WO2021253727A1

WO2021253727A1 - Method for preparing low dielectric hollow silica microsphere

Info

Publication number: WO2021253727A1
Application number: PCT/CN2020/131907
Authority: WO
Inventors: 尹亚玲; 郑海涛; 沈晓燕
Original assignee: 苏州锦艺新材料科技有限公司
Priority date: 2020-06-18
Filing date: 2020-11-26
Publication date: 2021-12-23
Also published as: CN113816388A; CN113816388B

Abstract

A method for preparing a low dielectric hollow silica microsphere. In the method, polystyrene is used as a template of the hollow microsphere, and a cationic comonomer, i.e. acryloyloxyethyl trimethyl ammonium chloride (DAC) is added to introduce positively charged groups into polymer chains so as to prepare positively charged polystyrene spheres. The present method does not need to add an activator, so that the surface of the spheres can be positively charged by itself to attract a silicon source to be uniformly coated on the template. By means of this calcination method, a dense spherical structure can be obtained. The microsphere prepared by the template method for preparing a silica microsphere has a high conglomeration rate, is dense and difficult to break, and has a low dielectric constant and an improved substrate modulus and heat resistance, making it particularly suitable for the needs of the copper clad plate industry.

Description

Preparation method of low-dielectric hollow silicon dioxide microspheres

Technical field

The invention relates to the technical field of non-metallic materials, in particular to a method for preparing hollow silica microspheres by using styrene polymerization to prepare polystyrene microspheres as a template body.

Background technique

Hollow silica microspheres are multi-scale and multi-level nanostructures with hollow cavities composed of nanoparticles, ranging in size from nanometers to micrometers. Compared with the corresponding bulk materials, it has a larger specific surface area, a smaller density, and special mechanical, optical, electrical and other physical properties and application values.

As a nano-scale inorganic material, silica microspheres have excellent characteristics such as low density, low thermal expansion coefficient, high insulation, low dielectric constant, and stable chemical properties in the filler used in copper clad laminates, and have a very broad application field. Especially in the integrated circuit packaging and copper clad laminate industries, hollow silica is used as a key core raw material, especially the application of this hollow structure silica filler to the copper clad laminate, which can not only reduce the cost, but also reduce its thermal expansion coefficient and improve the substrate Modulus and heat resistance, etc.

The methods for preparing hollow silica microspheres in the prior art include template method, gel method, microemulsion method and the like.

A Chinese invention patent with the publication number CN110775981A titled silica microspheres and its manufacturing method discloses a method for preparing silica microspheres by a template method. For details, please refer to the description in paragraph 008 of the specification "In order to produce micro-nano silica microspheres by using a template agent, the inventors have conducted in-depth research and tried to use various templates to produce micro-nano silica microspheres, and found that By using a graft copolymer of branched polyethyleneimine (hereinafter also referred to as bPEI) and polyalkyl methacrylate as a template, the particle size can be obtained at the micro-nano level, and the particle size distribution is uniform In addition, the particle size of the obtained silica microspheres can be controlled by changing the concentration of the graft copolymer during the manufacture of silica microspheres, thus completing the present invention". It can be seen that in this invention, tool compounds are used as template spheres to prepare silica microspheres to achieve the purpose of uniform particle size distribution and particle size control. But the disadvantage is that there are more mesopores on the surface of the silica prepared by this method, so the dielectric constant is higher.

In the publication number CN110683552A, the method for preparing nano-silica microspheres with a particle size of 10-20 nm discloses the preparation of silica microspheres by the gel method. For details, please refer to the description in paragraph 006 of the manual "A method for preparing nano-silica microspheres with a particle size of 10-20nm. First, dissolve ethyl orthosilicate in ethanol to prepare solution A, and dissolve ammonia in ethanol. To form solution B, dissolve the dispersant in ethanol to make solution C; then add solution A and solution C dropwise to solution B at the same time to react to obtain a wet gel; the wet gel is dried and foamed at a constant temperature in an air atmosphere to obtain a dry Gel and xerogel are calcined in an air atmosphere to obtain nano-silica microspheres.” However, the particle size and wall thickness of the hollow silica microspheres prepared by this method are difficult to control. The sol-gel method first Functionalization of the surface of the template particles generally involves adding a surfactant, self-assembly to the surface of the template particles, and then using silane hydrolysis/condensation to form a silica layer on the surface of the template. Finally, the hollow microspheres also need to be calcined to remove the template. Because the surfactant needs to be added, and the amount of the surfactant is difficult to control, it is easy to carry out the uniform nucleation of silica in the solution, instead of polymerizing into balls on the surface of the template, but polycondensing into balls in the solution.

In the publication number CN110482558A named as a method for preparing silica microspheres, a method for preparing silica microspheres by a microemulsion method is disclosed. For details, please refer to the description in paragraph 0027 of the manual "The precursor solution is sprayed to form uniform droplets by jet flow, and dispersed in the seed suspension. The polymer seed quickly absorbs the droplets and grows. After the reaction, a silica composite is obtained. The porous silica microspheres are calcined to obtain porous silica microspheres. Because the precursor solution of the present invention has a uniform particle size, it is easier to be completely absorbed by polymer seeds, which reduces the time required for the entire preparation process and improves production efficiency. "This invention patent uses the difference in polarity between silane and different solvents (including supercritical substances), under the action of surfactants, to obtain oil-in-water or water-in-oil emulsions to form a "pool" in the droplets. It is a micro-reaction vessel that uses interface chemical reactions to hydrolyze and condense silane on the surface of micro-droplets, and form hollow-structure silica microspheres after heat treatment. The control of the thickness, surface morphology and particle size of the hollow microsphere shell is achieved through the dynamic balance of surface tension and hydrostatic power. Because surface tension and hydrostatic power are related to the nature of the substance and the external environment Therefore, the preparation of hollow microspheres by the microemulsion method is susceptible to the constraints of process conditions and their own properties. Because of its too many influencing factors, its structure control is complicated. Therefore, this method is difficult to obtain hollow microspheres with uniform particle size and uniform wall thickness.

The applicant further researched that the preparation of hollow silica microspheres in addition to ensuring that the particle size distribution of the silica microspheres is uniform and does not cause agglomeration and other general requirements. It is also necessary to ensure that the wall thickness of the hollow microspheres is properly prevented from breaking through the sphere wall due to the gas pressure generated by the gasification of the internal template body during the calcination process. At the same time, the applicant found that the dielectric constant of the silica microspheres is affected by two factors in terms of the sphere structure, one is the hollow structure of the silica, and the other is the density of the surface of the silica. The former needs to control the wall thickness of the silica microspheres to achieve a proper hollow structure, and the latter needs to control the calcination process to make the silica surface dense. Based on this, the applicant provides a method for preparing hollow silica to achieve the purpose of preparing silica with a low dielectric constant.

Summary of the invention

In order to solve the above technical problems, the present invention provides a method for preparing low-dielectric hollow silica microspheres. Its purpose is to provide a method with good dispersibility, uniform particle size distribution, appropriate wall thickness and low dielectric constant. Preparation method of hollow silica microspheres.

A method for preparing low-dielectric hollow silica microspheres,

Step 1. Prepare a template ball solution. The template ball solution includes 1-6% by mass polyvinylpyrrolidone, 5-25% by mass styrene, and 0.2-1.2% by mass azobisisobutyl. Nitrile, a cationic comonomer with a mass percentage of 0.01-10% acryloyloxyethyltrimethylammonium chloride, water and ethanol;

Step two, prepare the template ball dispersion, stir the solution obtained in step one uniformly and then pour nitrogen into it for 10-30 minutes, heat the solution to 50-80°C and continue stirring for 10-30 hours to obtain the template ball dispersion;

Step 3: Prepare the hydrolysis solution of the organosilicon source, add an acidic catalyst to the methyltrimethoxysilane solution at a temperature of 30-50°C and stir for 2-5h at a stirring speed of 200-400r/min so that the pH of the solution is at 3-4;

Step 4: Preparation. Add a certain amount of alkaline catalyst to the template ball dispersion in step 2, and stir for 3-10 minutes to make the pH value of the template ball dispersion at 10-12;

Step 5: Add the organosilicon source hydrolysis solution prepared in Step 3 to Step 4, and after stirring, let it stand at room temperature for 6-24 hours;

Step 6. After washing the filtered solution, the filtered material is placed in an oven at 40-70° C., baked and dried, and then calcined to prepare silica microspheres.

Preferably, the filter in the step 6 is first heated to 400-600°C at 0.3°C/min and kept for 2-4 hours, and then heated to 800-1000°C at 3°C/min.

Preferably, the prepared silica microspheres have a wall thickness of 50-200nm and a particle size of 0.3-3um. Preferably, the acid catalyst in the third step is hydrochloric acid.

Preferably, the basic catalyst in the step 4 is ammonia water.

Preferably, the mass ratio of water and ethanol in the first step is 1:9.

Preferably, the solid content in the template ball dispersion in the second step is 10-30%.

Preferably, the mass ratio of methyltrimethoxysilicon to water in the trimethyltrimethoxysilane solution in the said step is 1:5-25.

Preferably, the mass ratio of the basic catalyst to methyltrimethylsilane in the fifth step is 1:5.

Preferably, the filtrate in the step 6 is first heated to 550°C at 0.3°C/min and kept for 3 hours, and then heated to 950°C at 3°C/min.

A copper clad laminate is prepared by applying the silica microspheres prepared by the above method as a filler.

The invention provides a method for preparing low-dielectric hollow silica microspheres, and its beneficial effects are:

1. The preparation method can obtain low-dielectric hollow silica microspheres with a controllable wall thickness and a smooth and compact surface. The invention adopts a hard template method to prepare hollow silica microspheres, and polystyrene (PS) microspheres are used as template spheres, which are not easy to deform and break. Through one feeding and adding the cationic comonomer acryloxyethyl trimethyl ammonium chloride (DAC), positively charged groups are introduced into the polymer chain to prepare positively charged polystyrene spheres. The positively charged polystyrene spheres are obtained by using the cationic comonomer acryloxyethyltrimethylammonium chloride (DAC) as the comonomer. This ensures that the polystyrene spheres can quickly capture the generated silica sol through electrostatic interaction, without the need to add cationic surfactants for surface modification in the later stage, and avoid the direct and uniform nucleation of silica in the solution.

2. In the choice of silicon source, choose methyl trimethoxysilane (MTMS) as the silicon source. There is a methyl group in the molecular structure, and the presence of methyl can prevent the silane from agglomeration during the condensation polymerization process, which is beneficial to obtain The hydrolysis and polycondensation process of monodisperse hollow silica microspheres is carried out at a relatively low temperature without stirring and can be left standing, which can effectively reduce the energy consumption in the reaction process.

3. The calcination process of the present invention can make the surface of the calcined hollow silica microspheres compact, without holes, and have a low dielectric constant. In the present invention, the temperature is increased to 400-600°C at 0.3°C/min and kept for 2-4 hours, and the temperature is continued to rise to 800-1000°C at 3°C/min. The purpose is to control the calcination temperature of the polystyrene microspheres after heating the phase change gas volatilization The rate is controlled within a proper range, it is not easy to break through the shell layer and cause the ball to be broken, and at the same time, the surface of the ball is more dense under the calcination of this process. At the same time, control the wall thickness and particle size by adjusting the ratio of ammonia water and organic silicon source.

Description of the drawings

FIG. 1 is a scanning electron micrograph of hollow silica microspheres prepared under the process conditions of Example 1 of the present invention.

2 is a scanning electron micrograph of hollow silica microspheres prepared under the process conditions of Example 2 of the present invention.

3 is a scanning electron micrograph of hollow silica microspheres prepared under the process conditions of Example 3 of the present invention.

4 is a scanning electron microscope image of hollow silica microspheres prepared under the process conditions of Example 4 of the present invention.

5 is a scanning electron microscope image of hollow silica microspheres prepared under the process conditions of Example 5 of the present invention.

6 is a scanning electron micrograph of hollow silica microspheres prepared under the process conditions of Example 6 of the present invention.

FIG. 7 is a scanning electron micrograph of hollow silica microspheres prepared under the process conditions of Example 7 of the present invention.

detailed description

Hereinafter, the present invention will be described in detail with reference to the specific embodiments shown in the drawings. But these implementations do not limit

In the present invention, the structural, method, or functional changes made by those of ordinary skill in the art according to these embodiments are all

It is included in the protection scope of the present invention.

Example one:

Step 1.1, dissolve 1.5g polyvinylpyrrolidone, 45g ethanol, 5g distilled water, 15g styrene, 0.29g initiator azobisisobutyronitrile for 10 minutes, and then put it into a 250mL three-necked flask (including nitrogen inlet, stirring blade inlet and condensation口), stir at room temperature to form a homogeneous solution;

Step 1.2, deoxygenate the homogeneous solution by bubbling nitrogen at room temperature for 30 minutes, and then heat to 70°C and continue to stir and react for 24 hours to obtain a polystyrene ball dispersion;

Step 1.3: Add 10g of methyltrimethoxysilane to 50ml of water and mix uniformly. After heating to 35°C, add hydrochloric acid, with a pH of 3, and continue to stir for 3h to obtain an organosilane precursor hydrolysate;

Step 1.4: Add 2g cetyltrimethylammonium bromide (CTAB) and 3ml ammonia to the polystyrene ball dispersion obtained in step 1.2, stir for 6min, and add the organic silicon source precursor hydrolyzate prepared in step 1.3 , Stop stirring, and let stand at room temperature for 8h;

Step 1.5, filter the solution obtained in step 1.4, wash it with distilled water and ethanol, and then put it in an oven at 50℃ to dry for 3h, then in a muffle furnace at 0.3℃/min to 550℃ and keep it for 3h to remove the polystyrene balls After that, the temperature was continued to rise to 950°C at 3°C/min to obtain low-dielectric hollow silica microspheres with a smooth and compact surface.

As shown in Figure 1, Figure 1 is a hollow dioxide prepared by adding CTAB to the surface of the polystyrene ball without adding acryloyloxyethyltrimethylammonium chloride during the synthesis of the polystyrene ball. Scanning electron micrograph of silicon microspheres.

The figure shows that the particle size of the sphere is not uniform, and self-aggregation occurs on the surface of the sphere. The measured dielectric constant is 3.0.

Example two

Step 2.1, after ultrasonic dissolving 1.5g polyvinylpyrrolidone, 45g ethanol, 5g distilled water, 15g styrene, 0.29g initiator azobisisobutyronitrile and cationic comonomer acryloxyethyltrimethylammonium chloride for 10 minutes Put it into a 250mL three-necked flask (including nitrogen inlet, stirring blade inlet and condenser), and stir at room temperature to form a homogeneous solution;

Step 2.2, deoxygenate the homogeneous solution by bubbling nitrogen at room temperature for 30 minutes, then heat to 70°C and continue to stir and react for 24 hours to obtain a positively charged polystyrene ball dispersion;

Step 2.3: Add 5g of methyltrimethoxysilane to 50ml of water and mix evenly, add hydrochloric acid after raising the temperature to 35°C, adjust the pH to 3, and continue to stir for 3h to obtain the organosilane precursor hydrolysate;

Step 2.4: Add 3 ml of ammonia to the polystyrene ball dispersion obtained in step 2.2, stir for 6 minutes, add the organic silicon source precursor hydrolyzate prepared in step 2.3, stop stirring, and let stand at room temperature for 8 hours;

Step 2.5, filter the solution obtained in step 2.4, wash it with distilled water and ethanol respectively, and then put it in an oven at 50℃ to dry for 3h, and then in a muffle furnace at 0.3℃/min to 550℃ and keep it for 3h to remove the polystyrene balls After that, the temperature was continued to rise to 950°C at 3°C/min to obtain low-dielectric hollow silica microspheres with a smooth and compact surface. As shown in Figure 2, Figure 2 is a scanning electron micrograph of hollow silica microspheres prepared by adding acryloyloxyethyltrimethylammonium chloride during the synthesis of polystyrene spheres.

Compared with Example 1, after adding 5g of methyltrimethoxysilane in Example 2, the wall thickness of the sphere is 30nm, the particle size of the sphere is uniform, and the surface of the sphere is smooth without self-aggregation. However, because the wall thickness is too thin, the ball is broken. Phenomenon, the measured dielectric constant is 3.3.

Example three

Step 3.1, after ultrasonic dissolving 1.5g polyvinylpyrrolidone, 45g ethanol, 5g distilled water, 15g styrene, 0.29g initiator azobisisobutyronitrile and cationic comonomer acryloxyethyltrimethylammonium chloride for 10 minutes Put it into a 250mL three-necked flask (including nitrogen inlet, stirring blade inlet and condenser), and stir at room temperature to form a homogeneous solution;

Step 3.2, deoxygenate the homogeneous solution by bubbling nitrogen at room temperature for 30 minutes, then heat to 70°C and continue to stir the reaction

24h, obtain a positively charged polystyrene ball dispersion;

Step 3.3, add 8g of methyltrimethoxysilane to 50ml of water and mix uniformly, add hydrochloric acid after raising the temperature to 35°C, adjust the pH to 3, and continue to stir for 3h to obtain the organosilane precursor hydrolysate;

Step 3.4, add 3ml of ammonia to the polystyrene ball dispersion obtained in step 3.2, stir for 6min, add the organosilicon source precursor hydrolysate prepared in step 3.3, stop stirring, and let stand at room temperature for 8h;

Step 3.5, filter the solution obtained in step 3.4, wash it with distilled water and ethanol, and then put it in an oven at 50℃ to dry for 3h, then in a muffle furnace at 0.3℃/min to 550℃ and keep it warm for 3h to remove the polystyrene balls After that, the temperature was continued to rise to 950°C at 3°C/min to obtain low-dielectric hollow silica microspheres with a smooth and compact surface. As shown in Figure 3, Figure 3 is a scanning electron micrograph of hollow silica microspheres prepared by adding acryloyloxyethyltrimethylammonium chloride during the synthesis of polystyrene spheres.

Compared with Example 2, after adding 8 g of methyltrimethoxysilane in Example 3, the wall thickness of the sphere is 50 nm, the particle size of the sphere is uniform, and the surface of the sphere is smooth without self-polymerization, and the measured dielectric constant is 2.5.

Embodiment four

Step 4.1, after ultrasonic dissolving 1.5g polyvinylpyrrolidone, 45g ethanol, 5g distilled water, 15g styrene, 0.29g initiator azobisisobutyronitrile and cationic comonomer acryloxyethyltrimethylammonium chloride for 10 minutes Put it into a 250mL three-necked flask (including nitrogen inlet, stirring blade inlet and condenser), and stir at room temperature to form a homogeneous solution;

Step 4.2, deoxygenate the homogeneous solution by bubbling nitrogen at room temperature for 30 minutes, and then heat to 70°C and continue to stir and react for 24 hours to obtain a positively charged polystyrene ball dispersion;

Step 4.3, add 10g of methyltrimethoxysilane to 50ml of water and mix uniformly, add hydrochloric acid after raising the temperature to 35°C, adjust the pH to 3, and continue to stir for 3h to obtain the organosilane precursor hydrolyzate;

Step 4.4, add 3ml of ammonia to the polystyrene ball dispersion obtained in step 4.2, stir for 6min, add the organosilicon source precursor hydrolyzate prepared in step 4.3, stop stirring, and let stand for 8h at room temperature;

Step 4.5, filter the resulting solution, wash it with distilled water and ethanol, and then put it in an oven at 50°C to dry for 3 hours, and then heat it in a muffle furnace at 0.3°C/min to 550°C and keep it warm for 3 hours to remove the polystyrene balls. Continue to heat up to 950°C at 3°C/min to obtain low-dielectric hollow silica microspheres with a smooth and compact surface. As shown in FIG. 4, FIG. 4 is a scanning electron micrograph of hollow silica microspheres prepared with a methyltrimethylsilane addition amount of 10 g.

In implementation 4, the addition ratio of methyltrimethoxysilane was increased, the wall thickness of the sphere was 80nm, the sphere had a uniform particle size, and the surface was smooth without self-polymerization. The measured dielectric constant was 2.3.

Embodiment five

Step 5.1, after ultrasonic dissolving 1.5g polyvinylpyrrolidone, 45g ethanol, 5g distilled water, 15g styrene, 0.29g initiator azobisisobutyronitrile and cationic comonomer acryloxyethyltrimethylammonium chloride for 10 minutes Put it into a 250mL three-necked flask (including nitrogen inlet, stirring blade inlet and condenser), and stir at room temperature to form a homogeneous solution;

Step 5.2: Deoxygenate the homogeneous solution by bubbling nitrogen at room temperature for 30 minutes, then heat to 70°C and continue to stir and react for 24 hours to obtain a positively charged polystyrene ball dispersion;

Step 5.3: Add 15g of methyltrimethoxysilane to 50ml of water and mix uniformly. After heating to 35°C, add hydrochloric acid, adjust the pH to 3, and continue to stir for 3h to obtain the organosilane precursor hydrolysate;

Step 5.4: Add 3 ml of ammonia to the polystyrene ball dispersion obtained in step 5.2, stir for 6 min, add the organic silicon source precursor hydrolyzate prepared in step 5.3, stop stirring, and let stand at room temperature for 8 hours;

Step 5.5, filter the resulting solution, wash it with distilled water and ethanol once, and then put it in an oven at 50℃ to dry for 3h, and then heat it in a muffle furnace at 0.3℃/min to 550℃ and keep it for 3h to remove the polystyrene balls. Continue to heat up to 950°C at 3°C/min to obtain low-dielectric hollow silica microspheres with a smooth and compact surface. As shown in Fig. 5, Fig. 5 is a scanning electron micrograph of hollow silica microspheres prepared with 15 g of methyltrimethylsilane added.

In Example 5, the addition ratio of methyltrimethoxysilane continued to increase, the wall thickness of the sphere was 100 nm, the particle size of the sphere was uniform, and the surface was smooth without self-polymerization. The measured dielectric constant was 1.9.

Example Six

Step 6.1, after ultrasonically dissolving 1.5g polyvinylpyrrolidone, 45g ethanol, 5g distilled water, 15g styrene, 0.29g initiator azobisisobutyronitrile and cationic comonomer acryloxyethyltrimethylammonium chloride for 10 minutes Put it into a 250mL three-necked flask (including nitrogen inlet, stirring blade inlet and condenser), and stir at room temperature to form a homogeneous solution;

Step 6.2, deoxygenate the homogeneous solution by bubbling nitrogen at room temperature for 30 minutes, and then heat to 70°C and continue to stir and react for 24 hours to obtain a positively charged polystyrene ball dispersion;

Step 6.3, add 15g of methyltrimethoxysilane to 50ml of water and mix uniformly, add hydrochloric acid after raising the temperature to 35°C, adjust the pH to 3, and continue to stir for 3h to obtain the organosilane precursor hydrolysate;

Step 6.4, add 6ml of ammonia to the polystyrene ball dispersion obtained in step 6.2, stir for 6min, add the organosilicon source precursor hydrolyzate prepared in step 6.3, stop stirring, and let stand at room temperature for 8h;

Step 6.5, filter the resulting solution, wash it with distilled water and ethanol once, and then put it in an oven at 50℃ to dry for 3h, and then heat it in a muffle furnace at 0.3℃/min to 550℃ and keep it warm for 3h after removing the polystyrene balls. Continue to heat up to 950°C at 3°C/min to obtain low-dielectric hollow silica microspheres with a smooth and compact surface. As shown in Fig. 6, Fig. 6 is a scanning electron microscope image of hollow silica microspheres prepared when the amount of ammonia added is increased to 6 ml.

The difference between Example 6 and Example 5 is mainly reflected in the amount of ammonia added. The addition ratio of ammonia continued to increase. It was found that the surface of the sphere was rough, the shell particles were loosely packed, and there were many holes. The measured dielectric constant was 3.5.

Example Seven

Step 7.1, after ultrasonic dissolving 1.5g polyvinylpyrrolidone, 45g ethanol, 5g distilled water, 15g styrene, 0.29g initiator azobisisobutyronitrile and cationic comonomer acryloxyethyltrimethylammonium chloride for 10 minutes Put it into a 250mL three-necked flask (including nitrogen inlet, stirring blade inlet and condenser), and stir at room temperature to form a homogeneous solution;

Step 7.2, deoxygenate the homogeneous solution by bubbling nitrogen at room temperature for 30 minutes, and then heat to 70°C and continue to stir and react for 24 hours to obtain a positively charged polystyrene ball dispersion;

Step 7.3, add 15g of methyltrimethoxysilane to 50ml of water and mix uniformly, add hydrochloric acid after raising the temperature to 35°C, adjust the pH to 3, and continue to stir for 3h to obtain the organosilane precursor hydrolysate;

Step 7.4, add 3 ml of ammonia to the polystyrene ball dispersion obtained in step 7.2, stir for 6 minutes, add the organic silicon source precursor hydrolyzate prepared in step 7.3, stop stirring, and let stand at room temperature for 8 hours;

Step 7.5, filter the resulting solution, wash it with distilled water and ethanol, and then put it in an oven at 50℃ to dry for 3h, and then in a muffle furnace at 5℃/min to 550℃ and keep it for 8h to remove the polystyrene balls to obtain hollow Silica microspheres.

As shown in FIG. 7, FIG. 7 is a scanning electron micrograph of hollow silica microspheres obtained by changing the calcination process.

The difference between Example 7 and Example 5 is mainly reflected in the calcination process, the heating speed is increased, the volatilized gas is too fast to break through the shell layer and cause the ball to be broken, and the dielectric constant is 3.1.

Detection method:

1. Dielectric constant

Use the plate method in accordance with IPC-TM-6502.5.5.9 to measure the dielectric constant at 1 GHz.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions recorded in the foregoing embodiments are modified, or some of the technical features are equivalently replaced; these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

A method for preparing low-dielectric hollow silica microspheres, which is characterized in that:

Step 1. Prepare a template ball solution. The template ball solution includes 1-6% by mass polyvinylpyrrolidone, 5-25% by mass styrene, and 0.2-1.2% by mass azobisisobutyl. Nitrile, a cationic comonomer with a mass percentage of 0.01-10% acryloxyethyltrimethylammonium chloride, water and ethanol;

Step 2: Prepare template ball dispersion. Stir the solution obtained in step 1 and then pour nitrogen into it for 10-30min. Heat the solution to 50-80℃ and keep stirring for 10-30h to obtain template ball dispersion; add acidic catalyst to the solution After stirring at a stirring speed of 200-400r/min for 2-5h, the pH of the solution will be 3-4;

Step 4: Preparation. Add a certain amount of alkaline catalyst to the template ball dispersion in step 2, and stir for 3-10 minutes to make the pH value of the template ball dispersion at 10-12;

Step 5: Add the organosilicon source hydrolysis solution prepared in Step 3 to Step 4, and after stirring, let it stand at room temperature for 6-24 hours;

Step 6. After washing the filtered solution, the filtered material is placed in an oven at 40-70° C., baked and dried, and then calcined to prepare silica microspheres.
The method for preparing low-dielectric hollow silica microspheres according to claim 1, wherein the filter of step 6 is first heated to 400-600°C at a rate of 0.3°C/min and kept at a temperature of 2- 4h, continue to heat up to 800-1000°C at 3°C/min.
The method for preparing low-dielectric hollow silica microspheres according to claim 1 or 2, characterized in that the thickness of the prepared silica microspheres is 50-200nm, and the particle size is 0.3-3um. .
The method for preparing low-dielectric hollow silica microspheres according to claim 1 or 2, wherein the acidic catalyst in the third step is hydrochloric acid.
The method for preparing low-dielectric hollow silica microspheres according to claim 1 or 2, wherein the basic catalyst in the step 4 is ammonia water.
The method for preparing low-dielectric hollow silica microspheres according to claim 1 or 2, wherein the mass ratio of water and ethanol in the first step is 1:9.
The method for preparing low-dielectric hollow silica microspheres according to claim 1 or 2, wherein the solid content in the template ball dispersion in the second step is 10-30%.
The method for preparing low-dielectric hollow silica microspheres according to claim 1 or 2, characterized in that, in the step of the trimethyltrimethoxysilane solution, the mixture of methyltrimethoxysilicon and water The mass ratio is 1:5-25.
The method for preparing low-dielectric hollow silica microspheres according to claim 1 or 2, wherein the mass ratio of the basic catalyst to methyltrimethylsilane is 1:1~
The method for preparing low-dielectric hollow silica microspheres according to claim 2, characterized in that, the filter of step 6 is first heated to 550°C at 0.3°C/min and kept for 3h, and then The temperature is raised to 950°C at 3°C/min.
A copper clad laminate, characterized in that the hollow silica microspheres prepared by the method of claims 1 to 9 are prepared as fillers.