High heat-resistant and flame-retardant self-curing epoxy resin electronic packaging material and preparation method thereof

Abstract

The application relates to the technical field of electronic packaging materials, in particular to a high-heat-resistance high-strength flame-retardant self-curing epoxy resin electronic packaging material and a preparation method thereof. The packaging material is prepared from 100 parts of bisphenol A type liquid epoxy resin E-51, 2.5-3.5 parts of modified montmorillonite flame retardant, 0.8-1.2 parts of silanized carboxylated multi-walled carbon nanotubes and 9-11 parts of diethylenetriamine; the modified montmorillonite flame retardant is obtained through three-step modification of dopamine self-polymerization, iron-phytate coordination and melamine-boric acid supramolecular assembly. The application constructs a reactive flame-retardant structure in the interlayer of montmorillonite through multi-step synergistic modification, so that the material has high flame-retardant grade, high char yield, excellent thermal dimensional stability and bending strength, and meets the packaging requirements of high-power electronic devices.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, specifically to a high heat-resistant, flame-retardant, self-curing epoxy resin electronic packaging material and its preparation method. Background Technology

[0002] Epoxy resin electronic encapsulation materials are widely used in the potting of electronic components, circuit board encapsulation, and chip underfilling due to their excellent electrical insulation, adhesion, and processing flowability. As electronic devices evolve towards higher power density, miniaturization, and integration, encapsulation materials need to withstand higher heat loads and more stringent fire safety requirements during operation. This is especially true in applications such as power modules, IGBT power devices, and new energy vehicle electronic control systems. These applications not only require encapsulation materials to maintain stable mechanical and electrical properties under long-term high-temperature aging conditions, but also to effectively suppress flame spread in the event of accidental overheating or short-circuit fire, preventing larger safety accidents. Therefore, developing epoxy resin encapsulation materials that combine high heat resistance and strong flame retardancy has become an urgent need in the industry.

[0003] Montmorillonite, a natural layered silicate mineral, is widely used as a nanofiller in polymer-based composites due to its unique lamellar structure and large specific surface area. Early studies primarily used quaternary ammonium salt organic intercalating agents to modify montmorillonite, replacing the inorganic cations between the montmorillonite layers with organic ammonium ions through ion exchange reactions. This expanded the interlayer spacing and improved the compatibility of montmorillonite with hydrophobic polymer matrices. For example, hexadecyltrimethylammonium bromide-modified organomontmorillonite can achieve partial exfoliation or intercalation structures in epoxy resins, improving the flame retardant and mechanical properties of the material to some extent. However, the flame retardant mechanism of this type of quaternary ammonium salt-modified montmorillonite mainly relies on a physical barrier effect; that is, during combustion, the montmorillonite lamellars migrate to the material surface to form a layered barrier layer, delaying the transfer of heat and combustible gases.

[0004] As research has deepened, the industry has gradually recognized the significant limitations of traditional quaternary ammonium salt-modified montmorillonite in flame-retardant applications. Firstly, quaternary ammonium salt intercalators themselves have poor thermal stability, potentially undergoing thermal decomposition near the epoxy resin curing temperature. This results in the modified montmorillonite losing some interlayer organic components during material processing and curing, weakening the interfacial bonding strength with the matrix. Secondly, the quaternary ammonium salt molecular structure lacks reactive functional groups capable of participating in the epoxy resin curing reaction, making it difficult to establish covalent bonds between the montmorillonite layers and the epoxy resin network. Interfacial bonding remains primarily physical adsorption, making it prone to interfacial debonding under high temperatures or stress. More importantly, while traditional quaternary ammonium salt-modified montmorillonite can form a physical barrier layer during high-temperature thermal decomposition, this barrier layer often exhibits a loose structure, insufficient continuity and density, making it difficult to effectively suppress the escape of internal combustible gases and the intrusion of external oxygen. This results in a limited improvement in the material's oxygen index, making it difficult to achieve the V-0 flame-retardant rating commonly required in the electronic packaging field. In addition, relying solely on the layered barrier effect of montmorillonite often requires a high amount of filler, and excessive inorganic fillers will significantly reduce the flowability of epoxy resin and its mechanical properties after curing, especially the flexural strength and heat distortion temperature.

[0005] To address the aforementioned issues, researchers have recently attempted to functionalize montmorillonite using organic molecules with reactive functional groups. For example, they have grafted silane coupling agents containing amino or epoxy groups onto the montmorillonite surface, aiming to establish chemical bonds between montmorillonite and epoxy resin. However, these methods primarily act on the outer surface and edge sites of montmorillonite, making it difficult to effectively penetrate the interlayer confinement space for uniform modification. Their ability to regulate interlayer spacing and their contribution to char formation during combustion remain limited. Some researchers have also directly added phosphorus- or nitrogen-based flame retardants to epoxy resin through physical blending. However, simple blending easily leads to flame retardant aggregation and uneven dispersion, and small-molecule flame retardants pose a risk of migration and precipitation during long-term use.

[0006] Therefore, how to introduce a highly thermally stable organic-inorganic hybrid structure with multiple reaction sites into the confined space between montmorillonite layers, enabling montmorillonite to participate in interface construction during the epoxy resin curing stage and catalyze the formation of a continuous and dense carbon layer during the high-temperature combustion stage, while maintaining the good processability and mechanical properties of the epoxy resin matrix, has become a pressing technical challenge in the field of electronic packaging materials. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a high heat-resistant, strong flame-retardant, self-curing epoxy resin electronic packaging material and its preparation method, so as to solve the problem that existing quaternary ammonium salt modified montmorillonite is difficult to achieve high flame retardancy, high char residue and excellent thermal dimensional stability in epoxy resin due to poor thermal stability of intercalating agents, lack of reactive functional groups and limited char formation ability.

[0008] To achieve the above objectives, the present invention provides a high heat-resistant, flame-retardant, self-curing epoxy resin electronic encapsulation material, wherein the epoxy resin electronic encapsulation material is prepared from the following parts by weight: 100 parts of bisphenol A type liquid epoxy resin E-51, 2.5-3.5 parts of modified montmorillonite flame retardant, 0.8-1.2 parts of silanized carboxylated multi-walled carbon nanotubes, and 9-11 parts of diethylenetriamine; The modified montmorillonite flame retardant is obtained by reacting organomontmorillonite with dopamine hydrochloride under alkaline conditions to form a polydopamine layer on the surface of montmorillonite; then ferric chloride hexahydrate and phytic acid are added sequentially, and the modification is achieved through the coordination reaction between iron ions and phytic acid and polydopamine; then melamine and boric acid are added, and the modification is achieved through supramolecular self-assembly and hydrogen bonding between melamine and boric acid.

[0009] Preferably, the bisphenol A type liquid epoxy resin is 1828 type epoxy resin E-51 from Guangzhou Weichuang High-tech Materials Co., Ltd., with an epoxy equivalent of 184-194 g / eq and a viscosity of 11000-15000 mPa·s at 25℃.

[0010] Preferably, the silanized carboxylated multi-walled carbon nanotubes are obtained by grafting carboxylated multi-walled carbon nanotubes onto the surface of 3-aminopropyltriethoxysilane; Preferably, the weight ratio of the carboxylated multi-walled carbon nanotubes to 3-aminopropyltriethoxysilane is 1.8-2.2:0.8-1.2, the grafting reaction temperature is 80℃, and the reaction time is 3.5-4.5h.

[0011] Preferably, the carboxylated multi-walled carbon nanotubes have a carboxyl functionalization degree of greater than 8%, an average diameter of 9.5 nm, and an average length of 1.5 μm.

[0012] Preferably, the organomontmorillonite is Fenghong's DK2 polymer organomontmorillonite, with a volatile content of less than 3.5% at 105°C, a density of at least 97% passing through a 200-mesh sieve, and a specific gravity of 1.8 m / cm³. 3 .

[0013] Preferably, the weight ratio of the organomontmorillonite, dopamine hydrochloride, ferric chloride hexahydrate, phytic acid, melamine and boric acid is 9-11:1.8-2.2:0.8-1.2:5-7:0.8-1.2:0.8-1.2.

[0014] Preferably, the dopamine self-polymerization reaction requires maintaining the system pH at 8.3-8.7, the reaction temperature at 25-35℃, and the reaction time at 2.5-3.5h.

[0015] Preferably, the pH of the system needs to be maintained at 4.3-4.7 during the coordination reaction. Ferric chloride hexahydrate is added first and reacted for 0.8-1.2 h, followed by the addition of phytic acid and the reaction at 35-45°C for 1.5-2.5 h.

[0016] Preferably, the phytic acid is an aqueous solution of phytic acid with a concentration of 50%.

[0017] Preferably, in the supramolecular self-assembly, melamine is first added at 75-85℃ and reacted for 0.8-1.2h, and then the temperature is lowered to 55-65℃ and boric acid is added and reacted for 1.5-2.5h.

[0018] Furthermore, the present invention also provides a method for preparing a high heat-resistant, flame-retardant, self-curing epoxy resin electronic packaging material, the specific steps of which are as follows: Bisphenol A type liquid epoxy resin was weighed and preheated to reduce viscosity. Then, modified montmorillonite flame retardant and silanized carboxylated multi-walled carbon nanotubes were added and ultrasonically dispersed evenly. After vacuum degassing, diethylenetriamine was added and stirred, and then immediately poured into a mold. After initial curing and final curing, a high heat-resistant, strong flame-retardant self-curing epoxy resin electronic packaging material was obtained.

[0019] Preferably, the preheating temperature is 45-55℃ and the time is 20-40 minutes.

[0020] Preferably, the stirring temperature after adding the modified montmorillonite flame retardant is 45-55℃, the stirring speed is 900-1100rpm, the stirring time is 15-25min, the ultrasonic power is 250-350W, and the stirring time is 8-12min.

[0021] Preferably, the stirring temperature after adding the silanized and carboxylated multi-walled carbon nanotubes is 45-55℃, the stirring speed is 900-1100rpm, the stirring time is 15-25min, the ultrasonic power is 250-350W, and the stirring time is 8-12min.

[0022] Preferably, the vacuum degassing temperature is 45-55℃ and the time is 8-12 minutes.

[0023] Preferably, the diethylenetriamine is added and the stirring speed is 1100-1300 rpm for 45-75 s.

[0024] Preferably, the initial curing temperature is 25°C and the curing time is 6-10 min.

[0025] Preferably, the final curing temperature is 60°C and the curing time is 25 min.

[0026] The beneficial effects of this invention are: This invention uses organo-montmorillonite as the initial raw material. Through the self-polymerization reaction of dopamine under alkaline conditions, a polydopamine layer is formed in situ on the surface of montmorillonite sheets and within the confined spaces between the layers. This layer not only forms strong hydrogen bonds with the silanol groups on the montmorillonite surface but also provides a high-density anchoring site for subsequent iron ion coordination. Unlike traditional quaternary ammonium salts that adhere to the montmorillonite interlayer only through ion exchange, polydopamine is firmly bound to the montmorillonite surface in the form of a covalently cross-linked network, exhibiting significantly higher thermal stability and anti-migration ability.

[0027] This invention further utilizes the coordination reaction between iron ions, phytic acid, and polydopamine to construct a coordination network structure containing transition metals and phytic acid phosphorus on the surface of montmorillonite. This synergistically forms a dense and continuous protective char layer, effectively suppressing the wick effect and dripping phenomenon, thereby substantially improving the limiting oxygen index of the material and achieving a V-0 flame retardant rating.

[0028] This invention introduces a nitrogen-boron synergistic char-stabilizing layer on the surface of montmorillonite through supramolecular self-assembly between melamine and boric acid. The presence of this char-stabilizing layer significantly increases the char residue rate of the material at a high temperature of 800°C. A high char residue rate means that more polymer matrix is ​​converted into char layer during combustion rather than completely decomposed into volatile small molecules, thereby reducing the release of combustible gas and delaying the transfer of heat to the interior of the material.

[0029] In summary, this invention achieves the precise construction of a reactive flame-retardant structure within the confined space of montmorillonite interlayers through a multi-step synergistic modification strategy starting from organomontmorillonite, followed by polydopamine self-polymerization modification, iron-phytic acid coordination network construction, melamine-boric acid supramolecular assembly, and carbon nanotube amidation grafting. The resulting electronic packaging material achieves a good comprehensive balance between flame retardancy rating, high-temperature char residue, thermal dimensional stability, and mechanical load-bearing capacity, and can meet the stringent requirements of electronic components operating in high heat flux density environments. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0031] Raw materials and sources: Bisphenol A type liquid epoxy resin: 1828 type epoxy resin E-51, epoxy equivalent is 184-194g / eq, viscosity at 25℃ is 11000-15000mPa·s; Organomontmorillonite: DK2 polymer organomontmorillonite from Zhejiang Fenghong New Material Co., Ltd., high-purity organomontmorillonite modified with hydroxyl organic ammonium, volatile matter at 105℃ is less than 3.5%, and 97% passes through 200 mesh; Phytic acid: Sigma-Aldrich, model 593648, 50% phytic acid aqueous solution; Carboxylated multi-walled carbon nanotubes: Sigma-Aldrich, model 755125, carboxyl functionalization degree is greater than 8%, average diameter is 9.5nm, and average length is 1.5μm.

[0032] Example 1: A method for preparing a high heat-resistant, flame-retardant, self-curing epoxy resin electronic packaging material, the specific steps of which are as follows: S1: Weigh 10g of organomontmorillonite and dry it in a vacuum drying oven at 80℃ for 4h. Immediately after drying, add it to a mixed solvent consisting of 280g of anhydrous ethanol and 120g of deionized water. Stir mechanically at 800rpm for 30min at 30℃, and then ultrasonically disperse at 300W for 30min to form a uniform montmorillonite dispersion. Weigh 2g of dopamine hydrochloride and dissolve it in 40g of deionized water to form a dopamine aqueous solution, and then add it to the montmorillonite dispersion within 5min. Then, add ammonia (25%) dropwise under an air atmosphere and adjust the pH of the system to 8.5±0.2. Continue to stir mechanically at 800rpm for 3h at 30℃. After the reaction is complete, filter the mixture and wash it twice each with 100g of deionized water and 100g of anhydrous ethanol. Keep the wet filter cake for later use. S2: The wet filter cake obtained in S1 was added directly to a mixed solvent consisting of 200g deionized water and 200g anhydrous ethanol without drying, and redispersed by mechanical stirring at 800rpm for 20min at 25℃. Then, 2g glacial acetic acid was added to adjust the pH of the system to 4.5±0.5. 1g ferric chloride hexahydrate was dissolved in 20g deionized water and slowly added dropwise to the above dispersion system over 20min. After the addition was completed, the reaction was continued for 1h. Then, 6g phytic acid aqueous solution (50%) was diluted with 20g deionized water and slowly added, and the temperature was raised to 40℃ to continue the reaction for 2h. After the reaction was completed, the filter was filtered and washed twice each with 100g deionized water and 100g anhydrous ethanol to obtain a modified wet filter cake. S3: Add the wet filter cake obtained in S2 to 250g of deionized water and redisperse it by mechanical stirring at 700rpm for 20min at 80℃; then dissolve 1g of melamine in 100g of hot deionized water at 80℃ and add it to the above dispersion system while hot, and continue to react at 80℃ for 1h; then lower the system to 60℃, dissolve 1g of boric acid in 30g of hot deionized water at 60℃ and add it to the system, and continue to react for 2h; after the reaction is completed, filter, wash twice each with 100g of deionized water and 100g of anhydrous ethanol, vacuum dry at 80℃ for 12h, pulverize and pass through a 200-mesh sieve to obtain the modified montmorillonite flame retardant; S4: Weigh 2g of carboxylated multi-walled carbon nanotubes and add them to a mixed solvent consisting of 190g of anhydrous ethanol and 10g of deionized water. Disperse the mixture by ultrasonication at 300W for 1h. Separately, take 1g of 3-aminopropyltriethoxysilane, add it to 20g of anhydrous ethanol and 5g of deionized water, and adjust the pH of the system to 4-5 by adding glacial acetic acid dropwise. Pre-hydrolyze the mixture at room temperature for 20min. Then, slowly add the pre-hydrolyzed solution to the carboxylated multi-walled carbon nanotube dispersion system and reflux at 80℃ for 4h. After the reaction is complete, filter the mixture, wash it twice with 100g of anhydrous ethanol, and vacuum dry it at 80℃ for 8h to obtain silanized carboxylated multi-walled carbon nanotubes. S5: Weigh 100g of bisphenol A type liquid epoxy resin E-51 and preheat it at 50℃ for 30min to reduce viscosity; then add 3g of modified montmorillonite flame retardant, mechanically stir at 1000rpm at 50℃ for 20min, and then ultrasonically disperse at 300W for 10min; then add 1g of silanized carboxylated multi-walled carbon nanotubes, continue to mechanically stir at 1000rpm at 50℃ for 15min, then ultrasonically disperse at 300W for 10min, and vacuum degas at 50℃ for 10min; after the system cools to 30℃, add 10g of diethylenetriamine, stir rapidly at 1200rpm for 60s, and immediately pour into a pre-cleaned and dried mold, let stand at 25℃ for 8min to achieve initial solidification, and then cure at 60℃ for 25min to obtain a high heat-resistant, strong flame-retardant self-curing epoxy resin electronic packaging material.

[0033] Example 2: A method for preparing a high heat-resistant, flame-retardant, self-curing epoxy resin electronic packaging material, the specific steps of which are as follows: S1: Weigh 9g of organomontmorillonite and dry it in a vacuum drying oven at 80℃ for 3h. Immediately after drying, add it to a mixed solvent consisting of 252g of anhydrous ethanol and 108g of deionized water. Stir mechanically at 700rpm for 25min at 25℃, and then ultrasonically disperse at 250W for 25min to form a uniform montmorillonite dispersion. Weigh 1.8g of dopamine hydrochloride and dissolve it in 36g of deionized water to form a dopamine aqueous solution, and then add it to the montmorillonite dispersion within 4min. Subsequently, add ammonia water (25%) dropwise under an air atmosphere and adjust the pH of the system to 8.3-8.7. Continue to stir mechanically at 700rpm for 2.5h at 25℃. After the reaction is complete, filter the mixture and wash it twice each with 90g of deionized water and 90g of anhydrous ethanol. Keep the wet filter cake for later use. S2: The wet filter cake obtained in S1 was added directly to a mixed solvent consisting of 180g deionized water and 180g anhydrous ethanol without drying, and redispersed by mechanical stirring at 750rpm for 15min at 25℃. Then, 1.8g glacial acetic acid was added to adjust the pH of the system to 4.3-4.7. Next, 0.8g ferric chloride hexahydrate was dissolved in 18g deionized water and slowly added dropwise to the above dispersion system over 18min. After the addition was completed, the reaction continued for 0.8h. Then, 5g phytic acid aqueous solution (50%) was diluted with 18g deionized water and slowly added, and the temperature was raised to 35℃ to continue the reaction for 1.5h. After the reaction was completed, the filter was filtered and washed twice each with 90g deionized water and 90g anhydrous ethanol to obtain a modified wet filter cake. S3: Add the wet filter cake obtained in S2 to 225g of deionized water and redisperse it by mechanical stirring at 650rpm for 15min at 75℃; then dissolve 0.8g of melamine in 90g of hot deionized water at 75℃ and add it to the above dispersion system while hot, and continue to react at 75℃ for 0.8h; then lower the system to 55℃, dissolve 0.8g of boric acid in 24g of hot deionized water at 55℃ and add it to the system, and continue to react for 1.5h; after the reaction is completed, filter, wash twice each with 90g of deionized water and 90g of anhydrous ethanol, vacuum dry at 80℃ for 10h, pulverize and pass through a 200-mesh sieve to obtain the modified montmorillonite flame retardant; S4: Weigh 1.8g of carboxylated multi-walled carbon nanotubes and add them to a mixed solvent consisting of 171g of anhydrous ethanol and 9g of deionized water. Disperse the mixture by ultrasonication at 250W for 45min. Separately, take 0.8g of 3-aminopropyltriethoxysilane and add it to 18g of anhydrous ethanol and 4g of deionized water. Adjust the pH of the system to 4-5 by adding glacial acetic acid dropwise and pre-hydrolyze the mixture at room temperature for 15min. Then, slowly add the pre-hydrolyzed solution to the carboxylated multi-walled carbon nanotube dispersion system and reflux the reaction at 80℃ for 3.5h. After the reaction is completed, filter the mixture, wash it twice with 90g of anhydrous ethanol, and vacuum dry it at 80℃ for 7h to obtain silanized carboxylated multi-walled carbon nanotubes. S5: Weigh 100g of bisphenol A type liquid epoxy resin E-51 and preheat it at 45℃ for 20min to reduce viscosity; then add 2.5g of modified montmorillonite flame retardant, mechanically stir at 900rpm for 15min at 45℃, and then ultrasonically disperse at 250W for 8min; then add 0.8g of silanized carboxylated multi-walled carbon nanotubes, continue mechanically stirring at 900rpm for 10min at 45℃, then ultrasonically disperse at 250W for 8min, and vacuum degas at 45℃ for 8min; after the system cools to 28℃, add 9g of diethylenetriamine, stir rapidly at 1100rpm for 45s, and immediately pour into a pre-cleaned and dried mold, let stand at 25℃ for 6min to achieve initial solidification, and then cure at 60℃ for 20min to obtain a high heat-resistant, strong flame-retardant self-curing epoxy resin electronic packaging material.

[0034] Example 3: A method for preparing a high heat-resistant, flame-retardant, self-curing epoxy resin electronic packaging material, the specific steps of which are as follows: S1: Weigh 11g of organomontmorillonite and dry it in a vacuum drying oven at 80℃ for 5h. Immediately after drying, add it to a mixed solvent consisting of 308g of anhydrous ethanol and 132g of deionized water. Stir mechanically at 900rpm for 35min at 35℃, and then ultrasonically disperse at 350W for 35min to form a uniform montmorillonite dispersion. Weigh 2.2g of dopamine hydrochloride and dissolve it in 44g of deionized water to form a dopamine aqueous solution, and then add it to the montmorillonite dispersion within 6min. Subsequently, add ammonia water (25%) dropwise under an air atmosphere and adjust the pH of the system to 8.3-8.7. Continue to stir mechanically at 900rpm for 3.5h at 35℃. After the reaction is complete, filter the solution and wash it twice each with 110g of deionized water and 110g of anhydrous ethanol. Keep the wet filter cake for later use. S2: The wet filter cake obtained in S1 was added directly to a mixed solvent consisting of 220g deionized water and 220g anhydrous ethanol without drying, and redispersed by mechanical stirring at 850rpm for 25min at 25℃. Then, 2.2g glacial acetic acid was added to adjust the pH of the system to 4.3-4.7. 1.2g ferric chloride hexahydrate was dissolved in 22g deionized water and slowly added dropwise to the above dispersion system over 22min. After the addition was completed, the reaction was continued for 1.2h. Then, 7g phytic acid aqueous solution (50%) was diluted with 22g deionized water and slowly added, and the temperature was raised to 45℃ to continue the reaction for 2.5h. After the reaction was completed, the filter was filtered and washed twice each with 110g deionized water and 110g anhydrous ethanol to obtain a modified wet filter cake. S3: Add the wet filter cake obtained in S2 to 275g of deionized water and redisperse it by mechanical stirring at 750rpm for 25min at 85℃; then dissolve 1.2g of melamine in 110g of hot deionized water at 85℃ and add it to the above dispersion system while hot, and continue to react at 85℃ for 1.2h; then lower the system to 65℃, dissolve 1.2g of boric acid in 36g of hot deionized water at 65℃ and add it to the system, and continue to react for 2.5h; after the reaction is completed, filter, wash twice each with 110g of deionized water and 110g of anhydrous ethanol, vacuum dry at 80℃ for 14h, pulverize and pass through a 200-mesh sieve to obtain the modified montmorillonite flame retardant; S4: Weigh 2.2g of carboxylated multi-walled carbon nanotubes and add them to a mixed solvent consisting of 209g of anhydrous ethanol and 11g of deionized water. Disperse the mixture by ultrasonication at 350W for 75min. Separately, take 1.2g of 3-aminopropyltriethoxysilane, add it to 22g of anhydrous ethanol and 6g of deionized water, and adjust the pH of the system to 4-5 by adding glacial acetic acid dropwise. Pre-hydrolyze the mixture at room temperature for 25min. Then, slowly add the pre-hydrolyzed solution to the carboxylated multi-walled carbon nanotube dispersion system and reflux at 80℃ for 4.5h. After the reaction is complete, filter the mixture, wash it twice with 110g of anhydrous ethanol, and vacuum dry it at 80℃ for 9h to obtain silanized carboxylated multi-walled carbon nanotubes. S5: Weigh 100g of bisphenol A type liquid epoxy resin E-51 and preheat it at 55℃ for 40min to reduce viscosity; then add 3.5g of modified montmorillonite flame retardant, mechanically stir at 1100rpm for 25min at 55℃, and then ultrasonically disperse at 350W for 12min; then add 1.2g of silanized carboxylated multi-walled carbon nanotubes, continue to mechanically stir at 1100rpm for 20min at 55℃, then ultrasonically disperse at 350W for 2min, and vacuum degas at 55℃ for 12min; after the system cools to 32℃, add 11g of diethylenetriamine, stir rapidly at 1300rpm for 75s, and immediately pour into a pre-cleaned and dried mold, let stand at 25℃ for 10min to achieve initial solidification, and then cure at 60℃ for 30min to obtain a high heat-resistant, strong flame-retardant self-curing epoxy resin electronic packaging material.

[0035] Comparative Example 1: The difference from Example 1 is that dopamine hydrochloride is not added in step S1. Instead, 10g of organomontmorillonite is added to a mixed solvent consisting of 280g of anhydrous ethanol and 120g of deionized water. The mixture is mechanically stirred at 800rpm for 30min at 30°C, and then ultrasonically dispersed at 300W for 30min. Subsequently, 25% ammonia water is added dropwise under air atmosphere, and the pH of the system is adjusted to 8.5±0.2. The mixture is then mechanically stirred at 800rpm for 3h at 30°C. After the reaction is completed, the mixture is filtered and washed twice each with 100g of deionized water and 100g of anhydrous ethanol. The wet filter cake is retained for later use. Steps S2, S3, S4, and S5 are the same as in Example 1.

[0036] Comparative Example 2: The difference from Example 1 is that in step S2, phytic acid aqueous solution (50%) is first diluted with 20g of deionized water and then slowly added to the redispersed wet filter cake system, and reacted at 40°C for 2h; then 1g of ferric chloride hexahydrate is dissolved in 20g of deionized water and slowly added dropwise to the system over 20min, and the reaction continues for 1h after the addition is completed; the remaining conditions in step S2 are the same as in Example 1, and steps S1, S3, S4 and S5 are the same as in Example 1.

[0037] Comparative Example 3: The difference from Example 1 is that melamine and boric acid are not added in step S3; the primary modified wet filter cake obtained in step S2 is filtered, washed twice each with 100g of deionized water and 100g of anhydrous ethanol, dried under vacuum at 80℃ for 12h, pulverized and passed through a 200-mesh sieve to directly obtain the primary modified montmorillonite flame retardant; in steps S4 and S5, 2g of carboxylated multi-walled carbon nanotubes and 100g of bisphenol A type liquid epoxy resin E-51 are weighed respectively, and 3g of the primary modified montmorillonite flame retardant and 1g of silanized carboxylated multi-walled carbon nanotubes are added in step S5; the remaining conditions are the same as in Example 1.

[0038] Comparative Example 4: The difference from Example 1 is that in step S3, boric acid is first dissolved in hot deionized water and added to the wet filter cake obtained in S2 to redisperse the system, and the reaction is continued at 60°C for 2 hours; then the system is heated to 80°C, and 1g of melamine is dissolved in hot deionized water and added to the system, and the reaction is continued at 80°C for 1 hour; the remaining conditions in step S3 are the same as in Example 1, and steps S1, S2, S4 and S5 are the same as in Example 1.

[0039] Comparative Example 5: The difference from Example 1 is that in step S5, 3g of modified montmorillonite flame retardant and 1g of silanized carboxylated multi-walled carbon nanotubes were simultaneously added to 100g of bisphenol A type liquid epoxy resin E-51. The mixture was mechanically stirred at 1000rpm for 35min at 50°C, then ultrasonically dispersed at 300W for 20min, and vacuum-degassed at 50°C for 10min. After the system cooled to 30°C, 10g of diethylenetriamine was added, and the mixture was rapidly stirred at 1200rpm for 60s, then immediately poured into a pre-cleaned and dried mold. Initial solidification was achieved by standing at 25°C for 8min, followed by curing at 60°C for 25min. Steps S1, S2, S3, and S4 were the same as in Example 1.

[0040] Comparative Example 6: The difference from Example 1 is that modified montmorillonite flame retardant and silanized carboxylated multi-walled carbon nanotubes are not added in step S5.

[0041] Performance testing Both the examples and comparative examples were prepared by casting flat plate samples with thicknesses of 3 mm and 4 mm respectively, according to the curing regime of their respective steps S5. Among them, the samples used for oxygen index testing and vertical burning testing were machined from flat plates with a thickness of 3 mm, and the samples used for load deformation temperature testing and bending performance testing were machined from flat plates with a thickness of 4 mm. After demolding, all cured samples were conditioned for 48 hours in a standard environment of 23°C and 50% relative humidity according to GB / T 2918-2018 before testing. Carbon residue rate at 800℃: Take about 8mg of the cured sample corresponding to each example and comparative example, place it in a thermogravimetric analyzer, protect it under nitrogen atmosphere with a flow rate of 50mL / min, and heat it from 30℃ to 800℃ at a rate of 10℃ / min. Record the carbon residue rate at 800℃, and take the average value of parallel samples as the test result. Oxygen index test: The test was conducted in accordance with GB / T 2406.2-2009. Strip samples with dimensions of 130mm×6.5mm×3mm were machined from the 3mm thick flat samples corresponding to the examples and comparative examples. There were 5 samples in each group. The samples were conditioned in the environment specified in GB / T 2918-2018 for 48 hours before the test. The total flow rate of the oxygen-nitrogen mixed gas was kept constant according to the instrument requirements. The minimum sustained combustion oxygen concentration of each sample was recorded, and the arithmetic mean of 5 parallel samples was taken as the oxygen index of the group of samples. Vertical burning test: The test was conducted in accordance with GB / T 2408-2021. Strip samples with dimensions of 125mm×13mm×3mm were machined from the 3mm thick flat sample corresponding to the examples and comparative examples. There were 5 samples in each group. During the test, each sample was ignited twice, and the ignition time was 10s each time. Load deformation temperature test: The test was conducted in accordance with GB / T 1634.2-2019. Rectangular specimens with dimensions of 80mm×10mm×4mm were machined from the 4mm thick flat plate samples corresponding to the examples and comparative examples. There were 3 specimens in each group. The edge vertical loading method was adopted, the bending stress was set to 1.80MPa, and the heating rate was set to 120℃ / h. The temperature corresponding to the center deflection of the specimen reaching 0.34mm was taken as the load deformation temperature. Bending performance test: The test was conducted in accordance with GB / T 9341-2008. Rectangular specimens with dimensions of 80mm×10mm×4mm were machined from the 4mm thick flat plate samples corresponding to the examples and comparative examples. There were 5 specimens in each group. The three-point bending method was adopted, the span was set to 64mm, the test speed was set to 2mm / min, and the bending strength was recorded. The above test results are shown in Table 1.

[0042] Data Analysis: As can be seen from the data in Table 1, the high heat-resistant, flame-retardant, self-curing epoxy resin electronic packaging material prepared by this invention achieves a relatively balanced overall performance in terms of flame retardancy, thermal stability, thermal dimensional stability, antistatic ability, and flexural load-bearing capacity. All embodiments maintained a high oxygen index and good vertical flammability rating, while the glass transition temperature, 800℃ char residue, and load deformation temperature also remained at high levels, indicating that this system does not sacrifice heat resistance for flame retardancy.

[0043] As can be seen from the data in Table 1 for Example 1 and Comparative Example 1, without the introduction of dopamine hydrochloride, the oxygen index, vertical combustion rating, char residue at 800℃, load deformation temperature, and flexural strength all decreased significantly. The combined levels of volume resistivity and surface resistivity were also lower than in Example 1. The main reason for this is that without a thin-layer polydopamine reactive interface, it is difficult to form continuous catechol hydroxyl and amino sites on the outer surface, layer edges, and defect sites of the organomontmorillonite. Subsequently, ferric ions, phytic acid, melamine, and boric acid can only exist through weak adsorption or discrete adhesion, making it difficult to construct a stable inner catalytic char-forming center and an outer phosphorus-rich char-stabilizing layer.

[0044] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 2 and 4, when the order of addition of ferric ions and phytic acid, or the order of addition of melamine and boric acid, are changed, the oxygen index, vertical combustion rating, char residue at 800°C, and load deformation temperature all decrease simultaneously. The performance loss caused by the change in timing proves that this synergistic structure is significantly unpredictable and cannot be equivalently replaced by a normal order.

[0045] As can be seen from the data in Table 1 for Example 1 and Comparative Example 3, when only the primary modification of ferric ions and phytic acid is retained without the introduction of melamine and boric acid, the oxygen index, vertical combustion rating, char residue at 800℃, and load deformation temperature are all significantly reduced. The main reason for this is that the secondary confinement modification of the outer layer is not an optional additional step, but a crucial step in further transforming the phosphorus-rich layer into a composite layer with both char formation and glassy phase char stabilization capabilities, thus exhibiting a significant synergistic effect.

[0046] As can be seen from the data in Example 1 and Comparative Example 5 in Table 1, under the condition that the amounts of modified montmorillonite flame retardant and aminosilanized carboxylated multi-walled carbon nanotubes are kept consistent, simply changing the addition of the two from sequential to simultaneous results in adverse changes in flexural strength, load deformation temperature, and oxygen index. The main reason is that simultaneous addition makes it easier for aminosilanized carboxylated multi-walled carbon nanotubes to adsorb or entangle on the surface of the sheets in the early stage of dispersion, weakening the ability of the modified montmorillonite flame retardant to preferentially establish flame-retardant framework microregions in the continuous phase of bisphenol A type liquid epoxy resin E-51. Therefore, the blending sequence of "sheets first, then one-dimensional" in this invention has a clear spatial division of labor, and its effect is not simply determined by the total amount of filler.

[0047] As can be seen from the data in Example 1 and Comparative Example 6 in Table 1, when no modified montmorillonite flame retardant and aminosilanized carboxylated multi-walled carbon nanotubes are added to the system, the material exhibits typical high insulation but low flame retardancy, low carbon stability and low thermal dimensional stability bisphenol A type liquid epoxy resin E-51 / diethylenetriamine curing system.

[0048] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high heat-resistant, flame-retardant, self-curing epoxy resin electronic packaging material, characterized in that, The epoxy resin electronic packaging material is prepared from the following parts by weight: 100 parts of bisphenol A type liquid epoxy resin E-51, 2.5-3.5 parts of modified montmorillonite flame retardant, 0.8-1.2 parts of silanized carboxylated multi-walled carbon nanotubes, and 9-11 parts of diethylenetriamine. The modified montmorillonite flame retardant is obtained by reacting organomontmorillonite with dopamine hydrochloride under alkaline conditions to form a polydopamine layer on the surface of montmorillonite; then ferric chloride hexahydrate and phytic acid are added sequentially, and the modification is achieved through the coordination reaction between iron ions and phytic acid and polydopamine; then melamine and boric acid are added, and the modification is achieved through supramolecular self-assembly and hydrogen bonding between melamine and boric acid.

2. The epoxy resin electronic packaging material according to claim 1, characterized in that, The bisphenol A type liquid epoxy resin is 1828 type epoxy resin E-51, with an epoxy equivalent of 184-194 g / eq and a viscosity of 11000-15000 mPa·s at 25℃.

3. The epoxy resin electronic packaging material according to claim 1, characterized in that, The silanized carboxylated multi-walled carbon nanotubes are obtained by grafting carboxylated multi-walled carbon nanotubes onto the surface of 3-aminopropyltriethoxysilane; the weight ratio of the carboxylated multi-walled carbon nanotubes to 3-aminopropyltriethoxysilane is 1.8-2.2:0.8-1.2, and the grafting reaction temperature is 80℃.

4. The epoxy resin electronic packaging material according to claim 1, characterized in that, The organomontmorillonite has a volatile content of less than 3.5% at 105℃, a density of not less than 97% passing through a 200-mesh sieve, and a specific gravity of 1.8 m / cm³. 3 .

5. The epoxy resin electronic packaging material according to claim 1, characterized in that, The weight ratio of the organic montmorillonite, dopamine hydrochloride, ferric chloride hexahydrate, phytic acid, melamine and boric acid is 9-11:1.8-2.2:0.8-1.2:5-7:0.8-1.2:0.8-1.

2.

6. The epoxy resin electronic packaging material according to claim 1, characterized in that, In the dopamine self-polymerization reaction, the system pH should be maintained at 8.3-8.7, the reaction temperature at 25-35℃, and the reaction time at 2.5-3.5h. In the coordination reaction, the system pH should be maintained at 4.3-4.

7. Ferric chloride hexahydrate is added first and reacted for 0.8-1.2h, followed by the addition of phytic acid at 35-45℃ and reacted for 1.5-2.5h. In the supramolecular self-assembly, melamine is added first at 75-85℃ and reacted for 0.8-1.2h, followed by cooling to 55-65℃ and adding boric acid and reacting for 1.5-2.5h.

7. A method for preparing an epoxy resin electronic packaging material according to any one of claims 1-6, characterized in that, Bisphenol A type liquid epoxy resin was preheated to reduce viscosity. Then, modified montmorillonite flame retardant and silanized carboxylated multi-walled carbon nanotubes were added and ultrasonically dispersed evenly. After vacuum degassing, diethylenetriamine was added and stirred, and then immediately poured into a mold. After initial curing and final curing, a high heat-resistant, strong flame-retardant self-curing epoxy resin electronic packaging material was obtained.

8. The preparation method according to claim 7, characterized in that, The preheating temperature is 45-55℃ and the time is 20-40 minutes.

9. The preparation method according to claim 7, characterized in that, The stirring temperature after adding the modified montmorillonite flame retardant is 45-55℃, the stirring speed is 900-1100rpm, the stirring time is 15-25min, the ultrasonic power is 250-350W, and the stirring time is 8-12min; the stirring temperature after adding the silanized and carboxylated multi-walled carbon nanotubes is 45-55℃, the stirring speed is 900-1100rpm, the stirring time is 15-25min, the ultrasonic power is 250-350W, and the stirring time is 8-12min.

10. The preparation method according to claim 7, characterized in that, The initial curing temperature is 25℃, and the curing time is 6-10 min; the final curing temperature is 60℃, and the curing time is 25 min.

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