JP2003092232A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a manufacturing time for a solid electrolytic capacitor using a conductive polymer for a solid electrolytic. SOLUTION: A sintered compact of tantalum powder is used as a capacitor element, and a conductive polymer layer is formed by oxidatively polymerizing 3,4-ethylene dioxythiophene with oxidizing reagent include silver (I) salt. A catalyst, ie, the silver (I) salt promotes the polymerization of the 3,4-ethylene dioxythiophene to shorten a polymerization time, capable of forming a conductive layer polymer layer with required thickness and manufacturing a solid electrolytic capacitor excellent in an electrical property within a short period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer as a solid electrolyte.

[0002]

2. Description of the Related Art In recent years, solid electrolytic capacitors using a conductive polymer as a solid electrolyte have been put into practical use for the purpose of lowering ESR. Generally, as these conductive polymers, there are polythiophene, polypyrrole, polyaniline, and the like. Among them, polythiophene has been attracting attention in recent years because it has high electrical conductivity and excellent thermal stability as compared with polypyrrole or polyaniline. As a solid electrolytic capacitor using polythiophene as a solid electrolyte, there is a solid electrolytic capacitor disclosed in JP-A-2-15611.

Polythiophene can be produced by chemical oxidative polymerization and electrolytic polymerization. However, when electrolytic polymerization means is adopted, it is necessary to attach several polymerization electrodes to one piece, and a conductive polymer. Since it is formed as a film on the electrode, it has a problem that it is difficult to manufacture in large quantities, whereas in the case of the chemical oxidative polymerization means, there is no such problem, and it is compared with electrolytic polymerization. It is well known to those skilled in the art that a large amount of conductive polymer layers can be easily obtained.

[0004]

However, since polythiophene has a smaller polymerization rate in the chemical oxidative polymerization than other conductive polymers such as polypyrrole or polyaniline, the conductivity of polythiophene is higher than the desired degree of polymerization. In order to form the polymer layer, it is necessary to lengthen the polymerization time or devise to increase the polymerization rate, which causes problems such as poor productivity and high cost, and when water is used as the solvent. Had a problem that the polymerization reaction was significantly suppressed.

Since the conductive polymer layer obtained by chemical polymerization has a wide molecular weight distribution from residual monomers and low melting point oligomers to high melting point high polymers, in the resin exterior structure by the transfer molding method, molding is performed. The low boiling point low molecular weight substance evaporates and scatters depending on the temperature. In this case, the conductive polymer layer is made porous to lower the electrical conductivity, and the strength is also lowered, and the stress at the time of molding damages the dielectric oxide film, resulting in a short circuit, an increase in leakage current and an increase in ESR. It also resulted in the problem of becoming. Similarly, the above-mentioned problem becomes apparent depending on the temperature when the capacitor is soldered to the circuit board, and when the temperature becomes higher (about 260 ° C) due to lead-free soldering in the future, such a defect will occur. It was a big problem.

The present invention solves the above problems by forming a polymer layer having a desired degree of polymerization or higher containing no low boiling point low molecular weight substance on a capacitor element and enduring temperature and stress during molding. Another object of the present invention is to provide a solid electrolytic capacitor having excellent characteristics in which a conductive polymer layer having excellent solder heat resistance is formed.

[0007]

The present invention has been completed as a result of studies to solve the above-mentioned problems of the prior art. That is, a capacitor element in which a dielectric oxide film is formed on the surface of a valve action metal base serving as an anode is impregnated with a polymerizable monomer and an oxidizing agent, and a conductive polymer layer is formed on the surface of the dielectric oxide film. In the method for manufacturing a solid electrolytic capacitor, after forming a conductive polymer layer in the capacitor element, the capacitor element is washed with an organic solvent to remove a substance in the conductive polymer layer that evaporates at 300 ° C. or less. It is characterized by reducing to 5% or less.

As described above, the melting temperature of solder in lead-free solder is considered to be about 260 ° C.
By lowering the content of low-boiling low-molecular substances that evaporate below 00 ° C (5% or less by weight), it is possible to suppress the amount of evaporation of these substances due to the temperature during molding or the temperature during soldering. Therefore, it is possible to prevent the structural change or characteristic deterioration of the polymer layer due to evaporation / scattering, and to maintain the dense conductive polymer layer. As a result, the mechanical strength is improved, and it is possible to obtain a good solid electrolytic capacitor that can withstand stress and temperature during resin coating or soldering, and that is free from short circuit, increase in leakage current, and increase in ESR.

It is preferable that the washing step is performed after the conductive polymer layer is formed and the chemical conversion is further performed.

A low boiling point and a low molecular weight product are also produced during re-formation, but if the washing step is performed after forming the conductive polymer layer and further re-formation, the low boiling point produced during re-formation, Low molecular weight substances can be effectively removed by the washing process.

It is preferable to carry out final polymerization of the conductive polymer layer after the washing step.

This final polymerization is carried out in order to obtain a dense state of the surface layer of the capacitor element, and further prevents short-circuiting and increase in leakage current by preventing the carbon fine particles from entering the inside during the subsequent formation of the carbon layer. become able to. Although low boiling point and low molecular weight substances are produced even in the final polymerization, the amount is small when seen from the whole conductive polymer layer, and the influence on the characteristics of the solid electrolytic capacitor is small.

It is preferable that the polymerizable monomer is a monomer composed of thiophene or a derivative thereof.

Examples of thiophene derivatives include those having the following structures. Thiophene or its derivative is
As compared with polypyrrole or polyaniline, the solid electrolytic capacitor has a high electric conductivity and particularly excellent thermal stability, and thus a solid electrolytic capacitor having low ESR and excellent heat resistance can be obtained.

[0015]

[Chemical 1] X is O or S When X is O, A is alkylene, or polyoxyalkylene When at least one of X is S, A is alkylene, polyoxyalkylene, substituted alkylene, substituted polyoxyalkylene: where the substituent is Alkyl group, alkenyl group, alkoxy group

Among the derivatives of thiophene, it is preferable to use 3,4-ethylenedioxythiophene.

3,4-ethylenedioxythiophene is
Upon contact with an oxidant, poly- (3,4-ethylenedioxythiophene) is generated by a gradual polymerization reaction, so that a monomer solution of 3,4-ethylenedioxythiophene is used in a capacitor element having a fine structure. It is possible to polymerize while penetrating to the inside. As a result,
The conductive polymer layer can be formed even inside the capacitor element, and the capacitance of the solid electrolytic capacitor can be increased.

Further, the present invention is characterized in that the capacitor element is washed in an organic solvent for 20 minutes or more.

By washing the capacitor element in the organic solvent for 20 minutes or more, the amount of substances that evaporate at 300 ° C. or less in the conductive polymer layer can be reduced to 5% or less.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in more detail. FIG. 1 is a sectional view showing the internal structure of a solid electrolytic capacitor. Reference numeral 1 is a capacitor element, which is formed by molding fine tantalum powder into a predetermined shape, embedding an anode lead wire such as tantalum wire, and further sintering to obtain a tantalum sintered body, which is further dipped in a phosphoric acid aqueous solution or the like. A predetermined voltage is applied to form an anodized film as a dielectric on the surface of the tantalum fine powder. The sintered body is not limited to tantalum, and valve metal such as aluminum, niobium, or titanium can be used.

Reference numeral 2 is a conductive polymer layer formed on the anodized film. The conductive polymer layer is prepared by dipping the capacitor element in a monomer solution prepared by diluting 3,4-ethylenedioxythiophene with a predetermined solvent, and further dipping the capacitor element in an oxidant solution to obtain 3,4-ethylenedioxythiophene. It is formed by oxidative polymerization of thiophene.

The capacitor element on which the conductive polymer layer is formed is re-formed by applying a predetermined voltage in phosphoric acid aqueous solution,
Further, it is washed with running deionized water and dried.
Thereafter, the number of polymerizations from dipping in the monomer solution to drying is repeated until the polymer layer has a desired thickness.

Thereafter, the capacitor element is immersed in an organic solvent such as chloroform for 20 minutes or more to wash the capacitor element. The washing with the organic solvent may be performed each time the conductive polymer layer is formed (polymerization step), or may be performed after repeating the polymerization step a plurality of times.

After washing with an organic solvent, the capacitor element is again immersed in a monomer solution prepared by diluting 3,4-ethylenedioxythiophene with a predetermined solvent, and further immersed in an oxidant solution for final polymerization. I do. This final polymerization is carried out in order to obtain a dense state of the surface layer part of the capacitor element, and further short-circuits by blocking the ingress of carbon fine particles during the subsequent carbon layer formation,
It becomes possible to suppress an increase in leakage current. The final polymerization may be carried out by immersing the monomer solution and the oxidant solution once, and performing the polymerization once, or by repeating the polymerization step a plurality of times.

Reference numeral 3 is a carbon layer formed on the conductive polymer layer 2, and reference numeral 4 is a silver paste layer formed on the carbon layer. The carbon layer and the silver paste layer can be formed by known means.

Reference numeral 5 denotes an anode lead wire, which is welded to the anode lead wire of the capacitor element and electrically connected to the outside. 6
Is a cathode lead wire, which is connected by a silver paste layer and is in electrical communication with the outside.

Then, the anode lead wire and the cathode lead wire are bent along the end faces of the exterior resin to be described later so that they can be surface-mounted.

Reference numeral 7 denotes an exterior resin, which is formed by coating the capacitor element with transfer molding except for a part of the anode lead wire and the cathode lead wire.

[0029]

Example (Embodiment 1) The size of the anode is 3.9 ×
Using a tantalum sintered body of 3.3 × 1.6 mm ³ and using a tantalum wire as an anode wire, an anode body having a weight of about 100 mg was anodized in a 0.05% phosphoric acid aqueous solution at 90 ° C. and 40 V for 180 minutes. It was washed with running deionized water and dried to obtain a capacitor element. Assuming that this state is a condenser, the result of measuring the capacity in the chemical conversion liquid is 104 μF
Met.

Next, this capacitor element was replaced with butanol 5
Immersion in a monomer solution prepared by mixing 0 g and 50 g of 3,4-ethylenedioxythiophene for 7 minutes, and then dissolving 40 g of ferric paratoluenesulfonate as an oxidizing agent containing a transition metal ion in 60 g of butanol. The obtained oxidant solution was immersed in the solution for 15 minutes to carry out chemical oxidative polymerization to form a conductive polymer layer on the anodic oxide film constituting the capacitor element. Further, after washing with butanol for removing the oxidizing agent solution for 5 minutes, it was dried at 105 ° C. for 5 minutes. Next, the capacitor element was re-formed in a 0.4% phosphoric acid aqueous solution at 60 ° C. and 20 V for 30 minutes, washed with running deionized water, and dried. Then, the number of times of polymerization from dipping in a monomer solution to drying was repeated 60 times until the polymer layer had a desired thickness.

The weight of this capacitor element was measured, the weight of the conductive polymer was obtained from the weight difference before the formation of the conductive polymer layer, and the weight of the polymer was washed in chloroform for 10 to 60 minutes with an organic solvent. When the rate of decrease was measured, a rapid weight loss due to the dissolution and removal of the conductive polymer was observed within 10 minutes, but the weight loss was saturated in 20 to 30 minutes and was about 7%.
Was (Fig. 2).

When the capacitor element washed with the above-mentioned organic solvent for 20 minutes is heated and the weight change before and after the heating is observed, it is 2
From 00 ° C to 300 ° C, it was almost constant and was 5% or less (Fig. 3). On the other hand, in the temperature range exceeding 300 ° C., the weight reduction is remarkable. It is considered that at 300 ° C. or higher, the conductive polymer having a high molecular weight starts to decompose and causes a weight reduction.

From these results, it was found that the substance evaporated at 300 ° C. or lower can be reduced to 5% by weight or less by washing in an organic solvent for 20 minutes or longer.

Next, a carbon layer is formed on the conductive polymer layer of the washed capacitor element, and a silver paint layer serving as a cathode is formed on the carbon layer, and the cathode is formed on the silver paint layer. Attaching the lead-out terminals to the anode wire drawn out from the anode body, mounting the anode lead-out terminals with resin by transfer molding, and bending the cathode lead-out terminal and the anode lead-out terminal to predetermined positions to form a chip-shaped solid electrolytic capacitor. Was completed. The final product inspection of the capacitor is 3.
Occurrence of short circuit of 5% and LC failure of 10.8% was observed.
Furthermore, the initial characteristics were measured excluding this defect, and then evaluation was performed in a solder reflow test. The result is shown in FIG.

E of the product after cleaning the capacitor element
The SR exhibits different characteristics depending on the cleaning time, and the ESR tends to increase as the cleaning time increases, but the SR takes a substantially constant value in 20 to 30 minutes.
Short-circuit defects due to reflow are seen to occur at a few% when the capacitor element is not washed, but it is reduced by washing the capacitor element, and takes a minimum value when the capacitor element is washed for 20 minutes or more. There was found.
From this result, it was confirmed that the occurrence of short circuit during reflow can be reduced by cleaning the capacitor element with an organic solvent.

The results also show that washing of the capacitor element for 20 minutes or more provides a capacitor having stable characteristics. In this case, a low boiling point low molecular weight substance that evaporates in the range of 300 ° C. or less is used. Was found to be 5% by weight or less.

The butanol cleaning performed in the polymerization step is performed to remove the oxidant adhering to the capacitor element, and the same butanol as the solvent for the oxidant is used. In this example, the time for butanol washing was as short as 5 minutes, and it was not possible to sufficiently remove low-molecular-weight substances (in the case where the butanol washing was carried out and the chloroform washing was not carried out thereafter). Short circuit occurred,
It is estimated from the high LC failure rate). Therefore, butanol cleaning here is not within the scope of the present invention.

(Second Embodiment) Next, another embodiment will be described in detail. That is, the short circuit at the time of molding, LC defect rate, and ESR characteristics of the following Examples 1 to 5, short circuit after repeating 240 ° C. solder reflow four times, LC defect and the increase amount of ESR at that time were measured. The results are as shown in Table 1.

(Example 1) A conductive polymer layer was formed on an anodized film constituting a capacitor element by the same means as in the above-described embodiment, and then the capacitor element was formed by the same means. Reforming, washing with pure water, and drying were performed. Thereafter, the capacitor element was washed in chloroform for 30 minutes, and the polymerization from dipping in a monomer solution to washing was repeated 50 times until the polymer layer had a desired thickness.

Next, the capacitor element having the conductive polymer layer thus formed is again immersed in the monomer solution for 7 minutes and in the oxidant solution for 15 minutes to carry out chemical oxidative polymerization and washed with butanol. After 5 minutes, 10
The steps of drying at 5 ° C. for 5 minutes and then performing re-formation, washing, and drying by the same means as in the previous embodiment are repeated 10 times,
A conductive polymer layer having a desired thickness was formed on the surface of the capacitor element.

That is, in Example 1, the step of washing the capacitor element with an organic solvent after polymerization / re-formation / washing with pure water / drying was carried out 50 times, and further final polymerization (polymerization / re-forming / washing with pure water). -This is an example in the case of performing the steps up to drying 10 times).

The weight of a part of this capacitor element was measured, the weight of the conductive polymer was determined from the weight difference before the formation of the conductive polymer layer, and the weight was heated in an oven at a temperature of 200 ° C. to 300 ° C. for 10 minutes. The polymer weight loss rate was measured to be 3.7% to 4.8%.

Next, a carbon layer is formed on the conductive polymer layer, a silver paint layer serving as a cathode is formed on the carbon layer, and a cathode lead terminal is formed on the silver paint layer. Anode lead terminals were attached to the anode wires drawn from, respectively, and resin coating was performed by transfer molding, and the cathode lead terminal and the anode lead terminal were bent at predetermined positions to complete a chip-shaped solid electrolytic capacitor. The final product inspection of the capacitor showed 0% short circuit and 3.8% LC defect, but the initial characteristics were measured and solder reflow test was performed after the initial characteristic was excluded. The results are shown in Table 1.

Example 2 A conductive polymer layer was formed on the anodic oxide film constituting the capacitor element by the same means as in Reference Example 1, and then the capacitor element was washed in chloroform for 30 minutes. After that, re-formation, washing and drying were performed, and the number of polymerizations from dipping in the monomer solution to drying was repeated 50 times until the polymer layer had a desired thickness.

Next, the capacitor element having the conductive polymer layer thus formed is again immersed in the monomer solution for 7 minutes and in the oxidant solution for 15 minutes to carry out chemical oxidative polymerization and washed with butanol. After 5 minutes, 10
The steps of drying at 5 ° C. for 5 minutes and then re-forming, washing and drying by the same means as in Reference Example 1 were repeated 10 times to form a conductive polymer layer having a desired thickness on the surface of the capacitor element.

That is, in Example 2, after polymerization,
This is an example in which the steps of washing the capacitor element with an organic solvent, re-forming, washing with pure water, and drying are repeated 50 times, and further the final polymerization (the number of times of polymerization is 10 times).

The weight of a part of this capacitor element was measured, the weight of the conductive polymer was obtained from the weight difference before the formation of the conductive polymer layer, and the weight was heated in an oven at a temperature of 200 ° C. to 300 ° C. for 10 minutes. The polymer weight loss rate was measured to be 3.6% to 4.6%.

Next, a carbon layer is formed on the conductive polymer layer, a silver paint layer serving as a cathode is formed on the carbon layer, and a cathode lead terminal is formed on the silver paint layer and the anode body is formed. Anode lead terminals were attached to the anode wires drawn from, respectively, and resin coating was performed by transfer molding, and the cathode lead terminal and the anode lead terminal were bent at predetermined positions to complete a chip-shaped solid electrolytic capacitor. The final product inspection of the capacitor caused a short circuit of 0.6% and an LC defect of 15.6%. Except for this defect, initial characteristics were measured and evaluated by a solder reflow test. The results are shown in Table 1.

Example 3 A conductive polymer layer was formed on the anodic oxide film constituting the capacitor element by the same means as in the previous embodiment, and then the capacitor element was reformed by the same means. It was washed with water and dried. The formation of such a conductive polymer layer was repeated 10 times, and then the step of washing the capacitor element with chloroform for 30 minutes was repeated until the polymer layer had a desired thickness. As the number of times of polymerization, the number of times of polymerization from dipping in a monomer solution to drying was 10 times, and washing with chloroform was added once every 10 times of polymerization, and this was repeated 5 times in total.

Next, the capacitor element having the conductive polymer layer thus formed is again immersed in the monomer solution for 7 minutes and in the oxidant solution for 15 minutes for chemical oxidative polymerization, and washed with butanol. After 5 minutes, 10
The steps of drying at 5 ° C. for 5 minutes, and then re-forming, washing with water and drying by the same means as in Reference Example 1 were repeated 10 times to form a conductive polymer layer having a desired thickness on the surface of the capacitor element.

That is, in Example 3, the step of washing the capacitor element with an organic solvent after repeating the polymerization 10 times was repeated 5 times, and further re-forming and final polymerization (polymerization / re-forming / washing with pure water / drying). This is an example in the case of performing the steps up to 10 times).

The weight of a part of this capacitor element was measured, the weight of the conductive polymer was obtained from the weight difference before the formation of the conductive polymer layer, and the weight was heated in an oven at a temperature of 200 ° C. to 300 ° C. for 10 minutes. The weight loss rate of the polymer was measured and found to be 3.9% to 4.9%.

Next, a carbon layer is formed on the conductive polymer layer, a silver coating layer serving as a cathode is formed on the carbon layer, and a cathode lead terminal is formed on the silver coating layer. Anode lead terminals were attached to the anode wires drawn from, respectively, and resin coating was performed by transfer molding, and the cathode lead terminal and the anode lead terminal were bent at predetermined positions to complete a chip-shaped solid electrolytic capacitor. The capacitor had a short circuit of 0% in the final product inspection and an LC defect of 4.2%, and thus Example 1 in which organic solvent washing is performed for each polymerization
It was as good as that of. Except for this defect, initial characteristics were measured and evaluated by a solder reflow test. The results are shown in Table 1.

Example 4 A conductive polymer layer was formed on the anodized film forming the capacitor element by the same means as in the previous embodiment, and then the capacitor element was reformed by the same means. It was washed with water and dried. The formation of such a conductive polymer layer was repeated 10 times, and then the step of washing the capacitor element with chloroform for 30 minutes was repeated until the polymer layer had a desired thickness. As for the number of polymerizations, the number of polymerizations from dipping in a monomer solution to drying is 10 times, and washing with chloroform is 1 in 10 polymerizations.
This was repeated 5 times in total.

Next, the capacitor element having the conductive polymer layer thus formed is again immersed in the monomer solution for 7 minutes and in the oxidant solution for 15 minutes for chemical oxidative polymerization, and washed with butanol. After 5 minutes, 10
The steps of drying at 5 ° C. for 5 minutes, followed by re-formation, washing with water, drying, and washing with an organic solvent with chloroform were repeated 9 times in the same manner as in Example 2, and the final step was dipping in a monomer solution and polymerization until drying. And re-forming-drying ends,
A conductive polymer layer having a desired thickness was formed on the surface of the capacitor element.

That is, in Example 3, the step of washing the capacitor element with an organic solvent after repeating the polymerization 10 times was repeated 5 times, and the steps of re-formation, polymerization and washing with an organic solvent were repeated 9 times, and finally, It is an example in the case where it is polymerized (final polymerization) and dried.

The weight of a part of this capacitor element was measured, the weight of the conductive polymer was determined from the weight difference before the formation of the conductive polymer layer, and the weight was heated in an oven at a temperature of 200 ° C. to 300 ° C. for 10 minutes. The polymer weight loss was measured to be 3.3% to 4.7%.

Next, a carbon layer is formed on the conductive polymer layer, and a silver paint layer serving as a cathode is formed on the carbon layer. A cathode lead terminal is formed on the silver paint layer, and the anode body is formed. Anode lead terminals were attached to the anode wires drawn from, respectively, and resin coating was performed by transfer molding, and the cathode lead terminal and the anode lead terminal were bent at predetermined positions to complete a chip-shaped solid electrolytic capacitor. In the final product inspection, the capacitor was found to have a short circuit of 0% and an LC defect of 4.7%, which was comparable to Example 2 in which cleaning was performed for each polymerization. Except for this defect, initial characteristics were measured and evaluated by a solder reflow test.

(Embodiment 5) A conductive polymer layer is formed on the anodic oxide film constituting the capacitor element by the same means as in Embodiment 5, and then the capacitor element is reformed and washed by the same means. , Dried. The formation of such a conductive polymer layer was repeated 10 times, and then the step of washing the capacitor element with chloroform for 30 minutes was repeated until the polymer layer had a desired thickness. As the number of polymerizations, the number of polymerizations from dipping in a monomer solution to drying is 1
The washing was repeated 0 times, once every 10 times of polymerization, and this was repeated 5 times in total.

Next, the capacitor element having the conductive polymer layer thus formed is again immersed in the monomer solution for 7 minutes and in the oxidant solution for 15 minutes for chemical oxidative polymerization, and washed with butanol. After 5 minutes, 10
The steps of drying at 5 ° C. for 5 minutes, followed by re-formation, washing with water, drying, and washing with an organic solvent with chloroform were repeated 10 times in the same manner as in Example 2, and the surface of the capacitor element was made to have a desired high conductivity. A molecular layer was formed.

That is, in this Example 5, the step of washing the capacitor element with an organic solvent after repeating the polymerization 10 times was repeated 5 times, and the steps of re-forming, polymerization and washing with an organic solvent were repeated 10 times. It is an example of.

The weight of a part of this capacitor element was measured, the weight of the conductive polymer was determined from the weight difference before the formation of the conductive polymer layer, and the weight was heated in an oven at a temperature of 200 ° C. to 300 ° C. for 10 minutes. The polymer weight loss rate was 3.3 to 4.5%.

Next, a carbon layer is formed on the conductive polymer layer, a silver coating layer serving as a cathode is formed on the carbon layer, and a cathode lead terminal is formed on the silver coating layer and the anode body is formed. Anode lead terminals were attached to the anode wires drawn from, respectively, and resin coating was performed by transfer molding, and the cathode lead terminal and the anode lead terminal were bent at predetermined positions to complete a chip-shaped solid electrolytic capacitor. The capacitor had a short circuit of 2.7% in the final product inspection, an LC defect of 11.9%, and was not washed after the final polymerization.
It was inferior to. Except for this defect, initial characteristics were measured and evaluated by a solder reflow test. The results are shown in Table 1.

[0064]

[Table 1]

As is clear from Table 1, Examples 1, 3 and
Nos. 4 and 5 can obtain a highly reliable solid electrolytic capacitor having excellent short circuit, leakage current and ESR characteristics, while those of Examples 2 and 5 have many ESR characteristics but no short circuit. The leakage current characteristics are also inferior to those of the first, third and fourth embodiments. It is considered that this difference was caused by the presence or absence of organic solvent cleaning after reforming, and it was confirmed that by performing organic solvent cleaning after reforming, it is possible to reduce the frequency of occurrence of short-circuit rate and LC defect rate in final product inspection. did it.

Further, comparing Examples 1, 3, and 4, there is no great difference in their characteristics. From this result, it is understood that the cleaning of the capacitor element with the organic solvent does not necessarily have to be performed for each polymerization, and the cleaning with the organic solvent may be performed after repeating the polymerization a plurality of times.

[0067]

As described above, according to the present invention, in the solid electrolytic capacitor having the conductive polymer layer formed on the surface of the oxide film forming the capacitor element made of the valve metal, The capacitor element on which the molecular layer is formed is washed with an organic solvent to dissolve and remove the low-boiling low-molecular substance to suppress the content of the substance, and to reduce the content of the conductive polymer layer at 200 ° C to 300 ° C. By setting the amount of the substance to be evaporated to 5% or less, the amount of evaporation of the substance due to the temperature during molding or the temperature during soldering can be suppressed. For this reason, it is possible to prevent structural change or characteristic deterioration of the polymer layer due to evaporation / scattering of low molecular weight substances, to form a dense conductive polymer layer, improve mechanical strength, It is possible to obtain a good solid electrolytic capacitor which can withstand stress and temperature and is free from short circuit, increase in leakage current and increase in ESR.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic structure of a solid electrolytic capacitor of the present invention.

FIG. 2 is a graph showing a weight reduction rate of a conductive polymer layer according to a cleaning time of organic solvent cleaning.

FIG. 3 is a graph showing the weight reduction rate of the conductive polymer layer when the organic cleaned capacitor element is heated.

FIG. 4 is a graph showing changes in the characteristics of a solid electrolytic capacitor depending on the cleaning time of organic solvent cleaning.

[Explanation of symbols]

1 Capacitor element 2 Conductive polymer layer 3 carbon layer 4 Silver paste layer 5 Anode lead wire 6 Cathode lead wire 7 Exterior resin

Claims (6)

[Claims] 1. A capacitor element in which a dielectric oxide film is formed on the surface of a valve action metal substrate serving as an anode is impregnated with a polymerizable monomer and an oxidizing agent, and a conductive polymer layer is formed on the surface of the dielectric oxide film. In the method for producing a solid electrolytic capacitor comprising, after forming a conductive polymer layer in the capacitor element,
A method for producing a solid electrolytic capacitor, characterized in that the capacitor element is washed with an organic solvent to reduce the amount of substances that evaporate at 300 ° C. or less in the conductive polymer layer to 5% or less. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the cleaning step is performed after forming a conductive polymer layer and further performing re-chemical conversion. 3. The method for producing a solid electrolytic capacitor according to claim 1, wherein the conductive polymer layer is subjected to final polymerization after the washing step. 4. The method for producing a solid electrolytic capacitor according to claim 1, wherein the polymerizable monomer is a monomer composed of thiophene or a derivative thereof. 5. The method for producing a solid electrolytic capacitor according to claim 4, wherein the derivative of thiophene is 3,4-ethylenedioxythiophene. 6. Washing the capacitor element in an organic solvent
The method for producing a solid electrolytic capacitor according to claim 1, wherein the method is performed for 0 minutes or more.