JPH07130582A - Manufacture of tantalum anode - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a tantalum anode through a simple process, wherein tantalum powder is micronized, lessened in molding density, and set low in sintering temperature, and a tantalum sintered body can be formed porous. CONSTITUTION:A porous tantalum sintered body 14 and a tantalum wire 19 are joined together for the formation of a tantalum anode through a butt resistance-welding method, wherein a butting pressure is set to 1.5 to 3.0kgf suitable for enhancing the tantalum anode most in welding strength, the welding spot 18 of the sintered body 14 is formed comparatively high in density and has a surface where tantalum powder is two-dimensionally orientated, and a high dense compressed spot is provided to the welding spot of the sintered body through a dimple processing. By this setup, a tantalum anode composed of a tantalum sintered body and a tantalum wire is much enhanced in welding strength between the sintered body and the wire and protected against cracking around a welded spot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tantalum solid electrolytic capacitor, and more particularly to a method for producing a tantalum anode body which is a basic material of a tantalum solid electrolytic capacitor.

[0002]

2. Description of the Related Art A method for manufacturing a tantalum anode body, which is a basic material of a tantalum solid electrolytic capacitor, is such that, when tantalum powder is pressure-molded, a tantalum wire that serves as an anode lead wire is simultaneously embedded in the molded body, and a vacuum A method of sintering to obtain a porous tantalum anode body, a method of press-molding tantalum powder with a molding die, and vacuum sintering to form a porous tantalum sintered body, and then forming a tantalum wire on the sintered body. Is a tandem anode body attached by butt resistance welding.

In particular, the latter method is capable of increasing the capacity by approximately the volume of the tantalum wire embedded as compared with the former method, and is extremely excellent in molding workability by wireless molding, and the molding density of the molded body is uniform. And the loading rate of the sintering furnace is greatly improved, and the effect is more remarkable as the tantalum anode body becomes smaller. Conventional butt resistance welding has been performed by taking advantage of such advantages.

[0004]

However, in recent years, tantalum powder has been made finer, the compacting density has been made lower, and the sintering temperature has been lowered in response to the demand for larger capacity and smaller size of capacitors. The aggregate is more practical, and the binding force of the tantalum powder is further weakened and put to practical use.

This has an extremely disadvantageous effect on the butt resistance welding of the porous tantalum sintered body and the tantalum wire, and in the extreme, the tantalum wire falls off due to the reduction of the welding strength, and the porous tantalum firing around the welded portion occurs. Deterioration of capacitor characteristics due to the effect of cracks that occur in the united body,
Further, since the reliability is deteriorated, it is inevitable to limit the practical use to the grade of tantalum powder of 18000 CV / g or less, which is less susceptible to these influences.

Further, Japanese Patent Publication No. 5-1609 and Japanese Patent Laid-Open No. 62-
Although there is a method shown in the 9619 publication, these require complicated operations and processing such as embedding a high density molded body or a metal ball in a tantalum molded body.

[0007]

Therefore, the present invention can be applied to finer tantalum powder, lower compacting density, lower sintering temperature, and porous porous tantalum sintered body,
Moreover, it is intended to provide a tantalum anode body by a simple operation.

[0008]

In the tantalum anode body according to the present invention, in the butt resistance welding of the porous tantalum sintered body and the tantalum wire, the butt pressure force is limited to the strongest and stable range in terms of welding strength. And that the welded portion of the sintered body is a surface having a relatively high density and the tantalum powder has a planar alignment direction, and the welded portion of the sintered body is provided with a high-density compressed portion by dimple processing. By providing it, the welding strength is made extremely excellent, and cracks are not generated around the welded portion.

The present invention will be described with reference to the embodiments shown in the drawings.
FIG. 3 shows a pressure molding procedure for tantalum powder 12, in which a fixed middle mold 11 to which a lower mold 10 to be pressed is fitted.
Then, a fixed amount of tantalum powder 12 is filled in, and then the upper mold 13 for pressing is pressed at a constant pressure while being fitted to the middle mold 11, thereby forming a tantalum compact which becomes a porous tantalum sintered body 14.

The tantalum powder used is 30,000 CV /
As shown in FIG. 2, the size of the porous tantalum sintered body 14 is 1.5T (thickness) 4.0W (width) x 2.0H (height). ) Mm, and the sintering conditions were 1450 ° C. and 20 minutes.

FIG. 1 or FIG. 2 shows a porous tantalum sintered body 14 obtained under the above-mentioned conditions, which is an upper mold 13 of a molding die.
The contact surface 15 with and the contact surface 16 with the lower mold 10 have a relatively high density, and the contact surface 17 with the middle mold 11 has a relatively low density in the central portion.

The central portion of the contact surface 17 of the porous tantalum sintered body 14 with the middle die 11 of the molding die is used as a welded portion 18, and butt resistance welding of the tantalum wire 19 is performed by a general welding method. , The appropriate value of the butt pressure based on the weld strength and weld cross-section evaluation is 1.5 to 3.0 kg.
As t, the tantalum anode body of FIG. 1 is manufactured. The tantalum wire-19 has a diameter of 0.3 mm.

Further, as shown in FIG. 2, the welded portion 18 of the butt resistance welding of the porous tantalum sintered body 14 and the tantalum wire-19 is contacted with the upper die 13 of the forming die or the lower die 10. It has been found that the contact surface 16 is in a better welded state than the contact surface 17 with the middle die 11 and a better welding proper surface can be obtained. Proper value of butt pressure is 1.5-3.0k
gf.

Further, as a countermeasure against cracks, the welded portion 18 (contact surfaces 15, 16, 17) of the sintered body 14 as shown in FIG.
5 is provided with a high-density compression portion 20 by dimple processing,
Butt resistance welding of the tantalum wire-19 is performed according to FIG.

In the high-density compression part 20, the conical diamond tool 21 shown in FIG. 4 has a conical angle of 60 °, and the tip part thereof has a spherical surface of SR2.5 mm, and the sintered body 14 is applied with a pressing force of about 3 kgf. Rotate while pressing against 0.5m diameter
m, depth 0.2 mm, and density 7.0 g / CC or more.

Abrasion resistant materials other than diamond may be used for the dimple processing. Further, the conical angle, the tip shape, the pressing force, etc. are set according to the necessary conditions of the high-density compression section 20.

[0017]

FIG. 7 shows the porous tantalum sintered body 14 and the tantalum wire-19 obtained under the above various welding conditions.
3 is a data diagram showing the relationship between the butt pressure and the welding strength (tensile strength) in the butt resistance welding of FIG. In the figure, a is a welded portion 1 of the porous tantalum sintered body 14.
8 is a contact surface 17 of the sintered body 14 shown in FIG.
Indicates the welding strength (tensile strength).

According to the analysis result of the data diagram of FIG. 7,
Welding strength (tensile strength) is butt pressure of 1.0
When the pressure is less than or equal to kgf, the welding of the tantalum wire-19 remains on the extreme surface of the porous tantalum sintered body 14, and the joint area between the two is small, so that practical strength cannot be obtained.

On the other hand, if the pressure is 3.5 kgf or more, the butting pressure becomes excessive, and the tantalum wire-19 is mechanically pressed into the porous tantalum sintered body 14 to a large extent, and the strength cannot be maintained. Therefore, practical welding strength (tensile strength)
Is obtained when the butt pressure is in the range of 1.5 to 3.0 kgf.

In FIG. 7, b is a porous tantalum sintered body 14
3 shows the welding strength (tensile strength) when the welded portion 18 is the contact surface 15 with the upper die 13 or the contact surface 16 with the lower die 10 shown in FIG. Contact surface 17 with the middle mold 11
This surface compared to the tantalum powder 1 as shown in FIG.
Since the alignment direction of 2 is flat and the molded body is formed at a relatively high density for reasons of mechanical strength such as prevention of shape collapse, the welding strength (tensile strength) on this surface is shown in FIG.
A value about 0.5 kg higher than the condition a) is obtained, and practical welding strength (tensile strength) at this time is also obtained when the butt pressure is in the range of 1.5 to 3.0 kgf.

Further, in FIG. 7C, the welded portion 18 of the porous tantalum sintered body 14 is used as a contact surface 15 with the upper die 13 of the molding die or a contact surface 16 with the lower die 10, and This shows the welding strength (tensile strength) when resistance-welding the tantalum wire-19 to the high-density compressed portion 20 by performing dimple processing. Contact surface 17 with the middle mold 11
Even if the tantalum wire is resistance-welded by making a high-density compressed portion by dimple processing, excellent welding strength can be obtained.

Since the high-density compressed portion 20 is a hemispherical hollow and the density is as high as 7.0 g / CC or more, the porous tantalum sintered body 14 and the tantalum wire-19 are contained.
Has a very large welded area, and extremely excellent weldability can be obtained.

The welding strength (tensile strength) thereof exceeds the condition of b in FIG. 7 by 0.5 kg or more, and the tantalum wire-19 is all cut when the butt pressure is in the range of 2.0 kgf to 3.0 kgf.

Further, cracks around the welded portion 18 observed under the conditions a and b in FIG. 7 are not observed at a butt pressure of 3.0 kgf or less under these conditions.

[Brief description of drawings]

FIG. 1 is an external view of a tantalum anode body manufactured by the manufacturing method of the present invention.

FIG. 2 is an external view of a tantalum anode body manufactured by the manufacturing method of the present invention.

FIG. 3 is an explanatory view of a tantalum powder molding procedure according to the present invention.

FIG. 4 is an explanatory view showing a procedure for performing dimple processing on the porous tantalum sintered body according to the present invention.

FIG. 5 is an explanatory view showing a procedure for butt resistance welding a tantalum wire to a high-density compressed portion of the porous tantalum sintered body according to the present invention.

FIG. 6 is an explanatory view showing a procedure for butt resistance welding a tantalum wire to a high-density compressed portion of the porous tantalum sintered body according to the present invention.

FIG. 7 is a data diagram showing the relationship between the butt pressure and the welding strength (tensile strength) of resistance welding of the tantalum anode body obtained by the manufacturing method according to the present invention under various conditions.

[Explanation of symbols]

 10 Lower Mold of Molding Mold 11 Medium Mold of Molding Mold 12 Tantalum Powder 13 Upper Mold of Molding Mold 14 Porous Tantalum Sintered Body 15 Contact Surface with Upper Mold 16 Contact Surface with Lower Mold 17 Contact Surface with Medium Mold 18 Welded portion 19 Tantalum wire-20 High-density compressed portion 21 Diamond tool

Claims (3)

[Claims] 1. A porous tantalum sintered body is formed by press-molding and vacuum-sintering tantalum powder with a molding die having a predetermined shape including an upper die, a lower die, and a middle die. In the tantalum anode body in which the tantalum wire was butt resistance welded to, the pressure force of the butt resistance welding was 1.5 to 3.
A method for producing a tantalum anode body having a range of 0 kgf. 2. A butt resistance welding of a porous tantalum sintered body and a tantalum wire, wherein the welded portion of the sintered body is a contact surface with a molding die to be pressed. For manufacturing a tantalum anode body of. 3. In butt resistance welding of a porous tantalum sintered body and a tantalum wire, a high-density compressed portion by dimple processing is previously provided in the welded portion of the sintered body, and the high-density compressed portion is tantalum wire-bonded. A method for producing a tantalum anode body, comprising: