JPH0338011A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve yield in manufacture without causing defective leakage currents by applying constant voltage for a fixed time during a process in which a capacitor element with an anode body element, to which a solid electrolytic layer composed of a conductive high molecule is formed, is sheathed by a resin for sheathing. CONSTITUTION:A capacitor element 10 is coated with a thermo-setting epoxy resin as a resin for sheathing through dipping, constant voltage is applied between an anode leader 2 and a cathode lead 9, the capacitor element 10 is introduced into a resin curing furnace, and aging treatment is executed while the capacitor element 10 is cured. That is, since a process in which constant voltage is applied for a fixed time is provided in a sheathing process, aging treatment simultaneously progresses in the process of curing the resin. Restoration progresses during the time of the small damage of a dielectric oxide film generated due to mechanical stress at the time of resin curing, thus preventing the elevation of the level of leakage currents. Accordingly, defective leakage currents in a resin sheathing process is reduced, thus decreasing manhours.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer as a solid electrolyte, and particularly to a method for aging the capacitor.

Conventional technology Solid electrolytic capacitors, which use tantalum or aluminum as electrodes and manganese dioxide as a solid electrolyte, are generally coated with resin, and are manufactured by dipping, botting, and casting.

The exterior is usually formed using methods such as injection molding or powder coating.

In general, in solid electrolytic capacitors, leakage current tends to increase due to mechanical stress during resin packaging, and in order to reduce this, a voltage is applied between the two electrode terminals after the packaging process.
It is necessary to provide a so-called aging process, and this process has been used to reduce leakage current.

In addition, in the case of solid-state capacitors that use conductive polymers as the solid electrolyte, since the solid electrolyte is a thin film of polymer, stress caused by thermal deformation during resin curing tends to directly damage the dielectric oxide film. is believed to be greater than manganese dioxide, which results in increased leakage current.

In order to reduce this increased leakage current, for example, as shown in Japanese Patent Application Laid-Open No. 64-32621, aging treatment is carried out in water or in high humidity of 80% or more relative humidity after resin packaging. A method that includes a step of applying a voltage between both electrode terminals has been disclosed.

Problems to be Solved by the Invention However, as mentioned above, in cases where the dielectric oxide film is severely damaged due to mechanical stress during resin sheathing and the level of leakage current has increased, aging treatment may be performed after resin sheathing. However, even if this method is used, the level of leakage current cannot be sufficiently reduced, and as a result, leakage current defects may occur, which causes a decrease in manufacturing yield.

In addition, after the resin exterior process, an aging process is performed in water or in high humidity, so this aging process is difficult.

It is necessary to provide a process for drying moisture from the capacitor element afterwards, and it is also necessary to control the atmosphere, which results in an increase in the number of steps and the problem of complication.

An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor that solves these problems.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a solid electrolytic capacitor of the present invention includes forming an anodized film on an anode body made of a valve metal and a solid electrolyte layer made of a conductive polymer. During the process of equipping the formed anode body element and packaging the capacitor element including the anode body element with an exterior resin,
This method includes a step of applying a constant voltage for a certain period of time.

Effects According to the method for manufacturing a solid electrolytic capacitor of the present invention described above, a step of applying a constant voltage for a certain period of time is provided during the step of packaging with the resin for packaging, so that the aging treatment is simultaneously performed during the process of curing the resin. As a result, the repair progresses while the damage to the dielectric oxide film caused by mechanical stress during resin curing is small, so that the level of leakage current does not increase. Therefore, leakage current defects in the resin packaging process are significantly reduced.

Furthermore, since aging treatment can be performed simultaneously during the resin exterior packaging, the number of man-hours can be reduced, and thereby the complicated aging treatment in water or high humidity can be eliminated.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Example 1) First, as shown in Fig. 1, an anode lead 1II made of aluminum was attached to a part of an anode body 1 of 7m x 1O made of aluminum foil electrolytically etched with hydrochloric acid or the like.
2 were welded, and an anodic oxide film 3 was formed by constant voltage anodization at 70 V in an aqueous solution of 3% ammonium adipate.

Next, the anode body 1 is immersed in a manganese nitrate aqueous solution with a specific gravity of 1.36, and thermally decomposed at 205°C for 5 minutes to form a manganese oxide layer 4 on the anodic oxide film 3, and further undergoes a thermal decomposition reaction. In order to repair the defective parts of the oxide film that had been destroyed, reconversion was performed again in a conversion solution containing 3% ammonium adipate.

A solid electrolyte layer 6 made of a conductive polymer was formed on the surface of the anode element 5 thus produced by the following method. That is, 0.1 mol/e of sodium triisopropylnaphthalene sulfonate and 0.2 wt% of polyacrylic acid were used as supporting electrolytes.

The anode element 5 on which the manganese oxide layer 4 was formed was immersed in a polymerization solution consisting of an aqueous solution containing 0.5 mol/e of virol as a monomer. Then, a constant current of 2 mA was applied for 30 minutes, using the stainless steel electrode arranged so as to lightly contact the manganese oxide layer 4 on the surface of the anode body element 5 as an anode, and the stainless steel plate in the polymerization solution as a cathode. A solid electrolyte layer 6 made of a conductive polymer of polypyrrole was formed on the surface of the body element 1 by electrolytic polymerization.

Furthermore, a graphite layer 7. The silver paint layers 8 are applied and dried to form one after another, and furthermore, by soldering lead wires on the silver paint layers 8, cathode leads &! I pulled out a 9.

The structure of the capacitor element 10 constructed as described above is shown in FIGS. 2(a) and 2(b).

The capacitor element 10 thus constructed is covered with an exterior resin, and after coating the capacitor element 10 with thermosetting resin by dipping as the exterior resin, the anode is drawn out. A voltage of 20V is applied between the lead wire 2 and the cathode lead wire 9, and 1
The resin was placed in a resin curing oven at 05° C., and aged for 2 hours.

Fifty such solid electrolytic capacitors with a rating of 16V were manufactured, and the average values of their initial characteristics and yields are shown in Table 1. Further, the change in leakage current value over time during this aging process is shown in FIG. 3 together with Comparative Example 1. This third
As is clear from the figure, in Example 1, in which aging treatment was performed at the same time as resin curing, there was a temporary increase in leakage current and subsequent recovery every time mechanical stress was applied during resin curing. , and it is clearly seen that the repair is performed while the dielectric oxide film is only slightly damaged.However, in the aging treatment after the resin curing (Comparative Example 1), the level of leakage current was high from the beginning, and the repair was not completed. I know that it won't happen.

(Example 2) The process up to the production of the capacitor element 10 is the same as in Example 1. After coating the capacitor element 10 with an ultraviolet curing epoxy resin as the exterior resin by dipping, the anode lead wire is attached as in Example 1. 20 between 2 and cathode lead wire 9
The material was placed in a UV curing oven without applying a voltage of V, and was subjected to an aging treatment while being cured for about 3 minutes. After this, 10
Further aging treatment was continued at 5°C. In this way, 50 solid electrolytic capacitors with a rating of 16V were manufactured, and the average values of their initial characteristics and yields are shown in Table 1.

(Example 3) A solid electrolytic capacitor was manufactured in the same manner as in Example 1, except that the exterior resin was a thermosetting phenolic resin.
Table 1 shows the average value of initial characteristics and yield.

(Example 4) The process up to the production of the capacitor element 10 was the same as in Example 1. As the exterior resin, an epoxy resin for powder coating was repeatedly applied to the capacitor element 10 10 times using a powder coater, and then cured. After that, as in Example 1, while applying a voltage of 20V between the anode lead wire 2 and the cathode cooler 1419,
The resin was placed in a resin curing oven at 05° C. and was cured for 1 hour while being subjected to aging treatment. Thereafter, resin curing was continued for an additional hour at 105°C. In this way, 50 solid electrolytic capacitors with a rating of 16V were manufactured, and the average values of their initial characteristics and yields are shown in Table 1.

(Comparative Examples 1 to 4) Examples 1 to 4 except that the aging treatment was not performed by applying a voltage during resin curing, and the aging treatment was performed by applying a voltage of 20 V for 2 hours at 105 ° C. after the resin curing. Fifty solid electrolytic capacitors were manufactured in exactly the same manner as in Example 4, and the average value of initiality I1 and yield are shown in Table 1.

(Leaving space below) Table 1 Initial characteristics and yield of solid electrolytic capacitors As is clear from Table 1, the leakage current level of capacitors in which voltage was applied during the resin curing process and aging treatment was performed at the same time. It can be seen that the yield is almost 100%.

In each of the above embodiments, aluminum was used as the valve metal constituting the anode body 1.
A similar study was conducted using tantalum as the valve metal, and results similar to those of the above embodiments were obtained.

Furthermore, in the above embodiment, polypyrrole was used as the conductive polymer forming the solid electrolyte layer 6, but as a conductive polymer other than polypyrrole, studies were conducted using polythiophene, polyfuran, or polyaniline. Also, results with exactly the same tendency as in each of the above-mentioned Examples were obtained.

Effects of the Invention As is clear from the description of the above embodiments, according to the present invention,
This is an excellent technology that not only reduces the leakage current level of solid electrolytic capacitors that use conductive polymers as solid electrolytes and improves the yield of finished products, but also reduces the number of steps and time. It is effective. In other words, by providing a process of applying a constant voltage for a certain period of time during the process of encasing the capacitor element with an exterior resin, the aging process proceeds at the same time as the resin hardens, and the mechanical stress caused by the resin curing process causes the aging process to proceed simultaneously. Since the repair progresses to a tube with less damage to the dielectric oxide film that has occurred, and the level of leakage current does not increase, leakage current defects in the resin sheathing process can be significantly reduced. In addition, since aging treatment can be performed simultaneously during the resin exterior, the number of man-hours can be reduced, and this has the excellent effect of eliminating the complicated aging treatment in water or at high temperatures. be.

[Brief explanation of drawings]

Figure T%1 is a perspective view showing the structure of the anode body of the solid electrolytic capacitor used in one embodiment of the present invention, and Figure 2 shows the structure of the capacitor element of the same solid electrolytic capacitor.
) is a cross-sectional view, (b) is a longitudinal cross-sectional view, and FIG. 3 is a graph showing changes in leakage current value over time during aging treatment. ■・・・Anode body, 3...Anodized film,
4... Manganese oxide layer, 5... Anode element, 6... Solid 'Fi desolate layer, 10...
...Capacitor element.

Claims (5)

[Claims] (1) Equipped with an anode element in which an anode body made of a valve metal is coated with an anodized film and a solid electrolyte layer made of a conductive polymer is formed, and the capacitor element including this anode body element is exteriorized with an exterior resin. A method for manufacturing a solid electrolytic capacitor, comprising a step of applying a constant voltage for a certain period of time during the step of applying a constant voltage. (2) Manufacturing a solid electrolytic capacitor according to claim 1, wherein the exterior resin is a thermosetting resin or a photocurable resin such as an epoxy resin, a phenol resin, a urea resin, or a xylene resin. Method. (3) The time during which constant voltage is applied during the process of sheathing the capacitor element with the sheathing resin is part or all of the time from the beginning of the heat curing process or photocuring process of the sheathing resin to the completion of curing the resin. A method for manufacturing a solid electrolytic capacitor according to claim 1, characterized in that: (4) The conductive polymer is polypyrrole, polythiophene,
A method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is made of either polyfuran or polyaniline. (5) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the valve metal is aluminum or tantalum.