JPH05234826A - Manufacture of capacitor - Google Patents

Abstract

PURPOSE:To provide a manufacturing method which easily obtains a capacitor whose impedance characteristic in a high-frequency region has been enhanced further regarding the manufacturing method of the capacitor wherein it is excellent in a frequency characteristic, a temperature characteristic and a loss characteristic, it is small-sized and its capacitance large. CONSTITUTION:When an electrode for a capacitor using an electrolytically polymerized conductive polymer as the electrode at least on one side is formed, the surface of a dielectric is made hydrophobic in advance and an electrolytically polymerized polymer film is formed. Thereby, a growth speed in a face direction can be made large. As a result, it is possible to restrain the undesirable growth in a film-thickness direction. Consequently, it is possible to easily obtain the capacitor whose impedance characteristic in a high-frequency region has been enhanced further.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a capacitor which has excellent capacitor characteristics, particularly frequency characteristics, and which uses a conductive polymer for at least one electrode.

[0002]

2. Description of the Related Art In recent years, with the digitization of electrical equipment,
The capacitors are also required to be small in size, large in capacity, and low in impedance in the high frequency range. Conventionally, capacitors used in the high frequency region include plastic capacitors, mica capacitors, and laminated ceramic capacitors, but it is difficult to increase the capacity of these capacitors due to their large size.

On the other hand, as a large-capacity capacitor, there is an electrolytic capacitor such as an aluminum dry electrolytic capacitor or an aluminum or tantalum solid electrolytic capacitor.
In these capacitors, the oxide film that serves as a dielectric is extremely thin, so a large capacity can be realized.However, since the oxide film is easily damaged, it is necessary to provide an electrolyte between it and the cathode to repair it. is there.

In an aluminum dry type capacitor, an etched positive and negative aluminum foil is wound around a separator and a liquid electrolyte is impregnated into the separator for use. Since this liquid electrolyte is ionic conductive and has a large specific resistance, the loss is large and the impedance frequency characteristic and temperature characteristic are significantly inferior.In addition, liquid leakage, evaporation, etc. are unavoidable, and the capacity decreases and the loss with the passage of time. I had a problem with an increase.

Further, since the manganese dioxide is used as the electrolyte in the tantalum solid electrolytic capacitor, the problems of temperature characteristics and changes with time such as capacity and loss are improved, but since the specific resistance of manganese dioxide is relatively high, the loss and impedance are relatively high. Was inferior in frequency characteristics to the monolithic ceramic capacitor or film capacitor.

In recent years, a frequency characteristic using a conductive polymer containing anion of a supporting electrolyte as a dopant by electrolytically oxidatively polymerizing a heterocyclic monomer such as pyrrole or thiophene using a supporting electrolyte as an electrolyte (true cathode). Also, solid electrolytic capacitors having excellent temperature characteristics have been proposed (JP-A-60-37114 and JP-A-60-244017).

Furthermore, a large-capacity film capacitor has been proposed in which a dielectric made of an electrodeposited polyimide thin film is formed on an etched aluminum foil and then an electrolytically polymerized conductive polymer layer is formed to serve as an electrode (electrochemistry. Annual Meeting of the 58th Annual Meeting, pp. 251-252, 1991).

[0008]

However, in the above-mentioned conventional method, it is necessary to use the external electrode for forming the electrolytically polymerized polymer film because the current cannot flow through the dielectric layer. .. Therefore, the growth of the electropolymerized film starts from the contact portion between the dielectric and the external electrode, and it takes a relatively long time to finish covering the entire surface of the dielectric. However, it has a problem that it becomes thicker and the equivalent series resistance tends to increase.

The present invention solves the above-mentioned problems of the prior art. By increasing the coating speed of the electropolymerized polymer, the nonuniformity of the coating film thickness is alleviated, and particularly the impedance characteristics in the high frequency range are excellent. The purpose is to efficiently provide a capacitor.

[0010]

In order to achieve this object, the present invention is directed to a surface growth rate of an electrolytically polymerized polymer film to be an electrode by hydrophobizing the surface of a dielectric layer and then performing electrolytic polymerization. Is designed to be large.

As an example of the hydrophobic treatment of the dielectric surface,
A method of adsorbing a highly hydrophobic substance, that is, a hydrophobizing agent on the surface can be mentioned. As the hydrophobizing agent, any substance can be used as long as it is a substance that is adsorbed on the surface of a substance forming a dielectric and increases the hydrophobicity, but a silane of a silicon compound that gives a particularly high effect is suitable. Examples of such silanes include inorganic silanes, methyl silanes, phenyl silanes, vinyl silanes, and alkoxy silanes.

The thickness of the adsorption layer is not limited as long as it does not substantially reduce the capacitance of the capacitor, but is preferably thin, and particularly preferably the thickness of the monomolecular film.

As the polymerizable monomer, any one can be used as long as it produces a conductive polymer having an electric conductivity such that it can substantially become an electrode by electrolytic polymerization, but it is preferably pyrrole or The derivatives may be used alone or as a mixture.

Any material can be used as the dielectric as long as it is a material that substantially constitutes a capacitor.
In addition to anodized films of valve metals such as aluminum and tantalum, polymer thin films such as polyimide and polyphenylene sulfide, or ferroelectrics such as barium titanate are preferably used.

As the electrolytic polymerization solvent, any solvent can be used as long as it can dissolve or disperse the polymerizable monomer and the supporting electrolyte, but water is preferable from the viewpoint of safety and cost. Further, a mixed solvent containing a compatible organic solvent containing water as a main component is also preferably used. Further, as the supporting electrolyte, any one can be used as long as it is a dopant that gives a conductive polymer having good film forming property, excellent chemical conversion property of aluminum, and excellent heat resistance and humidity resistance. For this purpose, naphthalene sulfonate having at least one alkyl group having 1 to 6 carbon atoms may be used alone or in combination.

Prior to the hydrophobic treatment of the dielectric surface,
A conductive underlayer for electrolytic polymerization, such as manganese dioxide, can also be provided. This can be expected to further improve the effect of the hydrophobic treatment.

[0017]

In the present invention, by pre-hydrophobizing the surface of the dielectric substance to be coated with the electropolymerized polymer film, the conductive polymer having increased hydrophobicity due to polymerization is easily adsorbed or oriented on the surface. , The growth rate in the plane direction increases. As a result, the time required for coating with the electrolytically polymerized polymer is shortened, and undesired growth in the film thickness direction in the vicinity of the external electrode contact portion is suppressed, so that a capacitor having excellent impedance characteristics in the high frequency range can be obtained.

[0018]

(Embodiment 1) A first embodiment of the present invention will be described below.

The anode lead was attached to an 8 × 10 mm aluminum etched foil, and a 3% ammonium adipate aqueous solution was used to apply a voltage of 35 V at about 70 ° C. to form a dielectric film by anodic oxidation. The anode was prepared by immersing and further heating at 250 ° C. for 10 minutes to deposit pyrolytic manganese oxide on the surface. This anode foil was coated with 0.1% n- of octadecyltriethoxysilane (OTES).
It was immersed in a hexane solution and air dried at 125 ° C. for 1 hour.

This was brought into contact with a stainless steel electrolytic polymerization electrode previously coated with polypyrrole, and pyrrole (0.3 mol / l), sodium mono-n-butylnaphthalene sulfonate (SMnBNS) (0.1 mol / l)
l) A voltage of 3 V was applied between the electrolytic polymerization electrode and the second electrode for electrolytic polymerization, which was separated from the electrolytic polymerization electrode, to form an electrolytic polymerization film made of polypyrrole. The time required for coating the polypyrrole was 15 to 20 minutes. After removing the electrolytically polymerized electrode, washing with water and drying, carbon paste and silver paste were applied on the electrolytically polymerized film, and the cathode lead was taken out to complete 10 capacitor elements. The capacitance and loss at 120 Hz and the impedance at 400 kHz after aging at 13 V are shown in (Table 1).

For comparison, as Comparative Example 1, a capacitor was completed under the same conditions as in Example 1 except that the hydrophobic treatment was not performed. The time required to coat polypyrrole is 30-
It took about 40 minutes. Further, the same characteristic evaluation as in Example 1 was performed, and the results are shown in (Table 1).

[0022]

[Table 1]

As is clear from the comparison of the time required for coating the polypyrrole and the result (Table 1), the capacitor according to this embodiment can shorten the time required for coating the polypyrrole and further reduce the impedance of 400 kHz. Excellent effect can be obtained.

As described above, according to this embodiment, the surface of the dielectric material is hydrophobized to promote the growth of the electrolytically polymerized film in the surface direction, shorten the coating time, and reduce the impedance in the high frequency range. It is possible to realize a small capacitor.

(Embodiment 2) 0.1 of OTES of Embodiment 1
% N-hexane solution, n-propyltrichlorosilane (nPTCS), dimethoxydiphenylsilane (D
MDPS), methylphenyldichlorosilane (MPDC)
Ten capacitors of each of three types were produced in the same manner as in Example 1 except that the hydrophobization treatment was performed using each 0.1% n-hexane solution of S). The time required for coating was 15 to 20 minutes in each case. The results of evaluation of these capacitors similar to those in Example 1 are shown in (Table 1).

As is clear from the comparison of the time required for coating the polypyrrole and this (Table 1), the capacitor according to the present embodiment can shorten the time required for coating the polypyrrole and further reduce the impedance of 400 kHz. Excellent effect can be obtained.

As described above, according to the present embodiment, the surface of the dielectric material is hydrophobized to accelerate the growth of the electropolymerized film in the plane direction, shorten the coating time, and reduce the impedance in the high frequency range. It is possible to realize a small capacitor.

Example 3 Ten capacitors were produced in the same manner as in Example 1 except that an aqueous solution containing 10% by weight of ethanol was used as a solvent instead of water. The time required for coating with polypyrrole was 15 to 20 minutes. The results of the same evaluation as in Example 1 of this capacitor are shown (Table 1).
Shown in.

As is clear from the comparison of the time required for coating the polypyrrole and this (Table 1), the capacitor according to the present embodiment can shorten the time required for coating the polypyrrole and further reduce the impedance of 400 kHz. Excellent effect can be obtained.

As described above, according to the present embodiment, by making the surface of the dielectric material hydrophobic, the growth of the electropolymerized film in the surface direction is promoted, the coating time is shortened, and the impedance in the high frequency range is also increased. It is possible to realize a small capacitor.

(Example 4) Pyrrole (0.3 mol /
1) instead of pyrrole (0.21 mol / l) and N-
Ten capacitors were produced in the same manner as in Example 1 except that a mixed monomer composed of methylpyrrole (0.09 mol / l) was used. The time required for coating with polypyrrole was 15 to 20 minutes. In addition, this capacitor is used in the first embodiment.
Evaluations similar to those were performed and the results are shown in (Table 1).

For comparison, as Comparative Example 2, a capacitor was completed under the same conditions as in Example 4 except that the hydrophobic treatment was not performed. The time required to coat polypyrrole is 30-
It took about 40 minutes. Further, the same characteristic evaluation as in Example 1 was performed, and the results are shown in (Table 1).

As is clear from the comparison of the time required for coating the polypyrrole and this (Table 1), the capacitor according to this embodiment can shorten the time required for coating the polypyrrole and further reduce the impedance of 400 kHz. Excellent effect can be obtained.

As described above, according to this embodiment, the surface of the dielectric film is hydrophobized to promote the growth of the electropolymerized film in the surface direction, shorten the coating time, and reduce the impedance in the high frequency range. It is possible to realize a small capacitor.

(Example 5) 10 instead of aluminum foil
% Ten phosphoric acid aqueous solution was used, and ten capacitors were prepared in the same manner as in Example 1 except that tantalum foil formed at 90 ° C. was used. The time required for coating polypyrrole is 10 to 1
It was 5 minutes. This capacitor was evaluated in the same manner as in Example 1 and the results are shown in (Table 1).

For comparison, as Comparative Example 3, a capacitor was completed under the same conditions as in Example 5 except that the hydrophobic treatment was not performed. The time required for coating polypyrrole is 20 to 2
It was 5 minutes. In addition, the same characteristic evaluation as in Example 1 was performed,
The results are shown in (Table 1).

As is clear from the comparison of the time required for coating with polypyrrole and this (Table 1), the capacitor according to the present embodiment can shorten the time required for coating with polypyrrole and further reduce the impedance of 400 kHz. Excellent effect can be obtained.

As described above, according to the present embodiment, the surface of the dielectric material is hydrophobized to accelerate the growth of the electropolymerized film in the surface direction, shorten the coating time, and reduce the impedance in the high frequency range. It is possible to realize a small capacitor.

Example 6 Ten capacitors were produced in the same manner as in Example 1 except that sodium p-toluenesulfonate was used instead of SMnBNS of the supporting electrolyte. The time required for coating with polypyrrole was 15 to 20 minutes. This capacitor was evaluated in the same manner as in Example 1, and the results are shown in (Table 1).

For comparison, as Comparative Example 4, a capacitor was completed under the same conditions as in Example 6 except that the hydrophobic treatment was not performed. The time required to coat polypyrrole is 30-
It was 40 minutes. Further, the same characteristic evaluation as in Example 1 was performed, and the results are shown in (Table 1).

As is clear from the comparison of the time required for coating with polypyrrole and this (Table 1), the capacitor according to this embodiment can shorten the time required for coating with polypyrrole and further reduce the impedance of 400 kHz. Excellent effect can be obtained.

As described above, according to this embodiment, the surface of the dielectric film is hydrophobized to promote the growth of the electrolytically polymerized film in the plane direction, shorten the coating time, and reduce the impedance in the high frequency range. It is possible to realize a small capacitor. In the examples, only the case where silane is used for the hydrophobizing treatment is described, but other hydrophobizing agents selected from fluorine compounds and the like may be used, and the present invention is not limited to the kind.

In the examples, only the case where the oxide film of the valve metal is used as the dielectric is described, but the present invention is also applied to the case where polyimide formed by electrodeposition on the metal surface is used as the dielectric. The present invention is not limited to the kind of the dielectric material, and can be similarly applied when the ferroelectric material barium titanate is used as the dielectric material.

In the examples, only the case where the electrode made of the electrolytically polymerized polymer is used for only one electrode of the capacitor has been described, but it is also possible to use for both electrodes.

In the examples, only the case of using an electrolytically polymerized polymer having pyrrole and its derivative as a repeating unit was described, but thiophene or its derivative, aniline or the like can also be used.

In the examples, only the case of using a medium containing water as a main component has been described, but an organic solvent can be similarly used.

[0047]

As described above, according to the present invention, the formation of at least one electrode of a capacitor having two electrodes via a dielectric layer is performed by hydrophobizing the surface of the dielectric layer and then electrolyzing the surface of the dielectric layer. The coating is performed by coating with a conductive polymer film having a polymerizable monomer as a repeating unit by polymerization, and the time required for the coating can be shortened, and as a result, undesirable growth in the film thickness direction is suppressed. Therefore, a capacitor having further improved impedance characteristics in the high frequency range can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Yoshida 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (6)

[Claims] 1. A dielectric layer is formed on the surface of a valve metal, and at least one of the surfaces of the dielectric layer is hydrophobized, and then a conductive monomer containing a polymerizable monomer as a repeating unit by electrolytic polymerization is formed on the dielectric surface. A method of manufacturing a capacitor, which comprises forming a polymer film. 2. The method for manufacturing a capacitor according to claim 1, wherein the dielectric layer is an oxide of a valve metal. 3. The method for producing a capacitor according to claim 1, wherein the polymerizable monomer is composed of at least one kind of pyrrole or its derivative. 4. The method for manufacturing a capacitor according to claim 2, wherein the valve metal is one selected from aluminum and tantalum. 5. The method for producing a capacitor according to claim 1, wherein the electrolytic polymerization is performed in an aqueous medium. 6. The method for manufacturing a capacitor according to claim 1, wherein the hydrophobic treatment is performed using silane.