JPH1079326A - Capacitor and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact large-capacity capacitor with less leakage current and lower dielectric loss tangent and a method for manufacturing it. SOLUTION: Electrodeposition liquid comprising aqueous solution containing polycarboxylic acid with electrolytic aqueous solution including organic acid, inorganic acid or their salt for facilitating anodization is used to provide a dielectric layer comprising a polycarboxylic acid resin coat 2 and a conductive anodizing coat 3 on a roughened surface of a conductor 1, and conductive layers 4, 5, 6 are further formed as opposite electrodes on a surface of the dielectric layer. Thus, a leakage current value is lower and withstanding voltage is higher than that of a capacitor comprising only a polycarboxylic acid resin coat with the dielectric layer formed by electrodeposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor used for an electronic circuit of electric equipment, electronic equipment, and audio equipment.

[0002]

2. Description of the Related Art In recent years, devices have become smaller, thinner and lighter.
With the increase in the density and digitalization of electric device circuits, there is an increasing demand for miniaturization, higher performance, and higher reliability of electronic components. Under such circumstances, there is a strong demand for a capacitor having a small size, a large capacity, and a low impedance in a high frequency region.

[0003] Capacitors having a low impedance in a high frequency region include various types of ceramic capacitors and film capacitors using a ceramic or polymer film as a dielectric material. Will also be higher.

On the other hand, an electrolytic capacitor using an aluminum or tantalum oxide film as a dielectric is relatively small and has a large capacity, but the impedance and dielectric characteristics in a high frequency region are inferior to those of the above-mentioned ceramic and film capacitors. There is.

Therefore, in order to improve impedance characteristics in a high frequency region, a solid electrolytic capacitor has been developed in which the electrolytic solution portion of the electrolytic capacitor is replaced with manganese dioxide, polypyrrole, or the like having higher conductivity.

Further, a new type of compact type in which a high insulating polymer film is formed on an etched aluminum foil by an electrodeposition method instead of an aluminum oxide film, and a conductive polymer is formed on the surface. A method for manufacturing a high-capacity film capacitor has also been proposed (for example, Japanese Patent Application Laid-Open No. 4-87312).

[0007]

The etched aluminum foil used in the above invention has a thickness of about 100 μm, and the shape of the etching hole has a hole diameter of 1 to 3 μm and a hole depth of 3 μm.
0 to 50 μm. We formed a polymer film that conformed to the shape of the holes by electrodeposition on the surface of such an etched aluminum foil that had many holes with a large aspect ratio, and evaluated and evaluated it as a dielectric thin film for capacitors. We have been doing various things so far.

As a result, for example, when several capacitors are manufactured by forming a polycarboxylic acid-based resin on the surface of an etched aluminum foil so as to have a thickness of 0.2 μm or less, the leakage current becomes extremely large. It turns out that there may be cases.

The following can be considered as the cause. One is that the etched aluminum foil has an extremely complicated shape, and it is difficult to keep the electric field strength of the entire foil uniform during electrodeposition, so that an extremely thin portion may occur in some places. The other is, simultaneously with electrodeposition film deposition,
Since gas generation due to electrolysis of water occurs near the electrode (substrate), pinholes may be generated in the film.

Further, in the electrodeposition process, the polycarboxylic acid particles charged by applying a voltage in the electrodeposition liquid filled in the pores adhere to the pore walls. At this time, since the depth of the hole of the etched aluminum foil is several tens times longer than the hole diameter, it is considerably slow that new polycarboxylic acid particles are supplied from the outside of the hole to the inside of the hole by diffusion. For this reason, defects were easily generated in the electrodeposited film near the back of the hole, and the film thickness was likely to be thinner than near the entrance of the hole.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a new type of capacitor having a small leakage current, a small size and a large capacity, and a method of manufacturing the same.

[0012]

In order to achieve the above object, a capacitor according to the present invention comprises a dielectric layer comprising a polycarboxylic acid resin and an anodic oxide film of the conductor on a roughened conductor surface. And a conductive layer as a counter electrode on the dielectric surface.

As a roughened conductor, an etched aluminum foil is suitable for this purpose.

Here, the polycarboxylic acid-based resin refers to a polymer having a carboxylic acid group in a main chain or a side chain of a polymer. For example, polyacrylic acid, polymethacrylic acid, polyamic acid, and the like. Also, a mixture of a copolymer of these materials and a curing agent such as melamine can be used as long as it is suitable for the purpose. Among these, a polyacrylic acid resin which is water-soluble and excellent in workability, and excellent in adhesiveness to aluminum and flexibility is suitable for this purpose.

Further, as the counter electrode, a highly conductive polymer such as polypyrrole doped with an anion is preferable.

In order to achieve the above object, a method of manufacturing a capacitor according to the present invention is characterized in that an aqueous solution containing an organic acid, an inorganic acid or an salt thereof for promoting anodic oxidation is added to an aqueous solution containing a polycarboxylic acid. A step of adding and synthesizing an electrodeposition solution, and a dielectric comprising a polycarboxylic acid-based resin film and an anodized film of the conductor on the surface of the conductor roughened using the electrodeposition solution to which the electrolyte aqueous solution is added. A step of forming a layer and a step of further forming a conductor layer as a counter electrode on the dielectric surface.

The electrolyte added to the aqueous solution containing polycarboxylic acid is preferably adipic acid, maleic acid, succinic acid, malic acid, phosphoric acid, boric acid, or a salt thereof.

Further, after adding an aqueous electrolyte solution for promoting anodization to the aqueous polycarboxylic acid solution, the pH of the
An appropriate amount of ammonia or amines may be added to the aqueous electrolyte solution or the aqueous solution containing polycarboxylic acid in advance so that H is in the range of 7 to 9, or the amount of polycarboxylic acid particles in the electrodeposition solution in the present invention may be adjusted. This is important when considering dispersibility.

[0019]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, a highly insulating anodic oxide film is formed on a portion of a polycarboxylic acid resin film having a low electric resistance or a conductor underlying a defective portion. Therefore, the capacitor has an effect that the leakage current value is lower and the withstand voltage is higher than that of the capacitor in which the dielectric layer is formed only of the polycarboxylic acid resin film.

According to the second aspect of the present invention, since an etched aluminum foil is used as the roughened conductor, the electrode has a large surface area and is suitable for increasing the capacity. It has the effect of easily forming a film.

According to the third aspect of the present invention, since a polyacrylic acid resin is used as the polycarboxylic acid-based resin, it has an effect of being excellent in flexibility, adhesion to a substrate, and workability.

According to a fourth aspect of the present invention, since the counter electrode is a conductive polymer doped with an anion, a conductive polymer is easily formed on the surface of the dielectric layer by chemical polymerization or a combination of chemical polymerization and electrolytic polymerization. Has the effect of forming a conductor layer having a high density.

The fifth aspect of the invention has the effect of using polypyrrole among conductive polymers to achieve excellent conductivity and stability.

According to a sixth aspect of the present invention, there is provided a process for synthesizing an electrodeposition solution by adding an aqueous solution of an organic acid, an inorganic acid or an electrolyte comprising a salt thereof for promoting anodization to an aqueous solution containing a polycarboxylic acid. Forming a dielectric layer comprising a polycarboxylic acid-based resin film and an anodic oxide film of the conductor on the surface of the conductor roughened using an electrodeposition solution to which the electrolyte aqueous solution has been added; and Forming a conductive layer as a counter electrode on the surface of the layer, thereby enabling a dielectric having high electric resistance to be efficiently formed in a short time, thereby producing an excellent capacitor.

According to a seventh aspect of the present invention, the electrolyte added to the aqueous solution containing a polycarboxylic acid is adipic acid, maleic acid, succinic acid, malic acid, phosphoric acid, boric acid, or a salt thereof. It is also possible to form a dense and high-resistance anodic oxide film on the underlying conductive portion of the low-resistance portion of the polycarboxylic acid-based resin film.

The invention according to claim 8 is characterized in that the pH of the electrodeposition solution after adding an aqueous electrolyte solution for accelerating anodic oxidation to the aqueous solution containing polycarboxylic acid is adjusted so as to be in the range of 7-9. By adding an appropriate amount of ammonia or amines to an aqueous electrolyte solution or an aqueous solution containing a polycarboxylic acid, the aggregation and precipitation of particles due to a decrease in pH during the addition of the aqueous electrolyte solution are suppressed, and the It is intended to enhance the dispersibility of the polycarboxylic acid particles, facilitate the migration of the particles, and easily form a dense anodic oxide film.

(Embodiments) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a capacitor described in an embodiment of the present invention, FIG. 2 is a flowchart showing a method of manufacturing the capacitor of the embodiment, and FIG. 3 is a manufacturing method of the capacitor of the embodiment. It is the schematic of the electrophoresis electrodeposition apparatus used for the method.

First, the configuration of a target capacitor is shown in FIG.
This will be described in detail with reference to FIG. Reference numeral 1 in the drawing denotes an etched aluminum foil electrode having an average pore diameter of 2 μm generated by etching and having a surface area approximately 30 times roughened. A polycarboxylic acid-based resin film 2 is formed by electrodeposition so as to follow the surface shape of the electrode 1. Further, an anodic oxide film 3 of aluminum is formed on a thin portion or a defective portion of the polycarboxylic acid resin film 2. The counter electrode of the etched aluminum foil electrode 1 is composed of a current collector 6 attached to a first polypyrrole layer and a second polypyrrole layer 5 of a conductive polymer so as to collect current. Reference numeral 7 denotes an epoxy resin attached for insulating the electrodes. Then, if a lead wire is provided on the two electrodes shown in this figure and the package is covered with epoxy resin, the structure of the capacitor of the present embodiment is obtained.

Next, a method of manufacturing the capacitor having the above configuration will be described in detail with reference to FIGS.

First, the step of synthesizing the electrodeposition solution in step 1 will be described. The aqueous solution containing the polycarboxylic acid used was an emulsion solution containing 10% by weight of solid content, 86% by weight of ion-exchanged water, and 4% by weight of butyl cellosolve. The solid content used herein was a mixture of a copolymer of polyacrylic acid and polymethacrylic acid (molecular weight: about 50,000) (main ingredient) and a melamine resin (curing agent) in a weight ratio of 7: 3. When dispersing the solid content in a liquid,
It is needless to say that a part of the carboxylic acid groups in the solid content is neutralized by adding an appropriate amount of triethylamine to improve the dispersibility, as is often the case with the anion electrodeposition method. In addition, 5
An electrodeposition solution 8 (pH = 7.5 to 7.5) was added to a 200% aqueous solution containing the above polycarboxylic acid with stirring, and 10 ml of a solution prepared to pH = 8 by adding triethylamine to an aqueous solution of ammonium adipate (wt%). 8.5).

Next, the step of forming a dielectric layer in step 2 will be described. The etched aluminum foil electrode 1 cut to a size of 20 mm × 10 mm is immersed in an electrodeposition liquid 8 contained in a cylindrical stainless steel container 9 having a diameter of 80 mm serving as a cathode, and is immersed in the electrode forming liquid 8 as a dielectric forming portion. did. Next, a current is applied between the two electrodes at an applied voltage of 30 V (constant) for 30 minutes to form a dielectric layer comprising a polycarboxylic acid resin film 2 and an aluminum anodic oxide film 3 on the surface of the etched aluminum foil electrode 1. Was formed.

The phenomenon in which the dielectric layer is formed will be described in more detail below. The generation of the polycarboxylic acid resin film 2 by applying a voltage is considerably faster than the case where the substrate is sufficiently anodized. Therefore, simultaneously with the application of the voltage, the polycarboxylic acid-based resin film 2 is etched with the etched aluminum foil electrode 1.
From the vicinity of the surface toward the inside of the hole. As described above, in the electrodeposition process, the polycarboxylic acid resin film 2 (diameter of about 0.05 μm) migrates to a portion having a lower resistance, so that the polycarboxylic acid-based resin film 2 is formed on the etched aluminum foil electrode 1 substrate. Gradually formed a coating,
Insulated.

However, since the shape of the etched aluminum foil electrode 1 is extremely complicated, depending on the location,
Some parts have a small thickness. In addition, pinholes may be formed in the polycarboxylic acid resin film 2 due to generation of oxygen gas due to electrolysis of water.

Further, in the electrodeposition process, the charged polycarboxylic acid particles in the electrodeposition solution filled in the pores adhere to the pore walls. At this time, since the depth of the hole of the etched aluminum foil electrode 1 is several tens times longer than the hole diameter, it is considerably slow that new polycarboxylic acid particles are supplied from the outside of the hole to the inside of the hole by diffusion. . For this reason, defects are easily generated in the polycarboxylic acid-based resin film 2 near the back of the hole,
The film thickness tends to be thinner than near the entrance of the hole.

Therefore, as in the present embodiment, if an electrolyte which promotes anodic oxidation of a conductor such as ammonium adipate (having a high chemical conversion) is added to the electrodeposition solution in advance, the polycarboxylic acid resin film can be formed. An anodic oxide film 3 of aluminum having high insulating property can be efficiently formed at the same time when the polycarboxylic acid-based resin film 2 is electrodeposited, only on the underlayer where it is difficult to form 2. The amount of the electrolyte having high chemical conversion added to the aqueous solution containing such a polycarboxylic acid, the applied voltage,
It is needless to say that the thickness of the polycarboxylic acid resin film 2 and the thickness of the anodic oxide film 3 of aluminum can be controlled by adjusting the electrodeposition time and the like.

Next, in step 3, the sample on which the dielectric layer was formed in step 2 was washed with water, dried at 80 ° C. for 20 minutes, and heat-treated at 180 ° C. to obtain a melamine resin and a polycarboxylic acid-based resin. A device having a highly insulating dielectric layer was produced by curing reaction with a resin. Next, in step 4, the operation of alternately immersing the device in a 1.0 mol / l pyrrole ethanol solution and a 1.0 mol / l ammonium persulfate aqueous solution for 2 minutes is repeated three times to chemically oxidize polypyrrole. A first polypyrrole layer 4 as a film was formed.

Subsequently, in step 5, the element having the first polypyrrole layer 4 formed thereon is replaced with the second pyrrole 1
Of a 40% by weight aqueous solution of sodium butylnaphthalenesulfonate as a supporting electrolyte and 40 parts of distilled water were immersed in a mixed solution to form an anode, and a cylindrical stainless steel container was used as a cathode. The second polypyrrole layer 5 was formed by electrolytic polymerization at a constant current of cm ⁻² for 30 minutes.

Next, at step 6, a current collector 6 is formed by applying a conductive material such as colloidal carbon or silver paste to the device. As a result, a counter electrode composed of the first and second polypyrrole layers 4 and 5 collected by the current collector 6 is formed.

Further, in step 7, a lead wire was attached and the package was covered with an epoxy resin (not shown) to complete the capacitor of the present embodiment.

(Performance Study 1) The characteristics of the capacitor obtained in the present embodiment are shown in Table 1 in comparison with a comparative example. As is clear from Table 1, the capacitor according to the present embodiment has excellent effects in terms of dielectric loss tangent and leakage current.

[0042]

[Table 1]

The capacitor shown as a comparative example is the same as the capacitor in the above embodiment except that an aqueous electrolyte solution for promoting anodic oxidation was not added to the aqueous solution containing polycarboxylic acid. It was produced in. The characteristics of the capacitor are shown in the comparative example of Table 1. The capacitor of the comparative example has a large leakage current because the polycarboxylic acid film has a lot of defects (pinholes) and a part with low electric resistance.

[0044]

As described above, the capacitor according to the present invention and the method for manufacturing the same are more effective than the capacitor in which the dielectric layer is formed only by the polycarboxylic acid resin film formed by the electrodeposition method.
By forming an anodic oxide film of a highly insulating conductor on the weak point of the polycarboxylic acid resin film, the leakage current value is reduced.

Further, the method of manufacturing a capacitor according to the present invention comprises:
The productivity is excellent because the anodic oxide film of the conductor can be efficiently formed only in the polycarboxylic acid-based resin film and the weak points thereof in the same process.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a capacitor according to an embodiment of the present invention.

FIG. 2 is a flowchart of a method for manufacturing a capacitor according to an embodiment of the present invention;

FIG. 3 is a schematic view of an electrophoretic electrodeposition apparatus used for manufacturing a capacitor according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Etched aluminum foil electrode 2 Polycarboxylic acid resin film 3 Aluminum anodic oxide film 4 First polypyrrole layer 5 Second polypyrrole layer 6 Current collector 7 Epoxy resin 8 Electrodeposition liquid 9 Stainless steel container

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junichiro Umeda 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] A dielectric layer comprising a polycarboxylic acid resin and an anodic oxide film of the conductor is provided on a roughened surface of the conductor, and a conductor layer is provided as a counter electrode on the dielectric surface. A capacitor. 2. The capacitor according to claim 1, wherein the roughened conductor is an etched aluminum foil. 3. The capacitor according to claim 1, wherein the polycarboxylic acid resin is a polyacrylic resin. 4. The capacitor according to claim 1, wherein the counter electrode is a conductive polymer doped with an anion. 5. The capacitor according to claim 4, wherein the conductive polymer is polypyrrole. 6. A process for adding an aqueous solution of an organic acid, an inorganic acid or an electrolyte thereof for promoting anodic oxidation to an aqueous solution containing a polycarboxylic acid to synthesize an electrodeposition solution; Forming a dielectric layer consisting of a polycarboxylic acid-based resin film and an anodic oxide film of the conductor on the surface of the conductor roughened using the added electrodeposition solution, and forming a counter electrode on the dielectric surface. A method for manufacturing a capacitor, further comprising a step of forming a conductor layer. 7. The method according to claim 6, wherein the electrolyte added to the aqueous solution containing a polycarboxylic acid is adipic acid, maleic acid, succinic acid, malic acid, phosphoric acid, boric acid, or a salt thereof. Manufacturing method of capacitor. 8. An electrodeposition solution in which an electrolyte for promoting anodic oxidation is added to an aqueous solution containing a polycarboxylic acid has a pH of 7 to 10.
7. The method for manufacturing a capacitor according to claim 6, wherein an appropriate amount of ammonia or amine is added to the aqueous electrolyte solution or the aqueous solution containing polycarboxylic acid in advance so as to fall within the range of 9.