JPH03183111A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To eliminate that a five-membered heterocyclic compound solution is diffused to an oxidizing-agent solution at a chemical oxidative polymerization operation and to form an excellent chamically polymerized film on an oxide film by a method wherein a valve-action metal on which the oxide film has been formed is immersed in the five-membered heterocyclic compound solution composed of pyrrole, thiophene or furan and, immediately after that, the chemical oxidative polymerization operation is executed in the oxidizer solution at a low temperature. CONSTITUTION:An anode foil 2 in which an oxide film 1 has been formed on the surface and which is composed of high-purity aluminum is immersed, for five minutes, in an aqueous solution of pyrrole, thiophene or furan/ethanol; after that, it is immersed in an aqueous solution of ammonium persulfate whose temperature is lower than that of the aqueous solution; a chemical oxidative polymerization operation is executed; a chemically polymerized film 4 composed of a conductive high polymer is formed on the oxide film 1. After that, the anode foil 2 on which the chemically polymerized film 4 has been formed is immersed in an electro lytic solution which contains a supporting electrolyte and a five-membered heterocyclic com pound such as pyrrole, thiophene, furan or the like; an electrolytic oxidative polymerization operation is executed; a conductive electrolytically polymerized film 5 is formed on the chemi cally polymerized film 4. Then, the electro-chemically polymerized film 5 is coated with colloidal carbon and a silver paste; this assembly is fired; a cathode layer 6 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer membrane as a solid electrolyte.

(Prior art) In recent years, solid electrolytic capacitors that meet the demand for smaller size and higher performance have been developed as disclosed in Japanese Patent Application Laid-open No. 60-244017 or Japanese Patent Application Laid-open No. 60-244017.
There is one disclosed in Publication No. 3-181308.

The technology disclosed in these publications is that an anode body obtained by chemically converting a valve metal with a roughened surface to form an oxide film is used as an anode, immersed in an electrolytic solution and energized to form an oxide film on the oxide film. It uses an electrolytic polymer membrane as a solid electrolyte,
Since the oxide film is an insulator, effective current conduction with the cathode is not carried out, and current concentrates in defective parts of the oxide film or in areas close to the cathode, resulting in a uniform electrolytic polymer film as a solid electrolyte. was extremely difficult.

Therefore, a chemical oxidative polymerization method is taken in which the anode body is immersed in, for example, a virol solution and then immersed in an oxidizing agent solution to form a chemically polymerized film on the anode body in advance.
Electrolytic oxidation polymerization is performed in an electrolytic solution using this chemically polymerized film as an anode to form an electrolytically polymerized film that is integrated with the oxide film via the chemically polymerized film.

However, chemical oxidation polymerization is generally carried out at room temperature, and at this time, the time required for the flow of the throat roll solution into the oxidizer solution is extremely long compared to the time required to form a chemically polymerized film at the interface between the virole solution and the oxidizer solution and within the bit. Because of the short length, a chemical polymer film was not uniformly and sufficiently formed on the surface of the oxide film, resulting in a low capacity appearance rate. In addition, the particulate polymer formed when the pyrrole diffused in the oxidant solution polymerizes in the oxidant solution adheres to the chemical polymerization layer formed on the surface of the oxide film, resulting in a thin and non-uniform chemically polymerized film. This results in a state where there are particulate protrusions on the film. Therefore, the electrolytic oxidation polymerization carried out in the next step will be carried out using this thin, non-uniform, chemically polymerized film with particulate protrusions as an anode.
If there is a protrusion on a part of the electrode surface, electrolytic oxidation polymerization occurs selectively at the protrusion because boundary breaking concentration occurs there, and current flows toward the protrusion. For this reason, the electropolymerized film that is formed is very non-uniform, leaving some very thin parts and some parts that are not formed, so that on average the entire surface of the anode body is covered with the chemically polymerized film. The desired electropolymerized film could not be obtained and the tan δ characteristics deteriorated, and furthermore, during the subsequent formation of the graphite and silver paste layers, the graphite and silver paste penetrated from areas where the electropolymerized film was insufficiently formed, resulting in direct oxidation. Contact with the film surface caused leakage current characteristics to deteriorate and short-circuit failures to occur.

In addition, since the adhesion between the chemically polymerized film and the oxide film is generally poor, in areas where the electrolytically polymerized film is insufficiently formed, the chemically polymerized film and the oxide film will peel off over time, resulting in changes in capacitance and tanδ characteristics. This was the cause of deterioration in life characteristics.

(Problems to be Solved by the Invention) As described above, solid electrolytic capacitors that use a conductive polymer film as a solid electrolyte are worthy of attention as they meet the demand for smaller size and higher performance. There were problems to be solved in forming the desired electrolytically polymerized membrane.

The present invention has been made in view of the above points, and is a method for manufacturing a solid electrolytic capacitor that can form an excellent chemically polymerized film on the oxide film that constitutes the anode body, which is a condition for obtaining the desired electrolytically polymerized film. The purpose is to provide the following.

[Structure of the Invention] (Means for Solving the Problems) The method for manufacturing a solid electrolytic capacitor of the present invention includes forming a chemically polymerized film by chemical oxidation polymerization on an oxide film formed on a valve metal, and then forming a chemically polymerized film by chemical oxidation polymerization. In a method for manufacturing a solid electrolytic capacitor in which an electrolytically polymerized film is formed on the film by electrolytic oxidative polymerization, the valve metal on which the oxide film is formed is virol.

It is characterized in that it is immersed in a solution of a five-membered heterocyclic compound consisting of thiophene or furan, and then immediately subjected to chemical oxidative polymerization in an oxidizing agent solution at a temperature at least lower than that of the compound solution.

(Function) According to the above structure, during chemical oxidative polymerization which is performed by immersing the anode body in a five-membered heterocyclic compound solution and then immediately immersing it in an oxidizing agent solution, the five-membered heterocyclic compound solution becomes an oxidizing agent. There is almost no diffusion into the solution, and polymerization occurs all at once at the interface between the five-membered heterocyclic compound solution and the oxidizing agent solution on the surface of the anode body, and is then retained in the pit by the oxidizing agent solution that gradually penetrates. All of the five-membered heterocyclic compounds are also polymerized within the pits, so that a uniform and sufficient chemical polymerization film is formed over the entire surface of the anode body, including the insides of the bits. In addition, since there is no diffusion of the five-membered heterocyclic compound into the oxidizing agent solution, the particulate polymer does not adhere to the chemically polymerized film formed on the surface of the anode, and the surface of the resulting chemically polymerized film has no protrusions. It becomes extremely smooth with no parts.

Therefore, it greatly contributes to the formation of a uniform electrolytic polymer film through the subsequent electrolytic oxidation polymerization, and the resulting electrolytic polymer film is integrated with the oxide film in a state that on average covers the entire surface of the anode body via the chemical polymer film. It becomes stopped.

(Example) An example of the present invention will be described below. That is, the first
As shown in the figure, an anode foil 2 made of, for example, high-purity aluminum, whose surface area has been expanded by etching and an oxide film 1 formed on the surface through a chemical conversion process, is immersed in virol, thiophene, or a 7-run/ethanol aqueous solution for 5 minutes. Furthermore, this virol or thiophene or furan/
Chemical oxidation polymerization is carried out by immersion in an ammonium persulfate aqueous solution at a temperature at least lower than that of an ethanol aqueous solution, and the oxidation degree l
! A chemically polymerized film 4 made of a 34-electrode polymer is formed on top of the film 1 . After that, this chemical polymerization! l! Immersing the electrode foil 2 with i14 formed therein in an electrolytic solution containing a supporting electrolyte and a five-membered heterocyclic compound such as virol, thiophene or furan,
Electrolytic oxidation polymerization is performed to form a conductive electrolytic polymeric film 5 on the chemically polymerized film 4 . Next, colloidal carbon and silver paste are applied and fired on this electrolytic polymer film 5 to form a cathode layer 6.
A cathode lead (not shown) is attached to the cathode 16 portion, and finally an exterior is applied.

According to the method for manufacturing a solid electrolytic capacitor with the above configuration, chemical polymerization can be uniformly and sufficiently smoothed on the anode foil 2!
l! 4 formation is possible, and the electrolytic polymer film 5 as a solid electrolyte obtained by electrolytic oxidation polymerization is integrated with the oxide film 1 on the entire surface of the anode foil 2 via the chemical polymer film 4.
Moreover, it can be formed uniformly and sufficiently, and the capacitance t and tan δ characteristics are improved, and the graphite and silver paste do not come into direct contact with the oxide film 1, which greatly contributes to improving leakage current characteristics and short circuit defects. .

Also, electrolytic polymerization! Since I5 is uniformly formed by wrapping the uniform chemical polymer film 4, the adhesion of the chemical polymer film 4 to the oxidation degree WIA1 is improved through the electrolytic polymer film 5, and there is little change over time and the life characteristics are greatly improved. Contribute.

Next, a solid electrolytic capacitor obtained by the present invention,
A comparison of various characteristics of solid electrolytic capacitors obtained by conventional examples and comparative examples will be described.

The figure shows a comparison of the characteristics of solid electrolytic capacitors with a rating of 10V-3μF according to Examples A-C, conventional example, and Comparative Example E described below. This shows the life characteristics for

Note that the values in the table excluding short-circuit defects are the average values of 100 samples, and the numbers in parentheses indicate variations.

Example A (1) Chemical oxidation polymerization conditions After immersing a chemically treated aluminum anode foil in a virol/ethanol solution at 45°C for 5 minutes, 0.05% tetraethylammonium paratoluenesulfonate was added as a supporting electrolyte.
Infiltrate into a 0.1 mol/J ammonium persulfate aqueous solution at 10°C containing mol/j for 5 minutes.

(2) Capacitor element shape: Flat plate shape (3) Electrolytic oxidation polymerization conditions: 1 mol/J of pyrrole monomer and 1 mo of tetraethylammonium para-toluenesulfonate as supporting electrolyte.
It is immersed in an electrolytic solution consisting of acetonitrile containing 1/J, and constant current oxidation polymerization (1 mA/i, 30 minutes) is performed.

Example B (1) Chemical oxidative polymerization conditions Aluminum positive If! chemical conversion treated in pyrrole/ethanol solution at 35°C. After soaking the foil for 5 minutes, 0.0% tetraethylammonium para-toluenesulfonate was added as the supporting electrolyte.
05mol/j! 0.1mol/j at 10℃ containing
Immerse in ammonium chloride solution for 5 minutes.

(2) Capacitor element shape Same as Example (3) Electrolytic oxidation polymerization conditions Same as Example C (1) Chemical oxidation polymerization conditions Aluminum anode foil chemically treated in pyrrole/ethanol solution at 15°C for 5 minutes After immersion, add 0.05 tetraethylammonium paratoluenesulfonate as a supporting electrolyte.
0.1 mol/fJ at 10°C including mol/A
WR immersion in 1iR17 ammonium aqueous solution for 5 minutes.

(2) Capacitor element shape Same as Example A (3) N deoxidation polymerization conditions Same as Example A Conventional Example D (1) Chemical oxidation polymerization conditions After soaking for 1 minute, 0.05% tetraethylammonium para-toluenesulfonate was used as the supporting electrolyte.
Immerse for 5 minutes in a 0.1 mol/IJ ammonium persulfate aqueous solution at 25°C containing mo I/J.

(2) Capacitor element shape Same as Example A (3) Electrolytic oxidation polymerization conditions Same as Example A Comparative Example E (1) Chemical oxidation polymerization conditions Aluminum anode foil chemically treated in pyrrole/ethanol solution at 25°C for 5 minutes After immersion, add 0.05 tetraethylammonium paratoluenesulfonate as a supporting electrolyte.
Immersed in a 0.1 molzl ammonium persulfate aqueous solution containing mo I/1 at 40°C for 5 minutes.

(2) Capacitor element shape Same as Example A [3) Electrolytic oxidative polymerization conditions Same as Example A The capacitance, tan δ, and leakage current characteristics are all significantly improved compared to those related to the above, and there is also a significant improvement in short-circuit defects.

Further, as is clear from FIGS. 2 to 4, it is found that it contributes to improving the rate of change in volume field and the we characteristics of tan δ, and at the same time contributes to a significant improvement in the leakage current in the life characteristics.

Furthermore, from the experimental results shown in the table above and Figures 2 to 4,
The temperature of the five-membered heterocyclic compound solution and the oxidizing agent solution is
It can be seen that the larger the difference in the relationship of Jl<multiple fi-membered ring compound solution, the more effective it is in terms of initial characteristics and life characteristics, and when this relationship is reversed, it is less preferable than when there is no temperature difference between the two.

In the above embodiments, aluminum foil was used as the anode foil, but it is also applicable to valve metal foils such as tantalum foil or niobium foil. Of course, it can be applied to a sintered body obtained by winding or sintering a powder made of these valve metals.

[Effect of the invention j According to the present invention, it is possible to form a uniform, sufficient, and submerged chemically polymerized film on an anode foil, and an electrolytic polymerized film formed using this as an anode can also be uniformly and sufficiently formed. As a result, it is possible to obtain a method for manufacturing a solid electrolytic capacitor that can greatly contribute to improving initial characteristics and, at the same time, contributing to improving life characteristics.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway schematic sectional view showing the configuration of a capacitor element in the process of being manufactured according to an embodiment of the present invention, FIG. 2 is a time-capacitance change rate characteristic curve diagram, and FIG. 3 is a time-tan δ characteristic curve diagram. , FIG. 4 is a time-leakage current characteristic curve diagram. 1...Oxide film 2...Anode part 4...Chemical polymerization membrane 5...Electrolytic polymerization membrane patent application
Hito Marcon Electronics Co., Ltd. Japan Carlit Co., Ltd. Figure Time (h) Figure

Claims (1)

[Claims] (1) In the method for manufacturing a solid electrolytic capacitor, the method of manufacturing a solid electrolytic capacitor includes forming a chemically polymerized film by chemical oxidation polymerization on an oxide film formed on a valve metal, and then forming an electrolytically polymerized film on this chemically polymerized film by electrolytic oxidation polymerization. The valve metal on which the oxide film has been formed is immersed in a solution of a five-membered heterocyclic compound consisting of pyrrole, thiophene, or furan, and then chemical oxidative polymerization is immediately carried out in an oxidizing agent solution at a temperature lower than that of the compound solution. Features: Manufacturing method of solid electrolytic capacitors.