JPS6037613B2 - 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 are made by press-molding metal powder such as tantalum, niobium, aluminum, etc., which has a valve action, into a cylindrical shape and sintering the capacitor element A, as shown in Figure 1. A metal wire having the following properties is stood up as an anode lead B, a first external lead member C is welded to the protruding part of this anode lead B, and a 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.
By the way, on the surface of this capacitor element A, there is an oxide layer E as a dielectric material formed by chemical conversion treatment.
is formed, and a semiconductor layer F such as manganese dioxide is formed thereon. However, in the semiconductor layer formation process in particular, a heat treatment of 200 to 40,000 degrees Celsius is sometimes performed, so the oxide layer deteriorates. Leakage current characteristics etc. tend to be impaired.

Therefore, in the past, for example, as shown in Fig. 2, capacitor element A is immersed in reconversion liquid, and capacitor element A and reconversion liquid have a positive value and a negative value of the reconversion liquid. Reconversion treatment is performed by applying a direct current voltage.

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.

Capacitor element A like this completely loses its function as a capacitor and becomes defective, but capacitor element A located around it also becomes defective due to deterioration of withstand voltage characteristics after production, and due to the formation of an oxide layer. The higher the ratio of the reforming voltage to the voltage, the higher the defect occurrence rate will be. The cause of this is not clear, but since the outer surface of capacitor element A, which is placed around the circumference of capacitor element A through which an excessive current has flowed, is discolored to blackish brown, it is difficult to use it as semiconductor layer F. It is thought that the properties are deteriorated due to the adhesion of manganese ions, etc., which are released from manganese dioxide.

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 to 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 high 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 and 4. First, as shown in Fig. 3, a metal wire having a valve action is placed in advance as an anode lead 2 on a capacitor element formed by press-molding metal powder having a valve action into a cylindrical shape and sintering 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 band-shaped parts 4 are arranged and placed in a container 7 at a constant pitch. Incidentally, a pipe 9 for supplying the reconversion liquid 8 to the container 7 is provided on one wall surface 7a of the container 7, and a pipe 10 for discharging the reconversion liquid 8 is provided at appropriate locations on the other wall surface 7b. ing. Further, an electrode plate 11 is provided at the bottom of the container 7, and a partition wall 13 having a hole 12 is provided at a portion corresponding to the top surface of the reconversion liquid 8 and a portion corresponding to the bottom surface of the capacitor element 1. . In this state, pipe 9
When the reconstituted liquid 8 is pumped into the container 7, the reconstituted liquid 8 squirts up from the hole 12 of the partition wall 13, contacts the bottom and side surfaces of the condenser element 1, and a part of the reconstituted liquid 8 flows into the condenser element 1. Impregnated. Then, when the reconversion liquid 8 is sufficiently impregnated into the capacitor element 1, a DC voltage is applied to the holder 3 and the electrode plate 11 so that the holder 3 becomes positive and the electrode plate 11 becomes negative. The capacitor element 1' is then reconstituted. and,
The reconversion liquid 8 that has come into contact with the condenser element 1 and flowed down onto the partition wall 13 is forcibly discharged through the pipe 10. In this state, if the oxide layer 5 of a particular capacitor element is destroyed and an excessive current flows, a large amount of manganese ions will be liberated if manganese dioxide is used as the semiconductor layer 6. However, it does not adhere to the surrounding capacitor element 1 because it is washed away by contact with the reconversion liquid 8. Hereinafter, a solid electrolytic capacitor is obtained by a conventional method. In this way, during the reconversion treatment of the capacitor elements 1, each condenser element 1 is contacted with the reconversion liquid 8 independently, so that even if a defect in a particular capacitor element is caused, Even if a large amount of manganese ions are released, they are immediately washed away.

For this reason, adhesion of manganese ions to the surrounding capacitor element 1 can be prevented, and characteristic deterioration can also be prevented. Note that even if a small amount of the recycled liquid 8 after contact is mixed into the recycled liquid 8 to be spouted, the effect on the characteristics can be ignored.

Furthermore, even if the reconversion liquid 8 is not spouted up to the capacitor element 1 independently, if the reconversion liquid 8 that is constantly spouted up comes into contact with the condenser element 1 and flows down, the condenser element 1 can be sprayed as described above. Even if a large amount of manganese ions are released due to a defect in element 1, it is possible to prevent them from adhering to surrounding capacitor elements.

In particular, if the re-forming voltage is higher than normal, some capacitor elements 1 will become defective during the re-forming process;
Partly because it is possible to prevent an adverse effect on the surrounding capacitor element 1, the characteristic grade of the capacitor element 1 that has survived the reconversion treatment can be significantly improved.

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

Next, specific examples will be described.

Using tantalum powder, 3.5 x 4. An oxidized 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. This capacitor element is divided into two groups, one group sets the re-formation voltage to 50% of the formation voltage, and the other group sets it to 70%, and the bottom and side circumferential surfaces of the capacitor element are Reconversion treatment is carried out by bringing the reconversion liquid into contact with the product by blowing up the reconversion liquid. A solid tantalum electrolytic capacitor is manufactured using the following conventional method. We investigated the failure rate during the re-forming process of this capacitor, and the results shown in the table below were obtained.

As is clear from the table above, the product of the present invention has a significantly lower failure rate than the conventional product, regardless of whether the reconstitution voltage is high or low. This is due to the fact that there is almost no negative impact on the surrounding area due to defects that occur during the reconversion process. still,
The present invention is not limited to the above-described 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, a wire material, or the like.

In addition, the re-forming liquid can be spouted up not only by a jet method but also by pressure feeding, and the spouting location is not limited to the portion facing the bottom of the condenser element. 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. I can do it.

[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 4.
The figures are explanatory diagrams of the method of the present invention, and Fig. 3 is a cutaway side view of the main part showing a state in which the capacitor element is suspended in a holder, and Fig. 4 is a side sectional view for explaining the reconversion method. be. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. When simultaneously reconforming multiple capacitor elements that are made of a metal member with valve action and have an oxide layer and a semiconductor layer formed on their surfaces, the capacitor elements are treated with a reconversion liquid by spraying it out. 1. A method for manufacturing a solid electrolytic capacitor, comprising the steps of: contacting the solid electrolytic capacitor; and discharging the recycled liquid after contact so as to prevent it from mixing with the recycled liquid to be spouted as much as possible.