JPH03280520A - Manufacture of organic semiconductor solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To suppress an increase in the equivalent series resistance of the title capacitor by a method wherein TCNQ salt, which is fused and liquefied, is impregnated in a capacitor element and after the salt is cooled and solidified, a solving, in which the value of a dipole moment in one molecule is less than the value of one water molecule, is replaced with water and is impregnated in the interior of the element. 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 wound up on a cylinder and a capacitor element 6 is formed. Then, powder 8 of TCNQ salt is housed in a case, the TCNQ salt is fused and liquefied, the element 6 is dipped into the TCNQ salt and the TCNQ salt is impregnated in the element 6. The TCNQ salt is cooled and solidified and the element 6 is fixed in the case 7. Then, a solvent, in which the value of a dipole moment in one molecule is less than the value in one water molecule, such as such a liquid as benzene, hexane and the like, is injected, the element is left to stand at a temperature of 850 deg.C after the injection and after the disappearance of the liquid, the opening part of the case is sealed with the resin 9 or rubber and a rated voltage is applied to the capacitor element for one hour at 125 deg.C.

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. More specifically, the present invention relates to a method for manufacturing a capacitor that can suppress equal series resistance and leakage current in an organic semiconductor solid electrolytic capacitor using a TCNQ complex salt as an electrolyte.

(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 application. That is, JP-A-58-191414 (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. The 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
Put the CNQCN upper 8) into the case (7) and place the aluminum case (7) on the 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 TCNQCN mixture, which is immediately cooled and solidified. After that, a resin that is difficult to react on TCNQCN (
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 re-formed and heat-treated with an aqueous solution of ammonium adipate to repair the chemical conversion film on the anode foil that was damaged during element formation.

Then, melted and liquefied TCNQ salt (8
) and sealed with resin (9) or rubber, and then goes through the process of applying a positive rated DC voltage (forward direction) between the anode lead wire (5) and cathode lead wire (5') of the capacitor. He had completed 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 filed the patent application No. 63-2645.
No. 71 (filing date: October 20, 1988),
Impregnating a capacitor element with a molten and liquefied organic semiconductor,
We proposed a method for manufacturing solid electrolytic capacitors in which the interior of the element is impregnated with pure water after cooling and solidifying, and then the moisture in the element is dried. 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 removed by voltage treatment (aging). Repairability is significantly improved.

However, in such a conventional manufacturing method, since water is impregnated into the TCNQ salt-impregnated element, there is a drawback that the equivalent series resistance increases.

(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.
This suppresses an increase in equivalent series resistance caused by impregnation of water into the capacitor element.

(d) Means for Solving the Problems The present invention impregnates a capacitor element with molten and liquefied TCNQ salt, cools and solidifies it, and then contains a solvent in which the dipole moment value of the molecules is less than the value of water molecules inside the element. For example, methanol, ethanol, 1-furopanol, 2-propanol, benzene, hexane, carbon tetrachloride, chloroform, toluene, etc. are used instead of water for impregnation.

(e) Effect Although there are some parts that are currently unknown about the detailed effect, it is assumed that it is roughly as follows. That is, when liquid molecules act on the TCNQ salt, it is thought that the leakage current is reduced due to interactions between the TCNQ salt and the liquid molecules, such as Coulomb force, van der Waals force, or exchange repulsion. However, when water or a polar molecule with a dipole moment value greater than that of a water molecule is used as a liquid molecule, each heteroatom such as oxygen in each molecule has
These interactions are especially strong on the cation side of the TCNQ salt because it has non-bonding electron pairs. Therefore, although the leakage current is reduced, at the same time, the function as a semiconductor is weakened due to the unnecessary coordination of the TCNQ salt to the cation side, and as a result, it is considered that the equal series resistance increases.

In the present invention, by using molecules whose dipole moment value is less than that of water molecules, that is, liquid molecules that are more nonpolar than water molecules, the coordination of the TCNQ salt to the cation side is improved compared to that of conventional water molecules. This is to suppress the increase in equal series resistance.

(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 up into a cylinder. form. Next, the TCNQ salt powder (8) is stored in a case, the TCNQ salt is melted and liquefied at a temperature of 290 to 300°C, and the capacitor element (6) is immersed to be impregnated with the TCNQ salt. After the impregnation, the case (7) is cooled, and the TCNQ salt impregnated into the capacitor element is cooled and solidified.
A capacitor element (6) is fixed inside.

Next, up to the opening of the case (7), a solvent whose molecule has a dipole moment value less than that of a water molecule, such as benzene, hexane, carbon tetrachloride, chloroform, toluene, ethanol, methanol, 1-propanol, 2-
A propanol liquid is injected and left at a temperature of 85°C after injection. After the liquid remaining in the case disappears, the opening of the case is sealed with resin (9) or rubber.
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 value and equivalent series resistance in the case of manufacturing using a solvent in which the value of the dipole moment in the molecule is larger than the value of the water molecule, which is an example of the present invention, and in the case of water, which is the conventional example. This shows value comparison data.

In addition, C, is the leakage current data, and the rated voltage application 1
The value after 0 seconds shows the average value of the 10 values of the sample.

E, S, and R are equivalent series resistance values at 100 KHz, and indicate the average value of the values of 10 samples.

In Table 1, (a) has a rated voltage of 35V and a capacity of 0.68.
A capacitor using N-n-butylisoquinolinium TCNQ as μF, TCNQ salt, (b) has a rated voltage of 25 V, a capacitance of 1 μF, and N-pentamethylene lutidinium, TCNQ as TCNQ salt, and N - A capacitor using an equal mixture of phenethyl rutidinium TCNQ. (A) (B) (C) (D) (E
)(F)(G)(H)(1) is an example of the present invention, and is based on a production method using a solvent in which the value of the dipole moment in the molecule is less than the value of the water molecule. (J) is a conventional manufacturing method using water. For reference, (K) and (L) show data when using a solvent with a molecule whose dipole moment value is larger than that of water molecules, and (M) shows data when nothing was used. Describe it.

The following can be seen from Table 1. That is, regardless of the value of the dipole moment, the leakage current is significantly reduced when liquid molecules act on the TCNQ salt. However, regarding the equal series resistance, there is a considerable difference depending on the value of the dipole moment of the molecule (solvent) used. In other words, when a molecule (solvent) with a dipole moment value greater than or equal to a water molecule is used (including the use of water), the equivalent series resistance deteriorates rapidly; When using molecules (solvent), the degradation of equivalent series resistance is small. In particular, when a so-called nonpolar molecule (solvent) whose dipole moment value is close to zero is used, there is almost no deterioration of the equivalent series resistance. From these things, T
It can be seen that there is a close relationship between the value of the dipole moment of the molecule (solvent) acting on the CNQ salt and the performance of the capacitor (especially the deterioration of the equivalent series resistance). If a molecule (solvent) with a dipole moment smaller than that of a water molecule acts on the TCNQ salt, an increase in the equivalent series resistance can be significantly suppressed compared to the conventional method (when water is used).

Note that the present invention is not limited to the case where a wound element in which an anode foil and a cathode foil are wound with a separator paper interposed therebetween is used as a capacitor element. Needless to say, the present invention is also applicable to the case where a sintered element is used.

(g) Effects of the invention As described above, according to the present invention, in an organic semiconductor solid electrolytic capacitor using TCNQ salt, molecules (solvent) having a dipole moment smaller than water molecules are made to act on the TCNQ salt, so that the equivalent series resistance This suppresses the increase in leakage current and significantly reduces leakage current.

[Brief explanation of the drawing]

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

Claims (2)

[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. In an organic semiconductor solid electrolytic capacitor in which the element is heated and impregnated with TCNQ salt that can be heated and melted and has a conductivity that can be used as an electrolyte for a capacitor after cooling and solidifying, and cooling and solidifying, the value of the dipole moment in the molecule A method for manufacturing an organic semiconductor solid electrolytic capacitor, comprising the steps of: impregnating the interior of the capacitor element impregnated with the TCNQ salt with a solvent having a value of less than the value of water molecules, and then drying the capacitor element. (2) Solvents in which the value of the dipole moment in the molecule is less than that of water molecules include methanol, ethanol, 1-
The method for producing an organic semiconductor solid electrolytic capacitor according to claim 1, wherein propanol, 2-propanol, benzene, hexane, carbon tetrachloride, chloroform, and toluene are used.