Design method of dual-functional organic-inorganic thermal interface materials based on incomplete coating

Abstract

The present invention discloses a method for designing a dual-function organic-inorganic thermal interface material based on an incomplete coating layer; the organic-inorganic composite thermal interface material designed by the method is composed of a filler and an organic polymer material matrix, wherein: the filler includes an inorganic filler and an incomplete coating layer, the inorganic filler is an electrical insulating material or a metal material, and the incomplete coating layer can be selected as a conductive coating layer or an insulating coating layer according to the properties of the inorganic filler, and the difference in percolation threshold is used to allow the filler to thermally percolate in the matrix without electrical percolation, thereby obtaining a composite thermal interface material with ultra-high thermal conductivity and electrical insulation properties. The thermal conductive interface material designed by the method has good ductility and can be filled between various thermal interfaces, and the ultra-high thermal conductivity and electrical insulation properties enable it to quickly extract excess heat from the device without causing electrical damage to the device, thereby improving the performance release and service life of the device.

Description

Technical Field

[0001] The invention relates to the field of new materials and application technology, and in particular to a design method for a dual-functional organic-inorganic thermal interface material based on an incomplete coating layer. Background Art

[0002] With the progress of the times, the miniaturization of electronic components has led to a rapid increase in the thermal density per unit area of ​​the device, which in turn puts forward higher requirements for the thermal design of the device. Thermal interface materials are widely used to dissipate excess heat from electronic components (such as CPU, GPU and other computing units, LED boards, etc.). The principle is mainly to fill the thermal interface material on the contact surface between the electronic components and the heat dissipation structure, remove the air in the pores of the contact interface, and thus improve the heat dissipation efficiency of the device.

[0003] Traditional filled thermal interface materials are usually composite materials made of thermally conductive particles and organic polymer materials. There are two main problems with this type of material: first, due to the large interfacial thermal resistance between the fillers, there will be no thermal percolation inside the composite material, resulting in relatively poor thermal conductivity; second, due to the good electrical conductivity of the filler itself, thermal percolation will also occur inside the composite material, which will lead to electrical problems such as breakdown caused by electron transport, damage the electrical performance of the device, and affect the performance and life of the device.

[0004] Generally speaking, heat conduction mainly depends on the transport behavior of two types of carriers, one is electrons and the other is phonons; and the generation of current mainly depends on the transport of electrons and holes (existing in semiconductors). The interfacial thermal resistance of the conductor / conductor interface is much smaller than that of the insulator / insulator interface because the conductor / conductor interface has both electron heat transport and phonon / phonon coupling, while the insulator / insulator interface only has phonon / phonon coupling. Due to the large interfacial thermal resistance between fillers, the thermal conductivity of commonly used electrical insulation thermal interface materials is generally not high. There is a certain theoretical contradiction between reducing the interfacial thermal resistance between fillers and the electrical insulation properties of composite materials. Percolation is a widely existing physical phenomenon. In a large disordered system, a certain long-range connectivity that suddenly appears with the increase in the degree of component connection is called a certain percolation phenomenon. The special dependence of this phenomenon can be used to reconcile the high thermal conductivity and electrical insulation properties of thermal interface materials. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for designing a dual-functional organic-inorganic thermal interface material based on an incomplete coating layer; the organic-inorganic composite thermal interface material designed by this method is composed of an electrically insulating filler with an incomplete conductive coating layer and an organic polymer material matrix, and the filler can undergo thermal percolation in the matrix without undergoing electrical percolation, that is, the filler forms a heat flow path in the matrix without forming an electric current path.

[0006] The technical solution of the present invention is specifically described as follows.

[0007] The present invention provides a method for designing a dual-functional organic-inorganic thermal interface material based on an incomplete coating layer, wherein the dual-functional organic-inorganic thermal interface material is composed of an organic polymer material matrix and a filler with an incomplete coating layer filled in the matrix, wherein the filler with an incomplete coating layer includes an inorganic filler and an incomplete coating layer constructed on the inorganic filler; the method comprises the following steps:

[0008] Step 1: Constructing a filler with an incomplete coating

[0009] The incomplete coating layer is wrapped on the outer surface of the inorganic filler in one or more sections; the inorganic filler is an electrically insulating material or a conductive metal material; wherein: when the inorganic filler is an electrically insulating material, the incomplete coating layer is a conductive metal material or a conductive carbon-based material; when the inorganic filler is a metal material, the incomplete coating layer is an electrically insulating organic material;

[0010] Step 2: Constructing dual-functional organic-inorganic thermal interface materials

[0011] The fillers with incomplete coating layers are randomly filled into the organic polymer material matrix, the heat transport channel and the electrical transport channel of the organic-inorganic thermal interface material are designed, and the thermal conductivity and electrical conductivity of the organic-inorganic thermal interface material are solved by numerical simulation calculation.

[0012] According to the thermal conductivity and electrical conductivity results, one or more of the design parameters including the material of the inorganic filler, characteristic size, material of the incomplete coating layer, coating method, coating rate and volume fraction of the filler filled into the organic polymer matrix are adjusted. When the thermal conductivity and electrical conductivity calculated by numerical simulation meet certain requirements, the design of the dual-functional organic-inorganic thermal interface material is completed.

[0013] In the present invention, in step one, the shape of the inorganic filler can be designed to be spherical, rod-shaped, linear, various geometrically shaped sheets (such as polygons such as rectangles and triangles) and various blocks (such as rectangular blocks, ellipsoidal blocks, etc.), preferably in the shape of long strips; the characteristic size design range of the inorganic filler is 0.05~1000 microns, such as the diameter and radius of the sphere; the diameter and length of the rod; the thickness and diameter of the sheet, etc.

[0014] In the present invention, in step 1, the inorganic filler has good thermal conductivity, and its thermal conductivity ranges from 30 to 220 Wm -1 K -1 When the inorganic filler is a conductive metal material, its conductivity ranges from 3×10 7 ~8×10 7 Sm -1 between.

[0015] In the present invention, in step 1, when the inorganic filler is an electrical insulating material, it is selected from aluminum nitride AlN, silicon dioxide SiO 2 、Aluminum oxide Al 2 O 3 , silicon carbide SiC, boron nitride BN; when the inorganic filler is a conductive metal material, it is selected from one or more of silver Ag, gold Au, copper Cu, and aluminum Al.

[0016] In the present invention, in step 1, the thickness of the incomplete coating layer is designed to be in the range of 0.01 to 200 microns, preferably about one fifth of the characteristic size of the inorganic filler. The outer surface coverage of the incomplete coating layer is designed to be in the range of 10% to 90%, preferably 50% to 80%.

[0017] In the present invention, in step 1, when the incomplete coating layer is a conductive metal material or a conductive carbon-based material, the range of the interface thermal resistance is 1×10 -10 ~1×10 -8 m 2 KW -1 .

[0018] In the present invention, in step one, when the incomplete coating layer is a conductive metal material, it is selected from one or more of silver Ag, gold Au, copper Cu or aluminum Al; when the incomplete coating layer is a conductive carbon-based material, it is selected from one or more of graphene, graphite or carbon nanotubes; when the incomplete coating layer is an electrically insulating organic material, it is selected from one or more of epoxy resin, polylactide, methyl vinyl silicone rubber, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate, and polyacrylate.

[0019] In the present invention, in step 2, the coating method refers to an incomplete coating layer wrapped on the outer surface of the inorganic filler in one or more sections, including one-stage coating or multi-stage coating, which can be one-stage, two-stage coating, three-stage coating, etc.; one-stage coating refers to a coating layer along the longest direction of the filler, two-stage coating refers to two discontinuous coating layers along the longest direction of the filler, and three-stage coating refers to three discontinuous coating layers along the longest direction of the filler, and so on; each coating layer wraps the outer surface of the filler for one week in a direction perpendicular to the longest direction of the filler. Segmented coating can reduce the aspect ratio of the coating structure and increase the percolation threshold, so that electrical percolation will not occur while the coating rate is increased.

[0020] In the present invention, in step 2, the organic polymer material matrix is ​​an organic polymer elastic material with good elasticity and flexibility and electrical insulation.

[0021] In the present invention, in step 2, the organic polymer material matrix is ​​one or more of epoxy resin, polylactide, methyl vinyl silicone rubber, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate or polyacrylate.

[0022] In the present invention, in step 2, the volume percentage of the filler with an incomplete coating layer in the organic-inorganic thermal interface material is designed to be in the range of 0.05% to 70%, preferably 15% to 50%.

[0023] In the present invention, in step 2, numerical simulation can be used to calculate the electrical percolation threshold or thermal percolation threshold (i.e., the volume fraction of the filler with an incomplete coating layer in the composite material) when the filler forms an electrical percolation network or a thermal percolation network. The specific method includes:

[0024] First, the system is dimensionless, the side length of the system is set to 1, inorganic fillers of different materials are selected, the aspect ratio of the inorganic filler is adjusted (the length and diameter are set), the volume fraction of the inorganic filler in the system is adjusted, the material, coating method and coating rate of the incomplete coating layer are adjusted, and the fillers are filled into the cube with a side length of 1 in sequence through Monte Carlo simulation. Geometric doping is performed through boundary condition processing, and the percolation threshold when the filler forms a percolation network (electrical percolation network or thermal percolation network) is calculated.

[0025] In the present invention, in step 2, according to the basic properties of the inorganic filler material, namely, electrical conductivity, thermal conductivity, electrical resistance and thermal resistance, as well as the interface resistance and thermal resistance between the filler and the matrix, and the electrical conductivity and thermal conductivity of the matrix itself, a resistance network algorithm and Kirchhoff's current law are used to obtain the heat flow or current, and a conjugate gradient algorithm is used for self-consistent solution, that is, the electrical conductivity or thermal conductivity of the system is solved.

[0026] In the present invention, in step 2, by numerical simulation calculation, when the thermal conductivity ranges from 2 to 12 Wm -1 K -1 , the conductivity is 1×10 -4 ~1×10 -3 Sm -1 The design of the dual-functional organic-inorganic composite thermal interface material is completed.

[0027] According to the design method of the organic-inorganic thermal interface material of the present invention, any one or more process methods of wrapping the coating material on the outer surface of the filler and mixing the inorganic filler with the polymer matrix can be used to prepare the organic-inorganic thermal interface material.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention utilizes the basic principle of percolation phenomenon to reconcile the high thermal conductivity and electrical insulation properties of thermal interface materials, and designs a dual-functional organic-inorganic composite thermal interface material. The designed thermal interface material is composed of a filler with an incomplete coating layer and an organic polymer material matrix. The material is not completely coated on the filler so that the filler can thermally percolate in the matrix without electrical percolation. By utilizing this principle, a composite thermal interface material with ultra-high thermal conductivity and electrical insulation properties can be obtained. The designed thermal interface material has good ductility and can be filled between various thermal interfaces, and the ultra-high thermal conductivity and electrical insulation properties enable it to quickly conduct excess heat from the device without causing electrical damage to the device (such as short circuit, breakdown), thereby improving the performance release and service life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic cross-sectional view of the incompletely covered structure of the rod-shaped material of the present invention.

[0031] Figure 2 It is a schematic diagram of the design process of the present invention.

[0032] Figure 3 It is a schematic diagram of the design results of the organic-inorganic composite thermal interface material designed based on the method of the present invention in Example 1.

[0033] Figure 4 This is the numerical calculation temperature field cloud map in Example 1. DETAILED DESCRIPTION

[0034] The present invention will be further described below.

[0035] like Figure 2 As shown, the design method of the dual-functional organic-inorganic thermal interface material based on the incomplete coating layer provided by the present invention comprises the following steps:

[0036] Step 1: Design the packing

[0037] According to actual needs, the material, shape, characteristic parameters of inorganic fillers and the volume fraction of fillers in thermal interface materials are designed through theory.

[0038] Step 2: Design the cladding

[0039] Based on step one, the material, coating method and coating rate of the incomplete coating layer are designed.

[0040] Step 3: Finalize the design

[0041] On the basis of step 2, fillers with incomplete coating layers are randomly filled into the organic polymer material matrix to design the heat transport channel and electrical transport channel of the organic-inorganic composite thermal interface material. Through numerical calculation, the thermal conductivity and electrical conductivity of the organic-inorganic composite thermal interface material are solved, the design of the organic-inorganic composite thermal interface material is completed, and the organic-inorganic composite thermal interface material is prepared by a suitable method.

[0042] Furthermore, in step 1, the material of the inorganic filler can be designed to be an electrical insulating material, such as aluminum nitride (AlN), silicon dioxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), silicon carbide (SiC), boron nitride (BN) and other one or more materials with good thermal conductivity and electrical insulation properties, can also be designed as metal materials, such as silver (Ag), gold (Au), copper (Cu), aluminum (Al) and other one or more metal materials with good thermal conductivity and electrical conductivity.

[0043] Furthermore, in step 1, the shape of the inorganic filler can be designed to be spherical, rod-shaped, linear, various geometrically shaped sheets (such as polygons such as rectangles and triangles), and various blocks (such as rectangular blocks, ellipsoidal blocks, etc.), preferably in the shape of long strips.

[0044] Furthermore, in the step 1, the characteristic size design range of the inorganic filler is 0.05 to 1000 microns, such as the diameter and radius of a sphere; the diameter and length of a rod; the thickness and diameter of a sheet, etc.

[0045] Furthermore, in the step 2, the material of the incomplete coating layer can be designed to be one or more materials with good interface thermal resistance reduction, such as metal (such as silver (Ag), gold (Au), copper (Cu), aluminum (Al), etc.), carbon-based materials (such as graphene, graphite, carbon nanotubes, etc.), or can be designed to be one or more materials with good electrical insulation properties, such as electrically insulating organic materials (such as epoxy resin, polylactide, methyl vinyl silicone rubber, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate, polyacrylate, etc.).

[0046] Furthermore, in the step 2, the design principle of the material of the incomplete coating layer is that when the filler is an electrically insulating material, the incomplete coating layer is a conductive material, and when the filler is a metal material, the incomplete coating layer is an electrically insulating material.

[0047] Furthermore, in step 2, incomplete coating is defined as the coating layer being coated on the outer surface of the electrical insulating filler in one or more sections, but not completely coating the outer surface of the filler. Figure 1 As shown, it is a cross-sectional schematic diagram of the incomplete coating structure of the rod-shaped filler material; the coating method can be a one-stage coating, a two-stage coating or a three-stage coating as shown in the figure, and the outer circumference along the length direction of the rod-shaped filler is respectively wrapped with a one-stage coating layer, two discontinuous coating layers, and three discontinuous coating layers.

[0048] Furthermore, in the step 2, the thickness of the incomplete coating layer is designed to be in the range of 0.01 to 200 microns, preferably about one fifth of the characteristic size of the filler.

[0049] Furthermore, in the step 2, the design range of the outer surface coverage of the incomplete coating layer (ie, the ratio of the outer surface area of ​​the coating layer to the outer surface area of ​​the filler) is 10% to 90%, preferably 50% to 80%.

[0050] Furthermore, in step three, the volume percentage of the filler in the composite material is designed to be in the range of 0.05% to 70%, preferably 15% to 50%.

[0051] Furthermore, in step three, the organic polymer material matrix is ​​one or more organic polymer elastic materials with good elasticity and flexibility and electrical insulation, such as epoxy resin, polylactide, methyl vinyl silicone rubber, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate, polyacrylate, etc.

[0052] Furthermore, in the step three, the suitable method is any one or more process methods of wrapping the coating material on the outer surface of the filler and mixing the inorganic filler with the polymer matrix.

[0053] Example 1

[0054] like Figure 3 As shown in the figure, the filler material is SiC filler with a one-stage Ag coating layer and the matrix of PVDF is designed to design a one-stage coated thermal interface composite material. Through research, it is found that the thermal conductivity is a function of the filler filling volume fraction and the coating coverage. The area below the black line is electrical insulation. Through analysis, it is found that when the filler filling volume fraction is between 0.22-0.3 and the coating coverage is 30%, the one-stage coated thermal interface composite material has an ultra-high thermal conductivity (8 W m -1 K -1 ) and excellent electrical insulation properties, where the electrical conductivity of the composites increases with the increase of coverage.

[0055] The invention designs a high thermal conductivity and electrical insulation dual-function organic-inorganic composite thermal interface material based on an incomplete coating layer on a filler, and the selected thermal conductivity is 0.19Wm -1 K -1 Polyvinylidene fluoride (PVDF) is used as the organic polymer matrix, and the thermal conductivity is selected to be 490Wm -1 K -1 Cylindrical SiC was used as filler, and the conductivity was selected to be 6.3×10 7 Sm -1 Ag is used as the coating, and the interfacial thermal resistance between Ag and SiC is calculated by weighted average, R Ag-Ag , R Ag-SiC , R SiC-SiC The interface thermal resistance is 2×10 -10 , 2×10 -9 , 1×10 -8 m 2 KW -1, using numerical simulation calculations in programming software, first non-dimensionalize the system, set the system side length to 1, select the system ratio as l / L=0.4, l=4μm (nanowire length), aspect ratio l / d=20, and adjust the volume fraction of inorganic fillers in the system, the material, coating method and coating rate of the incomplete coating layer. By using numerical simulation methods, cylindrical SiC nanowires with a length of 4μm and a diameter of 0.2μm are randomly dispersed in a unit cube with a width of 1. Monte Carlo simulation is used in three-dimensional space, and a soft core model is used to set the Ag coating coating. The rate is processed by boundary conditions, that is, the nanowires that exceed the area along the x direction are cut off, and the nanowires in the y and z directions are cut and periodically translated into the cube. Through numerical model doping calculation, the percolation threshold of the electrical percolation network or thermal percolation network can be calculated, and then the basic properties of the material (electrical conductivity, thermal conductivity, resistance, thermal resistance) and the interface resistance and thermal resistance between the filler and the matrix, as well as the electrical conductivity and thermal conductivity of the matrix itself are given. The resistance network algorithm and Kirchhoff's current law are used to obtain the heat flow or current. The conjugate gradient algorithm is used for self-consistent solution to solve the electrical conductivity or thermal conductivity of the system. Figure 3 As shown in Figure 2, when the filler filling volume fraction is between 0.22 and 0.3 (i.e., 22% to 30%) and the coverage is 30%, the successfully designed ultra-high thermal conductivity and electrical insulation composite thermal interface material has a thermal conductivity of up to 8Wm -1 K -1 . Figure 4 It is a 2D plane cloud map of the temperature field inside the system. You can intuitively see the thermal percolation network channels inside the system and the gradual transfer of heat from the left to the right.

[0056] As mentioned above, the method of the present invention achieves high thermal conductivity and electrical insulation properties of organic-inorganic composite thermal interface materials by constructing an incomplete coating layer on the filler, and regulating the thermal percolation threshold and electrical percolation threshold of the system by using parameters such as the filler aspect ratio, the coating method, and the coating rate. The thermal interface material designed by this method is composed of a filler with an incomplete coating layer (such as nanoparticles, nanowires, nanorods, and nanosheets, etc.) and an organic polymer material matrix. The thermal interface material has good ductility and can be filled between various thermal interfaces. Its ultra-high thermal conductivity and electrical insulation properties enable it to quickly conduct excess heat from electronic components (such as various computing chips such as CPUs and GPUs) to heat dissipation structures (such as heat sinks, device housings, etc.) without causing electrical damage to the device (such as short circuits, breakdowns), thereby improving the performance release and service life of the device.

Claims

1. A design method for a dual-functional organic-inorganic thermal interface material based on an incomplete coating layer, characterized in that: The dual-functional organic-inorganic thermal interface material is composed of an organic polymer material matrix and a filler with an incomplete coating layer filled in the matrix, wherein the filler with an incomplete coating layer includes an inorganic filler and an incomplete coating layer constructed on the inorganic filler; and comprises the following steps: Step 1: Constructing a filler with an incomplete coating The incomplete coating layer is wrapped on the outer surface of the inorganic filler in one or more sections, and the inorganic filler is an electrically insulating material or a conductive metal material; when the inorganic filler is an electrically insulating material, the incomplete coating layer is a conductive metal material or a conductive carbon-based material; when the inorganic filler is a metal material, the incomplete coating layer is an electrically insulating organic material; Step 2: Constructing dual-functional organic-inorganic thermal interface materials The fillers with incomplete coating layers are randomly filled into the organic polymer material matrix, the heat transport channel and the electrical transport channel of the organic-inorganic thermal interface material are designed, and the thermal conductivity and electrical conductivity of the organic-inorganic thermal interface material are solved by numerical simulation calculation. According to the results of thermal conductivity and electrical conductivity, one or more of the design parameters including the material of the inorganic filler, characteristic size, material of the incomplete coating layer, coating method, coating rate and volume fraction of the filler filled into the organic polymer matrix are adjusted. When the thermal conductivity and electrical conductivity calculated by numerical simulation meet the following conditions: The thermal conductivity ranges from 2 to 12 Wm -1 K -1 , the conductivity is 1×10 -4 ~1×10 -3 Sm -1 , that is, completing the design of dual-functional organic-inorganic thermal interface materials.

2. The design method of dual-functional organic-inorganic thermal interface material based on incomplete coating layer according to claim 1, characterized in that: In step one, the shape of the inorganic filler is designed to be any one of a sphere, an ellipsoid, a rod, a line, a rectangle, a polygon or a block, and the characteristic size of the inorganic filler is designed to range from 0.05 to 1000 microns; the thickness of the incomplete coating layer is designed to range from 0.01 to 200 microns, and the outer surface wrapping degree of the incomplete coating layer, that is, the ratio of the outer surface area of ​​the coating layer to the outer surface area of ​​the filler is 10% to 90%.

3. The design method of dual-functional organic-inorganic thermal interface material based on incomplete coating layer according to claim 1, characterized in that: In step 1, when the inorganic filler is an electrical insulating material, it is selected from one or more of aluminum nitride AlN, silicon dioxide SiO2, aluminum oxide Al2O3, silicon carbide SiC, and boron nitride BN; when the inorganic filler is a conductive metal material, it is selected from one or more of silver Ag, gold Au, copper Cu, and aluminum Al.

4. The design method of dual-functional organic-inorganic thermal interface material based on incomplete coating layer according to claim 1, characterized in that: In step one, when the incomplete coating layer is a conductive metal material, it is selected from one or more of silver Ag, gold Au, copper Cu or aluminum Al; when the incomplete coating layer is a conductive carbon-based material, it is selected from one or more of graphene, graphite or carbon nanotubes; when the incomplete coating layer is an electrically insulating organic material, it is selected from one or more of epoxy resin, polylactide, methyl vinyl silicone rubber, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate, and polyacrylate.

5. The design method of dual-functional organic-inorganic thermal interface material based on incomplete coating layer according to claim 1, characterized in that: In step 2, the organic polymer material matrix is ​​one or more of epoxy resin, polylactide, methyl vinyl silicone rubber, vinyl silicone oil, polyurethane, polydimethylsiloxane, polybenzoxazine, polyimide, silicone resin, polycarbonate or polyacrylate.

6. The design method of dual-functional organic-inorganic thermal interface material based on incomplete coating layer according to claim 1, characterized in that: In step 2, the volume percentage of the filler with an incomplete coating layer in the organic-inorganic thermal interface material is designed to be in the range of 0.05% to 70%.

7. The design method of dual-functional organic-inorganic thermal interface material based on incomplete coating layer according to claim 1, characterized in that: In step 2, numerical simulation is used to obtain heat flow or current using a resistance network algorithm and Kirchhoff's current law based on the basic properties of the inorganic filler material, which include electrical conductivity, thermal conductivity, electrical resistance and thermal resistance, as well as the interface resistance and thermal resistance between the filler and the matrix, and the electrical conductivity and thermal conductivity of the matrix itself. The conjugate gradient algorithm is used for self-consistent solution to solve the electrical conductivity or thermal conductivity of the system.

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