JP2003309041A - Solid electrolytic capacitors - Google Patents

Abstract

(57) [Problem] To provide a solid electrolytic capacitor capable of preventing occurrence of short circuit and stabilizing electric characteristics. SOLUTION: An anode foil 11 having a dielectric oxide film formed on a surface obtained by roughening an aluminum foil and a cathode foil 13 having a roughened aluminum foil are wound through a separator 12 so that a core portion is elliptical. Capacitor element 16 connected to the anode foil 11 and the cathode foil 13 of the capacitor element 16, and each led out from the vicinity of the center line on the short side with respect to the center line on the long side of the elliptical shape. The anode lead 14 and the cathode lead 15 for external derivation are connected by the configuration including the anode lead 14 and the cathode lead 15 for use with the conductive polymer formed between the anode foil 11 and the cathode foil 13. The curvature of the portions of the anode foil 11 and the cathode foil 13 thus increased increases, short-circuiting can be suppressed, leakage current can be reduced, and electric characteristics can be stabilized.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid electrolytic capacitor having a conductive polymer formed between an anode foil and a cathode foil.

[0002]

2. Description of the Related Art With the increase in frequency of electronic equipment, there has been a demand for electrolytic capacitors, which are electronic components, to be large-capacity capacitors having more excellent impedance characteristics in the high frequency range than ever before. Recently, in order to reduce the impedance in the high frequency region, solid electrolytic capacitors using a conductive polymer with high electrical conductivity as an electrolyte have been studied, and in order to meet the demand for large capacity, electrode A solid electrolytic capacitor using a conductive polymer in a wound form (a structure in which an anode foil and a cathode foil are wound with a separator interposed between them) that is structurally easy to increase in capacity as compared with a case where foils are laminated. Consideration is being made.

In the above wound solid electrolytic capacitor, if a conductive polymer is to be formed between electrodes of a capacitor element by electrolytic polymerization, it is difficult to fill the conductive polymer up to the center of the capacitor element. Therefore, in most cases, the study of forming a conductive polymer by chemical polymerization has become the mainstream.

[0004]

However, the above-mentioned wound-type solid electrolytic capacitor can reduce impedance, which is an electrical characteristic, but has a self-repair ability as compared with a capacitor using a conventional electrolytic solution. Because it is scarce,
There is a problem that it is difficult to reduce the leakage current.

Further, among solid electrolytic capacitors, miniaturized products (case diameter 4 to 16 mm) are externally derived because the ratio of the short side to the long side of the winding core diameter is equal when forming the capacitor element. However, there is a problem in that the curvature of the portion where the anode lead and the cathode lead are connected to the anode foil and the cathode foil is reduced, the leakage current is increased, and the occurrence of short circuit is increased.

The present invention solves the above-mentioned conventional problems,
It is an object of the present invention to provide a small-sized solid electrolytic capacitor capable of preventing occurrence of short circuit, reducing leakage current, and stabilizing electric characteristics.

[0007]

In order to solve the above problems, the invention according to claim 1 of the present invention provides an anode foil and an aluminum foil each having a dielectric oxide film formed on a roughened surface of the aluminum foil. A capacitor element in which the core part is wound into an elliptical shape with a roughened cathode foil and a separator interposed therebetween, and the capacitor element is connected to the anode foil and the cathode foil, respectively, and the center line on the long side of the elliptical shape. A configuration including an anode lead and a cathode lead for external extraction that are respectively drawn out from the vicinity of the center line on the short side with the conductive polymer formed between the anode foil and the cathode foil. Therefore, the curvature of the anode foil and the cathode foil to which the anode lead and the cathode lead for external extraction are connected becomes large, the occurrence of short circuit can be suppressed, the leakage current can be reduced, and the electrical characteristics can be stabilized. If you can Cormorant having an effect.

According to the second aspect of the invention, in particular, the ratio of the short side to the long side of the elliptical shape of the winding core is 1: 1.1 to 1.9.

If the ratio of the short side to the long side of the core of the capacitor element is less than 1: 1.1, the curvature rate of the anode foil and the cathode foil connected to the external lead anode lead and the cathode lead is reduced. If the ratio of the short side to the long side of the winding core exceeds 1: 1.9, the radius of curvature on the short side becomes smaller, and the leakage current becomes larger at that portion, which is preferable. Absent. The preferred short side to long side ratio is 1: 1.2.
~ 1.6.

According to a third aspect of the present invention, in particular, the conductive polymer is composed of at least one of polypyrrole, polyethylenedioxythiophene, polyaniline and its derivatives or compounds thereof, and a solid electrolytic capacitor. It has the effect that the impedance of can be reduced.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, specific embodiments of the present invention will be described.

(First Embodiment) FIGS. 1 (a) and 1 (b) show the structure of a capacitor element according to the first embodiment.
(A) is a partially expanded perspective view of a capacitor element, and (b) is a top plan view of the capacitor element. The capacitor element 16 is formed by forming a dielectric oxide film (not shown) having a withstand voltage of 30 V on a roughened aluminum foil surface as the anode foil 11 and connecting the anode lead 14 for external extraction. As the cathode foil 13, an aluminum foil having a roughened surface (not shown) and connected to a cathode lead 15 for external extraction was used.

Further, the anode foil 11 and the cathode foil 13 are connected to a separator 12 (thickness 5) made of polyethylene terephthalate.
0 μm, weighed 25 g / m ² ) is interposed, and the winding core is wound into an elliptical shape.

Further, the anode lead 14 for leading out to the outside is provided.
The cathode lead 15 is connected to the anode foil 11 and the cathode foil 13 so as to face each other near the center of the elliptical long side.

In the above capacitor element 16, when the anode foil 11 and the cathode foil 13 are wound, the ratio of the short side to the long side of the elliptical shape of the winding core is 1: 1.1, 1: 1.2, and 1. : 1.
4, 1: 1.6, 1: 1.8, 1: 1.9, 1: 2.0
Was prepared (the length of the anode foil or the cathode foil is all the same size).

Next, the capacitor element 16 contains 1 part of ethylenedioxythiophene which is a heterocyclic monomer, 2 parts of ferric p-toluenesulfonate which is an oxidizing agent, and 4 parts of n-butanol which is a polymerization solvent. After being immersed in the polymerization solution and pulled up, a conductive polymer of polyethylenedioxythiophene (not shown) was formed between the electrode foils by standing at 85 ° C. for 60 minutes.

Next, the capacitor element 16 is composed of a resin-vulcanized butyl rubber sealing material (30 parts of butyl rubber polymer, 20 parts of carbon, and 50 parts of inorganic filler, sealing material hardness: 7).
0IRHD [International Rubber Hardness Unit]) and then enclosed in an aluminum outer case (case diameter 8 mm), and then the anode lead 14 and the cathode lead 15 for external extraction are exposed from the sealing material and the opening of the outer case Were sealed by curling treatment to produce solid electrolytic capacitors.

(Second Embodiment) In the first embodiment, the ratio of the short side to the long side of the elliptical shape of the winding core of the capacitor element 16 is set to 1: 1.4 and the conductive polymer is formed by the pyrrole monomer. The operation of immersing the capacitor element 16 in the solution, bringing the capacitor element 16 into contact with the oxidant solution and drying is repeated three times, and subsequently, the dielectric oxide film is repaired with an aqueous acetic acid solution to form a conductive polymer of polypyrrole. A solid electrolytic capacitor was produced in the same manner as in Embodiment 1 except that the above was formed.

The pyrrole monomer solution was prepared by dissolving pyrrole in an aqueous solution containing 10% by weight of ethylene glycol in an amount of 1.0 mol / l and sodium alkylnaphthalenesulfonate as a dopant in an amount of 0.25 mol / l. The oxidant solution used was an aqueous solution containing 10 wt% of ethylene glycol and 0.750 mol / l of iron (III) sulfate as an oxidant,
Sodium alkyl naphthalene sulfonate as a dopant is 0.05 mol / l, and sulfuric acid is 0.7 as an additive.
What was prepared by dissolving so as to be 5 mol / l was used.

(Third Embodiment) In the first embodiment, the ratio of the short side to the long side of the elliptical shape of the winding core of the capacitor element 16 is set to 1: 1.4, and the conductive polymer is formed by ultrasonic waves. After immersing the capacitor element 16 in a treated 1.0% aqueous solution of polyethylenedioxythiophene polystyrene sulfonic acid and pulling it up, the capacitor element 16 was dried at 150 ° C. for 5 minutes to form polyethylene on the dielectric oxide film, the cathode foil and the separator. A dioxythiophene polystyrene sulfonic acid layer is formed, and then the capacitor element 16 is mixed with 1 part of ethylenedioxythiophene, which is a heterocyclic monomer, 2 parts of ferric p-toluenesulfonate, which is an oxidizing agent, and a polymerization solvent. After dipping it in a solution containing 4 parts of a certain n-butanol, pulling it up, and leaving it at 85 ° C. for 60 minutes, polyethylenedioxythiof Except for forming a down of the conductive polymer was produced a solid electrolytic capacitor in the same manner as in the first embodiment.

(Comparative Example 1) In the first embodiment,
A solid electrolytic capacitor was produced in the same manner as in Embodiment 1 except that the shape of the core of the capacitor element 16 was made into a perfect circle.

(Comparative Example 2) In the first embodiment,
The shape of the core of the capacitor element 16 is made into a perfect circle, and γ-butyrolactone is used as a solvent instead of forming the conductive polymer,
A solid electrolytic capacitor was produced in the same manner as in Embodiment 1 except that a driving electrolytic solution containing a quaternary ammonium salt as a solute was used.

Embodiments 1 to 3 and Comparative Examples 1 and 2
After applying the rated voltage at 105 ° C for 1000 hours, the capacitance (measurement frequency 1
20 Hz), ESR (measurement frequency 100 kHz), leakage current, and short circuit occurrence status are shown in Table 1 below.

The number of test pieces is 50 in each case,
The capacitance and leakage current values are shown as the average values of the samples excluding the short-circuited products.

[0025]

[Table 1]

As is clear from Table 1, in the solid electrolytic capacitor of Embodiment 1, the ratio of the short side to the long side of the winding core of the capacitor element is in the range of 1: 1.1 to 1: 1.9. The solid electrolytic capacitor had a smaller leakage current than the solid electrolytic capacitor of Comparative Example 1 and did not cause short circuit.
This is because the curvature of the portions of the anode foil 11 and the cathode foil 13 to which the anode lead 14 and the cathode lead 15 for external extraction are connected is increased, and the mechanical stress on the anode foil 11 is reduced.

In particular, when the ratio of the short side to the long side of the elliptical shape of the winding core of the capacitor element 16 is 1: 1.2 to 1: 1.6, the leakage current and the ESR characteristic can be further improved. .

As is clear from the solid electrolytic capacitors of Embodiments 2 and 3, the ESR characteristic can be further reduced by changing the structure of the conductive polymer.

Further, even when compared with the electrolytic capacitor using the conventional driving electrolytic solution of Comparative Example 2, the same result can be obtained in the leakage current characteristic. Therefore, the winding core of the capacitor element 16 has an elliptical shape, Further, this is due to the effect that the external lead-out anode lead 14 and the cathode lead 15 connected to the anode foil 11 and the cathode foil 13 of the capacitor element 16 are connected near the center of the long side of the elliptical shape.

The present invention is not limited to the electroconductive polymer used in each of the above-mentioned embodiments, but polypyrrole, polyethylenedioxythiophene, polyaniline and its derivatives or at least one of those compounds.
Any structure may be used as long as it is composed of seeds.

[0031]

As described above, according to the present invention, an anode foil having a dielectric oxide film formed on a roughened surface of an aluminum foil and a cathode foil having a roughened surface of an aluminum foil are wound via a separator to form a core. Has an elliptical wound capacitor element, the anode lead and the cathode lead for external lead connected to the anode foil and cathode foil of this capacitor element are connected near the center of the long side of the ellipse, And by having a configuration in which a conductive polymer is formed between the anode foil and the cathode foil, the curvature of the portion of the anode foil and the cathode foil to which the anode lead for external lead and the cathode lead are connected becomes large. It is possible to obtain a solid electrolytic capacitor with stable electrical characteristics by suppressing the occurrence of short circuit and reducing leakage current, and its industrial value is great.

[Brief description of drawings]

FIG. 1A is a partially developed perspective view showing a configuration of a capacitor element according to a first embodiment of the present invention, and FIG. 1B is an upper plan view of the same capacitor element.

[Explanation of symbols]

11 Anode foil 12 separators 13 cathode foil 14 Anode lead 15 Cathode lead 16 Capacitor element

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takuya Maruta             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (3)

[Claims] 1. A winding core part is wound in an elliptical shape with a separator between an anode foil having a dielectric oxide film formed on a roughened surface of an aluminum foil and a cathode foil having a roughened surface of an aluminum foil with a separator interposed therebetween. A capacitor element and an anode lead and a cathode for external extraction, which are respectively connected to the anode foil and the cathode foil of this capacitor element and are drawn out from the vicinity of the center line on the short side with the center line on the long side of the ellipse sandwiched between A solid electrolytic capacitor comprising a lead and a conductive polymer formed between the anode foil and the cathode foil. 2. The solid electrolytic capacitor according to claim 1, wherein the ratio of the short side to the long side of the elliptical shape of the winding core is 1: 1.1 to 1.9. 3. The solid electrolytic capacitor according to claim 1, wherein the conductive polymer is at least one selected from the group consisting of polypyrrole, polyethylenedioxythiophene, polyaniline and its derivatives or compounds thereof.