Copper-aluminum composite wire crimping method and structure

Abstract

This invention discloses a method and structure for crimping copper-aluminum composite wires, relating to the field of power connection technology. The method, used for ultrasonic crimping of a wire core and a crimping terminal, includes: a pretreatment step: spraying a mixture containing conductive metal nanoparticles and a silane coupling agent onto one of the surfaces of the wire core and the inner hole of the crimping terminal, followed by drying; filling the other with conductive material; a pre-forming step: inserting the wire core into the inner hole of the crimping terminal, and then applying a first crimping pressure at a first frequency to the crimping area of ​​the wire core and the crimping terminal; a main crimping step: applying a second crimping pressure at a second frequency to the crimping area of ​​the wire core and the crimping terminal using a crimping device, for a second duration; and a stabilization step: applying a third crimping pressure at a third frequency to the crimping area of ​​the wire core and the crimping terminal using a crimping device. The technical solution provided by this invention aims to improve the connection quality of terminals and wires.

Description

Technical Field

[0001] This invention relates to the field of electrical connection technology, and in particular to a method and structure for crimping copper-aluminum composite conductors. Background Technology

[0002] With the development of domestic power technology, the demand for conductors is increasing daily, and is continuously evolving towards lightweight, high-efficiency, and sustainable designs. However, this also places diverse demands on conductor materials. For example, in applications with stringent reliability requirements, such as aerospace and new energy vehicles, traditional aluminum and copper conductors are no longer suitable. Therefore, copper-aluminum composite conductors have been proposed, with common types including copper-clad aluminum conductors and aluminum-clad copper conductors. As a conductive material with excellent conductivity and economic efficiency, copper-aluminum composite conductors have significant application value in the field of power transmission.

[0003] Traditional copper-aluminum composite cables are generally manufactured using processes such as copper plating on aluminum wire, roll bonding, or hydrostatic extrusion.

[0004] In existing technologies, ordinary ultrasonic crimping technology can solve basic connection problems. However, during ultrasonic crimping, there are complex effects of multiple physical processes such as high-frequency vibration energy transmission, rheological response of heterogeneous materials, and dynamic interface reaction. This can easily lead to uneven pressure distribution, abnormal growth of intermetallic compound layers (IMCs), formation of unbonded areas, and residual stress concentration, making it difficult to meet the current requirements for high-quality connections of copper-aluminum composite cables. Summary of the Invention

[0005] The main objective of this invention is to propose a method and structure for crimping copper-aluminum composite wires, which aims to improve the connection quality between terminals and wires.

[0006] To achieve the above objectives, the present invention proposes a method for ultrasonically crimping copper-aluminum composite wires, used for the wire core and crimping terminals. In one embodiment, the method includes the following steps: Pretreatment steps: Spray a mixture containing conductive metal nanoparticles and silane coupling agent onto one of the surfaces of the conductor core and the inner hole of the crimp terminal and dry it; fill the other with conductive material. Pre-forming step: Insert the conductor core into the inner hole of the crimp terminal, and then apply a first crimping pressure to the crimping part of the conductor core and the crimp terminal at a first frequency for a first time using a crimping device; Main crimping step: Apply a second crimping pressure to the crimping portion of the conductor core and the crimping terminal using a crimping device at a second frequency for a second duration; so that the conductor core is in contact with the inner wall of the crimping terminal; Stabilization step: Apply a third crimping pressure to the crimping portion of the conductor core and the crimping terminal using a crimping device at a third frequency for a third duration; Wherein, the second frequency is greater than the first frequency and the third frequency, and the second pressing pressure is greater than the first pressing pressure and the third pressing pressure.

[0007] In one embodiment, the pretreatment step, which involves spraying a mixture containing conductive metal nanoparticles and a silane coupling agent onto one of the surfaces of the conductor core and the inner bore of the crimp terminal and then drying it, further includes the following steps prior to the step of filling with conductive material: Remove the oxide layer from the surface of the conductor core and the inner wall of the crimp terminal.

[0008] In one embodiment, the mixture containing conductive metal nanoparticles and silane coupling agent comprises 7% to 12% conductive metal nanoparticles and 3% to 5% silane coupling agent by mass.

[0009] In one embodiment, the first frequency ranges from 20 kHz to 25 kHz, the first crimping pressure ranges from 5 MPa to 10 MPa, and the first time ranges from 25 min to 35 min; and / or, The second frequency ranges from 25kHz to 30kHz, the second crimping pressure ranges from 20MPa to 25MPa, and the second time ranges from 25min to 30min; and / or, The third frequency ranges from 15kHz to 20kHz, the third pressing pressure ranges from 8MPa to 12MPa, and the third time ranges from 15min to 25min.

[0010] In one embodiment, the conductive material includes copper-plated carbon fiber conductive silicone grease containing corrosion inhibitors or nickel-coated graphite fiber conductive silicone grease containing corrosion inhibitors; and / or, The pretreatment step includes: spraying a mixture containing conductive metal nanoparticles and silane coupling agent onto the surface of the conductor core and drying it, and filling the inner hole of the crimp terminal with conductive material.

[0011] In one embodiment, the copper-plated carbon fiber conductive silicone grease containing corrosion inhibitor is a copper-plated carbon fiber conductive silicone grease containing BTA benzotriazole corrosion inhibitor, wherein the amount of copper-plated carbon fiber added is 15% to 20%.

[0012] In one embodiment, the copper-aluminum composite wire crimping method further includes: Subsequent processing steps: Grind the surface of the crimped portion and install an insulating structure on the outside of the conductor core and the crimped terminal.

[0013] In one embodiment, after the preforming step, the copper-aluminum composite wire crimping method further includes a testing step, the testing step comprising: Test the contact resistance between the conductor core and the crimp terminal to determine whether the contact resistance value meets the requirements; If the contact resistance value meets the requirements, proceed to the main crimping step; otherwise, increase the amplitude of the crimping equipment and return to the preforming step.

[0014] The present invention also proposes a copper-aluminum composite wire crimping structure, which is obtained by the copper-aluminum composite wire crimping method described in any of the above claims, and in one embodiment includes: Copper-clad aluminum conductor, including the conductor core; A crimp terminal includes a crimping portion having an inner hole for crimping the conductor core; and... A connecting layer is disposed between the inner wall of the crimping portion and the conductor core, and the connecting layer includes a conductive material layer and a nanomaterial layer.

[0015] In one embodiment, the inner wall of the crimping portion is provided with a groove for crimping with the conductor core; and / or, The nanomaterial layer comprises ZnO nanoparticles and a silane coupling agent.

[0016] This technical solution employs a pretreatment step to enhance the bonding strength and conductivity between the conductor core and the crimp terminal during crimping. After drying, the silane coupling agent firmly anchors the conductive metal nanoparticles to the metal surface. The addition of the silane coupling agent and conductive metal nanoparticles helps fill crimp gaps and micro-cracks on the material surface after crimping, and improves the hydrophobicity of the material surface, thereby improving the overall electrical connection quality. The conductive material is used to fill the crimp gaps and improve the conductivity between the conductor core and the crimp terminal. The pre-forming step involves inserting the conductor core into the inner hole of the crimp terminal for crimping. The crimping equipment precisely controls the crimping frequency and pressure, ensuring a tight initial bond between the conductor core and the crimp terminal, laying a good foundation for the subsequent main crimping step and avoiding damage to the workpiece due to excessive single crimping pressure. The main crimping step is the crucial stage in the entire crimping process. Using a higher frequency and greater pressure than the pre-forming step, it ensures a tight fit between the conductor core and the inner wall of the crimp terminal. Simultaneously, it allows the silane coupling agent, conductive metal nanoparticles, and conductive material to fill the gaps and fully spread across the crimping surface, thus ensuring the stability and reliability of the electrical connection. The stabilization step, using a lower frequency and pressure than the main crimping step, further stabilizes the crimped area, helping to eliminate internal stresses in the conductor core and crimp terminal, and improving the long-term stability of the crimped structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 A schematic diagram illustrating the steps of an embodiment of the copper-aluminum composite wire crimping method provided by the present invention; Figure 2 A schematic diagram of the test steps in one embodiment of the copper-aluminum composite wire crimping method provided by the present invention; Figure 3 A schematic diagram of an embodiment of the copper-aluminum composite wire crimping structure provided by the present invention; Figure 4 for Figure 3 Schematic diagram of the structure of the medium pressure terminal Figure 5 for Figure 3 Schematic diagram of the structure of copper-clad aluminum conductor; Figure 6 for Figure 3 Schematic diagram of the middle trench; Figure 7 for Figure 3 A schematic diagram of the intermediate connecting layer.

[0019] Explanation of icon numbers: 1. Copper-clad aluminum conductor; 11. Conductor core; 2. Crimping terminal; 21. Inner hole; 22. Crimping part; 221. Groove; 3. Connecting layer; 31. Conductive material layer; 32. Nanomaterial layer.

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, and back), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0023] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0024] With the development of domestic power technology, the demand for conductors is increasing daily, and is continuously evolving towards lightweight, high-efficiency, and sustainable designs. However, this also places diverse demands on conductor materials. For example, in applications with stringent reliability requirements, such as aerospace and new energy vehicles, traditional aluminum and copper conductors are no longer suitable. Therefore, copper-aluminum composite conductors have been proposed, with common types including copper-clad aluminum conductors and aluminum-clad copper conductors. As a conductive material with excellent conductivity and economic efficiency, copper-aluminum composite conductors have significant application value in the field of power transmission.

[0025] Traditional copper-aluminum composite cables are generally manufactured using processes such as copper plating on aluminum wire, roll bonding, or hydrostatic extrusion.

[0026] In existing technologies, ordinary ultrasonic crimping technology can solve basic connection problems. However, during ultrasonic crimping, there are complex effects of multiple physical processes such as high-frequency vibration energy transmission, rheological response of heterogeneous materials, and dynamic interface reaction. This can easily lead to uneven pressure distribution, abnormal growth of intermetallic compound layers (IMCs), formation of unbonded areas, and residual stress concentration, making it difficult to meet the current requirements for high-quality connections of copper-aluminum composite cables.

[0027] Please see Figure 1 In one embodiment of the present invention, a method for ultrasonically crimping copper-aluminum composite wires, used for ultrasonic crimping of wire core 11 and crimping terminal 2, includes the following steps: S100: Pretreatment step: Spray a mixture containing conductive metal nanoparticles and silane coupling agent onto one of the surfaces of the conductor core 11 and the inner hole 21 of the crimp terminal 2 and dry it, and fill the other with conductive material. S200: Pre-forming step: Insert the conductor core 11 into the inner hole 21 of the crimp terminal 2, and then apply a first crimping pressure to the crimping part of the conductor core 11 and the crimp terminal 2 at a first frequency for a first time using a crimping device; S300: Main crimping step: Apply a second crimping pressure to the crimping portion of the conductor core 11 and the crimping terminal 2 at a second frequency using a crimping device, and continue for a second time; so that the conductor core 11 is in contact with the inner wall of the crimping terminal 2; S400: Stabilization step: Apply a third crimping pressure to the crimping portion of the conductor core 11 and the crimping terminal 2 at a third frequency using a crimping device, and continue for a third time; Wherein, the second frequency is greater than the first frequency and the third frequency, and the second pressing pressure is greater than the first pressing pressure and the third pressing pressure.

[0028] This technical solution employs a pretreatment step to enhance the bonding strength and conductivity between the conductor core 11 and the crimp terminal 2 during crimping. After drying, the silane coupling agent firmly anchors the conductive metal nanoparticles to the metal surface. The addition of the silane coupling agent and conductive metal nanoparticles helps fill the crimp gaps and micro-cracks on the material surface after crimping, and improves the hydrophobicity of the material surface, thereby improving the overall electrical connection quality. The conductive material is used to fill the crimp gaps and improve the conductivity between the conductor core 11 and the crimp terminal 2. The pre-forming step involves inserting the conductor core 11 into the inner hole 21 of the crimp terminal 2 for crimping. The crimping equipment precisely controls the crimping frequency and pressure, ensuring a tight initial bond between the conductor core 11 and the crimp terminal 2, laying a good foundation for the subsequent main crimping step and avoiding damage to the workpiece due to excessive single crimping pressure. The main crimping step is the key step in the entire crimping process. Using a higher frequency and greater pressure than the pre-forming step, it ensures a tight fit between the conductor core 11 and the inner wall of the crimp terminal 2. Simultaneously, it allows the silane coupling agent, conductive metal nanoparticles, and conductive material to fill the gaps and spread fully on the crimping surface, thus ensuring the stability and reliability of the electrical connection. The stabilization step, using a lower frequency and pressure than the main crimping step, further stabilizes the crimped area, helping to eliminate internal stresses in the conductor core 11 and the crimp terminal 2, and improving the long-term stability of the crimped structure.

[0029] In the specific implementation process, the specific components and amounts of the mixture of conductive metal nanoparticles and silane coupling agent are not limited. For example, it may also include ethanol, conductive fibers, or other conductive metal particles. The total content of conductive metal nanoparticles and silane coupling agent is 10% or 17%. The specific material of the conductive material is not limited; for example, it may include conductive silicone grease or conductive fibers. The specific shape and material of the crimp terminal 2 are not limited; for example, it may be an aluminum alloy DT terminal or a copper ring terminal. The relationship between the first frequency and the third frequency is not limited; they can be the same or the first frequency can be lower than the third frequency. The relationship between the first crimping pressure and the third crimping pressure is not limited; they can be the same or the first crimping pressure can be greater than the third crimping pressure. The inner hole 21 of the crimp terminal 2 can be formed by a tube or by two connecting pieces. An ultrasonic terminal crimping device is used.

[0030] In one embodiment, the pretreatment step, which involves spraying a mixture containing conductive metal nanoparticles and a silane coupling agent onto one of the surfaces of the conductor core 11 and the inner hole 21 of the crimp terminal 2 and drying it, further includes the following steps before another step of filling with conductive material: S60: Remove the oxide layer from the surface of the conductor core 11 and the inner wall of the crimp terminal 2.

[0031] Removing the oxide layer is an important step in the pretreatment process. It helps to eliminate oxides on the surfaces of the conductor core 11 and the crimp terminal 2, improves the conductivity and bonding strength between them, facilitates the electrical connection between the conductor core 11 and the crimp terminal 2 by conductive metal nanoparticles, silane coupling agents and conductive materials, and reduces the crimping resistance.

[0032] In practice, the oxide layer can be removed by grinding or by using a plasma cleaner.

[0033] In one embodiment, the mixture containing conductive metal nanoparticles and silane coupling agent comprises 7% to 12% ZnO nanoparticles and 3% to 5% silane coupling agent by mass.

[0034] The proportions of each component in the mixture have a significant impact on the crimping effect. A proper ratio of ZnO nanoparticles and silane coupling agent can fully leverage the advantages of both, improving the conductivity and bonding strength of the crimped joint.

[0035] In practice, the specific mass ratio of ZnO nanoparticles is not limited, for example, it can be 7%, 10%, or 12%, and the specific mass ratio of silane coupling agent is not limited, for example, it can be 3%, 3.8%, or 5%. Within this ratio range, the ZnO nanoparticles reach the desired percolation concentration, forming a dense conductive network. Simultaneously, the number of functional groups provided by the 3% to 5% silane coupling agent is highly matched to the specific surface area of ​​the ZnO nanoparticles, ensuring strong covalent bonding at the interface. If this range is exceeded, excessive inorganic particles will cause agglomeration leading to cracking, while excessive coupling agent will increase tunnel resistance due to the thickness effect, thus disrupting the balance between conductivity and bonding strength.

[0036] In one embodiment, the first frequency ranges from 20kHz to 25kHz, the first crimping pressure ranges from 5MPa to 10MPa, and the first time ranges from 25min to 35min. In another embodiment, the second frequency ranges from 25kHz to 30kHz, the second crimping pressure ranges from 20MPa to 25MPa, and the second time ranges from 25min to 30min. In yet another embodiment, the third frequency ranges from 15kHz to 20kHz, the third crimping pressure ranges from 8MPa to 12MPa, and the third time ranges from 15min to 25min. Any one of these three embodiments may be used, or two or three may be used simultaneously.

[0037] The appropriate range of frequency, pressure, and time values ​​in each step is crucial for ensuring the crimping effect. By precisely controlling these parameters, the optimal bonding state between the conductor core 11 and the crimping terminal 2 can be achieved. The second frequency is greater than the first and third frequencies, and the second crimping pressure is greater than the first and third crimping pressures. This pre-forming crimping step avoids excessive deformation during a single crimping operation, which could damage the workpiece.

[0038] In practice, the frequency and pressure can be adjusted as needed. For example, when the second frequency is 25kHz, the first and third frequencies are 20kHz, the second crimping pressure is 20MPa, and the first and third crimping pressures are 8MPa; or, when the second frequency is 30kHz, the first and third frequencies are 20kHz, the second crimping pressure is 25MPa, and the first and third crimping pressures are 10MPa. The selection of these parameter ranges is based on the yield strength and ultrasonic energy absorption rate of the cable and terminal materials. The stepped pressure and frequency design ensures that interface impurities are removed through low-to-medium energy vibration during the preforming stage, that peak pressure (20MPa to 25MPa) guides the metal plastic fluid to fill the gaps during the main crimping stage, and that sufficient atomic diffusion is ensured through time control at the end stage. This range avoids the material's resonant damage zone, achieving optimization of conductivity and bonding strength.

[0039] The present invention has the following advantages over the prior art: (1) Through three gradient crimping steps, the pre-forming crimping achieves initial positioning and avoids initial damage to the copper foil; the main crimping step promotes the plastic flow of the material, so that the conductor core and the inner wall of the crimping terminal 2 are tightly attached to form a good electrical and mechanical connection and a better fit; the stabilization step further consolidates the metal of the crimping part, eliminates internal stress, and seals microcracks, which can improve the connection stability and reliability. (2) Through the nanocomposite interface protective layer ZnO nanoparticles + silane coupling agent, by controlling its content and ultrasonic crimping frequency and pressure, insulation areas of different thicknesses are formed to protect the crimping area and meet different crimping requirements; Ultrasonic waves are sound waves with frequencies higher than 2 Hz; The theoretical model of ultrasonic welding: Energy input formula: E=P·t·f reflects the synergy of pressure, time and frequency; By breaking the interface oxide layer through high-frequency friction, the problem of poor contact caused by easy oxidation of materials such as aluminum alloys is solved; Secondly, by utilizing the acoustic softening effect of ultrasonic waves, the metal is guided to generate micro-plastic flow under low pressure, filling the gap and coating ZnO nanoparticles; Finally, by inducing atomic diffusion through vibration, the wire core and the terminal are integrated, thereby obtaining extremely low contact resistance and extremely high bonding strength; (3) Through the crimping area where the anti-corrosion crimping terminal 2 structure is located, the ultrasonic vibration direction has an angle with the crimping force direction, for example, an angle of 35° to 45°, so that the nanocomposite interface protective layer can better fit with the conductor core and the inner wall of the crimping terminal 2; (4) Through the copper-aluminum composite wire crimping method and the copper-aluminum composite wire crimping structure design, copper-aluminum composite wires with higher copper foil integrity rate, better overall performance such as durability and corrosion resistance can be obtained.

[0040] During crimping, the crimping force and the ultrasonic crimping direction form an angle, achieving a dual effect of shearing and extrusion; the first crimping pressure, the second crimping pressure, and the third crimping pressure refer to the compressive stress per unit contact area of ​​the wire / terminal applied by the crimping die; Compared to conventional one-time crimping of wire terminals, the main crimping stage in this application, with its long duration and high frequency, can fully activate the diffusion of copper and aluminum atoms, forming a thin and uniform intermetallic compound layer. This avoids excessive growth of the brittle CuAl2 phase and ensures sufficient plastic deformation of the metal, resulting in a gapless fit between the conductor core 11 and the inner wall of the crimp terminal 2. Furthermore, the long-term ultrasonic vibration allows the silane coupling agent to fully exert its "molecular bridge" effect, firmly anchoring the conductive metal nanoparticles to the metal surface and filling microcracks to form a dense hydrophobic layer. Moreover, the conductive material uniformly fills the gap between the terminal groove 221 and the conductor core, improving conductivity and forming a corrosion barrier to prevent electrochemical corrosion caused by direct contact between copper and aluminum.

[0041] In one embodiment, the conductive material includes copper-plated carbon fiber conductive silicone grease containing corrosion inhibitors or nickel-coated graphite fiber conductive silicone grease containing corrosion inhibitors; in another embodiment, the pretreatment step includes: spraying a mixture containing conductive metal nanoparticles and a silane coupling agent onto the surface of the conductor core 11 and drying it, and filling the inner hole 21 of the crimp terminal 2 with conductive material. The above two embodiments can be performed selectively or simultaneously.

[0042] The choice of conductive materials has a significant impact on the conductivity of the crimped joint. Nickel and corrosion inhibitors can effectively suppress the electrochemical corrosion of the copper-aluminum interface, while graphite fiber and copper-plated carbon fiber conductive grease can significantly improve the continuity and stability of the conductive path. Nickel-coated graphite fiber, with its excellent conductivity of nickel layer and the flexibility of graphite fiber, can fill the tiny gaps between the wire core and the terminal during the crimping process as the metal deforms, forming multi-point conductive contact. Copper-plated carbon fiber conductive grease containing corrosion inhibitors forms a uniformly covered conductive film layer on the metal surface through the fluidity of the grease. The corrosion inhibitor component is slowly released, continuously preventing the intrusion of corrosive media. At the same time, the copper-plated carbon fiber acts as a reinforcing phase, further reducing the contact resistance of the crimped joint. The surface of the wire core 11 is sprayed with a mixture containing conductive metal nanoparticles and silane coupling agent and dried. The inner hole 21 of the crimped terminal 2 is then filled with conductive material, making the operation convenient.

[0043] In practice, nickel-coated graphite fiber conductive silicone grease and copper-plated carbon fiber conductive silicone grease can be selected as needed. Copper-plated carbon fiber conductive silicone grease containing corrosion inhibitors offers better cost-effectiveness, but it will lead to an increase in resistivity. Multiple conductive materials can also be used in combination during implementation.

[0044] In other embodiments, the conductive material may also include conductive silicone grease composed of copper-plated carbon fibers containing corrosion inhibitors and nickel-coated graphite fibers.

[0045] In a further embodiment, the copper-plated carbon fiber conductive silicone grease containing corrosion inhibitor is a copper-plated carbon fiber conductive silicone grease containing BTA benzotriazole corrosion inhibitor, wherein the amount of copper-plated carbon fiber added is 15% to 20%.

[0046] BTA benzotriazole corrosion inhibitor effectively improves the corrosion resistance of conductive silicone grease and extends the service life of crimped parts. The high copper-plated carbon fiber content ensures the conductivity of crimped parts.

[0047] In the specific implementation process, the copper-plated carbon fiber conductive silicone grease containing corrosion inhibitor is a copper-plated carbon fiber conductive silicone grease containing 2% BTA benzotriazole corrosion inhibitor by mass. The copper-plated carbon fiber has a diameter of 10 μm and an aspect ratio of 70 to 80. The combination of copper-plated carbon fiber and conductive silicone grease fully utilizes the functions of filling the crimping gap and conducting electricity. The selection of the above parameters is the optimal solution determined through orthogonal experiments: 15% to 20% copper-plated carbon fiber constructs the optimal conductive network while ensuring the fluidity of the slurry; the fiber with an aspect ratio of 70 to 80 improves the conductivity through geometric topological advantages; and the 2% BTA achieves saturated adsorption at the interface. The three factors work synergistically to ensure the long-term service stability of the copper-aluminum crimping part under high temperature and high humidity environments.

[0048] In one embodiment, the copper-aluminum composite wire crimping method further includes: S500: Subsequent processing steps: Grind the surface of the crimped part and provide an insulating structure on the outside of the conductor core 11 and the crimped terminal 2.

[0049] Subsequent processing steps are crucial for ensuring the quality and safety of the crimped joint. By grinding the surface and installing insulation, potential electrical safety hazards can be eliminated, and the overall performance of the crimped joint can be improved.

[0050] In practical implementation, insulating tape or insulating colloid can be used as an insulation structure.

[0051] Please see Figure 2 In one embodiment, after the preforming step, the copper-aluminum composite wire crimping method further includes a testing step, the testing step comprising: S260: Test the contact resistance between the conductor core 11 and the crimp terminal 2, and determine whether the contact resistance value meets the requirements; S261: If the contact resistance value meets the requirements, proceed to the main crimping step; otherwise, increase the amplitude of the crimping equipment and return to the preforming step.

[0052] Testing is a crucial step in ensuring crimping quality. By testing the contact resistance after the pre-forming step, it's possible to promptly determine if the conductivity of the crimped area meets the standards. If it doesn't, because the crimped structure hasn't undergone the shaping process with higher frequencies and pressures in the main crimping step, the workpiece's deformation is relatively small. In this case, the pre-forming step can be repeated by adjusting the amplitude of the crimping equipment until satisfactory results are achieved.

[0053] In the specific implementation process, the contact resistance value can be set as needed, for example, it can be less than 30μΩ or less than 50μΩ, and the amplitude adjustment degree of the crimping equipment can be set as needed, for example, the amplitude of the crimping equipment can be increased by 3% or 6%.

[0054] In one embodiment, a method for crimping copper-aluminum composite wires includes the following steps.

[0055] (1) Pretreatment steps: First, use a plasma cleaner to remove the oxide layer on the surface of the copper-clad aluminum conductor core 11 and the inner hole 21 wall of the crimp terminal 2 to expose the metallic luster. Then wipe it with a clean cloth and spray the prepared mixture containing 7% to 12% ZnO nanoparticles and 3% to 5% silane coupling agent (the remainder is ethanol solvent) onto the surface. Then dry it at 80°C to 100°C for 2 to 3 minutes. Fill the groove 221 of the crimp terminal 2 with a thickness of 50μm to 80μm of copper-plated carbon fiber conductive silicone grease containing 2% BTA benzotriazole corrosion inhibitor (diameter 10μm, aspect ratio 70 to 80, copper-plated carbon fiber addition amount 15% to 20%). Alternatively, nickel-clad graphite fiber with a higher cost-performance ratio can be used, which is about 30% cheaper, but has a higher resistivity.

[0056] (2) Pre-forming step: The processed copper-clad aluminum conductor core 11 is slowly and accurately inserted into the inner hole 21 of the crimp terminal 2, and the gap between the conductor core and the hole wall of the crimp terminal 2 is uniform. Then the crimping equipment is started to apply pressure to the conductor and the crimp terminal 2. The pressure setting value of the pre-forming step is 5MPa to 10MPa, and the frequency is set to 20kHz to 25kHz. The time is usually 25min to 35min, preferably about 30min.

[0057] (3) Main crimping step: Increase the pressure of the crimping equipment to 20MPa to 25MPa, adjust the frequency to 25kHz to 30kHz, and continue crimping for 25min to 30min to make the conductor core 11 fit tightly against the inner wall of the crimping terminal 2, and the metal undergoes large plastic deformation to form a good electrical and mechanical connection.

[0058] (4) Stabilization step: Reduce the pressure of the crimping equipment to 8MPa to 12MPa, adjust the frequency to 15kHz to 20kHz, and apply pressure to the crimping part for 15min to 25min, preferably about 20min, so that the metal of the crimping part can be further consolidated and bonded, eliminate internal stress, and improve the stability and reliability of the connection.

[0059] (5) Subsequent processing steps: Use sandpaper to file or grind away the sharp edges and burrs on the edge of the crimped part to make the surface smooth. Wrap the crimped part and insulation layer with insulating tape to restore the overall insulation performance of the wire.

[0060] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0061] Example 1 This embodiment provides a method for crimping copper-aluminum composite wires using ultrasonic crimping of the wire core and crimping terminals, comprising the following steps: (1) Pretreatment steps: The copper-clad aluminum wire ends were treated with a plasma cleaner (power of 200W, argon treatment) for 30s, and then a mixture containing 7% ZnO nanoparticles and 3% silane coupling agent by mass was sprayed on the surface. After that, it was dried at 100°C for 2 minutes. The inner wall and groove 221 of the crimp terminal 2 were filled with copper-plated carbon fiber conductive silicone grease containing 2% BTA benzotriazole corrosion inhibitor with a thickness of 50μm. The amount of copper-plated carbon fiber added was 15%, wherein the copper-plated carbon fiber had a diameter of 10μm and an aspect ratio of 70 to 80.

[0062] (2) Three-step controlled crimping: First, a pre-forming step is performed, in which the prepared copper-clad aluminum conductor core is slowly and accurately inserted into the inner hole 21 of the crimping terminal 2, and the gap between the conductor core and the hole wall of the crimping terminal 2 is ensured to be uniform. Then, the crimping equipment is started, the pressure is set to 10MPa, and the frequency is set to 25kHz. Pressure is applied to the conductor and the crimping terminal 2 for 35 minutes. Then, the main crimping step is performed, in which the pressure of the crimping equipment is increased to 25MPa, the frequency is adjusted to 30kHz, and the crimping is continued for 30 minutes, so that the conductor core 11 and the inner wall of the crimping terminal 2 are tightly attached to form a good electrical and mechanical connection. Finally, a stabilization step is performed, in which the pressure is reduced to 12MPa, the frequency is adjusted to 20kHz, and the crimping part is continuously pressured for 25 minutes, so that the metal of the crimping part is further consolidated and bonded, internal stress is eliminated, and connection stability and reliability are improved. During the three-step controlled crimping process, the ultrasonic vibration direction is at a 45° angle to the crimping force direction.

[0063] (3) Subsequent processing steps: Use sandpaper to sand away the edges and burrs of the crimped part to make the surface smooth, and wrap the crimped part and insulation layer with insulating tape to restore the overall insulation performance of the wire.

[0064] (4) Performance testing: Metallographic examination revealed that the copper foil integrity rate was as high as 99.2%; the initial contact resistance of the crimp joint was measured to be 19.5 μΩ using the four-wire method; durability testing showed that after 1000 insertion and removal cycles, the average increase in resistance at the crimp joint of the copper-clad aluminum conductor 1 end was 4.89%. After 1000 hours of salt spray testing, there was basically no corrosion, and after 500 temperature cycles (from 55℃ to 125℃), the resistance change rate was 2.11%.

[0065] The differences between Examples 2 to 12 and Comparative Examples 1 and 2 and Example 1 are shown in Table 1.

[0066] Table 1 Parameter settings for Examples 2 to 12 and Comparative Examples 1 to 2

[0067] The test results are shown in Table 2.

[0068] Table 2 Performance characterization of copper-aluminum composite conductors in Examples 2 to 12 and Comparative Examples 1 to 2

[0069] Through comparative experiments using the above examples, it can be found that after testing, the copper foil integrity rate obtained by the three-step controlled crimping in Example 1 reached as high as 99.2%; the initial contact resistance at the crimped joint was 19.5 μΩ; the average resistance increase at the crimped joint of the copper-clad aluminum conductor 1 end in the durability test was 4.89%; after 1000 hours of salt spray testing, there was basically no corrosion; and the resistance change rate after temperature cycling was 2.11%. Its performance is obviously better than that of the conductors prepared by the direct forming and two-step forming controlled processes of Comparative Examples 1 and 2. This proves that the three-step controlled crimping has excellent effects in reducing the abnormal growth of brittle intermetallic compound CuAl2 and promoting the formation of ductile Cu9Al4 phase, resulting in the best conductivity of copper-aluminum conductors. This allows the processed conductors to break through the limitations of traditional processes and obtain copper-aluminum composite conductors with better comprehensive performance.

[0070] This invention also proposes a copper-aluminum composite wire crimping structure, which is obtained by the above-described copper-aluminum composite wire crimping method. The manufacturing method of the copper-aluminum composite wire crimping structure refers to the above embodiments. Since this copper-aluminum composite wire crimping structure adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0071] Please see Figures 3 to 5 and Figure 7 A copper-aluminum composite wire crimping structure, in one embodiment, includes: a copper-clad aluminum wire 1, a crimping terminal 2, and a connecting layer 3.

[0072] The copper-clad aluminum conductor 1 includes a conductor core 11; the crimp terminal 2 includes a crimping part 22, which has an inner hole 21 for crimping the conductor core 11; the connecting layer 3 is disposed between the inner wall of the crimping part 22 and the conductor core 11, and the connecting layer 3 includes a conductive material layer 31 and a nanomaterial layer 32.

[0073] During the crimping process, the conductive material layer 31 effectively reduces the contact resistance between the inner wall of the crimping part 22's hole 21 and the conductor core 11, improving overall conductivity and ensuring the stability and efficiency of current transmission. Meanwhile, the nanomaterial layer 32, with its unique nanoscale structure, not only enhances the mechanical strength of the connection interface and improves the tensile and vibration resistance of the crimped structure, but also forms a protective film at the interface, effectively inhibiting oxidation and corrosion, thereby extending the service life of the copper-aluminum composite conductor crimped structure.

[0074] In specific implementation, the conductor core 11 is a copper-clad aluminum conductor core 11, the conductive material layer 31 may include graphite fibers or conductive silicone grease, and the nanomaterial layer 32 may include conductive metal nanoparticles. The conductive metal nanoparticles may be selected from highly conductive metal materials such as pure copper, silver, or their alloys, and are formed on the inner wall of the crimping part 22 or the surface of the conductor core 11 by electroplating, sputtering, or coating. The copper-aluminum composite conductor crimping structure described in this embodiment can be applied to the three-phase high-voltage wiring harness of the drive motor of new energy vehicles, the high-voltage output main line of the power battery pack, the vehicle AC charging system, the vehicle low-voltage power supply system, and the internal connection of the battery pack.

[0075] Please see Figure 6 In one embodiment, the inner wall of the crimping portion 22 is provided with a groove 221 for crimping with the conductor core 11; in another embodiment, the nanomaterial layer 32 includes ZnO nanoparticles and a silane coupling agent. Either of these two embodiments may be used, or both may be used simultaneously.

[0076] During crimping, the conductor core 11 is pressed into the groove 221, forming a stable interlocking structure, which helps to improve the tensile strength and electrical connection stability of the crimped part. ZnO nanoparticles and silane coupling agents can improve the conductivity and bonding strength of the crimped part.

[0077] In the specific implementation process, the specific shape and number of the trench 221 are not limited. For example, it can be a spiral or multiple parallel annular lines.

[0078] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method of crimping a copper-aluminum composite wire for ultrasonic crimping of a wire core and a crimping terminal, characterized by, Includes the following steps: Pretreatment steps: Spray a mixture containing conductive metal nanoparticles and silane coupling agent onto one of the surfaces of the conductor core and the inner hole of the crimp terminal and dry it; fill the other with conductive material. Pre-forming step: Insert the conductor core into the inner hole of the crimp terminal, and then apply a first crimping pressure to the crimping part of the conductor core and the crimp terminal at a first frequency for a first time using a crimping device; Main crimping step: Apply a second crimping pressure to the crimping portion of the conductor core and the crimping terminal using a crimping device at a second frequency for a second duration; So that the conductor core fits against the inner wall of the crimp terminal; Stabilization step: Apply a third crimping pressure to the crimping portion of the conductor core and the crimping terminal using a crimping device at a third frequency for a third duration; Wherein, the second frequency is greater than the first frequency and the third frequency, and the second pressing pressure is greater than the first pressing pressure and the third pressing pressure.

2. The copper-aluminum composite wire crimping method according to claim 1, wherein The pretreatment step further includes spraying a mixture containing conductive metal nanoparticles and a silane coupling agent onto one of the surfaces of the conductor core and the inner holes of the crimp terminal, followed by drying. Prior to the other step of filling with conductive material, the pretreatment step further includes: Remove the oxide layer from the surface of the conductor core and the inner wall of the crimp terminal.

3. The copper-aluminum composite wire crimping method according to claim 1, wherein The mixture containing conductive metal nanoparticles and silane coupling agent comprises 7% to 12% conductive metal nanoparticles and 3% to 5% silane coupling agent by mass.

4. The copper-aluminum composite wire crimping method according to claim 1, wherein The first frequency ranges from 20kHz to 25kHz, the first crimping pressure ranges from 5MPa to 10MPa, and the first time ranges from 25min to 35min; and / or, The second frequency ranges from 25kHz to 30kHz, the second crimping pressure ranges from 20MPa to 25MPa, and the second time ranges from 25min to 30min; and / or, The third frequency ranges from 15kHz to 20kHz, the third pressing pressure ranges from 8MPa to 12MPa, and the third time ranges from 15min to 25min.

5. The copper-aluminum composite wire crimping method according to claim 1, wherein The conductive material includes copper-plated carbon fiber conductive silicone grease containing corrosion inhibitors or nickel-coated graphite fiber conductive silicone grease containing corrosion inhibitors. And / or, The pretreatment step includes: spraying a mixture containing conductive metal nanoparticles and silane coupling agent onto the surface of the conductor core and drying it, and filling the inner hole of the crimp terminal with conductive material.

6. The copper-aluminum composite wire crimping method according to claim 5, wherein The copper-plated carbon fiber conductive silicone grease containing corrosion inhibitor is a copper-plated carbon fiber conductive silicone grease with a thickness of 50μm to 80μm containing 2% BTA benzotriazole corrosion inhibitor by total mass, wherein the amount of copper-plated carbon fiber added is 15% to 20%.

7. The copper-aluminum composite wire crimping method according to claim 1, wherein The copper-aluminum composite wire crimping method further includes: Subsequent processing steps: Grind the surface of the crimped portion and install an insulating structure on the outside of the conductor core and the crimped terminal.

8. The method for crimping copper-aluminum composite conductors as described in claim 1, characterized in that, Following the preforming step, the copper-aluminum composite wire crimping method further includes a testing step, which includes: Test the contact resistance between the conductor core and the crimp terminal to determine whether the contact resistance value meets the requirements; If the contact resistance value meets the requirements, proceed to the main crimping step; otherwise, increase the amplitude of the crimping equipment and return to the preforming step.

9. A copper-aluminum composite wire crimping structure, manufactured by the copper-aluminum composite wire crimping method as described in any one of claims 1 to 8, characterized in that... include: Copper-clad aluminum conductor, including the conductor core; A crimping terminal includes a crimping portion, wherein the crimping portion is provided with an inner hole for crimping the conductor core; as well as, A connecting layer is disposed between the inner wall of the crimping portion and the conductor core, and the connecting layer includes a conductive material layer and a nanomaterial layer.

10. The copper-aluminum composite wire crimping structure as described in claim 9, characterized in that, The inner wall of the crimping portion is provided with grooves for crimping with the conductor core; and / or, The nanomaterial layer comprises ZnO nanoparticles and a silane coupling agent.

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