body 13 : Anode lead frame 14: Cathode lead frame

Claims (12)

a capacitor element including an anode part and a cathode part;
a cathode lead frame including a first portion and electrically connected to the cathode portion;
A solid electrolytic capacitor comprising: an exterior body covering the capacitor element and the first portion;
The cathode section includes at least a cathode extraction layer,
The cathode extraction layer is electrically connected to at least a portion of the first portion via a conductive adhesive layer,
The conductive adhesive layer includes a first stress buffer,
The cathode extraction layer does not include a second stress buffer or includes a second stress buffer,
In a cross section A parallel to the thickness direction _DT and length direction _DL of the conductive adhesive layer and the cathode extraction layer, the area occupied by the first stress buffer part is larger than the area occupied by the second stress buffer part. Large, solid electrolytic capacitor. The first stress buffer section is configured with at least one first void,
2. The solid electrolytic capacitor according to claim 1, wherein the second stress buffer includes at least one second void. In the cross section A, when the average thickness of the conductive adhesive layer is T, the maximum length a of the first gap in the direction parallel to the thickness direction D _T is 0.4 T or more and T or less. The solid electrolytic capacitor according to claim 2. 4. The solid electrolytic capacitor according to claim 3, wherein in the cross section A, a ratio of the total area of the first voids to the entire area of the conductive adhesive layer is 25% or more and 75% or less. 5. The solid electrolytic capacitor according to claim 1, wherein the conductive adhesive layer includes first metal particles and a first resin binder or a cured product thereof. The cathode drawing layer includes a metal particle-containing layer,
The metal particle-containing layer is electrically connected to at least a portion of the first portion via the conductive adhesive layer,
The metal particle-containing layer includes second metal particles and a second resin binder or a cured product thereof,
6. The solid electrolytic capacitor according to claim 1, wherein when the cathode extraction layer includes the second stress buffer, the second stress buffer is included in the metal particle-containing layer. A first step of preparing a capacitor element including an anode portion and a cathode portion including at least a cathode extraction layer;
A conductive adhesive layer is formed between the cathode extraction layer and at least a portion of the first portion of the cathode lead frame including the first portion, and the cathode extraction layer and the a second step of electrically connecting the cathode lead frame; and a third step of covering the capacitor element and the first portion of the cathode lead frame with an exterior body,
The method for manufacturing a solid electrolytic capacitor, wherein the second step includes a substep of forming a first stress buffer within the conductive adhesive layer. 8. The method for manufacturing a solid electrolytic capacitor according to claim 7, wherein the first stress buffer portion includes at least one first void. In a cross section A parallel to the thickness direction and length direction of the conductive adhesive layer and the cathode extraction layer of the solid electrolytic capacitor, when the average thickness of the conductive adhesive layer is T, the first gap is 9. The method for manufacturing a solid electrolytic capacitor according to claim 8, wherein the maximum length a in the direction parallel to the thickness direction _DT is 0.4T or more and T or less. 10. The method for manufacturing a solid electrolytic capacitor according to claim 9, wherein in the cross section A, a ratio of the total area of the first voids to the entire area of the conductive adhesive layer is 25% or more and 75% or less. The first step includes a substep of forming a second stress buffer within the cathode extraction layer,
In a cross section A parallel to the thickness direction _DT and length direction _DL of the conductive adhesive layer and the cathode extraction layer of the solid electrolytic capacitor, the area occupied by the first stress buffer section is equal to the area occupied by the second stress buffer section. The method for manufacturing a solid electrolytic capacitor according to any one of claims 7 to 10, wherein the solid electrolytic capacitor is larger in area than the area occupied by the solid electrolytic capacitor. 12. The method for manufacturing a solid electrolytic capacitor according to claim 11, wherein the second stress buffer includes at least one second void.

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