JPH10270291A - Solid-state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the tendency of spontaneous oxide films to be formed by roughing the surface of metal foil by etching, and forming a non-valve-action metal film on the surface of the metal foil by deposition. SOLUTION: The surface of a metal foil 1 as a cathode foil, composed of aluminum and so on, is subjected to etching to roughen the surface. Thereafter, a non-valve-action film 2, composed of nickel and so on, is deposited on the roughed surface by electroless plating or the like. Here gold, silver, copper, platinum, iron or their alloy may be used for the non-valve-action film 2. Tantalum foil, niobium foil or the like may be used for the cathode foil. The cathode foil 1, 2 and anode foil, composed of aluminum foil which has been subjected to etching and formation, are wound with separator paper in-between to form a capacitor element. As a result, reduction in capacitance due to the influence of a spontaneously oxidized film on the cathode foil is prevented, and further the effective area of contact between the cathode foil and solid electrolyte is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a solid electrolytic capacitor in which a solid electrolyte is impregnated into a capacitor element in which an anode foil and a counter cathode foil each having a chemical conversion film formed thereon are wound via a separator.

[0002]

2. Description of the Related Art An anode foil having a valve-acting metal foil such as an aluminum foil which has been subjected to an etching treatment for roughening and a chemical conversion treatment for forming a dielectric film, and an opposing cathode foil are interposed via a separator. A solid electrolytic capacitor in which a wound capacitor element is impregnated with a TCNQ complex salt as a solid electrolyte is disclosed in JP-B-62-51489 and JP-B-4-663.
No. 73, for example. Here, TCNQ is
It means 7,7,8,8-tetracyanoquinodimethane.

Such a solid electrolytic capacitor has particularly excellent high-frequency characteristics in addition to life and temperature characteristics, and is therefore widely used in power supply circuits of personal computers and the like.

[0004] In recent years, with the lowering of the drive voltage of the arithmetic element and the higher speed of arithmetic processing in personal computers,
For such a solid electrolytic capacitor, a capacitor having a low rated voltage and a large capacitance has been required.

[0005] According to the common wisdom in the art, the capacitance C of the electrolytic capacitor is inversely proportional to the thickness of the chemical conversion film of the anode foil, the thickness of the chemical conversion film is proportional to the chemical formation voltage, and the rated voltage V is also the chemical formation voltage. Since the voltage is proportional to the voltage, CV = constant relationship holds between the capacitance C of the electrolytic capacitor and the rated voltage V. If the rated voltage V is allowed to be reduced, a capacitor having a large capacitance C is provided. can do.

However, in an actual solid electrolytic capacitor, in order to increase the effective contact area between the cathode foil and the solid electrolyte to reduce the equivalent series resistance as a completed capacitor, the cathode foil is also made of a valve metal. Since an etching foil is often used, a natural oxide film 3 is easily formed on the surface of the valve-action metal etching foil 1 as shown in FIG. Even if an attempt is made to increase the capacitance as a finished product, the capacitor is completed by connecting the cathode capacitance of the natural oxide film of the cathode foil in series with the anode capacitance of the conversion film of the anode foil. The decrease in capacitance as a product cannot be ignored.

[0007] To solve this problem, a technique for making the cathode capacitance substantially infinite by using a non-valve-acting metal foil such as a nickel foil, on which a natural oxide film is unlikely to be formed, as the cathode foil has been proposed. No. 7086.

However, the non-valve effect metal foil 4 such as a nickel foil cannot be roughened by an etching process like a valve action metal foil such as an aluminum foil, and is a so-called plain foil as shown in FIG. Therefore, when the non-valve metal plain foil 4 is used as the cathode foil, the cathode capacitance becomes substantially infinite, but the effective contact area between the cathode foil and the solid electrolyte is reduced, and the capacitor is completed. The equivalent series resistance as a product increases.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a solid electrolytic capacitor in which a solid electrolyte is impregnated in a capacitor element in which an anode foil having a chemical conversion film formed thereon and an opposite cathode foil are wound through a separator. It is intended to suppress a decrease in capacitance and an increase in equivalent series resistance as a finished capacitor due to the above-mentioned structure.

[0010]

In the solid electrolytic capacitor according to the present invention, a nickel plating film is formed on the surface of a metal foil whose surface has been roughened by etching, such as an etched aluminum foil, as a cathode foil. A non-valve metal film such as a vapor-deposited film is used.

In the solid electrolytic capacitor using the cathode foil having such a structure, the surface of the cathode foil is covered with a non-valve metal film, so that a natural oxide film is hardly formed and the cathode capacitance is substantially reduced. In addition, the surface of the non-valve-acting metal film also has an uneven surface which directly reflects the unevenness of the surface to be etched of the underlying metal foil, so that the effective contact area with the solid electrolyte increases.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A solid electrolytic capacitor according to one embodiment of the present invention is manufactured through the following steps.

First, a cathode foil having a sectional structure as shown in FIG. 1 is prepared. This cathode foil is formed by subjecting an aluminum foil 1 having a thickness of about 60 μm to an etching treatment to roughen the surface, and then electrolessly plating the rough surface to a thickness of about 1 μm.
The nickel film 2 is formed by deposition.

Here, instead of the nickel film, gold,
A non-valve effect metal film made of silver, copper, platinum, iron, an alloy thereof, or the like may be deposited. Instead of the electroless plating, a non-valve metal film may be formed by electroplating, vacuum deposition, sputtering, or the like.
Further, instead of the aluminum foil, a metal foil whose surface is easily roughened by etching treatment, such as a valve metal foil such as a tantalum foil or a niobium foil, may be used.

Next, the cathode foil and an anode foil made of an aluminum foil subjected to an etching treatment and a chemical conversion treatment are wound via a separator paper to produce a capacitor element.

On the other hand, a powder of a TCNQ complex salt such as Nn-butyl / isoquinolinium / TCNQ ₂ is charged in a bottomed cylindrical aluminum case, and this case is heated to about 290 ° C.
Is placed on a heated metal plate to melt the TCNQ complex salt in the case.

The capacitor element preheated to 250 to 300 ° C. is melted and liquefied in the case.
Immediately after immersion in the complex salt, immediately cool the entire case.

Thus, the TCNQ complex salt as a solid electrolyte is solidified on the rough surfaces of the anode foil and the cathode foil constituting the capacitor element and in a state of being impregnated in the separator paper.

Finally, an epoxy resin or the like is injected into the opening of the case, solidified, sealed, and aged to complete a solid electrolytic capacitor.

Table 1 shows the characteristics of the solid electrolytic capacitor according to the above-described embodiment and the solid electrolytic capacitors according to the above two types of conventional examples.

[0021]

[Table 1]

In Table 1, the solid electrolytic capacitor according to the embodiment of the present invention uses a cathode foil (cross-sectional structure as shown in FIG. 1) in which a nickel plating film is formed on the surface of an aluminum etching foil. (1) The solid electrolytic capacitor according to the conventional example uses a cathode foil (a cross-sectional configuration as shown in FIG. 2) in which a natural oxide film is formed on the surface of an aluminum etching foil. Cathode foil made of nickel plain foil (Fig. 3
(A cross-sectional configuration as described above).

In each of the embodiment, the first conventional example, and the second conventional example, an aluminum etching foil on which a chemical conversion film was formed at a chemical conversion voltage of 15 V was used as the anode foil. Is φ6.3mm × L5
mm.

As can be seen from Table 1, in the solid electrolytic capacitor according to the embodiment of the present invention, both large capacitance and small equivalent series resistance are compatible.

As the solid electrolyte in the solid electrolytic capacitor according to the present invention, a conductive polymer such as polypyrrole, polythiophene, polyaniline or a derivative thereof, manganese dioxide or the like may be used instead of the TCNQ complex salt.

[0026]

According to the present invention, there is provided a solid electrolytic capacitor in which a solid electrolyte is impregnated in a capacitor element in which an anode foil having a chemical conversion film formed thereon and an opposing cathode foil are wound via a separator. In addition to suppressing the decrease in capacitance as a finished capacitor due to the effects of
The effective contact area between the cathode foil and the solid electrolyte is also ensured, and the equivalent series resistance as a completed capacitor does not increase.

[Brief description of the drawings]

FIG. 1 is a sectional view of a cathode foil according to an embodiment of the present invention.

FIG. 2 is a sectional view of a cathode foil in the first conventional example.

FIG. 3 is a sectional view of a cathode foil in a second conventional example.

[Explanation of symbols]

1 Metal foil whose surface has been roughened by etching, such as aluminum etching foil 2 Non-valve action metal film such as nickel film 3 Natural oxide film 4 Non-valve action metal foil such as nickel foil

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01G 9/05 G

Claims (5)

[Claims] 1. A solid electrolytic capacitor in which a solid electrolyte is impregnated in a capacitor element in which an anode foil having a chemical conversion film formed thereon and an opposite cathode foil are wound via a separator, wherein the surface of the cathode foil is roughened by etching treatment. A solid electrolytic capacitor characterized in that a non-valve action metal film is formed on the surface of a metal foil. 2. The solid electrolytic capacitor according to claim 1, wherein said cathode foil is formed by depositing a nickel plating film on a surface of an etched aluminum foil. 3. The solid electrolytic capacitor according to claim 1, wherein said solid electrolyte is made of a TCNQ complex salt. 4. The solid electrolytic capacitor according to claim 1, wherein said solid electrolyte is made of a conductive polymer. 5. The solid electrolytic capacitor according to claim 1, wherein said solid electrolyte is made of manganese dioxide.