JPH07201662A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a solid electrolytic capacitor in which a reactive solution is prevented from creeping up a tantalum wire through capillary phonomenon at the time of formation of a conductive polymer. CONSTITUTION:A block 4 is formed of any one of Freon resin, silicon resin, acryl resin or epoxy resin at a part for leading out a tantalum wire 2. The angle a formed between the block and the lead-out face of tantalum wire is set smaller than the contact angle between a reaction liquid for forming a conductive polymer and the block thus preventing the reaction liquid perfectly from creeping up the tantalum wire, i.e., preventing the formation of a conductive polymer at the tantalum wire part.

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 conductive polymer compound as a solid electrolyte.

[0002]

2. Description of the Related Art In a conventional solid electrolytic capacitor, for example, an oxide film is formed on a capacitor element formed by sintering tantalum powder by a known method, and manganese dioxide is formed on the oxide film as a solid electrolyte. Further, in recent years, a material using a conductive polymer such as polypyrrole in place of manganese dioxide has also been proposed (Japanese Patent Publication No. 4-56445).

The one using a conductive polymer as a solid electrolyte has excellent high-frequency characteristics because the conductivity of a conductive polymer is several tens of times higher than that of manganese dioxide. And has been attracting attention as a means for coping with the recent increase in the operating frequency of electronic devices. Further, since manganese dioxide is formed by thermally decomposing manganese nitrate, 200 ° C. to 300 ° C.
A certain degree of thermal stress is repeatedly applied to the capacitor element, which causes defects in the oxide film and increases leakage current. On the other hand, when a conductive polymer is used as a solid electrolyte, it is not necessary to treat the capacitor element at high temperature, so there is a report that there is no deterioration of the oxide film and a highly reliable product can be provided. Yes (Tokuhei 4-
56445 and JP-A-62-29124).

In these solid electrolytic capacitors, a manganese nitrate solution is used when manganese dioxide is used as a solid electrolyte, and a monomer solution and an oxidant solution are used when a conductive polymer is used as a solid electrolyte. Impregnated therein to form a solid electrolyte. That is,
These solutions are required to have high wettability with the tantalum oxide film in order to form a solid electrolyte even inside the sintered body. As a result, these solutions tend to crawl up to the tantalum wire (Fig. 4). In order to solve this problem, when manganese dioxide is used as the solid electrolyte, a solution resin is applied to the lead-out surface of the tantalum wire and then cured to form a block material (Fig. 5), or a washer is inserted into the tantalum wire. A method (Fig. 6) has been proposed.

[0005]

However, in the case of a solid electrolytic capacitor using a conductive polymer as a solid electrolyte,
When the conductive polymer is formed, the capacitor element is dipped in a solution to form the conductive polymer, so that the conductive polymer is also formed in the tantalum wire lead-out portion. As a result, there has been a drawback that an electrical short circuit occurs between the cathode layer and the anode lead when connecting the anode lead in the next step. In addition, when the block material described in the previous section is formed, some degree of prevention effect is obtained, but since manganese dioxide is formed by the thermal decomposition of manganese nitrate, the manganese nitrate solution crawling up on the tantalum wire due to the capillary phenomenon is scattered. However, while the formation on the tantalum wire is suppressed, in the case of the conductive polymer, the effect is not sufficient because the chemical reaction that generates a gas, such as when forming manganese dioxide, does not proceed.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, have found that the conventional method for forming a block material in a solid electrolytic capacitor using a conductive polymer as a solid electrolyte is not known. It has been found that there are different effective formation conditions than solid electrolytic capacitors that use manganese dioxide as the solid electrolyte. That is, the present invention, the block material formed in the lead-out portion of the anode wire such as tantalum wire, the angle made by the block material with the tantalum wire lead-out surface is smaller than the contact angle between the reaction liquid for forming the conductive polymer and the block material. The present invention provides a solid electrolytic capacitor capable of completely preventing the conductive polymer reaction liquid from climbing up to the tantalum wire, that is, forming the conductive polymer on the tantalum wire portion.

[0007]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 A capacitor element obtained by sintering a tantalum powder has a viscosity of 50 cps and 500 cp on the lead-out surface of a tantalum wire.
s and 100 cps of fluororesin were applied to each by 20 pieces with a microsyringe.

At this time, in order to avoid the creeping up to the anode lead due to the capillary phenomenon when forming the conductive polymer,
Care was taken so that the resin would wrap around the entire outer circumference of the tantalum wire, and the polyflon resin was cured by leaving it in a constant temperature bath at 150 ° C. for 1 hour.

After anodizing in a phosphoric acid aqueous solution to form an oxide film on the sintered body, it is immersed in a pyrrole solution containing pyrrole and ethanol in a weight ratio of 30:70,
Next, the iron (III) dodecylbenzene sulfonate and ethanol were immersed in an oxidant solution containing 40:60 by weight to polymerize the conductive polymer on the oxide film. After completion of the reaction, the unreacted oxidizing agent and excess acid were washed with water and dried in vacuum at 50 ° C. for 1 hour. After repeating the above operation three times, a graphite tank and a silver layer were sequentially formed, and the formation state of polypyrrole in the tantalum wire portion and the angle formed by the block material with the tantalum wire lead-out surface were observed with a 50 × microscope. A sample coated with a fluororesin having a viscosity of 50 cps was designated as sample 1, a sample coated with a fluororesin having a viscosity of 50 cps was designated as sample 2, and a sample coated with a fluororesin having a viscosity of 1000 cps was designated as sample 3. Next, connect the cathode lead with silver paste and the anode lead with electric welding,
The electrical characteristics were measured after packaging by the powder packaging method.

Next, in order to measure the contact angle between the reaction liquid for forming the conductive polymer and the block material, the above-mentioned fluorine-based resin was formed into a film on a glass plate to form a solid electrolyte, and oxidation was performed. The contact angle with the agent solution (Fig. 2) was examined.

Comparative Example 1 Using the same capacitor element as in Example 1, an oxide film, a solid electrolyte were formed, a graphite layer and a silver layer were sequentially formed by the same method as in Example 1 without forming a block material. The formation state of polypyrrole in the tantalum wire portion was observed with a microscope with a magnification of 2. Next, the cathode lead was connected with a silver paste and the anode lead was connected with electric welding, and the electrical characteristics were measured after the packaging by the powder packaging method.

Example 2 The same capacitor element as in Example 1 was used, and a fluorine resin having a viscosity of 1000 cps was used on the lead-out surface of the tantalum wire.
Individual pieces were applied with a microsyringe. After curing the polyflon resin, anodized in a phosphoric acid aqueous solution to form an oxide film in the sintered body, and using methanol and isopropyl alcohol as solvents, two types of pyrrole containing 30% by weight of pyrrole are used. Dip 20 pieces each in the pyrrole solution, and then dip it in an oxidant solution containing iron (III) dodecylbenzenesulfonate and ethanol in a weight ratio of 40:60 to obtain high conductivity on the oxide film. The molecule was polymerized. After completion of the reaction, the unreacted oxidizing agent and excess acid were washed with water and dried in vacuum at 50 ° C. for 1 hour. After repeating the above operation 3 times, form a graphite layer and a silver layer one after another, and observe the polypyrrole formation state of the tantalum wire part and the angle that the block material makes with the tantalum wire lead-out surface with a microscope of 50 times. did. A sample using methanol as the solvent of the pyrrole solution was sample 4, and a sample using isopropyl alcohol as the solvent of the pyrrole solution was sample 5. Next, the cathode lead was connected with a silver paste and the anode lead was connected with electric welding, and the electrical characteristics were measured after packaging by the powder packaging method.

Next, in order to measure the contact angle between the reaction liquid for forming the conductive polymer and the block material, the above-mentioned fluororesin was formed into a film on a glass plate to form a solid electrolyte. The contact angle with the agent solution was examined.

Example 3 As shown in FIG. 3, the thickness is 0.2 mm, the radius is 0.4 mm,
The angle formed with the tantalum wire lead-out surface is 120 degrees, respectively. 45 degrees Two types of fluorine resin washers shown in FIG. 6 (B) are inserted into the tantalum wire of the same capacitor element as in Example 1 to obtain Sample 7 , And 8. Polypyrrole was formed on this capacitor element in the same manner as in Example 1, then a graphite layer and an iron layer were sequentially formed, and the formation state of polypyrrole in the tantalum wire portion was observed with a 50 × microscope. Next, the cathode lead was connected with a silver paste and the anode lead was connected with electric welding, and the electrical characteristics were measured after packaging by the powder packaging method.

Table 1 shows the electrical characteristics of the capacitor produced above, the relationship between the polypyrrole formation state of the tantalum wire portion, the angle formed by the block material with the tantalum wire lead-out surface, and the contact angle between the block material and the oxidizer solution. It was

[0017]

[Table 1]

[0018]

As is apparent from the above results, when the angle formed by the block material with respect to the tantalum wire lead-out surface of the tantalum sintered body is smaller than the contact angle between the reaction liquid for forming the conductive polymer and the block material. Since the formation of the conductive polymer on the tantalum wire is suppressed and the leakage current defect is remarkably reduced, a highly reliable tantalum capacitor can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view when forming a block material according to the present invention.

FIG. 2 is a diagram showing a contact angle between a conductive polymer reaction solution and a block material.

FIG. 3 is a sectional view of the Teflon washer of the present invention.

FIG. 4 is a cross-sectional view of a tantalum element immersed in a conductive polymer forming liquid.

FIG. 5 is a sectional view of a tantalum element immersed in a manganese nitrate solution in which a block material of a conventional example is formed.

FIG. 6 is an insertion view of a conventional Teflon washer.

[Explanation of symbols]

 1 Tantalum sintered body element 2 Tantalum wire 3 Conductive polymer forming liquid 4 Block material 5 Teflon washer 6 Oxidizer solution

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location H01G 9/04 349 (72) Inventor Setsu Mukono 5-7-1 Shiba 5-chome, Minato-ku, Tokyo NEC Corporation (72) Inventor Takashi Fukaumi 5-7-1, Shiba, Minato-ku, Tokyo Inside NEC Corporation

Claims (3)

[Claims] 1. A solid electrolytic capacitor using a conductive polymer as a solid electrolyte, wherein a block material is formed at the lead-out portion of the positive wire. 2. The block material according to claim 1, wherein an angle formed by the block material with respect to the anode wire lead-out surface of the anode sintered body is smaller than a contact angle formed by the reaction liquid for forming a conductive polymer and the block material. Solid electrolytic capacitor. 3. The solid electrolytic capacitor according to claim 1, wherein the block material is one of fluororesin, silicon resin, acrylic resin, and epoxy resin.