Neodymium-iron-boron magnet surface coating device

Abstract

The application discloses a neodymium-iron-boron magnet surface coating device and relates to the technical field of coating. The device comprises a coating machine main body, the coating machine main body is provided with a vacuum tank body and a sealing cover, a plurality of sputtering targets are arranged in the vacuum tank body, the sputtering target comprises a target material, a target shell and a compression ring, a magnetic circuit module is arranged in the target shell, a cooling cavity is arranged in the magnetic circuit module, a flow guide water channel is arranged in the cooling cavity to divide the cooling cavity into an upper chamber and a lower chamber, a water outlet is arranged on the lower chamber, the flow guide water channel is in a closed loop structure extending downward in a spiral shape, an upward protruding water stop boss is arranged at the joint of the head and the tail of the flow guide water channel, a water inlet is arranged on the upstream side of the water stop boss, and a drainage groove is arranged on the downstream side of the water stop boss and connected to the lower chamber. The application guides the cooling liquid, accelerates the flow rate of the cooling liquid, effectively eliminates the local stagnant area of the traditional meandering water channel, increases the thermal contact area, solves the problem of the accumulation and blockage of the magnetic steel corrosion products, and enables the impurities to be smoothly discharged with the cooling liquid.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more particularly to a coating device for the surface of neodymium iron boron magnets. Background Technology

[0002] Sputtering coating on the surface of NdFeB magnets is a process that uses physical vapor deposition (PVD) technology to prepare a protective coating on the surface of a magnet. Its core principle is to bombard the target material (usually metallic nickel, chromium, aluminum, or alloy) with high-energy particles (such as argon ions), causing the target atoms to be sputtered out and deposited on the surface of the NdFeB magnet to form a uniform and dense thin film.

[0003] This thin film primarily serves a crucial protective function, isolating the magnet from corrosive media and preventing oxidation and corrosion. It also improves appearance (such as providing a metallic luster or colored decoration), enhances surface hardness and wear resistance, and even imparts specific electrical conductivity. Compared to traditional electroplating, sputtering coating offers significant advantages such as a denser and more uniform film, stronger adhesion, and better environmental friendliness (no harmful chemical solutions). Furthermore, it can be performed at relatively low temperatures, effectively avoiding the damage to NdFeB magnetic properties caused by high temperatures. It is a key surface treatment technology for improving the durability and reliability of high-performance NdFeB magnets in harsh environments, and is widely used in fields such as new energy vehicles, electronic devices, and medical equipment where high magnet stability and durability are required.

[0004] The core structure of a sputtering coating machine includes a vacuum chamber (providing a high vacuum or low-pressure inert gas environment), a sputtering target (containing high-purity target material, which generates plasma through electric and magnetic fields), a sample stage (carrying and rotating the workpiece to be coated to ensure uniform film layer), a vacuum system (including mechanical pumps, molecular pumps, etc., to establish and maintain vacuum), a power supply system (providing DC, RF, or pulsed power to excite sputtering), and a gas control system (precisely introducing reactive gases such as argon).

[0005] During the sputtering coating process, the sputtering target generates a large amount of heat. If the target temperature is too high, it will directly affect the sputtering rate and film quality. Therefore, a dedicated cooling system is installed inside the sputtering target (see patent CN201520580983.0, "A Magnetron Sputtering Target"). This system uses circulating coolant to remove heat, preventing the target from overheating, ensuring the stability of the target's performance, and allowing the sputtering process to continue. However, existing sputtering target cooling systems have the following problems: First, existing cooling chambers often use U-shaped water channels, which can easily lead to local stagnation zones. Since the flow rate of the coolant in the cooling chamber is closely related to the cooling effect, the presence of stagnation zones will reduce cooling efficiency and affect the cooling effect. Second, when the magnet is immersed in the coolant, the rust and corrosion residue produced by its corrosion cannot be smoothly discharged with the coolant and are prone to accumulate in the cooling chamber, causing blockage and affecting the normal operation of the cooling system. Summary of the Invention

[0006] The purpose of this invention is to solve the problems mentioned in the background art by providing a coating device for the surface of neodymium iron boron magnets.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A surface coating device for neodymium iron boron magnets includes a coating machine body. The coating machine body is equipped with a vacuum tank and a sealing cover. Multiple sputtering targets are arranged inside the vacuum tank. A rotating sample stage is arranged on the sealing cover. The sputtering target includes a target material, a target shell, and a pressure ring. The pressure ring presses and fixes the target material to the upper surface of the target shell. A shielding cover is sleeved on the outside of the pressure ring and the target shell. A flange seat is fixedly connected to the bottom of the target shell. The shielding cover is fixedly connected to the flange seat.

[0009] The target shell has a vacuum chamber inside, and a magnetic circuit module is installed in the vacuum chamber. A cooling chamber is arranged in the magnetic circuit module, and a guide water channel is set in the cooling chamber to divide the cooling chamber into an upper chamber and a lower chamber. The lower chamber has a water outlet. The guide water channel is a closed loop structure that extends downward in a spiral. A water-stopping boss is provided at the end of the channel. A water inlet is provided on the upstream side of the water-stopping boss, and a drainage channel is provided on the downstream side to connect to the lower chamber. The water inlet is located in the upper chamber. The magnetic circuit module includes a magnetic base that can move up and down to adjust the size of the upper chamber to adapt to different cooling requirements and to assist in the discharge of impurities in the cooling chamber.

[0010] As a further aspect of the present invention: the magnetic circuit module includes an inner magnet, an outer magnet, and a magnetic base. The bottom of the magnetic base is elastically connected to the bottom wall of the vacuum cavity by a spring. An installation groove is provided at the center of the upper surface of the magnetic base for installing the inner magnet. The outer magnet is coaxially arranged with the inner magnet and surrounds the outer side of the inner magnet.

[0011] As a further aspect of the present invention: the guide channel is fixedly connected to the magnetic base, and the central axis of the mounting groove is the spiral center;

[0012] The surface of the guide channel is inclined towards the spiral center, and the opening of the drainage channel is located on the side of the guide channel close to the installation groove.

[0013] As a further embodiment of the present invention: the water outlet is opened on the magnetic base, the water outlet is fixedly installed with the water outlet pipe, the top of the water outlet pipe is flush with the upper surface of the magnetic base, and the upper surface of the magnetic base is inclined towards the water outlet.

[0014] The water inlet is fixedly installed with a water inlet pipe, and the magnetic base is provided with a through hole at the water inlet position for the water inlet pipe to pass through. The top of the water inlet pipe is flush with the upper surface of the guide channel.

[0015] As a further aspect of the present invention: the target housing includes an upper housing and a lower housing, the upper housing and the lower housing are connected by a threaded seal, and together they form a vacuum cavity;

[0016] The inlet pipe and outlet pipe pass through the lower shell and flange seat, and are connected to the external water tank. Sealing bolts are fitted at the parts of the inlet pipe and outlet pipe that pass through the lower shell and flange seat, and the sealing bolts are fixedly connected to the lower shell and flange seat.

[0017] As a further aspect of the present invention: the external magnet is a ring magnet, or a magnet group composed of multiple magnets arranged in a ring array.

[0018] As a further aspect of the present invention: the portions of the water inlet pipe and water outlet pipe located within the vacuum cavity are provided with a section of elastic corrugated pipe at the corresponding spring position.

[0019] As a further aspect of the present invention: the inner wall of the target housing is provided with downward vortex protrusions at the corresponding positions of the cooling cavity, and the spiral direction of the vortex protrusions is consistent with the spiral direction of the guide channel.

[0020] As a further embodiment of the present invention: the pressure ring and the target housing are fixedly connected by threads;

[0021] Insulating pads are installed between the pressure ring and the shield, and between the target housing and the shield.

[0022] Compared with existing technologies, the advantages of this invention are:

[0023] The spring connection at the bottom of the magnetic base and the design of the flexible corrugated pipe section allow the magnetic circuit module to move up and down to adjust the size of the upper chamber. On the one hand, the cooling space of the upper chamber can be dynamically adjusted according to the heat load of the sputtering process. Under high heat load, the space can be increased to increase heat exchange and improve the cooling effect, while under low heat load, the space can be reduced to increase the coolant flow rate and optimize energy efficiency. On the other hand, by changing the size of the upper chamber, the flow state of the coolant can be flexibly controlled. When it is necessary to remove stagnant impurities, reducing the space can make the coolant generate a stronger impact force, pushing the impurities to move quickly towards the drain channel and be discharged. When there are many impurities, increasing the space can prevent impurities from clogging in the narrow space and ensure smooth impurity discharge. In addition, the spring and corrugated pipe themselves can also buffer vibration and impact, reduce wear, adapt to the slight displacement of the magnetic circuit module, ensure reliable cooling water circuit connection, and improve the overall durability of the equipment.

[0024] By employing a spirally extending closed-loop guide channel, combined with vortex protrusions on the inner wall of the target shell in the same direction of rotation, the coolant is guided to accelerate the coolant flow rate, effectively eliminating the local stagnation zone of the traditional loop channel. At the same time, it increases the heat contact area and improves the cooling efficiency. In addition, the spiral structure, drainage channel and inclined design of the guide channel solve the problem of accumulation and blockage of magnet corrosion products, ensuring that impurities are smoothly discharged with the coolant and guaranteeing the long-term stable operation of the cooling system. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the overall structure of the present invention from another perspective;

[0027] Figure 3 This is a schematic diagram of the external structure of the sputtering target of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure inside the sputtering target shield of the present invention;

[0029] Figure 5 This is a schematic diagram of the internal structure of the sputtering target of the present invention;

[0030] Figure 6 This is a schematic cross-sectional view of the sputtering target of the present invention;

[0031] Figure 7 This is a schematic diagram of the disassembled structure of the sputtering target of the present invention;

[0032] Figure 8 This is a schematic diagram of the installation structure of the water guide channel, magnetic base, water outlet pipe, and water inlet pipe of the present invention;

[0033] Figure 9 This is a schematic diagram of the installation structure of the water guide channel, magnetic base, and water inlet pipe of the present invention;

[0034] Figure 10 This is a schematic diagram of the installation structure of the guide channel and magnetic base of the present invention;

[0035] Figure 11 This is a schematic diagram of the vortex protrusion structure of the present invention.

[0036] In the diagram: 1. Coating machine body; 2. Vacuum tank; 3. Sealing cover; 4. Sputtering target; 5. Sample base; 6. Target material; 7. Target shell; 8. Pressure ring; 9. Shielding cover; 10. Flange seat; 11. Vacuum chamber; 12. Magnetic circuit module; 13. Cooling chamber; 14. Vortex protrusion; 15. Guide channel; 16. Upper chamber; 17. Lower chamber; 18. Water outlet; 19. Water-stopping protrusion; 20. Water inlet; 21. Drainage channel; 22. Inner magnet; 23. Outer magnet; 24. Magnetic base; 25. Spring; 26. Mounting groove; 27. Water outlet pipe; 28. Water inlet pipe; 29. ​​Through hole; 30. Upper shell; 31. Lower shell; 33. Sealing bolt. Detailed Implementation

[0037] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Reference Figures 1 to 11 A coating apparatus for neodymium iron boron magnets includes a coating machine body 1, which comprises a vacuum tank 2 and a sealing cover 3. The vacuum tank 2 provides the vacuum environment required for sputtering coating. The sealing cover 3 is rotatably mounted on the upper edge of the vacuum tank 2, and can seal the vacuum tank 2. Inside the vacuum tank 2, four sputtering targets 4 are installed. These sputtering targets 4 are key components for providing the target atoms required for sputtering. A rotating sample stage 5 is provided on the sealing cover 3. The neodymium iron boron magnet to be coated is placed on the sample stage 5. The rotation of the sample stage 5 can ensure uniform coating on the magnet surface.

[0039] The sputtering target 4 consists of a target material 6, a target housing 7, and a pressure ring 8. The pressure ring 8 is fixedly connected to the target housing 7 by threads, thereby pressing and fixing the target material 6 to the upper surface of the target housing 7. This threaded connection method not only ensures the stability of the target material 6 installation, but also facilitates the replacement of the target material 6. A shielding cover 9 is fitted on the outside of the pressure ring 8 and the target housing 7. At the same time, insulating pads are installed between the pressure ring 8 and the shielding cover 9, and between the target housing 7 and the shielding cover 9. The installation of insulating pads can effectively avoid unnecessary electrical conductivity during sputtering and ensure the safe operation of the device. The shielding cover 9 can prevent sputtered particles from contaminating other components inside the vacuum tank 2. A flange seat 10 is fixedly connected to the bottom of the target housing 7. The flange seat 10 is fixedly installed at the bottom of the vacuum tank 2 and serves to support and fix the sputtering target 4.

[0040] Reference Figures 3 to 11The target housing 7 includes an upper housing 30 and a lower housing 31, which are connected by a threaded seal and together form a vacuum chamber 11. This split-type threaded seal structure not only ensures the sealing performance of the vacuum chamber 11, but also facilitates disassembly and maintenance. When it is necessary to repair or replace the internal components of the vacuum chamber 11, it is only necessary to unscrew the upper housing 30 and the lower housing 31, which improves maintenance efficiency.

[0041] A magnetic circuit module 12 is installed inside the vacuum chamber 11. The magnetic circuit module 12 includes an inner magnet 22, an outer magnet 23, and a magnetic base 24. The bottom of the magnetic base 24 is elastically connected to the bottom wall of the vacuum chamber 11 by a spring 25. This spring connection design can buffer vibration and impact, reduce wear, and accommodate the slight displacement of the magnetic circuit module 12. A mounting groove 26 is provided at the center of the upper surface of the magnetic base 24 for mounting the inner magnet 22. The outer magnet 23 is coaxially arranged with the inner magnet 22 and surrounds the outer side of the inner magnet 22. In this embodiment, the outer magnet 23 is a ring magnet. The inner magnet 22 and the outer magnet 23 work together to generate a magnetic field. This magnetic field can confine the plasma and improve sputtering efficiency and thin film quality.

[0042] A cooling chamber 13 is arranged inside the magnetic circuit module 12. The top wall of the upper shell 30 has a downward vortex protrusion 14 at the corresponding position of the cooling chamber 13. A guide water channel 15 is arranged in the cooling chamber 13. The guide water channel 15 is fixedly connected to the magnetic base 24. With the central axis of the mounting groove 26 as the spiral center, the guide water channel 15 divides the cooling chamber 13 into an upper chamber 16 and a lower chamber 17. The whole structure is a closed loop structure extending downward spirally. A water-stopping boss 19 is provided at the end of the connection. A water inlet 20 is provided on the upstream side of the water-stopping boss 19. A drainage channel 21 is opened on the downstream side to connect to the lower chamber 17. The water inlet 20 is located in the upper chamber 16.

[0043] The vortex protrusion 14 rotates in the same direction as the spiral direction of the guide channel 15, together guiding the coolant and accelerating the coolant flow rate. This effectively eliminates the local stagnation zone of the traditional loop channel, while also increasing the heat contact area and improving cooling efficiency.

[0044] The surface of the guide channel 15 is inclined towards the spiral center, and the opening of the drain channel 21 is located on the side of the guide channel 15 close to the installation groove 26. This structural design allows impurities such as water rust and corrosion slag generated by the corrosion of the magnet to flow smoothly to the drain channel 21 with the coolant, solving the problem of impurity accumulation and blockage, and ensuring the long-term stable operation of the cooling system.

[0045] It should be noted that there are two ways to install the sputtering target 4 of the coating machine body 1. The first way is to install the sputtering target 4 inside the vacuum tank 2 and the sample base 5 on the sealing cover 3. The second way is to install the sample base 5 inside the vacuum tank 2 and the sputtering target 4 on the sealing cover 3. This application adopts the first installation method, which sets the sputtering target 4 inside the vacuum tank 2.

[0046] This installation method ensures that the upper chamber 16 is always above the lower chamber 17. From the perspective of cooling efficiency, the water will naturally flow downward under its own weight, which works synergistically with the spiral downward structure of the guide channel 15 to further accelerate the flow rate of the coolant. The original design of the vortex protrusion 14 and the spiral direction of the guide channel 15 were already able to accelerate the flow rate. The superposition of the water's own weight increases the flow rate of the coolant through the cooling chamber 13 per unit time, resulting in more thorough heat exchange with the target material 6 and the magnetic circuit module 12.

[0047] Regarding impurity discharge, the upper chamber 16 is located above the lower chamber 17, and the water flows downwards due to its own weight. This, combined with the inclined surface of the guide channel 15 towards the spiral center and the positional design of the drainage channel 21, forms a more optimized impurity discharge path. Impurities generated by the corrosion of the magnet tend to settle downwards under the influence of gravity, while the downward flow driven by the weight of the water will cause the impurities to move towards the drainage channel 21 more quickly. This reduces the possibility of impurities remaining on the surface of the guide channel 15, further reducing the risk of cooling system blockage and ensuring the long-term stable operation of the cooling system.

[0048] It should be noted that the spring 25 at the bottom of the magnetic base 24 not only acts as a buffer but also pushes the magnetic base 24 up and down, thereby adjusting the size of the upper chamber 16. The advantage of this design is that when the target material 6 generates a lot of heat during sputtering, the space of the upper chamber 16 can be increased by adjusting the position of the magnetic base 24, allowing more coolant to enter the upper chamber 16, increasing the heat exchange and improving the cooling effect; while under conditions of less heat, reducing the space of the upper chamber 16 can increase the flow rate of the coolant and reduce unnecessary energy consumption.

[0049] This adjustment function also plays a positive role in expelling impurities. When impurities are trapped, the space of the upper chamber 16 can be reduced to allow the coolant to form a stronger impact force in the limited space, pushing the impurities to move quickly toward the drain channel 21 and be discharged. When there are many impurities, the space of the upper chamber 16 can be appropriately increased to accommodate more coolant carrying impurities, avoid impurities from clogging in the narrow space, and ensure the smooth discharge of impurities.

[0050] This application provides two methods for adjusting the magnetic base 24 and spring 25 to control the size of the upper chamber 16: First, an electromagnet is set below the spring 25, and the magnetic force is adjusted by changing the current intensity of the electromagnet, thereby attracting the magnetic base 24 to move up and down. This method has a rapid response and can achieve fine adjustment. Second, by adjusting the water inlet flow of the water inlet pipe 28 or the water outlet flow of the water outlet pipe 27, the water pressure difference in the cooling chamber is used to drive the magnetic base 24 to move up and down. This method relies on the existing water circuit system, does not require additional complex structures, and the adjustment process is coordinated with the cooling process, making it easy to operate and highly stable.

[0051] Furthermore, the structure of dividing the cooling chamber 13 into an upper chamber 16 and a lower chamber 17 allows the coolant to first pass through the upper chamber 16 and fully exchange heat with components such as the magnetic circuit module 12 before entering the lower chamber 17 for discharge. This forms an orderly water flow path, avoiding chaotic flow of the coolant within the cooling chamber 13 and ensuring high efficiency in heat exchange. At the same time, the placement of the upper chamber 16 above the lower chamber 17 allows the coolant to complete the entire process from entry to discharge more smoothly under the influence of gravity, reducing water flow resistance, further improving the operating efficiency of the cooling system, and also reducing the probability of problems such as localized overheating caused by poor water flow.

[0052] Reference Figures 5 to 11 The lower chamber 17 has a water outlet 18, which is located on the magnetic base 24. A water outlet pipe 27 is fixedly installed on the water outlet 18. The top of the water outlet pipe 27 is flush with the upper surface of the magnetic base 24. The upper surface of the magnetic base 24 is inclined towards the water outlet 18. This inclined design facilitates the collection of coolant into the water outlet 18 for discharge. A water inlet pipe 28 is fixedly installed on the water inlet 20. The magnetic base 24 has a through hole 29 at the position of the water inlet 20 for the water inlet pipe 28 to pass through. The top of the water inlet pipe 28 is flush with the upper surface of the guide channel 15 to ensure smooth water intake.

[0053] The inlet pipe 28 and outlet pipe 27 pass through the lower housing 31 and flange seat 10, and connect to the external water tank to provide a continuous coolant for the cooling system. Sealing bolts 33 are fitted at the parts of the inlet pipe 28 and outlet pipe 27 that pass through the lower housing 31 and flange seat 10. The sealing bolts 33 are fixed to the lower housing 31 and flange seat 10, which further ensures the sealing of the vacuum chamber 11.

[0054] In addition, the portions of the water inlet pipe 28 and water outlet pipe 27 located inside the vacuum chamber 11 are provided with a section of elastic corrugated pipe at the corresponding position of the spring 25. This elastic corrugated pipe section cooperates with the spring 25 at the bottom of the magnetic base 24 to better buffer vibration, adapt to the displacement of the magnetic circuit module 12, ensure reliable connection of the cooling water circuit, and significantly improve the overall durability of the equipment.

[0055] To further clarify, the aforementioned fixed connection should be interpreted broadly unless otherwise explicitly specified and limited. For example, it may be welding, gluing, or integral molding, or other conventional methods well known to those skilled in the art.

[0056] The steps involved in this application are as follows:

[0057] S1: Place the neodymium iron boron magnet to be coated on the rotating sample stage 5, close the sealing cover 3 to form a closed space in the vacuum tank 2, start the vacuum system to evacuate the inside of the vacuum tank 2 until the vacuum environment required for sputtering coating is achieved.

[0058] S2: A suitable amount of inert gas (such as argon) is precisely introduced into the vacuum tank 2 through the gas control system to provide a suitable gas atmosphere for the sputtering process;

[0059] S3: Start the power supply to provide the sputtering target 4 with the appropriate DC, RF or pulse power, so that the sputtering target 4 generates plasma, and high-energy particles begin to bombard the target material 6, and the target material atoms are sputtered out.

[0060] S4: Activate the rotation function of the rotating sample stage 5, so that the NdFeB magnet to be coated rotates with the sample stage 5, ensuring that the magnet surface can uniformly receive the sputtered target atoms and form a uniform thin film.

[0061] S5: Start the cooling system. The coolant in the external water tank enters the guide channel 15 through the water inlet pipe 28. Under the combined action of the spiral structure, the vortex protrusion 14 and the weight of the water flow, it flows rapidly and absorbs the heat generated by the target material 6 and the magnetic circuit module 12.

[0062] S6: After absorbing heat, the coolant enters the lower chamber 17 through the drain channel 21, and then flows back to the external water tank through the water outlet pipe 27 to achieve the circulation cooling of the coolant and continuously cool the sputtering target 4.

[0063] S7: During the coating process, the inner magnet 22 and the outer magnet 23 of the magnetic circuit module 12 work together to generate a magnetic field, which confines the plasma and improves sputtering efficiency and film quality.

[0064] S8: Once the coating on the magnet surface reaches the required thickness, turn off the power system, stop the sputtering process, and stop introducing inert gas into the vacuum tank 2.

[0065] S9: Turn off the cooling system and stop the coolant circulation. After the air pressure in the vacuum tank 2 returns to normal pressure, open the sealing cover 3 and take out the coated neodymium iron boron magnet.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A coating apparatus for the surface of a neodymium iron boron magnet, comprising a coating machine body (1), characterized in that, The coating machine body (1) is provided with a vacuum tank (2) and a sealing cover (3). Multiple sputtering targets (4) are set inside the vacuum tank (2). A rotating sample base (5) is set on the sealing cover (3). The sputtering target (4) includes a target material (6), a target shell (7) and a pressure ring (8). The pressure ring (8) presses and fixes the target material (6) to the upper surface of the target shell (7). A shielding cover (9) is sleeved on the outside of the pressure ring (8) and the target shell (7). A flange seat (10) is fixedly connected to the bottom of the target shell (7). The shielding cover (9) is fixedly connected to the flange seat (10). The target housing (7) is provided with a vacuum chamber (11), a magnetic circuit module (12) is installed in the vacuum chamber (11), a cooling chamber (13) is arranged in the magnetic circuit module (12), a guide water channel (15) is provided in the cooling chamber (13) to divide the cooling chamber (13) into an upper chamber (16) and a lower chamber (17), an outlet (18) is opened in the lower chamber (17), the guide water channel (15) is a closed loop structure extending downward in a spiral, and a water-stopping boss (19) is provided at the end of its connection. An inlet (20) is provided on the upstream side of the water-stopping boss (19), and a drainage channel (21) is opened on the downstream side to connect to the lower chamber (17). The inlet (20) is located in the upper chamber (16). The magnetic circuit module (12) includes a magnetic base (24) that can move up and down to adjust the size of the upper chamber (16) to adapt to different working conditions and to assist in the discharge of impurities in the cooling chamber (13). The magnetic circuit module (12) includes an inner magnet (22), an outer magnet (23) and a magnetic base (24). The bottom of the magnetic base (24) is elastically connected to the bottom wall of the vacuum chamber (11) by a spring (25). An installation groove (26) is provided at the center of the upper surface of the magnetic base (24) for installing the inner magnet (22). The outer magnet (23) is coaxially arranged with the inner magnet (22) and surrounds the outer side of the inner magnet (22). The guide channel (15) is fixedly connected to the magnetic base (24), and the central axis of the mounting groove (26) is the spiral center; The surface of the guide channel (15) is inclined towards the spiral center, and the opening of the drainage channel (21) is located on the side of the guide channel (15) close to the mounting groove (26). The water outlet (18) is opened on the magnetic base (24), and the water outlet (18) is fixedly installed with the water outlet pipe (27). The top of the water outlet pipe (27) is flush with the upper surface of the magnetic base (24), and the upper surface of the magnetic base (24) is inclined towards the water outlet (18). The water inlet (20) is fixedly installed with the water inlet pipe (28). The magnetic base (24) is provided with a through hole (29) at the position of the water inlet (20) for the water inlet pipe (28) to pass through. The top of the water inlet pipe (28) is flush with the upper surface of the guide channel (15).

2. The neodymium iron boron magnet surface coating device according to claim 1, characterized in that, The target housing (7) includes an upper housing (30) and a lower housing (31), which are connected by a threaded seal and together form a vacuum chamber (11). The inlet pipe (28) and outlet pipe (27) pass through the lower housing (31) and flange seat (10) and are connected to the external water tank. The inlet pipe (28) and outlet pipe (27) are fitted with sealing bolts (33) at the parts where they pass through the lower housing (31) and flange seat (10). The sealing bolts (33) are fixedly connected to the lower housing (31) and flange seat (10).

3. The neodymium iron boron magnet surface coating device according to claim 2, characterized in that, The external magnet (23) is a ring magnet or a magnet group composed of multiple magnets arranged in a ring array.

4. The neodymium iron boron magnet surface coating device according to claim 3, characterized in that, The portion of the inlet pipe (28) and outlet pipe (27) located inside the vacuum chamber (11) has an elastic corrugated pipe section at the corresponding spring (25) position.

5. The neodymium iron boron magnet surface coating device according to claim 4, characterized in that, The inner wall of the target housing (7) has a downward vortex protrusion (14) at the corresponding position of the cooling cavity (13), and the direction of the vortex protrusion (14) is consistent with the spiral direction of the guide channel (15).

6. The neodymium iron boron magnet surface coating device according to claim 5, characterized in that, The pressure ring (8) is fixedly connected to the target housing (7) by threads; Insulating pads are installed between the pressure ring (8) and the shield (9), and between the target housing (7) and the shield (9).

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