A manufacturing method of a copper-aluminum composite liquid cooling box

Abstract

The application relates to a manufacturing method of a copper-aluminum composite liquid cooling box, which comprises a high-frequency welding process, and the high-frequency welding process comprises the following steps: clamping an aluminum-based shell on one side of a copper-aluminum composite needle plate provided with heat dissipation needles and pressing the aluminum-based shell along the thickness direction; the peak temperature of a functional copper layer is controlled to be not higher than 600 DEG C in a welding heating stage, high-frequency induction brazing is performed on an aluminum-aluminum butt joint between the aluminum-based shell and the copper-aluminum composite needle plate, the end of the heat dissipation needle is fused and connected with the inner bottom surface of the aluminum-based shell to form an integrated body, and the workpiece is released after the brazing and heat preservation are completed and the overall temperature of the functional copper layer is continuously cooled to below 300 DEG C. The temperature control mode is divided into zones, the aluminum-aluminum joint is concentratedly heated through a high-frequency induction heating coil, the functional copper layer is forcedly cooled through a built-in cooling pipe of a cover plate, local high temperature of a welding area and low temperature of a copper-aluminum composite interface are controllable, and the connection failure of the copper-aluminum joint surface in the overall high-frequency welding is avoided.

Description

Technical Field

[0001] This invention relates to the field of heat exchange device technology, and in particular to a method for manufacturing a copper-aluminum composite liquid cooling box. Background Technology

[0002] High-power electronic devices continuously release a large amount of heat during operation. If this heat cannot be quickly conducted away, it can cause the device temperature to rise excessively, leading to decreased electrical performance, reduced service life, and in severe cases, thermal burnout. Developing heat dissipation components that combine high thermal conductivity, excellent structural strength, and economic advantages is an urgent technological requirement in fields such as high-power power electronics, computing servers, and new energy electronic control. Copper possesses excellent thermal conductivity, while aluminum is lightweight, easy to process, and inexpensive. Copper-aluminum composite heat dissipation structures combine the advantages of both metals, making them a mainstream heat dissipation solution for high heat flux density scenarios.

[0003] However, copper and aluminum have vastly different physical and chemical properties, making reliable bonding at the copper-aluminum interface a key challenge in manufacturing such heat dissipation structures. Existing technologies typically employ diffusion welding to create a diffusion bonding layer between the copper and aluminum, as disclosed in Chinese Patent CN121536043A, which describes a multi-faceted composite copper-aluminum substrate, a copper-aluminum composite heat dissipation device, and its manufacturing method. This process forms a diffusion bonding layer with a thickness of 200nm-2µm, resulting in good bonding between the copper and aluminum plates. However, in manufacturing liquid-cooled boxes, the top surface of the heat dissipation pins needs to be welded to the inner wall of the casing. While aluminum can be used to create a good bond at the welding points between the heat dissipation pins and the casing, this location within the entire heat dissipation device prevents the use of laser welding or arc welding. Instead, a method of overall heating (such as high-frequency welding or furnace welding) is employed to raise the overall temperature of the heat dissipation device, thus connecting the points together.

[0004] The problem is that since this welding is done on the entire heat dissipation device, the temperature at the copper-aluminum interface will also rise. However, copper and aluminum have different coefficients of thermal expansion and low solid-state miscibility, making them highly susceptible to continuous reaction at high temperatures to form brittle and hard Cu-Al intermetallic compounds (IMC, CuAl2, Cu9Al4, etc.). These phases are highly brittle and have extremely poor plasticity, which can lead to delamination and cracking of the copper-aluminum composite interface, a surge in thermal resistance, and extreme deterioration of the heat dissipation performance of the liquid cooling box.

[0005] Therefore, it is necessary to improve welding methods to solve the above problems. Summary of the Invention

[0006] The main objective of this invention is to provide a method for manufacturing a copper-aluminum composite liquid cooling box. By using a zoned temperature control method of overall high-frequency heating and localized cooling, the connection strength of the copper-aluminum composite interface can be maintained after internal welding, thus preventing the performance of the liquid cooling box from deteriorating.

[0007] This invention achieves the above objective through the following technical solution: a method for manufacturing a copper-aluminum composite liquid cooling box, wherein the copper-aluminum composite liquid cooling box includes a copper-aluminum composite pin plate and an aluminum-based shell, wherein the front side of the copper-aluminum composite pin plate is provided with aluminum-coated heat dissipation pins, and the back side is embedded with a functional copper layer; the aluminum-based shell covers all the heat dissipation pins and is welded and sealed to the edge of the copper-aluminum composite pin plate; the manufacturing method includes a high-frequency welding process, wherein the high-frequency welding process comprises the following steps: The aluminum-based shell is fastened to the side of the copper-aluminum composite needle plate with the heat dissipation needle and pressed tightly along the thickness direction; during the welding heating stage, the peak temperature of the functional copper layer is controlled not to exceed 600℃, and high-frequency induction brazing is performed on the aluminum-aluminum butt joint of the aluminum-based shell and the copper-aluminum composite needle plate to fuse the end of the heat dissipation needle with the inner bottom surface of the aluminum-based shell into one piece; after the brazing and heat preservation are completed, the workpiece is continuously cooled until the overall temperature of the functional copper layer drops below 300℃ before it is released.

[0008] Specifically, the functional copper layer includes several embedded copper layers, which are composite-formed on the bottom of the copper-aluminum composite pin plate by diffusion bonding.

[0009] Specifically, the high-frequency welding process uses a special welding device, which includes a high-frequency induction heating coil and a workpiece clamping fixture; the workpiece clamping fixture includes a base and a cover plate, and the cover plate is provided with cooling pipes for heat dissipation. During high-frequency welding, an aluminum-based welding sheet is placed at the joint between the heat dissipation pin and the aluminum-based shell; the aluminum-based shell and the copper-aluminum composite pin plate are clamped and fixed between the base and the cover plate, and the back of the copper-aluminum composite pin plate is in close contact with the cover plate; the high-frequency induction heating coil surrounds the outside of the workpiece pressing fixture to concentrate the heating of the aluminum-aluminum joint, while the cooling medium is circulated in the cooling pipe to continuously force the functional copper layer to cool down.

[0010] Furthermore, the high-frequency welding single heating time is 2-6 minutes, and the holding time is 1-3 minutes.

[0011] Furthermore, when using low-temperature aluminum solder sheets with a melting point of 420℃, the peak temperature of the functional copper layer interface is controlled to be ≤530℃ during the welding process.

[0012] Furthermore, when using 4045 aluminum-silicon solder with a melting point of 605℃, the stable temperature range of the functional copper layer interface during the welding process is 570~600℃.

[0013] Furthermore, the tensile strength of the aluminum-aluminum brazed joint formed by high-frequency welding is 35-40 MPa.

[0014] Specifically, the manufacturing method further includes a laser welding process, which is performed after the high-frequency welding process; the laser welding process is: performing laser sealing welding on the edge joint between the outer periphery of the copper-aluminum composite needle plate and the aluminum base shell.

[0015] Furthermore, the laser-welded weld penetration depth is 1–2 mm.

[0016] Furthermore, the tensile strength of the laser-welded joint is 45–50 MPa.

[0017] The beneficial effects of the technical solution of this invention are: 1. Adopting a zoned temperature control mode, the aluminum-aluminum joint is heated in a concentrated manner by a high-frequency induction heating coil, and the functional copper layer is cooled by a built-in cooling pipe in the cover plate. This achieves local high temperature in the welding area and low temperature control at the copper-aluminum composite interface, thus avoiding connection failure of the copper-aluminum interface during overall high-frequency welding. 2. Precisely define temperature thresholds, match corresponding temperature ranges according to different solder pad materials, and strictly control the peak temperature of the copper layer to not exceed 600℃, thus inhibiting the excessive growth of intermetallic compounds from the temperature source. 3. Set a low-temperature depressurization sequence. The pressure must be released only after the copper layer has cooled down to below 300°C to avoid high-temperature stress deformation and secondary growth of subsequent compounds, thus completely locking in the bonding performance of the copper-aluminum composite layer. Attached Figure Description

[0018] Figure 1 Exploded view of a copper-aluminum composite liquid cooling box; Figure 2 This is a schematic diagram of the working principle of the welding device; Figure 3 A flowchart illustrating the manufacturing process of a copper-aluminum composite liquid cooling box.

[0019] The diagram is marked as follows: 100-Copper-aluminum composite liquid cooling box, 11-Copper-aluminum composite pin plate, 111-Heat dissipation pin, 112-Functional copper layer, 12-Aluminum-based shell, 121-Inner bottom surface, 122-Side wall; 200-Welding device, 1-Heating coil, 2-Workpiece clamping fixture, 21-Base, 22-Cover plate, 221-Cooling pipe. Detailed Implementation

[0020] The manufacturing method of the copper-aluminum composite liquid cooling box of the present invention will be further described in detail and completely below with reference to the accompanying drawings and all the technical solutions of the claims.

[0021] The copper-aluminum composite liquid cooling box 100 protected by this invention consists of two main structures: a copper-aluminum composite pin plate 11 and an aluminum-based shell 12. The copper-aluminum composite pin plate 11 has an array of aluminum-coated heat dissipation pins 111 on its front side and a functional copper layer 112 embedded and fixed on its back side. The aluminum-based shell 12 completely covers all the heat dissipation pins 111, and the edges of the aluminum-based shell 12 and the copper-aluminum composite pin plate 11 are sealed by welding, forming a closed liquid cooling cavity. This invention can be widely used in high heat flux density heat dissipation scenarios such as new energy electronic control, high-power chips, and energy storage devices. The core improvement of this invention lies in optimizing the high-frequency welding process, precisely controlling the welding temperature and cooling sequence, and suppressing excessive growth of intermetallic compounds at the copper-aluminum interface. This solves the industry pain points of traditional copper-aluminum composite liquid cooling boxes, such as weakened composite layer bonding strength, easy weld cracking, and poor sealing performance after welding. Furthermore, the addition of a post-laser sealing welding process further enhances the product's structural strength and sealing performance. This invention provides two differentiated embodiments, each adapted to different types of aluminum-based welding sheets and corresponding to different welding process parameters. The specific implementation steps, operating principles, and process details are as follows.

[0022] I. Pre-treatment process of product basic structure Both embodiments of this invention employ a unified pretreatment process to ensure the welding performance of the substrate and the stability of the composite layer bonding. The pretreatment objects include the copper-aluminum composite needle plate 11 and the aluminum base shell 12. The functional copper layer 112 of the copper-aluminum composite needle plate 11 is formed by diffusion welding of several embedded copper elements to the bottom of the copper-aluminum composite needle plate 11. The diffusion welding process is completed before welding, and the high-temperature, high-pressure diffusion process enables the embedded copper to form a dense metallurgical bond with the aluminum base, ensuring the thermal conductivity and structural stability of the functional copper layer 112, laying the structural foundation for subsequent high-frequency welding temperature control.

[0023] The specific pretreatment steps are as follows: First, the copper-aluminum composite pin plate 11 and the aluminum-based shell 12 undergo fine surface treatment. Ultrasonic degreasing agent is used to clean the workpiece surface, removing residual oil, cutting chips, and impurities from stamping and processing. The cleaning time is 15-20 minutes. After cleaning, high-purity compressed air is used for drying, followed by drying in a constant temperature oven at 80-100℃ for 30 minutes to thoroughly remove surface moisture and prevent moisture vaporization during welding, which could lead to bubbles and porosity defects. Subsequently, the ends of the heat dissipation pin 111, the inner bottom surface 121 of the aluminum-based shell 12, and the joints of the side walls 122 are polished to remove the surface oxide film, ensuring a smooth and clean welding contact surface with a gap controlled within 0.05mm, providing good contact conditions for subsequent aluminum-aluminum brazing. After pretreatment, the workpieces undergo visual inspection and dimensional verification, rejecting deformed or defective pieces to ensure accurate subsequent welding processes.

[0024] II. Example 1: Manufacturing method of copper-aluminum composite liquid cooling box adapted to low-temperature aluminum welding sheet like Figure 2 As shown, this embodiment uses a low-temperature aluminum-based welding sheet with a melting point of 420℃ to carry out a high-frequency welding process. It is equipped with a dedicated welding temperature, heating time, and cooling parameters, and is used with a dedicated welding device 200 to complete the core welding operation. The welding device 200 includes a high-frequency induction heating coil 1 and a workpiece clamping fixture 2. The workpiece clamping fixture 2 includes a base 21 and a cover plate 22 with an internal cooling pipe 221. It achieves precise heating, directional cooling, and stable pressure bonding throughout the process. The specific manufacturing steps are as follows.

[0025] 1. Workpiece assembly and tooling clamping The pre-treated copper-aluminum composite pin plate 11 is aligned and assembled with the aluminum base shell 12, ensuring that the aluminum base shell 12 precisely engages with the side of the copper-aluminum composite pin plate 11 where the heat dissipation pins 111 are located. The heat dissipation pins 111 completely correspond to the inner bottom surface 121 of the aluminum base shell 12, ensuring that all ends of the heat dissipation pins 111 are tightly joined to the inner bottom surface 121 of the aluminum base shell 12. At the aluminum-aluminum joint between the heat dissipation pins 111 and the aluminum base shell 12, uniformly sized low-temperature aluminum-based brazing sheets are placed, completely covering the joint area without offset or gaps, ensuring uniform brazing fusion.

[0026] After assembly, the entire workpiece is placed on the base 21 of the workpiece clamping fixture 2. The workpiece position is adjusted to achieve precise positioning. Then, the cover plate 22 is closed, and a uniform clamping force is applied along the thickness direction of the workpiece to clamp and fix the aluminum-based shell 12 and the copper-aluminum composite needle plate 11 together between the base 21 and the cover plate 22. During the clamping process, the contact position is strictly controlled to ensure that the back of the copper-aluminum composite needle plate 11 is completely and tightly attached to the working surface of the cover plate 22 without gaps or warping. This ensures that the cooling pipe 221 inside the cover plate 22 can achieve all-round and uniform forced cooling of the functional copper layer 112, providing structural protection for subsequent temperature control. The clamping pressure of the fixture is controlled at 0.3-0.5 MPa to ensure a tight fit of the welded joints, avoiding defects such as incomplete welding or missing welding, and to prevent excessive pressure from causing deformation, bending, or damage to the thin-walled heat dissipation needle 111.

[0027] 2. Precise temperature control during high-frequency welding process This process is the core process of the invention. It uses a high-frequency induction heating coil 1 arranged around the outside of the workpiece pressing fixture 2 to achieve concentrated directional heating of the aluminum-aluminum butt joint, avoiding the problem of excessively high temperature of the functional copper layer 112 caused by traditional overall heating. At the same time, it works in conjunction with the cooling medium circulating through the cooling pipe 221 inside the cover plate 22 to form a temperature difference welding mode of "local high temperature heating of the joint and forced cooling of the copper layer as a whole", which inhibits the rapid and excessive growth of intermetallic compounds at the copper-aluminum interface from the root.

[0028] The specific welding parameters and operating procedures are as follows: Before welding, the cooling circulation system is activated, and room-temperature cooling water is continuously circulated through the cooling pipe 221 as the cooling medium to ensure that the cover plate 22 is in a low-temperature constant-temperature state, which can remove the heat conducted by the functional copper layer 112 in real time. Then, the high-frequency induction heating equipment is started to enter the welding heating stage. In this embodiment, the peak temperature of the functional copper layer 112 interface is strictly controlled to be ≤530℃, far below the critical temperature for the violent formation of copper-aluminum intermetallic compounds, and higher than the melting point of the low-temperature aluminum weldment at 420℃, ensuring that the weldment is fully melted and spread, achieving metallurgical bonding at the aluminum-aluminum interface.

[0029] The heating time for a single high-frequency welding cycle is controlled to be 2–6 minutes, preferably 4 minutes. The heating process is uniform and controllable to avoid sudden temperature rises that could lead to localized overheating. After heating, a heat preservation stage is entered, with a heat preservation time controlled to be 1–3 minutes, preferably 2 minutes. During the heat preservation stage, the joint temperature is kept stable to ensure that the molten solder fully wets the end of the heat dissipation pin 111 and the inner bottom surface 121 of the aluminum base shell 12, so that the end of the heat dissipation pin 111 and the inner bottom surface 121 of the aluminum base shell 12 are completely fused together to form a dense brazed bond layer. During the heat preservation process, the cooling system operates continuously, constantly providing forced heat dissipation to the functional copper layer 112, limiting the continuous rise in copper layer temperature, and stably controlling the copper-aluminum interface temperature within a safe range.

[0030] 3. Constant temperature cooling and workpiece unloading After the high-frequency brazing and heat preservation process is completed, immediately turn off the high-frequency induction heating coil 1 to stop the heating operation. Maintain the tooling clamping state and the cooling medium circulation state unchanged, and continuously cool the workpiece at a constant temperature. It is strictly forbidden to loosen the workpiece at high temperature. Monitor the overall temperature of the functional copper layer 112 in real time throughout the process. Only when the overall temperature of the functional copper layer 112 has completely dropped below 300°C can the tooling clamping state be released and the welded semi-finished product be removed. This cooling sequence is a key technical point of this invention. At high temperatures, the atomic activity at the copper-aluminum interface is extremely high, and brittle and hard intermetallic compounds are easily and rapidly generated. Premature loosening of the clamping will cause stress release deformation of the workpiece and accelerate compound growth. However, below 300°C, the diffusion rate of copper and aluminum atoms is greatly reduced, which can effectively inhibit the excessive thickening of intermetallic compounds and completely avoid the problems of weakening of the bonding strength and delamination cracking of the copper-aluminum composite layer.

[0031] The aluminum-aluminum brazed joint formed by high-frequency welding in this embodiment has a dense structure, no pores, and no defects in the weld. After mechanical property testing, the tensile strength of the brazed joint is stably 35-40 MPa, which meets the structural load-bearing and sealing requirements of the liquid cooling box under high-pressure liquid cooling conditions.

[0032] 4. Post-laser welding sealing process After the high-frequency welding process is completed and the workpiece is completely cooled and unloaded, the subsequent laser welding sealing process begins. This process, following the high-frequency welding, is used to enhance the overall sealing performance and edge structural strength of the workpiece. The specific operation involves using fiber laser welding equipment, focusing on the edge joint between the outer periphery of the copper-aluminum composite needle plate 11 and the aluminum base shell 12, and performing continuous laser sealing welding. The welding process employs a uniform speed welding technique, with the welding speed controlled at 800–1000 mm / min. The laser power is output stably, and the weld penetration depth is precisely controlled to 1–2 mm to ensure complete penetration and a gapless seal at the edge joint.

[0033] Laser welding can compensate for the insufficient edge sealing precision of high-frequency welding, achieving a fully sealed metallurgical bond at the outer perimeter of the workpiece, effectively preventing coolant leakage during subsequent use of the liquid-cooled box. Testing showed that the tensile strength of the laser-welded joint in this embodiment consistently reached 45–50 MPa, significantly improving the overall structural strength and enhancing the product's resistance to compression and deformation.

[0034] III. Example 2: Manufacturing method of copper-aluminum composite liquid cooling box adapted to 4045 aluminum-silicon solder sheet like Figure 2 As shown, this embodiment uses 4045 aluminum-silicon welding sheets with a melting point of 605℃ for high-frequency welding. 4045 aluminum-silicon welding sheets have superior fluidity and wettability, resulting in denser welds, making them suitable for the production needs of large-size, high-pressure copper-aluminum composite liquid cooling boxes 100. The overall process flow of this embodiment is consistent with Embodiment 1, including workpiece pretreatment, tooling clamping, high-frequency welding, cooling and shaping, and laser welding sealing. The core difference lies in the temperature control range during the high-frequency welding stage. The same dedicated welding device 200 and tooling structure are used. The specific differentiated process steps and parameters are as follows.

[0035] 1. Workpiece assembly and tooling positioning and clamping The pretreatment, workpiece assembly, and tooling clamping process in this embodiment are completely consistent with those in Embodiment 1. The pretreated aluminum-based shell 12 is fastened to the heat dissipation pin 111 side of the copper-aluminum composite pin plate 11. 4045 aluminum-silicon welding sheets are laid at the aluminum-aluminum butt joint between the heat dissipation pin 111 and the inner bottom surface 121 of the aluminum-based shell 12, ensuring tight adhesion and complete coverage of the joint area. The workpiece is then placed on the base 21 of the workpiece clamping fixture 2, aligned, and then clamped and fixed by the cover plate 22, ensuring that the back of the copper-aluminum composite pin plate 11 is completely flush with the cover plate 22. The cooling pipe 221 provides omnidirectional forced cooling of the functional copper layer 112. The clamping force of the tooling is also controlled at 0.3–0.5 MPa to ensure the precision of the welded joint.

[0036] 2. High-frequency welding precision temperature control fusion process Because the 4045 aluminum-silicon solder sheet has a higher melting point and requires a higher melting temperature for welding, this embodiment specifically optimizes the temperature control range. During the welding heating stage, the stable temperature range of the functional copper layer 112 interface is strictly controlled to be 570-600℃, and the peak temperature is strictly not higher than 600℃. This satisfies the melting and wetting requirements of the high-melting-point aluminum-silicon solder sheet, ensures that the solder flows fully to fill the joint gap, and realizes the integrated fusion connection between the end of the heat dissipation pin 111 and the inner bottom surface 121 of the aluminum base shell 12. At the same time, it strictly limits the maximum temperature of the copper layer to avoid excessive growth of intermetallic compounds at the copper-aluminum interface due to overheating.

[0037] In this embodiment, the high-frequency welding heating and holding times are consistent with those in Embodiment 1. The heating time for a single session is controlled at 2–6 minutes, preferably 5 minutes, and the holding time is 1–3 minutes, preferably 3 minutes. Sufficient holding time allows the high-melting-point 4045 aluminum-silicon brazing sheet to fully spread, eliminating weld voids and gap defects, and improving the uniformity of brazing bonding. Throughout the welding process, the cooling pipe 221 continuously circulates cooling medium to continuously and forcibly cool the functional copper layer 112, creating a process environment of localized high-temperature welding and overall low-temperature temperature control. This precisely balances the welding quality and the structural stability of the copper-aluminum composite layer, preventing the copper-aluminum bonding surface from failing during overall high-frequency welding.

[0038] 3. Low-temperature cooling and shaping and workpiece removal After the heat preservation process is completed, immediately turn off the high-frequency induction heating coil 1, stop the heat source input, and maintain the tooling in a clamped state and the cooling circulation system in continuous operation to slowly and evenly cool the workpiece. Monitor the overall temperature of the functional copper layer 112 in real time. Only after the temperature drops uniformly to below 300℃ can the tooling be loosened and the workpiece removed. Compared with the low-temperature aluminum welding process, the welding temperature in this embodiment is higher and the atomic activity at the copper-aluminum interface is stronger. Therefore, the process control of constant temperature cooling and delayed pressure relief is more critical. This can effectively avoid workpiece deformation caused by high-temperature residual stress, and at the same time, minimize the formation thickness and quantity of brittle and hard intermetallic compounds, ensuring the bonding strength of the composite layer of the copper-aluminum composite needle plate 11 and preventing delamination, peeling, and strength reduction problems during later use.

[0039] The aluminum-aluminum brazed joint formed by high-frequency welding in this embodiment also has excellent mechanical properties, with tensile strength stably maintained at 35-40MPa. The weld density and flatness are better than those in Embodiment 1, making it more suitable for liquid cooling heat dissipation equipment under high power, high pressure, and long service life conditions.

[0040] 4. Laser welding edge sealing reinforcement process In this embodiment, the parameters and operation methods of the post-laser welding process are completely consistent with those of Embodiment 1. After the high-frequency welded semi-finished product has cooled, fully automated laser sealing welding is performed on the edge joint between the outer periphery of the copper-aluminum composite needle plate 11 and the aluminum base shell 12. The weld penetration depth is precisely controlled to 1-2 mm, and the weld is continuous, uniform, without breaks or cracks. The tensile strength of the formed laser-welded joint is stably 45-50 MPa. Through the dual welding structure of high-frequency welding internal fusion and laser welding edge sealing, the copper-aluminum composite liquid cooling box 100 forms a completely sealed integrated structure, significantly improving the overall structural strength, sealing performance, and pressure resistance.

[0041] IV. Overall Process Principles and Beneficial Effects This invention addresses the core defects of traditional copper-aluminum composite liquid cooling box manufacturing by improving the high-frequency welding core process and combining it with post-laser sealing welding. In traditional manufacturing processes, the high-frequency welding process involves overall temperature rise, with no temperature control for the functional copper layer 112. The peak temperature easily exceeds 600℃, and direct pressure relief and cooling at high temperatures leads to the rapid formation of a large number of thick, brittle, and hard intermetallic compounds at the copper-aluminum interface. These compounds have poor ductility and weak bonding strength, directly causing a significant decrease in the bonding strength of the copper-aluminum composite layer. After long-term use, the product is prone to delamination, cracking, and leakage failure.

[0042] The core innovative principles of this invention are reflected in three points: 1. Adopting a zoned temperature control mode, the aluminum-aluminum joint is heated in a concentrated manner by a high-frequency induction heating coil 1, and the functional copper layer 112 is cooled by a built-in cooling pipe 221 in the cover plate 22. This achieves local high temperature in the welding area and low temperature control at the copper-aluminum composite interface, thus avoiding connection failure of the copper-aluminum bonding surface during the overall high-frequency welding. 2. Precisely define temperature thresholds, match corresponding temperature ranges according to different solder pad materials, and strictly control the peak temperature of the copper layer to not exceed 600℃, thus inhibiting the excessive growth of intermetallic compounds from the temperature source. 3. Set a low-temperature depressurization sequence. The pressure must be released only after the copper layer has cooled down to below 300°C to avoid high-temperature stress deformation and secondary growth of subsequent compounds, thus completely locking in the bonding performance of the copper-aluminum composite layer.

[0043] Meanwhile, this invention employs a composite welding process of "high-frequency internal brazing + laser edge sealing welding." High-frequency welding achieves integrated fusion of the heat dissipation pin 111 and the inner bottom surface 121 of the aluminum base shell 12, ensuring the stability of the internal heat conduction structure. Laser welding achieves full sealing of the outer peripheral seams, improving the overall sealing performance and structural strength of the product. The two processes complement each other and enhance efficiency. Actual testing shows that the copper-aluminum composite liquid cooling box 100 manufactured by this invention exhibits no significant thickening of the brittle and hard compound layer, a bonding strength stability improvement of over 40%, weld seams free of porosity and cracks, a 100% sealing pass rate, and mechanical properties far exceeding those of products manufactured using traditional processes. It can meet the long-term stable operation requirements of various high-end, high-power heat dissipation equipment.

[0044] V. Product Post-Processing and Performance Testing After welding in both embodiments, the workpieces underwent uniform subsequent finishing and performance testing. First, the weld seams at the workpiece edges were ground and deburred to ensure a smooth and regular product appearance. Then, a pressure sealing test was conducted, with high-pressure nitrogen gas introduced and held for 5 minutes; no pressure drop or leakage was observed. Finally, mechanical sampling tests were performed, showing that the tensile strength of the brazed joint was consistently between 35 and 40 MPa, and the tensile strength of the laser-welded joint was consistently between 45 and 50 MPa, with all parameters meeting standards. The final copper-aluminum composite liquid cooling box 100 features a compact structure, excellent thermal conductivity, reliable sealing, high structural strength, and a significantly improved yield rate, making it suitable for large-scale industrial production.

[0045] The above are merely some embodiments of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and all such modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a copper-aluminum composite liquid cooling box, the copper-aluminum composite liquid cooling box comprising a copper-aluminum composite pin plate and an aluminum-based shell, wherein the front side of the copper-aluminum composite pin plate is provided with aluminum-coated heat dissipation pins, and the back side is embedded with a functional copper layer; the aluminum-based shell covers all the heat dissipation pins and is welded and sealed to the edge of the copper-aluminum composite pin plate; the manufacturing method includes a high-frequency welding process, characterized in that... The high-frequency welding process steps are as follows: The aluminum-based shell is fastened to the side of the copper-aluminum composite needle plate with the heat dissipation needle and pressed tightly along the thickness direction; during the welding heating stage, the peak temperature of the functional copper layer is controlled not to exceed 600℃, and high-frequency induction brazing is performed on the aluminum-aluminum butt joint of the aluminum-based shell and the copper-aluminum composite needle plate to fuse the end of the heat dissipation needle with the inner bottom surface of the aluminum-based shell into one piece; after the brazing and heat preservation are completed, the workpiece is continuously cooled until the overall temperature of the functional copper layer drops below 300℃ before it is released.

2. The manufacturing method of the copper-aluminum composite liquid cooling box according to claim 1, characterized in that: The functional copper layer includes several embedded copper layers, which are formed on the bottom of the copper-aluminum composite pin plate by diffusion bonding.

3. The manufacturing method of the copper-aluminum composite liquid cooling box according to claim 1, characterized in that: The high-frequency welding process uses a special welding device, which includes a high-frequency induction heating coil and a workpiece clamping fixture. The workpiece clamping fixture includes a base and a cover plate, and the cover plate is provided with cooling pipes for heat dissipation. During high-frequency welding, an aluminum-based welding sheet is placed at the joint between the heat dissipation pin and the aluminum-based shell; the aluminum-based shell and the copper-aluminum composite pin plate are clamped and fixed between the base and the cover plate, and the back of the copper-aluminum composite pin plate is in close contact with the cover plate; the high-frequency induction heating coil surrounds the outside of the workpiece pressing fixture to concentrate the heating of the aluminum-aluminum joint, while the cooling medium is circulated in the cooling pipe to continuously force the functional copper layer to cool down.

4. The manufacturing method of the copper-aluminum composite liquid cooling box according to claim 3, characterized in that: The high-frequency welding process involves a single heating time of 2–6 minutes and a holding time of 1–3 minutes.

5. The method for manufacturing the copper-aluminum composite liquid cooling box according to claim 3, characterized in that: When using low-temperature aluminum solder sheets with a melting point of 420℃, the peak temperature of the functional copper layer interface is controlled to be ≤530℃ during the welding process.

6. The method for manufacturing the copper-aluminum composite liquid cooling box according to claim 3, characterized in that: When using 4045 aluminum-silicon solder with a melting point of 605℃, the stable temperature range of the functional copper layer interface during the welding process is 570~600℃.

7. The manufacturing method of the copper-aluminum composite liquid cooling box according to claim 3, characterized in that: The tensile strength of the aluminum-aluminum brazed joint formed by high-frequency welding is 35-40 MPa.

8. The method for manufacturing the copper-aluminum composite liquid cooling box according to claim 1, characterized in that: The manufacturing method further includes a laser welding process, which is performed after the high-frequency welding process; the laser welding process is: performing laser sealing welding on the edge joint between the outer periphery of the copper-aluminum composite needle plate and the aluminum base shell.

9. The method for manufacturing the copper-aluminum composite liquid cooling box according to claim 8, characterized in that: The laser-welded weld has a penetration depth of 1–2 mm.

10. The method for manufacturing the copper-aluminum composite liquid cooling box according to claim 8, characterized in that: The tensile strength of the laser-welded joint is 45-50 MPa.

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