JP2002246273A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

(57) [Summary] [Problem] A dielectric oxide film layer formed on the outer surface of an anode body becomes non-uniform due to a gas or the like generated during anodic oxidation, resulting in leakage current characteristics and strength of the dielectric oxide film layer. It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor capable of solving the problem of deterioration and forming a uniform dielectric oxide film layer to stably exhibit excellent performance. SOLUTION: In the course of anodic oxidation, the anode body is once pulled up from the chemical conversion solution and heat-treated, and then the anode body is returned to the chemical formation solution and anodized again, so that a defective portion or an impurity in the dielectric oxide film layer is formed. To form a homogeneous dielectric oxide film layer with less leakage, and as a result, to reduce leakage current and improve the withstand voltage of the dielectric oxide film layer to provide a solid electrolytic capacitor with higher performance and higher reliability. Can be.

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 valve metal powder such as tantalum.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view showing the structure of a solid electrolytic capacitor of this type. In FIG.
Reference numeral 2 denotes an anode lead wire made of a tantalum wire buried in the anode body 1, reference numeral 3 denotes a dielectric oxide film layer formed on the outer surface of the anode body 1, and reference numeral 4 denotes a dielectric oxide film layer formed on the dielectric oxide film layer 3. The solid electrolyte layers 5, 5 and 6 are a carbon layer and a silver paste layer formed on the solid electrolyte layer 4, and the carbon layer 5 and the silver paste layer 6 constitute a cathode layer.

Next, a conventional method for manufacturing a solid electrolytic capacitor having the above-described structure will be described with reference to FIG. 9. First, in a molding step, a powder of tantalum, which is a valve metal, is placed in a pressure molding die. And molded into a desired shape with the anode lead wire 2 made of tantalum wire embedded. Next, the formed anode body 1 is sintered in a high vacuum atmosphere. Next, the anode body 1 is anodized in a chemical solution such as a phosphoric acid aqueous solution or a nitric acid aqueous solution by applying a voltage corresponding to a desired capacity, thereby forming a dielectric oxide film layer 3 on the outer surface of the anode body 1. Form. Next, a solid electrolyte layer 4 made of manganese dioxide or a conductive polymer is formed on the dielectric oxide film layer 3 by electrolytic polymerization or chemical polymerization. Next, a carbon layer 5 and a silver paste layer 6 were provided on the solid electrolyte layer 4 to form a cathode layer, whereby a solid electrolytic capacitor was manufactured.

[0004]

However, in the above-mentioned conventional method for manufacturing a solid electrolytic capacitor, in the formation step for forming the dielectric oxide film layer 3 on the outer surface of the anode body 1 by anodic oxidation, a desired capacity is obtained. The anodic oxidation is performed by applying the appropriate voltage and holding it for a certain period of time.However, simply applying the voltage corresponding to the desired capacity for a certain period of time applies to the gas and dielectric oxide film generated during anodic oxidation. The dielectric oxide film layer 3 formed on the outer surface of the anode body 1 is likely to be non-uniform due to current concentration on the defective portion of the layer 3 and impurities in the powder and the chemical conversion solution. There is a problem that the electrical and physical strength of the dielectric oxide film layer 3 is reduced.

The present invention solves such a conventional problem,
It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor capable of obtaining a highly reliable solid electrolytic capacitor capable of stably exhibiting excellent performance by forming a uniform dielectric oxide film layer. Things.

[0006]

In order to solve the above-mentioned problems, the invention according to the first aspect of the present invention is particularly directed to a method of forming a valve metal powder into a desired shape, and sintering the powder to form an anode body. The anode body is anodized in a chemical conversion solution to form a dielectric oxide film layer on the outer surface, and a solid electrolyte layer and a cathode layer are sequentially formed on the dielectric oxide film layer. In the manufacturing method, a method for manufacturing a solid electrolytic capacitor in which the anode body is once pulled up from the chemical conversion solution during the anodization and heat-treated, and then the anode body is returned to the chemical formation solution and anodized again, According to the method, a uniform and dense dielectric oxide film layer can be formed, so that the leakage current is reduced and the effect of improving reliability can be obtained.

According to a second aspect of the present invention, in the first aspect of the invention, the timing at which the anode body is pulled up from the chemical conversion solution and heat-treated is performed in the first half of the holding time of the anodizing voltage. In this case, this method has an effect that the effect obtained by the first aspect can be obtained more efficiently.

According to a third aspect of the present invention, in the first aspect of the present invention, the anode body pulled up from the chemical conversion solution is 200 times.
The heat treatment is performed at a temperature of up to 400 ° C. for 20 to 60 minutes. According to this method, the operation and effect obtained by the invention of claim 1 can be obtained more efficiently.

According to a fourth aspect of the present invention, in the first aspect, the anode body pulled up from the chemical conversion solution is heat-treated in a humid atmosphere. The operation and effect that the operation and effect obtained by the described invention can be obtained more efficiently can be obtained.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the anode body pulled up from the chemical conversion solution is heat-treated in an active or inert gas atmosphere. The operation and effect obtained by the invention according to claim 1 can be obtained more efficiently.

According to a sixth aspect of the present invention, in the first aspect, the anode body pulled up from the chemical conversion solution is heat-treated in a vacuum atmosphere. The operation and effect that the operation and effect obtained by the described invention can be obtained more efficiently can be obtained.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the anode body lifted from the chemical conversion solution is washed before heat-treating the anode body. Since the adhering chemical solution is forcibly removed, the operation and effect obtained by the invention of claim 1 can be obtained more efficiently.

[0013] By performing this washing with warm water,
An even more remarkable effect is obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described in detail with reference to claims 1 to 7 of the present invention.

FIG. 2 is a sectional view showing the structure of a solid electrolytic capacitor according to an embodiment of the present invention. In FIG. 2, reference numeral 1 denotes an anode body, and 2 denotes a tantalum wire embedded in the anode body 1. Anode lead wire 3 is a dielectric oxide film layer formed on the outer surface of anode body 1, 4 is a solid electrolyte layer formed on dielectric oxide film layer 3, 5 and 6 are solid electrolyte layers 4 The carbon layer and the silver paste layer formed thereon, and the cathode layer is constituted by the carbon layer 5 and the silver paste layer 6 are the same as those of the conventional solid electrolytic capacitor described in the section of the prior art. is there.

Next, a method of manufacturing the solid electrolytic capacitor according to the present embodiment thus configured will be described with reference to FIG. First, in a molding step, powder of tantalum as a valve metal is filled in a pressure molding die, and is molded into a desired shape with the anode lead-out wire 2 made of a tantalum wire embedded. Next, the formed anode body 1 is sintered in a high vacuum atmosphere.

Next, the anode body 1 is anodized by applying a voltage corresponding to a desired capacity in a chemical conversion solution composed of a phosphoric acid aqueous solution, thereby forming a dielectric oxide film layer 3 on the outer surface of the anode body 1. Form. Next, during the anodic oxidation, the anode body 1 is pulled out of the chemical conversion solution, the remaining phosphoric acid is washed away using warm water, and then heat treatment is performed in a heat treatment furnace. Next, the anode body 1 after the heat treatment is returned to the chemical conversion solution, and a voltage is applied again to perform anodic oxidation, thereby forming a dielectric oxide film layer 3 on the outer surface of the anode body 1.

Next, a solid electrolyte layer 4 made of a conductive polymer (or manganese dioxide) is formed on the dielectric oxide film layer 3 by electrolytic polymerization (or chemical polymerization). Next, a cathode layer was formed by providing a carbon layer 5 and a silver paste layer 6 on the solid electrolyte layer 4 to produce a solid electrolytic capacitor of the present invention.

(Example 1) The timing of pulling up the anode body 1 from the chemical conversion solution during the above-described anodic oxidation was set to １ ／ of the time required for anodic oxidation (basically 120 minutes),
The operation is performed at each timing of 2/4, 3/4, and 4/4.
Heat treatment was performed for 0 minute, 30 minutes, 60 minutes, and 90 minutes, respectively.

The anode body 1 of Example 1 thus manufactured and a conventional product as a comparative example were inspected in a liquid, and the relationship between the timing of heat treatment at the formation voltage holding time and the leakage current was measured. FIG. 3 shows the results, and FIG. 4 shows the results of measuring the relationship between the timing of heat treatment during the formation voltage holding time and the withstand voltage of the dielectric oxide film layer.

The test conditions were a 10 vol% phosphoric acid aqueous solution, a temperature of 25 ° C., and an applied voltage of 70% of the formation voltage.
Was measured. The strength of the dielectric oxide film layer 3 is 15 V
ol% ammonium adipate aqueous solution, applied current 100
μA / element was compared, and the conventional product was compared with 100.

(Example 2) In Example 1, the heat treatment temperature was set at 150 ° C, 200 ° C, 250 ° C, 300 ° C,
Inspection was performed in the same manner as in Example 1 except that the test was performed at each of 50 ° C., 400 ° C., 450 ° C., 500 ° C., and 550 ° C., and the results of measuring the relationship between the timing of heat treatment and the leakage current during the formation voltage holding time FIG. 5 shows the relationship between the timing of heat treatment during the formation voltage holding time and the breakdown voltage of the dielectric oxide film layer, and FIG. 6 shows the results.

Example 3 Example 2 was repeated except that the heat treatment was performed in air, 30% H ₂ O, 85% H ₂ O, vacuum, N ₂ , and Ar. Inspection was performed in the same manner as in Example 2, and the result of measuring the relationship between the timing of the heat treatment at the formation voltage holding time and the leakage current was shown in FIG. FIG. 8 shows the result of measuring the relationship between the breakdown voltages.

As is clear from the results of Examples 1 to 3, after the anode body 1 is once pulled up from the chemical forming solution during the anodic oxidation and heat-treated, the anode body 1 is returned to the chemical forming solution. It can be seen that by performing the anodic oxidation again, the amount of carbon that adversely affects the leakage current of the anode body 1 is reduced, which is effective in reducing the leakage current.

Further, the defective portion existing in the dielectric oxide film layer 3 is once broken into a larger defect portion, and a new dielectric oxide film is formed on the large broken defect portion by the second anodic oxidation after the heat treatment. By forming the layer 3 again, a more uniform and dense dielectric oxide film layer 3 can be formed. This has the effect of reducing the leakage current and improving the electrical and physical strength of the dielectric oxide film layer 3.

The heat treatment conditions of the present invention are preferably carried out at the timing when the first half of the total voltage holding time has elapsed, and the temperature is 200 ° C. to 400 ° C., the humidity is 85% or more, or the vacuum is applied. In this case, it is desirable to perform the process for 20 minutes to 40 minutes. This is because if the heat treatment is excessive,
This is because the dielectric oxide film layer 3 is excessively broken, and it becomes difficult to form the dense dielectric oxide film layer 3 by anodic oxidation again after the heat treatment.

[0027]

As described above, according to the present invention, the anode body is once pulled up from the chemical conversion solution during the anodization and heat-treated, and then the anode body is returned to the chemical formation solution and anodized again. , A homogeneous dielectric oxide film layer with few defects and impurities in the dielectric oxide film layer can be formed,
As a result, the leakage current is reduced and the dielectric breakdown voltage of the dielectric oxide film layer is improved, so that a higher performance and higher reliability solid electrolytic capacitor can be provided.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an embodiment of the present invention and a configuration of a conventional solid electrolytic capacitor.

FIG. 3 is a characteristic diagram obtained by measuring the relationship between the timing of heat treatment and the leakage current during the formation voltage holding time according to the first embodiment of the present invention.

FIG. 4 is a characteristic diagram obtained by measuring the relationship between the timing of heat treatment during the assimilation voltage holding time and the withstand voltage of the dielectric oxide film layer.

FIG. 5 is a characteristic diagram obtained by measuring the relationship between the timing of heat treatment and the leakage current during the formation voltage holding time according to the second embodiment of the present invention.

FIG. 6 is a characteristic diagram obtained by measuring the relationship between the timing of heat treatment during the formation voltage holding time and the withstand voltage of the dielectric oxide film layer.

FIG. 7 is a characteristic diagram obtained by measuring the relationship between the timing of heat treatment and the leakage current during the formation voltage holding time according to the third embodiment of the present invention.

FIG. 8 is a characteristic diagram obtained by measuring the relationship between the timing of heat treatment during the assimilation voltage holding time and the withstand voltage of the dielectric oxide film layer.

FIG. 9 is a manufacturing process diagram showing a conventional method for manufacturing a solid electrolytic capacitor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 anode body 2 anode lead 3 dielectric oxide film layer 4 solid electrolyte layer 5 carbon layer 6 silver paste layer

Claims (7)

[Claims] 1. A molding step for molding a valve metal powder into a desired shape using a pressure molding die, a sintering step for producing an anode body by sintering the metal powder, and a chemical liquid A formation step of forming a dielectric oxide film layer on the outer surface of the anode body by anodizing in the anode body; an electrolyte layer forming step of forming a solid electrolyte layer on the dielectric oxide film layer; And a cathode layer forming step of forming a cathode layer. Of manufacturing a solid electrolytic capacitor in which anodization is performed again. 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the timing of heat-treating the anode body from the chemical conversion liquid is performed in the first half of the holding time of the anodizing voltage. 3. The anode body pulled up from the chemical conversion solution is 200 to
The method for producing a solid electrolytic capacitor according to claim 1, wherein the heat treatment is performed at 400C for 20 to 60 minutes. 4. The method for producing a solid electrolytic capacitor according to claim 1, wherein the anode body pulled up from the chemical conversion solution is heat-treated in a humid atmosphere. 5. The method for producing a solid electrolytic capacitor according to claim 1, wherein the anode body pulled up from the chemical conversion solution is heat-treated in an active or inert gas atmosphere. 6. The method for producing a solid electrolytic capacitor according to claim 1, wherein the anode body pulled up from the chemical conversion solution is heat-treated in a vacuum atmosphere. 7. The method for producing a solid electrolytic capacitor according to claim 1, wherein cleaning is performed before heat-treating the anode body pulled up from the chemical conversion solution.