High-dielectric low-dielectric constant temperature coefficient composite substrate and preparation method thereof

Abstract

A kind of high dielectric low dielectric constant temperature coefficient composite substrate and preparation method thereof, belong to high frequency miniaturization composite material substrate technical field.The component of the composite substrate and each component in composite substrate weight parts are as follows:ZnO-TiO2-Nb2O5 Base ceramic powder filling:70~85 parts;Silane coupling agent:0.5~2 parts;Curing agent:2~4 parts;Polyolefin resin:5~20 parts;Auxiliary crosslinking agent:3~5 parts.The ZnO-TiO2-Nb2O5 Base ceramic powder proposed in the application has the characteristics of adjustable high dielectric constant, low dielectric loss, adjustable low resonance frequency temperature coefficient and low sintering temperature, and the composite substrate prepared as filler has high dielectric constant, low dielectric loss and low dielectric constant temperature coefficient.

Description

Technical Field

[0001] This invention belongs to the field of high-frequency miniaturized composite material substrate technology, specifically relating to a high dielectric and low dielectric constant temperature coefficient composite substrate and its preparation method. Background Technology

[0002] Microwave composite dielectric substrate materials are widely used in airborne radar devices, phased array systems, remote sensing and other airborne satellite microstrip planar antennas, BeiDou navigation antennas, portable mobile antennas, and other fields. With the popularization of 5G technology and automotive radar technology, digital circuits are gradually developing towards miniaturization of device scale, high-speed information processing, and high-frequency operation. In order to meet the growing requirements of miniaturization and high temperature stability of practical microwave circuits, there is an urgent need to develop high-frequency substrate products with high dielectric constant and low dielectric constant temperature coefficient.

[0003] Currently, widely used high-dielectric substrates generally use epoxy resin and polytetrafluoroethylene (PTFE) as organic matrices, with simple high-dielectric ceramic fillers added. While these materials offer excellent dielectric properties, they also have certain drawbacks. Regarding the selection of organic matrices, epoxy resin substrates have high viscosity and relatively high losses, making them unsuitable for the demands of high-frequency and high-speed signal transmission. While PTFE substrates offer excellent high-frequency dielectric properties, their processing is complex, requires high temperatures, and contains sulfur (F) which pollutes the environment. Therefore, thermosetting resin materials based on polyolefins are a promising high-frequency composite substrate material due to their excellent dielectric properties, ease of processing, and environmental friendliness. As for the selection of high-dielectric fillers, ceramic powders with simple structures and high dielectric constants, such as titanium dioxide, calcium titanate, and strontium titanate, are commonly used. However, these high-dielectric ceramics all possess a significant temperature coefficient of dielectric constant, which cannot meet the high-temperature stability requirements of practical applications.

[0004] US Patent (USPat. No. 5358775) proposes a method for obtaining high dielectric constant (4–12.3) and low temperature coefficient of dielectric constant (≤150 ppm / ℃) by using a combination of various ceramic fillers. However, the method uses a wide variety of ceramic fillers, and the problem of fluorine pollution in the resin matrix remains unresolved, making it difficult to apply in actual production.

[0005] Chinese patents, namely "A ceramic material and its preparation method, polytetrafluoroethylene-ceramic composite material and its preparation method and substrate" (application number CN201410431320.2) and "Microwave dielectric ceramic, polytetrafluoroethylene-ceramic composite substrate and its preparation method" (application number CN201710700372.9), both prepare ceramic fillers by sintering raw materials and then composite the fillers with polytetrafluoroethylene after modification with coupling agents to obtain high-frequency substrates with high dielectric constant and low dielectric constant temperature coefficient. However, they still cannot avoid the problems of high filler sintering temperature (≥1200℃), high substrate processing temperature (≥350℃), and environmental pollution caused by fluorine.

[0006] Chinese patents "A Resin Composition for Copper-Clad Foil Substrates in High-Frequency and High-Speed ​​Applications and Its Application" (application number 201611077031.2) and "A Composite Material, a High-Frequency Circuit Board Made Therefrom and Its Manufacturing Method" (application number 201710142130.2) both use readily available ceramic powder and hydrocarbon resin to composite high-frequency substrates. However, the dielectric constant of the composite material they produce can only cover the low dielectric range (<5), and the ceramic raw materials are all simple structural ceramics (SiO2, Al2O3, MgO, TiO2, etc.) with extremely high processing temperatures. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the prior art by proposing a composite substrate with high dielectric constant and low temperature coefficient of dielectric constant and its preparation method. This invention uses ZnO-TiO2-Nb2O5-based ceramic powder with high dielectric constant and low dielectric loss as a filler to obtain a composite substrate with high dielectric constant and low temperature coefficient of dielectric constant. Furthermore, the preparation temperature of both the ZnO-TiO2-Nb2O5-based ceramic powder and the composite substrate is low, making it easy for industrial production.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A composite substrate with high dielectric constant and low temperature coefficient, wherein the components of the composite substrate and the weight proportions of each component in the composite substrate are as follows:

[0010] ZnO-TiO2-Nb2O5-based ceramic powder filler: 70-85 parts;

[0011] Silane coupling agent: 0.5–2 parts;

[0012] Hardener: 2-4 parts;

[0013] Polyolefin resin: 5-20 parts;

[0014] Crosslinking agent: 3-5 parts.

[0015] The ZnO-TiO2-Nb2O5-based ceramic powder filler comprises a main crystalline phase and a sintering aid, wherein the mass percentage of the sintering aid is less than 0.001 wt.%; the main crystalline phase is Zn. 0.15+0.35x Nb 0.3+0.7x Ti 0.55-0.05x O 2+2x The sintering aid is (0.3y+xy)Li2CO3-(0.5y+xy)B2O3-(0.2y+xy)SiO2, where x = 0 to 1 and y = 0.01 to 0.04.

[0016] Furthermore, the ZnO-TiO2-Nb2O5-based ceramic powder filler has a particle size of 1–5 micrometers and a dielectric constant of 85–100.

[0017] Furthermore, the preparation process of the ZnO-TiO2-Nb2O5-based ceramic powder filler is as follows:

[0018] Step 1: Weigh ZnO, TiO2, Nb2O5, Li2CO3, B2O3, and SiO2 as raw materials according to the stoichiometric ratio of "(0.15+0.35x)ZnO-(0.55-0.05x)TiO2-(0.15+0.35x)Nb2O5-(0.3y+xy)Li2CO3-(0.5y+xy)B2O3-(0.2y+xy)SiO2".

[0019] Step 2: According to the mass ratio of powder:deionized water:zirconium balls = 1:(2~4):(6~8), add the powder weighed in Step 1, deionized water, and zirconium balls together into a planetary ball mill jar, and ball mill for 8~10 hours. The resulting slurry is dried at 80~100℃ and passed through an 80~120 mesh sieve to obtain an abrasive.

[0020] Step 3: Press the abrasive obtained in Step 2 into a block using a mold. The molding pressure is 15-25 MPa and the molding time is 1-2 minutes. Then, sinter the block at 900-1000℃ in air atmosphere for 6-8 hours to obtain ZnO-TiO2-Nb2O5 based ceramic block.

[0021] Step 4: The ZnO-TiO2-Nb2O5-based ceramic block obtained in Step 3 is crushed using a crusher to obtain primary crushed powder with a particle size of 0.5-5 mm;

[0022] Step 5: According to the mass ratio of primary crushed powder: deionized water: zirconium balls = 1:(2~3):(6~8), add the primary crushed powder obtained in step 4, deionized water, and zirconium balls together into a planetary ball mill jar, and perform secondary ball milling for 60~80 minutes. The resulting slurry is dried at 80~100℃ to obtain ZnO-TiO2-Nb2O5 based ceramic powder filler.

[0023] Furthermore, the zirconium sphere is a circular zirconium sphere with a diameter of 1 to 5 millimeters.

[0024] Furthermore, the particle size of the ceramic powder filler obtained in step 5 is 1–5 micrometers.

[0025] Preferably, the silane coupling agent is one or more of 3-methacryloyloxypropyltrimethoxysilane (KH570), vinyltrimethoxysilane (A171), vinyltriethoxysilane (A151), and vinyl-tris(2-methoxyethoxy)silane (KH-A172) containing double bonds.

[0026] Preferably, the curing agent is one or more of di-tert-butyl peroxide, dicumyl peroxide, and benzoic acid peroxide.

[0027] Preferably, the polyolefin resin is one or more copolymers of polybutadiene, polystyrene, polystyrene-isoprene, etc., whose main chain contains double bonds.

[0028] Preferably, the crosslinking agent is one or more of triallyl isocyanurate, triallyl cyanurate, and triallyl cyanurate.

[0029] A method for preparing a composite substrate with high dielectric constant and low temperature coefficient of dielectric constant includes the following steps:

[0030] Step 1: Add ZnO-TiO2-Nb2O5-based ceramic powder filler and silane coupling agent to a mixed solvent of deionized water and anhydrous ethanol, stir and mix evenly to obtain a mixed solution, wherein the mass ratio of anhydrous ethanol to deionized water is 1:(8-9); then adjust the pH value of the mixed solution to 3-5 with acetic acid, stir and mix at 60-80℃ for 90-120 minutes, and then dry in an oven at 100-120℃; finally, pass through a 100-120 mesh sieve to obtain modified ZnO-TiO2-Nb2O5-based ceramic powder filler;

[0031] Step 2: Add the curing agent, polyolefin resin, crosslinking agent, and modified ZnO-TiO2-Nb2O5-based ceramic powder filler obtained in Step 1 to an organic solvent, stir and mix evenly to obtain a binder; wherein, the mass ratio of solute (curing agent, polyolefin resin, crosslinking agent, and modified ZnO-TiO2-Nb2O5-based ceramic powder filler obtained in Step 1) to organic solvent is 1:(1~1.5);

[0032] Step 3: Pour the adhesive obtained in Step 2 into a rectangular mold to form a film with a thickness of 1-5 mm;

[0033] Step 4: Place the film formed in step 3 into a vacuum oven for drying and semi-curing. Set the oven temperature to 100℃~120℃ and the holding time to 4~6 hours.

[0034] Step 5: After cutting the copper foil and the film obtained in Step 4, stack them in the order of "copper foil-film-copper foil" and then put them into a vacuum hot press for hot pressing. The hot pressing temperature is 170-200℃, the holding time is 1-3h, and the hot pressing pressure is 4-6MPa. After hot pressing, the composite substrate is obtained.

[0035] The organic solvent mentioned in step 2 is one or more of toluene, xylene, cyclohexane, and N,N-dimethylformamide.

[0036] The mass fractions of ZnO-TiO2-Nb2O5-based ceramic powder filler, silane coupling agent, curing agent, polyolefin resin, and crosslinking agent are as follows:

[0037] ZnO-TiO2-Nb2O5-based ceramic powder filler: 70-85 parts;

[0038] Silane coupling agent: 0.5–2 parts;

[0039] Hardener: 2-4 parts;

[0040] Polyolefin resin: 5-20 parts;

[0041] Crosslinking agent: 3-5 parts.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1. The ZnO-TiO2-Nb2O5-based ceramic powder proposed in this invention has the characteristics of adjustable high dielectric constant, low dielectric loss, adjustable low resonant frequency temperature coefficient and low sintering temperature. The composite substrate prepared as a filler has high dielectric constant, low dielectric loss and low dielectric constant temperature coefficient.

[0044] 2. This invention simplifies the sintering process of ZnO-TiO2-Nb2O5-based ceramic powder fillers. First, the raw materials are uniformly mixed and pressed into shape, and the sintering temperature of the ceramic is reduced through internal stress. Then, the target ceramic is directly sintered in one step at a low sintering temperature of 900–1000℃, thereby generating more pores in the ceramic block and making it easier to break. Finally, a two-stage crushing method using a crusher and ball mill is used to control the particle size of the ceramic powder filler within 1–5 micrometers. This method simplifies the traditional solid-state sintering process, reduces the sintering temperature for filler preparation, and yields ceramic powder fillers for composite substrates with controllable particle size, which can be used for mass production.

[0045] 3. This invention uses one or more polyolefin resins, such as polybutadiene, polystyrene, and polystyrene-isoprene copolymers, as the organic matrix of the composite substrate. During hot pressing, a large number of double bonds on the main chain of the polyolefin resin open and crosslink, significantly improving the degree of crosslinking of the matrix resin. This results in a composite material with lower dielectric loss and higher thermal stability. Furthermore, the addition of curing agents and co-crosslinking agents allows the hot pressing of the substrate to be carried out at a low temperature of 170–200°C, thus producing a composite material that is both environmentally friendly and easy to process.

[0046] 4. The composite substrate with high dielectric constant and low temperature coefficient of dielectric constant provided by the present invention has high dielectric constant (11~18), low dielectric loss (less than 0.003), and low temperature coefficient of dielectric constant (-130~-40ppm / ℃) in the microwave frequency band (10GHz). Its dielectric constant and temperature coefficient of dielectric constant are both stable and adjustable, making it an ideal high-frequency miniaturized composite substrate material. Detailed Implementation

[0047] The present invention will be described in detail below through specific embodiments; however, the embodiments are only typical and not limiting.

[0048] Example 1

[0049] (1) Weigh 25.43g ZnO, 91.51g TiO2, 83.06g Nb2O5, 0.0001g Li2CO3, 0.0002g B2O3 and 0.0001g SiO2 to make the ingredients;

[0050] (2) The powder weighed in step (1), 400g of deionized water and 1.2kg of zirconium balls are put into a planetary ball mill jar and milled for 9 hours. The resulting slurry is dried at 100℃ and passed through a 120-mesh sieve to obtain an abrasive.

[0051] (3) An abrasive is pressed into a block using a mold at a pressure of 20 MPa for 1.5 minutes. The block is then sintered at 1000℃ in air for 8 hours to obtain a ZnO-TiO2-Nb2O5-based ceramic block.

[0052] (4) The ZnO-TiO2-Nb2O5-based ceramic block was crushed by a crusher to obtain primary crushed powder with a particle size of 0.5-5 mm;

[0053] (5) According to the mass ratio of primary crushed powder: deionized water: zirconium balls = 1:2:6, add the primary crushed powder, deionized water, and zirconium balls together into a planetary ball mill jar, and perform secondary ball milling for 60 minutes. The resulting slurry is dried at 100℃ to obtain ZnO-TiO2-Nb2O5 based ceramic powder filler.

[0054] (6) Add 100g of ZnO-TiO2-Nb2O5-based ceramic powder filler and 2g of silane coupling agent KH570 to a mixed solvent of 90g of deionized water and 10g of anhydrous ethanol, stir and mix evenly to obtain a mixed solution; then adjust the pH of the mixed solution to 3.5 with acetic acid, stir and mix at 60℃ for 90 minutes, and then dry in an oven at 100℃; finally pass through a 120-mesh sieve to obtain the modified ZnO-TiO2-Nb2O5-based ceramic powder filler;

[0055] (7) Add 83g of modified ZnO-TiO2-Nb2O5-based ceramic powder filler, 10g of polybutadiene, 7g of polystyrene-isoprene, 0.4g of triallyl isocyanurate and 0.51g of benzoic acid peroxide to 90g of toluene, and mix evenly by magnetic stirring for 12h to obtain the adhesive.

[0056] (8) Pour the adhesive into a rectangular mold to form a film with a thickness of 2mm;

[0057] (9) The formed film is placed in a vacuum oven for drying and semi-curing. The oven temperature is set to 100℃ and the heat preservation time is 5h.

[0058] (10) After cutting the copper foil and the semi-cured film, they are stacked in the order of "copper foil-film-copper foil" and then placed in a vacuum hot press for hot pressing. The hot pressing temperature is 200℃, the holding time is 2h, and the hot pressing pressure is 6MPa. After hot pressing, the composite substrate is obtained. The copper foil on the surface of the prepared composite substrate is etched off and then cut into 70mm×30mm square pieces for testing the microwave dielectric properties of the material at 10GHz.

[0059] Examples 2-5:

[0060] Compared with Example 1, Examples 2-5 differ in that the raw material ratio for preparing ZnO-TiO2-Nb2O5-based ceramic powder filler in step 1 is adjusted. The raw material content of each example is shown in Table 1.

[0061] Table 1 Raw material content of each embodiment

[0062]

[0063] Table 2. Properties of substrates prepared in each embodiment.

[0064]

[0065]

[0066] As shown in Table 2, compared with the Rogers RT / duroid 6010 high-dielectric-frequency-high-speed substrate commonly used in the market, all embodiments have higher dielectric constants and lower dielectric constant temperature coefficients. Dielectric loss and water absorption are also kept at extremely low values. The samples of the embodiments achieve adjustable dielectric constants between 11.21 and 17.40 and adjustable dielectric constant temperature coefficients between -40 and -130 ppm / ℃, which have extremely high practical value.

[0067] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A composite substrate with high dielectric constant and low temperature coefficient of dielectric constant, characterized in that, The components of the composite substrate and the weight percentage of each component in the composite substrate are as follows: ZnO-TiO2-Nb2O5-based ceramic powder filler: 70-85 parts; Silane coupling agent: 0.5–2 parts; Hardener: 2-4 parts; Polyolefin resin: 5-20 parts; Crosslinking agent: 3-5 parts; The ZnO-TiO2-Nb2O5-based ceramic powder filler comprises a main crystalline phase and a sintering aid, wherein the mass percentage of the sintering aid is less than 0.001 wt.%; the main crystalline phase is Zn. 0.15+0.35x Nb 0.3+0.7x Ti 0.55-0.05x O 2+2x The sintering aid is (0.3y+xy)Li2CO3-(0.5y+xy)B2O3-(0.2y+xy)SiO2, where x = 0 to 1 and y = 0.01 to 0.

04.

2. The composite substrate with high dielectric constant and low temperature coefficient according to claim 1, characterized in that, The ZnO-TiO2-Nb2O5-based ceramic powder filler has a particle size of 1–5 micrometers and a dielectric constant of 85–100.

3. The composite substrate with high dielectric constant and low temperature coefficient according to claim 1, characterized in that, The preparation process of the ZnO-TiO2-Nb2O5-based ceramic powder filler is as follows: Step 1: Weigh ZnO, TiO2, Nb2O5, Li2CO3, B2O3, and SiO2 as raw materials according to the stoichiometric ratio of "(0.15+0.35x)ZnO-(0.55-0.05x)TiO2-(0.15+0.35x)Nb2O5-(0.3y+xy)Li2CO3-(0.5y+xy)B2O3-(0.2y+xy)SiO2". Step 2: Grind the powder weighed in Step 1 into a ball mill for 8-10 hours. After drying and sieving, the resulting slurry is used to obtain an abrasive. Step 3: Press the abrasive obtained in Step 2 into a block shape with a molding pressure of 15-25 MPa and a molding time of 1-2 minutes; then sinter the obtained block shape at a temperature of 900-1000℃ in air atmosphere for 6-8 hours to obtain a ZnO-TiO2-Nb2O5 based ceramic block. Step 4: The ZnO-TiO2-Nb2O5-based ceramic block obtained in Step 3 is crushed using a crusher to obtain primary crushed powder with a particle size of 0.5-5 mm. Step 5: The primary crushed powder obtained in Step 4 is ball-milled for 60-80 minutes. After drying the resulting slurry, ZnO-TiO2-Nb2O5-based ceramic powder filler can be obtained.

4. The composite substrate with high dielectric constant and low temperature coefficient according to claim 1, characterized in that, The silane coupling agent is one or more of 3-methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyl-tris(2-methoxyethoxy)silane containing a double bond.

5. The composite substrate with high dielectric constant and low temperature coefficient according to claim 1, characterized in that, The curing agent is one or more of di-tert-butyl peroxide, dicumyl peroxide, and benzoic acid peroxide.

6. The composite substrate with high dielectric constant and low temperature coefficient according to claim 1, characterized in that, The polyolefin resin is one or more of polybutadiene, polystyrene, and polystyrene-isoprene.

7. The composite substrate with high dielectric constant and low temperature coefficient according to claim 1, characterized in that, The crosslinking agent is one or more of triallyl isocyanurate, triallyl cyanurate, and triallyl cyanurate.

8. A method for preparing a composite substrate with high dielectric constant and low temperature coefficient, characterized in that, Includes the following steps: Step 1: Add ZnO-TiO2-Nb2O5-based ceramic powder filler and silane coupling agent to a mixed solvent of deionized water and anhydrous ethanol, stir and mix evenly to obtain a mixed solution, wherein the mass ratio of anhydrous ethanol to deionized water is 1:(8-9); then adjust the pH value of the mixed solution to 3-5 with acetic acid, stir and mix at 60-80℃ for 90-120 minutes, and then dry in an oven at 100-120℃; finally, pass through a 100-120 mesh sieve to obtain modified ZnO-TiO2-Nb2O5-based ceramic powder filler; Step 2: Add the curing agent, polyolefin resin, crosslinking agent and modified ZnO-TiO2-Nb2O5-based ceramic powder filler obtained in Step 1 to an organic solvent, stir and mix evenly to obtain a binder; wherein, the mass ratio of solute to organic solvent is 1:(1~1.5); Step 3: Pour the adhesive obtained in Step 2 into a rectangular mold to form a film with a thickness of 1-5 mm; Step 4: Place the film formed in step 3 into a vacuum oven for drying and semi-curing. Set the oven temperature to 100℃~120℃ and the holding time to 4~6 hours. Step 5: After cutting the copper foil and the film obtained in Step 4, stack them in the order of "copper foil-film-copper foil" and then put them into a vacuum hot press for hot pressing. The hot pressing temperature is 170-200℃, the holding time is 1-3h, and the hot pressing pressure is 4-6MPa. After hot pressing, the composite substrate is obtained.

9. The method for preparing a composite substrate with high dielectric constant and low temperature coefficient according to claim 8, characterized in that, The organic solvent mentioned in step 2 is one or more of toluene, xylene, cyclohexane, and N,N-dimethylformamide.

Images