JPH036217A - Production of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve electric characteristics, thermal stability and durability by forming a conductive polymer layer of polypyrrole by vapor-phase polymerization and another conductive polymer layer of polypyrrole by electrolytic polymerization on a eutectic film. CONSTITUTION:A eutectic film prepared by oxidizing the surface of a substrate comprising a valve metal such as Al, Ta or Nb is coated with an aqueous solution containing 7-15wt.% oxidizing agent, e.g. (NH4)2S2O8, and vapor-phase polymerization is conducted at -60 to 200 deg.C in the vapor phase containing a pyrrole compound of the formula (wherein R1 to R3 are each H, alkyl or aryl) to give a conductive polymer layer of polypyrrole. The product is dipped in an electrolytic bath containing 0.01-2mol/l of a supporting electrolyte, e.g. hexafluorophosphate, and 0.01-5mol/l of the pyrrole compound of the formula and electrolytically polymerized at a current density of 0.01-100mA/cm<2> and an electrolytic voltage of 1-300V to give another conductive polymer layer of polypyrrole.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a solid electrolytic capacitor having a conductive polymer film.

(Prior art) Conventionally, in solid electrolytic capacitors whose anodes are metals with valve action such as aluminum or tantalum, manganese dioxide (MnOz) or tetracyanoquinodimethane (T CN Q ) complex salts have been used as solid electrolytes. something is well known. These solid electrolytes are immersed in coating components,
This is done by repeating heating and solidification, but the process is complicated and it is difficult to control the thickness of the solid electrolyte. Since it is a complicated process and has low productivity, it is not suitable for manufacturing capacitors of Small Party 1, and conversely, since 4i high temperature heating is performed to manufacture large capacity capacitors, the influence of thermal distortion becomes large. Since these solid electrolytes are immersed and heated at a considerably high temperature, a pattern is formed on the surface of the anode body using a resist material.
Processes that locally form electrolyte layers are difficult, and these solid electrolytes are granular and cannot be cut into chips after solid electrolyte or other formation. Currently, only capacitors of

In recent years, polypyrrole has been used as a solid electrolyte to compensate for these drawbacks. Attempts have been made to provide solid electrolytic capacitors having conductive polymer layers such as polythiophene. (JP-A-60-244017, JP-A-61-231
(Refer to 5, etc.) Using this technology, most of the above problems are solved, and there is a large degree of freedom in process selection, making it possible to manufacture a wide range of products from small-capacity chip capacitors to large-capacity capacitors using appropriate processes. Become.

(Problems to be Solved by the Invention) Self-control methods for conductive polymers include liquid phase polymerization, gas phase polymerization, and electrolytic polymerization methods. On the other hand, with the electrolytic polymerization method, it is not possible to form a strong and thermally stable film on top of the capacitor, making it impossible to obtain an electrolytic capacitor with excellent thermal stability and durability.
Since the dielectric metal oxide film such as aluminum or tantalum is an electrical insulator, it is not possible to form a strong film with excellent adhesion, and to obtain an electrolytic capacitor with excellent durability and electrical characteristics. I couldn't do it.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a solid electrolytic capacitor with excellent electrical characteristics, thermal stability, and durability, and a method for manufacturing the same.

(Means for Solving the Problems) The present invention has been made to solve problem 2, and it forms a conductive polymer layer on a dielectric film by a vapor phase method using an oxidizing agent. Then, a conductive polymer layer is formed on the dielectric water polymer layer by an electrolytic weight method to produce an open-ended electrolytic capacitor having a laminated conductive polymer film. This makes it possible to easily provide a solid electrolytic capacitor with excellent physical properties, thermal stability, and durability.

In the present invention, the monomers used as polymerization raw materials (in the formula R
1, R2 and R1 may be the same or different, hydrogen,
Specific examples of such compounds (representing an alkyl group or an aryl group) include virol, 3-methylvirol, 3.4
-Dimethylvirol, 3-ethylvirol, 3-phenylvirol, and the like.

37! used in the present invention! The type of electric coating is not particularly limited, but examples include metal acids (formed by oxidizing the surface of valve metal substrates such as aluminum, tantalum, and niobium).
A firefly film can be suitably used.

According to the present invention, as a first step, the monomer is vapor-phase polymerized on the dielectric film using an oxidizing agent. As this gas phase polymerization method, a method is used in which a dielectric film impregnated with, coated with, or sprayed with an oxidizing agent is exposed to the monomer vapor to form a polymer on the dielectric film. In addition, instead of monomer vapor, the liquid monomer may be placed in an inert gas such as nitrogen or argon, and the liquid monomer may be heated on the dielectric film treated with the oxidizing agent. There is no particular limitation on the vapor phase temperature. However, in general, 16
It is carried out at temperatures between 0°C and 200°C.

The vapor phase polymerized polymer layer is an essential layer to improve the adhesion between the dielectric film and the conductive polymer film, but because the vapor phase polymer has low thermal stability, its film thickness is extremely thin. It's better,
The polymerization time may be appropriately selected from several minutes to several hours while observing and determining the degree of formation of a gas phase-heavy polymer layer.

It is preferable that the acidic arsenic used in the above vapor phase method be one that is not harmful to the dielectric film, but there are particular restrictions if it can be used as a solid electrolytic capacitor even if it has some problems. No, the oxidizing agents include persulfates such as ammonia persulfate 11, sodium persulfate, potassium persulfate, ferric chloride, ferric bromide, ferric nitrate, ferric oxalate, and perchlorate. Ferric salts such as ferric acids, cupric chloride, cupric bromide, cupric sulfate, cupric salts such as nitric acid, protonic acids such as sulfuric acid and nitric acid, sulfur trioxide , oxygenated compounds such as nitrogen diacid, hydrogen peroxide, peroxides such as peracetic acid, quinone, ozone, diazonium salts, etc. Ammonium persulfate, ferric chloride or quinone are particularly preferred, Among these, ammonium persulfate is particularly preferred.

These oxidizing agents are impregnated or sprayed onto the dielectric film as a solution, such as an aqueous solution, and the stability of the capacitor is affected by the concentration of the oxidizing agent used. In the method of the present invention, the oxidizing agent concentration is preferably 7 to 15% by weight;
Particularly good results can be obtained when the amount is 0 to 15% by weight.

An organic acid can be used in combination with the impregnation, coating, or spraying of the above-mentioned oxidizing agent. As the alpha acid, arylsulfonic acids such as benzenesulfonic acid and toluenesulfonic acid may be used in an amount of 0.2 to 20 moles per mole of the oxidizing agent.

The second step of the present invention consists of laminating an electrolytically heavy polymer layer on the vapor phase type polymer layer.

In the electrolytic polymerization method, when an electrolytic acid is added in an electrolytic solution containing a supporting electrolyte and the above monomers, a strong conductive polymer is formed in which an electrolytically heavy polymer layer is laminated on a gas phase polymerized polymer layer. A molecular film is formed. As the heavy electrolytic conditions, for example, an electrolytic solution with a supporting electrolyte concentration of 0.01 mol/1 to 2 mol/Z and a monomer concentration of 0.01 mol/β to 5 mol/l is used. use,
It is carried out at a current density of 001 to LOO+IIA/cm" and an electrolytic voltage of 1 to 300 V, and a constant current method, a constant voltage method, and any other method can be used.

The supporting electrolytes used in the electrolytic polymerization method include, for example, anions such as halide anions such as hexafluoroline, hexafluoroline, and tetrafluoroborine, iodine, bromine,
Halogen anions such as chlorine, sulfonic acid anions such as benzenesulfonic acid, toluenesulfonic acid, and β-naphthalenesulfonic acid, carboxylic acid anions such as salicylic acid, oxalic acid, and adipic acid, and perchlorate anions, and the cations are sodium and potassium. , alkali metal cations such as lithium, and quaternary ammonium cations such as ammonium and tetraalkylammonium.

Examples of the compound include tetrabutylammonium benzenesulfonate, tetrabutylammonium toluenesulfonate, sodium naphthalene-2-sulfonate, LiPFa, L1AsF6, NapF6.
, K u F 6 , K A s F a
, LiBF, , NaCl0, L
Examples include iC110, KCl01K1, Nal, and tetraethylammonium borodisalicylate.

The electrolytic solution is prepared by dissolving the monomer and supporting electrolyte in a solvent that can dissolve them. The solvent is not particularly limited as long as it can dissolve both substances, but examples include nitriles such as acetonitrile and benzonitrile, alcohols such as ethanol and propatool, dimethylformamide, propylene carbonate, dimethyl sulfoxide, and water. It will be done.

(Examples) The present invention will be specifically explained below using Examples, but the present invention is not limited to these Examples.

Example 1 Using high-purity aluminum foil (99.99% purity) as a material, the surface of this aluminum foil was subjected to AC electrolytic etching to increase the surface area, and then the surface was thoroughly washed with water. Voltage 7 as anode
Perform anodic oxidation treatment at 0V and form a dielectric film of aluminum oxide on the surface. An aqueous solution of ammonium persulfate containing 4% ammonium persulfate and 10% ammonium persulfate was applied onto the aluminum oxide film on the aluminum foil obtained. The aluminum foil treated in this way was exposed to the vapor of pyrrole monomer at room temperature for about 20 minutes, and a polypyrrole layer was formed on the dielectric film by the gas phase overtone reaction of pyrrole.

Next, the aluminum foil subjected to the above treatment was made into lrf%I, 0.02 mol/& of naphthalene-2 sulfonic acid, and 0.1 rnol of triethylammonium borodisalicylate.
/&, was immersed in an electrolytic solution containing 0.2 mol/1 pyrrole and electrolytically polymerized at a current density of 1 and OmA/eIa2 for about 1 hour to form a black polypyrrole layer.

After the electrode obtained by the above method was taken out, washed, and dried, the counter electrode lead was taken out using carbon paste and silver paste, and the exterior was sealed with epoxy resin to form an electrolytic capacitor.

Examples 2 to 4 The concentration of ammonium persulfate used in the gas phase polymerization reaction of virol was set to 15]ifl? (Example 2), 25% (Example 3), and 3 Q @ fJfl q, <
One layer of electrolytic capacitors was fabricated in the same manner as in Example 1 except for the changes in Example 4.

Comparative Example A roll was electrolytically polymerized according to Example 1 without forming a polypyrrole layer by vapor phase polymerization on the anode foil, but it was not possible to form an adhesive film on the aluminum oxide dielectric. could not.

The electrical characteristics of the electrolytic capacitor obtained in the above example are shown in terms of capacitance jt (Cap), tangent of loss angle (tan δ), equivalent series resistance (at ESR 1100KHz), and leakage current (value at LC6.3V). It was determined that it was lit. In addition, in order to investigate the stability and durability of electrolytic capacitors, we tested them after 2000 hours at 110°C and at
Changes in capacitance (LC) and equivalent series resistance after 0 hours were measured. These results are shown in Tables 1 and 2.

Table 1 Table 2 Tables 1 and 2 show that the solid electrolytic capacitor of the present invention has high capacitance per unit area, and exhibits characteristics of low loss angle tangent value, equivalent series resistance value, and leakage current. Even in durability tests, there was little decrease in capacitance and little increase in equivalent series resistance, and it was found to be extremely stable and durable. In addition, the concentration of oxidizing agent used for one cycle in gas phase polymerization is particularly 15
It can be seen that less than 1% by weight brings about a significant effect.

(Effect of the invention) As explained in detail above, according to the method of the present invention, (1
) Since the dielectric film and the electrolytic heavy layer are bonded through the gas phase heavy layer, the adhesion between the conductive polymer film and the dielectric film is good, the leakage current is small, the capacitance is reduced, and the equivalent series resistance is reduced. It is possible to obtain a high voltage resistant capacitor with little increase in value. (2) Gas phase polymerization polymer layer and electrolytic polymerization polymer layer? 1
Because of the layered structure, the shortcomings of gas-phase polymerized films, which have low thermal stability, are covered, and a capacitor with good thermal stability can be obtained.
(3) Since high-temperature treatment is not performed during manufacturing, the dielectric material is not depleted and the rated voltage can be increased. Therefore, it is possible to obtain a capacitor with the same capacity and the same rated voltage as the conventional capacitor. This has the effect of making the shape more compact.

Therefore, the present invention can achieve significant advantages in terms of electrical properties, stability, durability, and economy.

Claims (3)

[Claims] (1) A conductive polymer layer of polypyrrole is formed on the dielectric film by vapor phase polymerization using an oxidizing agent, and then a conductive polymer layer of polypyrrole is formed on the conductive polymer layer by electrolytic polymerization. A method for manufacturing a solid electrolytic capacitor, characterized by forming layers. (2) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the gas phase polymerization is carried out at an oxidizing agent concentration of 7 to 15% by weight. (3) The method for manufacturing a solid electrolytic capacitor according to claim 2 or 3, wherein ammonium persulfate is used as the oxidizing agent.