Epoxy resin-based encapsulating material, method for preparing the same, and use thereof

Abstract

The application relates to the technical field of electronic packaging materials, and specifically provides an epoxy resin-based packaging material and a preparation method and application thereof. The preparation method of the epoxy resin-based packaging material comprises the following steps: S1, Fe3O4 nano microspheres are added into a polyethylene imine aqueous solution, oscillation is carried out, and the first product is obtained after drying after the oscillation is completed; and S2, the first product is uniformly mixed with 4,4'-diamino diphenyl methane and an epoxy resin, and then is reacted at 50-200 DEG C for 1-12 h. The application also provides the application of the epoxy resin-based packaging material prepared by the above method in electronic devices. The pure physical adsorption modification process adopted by the application has the advantages of mild preparation condition, simple process, strong controllability, greatly simplified production process, reduced cost compared with a traditional chemical grafting modification process, and easy industrialized large-scale production. The obtained packaging material can meet the packaging requirements of various high-end electronic devices.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, specifically providing an epoxy resin-based packaging material, its preparation method, and its application. Background Technology

[0002] With the rapid development of high-end electronic technologies such as 5G communication, power semiconductors, automotive electronics and artificial intelligence chips, electronic chips are evolving towards ultra-high density integration, miniaturized packaging and high power density, which leads to a sharp increase in chip heat flux density and puts extremely high demands on the thermal conductivity and service reliability of packaging materials.

[0003] Epoxy resins are widely used in electronic chip packaging and device potting due to their excellent electrical insulation, mechanical strength, chemical stability, and molding processability. However, pure epoxy resins have extremely low intrinsic thermal conductivity (only about 0.18–0.22 W / m·K), resulting in severely insufficient heat dissipation capacity. This makes it difficult to effectively dissipate the heat generated by high-power chips, easily leading to localized overheating, thermal stress damage, and shortened device lifespan.

[0004] To improve thermal conductivity, the industry commonly uses composite modification by introducing inorganic thermally conductive fillers (such as boron nitride, alumina, and silicon carbide) into epoxy resin. However, direct blending has three major technical bottlenecks: First, the inorganic filler has poor interfacial compatibility with the organic resin, resulting in weak bonding and easy formation of micropores and interfacial thermal resistance, leading to failure problems such as delamination and debonding; second, the filler is prone to agglomeration and uneven dispersion, making it difficult to form a continuous thermally conductive network, and affecting mechanical properties and processability; third, the interfacial interaction relies solely on van der Waals forces, lacking strong chemical bonds, resulting in insufficient aging resistance and long-term reliability.

[0005] Existing surface modification methods (such as silane coupling agent treatment) cannot introduce active functional groups that can react with epoxy groups on the filler surface, and cannot simultaneously solve the problems of agglomeration, interfacial compatibility and the construction of efficient thermal conduction pathways, resulting in the difficulty in synergistically improving the mechanical properties, insulation properties, interfacial reliability and thermal conductivity of the encapsulation material.

[0006] Therefore, there is a need to develop a modified epoxy encapsulation material that can be used on a large scale in the field of high-power, high-density advanced electronic packaging. Summary of the Invention

[0007] To overcome the above-mentioned defects, this invention proposes an epoxy resin-based encapsulation material, its preparation method, and its application. The obtained epoxy resin-based encapsulation material can effectively improve the interfacial compatibility between inorganic fillers and epoxy groups, significantly enhance the thermal conductivity of the material, and maintain excellent mechanical properties. The preparation method is simple to operate and has mild conditions, making it suitable for the large-scale production needs of high-end high-power electronic device packaging.

[0008] In a first aspect, the present invention provides a method for preparing an epoxy resin-based encapsulation material, comprising: S1, Fe3O4 nanospheres were added to an aqueous solution of polyethyleneimine and shaken. After shaking, the mixture was dried to obtain the first product. S2, the first product is mixed evenly with 4,4'-diaminodiphenylmethane and epoxy resin, and then reacted at 50-200℃ for 1-12h.

[0009] Furthermore, in step S1, the particle size of the Fe3O4 nanospheres is 20-500 nm.

[0010] Furthermore, in step S1, the molecular weight of polyethyleneimine is 600-70000, and the mass fraction of the polyethyleneimine aqueous solution is 0.1%-10%.

[0011] Furthermore, in step S1, the mass ratio of polyethyleneimine to Fe3O4 nanospheres is (0.06-6):1.

[0012] Furthermore, in step S1, the oscillation time is 12-48h; the oscillation temperature is 20-50℃; and the rotation speed during oscillation is 100-500 rpm.

[0013] Further, in step S1, drying and collecting the first product after the oscillation is completed includes: S11, after shaking, wash with deionized water and anhydrous ethanol alternately to obtain the second product; S12, the second product is dried and collected to obtain the first product.

[0014] Further, in step S2, the mass ratio of the product obtained in step S1, 4,4'-diaminodiphenylmethane, and epoxy resin is (0.01-100):50:(50-400).

[0015] Furthermore, in step S2, the mixing conditions are: stirring for 5-60 minutes at a temperature of 40-100℃ and a rotation speed of 100-500 rpm.

[0016] In a second aspect, the present invention provides an application of an epoxy resin-based encapsulation material prepared by the method of the first aspect in electronic devices.

[0017] Furthermore, the electronic device is an electronic chip.

[0018] The above-described technical solutions of the present invention have at least one or more of the following beneficial effects: In implementing the technical solution of the present invention, the pure physical adsorption modification process adopted by the present invention does not require complex equipment, crosslinking aids and multi-layer transition interfaces. The preparation conditions are mild, the process is simple and highly controllable. Compared with the traditional chemical grafting modification process, it greatly simplifies the production process, reduces the preparation cost, and is easy to industrialize and scale up production.

[0019] The packaging material prepared by this invention significantly improves the heat dissipation reliability of electronic chip packaging.

[0020] The encapsulation material prepared by this invention enhances the interfacial bonding stability of the encapsulation structure.

[0021] The packaging material prepared by this invention has extremely strong compatibility and can be adapted to mainstream electronic packaging processes. It does not require modification of existing production equipment, has wide process adaptability and strong implementation, and has extremely high industrial application value. Attached Figure Description

[0022] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Furthermore, similar numbers in the drawings are used to denote similar components, wherein: Figure 1 This is a schematic flowchart of the main steps in a method for preparing an epoxy resin-based encapsulation material according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the synthesis route of step S1 according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the synthesis route of step S2 according to an embodiment of the present invention; Figure 4 Fourier transform infrared spectra of EP-DDM / Fe3O4@PEI, EP-DDM / Fe3O4 and EP-DDM according to the present invention; Figure 5 The tensile stress-strain diagrams of EP-DDM / Fe3O4@PEI, EP-DDM / Fe3O4, and EP-DDM according to the present invention are shown. Detailed Implementation

[0023] Some embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] The term "A and / or B" refers to all possible combinations of A and B, such as only A, only B, or A and B. The terms "at least one A or B" or "at least one of A and B" have a similar meaning to "A and / or B" and can include only A, only B, or A and B. The singular forms of the terms "a" or "this" can also include plural forms.

[0025] The main compounds involved in this invention are abbreviated.

[0026] PEI: Polyethyleneimine. DDM: 4,4'-Diaminodiphenylmethane. EP: Epoxy resin.

[0027] This invention provides a method for preparing an epoxy resin-based encapsulation material, referring to... Figure 1 ,include: S1, Synthesis of polyethyleneimine-modified iron oxide nanospheres (Fe3O4@PEI).

[0028] The specific process is as follows: Fe3O4 nanospheres are added to an aqueous solution of polyethyleneimine to form a mixed system. This mixed system is then placed in a shaker and vibrated to ensure that PEI fully coats the surface of the Fe3O4 nanospheres. After vibration, the mixture is dried to obtain the first product, which is Fe3O4@PEI nanospheres.

[0029] S2, Synthesis of epoxy encapsulation material doped with iron oxide nanospheres (EP-DDM / Fe3O4@PEI).

[0030] The specific process is as follows: The Fe3O4@PEI nanospheres synthesized in step S1 are stirred and mixed evenly with 4,4'-diaminodiphenylmethane and epoxy resin at a certain temperature, and then reacted at 50-200℃ for 1-12 hours. After the reaction is completed, the mixture is dried to obtain an epoxy encapsulation material doped with iron oxide nanospheres (EP-DDM / Fe3O4@PEI).

[0031] This invention first uses iron oxide (Fe3O4) nanospheres and polyethyleneimine (PEI) as raw materials to prepare polyethyleneimine-modified iron oxide nanospheres (Fe3O4@PEI); then, Fe3O4@PEI, 4,4'-diaminodiphenylmethane (DDM) and epoxy resin (EP) are blended and cured to prepare an epoxy encapsulation material doped with iron oxide nanospheres (EP-DDM / Fe3O4@PEI).

[0032] Compared with existing technologies, this invention can solve the following two types of problems existing in existing technologies: (1) Insufficient basic thermal conductivity: Traditional epoxy resin encapsulation materials have low intrinsic thermal conductivity, which cannot meet the heat dissipation requirements of high heat flux density of high power electronic chips; when inorganic thermally conductive fillers are directly doped, due to the large difference in physicochemical properties between inorganic and organic phases, poor interfacial compatibility and weak bonding force, interfacial pores and high interfacial thermal resistance are easily generated, which leads to delamination and debonding of the encapsulation interface and reduces the reliability of device encapsulation.

[0033] (2) Low efficiency of filler dispersion and thermal conductivity network construction: Nano / micron-level inorganic thermal conductivity fillers have high surface energy and are prone to agglomeration and sedimentation in epoxy resin systems. They have poor dispersion uniformity and are difficult to construct continuous and stable thermal conductivity pathways, thus limiting the improvement of thermal conductivity. Existing conventional filler modification methods cannot simultaneously solve the core problems such as filler agglomeration, insufficient interfacial compatibility, and low efficiency of thermal conductivity network construction. It is difficult to achieve synergistic optimization of the interfacial performance and thermal conductivity of epoxy encapsulation materials, and cannot meet the encapsulation application requirements of high-end high-power electronic devices.

[0034] The epoxy encapsulation material (EP-DDM / Fe3O4@PEI) prepared by this invention can effectively improve the interfacial compatibility between inorganic fillers and epoxy groups, inhibit filler agglomeration, construct efficient thermal conduction pathways, and significantly improve the thermal conductivity of the material, while maintaining excellent electrical insulation, mechanical properties, and process adaptability. In addition, the preparation method is simple to operate, has mild conditions, and is cost-controllable, requiring no complex equipment, and is suitable for the large-scale production needs of high-end high-power electronic device packaging.

[0035] The synthetic route of the preparation method of the present invention is described in detail below.

[0036] The synthetic route for step S1 is shown below. Figure 2 .from Figure 2 It can be seen that the solvent water environment promotes the stretching of PEI polymer chains, and the amino groups on the PEI molecules can be mutually adsorbed with the polar groups on the surface of Fe3O4 particles through hydrogen bonding, electrostatic interaction, and van der Waals forces.

[0037] After a prolonged period of oscillation, the PEI polymer fully migrates, entangles, and spreads, gradually coating the outer surface of the iron oxide nanoparticles.

[0038] Figure 2 In the diagram, Fe3O4 is represented as a solid sphere, and PEI can be used for simplification. The rightmost equal sign connecting the two parts illustrates the simplification process.

[0039] The Fe3O4@PEI prepared in step S1 has a core of magnetic Fe3O4 nanoparticles and an adsorbed PEI polymer layer, which introduces a large number of active amino groups onto the surface of the nanoparticles, facilitating subsequent grafting modification.

[0040] After step S1, the complete PEI long chain is adsorbed and fixed on the particle surface, exposing a large number of amino branches, which directly reflects the amino-rich structure of the coated surface.

[0041] The synthetic route for step S2 is shown below. Figure 3 ,from Figure 3 It can be seen that among the three reactants, the polyethyleneimine-modified magnetic nanoparticles prepared by S1 have a large number of active amino groups -NH2 on their surface, which not only have magnetic response characteristics, but can also participate in the epoxy ring-opening crosslinking reaction.

[0042] DDM (4,4'-diaminodiphenylmethane) is an aromatic diamine epoxy resin curing agent. The -NH2 at both ends of the molecule is the core reactive component for cross-linking and molding of epoxy systems.

[0043] EP (Bisphenol A type epoxy resin): The molecule has epoxy three-membered rings (epoxy groups) at both ends, which are the main body of the matrix resin. The epoxy rings have high reactivity and can undergo ring-opening addition reactions with amino groups.

[0044] The overall system undergoes a nucleophilic ring-opening polymerization and crosslinking reaction of amino and epoxy groups, involving two types of amino groups participating in the reaction simultaneously: 1. The primary amine group of DDM reacts with the epoxy group of epoxy resin EP. The active hydrogen at the -NH2 end of the DDM molecule attacks the epoxy three-membered ring of EP, causing the epoxy ring to open and generate a secondary amine and a hydroxyl group -OH. The secondary amine can continue to attack another epoxy group, gradually extending the molecular chain and forming a linear, network-crosslinked epoxy resin matrix framework.

[0045] 2. PEI amino groups on the Fe3O4@PEI surface participate in cross-linking grafting. The large number of primary and secondary amines carried by PEI on the nanoparticle surface can also attack the EP epoxy groups to undergo ring-opening reactions, allowing the Fe3O4@PEI nanoparticles to be chemically bonded into the epoxy resin cross-linking network, rather than being a simple physical doping.

[0046] Figure 3 In the text, the solid sphere and the outer ring of its outline together refer to Fe3O4@PEI nanoparticles.

[0047] The black curved lines represent epoxy resin polymer segments formed after the cross-linking polymerization of DDM and EP.

[0048] Overall structure: Fe3O4@PEI is uniformly dispersed and chemically bonded within the three-dimensional cross-linked network of epoxy resin.

[0049] The selection of raw materials for the preparation method of the present invention is described in detail below.

[0050] In one embodiment, in step S1, the particle size of the Fe3O4 nanospheres is 20-500 nm. Preferably, the particle size of the Fe3O4 nanospheres is 200 nm.

[0051] In one embodiment, in step S1, the molecular weight of polyethyleneimine is 600-70000, preferably 10000.

[0052] In one embodiment, in step S1, the mass fraction of the polyethyleneimine aqueous solution is 0.1-10%. Preferably, the mass fraction is 1.6%.

[0053] In one embodiment, in step S2, the epoxy resin is a bisphenol A type epoxy resin.

[0054] The raw material ratios of the preparation method of the present invention are described in detail below.

[0055] In one embodiment, in step S1, the mass ratio of polyethyleneimine to Fe3O4 nanospheres is (0.06-6):1.

[0056] In one embodiment, in step S2, the mass ratio of the product obtained in step S1, 4,4'-diaminodiphenylmethane, and epoxy resin is (0.1-100):50:(50-400).

[0057] In one embodiment, the amount of the product Fe3O4@PEI obtained in step S2 is typically selected as 0.01-1 g.

[0058] The process parameters of the preparation method of the present invention are described in detail below.

[0059] In one embodiment, in step S1, the oscillation time is 12-48 hours, which can be 12 hours, 24 hours, 36 hours, or 48 hours; the oscillation temperature is 20-50°C, which can be 20°C, 30°C, 40°C, or 50°C. The rotation speed during oscillation is 100-500 rpm, which can be 100 rpm, 200 rpm, 300 rpm, 400 rpm, or 500 rpm. In one embodiment, the oscillation time is 24 hours, the oscillation temperature is 25°C, and the rotation speed during oscillation is 300 rpm.

[0060] In one embodiment, step S1, drying and collecting the first product after the oscillation is completed, includes: S11, after shaking, the shaken product is washed alternately with deionized water and anhydrous ethanol to obtain the second product. Specifically, the mixture of Fe3O4 nanospheres and polyethyleneimine (PEI) aqueous solution is placed in a shaker and shaken to allow PEI to fully coat the Fe3O4 surface; after shaking, the product is collected and washed alternately with deionized water and anhydrous ethanol to remove unbound free PEI, obtaining the second product. The washing in S11 removes unreacted polyethyleneimine by washing 1-5 times with alternating deionized water and anhydrous ethanol; the number of washes can be 1, 2, 3, 4, or 5 times; preferably 3 times.

[0061] S12, the second product is dried and collected to obtain the first product. Specifically, the second product is placed in a vacuum drying oven to dry, obtaining the first product, namely Fe3O4@PEI nanospheres.

[0062] Since the preparation process involved in this invention includes multiple consecutive and different reaction stages, each stage generates an intermediate with a specific morphology or property. In order to be clear and distinct in describing and distinguishing these intermediate products and to avoid conceptual confusion, the terms "first product" and "second product" are used here for reference and distinction.

[0063] In one embodiment, in step S12, the process of placing the second product in a vacuum drying oven for drying is as follows: drying at 60°C for 12 h under vacuum conditions.

[0064] In one embodiment, in step S2, the mixing conditions are: stirring for 5-60 minutes at a temperature of 40-100°C and a rotation speed of 100-500 rpm.

[0065] In one embodiment, in step S2, the reaction process is a curing process and does not require stirring.

[0066] In one embodiment, the molar ratio of 4,4'-diaminodiphenylmethane to epoxy resin is 1:(1-4).

[0067] In one embodiment, in step S2, after the reaction is completed, the drying conditions are drying at 80°C for 1 hour under vacuum.

[0068] The present invention also provides the application of the epoxy resin-based encapsulation material prepared by the above method in electronic devices.

[0069] In one embodiment, the electronic device is an electronic chip (i.e., an integrated circuit chip). Electronic chips include, but are not limited to, high-power electronic chips, flexible electronics, temperature-sensitive devices, and MEMS devices.

[0070] Electronic chips place far greater demands on packaging materials than ordinary electronic devices. As the core computing and control unit of modern electronic systems, they integrate hundreds of millions of transistors and are extremely sensitive to the external environment. The low-k dielectric constant (low-k) material layer on the chip is very fragile. This invention requires precise control to minimize the curing shrinkage rate of the material. Electronic chip packaging often involves molding, with mold gaps of only a few micrometers. The method of this invention ensures excellent material flowability before curing and no flash after curing by controlling the molecular weight distribution of the epoxy resin and the particle size distribution of the spherical filler.

[0071] The material prepared in this invention uses epoxy resin (EP) as the base matrix and 4,4'-diaminodiphenylmethane (DDM) as the curing system. Polyethyleneimine-modified iron(III) oxide nanospheres (Fe3O4@PEI) are introduced as functional modified fillers. Through cross-linking polymerization reactions between the components, a stable and high-performance three-dimensional cross-linked network structure is constructed. The Fe3O4@PEI modified filler used in this invention, through polyethyleneimine (PEI) molecular coating modification, can form a highly efficient interfacial bond with the epoxy resin matrix and DDM curing agent, fundamentally improving the defects of poor interfacial compatibility and weak bonding between traditional inorganic fillers and organic resin matrices. Simultaneously, relying on the inherent thermal conductivity of iron(III) oxide, a continuous and stable thermal conductivity pathway can be built within the epoxy system, ultimately achieving a synergistic improvement in both the interfacial bonding reliability and overall thermal conductivity of the encapsulation material.

[0072] The epoxy resin-based encapsulation material prepared by this invention can significantly improve the mechanical strength, corrosion resistance and heat dissipation performance of electronic chips when applied to them.

[0073] The preparation process of the present invention and its performance are described below through different embodiments.

[0074] Raw materials used in the examples and testing process: Fe3O4 nanospheres, polyethyleneimine, ethanol, bisphenol A epoxy resin, 4,4'-diaminodiphenylmethane, and 1-methylimidazole were all purchased from Sinopharm Chemical Reagent Co., Ltd.

[0075] Example 1 The preparation method of the epoxy resin-based encapsulation material in this embodiment includes the following steps: S1, Synthesis of polyethyleneimine-modified iron(III) oxide nanospheres (Fe3O4@PEI) 0.5 g of Fe3O4 nanospheres (particle size 20-500 nm) were added to 30 mL of 1.6% (w / w) aqueous solution of polyethyleneimine (molecular weight 600-70000). The mixture was placed in a shaker and shaken at 25 °C and 300 rpm for 24 h to allow PEI to fully coat the Fe3O4 surface. After the shake-up, the product was collected and washed three times alternately with deionized water and anhydrous ethanol to remove unbound free PEI. The product was then dried in a vacuum drying oven at 60 °C for 12 h to obtain Fe3O4@PEI nanospheres.

[0076] S2, synthesized epoxy encapsulation material doped with iron oxide nanospheres (EP-DDM / Fe3O4@PEI).

[0077] The synthesized 0.05 g Fe3O4@PEI, 4,4'-diaminodiphenylmethane (0.50 g, 2.5 mmol), and bisphenol A type epoxy resin (1.71 g, 5 mmol) were stirred and mixed at 60 °C and 300 rpm for 20 min until the system was homogeneous. Then, the mixture was cured at 130 °C for 6 h. After the reaction was completed, the mixture was dried to obtain an epoxy encapsulation material doped with iron oxide nanospheres (EP-DDM Fe3O4@PEI).

[0078] Example 2 The difference between this embodiment and Embodiment 1 is that: In step S2, the synthesized 0.025 g Fe3O4@PEI nanospheres, 4,4'-diaminodiphenylmethane (0.50 g, 2.5 mmol), and bisphenol A type epoxy resin (1.71 g, 5 mmol) were stirred and mixed at 60℃ and 300 rpm for 20 min until the system was homogeneous; then, it was cured at 130℃ for 6 h; after the reaction was completed, it was dried to obtain the epoxy encapsulation material doped with iron oxide nanospheres (EP-DDM Fe3O4@PEI-0.025).

[0079] Example 3 The difference between this embodiment and Embodiment 1 is that: In step S2, the synthesized 0.01 g Fe3O4@PEI, 4,4'-diaminodiphenylmethane (0.73 g, 5 mmol), and bisphenol A type epoxy resin (1.71 g, 5 mmol) were stirred and mixed at 60℃ and 300 rpm for 20 min until the system was homogeneous; then, it was cured at 130℃ for 6 h; after the reaction was completed, it was dried to obtain the epoxy encapsulation material doped with iron oxide nanospheres (EP-DDM Fe3O4@PEI-0.01).

[0080] Example 4 The difference between this embodiment and Embodiment 1 is that: In step S1, the mass fraction of the polyethyleneimine aqueous solution was 0.1%, and the mass ratio of polyethyleneimine to Fe3O4 nanospheres was 0.06:1. The shaking time was 12 h; the shaking temperature was 50 °C, and the rotation speed during shaking was 500 rpm. After the shaking was completed, the product was collected and washed five times alternately with deionized water and anhydrous ethanol.

[0081] In step S2, the mass ratio of the product Fe3O4@PEI, 4,4'-diaminodiphenylmethane, and bisphenol A epoxy resin obtained in step S1 is 0.01:50:50. The Fe3O4@PEI, 4,4'-diaminodiphenylmethane, and bisphenol A epoxy resin are stirred and mixed at 40℃ and 500 rpm for 5 minutes to ensure homogeneity; then cured at 50℃ for 12 hours.

[0082] Example 5 The difference between this embodiment and Embodiment 1 is that: In step S1, the mass fraction of the polyethyleneimine aqueous solution was 10%, and the mass ratio of polyethyleneimine to Fe3O4 nanospheres was 6:1. The shaking time was 48 h; the shaking temperature was 20 °C, and the rotation speed during shaking was 100 rpm. After the shaking was completed, the product was collected and washed once each with deionized water and anhydrous ethanol, alternatingly.

[0083] In step S2, the mass ratio of the product Fe3O4@PEI, 4,4'-diaminodiphenylmethane, and bisphenol A epoxy resin obtained in step S1 is 10:5:40. The Fe3O4@PEI, 4,4'-diaminodiphenylmethane, and bisphenol A epoxy resin are stirred and mixed at 100℃ and 100 rpm for 60 min to ensure homogeneity; then cured at 200℃ for 1 h.

[0084] Comparative Example 1 Synthesized epoxy encapsulation material (EP-DDM / Fe3O4) doped with iron oxide nanospheres.

[0085] 0.05 g of Fe3O4 nanospheres, 0.50 g of 4,4'-diaminodiphenylmethane (2.5 mmol), and 1.71 g of bisphenol A epoxy resin (5 mmol) were stirred at 60 °C and 300 rpm for 20 min to homogenize the system. The mixture was then cured at 130 °C for 6 h. After the reaction was completed, the mixture was dried to obtain an epoxy encapsulation material (EP-DDM / Fe3O4) doped with Fe3O4 nanospheres.

[0086] Comparative Example 2 Synthetic epoxy encapsulation material (EP-DDM).

[0087] 4,4'-Diaminodiphenylmethane (0.73 g, 5 mmol) and bisphenol A type epoxy resin (1.71 g, 5 mmol) were stirred at 60 °C and 300 rpm for 20 min to homogenize the system; then cured at 130 °C for 6 h; after the reaction was completed, the mixture was dried to obtain an epoxy encapsulation material (EP-DDM) doped with iron oxide nanospheres.

[0088] The products prepared in Example 1 and Comparative Examples 1-2 were subjected to performance tests, including infrared testing, mechanical property testing, and thermal constant testing.

[0089] First, let me explain the testing method.

[0090] 1. Infrared testing: The functional group structure of the samples was characterized using Fourier transform infrared spectroscopy (FT-IR), with a scanning wavenumber range of 500–4000 cm⁻¹. -1 The chemical bonds and functional groups of each substance are analyzed by characteristic absorption peaks.

[0091] 2. Mechanical property testing: A universal testing machine was used to perform a room temperature uniaxial tensile test on a standard specimen (10 mm long, 4 mm wide, and 1 mm thick). Tensile force was applied at a constant rate (5 mm / min), and stress-strain data were collected.

[0092] 3. Thermal constant test: The thermal constant of the sample was tested using a thermal constant analyzer with an isotropic module; the heating power was 400mW; the heating time was 20 s, and the thermal conductivity was obtained.

[0093] The test results are described below.

[0094] (1) The infrared test results are shown in Figure 4 , Figure 4 Fourier transform infrared spectra of EP-DDM / Fe3O4@PEI in Example 1, EP-DDM / Fe3O4 in Comparative Example 1, and EP-DDM in Comparative Example 2.

[0095] from Figure 4 It can be seen that: 3200-3500 cm -1 This peak is attributed to the stretching vibrations of the hydroxyl (-OH) and amino (NH) groups formed by the ring-opening of the epoxy group. This peak directly demonstrates that the epoxy group underwent a ring-opening reaction with the carboxyl group of 4,4'-diaminodiphenylmethane, forming a hydroxyl-containing cross-linked network; 2800–3000 cm⁻¹ -1This is a stretching vibration belonging to a saturated CH bond, corresponding to the asymmetric / symmetric stretching vibration of the -CH3 and -CH2- (methylene) segments in the 4,4'-diaminodiphenylmethane chain of bisphenol A. It is a characteristic peak of the resin's organic skeleton; 1609 cm⁻¹ -1 and 1506 cm -1 The peak representing the C=C skeleton stretching vibration of the benzene ring in bisphenol A type epoxy resin is a "fingerprint peak" of the resin matrix, proving that the aromatic skeleton structure of the resin is completely preserved; 1312 cm⁻¹ -1 The asymmetric stretching vibration peak, belonging to the aryl ether bond (Ar-OC), corresponds to the ether bond in the bisphenol A structure and is a typical characteristic marker of epoxy resins. At 553 cm⁻¹ -1 The presence of a clear Fe-O bond stretching vibration peak (a characteristic peak of magnetite) directly proves that the Fe3O4 microspheres have been successfully incorporated into the resin matrix.

[0096] The above analysis shows that all characteristic peaks of EP-DDM (-OH, CH, ester bond C=O, benzene ring, ether bond) are completely preserved, and the peak positions are not significantly shifted, indicating that the addition of Fe3O4 did not change the chemical structure of the resin matrix, and the curing reaction proceeded normally; at 552 cm⁻¹ -1 The presence of a clear Fe-O bond stretching vibration peak (a characteristic peak of magnetite) directly proves that the Fe3O4 microspheres have been successfully incorporated into the resin matrix.

[0097] (2) The mechanical property test results are shown in Figure 5 . Figure 5The tensile stress-strain curves of three epoxy encapsulation materials visually demonstrate the regulatory effect of filler introduction and surface modification on the mechanical behavior of the matrix. As a reference, the pure EP-DDM system (green curve) shows an approximately linear increase in stress with strain, exhibiting the rigid mechanical characteristics typical of epoxy resins. Its fracture strength is approximately 33 MPa, and its elongation at break is close to 28%. There is no obvious plastic yielding stage, reflecting the limited intrinsic toughness of the unmodified matrix, which is prone to brittle fracture due to stress concentration under external forces. The EP-DDM / Fe3O4 system directly filled with unmodified Fe3O4 (orange curve) shows significantly worse mechanical properties than the pure resin: its stress rise rate is faster, but fracture occurs at approximately 11% strain, with a fracture strength of only about 24 MPa, far lower than that of the pure EP-DDM matrix. This phenomenon stems from the poor interfacial compatibility between unmodified Fe3O4 and the epoxy matrix. Filler agglomeration and interfacial defects become weak points for stress concentration. Under external force, cracks preferentially initiate and rapidly propagate at these defects, failing to effectively transfer and disperse stress, thus exacerbating the mechanical failure of the matrix. In contrast, the PEI-modified EP-DDM / Fe3O4@PEI system (brown curve) exhibits superior mechanical properties, achieving a synergistic improvement in strength and toughness. Its stress-strain curve has a higher slope, indicating a significant increase in the material's elastic modulus. The fracture strength is close to 40 MPa, approximately 21% higher than the pure EP-DDM matrix; the elongation at break is approximately 23%, slightly lower than the pure resin, but far superior to the unmodified Fe3O4-filled system, demonstrating excellent deformation resistance.

[0098] This result fully confirms that PEI surface modification effectively optimizes the interfacial bonding state between Fe3O4 and the epoxy matrix: the amino groups on the PEI molecular chain can form chemical bonds or hydrogen bonds with the epoxy matrix, significantly reducing interfacial defects and promoting the uniform dispersion of fillers in the matrix; under external force, stress can be efficiently transferred through the optimized interface, and the modified filler can absorb fracture energy through crack deflection, bridging and other methods, which greatly improves the strength of the material while maintaining the toughness of the matrix, thus ensuring the mechanical stability of the material.

[0099] (3) The results of the thermal constant test are shown in Table 1.

[0100] Table 1 Thermal conductivity of different epoxy encapsulation materials

[0101] Table 1 shows the thermal conductivity test results of different epoxy encapsulation materials, intuitively demonstrating the regulatory effect of filler type and surface modification on the thermal conductivity of the system. The thermal conductivity of the pure EP-DDM matrix is ​​0.2120 W / (m·K), forming the performance benchmark of the modified system. The thermal conductivity of the EP-DDM / Fe3O4 system directly doped with unmodified Fe3O4 drops to 0.1314 W / (m·K), significantly lower than that of the pure resin matrix. This phenomenon stems from the poor interfacial compatibility between unmodified Fe3O4 and the epoxy matrix, which makes the filler prone to agglomeration. This results in a large number of micropores and defects at the interface between the two phases, introducing additional interfacial thermal resistance, hindering heat transfer, and preventing the construction of an effective thermal conduction pathway, thus deteriorating the thermal conductivity of the material. The PEI-modified EP-DDM / Fe3O4@PEI system exhibited a significantly improved thermal conductivity of 0.6855 W / (m·K), representing an increase of approximately 223.35% compared to the pure EP-DDM matrix and approximately 421.7% compared to the unmodified EP-DDM / Fe3O4 system. This result confirms that PEI modification significantly improves the interfacial compatibility between Fe3O4 and the epoxy matrix, effectively inhibiting filler agglomeration and ensuring uniform dispersion of Fe3O4 nanospheres within the matrix, thereby substantially reducing the interfacial thermal resistance between the filler and the matrix. Simultaneously, the uniformly distributed modified filler constructs a continuous and interconnected thermally conductive network within the epoxy matrix, providing an efficient channel for heat transfer and achieving a breakthrough improvement in thermal conductivity.

[0102] Furthermore, the thermal conductivity of EP-DDM / Fe3O4@PEI systems with different filler additions (such as EP-DDM / Fe3O4@PEI-0.025 and EP-DDM / Fe3O4@PEI-0.01) showed a clear content dependence: as the filler addition decreased, the thermal conductivity decreased from 0.6855 W / (m·K) to 0.4177 W / (m·K) and 0.2976 W / (m·K), indicating that the filler addition is a key factor affecting the efficiency of thermal conductive network construction. Only when the addition reaches a certain threshold can the modified filler form a continuous thermal conductive path in the matrix and achieve maximum optimization of thermal conductivity.

[0103] The test results show that the epoxy resin-based encapsulation material prepared by this invention has the following advantages: (1) Significantly improves the heat dissipation reliability of electronic chip packaging: This invention innovatively adopts a pure physical adsorption method without crosslinking agents, intermediate layers, or complex equipment to construct a high-density PEI molecular brush on the surface of Fe3O4 nanospheres, and deliberately retains the highly active amine groups at the ends of PEI molecules to avoid the deactivation problem of groups caused by PEGylation, acetylation, and other modifications. With the help of the excellent thermal conductivity of Fe3O4 and the uniform dispersion brought by PEI modification, a continuous and efficient thermally conductive network can be constructed, which significantly reduces the interfacial thermal resistance, effectively conducts the heat generated during the operation of high-power electronic chips, avoids local heat accumulation in the chip, significantly improves the chip's operating stability, and extends the device's service life; at the same time, the material also has excellent electrical insulation properties, which can avoid the risk of leakage caused by the introduction of thermally conductive fillers and ensure the electrical safety of chip packaging.

[0104] (2) Enhanced interfacial bonding stability of the encapsulation structure: This invention relies on a unique three-dimensional network structure of fully covalent bonding between filler, interface, and matrix, overcoming the inherent drawbacks of poor interfacial compatibility and weak interfacial bonding between traditional modified materials' inorganic fillers and epoxy organic matrix. Through the special mechanism of physical adsorption pre-modification and in-situ covalent anchoring, the Fe3O4 filler and epoxy curing network are integrated at the molecular level, completely eliminating the weak interfacial layer between the filler and the matrix. From the structural root, it avoids defects such as interfacial delamination, debonding, micro-cracking, and filler agglomeration and shedding that are prone to occur during encapsulation molding and subsequent use, significantly improving the interfacial bonding stability, temperature resistance, and damp heat resistance of the encapsulation system. It effectively solves the core pain point of insufficient interfacial reliability of traditional epoxy encapsulation materials in precision electronic chip encapsulation, and accurately adapts to the stringent structural and operating requirements of high-end electronic chip encapsulation.

[0105] Application Cases The epoxy encapsulation material (EP-DDM / Fe3O4@PEI) doped with iron oxide nanospheres synthesized in Example 1 is applied in electronic chip packaging. The encapsulation process includes, but is not limited to, the following three typical scenarios.

[0106] (1) Flip chip bottom filling: The liquid after heat preservation in step S2 of Example 1 is applied or injected to the edge of the chip. The gap between the chip and the substrate is automatically filled by capillary flow. Then, it is dried at 80°C for 1 hour to achieve bottom filling of the flip chip.

[0107] (2) Ultra-thin chip processing: The liquid after heat preservation in step S2 of Example 1 (glass / silicon) coating is then applied to the substrate (glass / silicon), followed by the attachment of an ultra-thin wafer, slight pressure, and drying at 80°C for 1 hour to complete the grinding, cutting, metallization and other processes; after use, the wafer is degraded by ultraviolet light and stress-free peeling is performed, and the substrate can be reused.

[0108] (3) Optoelectronic chip packaging: The liquid obtained after heat preservation in step S2 of Example 1 is applied to the edge of the chip, and then dried at 80°C for 1 hour to achieve optoelectronic chip packaging.

[0109] The packaging material of this invention is suitable for various electronic chip packaging scenarios and is highly practical.

[0110] This invention employs a purely physical adsorption modification process, eliminating the need for complex equipment, crosslinking agents, and multi-layer transition interfaces. The preparation conditions are mild, the process is simple, and highly controllable. Compared to traditional chemical grafting modification processes, it significantly simplifies the production process, reduces preparation costs, and facilitates large-scale industrial production. The PEI molecular brush not only achieves uniform dispersion and covalent anchoring of Fe3O4 but also acts as a flexible toughening agent within the epoxy matrix network, effectively improving the brittleness and poor impact resistance of epoxy materials. This endows the encapsulation material with excellent mechanical toughness, fatigue resistance, and temperature resistance. This material system exhibits extremely high compatibility, adapting to the packaging needs of various high-end electronic devices such as high-power logic chips, MEMS microelectromechanical devices, flexible electronic devices, and temperature-sensitive precision chips. It is also compatible with mainstream electronic packaging processes such as potting and molding, requiring no modification to existing production equipment. With broad process adaptability and strong feasibility, it possesses extremely high industrial application value.

[0111] It should be noted that although the steps in the above embodiments are described in a specific order, those skilled in the art will understand that in order to achieve the effects of the present invention, different steps do not necessarily have to be executed in such an order. They can be executed simultaneously (in parallel) or in other orders, and these variations are all within the scope of protection of the present invention.

[0112] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an epoxy resin-based encapsulation material, characterized in that, include: S1, Fe3O4 nanospheres were added to an aqueous solution of polyethyleneimine and shaken. After shaking, the mixture was dried to obtain the first product. S2, the first product is mixed evenly with 4,4'-diaminodiphenylmethane and epoxy resin, and then reacted at 50-200℃ for 1-12h; In step S1, the particle size of the Fe3O4 nanospheres is 20-500 nm; In step S1, the molecular weight of polyethyleneimine is 600-70000, and the mass fraction of the polyethyleneimine aqueous solution is 0.1-10%. In step S1, the mass ratio of polyethyleneimine to Fe3O4 nanospheres is (0.06-6):1; In step S2, the mass ratio of the product obtained in step S1, 4,4'-diaminodiphenylmethane, and epoxy resin is (0.01-100):50:(50-400).

2. The method according to claim 1, characterized in that, In step S1, the oscillation time is 12-48h; the oscillation temperature is 20-50℃; and the rotation speed during oscillation is 100-500 rpm.

3. The method according to claim 1, characterized in that, In step S1, the drying process after oscillation to obtain the first product includes: S11, after shaking, wash with deionized water and anhydrous ethanol alternately to obtain the second product; S12, the second product is dried and collected to obtain the first product.

4. The method according to claim 1, characterized in that, In step S2, the mixing conditions are: stirring for 5-60 minutes at a temperature of 40-100℃ and a rotation speed of 100-500 rpm.

5. The application of the epoxy resin-based encapsulation material prepared by the method according to any one of claims 1-4 in electronic devices.

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