Liquid cooling microchannel powder metallurgy fabrication method

Abstract

This invention discloses a liquid-cooled microchannel powder metallurgy fabrication method, belonging to the field of radiator manufacturing technology. The invention employs a pre-stamping process to prepare copper heat dissipation fins, combined with customized spherical high-purity copper powder and composite polymer bonding particles. A uniform mixture is prepared through segmented high and low temperature and high and low speed stirring. This is then combined with metal powder injection molding, oxalic acid degreasing, nitrogen atmosphere constant temperature anti-oxidation pretreatment, and high-vacuum sintering processes, along with controllable molding and sintering parameters, to fabricate a copper liquid-cooled microchannel radiator. This invention effectively solves the problems of difficult molding of thin-walled pure copper microchannel structures, poor dimensional consistency, and susceptibility to defects and springback. It significantly improves the extrusion of copper materials in microchannel structures, the smoothness of the inner wall, and the overall density, strengthens the bond strength between the fins and the substrate, and eliminates leakage, corrosion, and heat dissipation attenuation under long-term liquid cooling cycles. The product yield is high, and the stability is excellent.

Description

Technical Field

[0001] This invention relates to the field of radiator processing technology, specifically to a liquid-cooled microchannel powder metallurgy fabrication method. Background Technology

[0002] With the rapid iteration and upgrading of 5G communication, big data servers, new energy storage, and high-power semiconductor equipment, the integration and operating power of electronic devices are continuously and significantly increasing, and the heat density per unit area of ​​equipment is constantly increasing. Traditional air cooling methods have low heat dissipation efficiency and poor heat dissipation uniformity, and can no longer meet the continuous heat dissipation requirements of high-power electronic devices. Liquid cooling has the advantages of high heat exchange efficiency, low operating noise, uniform heat dissipation, and strong adaptability, and has now become the mainstream heat dissipation solution for high-end high-power electronic devices.

[0003] Liquid-cooled microchannel radiators are the core functional components of liquid cooling systems. The density of their internal microchannel structure, surface flatness, dimensional accuracy, and the bonding strength between the heat dissipation fins and the substrate directly determine the heat exchange efficiency, sealing performance, and overall service life of the radiator, which is crucial for ensuring the stable operation of high-power equipment.

[0004] Currently, the mainstream fabrication processes for liquid-cooled microchannel devices in the industry include mechanical milling, die casting, and conventional powder metallurgy. Among these, mechanical milling suffers from high processing losses, low material utilization, and high processing costs, and it is difficult to form fine and complex thin-walled microchannel structures, resulting in significant structural limitations. Die casting produces products with high internal porosity and poor overall density, making it easy for the liquid cooling medium to leak through the pores, leading to substandard sealing performance. Conventional powder metallurgy suffers from defects such as uneven powder mixing, incomplete degreasing of the preform, easy oxidation during sintering, and a large amount of residual impurities in the preform, ultimately resulting in rough inner walls of the microchannels, loose bonding between the fins and the substrate, and weak oxidation resistance. Under long-term liquid cooling cycle conditions, the finished products are prone to problems such as internal wall corrosion, medium leakage, and continuous decline in heat dissipation efficiency, resulting in poor product yield and operational stability, making them unsuitable for the long-term, high-intensity heat dissipation requirements of high-end, high-power equipment.

[0005] In addition, most existing microchannel liquid cooling radiators on the market are manufactured using aluminum extrusion molding processes, making mass production of copper microchannel radiators extremely difficult. While aluminum has good plasticity and is easy to extrude, allowing for the adaptation to various microchannel structures, copper has far superior thermal conductivity and heat dissipation performance. However, copper's high hardness, high resistance to plastic deformation, and sluggish material flow make it prone to defects during extrusion molding, such as insufficient filling, channel wall tearing, edge material shortages, and profile twisting and springback. This results in poor microchannel dimensional consistency and a high product scrap rate. Summary of the Invention

[0006] The purpose of this invention is to provide a liquid-cooled microchannel powder metallurgy manufacturing method to solve the technical problems in the prior art, such as poor heat dissipation performance of aluminum extrusion radiators, numerous defects in copper radiator extrusion molding, low density, easy leakage and corrosion, low yield of finished products, high production cost, and inability to mass produce.

[0007] The technical problem to be solved by this invention is achieved through the following technical solution: This application provides a liquid-cooled microchannel powder metallurgy fabrication method, the technical solution of which is as follows: Includes the following steps: Step S1: Prepare combined heat dissipation fins or single heat dissipation fins using a pre-stamping process; Step S2: Mix and stir the copper powder with the polymer adhesive particles to form a mixture; Step S3: Place the heat dissipation fins into the mold, and use metal powder injection molding process to inject the heated mixture into the mold, and cool it to form a molded blank; Step S4: Degrease the formed blank; Step S5: Vacuum sinter the degreased green body; Step S6: Perform shaping, machining, and surface treatment in sequence, and finally inspect and package to obtain the finished liquid-cooled microchannel product.

[0008] Furthermore, this application also proposes that in step S1, the heat dissipation fins are made of copper.

[0009] Furthermore, this application also proposes that the parameters of the copper powder used in step S2 are: particle size distribution 10–45 μm, purity ≥99.5%, oxygen content <1500 ppm, loose density 4.5–5.5 g / cm³, flowability 10 s / (40–60 g), and spherical particle shape.

[0010] Furthermore, this application also proposes that in step S4, the degreasing process uses oxalic acid as a degreasing auxiliary material, with an oxalic acid concentration of 70–90%, a degreasing temperature of 110–130°C, and a degreasing time of 6–10 hours.

[0011] Furthermore, this application also proposes that, in step S5, vacuum sintering is completed in a vacuum sintering furnace with a vacuum degree ≥10. - ³Pa, sintering temperature 900–1070℃, sintering time 12–26 hours.

[0012] Furthermore, this application also proposes that in step S2, the polymer adhesive particles are compounded from polyethylene, polyoxymethylene, paraffin and stearic acid in a mass ratio of 2:3:4:1, and the mass ratio of copper powder to polymer adhesive particles is 88:12–92:8. The mixing process of copper powder and polymer bonding particles is as follows: first, stir at a low speed of 300–400 r / min for 15–25 min at room temperature, then heat to 85–95℃ and stir at a high speed of 800–1000 r / min for 40–60 min to obtain a uniform mixture.

[0013] Furthermore, this application also proposes that, in step S3, the metal powder injection molding process parameters are: material heating temperature 160–185℃, mold preheating temperature 70–90℃, injection pressure 80–110MPa, holding pressure 50–70MPa, holding time 8–15s, and molding cooling rate 3–5℃ / min.

[0014] Furthermore, this application proposes to add a constant temperature anti-oxidation pretreatment step between step S4 degreasing and step S5 vacuum sintering; the degreased green body is placed in an inert nitrogen atmosphere and heated to 200–260°C at a heating rate of 5–8°C / min, and kept at a constant temperature for 2–4 hours to remove residual trace amounts of organic acids and water vapor inside the green body.

[0015] Compared with the prior art, the present invention has the following significant advantages: 1. This invention adopts a composite process of pre-stamped fin forming combined with metal powder injection molding and vacuum sintering, replacing the traditional mechanical milling, die casting, ordinary sintering and copper extrusion processes. It effectively and thoroughly solves the forming defects such as insufficient filling, inner wall scratches, missing material at the edges and corners, and twisting and springback in the thin-walled structure of pure copper microchannels, greatly improves the dimensional accuracy and consistency of microchannels, significantly reduces the product scrap rate, and at the same time improves material utilization and reduces production costs.

[0016] 2. This invention uses spherical copper powder and a compound polymer bonding system, combined with a segmented stirring process, to achieve extremely uniform mixing of the powder and eliminate the problem of powder agglomeration; combined with oxalic acid degreasing, nitrogen pretreatment and high vacuum sintering process, it thoroughly removes impurities, moisture and residual additives from the blank, eliminates defects such as porosity, oxidation and leakage in the product, and greatly improves the density and sealing performance of the radiator structure.

[0017] 3. An additional nitrogen constant temperature anti-oxidation pretreatment process is added to effectively eliminate trace residual impurities inside the billet, enhance the structural stability of the billet, significantly improve the bonding strength between the heat dissipation fins and the substrate, avoid problems such as structural loosening, heat dissipation attenuation, corrosion and leakage under long-term liquid cooling cycle conditions, effectively extend the product service life, and improve the yield and operational stability of finished products.

[0018] 4. The heat sink prepared by this invention is made of pure copper material, and its thermal conductivity and heat dissipation performance is far superior to that of traditional aluminum heat sinks. It has a higher heat dissipation limit and can fully meet the long-term high-intensity heat dissipation requirements of high-end high-power electronic devices such as 5G communication, big data servers, new energy storage, and high-power semiconductors. It has extremely strong industrial adaptability. Attached Figure Description

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] Figure 1 This is a schematic flowchart of a liquid-cooled microchannel powder metallurgy fabrication method according to the present invention. Figure 2 This is a schematic diagram of step S3 in the liquid-cooled microchannel powder metallurgy fabrication method of the present invention.

[0021] Figure 3 This is a schematic diagram of the structure of the preform for a liquid-cooled microchannel powder metallurgy fabrication method according to the present invention.

[0022] Reference numerals: 1. Heat dissipation fins; 2. Mixture; 3. Mold. Detailed Implementation

[0023] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] Traditional manufacturing processes for liquid-cooled microchannel heat sinks, such as mechanical milling, die casting, and conventional powder sintering, have significant limitations.

[0026] Mechanical milling is costly and difficult to form fine microchannel structures; die-cast products have high porosity, poor sealing performance, and are prone to leakage; ordinary powder metallurgy faces problems such as uneven powder mixing, incomplete degreasing, easy oxidation during sintering, and residual impurities, resulting in rough inner walls of microchannels, loose bonding between fins and the substrate, weak oxidation resistance, and difficulties in extruding copper materials in metal extrusion molding processes. These defects together result in low product yield, poor operational stability, and inability to meet the long-term, high-intensity heat dissipation requirements of high-end, high-power equipment.

[0027] like Figure 1 -like Figure 3 As shown, this application proposes a powder metallurgy method for manufacturing liquid-cooled microchannels, including: preparing combined heat dissipation fins 1 or single heat dissipation fins 1 using a pre-stamping process; mixing copper powder with polymer adhesive particles to form a mixture 2; placing the heat dissipation fins 1 into a mold 3; injecting the mixture 2 into the mold 3 after heating using a metal powder injection molding process; cooling to form a molded blank; degreasing the molded blank; vacuum sintering the degreased blank; and sequentially performing shaping, machining, and surface treatment, finally inspecting and packaging to obtain the finished liquid-cooled microchannel.

[0028] For ease of understanding, the following explains some key terms in this embodiment: Liquid-cooled microchannel powder metallurgy fabrication method: This method is a process for manufacturing liquid-cooled heat sinks with microchannel structures using powder metallurgy technology. Its core lies in mixing metal powder with binder and then forming a complex-shaped blank through injection molding. The binder is then removed and the metal is densified through degreasing and sintering, ultimately obtaining a high-performance liquid-cooled heat sink component.

[0029] Pre-stamping process: This process refers to pre-fabricating the shape and structure of the heat dissipation fins 1 through stamping before metal powder injection molding. This aims to ensure the dimensional accuracy and structural integrity of the fins, providing a stable foundation for subsequent bonding with the substrate.

[0030] Combined heat dissipation fins 1 or single heat dissipation fins 1: Heat dissipation fins 1 are key components in liquid-cooled radiators used to increase the heat exchange area. Combined heat dissipation fins 1 refer to fins assembled from multiple independent fins, while single heat dissipation fins 1 refer to independent fins formed in one piece.

[0031] Copper powder: As the main metal substrate in this method, copper powder is the raw material for constructing the metal framework of the liquid-cooled microchannel heat sink. Its excellent thermal conductivity is the foundation for achieving efficient heat dissipation.

[0032] Polymer binder particles: These particles act as a temporary binder during metal powder injection molding. When mixed with copper powder, they impart good flowability and plasticity to the mixture, enabling it to be injection molded into complex shapes. These binders are removed during the subsequent debinding process.

[0033] Metal powder injection molding: This process involves mixing metal powder with a polymer binder, heating and plasticizing the mixture 2 using an injection molding machine, and then injecting it into the cavity of a mold 3, where it cools and solidifies to form a near-net-shape preform. Its advantage lies in its ability to efficiently and precisely manufacture metal parts with complex geometries and intricate structures.

[0034] Preform: refers to a preliminary molded part that has not yet undergone debinding and sintering treatment, and is composed of metal powder and polymer binder after metal powder injection molding.

[0035] Degreasing treatment: This treatment aims to remove polymer binder particles from the molded preform by heating or solvent action, creating a pure metal skeleton for the subsequent sintering process.

[0036] Vacuum sintering: This sintering process is carried out in a vacuum environment. High temperatures cause diffusion and bonding between metal powder particles, thereby densifying the green body and forming a final product with the desired mechanical and physical properties. The vacuum environment helps prevent metal oxidation at high temperatures and promotes the complete removal of binders.

[0037] Shaping, machining, and surface treatment: these are the finishing steps performed on the product after sintering. Shaping is used to correct the macroscopic shape and size of the product; machining is used to achieve high-precision dimensions and surface requirements; and surface treatment is used to improve the product's corrosion resistance, aesthetics, or functionality.

[0038] This application provides a liquid-cooled microchannel powder metallurgy fabrication method, the specific implementation of which is as follows: First, in step S1, a pre-stamping process is used to prepare either the combined heat dissipation fins 1 or a single heat dissipation fin 1. This pre-stamping process can be implemented in various ways. For example, traditional mechanical stamping equipment can be used to cold stamp the metal sheet using a mold 3 to obtain the heat dissipation fins 1 of the required shape and size. Alternatively, automated stamping can be performed using CNC stamping equipment to improve production efficiency and precision. These fins will then be bonded to the substrate in the subsequent injection molding process to form a liquid-cooled microchannel structure.

[0039] Secondly, in step S2, copper powder and polymer binder particles are mixed and stirred to form mixture 2. The choice of copper powder, as the main metal substrate, affects the performance of the final product. For example, copper powder with different particle size ranges, such as copper powder with an average particle size of 20 micrometers, can be selected to meet different molding and sintering requirements. The polymer binder particles act as a temporary binder, giving mixture 2 good flowability. The mixing process can be carried out in various ways. For example, a simple roller mixer can be used for initial mixing to ensure a uniform distribution of copper powder and binder particles. Alternatively, a twin-screw extruder can be used for mixing to obtain a more uniform and denser mixture 2.

[0040] like Figure 2 -like Figure 3 As shown, in step S3, the heat dissipation fins 1 are placed into the mold 3, and the mixture 2 is injected into the mold 3 after heating using a metal powder injection molding process, followed by cooling to form a preform. Metal powder injection molding is a highly efficient near-net-shape forming technology.

[0041] Specifically, the mixture 2 can be heated to a molten state in the barrel of an injection molding machine, and then injected under high pressure into the cavity of a mold 3 pre-placed with heat dissipation fins 1. The temperature of the mold cavity 3 can be set according to the characteristics of the mixture 2, for example, it can be set to room temperature or slightly above room temperature. After injection, the mixture 2 cools and solidifies within the mold 3, forming a preform with a microchannel structure containing heat dissipation fins 1.

[0042] Subsequently, in step S4, the formed preform undergoes a degreasing treatment. The purpose of the degreasing treatment is to remove the polymeric adhesive particles from the formed preform, leaving a pure metal skeleton. This treatment can be carried out in various ways. For example, thermal degreasing can be used, placing the preform in an inert or reducing atmosphere and slowly heating it to decompose and volatilize the adhesive. Alternatively, solvent degreasing can be used, immersing the preform in a suitable organic solvent to dissolve and remove the adhesive from the preform.

[0043] Further, in step S5, the degreased billet is vacuum sintered. Vacuum sintering is a crucial step in densifying the metal powder. The degreased billet is placed in a vacuum sintering furnace, which is evacuated to a vacuum state to prevent the metal from oxidizing at high temperatures. The sintering temperature and time can be adjusted according to the characteristics of the copper powder and the desired degree of densification. For example, the sintering temperature can be set below the melting point of copper, and prolonged holding at that temperature promotes diffusion and bonding between powder particles, thereby obtaining a high-density liquid-cooled microchannel structure.

[0044] Finally, in step S6, shaping, machining, and surface treatment are performed sequentially, culminating in the final inspection and packaging of the liquid-cooled microchannel finished product. The sintered product may exhibit slight deformation or dimensional deviations, necessitating shaping to correct its form. Machining steps can be used to refine critical dimensions, such as machining the inlet and outlet of the microchannel to ensure smooth fluid flow. Surface treatment may include polishing, cleaning, or passivation to improve the product's surface quality and corrosion resistance. Finally, the finished product undergoes comprehensive inspection, including dimensional checks, sealing tests, and performance tests, and is packaged after passing these tests.

[0045] This application effectively solves the problems of difficult molding, poor density, low bonding strength, and easy oxidation in traditional liquid-cooled microchannel fabrication by integrating key processes such as pre-stamping, metal powder injection molding, debinding, and vacuum sintering. As a result, it enables precise molding of complex microchannel structures, improves the bonding strength between the heat dissipation fins 1 and the substrate, ensures the internal density of the product, and significantly enhances oxidation resistance, thereby obtaining a high-quality, long-life liquid-cooled microchannel heat sink to meet the stable heat dissipation requirements of high-end, high-power electronic devices.

[0046] In some of the solutions described above in this application, heat dissipation fins 1 are proposed to improve heat dissipation efficiency. However, in the process of implementation, the use of copper material may lead to molding defects such as insufficient filling, inner wall scratches, missing material at the edges or corners, or profile twisting and springback, which affect the compactness and bonding strength of the microchannel structure, thereby reducing product yield and long-term operational stability.

[0047] In this regard, this application further proposes that, in step S1, the heat dissipation fin 1 is made of copper.

[0048] Specifically, copper material refers to a metallic material with copper as its main element, possessing excellent thermal and electrical conductivity. Its high thermal conductivity makes it an ideal choice for heat dissipation applications. One implementation method is that the heat dissipation fins 1 can be pre-formed from pure copper (such as T2 copper) through methods such as stamping, etching, or precision machining. Another implementation method is that the heat dissipation fins 1 can be prepared from copper alloys (such as chromium zirconium copper, dispersion-strengthened copper, etc.) through similar processes, to maintain good thermal conductivity while also considering higher strength or corrosion resistance. The selection of copper material aims to fundamentally improve the thermal conductivity of the heat sink to meet the heat dissipation requirements of high-power electronic devices. Simultaneously, combined with subsequent powder metallurgy processes, the forming difficulties encountered in traditional copper material processing can be avoided.

[0049] Through the above technical solution, this application fully utilizes the excellent thermal conductivity of copper, significantly improving the overall heat exchange efficiency of the liquid-cooled microchannel radiator. Simultaneously, the combination of the copper heat dissipation fins 1 with powder metallurgy manufacturing effectively avoids molding defects such as insufficient filling, inner wall scratches, missing material at edges, or profile twisting and springback caused by the high hardness and large plastic deformation resistance of traditional copper materials during mechanical milling or extrusion molding. This combination ensures the compactness of the microchannel structure, surface flatness, and high bonding strength between the heat dissipation fins 1 and the substrate, thereby avoiding problems such as liquid cooling medium leakage and inner wall corrosion. This significantly improves the product's yield, long-term operational stability, and service life, enabling it to better meet the long-term, high-intensity heat dissipation requirements of high-end, high-power equipment.

[0050] In some of the above-mentioned solutions in this application, copper powder parameters are proposed to ensure the quality of the mixture 2. However, if the particle size distribution, purity, oxygen content, loose density, flowability and particle shape of the copper powder are not appropriate, it will lead to uneven mixing of the powder, easy oxidation during sintering, and residual impurities in the blank, which will affect the smoothness of the inner wall of the microchannel, dimensional accuracy and bonding strength between the heat dissipation fins 1 and the substrate, ultimately resulting in low heat exchange efficiency, poor sealing and shortened service life of the liquid-cooled microchannel finished product.

[0051] In this regard, this application further proposes that the parameters of the copper powder used in step S2 are as follows: particle size distribution 10–45 μm, purity ≥99.5%, oxygen content <1500 ppm, loose density 4.5–5.5 g / cm³, flowability 10 s / (40–60 g), and spherical particle shape.

[0052] Particle size distribution refers to the statistical distribution of powder particle sizes, which directly affects the powder's bulk density, flowability, and shrinkage behavior during sintering. Particle size distribution can be controlled through various powder preparation methods (such as atomization, electrolysis, and reduction) and measured using techniques such as sieving, sedimentation, and laser diffraction. In practical applications, in addition to the range defined in this application, a wider or narrower particle size range can be selected based on the specific molding process and the performance requirements of the final product. For example, for products requiring higher density, finer powders may be chosen; for products with higher flowability requirements, powders with a more concentrated particle size distribution may be selected.

[0053] Purity refers to the content of the main metallic element in a metal powder. High purity means a low content of impurity elements. The presence of impurity elements affects the sintering activity, mechanical properties, and electrical and thermal conductivity of the powder. Purity is usually detected by chemical analysis methods (such as ICP-OES, atomic absorption spectroscopy, etc.). In the powder preparation process, the purity of the powder can be improved by selecting high-purity raw materials and optimizing the preparation process (such as vacuum melting, refining, etc.). In addition to the purity specified in this application, depending on the application scenario, for example, structural components with less stringent requirements for electrical and thermal conductivity may allow for slightly lower purity; while for fields such as semiconductor packaging with extremely high purity requirements, a purity of 99.99% or even higher may be required.

[0054] Oxygen content refers to the mass fraction of oxygen in metal powder, present in the form of oxides or adsorbed oxygen. Oxygen is one of the main harmful impurities in the sintering process of copper powder. Excessive oxygen content can lead to poor sintering, decreased mechanical properties, and affect electrical and thermal conductivity. Oxygen content is usually determined by inert gas melting-infrared absorption. During powder preparation and storage, oxygen content can be effectively reduced and controlled by adopting measures such as inert gas protection, vacuum treatment, and controlling ambient humidity. In addition to the oxygen content specified in this application, higher oxygen contents may be permissible for some materials or processes with lower oxidation sensitivity; while for applications requiring extremely high oxidation resistance or special sintering atmospheres, an oxygen content below 100 ppm may be required.

[0055] Loose packing density refers to the mass of powder per unit volume when it is freely filled into a container under specified conditions. It reflects the compactness of powder particles and directly affects the filling performance and green density during injection molding. Loose packing density is usually measured using devices such as a Hall flow meter or a Carney funnel. The loose packing density of powder is affected by various factors such as particle shape, particle size distribution, and surface roughness. Beyond the scope defined in this application, processes requiring higher filling efficiency may require higher loose packing densities; while certain special molding methods, such as compression molding, may have different requirements for loose packing density.

[0056] Flowability refers to the time required for powder to pass through a standard-aperture funnel under gravity. It reflects the magnitude of frictional and cohesive forces between powder particles and is an important indicator of the powder's filling ability in mold 3. Flowability is usually measured using devices such as a Hall flow meter or a Carney funnel. The flowability of powder is affected by factors such as particle shape, particle size distribution, surface condition, and humidity. In addition to the flowability defined in this application, processes requiring rapid filling of complex molds 3 may require higher flowability; while for some vibration filling or compression molding processes, the flowability requirements may be relatively lenient.

[0057] Particle shape refers to the geometric morphology of powder particles. Spherical particles have the smallest specific surface area and optimal flowability, which is beneficial for uniform powder mixing and mold filling. Particle shape can be observed and analyzed using equipment such as scanning electron microscopy (SEM). In addition to spherical particles, common powder particle shapes include irregular shapes, flakes, and dendritic shapes. For example, irregularly shaped particles may have better compact strength during compression molding, but poorer flowability; flake particles may provide anisotropic properties in certain composite materials. This application chose spherical particles mainly to optimize flowability and filling uniformity in the injection molding process.

[0058] Through the above technical solution, this application solves the quality problem caused by improper copper powder characteristics in the preparation of mixture 2 by precisely defining various parameters of copper powder.

[0059] Specifically, controlling the particle size distribution within the range of 10–45 μm facilitates sufficient contact and uniform dispersion of copper powder particles and polymer binder particles, effectively avoiding the filling of voids caused by excessively large particles or the agglomeration caused by excessively small particles, thus ensuring the uniformity of mixture 2. Simultaneously, setting the purity to ≥99.5% significantly reduces the interference of impurity elements on subsequent sintering reactions, effectively preventing the generation of internal defects in the green body. Limiting the oxygen content to <1500 ppm reduces the oxidation tendency of copper powder during mixing and subsequent processing, ensuring the reliability of material properties and avoiding excessive oxidation during sintering. Furthermore, maintaining the loose packing density at 4.5–5.5 g / cm³ optimizes the powder's packing characteristics, facilitating tight filling and smooth flow of the material during injection molding. Controlling the flowability to 10 s / (40–60 g) ensures smooth transport of mixture 2 during injection, reducing the risk of channel blockage or uneven molding. Finally, the adoption of spherical particle shape further enhances the powder's flowability and filling consistency, improving mixing uniformity and molding quality. The synergistic effect of these parameters fundamentally eliminates problems such as uneven mixture 2, easy oxidation during sintering, and residual impurities in the green body, laying a solid foundation for the high-precision manufacturing of liquid-cooled microchannels. This effectively improves the smoothness of the microchannel's inner wall, dimensional accuracy, and the bonding strength between the heat dissipation fins 1 and the substrate, ultimately ensuring the high heat exchange efficiency, excellent sealing performance, and long service life of the finished liquid-cooled microchannel.

[0060] In some embodiments described above, a degreasing process is proposed to remove polymeric adhesive particles from the shaped green body. However, in its implementation, incomplete degreasing can lead to residual impurities in the green body, affecting the subsequent sintering quality and the density and bonding strength of the final product. To address this, this application further proposes that in step S4, the degreasing process uses oxalic acid as a degreasing agent, with an oxalic acid concentration of 70–90%, a degreasing temperature of 110–130°C, and a degreasing time of 6–10 hours.

[0061] Degreasing is a crucial step in removing polymeric adhesive particles from the molded preform. Oxalic acid is used as a degreasing agent because it can effectively decompose and dissolve these particles.

[0062] Specifically, oxalic acid can chemically react with polymer binder particles, decomposing them into easily removable products, thus avoiding the use of other degreasing agents that may produce harmful residues or corrode the green body. This process can be carried out by immersing the molded green body in an oxalic acid solution, or by uniformly applying oxalic acid to the surface of the green body through spraying, steam assistance, or other methods to ensure full contact between the oxalic acid and the binder particles.

[0063] Oxalic acid concentration is a crucial parameter affecting degreasing efficiency and the safety of the green body. Limiting the oxalic acid concentration to the range of 70–90% ensures sufficient activity for efficient decomposition of polymeric binders, while avoiding excessive concentrations that could lead to resource waste or potential corrosion of the green body material. Oxalic acid solutions within this concentration range can be prepared by accurately weighing industrial-grade oxalic acid crystals and dissolving them in deionized water, or by directly using commercially available oxalic acid products that meet this concentration standard.

[0064] Degreasing temperature has a significant impact on the reaction rate and degreasing effect of oxalic acid. Controlling the degreasing temperature between 110–130℃ optimizes the reaction rate between oxalic acid and polymer-bound particles, allowing for complete decomposition within a reasonable timeframe and thus thoroughly removing impurities. Within this temperature range, degreasing efficiency is ensured while avoiding potential damage to the green body structure or excessive volatilization of oxalic acid due to excessively high temperatures. Temperature control can be achieved by placing the green body in an oven, heating tank, or reaction vessel with precise temperature control, and various methods such as electric heating and steam heating can be used for temperature regulation and maintenance.

[0065] Degreasing time is a critical factor in ensuring a complete degreasing reaction. A degreasing time of 6–10 hours is set to provide sufficient time for the oxalic acid to react fully with the polymer binder particles, ensuring that all organic components are effectively removed and preventing organic residues due to insufficient time. This time range is optimized to balance thorough degreasing with production efficiency. Degreasing time can be controlled by setting a precise timer or by using an online monitoring system to determine the endpoint of the degreasing process based on real-time data on the amount of residual organic matter in the green body.

[0066] Through the above technical solution, this application can effectively solve the problem of residual impurities in the green body caused by incomplete degreasing.

[0067] Specifically, oxalic acid is used as a degreasing agent, and its concentration, degreasing temperature, and degreasing time are precisely controlled to ensure the efficient and thorough decomposition and removal of polymeric adhesive particles. At a concentration of 70–90%, oxalic acid exhibits moderate activity, ensuring decomposition efficiency while avoiding potential damage to the green body. A degreasing temperature of 110–130℃ optimizes the reaction rate of oxalic acid, ensuring complete removal of organic matter. A degreasing time of 6–10 hours provides ample time for the reaction, preventing residues caused by insufficient time. The synergistic effect of these parameters significantly improves the thoroughness of the degreasing process, thereby reducing impurities remaining inside the green body. This not only provides a clean green body for the subsequent vacuum sintering step, effectively avoiding defects caused by impurities during sintering, but also further ensures the density, surface smoothness, and bonding strength between the heat dissipation fins 1 and the substrate of the final liquid-cooled microchannel product, thereby improving the overall performance and service life of the product.

[0068] In some of the embodiments described above in this application, vacuum sintering is proposed to remove organic residues and form a dense structure. However, if the vacuum level, sintering temperature and time are not precisely controlled during its implementation, it may lead to oxidation of the green body, insufficient sintering or residue of impurities, which may affect the sealing performance and service life of the final product.

[0069] In this regard, this application further proposes that in step S5, vacuum sintering is completed in a vacuum sintering furnace with a vacuum degree ≥10. - ³Pa, sintering temperature 900–1070℃, sintering time 12–26 hours.

[0070] Vacuum sintering is a heat treatment process for materials in a vacuum environment. Its core function is to isolate oxygen and other active gases, thereby effectively preventing oxidation reactions in the green body during high-temperature sintering, maintaining the purity of the material, and promoting the densification of the material.

[0071] Specifically, a resistance heating vacuum sintering furnace can be used, which can achieve uniform distribution and stable control of the temperature inside the furnace by precisely controlling the heating power of the resistance wire; or, an induction heating vacuum sintering furnace can be used, which can use induction coils to generate eddy currents to heat the billet quickly and efficiently to meet different sintering requirements.

[0072] Vacuum level is a key parameter for measuring the rarefaction of the sintering environment; a high vacuum level means that the number of residual gas molecules inside the furnace is extremely low. The vacuum level is set to ≥10. -³Pa aims to maximize the removal of air and other volatile impurities from the furnace, thereby significantly reducing the risk of the green body reacting with reactive gases such as oxygen and nitrogen at high temperatures. This effectively inhibits adverse phenomena such as oxidation and nitriding, ensuring the chemical purity of the sintered body and the performance stability of the final product. This high vacuum can be achieved using a vacuum system combining a mechanical pump and a diffusion pump, where the mechanical pump handles rough evacuation and the diffusion pump raises the vacuum level to the required high vacuum range. Alternatively, a vacuum system combining a turbomolecular pump and a dry pump can be used. This system is characterized by its cleanliness and lack of oil contamination, making it particularly suitable for precision manufacturing applications with extremely high requirements for product cleanliness.

[0073] Sintering temperature is a core process parameter for controlling the densification of materials in powder metallurgy. Controlling the sintering temperature within the range of 900–1070℃ ensures sufficient atomic diffusion and grain boundary migration of copper powder particles at high temperatures, resulting in a dense sintered body. This temperature range effectively promotes particle bonding and eliminates porosity, while avoiding problems such as excessive grain growth, material deformation, or melting due to excessively high temperatures, and insufficient sintering and densification due to excessively low temperatures. To achieve precise temperature control, advanced temperature sensors and feedback control systems equipped in the sintering furnace can be used to ensure that the furnace temperature is maintained uniformly and stably within the target range; alternatively, a multi-zone temperature-controlled sintering furnace can be used to independently adjust the temperature of different zones to adapt to the sintering requirements of blanks of different sizes and shapes, further improving temperature uniformity.

[0074] Sintering time is a crucial parameter for ensuring the sintering process proceeds fully and achieving the desired densification effect. Setting the sintering time to 12–26 hours aims to provide sufficient time for atomic diffusion and grain growth, resulting in stronger bonding between powder particles, further reducing internal porosity, and thus significantly improving the density, strength, and thermal conductivity of the sintered body. Too short a sintering time may lead to incomplete sintering, affecting product performance; while too long a sintering time may cause excessive grain growth, reducing the material's mechanical properties and increasing unnecessary energy consumption. To precisely control the sintering time, precise timing and operation can be achieved through the sintering furnace's program control system based on the specific characteristics of the green body and experimental verification results. Alternatively, an online monitoring system can be used to track key parameters such as the green body's shrinkage rate and density changes in real time during sintering. When the preset densification level is reached, the sintering process automatically ends to optimize production efficiency and product quality.

[0075] Through the above technical solution, this application can effectively solve the problems of blank oxidation, insufficient sintering and impurity residue that may occur during vacuum sintering.

[0076] Specifically, sintering is carried out in a vacuum sintering furnace, with the vacuum level strictly controlled to be ≥10. -³Pa effectively isolates oxygen to the maximum extent, preventing oxidation of the copper powder blank at high temperatures and maintaining material purity. Simultaneously, precise control of the sintering temperature between 900 and 1070°C ensures sufficient diffusion and bonding of copper powder particles, forming a dense sintered body and avoiding problems such as incomplete sintering or excessive grain growth. Furthermore, a sintering time of 12–26 hours provides ample time for the sintering reaction, allowing residual organic matter to completely volatilize and further enhancing the bonding strength between particles, ensuring uniform and dense compaction of the blank. Through these precise parameter controls, the final liquid-cooled microchannel product exhibits higher density, lower porosity, and superior oxidation resistance, significantly improving product sealing and service life, thus better meeting the long-term, high-intensity heat dissipation requirements of high-end, high-power equipment.

[0077] In some of the above-mentioned solutions of this application, copper powder and polymer bonding particles are mixed to form a uniform mixture 2. However, in this process, there may be problems with uneven powder mixing, which leads to the presence of impurities and incomplete degreasing inside the subsequently formed blank, thereby affecting the smoothness of the inner wall of the microchannel and the bonding strength, and ultimately reducing the heat exchange efficiency and service life of the radiator.

[0078] In this regard, this application further proposes that in step S2, the polymer adhesive particles are compounded from polyethylene, polyoxymethylene, paraffin and stearic acid in a mass ratio of 2:3:4:1, and the mass ratio of copper powder to polymer adhesive particles is 88:12–92:8; the mixing process of copper powder and polymer adhesive particles is as follows: first, at room temperature, stir at a low speed of 300–400 r / min for 15–25 min, then heat to 85–95℃ and stir at a high speed of 800–1000 r / min for 40–60 min to obtain a uniform mixture 2.

[0079] Specifically, the composition and mass ratio of the polymer adhesive particles are crucial to ensuring the uniformity of mixture 2. Polyethylene, as the base adhesive, provides the primary bonding force, effectively binding the copper powder particles to form mixture 2 with a certain strength, facilitating subsequent injection molding. Besides polyethylene, polymers with good thermoplasticity and adhesive properties, such as polypropylene and polystyrene, can also be used as base adhesives. Polyoxymethylene (POM) enhances the thermal stability of the adhesive system, preventing premature decomposition or performance degradation during subsequent heating, thus ensuring the stability of mixture 2 during injection molding. Materials that can replace POM include polycarbonate and polyamide. The addition of paraffin wax aims to improve the flowability of mixture 2, reducing its viscosity and allowing it to fill the mold 3 more smoothly during injection molding, reducing molding defects. Microcrystalline wax and polyethylene wax can also be used as flowability improvers. Stearic acid, as a lubricant, effectively reduces friction between the copper powder particles and the adhesive, as well as between mixture 2 and the equipment, further improving the flowability of mixture 2 and aiding in demolding. Oleic acid and zinc stearate can also be used as lubricants. When these four components are blended in a specific mass ratio, they work synergistically to ensure the overall performance of the adhesive system, avoiding uneven mixing or molding difficulties caused by insufficient performance of a single component or improper proportions.

[0080] The mass ratio of copper powder to polymer binder particles, controlled within the range of 88:12–92:8, is crucial to the performance of mixture 2. If the proportion of binder particles is too high, excessive organic matter may remain in mixture 2 during sintering, affecting the density and purity of the final product. If the proportion is too low, insufficient adhesion will make mixture 2 difficult to form, or the formed green body will have poor strength and be easily broken. This ratio range ensures a moderate binder content, providing sufficient adhesion to form a stable green body while minimizing residue after sintering, thereby guaranteeing the performance of the final product.

[0081] The mixing process of copper powder and polymer binder particles adopts a staged control approach. First, low-speed stirring is performed at room temperature, with the speed controlled at 300–400 rpm for 15–25 minutes. The main purpose of this stage is to initially and uniformly disperse the copper powder and polymer binder particles, avoiding powder splashing or localized agglomeration due to excessive impact at the beginning of high-speed stirring. Low-speed stirring gently mixes the different components, laying the foundation for subsequent fine mixing. For example, the low-speed stirring speed can also be controlled at 200–500 rpm for 10–30 minutes. Subsequently, the mixture 2 is heated to 85–95℃ and stirred at high speed at 800–1000 rpm for 40–60 minutes. The purpose of heating is to soften or melt the polymer binder particles, reducing their viscosity and allowing them to better wet the surface of the copper powder particles. High-speed stirring provides strong shear force, which promotes thorough mixing of the binder and copper powder particles to form a uniform coating layer, thereby producing a homogeneous mixture with consistent internal structure and no agglomeration. For example, the heating temperature can be controlled at 80-100℃, the high-speed stirring speed can be 700-1100 r / min, and the stirring time can be 30-70 min.

[0082] Through the above technical solution, this application effectively solves the problem of uneven powder mixing in traditional methods by optimizing the compound composition of polymer adhesive particles, the mass ratio of copper powder to adhesive particles, and a refined staged mixing process. This precisely controlled mixing process ensures the uniform distribution of each component in the mixture 2, avoiding local over- or under-adhesive situations, thus guaranteeing the quality of the subsequent molded blank from the source. The uniform mixture 2 can effectively reduce the risk of impurity residue and incomplete degreasing inside the blank, thereby significantly improving the smoothness of the inner wall of the liquid-cooled microchannel and the bonding strength between the heat dissipation fins 1 and the substrate. Ultimately, this not only improves the heat exchange efficiency of the liquid-cooled microchannel radiator and extends its service life, but also provides a solid foundation for the preparation of high-quality, high-performance liquid-cooled microchannel finished products, enabling them to better meet the long-term, high-intensity heat dissipation requirements of high-end, high-power equipment.

[0083] In some of the above-mentioned solutions of this application, a metal powder injection molding process is proposed to inject the mixture 2 into the mold 3 in step S3 to form a molded preform. However, in this process, if the process parameters are not precisely controlled, insufficient or excessive heating temperature of the material will lead to poor fluidity or thermal decomposition. Improper preheating of the mold 3 will cause uneven filling or premature solidification. Insufficient injection pressure will result in insufficient filling of the microchannel thin-wall structure. Mismatch between holding pressure and time will cause preform shrinkage or internal porosity. Excessive cooling rate will cause cracks or deformation, thereby causing internal defects in the preform, rough inner wall of the microchannel, and loose fin bonding, which will affect the density, dimensional accuracy and heat dissipation performance of the product.

[0084] In this regard, this application further proposes that in step S3, the metal powder injection molding process parameters are as follows: material heating temperature 160–185℃, mold 3 preheating temperature 70–90℃, injection pressure 80–110MPa, holding pressure 50–70MPa, holding time 8–15s, and molding cooling rate 3–5℃ / min.

[0085] The material heating temperature refers to the temperature at which the mixture 2, formed by mixing copper powder and polymer binder particles, is heated to a molten state before injection. This temperature is a key parameter to ensure that the mixture 2 has good fluidity. Its function is to fully melt the polymer binder particles, thereby uniformly coating the copper powder and forming a slurry with sufficient plasticity to smoothly fill the cavity of the mold 3. In addition to the 160–185℃ range specified in this application, the material heating temperature can also be adjusted according to the specific type of polymer binder used and its thermal decomposition temperature, the particle size distribution of the copper powder, and other factors. For example, some binders with poor thermal stability may require a lower heating temperature, while the mixture 2 with higher viscosity may require a higher temperature to reduce its viscosity.

[0086] The preheating temperature of mold 3 refers to the temperature reached by preheating mold 3 before injecting mixture 2. This temperature prevents mixture 2 from solidifying prematurely due to excessively low mold 3 temperature upon injection, ensuring that mixture 2 can uniformly and fully fill the various fine structures of mold 3, especially the thin-walled portions of microchannels. It also helps improve the surface quality of the molded blank. Preheating of mold 3 can be achieved through internal electric heating rods, circulating hot oil, or hot water. Besides the 70–90°C range specified in this application, the preheating temperature of mold 3 can also be adjusted according to the thermal conductivity of the mold 3 material, the solidification characteristics of mixture 2, and the required dimensional accuracy and surface finish of the molded blank. For example, products requiring higher surface precision may require more precise temperature control.

[0087] Injection pressure refers to the pressure applied during metal powder injection molding to force molten mixture 2 into the cavity of mold 3. This pressure overcomes the flow resistance of mixture 2 in the runners and cavity, ensuring that mixture 2 completely fills every corner of mold 3. Sufficient injection pressure is crucial for ensuring complete filling and avoiding material shortages, especially for microchannel heat sinks with complex geometries and fine structures. Injection pressure is typically provided by the hydraulic or electric system of the injection molding machine. In addition to the 80–110 MPa range specified in this application, the injection pressure can be adjusted based on the viscosity of mixture 2, the design of the mold 3 runners, the complexity of the cavity, and the required density of the molded preform. For example, higher injection pressure may be required for mixture 2 with poor flowability or more complex microchannel structures.

[0088] Holding pressure refers to the pressure applied to the mixture 2 within the cavity of mold 3 after injection filling. This pressure compensates for the volume shrinkage of the mixture 2 during cooling and solidification, preventing defects such as shrinkage cavities, depressions, or dimensional instability within the molded preform, thereby improving the density and dimensional accuracy of the preform. Holding pressure is typically lower than the injection pressure and continues to apply for a certain period. In addition to the 50–70 MPa range specified in this application, the holding pressure can be adjusted according to the shrinkage characteristics of the mixture 2, the wall thickness of the preform, and the required product density. For example, higher holding pressure may be required for materials with higher shrinkage rates or thicker parts.

[0089] Holding time refers to the duration of continuous application of holding pressure. This time ensures that the holding pressure is fully effective during the cooling and solidification of the mixture 2, effectively compensating for material shrinkage and preventing molten material backflow, thereby stabilizing the size and shape of the formed blank. Too short a holding time may result in insufficient compensation, while too long a time may increase the production cycle without significant benefit. In addition to the 8–15s range specified in this application, the holding time can be adjusted according to factors such as the wall thickness of the formed blank, the cooling rate of the mixture 2, and the temperature of the mold 3. For example, for thicker formed blanks, a longer holding time may be required to ensure sufficient internal solidification.

[0090] The molding cooling rate refers to the speed at which the molded preform cools and solidifies within the mold 3. This rate controls the crystallization process and internal stress distribution of the preform, preventing cracks, warping, or internal stress concentration caused by excessively rapid cooling, which could affect the structural integrity and subsequent sintering performance of the preform. A reasonable cooling rate helps obtain a uniform, dense, and defect-free preform. In addition to the 3–5 °C / min range specified in this application, the molding cooling rate can also be controlled by adjusting the temperature of the mold 3, the flow rate of the cooling medium, etc. For example, for some cooling-sensitive materials, a slower cooling rate may be necessary to avoid defects.

[0091] By using the above technical solutions, the key parameters of the metal powder injection molding process can be precisely controlled, including the material heating temperature, the mold 3 preheating temperature, the injection pressure, the holding pressure, the holding time, and the molding cooling rate. This can effectively solve problems such as internal defects in the preform, rough inner walls of the microchannels, and loose fin bonding caused by improper parameters.

[0092] Specifically, the material heating temperature is controlled at 160–185℃ to ensure that the mixture 2 is fully melted and has good fluidity, which is conducive to filling the microchannels; the mold 3 preheating temperature is controlled at 70–90℃ to prevent the material from solidifying too early and to ensure uniform filling and surface smoothness; the injection pressure is set at 80–110MPa to provide sufficient power for the mixture 2 to completely fill the cavity of the mold 3, especially for the thin-walled structure of the microchannels, to prevent incomplete filling; the holding pressure is maintained at 50–70MPa to effectively compensate for material shrinkage and eliminate internal porosity; the holding time is limited to 8–15s to ensure sufficient pressure application and reduce residual stress; the molding cooling rate is controlled at 3–5℃ / min to avoid cracking or deformation caused by excessively rapid cooling, and to ensure the dimensional stability and structural integrity of the blank. The synergistic optimization of these parameters improves the quality of the molded blank from the source, ensuring the density, dimensional accuracy and surface smoothness of the internal structure of the microchannel radiator, laying a solid foundation for the subsequent debinding and sintering processes, thereby significantly improving the overall performance and reliability of the liquid-cooled microchannel product.

[0093] In some embodiments of this application, degreasing and vacuum sintering steps are proposed to prepare the green body. However, in the process of implementation, trace amounts of organic acids and water vapor remain inside the green body after degreasing, which may lead to oxidation or defects during vacuum sintering.

[0094] In this regard, this application further proposes to add a constant temperature anti-oxidation pretreatment process between step S4 degreasing and step S5 vacuum sintering; the degreased green body is placed in an inert nitrogen atmosphere and heated to 200–260°C at a heating rate of 5–8°C / min, and kept at a constant temperature for 2–4 hours to remove residual trace organic acids and water vapor inside the green body.

[0095] Specifically, the addition of a constant-temperature anti-oxidation pretreatment process aims to address the issue of trace amounts of organic acids and moisture residues that may remain inside the green body after degreasing. If these residues are not removed, they can easily cause oxidation reactions during subsequent high-temperature sintering, thus affecting the performance of the final product. This pretreatment process can be carried out in a dedicated pretreatment furnace, or in a sintering furnace with multi-zone temperature control capabilities, by setting up an independent pretreatment temperature zone before entering the main sintering zone. Placing the degreased green body in an inert nitrogen atmosphere effectively isolates oxygen and prevents oxidation during heating and holding. Besides nitrogen, other inert gases, such as argon, can also be used, or the process can be conducted under a strict vacuum environment to ensure the chemical stability of the green body's surface and interior. Heating to 200–260°C at a controlled rate of 5–8°C / min ensures uniform heating of the green body and avoids thermal stress concentration or localized overheating caused by rapid heating. Meanwhile, the optimal temperature range of 200–260℃ effectively promotes the volatilization of residual organic acids and moisture without causing significant changes in the green body structure or unnecessary side reactions. After reaching the preset temperature, a constant temperature holding period of 2–4 hours is performed to provide sufficient time for the trace amounts of organic acids and moisture inside the green body to fully volatilize and dissipate. The specific holding time can be adjusted appropriately according to the size, complexity, and residue content of the green body to ensure complete removal. Through this series of precisely controlled conditions, it is ensured that these substances that may cause defects are effectively removed, providing a clean and stable green body state for subsequent vacuum sintering, thereby removing residual trace amounts of organic acids and moisture from the inside of the green body.

[0096] By introducing a constant-temperature antioxidant pretreatment process between degreasing and vacuum sintering, the problem of residual trace organic acids and water vapor inside the green body after degreasing can be effectively solved.

[0097] Specifically, the preform is placed in an inert nitrogen atmosphere and heated to a specific temperature range at a controlled rate, then held at that temperature to allow for the full volatilization and removal of these residues. This significantly reduces the risk of oxidation reactions during subsequent vacuum sintering, avoiding sintering defects caused by oxidation, such as increased porosity and decreased density. Consequently, the sintered liquid-cooled microchannel product exhibits higher density, superior mechanical properties, and oxidation resistance, improving the overall quality and service life of the product. Especially under long-term liquid-cooled circulation conditions, it effectively prevents problems such as internal wall corrosion and media leakage, ensuring the stable operation of high-end, high-power equipment.

[0098] like Figure 1 -like Figure 3 As shown, the above technical solution will be explained in more detail through a more specific example: A high-power electronics manufacturer needed a new type of liquid-cooled microchannel heatsink to meet the growing cooling demands of its server products. Existing technologies, such as machine milling, struggled to manufacture the fine and complex copper microchannel structures and were prohibitively expensive; die casting often resulted in high internal porosity and poor sealing; conventional powder metallurgy processes frequently encountered problems with copper applications, including uneven powder mixing, incomplete degreasing, and easy oxidation during sintering, leading to rough microchannel walls, weak bonding between fins and the substrate, poor oxidation resistance, and long-term leakage and efficiency degradation. Furthermore, copper extrusion molding was difficult, prone to incomplete filling and poor dimensional consistency. To address these challenges, the manufacturer decided to adopt a liquid-cooled microchannel powder metallurgy fabrication method.

[0099] First, in step S1, the manufacturer uses a pre-stamping process to fabricate the combined heat dissipation fins 1. These heat dissipation fins 1 are made of copper, ensuring excellent thermal conductivity, and the pre-stamping process allows for precise control of the fin geometry and dimensions, laying the foundation for subsequent molding.

[0100] Next, in step S2, the manufacturer mixes spherical copper powder with a particle size distribution of 10–45 μm, purity ≥99.5%, oxygen content <1500 ppm, loose density of 4.5–5.5 g / cm³, and flowability of 10 s / (40–60 g) with polymer binder particles composed of polyethylene, polyoxymethylene, paraffin wax, and stearic acid in a mass ratio of 2:3:4:1. The mass ratio of copper powder to polymer binder particles is set at 90:10. The mixing process is divided into two stages: first, at room temperature, the mixture is stirred at a low speed of 350 r / min for 20 min to ensure initial uniformity; then, the temperature is raised to 90°C and the mixture is stirred at a high speed of 900 r / min for 50 min to obtain a uniform mixture 2. This precise powder parameter and two-stage mixing process effectively avoid the problem of uneven powder mixing common in ordinary powder metallurgy, ensuring the material flowability and filling properties of subsequent injection molding. In particular, it overcomes the inherent defect of copper's sluggish flow.

[0101] In step S3, the manufacturer precisely places the pre-stamped heat sink fins 1 into the mold 3. Then, using metal powder injection molding, the mixture 2 heated to 175°C is injected into the mold 3, which is preheated to 80°C. The injection pressure is set to 95 MPa, the holding pressure to 60 MPa, the holding time to 10 seconds, and the cooling rate to 4°C / min. After cooling, a preform with a microchannel structure is formed. Metal powder injection molding can achieve complex and precise microchannel structure formation, which is difficult to achieve with machine milling. Simultaneously, compared to die casting, injection molding can significantly reduce the porosity of the preform and improve its density, thus ensuring subsequent sealing performance. The heat sink fins 1 are tightly bonded to the substrate during injection, forming a strong connection and avoiding the problem of loose bonding between the fins and the substrate in traditional processes.

[0102] Subsequently, in step S4, the formed green body undergoes a degreasing treatment. Oxalic acid is used as the degreasing agent, with a concentration of 80%. The degreasing temperature is controlled at 120°C, and the degreasing time is 8 hours. This precisely controlled degreasing condition ensures the complete removal of the binder inside the green body, avoiding residual impurities and internal defects caused by incomplete degreasing in ordinary powder metallurgy.

[0103] Between step S4 (degreasing) and step S5 (vacuum sintering), a constant-temperature anti-oxidation pretreatment step is added. The degreased green body is placed in an inert nitrogen atmosphere and heated to 230°C at a rate of 6°C / min, then held at that temperature for 3 hours. This pretreatment step aims to remove trace amounts of residual organic acids and moisture from the green body, effectively reducing the risk of oxidation during sintering and solving the problem of easy oxidation during sintering in ordinary powder metallurgy processes. This lays the foundation for obtaining high-purity, high-density products.

[0104] Next, in step S5, the pretreated blank is vacuum sintered. Sintering is performed at a vacuum level of 10... - 4 The sintering process was completed in a vacuum sintering furnace at 980℃ for 18 hours. The high vacuum environment and precise temperature and time control ensured thorough sintering between copper powder particles and between the heat sink fins 1 and the substrate, forming a dense metallurgical bond. This resulted in a highly dense and strong liquid-cooled microchannel structure. This effectively solved the problems of high porosity in die-casting and poor density and loose fin bonding in ordinary powder metallurgy processes, ensuring the heat sink's sealing performance and heat exchange efficiency.

[0105] Finally, in step S6, the sintered finished product is sequentially shaped, machined, and surface-treated to achieve the final dimensional accuracy and surface quality requirements. After rigorous testing and packaging, the final liquid-cooled microchannel product that meets the heat dissipation requirements of high-power electronic devices is obtained. Through the above series of synergistic process steps, this manufacturing method successfully overcomes the challenges faced by existing technologies in the manufacture of copper liquid-cooled microchannel heat sinks, such as structural complexity, density, sealing, bonding strength, and oxidation resistance, significantly improving the performance and reliability of the product.

[0106] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating liquid-cooled microchannel powder metallurgy, characterized in that, Includes the following steps: Step S1: Prepare combined heat dissipation fins or single heat dissipation fins using a pre-stamping process; Step S2: Mix and stir the copper powder with the polymer adhesive particles to form a mixture; Step S3: Place the heat dissipation fins into the mold, and use metal powder injection molding process to inject the heated mixture into the mold, and cool it to form a molded blank; Step S4: Degrease the formed blank; Step S5: Vacuum sinter the degreased green body; Step S6: Perform shaping, machining, and surface treatment in sequence, and finally inspect and package to obtain the finished liquid-cooled microchannel product.

2. The manufacturing method according to claim 1, characterized in that, In step S1, the heat dissipation fins are made of copper.

3. The manufacturing method according to claim 1, characterized in that, In step S2, the parameters of the copper powder used are: particle size distribution 10–45 μm, purity ≥99.5%, oxygen content <1500 ppm, loose density 4.5–5.5 g / cm³, flowability 10 s / (40–60 g), and spherical particle shape.

4. The manufacturing method according to claim 1, characterized in that, In step S4, the degreasing process uses oxalic acid as a degreasing adjuvant, with an oxalic acid concentration of 70–90%, a degreasing temperature of 110–130°C, and a degreasing time of 6–10 hours.

5. The manufacturing method according to claim 1, characterized in that, In step S5, the vacuum sintering is completed in a vacuum sintering furnace with a vacuum degree ≥10. - ³Pa, sintering temperature 900–1070℃, sintering time 12–26 hours.

6. The manufacturing method according to claim 1, characterized in that, In step S2, the polymer adhesive particles are compounded from polyethylene, polyoxymethylene, paraffin and stearic acid in a mass ratio of 2:3:4:1, and the mass ratio of copper powder to polymer adhesive particles is 88:12–92:

8. The mixing process of copper powder and polymer bonding particles is as follows: first, stir at a low speed of 300–400 r / min for 15–25 min at room temperature, then heat to 85–95℃ and stir at a high speed of 800–1000 r / min for 40–60 min to obtain a uniform mixture.

7. The manufacturing method according to claim 1, characterized in that, In step S3, the metal powder injection molding process parameters are as follows: material heating temperature 160–185℃, mold preheating temperature 70–90℃, injection pressure 80–110MPa, holding pressure 50–70MPa, holding time 8–15s, and molding cooling rate 3–5℃ / min.

8. The manufacturing method according to claim 1, characterized in that, A constant temperature anti-oxidation pretreatment process is added between step S4 degreasing and step S5 vacuum sintering; the degreased green body is placed in an inert nitrogen atmosphere and heated to 200–260℃ at a heating rate of 5–8℃ / min, and kept at a constant temperature for 2–4 hours to remove residual trace organic acids and water vapor inside the green body.

Images