CN114836744A - Chromium-free passivation solution for copper foil and preparation method thereof - Google Patents

Abstract

The invention discloses a chromium-free passivation solution for copper foil and a preparation method. The chromium-free passivation solution includes components: 0.1-5 parts of benzoate, 0.1-3 parts of tannic acid, 0.2-4 parts of benzoic acid, 1-20 parts of n-propyl acetate, and 100 parts of water. The steps of preparing the chromium-free passivation solution are as follows: at normal temperature, benzoic acid and benzoic acid are dissolved in n-propyl acetate to form a first solution, and benzoic acid is easily dissolved in n-propyl acetate. An electrophilic substitution reaction is generated; the first solution is mixed with tannic acid to form a second solution, and the tannic acid and benzoic acid act together on benzoate to promote the formation of a polymer precursor; the second solution is dissolved in water, Mix evenly to form the chromium-free passivation solution. Use the chromium-free passivation solution to passivate the copper foil: the copper foil is immersed in the chromium-free passivation solution for 0.1 to 10 s; the copper foil is taken out, rinsed with clean water and air-dried to complete the passivation. Compared with the conventional chromium-containing passivation agent, the present invention is more environmentally friendly, and meanwhile, the passivation performance is improved.

Description

A kind of chromium-free passivation solution for copper foil and preparation method thereof

technical field

The invention belongs to the technical field of copper foil production, and particularly relates to a chromium-free passivation solution for copper foil, a preparation method thereof, and a passivation method for copper foil.

technical background

The prepared copper foil needs a passivation process to form a passivation film on the surface of the copper foil to prevent oxidation of the surface of the copper foil to increase the storage time of the copper foil. The surface of unprotected copper foil will oxidize to form local spots in the process of contacting with air, which will affect the intrinsic properties of copper foil and subsequent processing.

Traditionally, a solution containing chromate is used to form a protective layer, which is low in cost but controversial in effect. For example, the chromium oxide layer is cracked, and a layer of zinc or zinc alloy needs to be plated under the oxide layer to isolate the surface of the copper foil. At the same time, chromium-containing ions have certain toxicity, which will pollute the environment. If the chromium-containing ions in sewage are treated, a certain cost is required.

Organic passivation solution is another way to solve the passivation problem of copper foil. Different from the complex passivation process of chromium-containing passivation solution, copper foil only needs to be immersed in organic passivation solution for a period of time to form a uniform and dense protective layer on the surface.

However, the performance of organic passivation solutions is usually inferior to that of chromium-containing passivation solutions. The organic passivation solution mainly uses water as the solvent. During the preparation process, the dissolution rate of organic active substances is slow and the volatility is strong, which reduces the preparation efficiency of the organic passivation agent and the concentration of active ingredients in the passivation agent.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a kind of chromium-free organic passivation solution of copper foil and preparation method thereof in view of the above-mentioned problems, adopt specific organic solution to realize the purpose of passivation, this method reduces the discharge of pollutants, is conducive to environmental protection, and simultaneously Selecting to add organic components to promote dissolution, speed up the preparation efficiency of passivation solution, and improve passivation effect has significant economic and social benefits.

To achieve the above purpose of the invention, the present invention provides the following technical solutions.

A kind of chromium-free passivation liquid of copper foil, described chromium-free passivation liquid is a kind of organic passivation liquid, and its composition is to be made up of following components, and wherein following proportioning is mass ratio:

Benzene: 0.1 to 5 parts;

Tannin: 0.1 to 3 parts;

Benzoic acid: 0.2 to 4 parts;

n-Propyl acetate: 1 to 20 parts;

Water: 100 parts.

In the chromium-free passivation solution, benzene and copper atoms form covalent bonds and coordination bonds, and replace each other to form a chain polymer, forming a protective film on the copper surface to avoid the contact between copper and oxygen molecules. Tannic acid plays an antioxidant role. On the one hand, it reduces the oxygen content on the surface of copper through a reduction reaction. On the other hand, it releases hydrogen as a hydrogen donor and combines with oxygen free radicals in the environment to stop the chain reaction caused by free radicals in the polymer. reaction, preventing the transmission and development of oxidation reactions. Benzoic acid is not easily oxidized, and electrophilic substitution reaction can occur on its benzene ring, mainly to obtain meta-substituted products. N-propyl acetate can increase the solubility of the above three organic compounds. Compared with traditional solvents ethanol and glycerol, it is easier to release active substances from the solution to the surface of copper foil for adsorption. Therefore, when it is used as a co-solvent, the passivation efficiency is higher. When benzoic acid, tannic acid, benzoic acid and n-propyl acetate are organically mixed, benzoic acid and tannic acid synergize with benzoic acid under the action of n-propyl acetate to form a polymer with complex configuration. The π bond and the outer unsaturated empty orbital of the copper atom form a stable chelate compound, and the formed passivation film is colorless, transparent and dense, thereby preventing the copper parts from being oxidized, discolored and blackened.

Among them, preferably,

Benzene: 0.2 to 1.5 parts;

Tannin: 0.3 to 1.1 parts;

Benzoic acid: 0.4 to 1.6 parts;

n-Propyl acetate: 1 to 10 parts;

Water: 100 parts.

Among them, more preferably 0.5 part of benzoic acid; 1 part of tannic acid; 0.8 part of benzoic acid; 5 parts of n-propyl acetate; and 100 parts of water.

The present invention also provides the preparation method of the chromium-free passivation solution of the above-mentioned copper foil, comprising the following steps:

Benzoic acid and benzoic acid are dissolved in n-propyl acetate at room temperature to form a first solution; benzoic acid is easily dissolved in n-propyl acetate, and in the n-propyl acetate solution, benzoic acid and benzoic acid generate an electrophilic substitution reaction.

The first solution is mixed with tannic acid to form a second solution; the addition of tannic acid makes tannic acid and benzoic acid work together on benzoic acid, and promotes benzoic acid to form a polymer precursor.

The second solution is dissolved in water and mixed evenly to form an organic passivation solution containing different active components, namely the chromium-free passivation solution.

The present invention also provides the method for the passivation of copper foil by applying the chromium-free passivation solution of the above-mentioned copper foil as follows:

The copper foil is immersed in the chromium-free passivation solution, so that the upper and lower surfaces are fully infiltrated, and kept for 0.1 to 10 s; the copper foil is taken out, and the copper foil is rinsed with water and air-dried, and the passivation process is completed.

After extensive research, the inventors of the present invention found that adding an organic solvent to the passivator formula can effectively improve the situation that the active ingredients of organic compounds are difficult to dissolve. In the research, the inventors tried various organic solvents, such as ethanol, glycerol, n-propyl acetate, and the like. In the experiment, it was found that when organic solvents containing a large number of hydroxyl groups such as ethanol and glycerol were used, the dissolution efficiency was greatly improved, but the passivation effect of the passivating agent was significantly affected, and it was speculated that it may be caused by the relationship between the solvent and the active ingredients. A large number of hydrogen bonds prevent the adsorption of active ingredients to the surface of the copper foil. For ester-based organic substances, although the dissolution efficiency is not as good as that of alcohol-based substances, there is still a considerable improvement in efficiency compared to using water alone as a solvent. In particular, n-propyl acetate, as a solvent for benzoic acid and benzoic acid, when used in combination with benzoic acid, benzoic acid and tannic acid, promotes copper to replace the hydrogen atom in the NH functional group of a benzoic acid molecule at the solid-liquid interface, so that It is connected by covalent bond, and is connected with the free electron of nitrogen atom in another benzopium molecule by coordination bond to form a semi-permeable chelate, thus showing a good passivation effect.

Compared with the prior art, the method of the invention changes the conventional method of obtaining the copper foil oxide layer with a chromium-containing passivation agent, so that the passivation process is improved in terms of manufacturability and environmental protection, and the passivation performance is also better than that in the market. The passivator effect has improved. And due to the introduction of n-propyl acetate, the efficiency of the preparation of the passivation solution is significantly improved, the affinity of the active ingredient and the solvent is also significantly increased, and the loss of the active ingredient in the preparation process is reduced. Therefore, the cost is reduced and the economic benefit is improved.

Description of drawings

Figure 1 is a photo of the surface state of the copper foil sample of Example 1 after being heated at 130°C for one hour, still revealing the unobviously oxidized copper color.

Figure 2 is a photo of the surface state of the copper foil sample of Comparative Example 1 after being heated at 130°C for one hour. The surface is obviously oxidized and the color is uneven.

Detailed ways

The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

Example 1

Dissolve 0.1 part of benzoic acid and 0.2 part of benzoic acid in 1 part of n-propyl acetate, then mix with 0.1 part of tannic acid and dissolve together in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution The upper and lower surfaces are fully wetted and kept for 10s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Example 2

Dissolve 5 parts of benzoic acid and 4 parts of benzoic acid in 20 parts of n-propyl acetate, then mix with 3 parts of tannic acid and dissolve together in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution Make the upper and lower surfaces fully wet and hold for 0.1 s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Example 3

Dissolve 0.2 parts of benzoic acid and 0.4 parts of benzoic acid in 1 part of n-propyl acetate, then mix with 0.3 parts of tannic acid and dissolve together in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution The upper and lower surfaces are fully wetted and kept for 10s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Example 4

Dissolve 1.5 parts of benzoic acid and 1.6 parts of benzoic acid in 10 parts of n-propyl acetate, then mix with 1.1 parts of tannic acid and dissolve together in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution Make the upper and lower surfaces fully wet and hold for 0.1 s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Example 5

Dissolve 0.5 parts of benzoic acid and 1 part of benzoic acid in 5 parts of n-propyl acetate, then mix with 0.8 parts of tannic acid and dissolve together in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution The upper and lower surfaces are fully wetted and kept for 1 s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Comparative Example 1

Dissolve 0.2 parts of benzoin, 0.3 parts of benzoic acid and 0.4 parts of tannic acid together in 100 parts of water, and mix them evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution to fully infiltrate the upper and lower surfaces and keep for 10 s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Comparative Example 2

Dissolve 0.2 part of benzopyridine in 1 part of n-propyl acetate, then dissolve it together with 0.3 part of tannic acid in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution to fully infiltrate the upper and lower surfaces, keep the 10s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Comparative Example 3

Dissolve 0.4 part of benzoic acid in 1 part of n-propyl acetate, then dissolve together with 0.3 part of tannic acid in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution to fully infiltrate the upper and lower surfaces, keep the 10s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Comparative Example 4

Dissolve 0.2 parts of benzoyl and 0.4 parts of benzoic acid in 1 part of n-propyl acetate, then dissolve in 100 parts of water, and mix evenly to obtain an organic passivation solution; immerse the copper foil in the passivation solution to fully infiltrate the upper and lower surfaces, and keep for 10 s . The copper foil taken out is rinsed with water and air-dried to complete the preparation.

Comparative Example 5

Purchase conventional hexavalent chromium passivation solution from the market; immerse the copper foil in the passivation solution to fully infiltrate the upper and lower surfaces for 2s. The copper foil taken out is rinsed with water and air-dried to complete the preparation.

The air-dried copper foils of the above examples and comparative examples were placed in an oven at 130° C., heated for one hour, and subjected to chemical analysis to obtain the thickness of the surface oxide film, as shown in Table 1. Figure 1 is a photo of the surface state of the copper foil sample of Example 1 after being heated for one hour at 130°C, still revealing the unobviously oxidized copper color. Figure 2 is a photo of the surface state of the copper foil sample of Comparative Example 1 after being heated for one hour at 130° C. The surface is obviously oxidized and the color is uneven.

Table 1: Surface oxide film thickness after drying treatment after passivation of copper foil of each embodiment and comparative example Copper foil sample Oxide film thickness (unit: microns) Example 1 2.39 Example 2 2.21 Example 3 2.18 Example 4 2.01 Example 5 1.82 Comparative Example 1 4.92 Comparative Example 2 3.91 Comparative Example 3 6.35 Comparative Example 4 4.23 Comparative Example 5 2.51

It can be seen from the results of the oxide film thickness of Examples 1 to 5 that when the passivation solution used is in accordance with the proportion and configuration of the technical solution, the copper foil can obtain good anti-oxidation performance, and the thickness of the oxide film is even slightly lower than Oxide film thickness of copper foil after conventional hexavalent chromium passivation solution (Comparative Example 5). The passivation solution in the preferred range can further reduce the oxide film and achieve a more excellent anti-oxidation effect.

From the oxide film thicknesses of Example 1 and Comparative Examples 1 to 4, it can be seen that when the ratio or configuration of the technical solution is not followed, the passivation effect of the solution is not good, and the obtained copper foil oxide film thickness is obviously thicker. According to the above data, the chromium-free passivation solutions for copper foil in each embodiment of the present invention have excellent properties and can fully meet the requirements of the industry. Compared with the traditional chromate passivation process, it has better anti-oxidation performance; and because it does not contain heavy metal hexavalent chromium, it does not emit toxic and harmful substances. Moreover, the preparation and passivation process is simple, the operability is strong, and it is green and non-toxic.

Claims (6)

1. The chromium-free passivation solution for the copper foil is an organic passivation solution and is characterized by comprising the following components:

and (3) benzene synthesis: 0.1-5 parts;

tannic acid: 0.1-3 parts;

benzoic acid: 0.2-4 parts;

n-propyl acetate: 1-20 parts;

water: 100 parts of (A);

wherein the mixture ratio is mass ratio.

2. The chromium-free passivation solution for copper foil according to claim 1, characterized in that it consists of the following components:

and (3) benzene synthesis: 0.2-1.5 parts;

tannic acid: 0.3-1.1 parts;

benzoic acid: 0.4-1.6 parts;

n-propyl acetate: 1-10 parts;

water: 100 parts of (A);

wherein the proportion of the components is mass ratio.

3. The chromium-free passivation solution for copper foil according to claim 2, characterized in that it consists of the following components: 0.5 part of benzene; 1 part of tannic acid; 0.8 part of benzoic acid; 5 parts of n-propyl acetate; 100 parts of water; wherein the proportion of the components is mass ratio.

4. The method for preparing the chromium-free passivation solution for copper foil according to any one of claims 1 to 3, characterized by comprising the steps of:

1) dissolving benzo and benzoic acid in n-propyl acetate at normal temperature to form a first solution;

2) mixing the first solution with tannic acid to form a second solution;

3) and dissolving the second solution in water, and uniformly mixing to form organic passivation solution containing different effective components, namely the chromium-free passivation solution.

5. The use of the chromium-free passivation solution for copper foil according to any one of claims 1 to 3, wherein the chromium-free passivation solution passivates the copper foil by: and the copper foil is immersed into the chromium-free passivation solution to fully infiltrate the upper surface and the lower surface, and then the copper foil is taken out to be washed by clear water and dried in the air.

6. The use of the chromium-free passivation solution for copper foil according to claim 5, characterized in that: and the copper foil is kept soaked in the chromium-free passivation solution for 0.1-10 s.

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