Aluminum-based copper foil and preparation method thereof

Abstract

The invention relates to an aluminum-based copper foil which comprises an aluminum base material layer, a transition layer and a copper foil layer, the transition layer is positioned between the aluminum substrate layer and the copper foil layer; a micron-sized concave-convex structure is arranged on the surface of the aluminum base material layer; and the transition layer is filled in the concave-convex structure and is connected with the copper foil layer. The preparation method of the aluminum-based copper foil comprises the following steps: sequentially carrying out degreasing, alkali washing and electrolytic etching treatment on an aluminum base material, and forming a micron-sized concave-convex structure on the surface of an aluminum base material layer; depositing a zinc-nickel alloy transition layer on the surface of the aluminum substrate by adopting an electroplating process; compounding the copper foil with the aluminum base material with the transition layer by adopting a vacuum hot-pressing compounding process; and passivating the surface of the compounded copper foil layer. The aluminum-based copper foil prepared by the method has the advantages of high bonding strength and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of metal composite materials technology, and in particular to an aluminum-based copper foil and its preparation method. Background Technology

[0002] Aluminum-based copper foil is a double-layer metal material formed by a composite process of aluminum substrate and copper foil. It combines the lightweight properties of aluminum with the high conductivity of copper and is widely used in the electronics industry. However, existing aluminum-based copper foils have the following technical drawbacks: The interfacial bonding strength between the aluminum substrate and copper foil is low, making it prone to delamination during bending, stamping, and other processing, affecting product reliability and lifespan. An oxide film easily forms on the surface of the aluminum substrate, hindering effective bonding between the copper foil and the aluminum substrate, resulting in poor stability of the composite process. The copper foil layer is susceptible to corrosion in humid or high-temperature environments, especially at the edges, reducing conductivity stability and product lifespan. Summary of the Invention

[0003] To address the technical problems of low bonding strength and easy corrosion of aluminum-based copper foil in the prior art, this invention provides an aluminum-based copper foil and its preparation method.

[0004] To achieve the above objectives, the present invention provides the following technical solution: An aluminum-based copper foil includes: an aluminum substrate layer, a transition layer, and a copper foil layer; the transition layer is located between the aluminum substrate layer and the copper foil layer; the surface of the aluminum substrate layer has a micron-level uneven structure; the transition layer fills the uneven structure and is connected to the copper foil layer.

[0005] Furthermore, the depth of the uneven structure is 1-5 μm.

[0006] Furthermore, the transition layer is composed of a zinc-nickel alloy and has a thickness of 0.5-2 μm; the copper foil layer has a thickness of 5-20 μm; and the aluminum substrate layer has a thickness of 0.1-5 mm.

[0007] Furthermore, the aluminum substrate layer is made of aluminum or aluminum alloy with a purity of ≥99.5%; the copper foil layer is made of electrolytic copper foil with a purity of ≥99.9%.

[0008] Furthermore, a passivation layer is provided on the outer surface of the copper foil layer, and the thickness of the passivation layer is 50-200 nm.

[0009] This invention also provides a method for preparing aluminum-based copper foil, comprising the following steps: S1. The aluminum substrate is subjected to degreasing, alkaline washing and electrolytic etching in sequence, and a micron-level uneven structure is formed on the surface of the aluminum substrate layer; S2. A zinc-nickel alloy transition layer is deposited on the surface of an aluminum substrate using an electroplating process; S3. A vacuum hot-pressing composite process is used to combine copper foil with an aluminum substrate having a transition layer; S4. Passivate the surface of the composite copper foil layer.

[0010] Further, in step S1, the electrolytic etching uses a mixed electrolyte of sulfuric acid and oxalic acid, wherein the concentration of sulfuric acid is 50-100 g / L, the concentration of oxalic acid is 10-30 g / L, the electrolysis temperature is 25-40℃, the current density is 10-20 A / dm², and the etching time is 30-120 s.

[0011] Further, in step S2, the electroplating solution contains 30-60 g / L zinc sulfate, 10-20 g / L nickel sulfate, and 20-30 g / L boric acid; the pH value of the electroplating solution is 3.0-5.0, the temperature is 40-50℃, the current density is 5-15 A / dm², and the electroplating time is 10-30 s.

[0012] Furthermore, in step S3, the hot-pressing temperature is 200-300℃, the pressure is 5-15MPa, the holding time is 30-60min, and the vacuum degree is ≤1×10 -3 Pa.

[0013] Furthermore, in step S4, the passivation treatment uses a sodium chromate solution with a concentration of 2-5 g / L or a silane coupling agent solution with a concentration of 2-5%, the treatment temperature is 25-40℃, and the treatment time is 10-30 s.

[0014] The aluminum-based copper foil and its preparation method provided by this invention have the following beneficial effects: The method for preparing aluminum-based copper foil provided by this invention involves removing the oxide film from the aluminum substrate and then forming a micron-level uneven structure on the surface of the aluminum substrate through electrolytic etching, providing a foundation for the subsequent physical bonding transition layer. A zinc-nickel alloy transition layer is further anchored within the uneven structure. Vacuum hot-pressing lamination in an oxygen-free environment enables the interdiffusion of interface atoms, achieving bonding between the copper foil and the aluminum substrate with the transition layer, resulting in high adhesion between the aluminum-based copper foil and the substrate. Finally, surface passivation treatment forms a dense external protective layer, which, together with the internal zinc-nickel alloy layer, provides dual corrosion resistance. The aluminum-based copper foil prepared by this method has the advantages of high bonding strength and strong corrosion resistance. Attached Figure Description

[0015] Figure 1 A flowchart illustrating the preparation method of aluminum-based copper foil provided in this embodiment of the invention. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] Example 1 See Figure 1 This invention provides a method for preparing aluminum-based copper foil, comprising the following steps S1-S4: Step S1. The aluminum substrate is subjected to degreasing, alkaline washing and electrolytic etching in sequence, and a micron-level uneven structure is formed on the surface of the aluminum substrate layer.

[0019] In step S1, the electrolytic etching uses a mixed electrolyte of sulfuric acid and oxalic acid, wherein the sulfuric acid concentration is 50-100 g / L, the oxalic acid concentration is 10-30 g / L, the electrolysis temperature is 25-40℃, the current density is 10-20 A / dm², and the etching time is 30-120 s.

[0020] In step S1, the aluminum substrate is sequentially degreased, alkaline washed, and electrolytic etched, forming a micron-scale uneven structure on the surface of the aluminum substrate layer. The purpose of degreasing and alkaline washing is to clean and activate the substrate surface, while electrolytic etching removes the oxide film and forms the uneven microstructure. This uneven structure eliminates the obstruction of interfacial bonding by the dense oxide film, exposing a highly active, fresh metal surface. Furthermore, this uneven structure increases the surface area of ​​the substrate, providing physical anchoring points for subsequent transition layers, thus significantly improving the peel strength of the final product.

[0021] A specific embodiment further describes step S1: The aluminum substrate undergoes pretreatment by immersing it in a 5% sodium hydroxide solution at 60°C for 30 seconds to remove rolling oil and organic contaminants. Residual alkaline solution is rinsed off with deionized water, and the substrate is then transferred to a 10% nitric acid solution and treated at room temperature for 20 seconds to neutralize the residual alkaline solution and activate the surface. After cleaning, the substrate proceeds to the electrolytic etching process.

[0022] Electrolytic etching was performed in a mixed electrolyte consisting of 80 g / L sulfuric acid and 20 g / L oxalic acid. An aluminum substrate was used as the anode, and etching was performed for 60 seconds at 30°C and a current density of 15 A / dm². During this process, the anolyte current induced selective dissolution of the aluminum surface, while the oxalic acid acted as a complexing agent, ensuring uniform etching and ultimately forming a micron-level uneven structure with a depth of 3 μm on the surface. This structure completely removed the original natural oxide film, resulting in a highly active and clean metal surface.

[0023] S2. A zinc-nickel alloy transition layer is deposited on the surface of an aluminum substrate using an electroplating process.

[0024] In step S2, the electroplating solution contains 30-60 g / L zinc sulfate, 10-20 g / L nickel sulfate and 20-30 g / L boric acid; the pH value of the electroplating solution is 3.0-5.0, the temperature is 40-50℃, the current density is 5-15 A / dm², and the electroplating time is 10-30 s.

[0025] In step S2, a zinc-nickel alloy transition layer is deposited on the surface of the aluminum substrate using an electroplating process. The function of this step is to achieve effective bonding and internal protection between the materials. The electroplating process ensures that the zinc-nickel alloy layer accurately and uniformly fills and adheres to the micron-level uneven structure formed in step S1. The selected zinc-nickel alloy material itself possesses excellent properties, with chemical properties between aluminum and copper. As a compatibility layer, it effectively alleviates internal stress caused by the mismatch in thermal expansion coefficients and enhances the interfacial chemical bonding force by forming a stable metallic bond. This alloy layer also serves as a "sacrificial anode" protection, preferentially corroding the core copper conductive layer when corrosive media penetrates from the edges.

[0026] A specific embodiment further describes step S2: A zinc-nickel alloy was deposited on the surface of a pretreated aluminum substrate using an electroplating process. The electroplating solution consisted of 45 g / L zinc sulfate, 15 g / L nickel sulfate, and 25 g / L boric acid. The electroplating process was controlled with a pH of 4.0, a solution temperature of 45°C, an applied current density of 10 A / dm², and a plating time of 20 seconds. Under this electrochemical environment, zinc and nickel ions co-deposited on the uneven surface of the aluminum substrate, forming a dense, 1.0 μm thick zinc-nickel alloy layer. This alloy layer completely wetted and filled the micron-sized pits on the surface, forming a strong mechanical bond.

[0027] S3. A vacuum hot-pressing composite process is used to composite copper foil with an aluminum substrate having a transition layer.

[0028] In step S3, the hot-pressing temperature is 200-300℃ (250℃ in this embodiment), the pressure is 5-15MPa (10MPa in this embodiment), the holding time is 30-60min (45min in this embodiment), and the vacuum degree is ≤1×10 -3 Pa (as set to 1×10 in this embodiment) -3 Pa).

[0029] In step S3, a vacuum hot-pressing composite process is used to bond copper foil to an aluminum substrate with a transition layer. The vacuum environment is used to eliminate oxygen and moisture, preventing oxidation of the interface at high temperatures and ensuring high cleanliness of the bonding interface. Hot pressing causes interatomic diffusion between the copper foil and the zinc-nickel alloy transition layer at the interface, forming a strong metallurgical bond interface rather than simple physical adhesion, thus significantly improving the bonding strength of the product.

[0030] A specific embodiment further describes step S3: After the transition layer is prepared, the copper foil lamination stage begins. Electrolytic copper foil is applied to the aluminum substrate with the transition layer and placed in a vacuum hot-pressing apparatus. The vacuum level of the hot-pressing environment is maintained at no higher than 5 × 10⁻⁶. -4 The pressure was set at 250℃ and 10MPa to completely eliminate the oxidizing effect of oxygen on the interface. The hot-pressing temperature was set at 250℃ and the pressure at 10MPa, and the temperature and pressure were maintained under these conditions for 45 minutes. Under these thermodynamic conditions, the atoms at the interface between the copper foil and the zinc-nickel alloy transition layer gain sufficient kinetic energy to undergo interdiffusion, thus forming a metallurgical bond rather than a simple physical adhesion.

[0031] S4. Passivate the surface of the composite copper foil layer.

[0032] In step S4, the passivation treatment uses a sodium chromate solution with a concentration of 2-5 g / L (3 g / L in this embodiment) or a silane coupling agent solution with a concentration of 2-5% (3% in this embodiment), the treatment temperature is 25-40℃ (32℃ in this embodiment), and the treatment time is 10-30 s (20 s in this embodiment).

[0033] In step S4, the surface of the composite copper foil layer is passivated. This step forms a physical barrier on the outermost copper foil surface after the overall composite structure is formed. The dense conversion film generated by the passivation treatment effectively blocks the direct attack of moisture, oxygen, and corrosive ions from the external environment on the copper layer, significantly improving the product's corrosion resistance.

[0034] A specific embodiment further describes step S4: The outer surface of the successfully laminated copper foil layer was passivated. It was immersed in a 3 g / L sodium chromate solution at 30°C for 20 seconds. After removal, cleaning and drying resulted in a colorless to light iridescent chromate conversion film approximately 100 nm thick on the copper foil surface. This film is chemically stable and, together with the internal zinc-nickel alloy transition layer, forms a synergistic protective system from the outside in.

[0035] Example 2 This invention provides an aluminum-based copper foil, comprising: an aluminum substrate layer, a transition layer, and a copper foil layer. The transition layer is located between the aluminum substrate layer and the copper foil layer; the surface of the aluminum substrate layer has a micron-level uneven structure with a depth of 1-5 μm; the transition layer fills the uneven structure and is connected to the copper foil layer.

[0036] The transition layer is composed of a zinc-nickel alloy with a thickness of 0.5-2 μm; the copper foil layer has a thickness of 5-20 μm; and the aluminum substrate layer has a thickness of 0.1-5 mm. The aluminum substrate layer uses aluminum or aluminum alloy with a purity ≥99.5%; the copper foil layer uses electrolytic copper foil with a purity ≥99.9%. A passivation layer with a thickness of 50-200 nm is provided on the outer surface of the copper foil layer.

[0037] The aluminum-based copper foil is further described below through a specific embodiment: A high-adhesion, corrosion-resistant aluminum-based copper foil comprises, from top to bottom, a passivation layer, a copper foil layer, a zinc-nickel alloy transition layer, and an aluminum substrate layer. The aluminum substrate layer uses 1.0 mm thick, 99.7% pure industrial-grade 1060 aluminum as the supporting matrix. On the upper surface of this aluminum substrate layer, a micron-level uneven structure with a depth of approximately 3 μm is formed through electrolytic etching. This uneven structure exhibits a uniformly distributed peak-valley morphology, which increases the effective bonding area and provides physical anchor points for subsequent interfacial bonding.

[0038] A zinc-nickel alloy transition layer is deposited directly on the surface of the aluminum substrate with an uneven structure, with a thickness controlled at 1.0 μm. This transition layer completely fills and adheres to the uneven structure of the aluminum substrate, forming a mechanical interlock. The composition of the zinc-nickel alloy is chosen based on its physicochemical properties, which fall between those of aluminum and copper, allowing it to act as a compatibility bridge and alleviate internal stress caused by differences in thermal expansion coefficients.

[0039] The copper foil layer uses electrolytic copper foil with a purity of 99.95% and a thickness of 10μm, which is brought into surface contact with the zinc-nickel alloy transition layer through a hot-pressing process. The outer surface of the copper foil layer is covered with a chromate passivation layer with a thickness of approximately 100nm. This passivation layer is a dense amorphous film formed by chemical conversion, which is mainly used to block the direct erosion of the copper layer by corrosive media such as water vapor and oxygen in the external environment.

[0040] The performance of the aluminum-based copper foil was verified using standard testing methods. A 90° peel strength test, conducted according to the IPC-TM-650 standard, showed a peel strength of 3.5 N / cm. This significant improvement in peel strength is attributed to the mechanical interlocking effect created by the micron-level uneven structure on the aluminum substrate surface and the zinc-nickel alloy transition layer, as well as the metallurgical bonding interface formed by the hot-pressing process. This composite bonding mechanism overcomes the insufficient bonding strength caused by interface flatness and the presence of oxide films in traditional processes.

[0041] Neutral salt spray tests conducted according to ASTM B117 showed no red rust observed in the samples after 500 hours. The corrosion resistance is a result of the combined physical barrier effect of the surface chromate passivation layer and the sacrificial anodic protection of the zinc-nickel alloy transition layer. When corrosive media accidentally penetrate the passivation layer or intrudes from the edges, the relatively negatively charged zinc-nickel alloy reacts preferentially over copper, thus protecting the integrity of the core conductive copper foil layer.

[0042] The material's conductivity was tested to be no less than 98% IACS, meeting the requirements for high conductivity applications. After undergoing a test of 10 repeated 180° bends, no delamination or cracks appeared at the interface, demonstrating the composite structure's strong reliability under mechanical deformation.

[0043] The aluminum-based copper foil and its preparation method provided by this invention have the following beneficial effects: The method for preparing aluminum-based copper foil provided by this invention involves removing the oxide film from the aluminum substrate and then forming a micron-level uneven structure on the surface of the aluminum substrate through electrolytic etching, providing a foundation for the subsequent physical bonding transition layer. A zinc-nickel alloy transition layer is further anchored within the uneven structure. Vacuum hot-pressing lamination in an oxygen-free environment enables the interdiffusion of interface atoms, achieving bonding between the copper foil and the aluminum substrate with the transition layer, resulting in high adhesion between the aluminum-based copper foil and the substrate. Finally, surface passivation treatment forms a dense external protective layer, which, together with the internal zinc-nickel alloy layer, provides dual corrosion resistance. The aluminum-based copper foil prepared by this method has the advantages of high bonding strength and strong corrosion resistance.

[0044] 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. An aluminum-based copper foil, characterized by: The application relates to an aluminum-based copper foil and a preparation method thereof. The aluminum substrate layer, the transition layer and the copper foil layer; the transition layer is located between the aluminum substrate layer and the copper foil layer; the surface of the aluminum substrate layer is provided with a micron-level concave-convex structure; the transition layer is filled in the concave-convex structure and connected with the copper foil layer.

2. The aluminum-based copper foil according to claim 1, characterized by: The depth of the concave-convex structure is 1-5 mu m.

3. The aluminum-based copper foil according to claim 1, characterized by: The transition layer is composed of a zinc-nickel alloy, the thickness of the transition layer is 0.5-2 mu m; the thickness of the copper foil layer is 5-20 mu m; and the thickness of the aluminum substrate layer is 0.1-5 mm.

4. The aluminum-based copper foil according to claim 1, characterized by: The aluminum substrate layer adopts aluminum or aluminum alloy with a purity of greater than or equal to 99.5%; and the copper foil layer adopts electrolytic copper foil with a purity of greater than or equal to 99.9%.

5. The aluminum-based copper foil according to claim 1, characterized by: The outer surface of the copper foil layer is provided with a passivation layer, and the thickness of the passivation layer is 50-200 nm.

6. A method of producing the aluminum-based copper foil according to any one of claims 1 to 5, characterized by: The application further discloses a preparation method of the aluminum-based copper foil. In step S1, electrolytic etching is carried out by using a mixed electrolyte of sulfuric acid and oxalic acid, wherein the concentration of sulfuric acid is 50-100 g / L, the concentration of oxalic acid is 10-30 g / L, the electrolysis temperature is 25-40 DEG C, the current density is 10-20 A / dm2, and the etching time is 30-120 s. In step S2, the electroplating solution contains 30-60 g / L of zinc sulfate, 10-20 g / L of nickel sulfate and 20-30 g / L of boric acid; the pH value of the electroplating solution is 3.0-5.0, the temperature is 40-50 DEG C, the current density is 5-15 A / dm2, and the electroplating time is 10-30 s.

10. The preparation method of the aluminum-based copper foil according to claim 5, wherein in step S4, the passivation treatment is carried out by using a sodium chromate solution with a concentration of 2-5 g / L or a silane coupling agent solution with a concentration of 2-5%, the treatment temperature is 25-40 DEG C, and the treatment time is 10-30 s. ​ 7. The method of producing an aluminum-based copper foil according to claim 5, characterized by: ​ 8. The method of producing an aluminum-based copper foil according to claim 5, characterized by: ​ 9. The method of producing an aluminum-based copper foil according to claim 1, characterized in that: In step S3, the hot-pressing temperature is 200-300℃, the pressure is 5-15MPa, the holding time is 30-60min, and the vacuum degree is ≤1×10 -3 Pa. ​ ​

Images