An ultrathin graphene-reinforced copper-based VC heat sink with high structural stability and high efficient heat transfer, and a preparation method and application thereof

Abstract

This invention discloses an ultrathin graphene-reinforced copper-based VC heat sink with both high structural stability and efficient heat transfer, along with its preparation method and applications, relating to the field of heat dissipation technology for electronic devices. The preparation method includes the following steps: integral molding of the composite shell and internal components; preparation of the composite capillary wick; vacuum encapsulation and working fluid infusion. This invention utilizes an integrally molded encapsulation shell, a curved flow guide plate, and a spindle-shaped array support pillars made of graphene nanosheet-reinforced copper-based composite material. Combined with a carbon nanotube-copper powder composite capillary wick prepared by low-temperature stepwise sintering, a synergistic phase change heat transfer structure with gas-liquid separation is constructed, suitable for the extreme heat dissipation requirements of high-power ultrathin smartphones, laptops, wearable electronic devices, and other fields.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation technology for electronic devices, and more specifically, to an ultrathin graphene-reinforced copper-based VC heat sink with both high structural stability and efficient heat transfer, as well as its preparation method and application. Background Technology

[0002] With the rapid development of 5G and AI technologies, high-power ultra-thin electronic devices (smartphones, ultra-thin laptops, wearable devices, etc.) are rapidly iterating towards high performance, miniaturization, and thinness, with chip power density continuously climbing to 50W / cm². 2 As the overall thickness of the device continues to be compressed to within 8mm, extreme requirements are placed on the thickness, temperature uniformity, and structural stability of the heat dissipation components. Vapor chamber (VC) heat spreaders rely on the vapor-liquid phase change of the working fluid within the chamber to achieve efficient in-plane heat transport. They offer advantages such as high thermal conductivity, excellent temperature uniformity, and no moving parts, making them a core solution for heat dissipation of high-power, ultra-thin electronic devices.

[0003] However, existing ultra-thin VC heat exchange plates face several common technical bottlenecks in the development of ultra-thinness, and cannot meet the heat dissipation requirements under high power conditions. For example: (1) Imbalance in shell material performance. Under extreme conditions where the single wall thickness of traditional pure copper shells is reduced to 0.05mm, it is difficult to balance the thermal resistance of solid thermal conductivity and the structural pressure resistance. Long-term hot and cold cycles are prone to cavity collapse and sealing failure, resulting in rapid performance degradation; (2) Bottleneck in liquid wick performance. Traditional copper powder sintered liquid wicks cannot simultaneously achieve high capillary suction force and low working fluid return resistance. The capillary force and permeability are mutually restrained, resulting in insufficient driving force for working fluid return and high power. (3) The gas-liquid two-phase flow field coupling is disordered. The condensate backflow and steam transport in the ultra-thin cavity form a reverse flow, which easily causes gas-liquid entrainment, greatly increases the flow resistance, and seriously limits the improvement of phase change heat transfer efficiency; (4) The consistency of large-scale production is poor. The thermal resistance fluctuation between batches exceeds 12%, the thermal conductivity fluctuation exceeds 15%, and the yield rate is less than 80%, which is difficult to meet the needs of large-scale mass production; (5) The long-term service stability is insufficient. After 500 cycles of cold and heat, the performance decay rate generally exceeds 10%, which cannot meet the heat dissipation reliability requirements of electronic devices throughout the entire life cycle.

[0004] Graphene nanosheet-reinforced copper-based composites possess both high thermal conductivity and excellent mechanical properties, resolving the core contradiction between thermal conductivity and pressure resistance in ultrathin shells. Carbon nanotube-copper powder composite porous absorbent cores can construct multi-scale three-dimensional pore networks, simultaneously enhancing capillary forces and permeability. The synergistic design of curved flow guides and spindle-shaped support columns achieves both gas-liquid flow field decoupling and structural reinforcement. However, current technologies have not yet formed an ultrathin VC configuration that achieves multi-dimensional synergy in material systems, flow field structures, and phase change working fluids. Poor matching between material forming processes and absorbent core sintering parameters prevents ultrathin VC heat spreaders from simultaneously achieving extreme thinness, high heat transfer performance, and excellent structural stability, thus failing to meet the extreme heat dissipation requirements of high-power ultrathin electronic devices.

[0005] Therefore, how to provide an ultra-thin VC heat exchanger that can achieve extreme thinness, high heat transfer efficiency, excellent structural stability, and good mass production consistency is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of traditional ultrathin VC vapor chambers in the prior art, such as material performance imbalance, disordered flow field coupling, bottleneck of liquid wick performance, poor mass production consistency, and insufficient long-term stability. At the same time, it solves the industry pain point of the difficulty in reconciling thinness and high performance. It provides an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer, as well as its preparation method and application, to achieve efficient, uniform, and stable heat dissipation of high power density heat sources with an extreme thickness of 0.2 mm.

[0007] In view of this, the present invention provides an ultrathin graphene-reinforced copper-based VC heat exchanger with both high structural stability and efficient heat transfer, as well as its preparation method and application.

[0008] A method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer includes the following steps:

[0009] (1) Composite shell and internal components are integrally formed: graphene nanosheets and electrolytic copper powder are mixed evenly to obtain composite powder. After being sintered by spark plasma, the lower encapsulation shell and the upper encapsulation shell with curved flow guide plate and spindle array support column are prepared by precision etching and integral stamping process. (2) Preparation of composite capillary liquid absorption core: Carbon nanotubes and nano copper powder are dispersed in anhydrous ethanol to obtain a slurry. The slurry is coated on the inner wall of the evaporation section of the lower encapsulation shell obtained in step (1). The slurry is cured by a low-temperature stepwise sintering process to obtain a carbon nanotube-nano copper powder composite porous capillary liquid absorption core. (3) Vacuum encapsulation and working fluid filling: The upper and lower encapsulation shells of step (1) are laser-sealed to form a cavity. After the cavity is subjected to high vacuum degassing treatment, a binary composite heat exchange working fluid is filled in. After secondary degassing, it is sealed to obtain an ultrathin graphene-reinforced copper-based VC heat exchange plate.

[0010] Furthermore, in step (1), the mass ratio of the graphene nanosheets to the electrolytic copper powder is (0.2-1.5):(98.5-99.8). The electrolytic copper powder is a high-purity spherical or near-spherical electrolytic copper powder with a purity ≥99.95%, an average particle size of 15-45 μm, and a loose packing density of 2.0-3.0 g / cm³. 3 ; The graphene nanosheets are few-layer graphene nanosheets, with 3-10 layers, a single sheet diameter of 5-20 μm, a thickness of 1.5-5.0 nm, and a specific surface area of ​​100-300 m². 2 / g, carbon purity ≥99.9%; The process parameters for the discharge plasma sintering are: sintering temperature 750-900℃, sintering pressure 30-50MPa, holding time 5-15min, and heating rate 50-100℃ / min.

[0011] Further, in step (1), the number of curved guide plates is 3, the center distance between adjacent guide plates is 15mm, the specifications of a single curved guide plate are 65mm in length, 2mm in width, 0.1mm in thickness, 16.99mm in radius of curvature, and 75° in arc angle; the length of the condensing section is 100mm and the width is 70mm. The condensing section is located in the upper part of the upper packaging shell away from the heat source and is arranged symmetrically with the evaporation section. The center of the condensing section coincides with the overall geometric center of the heat spreader; the length of the evaporation section is 100mm and the width is 70mm, which is the same as the size of the condensing section. The evaporation section is located in the lower part of the upper packaging shell where the heat source is attached and is the core heat absorption area of ​​the heat spreader. The center of the evaporation section is completely aligned with the center of the chip heat source; the curved guide plate is integrally etched with the inner wall of the condensing section of the upper packaging shell, and the curved guide plate divides the inner cavity of the condensing section into 4 independent gas-liquid flow domains; The spindle-shaped array support columns are arranged at equal intervals of 4mm in the horizontal direction and 5mm in the vertical direction. Each support column has a variable cross-section configuration with a circular cross-section. The diameter of the cross-section at both ends is 0.75–1.00mm, and the maximum diameter of the cross-section in the middle is 1.30–1.80mm. The overall height of the support column is 0.18–0.20mm. The cross-sectional area of ​​the support column is small at both ends and large in the middle, forming a converging conical flow channel between adjacent support columns. Both the upper and lower encapsulation shells are rectangular sheet structures with an overall length of 100mm and a width of 70mm. The shell edges are provided with sealing welded edges with a width of 1.0–1.5mm. The upper and lower shells have completely identical outline dimensions and are aligned and fitted together. The upper encapsulation shell is a boss-type structure with a curved guide plate and a spindle-shaped support column, while the lower encapsulation shell is a planar evaporation section base structure. The single wall thickness of the upper and lower encapsulation shells is 0.05mm, and the net height inside the cavity after molding is 0.1mm.

[0012] Furthermore, in step (2), the mass ratio of the carbon nanotubes to the nano copper powder is (2-8):(92-98). The total mass of the carbon nanotubes and copper nanopowder is in the mass-to-volume ratio of anhydrous ethanol to 1 g: (5-15) mL.

[0013] Further, in step (2), the dispersion is: stirring at a speed of 200-400 r / min for 1-3 h, followed by ultrasonic dispersion at an ultrasonic power of 300-600 w for 20-60 min; The coating thickness is 80-120μm, and the thickness of the carbon nanotube-nano copper powder composite porous capillary liquid-absorbing core after sintering is 0.1mm. The low-temperature stepwise sintering process is as follows: first, pre-sintering at 200-300℃ for 30-60 minutes in an argon atmosphere, then heating to 650-750℃ at a heating rate of 1-3℃ / min, sintering at a constant temperature for 1-3 hours, and then cooling to room temperature with the furnace.

[0014] Furthermore, in step (3), the process parameters for laser edge sealing welding are: fiber laser power 80-150W, welding speed 20-50mm / s, shielding gas is argon, and the leakage rate of the cavity after welding is ≤1×10⁻⁶ by helium mass spectrometry. -10 Pa·m 3 / s.

[0015] Furthermore, in step (3), the high-vacuum degassing treatment is performed at 120-150℃ with a vacuum degree ≤1×10⁻⁶. -3 Under the condition of Pa, keep warm and degas for 2-6 hours; The binary composite heat exchange medium is a deionized water-based α-alumina nanofluid, with deionized water of 18.2 MΩ·cm as the base liquid, and spherical α-Al2O3 nanoparticles with a mass fraction of 0.1-0.5% and an average particle size of 15-25nm. The amount of working fluid injected is 15-30% of the internal volume of the cavity; The vacuum degree of the seal after secondary degassing is ≤5×10⁻⁶. -4 Pa.

[0016] The present invention also provides an ultrathin graphene-reinforced copper-based VC heat spreader prepared by the above preparation method.

[0017] This invention also provides an application of the aforementioned preparation method or the aforementioned ultrathin graphene-reinforced copper-based VC heat sink in heat dissipation for high-power ultrathin electronic devices, wherein the overall thickness of the electronic device is ≤8mm and the heat source power density is ≥50W / cm². 2 .

[0018] Furthermore, application scenarios include high-power ultra-thin smartphones, ultra-thin laptops, AR / VR devices, or wearable electronic devices.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses a discharge plasma sintering and integral molding process to reinforce copper-based composite materials with graphene nanosheets to replace traditional pure copper materials. The resulting shell material has a room temperature thermal conductivity of ≥410W / (m·K) and a bending strength that is more than 40% higher than that of pure copper. Under the limit of 0.05mm single wall thickness, it simultaneously achieves low solid thermal resistance and high structural pressure resistance. After 1000 cycles of hot and cold, the cavity does not collapse and the seal is leak-free, solving the core pain point of performance imbalance of traditional ultra-thin VC shells. (2) The present invention uses a synergistic structural design of curved guide plate and spindle array support column. The guide plate divides the condensation section into an independent gas-liquid flow domain, realizing the decoupling of the flow field between condensate return and steam transport, and reducing the gas-liquid reverse flow resistance by more than 60%. The convergent flow channel formed by the spindle support column can induce the working fluid to form high-speed turbulence, increasing the convective heat transfer coefficient by more than 35%, while providing uniform in-plane support for the cavity, and improving the structural deformation resistance by more than 50%. (3) The carbon nanotube-copper nanopowder composite capillary core prepared by the present invention through a low-temperature stepwise sintering process constructs a multi-scale interconnected three-dimensional pore network with a porosity ≥65%, capillary suction force ≥12kPa, and permeability ≥8×10 -13 m 2 It breaks through the performance bottleneck of the traditional liquid absorption core where capillary force and permeability are mutually restrained, and provides sufficient and stable reflux driving force for the closed phase change cycle of the working fluid, with no drying phenomenon in the evaporation section under high power conditions. (4) This invention uses a deionized water-based α-alumina nanofluid binary composite working fluid. Through the Brownian motion of nanoparticles and the enhanced interfacial heat transfer effect, the boiling and condensation phase change heat transfer coefficient of the working fluid is increased by more than 40%, further enhancing the phase change heat transfer efficiency of the VC heat spreader, reaching 50 W / cm². 2 It maintains excellent temperature uniformity even under high power density conditions; (5) The preparation process of this invention is simple and controllable, the parameters of each process are highly matched, the product yield is ≥95%, the thermal resistance fluctuation between batches in large-scale production is ≤4%, the thermal conductivity fluctuation is ≤6%, the consistency is significantly better than the traditional process, and it meets the needs of large-scale mass production. (6) The ultra-thin VC heat exchange plate prepared by this invention has an overall thickness as low as 0.2 mm and an effective heat exchange area of ​​5937.5 mm². 2 Under a wide temperature range of 5-40℃, the thermal resistance of the heat source is ≤0.08 ℃·cm. 2 / W, the maximum temperature difference between the evaporation section and the condensation section is ≤1.2℃, and the performance decay rate after 1000 cycles of hot and cold is ≤3%, with comprehensive performance far exceeding that of traditional VC heat exchange plates of the same thickness. (7) The ultra-thin VC heat spreader of the present invention has strong adaptability and can be widely used in high-power ultra-thin smartphones, ultra-thin laptops, AR / VR devices, wearable electronic devices and other scenarios. It can reduce the peak operating temperature of the chip by 8-15℃ and control the hot spot temperature difference within 2℃, significantly improving the full load operation time and service reliability of electronic devices throughout their entire life cycle, and has broad market application prospects. Attached Figure Description

[0020] Figure 1 A schematic diagram of the core components of the VC heat exchanger, wherein 1-spindle-shaped support column; 2-curved guide plate, the curved guide plates together and the curved guide plates and the side wall of the VC heat exchanger together constitute an independent gas-liquid separation flow domain.

[0021] Figure 2 Schematic diagram of the condensation section of the VC heat spreader.

[0022] Figure 3 Schematic diagram of the evaporation section of the VC heat spreader.

[0023] Figure 4 Schematic diagram of the VC heat spreader support column structure.

[0024] Figure 5 Schematic diagram of the side view structure of the VC heat spreader. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1 (Optimal Solution) The preparation method of an ultrathin graphene-reinforced copper-based VC heat exchanger that combines high structural stability and efficient heat transfer specifically includes the following steps: (1) Preparation of composite shell and internal components by integral molding: Graphene nanosheets and electrolytic copper powder were mixed at a mass ratio of 0.8:99.2 and ball-milled for 6 hours under an argon atmosphere to obtain a uniform composite powder; the electrolytic copper powder was high-purity spherical or near-spherical electrolytic copper powder with a purity ≥99.95%, an average particle size of 15-45μm, and a loose packing density of 2.0-3.0g / cm³. 3 The graphene nanosheets are few-layer graphene nanosheets, with 3-10 layers, a single sheet diameter of 5-20 μm, a thickness of 1.5-5.0 nm, and a specific surface area of ​​100-300 m². 2 / g, carbon purity ≥99.9%; Composite powder was placed in a graphite mold and subjected to spark plasma sintering at 820℃, 40MPa, and 10min for 10min, with a heating rate of 80℃ / min to obtain a graphene-reinforced copper-based composite board. Through precision etching and integrated stamping, an upper encapsulation shell (condensation section) with three 65mm×2mm curved guide vanes and a lower encapsulation shell (evaporation section) with a spindle-shaped array of support columns were fabricated on the composite board. The center-to-center distance between adjacent guide vanes was 15mm. The specifications of a single curved guide vane were 65mm in length, 2mm in width, 0.1mm in thickness, and a curvature radius of 1. The condensing section is 6.99mm long and 75° wide. It is located in the upper part of the upper packaging shell away from the heat source and is arranged symmetrically and parallel to the evaporation section. The center of the condensing section coincides with the overall geometric center of the heat spreader. The evaporation section is 100mm long and 70mm wide, the same size as the condensing section. It is located in the lower part of the upper packaging shell where the heat source is in contact, and is the core heat absorption area of ​​the heat spreader. The center of the evaporation section is completely aligned with the center of the chip heat source. The curved flow guide plate is integrally etched with the inner wall of the condensing section of the upper packaging shell. The curved flow guide plate divides the inner cavity of the condensing section into 4 independent gas-liquid flow domains. The spindle-shaped array support columns are arranged at equal intervals of 4mm in the horizontal direction and 5mm in the vertical direction. Each support column has a variable cross-section configuration with a circular cross-section. The diameter of the cross-section at both ends is 0.75–1.00mm, and the maximum diameter of the cross-section in the middle is 1.30–1.80mm. The overall height of the support column is 0.18–0.20mm. The cross-sectional area of ​​the support column is small at both ends and large in the middle, forming a converging conical flow channel between adjacent support columns. Both the upper and lower encapsulation shells are rectangular sheet structures with an overall length of 100mm and a width of 70mm. The shell edges are provided with sealing welded edges with a width of 1.0–1.5mm. The upper and lower shells have completely identical outline dimensions and are perfectly aligned. The upper encapsulation shell is a boss-type structure with a curved guide plate and a spindle-shaped support column, while the lower encapsulation shell is a planar evaporation section base structure. The single wall thickness of the upper and lower encapsulation shells is 0.05mm, and the net height inside the cavity after molding is 0.1mm.

[0027] (2) Preparation of composite capillary core: Carbon nanotubes and nano-copper powder were mixed at a mass ratio of 5:95 and added to anhydrous ethanol at a solid-liquid ratio of 1g:10mL. The mixture was stirred at 300r / min for 2h and then ultrasonically dispersed at 450w for 40min to obtain a uniform slurry. The slurry was uniformly coated on the inner wall of the evaporation section of the lower encapsulation shell with a coating thickness of 100μm. A low-temperature stepwise sintering process was adopted. First, the mixture was pre-sintered at 250℃ for 45min in an argon atmosphere, and then heated to 700℃ at a heating rate of 2℃ / min and sintered at a constant temperature for 2h. The mixture was then cooled to room temperature with the furnace to obtain a carbon nanotube-nano-copper powder composite capillary core with a thickness of 0.1mm, a porosity of 68%, a capillary suction force of 13.2kPa, and a permeability of 8.5×10⁻⁶. -13 m 2 ; (3) Vacuum sealing and working fluid filling: The upper and lower sealing shells are aligned and bonded together, and fiber laser edge sealing welding is used. The laser power is 120W, the welding speed is 35mm / s, and argon gas protection is used. After welding, the leakage rate of the cavity detected by helium mass spectrometry is ≤5×10 -11 Pa·m 3 / s; Place the welded cavity in a vacuum oven at 135℃ and a vacuum degree of 8×10⁻⁶. -4 Under the condition of Pa, heat preservation and degassing were carried out for 4 hours; then, a binary composite heat exchange working fluid was injected, with 18.2 MΩ·cm high-purity deionized water as the base liquid, compounded with 0.3% by mass of spherical α-Al2O3 nanoparticles with an average particle size of 20 nm, and the injection volume was 22% of the cavity volume; after injection, a second vacuum degassing was carried out, and the final cavity vacuum degree was ≤3×10 -4 Pa, cold welding and sealing, yielded an ultrathin graphene-reinforced copper-based VC heat exchange plate with an overall thickness of 0.2 mm and an effective heat exchange area of ​​5937.5 mm². 2 .

[0028] The performance test results of the VC heat spreader prepared in this embodiment are as follows: at room temperature (25℃), the thermal conductivity is 428 W / (m·K), and the thermal resistance of the heat source is 0.072 ℃·cm. 2 / W, maximum temperature difference between evaporation and condensation sections is 1.0℃, performance degradation rate after 1000 thermal cycles is 2.1%, flexural strength is 385MPa; in the low temperature range of 5-15℃, thermal conductivity is 422 W / (m·K), thermal resistance is 0.075 ℃·cm 2 / W, maximum temperature difference 1.1℃; in the high temperature range of 28-40℃, thermal conductivity 425 W / (m·K), thermal resistance 0.070 ℃·cm 2 / W, maximum temperature difference 0.9℃.

[0029] Example 2 The preparation method of an ultrathin graphene-reinforced copper-based VC heat exchanger that combines high structural stability and efficient heat transfer specifically includes the following steps: (1) Preparation of composite shell and internal components by integral molding: Graphene nanosheets and electrolytic copper powder were mixed at a mass ratio of 1.2:98.8 and ball-milled for 8 hours under an argon atmosphere to obtain a uniform composite powder; the electrolytic copper powder was high-purity spherical or near-spherical electrolytic copper powder with a purity ≥99.95%, an average particle size of 15-45μm, and a loose packing density of 2.0-3.0g / cm³. 3 The graphene nanosheets are few-layer graphene nanosheets, with 3-10 layers, a single sheet diameter of 5-20 μm, a thickness of 1.5-5.0 nm, and a specific surface area of ​​100-300 m². 2 / g, carbon purity ≥99.9%; Composite powder was placed in a graphite mold and subjected to spark plasma sintering at 880℃, 45MPa, and 8min for 100℃ / min to obtain a graphene-reinforced copper-based composite board. Through precision etching and integrated stamping, an upper encapsulation shell (condensation section) with three 65mm×2mm curved guide vanes and a lower encapsulation shell (evaporation section) with a spindle-shaped array of support columns were fabricated on the composite board. The center-to-center distance between adjacent guide vanes was 15mm. Each curved guide vane had a length of 65mm, a width of 2mm, a thickness of 0.1mm, and a curvature radius of 1. The condensing section is 6.99mm long and 75° wide. It is located in the upper part of the upper packaging shell away from the heat source and is arranged symmetrically and parallel to the evaporation section. The center of the condensing section coincides with the overall geometric center of the heat spreader. The evaporation section is 100mm long and 70mm wide, the same size as the condensing section. It is located in the lower part of the upper packaging shell where the heat source is in contact, and is the core heat absorption area of ​​the heat spreader. The center of the evaporation section is completely aligned with the center of the chip heat source. The curved flow guide plate is integrally etched with the inner wall of the condensing section of the upper packaging shell. The curved flow guide plate divides the inner cavity of the condensing section into 4 independent gas-liquid flow domains. The spindle-shaped array support columns are arranged at equal intervals of 4mm in the horizontal direction and 5mm in the vertical direction. Each support column has a variable cross-section configuration with a circular cross-section. The diameter of the cross-section at both ends is 0.75–1.00mm, and the maximum diameter of the cross-section in the middle is 1.30–1.80mm. The overall height of the support column is 0.18–0.20mm. The cross-sectional area of ​​the support column is small at both ends and large in the middle, forming a converging conical flow channel between adjacent support columns. Both the upper and lower encapsulation shells are rectangular sheet structures with an overall length of 100mm and a width of 70mm. The shell edges are provided with sealing welded edges with a width of 1.0–1.5mm. The upper and lower shells have completely identical outline dimensions and are perfectly aligned. The upper encapsulation shell is a boss-type structure with a curved guide plate and a spindle-shaped support column, while the lower encapsulation shell is a planar evaporation section base structure. The single wall thickness of the upper and lower encapsulation shells is 0.05mm, and the net height inside the cavity after molding is 0.1mm.

[0030] (2) Preparation of composite capillary wick: Carbon nanotubes and nano-copper powder were mixed at a mass ratio of 7:93 and added to anhydrous ethanol at a solid-liquid ratio of 1g:12mL. The mixture was stirred at 350r / min for 1.5h and ultrasonically dispersed at 400w for 50min to obtain a uniform slurry. The slurry was coated on the inner wall of the evaporation section of the lower encapsulation shell with a coating thickness of 110μm. The sintering was carried out in stages at low temperature: pre-sintering at 280℃ for 40min under an argon atmosphere, heating to 720℃ at 3℃ / min, and constant-temperature sintering for 1.5h. The sintering was then cooled with the furnace to obtain a 0.1mm thick composite wick with a porosity of 66%, a capillary suction force of 12.8kPa, and a permeability of 8.2×10⁻⁶. -13 m 2 ; (3) Vacuum sealing and working fluid filling: Laser edge sealing welding of upper and lower packaging shells, laser power 140W, welding speed 40mm / s, argon protection, leak detection leakage rate ≤8×10 -11 Pa·m 3 / s; 145℃, vacuum degree 6×10 -4 The chamber was kept at a pressure of 3 Pa for 3 hours for degassing; a binary composite working fluid was then injected, with 0.4% α-Al₂O₃ nanoparticles by mass, an average particle size of 20 nm, and the injection volume being 25% of the chamber volume; after secondary degassing, the vacuum degree was ≤4×10⁻⁶. -4 Pa, cold welding and sealing, to obtain an ultra-thin VC heat exchange plate with an overall thickness of 0.2mm.

[0031] The performance test results of the VC heat spreader prepared in this embodiment are as follows: at room temperature of 25℃, the thermal conductivity is 418 W / (m·K), and the thermal resistance of the heat source is 0.076 ℃·cm. 2 / W, maximum temperature difference between evaporation and condensation sections is 1.1℃, performance degradation rate after 1000 thermal cycles is 2.6%, and bending strength is 392MPa.

[0032] Example 3 (Graphene Addition Gradient Verification Group) This example is a graphene addition gradient verification group. The only difference from Example 1 is the mass ratio of graphene nanosheets to electrolytic copper powder. All other raw material ratios, preparation steps, and process parameters are completely consistent with Example 1.

[0033] This embodiment sets up 6 parallel samples, with the added mass percentages of graphene nanosheets being 0.2%, 1.5%, 2.0%, 3.0%, 4.0%, and 5.0%, respectively. The corresponding performance test results are as follows: (1) Group with 0.2% graphene addition: At room temperature of 25℃, the thermal conductivity is 405 W / (m·K) and the thermal resistance is 0.078 ℃·cm. 2 / W, maximum temperature difference 1.15℃, 2.8% decay rate after 1000 cycles of thermal cycling, flexural strength 352MPa; (2) Group with 1.5% graphene addition: At room temperature of 25℃, the thermal conductivity is 412 W / (m·K) and the thermal resistance is 0.077 ℃·cm. 2 / W, maximum temperature difference 1.1℃, 2.5% decay rate after 1000 cycles of thermal cycling, flexural strength 378MPa; (3) Group with 2.0% graphene addition: At room temperature of 25℃, the thermal conductivity is 395 W / (m·K) and the thermal resistance is 0.085 ℃·cm. 2 / W, maximum temperature difference 1.3℃, 1000 cycles of thermal cycling attenuation rate 3.8%, flexural strength 345MPa; (4) Group with 3.0% graphene addition: At room temperature of 25℃, the thermal conductivity is 372 W / (m·K) and the thermal resistance is 0.092 ℃·cm. 2 / W, maximum temperature difference 1.5℃, 4.5% decay rate after 1000 cycles of thermal cycling, flexural strength 320MPa; (5) Group with 4.0% graphene addition: At room temperature of 25℃, the thermal conductivity is 350 W / (m·K) and the thermal resistance is 0.105 ℃·cm. 2 / W, maximum temperature difference 1.8℃, 5.8% decay rate after 1000 cycles of thermal cycling, flexural strength 290MPa; (6) Group with 5.0% graphene addition: At room temperature of 25℃, the thermal conductivity is 325 W / (m·K) and the thermal resistance is 0.120 ℃·cm. 2 / W, maximum temperature difference 2.2℃, 7.5% decay rate after 1000 thermal cycles, flexural strength 260MPa.

[0034] Comparative Example 1 (Traditional pure copper shell, without graphene reinforcement) The only difference from Example 1 is that pure electrolytic copper powder is used to prepare the shell and internal components in step (1), and no graphene nanosheets are added. All other process steps, raw material ratios, and parameter settings are completely consistent with Example 1.

[0035] The performance test results of the VC heat spreader prepared in this comparative example are as follows: at room temperature (25℃), the thermal conductivity is 390 W / (m·K), and the thermal resistance of the heat source is 0.095 ℃·cm. 2 / W, maximum temperature difference 1.6℃, performance degradation rate after 1000 thermal cycles 11.5%, bending strength 275MPa.

[0036] Comparative Example 2 (No guide vanes + traditional cylindrical support columns, no synergistic flow field structure) The only difference from Example 1 is that the inner wall of the condensation section of the upper encapsulation shell prepared in step (1) does not have a curved guide plate, the support column is a cylindrical structure with equal diameter, the cylinder diameter is 1.8 mm and the column height is 0.2 mm, and there is no spindle-shaped variable cross section design. All other parameters and steps are completely consistent with Example 1.

[0037] The performance test results of the VC heat spreader prepared in this comparative example are as follows: at room temperature (25℃), the thermal conductivity is 385 W / (m·K), and the thermal resistance of the heat source is 0.102 ℃·cm. 2 / W, maximum temperature difference 1.8℃, performance degradation rate after 1000 thermal cycles 8.5%, bending strength 320MPa.

[0038] Comparative Example 3 (Traditional pure copper powder sintered liquid absorbent core, carbon nanotube-free composite). The only difference from Example 1 is that pure nano copper powder is used to prepare the liquid absorption core in step (2), and no carbon nanotubes are added. All other parameters and steps are completely consistent with Example 1.

[0039] The performance test results of the VC heat spreader prepared in this comparative example are as follows: at room temperature (25℃), the thermal conductivity is 370 W / (m·K), and the thermal resistance of the heat source is 0.110 ℃·cm. 2 / W, maximum temperature difference 2.0℃, performance degradation rate after 1000 thermal cycles 12.8%, bending strength 382MPa.

[0040] Comparative Example 4 (Core Solution Completely Deviated Group) The only difference from Example 1 is that it uses a pure copper shell, no guide plate, a cylindrical support column, a pure copper powder liquid absorption core, and pure deionized water working fluid. All core innovative structures and parameters deviate from the scope of this invention, while the remaining steps are completely consistent with Example 1.

[0041] The performance test results of the VC heat spreader prepared in this comparative example are as follows: at room temperature (25℃), the thermal conductivity is 320 W / (m·K), and the thermal resistance of the heat source is 0.150 ℃·cm.2 / W, maximum temperature difference 2.8℃, performance degradation rate after 1000 thermal cycles 19.2%, bending strength 270MPa.

[0042] Performance testing and comparison: (1) Test baseline conditions: All samples were tested at room temperature of 25℃ and standard atmospheric pressure, and the heat source power density was fixed at 50W / cm². 2 Effective heating area 1cm 2 Unless otherwise specified, the ambient temperature for all other samples was 25℃; all performance values ​​are the average values ​​of three parallel samples.

[0043] (2) Test equipment: The test system includes a DC regulated power supply, a simulated heat source (ceramic heating element), a heat spreader plate of the VC under test, a heat insulation module, a data acquisition unit (T-type thermocouple, accuracy ±0.1℃), a cold and hot cycle test chamber, a vacuum leak detection unit and an industrial control computer.

[0044] (3) Formula for calculating core indicators: Thermal resistance calculation formula:

[0045] In the formula: The thermal resistance of the VC heat sink is expressed in °C·cm. 2 / W; This represents the temperature difference between the center of the heat source in the evaporation section and the center of the condensation section, expressed in °C. Power density of the heat source surface, in W / cm² 2 .

[0046] Formula for calculating thermal conductivity:

[0047] In the formula: The thermal conductivity of the material is expressed in W / (m·K). Heat transfer flux, expressed in W; This refers to the heat conduction distance, expressed in meters (m). This refers to the heat transfer cross-sectional area, in meters (m²). 2 ; This represents the temperature difference across the heat transfer surface, expressed in Kelvin (K).

[0048] Formula for calculating performance degradation rate:

[0049] In the formula: The performance degradation rate after 1000 thermal cycles; Initial thermal resistance before cycling, in °C·cm 2 / W; Thermal resistance after cycling, in °C·cm 2 / W.

[0050] (4) The test results are shown in Table 1: Table 1 Test data for comparative and example cases

[0051] As can be seen from the measured data in Table 1: (1) The optimal formulation of this invention (Example 1, 0.8% graphene addition) has a stable thermal conductivity of 422-428 W / (m·K) and a stable thermal resistance of the heat source of 0.070-0.075 ℃·cm in the full room temperature range of 5-40℃. 2 / W, the maximum temperature difference between the evaporation and condensation sections is ≤1.1℃, the performance degradation rate after 1000 cycles of thermal cycling is only 2.3%, while maintaining a bending strength of 385MPa, and the performance does not fluctuate significantly over a wide temperature range, with outstanding overall performance; (2) When the graphene content is in the range of 0.2-1.5%, the thermal conductivity of the VC heat spreader is ≥405 W / (m·K), and the thermal resistance of the heat source is ≤0.078 ℃·cm. 2 / W, the overall performance is at its optimal level; when the addition amount exceeds 1.5%, the thermal conductivity continues to decrease with increasing addition amount, while the thermal resistance and temperature difference increase simultaneously. At an addition amount of 5.0%, the thermal conductivity drops to 325 W / (m·K) and the thermal resistance rises to 0.120 ℃·cm. 2 / W, the performance degradation was significant, verifying that 0.2-1.5% is the optimal range for graphene addition in this invention; (3) Compared with the traditional pure copper shell VC heat exchanger (Comparative Example 1), the optimal embodiment of the present invention has a 9.7% increase in thermal conductivity, a 24.2% decrease in thermal resistance, and an 81.7% decrease in performance degradation rate after 1000 thermal cycles; compared with the VC heat exchanger without a cooperative flow field structure (Comparative Example 2), the thermal conductivity is increased by 11.2% and the thermal resistance is reduced by 29.4%; compared with the traditional pure copper powder wick VC heat exchanger (Comparative Example 3), the thermal conductivity is increased by 15.7% and the thermal resistance is reduced by 34.5%; (4) Comparative Examples 1-4 verified the synergistic advantages of the graphene-reinforced copper-based composite shell, gas-liquid splitting synergistic structure, composite capillary liquid-absorbing core, binary composite working fluid and core process parameters of the present invention. Only the technical solutions defined in the claims of the present invention can simultaneously achieve extreme thinness, high heat transfer performance, excellent structural stability and mass production consistency.

[0052] Industrial Application Cases 1. Industrial applications for heat dissipation in high-power, ultra-thin smartphone chips A leading mobile phone manufacturer's flagship model uses a Qualcomm Snapdragon flagship chip with a peak power density of 55W / cm². 2The overall thickness of the device is 7.6mm, with a heat dissipation space thickness of only 0.25mm. Traditional 0.3mm thick VC heat sinks are unsuitable, and under high-power conditions, the chip peak temperature exceeds 48℃, with hotspot temperature differences exceeding 5℃, failing to meet performance demands. This manufacturer uses a 0.2mm ultra-thin VC heat sink prepared according to Embodiment 1 of this invention to build the overall cooling system. The effective heat exchange area of ​​the VC heat sink is 5937.5mm². 2 It is designed to fit the internal stacking space of the entire machine. The system includes a heat source bonding module, an ultra-thin VC heat spreader, a mid-frame heat conduction bracket, a graphite heat sink, a control system, and a temperature monitoring unit.

[0053] The results show that, under ambient temperature of 25℃, the chip operates at full load for 30 minutes with a peak temperature that remains stable below 40℃, a 9℃ reduction compared to traditional heat dissipation solutions. The temperature difference between hot spots is controlled within 1.5℃, with no obvious hot spot concentration. Within a wide ambient temperature range of -10℃ to 45℃, the heat dissipation performance shows no significant fluctuations. After 1000 power-on / off cycles, the performance degradation rate is only 2.2%, meeting the requirements for the entire lifecycle of a mobile phone. In mass production, the thermal resistance fluctuation of five batches of products is only 3.2%, and the thermal conductivity fluctuation is only 4.5%, with a yield rate of 96.2%, far exceeding traditional processes. After this model is equipped with the VC heat dissipation plate of this invention, the chip's full-load operating time increases by 45%, and the frame rate stability in game scenarios improves by 38%, achieving excellent market feedback.

[0054] 2. Industrial Applications of CPU Cooling in Ultra-thin Laptops A computer manufacturer's 14-inch ultra-thin business laptop, with an overall thickness of 12.9mm and a CPU peak power of 45W, uses a traditional cooling solution with a dual heat pipe and fin structure. Under high load, the CPU temperature exceeds 90℃, resulting in significant frequency throttling and severely impacting the user experience. This manufacturer replaced the traditional heat pipe cooling solution with an ultra-thin VC vapor chamber prepared according to Embodiment 1 of this invention. The VC vapor chamber has an overall thickness of 0.3mm and an effective heat exchange area of ​​12000 mm². 2 It is designed to fit the internal space of a laptop and includes a CPU bonding module, an ultra-thin VC heat dissipation plate, a cooling fin at the condenser end, a low-noise fan, a control system, and a temperature monitoring unit.

[0055] Application results show that, under a room temperature of 25℃, the CPU operates at full load for 60 minutes with a stable temperature below 78℃, which is 13℃ lower than traditional cooling solutions, and no frequency throttling occurs; the CPU core temperature difference is controlled within 1.2℃, demonstrating excellent temperature uniformity; the cooling system noise is reduced by 8dB compared to traditional solutions, achieving silent cooling; compared to traditional heat pipe cooling solutions, this system improves cooling efficiency by 42% and increases overall battery life by 12%; the VC heat pipe's performance degradation rate is ≤2.5% after 1000 hours of continuous operation, demonstrating excellent long-term operational stability. It simultaneously achieves the dual goals of improved cooling performance and a thinner, lighter overall design, resulting in good economic benefits and positive user feedback.

[0056] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer, characterized in that, Includes the following steps: (1) Composite shell and internal components are integrally formed: graphene nanosheets and electrolytic copper powder are mixed evenly to obtain composite powder. After being sintered by spark plasma, the lower encapsulation shell and the upper encapsulation shell with curved flow guide plate and spindle array support column are prepared by precision etching and integral stamping process. (2) Preparation of composite capillary liquid absorption core: Carbon nanotubes and nano copper powder are dispersed in anhydrous ethanol to obtain a slurry. The slurry is coated on the inner wall of the evaporation section of the lower encapsulation shell obtained in step (1). The slurry is cured by a low-temperature stepwise sintering process to obtain a carbon nanotube-nano copper powder composite porous capillary liquid absorption core. (3) Vacuum encapsulation and working fluid filling: The upper and lower encapsulation shells of step (1) are laser-sealed to form a cavity. After the cavity is subjected to high vacuum degassing treatment, a binary composite heat exchange working fluid is filled in. After secondary degassing, it is sealed to obtain an ultrathin graphene-reinforced copper-based VC heat exchange plate.

2. The method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer as described in claim 1, characterized in that, In step (1), the mass ratio of the graphene nanosheets to the electrolytic copper powder is (0.2-1.5):(98.5-99.8). The electrolytic copper powder is a high-purity spherical or near-spherical electrolytic copper powder with a purity ≥99.95%, an average particle size of 15-45 μm, and a loose packing density of 2.0-3.0 g / cm³. 3 ; The graphene nanosheets are few-layer graphene nanosheets, with 3-10 layers, a single sheet diameter of 5-20 μm, a thickness of 1.5-5.0 nm, and a specific surface area of ​​100-300 m². 2 / g, carbon purity ≥99.9%; The process parameters for the discharge plasma sintering are: sintering temperature 750-900℃, sintering pressure 30-50MPa, holding time 5-15min, and heating rate 50-100℃ / min.

3. The method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer as described in claim 1, characterized in that, In step (1), there are 3 curved guide plates, the center distance between adjacent guide plates is 15mm, the specifications of a single curved guide plate are 65mm in length, 2mm in width, 0.1mm in thickness, 16.99mm in radius of curvature, and 75° in arc angle; the condensation section is 100mm long and 70mm wide, located in the upper part of the upper packaging shell away from the heat source, and is arranged parallel and symmetrically with the evaporation section, the center of the condensation section coincides with the overall geometric center of the heat spreader; the evaporation section is 100mm long and 70mm wide, the same size as the condensation section, located in the lower part of the upper packaging shell where the heat source is attached, and is the core heat absorption area of ​​the heat spreader, the center of the evaporation section is completely aligned with the center of the chip heat source; the curved guide plate is integrally etched with the inner wall of the condensation section of the upper packaging shell, and the curved guide plate divides the inner cavity of the condensation section into 4 independent gas-liquid flow domains; The spindle-shaped array support columns are arranged at equal intervals of 4mm in the horizontal direction and 5mm in the vertical direction. Each support column has a variable cross-section configuration with a circular cross-section. The diameter of the cross-section at both ends is 0.75–1.00mm, and the maximum diameter of the cross-section in the middle is 1.30–1.80mm. The overall height of the support column is 0.18–0.20mm. The cross-sectional area of ​​the support column is small at both ends and large in the middle, forming a converging conical flow channel between adjacent support columns. Both the upper and lower encapsulation shells are rectangular sheet structures with an overall length of 100mm and a width of 70mm. The shell edges are provided with sealing welded edges with a width of 1.0–1.5mm. The upper and lower shells have completely identical outline dimensions and are aligned and fitted together. The upper encapsulation shell is a boss-type structure with a curved guide plate and a spindle-shaped support column, while the lower encapsulation shell is a planar evaporation section base structure. The single wall thickness of the upper and lower encapsulation shells is 0.05mm, and the net height inside the cavity after molding is 0.1mm.

4. The method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer according to claim 1, characterized in that, In step (2), the mass ratio of the carbon nanotubes to the nano copper powder is (2-8):(92-98). The total mass of the carbon nanotubes and copper nanopowder is in the mass-to-volume ratio of anhydrous ethanol to 1 g: (5-15) mL.

5. The method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer according to claim 1, characterized in that, In step (2), the dispersion is carried out by stirring at a speed of 200-400 r / min for 1-3 h, followed by ultrasonic dispersion at an ultrasonic power of 300-600 w for 20-60 min. The coating thickness is 80-120μm, and the thickness of the carbon nanotube-nano copper powder composite porous capillary liquid-absorbing core after sintering is 0.1mm. The low-temperature stepwise sintering process is as follows: first, pre-sintering at 200-300℃ for 30-60 minutes in an argon atmosphere, then heating to 650-750℃ at a heating rate of 1-3℃ / min, sintering at a constant temperature for 1-3 hours, and then cooling to room temperature with the furnace.

6. The method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer according to claim 1, characterized in that, In step (3), the process parameters for laser edge sealing welding are: fiber laser power 80-150W, welding speed 20-50mm / s, shielding gas is argon, and the leakage rate of the cavity after welding is ≤1×10⁻⁶ by helium mass spectrometry. - 10 Pa·m 3 / s.

7. The method for preparing an ultrathin graphene-reinforced copper-based VC vapor chamber with both high structural stability and efficient heat transfer according to claim 1, characterized in that, In step (3), the high-vacuum degassing treatment is performed at 120-150℃ with a vacuum degree ≤1×10⁻⁶. -3 Under the condition of Pa, keep warm and degas for 2-6 hours; The binary composite heat exchange medium is a deionized water-based α-alumina nanofluid, with deionized water of 18.2 MΩ·cm as the base liquid, and spherical α-Al2O3 nanoparticles with a mass fraction of 0.1-0.5% and an average particle size of 15-25nm. The amount of working fluid injected is 15-30% of the internal volume of the cavity; The vacuum degree of the seal after secondary degassing is ≤5×10⁻⁶. -4 Pa.

8. An ultrathin graphene-reinforced copper-based VC heat exchanger prepared by the preparation method according to any one of claims 1-7.

9. The application of the preparation method according to any one of claims 1-7 or the ultrathin graphene-reinforced copper-based VC heat sink according to claim 8 in heat dissipation of high-power ultrathin electronic devices, characterized in that, The overall thickness of the electronic device is ≤8mm, and the heat source power density is ≥50W / cm². 2 .

10. The application of the preparation method according to claim 9 or the ultrathin graphene-reinforced copper-based VC heat sink in heat dissipation of high-power ultrathin electronic devices, characterized in that, Application scenarios include high-power ultra-thin smartphones, ultra-thin laptops, AR / VR devices, or wearable electronic devices.

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