Spherical silicon dioxide, high-frequency and high-speed copper-clad plate and preparation method thereof

Abstract

The invention discloses spherical silicon dioxide, a high-frequency high-speed copper-clad plate and a preparation method of the spherical silicon dioxide. The dielectric constant Dk of the spherical silicon dioxide is 3.5 F / m-4. 0F / m, the dielectric loss Df is 0.0001-0.005, the amorphous state proportion is larger than or equal to 99%, the spheroidization rate is larger than or equal to 99%, and the porosity is 0.1%-2%. During preparation, the hydrolysis degree is controlled till partial polycondensation is achieved, then under the oxygen introduction condition, pre-oxidation is conducted at the low temperature to remove alkyl, gradient calcination is conducted at the high temperature, local crystallization influence and defect influence caused by powder spontaneous combustion are prevented, meanwhile, viscous bodies in the microspheres are accurately controlled to flow to fill nanoscale pores, and the particle size is reduced. The spherical silicon dioxide with high purity, high spheroidization rate and low dielectric loss is obtained, the dielectric property of the high-frequency and high-speed copper-clad plate can be met, and the high thermal stability and high reliability of the high-frequency and high-speed copper-clad plate are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon dioxide preparation, and in particular relates to spherical silicon dioxide, a high-frequency and high-speed copper-clad laminate and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of 5G communications, artificial intelligence computing power, autonomous driving, and the Internet of Things (IoT) technology, high-frequency and high-speed electronic devices have placed increasingly stringent performance requirements on copper clad laminates (CCLs). High-frequency signal transmission (such as millimeter waves) and high-speed digital circuits (such as 400G optical modules) require substrate materials with ultra-low dielectric loss (Df), low dielectric constant (Dk), high thermal stability, and excellent mechanical strength.

[0003] As the core functional filler of copper-clad laminates, high-purity spherical silica, due to its unique physical and chemical properties, has become a key material for achieving the above performance goals. Traditional copper-clad laminates use angular fused silica or glass fiber as fillers, which have the following limitations: (1) High dielectric loss: The interface polarization of angular particles is significant, with Df > 0.005 @ 10GHz, making it difficult to meet millimeter wave requirements; (2) Low filling uniformity: Irregular particles lead to poor resin fluidity, with a filling rate of < 50%, limiting performance improvements.

[0004] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0005] The object of the present invention is to provide a spherical silica, a high-frequency and high-speed copper clad laminate and a preparation method thereof. The spherical silica is used to prepare a high-frequency and high-speed copper clad laminate, so that the copper clad laminate has the advantages of high thermal stability, ultra-low dielectric loss and high reliability.

[0006] In order to achieve the above object, a specific embodiment of the present invention provides the following technical solutions:

[0007] The invention discloses spherical silicon dioxide, which has a dielectric constant Dk of 3.5F / m to 4.0F / m, a dielectric loss Df of 0.0001 to 0.005, an amorphous proportion of ≥99%, a spheroidization rate of ≥99%, and a porosity of 0.1% to 2%.

[0008] In one or more embodiments of the present invention, the spherical silica satisfies at least any of the following: D50 is 0.3 μm to 8 μm; D90 / D10 is 1.7 to 8; BET surface area is 0.3 m 2 / g~8m 2 / g; surface hydroxyl content ≤3 / nm 2 .

[0009] In one or more embodiments of the present invention, the spherical silica satisfies at least any one of the following conditions: surface roughness Ra<10 nm; and does not contain silica particles ≤100 nm.

[0010] In one or more embodiments of the present invention, the surface of the spherical silica is grafted with a first graft and a second graft, the first graft is at least one of an epoxy group, an aniline group, a vinyl group, and a long-chain alkyl group, and the second graft is at least one of a fluorine-containing group and a silazane group.

[0011] In one or more embodiments of the present invention, the surface group grafting equivalent of the spherical silica is 0.1% to 0.3%.

[0012] Another specific embodiment of the present invention provides a technical solution as follows:

[0013] A method for preparing spherical silicon dioxide comprises the following steps:

[0014] mixing a silicon source, a solvent, and water to prepare a dispersion;

[0015] The dispersion and the alkaline catalyst are mixed at 30-35°C, the pH is controlled at 9-10, and the mixture is allowed to stand for 2-3 hours; the mixture is then heated to 55-60°C, stirred and reacted for 2-3 hours; the mixture is then heated to 70-85°C, stirred and reacted for 2-3 hours to obtain a silicone ball slurry;

[0016] Separating the organosilicon balls from the organosilicon ball slurry to obtain monodispersed organosilicon ball powder;

[0017] The silicone ball powder is processed in the following stages:

[0018] Low-temperature pre-oxidation stage: in an oxygen atmosphere, raise the temperature to 200°C to 400°C and keep it warm for 4h to 6h;

[0019] High-temperature densification stage: the first stage: the temperature is raised to 750℃~800℃, and kept warm for 1h~2h; the second stage: the temperature is raised to 850℃~900℃, and kept warm for 1h~2h; the third stage: the temperature is raised to 950℃~1000℃, and kept warm for 1h~2h; the fourth stage: the temperature is raised to 1050℃~1100℃, and kept warm for 1h~2h; then cooled.

[0020] In one or more embodiments of the present invention, the heating rate in the low-temperature pre-oxidation stage is 2°C / min to 5°C / min;

[0021] In the high-temperature densification stage, the heating rate of the first stage is 8°C / min to 10°C / min, the heating rate of the second stage is 2°C / min to 5°C / min, the heating rate of the third stage is 2°C / min to 5°C / min, and the heating rate of the fourth stage is 2°C / min to 5°C / min.

[0022] In one or more embodiments of the present invention, the oxygen concentration in the low-temperature pre-oxidation stage and the high-temperature densification stage is 30% to 50%.

[0023] In one or more embodiments of the present invention, the cooling rate is ≥50°C / min.

[0024] In one or more embodiments of the present invention, the mass of the solvent is 10% to 20% of the mass of water, and the mass of the silicon source is 5% to 20% of the sum of the mass of the solvent and the mass of water.

[0025] In one or more embodiments of the present invention, the spherical silica is further modified:

[0026] First, the spherical silica is reacted at 80°C to 120°C for 25 minutes to 35 minutes to introduce the first graft; then, the second graft is introduced at 80°C to 120°C for 25 minutes to 35 minutes;

[0027] The first grafted substance is at least one of an epoxy group, an aniline group, a vinyl group, and a long-chain alkyl group, and the second grafted substance is at least one of a fluorine-containing group and a silazane group.

[0028] Another specific embodiment of the present invention provides a technical solution as follows:

[0029] A high-frequency and high-speed copper-clad laminate comprises raw materials comprising at least epoxy resin, a curing agent and spherical silica. The spherical silica is the above-mentioned spherical silica or the spherical silica prepared by the above-mentioned preparation method.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. Using a microemulsion template and gradient hydrolysis process, by adjusting the precursor, i.e., silicon source concentration, pH value and stirring rate, monodisperse nucleation is achieved, and the particle size range is adjustable from 0.3 to 8 μm. A mixed solvent is used to reduce surface tension and promote uniform nucleation of the sol. The silicon source concentration is controlled at 5-20wt%, which can control the size of the spherical silica particles and avoid high concentrations causing the gel to shrink too quickly and crack. The gel is aged at 70-80°C in the mother liquor to promote the reconstruction of the silicon-oxygen network, eliminate micropores (pore diameter <2nm), and reduce internal defects in the spheres. By precisely controlling the particle size, sphericity and purity, the filling uniformity of the spherical silica is improved, the interface polarization is reduced, and the dielectric loss is reduced.

[0032] 2. The high purity of the spherical silica in the present invention (metal impurities < 5ppm) can inhibit ion migration and reduce the Df of the copper clad plate to 0.0001-0.005@10GHz, solving the problem of metal ions (Na + 、Fe 3+ The residual amount is greater than 50ppm, which aggravates the problem of high-frequency signal attenuation.

[0033] 3. The spherical silica in this invention has a high spheroidization rate and a high packing density, which can reduce the resin ratio (resin Df is generally >0.01), thereby optimizing overall performance. The spherical structure can evenly disperse stress. The thermal expansion coefficient (CTE) of spherical silica is approximately 0.5 ppm / °C. When cured with high resin filling, the CTE of the substrate formed is 10-15 ppm / °C, which matches copper foil. This solves the problem of existing substrates with a CTE >20 ppm / °C, which is mismatched with copper foil and prone to delamination and warping at high temperatures.

[0034] 4. The pre-oxidation stage slowly removes organic matter, the densification stage gradient calcination promotes the flow of viscous body to close the internal micropores and the rapid cooling locks the amorphous state, controls the amorphous phase and structural density of spherical silica, eliminates the crystalline phase (cristobalite content <0.1%), and reduces dielectric loss.

[0035] 5. The surface of spherical silica is functionalized by surface grafting to improve compatibility and reliability, so that the dielectric loss retention rate of the prepared copper clad laminate after thermal aging is greater than 98%, and the service life is extended to 15 years. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 This is the SEM image in Example 1 of the present invention;

[0038] Figure 2 TEM image in Example 1 of the present invention;

[0039] Figure 3 is the XRD pattern in Example 1 of the present invention;

[0040] Figure 4 This is the Raman graph in Example 1 of the present invention;

[0041] Figure 5This is the SEM image in Example 2 of the present invention;

[0042] Figure 6 This is the SEM image of Comparative Example 7 of the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only 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 making creative efforts should fall within the scope of protection of the present invention.

[0044] A specific embodiment of the present invention provides spherical silica, which has a dielectric constant Dk of 3.5F / m to 4.0F / m, a dielectric loss Df of 0.0001 to 0.005, an amorphous ratio ≥99%, a spheroidization rate ≥99%, and a porosity of 0.1% to 2%.

[0045] Specifically, the silica in the present invention has low porosity and high density. The high density makes its silica structure compact, reducing electron transmission barriers and energy loss, thereby exhibiting low dielectric constant and dielectric loss. At the same time, silica has a high sphericity. When used in the production of copper-clad laminates, it can improve the fluidity of the resin. The high packing density of spherical particles can reduce the resin content, increase the filling rate, and reduce the dielectric loss of the copper-clad laminate. Moreover, the spherical structure can reduce interface defects and stress concentration, can evenly distribute stress, and improve the thermal stability of the copper-clad laminate.

[0046] Furthermore, the spherical silica satisfies at least any of the following requirements: D50 is 0.3 μm to 8 μm; D90 / D10 is 1.7 to 8; and the specific surface area BET is 0.3 m 2 / g~8m 2 / g; surface hydroxyl content ≤3 / nm 2 ; Surface roughness Ra<10nm; does not contain ≤100nm silica particles.

[0047] Specifically, the aforementioned particle size range ensures silica's excellent additivity, facilitating uniform filling within the resin. A suitable specific surface area reduces interfacial polarization, helping lower the dielectric constant of the copper-clad laminate. A low surface hydroxyl content reduces silica's polarization, contributing to lower dielectric constant and dielectric loss. A low surface roughness gives silica a smooth surface, improving compatibility with the resin and reducing processing viscosity.

[0048] In addition, the silicon dioxide in the present invention has a purity of ≥99.5%, magnetic impurities ≤5 ppm, electrical conductivity ≤10 μS / cm, and moisture absorption rate <0.01%, showing high-purity and low-conductivity performance.

[0049] Furthermore, the surface of the spherical silica is grafted with a first graft and a second graft, the first graft is at least one of epoxy, phenylamino, vinyl, and long-chain alkyl, and the second graft is at least one of fluorine-containing groups and silazane groups.

[0050] Specifically, copper-clad laminates are typically made of epoxy resin. Grafting a first graft can enhance the interfacial bonding between silica and the resin and reduce interfacial defects. Grafting a second graft can reduce the surface energy of silica, achieving a contact angle greater than 120° and a moisture absorption rate less than 0.1%. Specifically, grafting epoxy groups and fluorosilanes, where the epoxy groups complement the epoxy resin, can enhance the chemical bond between spherical silica and the epoxy resin, resulting in a peel strength greater than 1.5 N / mm. Fluorosilane is a hydrophobic group, and the two synergistically form a dense interfacial layer. Furthermore, the fluorinated layer formed by the fluorosilane increases the contact angle of the spherical silica to greater than 120°, inhibiting moisture absorption and copper ion migration.

[0051] Furthermore, the grafting equivalent of the spherical silica surface groups is 0.1 to 0.3%.

[0052] Specifically, by controlling the group grafting equivalent, the dispersibility and compatibility of spherical silica in the resin can be improved.

[0053] Another specific embodiment of the present invention provides a method for preparing spherical silica, comprising steps 1-6.

[0054] Step 1: Mix a silicon source, a solvent and water to prepare a dispersion.

[0055] Specifically, the solvent is 10% to 20% of the mass of water, and the silicon source is 5% to 20% of the mass of the solvent and water combined. After mixing, the mixture is stirred at 200 to 300 rpm / min for 30 minutes. By controlling the raw material dosage, the resulting silica spheres have a particle size of 0.3 μm to 8 μm. A silicon source dosage of 5 to 20 wt% can control the particle size of the spherical silica while avoiding excessive shrinkage and cracking of the gel caused by high concentrations.

[0056] The silicon source is at least one of methyltrimethoxysilane, ethyltrimethoxysilane, ethyl orthosilicate, and ethyltriethoxysilane, and the solvent is at least one of ethanol and isopropanol. Preferably, ethanol and isopropanol are mixed to reduce surface tension and promote uniform nucleation of the sol.

[0057] Step 2: Mix the dispersion and the alkaline catalyst at 30°C to 35°C, control the pH to 9 to 10, and allow to stand for 2 to 3 hours; then heat to 55°C to 60°C, stir and react for 2 to 3 hours; then heat to 70°C to 85°C, stir and react for 2 to 3 hours to obtain a silicone ball slurry.

[0058] Specifically, the alkaline catalyst is ammonia water or sodium hydroxide. Steps 1 and 2 can control the degree of hydrolysis of the silicon source, achieve partial polycondensation, and avoid complete cross-linking to form a "silicon half oxane" structure rich in Si-O-Si network but retaining some alkyl groups.

[0059] When the dispersion and the alkaline catalyst are mixed, the stirring speed is 400 rpm / min to 500 rpm / min, and the alkaline catalyst is added to the dispersion within 15s to 20s. After mixing, the dispersion is allowed to stand and age. This process can form an ordered gradient interface with the help of the hydrophobic alkyl group and the polarity of the Si-O-Si network, promote the reconstruction of the silicon-oxygen network, and reduce the internal defects of the spheres. After aging, start stirring at a speed of 200rpm / min~300rpm / min, heat to 55℃~60℃, and stir to react for 2h~3h. In this process, the remaining hydrolyzed monomers in the solvent are adsorbed onto the silicone balls and the silicon-oxygen network is reconstructed; then heat to 70℃~85℃ and react for 2h~3h. In this process, the silicone balls are aged, the silicon-oxygen network is reconstructed, micropores with a pore size of <2nm are eliminated, and internal defects of the spheres are reduced. The preferred temperature is 70℃~80℃. If the temperature exceeds 80℃, although the product performance can meet the use requirements, the product performance cannot be further optimized, and increasing the aging temperature will increase the energy consumption cost. Therefore, the temperature is preferably 70℃~80℃, which can effectively reduce the energy consumption cost.

[0060] By controlling the pH value and stirring rate, monodisperse nucleation is achieved, and the particle size range is adjustable from 0.3 μm to 8 μm.

[0061] Step 3: Separate the organosilicon balls from the organosilicon ball slurry to obtain monodisperse organosilicon ball powder.

[0062] Specifically, the silicone ball slurry is filtered, washed, demagnetized, and spray-dried to obtain agglomerated silicone balls, which are then subjected to ultrafine classification. The airflow pressure is controlled to 0.2 MPa to 0.3 MPa to achieve a monodisperse particle size distribution, thereby obtaining silicone ball powder. The D90 / D10 value of the silicone ball powder after ultrafine classification is 2 to 10. Distilled water is used for washing, and conventional methods such as using a magnetic rod to remove magnetic impurities and reduce metal ions (Na + 、Fe 3+ ) remain, so that the magnetic impurities ≤ 5ppm. The spray drying inlet temperature is 250℃~280℃, and the outlet temperature is 105℃~120℃.

[0063] Step 4: treating the organosilicon ball powder in a low-temperature pre-oxidation stage and a high-temperature densification stage, and then cooling to obtain spherical silica agglomerates.

[0064] Specifically, the low-temperature pre-oxidation stage involves introducing oxygen (at a flow rate of 1L / min to 2L / min), controlling the oxygen concentration at 30% to 50%, slowly raising the temperature to 200°C to 400°C at a rate of 2°C / min to 5°C / min, and maintaining the temperature for 4 to 6 hours. During this stage, the alkyl groups are gradually oxidized and removed. Increasing the temperature too quickly can easily lead to localized carbon residues, and the shedding of methyl groups can generate steam. Increasing the temperature too quickly can easily lead to concentrated release of methyl vapor, which can cause pore formation and reduce density. Therefore, the temperature is raised slowly at a lower rate.

[0065] The high-temperature densification stages are as follows: Stage 1: Raise the temperature to 750°C-800°C and hold for 1-2 hours, which promotes the reconstruction of the silicon-oxygen network; Stage 2: Raise the temperature to 850°C-900°C and hold for 1-2 hours; Stage 3: Raise the temperature to 950°C-1000°C and hold for 1-2 hours; Stage 4: Raise the temperature to 1050°C-1100°C and hold for 1-2 hours. During the high-temperature densification stage, gradient calcination is performed. On the one hand, during the calcination process, the temperature transfers from the outside to the inside of the silicone sphere, and the alkyl groups inside fall off more slowly. Under gradient calcination, the alkyl groups inside the center of the silicone sphere fall off, slowly eliminating the alkyl groups in the silicone sphere, achieving complete oxidation and preventing residual carbon from forming crystal nuclei. On the other hand, the alkyl group shedding will create pores. Under gradient calcination, after the alkyl groups on the outside of the silicone sphere fall off, the viscous liquid inside flows at high temperature, filling the pores and increasing the density. If calcined directly at a higher temperature, the temperature rises too quickly and the internal viscous body cannot fill the pores in time, which will lead to the formation of pores and reduce the density.

[0066] The heating rate in the first stage is 8°C / min to 10°C / min, in the second stage 2°C / min to 5°C / min, in the third stage 2°C / min to 5°C / min, and in the fourth stage 2°C / min to 5°C / min. A higher heating rate in the first stage allows the temperature to quickly reach 750°C to 800°C, causing the alkyl groups on the exterior of the silicone spheres to begin shedding. This shedding of the alkyl groups generates vapor. A rapid temperature increase causes the alkyl vapor to rapidly escape from the silicone spheres, creating new pores. This rapid heating also hinders the timely filling of the pores by the viscous substance within the silicone spheres. Furthermore, a rapid temperature increase results in an excessively high impact velocity of the alkyl vapor, which in turn leads to the formation of macropores, preventing the formation of nanopores. These macropores are difficult to fill with the viscous substance, ultimately increasing the silica pore size, porosity, and density. Therefore, a higher heating rate is used in the first stage to quickly reach the target temperature. Lower heating rates are used in the second, second, and fourth stages to minimize the formation of macropores and encourage the viscous substance within the silicone spheres to fill the pores.

[0067] The temperature used in step 4 is lower than the SiO2 crystallization starting temperature (about 1200°C), which can prevent the formation of cristobalite or quartz phase.

[0068] The low-temperature pre-oxidation stage and the high-temperature densification stage are carried out in an oxygen atmosphere. The reason is that the organic silicon spheres contain alkyl groups and Si-O-Si networks. During oxygen-free calcination, the alkyl groups cannot be stably removed by oxidation reaction (which requires the participation of O2) and instead undergo thermal cracking: The products are combustible gases such as methane (CH4) and ethylene (C2H4), as well as a large number of silicon oxide free radicals. The auto-ignition temperature of methane is approximately 580°C, and that of ethylene is approximately 490°C. When the calcination temperature rises to this range, the released gases spontaneously combust in the high-temperature environment of the furnace (without the need for external ignition), forming a flame. Even without oxygen, trace amounts of O2 may remain in the furnace (e.g., if the air is not completely exhausted), or the organosilicon itself may contain oxygen (e.g., when Si-O bonds break and release reactive oxygen), providing an oxidant for combustion. The combustion of gases releases a large amount of heat (the heat of combustion of CH4 is approximately 890 kJ / mol), further accelerating the thermal decomposition of undecomposed organosilicon, forming a self-sustaining combustion cycle. Once combustion occurs, it is impossible to control whether the flame temperature exceeds 1200°C, resulting in localized crystallization of the spherical silica. At the same time, the escaping silicon oxide free radicals deposit on the surface of the spherical silica to form nanoparticles, leading to defects within the spherical silica.

[0069] Dielectric loss is primarily related to polarization relaxation within the material. The presence of crystalline phases can lead to local structural inhomogeneities, increasing polarization relaxation losses. Internal defects can also increase dipole polarization, leading to increased dielectric loss. Therefore, oxygen must be introduced during the low-temperature pre-oxidation and high-temperature densification stages to ensure the gradual oxidation and removal of alkyl groups, ensuring complete oxidation and preventing residual carbon from forming crystal nuclei, thereby maintaining a dense amorphous structure for spherical silica.

[0070] After calcination, cooling to room temperature at a rate of ≥50°C / min can inhibit the ordering of the silicon-oxygen network, i.e., amorphous locking, and increase the amorphous ratio of spherical silica to reach an amorphous ratio of ≥99%.

[0071] Step 5: Ultrafinely classify the spherical silica agglomerates, and control the air flow pressure to 0.4 MPa to 0.6 MPa to obtain monodisperse spherical silica.

[0072] Specifically, after ultrafine classification, the D90 / D10 value of the spherical silica is 1.7 to 8.

[0073] Step 6, modifying the spherical silica: adding the spherical silica to a high-speed stirring mixing equipment, controlling the speed to 300 rpm / min to 500 rpm / min and the temperature to 80°C to 120°C; spraying the modifying liquid containing the first graft onto the powder, stirring and reacting for 25min to 35min; then spraying the modifying liquid containing the second graft onto the powder, stirring and reacting for 25min to 35min, and cooling to room temperature.

[0074] Specifically, the first grafted substance is an epoxy group, an aniline group, a vinyl group or a long-chain alkyl group. The preparation of the modified liquid is to add a silane coupling agent containing an epoxy group, an aniline group, a vinyl group or a long-chain alkyl group to an acetic acid aqueous solution with a pH of 3 to 4, stir at room temperature for 10 to 20 minutes, and continue stirring in ethanol for 10 to 20 minutes. The mass ratio of the silane coupling agent, the acetic acid aqueous solution and the ethanol is 100:30:15.

[0075] The second grafted substance is a fluorine-containing group or a silazane group. The preparation of the modified liquid is to add a silane coupling agent containing a fluorine group or a silazane group to an acetic acid aqueous solution with a pH of 3 to 4, stir at room temperature for 10 to 20 minutes, and continue stirring in ethanol for 10 to 20 minutes. The mass ratio of the silane coupling agent, the acetic acid aqueous solution and the ethanol is 100:30:15.

[0076] The mass ratio of the modification liquid containing the first grafted substance to the modification liquid containing the second grafted substance is (4-5):1. Through the modification treatment, the surface group grafting equivalent of the spherical silica is 0.1% to 0.3%.

[0077] Another specific embodiment of the present invention provides a high-frequency and high-speed copper-clad laminate, the raw materials of which are composed of at least epoxy resin, curing agent and the above-mentioned spherical silica.

[0078] Specifically, the epoxy resin is a bisphenol A epoxy resin (such as E-51), and the curing agent is diaminodiphenyl sulfone. During preparation, the epoxy resin, spherical silica, and curing agent are added to a planetary mixer and stirred for 25 to 35 minutes at a speed of 2000 rpm. The mixture is then ground with three rollers three times to obtain a resin mixture. The glass fiber cloth is impregnated in the resin mixture, then removed and dried at 100°C to 120°C for 2 minutes to obtain a prepreg. Several prepregs are stacked, covered with copper foil on both sides, and hot pressed at 180°C to 200°C and 35MPa pressure for 2.5 hours to obtain a copper clad laminate.

[0079] By using the above-mentioned spherical silica to prepare copper-clad laminates, the dielectric constant Dk of the copper-clad laminates can reach 3.5F / m-4.0F / m, the dielectric loss Df can reach 0.0001-0.005@10GHz, the thermal expansion coefficient CTE is 10-15ppm / ℃, the moisture absorption rate is less than 0.1%, and the dielectric loss retention rate is greater than 98% after aging in a hot and humid environment (85℃ / 85%RH), and the service life can be extended to 15 years.

[0080] The present invention is further described in detail below with reference to specific embodiments.

[0081] Example 1

[0082] Take methyltrimethoxysilane, ethanol and isopropanol, mix ethanol and isopropanol in a mass ratio of 1:1 to make a solvent, according to the mass of the solvent being 10% of the mass of water and the mass of methyltrimethoxysilane being 12% of the sum of the mass of the solvent and water, put methyltrimethoxysilane, pure water and solvent into a reactor, control the speed to 200 rpm / min, and stir for 30 minutes.

[0083] The reactor temperature was controlled at 30°C, and sodium hydroxide (alkali catalyst) was added at a stirring speed of 400 rpm / min. The addition of sodium hydroxide was completed within 15 seconds, and the pH was controlled to 9.5. Stirring was stopped, and the mixture was allowed to stand for 3 hours. Stirring was resumed, the speed was controlled at 200 rpm / min, the temperature was raised to 55°C, and the mixture was stirred for 3 hours. The temperature was then raised to 70°C, and the mixture was stirred at 200 rpm / min for another 3 hours to obtain an organosilicon slurry.

[0084] The organosilicon slurry was filtered, washed with water, demagnetized, and spray-dried at an inlet temperature of 260° C. and an outlet temperature of 110° C. to obtain agglomerated organosilicon balls.

[0085] The agglomerated silicone spheres were subjected to ultrafine classification and the air flow pressure was controlled at 0.2 MPa to achieve a monodisperse particle size distribution for calcination.

[0086] The calcination process was as follows: a low-temperature pre-oxidation stage was performed: oxygen was introduced at a flow rate of 1 L / min, maintaining an oxygen concentration of 50%, and the temperature was slowly increased to 200°C at a rate of 2°C / min and held for 4 hours. A high-temperature densification stage was then performed: the temperature was increased to 800°C at a rate of 10°C / min and held for 1 hour; then to 900°C at a rate of 5°C / min and held for 1 hour; then to 1000°C at a rate of 5°C / min and held for 1 hour; and finally to 1100°C at a rate of 5°C / min and held for 1 hour.

[0087] After calcination, the mixture was cooled to room temperature at a rate of 50°C / min to obtain spherical silica agglomerates.

[0088] The spherical silica agglomerates were ultrafinely classified, and the air flow pressure was controlled at 0.4 MPa to obtain monodispersed spherical silica.

[0089] A silane coupling agent (KH560, Evonik) was added to an aqueous acetic acid solution at pH 3, stirred at room temperature for 10 minutes, and then ethanol was added and stirred for another 10 minutes to prepare a first modifier. The mass ratio of the silane coupling agent, aqueous acetic acid solution, and ethanol was 100:30:15.

[0090] A silane coupling agent (Protectosil SC60, Evonik) was added to an aqueous acetic acid solution at pH 3, stirred at room temperature for 10 minutes, and then ethanol was added and stirred for another 10 minutes to prepare a second modifier. The mass ratio of the silane coupling agent, aqueous acetic acid solution, and ethanol was 100:30:15.

[0091] Spherical silica was added to a high-speed stirring mixing device, the speed was controlled to 300 rpm / min, the powder was stirred up and down in the device, and the temperature was controlled to 80°C. According to the mass ratio of silane coupling agent (KH560, Evonik) to spherical silica of 5:1000, the first modifier was evenly sprayed on the powder through a pressure spray device, the first modifier was added within 5 minutes, and the reaction was continued by heating and stirring for 30 minutes. Then, according to the mass ratio of the first modifier to the second modifier of 5:1, the second modifier was evenly sprayed on the powder through a pressure spray device, the second modifier was added within 5 minutes, and the reaction was continued by heating and stirring for 30 minutes. Then it was cooled to room temperature to obtain modified spherical silica.

[0092] E-51 bisphenol A epoxy resin, diaminodiphenyl sulfone, and 7628 glass fiber cloth were prepared. Separately, copper foil (18 μm thick, with a surface roughness of Ra <0.5 μm) that had been ultrasonically degreased with ethanol was prepared. The epoxy resin, spherical silica, and curing agent were added in a planetary mixer at a mass ratio of 40:60:12, stirred for 30 minutes at 2000 rpm, and then subjected to three three-roll milling cycles to obtain a uniform resin mixture. The 7628 glass fiber cloth was then impregnated with the resin mixture, removed, and dried at 110°C for 2 minutes to obtain a prepreg. Three prepregs were then stacked, covered with copper foil on both sides, and hot-pressed at 190°C and 35 MPa for 2.5 hours to obtain a copper-clad laminate.

[0093] Example 2

[0094] The difference between this embodiment and embodiment 1 is that, in terms of the amount of raw materials used, the mass of methyltrimethoxysilane is 5% of the sum of the mass of the solvent and water.

[0095] A silane coupling agent (KH560, Evonik) was added to an aqueous acetic acid solution at pH 4, stirred at room temperature for 20 minutes, and then ethanol was added and stirred for a further 20 minutes to prepare a first modifier. The mass ratio of the silane coupling agent, aqueous acetic acid solution, and ethanol was 100:30:15.

[0096] A second modifier was prepared by adding a silane coupling agent (Protectosil SC60, Evonik) to an aqueous acetic acid solution at pH 4, stirring at room temperature for 20 minutes, and then adding ethanol and stirring for a further 20 minutes. The mass ratio of the silane coupling agent, aqueous acetic acid solution, and ethanol was 100:30:15.

[0097] Spherical silica was added to a high-speed stirring mixing equipment, the speed was controlled to 500 rpm / min, the powder was stirred up and down in the equipment, and the temperature was controlled to 120°C. According to the mass ratio of silane coupling agent (KH560, Evonik) to spherical silica of 10:1000, the first modifier was evenly sprayed on the powder through a pressure spraying device, the first modifier was added within 5 minutes, and the reaction was continued by heating and stirring for 30 minutes. Then, according to the mass ratio of the first modifier to the second modifier of 4:1, the second modifier was evenly sprayed on the powder through a pressure spraying device, the first modifier was added within 5 minutes, and the reaction was continued by heating and stirring for 30 minutes. Then it was cooled to room temperature to obtain modified spherical silica.

[0098] Example 3

[0099] The difference between this embodiment and embodiment 1 is that, in terms of the amount of raw materials used, the mass of methyltrimethoxysilane is 10% of the sum of the mass of the solvent and water.

[0100] Example 4

[0101] The difference between this embodiment and embodiment 1 is that, in terms of the amount of raw materials used, the mass of methyltrimethoxysilane is 17% of the sum of the mass of the solvent and water.

[0102] Example 5

[0103] The difference between this embodiment and embodiment 1 is that, in terms of the amount of raw materials used, the mass of methyltrimethoxysilane is 20% of the sum of the mass of the solvent and water.

[0104] A silane coupling agent (KH560, Evonik) was added to an aqueous acetic acid solution at pH 4, stirred at room temperature for 20 minutes, and then ethanol was added and stirred for a further 20 minutes to prepare a first modifier. The mass ratio of the silane coupling agent, aqueous acetic acid solution, and ethanol was 100:30:15.

[0105] A second modifier was prepared by adding a silane coupling agent (Protectosil SC60, Evonik) to an aqueous acetic acid solution at pH 4, stirring the solution at room temperature for 20 minutes, and then adding ethanol and stirring for a further 20 minutes. The mass ratio of the silane coupling agent, aqueous acetic acid solution, and ethanol was 100:30:15.

[0106] Spherical silica was added to a high-speed stirring mixing device, the speed was controlled at 500 rpm / min, the powder was stirred up and down in the device, and the temperature was controlled at 120°C. According to the mass ratio of silane coupling agent (KH560, Evonik) to spherical silica of 1:1000, the first modifier was evenly sprayed on the powder through a pressure spray device, the first modifier was added within 5 minutes, and the reaction was continued by heating and stirring for 30 minutes. Then, according to the mass ratio of the first modifier to the second modifier of 5:1, the second modifier was evenly sprayed on the powder through a pressure spray device, the first modifier was added within 5 minutes, and the reaction was continued by heating and stirring for 30 minutes. Then it was cooled to room temperature to obtain modified spherical silica.

[0107] Example 6

[0108] The difference between this embodiment and embodiment 1 is that after adding the alkaline catalyst sodium hydroxide to the reactor, stirring is started, the speed is controlled to 200 rpm / min, the temperature is raised to 55°C, and the stirring reaction is carried out for 3 hours, and then the temperature is raised to 85°C, and the stirring reaction is continued at a speed of 200 rpm / min for 3 hours to obtain a silicone slurry.

[0109] Comparative Example 1

[0110] The difference between this comparative example and Example 1 is that, in terms of the amount of raw materials used, the mass of methyltrimethoxysilane is 4% of the sum of the mass of the solvent and water.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 1 is that, in terms of the amount of raw materials used, the mass of methyltrimethoxysilane is 21% of the sum of the mass of the solvent and water.

[0113] Comparative Example 3

[0114] The difference between this comparative example and Example 1 is that an alkaline catalyst, sodium hydroxide, is added to the reactor to control the pH to 11.

[0115] Comparative Example 4

[0116] The difference between this comparative example and Example 1 is that an alkaline catalyst, sodium hydroxide, was added to the reactor to control the pH to 8.0.

[0117] Comparative Example 5

[0118] The difference between this comparative example and Example 1 is that after adding the alkaline catalyst sodium hydroxide to the reactor, stirring was started, the speed was controlled to 200 rpm / min, the temperature was raised to 55°C, and the stirring reaction was carried out for 3 hours, and then the stirring reaction was continued at 55°C at a speed of 200 rpm / min for 3 hours to obtain a silicone slurry.

[0119] Comparative Example 6

[0120] This comparative example differs from Example 1 in that the calcination operation is as follows: in the absence of oxygen, the temperature is slowly raised to 200°C at a rate of 2°C / min and held for 4 hours. A high-temperature densification stage is then performed: the temperature is raised to 800°C at a rate of 10°C / min and held for 1 hour; then the temperature is raised to 900°C at a rate of 5°C / min and held for 1 hour; then the temperature is raised to 1000°C at a rate of 5°C / min and held for 1 hour; then the temperature is raised to 1100°C at a rate of 5°C / min and held for 1 hour.

[0121] Comparative Example 7

[0122] This comparative example differs from Example 1 in that the calcination operation is as follows: first, a low-temperature pre-oxidation stage is performed: oxygen is introduced at a flow rate of 1 L / min to maintain an oxygen concentration of 25%, and the temperature is slowly increased to 200°C at a rate of 2°C / min and held for 4 hours. Then, a high-temperature densification stage is performed: the temperature is increased to 800°C at a rate of 10°C / min and held for 1 hour; then, the temperature is increased to 900°C at a rate of 5°C / min and held for 1 hour; then, the temperature is increased to 1000°C at a rate of 5°C / min and held for 1 hour; then, the temperature is increased to 1100°C at a rate of 5°C / min and held for 1 hour.

[0123] Comparative Example 8

[0124] The difference between this comparative example and Example 1 is that the calcination operation is as follows: oxygen is introduced at a flow rate of 1 L / min, the oxygen concentration is maintained at 50%, the temperature is raised to 1000°C at a rate of 5°C / min, and kept at this temperature for 8 hours.

[0125] Comparative Example 9

[0126] This comparative example differs from Example 1 in that the calcination operation is as follows: a low-temperature pre-oxidation stage is first performed: oxygen is introduced at a flow rate of 1 L / min to maintain an oxygen concentration of 50%, and the temperature is slowly increased to 200°C at a rate of 2°C / min and held at this temperature for 4 hours. Then, a high-temperature densification stage is performed: the temperature is increased to 1000°C at a rate of 5°C / min and held at this temperature for 4 hours.

[0127] Comparative Example 10

[0128] This comparative example differs from Example 1 in that the calcination operation is as follows: first, a low-temperature pre-oxidation stage is performed: oxygen is introduced at a flow rate of 1 L / min to maintain an oxygen concentration of 50%, and the temperature is slowly increased to 200°C at a rate of 2°C / min and held for 4 hours. Then, a high-temperature densification stage is performed: the temperature is increased to 800°C at a rate of 10°C / min and held for 1 hour; then the temperature is increased to 1000°C at a rate of 5°C / min and held for 3 hours.

[0129] Comparative Example 11

[0130] This comparative example differs from Example 1 in that the calcination operation is as follows: first, a low-temperature pre-oxidation stage is performed: oxygen is introduced at a flow rate of 1 L / min to maintain an oxygen concentration of 50%, and the temperature is slowly increased to 200°C at a rate of 2°C / min and held for 4 hours. Then, a high-temperature densification stage is performed: the temperature is increased to 800°C at a rate of 10°C / min and held for 1 hour; then the temperature is increased to 900°C at a rate of 5°C / min and held for 1 hour; and then the temperature is increased to 1100°C at a rate of 5°C / min and held for 2 hours.

[0131] Comparative Example 12

[0132] This comparative example differs from Example 1 in that the calcination operation is as follows: first, a low-temperature pre-oxidation stage is performed: oxygen is introduced at a flow rate of 1 L / min to maintain an oxygen concentration of 50%, and the temperature is slowly increased to 200°C at a rate of 2°C / min and held for 4 hours. Then, a high-temperature densification stage is performed: the temperature is increased to 800°C at a rate of 10°C / min and held for 1 hour; then, the temperature is increased to 900°C at a rate of 5°C / min and held for 1 hour; then, the temperature is increased to 1000°C at a rate of 5°C / min and held for 1 hour; then, the temperature is increased to 1200°C at a rate of 5°C / min and held for 1 hour.

[0133] Comparative Example 13

[0134] The difference between this comparative example and Example 1 is that after the calcination, the mixture is cooled to room temperature at a rate of 45° C. / min to obtain spherical silica agglomerates.

[0135] Comparative Example 14

[0136] This comparative example differs from Example 1 in that the reactor temperature was controlled at 30°C, and the alkaline catalyst, sodium hydroxide, was added within 15 seconds while stirring at 400 rpm / min. The pH was controlled at 9.5, stirring was stopped, and the mixture was allowed to stand for 3 hours. Stirring was then resumed, the speed controlled at 200 rpm / min, the temperature was raised to 70°C, and the reaction was stirred for 6 hours to obtain an organosilicon slurry.

[0137] The prepared unmodified spherical silica was subjected to the following tests:

[0138] XRD analysis: A broad diffuse scattering peak (amorphous characteristics) was detected in the range of 2θ = 20-30°, without a sharp crystalline peak (such as 21.8° for cristobalite).

[0139] Raman spectrum: 420 cm -1 The main peak of amorphous SiO2 is broad and asymmetric, 490 cm -1 and 600cm -1 The shoulder peak is obvious. No 465cm -1 (crystalline phase) signal.

[0140] The BET test method is used to test the specific surface area and porosity of spherical silica: the specific surface area is less than 8m2 / g, and the total porosity is less than 2% (the density meets the standard).

[0141] SEM / TEM observation: The surface is smooth and defect-free, and there are no grain boundaries or holes inside.

[0142] Table 1 Performance test results of unmodified spherical silica

[0143]

[0144]

[0145] The modified spherical silica was tested for performance: surface hydroxyl groups were tested using sodium hydroxide titration; surface group grafting equivalent weight was tested using the loss on ignition method (after measuring moisture content, igniting from room temperature to 1000°C for one hour), according to JYQW-QA-09, "Chemical Analysis Methods for High Silicon Content"; moisture absorption was tested using a Karl Fischer moisture analyzer after the product was left for one month; and contact angle was tested according to JB / T10606-2006, "Determination of Contact Angle of Ultrafine Powders." The test results are shown in Table 2.

[0146] Table 2 Performance test results of modified spherical silica

[0147]

[0148] The resulting high-frequency, high-speed copper-clad laminate was cut into 50mm×50mm×1mm specimens and subjected to performance testing: Dk\Df test method: IPC TM-6502.5.5.5 (using 10GHz); CTE test method: JIS C6481; Moisture Absorption test method: IPC-TM-6502.6.2.1; Double 85°C damp heat aging test: temperature: 85°C±2°C, humidity: 85%RH±5%, time: 500h, equipment: constant temperature and humidity test chamber. Df was measured after aging; Df retention = Df / (Df after aging). The results are shown in Table 3.

[0149] Table 3 High-frequency and high-speed copper-clad laminate test results

[0150]

[0151]

[0152] From the above, it can be seen that the spherical silica prepared by the present invention has high purity, high spheroidization rate and high density, and low dielectric constant and dielectric loss, which can meet the dielectric properties of high-frequency and high-speed copper clad laminates, making them have high thermal stability and high reliability.

[0153] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0154] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A spherical silica, characterized in that The dielectric constant Dk of the spherical silicon dioxide is 3.5F / m-4.0F / m, the dielectric loss Df is 0.0001-0.005, the amorphous ratio is ≥99%, the spheroidization rate is ≥99%, and the porosity is 0.1%-2%.

2. The spherical silica according to claim 1, wherein The spherical silica satisfies at least any of the following conditions: D50 is 0.3 μm to 8 μm; D90 / D10 is 1.7 to 8; and BET specific surface area is 0.3 m 2 / g~8m 2 / g; surface hydroxyl content ≤3 / nm 2 .

3. The spherical silica according to claim 1, wherein The spherical silica satisfies at least any one of the following requirements: surface roughness Ra < 10 nm; and does not contain silica particles ≤ 100 nm.

4. The spherical silica according to claim 1, wherein The surface of the spherical silica is grafted with a first graft and a second graft, the first graft is at least one of an epoxy group, an aniline group, a vinyl group, and a long-chain alkyl group, and the second graft is at least one of a fluorine-containing group and a silazane group.

5. The spherical silica according to claim 4, wherein The grafting equivalent of the surface groups of the spherical silica is 0.1% to 0.3%.

6. A method for preparing spherical silicon dioxide, characterized in that: The steps include: mixing a silicon source, a solvent, and water to prepare a dispersion; The dispersion and the alkaline catalyst are mixed at 30-35°C, the pH is controlled at 9-10, and the mixture is allowed to stand for 2-3 hours; the mixture is then heated to 55-60°C, stirred and reacted for 2-3 hours; the mixture is then heated to 70-85°C, stirred and reacted for 2-3 hours to obtain a silicone ball slurry; Separating the organosilicon balls from the organosilicon ball slurry to obtain monodispersed organosilicon ball powder; The silicone ball powder is processed in the following stages: Low-temperature pre-oxidation stage: in an oxygen atmosphere, raise the temperature to 200°C to 400°C and keep it warm for 4h to 6h; High-temperature densification stage: the first stage: the temperature is raised to 750℃~800℃, and kept warm for 1h~2h; the second stage: the temperature is raised to 850℃~900℃, and kept warm for 1h~2h; the third stage: the temperature is raised to 950℃~1000℃, and kept warm for 1h~2h; the fourth stage: the temperature is raised to 1050℃~1100℃, and kept warm for 1h~2h; then cooled.

7. The method for preparing spherical silicon dioxide according to claim 6, wherein The heating rate in the low-temperature pre-oxidation stage is 2°C / min to 5°C / min; In the high-temperature densification stage, the heating rate of the first stage is 8°C / min to 10°C / min, the heating rate of the second stage is 2°C / min to 5°C / min, the heating rate of the third stage is 2°C / min to 5°C / min, and the heating rate of the fourth stage is 2°C / min to 5°C / min.

8. The method for preparing spherical silicon dioxide according to claim 6, wherein In the low-temperature pre-oxidation stage and the high-temperature densification stage, the oxygen concentration is 30% to 50%.

9. The method for preparing spherical silicon dioxide according to claim 6, wherein The cooling rate is ≥50°C / min.

10. The method for preparing spherical silicon dioxide according to claim 6, wherein The mass of the solvent is 10% to 20% of that of water, and the mass of the silicon source is 5% to 20% of the sum of the mass of the solvent and water.

11. The method for preparing spherical silicon dioxide according to claim 6, wherein The spherical silica is also modified: First, the spherical silica is reacted at 80°C to 120°C for 25 minutes to 35 minutes to introduce the first graft; then, the second graft is introduced at 80°C to 120°C for 25 minutes to 35 minutes; The first grafted substance is at least one of an epoxy group, an aniline group, a vinyl group, and a long-chain alkyl group, and the second grafted substance is at least one of a fluorine-containing group and a silazane group.

12. A high-frequency and high-speed copper-clad laminate, characterized in that: The raw material composition comprises at least epoxy resin, curing agent and spherical silica, and the spherical silica is the spherical silica according to any one of claims 1 to 5 or the spherical silica prepared by the preparation method according to any one of claims 6 to 11.

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