JPH01105525A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent the development of aluminum hydroxide when the section of an anode foil is formed, by boiling and cleaning a capacitor element prior to a process where a section part of the anode foil in the capacitor element is formed. CONSTITUTION:An anode foil which is made by slitting a formed aluminum foil and a cathode foil consisting of the aluminum foil are wound through a separatory paper to form a capacitor element and the capacitor element is impregnated with an organic semiconductor which is fusible to liquefy and it is cooled for solidification. In such a case, the capacitor element is boiled and cleaned prior to a process where a section part of the anode foil in the capacitor element is formed. Then a boehmite film is formed at the section part of the anode foil. The formation of this film prevents the development of aluminum hydroxide when the foregoing section is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION - (A) Field of Industrial Application The present invention relates to a method for manufacturing a solid electrolytic capacitor using an organic semiconductor made of TCNQ salt as a solid electrolyte.

(b) Prior Art It is already known that an organic semiconductor made of TCNQ salt can be used as a solid electrolyte of a solid electrolytic capacitor. In this case, the solid electrolyte is directly attached to a film-forming metal such as aluminum that has an oxide film, but in a different form, positive) l@i^, negative F, and 9M are wrapped with separator paper in between. It has also been proposed in Japanese Patent Application No. 116861/1986 to impregnate the above-mentioned separate paper with the above-mentioned solid electrolyte. What is T and CNQ?7,7
, 8.8 means tetracyanoquinodimethane. In such conventional technology, organic semiconductor powder is appropriately pressurized and packed in an aluminum case with good thermal conductivity.
The capacitor element is melted and liquefied at 0°C to 300°C, and the cut end of the anode foil is chemically formed. After preheating, the capacitor element is immersed to be impregnated. After soaking and impregnating, the device is cooled and solidified together with the aluminum case, sealed with resin or rubber, and aged (voltage treatment) to complete the process.

Here, we will discuss the purpose of chemically converting the cut edges of the anode foil of a capacitor element. The aluminum foil is etched in advance and then chemically converted to form an anodic oxide film, but since this aluminum foil is slit according to the capacitor used, there is no film at the cut holes created during the slitting.

Therefore, there is a problem that leakage current increases due to this cut. In general electrolytic capacitors, no chemical conversion is performed to repair the cut edges, and the repair is performed during the aging process, but in the case of solid electrolytic capacitors, the repair mechanism is different from that of electrolytic capacitors.
Since the degree of repair is not sufficient, it is necessary to repair it separately. Furthermore, a very thin oxide film is formed on the cut end by oxidation in the air, increasing the capacitance, but in order to finely adjust this capacitance, it is necessary to form an oxide film and increase the film thickness.

Aluminum hydroxide is generated by this cutting process, which is carried out for this purpose. This clogs the etching holes in the chemically formed foil or the holes in the separator paper, lowering the impregnation rate of the organic semiconductor and deteriorating various properties such as capacitance and equivalent series resistance.

Furthermore, if the impregnation rate of the organic semiconductor is reduced, there is a problem that not only the initial capacitance decreases but also the rate of decrease in capacitance increases in a life test at a high temperature (105° C.).

(c) Problems to be Solved by the Invention The present invention solves the above-mentioned problems, namely, aluminum hydroxide is generated by the chemical formation of the cut edges of solid electrolytic capacitors, which reduces the impregnation rate of organic semiconductors, and reduces capacitance and equivalent series resistance. This is to solve the problem of deteriorating various characteristics such as, and furthermore, increasing the rate of decrease in capacitance in high-temperature life tests.

(d) Means for Solving the Problems The present invention provides a capacitor element in which an anode foil made by slitting chemically formed aluminum foil and a cathode foil made of aluminum foil are wrapped around a capacitor element with separator paper interposed therebetween. In the manufacturing method of a solid electrolytic capacitor impregnated with a possible organic semiconductor and solidified by cooling, the capacitor element is boiled and washed before or after the step of chemically forming the cut end of the anode foil of the capacitor element.

(E) Action If boiling and cleaning is performed before cut end chemical formation, a Boehmit film will be formed on the cut end of the anode foil, making it difficult for aluminum hydroxide to be generated during cut end chemical formation.Also, if boiling and cleaning is performed after cut end chemical formation, aluminum hydroxide will be generated during cut end chemical formation. The aluminum hydroxide removed prevents clogging of separator paper and etching eraser.

(f) Examples The present invention will be described below with reference to Examples (i) to (-).

(i) The chemical aluminum foil for the VH electrode and the aluminum foil for the cathode are wrapped around a 50μ thick manila paper, and the capacitor element is wrapped with tape and washed by boiling in pure water at 95°C or higher for about 7 minutes. The cut end of the anode foil of the zero-order capacitor element is heated to a voltage equal to the anodizing voltage or from 0 to several volts (20 volts in the example) to adjust the capacitance using a chemical solution consisting of 2% ammonium adipate. ) A high voltage is applied to form a chemical compound. After drying the capacitor element and preheating for 3 to 5 minutes, the n-butyl-isoquinolinium TC
It is impregnated with a melted and liquefied organic semiconductor made of NQ salt, and then cooled and solidified. The solid electrolytic capacitor is then sealed with resin and subjected to aging (voltage treatment).

(i) The same capacitor element as in Example (i) is rotated at 95°.
Ammonia aqueous solution adjusted to a pH of approximately 8.0 above C°
After that, in the same manner as in Example (i), the material is boiled for about 7 minutes, and after the process of chemically cutting the cut, impregnating with an organic semiconductor, cooling and solidifying, it is sealed with resin and aged (voltage treatment) to complete the product.

(i) The same capacitor element as in Example (i) was heated to 95°C.
Boiling cleaning is performed for about 7 minutes in the above phosphoric acid aqueous solution adjusted to pH about 3.0, and then, in the same manner as in Example (i), after the steps of cut chemical formation, organic semiconductor impregnation, and cooling solidification, resin sealing, Aging (press treatment 1) to complete.

(iv) The cut end of the anode foil of the same Fundensa element as in Example (+) is chemically treated by applying a voltage 20V higher than the anodizing voltage using a chemical solution consisting of 2% ammonium adipate.Then, the temperature is increased to 95°C or higher. Cleaning is performed by boiling in pure water for about 7 minutes, and then the cut anodization is performed again at a voltage 20 V higher than the anodization voltage, and the device is dried, preheated, impregnated with an organic semiconductor, and cooled and solidified in the same manner as in Example (i). After this process, the solid electrolytic capacitor is completed by resin sealing and aging (voltage treatment).

(V) PH instead of boiling with pure water in Example (cypress)
After boiling and cleaning in an ammonia aqueous solution of about 8.0 for about 7 minutes, and then performing cut chemical formation again, the process of drying the device, preheating the device, impregnating the organic semiconductor, and solidifying by cooling was performed in the same manner as in Example (i). , resin sealing, aging (voltage treatment) and completion.

(-) PH instead of boiling with pure water in Examples (~)
Boiling cleaning was performed for about 7 minutes in a phosphoric acid aqueous solution adjusted to about 3 L O, and then the cut surface was chemically formed again, and the steps of drying the device, preheating the device, impregnating the organic semiconductor, and solidifying by cooling were performed in the same manner as in Example (i). Afterwards, it is sealed with resin and subjected to aging (voltage treatment).

Next, Table 1 shows comparative data between the conventional example and the examples <+) to (-). Each data in Table 1 is 25V, 6.8μF.
, shows the average value of 20 capacitors with external dimensions d6.3x6.8, (ap is capacitance, LC is leakage current, ESR
represents equal series resistance, the measurement frequency of Cap and tan δ is 120Hz, ΔC/d is the rate of change in the amount of electrostatic charge at 85°C with respect to the capacitance at 20°C, and MuC/C is 20
Applying a voltage of 25V at 105℃ for the capacitance of ℃1
The rate of change in capacitance after 000 hours is shown.

Here, Cap (20°C): Initial capacitance at 20°C (μF) Cap (85°C): Initial capacitance at 85°C (
μF) (ap(105℃) 7105”CX 25V x 1
Capacitance (μF) after 000 hours of high temperature load test As is clear from Table 1 in the margin below, Examples (i) and (i
), (i) and examples (N, (V), (vi) in which the capacitor element is boiled and washed after the process of chemically converting the cut portion)
In each case, the initial capacitance is 5% to 9% compared to the conventional example.
The capacity change rate due to temperature change is smaller than the conventional example, and high temperature load test <105℃ x 25V x 1
The capacity reduction rate after 00OH) is also small. This is because, as mentioned above, if boiling is performed before the cut end is chemically formed, a Boehmit film is formed on the cut end of the anode whistle, making it difficult for aluminum hydroxide to be generated during the cut end chemical formation. This is because boiling and cleaning after the cut surface formation removes the aluminum hydroxide generated during the cut surface formation, thereby preventing clogging of the separator paper and the etching plate.

(G) According to the invention as described in detail, aluminum hydroxide is generated by the chemical formation of the cut surface of the solid electrolytic capacitor, which reduces the impregnation rate of the organic semiconductor and increases capacitance, equal series resistance, etc. The problem of deteriorating various properties of the material and increasing the rate of decrease in capacitance in high-temperature load tests can be easily solved by boiling and washing before and after the cut-edge chemical formation.

Claims (2)

[Claims] (1) A capacitor element made by winding an anode foil made by slitting chemically formed aluminum foil and a cathode foil made of aluminum foil with separator paper interposed therebetween is impregnated with an organic semiconductor that can be melted and liquefied, and solidified by cooling. A method for manufacturing a solid electrolytic capacitor, characterized in that the capacitor element is washed by boiling before a step of chemically converting the cut portion of the anode foil of the capacitor element. (2) A solid electrolyte made by impregnating an organic semiconductor that can be melted and liquefied into a capacitor element made by winding an anode foil made by slitting chemically formed aluminum foil and a cathode foil made of aluminum foil with separator paper interposed therebetween, and then cooling and solidifying the capacitor element. A method for manufacturing a solid electrolytic capacitor, characterized in that the capacitor element is washed by boiling after the step of chemically converting the cut portion of the anode foil of the capacitor element.