JPS63216328A - Manufacture of electrolytic capacitor anode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an anode body for an electrolytic capacitor,
In particular, the present invention relates to a method for manufacturing an anode body of an aluminum-titanium alloy.

[Conventional extraction technique]

Aluminum-titanium alloy electrolytic capacitors were developed as electrolytic capacitors that are as low-priced as M electrolytic capacitors and as compact as Ta electrolytic capacitors (Japanese Patent Laid-Open No. 11477.60-48090.60-4482).
2 or USP 4, 331, 477.4, 468
, 719.4, 432, 935), the mixed composition of which is conventionally 50 to 80% aluminum to titanium.
Atom % ranges have been used.

[Problem that the invention seeks to solve]

Electrolytic capacitors that have a porous anode body made of aluminum-chik 2 alloy have a lower electrostatic charge per unit volume when the mixed composition of titanium and aluminum powder contains more titanium due to the inherent characteristics of the porous formation process. The capacitance value tends to increase. Therefore, by applying a mixed composition containing a large amount of titanium and gold, it becomes possible to manufacture a smaller-sized electrolytic capacitor. However, the conventional mixed composition of 50 atomic % titanium had large leakage current and loss, and had poor electrical characteristics, making it impossible to put it to practical use as an electrolytic capacitor.

The purpose of the present invention is to improve such defects in electrical characteristics,
It is an object of the present invention to provide a method for manufacturing an electrolytic capacitor having a porous anode body made of an aluminum-titanium alloy having a mixed composition with a high titanium content and excellent in small size and large capacity.

Means for Solving Problems] The method for manufacturing an anode body for an electrolytic capacitor of the present invention involves press-molding and re-sintering a mixed powder of titanium and aluminum that has been nitrided in advance to form a porous sintered aluminum-titanium alloy. body.

[Effect]

This manufacturing method improves the characteristics of aluminum-titanium alloy electrolytic capacitors, which have a mixed composition with a high titanium content, which had poor characteristics when titanium powder was mixed with aluminum as it is, making it possible to make it smaller, with larger capacitance, and with stable electrical characteristics. It is possible to obtain a high-quality electrolytic capacitor.

In the present invention, the reason why a mixed composition with a high titanium content is effective in improving electrical characteristics is as follows.

First, the situation in the prior art will be explained.

In the aluminum-titanium binary system, atomic % is approximately proportional to volume %. Therefore, if the average particle diameters of aluminum particles and titanium particles are the same, the mixed composition is 50 atomic % titanium. The number of aluminum particles becomes almost equal, making it easy to mix uniformly. However, when the composition has a high titanium content, the number of aluminum particles relative to the titanium particles rapidly decreases, making it difficult to ensure uniformity of the mixed state.

By the way, when a press molded body of mixed powder of aluminum and titanium is sintered, an alloying reaction occurs at 500 to 600°C due to a solid phase reaction in which aluminum diffuses unilaterally into titanium, and at this time, the places where aluminum particles were present are A unique process of forming a porous body occurs in which pores form, and the places where titanium particles were present become aluminum-titanium alloy particles, forming skeletal channels of the porous body. Therefore, the final sintering temperature (1000 to 11
Although alloy particles with a uniform composition are likely to be formed at temperatures of 00℃), the balance of the number of particles is lost, making it difficult to maintain a mixed state in which aluminum particles are evenly distributed around individual titanium particles. Regarding the composition, even at the final sintering temperature, compositional unevenness tends to occur within the alloy particles. When the mixed composition has a high titanium content, the average composition of the alloy particles after sintering also has a high titanium content. Therefore, there is a high probability that the compositional uneven portion that has occurred will have a composition that is considerably rich in titanium and deficient in aluminum, and such a portion will lead to a decisive deterioration of characteristics. This situation is shown in FIG. 2 as a cross-sectional view of the alloy particles forming the porous body after sintering (the mixed composition was 30 atomic percent aluminum). In the figure, 3 is a void portion, 4 is a portion inside the alloy particle with an alloy composition of approximately 30 atom% aluminum, and 5 is a composition irregularity that appears on the surface of the alloy particle and has an alloy composition far more titanium than 30 atom% aluminum. It is a part.

Next, a case using the manufacturing method of the present invention will be explained.

When a mixed powder press molded body of titanium powder and aluminum powder that has been nitrided in advance is sintered, the nitrogen in the titanium acts as a barrier against the diffusion of the aluminum component and suppresses the diffusion, so that alloying does not occur to the inside of the titanium particles. First, only the surfaces of the titanium particles are alloyed, and the composition becomes an alloy composition containing more aluminum than the mixed composition. Because only the particle surface is alloyed, the number of aluminum and titanium particles is unbalanced, and even in the case of a mixed composition with a high titanium content, which is difficult to mix uniformly, the alloy layer formed on the surface may be extremely excessive in titanium or insufficient in aluminum. It is not a composition. In other words, even if a porous sintered body is manufactured from a mixed composition with a high titanium content, the surface alloy composition of the particles constituting the porous sintered body, which determines the characteristics of an electrolytic capacitor, is different from a mixed composition with a low titanium content and a high aluminum content. The state is the same as that produced from scratch, and this is the reason why the effects of the present invention are achieved.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of aluminum-titanium-containing metal particles forming a porous body after sintering, showing an embodiment of the method for manufacturing a positive body for an electrolytic capacitor of the present invention.

The mixed composition of this porous body is the same as that of the conventional example shown in Fig. 2.
It was made of atomic percent aluminum. In the figure, 1 is an alloy layer having an alloy composition of about 50 atomic % aluminum, 2
is a nitrided titanium layer containing almost no aluminum component,
3 is a hole.

Using titanium powder and aluminum powder that had been nitrided at 800°C for 20 minutes in nitrogen gas,
Eight levels of mixed powders with mixed compositions of 20 to 55 atom % aluminum were prepared at atomic % intervals.

Next, press molding of 2.5 orchid φX2all was performed for all levels, followed by 1050°C in a vacuum of 1 x 10--110
The material was sintered to form a porous sintered body of aluminum-titanium alloy. 200 sintered bodies of each level were placed in a phosphoric acid aqueous solution at 80%
Perform anodization of V, and the capacitance fl(C
+2o) (measured in 30% H2S Oa) and 16V
Leakage current (LC) during application was measured. In addition, the capacitance per unit volume (CV/VOI) was calculated. The number of measurement samples is all for LC, C+2o.

Regarding Cvchi/vol, there were 20 pieces for each level.

(The calculated data are shown in Table 1. The average values of JI and V for each term are shown.

Next, for each level, 1 except for the 20 used for Cl2o measurement.
For all 80 pieces, solid electrolyte con- 1 no'El
A solid electrolytic capacitor was obtained by the usual methods applied to manufacturing, namely, impregnation with manganese nitrate, cathoding of manganese dioxide (In02) by thermal decomposition, followed by coating with graphite, silver paste, solder dipping, and resin sheathing.

After solidification, Cl2O, tan δ120,
d3 cJ: and LC were measured, and the measured data (average values) are shown in Table 1 in the same manner as after anodization.

For comparison, nitriding treatment ■lI! is used as a conventional example. In the case of using sushi titanium powder, porous sintered bodies with 8 levels of mixed composition were fabricated, anodized and solidified using exactly the same method, and the measurement data is also shown in Table 1 (lower part of the middle row). Indicated.

The following can be seen from Table 1. LC values are generally larger in the case of conventional technology both after anodization and after solidification, and CVf/
The value increases as the vol value increases and the titanium-containing composition increases, but in the case of this example, the value decreases within the range of a mixed composition of 50 to 25 at% aluminum to titanium. and stable. tar+ after solidification
6+20 also shows a large value of 4 to 25% in the mixed composition range of 50 to 25 atom% aluminum in the case of the conventional technology, whereas in the case of this example it shows a stable small value of 3 to 5%. ing. Furthermore, when the maximum coverage is defined as the ratio of Cm after solidification to CI20 after anodization, in the case of the conventional technology, it is 92 → 40% in the mixed composition range of 50 to 25 atoms.
The coverage rate is significantly lower on the side where titanium has more golden color. On the other hand, in the case of this example, a stable high coverage of 95 to 90% is shown within the same mixed composition range.

The electrostatic capacitance Cv/VOI per unit volume is also larger in this embodiment as a whole than in the prior art, and its maximum value extends to the mixed composition side where titanium self-loss is higher.

As explained above, according to this example, aluminum-titanium was manufactured by applying a mixed composition with a high titanium content (50 to 25 at% aluminum), which was excellent in small size and large capacity (Cv chi/VOI large). The electrical characteristics of the metal-containing M capacitor were significantly improved, and it became possible to put into practical use an even better electrolytic capacitor.
When the mixed composition becomes 20 atomic% aluminum, the electrical properties of this example also become poor, and when the mixture composition is 55 atomic% aluminum, there is almost no difference in characteristics from that of the conventional technology. Preferably, the mixture composition ranges from 25 to 50 atomic percent aluminum.

〔Effect of the invention〕

As explained above, the present invention is a porous sintered aluminum-titanium alloy obtained by press-molding and sintering pre-nitrided titanium powder or a mixed powder of pre-nitrided titanium hydride powder and aluminum powder. By using a porous titanium-aluminum alloy with a mixed composition of 25 to 50 atomic percent aluminum, which has conventionally been excellent in small size and large capacity, but could not be used due to problems with electrical characteristics as an electrolytic capacitor. This has the effect that the positive electrode body can be made into an electrolytic capacitor that is small in size, has a large capacity, and has excellent electrical characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of aluminum-titanium alloy particles forming a porous sintered body showing an example of the method of manufacturing an anode body for an electrolytic capacitor of the present invention, and FIG. 2 is a cross-sectional view of the porous sintered body obtained by the conventional technique. FIG. 3 is a cross-sectional view of the same alloy particles forming a compact. 1... Alloy layer having an alloy composition of titanium-50 atomic % aluminum, 2... Titanium layer containing almost no aluminum component 3...
...Vacancy, 4...Alloy part having an alloy composition of approximately titanium-30 atomic% aluminum, 5...Alloy part having an alloy composition of titanium-30 atomic% aluminum or less (composition uneven part; aluminum deficiency) .

Claims (1)

[Claims] 1. A method for producing an anode body for an electrolytic capacitor, in which a mixed powder of titanium powder and aluminum powder, which has been nitrided in advance, is press-molded and then sintered. 2. The mixed composition of the nitrided titanium powder and aluminum powder is 25 to 50% aluminum to titanium.
A method for manufacturing an anode body for an electrolytic capacitor according to claim 1, wherein the content is in the atomic % range.