JP3485848B2 - Solid electrolytic capacitors - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid electrolytic capacitor.

[0002]

2. Description of the Related Art In recent years, solid electrolytic capacitors using a conductive polymer as a solid electrolyte have been put into practical use for the purpose of lowering ESR. Generally, as these conductive polymers, there are polythiophene, polypyrrole, polyaniline, and the like. Among them, polythiophene has been attracting attention in recent years because it has particularly high electrical conductivity and thermal stability as compared with polypyrrole or polyaniline, As a solid electrolytic capacitor using polythiophene as a solid electrolyte, there is a solid electrolytic capacitor disclosed in JP-A-2-15611.

Although polythiophene can be formed by chemical polymerization and electrolytic polymerization, when electrolytic polymerization is carried out, it is necessary to attach several polymerization electrodes to one, and a conductive polymer is placed on the electrode. Since it has a problem that it is difficult to mass-produce because it is formed into a film, there is no such problem in the case of chemical oxidative polymerization. It is well known to those skilled in the art that the conductive polymer layer can be easily obtained.

[0004]

However, since polythiophene has a smaller polymerization rate in the chemical oxidative polymerization than other conductive polymers such as polypyrrole or polyaniline, it has a high conductivity with a desired thickness. In order to form a molecular layer, the polymerization time must be lengthened or the number of polymerizations must be increased, which has the problem of poor productivity and high cost. It had a problem that the reaction was significantly suppressed. Furthermore, since the conductive polymer layer obtained by chemical polymerization is formed from an aggregate of fine crystals, when the formed conductive polymer layer peels from the element surface or separates when immersed in a chemical polymerization solution. Therefore, it is difficult to form a thick conductive polymer layer on the surface of the capacitor element. Further, the resin exterior structure formed by the transfer molding method has a problem that the conductive polymer layer is damaged due to stress during molding, resulting in an increase in leakage current and a decrease in reliability.

The present invention is intended to solve the above-mentioned problems, and is produced by forming a conductive polymer layer having a uniform thickness and a desired thickness on the surface of a capacitor element and having excellent mechanical strength, with good characteristics. An object of the present invention is to provide a solid electrolytic capacitor having excellent properties.

[0006]

The present invention has been completed as a result of studies to solve the above-mentioned problems of the prior art. That is, the invention according to claim 1 is a capacitor element having a dielectric oxide film formed on the surface of an element body made of a valve metal into which an anode lead wire is implanted, and a creeping-up prevention portion provided on the anode lead wire. And a conductive polymer layer formed on the surface of the dielectric oxide film, a carbon layer formed on the conductive polymer, and a silver paint layer serving as a cathode formed on the carbon layer. In a solid electrolytic capacitor, the conductive polymer layer is a composite conductive polymer layer formed containing pulp, and the pulp adheres to the creep-up prevention portion, and the creep-up prevention portion and the creep-up prevention portion. By forming the first resin coating portion so as to cover the pulp adhered to the portion, it is possible to form a solid electrolytic capacitor having excellent mechanical strength, which improves workability and does not deteriorate characteristics. And Akira.

By constructing a composite of a conductive polymer and pulp, the thickness of the pulp is increased, the polymerization time and the number of times are reduced to improve the productivity, and the surface of the capacitor element has a uniform and thick conductivity. It is possible to form a polymer layer, improve mechanical strength, withstand the stress at the time of resin coating, and obtain a good solid electrolytic capacitor that does not increase leakage current or decrease reliability.

Further, in order to effectively form a pulp layer on the surface on which the anode lead wire is planted, it is necessary to form the pulp so that it adheres to the creeping-up prevention portion, but before the chemical oxidative polymerization, Since the creep-up prevention part and the attached pulp are covered with the first resin coating part, during the chemical polymerization, the creeping-up due to the capillarity phenomenon of the monomer or the oxidant is prevented, and the short circuit due to the contact with the anode lead wire is prevented. Can be prevented. Further, the first resin coating portion relieves the stress on the anode lead wire and improves the mechanical strength.

According to a second aspect of the present invention, at least the composite conductive polymer layer on the surface of the capacitor element on which the anode lead wire is formed is covered with the second resin coating portion. In addition to the effects described above, the surface on which the anode lead wire is planted is reinforced to further improve mechanical strength, withstand the stress during resin coating and soldering, and with good leakage current and no deterioration in reliability. An electrolytic capacitor can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is
A capacitor element formed by forming a dielectric oxide film on a surface of an element body made of a valve action metal such as tantalum, aluminum, niobium, or titanium, which is an anode into which an anode lead wire is implanted, and the anode lead wire. A creeping-up preventing portion such as a Teflon washer, a conductive polymer layer made of polythiophene or a derivative thereof formed on the surface of the dielectric oxide film, a carbon layer formed on the conductive polymer, and the carbon layer In a solid electrolytic capacitor comprising a cathode silver paint layer formed on the conductive polymer layer, the conductive polymer layer is a composite conductive polymer layer formed by containing pulp, and the pulp is prevented from creeping up. And a first resin coating portion is formed so as to cover the creep-up prevention portion and the pulp attached to the creep-up prevention portion. A solid electrolytic capacitor.

In the invention according to claim 1,
The structure of the capacitor element may be either a fine powder sintered body type or a foil winding type, and the means for forming the dielectric oxide film is not limited to a special one, but may be a known means.

As the pulp used for forming the composite conductive polymer layer, unbeaten pulp is used as the main component.
The unbeaten pulp, which is the main component, is a thick and long pulp, and the presence of the unbeaten pulp adhering to the surface of the capacitor element can effectively form a pulp layer having a desired thickness, and the thickness of the pulp is large. When forming the composite conductive polymer layer, the number of times of polymerization and the polymerization time can be reduced, which can contribute to the improvement of productivity. Further, since the composite conductive polymer layer has improved mechanical strength, it can endure the stress at the time of resin coating, and a good solid electrolytic capacitor without increase in leakage current and deterioration in reliability can be obtained.
Further, in order to easily attach the pulp to the surface of the capacitor element, a long and thick unbeaten pulp can be mixed as a main component with a sufficiently beaten pulp.

The invention according to claim 2 of the present invention is characterized in that at least the composite conductive polymer layer on the surface of the capacitor element on which the anode lead wire is formed is covered with the second resin coating portion. It is a thing.

At this time, the same effect can be obtained even if the second resin coating portion covers not only the composite conductive polymer layer but also the entire surface on which the anode lead wire is formed such as the first resin coating portion. It is a thing.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure of the solid electrolytic capacitor of the present invention will be described below with reference to the drawings. In FIG. 1, 1
Is a capacitor element formed by forming an anodized film on the surface of a sintered body made of fine tantalum powder as a valve-acting metal serving as an anode, and 2 is a composite formed by incorporating pulp 3 attached to the surface of the capacitor element 1. 4 with conductive polymer layer
Is a carbon layer formed on the composite conductive polymer layer 2, 5 is a silver coating layer serving as a cathode formed on the carbon layer 4, and 6 is an anode lead wire embedded in the sintered body,
7 is a creeping-up prevention part provided on the anode lead wire, and 8
Is a first resin coating portion formed by taking in pulp attached to the creeping-up prevention portion 7, and 9 is a first resin coating portion which is in contact with the first resin coating portion 8 and covers the surface where the anode lead wire is planted. 2 is a resin coating portion.

Next, specific examples will be described in detail in comparison with comparative examples. That is, Example 1 shown below
2 and the comparative examples 1 to 3 according to the related art, the results of measuring the capacity, leakage current and ESR characteristics are shown in Table 1.

(Example 1) The size of the anode was 3.9 ×
Using a tantalum sintered body of 3.3 × 1.6 mm ³ and using a tantalum wire as an anode lead wire, an anode body having a weight of about 100 mg is covered with a Teflon washer as a creeping-up prevention portion at the base of the anode lead wire. , 0.05 wt% phosphoric acid aqueous solution was anodized at 90 ° C. and 40 V for 180 minutes, washed with running deionized water, and dried to obtain a capacitor element. It was noted that this state was regarded as a capacitor and the capacity in the chemical conversion liquid was measured and the result was 104 μF.

Next, 50 g of butyl alcohol and 50 g of 3,4-ethylenedioxythiophene were added to this capacitor element.
dip for 7 minutes in a monomer solution prepared by mixing
Next, as an oxidant containing a transition metal ion, 40 g of ferric p-toluenesulfonate is dissolved in 60 g of butanol and immersed in an oxidant solution for 15 minutes to carry out chemical oxidative polymerization to perform anodic oxidation to form a capacitor element. A conductive polymer layer was formed on the film, washed with butanol for 5 minutes, and then dried at 105 ° C for 5 minutes. The number of times of polymerization from dipping in a monomer solution to drying was repeated 10 times until the conductive polymer layer had a desired thickness.

Next, the capacitor element having the conductive polymer layer thus formed was mixed with 2% by weight of pulp, 0.
The top surface of the element is dipped in a 05 wt% suspension and the pulp is attached to the surface of the capacitor element so that the teflon washer of the creeping-up prevention part also attaches the pulp. In this case, the suspension is agitated, and the pulp can be effectively attached to the surface of the capacitor element by immersing it in the flowing pulp, and especially the edge portion of the capacitor element where mechanical strength is required. Can be effectively attached. Then, the capacitor element to which pulp is attached in this way is heated at 105 ° C for 5 minutes.
Dry for minutes. The process from immersion in the suspension to drying was repeated twice until the pulp layer had a desired thickness.

Next, the epoxy resin was discharged onto the creeping-up prevention portion of the capacitor element having the pulp adhered to the surface, and the pulp adhered to the portion was formed to form the first resin portion.

Next, the capacitor element having the pulp adhered to the surface is again immersed in the monomer solution for 7 minutes, immersed in the oxidant solution for 15 minutes for chemical oxidative polymerization, and washed with butanol for 5 minutes. The step of drying at 105 ° C. for 5 minutes was repeated 5 times to form a composite conductive polymer layer incorporating pulp of a desired thickness on the surface of the capacitor element. Then, a carbon layer is formed on the composite conductive polymer layer, and a silver paint layer serving as a cathode is formed on the carbon layer, and a cathode lead terminal is drawn out from the anode body on the silver paint layer. The anode lead terminal is attached to the anode wire as close as possible to the creeping-up prevention part, resin is coated by transfer molding, and the cathode lead terminal and the anode lead terminal are bent at predetermined positions to form a chip-shaped solid electrolytic capacitor. Was completed.

(Example 2) Completed in the same manner as in Example 1 except that after forming the silver coating layer which becomes the cathode, the surface on which the anode lead wire is planted is covered with an epoxy resin to form the second resin portion. It was done.

(Comparative Example 1) A finished product is obtained through the same steps as in Example 1 except for the step of depositing the pulp on the surface of the capacitor element, but the pulp is not deposited on the surface of the capacitor element. The conductive polymer layer structure on the surface of the capacitor element is not a composite with pulp, but is a simple conductive polymer layer, and the number of polymerizations in this case is 61 times.

(Comparative Example 2) This is completed in the same manner as in Example 1 except that the step of forming the first resin portion is not performed.

(Comparative Example 3) Dip to the upper surface of the element to prevent pulp from adhering to the Teflon washer so that pulp does not adhere to the surface of the capacitor element so that pulp also adheres to the Teflon washer in the creeping-up prevention section. It was completed as in Comparative Example 2 except that the pulp layer was formed.

[0026]

[Table 1]

As is clear from Table 1, the solid electrolytic capacitors of Examples 1 and 2 have excellent leakage current and ESR characteristics and high reliability, while those of Comparative Example 1 It can be seen that the leakage current characteristic is not good even when the number of times of polymerization is 61 times. Further, in Comparative Example 2, a short circuit failure was caused due to all creeping up. In order to prevent a short circuit defect, if the adhesion of the pulp on the anode lead wire surface is insufficient as in Comparative Example 3, the leakage current characteristics deteriorate. This is because the mechanical strength of the surface of the anode lead wire is weak, and the characteristics are deteriorated by the stress during resin coating or soldering.

[0028]

As described above, according to the present invention, a capacitor element in which a dielectric oxide film is formed on the surface of an element body made of a valve metal into which an anode lead wire is implanted, and the anode lead wire are provided. A creeping-up prevention portion provided, a conductive polymer layer formed on the surface of the dielectric oxide film, a carbon layer formed on the conductive polymer, and a cathode formed on the carbon layer. In the solid electrolytic capacitor comprising a silver paint layer, the conductive polymer layer is a composite conductive polymer layer formed by containing pulp, and the pulp adheres to the creeping-up prevention part, Since the first resin coating part is formed so as to cover the pulp attached to the rising prevention part and the creeping prevention part, it has excellent mechanical strength, good workability, and good leakage current characteristics. Naken It is possible to obtain an electrolytic capacitor.

Further, by covering at least the composite conductive polymer layer of the surface of the capacitor element on which the anode lead wire is formed with the second resin coating portion, in addition to the above-mentioned effect, the surface on which the anode lead wire is planted. Since it is reinforced, the mechanical strength is further improved, and it is possible to obtain a good solid electrolytic capacitor which can withstand the stress at the time of resin coating or soldering, and which does not increase leakage current or decrease reliability.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic structure of a solid electrolytic capacitor of the present invention.

[Explanation of symbols]

1 Capacitor element 2 Composite conductive polymer layer 3 pulp 4 carbon layer 5 Silver paint layer 6 Anode lead wire 7 Climbing prevention section 8 First resin coating 9 Second resin coating

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Fumihiko Haga 1-1, Sachimachi, Nagai City, Yamagata Prefecture Marcon Denshi Co., Ltd. (72) Gensaburo Watanabe 1-1, Sachimachi, Nagai City, Yamagata Prefecture Marcon Denshi (56) References JP-A-9-320901 (JP, A) JP-A-6-342742 (JP, A) JP-A-11-87178 (JP, A) JP-A-3-255607 (JP, A) A) JP 10-261548 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01G 9/00-9/028

Claims (2)

(57) [Claims] 1. A capacitor element formed by forming a dielectric oxide film on a surface of an element body made of a valve metal in which an anode lead wire is implanted, a creeping-up prevention portion provided on the anode lead wire, and the dielectric. In a solid electrolytic capacitor comprising a conductive polymer layer formed on the surface of a body oxide film, a carbon layer formed on the conductive polymer, and a silver paint layer serving as a cathode formed on the carbon layer The conductive polymer layer is a composite conductive polymer layer formed by containing pulp, and the pulp adheres to the creep-up prevention portion, and adheres to the creep-up prevention portion and the creep-up prevention portion. A solid electrolytic capacitor, wherein a first resin coating portion is formed so as to cover the pulp. 2. The solid electrolytic capacitor according to claim 1, wherein at least the composite conductive polymer layer on the surface of the capacitor element on which the anode lead wire is formed is covered with the second resin coating portion.