Uniform temperature plate, its application and preparation method

Abstract

The application belongs to the technical field of electronic device heat dissipation, and particularly relates to a uniform temperature plate and an application and a preparation method thereof. 3 The application is characterized in that the capillary structure comprises a lattice-matched diamond / carbon nanotube heteroepitaxial structure in an evaporation area, wherein the gradient transition interface layer realizes a continuous transition of a lattice constant from diamond sp3 to carbon nanotube sp2, carbon atoms form a covalent bonding network at the interface, and the interface thermal resistance tends to be zero. Compared with the prior art, the lattice-matched interface thermal conductivity of the application is improved by more than 5 times, and the overall structure equivalent thermal conductivity breaks through 10,000 W / (m*K).

Description

Technical Field

[0001] This invention belongs to the field of heat dissipation technology for electronic devices, specifically relating to heat spreaders, their applications, and preparation methods. Background Technology

[0002] With the continuous improvement of CPU / GPU computing power, its heat flux density has exceeded 500W / cm³. 2 and toward 1000W / cm 2 With the heatsinking process nearing its limits, traditional air cooling and heat pipe cooling are approaching their limits. As a highly efficient two-phase heat transfer element, vapor chambers achieve rapid heat diffusion through the phase change cycle of the internal working fluid, becoming a key solution for heat dissipation in high heat flux densities.

[0003] The capillary wicks of existing heat spreaders are mostly made of sintered copper powder. This material has inherent defects: the thermal conductivity of copper is only about 400 W / (m·K), which is difficult to meet the thermal diffusion requirements of ultra-high power chips; the porosity of sintered copper powder is negatively correlated with capillary force, and it is prone to drying out under high heat flux; moreover, the chemical compatibility between copper and working fluid is limited, and there is a risk of performance degradation during long-term high-temperature operation.

[0004] Diamond possesses the highest known thermal conductivity (>2000 W / (m·K)) and excellent chemical inertness, while carbon nanotubes exhibit ultra-high axial thermal conductivity (>3000 W / (m·K)) and a very large aspect ratio. Combining these two materials promises a breakthrough in both thermal conductivity and phase change heat transfer. However, current methods cannot directly construct diamond / carbon nanotube composite arrays with oriented structures on metal substrates, making their application in electronic heat dissipation scenarios such as vapor chambers difficult.

[0005] Therefore, how to directly construct diamond / carbon nanotube composite arrays with oriented structures on metal substrates is a technical problem that urgently needs to be solved in the field of electronic heat dissipation, such as heat spreaders.

[0006] It should be noted that the information disclosed in this background section is only for understanding the background technology of this application concept, and therefore, the above description is not considered to constitute prior art information. Summary of the Invention

[0007] This disclosure provides at least one heat spreader, its application, and a method for its preparation.

[0008] In a first aspect, embodiments of this disclosure provide a heat spreader, including an upper cover plate and a lower cover plate, with a vacuum cavity formed between them. The vacuum cavity is filled with a working fluid and also has a capillary structure. The capillary structure, from bottom to top, includes: a diamond micropillar array layer located on the inner wall of the lower cover plate; and a gradient transition interface layer located on the surface of the diamond micropillar array layer, which is sp... 3A multilayer composite structure with a continuous transition from hybrid carbon to sp2 hybrid carbon; an array of oriented carbon nanotubes located on the gradient transition interface layer.

[0009] In one optional implementation, the gradient transition interface layer includes: a first transition sublayer, which is sp 3 A hybrid carbon layer is located on the diamond micropillar array layer; a second transition sublayer is a sp³ and sp² hybrid carbon layer located on the first transition sublayer; a third transition sublayer is a sp² hybrid carbon layer located between the second transition sublayer and the oriented carbon nanotube array layer.

[0010] In one optional embodiment, the cross-section of the micropillars in the diamond micropillar array layer is either circular or polygonal; the height of the micropillars in the diamond micropillar array layer is 200-800 μm, the diameter is 50-200 μm, and the spacing is 100-500 μm; the proportion of the top and sidewall (100) crystal planes and / or (111) crystal planes of the micropillars in the diamond micropillar array layer is ≥80%.

[0011] In one optional embodiment, the carbon nanotubes in the oriented carbon nanotube array layer have a diameter of 10-30 nm, a length of 50-200 μm, and an orientation degree of ≥98%; the walls of the carbon nanotubes in the oriented carbon nanotube array layer form continuous covalent bonds with the third transition sublayer.

[0012] Secondly, embodiments of this disclosure also provide an application of the above-described heat spreader in electronic devices or electrical equipment.

[0013] Thirdly, this disclosure also provides a method for preparing a heat spreader, which includes the following steps: Step 1, preparing a diamond / carbon nanotube heteroepitaxial structure on a lower cover plate; Step 2, preparing an upper cover plate, performing surface treatment, and preparing a capillary core for the condensation region; Step 3, assembling the heat spreader, aligning and assembling the lower cover plate and upper cover plate with the prepared diamond / carbon nanotube heteroepitaxial structure, injecting working fluid and sealing; wherein, the diamond / carbon nanotube heteroepitaxial structure includes the following steps: S1, crystal plane controlled growth of a diamond micropillar array; S2, atomic-level construction of a gradient transition interface layer; S3, epitaxial growth of a directional carbon nanotube array.

[0014] In one optional embodiment, S1, the crystal plane controlled growth of the diamond micropillar array includes the following steps: S11, atomic-level planarization treatment of the copper substrate; that is, using an oxygen-free copper sheet with a preferred orientation of the (100) crystal plane as the lower cover plate, placing the copper substrate in hydrogen plasma, and treating it at 950-1050℃ for 2-4 hours to reconstruct the surface atoms into a regular step flow morphology, and then cooling it in a vacuum to maintain the stability of the surface structure; S12, bias-enhanced nucleation and crystal orientation locking; that is, placing the treated copper substrate in an MPCVD reaction chamber, evacuating, introducing hydrogen gas, heating, applying a negative bias, and introducing methane to make the diamond crystal nuclei preferentially arranged in the (100) orientation, with a nucleation density ≥5×10 10 / cm 2 S13, Hard mask preparation and selective growth: A SiO2 hard mask layer is deposited on the nucleated substrate surface using plasma-enhanced chemical vapor deposition (PECVD). Photoresist is spin-coated, and a micropillar array pattern is formed by UV lithography. After development, the area to be etched is exposed. Reactive ion etching is used to remove the exposed SiO2, forming hard mask openings. The photoresist is then removed to obtain a substrate with a SiO2 hard mask. S14, Selective growth of diamond micropillars: The substrate with the SiO2 hard mask is placed in an MPCVD reaction chamber. Diamond is grown in the mask opening area to form a micropillar array. After growth, the SiO2 mask is removed using hydrofluoric acid to obtain a diamond micropillar array. S15, Surface hydrogenation and activation: The diamond micropillar array is placed in hydrogen plasma and treated at 800℃ for 20 min to terminate the surface with CH bonds. Subsequently, the surface is rapidly heated to 1000℃ in an argon atmosphere and immediately cooled to generate a controllable density of carbon dangling bonds on the surface.

[0015] In one optional embodiment, S2, atomic-level construction of the gradient transition interface layer includes the following steps: S21, plasma-assisted gradient carbon deposition, in which a hydrogenated diamond micropillar array is placed in a PECVD reaction chamber, and a methane / hydrogen mixed gas is introduced, with the methane concentration linearly increasing from 0.5% to 5% over a time of 30 min, while simultaneously controlling the RF power to linearly increase from 50 W to 200 W and the substrate temperature to linearly increase from 600 °C to 750 °C. During this process, carbon atoms are deposited on the diamond surface to form a gradient layer that continuously transitions from sp³-dominated to sp²-dominated; S22, the substrate with the gradient layer is placed in an ultra-high vacuum environment and annealed to rearrange the sp² carbon regions on the surface of the gradient layer to form nanoscale graphene fragments.

[0016] In one optional embodiment, S3, the epitaxial growth of the directional carbon nanotube array, includes the following steps: S31, atomic layer deposition of a catalyst, depositing an iron catalyst on the surface of a gradient layer using atomic layer deposition technology, with ferrocene and oxygen plasma as precursors, obtaining a continuous iron film by controlling the number of cycles, and annealing in a hydrogen atmosphere after deposition, whereby the iron film spontaneously agglomerates to form nanoparticles with a particle size of 5-15 nm and a density of 10. 11 -10 12 / cm 2 S32, Electric-Magnetic Field Synergistic Orientation Growth: The substrate with catalyst nanoparticles is placed in a PECVD reaction chamber, vacuumed, hydrogen is introduced, and the temperature is raised. After the temperature stabilizes, carbon source gas is introduced, and a vertical electric field and a vertical magnetic field are applied. The dual fields synergistically induce the vertical orientation of carbon nanotubes. During the growth process, the carbon source concentration and bias voltage are adjusted to ensure the continuous growth of the carbon nanotube wall and the graphene fragments in the gradient layer. S33, In-situ Passivation Treatment: After the growth is completed, the carbon source and bias voltage are turned off, and the substrate is annealed in a hydrogen atmosphere to eliminate structural defects.

[0017] In one optional embodiment, step two, the preparation of the upper cover plate, includes the following steps: surface treatment of the upper cover plate, preparing radial flow channels and support column arrays on the inner wall of the copper upper cover plate by photolithography-electroplating or precision machining, using femtosecond laser to open spiral microchannels inside the support columns as auxiliary liquid return channels, hydrophobizing the condensation area, and depositing a fluorinated carbon film by magnetron sputtering; preparation of the capillary core in the condensation area, using a mixture of atomized copper powder and graphene nanosheets, forming a gradient porosity sintered core in the condensation area by selective laser sintering, and adjusting the laser energy density to make the porosity gradually increase from the condensation end to the evaporation end.

[0018] The beneficial effects of this invention are that the capillary structure within the vacuum cavity between the upper and lower cover plates of this vapor chamber includes a lattice-matched diamond / carbon nanotube heteroepitaxial structure located in the evaporation region, comprising a diamond micropillar array layer, a gradient transition interface layer, and a oriented carbon nanotube array layer. The gradient transition interface layer achieves a continuous transition of the lattice constant from sp³ diamond to sp² carbon nanotubes, with carbon atoms forming a covalent bond network at the interface, resulting in near-zero interfacial thermal resistance. Compared to the prior art's physical connection via a catalyst, the lattice-matched interface of this invention exhibits a more than 5-fold increase in thermal conductivity, and the lattice-matched interface reduces the interfacial thermal resistance between diamond and carbon nanotubes to 10. -9 m 2Below K / W, the overall structural equivalent thermal conductivity exceeds 10000 W / (m·K). A diamond micropillar array is fabricated using selective growth technology; the columnar structure has a higher specific surface area (3-5 times greater) than microchannels, and the inter-pillar gaps form multi-scale capillary channels, significantly enhancing liquid transport capacity. The overall all-carbon material system of the heat spreader exhibits excellent chemical inertness, with no risk of fatigue failure due to interfacial covalent bonding; performance degradation is ≤2% after 20000 hours of high-temperature operation.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 A perspective view of a heat spreader provided in an embodiment of this disclosure; Figure 2 A schematic diagram of a diamond / carbon nanotube heteroepitaxial structure; Figure 3 Electron micrograph of the capillary structure; Figure 4 This is an electron microscope image of the formed diamond micropillar array layer; Figure 5 This is an electron microscope image of a oriented carbon nanotube array layer.

[0023] In the picture: 1. Upper cover plate, 2. Lower cover plate, 3. Vacuum cavity, 4. Working fluid, 5. Diamond micropillar array layer, 10. Capillary structure, 6. Gradient transition interface layer, 61. First transition sublayer, 62. Second transition sublayer, 63. Third transition sublayer, 7. Directed carbon nanotube array layer. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Research has revealed that the capillary cores of existing heat spreaders are mostly made of sintered copper powder, which has inherent defects: copper has a thermal conductivity of only about 400 W / (m·K), which is difficult to meet the thermal diffusion requirements of ultra-high power chips; the porosity of sintered copper powder is negatively correlated with capillary force, and it is prone to drying out under high heat flux; moreover, copper has limited chemical compatibility with the working fluid, and there is a risk of performance degradation during long-term high-temperature operation.

[0026] Diamond possesses the highest known thermal conductivity (>2000 W / (m·K)) and excellent chemical inertness, while carbon nanotubes exhibit ultra-high axial thermal conductivity (>3000 W / (m·K)) and a very large aspect ratio. Combining these two materials promises a breakthrough in both thermal conductivity and phase change heat transfer. However, current methods cannot directly construct diamond / carbon nanotube composite arrays with oriented structures on metal substrates, making their application in electronic heat dissipation scenarios such as vapor chambers difficult.

[0027] Based on the above research, this disclosure provides a vapor chamber, its application, and a preparation method. The capillary structure within the vacuum cavity between the upper and lower cover plates includes a lattice-matched diamond / carbon nanotube heteroepitaxial structure located in the evaporation region. This structure comprises a diamond micropillar array layer, a gradient transition interface layer, and a oriented carbon nanotube array layer. The gradient transition interface layer achieves a continuous transition of the lattice constant from diamond sp³ to carbon nanotube sp², with carbon atoms forming a covalent bond network at the interface, resulting in near-zero interfacial thermal resistance. Compared to existing technologies that use catalysts for physical bonding, the interfacial thermal conductivity of this invention is improved by more than 5 times. The diamond micropillar array is prepared using selective growth technology. The columnar structure has a higher specific surface area (3-5 times higher) than microchannels, and the inter-pillar gaps form multi-scale capillary channels, significantly enhancing liquid transport capacity.

[0028] The shortcomings of the above solutions are the result of the inventor's practical experience and careful research. Therefore, the discovery process of the above problems and the solutions proposed in this disclosure should be considered as the inventor's contribution to this disclosure.

[0029] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0031] See Figure 1 , Figure 2 At least one embodiment illustrates a heat spreader, including an upper cover plate 1 and a lower cover plate 2, with a vacuum cavity 3 formed between them. The vacuum cavity 3 is filled with a working fluid 4, and a capillary structure 10 is also provided within the vacuum cavity 3. The capillary structure 10, from bottom to top, includes: a diamond micropillar array layer 5 located on the inner wall of the lower cover plate 2; a gradient transition interface layer 6 located on the surface of the diamond micropillar array layer 5, which is sp 3 A multilayer composite structure with a continuous transition from hybrid carbon to sp2 hybrid carbon; oriented carbon nanotube array layer 7, located on gradient transition interface layer 6.

[0032] In short, the working fluid is a mixture of deionized water and 0.01% surfactant, with a filling rate of 25%. Within the vacuum cavity 3 between the upper cover plate 1 and the lower cover plate 2, in addition to the conventionally provided working fluid 4, a capillary structure 10 is also provided; see electron micrograph for details. Figure 3 It includes a lattice-matched diamond / carbon nanotube heteroepitaxial structure located in the evaporation region. The lattice-matched diamond / carbon nanotube heteroepitaxial structure includes three layers: a diamond micropillar array layer 5, a gradient transition interface layer 6, and a oriented carbon nanotube array layer 7.

[0033] See Figure 4 The diamond micropillar array layer 5, due to its columnar structure, has a higher specific surface area than existing microchannel technologies, increasing it by 3-5 times. Furthermore, the inter-pillar gaps form multi-scale capillary channels, significantly enhancing liquid transport capacity. The three-dimensional micropillar array of the diamond micropillar array layer 5 provides ample evaporation sites, and combined with ultra-strong capillary suction, it can withstand heat flux densities exceeding 1200 W / cm², which is 4 times higher than traditional vapor chambers.

[0034] Furthermore, the gradient transition interface layer 6 achieves a continuous transition of the lattice constant from diamond sp³ to carbon nanotube sp², with carbon atoms forming a covalent bond network at the interface, resulting in near-zero interfacial thermal resistance. Compared to the physical connection via catalysts in existing technologies, the lattice-matched interface of this invention exhibits a more than 5-fold increase in thermal conductivity, and the lattice-matched interface reduces the interfacial thermal resistance between diamond and carbon nanotubes to 10. -9 m 2 Below K / W, the overall structural equivalent thermal conductivity exceeds 10000 W / (m·K).

[0035] Furthermore, the overall carbon material system of the temperature riser exhibits excellent chemical inertness, with no risk of fatigue failure due to interfacial covalent bonding, and its performance degradation is ≤2% after 20,000 hours of high-temperature operation.

[0036] See Figure 2 In some embodiments, the gradient transition interface layer 6 includes: a first transition sublayer 61, which is sp 3 A hybrid carbon layer is located on the diamond micropillar array layer 5; the second transition sublayer 62 is a mixed sp³ and sp² hybrid carbon layer located on the first transition sublayer 61; the third transition sublayer 63 is a sp² hybrid carbon layer located between the second transition sublayer 62 and the oriented carbon nanotube array layer 7.

[0037] In short, the gradient transition interface layer 6 is located on the surface of the diamond micropillar array layer 5, and is a multilayer composite structure with a continuous transition from sp³ hybrid carbon to sp² hybrid carbon, with a total thickness of 10-50 nm. The first transition sublayer 61 is sp³ hybrid carbon. 3 The first layer is a hybrid carbon layer, 2-5 nm thick, with carbon atoms arranged continuously in the diamond lattice. The second transition sublayer, 62, is a mixed sp³ and sp² hybrid carbon layer, with the sp² ratio gradually increasing along the thickness direction, and a thickness of 5-20 nm. The third transition sublayer, 63, is an sp² hybrid carbon layer with a graphene fragment structure, 3-10 nm thick, serving as a template for carbon nanotube growth.

[0038] See Figure 4 In some embodiments, the cross-section of the diamond micropillar array layer 5 is either circular or polygonal; the height of the micropillars in the diamond micropillar array layer 5 is 200-800 μm, the diameter is 50-200 μm, and the spacing is 100-500 μm; the proportion of (100) and / or (111) crystal planes on the top and sidewalls of the micropillars in the diamond micropillar array layer 5 is ≥80%. The diamond micropillar array 5 has the dual functions of capillary core and support pillar, and the overall thickness can be reduced to below 1.0 mm, meeting the requirements of next-generation ultra-thin devices. In short, the cross-section of the micropillars in the diamond micropillar array layer 5 is circular or polygonal, and the top and sidewalls of the micropillars have a defined crystal plane orientation, wherein the proportion of (100) or (111) crystal planes is ≥80%.

[0039] See Figure 5 In some embodiments, the carbon nanotubes in the oriented carbon nanotube array layer 7 have a diameter of 10-30 nm, a length of 50-200 μm, and an orientation degree of ≥98%; the walls of the carbon nanotubes in the oriented carbon nanotube array layer 7 form continuous covalent bonds with the third transition sublayer 63.

[0040] In short, the gradient transition interface layer 6 achieves a continuous transition of the lattice constant from diamond sp³ to carbon nanotube sp², and a continuous covalent bond network is formed at the interface between the carbon nanotube wall and the third transition sublayer 63 in the oriented carbon nanotube array layer 7, resulting in near-zero interfacial thermal resistance. Compared with the prior art that uses catalysts for physical bonding, the interfacial thermal conductivity of this invention is improved by more than 5 times. At least one embodiment of the present invention also illustrates the application of the heat spreader as described above in electronic devices or electrical equipment. Electronic devices include, but are not limited to, smartphones, tablets, laptops, etc.; electrical equipment includes, but is not limited to, battery packs, inverters, frequency converters, avionics, etc.

[0041] At least one embodiment of the present invention also illustrates a method for preparing a heat spreader, comprising the following steps: Step 1, preparing a diamond / carbon nanotube heteroepitaxial structure on a lower cover plate; Step 2, preparing an upper cover plate, performing surface treatment, and preparing a capillary wick for the condensation region; Step 3, assembling the heat spreader by aligning and assembling the lower cover plate and the upper cover plate with the prepared diamond / carbon nanotube heteroepitaxial structure, and using laser welding at a vacuum degree of 10. -3 Sealing under Pa conditions, weld width ≤100μm. Injection of working fluid (deionized water + 0.01% surfactant), filling rate 25%, and cold welding sealing. Helium mass spectrometry leak detection leak rate <1×10⁻⁶. -10 Pa·m 3 / s; wherein, the diamond / carbon nanotube heteroepitaxial structure includes the following steps: S1, crystal plane controlled growth of diamond micropillar array; S2, atomic-level construction of gradient transition interface layer; S3, epitaxial growth of directional carbon nanotube array.

[0042] In summary, the gradient transition interface layer of this invention uses an atomic-level transition layer construction method and develops a plasma-assisted gradient carbon deposition technology. By continuously adjusting process parameters, the hybridization state and arrangement of carbon are precisely controlled at the atomic scale, providing a lattice template for the epitaxial growth of carbon nanotubes.

[0043] S1, Crystal plane-controlled growth of diamond micropillar arrays, the final formation of which is described in [reference needed]. Figure 4 The process includes the following steps: S11, atomic-level planarization of the copper substrate, using an oxygen-free copper sheet with a preferred orientation of the (100) crystal plane as the lower cover plate, with a thickness of 0.3-1.0 mm, placing the copper substrate in hydrogen plasma, and treating it at 950-1050℃ for 2-4 h, so that the surface atoms are reconstructed into a regular step flow morphology, with a step width of 50-100 nm and a step height of 0.2-0.3 nm. After treatment, the substrate is cooled in a vacuum at a cooling rate ≤2℃ / min to maintain the stability of the surface structure; S12, bias-enhanced nucleation and crystal orientation locking, placing the treated copper substrate in an MPCVD reaction chamber, and evacuating it to 10℃. -3 Below Pa, hydrogen gas is introduced at a flow rate of 300-500 sccm, the temperature is raised to 850-900℃, a negative bias voltage of -250V to -350V is applied, and methane is introduced at a concentration of 1-3%, and maintained for 30-60 minutes. By adjusting the bias voltage and methane concentration, diamond crystal nuclei are preferentially aligned in the (100) orientation, with a nucleation density ≥5×10⁻⁶. 10 / cm2 S13, Hard mask preparation and selective growth: A SiO2 hard mask layer is deposited on the nucleated substrate surface using plasma-enhanced chemical vapor deposition. Photoresist is spin-coated, and a micropillar array pattern is formed by ultraviolet lithography. After development, the area to be etched is exposed. Reactive ion etching using a mixture of CF4 and O2 gases removes the exposed SiO2, forming openings in the hard mask. The photoresist is then removed, yielding a substrate with a SiO2 hard mask. S14, Selective growth of diamond micropillars: The substrate with the SiO2 hard mask is placed in an MPCVD reaction chamber. Process parameters: microwave power 3-5kW, reaction pressure 20-30kPa, substrate temperature 900-980℃; reaction gases: methane 1-2%, hydrogen 98-99%, flow rate 300-500sccm; growth time: 20-60h. Diamond is grown in the mask opening area to form a micropillar array. After growth, the SiO2 mask is removed using hydrofluoric acid to obtain the diamond micropillar array. Scanning electron microscopy revealed that the micropillars had smooth sidewalls and a (100) crystal plane at the top. S15, surface hydrogenation and activation: the diamond micropillar array was placed in hydrogen plasma and treated at 800℃ for 20 min to terminate the surface with CH bonds. Subsequently, the surface was rapidly heated to 1000℃ in an argon atmosphere and immediately cooled to generate carbon dangling bonds of controllable density on the surface.

[0044] S2, Atomic-level construction of the gradient transition interface layer, including the following steps: S21, Plasma-assisted gradient carbon deposition, placing the hydrogenated diamond micropillar array in a PECVD reaction chamber with a base vacuum of 10... -4 Pa, a methane / hydrogen mixture is introduced at a total flow rate of 100 sccm. The methane concentration is linearly increased from 0.5% to 5% over a period of 30 minutes. Simultaneously, the RF power is linearly increased from 50W to 200W, and the substrate temperature is linearly increased from 600℃ to 750℃. During this process, carbon atoms are deposited on the diamond surface, forming a matrix composed of sp... 3 Dominant towards sp 2 The gradient layer, which dominates the continuous transition, was annealed at 650℃ for 30 min in a hydrogen atmosphere after deposition to stabilize the interface structure. High-resolution transmission electron microscopy (HRTEM) observation showed that the gradient layer was continuous with the diamond lattice and had no interface defects. In S22, a substrate with the gradient layer was placed in an ultra-high vacuum environment and annealed at 800℃ for 10 min, causing the sp² carbon regions on the surface of the gradient layer to rearrange to form nanoscale graphene fragments. Atomic force microscopy showed that the graphene fragments were 5-20 nm in size and aligned with the diamond lattice.

[0045] S3, Epitaxial growth of oriented carbon nanotube arrays, the final formation of which is shown in [reference]. Figure 5The process includes the following steps: S31, Catalyst Atomic Layer Deposition (ALD), where an iron catalyst is deposited on the surface of a gradient layer using ALD technology. The precursors are ferrocene and oxygen plasma. Deposition parameters are: deposition temperature 300℃, number of cycles 50-100, and deposition depth per cycle 0.02 nm / cycle. By controlling the number of cycles, a continuous iron film with a thickness of 1-3 nm is obtained. After deposition, the film is annealed at 600℃ for 10 min in a hydrogen atmosphere. The iron film spontaneously agglomerates to form nanoparticles with a particle size of 5-15 nm and a density of 102. 11 -10 12 / cm 2 S32, electric field-magnetic field synergistic orientation growth, the substrate with catalyst nanoparticles is placed in the PECVD reaction chamber, and the vacuum is evacuated to 10. -3 The process involves introducing hydrogen gas at 100 sccm, heating to 650-750℃, and then, after stabilization, introducing a carbon source gas, such as acetylene or ethanol vapor, at a flow rate of 20-50 sccm. A vertical electric field of 1-2 kV / cm and a vertical magnetic field of 0.1-0.5 T are applied to synergistically induce the vertical orientation of carbon nanotubes. This is the first time that electric and magnetic fields have been synergistically applied to carbon nanotube growth. The electric field induces dipole orientation, while the magnetic field suppresses thermal motion, achieving ultra-high directional growth with an orientation degree ≥98%. Growth time: 20-80 min, with the carbon nanotube length controlled by time. During growth, the carbon source concentration and bias voltage are adjusted to ensure continuous growth of the carbon nanotube wall and the graphene fragments in the gradient layer. After in-situ passivation (S33), the carbon source and bias voltage are turned off, and the nanotubes are annealed at 700℃ for 30 min in a hydrogen atmosphere to eliminate structural defects.

[0046] Step two, upper cover plate fabrication, includes the following steps: Surface treatment of the upper cover plate: Radial guide grooves and a support column array are fabricated on the inner wall of the copper upper cover plate using photolithography-electroplating or precision machining. The radial guide grooves are 200 μm wide, 300 μm deep, and have a radiation angle of 30°-60°. The support column array has a diameter of 200 μm, and its height matches the cavity gap. A femtosecond laser is used to create spiral microchannels with a diameter of 50 μm and a pitch of 100 μm inside the support columns, serving as auxiliary liquid reflux channels. The condensation region is hydrophobically treated, and a fluorinated carbon film with a thickness of 50 nm and a water contact angle ≥130° is deposited by magnetron sputtering. Capillary core fabrication in the condensation region: A mixture of atomized copper powder with a particle size of 50-100 μm and 1% graphene nanosheets is used, and a gradient porosity sintered core is formed in the condensation region by selective laser sintering. Laser power: 150-250W, scanning speed: 1000-2000mm / s, layer thickness: 50μm. By adjusting the laser energy density, the porosity gradually increases from 30% at the condensation end to 70% at the evaporation end.

[0047] In this document, when it is mentioned that a first component is located on a second component, this can mean that the first component can be directly formed on the second component, or that a third component can be inserted between the first and second components. Furthermore, in the accompanying drawings, the thickness of the components may be exaggerated or reduced for the purpose of effectively describing the technical content.

[0048] In this document, when an element or layer is referred to as “located,” “joined to,” “connected to,” “attached to,” or “coupled to” another element or layer, it may be directly located, joined, connected, attached to, or coupled to the other element or layer, or there may be intermediate elements or layers present. Conversely, when an element is referred to as “directly on another element or layer,” “directly joined to,” “directly connected to,” “directly attached to,” or “directly coupled to” another element or layer, there may be no intermediate elements or layers present. Other terms used to describe relationships between elements should be interpreted in a similar manner (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and / or” includes any and all combinations of one or more of the related listed items.

[0049] In this document, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as “at least one of…” modify the entire list of elements when following a list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0050] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0051] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0052] In the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0053] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence unless expressly indicated herein. Therefore, without departing from the teachings of the exemplary embodiments, the first element, component, region, layer, or segment discussed above may be referred to as a second element, component, region, layer, or segment.

[0054] Spatially relative terms, such as “inside,” “outside,” “below,” “below,” “down,” “above,” “up,” etc., may be used herein to describe the relationship between one element or feature illustrated in the figures and another element or feature. In addition to the orientations depicted in the figures, spatially relative terms may be intended to cover different orientations of the device in use or operation. For example, if the device in the figure is flipped, an element described as “below” or “below” other elements or features would be oriented as “above” other elements or features. Thus, the example term “below” can cover both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0055] In the above discussion, unless otherwise stated, when used to describe numerical values, the terms “about,” “approximately,” “basically,” etc., indicate a change of + / - 10% in that value.

[0056] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A heat spreader, comprising an upper cover plate (1) and a lower cover plate (2), wherein a vacuum cavity (3) is formed between the two, the vacuum cavity (3) being filled with a working fluid (4), characterized in that, The vacuum cavity (3) is also provided with a capillary structure (10); The capillary structure (10) comprises, from bottom to top: A diamond micropillar array layer (5) is located on the inner wall of the lower cover plate (2); A gradient transition interface layer (6) is located on the surface of the diamond micropillar array layer (5), and is sp 3 A multilayer composite structure with a continuous transition from hybrid carbon to sp2 hybrid carbon; The oriented carbon nanotube array layer (7) is located on the gradient transition interface layer (6).

2. The temperature distribution plate according to claim 1, characterized in that, The gradient transition interface layer (6) includes: The first transitional sublayer (61) is sp 3 A hybrid carbon layer is located on the diamond micropillar array layer; The second transition sublayer (62) is a mixed sp³ and sp² carbon layer located on the first transition sublayer (61); The third transition sublayer (63) is an sp² hybrid carbon layer located between the second transition sublayer (62) and the oriented carbon nanotube array layer (7).

3. The temperature distribution plate according to claim 1, characterized in that, The cross-section of the diamond micropillar array layer (5) is either circular or polygonal; The diamond micropillar array layer (5) has a micropillar height of 200-800μm, a diameter of 50-200μm, and a spacing of 100-500μm; In the diamond micropillar array layer (5), the top and sidewall (100) crystal planes and / or (111) crystal planes of the micropillars account for ≥80%.

4. The temperature distribution plate according to claim 2, characterized in that, The oriented carbon nanotube array layer (7) has carbon nanotubes with a diameter of 10-30 nm, a length of 50-200 μm, and an orientation degree of ≥98%. In the oriented carbon nanotube array layer (7), the walls of the carbon nanotubes form continuous covalent bonds with the third transition sublayer (63).

5. The application of a heat spreader as described in any one of claims 1-4 in electronic devices or electrical equipment.

6. A method for preparing a heat spreader, characterized in that, Includes the following steps: Step 1: Prepare a diamond / carbon nanotube heteroepitaxial structure on the lower cover plate; Step 2: Prepare the upper cover plate, perform surface treatment, and prepare the capillary wick for the condensation zone; Step 3: Assemble the heat spreader. Align and assemble the lower and upper cover plates of the prepared diamond / carbon nanotube heteroepitaxial structure, inject the working fluid, and seal the opening. The preparation of the diamond / carbon nanotube heteroepitaxial structure includes the following steps: S1, Crystal plane-controlled growth of diamond micropillar array; S2, atomic-level construction of gradient transition interface layer; S3, epitaxial growth of directional carbon nanotube arrays.

7. The method for preparing a heat spreader according to claim 6, characterized in that, S1, Crystal plane controlled growth of diamond micropillar arrays, including the following steps: S11, Atomic-level planarization of copper substrate; that is, oxygen-free copper sheet with preferred orientation of (100) crystal plane is selected as the lower cover plate, and the copper substrate is placed in hydrogen plasma and treated at high temperature so that the surface atoms are reconstructed into a regular step flow morphology. After treatment, the surface structure is cooled in vacuum to maintain stability. S12, bias-enhanced nucleation and crystal orientation locking; that is, the treated copper substrate is placed in the MPCVD reaction chamber, vacuumed, hydrogen is introduced, heated, a negative bias is applied, and methane is introduced, so that the diamond crystal nuclei preferentially align with the (100) crystal plane, and the nucleation density is ≥5×10 10 / cm 2 ; S13, Hard mask preparation and selective growth: that is, SiO2 hard mask layer is deposited on the surface of the nucleated substrate by plasma-enhanced chemical vapor deposition, photoresist is spin-coated, micropillar array pattern is formed by ultraviolet lithography, the area to be etched is exposed after development, the exposed SiO2 is removed by reactive ion etching to form hard mask opening, the photoresist is removed, and the substrate with SiO2 hard mask is obtained. S14, selective growth of diamond micropillars; that is, a substrate with a SiO2 hard mask is placed in an MPCVD reaction chamber, diamond is grown in the mask opening area to form a micropillar array, and after growth, the SiO2 mask is removed with hydrofluoric acid to obtain a diamond micropillar array. S15, surface hydrogenation and activation: that is, placing a diamond micropillar array in a hydrogen plasma and treating it at high temperature to terminate the surface with CH bonds, followed by rapid heating in an argon atmosphere and then immediate cooling to generate carbon dangling bonds of controllable density on the surface.

8. The method for preparing a heat spreader according to claim 6, characterized in that, S2, the atomic-level construction of the gradient transition interface layer includes the following steps: S21, Plasma-assisted gradient carbon deposition, involves placing a hydrogenated diamond micropillar array in a PECVD reaction chamber, introducing a methane / hydrogen mixed gas to increase the methane concentration, while simultaneously increasing the radio frequency power and substrate temperature. During this process, carbon atoms are deposited on the diamond surface, forming a gradient layer that continuously transitions from sp³-dominated to sp²-dominated. S22, a substrate with a gradient layer is placed in an ultra-high vacuum environment and annealed, causing the sp² carbon regions on the surface of the gradient layer to rearrange to form nanoscale graphene fragments.

9. The method for preparing a heat spreader according to claim 6, characterized in that, S3, Epitaxial growth of oriented carbon nanotube arrays, including the following steps: S31, Catalyst Atomic Layer Deposition (ALD), employs ALD technology to deposit an iron catalyst on the surface of a gradient layer. The precursors are ferrocene and oxygen plasma. By controlling the number of cycles, a continuous iron film is obtained. After deposition, annealing is performed in a hydrogen atmosphere, causing the iron film to spontaneously aggregate into nanoparticles with a particle size of 5-15 nm and a density of 10⁻⁶. 11 -10 12 / cm 2 ; S32, electric field-magnetic field synergistic orientation growth, the substrate with catalyst nanoparticles is placed in the PECVD reaction chamber, vacuum is drawn, hydrogen gas is introduced, the temperature is raised, and after the temperature stabilizes, carbon source gas is introduced, and a vertical electric field and a vertical magnetic field are applied. The dual fields synergistically induce the vertical orientation of carbon nanotubes. During the growth process, by adjusting the carbon source concentration and bias voltage, the carbon nanotube wall and the graphene fragments of the gradient layer grow continuously. S33, in-situ passivation treatment, after growth, the carbon source and bias voltage are turned off, and annealing is carried out in a hydrogen atmosphere to eliminate structural defects.

10. The method for preparing a heat spreader according to claim 6, characterized in that, Step two, preparation of the upper cover plate, includes the following steps: The surface treatment of the top cover plate involves preparing radial flow channels and support column arrays on the inner wall of the copper top cover plate by photolithography-electroplating or precision machining. A femtosecond laser is used to open spiral microchannels inside the support columns as auxiliary liquid return channels. The condensation area is hydrophobically treated, and a fluorinated carbon film is deposited by magnetron sputtering. The capillary core in the condensation region is prepared by mixing atomized copper powder with graphene nanosheets and selectively laser sintering to form a gradient porosity sintered core in the condensation region. By adjusting the laser energy density, the porosity gradually increases from the condensation end to the evaporation end.

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