JPH03250724A - Manufacture of organic semiconductor solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To stabilize an oxide film on an aluminum foil and reduce leakage current by conversion heat treating an anode foil using solution which includes at least either the alkaline metal salt or the alkaline earth metal salt of phosphoric acid after forming a winding up element. CONSTITUTION:After a capacitor element is formed, an anode foil 1 is formed by solution containing at least either the alkaline metal salt or the alkaline earth metal salt of phosphoric acid. Then, through heat treatment, chemical conversion coating is performed on the chemical conversion coating of a metal which has been present since before the capacitor element is formed by using the forming liquid containing at least either the alkaline metal salt or the alkaline earth metal salt of the phosphoric acid. Thus, an oxide film which is remarkably stable mechanically, thermally and chemically is obtained and leakage current is reduced.

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 solves leakage problems in organic semiconductor solid electrolytic capacitors using TCNQ complex salt as an electrolyte. The present invention relates to a method of manufacturing a capacitor that can suppress L current.

(b) Prior Art Regarding organic semiconductor solid electrolytic capacitors using TCNQ complex salt as an electrolyte, various proposals have already been made by Yorito Motoyori. That is, JP-A-58-]991414 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 a conventionally used capacitor element. First, high purity (9
9.99% or more) aluminum foil is chemically treated to roughen it and increase its effective surface area.
/Perform the chiming process. 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, etching treatment,
An aluminum foil subjected to chemical conversion treatment is used as an anode foil (1), manila paper is sandwiched between it and a counter cathode foil (2) as a separator (3), and the aluminum foil is rolled up into a cylindrical shape as shown in FIG.

Anode foil with an oxide film formed on aluminum foil (
A capacitor element (6) is formed by rotating the cathode foil (2) and the separator (3) inserted between the two electrode foils. Note that (4) (4') is aluminum lead, (5) (5
') is the lead wire.

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 various TCNQCN (8) is placed in the case (7), and the aluminum case (7) is placed on a heated hot plate. Powdered TCNQ
Heat and melt the complex salt.

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). (11) is a lead wire groove. In the prior art as described above, a capacitor element (6) in which a chemically etched aluminum foil (1) and a cathode foil (2) are wound with a separator (3) interposed therebetween is repaired with a chemical conversion coating on an anode foil that is damaged during element formation. Therefore, it was re-formed using an aqueous solution of ammonium adipate and heat treated. Then, the capacitor element was impregnated with melted and liquefied TCNQ salt (8), and the resin (9) was impregnated with the melted and liquefied TCNQ salt (8).
) or rubber sealing, voltage treatment (aging), and other processes to complete the desired 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 the film formed by reconstitution of ammonium adipate also suffers from mechanical stress during impregnation with TCNQ salt.
A weak portion exists in the chemical conversion coating due to thermal stress or chemical stress. Due to these factors, the weakened portion breaks down when high voltage is applied, increasing leakage current.

(c) Problems to be Solved by the Invention The present invention is intended to solve the problem of an increase in leakage current when a high voltage is applied in an organic semiconductor solid electrolytic capacitor using a TCNQ salt as a solid electrolyte.

(d) Means for Solving the Problems The present invention provides that after forming the winding element, the anode foil is subjected to a chemical maturation treatment in a solution containing at least one of an alkali metal salt and an alkaline earth metal salt of phosphoric acid. A new chemical conversion film containing at least one of an alkali metal salt of phosphoric acid and an alkaline earth metal salt is applied to the chemical conversion film of the aluminum foil that existed before the formation of the winding element (capacitor element). It forms a chemical conversion film.

(E) Operation A chemical conversion film formed with a chemical liquid containing at least one of an alkali metal salt of phosphoric acid and an alkaline earth metal salt is applied onto the chemical conversion film existing before the formation of the winding element. By forming this, a mechanically, thermally and chemically very stable oxide film can be obtained.

(f) Examples Table 1 shows chemical conversion liquids used for re-chemical conversion (chemical conversion after formation of the winding element) used in the examples of the present invention and conventional examples.

Margin below Table 1 Rating 35 treated with the chemical liquid shown in Table 1
The yield of leakage current after voltage treatment (aging) of an organic semiconductor solid electrolytic capacitor prototyped using an element with a capacitance of 0.68 uF and a capacitance of 0.68 uF will be described. (Condition = 125℃, 35V
1 hour) In Table 2, C1 is the leakage current data, indicating the number of defects in 100 samples and the yield.
5 (IIA/10 sec, ) or less. The measurement conditions were 125° C., an applied voltage of 35 V, and the results were obtained after 1 hour.

It can be seen from Table 2 that the present invention is significantly more effective in preventing an increase in leakage current than the conventional method. Also, in a life test under high temperature load, the short circuit rate is significantly reduced when the alkali metal salt or alkaline earth metal salt of phosphoric acid of the present invention is used, compared to when conventional ammonium adipate or ammonium phosphate is used. . As can be understood from this fact, the oxide film formed according to the present invention is a very stable oxide film, and is found to be very useful in reducing leakage current.

Table 3 (a) shows 5 in the life test at 105°C and 35V.
The results of measuring the number of short circuits up to 00 hours are shown.

Below is a blank table (a).The number of shorts shown above is for 10 good LC samples after aging.
This is the result for 0 pieces.

(G) Effects of the Invention As described above, according to the present invention, in an organic semiconductor solid electrolytic capacitor using TCNQ salt, the oxide film on the aluminum foil becomes extremely stable, and leakage current is significantly reduced.

[Brief explanation of drawings]

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 (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. 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, after forming the capacitor element, The anode foil is chemically formed with a solution containing at least one of an alkali metal salt and an alkaline earth metal salt of phosphoric acid, and then heat-treated to remove the anode that is present before the formation of the capacitor element. Alkali metal salt of phosphoric acid on chemical conversion coating of metal,
A method for manufacturing an organic semiconductor solid electrolytic capacitor, comprising applying a chemical conversion film using a chemical liquid containing at least one of alkaline earth metal salts.