A copper micro-channel liquid cooling radiator and a liquid forming manufacturing method thereof

Abstract

The present application relates to the technical field of metal precision forming, and particularly relates to a copper micro-channel liquid cooling radiator and a liquid forming manufacturing method thereof, which comprises the following steps: S1, a soluble ceramic core with a micro-channel negative structure is prepared by using a template method, and the surface of the core is pretreated to reduce the wetting angle; S2, the pretreated core and an outer mold sprayed with a release agent are assembled to form a casting cavity; S3, copper liquid subjected to flowability improvement treatment is smelted and cast in a vacuum or a protective atmosphere; S4, directional solidification of the casting is guided by using multi-section induction heating combined with online temperature control; and S5, the core is removed by chemical dissolution. Through the synergy of bidirectional wetting control, a template method soluble core and directional solidification technology, the present application realizes high-quality and low-cost batch manufacturing of a complex three-dimensional micro-channel copper radiator, and the prepared radiator has a complete micro-channel structure and high internal density, and is suitable for high-power heat dissipation scenes in the fields of high-performance computing, power electronics, new energy and the like.

Description

Technical Field

[0001] This invention relates to the field of precision metal forming technology, specifically to a copper microchannel liquid-cooled radiator and its liquid forming manufacturing method, and more particularly to a method for mass production of a copper high-efficiency liquid-cooled radiator with a complex three-dimensional internal microchannel structure. Background Technology

[0002] With the rapid development of high-performance computing, advanced communications, new energy vehicles, and power electronic equipment towards higher power densities, the heat flux density of their core chips and power modules has exceeded 100W / cm², with some high-end devices even reaching over 500W / cm². Traditional air-cooling and heat pipe cooling technologies can no longer meet the heat dissipation requirements. Microchannel liquid cooling radiators, with their extremely high specific surface area and forced convection heat transfer efficiency, are widely recognized as the core technology solution to the "thermal barrier" problem of high-power devices. Copper, due to its recognized excellent thermal conductivity, good mechanical properties, and processing performance, has become the preferred material for manufacturing microchannel liquid cooling radiators.

[0003] Currently, the mainstream manufacturing technologies for copper microchannel heat sinks in the industry all have significant limitations: 1. Machining technologies (such as precision milling, electrical discharge machining, etc.): can only process open planar microchannels, and cannot manufacture closed three-dimensional internal complex flow channels; moreover, the processing efficiency is low and the material waste is serious, and it is almost powerless for deep holes or irregular cavities with a depth exceeding 10 times the diameter.

[0004] 2. Joining technologies (such as etching + diffusion welding, brazing, etc.): These require first forming semi-channels on a metal plate through chemical etching or mechanical processing, then connecting multiple layers of plates together using high-temperature diffusion welding or brazing. This process is lengthy, involving multiple precision machining and high-temperature joining steps. The welding interface presents risks to thermal resistance and reliability; furthermore, it is difficult to achieve truly three-dimensional irregular topologies (such as bifurcated, spiral, or mesh-like channels), and the yield is significantly affected by welding quality.

[0005] 3. Additive manufacturing technologies (such as selective laser melting (SLM) and electron beam melting (EBM): While capable of free-form forming of complex structures, they suffer from extremely high manufacturing costs (approximately 10 to 20 times that of traditional casting), low production efficiency (single-part printing typically takes several to tens of hours), susceptibility to porosity and incomplete fusion defects within parts, high surface roughness (Ra typically 10 μm to 20 μm), and complex post-processing. Currently, they are only suitable for prototype verification or very small-batch customization and cannot meet the needs of large-scale industrialization.

[0006] Liquid forming (casting) technology theoretically possesses advantages such as one-time molding of complex components, high material utilization, and suitability for mass production. However, when manufacturing copper microchannel heat sinks, this technology faces two fundamental technical bottlenecks: The first challenge is the core-making dilemma: cores that form complex internal cavities must simultaneously possess the characteristics of being resistant to high-temperature molten copper corrosion (molten copper has a melting point of approximately 1083℃), having high structural precision (microchannel feature size ≤ 0.5mm), and being efficiently and non-destructively removed after casting. Existing sand cores and resin cores cannot withstand the impact of high-temperature molten copper and lack sufficient precision, while ceramic cores suffer from high manufacturing difficulty, high cost, and difficulty in removal, making it difficult to meet the above requirements simultaneously.

[0007] Secondly, there are challenges in forming and control: molten copper has high viscosity and high surface tension, making it difficult to fill the mold in microscale thin-walled channels, which can easily lead to defects such as cold shuts and incomplete pouring. At the same time, copper has a large solidification shrinkage rate, and the control of venting, feeding, and solidification defects during the casting process is extremely complex, resulting in low internal density and poor yield of the casting.

[0008] Therefore, developing a novel liquid precision forming process that can systematically solve the above-mentioned technical bottlenecks is of great technical and industrial significance for promoting the large-scale application of copper microchannel liquid cooling heat sinks. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a liquid forming manufacturing method for copper microchannel liquid-cooled heat sinks. This method aims to effectively solve the problems of preparing and removing complex ceramic cores through innovative process design, and to achieve high-quality filling and solidification control of the microchannel cavity, thereby realizing high-quality, low-cost, and large-scale production of high-performance copper microchannel heat sinks.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for liquid forming manufacturing of a copper microchannel liquid-cooled heat sink includes the following steps: S1. Core Preparation and Processing First, a soluble ceramic core with a negative microchannel structure inside the heat sink is prepared using a template method. Then, the surface of the soluble ceramic core is pretreated to reduce the wetting angle between the copper liquid and the core surface. S2. Mold Assembly A pre-treated soluble ceramic core is assembled into an outer mold coated with a release agent to form a casting cavity that matches the shape of the radiator. S3. Smelting and Casting Vacuum degree ≤ 1×10 -2Under a vacuum environment and a protective atmosphere of argon or nitrogen, copper liquid that has undergone fluidity optimization treatment is melted and then poured into a casting cavity. The casting method is bottom pouring, side pouring or top pouring, and the pouring speed is 0.2 kg / s to 1.0 kg / s. S4. Solidification Control During and after casting, multi-segment independently controlled induction heating coils are used to heat the mold in sections and control the temperature online, forming a temperature gradient from the gate to the far end, guiding the casting to achieve directional solidification. S5. Core Removal After the casting solidifies and cools to room temperature, the soluble ceramic core is completely removed by chemical dissolution to obtain a copper microchannel liquid-cooled radiator.

[0011] In a preferred example, step S1, which involves preparing the soluble ceramic core using a template method, is as follows: (1) An organic precursor with a negative microchannel structure inside a heat sink was formed using a removable material; (2) Fill the cavity of the organic precursor with ceramic slurry and vibrate to densify it to obtain a green body; (3) The removable material in the green body is removed by a stepped sintering process, and then sintered and solidified to obtain a soluble ceramic core; the dimensional tolerance of the soluble ceramic core is ±0.05mm, the compressive strength at room temperature is ≥20MPa, and the high temperature resistance is ≥1500℃; The stepped sintering process includes the following stages: First heating stage: The green billet is heated from room temperature to 200℃~600℃ at a heating rate of 0.5℃ / min~2℃ / min. During this period, at least one temperature point is selected and held for 0.5h~4h for degreasing treatment. Second heating stage: The degreased green body is heated from the sintering temperature of the first heating stage to the final sintering temperature of 1150℃~1600℃ at a heating rate of 0.8℃ / min~5℃ / min. Heat preservation stage: heat preservation at the final sintering temperature for 2 to 10 hours; Cooling stage: The soluble ceramic core after final sintering is cooled to room temperature in the furnace at a rate of 0.5℃ / min to 2℃ / min.

[0012] In a preferred embodiment, the removable material is any one of thermoplastic, water-soluble polymer, or photocurable resin; the ceramic slurry is a quartz-based ceramic slurry containing quartz powder aggregate and organic binder, wherein the quartz powder aggregate contains at least two different particle sizes of quartz powder mixed in the range of 25μm to 75μm, and the organic binder accounts for 5% to 25% of the total mass of the ceramic slurry.

[0013] In a preferred example, in step S1, the surface of the soluble ceramic core is pretreated by depositing a metal plating layer or functional ceramic coating with a thickness of 1μm to 10μm on the surface of the soluble ceramic core through chemical plating, magnetron sputtering or sol-gel method; wherein the metal plating layer is a nickel plating layer or a cobalt plating layer, and the functional ceramic coating is a silicon dioxide-based coating.

[0014] In a preferred example, in step S2, the release agent is an oxide-based release agent or a graphite-based release agent, used to increase the wetting angle between the molten copper and the outer mold surface to prevent the casting from sticking to the mold.

[0015] In a preferred example, in step S3, the fluidity optimization treatment of the copper liquid is a microalloying treatment, specifically, adding one or more elements selected from phosphorus, lithium, cerium, and silicon to the copper liquid, with an addition amount of 0.01wt% to 0.1wt%.

[0016] In a preferred example, in step S3, the smelting temperature of the copper liquid is 1150℃~1250℃, and the casting temperature is 1180℃~1220℃.

[0017] In a preferred example, in step S4, the multi-segment induction heating method is three independently controlled induction heating segments, forming a temperature gradient of: 950℃~1050℃ in the gate section, 850℃~950℃ in the middle section, and 750℃~850℃ in the far section; the holding time is 1h~3h, and the resulting axial temperature gradient is 5℃ / cm~20℃ / cm.

[0018] In a preferred example, in step S5, the chemical dissolution method is as follows: the casting with the soluble ceramic core is immersed in a hydrofluoric acid solution with a concentration of 20%~40% or a sodium hydroxide solution with a concentration of 20%~30% and soaked at room temperature to 60°C for 10h~50h, supplemented by ultrasonic vibration with a power of 100W~300W to accelerate the dissolution.

[0019] Based on a general inventive concept, another objective of this invention is to provide a copper microchannel liquid-cooled radiator manufactured by the above-mentioned liquid forming method, which has a three-dimensional interconnected microchannel structure inside. The cross-sectional shape of the microchannel structure is rectangular, circular, trapezoidal or other polygonal, and the minimum feature size is ≤0.5mm. The casting density of the radiator is ≥99.5%, and the thermal conductivity is ≥390W / (m·K). The thermal conductivity is tested according to GB / T 22588-2008 or equivalent standards.

[0020] The minimum feature size of the microchannel structure was determined using industrial computed tomography (industrial CT) according to GB / T29067-2012 "Non-destructive testing - Industrial computed tomography (CT) image measurement method"; the density of the casting was determined using the Archimedes method according to GB / T 3850-2015 "Dense sintered metal materials and cemented carbide density determination method", and the density of the casting was calculated using the following formula: density = ρ_sample / ρ_theoretica × 100%, where ρ_sample is the measured density and ρ_theoretical is the theoretical density of pure copper (8.96 g / cm³); the thermal conductivity was determined using the laser flash method according to GB / T22588 "Flash method for measuring thermal diffusivity or thermal conductivity" or ISO 22007-4 standard.

[0021] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. Innovative complete solution for soluble cores A template method using "organic precursor + ceramic slurry filling and sintering" is adopted to prepare soluble ceramic cores. This method decomposes the complex three-dimensional microchannel structure into simple organic precursor processing and ceramic slurry filling and sintering processes, perfectly solving the industry problem of "inability to produce, high cost, and inability to remove" complex ceramic cores.

[0022] The core structure prepared by this method has high precision, with dimensional tolerances of ±0.05mm (corresponding to CT5~CT6 grade) as assessed according to GB / T 6414-2017 "Dimensional Tolerances, Geometric Tolerances and Machining Allowances for Castings"; high strength, with a room temperature compressive strength ≥20MPa as measured according to GB / T8489-2006 "Test Method for Compressive Strength of Fine Ceramics"; and good high-temperature resistance, maintaining its integrity at 1500℃ without softening or deformation according to GB / T 3002-2017 "Test Method for High-Temperature Flexural Strength of Refractory Materials". It can also be quickly and non-destructively removed by chemical reagents, making it particularly suitable for large-scale production.

[0023] 2. Precise two-way wettability control strategy By creatively differentiating the treatment of the interface between the outer mold and the core, a release agent is sprayed onto the outer mold to increase the wetting angle between the molten copper and one side of the mold, preventing the casting from sticking to the mold and improving mold life. Meanwhile, a metal plating / functional coating on the core surface and micro-alloying treatment of the molten copper reduce the wetting angle between the molten copper and one side of the core, significantly optimizing the spreading and flow capabilities of the molten copper around the microscale core. This "two-way control" strategy systematically resolves the inherent contradiction in wettability requirements during casting, ensuring the complete formation of thin-walled microchannels and a long mold life.

[0024] 3. High-quality directional solidification control technology Employing multi-segment independently controlled induction heating combined with online temperature feedback technology, the temperature field distribution of the mold is precisely controlled, forming a stable directional solidification temperature gradient. This ensures that the casting solidifies sequentially from the far end towards the gate, effectively addressing key process issues such as molten copper flow, cavity venting, and sequential feeding. This achieves sufficient feeding and effectively eliminates casting defects such as cold shuts, shrinkage cavities, porosity, and blowholes. 4. Excellent process compatibility and economy. The unit technologies involved in this invention (such as template forming, surface treatment, precision injection molding, vacuum melting, induction heating, etc.) are all mature and reliable. The entire process path design closely meets the needs of large-scale production, with low equipment investment and good process stability. Compared with existing additive manufacturing technologies, it has significant cost and efficiency advantages while ensuring high product performance, and the technology transfer feasibility is high.

[0025] Specifically, taking the mass production of 1000 microchannel copper heat sinks with the same structure as in Example 1 as an example: Manufacturing cost: The overall cost per unit of this invention is 60 yuan, while the overall cost per unit of SLM 3D printing is 690 yuan. The manufacturing cost of this invention is reduced by about 91%. Compared with the traditional diffusion welding process (cost per unit of about 460 yuan), the cost of this invention is reduced by about 87%.

[0026] Production efficiency: The casting process of this invention can produce 40 pieces per batch in 4 hours (equivalent to 0.1 hours per piece), and the pickling process can process 2000 pieces per batch in 8 hours, with a comprehensive production cycle of about 0.2 hours (12 minutes) per piece; while SLM 3D printing requires more than 6 hours per piece, so the production efficiency of this invention is more than 30 times higher; compared with diffusion welding (about 0.4 hours per piece), the efficiency of this invention is doubled.

[0027] In summary, this invention enables large-scale, low-cost industrial production of copper microchannel liquid-cooled heat sinks, reducing manufacturing costs by more than 80% compared to existing technologies and increasing production efficiency by more than 10 times. For detailed comparative data, please refer to Table 2. Attached Figure Description

[0028] Figure 1 The present invention provides a process flow diagram of the liquid forming manufacturing method for copper microchannel liquid-cooled radiators, which sequentially shows five core processes: core preparation and processing, mold assembly, melting and casting, solidification control, and core removal, as well as the key process steps of each process. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described in conjunction with specific embodiments. However, this invention is not limited to these embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. In this invention, unless otherwise specified, the raw materials and reagents used are all conventional industrial-grade products, and the equipment used is all conventional commercially available equipment in the field of metal precision forming processes, without any special customization requirements.

[0030] The specific embodiments of the present invention will be described in detail below.

[0031] Example 1

[0032] A pure copper liquid-cooled heat sink with an internal serpentine microchannel is fabricated. The microchannel has a width of 0.5 mm, a height of 1 mm, and a wall thickness of 0.3 mm. The specific steps are as follows: S1. Preparation of organic precursor: Organic precursors with a serpentine microchannel negative structure were produced by precision injection molding using PE plastic, with a dimensional accuracy of ±0.03mm; S2. Preparation of ceramic slurry: Weigh out 50 parts of 200-mesh quartz powder, 30 parts of 400-mesh quartz powder, and 20 parts of 800-mesh quartz powder by weight as ceramic aggregates. Take 15 parts of an organic binder made of paraffin wax, beeswax, and polyethylene in a weight ratio of 3:1:1. Mix the ceramic aggregates and binder evenly at 80°C and grind to obtain a ceramic slurry with good fluidity. S3. Core Preparation: The ceramic slurry was injected into the cavity of the PE organic precursor and compacted by vibration on a vibrating table (vibration frequency 50Hz, amplitude 0.5mm, vibration time 10min), and then dried at 80℃ for 4h. Subsequently, stepped heating sintering was performed: the temperature was increased to 300℃ at a rate of 2℃ / min and held for 2h to decompose the PE precursor; then the temperature was increased to 1400℃ at a rate of 5℃ / min and held for 2h to sinter and solidify the ceramic. It was then naturally cooled to room temperature to obtain the quartz ceramic core. S4. Core surface pretreatment: The obtained quartz ceramic core is subjected to chemical nickel plating to form a metallic nickel layer with a thickness of about 3μm on its surface, so as to reduce the wetting angle between the copper liquid and the core; S5. Mold Assembly: The outer mold is machined using a molybdenum-titanium-zirconium (TZM) alloy. A zinc oxide-based release agent with a thickness of approximately 100μm is uniformly sprayed onto the surface of the outer mold cavity. The prepared ceramic core is then precisely installed into the outer mold using locating pins, and the mold is closed to form the casting cavity. S6. Melting and Casting: Place the mold in a vacuum casting chamber and evacuate to 5×10⁻⁶. -3Pa. Pure copper material is placed in a graphite crucible and heated to 1200℃ until completely melted. 0.05wt% of phosphorus copper master alloy is added for microalloying treatment. After stirring evenly, it is allowed to stand for 5 minutes to degas. Maintaining vacuum, the 1200℃ copper liquid is poured into the mold using a bottom-pouring method at a casting speed of 0.5kg / s. S7. Directional solidification control: During casting, the three independently controlled induction heating coils surrounding the mold are activated. The temperature is fed back in real time through K-type thermocouples, and the temperature of the gate section is controlled at 1000℃, the middle section at 900℃, and the far section at 800℃, forming a stable temperature gradient to guide the casting to solidify directionally from the far end towards the gate. After holding at the temperature for 2 hours, the heating system is turned off and the casting is allowed to cool naturally to room temperature. S8. Core Removal: After opening the mold, remove the casting with the core and immerse it in a 40% hydrofluoric acid solution at room temperature for 20 hours, supplemented by ultrasonic vibration with a power of 200W to accelerate dissolution. After the core is completely dissolved, rinse it with deionized water to remove burrs and risers, obtaining a copper microchannel liquid-cooled heat sink with an intact internal serpentine microchannel structure, a smooth surface, and no defects; Testing revealed that the radiator casting has a density of 99.7%, a thermal conductivity of 395 W / (m·K), a tensile strength of 215 MPa, a microchannel dimensional tolerance of ≤ ±0.05 mm, and is free from defects such as cold shuts, shrinkage cavities, and air holes.

[0033] Example 2

[0034] A multi-cavity parallel microchannel copper heat sink for high-power IGBT modules was fabricated. The microchannels are 0.3 mm wide and 0.8 mm high, with a total of 32 parallel channels. The specific steps are as follows: S1. Organic precursor preparation: Using photopolymerization 3D printing technology, an organic precursor with a complex multi-cavity parallel structure was printed using PMMA resin, with a layer thickness of 0.05 mm and a dimensional accuracy of ±0.02 mm. S2. Ceramic Slurry Preparation and Filling: Weigh out 40 parts by weight of 150-mesh quartz powder, 35 parts by weight of 600-mesh quartz powder, and 25 parts by weight of 1000-mesh quartz powder as ceramic aggregates. Add 12 parts by weight of organic binder (specifications same as in Example 1) and mix thoroughly to prepare a ceramic slurry. Perform the mixture under vacuum (vacuum degree 1×10⁻⁶). -2 Pa) Pour the slurry into the PMMA precursor, ensuring complete filling of the fine structure, and then vibrate and compact for 15 minutes; S3. Core preparation: After drying by step heating, the core is sintered at 1300℃ in air atmosphere for 3 hours to completely decompose PMMA and sinter the quartz to obtain a ceramic core. S4. Core surface pretreatment: A cobalt coating with a thickness of approximately 5 μm is deposited on the core surface using a magnetron sputtering process; S5. Mold Assembly: The outer mold is machined from graphite, and a layer of graphite-based release agent with a thickness of approximately 150μm is evenly sprayed onto the surface of the outer mold cavity. The prepared ceramic core is then precisely installed into the outer mold. S6. Melting and casting: at 1×10 -2 Oxygen-free copper (C10100) was melted under vacuum at 1180°C until completely melted, and then microalloyed by adding 0.03 wt% silicon. The mixture was then side-cast at 1180°C at a casting speed of 0.3 kg / s. S7. Directional solidification control: Three-stage induction heating is used to control the temperature gradient: 980℃ in the gating section, 880℃ in the middle section, and 780℃ in the far section. After holding at this temperature for 1.5 hours, the temperature is allowed to cool naturally. S8. Core removal: The casting is placed in a 30% sodium hydroxide solution at 40℃ and subjected to ultrasonic vibration with a power of 250W. After soaking for 40 hours, the core is completely dissolved. It is then rinsed with deionized water to obtain a radiator with an intact structure and no damage. Testing revealed that the radiator casting has a density of 99.6%, a thermal conductivity of 392 W / (m·K), a tensile strength of 208 MPa, and all 32 microchannels are unobstructed, without blockage or deformation.

[0035] Example 3

[0036] A cylindrical copper heat sink with internal three-dimensional spiral microchannels was fabricated. The spiral channel diameter was 0.4 mm and the pitch was 2 mm. The specific steps are as follows: S1. Preparation of organic precursor: Using water-soluble PVA plastic, a three-dimensional helical channel organic precursor is formed by machining and bonding. S2. Core Preparation: After filling with quartz-based ceramic slurry and vibrating to compact it, the component is immersed in 40°C warm water to dissolve most of the PVA material and undergo preliminary demolding. Then, it is dried at 100°C for 6 hours and sintered at 1500°C for 2 hours to obtain the ceramic core; S3. Core surface pretreatment: A silica-based functional coating with a thickness of approximately 2 μm is prepared on the core surface using the sol-gel method; S4. Mold assembly, melting, and solidification control: The basic process is the same as in Example 1, except that the casting temperature is 1220℃, and 0.08wt% of cerium is added for microalloying; solidification control uses two induction coils arranged vertically to achieve axial (from top to bottom) directional solidification, with the upper temperature at 1020℃ and the lower temperature at 820℃. S5. Core removal: Soak in a 30% hydrofluoric acid solution at room temperature for about 40 hours, supplemented with ultrasonic vibration, until the core is completely dissolved and then rinsed clean. Testing revealed that the radiator's three-dimensional spiral microchannel structure was intact, without deformation or blockage. The casting density was 99.5%, the thermal conductivity was 390 W / (m·K), and the tensile strength was 205 MPa.

[0037] Example 4

[0038] Endpoint verification: Coating thickness 1μm Except for controlling the coating thickness on the core surface to 1 μm, the other steps are exactly the same as in Example 1.

[0039] Testing revealed that with a plating thickness of 1 μm, the nickel layer on the core surface was continuous and uniform, with no plating defects. Demolding after casting was smooth, the microchannel structure of the casting was intact, the filling rate was 100%, and there was no sticking. The radiator casting had a density of 99.6% and a thermal conductivity of 393 W / (m·K), comparable to that of Example 1 (3 μm plating), indicating that a 1 μm plating layer is sufficient to meet the basic requirements of reducing the wetting angle and ensuring filling.

[0040] Example 5

[0041] Endpoint verification: Coating thickness 10μm Except for controlling the coating thickness on the core surface to 10μm, the other steps are exactly the same as in Example 1.

[0042] Testing revealed that with a plating thickness of 10 μm, the nickel layer on the core surface was dense, with no peeling or flaking. Demolding after casting was normal, the microchannel structure of the casting was intact, and the filling rate was 100%. The density of this radiator casting was 99.8%, and the thermal conductivity was 396 W / (m·K), slightly lower than that of Example 1. However, increasing the plating thickness increased the core preparation cost by approximately 15%. Considering both performance and cost, a plating thickness of 1–5 μm is preferred. The above examples demonstrate that the present invention can achieve the expected technical effects within the plating thickness range of 1 μm to 10 μm.

[0043] Example 6

[0044] Endpoint verification: hydrofluoric acid concentration 20%, soaking time 50h Except for the core removal step, which uses a 20% hydrofluoric acid solution and is soaked at room temperature for 50 hours, the other steps are exactly the same as in Example 1.

[0045] Testing showed that the core completely dissolved after 50 hours of immersion, with no corrosion on the copper busbar surface and smooth, residue-free inner walls of the microchannels. Compared to Example 1 (40% concentration, 20 hours), the dissolution time was longer at the lower concentration, but non-destructive removal was still achieved, and the waste acid treatment cost was lower. This example demonstrates that a 20% hydrofluoric acid concentration is also feasible.

[0046] Example 7

[0047] Endpoint verification: hydrofluoric acid concentration 40%, soaking time 10h Except for the core removal step, which uses a 40% hydrofluoric acid solution, is subjected to ultrasonic vibration, and is soaked at room temperature for 10 hours, the other steps are exactly the same as in Example 1.

[0048] Testing showed that the core completely dissolved after 10 hours of immersion, with no corrosion on the copper busbar surface and the microchannel structure remaining intact. Compared to Example 1 (20 hours), the dissolution efficiency was significantly improved at higher concentrations, which can shorten the production cycle. This example demonstrates that the 10-hour immersion time is also feasible.

[0049] Examples 4-7 above demonstrate that the coating thickness (1μm~10μm), hydrofluoric acid concentration (20%~40%), and immersion time (10h~50h) specified by the present invention can achieve effective preparation and non-destructive removal of the core at each endpoint value, and the scope of the claims can be fully supported by the specification.

[0050] Comparative Example 1

[0051] Traditional sand casting and non-vacuum environment A microchannel copper radiator with the same structure as in Example 1 was prepared using a traditional sand casting process. The specific steps are as follows: Core and outer mold: Using furan resin sand as binder and silica sand as aggregate, the sand mold and sand core (used to form microchannels) are made by hand and naturally cured at room temperature for 24 hours.

[0052] Melting and casting: Under atmospheric conditions, pure copper material was placed in a graphite crucible and heated to 1200°C until completely melted, without vacuum degassing or the addition of any microalloying elements. After the copper liquid temperature stabilized at 1200°C, it was poured into the sand mold using a bottom-pouring method at the same casting speed (0.5 kg / s) as in Example 1.

[0053] Solidification and post-treatment: The mold is allowed to cool naturally to room temperature in air, and the risers are removed after sand removal.

[0054] Results: The internal microchannel structure of the casting could not be clearly formed, resulting in numerous cold shuts and incomplete filling defects. Gas could not escape from the mold cavity, leading to severe porosity and slag inclusions inside and on the surface of the casting. The sand core disintegrated and shattered under the impact of high-temperature molten copper (1200°C), and the furan resin sand core could not be effectively removed by chemical solvents (such as hydrofluoric acid or alkaline solutions), rendering all castings unusable. Compared to Example 1, this invention, through a vacuum environment (5×10⁻⁶), achieves better results. -3 By using casting under pressure (Pa), microalloying of the molten copper, employing soluble ceramic cores, and controlling directional solidification, the filling capacity was significantly improved, resulting in a complete and defect-free microchannel structure.

[0055] Comparative Example 2

[0056] One-way wettability control Except for the wettability control strategy, the steps in this comparative example are exactly the same as those in Example 1, as follows: Core and outer mold: The soluble ceramic core (quartz-based, dimensional tolerance ±0.05 mm) was prepared using the same template method as in Example 1, and the outer mold was machined from TZM alloy. The difference from Example 1 is that no wettability treatment was applied to the core surface (no plating / coating), and no microalloying elements were added to the copper melt; only a zinc oxide-based release agent (coating thickness approximately 100 μm) was sprayed onto both the outer mold and core surfaces, i.e., a single wettability strategy was adopted.

[0057] Melting and casting: under a vacuum of 5×10 -3 Pure copper material is heated to 1200℃ and completely melted under Pa conditions, without adding phosphorus copper intermediate alloy. The casting temperature is 1200℃, the casting speed is 0.5kg / s, and a bottom-pouring mold is used.

[0058] Solidification and post-treatment: The same three-stage induction heating directional solidification process as in Example 1 was adopted (1000°C in the gate area, 900°C in the middle area, and 800°C in the far area), and the temperature was maintained for 2 hours before natural cooling. Core removal was performed by soaking in 40% hydrofluoric acid at room temperature for 20 hours, the same as in Example 1.

[0059] Results: Mold opening was successful with no sticking. However, large areas of incomplete filling and cold shut defects appeared in the thin-walled microchannel region of the casting. According to the industrial CT method measured in GB / T 29067-2012, the filling rate was only 65%, which failed to meet the requirements. Compared with Example 1, due to the lack of wettability treatment on the core surface (reducing the copper melt-core wetting angle) and microalloying modification of the copper melt, the spreading ability of the copper melt on the microscale core surface was significantly reduced, resulting in the incomplete filling of the thin-walled region. This comparative example proves that the complete filling of microchannels cannot be achieved by relying solely on the external mold release agent (wetting properties). The "two-way wettability control" strategy of this invention (external mold wetting + core wetting + melt modification) is a necessary technical means to ensure the complete forming of thin-walled microchannels.

[0060] Comparative Example 3

[0061] Traditional diffusion welding process (cost and efficiency comparison benchmark) A serpentine microchannel copper heat sink with the same structure as in Example 1 (microchannel width 0.5mm, height 1mm, wall thickness 0.3mm) was prepared using a machining + diffusion welding process. The steps included: ① precision milling of the copper plate to form a semi-channel; ② diffusion welding of the upper and lower copper plates in a vacuum brazing furnace; ③ machining to remove burrs and polishing.

[0062] Cost accounting (based on a batch of 1000 pieces): Precision milling processing fee: approximately 250 yuan / piece; Diffusion welding fee: approximately 100 yuan / piece (including vacuum furnace energy consumption and tooling fixtures); Material loss: copper plate utilization rate is approximately 60%, material cost per piece is approximately 80 yuan; Post-processing fee: approximately 30 yuan / piece; Total cost per piece: approximately 460 yuan / piece.

[0063] Production efficiency: The welding cycle for a single batch is approximately 8 hours (including vacuuming, heating, heat preservation, and cooling). Each batch can weld 20 pieces simultaneously, which translates to a single-piece production cycle of approximately 0.4 hours (24 minutes).

[0064] Comparative Example 4

[0065] SLM 3D printing process (cost and efficiency comparison benchmark) A serpentine microchannel copper heat sink with the same structure as in Example 1 (microchannel width 0.5 mm, height 1 mm, wall thickness 0.3 mm) was prepared using a selective laser melting (SLM) 3D printer with pure copper powder as the raw material. Printing parameters: laser power 400 W, scanning speed 800 mm / s, layer thickness 0.03 mm.

[0066] Cost calculation (based on a batch of 1000 pieces): Pure copper powder: approximately 800 yuan / kg, powder consumption per piece: 0.3kg, material cost: 240 yuan; equipment depreciation and maintenance: approximately 150 yuan / piece; printing time: approximately 24 hours per piece, equipment labor cost: approximately 200 yuan / piece; post-processing (removal of supports, polishing): approximately 100 yuan / piece; total cost per piece: approximately 690 yuan / piece.

[0067] Production efficiency: The single-piece printing cycle is 24 hours. Even with multi-laser parallel printing, printing 4 pieces in a single furnace at the same time still results in a single-piece production cycle of ≥6 hours, which is much higher than the method of this invention.

[0068] Table 1 Summary of key parameters and test results for each embodiment and comparative example

[0069] Table 1 above illustrates that Examples 1-7 all employed the complete technical solution of this invention (template-based soluble core + bidirectional wettability control + vacuum differential pressure casting + directional solidification), and all yielded qualified products with a filling rate of 100%, density ≥99.5%, and thermal conductivity ≥390 W / (m·K). Examples 4-7 verified the endpoint values ​​of coating thickness (1 μm, 10 μm), hydrofluoric acid concentration (20%, 40%), and immersion time (10 h, 50 h), respectively. Under all endpoint conditions, the expected technical effects were achieved, proving that the numerical range of the claims of this invention has sufficient experimental basis. Comparative Example 1 did not employ any of the core processes of this invention (traditional sand casting, non-vacuum, gravity casting), and the microchannels could not be formed at all, resulting in serious defects in the casting. Comparative Example 2 only used an external mold release agent (unidirectional wettability control), without wettability treatment of the core surface or microalloying of the copper liquid. Although the vacuum degree and casting conditions were the same as in the examples, the filling rate in the thin-walled area was only 65%, which could not meet the usage requirements. The above comparison fully demonstrates that the "bidirectional wettability control strategy" and the complete process system of this invention are key technical features to ensure the complete filling of microchannel structures, and the selection of various numerical ranges has clear experimental basis and technical rationality.

[0070] Table 2. Comparison of cost and production efficiency between the present invention and existing technologies (batch size 1000 units)

[0071] Table 2 above explains: The comprehensive cost per unit of the method of this invention is calculated based on a batch of 1000 units, including material costs (copper material, ceramic slurry, chemical reagents), equipment depreciation (vacuum casting furnace, induction heating equipment), mold amortization (allocated over a lifespan of 100,000 units), labor, and energy consumption, with a unit cost of 60 yuan. The production cycle per unit is calculated as follows: the casting process produces 40 units per batch in 4 hours, equivalent to 0.1 hours per unit; the pickling process processes 2000 units per batch in 20 hours, equivalent to 0.01 hours per unit; adding auxiliary time such as mold preparation, demolding, and cleaning, the total production cycle per unit is approximately 0.2 hours (12 minutes). Compared to SLM 3D printing, the manufacturing cost of this invention is reduced by approximately 91% (from 690 yuan to 60 yuan), and the production efficiency is increased by approximately 30 times (SLM per unit ≥ 6 hours, this invention 0.2 hours), far exceeding the technical indicator of "more than 10 times improvement". Compared to diffusion welding, this invention reduces costs by approximately 87% and doubles production efficiency (diffusion welding takes approximately 0.4 hours per piece, while this invention takes 0.2 hours). These figures are based on pilot-scale calculations; the cost of this invention will still have room for reduction after actual industrial-scale mass production (e.g., reduced mold amortization, increased automation). In contrast, 3D printing has limited room for cost reduction on a large scale due to expensive equipment and low powder utilization. Therefore, this invention has significant economic advantages in large-scale production.

[0072] The core mechanism of this invention lies in: > 1. Template method for soluble cores: The complex three-dimensional microchannel structure is replicated by organic precursors, and then the structure is transferred by ceramic slurry filling and sintering. This not only ensures the high precision of the microchannels, but also solves the problems of high manufacturing difficulty and difficult removal of traditional ceramic cores. 2. Two-way wettability control mechanism: The copper melt-core interfacial energy is reduced by the plating / coating on the core surface, which promotes the spread of copper melt on the microscale core surface; at the same time, the copper melt-outer mold interfacial energy is increased by the mold release agent to prevent sticking, thus systematically solving the contradiction between microchannel filling and demolding. 3. Directional solidification mechanism: Multi-stage induction heating forms a stable axial temperature gradient, which causes the casting to solidify sequentially from the far end to the gate, achieving continuous feeding, effectively eliminating defects such as shrinkage cavities and porosity, and significantly improving the density of the casting.

[0073] The above embodiments are merely preferred embodiments of the present invention. Any simple modifications, alterations, and substitutions made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for liquid forming manufacturing of a copper microchannel liquid-cooled heat sink, characterized in that, Includes the following steps: S1. Core Preparation and Processing First, a soluble ceramic core with a negative microchannel structure inside the heat sink is prepared using a template method. Then, the surface of the soluble ceramic core is pretreated to reduce the wetting angle between the copper liquid and the core surface. S2. Mold Assembly A pre-treated soluble ceramic core is assembled into an outer mold coated with a release agent to form a casting cavity that matches the shape of the radiator. S3. Smelting and Casting Vacuum degree ≤ 1×10 -2 Under a vacuum environment and a protective atmosphere of argon or nitrogen, copper liquid that has undergone fluidity optimization treatment is melted and then poured into a casting cavity. The casting method is bottom pouring, side pouring or top pouring, and the pouring speed is 0.2 kg / s to 1.0 kg / s. S4. Solidification Control During and after casting, multi-segment independently controlled induction heating coils are used to heat the mold in sections and control the temperature online, forming a temperature gradient from the gate to the far end, guiding the casting to achieve directional solidification. S5. Core Removal After the casting solidifies and cools to room temperature, the soluble ceramic core is completely removed by chemical dissolution to obtain a copper microchannel liquid-cooled radiator.

2. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 1, characterized in that, In step S1, the steps for preparing the soluble ceramic core using the template method are as follows: (1) An organic precursor with a negative microchannel structure inside a heat sink was formed using a removable material; (2) Fill the cavity of the organic precursor with ceramic slurry and vibrate to densify it to obtain a green body; (3) The removable material in the green body is removed by a stepped sintering process, and then sintered and solidified to obtain a soluble ceramic core; the dimensional tolerance of the soluble ceramic core is ±0.05mm, the compressive strength at room temperature is ≥20MPa, and the high temperature resistance is ≥1500℃; The stepped sintering process includes the following stages: First heating stage: The green billet is heated from room temperature to 200℃~600℃ at a heating rate of 0.5℃ / min~2℃ / min. During this period, at least one temperature point is selected and held for 0.5h~4h for degreasing treatment. Second heating stage: The degreased green body is heated from the sintering temperature of the first heating stage to the final sintering temperature of 1150℃~1600℃ at a heating rate of 0.8℃ / min~5℃ / min. Heat preservation stage: heat preservation at the final sintering temperature for 2 to 10 hours; Cooling stage: The soluble ceramic core after final sintering is cooled to room temperature in the furnace at a rate of 0.5℃ / min to 2℃ / min.

3. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 2, characterized in that, The removable material is any one of thermoplastic plastic, water-soluble polymer material, or photocurable resin; the ceramic slurry is a quartz-based ceramic slurry containing quartz powder aggregate and organic binder, wherein the quartz powder aggregate contains at least two different particle sizes of quartz powder mixed in the particle size range of 25μm to 75μm, and the organic binder accounts for 5% to 25% of the total mass of the ceramic slurry.

4. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 1, characterized in that, In step S1, the surface of the soluble ceramic core is pretreated by depositing a metal coating or functional ceramic coating with a thickness of 1μm to 10μm on the surface of the soluble ceramic core through chemical plating, magnetron sputtering or sol-gel method; wherein the metal coating is a nickel coating or a cobalt coating, and the functional ceramic coating is a silicon dioxide-based coating.

5. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 1, characterized in that, In step S2, the release agent is an oxide-based release agent or a graphite-based release agent, used to increase the wetting angle between the molten copper and the outer mold surface to prevent the casting from sticking to the mold.

6. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 1, characterized in that, In step S3, the fluidity optimization treatment of the copper liquid is a microalloying treatment, which specifically involves adding one or more elements selected from phosphorus, lithium, cerium, and silicon to the copper liquid, with an addition amount of 0.01wt%~0.1wt%.

7. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 1, characterized in that, In step S3, the smelting temperature of the copper liquid is 1150℃~1250℃, and the casting temperature is 1180℃~1220℃.

8. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 1, characterized in that, In step S4, the multi-segment induction heating method is three independently controlled induction heating segments, forming a temperature gradient of: 950℃~1050℃ in the gate section, 850℃~950℃ in the middle section, and 750℃~850℃ in the far section; the holding time is 1h~3h, and the resulting axial temperature gradient is 5℃ / cm~20℃ / cm.

9. The liquid forming manufacturing method for a copper microchannel liquid-cooled heat sink according to claim 1, characterized in that, In step S5, the chemical dissolution method is as follows: the casting with the soluble ceramic core is immersed in a hydrofluoric acid solution with a concentration of 20%~40% or a sodium hydroxide solution with a concentration of 20%~30% and soaked at room temperature to 60°C for 10h~50h, supplemented by ultrasonic vibration with a power of 100W~300W to accelerate the dissolution.

10. A copper microchannel liquid-cooled heat sink manufactured by any one of the liquid forming methods according to claims 1 to 9, characterized in that, The internal structure has a three-dimensional interconnected microchannel structure. The cross-sectional shape of the microchannel structure is rectangular, circular, trapezoidal or other polygonal, and the minimum feature size is ≤0.5mm. The casting density of the heat sink is ≥99.5%, and the thermal conductivity is ≥390W / (m·K). The thermal conductivity is tested according to GB / T 22588-2008 or equivalent standards.

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