Heat-conducting and wave-absorbing composition and application thereof

Abstract

The embodiment of the invention provides a heat-conducting and wave-absorbing composition and application thereof. The composition comprises an organic matrix, a heat-conducting filler and a wave-absorbing filler, the heat-conducting filler comprises large-particle-size heat-conducting particles and small-particle-size heat-conducting particles, and the large-particle-size heat-conducting particles comprise high-sphericity and high-purity silicon carbide filler; wherein the sphericity degree of the high-sphericity-degree and high-purity silicon carbide filler is 0.8 or above, and the mass content of silicon carbide is greater than or equal to 99.0%; the wave-absorbing filler comprises spherical carbonyl iron and flaky carbonyl iron. The large-particle-size heat-conducting particles in the composition comprise the silicon carbide filler, so that the fluidity and the heat-conducting property of the composition are good, and the wave-absorbing property of the composition is good due to the synergistic cooperation of the silicon carbide filler, the spherical carbonyl iron and the flaky carbonyl iron; the requirements of the field of electronic equipment on heat-conducting and / or wave-absorbing functional materials with excellent comprehensive performance can be met.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of thermal conductive and wave absorbing materials, and specifically to a thermal conductive and wave absorbing composition and its application. Background Art

[0002] With the rapid development of electronic technology, the integration of electronic components (such as chips) in electronic devices continues to increase and their size continues to shrink. Heat dissipation and electromagnetic interference between these components are impacting the operation of electronic devices. A common approach to addressing these heat dissipation and electromagnetic interference issues is to place a material that combines thermal conductivity and microwave absorption between the heat-generating electronic components and the heat sink. This material is typically formed by curing a thermally conductive and microwave-absorbing composition containing thermally conductive and microwave-absorbing fillers. However, existing thermally conductive and microwave-absorbing compositions struggle to achieve both good flowability, microwave absorption, and thermal conductivity.

[0003] Silicon carbide is a typical dielectric absorbing material with extremely high theoretical thermal conductivity and theoretical breakdown strength, making it a promising filler with both thermal conductivity and absorption properties. However, existing silicon carbide powders, most of which come from the abrasives industry, suffer from shortcomings such as low sphericity and poor insulation resistance. Direct use of silicon carbide in thermally conductive and absorbing compositions can result in poor flowability and low breakdown strength. Consequently, silicon carbide is rarely used as the primary thermally absorbing filler in existing thermally conductive and absorbing compositions. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a composition containing silicon carbide filler with good fluidity, thermal conductivity and wave absorption properties, so as to better meet the demand for excellent performance thermal conductive and wave absorbing materials in the field of electronic equipment.

[0005] Specifically, in a first aspect, an embodiment of the present application provides a thermally conductive and absorbing composition, comprising an organic matrix, a thermally conductive filler, and an absorbing filler; the thermally conductive filler comprises large-particle-size thermally conductive particles and small-particle-size thermally conductive particles, and the large-particle-size thermally conductive particles comprise high-sphericity and high-purity silicon carbide fillers; wherein the high-sphericity and high-purity silicon carbide fillers have a sphericity of greater than 0.8 and a mass content of silicon carbide greater than or equal to 99.0%; the absorbing fillers comprise spherical carbonyl iron and flaky carbonyl iron.

[0006] The large-particle, highly spherical silicon carbide filler in the thermally conductive and absorbing composition maximizes the high thermal conductivity of silicon carbide, resulting in excellent thermal conductivity and flowability. Furthermore, the high purity of the silicon carbide filler provides strong breakdown resistance, resulting in a high critical breakdown field strength and excellent pressure resistance for the cured product. Furthermore, the silicon carbide filler and the spherical and flake-shaped carbonyl iron create a synergistic absorption effect, enhancing the overall absorption capacity of the composition.

[0007] In some embodiments of the present application, the mass content of silicon carbide in the high-sphericity and high-purity silicon carbide filler is greater than or equal to 99.9%. The purity of the silicon carbide in the silicon carbide filler is relatively high, which is more conducive to improving its breakdown resistance.

[0008] In some embodiments of the present application, the surface of the high-sphericity and high-purity silicon carbide filler further has an insulating coating layer. The presence of the insulating coating layer can improve the breakdown resistance of the silicon carbide filler and its compatibility with the organic matrix material.

[0009] In embodiments of the present application, the highly spherical, high-purity silicon carbide filler has a silicon carbide crystal form selected from one or more of the following: 2H phase, 3C phase, 4H phase, and 6H phase. This silicon carbide filler having a suitable crystal form can effectively enhance the thermal conductivity of the thermally conductive and absorbing composition and its cured product.

[0010] In the embodiment of the present application, the physicochemical parameters of the high sphericity and high purity silicon carbide filler meet the following requirements: the bulk density is greater than 1.5 g / cm 3 The breakdown field strength is greater than 200V / mm; the thermal conductivity is greater than 250W / mk. The silicon carbide filler particles are relatively round, exhibiting excellent breakdown resistance and thermal conductivity, which contributes to the excellent flowability, thermal conductivity, and breakdown resistance of the thermally conductive and absorbing composition.

[0011] In the embodiment of the present application, the ratio of the average particle size of the large-diameter thermally conductive particles to the average particle size of the small-diameter thermally conductive particles is greater than 3. The combination of large-diameter and small-diameter thermally conductive particles can increase the overall packing density of the thermally conductive filler and provide more effective thermal conduction pathways, thereby improving the thermal conductivity of the thermally conductive and absorbing composition.

[0012] In some embodiments of the present application, the average particle size of the small-particle thermally conductive particles is less than 5 μm, and the average particle size of the large-particle thermally conductive particles is greater than 20 μm. The average particle sizes of the large and small-particle thermally conductive fillers can be selected and controlled according to actual needs. The average particle sizes of the large and small-particle fillers provided herein are more conducive to the thermally conductive and absorbing composition meeting the heat dissipation requirements between electronic components such as chips and heat sinks in electronic devices.

[0013] In some embodiments of the present application, the large-particle thermally conductive particles include a thermally conductive filler having an average particle size of 60 μm or greater; the thermally conductive filler having an average particle size of 60 μm or greater includes a highly spherical, high-purity silicon carbide filler. In this case, the silicon carbide filler has a relatively large average particle size of 60 μm or greater, which is beneficial for improving the thermal conductivity of the thermally conductive and absorbing composition. In some embodiments, the average particle size of the highly spherical, high-purity silicon carbide filler is between 60 μm and 300 μm, and further between 60 μm and 150 μm.

[0014] In some embodiments of the present application, the small-particle thermally conductive particles include two types of filler particles: one having an average particle size of less than 1 μm and another having an average particle size greater than 1 μm and less than or equal to 5 μm. Using two types of small-particle thermally conductive fillers is more conducive to increasing the overall packing density of the thermally conductive filler.

[0015] In some embodiments of the present application, the small-size thermally conductive particles include one or more of zinc oxide, aluminum oxide, and magnesium oxide. Oxide thermally conductive particles generally have high sphericity, good fluidity, and generally contain hydroxyl groups on their surfaces, which provide good compatibility with organic matrices.

[0016] In some embodiments of the present application, the ratio of the average particle size of the large-sized thermally conductive particles to the average particle size of the small-sized thermally conductive particles is greater than 20. A larger average particle size ratio of the large-sized to small-sized thermally conductive particles is more conducive to achieving a higher packing density of the overall thermally conductive filler, thereby improving the thermal conductivity of the thermally conductive and absorbing composition.

[0017] In some embodiments of the present application, the thermally conductive filler further comprises medium-sized thermally conductive particles, wherein the average particle size of the medium-sized thermally conductive particles is between that of the large-sized thermally conductive particles and the small-sized thermally conductive particles. The introduction of medium-sized thermally conductive particles can adjust the rheological properties, stability, and thermal conductivity of the thermally conductive and absorbing composition.

[0018] In an embodiment of the present application, the medium-sized thermally conductive particles include one or more of oxides, carbides, and nitrides.

[0019] In the embodiment of the present application, the total mass proportion of the thermally conductive filler in the thermally conductive and wave-absorbing composition is 50%-98%, which ensures that the cured product of the thermally conductive and wave-absorbing composition using the thermally conductive filler can construct a good thermal conductive network.

[0020] In some embodiments of the present application, the high-sphericity, high-purity silicon carbide filler comprises 35-60% by weight of the thermally conductive and wave-absorbing composition. A suitably high percentage of the high-sphericity, high-purity silicon carbide filler, as a large-particle thermally conductive filler component, is beneficial for improving the thermal conductivity of the thermally conductive and wave-absorbing composition.

[0021] In an embodiment of the present application, the spherical carbonyl iron has an average diameter of 1 μm to 50 μm, and the flaky carbonyl iron has an average lateral dimension of 5 μm to 50 μm. These average diameters of the spherical carbonyl iron and the average lateral dimension of the flaky carbonyl iron are within suitable ranges, facilitating their good dispersion in the thermally conductive and absorbing composition without significantly affecting the composition's fluidity and improving the composition's absorbing properties.

[0022] In an embodiment of the present application, the mass ratio of the spherical carbonyl iron to the flake carbonyl iron in the thermally conductive and absorbing composition is within the range of (5-20):1. Controlling the use of a larger amount of spherical carbonyl iron than flake carbonyl iron, and maintaining a suitable mass ratio between the two, ensures that the introduction of the spherical carbonyl iron does not reduce the fluidity of the thermally conductive and absorbing composition. Furthermore, through the gradation of the spherical carbonyl iron and the addition of the highly spherical, high-purity silicon carbide filler, the thermally conductive and absorbing composition effectively absorbs electromagnetic waves across the entire frequency range.

[0023] In the embodiment of the present application, the mass of the highly spherical, high-purity silicon carbide filler is 1.2-10 times the mass of the spherical carbonyl iron and the flaky carbonyl iron combined. In this case, the silicon carbide filler and the two carbonyl iron morphologies are more conducive to the synergistically enhanced absorption effect.

[0024] In the embodiment of the present application, the absorbing filler accounts for 8% to 25% of the total mass of the thermal conductive wave absorbing composition. Adding an appropriate amount of absorbing filler to the thermal conductive wave absorbing composition will not significantly reduce the heat absorption performance of the thermal conductive wave absorbing composition.

[0025] In the embodiment of the present application, the organic matrix includes at least one of a silicone system, an epoxy system, an acrylic system, a polyurethane system, a polyimide system, a polyester system, and a polyolefin system.

[0026] In some embodiments of the present application, the organosilicon system is an addition reaction curing organosilicon system; and the thermal conductive and wave absorbing composition further includes a catalyst and an inhibitor.

[0027] In some embodiments of the present application, the thermal conductive and wave absorbing composition further comprises a filler treatment agent. The introduction of the filler treatment agent can reduce the agglomeration / sedimentation of the thermal conductive fillers and wave absorbing fillers in the thermal conductive and wave absorbing composition.

[0028] In an embodiment of the present application, the thermally conductive and absorbing composition has an extrusion rate of 8.0 g / min or greater at a pressure of 0.62 MPa; a thermal conductivity of 7.5 W / (m·K) or greater; a critical breakdown field strength of 200 V / mm or greater; and an electromagnetic wave isolation of less than -90 dB. This composition exhibits high fluidity, excellent thermal conductivity, excellent wave absorption, and good breakdown resistance.

[0029] A second aspect of the present invention provides the use of the thermally conductive and wave-absorbing composition or its cured product as described in the first aspect of the present invention in thermally conductive materials, wave-absorbing materials, and thermally conductive and wave-absorbing materials. Because the thermally conductive and wave-absorbing composition of the present invention exhibits excellent thermal conductivity and wave-absorbing properties, it or its cured product can be used as a material having at least one of thermal conductivity and wave-absorbing properties.

[0030] A third aspect of the present invention provides an electronic device comprising a cured product of the heat-conducting and wave-absorbing composition described in the first aspect of the present invention. The cured product is particularly suitable as a heat-conducting and wave-absorbing material with excellent performance in electronic devices.

[0031] In some embodiments of the present application, the electronic device includes an electronic component and a cured product of the thermally conductive and wave-absorbing composition disposed on the electronic component. The cured product can promptly and effectively conduct heat generated by the electronic component and reduce signal interference from the electronic component to adjacent components.

[0032] In some embodiments of the present application, the electronic device further includes a circuit board, on which a plurality of the electronic components and a heat dissipation structure are disposed. The heat dissipation structure and the circuit board define a housing space, and the plurality of electronic components are located within the housing space. A heat-conductive and absorbing material is disposed between each of the electronic components and the heat dissipation structure, and the heat-conductive and absorbing material includes a cured product of the heat-conductive and absorbing composition.

[0033] Thermally conductive and absorbing materials with excellent comprehensive performance are provided between each electronic component and the heat dissipation structure, which can not only effectively solve the thermal failure problem of electronic components, but also reduce the signal interference of multiple electronic components located in the same accommodation space, so that they can all operate well. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a structural diagram of a circuit board provided with a heat sink and multiple chips in the prior art.

[0035] Figure 2 A schematic structural diagram of a circuit board provided with a heat sink and multiple chips provided in this application.

[0036] Figure 3 The figure shows a fitting diagram of the thermal resistance values ​​of the cured thermal conductive and wave absorbing composition of Example 1 at different thicknesses measured according to ASTM D5470.

[0037] Figure 4 The following table shows the isolation test results of a blank isolation verification tool (a), the isolation test results of an isolation verification tool using the cured thermal conductive absorbing composition of Example 1 (b), and the isolation test results of an isolation verification tool using the cured thermal conductive absorbing composition of Comparative Example 4 (c). DETAILED DESCRIPTION

[0038] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0039] Electronic devices often contain numerous heat-generating electronic components (such as chips). These components generate significant heat during operation, and the accumulation of this heat can have a detrimental impact on their lifespan and reliability. Thermally conductive materials are needed to conduct this heat away. Furthermore, as the integration of electronic components continues to increase, the distances between adjacent components are getting closer, increasing the likelihood of electromagnetic interference and affecting the operation of precision electronic equipment. Consequently, measures are needed to reduce electromagnetic interference.

[0040] like Figure 1 As shown, a plurality of heat-generating electronic components are provided on the circuit board 11. In this embodiment, the electronic components are chips 12 as an example for explanation. A heat sink 14 is also provided on the circuit board 11. An interface thermal conductive material 13 is provided between each chip 12 and the heat sink 14 for heat conduction and heat dissipation. At the same time, a plurality of metal isolation ribs 15 are used to separate the receiving space enclosed by the heat sink 14 and the circuit board 11 into a plurality of isolation cavities, so that each chip 12 is located in a different isolation cavity to avoid signal interference. Among them, the chip 12 can be a single-function chip, or a system-on-chip (SOC) that integrates multiple functional modules.

[0041] However, due to the presence of the metal isolation rib 15, Figure 1 The architecture shown has the disadvantages of large single board layout area, complex structure, and heavy weight of the entire electronic equipment. Figure 2 The integrated circuit structure shown. Figure 2 and Figure 1 In comparison, the use of metal isolation ribs is reduced, and the thermal conductive material provided between the chip and the heat sink is replaced with a material having both thermal conductivity and wave absorption functions (i.e., thermal conductive wave absorbing material 23), so that a larger number of electronic components can be arranged together in a large cavity, and the overall area of ​​the single board is reduced by more than 20%.

[0042] With the application of 5G technology and the development of electronic devices towards high integration, multifunctionality, and miniaturization, the requirements for the electromagnetic wave absorption and heat conduction capabilities of the thermally conductive and absorbing material 23 are becoming increasingly stringent. Existing thermally conductive and absorbing materials generally achieve their thermal conductivity and absorbing properties by combining a single-function thermally conductive filler (which only conducts heat) with an absorbing filler (which only absorbs waves).

[0043] Among them, in terms of meeting the overall thermal conductivity of the material, thermal conductive fillers are generally dominated by large-particle powders, and fillers with higher thermal conductivity coefficients are used as large-particle components. Aluminum nitride, boron nitride, and diamond are common thermal conductive fillers with higher theoretical thermal conductivity coefficients. Among them, aluminum nitride cannot be spheroidized using the traditional high-temperature melting and spheroidization method, which makes the production cost of highly spherical aluminum nitride high. Boron nitride currently exists in the form of hexagonal boron nitride, and the industry has not yet made a breakthrough in the granulation and spheroidization technology of boron nitride. The content of surface active groups (such as hydroxyl groups) of diamond powder with a very high theoretical thermal conductivity coefficient is extremely low, and its compatibility with organic matrices (such as epoxy resins, silicone resins, etc.) is poor and cannot be filled in large quantities.

[0044] Among them, in terms of fillers with simple absorbing functions, the main ones are magnetic loss-type absorbing materials such as carbonyl, iron powder, and sendust, and in order to ensure the fluidity of the thermal conductive absorbing composition, the absorbing fillers are basically spherical. The absorbing range of the overall thermal conductive absorbing material is not wide enough, for example, it cannot cover low-frequency absorbing performance.

[0045] Silicon carbide is a typical dielectric absorber material with extremely high theoretical thermal conductivity, high theoretical breakdown strength, and good chemical resistance. It holds promise as a filler with both thermal conductivity and absorbency. However, existing silicon carbide powders, most of which come from the abrasives industry, suffer from shortcomings such as poor sphericity and breakdown resistance. Directly incorporating silicon carbide into thermally conductive cell compositions can result in poor fluidity, low fill rate, and low breakdown strength. Consequently, silicon carbide is rarely used in existing thermally conductive and absorbent compositions. Given this, the present invention provides a composition containing silicon carbide filler that combines excellent fluidity with both thermal conductivity and absorbency.

[0046] Specifically, an embodiment of the present application provides a thermally conductive and absorbing composition, comprising an organic matrix, a thermally conductive filler, and an absorbing filler; wherein the thermally conductive filler comprises large-particle-size thermally conductive particles and small-particle-size thermally conductive particles, and the large-particle-size thermally conductive particles comprise high-sphericity and high-purity silicon carbide fillers; wherein the sphericity of the high-sphericity and high-purity silicon carbide fillers is above 0.8, and the mass content of silicon carbide is greater than or equal to 99.0%; the absorbing filler comprises spherical carbonyl iron and flaky carbonyl iron.

[0047] The above-mentioned composition provided by the present application controls the large-particle thermal conductive filler to include a silicon carbide filler with a high thermal conductivity coefficient and a sphericity of more than 0.8, which is more conducive to the full play of the high thermal conductivity of the silicon carbide filler itself, and the morphology of the silicon carbide filler is closer to an ideal sphere. It can be added to the above-mentioned composition at a large mass ratio without significantly thickening the composition or affecting its fluidity, so that the above-mentioned composition has good applicability and good thermal conductivity. At the same time, the SiC purity of the silicon carbide filler is also relatively high, and its actual breakdown resistance is relatively strong, so that the critical breakdown field strength of the cured product of the above-mentioned composition is relatively high and the insulation withstand voltage is good. In addition, although the present application classifies the above-mentioned silicon carbide filler into the category of thermal conductive fillers, it is not only used as a thermal conductive filler, but it is actually also a dielectric absorbing material. When used in combination with spherical carbonyl iron and flaky carbonyl iron, it can play a synergistic absorbing role, enhance the absorbing ability of the overall composition, and achieve full absorbing coverage of medium, low and high frequencies. In particular, the introduction of flaky carbonyl iron can ensure that the above composition absorbs electromagnetic waves in the ultra-low frequency band.

[0048] Therefore, the thermally conductive and wave-absorbing composition provided in the present application can take into account good fluidity, thermal conductivity, wave-absorbing performance, and breakdown resistance.

[0049] Among them, sphericity is a parameter that characterizes the morphology of particles. The closer the particles are to spherical in morphology, the closer their sphericity is to 1; the more irregular the particle shape, the smaller their sphericity. The sphericity of the above-mentioned silicon carbide filler is above 0.8, and its morphology is closer to an ideal sphere. The silicon carbide filler can be a spherical or quasi-spherical particle. The "sphericity" of the above-mentioned silicon carbide filler specifically refers to its average sphericity, which can be determined based on a scanning electron microscope (SEM) photograph of the silicon carbide filler in combination with image analysis software. For example, the projected area A and projected perimeter PM of a single silicon carbide filler particle can be measured from an SEM photograph containing multiple (such as more than 100) silicon carbide filler particles. If the area of ​​the perfect circle corresponding to the perimeter PM is set to B, the sphericity of the particle is A / B. Since B=πr 2 , PM=2πr, so B=π×(PM / 2π) 2 , accordingly, the sphericity of each particle can be calculated according to A / B = A × 4π / (PM) 2 The sphericity of 100 random particles is thus calculated, and the average value thereof is taken as the average sphericity.

[0050] Silicon carbide material has a high hardness and melting point, making it difficult to spheroidize using conventional methods such as airflow crushing and melt-to-balling. However, in the embodiments of the present application, the silicon carbide filler with a sphericity of 0.8 or greater can be obtained by sand-grinding the carbide powder, melting it into balls using a high-temperature plasma flame, or granulating micron-sized silicon carbide powder into balls. This achieves the transformation of the silicon carbide powder from sharp-edged particles (sphericity less than 0.5) to highly spherical silicon carbide filler particles. This results in a less prone to thickening of the silicon carbide filler when added to the thermally conductive and wave-absorbing composition, while maintaining a high fill rate.

[0051] In the present application, the sphericity of the silicon carbide filler is within the range of 0.8-1.0, for example, 0.82, 0.83, 0.85, 0.86, 0.88, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.98, 0.99, etc. If the average sphericity of the silicon carbide filler is less than 0.8, the contact between the particles becomes significant, the interfacial thermal resistance increases, and the thermal conductivity of the overall thermally conductive and absorbing composition is poor. In some embodiments, the sphericity is within the range of 0.90-1.0.

[0052] In the present application, the mass content of silicon carbide in the high-sphericity and high-purity silicon carbide filler is greater than or equal to 99.0%. That is, the purity of silicon carbide in the silicon carbide filler is greater than or equal to 99.0%. It is understood that in this case, the mass content of impurity elements in the silicon carbide filler is less than or equal to 1%. Among them, the impurity elements include one or more of phosphorus (P), nitrogen (N), oxygen (O), boron (B), iron (Fe), nickel (Ni), etc., but are not limited thereto. Among them, the sum of each impurity element and all impurity elements is less than or equal to 1%.

[0053] Although silicon carbide materials have a high theoretical breakdown strength, reaching 280 kV / mm, as mentioned above, commercially available silicon carbide products typically come from the abrasive industry, are low in purity, and have angular particles that are prone to tip discharge. Their actual breakdown strength is only tens to hundreds of volts per millimeter. The silicon carbide fillers provided in the embodiments of this application not only have high sphericity, but also high purity and low impurity content, which are more conducive to improving their breakdown resistance.

[0054] In some embodiments of the present application, the mass content of silicon carbide in the highly spherical, high-purity silicon carbide filler is greater than or equal to 99.9%. It is understood that in this case, the mass content of impurity elements in the silicon carbide filler is less than or equal to 0.1%. In some embodiments, the mass content of silicon carbide in the silicon carbide filler is greater than or equal to 99.99%. The higher purity of the silicon carbide filler is more conducive to improving its breakdown resistance.

[0055] Exemplarily, in order to increase the content of silicon carbide in silicon carbide filler, when carbon powder and silicon powder are used to prepare silicon carbide powder by high-temperature curing reaction, the silicon powder used is controlled to be high-purity silicon powder with a purity greater than 99%, preferably greater than 99.99%. In addition, the synthesized / commercially available silicon carbide powder can be decarbonized under a high-temperature inert atmosphere to reduce the residual carbon content on the surface of the silicon carbide and reduce its effect on the breakdown resistance of the powder. In addition, in order to reduce the nitrogen content in the silicon carbide filler, the synthesized / commercially available silicon carbide powder can be denitrified. In addition, due to the high hardness of the silicon carbide material, during its air flow crushing and solid transportation process, the transported stainless steel / metal pipe will be scratched, thereby introducing impurity elements such as iron (Fe) and nickel (Ni), which ultimately leads to excessive impurity content. Therefore, it is necessary to perform secondary magnetic separation to purify and reduce the content of magnetic elements such as Fe and Ni.

[0056] In the present application, the content of silicon carbide and the content of impurity elements in the above-mentioned silicon carbide filler can be obtained by performing inductively coupled plasma (ICP) testing, X-ray photoelectron spectroscopy (XPS) testing, or other elemental analysis methods well known in the industry on the silicon carbide filler.

[0057] In some embodiments of the present application, the surface of the high-sphericity, high-purity silicon carbide filler further comprises a coating. The coating may be made of insulating materials such as aluminum oxide, magnesium oxide, and silicon oxide. The presence of the insulating coating can enhance the breakdown resistance of the silicon carbide filler and its compatibility with an organic matrix (such as a resin material), thereby improving the dispersibility and fluidity of the thermally conductive and wave-absorbing composition. The thickness of the coating is typically at the nanometer level. The coating may be constructed by one or more methods including, but not limited to, coprecipitation, sol-gel, hydrothermal / solvothermal, coating, ball milling, physical vapor deposition (such as evaporation, ion plating, sputtering, etc.), and chemical vapor deposition. It should be noted that, when a coating is present on the surface of the silicon carbide filler, the sphericity of the silicon carbide filler specifically refers to the sphericity of the core-shell composite material composed of the silicon carbide core and the outer coating. The particle size of the silicon carbide filler specifically refers to the particle size of the core-shell composite material composed of the silicon carbide core and the outer coating.

[0058] In an embodiment of the present application, the silicon carbide crystal form of the above-mentioned high-sphericity and high-purity silicon carbide filler can be selected from one or more of the 2H phase, 3C phase, 4H phase, and 6H phase. The thermal conductivity coefficients of silicon carbide materials of different crystal forms are somewhat different, and by controlling the silicon carbide material added to the above-mentioned thermal conductive and wave absorbing composition to be selected from the above-mentioned suitable crystal form, the thermal conductivity of the composition and its cured product can be effectively improved. Among them, the 2H phase silicon carbide crystal is an ABAB type hexagonal crystal; the 3C phase silicon carbide crystal is an ABCABC type face-centered cubic crystal; the 4H phase silicon carbide crystal is an ABCBABCB type hexagonal crystal; and the 6H phase silicon carbide crystal is an ABCACB type hexagonal crystal. In some embodiments, the silicon carbide crystal form of the above-mentioned silicon carbide filler is 3C phase (also known as β phase). The thermal conductivity coefficient of the 3C phase silicon carbide material is very high, and it can greatly improve the thermal conductivity of the above-mentioned composition and its cured product. Among them, the silicon carbide crystal form in the silicon carbide filler can be determined by powder X-ray diffraction.

[0059] In the embodiment of the present application, the physicochemical parameters of the high sphericity and high purity silicon carbide filler meet the following requirements: the bulk density is greater than 1.5 g / cm 3 The critical breakdown field strength is greater than 200V / mm; the thermal conductivity is greater than 250W / (m·K). The silicon carbide filler particles with high sphericity are rounder and can be densely packed. The bulk density (also known as tap density) can be greater than 1.5g / cm 3 . In addition, the silicon carbide filler with high sphericity has less contact between particles and reduces the interfacial thermal resistance, so the thermal conductivity of the silicon carbide filler is relatively high. At the same time, the silicon carbide filler with high sphericity is spherical or quasi-spherical with fewer or even no edges, which is not easy to produce tip discharge and has high breakdown resistance; and the silicon carbide content in the silicon carbide filler is greater than or equal to 99.0%. With the dual blessing of high sphericity and high purity, the critical breakdown field strength of the above-mentioned high-sphericity and high-purity silicon carbide filler is higher.

[0060] In some embodiments of the present application, the bulk density of the high-sphericity high-purity silicon carbide filler is greater than or equal to 2.0 g / cm 3 The critical breakdown field strength of the high-sphericity and high-purity silicon carbide filler is greater than or equal to 500 V / mm. The thermal conductivity of the high-sphericity and high-purity silicon carbide filler is greater than or equal to 280 W / (m·K).

[0061] In an embodiment of the present application, the particle size of the high-sphericity high-purity silicon carbide filler is between 1 μm and 300 μm. For example, the particle size can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 220 μm, 250 μm, 280 μm, etc. Wherein, the particle size of the silicon carbide filler does not exceed 300 μm, and can further be less than or equal to 200 μm, or less than or equal to 150 μm. In some embodiments, the particle size of the silicon carbide filler is between 1 μm and 150 μm. The particle size of the silicon carbide filler may be greater than or equal to 30 μm, or greater than or equal to 40 μm, or greater than or equal to 60 μm, or greater than or equal to 80 μm, or greater than or equal to 100 μm, etc.

[0062] In some embodiments, the particle size of the high-sphericity, high-purity silicon carbide filler is between 30 μm and 150 μm, and can further be between 40 μm and 150 μm, 60 μm and 150 μm, or 100 μm and 150 μm. A suitably large particle size range for the high-sphericity, high-purity silicon carbide filler ensures that high sphericity is easily achieved and effectively improves the thermal conductivity of the thermally conductive and absorbing composition using the filler, while also preventing sedimentation in the composition due to excessively large particle size.

[0063] In the present application, the average particle size of the large-particle-diameter thermally conductive particles is greater than the average particle size of the small-particle-diameter thermally conductive particles. In the embodiment of the present application, the ratio of the average particle size of the large-particle-diameter thermally conductive particles to the average particle size of the small-particle-diameter thermally conductive particles is greater than 3. In this way, the packing density of the overall thermally conductive filler can be made higher by means of the coordination between the large- and small-particle-diameter thermally conductive particles, that is, the more thermally conductive fillers there are in a unit space, the more effective thermal conductive paths formed by the mutual contact between the thermally conductive fillers, and thus the thermal conductivity of the above-mentioned composition containing such thermally conductive fillers is better. Exemplarily, the ratio of the average particle size of the large-particle-diameter thermally conductive particles to the small-particle-diameter thermally conductive particles is, for example, greater than 4, greater than 6, greater than 10, greater than 20, greater than 30, greater than 40, greater than 60, and the like.

[0064] In some embodiments of the present application, the ratio of the average particle size of the large-particle thermally conductive particles to the average particle size of the small-particle thermally conductive particles is greater than 20. If the large-particle thermally conductive particles and the small-particle thermally conductive particles each include two or more fillers with different average particle sizes, this specifically refers to the ratio of the average particle size of the large-particle thermally conductive filler with the largest average particle size to the small-particle thermally conductive filler with the smallest average particle size being greater than 20. According to theoretical calculations of thermally conductive filler fillings with multiple particle size combinations, a higher average particle size ratio of the large-particle thermally conductive particles to the small-particle thermally conductive particles facilitates a higher packing density of the overall thermally conductive filler, thereby improving the thermal conductivity of the composition.

[0065] In some embodiments of the present application, the average particle size of the small-particle thermally conductive particles is less than 5 μm, and the average particle size of the large-particle thermally conductive particles is greater than 20 μm. Wherein, the large-particle thermally conductive particles and the small-particle thermally conductive particles can independently include at least one filler with an average particle size. In some cases, the large-particle thermally conductive particles and / or the small-particle thermally conductive particles can independently include at least two fillers with different average particle sizes. Accordingly, the thermally conductive filler in the above-mentioned composition includes at least two filler particles with different average particle sizes (when there are two types, the large-particle thermally conductive particles and the small-particle thermally conductive particles only contain one filler with an average particle size), preferably including at least three filler particles with different average particle sizes (in this case, at least one of the small-particle thermally conductive particles and the large-particle thermally conductive particles includes at least two filler particles with different average particle sizes). In addition, taking small-particle thermally conductive particles as an example, the two fillers with different average particle sizes can be of the same material, or different materials.

[0066] In some embodiments, the small-particle thermally conductive particles include thermally conductive particles having an average particle size of less than 1 μm (referred to as first small-particle thermally conductive particles), and thermally conductive particles having an average particle size greater than 1 μm and less than or equal to 5 μm (referred to as second small-particle thermally conductive particles). Small-particle thermally conductive particles have a high gap-filling ability. The use of two types of small-particle thermally conductive particles is more conducive to improving the packing density of the overall thermally conductive filler and the filling rate of the small-particle thermally conductive particles themselves. Among them, the average particle size of the small-particle thermally conductive particles may be greater than or equal to 0.1 μm. The average particle size of small-particle thermally conductive particles with an average particle size of less than 1 μm may specifically be in the range of 0.1 μm-1 μm, for example, 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, or 1.0 μm, etc. The average particle size of the small-sized thermally conductive particles with an average particle size between (1 μm, 5 μm) can specifically be 1.2 μm, 1.5 μm, 2 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, or 5.0 μm.

[0067] For example, the large-particle-size thermally conductive particles may include one or more of thermally conductive particles having an average particle size of 30 μm or greater, thermally conductive particles having an average particle size of 40 μm or greater, thermally conductive particles having an average particle size of 60 μm or greater, thermally conductive particles having an average particle size of 80 μm or greater, thermally conductive particles having an average particle size of 100 μm or greater, and thermally conductive particles having an average particle size of 120 μm or greater. Accordingly, the average particle size of the carbonized filler may also be selected from one or more of these listed average particle size values.

[0068] In some embodiments of the present application, the average particle size of the large-particle thermally conductive particles is above 40 μm. In some embodiments, the large-particle thermally conductive particles include a thermally conductive filler having an average particle size of 60 μm or more; the thermally conductive filler having an average particle size of 60 μm or more includes the above-mentioned high-sphericity and high-purity silicon carbide filler. That is, in this case, the average particle size of the high-sphericity and high-purity silicon carbide filler is above 60 μm. In this case, the average particle size of the silicon carbide filler is less than or equal to 300 μm, and the average particle size of the silicon carbide filler is between 60 μm and 300 μm, for example, further between 60 μm and 150 μm, between 100 μm and 150 μm, etc. In other embodiments, the large-particle thermally conductive particles include thermally conductive fillers with an average particle size greater than 20 μm and less than or equal to 40 μm, and thermally conductive fillers with an average particle size greater than 60 μm, and the thermally conductive particle fillers with an average particle size greater than 60 μm include the above-mentioned high-sphericity and high-purity silicon carbide fillers.

[0069] In yet other embodiments, the large-particle thermally conductive particles include a thermally conductive filler having an average particle size of 100 μm or greater, and the thermally conductive filler having an average particle size of 100 μm or greater includes the aforementioned high-sphericity, high-purity silicon carbide filler. In this case, the average particle size of the silicon carbide filler is greater than 100 μm, for example, between 100 μm and 300 μm, and further may be between 100 μm and 150 μm.

[0070] In other embodiments of the present application, the above-mentioned large-particle thermally conductive particles may include, in addition to the above-mentioned high-sphericity high-purity silicon carbide filler, one or more of conventional silicon carbide fillers, aluminum nitride fillers, boron nitride fillers, silicon nitride fillers, diamond fillers, etc., but are not limited thereto. Among them, the sphericity of conventional silicon carbide fillers is below 0.5. The shape of conventional silicon carbide fillers can be spherical or spherical, or polyhedrons (such as hexahedrons, octahedrons, etc.), or irregular shapes, etc. In general, the thermal conductivity of large-particle thermally conductive particles is higher than that of small-particle thermally conductive particles, which is more conducive to improving the thermal conductivity of the above-mentioned composition containing thermally conductive fillers.

[0071] In the embodiments of the present application, the small-particle thermally conductive particles can be selected from one or more oxides such as zinc oxide, aluminum oxide, and magnesium oxide. Oxide thermally conductive fillers generally contain hydroxyl groups on their surfaces, which provide good compatibility with organic matrices. Furthermore, the morphology of the small-particle thermally conductive particles can be one or more of spherical or quasi-spherical, flake-like, fibrous, acicular, or amorphous, with spherical or quasi-spherical shapes being more common.

[0072] In some embodiments of the present application, the thermally conductive filler also includes medium-sized thermally conductive particles. That is, the thermally conductive filler includes large-sized thermally conductive particles, small-sized thermally conductive particles and medium-sized thermally conductive particles at the same time. Among them, the average particle size of the medium-sized thermally conductive particles is between the average particle size of the small-sized thermally conductive particles and the average particle size of the large-sized thermally conductive particles. In this case, the thermally conductive filler includes at least 3 types of thermally conductive particles with different average particle sizes. In this case, the ratio of the average particle size of the large-sized thermally conductive particles to the average particle size of the small-sized thermally conductive particles is generally above 20. With the help of the coordination between thermally conductive fillers with large, medium and small multi-level particle sizes, it is more conducive to improving the bulk density of the overall thermally conductive filler. Similarly, the medium-sized thermally conductive particles may include two or more fillers with different average particle sizes, or include a filler with one average particle size.

[0073] In some embodiments, the average particle size of the medium-sized thermally conductive particles is greater than 5 μm and less than or equal to 20 μm. For example, the average particle size of the medium-sized thermally conductive particles may include one or more of 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 20 μm, etc. In some embodiments, the average particle size of the medium-sized thermally conductive particles is between 10 μm and 20 μm.

[0074] In an embodiment of the present application, the material of the medium-sized thermally conductive particles may include one or more oxides, carbides, nitrides, and the like. For example, the oxide may be selected from one or more of zinc oxide, aluminum oxide, magnesium oxide, and the like. The carbide may be selected from one or more of silicon carbide, boron carbide, tungsten carbide, and the like. The nitride may be selected from one or more of aluminum nitride, boron nitride, silicon nitride, and the like. Furthermore, the morphology of the medium-sized filler may be selected from one or more of spherical or quasi-spherical, flaky, fibrous, acicular, amorphous, and the like.

[0075] It should be noted that the above-mentioned terms "large particle size" and "small particle size" in this application are all relative. In different application scenarios, the particle size ranges of large particle size and small particle size may be different. For example, in other embodiments of the present application, the average particle size of the small particle size thermal conductive particles is below 20 μm, and the average particle size of the large particle size thermal conductive particles is greater than 20 μm. For another example, in some other embodiments of the present application, the average particle size of the large particle size thermal conductive particles is above 10 μm, and the average particle size of the small particle size thermal conductive particles is less than 10 μm, or even at the nanometer level.

[0076] In this application, the average particle size of each of the materials mentioned above can be measured using a particle size distribution analyzer based on the laser diffraction method. From the obtained particle size distribution curve, the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50% can be read, which is the average particle size, also known as the median particle size or D50 particle size.

[0077] In embodiments of the present application, the total weight percentage of the thermally conductive filler in the thermally conductive and absorbing composition is greater than 50%, and further within the range of 50%-98%. This ensures that the cured thermally conductive and absorbing composition using the thermally conductive filler forms a good thermally conductive network and that the composition has suitable flowability. The total weight percentage of the thermally conductive filler herein refers to the total weight percentage of the large-particle thermally conductive particles, small-particle thermally conductive particles, and medium-particle thermally conductive particles (if any) contained in the thermally conductive and absorbing composition. For example, the total weight percentage of the thermally conductive filler in the thermally conductive and absorbing composition is 55%, 60%, 70%, 75%, 80%, 82%, 85%, 90%, 92%, 93%, 95%, or 97%. In some embodiments, the total weight percentage of the thermally conductive filler in the thermally conductive and absorbing composition is 70%-98%, or 80%-98%.

[0078] Large-particle thermally conductive particles play a primary role in conducting heat in the thermally conductive and wave-absorbing composition. In embodiments of the present application, the large-particle thermally conductive particles can comprise 35% to 60% by weight of the thermally conductive and wave-absorbing composition. This contributes to the excellent thermal conductivity of the composition while preventing phase separation and poor mechanical properties in the cured product. For example, the total mass fraction of the large-particle thermally conductive particles in the thermally conductive and wave-absorbing composition can be 36%, 38%, 40%, 42%, 45%, 48%, 50%, 55%, or 60%. Furthermore, based on the weight of all thermally conductive fillers, the mass fraction of the large-particle thermally conductive particles can be in the range of 40% to 70%, for example, 42%, 45%, 46%, 47%, 48%, 49%, 50%, 55%, 60%, 62%, 65%, or 68%. When the large-size thermally conductive particles are only the aforementioned high-sphericity and high-purity silicon carbide filler, the mass proportions of the aforementioned large-size thermally conductive particles are the corresponding mass proportions of the silicon carbide filler.

[0079] Small-particle thermally conductive particles play a key role in the rheological and stability properties of the thermally conductive and absorbing composition. Medium-particle thermally conductive particles can adjust the rheological, stability, and thermal conductivity of the thermally conductive and absorbing composition. In embodiments of the present application, the total weight percentage of small-particle thermally conductive particles in the thermally conductive and absorbing composition can be less than 40%, and further can be within the range of 10%-35%. This ensures excellent flowability of the composition. The total weight percentage of medium-particle thermally conductive particles in the thermally conductive and absorbing composition can be no more than 30%, and further can be within the range of 5%-20%. This ensures optimal filling of the overall thermally conductive filler. For example, the total weight percentage of small-particle thermally conductive particles in the thermally conductive and absorbing composition can be 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, etc. The total weight percentage of the medium-sized thermally conductive particles in the thermally conductive and absorbing composition can specifically be 6%, 8%, 10%, 12%, 13%, 15%, 16%, 18%, 20%, etc. Furthermore, based on the total weight of the thermally conductive filler, the weight percentage of the small-sized thermally conductive particles can be in the range of 20%-40%. Based on the total weight of the thermally conductive filler, the weight percentage of the medium-sized filler can be no more than 25%, for example, in the range of 10%-20%.

[0080] In embodiments of the present application, the average diameter of the spherical carbonyl iron used as the absorbing filler component is between 1 μm and 50 μm, for example, 2 μm, 3 μm, 5 μm, 6 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 48 μm. Adding spherical carbonyl iron of an appropriate diameter to the thermally conductive, absorbing composition, along with the highly spherical, high-purity silicon carbide filler, can improve the composition's fluidity and enhance its absorbing capability. In some embodiments, the average diameter of the spherical carbonyl iron is between 1 μm and 20 μm. This average diameter can be determined from the particle size distribution curve of the spherical carbonyl iron based on laser diffraction.

[0081] In an embodiment of the present application, the average lateral size of the flaky carbonyl iron as an absorbing filler component is between 5 μm and 50 μm. The flaky carbonyl iron has an average lateral size of a suitable size, which is conducive to its good dispersion in the above-mentioned thermal conductive absorbing composition, does not significantly reduce the fluidity of the composition, and helps it increase the absorption of electromagnetic waves in the ultra-low frequency band by the above-mentioned composition. The average lateral size can be obtained by statistical calculation based on an electron microscope photograph of the flaky carbonyl iron. For example, the average lateral size of the flaky carbonyl iron is specifically 6 μm, 8 μm, 10 μm, 12 μm, 13 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 48 μm. In some embodiments, the average lateral size of the flaky carbonyl iron is between 10 μm and 30 μm, and further between 10 μm and 20 μm. The thickness of the flaky carbonyl iron is less than its lateral size. Illustratively, the thickness of the flaky carbonyl iron may be in the range of 0.1 μm-5 μm, for example, 0.2 μm, 0.3 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, etc.

[0082] In an embodiment of the present application, in the thermally conductive and absorbing composition, the mass ratio of the spherical carbonyl iron to the flake carbonyl iron is within a range of (5-20):1. In the thermally conductive and absorbing composition, the amount of spherical carbonyl iron is controlled to be greater than that of flake carbonyl iron, and the mass ratio of the two is within an appropriate range. This ensures that the introduction of the spherical carbonyl iron does not reduce the fluidity of the thermally conductive and absorbing composition, and also ensures that the thermally conductive and absorbing composition absorbs electromagnetic waves across the entire frequency range through the gradation of the two. Specifically, the mass ratio of spherical carbonyl iron to flake carbonyl iron can be 6:1, 8:1, 10:1, 11:1, 12:1, 13:1, 15:1, 16:1, 18:1, or 19:1, among others. In some embodiments, this mass ratio is (10-20:1), and can further be (15-20:1).

[0083] In embodiments of the present application, the total mass percentage of the absorbing filler in the thermally conductive and absorbing composition can be in the range of 8%-25%, for example, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, etc. The addition of an appropriate amount of absorbing filler to the composition, combined with the highly spherical, high-purity silicon carbide filler, ensures that the composition has excellent absorbing properties without significantly reducing its heat absorption performance.

[0084] In an embodiment of the present application, the mass of the high-sphericity, high-purity silicon carbide filler is 1.2-10 times the sum of the mass of the spherical carbonyl iron and the flaky carbonyl iron, for example, 1.5 times, 1.8 times, 2.0 times, 2.5 times, 2.8 times, 3 times, 3.2 times, 3.5 times, 3.8 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times or 8 times. In this case, it is more conducive to the synergistically enhanced absorption effect of the silicon carbide filler and the two morphologies of carbonyl iron. In some embodiments, the mass of the silicon carbide filler is 1.5-6 times the sum of the mass of the spherical carbonyl iron and the flaky carbonyl iron.

[0085] In other embodiments of the present application, the above-mentioned absorbing filler, in addition to the spherical carbonyl iron and the flaky carbonyl iron, may also include one or more carbon-based materials, metal materials, transition metal carbides, transition metal nitrides, transition metal carbonitrides, etc. The morphology of these absorbing fillers can be independently selected from one or more of flake, needle, fiber, spherical, or quasi-spherical shapes. Among them, the carbon-based material with absorbing function can be selected from one or more of graphene, carbon nanotubes, carbon black, etc. The metal material with absorbing function can be one or more of iron (Fe), nickel (Ni), cobalt (Co), and their alloys.

[0086] In this application, the organic matrix in the thermally conductive and absorbing composition serves as a continuous phase, within which the dispersed phases (e.g., various thermally conductive and absorbing fillers) in the composition can be dispersed. The organic matrix is ​​particularly suitable for applications requiring insulating properties from the cured product of the thermally conductive and absorbing composition. The cured product of the thermally conductive and absorbing composition is the product obtained after the composition has been cured. The term "cured" primarily refers to the curing of the organic matrix. Within this cured product, the organic matrix serves to stabilize the dispersed phases.

[0087] In the embodiment of the present application, the organic matrix may include at least one of a silicone system, an epoxy system, an acrylic system, a polyurethane system, a polyimide system, a polyester system, a polyolefin system, and the like.

[0088] Examples of curable polymers include silicone polymers, epoxy polymers (such as epoxy resins), polyacrylates, urethane polymers (also known as polyurethanes), phenolic polymers, polyimide polymers, unsaturated polyesters, acrylonitrile butadiene rubber, ethylene-propylene-butadiene rubber, ethylene-propylene rubber, polybutadiene rubber, polyisoprene rubber, and natural rubber.

[0089] In some embodiments, the organic matrix is ​​made of an organosilicon material such as silicone rubber, silicone resin, silicone oil, or epoxy resin, with silicone materials being preferred. Silicone oil is a common name for organopolysiloxane. Generally, the organosilicon material can be an addition-curing organosilicon system or a condensation-curing organosilicon system. In some embodiments, the organosilicon system is an addition-curing organosilicon system, such as an addition polymerization-curing organosilicon rubber.

[0090] In some embodiments of the present application, an addition-curable organosilicon system may include two basic components: an alkenyl-containing organopolysiloxane and a hydrogen-containing (Si-H) organopolysiloxane. These two types of polysiloxanes can undergo an addition reaction under heating conditions to achieve system curing. The hydrogen group here specifically refers to a hydrogen atom bonded to a silicon atom. The alkenyl group can be located at the end of the main molecular chain of the organopolysiloxane or on a side chain of the molecular structure, with the end of the main molecular chain being more common. Furthermore, when the organic matrix is ​​an addition-curable organosilicon system, the above-mentioned thermal conductive and wave-absorbing composition typically also includes functional additives such as catalysts and inhibitors to obtain a composition with excellent physical and chemical properties. Furthermore, the above-mentioned thermal conductive and wave-absorbing composition may also include coupling agents and crosslinking agents.

[0091] Among them, the alkenyl-containing organopolysiloxane can be selected from one or more organopolysiloxanes with vinyl groups at both ends, such as polydimethylsiloxane with vinyl groups at both ends, polyphenylmethylsiloxane with vinyl groups at both ends, dimethylsiloxane-diphenylsiloxane copolymer with vinyl groups at both ends, dimethylsiloxane-phenylmethylsiloxane copolymer with vinyl groups at both ends, and dimethylsiloxane-diethylsiloxane copolymer with vinyl groups at both ends.

[0092] The viscosity of the alkenyl group-containing organopolysiloxane at 25° C. may be 5 mPa·s to 10,000 mPa·s, or further 30 mPa·s to 500 mPa·s. The viscosity of the alkenyl group-containing organopolysiloxane may be measured using a rotational viscometer.

[0093] The number of hydrogen atoms bonded to silicon atoms in the hydrogen-containing organopolysiloxane molecule is 2 or more, preferably 2-50. For example, the hydrogen-containing organopolysiloxane can be selected from one or more of methylhydrogensiloxane-dimethylsiloxane copolymer, polymethylhydrogensiloxane, polyethylhydrogensiloxane, methylhydrogensiloxane-phenylmethylsiloxane copolymer, and the like. The molar ratio of the silicon hydrogen groups in the hydrogen-containing organopolysiloxane to the alkenyl groups in the alkenyl-containing organopolysiloxane can be 0.3-3, for example, specifically 0.5, 0.8, 1.0, 1.2, 1.5, 2.0, 2.2, 2.5, or 2.8. This ensures that the mixed system containing these two polysiloxanes has a suitable curing speed and the cured product has a suitable hardness.

[0094] The viscosity of the hydrogen group-containing organopolysiloxane at 25°C is not particularly limited, but is, for example, within the range of 1 mPa·s to 1000 mPa·s. It is sufficient as long as the hydrogen group-containing organopolysiloxane can be mixed with the alkenyl group-containing organopolysiloxane and cured to form a polymer with good physical properties. The viscosity of the hydrogen group-containing organopolysiloxane can be measured using a rotational viscometer.

[0095] The catalyst is used to catalyze the hydrosilylation reaction between alkenyl groups and silyl groups. The catalyst can be a precious metal catalyst, specifically a platinum-based catalyst, a palladium-based catalyst, a rhodium-based catalyst, or the like. In some embodiments, the catalyst is a platinum-based catalyst, such as one or more common platinum-based catalysts, such as elemental platinum, oxyplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds. The catalyst content in the thermally conductive and wave-absorbing composition can range from 0.1 ppm to 300 ppm, and further can range from 0.1 ppm to 200 ppm.

[0096] The inhibitor is primarily used to inhibit the reaction between the silyl groups and alkenyl groups in the thermally conductive and absorbing composition at room temperature, preventing their premature consumption. This ensures the composition has good fluidity at room temperature and improves its room-temperature storage properties. In embodiments of the present application, the inhibitor can be selected from one or more of acetylene alcohols (such as 1-ethynyl-1-cyclohexanol and 3-butyn-1-ol), organophosphorus compounds (such as triphenylphosphine), nitrogen-containing compounds (such as triallyl isocyanurate or its derivatives), and diallyl maleate. The inhibitor can be present in the thermally conductive and absorbing composition in an amount of 0.01 wt% to 5 wt%, and more preferably 0.1 wt% to 1 wt%.

[0097] Furthermore, when using the aforementioned addition-curable silicone system as the organic matrix, the thermally conductive and absorbing composition can be formulated as a two-component system or a one-component system. A two-component system refers to a thermally conductive and absorbing composition consisting of two separately stored components that are then mixed and cured upon use. A one-component system involves adding various thermally conductive fillers and additives to the organic matrix to form a complete thermally conductive and absorbing composition.

[0098] Similarly, when the organic matrix is ​​an epoxy resin, acrylic resin, or urethane resin, the thermally conductive and absorbing composition may also contain a curing agent. The thermally conductive and absorbing composition can be a one-component or two-component system. In the case of a two-component system, the curing agent and the primary resin component with which it reacts are typically stored separately. Among these, amine compounds are the most common curing agents for epoxy resins. Isocyanate compounds are typically curing agents for acrylic resins. Urethane resins are typically curing agents with isocyanate compounds, and the primary resin is typically a polyol resin.

[0099] To improve the wettability and interaction between the thermally conductive filler and the absorbing filler and the organic matrix, and to prevent agglomeration of the thermally conductive filler and thus increased viscosity, the thermally conductive and absorbing composition of the present application may also contain a filler treatment agent. The filler treatment agent may be selected from one or more of silane compounds, organotitanium compounds, organoaluminum compounds, and phosphate compounds, with silane compounds being preferred. When the filler treatment agent is a silane compound, it may also be referred to as a silane coupling agent.

[0100] The siloxane compound used as the filler treatment agent can be selected from alkoxysilanes or chlorosilanes, preferably alkoxysilanes. For example, the alkoxysilane can be selected from one or more of n-decyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, dialkyldialkoxysilane, aryltrialkoxysilane, diaryldialkoxysilane, α-trimethylsiloxy-ω-(γ-trimethoxysilylethyl)dimethylsilyl-terminated polydimethylsiloxane, and the like.

[0101] In addition, the thermal conductive and wave absorbing composition of the embodiment of the present application may further be added with at least one additive such as an anti-settling agent, an antioxidant, a heat stabilizer, a colorant, a flame retardant, an antistatic agent, etc. as needed, but is not limited thereto.

[0102] The above-mentioned heat-conductive and wave-absorbing composition of the present application not only has high fluidity, but also has good thermal conductivity, wave-absorbing performance and breakdown resistance.

[0103] In an embodiment of the present application, the extrusion rate of the thermally conductive and wave-absorbing composition at a pressure of 0.62 MPa is greater than 8.0 g / min. A higher extrusion rate may reflect the composition's high fluidity. Specifically, the extrusion rate may be 8.0 g / min, 8.5 g / min, 8.8 g / min, 9.0 g / min, 9.5 g / min, 10.0 g / min, etc.

[0104] In embodiments of the present application, the thermal conductivity of the thermally conductive and absorbing composition is greater than 7.0 W / (m·K) (watts per meter per degree Kelvin). It is understood that the thermal conductivity of the thermally conductive and absorbing composition is substantially consistent with the thermal conductivity of its cured product. The thermal conductivity can be measured according to ISO 22007-2 or ASTM 5470.

[0105] In some embodiments, the thermal conductivity of the thermally conductive and absorbing composition, as measured according to ISO 22007-2, is greater than 8.0 W / (m·K), greater than 8.5 W / (m·K), greater than 8.8 W / (m·K), or greater than 9.0 W / (m·K). In some embodiments, the thermal conductivity is within the range of 8.0-12.0 W / (m·K), or further within the range of 9.0-12.0 W / (m·K). In other embodiments, the thermal conductivity of the thermally conductive and absorbing composition, as measured according to ASTM 5470, is greater than 7.0 W / (m·K), for example, within the range of 7.0-12.0 W / (m·K), and further can be greater than 7.8 W / (m·K), for example, within the range of 7.8-12.0 W / (m·K).

[0106] In the embodiments of the present application, the thermally conductive, wave-absorbing composition exhibits an electromagnetic wave isolation of less than -90 dB. This demonstrates the composition's excellent wave-absorbing properties. The composition's electromagnetic wave isolation is essentially the same as that of its cured product.

[0107] In embodiments of the present application, the thermally conductive and absorbing composition exhibits a critical breakdown field strength exceeding 180 V / mm, and further exceeding 200 V / mm. This higher critical breakdown field strength reflects the composition's strong breakdown resistance and excellent insulation properties. The critical breakdown field strength of the composition is essentially equivalent to that of its cured product.

[0108] The present invention also provides a method for preparing a heat-conducting and wave-absorbing composition, comprising the following steps:

[0109] (1) taking silicon carbide powder, purifying it and then sphering it to obtain a high-sphericity and high-purity silicon carbide filler; wherein the sphericity treatment includes one or more of sand grinding, high-temperature plasma flame melting into balls, and micro-powder granulation into balls; the high-sphericity and high-purity silicon carbide filler has a sphericity of greater than 0.8 and a mass content of silicon carbide greater than or equal to 99.0%;

[0110] (2) mixing large-diameter heat-conductive particles including the high-sphericity and high-purity silicon carbide filler, small-diameter heat-conductive particles, wave-absorbing fillers, and an organic matrix to obtain the composition.

[0111] In step (1), most of the silicon carbide powders on the market come from the abrasive industry and have a very low sphericity, generally below 0.5. In addition, due to the high hardness and melting point of silicon carbide, conventional sphericization methods such as air flow crushing and melting into balls cannot achieve sphericization. To this end, the applicant has provided an effective sphericization method for ultra-hard silicon carbide powder, which can be sand grinding, high-temperature plasma flame melting into balls, or granulation of micron-sized silicon carbide powder into balls, thereby transforming the silicon carbide powder from particles with sharp edges into particles with a sphericity of more than 0.8, or even more than 0.9, so that it can show a higher filling fraction and flow characteristics in the thermal conductive and wave absorbing composition.

[0112] Furthermore, in step (1), prior to spheroidizing the silicon carbide powder, the silicon carbide powder is purified to reduce the content of the manufacturing elements therein. In some embodiments of the present application, the purification treatment includes one or more of a decarbonization treatment, a denitrification treatment, and a magnetic separation treatment to reduce the residual carbon content, the residual nitrogen content, and the content of magnetic elements (such as iron and nickel).

[0113] In some embodiments of the present application, in step (1), after the spheroidization treatment, the process further comprises: coating the silicon carbide particles obtained after the spheroidization treatment to form a coating layer on the surface thereof. The material and formation method of the coating layer can be found in the description above.

[0114] In some embodiments of the present application, in step (2), the raw materials forming the thermally conductive and absorbing composition further include medium-sized thermally conductive particles. In this case, step (2) comprises: mixing the small-sized thermally conductive particles, the large-sized thermally conductive particles, and the medium-sized thermally conductive particles with an organic matrix material to obtain the composition. For properties such as the material, particle size, and content of the small-sized thermally conductive particles, the large-sized thermally conductive particles, and the medium-sized thermally conductive particles, please refer to the description above in this application.

[0115] In some embodiments of the present application, in step (2), the thermally conductive and absorbing composition may further include a catalyst, an inhibitor, a filler treatment agent (such as a coupling agent), a cross-linking agent, and other functional additives. Accordingly, during the mixing, these components should be weighed to participate in the mixing.

[0116] Step (2) is the mixing process of the components that constitute the thermally conductive and wave-absorbing composition. The "mixing" can be carried out in a mixing device such as a homogenizer, a planetary mixer, a meshing disperser, a mechanical fusion machine, a sand mill (such as a three-roll mill), etc. The components that constitute the thermally conductive and wave-absorbing composition can be added together or added in batches. An example of batch addition is as follows: first, the organic matrix material and optional functional additives such as filler treatment agents are added to the mixing device for mixing, and then small-particle-sized thermally conductive particles and medium-particle-sized thermally conductive particles (if any) are added. After mixing, large-particle-sized thermally conductive particles are added and mixed evenly. Generally, during or after the mixing, it is necessary to remove bubbles from the system. The methods for removing bubbles can be vacuuming, ultrasound, standing, etc.

[0117] The thermally conductive, wave-absorbing material 23 mentioned earlier in this application can be obtained by curing the aforementioned thermally conductive, wave-absorbing composition. "Curing" specifically refers to the curing of the organic matrix material. The curing process is not particularly limited and can be selected / controlled based on the type of organic matrix material. For example, when the organic matrix material is the aforementioned addition-curing organosilicon system, heat curing is typically used. Common heat curing temperatures range from 100-250°C, and the heating time can range from half an hour to several hours. For another example, when the organic matrix material is an epoxy resin, acrylic resin, or urethane resin, heat curing is also generally used. For another example, when the organic matrix material is the aforementioned condensation-curing organosilicon system, curing can be performed in the presence of moisture, such as in humid air or under humidified conditions. Furthermore, before curing, the thermally conductive, wave-absorbing composition can be applied into a gasket, film, or other irregular shape, depending on product requirements. After curing, the resulting cured product can be packaged or cut, depending on product requirements.

[0118] The embodiments of the present application also provide applications of the thermal conductive and wave absorbing composition or its cured product in thermal conductive materials, wave absorbing materials, and thermal conductive and wave absorbing materials.

[0119] The thermally conductive material, wave-absorbing material, and thermally conductive wave-absorbing material independently comprise a cured product of the aforementioned thermally conductive wave-absorbing composition. It is understood that because the aforementioned composition in the embodiments of the present application has both thermal conductivity and wave-absorbing functions, its cured product can be used as either a purely thermally conductive material or a purely wave-absorbing material. Of course, it is more suitable for use as a thermally conductive wave-absorbing material that combines both wave-absorbing and thermally conductive functions. It is understood that the aforementioned cured product comprises a cured product of an organic matrix material and thermally conductive and wave-absorbing fillers distributed therein.

[0120] In the embodiments of the present application, the cured thermally conductive and absorbing composition exhibits a thermal conductivity of 7.5 W / (m·K) or greater, a critical breakdown field strength of 200 V / mm or greater, and an electromagnetic wave isolation of less than -90 dB. For a detailed description of these parameters, please refer to the preceding description of this application.

[0121] The forms of the above-mentioned heat-conducting material, wave-absorbing material, and heat-conducting and wave-absorbing material are not limited, and can be gel-like, rubber-like, film-like, sheet-like, etc.

[0122] The present invention also provides an electronic device comprising a cured product of the thermally conductive and wave-absorbing composition described in the present invention. Specifically, the electronic device includes an electronic component capable of generating heat during operation, and the cured product of the thermally conductive and wave-absorbing composition described in the present invention disposed on the electronic component.

[0123] In some embodiments, as Figure 2 As shown, the electronic equipment includes Figure 2 The structure shown specifically includes an electronic component 22 and a heat-conducting and wave-absorbing material 23 disposed thereon. The heat-conducting and wave-absorbing material 23 includes a cured product of the heat-conducting and wave-absorbing composition described above in the embodiment of the present application. Figure 2 The structure shown may in some cases be referred to as an integrated circuit structure.

[0124] Furthermore, the electronic device includes a circuit board 21 and a heat dissipation structure 24. The electronic components 22 and the heat dissipation structure 24 are both arranged on the circuit board 21, and the heat dissipation structure 24 and the circuit board 21 enclose an accommodation space, and the electronic components 22 are located in the accommodation space. Figure 2 In the embodiment, a plurality of electronic components 22 are arranged on the circuit board 21, and the plurality of electronic components 22 are all located in the accommodation space. A heat-conducting absorbing material 23 is arranged between each electronic component 22 and the heat dissipation structure 24. The heat-conducting absorbing material 23 can be a cured product of the above-mentioned heat-conducting absorbing composition. Figure 2 Specifically, a heat-conducting and wave-absorbing material 23 is provided between the surface of each electronic component 22 facing away from the circuit board 21 and the heat dissipation structure 24 .

[0125] Among them, each electronic component 22 among the multiple electronic components 22 can be independently selected from one or more components with heat dissipation and / or wave absorption requirements, such as ordinary chips, system-on-chip SOC, filters, power amplifiers, power modules, CPUs (Central Processing Units), GPUs (Graphic Processing Units), temperature sensors, etc.

[0126] In the embodiment of the present application, the above-mentioned electronic devices may include but are not limited to one or more of mobile phones, tablet computers, laptop computers, wearable devices (such as glasses, watches, bracelets, etc.), televisions, burners, digital cameras, game consoles, adapters, routers, gateways, vehicle-mounted equipment, cars, battery systems, etc.

[0127] The embodiments of the present application are further described below with reference to a number of embodiments.

[0128] Before introducing the specific embodiments of the present application, the components involved below are introduced.

[0129] Silicone materials

[0130] a-1: vinyl group-containing organopolysiloxane, specifically dimethylvinylsiloxy-terminated dimethylpolysiloxane having a viscosity of 50 mPa·s (ie, 50 cps) at 25° C. and a vinyl content of 0.6 mmol / g.

[0131] a-2: Hydrogen-containing organopolysiloxane, specifically dimethylhydrogensiloxy-terminated dimethylpolysiloxane, having a viscosity of 30 mPa·s at 25° C. and a mass percentage of hydrogen atoms directly bonded to silicon atoms of 0.078%.

[0132] Filler treatment agent

[0133] b-1: polydimethylsiloxane terminated with α-trimethylsilyloxy-ω-(γ-trimethoxysilylethyl)dimethylsilyl, with a segment number n=22 and a viscosity of 30 mPa·s at 25° C.

[0134] b-2: n-Hexyltrimethoxysilane.

[0135] <c>Thermally conductive fillers

[0136] c-1: Zinc oxide (ZnO) with an average particle size of 0.2 μm, in a polyhedral shape.

[0137] c-2: Alumina (Al2O3) with an average particle size of 5 μm, spherical.

[0138] c-3: Alumina (Al2O3) with an average particle size of 20 μm, spherical.

[0139] c-4: unshaped silicon carbide (SiC) with an average particle size of 120 μm, a purity of 99.99%, and an average sphericity of 0.5.

[0140] c-5: Shaped silicon carbide with an average particle size of 120 μm and a purity of 99.99%, spherical or quasi-spherical, with an average sphericity of 0.9.

[0141] c-6: Shaped silicon carbide with an average particle size of 120 μm and a purity of 99.0%, spherical or quasi-spherical, and an average sphericity of 0.9.

[0142] c-7: Coated silicon carbide with an average particle size of 120 μm, spherical or quasi-spherical, an average sphericity of 0.9, a core of 99.0% pure shaped silicon carbide, and a coating of insulating oxide.

[0143] c-8: Shaped silicon carbide with an average particle size of 120 μm and a purity of 90%, spherical or quasi-spherical, and an average sphericity of 0.9.

[0144] <d>Absorbing fillers

[0145] d-1: spherical carbonyl iron with an average diameter of 5 μm.

[0146] d-2: plate-like carbonyl iron with an average lateral size of 15 μm.

[0147] <e>catalyst

[0148] e-1: 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex in polysiloxane diluent, with a platinum content of 1000 ppm.

[0149] <f>inhibitors

[0150] f-1: 2-Methyl-3-butyn-2-ol.

[0151] Examples 1-3 and Comparative Examples 1-3

[0152] The components of the thermally conductive and absorbing compositions listed in Table 1 and their weight percentages were weighed and mixed in a homogenizer to produce thermally conductive and absorbing compositions. Mixing in the homogenizer was performed by stirring at 1500 rpm for 30 seconds and then at 2000 rpm for 30 seconds. The resulting thermally conductive and absorbing compositions were allowed to stand overnight at room temperature and then tested for thermal conductivity, flowability, dielectric strength, and absorbing properties. The results are summarized in Table 1.

[0153] Thermal Conductivity Test 1: The thermal conductivity of the sample (denoted as TC-1) was measured using a Hot Disk transient technology thermal conductivity tester according to ISO 22007-2. Specifically, two cups were filled with each thermally conductive and absorbent composition, and a planar sensor equipped with a self-heating function was placed inside the cups. Using fine-tuning analysis, temperature drift compensation and time correction were selected between the 50-150 and 50-190 points on the instrument. During the test, the planar sensor was heated at 500 mW for 2-5 seconds, and the temperature (resistance) rise over time during heating was measured. The thermal conductivity of the sample was then determined using a mathematical model fit.

[0154] Thermal Conductivity Test 2: According to ASTM D5470, a steady-state thermal resistance meter was used to test the thermal conductivity of the samples (denoted as TC-2). Each thermally conductive and absorbing composition was applied to one end of a copper rod at varying thicknesses. Under a pressure of 40 psi, the temperature was gradually raised from room temperature to 80°C. Steady-state heat transfer was used to measure the thermal resistance of the thermally conductive and absorbing materials at varying thicknesses (0.5 mm, 1.0 mm, and 1.5 mm). The thermal conductivity of each composition was then fitted.

[0155] Flowability Testing: The extrusion rate (ER) of each thermally conductive and absorbing composition was measured using a fluid dispensing device to assess its flowability. Each thermally conductive and absorbing composition was packaged into a 50cc twin syringe, fitted with 21 sections of a two-component mixing hose, and dispensed at a pressure of 0.62 MPa. The weight of the sample dispensed within 1 minute was recorded as the ER.

[0156] Dielectric strength test: After curing each thermally conductive composition at 60° C. for 12 hours, the insulation breakdown electric field strength (ie, dielectric strength) of the cured product of each thermally conductive composition was tested according to ASTM D149.

[0157] Absorption Performance Test: Using an isolation verification tool (a hood-like heat dissipation structure is placed on the PCB board, which can enclose a cavity between the PCB and the PCB. A dummy chip is placed in this cavity. The inner surface of the heat dissipation structure facing the dummy chip is provided with a cured thermally conductive absorbing composition). The isolation (measured in dB) of the cured thermally conductive absorbing composition against electromagnetic waves is tested.

[0158] Table 1

[0159]

[0160]

[0161] Note: "NG" in Table 1 represents sample data that was not successfully measured.

[0162] in,< / f> < / e> < / d> < / c> Figure 3 The figure shows the fitting diagram of the thermal resistance value of the cured thermal conductive and wave absorbing composition of Example 1 at different thicknesses measured according to ASTM D5470. Figure 3 It was found that the thermal conductivity of the cured product was 9.0 W / (m·K).

[0163] A comparison of Example 1 and Comparative Example 1 in Table 1 shows that, given the same absorbing filler and other thermally conductive fillers other than silicon carbide in the thermally conductive and absorbing composition, Example 1, which uses high-sphericity, high-purity silicon carbide (C-5) as the large-particle thermally conductive component, exhibits significantly better fluidity than Comparative Example 1, which uses low-sphericity silicon carbide powder (C-4). Furthermore, its cured product exhibits high breakdown strength (excellent insulation properties), while its thermal conductivity remains essentially unchanged and remains high, demonstrating excellent reliability in application. While the composition in Comparative Example 1 meets the standards for both thermal conductivity and absorbing performance, its fluidity does not meet the standards and its breakdown resistance is also poor.

[0164] A comparison between Examples 1 and 3 and Comparative Example 2 shows that, with other components of the thermally conductive and absorbing composition being identical, the cured thermally conductive and absorbing composition of Comparative Example 2, which uses low-purity, high-sphericity SiC as the large-particle SiC filler, exhibits relatively low breakdown strength. Furthermore, the thermal conductivity of Comparative Example 2 is also lower than that of Examples 1 and 3, which use SiC fillers of higher purity.

[0165] From the comparison between Examples 2 and 3, it can be seen that when the purity of the high-sphericity SiC powder is the same (all 99%), the puncture strength of the cured thermal conductive and absorbing composition can be improved by coating its surface, but some thermal conductivity will be sacrificed accordingly.

[0166] In addition, a comparison between Comparative Example 3 and Example 3 shows that when the thermally conductive filler composition in the thermally conductive and absorbing composition has the same composition, Comparative Example 3, in which only spherical carbonyl iron is used as the absorbing filler, has poor low-frequency electromagnetic wave absorption performance despite meeting the thermal conductivity, breakdown resistance, and composition fluidity requirements.

[0167] in, Figure 4 The figures show the isolation test results of a blank isolation verification tool (no thermally conductive absorbing material is provided on the heat dissipation structure) (a), the isolation test results of an isolation verification tool using the cured thermally conductive absorbing composition of Example 1 (b), and the isolation test results of an isolation verification tool using the cured thermally conductive absorbing composition of Comparative Example 4 (which differs from Example 1 only in that the absorbing filler does not contain flaky carbonyl iron).

[0168] from Figure 4 It can be seen that after the isolation verification tool is provided with the heat-conducting and wave-absorbing material of Example 1 or Comparative Example 4 of the present application, the tool has a significant absorption effect on electromagnetic waves; Figure 4 Comparison between (c) and (b) shows that when the absorbing filler in the thermal conductive absorbing material of Example 1 uses both spherical carbonyl iron and flaky carbonyl iron, its isolation effect on electromagnetic waves is better, and the isolation degree can reach -90dB.

[0169] Furthermore, to verify the aging reliability of the cured thermally conductive and absorbing composition of the present application, a sandwich-structured thermal resistance fixture (i.e., a thermally conductive composition coated between two glass plates and cured by heating to obtain the thermal resistance fixture) containing the cured thermally conductive and absorbing composition of Example 1 was subjected to a double 85°C aging test, a high-temperature aging test, and a temperature cycle aging test. The quantitative results are summarized in Table 2 below.

[0170] Specifically, the double 85 aging test involves measuring the thermal resistance of the thermal resistance fixture at room temperature. The fixture is then placed in an environment at 85°C and 85% relative humidity (referred to as double 85) for 1700 hours. The cured film of the thermally conductive and absorbing composition is observed for any abnormalities in appearance. The thermal resistance of the cured film after the double 85 aging test is then measured, and the thermal resistance change rate is calculated (i.e., the ratio of the difference between the thermal resistance value before the double 88 aging test and the thermal resistance value after the double 85 aging test to the thermal resistance value before the double 85 aging test).

[0171] The high-temperature aging test specifically involves taking the thermal resistance fixture and measuring its thermal resistance at room temperature. The fixture is then placed in a high-temperature environment at 125°C for 1700 hours, observing the appearance of the cured film for cracks. The thermal resistance of the cured film after the high-temperature aging test is then measured, and the rate of change in thermal resistance is calculated.

[0172] The temperature cycle aging test specifically takes the above-mentioned sandwich structure thermal resistance fixture and tests its thermal resistance value at room temperature. The above-mentioned thermal resistance fixture is first placed at -40°C for 15 minutes and then at 125°C for 15 minutes (one temperature cycle). The appearance of the cured film after undergoing a certain cycle (total test time is 1700 hours) is observed (such as whether sag occurs), its thermal resistance value is tested, and the thermal resistance change rate of the cured film before and after the temperature cycle aging test is calculated.

[0173] Table 2 Aging test results of thermal resistance tooling with the product of Example 1

[0174] Test items Thermal resistance before test Thermal resistance before test Thermal resistance change rate (%) Double 85 aging 2.018 2.04 1.1 High temperature aging 2.05 2.06 -0.5 Temperature cycle aging 2.03 2.0 1.5

[0175] Testing revealed that the cured thermally conductive and absorbing composition of Example 1 of the present application exhibited no abnormalities in appearance, including cracking and sag, after undergoing dual 85°C aging, high-temperature aging, and temperature-cycle aging tests. Furthermore, the various aging test results shown in Table 2 show that the thermal resistance change rate of the cured composition after dual 85°C aging, high-temperature aging, and temperature-cycle aging tests was extremely low, demonstrating its high reliability.

[0176] The above merely represents several exemplary embodiments of the present application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art would be able to make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

[0177] It should be understood that the first, second and various numerical numbers involved in this document are only distinguished for the convenience of description and are not intended to limit the scope of this application.

[0178] In this application, "and / or" describes the relationship between related objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the related objects are in an "or" relationship.

[0179] In the description of this application, unless otherwise specified, "multiple" means greater than or equal to two. "At least one" means one or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or plural, respectively.

[0180] In addition, the numerical range represented by "-" in this application refers to the range that includes the numerical values ​​recorded before and after "-" as the minimum and maximum values, respectively. In this application, expressions about parameter ranges, such as "greater than or equal to (≥)", "less than or equal to (≤)", "above...", and "below..." all include the number itself. The numerical values ​​and numerical ranges involved in the embodiments of this application are approximate values. Due to the influence of manufacturing process / testing method, etc., there may be a certain range of errors, which can be considered negligible by those skilled in the art.

Claims

1. A thermally conductive and wave-absorbing composition, characterized in that: The thermally conductive and absorbing composition includes an organic matrix, a thermally conductive filler, and an absorbing filler; the thermally conductive filler includes large-particle-size thermally conductive particles and small-particle-size thermally conductive particles, and the large-particle-size thermally conductive particles include high-sphericity and high-purity silicon carbide fillers; wherein the high-sphericity and high-purity silicon carbide fillers have a sphericity of greater than 0.8 and a mass content of silicon carbide greater than or equal to 99.0%; and the absorbing fillers include spherical carbonyl iron and flaky carbonyl iron.

2. The thermally conductive and wave-absorbing composition according to claim 1, wherein: The mass content of silicon carbide in the high-sphericity and high-purity silicon carbide filler is greater than or equal to 99.9%.

3. The heat-conducting and wave-absorbing composition according to claim 1 or 2, wherein: The surface of the high-sphericity and high-purity silicon carbide filler also has an insulating coating layer.

4. The heat-conducting and wave-absorbing composition according to any one of claims 1 to 3, wherein: The silicon carbide crystal form of the high-sphericity and high-purity silicon carbide filler is selected from one or more of 2H phase, 3C phase, 4H phase and 6H phase.

5. The heat-conducting and wave-absorbing composition according to any one of claims 1 to 4, characterized in that: The physicochemical parameters of the high sphericity and high purity silicon carbide filler meet the following requirements: the bulk density is greater than 1.5 g / cm 3 ; Breakdown field strength greater than 200V / mm; thermal conductivity greater than 250W / mk.

6. The heat-conducting and wave-absorbing composition according to any one of claims 1 to 5, wherein: The ratio of the average particle size of the large-diameter thermally conductive particles to the average particle size of the small-diameter thermally conductive particles is greater than 3.

7. The heat-conducting and wave-absorbing composition according to any one of claims 1 to 6, wherein: The average particle size of the small-diameter heat-conducting particles is less than 5 μm, and the average particle size of the large-diameter heat-conducting particles is greater than 20 μm.

8. The heat-conducting and wave-absorbing composition according to claim 7, wherein: The large-particle-diameter heat-conducting particles include heat-conducting fillers with an average particle size of more than 60 μm; the heat-conducting fillers with an average particle size of more than 60 μm include the high-sphericity and high-purity silicon carbide fillers.

9. The heat-conducting and wave-absorbing composition according to claim 8, wherein: The average particle size of the high-sphericity and high-purity silicon carbide filler is between 60 μm and 300 μm.

10. The heat-conducting and wave-absorbing composition according to claim 9, wherein: The average particle size of the high-sphericity and high-purity silicon carbide filler is between 60 μm and 150 μm.

11. The heat-conducting and wave-absorbing composition according to any one of claims 7 to 10, wherein: The small-particle thermal conductive particles include two types of filler particles: one with an average particle size of less than 1 μm and the other with an average particle size greater than 1 μm and less than or equal to 5 μm.

12. The heat-conducting and wave-absorbing composition according to any one of claims 1 to 11, wherein: The small-diameter thermally conductive particles include one or more of zinc oxide, aluminum oxide, and magnesium oxide.

13. The heat-conducting and wave-absorbing composition according to any one of claims 1 to 12, wherein: The ratio of the average particle size of the large-diameter thermally conductive particles to the average particle size of the small-diameter thermally conductive particles is greater than 20.

14. The heat conductive and wave absorbing composition according to any one of claims 1 to 13, wherein: The thermally conductive filler further includes medium-sized thermally conductive particles, wherein the average particle size of the medium-sized thermally conductive particles is between that of the large-sized thermally conductive particles and the small-sized thermally conductive particles.

15. The heat-conducting and wave-absorbing composition according to claim 14, wherein: The medium-sized thermally conductive particles include one or more of oxides, carbides, and nitrides.

16. The heat conductive and wave absorbing composition according to any one of claims 1 to 15, wherein: The total mass proportion of the thermally conductive filler in the thermally conductive and wave-absorbing composition is 50%-98%.

17. The heat conductive and wave absorbing composition according to any one of claims 1 to 16, wherein: The mass proportion of the high-sphericity and high-purity silicon carbide filler in the thermal conductive and wave absorbing composition is in the range of 35-60%.

18. The heat conductive and wave absorbing composition according to any one of claims 1 to 17, wherein: The average diameter of the spherical carbonyl iron is 1 μm-50 μm; the average lateral size of the flaky carbonyl iron is 5 μm-50 μm.

19. The heat conductive and wave absorbing composition according to any one of claims 1 to 18, wherein: In the thermal conductive and wave absorbing composition, the mass ratio of the spherical carbonyl iron to the flaky carbonyl iron is in the range of (5-20):

1.

20. The heat conductive and wave absorbing composition according to any one of claims 1 to 19, wherein: The mass of the high-sphericity and high-purity silicon carbide filler is 1.2-10 times the sum of the masses of the spherical carbonyl iron and the flaky carbonyl iron.

21. The heat conductive and wave absorbing composition according to any one of claims 1 to 20, wherein: The total mass proportion of the wave-absorbing filler in the thermal conductive wave-absorbing composition is 8%-25%.

22. The heat conductive and wave absorbing composition according to any one of claims 1 to 21, wherein: The organic matrix includes at least one of an organic silicon system, an epoxy system, an acrylic system, a polyurethane system, a polyimide system, a polyester system, and a polyolefin system.

23. The heat-conductive and wave-absorbing composition according to claim 22, wherein: The organic silicon system is an addition reaction curing organic silicon system; the thermal conductive wave absorbing composition further comprises a catalyst and an inhibitor.

24. The heat-conducting and wave-absorbing composition according to any one of claims 1 to 23, wherein: The thermal conductive and wave absorbing composition further comprises a filler treating agent.

25. The heat conductive and wave absorbing composition according to any one of claims 1 to 24, wherein: The extrusion rate of the thermally conductive and wave-absorbing composition at a pressure of 0.62 MPa is greater than 8.0 g / min; the thermal conductivity of the thermally conductive and wave-absorbing composition is greater than 7.5 W / (m·K); the critical breakdown field strength of the thermally conductive and wave-absorbing composition is greater than 200 V / mm; and the isolation of the thermally conductive and wave-absorbing composition against electromagnetic waves is less than -90 dB.

26. Use of the thermal conductive and wave absorbing composition according to any one of claims 1 to 25 or a cured product thereof in thermal conductive materials, wave absorbing materials, and thermal conductive and wave absorbing materials.

27. An electronic device, characterized in that: A cured product comprising the heat-conducting and wave-absorbing composition according to any one of claims 1 to 25.

28. The electronic device according to claim 27, wherein: The electronic device includes an electronic component and a cured product of the heat-conductive and wave-absorbing composition disposed on the electronic component.

29. The electronic device according to claim 28, wherein The electronic device further includes a circuit board, on which a plurality of the electronic components and a heat dissipation structure are disposed. The heat dissipation structure and the circuit board define a housing space, and the plurality of electronic components are located within the housing space. A heat-conductive absorbing material is disposed between each electronic component and the heat dissipation structure, and the heat-conductive absorbing material includes a cured product of the heat-conductive absorbing composition.

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