JPS6046535B2 - Manufacturing method of electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an electrolytic capacitor, and particularly to an improvement in a method for forming a capacitor element of a solid electrolytic capacitor.

In general, this type of solid electrolytic capacitor is made by press-molding metal powder with a valve action, such as tantalum, niobium, or aluminum, into a cylindrical shape and sintering it.The capacitor element is made by using a metal wire with a valve action as an anode lead in advance. The first external lead member is welded to the protruding portion of the anode electrode, and the second external lead member is attached to the electrode formed on the circumferential surface of the capacitor element through an oxide layer and a semiconductor layer. The capacitor element is soldered to the lead-out layer, and then the entire circumferential surface of the capacitor element is covered with a resin material.

By the way, an oxide layer is formed as a dielectric on the surface (including the inner surface) of this capacitor element, and when forming this, for example, as shown in Figure 1, a strip-shaped metal plate is used. A capacitor element B is suspended from a holder A made of a holder A, and an anode lead C led out from the holder A is fixed at a constant pitch, and a part of the capacitor element B and anode lead C is exposed to the chemical solution. immersed.

However, if the temperature of the chemical liquid is insufficiently controlled, the vapor of the chemical liquid forms a bypass between the chemical liquid and the lower end of holder A, causing the condenser element B to The flowing anodization current decreases, making it impossible to obtain a desired oxide layer within a certain anodization time.

Moreover, the holder A is corroded by the vapor of the chemical liquid,
If these corrosive substances are mixed into the chemical solution, it becomes impossible to form a highly pure oxide layer. For this reason, leakage current characteristics and the like are significantly impaired. Therefore, in the past, by making the length of the anode lead C sufficiently long, even if the liquid temperature control of the chemical liquid becomes insufficient and a large amount of steam is generated, the holder A and the chemical liquid can be connected to each other. However, if the anode lead C is made of tantalum or niobium, for example, it is extremely expensive, so the capacitor's price also increases. be.

In view of these points, the present invention provides a method for manufacturing an electrolytic capacitor that can be reliably chemically treated without being affected by the vapor of the chemical liquid even if the hanging length of the capacitor element relative to the holder is shortened. One of the manufacturing methods will be explained below.

First, as shown in FIG. 2, an oxide layer 2 is formed on the lower end portion of the holder 1, which is made of a band-shaped metal member having a valve function, by, for example, chemical conversion treatment.

Next, as shown in FIG. 3, a capacitor element 3 made of a metal member having a valve action is attached to the oxide layer forming portion of the holder 1, and an anode lead made of a metal member having a valve action is drawn out from the capacitor element 3. 4 is hung by fixing it by welding, crimping, etc. Note that the hanging length L of the capacitor element 3 with respect to the holder 1 is set to less than half of the conventional length. Then, the capacitor element 3 and part of the anode and electrode 4 in this state are immersed in a chemical solution, and an oxide layer as a dielectric is formed on the surface thereof by a conventional method. Then, a semiconductor layer and an electrode lead layer 5 are further formed on the oxide layer. Next, as shown in FIG. 4, an L-shaped first external lead member 6 is welded to the protruding portion 4a of the anode lead 4 separated from the holder 1, and the second external lead member 7 is pulled out from the electrode. Solder to layer 5. Thereafter, a solid electrolytic capacitor is obtained by covering the entire circumferential surface of the capacitor element 3 with a resin 8. As described above, since the oxide layer 2 is formed on the lower end portion of the holder 1 prior to the chemical conversion treatment, the capacitor element 3
Even if the hanging length L from the holder 1 becomes extremely short, for example, about 5 wL (conventionally 20 TSfL), formation of a bypass between the holder and the chemical liquid due to the vapor of the chemical liquid can be prevented. For this reason, a predetermined anodizing current can be passed through the capacitor element 3, so that a desired oxide layer can be formed. Moreover, even if the vapor of the chemical liquid comes into contact with the oxidized layer forming portion of the holder 1, no corrosion of the holder 1 occurs, so no corrosive substances are mixed into the chemical liquid. do not have. Therefore, a highly pure oxide layer can be formed on the surfaces of the capacitor element 3 and the anode lead 4, and leakage current characteristics can be improved. Furthermore, the hanging length L of the capacitor element 3 with respect to the holder 1, that is, the length of the anode lead 4, can be greatly shortened as described above, so for example, when tantalum is used as the anode lead 4, Needless to say, this method is preferable not only because it can greatly reduce the price of the product, but also from the viewpoint of effective use of resources. Next, specific examples will be described.

An oxide layer (Al) is applied to the lower half of the holder 1 made of an aluminum plate of 300 x 30 x 2 tTI$L using ammonium borate as a chemical solution.

O3) is formed. Then, a capacitor element made by press-molding tantalum powder into a cylindrical shape and sintering it is crimped onto the oxide layer forming part of this holder, and anode leads made of tantalum wire derived from the element are crimped at a constant pitch. It is suspended by. Note that the hanging length is set to 4Tr$L. This capacitor element and a portion of the anode lead are immersed in a phosphoric acid aqueous solution and subjected to chemical conversion treatment by a conventional method to form an oxide layer on their respective surfaces. In the solid electrolytic capacitor manufactured in this manner, the failure rate due to leakage current was reduced to about 2 to 3% compared to the conventional one.

Also, in terms of price, by shortening the anode lead, the product price can be reduced by 2.
We were able to measure a reduction of approximately 0%. It should be noted that the present invention is not limited to the above-described embodiments; for example, the holder may be made of tantalum, niobium, etc. in addition to aluminum, and the range in which the oxide layer is formed can be increased or decreased as appropriate.

Further, the capacitor element may be formed by press-molding metal powder, or may also be formed from a wire rod, a plate material, or the like. Furthermore, the capacitor can also be applied to a wet electrolytic capacitor. As described above, according to the present invention, by forming an oxide layer on a desired portion of the holder, even if the hanging length of the capacitor element from the holder is shortened, it is not affected by the chemical liquid or its vapor. In addition to being able to reliably perform chemical conversion treatment without any problems, drastic improvements in properties and price are expected.

[Brief explanation of drawings]

FIG. 1 is a side view of a conventional holder member, FIGS. 2 to 4 are diagrams for explaining the method of the present invention, and FIG. 2 is a side view showing a state in which an oxide layer is formed on the holder. FIG. 3 is a side sectional view showing a capacitor element suspended from a holder, and FIG. 4 is a side sectional view showing a completed solid electrolytic capacitor. In the figure, 1 is a holder, 2 is an oxide layer, 3 is a capacitor element, and 4 is an anode lead.

Claims (1)

[Claims] 1. A step of forming an oxide layer on the lower end portion of a holder made of a band-shaped metal member having a valve action, and a step of forming a capacitor element made of a metal member having a valve action on the oxide layer forming portion of the holder. a step of suspending the anode lead by fixing it to the anode lead made of a metal member having a valve action, and a step of forming an oxide layer by chemical conversion treatment on the surfaces of the capacitor element and the anode lead suspended in the holder. A method for manufacturing an electrolytic capacitor, comprising: