JP2814585B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor in which a solid electrolyte film is laminated on a dielectric film of a metal foil having a dielectric film formed on the surface, and a method of manufacturing the same. About.

2. Description of the Related Art In recent years, with the digitization of circuits such as electric devices, it has been strongly required that capacitors used in the circuits have low impedance in a high frequency range, and have a small size and a large capacity.

Conventionally, high-frequency capacitors include plastic film capacitors, mica capacitors, and multilayer ceramic capacitors. However, it is difficult to increase the capacity of the former two plastic film capacitors and mica capacitors because the shape is too large, and the third type of multilayer ceramic capacitor is born from the demand for large capacity and small size. Yes, but very expensive.

In addition to the above capacitors, there are also aluminum dry electrolytic capacitors, aluminum solid electrolytic capacitors or tantalum solid electrolytic capacitors.

In an aluminum dry electrolytic capacitor, an etched positive and negative electrode aluminum foil is wound up through a paper separator so as to be impregnated with a liquid electrolyte. However, the aluminum dry electrolytic capacitor has a serious problem of deterioration of characteristics due to electrolyte leakage, evaporation, and the like. In order to improve this point, the latter two types of solid electrolytic capacitors are made of aluminum or tantalum solid electrolytic capacitors.

For aluminum solid electrolytic capacitors and tantalum solid electrolytic capacitors, immerse an anode foil (metal foil) such as aluminum foil or tantalum foil with a dielectric film on the surface by anodic oxidation or anodization in a manganese nitrate solution at 350 ° C.
It is thermally decomposed in a high-temperature furnace before and after it to form a solid electrolyte membrane composed of a manganese dioxide layer. These capacitors have a solid electrolyte, so there is no problem of electrolyte loss at high temperatures or deterioration of characteristics due to solidification of the electrolyte at low temperatures, and better frequency and temperature characteristics than capacitors using liquid electrolytes. In addition, since the thickness of the oxide film serving as a dielectric can be made extremely thin, it is suitable for increasing the capacity.

In addition to the above, instead of the manganese dioxide layer, a solid electrolytic capacitor using an organic semiconductor such as a 7,7,8,8-tetracyanoquinodimethane (TCNQ) salt as a solid electrolyte, furthermore, pyrrole, There is a type in which a conductive polymer layer formed by electrolytic polymerization of a polymerizable monomer such as furan is used as a solid electrolyte.

However, in a capacitor using a manganese dioxide layer as a solid electrolyte, the dielectric film is damaged by a plurality of thermal decomposition treatments during the manufacturing process. However, there is a problem that the loss at the site is not sufficient.

Capacitors that use an organic semiconductor such as TCNQ salt as a solid electrolyte have problems such as an increase in specific resistance when applying the organic semiconductor, and poor adhesion to the anode metal foil.
They cannot be said to have sufficient properties.

On the other hand, a capacitor using a conductive polymer layer as a solid electrolyte has excellent frequency characteristics, temperature characteristics, life characteristics, and the like, but has a problem that the withstand voltage is not sufficient.

In view of the above circumstances, an object of the present invention is to provide a solid electrolytic capacitor having excellent capacitor characteristics, especially excellent frequency characteristics, temperature characteristics, and withstand voltage characteristics, and a method for manufacturing the same.

Means for Solving the Problems According to the present invention, a heterocyclic compound is repeatedly formed on a manganese dioxide layer on a dielectric film of a metal foil having a dielectric film formed on a surface thereof. The solid electrolyte membrane in which the conductive polymer layer containing the polymer electrolyte is laminated is a solid electrolytic capacitor in which the laminate is formed, and at least the conductive polymer layer is formed by forming a dielectric film of the metal foil. Is a solid electrolytic capacitor formed so as not to cover the end of the solid electrolytic capacitor.

Examples of the heterocyclic compound of the present invention include pyrrole, thiophene, and at least one of these derivatives as in the invention of claim 2, but are not limited thereto, and may be, for example, furan.

Examples of the metal of the metal foil include, but are not limited to, at least one of aluminum and tantalum as in the invention of claim 3.

In order to prevent the solid electrolyte membrane from covering the end of the metal foil, for example, the end of the metal foil is covered with an insulator before forming the solid electrolyte membrane as in the manufacturing method according to claim 4. Preferably, it includes a step of performing the following steps.

The end of the metal foil may be covered with an insulator either before the dielectric film is formed or after the dielectric film is formed.
Examples of the insulator include polyimide and polyamideimide, but are not limited thereto.

The manganese dioxide layer of the solid electrolyte membrane can be laminated by applying and thermally decomposing manganese sulfate.
It goes without saying that the manganese dioxide layer may be formed by other methods.

The conductive polymer layer of the solid electrolyte membrane is supported on at least one of pyrrole, thiophene, and a derivative thereof on the manganese dioxide layer formed on the dielectric film as in the method of claim 5. It can be provided by forming an electrolytic polymerized layer using a solution containing an electrolyte. Of course, it is not limited to this method.

Specifically, the solid electrolytic capacitor of the present invention has, for example, a configuration shown in FIGS. 1 (a) and 1 (b).

Valve action metal foil 1 having a dielectric film (not shown) 2 formed on the surface by anodic oxidation or anodization (for example,
A solid electrolyte membrane 3 is formed on the substrate (made of aluminum, tantalum, titanium, or an alloy thereof). The electrolyte membrane 3 is composed of a conductive polymer layer 3b containing a heterocyclic compound as a repeating unit on a manganese dioxide layer 3a.
Is a layer configuration in which the layers are stacked. In this case, the electrolyte film 3 does not cover the end of the metal foil 1 where the dielectric film 2 is formed. This is mainly because the end face of the metal foil 1 is
After that, the electrolyte membrane 3 is formed. Of course, a sufficient distance to the end is secured on the side of the metal foil 1 from which the anode lead 8 is taken out, so that the end can be configured without using the insulator 6 without using the insulator 6. A graphite layer 4 and an Ag paste layer 5 are further formed on the electrolyte membrane 3. The anode lead 8 is bonded to the surface of the metal foil 1, and the cathode lead 9 is bonded to the surface of the Ag paste layer 5 by solder 10.

In the present invention, the solid electrolyte is composed of a conductive polymer layer containing a heterocyclic compound as a repeating unit on the manganese dioxide layer, so that it has excellent frequency characteristics and temperature characteristics, and at least the conductive polymer layer. Is not applied to the end of the metal foil on which the dielectric film is formed, so that the withstand voltage characteristics are excellent. In the conventional case, the conductive polymer layer is applied to the end of the metal foil. In this portion, defects are concentrated and dielectric breakdown occurs at a low voltage, so that a sufficient withstand voltage cannot be secured.

In addition, the manganese dioxide layer previously formed on the derivative film not only constitutes a part of the electrolyte but also serves as a polymerization initiation electrode when forming the conductive polymer layer, and does not damage the dielectric film and is complex. It functions to form an electropolymerized conductive polymer layer containing a cyclic compound as a repeating unit.

Examples Hereinafter, examples will be described.

Example 1 An amide-based material, Treeneth # 2000 (manufactured by Toray) was applied to the end surface of an 8 mm × 10 mm aluminum-etched foil.
The drying treatment was performed at 0 ° C. for 1 hour and at 150 ° C. for 1 hour. After the end face is covered with an insulating material, the aluminum-etched foil is coated with a 3% ammonium adipate aqueous solution using an approximately 3% aqueous solution.
Anodizing was performed at 70 ° C. for 40 minutes to form a dielectric film. A manganese nitrate solution was applied to the dielectric film and thermally decomposed at 200 ° C. for 30 minutes to form a manganese dioxide layer (conductive layer). afterwards,
With a stainless steel auxiliary electrode in contact with the surface of the manganese dioxide layer, pyrrole (0.5 mol /), monoisopropyl naphthalene sulphonate (0.15 M /),
It was immersed in an electrolytic solution composed of water, and a voltage of 3 V was applied to form an electrolytic polymerized film. It goes without saying that this electropolymerized film is a conductive polymer layer. After the formation of the electrolytic polymer film, the film was washed with water, then washed with ethanol, and dried. Thereafter, a carbon paste was applied to form a graphite layer, and further, an Ag paste layer was formed thereon, and then a cathode lead and an anode lead were attached to complete a solid electrolytic capacitor.

The withstand voltage of this solid electrolytic capacitor was 35V. For comparison, the withstand voltage of the solid electrolytic capacitor obtained by applying the electrolyte film to the end face of the metal foil was reduced by 25 V and 10 V.

After aging the solid electrolytic capacitor of the example at 20 V, the initial capacity (120 Hz), loss (120 Hz), and impedance (1 MHz) were measured. The results are as shown in Table 1.

Further, the temperature change rates of the capacitors at -55 ° C and 125 ° C were measured based on 20 ° C, and the loss change rates at -55 ° C, 20 ° C and 125 ° C were examined. Table 2 shows the measurement results.

Example 2 A polyamide varnish HI-400 (manufactured by Hitachi Chemical Co., Ltd.) was applied to the end surface of an 8 mm × 10 mm aluminum-etched foil.
A solid electrolytic capacitor was completed in the same manner as in Example 1 except that the drying process was performed at 180 ° C. for 2 hours.

The withstand voltage of this solid electrolytic capacitor was 33V. For comparison, the withstand voltage of the solid electrolytic capacitor obtained by applying the electrolyte film to the end face of the metal foil was as low as 25 V and 8 V.

After aging the solid electrolytic capacitor of the example at 20 V, the initial capacity, loss, and impedance were measured. The results are shown in Table 3.

Further, the temperature change rates of the capacitors at -55 ° C and 125 ° C were measured based on 20 ° C, and the loss change rates at -55 ° C, 20 ° C and 125 ° C were examined. Table 4 shows the measurement results.

Example 3 Etching was performed with an aqueous solution of tetraethylammonium P-toluenesulfonate, and a 10% aqueous solution of phosphoric acid was used.
Except that a 12 mm × 15 mm tantalum-etched foil subjected to anodization by applying 67 V at about 90 ° C. was used in the same manner as in Example 1,
The solid electrolytic capacitor was completed.

The withstand voltage of this solid electrolytic capacitor was 29V. For comparison, the withstand voltage of the solid electrolytic capacitor obtained by applying the electrolyte film to the end face of the metal foil was as low as 22V and 7V.

After aging the solid electrolytic capacitor of the example at 20 V, the initial capacity (120 Hz), loss (120 Hz), and impedance (1 MHz) were measured. The results are as shown in Table 5.

Further, the temperature change rates of the capacitors at -55 ° C and 125 ° C were measured based on 20 ° C, and the loss change rates at -55 ° C, 20 ° C and 125 ° C were examined. Table 6 shows the measurement results.

As can be seen from the measurement results of Examples 1 to 3, the solid electrolytic capacitor of the present invention has a sufficient initial capacity,
In addition, the change in capacitance with time is small, the high frequency characteristics are excellent, and the withstand voltage characteristics are excellent. Furthermore, variations in each characteristic such as capacitance with temperature change are small, and each characteristic of loss, high-frequency impedance, and LC is remarkably superior to a capacitor using a liquid electrolyte.

Effect of the Invention As described above, in the solid electrolytic capacitor according to claims 1 to 3 and the solid electrolytic capacitor obtained by the manufacturing method according to claims 4 and 5, the solid electrolyte film is formed by stacking manganese dioxide and manganese dioxide thereon. And a conductive polymer layer containing a heterocyclic compound as a repeating unit, which exhibits excellent frequency characteristics and temperature characteristics.In addition, since the solid electrolyte is not applied to the end face of the metal foil, excellent withstand voltage characteristics are obtained. It has high practicality.

[Brief description of the drawings]

1 (a) and 1 (b) show an embodiment of a solid electrolytic capacitor according to the present invention, FIG. 1 (a) is an explanatory view schematically showing a laminated structure, and FIG. It is a schematic plan view of a capacitor. 1 ... metal foil, 2 ... dielectric film, 3 ... solid electrolyte,
3a: manganese dioxide layer, 3b: conductive polymer layer, 4 ...
... Graphite layer, 5 ... Ag based layer, 6 ... Insulator, 8 ... Anode lead, 9 ... Cathode lead, 10 ... Solder.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masao Fukuyama 3-10-1, Higashi-Mita, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. (56) References JP-A-63-158829 (JP, A) 62-224015 (JP, A) (58) Fields surveyed (Int. Cl. ⁶ , DB name) H01G 9/028 H01G 9/04

Claims (5)

(57) [Claims] 1. A conductive polymer layer containing a heterocyclic compound as a repeating unit is laminated on a manganese dioxide layer on a dielectric film of a metal foil having a dielectric film formed on a surface thereof. Solid electrolyte membrane is a solid electrolytic capacitor formed by lamination, at least the conductive polymer layer,
A solid electrolytic capacitor which is laminated so as not to cover all the ends of the metal foil on which the dielectric film is formed. 2. The compound of claim 2, wherein the heterocyclic compound is pyrrole, thiophene,
The solid electrolytic capacitor according to claim 1, which is at least one of these derivatives. 3. The solid electrolytic capacitor according to claim 1, wherein the metal of the metal foil is at least one of aluminum and tantalum. 4. A solid electrolytic capacitor according to claim 1, further comprising a step of forming a solid electrolyte film after previously covering an end of the metal foil with an insulator. Production method. 5. An electroconductive layer is formed on a manganese dioxide layer laminated on a dielectric film by forming an electropolymerized layer using a solution containing at least one of pyrrole, thiophene and their derivatives and a supporting electrolyte. The method for producing a solid electrolytic capacitor according to claim 4, wherein the conductive polymer layer is laminated.