JPH03109714A - Solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain excellent high temperature durability and satisfactory frequency characteristic by incorporating a resin layer having 1000cc(STP)/m<2>hr- atm or less of oxygen transmission amount in a sheathing material for sheathing a capacitor element. CONSTITUTION: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, and a sheathing material 4 for sheathing the element are provided. A resin layer 3 having 1000cc(STP)/m<2>hr-atm or less of oxygen transmission amount is contained in the material 4. Thus, oxygen in the air is not transmitted through the material to eliminate oxidation of conductive polymer and reduction in conductivity. Accordingly, excellent high temperature durability and satisfactory frequency characteristic can be obtained.

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 fixed electrolyte.
anδ (tangent of loss angle) and ESR (equivalent series resistance)
Regarding solid electrolytic capacitors with little change in

〔overview〕

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 material made of an oxide film of a film-forming metal, and a conductive layer formed thereon as an exterior material. In the solid electrolytic capacitor packaged with a solid electrolytic capacitor, the package material includes a resin layer having an oxygen permeation rate of 1000 cc (STP)/m"hr-atm or less, which provides excellent high temperature durability and excellent tan δ and ESR ( This is a solid electrolytic capacitor with little change in equivalent series resistance (equivalent series resistance).

[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 high-capacity capacitors is increasing.

In response to these demands, manganese dioxide (Mn
Capacitors using solid electrolytes such as L) and tetracyanoquinodimethane (TCNQ) complexes have been developed.

These capacitors have excellent reliability because the electrolyte is solid, but the solid electrolyte still has insufficient electrical conductivity, high ESR, and large leakage current.

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. As a method of packaging solid electrolytic capacitors using conductive polymers as solid electrolytes, a method of packaging the capacitor element with epoxy resin or silicone resin is used.

[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 having excellent high-temperature durability and good frequency characteristics by solving the above-mentioned problems.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present inventors have conducted various studies and found that by employing a specific exterior material, a solid electrolytic capacitor with excellent high-temperature durability can be obtained, leading to the present invention.

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. In a solid electrolytic capacitor, the oxygen permeation amount in the exterior material is 1000 cc (STP)/
It is characterized by including a resin layer having a thickness of m''hr-at+n or less.

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

The inventors investigated various exterior materials for capacitor elements, and found that the amount of oxygen permeation through the resin layer in the exterior material was 1000 cc (
STP) If it exceeds 7m2hr-atrn, the high temperature will cause
s+: The conductive polymer is oxidized at 150°C, 1
It was found that the ESR (IMHz) increased five times as much as the initial value at 0 hours. On the other hand, if the amount of oxygen permeation through the resin layer in the exterior material is less than the above, the time required to increase ESH will be long (
, 1Qcc (STP) 7m2hr-atm is 1000
reach the time. Gas permeation measurement methods such as the pressure method and the isobaric electrode method are known as methods for measuring the oxygen permeation amount, and in the present invention, the pressure method is used for measurement.

The resin used for the resin layer in the exterior material is not particularly limited as long as it satisfies the above conditions, but in particular, polyesternope polyamide resin having an aromatic ring in the main chain,
Electron-conjugated aromatic polymers obtained by polymerizing monomers such as virol, thiophene, furan, benzene, or derivatives thereof are desirable. Examples of these resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, liquid crystal polymers represented by cocondensates of hydroxybenzoic acid, terephthalic acid, and ethylene glycol, polyparaphenylene terephthalamide, and polymethaxylene diamine adipate. , polypyrrole, polythiophene, polymethylthiophene, polyhexylthiophene, polyfuran, polyparaphenylene, polyaniline, and polyphenylenediamine.

Various methods can be used to form the resin layer in the present invention.

For example, a capacitor element with a conductive layer or a capacitor element molded with epoxy or silicone resin is immersed in a solution of polyester, polyamide, and electronically conjugated aromatic polymer dissolved in a solvent, and then the solvent is evaporated and dried. Is there a method for forming a resin layer on the capacitor element, or immersing a capacitor element with a conductor layer or a capacitor element molded with epoxy or silicone resin in an oxidizer solution? Examples include a method of forming an electronically conjugated aromatic polymer layer by oxidative polymerization by contacting with a monomer such as pyrrole, thiophene, furan, benzene or a derivative thereof after lt.

In the capacitor element of the present invention, after forming a conductive polymer layer formed by oxidative polymerization of an aromatic compound and then a conductive layer on a film-forming metal surface having a dielectric oxide film,
The cathode lead wire is shown taken out from the conductor layer.
Various commonly thought methods can be used to take out the cathode.

Film-forming metals in the present invention include tantalum, aluminum, niobium, and the like, 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 an externally 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 exterior resin 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 durability.

[Effect]

The resin layer of the present invention, that is, the oxygen permeation rate is 1000cc (
STP) By providing a resin layer of 7 m"hr-atm or less in the exterior material, oxygen in the air will not permeate through the exterior material, oxidize the conductive polymer, and reduce the conductivity. ESR does not increase in high-temperature durability tests of capacitors, 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 body pellet with a diameter of 5 mm and a height of 5 mm (porosity: 50%) was anodized in an aqueous nitric acid solution at 100 V, and after washing and drying, the pellet was
Iron(III) dodecylbenzenesulfonate Soak in methanol solution and dry. Thereafter, it is exposed to saturated steam of pyrrole at 25° C. to polymerize pyrrole. After polymerization for 5 hours, pellets in which the voids were filled with polypyrrole were obtained.

Next, use silver paste to pull out the leads from the polypyrrole on the surface of this pellet, and make this capacitor element
% Iron dodecylbenzenesulfonate (■) Soak in methanol solution and dry. Thereafter, it is exposed to saturated steam of pyrrole at 25° C. to polymerize pyrrole. Furthermore, the polypyrrole-coated capacitor element was wrapped with epoxy resin as the outer packaging material to complete the capacitor. The oxygen permeability of the polypyrrole formed in this exterior material is 100
cc(STP)/m'hr-atrn.

The resulting capacitor has a capacitance of 4.60 at 12011z. ! jFStanδ is 0,01, and I M
The ESR at Hz was 40 mΩ. 5 at 150℃
The capacitance of the capacitor after being left for 00 hours is 120
At Hz, tan δ was 4.55 t-t F and tan δ was 0.012, and ESR at I MHz was 45 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 poly-pyrrole was obtained.

Next, leads are drawn out from the polypyrrole on the surface of the etched aluminum foil using silver paste, and the capacitor element is immersed in a 40% methanol solution of iron(I) dodecylbenzenesulfonate and dried. Thereafter, it is exposed to saturated steam of pyrrole at 25° C. to polymerize pyrrole. The capacitor was then completed by wrapping the polypyrrole-coated capacitor element with epoxy resin. The oxygen permeability of the polypyrrole formed in this exterior material is 100cc.
(STP)/+n2hr-atm.

The resulting capacitor had a capacitance of 0.80 t-t F at 1201(z), a tan δ of 0.009, and an ESR of 35 mΩ at I MHz.

The capacitance of the capacitor after being left at 150℃ for 500 hours is 0.76μFs' tan δ at 12Ko2.
is 0.011, and the ESR at IM)Iz is 5(1m
Ω, and had excellent high-temperature durability.

Example 3 In the same manner as in Example 2, an aluminum foil whose surface was covered with polypyrrole was obtained. Leads are pulled out from the polypyrrole on the surface of this etched aluminum foil using silver paste.
This capacitor element is immersed in a chloroform solution of 10% poly-3-n-hexylthiophene, and the solvent is evaporated to dryness to form a poly-3-n-hexylthiophene layer on the surface of the capacitor element. The capacitor was then completed by covering it with epoxy resin. PoI formed in this exterior material
The oxygen permeation amount of the J-3-n-hexylthiophene layer is 4
00cc (STP) 7m"hr-atm The resulting capacitor has a capacitance of 0.80μF, tan δ of 0.009, and IMHz
The ESR at Ni was 35 mΩ. 500 at 150℃
The capacitance of the capacitor after standing for a period of time is 120Hz.
0.70 μFStan δ is 0.015 and I
The ESR in M)lz was 100 mΩ, and the product had 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. Pull out the lead for silver paste from the polypyrrole on the surface of this etched aluminum foil.
This capacitor element is immersed in a hexafluoroisopropanol solution of 10% aromatic polyester liquid crystal polymer, and the solvent is evaporated to dryness to form a liquid crystal polymer layer on the surface of the capacitor element. Furthermore, the capacitor baby was coated with a liquid crystal polymer and then covered with epoxy resin to complete the capacitor. The oxygen permeation rate of the liquid crystal polymer layer formed in this exterior material is 7Qcc (STP) 7m2hr-atm
Met.

The resulting capacitor has a capacitance of 0 at 120Hz.
．． 80 pF, tan δ is 0.009,
The ESR at I MHz was 35 mΩ. 150
The capacitance of the capacitor after being left at ℃ for 500 hours is
At 120Hz, 0.76 p F 5tan δ is 0
．． 011, the ESR at I MHz was 40 mΩ, and it had excellent high-temperature durability.

Example 5 In the same manner as in Example 2, an aluminum foil whose surface was covered with polypyrrole was obtained. Leads are pulled out from the polypyrrole on the surface of this etched aluminum foil using silver paste.
This capacitor element is coated with epoxy resin, and
A liquid crystal polymer layer is formed on the surface of the epoxy-molded capacitor element by immersing it in a hexafluoroinpropateur solution of 0% aromatic polyester liquid crystal polymer and evaporating the solvent to dryness. The capacitor element thus obtained was packaged with epoxy resin to complete a capacitor.

The amount of oxygen permeation through the liquid crystal polymer layer formed in this exterior material was 70 cc (STP)/m'hr-atm.

The resulting capacitor has a capacitance of 0 at 120Hz.
．． 80 pF, tan δ is 0.009,
The ESR at I MHz was 35 mΩ. 150
The capacitance of the capacitor after being left at ℃ for 500 hours is
Wipe at 120Hz, 0.78 pF, tan δ
is 0.010 and the ESR at I MHz is 38 mΩ
It had excellent high-temperature durability.

Comparative Example 1 Leads were pulled out using silver paste from the polypyrrole on the surface of the pellet filled with polypyrrole obtained in the same manner as in Example 1, and the capacitor element was covered with epoxy resin using an acid anhydride curing agent. Completed the capacitor. The oxygen permeation rate of this exterior material is 2000cc (STP
)/m2hr-atm.

The resulting capacitor has a capacitance ff at 120Hz
14.60 pF, tan δ was 0.01, and ESR at 1 MHz was 40 mΩ. 150
The capacitance of the capacitor after being left at ℃ for 500 hours is
Wipe at 120Hz and 3.1OAL F, tanδ
is 0.050 and ES at I MHz, R is 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 are pulled out from the polypyrrole on the surface of this etched aluminum foil using silver paste.
This capacitor element was packaged with an epoxy resin containing an imidazole curing agent to complete the capacitor. The oxygen permeation rate of this exterior material is 3000cc (STP)/r
It was n'hr-atm.

The resulting capacitor has a capacitance at 120Hz! 0
．． 80 , ZJ F , tan δ was 0.001, and the ESR at I MHz was 35 mΩ. 1
The capacitance of the capacitor after being left at 50°C for 500 hours is 0.27 pF, tan
δ is 0.50, 11. ESR at lHz is 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 the structure of an example of the solid electrolytic capacitor of the present invention. DESCRIPTION OF SYMBOLS 1...Film forming metal, 2...Conductor layer, 3...Resin layer, 4...Outer exterior material, 5...Anode lead, 6...
...Cathode IJ + de.

Claims (3)

[Claims] 1. A capacitor element has 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, and this capacitor element. What is claimed is: 1. A solid electrolytic capacitor equipped with an exterior packaging material, wherein the exterior packaging material includes a resin layer having an oxygen permeation rate of 1000 cc (STP)/m^2 hr-atm or less. 2. The solid according to claim 1, wherein the resin layer is composed of an electronically conjugated aromatic polymer obtained by oxidative polymerization of a monomer selected from pyrrole, thiophene, furan, benzene, or a derivative thereof. Electrolytic capacitor. 3. The solid electrolytic capacitor according to claim 1, wherein the resin layer is a polyester resin or a polyamide resin having an aromatic hydrocarbon ring in its main chain.