JP2730345B2 - Manufacturing method of 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 of manufacturing a capacitor having excellent performance and high reliability by using a conductive polymer film for at least one of electrodes facing each other via a dielectric film. Things.

[0002]

2. Description of the Related Art Recently, with the digitization of electrical equipment, the capacitors used therein have low impedance in the high frequency range, and there is an increasing demand for smaller and larger capacitors.

Conventionally, plastic film capacitors, mica capacitors, multilayer ceramic capacitors and the like have been used as high frequency capacitors. Other examples include an aluminum dry electrolytic capacitor and an aluminum or tantalum solid electrolytic capacitor.

In an aluminum dry electrolytic capacitor, an etched positive and negative electrode aluminum foil is wound through a paper separator, and a liquid electrolyte is used.

[0005] In the case of aluminum or tantalum solid electrolytic capacitors, the electrolyte is solidified to improve the characteristics of the aluminum electrolytic capacitors. The anode foil is immersed in a manganese nitrate solution at 350 ° C. to form this solid electrolyte.
Pyrolyze in high and low temperature furnaces to form a manganese dioxide layer. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as volatilization of the electrolyte at a high temperature and functional deterioration caused by solidification in a low temperature range, and the capacitor exhibits better frequency characteristics and temperature characteristics than a liquid electrolyte. Aluminum electrolytic capacitors, like tantalum electrolytic capacitors, can achieve a large capacity because an oxide film serving as a dielectric can be made very thin.

Further, in recent years, a solid electrolytic capacitor using an organic semiconductor such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) salt as a solid electrolyte (Japanese Patent Application Laid-Open No. 58-1983)
17609) has been developed. There is also a method in which a polymerizable monomer such as pyrrole, thiophene, or furan is electrolytically polymerized to form a conductive polymer, which is used for at least one of the electrodes of the capacitor.A polyimide thin film serving as a dielectric is formed on the electrode surface by an electrodeposition method. A capacitor formed by laminating a chemically polymerized conductive polymer film and further laminating an electrolytic polymerized conductive polymer film is disclosed in the 58th Annual Meeting of the Electrochemical Society of Japan in the spring of 1991 (collection of abstracts P2)
51 and P252).

[0007]

As described above, various types of capacitors are used. However, film capacitors and mica capacitors have large shapes because of their large shapes. However, it has disadvantages such as extremely high price and poor temperature characteristics.

In addition, since the aluminum electrolytic capacitor is easily damaged by the oxide film, it is necessary to repair the damage as needed by applying an electrolyte between the oxide film and the cathode. For this reason, those that use a liquid electrolyte as the electrolyte may cause a decrease in capacitance or an increase in loss over time due to electrolyte leakage or ionic conductivity, etc. It has disadvantages such as a large loss.

Next, the solid electrolyte will be described.
The loss in the high frequency range cannot be said to be sufficiently small because the oxide film is damaged by thermal decomposition several times at a high temperature and the specific resistance of manganese dioxide is high. Also, TCN
Solid electrolytic capacitors using organic semiconductors such as Q salt
It shows superior high-frequency characteristics compared to those using manganese dioxide, but exhibits ideal characteristics due to the increase in specific resistance when applying an organic semiconductor, weak adhesion to the anode foil, etc. I can't say. Further, when a conductive polymer thin film is used as an electrode of a capacitor, frequency characteristics, temperature characteristics, high-temperature life characteristics, and the like are excellent. However, since the dielectric film is easily attacked by moisture, it has a defect in the high-temperature constant-humidity life characteristic.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a manufacturing method for realizing a capacitor excellent in moisture resistance and heat resistance.

[0011]

SUMMARY OF THE INVENTION The present invention achieves the above object, and a method for producing the same comprises forming an electrode on which a dielectric film and a manganese oxide layer are sequentially formed in an aqueous solution of silicic acid or silicate. Then, electrolytic polymerization is performed, and an electrolytic polymerized conductive polymer film is laminated on the electrode surface to serve as a counter electrode.

[0012]

According to the present invention, as described above, the electrode on which the dielectric film and the manganese oxide layer are sequentially formed is immersed in an aqueous solution of silicic acid or silicate. Since a counter electrode is formed by laminating an electropolymerized conductive polymer film having excellent thermal stability on the surface of the capacitor, a capacitor having a small deterioration in characteristics even when left in a high-temperature constant humidity can be obtained.

[0013]

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

(Embodiment 1) As a first embodiment, the present invention is applied to an aluminum electrolytic capacitor.
This will be described with reference to the drawings.

A heat-resistant insulating tape 8 is applied to the surface of the valve metal 2 and divided into two regions. The small area is used as the anode lead mounting surface, and the large area (4 mm × 5 mm) is used as the dielectric film forming surface. did. The valve-acting metal foil 2 (aluminum-etched foil) is anodized using a 7% aqueous solution of ammonium adipate at about 70 ° C. for 40 minutes under an applied voltage of 42 V to form a dielectric film 3. And thermally decomposed at 300 ° C. for 20 minutes to form a conductive layer composed of the manganese oxide film 4.

Next, as shown in FIG. 1, the surface on which the dielectric film 3 and the manganese oxide film 4 were formed was immersed in an aqueous solution of sodium silicate 9 (0.01 mol / l, 25 ° C.) for 24 hours. Further, as shown in FIG. 2, pyrrole (0.25 mol /
l), a valve metal foil is immersed in an electrolytic polymerization solution 10 composed of triisopropylnaphthalene sulphonate (0.1 mol / l) and water, and the polymerization initiating electrode 7 is brought close to the manganese oxide film 4 so as to have a voltage of 2.5 V. A constant voltage is applied for 30 minutes to form a conductive polymer film 5 (polypyrrole film) for the counter electrode on the manganese oxide 4, and as shown in FIG.
1. A silver paint layer 12 was laminated, and an anode lead 1 and a cathode lead 6 were provided to obtain a capacitor. The number of samples is 10.

The characteristics of a capacitor obtained by laminating an electropolymerized conductive polymer film on an electrode treated with an aqueous solution of sodium silicate according to this embodiment are shown in Table 1. In addition, Table 1 shows the characteristics of a capacitor in which the electropolymerized conductive polymer film was laminated without performing the electrode treatment as Comparative Example 1.
As is clear from Table 1, the capacitor according to the present embodiment has significantly less deterioration of the characteristics left in a high-temperature and constant-humidity state for a long time compared to the initial characteristics, and can obtain an excellent effect as compared with Comparative Example 1.

As described above, according to the present embodiment, the hydration of the dielectric film is suppressed, and the electropolymerized conductive polymer film used for the electrode has excellent thermal stability. High performance capacitors can be realized.

In this embodiment, an electrolytic capacitor having a valve metal as an electrode and its anodic oxide film as a dielectric material has been described. However, in other types of capacitors, an electropolymerized conductive polymer is used as an electrode. Needless to say, it is included. In the embodiment, only the case where manganese oxide is formed using manganese nitrate has been described. However, the material is not limited to manganese nitrate, and any other material that can form manganese oxide can be used.

Example 2 The concentration of the aqueous solution of sodium silicate was adjusted to (a) 0.0005 mol / l and (b) 0.000
A capacitor was manufactured in the same manner as in Example 1 except that the amount was 1 mol / l and (c) 0.00005 mol / l. The number of samples is 10 each.

Table 1 shows the characteristics of the capacitor according to the present embodiment. As is clear from these (Table 1), the electropolymerized conductive polymer film was laminated on the electrode treated with the aqueous sodium silicate solution having a concentration of 0.0005 mol / l or 0.0001 mol / l according to the present example. In the capacitor made by the method, the deterioration of the characteristics left for a long time under high temperature and constant humidity was remarkably small compared to the initial characteristics, and excellent effects were obtained as in Example 1. However, when the concentration was 0.00005 mol / l, the deterioration of the characteristics was suppressed. It turns out that there is no effect, and it is judged that the concentration is desirably 0.0001 mol / l or more.

Example 3 0.05 m of sodium silicate
ol / l was stirred in water, and an insoluble content was removed by filtration. A capacitor was produced in the same manner as in (Example 1) except that a saturated sodium silicate aqueous solution was used. The number of samples is 10.

Table 1 shows the characteristics of the capacitor according to the present embodiment. As is clear from these (Table 1), the capacitor obtained by laminating the electropolymerized conductive polymer film on the electrode treated with the saturated sodium silicate aqueous solution according to the present example has a high temperature for a long time with respect to the initial characteristics. Deterioration of the characteristics left under constant humidity is extremely small, and excellent effects can be obtained as in Example 1.

Example 4 A capacitor was produced in the same manner as in Example 1 except that the immersion time of the electrode was changed to 48 hours. The number of samples is 10.

Table 1 shows the characteristics of the capacitor according to this embodiment. As is clear from these (Table 1), the capacitor obtained by laminating the electropolymerized conductive polymer film on the electrode treated with the aqueous solution of silicic acid according to the present embodiment has a long period of time under high temperature and humidity with respect to the initial characteristics. Deterioration of the characteristics left as it is is extremely small, and excellent effects can be obtained as in Example 1.

(Example 5) The electrode immersion time was set to (a) 1
Example 1 except that the minutes were (B) 3 minutes and (C) 5 minutes.
A capacitor was produced in the same manner as described above. 10 samples each
Individual.

Table 1 shows the characteristics of the capacitor according to the present embodiment. As is clear from these (Table 1), the capacitor obtained by laminating the electropolymerized conductive polymer film on the electrode treated with the aqueous solution of silicic acid for 5 minutes according to the present example has a high temperature and humidity for a long time with respect to the initial characteristics. The deterioration of the characteristics left undisturbed is extremely small, and excellent effects can be obtained as in Example 1. However, when the electrode treatment time is 1 minute and 3 minutes, the characteristic deterioration cannot be suppressed, and the immersion time is preferably 5 minutes or more. Is determined.

(Example 6) The temperature of the aqueous solution of sodium silicate was set to (a) 99 ° C and (b) 100 ° C, and the immersion time was set to 5 hours.
A capacitor was produced in the same manner as in Example 1 except that the above-mentioned steps were taken. The number of samples is 10 each.

Table 1 shows the characteristics of the capacitor according to the present embodiment. As is clear from these (Table 1), the capacitor obtained by laminating the electrolytic polymerized conductive polymer film on the electrode treated with the silicic acid aqueous solution at a temperature of 99 ° C. according to the present example has a longer initial characteristic. The deterioration of the characteristics left for a long time at a high temperature and a constant humidity is remarkably small, and excellent effects can be obtained as in Example 1. However, when the temperature is set to 100 ° C., the effect of suppressing the characteristic deterioration is reduced. Is determined to be desirable.

Example 7 A capacitor was manufactured in the same manner as in Example 1 except that the liquid temperature of the aqueous solution of sodium silicate was set at 1 ° C. and the immersion time was set at 24 hours. 1 sample
There are zero.

Table 1 shows the characteristics of the capacitor according to the present embodiment. In addition, when the liquid temperature of the aqueous solution of sodium silicate was set to 0 ° C., water solidified, and immersion treatment of the electrode was impossible. As is clear from these (Table 1),
The capacitor obtained by laminating the electropolymerized conductive polymer film on the electrode treated with the temperature of the aqueous solution of silicic acid at 1 ° C. according to the present embodiment has a longer initial characteristic compared to Comparative Example 1 in which no electrode treatment is performed. The deterioration of the characteristics left for a long time at a high temperature and a constant humidity is extremely small, and excellent effects can be obtained as in the first embodiment.

EXAMPLE 8 0.01 mol / l of silicic acid
A capacitor was manufactured in the same manner as in Example 1 except that a dissolved aqueous solution was used. The number of samples is 10.

Table 1 shows the characteristics of the capacitor according to this embodiment. As is clear from these (Table 1), the capacitor obtained by laminating the electropolymerized conductive polymer film on the electrode treated with the aqueous solution of silicic acid according to the present example is compared with Comparative Example 1 in which no electrode treatment is performed. In addition, the deterioration of the characteristics left for a long time under a high temperature and constant humidity with respect to the initial characteristics is extremely small, and excellent effects can be obtained as in Example 1.

[0034]

[Table 1]

[0035]

As described above, the present invention resides in a method for manufacturing a capacitor in which an electrolytically polymerized conductive polymer film is laminated on an electrode immersed in an aqueous solution of silicic acid or silicate and used as a counter electrode. This makes it possible to produce an excellent capacitor with less deterioration in characteristics even when left under moisture for a long time.

[Brief description of the drawings]

FIG. 1 is a process diagram of a method of manufacturing a capacitor according to an embodiment of the present invention, in which an electrode on which a dielectric film and a manganese oxide film are formed is immersed in an aqueous solution of silicic acid or silicate.

FIG. 2 is a process chart of forming an electropolymerized conductive polymer film on the electrode after the surface treatment, which is one step of the method of manufacturing the capacitor in the embodiment.

FIG. 3 is a cross-sectional view of the capacitor manufactured by the method for manufacturing a capacitor according to the embodiment.

FIG. 4 is a plan view of a capacitor manufactured by the method for manufacturing a capacitor according to the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 anode lead 2 valve metal 3 dielectric film 4 manganese oxide film 5 electropolymerized conductive polymer film 6 cathode lead 7 polymerization initiation electrode 8 heat-resistant insulating tape 9 aqueous solution of silicic acid or silicate 10 polymerization solution 11 carbon Paint film 12 Silver paint film

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tomonari Nanai 3-1-1, Higashi-Mita, Tama-ku, Kawasaki-shi, Kanagawa Prefecture Matsushita Giken Co., Ltd. JP-A-5-234822 (JP, A) JP-A-5-234821 (JP, A) JP-A-5-234820 (JP, A)

Claims (5)

(57) [Claims] An electrode on which a dielectric film and a manganese oxide layer are sequentially formed is immersed in an aqueous solution of silicic acid or silicate, and then subjected to electrolytic polymerization. A method for manufacturing a capacitor, comprising stacking molecular films to form a counter electrode. 2. The method according to claim 1, wherein the concentration of the aqueous solution of silicic acid or silicate is 0.0001 mol / l or more,
The method for producing a capacitor according to claim 1, wherein the immersion treatment time is 5 minutes or more. 3. The method according to claim 1, wherein the electrode on which the dielectric film and the manganese oxide layer are sequentially formed is a valve metal. 4. The method according to claim 3, wherein the valve metal is one selected from aluminum and tantalum. 5. The electropolymerized conductive polymer film comprises pyrrole,
5. The method for producing a capacitor according to claim 1, wherein the capacitor is formed in a solution containing at least one of thiophene or a derivative thereof and a supporting electrolyte.