A preparation method of an ultra-thin copper-aluminum composite foil

Abstract

The present invention discloses a method for preparing an ultra-thin copper-aluminum composite foil. The specific steps include: performing degreasing and deoxidation layer removal treatment on an aluminum substrate; performing electroplating tin treatment on the treated substrate; performing electroless nickel plating treatment on the tin-plated substrate; performing subsequent electroplating copper on the nickel-plated substrate and performing post-plating passivation treatment. After the aluminum substrate is treated through the above steps, an ultra-thin copper-aluminum composite foil with a smooth and flat surface and excellent mechanical properties can be obtained. By electroplating tin, the present invention avoids the problem of rapid dissolution of the zinc layer in the nickel plating solution in the traditional preparation method, and uses a weakly acidic plating solution during pre-nickel plating to avoid chemical reactions between the amphoteric substance aluminum and the plating solution. Compared with the traditional preparation process using secondary zinc immersion, the present invention effectively solves the problem of poor adhesion of electroplated copper on the aluminum substrate while greatly shortening the preparation process flow, and can successfully prepare an ultra-thin copper-aluminum composite foil with excellent electrical conductivity and mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-thin composite foil preparation, and particularly relates to a preparation method of an ultra-thin copper-aluminum composite foil. Background Art

[0002] With the rapid development of the new energy vehicle industry in recent years, the market demand for copper foil, an important component material of lithium-ion batteries, has been increasing day by day, and higher requirements have also been put forward for it. As the negative electrode current collector of lithium-ion batteries, the main function of copper foil is to converge the current generated by the battery active material on the negative electrode current collector into an output current. In lithium-ion batteries, the mass ratio of lithium copper foil is about 13%, and the cost ratio is about 8%. Therefore, excellent ultra-thin copper foil and composite copper foil can maintain a low internal resistance without affecting the total battery capacity, effectively reduce the raw material cost, and at the same time achieve the goal of lightweight and improve the energy density of lithium-ion batteries.

[0003] Due to the relatively active nature of aluminum itself, its standard electrode potential is relatively negative, and an oxide film will still form rapidly after treatment. At the same time, aluminum is an amphoteric substance and will react with the plating solution. Therefore, there has always been a problem of poor bonding force between the base and the coating in aluminum-based composite copper foil, which is not conducive to subsequent production and use. Summary of the Invention

[0004] To solve the above problems, the present invention overcomes the deficiencies of the existing preparation methods of aluminum-based composite copper foil and provides a preparation method of an ultra-thin copper-aluminum composite foil.

[0005] To achieve the above object, a preparation method of an ultra-thin copper-aluminum composite foil of the present invention includes the following steps:

[0006] (1) Immerse the base in a degreasing solution for soaking and cleaning. After cleaning, place it in a solution for removing the oxide layer to remove the aluminum oxide on its surface, and clean it after the treatment is completed;

[0007] (2) Place the base after the pretreatment in a tin plating solution for tin plating treatment, and clean it after the tin plating is completed;

[0008] (3) Place the composite foil obtained after the tin plating in electroless nickel plating for nickel plating treatment, and clean it again after the nickel plating is completed;

[0009] (4) Connect the obtained composite foil to a DC power supply for electroplating copper, and perform post-plating passivation treatment after the electroplating is completed; after cleaning and drying, an ultra-thin copper-aluminum composite foil with excellent electrical conductivity and mechanical properties can be obtained.

[0010] Specifically, the main components of the degreasing solution in the present invention are 5-40 g / L of sodium hydroxide, 5-30 g / L of sodium carbonate, and 30-70 g / L of dishwashing detergent; the main components of the deoxidizing layer treatment solution are 100-300 mL / L of ammonia water and 3-10 g / L of sodium citrate.

[0011] Preferably, in step (1), the soaking time for the degreasing process is 10-600 s, and the temperature is 20-55 °C; the deoxidizing layer treatment time is 10-300 s, and the temperature is 20-55 °C.

[0012] Preferably, the main components of the tin electroplating solution in step (2) are 30-65 g / L of stannate, 3-10 g / L of caustic alkali, 5-15 g / L of sodium acetate, and 0.5-5 mL / L of hydrogen peroxide.

[0013] Preferably, in the tin electroplating process of step (2), the working voltage is 0.5-8 V, the current is 0.1-4 A, the time is 30-600 s, and the temperature is 60-90 °C.

[0014] Preferably, the main components of the electroless nickel plating solution in step (3) are 15-45 g / L of nickel sulfate, 15-40 g / L of sodium hypophosphite, 5-15 mL / L of lactic acid, 10-30 g / L of complexing agent, 5-15 g / L of sodium acetate, and 5-15 g / L of sodium succinate.

[0015] Preferably, in the electroless nickel plating process of step (3), the electroless plating time is 5-30 min, and the temperature is 55-90 °C.

[0016] Preferably, the main components of the copper electroplating solution in step (4) are 350-500 g / L of copper nitrate, 20-60 g / L of copper sulfate, and 3-15 mL / L of brightening agent, and the pH of the copper plating solution is 1.5-3.

[0017] Preferably, in the copper electroplating process of step (4), the working voltage is 1-8 V, the current is 0.5-4 A, the time is 30-600 s, and the temperature is 20-45 °C.

[0018] To solve the problem of poor bonding force caused by the low standard electrode potential of aluminum during the preparation of aluminum-based composite copper foils, the present invention uses metals tin and nickel with electrode potentials between aluminum and copper as the transition layer. Furthermore, during the preparation process, the first transition layer is prepared by electroplating tin to replace the original secondary zinc immersion process. While ensuring the bonding force between the coatings, the preparation process flow is effectively simplified and shortened. Subsequently, the acidic electroless nickel plating and acidic copper electroplating processes are further adopted. On the one hand, the prepared copper-clad layer is smooth, dense, and has excellent electrical conductivity. On the other hand, it also avoids the problems of substrate corrosion and poor bonding performance caused by excessive reaction between the substrate and the plating solution.

[0019] The copper-aluminum composite foil obtained by the copper-aluminum composite foil preparation process provided by the present invention realizes the tight combination between the coating of the obtained copper-aluminum composite foil and the substrate, the uniform control of the thickness of the composite foil, and excellent conductivity and mechanical properties of the obtained copper-aluminum composite foil by controlling the relevant process parameters of electroless plating and electroplating processes.

[0020] The above preparation method can achieve the following technical effects:

[0021] (1) The present invention uses electroplating tin to replace secondary zinc immersion to prepare the first transition layer. Compared with the immersion plating method of obtaining a coating through a displacement reaction, the coating prepared by electroplating under the same conditions is more tightly combined with the substrate. At the same time, directly using electroplating tin avoids steps such as dezincification and multiple cleaning steps in the process of preparing the zinc transition layer, shortening the preparation process flow.

[0022] (2) The present invention uses acidic plating solutions in both electroless nickel plating and electroplating copper. Since the reaction between the aluminum substrate and the alkaline plating solution is very intense, the substrate is extremely easy to be corroded during the preparation process of the composite copper foil, resulting in poor strength and bonding performance of the composite foil, thus affecting subsequent actual use. After using the acidic plating solution, the situation of substrate corrosion is effectively solved, and a copper-aluminum composite foil with excellent performance can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD diagram of the ultra-thin copper-aluminum composite foil obtained in Example 1;

[0024] Figure 2 SEM diagram of the ultra-thin copper-aluminum composite foil obtained in Example 2;

[0025] Figure 3 SEM diagram of the ultra-thin copper-aluminum composite foil obtained in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following further describes in detail the specific implementation manners of the present invention in conjunction with the drawings and examples. The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0027] Example 1:

[0028] (1) Immerse the aluminum foil substrate in the degreasing treatment solution for 60 s for degreasing treatment, and wash it with deionized water after the treatment. The preparation raw materials of the degreasing treatment solution include 25 g / L of sodium hydroxide, 25 g / L of sodium carbonate, and 50 g / L of dishwashing detergent, and the treatment temperature is 25 °C.

[0029] (2) Immerse the substrate after degreasing treatment in the deoxidation layer treatment solution for 60 s to conduct deoxidation layer treatment, and wash it with deionized water after the treatment. The preparation raw materials of the deoxidation layer treatment solution include 250 mL / L of ammonia water and 5 g / L of sodium citrate, and the treatment temperature is 25 °C.

[0030] (3) Connect the aluminum foil after deoxidation layer treatment to a DC power supply for tin electroplating treatment, and wash it with deionized water after the tin electroplating is completed. The voltage for tin electroplating is 2 V, the current is 0.5 A, the time is 180 s, and the temperature is 75 °C. The preparation raw materials of the tin electroplating solution include 30 g / L of sodium stannate, 5 g / L of sodium hydroxide, 5 g / L of sodium acetate, and 3 mL / L of hydrogen peroxide.

[0031] (4) Immerse the composite foil after tin electroplating in the electroless nickel plating solution for electroless nickel plating treatment, and wash it with deionized water after the electroless nickel plating is completed. The time for electroless nickel plating is 10 min, and the nickel plating temperature is 80 °C. The preparation raw materials of the electroless nickel plating solution include 20 g / L of nickel sulfate, 25 g / L of sodium hypophosphite, 8 mL / L of lactic acid, 15 g / L of sodium citrate, 6 g / L of malic acid, 6 g / L of sodium acetate, and 5 g / L of sodium succinate.

[0032] (5) Connect the composite foil after electroless nickel plating to a DC power supply for copper electroplating treatment, and wash it with deionized water after the copper electroplating is completed. The voltage for copper electroplating is 4 V, the current is 1 A, the time is 60 s, and the temperature is 25 °C. The preparation raw materials of the copper electroplating solution include 400 g / L of copper nitrate and 45 g / L of copper sulfate, and the pH of the copper electroplating solution is 2.

[0033] (6) Immerse the obtained copper-aluminum composite foil in the anti-oxidation solution for 3 min for post-plating anti-oxidation treatment. The anti-oxidation solution is 5 g / L of benzotriazole. After the anti-oxidation treatment is completed, wash and dry it to obtain a copper-aluminum composite foil with excellent electrical conductivity and mechanical properties.

[0034] Example 2:

[0035] (1) Immerse the aluminum foil substrate in the degreasing treatment solution for 30 s to conduct degreasing treatment, and wash it with deionized water after the treatment. The preparation raw materials of the degreasing treatment solution include 25 g / L of sodium hydroxide, 25 g / L of sodium carbonate, and 50 g / L of detergent, and the treatment temperature is 45 °C.

[0036] (2) Immerse the substrate after degreasing treatment in the deoxidation layer treatment solution for 30 s to conduct deoxidation layer treatment, and wash it with deionized water after the treatment. The preparation raw materials of the deoxidation layer treatment solution include 250 mL / L of ammonia water and 5 g / L of sodium citrate, and the treatment temperature is 45 °C.

[0037] (3) Connect the aluminum foil after deoxidation treatment to a DC power supply for tin electroplating treatment, and wash it with deionized water after the tin electroplating is completed. The voltage for tin electroplating is 1V, the current is 0.3A, the time is 300s, and the temperature is 80°C. The raw materials for preparing the tin electroplating solution include 30g / L of sodium stannate, 5g / L of sodium hydroxide, 5g / L of sodium acetate, and 3mL / L of hydrogen peroxide.

[0038] (4) Place the composite foil after tin electroplating in a electroless nickel plating solution for nickel plating treatment, and wash it with deionized water after the electroless nickel plating is completed. The time for electroless nickel plating is 5 min, and the nickel plating temperature is 80°C. The raw materials for preparing the electroless nickel plating solution include 20g / L of nickel sulfate, 25g / L of sodium hypophosphite, 8mL / L of lactic acid, 15g / L of sodium citrate, 6g / L of malic acid, 6g / L of sodium acetate, and 5g / L of sodium succinate.

[0039] (5) Connect the composite foil after electroless nickel plating to a DC power supply for copper electroplating treatment, and wash it with deionized water after the copper electroplating is completed. The voltage for copper electroplating is 4V, the current is 1A, the time is 60s, and the temperature is 25°C. The raw materials for preparing the copper electroplating solution include 400g / L of copper nitrate and 45g / L of copper sulfate, and the pH of the copper electroplating solution is 2.

[0040] (6) Immerse the obtained copper-aluminum composite foil in an anti-oxidation solution for 3 min for post-plating anti-oxidation treatment. The anti-oxidation solution is 5g / L of benzotriazole. After the anti-oxidation treatment is completed, wash and dry it to obtain a copper-aluminum composite foil with excellent electrical conductivity and mechanical properties.

[0041] Example 3

[0042] (1) Immerse the aluminum foil substrate in a degreasing treatment solution for 60 s for degreasing treatment, and wash it with deionized water after the treatment is completed. The raw materials for preparing the degreasing treatment solution include 25g / L of sodium hydroxide, 25g / L of sodium carbonate, and 50g / L of dishwashing liquid, and the treatment temperature is 25°C.

[0043] (2) Immerse the substrate after degreasing treatment in a deoxidation layer treatment solution for 60 s for deoxidation layer treatment, and wash it with deionized water after the treatment is completed. The raw materials for preparing the deoxidation layer treatment solution include 250mL / L of ammonia water and 5g / L of sodium citrate, and the treatment temperature is 25°C.

[0044] (3) Connect the aluminum foil after deoxidation treatment to a DC power supply for tin electroplating treatment, and wash it with deionized water after the tin electroplating is completed. The voltage for tin electroplating is 2V, the current is 0.5A, the time is 90s, and the temperature is 75°C. The raw materials for preparing the tin electroplating solution include 35g / L of potassium stannate, 8g / L of potassium hydroxide, 6g / L of potassium acetate, and 3mL / L of hydrogen peroxide.

[0045] (4) Place the composite foil after tin electroplating in a electroless nickel plating solution for nickel plating treatment, and wash it with deionized water after the electroless nickel plating is completed. The time for electroless nickel plating is 10 min, and the nickel plating temperature is 80°C. The raw materials for preparing the electroless nickel plating solution include 20g / L of nickel sulfate, 25g / L of sodium hypophosphite, 8mL / L of lactic acid, 15g / L of sodium citrate, 6g / L of malic acid, 6g / L of sodium acetate, and 5g / L of sodium succinate.

[0046] (5) Connect the composite foil after electroless nickel plating to a DC power supply for copper electroplating treatment, and wash it with deionized water after the copper electroplating is completed. The voltage for copper electroplating is 2V, the current is 0.5A, the time is 150s, and the temperature is 25°C. The raw materials for preparing the copper electroplating solution include 400g / L of copper nitrate and 45g / L of copper sulfate, and the pH of the copper electroplating solution is 2.

[0047] (6) Immerse the obtained copper-aluminum composite foil in an anti-oxidation solution for 3 min for post-plating anti-oxidation treatment. The anti-oxidation solution is 5g / L of benzotriazole. After the anti-oxidation treatment is completed, wash and dry it to obtain a copper-aluminum composite foil with excellent electrical conductivity and mechanical properties.

[0048] Comparative example 1: There is no transition metal layer plated in this comparative example.

[0049] (1) Immerse the aluminum foil substrate in a degreasing treatment solution for 60 s for degreasing treatment, and wash it with deionized water after the treatment is completed. The raw materials for preparing the degreasing treatment solution include 25g / L of sodium hydroxide, 25g / L of sodium carbonate, 50g / L of dishwashing detergent, and the treatment temperature is 25°C.

[0050] (2) Immerse the substrate after degreasing treatment in a deoxidation layer treatment solution for 60 s for deoxidation layer treatment, and wash it with deionized water after the treatment is completed. The raw materials for preparing the deoxidation layer treatment solution include 250mL / L of ammonia water and 5g / L of sodium citrate, and the treatment temperature is 25°C.

[0051] (3) Connect the composite foil after the deoxidation layer treatment to a DC power supply for copper electroplating treatment, and wash it with deionized water after the copper electroplating is completed. The voltage for copper electroplating is 4V, the current is 1A, the time is 60s, and the temperature is 25°C. The raw materials for preparing the copper electroplating solution include 400 g / L of copper nitrate and 45 g / L of copper sulfate, and the pH of the copper electroplating solution is 2. After being taken out from the electroplating solution, the copper layer directly falls off, and the bonding strength between the coating and the substrate is poor.

[0052] Comparative Example 2. In this comparative example, electroless copper plating is used for copper plating.

[0053] (1) Immerse the aluminum foil substrate in the degreasing treatment solution for 60 s for degreasing treatment, and wash it with deionized water after the treatment is completed. The raw materials for preparing the degreasing treatment solution include 25 g / L of sodium hydroxide, 25 g / L of sodium carbonate, 50 g / L of dishwashing detergent, and the treatment temperature is 25°C.

[0054] (2) Immerse the substrate after degreasing treatment in the deoxidation layer treatment solution for 60 s for deoxidation layer treatment, and wash it with deionized water after the treatment is completed. The raw materials for preparing the deoxidation layer treatment solution include 250 mL / L of ammonia water and 5 g / L of sodium citrate, and the treatment temperature is 25°C.

[0055] (3) Connect the aluminum foil after the deoxidation layer treatment to a DC power supply for tin electroplating treatment, and wash it with deionized water after the tin electroplating is completed. The voltage for tin electroplating is 2V, the current is 0.5A, the time is 180s, and the temperature is 75°C. The raw materials for preparing the tin electroplating solution include 30 g / L of sodium stannate, 5 g / L of sodium hydroxide, 5 g / L of sodium acetate, and 3 mL / L of hydrogen peroxide.

[0056] (4) Immerse the composite foil after tin electroplating in the electroless nickel plating solution for nickel plating treatment, and wash it with deionized water after the electroless plating is completed. The time for electroless nickel plating is 10 min, and the nickel plating temperature is 80°C. The raw materials for preparing the electroless nickel plating solution include 20 g / L of nickel sulfate, 25 g / L of sodium hypophosphite, 8 mL / L of lactic acid, 15 g / L of sodium citrate, 6 g / L of malic acid, 6 g / L of sodium acetate, and 5 g / L of sodium succinate.

[0057] (5) Immerse the composite foil after electroless nickel plating in the alkaline electroless copper plating solution for copper plating treatment. The raw materials for preparing the electroless copper plating solution include 6 g / L of copper sulfate, 0.5 g / L of nickel sulfate, 15 g / L of sodium hypophosphite, 28 g / L of sodium citrate, 5 g / L of ammonium chloride, and 0.2 mg / L of thiourea. The temperature for electroless copper plating is 80°C. After the composite foil is placed in the electroless copper plating solution for 5 min, the substrate is completely corroded by the plating solution.

[0058] Comparative Example 3: In this comparative example, the transition layer adopts a secondary zinc immersion process.

[0059] (1) Immerse the aluminum foil substrate in the degreasing treatment solution for 60 s for degreasing treatment, and wash it with deionized water after the treatment. The preparation raw materials of the degreasing treatment solution include 25 g / L of sodium hydroxide, 25 g / L of sodium carbonate, 50 g / L of dishwashing liquid, and the treatment temperature is 25 °C.

[0060] (2) Immerse the substrate after degreasing treatment in the deoxidizing layer treatment solution for 60 s for deoxidizing layer treatment, and wash it with deionized water after the treatment. The preparation raw materials of the deoxidizing layer treatment solution include 250 mL / L of ammonia water and 5 g / L of sodium citrate, and the treatment temperature is 25 °C.

[0061] (3) Immerse the aluminum foil after deoxidizing layer treatment in the zinc immersion solution for the first zinc immersion treatment, and wash it repeatedly with a large amount of deionized water after the first zinc immersion. The first zinc immersion time is 40 s and the temperature is 25 °C. The preparation raw materials of the zinc immersion solution include 240 g / L of sodium hydroxide, 120 g / L of zinc sulfate, 120 g / L of potassium sodium tartrate, and 30 g / L of sodium citrate.

[0062] (4) Immerse the aluminum foil after the first zinc immersion treatment in the zinc stripping solution for zinc stripping treatment, and wash it repeatedly with a large amount of deionized water after zinc stripping. The zinc stripping time is 20 s and the temperature is 25 °C. The zinc stripping solution is a 50% nitric acid solution.

[0063] (5) Immerse the aluminum foil after zinc stripping treatment in the zinc immersion solution for the second zinc immersion treatment, and wash it repeatedly with a large amount of deionized water after the second zinc immersion. The second zinc immersion time is 20 s and the temperature is 25 °C. The preparation raw materials of the zinc immersion solution include 240 g / L of sodium hydroxide, 120 g / L of zinc sulfate, 120 g / L of potassium sodium tartrate, and 30 g / L of sodium citrate.

[0064] (6) Immerse the composite foil after the secondary zinc immersion in the electroless nickel plating solution for electroless nickel plating treatment, and wash it with deionized water after electroless plating. The electroless nickel plating time is 10 min and the nickel plating temperature is 80 °C. The preparation raw materials of the electroless nickel plating solution include 20 g / L of nickel sulfate, 25 g / L of sodium hypophosphite, 8 mL / L of lactic acid, 15 g / L of sodium citrate, 6 g / L of malic acid, 6 g / L of sodium acetate, and 5 g / L of sodium succinate.

[0065] (7) Connect the electroless nickel-plated composite foil to a DC power supply for electroplating copper treatment, and wash it with deionized water after the electroplating of copper is completed. The voltage for electroplating copper is 2V, the current is 0.5A, the time is 150s, and the temperature is 25°C. The raw materials for preparing the electroplating copper solution include 400 g / L of copper nitrate and 45 g / L of copper sulfate, and the pH of the electroplating copper solution is 2.

[0066] (8) Immerse the obtained copper-aluminum composite foil in an anti-oxidation solution for 3 minutes for post-plating anti-oxidation treatment. The anti-oxidation solution is 5 g / L of benzotriazole. After the anti-oxidation treatment is completed, wash and dry it to obtain the copper-aluminum composite foil.

[0067] Compare the copper foils obtained in the examples and comparative examples and list them in Table 1:

[0068] Table 1 Comparison between Examples and Comparative Examples

[0069] Examples, Comparative Examples Bonding state between copper layer and substrate Effect of the obtained product Example 1 Tightly bonded The surface of the composite foil is flat and dense Example 2 Tightly bonded The surface of the composite foil is flat and dense Example 3 Tightly bonded The surface of the composite foil is flat and dense Comparative Example 1 Copper layer peeling off Unable to obtain a complete composite foil Comparative Example 2 Substrate corroded Unable to obtain a complete composite foil Comparative Example 3 Relatively tightly bonded A complete composite foil can be obtained, but the process flow is complex

Claims

1. A preparation method of an ultra-thin copper-aluminum composite foil, characterized in that: The steps include: a) First, degrease the substrate, and then continue to remove the oxide layer. The substrate is a 5 cm × 5 cm ultra-thin aluminum foil with an aluminum content of ≥ 99.3%; b) Electroplate the substrate obtained in step a) with tin. Connect the substrate after oxide layer removal to a DC power supply for electroplating. The electroplating voltage is 0.5 - 8 V, the current is 0.1 - 4 A, the time is 30 - 600 s, and the temperature is 60 - 90 °C; c) Electroless nickel plate the substrate obtained in step b). After washing the electroplated tin composite foil, place it in an electroless nickel plating solution. The electroless plating time is 3 - 30 min, the temperature is 55 - 90 °C. The electroless nickel plating solution is a weakly acidic plating solution, including nickel sulfate, sodium hypophosphite, lactic acid, sodium citrate, sodium potassium tartrate, sodium acetate, and sodium succinate; d) Electroplate the substrate obtained in step c) with copper. Connect the electroless nickel plated composite foil to a DC power supply for electroplating. The electroplating voltage is 1 - 8 V, the current is 0.5 - 4 A, the time is 30 - 600 s, and the temperature is 20 - 45 °C. The electroplating copper solution includes copper nitrate, copper sulfate, sulfuric acid, and an appropriate amount of brightener; after electroplating, perform post-plating passivation treatment; after cleaning and drying, the ultra-thin copper-aluminum composite foil can be obtained.

2. The preparation method of an ultra-thin copper-aluminum composite foil according to claim 1, wherein: The degreasing treatment is to soak the substrate in a degreasing solution for 10 - 600 s. The degreasing solution is a mixed solution of sodium hydroxide, sodium carbonate, and dishwashing liquid.

3. The preparation method of an ultra-thin copper-aluminum composite foil according to claim 1, characterized in that: The oxide layer removal treatment is to soak the substrate in an oxide layer removal treatment solution for 10 - 600 s. The oxide layer removal treatment solution is ammonia water and sodium citrate.

4. The preparation method of an ultra-thin copper-aluminum composite foil according to claim 1, characterized in that: The electroplating tin solution in the electroplating tin treatment is stannate, caustic alkali, hydrogen peroxide, and acetate or bicarbonate.

5. The preparation method of an ultra-thin copper-aluminum composite foil according to claim 1, characterized in that: The passivation treatment is to soak the ultra-thin copper-aluminum composite foil obtained after electroplating copper in a benzotriazole aqueous solution for 3 - 10 min.

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