Composite heat plate integrated with phase change microcapsules and preparation method thereof

Abstract

This invention relates to the field of heat dissipation technology for electronic devices, specifically to a composite vapor chamber integrating phase change microcapsules and its preparation method. The vapor chamber includes a sealed cavity, a main capillary core, a working fluid, and a phase change microcapsule functional layer. The sealed cavity is formed by sealing the edges of an upper cover plate and a lower cover plate. The main capillary core is disposed on the inner surface of the lower cover plate. The working fluid fills the sealed cavity. The phase change microcapsule functional layer is disposed on the inner surface of the upper cover plate and corresponds to a preset hot spot area. The phase change microcapsule functional layer is composed of phase change microcapsules, a metal binder, and a high thermal conductivity additive. This invention, by integrating the phase change microcapsule functional layer inside the vapor chamber, achieves a synergistic effect of rapid heat diffusion and instantaneous heat buffering, effectively suppressing sudden temperature rises in chip hot spots and significantly improving the reliability and performance stability of high-power chips under transient loads.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation technology for electronic devices, and in particular to a composite heat spreader with integrated phase change microcapsules and its preparation method. Background Technology

[0002] As electronic devices develop towards higher integration and higher power density, especially core chips such as central processing units and graphics processing units, significant instantaneous peak power surges occur when running complex computing tasks, leading to millisecond- or even second-level high transient heat flux density shocks in local chip areas. As the current mainstream passive heat dissipation element, heat spreaders rely on the evaporation-condensation phase change cycle of the working fluid within the cavity to achieve rapid heat dissipation, performing well in steady-state thermal management. However, the thermal response of traditional heat spreaders depends on the directional flow of vapor and the liquid reflux of capillary structures. Their heat transfer rate has an inherent lag when facing instantaneous thermal shocks, making it difficult to quickly transfer the instantaneous heat accumulated in hot areas, resulting in a sharp increase in local chip temperature. When the temperature reaches the preset protection threshold, the system is forced to reduce its frequency, causing equipment performance degradation, lag, or even shutdown, severely restricting the release of the potential of high-performance chips.

[0003] To address the aforementioned issues, existing technologies attempt to introduce phase change materials (PCMs) into heat dissipation systems, utilizing their latent heat absorption characteristics during the solid-liquid phase change process to achieve thermal buffering. However, directly filling block or granular PCMs has significant drawbacks: First, PCMs themselves have extremely low thermal conductivity and slow thermal response, making it impossible to rapidly absorb heat during thermal shock. Second, the PCM and the vapor chamber of the vapor chamber are difficult to integrate effectively, resulting in significant thermal resistance between them. This prevents the heat absorbed by the PCM from being dissipated promptly through the efficient heat transfer mechanism of the vapor chamber, easily leading to heat accumulation. Furthermore, the volume changes and flowability issues of PCMs during the liquid-solid phase change process also pose challenges to encapsulation reliability and long-term stability. Therefore, this paper proposes a composite vapor chamber integrating phase change microcapsules and its preparation method to solve these problems. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a composite heat spreader with integrated phase change microcapsules and a method for preparing the same.

[0005] A composite heat spreader integrating phase change microcapsules includes a sealed cavity, a main capillary core, a working fluid, and a phase change microcapsule functional layer; the sealed cavity is formed by sealing the edges of an upper cover plate and a lower cover plate; the main capillary core is disposed on the inner surface of the lower cover plate; and the working fluid is filled in the sealed cavity.

[0006] Optionally, the phase change microcapsule functional layer is disposed on the inner surface of the upper cover plate and corresponds to a preset hot spot area; the phase change microcapsule functional layer is composed of phase change microcapsules, a metal binder, and a high thermal conductivity additive.

[0007] Optionally, the main capillary core has a porous sintered structure, and its material is copper, nickel or aluminum, with a porosity controlled at 50%-75%; the working fluid is deionized water, methanol or acetone, and its filling amount is 10%-20% of the internal volume of the sealed cavity.

[0008] A method for preparing a composite heat spreader with integrated phase change microcapsules includes the following steps: S1: Using chemical polymerization, a core-shell structured phase change microcapsule was prepared with a phase change material as the core and a polymer-metal composite material as the shell. S2: The phase change microcapsules obtained in S1 are mixed with the prepared metal binder and high thermal conductivity additive to form a composite powder; the composite powder is mixed with an organic carrier to form a slurry; and the slurry is coated on the preset hot spot area on the inner surface of the upper cover plate to form a functional layer preform. S3: The top cover plate with the functional layer preform is placed in a protective atmosphere for co-sintering treatment, so that the metal binder forms a porous metal skeleton, and the phase change microcapsules are fixed in the porous metal skeleton to obtain a top cover plate assembly with a porous network structure phase change microcapsule functional layer. S4: Spread metal powder on the inner surface of the lower cover plate and sinter it to form the main capillary core, thus obtaining the lower cover plate assembly. S5: Align and seal the upper cover plate assembly and the lower cover plate assembly to form a sealed cavity, and reserve a liquid injection port; after evacuating the sealed cavity, inject the working fluid through the liquid injection port; S6: Seal the injection port to obtain the finished composite heat spreader plate with integrated phase change microcapsules.

[0009] Optionally, S1 specifically includes: S11: Heat the paraffin-based phase change material to 10℃-30℃ above its melting point to completely melt it, add 0.5%-5% of thermally conductive reinforcing filler by mass of the phase change material, and ultrasonically disperse it at 50℃-70℃ for 20-60 minutes to obtain a uniformly mixed oil phase; the thermally conductive reinforcing filler is selected from carbon nanotubes, graphene or nanodiamond. S12: Mix polymer monomers and nano-metal particles at a mass ratio of 1:0.2 to 1:0.5, add deionized water, adjust the pH value to 3.0-5.0, and stir the reaction at 40℃-60℃ for 30-90 minutes to form an aqueous solution of polymer-metal composite shell material prepolymer. S13: Slowly add the oil phase obtained in S11 to the aqueous solution of the prepolymer obtained in S12. The volume ratio of the oil phase to the water phase is 1:2 to 1:5. Stir and emulsify at 1000-3000 rpm at 50℃-70℃ for 20-40 minutes to form an oil-in-water emulsion. S14: Add curing agent to emulsion, adjust the reaction system temperature to 60℃-85℃, and continue stirring for 2-6 hours to allow the prepolymer to crosslink and polymerize at the oil-water interface to form a phase change microcapsule suspension. S15: The phase change microcapsule suspension is centrifuged, washed 2-4 times alternately with deionized water and anhydrous ethanol, and then vacuum dried at 40℃-60℃ for 12-24 hours to obtain core-shell structured phase change microcapsule powder.

[0010] Optionally, S2 specifically includes: S21: Weigh 30-70 parts by weight of the phase change microcapsules prepared in S1, 20-60 parts by weight of the metal binder, and 1-10 parts by weight of the high thermal conductivity additive. Place them in a mixer and mix at 100-300 rpm for 30-90 minutes to obtain a uniformly dispersed composite powder. The metal binder is selected from copper powder, nickel powder, or silver powder, with an average particle size of 5μm-50μm. The high thermal conductivity additive is selected from one of graphene, diamond micropowder, or boron nitride nanosheets. S22: The composite powder obtained in S21 is mixed with an organic carrier at a mass ratio of 1:0.5 to 1:1.5, and stirred in a mixer at a speed of 200-500 rpm for 20-40 minutes until a uniform slurry is formed; the organic carrier is selected from one of terpineol, ethyl cellulose, and butyl carbitol acetate. S23: The slurry prepared in S22 is coated on the inner surface of the copper top cover plate at the position corresponding to the preset hot spot area. The coating thickness is controlled at 0.15mm-0.35mm. Then, it is pre-dried at 80℃-120℃ for 10-20 minutes to form a functional layer preform.

[0011] Optionally, S3 specifically includes: S31: Place the upper cover plate with the functional layer preform into the sintering furnace, first evacuate to below 10 Pa, then introduce a protective atmosphere to atmospheric pressure, and control the flow rate of the protective atmosphere at 5-15 L / min; the protective atmosphere is selected from nitrogen or argon. S32: Raise the furnace temperature to 200℃-300℃ at a heating rate of 2-5℃ / min, and hold for 30-60 minutes to allow the organic carrier in the functional layer preform to decompose and volatilize and be discharged. S33: Raise the furnace temperature to 750℃-950℃ at a heating rate of 5-10℃ / min and hold for 60-120 minutes to allow the metal binder particles to melt and sinter, forming a three-dimensional interconnected porous metal skeleton. At the same time, the phase change microcapsules are embedded and fixed in the pores of the skeleton. S34: After sintering and heat preservation, the furnace is naturally cooled to room temperature. The top cover plate is then removed to obtain a top cover plate assembly with a porous network structure phase change microcapsule functional layer.

[0012] Optionally, S4 specifically includes: S41: Select metal powder with an average particle size of 20μm-100μm as the main capillary core material; the metal powder is selected from copper powder, nickel powder or aluminum powder. S42: The selected metal powder is evenly spread on the inner surface of the copper lower cover plate, and the spreading thickness is controlled between 0.2mm and 0.5mm. S43: Place the lower cover plate covered with metal powder in a sintering furnace and heat it to 800℃-950℃ at a heating rate of 5-10℃ / min under a protective atmosphere. Hold it for 60-120 minutes to form sintering necks between the metal powder particles and connect them to each other, thus constructing a main capillary core with a three-dimensional porous network structure. S44: After sintering and heat preservation, the furnace is naturally cooled to room temperature. The lower cover plate is then removed to obtain a lower cover plate assembly with a main capillary core.

[0013] Optionally, S5 specifically includes: S51: Alignment and Assembly: Align and fasten the upper cover plate assembly obtained in S3 with the lower cover plate assembly obtained in S4, so that the inner surface of the upper cover plate with the phase change microcapsule functional layer is opposite to the inner surface of the lower cover plate with the main capillary core, forming an initial cavity. S52: Apply pressure along the edge joint of the upper cover plate and the lower cover plate for pre-fixation, and perform sealing welding to form a sealed cavity, and reserve an injection port on one side of the sealed cavity; S53: Place the sealed cavity with the liquid injection port in a vacuum oven, connect the vacuum line, and evacuate to 10°C. -3 Pa, and keep warm at 80℃-120℃ for 30-60 minutes to remove the gas and moisture adsorbed on the inner wall of the cavity and in the capillary core; S54: Maintain a vacuum state and inject a working medium into the sealed cavity through the injection port. The injection volume is 10%-20% of the internal volume of the sealed cavity. The working medium is one of deionized water, methanol, or acetone. S55: After the injection is completed, temporarily seal the injection port to prevent air from entering.

[0014] Optionally, S6 specifically includes: S61: The reserved injection port is permanently sealed by cold welding; S62: Place the vaporizer plate with the injection port sealed in a helium mass spectrometer leak detector for airtightness testing. The leak rate should not exceed 1×10⁻⁶. -9 Pa·m 3 / s; S63: Place the leak-tested heat spreader in a constant temperature oven and keep it at 80℃-100℃ for 2-4 hours. Then let it cool naturally to room temperature to obtain the finished composite heat spreader with integrated phase change microcapsules.

[0015] The beneficial effects of this invention are: This invention constructs a composite heat dissipation structure that combines rapid heat diffusion and instantaneous heat buffering by integrating a phase change microcapsule functional layer onto the inner surface of the vapor chamber's cover plate. When the chip experiences a sudden thermal shock, the phase change microcapsules above the hot spot rapidly absorb the latent heat of phase change, effectively suppressing a sharp rise in local temperature. After the thermal load decreases, the stored heat is rapidly released to the condenser end through the vapor chamber's main circulation. This organic combination of spatial heat diffusion and temporal heat buffering significantly reduces the chip's peak temperature and temperature fluctuation amplitude, extending the duration of high performance maintenance.

[0016] This invention achieves precise heat dissipation by precisely arranging the functional layer of phase change microcapsules in the corresponding hot spot areas, avoiding the introduction of additional thermal resistance in non-hot spot areas; and by using a co-sintering process to firmly fix the phase change microcapsules in a three-dimensional porous framework formed by a metal binder, it solves the reliability problems of traditional phase change materials, such as easy migration, poor thermal conductivity, and incompatibility with heat spreaders. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the composite heat spreader preparation method according to an embodiment of the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0020] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0021] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0022] Example 1 A composite heat exchanger integrating phase change microcapsules includes a sealed cavity, a main capillary core, a working fluid, and a phase change microcapsule functional layer. The sealed cavity is formed by sealing the edges of an upper cover plate and a lower cover plate. The main capillary core is disposed on the inner surface of the lower cover plate to provide capillary force for the recirculation of the working fluid. The working fluid fills the sealed cavity to transfer heat through gas-liquid phase change. The phase change microcapsule functional layer is disposed on the inner surface of the upper cover plate and corresponds to a preset hot spot area. The phase change microcapsule functional layer is composed of phase change microcapsules, a metal binder, and a high thermal conductivity additive.

[0023] like Figure 1 As shown, a method for preparing a composite heat spreader with integrated phase change microcapsules includes the following steps: S1: Using chemical polymerization, a core-shell structured phase change microcapsule was prepared with a phase change material as the core and a polymer-metal composite material as the shell. S2: The phase change microcapsules obtained in S1 are mixed with the prepared metal binder and high thermal conductivity additive to form a composite powder; the composite powder is mixed with an organic carrier to form a slurry; and the slurry is coated on the preset hot spot area on the inner surface of the upper cover plate to form a functional layer preform. S3: The top cover plate with the functional layer preform is placed in a protective atmosphere for co-sintering treatment, so that the metal binder forms a porous metal skeleton, and the phase change microcapsules are fixed in the porous metal skeleton to obtain a top cover plate assembly with a porous network structure phase change microcapsule functional layer. S4: Spread metal powder on the inner surface of the lower cover plate and sinter it to form the main capillary core, thus obtaining the lower cover plate assembly. S5: Align and seal the upper cover plate assembly and the lower cover plate assembly to form a sealed cavity, and reserve a liquid injection port; after evacuating the sealed cavity, inject the working fluid through the liquid injection port; S6: Seal the injection port to obtain the finished composite heat spreader plate with integrated phase change microcapsules.

[0024] S1 specifically includes: S11: The paraffin-based phase change material is heated to 20°C above its melting point to completely melt it. 2% of the thermally conductive reinforcing filler by mass of the phase change material is added, and the mixture is ultrasonically dispersed at 60°C for 40 minutes to obtain a uniformly mixed oil phase. The thermally conductive reinforcing filler is selected from graphene. S12: Mix polymer monomers and nano-metal particles at a mass ratio of 1:0.3, add deionized water, adjust the pH value to 4.0, stir and react at 50°C for 60 minutes to form an aqueous solution of polymer-metal composite shell material prepolymer; S13: The oil phase obtained in S11 is slowly added to the aqueous solution of the prepolymer obtained in S12. The volume ratio of the oil phase to the water phase is 1:3. The mixture is stirred and emulsified at 2000 rpm at 60°C for 30 minutes to form an oil-in-water emulsion. S14: Add curing agent to emulsion, adjust the reaction system temperature to 75℃, and stir continuously for 4 hours to allow the prepolymer to crosslink and polymerize at the oil-water interface, forming a phase change microcapsule suspension with paraffin-based phase change material as the core and polymer-metal composite material as the shell. S15: The phase change microcapsule suspension was centrifuged, washed three times alternately with deionized water and anhydrous ethanol, and then vacuum dried at 50°C for 18 hours to obtain core-shell structured phase change microcapsule powder.

[0025] S2 specifically includes: S21: Weigh 50 parts by mass of the phase change microcapsules prepared by S1, 40 parts by mass of the metal binder and 5 parts by mass of the high thermal conductivity additive, place them in a mixer and mix at 200 rpm for 60 minutes to obtain a uniformly dispersed composite powder; the metal binder is selected from copper powder with an average particle size of 20 μm; the high thermal conductivity additive is selected from diamond micro powder. S22: The composite powder obtained in S21 is mixed with the organic carrier at a mass ratio of 1:1, and stirred in a mixer at a speed of 350 rpm for 30 minutes until a uniform slurry is formed; the organic carrier is selected from terpineol. S23: The slurry prepared in S22 is coated on the inner surface of the copper top cover plate at the position corresponding to the preset hot spot area. The coating thickness is controlled at 0.25mm. Then, it is pre-dried at 100℃ for 15 minutes to form a functional layer preform.

[0026] S3 specifically includes: S31: Place the top cover plate with the functional layer preform into the sintering furnace, first evacuate to 8 Pa, then introduce a protective atmosphere to atmospheric pressure, and control the flow rate of the protective atmosphere at 10 L / min; the protective atmosphere is selected from argon. S32: Raise the furnace temperature to 250℃ at a heating rate of 3℃ / min and hold for 45 minutes to allow the organic carrier in the functional layer preform to decompose and volatilize and be discharged. S33: The furnace temperature is raised to 850℃ at a heating rate of 7℃ / min and held for 90 minutes to allow the metal binder particles to melt and sinter, forming a three-dimensional interconnected porous metal skeleton. At the same time, phase change microcapsules are embedded and fixed in the pores of the skeleton. S34: After sintering and heat preservation, the furnace is naturally cooled to room temperature. The top cover plate is then removed to obtain a top cover plate assembly with a porous network structure phase change microcapsule functional layer.

[0027] S4 specifically includes: S41: Select metal powder with an average particle size of 50μm as the main capillary core material; the metal powder is selected from copper powder; S42: The selected metal powder is evenly spread on the inner surface of the copper lower cover plate, and the spreading thickness is controlled at 0.35mm. S43: Place the lower cover plate covered with metal powder in a sintering furnace, heat it to 880°C at a heating rate of 8°C / min under a protective atmosphere, and hold it for 90 minutes to form sintering necks between the metal powder particles and connect them to each other, thus constructing a main capillary core with a three-dimensional porous network structure and a porosity controlled at 62%. S44: After sintering and heat preservation, the furnace is naturally cooled to room temperature. The lower cover plate is then removed to obtain a lower cover plate assembly with a main capillary core.

[0028] S5 specifically includes: S51: Alignment and Assembly: Align and fasten the upper cover plate assembly obtained in S3 with the lower cover plate assembly obtained in S4, so that the inner surface of the upper cover plate with the phase change microcapsule functional layer is opposite to the inner surface of the lower cover plate with the main capillary core, forming an initial cavity. S52: Apply pressure along the edge joint of the upper cover plate and the lower cover plate for pre-fixation, and perform sealing welding to form a sealed cavity, and reserve an injection port on one side of the sealed cavity; S53: Place the sealed cavity with the liquid injection port in a vacuum oven, connect the vacuum line, and evacuate to 10°C. -3 Pa, and keep warm at 100℃ for 45 minutes to remove the gas and moisture adsorbed on the inner wall of the cavity and in the capillary core; S54: Maintain a vacuum state and inject working fluid into the sealed cavity through the injection port. The injection volume is 15% of the internal volume of the sealed cavity; the working fluid is deionized water. S55: After the injection is completed, temporarily seal the injection port to prevent air from entering.

[0029] S6 specifically includes: S61: The reserved injection port is permanently sealed by cold welding; S62: Place the vaporizer plate with the injection port sealed in a helium mass spectrometer leak detector for airtightness testing. The leak rate should not exceed 1×10⁻⁶. -9 Pa·m 3 / s; S63: Place the leak-tested heat spreader in a constant temperature oven and keep it at 90°C for 3 hours. Then let it cool naturally to room temperature to obtain the finished composite heat spreader with integrated phase change microcapsules.

[0030] Example 2 S1: Weigh the paraffin-based phase change material and heat it to 10°C above its melting point until it is completely melted. Then add carbon nanotubes, accounting for 0.5% of the mass of the phase change material, and ultrasonically disperse them at 50°C for 20 minutes to obtain a uniform oil phase. Separately weigh the polymer monomer and nano-metal particles at a mass ratio of 1:0.2, add deionized water, adjust the pH to 3.0, and stir the reaction at 40°C for 30 minutes to obtain an aqueous solution of polymer-metal composite shell prepolymer. Slowly add the above oil phase to the prepolymer. In an aqueous solution, the volume ratio of the oil phase to the water phase was controlled at 1:2. The mixture was stirred and emulsified at 1000 rpm for 20 min at 50 °C to form an oil-in-water emulsion. Then, a curing agent was added to the emulsion, the reaction temperature was raised to 60 °C and stirred continuously for 2 h, so that the prepolymer crosslinked and polymerized at the oil-water interface to form a phase change microcapsule suspension. Finally, the mixture was separated by centrifugation at 4000 rpm for 8 min, washed twice alternately with deionized water and anhydrous ethanol, and vacuum dried at 40 °C for 12 h to obtain core-shell structured phase change microcapsule powder. S2: Weigh 30 parts by weight of phase change microcapsules, 20 parts by weight of nickel powder and 1 part by weight of graphene, wherein the average particle size of nickel powder is 5 μm. Place them in a mixer and mix at 100 rpm for 30 min to obtain a uniform composite powder. Then mix the composite powder with an organic carrier at a mass ratio of 1:0.5, wherein the organic carrier is ethyl cellulose, and stir at 200 rpm for 20 min in a mixer to obtain a uniform slurry. Subsequently, coat the slurry onto the preset hot spot area on its inner surface, and control the coating thickness to 0.15 mm. After coating, pre-dry at 80℃ for 10 min to obtain a functional layer preform. S3: Place the top cover plate with the functional layer preform in the sintering furnace, first evacuate to 9 Pa, then introduce nitrogen to atmospheric pressure, controlling the nitrogen flow rate to 5 L / min; then heat to 200℃ at a heating rate of 2℃ / min and hold for 30 min, so that the organic carrier in the functional layer preform is decomposed by heat and volatilized and discharged; then continue to heat to 750℃ at a heating rate of 5℃ / min and hold for 60 min, so that the metal binder particles melt and sinter to form a three-dimensional interconnected porous metal skeleton, while the phase change microcapsules are embedded and fixed in the pores of the skeleton; after the holding time is completed, let the furnace cool naturally to room temperature, remove the top cover plate, and obtain the top cover plate assembly with a porous network structure phase change microcapsule functional layer; S4: Select nickel powder with an average particle size of 20μm as the main capillary core material and spread it evenly on the inner surface of the copper lower cover plate with a thickness of 0.2mm. Then, place the lower cover plate with powder in a sintering furnace and heat it to 800℃ at a heating rate of 5℃ / min under a nitrogen protective atmosphere, and hold it for 60min to form sintering necks between the copper powder particles and connect them to each other, thus constructing a three-dimensional porous network structure of the main capillary core with a porosity of 50%. After sintering, allow it to cool naturally to room temperature in the furnace, and remove the lower cover plate to obtain the lower cover plate assembly with the main capillary core. S5: Align and fasten the upper cover plate assembly obtained in S3 with the lower cover plate assembly obtained in S4, so that the inner surface of the upper cover plate with the phase change microcapsule functional layer is opposite to the inner surface of the lower cover plate with the main capillary core, forming an initial cavity; apply a pressure of 0.4MPa along the edge joint of the upper and lower cover plates for pre-fixation, and perform sealing welding by brazing to form a sealed cavity, while reserving a liquid injection port with a diameter of 2.0mm on one side of the sealed cavity; then place the sealed cavity with the liquid injection port in a vacuum oven, connect the vacuum pipeline, evacuate to 1×10^-3Pa, and keep at 80℃ for 30min to remove the gas and moisture adsorbed in the inner wall of the cavity and the capillary core; while maintaining the vacuum state, inject methanol into the sealed cavity through the liquid injection port, the injection volume is 10% of the internal volume of the sealed cavity, and after the liquid injection is completed, temporarily seal the liquid injection port to prevent air from entering; S6: The reserved injection port is permanently sealed by cold welding. Then, the sealed heat spreader is placed in a helium mass spectrometer leak detector for air tightness testing. The heat spreader that passes the leak test is then placed in a constant temperature oven and kept at 80°C for 2 hours. Then, it is naturally cooled to room temperature to obtain the finished composite heat spreader with integrated phase change microcapsules.

[0031] Example 3 S1: Weigh the paraffin-based phase change material and heat it to 30°C above its melting point until it is completely melted; then add nanodiamonds, accounting for 5% of the mass of the phase change material, and ultrasonically disperse at 70°C for 60 min to obtain a homogeneous oil phase; separately weigh the polymer monomers and nano-metal particles at a mass ratio of 1:0.2, add deionized water, adjust the pH to 5.0, and stir the reaction at 60°C for 90 min to obtain an aqueous solution of polymer-metal composite shell material prepolymer; slowly add the above oil phase to the prepolymer water... In the solution, the volume ratio of the oil phase to the water phase was controlled at 1:5. The mixture was stirred and emulsified at 3000 rpm for 40 min at 70 °C to form an oil-in-water emulsion. Then, a curing agent was added to the emulsion, the reaction temperature was raised to 85 °C and stirred continuously for 6 h, so that the prepolymer crosslinked and polymerized at the oil-water interface to form a phase change microcapsule suspension. Finally, the mixture was separated by centrifugation at 4000 rpm for 8 min, washed four times alternately with deionized water and anhydrous ethanol, and vacuum dried at 60 °C for 24 h to obtain a core-shell structured phase change microcapsule powder. S2: Weigh 70 parts by weight of phase change microcapsules, 60 parts by weight of silver powder and 10 parts by weight of boron nitride nanosheets, wherein the average particle size of the silver powder is 50 μm. Place them in a mixer and mix at 300 rpm for 90 min to obtain a uniform composite powder. Then mix the composite powder with an organic carrier at a mass ratio of 1:1.5, wherein the organic carrier is butyl carbitol acetate, and stir at 500 rpm for 40 min in a mixer to obtain a uniform slurry. Subsequently, coat the slurry onto the preset hot spot area on its inner surface, and control the coating thickness to be 0.35 mm. After coating, pre-dry at 120℃ for 20 min to obtain a functional layer preform. S3: Place the top cover plate with the functional layer preform in a sintering furnace. First, evacuate to 10 Pa, then introduce nitrogen to atmospheric pressure, controlling the nitrogen flow rate at 15 L / min. Then, heat to 300℃ at a rate of 5℃ / min and hold for 60 min to allow the organic carrier in the functional layer preform to decompose and volatilize. Then, continue heating to 950℃ at a rate of 10℃ / min and hold for 120 min to allow the metal binder particles to melt and sinter, forming a three-dimensional interconnected porous metal skeleton. At the same time, embed and fix the phase change microcapsules in the skeleton pores. After the holding period, allow the furnace to cool naturally to room temperature, remove the top cover plate, and obtain the top cover plate assembly with a porous network structure phase change microcapsule functional layer. S4: Select aluminum powder with an average particle size of 100μm as the main capillary core material and spread it evenly on the inner surface of the copper lower cover plate with a thickness of 0.5mm. Then, place the lower cover plate after powder spreading in a sintering furnace and heat it to 950℃ at a heating rate of 10℃ / min under a nitrogen protective atmosphere, and hold it for 120min to form sintering necks between the copper powder particles and connect them to each other, thus constructing a three-dimensional porous network structure of the main capillary core with a porosity of 75%. After sintering, allow it to cool naturally to room temperature in the furnace, remove the lower cover plate, and obtain the lower cover plate assembly with the main capillary core. S5: Align and fasten the upper cover plate assembly obtained in S3 with the lower cover plate assembly obtained in S4, so that the inner surface of the upper cover plate with the phase change microcapsule functional layer is opposite to the inner surface of the lower cover plate with the main capillary core, forming an initial cavity; apply a pressure of 0.4MPa along the edge joint of the upper and lower cover plates for pre-fixation, and perform sealing welding by brazing to form a sealed cavity, while reserving a liquid injection port with a diameter of 2.0mm on one side of the sealed cavity; then place the sealed cavity with the liquid injection port in a vacuum oven, connect the vacuum pipeline, evacuate to 1×10^-3Pa, and keep at 120℃ for 60min to remove the gas and moisture adsorbed in the inner wall of the cavity and the capillary core; while maintaining the vacuum state, inject acetone into the sealed cavity through the liquid injection port, the injection volume is 20% of the internal volume of the sealed cavity, and after the liquid injection is completed, temporarily seal the liquid injection port to prevent air from entering; S6: The reserved injection port is permanently sealed by cold welding. Then, the sealed heat spreader is placed in a helium mass spectrometer leak detector for air tightness testing. The heat spreader that passes the leak test is then placed in a constant temperature oven and kept at 100℃ for 4 hours. Then, it is naturally cooled to room temperature to obtain the finished composite heat spreader with integrated phase change microcapsules.

[0032] Comparative Example 1 Step 1: Select the upper cover plate and the lower cover plate, sinter the inner surface of the lower cover plate to form a conventional capillary core structure, and then weld the upper cover plate and the lower cover plate together to form a heat spreader cavity, and reserve a liquid injection port on the side. Step 2: After heating and melting the paraffin wax, pour it directly into the cavity of the heat spreader through the injection port, so that the paraffin wax adheres to or accumulates at the bottom or in a local area of ​​the cavity; then inject the working liquid into the cavity. Step 3: After completing the injection of paraffin and working fluid, the injection port is sealed to obtain the finished traditional phase change heat exchanger plate.

[0033] Table 1 Comparison of Finished Product Performance Parameters

[0034] As can be seen from Table 1 above, Example 1 outperforms Examples 2, 3, and Comparative Example 1 in all aspects, including equivalent thermal conductivity, thermal diffusion response time, peak heat source temperature, temperature uniformity difference, heat transfer capacity per unit area, latent heat utilization rate of phase change, performance retention rate after thermal cycling, and airtightness. This indicates that Example 1 performs best in terms of comprehensive heat transfer performance, thermal buffering capacity, structural stability, and long-term service reliability. Specifically, Example 1 achieves an equivalent thermal conductivity of 842 W / m·K, a thermal diffusion response time shortened to 12.8 s, and a peak heat source temperature reduced to 68.4 °C, indicating that it can diffuse local heat more quickly and suppress hot spot temperature rise. Simultaneously, its temperature uniformity difference is only 3.2 °C, indicating that this composite heat spreader has stronger heat dissipation capability in the planar direction. Further analysis reveals that Example 1 is superior to Examples 2 and 3 because it achieves a better match between the phase change microcapsule content, metal binder ratio, thermally conductive filler type, and sintering parameters. This ensures both a continuous thermal conductivity pathway for the porous metal framework and a high effective distribution density of the phase change microcapsules in the hot spot region, thus achieving a better balance between local heat storage, rapid heat conduction, and overall heat homogenization. In contrast, although Example 2 has a better molding foundation, its smaller functional layer thickness and lower filler ratio result in relatively insufficient heat storage buffering and heat homogenization capabilities. Although Example 3 has a higher phase change microcapsule content and coating thickness, the higher filler ratio and higher sintering conditions enhance the local structural densification trend, resulting in overall performance not reaching the optimal balance of Example 1. The performance of Comparative Example 1 is significantly lower than that of the three examples, especially in terms of peak heat source temperature, temperature uniformity difference, latent heat utilization rate, and performance retention rate after thermal cycling. This indicates that the traditional method of directly injecting paraffin wax into the cavity of the heat spreader makes it difficult to form a stable, continuous, and controllable local functional layer. Paraffin wax tends to accumulate locally in the cavity, resulting in uneven distribution of phase change temperature regulation effect. Furthermore, it is more prone to migration, aggregation, and performance degradation during long-term thermal cycling, thereby reducing the overall heat dissipation stability and reliability of the heat spreader.

[0035] Table 2 Comparison of Cycle Life

[0036] The test method involved applying different heat flux densities to the evaporator end of the heat source plate under the same environmental conditions and installation method, and recording the temperature rise of the heat source center region relative to the initial ambient temperature under steady-state conditions. Table 2 shows that the performance retention rate of each sample decreased with increasing thermal cycling cycles, but Example 1 showed the smallest decrease, maintaining 91.5% of its performance after 300 cycles, significantly better than Examples 2, 3, and Comparative Example 1. This indicates that the functional layer of the phase change microcapsule in Example 1 has a more stable bond with the porous metal framework, making it less prone to phase change material migration, local aggregation, and structural loosening during repeated heating and cooling, thus exhibiting the best long-term stability. Comparative Example 1, due to its direct paraffin infusion method, lacked effective fixation of the phase change material inside the cavity, making it more prone to distribution imbalance and performance degradation during thermal cycling, resulting in the worst cycle life.

[0037] Table 3 Comparison of temperature rise under different heat flux densities

[0038] The test method involved applying different heat flux densities to the evaporation end of the heat source plate under the same environmental conditions and installation method, and recording the temperature rise of the heat source center area relative to the initial ambient temperature under steady-state conditions. Table 3 shows that as the heat flux density increases, the temperature rise of the hot spot area in each sample gradually increases. However, Example 1 consistently exhibits the lowest temperature rise under all heat flux densities, indicating that it has the strongest rapid diffusion and phase change buffering capacity for localized heat. Example 3 generally outperforms Example 2, indicating that the higher content of phase change microcapsules and the thickness of the functional layer have a certain enhancing effect on heat buffering. However, due to its inferior structural matching and balance compared to Example 1, its temperature rise control capability is still slightly weaker than that of Example 1. Comparative Example 1 shows the highest temperature rise under all heat flux density conditions, especially with a faster temperature rise under high heat flux density conditions. This indicates that the traditional method of directly injecting paraffin into the cavity is difficult to form a stable and effective localized phase change temperature regulation structure, and it is also difficult to balance uniform heat diffusion and long-term heat transfer stability.

[0039] Based on the aforementioned comparison tables of finished product performance, cycle life, and temperature rise under different heat flux densities, it can be seen that Example 1 exhibits the best performance in terms of initial heat transfer performance, long-term cycle stability, and hot spot suppression capability under high heat flux density conditions. This indicates that the present invention can effectively improve the overall thermal management performance of the heat spreader by constructing a composite functional layer of "phase change microcapsules + porous metal skeleton" in the hot spot area, while the traditional method of directly injecting paraffin wax is difficult to achieve the same effect.

[0040] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite heat spreader integrating phase change microcapsules, characterized in that, It includes a sealed cavity, a main capillary core, a working fluid, and a phase change microcapsule functional layer; the sealed cavity is formed by sealing the edges of an upper cover plate and a lower cover plate; the main capillary core is disposed on the inner surface of the lower cover plate; the working fluid is filled in the sealed cavity.

2. The composite heat spreader with integrated phase change microcapsules according to claim 1, characterized in that, The phase change microcapsule functional layer is disposed on the inner surface of the upper cover plate and corresponds to the preset hot spot area; the phase change microcapsule functional layer is composed of phase change microcapsules, metal binders and high thermal conductivity additives.

3. The composite heat spreader with integrated phase change microcapsules according to claim 1, characterized in that, The main capillary core has a porous sintered structure and is made of copper, nickel or aluminum, with a porosity controlled at 50%-75%; the working fluid is deionized water, methanol or acetone, and its filling amount is 10%-20% of the internal volume of the sealed cavity.

4. A method for preparing a composite heat spreader with integrated phase change microcapsules, used to prepare the composite heat spreader with integrated phase change microcapsules as described in any one of claims 1-3, characterized in that, Includes the following steps: S1: Using chemical polymerization, a core-shell structured phase change microcapsule was prepared with a phase change material as the core and a polymer-metal composite material as the shell. S2: The phase change microcapsules obtained in S1 are mixed with the prepared metal binder and high thermal conductivity additive to form a composite powder; the composite powder is mixed with an organic carrier to form a slurry; and the slurry is coated on the preset hot spot area on the inner surface of the upper cover plate to form a functional layer preform. S3: The top cover plate with the functional layer preform is placed in a protective atmosphere for co-sintering treatment, so that the metal binder forms a porous metal skeleton, and the phase change microcapsules are fixed in the porous metal skeleton to obtain a top cover plate assembly with a porous network structure phase change microcapsule functional layer. S4: Spread metal powder on the inner surface of the lower cover plate and sinter it to form the main capillary core, thus obtaining the lower cover plate assembly. S5: Align and seal the upper cover plate assembly and the lower cover plate assembly to form a sealed cavity, and reserve a liquid injection port; after evacuating the sealed cavity, inject the working fluid through the liquid injection port; S6: Seal the injection port to obtain the finished composite heat spreader plate with integrated phase change microcapsules.

5. The method for preparing a composite heat spreader with integrated phase change microcapsules according to claim 4, characterized in that, S1 specifically includes: S11: Heat the paraffin-based phase change material to 10℃-30℃ above its melting point to completely melt it, add 0.5%-5% of thermally conductive reinforcing filler by mass of the phase change material, and ultrasonically disperse at 50℃-70℃ for 20-60 minutes to obtain a uniformly mixed oil phase; the thermally conductive reinforcing filler is a high thermal conductivity powder selected from carbon nanotubes, graphene, boron nitride, or nanodiamond; S12: Mix polymer monomers and nano-metal particles at a mass ratio of 1:0.2 to 1:0.5, add deionized water, adjust the pH value to 3.0-5.0, and stir the reaction at 40℃-60℃ for 30-90 minutes to form an aqueous solution of polymer-metal composite shell material prepolymer. S13: Slowly add the oil phase obtained in S11 to the aqueous solution of the prepolymer obtained in S12. The volume ratio of the oil phase to the water phase is 1:2 to 1:

5. Stir and emulsify at 1000-3000 rpm at 50℃-70℃ for 20-40 minutes to form an oil-in-water emulsion. S14: Add curing agent to emulsion, adjust the reaction system temperature to 60℃-85℃, and continue stirring for 2-6 hours to allow the prepolymer to crosslink and polymerize at the oil-water interface to form a phase change microcapsule suspension. S15: The phase change microcapsule suspension is centrifuged, washed 2-4 times alternately with deionized water and anhydrous ethanol, and then vacuum dried at 40℃-60℃ for 12-24 hours to obtain core-shell structured phase change microcapsule powder.

6. The method for preparing a composite heat spreader with integrated phase change microcapsules according to claim 4, characterized in that, S2 specifically includes: S21: Weigh 30-70 parts by weight of the phase change microcapsules prepared in S1, 20-60 parts by weight of the metal binder, and 1-10 parts by weight of the high thermal conductivity additive. Place them in a mixer and mix at 100-300 rpm for 30-90 minutes to obtain a uniformly dispersed composite powder. The metal binder is selected from copper powder, nickel powder, or silver powder, with an average particle size of 5μm-50μm. The high thermal conductivity additive is selected from one of graphene, diamond micropowder, or boron nitride nanosheets. S22: The composite powder obtained in S21 is mixed with an organic carrier at a mass ratio of 1:0.5 to 1:1.5, and stirred in a mixer at a speed of 200-500 rpm for 20-40 minutes until a uniform slurry is formed; the organic carrier is selected from one of terpineol, ethyl cellulose, and butyl carbitol acetate. S23: The slurry prepared in S22 is coated on the inner surface of the copper top cover plate at the position corresponding to the preset hot spot area. The coating thickness is controlled at 0.15mm-0.35mm. Then, it is pre-dried at 80℃-120℃ for 10-20 minutes to form a functional layer preform.

7. The method for preparing a composite heat spreader with integrated phase change microcapsules according to claim 4, characterized in that, S3 specifically includes: S31: Place the upper cover plate with the functional layer preform into the sintering furnace, first evacuate to below 10 Pa, then introduce a protective atmosphere to atmospheric pressure, and control the flow rate of the protective atmosphere at 5-15 L / min; the protective atmosphere is selected from nitrogen or argon. S32: Raise the furnace temperature to 200℃-300℃ at a heating rate of 2-5℃ / min, and hold for 30-60 minutes to allow the organic carrier in the functional layer preform to decompose and volatilize and be discharged. S33: Raise the furnace temperature to 750℃-950℃ at a heating rate of 5-10℃ / min and hold for 60-120 minutes to allow the metal binder particles to melt and sinter, forming a three-dimensional interconnected porous metal skeleton. At the same time, the phase change microcapsules are embedded and fixed in the pores of the skeleton. S34: After sintering and heat preservation, the furnace is naturally cooled to room temperature. The top cover plate is then removed to obtain a top cover plate assembly with a porous network structure phase change microcapsule functional layer.

8. The method for preparing a composite heat spreader with integrated phase change microcapsules according to claim 4, characterized in that, S4 specifically includes: S41: Select metal powder with an average particle size of 20μm-100μm as the main capillary core material; the metal powder is selected from copper powder, nickel powder or aluminum powder. S42: The selected metal powder is evenly spread on the inner surface of the copper lower cover plate, and the spreading thickness is controlled between 0.2mm and 0.5mm. S43: Place the lower cover plate covered with metal powder in a sintering furnace and heat it to 800℃-950℃ at a heating rate of 5-10℃ / min under a protective atmosphere. Hold the temperature for 60-120 minutes to form sintering necks between the metal powder particles and connect them to each other, thus constructing a main capillary core with a three-dimensional porous network structure and controlling its porosity at 50%-75%. S44: After sintering and heat preservation, the furnace is naturally cooled to room temperature. The lower cover plate is then removed to obtain a lower cover plate assembly with a main capillary core.

9. The method for preparing a composite heat spreader with integrated phase change microcapsules according to claim 4, characterized in that, S5 specifically includes: S51: Alignment and Assembly: Align and fasten the upper cover plate assembly obtained in S3 with the lower cover plate assembly obtained in S4, so that the inner surface of the upper cover plate with the phase change microcapsule functional layer is opposite to the inner surface of the lower cover plate with the main capillary core, forming an initial cavity. S52: Apply pressure along the edge joint of the upper cover plate and the lower cover plate for pre-fixation, and perform sealing welding to form a sealed cavity, and reserve an injection port on one side of the sealed cavity; S53: Place the sealed cavity with the liquid injection port in a vacuum oven, connect the vacuum line, and evacuate to 10°C. -3 Pa, and keep warm at 80℃-120℃ for 30-60 minutes to remove the gas and moisture adsorbed on the inner wall of the cavity and in the capillary core; S54: Maintain a vacuum state and inject a working medium into the sealed cavity through the injection port. The injection volume is 10%-20% of the internal volume of the sealed cavity. The working medium is one of deionized water, methanol, or acetone. S55: After the injection is completed, temporarily seal the injection port to prevent air from entering.

10. The method for preparing a composite heat spreader with integrated phase change microcapsules according to claim 4, characterized in that, S6 specifically includes: S61: The reserved injection port is permanently sealed by cold welding; S62: Place the vaporizer plate with the injection port sealed in a helium mass spectrometer leak detector for airtightness testing. The leak rate should not exceed 1×10⁻⁶. -9 Pa·m 3 / s; S63: Place the leak-tested heat spreader in a constant temperature oven and keep it at 80℃-100℃ for 2-4 hours. Then let it cool naturally to room temperature to obtain the finished composite heat spreader with integrated phase change microcapsules.

Images