JPH03109712A - Solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve high temperature durability by providing a metal layer on a capacitor element having a conductive polymer layer formed by oxidation polymerization of aromatic compound on the surface of a dielectric material made of an oxide film of a film forming metal and a conductor layer formed on the polymer layer. CONSTITUTION:A metal layer 3 is formed on a capacitor element having a conductive polymer layer formed by oxidation polymerization of aromatic compound on the surface of a dielectric material made of an oxide film of film forming metal 1 and a conductor layer 2 formed thereon. Accordingly, transmission of oxygen in the air through a sheathing material is suppressed, and a reduction in conductivity due to oxidation of conductive polymer is eliminated. Thus, high temperature durability is improved.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is applicable to electrolytic capacitors using a conductive polymer compound as a solid electrolyte, and particularly has excellent high-temperature durability and
anδ (tangent of loss angle) and ESR (equivalent series resistance)
Regarding solid electrolytic capacitors with little change in

〔overview〕

The present invention includes a capacitor element having a conductive polymer layer formed by oxidative polymerization of an aromatic compound on the surface of a dielectric material made of an oxide film of a film-forming metal, and a conductor layer formed thereon. In this solid electrolytic capacitor, high-temperature durability is improved by providing a metal layer on the capacitor element.

[Conventional technology]

In recent years, advances in science and technology have required electronic devices to be smaller and more reliable.Coupled with the development of digital devices, the field of capacitors has also become more reliable, with good characteristics up to the high frequency range. Demand for superior large capacity capacitors is increasing. In response to such demands, capacitors using manganese dioxide (MnO2) or tetracyanoquinodimethane (TCNQ) complexes as solid electrolytes have been developed. These capacitors have excellent reliability because the electrolyte is solid, but the conductivity of the solid electrolyte is still insufficient and the ESR is large.
Another drawback was that the leakage current was large.

In order to improve these problems in capacitor characteristics, solid electrolytic capacitors have been proposed in which an aromatic conductive polymer such as polypyrrole having high electrical conductivity is used as a solid electrolyte. The solid electrolytic capacitors using these conductive polymers as solid electrolytes are packaged with epoxy resin or silicone resin.

[Problem to be solved by the invention]

However, in a solid electrolytic capacitor provided with the above-mentioned exterior, the conductive polymer tends to be oxidized in the air at high temperatures, and the ESR of the capacitor tends to increase, resulting in problems in high-temperature durability.

An object of the present invention is to provide a solid electrolytic capacitor that has excellent high-temperature durability and good frequency characteristics by solving the above-mentioned problems.

[Means to solve the problem]

As a result of various studies to solve the above-mentioned problems, the present inventors discovered that by adopting a specific packaging method, a solid electrolytic capacitor with excellent high-temperature durability could be obtained, and the present invention was achieved.

That is, the present invention provides a capacitor element having a conductive polymer layer formed by oxidative polymerization of an aromatic compound on the surface of a dielectric consisting of an oxide film of a film-forming metal, and a conductor layer formed thereon. A solid electrolytic capacitor comprising: a metal layer formed on the capacitor element;

The figure is a schematic cross-sectional view showing the configuration of an example of a solid electrolytic capacitor of the present invention. A film-forming metal 1 having a conductive polymer layer formed on its surface, a conductive layer 2, a metal layer 3, and an exterior material 4
, an anode lead 5 , and a cathode lead 6 .

The metal used for the metal layer is not particularly limited, but
For operational reasons, solder is preferable.

Various methods can be used to form the metal layer in the present invention. Examples include a method in which a capacitor element provided with a conductive layer is immersed in molten solder, and then the solder adhering to the surface is cooled and solidified to form a solder layer, and a method in which metal is vapor-deposited on the capacitor element.

The conductive polymer in the present invention is one obtained by polymerizing an aromatic compound by electrolytic oxidation, chemical oxidation, or a combination thereof. Examples of the aromatic compound include virol, thiophene,
Examples include benzene, aniline, phenylenediamine, methylpyronohemethylthiophene, and hexylthiophene.

The capacitor element of the present invention is one in which a conductive polymer layer is formed by oxidative polymerization of an aromatic compound on a film-forming metal surface having a dielectric oxide film, and then a conductor layer is formed, or a cathode lead is formed from the conductor layer. The material taken out is shown, and various commonly thought methods can be used to take out the cathode. For example, using silver paste to take out the cathode from the conductor layer, or after forming the metal layer,
Examples include a method of taking out the cathode from the metal layer using silver paste or solder.

The conductor layer in the present invention is made by solidifying carbon powder or metal powder such as silver, nickel, and copper alone;
These powders and polymers are mixed and solidified, and the mixture of these powders and polymers is solidified. It is desirable that the polymer to be mixed has a melting point of 180° C. or higher.

Examples of the film-forming metal in the present invention include kuntal, aluminum, and niobium, with tantalum and aluminum being preferred. For example, in the case of tantalum, it is used in the form of a fine sintered body, and in the case of aluminum, it is used in the form of a porous molded body such as etched foil, and the shape and size thereof are not particularly limited.

The solid electrolytic capacitor obtained by the present invention does not allow oxygen in the air to pass through the metal layer at high temperatures and oxidize the conductive polymer, compared to conventional solid electrolytic capacitors using conductive polymers. , has the advantage of excellent high-temperature resistance.

[Effect]

By forming a metal layer on the capacitor element of the present invention, 1'i! Because it suppresses permeation through the raw exterior material and does not cause a decrease in conductivity due to oxidation of the conductive polymer, ESR does not increase in capacitor high-temperature durability tests and high-temperature durability improves.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited only to these Examples.

Example 1 A cylindrical fine tantalum powder sintered pellet (porosity 50%) with a diameter of 5 ml and a height of 5 ml was anodized at 100 V in an aqueous nitric acid solution, and after washing and drying, the pellet was treated with 10% dodecylbenzenesulfone. Iron acid (II[)
Soak in methanol solution and dry. After that, 25℃
Expose to saturated steam of pyrrole to polymerize pyrrole.

After polymerization for 5 hours, pellets in which the voids were filled with polypyrrole were obtained.

Next, the leads were pulled out from the polypyrrole on the surface of the pellet using silver paste (Unix
(230°C) for 5 seconds, then pulled out and cooled to solidify. The capacitor was then completed by covering the solder-coated capacitor element with epoxy resin.

The resulting capacitor has a capacitance of 2.10 pF at 120 Hz and a tan δ of 0.01.
The ESR at LMflz was 60 mΩ. 150
The capacitance of the capacitor after being left at ℃ for 500 hours is
2.05 p F at 120 Hz, tan δ
was 0.011, and the ESR at IMHz was 63 mΩ, indicating excellent high-temperature durability.

Example 2 Etched aluminum foil was heated in ammonium borate for 10 minutes.
After electrolytic oxidation at 0 V, washing and drying, the aluminum foil is immersed in a 10% iron dodecylbenzenesulfonate (■) methanol solution and dried. Thereafter, it is exposed to saturated steam of pyrrole at 25° C. to polymerize pyrrole. After polymerization for 3 hours, aluminum foil whose surface was covered with polypyrrole was obtained.

Next, leads are drawn out from the polypyrrole on the surface of the aluminum foil using silver paste, and the capacitor element is immersed in molten solder (230° C.) for 5 seconds, pulled out, and cooled to solidify. The capacitor was then completed by covering the solder-coated capacitor element with epoxy resin.

The resulting capacitor has a capacitance of 0.80 pF at 120 Hz, a 5tan δ of 0.009, and an I
The ESR at MHz was 40 mΩ. 150℃
The capacitance of the capacitor after being left for 500 hours is 1
At 20 Hz, it was 0.78 pF, tan δ was 0.010, and ESR at I MHz was 43 mΩ, indicating excellent high-temperature durability.

Example 3 Etched aluminum foil was heated in ammonium borate for 10 minutes.
After electrolytic oxidation at 0 V, washing and drying, the aluminum foil is immersed in a 10% iron dodecylbenzenesulfonate (■) methanol solution and dried. Thereafter, it is exposed to saturated steam of pyrrole at 25° C. to polymerize pyrrole. After polymerization for 3 hours, aluminum foil whose surface was covered with polypyrrole was obtained.

Next, the leads are pulled out from the polypyrrole on the surface of this aluminum foil using silver paste (Silcoat GL-10 manufactured by Fukuda Metal Foil Co., Ltd.), and the capacitor element is soldered with molten solder (230
℃) for 5 seconds, then pulled out and cooled to solidify. The capacitor was then completed by covering the solder-coated capacitor element with epoxy resin.

The obtained capacitor has a capacitance of 0.80 μF Stan δ of 0.009 at 120 Hz, and I MH
The ESR at z was 40 mΩ. 50 at 150℃
The capacitance of the capacitor after being left for 0 hours is 120f.
1z, tan δ was 0.79, tan δ was 0.010, and ESR at I MHz was 42 mΩ, indicating excellent high-temperature durability.

Example 4 In the same manner as in Example 2, an aluminum foil whose surface was covered with polypyrrole was obtained. A silver paste is coated on the polypyrrole on the surface of the etched aluminum foil, and the capacitor element is immersed in molten solder (230° C.) for 5 seconds, pulled out, and cooled to solidify. A cathode lead was taken out from the soldered surface of this capacitor element using solder, and the capacitor was completed by covering it with epoxy resin.

The resulting capacitor had a capacitance of 0.80 pF at 120 Hz, a tan δ of 0.009, and an ESR of 40 mΩ at I MHz. 15
The capacitance of the capacitor after being left at 0℃ for 500 hours is 0.77μF at 120Hz, and tanδ is o
, oiote, IMH2l;l: ESR is 43'm
Ω, and had excellent high-temperature durability.

Comparative Example 1 Leads were pulled out from the polypyrrole on the surface of the pellet filled with polypyrrole obtained in the same manner as in Example 1 using silver paste, and the capacitor element was packaged with epoxy resin to complete a capacitor.

The resulting capacitor has a capacitance of 2.1011 F at 120 Hz, a tan δ of 0.01,
The ESR at I MHz was 40 mΩ. 15
The capacitance of the capacitor after being left at 0°C for 500 hours is 1.10 t-t F at 120 tlz,
The tan δ was 0.50, the ESR at IM)Iz was 900 mΩ, and the high temperature durability was poor.

Comparative Example 2 In the same manner as in Example 2, an aluminum foil whose surface was covered with polypyrrole was obtained. Leads were drawn out from the polypyrrole on the surface of the etched aluminum foil using silver paste, and the capacitor element was packaged with epoxy resin to complete the capacitor.

The resulting capacitor has a capacitance of 0.80 μF1 tan δ of 0.009 at 120 Hz, and I M
The ESR at Hz was 35 mΩ. 5 at 150℃
The capacitance of the capacitor after being left for 00 hours is 120
0.27 μF at Hz, tan δ is 0.5
0, the ESR at 1 MHz was 900 mΩ, and the high temperature durability was poor.

〔Effect of the invention〕

As described above, according to the present invention, a large capacity solid electrolytic capacitor having excellent high-temperature durability and good frequency characteristics can be easily manufactured, and its effects are significant.

[Brief explanation of drawings]

The figure is a schematic cross-sectional view showing an example of the solid electrolytic capacitor of the present invention. DESCRIPTION OF SYMBOLS 1... Film forming metal, 2... Conductor layer, 3... Metal layer, 4... Exterior material, 5... Anode lead, 6...
cathode lead.

Claims (2)

[Claims] 1. A solid electrolytic capacitor comprising a capacitor element having a conductive polymer layer formed by oxidative polymerization of an aromatic compound on the surface of a dielectric consisting of an oxide film of a film-forming metal, and a conductor layer formed thereon. A solid electrolytic capacitor comprising a metal layer formed on the capacitor element. 2. The solid electrolytic capacitor according to claim 1, wherein the metal layer is solder.