JP3459151B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor using a tetracyanoquinodimethane complex (hereinafter, referred to as a TCNQ complex) as a solid electrolyte. is there. [0002] In recent years, with the advancement of electronic information equipment,
Electronic components are required to be smaller and have higher performance. Therefore, in the field of electrolytic capacitors, in order to further downsize compared to electrolytic capacitors impregnated with the driving electrolyte,
A solid electrolytic capacitor using a TCNQ complex as a solid electrolyte has been put to practical use. [0003] Such a solid electrolytic capacitor is generally manufactured as follows. That is, a capacitor element is formed by winding a separator paper between a pair of anode foil and cathode foil made of aluminum or the like, and the element is preheated for a short time. Subsequently, the preheated capacitor element is impregnated with the TCNQ complex that has been heated and liquefied, and then immediately cooled and accommodated in a case. Further, aging is performed by applying a voltage, and defects of the dielectric oxide film generated during the manufacturing process are repaired to obtain a product. However, in the above solid electrolytic capacitor,
Since the fiber has a dense separator paper interposed between the electrode foils, the conduction path of electrons between the electrode foils is extremely reduced.
There is a disadvantage that the SR characteristics are deteriorated. In particular, when a high-temperature load test or a thermal shock test is performed, the ESR characteristics are significantly deteriorated, which has been a problem. In order to solve this problem, prior to impregnating the capacitor element with the TCNQ complex, the capacitor element is left at a high temperature, and the separator paper is fired and carbonized to form voids in the separator paper. It has been considered to secure an electron conduction path between the electrode foils. Specifically, the following method for manufacturing a solid electrolytic capacitor has been proposed. First, before the TCNQ complex is impregnated, the capacitor element is baked at 330 ° C. for 1 hour to carbonize the separator paper. Further, a metal case having an opening is prepared, and the TCNQ complex is put into the case and heated to melt and liquefy the TCNQ complex. The preheated capacitor element is impregnated in the metal case, and then immediately cooled, and the opening of the metal case is filled with resin to house the capacitor element in the metal case. According to such a method for manufacturing a solid electrolytic capacitor, even if separator paper is interposed between the electrode foils,
The capacitor element before the impregnation with the TCNQ complex was 33
By baking at 0 ° C. to carbonize the separator paper, the fibers of the separator paper are thinned, so that large voids can be formed in the separator paper. Therefore, the separator paper can take in a large amount of the TCNQ complex, and an electron conduction path between the electrode foils can be secured. Therefore, the capacitor can obtain excellent ESR characteristics. However, the above-described method for manufacturing a solid electrolytic capacitor has the following problems. That is, if the capacitor element is 3
Since it is fired at a high temperature of 00 ° C. or more for one hour, the anode foil is exposed to the high temperature for a long time. As a result, a defect may occur in the dielectric oxide film formed on the surface of the anode foil. When a defect occurs in the dielectric oxide film on the anode foil surface,
There is a problem that the leakage current of the capacitor becomes extremely large. The present invention has been proposed in order to solve the above-mentioned problems, and an object thereof is to obtain an excellent ESR characteristic by securing an electron conduction path between electrode foils,
An object of the present invention is to provide a method of manufacturing a solid electrolytic capacitor capable of preventing a defect of a dielectric oxide film on a surface of an anode foil and suppressing an increase in leakage current. [0010] In order to achieve the above object, the present invention provides a capacitor element formed by winding a separator paper between a pair of anode foil and cathode foil. After impregnating the cyanoquinodimethane complex, in a method for manufacturing a solid electrolytic capacitor in which the capacitor element is housed in a case, the separator paper is impregnated with an aqueous solution containing borate ions , and the solvent is evaporated.
After being emitted, winding to form a capacitor element, or after forming the capacitor element, impregnated with an aqueous solution containing borate ions in the separator paper, evaporate the solvent, heat treatment after this step, The voids are formed by thinning the fibers of the separator paper. In the method for manufacturing a solid electrolytic capacitor as described above, since the separator paper of the capacitor element is impregnated with an aqueous solution containing borate ions, boric acid oxidizes the separator paper. As a result, each fiber of the separator paper becomes thinner, and a large void can be formed. [0012] Thereby, the separator paper can take in a large amount of the TCNQ complex, and a sufficient electron conduction path between the electrode foils can be secured. Therefore, the capacitor can obtain excellent ESR characteristics. Moreover, since it is not necessary to bake the separator paper at a high temperature for a long time, there is no possibility that a defect occurs in the dielectric oxide film formed on the surface of the anode foil. Therefore, an increase in the leakage current of the capacitor can be suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Structure) FIG. 1 shows an embodiment of the present invention.
This will be specifically described with reference to FIG. In the solid electrolytic capacitor manufactured according to the present embodiment, as shown in FIG. 1, a capacitor element is configured by sandwiching and winding a separator paper 3 between a pair of anode foil 1 and cathode foil 2. More specifically, anode foil 1 is made of aluminum whose surface area is enlarged by etching and then a dielectric oxide film is formed, and cathode foil 2 is made of aluminum whose surface area is enlarged by etching. Have been. The separator paper 3 is made of, for example, fibers 4 mainly composed of Manila hemp. The capacitor element thus constructed is immersed in a 3% aqueous solution of ammonium adipate. Then, by applying a voltage, the dielectric oxide film on the surface of the anode foil 1 damaged by the winding is repaired. Further, the capacitor element is immersed in an aqueous solution containing borate ions, and the separator paper 3 inside the element is sufficiently impregnated with the aqueous solution, and then the solvent is evaporated. Next, the capacitor element is heated. By this heating, an oxidizing effect of boric acid acts on the separator paper 3, the fibers 4 of the separator paper 3 become thinner, and a large void portion 5 is formed. Further, the TCNQ complex is placed in a metal case such as aluminum and heated to be melted and liquefied. The capacitor element is immersed in the metal case to impregnate the capacitor element with the TCNQ complex, and then immediately cooled, the case opening is sealed with epoxy resin, and the capacitor element is sealed in the metal case. Housed in Further, an aging treatment is performed for 120 minutes by applying a rated voltage in a 105 ° C. atmosphere, and a defect of the dielectric oxide film generated in the manufacturing process is repaired to obtain a product. When the separator paper is impregnated with an aqueous solution containing borate ions, the separator paper may be impregnated with the aqueous solution and then wound to form a capacitor element. After the composition, an aqueous solution may be impregnated. Heating after impregnation is performed using TCNQ
Preheating for impregnating the complex may be used as it is, or a separate heating step may be provided if the conditions do not match the preheating. (Example) As an example in the present embodiment as described above, after a capacitor element is formed, this capacitor element is immersed in an aqueous solution containing borate ions.
Preheating was performed at 300 ° C. for 1 minute, and the TCNQ complex was accommodated in a melted and liquefied metal case, and the opening of the case was sealed with an epoxy resin. By changing the solute and the aqueous solution concentration in the aqueous solution containing borate ions in this case, five types of solid electrolytic capacitors (Examples 1 to 5) as shown in Table 1 were manufactured by 100 units. The solute and aqueous solution concentrations of the solution containing borate ions used in each example are as follows.
That is, in Example 1, a 0.5% aqueous phosphoric acid solution was used, in Example 2, a 1% aqueous phosphoric acid solution, in Example 3, a 5% aqueous phosphoric acid solution, and in Example 4, a 1% aqueous phosphoric acid solution was used. Ammonium hydrogen, and in Example 5, 1% potassium dihydrogen phosphate was used. These five types of capacitors have a rating of 16V-3.
Table 1 shows the initial ESR characteristics of the 3 μF sample,
Table 2 shows the characteristic changes after 1000 hours of the high-temperature load test at 105 ° C., and Table 3 shows the characteristic changes by the thermal shock test. Thermal shock test: -55 ° C, 30 minutes to + 105 ° C, 3
100 cycles of 0 minutes were performed. The ESR in the table
Indicates a value at 100 kHz. The characteristics of Conventional Examples 1 and 2 are shown in Tables 1 to 3 as comparison objects of Examples 1 to 5. Conventional examples 1 and 2
Indicates that the capacitor element was not immersed in an aqueous solution containing borate ions.
Each was fired at 00 ° C. for 1 hour, and was otherwise made of the same materials, manufacturing method and structure as in the examples. [Table 1] [Table 2] [Table 3] As apparent from Table 1 above, the initial ESR
The characteristics are small in Examples 1 to 5 and Conventional Example 2, but large in Conventional Example 1. On the other hand, when the firing temperature is 30
Conventional Example 2 at 0 ° C. is extremely large. That is, in the conventional example 2 fired at high temperature, the ESR is good, but the leakage current is extremely poor. In the conventional example 1 fired at low temperature, the leak current is good, but there is a problem in the ESR. As is clear from Tables 2 and 3, Conventional Example 1 has a large initial ESR and changes in ESR after the high-temperature load test and the thermal shock test are each 1.3.
It turns out that it is as large as 1.7 times and 1.7 times. In contrast to Conventional Examples 1 and 2, Embodiment 1
In the case of ５5, the leakage current is good and the initial ESR characteristic is sufficiently small. The change in ESR after the high-temperature load test was within 1.1 times, and the change in ESR in the thermal shock test was 1.2 times.
Within the range, the increase in ESR is small even after the high-temperature load test and the thermal shock test, and good characteristics are exhibited. (Effects) In the present embodiment including the above-described embodiments, the separator paper 3 of the capacitor element is impregnated with an aqueous solution containing borate ions, so that the separator paper 3 has an oxidizing effect of boric acid. Thereby, each fiber 4 of the separator paper 3 becomes thinner, and a large void portion 5 can be formed. Thereby, the separator paper 3 can take in a large amount of the TCNQ complex. As a result, a sufficient electron conduction path between the electrode foils 1 and 2 can be secured, and the capacitor can obtain excellent ESR characteristics. Further, in the present embodiment, a step of firing the capacitor element at a high temperature for a long time to carbonize the separator paper 3 is not required. Therefore,
The anode foil 1 is not exposed to a high temperature for a long time, and no defect occurs in the dielectric oxide film formed on the surface of the anode foil 1. Thereby, an increase in the leakage current of the capacitor can be suppressed. (Other Embodiments) The present invention is not limited to the above embodiment. For example, a calcium borate solution or a solution in which boric acid is dissolved is used as a solution containing borate ions. Even in this case, the same operation and effect can be obtained. As described above, according to the method for manufacturing a solid electrolytic capacitor of the present invention, the separator paper is immersed in an aqueous solution containing borate ions to reduce the fibers of the separator paper. Since large voids can be formed in the separator paper, the separator paper must be sufficiently T
An electron conduction path between the electrode foils can be secured by including the CNQ complex, and the capacitor can obtain excellent ESR characteristics. In addition, since it is not necessary to fire the capacitor element at a high temperature, no defect occurs in the dielectric oxide film on the surface of the anode foil, and an increase in leakage current of the capacitor can be suppressed.

[Brief description of the drawings] FIG. 1 is a sectional view of a main part of an embodiment of the present invention. [Explanation of symbols] 1: Anode foil 2: Cathode foil 3. Separator paper 4: Fiber 5 ... void

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-286110 (JP, A) JP-A-58-123715 (JP, A) JP-A-63-37610 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) H01G 9/00 H01G 9/02 H01G 9/028

Claims (1)

(57) [Claim 1] A capacitor element is formed by winding a separator paper between a pair of anode foil and cathode foil, and the capacitor element is impregnated with a tetracyanoquinodimethane complex. ,
In a method for manufacturing a solid electrolytic capacitor including the capacitor element housed in a case, the separator paper is impregnated with an aqueous solution containing borate ions , and the solvent is evaporated.
Then, after winding to form a capacitor element, or after forming a capacitor element, the separator paper is impregnated with an aqueous solution containing borate ions, the solvent is evaporated, and heat treatment is performed after this step, and the separator is heated. A method for producing a solid electrolytic capacitor, characterized in that a void is formed by thinning paper fibers.