Aluminum-based copper-plated film and preparation method thereof

Abstract

The invention relates to a preparation method of an aluminum-based copper-plated film. The preparation method comprises the following steps: immersing an aluminum base material into an alkaline degreasing agent for ultrasonic degreasing treatment; the deoiled aluminum base material is immersed in an alkali etching solution for alkali etching treatment; the aluminum base material subjected to alkali corrosion is immersed in a descaling solution for descaling; carrying out zinc deposition treatment on the descaled aluminum base material by adopting a secondary zinc deposition method; placing the aluminum base material subjected to zinc deposition treatment in a pyrophosphate copper plating solution for electroplating to form a copper plating film; the aluminum base material with the formed copper-plated film is placed in acid copper liquid to be electroplated, and the copper-plated film is thickened; carrying out passivation treatment on the thickened copper-plated film by adopting a working solution; and cleaning and drying the passivated copper-plated film. The aluminum-based copper-plated film prepared by the method comprises an aluminum base material, a zinc transition layer, a pyrophosphate copper bottom layer and an acid copper thickening layer. Compared with a traditional aluminum-based copper-plated film, the quality of the aluminum-based copper-plated film prepared through the method is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of conductive material preparation technology, and in particular to an aluminum-based copper-plated thin film and its preparation method. Background Technology

[0002] Copper plating on aluminum and aluminum alloys can take advantage of the lightweight nature of aluminum and the high conductivity of copper, but its application is limited by insufficient coating adhesion and surface defects.

[0003] The traditional "degreasing-alkaline etching-zinc immersion-copper plating" process is prone to over-corrosion of the aluminum substrate during alkaline etching, resulting in an uneven etched surface that affects the smoothness of subsequent plating layers. The bonding stability between the zinc immersion layer and the aluminum substrate is poor; a single zinc immersion layer is prone to incomplete displacement reactions and high porosity. Direct acid copper plating leads to a violent displacement reaction between copper ions and the zinc layer, resulting in decreased adhesion and the appearance of pinholes or pitting. The overall corrosion resistance of the plating layer is insufficient, making it susceptible to interlayer corrosion in complex environments. These process defects result in aluminum-based copper-plated films whose performance falls far short of market demands.

[0004] Existing improvement solutions, such as increasing the number of zinc immersions or adjusting the copper plating solution formula, do not address the problem from the perspective of synergistic treatment across the entire process chain, resulting in limited improvement in coating performance. Summary of the Invention

[0005] To address the technical problem of poor performance of aluminum-based copper-plated films prepared by existing methods, this invention provides an aluminum-based copper-plated film and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an aluminum-based copper-plated thin film includes the following steps: S1. Immerse the aluminum substrate in an alkaline degreasing agent for ultrasonic degreasing treatment; S2. Immerse the degreased aluminum substrate in an alkaline etching solution for alkaline etching treatment; S3. Immerse the alkaline etched aluminum substrate in a descaling solution for descaling; S4. Perform zinc immersion treatment on the descaled aluminum substrate using a secondary zinc immersion method; S5. Place the zinc-treated aluminum substrate in a copper plating solution for electroplating to form a copper plating film; S6. Place the aluminum substrate with the formed copper plating film in an acidic copper solution for electroplating to thicken the copper plating film; S7. Passivate the thickened copper plating film using a working solution; S8. Clean and dry the passivated copper plating film.

[0007] Further, in step S1, the alkaline degreasing agent is a mixture of sodium hydroxide 5~15g / L, sodium carbonate 20~30g / L, sodium silicate 5~10g / L and fatty alcohol polyoxyethylene ether 3~5g / L; the treatment temperature in step S1 is 45~60℃ and the treatment time is 3~8 minutes.

[0008] Further, in step S2, the alkaline etching solution is a mixture of sodium hydroxide (30-50 g / L), sodium gluconate (5-10 g / L), and potassium sodium tartrate (3-5 g / L); the treatment temperature in step S2 is 25-40°C, the treatment time is 10-60 seconds, and the corrosion rate is controlled at 0.5-2 g / m³. 2 Zn(OH) Further, in step S3, the descaling solution is a mixture of 100-150 mL / L nitric acid and 5-10 mL / L hydrofluoric acid; step S3 is performed at room temperature for 30-90 seconds.

[0009] Further, step S4 includes: Step S41. First zinc plating: Prepare a mixed solution containing 8~12g / L zinc oxide, 80~100g / L sodium hydroxide, 20~30g / L sodium potassium tartrate and 5~10g / L sodium nitrate. Place the descaled aluminum substrate in the mixed solution and treat it at a temperature range of 20~30℃ for 30~60 seconds to complete the first zinc plating process. Step S42. Place the aluminum substrate after the first zinc immersion in a 50~80mL / L nitric acid solution and treat it at room temperature for 5~15 seconds to complete the zinc stripping process; Step S43. Prepare a mixed solution containing 6~10g / L zinc oxide, 70~90g / L sodium hydroxide, 10~20g / L triethanolamine and 0.01~0.03g / L thiourea. Place the zinc-removed aluminum substrate in the mixed solution and treat it at a temperature range of 20~30℃ for 40~80 seconds to complete the secondary zinc plating process.

[0010] Further, in step S5, the copper plating solution is a mixture of 40-60 g / L copper pyrophosphate, 180-220 g / L potassium pyrophosphate, 10-20 g / L potassium nitrate, and 5-10 mL / L ammonia; the working pH of step S5 is 8.0-9.0, and the current density is 1-3 A / dm³. 2 The temperature should be 40-55℃ and the time should be 5-15 minutes.

[0011] Further, in step S6, the copper acid solution is a mixture prepared from 180-220 g / L copper sulfate, 50-70 g / L sulfuric acid, 50-80 mg / L chloride ions, 0.5-1 g / L polyethylene glycol 2000, and 0.005-0.01 g / L 2-mercaptobenzimidazole; the current density in step S6 is 2-5 A / dm³. 2 The temperature should be 20-30℃ and the time should be 15-60 minutes.

[0012] Furthermore, in step S7, the parameters of the working solution are controlled as follows: chromium anhydride: glucose = 1:3~1:5 by concentration, initial glucose concentration is 1.5-2.7g / L, Cr6+ concentration is 0.5-0.7g / L, pH = 5-6, and circulation flow rate is 1.8-2.5m3 / h.

[0013] Furthermore, the aluminum substrate is pure aluminum with a purity of ≥99% or a 3-series, 5-series, or 6-series aluminum alloy.

[0014] The present invention also provides a method for preparing an aluminum-based copper-plated thin film. The prepared aluminum-based copper-plated thin film includes: an aluminum substrate, a zinc transition layer, a pyrocopper underlayer, and an acid copper thickening layer; the total copper plating thickness of the product is 7~35μm, the peel strength between the plating and the substrate is ≥5N / cm, and the surface roughness Ra≤0.2μm.

[0015] The aluminum-based copper-plated thin film and its preparation method provided by the present invention have at least the following beneficial effects or advantages: This invention provides an aluminum-based copper-plated thin film and its preparation method. Through the synergistic effect of three innovative processes—mild alkaline etching controlled by organic corrosion inhibitors, secondary zinc deposition to refine grains, and copper plating without replacement risk—the problem of adhesion and surface quality of aluminum-based copper plating is solved. The quality of the prepared aluminum-based copper-plated thin film is significantly improved compared with traditional aluminum-based copper-plated thin films. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for preparing an aluminum-based copper-plated thin film according to an embodiment of the present invention. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be thorough and complete.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0019] See Figure 1 This invention provides a method for preparing an aluminum-based copper-plated thin film, comprising the following steps: Step S1. Immerse the aluminum substrate in an alkaline degreasing agent for ultrasonic degreasing treatment.

[0020] In step S1, the aluminum substrate is pure aluminum with a purity of ≥99% or a 3-series, 5-series, or 6-series aluminum alloy. For example, a 1060 pure aluminum foil with a thickness of 50μm (aluminum content ≥99.6%) and a size of 100mm × 50mm is selected. Pure aluminum is chosen because its composition is uniform and it has no second phase, which is beneficial for obtaining uniform corrosion and coating.

[0021] The alkaline degreasing agent is a mixture of sodium hydroxide (5-15 g / L, 10 g / L in this example), sodium carbonate (20-30 g / L, 25 g / L in this example), sodium silicate (5-10 g / L, 8 g / L in this example), and fatty alcohol polyoxyethylene ether (3-5 g / L, 4 g / L in this example). The treatment temperature in step S1 is 45-60℃ (52℃ in this example), and the treatment time is 3-8 minutes (5 minutes in this example). Sodium hydroxide is a strong alkali and primarily functions to saponify the grease. The concentration of sodium hydroxide is controlled at 5-15 g / L (10 g / L in this example) to effectively remove grease while avoiding excessive corrosion of the aluminum foil due to excessive concentration. Sodium carbonate acts as a pH buffer to maintain the alkalinity stability of the solution. Sodium silicate is an aluminum corrosion inhibitor that forms a protective aluminum silicate film on the aluminum surface, minimizing corrosion of the aluminum substrate while removing oil and ensuring a smooth substrate. Fatty alcohol polyoxyethylene ether is a nonionic surfactant that emulsifies and decomposes unsaponifiable greases, reduces solution surface tension, and enhances penetration and cleaning effects. Ultrasonic treatment, through cavitation, powerfully impacts the complex structure and micropores of the workpiece surface, ensuring thorough removal of oil stains.

[0022] Step S2. Immerse the degreased aluminum substrate in an alkaline etching solution for alkaline etching treatment.

[0023] In step S2, the alkaline etching solution is a mixture of sodium hydroxide 30-50 g / L (40 g / L in this embodiment), sodium gluconate 5-10 g / L (8 g / L in this embodiment), and potassium sodium tartrate 3-5 g / L (4 g / L in this embodiment); the treatment temperature in step S2 is 25-40℃ (32℃ in this embodiment), the time is 10-60 seconds (30 seconds in this embodiment), and the corrosion rate is controlled at 0.5-2 g / m. 2 (As in this embodiment, it is set to 1g / m 2 ).

[0024] Traditional processes use high-concentration NaOH (above 80 g / L) for vigorous corrosion, resulting in rough and uneven surfaces. This invention reduces the NaOH concentration to 30-50 g / L (40 g / L in this embodiment) and introduces two organic complex corrosion inhibitors: 5-10 g / L (8 g / L in this embodiment) of sodium gluconate and 3-5 g / L (4 g / L in this embodiment) of potassium sodium tartrate. These inhibitors preferentially adsorb at highly active sites on the aluminum surface, inhibiting excessive dissolution in these areas and guiding corrosion towards a more uniform direction, forming a microscopically uniform, less undulating activated surface. This surface ensures the adhesion of the subsequent zinc plating layer and guarantees a high-smoothness coating. The corrosion rate is precisely controlled at 0.5-2 g / m². 2 This is the core technology of the solution. By controlling time, temperature and concentration, it ensures the removal of surface oxide film and contaminants, while forming an ideal micro-anchoring structure without damaging the substrate.

[0025] S3. Immerse the alkaline-etched aluminum substrate in a descaling solution to remove scale.

[0026] In step S3, the descaling solution is a mixture of 100-150 mL / L nitric acid (120 mL / L in this embodiment) and 5-10 mL / L hydrofluoric acid (8 mL / L in this embodiment); step S3 is performed at room temperature for 30-90 seconds (60 seconds in this embodiment).

[0027] After alkaline etching, a layer of black residue remains on the surface, mainly composed of insoluble substances of elements such as Al, Si, and Fe. Step S3 utilizes the strong oxidizing power of nitric acid and the special dissolving ability of hydrofluoric acid for silicon to thoroughly remove this residue, exposing a clean and bright aluminum substrate.

[0028] S4. A secondary zinc plating method is used to perform zinc plating treatment on the descaled aluminum substrate.

[0029] Step S4 includes: Step S41. First zinc plating: Prepare a mixed solution containing 8~12g / L zinc oxide (10g / L in this embodiment), 80~100g / L sodium hydroxide (90g / L in this embodiment), 20~30g / L potassium sodium tartrate (25g / L in this embodiment), and 5~10g / L sodium nitrate (8g / L in this embodiment). Place the descaled aluminum substrate in the mixed solution and treat it at a temperature range of 20~30℃ (25℃ in this embodiment) for 30~60 seconds (50 seconds in this embodiment) to complete the first zinc plating process.

[0030] Step S41 rapidly displaces and forms a complete initial zinc layer. Sodium potassium tartrate acts as a complexing agent to prevent Zn(OH)₂ precipitation, ensuring solution stability, while sodium nitrate refines the zinc layer crystals.

[0031] Step S42. Place the aluminum substrate after the first zinc immersion in a 50~80mL / L (60mL / L in this embodiment) nitric acid solution and treat it at room temperature for 5~15 seconds (10 seconds in this embodiment) to complete the zinc stripping process.

[0032] The initially formed, uneven, and potentially porous zinc layer is completely dissolved using nitric acid. This process exposes an activated aluminum surface that has undergone a "zinc displacement-dissolution" process.

[0033] Step S43. Prepare a mixed solution containing 6~10g / L zinc oxide (8g / L in this embodiment), 70~90g / L sodium hydroxide (80g / L in this embodiment), 10~20g / L triethanolamine (15g / L in this embodiment), and 0.01~0.03g / L thiourea (0.02g / L in this embodiment). Place the zinc-removed aluminum substrate in the mixed solution and treat it at a temperature range of 20~30℃ (25℃ in this embodiment) for 40~80 seconds (60 seconds in this embodiment) to complete the secondary zinc plating process.

[0034] The second zinc plating solution had a slightly lower concentration than the first, and triethanolamine was introduced as a stronger complexing agent, making the displacement reaction rate controllable, thus forming a dense zinc layer with extremely low porosity. With the addition of trace amounts of thiourea as a grain refiner, this scheme further optimized the microstructure of the zinc layer, almost completely isolating it from the aluminum substrate and subsequent plating solutions.

[0035] S5. The aluminum substrate after zinc immersion treatment is placed in a copper plating solution for electroplating to form a copper plating film.

[0036] In step S5, the copper plating solution is a mixture of 40-60 g / L copper pyrophosphate (50 g / L in this embodiment), 180-220 g / L potassium pyrophosphate (200 g / L in this embodiment), 10-20 g / L potassium nitrate (15 g / L in this embodiment), and 5-10 mL / L ammonia (7 g / L in this embodiment); the working pH in step S5 is 8.0-9.0 (8.5 in this embodiment) and the current density is 1-3 A / dm³. 2 (In this embodiment, it is set to 2A / dm) 2 The temperature is 40~55℃ (48℃ in this embodiment) and the time is 5~15 minutes (10 minutes in this embodiment).

[0037] Pyrophosphate copper plating solution is weakly alkaline and has almost no chemical dissolving effect on the zinc layer. It relies entirely on electrodeposition to grow a copper layer on the zinc layer, fundamentally eliminating the degradation of adhesion caused by displacement reactions. The resulting "zinc-pyrophosphate copper" interface is a purely metallurgical bond with extremely strong adhesion. This pyrophosphate copper layer can serve as a barrier layer and a conductive layer for subsequent acidic copper plating.

[0038] S6. Place the aluminum substrate with the copper-plated film already formed in an acidic copper solution for electroplating to thicken the copper-plated film.

[0039] In step S6, the acid copper solution is a mixture of copper sulfate 180~220 g / L (200 g / L in this embodiment), sulfuric acid 50~70 g / L (60 g / L in this embodiment), chloride ions 50~80 mg / L (65 g / L in this embodiment), polyethylene glycol 2000 0.5~1 g / L (0.8 g / L in this embodiment), and 2-mercaptobenzimidazole 0.005~0.01 g / L (0.08 g / L in this embodiment); the current density in step S6 is 2~5 A / dm³. 2 (As in this embodiment, it is set to 3A / dm) 2 The temperature is 20~30℃ (25℃ in this embodiment) and the time is 15~60 minutes (45 minutes in this embodiment).

[0040] On a firmly bonded copper plating layer, acidic copper plating can be used to thicken it. The synergistic effect of polyethylene glycol and 2-mercaptobenzimidazole provides excellent brightening and leveling effects, resulting in an extremely low final surface roughness (Ra≤0.2μm), meeting high-gloss requirements.

[0041] S7. Passivate the thickened copper plating film.

[0042] In step S7, the thickened copper plating film is passivated using a working solution. The parameters of the working solution are controlled as follows: chromic anhydride (concentration): glucose (concentration) = 1:3~1:5 (e.g., 1:3.2 in this embodiment), initial glucose concentration 1.5-2.7 g / L (e.g., 2.0 g / L in this embodiment), hexavalent chromium (Cr6+) concentration 0.5-0.7 g / L (e.g., 0.6 g / L in this embodiment), pH = 5-6 (adjusted with 10%-15% KOH or NaOH), circulation flow rate 1.8-2.5 m³ / h (e.g., 2 m³ / h in this embodiment). 3 / h).

[0043] S8. Clean and dry the copper plating film after passivation.

[0044] In step S8, the copper plating film after passivation is cleaned three times with deionized water, and then dried in a clean environment at 70°C after cleaning.

[0045] The performance test results of the aluminum-based copper-plated thin film prepared by the method of this invention are as follows: Appearance: Scanning electron microscopy revealed a dense and continuous coating, free from wrinkles, rust, foreign matter, oil stains, and fingerprints. No significant color difference, scratches, pinholes, or dents were observed. Dyne value: 50. Tensile strength: 118.588 MPa longitudinally and 113.941 MPa transversely, far exceeding the 100 MPa of traditional processes. Elongation at break: 8.683% longitudinally and 8.727% transversely. Peel strength: 1.21 kgf / cn. Quantitative peel strength reached 5.2 N / cm, far exceeding the 3-4 N / cm of traditional processes, an improvement of over 40%. Profilometer measurement showed an Ra value of 0.18 μm, exhibiting a mirror-like finish. After 600 hours of neutral salt spray testing, no red rust appeared on the surface, only slight white rust at the edges, far exceeding the 96-hour requirement for conventional electronic components.

[0046] This invention also provides an aluminum-based copper-plated film, comprising: an aluminum substrate, a zinc transition layer, a coke bottom layer, and an acid copper thickening layer; the total copper plating thickness of the aluminum-based copper-plated film is 7~35μm, the peel strength between the plating and the substrate is ≥5N / cm, and the surface roughness Ra≤0.2μm.

[0047] The aluminum-based copper-plated thin film and its preparation method provided in this invention have at least the following beneficial effects or advantages: The present invention provides an aluminum-based copper-plated thin film and its preparation method. Through the synergistic effect of three innovative processes—mild alkaline etching controlled by organic corrosion inhibitors, secondary zinc deposition to refine grains, and copper plating without replacement risk—the problem of adhesion and surface quality of aluminum-based copper plating is solved. The quality of the prepared aluminum-based copper-plated thin film is significantly improved compared with traditional aluminum-based copper-plated thin films.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an aluminum-based copper-plated thin film, characterized by, The method comprises the following steps: S1. immersing the aluminum substrate into an alkaline degreasing agent for ultrasonic degreasing treatment; S2. immersing the degreased aluminum substrate into an alkaline etching solution for alkaline etching treatment; S3. immersing the alkaline-etched aluminum substrate into a descaling solution for descaling; S4. performing zinc deposition treatment on the descaled aluminum substrate by using a secondary zinc deposition method; S5. electroplating the zinc-deposited aluminum substrate into a pyro-copper plating solution to form a copper plating film; S6. electroplating the aluminum substrate with the formed copper plating film into an acid copper solution to thicken the copper plating film; S7. performing passivation treatment on the thickened copper plating film by using a working solution; S8. cleaning and drying the passivated copper plating film.

2. The method of claim 1, wherein: In step S1, the alkaline degreasing agent is a mixed solution prepared by mixing 5-15 g / L of sodium hydroxide, 20-30 g / L of sodium carbonate, 5-10 g / L of sodium silicate and 3-5 g / L of fatty alcohol polyoxyethylene ether; the treatment temperature in step S1 is 45-60 DEG C, and the treatment time is 3-8 minutes.

3. The method of claim 1, wherein the copper plating solution is prepared by mixing copper sulfate, sulfuric acid, and water. In step S2, the alkaline etching solution is a mixture of 30-50 g / L sodium hydroxide, 5-10 g / L sodium gluconate and 3-5 g / L potassium sodium tartrate; the processing temperature in step S2 is 25-40℃, the processing time is 10-60 seconds and the etching amount is controlled to 0.5-2 g / m 2 .

4. The method of claim 1, wherein: In step S3, the descaling solution is a mixed solution of 100-150 mL / L of nitric acid and 5-10 mL / L of hydrofluoric acid; step S3 is performed at room temperature for 30-90 seconds.

5. The method of claim 1, wherein: Step S4 comprises: Step S41. primary zinc deposition, a mixed solution containing 8-12 g / L of zinc oxide, 80-100 g / L of sodium hydroxide, 20-30 g / L of potassium sodium tartrate and 5-10 g / L of sodium nitrate is prepared, the descaled aluminum substrate is placed into the mixed solution and treated at a temperature of 20-30 DEG C for 30-60 seconds to complete the primary zinc deposition process; Step S42. the aluminum substrate after the primary zinc deposition is placed into a 50-80 mL / L nitric acid solution and treated at room temperature for 5-15 seconds to complete the zinc removal process; Step S43. a mixed solution containing 6-10 g / L of zinc oxide, 70-90 g / L of sodium hydroxide, 10-20 g / L of triethanolamine and 0.01-0.03 g / L of thiourea is prepared, the aluminum substrate after the zinc removal treatment is placed into the mixed solution and treated at a temperature of 20-30 DEG C for 40-80 seconds to complete the secondary zinc deposition process.

6. The method of claim 1, wherein: In step S5, the copper pyrophosphate plating solution is a mixed solution of copper pyrophosphate 40-60 g / L, potassium pyrophosphate 180-220 g / L, potassium nitrate 10-20 g / L, and ammonia water 5-10 mL / L; the working pH of step S5 is 8.0-9.0, the current density is 1-3 A / dm 2 , the temperature is 40-55°C, and the time is 5-15 minutes.

7. The method of claim 1, wherein: In step S6, the acid copper solution is a mixed solution of copper sulfate 180-220 g / L, sulfuric acid 50-70 g / L, chloride ion 50-80 mg / L, polyethylene glycol 2000 0.5-1 g / L, and 2-mercaptobenzimidazole 0.005-0.01 g / L; the current density in step S6 is 2-5 A / dm 2 , the temperature is 20-30 °C, and the time is 15-60 minutes.

8. The method of claim 1, wherein: In the S7, the parameters of the working solution are controlled as follows: chromic anhydride: glucose = 1:3 ~ 1:5 by concentration, the initial concentration of glucose is 1.5-2.7 g / L, the concentration of Cr6+ is 0.5-0.7 g / L, ph = 5-6, and the circulation flow rate is 1.8-2.5 m 3 / h.

9. The method of claim 1, wherein: The aluminum substrate is pure aluminum with a purity of ≥99% or 3-series, 5-series or 6-series aluminum alloy.

10. The aluminum-based copper-coated thin film prepared by the method of any one of claims 1-9, wherein: The aluminum substrate, the zinc transition layer, the pyro-copper underlayer and the acid copper thickening layer; the total copper plating layer thickness of the aluminum substrate plated with copper is 7-35 μm, the peeling strength between the plating layer and the substrate is ≥5 N / cm, and the surface roughness Ra is ≤0.2 μm. ​

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