阅读说明：本技术 一种改善低压阳极箔脆性的方法及制得的低压阳极箔 (Method for improving brittleness of low-voltage anode foil and low-voltage anode foil prepared by same ) 是由 杨海亮 冉亮 刘俊英 于 2021-05-07 设计创作，主要内容包括：本发明公开了一种改善低压阳极箔脆性的方法及制得的低压阳极箔。本发明方法包括在化成处理之前,对铝箔进行应力处理,经过应力处理后的铝箔表面具有宽度为0.5～5μm、深度为10～65μm的裂纹,相邻裂纹间的最小间距为50～150μm。本发明提供了一种改善低压阳极箔脆性的方法,通过在常规的低压阳极箔制造工序中,在铝箔化成处理前增加应力处理的工序,使得箔片表面出现密集细小的裂纹,从而低压阳极箔在弯折工序时,受到的挤压力可以通过缩小裂纹之间的空隙来进行分散,在维持铝箔原有厚度的前提下,大幅改善了低压阳极箔的脆性。(The invention discloses a method for improving the brittleness of a low-voltage anode foil and the prepared low-voltage anode foil. The method comprises the step of carrying out stress treatment on the aluminum foil before formation treatment, wherein cracks with the width of 0.5-5 mu m and the depth of 10-65 mu m are formed on the surface of the aluminum foil after the stress treatment, and the minimum distance between every two adjacent cracks is 50-150 mu m. The invention provides a method for improving the brittleness of a low-voltage anode foil, which is characterized in that in the conventional manufacturing process of the low-voltage anode foil, a stress treatment process is added before an aluminum foil formation treatment, so that dense and fine cracks appear on the surface of the foil, the extrusion force applied to the low-voltage anode foil in the bending process can be dispersed by reducing gaps among the cracks, and the brittleness of the low-voltage anode foil is greatly improved on the premise of maintaining the original thickness of the aluminum foil.)

1. A method of improving the brittleness of a low voltage anode foil, comprising the steps of:

before the formation treatment, the aluminum foil is subjected to stress treatment, cracks with the width of 0.5-5 mu m and the depth of 10-65 mu m are formed on the surface of the aluminum foil after the stress treatment, and the minimum distance between every two adjacent cracks is 50-150 mu m.

2. The method according to claim 1, wherein the surface of the aluminum foil after the stress treatment has cracks with a width of 2.5-4 μm and a depth of 30-50 μm, and the minimum distance between adjacent cracks is 70-120 μm.

3. The method according to claim 1, wherein the stress treatment is rolling the aluminum foil under a winding tension of 5 to 10 kg.

4. The method according to claim 2, wherein the stress treatment is rolling the aluminum foil under a winding tension of 7 to 9 kg.

5. The method according to claim 3, wherein the drawing rate of the rolling is 2 to 6 m/min.

6. The method according to claim 3, wherein the rolling is rolling using an upper roller.

7. The method according to claim 1, wherein the aluminum foil has a thickness of 100 to 140 μm.

8. A method of manufacturing a low voltage anode foil, comprising the steps of:

and sequentially carrying out pretreatment, corrosion treatment and post-treatment on the aluminum foil, and carrying out stress treatment and formation treatment according to any one of claims 1 to 7 to obtain the low-voltage anode foil.

9. A low-voltage anode foil produced by the production method according to claim 8.

10. Use of a low voltage anode foil according to claim 9 for the manufacture of a miniature capacitor.

Technical Field

The invention relates to the technical field of low-voltage anode foils for capacitors, in particular to a method for improving brittleness of a low-voltage anode foil and the low-voltage anode foil.

Background

The aluminum electrolytic capacitor is an energy storage element widely applied to the electronic and electrical industry, the anode foil for the aluminum electrolytic capacitor is an important raw material, and the structural characteristics of the anode foil determine the electrical property of the aluminum electrolytic capacitor. The production process of the low-voltage anode foil generally comprises the following steps: aluminum foil → pretreatment → corrosion treatment → post-treatment → formation treatment → low voltage anode foil is obtained. The pretreatment is to remove oil stains, oxidation films and impurities on the surface of the aluminum foil and improve the surface state; the corrosion treatment is to form a tunnel hole with a certain aperture and depth on the surface of the aluminum foil through electrochemical corrosion so that the surface area of the aluminum foil is enlarged to obtain high specific volume; the post-treatment is to clean the corroded aluminum foil and convert the surface state; the chemical conversion treatment is to form an oxide film on the surface of the aluminum foil by using the energization of a multi-stage power supply.

In the use process of the low-voltage anode foil, due to high brittleness, phenomena such as cracking, foil breaking and the like are easy to occur, and particularly, the brittleness is higher for the foil with high specific volume. The reason is that a layer of compact aluminum oxide film is formed on the surface of the corroded aluminum foil after formation, and the aluminum oxide is a compound with high hardness and poor toughness, so that the low-voltage anode foil is cracked and broken in the processes of cutting, winding, nailing and the like in the manufacturing process of the capacitor.

In order to reduce the phenomena of cracking and breaking of the low-voltage anode foil as much as possible in the manufacturing process of the capacitor, the prior art reports that the thickness of the aluminum core is increased under the condition of keeping the specific volume unchanged by increasing the thickness of the low-voltage anode foil, so that the brittleness of the low-voltage anode foil is improved, and the foil has good mechanical properties. However, the increase in thickness increases the production cost and is not favorable for the miniaturization of the capacitor.

Chinese patent application CN101030485A discloses a low-voltage anode foil pretreatment process, which comprises the following steps of: heat treatment, treatment with aqueous solution of sodium hydroxide and sodium dodecylbenzenesulfonate, washing with tap water, and treatment with dilute hydrochloric acid. Although the mechanical properties of the low-voltage anode foil are improved by the pretreatment method, the problems of high brittleness and easy cracking are not completely solved.

Therefore, it is required to develop a manufacturing method for improving the brittleness of the low-voltage anode foil.

Disclosure of Invention

The invention provides a method for improving the brittleness of the low-voltage anode foil, aiming at overcoming the defect of high brittleness of the low-voltage anode foil in the prior art, and the method can greatly improve the brittleness of the low-voltage anode foil on the premise of maintaining the original thickness of the aluminum foil by adding a stress treatment process before the formation treatment of the aluminum foil so that fine cracks appear on the surface of the foil.

Another object of the present invention is to provide a method for manufacturing a low voltage anode foil.

Another object of the present invention is to provide a low voltage anode foil manufactured by the above manufacturing method.

It is another object of the present invention to provide the use of the low voltage anode foil described above for the preparation of small capacitors.

In order to solve the technical problems, the invention adopts the technical scheme that:

a manufacturing method for improving the brittleness of a low-voltage anode foil comprises the following steps:

before the formation treatment, the aluminum foil is subjected to stress treatment, cracks with the width of 0.5-5 mu m and the depth of 10-65 mu m are formed on the surface of the aluminum foil after the stress treatment, and the minimum distance between every two adjacent cracks is 50-150 mu m.

The inventor researches and discovers that the low-voltage anode foil is easy to crack and break in the using process, mainly because of the following reasons: the holes of the low-voltage anode foil are fine spongy holes, the surface is smooth, and when the low-voltage anode foil is cut, wound and the like in a bending process, the bending of the foil can extrude the surface of the low-voltage anode foil to a certain extent; the force of the extrusion can be only borne by the bent part, and the compact aluminum oxide film formed on the surface of the aluminum foil after the formation treatment has high hardness and poor flexibility. The low voltage anode foil is easily cracked or even broken when pressed.

The aluminum foil is subjected to longitudinal and transverse stress by stress treatment, and dense and fine cracks are generated on the surface of the aluminum foil by pressing and pulling. Therefore, when the low-voltage anode foil is subjected to a bending process in a subsequent use process, the extrusion force can be dispersed by reducing the gaps among the cracks, and the cracking situation can not occur.

Generally, a method for manufacturing a low-voltage anode foil includes a pretreatment, an etching treatment, a post-treatment, and a chemical conversion treatment in this order. In the present invention, the aluminum foil is subjected to a stress treatment, that is, a stress treatment is performed on the etched foil, before the chemical conversion treatment.

By the manufacturing method, the brittleness of the low-voltage anode foil can be greatly improved and cracking can be avoided on the premise of maintaining the original thickness of the aluminum foil.

Preferably, the surface of the aluminum foil after stress treatment has cracks with the width of 2.5-4 μm and the depth of 30-50 μm, and the minimum distance between adjacent cracks is 70-120 μm.

Because the width and the depth of the surface crack of the aluminum foil after stress treatment are only in the micron level, the specific capacity of the low-voltage anode foil is not negatively affected.

In general, the thickness of the oxide film formed on the surface of the etched foil after the formation treatment is not more than 30 nm. Therefore, the aluminum foil with cracks on the surface after stress treatment is subjected to chemical forming treatment, and the width, the depth and the spacing of the cracks are not obviously changed.

Preferably, the stress treatment is to roll the aluminum foil under a winding tension of 5-10 kg.

The coiling tension is not too high or too low in the stress treatment, and when the coiling tension is too high, too deep cracks are easily formed on the surface of the aluminum foil, so that the capacitance of the low-voltage anode foil is influenced; when the winding tension is too low, no effective cracks are formed on the surface of the aluminum foil.

Preferably, the stress treatment is to roll the aluminum foil under a winding tension of 7-9 kg.

Preferably, the traction rate of the rolling is 2-6 m/min.

Preferably, the rolling is rolling using an upper roller.

The inventor researches and discovers that when only the upper roller is used for rolling, enough cracks can be generated on the surface of the aluminum foil, the coiling tension control is more stable, and the cracks generated on the surface of the aluminum foil are more regular. If the upper roller and the lower roller are used for rolling at the same time, the coiling tension is difficult to accurately control, cracks on the surface of the aluminum foil are easy to be disordered, and the proper width and depth cannot be achieved.

Optionally, the upper roller may be a smooth roller or a grooved roller.

Preferably, the upper roller is a smooth roller.

The thickness of the aluminum foil is 100-140 mu m.

Preferably, the thickness of the aluminum foil is 100-120 μm.

The aluminum foil is small in thickness, and the application of the prepared low-voltage anode foil in the preparation of small capacitors is facilitated.

The invention also provides a manufacturing method of the low-voltage anode foil, which comprises the following steps:

and sequentially carrying out pretreatment, corrosion treatment, post-treatment, stress treatment and formation treatment on the aluminum foil.

Preferably, the pretreatment is to soak the aluminum foil in a phosphoric acid solution, and then to clean and dry the aluminum foil.

Specifically, the pretreatment method comprises the following steps: and (3) placing the aluminum foil in a 3-10 wt% phosphoric acid solution at the temperature of 60-80 ℃ to soak for 40-80 s, taking out the aluminum foil, washing the aluminum foil with pure water, and drying the aluminum foil.

More preferably, the pretreatment method comprises the steps of soaking the aluminum foil in 10 wt% phosphoric acid solution at the temperature of 60 ℃ for 80s, taking out the aluminum foil, washing the aluminum foil with pure water, and drying the aluminum foil.

After pretreatment, the oxide film and oil stain on the surface of the aluminum foil can be removed.

Preferably, the method of corrosion treatment is: placing the pretreated aluminum foil in a mixed solution of sulfuric acid and chloride ions, and corroding holes by using an alternating current method; then placing the mixture in an ammonium oxalate solution, and treating the mixture by using direct current; then placing the mixture in sulfuric acid and chloride ion solution, and carrying out reaming corrosion by using alternating current.

Specifically, the corrosion treatment method comprises the following steps:

subjecting the pretreated aluminum foil to 0.5-2 wt.% at 40-55 ℃Sulfuric acid, 10-25 wt.% chloride ion solution, at a current density of 0.35-0.6A/cm²Carrying out pore-forming corrosion for 25-60 s under the alternating current;

then taking out the aluminum foil and placing the aluminum foil in 7.5 to 15 wt.% ammonium adipate solution at the temperature of 70 to 85 ℃, wherein the current density is 0.05 to 0.2A/cm²Carrying out intermediate treatment for 30-50 s under direct current;

then taking out the aluminum foil, and then placing the aluminum foil in a solution of 0.5-2 wt% sulfuric acid and 10-25 wt% chloride ions at the temperature of 35-50 ℃ under the condition that the current density is 0.15-0.35A/cm²The alternating current of (2) is used for reaming and corroding for 300-400 s.

More preferably, the method of the corrosion treatment is:

placing the pretreated aluminum foil in a solution of 1 wt.% sulfuric acid and 20 wt.% chloride ions at 50 deg.C, and controlling the current density at 0.5A/cm²Performing pitting corrosion for 40s under the alternating current;

then taking out the aluminum foil and placing the aluminum foil in 10 wt.% ammonium adipate solution at the temperature of 75 ℃ under the condition that the current density is 0.1A/cm²Performing medium treatment for 40s under direct current;

then taking out the aluminum foil, placing the aluminum foil in a solution of 1 wt% sulfuric acid and 20 wt% chloride ions at the temperature of 35 ℃, and controlling the current density to be 0.3A/cm²Under the alternating current of (1) for 300 s.

Preferably, the post-treatment is to soak the aluminum foil subjected to the corrosion treatment in a phosphoric acid solution, and then to clean and dry the aluminum foil.

Specifically, the post-treatment method comprises the following steps: and (3) placing the aluminum foil in 5-15 wt% phosphoric acid solution at the temperature of 50-70 ℃ for soaking for 80-120 s, taking out, washing with pure water, and drying.

More preferably, the post-treatment method is as follows: and (3) placing the aluminum foil in 10 wt% phosphoric acid solution at the temperature of 60 ℃ for soaking for 80s, taking out the aluminum foil, washing the aluminum foil with pure water, and drying the aluminum foil.

After post-treatment, residual chlorine radicals and residual moisture on the surface of the aluminum foil after corrosion treatment can be removed.

Preferably, the drying is performed at a temperature of 230-350 ℃.

Preferably, the formation treatment is to place the aluminum foil in an ammonium oxalate solution for formation.

More preferably, the formation treatment is:

and (3) placing the aluminum foil after stress treatment in 10-15 wt% ammonium adipate solution at the temperature of 75-85 ℃ for 35-70V formation.

The invention also protects the low-voltage anode foil prepared by the preparation method.

The invention also protects the application of the low-voltage anode foil in the preparation of small capacitors.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a manufacturing method for improving the brittleness of a low-voltage anode foil, which is characterized in that in the conventional manufacturing process of the low-voltage anode foil, a stress treatment process is added before an aluminum foil formation treatment, so that dense and fine cracks appear on the surface of the foil, the extrusion force applied to the low-voltage anode foil in the bending process can be dispersed by reducing gaps among the cracks, and the brittleness of the low-voltage anode foil is greatly improved on the premise of maintaining the original thickness of the aluminum foil.

Drawings

Fig. 1 is a scanning electron microscope image of the surface of the aluminum foil of example 1 after the stress treatment at 200 times.

Fig. 2 is a scanning electron microscope image of the aluminum foil of example 1 with a cross section of 150 times the side after stress treatment.

Fig. 3 is a scanning electron microscope image of the surface of the aluminum foil of comparative example 1 after post-treatment and before chemical conversion treatment at 200 times.

Fig. 4 is a scanning electron microscope image of 150 times the cross section of the side portion of the aluminum foil of comparative example 1 after the post-treatment and before the formation treatment.

Fig. 5 is a scanning electron micrograph of the surface of the aluminum foil of comparative example 2 after stress treatment at 1000 times.

Fig. 6 is a scanning electron microscope image of the side cross section of the aluminum foil of comparative example 2 after stress treatment at 150 times.

Detailed Description

The present invention will be further described with reference to the following embodiments.

The raw materials in the examples and comparative examples are all commercially available;

reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Example 1

Embodiment 1 provides a low-voltage anode foil, and a manufacturing method thereof includes the steps of:

s1, pretreatment: placing 500mm aluminum foil with the thickness of 108 mu m and the aluminum purity of more than or equal to 99.99 percent in 10wt percent phosphoric acid solution at the temperature of 60 ℃ for soaking for 80s, taking out the aluminum foil, washing the aluminum foil by pure water, and drying the aluminum foil.

S2, corrosion treatment: placing the pretreated aluminum foil in a solution of 1 wt.% sulfuric acid and 20 wt.% chloride ions at 50 deg.C, and controlling the current density at 0.5A/cm²Performing pitting corrosion for 40s under the alternating current;

then taking out the aluminum foil and placing the aluminum foil in 10 wt.% ammonium adipate solution at the temperature of 75 ℃ under the condition that the current density is 0.1A/cm²Performing medium treatment for 40s under direct current;

then taking out the aluminum foil, placing the aluminum foil in a solution of 1 wt% sulfuric acid and 20 wt% chloride ions at the temperature of 35 ℃, and controlling the current density to be 0.3A/cm²Under the alternating current of (1) for 300 s.

S3, post-processing: and (3) placing the aluminum foil subjected to corrosion treatment in 10 wt% phosphoric acid solution at the temperature of 60 ℃ for soaking for 80s, taking out the aluminum foil, washing the aluminum foil with pure water, and drying the aluminum foil at the temperature of 250 ℃ for 30 s.

S4, stress treatment: the post-treated aluminum foil was passed through an upper roll having a diameter of 8cm at a pulling rate of 6m/min under a coiling tension of 7kg, the upper roll being a smooth roll.

S5, formation treatment: and (3) placing the aluminum foil subjected to stress treatment in a 10 wt% ammonium adipate solution at the temperature of 75 ℃ for 50V formation.

Example 2

Example 2a low voltage anode foil was provided, the manufacturing method being different from that of example 1,

the winding tension of the stress treatment in step S4 was 5 KG.

Example 3

Example 3a low voltage anode foil was provided, the manufacturing method differing from that of example 1,

the winding tension of the stress treatment in step S4 was 9 KG.

Example 4

Example 4 a low voltage anode foil was provided, the manufacturing method differing from that of example 1,

the coiling tension of the stress treatment in the step S4 is 10 KG.

Example 5

Example 5a low-voltage anode foil was provided, which was manufactured by a method different from that of example 1,

the pulling rate of the stress treatment in step S4 was 2 m/min.

Example 6

Example 6a low-voltage anode foil was provided, which was manufactured by a method different from that of example 1,

the top roll used in the stress treatment in step S4 is a grooved roll.

Comparative example 1

Comparative example 1 provides a low-voltage anode foil, and the manufacturing method is different from example 1 in that the post-treated aluminum foil is not subjected to step S4, but is directly subjected to a chemical conversion treatment, i.e., the manufacturing method does not include a stress treatment.

Comparative example 2

Comparative example 2 provides a low-voltage anode foil, and the manufacturing method is different from example 1 in that the method of stress treatment in S4 is:

the post-treated aluminum foil was rolled under a winding tension of 20kg

Performance testing

The performance of the low-voltage anode foils prepared in the above examples and comparative examples was tested by the following specific methods:

cracking condition: the surface and edge section of the low-voltage anode foil were observed for cracking using a scanning electron microscope.

Specific volume: and (3) detecting the specific value of the low-voltage anode foil according to an EIAJ-2364 standard method which is a test method of the aluminum electrolytic capacitor electrode foil.

And (3) brittleness test: cutting the low-voltage anode foil into sample pieces with the width of 3mm, winding, and observing whether cracking occurs in the winding process; grading according to cracking conditions, wherein grade 1 is no cracking; grade 2 is a fine crack, still within acceptable limits; grade 3 is marked by significant cracking; grade 4 is the occurrence of fracture.

According to fig. 1 and 2, it can be seen that the aluminum foil of example 1 has dense fine cracks on the surface after stress treatment, the width of the cracks is 2.5-3.5 μm, the depth of the cracks is 30-50 μm, and the minimum distance between adjacent cracks is 50-150 μm.

Referring to fig. 3 and 4, it can be seen that the aluminum foil of comparative example 1 has a very smooth surface and edge section without cracks after post-treatment and before chemical conversion treatment. This shows that, in the manufacturing process of the low-voltage anode foil, the aluminum foil has a smooth surface without cracks after pretreatment, corrosion treatment and post-treatment, and dense and fine cracks are generated on the surface after the stress treatment of the invention.

Because the thickness of the oxide film formed by the subsequent chemical conversion treatment is generally not more than 30nm, the appearance of cracks generated by the aluminum foil during stress treatment is not influenced.

On the other hand, as can be seen from fig. 5 and 6, when the winding tension is too high, the aluminum foil of comparative example 3 has a wide crack after stress treatment, the crack width is 6 to 8 μm, the depth is too deep, and the minimum interval between adjacent cracks is too small.

In the embodiment 2, under the condition of 5kg of coiling tension, the width of a crack generated on the surface of the aluminum foil after stress treatment is 0.5-2 μm, the depth of the crack is 10-30 μm, and the minimum distance between adjacent cracks is 50-120 μm;

in example 3, the aluminum foil was subjected to stress treatment under a winding tension of 9kg, and the surface of the aluminum foil had a crack width of 2.5 to 4 μm, a crack depth of 30 to 50 μm, and a minimum distance between adjacent cracks was 70 to 120 μm.

In example 4, under a winding tension of 10kg, the width of the cracks formed on the surface of the aluminum foil after the stress treatment was 3 to 5 μm, the depth of the cracks was 40 to 65 μm, and the minimum distance between adjacent cracks was 50 to 150 μm.

According to the embodiment 6, when the grooved roll is used as the upper roll, roll marks are easily generated on the surface of the aluminum foil during rolling, and the formation of cracks in the aluminum foil during stress treatment is influenced. Therefore, the upper roller is preferably a smooth roller.

The specific volume and brittleness test results of examples 1-6 and comparative examples 1-2 are shown in Table 1.

TABLE 1 test results of examples 1 to 6 and comparative examples 1 to 2

According to the test results in table 1, the brittleness of the low voltage anode foils prepared in examples 1 to 6 is good, and is 1 grade or 2 grades, i.e. no crack or fine crack exists, and still is within an acceptable range. Whereas comparative example 1 was rated 4 for brittleness and exhibited fracture, comparative example 3 was rated 3, i.e., had significant cracks. It can be seen that the brittleness of the low-voltage anode foil subjected to stress treatment was greatly improved by the manufacturing method of the present invention.

From the specific volume test results in table 1, the low-voltage anode foils subjected to stress treatment (examples 1 to 6) have no significant decrease or loss of specific volume value although cracks are generated on the surfaces of the low-voltage anode foils of examples 1 to 6, compared with the low-voltage anode foils not subjected to stress treatment (comparative example 1); in contrast, in comparative example 2, when the coiling tension during stress treatment was too high, the specific capacity was reduced due to the significant negative effect of the cracks generated in the low-voltage anode foil.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.