Electrolytic capacitor

Abstract

This electrolytic capacitor is provided with: a capacitor element provided with an anode section and a cathode section; a cathode foil electrically connected to the cathode part; and an exterior body that seals the capacitor element and constitutes a laminate in which the capacitor element and the conductive foil are laminated so that the cathode portion of the capacitor element is electrically connected to the cathode foil, the exterior body containing an epoxy resin, and the conductive foil is electrically connected to the cathode portion of the capacitor element when viewed from the lamination direction of the laminate. The thickness of the exterior body positioned above or below the laminated body is 24.9% or more of the thickness of the laminated body in the lamination direction.

Description

Technical Field

[0001] This invention relates to electrolytic capacitors. Background Technology

[0002] An electrolytic capacitor comprises: a capacitor element having an anode and a cathode, an outer casing that seals the capacitor element, and external electrodes that are electrically connected to the anode and cathode of the capacitor element, respectively.

[0003] As a component of a solid electrolytic capacitor, Patent Document 1 proposes "a solid electrolytic capacitor characterized in that it comprises: a capacitor element having a capacitor forming portion, an outer resin covering the capacitor forming portion, an anode terminal and a cathode terminal at least partially disposed outside the outer resin, and a lead wire, wherein the capacitor element includes an anode, a dielectric layer and a solid electrolyte layer sequentially stacked on a portion of the anode, the lead wire being electrically connected to the solid electrolyte layer, and at least one of the components selected from the connection portion between the anode and the anode terminal and the connection portion between the lead wire and the cathode terminal has an uneven surface shape on its surface."

[0004] In the solid electrolytic capacitor described in Patent Document 1, the leads are exposed outside the outer resin casing, and a portion of the exposed leads is electrically connected to the cathode terminal. According to Patent Document 1, the surface of the leads is processed in the connection portion with the cathode terminal to increase the surface area, thereby obtaining a solid electrolytic capacitor with low equivalent series resistance (ESR).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-086459 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In Patent Document 1, although the initial ESR of solid electrolytic capacitors can be reduced, the fact that the ESR may increase from the initial ESR due to high-temperature processing such as reflow soldering is not taken into account.

[0010] If the sealing using the outer resin is insufficient, the ESR increase after reflow soldering may occur due to the intrusion of air, moisture, etc., through unfilled areas of the outer resin. Furthermore, the outer resin expands and deforms due to stress caused by gas generation at high temperatures, sometimes resulting in cracks, which degrades the characteristics of the capacitor containing ESR. Additionally, sometimes the expansion of the outer resin can cause the metal foil (leads) to peel off from the capacitor element, increasing contact resistance and consequently raising the ESR.

[0011] In terms of suppressing the expansion of the outer resin, it is also considered to use a resin material that is difficult to deform as the outer resin. However, such resin materials often have low sealing performance or low fluidity during molding, which can easily lead to unfilled portions of the outer resin during the sealing process.

[0012] On the other hand, by increasing the thickness of the outer resin inside the capacitor, the deformation of the outer resin at high temperatures can be suppressed, but it is difficult to obtain a high-capacity solid electrolytic capacitor.

[0013] Methods for solving problems

[0014] One aspect of this disclosure relates to an electrolytic capacitor comprising: a capacitor element having an anode portion and a cathode portion; a cathode foil electrically connected to the cathode portion; and an outer casing for sealing the capacitor element, wherein a laminate consisting of the capacitor element and the conductive foil is formed such that the cathode portion of the capacitor element is electrically connected to the cathode foil, the outer casing comprising epoxy resin, and when viewed from the lamination direction of the laminate, the thickness of the outer casing located above or below the laminate is 24.9% or more of the thickness of the laminate in the lamination direction.

[0015] Another aspect of this disclosure relates to an electrolytic capacitor comprising: a capacitor element having a foil-shaped anode portion and a cathode portion; and an outer casing that seals the capacitor element, wherein the end face of the anode portion is exposed from the outer casing and the exposed portion is electrically connected to an external electrode, the outer casing comprising epoxy resin, and when viewed from a direction perpendicular to the main face of the anode portion, the thickness of the outer casing located above or below the capacitor element is 24.9% or more of the total thickness of the capacitor element in the vertical direction.

[0016] Invention Effects

[0017] According to this disclosure, it is possible to obtain electrolytic capacitors with low ESR even after a reflow soldering process.

[0018] The novel features of the invention are set forth in the appended claims; however, the invention should be more fully understood, in both its structure and content, together with its other objects and features, by referring to the following detailed description of the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment of the present disclosure.

[0020] Figure 2 This is a cross-sectional view schematically representing an example of the structure of a capacitor element.

[0021] Figure 3 This is a schematic cross-sectional view of an electrolytic capacitor according to another embodiment of the present disclosure.

[0022] Figure 4 This is a schematic cross-sectional view of an electrolytic capacitor according to another embodiment of the present disclosure.

[0023] Figure 5 This is a schematic cross-sectional view of an electrolytic capacitor according to another embodiment of the present disclosure.

[0024] Figure 6 This is a schematic cross-sectional view of an electrolytic capacitor according to another embodiment of the present disclosure. Detailed Implementation

[0025] The following examples illustrate embodiments of this disclosure, but this disclosure is not limited to the examples described below. In the following description, specific values ​​and materials are sometimes illustrated, but other values ​​and materials can be applied as long as the effects of this disclosure are achieved. In this specification, the phrase "value A to value B" includes both value A and value B, and can be replaced with "value A or higher and value B or lower." In the following description, when lower and upper limits of values ​​related to specific physical properties, conditions, etc., are illustrated, any of the illustrated lower limits can be arbitrarily combined with any of the illustrated upper limits, as long as the lower limit is not higher than the upper limit. When multiple materials are illustrated, one can be selected for use alone, or two or more can be used in combination.

[0026] Furthermore, this disclosure includes a combination of matters described in any two or more claimed technical solutions selected from the plurality of claimed technical solutions described in the appended scope of protection. That is, as long as no technical contradiction arises, matters described in any two or more claimed technical solutions selected from the plurality of claimed technical solutions described in the appended scope of protection can be combined.

[0027] "Electrolytic capacitor" can be replaced with "solid electrolytic capacitor", and "capacitor" can be replaced with "capacitor".

[0028] Electrolytic capacitors

[0029] An electrolytic capacitor according to one embodiment of the present invention includes a capacitor element. The shape of the capacitor element is not particularly limited. The capacitor element includes an anode portion and a cathode portion. The capacitor element, for example, includes an anode body, a dielectric layer, and a cathode layer. The anode portion includes at least a portion of the anode body. The cathode portion includes a cathode layer.

[0030] The capacitor element is sealed with an outer casing. The outer casing is made of a sealing material. The sealing material can be a cured product of a thermosetting resin composition including epoxy resin, etc. In this case, the outer casing contains epoxy resin. Preferably, the outer casing contains epoxy resin and filler.

[0031] In one embodiment, the electrolytic capacitor includes a cathode foil electrically connected to a cathode portion. A laminate comprising a capacitor element and a cathode foil is formed such that the cathode portion of the capacitor element is electrically connected to the cathode foil. Within the laminate, for example, the cathode foil has a protruding end portion protruding relative to the cathode portion in a direction parallel to the lamination direction. The cathode foil may be a metal foil. The laminate is sealed by an outer casing, but a portion of the cathode foil (including at least a portion of the end face of the protruding end portion) is exposed from the outer casing. Through the exposed portion, an electrical connection can be made between the cathode portion of the capacitor element and an external electrode (external cathode electrode).

[0032] However, sometimes the outer casing expands and deforms due to high-temperature processing steps such as reflow soldering. Along with this deformation, the cathode foil may sometimes peel off from the capacitor element, reducing the electrical connection between the capacitor element and the cathode foil. As a result, the ESR may increase after the reflow soldering process.

[0033] In electrolytic capacitors, when viewed from the stacking direction, the thickness T1 of the outer casing located above or below the stack is 24.9% or more of the thickness T2 of the stack in the stacking direction (T1 / T2 > 0.249). When the thickness T1 is 24.9% or more of the thickness T2, the peeling of the cathode foil caused by the expansion of the outer casing is significantly suppressed compared to the case where the thickness T1 is less than 24.9% of the thickness T2. Therefore, the rise in ESR at high temperatures can be significantly suppressed, and a low ESR can be maintained even after the reflow soldering process. The thickness T1 is preferably 25% or more of the thickness T2 (T1 / T2 > 0.25).

[0034] The thickness T1 of the outer casing located above the laminate can satisfy the above relationship relative to the thickness T2 of the laminate, and the thickness T1 of the outer casing located below the laminate can also satisfy the above relationship relative to the thickness T2 of the laminate. Preferably, the above relationship can be satisfied when the thicknesses of the outer casings located above and below the laminate are each set to T1.

[0035] There is no specific upper limit to the thickness T1 of the outer casing, but from the perspective of obtaining high capacity, it can be less than 200%, 100%, or 50% of the thickness T2 of the laminate.

[0036] In addition, by using epoxy resin as the resin for the outer casing, cracks are less likely to occur even at high temperatures, and the intrusion of air and moisture can be suppressed, thus preventing the degradation of capacitor characteristics.

[0037] Preferably, the outer casing contains filler with an average particle size of 12 μm to 32 μm. The filler accounts for 73% to 84% by mass of the outer casing. In this case, the outer casing resin has good flowability during molding, which can suppress the formation of gaps with unfilled portions between the outer casing and the laminate, thereby improving sealing performance. As a result, it is possible to further suppress the degradation of capacitor characteristics caused by the intrusion of air, moisture, etc. It should be noted that the average particle size here refers to the particle size that accumulates from the smallest particle size in the volumetric particle size distribution, making up 50% of the total volume (median particle size D50).

[0038] In the particle size distribution of the filler, the particle size D10, which represents 10% or more of the total volume from the smallest particle size in the volumetric particle size distribution, can be, for example, 1 μm or larger. In the particle size distribution of the filler, the particle size D90, which represents 90% or less of the total volume from the smallest particle size in the volumetric particle size distribution, can be, for example, 35 μm or smaller.

[0039] From the perspective of improving flowability during molding, fillers with particle sizes ranging from 12μm to 32μm can account for 30% to 90% of the total volume, or 30% to 70% of the total volume, in terms of filler particle size distribution. The filler proportion is determined by accumulating the particle size distribution of fillers in the volumetric range of 12μm to 32μm.

[0040] The average particle size D50 (as well as particle sizes D10 and D90) can be determined by observing the cross-section of the outer casing using a scanning electron microscope (SEM) and analyzing the cross-sectional image. The outline of each filler in the cross-sectional image is determined, and the area Sf occupied by each filler in the cross-section is calculated. Based on the area Sf, the diameter Df of the equivalent sphere with its average cross-sectional area as a sphere is calculated (Df = 8√(Sf / π)). 3 The distribution of diameter Df is determined. Each packing material is assumed to be spherical with a diameter Df, and the volumetric particle size distribution of the packing material is calculated, deriving D50, D10, and D90. Preferably, at least 100 packing materials are selected and their particle size distribution is determined.

[0041] Epoxy resins possess excellent electrical insulation, water resistance, and chemical resistance, and their glass transition temperature (Tg) and hardness are easily controlled. Epoxy resins are typically obtained through a crosslinking reaction between a monomer or polymer (prepolymer) containing epoxy groups and a curing agent. The main agent is not particularly limited, but polyaromatic epoxy resins are preferred. Prepolymers such as bisphenol-type epoxy resins, biphenyl-type epoxy resins, naphthalene-type epoxy resins, cresol-phenolic resins, and dicyclopentadiene-type epoxy resins can be used. It should be noted that polyaromatic epoxy resins are epoxy resins with multiple aromatic rings in their main backbone. Among these, biphenyl-type and naphthalene-type epoxy resins exhibit low viscosity at high temperatures and high flowability during molding.

[0042] There are no particular limitations on the curing agent; it can be selected appropriately based on the type of the main agent. Examples of curing agents include polyfunctional or polyaromatic phenolic curing agents such as phenol and phenolic resin, acid anhydride curing agents such as tetrahydrophthalic anhydride and hexahydrophthalic anhydride, and amine curing agents such as ethylenediamine and aromatic amines.

[0043] From the viewpoint of ease of molding and sufficient strength, epoxy resins preferably include biphenyl aralkyl type resins. More preferably, the epoxy resin can be a polycyclic biphenyl aralkyl type resin.

[0044] Regarding the coefficient of linear expansion of the outer casing, the coefficient of linear expansion α1 can be 13 × 10⁻⁶. -6 / ℃ or above and 21×10 -6 Below / ℃, the linear expansion coefficient α2 can be 52×10 -6 / ℃ or higher and 74×10 -6 / ℃ and below. Here, the coefficient of linear expansion α1 is the coefficient of linear expansion of the outer casing at a temperature lower than the glass transition temperature Tg of the resin (epoxy resin) contained in the outer casing. The coefficient of linear expansion α2 is the coefficient of linear expansion of the outer casing at a temperature higher than the glass transition temperature Tg of the resin (epoxy resin) contained in the outer casing. The coefficients of linear expansion α1 and α2 are determined by measurement according to JIS K 7197.

[0045] The glass transition temperature (Tg) of epoxy resin is, for example, above 110°C, or even higher. Tg can also be, for example, below 130°C. The glass transition temperature (Tg) depends on the crosslinking density and structure of the epoxy resin. Therefore, the glass transition temperature (Tg) can be controlled, for example, by the types of the main agent and curing agent, the mixing ratio of the main agent and curing agent, and the molecular weight of the main agent.

[0046] The moisture absorption rate of epoxy resin can be above 0.23% and below 0.34%. The moisture absorption rate is calculated as follows: The resin is placed in an environment of 85℃ and 85% relative humidity for 72 hours. The moisture absorption rate is calculated based on the formula ((M1-M0) / M0)×100 (%), using the mass M1 of the resin after 72 hours and the mass M0 of the resin before the test. The resin is assumed to be in the form of a cured sheet during the test.

[0047] The flexural modulus of the epoxy resin at 260°C is preferably 0.19 GPa or higher and 0.25 GPa or lower. The flexural modulus is determined according to JIS K 7171.

[0048] In addition to epoxy resin, the outer casing may also contain other resins. Examples of other resins include phenolic resin, urea-formaldehyde resin, polyimide resin, polyamide-imide resin, polyurethane resin, diallyl phthalate resin, and unsaturated polyester resin. When the outer casing contains other resins besides epoxy resin, the ratio of epoxy resin to the total of epoxy resin and other resins, by mass, may be 75% or more, 90% or more, or 95% or more.

[0049] There are no particular limitations on the filler material; known fillers can be used. For example, insulating fillers such as insulating particles and insulating fibers can be used. Insulating materials constituting the insulating filler material include, for example, insulating compounds such as silica, alumina, aluminum nitride, and boron nitride, as well as glass and mineral materials (talc, mica, clay, etc.). The outer casing may contain one type of filler or two or more types.

[0050] A high filler content in the outer casing results in higher strength and lower shrinkage during molding. Additionally, it reduces hygroscopicity and increases flame retardancy. Conversely, a low filler content leads to better adhesion of the outer casing to the capacitor elements, but also lower rigidity, making it more susceptible to heat-induced deformation. Furthermore, a low filler content promotes good flowability during molding, reducing the likelihood of unfilled resin portions. For example, in the case of a laminate containing multiple capacitor elements, it is easier to fill the gaps between the capacitor elements with resin. To achieve a good balance of these properties, the filler content in the outer casing is preferably in the range of 70% to 90% by mass. Alternatively, the content can be 73% by mass or more, or 84% by mass or less.

[0051] When the filler content in the outer casing is the same, a smaller filler particle size allows the resin between the fillers to act as a buffer, easily mitigating stress. As a result, the overall stress that the outer casing can mitigate increases. Furthermore, if the filler particle size is small, the resin becomes easier to fill the gaps in the laminate. In this respect, the maximum filler particle size can be 50 μm or less (e.g., 35 μm or less). By setting the maximum particle size to 35 μm or less, stress mitigation is easier as described above. Here, the maximum particle size refers to the particle size of the largest filler particle contained in the outer casing. The maximum particle size is determined by photographing a cross-section of the outer casing, arbitrarily selecting 100 particles, and measuring the cross-sectional area of ​​each particle. The diameter of the largest equivalent circle with an area equal to the cross-sectional area of ​​each particle is called the maximum particle size.

[0052] An electrolytic capacitor may also have a portion of its cathode foil exposed from the outer casing, with the exposed portion electrically connected to an external electrode (external cathode electrode). This configuration can reduce the ESR of the electrolytic capacitor. For example, a portion of the cathode foil may have a protruding end portion projecting relative to the capacitor element in a direction parallel to the stacking direction, with at least a portion of the protruding end portion including its end face electrically connected to the external electrode.

[0053] In this situation, due to the high-temperature processing steps such as reflow soldering, the outer casing expands and deforms, sometimes causing the cathode foil to peel off from the outer casing, creating a gap between them. Sometimes, air or moisture can penetrate through this gap, leading to an increase in ESR. Furthermore, with the expansion and deformation of the outer casing, the electrical connection between the end face of the cathode foil and the external electrode may decrease, further increasing the ESR. However, as described above, by setting the thickness T1 of the outer casing to 24.9% or more of the thickness T2 of the laminate, the expansion of the outer casing is suppressed, thus significantly suppressing the increase in ESR at high temperatures and maintaining a low ESR even after the reflow soldering process.

[0054] Similarly, a portion of the anode of the capacitor element may be exposed from the outer casing, with the exposed portion electrically connected to an external electrode (external anode electrode). The anode of the capacitor element has a protruding end portion that protrudes in a direction parallel to the stacking direction, and at least a portion of the end face of the protruding end portion of the anode portion can be electrically connected to the external electrode. The protruding end portion in the anode portion may also protrude in a direction different from the protruding direction of the protruding end portion of the cathode foil.

[0055] In this situation, due to the high-temperature processing steps such as reflow soldering, the outer casing expands and deforms, sometimes causing the seal between the outer casing and the anode portion to peel off at the protruding end, creating a gap between the outer casing and the anode portion. Sometimes, air or moisture can infiltrate through this gap, leading to an increase in ESR. Furthermore, with the expansion and deformation of the outer casing, the electrical connection between the end face of the anode portion and the external electrode may decrease, further increasing the ESR. However, as described above, by setting the thickness T1 of the outer casing to 24.9% or more of the thickness T2 of the laminate, the expansion of the outer casing is suppressed, thus significantly suppressing the increase in ESR at high temperatures and maintaining a low ESR even after the reflow soldering process.

[0056] Electrolytic capacitors may also lack a cathode foil electrically connected to the cathode portion of the capacitor element. Even in this case, by exposing a portion of the anode portion of the capacitor element from the outer casing and electrically connecting the exposed portion to an external electrode (external anode electrode), an electrolytic capacitor with low ESR can be achieved. Furthermore, by ensuring that the thickness T1 of the outer casing and the total thickness T2 of the capacitor element satisfy the aforementioned relationship, the expansion of the outer casing is suppressed, thereby significantly suppressing the rise in ESR at high temperatures.

[0057] In one embodiment, the electrolytic capacitor includes: a capacitor element having a foil-shaped anode and cathode portion, and an outer casing sealing the capacitor element, the end face of the anode portion protruding from the outer casing, the exposed portion being electrically connected to an external electrode (external anode electrode). The outer casing comprises the aforementioned epoxy resin. When viewed from a direction perpendicular to the main surface of the anode portion, the thickness T1 of the outer casing located above or below the capacitor element is 24.9% or more of the total thickness T2 of the capacitor element in the vertical direction. In the case of a laminate consisting of multiple capacitor elements stacked together, the direction perpendicular to the main surface of the anode portion can be the stacking direction of the multiple capacitor elements. In the case of a laminate consisting of multiple capacitor elements stacked together, the total thickness T2 refers to the thickness of the laminate in the vertical direction (i.e., the sum of the thicknesses of the multiple capacitor elements in the stacking direction).

[0058] The laminate can also be configured to include multiple capacitor elements. In this case, the laminate can include multiple cathode foils. The cathode foils can be inserted between adjacent capacitor elements. The cathode foils can electrically connect the cathode portion of one adjacent capacitor element to the cathode portion of another adjacent capacitor element. A portion of the anode portion of the multiple capacitor elements can also be exposed from the outer casing. The end faces of the multiple anode portions can also be exposed from the outer casing, and at least a portion of these end faces are electrically connected to an external electrode (external anode electrode). Additionally, a portion of the multiple cathode foils can be exposed from the outer casing. The end faces of the multiple cathode foils can also be exposed from the outer casing, and at least a portion of these end faces are electrically connected to an external electrode (external cathode electrode).

[0059] Within a stack, multiple capacitor elements can be oriented in the same direction or in different directions. For example, the anode and cathode portions can be stacked alternately in opposite directions, or in any order in opposite directions. The anode and cathode portions can also be stacked alternately at 90-degree angles, or in any order in a 90-degree angle.

[0060] Alternatively, only the end face of the anode portion may be exposed from the outer casing and electrically connected to the external electrode. Similarly, only the end face of the cathode foil may be exposed from the outer casing and electrically connected to the external electrode. However, from the viewpoint of obtaining a low ESR, it is preferable that both the end faces of the anode portion and the end faces of the cathode foil are exposed from the outer casing and electrically connected to their respective external electrodes.

[0061] The end face of the cathode foil can be exposed from the first main surface of the outer casing. In this case, the external electrode can be configured to cover the first main surface. At this time, the end face of the anode portion can also be exposed from a second main surface of the outer casing that is different from the first main surface (e.g., on the opposite side of the first main surface).

[0062] When the laminate includes multiple cathode foils, a portion of the end faces of the multiple cathode foils can be exposed from the first main surface of the outer casing, while the end faces of other cathode foils can be exposed from a second main surface of the outer casing that is different from the first main surface (e.g., opposite to the first main surface). In this case, two external electrodes (external cathode electrodes) are provided, one configured to cover the first main surface and the other configured to cover the second main surface. At this time, the end face of the anode portion can be exposed from a third main surface of the outer casing that is different from both the first and second main surfaces. In this case, the external electrode (external anode electrode) can be configured to cover the third main surface.

[0063] Similarly, when the laminate includes multiple capacitor elements, a portion of the end faces of the multiple anode portions can be exposed from the third main surface of the outer casing, while the end faces of the other anode portions can be exposed from a fourth main surface of the outer casing that is different from the first to third main surfaces (e.g., opposite to the third main surface). In this case, two external electrodes (external anode electrodes) are provided, one configured to cover the third main surface and the other configured to cover the fourth main surface.

[0064] There is no particular limitation on the size of the electrolytic capacitor, but the size of the electrolytic capacitor in the stacking direction can be 100μm or more and 10mm or less, or 300μm or more and 5mm or less. In this case, sufficient rigidity can be obtained, and the effect of suppressing the rise of ESR at high temperature is high by setting the thickness T1 of the outer casing to more than 24.9% of T2.

[0065] Next, an illustrative description of a method for manufacturing an electrolytic capacitor will be given, but the method for manufacturing an electrolytic capacitor disclosed herein is not limited to the following.

[0066] A method for manufacturing an electrolytic capacitor includes, for example, a step of preparing a capacitor element having an anode portion and a cathode portion, a step of stacking cathode foils on the cathode portion of the capacitor element to obtain a laminate, a step of sealing the capacitor element with an outer casing, a step of exposing the end face of the cathode foil from the outer casing, and a step of forming an external cathode electrode electrically connected to the cathode portion via the end face of the cathode foil.

[0067] The manufacturing method described above can further include a step of exposing the end face of the anode portion from the outer casing, and a step of forming an external anode electrode that is electrically connected to the end face of the anode portion. Each step will be further explained below.

[0068] (The process of preparing capacitor components)

[0069] The process of preparing a capacitor element includes the process of preparing the anode body. The process of preparing a capacitor element may include the process of configuring a separation layer (insulating member) on a portion of the anode body.

[0070] (Anode)

[0071] In the process of preparing the anode body, an anode body is prepared having a first portion (also called an "anode lead-out portion") including a first end and a second portion (also called a "cathode forming portion") including a second end. The anode portion includes the first portion (anode lead-out portion) of the anode body. The first portion of the anode body may include a predetermined removal end that is subsequently removed by cutting or the like. At least the second portion of the anode body has a porous portion. Subsequently, a dielectric layer is formed on at least the surface of the second portion.

[0072] The anode body comprises valve-acting metals, alloys containing valve-acting metals, and compounds containing valve-acting metals (intermetallic compounds, etc.). These materials can be used individually or in combination of two or more. Aluminum, tantalum, niobium, titanium, etc., can be used as valve-acting metals. The anode body can be a foil (anode foil) of valve-acting metal, alloy containing valve-acting metal, or compound containing valve-acting metal, or a porous sintered body of valve-acting metal, alloy containing valve-acting metal, or compound containing valve-acting metal.

[0073] When a foil (anode foil) is used as the anode body, a porous portion is formed on the surface of at least a second portion of the anode foil. That is, the second portion has a metal core and a porous portion formed on the surface of the metal core. The porous portion can be formed by roughening the surface of at least the second portion of the anode foil by etching or the like. Alternatively, a roughening treatment such as etching can be performed after a predetermined masking member is disposed on the surface of the first portion. On the other hand, the entire surface of the anode foil can be roughened by etching or the like. In the former case, an anode foil is obtained where the surface of the first portion does not have a porous portion and the surface of the second portion has a porous portion. In the latter case, a porous portion is formed on the surface of the first portion in addition to the surface of the second portion.

[0074] As an etching process, known methods can be used, such as electrolytic etching. The masking member is not particularly limited, but an insulator such as resin is preferred. The masking member can be a conductive material containing a conductive material.

[0075] When the entire surface of the anode foil is roughened, a porous portion also exists on the surface of the first part. The porous portion of the first part can also be pre-compressed to flatten the pores. This prevents air and moisture from entering the electrolytic capacitor through the porous portion from the end face of the anode portion exposed from the outer casing.

[0076] When a sintered body is used in the anode body, it is obtained by forming and sintering a powder containing a valve-acting metal (e.g., powder of a valve-acting metal, powder of an alloy or compound containing a valve-acting metal). For example, together with powder of a valve-acting metal, the powder is placed into a mold such that the embedded portion of the anode wire connected to the anode body is embedded in the powder, pressure forming is performed, and sintering is carried out, thereby forming a porous anode body in which a portion of the anode wire is embedded. Sintering is preferably performed under reduced pressure. The metal wire corresponds to the first part. The sintered body corresponds to the second part.

[0077] (Separation layer)

[0078] When a foil (anode foil) is used in the anode body, an insulating separation layer can be provided to electrically separate the first part from the second part. In this process, an insulating member is disposed on the first part of the anode body via a dielectric layer. The insulating member is disposed in such a way that it isolates the first part from the cathode portion formed in a subsequent process. The separation layer can be configured to be close to the cathode portion to cover at least a portion of the surface of the first part.

[0079] The separation layer is obtained, for example, by attaching a sheet-like insulating member (such as a resin tape) to the first part. When using an anode foil with a porous surface, the insulating member can be sealed to the first part after the porous surface of the first part is compressed and flattened. Preferably, the sheet-like insulating member has an adhesive layer on the surface of the side attached to the first part.

[0080] Liquid resin can be coated or impregnated into the first part to form an insulating member that adheres tightly to the first part. In the method of using liquid resin, the insulating member is formed by filling the unevenness of the surface of the porous portion of the first part. Liquid resin can easily enter the recesses on the surface of the porous portion, and the insulating member can also be easily formed within the recesses.

[0081] (Dielectric layer)

[0082] The dielectric layer is formed, for example, by anodizing the valve-acting metal on the surface of at least a second portion of the anode body through a chemical conversion process. The chemical conversion process can be performed, for example, by immersing the anode body in a chemical conversion solution, allowing the solution to permeate to the surface of the anode body, using the anode body as the anode, and applying a voltage between the anode body and the cathode immersed in the chemical conversion solution. When the surface of the anode body has a porous portion, the dielectric layer is formed along the uneven shape of the porous portion's surface. The dielectric layer contains an oxide of the valve-acting metal. For example, when aluminum is used as the valve-acting metal, the dielectric layer contains aluminum oxide. When tantalum is used as the valve-acting metal, the dielectric layer contains tantalum oxide. The dielectric layer is formed at least along the surface of the second portion where the porous portion is formed (including the inner wall surface of the pores in the porous portion). It should be noted that the method of forming the dielectric layer is not limited to this, as long as an insulating layer that functions as a dielectric can be formed on the surface of the second portion. The dielectric layer can also be formed on the surface of the first portion (e.g., on the porous portion of the surface of the first portion).

[0083] (Cathode section)

[0084] The cathode portion has a solid electrolyte layer covering at least a portion of the dielectric layer and a cathode lead-out layer covering at least a portion of the solid electrolyte layer.

[0085] (Solid electrolyte layer)

[0086] The solid electrolyte layer may contain, for example, a conductive polymer. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. The solid electrolyte layer can be formed, for example, by chemically polymerizing and / or electrolytically polymerizing the raw material monomers on the dielectric layer. Alternatively, it can be formed by coating the dielectric layer with a solution containing the conductive polymer or a dispersion of the conductive polymer. The solid electrolyte layer may contain a manganese compound.

[0087] (Cathode lead-out layer)

[0088] The cathode lead-out layer may include, for example, a carbon layer and a conductive paste layer. The carbon layer only needs to be conductive; for example, it can be constructed using a conductive carbon material such as graphite. The carbon layer is formed, for example, by coating a carbon paste onto at least a portion of the surface of a solid electrolyte layer. The conductive paste layer may be a cured product of a metal paste containing metal particles and resin (metal paste layer). The metal particles may be particles of silver, copper, nickel, etc. Silver is particularly preferred. That is, the metal paste layer is preferably a silver paste layer. The resin preferably includes epoxy resin. The metal paste may be a thermosetting resin composition containing metal particles and epoxy resin. The metal paste layer is formed, for example, by coating it onto the surface of the carbon layer. It should be noted that the structure of the cathode lead-out layer is not limited to this; it can be any structure with current-collecting function. The conductive paste layer may be a cured product of a conductive carbon material paste containing carbon particles and resin.

[0089] (The process of obtaining the laminated body)

[0090] Next, cathode foils are overlapped on the cathode portion of the capacitor elements to obtain a laminate. A laminate can be obtained by overlapping multiple capacitor elements and / or multiple cathode foils. The cathode foils are electrically connected to the cathode lead-out layer and to the external cathode electrode.

[0091] In the case of a laminate having multiple capacitor elements, the cathode foil may be located between one cathode lead-out layer and another cathode lead-out layer of adjacent capacitor elements within the laminate. However, this is not a limitation; the cathode lead-out layers of some capacitor elements may also be directly connected to the cathode lead-out layers of adjacent capacitor elements without passing through the cathode foil.

[0092] (Cathode foil)

[0093] The cathode foil, for example, is a metal foil, which can be a sintered foil, a vapor-deposited foil, or a coated foil. The cathode foil can be a sintered foil, a vapor-deposited foil, or a coated foil formed by depositing a conductive film onto the surface of a metal foil (e.g., Al foil, Cu foil). A vapor-deposited foil can also be an Al foil with Ni deposited on its surface. Examples of conductive films include Ti, TiC, TiO, and C (carbon) films. The conductive film can be a carbon coating.

[0094] (Substrate)

[0095] Electrolytic capacitors may have a substrate supporting one capacitor element or a stack of multiple capacitor elements. The substrate may be, for example, an insulating substrate. Where electrical separation between the external anode electrode and the external cathode electrode is possible, the substrate may also be a metal substrate or a printed substrate with wiring patterns applied.

[0096] When the substrate is an insulating substrate, a single capacitor element or a laminate having multiple capacitor elements can be placed on the substrate using an adhesive (e.g., an epoxy adhesive).

[0097] When the substrate is a metal substrate or the like, a metal foil can be disposed between the cathode portion of a single capacitor element and the substrate, or a metal foil can be disposed between the cathode portion of the capacitor element closest to the substrate in the element stack and the substrate. In this case, a conductive adhesive can be used to bond the metal foil to the cathode portion and the substrate. In this case, a conductive adhesive layer is formed not only between the metal foil and the cathode portion, but also between the metal foil and the substrate. The conductive adhesive layer may include: a first layer between the main surface of the metal foil on the cathode portion side and the cathode portion, a second layer between the main surface of the metal foil on the substrate side and the substrate, and a third layer that fills the through-holes of the metal foil and is integrally formed with the first and second layers. With the presence of the third layer, the adhesion strength between the cathode portion and the metal foil, as well as the adhesion strength between the substrate and the metal foil, is also improved.

[0098] Examples of insulating substrates include glass epoxy boards, paper phenolic substrates, glass polyimide substrates, and fluorine substrates. The thickness of the insulating substrate can be, for example, 500 μm or less, 250 μm or less, 200 μm or less, or 150 μm or less. Alternatively, the thickness of the insulating substrate can be, for example, 50 μm or more.

[0099] The substrate may have a coating covering at least one main surface of the insulating substrate. The coating may comprise at least one of a cured curable resin (e.g., epoxy resin) and a thermoplastic resin (e.g., fluoropolymer). The epoxy resin may be one of the epoxy resins exemplified above. Examples of fluoropolymers include polytetrafluoroethylene, perfluoroalkoxyalkane, perfluoroethylene-propylene copolymer, perfluoroethylene-propylene copolymer, polyvinylidene fluoride, and polyvinylidene fluoride copolymer.

[0100] (The process of sealing the capacitor element with an outer casing)

[0101] First, the capacitor element can be placed in a mold in which the end faces of the anode and cathode are exposed, and the remaining part of the capacitor element is sealed. Then, the capacitor element is sealed with a sealing material to form the outer casing. Second, the capacitor element can be placed in a mold in which the end faces of the anode and cathode are not exposed, and the entire capacitor element is sealed. Then, the capacitor element is sealed with a sealing material to form the outer casing. In either case, it is effective to form an assembly of multiple capacitor elements and seal the assembly with a sealing material to form the outer casing. Such a process can be performed by transfer molding, compression molding, etc. In the case of the first method, the step of exposing the end faces of the anode and cathode from the outer casing is also performed simultaneously.

[0102] The sealing material preferably comprises a thermosetting resin composition, but may also comprise a thermoplastic resin. In transfer molding or compression molding, the uncured sealing material is cured to form the outer casing. In addition to main resins such as epoxy resin, the thermosetting resin composition may also include fillers, curing agents, polymerization initiators, catalysts, etc.

[0103] The capacitor element is sealed with a sealing material such that the thickness of the outer casing above or below the laminate is more than 24.9% of the thickness of the laminate in the lamination direction when viewed from the lamination direction.

[0104] (The process of exposing the end face of the cathode foil or anode portion from the outer casing)

[0105] When exposing the end face of the cathode foil from the outer casing, a portion of the outer casing can be removed, for example. Specifically, examples include grinding the outer casing after covering the capacitor element with it, or cutting off a portion of the outer casing to expose the end face of the cathode foil. Alternatively, a portion of the cathode foil can be cut off together with a portion of the outer casing.

[0106] When exposing the end face of the anode portion from the outer casing, the outer casing can also be partially removed to expose the end face of the anode portion from the outer casing. The same method used to expose the end face of the anode portion from the outer casing can be used. Alternatively, a portion of the first part can be cut off together with a portion of the outer casing. Preferably, the surface of the outer casing from which the end face of the first end of the anode body is exposed is a different surface from the surface from which the end face of the cathode foil is exposed from the outer casing.

[0107] The anode body and insulating member of the laminate can be partially removed together with the outer casing, exposing the end face of the first end and the end face of the insulating member from the outer casing. In this case, flush end faces exposed from the outer casing are formed on the anode body and the insulating member, respectively. Thus, the end faces of the anode body and the insulating member, which are flush with the surface of the outer casing, can be easily exposed from the outer casing.

[0108] As described above, by cutting or the like, the end face of the anode body (first end) and the end face of the cathode foil, which have not formed a natural oxide film, can be easily exposed from the outer casing, resulting in a connection state with low resistance and high reliability between the anode body or the first part and the external anode electrode.

[0109] When forming a stack of multiple capacitor elements and sealing the assembly with a sealing material to form an outer casing, the connecting portions that link adjacent anode portions and adjacent cathode foils within the assembly can be cut off when the assembly is monolithically processed. In this case, the end faces of the anode portions and the end faces of the cathode foils are exposed at the cut surface. Such a cut surface can also be a dry etching process surface based on plasma or the like.

[0110] (Contact layer)

[0111] At least one of the exposed end faces of the anode and cathode portions from the outer casing can be connected to an external electrode via a contact layer. The contact layer can be formed, for example, by an electroless Ni plating layer, or by an electroless Ni plating layer and an electroless Ag plating layer covering it. Providing a contact layer makes the electrical connection between the end faces of the anode or cathode portion and the external electrode more reliable, which is advantageous in improving the reliability of the solid electrolytic capacitor.

[0112] The contact layer can also be selectively formed in a manner that minimizes the coverage of the outer casing surface and only covers the end faces of the anode or cathode portion exposed from the outer casing. In order to selectively form an electroless Ni plating layer on the end faces of the anode or cathode portion, a zincate treatment can also be performed prior to the formation of the electroless Ni plating layer.

[0113] (The process of forming an external cathode electrode or an external anode electrode)

[0114] The external electrodes typically include a first external electrode (external anode electrode) connected to the anode portion and a second external electrode (external cathode electrode) connected to the cathode portion. When the anode portion includes an anode body having a dielectric layer, the anode body (second part) may have a second end face exposed from the outer casing, and the second end face is electrically connected to the second external electrode. Each external electrode may include a metal layer. The metal layer is, for example, a plating layer. The metal layer may include, for example, at least one selected from nickel (Ni), copper (Cu), zinc (Zn), tin (Sn), silver (Ag), and gold (Au). To form the metal layer, film-forming techniques such as electrolytic plating, electroless plating, sputtering, vacuum evaporation, chemical vapor deposition (CVD), cold spraying, and spraying can be used.

[0115] Each external electrode may, for example, comprise a stacked structure of a Ni layer and a tin layer. The outer surface of each external electrode is preferably a metal with excellent wettability to solder. Examples of such metals include Sn, Au, Ag, and Pd.

[0116] Each external electrode may, for example, comprise a stacked structure of a conductive paste layer and a plating layer. From the viewpoint of excellent wettability with solder, a plating layer having the aforementioned stacked structure of a Ni layer and a tin layer (such as a Ni / Sn plating layer) may also be used as the plating layer.

[0117] To form a plating layer of sufficient thickness and to facilitate plating formation on the exposed surface of the outer casing, a conductive layer can be formed before plating, and then the plating layer can be formed on the conductive layer. The conductive layer can be a conductive paste layer. The conductive paste layer can be formed to cover the end face of at least one of the anode and cathode portions of a capacitor element or multiple capacitor elements. Alternatively, the conductive paste layer can be formed by covering the end face via a contact layer. Furthermore, the conductive paste layer can be formed to cover not only the end face of the anode or cathode portion but also the surface (side, etc.) of the outer casing exposed to that end face. In this way, the anode or cathode portion of the capacitor element is electrically connected to the conductive paste layer.

[0118] A conductive paste layer can be formed by applying a conductive paste containing conductive particles and resin material to the exposed surface of an outer casing at the end face of the anode or cathode and allowing it to dry. Therefore, a conductive paste layer can also be described as a conductive resin layer containing conductive particles. The resin material is suitable for bonding to the outer casing and contact layer, and the bonding strength can be improved through chemical bonds (e.g., hydrogen bonds). Conductive particles can be, for example, metallic particles such as silver and copper, or particles of conductive inorganic materials such as carbon.

[0119] The conductive paste layer can cover not only the surface of the outer casing (e.g., the side) exposed at the end face of the anode or cathode portion of the capacitor element, but also a portion of the surface intersecting with that surface (e.g., the upper or lower surface). Alternatively, when the surface of the substrate forms part of the outer surface of the capacitor element, a portion of the substrate surface can also be covered.

[0120] An external electrode can be formed from a lead frame that covers at least a portion of the conductive layer. To form a robust electrical connection between the lead frame and the conductive layer, a solder layer or other conductive layers can be formed between the conductive layer and the lead frame.

[0121] Hereinafter, the specific configuration of the electrolytic capacitor according to the embodiments of the present disclosure will be illustrated with reference to the accompanying drawings. However, the electrolytic capacitor of the present disclosure is not limited to these.

[0122] Figure 1 This is a schematic cross-sectional view of an electrolytic capacitor according to one embodiment. Figure 2 This is a cross-sectional view schematically representing an example of the structure of a capacitor element. Figure 3 This is a schematic cross-sectional view of an electrolytic capacitor according to another embodiment of the present disclosure. Figure 4 , 5 Figures 6 and 7 are schematic cross-sectional views of an electrolytic capacitor according to another embodiment of the present disclosure.

[0123] <First Embodiment>

[0124] like Figure 1 As shown, the electrolytic capacitor 100 includes a plurality of capacitor elements 10, an outer casing 14 sealing the capacitor elements 10, a plurality of cathode foils 20, a first external electrode (external anode electrode) 21, and a second external electrode (external cathode electrode) 22. The plurality of capacitor elements 10 and the cathode foils 20 are stacked to form a laminate.

[0125] The capacitor element 10 includes an anode body 3 and a cathode portion 6. The anode body 3 is an anode foil. The anode body 3 has a metal core portion 4 and a porous portion 5, and a dielectric layer (not shown) is formed on the surface of at least a portion of the porous portion 5. The cathode portion 6 covers at least a portion of the dielectric layer. The cathode foil 20 is electrically connected to the cathode portion 6 of the capacitor element.

[0126] In capacitor element 10, the end face 1a of one end (first end) is not covered by the cathode portion 6, exposing the anode body 3; on the other hand, the end face 2a of the other end (second end) is covered by the cathode portion 6. The portion of the anode body 3 not covered by the cathode portion is called first portion 1, and the portion of the anode body 3 covered by the cathode portion is called second portion 2. The end of first portion 1 is called the first end, and the end of second portion 2 is called the second end. A dielectric layer is formed at least on the surface of the porous portion 5 formed in second portion 2. The first portion 1 of the anode body 3 is also referred to as the anode lead-out portion. The second portion 2 of the anode body 3 is also referred to as the cathode forming portion.

[0127] More specifically, Part 2 has a metal core 4 and a porous portion 5 formed on the surface of the metal core 4 by roughening (etching, etc.). On the other hand, in Part 1, the porous portion 5 may or may not be present on the surface. A dielectric layer is formed along the surface of the porous portion 5. At least a portion of the dielectric layer covers the inner wall surface of the pores of the porous portion 5 and is formed along the inner wall surface.

[0128] The cathode portion 6, serving as the cathode layer, comprises a solid electrolyte layer 7 covering at least a portion of the dielectric layer and cathode lead-out layers 8 and 9 covering at least a portion of the solid electrolyte layer 7. The surface of the dielectric layer has an uneven shape corresponding to the shape of the surface of the anode body 3. The solid electrolyte layer 7 can be formed in a manner that fills the unevenness of the dielectric layer. The cathode lead-out layers, for example, comprise a carbon layer 8 covering at least a portion of the solid electrolyte layer 7 and a conductive paste layer 9 covering the carbon layer 8. The conductive paste layer 9 can, for example, be a silver paste layer containing silver particles as metal particles.

[0129] A cathode foil 20 is sandwiched between the cathode lead layers 8 and 9 of adjacent capacitor elements 10 in the stacking direction of the element stack. The cathode foil 20 is shared between adjacent capacitor elements 10 in the stacking direction of the stack. A conductive adhesive layer may be placed between the cathode foil 20 and the capacitor element 10. The adhesive layer may be, for example, a conductive adhesive. The adhesive layer may contain, for example, silver. The adhesive layer may be a silver paste layer, the same as the conductive paste layer 9.

[0130] Alternatively, the portion of the anode body 3 with a solid electrolyte layer 7 formed through the dielectric layer can be referred to as the second part 2, while the portion of the anode body 3 without a solid electrolyte layer 7 formed is referred to as the first part 1.

[0131] In at least the portion of the anode body 3 adjacent to the cathode layer in a region not opposite the cathode layer, an insulating separation layer (or insulating member) 12 may be formed in such a way as to cover the surface of the anode body 3. This restricts contact between the cathode portion 6 and the exposed portion (part 1) of the anode body 3. The separation layer 12 may be, for example, an insulating resin layer.

[0132] The structure sealed by the outer casing 14 has a generally cuboid shape, and the electrolytic capacitor 100 also has a generally cuboid shape. The outer casing 14 has a first main surface 14a, a second main surface 14b opposite to the first main surface 14a, and an upper surface 14c connected to the first main surface 14a and the second main surface 14b and intersecting the stacking direction of the laminate. In the element laminate, the first end 1a of the capacitor element 10 is exposed on the first main surface 14a.

[0133] The end faces 1a of the plurality of first ends (first portions) exposed from the outer casing 14 are electrically connected to the first external electrode 21 extending along the first main surface 14a. In this case, the proportion of the first portion in the anode body can be reduced, thereby increasing the capacity. In addition, the contribution of the first portion to ESR and ESL is reduced.

[0134] Additionally, the end face 20a of the cathode foil 20 is exposed from the outer casing 14 on the second main surface 14b. The end face of the cathode foil 20 exposed from the outer casing 14 is electrically connected to the second external electrode 22 extending along the second main surface 14b.

[0135] The first external electrode 21 includes, for example, a silver paste layer 21A and a Ni / Sn plating layer 21B. The silver paste layer 21A covers the end face of the first end 1a and the first main surface 14a (first surface) of the outer casing 14. The Ni / Sn plating layer 21B covers the silver paste layer 21A. The second external electrode 22 includes a silver paste layer 22A and a Ni / Sn plating layer 22B. The silver paste layer 22A covers the end face of the cathode foil 20 and the second main surface 14b (second surface) of the outer casing 14. The Ni / Sn plating layer 22B covers the silver paste layer 22A.

[0136] exist Figure 1 In this configuration, the end face of the first end portion 1a is on the same plane as the first main surface 14a. Furthermore, in... Figure 1 In this configuration, the end face 20a of the cathode foil 20 is on the same plane as the second main surface 14b. However, it is not necessary for the end face of the first end 1a and the end face 20a of the cathode foil 20 to be on the same plane as the main surface of the outer casing 14; the end face of the first end 1a may protrude or be recessed relative to the first main surface 14a. Similarly, the end face 20a of the cathode foil 20 may protrude or be recessed relative to the second main surface 14b.

[0137] exist Figure 1In the electrolytic capacitor shown, when viewed from the stacking direction, the thickness T1 of the outer casing located above the stack is more than 24.9% of the thickness T2 of the stack in the stacking direction (T1 / T2≥0.249). Therefore, even when the electrolytic capacitor is exposed to high temperatures due to reflow soldering, the adhesion and peeling between the cathode foil 20 and the cathode lead layer 9 caused by the expansion and deformation of the outer casing are suppressed, the increase in ESR is suppressed, and a low ESR can be maintained. It should be noted that... Figure 1 In the example, the thickness T1 refers to the minimum distance between the laminate and the upper surface 14c of the outer casing 14.

[0138] The laminate is supported by substrate 17. The substrate can be, for example, an insulating substrate, or a metal substrate or a printed substrate with wiring patterns, provided that the first external electrode 21 and the second external electrode 22 can be electrically isolated. A cathode foil can also be disposed between the bottommost cathode lead-out layer of the element laminate and substrate 17. Substrate 17 is, for example, a laminate substrate with conductive wiring patterns formed on its surface and back side, and the surface wiring patterns and the back wiring patterns can be electrically connected through vias. The surface wiring patterns can be electrically connected to the cathode portion 6 of the capacitor element stacked on the bottom layer, and the back wiring patterns can be electrically connected to the third external electrode (not shown). In this case, the third external electrode is electrically connected to the cathode portion 6 of each capacitor element in the element laminate via substrate 17. The third external electrode (cathode) can be arbitrarily disposed in the central region of the bottom surface of the electrolytic capacitor according to the back wiring pattern. For example, by distributing the third external electrode close to the first external electrode, ESL can be reduced.

[0139] The substrate 17 is a metal plate and may have a lead frame structure formed by bending a metal plate into a specified shape. A portion of the metal plate is exposed from the outer casing, and the exposed portion is electrically connected to external terminals.

[0140] <Second Implementation>

[0141] Figure 3 This is a cross-sectional view schematically showing the structure of an electrolytic capacitor according to another embodiment of the present disclosure. Figure 3 The electrolytic capacitor 101 shown includes multiple capacitor elements 10a and 10b, an outer casing 14 sealing the capacitor elements 10a and 10b, a first external electrode (external anode electrode) 21, and a second external electrode (external cathode electrode) 22. Multiple capacitor elements 10a and 10b are stacked to form an element stack. The two first external electrodes 21 are separately arranged, with one first external electrode 21 covering the first main surface 14a of the outer casing 14 and the other first external electrode 21 covering the second main surface 14b of the outer casing 14.

[0142] Multiple capacitor elements 10a and 10b include a first capacitor element 10a having a first direction from the first portion 1 of the anode body 3 toward the second portion 2, and a second capacitor element 10b having a second direction from the first portion 1 of the anode body 3 toward the second portion 2, opposite to the first direction. The end face 1a of the first end of the first capacitor element 10a is exposed from the outer casing 14 on the first main surface 14a and electrically connected to a first external electrode 21. The end face 1a of the first end of the second capacitor element 10b is exposed from the outer casing 14 on the second main surface 14b and electrically connected to another first external electrode 21. On the other hand, although not shown, on the third main surface intersecting the first main surface 14a and the second main surface 14b, and / or on the fourth main surface opposite to the third main surface, the end face of the cathode foil 20 is exposed from the outer casing 14 and electrically connected to a second external electrode 22.

[0143] For the electrolytic capacitor 101, the directions of current flow within the first capacitor element 10a and the second capacitor element 10b are different. Therefore, the directions of the magnetic field generated by the current are different, resulting in a reduction in the magnetic flux generated within the element stack. This reduces ESL (Electrostatic Discharge).

[0144] exist Figure 3 In the example, within the element stack, the first capacitor element 10a and the second capacitor element 10b are stacked alternately. However, the first capacitor element 10a and the second capacitor element 10b do not necessarily have to be stacked alternately; a portion of the element stack may have the first capacitor element 10a stacked adjacent to each other in the same direction, and / or the second capacitor element 10b stacked adjacent to each other in the same direction. Even in a portion, if the first capacitor element and the second capacitor element are stacked alternately, the magnetic flux generated within the element stack is effectively reduced, and ESL is effectively lowered, which is therefore preferable.

[0145] exist Figure 3 In the electrolytic capacitor shown, when viewed from the stacking direction (the direction perpendicular to the main surface of the anode body 3, which serves as the foil), the thickness T1 of the outer casing located above the stack is more than 24.9% of the thickness T2 of the stack in the stacking direction (T1 / T2≥0.249). Therefore, even when the electrolytic capacitor is exposed to high temperatures due to reflow soldering, the adhesion and peeling between the cathode foil 20 and the cathode lead-out layer 9 caused by the expansion and deformation of the outer casing is suppressed, the increase in ESR is suppressed, and a low ESR can be maintained.

[0146] <Third Implementation>

[0147] Figure 4This is a cross-sectional view schematically showing the structure of an electrolytic capacitor according to another embodiment of the present disclosure. The capacitor element 10 has an anode body 3, which is a sintered body of metal particles, and a metal wire 1 partially embedded in the anode body 3. The metal wire 1 corresponds to the first part, and the sintered body corresponds to the second part. Therefore, the end face of the anode portion is the end face 1a of the protruding end of the metal wire 1. A dielectric layer 5 is formed on the surface of at least a portion of the anode body 3. A cathode portion 6 covers at least a portion of the dielectric layer 5. The cathode portion 6 includes a solid electrolyte layer 7 and a cathode lead-out layer.

[0148] The anode body 3 can be obtained by forming and sintering powder containing valve-acting metal. For example, the embedded portion of the metal wire 1 connected to the anode body 3 can be placed into a mold along with the valve-acting metal powder in such a way that it is embedded in the powder, formed by pressure, and then sintered to form a porous anode body 3 in which a portion of the metal wire 1 is embedded. Sintering is preferably performed under reduced pressure. By performing a chemical conversion treatment on the sintered body, a dielectric layer 5 is formed on the surface of the sintered body.

[0149] The cathode lead-out layer, for example, comprises a carbon layer 8 covering at least a portion of the solid electrolyte layer 7 and a conductive paste layer 9 covering the carbon layer 8. The conductive paste layer 9 may, for example, be a silver paste layer containing silver particles as metal particles. The carbon layer 8 is composed of a composition containing a conductive carbon material such as graphite.

[0150] The cathode foil 20 is connected to the cathode lead-out layer via a conductive adhesive layer 30. The adhesive layer may use a conductive adhesive, for example. The adhesive layer may contain silver, for example. The adhesive layer may be the same silver paste layer as the conductive paste layer 9. A laminate is formed by stacking the cathode foil 20 in a manner that overlaps with the capacitor element 10.

[0151] The anode body 3 has a generally rectangular parallelepiped shape, and the electrolytic capacitor 200 also has a generally rectangular parallelepiped shape. The outer casing 14 has a first main surface 14a and a second main surface 14b opposite to the first main surface 14a. The end face 1a of the protruding end of the metal wire of the capacitor element 10 is exposed on the first main surface 14a. The end face 1a exposed from the outer casing 14 is electrically connected to a first external electrode 21 extending along the first main surface 14a. Additionally, the end face 20a of the cathode foil 20 is exposed from the outer casing 14 on the second main surface 14b. The end face 20a of the cathode foil 20 exposed from the outer casing 14 is electrically connected to a second external electrode 22 extending along the second main surface 14b. In this case, the length of the metal wire in the anode portion can be reduced, thereby increasing the capacitance. Furthermore, the contribution of the metal wire to ESR and ESL is reduced.

[0152] The end face 1a of the protruding metal wire exposed from the outer casing 14 and the end face 20a of the cathode foil 20 exposed from the outer casing 14 are respectively covered by the first external electrode 21 and the second external electrode 22. The first external electrode 21 and the second external electrode 22 have the same characteristics as... Figure 1 The first external electrode 21 and the second external electrode 22 of the electrolytic capacitor 100 shown have the same configuration.

[0153] exist Figure 4 In the electrolytic capacitor shown, when viewed from the stacking direction of the capacitor element 10 and the cathode foil 20, the thickness T1 of the outer casing located above the stack is more than 24.9% of the thickness T2 of the stack in the stacking direction (T1 / T2≥0.249). Therefore, even when the electrolytic capacitor is exposed to high temperatures due to reflow soldering, the adhesion and peeling between the cathode foil 20 and the cathode lead layer 9 caused by the expansion and deformation of the outer casing are suppressed, the increase in ESR is suppressed, and a low ESR can be maintained.

[0154] <Fourth Implementation>

[0155] Figure 5 This is a cross-sectional view schematically showing the structure of an electrolytic capacitor according to another embodiment of the present disclosure. The electrolytic capacitor 201 of this embodiment has the same structure as the electrolytic capacitor 200 of the third embodiment, except that the configurations of the first external electrode 21 and the second external electrode 22 are different.

[0156] The first external electrode 21 and the second external electrode 22 of the electrolytic capacitor 201 have silver paste layers (conductive layers) 21A and 22A respectively covering the first main surface 14a and the second main surface 14b of the outer casing 14. The silver paste layer 21A covers not only the first main surface 14a of the outer casing 14, but also the end face 1a of the protruding end of the metal wire. The silver paste layer 22A covers not only the second main surface 14b of the outer casing 14, but also the end face 20a of the cathode foil 20. The first external electrode 21 has a first lead frame 21B covering at least a portion of the silver paste layer 21A, and the second external electrode 22 has a second lead frame 22B covering at least a portion of the silver paste layer 22A.

[0157] exist Figure 5 In the electrolytic capacitor shown, when viewed from the stacking direction of the capacitor element 10 and the cathode foil 20, the thickness T1 of the outer casing located above the stack is more than 24.9% of the thickness T2 of the stack in the stacking direction (T1 / T2≥0.249). Therefore, even when the electrolytic capacitor is exposed to high temperatures due to reflow soldering, the adhesion and peeling between the cathode foil 20 and the cathode lead layer 9 caused by the expansion and deformation of the outer casing are suppressed, the increase in ESR is suppressed, and a low ESR can be maintained.

[0158] <Fifth Implementation>

[0159] Figure 6 This is a cross-sectional view schematically showing the structure of an electrolytic capacitor according to another embodiment of the present disclosure. The electrolytic capacitor 102 of this embodiment has the same configuration as the electrolytic capacitor 100 of the first embodiment, except that it lacks the cathode foil 20. Multiple capacitor elements are stacked with their cathode lead-out layers (conductive paste layer 9) overlapping each other to form a laminate. The stacking direction of the laminate is perpendicular to the main surface of the anode foil.

[0160] exist Figure 6 In the electrolytic capacitor shown, when viewed from the stacking direction, the thickness T1 of the outer casing located above the stack is more than 24.9% of the total thickness T2 of the stack in the stacking direction (T1 / T2≥0.249). Therefore, even when the electrolytic capacitor is exposed to high temperatures due to reflow soldering, the reduction in the seal between the first part 1 of the anode body 3 and the outer casing 14 caused by the expansion and deformation of the outer casing, as well as the intrusion of air and moisture into the space between the first part 1 and the outer casing 14 through gaps, are suppressed. As a result, even after high-temperature treatment, the increase in ESR is suppressed, and a low ESR can be maintained.

[0161] The capacitor element and the laminate can be electrically connected to the wiring pattern on the substrate 17 via the conductive adhesive layer 18. The conductive adhesive layer 18 can extend toward the second external electrode 22. The end face of the conductive adhesive layer 18 can be exposed from the outer casing on the second main surface 14b of the outer casing and electrically connected to the second external electrode 22.

[0162] Postscript

[0163] The following technology has been disclosed through the above description of the embodiments.

[0164] (Technology 1)

[0165] An electrolytic capacitor comprising:

[0166] A capacitor element having an anode portion and a cathode portion;

[0167] Cathode foil, which is electrically connected to the aforementioned cathode portion; and

[0168] The outer casing seals the aforementioned capacitor elements.

[0169] The laminate, comprising the capacitor element and the cathode foil, is configured such that the cathode portion of the capacitor element is electrically connected to the cathode foil.

[0170] The aforementioned outer casing contains epoxy resin.

[0171] When viewed from the stacking direction of the aforementioned laminate, the thickness of the outer casing located above or below the aforementioned laminate is 24.9% or more of the thickness of the aforementioned laminate in the aforementioned stacking direction.

[0172] (Technology 2)

[0173] According to the electrolytic capacitor described in Technique 1, a portion of the cathode foil is exposed from the outer casing, and the exposed portion is electrically connected to an external electrode.

[0174] (Technology 3)

[0175] An electrolytic capacitor comprising:

[0176] A capacitor element having a foil-shaped anode and a cathode; and

[0177] The outer casing seals the aforementioned capacitor elements.

[0178] The end face of the anode portion protrudes from the outer casing, and the exposed portion is electrically connected to the external electrode.

[0179] The aforementioned outer casing contains epoxy resin.

[0180] When viewed from a direction perpendicular to the main surface of the anode portion, the thickness of the outer casing located above or below the capacitor element is 24.9% or more of the total thickness of the capacitor element in the vertical direction.

[0181] (Technology 4)

[0182] According to any one of the techniques 1 to 3, the electrolytic capacitor wherein the outer casing comprises filler with an average particle size of 12 μm to 32 μm.

[0183] The proportion of the above-mentioned filler in the above-mentioned outer casing is more than 73% by mass and less than 84% by mass.

[0184] (Technology 5)

[0185] According to any one of the techniques 1 to 4, the electrolytic capacitor, wherein the outer casing includes filler.

[0186] In the particle size distribution of the above-mentioned fillers, the fillers with a particle size in the range of 12μm to 32μm account for 30% to 90% of the total volume.

[0187] (Technology 6)

[0188] According to any one of the techniques 1 to 5, the electrolytic capacitor wherein the epoxy resin comprises a biphenyl aralkyl type resin.

[0189] (Technology 7)

[0190] According to any one of the techniques 1 to 6, the electrolytic capacitor wherein the linear expansion coefficient α1 of the aforementioned outer casing is 13 × 10⁻⁶. -6 / ℃ or above and 21×10 -6 / ℃ below,

[0191] The linear expansion coefficient α2 of the aforementioned outer casing is 52 × 10⁻⁶. -6 / ℃ or higher and 74×10 -6 / ℃ below.

[0192] (Technology 8)

[0193] According to any one of the techniques 1 to 7, the electrolytic capacitor wherein the moisture absorption rate of the epoxy resin at 85°C and 85% relative humidity is 0.23% or more and 0.34% or less.

[0194] [Example]

[0195] The electrolytic capacitor of this disclosure will now be described in detail based on embodiments and comparative examples. This disclosure is not limited to the following embodiments.

[0196] <Example 1>

[0197] (1) Fabrication of electrolytic capacitors

[0198] In order to produce and Figure 1 The electrolytic capacitor 100 shown is an example of an electrolytic capacitor with multiple capacitor elements. The anode body uses an aluminum anode foil with porous sections formed by etching. Seven capacitor elements are stacked via a cathode foil made of aluminum foil with a carbon coating to obtain a laminate. The cathode foil is arranged such that a portion of it protrudes from the cathode layer toward the opposite side of the anode.

[0199] A substrate containing the laminate is placed in a designated position in a mold. An epoxy resin composition is poured into the mold, and the resin is cured. The entire laminate is then sealed with an outer casing by compression molding. The epoxy resin composition comprises filler and epoxy resin, with the filler comprising 73% by mass of the total solid components. The epoxy resin used is a biphenyl aralkyl type epoxy resin with multiple aromatic rings (Sumitomo Bakelite Co., Ltd., G720TD Ver.GR). The coefficient of linear expansion α1 of the outer casing, measured by the above method, is 21 × 10⁻⁶. -6 / ℃, the coefficient of linear expansion α2 is 74×10 -6 At ℃, the moisture absorption rate of epoxy resin is 0.34%.

[0200] The thickness T2 of the laminate in the lamination direction is 1.482 mm. The outer casing is set above the laminate with a thickness T1 of 0.369 mm. The ratio of thickness T1 to T2 is 24.9% (T1 / T2 = 0.249).

[0201] Next, a portion of the first end side of the first part of the anode body and the outer casing are removed simultaneously by cutting, exposing the end face of the anode portion. Similarly, the protrusion of the cathode foil and the outer casing are removed simultaneously by cutting, exposing the end face of the cathode foil.

[0202] Next, a 20 μm thick conductive layer (silver paste layer) is formed by covering the end face of the anode and the exposed surface of the outer casing of the anode, as well as the end face of the cathode foil and the exposed surface of the outer casing of the cathode foil, with silver paste. Then, by barrel plating, a Ni plating layer (5 μm thick) and a Sn plating layer (5 μm thick) are sequentially formed on the surface of the conductive layer to form the first external electrode and the second external electrode, thus obtaining the electrolytic capacitor A1.

[0203] (2) Evaluation

[0204] The following evaluation was performed on the manufactured electrolytic capacitors.

[0205] Connect the electrolytic capacitor to the impedance measuring device, apply an AC voltage, and measure the initial ESR and initial electrostatic capacitance C0 at 100 kHz.

[0206] The electrolytic capacitor was placed in an environment at 155°C for 24 hours. Then, it was further placed in an environment at 85°C and 85% relative humidity for 12 hours. Then, assuming reflow soldering, the electrolytic capacitor was heated to a maximum temperature of 260°C for a maximum of 30 seconds.

[0207] The heat-treated electrolytic capacitor was reconnected to the impedance measuring device, and its ESR and capacitance were measured in the same manner. The initial ESR was set as R0, the ESR after heat treatment as R1, and ΔESR = R1 - R0 was used as the rate of ESR increase for evaluation. The initial capacitance was set as C0, the capacitance after heat treatment as C1, and ΔCap = C0 - C1 was used as the reduction in capacitance for evaluation.

[0208] Additionally, for electrolytic capacitors after heat treatment, check whether expansion is observed in the outer casing. On the surface of the outer casing located above the laminate ( Figure 1On the upper surface 14c), the difference between the height Z1 in the stacking direction at the location with the largest displacement in the stacking direction and the height Z0 of the upper surface 14c before heat treatment, ΔZ = Z1 - Z0, is taken as the expansion amount and evaluated. When ΔZ is positive, it means that when viewed from the stacking direction, the outer casing has deformed in a convex expansion manner.

[0209] <Examples 2 and 3>

[0210] Two electrolytic capacitors with the same configuration as in Example 1 were fabricated and evaluated in the same manner.

[0211] <Examples 4-7, Comparative Examples 1 and 2>

[0212] In Example 1, the ratio T1 / T2 of the thickness T1 of the outer casing to the thickness T2 of the laminate in the lamination direction was changed. Otherwise, the electrolytic capacitor was fabricated and evaluated in the same manner as in Example 1.

[0213] In Examples 2 and 3, similarly to Example 1, the thickness T2 of the laminate in the lamination direction is set to 1.482 mm, and the thickness T1 of the upper part of the outer casing laminate is set to 0.369 mm. The ratio of thickness T1 to T2 is 24.9% (T1 / T2 = 0.249).

[0214] In Example 4, the thickness T2 of the laminate in the lamination direction is set to 1.482 mm, and the thickness T1 of the upper part of the outer casing laminate is changed to 0.370 mm. The ratio of thickness T1 to T2 is 24.97% (T1 / T2 = 0.2497).

[0215] In Example 5, the thickness T2 of the laminate in the lamination direction is set to 1.482 mm, and the thickness T1 of the upper part of the outer casing laminate is changed to 0.371 mm. The ratio of thickness T1 to T2 is 25.04% (T1 / T2 = 0.2504).

[0216] In Examples 6 and 7, the thickness T2 of the laminate in the lamination direction is set to 1.482 mm, and the thickness T1 of the upper part of the outer casing laminate is changed to 0.372 mm. The ratio of thickness T1 to T2 is 25.1% (T1 / T2 = 0.251).

[0217] The evaluation results are shown in Table 1. In Table 1, electrolytic capacitors A1 to A7 correspond to Examples 1 to 7, and electrolytic capacitors B1 and B2 correspond to Comparative Examples 1 and 2. According to Table 2, the ΔZ of electrolytic capacitors A1 to A7 with a thickness ratio T1 / T2 of 0.249 (24.9%) or higher is smaller, and the expansion of the outer casing is suppressed. Furthermore, it can be seen that when the thickness ratio T1 / T2 is 0.249 (24.9%) or higher, compared with electrolytic capacitors B1 and B2 with a thickness ratio T1 / T2 less than 0.249 (24.9%), the ΔESR is significantly reduced, and the sharp increase in ESR after high-temperature treatment is suppressed.

[0218] [Table 1]

[0219]

[0220] The electrolytic capacitor of the present invention can maintain a low ESR even in high temperature environments, and therefore can be used for a variety of applications.

[0221] Preferred embodiments of the present invention have been described, but such disclosure is not to be construed as limiting the invention. Various modifications and alterations will be readily apparent to those skilled in the art upon reading the foregoing disclosure. Therefore, the appended scope of protection should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0222] Explanation of reference numerals in the attached figures

[0223] 1. Part 1 (Anode Lead-out Section), Metal Wire

[0224] 1a End face of the first end

[0225] 2. Part 2 (Cathode Forming Section)

[0226] 2a End face of the second end

[0227] 3 Anode

[0228] 4 metal core

[0229] 5 Porous parts

[0230] 6. Cathode section

[0231] 7. Solid electrolyte layer

[0232] 8 carbon layers

[0233] 9. Silver paste layer

[0234] 10 Capacitor Components

[0235] 10a First capacitor element

[0236] 10b Second capacitor element

[0237] 12. Separation layer (insulating component)

[0238] 14 outer body

[0239] 14a First main face of the outer casing

[0240] 14b Second main face of the outer casing

[0241] 14c Top surface of the outer casing

[0242] 17 substrate

[0243] 18 Resin adhesive layer

[0244] 20 Cathode foil

[0245] 20a End face of cathode foil

[0246] 21. First external electrode (external anode electrode)

[0247] 21A Silver Paste Layer

[0248] 21B Ni / Sn plating, first lead frame

[0249] 22 Second external electrode (external cathode electrode)

[0250] 22A Silver Paste Layer

[0251] 22B Ni / Sn plating, second lead frame

[0252] 100-102, 200, 201 electrolytic capacitors

Claims

1. An electrolytic capacitor comprising: A capacitor element having an anode portion and a cathode portion; Cathode foil, which is electrically connected to the cathode portion; and An outer casing that seals the capacitor element. The capacitor element and the cathode foil are stacked together to form a laminate, such that the cathode portion of the capacitor element is electrically connected to the cathode foil. The outer casing contains epoxy resin. When viewed from the stacking direction of the laminate, the thickness of the outer casing located above or below the laminate is more than 24.9% of the thickness of the laminate in the stacking direction.

2. The electrolytic capacitor of claim 1, wherein, A portion of the cathode foil is exposed from the outer casing, and the exposed portion is electrically connected to the external electrode.

3. An electrolytic capacitor, comprising: A capacitor element having a foil-shaped anode and a cathode; and An outer casing that seals the capacitor element. The end face of the anode portion protrudes from the outer casing, and the exposed portion is electrically connected to the external electrode. The outer casing contains epoxy resin. When viewed from a direction perpendicular to the main surface of the anode portion, the thickness of the outer casing located above or below the capacitor element is 24.9% or more of the total thickness of the capacitor element in the vertical direction.

4. The electrolytic capacitor according to any one of claims 1 to 3, wherein The outer casing contains fillers with an average particle size of 12 μm to 32 μm. The filler accounts for more than 73% by mass and less than 84% by mass in the outer casing.

5. The electrolytic capacitor according to any one of claims 1 to 3, wherein The outer casing includes filler. In the particle size distribution of the filler, the filler with a particle size in the range of 12μm to 32μm accounts for 30% to 90% of the total volume.

6. The electrolytic capacitor according to any one of claims 1 to 3, wherein The epoxy resin comprises a biphenyl aryl type epoxy resin.

7. The electrolytic capacitor according to any one of claims 1 to 3, wherein The linear expansion coefficient α1 of the outer body is 13 x 10 -6 / °C or more and 21 x 10 -6 / °C or less, The linear expansion coefficient α2 of the outer body is 52 x 10 -6 / °C or more and 74 x 10 -6 / °C or more and 74 x 10 8. The electrolytic capacitor according to any one of claims 1 to 3, wherein The epoxy resin has a moisture absorption rate of more than 0.23% and less than 0.34% at 85°C and 85% relative humidity.

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