JPS6127891B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solid electrolytic capacitor, and in particular to reducing the phenomenon of a semiconductor layer forming member creeping up onto an anode lead led out from a capacitor element made of a molded body of metal powder having valve action. The purpose is to

In general, this type of solid electrolytic capacitor is manufactured by forming a capacitor element A in advance, which is made by press-molding metal powder having a valve action such as tantalum, niobium, or aluminum into a cylindrical shape and sintering it, as shown in Fig. 1. Connect the metal wire with valve action to the anode lead B
The first external lead member C is welded to the lead-out portion of the anode lead B from the capacitor element A, and the second external lead member D is
is soldered to an electrode lead layer formed on the circumferential surface of capacitor element A via an oxide layer and a semiconductor layer, and then the entire circumferential surface of capacitor element A is covered with resin material E. There is.

By the way, prior to welding the first external lead member C to the anode lead B led out from the capacitor element A, an oxide layer is formed on the surface of the capacitor element A by chemical conversion treatment together with the anode lead B.
Further, only the capacitor element A is immersed in the semiconductor mother liquor for a certain period of time to fully impregnate it, and then a thermal decomposition reaction is caused in a high temperature atmosphere to form a semiconductor layer on the oxide layer.

However, since there are many die scratches on the surface of the anode lead B, for example in the axial direction, the semiconductor mother liquid impregnated in the capacitor element A passes through the die scratches on the capacitor element A of the anode lead B. It adheres to the lead-out portion of the semiconductor layer and is thermally decomposed to cause what is called a creep-up of the semiconductor layer. Normally, the impregnation and thermal decomposition operation of the semiconductor mother liquor is repeated several times or more in view of the porous nature of the capacitor element A, and the creeping up of the semiconductor layer forming member tends to progress further.

Therefore, when welding the first external lead member C to the lead-out portion of the anode lead B, the first external lead member C and the semiconductor layer that has climbed up may come into contact, increasing leakage current, and sometimes the cathode There is a problem in that the capacitor and the anode are short-circuited and cannot function as a capacitor.

Therefore, before forming the semiconductor layer on the capacitor element, the applicant prevents the formation of the semiconductor layer by forming a water-repellent coating only on the anode lead portion led out from the surface of the capacitor element. We proposed a manufacturing method.

According to this method, even if a die scratch is formed on the anode lead, it is possible to reliably prevent the semiconductor mother liquor from creeping up due to the water-repellent effect of the water-repellent coating. This can prevent the formation of a semiconductor layer on the anode lead portion to which the anode lead is welded, and can prevent deterioration of leakage current characteristics.

However, to form a water-repellent coating on the anode lead B, for example, the capacitor element A and the anode lead B are immersed in a liquid water-repellent material, and then only the water-repellent material adhered to the capacitor element A is washed.
However, the water repellent material impregnated deep into the capacitor element A cannot be removed by simple cleaning. Therefore, since the product must be immersed in the cleaning solution for a long time, the workability is significantly impaired, and it is difficult to apply it to a mass production process.

In view of these points, the present invention is capable of suppressing the formation of a semiconductor layer creeping up to the anode lead portion led out from the surface of the capacitor element by the water-repellent member, and also prevents the water-repellent member from creeping up into the deep part of the capacitor element. The purpose of the present invention is to provide a method for manufacturing a solid electrolytic capacitor that can reliably prevent the seepage of solid electrolytic capacitors, and one manufacturing method will be described below with reference to FIGS. 2 to 7.

First, as shown in FIG. 2, a metal wire having a valve function is installed in advance as an anode lead 2 on a capacitor element 1 which is formed by press-forming metal powder having a valve function into a cylindrical shape and sintering it. The ends of the anode leads 2 extending from the capacitor element surface 1a are connected to the band-shaped metal plate 3 at regular pitch intervals to form a band-shaped component. Next, as shown in FIG. 3, the strip-shaped component is placed in the dipping tank 4 so that only the capacitor element 1 is immersed in the water 5 of the dipping tank 4. Incidentally, a window hole 7 is formed in the inner wall 6 of the immersion tank 4 to keep the liquid level of the water 5 constant.
After sufficiently impregnating the water 5 to the deep layer of the capacitor element 1, when the capacitor element 1 is pulled up, as shown in FIG. A water-based material impregnation prevention film ₅₁ is formed. Next, as shown in FIG. 5, the strip-shaped component is placed in a dipping tank 8 such that the capacitor element 1 and the portions of the anode lead 2 extending from the surface of the capacitor element are immersed in the liquid water-repellent member 9 of the dipping tank 8. Place it on. Incidentally, a window hole 11 is formed in the inner wall 10 of the immersion tank 8 to keep the liquid level of the water-repellent member 9 constant. Then, when the capacitor element 1 is pulled up from the water repellent member 9, the prevention film 5 of the capacitor element 1
As shown in FIG. 6, a coating ₉₁ of a water-repellent material is formed on the lead-out portions of the anode lead ₁ and the anode lead 2. As shown in FIG. Then, only the capacitor element 1 is immersed in a cleaning liquid to remove the water-repellent coating ₉₁ on the preventive film ₅₁ , and then heat-treated. Next, as shown in FIG. 7, an oxide layer is formed on the circumferential surface of the capacitor element 1.
An electrode lead layer is formed via the semiconductor layer. Then, the capacitor element surface 1a of the anode lead 2
A first external lead member 12 is attached to the lead-out portion from the
Welding is performed from above the water-repellent coating ₉₁ , and the second external lead member 13 is soldered to the electrode lead layer. Thereafter, a solid electrolytic capacitor is obtained by covering the entire circumferential surface of the capacitor element 1 with a resin material 14.

Since the water-repellent coating ₉₁ is formed on the anode lead portion led out from the capacitor element surface 1a before the semiconductor layer forming process, the semiconductor mother liquor is Even if the anode lead 2 tries to climb up through the die wound to the lead-out portion from the capacitor element surface 1a, the water-repellent action of the water-repellent coating ₉₁ can reliably prevent the anode lead 2 from climbing up. Therefore, even if the first external lead member 12 is welded to the anode lead 2, an increase in leakage current and a short circuit between the cathode and the anode can be prevented, and the quality of the capacitor can be improved.

Furthermore, prior to forming the water-repellent coating ₉₁ on the anode lead 2, the capacitor element 1 is coated with a film ₅₁ that prevents water-repellent material 9 from penetrating. Even when immersed in the water repellent member 9, it is possible to reliably prevent the water repellent member 9 from penetrating into the deep part of the capacitor element 1. Therefore, by removing the preventive film ₅₁ in the capacitor element 1 by heating or the like, it is possible to reliably form the semiconductor layer in the deep layer.
Capacitor characteristics can be improved.

Furthermore, since water or an organic solvent is used as the seepage prevention film ₅₁ of the water-repellent member 9, it can be easily and reliably removed by heating. In particular, when water is used, it is not necessary to remove it by heating, but by immersing it in a chemical liquid and performing a chemical conversion treatment, water in the deep layer can be replaced with the chemical liquid and removed as a result. Work efficiency can be significantly improved.

Next, specific examples will be described.

Example 1 Only the capacitor element is immersed in water and thoroughly soaked. After lifting, the capacitor element along with the anode lead is immersed for 5 seconds in an oil-based fluorine-based resin liquid (trade name ``Daifree FS-126'' manufactured by Daikin), which is a liquid water-repellent material. After pulling, use solvent (product name: “Daiflon Solvent” manufactured by Daikin)
immerse only the capacitor element in water for 30 seconds to remove the die-free coating from undesired areas. After that, a solid electrolytic capacitor was manufactured using the usual method, and the failure rate of leakage current and short circuit failure was investigated, and the failure rate, which was previously around 3%, was reduced to 0.01%. Moreover, the weldability between the anode lead and the first external lead member was not impaired at all. Furthermore, no decrease in capacitance due to penetration of dye-free was observed.

Example 2 In Example 1, when the capacitor element was impregnated with water and then the surface layer was frozen, dye-free on the preventive film could be removed more efficiently.

Example 3 In Example 1, when alcohol was used instead of water, the same effect as in Example 1 was obtained.

Example 4 After impregnating only the capacitor element with an aqueous phosphoric acid solution with a concentration of 0.5%, the capacitor element and anode lead were soaked in a water-based fluorine-based resin solution (product name: "Daifree ME"), which is a liquid water-repellent material.
104 (manufactured by Daikin) for 2 seconds. After pulling up, only the capacitor element is immersed in the same solvent as in Example 1 (trade name: Diflon Solvent) for 30 seconds to remove the Diflon coating from undesired areas. A solid electrolytic capacitor was manufactured using a conventional method, and the same effects as in Example 1 were obtained.

In addition, in the present invention, the water-repellent coating may be made of silicone, stearic acid, etc. in addition to fluorine-based resin (Teflon resin). Furthermore, the preventive film is not limited to water, alcohol, or chemical liquid.

As described above, according to the present invention, the water-repellent member can prevent the semiconductor layer from creeping up onto the anode lead portion led out from the capacitor element, and also prevent the water-repellent member from seeping into the capacitor element. Problems caused by the characteristics can also be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a conventional solid electrolytic capacitor, and FIGS. 2 to 7 are explanatory diagrams of the present invention.
Fig. 2 is a side sectional view of the band-shaped component, Fig. 3 is a side sectional view showing the state of the capacitor element immersed in water,
Figure 4 is a side sectional view showing the state of formation of the preventive film;
FIG. 6 is a side sectional view showing a state in which a capacitor element is immersed in a water-repellent member, FIG. 6 is a side sectional view showing a state in which a water-repellent coating is formed, and FIG. 7 is a side sectional view showing a completed state.

Claims (1)

[Claims] 1. Prior to forming a semiconductor layer on a capacitor element from which a metal powder having a valve action is pressure-molded into a desired shape and sintered, and a metal wire having a valve action is led out as an anode lead, the capacitor element is The anode lead and the capacitor element are immersed in the liquid water-repellent material by forming a water-repellent material impregnation prevention film on the capacitor element, and then cleaning and removing only the water-repellent film adhering to the capacitor element to remove the desired portion of the anode lead. A method for manufacturing a solid electrolytic capacitor, which comprises forming a water-repellent film on a solid electrolytic capacitor.