High-thermal-conductivity liquid epoxy plastic encapsulating material and preparation method thereof

Abstract

This invention discloses a high thermal conductivity liquid epoxy molding compound and its preparation method, belonging to the field of microelectronic packaging materials technology. The molding compound uses liquid epoxy resin as a matrix, compounded with spherical alumina, hexagonal boron nitride, aminated carbon nanotubes, and hydroxylated silicon carbide nanowires. In-situ interfacial crosslinking is achieved through bifunctional silanes, constructing a four-level synergistic thermal conductivity network. The material maintains a low-viscosity liquid state at 25°C, allowing for direct potting. It exhibits a thermal conductivity of 2.8–3.2 W / (m·K) and combines high insulation, low shrinkage, and excellent processability, making it suitable for high-heat-dissipation applications such as high-power devices and chip packaging.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging materials technology, specifically relating to a high thermal conductivity liquid epoxy molding compound and its preparation method. Background Technology

[0002] This invention relates to a high thermal conductivity liquid epoxy molding compound, belonging to the field of electronic packaging materials technology. With the development of microelectronic chips and high-power devices towards higher integration and power density, the heat generated during device operation increases dramatically. If this heat cannot be dissipated in time, it will seriously affect the stability and lifespan of the devices. Therefore, higher requirements are placed on the thermal conductivity of packaging materials. Existing liquid epoxy molding compounds mostly use single or binary fillers such as alumina and boron nitride, which suffer from discontinuous thermal conductive networks and high interfacial thermal resistance, making it difficult to exceed 2.5 W / (m·K) in thermal conductivity. Furthermore, high filler content easily leads to increased viscosity, affecting processing and potting performance. Some solutions attempt to introduce carbon nanotubes to improve thermal conductivity, but the interfacial bridging problem between multiple fillers remains unresolved, resulting in limited improvement in thermal conductivity. Simultaneously, existing technologies lack designs that construct multi-level synergistic thermal conductive networks using nanowires, making it difficult to achieve a significant improvement in thermal conductivity while maintaining low viscosity. Therefore, developing a liquid epoxy molding compound that combines high thermal conductivity, low viscosity, and excellent processing performance by constructing a continuous thermally conductive network and reducing interfacial thermal resistance has become an urgent need in the current electronic packaging field. Summary of the Invention

[0003] To address the aforementioned issues, this invention proposes a high thermal conductivity liquid epoxy molding compound and its preparation method. By constructing a continuous thermally conductive network through multi-level fillers, it combines the characteristics of high thermal conductivity, low viscosity, and excellent processability. Furthermore, it exhibits good insulation, low curing shrinkage, and good thermal stability, thus meeting the requirements for efficient heat dissipation and reliable potting of high-power devices and high-density packaging.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A high thermal conductivity liquid epoxy molding compound, wherein the molding compound is prepared from the following raw materials in parts by weight: The molding compound comprises 30-40 parts of bisphenol F type liquid epoxy resin, 10-15 parts of alicyclic epoxy resin, 5-8 parts of hyperbranched polysiloxane, 120-150 parts of spherical alumina, 30-40 parts of compounded hexagonal boron nitride, 2-3 parts of aminated carbon nanotubes, 1-2 parts of hydroxylated silicon carbide nanowires, 25-30 parts of methylhexahydrophthalic anhydride, 0.5-1.0 parts of imidazole accelerator, 1.5-2.0 parts of silane coupling agent, and 2-3 parts of polydimethylsiloxane; the molding compound has a viscosity of 800-1300 mPa·s at 25°C and a thermal conductivity of 2.8-3.2 W / (m·K).

[0005] Optionally, the compounded hexagonal boron nitride is composed of nanosheets and microsheets in a mass ratio of 1:2, with the nanosheets having a particle size of 50-100 nm and the microsheets having a particle size of 3-5 μm.

[0006] Optionally, the aspect ratio of the hydroxylated silicon carbide nanowire is 50-100, and the diameter is 20-50 nm.

[0007] Optionally, the molding compound has a curing shrinkage rate of 0.5%-0.8%, a volume resistivity of 1.0×10¹⁶-5.0×10¹⁶ Ω·cm, and a glass transition temperature of 135℃-145℃.

[0008] Optionally, the preparation method of the high thermal conductivity liquid epoxy molding compound is as follows: S1. Weigh out bisphenol F type liquid epoxy resin, alicyclic epoxy resin, hyperbranched polysiloxane, and polydimethylsiloxane by weight, add them to a planetary mixer, and stir for 10-15 minutes at 23℃-27℃ and 500-800rpm to obtain a uniform and transparent premixed liquid. S2. Add spherical alumina, compounded hexagonal boron nitride, aminated carbon nanotubes, hydroxylated silicon carbide nanowires and silane coupling agent sequentially to the premix. Close the planetary mixer chamber, evacuate to -0.090 to -0.095 MPa, heat to 30℃-35℃, and disperse at 1200-1500 rpm for 30-40 minutes. During this period, maintain the chamber temperature not exceeding 35℃ through the water cooling system. S3. Remove the vacuum, add methylhexahydrophthalic anhydride and imidazole accelerator according to the weight parts, and evacuate the vacuum again to -0.090 to -0.095 MPa. Stir at 800-1000 rpm for 15-20 minutes to complete the degassing. S4. Pass the above material through a 100-mesh stainless steel filter screen and filter it under a pressure of 0.1-0.2MPa to remove mechanical impurities and obtain a liquid product. The curing conditions of the liquid product are as follows: heat at 80℃±5℃ for 1-1.5h, heat to 120℃±5℃ for 2-2.5h, heat to 150℃±5℃ for 1-1.5h, and then cool naturally to room temperature.

[0009] Optionally, the planetary mixer in steps S1 and S2 has a dual-blade structure with a blade speed to revolution speed ratio of 1:3.

[0010] Optionally, in step S4, the filter uses an 80-120 mesh stainless steel filter screen, which is cleaned and dried with a 70-80% ethanol solution before filtration.

[0011] Optionally, the imidazole accelerator is 2-ethyl-4-methylimidazole with a purity ≥99.0%.

[0012] The beneficial effects of this invention are as follows: The epoxy molding compound prepared by this invention has excellent thermal conductivity, with a thermal conductivity coefficient of 2.8-3.2 W / (m·K) and a viscosity of only 800-1300 mPa·s at 25℃, combining high thermal conductivity with good liquid processing fluidity; the molding compound has low curing shrinkage and excellent insulation properties, with a volume resistivity of 1.0×10¹⁶-5.0×10¹⁶ Ω·cm, which can ensure the long-term stable operation of the device; various thermally conductive fillers form a continuous and interconnected multi-level thermally conductive network in the system, effectively reducing interfacial thermal resistance and significantly improving heat dissipation efficiency; at the same time, the molding compound has a moderate glass transition temperature, good mechanical properties and thermal stability, which can meet the requirements of high-density and high-reliability packaging of high-power microelectronic devices. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0014] Example 1: A method for preparing a high thermal conductivity liquid epoxy molding compound according to Example 1. The molding compound is prepared from the following raw materials in parts by weight: 35 parts of bisphenol F type liquid epoxy resin, 12 parts of alicyclic epoxy resin, 6 parts of hyperbranched polysiloxane, 135 parts of spherical alumina, 35 parts of compounded hexagonal boron nitride (nano BN 80nm, micron BN 4μm), 2.5 parts of aminated carbon nanotubes, 1 part of hydroxylated silicon carbide nanowires (diameter 25nm, aspect ratio 75), 28 parts of methylhexahydrophthalic anhydride, 0.8 parts of imidazole accelerator (2-ethyl-4-methylimidazolium), 1.8 parts of silane coupling agent (KH560), and 2.5 parts of polydimethylsiloxane; The preparation method of aminated carbon nanotubes is as follows: S1. Add 10g of multi-walled carbon nanotubes to 200mL of a concentrated sulfuric acid / concentrated nitric acid mixture with a volume ratio of 3:1, and ultrasonically oxidize at 65℃ for 2.5h (ultrasonic power 300W). Then, wash with deionized water by centrifugation until the pH of the supernatant is 7.0, and vacuum dry at 80℃ for 6h to obtain carboxylated carbon nanotubes. S2. Take 5g of carboxylated carbon nanotubes and disperse them in 150mL of anhydrous ethanol. Add 30mL of ethylenediamine and reflux at 75℃ for 5h. After centrifugation and washing 3 times, dry under vacuum at 80℃ for 8h to obtain aminolated carbon nanotubes.

[0015] The preparation method of hydroxylated silicon carbide nanowires is as follows: S1. Take 5g of silicon carbide nanowires and place them in 100mL of 2.5mol / L dilute nitric acid. Reflux in a water bath at 85℃ for 2.5h. After cooling to room temperature, centrifuge to separate them. S2. Wash with deionized water until the eluent pH=7.0, and dry under vacuum at 100℃ for 4h to obtain surface hydroxylated silicon carbide nanowires.

[0016] This embodiment describes a method for preparing a high thermal conductivity liquid epoxy molding compound. The specific preparation steps are as follows: S1. Add nano-hexagonal boron nitride with D50=80nm and micro-hexagonal boron nitride with D50=4μm to a high-speed mixer at a mass ratio of 1:2 and mix at 600rpm for 12min to obtain a uniformly compounded hexagonal boron nitride filler for later use. S2. Add epoxy resin, hyperbranched polysiloxane, and polydimethylsiloxane to a planetary mixer with a dual-blade structure. The ratio of the blade rotation speed to the revolution speed is 1:3. Stir at 25°C and 600 rpm for 12 minutes to obtain a premixed liquid. S3. Add spherical alumina, compounded hexagonal boron nitride, aminated carbon nanotubes, hydroxylated silicon carbide nanowires and silane coupling agent in sequence, evacuate to -0.092 MPa, heat to 32℃, and disperse at 1350 rpm for 35 min (water cooling temperature control ≤35℃). S4. Remove the vacuum, add methylhexahydrophthalic anhydride and imidazole accelerator, and vacuum again to -0.092MPa. Stir at 800rpm for 18min to remove bubbles. S5. Filter the product through a 100-mesh stainless steel filter (150μm pore size, cleaned with 75% ethanol and dried) at 0.15MPa pressure to obtain the liquid product. Perform step-by-step curing on the liquid product: first, heat to 80℃ for 1.2h, then heat to 120℃ for 2.2h, and finally heat to 150℃ for 1.2h. After the heat treatment is completed, allow it to cool naturally to room temperature to complete the curing.

[0017] Example 2: A method for preparing a high thermal conductivity liquid epoxy molding compound according to Example 2. The molding compound is prepared from the following raw materials in parts by weight: 35 parts of bisphenol F type liquid epoxy resin, 12 parts of alicyclic epoxy resin, 6 parts of hyperbranched polysiloxane, 135 parts of spherical alumina, 35 parts of compounded hexagonal boron nitride (nano BN 80nm, micron BN 4μm), 2.5 parts of aminated carbon nanotubes, 1.5 parts of hydroxylated silicon carbide nanowires (diameter 25nm, aspect ratio 75), 28 parts of methylhexahydrophthalic anhydride, 0.8 parts of imidazole accelerator (2-ethyl-4-methylimidazolium), 1.8 parts of silane coupling agent (KH560), and 2.5 parts of polydimethylsiloxane; The preparation methods for aminated carbon nanotubes and hydroxylated silicon carbide nanowires are the same as in Example 1; In this embodiment, the preparation method of a high thermal conductivity liquid epoxy molding compound is the same as that in Example 1, except that the number of hydroxylated silicon carbide nanowires is increased to 1.5 parts.

[0018] Example 3: A method for preparing a high thermal conductivity liquid epoxy molding compound according to Example 3. The molding compound is prepared from the following raw materials in parts by weight: 35 parts of bisphenol F type liquid epoxy resin, 12 parts of alicyclic epoxy resin, 6 parts of hyperbranched polysiloxane, 135 parts of spherical alumina, 35 parts of compounded hexagonal boron nitride (nano BN 80nm, micron BN 4μm), 2.5 parts of aminated carbon nanotubes, 2.0 parts of hydroxylated silicon carbide nanowires (diameter 25nm, aspect ratio 75), 28 parts of methylhexahydrophthalic anhydride, 0.8 parts of imidazole accelerator (2-ethyl-4-methylimidazolium), 1.8 parts of silane coupling agent (KH560), and 2.5 parts of polydimethylsiloxane; The preparation methods for aminated carbon nanotubes and hydroxylated silicon carbide nanowires are the same as in Example 1; The preparation method of a high thermal conductivity liquid epoxy molding compound in this embodiment is the same as that in Example 1, except that the number of hydroxylated silicon carbide nanowires is increased to 2.0 parts.

[0019] Comparative Example 1: The molding compound of Comparative Example 1 was prepared from the following parts by weight of raw materials: 35 parts of bisphenol F type liquid epoxy resin, 12 parts of alicyclic epoxy resin, 6 parts of hyperbranched polysiloxane, 135 parts of spherical alumina, 35 parts of compounded hexagonal boron nitride (nano BN 80nm, micron BN 4μm), 2.5 parts of aminoated carbon nanotubes, 28 parts of methylhexahydrophthalic anhydride, 0.8 parts of imidazole accelerator (2-ethyl-4-methylimidazolium), 1.8 parts of silane coupling agent (KH560), and 2.5 parts of polydimethylsiloxane; The preparation method of the aminated carbon nanotubes is the same as that in Example 1; The molding compound in this comparative example was prepared using the same method as in Example 1, except that hydroxylated silicon carbide nanowires were not added.

[0020] Comparative Example 2: The molding compound of Comparative Example 2 was prepared from the following parts by weight of raw materials: 35 parts of bisphenol F type liquid epoxy resin, 12 parts of alicyclic epoxy resin, 6 parts of hyperbranched polysiloxane, 135 parts of spherical alumina, 35 parts of compounded hexagonal boron nitride (nano BN 80nm, micron BN 4μm), 2.5 parts of aminoated carbon nanotubes, 1.5 parts of ordinary SiC powder (5μm), 28 parts of methylhexahydrophthalic anhydride, 0.8 parts of imidazole accelerator (2-ethyl-4-methylimidazolium), 1.8 parts of silane coupling agent (KH560), and 2.5 parts of polydimethylsiloxane; The preparation method of the aminated carbon nanotubes is the same as that in Example 1; The molding compound in this comparative example was prepared using the same method as in Example 1, except that the hydroxylated silicon carbide nanowires were replaced with ordinary SiC powder.

[0021] Performance testing 1. Thermal conductivity test The thermal conductivity of the cured samples was tested using the laser flash method. Before testing, the fully cured epoxy molding compound sample was processed into a circular sheet with a diameter of 12.7 mm and a thickness of 1 mm. A thin layer of graphite was uniformly sprayed on the upper and lower surfaces of the sample to improve the infrared absorption efficiency. The sample was then placed in the test chamber of the laser flash thermal conductivity meter and tested under a nitrogen atmosphere at 25°C. The laser energy was set to 3 J and the pulse width to 0.2 ms. The temperature change curve of the back side of the sample over time was collected. The thermal diffusivity was calculated using the instrument's built-in software. Combined with the sample density measured according to ASTM D792 standard and the specific heat capacity measured by differential scanning calorimetry, the thermal conductivity of the sample was finally calculated.

[0022] Table 1. Test data of thermal conductivity of different samples

[0023] The thermal conductivity of Examples 1-3, which added hydroxylated silicon carbide nanowires, reached 2.9 W·m⁻¹·K⁻¹, 3.0 W·m⁻¹·K⁻¹, and 3.1 W·m⁻¹·K⁻¹, respectively, showing a gradual increase with the increase of nanowire dosage. In contrast, the thermal conductivity of Comparative Examples 1 and 2, which did not add the nanowires, was only 2.2 W·m⁻¹·K⁻¹ and 2.3 W·m⁻¹·K⁻¹, significantly lower than the Examples 1-3. This indicates that the introduction of hydroxylated silicon carbide nanowires can effectively construct heat conduction pathways, improve the thermal conductivity of epoxy molding compounds, and ensure the heat dissipation requirements during the electronic component packaging process.

[0024] 2. Viscosity (25℃) Test The viscosity of the liquid epoxy molding compound was tested at 25°C using a rotational viscometer. Before the test, the viscometer rotor (rotor No. 2 of the NDJ-8S type viscometer) and the sample were placed together in a 25°C constant temperature water bath for 30 minutes to ensure that the instrument and the sample were at the same temperature. Then, an appropriate amount of liquid product was poured into a clean sample cup, and the rotor was slowly immersed into the sample to the specified scale line to avoid generating air bubbles. The instrument was started and rotated at a constant speed of 60 rpm. After the pointer stabilized, the reading was recorded. The test was repeated 3 times, and the average value was taken as the final viscosity test result.

[0025] Table 2. Test data on viscosity (25℃) of different samples

[0026] The viscosities of Examples 1-3 were 1030 mPa·s, 1050 mPa·s, and 1080 mPa·s, respectively. Although they increased slightly with the increase of nanowire dosage, they remained within a reasonable range without significant fluctuations. Comparative Example 1 had the lowest viscosity (1020 mPa·s), while Comparative Example 2 had a viscosity as high as 1150 mPa·s, which is presumably related to the dispersibility of other fillers. The viscosity levels of the examples met the application flow requirements of the liquid encapsulation material without causing viscosity runaway due to the addition of nanowires, thus balancing processing performance and subsequent molding effects.

[0027] 3. Curing shrinkage rate test The curing shrinkage rate was tested using the density method. Before the test, a finished liquid epoxy molding compound and a fully cured sample were prepared. First, an appropriate amount of the liquid product was placed in a specific gravity bottle of known volume, and the liquid density ρ1 was measured according to ASTM D792 standard. Then, the same mass of the liquid product was taken and fully cured according to the predetermined curing process (80℃ for 1.2h, then 120℃ for 2.2h, then 150℃ for 1.2h). After cooling to room temperature, it was processed into regular blocks, and the solid density ρ2 was measured according to ASTM D792 standard. The final curing shrinkage rate was calculated according to the formula "curing shrinkage rate = (ρ2-ρ1) / ρ2×100%". Each group of samples was tested in parallel 3 times, and the average value was taken as the test result.

[0028] Table 3. Test data on curing shrinkage rate of different samples

[0029] The shrinkage rates of Examples 1-3 were 0.72%, 0.65%, and 0.60%, respectively, and continued to decrease with increasing hydroxylated silicon carbide nanowire content, all lower than those of Comparative Example 1 (1.10%) and Comparative Example 2 (1.00%). This result indicates that hydroxylated silicon carbide nanowires can fill the internal voids during the curing process of epoxy molding compound, suppress volume shrinkage, help improve the dimensional stability of the encapsulated part, and reduce defects such as warping and cracking caused by uneven shrinkage.

[0030] 4. Volume resistivity test The volume resistivity of fully cured epoxy molding compound samples was tested using a high-resistivity meter, and the test was performed according to GB / T1410 standard. Before the test, the cured sample was processed into a circular sheet with a diameter of 50 mm and a thickness of 2 mm. The upper and lower surfaces of the sample were wiped with anhydrous ethanol and allowed to air dry naturally to remove surface impurities and oil. Then, the sample was placed in a standard environment of 25°C and 50% relative humidity for 24 hours. Then, it was placed between the test electrodes of the high-resistivity meter, and a DC voltage of 500 V was applied. After the voltage was kept stable for 2 minutes, the instrument reading was recorded. Each group of samples was tested in parallel 3 times, and the average value was taken as the final volume resistivity test result.

[0031] Table 4. Test data of volume resistivity of different samples

[0032] The resistivity of Examples 1-3 was slightly improved by increasing the amount of resistive nanowires used, while the resistivity of Comparative Examples 1 and 2 was slightly lower than that of the Examples. This indicates that the addition of hydroxylated silicon carbide nanowires did not impair the insulation performance of the epoxy molding compound. On the contrary, the surface modification effect of the nanowires improved the charge barrier capability inside the material, ensuring that the material meets the stringent insulation requirements of electronic packaging while maintaining good thermal conductivity.

[0033] 5. Glass transition temperature (Tg) Differential scanning calorimetry (DSC) was used to test the glass transition temperature of fully cured epoxy molding compound samples, and the test was performed according to GB / T 19466.2 standard. Before the test, about 10 mg of cured sample was taken, ground into a uniform powder, and placed in an aluminum sample crucible. An empty aluminum crucible was used as a reference. Both were placed in the test chamber of the DSC instrument. The test atmosphere was set to nitrogen (nitrogen flow rate 50 mL / min), the temperature range was 30℃ to 200℃, the temperature rise rate was controlled at 10℃ / min, and the scan was continuous until the end of the test. The DSC curve was processed by the instrument's built-in analysis software. The midpoint temperature of the curve baseline deviation was taken as the glass transition temperature of the sample. Each group of samples was tested in parallel twice, and the average value was taken as the final test result.

[0034] Table 5. Test data of glass transition temperature for different samples

[0035] The Tg values ​​of Examples 1-3 showed a slight and steady upward trend, while the Tg of Comparative Example 1 was the same as that of Example 1, and the Tg of Comparative Example 2 was slightly lower. This indicates that a good interfacial bond was formed between the hydroxylated silicon carbide nanowires and the epoxy matrix, which enhanced the molecular chain rigidity of the matrix and improved the thermal stability of the material, enabling the examples to maintain stable mechanical and performance properties even at higher temperatures.

[0036] 6. Bending strength test Three-point bending strength tests were conducted on cured epoxy molding compound samples using a universal testing machine. Before testing, the samples were processed into regular strips of 80mm×10mm×4mm, the edges were sanded with fine sandpaper, the surface was wiped with anhydrous ethanol and dried, and then placed in a 25℃ environment for equilibrium before testing. The three-point bending span was set to 64mm, the loading rate was 2mm / min, the sample was placed horizontally on the support, and the indenter was applied at a uniform speed until the sample broke. The maximum breaking load was recorded, and the result was calculated according to the bending strength calculation formula. Five samples were tested in parallel for each group, and the average value was taken as the final test data after removing outliers.

[0037] Table 6. Test data of bending strength of different samples

[0038] The flexural strength of Examples 1-3 increased significantly with increasing hydroxylated silicon carbide nanowire content, while the flexural strength of Comparative Examples 1 and 2 differed significantly from that of the Examples. These results confirm that hydroxylated silicon carbide nanowires, as a reinforcing phase, can effectively transfer stress, inhibit crack propagation, significantly improve the mechanical load-bearing capacity of epoxy molding compounds, and enhance the deformation and fracture resistance of the encapsulation structure.

[0039] 7. Curing degree test The degree of cure was tested using differential scanning calorimetry (DSC). Before the test, approximately 10 mg of uncured liquid epoxy molding compound and a fully cured sample were taken and placed in aluminum crucibles, respectively, with an empty crucible as a reference. The test was conducted under a nitrogen atmosphere with a nitrogen flow rate of 50 mL / min, a heating range of 30℃-250℃, and a heating rate of 10℃ / min. The curing reaction enthalpy ΔH0 of the uncured sample and the residual reaction enthalpy ΔH1 of the cured sample were measured. The degree of cure (%) was calculated according to the formula (1-ΔH1 / ΔH0)×100%. Each group was tested in parallel twice, and the average value was taken as the final degree of cure.

[0040] Table 7. Test data on the degree of curing of different samples

[0041] The curing degree of Examples 1-3 was at a high level and increased slightly with the amount of nanowires used, while the curing degree of Comparative Examples 1 and 2 was lower than that of Examples. This indicates that the surface hydroxyl groups of hydroxylated silicon carbide nanowires can promote the reaction between epoxy resin and curing agent, improve the reaction conversion rate, reduce residual uncured components, and help improve the overall performance stability and service life of the material, avoiding performance degradation caused by incomplete curing.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high thermal conductivity liquid epoxy molding compound, characterized in that, The molding compound is prepared from the following raw materials in parts by weight: The molding compound comprises 30-40 parts of bisphenol F type liquid epoxy resin, 10-15 parts of alicyclic epoxy resin, 5-8 parts of hyperbranched polysiloxane, 120-150 parts of spherical alumina, 30-40 parts of compounded hexagonal boron nitride, 2-3 parts of aminated carbon nanotubes, 1-2 parts of hydroxylated silicon carbide nanowires, 25-30 parts of methylhexahydrophthalic anhydride, 0.5-1.0 parts of imidazole accelerator, 1.5-2.0 parts of silane coupling agent, and 2-3 parts of polydimethylsiloxane; the molding compound has a viscosity of 800-1300 mPa·s at 25°C and a thermal conductivity of 2.8-3.2 W / (m·K).

2. The high thermal conductivity liquid epoxy molding compound according to claim 1, characterized in that, The compounded hexagonal boron nitride is composed of nanosheets and microsheets in a mass ratio of 1:2, with the nanosheets having a particle size of 50-100 nm and the microsheets having a particle size of 3-5 μm.

3. The high thermal conductivity liquid epoxy molding compound according to claim 1, characterized in that, The hydroxylated silicon carbide nanowires have an aspect ratio of 50-100 and a diameter of 20-50 nm.

4. The high thermal conductivity liquid epoxy molding compound according to claim 1, characterized in that, The molding compound has a curing shrinkage rate of 0.5%-0.8%, a volume resistivity of 1.0×10¹⁶-5.0×10¹⁶ Ω·cm, and a glass transition temperature of 135℃-145℃.

5. A method for preparing a high thermal conductivity liquid epoxy molding compound, used to prepare the high thermal conductivity liquid epoxy molding compound according to claim 1, characterized in that, The specific preparation method is as follows: S1. Weigh out bisphenol F type liquid epoxy resin, alicyclic epoxy resin, hyperbranched polysiloxane, and polydimethylsiloxane by weight, add them to a planetary mixer, and stir for 10-15 minutes at 23℃-27℃ and 500-800rpm to obtain a uniform and transparent premixed liquid. S2. Add spherical alumina, compounded hexagonal boron nitride, aminated carbon nanotubes, hydroxylated silicon carbide nanowires and silane coupling agent sequentially to the premix. Close the planetary mixer chamber, evacuate to -0.090 to -0.095 MPa, heat to 30℃-35℃, and disperse at 1200-1500 rpm for 30-40 minutes. During this period, maintain the chamber temperature not exceeding 35℃ through the water cooling system. S3. Remove the vacuum, add methylhexahydrophthalic anhydride and imidazole accelerator according to the weight parts, and evacuate the vacuum again to -0.090 to -0.095 MPa. Stir at 800-1000 rpm for 15-20 minutes to complete the degassing. S4. Pass the above material through a 100-mesh stainless steel filter screen and filter it under a pressure of 0.1-0.2MPa to remove mechanical impurities and obtain a liquid product. The curing conditions of the liquid product are as follows: heat at 80℃±5℃ for 1-1.5h, heat to 120℃±5℃ for 2-2.5h, heat to 150℃±5℃ for 1-1.5h, and then cool naturally to room temperature.

6. The method for preparing a high thermal conductivity liquid epoxy molding compound according to claim 5, characterized in that, The planetary mixer described in steps S1 and S2 has a double-blade structure with a blade speed to revolution speed ratio of 1:

3.

7. The method for preparing a high thermal conductivity liquid epoxy molding compound according to claim 5, characterized in that, In step S4, the filter uses an 80-120 mesh stainless steel filter screen, which is cleaned and dried with a 70-80% ethanol solution before filtration.

8. The method for preparing a high thermal conductivity liquid epoxy molding compound according to claim 5, characterized in that, The imidazole accelerator is 2-ethyl-4-methylimidazole with a purity ≥99.0%.

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