JPS5999712A - Anode forming material for electrolytic condenser - 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 applications The present invention relates to an anode molded body for solid electrolytic capacitors.

Structure of the conventional example and its problems - First, in a solid electrolytic capacitor, one end of a metal wire of the same type is embedded in fine powder of metal such as tantalum or niobium, and the metal powder is integrated with one end of the metal wire □. The anode molded body formed under pressure is anodized in an aqueous solution such as phosphoric acid to form a dielectric oxide film on the surface of the anode molded body. Electrolyte layer□ is deposited, and carbon, conductive silver pane,
After the electrodes were sequentially attached and the cathode lead wires were soldered, the entire body was covered.

In general, □. As an anode molded body for solid electrolytic capacitors, □ is used to increase the degree of adhesion between the constituent metal powder particles and between the metal powder particles and the metal wire in the embedded part, and to sufficiently lower the electrical resistance. - Generally, it is necessary to sinter at high vacuum and high temperature. However, due to this sintering, the surface area of the metal powder aggregate is reduced to □ phase or the like. .

In order to obtain high capacitance per unit weight of metal powder as an electrolytic capacitor, the sintering temperature should be as low as possible, but in low-temperature sintering, metal powder is sintered with metal wire. It is hard to wear, and mechanical processing leads to
The wire method may cause problems such as loss of capacitance or excessive loss coefficient when used as a capacitor.

As described above, in the past, it was generally difficult to manufacture an electrolytic capacitor with a high electric capacity by low-temperature sintering of an anode molded body for an electrolytic capacitor.

FIG. 1 shows a cross-sectional view of a conventional anode molded body for an electrolytic capacitor.

110 mq of high-purity tantalum powder for electrolytic capacitors was placed in a mold with a cylindrical cavity, and a tantalum wire with a diameter of 0.3 mm was embedded as a lead wire in the center of the mold.
Although it was integrally compression-molded into a cylindrical shape with a height of 8 mm and 28 mm, it shows a cut surface taken along a plane passing through the center of the lead wire. (1) is the compression molded tantalum powder part, (
2) shows a tantalum wire embedded in the center and fixed under pressure.

Purpose of the Invention The present invention provides an anode molded body for electrolytic capacitors which can be sintered at a low temperature and which can reduce the reduction in surface area and eventually capacitance caused by sintering, which is a drawback of conventional anode molded bodies for electrolytic capacitors. This is what we do.

Structure of the Invention In the anode molded body for a Tlj decomposition capacitor of the present invention, a part of the lead wire of a metal tank whose surface is coated with a thin film of aluminum is embedded in fine powder of high-purity metal tantalum,
It is characterized in that the tantalum fine powder and a part of the lead wire are integrally pressed and formed.

Description of examples The present invention will be explained in detail below.

FIG. 2 shows a cross-sectional view of a molded anode for an electrolytic capacitor according to the present invention. In the figure, (3) is compression-molded tantalum powder, (4) is tantalum wire, and the surface thereof is coated with a 3600 angstrom thick aluminum thin film (5) by vacuum deposition.

The anode molded body for electrolytic capacitors of the present invention (hereinafter simply referred to as the anode molded body) has a high capacitance per unit weight of the constituent metal powder, even when sintered at a lower temperature. Sintering is promoted due to the melting point lowering effect of the aluminum thin film coated on the surface of the lead wire, resulting in a good electrical and mechanical connection between the powder part and the metal wire.

Now, both the conventional @ electrode molded body and the @ pole molded body according to the present invention were heat-treated and sintered at 1000°C for 20 minutes in a high vacuum, and then they were placed in a 5% phosphoric acid aqueous solution at 85°C. The sample was anodized at 50 V DC to form a dielectric film on the surface, and was used as an anode for an electrolytic capacitor. These anodes are 3
The capacitance was measured by immersing it in a 0% sulfuric acid aqueous solution and using a silver plate as a counter electrode, and from this the ay product per 12 pieces of tantalum powder was found to be 18,340 μF-V for the conventional anode.

For the anode of the present invention, the value was 18480 μF·■, which is almost the same value. However, the loss coefficient (t
anδ) is 65% for the conventional anode and 45% for the anode of the present invention, and the lead wire pull-out strength is 2.2 kp for the conventional anode, but for the anode of the present invention. It was found that the lead wire itself broke at 37 to 7, and the σ1 extraction strength was larger than this. In view of these results, when sintered at the same temperature, the anode molded body of the present invention performs sintering and fusion between the lead wire and the tantalum metal powder part much better than the conventional anode molded body. You can see that it is true.

This is because the aluminum ram thin film on the surface of the tantalum wire used in the anode molded body of the present invention causes a eutectic reaction with the tantalum powder during sintering, producing an alloy melt phase between them.
It is thought that sintering was performed very well.

For example, in order to obtain mechanical strength, a conventional anode sintered body was sintered at 1500°C for 20 minutes in a high vacuum, and the resulting anode was anodized in the same manner as described above.
av (4iCi 16000μF・■).In contrast, in the case of the present invention, at a sintering temperature of 1400℃, the CV product is 15% compared to this while having the above-mentioned mechanical strength.
are improving.

Effects of the Invention If the conventional anode molded body is sintered only at a low temperature, that is, 1400°C, even if the CV product improves by 15%, the lead pull-out strength will decrease and the loss factor as a capacitor will increase. On the other hand, as mentioned above, the anode molded body of the present invention has a high lead wire pull-out strength, an improved aV product per 12 as a capacitor, and a high ta
It also has an excellent characteristic of having a small nδ. Furthermore, using the same powder weight, the electric capacity can be increased by as much as 15%, and the use of expensive tantalum powder can be saved.

[Brief explanation of the drawing]

FIG. 1 shows a conventional molded anode for an electrolytic capacitor, and FIG. 2 shows a sectional view of the molded anode for an electrolytic capacitor according to the present invention. 1: Compression molded tantalum powder 2: Tankle lead wire 3: Compression molded tantalum powder 4: Tankle lead wire 5: Coated aluminum

Claims (1)

[Claims] A part of a lead wire made of tantalum metal whose surface is coated with a thin film of aluminum is embedded in fine powder of high-purity tantalum metal, and the fine tantalum powder and part of the lead wire are integrally compressed under pressure. An anode molded body for electrolytic capacitors.