JPH01208827A - Aluminum electrolytic capacitor - Google Patents

Abstract

PURPOSE:To miniaturize an aluminum electrolytic capacitor while lowering leakage currents by impregnating an element, in which an anode obtained by forming a high purity aluminum film having the shape of a columnar projection onto the surface of a metallic foil and anodizing the film and a cathode foil through a separator, with an electrolytic solution for drive. CONSTITUTION:An electrolytic solution for drive is housed into a closed-end cylindrical case 1 together with a capacitor element 2. The element 2 is constituted by winding an anode foil 3 acquired by shaping high-purity aluminum having the shape of a columnar projection onto the surface of a metallic foil through evaporation and anodizing aluminum, a cathode foil 4 oppositely faced to the anode foil 3 and composed of aluminum, and separators 5 interposed among the anode foil 3 and the cathode foil 4. The thickness of the metallic foil used for forming the anode foil 3 extends over 15-40mum, aluminum is evaporated onto the surface of the metallic foil in an inert gas atmosphere having gas pressure of 1X10<-4>-8X10<-2>Torr, and the diameter of the columnar projection is shaped in 0.1-2mum. Accordingly, an aluminum electrolytic capacitor can be miniaturized while leakage currents can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an aluminum electrolytic capacitor used in various electronic devices.

Conventional technology Conventionally, this type of aluminum electrolytic capacitor is made by enlarging the effective surface area of high-purity aluminum foil by electrolytic etching, forming an anodized film by chemical conversion treatment, and winding the anode and cathode foils with a separator in between to drive the electrolyte. It was composed of impregnation.

There is a strong demand for aluminum electrolytic capacitors used in such electronic devices to be smaller, lower in profile, and higher in performance as various electronic devices become smaller, thinner, and higher in performance. Therefore, it is necessary to increase the capacitance and improve the characteristics of the anode foil.

In order to increase the total capacitance of the anode foil, conventional electrolytic etching has been used to expand the effective surface area and increase the capacitance. There was a limit to increasing capacitance using electrolytic etching technology.

In order to improve this problem, it is known to vacuum-deposit high-purity aluminum on the surface of etched aluminum or other metals and then anodize the surface (for example, Japanese Patent Publication No. 33-2281).

Problems to be Solved by the Invention With an anode foil made by such a conventional method (aluminum vapor deposition), for example, when vapor depositing it on a metal surface that has been subjected to etching treatment, the surface area is expanded and the capacitance is improved compared to before vapor deposition. If the four parts are deep, it will be difficult to deposit aluminum into the recesses, and there will be some areas where the aluminum will not be deposited.In those areas, the base material will be oxidized during anodization, and the base material may be made of low-purity aluminum or other materials. If it is made of metal, it has the disadvantage that the film properties deteriorate.

The present invention is intended to solve these conventional problems.

Means for Solving the Problems Therefore, the present invention provides a vacuum degree IXI Cf-4 to 8
A protruding high-purity aluminum film is formed by vapor deposition in an inert gas atmosphere and then anodized to be used as an anode foil.

action The effect of this technical means is as follows.

In the present invention, a metal surface that is smooth or has an unevenness in which the depth of the recess is 2/3 or less of the average radius of the opening is coated with a vacuum degree of 1 x 1 cr' to 8 x I Cr2 Torr (
When high-purity aluminum is vapor-deposited in an inert gas atmosphere, a high-purity aluminum film having the shape of columnar protrusions is formed as shown in FIG. 2, and the effective surface area is expanded and the capacitance is increased. Furthermore, the capacitance can be adjusted by controlling the film thickness.

Furthermore, since high-purity aluminum covers the surface of the base material, the film has excellent film properties even when anodized.

Furthermore, since there is a space between the columnar protrusions through which the chemical conversion liquid permeates appropriately, chemical conversion is easy and the leakage current is small.

Further, since the base material does not require etching, it has high strength even if the thickness is reduced, and the F-capacitor element can be made smaller by making the base material thinner.

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings. First, in FIG.
A driving electrolyte is housed therein together with the capacitor element 2. The capacitor element 2 includes an anode foil 3 made entirely of high-purity aluminum having a columnar projection shape by vapor deposition and anodized, a cathode foil 4 made of aluminum facing the anode foil 3, and the anode foil 3 and the cathode foil 4. and a separator 5 interposed between the anode foil 3. Lead wires are drawn out from the cathode foil 4, respectively. The opening of the case 1 is sealed with a sealing body 7 that does not allow the lead wire 6 to pass through.

Further, as shown in FIG. 2, which is an enlarged cross-sectional view of the main part of the anode foil 3, a high-purity aluminum vapor deposition film 9 having a columnar protrusion shape is formed on the surface of a smooth aluminum foil 8, and A chemical conversion film 1o is formed.

The experimental results shown in FIG. 3 will be explained.

This aluminum vapor deposition film 9 is formed on the surface of a smooth 99.8% aluminum foil 8 with a thickness of 20 μm at a vacuum degree of I
It can be formed by vapor-depositing high-purity aluminum and anodizing it under control of X 10-4 to 8 X 1 o-+2'rorr.

Figure 3 shows the capacitance value when 99.8% aluminum was vapor-deposited under vacuum f I show. As is clear from this Figure 3, the degree of vacuum is lX10'~8X10-2
It can be seen that the capacitance is improved within the Torr range. Furthermore, the capacitance obtained within this range is 99.98%
, 1ooooμF/d at 90μm), 4.5 times (1000/JF/20μF/d) per foil thickness
mln equivalent value: 4600 AIF/90 μm).

The results of incorporating the anode foil obtained as described above into an aluminum electrolytic capacitor are shown in the following table.

As shown in the table, when a foil deposited and anodized in a vacuum of IX1 o-5 Torr is used as an anode foil and incorporated into an aluminum electrolytic capacitor, the capacitance per volume increases significantly, and the leakage current also increases. small.

Furthermore, compared to an aluminum electrolytic capacitor in which an anode foil obtained by conventional electrolytic etching and anodizing is incorporated, the size can be significantly reduced for the same capacity (for example, 4V
, 470μF becomes φ6×5 instead of φ8×6, which is 44%.
Furthermore, since the vapor-deposited foil does not have foreign matter such as etching solution attached to its surface, the leakage current is also small (for example, at 47 degrees and 470 μF, 8 μm for a 15 μF person). According to the invention, an aluminum electrolytic capacitor can be downsized by increasing the capacitance of the anode foil and reducing the foil thickness, and moreover, it is possible to obtain the effect of reducing leakage current compared to conventional capacitors.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view showing one embodiment of the aluminum electrolytic capacitor of the present invention, Fig. 2 is a cross-sectional view of an anode foil used in the capacitor, and Fig. 3 is a characteristic showing the relationship between degree of vacuum and capacitance. It is a diagram. 1... Case, 2... Capacitor element, 3... Anode foil, 4... Cathode foil, 5...
... Separator, 8 ... Aluminum foil, 9 ... Aluminum vapor deposited film, 10 ...
・Chemical conversion film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (4)

[Claims] (1) A capacitor constructed by forming a high-purity aluminum film in the shape of columnar protrusions on the surface of a metal foil with a smooth or uneven surface, anodizing it to form an anode, and winding it together with a cathode foil through a separator. An aluminum electrolytic capacitor characterized by an element impregnated with a driving electrolyte. (2) The metal foil has a thickness of 15 to 40 μm, and by vapor-depositing high-purity aluminum on its surface in an inert gas atmosphere with a gas pressure of 1 x 10^-^4 to 8 x 10^-^2 Torr. The aluminum electrolytic capacitor according to claim 1, further comprising columnar projections. (3) The diameter of the columnar protrusions of the high-purity aluminum film is 0.1
The aluminum electrolytic capacitor according to claim 1, wherein the aluminum electrolytic capacitor has a diameter of 2 μm. (4) The average radius of the opening of the concave part of the unevenness of the metal surface is 0.
2. The aluminum electrolytic capacitor according to claim 1, wherein the depth of the recess is 2 to 5 μm, and the depth of the recess is 2/3 or less of the average radius of the opening.