Coreless silica gel-based flexible vapor chamber

Abstract

The invention discloses a coreless silica gel-based flexible vapor chamber, which belongs to the technical field of vapor chambers, and comprises a super-hydrophilic evaporation end silica gel plate, a silica gel support structure and a super-hydrophobic condensation end silica gel plate which are sequentially arranged along the thickness direction, the silica gel supporting structure is located in a closed cavity formed by the super-hydrophilic evaporation end silica gel plate and the super-hydrophobic condensation end silica gel plate, and the inner wall of the super-hydrophilic evaporation end silica gel plate and the inner wall of the super-hydrophobic condensation end silica gel plate are in bond connection with the silica gel supporting structure through siloxane bonds. The super-hydrophilic evaporation end silica gel plate is formed by compounding a hydrophobic silica gel plate and a hydrophilic coating, and the hydrophilic coating is located in the closed cavity. The hydrophobic silica gel plate is prepared from a silica gel substrate and a heat-conducting filler. Due to the fact that the super-hydrophilic evaporation end silica gel plate, the silica gel supporting structure and the super-hydrophobic condensation end silica gel plate are integrally formed through silica gel made of the same material, the full-flexible coreless design is matched with the self-adaptive flow channel structure, and the vapor chamber can still keep efficient heat transfer and temperature uniformity under the bending working condition.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and more specifically to a coreless silicone-based flexible heat exchanger. Background Technology

[0002] With the rapid development of fifth-generation mobile communication (5G), the Internet of Things, aerospace special equipment, wearable electronic devices and flexible display technology, some power electronic devices are evolving towards flexibility, lightweight, irregular shape and high integration. This trend has posed unprecedented challenges to the thermal management technology that supports them. Heat dissipation components not only need to efficiently handle the local rapid increase in heat flux density, but also must have excellent shape adaptability, be able to fit curved surfaces or work reliably in limited irregular spaces.

[0003] As a passive heat dissipation device that utilizes the latent heat of phase change of the working fluid for efficient heat transfer, vapor chambers have become one of the preferred solutions for addressing the challenges of high power density heat dissipation due to their extremely high equivalent thermal conductivity and good isothermal properties. Traditional vapor chambers typically use metals such as copper and aluminum as the cavity material, with sintered powder, metal mesh, or microgrooves as the capillary core structure, and solid pillars as the support structure. This type of metal-based rigid vapor chamber technology is mature and performs well on flat, rigid circuit boards.

[0004] However, the inherent rigidity of metal-based rigid vapor chambers (rigidity of the cavity material, capillary structure, and support structure) makes them completely unsuitable for any form of bending or twisting. Currently, commonly used flexible vapor chambers often employ metal mesh capillary structures. Compared to rigid metal vapor chambers (microgroove capillary wicks or sintered powder capillary wicks), although the deformation capability of the mesh structure is significantly improved, it still cannot guarantee that the flexible vapor chamber can be easily bent or folded at any angle. Furthermore, the mesh capillary wick is at risk of breakage with increasing folding frequency, greatly limiting its application in emerging and cutting-edge fields such as flexible electronics, wearable devices, curved screens, and aerospace irregular-shaped packaging. Summary of the Invention

[0005] This invention provides a coreless silicone-based flexible vapor chamber, effectively solving the technical problem that existing flexible vapor chambers are difficult to bend or fold easily at any angle, and are prone to breakage with increasing folding frequency. This invention utilizes and differentially controls the surface properties of the silicone material itself, leveraging the intrinsic hydrophobicity of the silicone cavity at the condenser end to modify the silicone cavity at the evaporator end to construct a superhydrophilic interface. This creates a self-driven working fluid circulation mechanism within the cavity, driven by a wettability gradient and requiring no additional capillary wick. Combined with an innovative homogeneous material support structure design, an ultrathin vapor chamber with low interfacial thermal resistance, high flexibility, and lightweight design, without an independent internal capillary wick, has been developed.

[0006] The first objective of this invention is to provide a coreless silicone-based flexible heat spreader, comprising a superhydrophilic evaporation end silicone plate, a silicone support structure, and a superhydrophobic condensation end silicone plate arranged sequentially along the thickness direction.

[0007] The superhydrophilic evaporation end silica gel plate is composed of a hydrophobic silica gel plate and a hydrophilic coating; the hydrophobic silica gel plate is prepared from a silica gel matrix and a thermally conductive filler.

[0008] The silicone support structure is an array of n support columns, one end of which is connected to the hydrophilic coating and the other end is connected to the superhydrophobic condensation end silicone plate; a sealed liquid-filled cavity is formed between the superhydrophobic evaporation end silicone plate and the superhydrophobic condensation end silicone plate through the silicone support structure.

[0009] The superhydrophobic condenser end silicone plate is made of the same material as the hydrophobic silicone plate.

[0010] In a preferred embodiment, the outer diameter of each support column is 2mm to 5mm, and the distance between two adjacent support columns is 6mm.

[0011] In a preferred embodiment, the height ratio of the superhydrophilic evaporation end silicone plate, the support column, and the superhydrophobic condensation end silicone plate is 1:0.8 to 1.5:1.5; the length ratio of the superhydrophilic evaporation end silicone plate to the outer diameter of the support column and the length ratio of the superhydrophobic condensation end silicone plate is 60:0.1 to 0.25:60; and the width ratio of the superhydrophilic evaporation end silicone plate to the outer diameter of the support column and the width ratio of the superhydrophobic condensation end silicone plate is 60:0.1 to 0.25:60.

[0012] In a preferred embodiment, the sealed liquid-filled cavity is provided with an injection port, and the injection port is connected to an injection pipe.

[0013] In a preferred embodiment, the contact angle of the hydrophilic coating is 1° to 3°.

[0014] In a preferred embodiment, the method for preparing the hydrophobic silica gel plate includes the following steps: A modified thermally conductive filler was obtained by modifying a mixture of alumina and boron nitride with γ-aminopropyltriethoxysilane.

[0015] Using a first addition-type silicone and a second addition-type silicone as the silicone matrix, the first addition-type silicone is diluted with silicone oil and mixed with the modified thermally conductive filler to obtain a colloidal solution. The colloidal solution is then mixed with the second addition-type silicone, degassed, pre-cured at 60°C, and cured under pressure and temperature to obtain a hydrophobic silicone sheet.

[0016] In a preferred embodiment, the mass ratio of alumina to boron nitride is 19:1; the mass ratio of the first addition-cure silica gel, the modified filler, and the second addition-cure silica gel is 1:0.6 to 1:1.

[0017] In a preferred embodiment, the hydrophilic coating is specifically formed by: using octafluorocyclobutane as a precursor, mixing it with oxygen, and under the action of plasma, causing the precursor to decompose and interact with oxygen free radicals, and polymerizing and depositing it on the surface of a hydrophobic silica gel plate to obtain a hydrophilic coating of a fluorocarbon polymer with a micro-nano rough structure.

[0018] The present invention also provides a method for assembling the coreless silicone-based flexible heat spreader as described in any one of the above claims, comprising the following steps: Using a dispensing method, silicone sealant is applied to the surface of the hydrophilic coating of the superhydrophilic evaporation end silicone plate to form n uncured support pillars. The superhydrophobic condensation end silicone plate is then stacked with the other end of the n uncured support pillars, pressurized, and cured at room temperature. The hydrophilic coating, the superhydrophobic condensation end silicone plate, and the two ends of the n support pillars are bonded together through siloxane bonds.

[0019] The joint edge between the superhydrophilic evaporation end silicone plate and the superhydrophobic condensation end silicone plate is sealed with silicone sealant to obtain a coreless silicone-based flexible heat spreader.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a coreless silicone-based flexible vapor chamber, comprising a superhydrophilic evaporation end silicone plate, a silicone support structure, and a superhydrophobic condensation end silicone plate arranged vertically from bottom to top. The silicone support structure is located within a closed cavity formed by the superhydrophilic evaporation end silicone plate and the superhydrophobic condensation end silicone plate. The inner walls of the superhydrophilic evaporation end silicone plate and the superhydrophobic condensation end silicone plate are respectively bonded to the silicone support structure via siloxane bonds. The superhydrophilic evaporation end silicone plate is composed of a hydrophobic silicone plate and a hydrophilic coating, with the hydrophilic coating located within the closed cavity. The hydrophobic silicone plate is prepared from a silicone matrix and a thermally conductive filler. Because the superhydrophilic evaporation end silicone plate, the silicone support structure, and the superhydrophobic condensation end silicone plate are integrally molded from the same silicone material, the main structure, entirely composed of flexible silicone material, ensures the functional integrity of the vapor chamber when it is bent. This fully flexible coreless design, combined with an adaptive flow channel structure, allows the vapor chamber to maintain efficient heat transfer and temperature uniformity even under bending conditions.

[0021] When the heat source comes into contact with the superhydrophilic evaporation end silicone plate, the superhydrophilic evaporation end silicone plate filled with thermally conductive filler diffuses heat evenly and laterally across the entire evaporation surface, effectively preventing localized overheating. Heat vertically penetrates the hydrophobic silicone plate and is rapidly conducted to the hydrophilic coating, causing the extremely thin liquid film adhering to the coating to evaporate quickly. Lateral diffusion ensures temperature uniformity, while vertical heat transfer drives efficient film evaporation. Together, these two processes cause the working fluid to vaporize instantaneously at the superhydrophilic evaporation end silicone plate, generating steam that flows towards the superhydrophilic condensation end silicone plate. The silicone support structure used in this invention not only maintains the stability of the steam flow channel, but also forms an ultra-low thermal resistance thermally conductive bridge with the upper and lower cavities of the superhydrophilic condensation end silicone plate and the superhydrophilic evaporation end silicone plate through integrated bonding of siloxane bonds, ensuring that heat can be efficiently directed to the condensation end. After flowing through this channel, the steam reaches the inner surface of the superhydrophobic condenser silicone plate and condenses at the hydrophobic interface, releasing heat. The condensed droplets rapidly coalesce and slide off due to surface tension, and, relying on the difference in wettability, return from the condenser end (superhydrophobic condenser silicone plate 4) to the evaporator end (superhydrophilic evaporator silicone plate 1) through the channels between the silicone support structures 2, completing the working fluid cycle. This invention achieves better coordinated heat transfer while overcoming the limitations of existing rigid heat spreaders that cannot be bent or twisted.

[0022] This invention achieves an ultra-flexible heat dissipation plate that is lightweight, ultra-thin, and can be bent at will through the synergistic design of a high thermal conductivity cavity, wettability gradient drive, and integrated silicone support structure, providing an innovative heat dissipation solution for advanced flexible electronic devices. Attached Figure Description

[0023] Figure 1 This is an exploded three-dimensional view of the coreless silicone-based flexible heat spreader of the present invention, wherein 1 is the superhydrophilic evaporation end silicone plate, 2 is the silicone support structure, 3 is the liquid injection pipe, and 4 is the superhydrophobic condensation end silicone plate.

[0024] Figure 2 This is a front view of the superhydrophilic evaporation end silicone plate in the coreless silicone-based flexible heat spreader of an embodiment of the present invention.

[0025] Figure 3 This is a top view of the superhydrophilic evaporation end silicone plate in the coreless silicone-based flexible heat spreader of an embodiment of the present invention.

[0026] Figure 4 This is a front view of the silicone support structure in the coreless silicone-based flexible heat spreader according to an embodiment of the present invention.

[0027] Figure 5 This is a top view of the silicone support structure in the coreless silicone-based flexible heat spreader according to an embodiment of the present invention.

[0028] Figure 6This is a front view of the superhydrophobic condenser end silicone plate in the coreless silicone-based flexible heat spreader of an embodiment of the present invention.

[0029] Figure 7 This is a top view of the superhydrophobic condenser end silicone plate in the coreless silicone-based flexible heat spreader of an embodiment of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0031] It should be noted that the technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Certain terms are used in this invention to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This invention does not distinguish components based on differences in terminology, but rather on differences in function. As used throughout the specification and claims, "comprising" is an open-ended term and should be understood as "including but not limited to".

[0032] To address the technical problem that existing rigid heat spreaders cannot be bent or twisted, making them unsuitable for applications in flexible electronics, wearable devices, curved screens, and aerospace irregular packaging, this invention provides a coreless silicone-based flexible heat spreader and its assembly method.

[0033] The technical solution of the present invention will be analyzed and described in detail below.

[0034] This invention first provides a coreless silicone-based flexible heat spreader, such as... Figure 1 As shown, it includes a superhydrophilic evaporation end silicone plate 1, a silicone support structure 2, and a superhydrophobic condensation end silicone plate 4 arranged sequentially along the thickness direction.

[0035] The superhydrophilic evaporation end silica gel plate 1 is composed of a hydrophobic silica gel plate and a hydrophilic coating; the hydrophobic silica gel plate is prepared by a silica gel matrix and a thermally conductive filler.

[0036] The silicone support structure 2 is an array of n support columns. One end of each of the n support columns is connected to the hydrophilic coating, and the other end is connected to the superhydrophobic condensing end silicone plate 4. The superhydrophobic evaporating end silicone plate 1 and the superhydrophobic condensing end silicone plate 4 form a sealed liquid-filled cavity through the silicone support structure 2.

[0037] The superhydrophobic condenser end silicone plate 4 is made of the same material as the hydrophobic silicone plate.

[0038] This invention proposes a coreless silicone-based flexible vapor chamber structure based on the principle of synergistic heat transfer through a high thermal conductivity filled silicone cavity, internal wettability gradient driving, and an integrated silicone support structure. After receiving heat from the heat source, the superhydrophilic evaporation end silicone plate 1 rapidly diffuses laterally through the highly thermally conductive and flexible silicone matrix (i.e., the superhydrophilic evaporation end silicone plate 1) and is vertically transferred to the hydrophilic coating interface on the inner surface of the superhydrophilic evaporation end silicone plate 1. This superhydrophilic interface, through strong capillary adsorption, rapidly spreads the liquid working fluid into a uniform thin liquid film, laying the foundation for efficient thin-film evaporation phase change heat transfer. The silicone support structure 2 not only provides a low-resistance channel for vapor diffusion with its regularly arranged array, but also forms an ultra-low thermal resistance vertical heat conduction path due to its integrated bonding with the upper and lower cavities, significantly improving the overall heat transfer efficiency and temperature uniformity of the vapor chamber. The inner surface of the superhydrophobic condensation end silicone plate 4 utilizes its intrinsic hydrophobic properties to promote the rapid coalescence and detachment of droplets formed by vapor condensation from the surface, greatly reducing the condensation thermal resistance. The condensate returns from the condensation end (superhydrophobic condensation end silicone plate 4) to the evaporation end (superhydrophilic evaporation end silicone plate 1) through the flow channels between the silicone support structures 2, relying on the difference in wettability, thus completing the cycle.

[0039] The vapor chamber provided by this invention has no metal capillary wick inside. Evaporation and condensation functions are directly achieved through the wettability modification of the inner surface of the cavity. Furthermore, at an ultra-thin scale, the reduced droplet radius at the condensation end (superhydrophobic silicone plate 4) leads to enhanced condensation heat transfer and a decrease in overall thermal resistance, a stark contrast to the increase in thermal resistance with decreasing thickness in traditional metal-core vapor chambers. When the vapor chamber is bent, the main structure, entirely composed of flexible silicone material, ensures the functional integrity of the vapor chamber. This synergistic design, based on a highly thermally conductive flexible cavity, wettability gradient drive, and integrated low-resistance support, enables the vapor chamber to maintain stable thermal cycling performance and excellent temperature uniformity even under bending deformation, fully meeting the heat dissipation requirements of flexible electronic devices under dynamic operating conditions.

[0040] The superhydrophobic condenser-end silicone plate 4 is made of the same material as the hydrophobic silicone plate. The superhydrophobic condenser-end silicone plate 4 is made of the same material as the hydrophobic silicone plate, and its inherent low surface energy makes it hydrophobic. When the gaseous working fluid condenses here, it forms easily sliding discrete droplets rather than a covering liquid film. This not only significantly reduces the thermal resistance caused by the liquid film but also accelerates the detachment and reflux of the condensate, thereby enhancing the condensation heat transfer coefficient. The combination of the superhydrophilic evaporator-end silicone plate 1 and the aforementioned superhydrophobic condenser-end silicone plate 4 in this invention creates a strong wettability gradient within the entire vapor chamber. This gradient replaces the capillary pump driving force provided by the metal capillary wick in traditional vapor chambers, realizing a self-driven circulation of the working fluid from the condenser end to the evaporator end.

[0041] In a preferred embodiment, the outer diameter of the support column is 2mm to 5mm, and the distance between two adjacent support columns is 6mm. If the outer diameter of the support column is too small, it will not provide support and will easily collapse; if it is too large, it will occupy the steam space. With the steam space reduced, the steam flow pressure drop will increase during the operation of the heat spreader. This increased pressure drop will prevent the steam from condensing quickly, causing the heat spreader to burn dry due to insufficient liquid replenishment, increasing thermal resistance, and ultimately leading to failure.

[0042] It should be noted that the silicone support structure 2 used in this invention employs silicone sealant of the same material as the cavity. A micropillar array is constructed on the inner surface of the superhydrophilic evaporation end silicone plate 1 using a dispensing technique. After curing, this array is chemically bonded (siloxane bonds) to the inner wall of the cavity formed by the superhydrophilic evaporation end silicone plate 1 and the superhydrophobic condensation end silicone plate 4. Mechanically, the silicone support structure 2 acts as a supporting framework, maintaining the stability of the ultra-thin vapor channel. Thermally, the silicone support structure 2 acts as a heat-conducting bridge, completely eliminating the inherent contact thermal resistance in traditional multilayer structures due to material consistency and integrated molding, achieving near-lossless heat transfer from the evaporation end to the condensation end.

[0043] In a preferred embodiment, the height ratio of the superhydrophilic evaporation end silicone plate 1, the support column, and the superhydrophobic condensation end silicone plate 4 is 1:0.8 to 1.5:1.5; the length ratio of the superhydrophilic evaporation end silicone plate 1, the outer diameter of the support column, and the length ratio of the superhydrophobic condensation end silicone plate 4 is 60:0.1 to 0.25:60; and the width ratio of the superhydrophilic evaporation end silicone plate 1, the outer diameter of the support column, and the width ratio of the superhydrophobic condensation end silicone plate 4 is 60:0.1 to 0.25:60.

[0044] In a preferred embodiment, the sealed cavity is provided with a liquid injection port, which is connected to a liquid injection pipe 3. The liquid injection pipe 3 is used to inject the working medium and maintain the vacuum environment inside the sealed cavity. As a key channel for working medium filling and vacuum maintenance, the liquid injection pipe 3 ensures the stability of the internal phase change environment.

[0045] In a preferred embodiment, the contact angle of the hydrophilic coating is 1° to 3°. Because the hydrophilic coating on the inner surface of the superhydrophilic evaporation end silicone plate 1 has a low contact angle, the liquid working fluid can be instantly spread into a uniform thin liquid film at the evaporation end (superhydrophilic evaporation end silicone plate 1), which greatly promotes the thin film evaporation process and improves the evaporation efficiency and critical heat flux density.

[0046] In a preferred embodiment, the method for preparing the hydrophobic silica gel plate includes the following steps: A modified thermally conductive filler was obtained by modifying a mixture of alumina and boron nitride with γ-aminopropyltriethoxysilane.

[0047] Using a first addition-cure silicone and a second addition-cure silicone as the silicone matrix, the first addition-cure silicone is diluted with silicone oil, and the modified thermally conductive filler is added and mixed to obtain a colloidal solution. The colloidal solution is mixed with the second addition-cure silicone, degassed, pre-cured at 60°C, and then cured under pressure and temperature to obtain a hydrophobic silicone sheet. The specific preparation method is as follows: the first addition-cure silicone is diluted with silicone oil, the modified thermally conductive filler is added and mixed to obtain a colloidal solution. The colloidal solution is mixed with the second addition-cure silicone, degassed, pre-cured in a flat vulcanizing mold at 60°C, then a pressure of 10MPa is applied and the temperature is stepped up to 100°C, and then cured under pressure and cooled to below 60°C to obtain a preliminary product. The preliminary product is then post-cured at 100°C to obtain a hydrophobic silicone sheet.

[0048] The hydrophobic silica gel plate in the superhydrophilic evaporation end silica gel plate uses addition-type silica gel as the matrix and incorporates alumina / boron nitride composite filler modified with γ-aminopropyltriethoxysilane (KH550). KH-550 significantly improves the dispersibility of the thermally conductive filler by constructing "molecular bridges" between the thermally conductive filler and the silica gel. The hydrolytic end of KH-550 forms chemical bonds with the surface of the thermally conductive filler, while the organic long chains at the other end of KH-550 are well compatible with the silica gel matrix. This not only changes the surface properties of the filler but also prevents direct contact between thermally conductive filler particles through the steric hindrance effect of the molecular chains, thereby effectively preventing agglomeration and achieving micron-level uniform dispersion of the thermally conductive filler. On this basis, the combination of alumina and boron nitride further exerts a shape synergistic effect. Spherical alumina is densely filled in the matrix to form a basic "thermal conductive node" network, while two-dimensional plate-like boron nitride overlaps between the nodes to form "thermal conductive shortcuts," significantly reducing the heat transfer resistance. This point-to-surface combination creates an efficient three-dimensional heat conduction path, ultimately increasing the thermal conductivity of the cavity material to 1.1 W / m·K.

[0049] Based on the raw materials and preparation process of the hydrophobic silica gel plate in the superhydrophilic evaporation end silica gel plate 1, when the superhydrophilic evaporation end silica gel plate 1 containing the above-mentioned hydrophobic silica gel plate is used, during the entire operation, the heat source transfers heat to the superhydrophilic evaporation end silica gel plate 1. On the one hand, the uniformly dispersed thermally conductive filler in the hydrophobic silica gel plate forms a three-dimensional thermally conductive network, which allows the heat to spread laterally and be transferred vertically to the hydrophilic coating interface on its inner surface, promoting the formation of a uniform thin liquid film of the working fluid and its rapid evaporation. On the other hand, the integrated silicone support structure 2 not only provides a low-resistance flow channel for steam and liquid, but also eliminates the interfacial contact thermal resistance through material consistency, significantly improving the heat transfer efficiency. After the working fluid is heated and evaporated, it diffuses into the condensation end (superhydrophilic condensation end silica gel plate 4) in the steam chamber, rapidly condenses into droplets on the inner surface of the superhydrophilic condensation end silica gel plate 4 and falls off. Relying on the difference in wettability, it returns from the condensation end (superhydrophilic condensation end silica gel plate 4) to the evaporation end (superhydrophilic evaporation end silica gel plate 1) through the flow channel between the silicone support structures 2. This self-driven circulation mechanism based on wettability gradient, combined with an integrated silicone support structure, ensures that the working fluid can maintain stable gas-liquid circulation even when bent.

[0050] It is particularly noteworthy that as the vapor space height decreases, the maximum radius of the droplets at the condensation end also decreases, significantly enhancing the condensation heat transfer coefficient and leading to a reduction in the overall thermal resistance of the vapor chamber. This characteristic is the complete opposite of the trend where the thermal resistance of a cored vapor chamber increases with decreasing height. This fully flexible, coreless design, combined with an adaptive flow channel structure, allows the vapor chamber to maintain efficient heat transfer and temperature uniformity even under bending conditions. This invention features ultra-thinness, lightweight, good flexibility, low thermal resistance, and excellent temperature uniformity, meeting the heat dissipation requirements of next-generation flexible electronic devices and irregularly shaped packaging equipment.

[0051] In a preferred embodiment, the mass ratio of alumina to boron nitride is 19:1; the mass ratio of the first addition-cure silica gel, modified filler, and second addition-cure silica gel is 1:0.6 to 1:1. When the mass ratio of the modified filler is less than the specified 0.6, the thermal resistance of the cavity material is high, resulting in a slower heat transfer from the cavity material to the liquid film within the capillary core, thus affecting the overall thermal resistance of the heat spreader. When the mass ratio of the modified filler is greater than the specified 1, the mechanical properties of the cavity material deteriorate, making it prone to breakage under repeated folding, leading to air leakage and failure of the heat spreader.

[0052] As a preferred embodiment, the hydrophilic coating is specifically as follows: using octafluorocyclobutane as a precursor, it is mixed with oxygen, and under the action of plasma, the precursor is decomposed and interacts with oxygen free radicals, and polymerized and deposited on the surface of a hydrophobic silicone plate to obtain a hydrophilic coating of fluorocarbon polymer with a micro-nano rough structure. Specifically, using octafluorocyclobutane as a precursor, it is mixed with oxygen at a volume ratio of 1:4, and plasma-enhanced chemical vapor deposition (PECVD) is used at a reaction pressure of 50 Pa and under the action of 100 W radio frequency power plasma to decompose the precursor and interact with oxygen free radicals, and polymerized and deposited on the surface of a hydrophobic silicone plate for 10 min to obtain a hydrophilic coating of fluorocarbon polymer with a micro-nano rough structure.

[0053] Furthermore, before deposition, the surface of the hydrophobic silica gel plate is first cleaned and dried to obtain a pretreated hydrophobic silica gel plate, which is then transferred to the vacuum reaction chamber of PECVD. Oxygen is introduced and the plasma source is started. At a reaction pressure of 40 Pa, the silica gel surface is activated for 2 minutes by a short discharge at a power of 100 W to enhance its surface activity and adhesion, resulting in an activated hydrophobic silica gel plate. Subsequent deposition is then carried out on the surface of the activated hydrophobic silica gel plate.

[0054] The technical effects of the present invention will be described below with reference to specific embodiments.

[0055] Example A coreless silicone-based flexible heat spreader, such as Figure 1 As shown, it includes a superhydrophilic evaporation end silicone plate 1, a silicone support structure 2, a liquid injection tube 3, and a superhydrophobic condensation end silicone plate 4 arranged vertically from bottom to top; the silicone support structure 2 is located in the closed cavity formed by the superhydrophilic evaporation end silicone plate 1 and the superhydrophobic condensation end silicone plate 4, and the inner walls of the superhydrophilic evaporation end silicone plate 1 and the superhydrophobic condensation end silicone plate 4 are respectively connected to the silicone support structure 2 by siloxane bonds.

[0056] The preparation method of the above-mentioned coreless silicone-based flexible heat spreader includes the following steps: S1, Preparation of modified conductive filler: Spherical alumina with an average particle size of 15 μm and plate-like boron nitride with an average particle size of 10 μm were dried in a forced-air drying oven at 110℃ for 4 h to remove adsorbed water; 1.64 g of γ-aminopropyltriethoxysilane (KH-550) was added to an ethanol solution and magnetically stirred for 30 min to form an ethanol solution of KH-550 with a concentration of 1.5 wt.%; 1 g of deionized water and 0.16 g of acetic acid were added to the KH-550 ethanol solution to adjust the pH to 5, and the solution was magnetically stirred for 30 min. After n, the KH-550 hydrolysate was obtained by ultrasonication in a water bath at 40℃ for 10 min. The dried thermally conductive filler (alumina to boron nitride weight ratio of 95:5) was slowly added to the KH-550 hydrolysate in batches. After magnetic stirring for 30 min, the solution was ultrasonicated in a water bath at 60℃ for 1 h to obtain a modified suspension. The modified suspension was filtered, and the filter cake was washed three times with anhydrous ethanol to remove residual silane coupling agent. Finally, the filter cake was dried in a forced-air drying oven at 110℃ for 8 h. After grinding, the modified conductive filler was obtained and stored in a sealed container.

[0057] S2, Preparation of superhydrophilic evaporation end silicone plate 1: The superhydrophilic evaporation end silicone plate 1 is composed of a hydrophobic silicone plate and a hydrophilic coating.

[0058] S21, Preparation of hydrophobic silica gel plate: Take 75g of first addition-type silica gel, add 10g of low-viscosity silicone oil, and magnetically stir for 10min to reduce the overall viscosity, facilitating the subsequent dispersion of modified conductive filler, to obtain a mixture; S1 modified conductive filler (100g) is slowly added to the above mixture in four batches, 25g per batch, and mechanically stirred at 500rpm for preliminary mixing, then transferred to a planetary vacuum mixer and stirred at a vacuum of 5pa for 15min until the mixture is uniform and free of obvious particles, to obtain a colloidal solution; Add the colloidal solution... 75g of second addition-type silicone was added to the liquid and stirred in a planetary vacuum mixer at a vacuum of 5pa for 15 minutes until the mixture was uniform and there were no visible bubbles in the colloid. The mixed colloid was then injected into a flat vulcanizing mold preheated to 60°C. After 5 minutes of pre-curing, a pressure of 10MPa was applied and the temperature was increased to 100°C in steps at 10°C / min. The mold was then held under pressure and cured for 1 hour. After that, the mold was cooled to 60°C and demolded. The resulting sample was then post-cured in an oven at 100°C for 2 hours to finally obtain a dense and flat hydrophobic silicone sheet.

[0059] S22, Preparation of hydrophilic coating: First, the hydrophobic silica gel plate prepared in S21 is ultrasonically cleaned in anhydrous ethanol for 10 minutes to remove contaminants, followed by vacuum drying to ensure surface cleanliness and dryness, resulting in a pretreated hydrophobic silica gel plate. Next, the pretreated hydrophobic silica gel plate is transferred into the vacuum reaction chamber of PECVD, oxygen is introduced and the plasma source is started. At a reaction pressure of 40 Pa, the silica gel surface is activated for 2 minutes with a short discharge of 100 W to enhance its surface activity and adhesion, resulting in an activated hydrophobic silica gel plate with enhanced surface activity and adhesion. The reaction gas was switched to a mixture of octafluorocyclobutane (C4F8) and oxygen. Using octafluorocyclobutane as a precursor, it was mixed with oxygen at a volume ratio of 1:4. Plasma-enhanced chemical vapor deposition (PECVD) was performed at a reaction pressure of 50 Pa under 100 W RF power plasma. This caused the precursor to decompose and interact with oxygen free radicals, resulting in polymerization deposition on a hydrophobic silica gel plate surface for 10 min. Then, in the plasma environment, the octafluorocyclobutane precursor was decomposed and interacted with oxygen free radicals, resulting in polymerization deposition of a fluorocarbon polymer film with embedded hydrophilic functional groups on the activated hydrophobic silica gel plate surface. After deposition, the sample was cooled under a vacuum of 5 Pa and removed, yielding a superhydrophilic evaporation-end silica gel plate 1. Figure 2 and Figure 3 As shown, the dimensions of the superhydrophilic evaporation end silica gel plate 1 are... l 1× l 2× h 1, length is l 1 = 120mm, width is l 2 = 120mm, overall height is h 1 = 0.2 mm.

[0060] S3, Preparation of superhydrophobic condenser end silicone plate 4: Following the same preparation process as step S21 above, the superhydrophobic condenser end silicone plate 4 is obtained, as follows... Figure 6 and Figure 7 As shown, the dimensions of the superhydrophobic condenser end silicone plate 4 are... l 3× l 4× h 4, length is l 3 = 120mm, width is l 4 = 120mm, overall height is h 4 = 0.3 mm).

[0061] S4, Assembly of the vapor chamber: A cover plate with pre-set micropillar array holes is placed on the surface of the superhydrophilic evaporation end silicone plate 1 as a temporary mold. Silicone sealant is precisely injected into the pores of the mold using a precision dispensing device. Then, the superhydrophobic condensation end silicone plate 4 and the superhydrophilic evaporation end silicone plate 1 with uncured micropillars are aligned and stacked. A constant pressure of 20 kPa is applied to ensure full contact and bonding at the interface. Finally, it is cured at room temperature for 3 hours. After curing, a silicone support structure 2 formed by n support pillars is obtained, as shown below. Figure 4 and Figure 5 As shown, the dimensions of the support columns in the silicone support structure are... d 1× h 2, outer diameter is d 1 = 4mm, overall height is h 2 = 0.2 mm, the spacing between two adjacent support columns is w 1=6mm, remove the cover plate. Apply silicone sealant to the edges of the mating surfaces of the upper and lower cavities, and pre-embed a copper injection tube 3 between the superhydrophilic evaporation end silicone plate 1 and the superhydrophobic condensation end silicone plate 4, as shown. Figure 4 and Figure 5 As shown, the dimensions of the injection tube are... d 2× d 3× h 3, outer diameter is d 2 = 0.8 mm, inner diameter is d 3 = 0.2 mm, overall height is h =3=20mm. The entire component is placed in the mold, and the bolts are tightened to apply constant pressure. It is cured at room temperature for 1 day to obtain an unfilled vapor chamber preform. The filling process is carried out on a vacuum injection system. The vacuum pump is turned on to pre-evacuate the system. Then the vapor chamber preform is connected to the system so that the pressure inside the vapor chamber reaches 2pa. Then, deionized water after degassing is poured into the vapor chamber to obtain a coreless silicone-based flexible vapor chamber.

[0062] This invention, based on a highly thermally conductive modified silicone cavity, an internal wettability gradient design, and a flexible support structure, presents a coreless silicone-based flexible ultrathin vapor chamber. On one hand, KH550 is used to surface-modify a conductive filler composed of a mixture of spherical alumina and plate-like boron nitride. Through the molecular bridging effect and steric hindrance effect constructed between the conductive filler and the silicone matrix by a silane coupling agent, the conductive filler is uniformly dispersed at the micron level within the silicone matrix, forming a high-density three-dimensional thermally conductive network. This results in excellent thermal conductivity of the silicone cavity material, increasing its thermal conductivity to 1.1 W / m·K, significantly reducing the cavity's thermal resistance, and promoting rapid heat transfer from the heat source to the evaporation meniscus of the evaporation capillary wick. On the other hand, this invention abandons the traditional rigid metal capillary core and instead utilizes the inherent properties of silicone material combined with surface modification to construct a wettability gradient-driven circulation within the cavity. At the condensation end, the inherent hydrophobicity of silicone directly promotes the rapid shedding and reflux of condensate in droplet form. At the evaporation end, a C4F8 superhydrophilic coating is deposited on the inner wall of the cavity using PECVD technology, enabling rapid spreading of the working fluid and efficient thin-film evaporation. This combination of superhydrophilic and superhydrophobic wettability creates a powerful self-driving liquid capability within the cavity, making it possible to compress the vapor chamber height to below 0.3 mm. At this ultra-thin scale, the reduced droplet radius at the condensation end leads to enhanced condensation heat transfer and a decrease in overall thermal resistance, exhibiting characteristics completely opposite to traditional cored vapor chambers. Specifically, the smaller the overall height of the coreless silicone-based flexible ultra-thin vapor chamber of this invention, the lower the thermal resistance; while the thermal resistance of traditional metal cored vapor chambers increases with decreasing thickness, achieving ultra-thin and lightweight vapor chamber design. In addition, to achieve low thermal resistance connection within the ultra-thin structure, the silicone support structure 2 uses a micro-pillar array formed by dotting silicone sealant of the same material as the cavity. After curing, the array is bonded to the upper and lower cavities of the condensing and evaporating ends, thus mechanically supporting the ultra-thin vapor channel while completely eliminating the contact thermal resistance between traditional multi-layer components and constructing an ultra-low thermal resistance heat transfer path from the evaporating end to the condensing end.

[0063] All components of this invention are made of flexible silicone-based material, without using any rigid metal core. The edges are not sealed with high-temperature welding, and are encapsulated through integrated silicone bonding. This allows the heat spreader to maintain stable sealing performance, temperature uniformity, and heat transfer performance even when subjected to complex deformations such as bending and twisting, demonstrating excellent repeatable flexibility and structural reliability.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A coreless silicone-based flexible heat spreader, characterized in that, It includes a superhydrophilic evaporation end silicone plate (1), a silicone support structure (2), and a superhydrophobic condensation end silicone plate (4) arranged sequentially along the thickness direction. The superhydrophilic evaporation end silica gel plate (1) is composed of a hydrophobic silica gel plate and a hydrophilic coating; the hydrophobic silica gel plate is prepared by a silica gel matrix and a thermally conductive filler. The silicone support structure (2) is an array of n support columns. One end of each of the n support columns is connected to the hydrophilic coating, and the other end is connected to the superhydrophobic condensing end silicone plate (4). A closed liquid-filled cavity is formed between the superhydrophobic evaporating end silicone plate (1) and the superhydrophobic condensing end silicone plate (4) through the silicone support structure (2). The superhydrophobic condenser end silicone plate (4) is made of the same material as the hydrophobic silicone plate.

2. The coreless silicone-based flexible heat spreader according to claim 1, characterized in that, The outer diameter of each support column is 2mm to 5mm, and the distance between two adjacent support columns is 6mm.

3. The coreless silicone-based flexible heat spreader according to claim 1, characterized in that, The height ratio of the superhydrophilic evaporation end silicone plate (1), the support column, and the superhydrophobic condensation end silicone plate (4) is 1:0.8 to 1.5:1.5; the length ratio of the superhydrophilic evaporation end silicone plate (1), the outer diameter of the support column, and the length ratio of the superhydrophobic condensation end silicone plate (4) is 60:0.1 to 0.25:60; the width ratio of the superhydrophilic evaporation end silicone plate (1), the outer diameter of the support column, and the width ratio of the superhydrophobic condensation end silicone plate (4) is 60:0.1 to 0.25:

60.

4. The coreless silicone-based flexible heat spreader according to claim 1, characterized in that, The closed liquid-filled cavity is provided with an injection port, and the injection port is connected to an injection pipe (3).

5. The coreless silicone-based flexible heat spreader according to claim 1, characterized in that, The contact angle of the hydrophilic coating is 1° to 3°.

6. The coreless silicone-based flexible heat spreader according to claim 5, characterized in that, The method for preparing the hydrophobic silica gel plate includes the following steps: A modified thermally conductive filler was obtained by modifying a mixture of alumina and boron nitride with γ-aminopropyltriethoxysilane. Using a first addition-type silicone and a second addition-type silicone as the silicone matrix, the first addition-type silicone is diluted with silicone oil and mixed with the modified thermally conductive filler to obtain a colloidal solution. The colloidal solution is then mixed with the second addition-type silicone, degassed, pre-cured at 60°C, and cured under pressure and temperature to obtain a hydrophobic silicone sheet.

7. The coreless silicone-based flexible heat spreader according to claim 6, characterized in that, The mass ratio of alumina to boron nitride is 19:1; the mass ratio of the first addition-cure silica gel, the modified filler, and the second addition-cure silica gel is 1:0.6 to 1:

1.

8. The coreless silicone-based flexible heat spreader according to claim 1, characterized in that, The hydrophilic coating is specifically formed by mixing octafluorocyclobutane as a precursor with oxygen and then, under the action of plasma, causing the precursor to decompose and interact with oxygen free radicals, and polymerizing and depositing on the surface of a hydrophobic silica gel plate to obtain a hydrophilic coating of fluorocarbon polymer with a micro-nano rough structure.

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