Heat-conducting composite phase change sheet and preparation method thereof

Abstract

The invention discloses a heat-conducting composite phase change sheet and a preparation method thereof, and relates to the technical field of energy devices. The heat-conducting composite phase change sheet is composed of a polymer matrix, a phase change material, a heat-conducting filler and a micro-nano convex-concave structure. The phase-change material and the heat-conducting filler are distributed in the sheet, and the micro-nano convex-concave structure is distributed on the surface of the sheet. The micro-nano convex-concave structure has an anchoring effect and is used for inducing the heat-conducting filler and the phase-change material to be accurately assembled in a target area and constructing a locally reinforced heat management unit; meanwhile, the micro-nano convex-concave structure can obviously increase the real contact area, reduce the interface thermal resistance between other parts and the sheet, optimize the heat conduction path and improve the heat conduction efficiency. An innovative solution is provided for efficient heat management of related energy devices, and the method has high engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of energy devices, and in particular to a thermally conductive composite phase-change sheet and a preparation method thereof. Background Art

[0002] With the deep integration and rapid iteration of 5G communication and artificial intelligence technologies, the application scenarios of semiconductor electronic components are accelerating to expand into diversified fields, and the problem of chip heat dissipation has become the core bottleneck restricting the performance improvement of electronic devices. Studies have shown that the combination of thermal conductive fillers and polymer matrix materials can produce composite materials with high thermal conductivity, which provides an effective way to solve the problem of chip thermal management. However, traditional thermal conductive composite materials only have a single thermal conductivity function and lack thermal energy storage characteristics, making it difficult to meet the needs of high-power electronic devices for dynamic regulation of temperature fields. Breaking through the technical bottleneck of thermal storage performance of thermal conductive composite materials has become an important prerequisite for expanding their application in smart electronic devices.

[0003] As a latent heat storage medium, solid-liquid phase change material (PCM) realizes directional absorption and release of heat through the solid-liquid phase change process, showing unique advantages in the field of semiconductor thermal management. However, the inherent low thermal conductivity and liquid leakage risk of solid-liquid PCM limit its engineering application. Breaking through the technical bottleneck of low thermal conductivity and liquid leakage of solid-liquid PCM is the core prerequisite for realizing its efficient thermal management function.

[0004] Among the methods to prevent liquid leakage of PCM, constructing a sealed container package is a relatively simple way. Common encapsulation strategies include core-shell structure-assisted microencapsulation, capillary force-induced porous encapsulation, and polymer matrix-supported encapsulation. Among them, polymer support systems (such as polyurethane, silicone rubber, polydimethylsiloxane, etc.) have become the most promising encapsulation forms for engineering applications due to their easy processing, interface compatibility, and mechanical adjustability. This system inhibits the liquid migration of PCM through physical restraint, while maintaining the flexibility of the material to adapt to complex interfaces. In response to the problem of low thermal conductivity of PCM, adding thermally conductive fillers (such as carbon fibers, carbon nanotubes, expanded graphite, etc.) is an effective solution. Thermally conductive fillers can enhance the thermal transport capacity of materials and significantly improve the thermal conductivity of PCM due to their excellent thermal conductivity.

[0005] When constructing a thermally conductive composite phase change material composed of polymer, PCM and thermally conductive filler as a thermal interface material, two key scientific issues need to be addressed: first, how to distribute the thermally conductive filler and phase change material inside the material to achieve efficient thermal management; second, how to minimize the interface thermal resistance when other components are connected to the material. Interface thermal resistance is a core factor affecting the working efficiency of the device, because it hinders the conduction of heat, resulting in heat accumulation, which not only reduces the thermal management efficiency, but also damages the device. Summary of the Invention

[0006] In view of the two major technical challenges of thermally conductive composite phase change materials, the present invention proposes a thermally conductive composite phase change sheet and a preparation method thereof. Its innovative design includes a dual synergistic mechanism: on the one hand, the anchoring effect of the micro-nano concave-convex structure induces the precise assembly of thermally conductive fillers and phase change materials in a preset area to construct a locally enhanced thermal management unit; on the other hand, the micro-nano concave-convex structure can increase the true contact area between other components and the sheet, synchronously optimize the overall heat conduction path, greatly improve the heat conduction efficiency, provide an innovative solution for the efficient thermal management of high-power integrated devices, and has high engineering application value.

[0007] The following technical solutions are specifically adopted:

[0008] A thermally conductive composite phase change sheet, characterized in that the thermally conductive composite phase change sheet includes a polymer matrix, thermally conductive fillers, phase change materials, and a micro-nano concave-convex structure;

[0009] The phase change material is distributed in the thermally conductive composite phase change sheet, and the phase change material is physically encapsulated by the polymer matrix to inhibit liquid leakage;

[0010] The thermally conductive fillers are distributed in the thermally conductive composite phase change sheet and form a thermally conductive network in the polymer matrix for transferring heat flow;

[0011] The micro-nano concave-convex structure is distributed on the surface of the thermally conductive composite phase change sheet;

[0012] The micro-nano concave-convex structure has an anchoring effect for inducing the precise assembly of thermally conductive fillers and phase change materials in the target area to construct a locally enhanced thermal management unit;

[0013] The micro-nano concave-convex structure can significantly increase the true contact area, reduce the interfacial thermal resistance between other components and the sheet, optimize the heat conduction path, and improve the heat conduction efficiency.

[0014] Preferably, the polymer matrix includes a flexible polymer matrix and a non-flexible polymer matrix;

[0015] The flexible polymer matrix includes one or more of ethylene-vinyl acetate copolymer (EVA), polydimethylsiloxane (PDMS), polyurethane (PU), silicone rubber (SR), polyolefin elastomer (POE), and styrene-butadiene-styrene (SBS);

[0016] The non-flexible polymer matrix includes one or more of polypropylene (PP), polyethylene (PE), epoxy resin (EP), polystyrene (PS), polyvinyl chloride (PVC), polycarbonate (PC), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), and polyamide (PA).

[0017] Preferably, the phase change material includes one or more of paraffin, polyethylene glycol, phase change polyols, and phase change polyacids;

[0018] Preferably, the total content of the phase change material is not less than 18 wt%.

[0019] Preferably, the types of the thermal conductive filler include at least one of carbon-based, ceramic-based, and metal-based fillers.

[0020] Preferably, the shape of the thermal conductive filler includes at least one of one-dimensional thermal conductive filler, two-dimensional thermal conductive filler, and three-dimensional thermal conductive filler; when multiple thermal conductive materials are selected, the scale of at least one thermal conductive filler is smaller than the micro-nano concave-convex structure, and at the same time, the scale of at least one thermal conductive filler is larger than the micro-nano concave-convex structure.

[0021] Preferably, the total content of the thermal conductive filler is 0 - 50 wt%.

[0022] Preferably, the thickness of the thermally conductive composite phase change sheet is 0.1 - 5 mm.

[0023] Preferably, the micro-nano concave-convex structure is at least distributed on one side surface of the sheet; when it is distributed on both side surfaces at the same time, the geometric parameters of the micro-nano concave-convex structure on each surface can be designed independently;

[0024] Preferably, the overall roughness of the micro-nano concave-convex structure is 0 - 500 μm, the height of the micro-nano concave-convex structure is 0 - 500 μm, the equivalent diameter of the micro-nano concave-convex structure is 0 - 500 μm, and the roughness of different regions can be set in a gradient according to the heat transfer requirements;

[0025] Preferably, the micro-nano concave-convex structure is at least one of the structures in the shape of a hemisphere, a triangular pyramid, a quadrangular pyramid, a cylinder, a cube, and a cuboid, and is distributed in an ordered array or randomly; when it is distributed in an ordered array, the distribution form of the micro-nano concave-convex structure covers but is not limited to square, rectangle, triangle, circle, hexagon, rhombus, and polygon.

[0026] A thermally conductive composite phase change sheet also includes its preparation method, which includes the following steps:

[0027] Step 1: Add the thermal conductive filler into the polymer matrix material, and use one or several of the centrifugal degassing machine and stirrer to obtain a homogeneous system of the thermal conductive filler and the polymer; then, add the phase change material into the homogeneous system of the thermal conductive filler and the polymer, and use one or several of the centrifugal degassing machine and stirrer to obtain a homogeneous system of the thermal conductive filler, the polymer and the phase change material;

[0028] Step 2: Place the homogeneous system of the polymer, the thermal conductive filler and the phase change material on a flat mold with microstructures, and after roller coating and rolling, perform constant temperature drying to obtain a thermally conductive composite phase change sheet;

[0029] Among them, in Step 2, the roller coating speed is 2-200 mm / s, the rolling speed is 2-200 mm / s, the rolling time is 1-5 min, and the rolling pressure is 0-5 MPa.

[0030] Before Step 1, it also includes necessary pretreatment steps for the polymer matrix, the thermal conductive filler and the phase change material. The pretreatment includes drying and other treatments for the polymer matrix and the thermal conductive filler, and preheating and liquefying treatment for the phase change material.

[0031] The present invention has the following beneficial effects:

[0032] For the thermally conductive composite phase change sheet involved in the present invention, physical encapsulation by the polymer matrix inhibits liquid leakage and realizes stable loading of the phase change material; the anchoring effect of the micro-nano concave-convex structure guides the distribution of the thermal conductive filler and the phase change material in the preset area, and constructs a locally strengthened thermal management unit; the micro-nano concave-convex structure is used to increase the true contact area and reduce the interface thermal resistance, providing a possibility for improving the service life of electronic components. Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of a thermally conductive composite phase change sheet in Example 1;

[0034] Figure 2 It is an SEM image of the PDMS / CFP / paraffin thermally conductive composite phase change sheet in Example 1;

[0035] Figure 3 It is an infrared curve of the PDMS / CFP / paraffin thermally conductive composite phase change sheet in Example 1;

[0036] Figure 4 It is an XRD curve of the PDMS / CFP / paraffin thermally conductive composite phase change sheet in Example 1;

[0037] Figure 5 It is a DSC curve of the PDMS / CFP / paraffin thermally conductive composite phase change sheet in Example 1;

[0038] Figure 6 For the thermal management effect of the PDMS / CFP / paraffin thermally conductive composite phase change sheet in Example 1;

[0039] Figure 7 For the leakage test results of the PDMS / CFP / paraffin thermally conductive composite phase change sheet in Example 1;

[0040] Figure 8 Schematic diagram of the structure of a thermally conductive composite phase change sheet in Example 2;

[0041] Figure 9 Schematic diagram of the structure of a thermally conductive composite phase change sheet in Example 3;

[0042] Figure 10 Schematic diagram of the structure of a thermally conductive composite phase change sheet in Example 4. Specific implementation manners

[0043] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0044] Example 1

[0045] As Figure 1 shown, a thermally conductive composite phase change sheet, the thermally conductive composite phase change sheet includes a polymer matrix material PDMS, a phase change material paraffin, fibrous high thermal conductivity carbon powder (CFP), and a micro-nano concave-convex structure. A preparation method of a thermally conductive composite phase change sheet includes the following steps:

[0046] Step 1: Manually premix 3.27 g of PDMS and 0.5 g of CFP, then put them into a planetary centrifugal vacuum stirring and degassing machine, mix at a speed of 1400 rpm for 15 min; then add 0.9 g of liquid paraffin preheated at 80 °C for 10 min, and put it into a planetary centrifugal vacuum stirring and degassing machine, mix at a speed of 1400 rpm for 15 min; subsequently, add 0.327 g of curing agent to the homogeneous system of PDMS, CFP, and paraffin, and mix at a speed of 1400 rpm for about 5 min. Finally, place the PDMS / CFP / paraffin homogeneous system in a vacuum oven at 45 °C for vacuum degassing, and keep the pressure for 30 min;

[0047] Step 2: Place the PDMS / CFP / paraffin homogeneous system on a flat mold with a surface roughness of 50 μm, and use a self-made roll coater to perform roll coating at a speed of 50 mm / s to obtain a PDMS / CFP / paraffin preformed material; Subsequently, adjust the distance between the roller and the mold to 0.4 mm, and roll back and forth at a speed of 50 mm / s for 2 min; Cure in an oven at 45 °C for 6 h to obtain a PDMS / CFP / paraffin thermally conductive composite phase change sheet with a thickness of 0.4 mm.

[0048] Observe the microscopic morphology of the PDMS / CFP / paraffin thermally conductive composite phase change sheet. As Figure 2 shown, CFP forms a dense network bundle in the PDMS matrix, indicating that local enhanced thermal management units have been constructed inside the sheet, providing an efficient heat conduction channel for heat conduction. A micro-nano multi-level concave-convex structure is formed on the upper surface of the sheet, and paraffin is distributed around the CFP network and at the micro-nano concave-convex structure. The formation of the micro-nano concave-convex structure and the distribution of paraffin inside it indicate that local enhanced thermal management units have been constructed on the surface of the sheet, providing a potential way to reduce the interfacial thermal resistance when the sheet contacts the outside, and is expected to improve the overall thermal management efficiency.

[0049] Detect the chemical structures of four samples: pure PDMS matrix, pure paraffin, pure CFP, and PDMS / CFP / paraffin thermally conductive composite phase change sheet. As Figure 3 shown, the FTIR results show that pure paraffin exhibits specific vibration peaks related to -CH2 (717, 1465, 2846 cm -1 ) and -CH3 (1372, 2914 cm -1 ), as well as vibration peaks related to -OH (1637, 3549 cm -1 ). Pure PDMS has characteristic peaks related to -CH3 (1411, 2960 cm -1 ), Si-CH3 (785, 1257 cm -1 ), Si-O-Si (1006 cm -1 ), and Si-OH (846, 866 cm -1 ). Pure CFP has no obvious characteristic peaks. The infrared spectrum of the PDMS / CFP / paraffin thermally conductive composite phase change sheet is basically the same as that of pure PDMS, and only characteristic peaks of paraffin appear at specific positions (2916 and 2847 cm -1 ). The results show that no chemical reaction occurs in the PDMS / CFP / paraffin thermally conductive composite phase change sheet.

[0050] As Figure 4 shown, the XRD pattern further indicates that compared with pure PDMS, pure CFP, and pure paraffin, no new diffraction peaks appear, indicating that only physical mixing occurs in this sheet.

[0051] Figure 5 It is the DSC curve of the thermally conductive composite phase change sheet. Comparing it with the DSC curves of pure paraffin, pure PDMS, and pure CFP, it can be seen that the performance parameters of the PDMS / CFP / paraffin thermally conductive composite phase change sheet are less than those of pure paraffin. The physical property parameters of the experimental samples are shown in the following table:

[0052] Table 1 is the table of physical property parameters of the experimental samples in Example 1:

[0053]

[0054] From the data in Table 1, it can be seen that the latent heat of fusion and solidification of the PDMS / CFP / paraffin thermally conductive composite phase change sheet are 16.78% and 16.51% of the latent heat of fusion and solidification of pure paraffin respectively. Compared with the theoretical value, the deviation ≤ 2.932 J / g.

[0055] Figure 6 It is the thermal management effect curve of the thermally conductive composite phase change sheet. It can be seen that when the PDMS / CFP / paraffin thermally conductive composite phase change sheet is used in combination with a radiator, the temperature of the heat source operating at 80 °C can be reduced to 46 °C, which is 5 °C lower than the temperature when only the radiator is working.

[0056] Figure 7 It is the leakage experiment result of the thermally conductive composite phase change sheet. The PDMS / CFP / paraffin thermally conductive composite phase change sheet is placed in an incubator at 80 °C, and the sample weight is measured every 1 h. The results show that the mass loss rate of the PDMS / CFP / paraffin thermally conductive composite phase change sheet within 5 h ≤ 0.6%, verifying the effectiveness of the encapsulation.

[0057] In summary, for the prepared PDMS / CFP / paraffin thermally conductive composite phase change sheet, on the one hand, the leakage problem of the phase change material is solved through physical encapsulation by the polymer matrix; on the other hand, the anchoring effect of the micro-nano concave-convex structure induces the distribution of the phase change material in the micro-nano concave-convex structure region, and the thermally conductive filler forms a dense thermally conductive network inside the polymer matrix, constructing a locally enhanced thermal management unit inside the sheet and in the micro-nano structure region; the micro-nano concave-convex structure increases the real contact area and reduces the interfacial thermal resistance, providing the possibility to ensure the normal operation of electronic components.

[0058] Example 2

[0059] Such as Figure 8As shown in the figure, a thermally conductive composite phase change sheet and a preparation method thereof. On the basis of Example 1, when implementing Step 1, a second thermally conductive filler is added. The scale of the second thermally conductive filler is smaller than that of the micro-nano concave-convex structure, while the remaining process remains the same as that of Example 1. Due to the anchoring effect of the micro-nano concave-convex structure, the first thermally conductive filler (CFP) presents a specific distribution state inside the sheet, and the second thermally conductive filler is mainly distributed in the micro-nano concave-convex structure area. The phase change material realizes uniform distribution both inside the sheet and at the micro-nano concave-convex structure due to its fluidity. Through the above process steps, local enhanced thermal management units located inside the sheet and in the micro-nano structure area are successfully constructed, and the required thermally conductive composite phase change sheet is obtained in this way.

[0060] Example 3

[0061] As Figure 9 shown in the figure, a thermally conductive composite phase change sheet and a preparation method thereof. On the basis of Example 2, the preparation of the micro-nano concave-convex structure only on one side surface in Step 2 is changed to the preparation of the same-grade micro-nano concave-convex structures on both side surfaces. The remaining preparation steps and conditions are the same as those of Example 2, and the required thermally conductive composite phase change sheet is obtained in this way.

[0062] Example 4

[0063] As Figure 10 shown in the figure, a thermally conductive composite phase change sheet and a preparation method thereof. For the surface treatment link of the thermally conductive composite phase change sheet in Example 3, the preparation method of the same-grade micro-nano concave-convex structures on both side surfaces is changed to the preparation of different-grade micro-nano concave-convex structures on both side surfaces of the sheet. In other aspects, it is the same as that of Example 3, and the target thermally conductive composite phase change sheet is finally obtained.

[0064] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The substitution may be the substitution of part of the structure, device, method steps, or a complete technical solution. Any equivalent substitution or change made according to the technical solution of the present invention and its inventive concept should be covered within the protection scope of the present invention.

Claims

1. A thermally conductive composite phase change sheet, characterized in that: The thermally conductive composite phase-change sheet comprises a polymer matrix, a thermally conductive filler, a phase-change material and a micro-nano concave-convex structure; The phase change material is distributed in the thermally conductive composite phase change sheet, and the phase change material is physically encapsulated by the polymer matrix to inhibit liquid leakage; The thermally conductive filler is distributed in the thermally conductive composite phase change sheet and forms a thermally conductive network in the polymer matrix for transferring heat flow; The micro-nano concave-convex structure is distributed on the surface of the thermally conductive composite phase change sheet; The micro-nano concave-convex structure has an anchoring effect, which is used to induce the thermal conductive filler and the phase change material to be accurately assembled in the target area to construct a local enhanced thermal management unit; The micro-nano convex-concave structure can significantly increase the actual contact area, reduce the interface thermal resistance between other components and the sheet, optimize the heat conduction path, and improve the heat conduction efficiency.

2. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The polymer matrix includes a flexible polymer matrix and a non-flexible polymer matrix; The flexible polymer matrix includes one or more of ethylene-vinyl acetate copolymer, polydimethylsiloxane, polyurethane, silicone rubber, polyolefin elastomer and styrene-butadiene-styrene; The non-flexible polymer matrix includes one or more of polypropylene, polyethylene, epoxy resin, polystyrene, polyvinyl chloride, polycarbonate, polyetheretherketone, polyphenylene sulfide and polyamide.

3. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The phase change material comprises one or more of paraffin, polyethylene glycol, phase change polyol and phase change polyacid; the total content of the phase change material is not less than 18wt%.

4. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The type of the thermally conductive filler includes at least one of carbon-based, ceramic-based and metal-based fillers.

5. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The shape of the thermally conductive filler includes at least one of a one-dimensional thermally conductive filler, a two-dimensional thermally conductive filler and a three-dimensional thermally conductive filler; When multiple thermally conductive materials are selected, at least one thermally conductive filler has a size smaller than the micro-nano concave-convex structure, and at least one thermally conductive filler has a size larger than the micro-nano concave-convex structure.

6. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The total content of the thermal conductive filler is 0 to 50 wt %.

7. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The thickness of the thermally conductive composite phase change sheet is 0.1-5 mm.

8. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The micro-nano concave-convex structure is distributed on at least one side of the surface of the sheet; When distributed on both surfaces at the same time, the geometric parameters of the micro-nano concave-convex structures on each surface can be designed independently; The overall roughness of the micro-nano concave-convex structure is 0-500 μm, the height of the micro-nano concave-convex structure is 0-500 μm, the equivalent diameter of the micro-nano concave-convex structure is 0-500 μm, and the roughness of different areas can be set in a gradient according to the heat transfer requirements.

9. The thermally conductive composite phase change sheet according to claim 1, characterized in that: The micro-nano concave-convex structure is at least one of a hemispherical, triangular pyramid, quadrangular pyramid, cylinder, cube and cuboid shape, and is distributed in an orderly array or in an irregular random distribution; When distributed in an ordered array, the distribution form of the micro-nano concave-convex structure includes but is not limited to square, rectangle, triangle, circle, hexagon, rhombus, and polygon.

10. A thermally conductive composite phase change sheet according to any one of claims 1 to 9, further comprising a method for preparing the thermally conductive composite phase change sheet, characterized in that: The following steps are involved: Step 1: adding a thermally conductive filler to a polymer matrix material, and using one or more of a centrifugal deaerator and a stirrer to obtain a homogeneous system of the thermally conductive filler and the polymer; then, adding a phase change material to the homogeneous system of the thermally conductive filler and the polymer, and using one or more of a centrifugal deaerator and a stirrer to obtain a homogeneous system of the thermally conductive filler, the polymer and the phase change material; Step 2: placing a homogeneous system of polymer, thermal conductive filler and phase change material on a flat plate mold with a microstructure, and then performing roller coating and roller pressing in sequence, and then drying at a constant temperature to obtain a thermal conductive composite phase change sheet; Wherein, the roller coating speed in step 2 is 2-200 mm / s, the roller pressing speed is 2-200 mm / s, the roller pressing time is 1-5 min, and the roller pressing pressure is 0-5 MPa. Before step one, the method also includes necessary pretreatment steps for the polymer matrix, thermal conductive filler and phase change material. The pretreatment includes drying the polymer matrix and thermal conductive filler, and preheating and liquefying the phase change material.

Images