JPS61240625A - Solid electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a solid electrolytic capacitor having a solid electrolyte.

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 a growing demand for smaller capacitors with larger capacitance. Conventionally, plastic film capacitors, mica capacitors, multilayer ceramic capacitors, and the like have been used as capacitors for high frequency regions. In addition, there are aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors! be. aluminum dry type i
In a T-solution capacitor, etched anode and cathode aluminum foils are wound up with a paper separator in between, and a liquid electrolyte is used. Further, in aluminum or tantalum solid electrolytic capacitors, the electrolyte is solidified in order to improve the characteristics of the aluminum electrolytic capacitor. To form this solid electrolyte, the anode foil is immersed in a manganese nitrate solution, and
It is thermally decomposed in a high-temperature furnace at around 50°C to create a manganese dioxide layer. In the case of this capacitor, since the electrolyte is solid, there are no drawbacks such as electrolyte leakage at high temperatures or functional deterioration caused by coagulation at low temperatures. Aluminum electrolytic capacitors exhibit better frequency and temperature characteristics than liquid electrolytes, and, like tank lumen decomposition capacitors, the oxide film that serves as the dielectric can be made very thin, making it possible to achieve large capacitance.

Problems to be Solved by the Invention However, although a variety of capacitors are used in this way, film capacitors and Himica capacitors have a large shape, making it difficult to increase the capacity. , which was born from the demand for small size and large capacity, has drawbacks such as extremely high price and poor temperature characteristics. Since the oxide film of aluminum electrolytic capacitors is easily damaged, it is necessary to apply an electrolyte between the oxide film and the cathode to repair the damage as needed. For this reason, products that use a liquid electrolyte tend to suffer from a decrease in capacitance and an increase in loss over time due to electrolyte leakage and ionic conductivity, and due to high frequency characteristics and low temperature range. It has disadvantages such as high loss. Furthermore, even with solid electrolytes, the loss in the high frequency range cannot be said to be sufficiently small due to damage to the oxide film caused by thermal decomposition several times at high temperatures and the high resistivity of manganese dioxide.

Furthermore, solid electrolytic capacitors using organic semiconductors such as TCNQ salt exhibit superior high-frequency characteristics compared to those using manganese dioxide, but the resistivity increases when the organic semiconductor is applied and the anode foil It cannot be said that it exhibits ideal characteristics because of its weak adhesive properties.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks and provide a solid electrolytic capacitor that is small and has good high frequency characteristics.

・Means for solving the problem The present invention achieves the above object, and its basic structure is as follows:
It has a conductive polymer obtained by electrolytic polymerization between the electrodes as a solid electrolyte.

Function: As described above, the present invention uses a conductive polymer obtained by electrolytic polymerization to adhere to an electrode as a solid electrolyte, thereby solving the problems of conventional capacitors such as deterioration of characteristics in the high frequency range and increase in capacity. The shortcomings of can be improved.

6...-.

Polypyrrole or polyfuran is suitable as the conductive polymer used in the solid electrolytic capacitor disclosed in the present invention. Electrolytic polymerization is performed as a method for synthesizing the conductive polymer used as the solid electrolyte of the solid electrolytic capacitor, and in the present invention, electrolytic polymerization in an aqueous solution is preferable. In order to dissolve conductive polymer monomers (pyrrole C4H4NH, furan C4H40) in a solvent (H2O), an organic acid (such as adipic acid) with lipophilicity and hydrophilicity is used as a supporting electrolyte. The anode of the capacitor was immersed in the above aqueous solution, and the voltage was 0.1 mA/ci to 10 mA/614.
When the constant current is continued to flow for about 10 to 60 minutes, a film obtained by electrolytic polymerization is formed on the anode. Furthermore, it has been found that when the anode to which this polymer film is attached is chemically formed in an aqueous boric acid solution, an anodic oxide film is formed under the polymer film. In this case, anodic oxidation may be carried out before or after the conductive polymer is attached, but it is more desirable to chemically form the anodic oxide film afterwards.

Example Examples are shown below.

[Example 1] Polymerizable monomer (pyrrole C4H4NH) 1M/l.

7 Dipic acid (HOOC(CH)4COOH)o, 1M/
g.

An aluminum foil whose surface has been etched is immersed in an aqueous solution of 11 solvents (H2O), and a current of 1 mA/C/! is applied to the anode area.
A current was applied for 30 minutes. At this time, the temperature of the aqueous solution is room temperature. Next, the anode and cathode foils of the winding unit that have undergone the electrolytic polymerization are immersed in an aqueous solution of water 11 and 30 g of adipic acid, and the voltage is increased to 10 oV with a constant current of 1 mA/ffl, and then at 100 V for 30 minutes to 60 minutes. Current 1μA/f per minute
Tighten below fl.

Note that the temperature of the aqueous solution at this time was 70°C. It was possible to conduct the reaction in exactly the same manner as in the case where the adipic acid aqueous solution was used or the electrolytically polymerized film was not present.

Furthermore, a counter electrode lead was taken out from this anode foil using Aquada Fugu and silver paste, and it was covered with epoxy resin to complete a capacitor element.

The resulting content exhibited a capacitance of 3.6 μF at 120 Hz and a loss of 1.0%. The liquid capacitance of the anode foil chemically formed under the same conditions was 3.7 μF, so 95
% capacity achievement rate. Moreover, the impedance at 1 MHz was 0.080. Furthermore, when o, 2M/l oxalic acid is used as the supporting electrolyte for virol electrolytic polymerization, the loss of the obtained capacitor is 0.6%.
and decreased, indicating an improvement.

[Example 2] Using furan (C4H40) as a polymerizable monomer,
A polymeric film with a thickness of 15 microns was formed on the aluminum surface using an oxalic acid aqueous solution (1M/l).

Next, in a boric acid aqueous solution (o, 1M/#), 1 mA/
The voltage was increased to 150 V with a constant current of 7.c and 7. The voltage of 160 .mu. was further maintained for 1 hour with a switch such that the current was 0.1 μA/CrI. Leads were attached and an exterior was applied in the same manner as in Example 1, a prototype capacitor was produced, and its initial characteristics were measured.

Capacitance at 120Hz is 3.1μF, loss is 1.5%
and the impedance at IMHz is 0.10
Met. Further, as a result of carrying out a load test at 85°C for 1 o○○ hours, the capacity decreased by 2% and the loss was 1.8%.

Effects of the Invention As described above, the present invention uses a conductive polymer obtained by electrolytic polymerization as the electrolyte of an electrolytic capacitor, which increases the initial capacity and significantly reduces the change in capacity over time, making it comparable to a liquid electrolyte. In comparison, tan δ, high frequency impedance, and L(4) are smaller.Furthermore, changes in various characteristics such as capacitance due to temperature changes are also reduced, and the effect is large.

Claims (3)

[Claims] (1) A solid electrolytic capacitor having a conductive polymer obtained by electrolytic polymerization as a solid electrolyte. (2) The solid electrolytic capacitor according to claim 1, wherein the conductive polymer is polypyrrole or polyfuran. (3) The solid electrolytic capacitor according to claim 1, wherein an organic acid such as oxalic acid or adipic acid is used as a supporting electrolyte when a conductive polymer is electrolytically polymerized and attached to the anode.