Radiation heat dissipation high thermal conductivity epoxy plastic packaging material, preparation method and application thereof

Abstract

The present application relates to the technical field of electronic packaging materials, and particularly relates to a radiation heat dissipation high-thermal-conductivity epoxy plastic packaging material and a preparation method and application thereof. The plastic packaging material is composed of the following raw materials in parts by weight: 4-10 parts of epoxy resin, 2-10 parts of phenolic resin, 70-95 parts of inorganic filler, 0.1-0.3 parts of colorant, 0.2-0.6 parts of release agent, 0.05-0.5 parts of curing accelerator, 1.5-4.5 parts of stress modifier, 0.3-1.0 parts of coupling agent and 0.3-1.0 parts of ion capture agent; the inorganic filler is composed of spherical nano-alumina, crystalline silica, silico-aluminate coated boron nitride powder and silicate coated boron nitride powder. The epoxy plastic packaging material prepared by the present application has excellent flowability, can effectively reduce the junction temperature of IGBT modules, photovoltaic junction boxes and high-power LEDs and the like, greatly improves the packaging yield and long-term reliability, and provides a packaging solution with excellent processability and high-efficiency heat dissipation performance for high-power-density electronic devices.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, specifically to a high thermal conductivity epoxy molding compound with radiative heat dissipation, its preparation method, and its application. Background Technology

[0002] With the rapid development of third-generation semiconductors (such as SiC and GaN) and high-power-density devices (IGBTs, photovoltaic junction boxes, etc.), the heat flux density of electronic components is increasing exponentially. The heat dissipation capacity of packaging materials has become the biggest problem restricting the reliability and lifespan of devices. Epoxy molding compound (EMC), as the mainstream packaging material, has extremely low intrinsic thermal conductivity (approximately 0.2 W / m·K), and thermal pathways must be constructed using highly filled inorganic thermally conductive fillers.

[0003] However, existing technologies have encountered an irreconcilable physical contradiction in the pursuit of high thermal conductivity and EMC. Firstly, to overcome the thermal conductivity bottleneck above 3 W / m·K, the industry generally adopts a high filler content (>80 wt%) strategy, particularly by introducing high thermal conductivity fillers such as lamellar hexagonal boron nitride (h-BN). However, h-BN is not only expensive, but its unique lamellar geometry is also highly susceptible to rheological disasters during melt mixing—the melt viscosity increases exponentially, leading to serious defects in the packaging process such as incomplete mold filling, broken gold wires, or air pockets, severely limiting its application in precision packaging. Although spherical alumina has good flowability, its thermal conductivity is limited, making it difficult to meet the extreme heat dissipation requirements of high-power devices.

[0004] More crucially, yet often overlooked, heat dissipation ultimately depends on convection and radiation from the package surface to the environment. In enclosed or passive heat dissipation scenarios where natural convection is limited, infrared radiation can contribute over 40% to heat dissipation. Existing high thermal conductivity designs often fall into the trap of solely focusing on thermal conductivity, simply pursuing improvements in bulk thermal conductivity (k-value). However, commonly used h-BN fillers have high reflectivity in the mid- and far-infrared bands. Highly filled BN layers create a thermal mirror-like effect on the EMC surface, which actually inhibits the outward emission of internal heat through radiation. While traditional alumina fillers have slightly better infrared emissivity, their low thermal conductivity makes it difficult for heat to be quickly transferred to the surface to participate in radiation.

[0005] In addition, in order to improve the interfacial compatibility of h-BN, existing technologies mostly use simple silane coupling agents. This physical or weak chemical adsorption is easily detached under high temperature and high shear, which cannot solve the problem of severe interfacial phonon scattering, resulting in the actual thermal conductivity being far lower than the theoretical prediction.

[0006] Therefore, there is an urgent need to develop a new type of epoxy molding compound, which not only needs to overcome the traditional problems such as the thermal conductivity bottleneck and processability deterioration of the pure alumina system, and the high cost and strong anisotropy of the pure boron nitride system, but also needs to fundamentally solve the problem of the mutual constraint between high thermal conductivity fillers and high radiation heat dissipation capacity. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a high thermal conductivity epoxy molding compound for radiation heat dissipation, its preparation method and application, so as to solve the problem of the dramatic increase in melt viscosity in a high-filler thermal conductivity system and the inability of a single thermal conduction mechanism to achieve efficient infrared radiation heat dissipation.

[0008] To achieve the above objectives, the present invention provides a high thermal conductivity epoxy molding compound with radiative heat dissipation, prepared from the following raw materials in parts by weight:

[0009] 4-10 parts epoxy resin, 2-10 parts phenolic resin, 70-95 parts inorganic filler, 0.1-0.3 parts colorant, 0.2-0.6 parts release agent, 0.05-0.5 parts curing accelerator, 1.5-4.5 parts stress modifier, 0.3-1.0 parts coupling agent, and 0.3-1.0 parts ion scavenger;

[0010] The inorganic filler is composed of spherical nano alumina powder, crystalline silica, aluminosilicate-coated boron nitride powder, and silicate-coated boron nitride powder in a weight ratio of 44-60g:16-20g:6-9g:4-6g.

[0011] The aluminosilicate-coated boron nitride powder is obtained by sol-gel hydrolysis and polycondensation reaction of pretreated boron nitride powder and high-concentration sodium silicate solution (containing γ-aminopropyltriethoxysilane coupling agent and spherical nano-alumina);

[0012] The silicate-coated boron nitride powder is obtained by sol-gel hydrolysis and polycondensation reaction of pretreated boron nitride with a low-concentration sodium silicate solution.

[0013] Preferably, the epoxy resin is selected from one or a mixture of several of the following: o-cresol aldehyde epoxy resin, dicyclopentadiene epoxy resin, polyaromatic epoxy resin, polyfunctional epoxy resin, biphenyl epoxy resin, naphthol epoxy resin, and thioether epoxy resin.

[0014] Preferably, the phenolic resin is one or a mixture of several of the following: phenolic ether phenolic resin, o-methyl phenolic resin, biphenyl phenolic resin, polyaromatic phenolic resin, aralkyl phenolic resin, and polyfunctional p-phenylaralkyl phenolic resin.

[0015] Furthermore, the spherical nano-alumina powder and crystalline silica crystals can be replaced by one of silica, fused silica, spherical silica, alumina, talc, kaolin, carbon fiber, and glass fiber.

[0016] Preferably, the release agent is one of natural wax or synthetic wax, more preferably one of palm wax, montmorillonite wax, polyethylene wax, oxidized polyethylene wax, and polyamide wax.

[0017] Preferably, the curing accelerator is one of imidazole compounds, tertiary amine compounds, organophosphorus compounds, and amide compounds.

[0018] Preferably, the stress modifier is one or more of silicone oil, silicone resin, and silicone rubber.

[0019] Preferably, the coupling agent is a silane coupling agent.

[0020] Preferably, the ion scavenger is an anion scavenger.

[0021] Preferably, the high-concentration sodium silicate solution has a mass fraction of 20%.

[0022] Preferably, the average particle size of the spherical nano-alumina powder is 50 nm.

[0023] Preferably, the low-concentration sodium silicate solution has a mass fraction of 5%;

[0024] Preferably, the weight ratio of the pretreated boron nitride powder, high-concentration sodium silicate solution, γ-aminopropyltriethoxysilane coupling agent, and spherical nano-alumina is 9-11g:25g:0.1-0.2g:0.9-1.1g.

[0025] Preferably, the weight ratio of the pretreated boron nitride powder to the low-concentration sodium silicate solution is 9-11g:24g.

[0026] Preferably, the pretreated boron nitride powder is obtained by acidifying hexagonal boron nitride powder with concentrated nitric acid solution;

[0027] Preferably, the weight ratio of the hexagonal boron nitride powder to the concentrated nitric acid solution is 18-22g:10-15g.

[0028] Preferably, the acidification treatment is carried out at a reaction temperature of 80°C and a reaction time of 120-180 min.

[0029] Preferably, the reaction temperature of the sol-gel hydrolysis condensation reaction is 60°C, and the reaction time is 3-5 hours.

[0030] Furthermore, the present invention also provides a method for preparing a high thermal conductivity epoxy molding compound with radiative heat dissipation, comprising the following steps:

[0031] The raw materials are weighed according to the proportion and premixed to form a mixture. The mixture is then melt-blended using a twin-screw extruder. The resulting blended product is then rolled into thin sheets by cooling rollers, crushed, and screened to obtain a high thermal conductivity epoxy molding compound with radiative heat dissipation.

[0032] Preferably, the temperature of the twin-screw extruder is 80-90℃ in zone one, 90-100℃ in zone two, 100-110℃ in zone three, and 105-115℃ in zone four.

[0033] The beneficial effects of this invention are:

[0034] This invention significantly solves the dual challenges of rheological processability and overall heat dissipation efficiency in high thermal conductivity epoxy molding compounds through a unique aluminosilicate-coated boron nitride powder and silicate-coated boron nitride powder gradation coating technology, as detailed below:

[0035] First, this invention innovatively constructs an aluminosilicate-coated boron nitride powder and a silicate-coated boron nitride powder gradation filler system. The aluminosilicate-coated boron nitride powder utilizes a thick inorganic gel layer and in-situ doped spherical nanoparticles to form a ball structure similar to a micro-bearing on the surface of the sheet-like boron nitride. Meanwhile, the silicate-coated boron nitride powder minimizes the interfacial thermal resistance caused by the inorganic coating layer while ensuring basic interfacial wetting. The synergistic effect of the two avoids the decrease in thermal conductivity caused by single coating and overcomes the viscosity runaway and processing defects caused by single coating or no coating, achieving a balance between high thermal conductivity and excellent processability.

[0036] Secondly, the present invention has a wider infrared absorption / emission spectrum than pure boron nitride or pure alumina by generating an aluminosilicate composite shell in situ on the surface of boron nitride, which effectively avoids the thermal reflection effect of sheet fillers. Under the same current impact, the material can significantly reduce the junction temperature of the device, proving the effectiveness of the dual heat dissipation mechanism of bulk conduction / surface radiation.

[0037] The epoxy molding compound prepared by this invention is particularly suitable for packaging scenarios with extremely high heat dissipation requirements, such as IGBT modules, photovoltaic junction boxes, and high-power LEDs. It also has good flowability and can adapt to the rapid filling of complex molds, greatly reducing the gold wire breakage and porosity defect rates, improving the packaging yield, and providing a highly competitive solution for thermal management of third-generation semiconductors and new energy vehicle electronics. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0039] In this invention, the amount of epoxy resin used is 4-10g, including but not limited to 4g, 6g, 9g, and 10g;

[0040] The amount of phenolic resin used is 2-10g, including but not limited to 2g, 4g, 4.4g, 6g, 8g, and 10g;

[0041] The amount of the inorganic filler is 70-95g, including but not limited to 70g, 84g, 90g, and 95g;

[0042] The amount of colorant used is 0.1-0.3g, including but not limited to 0.1g, 0.2g, and 0.3g;

[0043] The amount of the release agent used is 0.2-0.6g, including but not limited to 0.2g, 0.4g, 0.5g, and 0.6g;

[0044] The curing accelerator is used in an amount of 0.05-0.5g, including but not limited to 0.05g, 0.2g, 0.4g, and 0.5g;

[0045] The amount of stress modifier used is 1.5-4.5g, including but not limited to 1.5g, 2g, 2.5g, 3g, and 4.5g;

[0046] The amount of the coupling agent used is 0.3-1.0g, including but not limited to 0.3g, 0.5g, 0.7g, and 1.0g;

[0047] The amount of the ion scavenging agent used is 0.3-1.0g, including but not limited to 0.3g, 0.5g, 0.8g, and 1.0g;

[0048] The source or properties of the raw materials are as follows:

[0049] o-Cresol-type epoxy resin: Nanya NPCN-701; Naphthol-type epoxy resin: DIC HP-5000; Arylalkylphenol-type resin: Mitsubishi YX4000H; Spherical nano-alumina powder: 70μm; Crystalline silica: 10μm; Montanate wax: Clariant GmbH, Germany; Imidazole curing accelerator: 2-Phenylon-4-methylimidazolium, Shikoku Chemical Industry Co., Ltd.; Flaky hexagonal boron nitride powder: average particle size 30μm; Concentrated nitric acid solution: mass fraction 65%; Liquid sodium silicate: modulus 3; Spherical nano-alumina powder: average particle size 50nm.

[0050] Example 1: A method for preparing a high thermal conductivity epoxy molding compound with radiative heat dissipation, the specific steps of which are as follows:

[0051] (1) 18g of hexagonal boron nitride powder was dispersed in 90g of deionized water and 10g of concentrated nitric acid solution was added. The mixture was acidified for 120min in a constant temperature water bath at 80℃ and mechanical stirring at 400rpm. After the reaction was completed, the solid was separated by a vacuum filter funnel and washed repeatedly with deionized water until the pH of the filtrate reached 7. The obtained solid was dried in a 120℃ forced-air drying oven for 12h to obtain pretreated boron nitride powder with hydroxyl-rich surface.

[0052] (2) Take 9g of pretreated boron nitride powder for later use. Take 5g of liquid sodium silicate and add it to 20g of deionized water to prepare a high-concentration sodium silicate solution with a mass fraction of 20%. Add 0.1g of γ-aminopropyltriethoxysilane coupling agent and 0.9g of spherical nano alumina powder to the high-concentration sodium silicate solution and ultrasonically disperse for 30min to form a high-concentration coating solution. Disperse the pretreated boron nitride powder in 50g of anhydrous ethanol and heat it to 60℃. Add it dropwise to the high-concentration coating solution at a rate of 5mL / min under stirring at 600rpm. After the dropwise addition is completed, continue the reaction at a constant temperature for 3h. After centrifugation, washing and drying, obtain aluminosilicate coated boron nitride powder.

[0053] (3) Take 9g of pretreated boron nitride powder for later use. Take 1.2g of liquid sodium silicate and add it to 22.8g of deionized water to prepare a low-concentration sodium silicate solution with a mass fraction of 5 to form a low-concentration coating solution. Disperse the pretreated boron nitride powder in 50g of anhydrous ethanol and heat it to 60℃. Add it dropwise to the low-concentration coating solution at a rate of 5mL / min under stirring at 600rpm. After the addition is completed, continue to react at a constant temperature for 3h. After centrifugation, washing and drying, obtain silicate-coated boron nitride powder.

[0054] (4) Weigh out 7g of o-cresol epoxy resin, 2g of naphthol epoxy resin, 4.4g of arylalkylphenol resin, 44g of spherical nano-alumina powder, 30g of crystalline silica, 6g of aluminosilicate-coated boron nitride powder, 4g of silicate-coated boron nitride powder, 0.1g of carbon black, 0.2g of montmorillonite wax, 0.2g of imidazole curing accelerator, 0.5g of epoxy silicone oil, 1g of silicone rubber, and 0.3g of... γ-glycidyl etheroxypropyltrimethoxysilane coupling agent and 0.3g anion scavenger were weighed and added to a high-speed mixer. The mixture was premixed at 1200 rpm for 8 minutes to ensure that the components were initially and evenly dispersed. The mixture was then added to the feed hopper of a twin-screw extruder. The temperatures of the first zone of the extruder were set to 80℃, the second zone to 90℃, the third zone to 100℃, and the fourth zone to 105℃ for melt mixing. The mixed product was rolled into thin sheets by cooling rollers and then naturally cooled at room temperature of 25℃. Finally, it was pulverized by an ultra-fine pulverizer and passed through a 100-mesh sieve to obtain a high thermal conductivity epoxy molding compound with radiative heat dissipation.

[0055] Example 2: A method for preparing a high thermal conductivity epoxy molding compound with radiative heat dissipation, the specific steps of which are as follows:

[0056] (1) 20g of hexagonal boron nitride powder was dispersed in 100g of deionized water and 13g of concentrated nitric acid solution was added. The mixture was acidified for 150min in a constant temperature water bath at 80℃ and mechanical stirring at 400rpm. After the reaction was completed, the solid was separated by a vacuum filter funnel and washed repeatedly with deionized water until the pH of the filtrate reached 7. The obtained solid was dried in a 120℃ forced-air drying oven for 12h to obtain pretreated boron nitride powder with hydroxyl-rich surface.

[0057] (2) Take 10g of pretreated boron nitride powder for later use. Take 5g of liquid sodium silicate and add it to 20g of deionized water to prepare a high-concentration sodium silicate solution with a mass fraction of 20%. Add 0.15g of γ-aminopropyltriethoxysilane coupling agent and 1.0g of spherical nano alumina powder to the high-concentration sodium silicate solution and ultrasonically disperse for 30min to form a high-concentration coating solution. Disperse the pretreated boron nitride powder in 50g of anhydrous ethanol and heat it to 60℃. Add it dropwise to the high-concentration coating solution at a rate of 8mL / min under stirring at 600rpm. After the dropwise addition is completed, continue the reaction at a constant temperature for 4h. After centrifugation, washing and drying, obtain aluminosilicate coated boron nitride powder.

[0058] (3) Take 10g of pretreated boron nitride powder for later use. Take 1.2g of liquid sodium silicate and add it to 22.8g of deionized water to prepare a low-concentration sodium silicate solution with a mass fraction of 5 to form a low-concentration coating solution. Disperse the pretreated boron nitride powder in 50g of anhydrous ethanol and heat it to 60℃. Add it dropwise to the low-concentration coating solution at a rate of 8mL / min under stirring at 600rpm. After the addition is completed, continue to react at a constant temperature for 4h. After centrifugation, washing and drying, obtain silicate-coated boron nitride powder.

[0059] (4) Weigh out 7g of o-cresol epoxy resin, 2g of naphthol epoxy resin, 4.4g of arylalkylphenol resin, 44g of spherical nano-alumina powder, 30g of crystalline silica, 6g of aluminosilicate-coated boron nitride powder, 4g of silicate-coated boron nitride powder, 0.1g of carbon black, 0.2g of montmorillonite wax, 0.2g of imidazole curing accelerator, 0.5g of epoxy silicone oil, 1g of silicone rubber, and 0.3g of... γ-glycidyl etheroxypropyltrimethoxysilane coupling agent and 0.3g anion scavenger were weighed and added to a high-speed mixer. The mixture was premixed at 1200 rpm for 8 minutes to ensure that the components were initially and evenly dispersed. The mixture was then added to the feed hopper of a twin-screw extruder. The temperatures of the first zone of the extruder were set to 85℃, the second zone to 95℃, the third zone to 105℃, and the fourth zone to 110℃ for melt mixing. The mixed product was rolled into thin sheets by cooling rollers and then naturally cooled at room temperature of 25℃. Finally, it was pulverized by an ultra-fine pulverizer and passed through a 100-mesh sieve to obtain a high thermal conductivity epoxy molding compound with radiative heat dissipation.

[0060] Example 3: A method for preparing a high thermal conductivity epoxy molding compound with radiative heat dissipation, the specific steps of which are as follows:

[0061] (1) 22g of hexagonal boron nitride powder was dispersed in 110g of deionized water and 15g of concentrated nitric acid solution was added. The mixture was acidified for 180min in a constant temperature water bath at 80℃ and a mechanical stirring speed of 400rpm. After the reaction was completed, the solid was separated by a vacuum filter funnel and washed repeatedly with deionized water until the pH value of the filtrate reached 7. The obtained solid was dried in a 120℃ forced air drying oven for 12h to obtain pretreated boron nitride powder with hydroxyl-rich surface.

[0062] (2) Take 11g of pretreated boron nitride powder for later use. Take 5g of liquid sodium silicate and add it to 20g of deionized water to prepare a high-concentration sodium silicate solution with a mass fraction of 20%. Add 0.2g of γ-aminopropyltriethoxysilane coupling agent and 1.1g of spherical nano alumina powder to the high-concentration sodium silicate solution and ultrasonically disperse for 30min to form a high-concentration coating solution. Disperse the pretreated boron nitride powder in 50g of anhydrous ethanol and heat it to 60℃. Add it dropwise to the high-concentration coating solution at a rate of 10mL / min under stirring at 600rpm. After the dropwise addition is completed, continue the reaction at a constant temperature for 5h. After centrifugation, washing and drying, obtain aluminosilicate coated boron nitride powder.

[0063] (3) Take 11g of pretreated boron nitride powder for later use. Take 1.2g of liquid sodium silicate and add it to 22.8g of deionized water to prepare a low-concentration sodium silicate solution with a mass fraction of 5 to form a low-concentration coating solution. Disperse the pretreated boron nitride powder in 50g of anhydrous ethanol and heat it to 60℃. Add it dropwise to the low-concentration coating solution at a rate of 10mL / min under stirring at 600rpm. After the addition is completed, continue the reaction at a constant temperature for 5h. After centrifugation, washing and drying, obtain silicate-coated boron nitride powder.

[0064] (4) Weigh out 7g of o-cresol epoxy resin, 2g of naphthol epoxy resin, 4.4g of arylalkylphenol resin, 44g of spherical nano-alumina powder, 30g of crystalline silica, 6g of aluminosilicate-coated boron nitride powder, 4g of silicate-coated boron nitride powder, 0.1g of carbon black, 0.2g of montmorillonite wax, 0.2g of imidazole curing accelerator, 0.5g of epoxy silicone oil, 1g of silicone rubber, and 0.3g of... γ-glycidyl etheroxypropyltrimethoxysilane coupling agent and 0.3g anion scavenger were weighed and added to a high-speed mixer. The mixture was premixed at 1200 rpm for 8 minutes to ensure that the components were initially and evenly dispersed. The mixture was then added to the feed hopper of a twin-screw extruder. The temperatures of the first zone of the extruder were set to 90℃, the second zone to 100℃, the third zone to 110℃, and the fourth zone to 115℃ for melt mixing. The mixed product was rolled into thin sheets by cooling rollers and then naturally cooled at room temperature of 25℃. Finally, it was pulverized by an ultra-fine pulverizer and passed through a 100-mesh sieve to obtain a high thermal conductivity epoxy molding compound with radiative heat dissipation.

[0065] Comparative Example 1: The difference from Example 2 is that in step (2), spherical nano-alumina powder is not added, while the remaining steps and parameters are completely consistent with Example 2.

[0066] Comparative Example 2: The difference from Example 2 is that in the mixing process of step (4), the silicate-coated boron nitride powder is replaced with aluminosilicate-coated boron nitride powder. The remaining steps and parameters are completely consistent with Example 2.

[0067] Comparative Example 3: The difference from Example 2 is that in the mixing process of step (4), the aluminosilicate coated boron nitride powder is replaced with silicate coated boron nitride powder. The remaining steps and parameters are completely consistent with Example 2.

[0068] Comparative Example 4: The difference from Example 2 is that in the mixing process of step (4), the aluminosilicate-coated boron nitride powder and the silicate-coated boron nitride powder are replaced with pretreated boron nitride powder. The remaining steps and parameters are completely consistent with Example 2.

[0069] Comparative Example 5: The difference from Example 2 is that in the mixing process of step (4), all the spherical nano alumina powder, crystalline silica, aluminosilicate-coated boron nitride powder, and silicate-coated boron nitride powder are replaced with molten silica. The remaining steps and parameters are completely consistent with Example 2.

[0070] Comparative Example 6: The difference from Example 2 is that in the mixing process of step (4), aluminosilicate coated boron nitride powder and silicate coated boron nitride powder are not added. The remaining steps and parameters are completely consistent with Example 2.

[0071] Performance testing

[0072] According to GB / T40564-2021 "Test Method for Epoxy Molding Compounds for Electronic Packaging", the spiral flow length, gelation time, flash, viscosity, flexural strength, thermal hardness and thermal conductivity of the epoxy molding compounds prepared in the examples and comparative examples were determined. The results are shown in Table 1.

[0073] The spiral flow length was measured using an EMMI-1-66 standard spiral flow mold. The mold temperature was set to 175℃, the injection pressure to 6.9MPa, and the injection time to 120s. The weighed powder or preformed biscuit was placed into the injection molding machine barrel, injected into the mold channel, and after curing, the sample was taken out and the spiral flow length (cm) was read.

[0074] Gelation time was determined using the hot plate method, with the hot plate temperature set at 175℃. The test procedure involved placing 1.5g of sample on the hot plate and pressing it into a 10cm diameter using a flat spatula. 2 For thin slices, when the sample melts and the surface of the melt becomes shiny, press the stopwatch to start timing. Use a flat spatula to continuously scrape the sample and observe, or use a needle-shaped stirring rod to continuously stir the sample and observe. The timer stops when the sample changes from a molten state to a gel state, and the time is recorded as the gelation time (s).

[0075] Flash is tested using a dedicated flash test mold and molded under standard injection molding conditions (175℃, 6.9MPa). The longest overflow length (mm) of the overflow channel gap (typically with a gap depth of 10μm) is measured using a micrometer or microscope.

[0076] Viscosity: The viscosity was measured using a high-pressure capillary rheometer at a test temperature of 175°C. The pre-formed molding compound cake was placed into a preheated cylinder and the pressure head was driven to press the melt into a standard capillary die (the length-to-diameter ratio is usually 10:1). The pressure drop of the melt as it flows through the die was recorded by a high-precision pressure sensor. The apparent viscosity of the melt (Pa·s) was automatically calculated and output according to the Hagen-Poiseuille law.

[0077] Bending strength: Standard specimens were injection molded according to standard dimensions (80mm×15mm×4mm) and cured at 175℃ for 6 hours. The test procedure was to use a universal testing machine, adopt the three-point bending method, set the span to 68mm, the test speed to 2mm / min, and measure the failure load at room temperature (25℃) to calculate the bending strength.

[0078] Hot hardness: A Shore D hardness tester was used immediately upon mold opening. The molding compound was cured for 120 seconds in a standard mold cavity at 175℃ and an injection pressure of 6.9 MPa. Immediately afterward, the preheated hardness tester indenter was vertically pressed into the sample surface. Stable readings were recorded after the indenter penetrated the material. To ensure data accuracy, five points were randomly selected at different locations on the sample for measurement, and the average value was taken.

[0079] Thermal conductivity: After the injection-molded sample is cured at 175℃ for 6 hours, the power supply of the thermal conductivity meter is turned on, and the relevant parameters are set to I2. After the instrument has been preheated and stabilized for half an hour, the prepared sample is placed under the probe to start the test. The instrument automatically counts down for 60 seconds. After the test stops, the test result λ is automatically displayed on the screen. The results are shown in Table 1 below.

[0080] Junction temperature test: The epoxy molding compounds prepared in the examples and comparative examples were installed in junction boxes, and the junction temperature of the photovoltaic junction boxes was tested in accordance with the requirements of IEC-62790. The thermal conductivity was verified by the junction temperature test, and the results are shown in Table 2 below.

[0081] Table 1 Performance Test Results

[0082]

[0083] Table 2. Test results of photovoltaic junction box junction temperature

[0084]

[0085] Data Analysis: Data from Examples 1-3 in Tables 1 and 2 show that the high thermal conductivity epoxy molding compound prepared by this invention maintains both extremely high thermal conductivity and excellent processing flowability. This combination of high thermal conductivity and high flowability allows the junction temperature of the photovoltaic junction box to be stably controlled below 200℃ under a high current impact of 26A. This indicates that by constructing a silicate composite shell of varying thicknesses on the boron nitride surface, coupled with a specific thick / thin coating ratio and nano-alumina doping amount, this invention creates a network structure within the material that is optimal for heat conduction and infrared radiation. Simultaneously, the chemical bonding of the interface layer significantly enhances the material's mechanical strength, fully meeting the dual requirements of high-power-density semiconductor devices for heat dissipation efficiency and process stability in packaging materials.

[0086] As can be seen from the data in Tables 1 and 2 of Example 2 and Comparative Example 1, the introduction of spherical nano-alumina powder decisively improves the material properties. This is presumably because the nano-alumina acts as a key micro-nano ball bearing in the silicate coating layer, significantly reducing the internal frictional resistance between the modified filler and the resin matrix, thereby significantly improving the rheological behavior. Simultaneously, the significant difference in junction temperature suggests that the aluminum-containing composite shell has a higher emissivity in the infrared band, thus providing more efficient radiative heat dissipation.

[0087] As can be seen from the data in Examples 2 and Comparative Examples 2 and 3 in Tables 1 and 2, the thick / thin double-coating gradation strategy has a significant heat dissipation advantage compared to a single thick coating. This is presumably because while the excessively thick aluminosilicate coating provides excellent lubrication, it also introduces excessive interfacial thermal resistance, severely hindering phonon transmission between boron nitride layers. Conversely, a single thin coating cannot provide sufficient lubrication and spacing, leading to a dramatic increase in interlayer friction and excessive system viscosity under high filler content. During the compression molding process, the high viscosity hinders the expulsion of microbubbles, resulting in micropores within the cured material. These pores act as poor conductors of heat, severely weakening the overall thermal conductivity of the material.

[0088] As can be seen from the data in Examples 2 and Comparative Examples 4, 5, and 6 in Tables 1 and 2, the modified boron nitride / epoxy resin composite material prepared by this invention exhibits unparalleled advantages in solving the heat dissipation problem of high power density packaging. Through double aluminosilicate coating technology and specific thick / thin coating ratios and nano-alumina doping amounts, this invention not only significantly reduces the interfacial friction of the boron nitride filler and achieves excellent processing fluidity, but also constructs a three-dimensional thermally conductive network with low thermal resistance and high radiation. Under a 26A high current surge, the junction temperature is stably controlled at 185.2℃, perfectly balancing high thermal conductivity, high fluidity, and high reliability, filling the performance gap of existing materials in extreme heat dissipation scenarios.

[0089] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high thermal conductivity epoxy molding compound for radiative heat dissipation, characterized in that, It is prepared from the following raw materials in parts by weight: 4-10 parts epoxy resin, 2-10 parts phenolic resin, 70-95 parts inorganic filler, 0.1-0.3 parts colorant, 0.2-0.6 parts release agent, 0.05-0.5 parts curing accelerator, 1.5-4.5 parts stress modifier, 0.3-1.0 parts coupling agent, and 0.3-1.0 parts ion scavenger; The inorganic filler is composed of spherical nano alumina powder, crystalline silicon dioxide, aluminosilicate-coated boron nitride powder, and silicate-coated boron nitride powder.

2. The aluminosilicate-coated boron nitride powder is obtained by sol-gel hydrolysis and polycondensation reaction of pretreated boron nitride powder with a high-concentration sodium silicate solution containing γ-aminopropyltriethoxysilane coupling agent and spherical nano-alumina; The silicate-coated boron nitride powder is obtained by sol-gel hydrolysis and polycondensation reaction of pretreated boron nitride with a low-concentration sodium silicate solution.

3. The high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 1, characterized in that, The inorganic filler is composed of spherical nano alumina powder, crystalline silica, aluminosilicate-coated boron nitride powder, and silicate-coated boron nitride powder in a weight ratio of 44-60g:16-20g:6-9g:4-6g. The spherical nano alumina powder and crystalline silica can be replaced with one of silica, fused silica, spherical silica, alumina, talc, kaolin, carbon fiber, and glass fiber.

4. The high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 1, characterized in that, The high-concentration sodium silicate solution has a mass fraction of 20%; the low-concentration sodium silicate solution has a mass fraction of 5%; the sol-gel hydrolysis-condensation reaction is carried out at a reaction temperature of 60°C for 3-5 hours.

5. The high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 1, characterized in that, The weight ratio of the pretreated boron nitride powder, high-concentration sodium silicate solution, γ-aminopropyltriethoxysilane coupling agent, and spherical nano-alumina is 9-11g:25g:0.1-0.2g:0.9-1.1g; the weight ratio of the pretreated boron nitride powder and low-concentration sodium silicate solution is 9-11g:24g.

6. The high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 1, characterized in that, The pretreated boron nitride powder is obtained by acidifying hexagonal boron nitride powder with concentrated nitric acid solution, wherein the weight ratio of hexagonal boron nitride powder to concentrated nitric acid solution is 18-22g:10-15g.

7. The high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 1, characterized in that, The epoxy resin is selected from one or a mixture of several of the following: o-cresol aldehyde epoxy resin, dicyclopentadiene epoxy resin, polyaromatic epoxy resin, polyfunctional epoxy resin, biphenyl epoxy resin, naphthol epoxy resin, and thioether epoxy resin.

8. The high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 1, characterized in that, The release agent is one of natural wax or synthetic wax; the curing accelerator is one of imidazole compound, tertiary amine compound, organophosphorus compound, or amide compound.

9. The high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 1, characterized in that, The stress modifier is one or more of silicone oil, silicone resin, and silicone rubber; the coupling agent is a silane coupling agent; and the ion scavenger is an anion scavenger.

10. A method for preparing a high thermal conductivity epoxy molding compound for radiative heat dissipation according to any one of claims 1-8, characterized in that, Includes the following steps: The raw materials are weighed according to the proportion and premixed to form a mixture. The mixture is then melt-blended using a twin-screw extruder. The resulting blended product is then rolled into thin sheets by cooling rollers, crushed, and screened to obtain a high thermal conductivity epoxy molding compound with radiative heat dissipation.

11. The method for preparing a high thermal conductivity epoxy molding compound for radiative heat dissipation according to claim 9, characterized in that, The temperature of the twin-screw extruder is 80-90℃ in zone one, 90-100℃ in zone two, 100-110℃ in zone three, and 105-115℃ in zone four.

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