JP2001332457A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having superior leakage current characteristic, low ESR and high reliability. SOLUTION: The solid electrolytic capacitor, composed of a capacitor element having a solid electrolyte layer, outer electrodes and an exterior covering resin with the exterior covering resin having a modulus of bending elasticity of 1,200-1,400 kg/mm2 and a thermal expansion coefficient of 0.8-1.7×10-5/ deg.C at glass transition temperature or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exterior resin for a solid electrolytic capacitor.

[0002]

2. Description of the Related Art Solid electrolytic capacitors have a multilayer structure in which materials having different coefficients of thermal expansion are stacked. Stress is generated between the materials due to the difference in the coefficient of thermal expansion of the materials. This stress causes peeling of the bonding surface between the materials and damage of the dielectric oxide film, which adversely affects capacitor characteristics such as equivalent series resistance (ESR) and leakage current.

[0003] For the above reasons, the exterior resin used as the sealing material of the solid electrolytic capacitor is required to have a low stress, but often contradicts the improvement of properties such as moldability and moisture resistance.

[0004] For example, to reduce stress, there are three methods of reducing the coefficient of thermal expansion, increasing the glass transition temperature, and decreasing the elastic modulus. But,
When the content of an inorganic filler typified by silica is increased in order to reduce the coefficient of thermal expansion, the viscosity in a molten state is increased and the moldability is deteriorated. In addition, the modulus of elasticity increases, and cracks easily occur. To increase the glass transition temperature, there are methods such as using a highly active catalyst to increase the crosslink density of the resin and using a polyfunctional resin.However, such a method tends to increase the elastic modulus. is there. To reduce the elastic modulus, there are two methods of changing the composition of the resin or reducing the elasticity of the constituent material itself. However, there is a problem that the moldability and the hygroscopicity are reduced.

For the above reasons, it has been difficult to prevent the deterioration of the characteristics of the solid electrolytic capacitor by improving the characteristics of the exterior resin.

[0006]

Because of the above-mentioned problems, a solid electrolytic capacitor using a resin as a sealing material, which can reduce stress without deteriorating various properties such as moldability and moisture resistance, has been developed. Had been requested.

[0007]

According to the present invention, a flexural modulus is from 1200 to 1400 kg / mm ² and a coefficient of thermal expansion below the glass transition temperature is from 0.8 to 1.7 × 10 ⁻⁵ / ° C.
By using this resin as an exterior material, stress during assembly and mounting can be reduced, and a solid electrolytic capacitor having excellent leakage current characteristics, low ESR and high reliability can be provided. That is, in a solid electrolytic capacitor including a capacitor element having a solid electrolyte layer formed thereon, an external electrode, and an exterior resin, the flexural modulus of the exterior resin is 1200.
A ~1400kg / mm ^2, and the thermal expansion coefficient of less than a glass transition temperature of the solid electrolytic capacitor, which is a 0.8~1.7 × ^{10 -5} / ℃.

[0008] The solid electrolytic capacitor is characterized in that the solid electrolyte layer is a functional polymer.

As the material of the above functional polymer, aniline, thiophene, pyrrole or derivatives thereof can be mentioned.

[0010] As the aniline derivative described above,
Having an aniline skeleton, at least one of an alkyl group, a phenyl group, an alkoxy group, an ester group, and a thioether group;
An aniline derivative having a species as a substituent can be given.

Then, the above-mentioned thiophene derivative is added at the 3-, 3- and 4-positions or S-position of the thiophene skeleton.
Examples include a thiophene derivative having at least one of a hydroxyl group, an acetyl group, a carboxyl group, an alkyl group, and an alkoxy group as a substituent, or 3,4-alkylenedioxythiophene.

Further, the above-mentioned pyrrole derivative has a hydroxyl group at the 3-, 3- and 4-positions or the N-position of the pyrrole skeleton.
Examples include pyrrole derivatives having at least one of an acetyl group, a carboxyl group, an alkyl group, and an alkoxy group as a substituent.

The structure of the solid electrolyte layer may be a functional polymer formed by chemical polymerization, a functional polymer formed by chemical polymerization followed by electrolytic polymerization, or a functional polymer formed by chemical polymerization, electrolytic polymerization and chemical polymerization in this order. Molecules may be mentioned. The functional polymers may be the same or different materials.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The flexural modulus of the exterior resin is 1200
１1400 kg / mm ² and a coefficient of thermal expansion below the glass transition temperature of 0.8 to 1.7 × 10 ⁻⁵ / ° C. to reduce stress during assembly and mounting, and to reduce leakage current. A solid electrolytic capacitor having excellent characteristics, low ESR and high reliability can be provided.

[0015]

EXAMPLE After a dielectric oxide film made of tantalum pentoxide was formed on the surface of an anode body having a tantalum wire standing upright, a polypyrrole layer was formed by chemical polymerization as a conductive polymer layer to be a solid electrolyte layer. Next, a carbon paste layer and a silver paste layer were formed to form a capacitor element. Further, a tantalum wire serving as an anode was welded to a lead frame, and a solid electrolyte serving as a cathode was bonded to the lead frame with a conductive silver paste. After the capacitor element and the lead frame in the above state are covered with an epoxy resin based on the resin characteristics shown in Table 1 by the transfer molding method, the lead is bent along the side surface of the resin to obtain 6.3 V / 1.
100 solid electrolytic capacitors of 50 μF each were produced.

Examples 1 to 3 and Comparative Examples 1 to 3
The ESR at 0 kHz and the leakage current one minute after the application of the rated voltage were measured, and a heat resistance test was performed three times through a reflow furnace having a temperature profile capable of keeping at 240 ° C. for 10 seconds, and the same measurement was performed. The results are shown in Table 1.

[0017]

[Table 1]

As in Comparative Example 1, the flexural modulus was 1400
kg / mm ² and the coefficient of thermal expansion is 1.7 × 10 ⁻⁵ /
If the temperature exceeds ℃, a large stress is applied to the element, and the leakage current value is particularly deteriorated. Next, as in Comparative Example 2, when the flexural modulus is set to less than 1200 kg / mm ² in order to reduce the stress, the formability deteriorates, the appearance defect rate increases, and the characteristics deteriorate. Also, as in Comparative Example 3, when the coefficient of thermal expansion below the glass transition temperature is less than 0.8 × 10 ⁻⁵ / ° C., the moldability deteriorates, the appearance defect rate increases, and the characteristics deteriorate. As compared with these comparative examples, Examples 1 to 3 of the present invention have a low appearance defect rate, and the leakage current value at the initial stage, after any heat resistance test,
It can be seen that the ESR is small and the capacitor has excellent characteristics.

FIG. 1 shows a characteristic diagram of the flexural modulus, the appearance defect rate, and the leakage current when the coefficient of thermal expansion at the glass transition temperature or lower of the exterior resin is 1.7 × 10 ⁻⁵ / ° C. FIG.
It can be seen from the above that the flexural modulus is optimally 1200 to 1400 kg / mm ² .

The flexural modulus of the exterior resin is 1300 k.
FIG. 2 shows a characteristic diagram of a coefficient of thermal expansion equal to or lower than the glass transition temperature when g / mm ² , poor appearance, and leakage current.
From FIG. 2, the coefficient of thermal expansion is 0.8 to 1.7 × 10 ⁻⁵ / ° C.
Is found to be optimal.

In this embodiment, a functional polymer which is weak against stress is used as the solid electrolyte. However, manganese dioxide is not limited to the pyrrole of the embodiment as the solid electrolyte and the functional polymer material. When the derivative of was used, a result equivalent to that of the example was obtained.

[0022]

The solid electrolytic capacitor of the present invention has a bending elasticity.
The power factor is 1200 to 1400 kg / mm ²And glass
The coefficient of thermal expansion below the transition temperature is 0.8 to 1.7 × 10
^-5/ C resin is used for the exterior material,
Leakage current characteristics, low ESR and high reliability can be obtained.
It is industrially useful.

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[Procedure amendment]

[Submission date] June 12, 2000 (2006.1.
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of a flexural modulus, a defective appearance rate, and a leakage current.

FIG. 2 is a characteristic diagram showing a coefficient of thermal expansion below a glass transition temperature, a defective appearance rate, and a leakage current.

Claims (2)

[Claims] 1. A solid electrolytic capacitor comprising a capacitor element on which a solid electrolyte layer is formed, an external electrode and an exterior resin, wherein the exterior resin has a flexural modulus of 1200 to 1400 kg /
mm ^2, and a solid electrolytic capacitor characterized in that the thermal expansion coefficient of less than a glass transition temperature of 0.8~1.7 × ^{10 -5} / ℃. 2. A solid electrolytic capacitor according to claim 1, wherein the solid electrolyte layer is a functional polymer.