CN1280853C - Solid electrolytic capacitor making process - Google Patents

Abstract

To solve a problem that a dielectric oxide film layer formed on the outer surface of an anode body is rendered heterogeneous by gases generated during anodic oxidation to cause deterioration in the leak current characteristics or the strength of the dielectric oxide film layer, and to provide a method for producing a solid electrolytic capacitor exhibiting excellent performance stably by forming a homogeneous dielectric oxide film layer. When an anode body is lifted up temporarily from a forming liquid in the way of anodic oxidation and then returned back into the forming liquid and subjected again to anodic oxidation, a homogeneous dielectric oxide film layer in which defective parts and impurities are reduced can be formed. Consequently, leak current is reduced and breakdown strength of the dielectric oxide film layer is enhanced resulting in a highly reliable high performance solid electrolytic capacitor.

Description

Manufacturing method of solid electrolytic capacitor

technical field

The present invention relates to a method of manufacturing a solid electrolytic capacitor using valve metal powder such as tantalum.

Background of the invention

Fig. 2 is a sectional view showing the structure of the solid electrolytic capacitor. In this figure, 1 is an anode, 2 is an anode lead-out wire made of tantalum wire embedded in the anode, and 3 is an anode in the anode 1. Dielectric oxidation protection film layer formed on the outer surface, 4 is the solid electrolyte layer formed on the dielectric oxidation protection film layer 3, 5 and 6 are the carbon layer and silver paste formed on the solid electrolyte layer 4 layer, and the carbon layer 5 and the silver paste layer 6 form a cathode.

Next, the conventional manufacturing method of the solid electrolytic capacitor constituted as described above will be described with reference to FIG. In the state where the anode leads out the wire 2, the desired shape is formed. Then, the shaped anode 1 is sintered in a high vacuum atmosphere. The anode 1 is subjected to anodic oxidation by applying a voltage balanced with the required capacitance of an anolyte solution (anodizing liquid) such as phosphoric acid aqueous solution and nitric acid aqueous solution, thereby forming a dielectric oxidation protective film 3 on the outer surface of the anode body 1 . Subsequently, a solid electrolyte layer 4 composed of manganese dioxide and conductive polymers is formed on the dielectric oxidation protective film layer 3 by electrolytic polymerization and chemical polymerization. Then, a cathode layer was formed by providing a carbon layer 5 and a silver pasting layer 6 on the solid electrolyte layer 4 described above, thus manufacturing a solid electrolytic capacitor.

But, in the manufacturing method of above-mentioned existing solid electrolytic capacitor, in the electrolytic process that forms the dielectric oxidation protective film layer 3 on the outer surface of anode 1 by anodic oxidation, apply the voltage that balances with required electric capacity, its Hold for a certain period of time to carry out anodic oxidation, but because only the voltage balanced with the required capacitance is applied for a certain period of time, the gas and current generated in the anodic oxidation will concentrate on the concave part of the dielectric oxidation protective film layer 3, and the powder and impurities in the anolyte, the dielectric oxidation protection film layer 3 formed on the outer surface of the anode 1 will also become uneven. As a result, leakage current characteristics and electronic and physical strengths of the dielectric oxidation protective film layer 3 are problematic.

Contents of the invention

The present invention solves the above-mentioned problems in the prior art, and its purpose is to provide a method for manufacturing a solid electrolytic capacitor, which can form a uniform dielectric oxide protective film, and can be stable and exert better performance. reliability solid electrolytic capacitors.

In order to solve the above-mentioned problems, the present invention is a method for manufacturing a solid electrolytic capacitor. In particular, in the method for manufacturing a solid electrolytic capacitor, the valve metal powder is made into a desired shape, and then sintered to make an anode. In the process of anodizing the anode, a dielectric oxide protective film is formed on the outer surface, and a solid electrolyte layer and a cathode layer are sequentially formed on the dielectric oxidation protective film. Remove the anode from the anolyte for heat treatment, and then return the anode to the anolyte for anodic oxidation for no less than one time. Through this method, a uniform and fine dielectric oxidation protection film can be formed, thereby reducing leakage current and achieving the effect of increasing reliability.

In the aforementioned invention, the timing of taking out the anode from the anolyte for heat treatment is performed in the first half of the voltage holding time for anodic oxidation. By this method, better effects than those obtained in the aforementioned invention can be obtained.

In the foregoing invention, the present invention heats the anode taken out from the anolyte at a temperature of 200-400 degrees for 20-60 minutes at a time. By this method, a better effect than that obtained in the foregoing invention can be obtained. Effect.

In the foregoing invention, the present invention heat-treats the anode taken out of the anolyte in a humid atmosphere, and through this method, better effects than those obtained in the foregoing invention can be obtained.

In the aforementioned invention, the present invention heat-treats the anode taken out of the anolyte in an active or inert gas atmosphere, and by this method, a better efficiency effect than that obtained by the aforementioned invention can be obtained.

In the aforementioned invention, the present invention heat-treats the anode taken out of the anolyte in a vacuum atmosphere, and through this method, better effects than those obtained in the aforementioned invention can be obtained.

In the foregoing invention, the present invention cleans the anode taken out from the anolyte before heat-treating it. By this method, the anolyte attached to the anode can be forcibly removed, and the anode obtained in the foregoing invention can be obtained The effect is better.

And, by washing it off with warm water, you can get even more dramatic results.

In the aforementioned invention, any one or more of inorganic acid, organic acid, and molten salt can be used as the anolyte used in the electrolysis process in the present invention. Effect.

In the aforementioned invention, the electrolytic solution used for anodic oxidation in the electrolytic process used before and after the heat treatment process of the present invention may be the same or different, and by this method, a better effect than that obtained in the aforementioned invention can be obtained.

Brief description of the drawings

1 is a manufacturing process diagram illustrating a method of manufacturing a solid electrolytic capacitor according to an embodiment of the present invention;

Fig. 2 is a cross-sectional view showing the structure of an existing solid electrolytic capacitor according to an embodiment of the present invention;

Fig. 3 is a characteristic diagram of measuring the relationship between heat treatment timing and leakage current according to the electrolysis voltage holding time in Example 1 of the present invention;

Fig. 4 is a characteristic diagram of the relationship between the heat treatment timing and the withstand voltage of the dielectric oxide protective film in the electrolytic voltage holding time;

Fig. 5 is a characteristic diagram measuring the relationship between heat treatment timing and leakage current within the electrolytic voltage holding time according to Embodiment 2 of the present invention;

Fig. 6 is a characteristic diagram measuring the relationship between the heat treatment timing and the withstand voltage of the dielectric oxidation protective film within the electrolytic voltage holding time;

7 is a characteristic diagram of the relationship between the heat treatment temperature and the leakage current in various atmospheres during the electrolysis holding time according to Example 3 of the present invention;

Fig. 8 is a characteristic diagram measuring the relationship between the heat treatment within the electrolytic voltage holding time and the withstand voltage of the dielectric oxidation protective film in various atmospheres;

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

Embodiments of the invention

Next, the invention described in claims 1 to 9 of the present invention will be described in detail using examples of the present invention.

2 is a cross-sectional view showing the structure of a solid electrolytic capacitor according to an embodiment of the present invention. In this figure, 1 is an anode, 2 is an anode lead-out wire embedded in the anode and composed of a tantalum wire, and 3 is a The dielectric oxidation protection film layer formed on the outer surface of the above-mentioned anode 1, 4 is the solid electrolyte layer formed on the dielectric oxidation protection film layer 3, 5 and 6 are the carbon formed on the solid electrolyte layer 4 layer and the silver paste layer, the cathode is formed by the carbon layer 5 and the silver paste layer 6, and these are the same structure as the solid electrolytic capacitor in the prior art described in the background of the present invention.

Next, a method of manufacturing the thus-constructed solid electrolytic capacitor according to the present invention will be described with reference to FIG. 1 .

First, in the forming process, a desired shape is formed in a state where an anode lead-out wire 2 composed of a tantalum wire is buried while filling a press-forming metal mold with tantalum powder having a valve metal effect.

Then, the anode 1 thus formed is sintered in a high vacuum atmosphere.

Subsequently, the anode 1 is anodized to form a dielectric oxidation protective film layer 3 on the outer surface of the anode 1 by applying an electrolytic voltage in balance with a desired capacitance in an electrolytic solution composed of an aqueous phosphoric acid solution. And, the electrolytic voltage value is determined from the capacitance of the solid electrolytic capacitor and the like.

Next, in this anodizing process, the above-mentioned anode 1 is taken out from the electrolytic solution, and residual phosphoric acid is washed away with warm water, and then heat-treated in a heat-treating furnace.

Then, the anode 1 after the heat treatment is returned to the electrolyte solution again, and the voltage is applied again to form a dielectric oxidation protective film layer 3 on the outer surface of the anode 1 by anodic oxidation.

A solid electrolyte layer 4 composed of a conductive polymer (or manganese dioxide) is formed on the dielectric oxidation protective film layer 3 by electrolytic polymerization (or chemical polymerization).

Then, a cathode layer is formed by disposing a carbon layer 5 and a silver pasting layer 6 on the solid electrolyte layer 4, and the solid electrolytic capacitor of the present invention is produced.

(Example 1)

In the above-mentioned anodizing process, the timing of taking out the anode 1 from the electrolytic solution is determined as each of 1/4, 2/4, 3/4, and 4/4 of the time required for anodizing (basically 120 minutes). At regular intervals, the anode 1 taken out was subjected to heat treatment for 10 minutes, 30 minutes, 60 minutes, and 90 minutes in an air atmosphere at 300° C., respectively.

The thus manufactured anode 1 of Example 1 and a conventional product as a comparison were examined in a liquid, and the results of measuring the relationship between the timing of the heat treatment and the leakage current within the electrolytic voltage holding time are shown in FIG. 3 , shows the results of measuring the relationship between the timing of the heat treatment and the withstand voltage of the dielectric oxide protection film within the A electrolytic voltage holding time.

In addition, the test conditions were 10 vol (capacity) % phosphoric acid aqueous solution, the temperature was 25° C., and the applied voltage was 70% of the electrolysis voltage. In addition, the concentration of the dielectric oxidation protective film layer 3 was 15 vol % ammonium adipate aqueous solution, and the applied current was 100 μA/element, and the conventional product was taken as 100 for comparison.

(Example 2)

In the above-mentioned Example 1, except that the heat treatment temperature was determined to be 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, and 550°C, the same inspection as in Example 1 was carried out. , the results of measuring the timing of heat treatment within the electrolytic voltage holding time and the relationship between the leakage current are shown in Figure 5, and the results of measuring the timing of heat treatment within the electrolytic voltage holding time and the dielectric oxidation protection The result of the relationship between the pressure resistance of the membrane.

(Example 3)

In the above-mentioned Example 2, except that the heat treatment atmosphere is respectively set as air, 30% H ₂ O (humidity), 85% H ₂ O, vacuum, N ₂ , Ar, the same procedure as in Example 2 is carried out. Check, Figure 7 shows the results of measuring the relationship between the timing of heat treatment within the electrolytic voltage holding time and the leakage current, and Figure 8 shows the relationship between the timing of heat treatment within the electrolytic voltage holding time and the dielectric oxidation The result of the relationship between the pressure resistance of the protective film.

As reflected in the results of Examples 1-3 above, in the anodizing process, after the anode 1 is temporarily taken out from the electrolyte and subjected to heat treatment, by returning the anode 1 to the electrolyte to perform anodization again, the anode 1 can be There is obtained the effect of reducing the amount of carbon that has a bad influence on the leakage current, thereby reducing the leakage current.

And, the defect portion existing in the dielectric oxide protective film layer 3 is destroyed by heat treatment into a larger defect portion, and by re-anodizing after the heat treatment, a new defect portion is formed again in the above-mentioned greatly destroyed defect portion. The dielectric oxidation protection film layer 3 can form a relatively uniform and finer dielectric oxidation protection film layer 3 . Thereby, the effects of reducing the leakage current and improving the electrical and physical strength of the dielectric oxidation protection film layer 3 can be obtained.

Also, as shown in Figures 3 and 4, the electrolytic treatment in front is preferably that the anode 1 is taken out at 1/4 of the first half of the electrolytic voltage holding time. When taken out at this time, the rate of change of leakage current and the rate of change of withstand voltage of the protective film can obtain the best effect. However, it is best to range from about 1/4 of the time in the first half to about 15 minutes before and after (about 1/8 of the whole). In addition, as the heat treatment conditions of the present invention, as shown in Figs. 5 and 6, it is best to carry out at a temperature of 200°C to 400°C, and the optimum heat treatment temperature is around 300°C. In particular, as shown in FIGS. 7 and 8, as the conditions of the atmosphere of the heat treatment, it is preferable to use a humidity of 85% or more or an active or inert gas atmosphere or a vacuum. The heating time is preferably not less than 20 minutes and not more than 40 minutes. This is because, in the case of excessive heat treatment, the dielectric oxide protection film layer 3 is excessively damaged, making it difficult to form the dielectric oxide protection film layer 3 by re-anodizing after heat treatment.

Although the present embodiment has described the use of an electrolytic solution for anodic oxidation and an aqueous phosphoric acid solution as an example in the electrolysis process, the present invention is not limited thereto, and inorganic acids such as phosphoric acid, nitric acid, sulfuric acid, and aqueous solutions can also be used or Salts thereof, organic acids such as tartaric acid, adipic acid, oxalic acid, citric acid, succinic acid, and formic acid, or salts thereof, can obtain the same effect.

Moreover, in the electrolysis process, after the anode is temporarily taken out from the electrolyte solution and heat-treated, the anode is returned to the electrolyte solution again, and the heat treatment process of anodic oxidation is carried out several times. At this time, by using different electrolyte solutions (preferably Using the same), the effect of the present invention can be increased.

In the above-mentioned anodic oxidation process of the present invention, after the anode is temporarily taken out from the electrolyte for heat treatment, the anode is returned to the electrolyte again, and the anodic oxidation heat treatment process is performed more than once, so that the defective part in the dielectric oxidation protection film can be formed And a uniform dielectric oxidation protection film with less impurities. As a result, the leakage current can be reduced, the withstand voltage of the dielectric oxidation protective film layer can be increased, and a solid electrolytic capacitor with relatively high performance and high reliability can be provided.

Claims (9)

1. the manufacture method of a solid electrolytic capacitor; At least have these steps: use the extrusion forming mould valve metal powder to be made the forming step of desirable shape; Its sintering is made the sintering step of anode; By in anolyte, this anode being carried out anodic oxidation; Form the electrolysis step of dielectric substance oxidation protection rete in anode outer surface; Form the dielectric substrate step of solid electrolyte layer at this dielectric substance oxidation protection rete; The cathode layer that forms cathode layer at this dielectric substrate forms step; Wherein

In above-mentioned anode oxidation process, will temporarily from anolyte, pull anode out and do after the heat treatment, this anode is turned back to once again carry out anodised heat treatment process in the anolyte and carry out at least 1 time.

2. the manufacture method of solid electrolytic capacitor as claimed in claim 1 makes the timing that the taking-up anode is heat-treated from anolyte carry out at the first half of anodic oxidation with voltage hold-time.

3. the manufacture method of solid electrolytic capacitor as claimed in claim 1 is carried out 20-60 minute heat treatment to the anode that takes out under 200-400 degree temperature conditions from anolyte.

4. the manufacture method of solid electrolytic capacitor as claimed in claim 1, the anode that will take out from anolyte is heat-treated in many humid atmosphere.

5. the manufacture method of solid electrolytic capacitor as claimed in claim 1, the anode that will take out from anolyte is heat-treated in activity and inert gas atmosphere.

6. the manufacture method of solid electrolytic capacitor as claimed in claim 1, the anode that will take out from anolyte is heat-treated in vacuum atmosphere.

7. the manufacture method of solid electrolytic capacitor as claimed in claim 1 is first with its wash clean before the anode that will take out from anolyte is heat-treated.

8. the manufacture method of solid electrolytic capacitor as claimed in claim 1, employed anolyte can use more than in inorganic acid, organic acid, the molten salt any one in electrolytic process.

9. the manufacture method of solid electrolytic capacitor as claimed in claim 1, the electrolyte that the anodic oxidation of the electrolytic process that uses before and after heat treatment process is used is identical or different.

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