Electrolytic capacitor and method for manufacturing same

Abstract

This electrolytic capacitor is provided with: a capacitor element provided with an anode section and a cathode section; an exterior body that seals the capacitor element; a first external electrode electrically connected to the anode part and exposed from the exterior body; a second external electrode electrically connected to the cathode part and exposed from the exterior body; and a first base electrode that connects the anode portion and the first external electrode, the first base electrode contains a first sintered metal, the first sintered metal is in contact with an end surface of the anode portion not covered by the exterior body and is in contact with the first external electrode, and the ratio of the width Wp of the end surface of the anode portion to the thickness Tpc of the first sintered metal at the center of the width Wp: W1 / Tpc satisfies 0.5 < = W1 / Tpc < = 100.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor and a method for manufacturing the same. Background Art

[0002] An electrolytic capacitor includes: a capacitor element having an anode portion and a cathode portion; an outer package for sealing the capacitor element; and external electrodes electrically connected to the anode portion and the cathode portion of the capacitor element, respectively.

[0003] Patent Document 1 proposes "a solid electrolytic capacitor including: a first capacitor element having a first anode body made of a valve metal, a first dielectric oxide film layer provided on the surface of the first anode body, a first solid electrolyte layer made of a conductive polymer provided on the first dielectric oxide film layer, and a first cathode layer provided on the first solid electrolyte layer; an outer package having a first end face where the first anode body is exposed and covering the first capacitor element, made of an insulating resin; a first base electrode provided on the first end face of the outer package and bonded to the first anode body, made of a non-valve metal; a first diffusion layer made of the valve metal of the first anode body and the non-valve metal of the first base electrode, connecting the first anode body and the first base electrode; a first external electrode provided on the first base electrode; and a second external electrode connected to the first cathode layer".

[0004] The base electrode of the solid electrolytic capacitor of Patent Document 1 is "a metal layer formed by colliding metal particles made of a non-valve metal with the first end face of the outer package at a speed of 200 m / s or more and at a speed below the speed of sound".

[0005] Patent Document 2 proposes "an electrolytic capacitor characterized by including: a resin molded body including a laminate including a capacitor element and a sealing resin for sealing the periphery of the laminate; and an anode external electrode and a cathode external electrode provided on the outer surface of the resin molded body, the capacitor element including: a valve metal substrate having a core portion and a porous portion formed along its surface and having an end exposed on the outer surface of the resin molded body, a dielectric layer formed on the porous portion, a solid electrolyte layer formed on the dielectric layer, and a conductive layer formed on the solid electrolyte layer, the cathode external electrode being electrically connected to the conductive layer, and the anode external electrode including a first electrode layer in direct contact with the core portion and the porous portion of the valve metal substrate, and the thickness of the portion formed at the core portion of the valve metal substrate being thicker than the thickness of the portion formed at the porous portion of the valve metal substrate in the normal direction of the outer surface of the first electrode layer".

[0006] The first electrode layer of Patent Document 2 is formed by aerosol deposition method.

[0007] Patent Document 3 proposes, "An electrolytic capacitor, characterized in that it comprises: a rectangular parallelepiped resin molded body having a laminate and a sealing resin, the laminate including a capacitor element having an anode with a dielectric layer on its surface and a cathode opposite to the anode, and the sealing resin sealing the periphery of the laminate; a first external electrode formed on a first end face of the resin molded body and electrically connected to the anode exposed from the first end face; a second external electrode formed on a second end face of the resin molded body and electrically connected to the cathode exposed from the second end face; a third external electrode formed on the first end face side of the bottom face of the resin molded body; and a fourth external electrode formed on the second end face side of the bottom face of the resin molded body, wherein the first external electrode, the second external electrode, the third external electrode, and the fourth external electrode each have a base electrode layer formed on the resin molded body and a plating layer formed on the base electrode layer, the base electrode layer of the first external electrode is separated from the base electrode layer of the third external electrode, and the base electrode layer of the second external electrode is separated from the base electrode layer of the fourth external electrode".

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: International Publication No. 2009 / 028183

[0011] Patent Document 2: International Publication No. 2022 / 168769

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2020-141059 Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] In the electrolytic capacitors described in Patent Documents 1 and 2, the yield of metal particles in the manufacturing process of the base electrode or the first electrode layer is low, and material loss is likely to occur, so it is difficult to reduce the production cost.

[0015] The manufacturing process of the electrolytic capacitor described in Patent Document 3 takes a long time, and it is difficult to reduce the production cost. In addition, the base electrode of the plating layer is prone to surface oxidation. When the base electrode is oxidized, the adhesion strength between the base electrode and the external electrode decreases, and the ESR increases.

[0016] Solutions to the Problems

[0017] One aspect of the present disclosure relates to an electrolytic capacitor, comprising: a capacitor element having an anode portion and a cathode portion; an outer package sealing the capacitor element; a first external electrode electrically connected to the anode portion and exposed from the outer package; a second external electrode electrically connected to the cathode portion and exposed from the outer package; and a first base electrode connecting the anode portion and the first external electrode, the first base electrode including a first sintered metal that contacts an end face of the anode portion not covered by the outer package and contacts the first external electrode, and a ratio of a width Wp of the end face of the anode portion to a thickness Tpc of the first sintered metal at the center of the width Wp: Wp / Tpc satisfies 0.5 ≤ Wp / Tpc ≤ 100.

[0018] Another aspect of the present disclosure relates to a method for manufacturing an electrolytic capacitor, comprising: a step of preparing a capacitor element having an anode portion and a cathode portion; a step of sealing the capacitor element with an outer package; a step of exposing an end face of the anode portion from the outer package; a step of forming a first base electrode on the end face of the anode portion; and a step of forming the first external electrode electrically connected to the anode portion via the first base electrode, and the step of forming the first base electrode includes: step (i) of attaching a metal nanoink containing metal nanoparticles to the end face of the anode portion and a first surface of the outer package opposite to the first external electrode; and step (ii) of irradiating light on the metal nanoparticles after step (i) to sinter the metal nanoparticles with each other to form a first sintered metal.

[0019] Effects of the Invention

[0020] According to the present disclosure, an electrolytic capacitor having a base electrode including a sintered metal can be obtained at low cost and high efficiency.

[0021] Although the novel features of the present invention are described in the appended claims, the present invention can be better understood through the following detailed description that involves both structure and content, combines other objects and features of the present invention, and refers to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A cross-sectional view schematically showing an electrolytic capacitor according to an embodiment of the present disclosure.

[0023] Figure 2 A cross-sectional view schematically showing the structure of an example of a capacitor element.

[0024] Figure 3 For magnifying and showing Figure 1 A schematic cross-sectional view of a partial structure of the shown electrolytic capacitor.

[0025] Figure 4 To magnify and show Figure 1 A schematic cross-sectional view of another part of the structure of the electrolytic capacitor shown.

[0026] Figure 5 A cross-sectional view schematically showing an electrolytic capacitor according to another embodiment of the present disclosure.

[0027] Figure 6 A cross-sectional view schematically showing an electrolytic capacitor according to yet another embodiment of the present disclosure.

[0028] Figure 7 A cross-sectional view showing the structure of another example of a capacitor element schematically.

[0029] Figure 8 A cross-sectional view schematically showing an electrolytic capacitor according to yet another embodiment of the present disclosure.

[0030] Figure 9 A digital microscope image of the reference cross-section on the anode side.

[0031] Figure 10 A digital microscope image of the reference cross-section on the cathode side. Detailed embodiments

[0032] Hereinafter, embodiments of the present disclosure will be exemplified, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may sometimes be exemplified, but other numerical values and materials may also be used as long as the effects of the present disclosure can be obtained. In this specification, the description of "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "not less than numerical value A and not more than numerical value B". In the following description, when the lower limit and the upper limit of a numerical value related to a specific physical property, condition, etc. are exemplified, as long as the lower limit is not more than the upper limit, any combination of any one of the exemplified lower limits and any one of the exemplified upper limits can be made. When multiple materials are exemplified, one of them can be selected and used alone, or two or more of them can be used in combination.

[0033] In addition, the present disclosure includes combinations of the contents recited in two or more claims arbitrarily selected from the multiple claims recited in the appended claims. That is, as long as there is no technical contradiction, the contents recited in two or more claims arbitrarily selected from the multiple claims recited in the appended claims can be combined.

[0034] "Electrolytic capacitor" can also be read as "solid electrolytic capacitor", and "capacitor" can also be read as "capacitor".

[0035] [Electrolytic capacitor]

[0036] One embodiment of the present invention relates to an electrolytic capacitor including a capacitor element. The form of the capacitor element is not particularly limited. The capacitor element includes an anode portion and a cathode portion. The capacitor element includes, for example, an anode body, a dielectric layer, and a cathode layer. The anode portion includes at least a part of the anode body. The cathode portion includes the cathode layer.

[0037] The capacitor element is sealed with an outer package. The outer package is made of a sealing material. The sealing material can be, for example, a cured product of a thermosetting resin composition containing an epoxy resin or the like.

[0038] Among them, the end face of the anode portion has a portion not covered by the outer package (the exposed portion from the outer package) for ensuring electrical connection. The end face of the anode portion is connected to the first base electrode. The first base electrode is connected to the first external electrode. The first base electrode includes a first sintered metal. The first sintered metal is in contact with the end face of the anode portion not covered by the outer package.

[0039] The first sintered metal preferably also covers the first surface of the outer package opposite to the first external electrode. By covering the first surface of the outer package with the first sintered metal, the contact area between the first sintered metal and the first external electrode becomes larger. Therefore, an electrolytic capacitor with a lower resistance can be obtained.

[0040] The end face of the cathode portion may also have a portion not covered by the outer package (the exposed portion from the outer package). In this case, the end face of the cathode portion is connected to the second base electrode. The second base electrode is connected to the second external electrode. The second base electrode includes a second sintered metal. The second sintered metal is in contact with the end face of the cathode portion not covered by the outer package.

[0041] The second sintered metal preferably also covers the second surface of the outer package opposite to the second external electrode. By covering the second surface of the outer package with the second sintered metal, the contact area between the second sintered metal and the second external electrode becomes larger. Therefore, an electrolytic capacitor with a lower resistance can be obtained.

[0042] The anode body has, for example, a first portion including a first end portion (also referred to as an "anode lead-out portion") and a second portion including a second end portion (also referred to as a "cathode forming portion"). The anode portion includes the first portion (anode lead-out portion). The end face of the anode portion may be the end face of the first end portion of the first portion.

[0043] The dielectric layer is formed on the surface of at least the second portion of the anode body. The cathode layer covers at least a part of the dielectric layer. The cathode portion includes the cathode layer covering the second portion (cathode forming portion).

[0044] The cathode portion may also have a cathode foil (or current collector plate) that protrudes more toward the second end portion than the cathode layer. The cathode foil is connected to the cathode layer. In this case, the end face of the cathode portion may be the end face of the protruding portion of the cathode foil. Thus, it is easy to form the end face of the cathode portion that is not covered by the exterior body. The cathode foil may be a metal foil.

[0045] The first end portion and the second end portion of the anode body may respectively correspond to one end portion and the other end portion of the anode body when observing the anode body from a specified direction. The specified direction refers to the direction perpendicular to the paper surface of the attached Figures 1 to 6 paper surface. Alternatively, when observing in the vertical direction (longitudinal direction) of the paper surface of the attached Figures 1 to 6 paper surface, the first end portion and the second end portion may also correspond to two adjacent sides that form a 90-degree angle, for example.

[0046] The anode body includes an anode foil, for example. The anode foil has a metal core portion and a porous portion continuous with the metal core portion. In this case, the end face of the anode portion or the end face of the first end portion of the first part may include the end faces of the metal core portion and the porous portion. The anode foil may be a metal foil with a roughened surface, for example. The anode foil may be an etched foil whose surface is roughened by etching, for example. In this case, a plurality of capacitor elements may be overlapped to form a laminate.

[0047] The anode body may include a sintered body of metal particles, for example. In this case, the anode body has a metal wire (anode wire) partially embedded in the sintered body. The metal wire corresponds to the first part. The sintered body corresponds to the second part. The end face of the anode portion or the end face of the first end portion of the first part may include the end face of the protruding portion of the metal wire.

[0048] The sintered metal is formed by aggregation and sintering of metal nanoparticles. The sintered metal is structurally different from the metal forming the coating. The metal nanoparticles are bonded to each other by metal bonds. Necks may be formed between the metal nanoparticles. The sintered metal may be bonded to the end face of the anode portion or the end face of the cathode portion by metal bonds. As a specific example, the first sintered metal may be bonded to the end face of the metal core portion forming the anode body or the end face of the protruding portion of the metal wire by metal bonds. In addition, the second sintered metal may be bonded to the end face of the protruding portion of the cathode foil of the cathode portion by metal bonds. Thus, the bonding strength between the end face of the anode portion and the first base electrode or the bonding strength between the end face of the cathode portion and the second base electrode can be improved, making it difficult to cause peeling.

[0049] Sintered metal can be bonded to the end face of the anode part or the end face of the cathode part thinly and over a large area through a metal bond. Therefore, material loss in the manufacturing process is difficult to occur, and the production cost can be easily reduced. The process of forming the sintered metal is, for example, photo-firing (photo-sintering). Therefore, the time required for the process is greatly shortened compared to the formation of the coating. In addition, the base electrode of the coating is easily oxidized on the surface, and the ESR is easily increased. In contrast, it is easy to control the surface oxidation of the sintered metal. Therefore, by using sintered metal, the base electrode can be formed at low cost and efficiently.

[0050] The first sintered metal can be metal-bonded to the end face of the anode portion in a thin and large area. Specifically, the ratio of the width Wp of the end face of the anode portion to the thickness Tpc of the first sintered metal at the center of the width Wp: Wp / Tpc satisfies 0.5≤Wp / Tpc≤100. The width Wp only needs to be the width of the cross section of the electrolytic capacitor that is parallel to the thickness direction of the anode body and the direction from the first end toward the second end (hereinafter also referred to as the "reference cross section"). The reference cross section is the same as the attached Figures 1 to 6 In the case where the anode body includes an anode foil, the width Wp corresponds to the thickness of the anode foil. In the case where the anode body has a metal wire (anode wire) partially embedded in the sintered body, the width Wp corresponds to the diameter of the metal wire.

[0051] Wp / Tpc may satisfy 1≤Wp / Tpc, 1.5≤Wp / Tpc, 2≤Wp / Tpc, 3≤W1p / Tpc, 5≤Wp / Tpc, or 10≤Wp / Tpc. Wp / Tpc may satisfy Wp / Tpc≤90, Wp / Tpc≤85, Wp / Tpc≤80, Wp / Tpc≤75, or Wp / Tpc≤70. It may satisfy 1.5≤Wp / Tpc≤100, or 2≤Wp / Tpc≤100.

[0052] The second sintered metal can be metal-bonded thinly and over a large area to the end face of the cathode portion. Specifically, the ratio of the width Wn of the end face of the cathode portion to the thickness Tnc of the second sintered metal at the center of the width Wn: Wn / Tnc satisfies 0.5≤Wn / Tnc≤100. The width Wn is the width at the reference cross section. In the case where the cathode body includes a cathode foil, the width Wn corresponds to the thickness of the cathode foil.

[0053] Wn / Tnc can satisfy 1 ≤ Wn / Tnc, or can satisfy 1.5 ≤ Wn / Tnc, or can satisfy 2 ≤ Wn / Tnc, or can satisfy 3 ≤ Wn / Tnc, or can satisfy 5 ≤ Wn / Tnc, or can satisfy 10 ≤ Wn / Tnc. Wn / Tnc can satisfy Wn / Tnc ≤ 90, or can satisfy Wn / Tnc ≤ 85, or can satisfy Wn / Tnc ≤ 80, or can satisfy Wn / Tnc ≤ 75, or can satisfy Wn / Tnc ≤ 70. It can satisfy 1.5 ≤ Wn / Tnc ≤ 100, or can satisfy 2 ≤ Wn / Tnc ≤ 100.

[0054] The shape of the reference cross-section of the first sintered metal can be a flat shape. The ratio of the thickness Tpc at the center of the width Wp of the first sintered metal to the thickness Tpt at a position Wp / 3 away from the center of the width Wp: Tpc / Tpt is, for example, 0.5 or more, preferably 2 or less, and can also be 1.5 or less.

[0055] Similarly, the shape of the reference cross-section of the second sintered metal can be a flat shape. The ratio of the thickness Tnc at the center of the width Wn of the second sintered metal to the thickness Tnt at a position Wn / 3 away from the center of the width Wn: Tnc / Tnt is, for example, 0.5 or more, preferably 2 or less, and can also be 1.5 or less.

[0056] When the first sintered metal has a flat shape, the contact area Spo between the first sintered metal and the first external electrode increases to be greater than or equal to the contact area Spi between the first sintered metal and the end face of the anode portion. The ratio of Spo to Spi: Spo / Spi is, for example, 1.0 or more, and when the first sintered metal covers the surface (the first surface) of the outer package, it can also be 3 or more. On the other hand, when the first sintered metal hardly covers the surface (the first surface) of the outer package, the ratio of Spo / Spi can be 1.5 or less, even 1.2 or less.

[0057] Similarly, when the second sintered metal has a flat shape, the contact area Sno between the second sintered metal and the second external electrode increases to be greater than or equal to the contact area Sni between the second sintered metal and the end face of the cathode portion. The ratio of Sno to Sni: Sno / Sni is, for example, 1.0 or more. When the second sintered metal covers the surface (the second surface) of the outer package, the ratio of Sno / Sni can also be 3 or more. On the other hand, when the second sintered metal hardly covers the surface (the second surface) of the outer package, the ratio of Sno / Sni can be 1.5 or less, even 1.2 or less.

[0058] As described above, the thicknesses of the first and second sintered metals can both be formed very thin. Therefore, it is possible to suppress the reduction in productivity caused by the increase in the thickness of the sintered metal.

[0059] The first sintered metal and the second sintered metal may contain a phosphorus element. The first sintered metal and the second sintered metal may have the same structure or different structures from each other. Since the sintered metal layer containing a phosphorus element has high corrosion resistance, it is suitable for use as a base electrode. By forming a base electrode with high corrosion resistance, peeling between the base electrode and the external electrode, etc. is suppressed, and deterioration of the cathode portion caused by moisture and oxygen is suppressed.

[0060] The first sintered metal and the second sintered metal can be formed by a process of attaching a metal nanoink containing a phosphorus element and metal nanoparticles to the end face of the anode portion or the cathode portion, and a process of sintering the metal nanoparticles to each other by irradiating light on the metal nanoparticles on the end face. Such a process is simple and can be completed in a short time. In addition, the utilization rate of the metal nanoparticles is high, and it is easy to reduce the material cost. That is, a base electrode containing a sintered metal can be formed at low cost and efficiently.

[0061] In the first sintered metal and the second sintered metal, preferably, the phosphorus element is more distributed on the external electrode side than on the end face side of the anode portion or the cathode portion. According to such a distribution, even if the base electrode and the external electrode are locally peeled, the base electrode with high corrosion resistance will serve as a barrier. Therefore, deterioration of the cathode portion caused by moisture and oxygen is suppressed. For example, through the center line of the cross section of the sintered metal, the sintered metal is bisected into a first region on the end face side of the anode portion or the cathode portion and a second region on the external electrode side. At this time, as long as more phosphorus element is distributed in the second region on the external electrode side. In other words, the sintered metal may have a conventional layer containing no or only a small amount of phosphorus element and a phosphorus-rich layer containing a relatively large amount of phosphorus element. Even in the case where a layer structure is not clearly formed, a conventional region containing no or only a small amount of phosphorus element and a phosphorus-rich region containing a relatively large amount of phosphorus element can be formed. In addition, from a more microscopic perspective, a distribution of the phosphorus element also occurs within the metal particles constituting the sintered metal. The concentration of the phosphorus element may be higher in the outer region of the metal particles, and the concentration of the phosphorus element may be lower or the phosphorus element may not exist in the inner region of the metal particles.

[0062] The content rate Poe of the phosphorus element in the second region on the external electrode side may be 2 times or more the content rate Pts of the phosphorus element in the first region on the end face side. In 10 10000 nm including the centers in the thickness directions of the second region on the external electrode side and the first region on the end face side respectively 2The content ratios Poe and Pts are measured in the measurement area (e.g., a 100 nm square area on one side). For example, the amount of phosphorus element present in each measurement area is measured using SEM-EDX, and Poe / Pts can be obtained in the form of the ratio of their average values. The compositional ratio of the elements in each measurement area can also be obtained by other methods such as the method using an electron probe microanalyzer (EPMA).

[0063] The depth (Dp) from the outer electrode side (towards the end face side of the anode part or the cathode part) at which the count of the phosphorus element (phosphorus element concentration or detection intensity of the phosphorus element) measured by SEM-EDX, EPMA, etc. is 10% or less of the maximum value is, for example, 10% to 80% of the thicknesses (Tpc, Tnc) of the first and second sintered metals, and can also be 10% to 30%. In this case, the corrosion resistance of the base electrode is significantly improved. The local peeling between the base electrode and the outer electrode, and the deterioration of the cathode part caused by moisture and oxygen are also significantly suppressed.

[0064] Regarding the specified thicknesses of the first and second sintered metals and the depth Dp, measurements are made at any 10 or more points in the cross-sectional image of the laminated part of the end face of the anode part or the cathode part and the base electrode, and they can be calculated in the form of the average value of these measurement values.

[0065] The first outer electrode and / or the second outer electrode can be formed by various methods. For example, the outer electrode can be formed by film-forming techniques such as electroplating, electroless plating, sputtering, vacuum evaporation, chemical vapor deposition (CVD), cold spraying, and spraying.

[0066] The first or second outer electrode can have a coating layer covering at least a part of the first or second sintered metal. The coating layer contains, for example, nickel (Ni), copper (Cu), zinc (Zn), tin (Sn), silver (Ag), gold (Au), etc. The coating layer usually contains a Ni coating layer. The coating layer can also have a Sn coating layer covering at least a part of the Ni coating layer. Such a coating layer with a multi-layer structure has high conductivity and good connectivity between the outer electrode and various terminal electrodes.

[0067] The first or second external electrode including a plating layer may further have a conductive layer between the first or second sintered metal and the plating layer. The conductive layer is not particularly limited and may be composed of conductive particles and a resin. For example, the conductive layer may be a cured product of a conductive paste (conductive paste layer) containing conductive particles and a resin. As the conductive particles, for example, metal particles such as silver and copper, and carbon particles can be used. The resin preferably contains an epoxy resin. That is, the conductive paste may be a thermosetting resin composition containing conductive particles and an epoxy resin. The conductive paste layer can be formed by coating and drying in such a manner that the sintered metal layer is covered with the conductive paste. The conductive layer may cover a part of the surface (for example, the upper surface or the bottom surface) of the exterior body where the end face of the anode portion or the cathode portion of the capacitor element is exposed and intersects with the main surface.

[0068] The first or second external electrode may have a lead frame covering at least a part of the first or second sintered metal. The lead frame can be formed, for example, by punching and bending a metal foil. At this time, the first or second external electrode may further have a solder layer between the first or second sintered metal and the lead frame, and may also have the above-mentioned conductive layer (such as a conductive paste layer).

[0069] The outer surfaces of the first and second external electrodes are preferably metals with excellent wettability to solder. Examples of such metals include Sn, Au, Ag, Pd, etc.

[0070] Hereinafter, preferred examples of the combination of the end face of the anode portion or the cathode portion, the base electrode, and the external electrode are listed.

[0071] (1) End face / Sintered metal / First plating layer (for example, Ni plating layer) / Second plating layer (for example, Sn plating layer)

[0072] (2) End face / Sintered metal (wherein, a laminated structure of a conventional layer and a phosphorus-rich layer) / First plating layer (for example, Ni plating layer) / Second plating layer (for example, Sn plating layer)

[0073] (3) End face / Sintered metal / Conductive layer / First plating layer (for example, Ni plating layer) / Second plating layer (for example, Sn plating layer)

[0074] (4) End face / Sintered metal (wherein, a laminated structure of a conventional layer and a phosphorus-rich layer) / Conductive layer / First plating layer (for example, Ni plating layer) / Second plating layer (for example, Sn plating layer)

[0075] (5) End face / Sintered metal / Conductive layer / Lead frame

[0076] (6) End face / Sintered metal / Solder layer / Lead frame

[0077] (7) End face / Sintered metal (wherein, a laminated structure of a conventional layer and a phosphorus-rich layer) / Conductive layer / Lead frame

[0078] (8) End face / sintered metal (wherein, a laminated structure of a conventional layer and a phosphorus-rich layer) / solder layer / lead frame

[0079] In a Ni / Sn plating layer including two layers of a Ni plating layer and a Sn plating layer formed on its surface, an alloy layer of Ni and Sn can also be formed by diffusion of Ni in the Ni plating layer toward the Sn plating side and diffusion of Sn in the Sn plating layer toward the Ni plating layer side.

[0080] The electrolytic capacitor can have an element laminate including a plurality of capacitor elements. In this case, end faces of the plurality of anode portions can be exposed from the outer package. Moreover, at least a part of the end faces of these anode portions can be electrically connected to the first external electrode via the first sintered metal layer. In addition, end faces of the plurality of cathode portions can be exposed from the outer package. In addition, at least a part of the end faces of these cathode portions can be electrically connected to the second external electrode via the second sintered metal layer.

[0081] The plurality of capacitor elements can be oriented in the same direction or in different directions. For example, they can be laminated in such a manner that the anode portions and the cathode portions are alternately oriented in opposite directions. For example, the anode portions and the cathode portions can be laminated in such a manner that they are oriented in opposite directions in any order. For example, the anode portions and the cathode portions can be laminated in such a manner that they alternately cross at 90 degrees. For example, the anode portions and the cathode portions can be laminated in such a manner that they cross at 90 degrees in any order.

[0082] Only the end faces of the anode portions can be exposed from the outer package, and the end faces can be electrically connected to the first external electrode via the first sintered metal layer. Both the end faces of the anode portions and the end faces of the cathode portions can be exposed from the outer package, and the respective end faces can be electrically connected to the first external electrode and the second external electrode via the first and second sintered metal layers.

[0083] End faces of the plurality of anode portions can be exposed from the first main surface of the outer package. In this case, the first external electrode can be disposed so as to cover the first main surface. At this time, end faces of the plurality of cathode portions can also be exposed from a second main surface of the outer package different from (for example, on the side opposite to) the first main surface. In this case, the first main surface corresponds to the first surface, and the second main surface corresponds to the second surface.

[0084] It is also possible to expose a part of the end faces of multiple anode portions from the first main surface of the outer package, and expose the end faces of other anode portions from the second main surface of the outer package that is different from the first main surface (for example, the opposite side of the first main surface). In this case, two first external electrodes are provided. One first external electrode is arranged to cover the first main surface, and the other first external electrode is arranged to cover the second main surface. At this time, the end faces of multiple cathode portions can also be exposed from the third main surface of the outer package that is different from the first and second main surfaces. In this case, the second external electrode can be arranged to cover the third main surface. It is also possible to expose a part of the end faces of multiple cathode portions from the third main surface of the outer package, and expose the end faces of other cathode portions from the fourth main surface of the outer package that is different from the first to third main surfaces (for example, the opposite side of the third main surface). In this case, two second external electrodes are provided. One second external electrode is arranged to cover the third main surface, and the other second external electrode is arranged to cover the fourth main surface. It should be noted that the first main surface and the second main surface correspond to the first surface, and the third main surface and the fourth main surface correspond to the second surface.

[0085] Next, an exemplary manufacturing method of the electrolytic capacitor will be described, but the manufacturing method of the electrolytic capacitor according to the present disclosure is not limited to the following.

[0086] The manufacturing method of the electrolytic capacitor, for example, includes: a step of preparing a capacitor element having an anode portion and a cathode portion; a step of sealing the capacitor element with an outer package; a step of exposing the end face of the anode portion from the outer package; a step of forming a first base electrode on the end face of the anode portion; and a step of forming a first external electrode that is electrically connected to the anode portion via the first base electrode.

[0087] The above manufacturing method may further include: a step of exposing the end face of the cathode portion from the outer package; a step of forming a second base electrode on the end face of the cathode portion; and a step of forming a second external electrode that is electrically connected to the cathode portion via the second base electrode. Hereinafter, each step will be further described.

[0088] (Step of preparing the capacitor element)

[0089] The step of preparing the capacitor element includes the step of preparing the anode body. The step of preparing the capacitor element may include the step of disposing a separation layer (insulating member) on a part of the anode body. The step of preparing the capacitor element may further have the step of obtaining an element laminate by laminating multiple capacitor elements.

[0090] (Anode body)

[0091] In the process of preparing the anode body, an anode body having a first part including a first end portion and a second part including a second end portion is prepared. The anode portion includes the first part (anode lead-out portion) of the anode body. The first part of the anode body may include a removal predetermined end portion that will be removed later by cutting or the like. At least the second part of the anode body has a porous portion. For the surface of at least the second part, a dielectric layer is formed later.

[0092] The anode body includes a valve-acting metal, an alloy containing a valve-acting metal, and a compound containing a valve-acting metal (intermetallic compound, etc.). These materials can be used alone or in combination of two or more. As the valve-acting metal, aluminum, tantalum, niobium, titanium, etc. can be used. The anode body can be a foil (anode foil) of a valve-acting metal, an alloy containing a valve-acting metal, or a compound containing a valve-acting metal, or a porous sintered body of a valve-acting metal, an alloy containing a valve-acting metal, or a compound containing a valve-acting metal.

[0093] When the anode body uses a foil (anode foil), a porous portion is formed in the surface layer portion of at least the second part of the anode foil. That is, the second part has a metal core portion and a porous portion formed on the surface of the metal core portion. The porous portion can also be formed by roughening the surface of at least the second part of the anode foil by etching or the like. After disposing a prescribed mask member on the surface of the first part, roughening treatment such as etching treatment can be performed. On the other hand, the entire surface of the anode foil can be roughened by etching treatment or the like. In the former case, an anode foil having no porous portion on the surface of the first part and having a porous portion on the surface of the second part can be obtained. In the latter case, in addition to the surface of the second part, a porous portion is also formed on the surface of the first part.

[0094] As the etching treatment, a known method can be used. For example, electrolytic etching can be cited. The mask member is not particularly limited, but an insulator such as resin is preferred. The mask member can be a conductor containing a conductive material.

[0095] In the case of roughening the entire surface of the anode foil, a porous portion also exists on the surface of the first part. The porous portion of the first part can be pre-compressed to seal the pores. Thereby, intrusion of air and moisture from the end face of the anode portion exposed from the outer package body into the electrolytic capacitor through the porous portion can be suppressed.

[0096] When the anode body uses a sintered body, the sintered body is obtained by molding and sintering a powder containing a valve-acting metal (for example, a powder of a valve-acting metal, an alloy or compound powder containing a valve-acting metal). For example, the buried portion of the anode lead wire connected to the anode body is buried in the powder together with the powder of the valve-acting metal, placed in a mold, and compression-molded. Then, by sintering the molded body, a porous anode body in which a part of the anode lead wire is embedded can be formed. The sintering is preferably carried out under reduced pressure.

[0097] (Separation layer)

[0098] When the anode body uses a foil (anode foil), an insulating separation layer for electrically separating the first part and the second part can be provided. In this process, an insulating member is disposed on the first part of the anode body with a dielectric layer therebetween. The insulating member is disposed in such a way as to isolate the first part from the cathode portion formed in a subsequent process. The separation layer can be provided close to the cathode so as to cover at least a part of the surface of the first part.

[0099] The separation layer is obtained, for example, by adhering a sheet-like insulating member (such as a resin tape) to the first part. In the case of using an anode foil having a porous portion on the surface, the porous portion of the first part can be compressed to make it flat. Moreover, the insulating member can be made to conform to the flattened first part. The sheet-like insulating member preferably has an adhesive layer on the surface on the side pasted to the first part.

[0100] A liquid resin can be applied to or impregnated into the first part to form an insulating member that conforms to the first part. In the method using a liquid resin, the insulating member is formed in such a way as to fill the unevenness on the surface of the porous portion of the first part. The liquid resin easily enters the concave portions on the surface of the porous portion. Therefore, the insulating member can also be easily formed in the concave portions.

[0101] (Dielectric layer)

[0102] The dielectric layer is formed, for example, by anodizing the valve-acting metal on the surface of at least the second part of the anode body by using a chemical conversion treatment or the like. In the chemical conversion treatment, for example, the chemical conversion liquid is impregnated into the surface of the anode body by immersing the anode body in the chemical conversion liquid. Moreover, by using the anode body as an anode and applying a voltage between the cathode immersed in the chemical conversion liquid, the chemical conversion can be carried out. When the surface of the anode body has a porous part, the dielectric layer is formed along the uneven shape of the surface of the porous part. 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 along the surface of at least the second part where the porous part is formed (including the inner wall surface of the pores of the porous part). It should be noted that the formation method of 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 part. The dielectric layer can also be formed on the surface of the first part (for example, on the porous part of the surface of the first part).

[0103] (Cathode part)

[0104] The cathode part includes a solid electrolyte layer covering at least a part of the dielectric layer and a cathode lead-out layer covering at least a part of the solid electrolyte layer. The cathode part may include a cathode foil. The cathode foil is electrically connected to the cathode lead-out layer and is also electrically connected to the second external electrode.

[0105] (Solid electrolyte layer)

[0106] The solid electrolyte layer contains, for example, a conductive polymer. As the conductive polymer, for example, polypyrrole, polythiophene, polyaniline, and their derivatives can be used. The solid electrolyte layer can be formed, for example, by chemically polymerizing and / or electrolytically polymerizing the raw material monomers on the dielectric layer. Or, it can be formed by coating a solution in which a conductive polymer is dissolved or a dispersion in which a conductive polymer is dispersed on the dielectric layer. The solid electrolyte layer may contain a manganese compound.

[0107] (Cathode lead-out layer)

[0108] The cathode lead-out layer includes, for example, a carbon layer and a conductive paste layer. The carbon layer only needs to have conductivity, and for example, it can be composed of a conductive carbon material such as graphite. The carbon layer is formed, for example, by coating a carbon paste on at least a part of the surface of the solid electrolyte layer. The conductive paste layer can be a cured product of a metal paste (metal paste layer) containing metal particles and a resin. The metal particles can be particles of silver, copper, nickel, etc. Particularly preferably, it is silver. That is, the metal paste layer is preferably a silver paste layer. The resin preferably contains an epoxy resin. The metal paste can be a thermosetting resin composition containing metal particles and an epoxy resin. The metal paste layer is formed, for example, by coating on the surface of the carbon layer. It should be noted that the structure of the cathode lead-out layer is not limited to this, as long as it has a current collecting function.

[0109] (Cathode foil)

[0110] The cathode foil is, for example, a metal foil. The metal foil can be a sintered foil, an evaporated foil, or a coated foil. The cathode foil can be a sintered foil, an evaporated foil, or a coated foil obtained by covering the surface of a metal foil (e.g., Al foil, Cu foil) with a conductive film by evaporation or coating. The evaporated foil can be an Al foil with Ni evaporated on its surface. As the conductive film, Ti, TiC, TiO, C (carbon) film, etc. can be cited. The conductive film can be a carbon coating film.

[0111] (Process of sealing the capacitor element with an outer package)

[0112] First, a mold configured such that the end faces of the anode part and the cathode part are exposed and the remaining part of the capacitor element is sealed can be used. The capacitor element can be placed in the mold, and then the capacitor element can be sealed with a sealing material to form an outer package. Second, a mold configured such that the end faces of the anode part and the cathode part are not exposed and the entire capacitor element is sealed can be used. The capacitor element can be placed in the mold, and then the capacitor element can be sealed with a sealing material to form an outer package. In either case, first, it is efficient to form an aggregate of a plurality of capacitor elements. Second, it is efficient to seal the aggregate with a sealing material to form an outer package. Such a process can be carried out by a transfer molding method, a compression molding method, etc. In the case of the first method, the process of exposing the end faces of the anode part and the cathode part from the outer package is also carried out simultaneously.

[0113] The sealing material is preferably, for example, a thermosetting resin composition and can also contain a thermoplastic resin. In the transfer molding method or the compression molding method, the uncured sealing material is cured to form an outer package. The thermosetting resin composition can contain, in addition to a main resin such as an epoxy resin, a filler, a curing agent, a polymerization initiator, a catalyst, etc.

[0114] (Process of exposing the end face of the anode part or the cathode part from the outer package)

[0115] When exposing the end face of the anode portion from the outer package, for example, a part of the outer package can be removed. Specifically, methods include grinding the outer package in such a way that the end face of the anode portion is exposed from the outer package after covering the capacitor element with the outer package; and a method of cutting off a part of the outer package. A part of the first portion can also be cut off together with a part of the outer package. In this case, it is possible to easily expose the end face of the first end portion of the anode body having a surface on which a natural oxide film is not formed from the outer package. Therefore, a connection state with low resistance and high reliability can be obtained between the first portion, the first base electrode, and the first external electrode.

[0116] When the element laminate includes a cathode foil, the outer package can be locally removed to expose the end portion of the cathode foil from the outer package. As a method for exposing the end portion of the cathode foil from the outer package, the same method as that for exposing the end face of the first end portion of the anode body from the outer package can be used. A part of the cathode foil can be cut off together with a part of the outer package. The exposed surface of the end portion of the cathode foil from the outer package is preferably a surface different from the surface of the outer package where the end face of the first end portion of the anode body is exposed.

[0117] The anode body and the insulating member of the element laminate can be locally removed together with the outer package to expose the end face of the first end portion and the end face of the insulating member from the outer package. In this case, flush end faces are formed where the anode body and the insulating member are respectively exposed from the outer package. Thus, it is possible to easily expose the end face of the anode body and the end face of the insulating member, which are flush with the surface of the outer package, from the outer package respectively.

[0118] As described above, by cutting or the like, it is possible to easily expose the end faces of the anode body (first end portion) on which a natural oxide film is not formed and the end face of the cathode foil from the outer package. Therefore, a connection state with low resistance and high reliability can be obtained between the anode body or the first portion and the first external electrode.

[0119] An aggregate of a plurality of capacitor elements can be formed, and the aggregate can be sealed with a sealing material to form an outer package. In this case, when the aggregate is separated into individual pieces, the connection portions connecting adjacent anode portions in the aggregate and the connection portions connecting adjacent cathode portions in the aggregate can also be cut off. In this case, the end faces of the anode portions and the end faces of the cathode portions are exposed on the cut surface. Such a cut surface can be a dry etching processed surface using plasma or the like.

[0120] (Process of forming the base metal)

[0121] The process of forming the first base electrode, for example, includes: process (i), attaching a metal nanoink containing metal nanoparticles to the end face of the anode portion and the first surface of the outer package facing the first external electrode (coating process); and thereafter, process (ii), irradiating the metal nanoparticles with light to sinter (or photo-fire) the metal nanoparticles with each other to form the first sintered metal (photo-sintering process).

[0122] Similarly, the process of forming the second base electrode, for example, includes: process (i), attaching a metal nanoink containing metal nanoparticles to the end face of the cathode portion and the second surface of the outer package facing the second external electrode (coating process); and thereafter, process (ii), irradiating the metal nanoparticles with light to sinter (or photo-fire) the metal nanoparticles with each other to form the second sintered metal.

[0123] Among them, in the end face of the anode portion or the cathode portion and the first or second surface of the outer package, the sintering conditions of the metal nanoparticles with each other can be different. The end face of the anode portion or the cathode portion is a metal surface with high thermal diffusivity. Therefore, the metal nanoparticles on the end face of the anode portion or the cathode portion are more difficult to sinter than the metal nanoparticles on the first or second surface of the outer package. When photo-firing is performed under the conditions for sintering the metal nanoparticles on the end face of the anode portion or the cathode portion, the metal nanoparticles on the surface of the outer package will be burned off and sometimes no sintered metal will remain. On the other hand, even when photo-firing is performed under the conditions for sintering the metal nanoparticles on the surface of the outer package, the metal nanoparticles on the end face of the anode portion or the cathode portion sometimes will not sinter. In order to more reliably sinter the metal nanoparticles on the end face of the anode portion or the cathode portion and the first or second surface of the outer package, it is preferable to perform photo-firing in two or more stages.

[0124] Specifically, the process of forming the first sintered metal can perform the following processes: a process of irradiating the coated metal nanoparticles with the first light to sinter the metal nanoparticles on the first surface of the outer package with each other to form a part of the first sintered metal; and a process of irradiating the metal nanoparticles on the end face of the anode portion with the second light having an energy higher than that of the first light to sinter the metal nanoparticles on the end face of the anode portion with each other to form the remaining part of the first sintered metal.

[0125] Similarly, the process of forming the second sintered metal can perform the following processes: a process of irradiating the coated metal nanoparticles with the first light to sinter the metal nanoparticles on the second surface of the outer package with each other to form a part of the second sintered metal; and a process of irradiating the metal nanoparticles on the end face of the cathode portion with the second light having an energy higher than that of the first light to sinter the metal nanoparticles on the second end face of the cathode portion with each other to form the remaining part of the second sintered metal.

[0126] First, when sintering metal nanoparticles on the surface of the outer package at a low energy, sintered metal with a metallic luster is formed on the surface of the outer package. Then, even when irradiating the metal nanoparticles on the end face of the anode part or the cathode part with light of a higher energy, the sintered metal with a metallic luster is difficult to absorb heat energy, so it will not be burned off and remains. On the other hand, the metal nanoparticles on the end face of the anode part or the cathode part are also photo-fired to form sintered metal with a metallic luster.

[0127] As the metal nanoparticles, nanoparticles of copper (Cu), silver (Ag), etc. can be used. The nanoparticles can be substantially spherical particles or fibrous nanowires. The average particle size of the nanoparticles only needs to be less than 1000 nm. For example, it can be 30 nm to 100 nm. The average particle size of the nanoparticles is the cumulative volume 50% particle size (median diameter) in the volume-based particle size distribution measured by a particle size distribution measuring device using the dynamic light scattering method.

[0128] The metal nanoink can contain phosphoric esters. The phosphoric esters can be used as dispersants to stably disperse the metal nanoparticles in the dispersion medium. The phosphoric esters can be phosphites, phosphonates, etc. The organic groups forming the ester bond are not particularly limited. The ratio of the mass of the phosphorus (P) element contained in the metal nanoink to the mass of the metal nanoparticles can be, for example, 2% to 8%. As a result, the sintered metal can contain the phosphorus (P) element in a ratio of, for example, 1% to 3% by mass.

[0129] The metal nanoink preferably further contains a reducing agent. The reducing agent helps to form sintered metal with a low resistance, reduces the natural oxide film on the end face of the anode part or the cathode part, or prevents the oxidation of the metal nanoparticles. The reducing agent also helps to save the irradiation light required for photo-firing. The reducing agent can contain organic acids. By using organic acids, the energy required for sintering the metal nanoparticles can be reduced by about 30%.

[0130] The organic acids have a small environmental load and high volatility. Therefore, they are not easily left in the sintered metal and help to form sintered metal with a low resistance. The ratio of the mass of the reducing agent contained in the metal nanoink to the mass of the metal nanoparticles can be, for example, 5% to 20%.

[0131] Among the organic acids, organic acids with a melting point in the range of 95°C to 160°C are effective. Specifically, they can also be appropriately selected and used from the organic acids used in the fluxes of solders. Among them, from the perspectives of cost, reducing power, etc., it is preferable to use at least one of adipic acid and abietic acid.

[0132] The dispersion medium of the metal nanoink can use water or an organic solvent. As the organic solvent, a second organic solvent can be used. Examples of the second organic solvent include acetone, butanol, propanol, pentanol, ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether, ethylene glycol monomethyl ether, isobutyl acetate, isopropyl acetate, isoamyl acetate, ethyl acetate, n-butyl acetate, n-propyl acetate, n-pentyl acetate, methyl acetate, cyclohexanol, cyclohexanone, 1,4-dioxane, N,N-dimethylformamide, tetrahydrofuran, n-hexane, methyl ethyl ketone, etc.

[0133] In the coating process, a coater is used to coat the metal nanoink on the end face of the anode part or the cathode part. The coater can be, for example, an inkjet coater. In the case of an inkjet method, since the metal nanoink can be selectively coated on the required part at high speed, the material loss is very small.

[0134] Then, the volatile components (dispersion medium) contained in the metal nanoink are dried. The drying process is, for example, 5 minutes or less, and usually only takes a few seconds at a temperature environment of 100 °C or less.

[0135] In the photo-sintering process, for example, pulsed light with a duration of 0.1 ms to 10 ms is irradiated on the metal nanoparticles. The light source of the pulsed light is not particularly limited, and a xenon light source, a YAG laser, etc. can be used. The ambient temperature of the photo-sintering can be, for example, 50 °C or less or at room temperature. The photo-sintering can be carried out at atmospheric pressure or in an inert gas atmosphere such as nitrogen. Such a process is completed in a very short time. Therefore, it is easy to reduce the production cost.

[0136] During photo-sintering, sintered metal is instantaneously formed. At this time, since the metal nanoparticles aggregate, a lot of phosphorus element-containing components added as a dispersant remain in the gaps between the particles. The phosphorus element volatilizes during drying and photo-sintering. Therefore, there is a tendency for the phosphorus element to be unevenly distributed on the surface layer side opposite to the end face of the anode part or the cathode part. That is, as the sintered metal, a laminated structure of a conventional layer containing a small amount of phosphorus element and a phosphorus-rich layer containing a large amount of phosphorus element can be formed.

[0137] The process of forming the first base electrode and the process of forming the second base electrode can be carried out by different processes respectively, but it is efficient to carry them out by the above process in the same way.

[0138] Then, according to the specified method, the process of forming the first external electrode connected to the first base electrode and the process of forming the second external electrode connected to the second base electrode are carried out.

[0139] The external electrode can be easily formed by plating. The plating layer can be a single-layer structure or a multi-layer structure. For example, a Ni plating layer and a Sn plating layer are formed in sequence. The plating layer may be formed in such a manner as to cover at least a part of the sintered metal.

[0140] In order to form a plating layer having a sufficient thickness, a conductive layer or a conductive paste layer may be formed before forming the plating layer. The conductive layer can also be formed, for example, by coating a conductive paste on the surface of the base electrode and then curing the conductive paste. As the conductive paste, a thermosetting resin composition containing metal particles and an epoxy resin can be used. Then, the plating layer may be formed in such a manner as to cover at least a part of the conductive layer by a method such as barrel plating. The plating layer includes a Ni plating layer and may further have a Sn plating layer covering at least a part of such a Ni plating layer.

[0141] The external electrode can be formed by a lead frame covering at least a part of the sintered metal. In order to form a firm electrical connection between the lead frame and the sintered metal layer, a solder layer or the above-mentioned conductive layer may be formed between the sintered metal and the lead frame.

[0142] Hereinafter, with reference to the drawings, a specific structure of an electrolytic capacitor according to an embodiment of the present disclosure will be exemplified. Among them, the electrolytic capacitor according to the present disclosure is not limited to these.

[0143] Figure 1 FIG. is a cross-sectional view schematically showing an electrolytic capacitor according to an embodiment. Figure 2 FIG. is a cross-sectional view schematically showing the structure of an example of a capacitor element. Figure 3 To magnify and show Figure 1 FIG. is a schematic cross-sectional view showing a part of the structure of the electrolytic capacitor shown. Figure 4 To magnify and show Figure 1 FIG. is a schematic cross-sectional view showing another part of the structure of the electrolytic capacitor shown. Figure 5 , 6 FIGS. are cross-sectional views schematically showing an electrolytic capacitor according to another embodiment of the present disclosure, respectively. Figure 7 FIG. is a cross-sectional view schematically showing the structure of another example of a capacitor element. Figure 8 FIG. is a cross-sectional view schematically showing an electrolytic capacitor according to still another embodiment of the present disclosure.

[0144] <First Embodiment>

[0145] As Figure 1 shown, the electrolytic capacitor 100 includes: a plurality of capacitor elements 10, an outer package 14 that seals the capacitor elements 10, a first external electrode 21, and a second external electrode 22. A plurality of capacitor elements 10 are stacked to form an element stack.

[0146] The capacitor element 10 includes an anode body 3 and a cathode part 6. The anode body 3 is an anode foil. The anode body 3 has a metal core part 4 and a porous part 5, and a dielectric layer (not shown) is formed on at least a portion of the surface of the porous part 5. The cathode part 6 covers at least a portion of the dielectric layer. The cathode part 6 includes a cathode layer and a cathode foil 20.

[0147] In capacitor element 10, end face 1a of one end portion (first end portion) of anode body 3 is exposed without being covered by cathode portion 6. On the other hand, end face 2a of the other end portion (second end portion) is covered by cathode portion 6. The portion of anode body 3 not covered by cathode portion is first portion 1. The portion of anode body 3 covered by cathode portion is second portion 2. The end of first portion 1 is first end portion. The end of second portion 2 is second end portion. The dielectric layer is formed on the surface of porous portion 5 formed at least in second portion 2. First portion 1 of anode body 3 is also referred to as anode lead-out portion. Second portion 2 of anode body 3 is also referred to as cathode forming portion.

[0148] More specifically, the second part 2 has a metal core 4 and a porous part 5 formed on the surface of the metal core 4 by roughening (etching, etc.). On the other hand, in the first part 1, the porous part 5 may or may not be present on the surface. The dielectric layer is formed along the surface of the porous part 5. At least a part of the dielectric layer is formed along the inner wall surface of the pores of the porous part 5 so as to cover the inner wall surface.

[0149] The cathode layer includes: a solid electrolyte layer 7 that covers at least a portion of the dielectric layer and constitutes a portion of the cathode portion 6; and cathode lead layers 8 and 9 that cover at least a portion of the solid electrolyte layer 7. The surface of the dielectric layer is formed with a concavo-convex 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 concavo-convex of such a dielectric layer. The cathode lead layer includes, for example, a carbon layer 8 that covers at least a portion of the solid electrolyte layer 7 and a conductive paste layer 9 that covers the carbon layer 8. The conductive paste layer 9 can be, for example, a silver paste layer containing silver particles as metal particles.

[0150] The cathode foil 20 is interposed between the cathode lead layers 8 and 9 of the capacitor elements 10 adjacent in the stacking direction of the element stack. The cathode foil 20 constitutes a part of the cathode portion 6. The cathode foil 20 is shared between the capacitor elements 10 adjacent in the stacking direction of the element stack. An adhesive layer having conductivity may be sandwiched between the cathode foil 20 and the capacitor element 10. For example, a conductive adhesive is used for the adhesive layer. For example, the adhesive layer contains silver. The adhesive layer may be a silver paste layer that is the same as the conductive paste layer 9.

[0151] It can be said that the portion of anode body 3 where solid electrolyte layer 7 is formed via a dielectric layer is second portion 2 , and the portion of anode body 3 where solid electrolyte layer 7 is not formed is first portion 1 .

[0152] In a region of the anode body 3 that is not opposite to the cathode layer, at least in a portion adjacent to the cathode layer, an insulating separation layer (or insulating member) 12 may be formed. The separation layer (or insulating member) 12 may be formed so as to cover the surface of the anode body 3. Thereby, the contact between the cathode portion 6 and the exposed portion (first portion 1) of the anode body 3 is restricted. The separation layer 12 is, for example, an insulating resin layer.

[0153] The structure sealed by the outer package 14 has a substantially rectangular parallelepiped shape. The electrolytic capacitor 100 also has a substantially rectangular parallelepiped shape. The outer package 14 has a first main surface 14a and a second main surface 14b opposite to the first main surface 14a. In the element laminate, the first end portion 1a of the capacitor element 10 is exposed at the first main surface 14a.

[0154] The end faces 1a of the plurality of first end portions (first portions) exposed from the outer package 14 are respectively 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 to increase the capacitance. In addition, the effect of the first portion on the ESR and ESL is reduced.

[0155] In addition, the end face 20a of the cathode foil 20 is exposed from the outer package 14 at the second main surface 14b. The end faces of the cathode foil 20 exposed from the outer package 14 are respectively electrically connected to the second external electrode 22 extending along the second main surface 14b.

[0156] The end faces 1a of the plurality of first end portions exposed from the outer package 14 and the end faces 20a of the plurality of cathode foils 20 exposed from the outer package 14 are respectively covered by a first sintered metal 15a and a second sintered metal 15b. The end face 1a of the first end portion is electrically connected to the first external electrode 21 via the sintered metal 15a. The end face 20a of the cathode foil 20 is electrically connected to the second external electrode 22 via the sintered metal 15a.

[0157] Figure 3 and Figure 4 is a schematic cross-sectional view showing an enlarged part of the structure of the electrolytic capacitor 100. Figure 3 is for Figure 1 a cross-sectional view showing an enlarged area near the connection portion between the end face 1a of the first end portion of the capacitor element 10 and the first external electrode 21 in Figure 4 is a cross-sectional view showing an enlarged area near the connection portion between the end face 20a of the cathode foil 20 and the second external electrode 22. The sintered metal 15a and the sintered metal 15b each include a conventional layer 15A and a phosphorus-rich layer 15B.

[0158] The first sintered metal 15a is thinly and widely bonded to the end face 1a of the first end portion of the anode portion by a metallic bond. The ratio of the width Wp of the end face 1a of the first end portion of the anode portion to the thickness Tpc of the first sintered metal 15a at the center of the width Wp: Wp / Tpc satisfies 0.5 ≤ Wp / Tpc ≤ 100. The ratio of the thickness Tpc of the first sintered metal 15a at the center of the width Wp to the thickness Tpt at a position of Wp / 3 away from the center: Tpc / Tpt is 0.5 or more (substantially 1.0 in the illustrated example).

[0159] The contact area Spo between the first sintered metal 15a and the first external electrode 21 is substantially equal to the width of the first main surface 14a in the reference cross section. The contact area Spi between the first sintered metal 15a and the end face 1a of the first end portion of the anode portion is substantially equal to the product of Wp and the number of stacked capacitor elements. The ratio of Spo to Spi: Spo / Spi is sufficiently greater than 1.0, and in the illustrated example, is at least 3 or more.

[0160] The second sintered metal 15b is thinly and widely bonded to the end face 20a of the cathode foil 20 by a metallic bond. The ratio of the width Wn of the end face 20a of the cathode foil 20 to the thickness Tnc of the second sintered metal 15b at the center of the width Wn: Wn / Tnc satisfies 0.5 ≤ Wn / Tnc ≤ 100. The ratio of the thickness Tnc of the first sintered metal 15b at the center of the width Wn to the thickness Tnt at a position of Wn / 3 away from the center: Tnc / Tnt is 0.5 or more (substantially 1.0 in the illustrated example).

[0161] The contact area Sno between the second sintered metal 15b and the second external electrode 22 is substantially equal to the width of the second main surface 14b in the reference cross section. The contact area Sni between the second sintered metal 15b and the end face 20a of the cathode foil 20 is substantially equal to the product of Wn and the number of stacked capacitor elements. The ratio of Sno to Sni: Sno / Sni is sufficiently greater than 1.0, and in the illustrated example, is at least 3 or more.

[0162] As Figure 3 shown, the conventional layer 15A covers the end face of the first end portion 1a. The phosphorus-rich layer 15B covers the conventional layer 15A in an integrated state. In Figure 3 it, the phosphorus-rich layer 15B covers the first external electrode 21. Similarly, as Figure 4 shown, the conventional layer 15A covers the end face of the cathode foil 20. The phosphorus-rich layer 15B covers the conventional layer 15A. In Figure 4 it, the phosphorus-rich layer 15B is covered by the second external electrode 22. As the base metals, i.e., the sintered metals 15a and 15b, by forming the conventional layer 15A and the phosphorus-rich layer 15B, a current collecting path with excellent corrosion resistance can be formed, and deterioration of the cathode layer can be suppressed.

[0163] 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 sintered metal 15a and the first main surface 14a (the first surface) of the outer package 14, and the sintered metal 15a covers the end face of the first end portion 1a. 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 sintered metal layer 15 and the second main surface 14b (the second surface) of the outer package 14, and the sintered metal layer 15 covers the end face of the cathode foil 20. The Ni / Sn plating layer 22B covers the silver paste layer 22A.

[0164] In Figure 1 the end face of the first end portion 1a and the first main surface 14a are on the same plane. Further, in Figure 1 the end face 20a of the cathode foil 20 and the second main surface 14b are on the same plane. However, the end face of the first end portion 1a and the end face 20a of the cathode foil 20 do not necessarily have to be on the same plane as the main surface of the outer package 14. For example, the end face of the first end portion 1a may protrude or be recessed with respect to the first main surface 14a. Similarly, the end face 20a of the cathode foil 20 may protrude or be recessed with respect to the second main surface 14b.

[0165] The sintered metal 15a may also cover the end face of the separation layer 12 exposed from the first main surface 14a. Further, in the case where the porous layer 5 extends to the first main surface 14a, the metal sintering 15a may be formed so as to cover the porous layer 5 exposed from the first main surface 14a.

[0166] The element laminate is supported by a substrate 17. The substrate may be, for example, an insulating substrate. As long as the substrate can electrically separate the first external electrode 21 and the second external electrode 22, it may also be a metal substrate or a printed circuit board provided with a wiring pattern. A cathode foil may be disposed between the cathode lead-out layer at the bottom of the element laminate and the substrate 17. The substrate 17 may be, for example, a laminated substrate having conductive wiring patterns formed on its front and back surfaces. In this case, the wiring pattern on the front surface of the substrate and the wiring pattern on the back surface may be electrically connected by a via hole. The wiring pattern on the front surface may be electrically connected to the cathode portion 6 of the capacitor element laminated on the lowermost layer. Further, the wiring pattern on the back surface may be electrically connected to a third external electrode (not shown). In this case, the third external electrode is electrically connected to the cathode portion 6 of each capacitor element of the element laminate via the substrate 17. The third external electrode (cathode) may be arbitrarily disposed in the central region of the bottom surface of the electrolytic capacitor according to the wiring pattern on the back surface. For example, by disposing the third external electrode close to the first external electrode, the ESL can be reduced.

[0167] The substrate 17 is a metal plate and may have a lead frame structure formed by bending a metal plate processed into a specified shape. A part of the metal plate is exposed from the exterior body and is electrically connected to an external terminal at the exposed portion.

[0168] <Second Embodiment>

[0169] Figure 5 It is a cross-sectional view schematically showing the structure of an electrolytic capacitor according to another embodiment of the present disclosure. Figure 5 The illustrated electrolytic capacitor 101 includes: a plurality of capacitor elements 10a, b; an exterior body 14 that seals the capacitor elements 10a, b; a first external electrode 21; and a second external electrode 22. The plurality of capacitor elements 10a, b are stacked to form an element stack. Two first external electrodes 21 are separately arranged, one first external electrode 21 covers the first main surface 14a of the exterior body 14, and the other first external electrode 21 covers the second main surface 14b of the exterior body 14.

[0170] The plurality of capacitor elements 10a, b have: a first capacitor element 10a whose first direction is from the first part 1 of the anode body 3 toward the second part 2; and a second capacitor element 10b whose second direction is opposite to the first direction from the first part 1 of the anode body 3 toward the second part 2. The end face 1a of the first end of the first capacitor element 10a is exposed from the exterior body 14 at the first main surface 14a and is electrically connected to one first external electrode 21 via a sintered metal 15a. The end face 1a of the first end of the second capacitor element 10b is exposed from the exterior body 14 at the second main surface 14b and is electrically connected to the other first external electrode 21 via a sintered metal 15a. On the other hand, although not shown, at a third main surface intersecting the first main surface 14a and the second main surface 14b and / or a fourth main surface on the opposite side of the third main surface, the end face of the cathode foil 20 is exposed from the exterior body 14 and is electrically connected to the second external electrode 22 via a sintered metal 15.

[0171] The sintered metal 15a has the same structure as Figure 1 the sintered metal 15a of the illustrated electrolytic capacitor 100. The first external electrode 21 has the same structure as Figure 1 the first external electrode 21 of the illustrated electrolytic capacitor 100.

[0172] In the electrolytic capacitor 101, in the first capacitor element 10a and the second capacitor element 10b, the direction in which current flows within the element is different. Therefore, since the direction of the magnetic field generated by the current is different, the magnetic flux generated within the element stack is reduced. Thereby, the ESL can be reduced.

[0173] In Figure 5In the example, in the component laminate, the first capacitor element 10a and the second capacitor element 10b are alternately laminated. However, the first capacitor element 10a and the second capacitor element 10b are not necessarily alternately laminated. In a part of the component laminate, there may also be a part where the first capacitor elements 10a are adjacent to each other and laminated in the same direction and / or a part where the second capacitor elements 10b are adjacent to each other and laminated in the same direction. Even if only a part of the first capacitor elements and the second capacitor elements are alternately laminated, the magnetic flux generated in the component laminate will be effectively reduced and the ESL will be effectively lowered, so it is preferred.

[0174] <Third Embodiment>

[0175] Figure 6 A cross-sectional view schematically showing the structure of the electrolytic capacitor according to another embodiment of the present disclosure. The electrolytic capacitor 200 according to this embodiment includes Figure 7 the capacitor element shown. The capacitor element 10 has an anode body 3 that 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 part is the end face 1a of the protruding end of the metal wire 1. A dielectric layer 5 is formed on at least a part of the surface of the anode body 3. The cathode part 6 covers at least a part of the dielectric layer 5. The cathode part 6 includes a solid electrolyte layer 7, a cathode lead layer, and a cathode foil 20.

[0176] The anode body 3 can be obtained by molding and sintering a powder containing a valve-acting metal. For example, together with the powder of the valve-acting metal, the buried part of the metal wire 1 connected to the anode body 3 is buried in the powder and placed in a mold, and then molded by pressing. Then, by sintering the molded body, a porous anode body 3 in which a part of the metal wire 1 is buried can be formed. The sintering is preferably carried out 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.

[0177] The cathode lead layer includes, for example, a carbon layer 8 covering at least a part of the solid electrolyte layer 7 and a conductive paste layer 9 covering the carbon layer 8. The conductive paste layer 9 can be, for example, 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.

[0178] The cathode foil 20 forms a part of the cathode part 6. The cathode foil 20 is connected to the cathode layer by means of a conductive adhesive layer. A conductive adhesive is used in the adhesive layer, for example. The adhesive layer contains silver, for example. The adhesive layer can be the same silver paste layer as the conductive paste layer 9.

[0179] The anode body 3 has a substantially rectangular parallelepiped outer shape. The electrolytic capacitor 200 also has a substantially rectangular parallelepiped outer shape. The outer package 14 has a first main surface 14a and a second main surface 14b on the side opposite to the first main surface 14a. The end surface 1a of the protruding end portion of the metal wire of the capacitor element 10 is exposed on the first main surface 14a. The end surface 1a exposed from the outer package 14 is electrically connected to the first external electrode 21 extending along the first main surface 14a. In addition, the end surface 20a of the cathode foil 20 is exposed from the outer package 14 on the second main surface 14b. The end surface 20a of the cathode foil 20 exposed from the outer package 14 is electrically connected to the second external electrode 22 extending along the second main surface 14b. In this case, the length occupied by the metal wire in the anode portion can be reduced to increase the capacitance. In addition, the effect of the metal wire on the ESR and ESL is reduced.

[0180] The end surface 1a of the protruding end portion of the metal wire exposed from the outer package 14 and the end surface 20a of the cathode foil 20 exposed from the outer package 14 are covered with the first and second sintered metals 15a and 15b, respectively. The end surface 1a of the protruding end portion of the metal wire is electrically connected to the first external electrode 21 via the sintered metal 15a. The end surface 20a of the cathode foil 20 is electrically connected to the second external electrode 22 via the sintered metal 15b.

[0181] The first and second sintered metals 15a and 15b have the same structure as the first and second sintered metals 15a and 15b of the electrolytic capacitor 100 shown in Figure 1 The first external electrode 21 and the second external electrode 22 have the same structure as the first external electrode 21 and the second external electrode 22 of the electrolytic capacitor 100 shown in Figure 1 The electrolytic capacitor 100 shown.

[0182] <Fourth Embodiment>

[0183] Figure 8 FIG. is a cross-sectional view schematically showing the structure of an electrolytic capacitor according to still another embodiment of the present disclosure. The electrolytic capacitor 201 according to this embodiment has the same structure as the electrolytic capacitor 200 of the third embodiment except that the structures of the first external electrode 21 and the second external electrode 22 are different.

[0184] The first external electrode 21 and the second external electrode 22 of the electrolytic capacitor 201 include a first lead frame 21B and a second lead frame 22B that respectively cover at least a part of the first sintered metal 15a and the second sintered metal 15b. A solder layer 21A (conductive layer 21A) is formed between the first sintered metal 15a and the first lead frame 21B. Similarly, a solder layer 22A (conductive layer 22A) is formed between the second sintered metal 15a and the second lead frame 22B. Thereby, a firm electrical connection between the first lead frame 21B and the first sintered metal 15a and a firm electrical connection between the second lead frame 22B and the second sintered metal 15b can be formed.

[0185] <Enclosure>

[0186] Based on the description of the above embodiments, the following technologies are disclosed.

[0187] (Technology 1)

[0188] An electrolytic capacitor, comprising:

[0189] A capacitor element having an anode portion and a cathode portion;

[0190] An outer package that seals the capacitor element;

[0191] A first external electrode that is electrically connected to the anode portion and exposed from the outer package;

[0192] A second external electrode that is electrically connected to the cathode portion and exposed from the outer package; and

[0193] A first base electrode that connects the anode portion and the first external electrode,

[0194] The first base electrode includes a first sintered metal,

[0195] The first sintered metal contacts an end face of the anode portion not covered by the outer package and contacts the first external electrode,

[0196] The ratio of the width Wp of the end face of the anode portion to the thickness Tpc of the first sintered metal at the center of the width Wp: Wp / Tpc satisfies 0.5 ≤ Wp / Tpc ≤ 100, preferably satisfies 1.5 ≤ Wp / Tpc ≤ 100, and more preferably satisfies 2 ≤ Wp / Tpc ≤ 100.

[0197] (Technology 2)

[0198] The electrolytic capacitor according to Technology 1, wherein the ratio of the thickness Tpc of the first sintered metal at the center of the width Wp to the thickness Tpt at a position Wp / 3 away from the center: Tpc / Tpt is 0.5 or more, preferably 2 or less.

[0199] (Technology 3)

[0200] The electrolytic capacitor according to Technology 1 or 2, wherein,

[0201] The ratio of the contact area Spo between the first sintered metal and the first external electrode to the contact area Spi between the first sintered metal and the end face of the anode part: Spo / Spi is 1.0 or more, preferably 3 or more.

[0202] (Technology 4)

[0203] The electrolytic capacitor according to any one of Technologies 1 to 3, wherein,

[0204] The first sintered metal also covers the first surface of the outer package body opposite to the first external electrode.

[0205] (Technology 5)

[0206] The electrolytic capacitor according to any one of Technologies 1 to 4, wherein,

[0207] The first sintered metal contains a phosphorus element,

[0208] The phosphorus element is more distributed on the side of the first external electrode than on the end face side of the anode part.

[0209] (Technology 6)

[0210] The electrolytic capacitor according to any one of Technologies 1 to 5, wherein,

[0211] The first external electrode has a plating layer covering at least a part of the first sintered metal.

[0212] (Technology 7)

[0213] The electrolytic capacitor according to any one of Technologies 1 to 6, wherein,

[0214] The first external electrode further has a conductive layer interposed between the first sintered metal and the plating layer,

[0215] The conductive layer is composed of metal particles and resin.

[0216] (Technology 8)

[0217] The electrolytic capacitor according to any one of Technologies 1 to 7, wherein,

[0218] The first external electrode has a lead frame covering at least a part of the first sintered metal.

[0219] (Technology 9)

[0220] The electrolytic capacitor according to any one of Technologies 1 to 8, wherein,

[0221] The first external electrode further has a solder layer interposed between the first sintered metal and the lead frame.

[0222] (Technology 10)

[0223] The electrolytic capacitor according to any one of Technologies 1 to 9, wherein,

[0224] The capacitor element includes:

[0225] An anode body having a first part including a first end portion and a second part including a second end portion;

[0226] A dielectric layer formed on at least the surface of the second part of the anode body; and

[0227] A cathode layer covering at least a part of the dielectric layer,

[0228] The anode portion includes the first part,

[0229] The cathode portion includes the cathode layer,

[0230] On the end face of the first end portion, the first sintered metal is in contact with the end face of the anode body.

[0231] (Technology 11)

[0232] The electrolytic capacitor according to any one of Technologies 1 to 10, wherein,

[0233] The anode body includes an anode foil,

[0234] The anode foil has a metal core portion and a porous portion continuous with the metal core portion,

[0235] The end face of the first end portion includes the end faces of the metal core portion and the porous portion.

[0236] (Technology 12)

[0237] The electrolytic capacitor according to any one of Technologies 1 to 11, wherein,

[0238] The anode body has a sintered body of metal particles and a metal wire partially embedded in the sintered body,

[0239] The end face of the first end portion includes the end face of the protruding end portion of the metal wire.

[0240] (Technology 13)

[0241] The electrolytic capacitor according to any one of Technologies 1 to 12 further includes:

[0242] A second base electrode that connects the cathode portion and the second external electrode,

[0243] The second base electrode includes a second sintered metal,

[0244] The second sintered metal contacts an end surface of the cathode portion not covered by the exterior body and contacts the second external electrode,

[0245] The ratio of the width Wn of the end surface of the cathode portion to the thickness Tnc of the second sintered metal at the center of the width Wn: Wn / Tnc satisfies 0.5 ≤ Wn / Tnc ≤ 100, preferably satisfies 1.5 ≤ Wn / Tnc ≤ 100, and more preferably satisfies 2 ≤ Wn / Tnc ≤ 100.

[0246] (Technology 14)

[0247] The electrolytic capacitor according to any one of Technologies 1 to 13, wherein,

[0248] The ratio of the thickness Tnc of the second sintered metal at the center of the width Wn to the thickness Tnt at a position Wn / 3 away from the center: Tnc / Tnt is 0.5 or more.

[0249] (Technology 15)

[0250] The electrolytic capacitor according to any one of Technologies 1 to 14, wherein,

[0251] The ratio of the contact area Sno between the second sintered metal and the second external electrode to the contact area Sni between the second sintered metal and the end surface of the cathode portion: Sno / Sni is 1.0 or more.

[0252] (Technology 16)

[0253] The electrolytic capacitor according to any one of Technologies 1 to 15, wherein,

[0254] The second sintered metal also covers a second surface of the exterior body opposite to the second external electrode.

[0255] (Technology 17)

[0256] The electrolytic capacitor according to any one of Technologies 1 to 16, wherein,

[0257] The cathode portion further has a cathode foil connected to the cathode layer and protruding more than the cathode layer,

[0258] The second sintered metal contacts an end surface of the protruding portion of the cathode foil.

[0259] (Technology 18)

[0260] A method for manufacturing an electrolytic capacitor, comprising:

[0261] A step of preparing a capacitor element having an anode portion and a cathode portion;

[0262] A step of sealing the capacitor element with an outer package;

[0263] A step of exposing an end face of the anode portion from the outer package;

[0264] A step of forming a first base electrode on the end face of the anode portion; and,

[0265] A step of forming a first external electrode that is electrically connected to the anode portion via the first base electrode,

[0266] The step of forming the first base electrode includes:

[0267] Step (i) of attaching a metal nanoink containing metal nanoparticles to the end face of the anode portion and a first surface of the outer package opposite to the first external electrode; and

[0268] Step (ii) of, after step (i), irradiating the metal nanoparticles with light to sinter the metal nanoparticles with each other to form a first sintered metal.

[0269] (Technology 19)

[0270] The method for manufacturing an electrolytic capacitor according to Technology 18, wherein,

[0271] The step (ii) of forming the first sintered metal includes:

[0272] A step of irradiating the metal nanoparticles with a first light to sinter the metal nanoparticles on the first surface of the outer package with each other to form a part of the first sintered metal; and,

[0273] A step of irradiating the metal nanoparticles on the end face of the anode portion with a second light having an energy higher than that of the first light to sinter the metal nanoparticles on the end face of the anode portion with each other to form the remaining part of the first sintered metal.

[0274] (Technology 20)

[0275] The method for manufacturing an electrolytic capacitor according to Technology 18 or 19, wherein the metal nanoink contains phosphate.

[0276] (Technology 21)

[0277] The method for manufacturing an electrolytic capacitor according to any one of Techniques 18 to 20, wherein the metal nanoink further contains a reducing agent.

[0278] (Technique 22)

[0279] The method for manufacturing an electrolytic capacitor according to any one of Techniques 18 to 21, wherein the reducing agent contains an organic acid.

[0280] (Technique 23)

[0281] The method for manufacturing an electrolytic capacitor according to any one of Techniques 18 to 22, wherein the organic acid contains at least one of adipic acid and rosin acid.

[0282] (Technique 24)

[0283] The method for manufacturing an electrolytic capacitor according to any one of Techniques 18 to 23, wherein the ratio of the mass of the reducing agent contained in the metal nanoink to the mass of the metal nanoparticles is 5% or more and 20% or less.

[0284] (Technique 25)

[0285] The method for manufacturing an electrolytic capacitor according to any one of Techniques 18 to 24, wherein in the step (ii) of forming the first sintered metal, xenon light source light or YAG laser light is irradiated onto the metal nanoparticles.

[0286] (Technique 26)

[0287] The method for manufacturing an electrolytic capacitor according to any one of Techniques 18 to 25 further includes:

[0288] a step of exposing an end face of the cathode portion from the exterior body;

[0289] a step of forming a second base electrode on the end face of the cathode portion; and

[0290] a step of forming the second external electrode that is electrically connected to the cathode portion via the second base electrode,

[0291] The step of forming the second base electrode includes:

[0292] step (iii) of attaching a metal nanoink containing metal nanoparticles to the end face of the cathode portion and a second surface of the exterior body opposite to the second external electrode; and

[0293] step (iv) of irradiating light onto the metal nanoparticles after step (iii) to sinter the metal nanoparticles together to form a second sintered metal.

[0294] (Technique 27)

[0295] The manufacturing method of an electrolytic capacitor according to any one of Techniques 18 to 26, wherein,

[0296] The step (iii) of forming the second sintered metal includes:

[0297] A step of irradiating the first light to the metal nanoparticles to sinter the metal nanoparticles on the second surface of the outer package body to form a part of the second sintered metal; and,

[0298] A step of irradiating the second light having an energy higher than that of the first light to the metal nanoparticles on the end face of the cathode portion to sinter the metal nanoparticles on the end face of the cathode portion to form the remaining part of the second sintered metal.

[0299] [Examples]

[0300] In order to fabricate an electrolytic capacitor identical to the electrolytic capacitor 100 shown in Figure 1 , a plurality of capacitor elements were prepared. The anode body used an aluminum anode foil having a porous portion formed by etching. Seven capacitor elements were laminated with a cathode foil made of aluminum foil having a carbon coating to obtain an element laminate. The cathode foil was arranged such that a part thereof protruded from the cathode layer toward the opposite side of the anode portion. Then, the entire element laminate was sealed with an outer package. Next, by cutting, a part of the first end portion side of the first part of the anode body and the outer package were removed simultaneously to expose the end face of the anode portion. Similarly, by cutting, the protruding portion of the cathode foil and the outer package were removed simultaneously to expose the end face of the cathode portion.

[0301] Next, copper nanoink was coated on the end faces of the anode portion and the cathode portion, respectively. The coated copper nanoink was dried at 80 °C for 1 minute, and then pulsed light (pulse width 0.99 ms) of xenon flash (wavelength 250 nm to 800 nm) was irradiated to sinter the copper nanoparticles to form a sintered metal (sintered copper layer) having a thickness of 1.5 μm.

[0302] The composition of the copper nanoink is as follows.

[0303] 100 parts by mass of copper nanoparticles (average particle size 65 nm)

[0304] 8 parts by mass of a dispersant (phosphate (ethyl phosphate))

[0305] 5 parts by mass of a reducing agent (adipic acid)

[0306] 5 parts by mass of a reducing agent (abietic acid)

[0307] 25 parts by mass of an organic solvent (2-methyl-2,4-pentanediol)

[0308] Next, the sintered metal was covered with a silver paste and dried to form a conductive layer (silver paste layer) with a thickness of 20 μm. Further, by barrel plating, a Ni plating layer (thickness 5 μm) and a Sn plating layer (thickness 5 μm) were sequentially formed on the surface of the conductive layer, and the first external electrode and the second external electrode were formed. A total of three electrolytic capacitors were fabricated and the capacitance was evaluated. As a result, it was confirmed that when the target value was 470 μF, 530 μF, 526 μF, and 529 μF were obtained, and the target was achieved.

[0309] Next, the anode part or the cathode part, and the laminated part (reference cross-section) of the sintered metal and the silver paste layer were observed with a digital microscope (VH X-8000) manufactured by Keyence Corporation. An example of the captured image is shown in Figure 9 (anode side) and Figure 10 (cathode side). It was clearly confirmed from the outside that there were three layers: the Sn plating layer, the Ni plating layer, and the conductive layer (silver paste layer). In addition, at the interface between the end faces of the anode part and the cathode part and the conductive layer (silver paste layer), a thin layer of sintered metal with a more metallic luster than the other layers could be confirmed.

[0310] The ratio of the width Wp (115 μm) of the end face of the anode part to the thickness Tpc of the first sintered metal at the center of the width Wp: Wp / Tpc was 77. The ratio of the thickness Tpc of the first sintered metal at the center of the width Wp to the thickness Tpt at a position Wp / 3 away from the center: Tpc / Tpt was in the range of 1.0 to 1.1. The ratio of the contact area Spo between the first sintered metal and the first external electrode to the contact area Spi between the first sintered metal and the end face of the anode part: Spo / Spi was sufficiently greater than 3. In addition, in any of the electrolytic capacitors, no peeling was found between the first sintered metal and the silver paste layer.

[0311] The ratio of the width Wn (20 μm) of the end face of the cathode part to the thickness Tnc of the second sintered metal at the center of the width Wn: Wn / Tnc was 6.7. The ratio of the thickness Tnc of the second sintered metal at the center of the width Wn to the thickness Tnt at a position Wn / 3 away from the center: Tnc / Tnt was approximately 1.2. The ratio of the contact area Sno between the second sintered metal and the second external electrode to the contact area Sni between the second sintered metal and the end face of the cathode part: Sno / Sni was greater than 1.0 and sufficiently greater than 3. In addition, in any of the electrolytic capacitors, no peeling was found between the second sintered metal and the silver paste layer.

[0312] In addition, after analyzing the distribution state of phosphorus elements in each sintered metal, it was found that phosphorus elements were distributed throughout each sintered metal. It was observed that phosphorus elements were more distributed on the external electrode side than on the end face side of the anode part or the cathode part, forming a phosphorus-rich layer.

[0313] Industrial Applicability

[0314] The electrolytic capacitor according to the present invention can be manufactured at low cost and with high efficiency, and since deterioration of the cathode portion caused by moisture and oxygen hardly occurs, it can be used for various applications.

[0315] The present invention has been described by way of the presently preferred embodiments, but such disclosure should not be construed in a limiting sense. Various modifications and variations will be apparent to those skilled in the art of the present invention from reading the above disclosure. Accordingly, the appended claims should be construed to cover all modifications and variations without departing from the true spirit and scope of the present invention.

[0316] Description of Reference Numerals

[0317] 1: First portion (anode lead-out portion), metal wire; 1a: End face of the first end; 2: Second portion (cathode formation portion); 2a: End face of the second end; 3: Anode body; 4: Metal core portion; 5: Porous portion; 6: Cathode portion; 7: Solid electrolyte layer; 8: Carbon layer; 9: Silver paste layer; 10: Capacitor element; 10a: First capacitor element; 10b: Second capacitor element; 12: Separation layer (insulating member); 14: Outer package; 14a: First main surface of the outer package; 14b: Second main surface of the outer package; 15a: First sintered metal; 15b: Second sintered metal; 17: Substrate; 20: Cathode foil; 20a: End face of the cathode foil; 21: First external electrode; 21A: Silver paste layer, solder layer; 21B: Ni / Sn plating layer, first lead frame; 22: Second external electrode; 22A: Silver paste layer, solder layer; 22B: Ni / Sn plating layer, second lead frame; 100, 101, 200, 201: Electrolytic capacitor.

Claims

1. An electrolytic capacitor, comprising: A capacitor element having an anode portion and a cathode portion; An outer package that seals the capacitor element; A first external electrode that is electrically connected to the anode portion and exposed from the outer package; A second external electrode that is electrically connected to the cathode portion and exposed from the outer package; and A first base electrode that connects the anode portion and the first external electrode, The first base electrode includes a first sintered metal, The first sintered metal contacts an end face of the anode portion not covered by the outer package and contacts the first external electrode, The ratio of the width Wp of the end face of the anode portion to the thickness Tpc of the first sintered metal at the center of the width Wp: Wp / Tpc satisfies 0.5 ≤ Wp / Tpc ≤ 100.

2. The electrolytic capacitor according to claim 1, Wherein, The ratio of the thickness Tpc of the first sintered metal at the center of the width Wp to the thickness Tpt at a position Wp / 3 away from the center: Tpc / Tpt is 0.5 or more.

3. The electrolytic capacitor according to claim 1, Wherein, The ratio of the contact area Spo between the first sintered metal and the first external electrode to the contact area Spi between the first sintered metal and the end face of the anode portion: Spo / Spi is 1.0 or more.

4. The electrolytic capacitor according to claim 1, Wherein, The first sintered metal also covers a first surface of the outer package opposite to the first external electrode.

5. The electrolytic capacitor according to claim 1, Wherein, The first sintered metal contains a phosphorus element, Compared with the end face side of the anode portion, the phosphorus element is more distributed on the first external electrode side.

6. The electrolytic capacitor according to claim 1, Wherein, The first external electrode has a plating layer covering at least a part of the first sintered metal.

7. The electrolytic capacitor according to claim 6, Wherein, The first external electrode also has a conductive layer between the first sintered metal and the plating layer, The conductive layer is composed of metal particles and resin.

8. The electrolytic capacitor according to claim 1, Wherein, The first external electrode has a lead frame covering at least a part of the first sintered metal.

9. The electrolytic capacitor according to claim 8, Wherein, The first external electrode also has a solder layer between the first sintered metal and the lead frame.

10. The electrolytic capacitor according to claim 1, Wherein, The capacitor element includes: An anode body having a first portion including a first end portion and a second portion including a second end portion; A dielectric layer formed on at least a surface of the second portion of the anode body; And A cathode layer covering at least a part of the dielectric layer, The anode portion includes the first portion, The cathode portion includes the cathode layer, At the end face of the first end portion, the first sintered metal contacts the end face of the anode body.

11. The electrolytic capacitor according to claim 10, Wherein, The anode body includes an anode foil, The anode foil has a metal core portion and a porous portion continuous with the metal core portion. The end face of the first end portion includes the end faces of the metal core portion and the porous portion.

12. The electrolytic capacitor according to claim 10, wherein, The anode body has a sintered body of metal particles and a metal wire partially embedded in the sintered body, The end face of the first end portion includes the end face of the protruding end portion of the metal wire.

13. The electrolytic capacitor according to claim 1, further comprising: A second base electrode connecting the cathode portion and the second external electrode, The second base electrode includes a second sintered metal, The second sintered metal contacts the end face of the cathode portion not covered by the outer package and contacts the second external electrode, The ratio of the width Wn of the end face of the cathode portion to the thickness Tnc of the second sintered metal at the center of the width Wn: Wn / Tnc satisfies 0.5 ≤ Wn / Tnc ≤ 100.

14. The electrolytic capacitor according to claim 13, wherein, The ratio of the thickness Tnc of the second sintered metal at the center of the width Wn to the thickness Tnt at a position at a distance Wn / 3 from the center: Tnc / Tnt is 0.5 or more.

15. The electrolytic capacitor according to claim 13, wherein, The ratio of the contact area Sno between the second sintered metal and the second external electrode to the contact area Sni between the second sintered metal and the end face of the cathode portion: Sno / Sni is 1.0 or more.

16. The electrolytic capacitor according to claim 13, wherein, The second sintered metal also covers the second surface of the outer package opposite to the second external electrode.

17. The electrolytic capacitor according to claim 13, wherein, The cathode portion further has a cathode foil connected to the cathode layer and protruding more than the cathode layer, The second sintered metal contacts the end face of the protruding end portion of the cathode foil.

18. A method for manufacturing an electrolytic capacitor, comprising: A step of preparing a capacitor element having an anode portion and a cathode portion; A step of sealing the capacitor element with an outer package; A step of exposing the end face of the anode portion from the outer package; A step of forming a first base electrode on the end face of the anode portion; and, A step of forming the first external electrode electrically connected to the anode portion via the first base electrode, The step of forming the first base electrode includes: Step (i) of attaching a metal nanoink containing metal nanoparticles to the end face of the anode portion and the first surface of the outer package opposite to the first external electrode; and Step (ii) of irradiating light on the metal nanoparticles after step (i) to sinter the metal nanoparticles to form a first sintered metal.

19. The method for manufacturing an electrolytic capacitor according to claim 18, wherein, The step (ii) of forming the first sintered metal includes: A step of irradiating the first light on the metal nanoparticles to sinter the metal nanoparticles on the first surface of the outer package to form a part of the first sintered metal; and, A step of irradiating the metal nanoparticles on the end face of the anode portion with a second light having an energy higher than that of the first light, and sintering the metal nanoparticles on the end face of the anode portion to form the first sintered metal of the remaining portion.

20. The method for manufacturing an electrolytic capacitor according to claim 18, wherein, the metal nanoink contains phosphate ester.

21. The method for manufacturing an electrolytic capacitor according to claim 18, wherein, the metal nanoink further contains a reducing agent.

22. The method for manufacturing an electrolytic capacitor according to claim 21, wherein, the reducing agent contains an organic acid.

23. The method for manufacturing an electrolytic capacitor according to claim 22, wherein, the organic acid contains at least one of adipic acid and rosin acid.

24. The method for manufacturing an electrolytic capacitor according to claim 18, wherein, the ratio of the mass of the reducing agent contained in the metal nanoink to the mass of the metal nanoparticles is 5% or more and 20% or less.

25. The method for manufacturing an electrolytic capacitor according to claim 18, wherein, in the step (ii) of forming the first sintered metal, the metal nanoparticles are irradiated with xenon light source light or YAG laser light.

26. The method for manufacturing an electrolytic capacitor according to claim 18, further comprising: a step of exposing the end face of the cathode portion from the outer package; a step of forming a second base electrode on the end face of the cathode portion; and a step of forming the second external electrode electrically connected to the cathode portion via the second base electrode, the step of forming the second base electrode includes: step (iii) of attaching a metal nanoink containing metal nanoparticles to the end face of the cathode portion and the second surface of the outer package opposite to the second external electrode; and step (iv) of, after step (iii), irradiating the metal nanoparticles with light to sinter the metal nanoparticles to form the second sintered metal.

27. The method for manufacturing an electrolytic capacitor according to claim 26, wherein, the step (iii) of forming the second sintered metal includes: a step of irradiating the metal nanoparticles with the first light to sinter the metal nanoparticles on the second surface of the outer package to form a part of the second sintered metal; and a step of irradiating the metal nanoparticles on the end face of the cathode portion with a second light having an energy higher than that of the first light to sinter the metal nanoparticles on the end face of the cathode portion to form the remaining portion of the second sintered metal.

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