Design method for improving thermal performance of composite material by regulating and controlling cluster types and number

Abstract

The invention discloses a design method for improving the thermal performance of a composite material by regulating and controlling the cluster type and number. The composite material designed by the method consists of an inorganic filler and an organic polymer material matrix, wherein the inorganic filler is a high-thermal-conductivity material and is in a cluster form; and orderly construction of a heat conduction path in the system is realized by regulating and controlling the type and the number of the filler clusters, so that the composite thermal interface material with ultrahigh heat conductivity is obtained under the condition of lower filling volume fraction. The heat-conducting interface material prepared by the method has excellent ductility, can adapt to various thermal interface applications, effectively improves the thermal management efficiency of the device by virtue of the characteristics of ultrahigh heat-conducting property and low filling volume fraction, realizes energy consumption reduction and material saving, further improves the performance release of the device and prolongs the service life of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials and applications, and particularly to a design method for improving the thermal performance of composite materials by regulating the types and numbers of clusters. Background Art

[0002] With the rapid development of electronic components towards miniaturization, high integration and high performance, the thermal power density per unit area of devices has been continuously increasing, posing higher requirements for the thermal conductivity and adaptability of thermal management materials. As a key component in the heat dissipation system, thermal interface materials (TIMs) are widely used in fields such as computer processors (CPUs), mobile phone chips, power devices, new energy vehicles, etc. Their main function is to fill the microscopic voids between devices and heat dissipation components, reduce the interface thermal resistance, and improve the overall heat conduction efficiency.

[0003] Traditional thermal interface materials are usually made by filling high thermal conductivity inorganic fillers (such as alumina, boron dioxide, etc.) into an organic polymer matrix. However, limited by factors such as large interface thermal resistance between fillers and discontinuous filler connection paths, even under high filling volume fractions, the improvement of the overall thermal conductivity of the material is still limited. In addition, a high filling amount will lead to a decline in the processing performance of the composite material, worse flexibility, and at the same time increase the manufacturing cost and energy consumption, which is not conducive to practical application and promotion.

[0004] Existing methods for improving the thermal conductivity of composite materials mostly focus on optimizing a single factor, such as improving the surface interface compatibility of fillers, regulating the size and morphology of fillers, constructing a simple filler network, etc., but it is still difficult to achieve efficient thermal conduction performance while maintaining a low filling volume fraction. The percolation theory provides a new idea: in a random system, long-range continuity is achieved through a specific connection structure, thereby greatly improving the overall performance of the system.

[0005] Under this background, how to effectively construct an orderly, continuous and efficient heat conduction path by systematically regulating the organization form of inorganic fillers in the organic polymer matrix, precisely designing the number of isolated nanowires, the types and numbers of free filler clusters, as well as their spatial positions and distributions, has become the key to the design of low-filling and high-thermal-conductivity composite thermal interface materials.

[0006] Currently, the research on the action mechanism and cooperative regulation method of different morphological cluster structures in improving the thermal performance of composite materials is not sufficient, lacking a mature and systematic design theory and engineering implementation path. Therefore, there is an urgent need for a design method for organic-inorganic composite thermal interface materials that can significantly improve the thermal conductivity at a lower filling volume fraction by regulating the types and numbers of clusters, while taking into account the ductility and adaptability of the material, so as to meet the strict requirements of the new generation of high-performance electronic devices for heat dissipation materials. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a design method for improving the thermal performance of a composite material by regulating the types and numbers of clusters. The high thermal conductivity organic-inorganic composite thermal interface material designed by this method is composed of inorganic fillers and an organic polymer material matrix. By regulating one or more of the materials, aspect ratios, types, and numbers of inorganic filler clusters, a highly efficient heat conduction path is systematically constructed to achieve ultra-high thermal conductivity performance at a low filling volume fraction.

[0008] In the present invention, a cluster refers to a connected structural unit formed by the connection of several nanowires through end-point or spatial contact in a composite material system. Clusters are classified according to the number of nanowires contained therein, and are specifically defined as follows: a connected structure composed of 2 nanowires is called a "2-nanowire cluster", a connected structure composed of 3 nanowires is called a "3-nanowire cluster", and so on. A cluster composed of n nanowires is a "n-nanowire cluster". Clusters need to meet the connectivity, that is, there is a direct or indirect connection path between any two nanowires, and each nanowire belongs to only one cluster. The nanowires inside the cluster are randomly connected, and it is only necessary to ensure contact or end-point connection. The spatial distribution of the clusters shows a random coordinate distribution.

[0009] The technical solution of the present invention is specifically introduced as follows.

[0010] The present invention provides a design method for an organic-inorganic composite thermal interface material based on regulating the types and numbers of clusters. The composite material is an organic-inorganic composite thermal interface material, which is composed of an organic polymer material matrix and inorganic filler clusters filled in the matrix. The inorganic filler clusters are high-thermal-conductivity materials, and the filler clusters present various cluster morphologies; the method includes the following steps: Step 1. Construct an inorganic filler system with different types and structures Based on numerical simulation methods, regulate the types and numbers of filler clusters, construct types of filler clusters with different inorganic filler connection methods, and form an inorganic filler system with different internal microstructures; Step 2. Construct an organic-inorganic composite thermal interface material Randomly fill the constructed different inorganic filler systems into the organic polymer material matrix, design heat transfer paths based on regulation strategies for different types and numbers of clusters, regulate one or more of the types, numbers of filler clusters, and the materials and aspect ratios of the inorganic fillers constituting the filler clusters, and numerically simulate and calculate the thermal conductivity performance of the entire system. When the types of clusters existing inside the system are 2 to 4 types and the thermal conductivity satisfies the thermal conductivity range of 5 to 9 W·m -1 ·K -1 at this time, the design of an organic-inorganic composite thermal interface material with a low filling volume fraction and high thermal conductivity is completed by regulating the types and numbers of clusters.

[0011] In the present invention, in step one, the morphology of the inorganic filler forming the filler cluster is rod-shaped, with the designed length range being 0.5 to 5 microns and the designed diameter range being 1 to 100 nanometers.

[0012] In the present invention, in step one, the designed number range of the types of filler clusters is 2 to 10, and the filler combination of the filler clusters does not exceed 10 nanowires in size.

[0013] In the present invention, in step one, the filler clusters composed of nanowires adopt a random combination method.

[0014] In the present invention, in step one, the material of the inorganic filler is one of silver Ag, gold Au, copper Cu, aluminum Al, silicon dioxide SiO2, aluminum oxide Al2O3, zinc oxide ZnO, magnesium oxide MgO, titanium dioxide TiO2, aluminum nitride AlN, boron nitride BN, silicon carbide SiC, and boron carbide B4C.

[0015] In the present invention, in step two, the organic polymer material matrix is selected from one of epoxy resin, silicone rubber, polyurethane, polyimide, polyethylene, polypropylene, polymethyl methacrylate, polystyrene, polyester, polyamide, polyether ether ketone, or polytetrafluoroethylene.

[0016] In the present invention, in step two, the total volume fraction of the inorganic filler clusters filled into the organic polymer material matrix is 20% to 50%.

[0017] In the present invention, in step two, the percolation threshold (i.e., the volume fraction when the inorganic filler clusters undergo percolation) when the filler clusters form a thermal percolation network can be calculated by numerical simulation. The specific method includes: First, perform dimensionless processing on the system, that is, standardize the simulation system into a 1×1×1 cube. Select a rod-shaped metal material as the inorganic filler and construct filler clusters with different filler morphologies. By adjusting the aspect ratio of the inorganic filler (setting the length and diameter of the inorganic filler), adjust the types and numbers of the filler clusters in the system. Adopt the Monte Carlo simulation method, randomly fill the constructed different types of clusters into the simulation cube, and handle the complex boundary conditions of the system through periodic boundary conditions, that is, truncate the part of the cluster that exceeds the X direction, and truncate and periodically translate the part of the cluster that exceeds the Y and Z directions into the simulation cube, and calculate the types and numbers of the clusters inside the system at each moment.

[0018] In the present invention, in Step 2, according to the basic physical properties of the inorganic filler and the organic polymer matrix, including the thermal conductivity and thermal resistance of the inorganic filler, the interfacial thermal resistance between fillers, the interfacial thermal resistance between the filler and the matrix, and the thermal conductivity of the organic matrix itself, an equivalent thermal resistance network model is established. Based on the thermal resistance network algorithm, combined with the heat flow law rewritten by Kirchhoff's current law, self-consistent solution is carried out through the conjugate gradient algorithm. Finally, the thermal conductivity of the overall composite material is obtained, and the types and numbers of clusters inside the system are calculated and verified at this time.

[0019] According to the method proposed by the present invention, any one or several process routes can be combined to randomly disperse clusters of different types and numbers into the organic polymer matrix to prepare an organic-inorganic composite thermal interface material with controllable structure and excellent performance.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention first proposes to achieve the orderly construction of internal heat flow channels in the organic-inorganic composite thermal interface material by regulating the types and numbers of filler clusters. In the system, by regulating one or more of the material, aspect ratio of the inorganic filler, and the types and numbers of filler clusters, the design of the heat conduction path is effectively optimized, so that a thermal interface material with high thermal conductivity can be achieved at a low volume fraction of inorganic filler clusters. Through the method combining numerical simulation and percolation theory, the influence of different types of clusters and their numbers on the overall thermal performance is analyzed, thereby realizing the regulation of the thermal performance of the composite material. The organic-inorganic composite thermal interface material designed by the present invention is composed of inorganic high-thermal-conductivity filler clusters and an organic polymer matrix, and has excellent thermal conduction performance and good mechanical flexibility, and can be adapted to a variety of complex thermal interface application scenarios. In particular, the present invention can obtain high-efficiency thermal conduction performance under the condition of an inorganic filler volume fraction lower than that required by traditional designs by optimizing the cluster structure and the layout of internal heat flow channels in the system, significantly reducing the material cost and the preparation difficulty, and providing a new solution for the application of high-performance thermal interface materials. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the fillers inside the composite material system for regulating the types and numbers of clusters of the present invention.

[0022] Figure 2 It is a schematic diagram of the design flow of the present invention.

[0023] Figure 3 It is a diagram showing the volume fraction of the designed filler clusters and the types and numbers of filler clusters of the organic-inorganic composite thermal interface material designed based on the method of the present invention in Example 1.

[0024] Figure 4It is a graph showing the number of types of organic-inorganic composite thermal interface material design clusters designed by the method based on the present invention in Example 1 and the thermal conductivity of the composite material. Detailed implementation manners

[0025] The present invention will be further described below.

[0026] As Figure 1 、 Figure 2 shown, the specific steps of the present invention are as follows: A method for designing the thermal performance of an organic-inorganic composite thermal interface material based on regulating the types and numbers of filler clusters includes the following steps: Step 1: Construct the types and numbers of filler clusters composed of different combinations of nanowires. Step 2: Randomly fill filler clusters of different types and numbers into the organic polymer material matrix to design the heat transfer channels of the organic-inorganic composite thermal interface material. Through numerical calculation, solve the thermal conductivity of the organic-inorganic composite thermal interface material, complete the design of the organic-inorganic composite thermal interface material, and prepare the organic-inorganic composite thermal interface material using a suitable method and process.

[0027] Furthermore, the material of the inorganic filler in Step 1 can be designed as an electrically insulating material, such as materials with good thermal conductivity like silver (Ag), gold (Au), copper (Cu), aluminum (Al), silicon dioxide (SiO2), aluminum oxide (Al2O3), zinc oxide (ZnO), magnesium oxide (MgO), titanium dioxide (TiO2), aluminum nitride (AlN), boron nitride (BN), silicon carbide (SiC), boron carbide (B4C), etc.

[0028] Furthermore, in Step 1, the shape of the inorganic filler is designed as a rod shape, preferably a rod-like structure with an aspect ratio of 10.

[0029] Furthermore, in Step 1, the length of the inorganic filler is designed in the range of 0.5 to 5 micrometers, and the diameter is designed in the range of 1 to 100 nanometers.

[0030] Furthermore, in Step 1, the number of types of filler clusters is designed in the range of 2 to 10, and the size of each filler cluster does not exceed a filler combination of 10 nanowires.

[0031] Furthermore, in Step 1, the filler clusters composed of nanowires are randomly combined.

[0032] Furthermore, in Step 2, the organic polymer material matrix is an organic polymer elastic material with good elasticity, flexibility, and electrical insulation, such as epoxy resin, silicone rubber, polyurethane, polyimide, polyethylene, polypropylene, polymethyl methacrylate, polystyrene, polyester, polyamide, polyether ether ketone, polytetrafluoroethylene, etc.

[0033] Further, in the second step, the volume fraction of the inorganic filler filled into the organic polymer matrix is 20% - 50%.

[0034] Further, in the second step, select a process or manufacturing method to mix the isolated nanowires, filler clusters and the polymer matrix.

[0035] Example 1

[0036] As Figure 3 shown, the organic-inorganic composite thermal interface material designed by the present invention for regulating the type and number of clusters selects silver nanowires (Ag) with high thermal conductivity as the inorganic filler and polyvinylidene fluoride (PVDF) as the organic polymer substrate, and designs and regulates the type and number of clusters to construct a thermal interface composite material. Specifically, nine different types of nanowire clusters with the number of nanowire connections ranging from 2 to 10 are designed, and different types of clusters are randomly doped into the PVDF substrate in a ratio of 40:20:10:2:3:2:3:2:2. As the filler clusters are gradually filled, connections between the same type of clusters and connections between different types of clusters occur within the system, generating new clusters, and thus changing the type of clusters. When the number of cluster types k Ag in the system < the peak value of the number of cluster types k = 16 that can exist inside the system, most of the same or different types of clusters in the system are in a separated state, and only a small amount are connected. Continue to increase the number of clusters until the number of cluster types k Ag = the peak value of the number of cluster types k = 16 that can exist inside the system, significant connections begin to occur between the clusters, forming a preliminarily conductive heat transfer path. At this time, the number of cluster types inside the system is the largest. When the number of clusters is further increased, at this time the number of cluster types k Ag rapidly decreases and finally stabilizes at 2 - 4. Most of the clusters in the system are connected together to form an infinite conductive filler network that penetrates the left and right boundaries. If the number of clusters is continued to increase, the types of clusters will also tend to be stable.

[0037] The organic-inorganic composite thermal interface material designed by the present invention for regulating the type and number of clusters selects polyvinylidene fluoride (PVDF) with a thermal conductivity of 0.19 Wm -1 K -1 as the organic polymer matrix, selects rod-shaped Ag nanowires with a thermal conductivity of 429 Wm -1 K -1 as the filler, and calculates the interfacial thermal resistance between the Ag nanowires through weighted average. The interfacial thermal resistance R Ag-Ag is 210 -10 m 2 KW -1, in the programming software, use numerical simulation to first non-dimensionalize the system. Set the side length of the system to 1, the system ratio to l / L = 0.2, l = 2 μm (length of the nanowire), and the aspect ratio l / d = 10. By regulating the types and numbers of filler clusters, randomly disperse rod-shaped Ag nanowires with a length of 2 μm and a diameter of 0.02 μm in a unit cube with a side length of 1. Use Monte Carlo simulation in three-dimensional space, adopt a soft-core model, set the types and numbers of filler clusters, and through boundary condition processing, that is, cut off the nanowires exceeding the region along the x direction, and cut and periodically translate the nanowires in the y and z directions into the cube. Through numerical model calculation, the percolation threshold when percolation occurs in the filler clusters inside the system can be calculated. Then endow the material with basic properties (thermal conductivity, thermal resistance), the interfacial thermal resistance between fillers, and the thermal conductivity of the matrix itself, and use the thermal resistance network algorithm and the heat flow law rewritten by Kirchhoff's current law to obtain the heat flow, and use the conjugate gradient algorithm for self-consistent solution to solve the effective thermal conductivity of the system. As Figure 4 , design 9 different cluster types with the number of nanowire connections from 2 to 10, and fill the different types of clusters in the ratio of 40:20:10:2:3:2:3:2:2. When the number of final cluster types inside the system stabilizes at 2 to 4 types, a composite thermal interface material with excellent thermal performance is successfully designed. At this time, the volume fraction of the filler clusters filled inside the system is about 10% - 25% less than the volume fraction filled with single fillers, and the thermal conductivity is as high as 9.8 Wm -1 K -1 .

[0038] Above, the method of the present invention optimizes the heat flow channel structure inside the system by regulating the types and numbers of filler clusters, thereby achieving a significant increase in the ultra-high thermal conductivity of the organic-inorganic composite thermal interface material under the condition of a low filling volume fraction. The designed thermal interface material is jointly composed of inorganic fillers (including isolated nanowires, free clusters, and percolation network structures) and an organic polymer material matrix, and overall has excellent flexibility and ductility, can adapt to a more complex thermal interface environment, realize energy consumption reduction and material saving, and further improve the performance release and service life of the device.

Claims

1. A design method for improving the thermal properties of a composite material by regulating the types and numbers of clusters, characterized in that, The composite material is an organic-inorganic composite thermal interface material, which is composed of an organic polymer material matrix and inorganic filler clusters filled in the matrix. The inorganic filler clusters are high-thermal-conductivity materials, and the filler clusters exhibit various cluster morphologies. The method includes the following steps: Step 1: Construct inorganic filler systems of different types and structures Based on the numerical simulation method, regulate the types and quantities of the filler clusters, construct filler cluster types with different inorganic filler connection methods, and form inorganic filler systems with different internal microstructures; Step 2: Construct an organic-inorganic composite thermal interface material Randomly fill the constructed different inorganic filler systems into the organic polymer material matrix, design the heat transfer path based on the regulation strategy of different cluster types and numbers, and regulate one or more of the types, quantities of filler clusters, and the materials and aspect ratios of the inorganic fillers that make up the filler clusters. Numerically simulate and calculate the thermal conductivity performance of the entire system. When the number of cluster types existing in the system is 2 to 4, and the thermal conductivity satisfies the thermal conductivity range of 5 to 9 W·m -1 ·K -1 When it reaches this value, the design of the organic-inorganic composite thermal interface material with low filling volume fraction and high thermal conductivity is completed by regulating the cluster types and numbers.

2. The design method for improving the thermal performance of a composite material by regulating the type and number of clusters according to claim 1, characterized in that, In Step 1, the morphology of the inorganic fillers constituting the filler clusters is rod-shaped, and the designed length range is 0.5 to 5 micrometers, and the designed diameter range is 1 to 100 nanometers.

3. The design method for improving the thermal performance of a composite material by regulating the type and number of clusters according to claim 1, wherein In Step 1, the inorganic fillers are selected from one of silver (Ag), gold (Au), copper (Cu), aluminum (Al), silicon dioxide (SiO2), aluminum oxide (Al2O3), zinc oxide (ZnO), magnesium oxide (MgO), titanium oxide (TiO2), aluminum nitride (AlN), boron nitride (BN), silicon carbide (SiC), and boron carbide (B4C).

4. The design method for improving the thermal performance of a composite material by regulating the type and number of clusters according to claim 1, characterized in that In Step 1, the designed number range of the filler cluster types is 2 to 10, and each filler cluster is randomly connected by 2-10 nanowires.

5. The design method for improving the thermal performance of a composite material by regulating the type and number of clusters according to claim 1, characterized in that, In Step 2, the organic polymer material matrix is selected from one of epoxy resin, silicone rubber, polyurethane, polyimide, polyethylene, polypropylene, polymethyl methacrylate, polystyrene, polyester, polyamide, polyether ether ketone, and polytetrafluoroethylene.

6. The design method for improving the thermal properties of a composite material by regulating the type and number of clusters according to claim 1, characterized in that In Step 2, the total volume fraction of the inorganic filler clusters in the composite material is 20% to 50%.

7. The design method for improving the thermal properties of a composite material by regulating the type and number of clusters according to claim 1, characterized in that Through numerical simulation, according to the thermal conductivity and thermal resistance of the inorganic fillers, the interfacial thermal resistance between the filler clusters, the interfacial thermal resistance between the inorganic fillers and the matrix, and the thermal conductivity parameters of the matrix itself, the heat flow is solved by using the thermal resistance network algorithm and the heat flow law rewritten by Kirchhoff's current law, and the conjugate gradient algorithm is combined for self-consistent solution to obtain the effective thermal conductivity of the system.

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