A magnetic dielectric metal-clad foil, a preparation method and application thereof

Abstract

This invention provides a magnetically dielectric metal-coated foil, its preparation method, and its application. The preparation method includes: laminating a metal foil onto one or both sides of a magnetically dielectric substrate to obtain a composite material; hot-pressing the composite material to obtain the magnetically dielectric metal-coated foil; applying a magnetic field during the hot-pressing process, wherein the magnetic field generating device includes n groups of magnets with coincident center points, where n is an integer ≥2; each magnet group independently consists of a first magnet and a second magnet, with the N pole of the first magnet and the S pole of the second magnet in each magnet group positioned opposite each other, forming a magnetic field between the N and S poles; the included angle between any two adjacent magnet groups is equal. This invention, by employing a specific device to apply a magnetic field during the hot-pressing process, results in a magnetically dielectric metal-coated foil with higher permeability and dielectric constant, lower magnetic loss and dielectric loss, and excellent magnetic-dielectric performance and reliability, thereby improving the miniaturization factor and meeting the performance requirements of miniaturized antennas.

Description

Technical Field

[0001] This invention belongs to the field of circuit board technology, specifically relating to a magnetic dielectric metal foil board, its preparation method, and its application. Background Technology

[0002] With the continuous development of radio communication technology, especially the advent of 5G technology in recent years, electronic products require high integration and miniaturization. Since antennas are one of the key components in radio communication systems, higher performance requirements are placed on them, demanding characteristics such as small size, light weight, simple structure, and ease of integration with active devices. Antenna size accounts for a significant proportion of wireless communication equipment; reducing antenna size without sacrificing performance is the current development direction. The substrate is the basic electronic component for antenna fabrication, and the performance of the substrate material directly determines the antenna performance. Therefore, developing substrates suitable for radio communication is a focus of attention within the industry.

[0003] Since the resonant frequency of an antenna is inversely proportional to the square root of the product of the equivalent dielectric constant and the permeability of the medium, using a medium with a high dielectric constant as the substrate can reduce the size of the antenna. Magnetoperelectric materials can realize the function of microstrip antennas through the principle of radiation. Based on the input impedance, bandwidth, and matching degree, the high-frequency signal carrying information in the antenna can be effectively radiated, achieving transmission and reception. As the substrate material, the magnetic dielectric material influences the antenna size through its electromagnetic parameters, primarily based on its high refractive index. Miniaturization is achieved by using materials with high dielectric constants (εr) as the antenna substrate. Higher dielectric constants (εr) and permeability (μr) result in a higher miniaturization factor, which is more conducive to miniaturization. However, using high dielectric constant materials for antenna design also presents several drawbacks. Since antennas, especially microstrip antennas, inherently have narrow bandwidths, using high dielectric constant materials for miniaturization will further restrict electromagnetic waves within the dielectric region, leading to a further narrowing of the antenna's operating bandwidth, lower gain, design difficulties, significantly reduced antenna performance, and worsened impedance matching.

[0004] According to the aforementioned theory, when the dielectric constant cannot be changed, increasing the permeability can effectively reduce the antenna size while maintaining the antenna gain and bandwidth. Therefore, the industry is attempting to diversify the permeability and dielectric constant through substrate design to meet the performance requirements of dielectric constant and permeability of dielectric materials in miniaturized antenna applications. For example, CN104910823A discloses an adhesive film that can form an insulating layer, including a support and a resin composition layer disposed on the support. The resin composition layer contains thermosetting resin, magnetic filler, and inorganic filler material, wherein the content of magnetic filler is ≥10% by volume, and the ratio of magnetic filler to inorganic filler material is 0.3-3.0, which increases the permeability of the insulating layer and reduces magnetic loss. CN106797699A discloses a magnetic dielectric substrate, circuit material, and component. The magnetic dielectric substrate includes a first dielectric layer and a second dielectric layer, and at least one magnetic reinforcement layer disposed between and in close contact with the two dielectric layers. The magnetic reinforcement layer contains ferrite material, thereby giving the magnetic dielectric substrate good mechanical and magnetoelectronic properties. CN109553955A discloses a magnetic dielectric resin composition and a prepreg, laminate, and copper-clad laminate containing the same. The magnetic dielectric resin composition comprises 30-100 parts by weight of resin and 50-500 parts by weight of magnetic filler. The resistivity of the magnetic filler is 100 Ω·M-1000 Ω·M and the permeability is 5-1000, which gives the copper-clad laminate containing the composition good magnetic properties and insulation.

[0005] With the miniaturization of antennas, existing magnetic dielectric materials still have significant shortcomings in terms of properties such as dielectric constant and permeability. Improving dielectric constant and permeability is difficult, impedance matching is poor, and miniaturization factors are insufficient. Furthermore, improving dielectric constant and permeability is accompanied by increased magnetic loss, increased dielectric loss, and decreased reliability, greatly limiting the application of magnetic dielectric materials in antennas, communication equipment, and electronic products. Therefore, developing a magnetic dielectric material with high permeability and dielectric constant, and low magnetic and dielectric losses is a key research focus in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a magnetic dielectric metal-coated foil, its preparation method, and its application. By applying a magnetic field using a specific device during the hot pressing process, the resulting magnetic dielectric metal-coated foil exhibits higher permeability and dielectric constant, lower magnetic loss and dielectric loss, and excellent magnetic dielectric performance and reliability, thereby improving the miniaturization factor and meeting the performance requirements of miniaturized antennas.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a magnetically dielectric metal-coated foil, the method comprising the following steps:

[0009] A composite material is obtained by laminating a metal foil onto one or both sides of a magnetic dielectric sheet; the composite material is then hot-pressed to obtain the magnetic dielectric metal foil sheet; a magnetic field is applied during the hot-pressing process, and the magnetic field generating device includes n groups of magnets with coincident center points, where n is an integer ≥2; each group of magnets is independently composed of a first magnet and a second magnet, and the N pole of the first magnet and the S pole of the second magnet in each group of magnets are arranged opposite each other, forming a magnetic field between the N pole and the S pole; the included angle between any two adjacent groups of magnets is equal; the magnetic dielectric sheet includes at least one magnetic dielectric prepreg, which includes a reinforcing material and a magnetic dielectric resin composition attached to the reinforcing material; the magnetic dielectric resin composition includes a combination of resin and anisotropic magnetic filler.

[0010] To obtain a magnetic dielectric clad metal foil with high permeability, high dielectric constant, and low loss, this invention provides a method for preparing a magnetic dielectric clad metal foil by applying a magnetic field. This method uses anisotropic magnetic fillers and applies a magnetic field during hot pressing, causing the anisotropic magnetic fillers (orientable magnetic fillers) to align under the influence of the magnetic field. Under the combined effects of temperature, pressure, and magnetic field during hot pressing, the anisotropic magnetic fillers in the magnetic dielectric sheet form a specific "leaf-like" structure, resulting in a more orderly and higher-oriented arrangement of the anisotropic magnetic filler grains. This significantly improves the permeability and dielectric constant of the magnetic dielectric clad metal foil, while also exhibiting low magnetic loss, low dielectric loss, and excellent heat resistance and reliability. This invention solves the problems of low permeability, poor impedance matching, insufficient miniaturization factor, narrow antenna bandwidth, low gain, and design difficulties of existing magnetic dielectric materials by using the coupling effect of magnetic field, temperature, and thermal pressure. It obtains a magnetic dielectric metal foil with high permeability, high dielectric constant, low magnetic loss, low dielectric loss, and high reliability, which fully meets the performance requirements of the substrate in miniaturized antennas.

[0011] The magnetic field generating device provided in this invention includes n (n≥2) magnet groups with coincident center points. Each magnet group consists of a first magnet and a second magnet, with the N pole of the first magnet and the S pole of the second magnet facing each other, thereby forming a magnetic field between the N pole and the S pole. Since a magnetic field (denoted as a "sub-magnetic field") is formed between the N pole of the first magnet and the S pole of the second magnet in each magnet group, the center points of the n sub-magnetic fields also coincide. The n sub-magnetic fields are coupled to each other and form a magnetic field with dynamic rotational characteristics according to the characteristics of the magnetic field lines. In the generating device, the positions of each magnet group are fixed / static, and the sub-magnetic fields generated by each magnet group work together to form a rotating magnetic field. The hot-pressed composite is located in this magnetic field, so that the anisotropic magnetic filler in the composite is oriented under the coupled synergistic effect of the magnetic field, the temperature and pressure of hot pressing, forming a specific high orientation structure, thereby giving the magnetic dielectric clad metal foil high permeability, high dielectric constant, low magnetic loss and low dielectric loss.

[0012] Optionally, the composite to be hot-pressed is placed in a hot-pressing device and located in the magnetic field generated by the generating device. The hot-pressing device is a non-magnetic product, meaning that the materials of each component in the hot-pressing device are non-magnetic materials. Only the anisotropic magnetic filler in the magnetic dielectric sheet is responsive to the magnetic field, thus avoiding interference between the hot-pressing device and the interaction between the magnetic field and the anisotropic magnetic filler, which would affect the improvement effect on the permeability and dielectric constant of the magnetic dielectric clad metal foil.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0014] Preferably, the number n of magnet groups in the magnetic field generating device can be 2, 3, 4, 5, 6, 7 or 8, more preferably 2-4, and even more preferably 2 or 3.

[0015] The distance between the first magnet and the second magnet in each magnet group is adjustable. Preferably, the distance between the N pole of the first magnet and the S pole of the second magnet in each magnet group is ≥1cm, for example, it can be 2cm, 5cm, 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, 40cm, 45cm, 50cm, 55cm, 60cm, 65cm, 70cm, 80cm, 90cm or 100cm, as well as specific point values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range, and 2-60cm is further preferred.

[0016] Preferably, the surface field strength of the first magnet and the second magnet are each independently 0.1mT-1T, for example, 0.2mT, 0.5mT, 0.8mT, 1mT, 5mT, 8mT, 10mT, 30mT, 50mT, 80mT, 100mT, 200mT, 300mT, 400mT, 500mT, 600mT, 700mT, 800mT, or 900mT, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0017] Preferably, the field strength of the magnetic field is 0.1-50 mT, for example, it can be 0.5 mT, 1 mT, 3 mT, 5 mT, 8 mT, 10 mT, 12 mT, 15 mT, 18 mT, 20 mT, 22 mT, 25 mT, 28 mT, 30 mT, 32 mT, 35 mT, 38 mT, 40 mT, 42 mT, 45 mT or 48 mT, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range, but 5-30 mT is further preferred.

[0018] In this invention, the field strength of the magnetic field refers to the field strength of the magnetic field acting on / applied to the hot-pressed composite. The sub-magnetic fields generated by the n magnet groups work together to form a rotating magnetic field with a specific field strength, which couples with the temperature and pressure of the hot pressing. This causes the anisotropic magnetic fillers in the magnetic dielectric sheet to be oriented, forming a neat and orderly specific leaf-like structure in the magnetic dielectric metal-coated foil. With a high degree of orientation, and given a fixed amount of anisotropic magnetic fillers, the magnetic dielectric metal-coated foil is endowed with higher permeability and dielectric constant, while exhibiting low magnetic loss and dielectric loss, resulting in excellent overall performance. If the field strength is too low, the force exerted on the anisotropic magnetic fillers is insufficient, leading to the magnetic fillers not forming a suitable orientation structure in the magnetic dielectric metal-coated foil, thus failing to improve the permeability and dielectric constant. If the field strength is too high, it is difficult to form a magnetic field with rotational characteristics, thereby weakening the force exerted by the magnetic field on the anisotropic magnetic fillers, and the magnetic dielectric properties of the magnetic dielectric metal-coated foil are not significantly improved.

[0019] In this invention, the first magnet and the second magnet in the n magnet groups can be the same or different magnets, and are more preferably the same magnets. The positional relationship between the N pole and the S pole of the magnets can satisfy the requirements of this invention for forming a specific magnetic field.

[0020] Preferably, the application time of the magnetic field is less than the hot-pressing time, and the starting time of applying the magnetic field is the same as the starting time of the hot-pressing.

[0021] As a preferred embodiment of the present invention, the starting time of applying the magnetic field is the same as the starting time of the hot pressing, that is, the magnetic field is applied at the beginning of the hot pressing process, so that the anisotropic magnetic filler in the magnetic dielectric sheet is oriented and aligned under the coupling effect of temperature, pressure and magnetic field, forming a neat and orderly specific high-orientation structure in the magnetic dielectric metal-coated foil. As the hot pressing continues, the resin in the magnetic dielectric sheet solidifies, so that the anisotropic magnetic filler no longer moves. Therefore, it is not necessary to apply the magnetic field in the later stage of the hot pressing process, and the application time of the magnetic field is less than the hot pressing time.

[0022] Preferably, the application time of the magnetic field is 5-30 min, for example, it can be 6 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min or 28 min, as well as specific point values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0023] Preferably, the hot pressing time is 30-300 min, for example, it can be 60 min, 80 min, 100 min, 120 min, 150 min, 180 min, 200 min, 220 min, 240 min, 260 min or 280 min, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 30-180 min is further preferred.

[0024] Preferably, the hot pressing temperature is 150-360℃, for example, it can be 160℃, 180℃, 200℃, 220℃, 250℃, 280℃, 300℃, 350℃, 340℃ or 350℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, and 150-240℃ is further preferred.

[0025] Preferably, the pressure of the hot pressing is 1-10 MPa, for example, it can be 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa or 9 MPa, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0026] Preferably, the anisotropic magnetic filler includes any one or a combination of at least two of planar hexagonal ferrite, magnetoplumbago ferrite, and other soft magnetic ferrites.

[0027] Preferably, the planar hexagonal ferrite includes any one or a combination of at least two of the following: Y-type planar hexagonal ferrite, Co2Z-type planar hexagonal ferrite, and Co2W-type planar hexagonal ferrite.

[0028] Preferably, the median particle size of the anisotropic magnetic filler is 0.1-30 μm, for example, it can be 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm or 28 μm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, and 1-15 μm is further preferred.

[0029] For example, the particle size of the anisotropic magnetic filler was obtained by testing with an MS3000 Malvern laser particle size analyzer.

[0030] Preferably, the mass percentage of anisotropic magnetic filler in the magnetic dielectric resin composition is 10-80%, for example, it can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0031] Preferably, the resin comprises any one or a combination of at least two of epoxy resin, phenolic resin, cyanate ester resin, polyphenylene ether resin, polyolefin resin, styrene-butadiene resin, benzoxazine resin, maleimide compound, phenolic resin, fluorinated resin, and benzoxazine resin.

[0032] Preferably, the epoxy resin comprises any one or a combination of at least two of the following: bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, dicyclopentadiene (DCPD) type epoxy resin, phenolic epoxy resin, biphenyl type epoxy resin, phenolic epoxy resin, bisphenol A phenolic epoxy resin, organosilicon modified epoxy resin, phosphorus-containing epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, and o-cresol epoxy resin.

[0033] Preferably, the magnetic dielectric resin composition further includes any one or a combination of at least two of the following: curing agent, accelerator, crosslinking agent, initiator, flame retardant, coupling agent, and non-magnetic filler.

[0034] Preferably, the resin includes epoxy resin, and the curing agent includes any one or a combination of at least two of phenolic resin, amine curing agent, cyanate ester curing agent, reactive ester curing agent, carboxylic acid curing agent, and acid anhydride curing agent.

[0035] Preferably, the accelerator comprises any one or a combination of at least two of imidazole compounds, organometallic complexes, tertiary amines, tertiary phosphine, quaternary ammonium salts, and peroxides.

[0036] Preferably, the imidazole compound includes any one or a combination of at least two of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecylimidazole, 2-isopropylimidazole, 2-phenyl-4-methylimidazole, 2-dodecylimidazole, and 1-cyanoethyl-2-methylimidazole.

[0037] In a preferred embodiment, the magnetic dielectric resin composition comprises the following components in parts by weight:

[0038]

[0039] Specifically, the epoxy resin is 30-95 parts, for example, it can be 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts or 90 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0040] The curing agent is 5-70 parts, for example, it can be 10 parts, 20 parts, 30 parts, 40 parts, 50 parts or 60 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0041] The anisotropic magnetic filler is 10-400 parts, for example, it can be 20 parts, 50 parts, 80 parts, 100 parts, 120 parts, 150 parts, 180 parts, 200 parts, 220 parts, 250 parts, 280 parts, 300 parts, 320 parts, 350 parts, 380 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0042] The accelerator is 0.01-2 parts, for example, it can be 0.01 parts, 0.03 parts, 0.05 parts, 0.07 parts, 0.09 parts, 0.1 parts, 0.3 parts, 0.5 parts, 0.7 parts, 0.9 parts, 1 part, 1.2 parts, 1.5 parts or 1.8 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0043] Preferably, there is no particular limitation on the type of flame retardant. Flame retardants with flame retardant effect can be used in the magnetic dielectric resin composition, including but not limited to: any one or a combination of at least two of the following: inorganic flame retardants, phosphorus-based organic flame retardants, nitrogen-based organic flame retardants, silicon-containing organic flame retardants, and halogen-containing flame retardants (e.g., chlorine-containing flame retardants and / or bromine-containing flame retardants).

[0044] Preferably, the coupling agent includes any one or a combination of at least two of silane coupling agents, titanate coupling agents, and organosilicon oligomers; the coupling agent helps to improve the compatibility between the anisotropic magnetic filler and the resin.

[0045] Solvents may also be added to the magnetic dielectric resin composition. The amount of solvent added is selected by those skilled in the art based on experience and process requirements, so that the magnetic dielectric resin composition reaches a suitable viscosity for use, facilitating impregnation, coating, and other processes. Subsequently, during drying, semi-curing, or complete curing stages, the solvent in the magnetic dielectric resin composition will partially or completely evaporate.

[0046] The type of solvent is not particularly limited, but can generally be ketones such as acetone, butanone, and cyclohexanone; aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; alcohols such as methanol, ethanol, or butanol; alcohols such as ethyl cellosolve, butyl cellosolve, ethylene glycol monomethyl ether, carbitol, or butyl carbitol; and nitrogen-containing solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, or N-methyl-2-pyrrolidone. The solvent can be used alone or in mixtures of two or more. Ketones such as butanone, acetone, and cyclohexanone, and aromatic hydrocarbons such as toluene and xylene are preferred.

[0047] Preferably, the reinforcing material includes any one of glass fiber cloth, non-woven fabric, quartz cloth, quartz glass fiber blended fabric, fiber paper, or wood pulp paper.

[0048] Preferably, in the magnetic dielectric prepreg, the magnetic dielectric resin composition is attached to the reinforcing material after impregnation and drying.

[0049] Preferably, the method for preparing the magnetic dielectric prepreg includes: impregnating a reinforcing material with a liquid of the magnetic dielectric resin composition, and then drying it to obtain the magnetic dielectric prepreg.

[0050] Preferably, the drying temperature is 80-180℃, for example 90℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃ or 175℃, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0051] Preferably, the drying time is 1-30 min, for example, it can be 2 min, 5 min, 8 min, 10 min, 15 min, 20 min or 25 min, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0052] Preferably, the number of sheets of magnetic dielectric prepreg in the magnetic dielectric sheet is 1-20, for example, 2, 3, 5, 7, 9, 10, 11, 13, 15, 17 or 19, and the specific point values ​​between the above point values ​​are not exhaustively listed in this invention due to space limitations and for the sake of brevity.

[0053] Preferably, the metal foil includes any one or a combination of at least two of copper foil, aluminum foil, nickel foil, and alloy foil.

[0054] Preferably, the metal foil is copper foil, and the magnetic dielectric clad metal foil is a magnetic dielectric copper clad plate.

[0055] Preferably, the preparation method specifically includes the following steps:

[0056] (1) A composite material is obtained by laminating a metal foil on one or both sides of a magnetic dielectric sheet; the magnetic dielectric sheet includes at least one magnetic dielectric prepreg, the magnetic dielectric prepreg includes a reinforcing material and a magnetic dielectric resin composition attached to the reinforcing material; the magnetic dielectric resin composition includes a combination of resin and anisotropic magnetic filler; the mass percentage of the anisotropic magnetic filler in the magnetic dielectric resin composition is 10-80%;

[0057] (2) The composite is hot-pressed to obtain the magnetic dielectric metal-coated foil;

[0058] A magnetic field is applied during the hot pressing process. The dynamic magnetic field generating device includes n groups of magnets with coincident center points, where n is an integer from 2 to 4. Each group of magnets is independently composed of a first magnet and a second magnet. The N pole of the first magnet and the S pole of the second magnet in each group are arranged opposite each other, and a magnetic field is formed between the N pole and the S pole. The hot-pressed composite material is located in the magnetic field. The included angle between any two adjacent groups of magnets is equal.

[0059] The distance between the N pole of the first magnet and the S pole of the second magnet in each magnet group is 2-60cm, and the surface field strength of the first magnet and the second magnet is 0.1mT-1T respectively.

[0060] The starting time of applying the magnetic field is the same as the starting time of the hot pressing, the field strength of the magnetic field is 0.1-50 mT, and the application time is 5-30 min;

[0061] The hot pressing temperature is 150-360℃, the pressure is 1-10MPa, and the time is 30-300min.

[0062] On the other hand, the present invention provides a method for improving the magnetic dielectric properties of a magnetically dielectric metal-coated foil, wherein the method is the preparation method described in the first aspect. Through the coupling effect of hot pressing and a specific magnetic field, the anisotropic magnetic filler grains in the magnetically dielectric metal-coated foil form a specific high-orientation structure. Compared with conventional hot pressing processes, the magnetic permeability and dielectric constant of the magnetically dielectric metal-coated foil are significantly improved, and the magnetic loss and dielectric loss are low, resulting in superior overall magnetic dielectric performance.

[0063] In a second aspect, the present invention provides a magnetically dielectric metal-coated foil, which is prepared by the preparation method described in the first aspect.

[0064] Thirdly, the present invention provides a circuit board comprising a magnetic dielectric clad metal foil as described in the second aspect.

[0065] Preferably, the circuit board is a circuit board used in an antenna.

[0066] Fourthly, the present invention provides the application of a magnetically dielectric coated metal foil as described in the second aspect or a circuit board as described in the third aspect in an antenna.

[0067] Preferably, the antenna comprises a microstrip antenna.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] (1) In the preparation method provided by the present invention, a specific magnetic field is applied during the hot pressing process. Under the multiple coupling effects of temperature, pressure and magnetic field during hot pressing, the anisotropic magnetic filler is oriented and arranged, forming a neat and orderly high-orientation structure in the magnetic dielectric metal-coated foil. This significantly improves the permeability and dielectric constant of the magnetic dielectric metal-coated foil, while also resulting in low magnetic loss and dielectric loss, good heat resistance and reliability. The preparation method of the present invention solves the problems of low permeability, poor impedance matching, insufficient miniaturization factor, narrow antenna bandwidth, low gain and design difficulties in the prior art, and obtains a magnetic dielectric metal-coated foil with high permeability, high dielectric constant, low magnetic loss, low dielectric loss and high reliability, which fully meets the performance requirements of the substrate in miniaturized antennas.

[0070] (2) Through the design and process optimization of hot pressing and magnetic field, the present invention achieves a magnetic permeability of 2.70-2.84 and a dielectric constant of 6.45-7.0 at 300MHz. Compared with the conventional hot pressing process without applying a magnetic field, the magnetic permeability is increased by 7.3-23% and the dielectric constant is increased by 3.1-8.4%. Moreover, the magnetic loss is ≤0.046 and the dielectric loss is ≤0.067. With the significant improvement in both dielectric constant and magnetic permeability, it has low magnetic loss and low dielectric loss, and has excellent heat resistance and reliability. Attached Figure Description

[0071] Figure 1 This is a schematic diagram of the magnetic field generating device in a specific embodiment of the present invention;

[0072] Figure 2 This is a schematic diagram of the magnetic field generating device in another specific embodiment of the present invention;

[0073] Figure 3 This is a schematic diagram of the magnetic field generating device in Comparative Example 1;

[0074] Figure 4 This is a schematic diagram of the magnetic field generating device in Comparative Example 2;

[0075] Figure 5 This is a schematic diagram of the magnetic field generating device in Comparative Example 3;

[0076] Figure 6 This is a schematic diagram of the magnetic field generating device in Comparative Example 4;

[0077] Figure 7 This is a schematic diagram of the magnetic field generating device in Comparative Example 5;

[0078] Among them, 10 - first magnet group, 11 - first magnet of first magnet group, 12 - second magnet of first magnet group, 20 - second magnet group, 21 - first magnet of second magnet group, 22 - second magnet of second magnet group, 30 - third magnet group, 31 - first magnet of third magnet group, 32 - second magnet of third magnet group, and A - placement position of complex. Detailed Implementation

[0079] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0080] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not limited to those elements and may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0081] In this invention, features specified as "first" and "second" may explicitly or implicitly include one or more of these features, used to distinguish and describe features, without any order or emphasis. In the description of this invention, unless otherwise stated, "multiple" means two or more.

[0082] In one specific embodiment, a schematic diagram of the magnetic field generating device of the present invention is shown below. Figure 1 As shown, the system includes two magnet groups with coincident center points: a first magnet group 10 and a second magnet group 20, with an included angle of 90°. The first magnet group 10 consists of a first magnet 11 and a second magnet 12, with the N pole of the first magnet 11 and the S pole of the second magnet 12 facing each other to form a first sub-magnetic field. The second magnet group 20 consists of a first magnet 21 and a second magnet 22, with the N pole of the first magnet 21 and the S pole of the second magnet 22 facing each other to form a second sub-magnetic field. The center points of the first and second sub-magnetic fields also coincide, and the first and second sub-magnetic fields work together to form a rotating magnetic field. Point A is the location where the composite to be hot-pressed is placed.

[0083] In another specific embodiment, a schematic diagram of the magnetic field generating device of the present invention is shown below. Figure 2 As shown, there are three groups of magnets with their centers coinciding: a first magnet group 10, a second magnet group 20, and a third magnet group 30. The angle between any two adjacent magnet groups is 60°. The first magnet group 10 consists of a first magnet 11 and a second magnet 12, with the N pole of the first magnet 11 and the S pole of the second magnet 12 facing each other to form a first sub-magnetic field. The second magnet group 20 consists of a first magnet 21 and a second magnet 22, with the N pole of the first magnet 21 and the S pole of the second magnet 22 facing each other to form a second sub-magnetic field. The third magnet group 30 consists of a first magnet 31 and a second magnet 32, with the N pole of the first magnet 31 and the S pole of the second magnet 32 ​​facing each other to form a third sub-magnetic field. The centers of the first, second, and third sub-magnetic fields also coincide, and they work together to form a rotating magnetic field. Point A is the location where the composite to be hot-pressed is placed.

[0084] The specific information of the materials used in the following specific embodiments of the present invention is as follows:

[0085] (1) Epoxy resin

[0086] Epoxy resin, SQCN703, purchased from Shandong Shengquan New Material Co., Ltd.

[0087] Epoxy resin, SQ803EK75, purchased from Shandong Shengquan New Material Co., Ltd.

[0088] (2) Curing agent

[0089] Bisphenol A type phenolic resin, SH-2107, was purchased from Shandong Shengquan New Material Co., Ltd.

[0090] (3) Accelerator

[0091] 2-Methylimidazole, 2-MI, purchased from Shikoku Kasei.

[0092] (4) Anisotropic magnetic filler

[0093] Planar hexagonal ferrite Co2Z type, median particle size D 50 The size is 3-5μm, purchased from Shaanxi Yinghe.

[0094] (5) Isotropic magnetic filler

[0095] Spinel ferrite, median grain size D 50 The size is 3-5μm, purchased from Shaanxi Yinghe.

[0096] (6) Reinforcing materials

[0097] Non-woven fabric, 75g / m 2 Purchased from Shaanxi Huate.

[0098] (7) Copper foil

[0099] HVLP Luxembourg BF-TZA copper foil.

[0100] (8) Magnet

[0101] Magnet A1 has a surface electric field strength of 0.5T;

[0102] Magnet A2 has a surface electric field strength of 0.3T;

[0103] Magnet A3 has a surface electric field strength of 0.2T.

[0104] In this invention, the surface field strength of the magnet and the field strength generated by the magnetic field generating device are measured using a magnetic field strength tester (DW-733, digital display millitalas meter).

[0105] Example 1

[0106] A magnetic dielectric clad metal foil (magnetically dielectric copper clad laminate) and its preparation method are disclosed, wherein the preparation method comprises the following steps:

[0107] (1) Preparation of magnetic dielectric prepreg:

[0108] The magnetic dielectric prepreg comprises a reinforcing material and a magnetic dielectric resin composition attached thereto, the magnetic dielectric resin composition comprising, by weight: 70 parts epoxy resin, 30 parts bisphenol A phenolic resin, 0.2 parts accelerator 2-MI, and 60 parts planar hexagonal ferrite.

[0109] The magnetic dielectric resin composition was mixed with methyl ethyl ketone according to the aforementioned formula and mixed evenly at room temperature to prepare a resin solution with a solid content of 65%. The resin solution was impregnated with a reinforcing material and then dried in an oven at 150°C for 5 minutes to obtain a magnetic dielectric prepreg.

[0110] (2) Preparation of copper clad laminate:

[0111] Three sheets of magnetic dielectric prepreg are stacked together, and copper foil is covered on the top and bottom sides to obtain a composite. The composite is placed in a vacuum press for hot pressing, and a magnetic field is applied. The hot pressing temperature is 200°C, the pressure is 5MPa, and the time is 120min to obtain a magnetic dielectric copper-clad laminate.

[0112] A magnetic field is applied during the hot pressing process. A schematic diagram of the magnetic field generating device is shown below. Figure 1 As shown, the system includes a first magnet group 10 and a second magnet group 20 with two coincident center points, and the included angle between the two magnet groups is 90°. The first magnet group 10 consists of a first magnet 11 and a second magnet 12, with the N pole of the first magnet 11 and the S pole of the second magnet 12 facing each other to form a first sub-magnetic field. The second magnet group 20 consists of a first magnet 21 and a second magnet 22, with the N pole of the first magnet 21 and the S pole of the second magnet 22 facing each other to form a second sub-magnetic field. The center points of the first and second sub-magnetic fields coincide, and the first and second sub-magnetic fields work together to form a rotating magnetic field. Point A is the position where the composite to be hot-pressed is placed. The four magnets in the aforementioned two magnet groups are the same magnets, all of which are magnet A1. The distance between the N pole of the first magnet 11 and the S pole of the second magnet 12 is 5 cm, and the distance between the N pole of the first magnet 21 and the S pole of the second magnet 22 is 5 cm. The magnetic field strength generated by the generating device (i.e., the magnetic field strength applied to the composite) is 20 mT, and the application time is 15 min. The starting time of applying the dynamic magnetic field is the same as the starting time of hot pressing, that is, the dynamic magnetic field of 200℃, 5MPa and 20mT is applied to the composite in the vacuum press simultaneously. After 15 min, the motor is turned off and the dynamic magnetic field is removed. Hot pressing at 200℃ and 5MPa continues for 105 min to obtain a magnetic dielectric copper-clad laminate (denoted as "copper-clad laminate A").

[0113] In comparison, the same composite material and copper foil as in Example 1 were used to prepare the same composite material. The composite material was hot-pressed at 200°C and 5MPa for 120 min without the application of a dynamic magnetic field to obtain a magnetic dielectric copper-clad laminate (referred to as "copper-clad laminate B") obtained by conventional hot pressing process.

[0114] The following performance tests were performed on copper-clad laminate A provided in Example 1 and copper-clad laminate B as a comparison:

[0115] (1) Permeability and magnetic loss tangent: The test was conducted using an impedance analyzer. The test instrument was a Keysight E4991B impedance analyzer with a 16454A test fixture. The test frequency was 300MHz and the test temperature was 25℃.

[0116] (2) Dielectric constant Dk and dielectric loss factor Df: The dielectric constant Dk and dielectric loss factor Df of the copper-clad laminate were tested using a Keysight impedance analyzer E4991B+16453A test fixture at a frequency of 300MHz.

[0117] The test results are shown in Table 1.

[0118] Examples 2-6, Comparative Examples 1-6

[0119] A magnetic dielectric copper-clad laminate and its preparation method differ from Example 1 in that the formulation of the magnetic dielectric resin composition and / or the preparation process parameters are different, as shown in Tables 1 and 2. The unit for the amount of the magnetic dielectric resin composition is "parts," and "--" indicates that the component was not added or the condition was not applied. In "Magnet Position," the relative arrangement of the N pole of the first magnet and the S pole of the second magnet in each magnet group is denoted as "N / S×2," and all embodiments of this invention use the "N / S×2" arrangement (e.g., ...). Figure 1 (as shown); "Distance" represents the distance between the N pole of the first magnet and the S pole of the second magnet in each magnet group.

[0120] The schematic diagram of the magnetic field generating device in Comparative Example 1 is shown below. Figure 3 As shown, in each magnet group, the N poles of the first magnet and the second magnet are arranged opposite each other, denoted as "N / N×2". A schematic diagram of the magnetic field generating device in Comparative Example 2 is shown below. Figure 4 As shown, the S poles of the first magnet and the second magnet in each magnet group are arranged opposite each other, denoted as "S / S×2". A schematic diagram of the magnetic field generating device in Comparative Example 3 is shown below. Figure 5 As shown, in the first magnet group, the S poles of the first magnet and the second magnet are arranged opposite each other, and in the second magnet group, the N poles of the first magnet and the second magnet are arranged opposite each other, denoted as "S / S+N / N". A schematic diagram of the magnetic field generating device in Comparative Example 4 is shown below. Figure 6As shown, in the first magnet group, the N pole of the first magnet and the S pole of the second magnet are arranged opposite each other, and in the second magnet group, the N pole of the first magnet and the N pole of the second magnet are arranged opposite each other, denoted as "N / S+N / N". A schematic diagram of the magnetic field generating device in Comparative Example 5 is shown below. Figure 7 As shown, it has only one magnet group, in which the N pole of the first magnet 11 and the S pole of the second magnet 12 are arranged opposite each other, denoted as "N / S".

[0121] The parameters not shown in Tables 1 and 2 are the same as those in Example 1, and the performance testing methods for copper-clad laminates are the same as those in Example 1.

[0122] In Tables 1 and 2, the test data marked "A" are the test data of the magnetic dielectric copper-clad laminate provided in this embodiment, and the test data marked "B" are the test data of the magnetic dielectric copper-clad laminate prepared under the condition of no dynamic magnetic field applied; the improvement rate = 100% × (test value A - test value B) / test value B.

[0123] Table 1

[0124]

[0125]

[0126] Table 2

[0127]

[0128]

[0129]

[0130] The preparation method of Comparative Example 7 in Table 2 is as follows: the composite is first treated in a magnetic field for 15 minutes without hot pressing, i.e., the temperature is room temperature and there is no pressure; after the composite is treated in a magnetic field for 15 minutes, it is transferred to a vacuum press (without a magnetic field during hot pressing), and hot pressed at 200℃ and 5MPa for 120 minutes to obtain a copper-clad laminate. Comparative Example 8 is prepared without applying a magnetic field and using a conventional hot pressing process.

[0131] According to the performance test data in Tables 1 and 2, the present invention, by applying a specific magnetic field during the hot pressing process, causes anisotropic magnetic fillers to align under the multiple coupling effects of temperature, pressure, and magnetic field during hot pressing, forming a neat and orderly high-orientation structure in the magnetic dielectric copper-clad laminate. This results in a copper-clad laminate with a permeability of 2.70-2.84 and a dielectric constant of 6.45-7.0. Compared with the conventional hot pressing process without applying a dynamic magnetic field (using the same raw materials), the permeability is increased by 7.3-23%, the dielectric constant by 3.1-8.4%, the magnetic loss is 0.042-0.046, and the dielectric loss is 0.062-0.067, exhibiting good heat resistance and reliability. Based on the preparation process and test results of Examples 1-6, it is evident that the improvement effect of the magnetic dielectric properties of the copper-clad laminate can be adjusted by setting and adjusting parameters such as the magnetic field strength.

[0132] In the preparation method provided by this invention, hot pressing and a specific rotating magnetic field are coupled, causing the anisotropic magnetic filler to align in an orientation under the combined effects of temperature, pressure, and magnetic field, forming a neat and orderly structure in the copper-clad laminate, thus giving the copper-clad laminate higher magnetic permeability and dielectric constant. In Comparative Example 1, the N poles of the first magnet and the second magnet in each magnet group are arranged opposite each other; in Comparative Example 2, the S poles of the first magnet and the second magnet in each magnet group are arranged opposite each other; in Comparative Example 3, the S poles of the first magnet and the second magnet in the first magnet group are arranged opposite each other, and the N poles of the first magnet and the second magnet in the second magnet group are arranged opposite each other; in Comparative Example 4, the N poles of the first magnet and the second magnet in the first magnet group are arranged opposite each other, and the N poles of the first magnet and the second magnet in the second magnet group are arranged opposite each other; in Comparative Example 5, the generating device has only one magnet group. The aforementioned magnet arrangement methods cannot form a specific rotating magnetic field, and the resulting magnetic dielectric copper-clad laminate has the same performance as the copper-clad laminate obtained by conventional hot pressing. In Comparative Example 6, the magnetic dielectric resin composition uses isotropic spinel ferrite, which is a non-oriented magnetic filler. Even the magnetic field of this invention does not affect the arrangement of the magnetic filler, and the resulting copper-clad laminate has the same performance as that obtained by conventional hot pressing. In the preparation method of Comparative Example 7, the composite is first treated with a magnetic field, then the dynamic magnetic field is removed, and pressure and temperature are applied for hot pressing to obtain a copper-clad laminate. Because the magnetic field and pressure / temperature are applied stepwise, the anisotropic magnetic filler cannot form a good orientation structure. Therefore, the copper-clad laminate obtained in Comparative Example 6 has no significant performance difference compared with the copper-clad laminate obtained by conventional hot pressing. Comparative Example 8 uses a conventional hot pressing process and increases the magnetic permeability of the board by adding magnetic filler. However, the increase in magnetic permeability is accompanied by a significant increase in magnetic loss and dielectric loss, resulting in poor overall magnetic dielectric performance of the board.

[0133] The applicant declares that the present invention illustrates the magnetic dielectric coated metal foil, its preparation method, and its application through the above embodiments. However, the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a magnetically dielectric-coated metal foil, characterized in that, The preparation method includes the following steps: A composite material is obtained by laminating a metal foil onto one or both sides of a magnetic dielectric substrate; the composite material is then hot-pressed to obtain the magnetic dielectric metal foil-coated substrate. A magnetic field is applied during the hot pressing process. The magnetic field generating device includes n groups of magnets with coincident center points, where n is an integer ≥ 2. Each group of magnets independently consists of a first magnet and a second magnet. The N pole of the first magnet and the S pole of the second magnet in each group are positioned opposite each other, forming a magnetic field between the N and S poles. The included angle between any two adjacent groups of magnets is equal. The distance between the N pole of the first magnet and the S pole of the second magnet in each group is 3-60 cm. The surface field strength of each of the first and second magnets is independently 5-30 mT. The application time of the magnetic field is less than the hot pressing time, and the starting time of applying the magnetic field is the same as the starting time of the hot pressing. The magnetic field is driven by a motor. The application time of the magnetic field is 15-30 min. The magnetic dielectric sheet comprises at least one magnetic dielectric prepreg, the magnetic dielectric prepreg comprising a reinforcing material and a magnetic dielectric resin composition attached to the reinforcing material; the magnetic dielectric resin composition comprises a combination of resin and anisotropic magnetic filler.

2. The preparation method according to claim 1, characterized in that, The number of magnet groups n in the magnetic field generating device is 2-4.

3. The preparation method according to claim 2, characterized in that, The number n of magnet groups in the magnetic field generating device is 2 or 3.

4. The preparation method according to claim 1, characterized in that, The hot pressing time is 30-300 min.

5. The preparation method according to claim 1, characterized in that, The hot pressing temperature is 150-360℃.

6. The preparation method according to claim 5, characterized in that, The hot pressing temperature is 150-240℃.

7. The preparation method according to claim 1, characterized in that, The pressure of the hot pressing is 1-10 MPa.

8. The preparation method according to claim 1, characterized in that, The anisotropic magnetic filler includes any one or a combination of two of planar hexagonal ferrite and magnetoplumbago ferrite.

9. The preparation method according to claim 8, characterized in that, The planar hexagonal ferrite includes any one or a combination of at least two of the following: Y-type planar hexagonal ferrite, Co2Z-type planar hexagonal ferrite, and Co2W-type planar hexagonal ferrite.

10. The preparation method according to claim 1, characterized in that, The median particle size of the anisotropic magnetic filler is 0.1-30 μm.

11. The preparation method according to claim 10, characterized in that, The median particle size of the anisotropic magnetic filler is 1-15 μm.

12. The preparation method according to claim 1, characterized in that, The mass percentage of anisotropic magnetic filler in the magnetic dielectric resin composition is 10-80%.

13. The preparation method according to claim 1, characterized in that, The resin includes any one or a combination of at least two of the following: epoxy resin, phenolic resin, cyanate ester resin, polyphenylene ether resin, polyolefin resin, styrene-butadiene resin, benzoxazine resin, phenolic resin, and fluorinated resin.

14. The preparation method according to claim 1, characterized in that, The magnetic dielectric resin composition further includes any one or a combination of at least two of the following: curing agent, accelerator, crosslinking agent, initiator, flame retardant, coupling agent, and non-magnetic filler.

15. The preparation method according to claim 1, characterized in that, The reinforcing material includes any one of glass fiber cloth, non-woven fabric, quartz cloth, quartz glass fiber blended fabric, or fiber paper.

16. The preparation method according to claim 1, characterized in that, In the magnetic dielectric prepreg, the magnetic dielectric resin composition is attached to the reinforcing material after impregnation and drying.

17. The preparation method according to claim 1, characterized in that, The number of sheets of magnetic dielectric prepreg in the magnetic dielectric sheet is 1-20.

18. The preparation method according to claim 1, characterized in that, The metal foil includes any one or a combination of at least two of the following: copper foil, aluminum foil, nickel foil, and alloy foil.

19. The preparation method according to claim 1, characterized in that, The preparation method specifically includes the following steps: (1) A composite material is obtained by laminating a metal foil on one or both sides of a magnetic dielectric sheet; the magnetic dielectric sheet comprises at least one magnetic dielectric prepreg, the magnetic dielectric prepreg comprises a reinforcing material and a magnetic dielectric resin composition attached to the reinforcing material; the magnetic dielectric resin composition comprises a combination of resin and anisotropic magnetic filler; the mass percentage of the anisotropic magnetic filler in the magnetic dielectric resin composition is 10-80%; (2) The composite is hot-pressed to obtain the magnetic dielectric metal-coated foil; A magnetic field is applied during the hot pressing process. The magnetic field generating device includes n groups of magnets with their center points overlapping, where n is an integer from 2 to 4. Each group of magnets is independently composed of a first magnet and a second magnet. The N pole of the first magnet and the S pole of the second magnet in each group of magnets are arranged opposite each other, and a magnetic field is formed between the N pole and the S pole. The hot-pressed composite material is located in the magnetic field. The included angle between any two adjacent groups of magnets is equal; The distance between the N pole of the first magnet and the S pole of the second magnet in each magnet group is 3-60 cm, and the surface field strength of the first magnet and the second magnet is 5-30 mT each independently; The starting time of applying the magnetic field is the same as the starting time of the hot pressing, the field strength of the magnetic field is 0.1-50 mT, and the application time is 15-30 min; The hot pressing temperature is 150-360℃, the pressure is 1-10 MPa, and the time is 30-300 min.

20. A magnetically dielectric clad metal foil, characterized in that, The magnetic dielectric clad metal foil is prepared by the preparation method according to any one of claims 1-19.

21. A circuit board, characterized in that, The circuit board includes the magnetic dielectric clad metal foil as described in claim 20.

22. The application of a magnetically dielectric coated metal foil as described in claim 20 or a circuit board as described in claim 21 in an antenna.

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