Preparation method of polytetrafluoroethylene high-proportion ceramic filled low-loss high-frequency substrate

Abstract

The invention relates to the technical field of preparation of high-frequency substrates, in particular to a preparation method of a polytetrafluoroethylene high-proportion ceramic filled low-loss high-frequency substrate, which comprises the following steps: introducing high-dielectric, low-loss and low-temperature-drift ceramic powder into a material, innovatively designing slurry for gum dipping, and solving the problems of sedimentation and dispersion of high-proportion ceramic in the slurry. Finally, the dielectric constant is 2.94 + / -0.04, and the loss is less than or equal to 0.0012; the dielectric constant is 3.0 + / -0.04, and the loss is less than or equal to The dielectric constant is 3.5 + / -0.05, and the loss is less than or equal to The dielectric constant is 4.5 + / -0.09, and the loss is not more than 0.002; the dielectric constant is 6.15 + / -0.12 and the loss is less than or equal to 0.0023; according to the technical scheme, the low-loss high-frequency substrate with the dielectric constant of 10.2 + / -0.2, the loss smaller than or equal to 0.0023 and the like is adopted, meanwhile, the ultra-thin and ultra-fine No.106 glass fiber cloth is adopted in the technical scheme, and the impregnation amount can exceed 90% by adjusting the viscosity.

Description

Technical Field

[0001] The invention relates to the technical field of high-frequency substrate preparation, and in particular to a method for preparing a low-loss high-frequency substrate filled with high-proportion ceramics of polytetrafluoroethylene. Background Art

[0002] The development and production of high-frequency substrates in China started late. Currently, there are only a few companies engaged in the production of high-frequency substrates. Conventional high-frequency substrates use a large proportion of glass fiber cloth, and can only produce ordinary polytetrafluoroethylene high-frequency substrates with a dielectric constant of less than 6 and a loss of less than 0.005. This traditional high-frequency substrate contains a large amount of glass fiber components to increase the dielectric constant, and has no or only a small amount of ceramics. For example, the substrate with a dielectric constant of 2.94 has a loss greater than 0.0018, the substrate with a dielectric constant of 3.5 has a loss greater than 0.0025, and the product with a dielectric constant of 4.5 has a loss greater than 0.0035. A dielectric constant greater than 6 cannot be achieved through traditional processes; a large amount of glass fiber components increases the loss and anisotropy of the substrate; the glass fiber effect is large and the frequency of use is limited, and it can only be used for frequencies below 10GHz; the thermal expansion coefficient is large, the processability of the circuit board is limited, affecting reliability and stability; the dielectric constant thermal coefficient varies greatly, and the use temperature is limited; the thermal conductivity is low; and the dielectric constant cannot be improved.

[0003] As solid-state amplifiers in coordinate radars and phased array radars, fourth-generation receivers, T / R components, signal controllers in aerospace warehouses, satellite transceivers, electronic countermeasure equipment, power amplifiers and other equipment put forward higher requirements for high-frequency substrates, they require substrates with lower losses, better frequency stability, increased operating frequency, increased thermal conductivity, adaptability to the processing of multi-layer circuit boards, and excellent temperature stability.

[0004] Due to the polarity of PTFE, conventional ceramics cannot be mixed with PTFE slurry when the proportion exceeds 30% during the preparation of traditional polytetrafluoroethylene sheet slurry, resulting in a low proportion of ceramics in the prefabricated sheet; using traditional dipping processes and equipment, it is impossible to obtain a glue amount exceeding 68%. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a low-loss high-frequency substrate filled with polytetrafluoroethylene (PTFE) with a high proportion of ceramics, so as to solve the problem that when preparing a traditional polytetrafluoroethylene substrate slurry, due to the polarity of PTFE, the conventional ceramic proportion cannot be mixed with the PTFE slurry when it exceeds 30%, resulting in a low ceramic proportion in the prefabricated sheet; and the traditional dipping process and equipment cannot obtain a glue amount exceeding 68%.

[0006] To achieve the above object, the present invention provides a method for preparing a low-loss high-frequency substrate filled with a high-proportion ceramic of polytetrafluoroethylene, and the method for preparing a low-loss high-frequency substrate filled with a high-proportion ceramic of polytetrafluoroethylene comprises the following steps:

[0007] Adding ceramic powder, fluorine-loving modifier and thickener into PTFE emulsion to form slurry;

[0008] The slurry is added to a vertical dipping machine, and the slurry is impregnated and taken out with No. 106 glass fiber cloth through a vertical dipping method, and then the water and solvent in the impregnated slurry are dried and rolled up to form a prefabricated sheet roll with a dipping mass percentage greater than 90%;

[0009] Cutting the prefabricated sheet roll into prefabricated sheets;

[0010] Stacking multiple prefabricated sheets between two cut copper foils, and performing overlapping layout, and then performing vacuum hot pressing with a vacuum press to form a pressed part;

[0011] The pressed parts are trimmed to form the final product.

[0012] Among them, in the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the mass percentage of PTFE emulsion is 51-54%, the mass percentage of ceramic powder is 44%-49%, the mass percentage of fluorine-loving modifier is 0.4-1.6%, the mass percentage of thickener is 0.5-1.0%, and the dielectric constant range of the ceramic powder is 20-100.

[0013] Among them, in the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the mass percentage of thickener needs to be adjusted so that the viscosity of the slurry is 700-1100 mPa.s.

[0014] Among them, in the step of "adding ceramic powder, fluorine-philic modifier and thickener to PTFE emulsion to form slurry", the ceramic powder is selected from one or more combinations of SiO2, TiO2, BaO-Sm2O3-TiO2, BaO-Nd2O3-TiO2, CaO-Li2O-Sm2O3-TiO2, and the SiO2 particle size is selected as D50: 8-12um, D90<20um; the TiO2 particle size is selected as D50: 6-10um, D90<18um; the CaO-Li2O-Sm2O3-TiO2 particle size is selected as D50: 8-12um, D90<20um.

[0015] Among them, in the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the ceramic powder is angular particles.

[0016] Among them, in the step of "adding ceramic powder, fluorophilic modifier and thickener to PTFE emulsion to form slurry", the specific preparation process of the slurry is as follows: first add small molecule PTFE emulsion into the mixing tank according to the component ratio, and then add ceramic powder, fluorophilic modifier and thickener in sequence and then perform physical stirring, adjust the stirring speed to the required viscosity of 700-1100mPa.s, stir at 80-120 rpm, stir for 4-8 hours, obtain slurry, record the stop time after stirring stops, and pour into the dipping tank for dipping within 24 hours.

[0017] Among them, in the step of "stack a plurality of prefabricated sheets between two cut copper foils, overlap and layout them, and then use a vacuum press to perform vacuum hot pressing to form a pressed part", the specific steps of vacuum hot pressing are:

[0018] The first stage: the temperature is raised to 300°C at a heating rate of 3-5°C / min, and the pressure parameter is 3.5MPA;

[0019] The second stage: the temperature is raised to 360°C at a heating rate of 1-3°C / min, and the pressure parameter is 3.5MPA;

[0020] The third stage: the temperature is maintained at 360°C for 30 to 60 minutes, and the pressure parameter is 4.5 MPa;

[0021] The fourth stage: the temperature is raised to 390°C at a heating rate of 1-2.5°C / min, and the pressure parameter is 4.5MPA;

[0022] The fifth stage: the temperature is maintained at 390°C for 70 to 120 minutes, and the pressure parameter is 4.5 MPa;

[0023] The sixth stage: the temperature is reduced to 300°C at a cooling rate of 0.8-1.5°C / min, and the pressure parameter is 4.5MPA;

[0024] The seventh stage: the temperature is reduced to 200 at a cooling rate of 1.5-3℃ / min, and the pressure parameter is 3.5MPA;

[0025] The eighth stage: the temperature drops to below 50°C at a cooling rate of 1.5-3.5°C / min, and the pressure parameter is 3MPA;

[0026] Section 9: Remove the pressure and obtain the pressed parts.

[0027] The invention discloses a method for preparing a polytetrafluoroethylene high-proportion ceramic-filled low-loss high-frequency substrate. The method comprises the following steps: introducing the ceramic powder with high dielectric, low loss and low temperature floating into the material, innovatively designing a slurry for dipping, and solving the sedimentation and dispersion problem of the high-proportion ceramic in the slurry. Finally, a high-frequency substrate with multiple dielectric constants and low loss is obtained, such as a dielectric constant of 2.94±0.04 and a loss of ≤0.0012; a dielectric constant of 3.0±0.04 and a loss of ≤0.0012; a dielectric constant of 3.5±0.05 and a loss of ≤0.0018; a dielectric constant of 4.5±0.09 and a loss of ≤0.002; a dielectric constant of 6.15±0.12 and a loss of ≤0.0023; a dielectric constant of 10.2±0.2 and a loss of ≤0.0023. Meanwhile, the technical solution adopts ultra-thin and ultra-fine No. 106 glass fiber cloth, and the dipping amount can be made to exceed 90% by adjusting the viscosity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 The present invention provides a flow chart of the steps of preparing a method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics.

[0030] Figure 2 It is a flow chart of the steps of the method for preparing a low-loss high-frequency substrate filled with a high proportion of polytetrafluoroethylene ceramic with a dielectric constant of 10.2 in Example 1 provided by the present invention.

[0031] Figure 3 This is a compression curve diagram of a low-loss high-frequency substrate filled with high-proportion ceramic of polytetrafluoroethylene with a dielectric constant of 10.2 in Example 1 provided by the present invention.

[0032] Figure 4 This is a curve diagram showing changes in unit gram weight and thickness of the preform at different viscosities of a low-loss high-frequency substrate filled with high-proportion ceramic of polytetrafluoroethylene having a dielectric constant of 10.2 in Example 1 provided by the present invention.

[0033] Figure 5 This is a peel strength curve at different maximum temperatures during hot pressing of a low-loss high-frequency substrate filled with a high proportion of polytetrafluoroethylene with a dielectric constant of 10.2 in Example 1 provided by the present invention.

[0034] Figure 6This is a curve diagram of dielectric constant and loss variation at different maximum temperatures during hot pressing of a low-loss high-frequency substrate filled with a high proportion of polytetrafluoroethylene with a dielectric constant of 10.2 in Example 1 provided by the present invention.

[0035] Figure 7 This is a peel strength curve at different maximum pressures during hot pressing of a low-loss high-frequency substrate filled with a high proportion of polytetrafluoroethylene with a dielectric constant of 10.2 in Example 1 provided by the present invention.

[0036] Figure 8 This is a graph showing the change in dielectric constant and loss at different maximum pressures during hot pressing of a low-loss high-frequency substrate filled with a high proportion of polytetrafluoroethylene with a dielectric constant of 10.2 in Example 1 provided by the present invention. DETAILED DESCRIPTION

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0038] See also Figure 1 The present invention provides a method for preparing a low-loss high-frequency substrate filled with a high-proportion polytetrafluoroethylene ceramic. The method for preparing a low-loss high-frequency substrate filled with a high-proportion polytetrafluoroethylene ceramic comprises the following steps:

[0039] Adding ceramic powder, fluorine-loving modifier and thickener into PTFE emulsion to form slurry;

[0040] The slurry is added to a vertical dipping machine, and the slurry is impregnated and taken out with No. 106 glass fiber cloth through a vertical dipping method, and then the water and solvent in the impregnated slurry are dried and rolled up to form a prefabricated sheet roll with a dipping mass percentage greater than 90%;

[0041] Cutting the prefabricated sheet roll into prefabricated sheets;

[0042] Stacking multiple prefabricated sheets between two cut copper foils, and performing overlapping layout, and then performing vacuum hot pressing with a vacuum press to form a pressed part;

[0043] The pressed parts are trimmed to form the final product.

[0044] In this embodiment, by introducing the ceramic powder with high dielectric, low loss and low temperature floating into the material, and innovatively designing the slurry for dipping, and then solving the sedimentation and dispersion problem of high proportion of ceramics in the slurry, finally a dielectric constant of 2.94±0.04, loss ≤0.0012; dielectric constant 3.0±0.04, loss ≤0.0012; dielectric constant 3.5±0.05, loss ≤0.0018; dielectric constant 4.5±0.09, loss ≤0.002; dielectric constant 6.15±0.12, loss ≤0.0023; dielectric constant of 10.2±0.2, loss ≤0.0023 and other high-frequency substrates with low dielectric constants are obtained. At the same time, this technical solution adopts ultra-thin and ultra-fine 106 glass fiber cloth, and by adjusting the viscosity, the dipping amount can exceed 90%.

[0045] Furthermore, in the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the mass percentage of PTFE emulsion is 51-54%, the mass percentage of ceramic powder is 44%-49%, the mass percentage of fluorine-loving modifier is 0.4-1.6%, the mass percentage of thickener is 0.5-1.0%, and the dielectric constant range of the ceramic powder is 20-100.

[0046] Furthermore, in the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the mass percentage of thickener needs to be adjusted so that the viscosity of the slurry is 700-1100 mPa.s.

[0047] Furthermore, in the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the ceramic powder is selected from one or more combinations of SiO2, TiO2, BaO-Sm2O3-TiO2, BaO-Nd2O3-TiO2, CaO-Li2O-Sm2O3-TiO2, and the SiO2 particle size is selected to be D50: 8-12um, D90<20um; the TiO2 particle size is selected to be D50: 6-10um, D90<18um; the CaO-Li2O-Sm2O3-TiO2 particle size is selected to be D50: 8-12um, D90<20um.

[0048] In this embodiment, the parameters of the ceramic powder can be seen in the following table:

[0049]

[0050] Furthermore, in the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the ceramic powder is angular particles.

[0051] In this embodiment, the shapes of ceramic powders are mainly spherical, angular, and strip-shaped. Spherical ceramic powders have a smooth surface and a large contact area, are easy to settle in the dipping solution, and are easily fallen off by mechanical external forces after mixing with the resin. They are generally used in products of extrusion molding process and are not suitable for products of glue molding. Strip-shaped ceramic powders have high production costs, complex processes, and low pass rates. A high proportion of strip-shaped ceramic powders are easy to break and entangle in the dipping solution, which is not conducive to production control. Therefore, ceramic powders use angular particles, which are easy to disperse, not entangled, and not easy to fall off, with low manufacturing costs and low control costs.

[0052] Furthermore, in the step of "adding ceramic powder, fluorophilic modifier and thickener to PTFE emulsion to form slurry", the specific preparation process of the slurry is as follows: first add small molecule PTFE emulsion into the mixing tank according to the component ratio, and then add ceramic powder, fluorophilic modifier and thickener in sequence and then perform physical stirring, adjust the stirring speed to the required viscosity of 700-1100mPa.s, stir at 80-120 rpm, stir for 4-8 hours, obtain slurry, record the stop time after stirring stops, and pour into the dipping tank for dipping within 24 hours.

[0053] Furthermore, in the step of "stack a plurality of prefabricated sheets between two cut copper foils, perform overlapping layout, and then perform vacuum hot pressing with a vacuum press to form a pressed part", the specific steps of vacuum hot pressing are:

[0054] The first stage: the temperature is raised to 300°C at a heating rate of 3-5°C / min, and the pressure parameter is 3.5MPA;

[0055] The second stage: the temperature is raised to 360°C at a heating rate of 1-3°C / min, and the pressure parameter is 3.5MPA;

[0056] The third stage: the temperature is maintained at 360°C for 30 to 60 minutes, and the pressure parameter is 4.5 MPa;

[0057] The fourth stage: the temperature is raised to 390°C at a heating rate of 1-2.5°C / min, and the pressure parameter is 4.5MPA;

[0058] The fifth stage: the temperature is maintained at 390°C for 70 to 120 minutes, and the pressure parameter is 4.5 MPa;

[0059] The sixth stage: the temperature is reduced to 300°C at a cooling rate of 0.8-1.5°C / min, and the pressure parameter is 4.5MPA;

[0060] The seventh stage: the temperature is reduced to 200 at a cooling rate of 1.5-3℃ / min, and the pressure parameter is 3.5MPA;

[0061] The eighth stage: the temperature drops to below 50°C at a cooling rate of 1.5-3.5°C / min, and the pressure parameter is 3MPA;

[0062] Section 9: Remove the pressure and obtain the pressed parts.

[0063] In summary, the polytetrafluoroethylene high-proportion ceramic-filled low-loss high-frequency substrate prepared by this technical solution has the following advantages:

[0064] (1) By introducing high-dielectric, low-loss, low-temperature floating ceramic powder into the material, and innovatively designing a slurry for dipping, and then solving the sedimentation and dispersion problem of a high proportion of ceramics in the slurry, we finally obtained a variety of high-frequency substrates with low dielectric constants, such as a dielectric constant of 2.94±0.04, a loss ≤0.0012; a dielectric constant of 3.0±0.04, a loss ≤0.0012; a dielectric constant of 3.5±0.05, a loss ≤0.0018; a dielectric constant of 4.5±0.09, a loss ≤0.002; a dielectric constant of 6.15±0.12, a loss ≤0.0023; and a dielectric constant of 10.2±0.2, a loss ≤0.0023.

[0065] (2) By using ultra-thin and ultra-fine 106-gauge glass fiber cloth and adjusting the viscosity, the amount of glue impregnation can exceed 90%.

[0066] (3) The type of ceramic powder is selected to ensure that the dielectric constant of the ceramic powder is maintained in the range of 6 to 100 and the loss is less than 0.002.

[0067] (4) The use of angular particles of ceramic powder can make the ceramic powder easy to disperse, not entangled, and not easy to fall off; at the same time, the manufacturing cost and control cost are low.

[0068] (5) In order to ensure product density and high filling ratio, the particle size of ceramic powder should not be too large, and powder with very small particle size must be used. However, the smaller the particle size, the higher the viscosity of the dipping, the more difficult it is to disperse, the greater the probability of agglomeration, and the more likely it is to settle, affecting the consistency of the prefabricated sheet. This technical solution can effectively solve the above technical problems by limiting the particle size of ceramic powder.

[0069] (6) Due to polarity issues, PTFE emulsion cannot be mixed with ceramics in large quantities, and ceramics tend to clump and are difficult to disperse. The laminates formed tend to have many pores and inconsistent uniformity. To address these issues, modifiers and dispersants that match PTFE emulsions are selected to treat the surface of ceramics. While improving the dispersibility of the ceramics themselves, they can also produce a mild chemical reaction with the resin, further improving the dispersion effect. This allows PTFE and ceramics to be evenly dispersed, and allows PTFE and ceramics to have good interface properties, making the combination closer, and ultimately maintaining the material's extremely low water absorption and electrical performance consistency. The best effect is achieved when the modifier is F-8261.

[0070] (7) When the slurry components are determined and the prefabricated sheets are dipped in glue, since the glass fiber cloth used in each prefabricated sheet is the same, the different unit weights after dipping (i.e., the density after pressing) indicate that the proportion of glass fiber cloth is different, and the dielectric constant of glass fiber cloth is 6.0 and the loss is 0.0018. Therefore, the prefabricated sheets produced with different unit weights after dipping (i.e., the density after pressing) have different glue amounts, different thicknesses, different dielectric constants, and different losses, which seriously affect the dielectric constant and loss of the product and cannot meet the needs of customers for different thicknesses. After theoretical calculations and experiments, the dipping amount is greater than 90%, meeting the unit weight requirements, and the thickness reaches 0.16-17mm, which can ensure that the dielectric constant and loss of each prefabricated sheet after high-temperature pressing meet the requirements. The thickness after pressing is 0.127mm, which can be combined into finished products in multiples of 0.127mm to meet the needs of different thicknesses. The most critical parameter affecting the glue amount, unit weight and thickness of the prefabricated sheet is the viscosity parameter of the slurry. Different viscosities will produce prefabricated sheets with different unit weights and thicknesses. After many experiments, the slurry viscosity was adjusted to 700-1100mPa.s, which meets the requirements of unit weight and thickness.

[0071] (8) Vacuum high temperature and high pressure molding technology can make the fluffy prefabricated sheets tightly combined, and remove the residual air and moisture in the prefabricated sheets. The appropriate temperature and pressure have an impact on the dielectric constant, loss, peel strength and other properties of the material. Due to the addition of a large proportion of ceramic fillers in this technical solution, the glass fiber content is relatively low. Compared with conventional substrates, the thermal conductivity coefficient increases, the material hardness increases, and the resin content decreases. It cannot be implemented according to conventional pressing parameters. The highest temperature and the highest pressure during the hot pressing period have the greatest impact on the performance. If the temperature is too low and the pressure is too low, the hot melting effect is not good, the components cannot be tightly combined, the density is not enough, the material has interfaces, residual air, etc., which reduces the dielectric constant and peel strength of the material, and the product is easy to delaminate. If the temperature is too high and the pressure is too high, the resin fluidity is too strong, which affects the thickness; too much decomposition product affects the dielectric constant and increases the loss; at the same time, too high pressure and temperature will cause the copper foil teeth to break, but reduce the peel strength and resistance. After testing the material performance at different maximum temperatures and different maximum pressures, the best maximum temperature and maximum pressure parameters were tested.

[0072] Embodiment 1:

[0073] See also Figures 2 to 8 The present invention provides a method for preparing a low-loss high-frequency substrate filled with polytetrafluoroethylene with a high proportion of ceramics and a dielectric constant of 10.2. The method for preparing a low-loss high-frequency substrate filled with polytetrafluoroethylene with a high proportion of ceramics comprises the following steps:

[0074] S101: prepare No. 106 glass fiber cloth; prepare ceramic powder with a dielectric constant ranging from 20 to 100; prepare slurry raw materials; the slurry ratio is 51 to 54% PTEF emulsion, 35 to 37% TiO2, 9 to 11% CaO-Li2O-Sm2O3-TiO2, 1.2 to 1.6% fluorine-loving modifier, and 0.8 to 1% thickener;

[0075] S102: adding TiO2, CaO-Li2O-Sm2O3-TiO2, a fluorine-loving modifier, and a thickener to the PTFE emulsion to form a slurry;

[0076] S103: adding the slurry to a vertical dipping machine, using a vertical dipping method, dipping the slurry with a No. 106 glass fiber cloth, and then passing through a vertical drying oven to dry the water and solvent in the dipping slurry and roll it up to form a prefabricated sheet roll with a dipping mass percentage greater than 90%;

[0077] S104: cutting the prefabricated film roll into prefabricated films;

[0078] S105: stacking a plurality of prefabricated sheets between two cut copper foils, performing overlapping layout, and then performing vacuum hot pressing with a vacuum press to form a pressed part;

[0079] S106: trimming the pressed parts to form a final product.

[0080] Furthermore, the preparation process of the slurry is as follows: firstly add the small molecule PTFE emulsion into the mixing tank according to the component ratio, then add the ceramic, the modifier and the thickener in sequence, perform physical stirring, adjust the viscosity, stir at a speed of 80 to 120 rpm, stir for 4 to 8 hours, and obtain the slurry;

[0081] Further, vacuum hot pressing comprises the following steps:

[0082] The first stage: the temperature is raised to 300°C at a heating rate of 3-5°C / min, and the pressure parameter is 3.5MPA;

[0083] The second stage: the temperature is raised to 360°C at a heating rate of 1-3°C / min, and the pressure parameter is 3.5MPA;

[0084] The third stage: the temperature is maintained at 360°C for 30 to 60 minutes, and the pressure parameter is 4.5 MPa;

[0085] The fourth stage: the temperature is raised to 390°C at a heating rate of 1-2.5°C / min, and the pressure parameter is 4.5MPA;

[0086] The fifth stage: the temperature is maintained at 390°C for 70 to 120 minutes, and the pressure parameter is 4.5 MPa;

[0087] The sixth stage: the temperature is reduced to 300°C at a cooling rate of 0.8-1.5°C / min, and the pressure parameter is 4.5MPA;

[0088] The seventh stage: the temperature is reduced to 200°C at a cooling rate of 1.5-3°C / min, and the pressure parameter is 3.5MPA;

[0089] The eighth stage: the temperature drops to below 50°C at a cooling rate of 1.5-3.5°C / min, and the pressure parameter is 3MPA;

[0090] Section 9: Remove the pressure and obtain the pressed parts.

[0091] In this embodiment, the pressure curve diagram of step S103 can be found in Figure 3 The unit area weight (g / m2) and thickness are important indicators for evaluating the performance of the prefabricated film adhesive layer. By controlling the viscosity of the dipping solution, the changes in the adhesive content of the glass fiber cloth after dipping under different viscosities were studied. Figure 4 This is a curve chart of the weight per unit area and thickness of the prefabricated rolls obtained after dipping and high-temperature baking at different viscosities. It can be observed from the figure that the unit weight and thickness of the 10.2 dielectric constant substrate increase with the increase of slurry viscosity, and 850-1050mPa.s is the best viscosity value, reaching 390-410g / ㎡, 0.16-0.17mm requirements.

[0092] The maximum temperature during hot pressing has a great impact on the performance of the product. Figure 5 It is the variation of peel strength at different temperatures of 10.2 dielectric constant substrate. It can be seen from the figure that peel strength has a great relationship with temperature. The peel strength increases with the increase of temperature. The peel strength is best at about 395℃. When the temperature exceeds this value, the peel strength gradually decreases. The figure shows that the temperature range that is conducive to peel strength is 378~410℃. Figure 6 10.2 Dielectric constant The influence of substrate temperature on dielectric constant and loss. The higher the temperature, the higher the dielectric constant and loss values. When the temperature reaches about 390°C, the dielectric constant reaches the optimal value and the loss meets the requirements. When the temperature exceeds 404°C, the loss exceeds the standard requirements. When the temperature range is 378-404°C, the required values ​​of dielectric constant and loss are met at the same time.

[0093] The maximum pressure during hot pressing has a great impact on the performance of the product. Figure 7 It is the variation of peel strength under different pressures for the 10.2 dielectric constant substrate. It can be seen from the figure that there is a great relationship between peel strength and pressure. The peel strength increases with the increase of pressure. The peel strength is optimal when it reaches 4.8MPA. When the temperature exceeds this value, the peel strength gradually decreases. This indicates that the temperature range that is beneficial to the peel strength is 3.6~5.6MPA. Figure 8The 10.2 dielectric constant substrate is the influence of pressure on the dielectric constant and loss. The higher the pressure, the higher the dielectric constant and loss values. When the pressure reaches about 4.6MPA, the dielectric constant reaches the optimal value and the loss meets the requirements; when the pressure exceeds 5.8MPA, the loss exceeds the standard requirements. When the pressure range is 3.6~6MPA, the required values ​​of dielectric constant and loss are met at the same time.

[0094] Embodiment 2:

[0095] The present invention provides a method for preparing a low-loss high-frequency substrate filled with a high-proportion polytetrafluoroethylene ceramic with a dielectric constant of 2.94. The method comprises the following steps:

[0096] S201: prepare No. 106 glass fiber cloth; prepare ceramic powder with a dielectric constant ranging from 20 to 100; prepare slurry raw materials; the slurry ratio is 52 to 54% PTEF emulsion, 44 to 48% SiO2, 0.4 to 0.8% fluorine-loving modifier, and 0.6 to 0.9% thickener;

[0097] S202: adding SiO2, a fluorine-loving modifier, and a thickener to the PTFE emulsion to form a slurry;

[0098] S203: adding the slurry to a vertical dipping machine, using a vertical dipping method, dipping the slurry with a No. 106 glass fiber cloth, and then passing through a vertical drying oven to dry the water and solvent in the dipping slurry and roll it up to form a prefabricated sheet roll with a dipping mass percentage greater than 90%;

[0099] S204: cutting the prefabricated film roll into prefabricated films;

[0100] S205: stacking a plurality of prefabricated sheets between two cut copper foils, performing overlapping layout, and then performing vacuum hot pressing with a vacuum press to form a pressed part;

[0101] S206: trimming the pressed parts to form a final product.

[0102] Furthermore, the preparation process of the slurry is as follows: firstly add the small molecule PTFE emulsion into the mixing tank according to the component ratio, then add the ceramic, the modifier and the thickener in sequence, perform physical stirring, adjust the viscosity, stir at a speed of 80 to 120 rpm, stir for 4 to 8 hours, and obtain the slurry;

[0103] Further, vacuum hot pressing comprises the following steps:

[0104] The first stage: the temperature is raised to 300°C at a heating rate of 3-5°C / min, and the pressure parameter is 3.2MPA;

[0105] The second stage: the temperature is raised to 360°C at a heating rate of 1-3°C / min, and the pressure parameter is 3.2MPA;

[0106] The third stage: the temperature is maintained at 360°C for 30 to 60 minutes, and the pressure parameter is 4.0 MPA;

[0107] The fourth stage: the temperature is raised to 400°C at a heating rate of 1-2.5°C / min, and the pressure parameter is 4.0MPA;

[0108] The fifth stage: the temperature is maintained at 390°C for 70 to 120 minutes, and the pressure parameter is 4.0 MPa;

[0109] The sixth stage: the temperature is reduced to 300°C at a cooling rate of 0.8-1.5°C / min, and the pressure parameter is 4.0MPA;

[0110] The seventh stage: the temperature is reduced to 200°C at a cooling rate of 1.5-3°C / min, and the pressure parameter is 3.0MPA;

[0111] The eighth stage: the temperature drops to below 50°C at a cooling rate of 1.5-3.5°C / min, and the pressure parameter is 3.0MPA;

[0112] Section 9: Remove the pressure and obtain the pressed parts.

[0113] Embodiment 3:

[0114] The present invention provides a method for preparing a low-loss high-frequency substrate filled with a high-proportion polytetrafluoroethylene ceramic with a dielectric constant of 6.15. The method for preparing a low-loss high-frequency substrate filled with a high-proportion polytetrafluoroethylene ceramic comprises the following steps:

[0115] S301: prepare No. 106 glass fiber cloth; prepare ceramic powder with a dielectric constant ranging from 20 to 100; prepare slurry raw materials; the slurry ratio is 51 to 54% PTEF emulsion, 30 to 33% SiO2, 14 to 16% TiO2, 0.4 to 0.8% fluorine-loving modifier, and 0.6 to 0.9% thickener;

[0116] S302: Adding SiO2, TiO2, a fluorine-loving modifier, and a thickener to the PTFE emulsion to form a slurry;

[0117] S303: adding the slurry to a vertical dipping machine, using a vertical dipping method, dipping the slurry with a No. 106 glass fiber cloth, and then passing through a vertical oven to dry the water and solvent in the dipping slurry and roll it up to form a prefabricated sheet roll with a dipping mass percentage greater than 90%;

[0118] S304: cutting the prefabricated film roll into prefabricated films;

[0119] S305: stacking a plurality of prefabricated sheets between two cut copper foils, and performing overlapping layout, and then performing vacuum hot pressing with a vacuum press to form a pressed part;

[0120] S306: trimming the pressed parts to form a final product.

[0121] Furthermore, the preparation process of the slurry is as follows: firstly add the small molecule PTFE emulsion into the mixing tank according to the component ratio, then add the ceramic, the modifier and the thickener in sequence, perform physical stirring, adjust the viscosity, stir at a speed of 80 to 120 rpm, stir for 4 to 8 hours, and obtain the slurry;

[0122] Further, vacuum hot pressing comprises the following steps:

[0123] The first stage: the temperature is raised to 300°C at a heating rate of 3-5°C / min, and the pressure parameter is 3.5MPA;

[0124] The second stage: the temperature is raised to 360°C at a heating rate of 1-3°C / min, and the pressure parameter is 3.5MPA;

[0125] The third stage: the temperature is maintained at 360°C for 30 to 60 minutes, and the pressure parameter is 4.2MPA;

[0126] The fourth stage: the temperature is raised to 400°C at a heating rate of 1-2.5°C / min, and the pressure parameter is 4.2MPA;

[0127] The fifth stage: the temperature is maintained at 390°C for 70 to 120 minutes, and the pressure parameter is 4.2 MPa;

[0128] The sixth stage: the temperature is reduced to 300°C at a cooling rate of 0.8-1.5°C / min, and the pressure parameter is 4.2MPA;

[0129] The seventh stage: the temperature is reduced to 200°C at a cooling rate of 1.5-3°C / min, and the pressure parameter is 3.5MPA;

[0130] The eighth stage: the temperature drops to below 50°C at a cooling rate of 1.5-3.5°C / min, and the pressure parameter is 3MPA;

[0131] Section 9: Remove the pressure and obtain the pressed parts.

[0132] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics, characterized in that: The steps include: Adding ceramic powder, fluorine-loving modifier and thickener into PTFE emulsion to form slurry; The slurry is added to a vertical dipping machine, and the slurry is impregnated and taken out with No. 106 glass fiber cloth through a vertical dipping method, and then the water and solvent in the impregnated slurry are dried and rolled up to form a prefabricated sheet roll with a dipping mass percentage greater than 90%; Cutting the prefabricated sheet roll into prefabricated sheets; Stacking multiple prefabricated sheets between two cut copper foils, and performing overlapping layout, and then performing vacuum hot pressing with a vacuum press to form a pressed part; The pressed parts are trimmed to form the final product.

2. The method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics according to claim 1, characterized in that: In the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the mass percentage of PTFE emulsion is 51-54%, the mass percentage of ceramic powder is 44%-49%, the mass percentage of fluorine-loving modifier is 0.4-1.6%, the mass percentage of thickener is 0.5-1.0%, and the dielectric constant of the ceramic powder ranges from 20 to 100.

3. The method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics as claimed in claim 2, characterized in that: In the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the mass percentage of thickener needs to be adjusted so that the viscosity of the slurry is 700-1100 mPa.s.

4. The method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics as claimed in claim 3, characterized in that: In the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the ceramic powder is selected from one or more combinations of SiO2, TiO2, BaO-Sm2O3-TiO2, BaO-Nd2O3-TiO2, CaO-Li2O-Sm2O3-TiO2, and the SiO2 particle size is selected as D50: 8-12um, D90<20um; the TiO2 particle size is selected as D50: 6-10um, D90<18um; the CaO-Li2O-Sm2O3-TiO2 particle size is selected as D50: 8-12um, D90<20um.

5. The method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics as claimed in claim 4, characterized in that: In the step of "adding ceramic powder, fluorine-loving modifier and thickener to PTFE emulsion to form slurry", the ceramic powder is angular particles.

6. The method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics as claimed in claim 5, characterized in that: In the step of "adding ceramic powder, fluorophilic modifier and thickener to PTFE emulsion to form slurry", the specific preparation process of the slurry is as follows: first add small molecule PTFE emulsion into a mixing tank according to the component ratio, then add ceramic powder, fluorophilic modifier and thickener in sequence and then perform physical stirring, adjust the stirring speed to the required viscosity of 700-1100mPa.s, stir at 80-120 rpm, stir for 4-8 hours, obtain slurry, record the stop time after stirring stops, and pour into the dipping tank for dipping within 24 hours.

7. The method for preparing a low-loss high-frequency substrate filled with high-proportion polytetrafluoroethylene ceramics as claimed in claim 6, characterized in that: In the step of "stack a plurality of prefabricated sheets between two cut copper foils, perform overlapping layout, and then perform vacuum hot pressing with a vacuum press to form a pressed part", the specific steps of vacuum hot pressing are: The first stage: the temperature is raised to 300°C at a heating rate of 3-5°C / min, and the pressure parameter is 3.5MPA; The second stage: the temperature is raised to 360°C at a heating rate of 1-3°C / min, and the pressure parameter is 3.5MPA; The third stage: the temperature is maintained at 360°C for 30 to 60 minutes, and the pressure parameter is 4.5 MPa; The fourth stage: the temperature is raised to 390°C at a heating rate of 1-2.5°C / min, and the pressure parameter is 4.5MPA; The fifth stage: the temperature is maintained at 390°C for 70 to 120 minutes, and the pressure parameter is 4.5 MPa; The sixth stage: the temperature is reduced to 300°C at a cooling rate of 0.8-1.5°C / min, and the pressure parameter is 4.5MPA; The seventh stage: the temperature is reduced to 200 at a cooling rate of 1.5-3℃ / min, and the pressure parameter is 3.5MPA; The eighth stage: the temperature drops to below 50°C at a cooling rate of 1.5-3.5°C / min, and the pressure parameter is 3MPA; Section 9: Remove the pressure and obtain the pressed parts.

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