JPS5951737B2 - 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 more particularly to a method for removing an undesired semiconductor layer formed on an anode lead portion of a capacitor element during a semiconductor layer forming process. , this type of solid electrolytic capacitor is made of tantalum, niobium, tantalum, niobium,
Capacitor element A made by press-forming metal powder with valve action, such as aluminum, into a cylindrical shape and sintering it.
A metal wire having a valve action is installed in advance 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 is attached around the capacitor element A. It is constructed by soldering to an electrode lead layer formed on the surface via an oxide layer and a semiconductor layer, and then covering the entire circumferential surface of the capacitor (A) with a resin material E.

By the way, before the first external lead member C is welded to the protruding portion of the anode lead B led out from the capacitor element A, an oxide layer is formed on the surface of the anode lead B by chemical conversion treatment. 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 in the axial direction on the surface of the anode lead B, the semiconductor mother liquid impregnated in the capacitor element A' passes through these die scratches and forms the anode lead B. It adheres to the protruding part (lead-out part) of the capacitor A and is thermally decomposed to cause what is called a creep-up of the semiconductor layer.

Normally, the impregnation-pyrolysis operation of the semiconductor mother liquor is repeated several times or more in view of the porous nature of the capacitor A, and the creeping-up of the semiconductor layer tends to progress further.

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

- In view of these points, the present invention provides a method for manufacturing a solid electrolytic capacitor that can improve the quality of the capacitor by removing the undesired semiconductor layer in the anode lead portion led out from the surface of the capacitor element. Hereinafter, one manufacturing method will be explained with reference to FIGS. 2 and 3.

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.

Then, the capacitor element surface 1 of this anode lead 2
The lead-out ends from a are connected to the band-shaped metal plate 3 at regular pitch intervals to form a band-shaped component.

Then, an oxide layer and a semiconductor layer are formed on the surface of the capacitor element 1 by a conventional method.

Next, as shown in FIG. 3, the strip-shaped component is housed and fixed in the dipping tank 4 with the metal plate 3 at the bottom and the capacitor element 1 at the top.

Then, an organic solvent 6 that is insoluble in water and has a specific gravity of 1.3 to 1.4 or more is supplied to the dipping tank 4 from a supply line 5 disposed below.

Subsequently, a solution 8 having a specific gravity lower than that of the organic solvent 6 and containing an acid and an oxidizing agent is supplied from a supply line 7 disposed above the immersion tank 4 so that the liquid level thereof is lower than the capacitor element surface 1a, for example, by 1 to 1. Supplied so that it is located 2 mm below.

When left in this state for a certain period of time, the semiconductor layer formed on the portion of the anode lead 2 extending from the capacitor element surface 1a is dissolved and removed by the dissolving solution 8.

Next, after lifting the strip part slightly upward, the organic solvent 6 is gradually replenished into the dipping tank 4 through the supply line 5 to raise the liquid level, and the solution 8 overflows and is drained into the auxiliary tank 9. be done.

After that, the band-shaped portion was treated with an organic solvent 6. The capacitor is then pulled up and washed with pure water, and a solid electrolytic capacitor is then manufactured using the usual method.

In this way, the capacitor element surface 1a of the anode lead 2
By immersing the lead-out portion in the two-liquid layer of the organic solvent 6 and the dissolving solution 8, it is possible to reliably remove the undesired semiconductor layer formed on the anode lead 2. Short-circuiting of the leakage current boosting output electrode due to contact with the semiconductor layer when welding the first external lead member can be completely eliminated.

Moreover, when removing the undesired semiconductor layer on the anode lead 2, the anode lead 2 is immersed in a two-liquid layer of the organic solvent 6 and the solution 8. In particular, the metal plate 3 is immersed in the organic solvent 6. Since it is covered, corrosion caused by the solution 8 can be prevented.

Furthermore, since the organic solvent 6 is not soluble in water and has a higher specific gravity than the dissolving liquid 8, the dissolving liquid 8 will always be on top of the organic solvent 6 even if it is configured as a two-liquid layer with the dissolving liquid 8. Since the anode lead 2 is in a floating position, the solution 8 can be brought into contact with only a desired portion of the anode lead 2, and an undesired semiconductor layer can be reliably removed.

Next, specific examples will be described.

Example 1 In the state shown in Figure 3, trichlene was used as an organic solvent,
Hydrochloric acid (ECI) 8% by volume as a dissolving solution.

Using a mixture of hydrogen peroxide (H2O2) 10% by volume and water, the anode lead was immersed in the solution for 25 seconds, pulled out, washed with pure water, and a solid electrolytic capacitor was manufactured using the usual method, and the leakage current was measured. When examining the incidence of electrode short-circuit defects, it was found that 3% of defects occurred with the conventional method, but no defects occurred with the method of the present invention.

Example 2 By using the same organic solvent as in Example 1 and using the product name Daiflon S3 (specific gravity 1.565) sold by Daikin Corporation as a dissolving solution, an undesired semiconductor layer ( Manganese dioxide) could be completely removed, and the same results as in Example 1 were obtained.

Example 3 Trichlene was used as an organic solvent and sulfuric acid (H2
When a mixture of 12% by volume of SO4), 10% by volume of hydrogen peroxide (H2O2), and water was used, the undesired semiconductor layer (manganese dioxide) formed on the anode lead could be removed in about 1 minute.

Note that there was no effect on the metal plate.

Example 4 ・ Carbon tetrachloride was used as an organic solvent and nitric acid (HN) was used as a dissolving liquid.
O3) 10% by volume, hydrogen peroxide (H2O2) 10% by volume
When a water mixture was used, the semiconductor layer (Yangan dioxide) on the anode lead could be completely removed in about 30 seconds.

Furthermore, by constantly overflowing the dissolving solution, the dissolution rate became even faster and the working time could be shortened.

Example 5 Using Daiflon S3 of Example 2 as an organic solvent and the mixed solution of Example 4 as a dissolving solution, the thickness of the dissolving solution was 4 to 5.
mm, the undesired semiconductor layer (manganese dioxide) on the anode lead could be completely removed.

In addition, since the thickness of the dissolving solution on the organic solvent was thin, the amount used could be kept to a minimum, so even if the dissolving solution was replaced frequently, the amount used was small, and on the other hand, the dissolving ability could always be kept high. was completed.

In the present invention, the oxidizing agent in the solution is not limited to hydrogen peroxide, and organic solvents other than those in the above examples can also be used.

As described above, according to the present invention, it is possible to effectively remove the undesired semiconductor layer in the anode lead portion led out from the surface of the capacitor element, and to prevent defects such as leakage current and electrode short circuit caused by welding of the external lead member. The incidence can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a conventional solid electrolytic capacitor, FIGS. 2 and 3 are side sectional views for explaining the method of the present invention, and FIG. FIG. 3 is a diagram showing a state in which the strip-shaped component is immersed in the two liquid layers.

Claims (1)

[Claims] 1 Pressure-forming metal powder with valve action into a desired shape and sintering: And then: After forming an oxide layer and a semiconductor layer on a capacitor element from which a metal wire with valve action has been led out in advance as an anode lead. , remove the semiconductor layer from the anode lead portion by immersing only the portion of the anode lead leading out from the surface of the capacitor element into a two-liquid layer of a solution containing an acid and an oxidizing agent, or an organic solvent having a higher specific gravity than the solution. A method for manufacturing a solid electrolytic capacitor, characterized by: