JPH06151261A - Solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a solid-state electrolytic capacitor excellent in electrical properties, migration resistance, and mass productivity after it is subjected to a moisture-proof treatment, by a method wherein a cathode layer or/and conductive adhesive agent are made to contain organic binder, solvent, silver conductive filter, and a specific amount of boron powder. CONSTITUTION:An anode of valve action metal is subjected to a chemical conversion treatment for the formation of a dielectric layer 2, and a semiconductor electrolytic layer 3 and a carbon layer 4 are successively formed thereon. This element is dipped into conductive adhesive agent diluted by solvent to form a cathode layer 5. At this point, a cathode layer or/and conductive adhesive agent are made to contain organic binder, solvent, silver conductive filler, and 1 to 10% by weight of baron simplex powder, boron alloy powder or baron intermetallic compound powder. By this setup, a solid-state electrolytic capacitor of this design can be protected against migration and deterioration in electric properties after it is subjected to a moistureproof treatment.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a solid electrolytic capacitor having excellent electrical characteristics after moisture resistance and migration resistance.

[0001]

2. Description of the Related Art In a solid electrolytic capacitor, an anode body made of a metal having a valve action such as tantalum, aluminum or niobium is first subjected to a chemical conversion treatment to form a dielectric layer, and then a semiconductor electrolytic layer, A carbon layer and a cathode layer are sequentially formed. Next, the cathode layer and the cathode lead frame are joined together using a conductive adhesive, the anode body lead leading to the anode body is weld-connected to the anode lead frame, and the outer peripheral surface of the anode body is exteriorly constructed by an exterior resin. .

However, since a conventional silver-based conductive adhesive is used in the conventional cathode layer, the leakage current and tan δ of the solid electrolytic capacitor after the moisture-proof treatment are dependent on the performance of the silver-based conductive adhesive. There are drawbacks such as increase and short circuit failure. That is, when the solid electrolytic capacitor is exposed to a high temperature and high humidity environment, water penetrates through the exterior resin or the interface between the terminal and the exterior resin, the silver of the silver-based conductive adhesive is dissolved and ionized, and it is again The electrical characteristics deteriorate due to the phenomenon of so-called "silver migration" that precipitates. As a method of preventing this migration, silver-based conductive adhesive mixed with chromium powder, manganese powder, indium powder, etc., silver-based conductive adhesive mixed with porous filler, silver-based conductive adhesive It has been proposed to use an epoxy resin having a benzophenone imide group as a binder of the agent, a heat resistant thermoplastic resin, and the like.

[0003]

However, a mixture of silver-based conductive adhesive with manganese powder, porous filler, or the like certainly has the effect of preventing migration, but from the viewpoint of high reliability of electronic parts. Is not yet very satisfactory. Further, the conductive adhesive using a heat-resistant thermoplastic resin as a binder has a better migration preventing effect than the above-mentioned conductive adhesive, but the adhesiveness and the workability of the adhesive itself are very poor, It has a drawback that it is not suitable for mass production of electronic parts.

The present invention has been made in order to solve the above-mentioned drawbacks, and is a solid electrolytic capacitor which is excellent in electric characteristics after moisture-proof treatment, migration resistance, mass productivity, has no short-circuit defect, and has high reliability. Is to provide.

[0005]

Means for Solving the Problems As a result of earnest studies to achieve the above object, the present inventor has found that the above object can be achieved by using an adhesive having a composition described below, and It has been completed.

That is, according to the present invention, a dielectric layer, a semiconductor electrolyte layer, a carbon layer and a cathode layer are sequentially formed on an anode body made of a metal having a valve action, and the cathode layer and the cathode lead frame are made conductive. In a solid electrolytic capacitor which is joined with an adhesive and is packaged with a resin, the cathode layer or the cathode layer and the conductive adhesive are (A) an organic binder and a solvent,
(B) silver-based conductive filler and (C) 1 to 10% by weight of boron-based powder, boron-based alloy powder or boron-based intermetallic compound powder based on the silver-based conductive filler It is a solid electrolytic capacitor.

The present invention will be described in detail below.

The organic binder (A) used in the present invention may be a thermosetting type or a thermoplastic type and is not particularly limited.
Conventionally known epoxy type, phenol type, melamine type, cellulose type, acrylic type, polyimide type and mixed modified resin type of these are used. The modified resin system may be simply melt-mixed, or may be partially bound by heating reaction. If necessary for the reaction, a curing catalyst can be used. For organic binders with low heat resistance, the conductive paste cured film deteriorates under high temperature and high humidity conditions, such as the pressure cooker test at 121 ° C and 2 atm, and not only migration but also short circuit due to the outflow of silver powder itself. Occurs. Therefore, when migration prevention under such severe conditions is required, it is necessary to select a binder having high heat resistance. For example, polyimide-based fat and average number of epoxy groups
A system in which three or more novolac epoxy resins are cured with a phenol resin can be mentioned. Any solvent can be used as long as it can dissolve the resin for the organic binder.
Examples of the solvent include dioxane, hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl cellosolve acetate, butyl carbitol acetate, diethylene glycol diethyl ether, diacetone alcohol, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, γ-butyrolactone, 1 Examples thereof include 1,3-dimethyl-2-imidazolidinone, and these may be used alone or in combination of two or more. These solvents are used for dissolving and mixing the resin for the organic binder in advance before manufacturing the adhesive.

Examples of the (B) silver-based conductive filler used in the present invention include powders having a silver layer on the surface, such as silver powder and silver-plated copper powder. These may be used alone or in combination with copper powder, nickel powder, It can be used by mixing with other conductive powder such as carbon. That is, it is necessary that this silver-based conductive filler contains at least a conductive filler having a silver layer on the surface, such as silver powder or silver-plated copper powder.

Examples of the (C) boron-based metal powder used in the present invention include powders of boron alone, boron and other metals,
For example, it may be an alloy powder with iron, nickel, or the like, or an intermetallic compound powder of boron that is stable in the air at room temperature, for example, a powder of a compound of boron and aluminum, or boron and zirconium. These boron-based metal powders can be used alone or in combination of two or more. The boron-based metal preferably has an average particle size of 15 μm or less. If the average particle size exceeds 15 μm, the paste properties and workability are poor, and the coating film surface of the cured product becomes rough, which is not preferable. The content of the boron-based metal powder is preferably 1 to 10% by weight, more preferably 2 to 7% by weight, based on the silver-based conductive filler. If the compounding ratio is less than 1% by weight, the effect of preventing migration will be reduced, and if it exceeds 10% by weight, the coating film of the cured product will be brittle and weak, and the adhesion to the base material and the electrical conductivity will be reduced, resulting in a paint or adhesive. However, it is not preferable because of its lack of performance.

The conductive adhesive used in the present invention contains an organic binder and a solvent, a silver-based conductive filler, and a boron-based metal powder, but is used in a range not deviating from the object of the present invention and as necessary. A foaming agent, a coupling agent, a fine silica-based powder, and other additives can be added and blended. It is possible to produce a conductive adhesive by thoroughly mixing the above-mentioned components according to a conventional method, further kneading with a three-roll mill, and then defoaming under reduced pressure.

The solid electrolytic capacitor of the present invention is manufactured by using the conductive adhesive thus manufactured in particular. That is, as shown in FIG. 1, an anode body 1 made of a metal having a valve action such as tantalum, aluminum or niobium is subjected to a chemical conversion treatment to form a dielectric layer 2, and then a semiconductor electrolyte layer 3, The carbon layer 4 is sequentially formed. The device is dipped in the conductive adhesive diluted with an appropriate solvent to form the cathode layer 5. Next, the cathode layer 5 and the cathode lead frame 6 are joined together using a conductive adhesive 7, and the anode body lead 8 communicating with the anode body 1 is welded to the anode lead frame 9. After that, the outer peripheral surface is covered with the covering resin 10 by a transfer molding method or a dipping method, and the external lead frame is bent to manufacture a solid electrolytic capacitor.

[0013]

The solid electrolytic capacitor of the present invention is prepared by blending the conductive adhesive used with a boron compound.
When the conductive adhesive is cured or dried in air at 150 to 200 ° C, the boron-based metal powder is oxidized before other conductive powders. As a result, a dense boron oxide film is formed on the surface of the cured conductive adhesive, and as a result, oxidation of the conductive powder is prevented and moisture is prevented from entering the inside of the cured adhesive.
Even if silver is ionized under high temperature and high humidity conditions, boron chemically adsorbs silver ions due to the chemical interaction between silver ions and boron, and migration of silver ions is suppressed by suppressing the outflow of silver ions out of the cured product of the adhesive. Occurrence can be prevented. This makes it possible to prevent the deterioration of the electrical characteristics after the moisture resistance treatment.

[0014]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, "parts" means "parts by weight" unless otherwise specified.

Example 1 100 parts of epoxy resin EOCN103S (manufactured by Nippon Kayaku Co., Ltd.) and 54 parts of bisphenol A novolac resin Praiophen VH-4170 (manufactured by Dainippon Ink and Chemicals, Inc.) A viscous resin was obtained by carrying out a dissolution reaction in 154 parts of diethylene glycol diethyl ether at 100 ° C for 1 hour. To 100 parts of this resin, 1 part of amine complex of boron trifluoride as catalyst, 2.5 parts of silane coupling agent,
215 parts silver powder, Aerosil # 2 as fine silica powder
A conductive filler was manufactured by mixing 3.5 parts of 00 (trade name, manufactured by Nippon Aerozil Co., Ltd.) and 7 parts of boron simple substance powder (average particle size: 5 μm).

Example 2 100 parts of polyparabanic acid, which is a heat-resistant thermoplastic resin, was added to N
-Methylpyrrolidone / diethylene glycol dimethyl ether = 6/4 (weight ratio) 100 in 300 parts of mixed solvent
A dissolution reaction was carried out at ℃ for 2 hours, and a viscous resin was obtained. To 100 parts of this resin, 138 parts of the above mixed solvent, 0.12 part of antifoaming agent, 215 parts of silver powder, and Aerosil # 20 as fine silica powder.
A conductive filler was manufactured by mixing 10.4 parts of 0 (above) and 15 parts of an alloy powder of boron and nickel (average particle size: 10 μm).

Example 3 Polyimide resin AI-10 (manufactured by Amoco, trade name) 1
00 parts was dissolved and reacted in 300 parts of a mixed solvent of N-methylpyrrolidone / diethylene glycol dimethyl ether = 6/4 (weight ratio) at 50 ° C. for 3 hours to obtain a viscous resin.
To 200 parts of this resin, 2.5 parts of silane coupling agent, silver powder
A conductive filler was manufactured by mixing 215 parts, 3.5 parts of Aerosil # 200 (described above), and 10 parts of boron simple substance powder (average particle size 5 μm).

Comparative Example 1 A conductive filler was produced in the same manner as in Example 1 except that the simple substance powder of boron was not added.

Comparative Example 2 A commercially available solvent-type conductive adhesive based on a heat-resistant thermoplastic resin was obtained.

Using the conductive adhesives produced in Examples 1 to 3 and Comparative Examples 1 to 2, a capacitor element was dipped in the conductive adhesive to form a cathode layer, and the anode lead and the anode lead frame were welded and joined. After that, the cathode layer and the cathode lead frame were joined, and the resin was externally coated by a molding method to manufacture a solid electrolytic capacitor. Tan of this solid electrolytic capacitor under high temperature and high humidity environment of 85 ° C and 85% RH
Tests for δ and short circuit failure were conducted, and the results are shown in Table 1. The present invention was excellent in all cases, and the effect of the present invention was confirmed.

[0021]

[Table 1] * 1: 6 V, 15 μF solid electrolytic capacitor high temperature and high humidity (85
Environmental test result at ℃, 85% RH).

[0022]

As is clear from the above description and Table 1, the solid electrolytic capacitor of the present invention has excellent electrical characteristics and adhesiveness even under high temperature and high humidity conditions, and does not exude conductive powder and is migration resistant. It has excellent workability and high reliability.

[Brief description of drawings]

FIG. 1 is a sectional view of a solid electrolytic capacitor of the present invention.

[Explanation of reference numerals] 1 anode body 2 dielectric layer 3 semiconductor electrolyte layer 4 carbon layer 5 cathode layer 6 cathode lead frame 7 conductive adhesive 8 anode body lead 9 anode lead frame 10 exterior resin

Claims (1)

[Claims] 1. An anode body made of a metal having a valve action,
In a solid electrolytic capacitor in which a dielectric layer, a semiconductor electrolyte layer, a carbon layer, and a cathode layer are sequentially formed, a cathode layer and a cathode lead frame are bonded with a conductive adhesive, and which is packaged with a resin, the cathode layer Alternatively, the cathode layer and the conductive adhesive are 1 to the (A) organic binder and solvent, (B) the silver-based conductive filler, and (C) the silver-based conductive filler.
A solid electrolytic capacitor containing 10% by weight of boron simple substance powder, boron-based alloy powder or boron-based intermetallic compound powder.