JPH02264415A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To reduce the initial tan delta value, and to lessen electrical short circuits by a method wherein a cathode layer and the like is composed of a kind selected from grain diameter specified palladium flake-like powder and a conductor, on which a weight ratio is specified, consisting at least of a kind selected from acryloyl, polyethylene, vinyl, epoxy, phenol and the like. CONSTITUTION:An electrode body 2, which constitutes a chip-like button solid electrolytic capacitor, is composed of an encircling cathode layer 11 and a conductor or an adhesion layer, to be used to attach a cathode terminal 8 to the encircling cathode layer 11, as mentioned below. Palladium flake-like powder of grain diameter 1 to 30mum, high purity methyl methacrylic resin and a solvent are kneaded at the weight ratio of 9.5 to 6.0 and 0.5 to 40, conductive coating material for palladium cathode is formed, and a cathode layer 11 is constituted using said coating material. Also, palladium flake-like powder of the grain diameter as above, high purity bisphenol type epoxy resin, a phenol hardener, imidazole, a buthyl cell solve solvent are kneaded at the weight ratio of 85:9.1:5.9:0.1:15, and a conductive bonding agent is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to solid electrolytic capacitors made of tantalum, aluminum, etc.

2. Description of the Related Art Conventionally, solid electrolytic capacitors of this type, particularly chip-shaped tantalum solid electrolytic capacitors, have had a structure as shown in FIG. As shown in FIG. 4, after attaching an insulating plate to the base of the anode lead wire of the tantalum porous electrode body 2 equipped with the tantalum anode lead wire 1, a tantalum dielectric oxide film is applied to the tantalum porous electrode body 2 by anodization. 3, and further a solid electrolyte layer 4 such as manganese dioxide. carbon layer 5
A capacitor element is formed by sequentially laminating cathode layers 6 made by coating and drying a paint consisting of powders of silver, copper, nickel, carbon, etc., organic polymers, organic solvents, etc., and connecting the tantalum anode lead wire l of this capacitor element and the anode terminal 7 are connected by welding, and then the cathode layer 6 and the brass electrode terminal 8 are connected with solder or silver, copper, or nickel.

After applying a conductive adhesive 9 made of powder such as carbon, an organic polymer, an organic solvent, etc., drying and connecting, an exterior resin 10 is applied so that the anode terminal 7 and the cathode terminal 8 are pulled out in opposite directions. Both terminals were bent inward toward the bottom of the capacitor body along the end and bottom surfaces to form a chip-shaped tantalum solid electrolytic capacitor.

Problems that the invention aims to solve However, in the conventional configuration described above, the cathode layer.

When the conductive adhesive is composed of silver powder and an organic polymer, there is a problem in that silver migrates under high temperature and high humidity, resulting in electrical short circuit failure.

Next, when it is made of copper powder and an organic polymer or nickel powder and an organic polymer, it does not undergo migration like silver does in high temperature and high humidity, but it does have the problem that the metal powder is oxidized and the janδ value becomes large. had.

In addition, when it is made of carbon powder and organic polymer, it is very cheap and does not undergo migration like silver in high temperature and high humidity, but it has a high specific resistance value compared to the above metal powder, so the initial janδ The problem was that the value was very large.

The present invention solves the above-mentioned conventional problems.
It is an object of the present invention to provide a solid electrolytic capacitor having a small nδ value, a small change in tanδ value under high temperature and high humidity, and less electrical short circuit failure.

Means for Solving the Problems To achieve this object, the solid electrolytic capacitor of the present invention has a cathode layer made of palladium flake powder with a particle size of 1 to 30 μm and an acrylic, polyethylene, vinyl, or cellulose thermoplastic. The weight ratio of the resin or at least one of the epoxy, phenol, and polyimide thermosetting resins is 9.5 to 6.0:0. ``A conductor with a diameter of 5 to 4.0, or an adhesive consisting of palladium flake powder with a particle size of 1 to 30 μm, and an epoxy or phenol type.

The conductor has a weight ratio of at least one type of polyimide thermosetting resin of 9.5 to 6.0:0.5 to 4.0.

Effect Due to this structure, palladium powder has a property of having relatively low electrical conductivity among metals (and is chemically stable and resistant to ionization at high temperatures and high humidity). The particle size of the palladium powder should be selected by considering workability, the shape should be made into flakes with low contact resistance, and the weight ratio of palladium powder and organic polymer should be determined by considering the strength of the coating film. By adding a large amount of palladium powder, it is possible to reduce the specific resistance of the coating film, and it is possible to obtain a solid electrolytic capacitor with a small initial tan δ value, a small change in tan δ value under high temperature and high humidity, and fewer electrical short circuit failures. .

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of a chip-shaped tantalum solid electrolytic capacitor made of palladium powder and an organic polymer, which is a solid electrolytic capacitor according to a first embodiment of the present invention. 1 is a tantalum anode lead wire, 2 is a tantalum porous electrode body, 3 is a tantalum dielectric oxide film, 4 is a solid electrolyte layer, 5 is a carbon layer, 7 is an anode terminal, 8 is a cathode terminal, 10 is an exterior resin, 11 is a cathode layer made of palladium powder and an organic polymer (hereinafter referred to as palladium cathode layer),
12 is an adhesive (
(hereinafter referred to as palladium adhesive).

First, palladium flake powder with a particle size of 5 μm: high purity methyl methacrylic resin: xylene solvent = 8.5.1
．． A conductive paint for palladium cathode was prepared by kneading the mixture at a weight ratio of 5:3.0 using three rolls, and then palladium flake powder with a particle size of 5 μm: high-purity bisphenol type epoxy resin: phenol curing agent. : Imidazole: Butyl cellosolve solvent = 85': 9.1 F 5
．． A conductive paint for palladium adhesive was prepared by kneading at a weight ratio of 9:0.1:15.

Then, a tantalum wire with a circular cross section and a wire diameter of 0.3 mm was embedded in tantalum metal powder 100n++r and sintered as an anode lead wire by a general method to obtain a tantalum porous electrode body for 35V6.8μF, and an insulating plate After attaching it to the base of the anode lead wire, a tantalum dielectric oxide film, a solid electrolyte of manganese dioxide, and a carbon layer are sequentially formed. On this, the conductive paint for the palladium cathode layer prepared earlier was applied by the dipping method, and after being left at room temperature for 30 minutes, it was heated to 120℃ and IH.
Dry and form a palladium cathode layer to form a capacitor element. Next, the conductive paint for palladium adhesive prepared on the cathode terminal is applied with a dispenser, and the capacitor element is placed on top of this so that the palladium cathode layer and the tantalum anode lead wire are in the direction of the anode terminal, and the tantalum anode lead wire is placed on top of the palladium cathode layer. After the wire and the anode terminal are connected by welding, a little pressure is applied to ensure that the palladium cathode layer of the capacitor element is connected to the cathode terminal, and the connection is made by drying at 180° C. and IHr.

After that, the terminals are set in a transfer mold mold so that they are pulled out from both ends in opposite directions, and an exterior resin is applied.The terminals are bent inward along the end and bottom surfaces toward the bottom of the capacitor body. A chip-shaped solid electrolytic capacitor is obtained.

Since the resistance value of the conductive paint previously prepared can be used as a substitute value for the janδ value of the solid electrolytic capacitor, the shape of the palladium powder, the weight ratio of palladium powder to organic polymer, and the palladium powder particle size in making the conductive paint are The determination was evaluated based on the resistance value. .

Xylene was added to various palladium powders with a powder particle size of 5 μm and powder shapes of spherical and flake shapes in varying weight ratios and methyl methacrylic resin, kneaded to form a paint, and this was applied onto a glass substrate with an area of 1 cd and a thickness of The resistance value of the coating film was measured after coating at a thickness of 200 μm and drying at 120° C. for 30 minutes, and the results are shown in FIG. 2 (weight ratio of palladium powder and organic polymer weight ratio-resistance value characteristic curve). As can be seen from FIG. 2, the weight ratio of palladium powder to methyl methacrylic resin that can be used as a cathode material for capacitors is 9.
5-6.0: Range of 0.5-4.0. However, care must be taken as too much palladium powder will weaken the strength of the coating. Moreover, it is better for the palladium powder to have a flake shape.

Next, palladium powder with a particle size of 5 μm and a flake shape: methyl methacrylic resin: xylene = 8.5:
A coating was prepared by changing the particle size of palladium powder at a weight ratio of 1.5.3.0, and this was coated on a glass substrate with an area of 1 cnf and a thickness of 200 μm, and after drying at 120°C for 30 minutes, the resistance value of the coating film was determined. The measurement results are shown in FIG. 3 (palladium powder particle size-resistance value characteristic curve). Even if the particle size is too large, the resistance value will not change, but considering the sedimentation property of the paint, it should be 1 to 30μ.
m is good. Although the resin of the conductive paint for the cathode was used in the above study, similar results were obtained using the resin of the conductive paint for the adhesive.

In the examples, acrylic resin was used as the resin for the conductive paint for the cathode, but polyethylene, vinyl, or cellulose thermoplastic resins, or epoxy, phenol, or polyimide thermosetting resins that do not adversely affect capacitor characteristics may also be used. Resin may also be used. Since resins differ in heat resistance, water absorption, coating strength, and curability, they should be selected as necessary.

However, when using a thermosetting resin, special care must be taken since the jan δ value may become large in the moisture resistance test.

Although an epoxy resin was used as the resin for the conductive paint for the adhesive, a phenolic or polyimide thermosetting resin that does not adversely affect the capacitor characteristics may also be used. In particular, adhesive resins must have excellent coating strength and adhesion to metals. Other heat resistance, water absorption, and hardening properties may be selected as necessary.

The conductive paints for the cathode and adhesive used in the examples were those under optimal conditions.

The solid electrolytic capacitor constructed as above has a cathode layer and
The weight ratio of the adhesive to the palladium flake powder with a particle size of 1 to 30 μm and the organic polymer is 9.5 to 6.0: 0.5 to
4.0, the initial JAN δ value is small, and the JAN δ value change and leakage current value change are small in the moisture resistance test.

As described above, according to this embodiment, the moisture resistance can be improved by replacing the cathode layer and conductive adhesive with a palladium cathode layer and a palladium adhesive.

Table 1 below shows the jan δ value and the number of electrical short circuit failures in the moisture resistance test (85°C, 90%, 1000 Hr) of the inventive product and the conventional product (silver cathode layer/silver adhesive) of the example and the rated voltage of the sample. 35V, rated capacity 6.8μF *1 Tan δ is measured at frequency f = IKHz *2 The number of short circuit failures is the number that occurred out of 100. The measurement was performed by applying the rated voltage for 1 minute. The same conductors containing palladium powder were used, but a combination of a cathode layer made of thermal sprayed solder, nickel, etc., and a palladium adhesive, and, conversely, a combination of a palladium cathode layer and a conductive adhesive such as carbon or nickel.

A combination that connects with solder may also be used. However, solid electrolytic capacitors were created using various combinations of silver cathode layers and silver adhesives made of silver powder and organic polymers that cause migration, and palladium cathode layers and palladium adhesives, and moisture resistance tests (
(85℃, 90%, 1000Hr), electrical short circuit failures decrease in the following order: silver cathode layer/silver adhesive, silver cathode layer/palladium adhesive, palladium cathode layer/silver adhesive, palladium cathode layer/palladium adhesive. Therefore, it is best not to combine it with cathode layers and adhesives that cause migration as much as possible.

Effects of the Invention As described above, the present invention provides a palladium cathode layer or a palladium adhesive, so that the initial jan δ value is small.
It is possible to realize an excellent solid electrolytic capacitor that has a small change in jan δ value in a humidity test and has few electrical short circuit failures.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a solid electrolytic capacitor according to an embodiment of the present invention, Fig. 2 is a graph showing palladium powder of various shapes and organic polymer weight ratio-resistance value characteristic curve, and Fig. 3 is a graph showing palladium powder particle size-resistance value characteristic curve. The resistance value characteristic curve diagram, FIG. 4, is a side sectional view of a conventional solid electrolytic capacitor. DESCRIPTION OF SYMBOLS 1...Tantalum anode lead wire, 2...Tantalum porous electrode body, 3...Tantalum dielectric oxide film, 4...Solid electrolyte layer, 5・・・・・・
Carbon layer, 7... Anode terminal, 8...
Cathode terminal, lO...Exterior resin, 1'1...
...°Palladium cathode layer, 12...Palladium adhesive. Name of agent: Patent attorney Shigetaka Awano /n) Figure

Claims (2)

[Claims] (1) A dielectric oxide film is formed on the surface of the electrode body equipped with the anode lead wire, and then an electrolyte layer, a carbon layer, palladium flake powder with a particle size of 1 to 30 μm, and acrylic, polyethylene, or vinyl The weight ratio of at least one type of thermosetting resin, cellulose-based thermoplastic resin, or epoxy-based, phenol-based, or polyimide-based thermosetting resin is 9.
5 to 6.0: A solid electrolytic capacitor in which a cathode layer of 0.5 to 4.0 is sequentially formed, an anode lead wire is connected to an anode terminal, the cathode layer is connected to a cathode terminal, and a resin exterior is applied. (2) A dielectric oxide film is formed on the surface of the electrode body equipped with the anode lead wire, and an electrolyte layer, a carbon layer,
The cathode layer is formed in sequence, the anode lead wire is used as the anode terminal, and the particle size is 1.
~30μm palladium flake powder and epoxy system,
The weight ratio of at least one of phenolic and polyimide thermosetting resins is 9.5 to 6.0:0.5 to 4.0
A solid electrolytic capacitor, which connects the cathode layer and the cathode terminal with an adhesive made of the above-mentioned adhesive and is coated with a resin.