Aramid paper-based steam cavity and a preparation method thereof

Abstract

The application discloses a kind of steam cavity based on aramid paper and preparation method thereof, by the same aramid paper folding to form upper and lower substrate, except the folding edge, the rest of steam cavity edge is sealed by adhesive to form closed cavity;Cavity is provided with liquid-absorbing core layer and support channel structure;Working liquid is encapsulated in the cavity;The support channel structure is bonded with upper and lower substrate to support cavity, and a plurality of support structures made of aramid paper are formed and arranged radially in the center of the cavity to form a radial, forming an "eight" shaped steam flow path between support structures, to guide steam to converge to the center when heated and backflow along the inner wall after condensation, liquid-absorbing core is used to improve the backflow rate of working liquid, and realize in-plane uniform heating and heat diffusion.The application maintains good mechanical integrity and assembly compatibility.

Description

Technical Field

[0001] This invention belongs to the field of thermal management and phase change heat transfer technology, specifically relating to a thin vapor cavity with aramid paper as the matrix material and its preparation method, which is suitable for in-plane heat dissipation / heat dissipation of electronic devices, thermal management of lightweight structures, and application environments with requirements for electrical insulation. Background Technology

[0002] A vapor chamber is a passive thermal management device that utilizes the vaporization-condensation phase change of a working fluid within a sealed cavity to achieve rapid in-plane heat conduction and temperature uniformity. It typically consists of upper and lower shells, a liquid wicking layer (capillary structure), an internal support / flow channel structure, and a working fluid.

[0003] In existing technologies, steam chamber shells are mostly made of metal materials such as copper and stainless steel. Although metal steam chambers have high thermal conductivity and mature sintering / brazing processes, they have limitations in the following aspects: First, their high density and thickness limit are constrained by both manufacturing and strength requirements, making it difficult to balance a large heat dissipation area and a small thickness in lightweight or flexible load-bearing scenarios; Second, the outer shell is conductive, requiring an additional insulation layer when integrated near electromagnetically sensitive / high-voltage or weak-current systems, increasing thermal resistance and assembly complexity; Third, to prevent the upper plate from collapsing, ribs, point pillars, or sintered supports are often introduced, which can easily interfere with the steam channels and capillary reflux paths under large-area, thin-walled conditions, leading to decreased channel connectivity and uneven heating; Fourth, the equipment dependence and tolerance requirements of the vacuuming / filling process are high, resulting in high costs and timelines for small-batch customization.

[0004] In contrast, paper-based / fiber-based insulating materials (such as aramid paper) have advantages such as low density, high dielectric strength, heat resistance and stability, and the ability to be cut and folded into various shapes, providing a material basis for constructing lightweight, insulating vapor chambers. However, directly using paper-based materials also faces several engineering challenges: First, the out-of-plane stiffness of the paper-based shell is limited. Without proper internal support and flow guidance design, local sagging is likely to occur under vacuum and service loads, affecting the vapor-liquid phase pathway. Second, the wetting / penetration of porous materials by adhesives can easily cause blockage of capillary channels in the sealing area or the formation of micro-leakage, affecting vacuum maintenance and circulation stability. Third, if the liquid-absorbing core layer is fully bonded to the shell or sealing area, a "backflow dead zone" is easily formed at the boundary, reducing the in-plane heat homogenization capacity. Fourth, the dispersion of vacuum target value, working liquid type and filling ratio directly affects the foaming temperature, evaporation efficiency and the repeatability of condensation reflux. Summary of the Invention

[0005] The technical problem to be solved by this invention is to propose a lightweight, electrically insulating paper-based steam cavity structure with stable steam circulation capability, which takes into account out-of-plane support, steam channel connectivity and capillary reflux efficiency under the conditions of thinness and large area, so as to overcome the shortcomings of existing metal steam cavities, such as large mass, conductivity and complex integration, as well as paper-based cavities that are prone to collapse and have limited sealing / reflux.

[0006] The technical solution to achieve the purpose of this invention is as follows:

[0007] A steam chamber based on aramid paper is provided, comprising upper and lower substrates formed by folding the same sheet of aramid paper. The remaining portion of the steam chamber edge, except for the folded edges, is sealed with adhesive to form a closed cavity. A liquid-absorbing core layer and a support channel structure are provided inside the cavity. The working fluid is encapsulated within the cavity. The support channel structure is bonded to the upper and lower substrates to support the cavity and is composed of multiple support structures made of aramid paper, arranged radially around the center of the cavity. A figure-eight steam flow path is formed between the support structures to guide the steam to converge towards the center when heated and to flow back along the inner wall after condensation. The liquid-absorbing core is used to improve the return flow rate of the working fluid and to achieve in-plane heat homogenization and heat diffusion.

[0008] A method for preparing a steam cavity, comprising:

[0009] 1) Fold aramid paper to form upper and lower substrates, position the liquid-absorbing core layer and support structure, and bond the support channel structure to the upper and lower substrates to support the cavity. The liquid-absorbing core layer is fixed in the steam cavity by spot bonding. Except for the folded edge, the rest of the steam cavity edge is sealed with adhesive.

[0010] 2) Vacuum is drawn through the injection port, electronic working fluid is injected, and the injection port is sealed to form a closed cavity.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] First, the paper-based shell achieves low mass and electrical insulation, reducing the need for additional insulation layers and simplifying integration with electromagnetically sensitive / high-voltage systems. Second, the "∧-shaped" support and flow-guiding network provides out-of-plane support while guiding vapor convergence and return paths, improving channel connectivity and circulation under large-area conditions. Third, the spot adhesion and boundary recess design of the liquid-absorbing core layer avoids capillary blockage in the sealing area, improving return continuity. Fourth, standardized vacuum target values ​​and filling ratio parameters make the foaming temperature and condensation return more stable, facilitating batch reproduction. Fifth, folding and room-temperature adhesive sealing lower the process threshold, making it suitable for small-batch customization and rapid iteration.

[0013] Based on the above structure and parameters, the present invention can achieve large-area in-plane heat uniformity and heat diffusion under thin-film conditions, while maintaining good mechanical integrity and assembly compatibility.

[0014] Other features and advantages of the present invention will be further described in the detailed description section; any equivalent substitutions or improvements made without departing from the spirit and essence of the present invention should be included within the scope of protection of the present invention. Attached Figure Description

[0015] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort. The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the present invention.

[0016] Figure 1 This is a schematic diagram of the unfolded folded member and the liquid-absorbing core layer in a preferred embodiment of the present invention;

[0017] Figure 2 This is an assembly diagram of the device in a preferred embodiment of the present invention (with the cover open), and shows the cut position A-A;

[0018] Figure 3 This is a top view of the steam chamber in a preferred embodiment of the present invention;

[0019] Figure 4 This is a longitudinal section diagram of the steam chamber in a preferred embodiment of the present invention;

[0020] Figure 5 This is a detailed schematic diagram of the supporting channel unit (∧-shaped rib) in a preferred embodiment of the present invention;

[0021] Figure 6 This is a partial cross-sectional schematic diagram of the liquid-absorbing core layer attachment method in a preferred embodiment of the present invention;

[0022] Figure 7 This is a longitudinal sectional view of the working principle of the cavity in a preferred embodiment of the present invention;

[0023] Figure 8 This is a cross-sectional schematic diagram illustrating the working principle of the cavity in a preferred embodiment of the present invention.

[0024] In the diagram: 1-Upper substrate; 2-Lower substrate; 3-Folded edge; 4-Supporting through structure; 5-Sealing layer; 6-Injection port; 7-Suction core layer; 8-Working fluid; 9-Sealing film / tape; 10-Supporting surface Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, embodiments of the invention will be described in more detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Therefore, the detailed description of the embodiments of this invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention.

[0026] like Figures 1-3 As shown, this embodiment provides a thin vapor chamber based on aramid paper. The vapor chamber is formed by folding a single sheet of aramid paper along a central crease to form an upper substrate 1 and a lower substrate 2. The crease serves as a folded edge 3 on one side of the vapor chamber. The other three sides of the vapor chamber are sealed by bonding the upper substrate 1 and the lower substrate 2 with epoxy resin AB adhesive to form a sealing layer 5, thus constituting a sealed cavity. A liquid-absorbing core layer 7 and a supporting channel structure 4 are provided inside the cavity, and a liquid injection port 6 is provided to complete vacuuming and liquid filling. The working liquid 8 is encapsulated inside the cavity, preferably an electronic fluorinated liquid. This embodiment does not involve the structure and control of an external heat source, and external heat sources are not protected by this invention.

[0027] like Figure 3 and Figure 5 As shown, the support channel structure consists of multiple "∧"-shaped aramid paper sheets folded into "∧"-shaped support structures 4, preferably 4-10 sheets, arranged symmetrically in a radial pattern around the center of the cavity. The pointed ends of the support structures face the center of the cavity to provide support for the cavity and form a steam flow path under thin-walled conditions. The preferred height of the support structure is 6-7 mm; however, a height of 0.5-2.0 mm can also be used in scenarios with thickness limitations. The aramid paper sheet material has a thickness of 0.1-0.3 mm and can be formed as a single layer or in layers. The support structure uses rectangular paper strips, symmetrically cut along the middle of both long sides, with the cut distance being the same as the width of the upper and lower support surfaces 10. Four folds are made along the direction parallel to the long sides of the rectangular paper strip, i.e., perpendicular to the cut direction, forming the upper and lower support surfaces 10, creating a structure similar to a channel steel. Then, it is folded back against the slot along the cut direction, ultimately forming a "∧" shaped support structure, enhancing the out-of-plane support capability of the upper / lower substrates. The slots of adjacent support structures face each other, forming a figure-eight steam flow path.

[0028] like Figure 6As shown, the absorbent core layer 7 is selected from multilayer paper-based fiber layers, cotton fiber felt, or synthetic fiber felt; the upper and lower support surfaces 10 are fixed to the upper and lower inner walls of the cavity, i.e., the inner walls of the upper substrate 1 and the lower substrate 2, by linear / dot-shaped narrow strip adhesive bonding. To avoid the capillary channels being blocked by adhesive penetration, the diameter of the single dot adhesive is about 1-2 mm and the distance from the hole / slit is ≥2 mm; the outer edge of the absorbent core layer 7 is recessed from the three-sided sealing area by a distance ≥2-5 mm. Figure 1 The diagram shows a structure using multiple layers of paper-based fiber.

[0029] Key process points: The thickness of the upper and lower substrates is preferably 0.1-0.3mm; the sealing width on three sides is preferably 2-5mm; the support structure and the liquid absorption core are fixed by narrow strip or dot / line adhesive to prevent the formation of continuous sealing rings; the sealing area should avoid excessive wetting of the capillary structure by the adhesive.

[0030] Vacuum and filling range: Vacuum is drawn to ≤1000Pa through injection port 6; the working fluid is preferably an electronic fluorinated liquid (e.g., Novec 7100), with a filling volume fraction of 30%-40%. This section only lists the range parameters and does not limit the specific operating procedures.

[0031] Reliability and sealing (optional): After the injection port 6 is sealed with AB glue, it can be covered with a sealing film / paper tape 9 to form a secondary seal, so as to improve the vacuum holding capacity; the finished product is tested for leaks and reliability by immersion in water to observe the bubble method or static vacuum holding method.

[0032] One of the structural equivalent variations is that on a larger substrate (e.g., 200mm×200mm), the number of support sheets can be increased to 8-10, and they can be arranged in a circumferential or grid pattern. The support structure can be achieved by bonding 0.1-0.3mm aramid paper layers to obtain a target height of 0.5-2.0mm, so as to balance out-of-plane support and channel connectivity.

[0033] The second structural equivalent variation is that the liquid-absorbing core layer can be arranged in different zones with different apparent porosities and / or number of layers, so that the evaporation zone has a higher foaming capacity and the condensation zone has a higher reflux volume; if necessary, it can be attached to the support plate locally to enhance the continuity of the reflux channel along the wall.

[0034] Structural equivalent variation three: such as Figure 7 As shown, a reinforcing strip with a width of 1-2mm can be added to the outside of the sealing edge to improve the edge's shear / peel strength and adapt to transportation and assembly conditions; the reinforcing strip material can be paper tape, film or other compatible insulating materials.

[0035] The location and shape of the injection port can be selected and reinforced according to process conditions, such as at the end or side; secondary sealing is an optional solution.

[0036] Working principle explanation: Figures 7-8As shown, under the action of an external heat source, the working liquid 8 in the evaporation zone vaporizes. The vapor rapidly diffuses to the condensation surface along the "V"-shaped vapor flow path formed between the "∧"-shaped support structures 4 and the cavity space, releasing latent heat. The condensate flows back to the evaporation zone along the wall under the capillary action of the liquid-absorbing core layer 7 and the inner wall, forming a vapor-liquid closed-loop circulation, achieving large-area in-plane heat equalization and heat diffusion. After the heat source is removed, the circulation gradually weakens until it stops.

[0037] In operation, the local heat source causes the electronic fluorinated liquid to vaporize rapidly. The vapor preferentially condenses on the inner wall of the upper substrate and achieves capillary reflux along the side of the "∧" shaped channel and the inner wall of the shell, forming a closed-loop vapor-liquid circulation. This enables rapid diffusion of in-plane heat and temperature uniformity in a thin structure.

[0038] General statement: Unless otherwise stated, the above dimensions, materials and process parameters are preferred ranges; any equivalent substitutions made to the support structure hole type, pitch, arrangement, shell thickness, sealing width and injection port position without departing from the spirit and substance of the present invention are included within the protection scope of the present invention.

[0039] Example 1: Method for preparing a steam chamber

[0040] Folding and Positioning: Commercially available aramid paper is selected, cut, and folded along the centerline to form upper and lower substrates, completing the positioning and temporary fixation of the "∧" shaped support structure 4 and the liquid-absorbing core 7 (dot / line adhesive, single dot diameter approximately 1-2 mm, ≥2 mm away from holes / slits; the outer edge of the liquid-absorbing core protrudes ≥2-5 mm from the sealing area). The preferred dimensions of the cavity are 150 mm long and 100 mm wide, with a substrate thickness of 0.1 mm, and the material is commercially available aramid paper; the liquid-absorbing core layer 7 is attached to the inner surface of the substrate, preferably a three-layer paper-based fiber layer, and fixed to the inner surface of the aramid paper with a small amount of epoxy resin AB adhesive to ensure unobstructed capillary channels. The support structure is used to form a through-flow gap between the upper and lower aramid paper substrates, allowing the vaporized working liquid to quickly diffuse to all parts of the cavity and release latent heat on the condensation surface. The combination of the liquid-absorbing core layer and the porous structure of the aramid paper enhances the liquid return rate.

[0041] Three-sided sealing: Except for the folded edge 3, the other three sides of the steam chamber are coated with epoxy resin AB adhesive within a width of 2-5mm and then closed and cured to form a sealed cavity, while reserving a liquid injection port 6. The substrate thickness is preferably 0.1-0.3mm.

[0042] Vacuuming and filling: Vacuum is drawn to ≤1000Pa through the injection port 6, and then electronic fluorinated liquid is injected as working liquid 8, with a volume fraction of 30-40%, and the injection port is sealed to complete the seal (a thin film / paper tape can be attached to the outside to form a secondary seal to improve vacuum retention).

[0043] Leak detection and warehousing: Leak detection and reliability verification are carried out using the water immersion observation bubble method or the static vacuum holding method; after passing the test, the product is put into storage or assembled.

[0044] Example 2: Equivalent Variations in Structure and Parameters

[0045] The support channel structure can be increased to 8-10 pieces on a large substrate surface of 200mm×200mm, and is arranged in a circumferential / grid manner; the height of the support piece can be selected between 0.5-2.0mm according to the load and thickness requirements, or the target height can be obtained by laminating 0.1-0.3mm aramid paper.

[0046] The liquid-absorbing core layer can be configured with different porosities or number of layers according to the region to balance foaming ability and reflux efficiency.

[0047] A reinforcing strip with a width of 1-2 mm can be added to the outer side of the sealing edge to improve the edge's shear / peel strength; the position and shape of the injection port can be selected and reinforced at the end or side according to process conditions. The above modifications do not constitute a limitation of the claims.

[0048] Under the influence of a local heat source, bubbling occurs in the evaporation zone—steam diffuses along the channel—heat is released from the condensation surface—condensate flows back along the wall and the wicking core, forming a closed-loop vapor-liquid cycle, achieving in-surface heat equalization and thermal diffusion; the cycle weakens and eventually stops after the heat source is removed. This embodiment is used to explain the mechanism and does not limit the structure.

Claims

1. A steam chamber based on aramid paper, characterized in that, The upper and lower substrates are formed by folding the same sheet of aramid paper. Except for the folded edges, the remaining part of the steam chamber edge is sealed with adhesive to form a closed cavity. A liquid-absorbing core layer and a support channel structure are set inside the cavity. The working liquid is encapsulated in the cavity. The support channel structure is bonded to the upper and lower substrates to support the cavity. It is composed of multiple support structures made of aramid paper and arranged radially around the center of the cavity. The support structures form a figure-eight steam flow path to guide the steam to converge towards the center when heated and to flow back along the inner wall after condensation. The liquid-absorbing core is used to improve the return flow rate of the working liquid and to achieve in-plane heat homogenization and heat diffusion.

2. The steam chamber according to claim 1, characterized in that, The support structure is ∧-shaped, with support surfaces at both the top and bottom for bonding with the upper and lower substrates.

3. The steam chamber according to claim 2, characterized in that, The support structure is made by symmetrically cutting a distance along the middle of the two long sides of a rectangular paper strip. The cutting distance is the same as the width of the upper and lower support surfaces of the support structure. Four folds are made along the direction parallel to the long side of the rectangular paper strip to form the upper and lower support surfaces of the support structure. The paper strip is folded along the direction of the cut and back to the groove direction to finally form a ∧-shaped support structure.

4. The steam chamber according to claim 1, characterized in that, The absorbent core layer is selected from multi-layer paper-based fiber layers, cotton fiber felt, or synthetic fiber felt, and is fixed to the inner wall of the cavity by spot / line bonding, with a gap between its edge and the sealing area.

5. The steam chamber according to claim 1, characterized in that, The working fluid is an electronic fluorinated liquid, and the filling ratio is 30%-40% of the effective volume of the cavity.

6. The steam chamber according to claim 1, characterized in that, It is equipped with a liquid injection port for vacuuming and liquid filling.

7. The steam chamber according to claim 6, characterized in that, After the injection port is sealed, a sealing layer is applied to form a secondary seal.

8. The method for preparing a steam chamber according to any one of claims 1-7, characterized in that, include: 1) Fold aramid paper to form upper and lower substrates, position the liquid-absorbing core layer and support structure, and bond the support channel structure to the upper and lower substrates to support the cavity. The liquid-absorbing core layer is fixed in the steam cavity by spot bonding. Except for the folded edge, the rest of the steam cavity edge is sealed with adhesive. 2) Vacuum is drawn through the injection port, electronic working fluid is injected, and the injection port is sealed to form a closed cavity.

9. The method for preparing a steam chamber according to claim 8, characterized in that, The liquid-absorbing core layer is fixed by spot bonding, with a diameter of 1-2 mm and a gap between it and the holes and slits.

10. The steam chamber according to any one of claims 1-7, characterized in that, Applications of heat dissipation and thermal management in radomes, adjustable electromagnetic shielding devices, or smart antenna systems.

Images