Solid electrolytic capacitor and method for manufacturing same

Abstract

This solid electrolytic capacitor is provided with: a capacitor element that comprises a positive electrode part and a negative electrode part; a substrate that supports the capacitor element; a sealing body that seals the capacitor element; a first external electrode that is electrically connected to the positive electrode part; a second external electrode that is electrically connected to the negative electrode part; and an adhesive layer that is interposed between the capacitor element and a first surface of the substrate. At the interface between the first surface and the adhesive layer, the maximum height Rz1 of the surface roughness of the first surface is 5 μm or more, and the maximum height Rz2 of the surface roughness of the adhesive layer is 3 μm or more.

Description

Solid electrolytic capacitor and method of manufacturing the same

[0001] The present disclosure relates to a solid electrolytic capacitor and a method for manufacturing the same.

[0002] Patent Document 1 proposes a solid electrolytic capacitor comprising: a rectangular parallelepiped resin molded body including an element stack, an insulating substrate, and a sealing resin that seals the periphery of the element stack; a first external electrode provided on a first end surface of the resin molded body; and a second external electrode provided on a second end surface of the resin molded body, wherein the element stack is formed by stacking a first layer and a second layer; the first layer includes a valve action metal base having a dielectric layer formed on its surface and a solid electrolyte layer provided on the dielectric layer; the second layer comprises an electrode lead layer; the valve action metal base is exposed at the first end surface of the resin molded body; the electrode lead layer is exposed at the second end surface of the resin molded body; the first external electrode is connected to the valve action metal base; and the second external electrode is connected to the electrode lead layer; a dummy layer that does not contribute to capacitor capacitance is provided on either main surface of the element stack in the stacking direction; and the insulating substrate is located adjacent to the dummy layer.

[0003] International Publication No. 2021 / 112239

[0004] One aspect of the present disclosure relates to a solid electrolytic capacitor, the solid electrolytic capacitor comprising: a capacitor element including an anode portion and a cathode portion, a substrate supporting the capacitor element, a sealing body sealing the capacitor element, a first external electrode electrically connected to the anode portion, a second external electrode electrically connected to the cathode portion, and an adhesive layer interposed between the capacitor element and a first surface of the substrate, wherein at an interface between the first surface and the adhesive layer, the first surface has a maximum height Rz1 of 5 μm or more, and the adhesive layer has a maximum height Rz2 of 3 μm or more.

[0005] Another aspect of the present disclosure relates to a method for manufacturing the above-mentioned solid electrolytic capacitor, the method including the steps of: preparing the capacitor element; preparing a substrate for supporting the capacitor element; applying an adhesive to a first surface of the substrate to form the adhesive layer; and mounting the capacitor element on the substrate via the adhesive. The first surface of the substrate prepared in the substrate preparation step has a maximum height Rz3 of surface roughness of 10 μm or more.

[0006] Fluctuations in equivalent series resistance (ESR) can be reduced when a solid electrolytic capacitor equipped with the substrate is exposed to high temperatures.

[0007] 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present disclosure, a roughness curve of a first surface of a substrate according to an embodiment of the present disclosure, and an example of a cross-sectional image of a solid electrolytic capacitor E1 taken by a scanning electron microscope (SEM).

[0008] Substrates for solid electrolytic capacitors include, for example, insulating substrates, metal substrates, and laminated substrates (such as printed circuit boards) with wiring patterns. The substrate is a plate-like body including an insulating layer made of an organic material such as insulating resin. Therefore, substrates with an insulating layer are easily permeable to water vapor. If the substrate has a high water vapor permeability, moisture penetrates the interior, and when the solid electrolytic capacitor is exposed to high temperatures during a reflow process or other process, gas is generated inside, causing the volume to expand. The stress caused by the expansion is applied to the components within the capacitor, damaging them and causing fluctuations in the equivalent series resistance (ESR).

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

[0010] (Solid Electrolytic Capacitor) In solid electrolytic capacitors equipped with a substrate, if the substrate has a high water vapor permeability, moisture is likely to penetrate the interior. When the solid electrolytic capacitor is exposed to high temperatures during reflow processing or the like, the moisture that penetrates the interior vaporizes and expands, and the expansion easily applies stress to the internal components. When stress is applied to the capacitor element, encapsulant, or lead, cracks or peeling occur, increasing resistance and increasing the ESR of the solid electrolytic capacitor. Furthermore, because it is difficult to control the degree of stress caused by the expansion of the penetrated moisture and the parts to which the stress is applied, the ESR fluctuation range between individual capacitors is also likely to be large.

[0011] In view of the above, a solid electrolytic capacitor according to an embodiment of the present disclosure (hereinafter also referred to as "capacitor (C)") includes a capacitor element including an anode portion and a cathode portion, a substrate supporting the capacitor element, a sealing body sealing the capacitor element, a first external electrode electrically connected to the anode portion, a second external electrode electrically connected to the cathode portion, and an adhesive layer interposed between the capacitor element and a first surface of the substrate, wherein at the interface between the first surface and the adhesive layer, the maximum height Rz1 of the surface roughness of the first surface is 5 μm or more, and the maximum height Rz2 of the surface roughness of the adhesive layer is 3 μm or more.

[0012] When the maximum height Rz1 of the surface roughness of the first surface is 5 μm or more and the maximum height Rz2 of the surface roughness of the adhesive layer is 3 μm or more at the interface between the first surface and the adhesive layer, the surface of the adhesive layer facing the first surface of the substrate can be said to have a shape that generally follows the uneven shape of the first surface. Therefore, it can be said that the adhesive layer penetrates into the recesses of the first surface and is in close contact with the first surface. This reduces the amount of water vapor passing through the first surface of the substrate, thereby mitigating fluctuations (especially increases) in the ESR of the capacitor (C) when exposed to high temperatures, such as during reflow processing. Furthermore, in this disclosure, by reducing the penetration of moisture into the capacitor (C), the variation in the ESR fluctuation range between individual solid electrolytic capacitors can also be reduced.

[0013] Rz1 may be 6 μm or more, or 7 μm or more. The upper limit of Rz1 is not particularly limited, but may be, for example, 100 μm or less, or 50 μm or less.

[0014] Rz1 can be determined by cutting the capacitor (C) and capturing a cross-sectional image using a scanning electron microscope (SEM) as follows: The cross-sectional image is formed parallel to the stacking direction of the substrate, adhesive layer, and capacitor element. The cross-sectional image is captured, for example, at a magnification of 300x or more. The length of the cross-sectional image in the plane direction of the first surface is 200 μm or more. From the cross-sectional image, a "roughness curve" can be calculated by removing the waviness curve from the cross-sectional curve of the first surface. When the adhesive layer is sufficiently adhered to the first surface, the "roughness curve" of the interface between the first surface and the adhesive layer can be calculated from the cross-sectional image. Rz1 can then be calculated from the roughness curve. Cross-sectional images of the capacitor (C) to be measured are measured at multiple locations (e.g., five or more locations), Rz1 is calculated from the roughness curve for each cross-sectional image, and the average of all calculated Rz1 values ​​is calculated.

[0015] Like Rz1, Rz2 can be determined using a cross-sectional image of the capacitor (C) captured by SEM. From the cross-sectional image, a "roughness curve" of the surface of the adhesive layer or the interface between the first surface and the adhesive layer can be calculated. Rz2 is calculated from the roughness curve. Cross-sectional images of the capacitor (C) to be measured are measured at multiple locations (for example, five or more locations), Rz2 is calculated from the roughness curve for each cross-sectional image, and the average value of all calculated Rz2 values ​​is calculated.

[0016] (Adhesive Layer) The adhesive layer functions to adhere the capacitor element to the substrate. The adhesive layer is preferably formed from a curable adhesive. The curable adhesive contains a curable resin. The curable resin may be an insulating resin. The adhesive may be conductive, non-conductive, or insulating.

[0017] The conductive adhesive forms a conductive adhesive layer. The conductive adhesive or adhesive layer contains conductive filler particles. Examples of the conductive filler particles include metal particles such as silver particles, conductive carbon particles, and the like.

[0018] The non-conductive (insulating) adhesive forms a non-conductive (insulating) adhesive layer. The non-conductive (insulating) adhesive or adhesive layer contains insulating filler particles. Ceramic particles may be used as the insulating filler particles.

[0019] The insulating resin may include, for example, at least one selected from the group consisting of epoxy resin, acrylic resin, silicone resin, polyamide resin, and polyimide resin.

[0020] At the interface between the first surface and the adhesive layer, the maximum height Rz2 of the surface roughness of the adhesive layer may be 3 μm or more, but Rz2 may also be 6 μm or more, or 7 μm or more. The upper limit of Rz2 is not particularly limited, but may be, for example, 100 μm or less, or 50 μm or less.

[0021] Rz2 may be 50% or more, 80% or more, or 90% or more of Rz1. In this case, the surface of the adhesive layer on the first surface side can be said to have a shape that substantially follows the shape of the first surface. Furthermore, it can be said that the adhesive layer penetrates deep into the recesses of the first surface and is in close contact with the first surface.

[0022] The average porosity of the adhesive layer between the capacitor element and the first surface may be 50% or less, 20% or less, or 10% or less. In this case, the surface of the adhesive layer on the first surface side can be said to have a shape that substantially follows the shape of the first surface. Furthermore, the adhesive layer can be said to penetrate deep into the recesses in the first surface and to be in close contact with the first surface.

[0023] The average porosity (Rpav) of the adhesive layer can be determined using the cross-sectional image of the capacitor (C) used to determine Rz1. By binarizing the cross-sectional image, the area between the capacitor element and the first surface can be divided into the adhesive layer and the voids. The area Sa of the adhesive layer and the area Sp of the voids are determined, and the ratio (%) of Sp to the sum of Sa and Sp is calculated as the porosity Rp. Cross-sectional images of the capacitor (C) to be measured are measured at multiple locations (e.g., five or more locations), Rp is calculated for each cross-sectional image, and the average value Rpav of all calculated Rp is calculated.

[0024] The contact area between the capacitor element and the first surface preferably occupies 20% or more of the area of ​​the first surface of the substrate, more preferably 50% or more, even more preferably 80% or more, and even more preferably 90% or more. The larger the proportion of the contact area, the more significantly the amount of water vapor passing through the first surface of the substrate can be reduced.

[0025] Here, the adhesion region can be identified by taking an external photograph of the second surface (i.e., the outer surface) opposite the first surface of the substrate and binarizing the external photograph. The voids are visible through the outer surface of the region other than the adhesion region. On the other hand, the voids are not visible through the outer surface of the adhesion region, so the outer surface is observed as a relatively dark color with low brightness. Therefore, the binarized external photograph makes it easy to distinguish between the adhesion region and the non-adhesion region.

[0026] Specifically, the ratio of the contact area to the area of ​​the first surface of the substrate can be calculated as the ratio of the area of ​​the contact area to the area of ​​the portion of the second surface of the substrate that is exposed as the outer surface (the portion that is not covered by the external electrode).

[0027] In the contact region, the porosity of the adhesive layer between the capacitor element and the first surface is estimated to be approximately 10% or less.

[0028] Rz2 is preferably 30% or more of the average thickness Tav of the adhesive layer. That is, Rz2 is preferably a value significantly larger than the thickness of the adhesive layer. In other words, in this case, the adhesive layer can be said to be significantly thinner than Rz2. Rz2 may be 50% or more, 80% or more, 90% or more, or 100% or more of the average thickness Tav of the adhesive layer.

[0029] The average thickness Tav of the adhesive layer can be calculated as follows using a cross-sectional image of the capacitor (C) used to calculate Rz1. In the cross-sectional image, the thickness of the adhesive layer is calculated at 20 μm intervals along the surface direction of the first surface, using the interface between the capacitor element and the adhesive layer as a reference. Tav is calculated by averaging the multiple calculated values ​​(thicknesses) obtained.

[0030] When the adhesive layer contains an insulating resin and filler particles, the filler particles have the effect of reducing the amount of water vapor passing through the first surface of the substrate. From the viewpoint of enhancing this effect, the size of the filler particles contained in the adhesive layer is preferably such that the filler particles can penetrate deep into the recesses in the first surface. The average particle size of the filler particles contained in the adhesive layer is, for example, 10 μm or less, and may be 5 μm or less.

[0031] The average particle diameter of the filler particles is calculated from the cross-sectional image of the capacitor (C) used to determine Rz1. Specifically, 100 filler particles dispersed in the adhesive layer are arbitrarily selected, and their maximum diameters are determined. The average particle diameter of the filler particles is calculated by averaging all the maximum diameters obtained.

[0032] When the filler particles penetrate deep into the recesses in the first surface, the filler particles may be present at a distance of 80% or more, or even 100% or more of Tav, from the interface between the capacitor element and the adhesive layer.

[0033] The content of filler particles contained in the adhesive layer is preferably, for example, 5% by volume or more and 90% by volume or less, and more preferably 30% by volume or more and 90% by volume or less, in order to make it easier for the adhesive layer to penetrate deep into the recesses of the first surface.

[0034] The filler particle content in the adhesive layer can be determined using the cross-sectional image of the capacitor (C) used to determine Rz1. By binarizing the adhesive layer region of the cross-sectional image, the adhesive layer region can be divided into insulating resin and filler particles. The area Sr of the insulating resin and the area Sf of the filler particles are determined, and the percentage (%) of Sf relative to the total of Sr and Sf is calculated as the content. Alternatively, the cross-sectional image of the capacitor (C) to be measured may be measured at multiple locations (e.g., five or more locations), the content calculated for each cross-sectional image, and the average of all calculated contents calculated.

[0035] The capacitor (C) may include two or more stacked capacitor elements. In the present disclosure, moisture penetration into the capacitor (C) is reduced, thereby suppressing stress on the components even when the capacitor (C) is exposed to high temperatures. Therefore, even when the capacitor (C) includes two or more stacked capacitor elements, electrical connection between the capacitor elements and the external electrodes is easily ensured when exposed to high temperatures, and high capacitance is easily maintained.

[0036] (Substrate) The substrate has a first surface in contact with the adhesive layer. The capacitor element is mounted on the first surface of the substrate via the adhesive layer. The substrate includes at least one insulating layer. The first surface is usually the surface of the insulating layer. A substrate including an insulating layer is also called an insulating substrate.

[0037] The insulating layer is formed of an insulating resin and may contain ceramic particles, glass fibers, etc. Examples of ceramic particles include silica, alumina, glass, talc, and mica. The glass fibers may be contained in the form of a woven or nonwoven fabric (e.g., glass cloth). The ceramic particles and glass fibers have the effect of preventing moisture from penetrating into the capacitor (C). This further reduces fluctuations in the ESR of the capacitor (C) when exposed to high temperatures.

[0038] The amount of glass fiber contained in the insulating layer may be, for example, 50 parts by mass or more and 1000 parts by mass or less, or 60 parts by mass or more and 700 parts by mass or less, relative to 100 parts by mass of the insulating resin.

[0039] The amount of ceramic particles contained in the insulating layer may be, for example, 5 parts by mass or more and 300 parts by mass or less, or 10 parts by mass or more and 250 parts by mass or less, relative to 100 parts by mass of the insulating resin.

[0040] The insulating resin may include, for example, at least one selected from the group consisting of epoxy resin, polyimide resin, phenolic resin, and fluororesin. Specific examples of substrates containing such insulating resins include glass epoxy substrates, paper phenolic substrates, glass polyimide substrates, and fluororesin substrates. Glass epoxy substrates and glass polyimide substrates contain glass fiber. Such substrates are easily available, relatively inexpensive, and effectively reduce fluctuations in the ESR of the capacitor (C) when exposed to high temperatures.

[0041] The thickness of the substrate may be 50 μm or more and 500 μm or less. In this case, the substrate has a strength suitable for holding the capacitor element. Also, the thickness of the capacitor (C) can be made relatively small.

[0042] The substrate may include at least one metal layer. The substrate may have one metal layer and two insulating layers sandwiching the metal layer and adhering to the surface of the metal layer. The metal layers can further reduce the penetration of moisture into the capacitor (C). The metal layer may be laminated with the insulating layer, or may be formed on the insulating layer by a vapor phase method such as vapor deposition.

[0043] When the substrate has a metal layer, the thickness of the metal layer may be 5 μm or more and 100 μm or less. The content of the metal layer in the entire substrate may be 1 mass % or more and 55 mass % or less. This can reduce the penetration of moisture into the capacitor (C) and obtain a thin substrate. The metal layer may be at least one type selected from the group consisting of copper foil and copper alloy foil.

[0044] The thickness of the substrate or metal layer can be determined by measuring the thickness at any five or more selected locations on the substrate or metal layer and averaging the measured values.

[0045] (Method for manufacturing capacitor (C)) The capacitor (C) comprises the steps of: (i) preparing at least one capacitor element; (ii) preparing a substrate for supporting the capacitor element; (iii) applying an adhesive to a first surface of the substrate to form an adhesive layer; and (iv) mounting the capacitor element on the substrate via the adhesive.

[0046] The maximum height Rz3 of the surface roughness of the first surface of the substrate prepared in step (ii) is preferably 10 μm or more, and may be 30 μm or more. The first surface of the substrate can also be said to be roughened. This is thought to result in a compounding of the adhesive with the irregularities of the first surface when the adhesive is applied to the first surface in step (iii), allowing the adhesive to penetrate deep into the recesses, forming an adhesive layer with high adhesion to the first surface.

[0047] After applying the adhesive to the substrate, the adhesive may be allowed to penetrate into the first surface of the substrate (specifically, the irregularities of the first surface) under reduced pressure. Under reduced pressure, air remaining in the irregularities of the first surface is at least partially removed, allowing the adhesive to smoothly penetrate into the first surface having a large maximum height Rz3. "Under reduced pressure" refers to, for example, a pressure of 0.1 MPa or less, or even 0.07 MPa or less.

[0048] The viscosity of the adhesive at 25°C is, for example, 5 Pa·s or more and 75 Pa·s or less, and may be 50 Pa·s or less. The lower the viscosity at 25°C, the more smoothly the adhesive penetrates into the first surface having a larger maximum height Rz3. Here, the viscosity of the adhesive at 25°C refers to the viscosity measured using an E-type viscometer (cone plate).

[0049] As described above, if the adhesive is curable through steps (i) to (iii), the substrate after curing (i.e., the substrate on which the adhesive layer is formed) has a low water vapor permeability. The water vapor permeability of the substrate on which the adhesive layer is formed is, for example, 30 g / m ２ / day or less, 25 g / m ２ / day or less. By setting the water vapor permeability in this range, it is possible to significantly reduce the penetration of moisture through the substrate, and it is possible to further reduce the fluctuation of ESR when the capacitor (C) is exposed to high temperatures. The lower limit of the water vapor permeability of the substrate is preferably as low as possible, but it is not always possible to set it to exactly 0 g / m. ２ / day, for example, 0.1 g / m ２ / day or more.

[0050] The water vapor permeability of the substrate can be measured in accordance with JIS Z 0208:1976 "Test method for moisture permeability of moisture-proof packaging materials (cup method)." The test is performed under temperature and humidity conditions of a temperature of 85°C and a relative humidity of 85%. However, the measurement sample for the "substrate with an adhesive layer formed thereon" used to measure the water vapor permeability is a wide substrate without a capacitor element mounted thereon.

[0051] The water vapor permeability of the substrate (and the moisture absorption amount of the capacitor (C)) can be controlled by the state of the interface between the first surface and the adhesive layer, for example, the surface roughness Rz1 of the first surface. Therefore, when the water vapor permeability of the constituent material of the substrate itself is high (for example, 10 g / m ２ / day), the amount of moisture absorption of the capacitor (C) can be reduced.

[0052] (Capacitor Element) The capacitor element includes an anode part and a cathode part. An insulating separation layer may be provided to electrically separate the anode part and the cathode part. The capacitor (C) includes at least one capacitor element, and may include two or more capacitor elements. The two or more capacitor elements may be stacked, for example.

[0053] (Anode portion) The anode portion is typically at least a part of the anode body. The anode body may include a first portion and a second portion. The first portion includes one end (first end) of the anode body. The second portion includes the other end (second end). The cathode portion is formed in the second portion. The anode portion may be at least a part of the first portion.

[0054] The anode body may be a foil of an anode material (anode foil) or a sintered body of particles of the anode material. The anode material may include a valve metal, an alloy containing a valve metal, an intermetallic compound containing a valve metal, etc. The valve metal may be aluminum, tantalum, niobium, titanium, etc.

[0055] When an anode foil is used, a porous portion may be formed on the surface of at least the second portion of the anode foil. In this case, the anode foil has a core portion and a porous portion formed on the surface of the core portion. The porous portion may be formed, for example, by roughening the surface of at least the second portion of the anode foil by etching. The etching may be performed by a known method, for example, electrolytic etching.

[0056] After placing a masking member on the surface of the first portion, the second portion of the anode foil may be roughened, or the entire surface of the anode foil may be roughened. In the former case, no porous portion is formed on the surface of the first portion. In the latter case, porous portions are formed on the surfaces of both the first and second portions. The masking member is preferably an insulating material such as resin. The masking member may be removed before the formation of the solid electrolyte layer.

[0057] If the surface of the first portion has a porous portion, at least a portion of the porous portion may be removed or compressed in advance, thereby preventing deterioration of the reliability of the capacitor (C) due to air infiltration through the porous portion.

[0058] When a plurality of capacitor elements are stacked, the end faces of the plurality of first ends may be exposed from the outer surface of the sealing body and electrically connected to the first external electrodes. When the capacitor (C) has a generally rectangular parallelepiped shape, one surface (for example, the bottom surface) may correspond to the second surface of the substrate, and the remaining five surfaces may correspond to the outer surfaces of the sealing body.

[0059] The dielectric layer can be formed by anodizing at least the second portion of the anode body. The anodization (chemical conversion treatment) is performed, for example, by immersing the anode body in a chemical conversion solution and applying a voltage between the anode body as an anode and a cathode immersed in the chemical conversion solution.

[0060] The dielectric layer includes an oxide of a valve metal. When aluminum is used as the valve metal, the dielectric layer includes aluminum oxide. The dielectric layer is formed at least on the surface of the second portion where the porous portion is formed (including the inner wall surfaces of the pores of the porous portion).

[0061] The method for forming the dielectric layer is not limited as long as an insulating layer that functions as a dielectric can be formed on the surface of the second portion. The dielectric layer may also be formed on the surface of the first portion.

[0062] (Cathode portion) The cathode portion is formed in the second portion of the anode body having the dielectric layer. The cathode portion may cover the surface of the separation layer facing the second portion. The cathode portion includes, for example, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer. The cathode portion is formed by forming a solid electrolyte so as to cover at least a portion of the dielectric layer, and forming the cathode extraction layer so as to cover at least a portion of the solid electrolyte layer.

[0063] (Solid Electrolyte Layer) The solid electrolyte layer contains, for example, a conductive polymer (such as a conjugated polymer or a dopant). The solid electrolyte layer may contain a manganese compound.

[0064] The conjugated polymer may be, for example, a π-conjugated polymer (such as polypyrrole, polythiophene, polyaniline, or derivatives thereof). For example, polythiophene derivatives include poly(3,4-ethylenedioxythiophene) (PEDOT).

[0065] As the dopant, polystyrene sulfonic acid (PSS) or the like may be used, or naphthalene sulfonic acid, toluene sulfonic acid or the like may also be used.

[0066] The solid electrolyte layer can be formed, for example, by polymerizing a precursor of a conjugated polymer (monomer, oligomer, etc.) and a dopant (naphthalenesulfonic acid, toluenesulfonic acid, etc.) on a dielectric layer using at least one of chemical polymerization and electrolytic polymerization.

[0067] The solid electrolyte layer may be formed by applying a solution or dispersion of the conjugated polymer and the dopant to the dielectric layer and drying the applied solution or dispersion. The dispersion medium (solvent) may be, for example, water, an organic solvent, or a mixture thereof.

[0068] (Cathode Extraction Layer) The cathode extraction layer includes, for example, a conductive layer in contact with the solid electrolyte layer and covering at least a portion of the solid electrolyte layer. The conductive layer includes at least a first layer covering at least a portion of the solid electrolyte layer. The cathode extraction layer may include the first layer and a second layer covering at least a portion of the first layer. The cathode extraction layer may include a first layer containing conductive carbon and a second layer containing a metal layer (e.g., a metal foil). The conductive carbon included in the first layer may be, for example, graphite (artificial graphite, natural graphite, etc.).

[0069] The first layer may be composed of a metal foil. The first layer of metal foil may be formed, for example, of aluminum (Al) foil, copper (Cu) foil, valve metal (aluminum, tantalum, niobium, etc.) or an alloy thereof. The surface of the metal foil may be roughened. The surface of the metal foil may have a chemical conversion coating. The metal foil may have a second layer of a coating of a different metal or nonmetal different from the metal constituting the metal foil. The different metal or nonmetal may be, for example, a metal such as titanium (Ti) or nickel (Ni), or a nonmetal such as carbon (e.g., conductive carbon). The metal foil may be an Al foil with Ni vapor-deposited on its surface. The metal foil may have a Ti, TiC, TiO, C (carbon) film, etc.

[0070] The second layer may be a layer containing metal powder. For example, a conductive adhesive may be used for the second layer. A metal paste layer containing metal powder and resin may be used as the conductive adhesive. The metal paste layer may be a silver paste layer containing silver particles and resin. The resin is preferably a thermosetting resin such as an imide resin or an epoxy resin.

[0071] The metal foil may be attached to the solid electrolyte layer or the first layer via a layer containing conductive carbon, a metal paste layer, or the like.

[0072] When the cathode portion includes a metal foil, an end face of the metal foil can be exposed from the outer surface of the sealing body and can be easily electrically connected to the second external electrode. When multiple capacitor elements are stacked, the metal foil may be provided on at least one of the multiple capacitor elements, or the metal foil may be interposed between adjacent capacitor elements.

[0073] (Separation Layer) The separation layer is formed before the cathode portion is formed. The separation layer may be provided in proximity to the cathode portion so as to cover at least a portion of the surface of the first portion. From the viewpoint of suppressing air intrusion into the capacitor (C), the separation layer may be in close contact with the first portion and the sealing body. The separation layer may be disposed on the first portion via a dielectric layer. Such a separation layer is provided after the dielectric layer is formed. If necessary, the separation layer may be provided before the dielectric layer is formed.

[0074] The separation layer may be provided by, for example, attaching a sheet-like insulating member (such as a resin tape) to the first portion. The separation layer may be formed by applying or impregnating at least a portion of the first portion with a liquid resin to form an insulating member that adheres closely to the first portion. Applying or impregnating the liquid resin to the first portion and attaching a sheet-like insulating member may be used in combination.

[0075] (Spacer) The capacitor (C) may include a spacer. For example, the spacer is disposed at least one of between adjacent anode portions and between the ends of adjacent cathode portions of the stacked capacitor elements. The spacer may be conductive (made of metal, for example) or insulating. When an insulating spacer is used, the spacer may be exposed from the outer surface of the sealing body together with the end faces of the anode portions or cathode portions. The insulating spacer may be formed of, for example, a thermoplastic resin or a curable resin.

[0076] (Sealing Body) A capacitor element (or a plurality of stacked capacitor elements) is sealed by being covered with a sealing body. The capacitor element may be sealed so that at least one end face of the anode portion and the cathode portion is exposed from the outer surface of the sealing body, or after sealing, the sealing body may be partially removed so that at least one end face of the anode portion and the cathode portion is exposed from the outer surface of the sealing body.

[0077] The encapsulant preferably contains, for example, a cured product of a thermosetting resin. The encapsulant may contain a filler, a curing agent, a polymerization initiator, a catalyst, etc. The encapsulant may be formed using a molding technique such as injection molding. The encapsulant may be formed by using a predetermined mold to mold a composition containing a thermosetting resin so as to cover the capacitor element supported on the substrate.

[0078] (Contact Layer) At least one of the end faces of the anode and cathode exposed from the sealing body may be connected to an external electrode via a contact layer. The contact layer may be formed, for example, of an electroless Ni plating layer, an electrolytic Ni plating layer, or a Ni plating layer covered with an electroless Ag plating layer. The contact layer may be formed by sputtering, vacuum deposition, chemical vapor deposition (CVD), cold spraying, or thermal spraying. When a contact layer is provided, the contact layer can more reliably electrically connect the end face of the anode or cathode to the external electrode.

[0079] (External Electrodes) The external electrodes include a first external electrode connected to the anode portion of the capacitor element and a second external electrode connected to the cathode portion. Each external electrode may include a metal layer. The metal layer may be, for example, a plating layer. The metal layer may include at least one selected from the group consisting of nickel (Ni), copper (Cu), zinc (Zn), tin (Sn), silver (Ag), and gold (Au). The metal layer may be formed using a film formation technique such as electroplating, electroless plating, sputtering, vacuum deposition, chemical vapor deposition (CVD), cold spraying, or thermal spraying.

[0080] Each external electrode may include, for example, a laminated structure of a Ni layer and a Sn layer. The outer surface of each external electrode is preferably made of a metal that has excellent wettability with solder. Examples of such metals include Sn, Au, Ag, and Pd.

[0081] Each external electrode may include, for example, a laminate structure of a conductive paste layer and a plating layer. In view of excellent wettability with solder, a laminate structure of a Ni layer and a Sn layer (such as a Ni / Sn plating layer) may be adopted as the plating layer.

[0082] (Conductive Paste Layer) The conductive paste layer may be formed to cover at least one end face of the anode portion and the cathode portion of a capacitor element or a plurality of capacitor elements. The conductive paste layer may be formed to cover the end face via a contact layer. The conductive paste layer may be formed to cover not only the end face of the anode portion or the cathode portion but also the surface (side surface, etc.) of the sealing body where the end face is exposed.

[0083] The conductive paste layer can be formed by applying a conductive paste containing conductive particles and a resin material to the surface of the sealing body where the end face of the anode or cathode is exposed, and then drying the paste. Examples of the conductive particles that can be used include metal particles such as silver or copper, and particles of a conductive inorganic material such as carbon.

[0084] FIG. 1 is a cross-sectional view schematically illustrating the structure of a capacitor (C) according to an embodiment of the present disclosure. As shown in FIG. 1 , a solid electrolytic capacitor 100 includes a plurality of stacked capacitor elements 10, a sealing body 14 that seals the capacitor elements 10, a first external electrode 21, and a second external electrode 22. In the illustrated example, the stacked capacitor elements 10 are supported on an insulating substrate 17. An adhesive layer 18 is interposed between the substrate 17 and the capacitor element 10 closest to the substrate 17. The surface of the substrate 17 on which the adhesive layer 18 is formed is a first surface S1, and the opposite surface (outer surface) is a second surface S2.

[0085] 1, in reality, first surface S1 of substrate 17 is roughened, and at the interface between first surface S1 and adhesive layer 18, adhesive layer 18 penetrates into recesses in first surface S1 and is in close contact with first surface S1. This prevents moisture from penetrating into solid electrolytic capacitor 100 through substrate 17, reducing the amount of moisture absorbed by the solid electrolytic capacitor.

[0086] Each capacitor element 10 includes an anode body 3 constituting an anode portion, and a cathode portion 6. The anode body 3 is, for example, an anode foil. The anode body 3 has a core portion 4 and a porous portion 5 formed on the surface of the core portion 4 (surface layer of the anode body 3). A dielectric layer (not shown) is formed on at least a portion of the surface of the porous portion 5. The cathode portion 6 covers at least a portion of the dielectric layer. The cathode portion 6 includes a solid electrolyte layer 7 and a cathode extraction layer.

[0087] The anode body 3 is exposed at one end (first end) of the capacitor element 10 without being covered by the cathode portion 6. The other end (second end) of the capacitor element 10 is covered by the cathode portion 6. The portion of the anode body 3 covered by the cathode portion 6 (particularly the solid electrolyte layer 7) is referred to as the second portion 2, and the other portion is referred to as the first portion 1. The first portion 1 is not covered by the cathode portion 6 of the anode body 3. The end of the first portion 1 is the first end, and the end of the second portion 2 is the second end.

[0088] In the illustrated example, the second portion 2 has a core portion 4 and a porous portion 5 formed on the surface of the core portion 4. The first portion 1 may or may not have a porous portion 5 on its surface. The dielectric layer is formed along at least the surface of the porous portion 5 formed in the second portion 2.

[0089] The surface of the dielectric layer is formed with an uneven shape corresponding to the shape of the surface of the anode body 3. The solid electrolyte layer 7 can be formed to fill in the unevenness of the dielectric layer. The cathode extraction layer may include, for example, a first layer 8 such as a carbon layer that covers at least a portion of the solid electrolyte layer 7, and metal foil 20 as a second layer that covers at least a portion of the first layer 8.

[0090] The metal foil 20 is interposed between the second portions 2 of the capacitor elements 10 adjacent to each other in the stacking direction. The metal foil 20 constitutes a part of the cathode portion 6 of the capacitor element 10. The metal foil 20 has a carbon layer 20b on its surface. A conductive adhesive 9 may be interposed between the carbon layer 20b and the capacitor element 10. The conductive adhesive 9 contains, for example, carbon or silver.

[0091] In a region of the anode body 3 that does not face the cathode portion 6, at least a portion adjacent to the cathode portion 6 may be formed with an insulating separation layer (or insulating member) 12 so as to cover the surface of the anode body 3. This prevents contact between the cathode portion 6 and the exposed portion (first portion 1) of the anode body 3. The separation layer 12 is, for example, an insulating resin layer.

[0092] The sealing body 14 has a substantially rectangular parallelepiped outer shape, and the solid electrolytic capacitor 100 also has a substantially rectangular parallelepiped outer shape. In the illustrated example, the sealing body 14 has a first outer surface 14a and a second outer surface 14b opposite the first outer surface 14a. An end face 1a of a first end of the anode body 3, which is the anode portion of each capacitor element 10, is exposed at the first outer surface 14a. An end face 20a of the metal foil 20 constituting the cathode portion 6 is exposed from the sealing body at the second outer surface 14b.

[0093] The end surface 20a and second outer surface 14b of the metal foil 20 exposed from the sealing body 14 are covered with a second external electrode 22. A contact layer 15 is formed on the end surface 20a of the metal foil 20 so as to cover the end surface 20a. The second external electrode 22 is electrically connected to the end surface 20a of the metal foil 20 constituting the cathode portion 6 via the contact layer 15.

[0094] End faces 1 a and first outer surfaces 14 a exposed from sealing body 14 at the first ends of the multiple anode bodies 3 are covered with first external electrodes 21. A contact layer 15 is formed on end faces 1 a of anode bodies 3 so as to cover end faces 1 a. In the illustrated example, the end faces of separation layers 12 are also exposed from first outer surfaces 14 a of sealing body 14, and these exposed end faces are also covered with first external electrodes 21. First external electrodes 21 are electrically connected to end faces 1 a of anode bodies 3 via contact layers 15.

[0095] The first external electrode 21 includes a conductive paste layer 21A such as a silver paste layer, and a Ni / Sn plating layer 21B covering the conductive paste layer 21A. Similarly, the second external electrode 22 includes a conductive paste layer 22A such as a silver paste layer, and a Ni / Sn plating layer 22B covering the conductive paste layer 22A.

[0096] The first external electrode 21 covers the entire first outer surface 14a of the sealing body 14, as well as a third outer surface perpendicular to the first outer surface 14a and a portion of the substrate 17 facing the first outer surface 14a. The second external electrode 22 similarly covers the entire second outer surface 14b, as well as a third outer surface 14c perpendicular to the second outer surface 14b and a portion of the substrate 17 facing the second outer surface 14b. This configuration further enhances adhesion between the first external electrode 21 and the first outer surface 14a, and between the second external electrode 22 and the second outer surface 14b. The first external electrode 21 and the second external electrode 22, which cover a portion of the substrate 17, are exposed on the bottom surface of the solid electrolytic capacitor 100. These exposed portions constitute the anode and cathode terminals of the solid electrolytic capacitor 100, respectively.

[0097] (Additional Note) The above description discloses the following techniques.

[0098] (Technology 1) A solid electrolytic capacitor comprising: a capacitor element including an anode portion and a cathode portion; a substrate supporting the capacitor element; a sealing body sealing the capacitor element; a first external electrode electrically connected to the anode portion; a second external electrode electrically connected to the cathode portion; and an adhesive layer interposed between the capacitor element and a first surface of the substrate, wherein at an interface between the first surface and the adhesive layer, the first surface has a maximum height Rz1 of 5 μm or more of surface roughness, and the adhesive layer has a maximum height Rz2 of 3 μm or more of surface roughness.

[0099] (Technology 2) The solid electrolytic capacitor according to Technology 1, wherein the maximum height Rz2 is 50% or more of the maximum height Rz1.

[0100] (Technology 3) The solid electrolytic capacitor according to Technology 1 or 2, wherein the adhesive layer between the capacitor element and the first surface has an average porosity of 50% or less.

[0101] (Technology 4) The solid electrolytic capacitor according to any one of Technologies 1 to 3, wherein a contact area where the capacitor element and the first surface are in close contact with each other occupies 20% or more of the area of ​​the first surface of the substrate.

[0102] (Technology 5) The solid electrolytic capacitor according to any one of Technologies 1 to 4, wherein the maximum height Rz2 is 30% or more of the average thickness Tav of the adhesive layer.

[0103] (Technology 6) The solid electrolytic capacitor according to any one of Technologies 1 to 5, wherein the adhesive layer contains an insulating resin and filler particles, and the filler particles are present at a distance of 80% or more of the average thickness Tav from the interface between the capacitor element and the adhesive layer.

[0104] (Technology 7) The solid electrolytic capacitor according to Technology 6, wherein the insulating resin includes at least one selected from the group consisting of epoxy resin, acrylic resin, silicone resin, polyamide resin, and polyimide resin.

[0105] (Technology 8) The solid electrolytic capacitor according to any one of Technologies 1 to 7, comprising two or more stacked capacitor elements each including the capacitor element.

[0106] (Technology 9) A method for manufacturing a solid electrolytic capacitor according to any one of Technologies 1 to 8, comprising the steps of: preparing the capacitor element; preparing a substrate for supporting the capacitor element; applying an adhesive to a first surface of the substrate to become the adhesive layer; and mounting the capacitor element on the substrate via the adhesive; wherein the first surface of the substrate prepared in the substrate preparation step has a maximum height Rz3 of surface roughness of 10 μm or more.

[0107] (Technology 10) The method for manufacturing a solid electrolytic capacitor according to Technology 9, further comprising, after the step of applying an adhesive to the substrate, a step of allowing the adhesive to penetrate the first surface of the substrate under reduced pressure.

[0108] (Technology 11) The method for producing a solid electrolytic capacitor according to Technology 9 or 10, wherein the adhesive has a viscosity of 5 Pa·s or more and 75 Pa·s or less at 25°C.

[0109] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0110] The following substrates and adhesives were prepared:

[0111] <Substrate E> Substrate E is an insulating substrate comprising an insulating layer having a first surface with a maximum surface roughness height (Rz3) of 33.8 μm and a thickness of 100 μm, the insulating layer containing a glass fiber nonwoven fabric, the glass fiber content being 125 parts by mass per 100 parts by mass of insulating resin, the insulating resin being a cured product of a composition mainly composed of epoxy resin. An example of the roughness curve of the first surface of Substrate E measured using a commercially available surface roughness measuring device (laser microscope VK-9510 manufactured by Keyence Corporation) is shown in Figure 2.

[0112] <Adhesive A> Adhesive A is a thermosetting insulating resin composition containing an epoxy resin as a main component and 5% by volume of filler particles having an average particle size of 0.5 μm, and has a viscosity of 25 Pa·s at 25°C.

[0113] Substrate E on which an adhesive layer was formed was prepared by the following two methods, and the water vapor permeability (g / m ２ / day) was measured.

[0114] In the first method, adhesive A was applied to the first surface of substrate E by bar coating printing in an amount such that the average thickness Tav of the adhesive layer was 10 μm, and then the adhesive was cured by heating at 80° C. to form adhesive layer 18. The water vapor permeability of the substrate (hereinafter referred to as “substrate C1”) after the adhesive layer 18 was formed was 33.2 g / m ２ / day.

[0115] In the second method, adhesive A was applied by screen printing to the first surface of substrate E in an amount such that the average thickness Tav of the adhesive layer was 10 μm, and adhesive A was sufficiently penetrated into the first surface with a squeegee. The adhesive was then heated at 80° C. to harden the adhesive and form adhesive layer 18. The water vapor permeability of the substrate (hereinafter referred to as "substrate E1") after the adhesive layer 18 was formed was 20.2 g / m ２ / day.

[0116] <Solid Electrolytic Capacitor> Meanwhile, substrates C1 and E1 coated with adhesive were prepared using the two methods described above, and without curing, seven capacitor elements were mounted on the first surface of each substrate C1 and E1, to prepare solid electrolytic capacitors as shown in Figure 1 in the following manner.

[0117] (1) Preparation of Anode Body 3 Both surfaces of an aluminum foil (thickness: 100 μm) serving as a substrate were roughened by etching to prepare an anode body 3 .

[0118] (2) Formation of Dielectric Layer The second portion of the anode body 3 was immersed in a chemical conversion solution, and a DC voltage of 7 V was applied for 20 minutes to form a dielectric layer containing aluminum oxide.

[0119] (3) Formation of Solid Electrolyte Layer 7 Separation layer 12 was formed on the first end of anode body 3. Solid electrolyte layer 7 containing a conductive polymer was formed to cover the second portion of anode body 3 on which separation layer 12 was formed.

[0120] (4) Formation of Cathode Extraction Layer and Lamination of Capacitor Element 10 Anode body 3 obtained in (3) above was immersed in a dispersion liquid in which graphite particles were dispersed in water, and after being removed from the dispersion liquid, was heated and dried to form a carbon layer as first layer 8 at least on the surface of solid electrolyte layer 7.

[0121] Seven elements each having a first layer 8 formed thereon were stacked such that the first portions overlapped, with metal foil 20 (aluminum foil having a carbon layer 20b, thickness 20 μm) serving as a second layer interposed between the first layers 8 of adjacent elements. At this time, the metal foil 20 of the second layer was attached to the adjacent first layer 8 via conductive adhesive 9. In this way, a cathode extraction layer including the first layer 8 and the metal foil 20 serving as the second layer was formed, and a capacitor element 10 including the cathode extraction layer was completed. In each capacitor element 10, the cathode portion 6 included a solid electrolyte layer 7 and a cathode extraction layer.

[0122] (5) Sealing with Sealer 14 The seven stacked capacitor elements 10 obtained in (4) above were molded using a sealing material primarily composed of epoxy resin, with the second surface of the substrate 17 exposed, to form a sealer 14 made of insulating resin around the capacitor elements 10. The side portions of the sealer 14 were cut by dicing to form a first outer surface 14a and a second outer surface 14b. At this time, the sealer 14 was cut so that the end surface 1a of the anode body 3 of each capacitor element 10 and the substrate 17 were exposed from the first outer surface 14a, and the end surface 20a of the metal foil 20 and the substrate 17 were exposed from the second outer surface 14b, thereby obtaining a capacitor precursor.

[0123] (6) Formation of Contact Layer 15 Using the capacitor precursor obtained in (5) above, an electroless Ni plating layer was formed so as to cover the end surface 1 a of the anode body 3 exposed from the first outer surface 14 a, and then an electroless Ag plating layer was formed on the electroless Ni plating layer to form the contact layer 15. Similarly, an electroless Ni plating layer was formed so as to cover the end surface 20 a of the metal foil 20 exposed from the second outer surface 14 b, and then an electroless Ag plating layer was formed on the electroless Ni plating layer to form the contact layer 15.

[0124] (7) Formation of the first external electrode 21 and the second external electrode 22 The first external electrode 21 and the second external electrode 22 were formed so as to cover the contact layer 15 formed in (6) above and the first outer surface 14a and the second outer surface 14b, respectively.

[0125] More specifically, a conductive paste containing silver particles and resin was applied to the outer surfaces of the contact layer 15 and the sealing body, and then heated and dried to form conductive paste layers 21A and 22A, respectively. Next, electrolytic Ni plating layers and electrolytic Sn plating layers were formed to cover the conductive paste layers 21A and 22A, respectively. In this manner, Ni / Sn plating layers 21B and 22B were formed, respectively, to obtain solid electrolytic capacitors. A total of 20 solid electrolytic capacitors were fabricated for each example using the same procedure.

[0126] (8) Evaluation In an environment of 20° C., the capacitance (μF) and the initial ESR (mΩ) at a frequency of 100 kHz were measured for each of the 20 solid electrolytic capacitors using an LCR meter for four-terminal measurement.

[0127] Next, a moisture absorption test was carried out according to the following procedure.

[0128] First, the solid electrolytic capacitors were placed in a thermostatic chamber at 30°C and 60% RH for 192 hours. The solid electrolytic capacitors were removed from the chamber and cooled to 25°C. The mass increase of 20 solid electrolytic capacitors was measured and the average value was calculated. The moisture absorption amount of the solid electrolytic capacitors using substrate C1 was 104.2 μg / capacitor, and the moisture absorption amount of the solid electrolytic capacitors using substrate E1 was 63.4 μg / capacitor. After moisture absorption, the capacitance (μF) and ESR (mΩ) of each of the 20 solid electrolytic capacitors were measured using the same method as above.

[0129] Next, a reflow test was carried out in the following manner.

[0130] The solid electrolytic capacitors were subjected to a reflow process in accordance with IPC / JEDEC J-STD-020D. Specifically, the solid electrolytic capacitors were preheated at a holding temperature of 150-200°C for a holding time of 180 seconds or less. After preheating, the solid electrolytic capacitors were heated to a temperature of 255°C or higher (maximum temperature 260°C) for 30 seconds. The heating at the maximum temperature of 260°C was limited to 10 seconds or less. The capacitors were then cooled to 25°C over 10 minutes, and this heating and cooling process was repeated two more times (i.e., a total of three times). The capacitance (μF) and ESR (mΩ) of each of the 20 solid electrolytic capacitors after reflow were measured using the same method as above.

[0131] The results of the capacitance and ESR are shown in Table 1. In Table 1, E1 is an example and C1 is a comparative example.

[0132]

[0133] For the solid electrolytic capacitors C1 and E1, the maximum height Rz1, maximum height Rz2, average thickness Tav of the adhesive layer, average porosity Rpav, and ratio of the adhesion region to the area of ​​the first surface (Rx) were measured using the methods described above, with the following results.

[0134] <Solid electrolytic capacitor E1> Rz1: 7.5 μm Rz2: 7.4 μm Tav: 7.5 μm Rpav: 1.5% Rx: 99.0% <Solid electrolytic capacitor C1> Rz1: 7.5 μm Rz2: 2.8 μm Tav: 10.0 μm Rpav: 15.0% Rx: 62.0% A cross-sectional image (100,000 times the original magnification) of an example of solid electrolytic capacitor E1 is shown in Figure 3. In Figure 3, the interface between the adhesive layer and the first surface of the substrate is highlighted with a white line. The surface of the adhesive layer on the first surface side has a shape that substantially follows the shape of the first surface of the substrate, and it can be seen that the adhesive layer penetrates deep into the recesses in the first surface.

[0135] The solid electrolytic capacitor according to the present disclosure can suppress the penetration of moisture into the interior through a substrate including an insulating layer, and can suppress fluctuations in ESR when exposed to high temperatures such as during reflow processing. Therefore, the solid electrolytic capacitor according to the present disclosure can be used in a variety of applications requiring high reliability, and is useful for applications requiring high heat resistance and applications in high-humidity environments. However, the applications of the solid electrolytic capacitor are not limited to these.

[0136] REFERENCE SIGNS LIST 1 First portion (anode extraction portion) 1a End surface of first end portion 2 Second portion (cathode formation portion) 3 Anode body 4 Core portion 5 Porous portion 6 Cathode portion 7 Solid electrolyte layer 8 First layer 9 Second layer or conductive adhesive 10 Capacitor element 12 Separation layer (insulating member) 14 Sealing body 14a First outer surface of sealing body 14b Second outer surface of sealing body 15 Contact layer 17 Substrate 18 Adhesive layer 20 Cathode foil 20a End surface of metal foil 20b Carbon layer 21 First external electrode 21A Silver paste layer 21B Ni / Sn plating layer 22 Second external electrode 22A Silver paste layer 22B Ni / Sn plating layer 100 Solid electrolytic capacitor

Claims

1. a capacitor element including an anode portion and a cathode portion; a substrate supporting the capacitor element; a sealing body that seals the capacitor element; a first external electrode electrically connected to the anode portion; a second external electrode electrically connected to the cathode portion; an adhesive layer interposed between the capacitor element and the first surface of the substrate; Equipped with At the interface between the first surface and the adhesive layer, The maximum height Rz1 of the surface roughness of the first surface is 5 μm or more, A solid electrolytic capacitor, wherein the maximum height Rz2 of the surface roughness of the adhesive layer is 3 μm or more.

2. 2. The solid electrolytic capacitor according to claim 1, wherein the maximum height Rz2 is 50% or more of the maximum height Rz1.

3. 2. The solid electrolytic capacitor according to claim 1, wherein the adhesive layer between the capacitor element and the first surface has an average porosity of 50% or less.

4. 4. The solid electrolytic capacitor according to claim 1, wherein an area where the capacitor element and the first surface are in close contact with each other occupies 20% or more of the area of ​​the first surface of the substrate.

5. 4. The solid electrolytic capacitor according to claim 1, wherein the maximum height Rz2 is 30% or more of the average thickness Tav of the adhesive layer.

6. the adhesive layer contains an insulating resin and filler particles; 4. The solid electrolytic capacitor according to claim 1, wherein the filler particles are present at a distance of 80% or more of the average thickness Tav from the interface between the capacitor element and the adhesive layer.

7. 7. The solid electrolytic capacitor according to claim 6, wherein the insulating resin comprises at least one selected from the group consisting of an epoxy resin, an acrylic resin, a silicone resin, a polyamide resin, and a polyimide resin.

8. 4. The solid electrolytic capacitor according to claim 1, comprising two or more stacked capacitor elements each including the capacitor element.

9. A method for manufacturing the solid electrolytic capacitor according to any one of claims 1 to 3, comprising: providing the capacitor element; providing a substrate for supporting the capacitor element; applying an adhesive to a first surface of the substrate to form the adhesive layer; placing the capacitor element on the substrate via the adhesive; Equipped with a first surface of the substrate prepared in the step of preparing the substrate having a maximum height Rz3 of surface roughness of 10 μm or more;

10. 10. The method for manufacturing a solid electrolytic capacitor according to claim 9, further comprising the step of, after the step of applying an adhesive to the substrate, allowing the adhesive to penetrate into the first surface of the substrate under reduced pressure.

11. 10. The method for manufacturing a solid electrolytic capacitor according to claim 9, wherein the adhesive has a viscosity at 25°C of 5 Pa·s or more and 75 Pa·s or less.