JPH1050560A - Solid state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress electrode foils and org. semiconductor layers from peeling for obtaining high reliability by setting the liq. measured capacitance value of a capacitor element to a specified value below a rated capacitance value. SOLUTION: A craft paper spacer is inserted between an anode foil and cathode foil, cathode and anode lead terminals are attached to desired points of both foils and the foils are rolled to form a capacitor element. TCNQ complex is impregnated in this element and cooled to harden. Epoxy resin is poured into an opening of an Al case, hardened to real the opening and aged to obtain a solid state electrolytic capacitor covered with an armor sleeve, wherein the electrode foil etching condition and forming condition are controlled to use electrode foils having a liq. measured capacitance of less than 1.3 times the rated capacitance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid electrolytic capacitor using an organic semiconductor as a solid electrolyte.

[0002]

2. Description of the Related Art In recent years, with the advancement of electronic information equipment, miniaturization and high performance of electronic parts have been demanded, and even an electrolytic capacitor impregnated with a conventional driving electrolytic solution has been required. 2. Description of the Related Art Solid electrolytic capacitors using an organic semiconductor made of a TCNQ complex that can be smaller in size as a solid electrolyte have been put to practical use.

Conventionally, a solid electrolytic capacitor using an organic semiconductor made of a TCNQ complex as a solid electrolyte has a valve-acting metal foil such as aluminum, tantalum or niobium surface roughened with an etchant to increase the surface area and then anodized film. Produced anode foil, the same valve action metal foil surface roughened with an etching solution in the same manner as described above to produce a cathode foil having an increased surface area, kraft paper or cathode paper between these anode foil and cathode foil A capacitor element is formed by winding a state in which an anode lead terminal and a cathode lead terminal are attached to arbitrary portions of the anode foil and the cathode foil with a spacer made of manila paper or the like interposed therebetween.

[0004] An organic semiconductor comprising a TCNQ complex is placed in a metal case, and when the organic semiconductor is heated to a molten state, the capacitor element in a preheated state is inserted to insert the organic semiconductor into the capacitor element. It was impregnated, then cooled and solidified, and the metal case opening was sealed with a sealing resin made of epoxy resin or the like.

In the solid electrolytic capacitor having the above structure, the TCNQ complex as an organic semiconductor used as a solid electrolyte has a conductivity of about 10 S / cm and an electrolytic solution (0.01 S / cm) used in a conventional electrolytic capacitor. cm), and the use of this TCNQ complex as a solid electrolyte has attracted attention because of its excellent characteristics such as impedance frequency characteristics, leakage current characteristics, and temperature characteristics.

However, the solid electrolytic capacitor having the above-described structure usually has a smaller capacitance value after impregnation with an organic semiconductor than the capacitance value originally possessed by the capacitor. This means that the organic semiconductor did not sufficiently enter the inside of the etching pit of the electrolytic foil, and the ratio of the capacitor capacity after solidification to the original capacitor capacity (hereinafter referred to as the capacity appearance rate) is usually 65%. It is about. This indicates that the adhesion strength of the organic semiconductor to the electrode foil is low, and they are easily peeled off during thermal shock or high temperature, causing a decrease in capacitance, and lacking reliability. Had become.

[0007]

As described above, in the solid electrolytic capacitor using the organic semiconductor comprising the TCNQ complex having the above structure, the organic semiconductor does not sufficiently penetrate into the etching pits of the electrode foil. On the other hand, since the adhesion strength between the electrode foil and the organic semiconductor layer is small, the two are peeled off, the capacitor characteristics deteriorate with time, and the reliability is lacking.

The present invention has been made to solve the above problems, and has as its object to provide a highly reliable solid electrolytic capacitor in which peeling of an electrode foil and an organic semiconductor layer is suppressed. It is.

[0009]

According to the present invention, there is provided a solid electrolytic capacitor comprising a capacitor element wound between a positive electrode foil made of a valve action metal and a negative electrode foil with a lead terminal attached at an arbitrary position via a spacer. A metal case for housing the capacitor element, an organic semiconductor melted and liquefied in the metal case and impregnated in the capacitor element, and a solid electrolytic capacitor comprising a sealing resin for sealing the opening of the metal case. Is set to be 1.3 times or less of the rated capacitance value.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. That is, after the aluminum foil is roughened with an etchant to increase the surface area, a dielectric oxide film is formed to obtain an anode foil. Similarly, the aluminum foil is roughened with an etchant to increase the surface area to obtain a cathode foil. Was. A spacer made of kraft paper was interposed between the anode foil and the cathode foil, and an anode extraction terminal and a cathode extraction terminal were attached to arbitrary portions of the anode foil and the cathode foil, respectively, and wound to form a capacitor element. . The capacitor element is reformed using an aqueous solution of ammonium adipate to repair the damage of the dielectric oxide film caused in the above-mentioned winding step, and then the capacitor element is heated and maintained in a preheated state. On the other hand, a predetermined amount of the TCNQ complex is put into an aluminum case and heated and melted. The capacitor element which is maintained in the preheated state is housed in the aluminum case and impregnated with the molten TCNQ complex, and then cooled and solidified. did. The remaining TCNQ complex melt that is not impregnated solidifies between the bottom surface of the capacitor element and the inner bottom surface of the aluminum case.

Next, at the opening of the aluminum case,
An epoxy resin was injected, cured, and sealed. Thereafter, an aging treatment was performed by applying a rated voltage between the anode terminal and the cathode terminal in a high-temperature atmosphere, and the outer sleeve was covered to complete a solid electrolytic capacitor.

In constructing the above solid electrolytic capacitor,
An electrode foil having a liquid measurement capacitance of 1.3 times or less of the rated capacitance is used by controlling the etching condition and the formation condition of the electrode foil.

According to the solid electrolytic capacitor having the above-described structure, the electrode foil having a liquid measuring capacitance of 1.3 times or less of the rated capacitance is controlled by controlling the etching condition and the formation condition of the electrode foil. Is used, the adhesion strength between the TCNQ complex and the electrode foil increases due to the TCNQ complex sufficiently filled inside the etching pit, and the TC
The phenomenon that the NQ complex peels off from the electrode foil can be suppressed, and as a result, a highly reliable capacitor can be provided.

Next, the reason why the liquid measurement capacitance is set to be 1.3 times or less of the rated capacitance in the above configuration will be described.

In the solid electrolytic capacitor having the above-described configuration, the capacitance measured by the liquid is 1.7 times the rated capacitance.
A capacitor element was manufactured using the anode foil and the cathode foil set to 5 times and 1.3 times, and the decrease in capacity when left in a 105 ° C. high temperature atmosphere was investigated. As a result, as shown in FIG. 1, when the liquid measurement capacitance is set to 1.7 times and 1.5 times the rated capacitance, the capacitance decreases greatly.
In the case of 3 times, there was almost no change.

Next, a description will be given of a comparison of characteristics between the embodiment according to the present invention in which 100 capacitors each having a rated voltage of 10 V-220 μF are prototyped and the conventional examples A and B according to the prior art.

[0017]

EXAMPLE An aluminum foil was roughened with an etchant to increase its surface area, and then a chemical conversion treatment was performed to form a dielectric oxide film on the anode foil and the aluminum foil was roughened with an etchant to increase the surface area. A spacer made of kraft paper was interposed between the anode foil and the cathode foil, and an anode lead-out terminal and a cathode lead-out terminal were attached to arbitrary locations, respectively, and wound to form a capacitor element. The measured capacitance of this capacitor element is 1.3 times the rated capacitance, that is, 2 times.
86 μF.

A voltage was applied while the capacitor element was immersed in a chemical solution consisting of a 3% aqueous ammonium adipate solution, and the dielectric film damaged by winding was repaired.
On the other hand, the cylindrical aluminum case containing the TCNQ complex is placed on a flat heater heated to 310 ° C. to melt and liquefy the TCNQ complex. Next, the capacitor element preheated to 300 ° C. was accommodated in an aluminum case, and was impregnated with the TCNQ complex that had been liquefied. Immediately after impregnation, immerse the aluminum case in cooling water,
The NQ complex was cooled and solidified. Next, a required amount of epoxy resin was injected into the opening of the aluminum case and cured by heating in a high-temperature atmosphere. Then, aging was performed by applying a rated voltage between both electrode terminals for 1 hour in a 125 ° C. atmosphere.

[0019]

The conventional example is the same as the above-mentioned embodiment except that the liquid measurement capacitance of the capacitor element is 1.5 times as large as the rated capacitance in the conventional example A and 1.7 times in the conventional example B. Materials were prepared by means.

The samples prepared in the above manner and 100 samples of the conventional examples A and B were each placed at 105 ° C. for 200 hours.
When the average value and the variation of the capacitance decrease rate after leaving the apparatus unloaded for 0 hours were compared, the results shown in Table 1 were obtained.

[0021]

[Table 1]

As is clear from Table 1, the conventional example A has a large average value of the capacitance reduction rate and lacks reliability for long-term use, and the conventional example B has this tendency more remarkably. . This is due to the fact that the adhesion strength between the TCNQ complex and the electrode foil is low, and they are separated in a high-temperature atmosphere, so that the capacitance is greatly reduced.

On the other hand, in the case of the embodiment, since the etching pit of the electrode foil can be sufficiently filled with the TCNQ complex, the adhesion strength between the TCNQ complex and the electrode foil is greatly improved. The capacity appearance rate is about 1
We were able to raise it by about 0%. As a result, the phenomenon that these peeled off in a high-temperature atmosphere was reduced, so that the effect of obtaining a long-life and highly reliable solid electrolytic capacitor with a small capacitance reduction rate even in long-term use was demonstrated. .

[0024]

According to the present invention, by setting the liquid measuring capacitance of the capacitor element to 1.3 times or less of the rated capacitance, a high performance without deterioration of various characteristics even during long-term use is obtained. A solid electrolytic capacitor using a reliable organic semiconductor as a solid electrolyte can be obtained.

[Brief description of the drawings]

FIG. 1 is a curve diagram showing a decrease in capacitance when the capacitors according to the embodiment, the conventional example A, and the conventional example B are left at 125 ° C.

Claims (1)

[Claims] 1. A capacitor element wound via a spacer between an anode foil and a cathode foil made of a valve metal and having a lead terminal attached to an arbitrary position, a metal case for housing the capacitor element, and a metal case. In a solid electrolytic capacitor composed of an organic semiconductor that is melted and liquefied in the case and impregnated in the capacitor element and a sealing resin that seals the metal case opening, the measured capacitance value of the capacitor element is the rated capacitance value. The solid electrolytic capacitor is set to be 1.3 times or less of the following.