Preparation method of spherical silicon dioxide micropowder with ultralow dielectric loss

Abstract

The invention relates to a preparation method of spherical silicon dioxide micropowder with ultralow dielectric loss. The preparation method comprises the following steps: preparing an organic silicon polymer; preparing slurry; performing solid-liquid separation on the synthetic slurry to obtain concentrated slurry, and drying the concentrated slurry to obtain spherical silica powder; carrying out low-temperature heat treatment on the obtained spherical silica powder at 1500-7000 DEG C for h to remove residual organic matters and free water in the powder; then, high-temperature densification is carried out at the temperature of 3000-28000 DEG C for h, and moisture is further removed; adding a modifier into the stirring equipment for surface modification; and after surface modification, drying at 55-300 DEG C for h, and removing modified micromolecular byproducts to obtain the spherical silicon dioxide micro powder with ultralow dielectric loss. The method is simple in production process, short in production period, low in production cost, high in yield and capable of effectively reducing the dielectric loss of the spherical silicon dioxide micro powder.

Description

Technical Field

[0001] The invention relates to the technical field of spherical silicon micropowder preparation, in particular to a method for preparing spherical silicon dioxide micropowder with ultra-low dielectric loss. Background Art

[0002] Spherical silicon powder is an important functional material with excellent properties such as low dielectric, high heat resistance, high filling amount, low expansion, low stress, low density, low friction coefficient and good chemical stability. It is mainly used in large-scale integrated circuit packaging. In the fields of aviation, aerospace, fine chemicals, new energy vehicles, large-area electronic substrates, special ceramics and daily cosmetics, it is mainly used in copper clad laminates (CCL) as a filler in epoxy resin systems. It can enhance the hardness and mechanical strength of the resin, reduce the thermal expansion coefficient and curing shrinkage, and stabilize the function of components; 5G products have higher requirements for the transmission loss, heat resistance and reliability of copper clad laminates, so special copper clad laminates such as high-speed copper clad laminates are required; high-speed products pay more attention to the dielectric loss (Df) of the board. The size of the dielectric loss (Df) means the attenuation degree of signal transmission. This attenuation of signal transmission is often consumed by generating heat. Signal attenuation and heat consumption will inevitably increase rapidly with high-frequency and high-speed digital signal transmission; for high-frequency and high-speed digital signal transmission, the smaller the dielectric loss (Df), the better. Therefore, with the rapid development of high-speed CCL, there will be a large demand for ultra-low loss spherical silica. How to further reduce the Df value of silica has become a current research hotspot.

[0003] Chinese patent application CN110938238B manufactures silicon dioxide by dry process, and then heats it at a temperature exceeding 200°C, so that bound water except physically adsorbed water is also removed, and then gasifies the silane compound and directly contacts the silicon dioxide particles for modification, thereby providing an electronic material filler with excellent electrical properties. However, it has the following shortcomings: if the process is not properly handled and the type of surface modifier is not properly selected, the dielectric loss reduction will fluctuate greatly and the quality will be unstable; while Chinese patent application CN114702038B uses high temperature treatment in an oxidant atmosphere to remove moisture, carbon, metal and other impurities from silicon dioxide powder, and then directly cools it to room temperature in a non-polar gas atmosphere, and finally fills it with inert gas for packaging, thereby effectively reducing its dielectric loss. However, it has the following shortcomings: a large amount of oxidant, non-polar gas and inert gas are used in the production process, so the production cost is high, the equipment process is complicated, and the packaging filled with inert gas has a large storage space and is not easy to transport. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing spherical silica micropowder with simple production process, short production cycle, low production cost and high yield, which can effectively reduce the dielectric loss of spherical silica micropowder in view of the shortcomings of the prior art.

[0005] The technical problem to be solved by the present invention is achieved by the following technical solution. The present invention is a method for preparing spherical silica powder with ultra-low dielectric loss, and the steps are as follows: (1) Preparation of silicone polymers: Under stirring conditions, the organosilane is slowly added into the acidic solution, and the organosilicon polymer is obtained through hydrolysis and condensation; (2) Preparation of slurry: The organic silicon polymer obtained in step (1) is mixed with an alkaline aqueous solution, stirred sufficiently, and cured in situ to form a synthetic slurry of spherical silica; (3) performing solid-liquid separation on the synthetic slurry to obtain concentrated slurry, and then drying the concentrated slurry to obtain spherical silicon powder; (4) subjecting the obtained spherical silicon powder to low temperature heat treatment at 1500-7000°C·h to remove residual organic matter and free water in the powder; (5) Subsequently, high-temperature densification is performed at 3000-28000°C h to further remove moisture; (6) Adding a modifier into the stirring device for surface modification; (7) After surface modification, the surface is dried at 55-300 °C h to remove the small molecular by-products after modification, thereby obtaining spherical silica powder with ultra-low dielectric loss.

[0006] The technical problem to be solved by the present invention can also be further achieved by the following technical scheme. For the method for preparing the above-mentioned spherical silica powder with ultra-low dielectric loss, in step (1), the organosilane is selected from one or a mixture of two or more of tetraethyl orthosilicate, tetraethoxysilane, methyltrimethoxysilane, triethoxymethylsilane, trimethoxyphenylsilane and tetraethoxysilane.

[0007] The technical problem to be solved by the present invention can be further achieved by the following technical solution. For the method for preparing the spherical silica powder with ultra-low dielectric loss described above, in step (1), the acidic solution is selected from hydrochloric acid or nitric acid, acetic acid, sulfuric acid, perchloric acid, oxalic acid, or a mixture of two or more thereof.

[0008] The technical problem to be solved by the present invention can be further achieved by the following technical solution. For the method for preparing the spherical silica powder with ultra-low dielectric loss described above, in step (2), the alkaline aqueous solution is selected from one or a mixture of two or more of ammonia water, ethylenediamine, isopropylamine, and ethanolamine, and the pH is greater than 8.

[0009] The technical problem to be solved by the present invention can be further achieved by the following technical solution. For the method for preparing the spherical silica powder with ultra-low dielectric loss described above, in step (3), the solid-liquid separation method is distillation at a temperature of 100-150° C. to obtain a concentrated slurry; and the drying method is spray drying.

[0010] The technical problem to be solved by the present invention can be further achieved by the following technical solution. For the method for preparing the spherical silica micropowder with ultra-low dielectric loss described above, in step (4), the organic functional groups of the spherical silica micropowder after low-temperature heat treatment disappear, the hydrophobicity is less than 1min, and the appearance is white powder.

[0011] The technical problem to be solved by the present invention can be further achieved by the following technical solution. For the method for preparing the spherical silica powder with ultra-low dielectric loss described above, in step (5), the spherical silica powder is subjected to high-temperature densification at 3000~28000℃·h, and the particle size D50 of the spherical silica powder is 0.1~5μm, and the particle size D100 is ≤10μm.

[0012] The technical problem to be solved by the present invention can be further achieved by the following technical scheme. For the method for preparing the spherical silica powder with ultra-low dielectric loss as described above, in steps (4) and (5), the equipment for low-temperature and high-temperature treatment is an oven, a push-plate furnace, a lifting furnace, a muffle furnace, a rotary kiln, a mesh belt calcining furnace, a microwave high-temperature calcining equipment, a high-temperature drum rotary kiln, a high-temperature screw belt mixed calcining integrated machine, a high-temperature flash furnace, a high-temperature air flow calcining furnace or a high-temperature tunnel furnace.

[0013] The technical problem to be solved by the present invention can be further achieved by the following technical scheme. For the method for preparing the spherical silica powder with ultra-low dielectric loss as described above, in step (6), the modifier is selected from one of vinyl triethoxysilane A151, vinyl trimethoxysilane A171, vinyl tri-β-methoxyethoxysilane A172, and hexamethyldisilazane HMDS, or a mixture of two or more thereof.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention synthesizes high-purity spherical silicon micropowder by a liquid phase method, which has a short production cycle, simple operation and high yield. During post-treatment, low-temperature heating is first performed, which can effectively remove residual organic matter on the one hand, and on the other hand, can ensure the appearance of the product, that is, the whiteness value reaches above 92, and then high-temperature densification is performed without reducing the whiteness; calcination is performed using equipment with negative pressure or other specific equipment, and gas is discharged intermittently, which can effectively avoid material agglomeration and reduce moisture content; a suitable modifier is selected to modify the surface of silicon micropowder, so that the performance of silicon micropowder is more stable, and problems such as agglomeration, polarity difference, viscosity, and poor bonding strength can be improved, and the silicon micropowder is effectively combined with resin to reduce hydroxyl content, expansion rate, dielectric constant, dielectric loss, etc., wherein the mass percentage of hydroxyl before modification is 0.00843%, and the mass percentage of hydroxyl after modification is 0.00498%, and the effect is remarkable; 2. The method of the present invention has a simple production process, a short production cycle, a low production cost, and a high yield. It can effectively reduce the dielectric loss of spherical silica powder, prepare a resin composition, and measure the dielectric loss tangent (Df) of the cured material of the obtained resin composition to be ≤0.0002 (10GHz), which belongs to the M8 and M8+ levels, and the product quality is stable and controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is an electronic scanning image of the high-purity spherical silicon powder prepared by the present invention; Figure 2 The particle size diagram of the spherical silica powder prepared by the present invention; Figure 3 This is an electronic scanning image of the ultra-low dielectric loss spherical silica powder prepared by the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The invention principle of the method for preparing the spherical silicon dioxide powder with ultra-low dielectric loss provided by the present invention is as follows: firstly, spherical silicon is synthesized by chemical method, and the generation of initial particles can be accurately controlled by adjusting reaction conditions, such as pH, temperature, concentration, reaction time and other parameters, and the initial particles are concentrated and spray-dried, and the sol is rapidly evaporated by high-speed hot air flow to solidify into spherical particles; in addition, the spherical silicon obtained by chemical method can reduce the introduction of impurities, has high purity, good sphericity and surface smoothness; secondly, through low-temperature heat treatment, the residual organic matter can be slowly released to ensure the whiteness value of the product, and the organic matter will not be directly carbonized due to excessively high temperature; Subsequently, in order to further reduce the DK and DF values, high-temperature calcination is required. Agglomeration is easy to occur at high temperatures. Calcination by negative pressure or other specific equipment and intermittent exhaust of gas can effectively avoid material agglomeration and reduce moisture content, thereby achieving the desired effect. Finally, in order to further improve the electrical properties of silicon micropowder, surface modification can be used. The mechanism is as follows: the surface of silicon micropowder is modified by silane coupling agent to improve its interfacial bonding with the organic polymer matrix, thereby enhancing the electrical insulation and thermal conductivity of the composite material. One end of the silane coupling agent can react with the hydroxyl group on the surface of silicon micropowder to form a chemical bond, and the other end can form a covalent bond with the resin molecule or increase the interaction force through physical entanglement, thereby improving the overall electrical performance stability and anti-aging ability of the material. In summary, the present invention can improve the electrical properties of silicon micropowder at the micro and macro levels by means of particle size control, purification, morphology regulation, moisture control and surface modification, so as to make it better adapt to the manufacturing needs of various electronic materials and devices.

[0018] Embodiment 1, the specific steps of preparation include: Step 1, 1kg of purified tetraethyl orthosilicate, 200g of pure water and a small amount of hydrochloric acid are stirred evenly in a reactor to obtain an organosilicon polymer after hydrolysis and condensation, 15% aqueous ammonia solution is added to the reactor, and stirred sufficiently to allow the organosilicon polymer to react with the alkali and solidify, and aged for 20 hours, and solid-liquid separation is performed by distillation to obtain a concentrated slurry; and then the slurry is dried by spray drying. The electronic scanning imaging picture of the high-purity spherical silicon powder prepared by the above steps is as shown Figure 1 As shown, the spheroidization rate is over 90%; Step 2, subjecting the spherical silicon powder obtained in step 1 to low-temperature heat treatment at 2400° C. h to fully release its organic matter in the form of gas; Step 3, the spherical silicon powder after low temperature heat treatment is calcined in a high temperature device at 3900℃·h. The particle size D50 of the spherical silicon dioxide powder is 0.1 ~ 5μm, and the particle size D100 is ≤10μm. The particle size diagram is as shown in Figure 2 As shown; Step 4, placing the filler into a solid high-speed stirrer (high-speed solid stirrer HENSHEL or V-type solid stirrer, etc.), and spraying vinyl triethoxysilane directly on the filler and stirring; after the modification is completed, drying at 240° C.·h in the high-speed stirrer, and sealing and packaging in an aluminum foil bag; The electron scanning imaging picture of the silicon dioxide powder is as follows Figure 3 As shown; Its moisture, isolated hydroxyl group, dielectric constant (Dk), and dielectric loss (Df) are shown in Table 1: Table 1 Measured values ​​of moisture, isolated hydroxyl group, dielectric constant (Dk), and dielectric loss (Df) of the silicon dioxide powder

[0019] Embodiment 2, the specific steps of preparation include: Step 1, 1 kg of purified tetraethoxysilane, 200 g of pure water and a small amount of hydrochloric acid are stirred evenly in a reactor to obtain an organosilicon polymer after hydrolysis and condensation, 18% aqueous solution of ethylenediamine is added to the reactor, and stirred sufficiently to allow the organosilicon polymer to react with the alkali to solidify, aged for 20 hours, and separated from the solid by distillation to obtain a concentrated slurry; and then the slurry is dried by spray drying.

[0020] Step 2, subjecting the spherical silicon powder obtained in step 1 to low-temperature heat treatment at 2500° C. h to fully release its organic matter in the form of gas; Step 3, calcining the spherical silicon powder after low temperature heat treatment in a high temperature device at 4000°C·h; Step 4, placing the filler into a solid high-speed stirrer (high-speed solid stirrer HENSHEL or V-type solid stirrer, etc.), and spraying vinyl triethoxysilane directly on the filler and stirring; after the modification is completed, drying at 240° C.·h in the high-speed stirrer, and sealing and packaging with an aluminum foil bag, the mass percentage of hydroxyl group of the silicon dioxide powder is 0.0056%.

[0021] Embodiment 3, the specific steps of preparation include: Step 1, 1 kg of purified methyltrimethoxysilane, 150 g of pure water and a small amount of hydrochloric acid are stirred evenly in a reactor to obtain an organosilicon polymer after hydrolysis and condensation, 15% ethanolamine aqueous solution is added to the reactor, and stirred sufficiently to allow the organosilicon polymer to react with the base to solidify, and aged for 20 hours, and solid-liquid separation is performed by distillation to obtain a concentrated slurry, and then the slurry is dried by spray drying; Step 2, subjecting the spherical silicon powder obtained in step 1 to low-temperature heat treatment at 3000° C. h to fully release its organic matter in the form of gas; Step 3, calcining the spherical silicon powder after low temperature heat treatment in a high temperature device at 5000°C·h; Step 4, placing the filler into a solid high-speed stirrer (high-speed solid stirrer HENSHEL or V-type solid stirrer, etc.), and spraying vinyltrimethoxysilane directly on the filler and stirring, the higher the speed, the better the dispersion effect; after the modification is completed, drying at 280°C·h in the high-speed stirrer, and sealing and packaging with aluminum foil bags, the mass percentage of hydroxyl group of the silicon dioxide powder is 0.0061%.

[0022] Embodiment 4, the specific steps of preparation include: Step 1, 1 kg of purified triethoxymethylsilane, 180 g of pure water and a small amount of hydrochloric acid are stirred evenly in a reactor to obtain an organosilicon polymer after hydrolysis and condensation, 15% isopropylamine aqueous solution is added to the reactor, and stirred sufficiently to allow the organosilicon polymer to react with the base to solidify, aged for 25 hours, and separated the solid and liquid by distillation to obtain a concentrated slurry, and then the slurry is dried by spray drying; Step 2, subjecting the spherical silicon powder obtained in step 1 to low-temperature heat treatment at 4000° C. h to fully release its organic matter in the form of gas; Step 3, calcining the spherical silicon powder after low temperature heat treatment in a high temperature device at 6000°C·h; Step 4, placing the filler into a solid high-speed stirrer (high-speed solid stirrer HENSHEL or V-type solid stirrer, etc.), and spraying vinyltrimethoxysilane directly on the filler and stirring, the higher the speed, the better the dispersion effect; after the modification is completed, drying at 180°C·h in the high-speed stirrer, and sealing and packaging with an aluminum foil bag, the mass percentage of hydroxyl group of the silicon dioxide powder is 0.0054%.

[0023] Example 5, the specific steps of preparation include: Step 1, 1 kg of purified trimethoxyphenylsilane, 150 g of pure water and a small amount of hydrochloric acid are stirred evenly in a reactor to obtain an organosilicon polymer after hydrolysis and condensation, 15% of an aqueous solution of ethylenediamine is added to the reactor, and the mixture is stirred sufficiently to allow the organosilicon polymer to react with the base to solidify, and aged for 25 hours, and solid-liquid separation is performed by distillation to obtain a concentrated slurry, and then the slurry is dried by spray drying; Step 2, subjecting the spherical silicon powder obtained in step 1 to low-temperature heat treatment at 4800° C. h to fully release its organic matter in the form of gas; Step 3, calcining the spherical silicon powder after low temperature heat treatment in a high temperature device at 6500°C·h; Step 4, putting the filler into a solid high-speed stirrer (high-speed solid stirrer HENSHEL or V-type solid stirrer, etc.), and spraying vinyltrimethoxysilane directly on the filler and stirring. The higher the speed, the better the dispersion effect. After the modification is completed, drying at 280°C·h in the high-speed stirrer and sealing and packaging with aluminum foil bags. The mass percentage of hydroxyl group of the silicon dioxide powder is 0.00507%.

[0024] Comparative Example 1, using an average particle size of 15 μm and a hydroxyl content of 370 ppm as a raw material, heated in a muffle furnace at 900°C for 5 hours. After cooling to room temperature, the heat-treated silicon dioxide powder was placed in alkaline electrolyzed water with a pH of 13, heated at 60°C, stirred for 2 hours, centrifuged and washed with methanol and dried, the dried silicon dioxide was crushed with a ball mill, and sieved with a 150-mesh sieve. The mass percentage of hydroxyl groups in the silicon dioxide powder was 0.0270%.

[0025] Comparative Example 2, using an average particle size of 1.5 μm and a hydroxyl content of 290 ppm as raw material, heated in a muffle furnace at 900°C for 12 hours. After cooling to room temperature, the heat-treated silicon dioxide powder was placed in alkaline electrolyzed water with a pH of 13, heated at 60°C, stirred for 2 hours, centrifuged, washed and dried with methanol, and the mass percentage of hydroxyl in the silicon dioxide powder was 0.0240%.

[0026] Comparative Example 3, using an average particle size of 0.1 μm and a hydroxyl content of 475 ppm as raw material, heated in a muffle furnace at 900°C for 12 hours. After cooling to room temperature, the heat-treated silicon dioxide powder was placed in alkaline electrolyzed water with a pH of 13, heated at 60°C, stirred for 2 hours, centrifuged, washed and dried with methanol, and the mass percentage of hydroxyl groups in the silicon dioxide powder was 0.0135%.

[0027] Comparative Example 4, with an average particle size of 15 μm as raw material, heated to 100°C in a muffle furnace. After being kept in air at 400°C for 12 hours and cooled to room temperature, the heat-treated silicon dioxide powder was placed in alkaline electrolyzed water with a pH of 13, heated to 60°C, stirred for 2 hours, centrifuged and washed and dried with methanol, the dried silicon dioxide was crushed with a ball mill, and sieved with a 150-mesh sieve. The mass percentage of hydroxyl groups in the silicon dioxide powder was 0.0355%.

[0028] In comparative example 5, the average particle size of 15 μm was used as the raw material, and the raw material was heated to 100°C in a muffle furnace. After being kept in air at 900°C for 10 minutes and cooled to room temperature, the heat-treated silicon dioxide powder was placed in alkaline electrolyzed water with a pH of 13, heated to 60°C, stirred for 2 hours, washed and dried with methanol after centrifugation, and the dried silicon dioxide was crushed with a ball mill and sieved with a 150-mesh sieve. The mass percentage of hydroxyl groups in the silicon dioxide powder was 0.0365%.

[0029] Table 2 Performance results of various examples and comparative examples

[0030] It can be seen that the method for preparing the spherical silica powder with ultra-low dielectric loss provided by the present invention can effectively reduce the hydroxyl content and dielectric loss of the spherical silica powder, and the effect is remarkable.

Claims

1. A method for preparing spherical silica powder with ultra-low dielectric loss, characterized in that: The steps are as follows: (1) Preparation of silicone polymers: Under stirring conditions, the organosilane is slowly added into the acidic solution, and the organosilicon polymer is obtained through hydrolysis and condensation; (2) Preparation of slurry: The obtained in step (1) is mixed with an alkaline aqueous solution, stirred sufficiently, and solidified in situ to form a synthetic slurry of spherical silica; (3) performing solid-liquid separation on the synthetic slurry to obtain concentrated slurry, and then drying the concentrated slurry to obtain spherical silicon powder; (4) subjecting the obtained spherical silicon powder to low temperature heat treatment at 1500-7000°C·h to remove residual organic matter and free water in the powder; (5) Subsequently, high-temperature densification is performed at 3000-28000°C h to further remove moisture; (6) Adding a modifier into the stirring device for surface modification; (7) After surface modification, the surface is dried at 55-300 °C h to remove the small molecular by-products after modification, thereby obtaining spherical silica powder with ultra-low dielectric loss.

2. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1, characterized in that: In step (1), the organosilane is selected from tetraethyl orthosilicate, tetraethoxysilane, methyltrimethoxysilane, triethoxymethylsilane, trimethoxyphenylsilane, tetraethoxysilane, or a mixture of two or more thereof.

3. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1 or 2, characterized in that: In step (1), the acidic solution is selected from hydrochloric acid or nitric acid, acetic acid, sulfuric acid, perchloric acid, oxalic acid, or a mixture of two or more thereof.

4. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1, characterized in that: In step (2), the alkaline aqueous solution is selected from one or a mixture of two or more of ammonia water, ethylenediamine, isopropylamine, and ethanolamine, and the pH value is greater than 8.

5. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1, characterized in that: In step (3), the solid-liquid separation method is distillation at a temperature of 100-150° C. to obtain a concentrated slurry; the drying method is spray drying.

6. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1, characterized in that: In step (4), the organic functional groups of the spherical silica powder after the low-temperature heat treatment disappear, the hydrophobicity is less than 1min, and the appearance is white powder.

7. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1, characterized in that: In step (5), the spherical silica powder is subjected to high temperature densification at 3000-28000°C·h, and the particle size D50 of the spherical silica powder is 0.1-5 μm, and the particle size D100 is ≤10 μm.

8. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1, characterized in that: In steps (4) and (5), the equipment for low-temperature and high-temperature treatment includes an oven, a push-plate furnace, a lifting furnace, a muffle furnace, a rotary kiln, a mesh belt calcining furnace, a microwave high-temperature calcining equipment, a high-temperature drum rotary kiln, a high-temperature screw belt mixed calcining integrated machine, a high-temperature flash furnace, a high-temperature air flow calcining furnace or a high-temperature tunnel furnace.

9. The method for preparing spherical silica powder with ultra-low dielectric loss according to claim 1, characterized in that: In step (6), the modifier is selected from one or a mixture of two or more of vinyl triethoxysilane A151, vinyl trimethoxysilane A171, vinyl tri-β-methoxyethoxysilane A172, and hexamethyldisilazane HMDS.

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