Preparation method of low-loss ultra-thin PTFE microwave dielectric substrate

Abstract

This invention discloses a method for preparing a low-loss ultrathin PTFE microwave dielectric substrate. The method includes the following steps: 1. Preparation of PTFE composite adhesive; 2. Impregnation with glass fiber cloth; 3. Lamination of sheet substrates. The PTFE microwave dielectric substrate prepared by this method has fine filler particles and a high filling rate, improving the uniformity of the ultrathin substrate thickness and dielectric constant. The substrate thickness is 0.065mm ± 0.008mm, and the dielectric constant at 10GHz is 2.95 ± 0.03. It also reduces the loss factor at high frequencies, with a loss factor ≤ 0.0011 at 10GHz. The preparation process is simple, easy to scale up for continuous production, and the microwave substrate exhibits excellent performance, meeting the stringent performance requirements of multilayer circuit boards in high-frequency communication applications.

Description

Technical Field

[0001] This invention relates to a method for preparing PTFE microwave dielectric substrates for high-frequency communication, and particularly to a method for preparing low-loss ultrathin PTFE microwave dielectric substrates. Background Technology

[0002] Microwave composite dielectric substrates, as a crucial foundational material for electronic devices, are used in automotive electronics, communication equipment, industrial control, aerospace, and other fields. With the rapid development of information technology, electronic devices are evolving towards higher frequencies and speeds, and traditional substrate materials are gradually being replaced by high-frequency, high-reliability substrate materials. Among these, microwave composite dielectric substrate materials with low thermal expansion coefficients, low dielectric loss, and high peel strength are advantageous for high-speed, low-delay, and lossless output of high-frequency signals, and are beneficial for reliable and complex processing requirements. Microwave composite dielectric substrates are made by impregnating glass fiber cloth with a composite adhesive solution made of inorganic powders, organic solvents, and organic resins, drying it, coating it with copper foil, and finally hot-pressing it. Due to the differences in the physicochemical properties of organic resins and inorganic powders, the bonding force between them is poor, leading to increased dielectric loss, water absorption, and thermal expansion coefficient of the microwave composite dielectric substrate, severely affecting the substrate's performance. Chinese patent CN111216427A describes a method for preparing ceramic-filled PTFE copper-clad laminate: Composite ceramic filler, polytetrafluoroethylene emulsion, thickener, and water are mixed in a stirrer, allowed to stand to remove air bubbles, and an adhesive is obtained; fiberglass cloth is impregnated in the adhesive, and the amount of adhesive applied to the fiberglass cloth is controlled at 350 g / m² using a metering roller. 2 The process involves baking to obtain impregnated fiberglass cloth; finally, the impregnated fiberglass cloth is laminated with copper foil to obtain a copper-clad laminate. This method uses a composite ceramic filler with a three-layer structure (ceramic filler + coupling agent layer + fluororesin layer) mixed with polytetrafluoroethylene emulsion, thickener, and water to obtain a stable adhesive for impregnating the fiberglass cloth. However, the ceramic powder used has an excessively large particle size, increasing its steric hindrance in the PTFE resin network, making it difficult to obtain a fine and uniform adhesive, thus hindering the fabrication of ultra-thin PTFE substrates with uniform thickness and dielectric constant. Furthermore, the added thickeners and other additives degrade the loss factor performance of the PTFE substrate in the microwave frequency band. Summary of the Invention

[0003] To address the problems of poor thickness uniformity and excessive loss caused by excessive additives in existing ultrathin substrates, this invention provides a method for preparing a low-loss ultrathin PTFE microwave dielectric substrate. This invention uses modified nano- and submicron-sized ceramic powders in a specific ratio; the particle size distribution improves the ceramic powder's packing density and filler ratio. Ball milling premixing enhances the dispersibility and surface activity of the ceramic powder, improving component uniformity and consequently increasing the dielectric constant and thickness uniformity. This composite filler is mixed with PTFE to form a slurry, which is then impregnated and sintered at a high temperature of 360-400°C to remove organic matter, thereby reducing the microwave substrate's loss. The PTFE microwave dielectric substrate prepared by this invention has fine filler particles and high filling rate, which improves the thickness and dielectric constant uniformity of the ultrathin substrate. The substrate thickness is 0.065mm±0.008mm, and the substrate dielectric constant is 2.95±0.03 at 10GHz. It also reduces the loss factor at high frequencies, with a substrate loss factor ≤0.0011 at 10GHz. This meets the stringent performance requirements of microwave dielectric substrates for multilayer circuit boards in the field of high-frequency communication.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a low-loss ultrathin PTFE microwave dielectric substrate includes the following steps:

[0005] A. Preparation of PTFE composite adhesive

[0006] A1. Nano-sized ceramic powder and submicron-sized ceramic powder are spray-modified with silane coupling agent in a conical mixer. The mass of silane coupling agent is 1% to 10% of the mass of nano-sized ceramic powder and submicron-sized ceramic powder, respectively, to obtain modified nano-sized ceramic powder and modified submicron-sized ceramic powder.

[0007] A2. The modified nano-sized ceramic powder, modified submicron-sized ceramic powder, and deionized water are mixed evenly using a high-shear mixer, and then dispersed by ball milling in a horizontal ball mill at a speed of 1000-2000 rpm for 1-5 hours to obtain a modified ceramic powder slurry. The mass ratio of the modified nano-sized ceramic powder to the modified submicron-sized ceramic powder is 1:1 to 1:5, and the mass of the deionized water is equal to 10% to 30% of the total mass of the modified nano-sized ceramic powder and the modified submicron-sized ceramic powder.

[0008] A3. Using a low-speed three-blade mixer, the modified ceramic powder slurry and PTFE emulsion are mixed evenly at a speed of 100-300 rpm for 1-2 hours. Then, a surfactant is added, and the mixture is stirred for another 1-2 hours to obtain a PTFE composite adhesive. The mass ratio of the modified ceramic powder slurry to the PTFE emulsion is 1:2 to 1:4, and the mass of the surfactant is 0.5%-1.5% of the mass of the modified ceramic powder slurry.

[0009] B. Impregnation with fiberglass cloth

[0010] B1. Inject the PTFE composite adhesive into the impregnation tank of the high-temperature adhesive system, and immerse the glass fiber cloth into the PTFE composite adhesive at a uniform speed through the impregnation tank. The impregnation speed is controlled at 2~4m / min.

[0011] B2. The glass fiber cloth impregnated with PTFE composite adhesive is baked and cured in a high-temperature drying tunnel to form a roll substrate. The temperature of the first section of the drying tunnel is controlled at 240~280℃ to effectively remove moisture and organic additives from the substrate. The temperature of the second section of the drying tunnel is controlled at 320~360℃ to ensure that the PTFE composite adhesive is tightly bonded to the glass fiber cloth.

[0012] B3. Use a substrate cutting machine to cut the roll substrate into the required sheet substrate.

[0013] C. Lamination of sheet substrates

[0014] Sheet substrates are stacked to the required thickness, coated with copper foil on both sides, and then hot-pressed and sintered using a vacuum laminator. The hot-pressing temperature is controlled at 360~400℃, the vacuum degree is less than 60mmHg, the pressure is 6~10Mpa, and the sintering time is 2~4h. After natural cooling to room temperature, a low-loss ultrathin PTFE microwave dielectric substrate with a substrate thickness of 0.065mm±0.008mm, a substrate dielectric constant of 2.95±0.03 at 10GHz, and a substrate loss factor ≤0.0011 at 10GHz is obtained.

[0015] The beneficial effects of this invention are as follows: the PTFE microwave dielectric substrate prepared by this method has fine filler particles and a high filling rate, which improves the thickness and dielectric constant uniformity of the ultrathin substrate. The substrate thickness is 0.065mm ± 0.008mm, and the dielectric constant of the substrate at 10GHz is 2.95 ± 0.03. It also reduces the loss factor at high frequencies, with a loss factor ≤ 0.0011 at 10GHz. The preparation process is simple and easy to scale up for continuous production. The microwave substrate exhibits excellent performance, meeting the stringent performance requirements of multilayer circuit boards in high-frequency communication applications. Detailed Implementation

[0016] The present invention will now be described in detail with reference to specific embodiments.

[0017] The nano-sized ceramic powder is selected from one of SiO2, TiO2, ZnO, BN, and Al2O3, with an average particle size D50 of 10nm~50nm and an average particle size D100 of 50nm~100nm.

[0018] The submicron-sized ceramic powder is selected from one of the following: SiO2, TiO2, ZnO, BN, and Al2O3, with an average particle size D50 of 0.3μm to 0.9μm and an average particle size D100 of 3μm to 10μm.

[0019] The silane coupling agent is one of phenyltrimethoxysilane, aminopropyltrimethoxysilane, methyltrimethoxysilane, or tridecafluorooctyltriethoxysilane.

[0020] Fiberglass cloth with a face weight ≤85g / m 2 One of the following: type 106, type 1080, type 1280, type 2313, and type 3313. Example

[0021] Step 1: Add 10 kg of SiO2 ceramic powder with an average particle size D50 of 10 nm and an average particle size D100 of 50 nm to a conical mixer, and simultaneously add 0.1 kg of phenyltrimethoxysilane for spray modification to obtain modified nano-sized ceramic powder; after cleaning the equipment, add 10 kg of SiO2 ceramic powder with an average particle size D50 of 0.3 μm and an average particle size D100 of 3 μm to the conical mixer, and simultaneously add 0.1 kg of phenyltrimethoxysilane for spray modification to obtain modified submicron-sized ceramic powder.

[0022] Step 2: Mix 10 kg of modified nano-sized ceramic powder, 10 kg of modified submicron-sized ceramic powder and 2 kg of deionized water evenly using a high-shear mixer, and then disperse them by ball milling in a horizontal ball mill at a speed of 1000 rpm for 1 hour to obtain 22 kg of modified ceramic powder slurry.

[0023] Step 3: Using a low-speed three-blade mixer, mix 20 kg of modified ceramic powder slurry and 40 kg of PTFE emulsion evenly. Set the mixing speed to 100 rpm and the mixing time to 1 hour. Then add 0.1 kg of surfactant and continue mixing for 1 hour to obtain PTFE composite adhesive.

[0024] Step 4: Inject the PTFE composite adhesive into the impregnation tank of the high-temperature coating system, and immerse the 106 type glass fiber cloth into the PTFE composite adhesive at a uniform speed through the impregnation tank. The impregnation speed is set to 2m / min.

[0025] Step 5: The glass fiber cloth impregnated with PTFE composite adhesive is baked and cured in a high-temperature drying tunnel to form a roll substrate. The temperature of the first section of the drying tunnel is set to 240℃ to remove moisture and organic additives from the substrate. The temperature of the second section of the drying tunnel is set to 320℃ to ensure that the PTFE composite adhesive is tightly bonded to the glass fiber cloth.

[0026] Step 6: Then use a substrate cutter to cut the roll substrate into the required sheet substrate.

[0027] Step 7: Stack the sheet substrates according to the required thickness, cover both sides with copper foil, and sinter by hot pressing in a vacuum laminator. Set the hot pressing temperature to 360℃, vacuum degree to 50mmHg, pressure to 6Mpa, sintering time to 2h, and allow to cool naturally to room temperature to obtain a low-loss ultrathin PTFE microwave dielectric substrate.

[0028] Step 8: Test the following properties of the PTFE microwave dielectric substrate: substrate thickness, substrate dielectric constant at 10 GHz, and substrate loss factor at 10 GHz (test results are shown in Table 1). Example

[0029] Step 1: Add 10 kg of SiO2 ceramic powder with an average particle size D50 of 20 nm and an average particle size D100 of 60 nm to a conical mixer, and simultaneously add 0.5 kg of phenyltrimethoxysilane for spray modification to obtain modified nano-sized ceramic powder; after cleaning the equipment, add 20 kg of SiO2 ceramic powder with an average particle size D50 of 0.5 μm and an average particle size D100 of 5 μm to the conical mixer, and simultaneously add 1 kg of phenyltrimethoxysilane for spray modification to obtain modified submicron-sized ceramic powder.

[0030] Step 2: Mix 10 kg of modified nano-sized ceramic powder, 20 kg of modified submicron-sized ceramic powder and 6 kg of deionized water evenly using a high-shear mixer, and then disperse them by ball milling in a horizontal ball mill at a speed of 1500 rpm for 3 hours to obtain 36 kg of modified ceramic powder slurry.

[0031] Step 3: Using a low-speed three-blade mixer, mix 36 kg of modified ceramic powder slurry and 108 kg of PTFE emulsion evenly. Set the mixing speed to 200 rpm and the mixing time to 1.5 h. Then add 0.36 kg of surfactant and continue mixing for 1.5 h to obtain PTFE composite adhesive.

[0032] Step 4: Inject the PTFE composite adhesive into the impregnation tank of the high-temperature coating system, and immerse the 106 type glass fiber cloth into the PTFE composite adhesive at a uniform speed through the impregnation tank. The impregnation speed is set to 3m / min.

[0033] Step 5: The glass fiber cloth impregnated with PTFE composite adhesive is baked and cured in a high-temperature drying tunnel to form a roll substrate. The temperature of the first section of the drying tunnel is set to 260℃ to remove moisture and organic additives from the substrate. The temperature of the second section of the drying tunnel is set to 340℃ to ensure that the PTFE composite adhesive is tightly bonded to the glass fiber cloth.

[0034] Step 6: Then use a substrate cutter to cut the roll substrate into the required sheet substrate.

[0035] Step 7: Stack the sheet substrates according to the required thickness, cover both sides with copper foil, and sinter them by hot pressing in a vacuum laminator. Set the hot pressing temperature to 380℃, vacuum degree to 50mmHg, pressure to 8Mpa, sintering time to 3h, and allow to cool naturally to room temperature to obtain a low-loss ultrathin PTFE microwave dielectric substrate.

[0036] Step 8: Test the following properties of the PTFE microwave dielectric substrate: substrate thickness, substrate dielectric constant at 10 GHz, and substrate loss factor at 10 GHz (test results are shown in Table 1). Example

[0037] Step 1: Add 5 kg of SiO2 ceramic powder with an average particle size D50 of 30 nm and an average particle size D100 of 80 nm to a conical mixer, and simultaneously add 0.15 kg of phenyltrimethoxysilane for spray modification to obtain modified nano-sized ceramic powder; after cleaning the equipment, add 15 kg of SiO2 ceramic powder with an average particle size D50 of 0.6 μm and an average particle size D100 of 8 μm to the conical mixer, and simultaneously add 0.45 kg of phenyltrimethoxysilane for spray modification to obtain modified submicron-sized ceramic powder.

[0038] Step 2: Mix 5 kg of modified nano-sized ceramic powder, 15 kg of modified submicron-sized ceramic powder and 3 kg of deionized water evenly using a high-shear mixer, and then disperse them by ball milling in a horizontal ball mill at a speed of 1300 rpm for 2 hours to obtain 23 kg of modified ceramic powder slurry.

[0039] Step 3: Using a low-speed three-blade mixer, mix 20 kg of modified ceramic powder slurry and 50 kg of PTFE emulsion evenly. Set the mixing speed to 150 rpm and the mixing time to 1 hour. Then add 0.2 kg of surfactant and continue mixing for 2 hours to obtain PTFE composite adhesive.

[0040] Step 4: Inject the PTFE composite adhesive into the impregnation tank of the high-temperature coating system, and immerse the 106 type glass fiber cloth into the PTFE composite adhesive at a uniform speed through the impregnation tank. The impregnation speed is set to 3m / min.

[0041] Step 5: The glass fiber cloth impregnated with PTFE composite adhesive is baked and cured in a high-temperature drying tunnel to form a roll substrate. The temperature of the first section of the drying tunnel is set to 250℃ to remove moisture and organic additives from the substrate. The temperature of the second section of the drying tunnel is set to 330℃ to ensure that the PTFE composite adhesive is tightly bonded to the glass fiber cloth.

[0042] Step 6: Then use a substrate cutter to cut the roll substrate into the required sheet substrate.

[0043] Step 7: Stack the sheet substrates according to the required thickness, cover both sides with copper foil, and sinter them by hot pressing in a vacuum laminator. Set the hot pressing temperature to 370℃, vacuum degree to 50mmHg, pressure to 7Mpa, sintering time to 3h, and allow to cool naturally to room temperature to obtain a low-loss ultrathin PTFE microwave dielectric substrate.

[0044] Step 8: Test the following properties of the PTFE microwave dielectric substrate: substrate thickness, substrate dielectric constant at 10 GHz, and substrate loss factor at 10 GHz (test results are shown in Table 1). Example

[0045] Step 1: Add 5 kg of SiO2 ceramic powder with an average particle size D50 of 40 nm and an average particle size D100 of 90 nm to a conical mixer, and simultaneously add 0.4 kg of phenyltrimethoxysilane for spray modification to obtain modified nano-sized ceramic powder; after cleaning the equipment, add 20 kg of SiO2 ceramic powder with an average particle size D50 of 0.8 μm and an average particle size D100 of 8 μm to the conical mixer, and simultaneously add 1.6 kg of phenyltrimethoxysilane for spray modification to obtain modified submicron-sized ceramic powder.

[0046] Step 2: Mix 5 kg of modified nano-sized ceramic powder, 20 kg of modified submicron-sized ceramic powder and 6.25 kg of deionized water evenly using a high-shear mixer, and then disperse them by ball milling in a horizontal ball mill at a speed of 1800 rpm for 4 hours to obtain 31.25 kg of modified ceramic powder slurry.

[0047] Step 3: Using a low-speed three-blade mixer, mix 30 kg of modified ceramic powder slurry and 105 kg of PTFE emulsion evenly. Set the mixing speed to 250 rpm and the mixing time to 2 hours. Then add 0.45 kg of surfactant and continue mixing for 1 hour to obtain PTFE composite adhesive.

[0048] Step 4: Inject the PTFE composite adhesive into the impregnation tank of the high-temperature coating system, and immerse the 106 type glass fiber cloth into the PTFE composite adhesive at a uniform speed through the impregnation tank. The impregnation speed is set to 4m / min.

[0049] Step 5: The glass fiber cloth impregnated with PTFE composite adhesive is baked and cured in a high-temperature drying tunnel to form a roll substrate. The temperature of the first section of the drying tunnel is set to 270℃ to remove moisture and organic additives from the substrate. The temperature of the second section of the drying tunnel is set to 350℃ to ensure that the PTFE composite adhesive is tightly bonded to the glass fiber cloth.

[0050] Step 6: Then use a substrate cutter to cut the roll substrate into the required sheet substrate.

[0051] Step 7: Stack the sheet substrates according to the required thickness, cover both sides with copper foil, and sinter them by hot pressing in a vacuum laminator. Set the hot pressing temperature to 390℃, vacuum degree to 50mmHg, pressure to 9Mpa, sintering time to 4h, and allow to cool naturally to room temperature to obtain a low-loss ultrathin PTFE microwave dielectric substrate.

[0052] Step 8: Test the following properties of the PTFE microwave dielectric substrate: substrate thickness, substrate dielectric constant at 10 GHz, and substrate loss factor at 10 GHz (test results are shown in Table 1). Example

[0053] Step 1: Add 4 kg of SiO2 ceramic powder with an average particle size D50 of 50 nm and an average particle size D100 of 100 nm to a conical mixer, and simultaneously add 0.4 kg of phenyltrimethoxysilane for spray modification to obtain modified nano-sized ceramic powder; after cleaning the equipment, add 20 kg of SiO2 ceramic powder with an average particle size D50 of 0.9 μm and an average particle size D100 of 10 μm to the conical mixer, and simultaneously add 2 kg of phenyltrimethoxysilane for spray modification to obtain modified submicron-sized ceramic powder.

[0054] Step 2: Mix 4 kg of modified nano-sized ceramic powder, 20 kg of modified submicron-sized ceramic powder and 7.2 kg of deionized water evenly using a high-shear mixer, and then disperse them by ball milling in a horizontal ball mill at a speed of 2000 rpm for 5 hours to obtain 31.2 kg of modified ceramic powder slurry.

[0055] Step 3: Using a low-speed three-blade mixer, mix 30 kg of modified ceramic powder slurry and 120 kg of PTFE emulsion evenly. Set the mixing speed to 300 rpm and the mixing time to 2 hours. Then add 0.45 kg of surfactant and continue mixing for 2 hours to obtain PTFE composite adhesive.

[0056] Step 4: Inject the PTFE composite adhesive into the impregnation tank of the high-temperature coating system, and immerse the 106 type glass fiber cloth into the PTFE composite adhesive at a uniform speed through the impregnation tank. The impregnation speed is set to 4m / min.

[0057] Step 5: The glass fiber cloth impregnated with PTFE composite adhesive is baked and cured in a high-temperature drying tunnel to form a roll substrate. The temperature of the first section of the drying tunnel is set to 280℃ to remove moisture and organic additives from the substrate. The temperature of the second section of the drying tunnel is set to 360℃ to ensure that the PTFE composite adhesive is tightly bonded to the glass fiber cloth.

[0058] Step 6: Then use a substrate cutter to cut the roll substrate into the required sheet substrate.

[0059] Step 7: Stack the sheet substrates according to the required thickness, cover both sides with copper foil, and sinter them by hot pressing in a vacuum laminator. Set the hot pressing temperature to 400℃, vacuum degree to 50mmHg, pressure to 10Mpa, sintering time to 4h, and allow to cool naturally to room temperature to obtain a low-loss ultrathin PTFE microwave dielectric substrate.

[0060] Step 8: Test the following properties of the PTFE microwave dielectric substrate: substrate thickness, substrate dielectric constant at 10 GHz, and substrate loss factor at 10 GHz (test results are shown in Table 1).

[0061] The test results of the microwave composite dielectric substrates prepared in Examples 1-5 above are shown in Table 1.

[0062] Table 1

[0063] sample Thickness (mm) Dielectric constant (10 GHz) Loss (10GHz) Example 1 0.060 2.94 0.0010 Example 2 0.068 2.96 0.0008 Example 3 0.063 2.94 0.0010 Example 4 0.071 2.95 0.0010 Example 5 0.066 2.97 0.0007

[0064] As shown in Table 1, this invention uses modified nano- and submicron-sized ceramic powders in a certain proportion, and improves the dispersibility and surface activity of the ceramic powder through ball milling premixing. This composite filler is then mixed with PTFE to form a colloid, and the resulting PTFE microwave dielectric substrate, prepared through an impregnation and lamination process, has fine filler particles and a high filling rate, thus improving the thickness and dielectric constant uniformity of the ultrathin substrate. The microwave composite dielectric substrate prepared using this invention has a thickness of 0.065 mm ± 0.008 mm, a dielectric constant of 2.95 ± 0.03 at 10 GHz, and a loss factor ≤ 0.0011 at 10 GHz, meeting the requirements for low-loss ultrathin PTFE microwave dielectric substrates. The substrate exhibits high reliability in processing and application, a simple preparation process, and readily available raw materials, facilitating industrial production.

Claims

1. A method for fabricating a low-loss ultrathin PTFE microwave dielectric substrate, characterized in that, The preparation method includes the following steps: A. Preparation of PTFE composite adhesive A1. Nano-sized ceramic powder and submicron-sized ceramic powder are spray-modified with silane coupling agent in a conical mixer. The mass of silane coupling agent is 1% to 10% of the mass of nano-sized ceramic powder and submicron-sized ceramic powder, respectively, to obtain modified nano-sized ceramic powder and modified submicron-sized ceramic powder. A2. Modified nano-sized ceramic powder, modified submicron-sized ceramic powder, and deionized water are mixed evenly using a high-shear mixer, and then dispersed by ball milling in a horizontal ball mill at a speed of 1000-2000 rpm for 1-5 hours to obtain a modified ceramic powder slurry. The mass ratio of the modified nano-sized ceramic powder to the modified submicron-sized ceramic powder is 1:1 to 1:5, and the mass of deionized water is equal to 10%-30% of the total mass of the modified nano-sized ceramic powder and the modified submicron-sized ceramic powder. A3. Using a low-speed three-blade mixer, the modified ceramic powder slurry and PTFE emulsion are mixed evenly at a speed of 100-300 rpm for 1-2 hours. Then, a surfactant is added, and mixing continues for 1-2 hours to obtain a PTFE composite adhesive. The mass ratio of the modified ceramic powder slurry to the PTFE emulsion is 1:2-1:4, and the mass of the surfactant is 0.5%-1.5% of the mass of the modified ceramic powder slurry. B. Impregnation with fiberglass cloth B1. Inject the PTFE composite adhesive into the impregnation tank of the high-temperature adhesive system, and immerse the glass fiber cloth into the PTFE composite adhesive at a uniform speed through the impregnation tank. The impregnation speed is controlled at 2~4m / min. B2. The glass fiber cloth impregnated with PTFE composite adhesive is baked and cured in a high-temperature drying tunnel to form a roll substrate. The temperature of the first section of the drying tunnel is controlled at 240~280℃ to effectively remove moisture and organic additives from the substrate. The temperature of the second section of the drying tunnel is controlled at 320~360℃ to ensure that the PTFE composite adhesive is tightly bonded to the glass fiber cloth. B3. Use a substrate cutting machine to cut the roll substrate into the required sheet substrate; C. Lamination of sheet substrates Sheet substrates are stacked to the required thickness, coated with copper foil on both sides, and then hot-pressed and sintered using a vacuum laminator. The hot-pressing temperature is controlled at 360~400℃, the vacuum degree is less than 60mmHg, the pressure is 6~10MPa, and the sintering time is 2~4h. After natural cooling to room temperature, a low-loss ultrathin PTFE microwave dielectric substrate with a substrate thickness of 0.065mm±0.008mm, a substrate dielectric constant of 2.95±0.03 at 10GHz, and a substrate loss factor ≤0.0011 at 10GHz is obtained. The nano-sized ceramic powder is selected from one of SiO2, TiO2, ZnO, BN, and Al2O3, with an average particle size D50 of 10nm~50nm and an average particle size D100 of 50nm~100nm. The submicron-sized ceramic powder is selected from one of SiO2, TiO2, ZnO, BN, and Al2O3, with an average particle size D50 of 0.3μm to 0.9μm and an average particle size D100 of 3μm to 10μm. The silane coupling agent is one of phenyltrimethoxysilane, aminopropyltrimethoxysilane, methyltrimethoxysilane, and tridecafluorooctyltriethoxysilane.

2. The method for preparing a low-loss ultrathin PTFE microwave dielectric substrate according to claim 1, characterized in that, The fiberglass cloth has a surface weight ≤85g / m². 2 One of the following: type 106, type 1080, type 1280, type 2313, and type 3313.