JP2003115419A - Solid electrolytic capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which can secure the conducting path of a solid electrolyte by making the fibers of separator paper provided in a capacitor element thinner in thickness and is improved in initial characteristic, by surely impregnating the element with the solid electrolyte and the characteristics of which are little deteriorated even when the capacitor is subjected to high-temperature load tests and thermal shock tests. SOLUTION: The capacitor element is constituted by rolling two pieces of anode foil and cathode foil respectively fitted with lead-out terminals by sandwiching the separator paper between the two pieces of foil. Then the solid electrolytic capacitor is manufactured by heat-baking the separator paper after the element is impregnated with a dehydrating agent or oxidizing agent. After the separator paper is baked, the capacitor element is impregnated with the solid electrolyte and sealed in a case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a solid electrolytic capacitor using a solid electrolyte such as a tetracyanoquinodimethane (hereinafter referred to as TCNQ) complex and a method for producing the same, particularly impregnating separator paper with a dehydrating agent or an oxidizing agent, It is characterized by thinning the fibers of the separator paper by firing at a lower temperature than before, with the purpose of providing a solid electrolytic capacitor and a manufacturing method thereof that can secure a conduction path for a solid electrolyte. is there.

[0002]

2. Description of the Related Art With the sophistication of electronic information devices in recent years,
As electronic components are required to be smaller and have higher performance, solid electrolytic capacitors using solid electrolytes such as TCNQ complex that can be made smaller than electrolytic capacitors impregnated with a driving electrolyte have been put into practical use. . In these electrolytic capacitors, a separator element is sandwiched between a pair of electrode foils such as aluminum and wound to form a capacitor element, and this preheated capacitor element is melted and liquefied in a case to form a TCNQ complex. After dipping and impregnation and immediately cooling, the case opening was sealed with an epoxy resin or the like. A voltage was applied to this and aging was performed to repair defects in the dielectric oxide film of the electrode foil, which occurred during the manufacturing process, to obtain a product.

However, in such a solid electrolytic capacitor using a solid electrolyte such as a TCNQ complex, since the separator paper is interposed between the pair of electrode foils as described above, the conduction path of the solid electrolyte is extremely large. However, there is a problem that the ESR characteristic is deteriorated. This deterioration becomes remarkable when tests such as high temperature load and thermal shock are conducted.

In order to solve this problem, before impregnating a solid electrolyte such as a TCNQ complex, the capacitor element is left at a high temperature to bake the separator paper, and the fibers of the separator paper are thinned to remove the TCNQ complex or the like. It has been attempted to facilitate the impregnation of the solid electrolyte. For example, a capacitor element is fired at 330 ° C., and the capacitor element that has been heated in advance is stored in a case where the TCNQ complex is melted and liquefied, and immediately cooled,
The case sealing part was filled with resin and sealed.

However, in the solid electrolytic capacitor having such a structure, the dielectric oxide film formed on the surface is defective due to the anode foil being exposed to high temperature during firing, resulting in a significantly large leakage current of the capacitor. Had the problem of becoming.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, T
In a solid electrolytic capacitor impregnated with a solid electrolyte such as a CNQ complex, the dielectric oxide film of the anode foil is defective due to the high temperature during firing of the capacitor element, which causes an increase in leakage current.

The present invention has been made in order to eliminate the above-mentioned drawbacks. The separator paper before firing is impregnated with a dehydrating agent or an oxidizing agent and then fired at a low temperature of 290 ° C. or lower, and the capacitor element is solidified. It is an object of the present invention to provide a solid electrolytic capacitor capable of improving the ESR characteristics at the initial stage after high temperature load or thermal shock by impregnating with an electrolyte, and suppressing the increase of leakage current by reducing the firing temperature of the capacitor element. To do.

[0008]

A solid electrolytic capacitor according to claim 1 of the present invention comprises an anode foil, a cathode foil constituting a capacitor element, a separator paper impregnated with a dehydrating agent or an oxidizing agent and baked. It is characterized by comprising a solid electrolyte impregnated in the capacitor element, a case accommodating the capacitor element, and a resin sealing an opening of the case.

According to a second aspect of the present invention, there is provided a solid electrolytic capacitor manufacturing method, wherein separator paper is sandwiched between an anode foil and a cathode foil to which lead terminals are attached and wound to form a capacitor element, and a dehydrating agent is added to the capacitor element. Alternatively, it is obtained by impregnating with an oxidant and then heating to sinter the separator paper, impregnate the capacitor element with a solid electrolyte and seal the case.

According to the third and fourth aspects of the present invention, the dehydrating agents according to the first and second aspects are oxalic acid, metaphosphoric acid, polyphosphoric acid and acetic anhydride, and the oxidizing agents are ammonium nitrate and acetic acid peroxide. , And is characterized by being para-nitrophenol.

[0011]

The inventors examined firing of the capacitor element, and performed firing after impregnating the separator paper with the dehydrating agent or oxidizing agent before firing, as compared with firing without impregnating the dehydrating agent or oxidizing agent. We have found out that the effect of firing can be obtained at low temperature. As a result of such low temperature firing, it was found that the ESR characteristic can be improved and the leakage current characteristic is not deteriorated. In detail, if the separator paper is baked after impregnating it with a dehydrating agent or an oxidizing agent, even if the baking temperature is 290 ° C. or lower,
It has been found that the fibers of the separator paper become thin as in the case of firing at a high temperature of 300 ° C. or higher without impregnation. As a result, a conducting path for the solid electrolyte such as TCNQ complex is secured in the separator paper.
It was possible to obtain a solid electrolytic capacitor having good characteristics and a small leakage current.

[0012]

EXAMPLES The solid electrolytic capacitor of the present invention will be described below with reference to examples.

Example A Lead-out terminals were attached to an anode foil made of an aluminum foil having a dielectric oxide film formed thereon after the surface area was enlarged by etching, and a cathode foil made of an aluminum foil similarly having an enlarged surface area. A separator paper made of a fiber mainly composed of Manila hemp was sandwiched between the anode foil and the cathode foil and wound to form a capacitor element. This capacitor element is dipped in an aqueous solution containing 3% by weight of oxalic acid which acts as a dehydrating agent to impregnate the separator paper inside the capacitor element, and then the solvent is evaporated to leave it at 290 ° C. for 1 hour to remove the separator paper. Baked. Next, the capacitor element was immersed in a 3 wt% aqueous solution of ammonium adipate and a voltage was applied to repair the dielectric oxide film damaged by the winding when forming the capacitor element. A TCNQ complex was used as a solid electrolyte, and it was heated in a case made of aluminum to be melted and liquefied.
Immerse the capacitor element that has been heated for 0 seconds, and
Impregnated with Q complex. Immediately after the impregnation, it was cooled and the case opening was sealed with an epoxy resin to produce a capacitor.

A rated voltage was applied to this capacitor in an atmosphere of 105 ° C. to perform aging treatment for 120 minutes.

In the above steps, the steps of immersing the capacitor element in a 3 wt% aqueous oxalic acid solution to impregnate the separator paper inside the capacitor element and evaporating the solvent are the same, and the time for firing the separator paper is the same. Five hundred types of capacitors each having a different temperature were manufactured and used as samples. In addition,
The capacitor rating is 16V-33μF.

The initial characteristics of the thus-prepared sample are shown in Table 1 below.
Table 2 shows the results of the high temperature load test that was left for 3 hours at -55 ° C.
One cycle consists of 0 minutes to + 105 ° C for 30 minutes, and
Table 3 shows the results of the thermal shock test in which the property changes after repeating 0 cycles were observed. In addition, in the reference example 1 and the conventional example 1,
The capacitor element was fired without being immersed in a 3 wt% oxalic acid aqueous solution, and was made of the same material, manufacturing method, and constitution as those of the examples except that the firing was performed for 1 hour at temperatures of 280 ° C. and 300 ° C., respectively. It is a thing.

The ESR in the table shows the value at 100 kHz.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

As is clear from Table 1, the ESR is small in the embodiment and the conventional example 1, but is large in the reference example 1 and the leakage current is extremely large in the conventional example 1. ESR in Reference Example 1
Was further increased by the high temperature load test and the thermal shock test, and the values were 1.3 times and 1.9 times, respectively. On the other hand, in the examples, the values were 1.1 times after the high temperature load test and 1.2 times or less after the thermal shock test.

From the above phenomenon, in the high temperature firing as in Conventional Example 1, the ESR is good, but the leakage current is extremely bad,
It can be said that low temperature firing as in Reference Example 1 has a good leakage current but has a problem in ESR.

On the other hand, in the examples, even if the firing temperature is the same as or lower than that of the reference example 1, both the leakage current and the ESR are small and the change in the values is small even after the high temperature load test and the thermal shock test. Got This is because, as described above, as a result of the thinning of each fiber of the separator paper, the conduction path of the TCNQ complex in the separator paper is secured.

In the above embodiment, the case where oxalic acid was used as the dehydrating agent was described, but the same result can be obtained by using metaphosphoric acid, polyphosphoric acid, acetic anhydride and other dehydrating agents. These metaphosphoric acid (Example 6), polyphosphoric acid (Example 7), acetic anhydride (Example 8)
An example in which a 3 wt% aqueous solution of is used as a dehydrating agent solution will be described below. The capacitor rating, the number of samples, the material, the manufacturing method, and the configuration are the same as those in Examples 1 to 5, Table 4 shows the initial characteristics, and Table 5 shows the high temperature load test 1000.
The characteristics after h, and Table 6 shows the characteristics after the thermal shock test.

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

As is clear from Tables 4 to 6, in Examples 6, 7 and 8 as well, good results almost similar to those of the examples shown in Tables 1 to 3 were obtained.

Example B In Example A, the case where the separator element was impregnated with a dehydrating agent to thin the fibers and the capacitor element was fired was described. In Example B, an example will be described in which an oxidizing agent is used instead of the dehydrating agent, and the capacitor element is fired to thin the fiber. That is, a capacitor element manufactured in the same manner as in Example A was dipped in an aqueous solution containing 3% by weight of nitric acid acting as an oxidant to impregnate the separator paper inside the capacitor element, and then the solvent was evaporated.
The separator paper was baked by leaving it at 90 ° C. for 1 hour. Thereafter, in the same manner as in Example A, a capacitor having a rating of 16 V-33 μF was used by changing the firing temperature and firing time of the separator paper.
100 kinds each were produced.

Table 7 shows the initial characteristics of these samples, Table 8 shows the results of the high temperature load test, and Table 9 shows the results of the thermal shock test. It should be noted that the reference example 1 and the conventional example 1 are the same as those in the above-mentioned example A.

The ESR in the table shows the value at 100 kHz.

[0032]

[Table 7]

[0033]

[Table 8]

[0034]

[Table 9]

The results in Tables 7 to 9 are almost the same as in Example A.

In the above embodiments, nitric acid was used as the oxidizing agent. However, nitric acid-related compounds such as potassium nitrate and ammonium nitrate, peroxides, nitro compounds such as nitrobenzene and para-nitrophenol, and other oxides were used. Even if it does, the same result can be obtained.

Next, an example in which a 3 wt% aqueous solution of ammonium nitrate (Example 14), acetic acid peroxide (Example 15) and para-nitrophenol (Example 16) was used as the oxidizing agent as the oxidizing agent This will be described below. In addition,
The capacitor rating, the number of samples, the material, the manufacturing method, and the configuration are the same as those in Examples 9 to 13, and Table 10 shows the initial characteristics,
Table 11 shows the characteristics after the high temperature load test for 1000 hours, and Table 12 shows the characteristics after the thermal shock test.

[0038]

[Table 10]

[0039]

[Table 11]

[0040]

[Table 12]

As is clear from Tables 10 to 12, Examples 14, 15, and 16 also obtained substantially the same good results as the Examples shown in Tables 7 to 9 above.

[0042]

As described above, according to the present invention, each fiber of the separator paper can be made thin by impregnating the separator paper with a dehydrating agent or an oxidizing agent and then firing it. The voids are increased, and a sufficient conduction path is ensured when the capacitor element is impregnated with a solid electrolyte such as a TCNQ complex. Therefore, since the solid electrolyte is surely impregnated into the capacitor element, the increase in ESR value is suppressed even when the initial characteristics of the capacitor are subjected to the high temperature load test and the thermal shock test, and other characteristics are also little changed. A solid electrolytic capacitor having good characteristics can be provided.

Claims (4)

[Claims] 1. An anode foil and a cathode foil constituting a capacitor element, a separator paper impregnated with a dehydrating agent or an oxidizing agent and baked, a solid electrolyte impregnated in the capacitor element, and a case accommodating the capacitor element. , A solid electrolytic capacitor made of a resin in which the opening of the case is sealed. 2. A separator paper is sandwiched between an anode foil and a cathode foil to which lead-out terminals are attached and wound to form a capacitor element, and the capacitor element is impregnated with a dehydrating agent or an oxidizing agent and then heated to separate the separator paper. And a solid electrolyte is impregnated into the capacitor element to seal the case in a case. 3. The solid electrolytic capacitor according to claim 1, wherein the dehydrating agent is oxalic acid, metaphosphoric acid, polyphosphoric acid, and acetic anhydride, and the oxidizing agent is ammonium nitrate, peracetic acid, and paranitrophenol. . 4. The dehydrating agent is oxalic acid, metaphosphoric acid, polyphosphoric acid, acetic anhydride, and the oxidizing agent is ammonium nitrate.
The method for producing a solid electrolytic capacitor according to claim 2, wherein the acetic acid peroxide is para-nitrophenol.