JP2003059776A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having low ESR characteristics. SOLUTION: The solid electrolytic capacitor has an organic semiconductor formed in a capacitor element produced by winding an anode foil and a cathode foil through a separator wherein the foil resistivity per unit area of the anode foil or the cathode foil is set in the range of 0.15-0.6 mΩ, the foil width is set in the range of 3-16 mm and the foil area is set not smaller than 300 mm<2> . Consequently, resistor component of the electrode foils and an electrolyte between the electrode foils is decreased. Furthermore, contact resistance at the joint of the electrode foil and an electrode lead out terminal is also decreased resulting in a solid electrolytic capacitor having low ESR characteristics.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid electrolytic capacitor using an organic semiconductor as an electrolyte.

[0002]

2. Description of the Related Art In recent years, electronic information devices have been digitized,
Further, the drive frequency of the microprocessor (MPU), which is the heart of these electronic information devices, is being increased. Along with this, the increase in power consumption has progressed, and the problem of reliability due to heat generation has become apparent. As a countermeasure, the drive voltage has been reduced. Here, a DC-DC converter called a voltage control module (VRM) is widely used as a circuit for supplying high-precision power to a microprocessor, and a series equivalent resistance ( Many capacitors with low ESR are used. As the capacitor having this low ESR characteristic, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has been put into practical use, and is widely used as a capacitor suitable for these applications.

However, the driving frequency of the microprocessor is remarkably increased, the power consumption is increased accordingly, and in order to cope with the increase in the power consumption, it is required to increase the power supplied from the capacitor to prevent the voltage drop. That is, it is necessary to be able to supply a large amount of electric power in a short time. Therefore, the solid electrolytic capacitor is required to have a large capacity, a small size, a low voltage, and an ESR characteristic lower than ever. To be done.

Here, the solid electrolytic capacitor will be explained. After the valve action metal foil such as aluminum, tantalum or niobium is etched to increase the surface area, the anode foil having an anodic oxide film formed thereon and aluminum, tantalum or niobium, etc. Etching is applied to the valve action metal foil of to form a cathode foil. Kraft paper, manila paper, glass separator or separator such as vinylon, non-woven fabric made of synthetic fiber such as polyester fiber, etc. is interposed between the anode foil and the cathode foil, and the anode is drawn to any place of the anode foil and the cathode foil. A capacitor element is formed by winding the terminal and the cathode lead-out terminal attached to each other. A solid electrolyte is formed on this capacitor element and stored in a metal case, and the metal case opening is sealed with a sealing resin such as epoxy resin, or a sealing rubber is inserted and sealed by caulking. is there.

The solid electrolytic capacitor having the above-mentioned structure uses a solid electrolyte having a low specific resistance of not more than 10 Ω · cm as an electrolyte as compared with a conventional electrolytic solution having a specific resistance of 100 Ω · cm. It is a capacitor with excellent ESR characteristics.

By the way, as the solid electrolyte, manganese dioxide having a specific resistance of 10 Ωcm is conventionally used, and thereafter, a TCNQ complex having a specific resistance of 10 Ωcm or less, polypyrrole, a polymer of a thiophene dielectric, etc. Although solid electrolytic capacitors using organic semiconductors have been put to practical use, as the driving frequency of MPUs has been further increased,
Furthermore, there is a demand for capacitors that are small in size, have a large capacity, and have low ESR characteristics. According to the study by the inventors, the effect of reducing the ESR of the capacitor is not sufficient in such a solid electrolytic capacitor, although the specific resistance of the electrolyte is low.

[0007]

As described above, the ES of the capacitor cannot be improved by only improving the solid electrolyte by lowering the specific resistance.
There is a problem in that there is a limit in reducing R and it is difficult to further reduce ESR.

The present invention has been made to solve the above problems, and provides a solid electrolytic capacitor using an organic semiconductor having a low specific resistance, which realizes further low ESR. is there.

[0009]

In order to solve the above-mentioned problems, as a result of diligent studies by the inventor, in a solid electrolytic capacitor using an organic semiconductor having a low specific resistance, the resistance value per unit area of the electrode foil is That is, it has been found that the ESR of the capacitor can be further reduced by optimizing the resistance value between the end faces of the regular square electrode foil (hereinafter referred to as foil resistivity) and the foil width and foil area.

That is, although the ESR of the capacitor can be reduced by using the organic semiconductor as described above, there is a limit to the reduction of the electrolyte, and when the level of the ESR reduced by the organic semiconductor is reached as described above. The electrode resistivity, foil width, and foil area of the electrode foil are the ESR of the capacitor.
It was found to contribute to. Therefore, by optimizing these values, the ESR of the capacitor can be significantly reduced.

According to the present invention, by using an organic semiconductor having a specific resistance of 10 Ω · cm or less, and by using the following electrode foil, the low specific resistance characteristics of the organic semiconductor can be maximized and a low ESR which has never been achieved. This is a solid electrolytic capacitor with characteristics. The electrode foil used in the present invention has a foil resistivity of 0.15 to 0.6 mΩ, more preferably 0.17.
Is about 0.45 mΩ. By using the electrode foil in this range, the resistance of the electrode foil is reduced and the ESR is reduced. If it is less than this range, the effect of reducing ESR is small, and if it exceeds this range, the reduction rate of ESR is lowered.

The foil width is 3 to 16 mm, preferably 5 to 14 mm. Below this range, even if the foil resistivity is reduced, the contribution of the resistance component of the electrolyte becomes large and the ESR is not reduced. If it exceeds this range, the ESR reduction rate decreases, the length of the capacitor element increases, the impregnation property of the organic semiconductor decreases, and the electrolyte retention property decreases.
ESR rises.

The foil area must be 300 mm ² or more, preferably 500 mm ² or more. If it is less than this range, the area of the electrode foil and the electrolyte is small and the resistance value is not reduced, so that the ESR is not reduced. Since the solid electrolytic capacitor of the present invention uses the capacitor element formed by winding the electrode foil via the separator, the electrode foil having a long foil length can be used. This allows a sufficient foil area to be obtained and the ESR to be reduced.

As described above, the foil resistivity of the electrode foil is 0.15 to 0.6 mΩ, and more preferably 0.17 to 0.6 mΩ.
Residual core thickness is 50-170μ to make 0.45mΩ
m, more preferably 60 to 150 μm of electrode foil can be used.

Usually, the electrode foil for electrolytic capacitors is prepared as follows. First, the surface portion of the aluminum foil is roughened in an etching solution composed of an aqueous solution of hydrochloric acid or the like to form hole-shaped etching pits. Thus, a so-called etching foil is formed and this etching foil is used as a cathode foil. Then, as the anode foil, the etching foil is further energized in a chemical conversion solution containing a phosphoric acid aqueous solution or the like to form an oxide film on the surface thereof to form an anode foil.
Therefore, such an electrode foil is composed of an aluminum portion which is not etched (hereinafter referred to as a residual core) and an etched portion, and in the case of an anode foil, an oxide film portion, and the thickness of the residual core is 50 to 170 μm, more preferably 60 ~
By setting the thickness to 150 μm, the foil resistivity is 0.15 to
0.6 mΩ, more preferably 0.17 to 0.45 mΩ
Can be

Further, in the above-mentioned solid electrolytic capacitor, when the foil thickness becomes large, the foil length must be made small in order to house the capacitor element in a predetermined case size. Therefore, the ESR increases, so that the foil thickness is 200 μm. The following is preferably 150 μm or less. When the thickness of the etching pit is 10 μm or more, the adhesion of the organic semiconductor layer to the electrode foil is improved and the ESR is reduced,
The thickness of the etching pit is preferably 10 μm or more. Therefore, the foil thickness of the electrode foil is 50 to 200 μm.
m, preferably 60 to 150 μm.

When a TCNQ complex is used as the organic semiconductor, the ESR required in recent years is low E of 4 to 6 mΩ.
SR can be realized.

Further, even if a conductive polymer is used as the organic semiconductor, the ESR can obtain characteristics equal to or higher than those of the TCNQ complex. As a conductive polymer (Chemical formula 1)
It is preferable to use the polymer of the thiophene dielectric material shown by since it improves the heat resistance of the capacitor. Of these, 3,4-ethylenedioxythiophene, which has good reactivity and electric characteristics, is preferable.

[Chemical 1] Here, X is O or S, when X is O, A is alkylene or polyoxyalkylene, and when at least one of X is S, A is alkylene, polyoxyalkylene,
A substituted alkylene, a substituted polyoxyalkylene, where
The substituents are an alkyl group, an alkenyl group and an alkoxy group.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described. An aluminum foil is roughened by AC etching in an etching solution composed of an aqueous solution of hydrochloric acid or the like to form an etching foil, which is used as a cathode foil. further,
In order to form a dielectric film on the surface of this etching foil, it is subjected to chemical conversion in a chemical conversion solution such as a phosphoric acid aqueous solution and used as an anode foil. In the present invention, the foil resistance per unit area of such an electrode foil is 0.15 to 0.6 m.
Ω, and more preferably 0.17 to 0.45 mΩ.

Here, the thickness of the non-etched portion of the aluminum foil, that is, the residual core portion, is set to 50 at the time of etching.
It is possible to obtain an electrode foil having the foil resistivity as described above by setting the thickness to ˜170 μm, and more preferably 60 to 150 μm.

Then, these electrode foils are cut to form electrode foils for electrolytic capacitors, and the foil width at this time is 3 to 1.
It is 6 mm, preferably 5 to 14 mm. Further, the foil area needs to be 300 mm ² or more, preferably 500 mm ² or more.

The foil thickness of the electrode foil is 50 to 200 μm.
m, preferably 60 to 150 μm.

Further, it is preferable to form a chemical conversion film of 0.1 to 10 V, preferably 0.3 to 5 V on the cathode foil because ESR is reduced and high temperature life characteristics are improved.

Further, it is preferable to form a layer made of a metal compound or metal having a low oxidizing property such as titanium nitride or titanium on the surface of the cathode foil because the capacitance increases. Here, it is more preferable to form a chemical conversion film on the cathode foil and to form a layer made of the above-mentioned metal or metal compound having low oxidizing property on the chemical conversion film.

An anode lead terminal and a cathode lead terminal are attached to the above anode foil and cathode foil, and they are wound via a separator. After that, a voltage is applied in the chemical conversion liquid to repair the dielectric oxide film damaged in the previous steps. The effects of the present invention can be obtained by using the above-described anode foil of the present invention and the conventional cathode foil, the conventional anode foil and the cathode foil of the present invention, and both the anode foil and the cathode foil of the present invention can be obtained. The maximum effect can be obtained by using.

Here, as the separator, manila paper,
Kraft paper, glass separator, etc., or vinylon,
A nonwoven fabric made of synthetic fiber such as polyester, and a porous separator can be used.

When the lead-out terminal is attached to the electrode foil, the use of the electrode foil having an increased conductive portion according to the present invention lowers the contact resistance at the joint between the electrode foil and the lead-out terminal. The effect of reducing the ESR of the electrolytic capacitor is increased.

Next, the case of using a TCNQ complex as an organic semiconductor will be described. The TCNQ complex is put in a cylindrical metal case made of aluminum and placed on a heated flat heater to melt and liquefy the TCNQ complex. The preheated capacitor element is impregnated therein and the metal case is immersed in cooling water to cool and solidify the TCNQ complex. Further, an epoxy resin is injected into the case and cured by heating in a high temperature atmosphere, and then a heating voltage is applied and aging is performed to manufacture a solid electrolytic capacitor.

As an organic semiconductor, poly- which is a polymer of 3,4-ethylenedioxythiophene (EDT).
(3,4-ethylenedioxythiophene) (PEDT)
In the case of using, the capacitor element is immersed in a mixed solution prepared by mixing EDT, an oxidizing agent and a predetermined solvent to cause a polymerization reaction of EDT in the capacitor element to form an organic semiconductor layer made of PEDT. . Then, this capacitor element is inserted into a metal case, a sealing rubber is inserted into the opening end portion, and a caulking process is performed to seal the solid electrolytic capacitor.

As the EDT, an EDT monomer can be used, but the EDT and the volatile solvent are 1: 0.
It is also possible to use a monomer solution mixed in a volume ratio of ˜1: 3. As the volatile solvent, hydrocarbons such as pentane, ethers such as tetrahydrofuran, esters such as ethyl formate, ketones such as acetone, alcohols such as methanol, nitrogen compounds such as acetonitrile and the like can be used. However, among them, methanol, ethanol, acetone and the like are preferable. Also, as the oxidant,
Ferric p-toluenesulfonate dissolved in butanol,
Periodic acid or an aqueous solution of iodic acid can be used, and the concentration of the oxidizing agent in the solvent is preferably 40 to 55 wt%. If it is less than this range, the ESR increases, and if it exceeds this range, the capacitance decreases.

The mixing ratio of EDT and the oxidizing agent (excluding the solvent) is preferably in the range of 1: 0.9 to 1: 2.2 by weight, and 1: 1.3 to 1: 2.0. Is more preferable.
ESR rises outside this range. The reason is considered to be as follows. That is, when the amount of the oxidant with respect to the monomer is too large, the amount of the impregnated monomer relatively decreases, so that the amount of PEDT formed decreases and the ESR increases. On the other hand, if the amount of the oxidizing agent is too small, the oxidizing agent necessary for polymerizing the monomer will be insufficient,
The amount of PEDT formed decreases and the ESR increases.

In addition to the EDT described here, a polymerizable monomer can be used. As the polymerizable monomer,
Aniline, pyrrole, furan, acetylene or their derivatives, which are oxidatively polymerized by a predetermined oxidizing agent,
Any material can be applied as long as it forms a conductive polymer.

The solid electrolytic capacitor of the present invention as described above is a solid electrolytic capacitor using an organic semiconductor having a specific resistance of 10 Ω · cm or less.
Can be reduced to 80 to 60% of the conventional value, and an unprecedented ESR of 6 mΩ or less can be obtained. On the other hand, in the conventional electrolytic capacitors using the electrolytic solution having a specific resistance of several tens of Ω · cm and the solid electrolytic capacitors using the solid electrolyte of 10's Ω · cm, the ESR is 30 to
It is extremely high at about 50 mΩ, and even when the electrode foil of the present invention is used, it is reduced only to about 90% at the maximum, and the effect of greatly reducing ESR as in the present invention cannot be obtained.

[0034]

EXAMPLES Specific examples of the solid electrolytic capacitor of the present invention will be described below. Example 1 An example using a TCNQ complex as an organic semiconductor will be described. The aluminum foil is roughened by AC etching and further subjected to chemical conversion for forming a dielectric oxide film, to produce the anode foil of the present invention. In addition, aluminum foil is also roughened by AC etching,
A chemical conversion film is formed on the surface to prepare a cathode foil. A separator made of manila paper is interposed between the anode foil and the cathode foil, and an anode lead terminal and a cathode lead terminal are attached and wound at arbitrary positions. After that, a voltage is applied in the chemical conversion liquid to restore the chemical conversion of the dielectric oxide film damaged by the winding.

On the other hand, the TCNQ complex is put in a cylindrical metal case made of aluminum and placed on a flat heater heated to about 280 ° C. to melt and liquefy the TCNQ complex. The capacitor element preheated to about 300 ° C. is impregnated therein, and the metal case is immediately immersed in cooling water to solidify the TCNQ complex by cooling. Further, a required amount of epoxy resin was injected into the case and heat-cured in a high temperature atmosphere, and then a rated voltage was applied between terminals at 125 ° C. for 1 hour to perform aging to obtain a solid electrolytic capacitor.

Then, Examples 1-1 to 1-3 of the solid electrolytic capacitors thus formed and Comparative Examples 1-1 to 1-1
In Table 4, the foil resistivity, foil width, foil area, residual core thickness and ESR of each solid electrolytic capacitor used for No. 4 are shown. In addition, the foil thicknesses of Examples 1-1 to 1-3 were 110 μm, 115 μm, and 140 μm, respectively.

[0037]

[Table 1]

As is clear from Table 1, the solid electrolytic capacitors of Examples 1-1 to 1-3 of the present invention have an ESR of 6 or less.
It shows a low value of mΩ or less, which shows the effect of the present invention. On the other hand, Comparative Example 1-1 having a foil resistivity of 0.6 mΩ or more had a foil area of 1950 mm ² and Examples 1-1 to 1-1.
Despite being larger than -3, the value is as high as 8.1 mΩ. In addition, Comparative Example 1-2 in which the foil width is 3 mm or less,
The foil resistivity is 0.22 mΩ, which is lower than those of Examples 1-1 to 1-3, and the foil area is 2100 mm ² and Examples 1-1 to 1-1.
Although it is larger than 1-3, it shows a high value of 9.8 mΩ. Comparative Example 1 in which the foil width exceeds 16 mm
The ESR of 3 is as large as 7.1 mΩ. Furthermore, the foil area is 3
In Comparative Example 1-4 of 00 mm ² or less, the foil resistivity is 0.17 m.
Ω and E smaller than those of Examples 1-1 to 1-3, E
SR is large at 11.2 mΩ.

Further, a capacitor element formed in the same manner as in Example 1-1 is impregnated with an electrolytic solution having a low specific resistance characteristic as Comparative Example 1-5, and Comparative Example 1
Electrolytic capacitors each having manganese dioxide formed as -6 were prepared. The electrolytic solution used in Comparative Example 1-5 was γ-
Butyrolactone 75 parts, ethyl phthalate-dimethyl-imidazolinium 25 parts. The obtained ESRs show high values of 52 mΩ and 17 mΩ, respectively, and even if the electrode foil of the present invention is used, the effect of the present invention cannot be obtained unless an organic semiconductor having low specific resistance characteristics is used as an electrolyte. found.

Example 2 Next, PE was used as an organic semiconductor.
An example using DT will be described. A non-woven fabric made of vinylon fiber was used as a separator, a layer made of titanium nitride was formed on the chemical conversion film on the cathode foil, and a capacitor element was formed in the same manner as in Example 1 except for the above, and restoration chemical conversion was performed. Then, the formation of the organic semiconductor was performed as follows.
In a cup-shaped container, EDT and 45% ferric paratoluenesulfonate butanol solution were added at a weight ratio of 1 :.
A mixture was prepared by injecting the solution so that the mixture would be 0.8. Then, the capacitor element was immersed in the mixed solution for 10 seconds.
And it heated at 120 degreeC for 1 hour, the polymerization reaction of PEDT was generated in the capacitor element, and the organic-semiconductor layer was formed. Then, this capacitor element was inserted into a bottomed cylindrical aluminum case, the opening was rubber-sealed by drawing, and aging was performed to prepare a solid electrolytic capacitor. The foil resistivities, foil widths, foil areas, residual core thicknesses and ESRs of the respective solid electrolytic capacitors of the example and comparative examples used here are shown in (Table 2). In addition, Example 2-1 to
The foil thicknesses of 2-3 are 115 μm, 110 μm, and 13 respectively.
It was 5 μm.

[0041]

[Table 2]

As can be seen from Table 2, the results of Example 2 are similar to those of Example 1, and the effect of the present invention is clear.

[0043]

As described above, according to the present invention, there is provided a solid electrolytic capacitor in which an organic semiconductor is formed in a capacitor element formed by winding an anode foil and a cathode foil with a separator interposed therebetween. Provide a solid electrolytic capacitor having unprecedented low ESR characteristics by setting the foil resistivity per unit area of the cathode foil to 0.15 to 0.6 mΩ, the foil width to 3 to 16 mm, and the foil area to 300 mm ² or more. can do.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ichidai Saegusa             One day at 1-167 Higashi Ome, Ome City, Tokyo             Inside this Chemi-Con Corporation (72) Inventor Kazuhiro Hatanaka             One day at 1-167 Higashi Ome, Ome City, Tokyo             Inside this Chemi-Con Corporation

Claims (5)

[Claims] 1. A solid electrolytic capacitor in which an organic semiconductor is formed in a capacitor element formed by winding an anode foil and a cathode foil with a separator interposed therebetween, wherein the foil resistance per unit area of the anode foil or the cathode foil is 0. 15-0.6mΩ, foil width 3
A solid electrolytic capacitor having a thickness of ˜16 mm and a foil area of 300 mm ² or more. 2. The residual core thickness of the anode foil or cathode foil is 50.
The solid electrolytic capacitor according to claim 2, wherein the solid electrolytic capacitor has a thickness of ˜180 μm. 3. The foil thickness of the anode foil or cathode foil is 50 to 50.
It is 250 micrometers, The solid electrolytic capacitor of Claim 1 or 2 characterized by the above-mentioned. 4. The solid electrolytic capacitor according to claim 1, wherein a TCNQ complex is used as the organic semiconductor. 5. The solid electrolytic capacitor according to claim 1, wherein a conductive polymer is used as the organic semiconductor.