Anode member and electrolytic capacitor

Abstract

This anode member for an electrolytic capacitor comprises: a porous anode body; and an anode wire which is embedded in the anode body and has a portion that protrudes outward from the anode body. The anode body has a first block region which is a porous portion containing first particles of a valve action metal, and a second block region which is a porous portion containing second particles of the valve action metal. The anode body has a bonding surface bonded to a cathode lead terminal of the electrolytic capacitor, and has at least a portion of the first block region interposed between the anode wire and the bonding surface. The pore diameter of a first porous portion is larger than the pore diameter of a second porous portion.

Description

Anode member and electrolytic capacitor

[0001] The present disclosure relates to an anode member and an electrolytic capacitor using the same.

[0002] Electrolytic capacitors are used in a variety of electronic devices due to their low equivalent series resistance (ESR) and excellent frequency characteristics. An electrolytic capacitor typically includes a capacitor element having an anode portion and a cathode portion. The anode portion includes a porous anode body, and a dielectric layer is formed on the surface of the anode body. The dielectric layer is in contact with an electrolyte. Some electrolytic capacitors use a solid electrolyte, such as a conductive polymer, as the electrolyte (see, for example, Patent Document 1).

[0003] The anode body of an electrolytic capacitor is formed porous by, for example, placing a valve action metal powder together with an anode lead in a mold and sintering it. Patent Document 2 describes a method for manufacturing an anode body of a solid electrolytic capacitor, using two or more types of valve action metal powders of the same metal but with different particle sizes that differ in crushability during the sintering process. The valve action metal powder with the higher crushability and smaller particle size is placed near the implanted surface of the anode lead, and then the resulting powder is placed in a press mold and pressure-molded by a single press, followed by a sintering process. The valve action metal powder placed near the implanted surface of the anode lead is a fine powder with a primary powder particle size of 10 nm or more and less than 1 μm. Patent Document 2 describes that, during the sintering process, the valve action metal powder placed near the implanted surface of the anode lead is sufficiently crushed to form a porous valve action metal body with high compact strength, which is firmly bonded to the anode lead and other parts of the anode body, thereby increasing the strength of the implanted portion of the anode lead.

[0004] JP 2009-182157 A Japanese Patent No. 3233084

[0005] One aspect of the present disclosure relates to an anode member for an electrolytic capacitor. The anode member includes a porous anode body and an anode wire embedded in the anode body and having a portion protruding outside the anode body. The anode body has a first block region, which is a porous portion containing first particles of a valve metal, and a second block region, which is a porous portion containing second particles of a valve metal. The pore size of the first block region is larger than the pore size of the second block region. The anode body has a connection surface connected to a cathode lead of an electrolytic capacitor. At least a portion of the first block region is interposed between the anode wire and the connection surface.

[0006] Another aspect of the present disclosure relates to an anode member for an electrolytic capacitor. The anode member includes a porous anode body and an anode wire embedded in the anode body and having a portion protruding outside the anode body. The anode body has a first block region, which is a porous portion containing first particles of a valve metal, and a second block region, which is a porous portion containing second particles of a valve metal. The particle size of the first particles is larger than the particle size of the second particles. The anode body has a connection surface that is connected to a cathode lead terminal of an electrolytic capacitor. At least a portion of the first block region is interposed between the anode wire and the connection surface.

[0007] Yet another aspect of the present disclosure relates to an electrolytic capacitor. The electrolytic capacitor includes the anode member described above, a dielectric layer formed on a surface of the anode body of the anode member, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode lead electrically connected to the solid electrolyte layer. At least a portion of the first block region is interposed between the anode wire and the cathode lead. The cathode lead is connected to the connection surface.

[0008] The present disclosure makes it possible to realize an electrolytic capacitor that combines high capacitance and low ESR at a high level.

[0009] Fig. 1 is a perspective view schematically showing an example of an anode member according to an embodiment of the present disclosure; Fig. 2 is a perspective view schematically showing another example of an anode member according to an embodiment of the present disclosure; Fig. 3 is a cross-sectional view schematically showing an example of a capacitor element according to an embodiment of the present disclosure; Fig. 4 is a cross-sectional view schematically showing an electrolytic capacitor manufactured by a manufacturing method according to an embodiment of the present disclosure.

[0010] The problems in the prior art will be briefly described below.

[0011] In recent years, there has been a demand for further improvements in the capacitance of electrolytic capacitors. There is also a demand for further reductions in the ESR of electrolytic capacitors. Attempts to reduce the ESR have been made, such as reducing the contact resistance between the anode lead and the anode body, and the resistance between the anode lead and the cathode lead and the external terminals, but there are limitations to these efforts.

[0012] It is conceivable that the resistance due to the anode itself can be reduced by adjusting the properties (such as pore size) of the porous anode body, thereby reducing the ESR. However, reducing the ESR of an electrolytic capacitor tends to reduce the capacitance.

[0013] On the other hand, in order to increase the capacitance of an electrolytic capacitor, it is conceivable to fabricate an anode body using small valve metal particles and increase the surface area of ​​the porous portion. In this case, the resistance of the anode body itself tends to increase, and the ESR tends to rise. In other words, the capacitance and ESR of an electrolytic capacitor are in a mutually contradictory relationship, and it has been difficult to achieve both high capacitance and low ESR.

[0014] An anode member of an electrolytic capacitor according to one embodiment of the present disclosure includes a porous anode body and an anode wire embedded in the anode body and having a portion protruding to the outside of the anode body. The anode body has a first block region which is a porous portion containing first particles of a valve metal, and a second block region which is a porous portion containing second particles of a valve metal.

[0015] The pore size of the first block region is larger than the pore size of the second block region, or the particle size of the first particles forming the first block region is larger than the particle size of the second particles forming the second block region.

[0016] When an anode body is formed using valve metal particles with a large particle size, the conductive paths between the particles become thicker, resulting in a lower resistance of the anode body. As a result, the ESR of the electrolytic capacitor is reduced. On the other hand, the pore size of the porous portion becomes larger, resulting in a smaller surface area of ​​the porous portion of the anode body. As a result, the capacitance of the electrolytic capacitor tends to decrease. Conversely, when an anode body is formed using valve metal particles with a small particle size, the surface area of ​​the porous portion of the anode body becomes larger, resulting in a high-capacity electrolytic capacitor, but this results in an increased ESR.

[0017] In the anode member of this embodiment, the particle size of the first particles forming the first block region is larger than the particle size of the second particles forming the second block region, so the first block region has a lower resistance and a smaller surface area than the second block region. Therefore, an electrolytic capacitor using only the first block region has a lower ESR than an electrolytic capacitor using only the second block region. On the other hand, an electrolytic capacitor using only the second block region has a higher capacitance than an electrolytic capacitor using only the first block region. By using the anode member of this embodiment, the advantages of both the first block region and the second block region are combined, resulting in an electrolytic capacitor that achieves both high capacitance and low ESR at a high level.

[0018] The anode body is provided with a connection surface for connection to a cathode lead. At least a portion of the first block region is interposed between the anode wire and the connection surface. This forms a conductive path in the anode member from the anode wire to the connection surface via at least the first block region. Because the resistance of the first block region is lower than the resistance of the second block region, current flows preferentially through this conductive path. As a result, the ESR of the electrolytic capacitor can be reduced.

[0019] Each of the first block region and the second block region may be a single block region or may include a plurality of block regions.

[0020] At least a portion of the second block region may be interposed between the anode wire and the connection surface. In this case, it is preferable that more first block regions than second block regions be interposed between the anode wire and the connection surface. "More first block regions than second block regions" means that, when an imaginary plane is considered to pass through the anode wire and be parallel to the connection surface, the volume occupied by the first block regions in the anode body between the imaginary plane and the connection surface is larger than the volume occupied by the second block regions.

[0021] For example, in the anode member, the probability of the presence of the first block region may be higher than the probability of the presence of the second block region in a region where the distance between the anode wire and the connection surface is shorter.When the anode body is divided into two by an imaginary plane that passes through the anode wire and is parallel to the connection surface, the volume of the first block region included in the portion between the imaginary plane and the connection surface may be larger than the volume of the first block region included in the remaining portion.

[0022] The second block region can form a conductive path from the anode wire to the connection surface via at least the second block region. In this case, the conductive path from the anode wire to the connection surface via the first block region is preferably shorter than the conductive path from the anode wire to the connection surface via the second block region. In this case, a larger current tends to flow through the conductive path via the first block region, which has a lower resistance, thereby further reducing the ESR of the electrolytic capacitor.

[0023] When considering the conductive path from the anode wire to the connection surface, it is preferable that the conductive path always passes through the first block region. In other words, it is preferable that there is no conductive path from the anode wire to the connection surface of the anode body without passing through the first block region (i.e., only via the second block region). Alternatively, even if there is a conductive path from the anode wire to the connection surface of the anode body only via the second block region, it is preferable that the length of the conductive path from the anode wire to the connection surface of the anode body via the first block region be shorter than the length of the conductive path from the anode wire to the connection surface of the anode body only via the second block region.

[0024] When an electrolytic capacitor is fabricated using the anode member according to this embodiment, the anode member is disposed so that at least the first block region is interposed between the anode wire and the cathode lead. In this case, the electrolytic capacitor can be configured so that there is no conduction path via the second block region, or the length of the conduction path via the first block region is shorter than the length of the conduction path via the second block region, thereby reducing the ESR of the electrolytic capacitor. For example, the second block region is disposed farther from the cathode lead than the first block region, contributing to high capacitance.

[0025] The CV value is an index that represents the characteristics of valve action metal powder used in electrolytic capacitors. The CV value is expressed as the product of the capacitance Cx of the oxide film formed by chemical formation and the chemical formation voltage Vc, and has a substantially constant relationship regardless of the chemical formation voltage, provided that the anode surface area, chemical formation temperature, and dielectric constant of the oxide film are the same. Using valve action metal particles with a large CV value can increase the capacitance of the electrolytic capacitor, but the ESR of the electrolytic capacitor also increases.

[0026] Particles with a small CV value can be used as the first particles that form the first block region. Particles with a large CV value can be used as the second particles that form the second block region. The CV value of the first particles per unit mass (gram) may be, for example, 20,000 to 70,000 [μF·V / g]. The CV value of the second particles per unit mass (gram) may be, for example, 80,000 to 200,000 [μF·V / g].

[0027] The first block region and the second block region are each a separate region within the anode body, and occupy a predetermined volume within the anode body. The first block region and the second block region may each be separated into a plurality of regions.

[0028] The first block region and the second block region may each be a portion of an anode body separated by an imaginary plane that divides the anode body. One of the two portions separated by the imaginary plane may be the first block region, and the other may be the second block region. The imaginary plane is preferably flat, but is not particularly limited thereto and may be a curved or stepped surface. In this case, the anode body can be easily manufactured by filling a portion of a region in a mold with first particles and the remaining region with second particles, followed by pressure molding and sintering the compact. Alternatively, the anode body can be easily manufactured by filling a portion of a region in a mold with second particles and the remaining region with first particles, followed by pressure molding and sintering the compact. In this manner, an anode body having a first block region and a second block region can be manufactured.

[0029] The anode body usually has a substantially rectangular parallelepiped shape. The substantially rectangular parallelepiped anode body has six main surfaces, each of which constitutes the surface of the anode body. In this case, the imaginary plane may be a plane parallel to any of the six main surfaces of the anode body. In other words, the imaginary plane may be a plane parallel to two opposing main surfaces of the rectangular parallelepiped.

[0030] The imaginary plane may be a plane parallel to the direction in which the anode wire extends, or may be a plane perpendicular to the direction in which the anode wire extends.

[0031] The anode wire is usually implanted from a main surface perpendicular to the longest side of an anode body having a substantially rectangular parallelepiped shape so as to extend in a direction parallel to the longest side. If the imaginary plane is parallel to the direction in which the anode wire extends, the first block region and the second block region will have an elongated shape, and the anode body will be prone to warping due to the difference in shrinkage rate between the first block region and the second block region during sintering, and the anode body will be prone to cracking at the boundary between the first block region and the second block region.

[0032] In order to prevent warping and cracking of the anode body during sintering, it is preferable to select the first particles and the second particles and set sintering conditions such as the sintering temperature so that the difference in shrinkage rate during sintering falls within a certain range. For example, the difference in shrinkage rate (ratio of particle size after sintering to particle size before sintering) between the first particles and the second particles during sintering at a sintering temperature of 1330° C. may be 0.5% or less.

[0033] Here, the particle diameters of the first particles and the second particles are average particle diameters calculated by the following method based on cross-sectional images of the first block region and the second block region of the anode body, respectively. Similarly, the pore diameters of the first block region and the second block region are also calculated by the following method based on cross-sectional images of the first block region and the second block region of the anode body, respectively.

[0034] First, a discharged electrolytic capacitor is disassembled to remove the anode body. Next, the removed anode body is washed and dried, and a predetermined cross section of the anode body is exposed. An electron image of the exposed cross section is captured using a scanning electron microscope. The magnification when capturing is, for example, 800x. The obtained image is subjected to image processing to separate the area occupied by the first particles or the second particles from the other area. In the area occupied by the first particles or the second particles, the grain boundaries of each particle are determined, and the diameter of a circle having an area equal to the area occupied by each particle in the image is defined as the particle diameter of that particle. The particle diameter of the first particles is determined by averaging the particle diameters determined by the above method for 100 or more first particles. The particle diameter of the second particles is determined by averaging the particle diameters determined by the above method for 100 or more second particles.

[0035] In addition, image processing using image analysis software is performed to determine the pore diameter from the portion of the image occupied by voids. The cross-sectional image is divided into valve metal (tantalum), valve metal oxide (tantalum oxide), voids, and electrolyte layer (conductive polymer layer) based on differences in color tone. The region occupied by regions other than the valve metal (tantalum) and valve metal oxide (tantalum oxide) is the pores of the anode body, and their shape and area can be converted to the pore diameter. The pore diameter of the first block region is determined by selecting 100 or more regions within the first block region and averaging the pore diameters determined by the above method. The pore diameter of the second block region is determined by selecting 100 or more regions within the second block region and averaging the pore diameters determined by the above method.

[0036] An electrolytic capacitor according to an embodiment of the present disclosure includes the above-described anode member, a dielectric layer formed on a surface of an anode body of the anode member, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode lead electrically connected to the solid electrolyte layer, wherein at least a portion of the first block region is interposed between the anode wire and the cathode lead.

[0037] The anode member and the electrolytic capacitor using the anode member according to this embodiment will be described below with reference to the accompanying drawings as appropriate, although the present invention is not limited thereto.

[0038] Fig. 1 is a perspective view schematically illustrating an example of an anode member according to the present embodiment. The anode member 30 includes an anode body 1 and an anode wire 2. In Fig. 1, a portion of the cathode lead terminal 14 is shown at a position on the anode member 30 where it is expected to be connected to the anode body 1, in order to illustrate the connection relationship between the anode body 1 and a cathode lead 14 when an electrolytic capacitor is configured. The cathode lead terminal 14 is typically connected to the anode body 1 via a solid electrolyte layer and a cathode layer (see Fig. 4).

[0039] Anode body 1 has a first block region 1A and a second block region 1B. The porous portion of anode body 1 is divided into two parts by an imaginary plane that divides anode body 1, one of which is first block region 1A and the other is second block region 1B. In the example of Fig. 1 , the imaginary plane is a plane that is parallel to the direction in which anode wire 2 extends and is parallel to the longest side of anode body 1, which has a substantially rectangular parallelepiped shape.

[0040] The first block region 1A has a larger pore size and / or a larger particle size than the second block region 1B, so the first block region 1A has a lower resistance than the second block region 1B. On the other hand, the second block region 1B has a larger surface area than the first block region 1A, so that when an electrolytic capacitor is formed, the capacitance is higher.

[0041] The anode body 1 has a connection surface 15 connected to a cathode lead terminal 14. At least a portion of the first block region 1A is interposed between the anode wire 2 and the cathode lead terminal 14.

[0042] Consider a conduction path from the anode wire 2 through the porous portion of the anode body 1 to the connection surface 15. In the example of Fig. 1, the conduction path always passes through the first block region 1A, and there is no conduction path that does not pass through the first block region 1A (i.e., passes only through the second block region).

[0043] Because the first block region 1A has a lower resistance than the second block region 1B, a current path is formed in which current flows preferentially through the first block region 1A, which has a lower resistance. That is, when current flows from the anode wire 2 to the connection surface 15 closest to the cathode lead terminal 14, the current flows toward the connection surface 15 via the first block region 1A, which has a lower resistance. As a result, the ESR of the electrolytic capacitor is reduced. Meanwhile, the second block region 1B, which has a higher capacitance, allows the electrolytic capacitor to maintain a high capacitance.

[0044] 1 , when an electrolytic capacitor is configured, the entire surface of the anode body 1 including the second block region 1B is usually covered with a cathode layer with a solid electrolyte layer interposed therebetween (see FIGS. 3 and 4 ), so there may be a conduction path from the anode wire 2 through only the second block region without passing through the first block region 1A, and then through the cathode layer to the connection surface 15. However, because the length of the conduction path is long, most of the current flows toward the connection surface 15 via the first block region 1A, which has low resistance.

[0045] The position of the boundary between the first block region 1A and the second block region 1B (the height of the imaginary plane from the connection surface 15) is not particularly limited and is determined appropriately so that the electrolytic capacitor to be manufactured has the desired ESR and the desired capacitance.

[0046] Fig. 2 shows another example of the anode member 30. In the example of Fig. 2, the anode body 1 is divided by an imaginary plane that is perpendicular to the direction in which the anode wire 2 extends and divides the anode body 1, one of which is a first block region 1A and the other is a second block region 1B.

[0047] 1 , the first block region 1A is interposed between the anode wire 2 and the cathode lead terminal 14. In the example of Fig. 2 , when a current flows from the anode wire 2 to the connection surface 15, there are two possible current paths: a conductive path from the anode wire 2 to the connection surface 15 of the anode body via the first block region 1A, and a conductive path from the anode wire 2 to the connection surface 15 of the anode body via the second block region 1B. However, because the first block region 1A has a lower resistance than the second block region 1B, the current preferentially flows through the conductive path via the first block region 1A, which has a lower resistance.

[0048] In addition, the first block region 1A is located closer to the implantation surface of the anode wire 2 than the second block region 1B. In this case, the conduction path via the first block region 1A, which is closer to the implantation surface of the anode wire 2, is shorter than the conduction path via the second block region 1B, making it easier for current to flow. Therefore, due to the low resistance and short path length, current flows preferentially through the conduction path via the first block region 1A, resulting in a high current density. As a result, the ESR of the electrolytic capacitor is reduced. Meanwhile, the high capacitance of the second block region 1B allows the electrolytic capacitor to maintain a high capacitance.

[0049] The position of the boundary between the first block region 1A and the second block region 1B (the position on the imaginary plane in the direction in which the anode wire 2 extends) is not particularly limited, and is determined appropriately so that the electrolytic capacitor to be manufactured has the desired ESR and the desired capacitance.

[0050] A capacitor element is formed using the anode member 30, and an electrolytic capacitor is manufactured. Fig. 3 is a cross-sectional view schematically showing an example of a capacitor element using the anode member 30. Fig. 4 is a cross-sectional view schematically showing an electrolytic capacitor including the capacitor element.

[0051] Electrolytic capacitor 20 includes capacitor element 10 having anode portion 6 and cathode portion 7, exterior body 11 sealing capacitor element 10, anode lead terminal 13 electrically connected to anode portion 6 and partially exposed from exterior body 11, and cathode lead terminal 14 electrically connected to cathode portion 7 and partially exposed from exterior body 11. Anode portion 6 includes anode body 1 and anode wire 2. Dielectric layer 3 is formed on the surface of the anode body. Cathode portion 7 includes solid electrolyte layer 4 covering at least a portion of dielectric layer 3, and cathode layer 5 covering the surface of solid electrolyte layer 4.

[0052] <Capacitor Element> Hereinafter, the capacitor element 10 will be described in detail, taking as an example a case where the capacitor element 10 includes a solid electrolyte layer as the electrolyte.

[0053] The anode part 6 has an anode body 1 and an anode wire 2 that extends from one surface of the anode body 1 and is electrically connected to an anode lead terminal 13 .

[0054] The anode section 6 is the above-described anode member 30, and the dielectric layer 3 is formed on the surface of the anode body 1. Although not shown in Figures 3 and 4, the anode body 1 has a first block region 1A and a second block region 1B. The arrangement of the first block region 1A and the second block region 1B inside the anode body 1 may be the same as that shown in Figure 1 or that shown in Figure 2.

[0055] The anode body 1 is, for example, a rectangular parallelepiped porous sintered body obtained by sintering particles of a first metal. The particles of the first metal are particles of a valve metal such as titanium (Ti), tantalum (Ta), or niobium (Nb). The anode body 1 uses particles of one or more types of first metal. The particles of the first metal may be an alloy made of two or more metals. At least one of the two or more metals is the first metal. For example, an alloy containing a valve metal (first metal) and silicon, vanadium, boron, or the like may be used. Alternatively, a compound containing a valve metal and a typical element such as nitrogen may be used. The valve metal alloy contains the valve metal (first metal) as a main component, for example, 50 atomic % or more of the valve metal (first metal).

[0056] The anode wire 2 is made of a conductive material. The material of the anode wire 2 is not particularly limited and includes, for example, copper, aluminum, aluminum alloys, and the like, in addition to the valve metals described above. The anode body 1 and the anode wire 2 may be made of the same material or different materials. The anode wire 2 has a first portion 2a that is embedded inside the anode body 1 from one surface of the anode body 1, and a second portion 2b that extends from the above surface of the anode body 1. The cross-sectional shape of the anode wire 2 is not particularly limited and includes, for example, a circle, a track shape (a shape consisting of parallel straight lines and two curves connecting the ends of these straight lines), an ellipse, a rectangle, a polygon, and the like.

[0057] The anode part 6 is produced, for example, by press-molding the first portion 2a of the anode wire 2 into a rectangular parallelepiped shape while the first portion 2a is embedded in a powder of particles of the first metal, followed by sintering. This results in the second portion 2b of the anode wire 2 extending from one surface of the anode body 1 in an upright state. The second portion 2b is joined to the anode lead terminal 13 by welding or the like, thereby electrically connecting the anode wire 2 and the anode lead terminal 13. The welding method is not particularly limited, and examples include resistance welding and laser welding. The corners of the rectangular parallelepiped may then be processed to form curved surfaces.

[0058] A dielectric layer 3 is formed on the surface of the anode body 1. The dielectric layer 3 is made of, for example, a metal oxide. Methods for forming a layer containing a metal oxide on the surface of the anode body 1 include, for example, a method of immersing the anode body 1 in a chemical conversion solution to anodize the surface of the anode body 1, and a method of heating the anode body 1 in an oxygen-containing atmosphere. The dielectric layer 3 is not limited to the above-mentioned layer containing a metal oxide, and may be any layer that is insulating.

[0059] (Cathode Section) The cathode section 7 has a solid electrolyte layer 4 and a cathode layer 5 covering the solid electrolyte layer 4. The solid electrolyte layer 4 is formed so as to cover at least a portion of the dielectric layer 3.

[0060] For example, a manganese compound or a conductive polymer is used for the solid electrolyte layer 4. Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene. These may be used alone or in combination. The conductive polymer may also be a copolymer of two or more monomers. In terms of excellent conductivity, polythiophene, polyaniline, and polypyrrole may be used. In particular, in terms of excellent water repellency, polypyrrole may be used.

[0061] The solid electrolyte layer 4 containing the conductive polymer is formed, for example, by polymerizing a raw material monomer on the dielectric layer 3. Alternatively, it is formed by applying a solution or dispersion containing the conductive polymer to the dielectric layer 3. The solid electrolyte layer 4 is composed of one or more solid electrolyte layers. When the solid electrolyte layer 4 is composed of two or more layers, the composition and formation method (polymerization method) of the conductive polymer used in each layer may be different.

[0062] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene).

[0063] Various dopants may be added to the polymerization liquid for forming the conductive polymer, or the solution or dispersion of the conductive polymer in order to improve the conductivity of the conductive polymer. The dopant is not particularly limited, but examples thereof include naphthalenesulfonic acid, p-toluenesulfonic acid, and polystyrenesulfonic acid.

[0064] When the conductive polymer is dispersed in the dispersion medium in the form of particles, the average particle size D50 of the particles is, for example, 0.01 μm or more and 0.5 μm or less. If the average particle size D50 of the particles is in this range, the particles can easily penetrate into the interior of the anode body 1.

[0065] The cathode layer 5 has, for example, a carbon layer 5a formed to cover the solid electrolyte layer 4 and a metal paste layer 5b formed on the surface of the carbon layer 5a. The carbon layer 5a contains a conductive carbon material such as graphite and a resin. The metal paste layer 5b contains, for example, metal particles (e.g., silver) and a resin. The configuration of the cathode layer 5 is not limited to this configuration. The configuration of the cathode layer 5 may be any configuration that has a current collecting function.

[0066] <Anode lead terminal> The anode lead terminal 13 is electrically connected to the anode body 1 via the second portion 2b of the anode wire 2. The material of the anode lead terminal 13 is not particularly limited as long as it is electrochemically and chemically stable and conductive. The anode lead terminal 13 may be made of a metal such as copper, or a non-metal. The shape of the anode lead terminal 13 is not particularly limited as long as it is flat. The thickness of the anode lead terminal 13 (the distance between the main surfaces of the anode lead terminal 13) may be 25 μm or more and 200 μm or less, or may be 25 μm or more and 100 μm or less, from the viewpoint of reducing the height.

[0067] One end of the anode lead terminal 13 may be joined to the anode wire 2 with a conductive adhesive or solder, or may be joined to the anode wire 2 by resistance welding or laser welding. The other end of the anode lead terminal 13 is extended to the outside of the exterior body 11 and is exposed from the exterior body 11. The conductive adhesive is, for example, a mixture of a thermosetting resin (described later) with carbon particles or metal particles.

[0068] <Cathode lead terminal> The cathode lead terminal 14 is electrically connected to the cathode part 7 at the joint portion 14a. The joint portion 14a is a portion of the cathode lead terminal 14 that overlaps with the cathode layer 5 when the cathode layer 5 and the cathode lead terminal 14 joined to the cathode layer 5 are viewed from the normal direction of the cathode layer 5.

[0069] The cathode lead terminal 14 is joined to the cathode layer 5 via, for example, a conductive adhesive 8. One end of the cathode lead terminal 14 constitutes, for example, a part of the joining portion 14a and is disposed inside the exterior body 11. The other end of the cathode lead terminal 14 is led out to the outside. Therefore, a part of the cathode lead terminal 14, including the other end, is exposed from the exterior body 11.

[0070] The material of the cathode lead terminal 14 is not particularly limited as long as it is electrochemically and chemically stable and conductive. The cathode lead terminal 14 may be made of a metal such as copper, or a non-metal. The shape of the cathode lead terminal 14 is also not particularly limited, and may be, for example, a long, flat plate. From the viewpoint of reducing the height, the thickness of the cathode lead terminal 14 may be 25 μm or more and 200 μm or less, or 25 μm or more and 100 μm or less.

[0071] <Exterior Body> The exterior body 11 is provided to electrically insulate the anode lead terminal 13 and the cathode lead terminal 14, and is made of an insulating material (exterior body material). The exterior body material includes, for example, a thermosetting resin. Examples of thermosetting resins include epoxy resin, phenolic resin, silicone resin, melamine resin, urea resin, alkyd resin, polyurethane, polyimide, and unsaturated polyester.

[0072] <Method for Manufacturing Electrolytic Capacitor> An example of a method for manufacturing the electrolytic capacitor according to this embodiment will be described below.

[0073] (1) Anode Element Preparation Step First, an anode element is prepared. A first powder containing first particles of a valve metal and a second powder containing second particles of a valve metal are prepared. The first powder is placed in a mold, followed by the second powder, or the second powder is placed in the mold followed by the first powder, and then the anode wire 2 is pressed and molded so that the first portion 2a of the anode wire 2 is embedded in the first or second powder. The first or second powder may contain a binder in addition to the valve metal particles. The binder improves the flowability of the first or second powder and enhances moldability. Furthermore, during the sintering process, the particles are firmly bonded together, forming dense pores. Examples of binders include polyacrylic carbonate. The binder may be mixed with the first or second powder in the form of a solution or dispersion in a solvent such as butanol or methanol.

[0074] The compact is then sintered to obtain an anode member 30 including an anode body 1 having a first block region and a second block region. The first portion 2a of the anode wire is embedded inside the porous sintered body from one surface. The pressure during the compaction is not particularly limited. Sintering is preferably performed under reduced pressure. The sintering temperature is a high temperature, for example, 1200°C to 1400°C. The high temperature during sintering removes organic components, such as the binder and solvent, contained in the anode body powder. Prior to sintering, a heat treatment at a relatively low temperature, for example, 300°C to 500°C, may be performed to remove the binder. Sintering melts the surfaces of the valve metal particles, maintaining gaps between the particles and thereby bonding adjacent particles to each other and the particles to the first portion 2a of the anode wire, thereby forming an electrical connection.

[0075] The powder containing the valve metal particles is usually pressure-molded using a mold having a rectangular parallelepiped internal space, and then sintered. In this case, the shape of the anode body 1 after sintering is also rectangular parallelepiped.

[0076] (2) Dielectric Layer Forming Step Next, the anode body 1 is subjected to a chemical conversion treatment to cover at least a portion of the anode body 1 with the dielectric layer 3. Specifically, the anode body 1 is immersed in a chemical conversion tank filled with an electrolytic solution (e.g., an aqueous phosphoric acid solution), the second portion 2b of the anode wire 2 is connected to an electrode of the chemical conversion tank, and anodization is performed to form the dielectric layer 3 made of an oxide film of a valve metal on the surface of the porous portion. The electrolytic solution is not limited to an aqueous phosphoric acid solution, and nitric acid, acetic acid, sulfuric acid, or the like can also be used.

[0077] (3) Step of Forming Solid Electrolyte Layer Subsequently, at least a portion of the dielectric layer 3 is covered with the solid electrolyte layer 4. In this way, a capacitor element 10 including the anode body 1, the dielectric layer 3, and the solid electrolyte layer 4 is obtained.

[0078] Solid electrolyte layer 4 containing a conductive polymer is formed on at least a portion of dielectric layer 3, for example, by a method in which anode body 1 on which dielectric layer 3 has been formed is impregnated with a monomer or an oligomer, and then the monomer or oligomer is polymerized by chemical polymerization or electrolytic polymerization, or by impregnating anode body 1 on which dielectric layer 3 has been formed with a solution or dispersion of a conductive polymer and drying the impregnated anode body 1.

[0079] The solid electrolyte layer 4 can be formed, for example, by immersing the anode body 1 on which the dielectric layer 3 has been formed in a dispersion liquid containing a conductive polymer, a binder, and a dispersion medium, removing the anode body 1, and drying the anode body 1. The dispersion liquid may contain a binder and / or conductive inorganic particles (e.g., a conductive carbon material such as carbon black). The conductive polymer may also contain a dopant. The conductive polymer and the dopant may each be selected from those exemplified for the solid electrolyte layer 4. A known binder can be used. The dispersion liquid may contain known additives used in forming a solid electrolyte layer.

[0080] Next, a carbon paste and a metal paste are applied in this order to the surface of the solid electrolyte layer 4 to form a cathode layer 5 composed of a carbon layer 5a and a metal paste layer 5b. The configuration of the cathode layer 5 is not limited to this, and any configuration may be used as long as it has a current collecting function.

[0081] Next, an anode lead terminal 13 and a cathode lead terminal 14 are prepared. The second portion 2b of the anode wire 2 extending from the anode body 1 is joined to the anode lead terminal 13 by laser welding, resistance welding, or the like. After applying a conductive adhesive 8 to the cathode layer 5, the cathode lead terminal 14 is joined to the cathode part 7 via the conductive adhesive 8.

[0082] Next, the capacitor element 10 and the materials for the exterior body 11 (e.g., uncured thermosetting resin and filler) are placed in a mold, and the capacitor element 10 is sealed by transfer molding, compression molding, or the like. At this time, a portion of the anode lead terminal 13 and the cathode lead terminal 14 are exposed from the mold. The molding conditions are not particularly limited, and the time and temperature conditions may be set appropriately taking into consideration the curing temperature of the thermosetting resin used, etc.

[0083] Finally, the exposed portions of the anode lead terminal 13 and the cathode lead terminal 14 are bent along the exterior body 11 to form bent portions. As a result, parts of the anode lead terminal 13 and the cathode lead terminal 14 are disposed on the mounting surface of the exterior body 11.

[0084] By the above method, the electrolytic capacitor 20 is manufactured.

[0085] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0086] (Technology 1) An anode member for an electrolytic capacitor, comprising: a porous anode body; and an anode wire embedded in the anode body and having a portion protruding to the outside of the anode body, wherein the anode body has a first block region which is a porous portion containing first particles of a valve action metal and a second block region which is a porous portion containing second particles of a valve action metal, the pore diameter of the first block region being larger than the pore diameter of the second block region, the anode body having a connection surface which is connected to a cathode lead of an electrolytic capacitor, and at least a portion of the first block region being interposed between the anode wire and the connection surface.

[0087] (Technology 2) An anode member for an electrolytic capacitor, comprising: a porous anode body; and an anode wire embedded in the anode body and having a portion protruding to the outside of the anode body, wherein the anode body has a first block region which is a porous portion containing first particles of a valve action metal and a second block region which is a porous portion containing second particles of a valve action metal, wherein the particle diameter of the first particles is larger than the particle diameter of the second particles, and the anode body has a connection surface which is connected to a cathode lead of an electrolytic capacitor, and at least a portion of the first block region is interposed between the anode wire and the connection surface.

[0088] (Technology 3) The anode member for an electrolytic capacitor according to Technology 1 or 2, wherein the anode body is divided into two parts by a virtual plane that divides the anode body, one of the two parts being the first block region and the other of the two parts being the second block region.

[0089] (Technology 4) The anode member for an electrolytic capacitor according to Technology 3, wherein the anode body has a rectangular parallelepiped shape, and the imaginary plane is a plane parallel to two opposing main surfaces of the rectangular parallelepiped.

[0090] (Technology 5) The anode member for an electrolytic capacitor according to Technology 3 or 4, wherein the imaginary plane is a plane parallel to the direction in which the anode wire extends.

[0091] (Technology 6) The anode member for an electrolytic capacitor according to Technology 3 or 4, wherein the imaginary plane is a plane perpendicular to the direction in which the anode wire extends.

[0092] (Technology 7) The anode member for an electrolytic capacitor according to any one of Technologies 1 to 6, wherein there is no conductive path from the anode wire to the connection surface of the anode body without passing through the first block region.

[0093] (Technology 8) The anode member for an electrolytic capacitor according to any one of Technologies 1 to 6, wherein a length of a conduction path from the anode wire to the connection surface of the anode body via the first block region is shorter than a length of a conduction path from the anode wire to the connection surface of the anode body via only the second block region.

[0094] (Technology 9) An electrolytic capacitor comprising: the anode member according to any one of Technologies 1 to 8; a dielectric layer formed on a surface of the anode body in the anode member; a solid electrolyte layer covering at least a portion of the dielectric layer; and a cathode lead electrically connected to the solid electrolyte layer, wherein at least a portion of the first block region is interposed between the anode wire and the cathode lead, and the cathode lead is connected to the connection surface.

[0095] 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.

[0096] Example 1 An electrolytic capacitor was fabricated in the following manner.

[0097] (Preparation of Anode Component) Tantalum metal particles were used as the valve metal. The tantalum metal particles were molded into a rectangular parallelepiped so that one end of a copper anode wire was embedded in the tantalum metal particles. The molded body was then sintered in a vacuum. This resulted in an anode component including an anode body (1.7 mm × 3.3 mm × 4.4 mm) made of a porous tantalum sintered body and an anode wire whose one end was embedded in the anode body and whose remaining portion was embedded from one surface of the anode body.

[0098] The tantalum metal particles used were first particles (average particle size 0.5 μm) with a CV value of 50,000 μF·V / g and second particles (average particle size 0.3 μm) with a CV value of 100,000 μF·V / g. The first particles were filled into a mold so as to fill half of the mold volume, and the remaining volume of the mold was filled with the second particles, followed by pressure molding. The compact was sintered to produce an anode member 30 having a first block region 1A and a second block region 1B as shown in FIG. 1 .

[0099] Using the method described above, the pore diameters of the first block region 1A and the second block region 1B of the anode member 30 were calculated to be 0.45 μm and 0.33 μm, respectively. Using the method described above, the particle diameters of the first particles constituting the first block region 1A and the second particles constituting the second block region 1B were calculated to be 0.5 μm and 0.3 μm, respectively.

[0100] (Formation of Dielectric Layer) Next, the anode body of the anode member and a part of the anode wire embedded in the anode body were immersed in an anodization bath filled with an aqueous phosphoric acid solution as an electrolytic solution, and the other end of the anode wire was connected to an electrode in the anodization bath. Then, anodization was performed to form a tantalum oxide (TaO) layer on the surface of the anode body (the surface of the porous sintered body including the inner wall surfaces of the pores) and on the surface of a part of the anode wire. ２ O ５ ) to form a uniform dielectric layer.

[0101] (Formation of Solid Electrolyte Layer) Next, 3,4-ethylenedioxythiophene, which is a raw material for the first conductive polymer, iron(III) p-toluenesulfonate, and 1-butanol were mixed to prepare a first solution. After immersing the anode body in the first solution, the anode body was removed from the first solution and subjected to heat treatment in the air. In this case, iron(III) p-toluenesulfonate functioned as an oxidizing agent. In this way, a first conductive polymer layer containing poly(3,4-ethylenedioxythiophene) (PEDOT) was formed on the dielectric layer.

[0102] Next, poly(3,4-ethylenedioxythiophene) as a second conductive polymer, polystyrene sulfonate, and water were mixed to prepare a second dispersion. After immersing the anode body in the second dispersion, the anode body was removed from the second dispersion and subjected to a decompression treatment. After the decompression treatment, a drying treatment was performed at 80°C for 20 minutes under atmospheric pressure to form a second conductive polymer layer. In this way, a solid electrolyte layer having two layers, a first conductive polymer layer and a second conductive polymer layer, was formed on the dielectric layer.

[0103] (Formation of Cathode Layer) A carbon layer was formed by applying carbon paste to the surface of the solid electrolyte layer. Next, a silver paste layer was formed by applying silver paste to the surface of the carbon layer. In this way, a cathode layer composed of the carbon layer and the silver paste layer was formed, and a capacitor element was obtained.

[0104] (Fabrication of Electrolytic Capacitor) An anode lead terminal and a cathode lead terminal were further disposed on the capacitor element, and an outer casing was formed using a resin containing silica particles as a filler. Thereafter, the anode lead terminal and the cathode lead terminal protruding from the outer casing were bent along the outer casing to fabricate an electrolytic capacitor having the structure shown in FIG.

[0105] When placing the cathode lead terminal on the capacitor element, the capacitor element was placed on the cathode lead terminal so that the surface of the anode member 30 on which only the first block region 1A was exposed faced the cathode lead terminal, thereby obtaining an electrolytic capacitor A1.

[0106] [Evaluation] In an environment of 20°C, the capacitance C of the electrolytic capacitor was measured using an LCR meter for four-terminal measurement. ０ (F) was measured and evaluated as the initial capacity.

[0107] In addition, the ESR value (mΩ) of the electrolytic capacitor was measured at a frequency of 100 kHz, and the initial ESR value X ０ (mΩ).

[0108] Comparative Example 1 Similar to Example 1, an electrolytic capacitor was fabricated using the anode member 30. However, when the cathode lead terminal was disposed on the capacitor element, the anode member 30 was placed upside down on the cathode lead terminal. That is, the capacitor element was placed on the cathode lead terminal so that the surface of the anode member 30 on which only the second block region 1B was exposed faced the cathode lead terminal, thereby obtaining electrolytic capacitor B1. Electrolytic capacitor B1 was evaluated similarly to Example 1.

[0109] Comparative Example 2 In the anode member preparation step, only the first particles were filled into a mold, and the molded body was subjected to pressure molding and sintering to produce an anode member 31 having only the first block region 1A. Using the anode member 31, electrolytic capacitor B2 was obtained in the same manner as in Example 1, except for the above. Electrolytic capacitor B2 was evaluated in the same manner as in Example 1.

[0110] Using the method described above, the pore diameter of the first block region 1A of the anode member 31 was calculated to be 0.45 μm, and the particle diameter of the first particles constituting the first block region 1A was calculated to be 0.5 μm.

[0111] Comparative Example 3 In the anode member preparation step, only the second particles were filled into a mold, and the molded body was similarly subjected to pressure molding and sintering to produce an anode member 32 having only the second block region 1B. Using the anode member 32, electrolytic capacitor B3 was obtained in the same manner as in Example 1. Electrolytic capacitor B3 was evaluated in the same manner as in Example 1.

[0112] Using the method described above, the pore diameter of the second block region 1B of the anode member 32 was calculated to be 0.33 μm, and the particle diameter of the second particles constituting the second block region 1B was calculated to be 0.3 μm.

[0113] Comparative Example 4: In the anode member preparation step, tantalum metal particles (average particle size 0.41 μm) with a CV value of 70,000 μF·V / g were used. Only the tantalum metal particles having the above CV value were filled into a mold, and the molded body was similarly subjected to pressure molding and sintering to produce anode member 33. Using anode member 33, electrolytic capacitor B4 was obtained in the same manner as in Example 1. Electrolytic capacitor B4 was evaluated in the same manner as in Example 1.

[0114] The evaluation results of the electrolytic capacitors A1, B1 to B4 are shown in Table 1. In Table 1, the initial capacitance and initial ESR are each shown as relative values, with the electrolytic capacitor B1 of Comparative Example 1 being set at 100.

[0115]

[0116] The present invention can be used in electrolytic capacitors, and preferably in electrolytic capacitors that use a porous body as an anode body.

[0117] 20: Electrolytic capacitor 10: Capacitor element 1: Anode body 1A: First block region 1B: Second block region 15: Connection surface with cathode lead terminal 2: Anode wire 2a: First portion 2b: Second portion 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode layer 5a: Carbon layer 5b: Metal paste layer 6: Anode portion 7: Cathode portion 8: Conductive adhesive 11: Exterior body 13: Anode lead terminal 14: Cathode lead terminal 14a: Joint portion 30: Anode member

Claims

1. An anode member for an electrolytic capacitor comprising: a porous anode body; and an anode wire embedded in the anode body and having a portion protruding to the outside of the anode body, wherein the anode body has a first block region which is a porous portion containing first particles of a valve action metal, and a second block region which is a porous portion containing second particles of a valve action metal, the pore diameter of the first block region being larger than the pore diameter of the second block region, the anode body having a connection surface connected to a cathode lead of an electrolytic capacitor, and at least a portion of the first block region being interposed between the anode wire and the connection surface.

2. An anode member for an electrolytic capacitor comprising: a porous anode body; and an anode wire embedded in the anode body and having a portion protruding to the outside of the anode body, wherein the anode body has a first block region which is a porous portion containing first particles of a valve action metal, and a second block region which is a porous portion containing second particles of a valve action metal, the particle size of the first particles being larger than the particle size of the second particles, the anode body having a connection surface which is connected to a cathode lead of an electrolytic capacitor, and at least a portion of the first block region being interposed between the anode wire and the connection surface.

3. An anode member for an electrolytic capacitor as described in claim 1 or 2, wherein the anode body is divided into two parts by a virtual plane dividing the anode body, one of the two parts being the first block region and the other of the two parts being the second block region.

4. The anode member for an electrolytic capacitor according to claim 3, wherein the anode body has a rectangular parallelepiped shape, and the imaginary surface is a plane parallel to two opposing main surfaces of the rectangular parallelepiped.

5. The anode member for an electrolytic capacitor according to claim 3, wherein the imaginary surface is a plane parallel to the direction in which the anode wire extends.

6. The anode member for an electrolytic capacitor according to claim 3, wherein the imaginary plane is a plane perpendicular to the direction in which the anode wire extends.

7. The anode member for an electrolytic capacitor according to claim 1 or 2, wherein there is no conductive path from said anode wire to said connection surface of said anode body without passing through said first block region.

8. An anode member for an electrolytic capacitor as described in claim 1 or 2, wherein the length of the conductive path from the anode wire through the first block region to the connection surface of the anode body is shorter than the length of the conductive path from the anode wire through only the second block region to the connection surface of the anode body.

9. An electrolytic capacitor comprising: the anode member according to claim 1 or 2; a dielectric layer formed on a surface of the anode body in the anode member; a solid electrolyte layer covering at least a portion of the dielectric layer; and a cathode lead electrically connected to the solid electrolyte layer, wherein at least a portion of the first block region is interposed between the anode wire and the cathode lead, and the cathode lead is connected to the connection surface.

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