JP2596996B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor having good moisture resistance.

[Conventional technology]

In general, an element of a solid electrolytic capacitor has an oxide film layer formed on an anode substrate made of a valve metal, and a semiconductor layer such as manganese dioxide is formed on the outer surface of the oxide film layer as a counter electrode. In order to further reduce contact resistance, a layer of a conductive paste or the like is provided to form a conductor layer. And
In order to provide heat resistance and moisture resistance, the element of this solid electrolytic capacitor has a resin layer formed of a polymer sealing material such as an epoxy resin or a phenol resin, and is put to practical use.

[Problems to be solved by the invention]

However, in the case of packaging with the above-described sealing material, there is a problem that pinholes are formed in the conductive layer due to the influence of shrinkage of the resin after sealing on the conductive layer. There is a problem that the moisture resistance is deteriorated.

[Means for solving the problem]

The present invention has been made to solve the above-described problems, and a dielectric oxide film layer, a semiconductor layer, and a conductor layer are sequentially formed on the surface of an anode substrate made of a metal having a valve action. When laminating a resin layer on the conductor layer after drying and curing the conductor layer and drying and curing, the method for manufacturing a solid electrolytic capacitor by setting the drying and curing temperature of the conductor layer higher than the drying and curing temperature of the resin layer is there.

Hereinafter, a method for manufacturing the solid electrolytic capacitor of the present invention will be described.

As the valve metal substrate used as the anode of the solid electrolytic capacitor of the present invention, for example, aluminum, tantalum, niobium, titanium and alloys using these as a substrate,
Any metal having a valve action can be used.

The dielectric oxide film layer formed on the surface of the anode substrate may be the oxide layer of the anode substrate itself provided on the surface layer portion of the anode substrate, or may be another dielectric oxide layer provided on the surface of the anode substrate. But a layer composed of an oxide of the anode valve metal itself is particularly desirable. In any case, as a method of providing the oxide layer, a conventionally known method can be used.

Although there is no particular limitation on the composition and manufacturing method of the semiconductor layer used in the present invention, in order to enhance the performance of the capacitor, a conventionally known chemical deposition method using lead dioxide or lead dioxide and lead sulfate as main components is used. It is preferable that the electrode is formed by an electrochemical deposition method.

As the chemical deposition method, for example, a method of chemically depositing from a reaction mother liquor containing a lead-containing compound and an oxidizing agent proposed by the present inventors (JP-A-63-51621). A method of precipitating by electrolytic oxidation in an electrolytic solution containing a high-concentration lead-containing chemical substance (JP-A-62-185307) can be employed.

The conductor layer in the present invention is formed by bringing a conductive paste into contact with the semiconductor layer. As the conductive paste of the present invention, one or more conventionally known conductive pastes can be used.

It is important that the drying and curing temperature of the conductor layer of the present invention be higher than the drying and curing temperature of the resin layer described later. If the temperature is lower than the drying and curing temperature of the resin layer, the produced solid electrolytic capacitor will have insufficient moisture resistance. Although the drying and curing temperature of the conductor layer is lower than the decomposition temperature of the conductive paste to be used and higher than the drying and curing temperature of the resin layer, the optimal drying and curing temperature is determined by preliminary experiments performed in advance.

Next, the resin layer of the present invention is formed by a known method such as dipping, casting, molding, potting, and powder coating using a known polymer such as an epoxy resin or a phenol resin. It is important that the drying and curing temperature is lower than the drying and curing temperature of the conductor layer described above.

[Action]

A dielectric oxide film layer on the surface of the valve metal anode substrate,
When the semiconductor layer and the conductor layer are sequentially formed and the dielectric layer is dried and cured, by setting the drying and curing temperature of the conductor layer higher than the drying and curing temperature of the resin layer laminated on the conductor layer, It is considered that the influence of shrinkage after sealing on the conductor layer can be reduced, and as a result, the number of pinholes in the conductor layer is reduced.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Examples 1 to 4 Comparative Examples 1 to 4 After an aluminum foil having a length of 1 cm and a width of 1 cm was used as an anode and the surface of the foil was electrochemically etched by an alternating current, an anode terminal was caulked to the etched aluminum foil. Lead wire was connected. Next, an oxide film of alumina was formed by electrochemical treatment in an aqueous solution of phosphoric acid and aluminum phosphate to obtain a low-pressure etched aluminum conversion foil (about 10 μF / cm ² ). The part of this chemical conversion foil other than the anode lead wire was immersed in an aqueous solution of lead acetate trihydrate at 1.0 mol / mol. Electrolysis was carried out at 15 V using this chemically formed foil on the anode side and a normal unetched aluminum foil on the cathode side. After 3 hours, the semiconductor layer made of lead dioxide formed on the chemical conversion foil was washed with water to remove unreacted substances, and then heated at 120 ° C.
For 1 hour under reduced pressure. On the other hand, a commercially available silver paste prepared separately was applied on the semiconductor layer to form a conductor layer. 240 elements thus prepared up to the conductor layer were prepared, and 30 points were allocated to each of the test examples of Examples 1 to 4 and Comparative Examples 1 to 4 under the conditions shown in Table 1. Dry curing was performed. Next, in Examples 1 and 2 and Comparative Examples 1 and 2, the curing temperature was 165 ° C.
Nippon Pernox Co., Ltd. powder epoxy resin PCE2
Powder coating was performed 5 times at 165 ° C. at 73 to form a resin layer.
In Examples 3 and 4 and Comparative Examples 3 and 4, dipping was performed once with a liquid epoxy resin XNR1218 manufactured by Nippon Chiga Geigy Co., Ltd. having a curing temperature of 150 ° C., and drying and curing were performed at 150 ° C. for 2 hours. Was formed to produce a solid electrolytic capacitor.

Examples 5 to 6 Comparative Examples 5 to 6 The same chemical conversion foil as in Example 1 was immersed in a mixture of an aqueous solution of lead acetate trihydrate 2.4 mol / and an aqueous solution of ammonium persulfate 4 mol / 30 at 60 ° C. The semiconductor layer composed of lead dioxide and lead sulfate formed on the dielectric oxide film layer was sufficiently washed with water and then dried under reduced pressure at 120 ° C. for 1 hour. The formed semiconductor layer was composed of lead dioxide and lead sulfate, and it was confirmed by X-selective analysis and infrared spectroscopic analysis that about 25% by weight of lead dioxide was contained. Next, 120 elements each having a conductor layer formed in the same manner as in Example 1 were prepared, and 30 points were assigned to each of the test examples of Examples 5 and 6 and Comparative Examples 5 and 6, and the conditions shown in Table 1 were used. To dry and cure the conductor layer. Next, a resin layer was formed under the same conditions as in Example 1 to produce a solid electrolytic capacitor.

Examples 7 to 8 In the same manner as in Examples 1 to 4, two sets of 30 elements formed up to the conductor layer were prepared, and in Example 7, one of them was set at Showa Kogaku Co., Ltd. ) Phenolic resin B
Dipping was performed with RS-330, and drying and curing were performed at 160 ° C. for 2 hours to form a resin layer, thereby producing a solid electrolytic capacitor. Further, in Example 8, the remaining one set of devices was dipped with a diallyl phthalate resin dup tote manufactured by Toto Kasei Co., Ltd. having a curing temperature of 160 ° C.
For 3 hours to form a resin layer to produce a solid electrolytic capacitor.

Example 9 In Example 1, the conductor layer was composed of 35% by weight of silver powder and 53% by weight of lead dioxide powder.
% And an acrylic resin of 12 wt%, and a solid electrolytic capacitor was produced in the same manner as in Example 1 except that drying and curing were performed at 180 ° C. for 2 hours.

Example 10 Example 1 was the same as Example 1 except that the conductor layer was formed of a paste composed of 50% by weight of silver-coated copper powder, 35% by weight of silver powder and 15% by weight of fluororesin, and was dried and cured at 170 ° C. for 2 hours. A solid electrolytic capacitor was produced in the same manner as described above.

Table 2 shows the initial characteristics and the performance after the pressure cooker test (abbreviated as PCT) of the solid electrolytic capacitors produced in Examples 1 to 10 and Comparative Examples 1 to 6, and the moisture resistance was evaluated.

From the results in Table 2, it can be seen that the performance after PCT of the solid electrolytic capacitor element in which the drying and curing temperature of the conductor layer was higher than the drying and curing temperature of the resin layer was significantly improved as compared with the comparative example.

[Effects of the Invention] As described above, according to the method for manufacturing a solid electrolytic capacitor of the present invention, since the dry curing temperature of the conductor layer is higher than the dry curing temperature of the resin layer, the solid An electrolytic capacitor can be manufactured.

Claims (1)

(57) [Claims] 1. A dielectric oxide film layer, a semiconductor layer, and a conductor layer are sequentially formed on the surface of an anode substrate made of a metal having a valve action, and the conductor layer is dried and cured. When laminating a resin layer on the layer and performing drying and curing,
A method for manufacturing a solid electrolytic capacitor, wherein a drying and curing temperature of the conductor layer is higher than a drying and curing temperature of the resin layer.