Prepreg and application thereof

Abstract

The present invention provides a prepreg comprising: a first dielectric layer comprising a reinforcing material and a first dielectric material, the first dielectric material comprising polytetrafluoroethylene, a first filler and a water-soluble thickener; and a second dielectric layer formed on at least one side of the first dielectric layer and including a second dielectric material, where the second dielectric material is free of a fluoropolymer.

Description

Technical Field

[0001] The present invention relates to a prepreg, and more particularly, to a prepreg having a specific layer composition. The present invention also relates to a metal foil laminate and a printed circuit board made from the prepreg. Background Art

[0002] Portable electronic products are continuously moving towards higher performance and must be able to process a large amount of information at high speed. Therefore, the signals of base stations are also becoming higher in frequency, making printed circuit boards applicable to high-frequency applications more and more important. In order to transmit signals without reducing the high-frequency signal quality, the industry has been working hard to reduce the high-frequency transmission loss of printed circuit boards. A printed circuit board refers to a laminate of a conductive layer with a wiring pattern designed thereon and an insulating resin substrate. Generally, the transmission loss of a printed circuit board can be mainly divided into two parts, one part comes from the conductor loss of the conductive layer, and the other part comes from the dielectric loss of the insulating resin substrate.

[0003] In order to reduce the dielectric loss of the insulating resin substrate, thermosetting resins (such as epoxy resins or polyphenylene ether resins) with low dielectric constant (Dk) values and low dielectric dissipation factor (Df) values are often used as the insulating resin substrate in the market. However, the improvement of the Df of these thermosetting resins has its limit and it is difficult to meet the requirements of high-frequency and high-speed electronic materials. Therefore, there is still a need for an insulating resin substrate with a lower Df value. Summary of the Invention

[0004] In view of the above technical problems, the present invention provides a prepreg, which comprises a specific layer composition. The specific layer composition comprises a first dielectric layer having a specific composition and a second dielectric layer without a fluoropolymer. The prepreg of the present invention can have a low Df value, and the metal foil laminate made from the prepreg of the present invention can have a low Df value, good thickness uniformity, good appearance of the laminate after lamination, and good impregnation property, and is therefore particularly suitable for printed circuit boards with high-frequency and high-speed requirements.

[0005] Therefore, an object of the present invention is to provide a prepreg, which comprises:

[0006] a first dielectric layer, which comprises a reinforcing material and a first dielectric material, wherein the first dielectric material comprises polytetrafluoroethylene, a first filler and a water-soluble thickener; and

[0007] A second dielectric layer is formed on at least one side of the first dielectric layer and contains a second dielectric material, where the second dielectric material does not contain fluoropolymer. When second dielectric layers are formed on both sides of the first dielectric layer, the second dielectric layers on both sides can be the same or different.

[0008] In some embodiments of the present invention, the first filler is selected from the group consisting of: silica, alumina, magnesia, magnesium hydroxide, calcium carbonate, talc, clay, aluminum nitride, boron nitride, aluminum hydroxide, aluminum silicon carbide, silicon carbide, sodium carbonate, titanium dioxide, zinc oxide, zirconium oxide, quartz, diamond, diamond-like, graphite, calcined kaolin, kaolin, mica, hydrotalcite, polytetrafluoroethylene powder, glass beads, ceramic whiskers, carbon nanotubes, nano-scale inorganic powders, strontium titanate, and combinations thereof.

[0009] In some embodiments of the present invention, the first filler is a silane-modified filler.

[0010] In some embodiments of the present invention, based on the total weight of the first dielectric material, the content of the first filler is 1.5 wt% to 10 wt%.

[0011] In some embodiments of the present invention, the water-soluble thickener is selected from the group consisting of: hydroxyethyl cellulose, nitrocellulose, distarch phosphate, polymethylstyrene, polymethyl methacrylate, polyethylene glycol, and combinations thereof.

[0012] In some embodiments of the present invention, the reinforcing material is selected from the group consisting of: E-glass fabric, NE-glass fabric, S-glass fabric, L-glass fabric, D-glass fabric, quartz glass fabric, Kevlar fabric, PTFE fabric, polyester fabric, liquid crystal polymer (LCP) fabric, and combinations thereof.

[0013] In some embodiments of the present invention, the second dielectric material is formed from a thermosetting resin composition. The thermosetting resin composition may for example contain a thermosetting resin selected from the group consisting of: epoxy resin, thermosetting phenolic resin, thermosetting benzoxaine resin, thermosetting polyphenylene ether resin, and combinations thereof.

[0014] In some embodiments of the present invention, the thermosetting resin composition further comprises additives selected from the group consisting of catalysts, elastomers, second fillers, dispersants, toughening agents, viscosity modifiers, flame retardants, coupling agents, and combinations thereof. The second filler may be the same as or different from the first filler.

[0015] Another object of the present invention is to provide a metal foil laminate obtained by laminating the prepreg as described above with a metal foil.

[0016] Yet another object of the present invention is to provide a printed circuit board made from the metal foil laminate described above.

[0017] To make the above objects, technical features, and advantages of the present invention more obvious and understandable, the following provides a detailed description with some specific embodiments. Description of the Drawings

[0018] Figure 1 It is a cross-sectional schematic view of an embodiment of the prepreg of the present invention.

[0019] Figure 2 It is a cross-sectional schematic view of an embodiment of the metal foil laminate of the present invention.

[0020] Description of the Reference Numerals

[0021] 1, 20: prepreg

[0022] 2: metal foil laminate

[0023] 11, 21: first dielectric layer

[0024] 12, 13, 22, 23: second dielectric layer

[0025] 24, 25: conductive layer. Detailed Description of the Embodiments

[0026] The following will specifically describe some specific embodiments according to the present invention; however, the present invention can be practiced in many different forms of embodiments, and the protection scope of the present invention should not be limited to the described specific embodiments.

[0027] In the accompanying drawings, similar elements are represented by similar element symbols. For clarity, the thickness of each layer and region may be exaggerated. Unless otherwise specified, when a layer is described as being "on" another layer or substrate, the layer may be directly on the other layer or substrate, or there may be intervening layer(s).

[0028] Unless otherwise stated, the terms "a", "the", and similar terms used in this specification and the claims should be understood to include both singular and plural forms.

[0029] Unless otherwise specified, the terms "first", "second" and similar terms used in this specification and claims are only used to distinguish the described elements or components, and have no special meaning in themselves, nor are they used to represent the order of precedence.

[0030] Unless otherwise stated, when describing the content of components contained in a solution, mixture, composition, or glue in this specification and claims, the weight of the solvent is not included in the calculation.

[0031] Unless otherwise stated, the thicknesses mentioned in this specification and claims are measured using a thickness gauge micrometer (model: 293-821, purchased from Mitutoyo).

[0032] As used herein, the term "fluoropolymer" refers to a fluorocarbon polymer containing fluorine atoms.

[0033] The prepreg of the present invention can make the obtained metal foil laminate have a low Df value, good thickness uniformity, good appearance and good impregnation property by combining two dielectric materials with specific components respectively. The following provides a detailed description of the prepreg of the present invention and its related applications.

[0034] 1. Prepreg

[0035] The prepreg of the present invention includes a first dielectric layer and a second dielectric layer formed on at least one side of the first dielectric layer. In some embodiments of the present invention, the prepreg is substantially composed of the first dielectric layer and the second dielectric layer, or the prepreg is composed of the first dielectric layer and the second dielectric layer.

[0036] Figure 1 Shown is a cross-sectional schematic diagram of an embodiment of the prepreg of the present invention, wherein the prepreg 1 includes a first dielectric layer 11, and second dielectric layers 12 and 13 respectively disposed on two sides of the first dielectric layer 11.

[0037] The thickness of the prepreg of the present invention can be 320 microns or less, preferably 230 to 320 microns, such as 230 microns, 231 microns, 232 microns, 233 microns, 234 microns, 235 microns, 236 microns, 237 microns, 238 microns, 239 microns, 240 microns, 241 microns, 242 microns, 243 microns, 244 microns, 245 microns, 246 microns, 247 microns, 248 microns, 249 microns, 250 microns, 251 microns, 252 microns, 253 microns, 254 microns, 255 microns, 256 microns, 257 microns, 258 microns, 259 microns, 260 microns, 261 microns, 262 microns, 263 microns, 264 microns, 265 microns, 266 microns, 267 microns, 268 microns, 269 microns, 270 microns, 271 microns, 272 microns, 273 microns, 274 microns, 275 microns, 276 microns, 277 microns, 278 microns, 279 microns, 280 microns, 281 microns, 282 microns, 283 microns, 284 microns, 285 microns, 286 microns, 287 microns, 288 microns, 289 microns, 290 microns, 291 microns, 292 microns, 293 microns, 294 microns, 295 microns, 296 microns, 297 microns, 298 microns, 299 microns, 300 microns, 301 microns, 302 microns, 303 microns, 304 microns, 305 microns, 306 microns, 307 microns, 308 microns, 309 microns, 310 microns, 311 microns, 312 microns, 313 microns, 314 microns, 315 microns, 317 microns, 318 microns, 319 microns, or 320 microns, or within the range formed by any two of the above values.

[0038] 1.1. The first dielectric layer

[0039] In the prepreg of the present invention, the first dielectric layer includes a reinforcing material and a first dielectric material, or the first dielectric layer is substantially composed of the reinforcing material and the first dielectric material, or the first dielectric layer is composed of the reinforcing material and the first dielectric material. In some embodiments of the present invention, the first dielectric layer can be prepared by impregnating or coating the reinforcing material with the first dielectric material and drying the impregnated or coated reinforcing material. The impregnating or coating methods include but are not limited to dipping, roll coating, die coating, rod coating, and spraying. The drying conditions can be drying at 300°C to 400°C for 1 minute to 30 minutes.

[0040] The thickness of the first dielectric layer is not particularly limited. Generally, the thickness of the first dielectric layer can be 60 microns or less, preferably 40 to 60 microns, such as 40 microns, 41 microns, 42 microns, 43 microns, 44 microns, 45 microns, 46 microns, 47 microns, 48 microns, 49 microns, 50 microns, 51 microns, 52 microns, 53 microns, 54 microns, 55 microns, 56 microns, 57 microns, 58 microns, 59 microns, or 60 microns, or within the range formed by any two of the above values.

[0041] 1.1.1. Reinforcing material

[0042] There is no particular limitation on the type of reinforcing material that can be used in the prepreg of the present invention, and it can be any reinforcing material existing in the technical field to which the present invention pertains. Generally, the materials of the reinforcing material include, but are not limited to, fibers selected from the following groups: glass fibers, inorganic fibers other than glass fibers, organic fibers, and combinations thereof. Examples of glass fibers include, but are not limited to, E-glass, NE-glass, S-glass, L-glass, D-glass, T-glass, Q-glass, UN-glass, and spherical glass. Examples of inorganic fibers other than glass fibers include, but are not limited to, quartz fibers, paper fibers, and carbon fibers. Examples of organic fibers include, but are not limited to, polyimide, polyamide (such as Kevlar), polyester, liquid crystal polymer (such as liquid crystal polyester), polytetrafluoroethylene, ultra-high molecular weight polyethylene (UHMWPE), and high-modulus polypropylene (HMPP). The forms of the reinforcing material include, but are not limited to, woven fabric, non-woven fabric, roving, chopped strand mat, and surface mat. From the perspective of dimensional stability, it is preferred to use a woven fabric that has been subjected to super fibrillation treatment and filling treatment as the reinforcing material. From the perspective of moisture absorption and heat resistance, it is preferred to use a glass fiber woven fabric that has been surface-treated such as by epoxy silane treatment or silane coupling agent treatment as the reinforcing material. In some embodiments of the present invention, the reinforcing material of the first dielectric layer is selected from the following groups: E-glass fabric, NE-glass fabric, S-glass fabric, L-glass fabric, D-glass fabric, quartz glass fiber fabric, Kevlar fiber fabric, polytetrafluoroethylene fiber fabric, polyester fiber fabric, liquid crystal polymer fiber fabric, and combinations thereof.

[0043] 1.1.2. First dielectric material

[0044] In the prepreg of the present invention, the first dielectric material comprises polytetrafluoroethylene, a first filler, and a water-soluble thickening agent.

[0045] [Polytetrafluoroethylene]

[0046] Considering the convenience in the process, polytetrafluoroethylene in suspension form (also referred to as "polytetrafluoroethylene suspension" in this article) can be used to prepare the first dielectric material, but the present invention is not limited thereto, and polytetrafluoroethylene in other forms, such as polytetrafluoroethylene in powder form, can also be used. The preparation method of the polytetrafluoroethylene suspension is not the technical focus of the present invention and will not be elaborated herein. For the literature on the relevant preparation methods of the polytetrafluoroethylene suspension, reference can be made to, for example, US 3,391,099 A, the full text of which is incorporated herein by reference.

[0047] Commercially available polytetrafluoroethylene suspension products include, but are not limited to: the product with model D210 purchased from Daikin Industries (solid content: 60%); the product with model Teflon TM PTFE DISP 30LX purchased from Chemours (solid content: 60%); the product with model Algoflon D 3511F purchased from Solvay (solid content 59%); the product with model AD9300 purchased from Gujarat Fluorochemicals Limited (solid content: 60%); and the product with model Dyneon TM TF5050Z purchased from 3M (solid content: 58%). The polytetrafluoroethylene suspension products can be used alone or in any combination.

[0048] Based on the total weight of the first dielectric material, the content of polytetrafluoroethylene can be 80% to 98% by weight, such as 80% by weight, 80.5% by weight, 81% by weight, 81.5% by weight, 82% by weight, 82.5% by weight, 83% by weight, 83.5% by weight, 84% by weight, 84.5% by weight, 85% by weight, 85.5% by weight, 86% by weight, 86.5% by weight, 87% by weight, 87.5% by weight, 88% by weight, 88.5% by weight, 89% by weight, 89.5% by weight, 90% by weight, 90.5% by weight, 91% by weight, 91.5% by weight, 92% by weight, 92.5% by weight, 93% by weight, 93.5% by weight, 94% by weight, 94.5% by weight, 95% by weight, 95.5% by weight, 96% by weight, 96.5% by weight, 97% by weight, 97.5% by weight, or 98% by weight, or within the range formed by any two of the above values.

[0049] [First filler]

[0050] The first filler may be any filler existing in the technical field to which the present invention pertains and used for metal foil laminates. Examples of the first filler include, but are not limited to, silica (including spherical silica, fused silica, non-fused silica, porous silica, hollow silica, and nano-silica), alumina, magnesia, magnesium hydroxide, calcium carbonate, talc, clay, aluminum nitride, boron nitride, aluminum hydroxide, aluminum silicon carbide, silicon carbide, sodium carbonate, titanium dioxide, zinc oxide, zirconia, quartz, diamond, diamond-like, graphite, calcined kaolin, kaolin, mica, hydrotalcite, polytetrafluoroethylene powder, glass beads, ceramic whiskers, carbon nanotubes, nano-scale inorganic powders, and strontium titanate. Each of the aforementioned fillers may be used alone or in any combination.

[0051] The first filler may be surface-treated as needed to change its physical and chemical properties. Examples of functional groups that can be bonded to the surface of the first filler by surface treatment include, but are not limited to, alkyl, vinyl, acrylic, methacrylic, amine, urea, phenyl, glycidyl, anilino, triisocyanato, styryl, and fluorine atoms. In some embodiments of the present invention, the first filler is a silane-modified filler. Thus, the silane used for surface treatment may carry one or more selected from the group consisting of: alkyl, vinyl, acrylic, methacrylic, amine, urea, phenyl, glycidyl, anilino, triisocyanato, styryl, and fluorine atoms. Specifically, specific examples of the silane used for surface treatment include, but are not limited to, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)propylmethyldimethoxysilane, 3-anilinopropyltrimethoxysilane, 3-anilinopropyltrimethoxysilane, 3-ureidopropyltrimethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriphenoxysilane, n-propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, cyclohexyltrimethoxysilane, n-octyltrimethoxysilane, n-decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, phenyltrimethoxysilane, diphenyldimethoxysilane, p-styryltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 1,3,5-N-tris(trimethoxysilylpropyl)trimelamine, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane, (tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane, (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane, (3,3,3-trifluoropropyl)methyldimethoxysilane, (3,3,3-trifluoropropyl)methyldiethoxysilane, (3,3,3-trifluoropropyl)trimethoxysilane, (3,3,3-trifluoropropyl)triethoxysilane, trifluoromethyltrimethylsilane, trimethylsilyltrifluoromethanesulfonate, triethylsilyltrifluoromethanesulfonate, and tert-butyldimethylsilyltrifluoromethanesulfonate.In the appended examples, unmodified silica or silane-modified silica is used as the first filler.

[0052] Based on the total weight of the first dielectric material, the content of the first filler can be 1 wt% to 10 wt%, such as 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%, or within the range formed by any two of the above values.

[0053] [Water-soluble thickener]

[0054] In this article, a water-soluble thickener refers to a thickener that has a solubility greater than 25 mg / L in an aqueous solvent at room temperature. The aqueous solvent includes water and a mixture of alcohol and water (i.e., an alcohol aqueous solution). Examples of alcohols include, but are not limited to, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol, tertiary butanol, n-pentanol, isopentanol, secondary pentanol, tertiary pentanol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, and cyclohexanol.

[0055] The types of water-soluble thickeners include, but are not limited to, cellulose thickeners, acrylate thickeners, polyurethane thickeners, and inorganic thickeners. It is preferably to use cellulose thickeners because they can endow the dielectric material with better rheological properties and improve the adhesion of the dielectric material to the reinforcing material. Examples of cellulose thickeners include, but are not limited to, cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and nitrocellulose. Examples of acrylate thickeners include, but are not limited to, polymethyl methacrylate. Inorganic thickeners include, but are not limited to, inorganic salt thickeners and inorganic gel mineral thickeners. Examples of inorganic salt thickeners include, but are not limited to, sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, sodium phosphate, disodium phosphate, and pentasodium triphosphate. Examples of inorganic gel mineral thickeners include, but are not limited to, bentonite, palygorskite, and aluminum silicate. Each of the aforementioned thickeners can be used alone or in any combination.

[0056] In some embodiments of the present invention, the water-soluble thickener is selected from the group consisting of cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, nitrocellulose, distarch phosphate, polymethylstyrene, polymethyl methacrylate, polyethylene glycol, and combinations thereof.

[0057] Based on the total weight of the first dielectric material, the content of the water-soluble thickener may be from 0.1 wt% to 10 wt%, such as 0.1 wt%, 0.5 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or 10 wt%, or within the range formed by any two of the above values.

[0058] It is known that pretreatment of the reinforcing material with polytetrafluoroethylene can reduce the Df value. However, due to the non-polarity of polytetrafluoroethylene, its adhesion to the reinforcing material is poor, resulting in poor impregnation of the dielectric material, poor appearance of the laminated board after lamination, and poor thickness uniformity, and even an increase in the Df value of the laminated board. The inventors of the present invention have found that using a combination of polytetrafluoroethylene, the first filler, and a water-soluble thickener to prepare a dielectric material and combining it with the second dielectric layer described below can solve the above-mentioned technical problems and obtain a prepreg and a metal foil laminated board having the following advantages: low Df value, good thickness uniformity, good appearance of the laminated board after lamination, and good impregnation.

[0059] [Selected components]

[0060] In addition to polytetrafluoroethylene, the first filler, and the water-soluble thickener, the first dielectric material may further include other additives as needed, provided that there is no adverse effect on the physical and chemical properties and dielectric properties of the prepreg of the present invention, so as to adaptively improve the physical and chemical properties of the obtained prepreg and metal foil laminated board or the processability and impregnation of the first dielectric material. The other additives include, but are not limited to, dispersants, toughening agents, viscosity modifiers, etc. The other additives can be selected by those with ordinary knowledge in the technical field to which the present invention pertains according to actual needs after observing the present specification. They are not the key points of the present invention's technology and will not be elaborated herein.

[0061] 1.2. The second dielectric layer

[0062] In the prepreg of the present invention, the second dielectric layer is formed on at least one side of the first dielectric layer. In a preferred embodiment of the present invention, the second dielectric layer is formed on both sides of the first dielectric layer, and the second dielectric layers formed on both sides of the first dielectric layer may be the same or different. For example, the second dielectric layers formed on both sides of the first dielectric layer may have the same or different thicknesses and may have the same or different compositions.

[0063] The thickness of the second dielectric layer can be independently 130 micrometers or less, preferably 95 to 130 micrometers, such as 95 micrometers, 96 micrometers, 97 micrometers, 98 micrometers, 99 micrometers, 100 micrometers, 101 micrometers, 102 micrometers, 103 micrometers, 104 micrometers, 105 micrometers, 106 micrometers, 107 micrometers, 108 micrometers, 109 micrometers, 110 micrometers, 111 micrometers, 112 micrometers, 113 micrometers, 114 micrometers, 115 micrometers, 116 micrometers, 117 micrometers, 118 micrometers, 119 micrometers, 120 micrometers, 121 micrometers, 122 micrometers, 123 micrometers, 124 micrometers, 125 micrometers, 126 micrometers, 127 micrometers, 128 micrometers, 129 micrometers, or 130 micrometers, or within the range formed by any two of the above values.

[0064] In the prepreg of the present invention, the second dielectric layer contains a second dielectric material and does not contain a fluoropolymer. More specifically, the second dielectric layer may be substantially composed of the second dielectric material, or the second dielectric layer is composed of the second dielectric material.

[0065] 1.2.1. Second Dielectric Material

[0066] In some embodiments of the present invention, the second dielectric material is formed from a thermosetting resin composition. The thermosetting resin composition includes a thermosetting resin and, optionally, additives.

[0067] 1.2.1.1. Thermosetting Resin

[0068] A thermosetting resin refers to a component that can gradually cure by forming a network structure through a cross-linking reaction upon heating. Examples of thermosetting resins include, but are not limited to, epoxy resins, thermosetting phenolic resins, thermosetting benzoxazine resins, and thermosetting polyphenylene ether resins. Each of the foregoing thermosetting resins can be used alone or in combination. Herein, a reactive functional group refers to any functional group that can react with other groups to cure. Examples of reactive functional groups include, but are not limited to, hydroxyl groups, carboxyl groups, alkenyl groups, and amine groups. In some embodiments of the present invention, an epoxy resin, a thermosetting polyphenylene ether resin, or a combination thereof is used as the thermosetting resin.

[0069] [Epoxy Resin]

[0070] In this text, an epoxy resin refers to a thermosetting resin having at least two epoxy functional groups in one molecule, such as a polyfunctional epoxy resin and a linear phenolic epoxy resin. Examples of polyfunctional epoxy resins include, but are not limited to, difunctional epoxy resins, tetrafunctional epoxy resins, and octafunctional epoxy resins. There is no particular limitation on the type of epoxy resin that can be used to form the dielectric material, and those skilled in the art to which the present invention pertains can select it according to actual needs after reading the specification of this case. For example, considering the flame retardant properties of the resin composition, a phosphorus-containing or bromine-containing epoxy resin can be used, or a halogen-free epoxy resin can be used to meet the environmental requirements of halogen-free.

[0071] Examples of the epoxy resin include, but are not limited to, dicyclopentadiene (DCPD)-type epoxy resins, bisphenol-type epoxy resins, phenolic-type epoxy resins, stilbene-type epoxy resins, epoxy resins containing a triazine skeleton, epoxy resins containing a fluorene skeleton, triphenylmethane-type epoxy resins, biphenyl-type epoxy resins, xylylene-type epoxy resins, biphenyl aralkyl-type epoxy resins, naphthalene-type epoxy resins, and alicyclic epoxy resins. Examples of bisphenol-type epoxy resins include, but are not limited to, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins. Examples of phenolic-type epoxy resins include, but are not limited to, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, bisphenol A novolac-type epoxy resins, and bisphenol F novolac-type epoxy resins. Other examples of epoxy resins also include diglycidyl ether compounds of polyfunctional phenols and polycyclic aromatics such as anthracene. Examples of phosphorus-containing epoxy resins include, but are not limited to, epoxy resins modified with 9,10-dihydro-9-oxa-10-phosphahenanthrene-10-oxide (DOPO). Examples of bromine-containing epoxy resins include, but are not limited to, tetrabromobisphenol A-type epoxy resins. Each of the aforementioned epoxy resins can be used alone or in combination of multiple types. In the following attached examples, a phenolic-type epoxy resin is used.

[0072] In the embodiment where the thermosetting resin composition contains an epoxy resin, the amount of the epoxy resin can be adjusted according to actual needs. Generally, based on the total weight of the thermosetting resin composition, the content of the epoxy resin can be 10% by weight to 50% by weight, such as 10% by weight, 15% by weight, 20% by weight, 25% by weight, 30% by weight, 35% by weight, 40% by weight, 45% by weight, or 50% by weight, or within the range formed by any two of the above values.

[0073] [Thermosetting polyphenylene ether resin]

[0074] In this text, a thermosetting polyphenylene ether resin refers to a resin having at least a repeating unit in the main chain of the molecule A resin having an unsaturated group at the end, where each R is independently H or an alkyl group having 1 to 5 carbon atoms, and v is an integer from 1 to 100. The unsaturated group refers to a group that can undergo an addition polymerization reaction with other components having unsaturated groups, and the addition polymerization reaction can be initiated by light or heat in the presence of a polymerization initiator. Examples of the unsaturated group include, but are not limited to, vinyl, vinyl benzyl, allyl, acrylic, and methacrylic. Examples of the thermosetting polyphenylene ether resin include, but are not limited to, polyphenylene ether resin containing vinyl, polyphenylene ether resin containing allyl, polyphenylene ether resin containing vinyl benzyl, polyphenylene ether resin containing acrylic, and polyphenylene ether resin containing methacrylic. Each of the foregoing polyphenylene ether resins can be used alone or in combination.

[0075] The preparation method of the thermosetting polyphenylene ether resin is not the technical focus of the present invention and can be carried out by those skilled in the art based on the disclosure of this specification and their general knowledge, so it will not be elaborated here. References related to the preparation methods of thermosetting polyphenylene ether resins include US 6,995,195 B2 (polyphenylene ether resin containing vinyl benzyl), US 5,218,030 A (polyphenylene ether resin containing allyl), US 5,352,745 A (polyphenylene ether resin containing methacrylic), US 6,352,782 B2, and US 2016 / 0280913 A1, and the full texts of these references are incorporated herein by reference.

[0076] In some embodiments of the present invention, the thermosetting resin composition comprises a thermosetting polyphenylene ether resin having a structure represented by the following formula (I):

[0077]

[0078] In formula (I), R 3 , R 4 , R 5 and R 6 are each independently H or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms; m and n are each independently an integer from 0 to 100, provided that m and n are not both 0; Z is absent, -O-, or aryl, where R 7 and R 8 are each independently H or an alkyl group having 1 to 12 carbon atoms; X and Y are each independently absent, a carbonyl group, or a group having an alkenyl group; and A 1 and A 2 are each independently

[0079] In a preferred embodiment of the present invention, R of formula (I) 3 , R 4 , R 5 , and R 6 is -CH 3 , Z is X and Y are absent, and A 1 and A 2 are each independently

[0080] The weight average molecular weight (Mw) of the thermosetting polyphenylene ether resin can be from 1,000 to 50,000, preferably from 1,000 to 10,000, more preferably from 1,000 to 5,000. Examples of commercially available thermosetting polyphenylene ether resins include products with model numbers OPE-2St 1200 or OPE-2st 2200 available from Mitsubishi Gas Chemical, product with model number SA-9000 available from SABIC, product with model number PP807 available from Jin Yi Chemical Industry, and polyphenylene ether products available from Asahi Kasei. From the perspective of high-frequency applications, it is preferred to use a thermosetting polyphenylene ether resin to form the dielectric material.

[0081] In the embodiment where the thermosetting resin composition contains a thermosetting polyphenylene ether resin, the amount of the thermosetting polyphenylene ether resin can be adjusted according to actual needs and there are no special restrictions. Generally, based on the total weight of the resin composition, the content of the thermosetting polyphenylene ether resin can be from 15 wt% to 60 wt%, such as 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%, or within the range formed by any two of the above values.

[0082] 1.2.1.2. Optional additives

[0083] The thermosetting resin composition can further contain additives. Examples of the additives include but are not limited to catalysts, elastomers, fillers, dispersants, toughening agents, viscosity modifiers, flame retardants, and coupling agents. Each of the aforementioned additives can be used alone or multiple additives can be used in combination.

[0084] [Hardening agent]

[0085] A hardener refers to a component having unsaturated functional groups that can undergo a crosslinking reaction with other components having unsaturated functional groups (such as epoxy resins or thermosetting polyphenylene ether resins) to form a three-dimensional network structure, which can enhance the degree of crosslinking. There are no special restrictions on the types of hardeners, as long as they can enhance the degree of crosslinking.

[0086] In the case where the thermosetting resin composition contains an epoxy resin, suitable hardeners include, but are not limited to, -OH group-containing compounds, amine group-containing compounds, acid anhydride compounds, and active ester compounds. Each of the aforementioned hardeners can be used alone or in combination of multiple ones. Specific examples of the hardeners include, but are not limited to, phenolic resin (PN resin), styrene-maleic anhydride copolymer (SMA copolymer), bismaleimide (BMI), dicyandiamide (Dicy), 4,4'-diaminodiphenyl sulfone (DDS), bis(anilino)methane, aromatic diamines, aromatic dianhydrides, aliphatic dianhydrides, triazine, cyanate ester resin (CE), triazaphenolic resin, benzoxazine resin and its ring-opening polymer, and styrene-vinylphenol copolymer. In the appended examples, Dicy, BMI, or a combination thereof is used. In the case where the thermosetting resin composition contains a thermosetting polyphenylene ether resin, hardeners selected from the following group can be used: BMI, elastomers containing butadiene and / or styrene, and isocyanurates containing vinyl and / or allyl groups. Each of the aforementioned hardeners can be used alone or in combination of multiple ones. In the appended examples, an allyl group-containing isocyanurate is used.

[0087] The amount of the hardener can be adjusted according to actual needs. Generally, based on the total weight of the thermosetting resin composition, the content of the hardener can be 15 wt% to 65 wt%, such as 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or 65 wt%, or within the range formed by any two of the above values.

[0088] [Filler]

[0089] The filler can improve mechanical strength, thermal conductivity, and dimensional stability. In this text, the filler contained in the second dielectric layer is referred to as "second filler", and its type can be the same as or different from that of the first filler, and its examples are as described for the first filler above and will not be elaborated here. In the appended examples, silica is used as the second filler.

[0090] Based on the total weight of the thermosetting resin composition, the content of the second filler may be from 0 wt% to 60 wt%, such as 0 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, or 60 wt%, or within the range formed by any two of the above values.

[0091] [Catalyst]

[0092] A catalyst refers to a component that can promote the curing reaction, such as promoting the ring-opening reaction of epoxy functional groups and reducing the curing reaction temperature of the thermosetting resin composition. There is no particular limitation on the type of catalyst as long as it can promote the curing reaction. Suitable catalysts include but are not limited to organic peroxides, tertiary amines, quaternary ammonium salts, imidazole compounds, and pyridine compounds. Examples of organic peroxides include but are not limited to benzoyl peroxide (BPO), dicumyl peroxide (DCP), and α,α'-bis(t-butylperoxy)diisopropyl benzene. Examples of tertiary amines include but are not limited to dimethylbenzylamine, 2-(dimethylaminomethyl)phenol, and 2,4,6-tris(dimethylaminomethyl)phenol. Examples of imidazole compounds include but are not limited to 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole. Examples of pyridine compounds include but are not limited to 2,3-diaminopyridine, 2,5-diaminopyridine, 2,6-diaminopyridine, 4-dimethylaminopyridine, 2-amino-3-methylpyridine, 2-amino-4-methylpyridine, and 2-amino-3-nitropyridine. Each of the aforementioned catalysts can be used alone or in combination of multiple types.

[0093] In the case where the thermosetting resin composition contains an epoxy resin, the catalyst is preferably selected from tertiary amines, quaternary ammonium salts, imidazole compounds, and pyridine compounds. In the following examples, 2-methylimidazole is used as the catalyst for the epoxy resin. In the case where the thermosetting resin composition contains a thermosetting polyphenylene ether resin, the catalyst is preferably selected from organic peroxides. In the following examples, α,α'-bis(t-butylperoxy)diisopropyl benzene is used as the catalyst for the thermosetting polyphenylene ether resin.

[0094] [Flame retardant]

[0095] Flame retardants can enhance the flame retardancy of the resulting electronic materials. Types of flame retardants include, but are not limited to, phosphorus-containing flame retardants, bromine-containing flame retardants, and nitrogen-containing compounds. Each type of flame retardant can be used alone or in any combination. Examples of phosphorus-containing flame retardants include, but are not limited to, phosphate esters, phosphazenes, ammonium polyphosphate, metal phosphinates, and melamine phosphate. Each of the aforementioned phosphorus-containing flame retardants can be used alone or in combination of multiple types. Examples of bromine-containing flame retardants include, but are not limited to, tetrabromobisphenol A, decabromodiphenyl oxide, decabrominated diphenyl ethane, 1,2-bis(tribromophenyl)ethane, brominated epoxy oligomer, octabromotrimethylphenyl indane, bis(2,3-dibromopropyl ether), tris(tribromophenyl)triazine, brominated aliphatic hydrocarbon, and brominated aromatic hydrocarbon. Each of the aforementioned bromine-containing flame retardants can be used alone or in combination of multiple types. Examples of nitrogen-containing compounds include, but are not limited to, melamine and its derivatives. Commercially available phosphorus-containing flame retardants include the product with the model number Melapur 200 available from BASF.

[0096] 1.3. Preparation of prepreg

[0097] The prepreg of the present invention can be prepared in the following manner.

[0098] First, the components of the first dielectric material, including polytetrafluoroethylene, the first filler, the water-soluble thickener, and the optional components, are uniformly mixed and dissolved or dispersed in a solvent using a stirrer to form a slurry, colloidal group, varnish, etc. for subsequent processing. The solvent can be any inert solvent that can dissolve or disperse the components of the first dielectric material but does not react with these components. For example, the solvents that can be used to dissolve or disperse the components of the first dielectric material include but are not limited to: water, ethanol, isopropanol, and acetone. Each of the aforementioned solvents can be used alone or in combination. There is no special limitation on the amount of the solvent. In principle, as long as it can uniformly dissolve or disperse the components of the first dielectric material therein. In the appended examples, water is used as the solvent.

[0099] Next, a thermosetting resin composition is prepared to provide the second dielectric material. Specifically, the components of the thermosetting resin composition, including the thermosetting resin and optional additives, are uniformly mixed and dissolved or dispersed in a solvent using a stirrer to form a slurry, colloidal group, varnish, etc. for subsequent processing. The solvent can be any inert solvent that can dissolve or disperse the components of the thermosetting resin composition but does not react with these components. For example, the solvents that can be used to dissolve or disperse the components of the thermosetting resin composition include but are not limited to: toluene, γ-butyrolactone, methyl ethyl ketone, cyclohexanone, butanone, acetone, xylene, methyl isobutyl ketone, N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide (DMAc), and N-methyl-pyrrolidone (NMP). Each of the aforementioned solvents can be used alone or in combination. There is no special limitation on the amount of the solvent. In principle, as long as it can uniformly dissolve or disperse the components of the resin composition therein. In the appended examples, methyl ethyl ketone, toluene, or a combination thereof is used as the solvent.

[0100] Impregnate or coat a reinforcing material with the first dielectric material in the form of a slurry, micelle or varnish, and dry the impregnated or coated reinforcing material. Sinter the impregnated or coated reinforcing material at a temperature not lower than the melting point of polytetrafluoroethylene to form a first dielectric layer, wherein the impregnation and coating can be repeated multiple times, and the drying conditions can be drying at 300°C to 400°C for 1 minute to 30 minutes to form a first dielectric layer with a desired thickness. Then, impregnate or coat the first dielectric layer with a thermosetting resin composition, and dry the impregnated or coated first dielectric layer to form a second dielectric layer on both sides of the first dielectric layer, thereby obtaining a prepreg, wherein the impregnation and coating can be repeated multiple times, and the drying conditions can be drying at 160°C to 190°C for 2 minutes to 10 minutes to form a second dielectric layer with a desired thickness. The impregnation or coating methods include but are not limited to dipping, roll coating, die coating, bar coating, and spraying.

[0101] 2. Metal foil laminate and printed circuit board

[0102] The prepreg of the present invention can be laminated with a metal foil to form a metal foil laminate. Therefore, the present invention also provides a metal foil laminate, which is obtained by laminating the prepreg of the present invention with a metal foil. First, a plurality of layers of the above prepregs can be laminated, and then a metal foil is laminated on at least one outer surface of the dielectric layer structure formed by the laminated prepregs to provide a laminate, and the laminate is subjected to a hot pressing operation to obtain a metal foil laminate.

[0103] Figure 2 It is a cross-sectional schematic diagram of an embodiment of the metal foil laminate of the present invention. As Figure 2 shown, the metal foil laminate 2 includes a prepreg 20, and conductive layers 24 and 25 respectively disposed on both sides of the prepreg 20, wherein the prepreg 20 includes second dielectric layers 22 and 23 and a first dielectric layer 21 between the second dielectric layers 22 and 23, and the conductive layers 24 and 25 can be any metal foil that can be used for printed circuit boards. Examples of the metal foil include but are not limited to copper foil and aluminum foil, and preferably copper foil.

[0104] In addition, the metal foil laminate of the present invention can be formed into a printed circuit board by further patterning the metal foil on its outer side. Therefore, the present invention also provides a printed circuit board, which is obtained by further patterning the metal foil on the outer side of the metal foil laminate of the present invention, wherein the method of patterning the metal foil is not particularly limited, and examples thereof include but are not limited to photolithography, screen printing, and inkjet printing.

[0105] 3. Examples

[0106] 3.1. Description of measurement method

[0107] The present invention will now be further illustrated by the following specific examples. The measuring instruments and methods used are as follows:

[0108] [Measurement of Dielectric Loss Factor (Df)]

[0109] According to the IPC-TM-650 2.5.5.13 specification, the dielectric loss factor (Df) of the metal foil laminate is measured and calculated at a working frequency of 10 GHz.

[0110] [Thickness Uniformity Test]

[0111] First, the metal foil of the metal foil laminate with a length of 24 inches and a width of 18 inches is etched away to prepare a test sample. Then, five positions are taken on each of the long side and the wide side of the test sample, and the thickness of the test sample at these positions is measured to obtain a total of 25 values. The average value of the 25 values is taken, and the maximum and minimum values are found. The thickness uniformity is calculated according to the following formula.

[0112]

[0113] [Stain Test]

[0114] First, the metal foil of the metal foil laminate with a length of 24 inches and a width of 18 inches is etched away to prepare a test sample. Then, the appearance of the test sample is visually inspected for black stains or spots, and the evaluation is carried out according to the following criteria: If there are no stains or spots on the appearance of the test sample, it means passing the stain test and is recorded as "○"; and if there is at least one black stain larger than 1 cm × 1 cm or at least five black stains smaller than 1 cm × 1 cm on the appearance of the test sample, it means failing the stain test and is recorded as "×".

[0115] [Impregnation Test]

[0116] First, the metal foil of the metal foil laminate with a length of 24 inches and a width of 18 inches is etched away to prepare a test sample. Then, the appearance of the test sample is visually inspected for patterns, and the evaluation is carried out according to the following criteria: If there are no patterns on the appearance of the test sample, it means passing the impregnation test and is recorded as "○"; and if there are at least two patterns with a length greater than 0.5 cm or at least five patterns with a length less than 0.5 cm on the appearance of the test sample, it means failing the impregnation test and is recorded as "×".

[0117] 3.2. List of Raw Material Information for Examples and Comparative Examples

[0118] Table 1: List of Raw Material Information

[0119]

[0120] 3.3. Preparation of the first dielectric layer

[0121] Prepare the first dielectric materials 1 to 12 according to the ratios shown in Table 2. Each component is mixed using a stirrer at room temperature, and pure water is added as a solvent. Then, the resulting mixture is stirred at room temperature for 60 to 120 minutes to obtain these first dielectric materials.

[0122] Table 2: Composition of the first dielectric materials

[0123]

[0124] Prepare the first dielectric layers 1 to 12 in the following manner. First, a fiberglass cloth (model: E1035, thickness: 0.043 mm) is respectively impregnated in the first dielectric materials 1 to 12 via a roll coater, and the thickness of the first dielectric layer is controlled to an appropriate degree. Then, the impregnated fiberglass cloth is placed in an oven at 350 °C and heated and baked for 2 to 5 minutes to obtain the first dielectric layers 1 to 12.

[0125] In addition, prepare an untreated fiberglass cloth (model: E1035, thickness: 0.043 mm) as the first dielectric layer 13.

[0126] 3.4. Preparation of prepregs

[0127] Mix 50.0 g of polyphenylene ether SA9000, 50.0 g of TAIC, 10.0 g of elastomer Ricon 100, 1.0 g of catalyst Perbutyl P, and 100.0 g of filler SC-5500SVC using a stirrer at room temperature, and add methyl ethyl ketone (purchased from Genxiang Industrial Co., Ltd.) and toluene (purchased from Chuanqing Chemical Co., Ltd.). Then, the resulting mixture is stirred at room temperature for 60 to 120 minutes to obtain the second dielectric material 1.

[0128] Mix 13.0 g of epoxy resin BNE-210, 25.0 g of Dicy, 15.0 g of BMI-70, 0.01 g of catalyst 2MI, and 30.0 g of filler SC-5500SVC using a stirrer at room temperature, and add methyl ethyl ketone. Then, the resulting mixture is stirred at room temperature for 60 to 120 minutes to obtain the second dielectric material 2.

[0129] According to the compositions shown in Table 3-1 and Table 3-2, prepare the prepregs of Examples 1 to 16 and Comparative Examples 1 to 10 in the following manner. First, impregnate the first dielectric layer in the second dielectric material 1 or 2, and control the thickness of the prepreg to an appropriate degree. Then, place the impregnated first dielectric layer in a dryer at 175 °C and heat and dry it for 2 to 5 minutes to obtain the prepregs of Examples 1 to 16 and Comparative Examples 1 to 10.

[0130] Table 3-1: Composition of prepregs of Examples 1 to 16

[0131]

[0132] Table 3-2: Composition of prepregs of Comparative Examples 1 to 10

[0133]

[0134] 3.5. Preparation of metal foil laminates

[0135] The metal foil laminates of Examples 1 to 16 and Comparative Examples 1 to 10 were prepared using the prepregs of Examples 1 to 16 and Comparative Examples 1 to 10, respectively. First, several prepregs were laminated, and a 0.5-ounce copper foil was laminated on each of the outermost layers on both sides thereof, and then placed in a hot press for high-temperature hot pressing and curing to obtain the metal foil laminates of Examples 1 to 16 and Comparative Examples 1 to 10. The conditions of the hot pressing operation are as described below. The temperature was raised to 200°C to 220°C at a heating rate of 2°C / min to 4°C / min, and at this temperature, hot pressing was performed at a full pressure of 15 kg / cm² (initial pressure 8 kg / cm²) for 2 hours.

[0136] The properties of the metal foil laminates of Examples 1 to 16 and Comparative Examples 1 to 10, including Df value, stain situation, thickness uniformity, and impregnation property, were tested according to the method described above, and the results were recorded in Tables 4-1 and 4-2.

[0137] Table 4-1: Properties of metal foil laminates of Examples 1 to 16

[0138]

[0139]

[0140] Table 4-2: Properties of metal foil laminates of Comparative Examples 1 to 10

[0141]

[0142] As shown in Table 4-1, the metal foil laminates prepared from the prepregs of the present invention have a low Df value and good thickness uniformity, and can pass the stain test and impregnation test. Specifically, when the first dielectric material contains PTFE, the first filler, and a specific water-soluble thickener at a specific ratio, even if the second dielectric material is different, the metal foil laminates prepared can obtain a low Df and good thickness uniformity, and can pass the stain test and impregnation test. In addition, as shown in Examples 4, 5, 12, and 13, when the first filler is a silane-modified filler, the metal foil laminates prepared can obtain further improved Df.

[0143] In contrast, as shown in Table 4-2, the metal foil laminate made from the prepreg of the present invention cannot simultaneously have a low Df value and good thickness uniformity, and cannot pass the stain test or the impregnation test. Specifically, it can be seen from Comparative Examples 1 to 4 and 6 to 9 that as long as the first dielectric material does not simultaneously contain PTFE, the first filler, and the specific water-soluble thickener, the resulting metal foil laminate cannot simultaneously have a low Df value and good thickness uniformity, and cannot pass the stain test or the impregnation test. In addition, comparing Comparative Example 5 with Examples 1 to 8 or comparing Comparative Example 10 with Examples 9 to 16, when the prepreg is prepared without using the first dielectric material, although the resulting metal foil laminate can pass the stain test and the impregnation test, its Df value is relatively high and the thickness uniformity is significantly poor, indicating that the use of the specific first dielectric material can further reduce the Df value and improve the thickness uniformity.

[0144] The above embodiments are only illustrative of the principles and effects of the present invention, and illustrate the technical features of the present invention, rather than limiting the protection scope of the present invention. Any changes or arrangements that can be easily completed by those skilled in the art without departing from the technical principles of the present invention fall within the scope claimed by the present invention.

Claims

1. A prepreg, characterized in that, it comprises: a first dielectric layer comprising a reinforcing material and a first dielectric material, wherein the first dielectric material comprises polytetrafluoroethylene, a first filler, and a water-soluble thickener; and a second dielectric layer formed on at least one side of the first dielectric layer and comprising a second dielectric material, wherein the second dielectric material does not contain a fluoropolymer.

2. The prepreg according to claim 1, characterized in that, the first filler is selected from the group consisting of: silica, alumina, magnesia, magnesium hydroxide, calcium carbonate, talc, clay, aluminum nitride, boron nitride, aluminum hydroxide, aluminum silicon carbide, silicon carbide, sodium carbonate, titanium dioxide, zinc oxide, zirconium oxide, quartz, diamond, diamond-like, graphite, calcined kaolin, kaolin, mica, hydrotalcite, polytetrafluoroethylene powder, glass beads, ceramic whiskers, carbon nanotubes, nano-scale inorganic powders, strontium titanate, and combinations thereof.

3. The prepreg according to claim 1, characterized in that, the first filler is a silane-modified filler.

4. The prepreg according to any one of claims 1 to 3, characterized in that, based on the total weight of the first dielectric material, the content of the first filler is 1.5 wt% to 10 wt%.

5. The prepreg according to any one of claims 1 to 3, characterized in that, the water-soluble thickener is selected from the group consisting of: hydroxyethyl cellulose, nitrocellulose, distarch phosphate, polymethylstyrene, polymethyl methacrylate, polyethylene glycol, and combinations thereof.

6. The prepreg according to any one of claims 1 to 3, characterized in that, the reinforcing material is selected from the group consisting of: E-glass fabric, NE-glass fabric, S-glass fabric, L-glass fabric, D-glass fabric, quartz glass fabric, Kevlar fabric, polytetrafluoroethylene fabric, polyester fabric, liquid crystal polymer fabric, and combinations thereof.

7. The prepreg according to any one of claims 1 to 3, characterized in that, the second dielectric material is formed from a thermosetting resin composition.

8. The prepreg according to claim 7, characterized in that, the thermosetting resin composition comprises a thermosetting resin selected from the group consisting of: epoxy resin, thermosetting phenolic resin, thermosetting benzoxazine resin, thermosetting polyphenylene ether resin, and combinations thereof.

9. The prepreg according to claim 7, characterized in that, the thermosetting resin composition further comprises an additive selected from the group consisting of: catalyst, elastomer, second filler, dispersant, toughening agent, viscosity modifier, flame retardant, coupling agent, and combinations thereof.

10. A metal foil laminate, characterized in that, it is obtained by laminating the prepreg according to any one of claims 1 to 9 with a metal foil.

11. A printed circuit board, characterized in that, it is made from the metal foil laminate according to claim 10.

Images