JPS6018137B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solid electrolytic capacitor, and particularly aims at reducing defects caused by reconversion treatment of a capacitor element performed after a semiconductor layer forming process. be.

In general, solid electrolytic capacitors have a capacitor element A made by press-molding and sintering a metal powder that has a valve action, such as tantalum, niobium, or aluminum, into a cylindrical shape, as shown in Figure 1. The first external lead member C is welded to the protruding part of the anode lead B, and the second external lead member D is oxidized to the circumferential surface of the capacitor element A. The capacitor element A is soldered to the electrode lead layer G formed through the layer E and the semiconductor layer F, and then the entire circumferential surface of the capacitor element A is coated with a resin material. Incidentally, on the surface of this capacitor element A, an oxide layer E as a dielectric is formed by chemical conversion treatment, and a semiconductor layer F such as manganese dioxide is further formed on top of the oxide layer E. In, 200-400q
Since the heat treatment of 0 is performed, the oxide layer E tends to deteriorate and the leakage current characteristics are impaired.

Therefore, in the past, for example, as shown in FIG.
The reconversion treatment is performed by applying a DC voltage so that the reconversion liquid is positive and the reconversion liquid is negative.

This treatment repairs most of the oxide layer E in the capacitor element A, making it possible to obtain a high quality capacitor. However, in the capacitor element A where the oxide layer E is severely degraded during the semiconductor layer forming process, the oxide layer E is not repaired.
On the contrary, the application of the reformation voltage further destroys the oxide layer E, causing an excessive amount of current to flow intensively.

Such a capacitor element A completely loses its function as a capacitor and becomes defective, but capacitor elements A located around it also become defective due to deterioration of withstand voltage characteristics after production, and when an oxide layer is formed. The higher the ratio of the reformation voltage to the voltage of
The defect rate also increases. The cause of this is not clear, but capacitor element A is located near capacitor element A through which an excessive current flows.
Since the outer surface of the semiconductor layer F is discolored to blackish brown, it is thought that manganese ions and the like are released from the manganese dioxide used as the semiconductor layer F and adhered thereto, thereby deteriorating the characteristics.

Normally, the re-formation voltage must be set lower than the formation voltage due to process deterioration of the oxide layer E, but the closer it can be to the formation voltage, the better the characteristics of the capacitor element A that will remain as a good product. The grade is higher, which is preferable.

However, as mentioned above, some of the capacitor elements A become defective during the reconstitution process, and this may cause even more defects to occur.
Since the re-formation voltage is unavoidably set at a low voltage that can suppress the occurrence of such defects as much as possible, there is a problem that it is difficult to obtain a capacitor with a higher characteristic grade.

In view of these points, the present invention provides a method for manufacturing a solid electrolytic capacitor that can minimize the adverse effects on surrounding capacitor elements even if a specific capacitor element becomes defective during reconversion treatment. , one manufacturing method will be explained below with reference to FIGS. 3 to 6.

First, as shown in FIG. 3, a metal wire having a valve action is attached as an anode lead 2 to a capacitor element 1 which is formed by press-molding a metal powder having a valve action into a cylindrical shape and solidifying it.

Then, this capacitor element 1 is suspended from a holder 3 made of a band-shaped metal plate by fixing the upper end portions of the anode leads 2 at a constant pitch interval, thereby forming a band-shaped component 4. Then, an oxide layer 5 and a semiconductor layer 6 are sequentially formed on the surface of the capacitor element 1 by a conventional method. Next, as shown in FIG. 4, the entire circumferential surface of the capacitor element 1 is covered with a member 7 having at least thermoplasticity and conductivity.
Cover so that it is formed. Next, as illustrated in FIG.
is brought into contact with a reconstitution liquid 9 such as an aqueous solution, such as an aqueous phosphoric acid solution. In this state, when a DC voltage is applied to the holder 3 and the electrode plate 1 so that the holder 3 has a positive voltage and the electrode plate 10 has a negative voltage, each capacitor element 1 is reconstituted. In this state, if the oxide layer 5 of a specific capacitor element 1 is destroyed and an excessive current flows, the hanging portion 7a of the member 7 will melt as shown by the dotted streamlines due to the heat generated by the capacitor element 1. As a result, the electrical circuit of the capacitor element 1 to the reconversion liquid 9 is opened, and an adverse effect on the surrounding capacitor elements 1 can be prevented. Next, as shown in FIG. 6, the strip 4 is placed in a container 11 so that the condenser element 1 is completely immersed in hot water 12.
Then, the backing material 7 attached to the circumferential surface of the capacitor element 1 is melted and completely removed. Hereinafter, a solid electrolytic capacitor is obtained by a conventional method. In this way, when the capacitor elements 1 are subjected to reconversion treatment, at least the thermoplastic material 7 is applied to the entire circumferential surface of each capacitor element 1, and only the hanging portions 7a thereof are reconstituted. Since it is in contact with the liquid 9, even if a specific capacitor element 1 generates heat due to the destruction of the oxide layer 5, the contact with the reconversion liquid 9 is cut off by melting and removing the hanging portion 7a. . For this purpose, a specific capacitor element 1
It is possible to avoid concentration of the re-formation current of the capacitor elements 1, and re-formation processing of other capacitor elements 1 can be performed reliably. Furthermore, since the capacitor element 1 is coated with the thermoplastic material 7, even if a large amount of manganese ions are generated when a failure occurs, it is possible to prevent them from adhering to the surrounding capacitor element 1.

For this reason, it is possible not only to reduce the occurrence of defects in the re-forming process, but also to prevent adverse effects on the characteristics. In particular, if the reconstitution voltage is made higher than normal, some capacitor elements 1 will become defective during the reconstitution treatment, but it will be able to withstand the reconstitution treatment as it will prevent any adverse effects on the surrounding capacitor elements 1. The characteristic grade of capacitor element 1 can be significantly improved.

Moreover, by setting the characteristic grade to the same level as the conventional one, the amount of metal parts constituting the capacitor element 1 can be reduced by that amount, and costs can be effectively reduced.

Furthermore, the capacitor element 1 is coated with a thermoplastic coating 7 prior to reconversion treatment.
It may be melted by heating to about 100 qo, and can be easily removed by heating to such a temperature after reconversion treatment.

In particular, if pure water is used to remove the filler 7, the condenser element 1 can be cleaned at the same time as the filler 7 is removed, which simplifies the work. Next, specific examples will be described.

Example 1 An oxide layer (T
a205) is formed.

This capacitor element is immersed in a manganese nitrate solution, sufficiently impregnated, and then pulled up and heat treated to form a manganese dioxide layer (semiconductor layer) on the oxide layer. Meanwhile, 100cc of pure water, 5 crabs of potassium nitrate (KNQ),
Heat the mixed agar to 70-80 qo and stir until it becomes transparent. Then, by immersing the capacitor element in this electrolytic solution and pulling it up, the entire circumferential surface of the capacitor element is covered with a gel-like electrolyte (thermoplastic member). Note that a hanging portion of about three ribs is formed on the bottom surface of the capacitor element. This capacitor element is soaked in a phosphoric acid aqueous solution (reforming solution) so that only a part of the dripping part of the gel electrolyte comes into contact (see Figure 5).
do. In this state, the capacitor elements are divided into two groups, and the re-forming voltage of one group is set to 50% of the forming voltage, and the other group is set to 70% for re-forming treatment. After that, add 100 capacitor elements.
The gel electrolyte is melted and removed by immersing it in boiling water of 0.0 ℃. A solid tantalum electrolytic capacitor is manufactured using a conventional method. The failure rate during the reconstitution process of this capacitor was as shown in the table below. As is clear from the table above,
Compared to conventional products, the product of the present invention has a significantly lower failure rate regardless of whether the reconstitution voltage is high or low.

This is because when defects occur during reconversion treatment, the dripping portion of the gel electrolyte quickly melts and falls, cutting off contact with the reconversion solution, making it difficult to reconstitute other capacitor elements reliably. This is due to the fact that manganese ions were prevented from adhering to the surrounding capacitor elements by coating the capacitor elements with gel electrolyte. Example 2 The gel electrolyte in Example 1 was mixed with 100 cc of pure water, 40 ml of potassium chloride (KCI), and 3 ml of agar at 80°C.
Similar effects were obtained by changing to one prepared by heating to .

It should be noted that the present invention is not limited to the above-mentioned embodiments; for example, the capacitor element may be formed by pressure-molding metal powder into a desired shape, or may be formed from a plate material, graded material, or the like.

Further, the aqueous solution is not limited to the phosphoric acid aqueous solution, and can be applied to any solution having a reconstitution function. Furthermore, the melting temperature of the thermoplastic member can be appropriately set within a range that does not damage the oxidized layer. As described above, according to the present invention,
Even if a specific capacitor element becomes defective during reconstitution treatment, the adverse effect on capacitor elements located around it can be effectively reduced, and the quality of the capacitor can be improved.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of a conventional solid electrolytic capacitor, Figure 2 is a side sectional view for explaining the reconstitution method, and Figures 3 to 6.
The figure is an explanatory diagram of the method of the present invention, and FIG. 3 is a side sectional view showing a state in which the capacitor element is suspended from a holder.
Figure 4 is a side sectional view showing a capacitor element coated with thermoplastic material, Figure 5 is a side sectional view illustrating the reconstitution method, and Figure 6 is a side sectional view showing a state where the capacitor element is coated with thermoplastic material. It is a side sectional view explaining the melting removal method. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. When performing reconversion treatment on a plurality of capacitor elements that are made of metal members that have a valve action and that have an oxide layer and a semiconductor layer formed on their surfaces, the entire circumferential surface of the capacitor elements must be at least thermoplastic and conductive. 1. A method for manufacturing a solid electrolytic capacitor, which comprises covering the capacitor with a member and bringing the lower end of the member into contact with an aqueous solution.