JPH03280522A - Manufacture of organic semiconductor solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To contrive to make liberated water molecules act directly on TCNQ salt without making the TCNQ salt dissolve water molecules and to contrive the improvement of the leakage current characteristics and equivalent series resistance characteristics of the title capacitor by a method wherein the TCNQ salt is fused and impregnated in a capacitor element and after the TCNQ salt is cooled, the element is coated with a substance which generates water by dehydration and condensation. CONSTITUTION:An Al foil subjected to etching treatment and chemical formation is used as an anode foil 1, separators 3 are pinched between the foil 1 and an opposed cathode foil 2, the foils 1 and 2 and the separators 3 are cylindrically wound up and a capacitor element 6 is formed. Then, powder of TCNQ (7.7.8.8 tetracyanoquinodimethane) salt is housed in a case 7, the TCNQ salt 8 is fused and liquefied at a temperature of 320 deg.C, the element 6 is dipped in the salt 8 and the salt is impregnated in the element. The salt 8 is cooled and solidified and the element 6 is fixed in the case 7. Then, a furan resin is injected in the case 7 and the case is filled with the resin up to the upper end of the case opening part. The furan resin is hardened and a solid electrolytic capacitor is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing an organic semiconductor solid electrolytic capacitor. To explain in more detail, the present invention uses TCNQ complex salt (here, TCNQ salt is 7, 7, 8, 8) as an electrolyte.
The present invention relates to a method for manufacturing an organic semiconductor solid electrolytic capacitor using tetracyanoquinodimethane.

(b) Prior Art Regarding organic semiconductor solid electrolytic capacitors using TCNQ complex salt as an electrolyte, various proposals have already been made by the applicant of the present invention. That is, JP-A-58-19]4]4 (HOI
A solid electrolytic capacitor using a TCNQ complex salt with an isoquinoline substituted with an alkyl group at the N-position, which is disclosed in Japanese Patent Application No. G9102), has particularly excellent high frequency characteristics and is therefore widely used in switching power supplies.

Next, the capacitor element will be explained. FIG. 1 shows capacitor elements used conventionally and in the present invention. First, a high purity (99.99% or higher) aluminum foil is chemically treated to roughen its surface and subjected to a so-called etching process to increase its effective surface area. Next, an oxide film (thin film of aluminum oxide) is electrochemically formed on the surface of the aluminum foil in an electrolytic solution (chemical conversion treatment). Next, the etched and chemically treated aluminum foil is used as an anode foil (1), and a separator (
3) Sandwich the manila paper and roll it up into a cylindrical shape as shown in Figure 1. In this way, the anode foil (1) and cathode foil (2) with an oxide film formed on the aluminum foil and the separator (3) inserted between both electrode foils are wound to form a capacitor element (
6) is formed. Note that (4) and (4') are aluminum leads, and (5) and (5') are lead wires.

Further, the capacitor element (6) is subjected to heat treatment, and the manila paper forming the separator (3) is carbonized to reduce the density by reducing the diameter of the fibers.

Figure 2 shows this capacitor element (6) in an aluminum case (7).
) FIG. That is, a predetermined amount of T
The CNQ complex salt (8) was placed in the case (7), and the aluminum case (7) was placed on a heated hot plate.
The powdered TCNQ complex salt in case (7) is heated and melted at 0 to 315°C.

On the other hand, the preheated capacitor element (6) is inserted into the aluminum case (7), and the capacitor element (6) is impregnated with the molten TCNQ complex salt mixture, which is immediately cooled and solidified. Thereafter, epoxy resin or modified acrylic resin (9) is sealed, and further molded with epoxy resin or the like (10). In the prior art as described above, a chemically etched aluminum foil (1) and a cathode foil (2) are separated by a separator (3).
) The capacitor element (6) wound through the capacitor element (6) was reconstituted with an aqueous solution of ammonium adipate and heat treated again in order to repair the chemical conversion coating on the anode foil that was damaged during element formation. Then, melted and liquefied TCNQ salt (
8) and sealed with resin (9) or rubber, after which a positive rated DC voltage (forward direction) is applied between the anode lead wire (5) and cathode lead wire (5') of the capacitor. He had completed his goal, an organic semiconductor solid electrolytic capacitor.

However, the repairability of the oxide film in organic semiconductor solid electrolytic capacitors is slightly weaker than that of capacitors using general electrolytes, and even in the film formed by reconversion of ammonium adipate, mechanical stress during impregnation with TCNQ salt,
A weak portion exists in the chemical conversion coating due to thermal stress or chemical stress. These factors cause the problem that weak parts of the chemical conversion coating are destroyed, the equivalent series resistance and leakage current increase, and the yield becomes low.

To solve such problems, conventionally, after impregnating with an organic semiconductor or sealing with a resin, the oxide film is repaired and voltage treatment (aging) is performed at a high temperature of around 100° C. in order to reduce the leakage current value.

In addition, in order to solve this problem of leakage current, the applicant of the present application has filed Japanese Patent Application No. 63-264571
October 20, 2013), a method for manufacturing a solid electrolytic capacitor involves impregnating a capacitor element with a melted and liquefied organic semiconductor, cooling and solidifying it, impregnating the inside of the element with pure water, and then drying the moisture in the element. proposed. In this case, by impregnating the inside of the element impregnated with TCNQ salt with pure water and drying it, the organic semiconductor that has entered the defective part of the oxide film can easily become an insulator, and the oxide film can be repaired by voltage treatment (aging). performance is significantly improved.

However, in such a conventional manufacturing method, since water is impregnated inside the TCNQ salt-impregnated element, the TCNQ salt-impregnated element is impregnated with water.
Since the Q salt is exposed to a large amount of water at one time, the TCNQ salt naturally dissolves in the water. As a result,
Although the repairability of the oxide film is improved, on the other hand, the equivalent series resistance, which is one of the characteristics that determines the performance of a capacitor, is significantly degraded.

(c) Problems to be Solved by the Invention The present invention solves the above-mentioned problems in an organic semiconductor solid electrolytic capacitor using TCNQ salt as a solid electrolyte.
By impregnating water inside the capacitor element, TCNQ
The purpose is to suppress the salt from dissolving in the water and thereby increasing the equivalent series resistance of the capacitor and the leakage 'tL current.

(d) Means for Solving the Problems The present invention provides a substance that impregnates a capacitor element with melted and liquefied TCNQ salt, cools and assimilates it, and then generates water through dehydration condensation.
For example, the capacitor element is coated with furan resin.

(e) Function Furan resin is a resin molecule of furfuryl alcohol. Furfuryl alcohol has the following structure, and the reaction mechanism for its initial condensation is dehydration condensation, as shown below, whereby Furfuryl alcohol becomes a polymer and forms furan resin. It is. It should be noted that the amount of water produced by the condensation of Friful alcohol is not large enough to dissolve the TCNQ salt, and such an amount hardly causes any deterioration of the equivalent series resistance of the capacitor.

The following is a margin ↑ The present invention uses this property, that is, by allowing water molecules liberated during the condensation process of friful alcohol to act on TCNQ salt, it aims to improve the repairability of the oxide film and reduce the equivalent series resistance. The purpose is to obtain a stable organic semiconductor solid electrolytic capacitor.

(f) Example An aluminum foil that has been subjected to etching treatment and chemical conversion treatment is used as an anode foil (1), a separator (3) is sandwiched between it and a counter cathode foil (2), and the capacitor element (6) is wound into a cylindrical shape. ) to form. Next, powder of TCNQ salt, e.g.
N, N-pentamethylene lutidinium, ・TCNQ,
A mixture of equal amounts of N-phenethyl rutidinium TCNQ and
The NQ salt (8) is melted and liquefied, and the capacitor element (6) is immersed to be impregnated with the TCNQ salt. After impregnation, the case (7) is cooled, the TCNQ salt (8) is cooled and solidified, and the case (7)
A capacitor element (6) is fixed inside.

Next, instead of the epoxy resin (9) in FIG. 2, a furan resin (for example, Hitafuran VF302 manufactured by Hitachi Chemical Co., Ltd.) is injected into the case (7) to fill the case up to the upper end of the opening.

Then, the furan resin was cured at a temperature of 105°C, and 1
The rated voltage of the capacitor is applied (aging) at 25° C. for 1 hour to complete the desired solid electrolytic capacitor.

Table 1 shows the leakage current values and other values of the capacitor sealed with furan resin in the embodiment of the present invention and the conventional capacitor impregnated with water, dried, and sealed with epoxy resin (and modified acrylic resin). Comparison data of individual series resistance values is shown.

For reference, comparative data is also provided for capacitors that were sealed with epoxy resin (and modified acrylic resin) immediately after being impregnated with TCNQ salt without being impregnated with water.

Margin 1 below In Table 1, (A) (B) (C) (D) (E
) is a capacitor with a rated voltage of 25V and a capacitance of 1μF.

(A) is a capacitor according to an embodiment of the present invention in which furan resin is used as a sealant; (B) and (C) are conventional examples in which TCN
Q: A capacitor that is impregnated with salt, then water, and then dried.
(B) is a capacitor using an epoxy resin as a sealant, and (C) is a capacitor using a modified acrylic resin. (D) and (E) are capacitors that were immediately sealed with epoxy resin and modified acrylic resin, respectively, after being impregnated with TCNQ salt without using water.

In addition, L, C, are leakage current data, and 25V applied 1
The value after 0 seconds is the average value of the values of each 10 samples. ESR is an equivalent series resistance value at 100 KHz, and indicates the average value of the values of each 10 samples.

From Table 1, it can be seen that the capacitor using furan resin, which is a product of the present invention, has better characteristics in both leakage current characteristics and equal series resistance characteristics.

Furthermore, in the above embodiment, the capacitor element is placed in the case (7).
We have only described the case where the capacitor element (6) is covered with furan resin alone and the case opening is sealed, but after covering the capacitor element with furan resin, another resin such as epoxy resin is applied over it. The opening of the case may be sealed by double coating. It is also possible to use other sealing means, such as a so-called resin dip type, in which the entire surface of the capacitor element is sealed with resin without using a case.

As long as the present invention is a capacitor in which a furan resin layer is directly formed on a TCNQ salt-impregnated element, its effects will not be impaired in any way. In addition, in the examples, N,N-bentamethylenerutidinium, .TCNQ4 and N-phenethyl.
Although we have only described an electrolyte made by mixing equal amounts of rutidinium and TCNQ, other TCNQ salts may also be used alone or in combination. It is clear that similar effects can be obtained with any TCNQ salt that has enough thermal stability to allow impregnation, and the present invention is not limited to the type of TCNQ salt.

(G) Effects of the Invention As described above, the present invention is characterized in that a capacitor element is melted and impregnated with TCNQ salt, and after cooling, the capacitor element is coated with a substance that generates water through dehydration condensation, such as furan resin. It is an organic semiconductor solid electrolytic capacitor with excellent leakage current characteristics and equal series resistance characteristics because the water molecules liberated during furan resin formation act directly on the TCNQ salt without dissolving the TCNQ salt. A capacitor is obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a capacitor element, and FIG. 2 is a sectional view of an organic semiconductor solid electrolytic capacitor. (1) (2)...Positive, cathode foil, (3)...Separator, (6 units...Capacitor element, (7)...Aluminum case, (8)...TCNQ complex salt, (9 )···Epoxy resin.

Claims (1)

[Claims] (1) A capacitor formed by winding a separator paper between an anode foil made of a chemically etched foil of a metal with a valve action such as aluminum, tantalum, or niobium, and a cathode foil made of a thin foil of the metal. The capacitor element is heated and impregnated with TCNQ salt that can be melted by heating and has a conductivity that can be used as an electrolyte for a capacitor after cooling and solidifying, and after cooling and solidifying, the capacitor element is made of a substance that generates water through dehydration condensation. A method for manufacturing an organic semiconductor solid electrolytic capacitor, comprising coating the TCNQ salt with the TCNQ salt, and allowing the generated water to act on the TCNQ salt.