Manufacturing method of high-conductivity copper-clad aluminum flat wire

Abstract

The invention discloses a manufacturing method of a high-conductivity copper-clad aluminum flat wire, and relates to the technical field of electric metal flat wires. According to the method, the surface of the metal aluminum is modified through femtosecond laser, an ultra-clean amorphous layer is generated through non-thermal melting-solidification, and diffusion activation energy of subsequent cold pressure welding is greatly reduced. Secondly, inducing the aluminum surface to generate a micro-nano porous structure during femtosecond laser treatment, then depositing a copper layer on the aluminum surface through nano-copper particle gas, and forming a barb structure through micron pits of metal aluminum and nano-copper gas deposition permeation pore lines, so as to realize copper-aluminum atomic-scale mutual diffusion. Finally, a transverse high-intensity magnetic field is applied in the cold pressure welding process, and copper grains are induced to be preferentially oriented along the crystal face; and then the copper-clad aluminum flat wire is prepared through cold pressing treatment, effective utilization of the conductive cross section can be maximized through compact forming and surface polishing, grain growth caused by high temperature is avoided, a fine grain structure is reserved, and the material strength is improved. The prepared copper-clad aluminum flat wire has the effects of high strength and high conductivity.

Description

Technical Field

[0001] The invention relates to the technical field of conductive metal flat wires, in particular to a method for manufacturing a high-conductivity copper-clad aluminum flat wire. Background Art

[0002] In the field of electrical equipment manufacturing, traditional copper wires are widely used due to their excellent electrical conductivity. However, with the continuous improvement of material performance requirements and the need for cost control, the limitations of traditional copper wires are gradually emerging. Copper-clad aluminum flat wires have emerged as a new type of composite material. Its core advantages are low density, good electrical conductivity and high mechanical strength. In terms of conductivity, by optimizing the bonding process between the copper layer and the aluminum core, such as using argon arc welding to form a strong metallurgical bond, good electrical conductivity is ensured and the resistivity can be controlled at a low level. In terms of mechanical strength, copper-clad aluminum flat wires not only have the flexibility of the aluminum core, but also the high strength of the copper layer.

[0003] In terms of manufacturing technology, the development from early cladding welding to the current advanced processes such as continuous casting and rolling has made the production of copper-clad aluminum flat wire more efficient and accurate, and can meet the needs of orders with different specifications and performance requirements. These background factors have jointly promoted the continuous innovation and development of high-conductivity copper-clad aluminum flat wire manufacturing methods, making it play an increasingly important role in the manufacturing of electrical equipment such as transformers and motors.

[0004] In the manufacturing process of high-conductivity copper-clad aluminum flat wire, in terms of conductivity, since the copper-clad aluminum flat wire is a composite material of copper layer and aluminum core, its conductivity will be affected by many factors such as the thickness of the copper layer, the quality of the copper-aluminum interface bonding, and the manufacturing process. A copper layer that is too thin may lead to a decrease in conductivity, while a copper layer that is too thick will increase the cost. In addition, if there is an oxide layer or the bonding is not tight at the copper-aluminum interface, it will also hinder the flow of electrons and reduce conductivity. During the high-temperature annealing process, although annealing can eliminate the internal stress caused by cold working and improve the ductility and conductivity of the material, there are also some defects. High-temperature annealing may cause an intermetallic compound layer to form at the copper-aluminum interface. When the thickness of this layer exceeds a certain limit, the interface bonding strength will be significantly reduced, making the material prone to breakage during use. At the same time, high-temperature annealing may also cause the grain growth of the material, affecting the stability of its mechanical properties and conductive properties. Summary of the invention

[0005] The object of the present invention is to provide a method for manufacturing a high-conductivity copper-clad aluminum flat wire to solve the problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a high-conductivity copper-clad aluminum flat wire, comprising the following preparation steps: (1) Using a femtosecond laser at 2-3 J / cm under argon protection 2The energy density of the irradiation was 3.0-5.0mm diameter high purity aluminum rod surface, through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 12 -10 13 K / s, generating a 50-100nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 3-5J / cm 2 , a spiral scanning path was used to form a porous structure with micron pits of 2-5 μm in diameter and interlaced edge nanowires of 50-200 nm to produce a femtosecond laser pretreated high-purity aluminum rod; (2) Pre-treat the high-purity aluminum rod by 160-200W argon plasma cleaning for 3-5 minutes to remove subsurface impurities, and then preheat the cleaned high-purity aluminum rod in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor; deposit a 10-20μm copper layer by PVD deposition; then use a hot wall ALD system equipped with a copper precursor transport module to perform ALD deposition of the copper layer, and achieve a composition gradient by adjusting the copper / aluminum circulation ratio; deposit at 150-250°C, with a precursor pulse time of 0.1-1s of copper / aluminum precursor and 0.5-2s of hydrogen pulse; purge with high-purity argon for 10-20s; form a 3-5μm thick gradient transition layer to obtain a gradient high-purity aluminum rod; (3) The copper sheet and the gradient high-purity aluminum rod are cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers, and multi-pass drawing is performed at a speed of 60-600m / min and a pass reduction rate of 10-20% to prepare a round fine wire with a diameter of 0.3-3.0mm. A pressure of 80-120MPa is applied by hydraulic pressure under a transverse magnetic field of 1-2T for a holding time of 10-20s. A nitrogen atmosphere is used to prevent oxidation, and the copper-clad aluminum wire is obtained by cold pressing and welding. Finally, a four-roll precision rolling mill is used for cold pressing, and then low-temperature annealing is performed to obtain a high-conductivity copper-clad aluminum flat wire.

[0007] Furthermore, the copper sheet coating layer area ratio in the cross section of the copper-clad aluminum flat wire is 15% to 40%, the thickness is 0.02 to 0.05 mm, and the maximum width-to-thickness ratio of the flat wire is 10:1.

[0008] Furthermore, in step (1), the wavelength of the femtosecond laser is 1030 nm and the pulse width is 300 fs.

[0009] Furthermore, the scanning speed of the spiral scanning in step (1) is 500 mm / s, and the overlap rate is 15%.

[0010] Furthermore, in the step (2), the PVD deposition is performed by turning on the argon gas with a flow rate of 20 sccm, adjusting the gas pressure to 5-10 mTorr, using copper as the target material, applying 50 W low-power sputtering for 5 min, increasing the power to 300-400 W, and starting deposition.

[0011] Furthermore, in step (2), bis(hexafluoroacetylacetonate)copper(II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent.

[0012] Furthermore, in the step (2), during the gradient deposition, the initial stage is 100% copper circulation, and the aluminum circulation ratio is gradually increased to 5-10%, while the copper circulation ratio is reduced to maintain the total ratio of aluminum and copper at 100%.

[0013] Furthermore, in the step (2), the thickness of a single cycle is 0.05-0.1 nm / cycle.

[0014] Furthermore, in step (3), the thickness of the copper sheet is 0.1-0.16 mm.

[0015] Furthermore, the cold pressing conditions in step (3) are as follows: the surface of the rolling roller is hard chrome plated, the initial rolling pressure is 50 MPa, and gradually increases to 100 MPa; the width-to-thickness ratio is gradually reduced from 3:1 to 10:1, and the rolling speed is 100-300 m / min.

[0016] Furthermore, the annealing conditions in step (3) are as follows: Ar / H 2 Mixed gas, flow rate is 10-20L / min, including Ar:H 2 The volume ratio is 19:1, and the residual stress is released at 80-120℃ for 30-60min.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are: The present invention utilizes femtosecond laser pretreatment, vapor deposition wire infiltration combined with cold pressing magnetic field forming to prepare high-conductivity copper-clad aluminum flat wire to achieve the effects of high strength and high conductivity.

[0018] First, the pulse energy of the femtosecond laser is instantly absorbed by the free electrons on the surface of the metal aluminum. Through the nonlinear interaction between the extremely short pulse and the material, the aluminum on the metal surface is non-thermally melted and solidified before cold-pressing welding to generate an ultra-clean amorphous layer without oxidation and grain boundaries, which greatly reduces the diffusion activation energy of subsequent cold-pressing welding and achieves low-temperature and efficient atomic bonding, that is, full diffusion can be achieved without annealing, thereby avoiding the formation of brittle phases caused by high-temperature annealing (such as CuAl 2 ), reducing the ductility of the flat wire; at the same time, the femtosecond laser pulse instantly vaporizes the surface oxide, reducing the oxide's hindrance to atomic diffusion and improving the copper-aluminum interface bonding strength; Secondly, femtosecond laser treatment is used to induce the formation of a micro-nano porous structure on the aluminum surface, and then a PVD physical vapor deposition copper layer is deposited on the aluminum surface. The micron pits of the accumulated metal aluminum and the atomic layer deposition copper infiltrate the pore lines to form a "hook" structure, resulting in a three-dimensional mechanical interlocking; the micron pits are used as mechanical anchors, combined with the nano-network structure of the diffusion channel, and the ALD atomic layer deposition gradient layer is added. The gradient components of aluminum-aluminum-copper-copper act on stress buffering, realize the atomic-level interdiffusion of copper and aluminum, avoid the concentration of brittle phases, achieve the "macro-micro-nano" three-level synergistic strengthening, and improve the conductivity of the flat wire; Finally, the copper sheet is coated with a high-purity aluminum rod through cold welding to ensure clean bonding at the copper-aluminum interface at the atomic level and eliminate resistance jumps. A strong transverse magnetic field is applied during the cold welding process to induce the copper grains to preferentially orient along the crystal plane and improve the conductivity of the flat wire. Copper-clad aluminum flat wire is then prepared through cold pressing. Dense molding and surface polishing can maximize the effective utilization of the conductive cross section, avoid grain growth caused by high temperature, retain fine-grained structure, and improve material strength. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] Example 1: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used to irradiate the surface of a high-purity aluminum rod with a diameter of 3.0 mm at an energy density of 2 J / cm² under argon protection. The cooling rate was 10 12 K / s, generating a 50nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 3J / cm 2 , a spiral scanning path was used with a scanning speed of 500 mm / s and an overlap rate of 15%, forming a porous structure with micron pits of 2 μm in diameter and interlaced nanowires of 50 nm at the edge, and a femtosecond laser pretreated high-purity aluminum rod was obtained; (2) First, the high-purity aluminum rod was pretreated by 160W argon plasma cleaning for 3 minutes to remove subsurface impurities. The cleaned high-purity aluminum rod was preheated in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor. The argon gas was turned on with a flow rate of 20sccm and a pressure of 5mTorr. Copper was used as the target material and 50W low-power sputtering was applied for 5min. The power was increased to 300W to start deposition until a 10μm copper layer was deposited. Then, a hot wall ALD system was used with a copper precursor transport module to deposit a copper layer using ALD. Copper (II) di(hexafluoroacetylacetonate) was used as the copper source, trimethylaluminum was used as the aluminum source, and hydrogen was used as the reducing agent. The composition gradient was achieved by adjusting the copper / aluminum cycle ratio. The initial stage was 100%. Copper cycle, gradually increase the aluminum cycle ratio to 5%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%; deposit at 150°C, with a precursor pulse time of 0.1s of copper / aluminum precursor and 0.5s of hydrogen pulse; purge with high-purity argon for 10s; single cycle thickness is 0.05nm / cycle, forming a 3μm thick gradient transition layer, and a gradient high-purity aluminum rod is obtained; (3) A copper sheet with a thickness of 0.1 mm and a gradient high-purity aluminum rod were cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers. A multi-pass drawing process was performed at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. A pressure of 80 MPa was applied hydraulically under a 1 T transverse magnetic field. The pressure was maintained for 10 s and a nitrogen atmosphere was used to prevent oxidation. Copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used. The surface of the rolling rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1. The rolling speed was 100 m / min. Ar / H was then introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 10L / min, including Ar:H 2 The volume ratio is =19:1, and the residual stress is released by keeping warm at 80℃ for 30min to obtain a high-conductivity copper-clad aluminum flat wire. The copper sheet coating area ratio is 15%, the thickness is 0.02mm, and the flat wire width-to-thickness ratio is 10:1.

[0021] Example 2: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used under argon protection at 2.5 J / cm 2 The energy density of the irradiation was 4.0 mm in diameter on the surface of a high-purity aluminum rod. Through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 12 K / s, generating a 75nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 4J / cm 2, a spiral scanning path was used with a scanning speed of 500 mm / s and an overlap rate of 15%, forming a porous structure with micron pits of 3.5 μm in diameter and interlaced nanowires of 125 nm at the edge, and a femtosecond laser pretreated high-purity aluminum rod was obtained; (2) First, the high-purity aluminum rod was pretreated by 180W argon plasma cleaning for 4 minutes to remove subsurface impurities. The cleaned high-purity aluminum rod was preheated in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor. The argon gas was turned on with a flow rate of 20sccm and a pressure of 7.5mTorr. Copper was used as the target material and 50W low-power sputtering was applied for 5min. The power was increased to 350W to start deposition until a 15μm copper layer was deposited. Then, a hot wall ALD system was used with a copper precursor transport module to perform ALD deposition of the copper layer. Copper (II) was used as the copper source, trimethylaluminum was used as the aluminum source, and hydrogen was used as the reducing agent. The composition gradient was achieved by adjusting the copper / aluminum cycle ratio. The initial stage was 100%. Copper cycle, gradually increase the aluminum cycle ratio to 7.5%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%; deposit at 200°C, with a precursor pulse time of 0.55s of copper / aluminum precursor and 1.25s of hydrogen pulse; purge with high-purity argon for 15s; single cycle thickness is 0.075nm / cycle, forming a 4μm thick gradient transition layer, and a gradient high-purity aluminum rod is obtained; (3) A copper sheet with a thickness of 0.13 mm and a gradient high-purity aluminum rod were cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers. A multi-pass drawing process was performed at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. A pressure of 100 MPa was applied hydraulically under a 1.5 T transverse magnetic field. The pressure was maintained for 15 s. A nitrogen atmosphere was used to prevent oxidation. Copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used. The surface of the rolling rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1. The rolling speed was 200 m / min. Ar / H was then introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 15L / min, including Ar:H 2 The volume ratio is =19:1, and the residual stress is released by keeping it at 100℃ for 45min to obtain a high-conductivity copper-clad aluminum flat wire. The area ratio of the copper sheet coating is 25%, the thickness is 0.035mm, and the width-to-thickness ratio of the flat wire is 5:1.

[0022] Example 3: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used under argon protection at 3 J / cm 2 The energy density of the irradiation was 5.0 mm in diameter on the surface of a high-purity aluminum rod. Through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 13K / s, generating a 100nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 5J / cm 2 , a spiral scanning path was adopted with a scanning speed of 500 mm / s and an overlap rate of 15%, forming a porous structure with micron pits of 5 μm in diameter and interlaced nanowires of 200 nm at the edge, and a femtosecond laser pretreated high-purity aluminum rod was obtained; (2) First, the high-purity aluminum rod was pretreated by 200W argon plasma cleaning for 5 minutes to remove subsurface impurities. The cleaned high-purity aluminum rod was preheated in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor. The argon gas was turned on with a flow rate of 20sccm and a pressure of 10mTorr. Copper was used as the target material and 50W low-power sputtering was applied for 5 minutes. The power was increased to 400W to start deposition until a 20μm copper layer was deposited. Then, a hot wall ALD system was used with a copper precursor transport module to deposit a copper layer using ALD. Copper (II) di(hexafluoroacetylacetonate) was used as the copper source, trimethylaluminum was used as the aluminum source, and hydrogen was used as the reducing agent. The composition gradient was achieved by adjusting the copper / aluminum cycle ratio. The initial stage was 100%. Copper cycle, gradually increase the aluminum cycle ratio to 10%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%; deposit at 250°C, the precursor pulse time is 1s of copper / aluminum precursor and 2s of hydrogen pulse; use high-purity argon gas for purging, the time is 20s; the single cycle thickness is 0.1nm / cycle, forming a 5μm thick gradient transition layer, and a gradient high-purity aluminum rod is obtained; (3) A copper sheet with a thickness of 0.16 mm and a gradient high-purity aluminum rod were cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers. A multi-pass drawing process was performed at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. A pressure of 120 MPa was applied hydraulically under a 2T transverse magnetic field. The pressure was maintained for 20 s and a nitrogen atmosphere was used to prevent oxidation. Copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used. The surface of the rolling rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1. The rolling speed was 300 m / min. Ar / H was then introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 20L / min, including Ar:H 2 The volume ratio is =19:1, and the residual stress is released by keeping it at 120℃ for 60min to obtain a high-conductivity copper-clad aluminum flat wire. The area ratio of the copper sheet coating is 40%, the thickness is 0.05mm, and the maximum width-to-thickness ratio of the flat wire is 4:1.

[0023] Comparative Example 1: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used under argon protection at 4 J / cm 2energy density, using a spiral scanning path, a scanning speed of 500 mm / s, and an overlap rate of 15%, to form a porous structure of interlaced micron pits with a diameter of 3.5 μm and edge nanowires of 125 nm, and to produce a high-purity aluminum rod pretreated by femtosecond laser; (2) First, the high-purity aluminum rod was pretreated by 180W argon plasma cleaning for 4 minutes to remove subsurface impurities. The cleaned high-purity aluminum rod was preheated in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor. The argon gas was turned on with a flow rate of 20sccm and a pressure of 7.5mTorr. Copper was used as the target material and 50W low-power sputtering was applied for 5min. The power was increased to 350W to start deposition until a 15μm copper layer was deposited. Then, a hot wall ALD system was used with a copper precursor transport module to perform ALD deposition of the copper layer. Copper (II) was used as the copper source, trimethylaluminum was used as the aluminum source, and hydrogen was used as the reducing agent. The composition gradient was achieved by adjusting the copper / aluminum cycle ratio. The initial stage was 100%. Copper cycle, gradually increase the aluminum cycle ratio to 7.5%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%; deposit at 200°C, with a precursor pulse time of 0.55s of copper / aluminum precursor and 1.25s of hydrogen pulse; purge with high-purity argon for 15s; single cycle thickness is 0.075nm / cycle, forming a 4μm thick gradient transition layer, and a gradient high-purity aluminum rod is obtained; (3) A copper sheet with a thickness of 0.13 mm and a gradient high-purity aluminum rod were cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers. A multi-pass drawing process was performed at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. A pressure of 100 MPa was applied hydraulically under a 1.5 T transverse magnetic field. The pressure was maintained for 15 s. A nitrogen atmosphere was used to prevent oxidation. Copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used. The surface of the rolling rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1. The rolling speed was 200 m / min. Ar / H was then introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 15L / min, including Ar:H 2 The volume ratio is = 19:1, and the residual stress is released by keeping it at 100℃ for 45min to obtain a high-conductivity copper-clad aluminum flat wire.

[0024] Comparative Example 2: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used under argon protection at 2.5 J / cm 2 The energy density of the irradiation was 4.0 mm in diameter on the surface of a high-purity aluminum rod. Through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 12K / s, a 75nm thick ultra-clean amorphous layer is generated on the surface of the high-purity aluminum rod to obtain a femtosecond laser pretreated high-purity aluminum rod; (2) First, the high-purity aluminum rod was pretreated by 180W argon plasma cleaning for 4 minutes to remove subsurface impurities. The cleaned high-purity aluminum rod was preheated in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor. The argon gas was turned on with a flow rate of 20sccm and a pressure of 7.5mTorr. Copper was used as the target material and 50W low-power sputtering was applied for 5min. The power was increased to 350W to start deposition until a 15μm copper layer was deposited. Then, a hot wall ALD system was used with a copper precursor transport module to perform ALD deposition of the copper layer. Copper (II) was used as the copper source, trimethylaluminum was used as the aluminum source, and hydrogen was used as the reducing agent. The composition gradient was achieved by adjusting the copper / aluminum cycle ratio. The initial stage was 100%. Copper cycle, gradually increase the aluminum cycle ratio to 7.5%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%; deposit at 200°C, with a precursor pulse time of 0.55s of copper / aluminum precursor and 1.25s of hydrogen pulse; purge with high-purity argon for 15s; single cycle thickness is 0.075nm / cycle, forming a 4μm thick gradient transition layer, and a gradient high-purity aluminum rod is obtained; (3) A copper sheet with a thickness of 0.13 mm and a gradient high-purity aluminum rod were cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers. A multi-pass drawing process was performed at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. A pressure of 100 MPa was applied hydraulically under a 1.5 T transverse magnetic field. The pressure was maintained for 15 s. A nitrogen atmosphere was used to prevent oxidation. Copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used. The surface of the rolling rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1. The rolling speed was 200 m / min. Ar / H was then introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 15L / min, including Ar:H 2 The volume ratio is = 19:1, and the residual stress is released by keeping it at 100℃ for 45min to obtain a high-conductivity copper-clad aluminum flat wire.

[0025] Comparative Example 3: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used under argon protection at 2.5 J / cm 2 The energy density of the irradiation was 4.0 mm in diameter on the surface of a high-purity aluminum rod. Through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 12 K / s, generating a 75nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 4J / cm 2, a spiral scanning path was used with a scanning speed of 500 mm / s and an overlap rate of 15%, forming a porous structure with micron pits of 3.5 μm in diameter and interlaced nanowires of 125 nm at the edge, and a femtosecond laser pretreated high-purity aluminum rod was obtained; (2) A copper sheet with a thickness of 0.13 mm and a high-purity aluminum rod pretreated by femtosecond laser were cold-bent by a group of hole-shaped rollers into a copper sleeve with an aluminum core in the middle. A multi-pass drawing process was performed at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. A pressure of 100 MPa was applied hydraulically under a transverse magnetic field of 1.5 T. The pressure was maintained for 15 s. A nitrogen atmosphere was used to prevent oxidation. Copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used. The surface of the rolling rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1. The rolling speed was 200 m / min. Ar / H was then introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 15L / min, including Ar:H 2 The volume ratio is = 19:1, and the residual stress is released by keeping it at 100℃ for 45min to obtain a high-conductivity copper-clad aluminum flat wire.

[0026] Comparative Example 4: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used under argon protection at 2.5 J / cm 2 The energy density of the irradiation was 4.0 mm in diameter on the surface of a high-purity aluminum rod. Through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 12 K / s, generating a 75nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 4J / cm 2 , a spiral scanning path was used with a scanning speed of 500 mm / s and an overlap rate of 15%, forming a porous structure with micron pits of 3.5 μm in diameter and interlaced nanowires of 125 nm at the edge, and a femtosecond laser pretreated high-purity aluminum rod was obtained; (2) First, the high-purity aluminum rod was pretreated by 180W argon plasma cleaning for 4 minutes to remove subsurface impurities, and the cleaned high-purity aluminum rod was in-situ vacuum preheated at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor; the argon gas was turned on with a flow rate of 20sccm and a pressure of 7.5mTorr. With copper as the target material, 50W low-power sputtering was applied for 5 minutes, and the power was increased to 350W to start deposition, and a 15μm copper layer was deposited to obtain a high-purity aluminum rod with deposited copper; (3) A copper sheet with a thickness of 0.13 mm and a high-purity aluminum rod with deposited copper were cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers. A multi-pass drawing process was performed at a speed of 60 m / min and a pass reduction rate of 10% to prepare a round fine wire with a diameter of 0.3 mm. A pressure of 100 MPa was applied hydraulically under a transverse magnetic field of 1.5 T. The pressure was maintained for 15 s. A nitrogen atmosphere was used to prevent oxidation. Copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used. The surface of the rolling rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1. The rolling speed was 200 m / min. Ar / H was then introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 15L / min, including Ar:H 2 The volume ratio is = 19:1, and the residual stress is released by keeping it at 100℃ for 45min to obtain a high-conductivity copper-clad aluminum flat wire.

[0027] Comparative Example 5: (1) A femtosecond laser with a wavelength of 1030 nm and a pulse width of 300 fs was used under argon protection at 2.5 J / cm 2 The energy density of the irradiation was 4.0 mm in diameter on the surface of a high-purity aluminum rod. Through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 12 K / s, generating a 75nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 4J / cm 2 , a spiral scanning path was used with a scanning speed of 500 mm / s and an overlap rate of 15%, forming a porous structure with micron pits of 3.5 μm in diameter and interlaced nanowires of 125 nm at the edge, and a femtosecond laser pretreated high-purity aluminum rod was obtained; (2) First, the high-purity aluminum rod was pretreated by 180W argon plasma cleaning for 4 minutes to remove subsurface impurities. The cleaned high-purity aluminum rod was preheated in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor. The argon gas was turned on with a flow rate of 20sccm and a pressure of 7.5mTorr. Copper was used as the target material and 50W low-power sputtering was applied for 5min. The power was increased to 350W to start deposition until a 15μm copper layer was deposited. Then, a hot wall ALD system was used with a copper precursor transport module to perform ALD deposition of the copper layer. Copper (II) was used as the copper source, trimethylaluminum was used as the aluminum source, and hydrogen was used as the reducing agent. The composition gradient was achieved by adjusting the copper / aluminum cycle ratio. The initial stage was 100%. Copper cycle, gradually increase the aluminum cycle ratio to 7.5%, reduce the copper cycle ratio, and keep the total ratio of aluminum and copper at 100%; deposit at 200°C, with a precursor pulse time of 0.55s of copper / aluminum precursor and 1.25s of hydrogen pulse; purge with high-purity argon for 15s; single cycle thickness is 0.075nm / cycle, forming a 4μm thick gradient transition layer, and a gradient high-purity aluminum rod is obtained; (3) A copper sheet with a thickness of 0.13 mm and a gradient high-purity aluminum rod were cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers. A pressure of 100 MPa was applied by hydraulic pressure, and the pressure was maintained for 15 s. A nitrogen atmosphere was used to prevent oxidation, and the copper-clad aluminum wire was obtained by cold pressing. Finally, a four-roll precision rolling mill was used, and the surface of the rollers was hard chrome-plated. The initial rolling pressure was 50 MPa and gradually increased to 100 MPa. The width-to-thickness ratio was gradually reduced from 3:1 to 10:1, and the rolling speed was 200 m / min. Then, Ar / H was introduced into a tubular annealing furnace. 2 Mixed gas, flow rate 15L / min, including Ar:H 2 The volume ratio is = 19:1, and the residual stress is released by keeping it at 100℃ for 45min to obtain a high-conductivity copper-clad aluminum flat wire.

[0028] Effect example Table 1 below shows the performance analysis results of a high-conductivity copper-clad aluminum rectangular wire using Examples 1 to 3 of the present invention and Comparative Examples 1 to 5.

[0029] Table 1

[0030] From the comparison of the experimental data of the elongation at break of the embodiment and the comparative example, it can be found that the present invention utilizes the pulse energy of the femtosecond laser to be instantly absorbed by the free electrons on the surface of the metal aluminum, and the surface modification technology of the metal aluminum is non-thermally melted and solidified before cold-pressing welding through the nonlinear interaction between the extremely short pulse and the material, so as to generate an ultra-clean amorphous layer without oxidation and grain boundaries, greatly reduce the diffusion activation energy of the subsequent cold-pressing welding, and achieve low-temperature and efficient atomic bonding, that is, sufficient diffusion can be achieved without annealing, thereby avoiding the generation of brittle phases caused by high-temperature annealing and reducing the ductility of the flat wire. The comparison of the experimental data of the tensile strength of the embodiment and the comparative example shows that the present invention uses the femtosecond laser treatment to induce the generation of a micro-nano porous structure on the aluminum surface, and then deposits a copper layer on the aluminum surface with PVD physical vapor deposition, and the micron pits of the metal aluminum and the atomic layer deposition copper infiltrate the pore lines to form a "barb" structure, resulting in a three-dimensional mechanical interlocking. Comparison of the experimental data of resistivity of the embodiment and the comparative example shows that the micron pits of the present invention are used as mechanical anchors, combined with the nano-network structure of the diffusion channel, and coupled with the ALD atomic layer deposition gradient layer, the gradient components of aluminum-aluminum-copper-copper act on stress buffering, realize the atomic-level mutual diffusion of copper and aluminum, avoid the concentration of brittle phases, achieve the three-level synergistic strengthening of "macro-micro-nano", and improve the conductivity of the flat wire. The copper sheet is coated with a high-purity aluminum rod by cold-pressing welding to ensure the atomic-level clean bonding of the copper-aluminum interface and eliminate the resistance jump; a strong transverse magnetic field is applied during the cold-pressing welding process to induce the copper grains to preferentially orient along the crystal plane and improve the conductivity of the flat wire; then the copper-clad aluminum flat wire is prepared by cold-pressing treatment, and the dense molding and surface polishing can maximize the effective utilization of the conductive cross section, avoid the grain growth caused by high temperature, retain the fine-grained structure, and improve the material strength.

[0031] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a high-conductivity copper-clad aluminum flat wire, characterized in that: The method comprises the following preparation steps: (1) Using a femtosecond laser, the surface of a high-purity aluminum rod with a diameter of 3.0-5.0 mm was irradiated with an energy density of 2-3 J / cm² under argon protection. Through electron instantaneous excitation and ultrafast cooling, the cooling rate was 10 12 -10 13 K / s, generating a 50-100nm thick ultra-clean amorphous layer on the surface of the high-purity aluminum rod, and then increasing the energy density to 3-5J / cm 2 , a spiral scanning path was used to form a porous structure with micron pits of 2-5 μm in diameter and interlaced edge nanowires of 50-200 nm to produce a femtosecond laser pretreated high-purity aluminum rod; (2) Pre-treat the high-purity aluminum rod by 160-200W argon plasma cleaning for 3-5 minutes to remove subsurface impurities, and then preheat the cleaned high-purity aluminum rod in situ under vacuum at a vacuum degree of 0.5MPa, a temperature of 150°C, and a time of 1h to remove water vapor; deposit a 10-20μm copper layer by PVD deposition; then use a hot wall ALD system equipped with a copper precursor transport module to perform ALD deposition of the copper layer, and achieve a composition gradient by adjusting the copper / aluminum circulation ratio; deposit at 150-250°C, with a precursor pulse time of 0.1-1s of copper / aluminum precursor and 0.5-2s of hydrogen pulse; purge with high-purity argon for 10-20s; form a 3-5μm thick gradient transition layer to obtain a gradient high-purity aluminum rod; (3) The copper sheet and the gradient high-purity aluminum rod are cold-bent into a copper sleeve with an aluminum core in the middle by a set of hole-shaped rollers, and multi-pass drawing is performed at a speed of 60-600m / min and a pass reduction rate of 10-20% to prepare a round fine wire with a diameter of 0.3-3.0mm. A pressure of 80-120MPa is applied by hydraulic pressure under a transverse magnetic field of 1-2T for a holding time of 10-20s. A nitrogen atmosphere is used to prevent oxidation, and the copper-clad aluminum wire is obtained by cold pressing and welding. Finally, a four-roll precision rolling mill is used for cold pressing, and then low-temperature annealing is performed to obtain a high-conductivity copper-clad aluminum flat wire.

2. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: In the step (1), the wavelength of the femtosecond laser is 1030 nm and the pulse width is 300 fs.

3. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: The scanning speed of the spiral scanning in step (1) is 500 mm / s, and the overlap rate is 15%.

4. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: In the step (2), the PVD deposition is performed by turning on the argon gas with a flow rate of 20 sccm, adjusting the gas pressure to 5-10 mTorr, using copper as the target material, applying 50 W low-power sputtering for 5 minutes, increasing the power to 300-400 W, and starting deposition.

5. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: In the step (2), bis(hexafluoroacetylacetonate)copper(II) is used as the copper source, trimethylaluminum is used as the aluminum source, and hydrogen is used as the reducing agent.

6. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: In the step (2), during the gradient deposition, the initial stage is 100% copper circulation, and the proportion of aluminum circulation is gradually increased to 5-10%.

7. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: The thickness of a single cycle in the step (2) is 0.05-0.1 nm / cycle.

8. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: In the step (3), the thickness of the copper sheet is 0.1-0.16 mm.

9. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: The cold pressing conditions in step (3) are as follows: the surface of the rolling roller is hard chrome plated, the initial rolling pressure is 50 MPa, and the pressure is gradually increased to 100 MPa; the width-to-thickness ratio is gradually reduced from 3:1 to 10:1, and the rolling speed is 100-300 m / min.

10. The method for preparing a high-conductivity copper-clad aluminum rectangular wire according to claim 1, characterized in that: The annealing conditions in step (3) are as follows: introducing Ar / H2 mixed gas into a tubular annealing furnace at a flow rate of 10-20 L / min, wherein the volume ratio of Ar:H2 is 19:1, and the temperature is maintained at 80-120°C for 30-60 min to release residual stress.

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