JPH11345748A - Solid electrolytic capacitor and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor excellent in electric characteristics after moisture absorption using a silver based conductive paste excellent in mass productivity and migration preventive effect. SOLUTION: A dielectric layer, a semiconductor electrolytic layer, a carbon layer, and a cathode layer are formed sequentially on an anode body made of a metal having valve action, the cathode layer is bonded through a conductive adhesive layer to a cathode frame and the entirety is resin-molded to produce a solid electrolytic capacitor. The cathode layer 5 or the conductive adhesive layer 7 is composed of a conductive paste principally comprising an organic binder, a conductive filler composed entirely or partially of a magnetic conductive powder, e.g. nickel powder. The production method comprises a process for imparting anisotropic conductivity to the cathode layer and the conductive adhesive layer by subjecting the conductive paste to magnetic processing before it is cured.

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 using a resin for its exterior, and is a highly reliable solid electrolytic capacitor excellent in productivity and cost performance.

[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 formation, M
A semiconductor electrolyte layer 3 such as nO ₂ , a carbon layer 4, and a cathode layer 5 are sequentially formed, and the cathode layer 5 is adhered and fixed to a cathode lead frame 6 using a conductive adhesive 7. The anode lead 8 to the anode lead frame 9
To the exterior resin 10 by welding.
It consists of.

[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.

[0004] 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, or a porous filler 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 very poor, which is not suitable for mass production of solid electrolytic capacitors. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and uses a silver-based conductive paste excellent in mass productivity and migration prevention effect to provide a solid electrolytic capacitor having excellent electric characteristics after moisture absorption. It is intended to provide.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that the use of a conductive paste having a composition described later and a manufacturing method thereof can improve the reliability of adhesiveness and electrical characteristics. It has been found that a solid electrolytic capacitor excellent in productivity and cost performance can be obtained without impairing the present invention, and 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 using a resin, the cathode layer or the cathode layer and the conductive adhesive layer are composed of (A) an organic binder, and (B)
A solid electrolytic capacitor characterized by being formed entirely of a conductive filler which is a magnetic conductive powder and a conductive paste containing a solvent (C) as a component. A method for producing a solid electrolytic capacitor, comprising a step of imparting anisotropic conductivity to the cathode layer or the cathode layer and the conductive adhesive layer by performing a magnetic treatment before curing.

Hereinafter, the present invention will be described in detail.

The type of the organic binder (A) used in the present invention is not particularly limited, and may be a thermosetting type or a thermoplastic type, and may be a conventionally known epoxy type, phenol type, melamine type, or cellulose type. System, acrylic system,
Polyimide-based and mixed modified resin-based resins and the like are used. The modified resin may be simply dissolved and mixed, or may be partially bound by a heat reaction. If necessary for the reaction, a curing catalyst can be used.

In the case of an organic binder having low heat resistance, the conductive paste cured film deteriorates under high temperature and high humidity conditions, for example, a pressure cooker test at 121 ° C. and 2 atm. Short circuit occurs due to outflow of the substance. Therefore, when it is required to prevent migration under such severe conditions, it is necessary to select a binder having high heat resistance, and as the heat resistant binder, for example, a polyimide resin or a novolak having an average epoxy group number of 3 or more. A system in which an epoxy resin is cured with a phenol resin may be used.

It is desirable that these resins are dissolved and mixed in advance with the solvent (C) before the paste is produced. As the solvent used here, those capable of dissolving these resins, 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, 1,3-dimethyl-2-imidazolidinyl, and the like. The above are used in combination.

As the conductive filler (B) used in the present invention, at least a magnetic conductive powder such as nickel powder or iron powder or a high-temperature oxidized powder such as silver-coated nickel powder is used. Of magnetic powder coated with silver
The magnetic material powder contains one or two or more kinds as essential components, and has a mean particle size (D50) of 30%.
μm or less, and more preferably an average particle size of 5 to
Use a 15 μm one. If the average particle size is larger than 30 μm, the dispersion in the vehicle becomes poor, and there is a problem in the workability of the paste.

As the conductive filler, it is possible to use a mixture of two or more kinds of other conductive powders such as silver powder, copper powder and carbon together with the magnetic conductive powder. At this time, the magnetic conductive powder needs to be 30% by weight or more of the total conductive filler. If the blending ratio of the magnetic conductive powder is less than 30%, anisotropic conductivity cannot be obtained by the magnetic treatment described below.

The compounding amount of the conductive filler is from 250 to 450 parts by weight, preferably from 330 to 38 parts by weight, per 100 parts by weight of the resin.
0 parts by weight. If the amount is less than 250 parts by weight, no conductivity is exhibited, while if it exceeds 450 parts by weight, the anisotropic conductivity effect by the magnetic treatment is reduced.

The conductive paste used in the present invention comprises (A)
The organic binder, (B) a magnetic filler alone or a conductive filler containing the magnetic powder, and (C) a solvent are essential components, but the defoaming agent may be used within a range not inconsistent with the object of the present invention. , A coupling agent, a fine silica-based powder, and other additives. After thoroughly mixing the above-mentioned components according to a conventional method, the mixture is further kneaded with a three-roll mill.

The conductive paste thus obtained is diluted with an appropriate solvent to adjust the viscosity, and the solid electrolytic capacitor element 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.

Here, the cathode layer 5 and the conductive adhesive layer 7 formed by applying the conductive paste are subjected to a magnetic treatment before curing, and the magnetic powder is oriented in a direction in which the conductivity is to be increased.
The magnetic treatment is desirably performed as quickly as possible after the application of the conductive pastes 5 and 7, and is preferably performed within 30 seconds to 3 minutes after application (although it varies depending on the composition of the conductive paste). If the coating is left for a long time exceeding 3 minutes after application, the viscosity of the conductive paste increases due to the evaporation of the solvent, and the rotation of the magnetic powder is hindered, and the magnetic powder is not well oriented in one direction. The magnet used may be a permanent magnet or an electromagnet, and the magnetic flux density
More than 200 Gauss. The size is not particularly limited as long as it can cover the paste portion to be magnetically processed. Such a magnet is brought as close as possible to the paste layer, and is moved at a constant speed in a direction in which conductivity is to be increased to perform magnetic processing. 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 layer 7, the magnet is moved from the cathode lead frame 6 toward the capacitor element. After the magnetic treatment, the conductive paste is cured under predetermined conditions.

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.

[0019]

The conductive paste used in the present invention contains an organic binder and a conductive filler which is entirely or partially a magnetic conductive powder. The cathode layer 5 and the conductive adhesive layer 7 formed of such a conductive paste are
Before the curing, a magnetic treatment is performed to orient the magnetic substance powder in a direction in which the conductivity is to be increased. The cathode layer and the conductive adhesive layer thus obtained are capable of expressing sufficient conductivity because the magnetic conductive powder is oriented only in the direction in which the conductivity is desired to be developed. Since the content of silver powder that causes the problem of migration can be reduced, it is possible to significantly suppress the occurrence of migration as compared with a conventional silver-based conductive paste. Further, the use of nickel powder or iron powder, which is cheaper than silver powder, can reduce material costs. By utilizing this new conductive paste, a solid electrolytic capacitor having excellent electric properties after moisture absorption could be obtained.

[0020]

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 1 100 parts of epoxy resin EOCN103S (trade name, manufactured by Nippon Kayaku Co., Ltd.) and 54 parts of Plyofen VH-4170 (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) of bisphenol A novolac resin were used. A dissolution reaction was carried out in 154 parts of diethylene glycol diethyl ether at 100 ° C. for 1 hour to obtain a viscous resin. As a catalyst, 1 part of an amine complex of boron trifluoride, 2.5 parts of a silane coupling agent,
75 parts of Ni-based magnetic conductive powder, 100 parts of silver powder, and 3.5 parts of AERYL # 200 (trade name, manufactured by Nippon AERYL Co., Ltd.) as fine silica powder are mixed, further kneaded with a three-roll mill, and degassed under reduced pressure. To produce a conductive paste.

Example 2 100 parts of a polyesterimide which is a heat-resistant thermoplastic resin was dissolved in 300 parts of a mixed solvent of N-methylpyrrolidone / diethylene glycol dimethyl ether = 6/4 (weight ratio) to obtain a viscous resin. Was. To 200 parts of this resin, 138 parts of the above mixed solvent, 0.12 part of the defoamer,
80 parts, silver powder 95 parts, Aerizil # as fine silica powder
200 (manufactured by Nippon Aerosil Co., Ltd., trade name) were mixed, further kneaded with a three-roll mill, and defoamed under reduced pressure to produce a conductive paste.

Example 3 AI-10 polyimide resin (trade name, manufactured by AMOCO)
100 parts were mixed with a mixed solvent of N-methylpyrrolidone / diethylene glycol dimethyl ether = 6/4 (weight ratio) 300
The dissolution reaction was performed at 50 ° C. for 3 hours in the same part to obtain a viscous resin. To 200 parts of this resin, 2.5 parts of a silane coupling agent, N
75 parts of i-based magnetic conductive powder, 100 parts of silver powder, and 3.5 parts of AERYL # 200 (trade name, manufactured by Nippon AERIL Co., Ltd.) were mixed to prepare a conductive paste.

Comparative Example 1 A conductive paste was prepared by using 175 parts of silver powder instead of 75 parts of magnetic conductive powder in the formulation of Example 1.

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

Using the conductive pastes obtained in Examples 1 to 3 and Comparative Examples 1 and 2, a solid electrolytic capacitor element is dipped therein to form a cathode layer, and an anode lead and an anode lead frame are welded. After the joining, the cathode layer and the cathode lead frame are joined with the conductive paste of the first embodiment. Here, a permanent magnet with a magnetic flux density of 300 Gauss is applied along the surface of the capacitor element in the case of the cathode layer, or in the direction of the capacitor element from the cathode lead frame in the case of conductive paste for joining the cathode layer and the cathode lead frame. Is moved to orient the magnetic powder. Thereafter, the conductive paste was cured under predetermined conditions, and was covered with a resin by a molding method to produce a solid electrolytic capacitor. Table 1 shows the results of the high-temperature and high-humidity tests at 85 ° C. and 85% RH of the solid electrolytic capacitors thus obtained.

[0027]

[Table 1] Note: These are the environmental test results of a 6V, 15μF solid electrolytic capacitor at high temperature and high humidity (85 ° C, 85% RH).

[0028]

As is apparent from the above description and Table 1, the solid electrolytic capacitor of the present invention is excellent in electric characteristics after moisture absorption, and the electric characteristics are deteriorated even if it is of a type covered with a resin. Was slight.

[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]

 DESCRIPTION OF SYMBOLS 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 (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 cathode layer or the cathode layer and the conductive adhesive layer are each composed of (A) an organic binder, (B) a conductive filler containing all or a part of a magnetic conductive powder, and (C) a conductive paste containing a solvent as a component. A solid electrolytic capacitor characterized by being formed of: 2. An anode body made of a metal having a valve action,
A method for manufacturing a solid electrolytic capacitor in which a dielectric layer, a semiconductive electrolyte layer, a carbon layer, and a cathode layer are sequentially formed, the cathode layer and the cathode frame are connected with a conductive adhesive layer, and thereafter, the package is packaged using a resin. In the above, the cathode layer or the cathode layer and the conductive adhesive layer may be formed by: (A) an organic binder, (B) a conductive filler whose whole or a part is a magnetic conductive powder, and (C) a solvent containing a solvent. A solid material comprising a step of imparting anisotropic conductivity to the cathode layer or the cathode layer and the conductive adhesive layer by applying a magnetic treatment before curing of the conductive paste. Manufacturing method of electrolytic capacitor.