JP2001023869A - Conductive paste for solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductive paste for a solid electrolytic capacitor which is superior in electrical characteristics after moisture absorption, high volume productivity, and a migration preventing effect. SOLUTION: This is a solid electrolytic capacitor having such a structure that a dielectric layer 2, a semiconductor electrolytic layer 3, a carbon layer 4, and a cathode layer 5 are sequentially formed on an anode body 1 made of a valve action metal, that the layer 5 is connected to a cathode frame 6 through a conductive adhesive 7, and that the whole assembly is resin-sheathed 10. In this case, a material forming the layer 5 or both the layers 5 and 7 is a conductive paste consisting essentially of (A) a modified resin made from (a) an epoxy resin having a skeletal structure of dicyclopentadiene and (b) a phenol resin having a skeletal structure of dicyclopentadiene, (B) a solvent or a monomer, and (C) a conductive filler, and the solid electrolytic capacitor is formed by using such conductive paste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor having excellent electrical properties after moisture absorption and excellent migration resistance.

[0002]

2. Description of the Related Art As shown in FIG. 1, a solid electrolytic capacitor to which the present invention relates is formed by subjecting an anode body 1 made of a metal having a valve action such as tantalum, aluminum, and niobium to a chemical conversion treatment and forming a dielectric layer 2 thereon. After the formation, a semiconductor electrolyte layer 3, a carbon layer 4, and a cathode layer 5 are sequentially formed on the surface thereof, and the cathode layer 5 is adhered and fixed to a cathode lead frame 6 using a conductive adhesive 7, and the anode body is formed. An anode lead 8 communicating with 1 is connected to an anode lead frame 9 by welding, and the outer peripheral surface thereof is formed of an exterior resin 10.

[0003]

However, the conventional cathode layer is formed by a normal silver-based conductive paste, and the performance of the silver-based conductive paste of the cathode layer causes the electric resistance of the solid electrolytic capacitor after moisture absorption. There are disadvantages such as deterioration of characteristics, increase in leakage current and tan δ, and occurrence of short-circuit failure. That is, when the solid electrolytic capacitor is exposed to a high-temperature and high-humidity environment, water penetrates through the body of the exterior resin and the interface between the terminal and the exterior resin, and the silver of the silver-based conductive paste dissolves and ionizes. The electrical characteristics deteriorate due to the occurrence of so-called "silver migration" that precipitates again.

As a method of preventing the deterioration of the electric characteristics due to the migration, a method in which chromium powder, manganese powder, indium powder, or the like is mixed into a silver-based conductive paste used for a cathode layer or a conductive adhesive, a porous filler, or the like is used. Although mixed ones have been proposed, they are not yet satisfactory in terms of high reliability. In addition, there has been proposed a conductive paste in which a heat-resistant thermoplastic resin is used as an organic binder, but the adhesive property and the workability of the paste are extremely poor, which is not suitable for mass production of solid electrolytic capacitors. Was.

In recent years, as electronic devices have processed large amounts of digital information at high clock frequencies,
There has been an increasing demand for high-frequency, low-impedance solid-state electrolytic capacitors, and for conductive pastes used therein, stable high conductivity and improved electrical bonding reliability have come to be required.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks, and to provide a silver-based conductive paste which is excellent in electric properties after moisture absorption, mass productivity, and an effect of preventing migration. An object of the present invention is to provide a solid electrolytic capacitor having high humidity resistance and reliability by using a conductive paste.

[0007]

The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a solid electrolytic capacitor having excellent moisture resistance and reliability has been obtained by using a conductive paste having a composition described later. It has been found that the present invention 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 frame are electrically conductively bonded. In a solid electrolytic capacitor connected by an agent layer and packaged with a resin, the material forming the cathode layer or the cathode layer and the conductive adhesive layer is (A) (a) an epoxy having a dicyclopentadiene skeleton. A conductive paste comprising a resin and (b) a modified resin composed of a phenol resin having a dicyclopentadiene skeleton, (B) a solvent, a monomer or a mixture thereof, and (C) a conductive filler as essential components. And a cathode layer or a cathode layer and a conductive adhesive layer formed by the conductive paste.

Hereinafter, the present invention will be described in detail.

The epoxy resin having a (a) dicyclopentadiene skeleton in the component (A) used in the present invention includes:
For example, EXA7200 (manufactured by Dainippon Ink and Chemicals, Inc.
Product name). Furthermore, other curable epoxy resins, bisphenol A type epoxy resins, novolak type epoxy resins, glycidyl ester type epoxy resins,
It can be used as a mixture with a polyfunctional epoxy resin or the like. In this case, since the present invention aims to improve heat resistance and moisture resistance, it is desirable to use an epoxy resin having an average number of epoxy groups of 3 or more.

The phenol resin having a dicyclopentadiene skeleton (b) in the component (A) used in the present invention includes, for example, DPP-600M (trade name, manufactured by Nippon Petrochemical Co., Ltd.).

The above-mentioned (a) epoxy resin having a dicyclopentadiene skeleton and (b) phenol resin having a dicyclopentadiene skeleton are simply dissolved and mixed in (B) a solvent, a monomer or a mixture thereof described later. Alternatively, if necessary, the reaction may be partially controlled by controlling the heating reaction. In this reaction, a curing catalyst is used as necessary. When other epoxy resins are mixed, the solid content of ((a) an epoxy resin having a dicyclopentadiene skeleton + (b) a phenol resin having a dicyclopentadiene skeleton) is as follows:
(A) It is desirable that the modified resin is blended so as to be contained in a proportion of 40% by weight or more based on the solid content. When the compounding ratio is less than 40% by weight, there is no effect in improving heat resistance and moisture resistance.

It is desirable that these resins are dissolved and mixed in advance with the solvent (B) before the paste is produced.

The solvent (B) and the monomer used in the present invention are:
It dissolves the modified resin (A) and adjusts and improves the working viscosity of the paste. As the solvent, for example, 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 3-dimethyl-2-imidazolidinine and the like, which are used alone or in combination of two or more. Also,
Monomers include n-butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-
Butylphenyl glycidyl ether, glycidyl methacrylate, t-butylphenyl glycidyl ether, diglycidyl ether, (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, butanediol diglycidyl ether, trimethylolpropane triglycidyl ether,
Examples thereof include 1,6-hexanediol diglycidyl ether and the like, and these are used alone or in combination of two or more. Further, a mixture of a solvent and a monomer can be used. When a solvent is used, it is necessary to select a solvent having an appropriate boiling point according to the curing temperature, the curing time, and the working conditions.

Examples of the conductive filler (C) used in the present invention include silver powder, powder having a silver layer on its surface such as silver-coated copper powder, copper powder, nickel powder, and carbon. Are used alone or in combination of two or more. That is, the conductive filler desirably contains at least a conductive filler having a silver layer on its surface, such as silver powder or silver-coated copper powder. The particle shape of the conductive filler is not particularly limited, but preferably has an average particle diameter (D50) of 30 μm or less, and more preferably has an average particle diameter of 5 to 15 μm. If the average particle size exceeds 30 μm, the dispersion in the vehicle becomes poor, and there is a problem in the workability of the paste.

The amount of the conductive filler is not particularly limited. However, when importance is placed on the electrical characteristics, (conductive filler /
(Solid content of modified resin + conductive filler)) is 80 to 80%
It is desirably in the range of 95% by weight.

The conductive paste used in the present invention contains the above-mentioned (A) modified resin, (C) conductive filler and (B) solvent or monomer as essential components. If necessary, a curing catalyst, an antifoaming agent, a coupling agent, and other additives can be added and blended. After sufficiently mixing the above-described components according to a conventional method, a kneading treatment is further performed by a disperse, a kneader, a three-roll mill or the like, followed by defoaming under reduced pressure.

The conductive paste thus obtained is further diluted with an appropriate solvent to adjust the viscosity, and the solid electrolytic capacitor element shown in FIG. 1 is dipped to form the cathode layer 5. Next, the anode lead 8 of the capacitor element is connected to the anode lead frame 9 of the anode terminal by welding, and then the cathode layer 5 and the cathode lead frame 6 are connected with the conductive paste 7 obtained by the above method.

Thereafter, the resin sheathing 10 is performed by a transfer molding method or a dipping method, and the external lead frame is bent to complete a solid electrolytic capacitor.

[0020]

The conductive paste used in the present invention contains an epoxy resin having a dicyclopentadiene skeleton and a phenol resin having a dicyclopentadiene skeleton in a modified resin. The dicyclopentadiene skeleton has a large molecular weight, high rigidity, and large steric hindrance, so it has a high glass transition temperature, a low water absorption, a low dielectric constant, and a low dielectric loss tangent, which were conventionally considered difficult to combine. Can be imparted to the cured product in a well-balanced manner. By using a conductive paste using such a resin as a binder, a solid electrolytic capacitor excellent in impedance characteristics, heat resistance, migration resistance after moisture resistance, and electrical connection reliability can be obtained.

[0021]

Next, the present invention will be described in detail 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 EX of an epoxy resin having a dicyclopentadiene skeleton
A7200 (product name, manufactured by Dainippon Ink and Chemicals, Inc.) 10
0 parts and 76 parts of DPP-600M (trade name, manufactured by Nippon Petrochemical Co., Ltd.) of a phenol resin having a dicyclopentadiene skeleton as a curing agent were subjected to a dissolution reaction in 176 parts of diethylene glycol diethyl ether at 85 ° C. for 1 hour,
A viscous resin was obtained. To 30 parts of the resin, 0.20 part of imidazole 2-ethyl-4-methylimidazole as a curing catalyst, 0.02 part of an additive, 70 parts of silver powder, and 30 parts of silver-coated copper powder were mixed, and further three rolls were prepared. , And deaerated under reduced pressure to produce a conductive paste.

Example 2 EX of an epoxy resin having a dicyclopentadiene skeleton
A7200 (product name, manufactured by Dainippon Ink and Chemicals, Inc.) 60
Parts and 40 parts of an epoxy resin epicoat # 1001 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.), a phenol resin having a dicyclopentadiene skeleton as a curing agent
In a mixed solvent of 80 parts of diethylene glycol diethyl ether and 60 parts of butyl carbitol acetate, 76 parts of PP-600M (trade name, manufactured by Nippon Petrochemical Co., Ltd.) was used.
A dissolution reaction was performed at 1 ° C. for 1 hour to obtain a viscous resin. To 30 parts of this resin was added 2-ethyl-imidazole as a curing catalyst.
0.15 parts of 4-methylimidazole, additive 0.10
Parts and 70 parts of silver powder and 30 parts of silver-coated copper powder,
Further, kneading treatment was performed by three rolls, and deaeration was performed under reduced pressure to produce a conductive paste.

Comparative Example 1 A commercially available solvent-based semiconductor paste based on epoxy resin was obtained.

The conductive pastes obtained in Examples 1 and 2 and Comparative Example 1 were diluted to several poise with butyl acetate, and the solid electrolytic capacitor element was dipped in the diluted paste. It cures under curing conditions to form a cathode layer. Further, after the anode lead and the anode lead frame are welded and joined, the cathode layer and the cathode lead frame are joined with a conductive paste. Then, it was covered with a resin by a molding method to produce a solid electrolytic capacitor. 85 ° C., 85% R of the solid electrolytic capacitor thus obtained
The results of the high-temperature and high-humidity test of H are shown in Table 1, and all of them show that the present invention is excellent, and the effect of the present invention was confirmed.

[0026]

[Table 1] (Unit) Note: High temperature and high humidity (8V, 15μF solid electrolytic capacitor)
5 ° C., 85% RH).

[0027]

As is clear from the above description and Table 1, the solid electrolytic capacitor of the present invention has excellent migration resistance and electrical bonding reliability even under high temperature and high humidity conditions, and has a high frequency impedance. It can respond to the change.

[Brief description of the drawings]

FIG. 1 is a sectional view for explaining a solid electrolytic capacitor to which the present invention is related.

[Explanation of symbols]

 Reference Signs List 1 anode body 2 dielectric layer 3 semiconductive 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.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 63/00 C08L 63/00 B C09J 161/06 C09J 161/06 163/00 163/00 F-term (reference) 4J002 CC032 CD121 DA016 DA076 DA086 FD116 FD140 GJ01 GQ02 HA05 4J036 AA01 AJ08 DA02 DA05 DC40 FA02 FB08 JA06 KA07 4J040 DK022 EC001 EC041 GA05 HA066 HB36 HB44 KA03 KA16 KA23 KA42 LA09

Claims (2)

[Claims] 1. An anode body made of a metal having a valve action,
In a solid electrolytic capacitor having a structure in which a dielectric layer, a semiconductor electrolyte layer, a carbon layer, and a cathode layer are sequentially formed, the cathode layer and the cathode frame are connected by a conductive adhesive layer, and the package is externally formed using a resin. The material forming the cathode layer or the cathode layer and the conductive adhesive layer is (A) a modified resin comprising (a) an epoxy resin having a dicyclopentadiene skeleton and (b) a phenol resin having a dicyclopentadiene skeleton; A) A conductive paste comprising a solvent, a monomer or a mixture thereof, and (C) a conductive filler as essential components. 2. An anode body made of a metal having a valve action,
In a solid electrolytic capacitor having a structure in which a dielectric layer, a semiconductor electrolyte layer, a carbon layer, and a cathode layer are sequentially formed, the cathode layer and the cathode frame are connected by a conductive adhesive layer, and the package is externally formed using a resin. A cathode layer or a cathode layer and a conductive adhesive layer, wherein (A) a modified resin comprising (a) an epoxy resin having a dicyclopentadiene skeleton and (b) a phenol resin having a dicyclopentadiene skeleton, (B) a solvent,
A solid electrolytic capacitor comprising a conductive paste containing a monomer or a mixture thereof and (C) a conductive filler as essential components.