JPS622040B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for etching aluminum foil used in electrolytic capacitors, and is characterized in that chemical etching is performed after direct current etching. Conventionally, the method of etching aluminum foil used as electrode foil for electrolytic capacitors was to use a few percent aqueous solution of hydrochloric acid as an etching solution, keep the etching solution at a high temperature such as 80°C, and perform DC electrolytic etching. If the amount of electricity exceeds 4500C/ ^dm2 , there will be problems such as surface dissolution will be greater than formation of etching pits, and mechanical strength will also be impaired. Many of them were rough and penetrated through the aluminum foil, and had the disadvantage that it was not possible to improve the surface enlargement rate by etching. The present invention has been made in view of the above points, and is an aluminum foil for electrolytic capacitors that has dense etching pits and can maintain mechanical strength because the base metal of the aluminum foil remains even when pits are formed. A method of etching foil is provided. This will be explained below using examples. The present invention is a hydrochloric acid + sulfuric acid aqueous solution (liquid temperature 50 to 100℃)
The first stage of etching is performed by feeding direct current using a sulfuric acid solution, and the second stage of etching is chemically etched by immersion in a sulfuric acid aqueous solution (solution temperature: 50 to 100°C). The present invention provides an etching foil with excellent mechanical strength. The inventor etched the combinations shown in Table 1 and calculated the capacitance value and number of bends when the etched aluminum foil was subjected to chemical conversion treatment at 210V (lower a 500g weight and tilt it at right angles to one side). , the number of times when one time is when you return and perform the same action on the opposite side)
I got it.

[Table] FIG. 2 shows a cross-sectional view of the etched aluminum foil 10 obtained according to the present inventions 1 to 5 shown in the above table. Compared to the conventional example shown in FIG. It is understood that the aluminum base metal remains without penetrating the depth, and that it has great mechanical strength such as bending. The composition of the first stage etching solution is Hcl 2~15wt/V%+ _{H2SO4 1} ~35wt/
A range of V% is suitable. HCl has a rough etching pit density and acts deeply on aluminum foil, and H ₂ SO ₄ has a dense etching pit density but acts shallowly. Therefore, the present invention uses these in an appropriate composition range. By setting the following, each action is controlled. In the second stage of chemical etching, the etching pits formed in the first stage of etching have the effect of advancing the pits in the depth direction while avoiding dissolution of the aluminum foil surface as much as possible, so an appropriate type of liquid and its concentration range are required. However, in the present invention, we will consider the relationship with the pre-etching,
H2SO4 was used at a concentration of 5 to 50 wt/V%. In addition, the current density in the first stage etching, the etching liquid temperature, the liquid temperature in the second stage etching,
Although the immersion time and the like can be changed as appropriate depending on the etching condition, the range shown in Table 2 below is preferable as a suitable range, and it is possible to obtain an excellent surface enlargement ratio and mechanical strength.

[Table] As is clear from the capacitance and bending strength in Table 1, according to the etching method of the present invention, there is an increase in capacitance compared to the conventional and reference examples; It has the feature of significantly improved strength. In addition, the capacitance does not increase much depending on the etching conditions, but compared to the conventional example, the capacitance increases by 8.
The aluminum foil strength is increased by ~34%, and it is possible to obtain the effect of improving the aluminum foil strength and increasing the capacitance.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an aluminum foil obtained by a conventional etching method, and FIG. 2 is a cross-sectional view of an aluminum foil obtained by an etching method according to the present invention. 10...Etched aluminum foil, 11...Etching pit.

Claims (1)

[Claims] 1. Aluminum foil in hydrochloric acid 2~15wt/V% + sulfuric acid 1~
After direct current etching in a pre-etching solution consisting of a 35wt/V% aqueous solution, 5 to 50wt/V of sulfuric acid was applied.
1. A method for etching aluminum foil for electrolytic capacitors, characterized by immersion treatment in a subsequent etching solution consisting of a % aqueous solution. 2 Etching liquid temperature of DC etching 50~100
℃ and current density of 1 to 70 A/ ^dm2 ,
Immersion treatment at a liquid temperature of 50 to 100℃ and an immersion time of 4 to 20 minutes.
A method of etching aluminum foil for an electrolytic capacitor according to claim 1, wherein the etching method is carried out under the following conditions.