JP2019145726A - Solid electrolytic capacitor - Google Patents

Abstract

To reduce a compressional difference of a porous sintered compact as an anode body.SOLUTION: A solid electric capacitor comprises a capacitor element including: an anode body of a porous sintered compact; an anode wire extended from a first surface of the anode body; a dielectric layer formed on the anode body; a solid electrolyte layer formed on the dielectric layer; a cathode layer formed on the solid electrolyte layer. The anode body includes the first surface, and a second surface and a third surface which share one side with the first surface are opposite each other. The anode wire includes: a first part embedded in an inner part of the anode body from the first surface; and a second part extended from the first surface of the anode body. A ratio of D/T of a means value Dof a diameter in a direction A of the first part of the anode wire to a mean value T of the thickness in the direction A directed to the third surface from the second surface of the anode body is 90 to 110%, and one part of the first part is exposed from the second and third surfaces.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid electrolytic capacitor, and more particularly, to a solid electrolytic capacitor including an anode wire partially embedded in an anode body.

  In recent years, along with the reduction in size and weight of electronic devices, there has been a demand for small-sized and large-capacity high-frequency capacitors. As such a capacitor, development of a solid electrolytic capacitor having a small equivalent series resistance (ESR) and excellent frequency characteristics is being promoted. The solid electrolytic capacitor includes an anode body, a dielectric layer formed on the surface of the anode body, a solid electrolyte layer formed on the surface of the dielectric layer, and a cathode layer formed on the solid electrolyte layer. To do. As the anode body, a porous sintered body obtained by sintering valve action metal particles such as tantalum, niobium, and titanium is used.

  The porous sintered body is usually manufactured by placing an anode wire at a predetermined position of a mold, putting valve action metal particles into the mold, press-molding, and then sintering. For example, as shown in Patent Document 1, the pressure molding is performed from a direction in which the anode wire is horizontally arranged in a mold and intersects the longitudinal direction of the anode wire.

JP 2009-158579 A

  During pressure molding, particularly large pressure is easily applied to the valve metal particles in the region sandwiched between the mold and the anode wire, and the density of the valve metal particles in the region is increased. Therefore, a density difference occurs in the obtained porous sintered body, and the internal strength varies. When an external stress is applied to such a porous sintered body, the dielectric layer and the solid electrolyte layer formed on the surface of the region having a low internal strength are easily damaged. Therefore, the leakage current of the solid electrolytic capacitor may increase or the ESR may increase.

A first aspect of the present invention includes an anode wire, an anode body in which a part of the anode wire is embedded, a dielectric layer formed on the anode body, and a solid formed on the dielectric layer A capacitor element having an electrolyte layer and a cathode layer formed on the solid electrolyte layer, the anode body being a porous sintered body, and a first surface on which the remainder of the anode wire is planted, A first portion sharing one side with the first surface and having a second surface and a third surface facing each other, wherein the anode wire is embedded in the anode body from the first surface; A second portion extending from the first surface of the anode body, and the anode wire with respect to an average value T of a thickness in a direction A from the second surface to the third surface of the anode body the ratio of the average value _{D in} the diameter of the direction a of the first part _{of: D in} / T is 9 Was 110%, a part of the first portion is exposed from the second surface and the third surface, a solid electrolytic capacitor.

  According to the present invention, the density difference of the porous sintered body is reduced.

It is sectional drawing of the solid electrolytic capacitor which concerns on one Embodiment of this invention. It is a perspective view of the anode body and anode wire concerning one embodiment of the present invention. It is sectional drawing which cut | disconnected the anode body and anode wire which were shown in FIG. 2 by XX. It is sectional drawing of the solid electrolytic capacitor which concerns on other one Embodiment of this invention. It is sectional drawing of the solid electrolytic capacitor which concerns on another one Embodiment of this invention.

The anode body according to the present embodiment is a porous sintered body, and has a first surface on which an anode wire is planted, a second surface and a third surface that share one side with the first surface and face each other. doing. Ratio of average value D _in diameter of direction A of first portion of anode wire to average value T of thickness in direction A from second surface to third surface of anode body: D _in / T is 90 to 110% It is. That is, the average value T of the thickness in the direction A of the anode body and the average value D _in of the direction A of the first portion of the anode wire are substantially the same. A part of the first portion embedded in the anode body of the anode wire is exposed from the second surface and the third surface. The region exposed from the second surface of the anode wire (first exposed region) and the second surface of the anode body are substantially flush. The region exposed from the third surface of the anode wire (second exposed region) and the third surface of the anode body are substantially flush.

  That is, the pressure forming of the valve action metal particles is performed so that the region where the valve action metal particles are sandwiched between the mold and the anode wire is not formed. Therefore, the occurrence of a density difference in the porous sintered body is suppressed.

In a preferred embodiment, the ratio of the average value D _in to the average value D _out of the diameter A in the direction A of the second portion of the anode wire: D _in / D _out is 90 to 110%. That is, the diameter of the anode wire is substantially uniform between the first portion and the second portion.

  As described above, the anode body is formed by sintering particles such as valve action metal accommodated in a mold in a state where a part of the anode wire is embedded. Further, the dielectric layer is usually formed by chemical conversion of an anode body in which a part of the anode wire is embedded. Therefore, various loads such as heat treatment, pressure treatment, and chemical conversion treatment are applied to the anode wire. When only a part of the anode wire is flattened, the anode wire is easily broken at the boundary between the flattened portion and the non-flattened portion. In addition, when the above load is applied to this boundary, the boundary becomes further fragile and easily breaks. In this embodiment, for example, it is not necessary to flatten only a part of the anode wire or to flatten only a part of the anode wire in advance during the pressurizing process, so that the anode wire is unlikely to break.

The direction A is a direction of a straight line connecting the second surface and the third surface with the shortest distance. The average value T of the thickness of the anode body is obtained by averaging the lengths of the respective straight lines connecting the arbitrary three points on the second surface of the anode body 1 and the third surface with the shortest distance. The average value D _in of the diameter of the anode wire is obtained by measuring and averaging the diameters in the direction A in the cross section of any three points of the first part. Similarly, the average value D _out of the diameter of the anode wire can be obtained by measuring and averaging the diameters in the direction A in the cross section of any three points of the second portion.

  A solid electrolytic capacitor according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the solid electrolytic capacitor according to the present embodiment. FIG. 2 is a perspective view of the anode body and anode wire according to the present embodiment. FIG. 3 is a cross-sectional view of the anode body and anode wire shown in FIG. 2 cut along line XX.

<Solid electrolytic capacitor>
The solid electrolytic capacitor 100 includes, for example, a capacitor element 10 having a hexahedral outer shape, a resin outer body 70 that seals the capacitor element 10, an anode lead terminal 50 and a cathode lead terminal 60 that are exposed to the outside of the resin outer body 70, respectively. It is equipped with. As with the capacitor element 10, the solid electrolytic capacitor 100 has a substantially hexahedral outer shape.

  Capacitor element 10 includes anode body 1 which is a porous sintered body, anode wire 2 extending from first surface 1a of the anode body, and a dielectric layer (not shown) formed on anode body 1. The solid electrolyte layer 4 formed on the dielectric layer and the cathode layer 5 covering a part of the surface of the solid electrolyte layer 4 are provided. A first portion 2 a (see FIG. 2) including one end of the anode wire 2 is embedded in the anode body 1 from the first surface 1 a of the anode body 1. The second portion 2b including the other end of the anode wire 2 extends from the first surface 1a.

  A part of the anode lead terminal 50 is sealed with a resin sheathing body 70 and is electrically connected to the second portion 2b of the anode wire 2 by welding or the like. The remaining part of the anode lead terminal 50 is pulled out from the resin sheathing 70 and extends in an exposed state up to one main flat surface (the lower surface in FIG. 1). A part of the cathode lead terminal 60 is sealed with a resin sheathing body 70 and is electrically connected to the cathode layer 5 via a conductive adhesive (not shown). The remaining part of the cathode lead terminal 60 is pulled out from the resin sheath 70 and extends to the same surface as the anode lead terminal 50 in an exposed state. The exposed portions of the terminals on the flat surface are used for solder connection with a substrate (not shown) on which the solid electrolytic capacitor 100 is to be mounted.

(Anode wire)
A part of the first portion 2a of the anode wire 2 is exposed from the second surface 1b and the third surface 1c which share one side with the first surface 1a and face each other.

The ratio of the diameter D _in the direction A of the first portion 2a of the anode wire 2 to the average value T in the thickness A in the direction A of the anode body 1: D _in / T is 90 to 110%. D _in / T may be 100 to 108% or 100 to 103%. The first exposed region 2aa and the second surface 1b exposed from the second surface 1b of the anode wire 2 are substantially flush with each other. The second exposed region 2ab exposed from the third surface 1c of the anode wire 2 and the third surface 1c of the anode body 1 are substantially flush (see FIG. 3).

  The area ratio of the first exposed region 2aa to the second surface 1b is not particularly limited. The area ratio of the first exposed region 2aa to the second surface 1b is, for example, 1 to 10%. The area ratio of the second exposed region 2ab to the third surface 1c is not particularly limited. The area ratio of the second exposed region 2ab to the third surface 1c is, for example, 1 to 10%. The area of the first exposed region 2aa is an area when viewed from the normal direction of the second surface 1b. The area of the second exposed region 2ab is an area when viewed from the normal direction of the third surface 1c.

The ratio of the average value D _in the diameter A in the direction A of the first portion 2a to the average value D _{out in} the direction A of the second portion 2b of the anode wire 2: D _in / D _out may be 90 to 110% Good. That is, the diameter of the anode wire 2 may be substantially uniform between the first portion 2a and the second portion 2b. D _in / D _out may be 95 to 105%, 98 to 103%, or 98 to 100%.

The anode wire 2 is made of a conductive material. The material of the anode wire 2 is not specifically limited, For example, copper, aluminum, aluminum alloy etc. other than the said valve action metal are mentioned. The materials constituting the anode body 1 and the anode wire 2 may be the same or different. The cross-sectional shape of the anode wire 2 is not particularly limited, and is a circular shape or a shape obtained by crushing a circular shape (a shape consisting of straight lines parallel to each other and two curves connecting the ends of these straight lines. Hereinafter, referred to as a track shape. .), Oval, rectangular, polygonal and the like. Among these, the track shape is preferable in that rolling is suppressed during positioning with the anode lead terminal 50 and positioning is easy. The average value D _out of the diameter of the second portion 2b of the anode wire 2 (the long diameter in the case of the track shape and the elliptical shape) is not particularly limited, and is, for example, 0.15 mm to 0.50 mm.

(Anode body)
The anode body 1 is a porous sintered body obtained by sintering metal particles. Although the shape of the anode body 1 is not specifically limited, For example, it is a rectangular parallelepiped. The average value T of the thickness of the anode body 1 in the direction A is not particularly limited, and is, for example, 0.15 mm to 0.50 mm.

  Valve metal particles such as titanium (Ti), tantalum (Ta), and niobium (Nb) are used as the metal particles. One type or two or more types of metal particles are used for the anode body 1. The metal particles may be an alloy composed of two or more metals. For example, an alloy containing a valve action metal and silicon, vanadium, boron, or the like can be used. A compound containing a valve metal and a typical element such as nitrogen may be used. The alloy of the valve action metal preferably contains the valve action metal as a main component and contains 50 atom% or more of the valve action metal.

(Dielectric layer)
A dielectric layer is formed on the surface of the anode body 1. The dielectric layer is made of, for example, a metal oxide. As a method for forming a layer containing a metal oxide on the surface of the anode body 1, for example, a method of anodic oxidation of the surface of the anode body 1 by immersing the anode body 1 in a chemical conversion solution, The method of heating in the atmosphere containing is mentioned. The dielectric layer is not limited to the layer containing the metal oxide, and may be insulating. The dielectric layer can also be formed on the first exposed region 2aa and the second exposed region 2ab of the anode wire 2.

(Solid electrolyte layer)
The solid electrolyte layer 4 is formed so as to cover at least a part of the dielectric layer. The solid electrolyte layer 4 can also be formed on the dielectric layer formed in the first exposed region 2aa and the second exposed region 2ab.

  For example, a manganese compound or a conductive polymer is used for the solid electrolyte layer 4. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyparaphenylene vinylene, polyacene, polythiophene vinylene, polyfluorene, polyvinyl carbazole, polyvinyl phenol, polypyridine, and derivatives of these polymers. Can be mentioned. These may be used alone or in combination of two or more. The conductive polymer may be a copolymer of two or more monomers. Among these, polythiophene, polyaniline, polypyrrole, and the like are preferable in terms of excellent conductivity. Of these, polypyrrole is preferred because of its excellent water repellency.

  The solid electrolyte layer 4 containing the conductive polymer is formed, for example, by polymerizing a raw material monomer on a dielectric layer. Or it forms by apply | coating the liquid containing the said conductive polymer to a dielectric material layer. The solid electrolyte layer 4 is composed of one or more solid electrolyte layers. When the solid electrolyte layer 4 is composed of two or more layers, the composition and formation method (polymerization method) of the conductive polymer used in each layer may be different.

(Cathode layer)
The cathode layer 5 has, for example, a carbon layer and a metal (for example, silver) paste layer formed on the surface of the carbon layer. The carbon layer is formed so as to cover at least part of the solid electrolyte layer 4. The carbon layer is composed of a composition containing a conductive carbon material such as graphite. A metal paste layer is comprised by the composition containing silver particle and resin, for example. In addition, the structure of the cathode layer 5 is not restricted to this, What is necessary is just a structure which has a current collection function.

(Anode lead terminal)
The anode lead terminal 50 is electrically connected to the anode body 1 through the second portion 2 b of the anode wire 2. The material of the anode lead terminal 50 is not particularly limited as long as it is electrochemically and chemically stable and has conductivity, and may be a metal or a nonmetal. The shape is not particularly limited, and for example, it is long and flat. In this case, the thickness of the anode lead terminal 50 (distance between the main surfaces of the anode lead terminal 50) is preferably 25 to 200 μm and more preferably 25 to 100 μm from the viewpoint of reducing the height.

  The anode lead terminal 50 may be joined to the anode wire 2 by a conductive adhesive or solder, or may be joined to the anode wire 2 by resistance welding or laser welding. The conductive adhesive is, for example, a mixture of a thermosetting resin and carbon particles or metal particles.

(Cathode lead terminal)
The cathode lead terminal 60 is electrically connected to the cathode layer 5. The material of the cathode lead terminal 60 is not particularly limited as long as it is electrochemically and chemically stable and has conductivity, and may be a metal or a nonmetal. The shape is not particularly limited, and for example, it is long and flat. In this case, the thickness of the cathode lead terminal 60 is preferably 25 to 200 μm and more preferably 25 to 100 μm from the viewpoint of reducing the height. The cathode lead terminal 60 is bonded to the cathode layer 5 through, for example, a conductive adhesive.

(Resin exterior)
The resin sheathing body 70 is provided to electrically insulate the anode lead terminal 50 and the cathode lead terminal 60 from each other, and is made of an insulating material. The resin sheathing body 70 includes, for example, a cured product of a thermosetting resin. Examples of the thermosetting resin include epoxy resin, phenol resin, silicone resin, melamine resin, urea resin, alkyd resin, polyurethane, polyimide, unsaturated polyester, and the like.

  The capacitor element 10 is covered with the resin sheathing 70 so that at least a part of the anode lead terminal 50 and the cathode lead terminal 60 is led out from the resin sheathing 70. The outer shape of the resin outer package 70 is, for example, a rectangular parallelepiped.

As shown in FIG. 4, the solid electrolytic capacitor 100 may include a plurality of stacked capacitor elements 10. In the capacitor element 10 according to the present embodiment, the average value T of the anode body 1 in the direction A and the average value D _in the diameter A of the first portion 2a of the anode wire 2 are substantially the same. Therefore, the capacitor element 10 can be easily stacked. In addition, even when an external load (external mechanical stress) that presses the second surface 1b or the third surface 1c of the anode body is applied by lamination, the anode body 1 is damaged by the anode wire 2. It is suppressed. The number of stacked layers is not particularly limited, and may be 2 to 7, for example.

When the average value D _in of the first portion 2a of the anode wire 2 and the average value D _out of the second portion 2b are substantially the same, when the plurality of capacitor elements 10 are stacked, the second portions 2b of the anode wire 2 are The gap becomes smaller. The gap between the second portions 2b corresponds to approximately twice the total thickness of the solid electrolyte layer 4 and the cathode layer 5, and is at most several tens of μm. Therefore, the connection between the plurality of second portions 2b can be achieved by, for example, one-time welding. Therefore, productivity is improved. For example, a conductive adhesive is interposed between the cathode layers 5.

  A conductive sheet 80 (for example, a metal foil) may be interposed between the second portions 2b as necessary. Also in this case, a plurality of anode wires can be connected by performing welding once after the sheet 80 is disposed between the second portions 2b. The thickness of the sheet 80 may be approximately twice the total thickness of the solid electrolyte layer 4 and the cathode layer 5, and may be, for example, 30 μm to 100 μm. Usually, since the anode wire is thinner than the capacitor element 10, welding is performed by interposing a conductive member called a pillow member between the anode wires. After welding the pillow member and one of the anode wires, by arranging another anode wire so as to sandwich the pillow member and repeating the welding, the plurality of anode wires are connected via the pillow member.

  When two capacitor elements 10 are arranged, for example, as shown in FIG. 5, an anode lead terminal 50 and a cathode lead terminal 60 may be sandwiched between the capacitor elements 10. The portion sandwiched between the cathode layers 5 of the cathode lead terminal 60 is a portion sandwiched between the second portions 2 b of the anode lead terminal 50 in consideration of the total thickness of the solid electrolyte layer 4 and the cathode layer 5. It may be thinner. This is because the bending load applied to the capacitor element 10 is reduced and damage is easily suppressed.

An example of the manufacturing method of the solid electrolytic capacitor according to the present embodiment will be described.
≪Method for manufacturing solid electrolytic capacitor≫
(1) Production process of anode body The metal particles and the anode wire 2 are put into a mold so that a part of the anode wire 2 is embedded in the metal particles. After press molding so that the distance between the pair of opposing surfaces of the mold is equal to the diameter of the anode wire 2, sintering is performed in a vacuum. Thus, an anode body in which the first portion 2a is embedded from the first surface 1a of the anode body 1 is manufactured. However, a part of the first portion 2a is exposed from the second surface 1b and the third surface 1c. On the other hand, the first portion 2a and the second surface 1b or the third surface 1c are substantially flush. The pressure at the time of pressure molding is not specifically limited, For example, it is about 10-100N. If necessary, the metal particles may be mixed with a binder such as polyacrylic carbonate.

(2) Dielectric Layer Formation Step A dielectric layer is formed on the anode body 1. Specifically, the anode body 1 is immersed in a chemical conversion tank filled with an electrolytic aqueous solution (for example, phosphoric acid aqueous solution), and the second portion 2b of the anode wire 2 is connected to the anode body of the chemical conversion tank, thereby anodizing. By performing the above, a dielectric layer made of an oxide film of a valve metal can be formed on the surface of the anode body 1. The electrolytic aqueous solution is not limited to a phosphoric acid aqueous solution, and nitric acid, acetic acid, sulfuric acid, and the like can be used.

(3) Formation process of solid electrolyte layer In this embodiment, the formation process of the solid electrolyte layer 4 containing a conductive polymer is demonstrated.
The solid electrolyte layer 4 containing a conductive polymer is obtained by, for example, impregnating the anode body 1 on which the dielectric layer is formed with a monomer or oligomer, and then polymerizing the monomer or oligomer by chemical polymerization or electrolytic polymerization, or The anode body 1 on which the dielectric layer is formed is impregnated with a solution or dispersion of a conductive polymer and dried to form at least part of the dielectric layer.

(4) Cathode Layer Formation Step A carbon layer and a metal paste layer are sequentially applied on the surface of the solid electrolyte layer 4 to form a cathode layer 5 composed of a carbon layer and a metal paste layer.

(5) Joining step of anode lead terminal The second portion 2b of the anode wire 2 planted from the anode body 1 is joined to the anode lead terminal 50 by laser welding, resistance welding, or the like.

(6) Joining process of cathode lead terminal After applying a conductive adhesive to the cathode layer 5, the cathode lead terminal 60 is joined to the cathode layer 5 through the conductive adhesive.

(7) Sealing step by resin sheathing body Next, the capacitor element 10 and the resin (material of the resin sheathing body 70. For example, uncured thermosetting resin and filler) are accommodated in a mold, transfer molding method, compression molding. The capacitor element 10 is sealed with the resin sheathing 70 by a method or the like. At this time, at least a part of the anode lead terminal 50 and the cathode lead terminal 60 is exposed from the mold. The molding conditions are not particularly limited, and the time and temperature conditions may be appropriately set in consideration of the curing temperature of the thermosetting resin used.
The solid electrolytic capacitor 100 is manufactured by the above method.

  Since the solid electrolytic capacitor according to the present invention has high performance, it can be used for various applications.

DESCRIPTION OF SYMBOLS 100: Solid electrolytic capacitor 10: Capacitor element 1: Anode body 1a: 1st surface 1b: 2nd surface 1c: 3rd surface 2: Anode wire 2a: 1st part 2aa: 1st exposed area 2ab: 2nd exposed area 2b: Second part 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode layer 30: Metal case 40: Sealing member 50: Anode lead terminal 60: Cathode lead terminal 70: Resin sheath 80: Conductive sheet

Claims (3)

An anode wire,
An anode body in which a part of the anode wire is embedded;
A dielectric layer formed on the anode body;
A solid electrolyte layer formed on the dielectric layer;
A capacitor layer having a cathode layer formed on the solid electrolyte layer,
The anode body is a porous sintered body, and the first surface on which the remaining portion of the anode wire is planted, the second surface and the third surface facing each other while sharing one side with the first surface, Have
The anode wire has a first portion embedded in the anode body from the first surface, and a second portion extending from the first surface of the anode body,
Ratio of the average value D _in the diameter A of the first portion of the anode wire to the average value T of the thickness in the direction A from the second surface to the third surface of the anode body: D _in / T Is 90-110%,
Part of the first portion is a solid electrolytic capacitor exposed from the second surface and the third surface. 2. The solid according to claim 1, wherein a ratio of the average value D _in to the average value D _out of the diameter in the direction A of the second portion of the anode wire: D _in / D _out is 90 to 110%. Electrolytic capacitor. The solid electrolytic capacitor according to claim 1, comprising a plurality of the capacitor elements stacked.

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