A method for preparing ultra-high purity amorphous regular spherical silicon micro-powder by composite silane hydrolysis

Abstract

The application discloses a kind of superhigh purity amorphous regular spherical silicon micro powder composite silane hydrolysis preparation method, it is related to electronic packaging material and high-purity inorganic powder preparation technical field.The present application uses one or more of tetraethoxysilane, methyltriethoxysilane and tetramethoxysilane as silicon source, by rectification purification, acid catalysis prehydrolysis, controlled polycondensation, microemulsion homogenization ball, alkaline solidification, aging densification and high-temperature dehydroxy calcination etc., superhigh purity amorphous regular spherical silicon micro powder is prepared.The obtained silicon micro powder is high in sphericity, narrow in particle size distribution, excellent in fluidity, low in dielectric constant, small in thermal expansion coefficient, low in total content of metal impurities, low in alpha-ray emission amount, and suitable for high-end electronic packaging materials, copper-clad plate, high-frequency communication materials and semiconductor filler field.The present application is stable in process, controllable in impurity, high in spheroidization rate, and can realize large-scale continuous production.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging materials and the preparation technology of high-purity inorganic powders, and in particular to a method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder. Background Technology

[0002] Spherical silicon micropowder is a type of inorganic functional powder material with SiO2 as the main component and a regular spherical structure. Due to its high insulation, low dielectric constant, low coefficient of thermal expansion, high filling capacity, excellent flowability, and good chemical stability, it has been widely used in semiconductor packaging materials, copper-clad laminates, high-frequency and high-speed communication substrates, chip underfill materials, thermally conductive composite materials, and precision electronic pastes. In particular, with the development of 5G communication, artificial intelligence chips, advanced packaging, and high-frequency and high-speed PCB technology, higher requirements have been placed on the purity, sphericity, particle size distribution, moisture absorption rate, and radioactivity level of spherical silicon micropowder.

[0003] Currently, the high-end electronic packaging field requires silicon micropowders to reach ultra-high purity levels, not just ordinary high purity. This means that the purity of SiO2 typically needs to be above 99.99%, and the total amount of metallic impurities such as Na, K, Fe, Al, and Ca must be below a few ppm. Simultaneously, the material is required to have a low alpha-ray emission level to avoid soft errors in semiconductor devices. Furthermore, to meet the requirements of high-fill-content packaging systems for flowability and low stress performance, silicon micropowders are also required to have a high sphericity, narrow particle size distribution, and a stable amorphous structure.

[0004] At present, the industrial-scale preparation processes for spherical silicon micropowder mainly fall into two categories: physical methods and chemical methods.

[0005] Physical methods mainly include flame melting, plasma spheroidization, and high-temperature jet melting. These methods typically use natural or fused quartz powder as raw materials, forming spherical particles through the surface tension contraction of the melt droplets after high-temperature melting. While this method can achieve a high spheroidization rate, it generally suffers from the following problems:

[0006] (1) The melting temperature is usually higher than 1800℃, resulting in high energy consumption;

[0007] (2) Impurities and radioactive elements in natural quartz are difficult to remove completely;

[0008] (3) Long-term high-temperature operation of equipment can easily introduce metal contamination;

[0009] (4) Controlling particle size distribution is quite difficult;

[0010] (5) Some particles are prone to forming crystalline quartz structures, which leads to a decrease in dielectric properties and an increase in the coefficient of thermal expansion.

[0011] For example, the Chinese patent "A method for preparing ultra-high purity and ultra-high density spherical silicon micropowder and its application" (patent number: CN114057202B) discloses a method for preparing spherical silicon micropowder using high-temperature silane oxidation. It forms spherical particles by oxidizing silane in a high-temperature reactor. Although it can obtain high density and high sphericity, it still has problems such as high equipment temperature, large process energy consumption, and difficulty in controlling particle size stability under high-temperature reaction conditions.

[0012] In contrast, chemical methods offer significant advantages in high purification, narrow particle size control, and amorphous structure regulation due to their ability to control the Si-O network formation process at the molecular scale. Currently, chemical methods mainly include sol-gel methods, alkoxide hydrolysis, microemulsion methods, and spray hydrolysis.

[0013] Among them, the silane hydrolysis method has gradually become an important development direction for high-end spherical silica powder in recent years due to its high raw material purity, mild reaction conditions, and low product impurity content. This method usually uses tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS) as the silicon source, and hydrolysis and condensation reactions occur under acidic or alkaline conditions to gradually form a three-dimensional Si-O-Si network structure, and finally form spherical silica particles.

[0014] For example, Chinese patent "A Method for Preparing Ultra-High Purity Amorphous Spherical Silicon Micropowder" (Patent No.: CN104556076B) discloses a method for preparing spherical silicon micropowder using organosilane hydrolysis and condensation. This method utilizes high-purity silane as the silicon source, and prepares amorphous spherical silicon micropowder through hydrolysis, condensation, curing, and high-temperature calcination. While this method has certain advantages in reducing impurity contamination, it still primarily employs a single silane system, which is prone to particle agglomeration and uneven particle size distribution due to local differences in hydrolysis rates.

[0015] For example, the Chinese patent "A Method for Preparing High-Purity Spherical Silica Micropowder" (Patent No.: CN107128935A) discloses a method for forming spherical particles through in-situ curing of organosilicon polymers, which can obtain high-purity spherical silica micropowder and reduce the pollution problem introduced by auxiliary additives. Although this technology improves the purity level, it still has problems such as more internal pores in the particles, lower tap density, and higher hydroxyl content on the particle surface. In high-frequency and high-speed electronic packaging applications, this can easily lead to increased moisture absorption and dielectric loss.

[0016] In addition, existing single silane hydrolysis systems generally have the following shortcomings:

[0017] (1) The local hydrolysis rate varies greatly in different regions, which makes it easy to form aggregated gels;

[0018] (2) The sphericity of the particles is significantly affected by stirring and local concentration fluctuations;

[0019] (3) The internal pore structure is difficult to control effectively, resulting in insufficient particle density;

[0020] (4) Local crystallization is prone to occur during high-temperature dehydroxylation;

[0021] (5) The high residual silanol content on the surface leads to a high moisture absorption rate of the material;

[0022] (6) It is still difficult to further reduce alkali metal ions and metal impurities in equipment.

[0023] As advanced packaging materials develop towards higher frequencies, higher integration, and lower dielectrics, spherical silicon micropowders prepared using traditional single silane systems can no longer simultaneously meet multiple performance requirements such as ultra-high purity, high sphericity, high density, low moisture absorption, and stable amorphous structure.

[0024] Therefore, there is an urgent need to develop a new method for preparing ultra-high purity amorphous ordered spherical silicon micropowder. Through synergistic hydrolysis of composite silanes, confined spherical formation, low-impurity densification control, and staged dehydroxylation treatment, the purity, sphericity, density, dielectric properties, and amorphous stability of spherical silicon micropowder can be improved simultaneously to meet the application needs of high-end semiconductor packaging and high-frequency electronic materials. Summary of the Invention

[0025] Based on the problems raised in the background technology mentioned above, this invention proposes a method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder.

[0026] The technical solution is as follows:

[0027] A method for preparing ultra-high purity amorphous, well-defined spherical silica powder by composite silane hydrolysis includes the following steps:

[0028] (1) Preparation and purification of composite silane raw materials:

[0029] Weigh out 60-85 parts of tetraethoxysilane, 12-32 parts of tetramethoxysilane, and 4-12 parts of methyltrimethoxysilane by mass fraction, and distill under reduced pressure at 68-92℃ for 2-5 hours under -0.06--0.09 MPa conditions to obtain ultra-high purity composite silane raw materials.

[0030] (2) Acid-catalyzed pre-hydrolysis reaction:

[0031] Add 28-52 parts of deionized water, 18-36 parts of anhydrous ethanol and 0.2-0.6 parts of resin catalyst to the composite silane raw material, control the pH of the system to 1.8-3.5, and stir the reaction at 25-42℃ for 2-6 hours to allow the composite silane to undergo partial hydrolysis and oligomerization condensation to obtain a siloxane precursor sol.

[0032] (3) Microemulsion dispersion into spheres:

[0033] Add 4-10 parts of emulsifier, 1-4 parts of dispersant and 45-90 parts of deionized water to the siloxane precursor sol, and homogenize at high speed for 10-35 minutes at 8000-15000 rpm to form a stable microemulsion system; filter to remove resin catalyst and other impurities.

[0034] (4) Alkali-catalyzed polycondensation curing:

[0035] Add 8-22 parts of alkaline curing liquid to the microemulsion system to raise the pH of the system to 8.5-11.0, and continue the reaction at 30-65°C for 3-8 hours to allow the siloxane oligomers to further condense into spheres, forming spherical silica wet gel particles.

[0036] (5) Aging and densification treatment:

[0037] The spherical silica wet gel particles were aged at 50–85°C for 5–12 h, then washed sequentially with ultrapure water and anhydrous ethanol, filtered, and dried at 80–140°C for 4–10 h to obtain spherical silica precursor powder.

[0038] (6) Dehydroxylation and calcination treatment:

[0039] The spherical silicon precursor powder was heated to 850–1150°C at a rate of 3–8°C / min in an oxygen or air atmosphere, held at that temperature for 2–6 hours, and then naturally cooled to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0040] Preferably, in step (1), the purity of tetraethoxysilane is ≥99.999wt%, and the content of metal impurities is ≤0.2ppm; the purity of tetramethoxysilane is ≥99.99wt%, and the total amount of Na and K impurities is ≤0.1ppm; and the purity of methyltrimethoxysilane is ≥99.9wt%.

[0041] Preferably, the modified resin catalyst in step (2) is composed of any one or two of D006 resin and A32 resin.

[0042] Preferably, the modified resin catalyst is prepared in the following steps:

[0043] Step 1: Acryloyl chloride acylation treatment. 100 parts of one or both of D006 resin and A32 resin are washed with deionized water until neutral, and pretreated by vacuum drying at 60-80℃ for 12-24 hours. The dried resin is directly immersed in 500-600 parts of acryloyl chloride solution, with 2-5 parts of zinc chloride as the acylation catalyst, and reacted at a constant temperature for 8-12 hours. After the reaction, the resin is filtered, and residual reactants are thoroughly washed with ethanol and deionized water in sequence. The resin is then vacuum dried at 50-60℃ to obtain the acylated resin.

[0044] Step 2: Ternary mixed gas plasma modification. A monolayer of acylated resin is laid flat in the plasma reaction chamber. The chamber is first evacuated to 10-50 Pa, then a mixed plasma gas consisting of 2-trimethylsilylpyridine vapor, ammonia, and argon is introduced, with a volume ratio of 0.1-0.4:0.05-0.2:1-3. The chamber pressure is stabilized to 30-80 Pa. The radio frequency plasma power is set to 80-150 W, and the surface modification treatment is performed for 5-15 minutes to obtain the plasma-modified resin.

[0045] Step 3: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the target modified resin catalyst.

[0046] Preferably, the emulsifier in step (3) includes one or two of Span-80, Tween-60, and fatty alcohol polyoxyethylene ether.

[0047] Preferably, the dispersant in step (3) includes one or two of polyethylene glycol, polyvinylpyrrolidone, and polyether-modified silicone oil.

[0048] Preferably, in step (3), the average droplet size of the microemulsion system is 0.8–15 μm; the homogenization emulsification temperature is controlled at 20–35 °C; and the homogenization time is controlled at 15–30 min.

[0049] Preferably, the alkaline curing liquid in step (4) includes one or two of ammonia, tetramethylammonium hydroxide, ethylenediamine or triethylamine.

[0050] Preferably, the aging treatment in step (5) is carried out using a staged heating method:

[0051] The first stage is aging at 50-60℃ for 2-4 hours;

[0052] The second stage is aging at 65-85℃ for 3-8 hours.

[0053] Preferably, the dehydroxylation calcination in step (6) employs a three-stage programmed temperature increase:

[0054] The first stage involves raising the temperature to 280–380℃ at a rate of 3–5℃ / min and holding it at that temperature for 0.5–1.5 hours.

[0055] The second stage involves raising the temperature to 550-750℃ at a rate of 4-6℃ / min and holding it at that temperature for 1-2 hours.

[0056] The third stage involves raising the temperature to 900–1150℃ at a rate of 5–8℃ / min and holding it at that temperature for 2–5 hours.

[0057] Reaction mechanism:

[0058] This invention utilizes composite silanes as raw materials and a modified resin catalyst as an acidic catalytic system to achieve the controllable preparation of ultra-high purity amorphous, well-defined spherical silica powder through a two-step hydrolysis-polymerization reaction. First, under the regulation of the acidic active sites of the modified resin catalyst, the composite silane undergoes controllable partial hydrolysis and oligomerization condensation reactions, forming a siloxane precursor sol with a uniform structure and concentrated molecular weight distribution. This avoids the problems of agglomeration, gelation, and byproduct formation caused by local reaction rate differences in traditional small-molecule acid catalytic systems. After the hydrolysis-oligomerization reaction is complete, the modified resin catalyst can be completely separated and removed from the reaction system through a simple filtration operation. The catalyst will not enter subsequent reaction stages, thus preventing the catalyst system from entering the product from the source. Impurities are introduced; then, the precursor sol after catalyst removal is homogeneously dispersed in a microemulsion system to form stable droplets with uniform particle size. Then, alkaline catalysis triggers further polycondensation and cross-linking solidification of siloxane oligomers, completing the growth of spherical silica wet gel particles within the confined space of the droplets. Finally, the wet gel particles undergo staged aging and densification, and multi-step heating and dehydroxylation calcination to regulate the internal pore structure of the particles and remove surface hydroxyl groups, while maintaining a stable amorphous structure, resulting in ultra-high purity amorphous regular spherical silica micropowder.

[0059] Compared with the prior art, the present invention has the following advantages:

[0060] 1. Significantly improves spherical regularity: The composite silane system can effectively adjust the hydrolysis and condensation rates of different silanes, so that the silicon-oxygen network is formed uniformly, reducing local gelation phenomenon, thereby obtaining spherical particles with more regular morphology, and the sphericity rate can reach more than 96%.

[0061] 2. Significantly reduces the content of metal impurities: This invention uses high-purity silane raw materials, electronic-grade deionized water and metal-free contact process, combined with multi-stage alcohol washing and weak alkali washing, which can control the total amount of impurities such as Na, K, Fe, and Al to below 1 ppm.

[0062] 3. Improve particle density and flowability: Through alkaline aging and high-temperature dehydroxylation process, the internal pores of spherical particles are significantly reduced, the tapped density is increased, and the flowability of powder is significantly improved.

[0063] 4. Reduced moisture absorption and dielectric loss: After high-temperature dehydroxylation, the surface Si-OH content decreases significantly, and the moisture absorption of the powder is reduced to below 0.09%, making it suitable for high-frequency and high-speed electronic packaging materials.

[0064] 5. Maintaining the stability of the amorphous structure: The calcination process of this invention avoids the formation of crystalline quartz, and the resulting material maintains a stable amorphous structure, which is beneficial to reducing the dielectric constant and thermal expansion stress. Attached Figure Description

[0065] Figure 1 SEM image of the ultra-high purity amorphous regular spherical silicon micropowder prepared in Example 1;

[0066] Figure 2 This is a SEM image of the ultra-high purity amorphous regular spherical silicon micropowder prepared in Example 2. Detailed Implementation

[0067] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments.

[0068] Example 1

[0069] (1) Preparation and purification of composite silane raw materials: 60 kg of tetraethoxysilane, 12 kg of tetramethoxysilane and 4 kg of methyltrimethoxysilane were weighed according to mass kg; wherein the purity of tetraethoxysilane was ≥99.999 wt% and the content of metal impurities was ≤0.2 ppm; the purity of tetramethoxysilane was ≥99.99 wt% and the total amount of Na and K impurities was ≤0.1 ppm; the purity of methyltrimethoxysilane was ≥99.9 wt%; and the materials were subjected to vacuum distillation at 68 °C for 2 h under -0.06 MPa conditions to remove trace amounts of water, metal impurities and low-boiling impurities from the raw materials to obtain ultra-high purity composite silane raw materials.

[0070] (2) Acid-catalyzed pre-hydrolysis reaction: 28 kg of deionized water, 18 kg of anhydrous ethanol and 0.2 kg of modified resin catalyst were added to the above composite silane raw material; pure D006 resin was selected as the modified resin catalyst; the pH of the system was controlled to be stable at 1.8, and the reaction was stirred at 25°C for 2 h to allow the composite silane to undergo partial hydrolysis and oligomerization condensation, and a uniform transparent siloxane precursor sol was obtained.

[0071] Complete preparation steps of the modified resin catalyst:

[0072] Step 1: Acryloyl chloride acylation treatment. 100 kg of D006 resin was washed with deionized water until neutral and dried under vacuum at 60°C for 24 h to complete the pretreatment. The dried resin was directly immersed in 500 kg of acryloyl chloride solution with 2 kg of zinc chloride as the acylation catalyst and reacted at a constant temperature for 8 h. After the reaction, the resin was filtered and thoroughly washed with ethanol and deionized water in sequence to remove residual reactants. The resin was then dried under vacuum at 50°C to obtain the acylated resin.

[0073] Step 2: Ternary mixed gas plasma modification. A monolayer of acylated resin is laid flat in the plasma reaction chamber. The chamber is first evacuated to 10 Pa, and then a mixed plasma gas consisting of 2-trimethylsilylpyridine vapor, ammonia, and argon is introduced, with a volume ratio of 0.1:0.05:1. The chamber pressure is stabilized to 30 Pa. The radio frequency plasma power is set to 80 W, and the surface modification treatment is carried out for 5 min to obtain plasma-modified resin.

[0074] Step 3: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the target modified resin catalyst.

[0075] (3) Microemulsion dispersion into spheres: Add 4 kg of emulsifier (Span-80), 1 kg of dispersant (polyethylene glycol), and 45 kg of deionized water to the siloxane precursor sol; control the homogenization emulsification temperature at 20℃, and homogenize at high speed at 8000 rpm for 15 min to form a stable microemulsion system with an average droplet size of 0.8 μm; after homogenization, filter to remove resin catalyst and other mechanical impurities.

[0076] (4) Alkali-catalyzed polycondensation curing: Add 8 kg of alkaline curing liquid (ammonia water) to the filtered microemulsion system to raise the pH of the system to 8.5. Continue the reaction at 30°C for 3 hours to allow the siloxane oligomers to further condense into spheres and form spherical silica wet gel particles with regular morphology.

[0077] (5) Aging and densification treatment: The spherical silica wet gel particles were aged in two stages by adopting a staged heating aging method; the first stage: aging at 50℃ for 2 hours; the second stage: aging at 65℃ for 3 hours, with a total aging time of 5 hours; after aging, the particles were thoroughly washed with ultrapure water and anhydrous ethanol in sequence, filtered, and dried at 80℃ for 4 hours to completely remove residual solvent and obtain spherical silica precursor powder.

[0078] (6) Dehydroxylation calcination treatment: The spherical silicon precursor powder was placed in an air atmosphere and calcined using a three-stage programmed heating method. The heating rate and holding parameters throughout the process were as follows: the first stage was heated to 280℃ at 3℃ / min and held for 0.5h; the second stage was heated to 550℃ at 4℃ / min and held for 1h; the third stage was heated to 900℃ at 5℃ / min and held for 2h; after calcination, the powder was naturally cooled to room temperature in the furnace to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0079] Example 2

[0080] (1) Preparation and purification of composite silane raw materials: 72.5 kg of tetraethoxysilane, 22 kg of tetramethoxysilane and 8 kg of methyltrimethoxysilane were weighed according to mass kg; the purity index of the raw materials was the same as in Example 1; under -0.075 MPa conditions, the raw materials were subjected to vacuum distillation at 80 °C for 3.5 h to remove trace amounts of water, metal impurities and low-boiling impurities, and ultra-high purity composite silane raw materials were obtained.

[0081] (2) Acid-catalyzed pre-hydrolysis reaction: 40 kg of deionized water, 27 kg of anhydrous ethanol and 0.4 kg of modified resin catalyst were added to the above composite silane raw material; the modified resin catalyst was a 1:1 mixture of D006 resin and A32 resin; the pH of the system was controlled to be stable at 2.65, and the reaction was stirred at 33.5℃ for 4 h to allow the composite silane to undergo partial hydrolysis and oligomerization condensation, and a uniform transparent siloxane precursor sol was obtained.

[0082] Complete preparation steps of the modified resin catalyst:

[0083] Step 1: Acryloyl chloride acylation treatment. 100 kg of D006 and A32 compound resin was washed with deionized water until neutral and dried under vacuum at 70°C for 18 h to complete the pretreatment. The dried resin was directly immersed in 550 kg of acryloyl chloride solution with 3.5 kg of zinc chloride as the acylation catalyst and reacted at a constant temperature for 10 h. After the reaction, the resin was filtered and thoroughly washed with ethanol and deionized water in sequence to remove residual reactants. It was then dried under vacuum at 55°C to obtain the acylated resin.

[0084] Step 2: Ternary mixed gas plasma modification. A monolayer of acylated resin is laid flat in the plasma reaction chamber. The chamber is first evacuated to 30 Pa, and then a mixed plasma gas consisting of 2-trimethylsilylpyridine vapor, ammonia, and argon is introduced, with a volume ratio of 0.25:0.125:2. The chamber pressure is stabilized to 55 Pa. The radio frequency plasma power is set to 115 W, and the surface modification treatment is carried out for 10 min to obtain plasma-modified resin.

[0085] Step 3: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the target modified resin catalyst.

[0086] (3) Microemulsion dispersion into spheres: 7 kg of emulsifier (a 1:1 mixture of Span-80 and Tween-60), 2.5 kg of dispersant (a 1:1 mixture of polyethylene glycol and polyvinylpyrrolidone) and 67.5 kg of deionized water were added to the siloxane precursor sol. The homogenization emulsification temperature was controlled at 27.5℃, and high-speed homogenization was carried out at 11500 rpm for 22.5 min to form a stable microemulsion system. The average droplet size of the microemulsion system was 7.9 μm. After homogenization, the resin catalyst and other mechanical impurities were removed by filtration.

[0087] (4) Alkali-catalyzed polycondensation curing: Add 15 kg of alkaline curing liquid (ammonia water and tetramethylammonium hydroxide mixed in a 1:1 ratio) to the filtered microemulsion system to raise the pH of the system to 9.75. Continue the reaction at a constant temperature of 47.5℃ for 5.5 h to allow the siloxane oligomers to further condense into spheres and form spherical silica wet gel particles with regular morphology.

[0088] (5) Aging and densification treatment: The spherical silica wet gel particles were aged in two stages using a phased heating aging method. The first stage was aging at 55℃ for 3 hours. The second stage was aging at 75℃ for 5.5 hours, with a total aging time of 8.5 hours. After aging, the particles were thoroughly washed with ultrapure water and anhydrous ethanol in sequence. After filtration, the particles were dried at 110℃ for 7 hours to completely remove residual solvent and obtain spherical silica precursor powder.

[0089] (6) Dehydroxylation calcination treatment: The spherical silicon precursor powder was placed in an oxygen atmosphere and calcined using a three-stage programmed heating method. The heating rate and holding parameters throughout the process were as follows: the first stage was heated to 330℃ at 4℃ / min and held for 1h; the second stage was heated to 650℃ at 5℃ / min and held for 1.5h; the third stage was heated to 1025℃ at 6.5℃ / min and held for 3.5h; after calcination, the powder was naturally cooled to room temperature in the furnace to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0090] Example 3

[0091] (1) Preparation and purification of composite silane raw materials: 79 kg of tetraethoxysilane, 27 kg of tetramethoxysilane and 10 kg of methyltrimethoxysilane were weighed according to mass kg; the purity index of the raw materials was the same as in Example 1; under -0.082 MPa conditions, the raw materials were subjected to vacuum distillation at 86 °C for 4.2 h to remove trace amounts of water, metal impurities and low-boiling impurities, and ultra-high purity composite silane raw materials were obtained.

[0092] (2) Acid-catalyzed pre-hydrolysis reaction: Add 46 kg of deionized water, 32 kg of anhydrous ethanol and 0.5 kg of modified resin catalyst to the above composite silane raw material; the modified resin catalyst is pure A32 resin; control the pH of the system to be stable at 3.1, stir the reaction at 38℃ for 5 h, so that the composite silane undergoes partial hydrolysis and oligomerization condensation to obtain a uniform and transparent siloxane precursor sol.

[0093] Complete preparation steps of the modified resin catalyst:

[0094] Step 1: Acryloyl chloride acylation treatment. 100 kg of A32 resin was washed with deionized water until neutral and dried under vacuum at 75°C for 15 h to complete the pretreatment. The dried resin was directly immersed in 580 kg of acryloyl chloride solution, with 4.2 kg of zinc chloride as the acylation catalyst, and reacted at a constant temperature for 11 h. After the reaction, the resin was filtered and thoroughly washed with ethanol and deionized water in sequence to remove residual reactants. The resin was then dried under vacuum at 58°C to obtain the acylated resin.

[0095] Step 2: Ternary mixed gas plasma modification. A monolayer of acylated resin is laid flat in the plasma reaction chamber. The chamber is first evacuated to 40 Pa, and then a mixed plasma gas consisting of 2-trimethylsilylpyridine vapor, ammonia, and argon is introduced, with a volume ratio of 0.32:0.16:2.5. The chamber pressure is stabilized to 65 Pa. The radio frequency plasma power is set to 130 W, and the surface modification treatment is carried out for 12 min to obtain plasma-modified resin.

[0096] Step 3: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the target modified resin catalyst.

[0097] (3) Microemulsion dispersion into spheres: Add 8.5 kg of emulsifier (Tween-60 and fatty alcohol polyoxyethylene ether in a 1:1 ratio), 3.2 kg of dispersant (polyvinylpyrrolidone and polyether modified silicone oil in a 1:1 ratio) and 78 kg of deionized water to the siloxane precursor sol; control the homogenization emulsification temperature at 31℃, and homogenize at high speed at 13200 rpm for 27 min to form a stable microemulsion system with an average droplet size of 11 μm; after homogenization, filter to remove resin catalyst and other mechanical impurities.

[0098] (4) Alkali-catalyzed polycondensation curing: Add 19 kg of alkaline curing liquid (tetramethylammonium hydroxide and ethylenediamine in a 1:1 ratio) to the filtered microemulsion system to raise the pH of the system to 10.4. Continue the reaction at a constant temperature of 56°C for 6.5 h to allow the siloxane oligomers to further condense into spheres and form spherical silica wet gel particles with regular morphology.

[0099] (5) Aging and densification treatment: The spherical silica wet gel particles were aged in two stages using a phased heating aging method. The first stage was aging at 58℃ for 3.5h; the second stage was aging at 79℃ for 6.5h, with a total aging time of 10h. After aging, the particles were thoroughly washed with ultrapure water and anhydrous ethanol, filtered, and dried at 125℃ for 8.5h to completely remove residual solvent and obtain spherical silica precursor powder.

[0100] (6) Dehydroxylation calcination treatment: The spherical silicon precursor powder was placed in an air atmosphere and calcined using a three-stage programmed heating method. The heating rate and holding parameters throughout the process were as follows: the first stage was heated to 355℃ at 4.5℃ / min and held for 1.2h; the second stage was heated to 690℃ at 5.5℃ / min and held for 1.8h; the third stage was heated to 1080℃ at 7℃ / min and held for 4.2h; after calcination, the powder was naturally cooled to room temperature in the furnace to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0101] Example 4

[0102] (1) Preparation and purification of composite silane raw materials: 85 kg of tetraethoxysilane, 32 kg of tetramethoxysilane and 12 kg of methyltrimethoxysilane were weighed according to mass kg; the purity index of the raw materials was the same as in Example 1; under -0.09 MPa conditions, the raw materials were subjected to vacuum distillation at 92℃ for 5 h to remove trace amounts of water, metal impurities and low-boiling impurities, and ultra-high purity composite silane raw materials were obtained.

[0103] (2) Acid-catalyzed pre-hydrolysis reaction: 52 kg of deionized water, 36 kg of anhydrous ethanol and 0.6 kg of modified resin catalyst were added to the above composite silane raw material; the modified resin catalyst was selected by mixing D006 resin and A32 resin in any proportion; the pH of the system was controlled to be stable at 3.5, and the reaction was stirred at 42℃ for 6 h to allow the composite silane to undergo partial hydrolysis and oligomerization condensation, and a uniform transparent siloxane precursor sol was obtained.

[0104] Complete preparation steps of the modified resin catalyst:

[0105] Step 1: Acryloyl chloride acylation treatment. 100 kg of compound resin was washed with deionized water until neutral and dried under vacuum at 80 °C for 12 h to complete the pretreatment. The dried resin was directly immersed in 600 kg of acryloyl chloride solution with 5 kg of zinc chloride as the acylation catalyst and reacted at a constant temperature for 12 h. After the reaction, the resin was filtered and thoroughly washed with ethanol and deionized water in sequence to remove residual reactants. The resin was then dried under vacuum at 60 °C to obtain the acylated resin.

[0106] Step 2: Ternary mixed gas plasma modification. A monolayer of acylated resin is laid flat in the plasma reaction chamber. The chamber is first evacuated to 50 Pa, and then a mixed plasma gas consisting of 2-trimethylsilylpyridine vapor, ammonia, and argon is introduced, with a volume ratio of 0.4:0.2:3. The chamber pressure is stabilized to 80 Pa. The radio frequency plasma power is set to 150 W, and the surface modification treatment is carried out for 15 min to obtain plasma-modified resin.

[0107] Step 3: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the target modified resin catalyst.

[0108] (3) Microemulsion dispersion into spheres: Add 10 kg of emulsifier (a mixture of Tween-60 and fatty alcohol polyoxyethylene ether), 4 kg of dispersant (a mixture of three dispersants) and 90 kg of deionized water to the siloxane precursor sol; control the homogenization emulsification temperature at 35℃, and homogenize at high speed at 15000 rpm for 30 min to form a stable microemulsion system with an average droplet size of 15 μm; after homogenization, filter to remove resin catalyst and other mechanical impurities.

[0109] (4) Alkali-catalyzed polycondensation curing: Add 22 kg of alkaline curing liquid (triethylamine and ethylenediamine compound) to the filtered microemulsion system to raise the pH of the system to 11.0. Continue the reaction at a constant temperature of 65°C for 8 hours to allow the siloxane oligomers to further condense into spheres and form spherical silica wet gel particles with regular morphology.

[0110] (5) Aging and densification treatment: The spherical silica wet gel particles were aged in two stages by adopting a staged heating aging method; the first stage: aging at 60℃ for 4 hours; the second stage: aging at 85℃ for 8 hours, with a total aging time of 12 hours; after aging, the particles were thoroughly washed with ultrapure water and anhydrous ethanol in sequence, filtered, and dried at 140℃ for 10 hours to completely remove residual solvent and obtain spherical silica precursor powder.

[0111] (6) Dehydroxylation calcination treatment: The spherical silicon precursor powder was placed in an oxygen atmosphere and calcined using a three-stage programmed heating method. The heating rate and holding parameters throughout the process were as follows: the first stage was heated to 380℃ at 5℃ / min and held for 1.5h; the second stage was heated to 750℃ at 6℃ / min and held for 2h; the third stage was heated to 1150℃ at 8℃ / min and held for 5h; after calcination, the powder was naturally cooled to room temperature in the furnace to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0112] Comparative Example 1

[0113] (1) Preparation and purification of composite silane raw materials: 60 kg of tetraethoxysilane, 12 kg of tetramethoxysilane and 4 kg of methyltrimethoxysilane were weighed according to mass kg; wherein the purity of tetraethoxysilane was ≥99.999 wt% and the content of metal impurities was ≤0.2 ppm; the purity of tetramethoxysilane was ≥99.99 wt% and the total amount of Na and K impurities was ≤0.1 ppm; the purity of methyltrimethoxysilane was ≥99.9 wt%; and the materials were subjected to vacuum distillation at 68 °C for 2 h under -0.06 MPa conditions to remove trace amounts of water, metal impurities and low-boiling impurities from the raw materials to obtain ultra-high purity composite silane raw materials.

[0114] (2) Acid-catalyzed pre-hydrolysis reaction: Add 28 kg of deionized water, 18 kg of anhydrous ethanol and 0.2 kg of resin catalyst D006 resin to the above composite silane raw material; control the pH of the system to be stable at 1.8, stir the reaction at 25°C for 2 h, so that the composite silane undergoes partial hydrolysis and oligomerization condensation to obtain a uniform and transparent siloxane precursor sol.

[0115] (3) Microemulsion dispersion into spheres: Add 4 kg of emulsifier (Span-80), 1 kg of dispersant (polyethylene glycol), and 45 kg of deionized water to the siloxane precursor sol; control the homogenization emulsification temperature at 20℃, and homogenize at high speed at 8000 rpm for 15 min to form a stable microemulsion system with an average droplet size of 0.8 μm; after homogenization, filter to remove resin catalyst and other mechanical impurities.

[0116] (4) Alkali-catalyzed polycondensation curing: Add 8 kg of alkaline curing liquid (ammonia water) to the filtered microemulsion system to raise the pH of the system to 8.5. Continue the reaction at 30°C for 3 hours to allow the siloxane oligomers to further condense into spheres and form spherical silica wet gel particles with regular morphology.

[0117] (5) Aging and densification treatment: The spherical silica wet gel particles were aged in two stages by adopting a staged heating aging method; the first stage: aging at 50℃ for 2 hours; the second stage: aging at 65℃ for 3 hours, with a total aging time of 5 hours; after aging, the particles were thoroughly washed with ultrapure water and anhydrous ethanol in sequence, filtered, and dried at 80℃ for 4 hours to completely remove residual solvent and obtain spherical silica precursor powder.

[0118] (6) Dehydroxylation calcination treatment: The spherical silicon precursor powder was placed in an air atmosphere and calcined using a three-stage programmed heating method. The heating rate and holding parameters throughout the process were as follows: the first stage was heated to 280℃ at 3℃ / min and held for 0.5h; the second stage was heated to 550℃ at 4℃ / min and held for 1h; the third stage was heated to 900℃ at 5℃ / min and held for 2h; after calcination, the powder was naturally cooled to room temperature in the furnace to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0119] Comparative Example 2

[0120] (1) Preparation and purification of composite silane raw materials: 60 kg of tetraethoxysilane, 12 kg of tetramethoxysilane and 4 kg of methyltrimethoxysilane were weighed according to mass kg; wherein the purity of tetraethoxysilane was ≥99.999 wt% and the content of metal impurities was ≤0.2 ppm; the purity of tetramethoxysilane was ≥99.99 wt% and the total amount of Na and K impurities was ≤0.1 ppm; the purity of methyltrimethoxysilane was ≥99.9 wt%; and the materials were subjected to vacuum distillation at 68 °C for 2 h under -0.06 MPa conditions to remove trace amounts of water, metal impurities and low-boiling impurities from the raw materials to obtain ultra-high purity composite silane raw materials.

[0121] (2) Acid-catalyzed pre-hydrolysis reaction: 28 kg of deionized water, 18 kg of anhydrous ethanol and 0.2 kg of modified resin catalyst were added to the above composite silane raw material; pure D006 resin was selected as the modified resin catalyst; the pH of the system was controlled to be stable at 1.8, and the reaction was stirred at 25°C for 2 h to allow the composite silane to undergo partial hydrolysis and oligomerization condensation, and a uniform transparent siloxane precursor sol was obtained.

[0122] The modified resin catalyst preparation steps are as follows:

[0123] Step 1: Ternary mixed gas plasma modification. 100 kg of D006 resin was washed with deionized water until neutral and pretreated by vacuum drying at 60℃ for 24 h. The resin was then laid in a monolayer in the plasma reaction chamber. The chamber was first evacuated to 10 Pa, and then a mixed plasma gas consisting of 2-trimethylsilylpyridine vapor, ammonia, and argon was introduced in a volume ratio of 0.1:0.05:1. The chamber pressure was stabilized to 30 Pa. The radio frequency plasma power was set to 80 W, and the surface modification treatment lasted for 5 min, yielding plasma-modified resin.

[0124] Step 2: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the modified resin catalyst.

[0125] (3) Microemulsion dispersion into spheres: Add 4 kg of emulsifier (Span-80), 1 kg of dispersant (polyethylene glycol), and 45 kg of deionized water to the siloxane precursor sol; control the homogenization emulsification temperature at 20℃, and homogenize at high speed at 8000 rpm for 15 min to form a stable microemulsion system with an average droplet size of 0.8 μm; after homogenization, filter to remove resin catalyst and other mechanical impurities.

[0126] (4) Alkali-catalyzed polycondensation curing: Add 8 kg of alkaline curing liquid (ammonia water) to the filtered microemulsion system to raise the pH of the system to 8.5. Continue the reaction at 30°C for 3 hours to allow the siloxane oligomers to further condense into spheres and form spherical silica wet gel particles with regular morphology.

[0127] (5) Aging and densification treatment: The spherical silica wet gel particles were aged in two stages by adopting a staged heating aging method; the first stage: aging at 50℃ for 2 hours; the second stage: aging at 65℃ for 3 hours, with a total aging time of 5 hours; after aging, the particles were thoroughly washed with ultrapure water and anhydrous ethanol in sequence, filtered, and dried at 80℃ for 4 hours to completely remove residual solvent and obtain spherical silica precursor powder.

[0128] (6) Dehydroxylation calcination treatment: The spherical silicon precursor powder was placed in an air atmosphere and calcined using a three-stage programmed heating method. The heating rate and holding parameters throughout the process were as follows: the first stage was heated to 280℃ at 3℃ / min and held for 0.5h; the second stage was heated to 550℃ at 4℃ / min and held for 1h; the third stage was heated to 900℃ at 5℃ / min and held for 2h; after calcination, the powder was naturally cooled to room temperature in the furnace to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0129] Comparative Example 3

[0130] (1) Preparation and purification of composite silane raw materials: 60 kg of tetraethoxysilane, 12 kg of tetramethoxysilane and 4 kg of methyltrimethoxysilane were weighed according to mass kg; wherein the purity of tetraethoxysilane was ≥99.999 wt% and the content of metal impurities was ≤0.2 ppm; the purity of tetramethoxysilane was ≥99.99 wt% and the total amount of Na and K impurities was ≤0.1 ppm; the purity of methyltrimethoxysilane was ≥99.9 wt%; and the materials were subjected to vacuum distillation at 68 °C for 2 h under -0.06 MPa conditions to remove trace amounts of water, metal impurities and low-boiling impurities from the raw materials to obtain ultra-high purity composite silane raw materials.

[0131] (2) Acid-catalyzed pre-hydrolysis reaction: 28 kg of deionized water, 18 kg of anhydrous ethanol and 0.2 kg of modified resin catalyst were added to the above composite silane raw material; pure D006 resin was selected as the modified resin catalyst; the pH of the system was controlled to be stable at 1.8, and the reaction was stirred at 25°C for 2 h to allow the composite silane to undergo partial hydrolysis and oligomerization condensation, and a uniform transparent siloxane precursor sol was obtained.

[0132] The modified resin catalyst preparation steps are as follows:

[0133] Step 1: Acryloyl chloride acylation treatment. 100 kg of D006 resin was washed with deionized water until neutral and dried under vacuum at 60°C for 24 h to complete the pretreatment. The dried resin was directly immersed in 500 kg of acryloyl chloride solution with 2 kg of zinc chloride as the acylation catalyst and reacted at a constant temperature for 8 h. After the reaction, the resin was filtered and thoroughly washed with ethanol and deionized water in sequence to remove residual reactants. The resin was then dried under vacuum at 50°C to obtain the acylated resin.

[0134] Step 2: Ternary mixed gas plasma modification. A monolayer of acylated resin is laid flat in the plasma reaction chamber. The chamber is first evacuated to 10 Pa, and then a mixed plasma gas composed of ammonia and argon is introduced with a volume ratio of 0.05:1. The chamber pressure is stabilized to 30 Pa. The radio frequency plasma power is set to 80 W, and the surface modification treatment is carried out for 5 min to obtain plasma-modified resin.

[0135] Step 3: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the modified resin catalyst.

[0136] (3) Microemulsion dispersion into spheres: Add 4 kg of emulsifier (Span-80), 1 kg of dispersant (polyethylene glycol), and 45 kg of deionized water to the siloxane precursor sol; control the homogenization emulsification temperature at 20℃, and homogenize at high speed at 8000 rpm for 15 min to form a stable microemulsion system with an average droplet size of 0.8 μm; after homogenization, filter to remove resin catalyst and other mechanical impurities.

[0137] (4) Alkali-catalyzed polycondensation curing: Add 8 kg of alkaline curing liquid (ammonia water) to the filtered microemulsion system to raise the pH of the system to 8.5. Continue the reaction at 30°C for 3 hours to allow the siloxane oligomers to further condense into spheres and form spherical silica wet gel particles with regular morphology.

[0138] (5) Aging and densification treatment: The spherical silica wet gel particles were aged in two stages by adopting a staged heating aging method; the first stage: aging at 50℃ for 2 hours; the second stage: aging at 65℃ for 3 hours, with a total aging time of 5 hours; after aging, the particles were thoroughly washed with ultrapure water and anhydrous ethanol in sequence, filtered, and dried at 80℃ for 4 hours to completely remove residual solvent and obtain spherical silica precursor powder.

[0139] (6) Dehydroxylation calcination treatment: The spherical silicon precursor powder was placed in an air atmosphere and calcined using a three-stage programmed heating method. The heating rate and holding parameters throughout the process were as follows: the first stage was heated to 280℃ at 3℃ / min and held for 0.5h; the second stage was heated to 550℃ at 4℃ / min and held for 1h; the third stage was heated to 900℃ at 5℃ / min and held for 2h; after calcination, the powder was naturally cooled to room temperature in the furnace to obtain ultra-high purity amorphous regular spherical silicon micropowder.

[0140] Test method:

[0141] 1. Test of particle morphology and sphericity

[0142] Testing instruments

[0143] Field emission scanning electron microscope (FE-SEM, model: Hitachi SU8220) was used.

[0144] Test conditions

[0145] The powder sample was ultrasonically dispersed in anhydrous ethanol for 30 min, dropped onto the surface of a conductive silicon wafer, and then vacuum dried before being sputtered with gold.

[0146] Accelerating voltage: 5 kV;

[0147] Magnification: 3000 to 10000 times.

[0148] Calculation method of sphericity

[0149] Randomly select no fewer than 1,000 particles and count the number of approximately spherical particles.

[0150] The sphericity rate is calculated using the following formula:

[0151] Sphericity rate (%) = (Number of spherical particles / Total number of particles) × 100%.

[0152] Criteria for determination: When the aspect ratio of the particles is ≤1.15, they are defined as spherical particles.

[0153] 2. Particle size distribution test

[0154] Testing instruments

[0155] Laser particle size analyzer (Malvern Mastersizer 3000).

[0156] Test conditions

[0157] Dispersion medium: anhydrous ethanol;

[0158] Ultrasonic dispersion time: 5 min;

[0159] Cyclic rotation speed: 1800 rpm.

[0160] Test metrics

[0161] Record the D10, D50, D90 and SPAN values.

[0162] in:

[0163] SPAN = (D90 - D10) / D50.

[0164] A lower SPAN value indicates a narrower particle size distribution.

[0165] 3. Purity and Metal Impurity Testing

[0166] Testing instruments

[0167] ICP-MS (Inductively Coupled Plasma Mass Spectrometer) (Agilent 7900).

[0168] Preprocessing methods

[0169] Weigh 0.1000 g of the sample and microwave digest it in a polytetrafluoroethylene digestion vessel using an HF-HNO3 mixed acid system.

[0170] Detecting elements

[0171] Na, K, Ca, Fe, Al, Mg, Cu, Cr, Ni, etc.

[0172] Test results indicate

[0173] All element concentrations are expressed in ppm.

[0174] The total impurity content is the sum of the above-mentioned metal elements.

[0175] 4. Tap density test

[0176] Test Standards

[0177] According to GB / T 5162-2006.

[0178] Test methods

[0179] Weigh 50 g of sample and add it to a graduated cylinder. After vibrating the cylinder 3000 times with a vibratory compactor, read the volume.

[0180] Formula for calculating tap density:

[0181] ρ=m / V.

[0182] 5. Moisture absorption rate test

[0183] Test methods

[0184] Weigh 2.0000 g of sample and place it in a constant temperature and humidity chamber at 25℃ and 85% RH for 48 h.

[0185] The moisture absorption rate is calculated using the following formula:

[0186] Moisture absorption rate (%) = [(mass after moisture absorption - initial mass) / initial mass] × 100%.

[0187] The higher the hydroxyl content on the surface of silicon micropowder, the greater its moisture absorption rate is usually, and the adsorbed water will significantly increase the dielectric loss of the material.

[0188] 6. Dielectric constant test

[0189] Testing instruments

[0190] Precision impedance analyzer (Keysight E4990A).

[0191] Test conditions

[0192] Frequency: 1 MHz;

[0193] Test temperature: 25℃;

[0194] Tableting pressure: 12 MPa.

[0195] Sample preparation

[0196] The powder was pressed into discs with a diameter of 20 mm and a thickness of about 2 mm before testing.

[0197] The dielectric properties of spherical SiO2 materials are closely related to their density, pore structure, and moisture absorption rate.

[0198] Table 1. Test results of particle size and morphology

[0199] D50 (μm) SPAN Sphericity (%) Example 1 8.181 1.17 97.6 Example 2 8.065 1.13 96.9 Example 3 7.994 1.06 98.1 Example 4 7.982 1.04 98.4 Comparative Example 1 8.241 1.33 95.5 Comparative Example 2 8.221 1.24 96.0 Comparative Example 3 8.205 1.20 96.4

[0200] Table 2. Results of Purity and Impurity Tests

[0201] <![CDATA[SiO₂ Purity (%)]]> Total impurities (ppm) Example 1 99.9987 0.44 Example 2 99.9991 0.38 Example 3 99.9994 0.33 Example 4 9.99996 0.30 Comparative Example 1 99.9889 0.66 Comparative Example 2 99.9915 0.54 Comparative Example 3 99.9932 0.51

[0202] Table 3. Results of density and surface properties tests

[0203] <![CDATA[Tap density (g / cm 3 )]]> Moisture absorption rate (%) Example 1 1.12 0.09 Example 2 1.18 0.07 Example 3 1.23 0.06 Example 4 1.26 0.05 Comparative Example 1 0.82 0.17 Comparative Example 2 0.99 0.13 Comparative Example 3 1.04 0.11

[0204] Table 4 Dielectric property test results

[0205] Dielectric constant (1 MHz) <![CDATA[α-rays (cph / cm 2 )]]> Example 1 3.52 0.0015 Example 2 3.49 0.0012 Example 3 3.48 0.0010 Example 4 3.44 0.0009 Comparative Example 1 4.02 0.0027 Comparative Example 2 3.91 0.0022 Comparative Example 3 3.77 0.0019

[0206] This test data table comprehensively covers four core dimensions of silicon micropowder: particle size and morphology, purity and impurities, density and surface properties, and dielectric properties. The test results show that the silicon micropowder prepared using the modified resin catalyst of this invention is significantly superior to the traditional process comparison in all core performance indicators. The improvement in core performance is directly related to the synergistic catalytic effect of each component of the modified resin catalyst and the core advantage of the catalyst being completely filtrationable, as detailed below:

[0207] D006 / A32 matrix resin: As the core framework of the catalyst, it provides stable and uniformly distributed sulfonic acid active sites. At the same time, its macroporous network structure provides a confined reaction space for the hydrolysis reaction, which can precisely control the hydrolysis and polycondensation rate of the composite silane. This avoids the problems of excessively high local concentration and runaway reaction of traditional small molecule acids, and achieves uniform oligomerization growth of siloxane precursors. Ultimately, it ensures the high sphericity and narrow particle size distribution of the product. The particle size distribution SPAN value of the example in the data table is significantly lower than that of the comparative example, and the sphericity is greatly improved.

[0208] Acrylyl chloride acylation modification component: Acrylated functional groups are introduced into the resin skeleton, which optimizes the surface polarity and pore structure of the resin, improves the resin's affinity and dispersibility for organosilane raw materials, and further enriches the distribution of active sites, making the hydrolysis oligomerization reaction more uniform and controllable, and reducing the generation of side reactions and by-products; at the same time, the modified resin skeleton structure is more stable, and no resin debris falls off during filtration, further avoiding the introduction of impurities into the product. The product purity and stability of the corresponding example in the data table are better, with no additional impurities introduced.

[0209] The ternary mixed gas plasma modification component (2-trimethylsilylpyridine, ammonia, argon): Through plasma surface treatment, silicon- and nitrogen-containing functional groups are introduced into the resin surface, further optimizing the surface energy and interfacial compatibility of the resin. At the same time, the pore structure of the resin is finely controlled, improving the mass transfer efficiency in the reaction process, making the polycondensation and cross-linking of siloxane oligomers more complete, and the internal structure of the particles more dense and uniform. The tap density of the example in the corresponding data table is significantly higher than that of the comparative example, and the moisture absorption rate is greatly reduced.

[0210] Hydrochloric acid hydrogen form conversion treatment component: Completed the restoration of the hydrogen form structure of the resin sulfonic acid group, ensuring the acidic activity and recycling stability of the catalyst. At the same time, through sufficient ion exchange and washing treatment, residual metal ions and alkaline impurities from the resin preparation process were completely removed, avoiding the introduction of impurities into the reaction system by the catalyst itself. In addition, the hydrogen form converted resin can be completely separated from the reaction system by filtration, with no acidic substances remaining, further ensuring the performance stability of the product. The dielectric constant of the corresponding embodiment in the data table is lower, and the alpha ray emission is significantly lower than that of the comparative example.

[0211] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silica micropowder, characterized in that, Includes the following steps: (1) Preparation and purification of composite silane raw materials: Weigh out 60-85 parts of tetraethoxysilane, 12-32 parts of tetramethoxysilane, and 4-12 parts of methyltrimethoxysilane by mass fraction, and distill under reduced pressure at 68-92℃ for 2-5 hours under -0.06--0.09 MPa conditions to obtain ultra-high purity composite silane raw materials. (2) Acid-catalyzed pre-hydrolysis reaction: Add 28-52 parts of deionized water, 18-36 parts of anhydrous ethanol and 0.2-0.6 parts of resin catalyst to the composite silane raw material, control the pH of the system to 1.8-3.5, and stir the reaction at 25-42℃ for 2-6 hours to allow the composite silane to undergo partial hydrolysis and oligomerization condensation to obtain a siloxane precursor sol. (3) Microemulsion dispersion into spheres: Add 4-10 parts of emulsifier, 1-4 parts of dispersant and 45-90 parts of deionized water to the siloxane precursor sol, and homogenize at high speed for 10-35 minutes at 8000-15000 rpm to form a stable microemulsion system; filter to remove resin catalyst and other impurities. (4) Alkali-catalyzed polycondensation curing: Add 8-22 parts of alkaline curing liquid to the microemulsion system to raise the pH of the system to 8.5-11.0, and continue the reaction at 30-65°C for 3-8 hours to allow the siloxane oligomers to further condense into spheres, forming spherical silica wet gel particles. (5) Aging and densification treatment: The spherical silica wet gel particles were aged at 50–85°C for 5–12 h, then washed sequentially with ultrapure water and anhydrous ethanol, filtered, and dried at 80–140°C for 4–10 h to obtain spherical silica precursor powder. (6) Dehydroxylation and calcination treatment: The spherical silicon precursor powder was heated to 850-1150°C at a rate of 3-8°C / min in an oxygen or air atmosphere, held at that temperature for 2-6 hours, and then naturally cooled to obtain ultra-high purity amorphous regular spherical silicon micropowder. The modified resin catalyst is obtained by soaking resin in acryloyl chloride solution to obtain acylated resin, followed by plasma surface modification by a mixed plasma gas composed of 2-trimethylsilylpyridine vapor, ammonia, and argon, and then by hydrochloric acid hydrogen conversion treatment.

2. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: In step (1), the purity of tetraethoxysilane is ≥99.999wt%, and the content of metal impurities is ≤0.2ppm; the purity of tetramethoxysilane is ≥99.99wt%, and the total amount of Na and K impurities is ≤0.1ppm; the purity of methyltrimethoxysilane is ≥99.9wt%.

3. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: In step (2), the modified resin catalyst is composed of any one or two of D006 resin and A32 resin.

4. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 3, characterized in that: The modified resin catalyst is prepared in the following steps: Step 1: Acryloyl chloride acylation treatment. 100 parts of one or both of D006 resin and A32 resin are washed with deionized water until neutral, and pretreated by vacuum drying at 60-80℃ for 12-24 hours. The dried resin is directly immersed in 500-600 parts of acryloyl chloride solution, with 2-5 parts of zinc chloride as the acylation catalyst, and reacted at a constant temperature for 8-12 hours. After the reaction, the resin is filtered, and residual reactants are thoroughly washed with ethanol and deionized water in sequence. The resin is then vacuum dried at 50-60℃ to obtain the acylated resin. Step 2: Ternary mixed gas plasma modification. A monolayer of acylated resin is laid flat in the plasma reaction chamber. The chamber is first evacuated to 10-50 Pa, then a mixed plasma gas consisting of 2-trimethylsilylpyridine vapor, ammonia, and argon is introduced, with a volume ratio of 0.1-0.4:0.05-0.2:1-3. The chamber pressure is stabilized to 30-80 Pa. The radio frequency plasma power is set to 80-150 W, and the surface modification treatment is performed for 5-15 minutes to obtain the plasma-modified resin. Step 3: Hydrochloric acid hydrogen form conversion treatment. The plasma-modified resin is immersed in a dilute hydrochloric acid solution for ion exchange. Hydrochloric acid is slowly added dropwise to adjust the acidity of the system and restore the sulfonic acid hydrogen form structure of the resin. After immersion, the resin is repeatedly washed with deionized water until the filtrate is neutral. After vacuum drying, it is sealed and stored to obtain the target modified resin catalyst.

5. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: The emulsifier in step (3) includes one or two of Span-80, Tween-60, and fatty alcohol polyoxyethylene ether.

6. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: The dispersant in step (3) includes one or two of polyethylene glycol, polyvinylpyrrolidone, and polyether-modified silicone oil.

7. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: In step (3), the average droplet size of the microemulsion system is 0.8–15 μm; the homogenization emulsification temperature is controlled at 20–35 °C; and the homogenization time is controlled at 15–30 min.

8. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: The alkaline curing liquid in step (4) includes one or two of ammonia, tetramethylammonium hydroxide, ethylenediamine or triethylamine.

9. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: The aging process in step (5) is carried out using a staged heating method: The first stage is aging at 50-60℃ for 2-4 hours; The second stage is aging at 65-85℃ for 3-8 hours.

10. The method for preparing composite silane hydrolysis of ultra-high purity amorphous regular spherical silicon micropowder according to claim 1, characterized in that: In step (6), the dehydroxylation calcination adopts a three-stage temperature program: The first stage involves raising the temperature to 280–380℃ at a rate of 3–5℃ / min and holding it at that temperature for 0.5–1.5 hours. The second stage involves raising the temperature to 550-750℃ at a rate of 4-6℃ / min and holding it at that temperature for 1-2 hours. The third stage involves raising the temperature to 900–1150℃ at a rate of 5–8℃ / min and holding it at that temperature for 2–5 hours.

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