JPH1187176A - Solid electrolytic capacitor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor for significantly reducing an equivalent series resistance and leakage current by using a polyaniline or polyaniline derivative as a solid electrolyte and a method for manufacturing the capacitor. SOLUTION: In the solid electrolytic capacitor consisting of anode 1 made of valve action metal, a dielectric oxide film 3 formed by anodizing on a surface of the anode 1, and a conductive polymer layer 4 formed on the film 3, the layer 4 is formed of a polyaniline or polyaniline derivative formed by a chemical oxidation polymerization method, so that the reaction by-product of oxidizer used for a method of 6 wt.% or less to the polyaniline or polyaniline derivative is contained in the layer 4. At the time of manufacturing the capacitor, the layer 4 is formed by treating the by-product of the oxidizer used for the method with a soluble solution, further heat treating the by-product at its evaporating temperature and atmospheric pressure or lower in an atmosphere of air, inert gas, oxygen or the like, and the by-product is evaporated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a conductive polymer layer made of polyaniline or a polyaniline derivative as a solid electrolyte, wherein the conductive polymer layer contains polyaniline as a reaction by-product of an oxidizing agent used in a chemical oxidation polymerization method. Also, the present invention relates to a solid electrolytic capacitor having a weight fraction of 6% or less based on a polyaniline derivative and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, an anode is formed of a valve metal, such as tantalum or aluminum, and the surface of the anode is anodized to form a dielectric oxide film. A solid electrolyte is formed on the surface of the dielectric oxide film. In the formed solid electrolytic capacitor, manganese dioxide (MnO ₂ ), 7,7 ′, 8,8′-tetracyanoquinodimethane (TC) is used as the solid electrolyte.
A solid electrolytic capacitor using such a solid electrolyte, which used an NQ) complex salt,
When manganese dioxide (MnO ₂ ) is used as the solid electrolyte, the electric conductivity of manganese dioxide (MnO ₂ ) is not sufficiently large, so that the impedance of the solid electrolytic capacitor at high frequencies cannot be sufficiently reduced. And TC as a solid electrolyte
When the NQ complex salt is used, the TCNQ complex salt has a property of being easily thermally decomposed, and thus has a disadvantage that the heat resistance of the solid electrolyte capacitor cannot be improved.

In order to solve such a problem, recently, as a solid electrolyte of a solid electrolytic capacitor, it has a higher electric conductivity than manganese dioxide (MnO ₂ ),
Solid electrolytic capacitors using conductive polymers having higher heat resistance than TCNQ complex salts, for example, polypyrrole or polyaniline, have been developed.

Incidentally, polyaniline, for example, disclosed in Japanese Patent Application Laid-Open No. 61-258831, is manufactured by a chemical oxidation polymerization method. The conductivity of polyaniline produced by the chemical oxidative polymerization method is 2.
It reaches about 0 S / cm. However, since polyaniline having conductivity is insoluble and infusible, a polyaniline solution cannot be prepared while maintaining conductivity. As a result, after synthesizing polyaniline having conductivity, it is difficult to apply it to a solid electrolyte of a tantalum capacitor.

[0005]

In a solid electrolytic capacitor for producing polyaniline as a solid electrolyte by a chemical oxidation polymerization method, an oxidizing agent solution (first solution) for oxidizing aniline and a protonic acid as a dopant are used. The anode on which the dielectric oxide film is formed is alternately impregnated with the aniline solution containing the aniline solution (second solution) to cause a chemical oxidative polymerization reaction on the surface of the dielectric oxide film of the anode, and a solid electrolyte is formed on the surface of the dielectric oxide film. Of polyaniline is used. In this case, this method of forming polyaniline is such that when the capacitance of a solid electrolytic capacitor is desired to be a desired value, an anode having a dielectric oxide film formed on its surface is alternately formed in a first solution and a second solution. It is necessary to impregnate several times.

In particular, when metal tantalum is used as the valve metal for the anode, the sintered tantalum powder is sintered to form a sintered body, and the sintered body is used as the anode. Is alternately impregnated into the first solution and the second solution, it is difficult to sufficiently impregnate the inside of the anode with aniline, a dopant and an oxidizing agent. As a result, the capacity appearance rate of the solid electrolytic capacitor becomes small, It is difficult to obtain a solid electrolytic capacitor having the required capacitance.

Generally, not only solid electrolytic capacitors,
Equivalent series resistance (ESR) for all capacitors
And a small leak current are required. In this case, all of the known solid electrolytic capacitors have a limit in reducing the equivalent series resistance and the leakage current, and as a result, the solid electrolytic capacitor must be used in a state where the equivalent series resistance and the leakage current cannot be ignored. There is a problem that can not be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a solid electrolytic capacitor and a solid electrolytic capacitor which use polyaniline or a polyaniline derivative as a solid electrolyte and which can greatly reduce equivalent series resistance and leak current. It is to provide a manufacturing method thereof.

[0009]

Means for Solving the Problems The present inventors have energetically conducted research to develop a solid electrolytic capacitor having a relatively large capacitance appearance rate and a small equivalent series resistance and a small leakage current. As a result, it has been clarified that the reducing substance of the oxidizing agent remaining in the solid electrolyte of the solid electrolytic capacitor is a cause of deterioration of the characteristics of equivalent series resistance and leak current, and has led to the present invention. A solid electrolytic capacitor in which a reducing substance of an oxidizing agent remaining in a solid electrolyte is entirely eliminated from the solid electrolyte is formed.

That is, in order to achieve the above object, a solid electrolytic capacitor according to the present invention includes a valve metal anode,
A polyaniline or polyaniline derivative comprising a dielectric oxide film formed by anodizing the surface of the anode and a conductive polymer layer formed on the dielectric oxide film, wherein the conductive polymer layer is formed by a chemical oxidation polymerization method Wherein the content of the reaction by-product of the oxidizing agent used in the chemical oxidation polymerization method in the conductive polymer layer is reduced, and the reaction by-product is not more than 6% by weight based on polyaniline or the polyaniline derivative. 1 means is provided.

In order to achieve the above object, a method of manufacturing a solid electrolytic capacitor according to the present invention comprises a first step of forming a dielectric oxide film by anodizing a surface of a valve metal anode. The second step of forming a conductive polymer layer made of polyaniline or a polyaniline derivative on an oxide film by a chemical oxidation polymerization method. The conductive polymer layer can dissolve the reaction by-product of the oxidizing agent used in the chemical oxidation polymerization method. The temperature at which the by-products of the reaction by-products of the oxidizing agent used in the chemical oxidative polymerization process can evaporate in an atmosphere of air, an inert gas, or oxygen and at atmospheric pressure or lower. And a second means consisting of a third step of evaporating a reaction by-product.

According to the first and second means, in forming a conductive polymer layer made of polyaniline or a polyaniline derivative by a chemical oxidative polymerization reaction in a process of manufacturing a solid electrolytic capacitor, Since the reaction by-products of the oxidizing agent used are completely removed by solution acid treatment and heating and evaporation, the equivalent series resistance and leakage current are significantly higher than known solid electrolytic capacitors of this type. Can be reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In one embodiment of the present invention, a solid electrolytic capacitor includes an anode made of a valve metal, a dielectric oxide film formed on the surface of the anode by anodization, A conductive polymer layer formed by a chemical oxidative polymerization method, wherein the conductive polymer layer is polyaniline or a polyaniline derivative formed by a chemical oxidative polymerization method. The reaction by-product of the oxidizing agent used is not more than 6% by weight based on polyaniline or the polyaniline derivative.

In another embodiment of the present invention, a method for manufacturing a solid electrolytic capacitor includes an anode made of a valve metal, a dielectric oxide film formed on the surface of the anode, and a conductive film formed on the dielectric oxide film. A first step of anodizing the surface of the anode to form a dielectric oxide film, comprising polyaniline or a polyaniline derivative on the dielectric oxide film by a chemical oxidation polymerization method. The second step of forming the conductive polymer layer, the conductive polymer layer is treated with a solution capable of dissolving the reaction by-product of the oxidizing agent used in the chemical oxidation polymerization method, and further, air, an inert gas, At atmospheric pressure or below in any atmosphere of oxygen,
It is manufactured through a third step of performing heat treatment at a temperature at which a reaction by-product of the oxidizing agent used in the chemical oxidation polymerization method can evaporate and evaporating the reaction by-product. The solution used in the third step may be any solvent capable of dissolving the reaction by-product, such as pure water or an acidic solution such as nitric acid, phosphoric acid, sulfuric acid, and sulfonic acid. In particular, when a voltage is applied in an acidic solution, reaction by-products can be more effectively removed.

According to one embodiment of the present invention, when a solid electrolyte of a solid electrolytic capacitor, that is, a conductive polymer layer made of polyaniline or a polyaniline derivative is formed by a chemical oxidation polymerization reaction, Is subjected to solution treatment or heat treatment to completely remove the reaction by-product of the oxidizing agent used during the chemical oxidative polymerization reaction, so that the equivalent series resistance and the Leakage current can be reduced.

According to another embodiment of the present invention,
In the process of manufacturing a solid electrolytic capacitor, when a conductive polymer layer made of polyaniline or a polyaniline derivative is formed on a dielectric oxide film formed on the surface of the anode by a chemical oxidation polymerization method, the conductive polymer obtained is used. The layer is treated with a solution capable of dissolving the reaction by-product of the oxidizing agent used in the chemical oxidation polymerization method, to remove the reaction by-product, and to remove the reaction by-product remaining inside the capacitor, The conductive polymer layer is subjected to heat treatment in an atmosphere of air, an inert gas, or oxygen at atmospheric pressure or a pressure lower than the atmospheric pressure, at a temperature at which a reaction by-product of an oxidizing agent used in a chemical oxidation polymerization method can evaporate. As a result, the reaction by-products are completely evaporated, so that the equivalent series resistance and leakage current are significantly reduced compared to known solid electrolytic capacitors of this type. Get it becomes possible.

[0017]

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

FIG. 1 is a sectional view showing the structure of an embodiment of a solid electrolytic capacitor according to the present invention, and shows an example of a tantalum capacitor in which an anode is formed of a sintered body of metal tantalum.

In FIG. 1, 1 is an anode, 2 is an anode lead, 3 is a dielectric oxide film, 4 is a conductive polymer layer, 5 is a silver layer, 6 is an anode terminal, 7 is a cathode terminal, and 8 is an exterior. is there.

The anode 1 is made of a sintered body obtained by press-molding a fine powder of metal tantalum, which is a kind of valve action metal, and then sintering it. The anode lead 2 is made of a metal tantalum lead wire, one end of which is inserted into the anode 1 during pressure molding and fixed to the anode 1 during sintering. The dielectric oxide film 3 is formed by anodizing the anode 1 and is formed on the entire surface of the anode 1. Conductive polymer layer 4
Is formed on the dielectric oxide film 3 and is formed on the surface of the entire dielectric oxide film 3 except for the surface of the dielectric oxide film 3 on the side from which the anode lead 2 of the anode 1 is led out. Is done. The silver layer 5 forms a cathode and is formed on a part of the surface region of the conductive polymer layer 4. The anode terminal 6 constitutes an anode-side output terminal of the solid electrolytic capacitor.
The other end of the anode lead 2 is conductively connected by welding.
The cathode terminal 7 constitutes a cathode-side output terminal of the solid electrolytic capacitor, and is connected to the silver layer 5. The exterior 8 is made of resin and constitutes the exterior of the solid electrolytic capacitor, and covers the entire surface of the anode terminal 6 and the cathode terminal 7 except for the respective lead-out ends.

Here, the history of the manufacturing process of the solid electrolytic capacitor (tantalum capacitor) of the present embodiment is as follows.

First, pressure molding is performed with one end of the anode lead wire 2 inserted into fine powder of metal tantalum, and the obtained molded body is sintered at a high temperature in a vacuum atmosphere. An anode 1 made of a sintered body is formed (first step).

Next, the anode 1 obtained in the first step is immersed in a dilute nitric acid solution, and then a chemical conversion treatment is performed to form a dielectric oxide film 3 having a rated voltage of 7 V and 100 μF on the surface of the anode 1 (first step). 2 steps).

Next, a 0.5 M aqueous solution of ammonium peroxodisulfate is prepared using an aqueous solution obtained by mixing water and ethanol at a ratio of 1: 1. Then, the anode 1 on which the dielectric oxide film 3 has been formed in the second step (hereinafter referred to as a surface oxidation anode) 1 is immersed in a 0.5 M ammonium peroxodisulfate aqueous solution for 10 seconds (third step).

Subsequently, equal amounts of aniline and p-toluenesulfonic acid are added to an aqueous solution in which water and ethanol are mixed at a ratio of 1: 1 to prepare an aniline aqueous solution having a concentration of 0.5M. Then, 30 minutes after the immersion of the aqueous solution of ammonium peroxodisulfate in the third step, the surface oxidation anode 1 is immersed in the aniline aqueous solution for 10 seconds (fourth step).

Next, after immersing the aniline aqueous solution in the fourth step, the surface oxidation anode 1 is kept at 50 ° C. for 30 minutes to cause a chemical oxidation polymerization reaction on the surface oxidation anode 1 (fifth step). Process).

Further, the surface oxidation anode 1 that has undergone the fifth step is alternately immersed in the ammonium peroxodisulfate aqueous solution and the aniline aqueous solution 20 times, thereby chemically oxidizing the surface of the surface oxidation anode 1. The conductive polymer layer 4 obtained by the polymerization reaction is formed (sixth step).

During the formation of the conductive polymer layer 4 in the fifth and sixth steps, the surface oxidation anode 1 is immersed in pure water, and is produced by reduction of an aqueous solution of ammonium peroxodisulfate, which is an oxidizing agent for aniline. The removed ammonium hydrogen sulfate (reaction by-product) is removed from inside the conductive polymer layer 4. Further, the solution-treated surface oxidation anode 1 was heated at 150 ° C. in air at a pressure lower than atmospheric pressure.
Heat treatment at a temperature of By this heat treatment, ammonium hydrogen sulfate (reaction by-product) generated by reduction of ammonium peroxodisulfate, which is an oxidizing agent for aniline, is evaporated, and ammonium hydrogen sulfate is completely removed from the inside of the conductive polymer layer 4 (see FIG. 7 steps).

Next, a silver paste is applied to a predetermined portion of the surface oxidation anode 1 on which the conductive polymer layer 4 has been formed through the seventh step to form a silver layer 5 (eighth step).

Next, after the eighth step, an anode terminal 6 is conductively connected to the other end of the anode lead 2 by welding to form a silver layer 5.
Is connected to the cathode terminal 7 (ninth step).

Subsequently, after the ninth step is performed, a resin is applied to the entire surface by a molding method except for the lead-out ends of the anode terminal 6 and the cathode terminal 7, and the solid electrolytic capacitor ( (Tantalum capacitor) is formed (tenth
Process).

Here, FIG. 2 shows the conductive polymer layer 4 of the solid electrolytic capacitor (tantalum capacitor) of the present embodiment,
Comparative Examples 1 to 3 separately formed for comparison with the present example.
2 shows the endothermic state and the exothermic state at the time of temperature rise (heating temperature: 20 ° C./min) measured using a differential scanning calorimeter (DSC) for the conductive polymer layer of the solid electrolytic capacitor (tantalum capacitor). It is a characteristic diagram.

In FIG. 2, the vertical axis represents heat absorption and heat generation, and the horizontal axis represents temperature. The characteristic curve A is that of the solid electrolytic capacitor of this embodiment, and the characteristic curve B is that of the solid electrolytic capacitor of Comparative Example 1. , Characteristic curve C is for the solid electrolytic capacitor of Comparative Example 2, and characteristic curve D is for the solid electrolytic capacitor of Comparative Example 3.

By the way, the solid electrolytic capacitors of Comparative Examples 1 to 3 for comparison with this embodiment were manufactured as follows.

First, the solid electrolytic capacitor of Comparative Example 1
In the manufacturing process of the solid electrolytic capacitor of the present embodiment, the process of solution-treating and heat-treating the conductive polymer layer 4, that is, the process excluding the seventh process, except for the first process to the sixth process and the eighth process It is manufactured through the steps through the tenth step.

Next, the solid electrolytic capacitor of Comparative Example 2
In this embodiment, the step of alternately immersing in the aniline aqueous solution and the aqueous solution of ammonium peroxodisulfate 20 times, that is, instead of performing the alternate immersion 20 times as in the sixth step, it is more than 25 steps. (This step is referred to as a sixth step), and at the same time, as in the comparative example 1, the seventh step of the present example is excluded.
It is manufactured through the steps through the fifth step, the sixth 'step, and the eighth through tenth steps, respectively.

Next, in the solid electrolytic capacitor of Comparative Example 3, the step of alternately immersing in the aniline aqueous solution and the aqueous solution of ammonium peroxodisulfate 20 times in the present example, that is, alternate immersion as in the sixth step 20 times
The process is performed 30 times more than the above (this process is referred to as a sixth process). At the same time, the seventh process of the present embodiment is omitted as in the comparative example 1. 1st to 5th steps, 6th "step, 8th to 10th steps
It is manufactured through each process.

As shown by the characteristic curve A in FIG. 2, the solid electrolytic capacitor of this embodiment does not generate an endothermic peak or an exothermic peak as the temperature rises.

On the other hand, the solid electrolytic capacitor of Comparative Example 1
As shown by the characteristic curve B in FIG. 2, an endothermic peak was similarly generated at around 140 ° C. with an increase in temperature, and the cause of the endothermic peak was caused by ammonium peroxodisulfate remaining in the conductive polymer layer. Based on ammonium hydrogen sulfate (reaction by-product) produced by the reduction of

Next, in the solid electrolytic capacitor of Comparative Example 2, as shown by the characteristic curve C in FIG. 2, an endothermic peak similar to that of Comparative Example 1 was generated at around 140 ° C. with increasing temperature. The temperature range at which the endothermic peak occurs is wider than in Comparative Example 1. As in Comparative Example 1, the cause of the generation of the endothermic peak is based on ammonium hydrogen sulfate (reaction by-product) generated by reduction of ammonium peroxodisulfate remaining in the conductive polymer layer.

Subsequently, in the solid electrolytic capacitor of Comparative Example 3, as shown in the characteristic curve D of FIG. 2, an endothermic peak similar to that of Comparative Example 1 was generated at around 140 ° C. with an increase in temperature. The size of this endothermic peak is higher than that of Comparative Example 1. As in Comparative Example 1, the cause of the generation of the endothermic peak is based on ammonium hydrogen sulfate (reaction by-product) generated by reduction of ammonium peroxodisulfate remaining in the conductive polymer layer.

FIG. 3 shows the leakage current in the solid electrolytic capacitor (tantalum capacitor) of this embodiment and the solid electrolytic capacitors (tantalum capacitor) of Comparative Examples 1 to 3, and the equivalent series resistance (ES) at a frequency of 100 kHz.
R) is a characteristic diagram showing a comparison of the amount of residual ammonium hydrogen sulfate remaining in the conductive polymer layer. In this case, the amount of ammonium hydrogen sulfate remaining in the conductive polymer layer is as shown in FIG.
As shown in the characteristic curves A, B, C, and D, the values were calculated based on endothermic peaks measured by a differential scanning calorimeter (DSC).

As shown in FIG. 3, when the solid electrolytic capacitor of this embodiment is compared with the solid electrolytic capacitors of Comparative Examples 1 to 3, the leakage current and the equivalent series resistance (ESR)
Is that the solid electrolytic capacitor of the present embodiment is significantly smaller than the solid electrolytic capacitors of Comparative Examples 1 to 3, and the amount of residual ammonium hydrogen sulfate is smaller than that of the solid electrolytic capacitor of the present embodiment. Below detection limit,
That is, the solid electrolytic capacitors of Comparative Examples 1 to 3 each have a residual amount of a certain value, while being 0.

From the results shown in FIG. 3, it was found that the smaller the amount of residual ammonium hydrogen sulfate in the conductive polymer layer, the smaller the leak current and the equivalent series resistance (ESR). If the weight fraction of ammonium hydrogen is 6% or less based on polyaniline, the leak current is reduced to 10 μA or less and the equivalent series resistance is reduced to 0.25Ω or less. In particular, it can be seen that when the weight fraction of the residual ammonium hydrogen sulfate is 0, a solid electrolytic capacitor having extremely good characteristics can be obtained.

FIG. 4 is a characteristic diagram showing the results of spectroscopic analysis of the solid electrolytic capacitor (tantalum capacitor) of the present embodiment and the solid electrolytic capacitor (tantalum capacitor) of Comparative Example 1, and shows the results of infrared spectroscopy. (IR) was used for spectral analysis.

In FIG. 4, the ordinate represents the transmittance, the abscissa represents the wave number expressed in (cm ~ ¹ ), the characteristic curve A is that of the solid electrolytic capacitor of the present embodiment, and the characteristic curve B is One is a solid electrolytic capacitor of a comparative example.

[0047] In general, ion ammonium specific to ammonium bisulfate (NH ₄ ⁺⁾ and sulfate ions (SO ₂ ^-)
The vibration spectrum of 1390cm ~ ¹ ~ 1430cm
Wavelength range and 680 cm ~ of ~ ¹ is observed in ¹ to the wave number range of 610 ^cm-1.

As shown in the characteristic curve B of FIG. 4, the solid electrolytic capacitor of Comparative Example 1 has a wave number of 1400.
Although peaks are observed at cm- ¹ and 620 cm- ¹ , respectively, as shown by the characteristic curve A in FIG. 4, the solid electrolytic capacitor of this embodiment has a wave number of 1400 cm- ¹ and 620c.
No peak is observed at m- ¹ . From these results, the residual ammonium hydrogen sulfate in the conductive polymer layer produced in this example was below the detection limit of IR, that is, 0, but the residual ammonium hydrogen sulfate was not retained in the conductive polymer layer produced in Comparative Example 1. It is clear that ammonium hydrogen sulfate remains. Further, by performing a spectroscopic analysis using an infrared spectrometer, it is possible to evaluate the presence or absence of residual ammonium hydrogen sulfate (reaction by-product) in the conductive polymer layer and detect the amount of residual ammonium hydrogen sulfate.

As described above, according to the solid electrolytic capacitor and the method for manufacturing the solid electrolytic capacitor according to the present embodiment, the aniline is oxidized when the aniline-based conductive polymer layer 4 is formed by the chemical oxidation polymerization method. The reducing substance of the oxidizing agent used, i.e., ammonium hydrogen sulfate (reaction by-product) is removed by solution treatment and heat treatment, and the ammonium hydrogen sulfate in the conductive polymer layer 4 is completely removed. By removing the solid electrolytic capacitor, a solid electrolytic capacitor having significantly reduced leakage current and equivalent series resistance (ESR) can be obtained.

It should be noted that, in the above embodiment, at the time of heat treatment for forming the conductive polymer layer 4, that is, in the seventh step, in the air, the pressure was reduced from the atmospheric pressure.
Although an example in which the heat treatment is performed at a temperature of 150 ° C. has been described,
The conditions at the time of the heat treatment in the seventh step according to the present invention are not limited to such cases, and other conditions, for example, may be in an inert gas or oxygen instead of in air, and the pressure is reduced from the atmospheric pressure. The state may be an atmospheric pressure state instead of the pressure state. However, when the pressure state is selected to be the atmospheric pressure state, the heat treatment temperature must be selected to be equal to or higher than the melting point of the reducing substance of the oxidizing agent, that is, ammonium hydrogen sulfate (reaction by-product), preferably, its thermal decomposition temperature or its boiling point. There is. On the other hand, if the pressure is selected to be lower than the atmospheric pressure, it is not necessary to raise the heat treatment temperature to the melting point of ammonium hydrogen sulfate, and the heat treatment temperature can be selected to be lower as the pressure reduction is larger. An appropriate heat treatment temperature at the time of performing this heat treatment can be set by measuring a weight loss start temperature by a thermogravimetric analyzer (TG).

Further, in the above-described embodiment, an example has been described in which the resin is applied to the whole by the molding method at the time of the coating process of the exterior 8, that is, in the tenth step.
Is not limited to the molding method, and may be performed by another coating method, for example, a dipping method.

[0052]

As described above, according to the solid electrolytic capacitor of the present invention, when the solid electrolyte, that is, the conductive polymer layer made of polyaniline or polyaniline derivative is formed by the chemical oxidation polymerization reaction, Solution treatment and heat treatment of the polymer layer are performed to completely remove reaction by-products of the oxidizing agent used during the chemical oxidative polymerization reaction, so that the leakage current is lower than that of known solid electrolytic capacitors of this type. And the equivalent series resistance can be greatly reduced.

According to the method of manufacturing a solid electrolytic capacitor of the present invention, a conductive polymer layer made of polyaniline or a polyaniline derivative is formed on a dielectric oxide film formed on the surface of an anode by a chemical oxidation polymerization method. At this time, the conductive polymer layer is treated with a solution capable of dissolving the reaction by-product of the oxidizing agent used in the chemical oxidation polymerization method, and the conductive polymer layer is further treated with any of air, an inert gas, and oxygen. In an atmosphere of atmospheric pressure or lower pressure, a heat treatment is performed at a temperature at which the reaction by-products can evaporate, so that the reaction by-products are completely evaporated. In comparison, there is an effect that a solid electrolytic capacitor in which the leak current and the equivalent series resistance are significantly reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of a solid electrolytic capacitor according to the present invention.

FIG. 2 shows a measurement using a differential scanning calorimeter (DSC) of the conductive polymer layer of the solid electrolytic capacitor of the present example and the conductive polymer layers of the solid electrolytic capacitors of Comparative Examples 1 to 3. FIG. 4 is a characteristic diagram illustrating endothermic and exothermic states when the temperature rises.

FIG. 3 is a characteristic diagram showing a comparison between a leakage current, an equivalent series resistance, and an amount of residual ammonium hydrogen sulfate remaining in a conductive polymer layer in the solid electrolytic capacitor of the present embodiment and the solid electrolytic capacitors of Comparative Examples 1 to 3. is there.

FIG. 4 is a characteristic diagram showing spectroscopic analysis results of the solid electrolytic capacitor of the present example and the solid electrolytic capacitor of Comparative Example 1.

[Explanation of symbols]

 Reference Signs List 1 anode (sintered body) 2 anode lead wire 3 dielectric oxide film 4 conductive polymer layer 5 silver layer 6 anode terminal 7 cathode terminal 8 exterior

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Aoyama 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. Ohira 16 Sun AIC Co., Ltd. Miharu Plant Co., Ltd. (72) Inventor Shinji Sano Miharu Town, Fukushima Pref. Miharu-machi Oguni 16-gun, Aichi Aichi Miharu Plant Co., Ltd. (72) Inventor Eiji Endo Miharu-cho Ota 16, Tamura-gun, Fukushima Prefecture Oita 16 Miuchi Plant Co., Ltd.

Claims (4)

[Claims] 1. A solid electrolytic capacitor comprising an anode made of a valve metal, a dielectric oxide film formed on the surface of the anode by anodization, and a conductive polymer layer formed on the dielectric oxide film. In the above, the conductive polymer layer is polyaniline or a polyaniline derivative formed by a chemical oxidative polymerization method, and a reaction by-product of an oxidizing agent used in the chemical oxidative polymerization method is formed in the conductive polymer layer by the polyaniline. Alternatively, the solid electrolytic capacitor has a weight fraction of 6% or less based on the polyaniline derivative. 2. The solid electrolytic capacitor according to claim 1, wherein ammonium oxide is used as the oxide. 3. A method for manufacturing a solid electrolytic capacitor comprising an anode made of a valve metal, a dielectric oxide film formed on the surface of the anode, and a conductive polymer layer formed on the dielectric oxide film. A first step of anodizing the surface of the anode to form the dielectric oxide film; and the conductive polymer layer made of polyaniline or a polyaniline derivative on the dielectric oxide film by a chemical oxidation polymerization method. A second step of forming the conductive polymer layer, the conductive polymer layer is treated with a solution capable of dissolving a reaction by-product of an oxidizing agent used in the chemical oxidation polymerization method, and further, any of air, an inert gas, and oxygen In that atmosphere,
Performing a heat treatment at atmospheric pressure or lower pressure at a temperature at which a reaction by-product of the oxidizing agent used in the chemical oxidation polymerization method can be evaporated, and evaporating the reaction by-product; And a method for manufacturing a solid electrolytic capacitor. 4. The method for producing a solid electrolytic capacitor according to claim 3, wherein ammonium peroxodisulfate is used as the oxide.