JPWO2014046216A1 - Solid electrolytic capacitor - Google Patents

Abstract

An object of the present invention is to reduce ESR of a solid electrolytic capacitor. The present invention relates to a solid electrolytic capacitor in which a dielectric oxide film layer, a solid electrolyte layer, a conductive carbon layer, and a cathode lead layer are sequentially formed on the surface of an anode body made of a metal material. Alternatively, nanographene is contained in an amount of 0.5% by weight or more. When the conductive carbon layer contains graphene and / or nano graphene, the electrical conductivity of the conductive carbon layer is reduced, and a low ESR can be realized as a solid electrolytic capacitor.

Description

  The present invention relates to a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor used in a high-frequency circuit, such as for supplying power to a CPU.

  Conventionally, as an electrolytic capacitor, an electrolytic capacitor using a valve metal such as aluminum or tantalum as an anode body and an electrolytic solution or a solid electrolyte as an electrolyte serving as a true cathode is known.

  In recent years, in particular, CPU drive circuits are required to have low drive voltage, low power consumption, and high frequency response, and as a result, capacitors also have a larger capacitance and equivalent series resistance (hereinafter referred to as “equivalent series resistance”). The equivalent series resistance is described as ESR) and the equivalent series inductance (hereinafter, equivalent series inductance is described as ESL) are required to be further reduced. In order to meet such demands, a technique of using a conductive polymer having high electrical conductivity as a solid electrolyte of an electrolytic capacitor has been studied and developed particularly for the purpose of reducing ESR.

  Here, the structure of an electrolytic capacitor using a conventional conductive polymer as a solid electrolyte will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a configuration of a solid electrolytic capacitor using a conventional conductive polymer as a solid electrolyte. In FIG. 3, 31 is an electrode (aluminum electrode body for anode), 32 is a dielectric oxide film layer, 33 is a solid electrolyte layer, 34 is a conductive carbon layer, 35 is a silver paste layer, and 36 is a cathode lead as a cathode terminal. It is. In the solid electrolytic capacitor having this structure, the silver paste layer 35 constitutes the cathode lead layer.

  As shown in FIG. 1, the surface of the anode aluminum electrode body 31 is roughened, and a dielectric oxide film layer 32 is formed on the surface. A solid electrolyte layer 33 made of a conductive polymer such as polypyrrole, polythiophene, polyaniline and derivatives thereof is formed on the surface of the anode aluminum electrode body 31 having the dielectric oxide film layer 32 provided on the surface in this way. Yes. Further, a conductive carbon layer 34 and a silver paste layer 35 are sequentially formed on the solid electrolyte layer 33 to constitute a capacitor element. To this capacitor element, an anode terminal (not shown) is joined to the anode aluminum electrode body for the purpose of electrical communication to the outside, and a cathode lead 36 is joined to the silver paste layer 35. By sealing the capacitor element, a conventional solid electrolytic capacitor is formed.

  Such a solid electrolytic capacitor using a conventional conductive polymer as a solid electrolyte includes an electrolytic capacitor using an electrolytic solution as an electrolyte, and a solid electrolytic capacitor using manganese dioxide and TCNQ (tetracyanoquinodimethane) as a solid electrolyte. The characteristic is that ESR is lower than that. This is because the electrical conductivity of the conductive polymer is higher than that of the conventional electrolyte, manganese dioxide, and TCNQ. A solid electrolytic capacitor using such a conductive polymer as a solid electrolyte is a conventional electrolyte. The ESR can be reduced as compared with the solid electrolytic capacitor using the capacitor.

  However, as the CPU operates at a high frequency, the electrolytic capacitor as a power supply source is also required to have a lower ESR. Therefore, various studies have been conducted on the structure of the electrolytic capacitor and the respective materials constituting the solid electrolyte layer 33, the conductive carbon layer 34, and the silver paste layer 35.

  Among these, in a solid electrolytic capacitor in which a solid electrolyte layer made of a conductive polymer is formed on the surface of the anode body, conductive carbon is formed on the solid electrolyte layer for electrical connection between the solid electrolyte layer and the external electrode. It is common practice to form layers and silver paste layers.

  The characteristics required for the conductive carbon layer of such a solid electrolytic capacitor are required to have high adhesion to the solid electrolyte layer and low internal resistance inside the conductive carbon layer. Therefore, in order to satisfy such characteristics, relatively large graphite is used (Patent Document 1), carbon particles having a small particle diameter such as carbon black (Patent Document 2), and carbon nanotubes are used. It is known (Patent Document 3).

  Further, these carbon materials are mixed and used as a normal means. The reason why the conductive carbon layer is formed by mixing such carbon materials is as follows. That is, when the conductive carbon layer is formed with only carbon particles having a small particle diameter, it is preferable in that the contact area with the solid electrolyte layer is increased and the interface contact resistance with the solid electrolyte layer is reduced. On the other hand, when forming a conductive carbon layer only with carbon particles having a small particle size, in order to form a conductive carbon layer with a certain thickness, there are many carbon particles with respect to the thickness of the conductive carbon layer. As a result, the interfacial contact resistance between the carbon particles increases. For this reason, when the conductive carbon layer is formed using only carbon particles having a small particle diameter, the interfacial contact resistance with the solid electrolyte layer is reduced, but the internal resistance inside the conductive carbon layer is increased. However, a sufficient ESR reduction effect cannot be obtained.

  Therefore, it is necessary to reduce the internal resistance of the conductive carbon layer by mixing a carbon material having a relatively large particle size. When carbon materials having different particle sizes are mixed, carbon particles having a small particle size reduce interfacial contact resistance with the solid electrolyte layer, and carbon materials having a relatively large particle size exist in the conductive carbon layer. Thereby, the contact frequency of the carbon particles inside the conductive carbon layer is reduced, and the internal resistance can be reduced. As a result, the internal resistance can be reduced as the entire conductive carbon layer functioning as an extraction electrode from the solid electrolyte layer.

  As such a carbon material having a relatively large particle size, scaly graphite derived from natural graphite is known, and a material having a size of about 0.1 to 50 μm is often used. Carbon black is known as a carbon material having a small particle diameter, and among them, it is known that ketjen black having a high conductivity is particularly suitable.

  Furthermore, Patent Document 3 discloses that carbon nanotubes are contained in such a conductive carbon layer, thereby improving adhesion with the solid electrolyte layer and suppressing deterioration of ESR over time.

JP-A-2-265234 JP 2004-79838 A JP 2003-86464 A

  However, even if conventional carbon materials such as graphite and carbon black are combined at various ratios to form a carbon layer, it has become difficult to further reduce the ESR of the solid electrolytic capacitor.

  The present invention has been proposed to solve the above-described problems of the prior art, and an object thereof is to further reduce the ESR of the solid electrolytic capacitor.

  In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a dielectric oxide film layer, a solid electrolyte layer, a conductive carbon layer and a cathode lead layer are formed on the surface of an anode body made of a metal material having a valve action. In the solid electrolytic capacitor formed sequentially, the conductive carbon layer contains graphene and / or nano graphene.

Here, graphene refers to one in which carbon atoms are SP ² bonded with a thickness of one atom and the carbon atoms have a two-dimensional hexagonal lattice structure. Nanographene is a layered structure of the above-described graphene, and generally has a thickness of about 10 to 1000 nm.

Each layer of graphite has a structure called an ABA laminate or a benel laminate.
In this structure, the electron band structure of two adjacent layers consists of two sets of electron / hole bands. When a plurality of layers having such an electronic band structure are stacked, a part of the band is electron-doped and a part is hole-doped by the interlayer interaction. This electron doping increases the electrical resistance, and it is said that graphite becomes a semimetal.

  On the other hand, nanographene has a structure called ABC stacking in a structure in which graphene is stacked. This structure is different from the above-described graphite ABA stack, that is, a structure in which the stack is continuous with AB-AB-AB..., And has a C layer between the AB stacks. This C layer has the original electronic band structure of graphene, and has no interlayer interaction (or weak interaction) from adjacent layers. A part of the band is electron-doped or partly hole-doped. (Or its frequency is rare). For this reason, it is said that the electrical resistance does not increase.

  Thus, graphene and nano graphene have extremely high electrical conductivity compared to normal graphite. As such graphene and nanographene, nanographene in which about 50 layers are laminated is commercially available. Moreover, the aspect ratio (thickness: area of nanographene) of commercially available nanographene is about 1:10 to 1: 1000. However, the present invention is not limited to such nanographene, and if it has an electronic band structure of graphene and has high electrical conductivity derived from the graphene structure, the aspect ratio of graphene, the aspect ratio of nanographene The number of layers can be arbitrarily selected.

  As described above, graphene and nanographene have high electrical conductivity derived from the structure. For this reason, when a conductive carbon layer contains graphene and / or nano graphene, the electrical conductivity of a conductive carbon layer reduces and low ESR is realizable as a solid electrolytic capacitor.

  And as content of a graphene and / or nano graphene, it is suitable to add 0.5 weight% or more by the weight ratio of the whole solid component weight which forms an electroconductive carbon layer. Usually, in order to form the conductive carbon layer, a paste-like material containing a carbon material is applied and dried to remove the dispersion medium to form the conductive carbon layer. In the present invention, not the weight ratio in the paste for forming the conductive carbon layer but the weight ratio in the state where the paste is dried and the dispersion medium is evaporated is defined. In other words, it is the weight ratio of the solid component (nonvolatile component) contained in the paste for forming the conductive carbon layer.

  When graphite is included as the carbon material, graphene and / or nanographene may be generated in the graphite grinding step. There is also a report that graphite contains about 10% of graphene having an electronic band structure. However, in the present invention, the graphene and / or nano graphene having the electronic band structure of graphene originally present in graphite or produced in the graphite production process and contained in the graphite material is a part of the graphite material. I consider it. Therefore, the content with respect to the weight of the solid component constituting the conductive carbon is based on the amount of graphene and / or nanographene added to the graphite material or the like.

  By setting the content of graphene and / or nanographene to 0.5 wt% or more in terms of the weight ratio of the total weight of the solid component forming the conductive carbon layer, an effect of reducing ESR of the solid electrolytic capacitor can be obtained. When the content is less than 0.5% by weight, no significant difference appears in the ESR characteristics of the solid electrolytic capacitor. In addition, as content of graphene and / or nano graphene, the tendency for the reduction effect of ESR to become large is seen as content increases. On the other hand, when a paste is prepared with a setting such that the content of graphene and / or nanographene exceeds a predetermined amount, the viscosity of the paste increases, and the handleability of the paste application process is significantly reduced. This handling property depends on the total amount of graphite, carbon black, graphene and / or nanographene as a carbon material with respect to the organic solvent, and further the content of the resin as a binder. If these ratios are changed, graphene and In addition, since the upper limit of the amount of nanographene added (the upper limit that causes deterioration in handling properties) also changes, the upper limit of the amount of addition cannot be generally defined.

  According to the present invention, it is possible to provide a solid electrolytic capacitor in which the ESR of the solid electrolytic capacitor is reduced and excellent charge supply is possible in a high frequency circuit.

It is sectional drawing which shows the structure of an example of the solid electrolytic capacitor which concerns on this invention. It is a perspective view of the mounting substrate used for the structure of an example of the solid electrolytic capacitor of this invention. It is sectional drawing which shows the structure of the conventional solid electrolytic capacitor.

  Hereinafter, embodiments of the solid electrolytic capacitor according to the present invention (hereinafter referred to as embodiments) will be specifically described.

  Although there is no restriction | limiting in particular as a shape of the solid electrolytic capacitor applied by this invention, For example, it can apply to the solid electrolytic capacitor of the following structures.

  A dielectric oxide film layer, a solid electrolyte layer, and a cathode portion are sequentially formed on the inner surface of the recess formed in the center of the anode body made of a valve metal, and the capacitor element using the anode body around the recess as the anode portion; A capacitor element mounting surface and a mounting surface facing the wiring board are provided. Conductors corresponding to the anode part and the cathode part of the capacitor element are formed on the surface on which the capacitor element is mounted to face the wiring board. The mounting surface includes a cathode electrode and an anode electrode formed around the cathode electrode, and a solid substrate including a mounting substrate in which the conductor penetrates the inside and is electrically connected to the anode electrode and the cathode electrode, respectively. It is an electrolytic capacitor.

  Hereinafter, embodiments of the present invention will be described together with the structure of the solid electrolytic capacitor described above.

  1A shows a cross-sectional view of the solid electrolytic capacitor of the present invention, and FIG. 1B shows a cross-sectional view of the solid electrolytic capacitor disassembled into a capacitor element and a mounting substrate.

  A capacitor element 1 used in the present invention will be described with reference to FIG. First, a thin plate-like aluminum material is used as an 11 anode body, and a recess having a predetermined size is formed in the center of the anode body 11 by cutting, pressing, etching, or the like. Further, the inner surface of the recess is subjected to a surface expansion process by etching, and further anodized to form the dielectric oxide film layer 12. Next, a solid electrolyte layer 13 made of a conductive polymer is formed on the dielectric oxide film layer 12 on the inner surface of the concave portion serving as a cathode, and then a conductive carbon layer 14 and a silver paste layer are formed on the solid electrolyte layer 13. 15 is formed as the cathode portion 16 and the capacitor element 1 is obtained. In this capacitor element 1, the portion around the concave portion of the anode body 11 becomes the anode portion 17.

  In such a capacitor element 1, the thickness of the aluminum material as a starting material is about 100 to 500 μm, the thickness of the etching layer is 20 to 30 μm, and the depth of the recess from the top of the etching layer is about 15 to 50 μm. By doing so, a thin capacitor element can be created.

  By forming the depth of the concave portion of the capacitor element 1 to be shallow, the conductive distance from the dielectric oxide film layer 12 to the cathode portion 16 which is a power outlet of the capacitor element is short, which is preferable for the effect of reducing ESL. It is. However, a dielectric oxide film layer 12 is formed on the inner surface of the recess, and a solid electrolyte layer 13 and a cathode portion 16 (conductive carbon layer 14 and silver paste layer 15) are sequentially formed on the dielectric oxide film layer 12. However, it is necessary that the solid electrolyte layer 13 and the cathode portion 16 do not protrude from the recess. For this reason, even if the thickness of the solid electrolyte layer 13 is formed to a thickness of about 5 to 10 μm and the thickness of the cathode portion 16 is formed to about 10 to 15 μm, they do not protrude from the recess. The depth of the recess is required to be about 15 to 50 μm.

  Moreover, in order to form a recessed part in the depth of about 15-50 micrometers, the thickness of about 100 micrometers is required as the thickness of the aluminum material of a starting material. If it is thinner than this, the aluminum material 11 itself is deformed when the recess is formed, or the strength of the anode body after forming the recess becomes extremely weak.

  However, even when a capacitor element is formed using an aluminum material having a thickness of 100 μm, the strength is not necessarily strong. Therefore, in order to reinforce the strength of such a capacitor element, a steel material having a strength higher than that of aluminum can be attached to the opposite surface of the concave portion of the capacitor element for reinforcement. Also, the strength can be increased by anodizing one surface of the aluminum material in advance.

  If the thickness of the aluminum material 11 is about 500 μm and sufficient strength can be maintained even when the recess is formed, it is not necessary to attach the steel material or improve the strength by anodizing.

  Incidentally, in the capacitor element, it is necessary to avoid applying mechanical stress to the dielectric oxide film layer and the solid electrolyte layer. When mechanical stress is applied to the dielectric oxide film layer and the solid electrolyte layer, the dielectric oxide film may be damaged, leading to an increase in leakage current. In addition, when mechanical stress is applied to the solid electrolyte layer, the conductivity of the solid electrolyte layer may be reduced. However, in this capacitor element, the dielectric oxide film layer and the solid electrolyte layer are formed inside the recess of the anode body, and are protected by being surrounded by the anode body 11.

(Solid electrolyte layer)
The solid electrolyte layer 13 formed on the capacitor element 1 described above will be described.

  The solid electrolyte layer 13 is formed of a conductive polymer. As the conductive polymer, polythiophene, polypyrrole, polyaniline, or a derivative thereof is suitable. As a method for forming the solid electrolyte layer, a method of forming a solid electrolyte layer by chemical polymerization using the monomer and oxidant as the precursor of the conductive polymer described above, a solid electrolyte layer by electrolytic polymerization of the monomer And a method of forming a solid electrolyte layer by applying a conductive polymer dispersion in which fine particles of a conductive polymer are dispersed in a predetermined place and drying, and so on. A method for forming a solid electrolyte layer can be used.

(Conductive carbon layer)
A conductive carbon layer 14 is formed on the solid electrolyte layer 13 described above. The conductive carbon layer 14 is obtained by adding a predetermined amount of graphene and / or nano graphene to a paste in which a carbon material made of graphite or carbon black and a polyester resin, a phenol resin, an acrylic resin, or the like as a binder is dispersed in an organic solvent. The mixed paste is applied onto the solid electrolyte layer 13 and dried to form a conductive carbon layer. As a paste in which graphite, carbon black, polyester resin as a binder, phenol resin, acrylic resin, etc. are dispersed in an organic solvent, use what is usually used as a conductive carbon paint in the field of solid electrolytic capacitors Can do. Moreover, the process in application | coating and drying may be the formation method of the electroconductive carbon layer in a normal solid electrolytic capacitor. Furthermore, metal fine powder may be included as a material constituting the conductive carbon layer. The feature of the present application is that the conductive carbon layer contains a predetermined amount of graphene and / or nanographene.

  The carbon material constituting the conductive carbon layer 14 is not limited to the above-described graphite and carbon black. However, the ordinary conductive carbon layer often contains graphite and carbon black. Carbon black has a very small particle size of about 3 to 500 nm, and adheres widely to the solid electrolyte layer. For this reason, since carbon black can reduce the interface contact resistance between the solid electrolyte layer and the conductive carbon layer, it is preferable to add carbon black. The content of the carbon black is preferably 5 to 20% by weight, more preferably 10 to 16% by weight, based on the weight ratio of the entire solid component forming the conductive carbon layer. In this range, ESR can be reduced. Further, the carbon black is preferably spherical. Further, graphite having a relatively large particle size of about 0.1 to 50 μm is often used. Although the electrical conductivity of graphite itself is lower than that of graphene and / or nanographene, the particle size of graphite is large, so that the frequency of contact between carbon materials in the conductive carbon layer is reduced. For this reason, the contact resistance between carbon materials can be reduced as the whole conductive carbon layer. For this reason, it is preferable to add graphite. In addition, the graphene and / or nano graphene of the same size as the carbon black particle size and the graphite particle size as described above are prepared, mixed with various sizes of graphene and / or nano graphene, and only graphene and / or nano graphene If the conductive carbon layer made of is formed, the electric resistance of the conductive carbon layer can be further reduced.

  The content of graphene and / or nano graphene is preferably 0.5% by weight or more in terms of the weight ratio of the total weight of the solid component forming the conductive carbon layer. The reason for this is as described above.

(Silver paste layer)
The silver paste forming the silver paste layer 15 is obtained by dispersing silver particles as a conductive material in a resin or the like, and is roughly classified into a high-temperature fired type and a polymer type. In the high-temperature firing mold, the silver particles are fused to form a continuous conductive film by heating to about 500 to 900 ° C., and conductivity is obtained. On the other hand, the polymer type contains a resin for the purpose of improving the coating property, improving the dispersibility of the silver particles and improving the adhesion to the base material, and is heated by a temperature of about 200 ° C. from room temperature. By curing, the metal particles come into contact with each other at the same time to form a conductive film, and the conductivity appears.

  In the case of a solid electrolytic capacitor using a conductive polymer as the solid electrolyte, it is preferable to use a polymer type silver paste capable of forming a silver paste layer at a temperature lower than the decomposition temperature of the conductive polymer.

  More specifically, the silver paste can be a mixed paste obtained by mixing silver oxide nanoparticles and silver neodecanoate, which is an organic silver compound, in a predetermined organic solvent.

  In addition, as an organic silver compound used for a silver paste, the silver salt of tertiary fatty acids, such as pivalic acid, neoheptanoic acid, neononanoic acid other than silver neodecanoate, can be used.

  Since the silver oxide of this silver paste is nano-sized fine particles, the gap between the capacitor elements described above enters the surface irregularities, and a sufficient contact area with the solid electrolyte layer can be secured.

Then, the silver paste is first sintered at a temperature range of 150 to 160 ° C. for 30 minutes to cure the paste layer. And the residual organic component on the surface of a silver paste layer is volatilized by heat-processing for 30 minutes in the temperature range of 170-190 degreeC.

By this heat treatment, the silver particles are fused to each other, a conductive path is secured inside the silver paste layer, and the conductivity of the entire silver paste layer 15 is improved. In addition, microcracks are not generated in the silver paste layer 15 in the above temperature range. Therefore, the conductive path is not blocked by the microcracks, and the resistivity of the silver paste layer 15 can be reduced from this point.

  The silver paste layer 15 described above constitutes the cathode lead layer of the present invention. The method for forming the cathode lead layer is not limited to the method for forming the silver paste with the silver paste described above, and various methods such as a method for forming the cathode lead layer by vapor deposition of metal can be employed. .

  Next, the mounting substrate 2 will be described. The mounting substrate is based on an insulating substrate 21 such as a glass epoxy substrate, and includes an anode electrode 22 and a cathode electrode 23 on the lower surface, and an anode conductor 24 and a cathode conductor connected to the anode and cathode portions of the capacitor element on the upper surface, respectively. 25, and the anode conductor 24 and the anode electrode 22, and the cathode conductor 25 and the cathode electrode 23 on the top surface and the back surface are respectively conducted.

  Further, the configuration of the electrodes on the lower surface of the mounting substrate 2 can be formed in any shape in accordance with the specifications of the CPU and the like to be connected, but as in the shapes of the anode and cathode portions of the capacitor element, FIG. As shown in (b), it is preferable to form the cathode electrode 23 in the shape of an electrode surrounding the anode electrode 22.

  The anode conductor 24 and the cathode conductor 25 formed on the upper surface of the mounting substrate 2 may have shapes matching the anode portion 17 and the cathode portion 16 of the capacitor element 1, respectively. FIG. 2A shows a perspective view as seen from the top surface of the mounting substrate 2. As in the structure of the capacitor element 1 shown above, the cathode portion 16 is formed in the recess, and the cathode conductor 25 of the mounting substrate 2 is formed so as to match the shape of the capacitor element 1 with the periphery of the recess as the anode portion 17. An anode conductor 24 is arranged so as to surround it.

  In addition, since the anode electrode 22 and the cathode electrode 23 are placed close to each other, the currents flowing through the anode electrode 22 and the cathode electrode 23 are in opposite directions, so that the magnetic fields generated by the currents flowing through the respective electrodes cancel each other. As a result, the ESL can be reduced. In addition, a solder resist layer 26 is formed between the anode electrode 22 and the cathode electrode 23 in order to prevent a short circuit when the anode electrode 22 and the cathode electrode 23 are close to each other and mounted on the mounting substrate with solder. It is preferable to keep it.

  An insulating substrate serving as a base for such a mounting substrate is preferably about 200 μm thick in terms of strength, but can also be about 80 μm thick. The anode electrode, the cathode electrode, and the conductor formed on the insulating substrate are only required to have low electrical resistance and can be soldered, and it is preferable to use a conductor in which gold is plated on copper or nickel. The electrodes and conductors can be formed with a thickness of 30 to 100 μm on one side.

  As a method for conducting the conductors 24 and 25 on the upper surface of the mounting substrate 2 and the electrodes 22 and 23 on the lower surface, a predetermined portion of the mounting substrate 2 is drilled by a laser, and the inner surface of the hole is plated by through-hole plating. Can be planned. The position, the number, etc. of the through holes for this conduction can be arbitrarily designed according to the characteristics such as the current capacity required for the solid electrolytic capacitor.

  In such a mounting substrate, the distance from the anode part and the cathode part of the capacitor element to the anode electrode and the cathode electrode of the mounting substrate that is the outlet of the current can be achieved by the distance of only the thickness of the mounting substrate, The current path can be shortened. In particular, the thickness of the mounting substrate is preferably about 200 μm, but a thickness of about 80 μm can be manufactured, and the conductor and electrode are formed on the mounting substrate with a thickness of 30 μm. Therefore, the distance from the cathode portion of the capacitor element to the cathode electrode of the mounting substrate can be made extremely shorter than when the capacitor element is attached to the lead frame and resin molded. For this reason, the ESL of the solid electrolytic capacitor can be reduced, and power can be quickly supplied to the CPU or the like during a transient response.

  The capacitor element 1 as described above is mounted on the mounting substrate 2, and the anode portion 17 and the cathode portion 16 of the capacitor element 1 are joined to the anode conductor 24 and the cathode conductor 25 of the mounting substrate with a conductive adhesive or the like, respectively. Use a capacitor.

  In addition, the dielectric film layer, solid electrolyte layer, and cathode part of the solid electrolytic capacitor are protected by the mounting substrate, so that not only mechanical stress during manufacturing, but also when stress is applied to the solid electrolytic capacitor during mounting, The stress is relieved and the stress applied to the inside of the capacitor element is also relieved.

  In addition, the capacitor element can be molded with a mold resin as necessary.

  As described above, the capacitor element has a thickness of about 100 μm, and the mounting board has a thickness of about 140 μm including the thickness of the electrodes on both sides and the conductor layer. A solid electrolytic capacitor can be obtained.

  In addition, when making thickness still thinner, it can be achieved by manufacturing a resin film such as a flexible substrate as the base of the mounting substrate described above.

  In the solid electrolytic capacitor of the above embodiment, the distance from the interface between the dielectric oxide film layer, which is the capacitance forming portion, and the solid electrolyte layer to the cathode electrode, which is the external electrode, is short, and the internal resistance of the solid electrolytic capacitor is reduced as much as possible. It has a structure. In the solid electrolytic capacitor having such a structure for reducing the internal resistance, the effect of reducing the ESR of the solid electrolytic capacitor is improved by improving the electrical conductivity of the conductive carbon layer of the present invention. Become.

  The shape of the solid electrolytic capacitor is not limited to the above shape. For example, the present invention can be applied to a case where a solid electrolyte layer made of a conductive polymer is formed on an anode body obtained by sintering tantalum powder, and further a conductive carbon layer is formed on the solid electrolyte layer. it can. Further, the present invention is also applicable to a solid electrolytic capacitor in which a solid electrolyte layer and a conductive carbon layer are formed on an anode body made of an aluminum plate, and a plurality of anode bodies are laminated.

  Next, examples of the present invention will be described.

  An aluminum material having a size of 5 × 5 mm and a thickness of 500 μm was prepared as an anode body, and a recess having a size of 3 × 3 mm was formed at the center. Etching was applied to the inner surface of the recess, and anodization was performed at a formation voltage of 3.6 V to form a dielectric oxide film layer.

  Next, a dispersion of poly-3,4-ethylenedioxythiophene (PEDOT) was dropped into the recess and dried to form a solid electrolyte layer made of PEDOT.

  Further, a conductive carbon layer was formed on the solid electrolyte layer.

  As the paste used to form the conductive carbon layer, we used Bunny Height (trade name) of a capacitor current collector paint made by Nippon Graphite, and weighed “graphene” made by Bridgestone CBC to this paste. The paste material was adjusted by adding. Note that “graphene” manufactured by Bridgestone CBC has 2 to 40 layers and a thickness of 40 to 100 nm, and thus corresponds to the nanographene described in the present specification. Hereinafter, “graphene” described in the examples is a trade name and substantially represents nanographene.

  When the amount of “graphene” added was 0.3, 1, 3, 10, 20% by weight, and the paste material was adjusted, an increase in the viscosity of the prepared paste was observed when 10% by weight was added. Furthermore, when 20% by weight was added, even if an attempt was made to adjust the paste, the viscosity became too high and the materials were not mixed together, making it impossible to produce a uniform paste.

  Bunny height contains a polyester resin as a binder, and its content is approximately 10% by weight. For this reason, when the paste was prepared using bunny height as a raw material, it was estimated that the viscosity would be improved with a relatively small amount of “graphene” added.

  Therefore, in order to compare the limits of the amount of graphene added, various pastes were prepared by changing the amount of graphene and other carbon materials added using butyl carbitol as a solvent and phenol resin as a binder. Tried.

  As a result, the amount of each material added so that the weight ratio of the constituent materials of the conductive carbon layer after drying the paste is 54% by weight of “graphene”, 1% by weight of ketjen black, and 46% by weight of phenol resin. Even when set to, it was confirmed that the viscosity as a paste is not so high and can be applied to the solid electrolyte layer of the solid electrolytic capacitor (each material is almost uniformly mixed and the handling property is good). .

  Therefore, it was found that the amount of “graphene” added could be 50% by weight or more by changing the constituent material of the paste. In consideration of ESR characteristics as a capacitor, the amount of “graphene” added is preferably less than 50% by weight.

  Table 1 below shows the amount of “graphene” added and the abundance ratio (content) of “graphene” when the paste material prepared using bunny height as a raw material is dried. The bunny height includes spherical ketjen black, and the abundance ratio (content) is also described. In this table, it is stated that the abundance ratio has a range. The bunny height, which is the raw material, has a maximum value and a minimum value of the allowable range of solid components contained in the paste. It is calculated assuming that the organic solvent component in the inside is all dried and a conductive carbon layer composed of only the solid component is formed.

  Using the paste type shown in the above-described conventional example, Example 1 to Example 4, the paste was applied to the solid electrolyte layer and dried at 160 ° C. to form a conductive carbon layer.

  Further, a silver paste layer was formed on the conductive carbon layer by a known method.

  The capacitor element formed by the above method was mounted on a mounting substrate having the same projected area as that of the capacitor element, thereby completing the solid electrolytic capacitors of the conventional example, Example 1 to Example 4.

The electrostatic capacity and ESR of the solid electrolytic capacitors of the conventional example and Examples 1 to 4 were measured. Thereafter, the solid electrolytic capacitor was left unloaded at an ambient temperature of 170 ° C. for 100 hours, and the subsequent change in capacitance and ESR were measured.
The results are shown in Table 2 below.

  As can be seen from the results shown in Table 2, there is no significant difference in capacitance between the conventional example and Examples 1 to 4, even when the initial value and the rate of change after 170 hours at 170 ° C. are observed. However, the initial value of ESR is 13.9 mΩ in the prior art, whereas in Examples 1 to 4, the initial value is 11.8 to 10.4 mΩ and 2.1 to 3.5 mΩ is significantly reduced. You can see that In addition, it can be seen that in each example in which the content of ketjen black is 10 to 16% by weight, the effect of reducing ESR is obtained as compared with the conventional example. It was also found that Example 4, which has a higher content of “graphene” than Ketjen Black, has a higher ESR reduction effect.

  From the data of the above example, the correlation between the added amount of “graphene” and the initial value of ESR was calculated, and a simulation was performed when a very small amount of graphene was added. When 0.1% by weight of “graphene” was added in the same manner as in the above Example, the initial ESR was 13.3 mΩ (Reference Example 1), and when 0.2% by weight was added, 12.7 mΩ (Reference Example 2) ) The addition amount of “graphene” in Reference Example 1 and Reference Example 2 is 0.3-0.8 wt% and 0.6-1.6 wt%, respectively, when converted to the abundance ratio of “graphene”. Become.

The results of this simulation are shown in Table 3 below.

  The simulation results shown in Table 3 suggest that the effect of reducing ESR in the solid electrolytic capacitor can be seen even if the abundance ratio of “graphene” is 0.5% by weight.

  Furthermore, when comparing the ESR after 170 hours at 170 ° C., the ESR value increased by 25 times in the conventional example, whereas it increased by 13-4.3 times in Example 2 to Example 4. The magnification is low. Also in this respect, it can be seen that the heat resistance of the solid electrolytic capacitor is improved as the amount of “graphene” is increased.

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Connection board 11 Aluminum material 12 Dielectric oxide film layer 13 Solid electrolyte layer 14 Conductive carbon layer 15 Silver paste layer 16 Cathode part 17 Anode part 21 Insulating substrate 22 Anode conductor 23 Cathode conductor 24 Anode conductor 25 Cathode conductor 31 Electrode body 32 Dielectric oxide film layer 33 Solid electrolyte layer 34 Conductive carbon layer 35 Silver paste layer 36 Cathode lead

Claims (3)

In a solid electrolytic capacitor in which a dielectric oxide film layer, a solid electrolyte layer, a conductive carbon layer, and a cathode lead layer are sequentially formed on the surface of an anode body made of a metal material,
The conductive carbon layer is a solid electrolytic capacitor containing graphene and / or nano graphene.   The solid electrolytic capacitor according to claim 1, wherein the content of graphene and / or nanographene in the weight of the solid component constituting the conductive carbon layer is 0.5% by weight or more.   The conductive carbon layer further contains carbon black, and the content thereof is in the range of 5 to 20% by weight based on the weight of the solid component constituting the conductive carbon layer. Solid electrolytic capacitor.