Graphene phase change material polymerization packaged integrated heat dissipation device and preparation method thereof

Abstract

The invention provides a graphene phase change material polymerization packaged integrated heat dissipation device and a preparation method thereof, and the preparation method comprises the following steps: mixing a graphene material with a phase change material to prepare a graphene phase change matrix; processing in the graphene phase change matrix to form a micro-channel structure; the method comprises the following steps: depositing a polyamide acid precursor on the surface of a graphene phase change substrate to obtain a polyamide acid precursor film, then carrying out thermal imidization treatment to obtain a continuous polyimide polymer packaging film, then injecting a cooling liquid into a micro-channel of the heat dissipation device, and carrying out packaging to obtain the integrated heat dissipation device. The graphene phase change matrix improves the heat conductivity coefficient and realizes light weight, so that the requirements of high efficiency and low-weight heat dissipation are met; the micro-channel structure and the phase change material function cooperate to realize integration of energy storage, heat conduction and heat dissipation, and the heat dissipation power is improved; an ultrathin polyimide packaging film is formed through polymerization packaging, and zero-wrapping-edge insulation packaging of a complex structure is achieved.

Description

Technical Field

[0001] This disclosure relates to the technical field of heat dissipation management, and in particular to a method for preparing an integrated heat dissipation device using graphene phase change material polymer encapsulation. Background Technology

[0002] As 3C electronic devices develop towards higher integration and higher computing speeds, the heat generation of core components such as chips has increased dramatically. Overheating has become a key issue restricting device performance, lifespan, and user experience. Currently, the mainstream heat dissipation solutions mainly use copper heat pipes and vapor chambers, which work by utilizing the thermal conductivity of copper and the phase change of the internal working fluid to achieve heat transfer.

[0003] However, copper has a specific heat capacity of only 0.39 J / (g・℃), resulting in poor energy storage capacity per unit volume. When faced with instantaneous high-power heating, it cannot quickly absorb heat, which can easily lead to a sudden rise in local temperature. This makes copper heat pipes and heat sinks weak in energy storage capacity and heavy in weight, failing to meet the high-efficiency and low-weight heat dissipation requirements of electronic devices. On the other hand, traditional phase change materials have excellent energy storage capacity, but they are prone to leakage during the phase change process and have low thermal conductivity, making them difficult to apply directly to heat dissipation structures.

[0004] For example, prior art document CN202110928563.7 discloses a VC heat sink with a built-in copper / diamond sintered wick and its preparation method. The VC heat sink includes an upper shell plate and a lower shell plate, with a cavity between the upper and lower shell plates. A capillary wick B is installed in the upper shell plate, and a capillary wick A is installed in the lower shell plate. The capillary wick A is a copper / diamond sintered body with a three-dimensional porous structure. This solution cannot quickly absorb heat when facing instantaneous high-power heating, and it is also relatively heavy, failing to meet the requirements of electronic devices for high-efficiency and low-weight heat dissipation. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a lightweight heat dissipation structure and an integrated heat dissipation device and preparation method that integrates energy storage, heat conduction and heat dissipation, and achieves zero-edge insulating encapsulation of graphene phase change material polymerization encapsulation.

[0006] The purpose of this disclosure is achieved through the following technical solution: A method for preparing an integrated heat dissipation device encapsulated with graphene phase change material includes the following steps: Graphene materials are mixed with phase change materials to prepare graphene phase change matrix; Microchannel structures are formed within the graphene phase change matrix; A polyamic acid precursor is deposited on the surface of the graphene phase change matrix to obtain a polyamic acid precursor film. The polyamic acid precursor film is then subjected to thermal imidization treatment to obtain a continuous polyimide polymer encapsulation film to obtain a heat dissipation device. Coolant is injected into the microchannels of the heat dissipation device and then encapsulated to obtain an integrated heat dissipation device.

[0007] In one embodiment, graphene material is mixed with a phase change material to prepare a graphene phase change matrix, including the following steps: Graphene powder is mixed with phase change material particles and stirred and kept at 60℃-90℃ for 30min-60min to obtain graphene phase change powder. Graphene phase change powder is placed in a mold and subjected to low-temperature hot pressing. The pressure of the low-temperature hot pressing is 5MPa-20MPa, and the temperature of the low-temperature hot pressing is 25℃-40℃, in order to obtain a graphene phase change matrix.

[0008] In one embodiment, the mass ratio of the graphene powder to the phase change material particles is 5-15:85-95.

[0009] In one embodiment, the density of the graphene phase change matrix is ​​1.2 g / cm³. 3 -1.8g / cm 3 .

[0010] In one embodiment, the phase change material is at least one of paraffin-based, fatty acid-based, or composite phase change materials; and / or, the phase change temperature of the phase change material is 40°C-80°C.

[0011] In one embodiment, a polyamic acid precursor is deposited on the surface of the graphene phase change substrate to obtain a polyamic acid precursor film. The polyamic acid precursor film is then subjected to thermal imidization treatment to obtain a continuous polyimide polymer encapsulation film, thereby obtaining a heat dissipation device. This includes the following steps: The graphene phase change matrix is ​​placed in the deposition area and heated, and the heating temperature of the graphene phase change matrix is ​​35℃-45℃. The dianhydride monomer and the diamine monomer are heated and evaporated, wherein the heating temperature of the dianhydride monomer is 140℃-180℃ and the evaporation temperature of the diamine monomer is 80℃-150℃. Under the influence of nitrogen carrier gas, the dianhydride monomer vapor and the diamine monomer vapor are introduced into the deposition area where the graphene phase change matrix is ​​placed, so that the dianhydride monomer vapor and the diamine monomer vapor undergo gas phase adsorption and polymerization on the surface of the graphene phase change matrix for deposition to form a polyamic acid precursor film. The polyamic acid precursor film is heated to undergo thermal imidization treatment, which causes the polyamic acid precursor film to undergo a thermal imidization reaction, thereby transforming the polyamic acid precursor film into a polyimide polymer encapsulation film to obtain an integrated heat dissipation device.

[0012] In one embodiment, the polyamic acid precursor film has a thickness of 0.05 μm to 100 μm.

[0013] In one embodiment, the polyamic acid precursor film is subjected to thermal imidization treatment by heating, which includes the following steps: The deposition area was heated from 30℃-35℃ to 100℃ in the first stage, and the holding time was 20min-40min. The deposition area was heated from 100℃ to 150℃-180℃ in the second stage, and the temperature was maintained for 1-2 hours. The temperature in the deposition area during the third stage is 150℃-300℃, and the holding time is 2h-3h.

[0014] In one embodiment, a microchannel structure is formed within a graphene phase change matrix by means of laser etching, mechanical milling, plasma etching, or molding processes.

[0015] An integrated heat dissipation device is obtained by the preparation method of the integrated heat dissipation device by polymer encapsulation of graphene phase change material as described in any of the above embodiments.

[0016] Compared with the prior art, this disclosure has at least the following advantages: The above-mentioned method for preparing an integrated heat dissipation device by polymerizing and encapsulating graphene phase change materials involves combining graphene materials with phase change materials to construct a highly efficient three-dimensional continuous thermal conductive network in the phase change materials, which significantly improves the overall thermal conductivity of the matrix. At the same time, the graphene phase change matrix has low density, which realizes the lightweighting of the heat dissipation structure and meets the requirements of electronic devices for high-efficiency and low-weight heat dissipation. The synergistic effect of microchannel structure and phase change material functions forms a combination of deformation buffer and liquid cooling cycle heat dissipation, thereby efficiently absorbing high-power heat generation and continuously discharging heat, realizing the integration of energy storage, heat conduction and heat dissipation, and significantly improving heat dissipation power; A graphene phase change matrix is ​​formed by combining graphene material with phase change material, and an ultra-thin polyimide encapsulation film is polymerized and encapsulated on the surface of the graphene phase change matrix. This provides a robust, dense, insulating and firmly bonded encapsulation shell for the entire heat dissipation device, achieving zero-edge insulation encapsulation of complex structures, avoiding the problem of phase change material leakage, and ensuring the sealing reliability and safety of the integrated heat dissipation device in long-term use. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the steps of a method for preparing an integrated heat dissipation device for polymer encapsulation of graphene phase change material, as an example. Figure 2 This is a schematic diagram of the structure of the polyimide polymer encapsulation film for an integrated heat dissipation device. Detailed Implementation

[0019] To facilitate understanding of this disclosure, a more complete description will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, this disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0020] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] To better understand the technical solutions and beneficial effects of this disclosure, the following detailed description is provided in conjunction with specific embodiments: Please see Figure 1 The present invention provides a method for preparing an integrated heat dissipation device for polymer-encapsulated graphene phase change material, comprising the following steps: S101 involves mixing graphene with a phase change material to prepare a graphene phase change matrix. Understandably, the high specific surface area of ​​graphene facilitates adsorption and van der Waals forces, allowing the molten phase change material to be uniformly loaded onto the graphene material and its pores. Graphene, with its extremely high intrinsic thermal conductivity and large specific surface area, forms a highly efficient three-dimensional thermally conductive network within the phase change material. This graphene network rapidly diffuses heat laterally throughout the entire graphene phase change matrix. The mixture of graphene and the phase change material forms a leak-proof composite powder.

[0023] S103, a microfluidic structure is formed within the graphene phase change matrix. It is understood that when the coolant flows within the microfluidic channels, efficient heat exchange occurs between the channel walls and the coolant. Through the synergistic effect of the microfluidic structure and the heat storage function of the phase change material, under low or sudden heat loads, the phase change material primarily absorbs heat and buffers the load. When the heat load is sustained or excessively high, causing the phase change material temperature to rise to near its phase change point or partially melt and saturate, the microfluidic system activates. The stored heat and continuously input heat are carried away through the circulation of the coolant, thereby controlling the system temperature within a safe range.

[0024] S105, a polyamic acid precursor is deposited on the surface of the graphene phase change substrate to obtain a polyamic acid precursor film. The polyamic acid precursor film is then subjected to thermal imidization treatment to obtain a continuous polyimide polymer encapsulation film, thereby obtaining a heat dissipation device. It can be understood that the polyamic acid precursor undergoes a gas-phase polymerization reaction on the graphene phase change substrate with a complex three-dimensional structure to generate a uniformly covered polyamic acid precursor film. The polyamic acid precursor film is then heated, causing the molecular chains of the polyamic acid precursor film to undergo a ring-closure dehydration reaction and imidization, transforming the polyamic acid precursor film into a polyimide (PI) film with a rigid aromatic heterocyclic structure, thereby forming a robust, dense, insulating encapsulation shell that is firmly bonded to the substrate.

[0025] S107, coolant is injected into the microchannels of the heat dissipation device and encapsulated to obtain an integrated heat dissipation device. It is understood that graphene material improves the overall thermal conductivity of the substrate, allowing heat to diffuse from the heat source to the entire substrate and phase change material. By constructing microchannels and injecting a coolant with good fluidity and insulation into the encapsulated microchannels, a complete thermal management system is formed within the entire heat dissipation device. Heat is absorbed by the graphene phase change substrate and conducted to the microchannel walls, where the flowing coolant rapidly carries the heat away through convection.

[0026] The aforementioned method for preparing an integrated heat dissipation device using graphene phase change material polymerization and encapsulation involves combining graphene with phase change material to construct a highly efficient three-dimensional continuous thermally conductive network within the phase change material. This significantly improves the overall thermal conductivity of the substrate. Simultaneously, the low density of the graphene phase change substrate enables lightweight heat dissipation, meeting the demands of electronic devices for high-efficiency, low-weight heat dissipation. The synergistic function of the microchannel structure and phase change material forms a combination of deformation buffering and liquid cooling circulation, efficiently absorbing high-power heat and continuously dissipating heat, achieving integrated energy storage, heat conduction, and heat dissipation, and significantly improving heat dissipation power. Furthermore, by combining graphene with phase change material to form a graphene phase change substrate, and polymerizing and encapsulating an ultra-thin polyimide encapsulation film on the surface of the graphene phase change substrate, a robust, dense, insulating, and firmly bonded encapsulation shell is provided for the entire heat dissipation device. This achieves zero-edge insulation encapsulation of complex structures, avoiding leakage of the phase change material and ensuring the sealing reliability and safety of the integrated heat dissipation device during long-term use.

[0027] In one embodiment, graphene material is mixed with a phase change material to prepare a graphene phase change matrix, including the following steps: Graphene powder is mixed with phase change material particles and stirred and kept at 60℃-90℃ for 30min-60min to obtain graphene phase change powder. Graphene phase change powder is placed in a mold and subjected to low-temperature hot pressing. The pressure of the low-temperature hot pressing is 5MPa-20MPa, and the temperature of the low-temperature hot pressing is 25℃-40℃, in order to obtain a graphene phase change matrix.

[0028] In this embodiment, after the graphene powder and solid phase change material particles are initially mixed, constant-temperature stirring is performed at a temperature higher than the melting point of the phase change material. During heating, the phase change material melts into a liquid phase. Under continuous mechanical stirring, the phase change material melt fully wets and encapsulates the graphene sheets. The shear force provided by stirring effectively breaks up the soft agglomeration of graphene. Utilizing the adsorption effect and van der Waals forces of graphene's high specific surface area, the molten phase change material is uniformly loaded into the graphene sheets and pores, thereby obtaining a composite powder with uniform composition. Low-temperature hot pressing is then performed at a temperature of 25℃-40℃, which is lower than the melting point of the phase change material. This keeps the phase change material in a solid state, preventing it from being lost after melting. Hot pressing increases the density of the graphene phase change matrix, reduces the generation of internal pores, and allows the graphene sheets to form a continuous thermally conductive network. It also improves the mechanical strength of the graphene phase change matrix, providing a supporting framework for subsequent microfluidic processing.

[0029] In one embodiment, the mass ratio of graphene powder to phase change material particles is 85-95:5-15. In this embodiment, graphene forms the main matrix framework in the graphene phase change matrix, creating a three-dimensional support network with high mechanical and structural strength. The phase change material is uniformly filled into the network pores. While ensuring excellent structural integrity and thermal conductivity of the matrix, the amount of phase change material added is controlled to achieve effective phase change heat storage and thermal buffering functions. This achieves an optimal balance between high structural strength, high thermal conductivity, and sufficient latent heat of phase change, thereby optimizing the overall thermal management performance of the heat dissipation device.

[0030] In one embodiment, the density of the graphene phase change matrix is ​​1.2 g / cm³. 3 -1.8g / cm 3 In this embodiment, the density of the graphene phase change matrix is ​​approximately 1 / 4 to 1 / 6 of the density of copper, and is controlled to be 1.2 g / cm³. 3 -1.8g / cm 3 The graphene three-dimensional framework is fully compacted to form a continuous and dense thermally conductive network, while avoiding the process compression that would damage its multiple pore structures. This allows the graphene phase change matrix to achieve lightweighting while maintaining good mechanical support, efficient thermal diffusion capabilities, and reliable phase change thermal buffering performance, thus meeting the needs of electronic devices for efficient heat dissipation and lightweighting.

[0031] In one embodiment, the phase change material is at least one of paraffin-based, fatty acid-based, or composite phase change materials; and / or, the phase change temperature of the phase change material is 40℃-80℃. In this embodiment, the paraffin-based, fatty acid-based, or composite phase change materials possess high latent heat of phase change, good chemical stability, and are non-corrosive, and exhibit good wettability and compatibility with the graphene framework, ensuring reliability and long-term stability during phase change cycling; the phase change temperature of 40℃-80℃ ensures that the heat dissipation device initiates phase change heat absorption during normal equipment operation, effectively buffering temperature fluctuations, avoiding unnecessary frequent phase changes due to excessively low phase change temperatures, and preventing excessively high phase change temperatures from affecting timely protection of the chip, thereby achieving synergy and efficient thermal management with the heat source and microfluidic liquid cooling system.

[0032] Specifically, in one embodiment, the phase change material is at least one of n-octadecane, stearic acid, or paraffin wax. The phase change temperature of n-octadecane is 58°C-60°C, that of stearic acid is 69°C-71°C, and that of paraffin wax is 40°C-50°C. In this embodiment, n-octadecane, stearic acid, or paraffin wax all possess high latent heat of phase change, stable chemical properties, and good wettability with graphene. Paraffin wax is suitable for temperature-sensitive devices, n-octadecane can effectively suppress heat source fluctuations, and stearic acid is suitable for scenarios with higher heat resistance or those subject to instantaneous high thermal shock. By selecting the appropriate materials, the phase change buffering function of the heat dissipation device is precisely matched with the thermal characteristics of different electronic components and the microfluidic liquid cooling system, thereby achieving an optimized thermal management strategy and reliability assurance.

[0033] Further, in one embodiment, after stirring and holding at 60℃-90℃ for 30min-60min to obtain graphene phase change powder, the graphene phase change powder is placed in a mold and hot-pressed under a hot-pressing pressure of 5MPa-20MPa and a hot-pressing temperature of 25℃-40℃ to obtain the graphene phase change matrix, the following steps are also included: The graphene phase change powder was placed in an ozone reaction tower and ozone gas was introduced. At a reaction temperature of 40℃-50℃, the oxidation reaction was maintained for 4h-6h to obtain a surface-modified graphene mixture; The mixture was washed with anhydrous ethanol to remove reaction byproducts, and then dried to obtain modified graphene phase change powder.

[0034] In this embodiment, after ozone oxidation treatment, oxygen-containing functional groups such as hydroxyl and carboxyl groups are introduced in situ onto the surface of the graphene sheets. The introduced functional groups significantly increase the surface energy of graphene, enhance its polar interaction and physical adsorption capacity with phase change material molecules, so that during hot pressing, the molten phase change material can more thoroughly wet and encapsulate each graphene sheet, and after cooling and solidification, a robust interface combining mechanical interlocking and chemical anchoring is formed, preventing the phase change material from separating from the graphene skeleton during long-term phase change cycles, thus ensuring the structural integrity and functional durability of the composite material.

[0035] Understandably, during the subsequent low-temperature hot pressing process, the surface functional groups introduced by the graphene sheets increase the bonding points between the graphene sheets, thereby achieving a tighter and stronger connection between the graphene sheets. This promotes the directional arrangement and interconnection of the graphene sheets in the matrix, reduces the contact thermal resistance between the graphene sheets, and thus constructs a three-dimensional thermally conductive network with better continuity and smoother heat conduction paths, thereby improving the overall thermal conductivity of the graphene phase change matrix.

[0036] Understandably, the graphene phase change matrix treated with ozone oxidation forms a stronger interfacial bond with the graphene sheets through the introduction of surface functional groups, which gives the graphene phase change matrix higher mechanical strength, hardness and deformation resistance, reduces the risk of breakage or cracking during processing, and ensures the molding accuracy and reliability of complex heat dissipation structures.

[0037] In one embodiment, a polyamic acid precursor is first deposited on the surface of a graphene phase change substrate by vapor deposition polymerization to obtain a polyamic acid precursor film. The polyamic acid precursor film is then subjected to thermal imidization treatment to obtain a continuous polyimide polymer encapsulation film, thereby obtaining an integrated heat dissipation device. This process includes the following steps: The graphene phase change matrix is ​​placed in the deposition area and heated, and the heating temperature of the graphene phase change matrix is ​​35℃-45℃. The dianhydride monomer and the diamine monomer are heated and evaporated, wherein the heating temperature of the dianhydride monomer is 140℃-180℃ and the evaporation temperature of the diamine monomer is 80℃-150℃. Under the influence of nitrogen carrier gas, the dianhydride monomer vapor and the diamine monomer vapor are introduced into the deposition area where the graphene phase change matrix is ​​placed, so that the dianhydride monomer vapor and the diamine monomer vapor undergo gas phase adsorption and polymerization on the surface of the graphene phase change matrix for deposition to form a polyamic acid precursor film. The polyamic acid precursor film is heated to undergo thermal imidization treatment, which causes the polyamic acid precursor film to undergo a thermal imidization reaction, thereby transforming the polyamic acid precursor film into a polyimide polymer encapsulation film to obtain an integrated heat dissipation device.

[0038] In this embodiment, heating the graphene phase change matrix enhances the molecular activity of its surface while preventing premature condensation of monomer vapors due to excessively low matrix temperatures, which could affect the uniformity of the initial adsorption layer. This ensures the uniformity and cleanliness of the initial deposition layer, allowing for uniform and controllable adsorption of dianhydride and diamine monomer vapors. Using nitrogen as a carrier gas enables the controlled and stable delivery of both monomer vapors to the graphene phase change matrix surface for uniform mixing and reaction. This results in the formation of a defect-free, fully coated layer on the graphene phase change matrix with its complex pores and morphology. The polyamic acid film is covered; through heat treatment, the polyamic acid molecular chain undergoes a closed-loop dehydration reaction, and its chemical structure is transformed from polyamic acid to polyimide with rigid aromatic heterocycles. This fundamentally improves the mechanical strength, thermal stability, chemical inertness, and electrical insulation of the polyamic acid film, ultimately forming a polyimide encapsulation shell that is firmly bonded to the substrate. The polyimide encapsulation shell not only firmly bonds to the graphene phase change substrate, but also provides robust, dense, and insulating fully sealed protection for the internal microchannels and phase change materials, ensuring the sealing reliability and operational safety of the heat dissipation device under long-term operating conditions.

[0039] Furthermore, in one embodiment, the heating temperature of the graphene phase change matrix is ​​10°C-15°C lower than the phase change temperature of the phase change material. In this embodiment, by strictly controlling the heating temperature of the graphene phase change matrix below the phase change temperature of the phase change material, it is ensured that the phase change material remains solid throughout the encapsulation process. This ensures the stability of the graphene phase change matrix and the reliability of the encapsulation process. While maintaining the stability of the phase change material, preheating the graphene phase change matrix to an appropriate temperature enhances the surface molecular activity of the graphene phase change matrix, which is beneficial for the rapid and uniform diffusion and adsorption of gaseous monomer vapor on the complex three-dimensional structure surface.

[0040] Furthermore, in one embodiment, before heating and evaporating the dianhydride monomer and the diamine monomer, the following steps are also included: The dianhydride monomer and diamine monomer were preheated and dried under vacuum at 100℃-140℃ for 10-15 hours. In this embodiment, vacuum drying at a temperature higher than the boiling point of water improved the purity of the dianhydride and diamine monomers, avoiding residual trace amounts of water or solvent that could trigger uncontrollable side reactions during subsequent high-temperature evaporation and gas-phase transport. This ensured that subsequent vapor deposition polymerization and thermal imidization reactions were carried out under highly pure and controlled conditions, thereby guaranteeing the quality and performance of the polyimide polymer encapsulation film.

[0041] Furthermore, in one embodiment, after reheating to perform thermal imidization treatment, causing the polyamic acid precursor film to undergo a thermal imidization reaction, thereby transforming the polyamic acid precursor film into a polyimide polymer encapsulation film to obtain an integrated heat dissipation device, the following steps are further included: The integrated heat dissipation device is post-processed by annealing it in a vacuum environment at 130℃-170℃ for 1-2 hours. The device is then slowly cooled to room temperature at a rate of 1℃ / min-3℃ / min to obtain the integrated heat dissipation device for post-processing.

[0042] In this embodiment, during the initial deposition of the imidization film, microscopic internal stress is generated inside the film due to temperature difference and volume change of chemical reaction. By performing vacuum annealing near the glass transition temperature of polyimide, the internal stress is eliminated, preventing microcracks or warping of the polyimide polymer encapsulation film due to stress relaxation during long-term use, and also improving the dimensional stability of precision structures such as microchannels. The gentle annealing process also helps the mutual diffusion and entanglement of molecular chains at the interface between the encapsulation film and the graphene phase change matrix, forming a stronger physical and chemical bond in the interface region. The extremely slow cooling rate to room temperature allows all parts of the integrated heat dissipation device to shrink synchronously and uniformly, minimizing the generation of new thermal stress during cooling due to the difference in thermal expansion coefficients between different materials.

[0043] Furthermore, when dianhydride monomer vapor and diamine monomer vapor undergo gas-phase adsorption and polymerization on the surface of the graphene phase change matrix to deposit a polyamic acid precursor film, if whitening occurs during the deposition process, the following steps are also included: Reduce the evaporation temperature of dianhydride monomer vapor and diamine monomer vapor by 5℃-10℃; The flow rate of dianhydride monomer vapor and diamine monomer vapor introduced into the graphene phase change matrix through pipeline is increased by 10%-20%. In this embodiment, if the film appears locally white or opaque during vapor deposition polymerization, it is due to excessively fast deposition rate or unbalanced reaction conditions, resulting in an excessively wide molecular weight distribution of the generated polyamic acid precursor and the presence of oligomer aggregation. The evaporation source temperature of dianhydride monomer and diamine monomer is reduced by 5°C-10°C, thereby rapidly reducing their saturated vapor pressure and reducing the partial pressure and absolute amount of monomer vapor input to the deposition area. The lower concentration is conducive to the full diffusion and orderly arrangement of monomer molecules on the matrix surface, promoting the formation of a more uniform polymer structure. The flow rate of nitrogen, the carrier gas for transporting dianhydride monomer and diamine monomer vapor, is increased, further diluting the concentration of monomer vapor per unit volume, making the reaction environment more mild. The enhanced airflow can improve the flow field distribution in the reaction chamber, reduce stagnation or concentration unevenness during vapor transport, and ensure that the monomer vapor can more uniformly cover the surface of the graphene phase change matrix with a complex three-dimensional structure.

[0044] Further, in one embodiment, the dianhydride monomer is pyromellitic dianhydride (PMDA), and the diamine monomer is 4,4'-diaminodiphenyl ether (ODA). In this embodiment, pyromellitic dianhydride (PMDA) and the diamine monomer 4,4'-diaminodiphenyl ether (ODA) can undergo a highly efficient in-situ polycondensation reaction under gas-phase conditions. The reaction rate is controllable, and it is easy to generate high-molecular-weight linear polyamic acid, thereby forming a continuous, dense, and defect-free polyamic acid precursor film on the complex surface of the graphene phase change matrix. The obtained polyamic acid precursor film has a high glass transition temperature, can withstand the high-temperature environment of subsequent processes and equipment operation for a long time, and has high strength and high modulus mechanical properties, thus effectively resisting the pressure caused by external stress and internal phase change material volume changes.

[0045] Specifically, pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) are respectively introduced into the deposition region of the graphene phase change matrix through pipelines. The evaporation temperature of PMDA is 150°C, and the evaporation temperature of ODA is 92°C. In this embodiment, the output rate and partial pressure of the two monomer vapors are finely adjusted by the temperature difference, so that PMDA and ODA can be controllably reached into the deposition region. The lower evaporation temperature reduces heating energy consumption and also reduces the long-term heat load on the evaporation source equipment and pipeline materials.

[0046] In one embodiment, the polyamic acid precursor film has a thickness of 0.05 μm to 100 μm. In this embodiment, by precisely controlling parameters such as reaction time, monomer vapor concentration, and deposition cycle number through a vapor deposition polymerization process, a wide range of highly controllable thicknesses of polyamic acid precursor films, from molecular-level precision of 0.05 μm to 100 μm, can be achieved.

[0047] Specifically, ultrathin polyamic acid precursors with a film thickness of 0.05μm-1μm are beneficial for achieving ultimate conformal encapsulation and minimum curing stress; polyamic acid precursor films with a film thickness of 1μm-3μm, formed by vapor deposition, possess intrinsic density and can completely block the penetration or leakage of coolant and phase change material, and their insulation strength meets the safety requirements of electronic equipment; polyamic acid precursor films with a film thickness of 3μm-20μm provide more options for the encapsulation of industrial-grade equipment with extreme mechanical or insulation requirements.

[0048] In one embodiment, the pressure in the deposition region is 10. -5 Pa to 10 -6 Pa. In this embodiment, a vacuum environment is formed in the deposition region, which allows the dianhydride monomer and diamine monomer to be directionally transported to the surface of the graphene phase change matrix. At the same time, the dianhydride monomer and diamine monomer sublimate rapidly in the vacuum environment. The partial pressure of oxygen and water vapor in the deposition region is reduced to an extremely low level, protecting the amine monomer from oxidative degradation in the gas phase and on the surface, maintaining its high reactivity. Water molecules are excluded, avoiding hydrolytic interference of water on the polyamic acid condensation reaction and damage to the formed film. Water molecules, a byproduct generated during the formation of polyamic acid, can be rapidly desorbed from the reaction interface and effectively extracted by the vacuum system in a high vacuum environment.

[0049] In one embodiment, the polyamic acid precursor film is subjected to thermal imidization treatment by heating, which includes the following steps: The deposition area was heated from 30℃-35℃ to 100℃ in the first stage, and the holding time was 20min-40min. The deposition area was heated from 100℃ to 150℃-180℃ in the second stage, and the temperature was maintained for 1-2 hours. The deposition area is heated to 150℃-300℃ in the third stage, with a holding time of 2-3 hours. In this embodiment, the heating rate is 1℃ / min-5℃ / min. In the first stage, free water is removed and gentle preheating is performed to avoid thermal stress caused by temperature differences in the film, thus allowing residual solvent and water molecules in the film to overflow smoothly. In the second stage, the amyl acid structure in the polyamic acid molecular chain begins to undergo a closed-loop dehydration reaction to form an imide ring. With sufficient holding time, most of the imidization is completed, thereby reconstructing the molecular chain to form a preliminary polyimide skeleton, significantly improving the mechanical properties and chemical stability of the film. In the third stage, the imidization reaction is completed and the film structure is finally solidified, further orienting and densifying the polyimide molecular chain, promoting the complete removal of residual small molecules and effectively releasing internal stress. This results in excellent heat resistance, higher mechanical strength, lower shrinkage, and a stronger interfacial bond between the polyimide encapsulation film and the graphene phase change matrix.

[0050] Furthermore, in one embodiment, the phase change material is paraffin-based, and the phase change temperature is 40℃-50℃. The second stage and the heating temperature are 100℃-150℃, and the third stage heating temperature is 150℃. In the third stage, plasma is introduced for assisted imidization treatment, and the treatment time is 30-60 minutes. In this embodiment, when the phase change material in the graphene phase change matrix is ​​paraffin, the paraffin phase change temperature is 40℃-50℃. If a high-temperature imidization temperature greater than 200℃ is used, it will cause severe melting, loss, or even thermal decomposition of the paraffin, thereby damaging the matrix structure and losing its heat storage function. The upper limit of the second-stage temperature is set at 150℃, and the third-stage temperature is strictly controlled at 150℃. The heat treatment temperature is limited to a safe window that can drive the imidization reaction while minimizing the irreversible damage to paraffin. Understandably, a significant reduction in the third-stage temperature to 150℃ may lead to insufficient driving force for the thermal imidization reaction, resulting in incomplete imidization of the film and substandard performance. By introducing plasma such as Ar, a large number of highly active molecules are generated. These highly active molecules efficiently break CN, CO, and other bonds in polyamic acid and promote the ring-closure dehydration reaction, thereby achieving efficient and complete cyclization of the polyimide molecular chain at a relatively low temperature of 150℃. The surface activation effect of the plasma can also further enhance the compactness of the film and its interfacial bonding with the substrate.

[0051] In one embodiment, the microchannel structure is fabricated within the graphene phase change matrix using laser etching, mechanical milling, plasma etching, or molding processes. In this embodiment, the microchannel fabrication and sealing of the copper heat pipe and vapor chamber present significant challenges, resulting in high yield control costs. Graphene phase change substrates can be processed through laser etching, mechanical milling, plasma etching, or molding. Laser etching uses a high-energy-density laser beam focused on the surface of the graphene phase change substrate to directly remove material through ablation or vaporization, thereby precisely processing microfluidic structures. Mechanical milling uses a high-speed rotating micro-milling cutter to perform contact cutting and subtractive processing of microfluidic structures. Plasma etching uses highly active ions or free radicals in plasma to physically sputter or chemically react with the substrate surface material, selectively removing areas not protected by a mask to form microfluidic structures. Before filling the graphene phase change powder into the mold for low-temperature hot pressing, a core mold with a negative flow channel structure is placed in the mold. After hot pressing, the core mold is removed to directly form microfluidic structures inside the substrate.

[0052] Further, in one embodiment, the coolant includes at least one of water, ethanol, and propylene glycol, and the injection volume of the coolant is 60%-80% of the cavity volume of the microchannel. In this embodiment, water has extremely high specific heat capacity and thermal conductivity, making it an ideal medium for efficient heat transfer and suitable for scenarios with extremely high heat dissipation requirements; ethanol has a low freezing point, good fluidity, and volatility, making it suitable for scenarios where localized high temperatures may occur or rapid start-up is required; propylene glycol has good chemical stability, a high boiling point, a low freezing point, and excellent insulation properties, providing reliable and safe cooling protection in a wide temperature range environment; the injection volume of the coolant leaves 20%-40% of the volume space, providing necessary buffer space for the localized boiling and vaporization expansion that may occur when the coolant is heated, ensuring the long-term sealing integrity of the structure.

[0053] Furthermore, in one embodiment, injecting coolant into the microchannels of the heat dissipation device includes the following steps: The integrated heat dissipation device has a liquid injection hole, and the liquid is injected into the cavity of the microchannel by vacuum filling or pressure injection. The cavity of the microchannel is subjected to vacuum treatment; The injection hole is sealed by heat fusion sealing or ultrasonic sealing.

[0054] In this embodiment, the microchannel cavity is evacuated before injection to completely remove air, moisture, and other gases from the cavity, avoiding localized overheating and decreased heat transfer efficiency caused by the presence of gases. Negative pressure is used to naturally draw the coolant into the cavity, ensuring the coolant evenly fills the complex flow channels. Heat fusion sealing uses localized heating to melt and re-fuse the polyimide encapsulation material in the injection hole area, forming a sealed area that is uniform with the polyimide polymer encapsulation film material and has no interface after cooling. Ultrasonic sealing utilizes high-frequency vibration energy to cause the material molecules to solidify. Frictional heat is generated and diffuses and combines with each other, and both methods achieve seamless sealing, ensuring long-term sealing strength. The coolant is in a saturated vapor state at 40℃-80℃. Specifically, when the coolant is water, the cavity of the microchannel is evacuated to a pressure of 5kPa-15kPa, and the boiling point of water is about 32℃-53℃. When the coolant is ethanol, the cavity of the microchannel is evacuated to a pressure of 20kPa-30kPa. After evacuation, the pressure is maintained for 10min-20min to remove residual air inside the cavity and avoid air affecting the phase change heat transfer efficiency of the working fluid.

[0055] This application also includes an integrated heat dissipation device, obtained by the preparation method of the integrated heat dissipation device of graphene phase change material polymerization and encapsulation described in any of the above embodiments. In this embodiment, the integrated heat dissipation device includes a graphene phase change matrix, a coolant, and a polyimide polymer encapsulation shell. The graphene phase change matrix is ​​formed by uniformly mixing graphene and phase change material. Microchannel structures for liquid cooling circulation are formed within the graphene phase change matrix. The coolant is stored in the microchannel structures. The polyimide polymer encapsulation shell completely seals and encapsulates the graphene phase change matrix and the microchannels. The integrated heat dissipation device combines efficient heat storage, rapid heat conduction, and active liquid cooling heat dissipation with lightweight, highly insulating, and reliably sealed structural characteristics.

[0056] Furthermore, in one embodiment, the microchannel structure is a serpentine, honeycomb, or parallel straight-channel structure. In this embodiment, the serpentine channel forms one or a few long paths through continuous U-shaped bends, making the microchannel structure suitable for scenarios where heat sources are relatively concentrated or where enhanced heat dissipation is required for specific high-temperature areas; the honeycomb structure consists of a large number of interconnected hexagonal, square, or other polygonal unit chambers forming a mesh-like pathway, resulting in uniform flow and a large specific surface area, making the microchannel structure suitable for scenarios where heat sources are widely and uniformly distributed or where extremely high heat dissipation power density is required; the parallel straight-channel structure consists of multiple parallel straight channels, with low flow resistance, short flow paths, and good consistency, making the microchannel structure suitable for scenarios where heat load distribution is relatively uniform and where there are strict limitations on system flow resistance.

[0057] Furthermore, in one embodiment, the width of the microchannel structure is 100μm-500μm, the depth of the microchannel structure is 200μm-800μm, and the wall thickness of the microchannel is 50μm-150μm. In this embodiment, the width and depth of the microchannel structure limit the cross-sectional area, affecting the corresponding flow state and heat transfer capacity of the coolant. This ensures that the flow channels of the microchannel structure match the scale of the graphene network, ensuring efficient lateral diffusion of heat through the graphene framework to the channel wall, while maintaining sufficient distribution density of the channel itself in the matrix. This achieves a fast, low thermal resistance heat transfer path from the heat source to the coolant. The 50μm-150μm wall thickness provides sufficient mechanical strength for the polyimide polymer encapsulation film, ensuring the compactness and insulation reliability of the polyimide polymer encapsulation film.

[0058] Furthermore, in one embodiment, the total cross-sectional area of ​​the microchannels accounts for 30%-50% of the substrate surface area. In this embodiment, a large portion of the graphene phase change substrate surface area is allocated to construct the direct heat exchange interface for the liquid cooling cycle. This ensures that under continuous or peak heat load conditions, the effective convective heat transfer area of ​​the graphene phase change substrate rapidly transfers heat to the coolant and carries it away, thereby ensuring high heat dissipation flux and continuous heat dissipation capacity of the integrated heat dissipation device. The cross-sectional area of ​​the graphene phase change substrate is greater than 50%, enabling the graphene phase change substrate to maintain its overall mechanical strength and preventing collapse or breakage during processing, packaging, or use.

[0059] Compared with the prior art, this disclosure has at least the following advantages: The aforementioned method for preparing an integrated heat dissipation device using graphene phase change material polymerization and encapsulation involves combining graphene with phase change material to construct a highly efficient three-dimensional continuous thermally conductive network within the phase change material. This significantly improves the overall thermal conductivity of the substrate. Simultaneously, the low density of the graphene phase change substrate enables lightweight heat dissipation, meeting the demands of electronic devices for high-efficiency, low-weight heat dissipation. The synergistic function of the microchannel structure and phase change material forms a combination of deformation buffering and liquid cooling circulation, efficiently absorbing high-power heat and continuously dissipating heat, achieving integrated energy storage, heat conduction, and heat dissipation, and significantly improving heat dissipation power. Furthermore, by combining graphene with phase change material to form a graphene phase change substrate, and polymerizing and encapsulating an ultra-thin polyimide encapsulation film on the surface of the graphene phase change substrate, a robust, dense, insulating, and firmly bonded encapsulation shell is provided for the entire heat dissipation device. This achieves zero-edge insulation encapsulation of complex structures, avoiding leakage of the phase change material and ensuring the sealing reliability and safety of the integrated heat dissipation device during long-term use.

[0060] The following are some specific examples. When %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively list all possible scenarios, and unless otherwise specified, the materials used in the following examples are commercially available.

[0061] Example 1 Select flakes with a diameter of 5-20 μm and a specific surface area ≥1500 m². 2 High-purity graphene with a thermal conductivity ≥3000 W / (m・℃) and n-octadecane as the phase change material, with a phase change point of 59℃, was mixed and stirred at 70℃ for 40 min to obtain graphene phase change powder. The graphene phase change powder was then hot-pressed at 10 MPa and 30℃ to obtain a graphene phase change matrix. A micro-serpentine flow channel structure was formed within the graphene phase change matrix. The graphene phase change matrix was placed in an ozone reaction tower, and ozone at a concentration of 80 mg / L was introduced. The reaction temperature was controlled at 40℃-50℃, and the reaction was carried out for 4 h. After cooling under a nitrogen atmosphere, the oxidation byproducts were removed by washing with anhydrous ethanol, and the matrix was vacuum dried at 50℃ for 2 h. The graphene phase change matrix was then placed in a reaction chamber for preheating at 35℃.

[0062] Pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) were vacuum dried at 120℃ for 12 h and then placed in two independent precision-controlled evaporators. The PMDA evaporator temperature was set at 150℃, and the ODA evaporator temperature was set at 92℃. The PMDA and ODA evaporators were started simultaneously at a heating rate of 5℃ / min. After the temperature stabilized, the valves between the evaporators and the reaction chamber were opened, and the PMDA and ODA vapors entered the reaction chamber under the carry-on N2 gas. The pressure in the reaction chamber was controlled at 10. -5 A polyamic acid precursor film was obtained by deposition at Pa for 8 hours. The polyamic acid precursor film on the graphene phase change substrate was then thermally imidized. In the first stage, the temperature was increased from 35°C to 100°C and held for 30 minutes at a rate of 1°C / min. In the second stage, the temperature was increased from 100°C to 180°C and held for 1 hour at a rate of 2°C / min. In the third stage, the temperature was increased to 250°C and held for 2 hours, with N2 supplied throughout. After encapsulating the graphene phase change substrate with the polyamic acid precursor film, a heat dissipation device was obtained. The thickness of the polyamic acid precursor film was 2 μm. The heat dissipation device was annealed at 150°C under vacuum for 2 hours and then slowly cooled to room temperature at a rate of 1°C / min. Coolant water was injected into the microchannels of the heat dissipation device and then encapsulated.

[0063] Example 2 Select flakes with a diameter of 8-25 μm and a specific surface area ≥1300 m². 2High-purity graphene with a thermal conductivity ≥2800 W / (m·℃) was used as the phase change material, with stearic acid as the phase change material and a phase change point of 69℃. Graphene and stearic acid were mixed and stirred at 80℃ for 45 min to obtain graphene phase change powder. The graphene phase change powder was then hot-pressed at 12 MPa and 32℃ to obtain a graphene phase change matrix. A micro-honeycomb flow channel structure was formed within the graphene phase change matrix using laser etching. The graphene phase change matrix was placed in an ozone reaction tower, and ozone at a concentration of 90 mg / L was introduced. The reaction temperature was controlled at 45℃ for 5 h. After cooling under a nitrogen atmosphere, oxidation byproducts were removed by washing with anhydrous ethanol, and the matrix was vacuum dried at 55℃ for 2.5 h. The graphene phase change matrix was then placed in a reaction chamber for preheating at 38℃.

[0064] Pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) were vacuum dried at 125℃ for 13 h and then placed in two independent precision-controlled evaporators. The PMDA evaporator temperature was set at 180℃, and the ODA evaporator temperature was set at 105℃. The PMDA and ODA evaporators were started simultaneously at a heating rate of 5℃ / min. After the temperature stabilized, the valves between the evaporators and the reaction chamber were opened, and the PMDA and ODA vapors entered the reaction chamber under the carry-on N2 gas. The pressure in the reaction chamber was controlled at 8 × 10⁻⁻⁻⁻⁶. 6 A polyamic acid precursor film was obtained by deposition at Pa for 9 h. The polyamic acid precursor film on the graphene phase change substrate surface was then thermally imidized. In the first stage, the temperature was increased from 38℃ to 100℃ and held for 30 min at a rate of 1℃ / min. In the second stage, the temperature was increased from 100℃ to 190℃ and held for 1.2 h at a rate of 2℃ / min. In the third stage, the temperature was increased to 300℃ and held for 2.2 h, with N2 supplied throughout. After encapsulating the graphene phase change substrate with the polyamic acid precursor film, a heat dissipation device was obtained. The thickness of the polyamic acid precursor film was 2 μm. The heat dissipation device was annealed at 155℃ under vacuum for 1.8 h and then slowly cooled to room temperature at a rate of 1.2℃ / min. A 25% propylene glycol aqueous solution was injected into the microchannels of the heat dissipation device for encapsulation.

[0065] Example 3 Select flakes with a diameter of 15-40 μm and a specific surface area ≥1000 m². 2High-purity graphene with a thermal conductivity ≥2000 W / (m·℃) was used, with paraffin wax having a phase change temperature of 48℃ as the phase change material. Graphene and paraffin wax were mixed and stirred at 60℃ for 35 min to obtain graphene phase change powder. The graphene phase change powder was then hot-pressed at 8 MPa and 28℃ to obtain a graphene phase change matrix. Micro-parallel straight-channel flow structures were formed within the graphene phase change matrix through precision milling. The graphene phase change matrix was placed in an ozone reaction tower, and ozone at a concentration of 70 mg / L was introduced, controlling the reaction temperature at 42℃ for 3.5 h. After cooling under a nitrogen atmosphere, oxidation byproducts were removed by washing with anhydrous ethanol, and the matrix was vacuum dried at 48℃ for 1.5 h. The graphene phase change matrix was then placed in a reaction chamber for preheating at 36℃.

[0066] Pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) were vacuum dried at 115℃ for 11 h and then placed in two independent precision-controlled evaporators. The PMDA evaporator temperature was 170℃, and the ODA evaporator temperature was 98℃. The PMDA and ODA evaporators were started simultaneously at a heating rate of 5℃ / min. After the temperature stabilized, the valves between the evaporators and the reaction chamber were opened, and the PMDA and ODA vapors entered the reaction chamber under the carry-on N2 gas. The pressure in the reaction chamber was controlled at 5 × 10⁻⁻⁻⁶. 6 A polyamic acid precursor film was obtained by deposition at Pa for 7 h. The polyamic acid precursor film on the graphene phase change substrate was then thermally imidized. In the first stage, the temperature was increased from 36℃ to 95℃ and held for 25 min at a rate of 1℃ / min. In the second stage, the temperature was increased from 100℃ to 150℃ and held for 50 min at a rate of 2℃ / min. In the third stage, the temperature was increased to 150℃ and held for 1.8 h while introducing Ar plasma gas. The radio frequency power was 50 W, and N2 was introduced throughout. The polyamic acid precursor film encapsulated the graphene phase change substrate to obtain a heat dissipation device. The thickness of the polyamic acid precursor film was 2 μm. The heat dissipation device was annealed at 145℃ under vacuum for 1.5 h and then slowly cooled to room temperature at a rate of 0.8℃ / min. Anhydrous ethanol was injected into the microchannels of the heat dissipation device for encapsulation.

[0067] Comparative Example 1 It uses a traditional sintered copper-water heat pipe with the same dimensions as the heat dissipation device in the embodiment.

[0068] Comparative Example 2 A vacuum chamber heat exchanger plate with a copper powder sintered capillary core and water as the working fluid is used. The plate is 3.5 mm thick and has the same dimensions as the heat dissipation device in the embodiment.

[0069] It should be noted that the dimensions of the heat dissipation device in the embodiment are 80mm x 50mm x 3.5mm.

[0070] Steady-state thermal resistance test was conducted, with the power increasing in steps from 10W to 80W, stabilizing for 10 minutes at each step. The temperature rise ΔT of the heat source center relative to the ambient temperature was recorded under steady-state conditions. Thermal resistance R = ΔT / P.

[0071] Peak heat dissipation power, continuously increasing the power until it reaches the preset safety limit at 105℃; Temperature uniformity, the average temperature difference between the center of the heat source and the edge of the device under a fixed power of 50W; Transient thermal shock was conducted by switching the heat source power between 0W and 60W every 10 minutes, recording the maximum fluctuation value of the temperature at the center of the heat source.

[0072] Weight measurement: The total weight of each sample is measured using an electronic balance.

[0073] Table 1 Performance Tests of Examples and Comparative Examples As shown in the table above, compared with Comparative Examples 1 and 2, Examples 1-3 have a weight reduction of about 70%, and the transient thermal buffer temperature fluctuation is reduced, with higher heat dissipation power. This indicates that the integrated heat dissipation device, which combines graphene material and phase change material and polymerizes and encapsulates an ultra-thin polyimide encapsulation film, has high efficiency, low weight, impact resistance and high reliability, thus meeting the lightweight and high-efficiency heat dissipation requirements of electronic devices. Compared with Example 1, Example 2 has better steady-state heat dissipation power, thermal resistance and temperature uniformity. This shows that the combination of phase change material with higher phase change temperature and greater latent heat and honeycomb flow channel with higher heat exchange efficiency can enhance the heat conduction network and synergistic heat dissipation effect, so as to be suitable for extreme heat dissipation scenarios with continuous high load and high temperature uniformity. Compared with Example 3, Example 3 has better performance in suppressing transient thermal shock, indicating that using paraffin with a lower phase change temperature can achieve a faster response and buffering of heat. The plasma-assisted imidization encapsulation process ensures the integrity of the encapsulation layer under low temperature conditions, making it suitable for scenarios with drastic power fluctuations and sensitivity to temperature changes.

[0074] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing an integrated heat dissipation device encapsulated with graphene phase change material, characterized in that, Includes the following steps: Graphene materials are mixed with phase change materials to prepare graphene phase change matrix; Microchannel structures are formed within the graphene phase change matrix; A polyamic acid precursor is deposited on the surface of the graphene phase change matrix to obtain a polyamic acid precursor film. The polyamic acid precursor film is then subjected to thermal imidization treatment to obtain a continuous polyimide polymer encapsulation film to obtain a heat dissipation device. Coolant is injected into the microchannels of the heat dissipation device and then encapsulated to obtain an integrated heat dissipation device.

2. The preparation method of the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 1, characterized in that, The graphene phase change matrix is ​​prepared by mixing graphene materials with phase change materials, including the following steps: Graphene powder is mixed with phase change material particles and stirred and kept at 60℃-90℃ for 30min-60min to obtain graphene phase change powder. Graphene phase change powder is placed in a mold and subjected to low-temperature hot pressing. The pressure of the low-temperature hot pressing is 5MPa-20MPa, and the temperature of the low-temperature hot pressing is 25℃-40℃, in order to obtain a graphene phase change matrix.

3. The preparation method of the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 2, characterized in that, The mass ratio of the graphene powder to the phase change material particles is 5-15:85-95.

4. The preparation method of the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 2, characterized in that, The density of the graphene phase change matrix is ​​1.2 g / cm³. 3 -1.8g / cm 3 .

5. The method for preparing the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 2, characterized in that, The phase change material is at least one of paraffin-based, fatty acid-based, or composite phase change materials; and / or, the phase change temperature of the phase change material is 40℃-80℃.

6. The method for preparing the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 1, characterized in that, A polyamic acid precursor is deposited on the surface of the graphene phase change substrate to obtain a polyamic acid precursor film. The polyamic acid precursor film is then subjected to thermal imidization treatment to obtain a continuous polyimide polymer encapsulation film, thereby obtaining a heat dissipation device. The process includes the following steps: The graphene phase change matrix is ​​placed in the deposition area and heated, and the heating temperature of the graphene phase change matrix is ​​35℃-45℃. The dianhydride monomer and the diamine monomer are heated and evaporated, wherein the heating temperature of the dianhydride monomer is 140℃-180℃ and the evaporation temperature of the diamine monomer is 80℃-150℃. Under the influence of nitrogen carrier gas, the dianhydride monomer vapor and the diamine monomer vapor are introduced into the deposition area where the graphene phase change matrix is ​​placed, so that the dianhydride monomer vapor and the diamine monomer vapor undergo gas phase adsorption and polymerization on the surface of the graphene phase change matrix for deposition to form a polyamic acid precursor film. The polyamic acid precursor film is heated to undergo thermal imidization treatment, which causes the polyamic acid precursor film to undergo a thermal imidization reaction, thereby transforming the polyamic acid precursor film into a polyimide polymer encapsulation film to obtain an integrated heat dissipation device.

7. The method for preparing the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 6, characterized in that, The thickness of the polyamic acid precursor film is 0.05 μm-100 μm.

8. The method for preparing the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 6, characterized in that, The polyamic acid precursor film is subjected to thermal imidization treatment by heating, including the following steps: The deposition area was heated from 30℃-35℃ to 100℃ in the first stage, and the holding time was 20min-40min. The deposition area was heated from 100℃ to 150℃-180℃ in the second stage, and the temperature was maintained for 1-2 hours. The temperature in the deposition area during the third stage is 150℃-300℃, and the holding time is 2h-3h.

9. The method for preparing the integrated heat dissipation device of graphene phase change material polymerization encapsulation according to claim 1, characterized in that, Microchannel structures are formed within a graphene phase change matrix and processed using laser etching, mechanical milling, plasma etching, or molding processes.

10. An integrated heat dissipation device, characterized in that, The integrated heat dissipation device is obtained by the method of preparing graphene phase change material polymer encapsulation according to any one of claims 1-9.

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