Phase-change composite heat-conducting gasket with vertical corrugated channels and preparation method of phase-change composite heat-conducting gasket

Abstract

The invention relates to the technical field of heat dissipation, in particular to a phase-change composite heat-conducting gasket with vertical corrugated channels and a preparation method of the phase-change composite heat-conducting gasket. The invention aims to solve the problems of high hardness, poor compression compliance and large interface contact thermal resistance of the existing vertical orientation carbon-based heat conduction material and improve the actual heat dissipation efficiency of the thermal interface material in a high-power electronic device. According to the main scheme, high-heat-conductivity graphene paper or graphite paper serves as a framework base material, a composite heat conduction core with vertically-arranged bent heat conduction channels inside is constructed, and a phase-change material skin layer is combined on the surface of the composite heat conduction core. Rigid compression of the material can be converted into geometric bending deformation by utilizing an internal vertically-oriented micro-ripple structure (the section can be sine waves, sawtooth waves, trapezoidal waves or asymmetric ripples and the like), so that the compression resilience and the stress buffering capacity of the material are effectively improved; and meanwhile, the interface contact thermal resistance is effectively reduced by virtue of the self-adaptive wetting characteristic of the phase change material layer on the surface at the working temperature.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation technology, and in particular to a phase change composite thermal conductive pad with vertical corrugated channels and its preparation method, which is suitable for thermal interface management of high-power electronic devices. Background Technology

[0002] With the rapid development of 5G, AI, HPC, and new energy vehicle electronics, the integration and operating frequency of electronic components are constantly increasing, leading to a sharp rise in power density. In modern high-performance chips and power modules, local heat flux density often exceeds 100 W / cm², and even higher under some transient conditions. Heat dissipation has become a core bottleneck restricting device performance, operational reliability, and lifespan. To quickly and efficiently conduct the high heat generated by the chip to the external heat sink, thermal interface materials (TIMs) filling the gap between the chip and the heat sink play a crucial bridging role. However, traditional polymer-based composite materials (such as thermal grease and ordinary thermal pads) are limited by the extremely low intrinsic thermal conductivity of the polymer matrix, and their overall thermal conductivity is usually low (generally less than 5 W / m·K), making it difficult to meet the rapid heat dissipation requirements of high power density scenarios. To overcome this limitation, constructing vertical heat conduction channels using carbon-based materials such as graphite and graphene, which have extremely high axial thermal conductivity (theoretical values ​​can reach 500-1500 W / m·K), has become a research hotspot and mainstream technical route in the field of thermal management.

[0003] Despite the clear direction, existing vertically oriented carbon-based thermal conductive materials still face numerous challenges in practical applications. US patent application US20240407135A1 discloses a method for preparing a thermal pad based on laminated graphene films. This method involves stacking, bonding, and curing flat graphene films, then cutting them vertically to obtain vertically oriented graphene thermal conductive channels. While this technology utilizes graphene's high in-plane thermal conductivity to address the heat transfer problem in the thickness direction, the graphene layers inside the prepared pad are arranged in a straight line, resembling a dense array of rigid pillars. This structure has an extremely high compressive modulus in the thickness direction and poor resilience, making it difficult to adapt to the deformation tolerances between the chip and the heat sink during actual installation. This results in insufficient effective contact area and actual thermal resistance far exceeding the theoretical value.

[0004] To improve the flexibility of carbon-based materials, Chinese patent CN203675528U disclosed a graphite film heat-conducting fin with a corrugated structure, using processes such as mold pressing to impart corrugated deformation capability to buffer stress. However, such technologies typically use the corrugated graphite film directly as a two-dimensional planar heat dissipation film or buffer layer, without involving its use as an internal framework for multi-layer stacking, vacuum infusion, and vertical cutting. Existing technologies fail to transform the "corrugated structure" into a "micro-spring array" within a three-dimensional solid pad, thus failing to solve the compression and springback problem of vertical heat-conducting pads under large thicknesses.

[0005] Furthermore, to address the issue of high interfacial thermal resistance on hard surfaces, the industry commonly employs phase change materials (PCMs) for filling. For example, European patent EP1067164A1 discloses a typical PCM thermal interface material that utilizes the phase change flowability of the material at operating temperatures to fill interfacial voids. However, existing processes often mix PCMs with thermally conductive fillers and use them directly, or use them as a whole as a matrix filler. Since PCMs themselves have low thermal conductivity (typically less than 1-3 W / m·K), introducing large quantities can severely degrade the overall thermal conductivity of the gasket; if they are only coated onto the surface of a vertical graphite gasket, traditional coating processes struggle to precisely control the micron-level ultrathin thickness, which can easily lead to increased thermal resistance or pump-out effects during thermal cycling.

[0006] In summary, current technologies have not yet been able to simultaneously resolve the contradiction between "high bulk thermal conductivity," "high compression resilience," and "low interfacial contact thermal resistance" in vertical thermal pads. Therefore, a new fabrication process is urgently needed to construct composite thermal pads that combine vertical spring channels with a surface adaptive phase change layer. Summary of the Invention

[0007] The purpose of this invention is to provide a phase change composite thermal pad with vertical corrugated channels and its preparation method. Through structural design and process innovation, this invention aims to solve the problems of "high hardness" and "poor interface adhesion" in traditional graphite thermal pads.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] This invention provides a phase change composite thermal pad with vertical corrugated channels, comprising:

[0010] The thermally conductive framework is composed of multiple layers of corrugated graphene paper or graphite paper. Each layer of corrugated graphene paper or graphite paper has continuous peaks and troughs arranged periodically along the same extension direction. The peaks of adjacent layers are aligned with each other, and the troughs are aligned with each other, so as to form a continuous curved thermally conductive channel in the thickness direction of the pad. The shape of the curved thermally conductive channel is at least one of S-shape, serpentine shape, zigzag shape or spring shape.

[0011] The polymer matrix is ​​filled in the interlayer gaps of the multilayer corrugated graphene paper or graphite paper.

[0012] A phase change material skin layer is disposed on at least one surface of the thermal pad, with a thickness of 20 μm to 100 μm.

[0013] In the above scheme, the corrugated graphene paper or graphite paper has a corrugated cross section that is at least one of sine wave, sawtooth wave, Ω-shaped, trapezoidal wave or asymmetric corrugation.

[0014] In the above scheme, the polymer matrix is ​​at least one of thermally conductive silicone gel, polyurethane, aliphatic epoxy resin or acrylic resin.

[0015] In the above scheme, the phase change material skin layer includes a phase change material and a micro / nano framework material, wherein the micro / nano framework material is at least one of nanofiber mesh and boron nitride nanosheets; or when the phase change material is a low melting point metal alloy, the surface of the thermal pad is provided with a copper wetting layer.

[0016] The present invention also provides a method for preparing the phase change composite thermal pad, comprising the following steps:

[0017] Step 1, Texture Forming: High thermal conductivity graphene paper or graphite paper is plastically processed to form a corrugated sheet with continuous peaks and troughs along the same extension direction;

[0018] Step 2, Stacking and Mold Assembly: Multiple corrugated sheets are stacked in a manner with the corrugation extension direction consistent and the crests and troughs aligned, and then inserted into a mold cavity with a venting structure.

[0019] Step 3, Vacuum Impregnation: Add uncured polymer precursor to the mold cavity, evacuate to remove interlayer air, restore normal pressure or pressurize to fill the interlayer gaps with the precursor;

[0020] Step 4, Curing and Vertical Cutting: After curing, cut along a direction perpendicular to the plane of the sheet stack to obtain the thermal pad core;

[0021] Step 5, end face treatment: Perform plasma etching on the cut end face of the thermal pad core to remove polymer residue and expose the end of the thermal skeleton;

[0022] Step 6: Formation of surface phase change layer: The thermal pad core is clamped by a gap control fixture containing precision gaskets. Molten phase change material is impregnated on the surface in a vacuum environment. After cooling, a phase change material skin layer with a thickness of 20μm to 100μm is formed.

[0023] In the above scheme, in step 3, the polymer precursor is at least one of addition-type thermally conductive silicone gel, polyurethane, aliphatic epoxy resin or acrylic resin, and its viscosity during vacuum impregnation is less than 1000 mPa·s.

[0024] In the above scheme, in step 6, the gap control structure includes precision gaskets set on both sides of the heat-conducting pad core, an anti-stick isolation film is set on the outside of the precision gaskets, a rigid pressure plate is set on the anti-stick isolation film, and the precision gaskets are square hollow frame structures, so that a phase change material fills the gap between the heat-conducting pad core, the precision gaskets, and the anti-stick isolation film.

[0025] The thickness of the precision pad is set to be 20μm-100μm greater than the thickness of the thermal pad core, so as to precisely control the thickness of the formed phase change material skin layer.

[0026] In the above scheme, the corrugation period of the corrugated sheet in step 1 is 50μm to 2mm, and the amplitude is 10μm to 0.5mm.

[0027] In the above scheme, the vacuuming-repressurization cycle in step 3 is repeated 1 to 3 times; the viscosity of the polymer precursor during impregnation is preferably less than 1000 mPa·s.

[0028] The present invention has the following beneficial effects:

[0029] Significantly improve compressibility: By changing the "straight channel" to a "corrugated channel", the geometric bending deformation of graphite material is used to replace the compression of the material itself, which can theoretically greatly reduce the apparent modulus and provide excellent resilience similar to that of a spring.

[0030] Reduced interfacial thermal resistance: The PCM skin layer introduced on the surface can soften or liquefy at the operating temperature, automatically filling the micro-roughness of the interface; combined with the vacuum impregnation process, it ensures a dense bond between the PCM layer and the substrate.

[0031] High reliability in process and use: Both interlayer impregnation and surface phase change layer film formation adopt vacuum-assisted processes. Negative pressure degassing and differential pressure driven filling reduce the probability of bubble, void and local unwetted areas, which helps to maintain the continuity of vertical bending heat conduction channels and the stability of heat conduction paths. In addition, the thickness of the ultrathin phase change material skin layer formed by the confined gap is controllable, and it can be combined with composite phase change layer (micro-nano framework locking) or edge sealing structure design to suppress the lateral migration of phase change material in the liquefied state, reduce the risk of pumping out / loss, and improve long-term service stability. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the composite material manufacturing process;

[0033] Figure 2This is a schematic diagram of microwave texture forming;

[0034] Figure 3 This is a schematic diagram of stacking and vacuum impregnation.

[0035] Figure 4 Schematic diagram of the solidified block and the vertical cutting direction;

[0036] Figure 5 Schematic diagram of adsorption in the confined gaps of the surface PCM layer;

[0037] Figure 6 Final finished product cross-section conceptual diagram;

[0038] Figure 7 Comparison of stress distribution and average stress at the loading end section for corrugated structural element models with different aspect ratios under the same compressive displacement conditions;

[0039] Figure 8 Comparison of stress distribution and average stress at the loading end section for corrugated stacked overall models with different aspect ratios under the same compressive displacement conditions.

[0040] Figure 9 This is a schematic diagram of the gap control structure (it is worth noting that the thickness in the figure is not drawn strictly according to the size scale and is only used as a schematic reference).

[0041] Numbering on the map:

[0042] 1- Rigid pressure plate, 2- Anti-sticking isolation film, 3- Precision gasket, 4- Phase change material filling gaps, 5- Thermally conductive pad core. Detailed Implementation

[0043] The embodiments of the present invention will be described in detail below. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, any modifications or equivalent substitutions made to the present invention should be covered within the scope of the claims of the present invention.

[0044] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without these specific details.

[0045] This invention provides a method for preparing a phase change composite thermally conductive pad with vertical corrugated channels, comprising:

[0046] Step 1. Microwave Corrugation Forming: High thermal conductivity graphene paper or graphite paper is provided as a substrate, and it is plastically processed using microwave corrugation or asymmetric corrugation forming technology to form a corrugated sheet with continuous peaks and troughs along the same extension direction. As one possible implementation method, the specific details are as follows:

[0047] High thermal conductivity graphene paper or graphite paper undergoes microwave texturing treatment to give it a structurally elastic basis. The corrugated cross-section can be a sine wave, sawtooth wave, Ω-shaped, trapezoidal wave, asymmetric corrugation, or a combination thereof; the corrugation scale can be from micrometers to millimeters, for example, a period of 50 μm to 2 mm and an amplitude of 10 μm to 0.5 mm. The corrugation aspect ratio AR = amplitude / period can be defined to characterize geometric compliance, preferably 0.05 to 0.50.

[0048] In step 1, the microwave texture forming process is carried out by hot pressing with a toothed mold or rolling with micro-toothed rollers; the corrugated cross-section of the corrugated sheet is designed as a sine wave, sawtooth wave, Ω-shaped, trapezoidal wave, asymmetric corrugation, or a combination thereof. The corrugation period and amplitude can be selected in the range of micrometers to millimeters according to the application thickness and flexibility requirements. The aspect ratio AR = amplitude / period can be used to characterize geometric flexibility: the larger the AR, the lower the equivalent stiffness in the thickness direction, but the shape stability and the cutting forming window need to be comprehensively balanced. The corrugation period and amplitude of the corrugated structure can be selected in the range of micrometers to millimeters; preferably, the corrugation period is 50μm to 2mm, and the amplitude is 10μm to 0.5mm.

[0049] Step 2. Stacking and Mold Assembly: Multiple corrugated sheets processed in Step 1 are stacked in the same direction of corrugation extension. The stacked assembly is then placed into a mold that can fix the thickness and then into a mold cavity with a venting structure. As one possible implementation method, the details are as follows:

[0050] The corrugated paper is stacked and loaded into the mold. During the stacking process, the corrugation alignment accuracy can be controlled by means of positioning holes-positioning pins, edge limiting frames, alignment lines or optical alignment, so that the peaks and valleys of adjacent sheets correspond to each other. The alignment error is preferably controlled within 10% of the corrugation period to ensure the continuity and consistency of the heat conduction channel after vertical cutting.

[0051] Step 3. Vacuum impregnation of the skeleton layer: Uncured polymer precursor is added into the mold cavity, the mold is evacuated, the air between the sheet layers is discharged by negative pressure, and the polymer precursor is driven to fill the interlayer gaps of the corrugated sheet by the pressure difference when restoring normal pressure or pressurizing, thus constructing an elastic composite.

[0052] As one possible implementation, the polymer precursor is one or a mixture of addition-type thermally conductive silicone gel, polyurethane, aliphatic epoxy resin or acrylic resin, and its viscosity during vacuum impregnation is preferably less than 1000 mPa·s.

[0053] Step 4. Curing and Vertical Cutting: The mold filled with soft organic material is cured to form a composite block; then, the composite block is cut along a direction perpendicular to the stacking plane of the sheets to obtain a thermal pad core with corrugated thermal channels having S-shaped or spring-like bends inside. As one possible implementation, the details are as follows:

[0054] After curing, the material is cut vertically. Due to the corrugation of the base paper, the cut slices exhibit a continuous curved or zigzag / wave-like shape (e.g., S-shape, serpentine, or spring-like) in the thickness direction, forming a vertical elastic heat conduction path. Optionally, the cut surface is treated with decontamination and micro-substrate removal after cutting, such as low-power oxygen plasma cleaning / plasma etching, solvent wiping, or chemical polishing, to remove any polymer coating residue that may have been generated during the cutting process. This allows for moderate exposure of the graphite skeleton ends, thereby reducing the internal contact thermal resistance between the skeleton ends and the surface phase change layer and improving wetting.

[0055] Step 5. End face treatment after cutting: Perform plasma etching cleaning or equivalent decontamination treatment on the cut end face of the thermal pad core to remove polymer matrix coating residue generated during the cutting process, and to expose the thermal skeleton end (graphene / graphite skeleton end) to reduce the thermal resistance caused by surface organic matter and improve the subsequent phase change material wetting.

[0056] Step 6. Vacuum Impregnation of Surface Phase Change Layer: A release film is covered on the surface of the thermal pad core, and it is held in place in molten phase change material (PCM) using a tooling fixture with a gap control structure for vacuum impregnation. The phase change material fills the space defined by the gap control structure, and after cooling, a phase change material skin layer is formed on the surface of the thermal pad core. As one possible implementation, the details are as follows:

[0057] Using a confined gap tooling, molten phase change material (PCM) is adsorbed onto the surface of a gasket in a vacuum environment to form a skin layer with controllable thickness. To suppress pumping out and lateral leakage during thermal cycling, the PCM skin layer can optionally incorporate shape-stabilizing reinforcement schemes, such as using microencapsulated PCM, or introducing micro / nano frameworks / reinforcing phases (e.g., nanofiber networks, boron nitride nanosheets, etc.) into the PCM, and / or setting non-phase change polymer sealing edges around the gasket to form a dam structure.

[0058] As one possible implementation, the gap control structure includes a rigid pressure plate and a precision gasket disposed between the pressure plates. The thickness of the precision gasket is set to be 20μm-100μm greater than the thickness of the thermal pad core, so as to precisely control the thickness of the formed phase change material skin layer.

[0059] Example 1

[0060] Step 1: Microwave texture forming uses 40μm thick high thermal conductivity graphene paper as the substrate. It is placed in a precision toothed mold and pressed at 80℃ and 5MPa pressure. The mold teeth are designed as rounded-corner sine waves, with a ripple period of 100μm, an amplitude of 50μm, and an aspect ratio AR of 0.5. After demolding, the graphene paper exhibits a continuous, regular wavy structure.

[0061] The schematic diagram of the toothed mold is shown below. Figure 2 The manufacturing process is the same. This microwave texture forming mold is a precision pressing component made of high-hardness metal, mainly consisting of an upper mold and a lower mold that cooperate with each other. Its core feature is that the relative working surfaces of both molds adopt a continuous, parallel, and perfectly meshing rounded sinusoidal wave tooth structure. This smooth design without sharp corners can effectively avoid brittle fracture of high thermal conductivity graphite or graphene paper due to stress concentration under pressure. During operation, the flat two-dimensional graphite paper substrate is placed on the toothed surface of the lower mold. As the upper mold closes and presses vertically downwards under the set temperature and pressure, the graphite paper is forced to undergo conformal plastic deformation, and is finally pressed from a flat state into a three-dimensional wavy sheet with continuous peaks and troughs, thus successfully transforming the original two-dimensional high rigidity of the substrate into three-dimensional geometric flexibility with "micro-spring" characteristics.

[0062] Step 2: Stacking and Mold Assembly. Two hundred sheets of corrugated graphene paper are stacked in the same direction, aligning the peaks and troughs. The stack is then placed into a fixed-size mold and subsequently into a cavity with venting channels. Positioning holes / pins or edge limiting frames are used during the stacking process to improve corrugation alignment accuracy.

[0063] Step 3: Vacuum impregnation of the framework layer to prepare a two-component addition-type silica gel (initial viscosity after mixing: 800 mPa·s, mixing ratio: 1:1), injecting it into the mold until the stack is completely submerged. Place the mold in a vacuum chamber, evacuate to below 50 Pa and maintain for 15 minutes. After no more air bubbles escape, restore normal pressure and use the pressure difference to press the silica gel into the corrugated paper layers. Repeat the "vacuum-re-press" cycle twice.

[0064] Step 4: Curing and Vertical Cutting. After vacuum impregnation, the mold is placed in a forced-air drying oven and cured at 120℃ for 2 hours. After cooling and demolding, the composite block is obtained. Using a diamond wire cutter, slices are made along a direction perpendicular to the stacked plane of the graphene paper, with a slice thickness set to 1.5mm.

[0065] Step 5: Processing the cut end face. The thermal pad core obtained in Step 4 is placed in an RF plasma cleaner. Using an O2 / Ar mixed gas (volume ratio 1:1) as the working gas, the cut end face of the thermal pad core is processed with an RF power of 20W for 10s under a chamber pressure of 20-200 Pa to remove polymer matrix coating residue caused by mechanical cutting and to expose the graphene / graphite thermal skeleton end face appropriately. After the processing is completed, the surface PCM confined gap vacuum impregnation step is continued.

[0066] Step 6: Vacuum Impregnation of Surface Phase Change Layer: Prepare a paraffin-based phase change material with a melting point of 45℃ and heat it to melt. The thermal pad core is sandwiched between two layers of PET release film, with a glass plate on the outside. A 1.56mm thick steel gasket is placed between the glass plates (leaving a 60μm gap on both sides). The component is immersed in the molten liquid and vacuumed for 5 minutes. After cooling, the release film is peeled off to obtain a finished product with a uniform PCM skin layer on the surface. (The PCM is a paraffin-based phase change material with a small amount of micro / nano framework materials (such as boron nitride nanosheets, nanofiber networks, etc.) incorporated to improve dimensional stability; simultaneously, a non-phase change polymer can be used to seal the gasket edges to form a dam structure, reducing the risk of lateral leakage and pumping out during thermal cycling.)

[0067] To further illustrate the influence of the aspect ratio AR (amplitude / period) of the corrugated structure on the thickness-direction compliance of the thermal pad core, a simplified element model of the corrugated structure was established using the finite element method without limiting the specific material parameters. Quasi-static compression comparison analysis was then performed on different AR structures. A straight structure without corrugation (AR=0) was used as a comparative example, and two sets of corrugated structures (AR=0.25 and AR=0.5) were set up. Under the same boundary conditions, the same compressive displacement was applied, and stress distribution cloud diagrams were obtained (see...). Figure 7 Meanwhile, the average normal stress (N / m²) is extracted from the loading end section as a characterization of the equivalent stiffness: 1.2506 × 10⁻⁶ when AR = 0. 9 When AR=0.25, it is 5.0059×10 8 When AR=0.5, it is 3.4359×10. 8 The results show that, under the set conditions, as AR increases, the average normal stress at the loading end decreases significantly, and the structural deformation gradually shifts to be dominated by geometric bending deformation, thus reflecting a trend of decreasing equivalent stiffness in the thickness direction and increasing compliance. In the overall model of the multi-layer stacked structure, the average normal stress at the loading end (σ) is also extracted under the same compressive displacement boundary conditions. yy The results show that as AR increases, the average normal stress at the loading end increases from 5.0093 × 10⁻⁶. 8 Pa decreased to 1.7672 × 10 8Pa (AR=0.25) and 1.4391×10 8 Pa (AR=0.5) is consistent with the conclusion of the element model, indicating that increasing AR can reduce the equivalent stiffness in the thickness direction and improve compliance.

[0068] The thermal resistance of Example 1, measured according to ASTM 5470 standard, is 0.15 Kcm. 2 / W, the results indicate that the paraffin PCM skin layer effectively reduces interfacial contact thermal resistance and improves thermal conductivity.

[0069] Example 2

[0070] Step 1: Microwave texture forming uses 50μm thick high thermal conductivity graphene paper as the substrate. A toothed mold with an enlarged cycle is used for pressing at 80℃ and 5MPa pressure. The ripple period is set to 500μm and the amplitude to 80μm to obtain a flexible monomer with enhanced thermal conductivity.

[0071] Step 2: Stacking and Mold Assembly. 200 sheets of corrugated graphene paper are stacked in the same corrugation direction and placed into a mold identical to that in Example 1. Positioning holes / pins or edge limiting frames are provided during the stacking process to improve corrugation alignment accuracy.

[0072] Step 3: Vacuum impregnation of the skeleton layer with a low-viscosity polyurethane elastomer (initial viscosity 500 mPa·s) is injected into a mold to submerge the stack. The vacuum chamber is evacuated to below 50 Pa and maintained for 15 minutes, then restored to normal pressure, allowing the polyurethane precursor to completely fill the interlayer voids, providing higher mechanical support strength than silicone.

[0073] Step 4: Curing and Vertical Cutting. Place the mold in an 80℃ oven to cure for 4 hours. After demolding, use a diamond wire cutter to cut along the direction perpendicular to the stacking, setting the slice thickness to 1.5mm.

[0074] Step 5: The process of treating the cut end face is the same as in Example 1, but RF plasma is used to treat the cut end face to remove polymer residue and expose the end of the thermal skeleton appropriately.

[0075] Step 6: The vacuum impregnation process for the surface phase change layer is the same as in Example 1, using a confined gap tooling to form a paraffin-based phase change material skin layer on the surface.

[0076] According to ASTM 5470 standard, the thermal resistance of Example 2 is 0.11 Kcm. 2 / W, the results indicate that the paraffin PCM skin layer effectively reduces interfacial contact thermal resistance and improves thermal conductivity.

[0077] Example 3

[0078] Step 1: Microwave Texture Forming: Use ultra-thin graphene paper with a thickness of 15μm. Continuous forming is achieved using a micro-toothed roller pressing process, with the ripple period set to a very small 100μm and the amplitude to 20μm.

[0079] Step 2: Stacking and Mold Assembly: Stack 500 sheets of ultra-thin corrugated paper into the mold. Positioning holes / pins or edge limiting frames can be set during the stacking process to improve corrugation alignment accuracy.

[0080] Step 3: Vacuum impregnation of the skeleton layer: Inject low-viscosity silicone gel, and the vacuum impregnation process is the same as in Example 1.

[0081] Step 4: Curing and Vertical Cutting: After heat curing, set the cutting thickness to 0.5mm to suit the heat dissipation in the confined space of microelectronic devices.

[0082] Step 5: The process of treating the cut end face is the same as in Example 1, but RF plasma is used to treat the cut end face to remove polymer residue and expose the end of the thermal skeleton appropriately.

[0083] Step 6: Vacuum impregnation of the surface phase change layer: An indium-bismuth-tin low-melting-point alloy with a melting point of approximately 60℃ is selected as the phase change material. Before adsorption, the surface of the thermal pad core is first treated with magnetron sputtering copper plating to increase wettability. Then, the liquid alloy is adsorbed in a confined gap under vacuum. Afterward, it is taken out and placed to cool and solidify at room temperature. After cooling, the release film is peeled off to obtain a finished product with a uniform PCM skin layer on the surface.

[0084] According to ASTM 5470 standard, the thermal resistance of Example 3 is 0.06 Kcm. 2 / W, this result shows that the liquid metal PCM skin layer significantly reduces thermal resistance and further improves thermal conductivity.

Claims

1. A phase change composite thermal pad having a vertical wavy channel, characterized in that, The heat-conducting gasket comprises: a heat-conducting framework composed of multiple layers of corrugated graphene paper or graphite paper, each layer of corrugated graphene paper or graphite paper having continuous wave crests and troughs arranged periodically along the same extension direction, and the wave crests of adjacent layers being aligned with each other and the wave troughs of adjacent layers being aligned with each other, so that continuous curved heat-conducting channels are formed in the thickness direction of the gasket, the curved heat-conducting channels having at least one of an S shape, a snake shape, a broken line shape or a spring shape; a polymer matrix filled in the interlayer gaps of the multiple layers of corrugated graphene paper or graphite paper; and a phase-change material skin layer arranged on at least one surface of the heat-conducting gasket and having a thickness of 20 μm to 100 μm.

2. The phase change composite thermal pad of claim 1, wherein, The corrugated cross section of the corrugated graphene paper or graphite paper is at least one of a sine wave, a sawtooth wave, an omega shape, a trapezoidal wave or an asymmetric corrugation.

3. The phase change composite thermal pad of claim 1, wherein, The polymer matrix is at least one of a heat-conducting silicone gel, a polyurethane, an aliphatic epoxy resin or an acrylic resin.

4. The phase change composite thermal pad of claim 1, wherein, The phase-change material skin layer comprises a phase-change material and a micro-nano framework material, the micro-nano framework material being at least one of a nanofiber web or a boron nitride nanosheet; or when the phase-change material is a low-melting-point metal alloy, a copper wetting layer is arranged on the surface of the heat-conducting gasket.

5. The method for preparing the phase change composite thermal pad according to any one of claims 1-4, characterized in that, The method comprises the following steps: Step 1, corrugation forming: plastic processing of high-heat-conducting graphene paper or graphite paper to form a corrugated sheet having continuous wave crests and troughs along the same extension direction; Step 2, stacking and mold assembly: stacking multiple corrugated sheets in the same corrugation extension direction and aligning the wave crests and wave troughs of the corrugated sheets, and assembling the corrugated sheets into a mold cavity having an exhaust structure; Step 3, vacuum impregnation: adding an uncured polymer precursor into the mold cavity, evacuating the interlayer air, and recovering the normal pressure or pressurizing to make the precursor fill the interlayer gaps; Step 4, curing and vertical cutting: after curing, cutting in a direction perpendicular to the sheet stacking plane to obtain a heat-conducting gasket core; Step 5, end face treatment: plasma etching of the cutting end face of the heat-conducting gasket core to remove the polymer residue and expose the end of the heat-conducting framework; Step 6, formation of a surface phase-change layer: clamping the heat-conducting gasket core by a gap control tooling containing a precision gasket, immersing a molten phase-change material on the surface in a vacuum environment, and forming a phase-change material skin layer having a thickness of 20 μm to 100 μm after cooling.

6. The production method according to claim 5, wherein In Step 3, the polymer precursor is at least one of an addition-type heat-conducting silicone gel, a polyurethane, an aliphatic epoxy resin or an acrylic resin, and the viscosity of the polymer precursor is less than 1000 mPa·s when vacuum impregnation is performed.

7. The preparation method according to claim 5, characterized in that, In Step 6, the gap control structure comprises precision gaskets arranged on both sides of the heat-conducting gasket core, an anti-sticking separation film arranged outside the precision gaskets, and a rigid pressing plate arranged on the anti-sticking separation film, and the precision gaskets have a square hollow frame structure, so that a phase-change material filling gap is formed among the heat-conducting gasket core, the precision gaskets and the anti-sticking separation film. The thickness of the precision gaskets is set to be greater than the thickness of the heat-conducting gasket core by 20 μm to 100 μm, so as to accurately control the thickness of the formed phase-change material skin layer.

8. The production method according to claim 5, characterized by, In Step 1, the corrugation period of the corrugated sheet is 50 μm to 2 mm, and the amplitude is 10 μm to 0.5 mm.

9. The production method according to claim 5, characterized by, The vacuum-repressurization cycle described in Step 3 is repeated 1 to 3 times; the viscosity of the polymer precursor at the time of impregnation is less than 1000 mPa-s.

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