JPH05326345A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent a crack of an anodized film due to contraction stress of organic semiconductor when molten semiconductor is cooled and solidified and to improve leakage current characteristics by improving the anode foil structure. CONSTITUTION:A lateral end face of an anode foil 3 disposed on an end face of a solid electrolytic capacitor element 8 of a solid electrolytic capacitor in which organic semiconductor is used as solid electrolyte is coated with an UV curable resin thin film 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor having an improved anode foil end face structure which constitutes a capacitor element.

[0002]

2. Description of the Related Art Generally, a dry foil type electrolytic capacitor has, for example, a pair of positive and negative electrode foils made of high-purity aluminum foil and a pair of lead terminals also made of aluminum.
A capacitor element formed by winding a spacer between a pair of positive and negative electrode foils is impregnated with a driving electrolytic solution and housed in a case, and the case opening is sealed with a sealing body.

The driving electrolytic solution uses an organic carboxylate such as ammonium adipate as an organic solvent such as ethylene glycol.
There is a limit to the improvement of δ characteristics, and there is a problem to be solved in order to satisfy the market requirements such as low specific resistance at low temperature and extremely low temperature characteristics, and lack of reliability for use in a wide temperature range. Was there.

Therefore, in recent years, the TCN has been replaced with the driving electrolyte solution.
Various solid electrolytic capacitors using an organic semiconductor composed of a Q complex as a solid electrolyte have been proposed and put into practical use.

TC as an organic semiconductor for the capacitor element
Solution impregnation method, dispersion impregnation method, and vacuum vapor deposition method are generally used as the method for impregnating the NQ complex. However, since the characteristics of the TCNQ complex change under various conditions and it is a substance that is extremely difficult to handle, there are various ways to use it. Is devised.

[0006] In particular, as a condition for the solid electrolyte of the solid electrolytic capacitor, the resistance value itself which affects tan δ as a capacitor characteristic and the equivalent series resistance is small, and the specific resistance value is stable even at temperature, especially at high temperature. It is important to be.

From the above, TC to the capacitor element
As a means for impregnating the NQ complex, the heating melt liquefaction treatment is considered to be effective according to the patent publications or technical documents that have been proposed in the past, in order to industrially uniformly permeate a required amount into the inside of the capacitor element.

Incidentally, the specific means of the heating melt liquefaction treatment is as follows.
A capacitor element, which is preheated in a desired TCNQ complex solution which is placed in an outer case and melted by heating, is housed and impregnated through fibers of insulating paper (spacer) and fine etching pits of the electrode foil which constitute this element. It constitutes a solid electrolyte.

[0009] The specific means for obtaining the solid electrolytic capacitor obtained by subjecting the TCNQ complex to the heat-melting and liquefaction process will be described in detail. A certain amount of the TCNQ complex as an organic semiconductor is weighed in a container and raised to a heater. The TCNQ complex melt melted at about 220 ° C. is immersed in the capacitor element which has been heated to about 300 ° C. in advance. The temperature of the organic semiconductor melt at that time reaches 250 ° C. If it is left in the molten state for a long time, the resistance value will increase, and when it is made into a product, it causes problems such as increase in loss, increase in equivalent series resistance, and further decrease in capacitance in the reliability life test. , Need to be cooled promptly.

However, the TCNQ complex has a volume contraction of about 15% in the process of cooling and solidifying from the molten state, but the stress due to the cooling volume contraction is the largest at the end face of the capacitor element, and the stress causes the TCNQ complex to drive. Since it does not have a chemical conversion property like an electrolytic solution, it undergoes chemical conversion treatment after winding the capacitor element, and the anodized film formed at the corners in the width direction, which is the cut surface of the anode foil that constitutes the capacitor element end surface, deteriorates and the capacitor element deteriorates. As a result, there is a problem that the meaning of the chemical conversion performed after winding is lost and the leakage current increases.

[0011]

As described above, the solid electrolytic capacitor having the above-mentioned structure has TC as an organic semiconductor.
The NQ complex was impregnated by heating, melted, and liquefied, and contracted during cooling and solidification, which deteriorated the oxide film on the end face of the anode foil, causing an increase in leakage current.

The present invention has been made in view of the above points, and an object thereof is to omit the chemical conversion treatment after winding the capacitor element, and perform the cooling performed after the heat melting liquefaction impregnation of the TCNQ complex as the organic semiconductor. Another object of the present invention is to provide a solid electrolytic capacitor which suppresses deterioration of an oxide film due to stress during solidification and has excellent leakage current characteristics.

[0013]

A solid electrolytic capacitor according to the present invention is a solid electrolytic capacitor obtained by impregnating an organic semiconductor into a capacitor element wound with a spacer interposed between an anode foil and a cathode foil made of a valve metal. In the third aspect, the ultraviolet curable resin thin film is formed on the end face in the width direction of the anode foil forming the capacitor element.

[0014]

With the above-mentioned structure, since the ultraviolet curable resin thin film is formed on the end face of the anode foil, there is no need for chemical conversion treatment after winding the capacitor element, and as an organic semiconductor for the capacitor element. Melt-Liquefaction Impregnation of TCNQ Complex of Polypropylene-Mechanical Strain (Stress) Generated during Cooling and Solidification
It is possible to effectively prevent deterioration of the oxide film.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, as shown in FIG. 2, the surface of the aluminum foil is roughened with an etching solution to increase the surface area, and then an anodic oxide film is formed, which is cut into a width suitable for the product, and ultraviolet rays are applied to both end surfaces. A thin layer of cured resin is applied, the resin is rapidly irradiated with ultraviolet rays to cure the resin, and the anode foil winding 2 is provided with one layer of ultraviolet curable resin thin film on both end surfaces, and the aluminum foil surface is roughened with an etching solution to increase the surface area, Cathode foil winding cut into a width suitable for the product (not shown)
The cathode foil winding and the anode foil winding 2 are set on a winder (not shown), and the winder is driven to interpose a spacer in the middle to wind the two together. As shown in FIG. 3, a spacer 5 made of kraft paper or Manila paper is interposed between the anode foil 3 and the cathode foil 4 having the ultraviolet curable resin thin film 1 formed on both ends in the width direction, and the anode foil 3 and the cathode foil 4. A capacitor element 8 in which an anode lead terminal 6 and a cathode lead terminal 7 are attached and wound at arbitrary portions of 4 respectively.
To form.

Next, as shown in FIG. 4, an organic semiconductor made of a TCNQ complex is placed in a case 9 made of, for example, aluminum, and this organic semiconductor is heated and melted to form an organic semiconductor melt 10 as shown in FIG. The capacitor element 8 in a preheated state, and the organic semiconductor melt 10 is impregnated in the capacitor element 8 and then cooled and solidified, and the remaining organic semiconductor melt 10 not impregnated is left in the bottom surface of the case 9. The solidified organic semiconductor 11 is formed, and the opening of the case 9 is sealed with a sealing body 12.

According to the solid electrolytic capacitor having the above structure, since the ultraviolet curable resin thin film formed on the end face of the anode foil 3 constituting the capacitor element covers the end surface of the capacitor element anode foil, the organic semiconductor In the impregnation of the melted liquid 10, even if there is mechanical stress due to shrinkage during heating-cooling and solidification, deterioration of the oxide film can be prevented, and the leakage current characteristics can be greatly improved.

Next, an example of comparison between Example A and Conventional Example B will be described. That is, an ultraviolet curable resin is applied to both end faces by bar coating or spraying to a thickness of about 50 μm, and the resin is rapidly irradiated with ultraviolet rays to cure the resin, and an anode foil winding and a cathode foil winding having a width of 5 mm are used. Example A produced,
As a result of examining the leakage current distribution in Conventional Example B, which was manufactured in the same manner as in Example A, except that the ultraviolet curable resin was not applied to the end face of the anode foil winding, it is as shown in FIG. It was as shown in.

The rating is 16 for both Example A and Conventional Example B.
At V-47 μF, the organic semiconductor used the TCNQ complex of N-n-butylisoquinolinium in both Example A and Conventional Example B.

[0020]

[Table 1]

As is clear from FIG. 5 and Table 1, the conventional example B has a high level of leakage current, a large variation, and the yield rate is considerably low, whereas the example A has The leakage current level was low, the variation was small, and the non-defective rate was high, and the excellent effect of protecting the end face of the anode foil of Example A was verified.

[0022]

According to the present invention, by completely protecting the end face of the anode foil, variations in leakage current are eliminated,
It is possible to obtain a highly reliable solid electrolytic capacitor having a high level of practical value and capable of reducing the level.

[Brief description of drawings]

FIG. 1 is a sectional view showing a solid electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an anode foil winding that constitutes a capacitor element according to an embodiment of the present invention.

FIG. 3 is a developed perspective view showing a capacitor element according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a heated and melted state of an organic semiconductor.

FIG. 5 is a characteristic diagram showing a leakage current distribution.

[Explanation of symbols]

 1 UV curable resin thin film 2 Anode foil winding 3 Anode foil 4 Cathode foil 5 Spacer 6 Anode extraction terminal 7 Cathode extraction terminal 8 Capacitor element 9 Case 10 Organic semiconductor melt 11 Solidified organic semiconductor 12 Sealed body

Claims (1)

[Claims] 1. A solid electrolytic capacitor obtained by impregnating an organic semiconductor into a capacitor element wound with a spacer interposed between an anode foil and a cathode foil made of a valve metal, and the width of the anode foil constituting the capacitor element. A solid electrolytic capacitor having an ultraviolet curable resin thin film formed on the end face in the direction.