Surface coating process of low-dielectric spherical silicon micro-powder for high-frequency high-speed copper-clad plate

Abstract

This invention discloses a low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates and its surface coating process, belonging to the field of material surface modification technology. The spherical silicon micropowder is coated with a layer of hydrogenated polybutadiene modified with terminal ether-based siloxanes. This layer is formed by introducing large-volume nonpolar groups and / or fluorine-containing groups into the 1,2-vinyl side chains of hydroxyl-terminated polybutadiene via a mercapto-olefin click chemistry reaction, followed by hydrogenation to obtain hydrogenated polybutadiene. The terminal hydroxyl groups of the hydrogenated polybutadiene are then linked to the ether-based siloxane product via a Williamson ether synthesis reaction. This invention, through a three-pronged design of main chain saturation, terminal group anchoring, and large-volume / fluorine-containing functionalization of the side chains, significantly reduces the dielectric loss and water absorption rate of copper-clad laminates at high frequencies, while improving the interfacial compatibility between the filler and the hydrocarbon resin matrix. The resulting copper-clad laminate is suitable for high-frequency, high-speed applications such as 5G / 6G communication and AI servers.

Description

Technical Field

[0001] This invention belongs to the field of material surface modification technology, specifically relating to a low-dielectric spherical silicon micropowder for high-frequency and high-speed copper-clad laminates and its surface coating process. Background Technology

[0002] With the development of 5G / 6G communications, artificial intelligence servers, millimeter-wave radar, and high-speed data centers, signal transmission rates have evolved from 56Gbps to 112Gbps and even 224Gbps, placing extremely stringent requirements on the high-frequency dielectric properties of copper clad laminate (CCL) substrates. At high frequencies, signal transmission delay and energy loss mainly depend on the dielectric constant (Dk) and dielectric loss factor (Df) of the substrate. The industry typically requires high-frequency, high-speed CCLs of M7 grade and above to have Dk < 3.0 and Df < 0.005, while M8 / M9 grade products require Df < 0.002.

[0003] To achieve ultra-low dielectric loss, high-frequency and high-speed copper-clad laminates commonly use low-polarity matrix resins such as hydrocarbon resins, modified polyphenylene ether, or polytetrafluoroethylene. Among them, hydrocarbon resins, containing only CH and CC bonds, have a dipole moment close to zero, with a dielectric loss (Df) as low as 0.0005~0.002 at 10GHz, and extremely low water absorption. They have become the mainstream matrix choice for manufacturing AI server accelerator cards (M8 / M9 level CCLs) and semiconductor device-specific equipment.

[0004] However, hydrocarbon resins themselves have low modulus and insufficient rigidity, and poor adhesion to copper foil. Therefore, a high proportion of inorganic functional fillers must be added to compensate for dimensional stability and mechanical strength. Spherical fused silica powder, due to its high bulk density, low resin viscosity, and excellent drilling processability, has become the most widely used filler in high-frequency CCLs, with a volume fraction reaching 50-60%. However, the surface of spherical silica powder is rich in silanol groups, exhibiting strong polarity, which brings the following problems: (1) Moisture absorption increases loss: Silyl hydroxyl groups easily adsorb moisture in the air. Water molecules generate strong dipole orientation polarization under GHz electric field, which leads to a sharp deterioration of Df of copper clad laminate and serious performance degradation after humid heat aging. (2) Interface polarization: There is a huge dielectric mismatch between inorganic silicon micropowder and low polarity hydrocarbon resin, which forms Maxwell-Wagner polarization at the interface, further increasing the dielectric loss of the composite material. (3) Poor compatibility: The strong polar hydroxyl groups on the surface of silicon micro powder are thermodynamically incompatible with low polar hydrocarbon resin, resulting in uneven dispersion of fillers, weak interfacial bonding, and easy warping, delamination and insufficient copper foil peel strength of copper clad laminate.

[0005] To address the aforementioned issues, existing technologies primarily employ silane coupling agents (such as KH550, KH560, and KH570) to modify the surface of silicon micropowder. The silane coupling agent, through the hydrolysis of its alkoxy groups, condenses with the Si-OH groups on the surface of the silicon micropowder to form Si-O-Si bonds. The other end of the coupling agent interacts with the resin matrix through organic functional groups such as amino, epoxy, or vinyl groups, thereby improving dispersibility and interfacial adhesion.

[0006] However, the silane coupling agent route has fundamental drawbacks in high-frequency, high-speed copper-clad laminate applications: (1) Polar group contamination: The amino, epoxy or amide groups introduced by silane coupling agents are all strong polar groups with high dipole moments. They generate significant orientation polarization under GHz electric field, directly increasing dielectric loss and making it difficult to meet the requirement of M8 / M9 grade <0.002.

[0007] (2) Residual moisture absorption channels: The modified layer of silane coupling agent is extremely thin (the monolayer is about 1~2nm), which does not completely shield the hydroxyl groups on the surface of silicon micropowder. The residual hydroxyl groups and the polar groups of silane itself can still serve as adsorption sites for water molecules, resulting in a significant deterioration of Df after humid heat aging.

[0008] (3) Heterogeneous interface polarization: The chemical structure of the silane modified layer and the hydrocarbon resin matrix are heterogeneous and the polarity is mismatched. Dielectric mismatch and polarization loss still exist at the interface.

[0009] (4) Insufficient compatibility with hydrocarbon resins: The organic end groups of silane coupling agents are often thermodynamically incompatible with low polarity hydrocarbon resins, resulting in micro-phase separation or voids at the filler-resin interface, which in turn deteriorates the dielectric properties. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates and its surface coating process, aiming to solve the following technical problems: (1) A silicon micro powder surface coating layer that is completely homogeneous with the hydrocarbon resin matrix is ​​provided to eliminate heterogeneous interface polarization; (2) The siloxane anchoring group is linked by a weakly polar ether bond, avoiding the strong polar groups introduced by traditional silane coupling agents; (3) Eliminate the risk of oxidation by hydrogenation of the main chain, increase the free volume by large non-polar groups in the side chain to reduce Dk, and reduce the polarization rate and water absorption rate by fluorinated groups in the side chain. (4) Achieve excellent high-frequency dielectric properties of copper clad laminate at 10GHz, with Df≤0.002, Dk≤3.0 and water absorption rate≤0.05%, while maintaining high copper foil peel strength and filler filling rate.

[0011] The technical solution for achieving the objective of this invention is as follows: This invention provides a low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates. The surface of the spherical silicon micropowder is coated with a layer of hydrogenated polybutadiene modified with ether-terminated siloxane. The hydrogenated polybutadiene layer is obtained by hydrogenating the 1,2-vinyl side chain of hydroxyl-terminated polybutadiene after introducing large-volume nonpolar groups and / or fluorine-containing groups through a mercapto-olefin click chemistry reaction. The hydroxyl groups of the hydrogenated polybutadiene are then linked to the ether-terminated siloxane product through a Williamson ether synthesis reaction.

[0012] In one specific embodiment, the number-average molecular weight of the hydroxyl-terminated polybutadiene is 2000-10000, and the 1,2-vinyl content is 20-70 wt%.

[0013] In one specific embodiment, the bulky nonpolar group is selected from one or more of tert-butyl, tert-dodecyl, cyclohexyl, 2,5,5-trimethyl-2-norbornyl, and adamantyl.

[0014] In one specific embodiment, the fluorinated group is selected from one or more of trifluoroethyl and perfluorohexylethyl.

[0015] In one specific embodiment, the mass ratio of the spherical silica powder to the ether-terminated siloxane-modified hydrogenated polybutadiene is 100:(1~5); the spherical silica powder is molten spherical silica powder, D 50 The particle size is 0.5~5μm. Preferably, the D of the spherical silica powder is... 50 The particle size exhibits a bimodal distribution, specifically 60-70 wt% D. 50 It consists of 3~5μm molten spherical silica powder and 30~40wt% D 50 The gradation of molten spherical silica powder with a size of 0.5~1.0μm.

[0016] In one specific embodiment, the hydrogenation degree of the main chain double bond of the hydrogenated polybutadiene is 85-100%; the molar ratio of the bulky nonpolar group to the fluorinated group is 3-9:1.

[0017] In one specific embodiment, the ether-based siloxane is selected from one or more of 3-(trimethoxysilyl)propoxy or 3-(triethoxysilyl)propoxy.

[0018] This invention also protects the surface coating process of the low-dielectric spherical silicon micropowder for high-frequency and high-speed copper-clad laminates, comprising the following steps: S1. Side chain functionalization: Using hydroxyl-terminated polybutadiene as raw material, in the presence of a free radical initiator, it undergoes a mercapto-olefin click chemical reaction with a mercapto-containing compound to introduce bulk nonpolar groups and / or fluorine-containing groups into the vinyl side chain. S2. Main chain hydrogenation: In the presence of a hydrogenation catalyst, the main chain double bond of the product obtained in step S1 is catalytically hydrogenated, and the degree of hydrogenation is controlled to be 85~100% to obtain side chain functionalized hydrogenated polybutadiene. S3. End-group etherification: Under the action of a strong base, the terminal hydroxyl groups of the product obtained in step S2 are converted into sodium alkoxide, and then reacted with a haloalkylsilane to undergo Williamson ether synthesis reaction to obtain hydrogenated polybutadiene modified with terminal ether siloxane. S4. Coating: In the presence of water, the product obtained in step S3 is mixed and reacted with spherical molten silicon micropowder in a solvent, causing the siloxane end groups to hydrolyze and condense with the surface of the silicon micropowder. The mixture is then purified and dried to obtain the low-dielectric spherical silicon micropowder.

[0019] In one specific embodiment, the free radical initiator in step S1 is azobisisobutyronitrile or benzoyl peroxide, the reaction temperature is 60~80°C, and the reaction time is 1~4h; the hydrogenation catalyst in step S2 is a palladium / carbon catalyst, the reaction temperature is 25~120°C, and the hydrogen pressure is 0.5~5MPa; the strong base in step S3 is sodium hydride or metallic sodium; and the solvent in step S4 is toluene or a mixed solution of xylene and ethanol, the reaction temperature is 50~80°C, and the reaction time is 1~4h.

[0020] In one specific embodiment, the mercapto-containing compound in step S1 is selected from one or more of tert-butyl mercaptan, tert-dodecyl mercaptan, cyclohexane mercaptan, 2,5,5-trimethyl-2-norbornane mercaptan, 1-adamantane mercaptan, 2,2,2-trifluoroethanethiol, and 2-(perfluorohexyl)ethanethiol; the haloalkylsilane in step S3 is selected from one or more of 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane.

[0021] This invention also protects a high-frequency, high-speed copper-clad laminate, which, by weight, comprises 300-600 parts of the aforementioned low-dielectric spherical silicon micropowder, 80-120 parts of hydrocarbon resin, 20-40 parts of polyphenylene ether, 2-4 parts of peroxide initiator, and 1-3 parts of crosslinking agent.

[0022] Beneficial effects

[0023] Compared with the prior art, the low-dielectric spherical silicon micropowder for high-frequency and high-speed copper-clad laminates and its surface coating process provided by the present invention have the following significant advantages: This invention uses hydrogenated polybutadiene, chemically homogeneous with the hydrocarbon resin matrix, as the main body of the coating layer. The end groups are connected to siloxane anchoring groups via weakly polar ether bonds, avoiding strongly polar linking groups and creating a dielectrically continuous interface between the coating layer and the matrix resin. Simultaneously, the large-volume nonpolar groups introduced into the side chains reduce polarizability density by increasing the molecular free volume, and the fluorinated groups further suppress orientation polarization at high frequencies by utilizing the low polarizability of the CF bond. This invention eliminates the oxidation risk of the polybutadiene main chain double bonds through main chain hydrogenation, quantitatively converts the 1,2-vinyl side chain into saturated thioether bonds through a mercapto-ene reaction, and then forms a dense Si-O-Si covalent anchoring network with the silica powder surface through the end-group ether-based siloxanes, completely shielding the surface hydroxyl groups. Furthermore, the fluorinated side chains form a hydrophobic barrier on the coating layer surface, reducing water absorption.

[0024] This invention employs a three-pronged design—end-group anchoring, side-chain functionalization, and main-chain homogeneity—to achieve not only strong covalent anchoring between the coating layer and the silicon micropowder surface but also complete thermodynamic compatibility with the hydrocarbon resin matrix. The large-volume groups in the side chains increase the steric hindrance of the coating layer, preventing the aggregation of silicon micropowder particles; while the extremely weak polarity of the sulfide bonds does not compromise compatibility with the matrix. Therefore, the copper-clad laminate can maintain uniform dispersion of silicon micropowder even at a high filler content of 50-60 vol%.

[0025] The low-dielectric spherical silicon micropowder obtained by this invention breaks through the technical bottleneck of low dielectric, high adhesion, and high filling. The resulting copper-clad laminate has excellent comprehensive performance with Dk≤3.0, Df≤0.002, water absorption ≤0.05%, and copper foil peel strength ≥1N / mm. It can be widely used in high-frequency and high-speed printed circuit boards in fields such as 5G / 6G communication base stations, AI servers, millimeter-wave radar, and high-speed data centers. Attached Figure Description

[0026] Figure 1 Infrared spectra of hydroxyl-terminated polybutadiene and hydrogenated polybutadiene modified with ether-terminated siloxanes prepared in Example 2. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0029] The raw materials used in the examples and comparative examples are described below: Spherical silica powder: 65wt% D 50 It consists of 3~5μm molten spherical silica powder and 35wt% D 50 The gradation of molten spherical silica powder with a particle size of 0.5~1.0 μm, Na + <10ppm, sphericity>95%, Ji'an Yushun.

[0030] Hydroxyl-terminated polybutadiene: Krasol LBH 2000, molecular weight 2000, 1,2-vinyl content 65wt%, hydroxyl functionality 1.95, Krasol.

[0031] Hydrocarbon resin: hydrogenated polybutadiene, BI-2000, Nippon Soda; Polyphenylene oxide: NORYL™ SA9000, Sabic; Peroxide: Di-tert-butyl peroxide diisopropylbenzene (BIBP); Crosslinking agent: triallyl isocyanate (TAIC); Fiberglass cloth: 1078, Hung Ho Electronic Materials Technology Co., Ltd.

[0032] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0033] Examples and Comparative Examples Example 1

[0034] A low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates: The preparation method is as follows: S1. Dissolve 100g of hydroxyl-terminated polybutadiene in 200g of toluene, add 1.2mol of tert-dodecyl mercaptan and 1.5g of azobisisobutyronitrile (AIBN), and heat to 65°C under nitrogen protection for 2 hours. After the reaction is complete, remove unreacted mercaptan by vacuum distillation to obtain side-chain modified polybutadiene. S2. The product obtained in step S1 is transferred to a high-pressure reactor, and 5 wt% Pd / C catalyst equivalent to the mass of the side-chain modified polybutadiene is added. Toluene is used as the solvent, and the reaction is carried out at a hydrogen pressure of 3.0 MPa and a temperature of 80°C for 6 hours. After the reaction, Pd / C is removed by filtration, and toluene is removed from the filtrate by vacuum distillation to obtain side-chain functionalized hydrogenated polybutadiene with a main chain hydrogenation degree ≥85%. S3. Dissolve 100g of the product obtained in step S2 in 300g of anhydrous tetrahydrofuran. Under nitrogen protection, add 5g of sodium hydride (dispersed in mineral oil, concentration 60wt%) and stir at 0°C for 1h to induce sodium hydride oxidation. Then, add 22g of 3-chloropropyltrimethoxysilane dropwise and react at 60°C for 8h. After the reaction is complete, filter to remove sodium chloride, evaporate the solvent under reduced pressure, precipitate with methanol, filter, and dry under vacuum to obtain ether-terminated siloxane-modified hydrogenated polybutadiene.

[0035] S4. Dissolve 18g of the product obtained in step S3 in a mixed solvent of 80g toluene and 15g anhydrous ethanol, add 400g of molten spherical silica powder, and add 2g of deionized water dropwise. Stir at 60°C for 2 hours to hydrolyze the siloxane end groups and condense them on the surface of the silica powder. After the reaction is complete, filter to separate the solid, wash three times with ethanol to remove unreacted free polymer, and dry under vacuum at 120°C for 4 hours to obtain low-dielectric spherical silica powder.

[0036] Example 2

[0037] A low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates: The preparation method differs from Example 1 in that 0.9 mol of tert-dodecyl mercaptan and 1.2 g of AIBN are added in step S1, and the reaction is carried out at 65°C for 2 h. Subsequently, 0.3 mol of 2,2,2-trifluoroethanethiol and 0.5 g of AIBN are added, and the reaction is continued at 65°C for 2 h.

[0038] Example 3

[0039] A low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates: The preparation method differs from Example 1 in that, in step S1, 1.08 mol of tert-butyl mercaptan and 1.5 g of AIBN are added, and the reaction is carried out at 65°C for 2 h. Subsequently, 0.12 mol of perfluorohexylethyl mercaptan and 0.3 g of AIBN are added, and the reaction is continued at 65°C for 2 h.

[0040] Example 4

[0041] A low-dielectric spherical silicon micropowder for high-frequency and high-speed copper-clad laminates: The preparation method differs from that in Example 1 in that 1.2 mol of 1-adamanthiol and 1.5 g of AIBN are added in step S1, and the reaction is carried out at 65°C for 2 h.

[0042] Comparative Example 1 A silane-modified spherical silica powder: 400g of molten spherical silica powder is dispersed in 100ml of ethanol / water (95:5) mixture, 18g of 3-aminopropyltriethoxysilane is added, stirred at 60°C for 2h, filtered, and dried at 120°C to obtain silane-modified spherical silica powder.

[0043] Comparative Example 2 A pre-coated spherical silica powder: Compared with Example 1, the difference is that the side chain modification step S1 is omitted, and the hydroxyl-terminated polybutadiene is directly subjected to the main chain hydrogenation step S2, the end group etherification step S3, and the coating step S4 to obtain the pre-coated spherical silica powder.

[0044] Comparative Example 3 A spherical silica powder coated with urethane-terminated siloxane-modified hydrogenated polybutadiene: Compared with Example 1, the difference is that step S3 is modified as follows: 100g of the product obtained in step S2 is dissolved in toluene, 22g of 3-isocyanate-propyltrimethoxysilane and 0.5g of dibutyltin dilaurate catalyst are added, and the reaction is carried out at 60°C for 4h to obtain urethane-terminated siloxane-modified hydrogenated polybutadiene.

[0045] Comparative Example 4 A type of spherical silica powder coated with a polybutadiene layer modified with ether-terminated siloxane: Compared with Example 1, the difference is that the main chain hydrogenation step S2 is omitted, and only the side chain modification step S1, the end-terminated etherification step S3, and the coating step S4 are performed to obtain spherical silica powder coated with a polybutadiene layer modified with ether-terminated siloxane.

[0046] Application examples Application Example 1 100g of hydrocarbon resin, 30g of polyphenylene ether, 400g of low dielectric spherical silica powder prepared in Example 1, 2.5g of di-tert-butyl peroxide diisopropylbenzene, and 1.5g of triallyl isocyanurate were added to a mixed solvent of toluene and acetone (mass ratio 7:3) to prepare a glue solution with a solid content of 55%. Fiberglass cloth is impregnated with the above-mentioned adhesive solution and dried in an oven at 80°C for 15 minutes to obtain a prepreg. After drying, it is cut, and the resin content of the prepreg is controlled to be 65~75wt% and the flowability is within the range of 15~25%. Four prepregs are stacked together and covered with RTF low profile copper foil on the top and bottom. They are placed in a vacuum hot press and heated to 180°C at 2°C / min. During this period, a vacuum is drawn at 100°C to ≤-0.09MPa and held for 15 minutes to remove volatiles. Then the vacuum is released and the pressure is increased to 3MPa. The pressure is held at 180°C / 3MPa for 2 hours. Finally, the temperature is controlled and cooled to below 50°C to obtain a high-frequency high-speed copper-clad laminate. It is then milled to the target thickness according to the test requirements.

[0047] Application Examples 2-4 Compared with Application Example 1, the difference is that the low-dielectric spherical silicon micropowder obtained in Example 1 is replaced with the low-dielectric spherical silicon micropowder obtained in Examples 2 to 4.

[0048] Compare and contrast examples 1-4 Compared with Application Example 1, the difference is that the low dielectric spherical silicon micropowder obtained in Example 1 was replaced with the spherical silicon micropowder obtained in Comparative Examples 1 to 4.

[0049] The copper-clad laminates produced for the corresponding use cases and comparative application examples were subjected to the following performance tests, and the results are shown in Table 1: 1. Peel Strength: Tested according to the Printed Circuit Board Association (IPC) standard IPC-TM-650 (2.4.8.1). The sample width is (10±0.2) mm. Peel approximately 10 mm of copper foil from one end of the sample to the substrate. Then, clamp the sample on the sample holder of the peeling machine, holding the peeled copper foil with the sample clamp so that the peeled copper foil is perpendicular to the substrate. Start the peeling machine and apply a uniform tension. The tension direction should be perpendicular to the substrate direction. Continue until the peel length is more than 25 mm, and record the average peel force during the process, expressed in N / mm. The error value of peel strength between different effective samples should not exceed 5%. The test result is the average value of three effective samples. The test temperature is room temperature (25℃±5℃), and the humidity is below 60%.

[0050] 2. Water Absorption Rate: The water absorption rate of the samples was tested according to the Printed Circuit Board Association (IPC) standard IPC-TM-650 2.6. After etching the copper-clad laminate sample, the dielectric layer surface was cleaned with anhydrous ethanol. The sample was cut into 50mm × 50mm square specimens and dried in an oven at 105℃ for 2 hours. After cooling, it was weighed and recorded as M1. It was then placed at 85℃ / 85%RH for 24 hours, cooled, and weighed again, recording the weight after water absorption as M2. The water absorption rate of the sample was calculated using the formula: Water Absorption Rate = (M2 - M1) / M1 × 100%. The test temperature was room temperature (25℃ ± 5℃) and the humidity was below 60%.

[0051] 3. Bending Strength: A CMT-5305 electronic universal testing machine was used, and the test was conducted at room temperature according to the Printed Circuit Board Association (IPC) standard IPC-TM-650 2.4.4, at a test speed of 0.76 mm / min. The specimen length was (63.5±2) mm, width was (26±0.5) mm, span was (16±0.5) mm, and thickness was (0.5±0.05) mm. The measurement results were required to have a bending strength data error within 5%, and the test specimen was the average of three standard specimens. The test temperature was room temperature (25℃±5℃), and the humidity was below 60%.

[0052] 4. Dielectric Properties: The dielectric constant (Dk) and dielectric loss tangent (Df) were measured using a microwave frequency meter and the SPDR method. Three samples (50mm × 50mm × 0.5mm) were used. The test conditions were 25℃ and the frequency was 10GHz. The test results were required to have an error within 5%. Both the dielectric constant and dielectric loss are dimensionless properties. The test temperature was room temperature (25℃ ± 5℃), and the humidity was below 60%.

[0053] 5. Heat Resistance: The heat resistance of the samples was tested according to the Printed Circuit Board Association (IPC) standard IPC-TM-650 2.4.24.1. After etching away the copper foil from the copper-clad laminate sample, it was cut into 50mm × 50mm square specimens. These specimens were suspended 2.5mm above the surface of a tin bath at a preheated temperature of 288℃ for 10 seconds. The specimens were then completely immersed in the tin bath. The time elapsed from immersion until delamination, blistering, white spots, or significant deformation appeared on the specimen was recorded; this was the T-288 thermal delamination time. The error value of the three valid specimens should not exceed 10%, and the test result was the average of the three valid specimens. The test temperature was room temperature (25℃ ± 5℃), and the humidity was below 60%.

[0054] 6. Thermal aging performance: The copper-clad laminate samples were placed in a forced convection oven at 150℃ for thermal aging treatment for 500h and 1000h respectively. After aging, the samples were taken out and cooled to room temperature (25℃±5℃) in a desiccator. Then, the dielectric loss tangent (Df) of the aged samples was tested according to the dielectric performance test method (item 4) described above.

[0055] 7. Infrared Spectroscopy Test: Infrared spectra were measured using a Bruker Vertex-70 Fourier Transform Infrared Spectrometer. Resolution: 4cm². -1 32 scans, wavenumber range 4000~500cm -1 .

[0056] Table 1 Performance test results of application examples and comparative application examples

[0057] As can be seen from the data in Table 1, in Application Example 1, the side chain was modified with tert-dodecyl sulfide. The long-chain branched alkyl groups effectively widened the inter-chain spacing of polybutadiene through steric hindrance, significantly increasing the free volume and reducing the molecular packing density, thereby suppressing the polarizability density and dielectric constant. The ether-bonded siloxane end groups introduced by Williamson etherification contain only weakly polar COC bonds, avoiding the orientation polarization of strongly polar groups in urethane or silane coupling agents in the GHz band. After hydrogenation, the double bond oxidation sites of the main chain were completely eliminated, so that the coating layer and the hydrocarbon matrix formed a completely homogeneous nonpolar continuous phase, fundamentally eliminating the dielectric mismatch and polarization loss at the filler-matrix interface, while giving the board excellent heat-resistant delamination properties.

[0058] Application Example 2 further introduces trifluoroethyl sulfide on the basis of tert-dodecyl side chain. The large volume effect of tert-dodecyl reduces the molecular packing density and dielectric constant. At the same time, by taking advantage of the extremely low polarizability and high electronegativity of trifluoromethyl, a dense hydrophobic barrier is constructed on the surface of the coating layer, which effectively blocks the adsorption and permeation channels of water molecules at the filler-matrix interface. The synergistic effect of fluorinated side chain and long-chain alkyl sulfide not only further suppresses dipole orientation polarization at high frequency, but also significantly improves the interfacial stability under humid and hot environment, so that the copper clad laminate maintains extremely low dielectric loss and water absorption rate during long-term high temperature and high humidity service.

[0059] Application Example 3 uses tert-butyl sulfide to provide steric hindrance and increase free volume, while perfluorohexyl ethyl sulfide introduces long-chain fluoroalkyl groups into the side chain. Although the tert-butyl chain is relatively short, it has a high degree of branching, which can still effectively reduce the polarizability density. Compared with short-chain fluorinated groups, perfluorohexyl ethyl has a lower surface energy and a stronger hydrophobic shielding effect. The two work together to reduce the surface polarizability and moisture absorption sensitivity of the coating layer, so that the copper clad laminate achieves a good balance between dielectric properties and moisture resistance.

[0060] Application Example 4 uses adamantane alkyl sulfide to modify the side chain. The cage-like polycyclic rigid framework has extremely low electronic polarizability and large volume, which is effective in increasing free volume and reducing dielectric constant. At the same time, the rigid structure of adamantane improves the modulus and heat resistance of the coating layer itself, which helps to improve the glass transition temperature and dimensional stability of the plate. However, the interfacial stress between its rigid framework and the matrix resin increases slightly, which makes the dielectric loss factor slightly higher than that of the flexible long-chain alkyl system.

[0061] In contrast, Application Example 1 uses conventional 3-aminopropyltriethoxysilane (KH-550) to modify silicon micropowder. The amino group is a strongly polar group, which generates strong dipole orientation polarization under a GHz electric field, directly increasing dielectric loss. Moreover, the amino group is thermodynamically incompatible with low-polarity hydrocarbon resin, forming a significant heterogeneous interface, resulting in severe polarization of the Maxwell-Wagner interface. In addition, the amino group is hygroscopic and decomposes to produce gas at high temperatures, which not only increases the water absorption rate of the board, but also causes blistering and delamination under lead-free soldering thermal shock, resulting in a comprehensive deterioration of heat resistance and long-term reliability.

[0062] In contrast to Application Example 2, which omits the side chain functionalization step and retains only the main chain hydrogenation and end group etherification, although the end group ether bonds avoid strong polar contamination, the side chains lack large-volume nonpolar groups and fluorine-containing groups, resulting in dense packing of the coating layer molecular chains and insufficient free volume, making it difficult to effectively reduce the polarizability density. At the same time, the side chains lack hydrophobic barriers, and there are still trace water molecule adsorption channels at the interface, making the interface polarization and water absorption increase and decrease more obvious under humid and hot conditions, and the dielectric properties decay significantly after long-term aging.

[0063] In contrast, Application Example 3 uses 3-isocyanate-propyltrimethoxysilane for end-group modification to form urethane bonds. Uramates are highly polar groups with high dipole moments and readily form hydrogen bond networks, contributing significantly to orientation polarization in the GHz band. At the same time, urethane bonds are prone to hydrolysis under humid and hot conditions, generating amines and carbon dioxide, which further increases interfacial polarity and porosity, resulting in higher dielectric loss and water absorption than the Williamson ether route, and insufficient long-term humid and hot stability.

[0064] In contrast to Application Example 4, which omits the main chain hydrogenation step, although the side chains are modified and the end groups are etherified, the main chain retains a large number of 1,4-carbon double bonds. Under high-temperature long-term service conditions, the main chain double bonds undergo thermal oxidation reactions, generating highly polar oxidation products such as hydroperoxides, aldehydes, ketones, carboxylic acids, and alcohols. These products not only directly contribute to strong dipole orientation polarization, causing an exponential deterioration in dielectric loss, but also cause blistering, delamination, and embrittlement inside the board due to oxidation and decomposition, severely damaging the structural integrity and copper foil adhesion, and completely losing commercial application value.

[0065] Figure 1 The image shows a comparison of the FTIR spectra of the ether-terminated siloxane-modified hydrogenated polybutadiene and the hydroxyl-terminated polybutadiene obtained in Example 2. As can be seen from the image, the hydroxyl-terminated polybutadiene exhibits higher activity at approximately 3300 cm⁻¹. -1 The broad peak at approximately 1640 cm⁻¹ is attributed to the stretching vibration of the terminal hydroxyl groups in the raw material. This peak completely disappears in the hydrogenated polybutadiene modified with terminal ether-based siloxanes, indicating that the terminal hydroxyl groups have been converted to ether-based siloxane terminal groups via the Williamson ether synthesis reaction. -1 The peak at [value] is attributed to the stretching vibration of the carbon-carbon double bond (C=C), which is significantly weakened in hydrogenated polybutadiene modified with terminal ether-based siloxanes, with a hydrogenation degree ≥85%, and is approximately 910 cm⁻¹. -1 The fingerprint peaks at approximately 1,2-vinyl groups have largely disappeared, indicating that the side-chain double bonds have been consumed by the mercapto-olefin reaction, and the main-chain double bonds have been essentially saturated by the hydrogenation reaction. The terminal ether-terminated siloxane-modified hydrogenated polybutadiene reaches a peak at approximately 2830 cm⁻¹. -1 A new peak appears at approximately 1200–1350 cm⁻¹, attributed to the CH stretching vibration of the methoxy group in trimethoxysilane (-Si(OCH₃)₃), confirming successful insertion of the siloxane end group. -1 A strong and broad new peak appears in the range, attributed to the C–F stretching vibration of the trifluoroethyl group, proving that the fluorinated thiol has been incorporated into the side chain via a mercapto-alkene reaction. The peak is located at approximately 1000–1100 cm⁻¹. -1 A new broad absorption appears in the region, attributed to the overlap of stretching vibrations between the ether bond (C–O–C) and the siloxane (Si–O–C), confirming Williamson etherification and the formation of the siloxane structure. At approximately 700 cm⁻¹... -1The presence of weak absorption nearby, attributed to the skeletal vibration of an aliphatic thioether bond (C–S–C), further confirms the successful addition of the side-chain mercapto-olefin. This demonstrates that the terminal hydroxyl groups of the hydroxyl-terminated polybutadiene have been converted, the degree of hydrogenation exceeds 85%, and the methoxysiloxane terminal group and fluorinated thioether side chain have been successfully introduced, consistent with the designed structure of the ether-terminated siloxane-modified hydrogenated polybutadiene.

[0066] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates, characterized in that, The spherical silica powder is coated with a layer of hydrogenated polybutadiene modified with ether-terminated siloxane; the hydrogenated polybutadiene modified with ether-terminated siloxane is obtained by hydrogenating the 1,2-vinyl side chain of hydroxyl-terminated polybutadiene after introducing a large volume nonpolar group and / or a fluorine-containing group through a mercapto-olefin click chemistry reaction; the hydroxyl groups of the hydrogenated polybutadiene are then linked to the ether-terminated siloxane through a Williamson ether synthesis reaction.

2. The low-dielectric spherical silicon micropowder as described in claim 1, characterized in that, The number-average molecular weight of the hydroxyl-terminated polybutadiene is 2000-10000, and the 1,2-vinyl content is 20-70 wt%.

3. The low-dielectric spherical silicon micropowder as described in claim 1, characterized in that, The bulky nonpolar group is selected from one or more of tert-butyl, tert-dodecyl, cyclohexyl, 2,5,5-trimethyl-2-norborneyl, and adamantyl; the fluorinated group is selected from one or more of trifluoroethyl and perfluorohexylethyl.

4. The low-dielectric spherical silicon micropowder as described in claim 1, characterized in that, The mass ratio of the spherical silica powder to the ether-terminated siloxane-modified hydrogenated polybutadiene is 100:(1~5); the spherical silica powder is molten spherical silica powder, D 50 The value is 0.5~5μm.

5. The low-dielectric spherical silicon micropowder as described in claim 1, characterized in that, The hydrogenation degree of the main chain double bond of the hydrogenated polybutadiene is 85-100%; the molar ratio of the bulky nonpolar group to the fluorinated group is 3-9:

1.

6. The low-dielectric spherical silicon micropowder as described in claim 1, characterized in that, The ether-based siloxane is selected from one or more of 3-(trimethoxysilyl)propoxy or 3-(triethoxysilyl)propoxy.

7. The surface coating process for low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Side chain functionalization: Using hydroxyl-terminated polybutadiene as raw material, in the presence of a free radical initiator, it undergoes a mercapto-olefin click chemical reaction with a mercapto-containing compound to introduce bulk nonpolar groups and / or fluorine-containing groups into the vinyl side chain. S2. Main chain hydrogenation: In the presence of a hydrogenation catalyst, the main chain double bond of the product obtained in step S1 is catalytically hydrogenated, and the degree of hydrogenation is controlled to be 85~100% to obtain side chain functionalized hydrogenated polybutadiene. S3. End-group etherification: Under the action of a strong base, the terminal hydroxyl groups of the product obtained in step S2 are converted into sodium alkoxide, and then reacted with a haloalkylsilane to undergo Williamson ether synthesis reaction to obtain hydrogenated polybutadiene modified with terminal ether siloxane. S4. Coating: In the presence of water, the product obtained in step S3 is mixed and reacted with spherical molten silicon micropowder in a solvent, causing the siloxane end groups to hydrolyze and condense with the surface of the silicon micropowder. The mixture is then purified and dried to obtain the low-dielectric spherical silicon micropowder.

8. The surface coating process of low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates as described in claim 7, characterized in that, The free radical initiator in step S1 is azobisisobutyronitrile or benzoyl peroxide, the reaction temperature is 60~80°C, and the reaction time is 1~4h; the hydrogenation catalyst in step S2 is a palladium / carbon catalyst, the reaction temperature is 25~120°C, and the hydrogen pressure is 0.5~5MPa; the strong base in step S3 is sodium hydride or metallic sodium; the solvent in step S4 is toluene or a mixed solution of xylene and ethanol, the reaction temperature is 50~80°C, and the reaction time is 1~4h.

9. The surface coating process of low-dielectric spherical silicon micropowder for high-frequency, high-speed copper-clad laminates as described in claim 7, characterized in that, The mercapto-containing compound in step S1 is selected from one or more of tert-butyl mercaptan, tert-dodecyl mercaptan, cyclohexane mercaptan, 2,5,5-trimethyl-2-norbornane mercaptan, 1-adamantane mercaptan, 2,2,2-trifluoroethanethiol, and 2-(perfluorohexyl)ethanethiol; the haloalkylsilane in step S3 is selected from one or more of 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane.

10. A high-frequency, high-speed copper-clad laminate, characterized in that, Based on weight, it comprises 300-600 parts of the low dielectric spherical silica powder as described in any one of claims 1-6, 80-120 parts of hydrocarbon resin, 20-40 parts of polyphenylene ether, 2-4 parts of peroxide initiator, and 1-3 parts of crosslinking agent.

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