JP3100411B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

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 an NQ complex.

[0002]

2. Description of the Related Art A conventional solid electrolytic capacitor in which a solid electrolyte is interposed between an anode body electrode made of a valve action metal having an anodic oxide film on its surface and a cathode electrode formed to face the electrode is known. Manganese dioxide has been used.

However, in this method, when manganese dioxide is formed on the electrode, since the anode body electrode is generally immersed in a manganese nitrate solution and then thermally decomposed, the anodic oxide film is damaged. There is a drawback that the anodic oxide film is poorly repaired by manganese dioxide.

As a method for compensating for these disadvantages, a solid electrolytic capacitor using an organic semiconductor such as a TCNQ complex as a solid electrolyte has appeared. As a typical example of this impregnation method, as described in JP-A-57-173928, an organic semiconductor containing a TCNQ complex is liquefied by heating and melting, and the element is put into the device until decomposition, followed by rapid solidification. (Hereinafter referred to as a melt impregnation method).

[0005] However, according to this method, the TCNQ complex used has a melting point and a decomposition point, and impregnation becomes poor unless the temperature interval is to some extent. In addition, in this impregnation method, it is difficult to impregnate while controlling completely below the decomposition point, and at these temperatures the complex is decomposed due to the large amount of heat applied. Therefore, the ratio of defective products is large. The decomposition point of the TCNQ complex is TCNQ
The sublimation temperature is around 290 ° C., and in order to widen the temperature range from the melting point to the decomposition point, the melting temperature must be lowered.

On the other hand, solid electrolytic capacitors are required to have heat resistance. Particularly, chip products must be electrolytes that can withstand the temperature of solder dip and reflow during surface mounting. TCN suitable for
It is quite difficult for a Q complex to withstand the above heat resistance. That is, the TCNQ complex having excellent heat resistance has a high melting point and a small temperature difference from the decomposition point, so that the impregnation becomes extremely poor. Conversely, if the impregnation property is to be improved, the melting point will be lower, and the heat resistance will be extremely poor.

[0007]

SUMMARY OF THE INVENTION The present invention is to solve the above problems. That is, the heat-resistant complex had a high melting point and a sufficient difference from the decomposition point, so that impregnation was impossible, but once the complex once entered the etching hole was heated and reprocessed, it was made possible by the present invention. Electrode surface and TCNQ
This is to improve the bonding property of the complex and improve the tan δ of the capacitor.

[0008]

As a specific method of the present invention, an etching process is performed to increase the surface area, and an anode electrode made of a valve action metal having an anodic oxide film on the surface is used to convert the TCNQ complex into a chloride. Halogen-based organic solvents such as methylene and chloroform, alcohol-based organic solvents such as methanol and ethanol, organic solvents containing oxygen and nitrogen such as acetone and acetonitrile, and solvents in which the TCNQ complex is dissolved without decomposition Is sprayed onto the above-mentioned electrode heated from 100 ° C. to the decomposition point of the TCNQ complex or lower,
This implies that the TCNQ complex is impregnated by flowing down or dripping, and then heat treatment is further performed to rearrange the crystals of the TCNQ complex impregnated inside the etching pits to improve the bonding property with the anodic oxide film.

The basic gist of the present invention is that the TCNQ complex solution adheres to the anodic oxide film and the solvent evaporates and evaporates at the same time. The conductivity of the electrode is improved by increasing the density of the TCNQ complex, and at the same time, the electrode surface of the aluminum electrolytic capacitor and the inside of the etching hole that has been subjected to extremely fine etching treatment such as Al-Zr alloy foil are impregnated. It became possible to be. In addition, when the temperature is close to the boiling point of the solvent, the solvent affects the oxide film because the impregnation rate varies depending on the solvent (solvent treatment).
This increases the impregnation rate. Similarly, the same effect is observed for electrodes sintered like a tantalum electrolytic capacitor. In addition, since the crystal growth of the complex is suppressed as much as possible in the bonding with the anodic oxide film, the starting point of the precipitation of the TCNQ complex is increased, and the area bonded to the anodic oxide film is dramatically increased, and the impregnation rate is increased. This results in a reduction in resistance. However, when further attempts were made to improve the bonding with the anodized film, after the completion of the impregnation, a heat treatment was performed at a temperature not lower than the heating temperature during the impregnation and not higher than the decomposition point of the complex, and the crystal of the complex in the etching pit was removed. When rearranged, tan δ of the capacitor characteristics was further improved.

As described above, the point of the present invention is that T
By rapidly evaporating and evaporating the solvent of the CNQ complex solution, it is possible to perform TCNQ while performing solvent treatment on the aluminum oxide film.
The complex is precipitated in a fine state, and the TCNQ complex impregnated inside the etching pit is further heat-treated to impregnate the TCNQ complex.
By rearranging the crystals of the CNQ complex, the bonding strength between the dielectric film and the complex is increased to improve the tan δ of the product and the high-frequency characteristics. The effect of the heat treatment of the TCNQ complex impregnated inside the etching pit is improved when the complex is treated at a temperature equal to or higher than the melting point of the complex. It should be noted that good results are naturally obtained also in the case where the solvent used during the impregnation is rapidly evaporated and vaporized in a reduced-pressure atmosphere. The pressure reduction is preferably in the range of 1/3 atmosphere to 1 atmosphere.

As a result of investigations using various solvents, the present inventors have found that the heating temperature of the electrode is good between 100 ° C. and the decomposition point of the complex. If the temperature is lower than 100 ° C., the evaporation of the solvent becomes non-uniform, and the evaporation of the solvent is slowed, and the growth of the crystal proceeds, resulting in a decrease in the impregnation rate.

After completion of the impregnation, the effect of inducing the rearrangement of the impregnated complex and improving the bonding with the dielectric film is recognized from the temperature at the time of the impregnation, and the effect is observed up to the decomposition point of the complex. There was. Some of the TCNQ complexes naturally have a melting point and liquefy when the melting point or higher is reached. In this case, the impregnation state is such that the complex already impregnated in the etching pits is liquefied and reprecipitated. This is essentially different from the melt impregnation method conventionally used.

[0013]

Embodiment 1 Hereinafter, a specific embodiment of the present invention will be described. 90μm high-purity aluminum foil (purity 99.99%)
Was subjected to electrolytic etching with an alternating current, and then subjected to 20 V chemical conversion with a neutral phosphoric acid solution to form a dielectric film. (Electrode A)

The above-mentioned electrode foil was placed on a hot plate heated to 190 ° C., and a solution in which the isoamylisoquinoline TCNQ complex was saturated and dissolved in chloroform was mist for 150 seconds. Thereafter, the electrode foil was inverted and the same treatment was performed on the opposite surface, and this series of operations was repeated five times to complete the impregnation. Next, it was kept in an infrared reflecting furnace heated to 240 ° C. for 20 seconds, and heat treatment after impregnation was performed. After that, a colloidal carbon is applied and formed, and the cathode lead is taken out with silver paste, and is covered with an epoxy resin.
Was manufactured. For comparison, characteristics were also investigated for those not subjected to heat treatment after impregnation and those produced by the conventional melting and impregnation method. Table 1 shows the results.

[0015]

[Table 1]

[0016]

Example 2 An Al90Zr10 alloy foil having a thickness of 40 μm was prepared by a super-quenching method, and a 99.99% aluminum foil having a thickness of 70 μm was used as a core material to prepare a three-layer clad electrode foil. After electrolytically etching this electrode foil, the neutralized phosphoric acid solution is applied to 20 V
Chemical conversion was performed to form a dielectric film. (Electrode B)

The above-mentioned electrode foil was placed on a hot plate heated to 200 ° C., and a solution of diphenyloctylphenanthroline TCNQ complex saturated in methylene chloride was dissolved in
Made rage for 00 seconds. Thereafter, the electrode foil was inverted and the same treatment was performed on the opposite surface, and this series of operations was repeated five times to complete the impregnation. Next, it was kept in an infrared reflecting furnace heated to 250 ° C. for 20 seconds to perform a heat treatment. Thereafter, colloidal carbon is applied and formed, and further, a cathode paste is applied with silver paste.
Take out the package and cover it with epoxy resin, rated 10V100
A μF solid electrolytic capacitor was produced. For comparison,
The characteristics were also investigated for those not subjected to the heat treatment after the impregnation and those produced by the conventional melt impregnation method. Table 2 shows the results.

[0018]

[Table 2]

[0019]

As shown in Examples 1 and 2, the solid electrolytic capacitor impregnated with the TCNQ complex by the method of the present invention has improved tan δ and improved impregnation. It also shows electrical properties that may be compared to conventional melt impregnation methods. Also, the impregnation process is very simple, and the impregnation time and man-hour can be greatly reduced and the production cost can be significantly reduced as compared with the impregnation process of a conductive polymer represented by polypyrrole. It has a low industrial and practical value.

Claims (3)

(57) [Claims] An etching process is performed on the surface to increase the surface area, and a TCNQ complex dissolved in a solvent is sprayed onto the electrode while heating an anode electrode made of a valve action metal having an anodic oxide film on the surface. A method for producing a solid electrolytic capacitor, comprising performing an impregnation process while spraying, flowing down or dripping, and further subjecting the TCNQ complex impregnated in the etching pit to a heat treatment. 2. The heating temperature of the anode electrode during the impregnation is as follows:
2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the temperature is from 100 ° C. to a temperature not higher than the decomposition point of the TCNQ complex. 3. The method for producing a solid electrolytic capacitor according to claim 1, wherein the heating temperature after the completion of the impregnation is a temperature not lower than the heating temperature during the impregnation and not higher than the decomposition point of the complex.