JPS63290239A - Aluminum alloy foil for cathode of electrolytic condenser - Google Patents

Abstract

PURPOSE:To improve the electrostatic capacity of an Al foil without lowering the characteristics such as strength, etc., by specifying Si content for Fe content in Al to the specific range and regulating Ti content. CONSTITUTION:The titled foil is formed by the compsn. in which the Si content is regulated to 1.0-2.0 times the Fe content and the Ti content is regulated to <=0.001wt.%. Said Al alloy foil can be obtd. by melting primary electrolytic Al ground metal having about 540-560ppm Fe content and having about 99.8% Al purity, adding specific amounts of Si and Ti to the alloy, casting an Al alloy slab and executing foiling, etc., thereto. By the above-mentioned compsn., the potential difference between the Al matrix and the deposition in the matrix is increased and, as a result, the electrostatic capacity of the Al foil after etching can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an aluminum alloy foil for electrolytic capacitor cathodes.

Conventional technology and its problems In order to increase the capacitance (C) of an electrolytic capacitor,
It is necessary to increase not only the capacitance (CA) of the anode part but also the capacitance (co) of the cathode part.

Conventionally, in order to increase the capacitance of the cathode part, aluminum alloy foil has been used, for example, which is made by adding 0.1 to 0.5% copper to aluminum with a purity of 99.3% to 99.8%. (Japanese Patent Publication No. 44-25016). In such alloy foils, the potential difference between the aluminum matrix and the intermetallic compound becomes large, so the aluminum matrix can be selectively corroded during etching, resulting in the formation of many pits, and eventually the cathode foil It is possible to improve the capacitance as However, when trying to further improve the capacitance of such alloy foil by etching it for a long time, the area around the intermetallic compound dissolves excessively and falls off, making it impossible to use an efficient surface. Expansion may not occur.

Therefore, in response to rapid technological advances in various fields that use electrolytic capacitors, new technology has emerged that can further improve the capacitance of the cathode portion of electrolytic capacitors without the above-mentioned problems. is desired.

Means for Solving the Problems The inventor of the present invention, in view of the current state of the technology as described in (a), has carried out intensive research and has determined that the silicon content relative to the iron content in aluminum is within a certain range, It was found that when the titanium content is below a certain amount, the potential difference between the aluminum matrix and the precipitates in the matrix increases, and as a result, the capacitance of the aluminum foil after etching is significantly increased. . That is, the present invention provides the following aluminum alloy:
An aluminum alloy foil for an electrolytic capacitor cathode in which the amount of f is 1.0 to 2.0 times the iron content and the titanium content is 0.001% by weight or less. ] When silicon is added to alumina, a high potential difference between it and the aluminum matrix is created.
A Q 3 Fe becomes an ARFeSi compound, and the potential difference with aluminum decreases. In addition, excess silicon dissolves in aluminum and increases the potential of the matrix, so that the potential difference between the aluminum matrix and the intermetallic compound becomes even smaller. Therefore, even if the amount of electricity used during etching is increased, excessive dissolution on the alloy foil surface is less likely to occur, making it possible to efficiently enlarge the surface.

In the present invention, the silicon content is 1.5% of the iron content.
0 to 2.0 times. If the content of silicon is less than 1 times that of iron, A Q 3 Fe remains and the desired effect is not fully exhibited. On the other hand, if the silicon content is more than twice the iron content, silicon particles having a large potential difference with the aluminum matrix will increase, making etching non-uniform and promoting excessive dissolution. The silicon content is determined by the iron content -f'Tffi, so it is not particularly limited, but is usually 0.02 to 0.2% by weight.
(hereinafter simply referred to as %).

In the alloy foil of the present invention, the titanium content is 0.001
% or less. If the titanium content exceeds 0.001%, the surface of the foil will be violently dissolved during etching, reducing the effect of incorporating silicon.

Effects of the Invention According to the present invention, the capacitance of an aluminum foil for an electrolytic capacitor cathode can be significantly improved without substantially reducing other properties such as strength.

EXAMPLES Hereinafter, examples will be shown to further clarify the features of the present invention.

Example 1 A primary electrolytic aluminum ingot with an iron content of 540 ppm to 560 ppm and an aluminum purity of 99.8% was melted,
An aluminum alloy slab was cast by adding predetermined amounts of silicon and titanium.

° These slabs were subjected to a normal foil-making process to a thickness of 5
After obtaining a 0 μm alloy foil, it was annealed at 400° C. for 5 hours under vacuum. Table 1 shows the content (ppm) of substantial components other than aluminum in the alloy foil thus obtained.

Table 1 Samples Fe Si Ti Si/FeN
o.

1 540 150 5 0.28 2 550 240 5 0.44 3 550 430 5 0.78 4 540 630 5 1.17 5 580 820 5 1.46 6 540 1000 5 1.82 7 5501430 5 2.60 8 5602100 5 3.75 9 550 250 75 0.48 10 540 620 75 1.15 The obtained soft foil was immersed in an etching bath containing 15% by volume of hydrochloric acid and 1% by volume of sulfuric acid at a bath temperature of 60°C and an alternating current density. IA/crJ
Etching was performed for 1 minute under the following conditions.

Next, the obtained etched foil was chemically converted at 3V with 5% boric acid at 25°C, and the dissolution loss was <g/rr? ) and capacitance (tt F /cIli) were measured.

The results are shown in Table 2.

Table 2 Sample No. Dissolution loss Capacitance 1
45.9 73.0 2 45.9 73.2 3 45.6 76.3 4 43, 9 86. 75 4
0, 5 96. 06 39.2
121.3 7 43.6 71.4 8 46.4 43.8 9 46.8 54.2 10 45.3 76.9 As is clear from the results shown in Table 2, the aluminum alloy foil of the present invention (No.
, 4.5 and 6)! :In the case of iron, silicon is 1 to 1
By doubling the amount of titanium and reducing the titanium content to 0.001% or less, the amount lost by dissolution is reduced and a significant increase in capacitance is achieved.

(that's all)

Claims (1)

[Claims] (1) Silicon content is 1.0 to 2.0 times the iron content,
An aluminum alloy foil for electrolytic capacitor cathodes with a titanium content of 0.001% by weight or less.