JPH0729776A - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Abstract

PURPOSE:To enhance the conductivity in a specific direction by a method wherein a conductive bonding agent is magnetized before curing the agent to orient magnetic particles in the direction for enhancing the conductivity. CONSTITUTION:After the formation of a dielectric layer 2 by formation- processing an anode body 1 comprising a valve-acting metal, a semiconductor layer 3, a carbon layer 4 are formed on the surface of the dielectric layer 2 to manufacture a solid electrolytic capacitor element. Next, this element is dipped in a conductive bonding agent 7 using an organic binder diluted in a solvent and a conductive filler containing a solvent, magnetic body conductive particles as essential components so as to form a cathode layer 5. Next, an anode lead 8 of the element is welded into an anode lead frame 9 while the cathode 5 and a cathode lead frame 6 are junctioned with each other using the conductive bonding agent 7. At this time, the cathode layer 5 an the bonding agent 7 are magnetized before curing the agent to orient the magnetic particles in the direction for enhancing the conductivity. Next, after curing the conductive bonding agent 7, outer peripheral surface is coated by a coating resin 10 for bonding outer frame.

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 excellent in productivity and cost performance and a manufacturing method thereof.

[0002]

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 subjected to a chemical conversion treatment to form a dielectric layer, and then a semiconductor layer, a carbon layer and a cathode are further formed on the surface thereof. Form the layers. Next, the cathode layer and the cathode terminal are joined using a conductive adhesive, the anode body lead communicating with the anode body is welded and connected to the anode terminal, and the outer peripheral surface of the anode body is packaged with a packaging resin.

Conventionally, the cathode layer has been formed by using a conductive paste containing silver powder as a main component from the viewpoint of conductive characteristics.
This paste contains a large amount of silver powder in order to satisfy the electrical characteristics of a solid electrolytic capacitor, but this has the drawbacks of reduced productivity and high cost due to reduced workability. Further, when the solid electrolytic capacitor is exposed to a high temperature and high humidity environment, water penetrates through the exterior resin and the interface between the terminal and the exterior resin, the silver in this paste is dissolved and ionized, and it precipitates again, so-called. Leakage current and tan due to the occurrence of “silver migration”
There is a defect that the electrical characteristics are inferior such as increase of δ and occurrence of short circuit failure.

As a method for preventing the deterioration of electric characteristics due to the migration, there has been proposed a method in which copper powder, manganese powder, nickel powder or the like is mixed into a silver-based conductive paste used for a cathode layer or a conductive adhesive. , The adhesiveness and workability of the paste are very poor, and satisfactory results have not been obtained in terms of reliability.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned drawbacks, and is a solid electrolytic capacitor having excellent productivity, cost performance, electrical characteristics, conductivity, and adhesiveness and high reliability. And a method for producing the same.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that the use of a conductive adhesive having the composition described below provides excellent productivity and cost performance. The inventors have found that a solid electrolytic capacitor having the above characteristics can be obtained and completed the present invention.

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 anode body is bonded to an anode terminal,
Furthermore, in a solid electrolytic capacitor in which a cathode layer and a cathode terminal are joined with a conductive adhesive and which is packaged with a resin, the cathode layer or the cathode layer and the conductive adhesive layer is (A) an organic binder and a solvent, and ( B) A solid electrolytic capacitor, characterized in that it is formed by a conductive adhesive containing a conductive filler, which is a magnetic conductive powder, as a part or the whole, as an essential component. Further, it is a method for producing a solid electrolytic capacitor, characterized in that the cathode layer formed of a conductive adhesive or the cathode layer and the conductive adhesive layer are magnetically treated before curing of the conductive adhesive.

The present invention will be described in detail below.

The (A) organic binder of the conductive adhesive used in the present invention is not particularly limited, and may be a thermosetting type or a thermoplastic type, and 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, under high temperature and high humidity conditions, for example, 12
Under conditions such as a pressure cooker test at 1 ° C and 2 atm, the conductive paste cured film deteriorates, causing not only migration but also a short circuit due to the outflow of the conductive powder itself. Therefore, when migration prevention under such severe conditions is required, it is necessary to select a binder having high heat resistance. For example, a polyimide resin or a system in which a novolac epoxy resin having an average number of epoxy groups of 3 or more is cured with a phenol resin can be used. It is desirable to dissolve and mix these resins with a solvent in advance before manufacturing the paste.

The solvent used here is capable of dissolving the resin for the organic binder, such as dioxane, hexane, toluene, ethyl cellosolve,
Examples include cyclohexanone, butyl cellosolve, butyl cellosolve acetate, butyl carbitol acetate, diethylene glycol diethyl ether, diacetone alcohol, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone. These can be used alone or in combination of two or more.

As the conductive filler (B) of the conductive adhesive used in the present invention, magnetic conductive powder such as nickel powder and iron powder, or oxidation at high temperature such as silver-coated nickel powder is used. In order to prevent it, the magnetic conductive powder having the surface coated with silver is contained as a part or the whole thereof.
It is desirable that the magnetic conductive powder be flake-shaped particles and have an average particle diameter (D ₅₀ ) of 30 μm or less. It is preferable to use one having an average particle size of 5 to 15 μm. When it exceeds 30 μm, the dispersion in the vehicle becomes poor and the workability of the adhesive is poor, which is not preferable. These magnetic conductive powders may be used alone or
Two or more kinds can be mixed and used. It is desirable that the magnetic conductive powder is 30% by weight or more of the total conductive filler. If it is less than 30% by weight, anisotropic conductivity due to magnetic treatment described later cannot be obtained, which is not preferable. Examples of the conductive powder used in combination with the magnetic conductive powder as needed include silver powder, copper powder, carbon, etc. These may be used alone or in combination of two or more. The compounding ratio of the conductive filler, which is a part or all of the magnetic conductive powder, depends on the organic binder.
It is desirable to add 250 to 450 parts by weight to 100 parts by weight. It is preferably 330 to 380 parts by weight. Compounding amount
If it is less than 250 parts by weight, the conductivity will not be developed, and if it exceeds 450 parts by weight, the anisotropic conductivity effect by the magnetic treatment will be small, which is not preferable.

The conductive adhesive used in the present invention contains (A) an organic binder and a solvent, and (B) a conductive filler as essential components, but within a range not deviating from the object of the present invention.
Further, if necessary, a defoaming agent, a coupling agent, a fine silica-based powder, and other additives can be added and blended. It can be manufactured by thoroughly mixing the above-mentioned components according to a conventional method and further kneading them with a three-roll mill.

A solid electrolytic capacitor is manufactured using the conductive adhesive thus manufactured. 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 layer 3 and a carbon layer 4 are further formed on the surface thereof. A solid electrolytic capacitor element is formed by sequentially forming. The device is dipped in a conductive adhesive diluted with a suitable solvent to form the cathode layer 5. Next, the anode body lead 8 of the capacitor element is welded and connected to the anode lead frame 9 of the anode terminal,
Then, the cathode layer 5 and the cathode lead frame 6 of the cathode terminal are bonded together using a conductive adhesive 7. Here, the cathode layer 5 and the conductive adhesive 7 are magnetically treated before being cured, and the magnetic powder is oriented in the direction in which conductivity is desired to be increased. It is desirable that the magnetic treatment be carried out as soon as possible after applying the conductive adhesive. It is preferably within 30 seconds to 3 minutes after application (depending on the composition of the conductive adhesive). If it is left for a long time, the viscosity of the conductive adhesive increases due to the evaporation of the solvent, and the rotation of the magnetic powder is hindered so that the magnetic powder is not oriented in one direction.
The magnet used may be a permanent magnet or an electromagnet, and a magnetic flux density of 200 Gauss or more is desirable. The size is not particularly limited as long as it can cover the adhesive agent portion to be magnetically processed. Place such a magnet as close as possible to the adhesive layer,
The magnetic treatment is performed by moving at a constant speed in the direction in which conductivity is desired to be increased. That is, in the case of the cathode layer 5, the magnet is moved along the capacitor element surface, and in the case of the conductive adhesive 7, the magnet is moved from the cathode frame 6 toward the capacitor element. After the magnetic treatment, the conductive adhesive is cured under predetermined conditions. After that, the outer peripheral surface is covered with the exterior resin 10 by a transfer molding method or a dipping method, and the external frame is bent to manufacture a solid electrolytic capacitor.

[0014]

According to the solid electrolytic capacitor and the method of manufacturing the same of the present invention, a conductive adhesive containing an organic binder, a solvent, and a conductive filler containing a magnetic conductive powder as essential components is magnetically treated before curing. Then, the magnetic powder is oriented in the direction in which the conductivity is desired to be enhanced, whereby the conductivity in the specific direction can be enhanced. Therefore, even if silver powder is not used as the conductive powder, or the silver powder is reduced, the conductivity is not impaired, and the cost of the conductive adhesive can be reduced. In addition, since it is possible to reduce the amount of powder in the adhesive, it is possible to obtain a conductive adhesive having better workability and adhesiveness. Furthermore, since the amount of silver powder in the adhesive can be reduced, the occurrence of migration can be significantly suppressed as compared with the conventional silver-based conductive adhesive. Thus, using this conductive adhesive, it is possible to obtain a solid electrolytic capacitor having excellent productivity, cost performance, and electrical characteristics after moisture resistance.

[0015]

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 novolak resin Praiophen VH-4170 (manufactured by Dainippon Ink and Chemicals, Inc.) A dissolution reaction was performed in 154 parts of diethylene glycol diethyl ether at 100 ° C for 1 hour to obtain a viscous resin. To 100 parts of this resin, 1 part of amine complex of boron trifluoride as catalyst, 2.5 parts of silane coupling agent,
A conductive adhesive was manufactured by mixing 175 parts of nickel powder and 3.5 parts of Aerosil # 200 (manufactured by Nippon Aerogel Co., Ltd., trade name) as fine silica powder.

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 viscous resin was obtained by carrying out a dissolution reaction at ℃ for 2 hours. This resin
In 200 parts, 138 parts of the above mixed solvent, 0.12 parts of antifoaming agent, 175 parts of nickel powder, Aerosil # as fine silica powder
A conductive adhesive was manufactured by mixing 10.4 parts of 200 (described above).

Example 3 Polyimide resin AI-10 (trade name, manufactured by Amoco) 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, 175 parts of silver-coated nickel powder, Aerosil # 200 (mentioned above)
A conductive adhesive was manufactured by mixing 3.5 parts.

Comparative Example 1 In Example 1, instead of 175 parts of nickel powder,
Except for adding and mixing 150 parts of silver powder and 25 parts of nickel powder,
A conductive adhesive was produced in the same manner as in Example 1.

Comparative Example 2 A solvent-type conductive adhesive containing a commercially available heat-resistant thermoplastic resin base and using only silver powder as conductive powder was obtained.

Using the conductive adhesives obtained in Examples 1 to 3 and Comparative Examples 1 to 2, a solid electrolytic capacitor element was subjected to dipping treatment to form a cathode layer, and an anode lead and an anode frame were welded. After joining, the cathode layer and the cathode frame are joined with a conductive adhesive. Here, in the case of the cathode layer, in the case of the conductive adhesive 7 that joins the cathode layer and the cathode frame along the capacitor element surface, in the direction of the capacitor element from the cathode frame toward the capacitor element, a permanent magnet with a magnetic flux density of 300 gauss is used. Was moved to orient the magnetic powder. Then, the conductive adhesive was cured under predetermined conditions, and was externally coated with a resin by a molding method to manufacture a solid electrolytic capacitor. This solid electrolytic capacitor was tested for tan δ and short-circuit failure in a high temperature and high humidity environment of 85 ° C. and 85% RH. The results are shown in Table 1. The present invention was excellent in all cases, and the effect of the present invention was confirmed.

[0022]

[Table 1]

[0023]

As is clear from the above description and Table 1, the solid electrolytic capacitor and the method for producing the same according to the present invention are excellent in productivity and cost performance.
It is possible to manufacture a highly reliable solid electrolytic capacitor having excellent electrical characteristics, conductivity, and adhesiveness even under high temperature and high humidity conditions.

[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 (cathode terminal) 7 conductive adhesive 8 anode body lead 9 anode lead frame (anode terminal) 10 exterior resin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01R 4/04 6901-5E

Claims (2)

[Claims] 1. An anode body made of a metal having a valve action,
A dielectric layer, a semiconductor electrolyte layer, a carbon layer, and a cathode layer are sequentially formed, the anode body is joined to the anode terminal, the cathode layer and the cathode terminal are joined together with a conductive adhesive, and the exterior is coated with resin. In the solid electrolytic capacitor, the cathode layer or the cathode layer and the conductive adhesive layer are (A) an organic binder and a solvent, and (B) a conductive filler whose part or all is magnetic conductive powder is an essential component. A solid electrolytic capacitor formed of a conductive adhesive. 2. An anode body made of a metal having a valve action,
A dielectric layer, a semiconductor electrolyte layer, a carbon layer, and a cathode layer are sequentially formed, the anode body is joined to the anode terminal, the cathode layer and the cathode terminal are joined together with a conductive adhesive, and the exterior is coated with resin. In the solid electrolytic capacitor, the cathode layer or the cathode layer and the conductive adhesive layer are (A) an organic binder and a solvent, and (B) a conductive filler whose part or all is magnetic conductive powder is an essential component. And a cathode layer and a conductive adhesive layer are magnetically treated before curing of the conductive adhesive agent.