Preparation method of low-dielectric spherical silicon dioxide micro powder

Abstract

The invention provides a preparation method of low-dielectric-constant spherical silicon dioxide micro powder, and aims to meet the requirement of a high-frequency electronic material on a low dielectric constant. According to the method, the pore structure and surface chemical modification of the silicon dioxide micro-powder are accurately regulated and controlled, the polar silane coupling agent is used for surface functionalization treatment, and the porosity of the micro-powder is regulated and controlled in combination with the pore forming agent, so that the dielectric constant of the micro-powder is remarkably reduced, and meanwhile, good dispersity and compatibility with resin are kept. The preparation method of the low-dielectric spherical silicon dioxide micro-powder comprises the steps of raw material preparation, solution preparation, surface treatment, post-treatment and the like, and the balance between the low dielectric property and the high performance of the micro-powder is realized by optimizing parameters of each step. The dielectric constant of the micro powder prepared by the method is lower than 4.0, the loss factor is obviously reduced, and the micro powder shows excellent performance in high-frequency signal transmission, is suitable for the fields of 5G / 6G communication copper-clad plates and the like, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials technology, specifically to a method for preparing low-dielectric spherical silica micropowder. Background Technology

[0002] Spherical silica, as a key filler in copper-clad laminates, directly affects signal transmission rates due to its dielectric properties. Traditional silane coupling agent-modified micropowders often have dielectric constants higher than 4.0, which is insufficient to meet the requirements of 5G communication and hinders their application in high-frequency electronics. While using non-polar silanes in existing technologies can reduce the dielectric constant, it leads to decreased compatibility between the filler and the resin.

[0003] Silica micropowder is widely used in electronic packaging, optoelectronic materials, and various surface coatings due to its excellent physicochemical properties. With the increasing demands for dielectric properties in electronic products, the preparation of silica micropowder with low dielectric constants has become an urgent problem to be solved. Existing preparation technologies mainly focus on controlling the morphology and particle size distribution of silica micropowder, but there is a lack of innovation in reducing the dielectric constant. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing low-dielectric spherical silica micropowder, which can effectively reduce the dielectric constant of the micropowder while ensuring the spherical structure of the micropowder, thus meeting the requirements of high-frequency electronic equipment and materials for low dielectric constant.

[0005] This invention provides a method for preparing low-dielectric spherical silica micropowder. The method primarily involves chemically treating and functionalizing the surface of the spherical silica micropowder to obtain micropowder with low dielectric properties. This addresses the technical bottleneck of excessively high dielectric constants (>4.0) in fillers used in high-frequency electronic materials. Through precise modification with polar silanes and synergistic control of pore structure, a breakthrough reduction in dielectric constant (≤3.5) is achieved while maintaining the filler-resin interfacial bonding. The low-dielectric spherical silica micropowder prepared by this invention exhibits optimized dielectric properties, with a lower dielectric constant than traditional modified micropowders, meeting the requirements of 5G / 6G communication copper-clad laminates (Dk≤3.8). Atmospheric pressure drying and mechanical depolymerization avoid high-temperature densification, preserving the pore structure. The porosity can be flexibly controlled by the type and amount of "pore-forming agent" to adapt to different resin systems. This low-dielectric spherical silica micropowder can be widely used in the electronics, communications, and optoelectronic industries, especially suitable for the manufacture of high-frequency circuits and microelectronic devices, to reduce signal loss and interference during transmission.

[0006] This invention provides a method for preparing low-dielectric spherical silica micropowder, comprising the following steps: Step 1. Raw Material Preparation: Spherical silica with a D50 of 0.5~30μm is selected as the basic raw material; this ensures that the final microparticles have good dispersibility and appropriate particle size distribution, facilitating subsequent processing and application. Too fine (<0.5μm) leads to agglomeration, while too coarse (>30μm) increases the surface roughness of the copper-clad laminate; the spherical structure ensures powder flowability, preventing viscosity increase even with high resin filling rates. The selection of spherical silica microparticles ensures surface smoothness and high stability during the preparation process.

[0007] Step 2. Solution Preparation: Mix pure water and ethanol in a 3:1 ratio, add an inorganic acid to adjust the pH of the solution to an acidic environment less than 5, and add the silane coupling agent. The volume ratio of pure water, ethanol, and silane coupling agent is 3:1:(0.1~1.0). Hydrolyze at room temperature for 30~120 minutes until the solution is clear. The solution preparation process is a silane hydrolysis reaction, activating the silane reactivity. Mixing pure water and ethanol and adding an inorganic acid to adjust the pH to an acidic environment helps control the chemical activity of the solution, thus ensuring that the hydrolysis reaction of the silane coupling agent can proceed smoothly. Choosing an appropriate ratio and hydrolysis time ensures that the solution is clear and the reaction is complete, laying the foundation for subsequent surface treatment. Ethanol inhibits silane self-polymerization, and pure water provides the OH- required for hydrolysis. - An imbalance in the ratio will lead to gelation (exacerbated when pH > 5); an acidic environment with pH < 5 accelerates the hydrolysis of the X3 group (-OCH3 / -OC2H5) to Si-OH, preventing silanol condensation under neutral / alkaline conditions; hydrolysis time less than 30 minutes will result in insufficient hydrolysis, while time longer than 120 minutes will lead to silanol self-polymerization and deactivation.

[0008] Step 3. Surface Treatment: Mix spherical silica micropowder with liquid alcohol, ensuring a solid content of 40-50%. Mechanically disperse at 50-90°C for 10-60 minutes. Add a hydrolyzed silane coupling agent solution, with the amount of silane coupling agent added being 0.5-5% of the weight of the micropowder. Reflux the mixture for 2-6 hours. By mixing spherical silica micropowder with liquid alcohol and adding the hydrolyzed silane coupling agent, organic functional groups can be formed on the surface of the micropowder, constructing a low-dielectric composite structure. These functional groups can improve the interfacial compatibility of the micropowder with other materials, enhance its surface activity and functionality, and provide excellent electrical properties, especially low-dielectric properties, for high-frequency applications. When the solid content is too low, the reaction efficiency is low; when it is too high, the uneven dispersion leads to a coating thickness difference of >20%. The liquid alcohol carrier ethanol / isopropanol reduces the surface tension of the system and promotes the penetration of silane solution into the gaps between micro powders. The condensation and reflux reaction causes the silane Si-OH to dehydrate and condense with the Si-OH on the surface of the micro powder, forming Si-O-Si covalent bonds.

[0009] Step 4. Post-processing: The reaction product is dried in an oven at 80-120℃ under normal pressure, and then dispersed using a depolymerization device to obtain uniform low-dielectric spherical silica micropowder. Through drying and depolymerization after the reaction, residual solvents or unreacted substances are further removed, ensuring the purity of the final product and its stable particle structure. The depolymerization process helps refine the particles and increase their uniformity, thereby improving the application performance of the product and ensuring that the final low-dielectric spherical silica micropowder has good dispersibility and high electrical properties. Drying at 80-120℃ under normal pressure avoids pore collapse caused by vacuum drying; at temperatures >120℃, polar groups (such as epoxy groups) fail through ring opening; specific depolymerization equipment (high-speed flying knife / air jet mill) provides controllable shear force, avoiding damage to the surface coating layer caused by ball milling; air jet milling utilizes cavitation effect to peel off soft agglomerates, maintaining the integrity of the original pore structure.

[0010] The low-dielectric spherical silica micropowder obtained by this invention has a low dielectric constant, making it suitable for use in high-frequency materials. It can effectively reduce electromagnetic interference and improve the quality of signal transmission. By designing polar silane molecules to solve the contradiction of interfacial bonding forces and incorporating in-situ pore-forming technology, the technical dilemma of being unable to simultaneously achieve "low dielectric" and "high compatibility" is overcome.

[0011] The polar silane coupling agent selected in this invention helps to improve the surface activity of silica micropowder and enhance its performance in practical applications, especially in electronic applications that require low dielectric and high stability, thereby achieving better electrical performance and material stability.

[0012] In the preparation method of the present invention, the silane coupling agent in step 2 is a polar silane coupling agent, specifically YR-Si-X3, wherein X is a hydrolyzable group, a group that can react with water to form hydroxides, such as chloro or alcohol groups; R is a propyl group, a relatively common organic group, which acts as a linking group to enable the silane coupling agent to react with other organic or inorganic materials; Y is a polar organic functional group, at least one of epoxy, aliphatic amino, aromatic amino, methacryloyloxypropyl, acryloyloxypropyl, fluoromethyl, or mercaptopropyl. Among them, epoxy groups have excellent chemical reactivity and can react with many substances. They are often used to improve adhesion to organic substrates. Epoxy groups form covalent bonds with epoxy resins, improving interfacial strength. Amino groups can catalyze resin curing, shortening the copper clad laminate molding cycle. Aliphatic amino groups have excellent polarity and can form hydrogen bonds with the surface, improving interfacial bonding. Aromatic amino groups provide good reactivity and can improve the chemical resistance of materials. Methacryloxypropyl groups are used to form stable cross-linked structures, providing better heat resistance. Acryloyloxypropyl groups have good chemical reactivity and help form stable surface modification layers. Fluoromethyl groups are hydrophobic, which can increase the corrosion resistance and water resistance of micropowders. Mercaptopropyl groups have good bonding with metals and other materials, improving surface wettability.

[0013] The selection of polar silane coupling agents in this invention can effectively enhance the surface functionalization of silica micropowder, enabling it to chemically react with different matrix materials (such as polymers, metals, etc.) to form a robust interface. By adding different polar functional groups (such as epoxy groups, amino groups, etc.), the hydrophilicity, oleophilicity, and compatibility with other materials of the micropowder can be adjusted, which is crucial for the application of low-dielectric silica micropowder in high-frequency materials.

[0014] This invention selects epoxy or amino groups as the Y group, which can effectively enhance the surface modification effect of silane coupling agents, resulting in better dispersibility, chemical stability, and interfacial bonding of low-dielectric spherical silica micropowder in subsequent composite material applications. This is particularly important for the manufacture of high-performance electronic materials, as it ensures that the materials maintain stable electrical and mechanical properties over long periods in complex environments.

[0015] Preferably, the silane coupling agent Y group is an epoxy group or an amino group. Epoxy groups have high chemical reactivity and can undergo cross-linking reactions with many substrates (such as metals, polymers, etc.) to form strong chemical bonds. Epoxy groups can enhance interfacial bonding and improve the adhesion between silica micropowder and other materials, thereby improving the dispersibility and stability of the micropowder in the composite material. The introduction of epoxy groups helps enhance the mechanical properties of the composite material, especially maintaining good stability at high temperatures. Amino groups give silica micropowder higher hydrophilicity, improving the dispersibility of the micropowder in aqueous solutions. Amino groups can react chemically with many organic and inorganic materials, especially with epoxy groups and other functional groups, to enhance the overall functionality of the material. Amino groups are often used to enhance the compatibility between silica and polymers, especially in the electronics and coatings fields, where they can provide better interfacial adhesion.

[0016] In the preparation method of this invention, the liquid alcohol in step 3 is at least one of ethanol and isopropanol. Ethanol, as a common organic solvent, has good solubility and volatility, which helps to uniformly disperse silica micropowder in the solution, ensuring its stability during surface treatment. Ethanol has low toxicity and good biodegradability, meeting environmental protection requirements. In industrial production, the use of ethanol can reduce environmental pollution. Ethanol can effectively dissolve silane coupling agents, helping them to fully react with the surface of silica micropowder, thereby enhancing the bonding force between the coupling agent and the micropowder.

[0017] Isopropanol has a stronger solubility than ethanol, especially in dissolving certain organic substances. In some cases, isopropanol can further improve the dispersibility of silica micropowder. Isopropanol's high volatility means it evaporates from the reaction system more quickly, facilitating subsequent drying steps and reducing solvent residue. Isopropanol can enhance the wettability of silica micropowder, improve its dispersibility in liquids, and contribute to surface modification and uniform coating of the micropowder.

[0018] Choosing ethanol and isopropanol as at least one of the liquid alcohols allows for adjustment of solvent selection based on specific application requirements. Both provide good dispersion, but their evaporation rates and solubility characteristics differ. Liquid alcohols not only help to uniformly disperse silica micropowder but also promote the reaction between the silane coupling agent and the micropowder, thereby ensuring the consistency and effectiveness of surface treatment and improving the performance of the final product. The use of ethanol and isopropanol in surface treatment helps control the dispersibility, stability, and reaction effect of silica micropowder with silane coupling agents, ensuring the uniformity and low dielectric properties of the final product.

[0019] In the preparation method of this invention, step 3 describes mixing spherical silica micropowder with liquid alcohol, adding an appropriate amount of pore-forming agent, and controlling the formation of pores on the surface or inside of the micropowder through mechanical dispersion. This process has a significant impact on the performance of the final product, especially on the adjustment of the pore structure and specific surface area of ​​the micropowder. By adding the pore-forming agent and performing mechanical dispersion in step 3, the pore structure of the silica micropowder can be precisely adjusted, thereby optimizing its application performance in low-dielectric materials. The regulation of the pore structure not only helps to reduce the dielectric constant of the micropowder but also improves its surface activity, dispersibility, and compatibility with other materials, providing more possibilities for its application in high-frequency materials, composite materials, and other fields.

[0020] In the preparation method of this invention, step 3 involves mixing spherical silica micropowder with liquid alcohol, adding an appropriate amount of pore-forming agent, and then mechanically dispersing the mixture to control the formation of pores on the surface or inside the micropowder. The pore-forming agent generates pores on the surface or inside the micropowder through chemical or physical means. The presence of these pores effectively increases the specific surface area of ​​the silica micropowder, giving it stronger adsorption, dispersibility, and bonding with other materials in subsequent applications. By controlling the type, amount, and dispersion method of the pore-forming agent, the porosity of the micropowder can be precisely adjusted, thereby affecting its electrical, thermal, and mechanical properties. Especially in low-dielectric applications, a well-designed pore structure helps reduce the dielectric constant. The formation of pores significantly increases the surface area of ​​the micropowder, thereby increasing its contact area with other substances. This is crucial for enhancing the chemical reactivity of silane coupling agents and the bonding force between the micropowder and the substrate.

[0021] Mechanical dispersion effectively prevents the agglomeration of microparticles, ensuring their uniform distribution in liquid alcohol. This helps ensure that pore-forming agents act uniformly on the surface or interior of the microparticles, resulting in a uniform pore structure. Mechanical dispersion also aids in the uniform distribution of pore-forming agents and silane coupling agents, enhancing their reaction on the surface or interior of the microparticles and thus better controlling pore formation.

[0022] The presence of pores directly affects the dielectric properties of micronized powders. By precisely controlling the formation of pores, the dielectric constant of silica micronized powders can be reduced, achieving the requirement of low dielectric constant. Pore formation not only helps to reduce the dielectric constant but also increases the specific surface area and adsorption properties of the micronized powders, particularly in high-frequency electronic materials, conductive materials, or composite materials, effectively improving performance.

[0023] Surfactants can reduce the surface tension of micronized powders, promoting uniform dispersion of liquid alcohols and micronized powders and reducing agglomeration. Through the action of their hydrophilic and hydrophobic groups, surfactants form self-assembled structures on the surface of micronized powders, thereby promoting pore formation. Surfactants help form a uniform pore structure on the surface of silica micronized powders, adjusting their porosity. The addition of surfactants improves the dispersibility of micronized powders, making them more stable in solution, avoiding particle aggregation or uneven distribution, thus optimizing the surface and pore structure.

[0024] Preferably, the pore-forming agent is at least one selected from surfactants, organic amines, aminosilanes, and phosphates, and is added in an amount of 0.1% to 3.0% of the micropowder mass. Organic amines can provide amino groups, which can participate in the reaction to further modify the surface structure of the micropowder and enhance its interfacial bonding with other materials. Organic amines, through reaction with silane coupling agents, promote the uniform distribution of pores inside and on the surface of silica micropowder, thereby forming pores with a good structure. Organic amines can also help control the dispersion of micropowder in liquids and the formation of pore structures by adjusting the hydrophilicity or hydrophobicity of the micropowder surface.

[0025] Aminosilanes contain amino and silane groups, enabling them to react with the silica surface through the silane groups and interact with other substrates or functional molecules through the amino groups. Aminosilanes can form stable chemical bonds on the silica surface, regulating the pore structure and enhancing its bonding with other materials, thereby improving the performance of composite materials. The addition of aminosilanes helps to regulate the porosity and dispersibility of micropowders, improve their surface properties, and ultimately enhance the low-dielectric properties of the final product.

[0026] Phosphates possess excellent surface activity, promoting pore formation and regulating the pore structure of micronized powders. Their addition helps form more stable pores in silica micronized powders, further optimizing dielectric properties. Phosphates enhance the heat resistance and chemical stability of materials, especially in high-temperature applications, ensuring stable performance of the micronized powder. Phosphates also help improve the dispersibility of micronized powders, reduce agglomeration, and ensure a uniform pore structure.

[0027] The amount of pore-forming agent added directly affects pore formation and the surface properties of micronized powder. An addition of 0.1% to 3.0% can effectively regulate the size, distribution, and number of pores without causing performance loss due to excessive amounts. An appropriate amount of pore-forming agent can balance the performance and preparation cost of micronized powder, ensuring optimal electrical, chemical, and mechanical properties in applications.

[0028] By selecting surfactants, organic amines, aminosilanes, or phosphates as pore-forming agents and controlling their addition amount within the range of 0.1% to 3.0%, the pore structure of silica micropowder can be effectively adjusted, improving its dispersibility and surface properties, thereby enhancing its low dielectric properties and application effectiveness. This optimization method enables the micropowder to have better performance and broader application prospects in fields such as electronic materials and composite materials.

[0029] This invention, by precisely controlling the amount and type of different pore-forming agents, can generate a uniform and stable pore structure on the surface of silica micropowder, further improving the electrical, chemical, and physical properties of the micropowder. Specifically, surfactants help reduce surface tension, optimize dispersibility, and promote pore formation; organic amines can improve the surface hydrophilicity and reactivity of the micropowder, regulating pore uniformity; aminosilanes, through reaction with the micropowder surface, enhance surface adhesion and functionalization, regulating porosity; and phosphates can effectively increase porosity while improving heat resistance and corrosion resistance.

[0030] Further, the surfactant includes sodium dodecyl sulfate and hexadecyltrimethylammonium chloride, added at 0.1% to 2% of the mass of the micronized powder; the organic amine includes triethanolamine and dimethylethanolamine, added at 0.2% to 2% of the mass of the micronized powder; the aminosilane includes γ-aminopropyltriethoxysilane, added at 0.1% to 0.5% of the mass of the micronized powder; and the phosphate includes tributyl phosphate and diethyl phosphate, added at 0.5% to 3% of the mass of the micronized powder.

[0031] Sodium dodecyl sulfate is a common anionic surfactant with strong emulsifying, dispersing, and cleaning abilities. It can reduce the surface tension of silica micropowder, helping it to disperse evenly in solution and promoting pore formation. Hexadecyltrimethylammonium chloride is a cationic surfactant that can form a stable molecular layer on the surface of the micropowder, helping to regulate the surface charge and pore formation. Adding 0.1% to 2% of the micropowder mass allows the added surfactants to optimize the dispersibility and pore structure of the micropowder, ensuring uniform distribution in solution and preventing aggregation.

[0032] Triethanolamine is a commonly used organic amine with strong hydrophilicity, which helps form pores and improves the chemical reactivity of silica micropowder with other materials. Dimethylethanolamine is another common organic amine that can improve the surface properties of silica micropowder, enhance its dispersibility in liquids, and promote pore formation. Adding 0.2% to 2% (by weight) of organic amine to the micropowder can effectively regulate the size, shape, and uniformity of pores, further improving the surface activity and reactivity of the micropowder.

[0033] γ-aminopropyltriethoxysilane, a type of aminosilane, contains amino and silane groups, which can chemically react with the silica surface to enhance the surface functionality of the micropowder, improve its dispersibility, and effectively control its pore structure. Adding 0.1% to 0.5% aminosilane by weight of the micropowder can form stable chemical bonds on its surface, helping to improve the interfacial bonding force and regulate its porosity.

[0034] Tributyl phosphate is a common organophosphate that can generate pores through chemical reactions and provides good chemical stability and heat resistance, making it particularly suitable for high-temperature applications. Diethyl phosphate is a highly reactive phosphate that helps form a stable porous structure and improves the porosity of micronized powders. Adding 0.5% to 3% phosphate by weight to micronized powder can promote pore formation, and its high chemical stability helps improve the heat resistance and corrosion resistance of the micronized powder.

[0035] In the preparation method of this invention, the deagglomeration equipment mentioned in step 4 includes a high-speed flying knife disperser or an air jet mill. These two devices have different functions and advantages in the deagglomeration process, mainly used to ensure the uniformity of silica micropowder and optimize its particle size distribution.

[0036] In the preparation method of this invention, the deagglomeration equipment in step 4 is a high-speed fly-blade disperser or an air jet mill. The high-speed fly-blade disperser uses high-speed rotating blades to break up agglomerated silica micropowder into uniform small particles. Through strong shearing and impact forces, it can effectively decompose agglomerated micropowder, improving its dispersibility. This equipment can precisely control the particle size distribution of the micropowder, avoiding excessive fineness or agglomeration, and ensuring that the final particle size of the micropowder is within the required range. For high-viscosity slurries or solutions, the high-speed fly-blade disperser can provide sufficient shearing force to uniformly disperse the micropowder in the solution.

[0037] Air jet mills utilize high-pressure airflow to accelerate micro-powders, breaking down agglomerated powders into fine, uniform particles through the shearing and impact forces of the airflow. Air jet mills possess extremely high refining capabilities, achieving very fine particle sizes. The operation of an air jet mill generates virtually no heat, preserving the physical and chemical properties of the micro-powders and avoiding potential pyrolysis or sintering problems caused by high temperatures. This is crucial for maintaining the low dielectric properties of silica micro-powders. Air jet mills efficiently and rapidly deagglomerate micro-powders, significantly improving their dispersibility and uniformity, resulting in more uniform particle sizes suitable for applications requiring high precision and consistency.

[0038] High-speed fly knife dispersers are suitable for systems requiring high shear forces, effectively deagglomerating microparticles and improving dispersibility. They are suitable for high-viscosity liquids or slurries. Air jet mills are suitable for applications requiring finer microparticles while maintaining their low-temperature properties. They more efficiently deagglomerate microparticles, obtaining finer and more uniform particle sizes, making them particularly suitable for applications with low dielectric requirements. By using these two types of equipment, uniform, low-dielectric spherical silica microparticles can be obtained, enhancing their performance in high-frequency electronics and other precision materials applications.

[0039] In summary, the present invention has the following beneficial effects: 1. This invention successfully prepared spherical silica micropowder with low dielectric constant by precisely controlling the pore structure and surface chemical modification of silica micropowder. Compared with traditional silica micropowder, existing technologies can usually only change the dielectric properties of micropowder through simple physical treatment or limited surface modification. However, this invention can significantly reduce the dielectric constant and improve the low dielectric properties by precisely controlling the pore structure and using silane coupling agents for surface functionalization. It is particularly suitable for high-frequency circuits and microelectronic devices, and has obvious performance advantages. 2. Compared with the prior art, the present invention significantly improves the dispersibility and stability of micro powder by combining liquid alcohol dispersion with mechanical dispersion and supplementing it with deagglomeration equipment such as high-speed flying knife dispersers or air jet mills. Traditional dispersion methods often have the problem of micro powder agglomeration or uneven dispersion, while the present invention ensures the uniform distribution and stability of micro powder in solution through advanced dispersion and deagglomeration technology, which greatly improves the uniformity and consistency of the final product. 3. This invention employs precise selection and control of silane coupling agents and pore-forming agents to ensure that the surface of the micropowder can be fully functionalized. In the prior art, surface treatment is often limited to simple chemical modification or fails to precisely control the pore structure. However, this invention achieves dual control of the micropowder surface and pore structure by selecting polar silane coupling agents and different types of pore-forming agents (such as surfactants, organic amines, aminosilanes, etc.). This enables more precise chemical modification of the micropowder surface, improves its adhesion to the substrate, and effectively regulates the pore structure, thereby improving the overall performance of the material. 4. This invention achieves pore structure regulation of micropowders by introducing pore-forming agents (such as surfactants, phosphates, aminosilanes, etc.) and precisely controlling their addition amount. Unlike existing technologies that rely on traditional physical methods or simple pore-forming processes, this invention can create efficient and controllable pore structures on the surface and inside of micropowders through precise chemical regulation and optimization of the type and amount of pore-forming agents. This not only effectively reduces the dielectric constant but also increases the specific surface area, improving the adsorption and electrical properties of micropowders. It is particularly suitable for low dielectric and high frequency materials. 5. This invention uses environmentally friendly solvents and raw materials, such as ethanol, isopropanol, and low-toxicity pore-forming agents and silane coupling agents. Compared with the toxic solvents or high-cost materials that may be used in the prior art, the preparation method of this invention is not only more environmentally friendly, but also greatly reduces production costs and improves economic efficiency by optimizing the amount of pore-forming agent added and controlling the surface treatment process. 6. Traditional methods for deagglomerating micropowders often suffer from uneven deagglomeration or inaccurate particle size control. However, this invention solves these problems by using high-efficiency deagglomeration equipment such as high-speed flying knife dispersers or air jet mills. Air jet mills, in particular, can precisely control the particle size distribution of micropowders without heating, avoiding performance loss due to overheating, ensuring high uniformity and low dielectric properties of the micropowders, and maintaining the stability and performance consistency of the micropowders in high-frequency applications. Detailed Implementation

[0040] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

[0041] Example 1

[0042] Step 1: Take 100g of spherical silica with a D50 of 5μm; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 2.5 with hydrochloric acid; add 40mL of γ-glycidoxypropyltrimethoxysilane (Y=epoxy group) to achieve a volume ratio of 3:1:0.4, and hydrolyze for 60 minutes until clear; Step 3: Mix spherical silica micro powder with 200 mL of ethanol, with a solid content of 50%; add 1.0 g of sodium dodecyl sulfate (surfactant) (1% of the micro powder mass), and mechanically disperse at 70 °C for 30 minutes; add silane solution (silane accounts for 2% of the micro powder), and reflux at 85 °C for 4 hours; Step 4: The reaction product is dried at 105℃ and atmospheric pressure, and then depolymerized using a high-speed flying knife dispersant to obtain uniform low-dielectric spherical silica micro powder.

[0043] Example 2

[0044] Step 1: Take 100g of spherical silica with a D50 of 15μm; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 3.0 with nitric acid; add 30mL of γ-aminopropyltriethoxysilane (Y = aliphatic amino) at a volume ratio of 3:1:0.3, and hydrolyze for 90 minutes until clear; Step 3: Mix spherical silica micro powder with 180 mL of isopropanol, with a solid content of 45%; add 2.5 g of tributyl phosphate (phosphate) (2.5% of the micro powder mass), and mechanically disperse at 60 °C for 40 minutes; add silane solution (silane accounts for 3% of the micro powder), and reflux at 75 °C for 5 hours; Step 4: The reaction product is dried at 95°C and atmospheric pressure, and then depolymerized by air jet milling to obtain uniform low-dielectric spherical silica micropowder.

[0045] Example 3

[0046] Step 1: Take 100g of spherical silica with a D50 of 8μm; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 2.0 with sulfuric acid; add 50mL of tridecafluorooctyltriethoxysilane (Y = fluoromethyl) at a volume ratio of 3:1:0.5, and hydrolyze for 120 minutes until clear; Step 3: Mix spherical silica micro powder with 220 mL of ethanol, with a solid content of 42%; add 1.8 g of dimethylethanolamine (organic amine) (1.8% of the micro powder mass), and mechanically disperse at 80 °C for 20 minutes; add silane solution (silane accounts for 4% of the micro powder), and reflux at 90 °C for 3 hours; Step 4: The reaction product is dried at 110℃ and atmospheric pressure, and then depolymerized by air jet milling to obtain uniform low dielectric spherical silica micro powder.

[0047] Example 4

[0048] Step 1: Take 100g of spherical silica with a D50 of 3μm; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 4.0 with hydrochloric acid; add 20mL of γ-(methacryloyloxy)propyltrimethoxysilane (Y=methacryloyloxypropyl) at a volume ratio of 3:1:0.2, and hydrolyze for 45 minutes until clear; Step 3: Mix spherical silica micro powder with 150 mL of isopropanol, with a solid content of 48%; add 0.5 g of cetyltrimethylammonium chloride (surfactant) (0.5% of the micro powder mass), and mechanically disperse at 65 °C for 50 minutes; add silane solution (silane accounts for 1.5% of the micro powder), and reflux at 70 °C for 4.5 hours; Step 4: The reaction product is dried at 85°C under normal pressure and then depolymerized using a high-speed flying knife dispersant to obtain uniform low-dielectric spherical silica micropowder.

[0049] Example 5

[0050] Step 1: Take 100g of spherical silica with a D50 of 20μm; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 4.5 with acetic acid; add 60mL of γ-mercaptopropyltrimethoxysilane (Y = mercaptopropyl) at a volume ratio of 3:1:0.6, and hydrolyze for 100 minutes until clear; Step 3: Mix spherical silica micro powder with 250 mL of ethanol, with a solid content of 40%; add 0.3 g of γ-aminopropyltriethoxysilane (aminosilane pore-forming agent) (0.3% of the micro powder mass), and mechanically disperse at 75 °C for 25 minutes; add silane solution (silane accounts for 0.8% of the micro powder), and reflux at 65 °C for 6 hours; Step 4: The reaction product is dried at 100℃ and normal pressure, and then depolymerized by air jet milling to obtain uniform low dielectric spherical silica micro powder.

[0051] Example 6

[0052] Step 1: Take 100g of spherical silica with a D50 of 10μm; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 2.8 with phosphoric acid; add 25mL of N-phenyl-γ-aminopropyltrimethoxysilane (Y = aromatic amino) at a volume ratio of 3:1:0.25, and hydrolyze for 90 minutes until clear; Step 3: Mix spherical silica micro powder with 200 mL of isopropanol, with a solid content of 45%; add 1.2 g of diethyl phosphate (phosphate) (1.2% of the micro powder mass), and mechanically disperse at 85 °C for 15 minutes; add silane solution (silane accounts for 2.5% of the micro powder), and reflux at 80 °C for 3.5 hours; Step 4: The reaction product is dried at 120℃ and normal pressure, and then depolymerized by a high-speed flying knife dispersant to obtain uniform low-dielectric spherical silica micro powder.

[0053] Example 7

[0054] Step 1: Take 100g of spherical silica with a D50 of 1μm; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 3.2 with hydrochloric acid; add 35mL of γ-(acryloyloxy)propyltrimethoxysilane (Y=acryloyloxypropyl) at a volume ratio of 3:1:0.35, and hydrolyze for 30 minutes until clear; Step 3: Mix spherical silica powder with 120 mL of ethanol, with a solid content of 50%; add 0.6 g (0.6%) of triethanolamine (organic amine) and 1.0 g (1.0%) of tributyl phosphate, and mechanically disperse at 50 °C for 60 minutes; add silane solution (silane accounts for 3.5% of the powder), and reflux at 60 °C for 5 hours; Step 4: The reaction product is dried at 90°C and atmospheric pressure, and then depolymerized by air jet milling to obtain uniform low-dielectric spherical silica micropowder.

[0055] Comparative Example 1 Step 1: Take 100g of spherical silica with D50=5μm, as in Example 1; Step 2: Mix 300mL of pure water and 100mL of ethanol, adjust the pH to 2.5 with hydrochloric acid; add 40mL of methyltrimethoxysilane (non-polar silane) at a volume ratio of 3:1:0.4, and hydrolyze for 60 minutes until clear; Step 3: Mix spherical silica micro powder with 200 mL of ethanol, with a solid content of 50% and no pore-forming agent added, and mechanically disperse at 70 °C for 30 minutes; add silane solution (silane accounts for 2% of the micro powder), and reflux at 85 °C for 4 hours; Step 4: The reaction product is vacuum dried at 150℃ and depolymerized using a ball mill to obtain traditional spherical silica micro powder.

[0056] The spherical silica micropowder samples obtained in Examples 1-7 and Comparative Example 1 were subjected to performance testing, and the key performance indicators included: 1. Dielectric constant (Dk) and loss factor (Df) Testing standards: IPCTM-650 2.5.5.9 (copper clad laminate) / ASTM D150 (powder) Test method: Parallel plate capacitance method is used. The sample is made into a 25mm diameter disc (the powder needs to be mixed with paraffin at a ratio of 6:4 and pressed into a disc). It is placed between the two electrodes of the impedance analyzer and the frequency is swept in the 1MHz-10GHz band. The complex dielectric constant is calculated by the change in capacitance value. Test environment: 23±1℃ / 50%RH. The average value is taken for three measurements.

[0057] 2. Contact angle Testing standard: GB / T 30693-2014 Detection method: Using a contact angle meter, 2 μL of deionized water was dropped onto the flattened powder surface, allowed to stand for 30 seconds, and then the contact angle was measured. The droplet morphology was captured by a high-speed camera, and the contact angle value was fitted using the Young-Laplace equation. Five points were measured for each sample, and the maximum / minimum values ​​were discarded before averaging, with an accuracy of ±1°.

[0058] 3. BET specific surface area and porosity Testing standard: ISO 9277:2010 Detection method: Nitrogen adsorption was used. After the sample was degassed in a vacuum at 150℃ for 6 hours, the nitrogen adsorption isotherm was measured in a liquid nitrogen environment at -196℃. The specific surface area was calculated using the BET model, and the pore size distribution was analyzed using the BJH model.

[0059] 4. Settlement stability Testing standard: ISO 8780-5:1990 Test method: The micro powder was dispersed in epoxy resin (Epon 828) at 30 wt%, injected into a 100 mL settling tube, and placed in a constant temperature chamber at 25℃. The change in the concentration of particles at the bottom was monitored by a laser particle size analyzer, and the settling rate was calculated.

[0060] 5. High-frequency signal transmission loss Testing standard: IEC 61189-3-301 Detection method: A copper-clad laminate (100×100×0.8mm) with 70wt% micropowder filling was prepared. The scattering parameters were measured at 10GHz using a vector network analyzer combined with a microstrip line fixture, and the transmission loss was calculated.

[0061] 6. T288 stratification time Testing standard: IPC TM-650 2.4.24.1 Test method: Cut the copper-clad laminate into 50×50mm samples, place them in a 288℃ solder bath and float them, and record the time when the substrate delamination (board bursting) occurs. Test 5 samples in each group, and take the minimum value as the T288 value.

[0062] 7. Degree of powder deagglomeration (D100) Testing standard: GB / T 19077-2016 Testing method: Take the dried powder and test the volumetric particle size distribution using a laser particle size analyzer (wet dispersion, 0.1% sodium hexametaphosphate solution). D100 represents the maximum particle size (i.e., 100% of the particles are smaller than this value). It is required to be ≤50μm to meet the copper clad laminate filling process.

[0063] 8. Test Results Table 1 Summary of performance test results for each sample

[0064] Results analysis: The dielectric constants of Examples 1-7 range from 3.35 to 3.71, which is much lower than the 4.25 of Comparative Example 1; the loss factors of Examples 1-7 range from 1.25 to 1.32 × 10⁻⁶. -3 This is far lower than the 2.62 × 10⁻⁶ of Comparative Example 1. -3 Low dielectric constant and low loss factor are key performance indicators for high-frequency electronic materials. In high-frequency signal transmission, an excessively high dielectric constant can lead to signal delay, while an excessively high loss factor can lead to signal attenuation. Examples 1-7 successfully reduced the dielectric constant and loss factor through the synergistic effect of polar silane coupling agents and pore-forming agents. In particular, Example 3 (fluoromethylsilane + organic amine) exhibited the lowest dielectric constant of 3.35 and a loss factor of 1.25 × 10⁻⁶. -3 It exhibited the best high-frequency performance. In contrast, Comparative Example 1, which used nonpolar silane, failed to effectively reduce the dielectric constant and loss factor, demonstrating the importance of polar silane coupling agents in surface modification.

[0065] The contact angles of Examples 1-7 ranged from 33° to 112°, while Comparative Example 1 showed 72°. A smaller contact angle indicates better wettability of the micropowder with water and better compatibility with the resin. Good interfacial wettability helps improve the dispersibility of the micropowder in the resin. Example 3 (fluoromethylsilane + organic amine) had the largest contact angle at 112°, indicating strong hydrophobicity, making it suitable for applications requiring hydrophobic properties. Example 2 (aminosilane + phosphate) had the smallest contact angle at 33°, indicating strong hydrophilicity, which aids in dispersion in aqueous systems.

[0066] The BET specific surface area of ​​Examples 1-7 ranges from 25 to 80 m². 2 / g, with a porosity ranging from 12% to 28%; the BET specific surface area of ​​Comparative Example 1 was 3 m². 2 / g, porosity less than 1%. High specific surface area and high porosity contribute to a lower dielectric constant, as pores can reduce the dielectric constant of a material. Example 3 (fluoromethylsilane + organic amine) has the highest BET specific surface area, at 80m². 2The highest porosity was 28% (per g), indicating the presence of the most porous structure, which significantly reduced the dielectric constant. In contrast, Comparative Example 1, lacking a pore-forming agent, had extremely low porosity, resulting in a higher dielectric constant.

[0067] The resin settling rates of Examples 1-7 were all below 15%, while the settling rate of Comparative Example 1 was above 50%. A lower settling rate indicates better dispersibility of the micropowder in the resin, making it less prone to settling and contributing to improved material uniformity and stability. Example 4 (methacryloyloxy + surfactant) exhibited the lowest settling rate, <5%, indicating optimal dispersibility in the resin. Comparative Example 1 showed a higher settling rate, indicating poorer dispersibility and a tendency to agglomerate.

[0068] The signal transmission loss of Examples 1-7 ranged from 0.14 to 0.19 dB / cm, while that of Comparative Example 1 was 0.28 dB / cm. Lower signal transmission loss indicates better performance of the material in high-frequency signal transmission. Example 2 (aminosilane + phosphate) exhibited the lowest signal transmission loss at 0.14 dB / cm, demonstrating excellent performance in high-frequency applications. Comparative Example 1 showed higher signal transmission loss, indicating significant signal attenuation in high-frequency signal transmission.

[0069] The T288 delamination time in Examples 1-7 was greater than 18 minutes, while in Comparative Example 1 it was 18 minutes. A longer T288 delamination time indicates a stronger interfacial bond between the micropowder and the resin, and better material stability under high-temperature conditions. The T288 delamination times in Examples 1, 4, 6, and 7 were all greater than 45 minutes, indicating very strong interfacial bonds in these examples. In contrast, the T288 delamination time in Comparative Example 1 was relatively short, only 18 minutes, indicating poor interfacial bonds and unsuitability for high-temperature applications.

[0070] The D100 particle size range of Examples 1-7 is 36~45μm, while that of Comparative Example 1 is 62μm. A smaller D100 particle size indicates better deagglomeration of the micropowder and more uniform particle size, making it suitable for fine processes such as copper clad laminates. Example 6 (aromatic aminosilane + phosphate) has the smallest D100 particle size at 36μm, indicating the best deagglomeration effect. In contrast, Comparative Example 1 has a larger D100 particle size, indicating poorer deagglomeration and larger particles, making it unsuitable for fine processes.

[0071] Comparative Example 1 used methyltrimethoxysilane (non-polar), whose molecular chain lacks active groups (Y=CH3) and cannot react with the resin; this resulted in weak interfacial adhesion (peel strength of only 0.8 kN / m, compared to 1.8 kN / m in Example 1). Furthermore, Comparative Example 1 lacked pore structure regulation, did not add a pore-forming agent, and had a specific surface area of ​​only 3.0 m². 2 / g (Example 1 is 35m) 2 / g); the dense structure results in a dielectric constant as high as 4.2 (compared to 3.52 in Comparative Example 1). Meanwhile, in the post-processing operation of Comparative Example 1, vacuum drying at 150°C decomposed the silane layer due to the high temperature; ball milling depolymerized the silane, and mechanical shearing destroyed the surface coating.

[0072] In the embodiments 1-7 of the present invention, a synergistic process of polar silane, pore-forming agent and mild drying is used. Compared with the traditional solution of Comparative Example 1, the dielectric constant is reduced to 3.35~3.71, breaking through the 4.0 technical bottleneck; the pore-forming agent increases the specific surface area by 8-26 times, the interfacial bonding force is increased by more than 2 times, and the T288 delamination time is >45min, meeting the AEC-Q200 Grade 1 automotive reliability standard; high frequency loss is reduced, meeting the >40GHz transmission requirements of 5G base stations.

[0073] In summary, this invention successfully prepared spherical silica micropowder with low dielectric constant by precisely controlling the pore structure and surface chemical modification, significantly improving its application performance in high-frequency electronic materials and demonstrating broad application prospects. The synergistic effect of the polar silane coupling agent and the pore-forming agent significantly reduced the dielectric constant and loss factor, while improving the dispersibility and interfacial bonding of the micropowder. Examples 2 and 3 showed excellent performance in multiple performance indicators, indicating that the application prospects of this invention can be expanded by adjusting the raw material combination. This invention uses environmentally friendly solvents and raw materials, reducing production costs and improving economic efficiency. The prepared low-dielectric spherical silica micropowder is suitable for 5G / 6G communication copper-clad laminates, high-frequency circuits, and microelectronic devices, effectively reducing signal loss and interference during transmission.

Claims

1. A method for preparing low-dielectric spherical silica micropowder, characterized in that, The following steps are involved: Step 1. Raw material preparation: Select spherical silica with a D50 of 0.5~30μm as the basic raw material; Step 2. Solution preparation: Mix pure water and ethanol in a ratio of 3:1, add inorganic acid to adjust the pH of the solution to an acidic environment of less than 5, add silane coupling agent, and the volume ratio of pure water, ethanol and silane coupling agent is 3:1:(0.1~1.0). Hydrolyze at room temperature for 30~120 minutes until the solution is clear. Step 3. Surface treatment: Mix spherical silica micro powder with liquid alcohol to ensure a solid content of 40-50%, mechanically disperse at 50-90℃ for 10-60 minutes, add hydrolyzed silane coupling agent solution, the amount of silane coupling agent added is 0.5-5% of the weight of micro powder, and reflux reaction for 2-6 hours. Step 4. Post-processing: The reaction product is dried in an oven at 80~120℃ under normal pressure, and then dispersed by a depolymerization device to obtain uniform low dielectric spherical silica micro powder.

2. The preparation method according to claim 1, characterized in that, The silane coupling agent mentioned in step 2 is a polar silane coupling agent, specifically YR-Si-X3, wherein X is a hydrolyzable group, R is propyl, and Y is at least one of epoxy, aliphatic amino, aromatic amino, methacryloyloxypropyl, acryloyloxypropyl, fluoromethyl, or mercaptopropyl.

3. The preparation method according to claim 2, characterized in that, The silane coupling agent Y group is an epoxy or amino group.

4. The preparation method according to claim 1, characterized in that, The liquid alcohol mentioned in step 3 is at least one of ethanol and isopropanol.

5. The preparation method according to claim 1, characterized in that, Step 3: After mixing the spherical silica micro powder with liquid alcohol, add an appropriate amount of pore-forming agent and then mechanically disperse to control the formation of pores on the surface or inside the micro powder.

6. The preparation method according to claim 5, characterized in that, The pore-forming agent is at least one of surfactant, organic amine, aminosilane, and phosphate, and the amount added is 0.1% to 3.0% of the mass of the micro powder.

7. The preparation method according to claim 6, characterized in that, The surfactants include sodium dodecyl sulfate and hexadecyltrimethylammonium chloride, added at 0.1% to 2% of the mass of the micronized powder; the organic amines include triethanolamine and dimethylethanolamine, added at 0.2% to 2% of the mass of the micronized powder; the aminosilanes include γ-aminopropyltriethoxysilane, added at 0.1% to 0.5% of the mass of the micronized powder; and the phosphates include tributyl phosphate and diethyl phosphate, added at 0.5% to 3% of the mass of the micronized powder.

8. The preparation method according to claim 1, characterized in that, The depolymerization equipment mentioned in step 4 is a high-speed flying knife dispersing machine or an air jet mill.

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