Glass fiber composite material with low dielectric property

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a low-dielectric-property glass fiber composite material. The low-dielectric-property glass fiber composite material is prepared by the following steps: S1, pretreating glass fiber cloth: cutting the glass fiber cloth into a required size and drying the glass fiber cloth; s2, modification treatment and filler filling: soaking the dried glass fiber cloth in a silane coupling agent solution, taking out the glass fiber cloth, drying the glass fiber cloth, soaking the glass fiber cloth in a PTFE dispersion liquid, taking out the glass fiber cloth, and drying the glass fiber cloth again; s3, gum dipping: dipping the dried glass fiber cloth in a BT resin glue solution, taking out and drying to prepare a prepreg; and S4, hot press molding: carrying out compression molding on the prepreg through a stepped heating and boosting process. The low-cost composite material with the dielectric constant as low as 4.3, the water absorption as low as 0.0035 and stable mechanical property is prepared by filling the glass fiber cloth with the low-dielectric PTFE and combining a stepped hot pressing process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a low dielectric performance glass fiber composite material. BACKGROUND

[0002] As a kind of inorganic non-metallic material with excellent performance, glass fiber has the remarkable characteristics of good insulation, strong heat resistance, good corrosion resistance, high mechanical strength, etc., and is widely used in composite materials, electrical insulation materials, thermal insulation materials and circuit substrates, etc. It is a key reinforcing material for improving the comprehensive mechanical properties of products.

[0003] Printed circuit board (PCB) is the core interconnection component of electronic equipment, and is known as the "cornerstone of electronic products". With the rapid development of 5G communication, artificial intelligence, aerospace and other technologies, electronic equipment is evolving towards higher density, more layer structure and high integration, which puts forward higher requirements on the dielectric properties of PCB basic material substrate.

[0004] Copper-clad laminate (CCL) is an indispensable core substrate material in the PCB manufacturing process, and its performance directly determines the signal transmission quality, processing reliability, long-term stability and cost control level of PCB. Currently, the CCL industry is accelerating the transformation to high frequency and high speed fields, and during this process, how to further reduce the dielectric properties (including dielectric constant Dk and dielectric loss Df) of CCL has become one of the most critical technical challenges. According to the values of Dk and Df, CCL can be divided into two categories: high-speed CCL and high-frequency CCL.

[0005] Bismaleimide-triazine (BT) resin matrix is a type of CCL substrate with great development potential in high-frequency substrate materials, which has excellent thermal stability, mechanical properties and processing characteristics, and is widely used in high-frequency communication fields, and can be used as a modified matrix of structural materials and functional composite materials in the aerospace field. However, on the basis of fully utilizing the inherent characteristics of BT resin, how to further reduce its dielectric properties and improve its mechanical properties through modification is the core technical direction to realize its use as a high-performance low-dielectric high-frequency substrate material.

[0006] Polytetrafluoroethylene (PTFE) is a highly symmetrical and non-linear high molecular material, and the fluorine atoms on the molecular chain are symmetrically distributed, almost without polarity. This unique molecular structure endows PTFE with excellent dielectric properties: at a frequency of 10 GHz, the dielectric constant (εr) of PTFE is as low as 2.1, and the dielectric loss (tanδ) is only 0.0003; at the same time, PTFE also has the highest volume resistance (up to 10 18PTFE is a kind of low dielectric material with low dielectric constant (about 2.0), low dielectric loss (about 0.0001-0.001), high thermal stability (about 260-270 DEG C), high arc resistance (about 1000 V / mil) and excellent arc resistance, which is a kind of recognized excellent low dielectric material. Therefore, by introducing PTFE in the process of preparing glass fiber reinforced resin based CCL substrate, it is expected to significantly reduce the dielectric constant and dielectric loss of the composite material.

[0007] However, the surface energy of PTFE is high (about 19-20 mN / m), while the surface energy of glass fiber (about 5-10 mN / m) and BT resin (about 35-40 mN / m) is relatively low, and the difference in surface energy leads to poor interfacial compatibility of the composite material formed by the three, which is specifically manifested as: the mechanical properties of the composite material are decreased; the dielectric property improvement effect is limited; and phase separation is prone to occur in the processing process. Therefore, how to improve the interfacial bonding between PTFE and glass fiber and BT resin has become a key technical problem to be solved by the present application. SUMMARY

[0008] TECHNICAL PROBLEM

[0009] The technical problem to be solved by the present application is the interfacial bonding problem between inorganic material glass fiber and organic material PTFE and BT in the composite material and the compatibility problem between PTFE and BT when polytetrafluoroethylene (PTFE) is introduced into glass fiber fabric as a reinforcing material to prepare a low dielectric printed circuit board (PCB).

[0010] TECHNICAL SCHEME

[0011] The first aspect of the present application provides a low dielectric performance glass fiber composite material, characterized in that the low dielectric performance glass fiber composite material is prepared by the following steps: S1. Preprocessing glass fiber cloth: cutting the glass fiber cloth into the required size and drying; S2. Modification treatment and filler filling: soaking the dried glass fiber cloth in the step S1 in a silane coupling agent solution, taking out and drying, then soaking in a PTFE dispersion liquid, taking out and drying again; S3. Impregnation: impregnating the dried glass fiber cloth in the step S2 in a BT resin glue solution, taking out and drying to prepare a prepreg; S4. Hot pressing: the prepreg in the step S3 is pressed and formed by a stepwise temperature and pressure rising process to obtain a product, i.e. the low dielectric performance glass fiber composite material.

[0012] In some embodiments, the glass fiber cloth in the step S1 is an electronic grade glass fiber cloth which is treated by alkali and has a single fiber diameter of 7-11 um and a pore diameter of 0.15-0.22 mm.

[0013] In some embodiments, the electronic grade glass fiber cloth is one of an E type glass fiber cloth, a D type glass fiber cloth, an NE type glass fiber cloth or an S type glass fiber cloth; preferably, the electronic grade glass fiber cloth is an E type glass fiber cloth.

[0014] In some embodiments, the drying conditions in the S1 and S2 steps are 100-150℃ drying for 0.8-1.2h; the drying conditions in the S3 step are 80-100℃ drying for 20-40min.

[0015] In some embodiments, the preparation step of the silane coupling agent solution in the S2 step is: using ethanol and water to prepare a 1-3wt% silanol aqueous solution of the silane coupling agent, and then fully hydrolyzing at 70-90℃ for 5-8h; wherein the mass ratio of the ethanol and water is 8-10:1; the silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane (KH570), vinyltrimethoxysilane (A-171), vinyltriethoxysilane (A-151), and γ-methacryloxypropyltriethoxysilane (A-174 / Z-6030), preferably KH570.

[0016] In some embodiments, the preparation step of the PTFE dispersion liquid in the S2 step is: using water to prepare a 4-6wt% PTFE solution of PTFE, and breaking the emulsion by stirring at 800-1200rpm for 6-10h.

[0017] In some embodiments, the preparation step of the BT resin glue solution in the S3 step is: melt pre-polymerizing the cyanate ester and bismaleimide, adding diluent and curing agent after cooling to room temperature, and preparing a 40-60wt% glue solution.

[0018] In some embodiments, the mass ratio of the cyanate ester and bismaleimide is 2-3:1; the temperature of the melt pre-polymerization is 160-180℃, and the time is 1.5-3h; the diluent in the S3 step is acetone or butanone, and the curing agent is one or more of 2-methylimidazole, 2-propylimidazole, 2-isopropylimidazole, and ethylenediamine; the mass ratio of the diluent and curing agent is 30-35:1.

[0019] In some embodiments, the specific steps of the dipping are: pouring the BT resin into a clean flat-bottomed tray, then dipping the dried glass fiber cloth for 60-120s, taking out the glass fiber cloth, and repeating the dipping at least 3 times.

[0020] In some embodiments, the specific steps of the hot-pressing forming in the S4 step are: neatly stacking the prepreg between two aluminum sheets, laying them on the press, and placing them under the conditions of 130-150℃ and 1.5-2.5MPa to gel, then pressing and forming according to the staged temperature and pressure process, stopping heating after pressing, and naturally cooling to room temperature while maintaining the current pressure, to obtain the product, i.e., the low-dielectric-property glass fiber composite material.

[0021] In some embodiments, the stepwise temperature and pressure rising comprises a first stage temperature and pressure rising, a second stage temperature and pressure rising, a third stage temperature and pressure rising and a fourth stage temperature and pressure rising; wherein the first stage temperature and pressure rising is to 150-170 DEG C, 4.5-5.5 MPa, and the temperature and pressure are kept for 0.8-1.2 h; the second stage temperature and pressure rising is to 170-190 DEG C, 7.5-8.5 MPa, and the temperature and pressure are kept for 1.8-2.2 h; the third stage temperature and pressure rising is to 190-210 DEG C, 7.5-8.5 MPa, and the temperature and pressure are kept for 1.8-2.2 h; the fourth stage temperature and pressure rising is to 210-230 DEG C, 9.5-10.5 MPa, and the temperature and pressure are kept for 1.8-2.2 h. The stepwise temperature rising rate can make the two resins better combine with the glass fiber and make the curing more complete to optimize the product performance.

[0022] In some embodiments, the specific process of the stepwise temperature and pressure rising is 160 DEG C / 5 MPa / 1 h, 180 DEG C / 8 MPa / 2 h, 200 DEG C / 8 MPa / 2 h and 220 DEG C / 10 MPa / 2 h.

[0023] In some embodiments, the temperature and pressure rising in the S4 step is performed by using a flat vulcanizing machine.

[0024] In some embodiments, the thickness of the low dielectric performance glass fiber composite material is 1.5-2.0 mm.

[0025] Technical effects

[0026] Significant reduction of dielectric constant: by filling PTFE and compounding with BT resin, the dielectric constant is reduced to 4.3, and the dielectric loss is reduced to 0.006, which is suitable for high frequency and high speed signal transmission.

[0027] Superior comprehensive performance: the thermal decomposition temperature and carbon residue rate show excellent thermal stability; the bending strength is stable, which ensures the fatigue resistance; the water absorption rate is as low as 0.0035, which can improve the electrical insulation reliability; the glass transition temperature is increased to 230 DEG C, which can reduce the thermal stress cracking; the initial storage modulus is increased to about 27500, which can enhance the material's resistance to elastic deformation, improve the rigidity, carrying capacity and dimensional stability; the interface compatibility is enhanced, which makes the material modulus and heat resistance synergistically improved.

[0028] Innovative process improves quality: the PTFE is creatively introduced into the glass fiber fabric, combined with the modification process, and the stepwise temperature and pressure rising is used for hot pressing forming, so that the finished product plate surface is smooth, without pores and defects, which ensures the material uniformity.

[0029] The application takes common electronic-grade glass fiber cloth as a base material, combines an economical modification process, and takes into account performance and industrial applicability. All these characteristics promote the development of PCB boards to be light and thin, multi-layered and multi-functional, and the application is widely used in the field of high-speed copper-clad boards, and the market prospect is broad. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 SEM image of the pressed PCB board surface;

[0031] Figure 2 Dielectric constant of the composite material after adding PTFE at 1GHz;

[0032] Figure 3 Dielectric loss of the composite material after adding PTFE at 1GHz;

[0033] Figure 4 Thermogravimetric curve of the composite material after adding PTFE;

[0034] Figure 5 Bending strength test diagram of the composite material after adding PTFE;

[0035] Figure 6 Infrared test diagram of the glass fiber cloth after modification treatment by KH570 and KH550;

[0036] Figure 7 Water absorption test diagram of the composite material after adding PTFE;

[0037] Figure 8 Loss factor test diagram of the composite material after adding PTFE;

[0038] Figure 9 Storage modulus test diagram of the composite material after adding PTFE. DETAILED DESCRIPTION

[0039] In order to facilitate the review of the technical solutions of the application, the following first generally describes and defines the terms and expressions involved in the application.

[0040] The term "comprising" or "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of additional identical elements in the process, method, article or device including the element.

[0041] The "water" in the application is experimental-grade water, such as deionized water, distilled water, ultrapure water, etc.

[0042] The "room temperature" in the present application refers to 20-27℃.

[0043] The "immersion" in the present application refers to complete immersion of both front and back surfaces.

[0044] The test method of dielectric property in the present application refers to the test method of dielectric property in IPC-TM-650 "Test Methods for Printed Circuit Boards (PCB) and Modules".

[0045] The test method of dielectric loss in the present application refers to the test method of dielectric loss in IPC-TM-650 "Test Methods for Printed Circuit Boards (PCB) and Modules".

[0046] The test method of thermal gravimetric temperature in the present application refers to the test method of TGA in IPC-TM-650 "Test Methods for Printed Circuit Boards (PCB) and Modules".

[0047] The test method of carbon residue rate in the present application refers to the method of carbon residue rate analysis in IPC-TM-650 "Test Methods for Printed Circuit Boards (PCB) and Modules".

[0048] The test method of bending strength in the present application refers to CB / T 3356 "Test Method for Flexural Properties of Fiber Reinforced Polymer Matrix Composites".

[0049] The test method of water absorption rate in the present application refers to the test method of water absorption rate in IPC-TM-650 "Test Methods for Printed Circuit Boards (PCB) and Modules".

[0050] The test method of glass transition temperature in the present application refers to GB / T40396 "Test Method for Glass Transition Temperature of Polymer Matrix Composites Dynamic Mechanical Analysis (DMA)".

[0051] The test method of initial storage modulus in the present application refers to GB / T40396 "Test Method for Glass Transition Temperature of Polymer Matrix Composites Dynamic Mechanical Analysis (DMA)".

[0052] In each group of comparative experiments provided in the present application, unless otherwise specified, other experimental conditions, materials, etc. are kept consistent except for the differences indicated by each group, so as to have comparability.

[0053] The reagents and instruments used in the embodiments of the present application can be purchased from the market, unless otherwise specified.

[0054] The following further describes a low dielectric performance glass fiber composite material provided by the present application.

[0055] Preparation of a PCB board

[0056] (1) Pretreatment of the glass fiber cloth: First, cut the glass fiber cloth (E-type glass fiber cloth, manufacturer: Chongqing International Composite Material Co., Ltd., model: 7628, single-filament diameter: 9 um, aperture: 0.18 mm) into a size of 15 cm x 15 cm, and place 10 pieces of the cut glass fiber cloth into an oven to dry at 120°C for 1 h to remove moisture on the surface.

[0057] (2) Modification treatment: Measure 4 g of silane coupling agent KH570 (purchased from Jiangsu Maige Biological Technology Co., Ltd.), 19.6 g of deionized water, and 176.4 g of anhydrous ethanol to prepare a 2 wt% silanol aqueous solution. Hydrolyze at 80°C for 6 h, and then add the glass fiber cloth of (1) to soak for 6 h. After sufficient soaking, take out and place in an oven to dry at 120°C for 1 h.

[0058] (3) Filler filling: Take 10 g of polytetrafluoroethylene (PTFE) (concentration of 50 wt%) and 90 g of deionized water to prepare a 5 wt% PTFE solution, and stir at 1000 rpm for 8 h to break the emulsion. Then, add the dried glass fiber cloth of (2) to soak for 24 h, and then again dry in a 120°C oven for 1 h to remove the solvent, to obtain the glass fiber cloth for standby use.

[0059] (4) Synthesis of a bismaleimide-triazine (BT) resin: Weigh 60 g of cyanate ester (white crystalline powder, purity ≥ 99.0) and 20 g of bismaleimide (yellow powder, purity ≥ 98.0), and heat to melt and pre-polymerize at 170°C in an oven for 2 h. After taking out and waiting for the BT resin to cool to room temperature, add a mixture of 80 g of acetone and 2.4 g of 2-methylimidazole to the BT resin, and dilute the BT resin to a glue solution concentration of 40-60%.

[0060] (5) Glue dipping: Pour the glue solution of (4) into a clean flat-bottomed tray, and dip the glass fiber cloth of (3) in the glue solution for 60-120 s. Take out the glass cloth, repeat the dipping at least 3 times, and then place in a 90°C oven to dry for 30 min. After pre-drying, cool to room temperature to obtain a prepreg.

[0061] (6) Hot-pressing: The regular stack of prepreg in (5) was sandwiched between two aluminum sheets (for easy demolding) and placed in an upper press (flat vulcanizing machine). After being placed at 140°C until gelation, it was hot-pressed according to the process of 160°C / 5MPa / 1h, 180°C / 8MPa / 2h, 200°C / 8MPa / 2h, 220°C / 10MPa / 2h, and naturally cooled to room temperature after pressure holding. Finally, the glass fiber composite (BT+PTFE+KH570) was obtained.

[0062] Preparation of PCB board in Example 2

[0063] The difference from Example 1 is that:

[0064] In step (1) of pretreatment of glass fiber cloth, the E-type glass fiber cloth was replaced by D-type glass fiber cloth (model: CYDF-100; single filament diameter: 8um, aperture: 0.16mm).

[0065] Preparation of PCB board in Example 3

[0066] The difference from Example 1 is that:

[0067] In step (4) of synthesis of BT resin: After the BT resin was taken out and placed to wait for its cooling to room temperature, 80g of butanone and 2.4g of 2-propylimidazole were added to it.

[0068] Preparation of PCB board in Comparative Example 1

[0069] The difference from Example 1 is that:

[0070] There is no step (2) of modification treatment, and no step (4) of filler filling.

[0071] Finally, the glass fiber composite (BT) was obtained.

[0072] Preparation of PCB board in Comparative Example 2

[0073] The difference from Example 1 is that:

[0074] There is no step (2) of modification treatment.

[0075] Finally, the glass fiber composite (BT+PTFE) was obtained.

[0076] Preparation of PCB board in Comparative Example 3

[0077] The difference from Example 1 is that:

[0078] In step (2) of preparation of silane modifier, the silane coupling agent was replaced by γ-aminopropyltrimethoxysilane (KH550), and there is no step (4) of filler filling.

[0079] Preparation of the PCB board of Comparative Example 4

[0080] The difference from Example 1 is that:

[0081] There is no step (4) filler filling.

[0082] Preparation of the PCB board of Comparative Example 5

[0083] The difference from Example 1 is that:

[0084] Step (4) filler filling: 0.91 g, 2.8 g, 4.7 g, 6.8 g, 8.9 g of PTFE (concentration of 50 wt%) respectively, 90 g of deionized water, to prepare 1 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt% PTFE solution.

[0085] The dielectric properties, dielectric loss, thermal weight loss temperature, carbon residue rate, bending strength, infrared spectrum, water absorption rate, glass transition temperature and initial storage modulus of each product are tested, as shown in Table 1, and the specific results and analysis are as follows: Figures 1-9

[0086] According to the SEM diagram of Figure 1 It can be seen that the surface of the composite material is smooth and has no obvious defects. It shows that the mixing between PTFE and BT resin is relatively uniform and there is no obvious agglomeration phenomenon, and there is no air hole on the surface of the board. It can be seen that the oven pre-drying to remove the solvent and the stepwise temperature and pressure rising are important to the forming process of the PCB board.

[0087] By Figure 2 The effect of adding PTFE at low frequency on the dielectric properties of the PCB board can be seen from the figure. The dielectric constant of the composite material prepared by pure BT resin and glass fiber at low frequency is 4.7. Then the dielectric constant decreases after adding PTFE (5 wt%), and the dielectric properties of the PCB board pressed by the glass fiber fabric after modification treatment can be further improved. The current results show that the low frequency dielectric constant after modification treatment and adding PTFE (5 wt%) is 4.3. The reason for the decrease of dielectric properties is that the chemical bonding between the modified glass fiber fabric and the resin matrix is increased, so that the combination is more firm. And the low dielectric PTFE fills the holes of the glass fiber fabric, reduces the gap between the PCB boards and reduces the polarization, so the dielectric constant is reduced.

[0088] Figure 3 ​It can be seen that the initial dielectric loss is about 0.01, and after adding 5% PTFE, the dielectric loss is relatively lower than before. The dielectric properties of the PCB board pressed by the glass fiber after modification by KH570 can be further improved. The current results show that the low-frequency dielectric loss after modification and addition of PTFE (5wt%) is 0.006. The reduction of dielectric loss is due to the non-polar structure of PTFE, which makes its dielectric constant smaller and the dielectric loss very low. At the same time, the molecular chain structure of PTFE is stable and not easy to polarize and relax in the electric field, thereby reducing energy loss. In addition, the interface formed by PTFE particles in the BT resin can hinder the migration and accumulation of electric charges, thereby reducing the conductive loss, and the interface effect also helps to disperse the electric field strength, reducing the free loss caused by the too high local electric field strength.

[0089] From Figure 4 the TGA curve of the glass fiber, the following Table 1 is obtained.

[0090] Table 1 Effect of different contents of PTFE on the TGA of PCB board

[0091] PTFE content (wt%) T d5％ (°C) T d10％ (°C) Char yield at 800°C (%) 0 371.531 428.531 80.57 5 350.347 380.347 70.01

[0092] Table 1 shows the 5% thermal weight loss temperature, 10% thermal weight loss temperature and carbon residue rate at 800℃. It can be seen that the Td 5％ of the composite material without adding PTFE is 371.531℃, the Td 10％ temperature is 428.531, and the carbon residue rate at 800℃ is 80.58%. The Td 5％ of the composite material with 5wt% PTFE is 350.347℃, the Td 10％ temperature is 380.347, and the carbon residue rate at 800℃ is 70.01%, showing excellent thermal stability.

[0093] From Figure 5 it can be seen that with the increase of the addition amount of PTFE, when the addition amount of PTFE is 5wt%, the bending performance of the composite material changes not obviously, and the bending strength still remains relatively stable. When the PTFE content increases to 9%, the bending strength of the PCB board shows a certain amount of decrease. This is because PTFE shows a certain brittleness in material performance, and excessive addition of PTFE will increase the brittleness of the PCB board, thereby causing a certain degree of decrease of the mechanical properties of the PCB board. The molecular structure of PTFE is obtained by free radical polymerization of a large number of tetrafluoroethylene molecules, forming an extremely regular chain structure. This structure makes a large number of aromatic carbon-fluorine bonds pile up, resulting in weak affinity between polymer molecules, easy sliding and peeling.

[0094] FromFigure 6 The infrared spectrum shows that, compared to KH550, the glass fibers modified with KH570 exhibit significantly higher peak intensities at approximately 801 cm⁻¹ and 1028 cm⁻¹, corresponding to the symmetric and asymmetric stretching vibrations of Si-O-Si. This is because the trimethoxysilyl group (Si(OCH₃)₃) in KH570 undergoes hydrolysis to generate silanol groups (Si-OH). Si-OH is highly reactive and can undergo dehydration condensation with the hydroxyl groups (-OH) on the glass fiber surface to form Si-O-Si. More Si-O-Si further promotes interface formation, thereby improving the overall performance of the material. The Si-OH on the surface of the KH570-treated glass fiber cloth reacts with the silane coupling agent to form a Si-O-Si structure; therefore, the modification treatment of glass fiber cloth with KH570 yields better results.

[0095] Depend on Figure 7 It can be seen that the water absorption rate of pure BT PCB is 0.008%, while the water absorption rate is 0.0035% after adding 5wt% PTFE. F is a hydrophobic element, and the strong protective effect of F atoms on the carbon chain results in extremely strong intermolecular forces, making it difficult for water molecules to penetrate into the material's interior, thus reducing the water absorption rate. PTFE will not expand, deform, or deteriorate in performance due to water absorption, thereby ensuring the dimensional stability and electrical performance of the PCB. Secondly, the PTFE filling the pores of the glass fiber cloth reduces the overall porosity of the PCB, thereby reducing the water absorption rate.

[0096] Figure 8 The glass transition temperature (GTH) of the PCB board corresponding to pure BT resin is around 220℃, while the GTH of the board with 5 wt% PTFE is around 230℃. This represents a 10℃ increase in GTH compared to the previous values. The main reason for this is likely that PTFE itself is a crystalline polymer with a regular molecular chain arrangement and high crystallinity. When PTFE is added to BT resin, it may induce or promote the crystallization of the BT resin, or alter its orientation. Increased crystallinity and orientation lead to a more compact molecular chain arrangement and enhanced intermolecular interactions, thereby increasing the GTH.

[0097] according to Figure 9It can be seen that the initial storage modulus of the PCB prepared from pure BT resin is about 24000 MPa, and the initial storage modulus of the PCB prepared by adding 5wt% PTFE is about 27500, which is increased by 3500 MPa compared with the previous one. The reason may be that PTFE itself has high molecular chain rigidity. When PTFE is added to BT resin, the steric hindrance of PTFE limits the movement of the chain segments in BT resin. This hindering effect makes it more difficult for the material to deform when stressed, so the storage modulus is improved. Because the polarity of the PTFE molecular chain is low, it can form strong physical crosslinking points with the BT resin molecular chain, which limits the movement of the molecular chain, thereby improving the rigidity of the material. In addition, the fluorine atoms of the PTFE molecular chain have strong electronegativity, which can form hydrogen bonds or dipole-dipole interactions with certain groups in the BT resin, and these interactions also enhance the intermolecular bonding force, further improving the storage modulus.

[0098] The above specific embodiments further illustrate the purposes, technical solutions and beneficial effects of the present application. It should be understood that the above is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made on the basis of the technical solutions of the present application shall be included in the protection scope of the present application.

Claims

1. A low dielectric property glass fiber composite material, characterized by, The low dielectric performance glass fiber composite material is prepared by the following steps: S1. Pretreatment of glass fiber cloth: cutting the glass fiber cloth into the required size and drying; S2. Modification treatment and filler filling: soaking the dried glass fiber cloth in step S1 in a silane coupling agent solution, taking out and drying, then soaking in a PTFE dispersion liquid, taking out and drying again; S3. Resin impregnation: impregnating the dried glass fiber cloth in step S2 with a BT resin glue solution, taking out and drying to prepare a prepreg; S4. Hot pressing: the prepreg in step S3 is pressed and formed by a stepwise temperature and pressure increasing process to obtain the product, i.e. the low dielectric performance glass fiber composite material.

2. The low dielectric property glass fiber composite material according to claim 1, characterized by, The glass fiber cloth in step S1 is an electronic grade glass fiber cloth with a single filament diameter of 7-11 um, a pore size of 0.15-0.22 mm and an alkali treatment.

3. The low dielectric property glass fiber composite material according to claim 1, wherein, The drying conditions in steps S1 and S2 are 100-150℃ drying for 0.8-1.2h; the drying conditions in step S3 are 80-100℃ drying for 20-40min.

4. The low dielectric property glass fiber composite material according to claim 1, wherein, The preparation steps of the silane coupling agent solution in step S2 are: using ethanol and water to prepare a 1-3wt% silanol aqueous solution from a silane coupling agent, and then fully hydrolyzing at 70-90℃ for 5-8h; wherein the mass ratio of ethanol to water is 8-10:1; the silane coupling agent is one or more of γ-methacryloxypropyltrimethoxysilane (KH570), vinyltrimethoxysilane (A-171), vinyltriethoxysilane (A-151), and γ-methacryloxypropyltriethoxysilane (A-174 / Z-6030).

5. The low dielectric property glass fiber composite material of claim 1, wherein, The preparation steps of the PTFE dispersion liquid in step S2 are: using water to prepare a 4-6wt% PTFE solution from PTFE, and stirring at 800-1200rpm for 6-10h to break the emulsion.

6. The low dielectric property glass fiber composite material of claim 1, wherein, The preparation steps of the BT resin glue solution in step S3 are: melt pre-polymerizing cyanate ester and bismaleimide, adding diluent and curing agent after cooling to room temperature, and preparing a 40-60wt% glue solution.

7. The low dielectric property glass fiber composite material according to claim 6, characterized by, The mass ratio of cyanate ester to bismaleimide is 2-3:1; the temperature of melt pre-polymerization is 160-180℃, and the time is 1.5-3h; the diluent in step S3 is acetone or butanone, and the curing agent is one or more of 2-methylimidazole, 2-propylimidazole, 2-isopropylimidazole, and ethylenediamine; the mass ratio of diluent to curing agent is 30-35:

1.

8. The low dielectric property glass fiber composite material of claim 1, wherein, The specific steps of hot pressing in step S4 are: neatly stacking the prepreg between two aluminum sheets, laying it on the press, placing it under the conditions of 130-150℃ and 1.5-2.5MPa to gel, then pressing and forming according to the stepwise temperature and pressure increasing process, stopping heating after pressing, and naturally cooling to room temperature to maintain the current pressure to obtain the product, i.e. the low dielectric performance glass fiber composite material.

9. The low dielectric property glass fiber composite material according to claim 8, wherein, The stepwise temperature and pressure rising comprises a first stage temperature and pressure rising, a second stage temperature and pressure rising, a third stage temperature and pressure rising and a fourth stage temperature and pressure rising; wherein the first stage temperature and pressure rising is to 150-170 DEG C, 4.5-5.5 MPa, and the temperature and pressure are kept for 0.8-1.2 h; the second stage temperature and pressure rising is to 170-190 DEG C, 7.5-8.5 MPa, and the temperature and pressure are kept for 1.8-2.2 h; the third stage temperature and pressure rising is to 190-210 DEG C, 7.5-8.5 MPa, and the temperature and pressure are kept for 1.8-2.2 h; the fourth stage temperature and pressure rising is to 210-230 DEG C, 9.5-10.5 MPa, and the temperature and pressure are kept for 1.8-2.2 h.

10. The low dielectric property glass fiber composite material according to any one of claims 1 to 9, characterized in that, The thickness of the low dielectric performance glass fiber composite material is 1.5-2.0 mm.

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