High-reliability heat-conducting silicone grease as well as preparation method and application thereof

Abstract

The invention relates to the field of heat-conducting silicone grease, in particular to high-reliability heat-conducting silicone grease and a preparation method and application of the high-reliability heat-conducting silicone grease. The surface of the sheet-shaped heat-conducting filler is subjected to interfacial compatibility treatment; the surface of the spherical filler is provided with a reaction passivation layer for preventing the spherical filler from reacting with the organic silicon substrate; the surface of the nanoscale carbon material contains polar functional groups capable of forming a physical cross-linked network with the steric hindrance functional groups; the sheet-shaped heat-conducting filler, the spherical filler and the nanoscale carbon material are synergistically constructed to form a three-dimensional heat-conducting network. Through the three-dimensional heat conduction network constructed cooperatively, the overall heat conduction coefficient of the material is remarkably improved, and the heat dissipation requirement of a high-power-density electronic device can be met. Meanwhile, the migration of silicone oil is inhibited by utilizing a steric hindrance functional group, the side reaction of an interface is blocked by utilizing a reaction passivation layer, and the structural stability is enhanced by utilizing a physical cross-linked network, so that the oil seepage rate in a high-temperature environment is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of thermal grease, and more particularly to a high-reliability thermal grease, its preparation method, and its application. Background Technology

[0002] With the rapid development of electronic devices towards miniaturization and high power density, thermal management has become one of the bottlenecks restricting technological progress. Thermal grease, as a crucial thermal interface material filling the space between the chip and the heatsink, directly determines the efficiency and reliability of the entire heat dissipation system. Most products currently on the market are based on a simple composite of silicone oil and metal oxide fillers. While they possess some thermal conductivity, they have significant shortcomings in several key performance aspects. The limitations of traditional thermal grease are particularly pronounced in applications with high heat generation, such as processors, power modules, and high-density batteries.

[0003] Currently, the thermal conductivity of most commercial products still hovers between 4 and 5.5 W / m·K, making it difficult to handle heat flux densities exceeding 150 W / cm². This can easily lead to a sharp increase in interfacial thermal resistance, causing chip junction temperatures to exceed safe thresholds. Some attempts to improve thermal conductivity by increasing filler loading often result in a significant increase in viscosity, difficulties in construction, and a decrease in insulation performance. More importantly, with high filler content, the volume resistivity of the material can drop to the level of 10^9 Ω·cm, bringing potential electromigration and short-circuit risks, making it difficult to meet the insulation requirements of high-reliability electronic components.

[0004] In addition, oil seepage during long-term use is another major technical challenge. As a continuous phase, silicone oil gradually separates from the system and migrates to the surface under the influence of temperature changes and interfacial tension, causing the formation of dry areas. Current improvement methods mostly focus on adjusting the viscosity of silicone oil or adding thickeners. Although these methods can slightly delay oil seepage, they fail to fundamentally inhibit the interfacial reaction between the filler and the matrix. Slippage of molecular chain segments and interfacial chemical interactions at high temperatures remain the main causes of failure.

[0005] Furthermore, traditional thermal greases have poor adaptability to temperature changes. At low temperatures (such as -40°C), the viscosity of the material increases sharply, becoming hard and difficult to deform, making it prone to cracking during thermal cycling and losing interfacial contact. At high temperatures (such as 150°C), the viscosity decreases, making the material easier to flow and separate, accelerating oil seepage and filler sedimentation. Therefore, this severely limits its application in wide-temperature environments (such as automotive electronics and outdoor communication equipment).

[0006] Therefore, the industry urgently needs a new type of high-performance thermal grease. It must not only possess high thermal conductivity and excellent insulation properties, but also exhibit superior oil-proof performance, wide-temperature stability, and long-term reliability. An ideal material should balance process feasibility and cost control, effectively suppressing interfacial reactions and molecular migration while maintaining high-temperature chemical stability, truly meeting the stringent requirements of next-generation high-power electronic devices for thermal management materials. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of existing thermal greases, such as low thermal conductivity, poor insulation, and insufficient long-term reliability. Therefore, it provides a high-reliability thermal grease, its preparation method, and its application to overcome the above-mentioned deficiencies.

[0008] To achieve the above-mentioned objectives, the present invention is implemented through the following solution: In a first aspect, the present invention provides a high-reliability thermal grease, comprising: Organosilicon matrix containing sterically hindered functional groups; The sheet-like thermally conductive filler has an interface compatibility treatment on its surface. The spherical filler has a reaction passivation layer on its surface that prevents the spherical filler from reacting with the organosilicon matrix; Nanoscale carbon materials contain polar functional groups on their surface that can form physical cross-linking networks with sterically hindered functional groups. The sheet-like thermally conductive filler, spherical filler, and nanoscale carbon materials work together to form a three-dimensional thermally conductive network.

[0009] As described in the background section, the core challenge of traditional thermal greases lies in simultaneously achieving high thermal conductivity, long-term stability, and wide temperature range adaptability. Common solutions often aim to improve thermal conductivity by simply increasing the filler ratio, but this typically leads to a sharp increase in system viscosity and deterioration in application performance. More seriously, under high-temperature operating conditions, the interface between the silicone matrix and the filler is prone to reaction, resulting in silicone oil precipitation (i.e., oil seepage), which significantly increases thermal resistance over time and may even contaminate surrounding precision components. Furthermore, the random distribution of conventional fillers makes it difficult to construct efficient heat transfer paths, and the difference in thermal expansion coefficients between the matrix and filler during temperature cycling can easily cause cracking or pulverization, leading to interfacial contact failure. The interplay of these problems constitutes a long-standing technical dilemma that the industry has failed to effectively resolve.

[0010] The technical solution of this invention is a multi-dimensional and synergistic solution to the aforementioned complex problems. Its ingenuity lies in the functional design and system integration of each component. First, the core of this technical solution is to abandon the simple physical mixing approach and instead achieve synergistic improvement of multiple properties through the fine design of material interfaces. The steric functional groups introduced into the organosilicon matrix are not simply molecular modifications; their core function is to inhibit the migration and diffusion of silicone oil molecular chains under thermal conditions through stereochemical effects, providing the primary guarantee for inhibiting oil seepage at the molecular level. Second, the interfacial compatibility treatment of the sheet-like thermally conductive filler significantly enhances its bonding force with the organosilicon matrix. This not only reduces phonon scattering at the interface and improves heat conduction efficiency, but more importantly, it prevents the filler from falling off and agglomerating during long-term use, ensuring the long-term stability of the thermally conductive network.

[0011] Furthermore, the design of the reactive passivation layer on the spherical filler and the introduction of polar functional groups from the nanoscale carbon materials are another important innovation of this application. Specifically, the reactive passivation layer on the surface of the spherical filler does more than just simple physical isolation; it effectively blocks possible chemical reactions between the active sites on the filler surface and the organosilicon matrix, fundamentally eliminating the chemical root causes of material aging and silicone oil precipitation. Meanwhile, the polar functional groups on the surface of the nanoscale carbon materials form a physical cross-linking network with the steric functional groups in the matrix. This physical cross-linking differs from chemical cross-linking; while imparting good structural stability and oil resistance to the system, it avoids the problems of system brittleness and stress relaxation that may result from chemical cross-linking, thus maintaining the material's flexibility and long-term interfacial adhesion.

[0012] Most importantly, this application emphasizes the synergistic construction of a three-dimensional thermally conductive network using sheet-like thermally conductive fillers, spherical fillers, and nanoscale carbon materials. This is not a simple superposition of the three fillers, but a complementary architectural design. The sheet-like fillers tend to be in-plane oriented, forming the main heat diffusion plane; the spherical fillers fill the spaces between the sheet-like fillers, constructing vertical thermal conductive channels and reducing the limitations caused by the directionality of heat flow; the nanoscale carbon materials further fill the micro- and nano-scale voids, not only improving the continuity of the thermally conductive network, but also forming a physical cross-linked network that acts like a "skeleton," enhancing the mechanical strength and stability of the entire system. This synergistic design of multi-scale, multi-morphological fillers ensures that heat can be efficiently transferred within the material along low thermal resistance paths, thus achieving a qualitative leap in thermal conductivity.

[0013] Ultimately, this technical solution delivers significantly superior overall performance compared to existing technologies. In terms of thermal conductivity, the efficient construction of the three-dimensional continuous thermal network enables rapid and uniform heat transfer, significantly improving overall thermal conductivity. Regarding long-term reliability, the triple protection provided by steric hindrance, a reactive passivation layer, and a physical cross-linking network greatly enhances the material's resistance to oil seepage at high temperatures, effectively preventing performance degradation and surrounding contamination caused by silicone oil precipitation. In terms of environmental adaptability, the system exhibits excellent wide-temperature stability, maintaining good flexibility and interfacial wettability in both low and high temperature environments, preventing cracking or pulverization, and ensuring long-term reliable operation under various harsh conditions.

[0014] In summary, this invention is not a partial improvement or parameter optimization of existing technologies, but rather, starting from the initial intention of solving core pain points in the industry, it constructs a high-performance system in which each component has a clearly defined function, works synergistically, and interacts together through a series of innovative material designs and system integrations. This solution cleverly balances performance indicators such as high thermal conductivity, oil resistance, and high stability, which are traditionally difficult to achieve simultaneously, thus providing a completely new and highly innovative thermal grease solution.

[0015] Preferably, the sterically hindered functional group is phenyl, cyclohexyl or tert-butyl; The steric functional group has a content of 5-15 mol in the organosilicon matrix.

[0016] Preferably, the interfacial compatibility treatment of the sheet-like thermally conductive filler is performed using a silane coupling agent. The silane coupling agent is selected from KH-550, KH-560 or KH-570.

[0017] Preferably, the reactive passivation layer is silicon dioxide, aluminum oxide, or zirconium oxide, with a thickness of 25-35 nm.

[0018] Preferably, the polar functional group is a carboxyl group, a hydroxyl group, or an amino group, and the surface density is 5-15 groups / square nanometer.

[0019] Preferably, the sheet-like thermally conductive filler has an aspect ratio ≥ 80 and a thickness of 0.1 μm-0.05 μm; The particle size of the nanoscale carbon material is 50nm-70nm.

[0020] Preferably, the material comprises, by weight, 55-65 parts of an organosilicon matrix, 28-32 parts of sheet-like thermally conductive filler, 22-26 parts of spherical filler, and 7-9 parts of nanoscale carbon material.

[0021] Secondly, the present invention also provides a method for preparing a high-reliability thermal grease, comprising the following steps: (i) Under an inert atmosphere, the organosilicon matrix is ​​adjusted to 30-50°C, and then nanoscale carbon materials are added. Ultrasonic treatment causes the phenyl side chains of the organosilicon matrix to form a physical cross-linking network with the polar functional groups of the nanoscale carbon materials, thereby forming a primary network framework. (ii) After raising the system temperature to 70-90℃, add sheet-like thermally conductive filler, and under the action of shear field, make the sheet-like thermally conductive filler oriented; (iii) After lowering the temperature to room temperature, add spherical packing and stir to make the spherical packing evenly dispersed, thereby completing the construction of the three-dimensional heat conduction network.

[0022] The inventiveness of the thermal grease preparation method protected in this application stems from a systematic solution to a key contradiction in the material processing. Traditional processes often employ a "one-pot" mixing method, where all components are simultaneously mixed and dispersed under a single temperature and shear condition. While this simple operation is easy to implement, it is difficult to avoid multiple problems: high temperatures can easily damage the structure of sensitive components, high shear forces can easily damage the morphology of sheet-like fillers, and nanomaterials are prone to agglomeration, leading to uneven distribution. More importantly, random mixing cannot achieve the directional arrangement and orderly combination of fillers, resulting in a disordered and inefficient internal thermal conductive network, and insufficient stability of the filler-matrix interface, which poses a hidden danger of oil seepage and performance degradation during long-term use. Existing improved processes either focus on dispersion and homogenization while neglecting structural construction, or attempt to add components in stages but lack coordinated control of temperature and shear forces, making it difficult to achieve high-precision three-dimensional network construction in large-scale production. Based on a deep understanding of the above-mentioned process bottlenecks, this invention proposes a gradient control strategy with clearly defined functional divisions in each stage.

[0023] The innovation of this preparation method is primarily reflected in its ingenious stage design and parameter coordination. In the first stage, nanoscale carbon materials are introduced and ultrasonically treated under mild conditions (30-50℃). This is not a simple dispersion operation, but rather a creative use of the constraint effect of the low-temperature environment on molecular chain activity. This encourages the phenyl side chains in the organosilicon matrix to approach the polar functional groups on the nanomaterial surface, spontaneously weaving a stable primary network framework through physical action. This framework, like the steel reinforcement in a building, provides a supporting foundation for the efficient orientation of subsequent fillers. If the temperature is too high, the increased thermal motion of the molecular chains will weaken the physical cross-linking efficiency; if high-shear stirring is used, the surface functional group structure of the nanomaterial is easily destroyed. This step uses a combination of low-temperature ultrasound, ensuring the integrity of the nanomaterial while utilizing acoustic cavitation to enhance interfacial interactions, successfully achieving the precise construction of a molecular-level network.

[0024] The second stage, involving heating to the mid-temperature range (70-90℃), adding sheet-like thermally conductive fillers, and applying a shear field, is the core step in constructing efficient thermal conduction channels. Heating is not merely for improving fluidity; its core value lies in stimulating the kinetic activity of the sheet-like fillers, making them more easily oriented under external forces through appropriate heat input. The application of the shear field is not a simple mixing operation; its innovation lies in using a directional fluid force field to guide the sheet-like fillers to arrange themselves in an orderly manner along a specific direction, forming a dominant in-plane thermal conduction path. The coordinated control of temperature and shear force is particularly crucial in this stage: too low a temperature results in high resistance to filler rotation, making full orientation difficult; insufficient shear force cannot overcome the van der Waals forces between fillers, easily leading to disordered agglomeration; while excessively high temperatures or excessive shear may damage the established primary network framework or the sheet-like filler structure. This invention, by precisely defining the effective range of temperature and shear field, efficiently completes the horizontal directional arrangement of the sheet-like fillers while protecting the previously formed physical cross-linked network, laying the structural foundation for high thermal conductivity.

[0025] The third stage, involving cooling to room temperature, followed by the addition of spherical filler and gentle stirring, demonstrates a profound understanding of the integrity of the three-dimensional network. Building upon the previously established in-plane thermally conductive framework, the introduction of spherical filler is not merely about filling gaps; its core function is to construct vertical thermal conductive pathways and provide spatial support, preventing displacement and collapse of the sheet-like filler during subsequent processes or use. The choice of room temperature is crucial: on the one hand, it avoids thermal disturbances to the already constructed network caused by high temperatures; on the other hand, it prevents excessively high matrix viscosity due to low temperatures, which could affect the uniform dispersion of the spherical filler. Gentle stirring creatively avoids the risk of damage to the oriented structure of the sheet-like filler due to high shear forces, ensuring uniform interpenetration of the spherical filler between the sheet layers. This staged, temperature- and force-controlled filler introduction strategy successfully achieved the construction of a three-dimensional interpenetrating structure of "sheet-like horizontal thermally conductive layer + spherical vertical thermally conductive column + nano-network framework," with a structural precision far exceeding that of the disordered system obtained by conventional mixing processes.

[0026] The synergy of this method in process control is also reflected in its dynamic response to the system state. The temperature rise and fall between the three stages are not isolated operations: the heating process from the first stage to the second stage needs to balance the thermal stability of the primary network and the activation requirements of the sheet-like filler; the cooling operation from the second stage to the third stage needs to balance the contradiction between the solidification of the network structure and the dispersibility of the spherical filler. This precise control of the thermal history effect allows the microstructure formed in each step to be effectively inherited and strengthened, avoiding structural breaks caused by process switching.

[0027] Ultimately, this gradient control strategy yielded a significant leap in technical performance. In terms of structural quality, the oriented sheet-like packing and uniformly distributed spherical packing, supported by a nano-network framework, formed a highly interconnected three-dimensional thermally conductive network, greatly improving the efficiency of directional heat transfer. Regarding interfacial stability, the low-temperature constructed physical cross-linking network and precisely controlled packing dispersion effectively suppressed interfacial reactions, significantly enhancing the system's resistance to oil seepage. In terms of process adaptability, the phased, gentle treatment maximized the protection of the integrity of various packing types, avoiding damage to sensitive structures from high shear and high temperatures, and ensuring a high yield rate for large-scale production. The resulting product not only achieved a qualitative breakthrough in thermal conductivity but also exhibited excellent long-term stability and wide temperature range adaptability.

[0028] Preferably, in step (ii), the shear rate increases in three stages: initially 0-15 minutes, then 1200 ± 50 s. -1 16-30 minutes, 1500±50s -1 31-45 minutes 1800±50s -1 .

[0029] Thirdly, the present invention also provides the application of the high-reliability thermal grease described above in the heat dissipation of electronic devices.

[0030] Therefore, this application has the following beneficial effects: (1) Excellent thermal conductivity: Through the collaborative construction of a three-dimensional thermal conductivity network (planar heat conduction of sheet filler, vertical heat conduction of spherical filler, and filling of voids with nano-carbon material), the overall thermal conductivity of the material is significantly improved, which can meet the heat dissipation requirements of high power density electronic devices. (2) High long-term reliability: The three synergistic effects of the steric functional groups inhibit silicone oil migration, the reactive passivation layer blocks interfacial side reactions, and the physical cross-linking network enhances structural stability, which significantly reduces the oil seepage rate under high temperature conditions and effectively avoids the increase in thermal resistance and surrounding pollution caused by silicone oil precipitation. (3) Strong adaptability to wide temperature range: The material system can maintain good flexibility, interface wettability and structural integrity in both extremely low temperature and high temperature environments, effectively solving the problems of low temperature cracking, high temperature oil seepage and performance degradation of traditional materials, and is suitable for harsh temperature change environments such as automotive electronics. (4) Balanced comprehensive performance: While achieving high thermal conductivity and oil resistance, it maintains excellent electrical insulation performance and long-term stability, successfully overcoming the contradiction that high filler addition leads to insulation degradation or processability deterioration in traditional solutions. (5) Good process controllability: The innovative gradient dispersion preparation method (low temperature ultrasonic network building, medium temperature high shear orientation, room temperature mild dispersion) effectively protects the packing structure, accurately realizes the orientation and uniform dispersion of the packing, ensures the high-quality construction of the three-dimensional heat conduction network, and is conducive to large-scale stable production. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0032] Example 1 Formula composition: 60 parts of phenyl silicone oil (phenyl content 10 mol%), 30 parts of silane-treated boron nitride (aspect ratio 85), 25 parts of silica-coated alumina (coating thickness 30 nm), 8 parts of carboxylated nanodiamond (particle size 60 nm), 3.0 parts of methyl hydrogen silicone oil, and 0.18 parts of platinum catalyst.

[0033] Preparation process: (1) Boron nitride pretreatment: 30 parts of boron nitride flakes were immersed in an ethanol solution containing 5 wt% silane coupling agent, ultrasonically treated at 60°C for 120 minutes, and then vacuum dried at 120°C for 4 hours. (2) Alumina coating: A 30 nm silica layer was constructed on the surface of 25 spherical alumina using the sol-gel method, with TEOS:EtOH:H2O = 1:8:4 (molar ratio). (3) Matrix mixing: Add silicone oil to a nitrogen-protected reactor and stir at 80°C for 30 minutes; (4) Gradient dispersion: - Cool to 40℃, add nanodiamonds, and sonicate at 800W for 30 minutes; - Heat to 60℃, add boron nitride, and use progressive shear control: 0-10 min in 1200 s increments. -1 Cut, 11-25 min at 1450 s -1 Cut, 26-40 min at 1600 s -1 Cutting; - Cool to 25°C, add alumina, and stir at 300 rpm for 20 minutes; (5) Three-roll mill grinding: roller gap 10μm, reciprocating grinding 5 times, fineness control ≤12μm; (6) Post-treatment: Add methyl hydrogen silicone oil and platinum catalyst, and degas under vacuum at -0.1MPa for 20 minutes.

[0034] Example 2 The difference between Example 2 and Example 1 is as follows: Formula composition: The composition includes 60 parts of phenyl silicone oil (phenyl content 12 mol%), 10 parts of carboxylated nanodiamond, 26 parts of silane-treated boron nitride (diameter-to-thickness ratio 100), 3.0 parts of methyl hydrogen silicone oil, and 0.2 parts of platinum catalyst.

[0035] Process optimization: (1) During the dispersion stage 1, the temperature drops to 38℃ and the ultrasonic power increases to 1000W; (2) The gradient dispersion stage 2 adopts progressive shear control: 0-15 minutes 1200s -1 16-30 minutes 1500s -1 31-45 minutes 1800 -1 ; (3) The grinding roller gap is reduced to 8μm.

[0036] Example 3 Formulation composition: 55 parts of phenyl silicone oil (phenyl content 8 mol%, viscosity 750 cSt), 28 parts of silane-treated boron nitride (aspect ratio 80, thickness 0.15 μm), 26 parts of silica-coated alumina (coating layer 32 nm), and carboxylated nanodiamonds (particle size 55 nm, carboxyl group density 8 per nanometer). 2 7 parts, 3.5 parts methyl hydrogen silicone oil, and 0.21 parts platinum catalyst.

[0037] Preparation process: (1) Boron nitride pretreatment: Boron nitride was impregnated with 3wt% KH-550 silane ethanol solution and sonicated at 55℃ for 100 minutes; (2) Alumina coating: A 32nm silica layer was constructed on the surface of 26 spherical alumina using the sol-gel method, with TEOS:EtOH:H2O=1:10:3 (molar ratio). (3) Matrix mixing: Add silicone oil to a nitrogen-protected reactor and stir at 80°C for 30 minutes; (4) Gradient dispersion: - Cool down to 30℃, add nanodiamonds, and sonicate at 750W for 25 minutes; - Heat to 70°C, add boron nitride, and use progressive shear control: 0-10 min in 1200 s increments. -1 Cut, 11-25 min at 1450 s -1 Cut, 26-40 min at 1600 s-1 Cutting; - Cool to 24°C, add alumina, and stir at 280 rpm for 18 minutes; Post-processing: Three-roll mill grinding (roll gap 15μm, 3 times), addition of methyl hydrogen silicone oil crosslinking agent (hydrogen content 0.9wt%) and platinum catalyst for vacuum degassing.

[0038] Example 4 Formulation composition: 65 parts phenyl silicone oil (phenyl content 12 mol%, viscosity 850 cSt), 32 parts silane-treated boron nitride (aspect ratio 100, thickness 0.25 μm), 22 parts silica-coated alumina (coating layer 28 nm), and carboxylated nanodiamonds (particle size 65 nm, carboxyl group density 12 / nanometer). 2 9 parts, methyl hydrogen silicone oil 3.0 parts, platinum catalyst 0.18 parts.

[0039] Preparation process: (1) Boron nitride pretreatment: 30 parts of boron nitride flakes were immersed in an ethanol solution containing 5 wt% silane coupling agent, ultrasonically treated at 60°C for 120 minutes, and then vacuum dried at 120°C for 4 hours. (2) Alumina coating: A 30 nm silica layer was constructed on the surface of 25 spherical alumina using the sol-gel method, with TEOS:EtOH:H2O = 1:8:4 (molar ratio). (3) Matrix mixing: Add silicone oil to a nitrogen-protected reactor and stir at 80°C for 30 minutes; (4) Gradient dispersion: - Cool to 50℃, add nanodiamonds, and ultrasonically treat with 850W for 35 minutes; - Heat to 90℃, add boron nitride, and use progressive shear control: 0-10 min in 1200 s increments. -1 Cut, 11-25 min at 1450 s -1 Cut, 26-40 min at 1600 s -1 Cutting; - Cool to 26°C, add alumina and 0.5 parts of polyether modified silicone oil, stir at 320 rpm for 22 minutes; (5) Three-roll mill grinding: roller gap 10μm, reciprocating grinding 5 times, fineness control ≤20μm; (6) Post-treatment: Add methyl hydrogen silicone oil and platinum catalyst, and degas under vacuum at -0.1MPa for 20 minutes.

[0040] Example 5 Formulation composition: 60 parts phenyl silicone oil (phenyl content 10 mol%, viscosity 800 cSt), 30 parts silane-treated boron nitride (aspect ratio 90, thickness 0.2 μm), 24 parts silica-coated alumina (coating layer 30 nm), and carboxylated nanodiamonds (particle size 60 nm, carboxyl group density 10 / nm). 2 8 parts, 2.5 parts methyl hydrogen silicone oil, and 0.15 parts platinum catalyst.

[0041] Preparation process: (1) Boron nitride pretreatment: 30 parts of boron nitride flakes were immersed in an ethanol solution containing 5 wt% silane coupling agent, ultrasonically treated at 60°C for 120 minutes, and then vacuum dried at 120°C for 4 hours. (2) Alumina coating: A 30 nm silica layer was constructed on the surface of 25 spherical alumina using the sol-gel method, with TEOS:EtOH:H2O = 1:8:4 (molar ratio). (3) Matrix mixing: Add silicone oil to a nitrogen-protected reactor and stir at 78°C for 30 minutes; (4) Gradient dispersion: - Cool to 40℃, add nanodiamonds, and sonicate at 800W for 25 minutes; - Heat to 80℃, add boron nitride, and use progressive shear control: 0-15 min in 1200 s increments. -1 Cut, 16-30 min at 1500 s. -1 Cut, 31-45 min at 1800 s -1 Cutting; - Cool to 26°C, add alumina, and stir at 320 rpm for 22 minutes under a pressure of -0.1 MPa; (5) Three-roll mill grinding: roller gap 10μm, reciprocating grinding 5 times, fineness control ≤20μm; (6) Post-treatment: Add methyl hydrogen silicone oil and platinum catalyst, and degas under vacuum at -0.1MPa for 20 minutes.

[0042] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is as follows: Formulation composition: 60 parts dimethyl silicone oil (phenyl-free), 30 parts untreated boron nitride fragments (aspect ratio ≤ 30), 25 parts ordinary spherical alumina (uncoated), 3.0 parts methyl hydrogen silicone oil, 0.18 parts platinum catalyst, and no nanodiamond.

[0043] Preparation process: All components are mixed at 80℃ in one step for 1500 seconds. -1 Cut for 40 minutes.

[0044] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is as follows: Formula composition: 60 parts of phenyl silicone oil (phenyl content 10mol%), 30 parts of silane-treated boron nitride (aspect ratio 85), 25 parts of uncoated alumina, 8 parts of carboxylated nanodiamond (particle size 60nm), 3.0 parts of methyl hydrogen silicone oil, and 0.18 parts of platinum catalyst.

[0045] Comparative Example 3 The difference between Comparative Example 3 and Example 1 lies in the gradient dispersion process: (4) Gradient dispersion: - Cool to 40℃, add nanodiamonds and boron nitride, use 800W ultrasound, and simultaneously perform 1400s... -1 Cutting process for 35 minutes; - Heat to 60°C, add alumina and 0.5 parts of polyether modified silicone oil, and stir at 320 rpm for 22 minutes.

[0046] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is as follows: The formulations are different; Comparative Example 4 uses phenyl-free silicone oil (viscosity 800 cSt) and uncarboxylated nanodiamonds.

[0047] The thermal greases obtained in Examples 1-5 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1 below: project Thermal conductivity (W / m·K) Volume resistivity (Ω·cm) Oil penetration rate (500h, %) Performance retention rate after high-temperature aging (150℃*1000h) Low temperature characteristics (-40℃) Example 1 6.8 <![CDATA[2.5 x 10 15 ]]> 0.8% >98% Soft and without cracks Example 2 7.5 <![CDATA[1.8 x 10 15 ]]> 0.6% >97% Soft and without cracks Example 3 6.2 <![CDATA[3.2 x 10 15 ]]> 1.0% >98% Soft and without cracks Example 4 7.0 <![CDATA[2.0 x 10 15 ]]> 0.7% >97% Soft and without cracks Example 5 6.9 <![CDATA[2.3 x 10 15 ]]> 0.9% >98% Soft and without cracks Comparative Example 1 4.0 <![CDATA[5.0 x 10 9 ]]> 12.5% <60% (Severely hardened, powdery) Hardening, cracking Comparative Example 2 6.0 <![CDATA[6.5 x 10 10 ]]> 8.0% ~75% (significant oil seepage, increased thermal resistance) Slightly hardened Comparative Example 3 5.5 <![CDATA[1.5 x 10 15 ]]> 3.5% ~85% Soft and without cracks Comparative Example 4 5.2 <![CDATA[2.0 x 10 15 ]]> 4.8% ~82% Slightly hardened As shown in the table above, the thermal grease in this application significantly improves the overall thermal conductivity of the material through a synergistically constructed three-dimensional thermally conductive network (planar heat conduction by sheet-like fillers, vertical heat conduction by spherical fillers, and void filling by nano-carbon materials), thus meeting the heat dissipation requirements of high-power-density electronic devices. Simultaneously, the synergistic effect of steric functional groups suppressing silicone oil migration, the reactive passivation layer blocking interfacial side reactions, and the physical cross-linking network enhancing structural stability significantly reduces the oil seepage rate under high-temperature conditions, effectively preventing the increase in thermal resistance and surrounding contamination caused by silicone oil precipitation.

[0048] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A high-reliability thermal grease, characterized in that, Include: Organosilicon matrix containing sterically hindered functional groups; The sheet-like thermally conductive filler has an interface compatibility treatment on its surface. The spherical filler has a reaction passivation layer on its surface that prevents the spherical filler from reacting with the organosilicon matrix; Nanoscale carbon materials contain polar functional groups on their surface that can form a physical cross-linking network with sterically hindered functional groups. The sheet-like thermally conductive filler, spherical filler, and nanoscale carbon materials work together to form a three-dimensional thermally conductive network.

2. The high-reliability thermal grease according to claim 1, characterized in that, The sterically hindered functional group is phenyl, cyclohexyl or tert-butyl; The steric functional group has a content of 5-15 mol in the organosilicon matrix.

3. The high-reliability thermal grease according to claim 1, characterized in that, The interfacial compatibility treatment of the sheet-like thermally conductive filler is performed using a silane coupling agent. The silane coupling agent is selected from KH-550, KH-560 or KH-570.

4. The high-reliability thermal grease according to claim 1, characterized in that, The reactive passivation layer is made of silicon dioxide, aluminum oxide, or zirconium oxide, and has a thickness of 25-35 nm.

5. The high-reliability thermal grease according to claim 1, characterized in that, The polar functional groups are carboxyl, hydroxyl, or amino groups, and the surface density is 5-15 groups / square nanometer.

6. The high-reliability thermal grease according to claim 1, characterized in that, The sheet-like thermally conductive filler has a diameter-to-thickness ratio ≥80 and a thickness of 0.1μm-0.05μm; The particle size of the nanoscale carbon material is 50nm-70nm.

7. The high-reliability thermal grease according to claim 1, characterized in that, By weight, it includes 55-65 parts of organosilicon matrix, 28-32 parts of sheet-like thermally conductive filler, 22-26 parts of spherical filler, and 7-9 parts of nanoscale carbon material.

8. A method for preparing a high-reliability thermal grease as described in any one of claims 1-7, characterized in that, Includes the following steps: (i) Under an inert atmosphere, the silicone matrix is ​​adjusted to 30-50°C, and then nanoscale carbon material is added. Ultrasonic treatment causes the phenyl side chain of the silicone matrix to form a physical cross-linking network with the polar functional groups of the nanoscale carbon material, thereby forming a primary network framework. (ii) After raising the system temperature to 70-90℃, add sheet-like thermally conductive filler, and under the action of shear field, make the sheet-like thermally conductive filler oriented; (iii) After lowering the temperature to room temperature, add spherical packing and stir to make the spherical packing evenly dispersed, thereby completing the construction of the three-dimensional heat conduction network.

9. The method according to claim 8, characterized in that, In step (ii), the shear rate increases in three stages: initially 0-15 minutes, then 1200 ± 50 s. -1 16-30 minutes, 1500±50s -1 31-45 minutes 1800±50s -1 .

10. The application of the high-reliability thermal grease as described in any one of claims 1-7 in heat dissipation of electronic devices.