JP3180358B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, with the progress of electronics,
There is a demand for miniaturization and weight reduction of devices, and miniaturization and chip formation are also required for capacitors, and attention is being paid to improvement in performance such as low impedance and high capacity in a high frequency region. If a solid electrolyte is used as the electrolyte to improve the performance of the capacitor, it is possible to achieve good frequency characteristics in a high-frequency region and temperature characteristics over a wide range.
A solid electrolytic capacitor using a CNQ complex or the like has been developed.

In recent years, a method using a conductive polymer as a solid electrolyte has been proposed (JP-A-60-244017).
In this case, it is necessary to form a solid electrolyte layer on the dielectric oxide film without breaking the film, and when the chemical conversion film area is large, it grows uniformly. I can't let it. There is also a disadvantage that it is not suitable for mass production. On the other hand, a method of manufacturing a solid electrolytic capacitor using a five-membered heterocyclic conductive polymer that has been rendered soluble by introducing a substituent has also been proposed.
For example, in JP-A-63-80517, a solution of a soluble conductive polymer is applied and dried to form a conductive polymer layer on a dielectric film, and then a solid electrolyte layer is formed by vapor-phase doping. Let me. Japanese Patent Application Laid-Open No. 2-66921
In the publication, a conductive polymer is deposited on a dielectric oxide film by dip coating on a saturated solution of a conductive polymer synthesized by electrolytic polymerization, and the resultant is electrolytically polymerized as an anode to form a solid electrolyte layer. Let me.

[0004]

However, in the former case, the method of vapor phase doping has a problem that the conductivity is low and the dopant is apt to escape, so that the stability is lacking. There is a problem that the process is complicated. By the way, as a method for doping a conductive polymer, there is a method in which a conductive polymer is brought into contact with a dopant in a gas phase or a liquid phase. For example, Synthetic Metals (Syntheti Metals)
cMetals) vol.28 (1989) ppC427-C43
As in 4, de by immersing the film of polyalkylthiophene nitromethane solution of ferric chloride - in any way to ping, conductivity is low (<10 ^0), also decreases with time, lack of stability. On the other hand, a method of obtaining a doping film by mixing a solution of a conductive polymer and a solution of a dopant and distilling off the solvent,
Conductivity is high (10 ^2), a high stability is obtained even at high temperatures. The present invention makes use of this method,
An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor capable of simplifying a capacitor manufacturing process and improving the performance of the obtained solid electrolytic capacitor.

[0005]

Means for Solving the Problems The present inventors have proposed non-dope
The solid electrolyte layer can be easily formed directly on the dielectric oxide film layer in one step by dip-coating the metal foil on which the dielectric oxide film has been formed in a solution in which the soluble polymer and the dopant in the dissolved state are dissolved. In addition, the inventors have found that the obtained solid electrolyte layer has high conductivity and high stability, and has reached the present invention. That is, the present invention provides an undoped state on the surface of a dielectric oxide film layer formed by anodic oxidation.
A method for producing a solid electrolytic capacitor, comprising forming a solid electrolyte layer using a solution in which a soluble polymer and a dopant are dissolved .

The solid electrolytic capacitor formed according to the present invention comprises an anode foil, a dielectric oxide layer, a conductive polymer layer, a graphite paste layer, a silver paste layer, and a cathode. The dielectric oxide film forming metal used in the present invention may be any metal having a valve action,
For example, aluminum or tantalum is used. The soluble conductive polymer used in the present invention may be any as long as it is soluble in a solvent.

[0007]

Embedded image

Wherein R ¹ and R ² are a hydrogen atom, an alkyl group, an alkoxyl group or an aryl group (R ¹ and R ² may have a cyclic structure), and X is —O—, —S -,-Se
-, -Te- or -NR ³ (R ³ is a hydrogen atom, an alkyl group, an aryl group or an alkyl aryl group). ]
Polymers or copolymers containing at least one kind of monomer repeating unit represented by the formula (1) are preferred.

The dopant used in the present invention includes:
Any solvent can be used as long as it is soluble in a solvent, for example, halogens such as iodine, bromine and bromine iodide, iron trichloride, arsenic pentafluoride, antimony pentafluoride, silicon tetrafluoride, phosphorus pentachloride, phosphorus pentafluoride , Aluminum chloride, molybdenum chloride, etc .; protic acids such as sulfuric acid and nitric acid; benzenesulfonates such as sodium benzenesulfonate and sodium p-toluenesulfonate; and derivatives thereof, but are not limited thereto. The solvent used in the present invention may be any solvent that dissolves a conductive polymer or a dopant, such as chloroform, dichloromethane,
Examples thereof include, but are not limited to, chlorine-based solvents such as carbon tetrachloride, aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene, tetrahydrofuran, and the like, and a mixed solvent thereof. Dip coating is performed by mixing a solution containing a soluble conductive polymer and a solution containing a dopant, dipping the metal foil on which a dielectric oxide film is formed several times into this solution, and drying the solution. Is 0.3 mol / l or less, preferably 0.1 to 0.2 mol / l in the case of a soluble conductive polymer solution, and 0.1 mol / l or less, preferably in the case of a dopant solution. 0.01 ~
0.05 mol / l is suitable.

[0010]

According to the present invention, a metal foil having a valve action, in which a dielectric oxide film is formed by a chemical conversion treatment, is prepared by dip-coating a solution containing a soluble conductive polymer and a dopant synthesized and purified by chemical oxidation polymerization. In this way, the conductive polymer layer doped in one step can be easily formed on the dielectric oxide film, which simplifies the manufacturing process of the solid electrolytic capacitor and reduces the size and capacity of the solid electrolytic capacitor. And higher performance.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to poly (3-octylthiophene) (hereinafter referred to as POT) and POT and poly (3-methylthiophene) (hereinafter referred to as PMT).
The present invention is not limited to the following examples unless it exceeds the gist of the present invention. Example 1 16.5 g of iron trichloride (FeCl ₃ ) was dried in 200 ml of chloroform at 100 ° C. for 1 hour under reduced pressure.
1 mmol) was added thereto, and with stirring, 5 g of 3-octylthiophene was slowly added dropwise thereto, followed by stirring at room temperature for 2 hours. When the reaction solution was added to 1000 ml of methanol, a precipitate insoluble in methanol was obtained. This was filtered by suction to obtain a crude polymer. The method for purifying the polymer is shown below. First, methanol and acetone were extracted with a Soxhlet extractor to remove excess FeCl ₃ . Then, chloroform extraction was performed, and the solvent was distilled off to obtain 4 g of a solvent-soluble poly (3-octylthiophene). The molecular weight of this polymer was measured by gel permeation chromatography, and the weight average molecular weight (M _w ) was 150,000 in terms of polystyrene. Conductivity measurement was performed as follows. POT and FeCl ₃ in a molar ratio of 1: 0.2
(20 mol% doping), each chloroform solution was prepared, mixed, and the solvent was distilled off to obtain a film. The electrical conductivity of this film was measured by a four-point needle method, and was 40 S / cm. Further, even after being left at room temperature for 30 days, the conductivity was hardly reduced.

FIG. 1 is a sectional view of the internal structure of a solid electrolytic capacitor according to this embodiment. POT 0.035g
(0.18 mmol) in 1.5 ml of chloroform solution and 0.0059 g (0.018 mmol) of FeCl ₃ in 1 ml of chloroform solution, and a chemical conversion treatment was applied to the mixed solution to form a dielectric oxide film 2 on the surface. The formed anode foil 1 is dipped several times and dried to obtain a solid electrolyte layer 3.
Was formed. A graphite paste and a silver paste are applied to the surface of the solid electrolyte layer 3 to form a graphite layer 4 and a silver paste layer 5, respectively. The cathode 6 is taken out and packaged with an epoxy resin to produce a capacitor. did. Various characteristics of this capacitor were measured, and the results are shown in Table 1.

[0013]

[Table 1]

Example 2 A mixture of 3-octylthiophene and 3-methylthiophene in a molar ratio of 1: 1 was used as a monomer, and the same operation as in Example 1 was carried out to synthesize a copolymer. ,
After purification, a capacitor was prepared. This POT-P
Elemental analysis confirmed that the MT copolymer had a composition ratio of 1: 1. M _w is 4000 in terms of polystyrene.
The conductivity of the film doped with FeCl ₃ was 110 S / cm at room temperature, and almost no decrease in the conductivity was observed even after standing at room temperature for 30 days. The characteristics of the capacitor were almost the same as those of the first embodiment. In this embodiment, a method for manufacturing a solid electrolytic capacitor using POT and a copolymer of POT and PMT as a soluble conductive polymer has been described. Similar effects can be obtained by using a polymer. Further, although an example in which FeCl ₃ is used as a dopant has been described, similar effects can be obtained by using other dopants.

[0015]

As described above, according to the method of the present invention, it is possible to easily form a solid electrolyte layer having high conductivity and high stability on a dielectric oxide film. As a result, the manufacturing process of the solid electrolytic capacitor is simplified, and the size and capacity of the solid electrolytic capacitor can be increased and the performance thereof can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an internal structure of an example of a solid electrolytic capacitor obtained by a method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Anode 2 Dielectric oxide film 3 Solid electrolyte layer 4 Graphite layer 5 Silver paste layer 6 Cathode

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Narika Suzuki 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-2-309616 (JP, A) JP-A-Hei 4-245613 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 9/028

Claims (3)

(57) [Claims] An undoped soluble polymer and a dopa are provided on the surface of a dielectric oxide film layer formed by anodic oxidation.
A method for producing a solid electrolytic capacitor, comprising forming a solid electrolyte layer using a solution in which a solid electrolyte is dissolved . 2. The soluble polymer is represented by the general formula 1: [Wherein, R ¹ and R ² represent a hydrogen atom, an alkyl group, an alkoxyl group or an aryl group (R ¹ and R ² may form a cyclic structure), and X represents —O—, —S—, and —Se— , -T
e- or -NR ³ (R ³ is a hydrogen atom, an alkyl group, an aryl group or an alkylaryl group). The method for producing a solid electrolytic capacitor according to claim 1, wherein the polymer or the copolymer contains at least one kind of a repeating unit of a monomer represented by the following formula: 3. The method according to claim 1, wherein the dopant is a Lewis acid, a halogen, a protonic acid, a benzenesulfonate or a derivative thereof.