KR930003433B1 - Etching liquid of aluminium foil - Google Patents

Abstract

The etching solution for aluminum foil of an electrolytic condenser is prepared by adding 3-7 vol% sulphuric acid to 3 vol% hydrochloric acid solution at 60 deg.C. The etching method comprises (a) immersing the aluminum foil into the etching solution, (b) applying the alternate current with 0.1 A/cm2 current density and 400 Hz frequency for 60-75 sec. The mechanical strength and the electrostatic capacity of the aluminum foil increase, and the amount of corrosion decreases, by using this etching solution and method.

Description

Etching solution of aluminum foil for electrolytic capacitors and etching method using the same

1 is a graph showing the capacitance against the sulfuric acid concentration in the etching solution of the present invention.

* Explanation of symbols for main parts of the drawings

A: etching time is 60 seconds B: etching time is 75 seconds

The present invention relates to an etching solution of an aluminum foil for an electrolytic capacitor and an etching method using the same, and more particularly, to an etching solution of an aluminum foil for an electrolytic capacitor, which increases the capacitance of the foil, appropriately reduces corrosion, and improves mechanical strength. It relates to an etching method.

In general, an aluminum electrolytic capacitor is a polar capacitor made by impregnating an inhibitor solution by winding an aluminum electrode foil and an electrolytic cell, and in the aluminum electrode foil, fine and uniform unevenness is obtained by etching the foil surface to increase capacitance per unit area. ) Is used to increase the effective area.

In recent years, in the manufacture of the electrolytic capacitor as described above in accordance with the miniaturization and light weight of electronic products, the etching technology of the aluminum foil is required to have a minimum form and maximum capacity of the capacitor, and an electrode used to meet such a requirement It is necessary to increase the capacitance per unit area of foil.

Therefore, in the conventional etching method of electrode foil for aluminum electrolytic capacitors, aluminum foil is etched by electrochemically dissolving and precipitating aluminum in an electrolytic solution containing hydrochloric acid or the like as the main caustic.

At this time, in order to prevent excessive etching of foil, various inorganic compounds that inhibit corrosion are used as additives.

Nevertheless, in the etching method, the etching is often excessive. When the etching is excessive in this way, aluminum is dissolved in the etching solution, the thickness decreases, and the effective area of the aluminum foil is not increased proportionally due to the increase of the dissolved amount, and when the critical point is reached, the effective area is reduced. have.

SUMMARY OF THE INVENTION An object of the present invention is to improve the etching solution used for etching an aluminum foil for an electrolytic capacitor in view of the above problems, and thus, an etching solution for an aluminum foil for an electrolytic capacitor having excellent mechanical strength, capacitance, and corrosion loss, and an etching method using the same. To provide.

In order to achieve the above object, the present invention provides a method of etching aluminum foil for electrolytic capacitors, wherein aluminum foil is added to the etching solution and the etching solution generated by adding 3 to 7% by volume sulfuric acid to a 3% by volume hydrochloric acid solution having a liquid temperature of 60 ° C. It is characterized by depositing an alternating current having a current density of 0.1 A / cm 2 and a frequency of 400 Hz.

As described above, the addition of sulfuric acid increases the capacitance of the foil, but the effect is very small at less than 3% by volume, and more than 7% by volume, the capacitance is reduced because it inhibits the corrosion activity of chlorine ions. Therefore, the reason for increasing the capacitance of the foil by the addition of 3 to 7% by volume sulfuric acid is that the sulfuric acid group is attached to the aluminum surface, so that the place of attachment of highly corrosive chlorine ions is reduced, and the aluminum where chlorine ions are attached has a corrosion rate This is because aluminum in the place where sulfuric acid is attached fast and the corrosion rate is slow and the formation of irregularities on the surface becomes a spongy structure.

Referring to the manufacturing method according to the invention in detail as follows.

In the present invention, in order to increase the capacitance of the aluminum foil for electrolytic capacitors, the etching solution of the aluminum foil is improved, and the aluminum foil is etched using the improved etching solution.

That is, aluminum is treated in 3% by volume hydrochloric acid solution.

In this case, hydrochloric acid is separated into hydrogen ions (H ⁺ ) and chlorine ions (Cl ⁻ ) in an aqueous solution, and chlorine ions are attached to the aluminum surface to combine with aluminum ions, thereby producing aluminum chloride (AlCl ₃ ). By being produced in this way, the thin surface is corroded to increase the surface area.

In order to increase the capacitance of the aluminum foil, 3 to 7 volume% sulfuric acid was added to the 3 volume% hydrochloric acid solution to obtain an etching solution. In addition, aluminum foil was deposited on the etching liquid obtained above, and the aluminum foil was etched by energizing the alternating current of 0.1 A / cm <2> and the frequency of 400 Hz for 60 second-75 second.

The preferred embodiment of the present invention having the above-mentioned features will be described in detail.

Example 1

98% aluminum alloy foil containing 1% manganese was immersed in an etching solution formed by adding 3-7% by volume to 3% by volume hydrochloric acid solution having a liquid temperature of 60 ° C. The etching was performed by energizing the current for 60 to 75 seconds.

Example 2

The same process as in Example 1 was carried out, but the etching was performed by applying electricity for 75 seconds.

Thus, the capacitance of the etched aluminum foil was measured. The results are shown in FIG.

As can be seen from FIG. 1, in the etchant obtained by mixing 3 vol% hydrochloric acid and 3 to 7 vol% sulfuric acid obtained in the present invention, when the etching time is 60 seconds, the capacitance increases in proportion to the amount of sulfuric acid added. The maximum value was 6 vol% and then drastically decreased.

In addition, when the etching time was 75 seconds, it increased in a parabolic shape and reached a maximum value at 4% by volume, and above that, the capacitance decreased in a parabolic shape.

As described above, according to the present invention, as an etching method of an aluminum foil for an electrolytic capacitor using the improved etching solution of the aluminum foil for electrolytic capacitors and using the improved etching solution, etching is performed on the surface of the aluminum foil when the etching solution of the present invention is used. The pit is formed and its pit structure is very fine, so that a large capacitance of the foil is obtained, which is particularly useful for the method of etching the cathode foil.

Claims (3)

The etching solution of the aluminum foil for electrolytic capacitors produced by adding 3-7 volume% sulfuric acid to the 3 volume% hydrochloric acid solution whose liquid temperature is 60 degreeC, The etching liquid of the aluminum foil for electrolytic capacitors characterized by the above-mentioned. In the etching method of the aluminum foil for electrolytic capacitors, aluminum foil is dipped into an etching solution generated by adding 3 to 7 volume% sulfuric acid to a 3 volume% hydrochloric acid solution having a liquid temperature of 60 ° C., and the current density is 0.1 A / cm 2, and the frequency is A method of etching aluminum foil for an electrolytic capacitor, characterized by passing an alternating current of 400 Hz. The etching method of an aluminum foil for electrolytic capacitors according to claim 2, wherein the AC current is energized for 60 seconds to 75 seconds.

Images