Low-dielectric low-loss polyolefin-based composite substrate with low ceramic filling amount and preparation method of low-dielectric low-loss polyolefin-based composite substrate

Abstract

The invention provides a low-dielectric low-loss polyolefin-based composite substrate with low ceramic filling amount and a preparation method thereof, and particularly relates to the technical field of high-frequency composite material substrates. The composite substrate comprises the following components in parts by weight: 25 to 45 parts of polyolefin resin; 0.5 to 1.5 parts of a curing agent; 49 to 65 parts of ceramic powder; 5-7 parts of glass fiber cloth; 0.5 to 1.5 parts of a silane coupling agent; glass fiber cloth is used for supporting, and the raw rubber sheet is subjected to sealed hot-pressed sintering to control rubber flow. The method has the characteristics of low ceramic filling amount, low dielectric constant, low dielectric loss and low water absorption rate, is suitable for manufacturing high-precision high-frequency electronic device substrates for 5G communication, millimeter wave antennas and the like, is simple, and has large-scale production feasibility.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite material preparation, and particularly relates to a polyolefin-based composite substrate with low ceramic filling amount, low dielectric constant and low loss, and a preparation method thereof, which is applicable to the manufacture of high-frequency circuit substrates. Background Art

[0002] With the rapid development of artificial intelligence, autonomous driving and 5G / 6G communication technologies, the requirements for signal transmission rate and stability of high-frequency electronic devices have increased exponentially. As the core carrier of high-frequency circuits, dielectric substrates need to achieve coordinated optimization between low dielectric constant and low loss tangent to reduce signal delay and energy loss, while taking into account mechanical strength, thermal stability and processing adaptability.

[0003] Chinese patents "A Temperature-Stable, Large-Size Microwave Composite Dielectric Substrate and Preparation Method" (application number 202211563246.0) and "A Polytetrafluoroethylene-Based Ceramic Composite Material with Near-Zero Dielectric Constant Temperature Coefficient and Preparation Method Thereof" (application number CN201811435196.1) both use a specific proportion of multiple ceramic powders to be filled into a polytetrafluoroethylene substrate. The prepared substrate has a low dielectric constant (<5) and excellent high-frequency dielectric properties, but its resin matrix is polytetrafluoroethylene, and the processing process is complex and requires high-temperature sintering above 350°C.

[0004] Chinese patents "A Resin Composition for Copper-Clad Substrate in High-Frequency and High-Speed Fields and Its Application" (application number 201611077031.2) and "A Composite Material, a High-Frequency Circuit Substrate Made Thereof and a Manufacturing Method" (application number 201710142130.2) both use a hydrocarbon resin, a glass fiber cloth and a ceramic powder to compound and make a high-frequency substrate. Compared with PTFE or epoxy resin, the new hydrocarbon resin system realizes the coordinated optimization of dielectric constant (=2.0 - 2.8) and loss factor (tanδ = 0.0001 - 0.0006) through the low-polarity characteristics and high bond energy characteristics of C-H bonds in the molecular chain, and the three-dimensional network formed by unsaturated bond crosslinking. At the same time, the three-dimensional network has excellent thermal stability and mechanical strength. However, it uses the method of stacking and hot-pressing multiple prepregs, and the proportion of glass fiber cloth is relatively high, and the dielectric constant of the composite material made is between 3.4 and 4.

[0005] Chinese Patent "Ceramic / Hydrocarbon Resin-Based Microwave Dielectric Substrate Without Glass Fiber and Its Preparation Method" (Application No. 202210292711.5) adopts the technical solution of no glass fiber cloth. By introducing more high-molecular-weight components and filling more inorganic fillers (>70 wt.%), the ultra-high fluidity of low-molecular-weight hydrocarbon resin is controlled, making the substrate easier to form, and the dielectric constant is reduced to 3.2. Considering that the dielectric constant of ceramic fillers is usually high (>3), reducing the ceramic content will directly contribute to reducing the dielectric constant of the composite substrate, which requires solving the problem of difficult forming caused by the ultra-high fluidity of the resin. Summary of the Invention

[0006] In view of the above problems, a polyolefin-based composite substrate with low ceramic filling amount, low dielectric constant and low loss and its preparation method are proposed. The glass fiber cloth is used to solve the problem of the decrease in the strength of the substrate caused by reducing the ceramic content. At the same time, the sizing amount of the glass fiber cloth is increased and only a single piece of raw film is hot-pressed, so as to reduce the proportion of the glass fiber cloth in the composite substrate; and after improving the hot-pressing method, the hot-pressing process can press resins with higher fluidity, and the microwave dielectric substrate made in this way has the characteristics of low glass fiber cloth proportion, low ceramic filling amount, low dielectric constant, low dielectric loss and low water absorption.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A polyolefin-based composite substrate with low ceramic filling amount, low dielectric constant and low loss, characterized in that the components of the composite substrate and the weight parts of each component in the composite substrate are:

[0009] Polyolefin resin: 25 - 45 parts;

[0010] Curing agent: 0.5 - 1.5 parts;

[0011] Ceramic powder filler: 49 - 65 parts;

[0012] Glass fiber cloth: 5 - 7 parts;

[0013] Silane coupling agent: 0.5 - 1.5 parts.

[0014] Further, the polyolefin resin is one or more of polybutadiene, polyisoprene, polystyrene-isoprene, polystyrene, ethylene-propylene-diene terpolymer, and the dielectric constant is less than 2.6.

[0015] Further, the curing agent is one or more of ditert-butylperoxyisopropylbenzene, benzoic peroxide, benzoyl peroxide.

[0016] Further, the ceramic powder is one or more of silica and alumina, with a particle size of 2 - 10 μm, a dielectric constant of 3 - 10, a dielectric loss < 0.003, and is modified with a silane coupling agent.

[0017] Further, the fiberglass cloth is one or several of 106 and 1080, and is modified with a silane coupling agent.

[0018] Further, the silane coupling agent is one or several of A171, Z6124, KH570, and F8261.

[0019] Further, a method for preparing a low - ceramic - filled, low - dielectric - constant and low - loss polyolefin - based composite substrate includes the following steps:

[0020] Step 1: Add polyolefin resin, curing agent, and modified ceramic powder filler into a beaker containing an organic solvent in sequence, place it in a magnetic stirring container and stir to mix evenly to obtain a mixed slurry, and control the solid content of the slurry to be between 55% and 70%.

[0021] Step 2: Coat the slurry obtained in Step 1 on the surface of a polytetrafluoroethylene membrane as the first layer, lay the modified fiberglass cloth on it as the second layer, and finally coat the slurry on the fiberglass cloth again as the third layer to obtain a wet film with a "slurry - fiberglass cloth - slurry" structure. The film - forming thickness is 0.4 - 0.8 mm. Put the wet film into an oven at 60 °C to dry the solvent to obtain a green body.

[0022] Step 3: Cover both sides of the green body obtained in Step 2 with copper foil, fold the edge of the copper foil by 0.5 - 2 cm and seal the edge, then put it into a vacuum hot press for hot pressing. The heating rate is 5 °C / min. Under a pressure of 2 - 10 MPa, first hold at 100 - 160 °C for 0.5 - 4 h, and then hold at 180 - 240 °C for 0.5 - 4 h. After hot pressing, the composite substrate is obtained.

[0023] Preferably, there is a certain range of empty area between the sealed substrate green body and the edge of the copper foil to allow appropriate resin flow. The empty area range is 10% - 20% of the length and width of the substrate green body.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1. The low - ceramic - filled, low - dielectric - constant and low - loss polyolefin - based composite substrate proposed by the present invention uses fiberglass cloth to enhance the mechanical strength of the substrate, and has the characteristics of a low fiberglass cloth proportion, a low ceramic filling amount, a low dielectric constant (2.6 - 3.2), and a low dielectric loss (less than 0.003).

[0026] 2. The method for preparing the polyolefin-based composite substrate proposed by the present invention adopts the method of sealed hot pressing and sintering, which can hot press high-fluidity materials, realize controllable flow of glue, and has good consistency of the composite substrate in repeated production. At the same time, through appropriate flow of glue, the voids left after solvent volatilization can be filled, and finally a dense structure is formed. The preparation process is simple and controllable, compatible with the original hot pressing process, and has low cost. Detailed implementation mode

[0027] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in detail with reference to specific embodiments.

[0028] Example 1:

[0029] Step 1: Prepare 50 g of a mixed solvent according to the mass ratio of deionized water: absolute ethanol = 9:1, then add a small amount of glacial acetic acid to adjust the pH value of the mixed solution to between 3 and 4, add 0.75 g of silane coupling agent A171, stir and mix evenly to obtain mixed solution A; Weigh 50 g of ceramic powder filler and add it to the above mixed solution. After ultrasonic water bath at 60 °C for 240 min, place it in an oven at 100 °C to dry, and pass through a 120-mesh sieve to obtain modified ceramic powder.

[0030] Step 2: Weigh 50 g of the mixed solution A prepared in Step 1, immerse the glass fiber cloth in the mixed solution A, after ultrasonic water bath at 60 °C for 40 min, place it in an oven at 100 °C to dry to obtain modified glass fiber cloth.

[0031] Step 3: Weigh 5.0 g of polybutadiene, 4.5 g of ethylene propylene diene monomer rubber, 0.5 g of polystyrene-isoprene, and 25 g of toluene solvent and put them into a 250 mL beaker to fully dissolve, and place them in a magnetic stirring container to stir and mix evenly to obtain glue solution B.

[0032] Step 4: Take 0.3 g of ditert-butylperoxyisopropylbenzene and 12.22 g of modified SiO2 and add them to the glue solution B to obtain a mixed slurry, and control the solid content of the slurry to be: 55%.

[0033] Step 5: First, evenly scrape the slurry obtained in Step 4 onto a polytetrafluoroethylene film, control the thickness of the slurry to be 0.3 mm, lay the modified glass fiber cloth, and then scrape the second layer of slurry with a thickness of 0.6 mm. Put the wet film into an oven at 60 °C to dry the solvent to obtain a green body.

[0034] Step 6: Cover both sides of the green body obtained in Step 5 with copper foil. Fold the edges of the copper foil by 1 cm. After folding, the length and width of the copper foil exceed the length and width of the green body by 15%. Then seal the edges and place it in a vacuum hot press for hot pressing. The heating rate is 5 °C / min. Hold at 8 MPa and 120 °C for 1 h, and then hold at 16 MPa and 210 °C for 3 h. After hot pressing, the composite substrate is obtained. Corrode the copper foil on the surface of the prepared composite substrate and cut it into squares with a size of 50 mm × 30 mm for testing the microwave dielectric properties.

[0035] Examples 2 - 5:

[0036] Compared with Example 1, Examples 2 - 5 are different in that: the types and components of the resin solvents in Step 3 and the types and weights of the modified ceramic powders in Step 4 are adjusted. The raw material contents of each example are shown in Table 1.

[0037] Table 1 Raw material quality (g) of each example

[0039] Table 2 Substrate properties prepared in each example

[0041] As can be seen from Table 2, the present invention adopts the method of controlling the slurry density and sealed hot pressing, using SiO2 and Al2O3 as ceramic fillers to prepare a polyolefin-based composite substrate with a low ceramic filling amount. The dielectric constant is low and can be adjusted between 2.67 and 3.19 according to the added amount of ceramic. The water absorption rate is lower than 0.2%, having excellent practical value.

[0042] The above examples are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above examples without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A polyolefin-based composite substrate with low dielectric constant and low loss and low ceramic filling amount, characterized in that, The components of the composite substrate and the weight parts of each component in the composite substrate are as follows: Polyolefin resin: 25 - 45 parts; Curing agent: 0.5 - 1.5 parts; Ceramic powder filler: 49 - 65 parts; Glass fiber cloth: 5 - 7 parts; Silane coupling agent: 0.5 - 1.5 parts.

2. The low-dielectric and low-loss polyolefin-based composite substrate with low ceramic filling amount according to claim 1, wherein The polyolefin resin is one or more of polybutadiene, polyisoprene, polystyrene - isoprene, polystyrene, and ethylene - propylene - diene terpolymer, and the dielectric constant is less than 2.

6.

3. The low-dielectric and low-loss polyolefin-based composite substrate with low ceramic filling amount according to claim 1, wherein The curing agent is one or more of ditert - butyl peroxy - di - isopropylbenzene, benzoic acid peroxide, and benzoyl peroxide.

4. The low-dielectric and low-loss polyolefin-based composite substrate with a low ceramic filling amount according to claim 1, characterized in that The ceramic powder is one or more of silicon dioxide and alumina, with a particle size of 2 - 10 μm, a dielectric constant of 3 - 10, and a dielectric loss less than 0.003, and is modified with a silane coupling agent.

5. The low-dielectric and low-loss polyolefin-based composite substrate with a low ceramic filling amount according to claim 1, characterized in that The glass fiber cloth is one or more of 106 and 1080, and is modified with a silane coupling agent.

6. The low-dielectric and low-loss polyolefin-based composite substrate with low ceramic filling amount according to claim 1, characterized in that The silane coupling agent is one or more of A171, Z6124, KH570, and F8261.

7. The low-dielectric and low-loss polyolefin-based composite substrate with a low ceramic filling amount according to claim 1, characterized in that The preparation method of a polyolefin - based composite substrate with low ceramic filling amount, low dielectric constant and low loss includes the following steps: Step 1: Add the polyolefin resin, curing agent, and modified ceramic powder filler into a beaker containing an organic solvent in sequence, place it in a magnetic stirring container and stir to mix evenly to obtain a mixed slurry, and control the solid content of the slurry to be between 55% and 70%; Step 2: Scrap the slurry obtained in Step 1 on the surface of the polytetrafluoroethylene film as the first layer, lay the modified glass fiber cloth on it as the second layer, and finally scrape the slurry once again on the glass cloth as the third layer to obtain a wet film with a "slurry - glass cloth - slurry" structure. Put the wet film into an oven at 60 °C to dry the solvent to obtain a green body; Step 3: Cover both sides of the green body obtained in Step 2 with copper foil, fold the edges of the copper foil by 0.5 - 2 cm and seal the edges, then put it into a vacuum hot press for hot pressing. Under a pressure of 2 - 10 MPa, first hold at 100 - 160 °C for 0.5 - 4 h, and then hold at 180 - 240 °C for 0.5 - 4 h. After hot pressing, the composite substrate is obtained.

8. The preparation method of a low-dielectric and low-loss polyolefin-based composite substrate with a low ceramic filling amount according to claim 5, characterized in that, There is a certain range of empty area between the sealed green body and the edges of the copper foil in Step 3 to allow appropriate bleeding. The bleeding range is 10% - 20% of the length and width of the green body.

Images