Manufacturing method of harmonica-shaped heat spreader

Abstract

This invention relates to the field of thermal management technology, specifically to a method for manufacturing a harmonica-shaped vapor chamber. The method first provides a copper-aluminum composite billet, which is extruded into a harmonica-shaped shell and microchannels. Then, a differentiated capillary column array is deposited on the inner wall of the microchannels using selective laser melting. Next, copper powder slurry is sintered to form a porous substrate layer. Following this, a dendritic fractal microchannel network is constructed using electrochemical etching, and a nanocomposite coating is deposited. Finally, the shell is laser-welded to seal it. After vacuuming, a nanofluidic working fluid containing carbon nanotubes is filled in, and the process is completed by heat treatment. This method integrates additive manufacturing, micromachining, and surface modification technologies, aiming to manufacture a vapor chamber with high-efficiency thermal transport performance. The integrated manufacturing of the harmonica-shaped shell through copper-aluminum composite material extrusion completely eliminates peripheral welding joints in traditional processes, improving airtightness by over 95%, while maintaining high thermal conductivity and achieving a 35% weight reduction.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology, specifically to a method for manufacturing a harmonica-shaped vapor chamber, particularly a manufacturing process for a harmonica-shaped vapor chamber with a gradient capillary structure prepared using composite material extrusion molding combined with additive manufacturing technology. This method is particularly suitable for applications such as heat dissipation of high-power electronic devices, thermal management of communication equipment, electronic control systems for new energy vehicles, and thermal control of aerospace electronic equipment. Background Technology

[0002] With the rapid development of electronic technology and the continuous increase in power density, heat dissipation has become a key bottleneck restricting the development of high-performance electronic devices. As a highly efficient phase-change heat transfer device, a vapor chamber achieves rapid heat diffusion and transfer through the evaporation-condensation cycle of its internal working fluid, offering significant advantages over traditional solid-state heat conduction methods. However, traditional vapor chamber manufacturing technology still has many limitations.

[0003] Chinese utility model patent CN203231678U discloses a harmonica-shaped heat exchange base tube, which has a flat tubular appearance and internally divided into multiple parallel through holes by reinforcing ribs. It is formed in one piece using aluminum alloy material through a hot extrusion drawing process. Although this technology achieves the integrated molding of the harmonica-shaped structure, it is only suitable for single-phase fluid heat exchange and fails to utilize the efficient characteristics of phase change heat transfer. Furthermore, the internal structure consists of parallel channels with uniform cross-sections, lacking optimized design for the different heat transfer characteristics of the evaporation and condensation ends, and it does not incorporate a capillary wick structure, making reliable reflux of the working fluid impossible and limiting its application in high heat flux density applications.

[0004] Chinese utility model patent CN210805756U discloses a microchannel heat spreader with a cavity structure, which uses a microchannel array to replace the traditional sintered wick and increases the condensation area by setting a cavity structure in the microchannels. Although this technology improves heat transfer performance, it still uses the traditional manufacturing process of processing the upper and lower shells separately and then diffusion welding them. The welding path is long, which can easily lead to airtightness problems and thermal stress concentration, affecting product reliability. In addition, the capillary wick in this technology is a uniform sintered copper powder structure with a single porosity. It fails to perform gradient design according to the different requirements of the evaporation and condensation ends, making it difficult to effectively balance the contradiction between capillary force and flow resistance.

[0005] Existing heat spreader manufacturing technologies generally suffer from the following problems: First, although traditional sintered copper powder wicks have strong capillary force, they have high flow resistance and low permeability, which limits the liquid reflux rate and heat transfer limit; second, although microchannels have low flow resistance, they have weak capillary force and poor anti-gravity performance; third, the working fluid is mostly pure water or organic solvent, which suffers severe performance degradation over a wide temperature range; finally, existing manufacturing processes are complex, involving multiple welding and assembly processes, resulting in low production efficiency, high cost, and difficulty in guaranteeing yield.

[0006] Therefore, there is an urgent need to develop a new method for manufacturing harmonica-shaped heat spreaders that can fully leverage the advantages of integrated molding of the harmonica-shaped structure, achieve precise construction of high-performance capillary wicks, and optimize the working fluid formulation to meet increasingly stringent thermal management requirements. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for manufacturing a harmonica-shaped heat spreader. By organically combining innovative processes such as copper-aluminum composite material extrusion molding, selective laser melting gradient capillary column array, porous substrate sintering, biomimetic dendritic microchannel etching, nanocomposite coating deposition, and nanofluid working fluid filling, the high-performance manufacturing of the harmonica-shaped heat spreader is achieved, significantly improving heat transfer capacity, reducing thermal resistance, and widening the operating temperature range. At the same time, the manufacturing process is simplified, and production efficiency and product reliability are improved.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The manufacturing method of a harmonica-shaped vapor chamber includes the following steps: First, a copper-aluminum composite billet is provided as raw material. This composite billet comprises an oxygen-free copper core layer with a mass percentage of 40% to 50% and an aluminum alloy outer layer with a mass percentage of 50% to 60%. The harmonica-shaped shell is then prepared by extrusion molding at a temperature of 420℃ to 490℃. The resulting shell has 8 to 16 parallel microchannel structures inside, with the cross-sectional width of each microchannel controlled within the range of 0.8mm to 1.5mm and the height controlled within the range of 1.2mm to 2.0mm. This harmonica-shaped structure ensures sufficient steam flow space while providing good structural strength.

[0010] Secondly, a selective laser melting process was used to deposit copper powder on the inner wall of the microchannel to form a capillary column array with gradient porosity. Spherical copper powder with a particle size of 15μm to 45μm was selected as the raw material, the laser power was set in the range of 200W to 350W, and the scanning speed was controlled in the range of 800mm / s to 1500mm / s. In the evaporation end region near the heat source, a first capillary column structure with a column diameter of 200μm to 300μm, a column height of 400μm to 600μm, and a porosity of 55% to 65% was formed to provide strong capillary driving force; while in the condensation end region, a second capillary column structure with a column diameter of 150μm to 250μm, a column height of 200μm to 350μm, and a porosity of 60% to 70% was formed to reduce flow resistance and accelerate liquid reflux.

[0011] Subsequently, a slurry containing copper powder of various particle sizes was prepared and coated onto the surface of the capillary column array. The composition of this copper powder slurry was carefully optimized, comprising 70% to 80% by mass of ultrafine copper powder with a particle size of 3 μm to 8 μm, 15% to 25% by mass of micron-sized copper powder with a particle size of 20 μm to 35 μm, 3% to 6% by mass of nano-sized copper powder with a particle size of 80 nm to 150 nm, and 8% to 12% by mass of ammonium bicarbonate pore-forming agent with a particle size of 50 μm to 100 μm. After coating, the mixture was sintered at 750°C to 850°C for 60 to 90 minutes in a hydrogen protective atmosphere to form a continuous porous substrate layer with a porosity of 35% to 50%. This combination of multi-particle size formulation and pore-forming agent technology significantly improves permeability while maintaining strong capillary forces.

[0012] Next, a dendritic fractal microchannel network was further formed within the microchannels using an electrochemical etching process. Sulfuric acid with a concentration of 150 g / L to 220 g / L was used as the main electrolyte, and the current density was controlled at 8 A / dm³. 2 Up to 15A / dm 2 Within a certain range, a tree-like microchannel structure with a main channel width of 600 μm to 800 μm, a secondary branch width of 300 μm to 450 μm, and a tertiary branch width of 100 μm to 200 μm is etched using a pre-designed mask pattern. This biomimetic design effectively improves the uniformity of liquid distribution and avoids localized drying.

[0013] Then, a nano-coating dispersion was prepared and deposited on the inner surface of the microchannel to further enhance heat transfer performance. The nano-coating dispersion comprises 40% to 50% by mass of alumina nanoparticles with a particle size of 20 nm to 40 nm, 20% to 30% by mass of silica nanoparticles with a particle size of 15 nm to 30 nm, and 5% to 10% by mass of multi-walled carbon nanotubes with an outer diameter of 8 nm to 15 nm. A nanocomposite coating with a thickness of 3 μm to 5 μm was formed by dip-coating, which imparts superhydrophilic properties to the surface, reducing the contact angle to below 10° while simultaneously lowering interfacial thermal resistance.

[0014] Next, laser welding technology was used to seal both ends of the outer casing. The laser power was set to 1000W to 2000W, with a vacuum level of 1×10⁻⁶. -4 The vacuum chamber is evacuated below Pa to thoroughly remove air and adsorbed moisture, ensuring the efficient execution of the subsequent phase change heat transfer process.

[0015] Next, an optimized nanofluid working fluid was formulated and filled into the shell. This nanofluid working fluid contained 70% to 85% by volume of deionized water as a base fluid, 10% to 25% by volume of ethylene glycol to lower the freezing point and regulate surface tension, 0.05% to 0.3% by mass of multi-walled carbon nanotubes relative to the base fluid to enhance thermal conductivity, and 0.5% to 1.5% by mass of surfactant to stabilize the nanoparticle dispersion. The filling volume was controlled to be 75% to 85% of the effective cavity volume, ensuring sufficient working fluid mass while allowing adequate vapor space.

[0016] Finally, after sealing the filling port, the plate is heat-treated at 200°C to 250°C for 6 to 10 hours. This aging process eliminates residual stress, stabilizes the microstructure, improves interfacial bonding strength, and promotes further curing of the nano-coating, thereby improving the reliability and lifespan of the heat spreader.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] First, the harmonica-shaped shell is manufactured in one piece by extruding copper-aluminum composite materials, which completely eliminates the peripheral welding joints in the traditional process, improves airtightness by more than 95%, and achieves a 35% weight reduction while maintaining high thermal conductivity, making it particularly suitable for weight-sensitive applications such as aerospace.

[0019] Second, the innovative selective laser melting technology is used to directly construct a gradient porosity capillary column array on the inner wall of the microchannel. The synergistic cooperation between the high capillary force structure at the evaporation end and the low flow resistance structure at the condensation end increases the capillary driving force by 40% while reducing the flow resistance by 60%, effectively solving the contradiction between capillary force and permeability in traditional capillary core design.

[0020] Third, the porous substrate layer formed by sintering multi-size copper powder with a pore-forming agent has a controllable pore structure and a permeability that is 2 to 3 times higher than that of traditional single-size sintering. At the same time, it maintains sufficient capillary force to ensure the speed and reliability of liquid reflux.

[0021] Fourth, the biomimetic tree-like fractal microchannel network formed by electrochemical etching technology improves liquid distribution uniformity by 80%, enhances anti-drying ability by 3 times, and achieves a maximum heat transfer flux density of 250 W / cm². 2 The above far surpasses traditional parallel channel designs.

[0022] Fifth, the introduction of the alumina-silica-carbon nanotube ternary nanocomposite coating reduces the contact angle of the microchannel inner surface to below 10°, achieving a superhydrophilic state, increasing the capillary suction speed by 35% to 50%, reducing the interfacial thermal resistance by 45%, and increasing the boiling heat transfer coefficient by more than 60%.

[0023] Sixth, the optimized nanofluid working fluid formulation, with the addition of multi-walled carbon nanotubes and graphene oxide nanosheets to the base fluid, increases the thermal conductivity by 25%. Combined with ethylene glycol for adjustment, the operating temperature range is widened to -40℃ to +150℃, greatly enhancing adaptability.

[0024] Seventh, the equivalent thermal conductivity reaches 5000W / (m·K) to 10000W / (m·K), which is more than 12 times that of pure copper. The total thermal resistance is reduced to below 0.08℃ / W, with excellent temperature uniformity and a plane temperature difference of less than 3℃, which greatly improves the heat dissipation performance.

[0025] Eighth, the manufacturing process is simplified and highly integrated, reducing multiple welding and assembly steps, increasing production efficiency by more than 30%, improving the yield rate from 75% to 85% in traditional processes to more than 95%, and reducing overall manufacturing costs by 10% to 20%.

[0026] Ninth, the product reliability is significantly improved. Through rigorous thermal cycling tests, vibration tests and life tests, the service life is extended to more than 15,000 hours, which is 2 to 3 times that of traditional heat spreaders, meeting the requirements for long-term stable operation under harsh working conditions.

[0027] Tenth, the harmonica-shaped heat dissipation plate manufactured by this invention can be widely used in many fields such as heat dissipation of 5G mobile phone chips, thermal management of ultra-thin laptops, heat dissipation of 5G base station power amplifier modules, thermal management of new energy vehicle electronic control systems, heat dissipation of high-power LED lighting, and thermal control of aerospace electronic equipment, and has broad market application prospects and significant economic and social benefits. Attached Figure Description

[0028] Figure 1 This is a perspective view of the harmonica-shaped heat spreader of the present invention.

[0029] Figure 2 This is a cross-sectional schematic diagram of the overall structure of the harmonica-shaped heat spreader of the present invention. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0031] In specific embodiments of the present invention, the raw materials and equipment used are all commercially available products or can be obtained by conventional methods. Specifically, oxygen-free copper (T2 copper, purity greater than or equal to 99.95%) can be purchased from the China General Research Institute of Nonferrous Metals in Beijing; aluminum alloy 6063-T5 can be purchased from China Zhongwang Group; spherical copper powder (particle size 15μm to 45μm, sphericity greater than 0.92) can be purchased from Carpenter Technology Corporation, USA; ultrafine copper powder (particle size 3μm to 8μm) can be purchased from Eckart GmbH, Germany; and nano copper powder (particle size 80nm to 150nm) can be purchased from SkySpring, USA. Ammonium bicarbonate (analytical grade) was purchased from Nanomaterials Inc.; multi-walled carbon nanotubes (outer diameter 8 nm to 15 nm, length 2 μm to 10 μm, purity greater than 95%) were purchased from Suzhou Carbon-rich Graphene Technology Co., Ltd.; graphene oxide nanosheets (thickness 0.8 nm to 1.5 nm, lateral dimension 500 nm to 2000 nm) were purchased from Ningbo RouCarbon Electronics Technology Co., Ltd.; alumina nanoparticles ( The nanoparticles (with a particle size of 20 nm to 40 nm) are available from Nanostructured & Amorphous Materials Inc., USA; silica nanoparticles (with a particle size of 15 nm to 30 nm) are available from Evonik Industries AG, Germany; and the surfactants sodium dodecyl sulfate and Triton X-100 are available from Sigma-Aldrich Corporation, USA.

[0032] In this invention, the selective laser melting equipment uses the EOSINT M 280 metal 3D printer manufactured by EOS GmbH, Germany; the electrochemical etching equipment uses a self-built pulse power supply system, with the workpiece as the anode and a titanium alloy tool electrode as the cathode; the laser welding equipment uses the TruDisk series fiber laser manufactured by TRUMPF, Germany; the vacuum system uses a combination system of dry vacuum pump and molecular pump manufactured by ULVAC, Japan; the ultrasonic dispersion equipment uses the VCX 750 ultrasonic processor manufactured by Sonics & Materials Inc., USA; the heat flow meter in the performance testing system uses the HFS-4 thin-film heat flow sensor manufactured by Omega Engineering Inc., USA; the temperature acquisition uses the NI-9211 thermocouple acquisition module manufactured by National Instruments, USA; and the infrared thermal imager uses the FLIR T640 device manufactured by FLIR Systems Inc., USA.

[0033] The test methods involved in this invention are performed in accordance with the following standards: air tightness testing is performed in accordance with GB / T 32218-2015 "Vacuum Technology Leakage Test Method"; thermal resistance testing is performed in accordance with JEDEC JESD51-14 "Transient Two-Interface Method for Measuring Thermal Resistance Using Thermal Test Chips"; equivalent thermal conductivity calculation is performed in accordance with ASTM E1530-19 "Standard Test Method for Evaluating the Thermal Transfer Properties of Materials by Heat-Protecting Plate Method"; reliability testing is performed in accordance with IEC 60068-2-14 "Environmental Testing - Part 2-14: Tests - Test N: Temperature Change" and GB / T 2423.10 "Environmental Testing for Electrical and Electronic Products - Part 2: Test Methods - Test Fc: Vibration (Sine)".

[0034] Example 1: Standard Harmonica-Shaped Heat Evaporator

[0035] This embodiment prepares an ultra-thin harmonica-shaped heat dissipation plate for the main chip of a smartphone. The external dimensions are designed to be 120mm×60mm×3.5mm, which is suitable for integration into the limited space inside the phone.

[0036] Step 1: Preparation of the copper-aluminum composite billet. Weigh 45% oxygen-free copper (T2 copper, 99.96% purity) and 54.3% aluminum alloy 6063-T5. Add 0.5% silicon carbide nanoparticles with an average particle size of 60nm and 0.1% lanthanum (a rare earth element). Prepare the copper-clad aluminum composite billet using a composite ingot casting method. The copper layer thickness is 2.0mm, and the aluminum core diameter is 30mm. After holding at 480℃ for 40 minutes, extrude at an extrusion ratio of 20 and an extrusion speed of 0.8m / min to obtain a harmonica-shaped shell containing 14 parallel microchannels. Each microchannel has a width of 1.2mm, a height of 1.6mm, and a wall thickness of 0.5mm at the evaporation end and 0.3mm at the condensation end. After extrusion, air cooling is used, with the cooling rate controlled at 20℃ / s.

[0037] Step 2: Construct a gradient porosity capillary column array. A harmonica-shaped shell is fixed to the stage of a selective laser melting device, and spherical copper powder (99.85% purity) with a particle size of 30 μm is laid. In the evaporation region (occupying 40% of the total area), the laser power is set to 280 W, the scanning speed to 1100 mm / s, the scanning spacing to 0.10 mm, the powder layer thickness to 40 μm, and the protective atmosphere to 99.999% pure argon gas. Layer-by-layer melting and deposition forms a first capillary column structure with a diameter of 250 μm, a height of 500 μm, a spacing of 320 μm, and a porosity of 60%. In the condensation region (occupying 40% of the total area), the laser power is adjusted to 240 W, and the scanning speed to 1200 mm / s, forming a second capillary column structure with a diameter of 200 μm, a height of 280 μm, a spacing of 240 μm, and a porosity of 65%. In the transition zone between the two regions (accounting for 20% of the total area), a gradual parameter is used to achieve a smooth transition.

[0038] Step 3: Sintering the porous substrate layer. Prepare the copper powder slurry: Weigh 75% by mass of 5μm ultrafine copper powder, 20% by mass of 25μm micron copper powder, 4% by mass of 100nm nano copper powder, and 10% by mass of 70μm ammonium bicarbonate pore-forming agent. The binder system includes 3.2% by mass of polyvinyl alcohol with a degree of polymerization of 1800 and 0.7% by mass of sodium carboxymethyl cellulose, adjusting the solid content to 50% with deionized water. Apply the slurry to the surface of the capillary column array using a micro-spraying method, controlling the coating thickness to 160μm. After drying at 100℃ for 2.5 hours, degrease in air at 380℃ for 1.8 hours. Subsequently, in a hydrogen atmosphere (99.98% purity), heat to 800℃ at a rate of 6℃ / min, hold for 75 minutes, and then cool in the furnace to 200℃ before air cooling. After sintering, the porosity of the evaporation end substrate layer was 40%, and the porosity of the condensation end substrate layer was 45%. The permeability was measured to be 2.3 × 10⁻⁶. -10 m 2 .

[0039] Step four: Etching the dendritic microchannels. First, a 25 μm thick photosensitive polymer resist mask is fabricated on the microchannel surface using photolithography. The mask pattern is designed with a fractal dimension of 1.7. The electrolyte is prepared using deionized water: 185 g / L sulfuric acid, 40 g / L phosphoric acid, 28 g / L glycerol, and 1.0 g / L benzotriazole corrosion inhibitor. A titanium alloy is used as the tool cathode, and the current density is set to 11 A / dm³. 2The processing voltage was 14V, the electrolyte flow rate was 4.5m / s, and the temperature was controlled at 25℃ ± 2℃. After electrochemical machining for 30 minutes, a tree-like structure was formed with a main channel width of 700μm and a depth of 400μm, secondary branches with a width of 380μm and a depth of 280μm, and tertiary branches with a width of 150μm and a depth of 120μm, with a branch angle of 40°. The resist was removed by ultrasonic cleaning with acetone for 12 minutes, passivated in 0.8% potassium dichromate solution for 7 minutes, and then dried with nitrogen.

[0040] Step 5: Deposition of the nano-coating. Preparation of the nano-coating dispersion: Weigh 45% by mass of 30nm alumina nanoparticles, 25% by mass of 22nm silica nanoparticles, 6% by mass of 10nm zinc oxide nanoparticles, 7.5% by mass of 12nm multi-walled carbon nanotubes, and 3% by mass of silane coupling agent KH-570. Prepare the dispersion using a 1:1 volume ratio of anhydrous ethanol and deionized water. Disperse the dispersion ultrasonically (400W, 20kHz) for 75 minutes. Apply the coating using a dip-coating method at a speed of 3.5mm / s. Dry each layer at 110℃ for 35 minutes, repeating the coating process three times for a total coating thickness of 4μm. Finally, cure the coating by heat treatment at 200℃ for 1.8 hours. The measured contact angle is 8°, adhesion is 22MPa, and thermal conductivity is 10W / (m·K).

[0041] Step Six: Laser Welding and Sealing. A pure copper plate (1.2mm thick) was used as the end cap material, with a 2.0mm diameter filling hole pre-drilled on the end cap. The sealing surface of the end cap was mechanically ground to a surface roughness Ra less than or equal to 0.4μm. Welding was performed using a fiber laser with a laser power of 1600W, pulsed mode, pulse frequency of 35Hz, pulse width of 5.5ms, welding speed of 12mm / s, and shielding gas of argon gas with a purity of 99.999% or higher, a flow rate of 20L / min, and a spot diameter of 0.45mm. Post-weld, a helium mass spectrometry leak test was performed, with a leak rate of 5×10⁻⁶. -10 Pa·m 3 / s. Place the vapor chamber with the heat spreader, pump the vacuum to 10 Pa using a mechanical pump, and then pump the vacuum to 3 × 10 Pa using a molecular pump. -4 Pa was degassed by heating at 90°C for 35 minutes under vacuum.

[0042] Step 7: Filling the nanofluid working fluid. Prepare the nanofluid: Weigh 77% deionized water (resistivity 18.5 MΩ·cm), 18% ethylene glycol (analytical grade), and 5% n-propanol (volume percentage). Add, relative to the base solution, 0.18% multi-walled carbon nanotubes (outer diameter 12 nm, length 5 μm), 0.06% graphene oxide nanosheets (thickness 1.2 nm), 1.0% sodium dodecyl sulfate, and 0.5% Triton X-100. Disperse using ultrasound (800 W, 22 kHz) for 120 minutes in an ice bath. Stir magnetically (800 rpm) for 45 minutes, let stand for 24 hours, and collect the supernatant. Filter through a 0.45 μm filter membrane. The nanofluid was measured to have a thermal conductivity of 0.78 W / (m·K), a viscosity of 1.5 mPa·s, a surface tension of 40 mN / m, and an absolute zeta potential of 38 mV at 25 °C. Based on a cavity volume of 10.5 cm³... 3 Based on a porosity of 0.48, the filling volume is calculated to be 4.0 mL (80% filling rate). Under vacuum, the pressure is increased to 0.10 MPa with argon gas, and filling is performed slowly at a rate of 1.0 mL / min. After filling, the vacuum state is maintained for 8 minutes to ensure sufficient wetting of the working fluid. The filling volume error is verified to be less than 1.5% by weighing.

[0043] Step 8, Sealing and Heat Treatment. A copper cap and Sn-3.0Ag-0.5Cu solder were used to braze and seal the filling port at 240℃. After sealing, helium mass spectrometry leak testing was performed, and the leak rate was 3×10⁻⁶. -10 Pa·m 3 / s. Place the heat spreader in a tube furnace, introduce nitrogen protective atmosphere, raise the temperature to 225℃ at a rate of 45℃ / h, hold for 8 hours, cool with the furnace to 100℃, and then remove and air cool to room temperature.

[0044] The harmonica-shaped heat spreader prepared in this embodiment is intact, without deformation or leakage. Performance test results show that under a heating power of 100W, the total thermal resistance is 0.067℃ / W, the surface temperature uniformity at the evaporation end is excellent, the maximum temperature difference is 2.8℃, the equivalent thermal conductivity reaches 7200W / (m·K), and the maximum heat transfer flux density is 275W / cm³. 2 The startup time is 12 seconds. After thermal cycling tests (from -40°C to +120°C, 3000 cycles) and vibration tests (10Hz to 2000Hz, 20g acceleration, 2 hours in each direction), the performance degradation is less than 5%. After 15,000 hours of continuous operation, the total thermal resistance increases by only 8%, demonstrating excellent long-term reliability.

[0045] This embodiment is applied to the main chip heat dissipation system of a flagship 5G smartphone from a certain brand, replacing the original graphite sheet heat dissipation solution. Actual application testing shows that, under the same usage scenario, the chip's peak temperature is reduced by 9°C, and temperature fluctuations are reduced by 60%, effectively avoiding processor throttling caused by overheating and improving the user experience. Simultaneously, due to the improved heat dissipation efficiency, the chip can continue to operate at higher power, resulting in an overall performance improvement of approximately 15%.

[0046] Example 2: Lightweight Harmonica-Shaped Heat Evaporator

[0047] This embodiment prepares a lightweight harmonica-shaped vapor chamber for cooling laptop CPUs, with external dimensions of 150mm×80mm×4.0mm.

[0048] Step one: In preparing the copper-aluminum composite billet, oxygen-free copper (40% by mass) and aluminum alloy (59.2% by mass) were used, along with silicon carbide (0.3% by mass, average particle size 50 nm) and lanthanum (0.5% by mass). The extrusion temperature was set at 450℃, held for 30 minutes, with an extrusion ratio of 18 and an extrusion speed of 0.6 m / min, resulting in a harmonica-shaped shell containing 12 parallel microchannels, each microchannel having a width of 1.0 mm and a height of 1.4 mm.

[0049] Step two involves selective laser melting using spherical copper powder with a particle size of 20 μm. In the evaporation region, the laser power is 220 W, the scanning speed is 900 mm / s, the scanning spacing is 0.09 mm, and the powder layer thickness is 35 μm, forming a first capillary column structure with a diameter of 220 μm, a height of 450 μm, a spacing of 280 μm, and a porosity of 58%. In the condensation region, the laser power is 200 W, the scanning speed is 1000 mm / s, forming a second capillary column structure with a diameter of 170 μm, a height of 250 μm, a spacing of 200 μm, and a porosity of 68%.

[0050] Step 3, Copper Powder Slurry Formulation: 72% by mass of 4μm ultrafine copper powder, 18% by mass of 22μm micron copper powder, 4.5% by mass of 90nm nano copper powder, 9% by mass of 60μm ammonium bicarbonate, 2.8% by mass of polyvinyl alcohol (degree of polymerization 1750), and 0.6% by mass of sodium carboxymethyl cellulose. Coating thickness: 140μm. Drying temperature: 95℃ for 2 hours. Degreasing temperature: 360℃ for 1.6 hours. Sintering temperature: 780℃, holding time: 65 minutes. Porosity after sintering: 38% at the evaporation end and 43% at the condensation end.

[0051] Step 4, Electrolyte formulation: 160 g / L sulfuric acid, 35 g / L phosphoric acid, 23 g / L glycerol, and 0.7 g / L benzotriazole. Current density: 9 A / dm³2 The processing voltage was 12V, the flow rate was 3.8m / s, the temperature was 25℃ ±2℃, and the processing time was 25 minutes. This resulted in a main channel with a width of 650μm and a depth of 350μm, secondary branches with a width of 330μm and a depth of 250μm, tertiary branches with a width of 120μm and a depth of 90μm, a branch angle of 35°, and a fractal dimension of 1.6.

[0052] Step 5, Nanocoating Formulation: 42% by mass of 25nm alumina, 22% by mass of 18nm silica, 4% by mass of 28nm zinc oxide, 6% by mass of 10nm carbon nanotubes, and 2.5% by mass of KH-570. Ultrasonic treatment (400W power) for 65 minutes, lifting speed 2.8mm / s, drying temperature 105℃ for 32 minutes, three coats, total thickness 3.5μm, curing temperature 190℃ for 1.6 hours. Contact angle 7°, adhesion 19MPa.

[0053] Step 6: Laser welding power 1200W, pulse frequency 25Hz, pulse width 4ms, welding speed 10mm / s, argon flow rate 18L / min. Vacuum level evacuated to 2×10⁻⁶. -4 Pa, degassing temperature 85℃, time 32 minutes.

[0054] Step 7, Nanofluid Formulation: 74% deionized water (volume percentage), 20% ethylene glycol (volume percentage), 6% n-propanol (volume percentage), 0.12% 10nm multi-walled carbon nanotubes (mass percentage), 0.04% graphene oxide (mass percentage), 0.8% sodium dodecyl sulfate (mass percentage), and 0.4% Triton X-100 (mass percentage). Ultrasonic treatment (700W power) for 100 minutes. Thermal conductivity 0.74 W / (m·K), viscosity 1.3 mPa·s. Filling volume 5.8 mL (78% filling rate), filling rate 0.8 mL / min, pressurization 0.08 MPa.

[0055] Step 8: Brazing temperature 230℃, heat treatment temperature 215℃, holding temperature for 7 hours, heating rate 40℃ / h.

[0056] Performance test results: Total thermal resistance at 100W power is 0.072℃ / W, temperature difference is 2.5℃, equivalent thermal conductivity is 6800W / (m·K), and maximum heat transfer flux is 260W / cm². 2 Weighing only 32g, it is 38% lighter than the pure copper solution. Applied to a certain brand of ultra-thin laptops, it effectively resolves the conflict between lightweight design and high-performance heat dissipation.

[0057] Example 3: Wide-temperature harmonica-shaped heat spreader

[0058] This embodiment prepares a wide-temperature harmonica-shaped heat spreader for outdoor power amplifier modules of 5G base stations, with external dimensions of 200mm×100mm×4.5mm, focusing on enhancing low-temperature start-up and high-temperature operating performance.

[0059] Step 1: Using 50% oxygen-free copper and 49.2% aluminum alloy by mass, 0.8% silicon carbide with an average particle size of 80nm and 0.15% lanthanum by mass were added. The extrusion temperature was 490℃, the holding time was 45 minutes, the extrusion ratio was 25, and the extrusion speed was 1.2m / min, resulting in a shell containing 10 microchannels, with a width of 1.5mm, a height of 2.0mm, a wall thickness of 0.6mm at the evaporation end, and a wall thickness of 0.4mm at the condensation end.

[0060] Step two involves selecting copper powder with a particle size of 45 μm, using a laser power of 350 W at the evaporation end, a scanning speed of 800 mm / s, a scanning spacing of 0.12 mm, and a powder layer thickness of 50 μm to form a first capillary column structure with a diameter of 300 μm, a height of 600 μm, a column spacing of 400 μm, and a porosity of 55%, providing the strongest capillary force. At the condensation end, a laser power of 280 W and a scanning speed of 1500 mm / s are used to form a second capillary column structure with a diameter of 150 μm, a height of 200 μm, a column spacing of 180 μm, and a porosity of 70%, achieving the lowest flow resistance design.

[0061] Step 3, Copper Powder Slurry: 80% by mass of 8μm ultrafine copper powder, 15% by mass of 35μm micron copper powder, 3% by mass of 150nm nano copper powder, 12% by mass of 100μm ammonium bicarbonate, 4.0% by mass of polyvinyl alcohol (degree of polymerization 2000), and 1.0% by mass of sodium carboxymethyl cellulose. Coating thickness 200μm, drying at 100℃ for 2.8 hours, degreasing at 400℃ for 2 hours, and sintering at 850℃ for 90 minutes. Evaporation end porosity 35%, condensation end porosity 50%, permeability 3.2×10⁻⁶. -10 m 2 .

[0062] Step 4, Electrolyte: 220 g / L sulfuric acid, 50 g / L phosphoric acid, 35 g / L glycerol, 1.5 g / L benzotriazole. Current density: 15 A / dm³ 2 Voltage 18V, flow rate 6m / s, processing time 45 minutes. Main channel 800μm×500μm, secondary branch 450μm×350μm, tertiary branch 200μm×150μm, branch angle 50°, fractal dimension 1.8.

[0063] Step 5, Nanocoating: 50% by mass of 40nm alumina, 30% by mass of 30nm silica, 8% by mass of 45nm zinc oxide, 10% by mass of 15nm carbon nanotubes, and 4% by mass of KH-570. Ultrasonic treatment (600W power) for 90 minutes, lifting speed 5mm / s, drying at 120℃ for 40 minutes, four coats, total thickness 5μm, curing at 220℃ for 2 hours. Contact angle 5°, adhesion 24MPa, thermal conductivity 12W / (m·K).

[0064] Step 6: Laser power 2000W, pulse 50Hz, pulse width 8ms, velocity 15mm / s, argon gas 25L / min. Vacuum 5×10⁻ 5 Pa, degas at 100℃ for 45 minutes.

[0065] Step 7, Wide-Temperature Formulation of Nanofluid: 70% deionized water (volume percentage), 25% ethylene glycol (volume percentage, significantly lowering the freezing point), 8% isopropanol (volume percentage), 0.3% multi-walled carbon nanotubes (outer diameter 15nm, length 10μm) (mass percentage), 0.1% graphene oxide (mass percentage), 1.5% sodium dodecyl sulfate (mass percentage), and 0.8% Triton X-100 (mass percentage). Ultrasonication (1000W power) for 180 minutes. Thermal conductivity 0.85 W / (m·K), viscosity 1.8 mPa·s, freezing point -28℃, boiling point 112℃. Filling volume 10.5 mL (85% filling rate), filling rate 1.5 mL / min, pressurization 0.15 MPa.

[0066] Step 8: Brazing at 260℃, heat treatment at 250℃ for 10 hours, heating rate 50℃ / h.

[0067] Performance Testing: At 100W power, the total thermal resistance is 0.075℃ / W, the temperature difference is 2.2℃, and the equivalent thermal conductivity is 7500W / (m·K). Wide-temperature performance testing shows that it successfully started up and reached steady-state operation within 12 seconds in a -30℃ low-temperature environment, and operated continuously at 200W power for 24 hours in a +55℃ high-temperature environment without failure. After 5000 temperature cycles from -40℃ to +120℃, the performance degradation is less than 8%. It has been successfully applied to a 5G macro base station AAU module of a telecommunications equipment manufacturer, demonstrating excellent performance in both the frigid Northeast and the scorching Northwest environments.

[0068] Example 4: High-power harmonica-shaped heat spreader

[0069] This embodiment prepares a high-power harmonica-shaped vapor chamber for cooling the CPU of a data center server. The outer dimensions are 160mm×90mm×4.2mm, and the designed heat dissipation power is over 200W.

[0070] Step 1: The composite billet contains 47% oxygen-free copper, 52.4% aluminum alloy, 0.6% silicon carbide with an average particle size of 65 nm, and 0.12% lanthanum by mass. The extrusion temperature is 470℃, the holding time is 38 minutes, the extrusion ratio is 22, and the extrusion speed is 0.9 m / min, resulting in a shell with 11 microchannels, a width of 1.3 mm, and a height of 1.8 mm.

[0071] Step two: Using copper powder with a particle size of 35 μm, the laser power at the evaporation end is 300 W, the scanning speed is 1000 mm / s, the scanning spacing is 0.11 mm, and the powder layer thickness is 45 μm, forming a first capillary column structure with a column diameter of 270 μm, a column height of 550 μm, a column spacing of 350 μm, and a porosity of 62%. At the condensation end, the laser power is 260 W, and the scanning speed is 1300 mm / s, forming a second capillary column structure with a column diameter of 180 μm, a column height of 300 μm, a column spacing of 260 μm, and a porosity of 67%.

[0072] Step 3, Copper Powder Slurry: 77% by mass of 6μm particles, 22% by mass of 28μm particles, 5% by mass of 120nm particles, 11% by mass of 80μm ammonium bicarbonate particles, 3.5% by mass of polyvinyl alcohol (degree of polymerization 1900), and 0.8% by mass of sodium carboxymethyl cellulose. Coating to 180μm, drying at 98℃ for 2.3 hours, degreasing at 375℃ for 1.7 hours, and sintering at 820℃ for 80 minutes. Evaporation end porosity 42%, condensation end porosity 48%.

[0073] Step 4, Electrolyte: 195 g / L sulfuric acid, 45 g / L phosphoric acid, 30 g / L glycerol, and 1.2 g / L benzotriazole. Current density: 13 A / dm³ 2 Voltage 16V, flow rate 5m / s, processing time 38 minutes. Main channel 750μm×460μm, secondary branch 400μm×310μm, tertiary branch 170μm×130μm, branch angle 45°, fractal dimension 1.75.

[0074] Step 5, Nanocoating: 47% by mass of 35nm alumina, 27% by mass of 24nm silica, 7% by mass of 38nm zinc oxide, 9% by mass of 13nm carbon nanotubes, and 3.5% by mass of KH-570. Ultrasonic treatment (550W) for 80 minutes, pulling speed 4mm / s, drying at 115℃ for 38 minutes, three coats applied, total thickness 4.5μm, curing at 210℃ for 1.9 hours. Contact angle 9°, adhesion 21MPa.

[0075] Step 6: Laser 1800W, pulse 42Hz, pulse width 7ms, velocity 13mm / s, argon gas 23L / min. Vacuum 8×10⁻ 5 Pa, degas at 95℃ for 40 minutes.

[0076] Step 7, Nanofluid: 80% deionized water (volume percentage), 15% ethylene glycol (volume percentage), 5% n-propanol (volume percentage), 0.22% multi-walled carbon nanotubes (outer diameter 13 nm, length 7 μm) (mass percentage), 0.08% graphene oxide (mass percentage), 1.2% sodium dodecyl sulfate (mass percentage), and 0.6% Triton X-100 (mass percentage). Ultrasonication (850 W power) for 150 minutes. Thermal conductivity 0.81 W / (m·K), viscosity 1.6 mPa·s. Filling volume 7.5 mL (82% filling rate), filling rate 1.2 mL / min, pressurization 0.12 MPa.

[0077] Step 8: Brazing at 245℃, heat treatment at 235℃ for 9 hours, heating rate 47℃ / h.

[0078] Performance testing: Total thermal resistance at 150W power is 0.053℃ / W, temperature difference is 1.8℃, equivalent thermal conductivity is 8500W / (m·K), and maximum heat transfer flux is 295W / cm². 2 It can operate stably at a power level of 220W. Applied to a high-performance server in a cloud computing data center, it effectively reduced cooling energy consumption and improved the PUE value by 12%.

[0079] Example 5: Ultra-thin harmonica-shaped heat spreader (covering the thinnest possible area)

[0080] This embodiment prepares an ultra-thin harmonica-shaped heat spreader for ultra-thin tablet computers, with external dimensions of 110mm×70mm×3.0mm, pursuing the ultimate thinness.

[0081] Step 1: The composite billet contains 43% oxygen-free copper, 56.5% aluminum alloy, 0.4% silicon carbide with an average particle size of 55 nm, and 0.08% lanthanum by mass. The extrusion temperature is 440℃, the holding time is 35 minutes, the extrusion ratio is 16, and the extrusion speed is 0.7 m / min, resulting in a shell with 9 microchannels, a width of 0.9 mm, a height of 1.3 mm, an evaporation end wall thickness of 0.4 mm, and a condensation end wall thickness of 0.25 mm.

[0082] Step two: Using copper powder with a particle size of 18 μm, the laser power at the evaporation end is 230 W, the scanning speed is 950 mm / s, the scanning spacing is 0.085 mm, and the powder layer thickness is 32 μm, forming a first capillary column structure with a column diameter of 210 μm, a column height of 420 μm, a column spacing of 270 μm, and a porosity of 59%. At the condensation end, the laser power is 210 W, and the scanning speed is 1100 mm / s, forming a second capillary column structure with a column diameter of 160 μm, a column height of 230 μm, a column spacing of 190 μm, and a porosity of 66%.

[0083] Step 3, Copper Powder Slurry: 73% by mass of 3.5μm particle size, 19% by mass of 23μm particle size, 3.8% by mass of 85nm particle size, 8.5% by mass of 55μm ammonium bicarbonate, 2.7% by mass of polyvinyl alcohol (degree of polymerization 1720), and 0.55% by mass of sodium carboxymethyl cellulose. Coating thickness 120μm, drying at 92℃ for 2.2 hours, degreasing at 355℃ for 1.5 hours, and sintering at 770℃ for 68 minutes. Evaporation end porosity 36%, condensation end porosity 42%.

[0084] Step 4, Electrolyte: 170 g / L sulfuric acid, 38 g / L phosphoric acid, 25 g / L glycerol, 0.85 g / L benzotriazole. Current density: 10 A / dm³ 2 Voltage 13V, flow rate 4.2m / s, processing time 22 minutes. Main channel 670μm×380μm, secondary branch 350μm×270μm, tertiary branch 130μm×100μm, branch angle 38°, fractal dimension 1.65.

[0085] Step 5, Nanocoating: 43% by mass of 28nm alumina, 23% by mass of 20nm silica, 5% by mass of 32nm zinc oxide, 6.5% by mass of 11nm carbon nanotubes, and 2.8% by mass of KH-570. Ultrasonic treatment (450W power) for 70 minutes, pulling speed 3.2mm / s, drying at 108℃ for 35 minutes, three coats, total thickness 3.8μm, curing at 195℃ for 1.7 hours. Contact angle 6.5°, adhesion 20MPa.

[0086] Step 6: Laser 1400W, pulse 32Hz, pulse width 5ms, velocity 11mm / s, argon gas 19L / min. Vacuum 4×10 - 4 Pa, degas at 88℃ for 35 minutes.

[0087] Step 7, Nanofluid: 78% deionized water (volume percentage), 17% ethylene glycol (volume percentage), 4.5% n-propanol (volume percentage), 0.15% multi-walled carbon nanotubes (outer diameter 11 nm, length 4 μm) (mass percentage), 0.055% graphene oxide (mass percentage), 0.95% sodium dodecyl sulfate (mass percentage), and 0.48% Triton X-100 (mass percentage). Ultrasonication (750 W power) for 115 minutes. Thermal conductivity 0.76 W / (m·K), viscosity 1.4 mPa·s. Filling volume 2.8 mL (79% filling rate), filling rate 0.9 mL / min, pressurization 0.09 MPa.

[0088] Step 8: Brazing at 235℃, heat treatment at 220℃ for 7.5 hours, heating rate 43℃ / h.

[0089] Performance testing: Total thermal resistance at 80W power is 0.078℃ / W, temperature difference is 2.6℃, and equivalent thermal conductivity is 6500W / (m·K). Weighing only 15g and with a thickness of 3.0mm, it has been successfully integrated into an ultra-thin tablet computer with a thickness of only 8mm, verifying the enormous potential of this invention in ultra-thin design.

[0090] Comparative Example 1: Comparative Example of Gradient-Free Capillary Array

[0091] The main difference between this comparative example and Example 1 is that, in step two, a gradient porosity design was not used. Instead, a capillary column array with the same parameters was used throughout the entire inner wall of the microchannel. Specifically, the parameters were: laser power 260W, scanning speed 1050mm / s, resulting in a uniform capillary column structure with a column diameter of 225μm, a column height of 380μm, a column spacing of 280μm, and a porosity of 62%. All other steps were identical to those in Example 1.

[0092] Performance test results show that: at 100W power, the total thermal resistance is 0.092℃ / W, which is 37% higher than that of Example 1; the temperature difference is 4.5℃, which is 61% higher than that of Example 1; the equivalent thermal conductivity is 5200W / (m·K), which is 28% lower than that of Example 1; and the maximum heat transfer flux is 210W / cm². 2 The temperature was 24% lower than in Example 1. During the test, a slight abnormal temperature rise was observed in the central region of the evaporator when operating at high power, indicating insufficient liquid reflux and a risk of localized drying.

[0093] This comparative example verifies the importance of gradient porosity capillary column array design. The evaporation end requires high capillary force to ensure liquid supply, while the condensation end requires low flow resistance to accelerate liquid reflux. A uniform design cannot satisfy both requirements, leading to a decline in overall performance.

[0094] Comparative Example 2: Comparative Example without Dendritic Microchannels

[0095] The main difference between this comparative example and Example 1 is that in step four, electrochemical etching was not performed to form dendritic microchannels; only the extruded parallel channel structure was retained. The other steps are exactly the same as in Example 1.

[0096] Performance test results: At 100W power, the total thermal resistance was 0.085℃ / W, 27% higher than Example 1; the temperature difference was 3.8℃, 36% higher than Example 1; the equivalent thermal conductivity was 5800W / (m·K), 19% lower than Example 1; and the maximum heat transfer flux was 230W / cm². 2 The temperature was 16% lower than in Example 1. Infrared thermography showed that the temperature distribution at the evaporation end was uneven, with the temperature in areas far from the main path of the microchannel being significantly higher, indicating uneven liquid distribution.

[0097] This comparative example demonstrates the crucial role of dendritic fractal microchannel networks in improving the uniformity of liquid distribution. Although parallel channels have low flow resistance, the liquid can only flow along the main channel and cannot effectively cover the entire evaporation surface, resulting in insufficient working fluid supply in local areas and limiting heat transfer performance.

[0098] Comparative Example 3: Comparative Example without Nanocoating

[0099] The main difference between this comparative example and Example 1 is that no nano-coating deposition was performed in step five. All other steps are exactly the same as in Example 1.

[0100] Performance test results: The total thermal resistance at 100W power is 0.078℃ / W, which is 16% higher than that of Example 1; the start-up time is 19 seconds, which is 58% longer than that of Example 1; the performance is similar when running at low power (below 30W), but the performance difference is significant when running at high power (above 100W). The contact angle measurement value is 45°, which is much higher than 8° in Example 1, indicating poor surface wettability.

[0101] This comparative example demonstrates the significant effect of nano-coatings on enhancing the hydrophilicity of capillary structures and reducing interfacial thermal resistance. The superhydrophilic coating accelerates the spreading and penetration of liquids within the capillary structure, improving capillary suction efficiency, particularly during start-up and under high-power conditions.

[0102] Comparative Example 4: Comparative Example Using Pure Water as the Working Medium

[0103] The main difference between this comparative example and Example 1 is that no nanoparticles or ethylene glycol were added in step seven; only pure deionized water was used as the working fluid. The filling volume was adjusted to 3.8 mL to maintain the same filling ratio. All other steps were exactly the same as in Example 1.

[0104] Performance test results: At 25℃ and 100W power operation, the total thermal resistance is 0.075℃ / W, which is close to that of Example 1; however, at a low temperature of -10℃, it failed to start up, and the internal working fluid froze, leading to failure; after long-term operation at a high temperature of 80℃, the performance degraded by 20%, and the internal pressure increased significantly. Poor wide temperature adaptability is the biggest drawback.

[0105] This comparative example highlights the superiority of nanofluids. While pure water performs reasonably well at room temperature, its high freezing point and relatively low boiling point limit its operating temperature range. The addition of nanoparticles improves thermal conductivity and boiling heat transfer coefficient, while the addition of ethylene glycol expands the liquid temperature range. The synergistic effect of multiple components significantly improves adaptability under all operating conditions.

[0106] Comparative Example 5: A Comparative Example of Traditional Diffusion Welding Process

[0107] This comparative example uses a traditional upper and lower shell diffusion welding process to manufacture a harmonica-shaped heat spreader, with the same external dimensions as Example 1. Specific process: Upper and lower copper shells are machined separately, and a copper powder absorbent core (with a uniform porosity of 42%) is sintered onto the inner surface. After cleaning the surrounding area, vacuum diffusion welding is performed (temperature 1050℃, pressure 5MPa, holding time 90 minutes). After welding, a vacuum is drawn and the same nanofluid working fluid as in Example 1 is filled.

[0108] Performance test results: The total thermal resistance at 100W power is 0.095℃ / W, which is 42% higher than that of Example 1; the temperature difference is 4.2℃, which is 50% higher than that of Example 1; the airtightness test leak rate is 8×10 -9 Pa·m 3 / s, which is one order of magnitude higher than that of Example 1. After 1500 thermal cycling tests, microcracks appeared at the welded joint, and the performance degraded by 35%, much earlier than in Example 1. The yield rate during manufacturing was only 82%, lower than the 96% of Example 1.

[0109] This comparative example fully demonstrates the advantages of integrated extrusion molding compared to traditional welding processes. Peripheral welding paths can be over 400mm long, and the welding process involves high temperatures and long durations, easily leading to deformation, porosity, and stress concentration, affecting airtightness and reliability. Extrusion molding, on the other hand, eliminates the welded joints, essentially eliminating this weak point.

[0110] Comparative Example 6: Copper-free aluminum composite using only pure copper

[0111] The main difference between this comparative example and Example 1 is that, in step one, copper-aluminum composite material is not used; instead, pure copper (T2 copper) is extruded. The other steps are exactly the same as in Example 1.

[0112] Performance test results: The total thermal resistance at 100W power is 0.064℃ / W, which is 4.5% lower than that of Example 1, showing slightly better performance; however, the weight is 28.5g, which is 48% heavier than the 19.2g of Example 1. For weight-sensitive applications such as laptops, drones, and satellites, this increase in weight is unacceptable. Furthermore, pure copper materials cost approximately 35% more than copper-aluminum composite materials, making them less economical.

[0113] This comparative example illustrates that the application of copper-aluminum composite materials seeks the optimal balance between performance and weight. While pure copper offers the best thermal conductivity, it suffers from significant disadvantages in weight and cost. The copper-aluminum composite design achieves significant weight reduction and cost optimization while maintaining sufficient thermal conductivity, making it more in line with the trend towards thinner and lighter modern electronic products.

[0114] To comprehensively evaluate the performance of the harmonica-shaped heat spreader of this invention, a standardized testing platform and method were established. The testing apparatus mainly includes a silicon controlled rectifier (SCR) heating module, a thin-film heat flow sensor, a K-type thermocouple temperature measurement array, an infrared thermal imager, a data acquisition system, and a circulating water cooling system. The testing environment is a constant temperature and humidity laboratory with a temperature of 25℃ ± 1℃ and a relative humidity of 45% ± 5%.

[0115] Thermal resistance testing employed a steady-state method. The center of the evaporator end of the vapor chamber was placed against the heating module, and the condenser end was in close contact with the water-cooled radiator via thermal grease. Heating power was gradually increased (20W, 50W, 80W, 100W, 120W, 150W), and data was recorded after the temperature fluctuation at each measurement point remained below 0.1℃ for 5 minutes. The total thermal resistance was calculated using the formula R = (Tevaporator - Tambient) / Q, where Tevaporator is the center temperature of the evaporator end, Tambient is the ambient temperature, and Q is the heating power.

[0116] The equivalent thermal conductivity was tested according to ASTM E1530 standard. The heat flux density of the vapor chamber was measured under different temperature gradients using the heat shield method, and the equivalent thermal conductivity was calculated using Fourier's law of thermal conductivity. Considering that the phase change heat transfer mechanism of the vapor chamber is quite different from that of solid heat conduction, the equivalent thermal conductivity is only used as a reference indicator for performance comparison.

[0117] Temperature uniformity testing was conducted by evenly distributing nine temperature measurement points (3×3 array, 20mm spacing) on ​​the evaporator surface, simultaneously recording the temperature at each point, and calculating the maximum temperature difference and the standard deviation of the temperature distribution. An infrared thermal imager was used to monitor the surface temperature field distribution in real time, generating a temperature cloud map.

[0118] The maximum heat transfer flux test adopts the method of gradually increasing the power until the heat spreader dries out, and the judgment criteria are a sudden and sharp rise in the center temperature of the evaporation end or a sharp increase in the temperature difference between the temperature measurement points.

[0119] To start the characteristic test, the heat spreader was heated from room temperature (25°C), and the time required from power-on to reaching steady-state operation (temperature fluctuation less than 0.5°C for 2 minutes) was recorded.

[0120] Reliability testing includes thermal cycling, vibration, and life testing. Thermal cycling is conducted in a high and low temperature chamber, with a temperature range of -40°C to +120°C, a holding time of 30 minutes for each temperature change, a heating / cooling rate of 10°C / min, and 3000 cycles before performance changes are assessed. Vibration testing is performed on an electromagnetic vibration table, with a frequency range of 10Hz to 2000Hz, an acceleration amplitude of 20g, and vibration for 2 hours in each of the X, Y, and Z directions. Life testing involves continuous operation for 15,000 hours under rated operating conditions (100W power, ambient temperature 25°C), with performance parameters measured every 1000 hours to evaluate performance degradation patterns.

[0121] Table 1 lists detailed test data for 5 embodiments and 6 comparative examples, clearly demonstrating the contribution of each technical feature to performance.

[0122] Table 1 Comparison of performance test results between the examples and the comparative examples

[0123]

[0124] Table 1 clearly shows that the embodiments have significant advantages in overall performance compared to the comparative examples. Comparative Example 1 lacks a gradient capillary column array, leading to an imbalance between capillary force and flow resistance, increasing thermal resistance by 37%, temperature difference by 61%, and significantly reducing reliability. Comparative Example 2 lacks dendritic microchannels, resulting in uneven liquid distribution, increasing temperature difference by 36%, and reducing maximum heat flux density by 16%. Comparative Example 3 does not employ a nano-coating, extending start-up time by 58% and limiting high-power performance. Comparative Example 4 uses pure water as the working fluid, exhibiting extremely poor wide-temperature adaptability and complete failure in negative temperature environments. Comparative Example 5 uses traditional welding processes, resulting in poor airtightness, low reliability, and performance degradation of up to 35% after thermal cycling. While Comparative Example 6 has slightly better performance, its weight increases by 48%, failing to meet the requirements for lightweight design.

[0125] The comparison between the embodiments is also meaningful. Embodiment 4 is optimized for high-power applications, with a thermal resistance as low as 0.053℃ / W and a maximum heat flux density of 295W / cm³. 2 Example 5 is the best among all samples; Example 5 pursues extreme thinness, with a thickness of only 3.0 mm and a weight of only 15.0 g, demonstrating the excellent thinness potential of the present invention; Example 3 enhances wide-temperature performance, performing excellently in both low-temperature environments of -30°C and high-temperature environments of +55°C, making it suitable for harsh outdoor environments. These examples fully demonstrate the flexibility and wide applicability of the process of the present invention.

[0126] Example 1 maintains a low and stable thermal resistance across the entire power range, while the comparative example shows a significant increase in thermal resistance with increasing power, especially in the high-power region, indicating that the design of this invention has a more prominent advantage under high-power conditions.

[0127] In Example 1, during steady-state operation at 100W power, the surface temperature distribution at the evaporation end was very uniform, with a maximum temperature of 60.8℃ and a minimum temperature of 58.2℃, a temperature difference of only 2.6℃. There were no obvious local hot spots, demonstrating the high uniformity of liquid distribution under the synergistic effect of the dendritic microchannel network and gradient capillary structure.

[0128] Example 1 shows the performance changes during 15,000 hours of continuous operation testing. The thermal resistance increased slightly by about 3% in the first 3,000 hours, and then tended to stabilize. After 15,000 hours, the total thermal resistance was 0.073℃ / W, which was only 9% higher than the initial value, far below the 20% failure criterion, verifying the product's excellent long-term stability and reliability.

[0129] The excellent performance of the harmonica-shaped heat spreader of this invention is due to the synergistic effect and careful design of multiple technical features.

[0130] First, the integrated manufacturing achieved by extrusion molding of copper-aluminum composites fundamentally eliminates the weak points of welding in traditional processes. Welding inevitably produces uneven microstructure, porosity, inclusions, and residual stress at the interface. These microscopic defects gradually expand under thermal cycling and mechanical stress, ultimately leading to leakage and failure. Extrusion molding, on the other hand, uses the plastic deformation of the metal to extrude the composite billet as a whole, resulting in continuous and uniform material without interface defects, and its airtightness is inherently superior to welded structures. Simultaneously, copper-aluminum composites fully leverage the advantages of both metals: the copper layer ensures high thermal conductivity, the aluminum shell provides structural strength and lightweighting, the addition of silicon carbide nanoparticles further strengthens the matrix, and the rare earth element lanthanum refines the grain and improves the bonding between the copper and aluminum interfaces.

[0131] Secondly, the innovative design of the gradient porosity capillary column array cleverly balances the contradiction between capillary force and permeability. Traditional vapor chamber capillary cores have a single porosity, failing to simultaneously meet the requirements of strong capillary force at the evaporation end and low flow resistance at the condensation end. This invention differentiates the design based on the different heat transfer mechanisms at the evaporation and condensation ends: at the evaporation end, a large amount of liquid vaporizes, requiring a strong capillary driving force to continuously draw liquid from the condensation end. Therefore, a coarser, taller, and more spaced columnar structure is designed with a relatively low porosity (55% to 65%), a small capillary radius, and high capillary pressure. According to the Young-Laplace equation ΔPc = 2σcosθ / r, capillary pressure is inversely proportional to pore radius; smaller pores provide stronger suction force. At the condensation end, vapor condenses into liquid and requires rapid reflux, making it sensitive to flow resistance. Therefore, a thinner, shorter, and more spaced columnar structure is designed with a higher porosity (60% to 70%). According to Darcy's law... The flow rate is directly proportional to the permeability K and inversely proportional to the viscosity μ. High porosity increases permeability, reduces flow resistance, and accelerates liquid reflux. This gradient design allows the two zones to perform their respective functions and cooperate effectively, significantly improving overall circulation efficiency.

[0132] Furthermore, the sintering technology using multi-size copper powder combined with a pore-forming agent further optimizes the pore structure. Single-size copper powder sintering results in narrow pore size distribution, strong capillary force but low permeability. This invention employs a three-tiered particle size distribution: ultrafine (3μm to 8μm), micron (20μm to 35μm), and nano (80nm to 150nm). Ultrafine copper powder forms the sintering skeleton to ensure strength and capillary force; micron copper powder fills large pores to improve permeability; and nano copper powder acts as an active powder during sintering, promoting diffusion and bonding, lowering the sintering temperature, and improving sintering quality. More importantly, the introduction of ammonium bicarbonate as a pore-forming agent: ammonium bicarbonate decomposes at 350℃ to 400℃ to produce ammonia, carbon dioxide, and water vapor, leaving regular pores between copper powder particles. These artificially created pores, together with the naturally formed sintered pores, form a composite pore network with hierarchical interconnection of macropores and micropores. Large pores provide a fast, low-resistance liquid channel, while small pores provide strong capillary force. Together, they increase permeability by 2 to 3 times while maintaining sufficient capillary pressure.

[0133] Fourth, the design inspiration for the biomimetic tree-like fractal microchannel comes from the vascular bundles of plants and the human circulatory system. The fluid transport network that nature has evolved over millions of years possesses extremely high efficiency: the hierarchical structure of trunk-branch-capillary ensures both high-flow-rate transport and uniform distribution at the ends. This invention mimics this structure, forming a tree-like network of main channels, secondary branches, and tertiary branches on a sintered capillary core through electrochemical etching, with the fractal dimension controlled between 1.6 and 1.8. The main channels are wide and deep, handling rapid liquid transport; secondary branches distribute the liquid to different areas; and tertiary capillary branches extend deep beneath each LED chip, ensuring localized working fluid supply. The branch angles of 30° to 50° are optimized through fluid dynamics, ensuring smooth flow while minimizing dead zones. This design improves the uniformity of liquid distribution by 80%, ensuring sufficient working fluid supply beneath each chip, avoiding the problem of insufficient liquid supply in areas far from the main channel in traditional parallel channel designs, and improving anti-drying capability by 3 times.

[0134] Fifth, the role of the alumina-silica-carbon nanotube ternary nanocomposite coating is multifaceted. Alumina nanoparticles provide the coating matrix and mechanical strength, and their high thermal conductivity (25 W / (m·K) to 30 W / (m·K)) helps reduce interfacial thermal resistance. Silica nanoparticles are rich in hydroxyl groups (-OH), which form hydrogen bonds with water molecules, significantly reducing the surface contact angle and transforming the surface from hydrophobic or neutral wetting to superhydrophilic (contact angle less than 10°). In addition to providing antibacterial and anti-corrosion functions, zinc oxide's amphoteric oxide properties also help improve the surface chemical properties of the coating. Most importantly, the addition of multi-walled carbon nanotubes is crucial: carbon nanotubes have ultra-high axial thermal conductivity (2000 W / (m·K) to 6000 W / (m·K)), forming a thermally conductive network in the coating and significantly reducing the coating's thermal resistance; simultaneously, the high aspect ratio and nanoscale rough surface of carbon nanotubes further enhance the capillary effect of the surface. The role of silane coupling agent KH-570 is to improve the interfacial bonding between nanoparticles and the copper matrix. The siloxane groups at one end of its molecule undergo a condensation reaction with the hydroxyl groups on the surface of alumina and silica to form covalent bonds, while the organic groups at the other end act as molecular bridges with carbon nanotubes through van der Waals forces, significantly improving the adhesion and stability of the coating. Ultrasonic dispersion treatment breaks up the agglomeration of nanoparticles, ensuring their uniform distribution in the coating and avoiding uneven thermal conductivity and capillary properties caused by localized accumulation.

[0135] Sixth, the design of the nanofluid working fluid follows the principle of multifunctional synergistic optimization. Water was chosen as the main component of the base fluid because it has advantages such as high specific heat capacity (4.18 kJ / (kg·K)), high latent heat of vaporization (2260 kJ / kg), low viscosity (0.89 mPa·s, 25℃), and environmental friendliness, making it the most ideal working medium. However, pure water has disadvantages such as a high freezing point (0℃) and relatively low thermal conductivity (0.60 W / (m·K), 25℃). The addition of ethylene glycol lowers the freezing point to -15℃ to -28℃, significantly widening the low-temperature working range. At the same time, the appropriate addition of ethylene glycol also reduces surface tension, which is beneficial for the liquid to permeate through micropores. The addition of small amounts of n-propanol or isopropanol further modulated the surface tension to 35 mN / m to 45 mN / m. This range was optimized: if the surface tension was too high, the liquid would be difficult to spread; if it was too low, the capillary force would be insufficient. The appropriate surface tension promoted rapid wetting of the liquid while ensuring capillary drive.

[0136] The mechanism of multi-walled carbon nanotubes in nanofluids has been extensively studied: on the one hand, the ultra-high thermal conductivity of carbon nanotubes (3000 W / (m·K) to 6000 W / (m·K) axially) is significantly higher than that of the base fluid. Even with a small mass fraction (0.05% to 0.3%), they can form a thermally conductive network that significantly improves the overall thermal conductivity of the fluid, which is consistent with the prediction of the Hamilton-Crosser model. On the other hand, the Brownian motion of carbon nanotubes in liquids enhances micro-convective heat transfer, further improving the heat transfer effect. Furthermore, carbon nanotubes act as vaporization nuclei in boiling heat transfer, reducing superheat and increasing the boiling heat transfer coefficient by more than 60%. Graphene oxide nanosheets, with their two-dimensional layered structure and numerous oxygen-containing functional groups, not only improve the dispersion stability of nanoparticles and provide additional hydrophilicity, but also contribute to enhanced thermal conductivity through layered thermal conduction pathways.

[0137] The selection and formulation of surfactants were carefully optimized. The anionic surfactant sodium dodecyl sulfate (SDS) stabilized the nanoparticle dispersion and prevented agglomeration through electrostatic repulsion; the nonionic surfactant Triton X-100 enhanced dispersion stability through steric hindrance. The synergistic effect of both surfactants maintained the absolute value of the zeta potential of the nanofluid above 30 mV, ensuring long-term dispersion stability. Ultrasonic dispersion, which breaks up nanoparticle agglomeration through cavitation, is a crucial step in achieving uniform dispersion; the processing time, power, and temperature were all optimized.

[0138] Finally, the heat treatment process, though seemingly simple, is crucial to the final performance. A temperature range of 200℃ to 250℃ is sufficient to eliminate residual stress accumulated during processing, while remaining below the critical temperature of the working fluid to avoid excessive pressure on the already filled fluid. A holding time of 6 to 10 hours allows for full stress release, stabilizes the microstructure, further solidifies the nano-coating, and strengthens the bonding between interfaces (copper-aluminum interface, coating-substrate interface, and sintered particle interfaces). A heating rate controlled below 50℃ / h avoids the generation of new stress due to rapid heating. A nitrogen or argon protective atmosphere prevents high-temperature oxidation.

[0139] All these technical features are not simply superimposed, but form an organic synergistic system: integrated extrusion molding provides a reliable container and high thermal conductivity channels; gradient capillary column arrays construct an efficient evaporation-condensation platform; the porous substrate layer further optimizes the capillary network based on the column array; dendritic microchannels ensure uniform liquid distribution; nano-coatings enhance surface capillary properties and reduce interfacial thermal resistance; nanofluidic working fluids comprehensively improve phase change heat transfer efficiency and temperature adaptability; and heat treatment stabilizes the overall structure. Each step is optimized to address key bottlenecks in the operation of the vapor chamber, and each is interconnected and indispensable. Comparative test results fully demonstrate that the absence of any one of these technical features will lead to a significant performance degradation.

[0140] Analyzing the complete heat transfer path provides a clearer understanding of the role of each technical feature: Heat first enters the surface of the vapor chamber from the heat source (such as a chip), passes through a nano-coating (superhydrophilicity and high thermal conductivity reduce contact and coating thermal resistance), and enters the sintered porous substrate and capillary array (large surface area and good solid-liquid contact promote rapid heat transfer). The liquid working fluid absorbs heat and evaporates into steam (high latent heat of vaporization carries a large amount of heat). Driven by pressure, the steam flows rapidly through harmonica-shaped microchannels (low flow resistance ensures rapid steam transport), reaching the capillary columns at the condensation end and the inner surface of the condensation shell (also with a nano-coating to enhance heat transfer). It releases its latent heat of vaporization and condenses into liquid. Through the copper-aluminum composite shell (high thermal conductivity), the heat is transferred to the external heat dissipation fins or cooling system. The condensed liquid, driven by capillary force (gradient porosity design provides strong driving force and low flow resistance), flows back to the evaporation end through a tree-like microchannel network (uniformly distributed to each evaporation point), completing the cycle. Throughout the process, phase change heat transfer (evaporation and condensation) undertakes the majority of heat transfer, and its efficiency is far higher than that of solid conduction. The various technical measures of this invention are optimized for each key link of this phase change cycle, thereby achieving heat dissipation performance far exceeding that of traditional solutions.

[0141] The harmonica-shaped heat spreader manufactured by this invention has been successfully applied in multiple fields and has achieved remarkable results.

[0142] Application Example 1: A well-known brand's flagship 5G smartphone adopted the ultra-thin harmonica-shaped vapor chamber from Embodiment 1 of this invention for main chip heat dissipation. This phone is equipped with the latest 5nm flagship processor, with power consumption reaching 8W to 12W. Traditional graphite sheet heat dissipation solutions often resulted in chip temperatures exceeding 85℃ under high loads, triggering temperature-controlled frequency throttling and impacting performance and user experience. After adopting the vapor chamber of this invention, under the same test scenario, the peak chip temperature dropped to 76℃, a reduction of 9℃, and temperature fluctuation decreased from 12℃ to 4.5℃, a reduction of 62%. No frequency throttling occurred, and AnTuTu benchmark scores improved by approximately 15%. User satisfaction surveys showed that the phone's surface temperature was more uniform during use, with no noticeable burning sensation, and continuous game running time was extended by more than 30%. After its launch, this model received widespread praise for its excellent heat dissipation performance, resulting in a significant increase in market share.

[0143] Application Example 2: A communication equipment manufacturer's 5G macro base station AAU module uses the wide-temperature harmonica-shaped vapor chamber of Embodiment 3 of this invention. The 5G base station power amplifier chip consumes 30W to 50W and needs to operate reliably in a wide outdoor temperature range of -40℃ to +55℃. Traditional air-cooling solutions are bulky, energy-intensive, and unreliable. Using the vapor chamber of this invention, combined with natural convection cooling, meets the requirements, eliminating the need for a fan. Overall power consumption is reduced by 8%, size by 25%, and reliability is significantly improved. In extreme field tests in Mohe, Northeast China (winter -35℃), and Turpan, Xinjiang (summer 52℃), the vapor chamber started up quickly and operated stably, with the power amplifier chip temperature controlled below 80℃. It operated continuously for 6 months without failure, with performance degradation of less than 3%, verifying its excellent environmental adaptability. This equipment has been deployed in batches, accumulating over 5 million hours of operation, with a failure rate 70% lower than traditional solutions.

[0144] Application Example 3: A car manufacturer's pure electric vehicle's electronic control inverter uses the high-power harmonica-shaped vapor chamber plate of Embodiment 4 of this invention. The instantaneous power consumption of the electric vehicle's IGBT module can reach over 200W, while requiring compact size, light weight, and high reliability. Traditional liquid cooling solutions, although effective, are complex and costly. Using the vapor chamber plate of this invention, inserted between the IGBT module and the heat sink, its excellent heat diffusion capability rapidly and evenly distributes heat to the entire heat sink surface, reducing the heat sink size by 40%, weight by 35%, and system cost by 25%. Thermal tests of the vehicle under different operating conditions (starting acceleration, high-speed cruising, frequent braking) show that the peak IGBT junction temperature is reduced by 12℃, temperature fluctuation is reduced by 55%, and the thermal fatigue life of the power devices is extended by more than 2 times. After automotive-grade reliability tests including high and low temperature alternation, vibration and shock, and long-term aging, the performance remains stable without degradation. This model has been mass-produced and launched, and user feedback indicates fast power response and stable range, earning it a good reputation.

[0145] Application Example 4: A data center uses the high-power harmonica-shaped vapor chamber of Embodiment 4 of this invention for high-density server CPU cooling. Cooling energy consumption accounts for 30% to 40% of data center energy consumption; reducing the thermal resistance of the cooling system can significantly reduce cooling requirements. After replacing the traditional copper heat sink with the vapor chamber of this invention, under the same chip power consumption, the required airflow for the heat sink is reduced by 20%, fan power consumption is reduced by 18%, and the overall PUE (Power Usage Effectiveness) improves from 1.45 to 1.32, saving over 1 million yuan in electricity costs annually. More importantly, the superior heat dissipation performance allows the CPU to operate stably at higher frequencies, increasing computing power by approximately 8%, resulting in significant economic benefits. This data center has now fully implemented the invention, and after more than two years of operation, no failures have occurred due to heat dissipation issues, significantly reducing maintenance costs.

[0146] Application Example 5: A customized harmonica-shaped vapor chamber is used in the thermal control system of satellite electronic equipment of a certain aerospace technology group. The satellite operates in a harsh environment, with temperatures reaching 150°C on the sun-facing side and dropping to -180°C on the shaded side. There is no gas convection for heat dissipation; it relies solely on heat conduction and radiation. Traditional heat pipes, while functional, have limited performance. This invention uses a titanium alloy shell instead of copper-aluminum composite materials (corrosion resistant and suitable for vacuum environments), and selects a special solvent with low vapor pressure as the working fluid. It has undergone rigorous space environment adaptability design and testing. On-orbit operation shows that the vapor chamber operates normally under microgravity conditions, with the temperature of each electronic device controlled within the range of -10°C to 50°C, exhibiting excellent temperature uniformity and providing a reliable guarantee for the stable operation of the satellite. This technology provides a new technical approach for upgrading the thermal control system of my country's spacecraft and has significant strategic importance.

[0147] These application examples fully demonstrate the superiority, reliability, and wide applicability of the technical solution of this invention. From consumer electronics to industrial equipment, from ground applications to space exploration, they all demonstrate great application value and market prospects.

[0148] The manufacturing method of the harmonica-shaped vapor chamber provided by this invention successfully solves the key technical problems faced by traditional vapor chamber manufacturing technology, such as poor airtightness, low reliability, difficulty in balancing capillary force and permeability, and narrow temperature adaptability, through the synergistic integration of a series of innovative processes including copper-aluminum composite material extrusion molding, selective laser melting gradient capillary column array, porous substrate sintering, biomimetic dendritic microchannel etching, nanocomposite coating deposition, and nanofluid working fluid filling. This achieves efficient manufacturing of high-performance harmonica-shaped vapor chambers. The product has an equivalent thermal conductivity of 5000 W / (m·K) to 10000 W / (m·K), a total thermal resistance as low as below 0.08℃ / W, excellent temperature uniformity, strong wide temperature adaptability, significant weight reduction effect, and a service life of over 15000 hours, comprehensively surpassing existing technologies in overall performance.

[0149] This invention is not only innovative and advanced in academic terms, but also possesses significant practical value and broad market prospects in engineering applications. With the rapid development of high-tech fields such as 5G communication, artificial intelligence, new energy vehicles, and aerospace, the demand for high-performance thermal management technology is becoming increasingly urgent. This invention provides a feasible technical solution that will undoubtedly play a vital role in promoting technological progress in related industries, enhancing product competitiveness, and generating significant economic and social benefits.

[0150] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and improvements can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing a harmonica-shaped heat spreader, characterized in that... This includes the following steps: Step 1: Provide a copper-aluminum composite billet, which comprises an oxygen-free copper core layer of 40%–50% by mass and an aluminum alloy outer layer of 50%–60% by mass. Prepare a harmonica-shaped outer shell by extrusion molding at a temperature of 420℃–490℃. The outer shell contains 8 to 16 parallel microchannels, each with a width of 0.8 mm to 1.5 mm and a height of 1.2 mm to 2.0 mm. Step 2: Copper powder is deposited on the inner wall of the microchannel using a selective laser melting process to form a capillary column array. The copper powder has a particle size of 15μm to 45μm, the laser power is 200W to 350W, and the scanning speed is 800mm / s to 1500mm / s. A first capillary column structure with a column diameter of 200μm to 300μm, a column height of 400μm to 600μm, and a porosity of 55% to 65% is formed in the evaporation end region. A second capillary column structure with a column diameter of 150μm to 250μm, a column height of 200μm to 350μm, and a porosity of 60% to 70% is formed in the condensation end region. Step 3: Prepare a copper powder slurry and coat it onto the surface of the capillary column array. The copper powder slurry comprises 70%–80% by mass of ultrafine copper powder with a particle size of 3 μm to 8 μm, 15%–25% by mass of micron-sized copper powder with a particle size of 20 μm to 35 μm, 3%–6% by mass of nano-sized copper powder with a particle size of 80 nm to 150 nm, and 8%–12% by mass of ammonium bicarbonate pore-forming agent with a particle size of 50 μm to 100 μm. Sinter the slurry at 750°C to 850°C for 60 to 90 minutes in a hydrogen protective atmosphere to form a porous substrate layer with a porosity of 35% to 50%. Step four: A tree-like fractal microchannel network is formed within the microchannels using an electrochemical etching process. The electrochemical etching employs a sulfuric acid electrolyte with a concentration of 150 g / L to 220 g / L and a current density of 8 A / dm³. 2 Up to 15A / dm 2 Etching creates a tree-like structure with a main channel width of 600 μm to 800 μm, secondary branches width of 300 μm to 450 μm, and tertiary branches width of 100 μm to 200 μm; Step 5: Prepare a nano-coating dispersion and deposit it on the inner surface of the microchannel. The nano-coating dispersion contains 40%–50% by mass of alumina nanoparticles with a particle size of 20 nm to 40 nm, 20%–30% by mass of silica nanoparticles with a particle size of 15 nm to 30 nm, and 5%–10% by mass of multi-walled carbon nanotubes with an outer diameter of 8 nm to 15 nm. A nanocomposite coating with a thickness of 3 μm to 5 μm is formed by dip-coating. Step six: Seal both ends of the outer casing using laser welding with a laser power of 1000W to 2000W, under a vacuum degree of 1×110⁻⁶. -4 Vacuum treatment is performed in a vacuum chamber with a pressure below Pa. Step 7: Prepare the nanofluid working medium and fill it into the shell. The nanofluid working medium contains 70%–85% deionized water (by volume), 10%–25% ethylene glycol (by volume), 0.05%–0.3% multi-walled carbon nanotubes (by mass relative to the base liquid), and 0.5%–1.5% surfactant (by mass). The filling amount is 75%–85% of the effective volume of the cavity. Step 8: After sealing the filling port, perform heat treatment at 200℃ to 250℃ for 6 to 10 hours.

2. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step one, the copper-aluminum composite billet also contains 0.3% to 0.8% by mass of silicon carbide nanoparticles with an average particle size of 50 nm to 80 nm and 0.05% to 0.15% by mass of rare earth element lanthanum. The extrusion ratio of the extrusion molding is 15 to 25, and the extrusion speed is 0.5 m / min to 1.2 m / min.

3. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step two, the thickness of the powder layer in the selective laser melting process is 30μm to 50μm, the scanning interval is 0.08mm to 0.12mm, the protective gas is argon with a purity of 99.999% or higher, the column spacing of the capillary column array is 250μm to 400μm in the evaporation end region, and the column spacing is 180μm to 300μm in the condensation end region.

4. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step three, the copper powder slurry also contains 2.5% to 4.0% by mass of a polyvinyl alcohol binder with a degree of polymerization of 1700 to 2000 and 0.5% to 1.0% by mass of sodium carboxymethyl cellulose. Before sintering, it is degreased at a temperature of 350°C to 400°C for 1.5 to 2 hours.

5. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step four, the fractal dimension of the dendritic fractal microchannel network is 1.6 to 1.8, and the branching angle is 30° to 50°. The electrolyte also contains phosphoric acid at a concentration of 30 g / L to 50 g / L and glycerol at a concentration of 20 g / L to 35 g / L. The electrolyte temperature is controlled within the range of 25°C ± 3°C.

6. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step five, the nano-coating dispersion also contains 3% to 8% by mass of zinc oxide nanoparticles with a particle size of 25 nm to 45 nm and 2% to 4% by mass of silane coupling agent KH-570. The nano-coating is dispersed by ultrasonic treatment at a power of 400 W and a frequency of 20 kHz for 60 to 90 minutes, and after deposition, it is cured at a temperature of 180°C to 220°C for 1.5 to 2 hours.

7. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step six, the laser welding adopts a pulse mode with a pulse frequency of 20Hz to 50Hz, a pulse width of 3ms to 8ms, a welding speed of 8mm / s to 15mm / s, and a shielding gas of argon with a purity of 99.999% or higher and a flow rate of 15L / min to 25L / min.

8. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step seven, the nanofluid working medium also includes 3% to 8% n-propanol by volume, 0.02% to 0.1% graphene oxide nanosheets by mass relative to the base liquid, and 0.3% to 0.8% nonionic surfactant Triton X-100 by mass. The length of the multi-walled carbon nanotubes is 2 μm to 10 μm.

9. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... In step seven, before filling, the nanofluid working medium is heated at 80°C to 100°C for 30 to 45 minutes under vacuum to remove gas. During the filling process, argon gas is used for pressurization at a pressure of 0.05 MPa to 0.15 MPa and a filling speed of 0.5 mL / min to 1.5 mL / min.

10. The method for manufacturing a harmonica-shaped heat spreader according to claim 1, characterized in that... The heat treatment in step eight is carried out in a nitrogen or argon protective atmosphere, with a heating rate of less than or equal to 50°C / h. After holding at the temperature, the furnace is cooled to below 100°C and then air-cooled to room temperature. The sealed liquid filling port is sealed by brazing a copper cap with tin-based brazing filler metal at a temperature of 220°C to 260°C.

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