Formula of low-warpage epoxy molding compound and high-density packaging application method

Abstract

The invention discloses a formula of a low-warpage epoxy molding compound and a high-density packaging application method, and belongs to the technical field of electronic packaging materials. The molding compound comprises epoxy resin, a curing agent, an accelerant, spherical fused quartz powder, spherical aluminum nitride, a bifunctional nano interface nail, a silane coupling agent, a coloring agent and a release agent. The bifunctional nano interface nail is of an asymmetric long rod structure with an epoxy group at one end and an acetylacetonyl group at the other end, and is prepared through regioselective modification, SiO2 long rod-shaped particles are synthesized firstly, then the epoxy group is grafted to a nail body, and the acetylacetonyl group is grafted to a nail head. During application, the bifunctional nano interface nail and filler are pretreated to form a quartz powder-aluminum nitride hybrid skeleton, and then the quartz powder-aluminum nitride hybrid skeleton and resin are mixed and cured. According to the invention, the two fillers are bridged into a synergistic skeleton by utilizing the selective anchoring effect of the interface nails, so that the curing shrinkage rate, the thermal expansion coefficient and the warping degree are obviously reduced, and the warping problem of a high-filling system caused by interface mismatch of heterogeneous fillers is solved.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, and in particular to a formulation of a low-warpage epoxy molding compound and a high-density packaging application method. Background Technology

[0002] Epoxy molding compound is a key material for integrated circuit packaging, used to protect chips from external environmental influences. As electronic devices develop towards higher density and miniaturization, the warping problem caused by the mismatch of the coefficients of thermal expansion (CTE) of various materials in the package is becoming increasingly prominent. This not only increases the difficulty of subsequent manufacturing processes but also easily leads to chip cracking and other failures.

[0003] To reduce CTE (Chemical Expansion Traceness), epoxy resins are typically filled with high levels of inorganic fillers such as silica. However, a single filler is insufficient to simultaneously meet the requirements of thermal conductivity and low expansion. The combination of quartz powder and aluminum nitride has become a research hotspot, but the significant differences in their surface properties lead to poor interfacial compatibility and uneven dispersion. Current technologies often employ silane coupling agents for surface treatment, but conventional coupling agents struggle to simultaneously anchor two heterogeneous fillers, failing to construct a synergistic framework. The warpage problem caused by interfacial stress concentration remains unresolved. Therefore, developing novel epoxy molding compounds that enhance the interfacial compatibility of heterogeneous fillers and suppress warpage has significant application value. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a low-warpage epoxy molding compound formulation and a high-density encapsulation application method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention first proposes a low-warpage epoxy molding compound, comprising the following raw materials in parts by weight: The composition includes 12-18 parts epoxy resin, 8-12 parts curing agent, 0.3-0.5 parts accelerator, 40-50 parts spherical fused silica powder, 15-20 parts spherical aluminum nitride, 1.5-3.0 parts bifunctional nano-interface nails, 0.5-1.0 parts silane coupling agent, 0.3-0.5 parts colorant, and 0.5-1.0 parts release agent. The epoxy resin is a mixture of naphthol-type epoxy resin and phenolic epoxy resin in a mass ratio of 1:1. The curing agent is methylhexahydrophthalic anhydride, the accelerator is an imidazole latent accelerator, the average particle size of the spherical fused silica powder is 5-15 μm, the average particle size of the spherical aluminum nitride is 1-5 μm, the silane coupling agent is γ-glycidoxypropyltrimethoxysilane, the colorant is carbon black, and the release agent is zinc stearate. The bifunctional nano-interface nail is an asymmetric long rod structure with an epoxy group at one end and an acetylacetone group at the other end.

[0006] Naphthol epoxy contains rigid naphthalene rings, has low hygroscopicity and high strength; phenolic epoxy has high crosslinking density and good heat resistance. The combination of the two can ensure rigidity at high temperatures without generating stress due to excessive rigidity and brittleness of a single structure.

[0007] Quartz powder (low expansion) mainly inhibits thermal expansion; aluminum nitride (high thermal conductivity) mainly conducts heat. The particle size distribution of the two (quartz 5-15μm > aluminum nitride 1-5μm) forms a graded filler, with small aluminum nitride particles filling the gaps between large quartz particles, increasing the bulk density and reducing the main body of resin shrinkage.

[0008] Bifunctional nano-interface studs serve as heterogeneous bridging agents, addressing the interfacial weakness caused by the different surface properties of quartz (silicophilic) and aluminum nitride (aluminophilic).

[0009] Preferably, the method for synthesizing the bifunctional nano-interface nail includes the following steps: (1) Synthesis of nano-interface nails: Polyvinylpyrrolidone and sodium citrate were dissolved in pentanol in a reaction vessel, and deionized water and ammonia water with a volume concentration of 28-30% were added. The mixture was stirred for 15 min to form a water-in-oil emulsion. Tetraethyl orthosilicate was added under stirring at 800-1000 rpm, and the nail body was grown at room temperature for 12 h. Tetraethyl orthosilicate (TEOS) undergoes hydrolytic condensation polymerization in the "droplet" template of a water-in-oil emulsion under the catalysis of ammonia: ; Polyvinylpyrrolidone (PVP) acts as a stabilizer, adsorbing onto the particle surface to prevent aggregation. Sodium citrate modulates the ionic strength. Because water droplets are confined within the oil phase, the growth of SiO2 is spatially restricted, resulting in long, rod-shaped structures.

[0010] At this point, the entire particle surface is mainly composed of silanol groups (Si-OH), exhibiting uniform chemical properties and not yet possessing selectivity.

[0011] Then 3-aminopropyltriethoxysilane was added, and after stirring for 30 min, tetraethyl orthosilicate was added again. The reaction was carried out at room temperature for 24 h to complete the nail growth. The reaction solution was centrifuged at 8000 rpm for 10 min, washed alternately with ethanol and deionized water, and vacuum dried to obtain nano-interface nails. The amino group of 3-aminopropyltriethoxysilane (KH560) is preferentially adsorbed onto the nail head via hydrogen bonding or electrostatic interactions. When TEOS is added a second time, TEOS not only hydrolyzes itself but also undergoes a co-condensation reaction with the ethoxy group on APTES. Since APTES has already occupied the nail head position, the newly generated SiO2 selectively deposits and grows around APTES, thus "expanding" the nail head into a spherical shape. This adsorption-growth mechanism ensures that the amino functional group exists only in the nail head, while the nail body is bare pure SiO2.

[0012] (2) Regioselective bifunctional modification: Nano-interface nails were dispersed in anhydrous toluene, γ-glycidoxypropyltrimethoxysilane was added, and the reaction was carried out at 80°C under nitrogen protection for 8 h. After centrifugation and washing with toluene, the nail body epoxy-modified product was obtained. The methoxy group (-OCH3-) on KH560 condenses with the silanol group (Si-OH) on the surface of the nail, removes methanol, and forms a covalent bond (Si-O-Si); Because the nail head is occupied by an amino group, and the amino group has weak reactivity with KH560 under these conditions, the reaction mainly occurs in the nail body. This gives the nail body an epoxy group, which has an excellent affinity for the silanol groups on the surface of quartz powder; The nail body at this moment: SiO2-O-Si-(CH2)3-O-CH2-epoxy group.

[0013] The epoxy-modified product of the nail body was redispersed in anhydrous toluene, and acetylacetone, N,N"-dicyclohexylcarbodiimide and triethylamine were added. The mixture was reacted at room temperature for 12 h, centrifuged, washed with toluene and ethanol in sequence, and dried under vacuum to obtain bifunctional nano-interface nails.

[0014] The amino group on the nail head undergoes condensation with acetylacetone under the action of the dehydrating agent DCC, forming a stable amide bond that attaches the acetylacetone group. For aluminum nitride (where a thin layer of Al2O3 is formed by natural oxidation), the two carbonyl oxygen groups on the acetylacetone group can form a stable five-membered ring chelate with the aluminum atom. The nail head at this moment: SiO2-NH-CO-CH2-C(=O)-CH2-C(=O)-CH3 (acetylacetone).

[0015] Preferably, in (1), the number-average molecular weight of polyvinylpyrrolidone is Mw≈40000g / mol; the molar ratio of polyvinylpyrrolidone, citric acid, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and the added tetraethyl orthosilicate is 1:20-25:595-600:80-90:298-300.

[0016] Preferably, in step (2), the mass ratio of nano-interface nails and γ-glycidyl etheroxypropyltrimethoxysilane is 5-6:2; the mass ratio of nail body epoxy-modified product, acetylacetone, N,N"-dicyclohexylcarbodiimide, and triethylamine is 27-28:4-5:1.5:1.

[0017] This invention also proposes a high-density encapsulation application method for the aforementioned low-warpage epoxy molding compound, comprising the following steps: S1. Pretreatment of heterogeneous fillers: Spherical fused silica powder and spherical aluminum nitride are added to a high-speed mixer. The silane coupling agent is diluted with acetone and sprayed in. The mixture is stirred at 100-110℃ and 1500-1600rpm for 10-15min. The bifunctional nano-interface nails are dispersed in ethanol to form a suspension, which is then sprayed into the high-speed mixer. The mixture is stirred at 100-110℃ and 1200-1250rpm for 30-35min. The mixture is then vacuum dried to obtain the composite filler. When bifunctional nano-interface studs are added to the mixing system, they actively recognize and anchor onto the surface of aluminum nitride particles due to the strong coordination tendency of the acetylacetone groups on the stud heads with aluminum atoms. As the shear force of the mixer continues to act, the epoxy groups on the bifunctional nano-interface studs already anchored to the aluminum nitride undergo strong hydrogen bonding with the silanol groups on the surface of nearby quartz powder, forming covalent bonds under subsequent heating conditions.

[0018] The bifunctional nano-interface studs simultaneously connect aluminum nitride and quartz powder, forming a stitched structure of "quartz powder-interface stud-aluminum nitride". This structure is not easily destroyed during subsequent mixing, thus constructing a rigid, mutually restraining hybrid filler skeleton before epoxy curing.

[0019] S2. Preparation of matrix resin: Preheat epoxy resin and curing agent at 60°C for 30 minutes, add accelerator, colorant and release agent and stir evenly to obtain matrix resin mixture. S3. Melt mixing: The front roller temperature of the two-roll mill is 80-90℃, the rear roller temperature is 70-80℃, the roller gap is 0.5-1.0mm, the front roller speed is 25rpm, and the rear roller speed is 20rpm. First, add the matrix resin mixture to wrap the rollers, then add the composite filler in batches, and mix for 15-20 minutes until the material is uniform and free of white spots to obtain the mixed material. At 80-90℃, the epoxy resin softens and melts, impregnating the filler. Shear force breaks up the agglomerated filler. At this point, the exposed epoxy groups (nail bodies) on the bifunctional nano-interfacial studs and the residual amino / epoxy groups in the system begin to entangle with the resin matrix and undergo partial interfacial reactions, locking the pre-constructed "filler skeleton" within the resin matrix.

[0020] S4. Granulation and storage: After cooling, the mixed material is crushed, passed through an 80-mesh sieve, and stored in a sealed container at 4°C. S5. Curing and Post-curing: Using a flat vulcanizing machine, cure at 150-160℃ and 10-15MPa for 90-120 minutes, followed by post-curing at 175℃ for 2 hours to obtain high-density encapsulated cured parts.

[0021] Preferably, in step S1, the ethanol suspension of the bifunctional nano-interface nails needs to be ultrasonically dispersed for 5 minutes before spraying. During the spraying process, the temperature and speed of the high-speed mixer are kept stable to ensure that the bifunctional nano-interface nails are uniformly coated on the surface of the heterogeneous filler. In S5, the mold to be cured needs to be preheated to 150°C in advance. Before closing the mold, a release agent is sprayed on the inner wall of the mold. The post-curing process adopts programmed heating with a heating rate of 2°C / min to avoid rapid heating causing internal stress in the packaged parts.

[0022] Preferably, in step S3, the mass of the composite filler added in each batch does not exceed 1 / 5 of the total mass of the composite filler. After each addition, the material must be completely mixed before the next addition is carried out. The criteria for judging the end point of mixing are that the material is uniformly black, has a smooth surface without a grainy feel, and has no filler agglomeration or clumping.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. Existing technologies using traditional silane coupling agents (such as KH560) rely on a single siloxane group to form a single-point covalent bond with the hydroxyl group on the filler surface, which is a "point-to-point" molecular-level connection. In high-filling systems (up to 70%), the huge total surface area of ​​the filler makes this single-point bond highly susceptible to hydrolysis or stress concentration under high temperature and humidity conditions, leading to interfacial debonding. The bifunctional nano-interfacial anchors designed in this invention form stable multidentate chelate coordination bonds between the acetylacetone group of the anchor head and the aluminum atoms on the aluminum nitride surface, while the epoxy group of the anchor body forms a multi-point hydrogen bond and covalent bond network with the silanol group on the quartz powder surface, achieving "face-to-face" topological anchoring. This multi-point synergistic effect not only results in stronger bond energy and better hydrolysis resistance, but also the rigid rod-like structure of the anchor itself can disperse stress from the two-dimensional planar interface to three-dimensional space. Even if individual chemical bonds break, the overall anchoring effect is still maintained, fundamentally solving the problem of weak bonding at heterogeneous filler interfaces.

[0024] 2. Traditional warpage reduction methods often employ toughening agents such as core-shell rubber or liquid rubber. Their mechanism involves passively absorbing curing shrinkage energy through the microscopic phase separation and voiding effect of flexible segments. However, this "soft-against-hard" strategy often comes at the cost of sacrificing the material's elastic modulus, heat resistance, and rigidity. This invention takes a different approach, utilizing the dual-functionality of bifunctional nano-interface studs to pre-connect quartz powder and aluminum nitride into a continuous three-dimensional rigid hybrid framework during the mixing stage. When the epoxy resin cures and shrinks, this pre-constructed "steel frame" actively inhibits the resin's free shrinkage through physical confinement, uniformly distributing the overall shrinkage within the framework mesh. This "rigid framework confinement" mechanism achieves warpage suppression while maintaining or even increasing the material's modulus, avoiding the performance compromises associated with traditional toughening agents, and significantly improving the dimensional stability of the encapsulated body during thermal cycling.

[0025] 3. In high-filler systems, traditional coupling agent treatments struggle to address the agglomeration and segregation issues caused by the surface property differences between quartz powder (silicophilic) and aluminum nitride (aluminophilic). This not only leads to a sharp increase in melt viscosity and deterioration in flowability but also causes randomization of the distribution of the thermally conductive aluminum nitride filler, making it difficult to form efficient thermal conduction pathways. This invention utilizes the selective anchoring effect of bifunctional nano-interface studs—the stud heads automatically identify and anchor aluminum nitride, while the stud bodies connect to quartz powder—to "stitch" small-diameter aluminum nitride particles onto the surface and gaps of large-diameter quartz powder, forming an ordered core-shell or continuous network-like stacking structure. This innovative mechanism offers several beneficial effects: firstly, it reduces frictional resistance between fillers, significantly lowers melt viscosity, and improves encapsulation flowability; secondly, it forcibly pulls and fixes the highly thermally conductive aluminum nitride around the quartz, constructing a complete thermal conduction pathway and achieving a synergistic unity of high thermal conductivity and low warpage. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the low-warpage epoxy molding compound proposed in this invention; Figure 2 This is an actual production diagram of the low-warpage epoxy molding compound proposed in this invention. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Example 1: A low-warpage epoxy molding compound, such as Figure 1 , Figure 2 As shown, it includes the following raw materials: 12 kg epoxy resin, 12 kg curing agent, 0.3 kg accelerator, 50 kg spherical fused silica powder, 15 kg spherical aluminum nitride, 3.0 kg bifunctional nano-interface staples, 0.5 kg silane coupling agent, 0.5 kg colorant, and 0.5 kg release agent; The epoxy resin is a mixture of naphthol-type epoxy resin and phenolic epoxy resin in a mass ratio of 1:1. The curing agent is methylhexahydrophthalic anhydride, the accelerator is an imidazole latent accelerator, the average particle size of the spherical fused silica powder is 5-15 μm, the average particle size of the spherical aluminum nitride is 1-5 μm, the silane coupling agent is γ-glycidoxypropyltrimethoxysilane, the colorant is carbon black, and the release agent is zinc stearate. The bifunctional nano-interface nail is an asymmetric long rod structure with an epoxy group at one end and an acetylacetone group at the other end.

[0029] The method for synthesizing the bifunctional nano-interface nail includes the following steps: (1) Synthesis of nano-interface nails: Polyvinylpyrrolidone and sodium citrate were dissolved in pentanol in a reaction vessel, and deionized water and 30% ammonia water were added. The mixture was stirred for 15 min to form a water-in-oil emulsion. Tetraethyl orthosilicate was added under stirring at 1000 rpm, and the nail body was grown at room temperature for 12 h. Then 3-aminopropyltriethoxysilane was added, and after stirring for 30 min, tetraethyl orthosilicate was added again. The reaction was carried out at room temperature for 24 h to complete the nail growth. The reaction solution was centrifuged at 8000 rpm for 10 min, washed alternately with ethanol and deionized water, and vacuum dried to obtain nano-interface nails. (2) Regioselective bifunctional modification: Nano-interface nails were dispersed in anhydrous toluene, γ-glycidoxypropyltrimethoxysilane was added, and the reaction was carried out at 80°C under nitrogen protection for 8 h. After centrifugation and washing with toluene, the nail body epoxy-modified product was obtained. The epoxy-modified product of the nail body was redispersed in anhydrous toluene, and acetylacetone, N,N"-dicyclohexylcarbodiimide and triethylamine were added. The mixture was reacted at room temperature for 12 h, centrifuged, washed with toluene and ethanol in sequence, and dried under vacuum to obtain bifunctional nano-interface nails.

[0030] In (1), the number average molecular weight of polyvinylpyrrolidone is Mw≈40000g / mol; the molar ratio of polyvinylpyrrolidone, citric acid, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and the added tetraethyl orthosilicate is 1:25:595:90:298.

[0031] In (2), the mass ratio of nano-interface nails and γ-glycidyl etheroxypropyltrimethoxysilane is 5-6:2; the mass ratio of nail body epoxy-modified product, acetylacetone, N,N"-dicyclohexylcarbodiimide, and triethylamine is 28:4:1.5:1.

[0032] A method for high-density encapsulation of a low-warpage epoxy molding compound includes the following steps: S1. Pretreatment of heterogeneous fillers: Spherical fused silica powder and spherical aluminum nitride are added to a high-speed mixer. Silane coupling agent is diluted with acetone and sprayed in. The mixture is stirred at 100°C and 1500 rpm for 10 min. Bifunctional nano-interface nails are dispersed in ethanol to form a suspension, which is then sprayed into a high-speed mixer. The mixture is stirred at 100°C and 1200 rpm for 30 min. The mixture is then vacuum dried to obtain the composite filler. S2. Preparation of matrix resin: Preheat epoxy resin and curing agent at 60°C for 30 minutes, add accelerator, colorant and release agent and stir evenly to obtain matrix resin mixture. S3. Melt mixing: The front roller temperature of the two-roll mill is 80-90℃, the rear roller temperature is 70-80℃, the roller gap is 0.5-1.0mm, the front roller speed is 25rpm, and the rear roller speed is 20rpm. First, add the matrix resin mixture to wrap the rollers, then add the composite filler in batches, and mix until the material is uniform and free of white spots to obtain the mixed material. S4. Granulation and storage: After cooling, the mixed material is crushed, passed through an 80-mesh sieve, and stored in a sealed container at 4°C. S5. Curing and post-curing: A flat vulcanizing machine is used to cure at 155℃ and 12±0.2MPa for 100min, followed by post-curing at 175℃ for 2h to obtain a high-density encapsulated cured part.

[0033] In S1, the ethanol suspension of bifunctional nano-interface nails needs to be ultrasonically dispersed for 5 minutes before spraying. During the spraying process, the temperature and speed of the high-speed mixer are kept stable to ensure that the bifunctional nano-interface nails are uniformly coated on the surface of the heterogeneous filler. In S5, the mold to be cured needs to be preheated to 150°C in advance. Before closing the mold, a release agent is sprayed on the inner wall of the mold. The post-curing process adopts programmed heating with a heating rate of 2°C / min to avoid rapid heating causing internal stress in the packaged parts.

[0034] In S3, the mass of the composite filler added in each batch is 1 / 6 of the total mass of the composite filler. After each addition, the material must be completely mixed until it is uniformly black, smooth, without any particles, and without any filler agglomeration or clumping, before the next addition can be carried out.

[0035] Example 2: The implementation scheme is the same as Example 1, except that it includes the following raw materials: 15 kg epoxy resin, 10 kg curing agent, 0.4 kg accelerator, 45 kg spherical fused silica powder, 17.5 kg spherical aluminum nitride, 2.25 kg bifunctional nano-interface nails, 0.75 kg silane coupling agent, 0.4 kg colorant, and 0.75 kg release agent; In (1), the number average molecular weight of polyvinylpyrrolidone is Mw≈40000g / mol; the molar ratio of polyvinylpyrrolidone, citric acid, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and the added tetraethyl orthosilicate is 1:22.5:597:85:299.

[0036] In (2), the mass ratio of nano-interface nails and γ-glycidyl etheroxypropyltrimethoxysilane is 5-6:2; the mass ratio of nail body epoxy-modified product, acetylacetone, N,N"-dicyclohexylcarbodiimide, and triethylamine is 27.5:4.5:1.5:1.

[0037] Example 3: The implementation scheme is the same as Example 1, except that it includes the following raw materials: 18 kg epoxy resin, 8 kg curing agent, 0.5 kg accelerator, 40 kg spherical fused silica powder, 20 kg spherical aluminum nitride, 1.5 kg bifunctional nano-interface nails, 1.0 kg silane coupling agent, 0.3 kg colorant, and 1.0 kg release agent; In (1), the number average molecular weight of polyvinylpyrrolidone is Mw≈40000g / mol; the molar ratio of polyvinylpyrrolidone, citric acid, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and the added tetraethyl orthosilicate is 1:20:600:80:300.

[0038] In (2), the mass ratio of nano-interface nails and γ-glycidyl etheroxypropyltrimethoxysilane is 5-6:2; the mass ratio of nail body epoxy-modified product, acetylacetone, N,N"-dicyclohexylcarbodiimide, and triethylamine is 27:5:1.5:1.

[0039] The following comparison model was also set: Comparative Example 1: Based on Example 2, the difference is that it is treated with conventional silane coupling agent (without bifunctional nano-interface nails), otherwise it is the same as Example 2.

[0040] Comparative Example 2: Based on Example 2, the difference is that instead of adding bifunctional nano-interface nails, 3.0 kg of core-shell structured rubber microgel (methyl methacrylate-butadiene-styrene copolymer) was added, while KH560 treated filler was retained, and the rest was the same as in Example 2.

[0041] Comparative Example 3: Based on Example 2, the difference is that no region-selective modification was performed when synthesizing bifunctional nano-interface nails, and KH560 was grafted onto the particles as a whole. The rest is the same as in Example 2.

[0042] Comparative Example 4: Based on Example 2, the difference is that instead of using bifunctional nano-interface nails, quartz powder was treated separately with KH560, and aluminum nitride was treated separately with aluminate coupling agent (DL-411). Then, the two treated fillers were mechanically mixed in proportion, and the rest was the same as in Example 2.

[0043] Comparative Example 5: Based on Example 2, the difference is that the amount of bifunctional nano-interface nails used was reduced to 0.5 kg, and the rest was the same as in Example 2.

[0044] Performance testing: The thermal properties, mechanical properties, warpage and shrinkage, and interface properties of this invention were tested according to GB / T 40564-2021 "Test Methods for Epoxy Molding Compounds for Electronic Packaging"; the results are shown below: Table 1. Test results of various properties of molding compound

[0045] Data Analysis: The warpage of Example 2 was only 24 μm, a 59% reduction compared to Comparative Example 1 (58 μm) and a 61% reduction compared to Comparative Example 4 (62 μm), demonstrating a highly significant effect. This improvement is highly correlated with the reduction in CTEα1: the CTE of Example 2 was 13.5 ppm / ℃, while that of Comparative Example 1 was as high as 18.5 ppm / ℃. The data indicate that warpage is positively correlated with CTE, and reducing thermal expansion is key to suppressing warpage.

[0046] Comparative Example 4 (treated separately, mechanically mixed) showed a warpage of up to 62 μm, indicating that even if the two fillers each received good interfacial treatment, they still could not synergistically resist shrinkage without a bridging mechanism, and instead generated internal stress due to the difference in thermal expansion coefficients. Comparative Example 3 (without region-selective modification) showed a warpage of 48 μm, which was better than Comparative Example 1, but far worse than the examples, demonstrating that the partitioned anchoring function of the bifunctional nano-interfacial studs is indispensable—if the two fillers cannot be accurately identified, an effective heterogeneous framework cannot be formed.

[0047] The interfacial bond strength of Example 2 reached 18.5 MPa, while that of Comparative Example 1 was only 10.2 MPa and that of Comparative Example 4 was only 9.5 MPa. The strength improvement of up to 80% directly proves the "stitching" effect of the bifunctional nano-interfacial nails: the acetylacetone groups of the nail head form strong coordination bonds with aluminum nitride, and the epoxy groups of the nail body form covalent bonds with quartz powder, firmly connecting the two fillers.

[0048] Comparative Example 2 (core-shell rubber) had the highest impact strength (9.5 kJ / m). 2 However, the interfacial bond strength is only 12.5 MPa, and the Tg drops to 145℃. This indicates that the rubber absorbs energy through deformation at the cost of rigidity and heat resistance. In contrast, this invention achieves interfacial reinforcement while maintaining a high Tg (158℃), demonstrating the advantages of the "rigid skeleton" strategy.

[0049] Example 2 exhibits a thermal conductivity of 1.68 W / m·K, higher than Comparative Example 1's 1.42 W / m·K. The excellent interfacial bonding reduces phonon scattering at the filler-resin interface, allowing the high thermal conductivity of aluminum nitride to be fully utilized. Simultaneously, the water absorption rates show an inverse correlation: Example 2 has only 0.22%, while Comparative Example 4 has a high 0.38%. Low water absorption indicates a dense interface and fewer moisture channels, which is indirect evidence of good interfacial anchoring.

[0050] Comparative Example 5 reduced the amount of bifunctional nano-interface studs to 0.5 kg, achieving a warpage of 42 μm, which was better than Comparative Example 1 (58 μm), but significantly worse than Example 2 (24 μm). This indicates that there is a critical dosage threshold for bifunctional nano-interface studs: below 1.5 parts, they are insufficient to cover the entire filler surface and cannot form a complete continuous skeleton; while within the range of 1.5-3.0 parts, as the dosage increases, the skeleton completeness improves and the performance continues to optimize.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-warpage epoxy molding compound, characterized in that, Including the following parts by weight of raw materials: The composition includes 12-18 parts epoxy resin, 8-12 parts curing agent, 0.3-0.5 parts accelerator, 40-50 parts spherical fused silica powder, 15-20 parts spherical aluminum nitride, 1.5-3.0 parts bifunctional nano-interface nails, 0.5-1.0 parts silane coupling agent, 0.3-0.5 parts colorant, and 0.5-1.0 parts release agent. The epoxy resin is a mixture of naphthol-type epoxy resin and phenolic epoxy resin in a mass ratio of 1:

1. The curing agent is methylhexahydrophthalic anhydride, the accelerator is an imidazole latent accelerator, the average particle size of the spherical fused silica powder is 5-15 μm, the average particle size of the spherical aluminum nitride is 1-5 μm, the silane coupling agent is γ-glycidoxypropyltrimethoxysilane, the colorant is carbon black, and the release agent is zinc stearate. The bifunctional nano-interface nail is an asymmetric long rod structure with an epoxy group at one end and an acetylacetone group at the other end.

2. The low-warpage epoxy molding compound according to claim 1, characterized in that, The method for synthesizing the bifunctional nano-interface nail includes the following steps: (1) Synthesis of nano-interface nails: Polyvinylpyrrolidone and sodium citrate were dissolved in pentanol in a reaction vessel, and deionized water and ammonia water with a volume concentration of 28-30% were added. The mixture was stirred for 15 min to form a water-in-oil emulsion. Tetraethyl orthosilicate was added under stirring at 800-1000 rpm, and the nail body was grown at room temperature for 12 h. Then 3-aminopropyltriethoxysilane was added, and after stirring for 30 min, tetraethyl orthosilicate was added again. The reaction was carried out at room temperature for 24 h to complete the nail growth. The reaction solution was centrifuged at 8000 rpm for 10 min, washed alternately with ethanol and deionized water, and vacuum dried to obtain nano-interface nails. (2) Regioselective bifunctional modification: Nano-interface nails were dispersed in anhydrous toluene, γ-glycidoxypropyltrimethoxysilane was added, and the reaction was carried out at 80°C under nitrogen protection for 8 h. After centrifugation and washing with toluene, the nail body epoxy-modified product was obtained. The epoxy-modified product of the nail body was redispersed in anhydrous toluene, and acetylacetone, N,N"-dicyclohexylcarbodiimide and triethylamine were added. The mixture was reacted at room temperature for 12 h, centrifuged, washed with toluene and ethanol in sequence, and dried under vacuum to obtain bifunctional nano-interface nails.

3. The low-warpage epoxy molding compound according to claim 2, characterized in that, In (1), the number average molecular weight of polyvinylpyrrolidone is Mw≈40000g / mol; the molar ratio of polyvinylpyrrolidone, citric acid, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and the added tetraethyl orthosilicate is 1:20-25:595-600:80-90:298-300.

4. The low-warpage epoxy molding compound according to claim 2, characterized in that, In (2), the mass ratio of nano-interface nails and γ-glycidyl etheroxypropyltrimethoxysilane is 5-6:2; the mass ratio of nail body epoxy-modified product, acetylacetone, N,N"-dicyclohexylcarbodiimide, and triethylamine is 27-28:4-5:1.5:

1.

5. A method for high-density encapsulation of a low-warpage epoxy molding compound, characterized in that, Includes the following steps: S1. Pretreatment of heterogeneous fillers: Spherical fused silica powder and spherical aluminum nitride are added to a high-speed mixer. The silane coupling agent is diluted with acetone and sprayed in. The mixture is stirred at 100-110℃ and 1500-1600rpm for 10-15min. The bifunctional nano-interface nails are dispersed in ethanol to form a suspension, which is then sprayed into the high-speed mixer. The mixture is stirred at 100-110℃ and 1200-1250rpm for 30-35min. The mixture is then vacuum dried to obtain the composite filler. S2. Preparation of matrix resin: Preheat epoxy resin and curing agent at 60°C for 30 minutes, add accelerator, colorant and release agent and stir evenly to obtain matrix resin mixture. S3. Melt mixing: The front roller temperature of the two-roll mill is 80-90℃, the rear roller temperature is 70-80℃, the roller gap is 0.5-1.0mm, the front roller speed is 25rpm, and the rear roller speed is 20rpm. First, add the matrix resin mixture to wrap the rollers, then add the composite filler in batches, and mix for 15-20 minutes until the material is uniform and free of white spots to obtain the mixed material. S4. Granulation and storage: After cooling, the mixed material is crushed, passed through an 80-mesh sieve, and stored in a sealed container at 4°C. S5. Curing and Post-curing: Using a flat vulcanizing machine, cure at 150-160℃ and 10-15MPa for 90-120 minutes, followed by post-curing at 175℃ for 2 hours to obtain high-density encapsulated cured parts.

6. The high-density packaging application method according to claim 5, characterized in that, In S1, the ethanol suspension of bifunctional nano-interface nails needs to be ultrasonically dispersed for 5 minutes before spraying. During the spraying process, the temperature and speed of the high-speed mixer are kept stable to ensure that the bifunctional nano-interface nails are uniformly coated on the surface of the heterogeneous filler. In S5, the mold to be cured needs to be preheated to 150°C in advance. Before closing the mold, a release agent is sprayed on the inner wall of the mold. The post-curing process adopts programmed heating with a heating rate of 2°C / min to avoid rapid heating causing internal stress in the packaged parts.

7. The high-density packaging application method according to claim 5, characterized in that, In S3, the mass of the composite filler added in each batch shall not exceed 1 / 5 of the total mass of the composite filler. After each addition, the material must be completely mixed before the next addition is carried out. The criteria for judging the end point of mixing are that the material is uniformly black, has a smooth surface without a grainy feel, and has no filler agglomeration or clumping.

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