Synthesis method of low-interface-thermal-resistance full-aromatic polymer modified alumina and application of low-interface-thermal-resistance full-aromatic polymer modified alumina in high-thermal-conductivity epoxy packaging

Abstract

The invention relates to the technical field of epoxy electronic packaging adhesives, and discloses a preparation method of a low-interface-thermal-resistance fully-aromatic Al2O3-coated PGA-MDA filler and application of the filler in epoxy packaging, chemical modification is performed on the surface of the Al2O3 filler through fully-aromatic PGA-MDA, the preparation method of the filler Al2O3-coated PGA-MDA with a core-shell structure is designed, the fully-aromatic PGA-MDA is modified on the surface of Al2O3, and the filler Al2O3-coated PGA-MDA with a core-shell structure is prepared. The interface wettability between the epoxy resin and the filler is promoted, the binding force between the filler and the epoxy resin is increased, and the dispersibility and fluidity of EMC are improved. More importantly, a large number of rigid benzene ring structures on a main chain structure of the full-aromatic PGA-MDA are beneficial to phonon conduction, a heat conduction path is easily formed among filler, an interface and matrix resin, the overall heat conduction performance and temperature resistance of the composite material are improved, and the full-aromatic PGA-MDA can be widely applied to packaging of semiconductor integrated circuits.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy electronic packaging adhesives, and in particular to a preparation method of a high thermal conductivity epoxy adhesive based on alumina@poly(trihydroxybenzoic acid-diaminodiphenylmethane) (Al2O3@PGA-MDA) and research on its application in electronic packaging. Background Art

[0002] As electronic components gradually move towards miniaturization, integration and high frequency, higher requirements are placed on the thermal conductivity of electronic packaging materials. Among them, epoxy molding compound (EMC) has excellent electrical insulation properties, excellent chemical stability, easy processing and other excellent properties. It is an indispensable solid insulating material in the field of electronic packaging insulation. However, the thermal conductivity of a single epoxy packaging material itself is poor, which makes it impossible for electronic devices working at high frequencies to dissipate heat in time, resulting in a decrease in performance. At present, the common method is to add a high thermal conductivity filler Al2O3 to epoxy resin, and its thermal conductivity coefficient is 2.7W / (m·K). Although the thermal conductivity of epoxy resin is improved by compounding high thermal conductivity fillers, alumina is an inert material and is not easy to modify; and because of its large specific surface energy, it has poor compatibility with epoxy and a large interface thermal resistance. The traditional interface modification method is to add silane coupling agent, but it is difficult to achieve the desired effect. The main reason is that silane coupling agent is mainly composed of small molecular carbon chain and -Si-O- chain, which is an amorphous phase material with large phonon scattering and poor thermal conductivity. It forms a layer of interfacial thermal resistance effect on the surface of spherical alumina, destroying the heat conduction path and greatly reducing the overall thermal conductivity of the rubber. Summary of the invention

[0003] In view of the above technical difficulties, a fully aromatic poly (trihydroxybenzoic acid-diaminodiphenylmethane) was designed through molecular surface technology to modify the surface of spherical alumina, namely alumina@poly (trihydroxybenzoic acid-diaminodiphenylmethane). Compared with the newly synthesized semi-aromatic PGA-LDA, the main chain structure of the fully aromatic PGA-MDA has a large number of rigid benzene ring structures, which is conducive to phonon conduction, easy to form a heat conduction path, and improve the overall thermal conductivity and processability of the composite material. This method is simple and efficient, greatly improves the thermal conductivity and dispersibility of epoxy resin, and greatly reduces the cost of the modified formula, which is expected to be widely promoted in electronic packaging.

[0004] In order to achieve the above object, the present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a method for synthesizing a low interfacial thermal resistance fully aromatic polymer modified alumina, the method comprising the following steps:

[0006] Step S1: weigh Al2O3 and add it to a Tris buffer solution of pH=8, and stir to obtain solution 1;

[0007] Step S2: Add 3,4,5-trihydroxybenzoic acid to the solution I obtained in Step S1, and stir evenly to obtain solution II;

[0008] Step S3: Dissolve 4,4'-diaminodiphenylmethane in ethanol, and add it to the solution II obtained in Step S2, stir, and modify PGA-MDA on the surface of Al2O3 by oxidative polymerization method;

[0009] Step S4: Then wash off the ungrafted PGA-MDA by filtration and static settling method, and dry it to obtain Al2O3@PGA-MDA;

[0010] Among them, the mass ratio of Al2O3, 3,4,5-trihydroxybenzoic acid and 4,4'-diaminodiphenylmethane is 150:3-10:3-10.

[0011] Preferably, the drying temperature in Step S4 is 90-120 °C.

[0012] In the second aspect, the present invention provides an epoxy molding compound EMC, which comprises the following components in parts by weight: 59.5-61.5 parts of epoxy resin, 40-42 parts of phenolic resin, 735 parts of high thermal conductivity filler, 145 parts of crystalline silica powder, 2 parts of carbon black, 4-5 parts of coupling agent, 3 parts of wax, 1.4-1.7 parts of accelerator, 4-6 parts of stress modifier and 2-3 parts of ion scavenger, 59.5 parts of epoxy resin, 40 parts of phenolic resin, 735 parts of high thermal conductivity filler, 145 parts of crystalline silica powder, 2 parts of carbon black, 5 parts of coupling agent, 3 parts of wax, 1.7 parts of accelerator, 6 parts of stress modifier and 3 parts of ion scavenger, wherein the high thermal conductivity filler is prepared by the above method.

[0013] Preferably, the epoxy resin is selected from one or more of bisphenol A type epoxy resin, novolac epoxy resin, biphenyl type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, dithioether type epoxy resin, naphthol type epoxy resin.

[0014] Preferably, the phenolic resin is selected from one or more of o-methylphenolic resin, phenol-formaldehyde type phenolic resin, biphenyl type phenolic resin, polyaromatic type phenolic resin, epoxy modified phenolic resin.

[0015] Preferably, the wax is selected from one or more of polyethylene wax, natural palm wax, stearic acid, oxidized polyethylene wax, montanate, ester wax or polyamide wax.

[0016] Preferably, the accelerator is selected from one or more of imidazole type curing accelerators, amine type curing accelerators, organic phosphorus based curing accelerators, anhydride type curing accelerators.

[0017] Preferably, the coupling agent is selected from one or more of titanate coupling agents, siloxane coupling agents and their modified derivatives, and the siloxane coupling agent includes mercapto-type siloxane coupling agents, amino-type siloxane coupling agents or epoxy-type siloxane coupling agents.

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

[0019] In a third aspect, the present invention provides a method for preparing the epoxy molding compound EMC, and the method includes the following steps: weighing epoxy resin, phenolic resin, high thermal conductivity filler, crystalline silicon powder, carbon black, coupling agent, wax, accelerator, stress modifier and ion scavenger according to the ratio, melting and kneading the materials evenly on an open mill preheated at a temperature of 60-110°C, taking the evenly mixed materials off the open mill, naturally cooling and pulverizing them to obtain powdery materials, and preforming them into cake materials to obtain the epoxy molding compound EMC.

[0020] The present invention has the following beneficial effects: to solve the key pain points such as large interfacial thermal resistance, poor heat resistance and poor compatibility between the filler and the epoxy matrix resin, the surface of the filler is chemically modified by fully aromatic PGA-MDA, and a preparation method of the core-shell structure filler Al2O3@PGA-MDA is designed. The method path is simple and efficient. The fully aromatic PGA-MDA is modified on the surface of Al2O3. On the one hand, the rigid group composition of PGA-MDA is more conducive to phonon conduction, forming a heat conduction path between the filler-interface-matrix resin, and improving the thermal conductivity of the EMC system itself; on the other hand, the surface of PGA-MDA contains rich amino and hydroxyl groups, which can be used for the ring-opening reaction of epoxy monomers and participate in the reaction of the main chain, increasing the binding force between the filler and the epoxy resin, and improving the heat resistance and mechanical strength of the EMC under high temperature conditions. Description of the Drawings

[0021] Figure 1 is a schematic diagram of the preparation process of the core-shell structure high thermal conductivity filler Al2O3@PGA-MDA.

[0022] Figure 2 are the colors of Al2O3 before modification and Al2O3@PGA-MDA after modification.

[0023] Figure 3 is a TEM schematic diagram of unmodified Al2O3 in Example 2.

[0024] Figure 4 is a TEM schematic diagram of the core-shell structure high thermal conductivity filler Al2O3@13nm PGA-MDA prepared in Example 2.

[0025] Figure 5It is a TEM schematic diagram of the core-shell structured high thermal conductivity filler Al2O3@22nm PGA-MDA prepared in Example 1.

[0026] Figure 6 It is an XRD schematic diagram of the core-shell structured high thermal conductivity filler Al2O3@PGA-MDA in Examples 1 and 2.

[0027] Figure 7 It is a thermogravimetric analysis chart of the fully aromatic Al2O3@PGA-MDA filler in Examples 1 and 2.

[0028] Figure 8 It is the actual effect diagram of the modified filler formula in EMC (a is the scanning diagram of the unmodified Al2O3 filler, b is the scanning diagram of the Al2O3@PGA-MDA filler in Example 1). Specific implementation mode

[0029] The present invention will be further described below in conjunction with the embodiments, but it shall not be used as the basis for limiting the present invention.

[0030] Example 1

[0031] Step 1: Prepare 4.0 L of Tris buffer solution with a pH of 8, then weigh 1500 g of Al2O3 and add it to the Tris buffer solution. After stirring for half an hour, add 30 g of 3,4,5-trihydroxybenzoic acid (scientific name: gallic acid, GA) to make it fully dissolve. Secondly, dissolve 50 g of 4,4'-diaminodiphenylmethane (MDA) in 100 ml of ethanol and then add it to the above solution. After that, stir at room temperature for 24 hours, and successfully modify poly(trihydroxybenzoic acid-diaminodiphenylmethane) PGA-MDA on the surface of Al2O3 by the method of oxidative polymerization. Wash away the ungrafted PGA-MDA by the filtration and standing method, and dry it in an oven at 100 °C to obtain the core-shell structured alumina@poly(trihydroxybenzoic acid-diaminodiphenylmethane) of the high thermal conductivity filler (fully aromatic Al2O3@22nm PGA-MDA filler is prepared);

[0032] Step 2: Weigh 59.5 g of naphthalene ring-type epoxy resin (HP5000), 40 g of epoxy-modified phenolic resin (MEHC-7800M), 735 g of highly thermally conductive filler Al2O3@22nm PGA-MDA, 145 g of crystalline silica powder (LG03), 2 g of carbon black (MA-600), 2 g of coupling agent (KEM014), 3 g of coupling agent (CG-0187), 2 g of oxidized polyethylene wax (LICOWAX PED522), 1 g of monoglyceride stearate (MG), 1.7 g of triphenylphosphine (TPP), 6 g of epoxy group-containing silicone oil, and 3 g of ion scavenger. Mix them uniformly by melt-kneading on an open mill preheated to 110°C. Take the uniformly mixed material off the open mill, let it cool naturally, and crush it to obtain a powdery material. Preform it into a cake-shaped material to obtain EMC.

[0033] Example 2

[0034] The difference between Example 2 and Example 1 is that: in Step 1, the mass of 4,4'-diaminodiphenylmethane (MDA) is 30 g; in Step 2, melt-knead uniformly on an open mill preheated to 60°C.

[0035] The specific steps are as follows:

[0036] Step 1: Prepare 4.0 L of Tris buffer solution with a pH of 8. Then weigh 1500 g of Al2O3 and add it to the Tris buffer solution. After stirring for half an hour, add 30 g of 3,4,5-trihydroxybenzoic acid (scientific name: gallic acid, GA) to make it fully dissolve. Secondly, dissolve 30 g of 4,4'-diaminodiphenylmethane (MDA) in 100 ml of ethanol and then add it to the above solution. Then stir at room temperature for 24 hours. Poly(trihydroxybenzoic acid-diaminodiphenylmethane) PGA-MDA is successfully modified on the surface of Al2O3 by the oxidative polymerization method. Wash off the ungrafted PGA-MDA by the filtration and standing method, and dry it in an oven at 100°C to obtain the core-shell structured alumina@poly(trihydroxybenzoic acid-diaminodiphenylmethane) of the highly thermally conductive filler (prepare the fully aromatic Al2O3@13nm PGA-MDA filler).

[0037] Step 2: Weigh 59.5 g of naphthalene ring type epoxy resin (HP5000), 40 g of epoxy modified phenolic resin (MEHC-7800M), 735 g of highly thermally conductive filler Al2O3@22nm PGA-MDA, 145 g of crystalline silica powder (LG03), 2 g of carbon black (MA-600), 2 g of coupling agent (KEM014), 3 g of coupling agent (CG-0187), 2 g of oxidized polyethylene wax (LICOWAX PED522), 1 g of monoglyceride stearate (MG), 1.7 g of triphenylphosphine (TPP), 6 g of epoxy group silicone oil, and 3 g of ion scavenger. Mix them evenly by melt kneading on an open mill preheated to 110°C. Take the evenly mixed material off the open mill, let it cool naturally, crush it to obtain a powdery material, and preform it into a cake to obtain EMC.

[0038] Example 3

[0039] The difference between Example 3 and Example 2 is as follows:

[0040] In Step 2: Weigh 61.5 bisphenol A type epoxy resin (NPES-901), 42 g of biphenol phenolic resin (MEHC-7851SS), 735 g of highly thermally conductive filler Al2O3@22nm PGA-MDA, 145 g of crystalline silica powder (LG03), 2 g of carbon black (MA-600), 1.5 g of coupling agent (KEM014), 2.5 g of coupling agent (CG-0187), 2 g of oxidized polyethylene wax (LICOWAX PED522), 1 g of monoglyceride stearate (MG), 1.5 g of triphenylphosphine (TPP), 4 g of epoxy group silicone oil, and 2 g of ion scavenger. Mix them evenly by melt kneading on an open mill preheated to 110°C. Take the evenly mixed material off the open mill, let it cool naturally, crush it to obtain a powdery material, and preform it into a cake to obtain EMC.

[0041] Example 4

[0042] The difference between Example 4 and Example 2 is as follows:

[0043] In Step 2: Weigh 61.2 g of biphenyl epoxy resin (BNPE-3501LL), 41.5 g of o-cresol novolac resin (PF-8011), 735 g of highly thermally conductive filler Al2O3@22nm PGA-MDA, 145 g of crystalline silica powder (LG03), 2 g of carbon black (MA-600), 1.7 g of coupling agent (KEM014), 2.5 g of coupling agent (CG-0187), 2 g of oxidized polyethylene wax (LICOWAX PED522), 1 g of monoglyceride stearate (MG), 1.4 g of triphenylphosphine (TPP), 4.7 g of epoxy silicone oil, and 2 g of ion scavenger, mix them, melt and knead them evenly on an open mill preheated at 110°C, take the evenly mixed material off the open mill, cool it naturally, crush it to obtain a powdery material, and preform it into a cake material to obtain EMC.

[0044] Comparative Example 1

[0045] The difference between Comparative Example 1 and Example 1 is that in Step 1, 30 g of hexamethylenediamine (LDA) is dissolved in 100 ml of ethanol.

[0046] The specific steps are as follows:

[0047] Step 1: Prepare 4.0 L of Tris buffer solution with a pH of 8, then weigh 1500 g of Al2O3 and add it to the Tris buffer solution. After stirring for half an hour, add 30 g of 3,4,5-trihydroxybenzoic acid (scientific name: gallic acid, GA) to make it fully dissolve. Secondly, dissolve 30 g of hexamethylenediamine (LDA) in 100 ml of ethanol and then add it to the above solution. Then stir at room temperature for 24 hours, and successfully modify poly(3,4,5-trihydroxybenzoic acid-hexamethylenediamine) PGA-LDA on the surface of Al2O3 by the method of oxidative polymerization. Wash off the ungrafted PGA-LDA by the method of filtration and standing, and dry it in an oven at 100°C to obtain semi-aromatic alumina@poly(3,4,5-trihydroxybenzoic acid-hexamethylenediamine) (semi-aromatic Al2O3@PGA-LMDA)

[0048] Step 2: Weigh 59.5 g of naphthalene ring-type epoxy resin (HP5000), 40 g of epoxy-modified phenolic resin (MEHC-7800M), 735 semi-aromatic filler Al2O3@PGA-LDA, 145 g of crystalline silica powder (LG03), 2 g of carbon black (MA-600), 2 g of coupling agent (KEM014), 3 g of coupling agent (CG-0187), 2 g of oxidized polyethylene wax (LICOWAX PED522), 1 g of monoglyceride stearate (MG), 1.7 g of triphenylphosphine (TPP), 6 g of epoxy group silicone oil, and 3 g of ion scavenger. Mix them evenly by melt mixing on an open mill preheated to 110°C. Take the evenly mixed material off the open mill, cool it naturally, crush it to obtain a powdery material, and preform it into a cake to obtain EMC.

[0049] Comparative Example 2

[0050] The difference between Comparative Example 2 and Example 1 is that: in Step 2, the highly thermally conductive filler Al2O3@22nm PGA-MDA is unmodified SiO2 filler;

[0051] The specific steps are as follows:

[0052] Weigh 59.5 g of naphthalene ring-type epoxy resin (HP5000), 40 g of linear phenolic resin (MEHC-7800M), 735 g of unmodified SiO2 filler, 145 g of crystalline silica powder (LG03), 2 g of carbon black (MA-600), 2 g of coupling agent (KEM014), 3 g of coupling agent (CG-0187), 2 g of oxidized polyethylene wax (LICOWAX PED522), 1 g of monoglyceride stearate (MG), 1.7 g of triphenylphosphine (TPP), 6 g of epoxy group silicone oil, and 3 g of ion scavenger. Mix them evenly by melt mixing on an open mill preheated to 110°C. Take the evenly mixed material off the open mill, cool it naturally, crush it to obtain a powdery material, and preform it into a cake to obtain EMC.

[0053] Comparative Example 3

[0054] The difference between Comparative Example 3 and Example 1 is that: in Step 2, the highly thermally conductive filler Al2O3@22nm PGA-MDA is unmodified Al2O3 filler;

[0055] The specific steps are as follows:

[0056] Weigh 59.5 g of naphthalene ring-type epoxy resin (HP5000), 40 g of linear phenolic resin (MEHC-7800M), 735 g of unmodified Al2O3 filler, 145 g of crystalline silica powder (LG03), 2 g of carbon black (MA-600), 2 g of coupling agent (KEM014), 3 g of coupling agent (CG-0187), 2 g of oxidized polyethylene wax (LICOWAX PED522), 1 g of monoglyceride stearate (MG), 1.7 g of triphenylphosphine (TPP), 6 g of epoxy silicone oil, and 3 g of ion scavenger, mix them evenly by melt mixing on an open mill preheated to 110 °C, take the evenly mixed material off the open mill, cool it naturally, and pulverize it to obtain a powdery material, and preform it into a cake to obtain EMC.

[0057] Performance Testing

[0058] Testing Method:

[0059] Infrared Spectrum: Blend the powder sample with KBr and press it into a tablet. The prepared sample is used for infrared testing. It is characterized by a Bruker Tensor Fourier infrared spectrometer from Germany. Its scanning resolution is 2 cm -1 , and the scanning range is 400 - 4000 cm -1 , and it is scanned 32 times.

[0060] XRD Diffraction Pattern: Place the powder sample on the sample stage, then flatten it, and then scan it with an X-ray diffractometer (SmartLab9KW). Its scanning angle is 10 - 90 °C, and its scanning speed is 5 ° / min for scanning.

[0061] Transmission Electron Microscope (TEM): Dissolve the powder sample in water, disperse it with ultrasonic waves for 15 min, take a small drop of the liquid and place it on the carbon film, and finally use a transmission electron microscope (TEM, ThermoFisher Talos F200S) to observe the morphology of the core-shell structured Al2O3@PGA-MDA nanoparticles.

[0062] Spiral Flow Length (SF): This measurement is based on EMMI-1-66, and a mold is used to measure the spiral flow length. Under the conditions of a mold press temperature of 175 °C, an injection clamping pressure of 6.9 MPa, and a curing time of 120 seconds, the measured spiral flow length is in cm.

[0063] Gel Time (GT): This method is used to determine the molding and curing characteristics and mixing uniformity of epoxy molding compounds. Pour the epoxy molding compound powder onto the center of an electric hot plate at 175 ± 2 °C, and immediately flatten the powder with a tongue depressor. The flattened area is controlled within 5 cm 2Start timing from the powder melting. Use a tongue depressor to knead the melt at a frequency of 1 time per second. When the melt changes from a fluid state to a gel state, it is judged as the end point, and record the time used. Operate in the same way three times (the difference between the three measured values is not more than 2 s), and take the average of the three gelation times.

[0064] Flash length: Generally used to characterize the mixing degree of each component in the molding compound. If the mixing effect is good, the flash is small. Measure it on a molding press with the help of a flash metal mold. The mold temperature is 175 ± 2 °C, and the transfer pressure is 70 kg ± 2 kg / cm 2 Take 20 ± 2 g of the sample powder and pour it into the plastic sealing machine cavity for molding. After opening the mold 120 seconds after molding, move the mold to the operating table, and measure the length of the flash overflowing from different grooves with the Flash mold. The unit is expressed in mm.

[0065] Flexural strength modulus: Press a spline (the spline size is 80 mm long, 10 mm wide, and 4 mm high) on a molding press. The molding conditions are: the metal mold temperature is 175 ± 2 °C, and the injection pressure is 70 ± 2 kg / cm 2 , and the curing time is 120 s. After the molded spline is post-cured at 175 ± 2 °C for 6 hours, take it out and cool it to room temperature. Then measure the flexural strength modulus on a universal tensile machine using the three-point bending test method.

[0066] Thermal conductivity: When preparing the spline, the punching rod pressure of the plastic sealing machine is set to 70 ± 2 kg / cm 2 , the stroke rate of the punching rod is about 22 ± 3 mm / sec, the molding press temperature is 175 ± 2 °C, the molding time is 300 s, the molded spline is post-cured in an oven at 175 ± 5 °C for 6 hr, taken out and cooled to room temperature, and then the bulk thermal conductivity is tested with a thermal conductivity meter.

[0067] Reliability test: First, encapsulate the required devices with a molding press, and then place the encapsulated frame in a constant temperature and humidity chamber at 60 °C and 60% humidity for 40 hours. After taking out the frame, use an ultrasonic scanning microscope to analyze the delamination situation.

[0068] The test results are shown in Table 1:

[0069] Table 1. Physical property parameters of the epoxy resin formulation

[0070]

[0071] The present invention prepares a core-shell structure high thermal conductivity filler Al2O3@PGA-MDA through a polymerization reaction. By changing the feeding ratio of GA:MDA:Al2O3, Al2O3@PGA-MDA with different shell layer thicknesses is obtained, and then the relevant physical property analysis of the formulation is verified by substituting in the same proportion in the epoxy resin formulation.

[0072] Figure 2 are the colors of Al2O3 before and after modification. The color of Al2O3 before modification is white, and the color of Al2O3@PGA-MDA after modification is beige, indicating that a layer of polymer material PGA-MDA has been successfully modified on the surface of alumina.

[0073] Figures 3 - 5 are the shell thicknesses of Al2O3 before and after modification. For unmodified Al2O3, its shell surface is relatively smooth and there is no polymer shell. After the oxidative polymerization reaction of 30 g GA and 30 g MDA, a polymer with a shell thickness of about 13 nm can be prepared. As the mass of the reactants of 30 g GA and 50 g MDA for oxidative polymerization increases, the prepared shell thickness further thickens, and a polymer with a shell thickness of about 22 nm is obtained.

[0074] Figure 6 Infrared spectra of unmodified Al2O3 and Al2O3@PGA-MDA with different shells prepared in Examples 1-2. The modified Al2O3 is compared with the unmodified Al2O3 at a wavenumber of -1 An obvious N-H absorption peak appears, indicating that PGA-MDA has been successfully modified on the surface of Al2O3. The surface of Al2O3 is rich in a large number of -NH2 groups, which is beneficial to the ring-opening reaction of epoxy groups and improves the bonding force between the resin and the filler.

[0075] Figure 7 are the XRD diffraction patterns of Al2O3 before and after modification. The diffraction peaks of the sample between 0-90° do not show obvious shifts, indicating that the crystal structure of Al2O3 has not changed during use. In addition, no crystal peaks of PGA-MDA are found between 17-22°, indicating that PGA-MDA belongs to an amorphous phase and has poor crystallization performance.

[0076] As can be seen from the test results in Table 1, through the comparison of Examples 1-4 and Comparative Examples 1, 2, and 3, it is found that since Al2O3@PGA-MDA is coated on the surface of Al2O3, the longer the fluidity, the better the operability. Combining with Flash, it has better compatibility and dispersibility. The gelation time indicates that modifying alumina does not change the curing degree of the system, does not affect the activity of the accelerator, and also confirms that we have successfully modified the surface of alumina without changing the curing degree of the system. Compared with the semi-aromatic PGA-LDA polymer, the fully aromatic PGA-MDA structure contains a large number of rigid group structures, has good crystallization performance, is conducive to phonon conduction, and is easy to form a heat conduction path among the filler-interface-epoxy resin, improving the overall thermal conductivity of the EMC resin. On the other hand, the fully aromatic PGA-MDA surface contains a large number of hydroxyl and amino groups, which can participate in the ring-opening reaction of epoxy resin, increase the binding force between the filler and epoxy resin, and improve the heat resistance and mechanical properties of the EMC. Specifically, compared with unmodified Al2O3 and semi-aromatic Al2O3@PGA-LDA, introducing more rigid benzene ring structures is conducive to phonon conduction, specifically manifested as a significant increase in the thermal conductivity. In the high-temperature test at 175 °C, it can be seen that its flexural strength is significantly improved compared with unmodified Al2O3 and semi-aromatic Al2O3@PGA-LDA. Finally, the prepared EMC raw material achieves high fluidity, and the overflow is significantly reduced. The fully aromatic PGA-MDA shell material is beneficial to increasing the compatibility and fluidity between the filler and the matrix resin, reducing the formation probability of interface defects, and reducing the delamination of the finished material.

[0077] Through Comparative Examples 1, 2, and 3, there are obvious improvements in the fluidity, thermal conductivity, high-temperature resistance, strength, and delamination of the EMC, thus determining the key of the surface modification technology of the fully aromatic Al2O3@PGA-MDA filler in this patent.

[0078] The above shows and describes the basic principles, main features, and advantages of the present invention. However, the above are only specific embodiments of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation manners obtained by those skilled in the art without departing from the technical solution of the present invention should be covered within the patent scope of the present invention.

Claims

1. A method for synthesizing a low interfacial thermal resistance fully aromatic polymer modified alumina, characterized in that: The method comprises the following steps: Step S1: weigh Al2O3 and add it to a Tris buffer solution of pH=8, and stir to obtain solution 1; Step S2: adding 3,4,5-trihydroxybenzoic acid to the solution 1 obtained in step S1, and stirring evenly to obtain a solution 2; Step S3: dissolving 4,4'-diaminodiphenylmethane in ethanol, and adding it to the solution 2 obtained in step S2, stirring, and modifying the surface of Al2O3 with PGA-MDA by an oxidative polymerization method; Step S4: washing away the ungrafted PGA-MDA by filtering and standing, and drying to obtain a high thermal conductivity filler Al2O3@PGA-MDA; The mass ratio of Al2O3, 3,4,5-trihydroxybenzoic acid and 4,4'-diaminodiphenylmethane is 150:3-10:3-10.

2. The method for synthesizing the low interfacial thermal resistance fully aromatic polymer modified alumina according to claim 1, characterized in that: The drying temperature in step S4 is 90-120°C.

3. An epoxy molding compound EMC, characterized in that: The invention comprises the following ingredients in parts by weight: 59.5 to 61.5 parts of epoxy resin, 40 to 42 parts of phenolic resin, 735 parts of high thermal conductivity filler, 145 parts of crystalline silicon powder, 2 parts of carbon black, 4 to 5 parts of coupling agent, 3 parts of wax, 1.4 to 1.7 parts of accelerator, 4 to 6 parts of stress modifier and 2 to 3 parts of ion capture agent, wherein the high thermal conductivity filler is prepared by the method according to any one of claims 1 to 2.

4. The epoxy molding compound EMC according to claim 3, characterized in that: The epoxy resin is selected from one or more of bisphenol A epoxy resin, novolac epoxy resin, biphenyl epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, disulfide epoxy resin, and naphthol epoxy resin.

5. The epoxy molding compound EMC according to claim 3, characterized in that: The phenolic resin is selected from one or more of o-methylphenolic resin, phenol formaldehyde phenolic resin, biphenyl phenolic resin, polyaromatic phenolic resin and epoxy modified phenolic resin.

6. The epoxy molding compound EMC according to claim 3, characterized in that: The wax is selected from one or more of brown polyethylene wax, natural palm wax, stearic acid, oxidized polyethylene wax, montanic acid ester, ester wax or polyamide wax.

7. The epoxy molding compound EMC according to claim 3, characterized in that: The accelerator is selected from one or more of imidazole curing accelerators, amine curing accelerators, organic phosphorus curing accelerators, and acid anhydride curing accelerators.

8. The epoxy molding compound EMC according to claim 3, characterized in that: The coupling agent is selected from one or more of titanate coupling agents, siloxane coupling agents and modified derivatives thereof, and the siloxane coupling agent includes a mercapto-type siloxane coupling agent, an amino-type siloxane coupling agent or an epoxy-type siloxane coupling agent.

9. The epoxy molding compound EMC according to claim 3, characterized in that: The stress modifier is selected from one or more of silicone oil, silicone resin and silicone rubber.

10. The method for preparing the epoxy molding compound EMC according to any one of claims 3 to 9, characterized in that: The method comprises the following steps: epoxy resin, phenolic resin, high thermal conductive filler, crystalline silicon powder, carbon black, coupling agent, wax, accelerator, stress modifier and ion capture agent are weighed according to a ratio, the materials are melted and mixed evenly on an open rubber mixer preheated at a temperature of 60 to 110 DEG C, the evenly mixed materials are taken out of the open rubber mixer, naturally cooled, crushed to obtain powdery materials, preformed into cake materials, and obtain epoxy molding compound EMC.

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