JPS63290238A - 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 incorporating specific amt. of Cu into Al and regulating Si content for Fe content to the specific range. CONSTITUTION:The titled foil consists of the compsn. in which the Cu content is regulated to 0.01-0.1wt.% and the Si content is regulated to 1.0-2.0 times the Fe content. Said Al alloy foil can be obtd. by melting primary electrolytic Al ground metal having about 540-550ppm Fe content and having about 99.8% Al purity, adding specific amounts of Si and Cu 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. be.

Conventionally, 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% of copper to aluminum with a purity of 99.3% to 99.8%. (Japanese Patent Publication No. 44-25016). In such an alloy foil, the potential difference between the aluminum matrix and the intermetallic compound is large, so the aluminum matrix can be selectively corroded during etching, resulting in the formation of many bits, and the final result is It is possible to improve the capacitance as However, when attempting to further improve the capacitance of such alloy foils by etching them for a long time, the area around the intermetallic compounds dissolves excessively and falls off, making it difficult to form 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 In view of the current state of the technology as described above, the inventor of the present invention, as a result of intensive research, has determined that aluminum contains a specific amount of copper and that the silicon content is constant relative to the iron content. It has been found that within this range, 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: "Contains 0.01 to 0.1% by weight of copper and has a silicon content of 1.0 to 2.0 times the iron content. Aluminum alloy foil for electrolytic capacitor cathodes.'' When silicon is added to aluminum, it has a high potential difference with the aluminum matrix.
becomes an ARFeSi compound, and the potential difference with aluminum decreases. In addition, excess silicon and copper are dissolved in aluminum and increase 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 -Nm content of iron, so it is not particularly limited, but is usually about 0.02 to 0.2% by weight (hereinafter simply referred to as %).

In the present invention, the copper content is 0.01 to 0.1% by weight. If the copper content is less than 0.01%, A
The amount of R-Cu-Fe compound precipitated decreases, and almost no increase in capacitance is observed. On the other hand, when the copper content exceeds 0.1%, the potential of the aluminum matrix increases as the amount of solid solution of copper increases, and the potential difference with the precipitate becomes smaller. In this case, dissolution of the entire aluminum foil progresses and pit formation becomes insufficient.

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 or 550 ppm and an aluminum purity of 99.8% was melted,
An aluminum alloy slab was cast by adding predetermined amounts of silicon and copper.

These slabs were subjected to a normal foil manufacturing process to a thickness of 50 μm.
After obtaining the alloy foil of m, it was annealed at 400° C. for 5 hours under vacuum. Table 1 shows the content ffi (ppm) of substantial components other than aluminum in the alloy foil thus obtained.

Table 1 Samples Fe Si Cu Si/FeN
o.

1 540 800 200 1.482 550 2
50 500 0.453 550 600 500
1.094 540 1000 500 1.855
550 1450 500 2.646 540 61
01000 1.137 550 6001500 1
．． 098 550 250 20 0.45 9 550 800 20 1.45 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 6°C and an alternating current density of IA/cJ. Etching was performed for 60 seconds under the following conditions. Next, the obtained etched foil was chemically converted with 5% boric acid at 25°C at 3V to reduce the dissolution weight (g/rr?)
and capacitance (μF/cd) were measured. The results are shown in Table 2.

Table 2 Sample Nα Dissolution loss Capacitance 1
40.8 103.02 40,6
99.43 40.3 117.44
40.9 128.55 43,
1 92. 06 40.6
122.67 48, 1 88.08
45.9 73.29 40.
9 96.0 As is clear from the results shown in Table 2, the aluminum alloy foil of the present invention (No. 1.3.4
and 6), by blending 1 to 2 times as much silicon as iron and 0.01 to 0.1% copper, the melt loss was reduced and a significant improvement in capacitance was achieved. has been done.

(that's all)

Claims (1)

[Claims] (1) An aluminum alloy foil for an electrolytic capacitor cathode containing 0.01 to 0.1% by weight of copper and having a silicon content of 1.0 to 2.0 times the iron content.