A copper-aluminum composite coating transition wire clamp and a preparation process thereof

Abstract

The application discloses a copper-aluminum composite coating transition wire clamp and a preparation process thereof, and mainly relates to the technical field of power connection hardware preparation. The copper-aluminum composite coating transition wire clamp comprises a copper base material and an aluminum base material, and a TiN+Ag composite coating deposited by magnetron sputtering is arranged between the combined surfaces of the copper base material and the aluminum base material; a copper-silver-aluminum metallurgical diffusion layer is formed by hot pressing to realize integrated connection; and a silicone rubber sealing layer is coated on the joint edge to make the protection level reach IP65. The copper-aluminum composite coating transition wire clamp has the beneficial effects that the copper-aluminum primary cell reaction can be inhibited, and the connection reliability and weather resistance can be improved.

Description

Technical Field

[0001] This invention relates to the field of electrical connection hardware manufacturing technology, specifically a copper-aluminum composite coated transition clamp and its manufacturing process. Background Technology

[0002] Copper-aluminum transition connections are widely used in power systems. Traditional techniques employ brazing or explosive welding to achieve these connections. The brazing process requires the use of flux to remove the oxide film from the aluminum surface, forming a bond at the connection interface. The intermetallic compound layer is brittle and prone to cracking under long-term thermal cycling and vibration conditions, which leads to a sharp increase in contact resistance and causes overheating and burn-out.

[0003] While explosive welding can achieve metallurgical bonding, it is limited by a narrow process window, difficulty in precisely controlling interface waviness, and special requirements for the operating environment, making it difficult to implement on a large scale in power distribution network sites or general factory conditions. Furthermore, in existing copper-aluminum transition components, the connection interface is exposed to the atmosphere. There is a potential difference of approximately 2V between copper and aluminum. When moisture or salt spray penetrates the interface, the aluminum side acts as the anode, accelerating corrosion and generating loose alumina and aluminum hydroxide corrosion products. This further exacerbates the increase in contact resistance and temperature rise, creating a vicious cycle and severely shortening the maintenance cycle.

[0004] Therefore, there is an urgent need for a copper-aluminum transition connection solution that can balance interface bonding strength and long-term environmental protection to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a copper-aluminum composite coated transition clamp and its preparation process, which can suppress the copper-aluminum galvanic cell reaction and improve connection reliability and weather resistance.

[0006] To achieve the above objectives, the present invention employs the following technical solution: On one hand, the present invention provides a manufacturing process for a copper-aluminum composite coated transition clamp, comprising the following steps: Step S1: Pre-treat the surfaces of the copper and aluminum substrates to be in contact, so that their surface roughness Ra reaches 0.08-0.15μm; Step S2: Using magnetron sputtering, in a mixed atmosphere of argon and nitrogen, a titanium target is used as the sputtering source to deposit a TiN transition layer on the contact surface of the copper substrate. Then, an Ag layer is sputtered to form a TiN+Ag composite coating with a total thickness of 1.5-3 μm. Step S3: The copper substrate processed in step S2 and the pre-treated aluminum substrate are stacked and assembled with a composite coating as the intermediate layer, and then placed into a hot press mold. Step S4: Perform hot pressing process, heat the mold to 180-220℃, apply directional pressure of 80-100MPa to the stacked parts, and hold the pressure at this temperature and pressure for 15-30 minutes to allow atomic diffusion to occur at the interface of the copper substrate, composite coating and aluminum substrate to form a metallurgical bonding layer. Step S5: After hot pressing, the obtained wire clamp blank is cooled to room temperature. A silicone rubber sealing layer is applied to the junction edge area between the composite coating and the substrate so that the sealing layer completely covers the junction edge. After curing, the protection level of the entire bonding area reaches IP65.

[0007] Preferably, the magnetron sputtering process in step S2 specifically includes: The copper substrate to be processed is placed in the vacuum chamber of the magnetron sputtering equipment, and the vacuum level is evacuated to a background vacuum level better than [missing value]. Pa, then a mixture of high-purity argon and nitrogen is introduced as the working gas, wherein the volume flow ratio of argon to nitrogen is [value missing]. to Adjust the working air pressure to 0.5-0.8 Pa; Turn on the titanium target power supply and use DC pulse magnetron sputtering mode with a sputtering power density of 4-6 W / cm² and a bias voltage of -80 to -120V. Deposit for 15-25 minutes to form a TiN transition layer with a thickness of 0.8-1.5μm on the copper substrate surface. The TiN layer has a columnar crystal structure and its nanoindentation hardness is greater than or equal to 20 GPa. Nitrogen gas inlet was shut off, argon atmosphere was maintained, silver target was switched and power was turned on, DC magnetron sputtering mode was adopted, sputtering power density was 1-3 W / cm², bias voltage was set to -40 to -60V, deposition time was 5-10 minutes, and an Ag layer with a thickness of 0.7-1.5 μm was deposited on the TiN transition layer to form a composite coating composed of TiN layer and Ag layer. The Ag layer grows along the grain boundary gaps of columnar crystals of TiN layer to form a mechanical interlocking structure.

[0008] Preferably, after completing the magnetron sputtering process in step S2, a pure Ag transition layer with a thickness of 0.3-0.5 μm is deposited on the contact surface of the aluminum substrate using the same magnetron sputtering process.

[0009] Preferably, the effective bonding area of ​​the metallurgical bonding layer formed by the hot pressing process in step S4 is not less than 98% of the total area of ​​the surfaces to be contacted, and the room temperature shear strength of the bonding interface is greater than 85 MPa.

[0010] Preferably, the coating area of ​​the silicone rubber sealing layer in step S5 includes an annular sealing groove with a depth of 0.3-0.5 mm and a width of 1-2 mm, pre-processed at the edge of the bonding line between the copper substrate and the aluminum substrate. The silicone rubber completely fills the sealing groove and protrudes 0.5-1 mm above the surface of the substrate, forming a double-part sealing structure.

[0011] On the other hand, the present invention also provides a copper-aluminum composite coating transition clamp prepared according to the above-described copper-aluminum composite coating transition clamp manufacturing process, comprising: A copper substrate and an aluminum substrate, wherein the copper substrate has a first bonding plane and the aluminum substrate has a second bonding plane; A transition connection layer is located between the first bonding plane and the second bonding plane. The transition connection layer is composed of a TiN+Ag composite coating and a copper-silver-aluminum metallurgical diffusion layer formed by hot pressing. The TiN+Ag composite coating includes a TiN layer that is metallurgically bonded to the copper substrate and an Ag layer that forms a mechanical interlocking structure with the TiN layer. The copper-silver-aluminum metallurgical diffusion layer is formed in situ through atomic interdiffusion between the Ag layer and the substrates on both sides, so that the copper substrate and the aluminum substrate achieve an integrated metallurgical connection. The sealed encapsulation structure includes a silicone rubber sealing layer that completely covers all the junction edges of the transition connection layer, the copper substrate, and the aluminum substrate, thus isolating the connection area from the external environment.

[0012] Preferably, the total thickness of the TiN+Ag composite coating The following relationship must be satisfied: ; in: The value represents the thickness of the TiN layer, in μm, and ranges from 0.8 to 1.5. This represents the thickness of the Ag layer, in μm, ranging from 0.7 to 1.5. This is the thickness weighting coefficient for the TiN layer, with a value of 1.0; This is the thickness weighting coefficient for the Ag layer, with a value ranging from 0.8 to 1.2. and The value range is limited to 1.5-3μm.

[0013] Preferably, the overall contact resistance of the clamp is less than or equal to 5 μΩ, and in the neutral salt spray test, the continuous test time is greater than or equal to 1000 h, and no red rust caused by substrate corrosion appears in the tested area.

[0014] Preferably, the copper substrate has a first terminal for connecting copper wires at the end away from the first bonding plane, and the aluminum substrate has a second terminal for connecting aluminum wires at the end away from the second bonding plane. Both the first terminal and the second terminal are provided with fastening screw holes.

[0015] Preferably, the silicone rubber sealing layer is made of room temperature vulcanizing deketoxime type one-component silicone rubber, which has a Shore A hardness of 25-35 after curing and a volume resistivity greater than or equal to 100%. Ω·cm, dielectric strength greater than or equal to 20 kV / mm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The copper-aluminum composite coated transition clamp and its preparation process disclosed in this invention effectively overcome the reliability problems of traditional copper-aluminum connectors caused by galvanic corrosion and contact deterioration through the synergistic effect of "nano-coating barrier - metallurgical bonding reinforcement - sealing and encapsulation isolation". 1. A composite coating is formed by first depositing TiN and then Ag on a copper substrate using magnetron sputtering. The high chemical inertness, high hardness and density of TiN are used to build the first barrier to isolate oxygen, water vapor and corrosive ions, and it can withstand fretting wear. 2. During subsequent hot pressing, the soft Ag layer undergoes plastic flow, not only densifying and filling the intergranular spaces of TiN to form mechanical interlocking reinforcement, but also acting as a diffusion medium to generate a continuous solid solution metallurgical bonding layer in situ between copper and aluminum, eliminating the brittleness in traditional brazing. The formation conditions of the compound layer ensure high bonding strength while achieving extremely low contact resistance, thus eliminating the potential for localized heating at the source. 3. The hot pressing process promotes atomic diffusion under certain temperature and pressure, enabling the entire bonding surface to achieve an integrated connection without flux or macroscopic defects. After hot pressing, silicone rubber is applied to the edges of the coating and the substrate, and a pre-made sealing groove is used to form a double seal, so that the connection area reaches the IP65 protection level, completely blocking the intrusion of environmental moisture and salt spray, effectively inhibiting the occurrence of copper-aluminum galvanic cell reaction, and ensuring no substrate corrosion in long-term salt spray environment. 4. The process of this invention is controllable and environmentally friendly. The resulting wire clamp has excellent conductivity, corrosion resistance and mechanical strength. It can replace traditional brazing or explosive welding wire clamps, and greatly improve the operational safety and maintenance cycle of copper-aluminum transition connections in power distribution networks. Attached Figure Description

[0017] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 This is a schematic diagram of the wire clamp structure of the present invention; Figure 3 This is a partial enlarged view of the wire clamp of the present invention.

[0018] The labels shown in the diagram: 1. Copper substrate; 2. Aluminum substrate; 3. First bonding plane; 4. Second bonding plane; 5. Transition connection layer; 6. Encapsulation structure; 7. Annular sealing groove; 8. Silicone rubber sealing layer; 9. First terminal; 10. Second terminal; 11. Fastening screw hole. Detailed Implementation

[0019] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0020] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0021] Example 1: This embodiment provides a manufacturing process for a copper-aluminum composite coated transition clamp, the process of which is as follows: Figure 1 As shown, the specific steps are as follows.

[0022] Step S1: Substrate pretreatment: T2 copper was selected as the copper substrate and 1060 industrial pure aluminum as the aluminum substrate. Both copper and aluminum substrates were processed into plate-shaped samples with a contact surface size of 50mm×30mm. The contact surfaces of the copper and aluminum substrates were mechanically ground and polished sequentially. Mechanical grinding was carried out using silicon carbide sandpaper, gradually grinding up to 2000 grit, followed by polishing with diamond polishing paste. After polishing, the substrates were ultrasonically cleaned in acetone and anhydrous ethanol for 15 minutes each to remove surface oil and impurities. Finally, they were dried with high-purity nitrogen. After the above pretreatment, the surface roughness Ra of the contact surfaces of the copper and aluminum substrates was controlled within the range of 0.10-0.12μm. A micro engraving machine is used to process a ring-shaped sealing groove on the circumferential edge of the copper substrate to be contacted. The groove is 0.4 mm deep and 1.5 mm wide. This ring-shaped sealing groove is used to fill the silicone rubber sealing layer in the subsequent step S5. The cross-section of the ring-shaped sealing groove is rectangular. The bottom and walls of the groove are trimmed to ensure that there are no burrs or sharp edges.

[0023] Step S2: Magnetron sputtering deposition of TiN+Ag composite coating: This step employs magnetron sputtering to sequentially deposit a TiN transition layer and an Ag layer on the contact surface of a copper substrate, forming a TiN+Ag composite coating. The specific operations include the following steps: In the first step, TiN transition layer deposition, the pretreated copper substrate from step S1 is fixed on the workpiece holder of the magnetron sputtering equipment, with the contact surface facing the sputtering target. The vacuum chamber door is closed, and the mechanical pump and molecular pump are turned on to evacuate the vacuum, achieving a background vacuum level of [missing information]. After reaching the background vacuum level, a mixture of high-purity argon and nitrogen is introduced as the working gas. The purity of argon is 99.999%, and the purity of nitrogen is 99.999%. The volumetric flow rate of argon is set to 40 sccm, and the volumetric flow rate of nitrogen is set to 4 sccm. What is the volumetric flow rate ratio of argon to nitrogen? The working gas pressure was stabilized at 0.6 Pa by adjusting the throttle valve to a ratio of 10:1. The titanium target power supply was started, and DC pulse magnetron sputtering mode was adopted with a pulse frequency of 100 kHz, a duty cycle of 80%, and a sputtering power density of 5 W / cm². A DC bias of -100 V was applied to the substrate. Before the formal deposition, the baffle in front of the titanium target was closed for 5 minutes for pre-sputtering to remove the oxide layer and adsorbed impurities on the surface of the titanium target. After the pre-sputtering was completed, the baffle was opened to start the formal deposition. The deposition time was 20 minutes, and a TiN transition layer with a thickness of about 1.2 μm was formed on the surface of the copper substrate. The nanoindentation hardness of the TiN transition layer was 22 GPa, and its microstructure was columnar crystal morphology with columnar crystals growing perpendicular to the substrate surface. The second step involves Ag layer deposition. After the TiN transition layer is deposited, the nitrogen inlet is closed, while argon gas is continuously supplied. The working pressure is maintained at 0.6 Pa by adjusting the throttle valve. The titanium target power supply is turned off, and the silver target power supply is switched on and started. The silver target purity is 99.99%. DC magnetron sputtering mode is used, with the sputtering power density set to 2 W / cm² and the bias voltage set to -50V. After pre-sputtering for 3 minutes, the baffle is opened for formal deposition, which takes 8 minutes. An Ag layer is then deposited on top of the TiN transition layer, with a thickness of approximately 1.0 μm. Due to the columnar crystal morphology of the TiN transition layer surface, silver atoms preferentially fill the intergranular gaps during deposition, forming a mechanical interlocking structure between the Ag layer and the TiN transition layer, enhancing the interlayer bonding force. Finally, a TiN+Ag composite coating consisting of a TiN layer and an Ag layer is obtained on the copper substrate surface. The total thickness of this composite coating is... According to the formula Perform calculations, where It is 1.2μm. It is 1.0 μm. Take 1.0, Taking 1.0, the calculation yields The thickness is 2.2μm, which meets the design range of 1.5-3μm.

[0024] Step S3: Overlapping Assembly: The copper substrate processed in step S2 is removed from the magnetron sputtering equipment. Its contact surface has been deposited with a complete TiN+Ag composite coating. The aluminum substrate, which has been pretreated in step S1 and has a surface roughness that meets the standard, is then stacked and assembled with the copper substrate with the pretreated contact surface facing the composite coating. The second bonding plane of the aluminum substrate is made to be completely bonded to the composite coating on the first bonding plane of the copper substrate. During the assembly process, care is taken to avoid particulate contaminants from entering the interface. After the assembly is completed, the stacked part is placed into the mold cavity of the hot press mold. The mold material is high-temperature alloy steel, and the surface of the mold cavity is pre-coated with boron nitride release agent to facilitate subsequent demolding. The mold and the stacked part are placed between the upper and lower pressure heads of the hot press, and the position is adjusted so that the pressure center coincides with the geometric center of the stacked part.

[0025] Step S4: Hot pressing process: The heating system of the hot press is started, and the mold is heated by the resistance heating element embedded in the mold at a heating rate of 10℃ / min, raising the mold temperature from room temperature to 200℃. During the heating process, the upper pressure head of the hot press moves downward at the same time, applying an initial pre-pressure of 10MPa to the laminated parts to ensure good physical contact between the copper substrate, composite coating and aluminum substrate. When the mold temperature reaches 200℃ and stabilizes, the pressure is increased to 90MPa and held under this temperature and pressure conditions for 25 minutes. During the pressure holding process, the Ag layer undergoes plastic flow under the combined effects of a high pressure of 90 MPa and a temperature of 200 °C. Due to its good ductility, the Ag layer material densifies under pressure and fills the microscopic unevenness of the interface. Simultaneously, Ag atoms undergo thermal diffusion towards the copper substrate and the aluminum substrate, while copper and aluminum atoms also diffuse towards the Ag layer. Ag and Cu are completely miscible in the solid state, forming a continuous Cu-Ag solid solution. Ag and Al form an Ag-Al diffusion region at the interface. Since the diffusion process takes place in the solid state and the temperature is controlled below 220 °C, which is far below the trigger temperature of the Cu-Al eutectic reaction, brittleness is effectively suppressed. After the formation of intermetallic compounds, and after 25 minutes of pressure-holding diffusion, a copper-silver-aluminum metallurgical diffusion layer with Ag as the continuous medium is formed in situ between the copper substrate and the aluminum substrate. This metallurgical diffusion layer, together with the TiN layer and the Ag layer, constitutes a complete transition connection layer, enabling the copper substrate and the aluminum substrate to achieve integrated metallurgical connection. After the pressure holding period, the heating power is turned off, and the mold is cooled with the furnace under pressure. When the temperature drops below 100℃, the pressure is released, the mold is removed from the hot press, and it continues to cool to room temperature in the air. Then the mold is opened and the wire clamp blank is removed. Ultrasonic C-scan testing shows that the effective bonding area of ​​the metallurgical bonding layer accounts for 99.2% of the total area of ​​the contact surface. Shear testing is performed on a universal testing machine, and the room temperature shear strength of the bonding interface is 92 MPa.

[0026] Step S5: Sealing and sealing: The area to be sealed in the wire clamp blank obtained in step S4 was wiped clean with anhydrous ethanol and dried. Room temperature vulcanizing deketogenic oxime type one-component silicone rubber was selected as the sealing material, with a Shore A hardness of 30 and a volume resistivity of [missing information]. With a dielectric strength of 22 kV / mm and Ω·cm, silicone rubber was uniformly coated onto the interface edge area between the composite coating, the copper substrate, and the aluminum substrate using a dispensing machine. During coating, care was taken to ensure that the silicone rubber completely filled the annular sealing groove pre-processed in step S1 and protruded approximately 0.8 mm above the surfaces of the copper and aluminum substrates, forming a continuous annular sealing band. The silicone rubber simultaneously adhered to the surfaces of the copper substrate, the aluminum substrate, and the edge end face of the transition connection layer. After curing, it formed an all-round coverage of the connection area. After coating, the wire clamp was placed in an environment with a temperature of 25℃ and a relative humidity of 50% and allowed to cure for 24 hours to allow the silicone rubber to fully vulcanize into an elastomer. After curing, the sealing area was verified using the IP65 protection level test method. The results showed that the dustproof and water-spray-proof performance of the wire clamp connection area met the IP65 level requirements. The copper-aluminum composite coated transition clamp obtained through the above steps has the following structure: Figure 2 Overall structural diagram and Figure 3 As shown in the enlarged view, the wire clamp includes a copper substrate 1 and an aluminum substrate 2. The copper substrate 1 has a first mating plane 3, and the aluminum substrate 2 has a second mating plane 4. The end of the copper substrate 1 away from the first mating plane 3 is provided with a first terminal 9 for connecting copper wires, and the end of the aluminum substrate 2 away from the second mating plane 4 is provided with a second terminal 10 for connecting aluminum wires. Both the first terminal 9 and the second terminal 10 are machined with M10 fastening screw holes 11 to facilitate fastening connection with external wires by bolts. A transition connection layer 5 is provided between the first bonding plane 3 and the second bonding plane 4. This transition connection layer 5 is composed of a TiN+Ag composite coating and a copper-silver-aluminum metallurgical diffusion layer formed by hot pressing. The TiN+Ag composite coating comprises two parts: The TiN layer is metallurgically bonded to the copper substrate 1, and the Ag layer forms a mechanically interlocked structure with the TiN layer. Since the Ag layer is deposited and grown on the columnar crystal surface of the TiN layer and fills the grain boundary gaps, the two form a structure relationship similar to "root-soil" interlocking, which has extremely high interlayer bonding strength. The copper-silver-aluminum metallurgical diffusion layer is a continuous diffusion layer formed in situ by atomic interdiffusion between the Ag layer and the copper substrate 1 and the aluminum substrate 2 during the hot pressing process. This diffusion layer enables the copper substrate 1 and the aluminum substrate 2 to achieve an integrated metallurgical connection without macroscopic interface. A sealing encapsulation structure 6 is provided around the periphery of the online clamp. The sealing encapsulation structure 6 includes an annular sealing groove 7 pre-processed at the edge of the joint line between the copper substrate 1 and the aluminum substrate 2, and a silicone rubber sealing layer 8 that completely fills the annular sealing groove 7 and extends above the surface of the substrate to form an outer covering. The silicone rubber sealing layer 8 is in a continuous closed-loop shape and completely covers all the junction edges of the transition connection layer 5 with the copper substrate 1 and the aluminum substrate 2, thus completely isolating the connection area from the external atmospheric environment. The copper-aluminum composite coated transition clamp prepared in this embodiment was subjected to performance testing. The overall contact resistance of the clamp was measured using the four-wire method, and the measured contact resistance value was 3.8 μΩ, which is much lower than the design requirement of 5 μΩ upper limit. A neutral salt spray test was conducted according to GB / T2423.17 standard, with test conditions of 5% sodium chloride solution concentration, test chamber temperature of 35℃, and sedimentation of 1.5 mL / (80 cm²·h). After 1000 hours of continuous testing, the clamp was removed for observation. The sealing area of ​​the clamp was intact, and the silicone rubber sealing layer showed no cracking or peeling. Upon peeling off the sealing layer to inspect the internal transition connection layer area, no red rust or other corrosion products were found on either the copper substrate or the aluminum substrate. The test time was extended to 1500 hours, and the sealing and anti-corrosion effects remained good. The clamp was then connected to an electrical circuit for thermal cycling test. After 500 cycles between room temperature and 150℃, the contact resistance increased only from the initial 3.8 μΩ to 4.2 μΩ, with a change rate of less than 11%, indicating that the clamp has excellent resistance to thermal cycling aging.

[0027] Example 2: This embodiment provides another preparation process for copper-aluminum composite coating transition clamps, which adds magnetron sputtering treatment to the aluminum substrate contact surface based on Embodiment 1.

[0028] Step S1 is the same as in Example 1, where the copper substrate and aluminum substrate are pretreated and an annular sealing groove is processed.

[0029] Step S2 is the same as in Example 1, depositing a TiN+Ag composite coating with a total thickness of 2.2 μm on the contact surface of the copper substrate. The difference is that after the copper substrate side deposition in Step S2, the aluminum substrate pretreated in Step S1 is also placed in the vacuum chamber of the magnetron sputtering equipment, and a pure Ag transition layer is deposited on the contact surface of the aluminum substrate using the same magnetron sputtering process. Specifically, the vacuum is evacuated until the base vacuum level reaches... After Pa, high-purity argon gas was introduced at a flow rate of 40 sccm, and the working pressure was maintained at 0.6 Pa. The system was then switched to a silver target, and DC magnetron sputtering was employed with a sputtering power density of 2 W / cm², a bias voltage of -50V, and a deposition time of 4 minutes, forming a pure Ag transition layer with a thickness of approximately 0.4 μm on the aluminum substrate surface. This pure Ag transition layer covers the second bonding plane of the aluminum substrate, further improving the interfacial wettability and diffusion uniformity on the aluminum substrate side during subsequent hot pressing.

[0030] The stacking and assembly operation in step S3 is the same as in Example 1. The TiN+Ag composite coating of the copper substrate and the pure Ag transition layer of the aluminum substrate are bonded face to face and assembled, and then placed in a hot press mold.

[0031] The hot pressing process parameters in step S4 are the same as in Example 1. The mold is heated to 200°C and pressure is applied at 90 MPa for 25 minutes. During the pressure holding process, the Ag layer on the copper substrate side and the pure Ag transition layer on the aluminum substrate side fuse into a unified silver diffusion medium layer under pressure, effectively eliminating the physical interface between the two plating layers. The diffusion of silver atoms to the copper and aluminum sides is more uniform, and the thickness consistency of the formed copper-silver-aluminum metallurgical diffusion layer is better. The composition gradient of the interface diffusion zone is smoother. According to ultrasonic C-scan detection, the effective bonding area of ​​the metallurgical bond reaches 99.5%; the room temperature shear strength is 96 MPa, which is further improved compared to Example 1.

[0032] The sealing and curing process in step S5 is exactly the same as in Example 1.

[0033] The wire clamp produced in this embodiment has an overall structure similar to... Figure 2 , Figure 3 The results are consistent with those shown, except that a pure Ag transition layer is added to the aluminum substrate 2 side of the transition connection layer 5. This pure Ag transition layer is completely integrated into the copper-silver-aluminum metallurgical diffusion layer 53 after hot-pressing diffusion. There is no obvious independent layering in the final metallographic structure. Performance tests show that the contact resistance of the clamp in this embodiment is 3.2 μΩ, there is no red rust after 1000 hours of salt spray test, and there is no corrosion after 1500 hours of salt spray test. After 500 thermal cycles, the contact resistance change rate is less than 9%. The overall performance is better than that of Example 1.

[0034] Example 3: This embodiment provides a preparation process for a copper-aluminum composite coating transition clamp, focusing on optimizing the thickness ratio of the TiN+Ag composite coating.

[0035] Steps S1, S3, and S5 are the same as in Example 1.

[0036] In step S2, the thickness ratio of the TiN layer to the Ag layer is changed by adjusting the sputtering deposition parameters. During the TiN transition layer deposition stage, the sputtering power density is adjusted to 4.5 W / cm², and the deposition time is shortened to 15 minutes, resulting in a TiN layer with a thickness of approximately 0.9 μm. During the Ag layer deposition stage, the sputtering power density was adjusted to 2.5 W / cm², and the deposition time was extended to 10 minutes to obtain an Ag layer with a thickness of approximately 1.4 μm. The final total thickness of the TiN+Ag composite coating According to the formula Calculation, where Take 0.9μm, Take 1.4μm, Take 1.0, Taking 1.0, the calculation yields It is 2.3 μm.

[0037] In step S4, the hot pressing process parameters are adjusted. The mold heating temperature is set to 185°C, the pressure is set to 85MPa, and the holding time is extended to 30 minutes to accommodate the diffusion time required for a thicker Ag layer. In this embodiment, the thicker Ag layer provides more diffusion medium at the interface, which is beneficial for forming a more complete metallurgical diffusion layer.

[0038] The contact resistance of the wire clamp is 3.5μΩ, the shear strength is 88 MPa, and no red rust was observed after 1000 hours of salt spray testing. All indicators meet the design requirements.

[0039] Comparative example: To verify the technical effects of the present invention, the following comparative examples are provided for comparison and explanation.

[0040] A comparative example was prepared using a conventional brazing process for copper-aluminum transition clamps. T2 copper substrate and 1060 industrial pure aluminum substrate of the same specifications as in Example 1 were used, and the pretreatment method was the same as step S1 in Example 1. Zinc-aluminum brazing filler metal and cesium fluoroaluminate flux were used for brazing under flame heating conditions. After brazing, the clamps were allowed to cool naturally, and residual flux was removed from the surface to obtain a conventionally brazed copper-aluminum transition clamp.

[0041] The initial contact resistance of the comparative wire clamp was 6.5 μΩ, which, while meeting general usage requirements, was higher than the contact resistance values ​​of the embodiments of this invention. Under the same neutral salt spray test conditions, white corrosion spots began to appear on the aluminum substrate side after 240 hours; after 500 hours, obvious red rust appeared at the brazed joint, and the corrosion area on the aluminum substrate side expanded, accompanied by volume expansion. Metallographic analysis revealed a large number of needle-like and blocky CuAl2 intermetallic compounds at the brazed interface, with the brittle phase accounting for more than 30% of the total interface area. In the thermal cycling test, after only 200 cycles from room temperature to 150°C, the contact resistance of the comparative wire clamp increased from 6.5 μΩ to 15.8 μΩ, a change exceeding 140%, showing a significant trend of contact deterioration.

[0042] The comparison between the above embodiments and comparative examples shows that the copper-aluminum composite coating transition clamp and its preparation process proposed in this invention effectively suppress the copper-aluminum galvanic cell reaction and avoid the formation of brittle intermetallic compounds through the synergistic effect of magnetron sputtering deposition of TiN+Ag composite coating, hot pressing to form metallurgical bond, and silicone rubber sealing and encapsulation. This significantly reduces contact resistance and improves salt spray corrosion resistance and thermal cycling stability. The overall performance of the resulting clamp is superior to that of traditional brazed copper-aluminum transition clamps.

[0043] The above is a detailed description of the preferred embodiments of the present invention, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A manufacturing process for a copper-aluminum composite coated transition clamp, characterized in that, Includes the following steps: Step S1: Pre-treat the surfaces of the copper and aluminum substrates to be in contact, so that their surface roughness Ra reaches 0.08-0.15μm; Step S2: Using magnetron sputtering, in a mixed atmosphere of argon and nitrogen, a titanium target is used as the sputtering source to deposit a TiN transition layer on the contact surface of the copper substrate. Then, an Ag layer is sputtered to form a TiN+Ag composite coating with a total thickness of 1.5-3 μm. Step S3: The copper substrate processed in step S2 and the pre-treated aluminum substrate are stacked and assembled with a composite coating as the intermediate layer, and then placed into a hot press mold. Step S4: Perform hot pressing process, heat the mold to 180-220℃, apply directional pressure of 80-100MPa to the stacked parts, and hold the pressure at this temperature and pressure for 15-30 minutes to allow atomic diffusion to occur at the interface of the copper substrate, composite coating and aluminum substrate to form a metallurgical bonding layer. Step S5: After hot pressing, the obtained wire clamp blank is cooled to room temperature. A silicone rubber sealing layer is applied to the junction edge area between the composite coating and the substrate so that the sealing layer completely covers the junction edge. After curing, the protection level of the entire bonding area reaches IP65.

2. The preparation process of a copper-aluminum composite coating transition clamp according to claim 1, characterized in that, The magnetron sputtering process in step S2 specifically includes: The copper substrate to be processed is placed in the vacuum chamber of the magnetron sputtering equipment, and the vacuum level is evacuated to a background vacuum level better than [missing value]. Pa, then a mixture of high-purity argon and nitrogen is introduced as the working gas, wherein the volume flow ratio of argon to nitrogen is [value missing]. to Adjust the working air pressure to 0.5-0.8 Pa; Turn on the titanium target power supply and use DC pulse magnetron sputtering mode with a sputtering power density of 4-6 W / cm² and a bias voltage of -80 to -120V. Deposit for 15-25 minutes to form a TiN transition layer with a thickness of 0.8-1.5μm on the copper substrate surface. The TiN layer has a columnar crystal structure and its nanoindentation hardness is greater than or equal to 20 GPa. Nitrogen gas inlet was shut off, argon atmosphere was maintained, silver target was switched and power was turned on, DC magnetron sputtering mode was adopted, sputtering power density was 1-3 W / cm², bias voltage was set to -40 to -60V, deposition time was 5-10 minutes, and an Ag layer with a thickness of 0.7-1.5 μm was deposited on the TiN transition layer to form a composite coating composed of TiN layer and Ag layer. The Ag layer grows along the grain boundary gaps of columnar crystals of TiN layer to form a mechanical interlocking structure.

3. The preparation process of a copper-aluminum composite coating transition clamp according to claim 1, characterized in that, After completing the magnetron sputtering process in step S2, a pure Ag transition layer with a thickness of 0.3-0.5 μm is deposited on the contact surface of the aluminum substrate using the same magnetron sputtering process.

4. The preparation process of a copper-aluminum composite coating transition clamp according to claim 1, characterized in that, The effective bonding area of ​​the metallurgical bonding layer formed by the hot pressing process in step S4 shall not be less than 98% of the total area of ​​the contact surfaces, and the room temperature shear strength of the bonding interface shall be greater than 85 MPa.

5. The preparation process of a copper-aluminum composite coating transition clamp according to claim 1, characterized in that, The coating area of ​​the silicone rubber sealing layer in step S5 includes an annular sealing groove with a depth of 0.3-0.5 mm and a width of 1-2 mm, which is pre-processed at the edge of the joint line between the copper substrate and the aluminum substrate. The silicone rubber completely fills the sealing groove and protrudes 0.5-1 mm above the surface of the substrate, forming a double-part sealing structure.

6. A copper-aluminum composite coated transition clamp prepared according to any one of claims 1-5, characterized in that, include: A copper substrate and an aluminum substrate, wherein the copper substrate has a first bonding plane and the aluminum substrate has a second bonding plane; A transition connection layer is located between the first bonding plane and the second bonding plane. The transition connection layer is composed of a TiN+Ag composite coating and a copper-silver-aluminum metallurgical diffusion layer formed by hot pressing. The TiN+Ag composite coating includes a TiN layer that is metallurgically bonded to the copper substrate and an Ag layer that forms a mechanical interlocking structure with the TiN layer. The copper-silver-aluminum metallurgical diffusion layer is formed in situ through atomic interdiffusion between the Ag layer and the substrates on both sides, so that the copper substrate and the aluminum substrate achieve an integrated metallurgical connection. The sealed encapsulation structure includes a silicone rubber sealing layer that completely covers all the junction edges of the transition connection layer, the copper substrate, and the aluminum substrate, thus isolating the connection area from the external environment.

7. A copper-aluminum composite coating transition clamp according to claim 6, characterized in that, The total thickness of the TiN+Ag composite coating The following relationship must be satisfied: ； in: The value represents the thickness of the TiN layer, in μm, and ranges from 0.8 to 1.

5. This represents the thickness of the Ag layer, in μm, ranging from 0.7 to 1.

5. This is the thickness weighting coefficient for the TiN layer, with a value of 1.0; This is the thickness weighting coefficient for the Ag layer, with a value ranging from 0.8 to 1.

2. and The value range is limited to 1.5-3μm.

8. A copper-aluminum composite coating transition clamp according to claim 6, characterized in that, The overall contact resistance of the clamp is less than or equal to 5μΩ, and in the neutral salt spray test, the continuous test time is greater than or equal to 1000h, and no red rust caused by substrate corrosion appears in the tested area.

9. A copper-aluminum composite coating transition clamp according to claim 6, characterized in that, The copper substrate has a first terminal for connecting copper wires at the end away from the first bonding plane, and the aluminum substrate has a second terminal for connecting aluminum wires at the end away from the second bonding plane. Both the first terminal and the second terminal are provided with fastening screw holes.

10. A copper-aluminum composite coating transition clamp according to claim 6, characterized in that, The silicone rubber sealing layer is made of room temperature vulcanized deketoxime type one-component silicone rubber, which has a Shore A hardness of 25-35 after curing and a volume resistivity greater than or equal to 100%. Ω·cm, dielectric strength greater than or equal to 20 kV / mm.

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