JPS60948B2 - 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 in particular, to reduce creeping of the semiconductor layer forming part onto an anode lead led out from an anode body made of a molded body of metal powder having valve action. The purpose is to

In general, this type of solid electrolytic capacitor is made by press-molding metal powder having a valve action, such as tantalum, niobium, or aluminum, into a cylindrical shape and sintering the anode body A, as shown in Fig. A functional metal wire is erected as an anode lead B, and a first external lead C bent in an L shape is welded to the protruding portion of this anode lead B.
The external lead wire D is soldered to the cathode layer formed on the circumferential surface of the anode body A through an oxide layer and a semiconductor layer, and the anode lead B
The peripheral surface of the anode body A including the protruding portion thereof is covered with a resin material E.

By the way, before the first external lead wire C is welded to the protruding portion of the anode lead B, an oxide layer is formed on the surface of the anode body A by chemical conversion treatment together with the anode lead B, and only the anode body A is treated with nitric acid. It is soaked in a semiconductor mother solution such as a manganese solution for a certain period of time to be impregnated into the anode body A, and then heated at 200°C.
A semiconductor layer of manganese dioxide or the like is formed on the oxidized layer of the anode body A by causing a thermal decomposition reaction in the above-mentioned high-temperature atmosphere.

However, in this thermal decomposition process, the temperature of the anode body A inserted into the high-temperature atmosphere rises rapidly.
The semiconductor mother liquor impregnated inside causes a thermal decomposition reaction, and decomposed gases such as water vapor and nitrogen oxides blow out from the inside to the surface layer, so bubbles are generated in the semiconductor mother liquor layer in the middle of thermal decomposition in the surface layer. This adheres to the protruding portion of the anode lead B, causing so-called creeping of the semiconductor layer forming member.

Normally, the impregnation-pyrolysis process of the semiconductor mother liquor is repeated several times or more because the anode body A is porous, and as the number of times of thermal decomposition increases, the creeping up of the semiconductor layer forming member tends to progress further. be. Therefore, when attaching the first external lead wire C to the protruding portion of the anode lead B, the first external lead wire C. There is a problem in that the external lead wire C of No. 1 comes into contact with the semiconductor layer that has climbed up, and the cathode and anode are short-circuited, making it impossible to function as a capacitor. Therefore, in the past, a configuration was adopted in which a Teflon washer F was attached to the top surface of the anode body A, and the anode lead B was inserted through the center hole of the Teflon washer F, as shown in FIGS. 2 and 3. ing.

According to this method, although it is possible to effectively suppress the creep-up phenomenon of the semiconductor layer at the protruding portion of the anode lead B, the workability is poor and it requires an extremely large number of man-hours, making it difficult to mass-produce. There are drawbacks. In view of these points, the present invention has an object to effectively suppress the creeping up of the semiconductor layer forming member to the anode lead led out from the anode body without impairing workability, and to also improve the quality of the capacitor. The present invention provides a method for manufacturing a solid electrolytic capacitor, and examples thereof will be described below.

In FIG. 4, reference numeral 1 denotes an anode body constituted by a molded body of metal powder having a valve action, and the illustrated example is formed by press-molding metal powder into a cylindrical shape and solidifying it.

Reference numeral 2 denotes an anode lead made of a metal wire having a valve action and led out from the top surface of the anode body 1; has been done.

Reference numeral 3 denotes a heat-resistant insulating member which is attached to the top surface of the anode body 1 so that the root portion of the anode lead 2 is hidden by a method described later, and is preferably made of, for example, frit glass or fine alumina powder.

Reference numeral 4 denotes a first external lead wire bent into an L shape, for example, and a bent portion 4a thereof is welded to cross the protrusion 2a of the anode lead 2.

Reference numeral 5 denotes a second external lead wire formed in a straight shape, for example, and the end thereof is connected to a cathode layer (not shown) formed on the circumferential surface of the anode body 1 via an oxide layer and a semiconductor layer. They are connected by solder members 6.

Reference numeral 7 denotes an exterior insulating material such as epoxy resin that covers the entire circumferential surface of the anode body 1 including the protrusion 2a of the anode lead 2.

Next, an example of a specific method for attaching the heat-resistant insulating member 3 to the top surface of the anode body 1 will be explained with reference to FIG.

First, as shown in Figure a, 40 ml of polyethylene oxide with a molecular weight of 400,000 to 500,000 is mixed with 50 ml of isopyl alcohol.
After dispersing the powder, add 2,000 ml of 200 mesh frit glass (softening temperature 382°C) containing lead as the main component and 2,000 ml of water and thoroughly stir the mixture. 8. Then, a plurality of anode bodies 1 fixed to a band-shaped metal plate 9 are immersed in the suspension 3'' and pulled up. Then, the suspension 3'' is applied to the top surface of the anode body 1 so as to hide the root portion of the anode lead 2. Next, as shown in FIG. Remove any adhering suspension. Next, as shown in FIG. 13 is brought close to the top surface of the anode body 1, the solvent and binder in the suspension 3'' are scattered, and the frit glass is melted and firmly and integrally attached to the top surface. The solid electrolytic capacitor shown in FIG. 4 was fabricated using the anode body 1 equipped with the heat-resistant insulating member 3 using a conventional method (see FIG. 1). Composition) What used to occur at about 2-4% has decreased to 0.1% or less.

As a result, short circuit failures between the cathode and the anode that occur when the first external lead wire 4 is welded to the anode lead 2 can be reduced to a negligible level. In addition, since the root portion of the anode lead 2 is hardened together with the top surface of the anode body 1 by the heat-resistant insulating layer 3, the anode lead 2 is
Even if a bending force is applied to the anode body 1, there will be no cracks in the part where it is embedded in the anode body 1.

Therefore, since there is no deterioration of capacitor characteristics such as leakage current due to damage to the oxide layer due to cracks or the like, the capacitor can be maintained in high quality. In particular, since the heat-resistant insulating layer 3 is applied to the top surface of the anode body 1 simultaneously for a large number of anode bodies fixed to the metal plate 9, mass productivity is significantly improved. The present invention is not limited to the above-mentioned embodiments; for example, the heat-resistant insulating member can be made of glass frit, alumina, silica, zirconium, or other fine powder, or The suspension adhering to a desired portion can be removed using not only water but also an organic solvent.

As described above, according to the present invention, since the heat-resistant insulating member that can sufficiently withstand the temperature of the thermal decomposition process of the semiconductor layer forming member is attached to the root portion of the anode lead, the semiconductor layer forming member on the anode lead is coated. In addition, by reinforcing the anode lead, it is possible to prevent deterioration of the capacitor characteristics due to cracks in the anode body and maintain the high quality of the capacitor.

[Brief explanation of drawings]

1 to 2 are front sectional views showing different embodiments of the conventional example, FIG. 3 is a perspective view of the main part of FIG. 2, and FIG. FIG. 5 is a front sectional view for explaining the method of the present invention. O figure, 2 figures, 3 figures, 4 figures, S figure

Claims (1)

[Claims] 1. An anode body made of a molded body of metal powder having a valve action is immersed in a suspension containing a heat-resistant insulating member, and the base portion of an anode lead made of a metal wire having a valve action led out from the top surface of the anode body is immersed. A process of immersing the anode body in a similar manner, a process of removing the suspension adhering to the circumferential surface except for the top surface of the anode body, and a process of heating the suspension liquid on the top surface of the anode body to make the anode body and anode lead heat-resistant. The method is characterized by comprising the steps of: integrating a heat-resistant insulating member; forming an oxide layer on the anode body into which the heat-resistant insulating member is integrated; and forming a semiconductor layer on the oxide layer of the anode body. Method of manufacturing solid electrolytic capacitors.