A halogen-free flame-retardant resin composition, prepreg, laminate and printed circuit board

Abstract

The present invention provides a halogen-free flame-retardant resin composition, a prepreg, a laminate and a printed circuit board. The halogen-free flame-retardant resin composition comprises the following components in parts by weight: (A) epoxy resin: 100 parts by weight; (B) low-dielectric curing agent: 10-75 parts by weight; (C) benzoxazine resin: 5-40 parts by weight; (D) phosphorus-containing flame retardant: 20-50 parts by weight. In the benzoxazine resin, the weight percentage of the component with a number-average molecular weight of 250-350 is ≤51%, and the weight percentage of the component with a number-average molecular weight above 1500 is <32%. The resin composition of the present invention can improve the compatibility of benzoxazine in the resin composition, achieve the effect of eliminating the resin defect of the prepreg, and at the same time maintain the good viscosity of the prepreg, ensuring that the Tg, dielectric properties, heat resistance, water absorption rate and flame retardancy of the copper clad laminate are not deteriorated.

Description

Technical Field

[0001] The present invention belongs to the technical field of laminates, and relates to a halogen-free flame-retardant resin composition, a prepreg, a laminate and a printed circuit board. Background Art

[0002] Currently, the halogen-free low-dielectric materials basically follow the technical route of epoxy + composite curing agent. In addition to the contribution of the epoxy resin itself, the low-dielectric curing agent is the most commonly used technical means to reduce the dielectric constant, and the anhydride compound is the first choice. However, the anhydride compound has relatively high water absorption and CTE, and poor flame retardancy. Therefore, the benzoxazine resin is selected as the co-curing agent of epoxy in the industry to improve the performance of the resin composition in terms of water absorption, CTE and flame retardancy.

[0003] Although the benzoxazine has many advantages, it has problems such as poor solubility and easy precipitation. Introducing the benzoxazine into the halogen-free low-dielectric formula will encounter the problem of poor compatibility, resulting in resin deficiency or "fish-eye" defects in the prepreg. Since the circuits of the HDI circuit board are very fine, the line width / line pitch has developed to about 30 μm, and these apparent defects of the prepreg are likely to cause problems with the circuits during the processing of the HDI circuit board. Therefore, it is necessary to find the key points for controlling the benzoxazine product. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a halogen-free flame-retardant resin composition, a prepreg, a laminate and a printed circuit board.

[0005] To achieve this purpose, the present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a halogen-free flame-retardant resin composition, comprising the following components in parts by weight:

[0007] (A) Epoxy resin: 100 parts by weight;

[0008] (B) Low-dielectric curing agent: 10-75 parts by weight;

[0009] (C) Benzoxazine resin: 5-40 parts by weight;

[0010] (D) Phosphorus-containing flame retardant: 20-50 parts by weight;

[0011] The weight percentage of the component with a number average molecular weight of 250 - 350 (e.g., it can be 250, 280, 300, 330 or 350) in the benzoxazine resin ≤ 51% (e.g., 51%, 50%, 48%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 3%, etc.), and the weight percentage of the component with a number average molecular weight above 1500 (e.g., 1500, 1800, 2000, 2500, 3000, 3500, etc.) < 32% (e.g., it can be 31%, 30%, 28%, 25%, 20%, 18%, 15%, 13%, 10%, 8%, 5%, 3%, etc.).

[0012] Through laboratory control tests, it is found that in the GPC curve, when the proportion of the oligomer (250 ≤ Mn ≤ 350) of benzoxazine exceeds 51%, obvious resin deficiency problems will occur in the adhesive sheet produced from this benzoxazine. When the proportion of the oligomer is lower than or equal to 51%, there is no obvious resin deficiency problem on the surface of the adhesive sheet. However, when the content of the high polymer (Mn ≥ 1500) in the benzoxazine resin is higher than 32%, the viscosity of the resin composition will increase significantly, which is not conducive to the glue filling performance of the adhesive sheet in the lamination stage. Therefore, to obtain good appearance of the adhesive sheet and low viscosity of the resin composition, it is necessary to control the molecular weight distribution of the benzoxazine resin.

[0013] In the present invention, by controlling the content of the oligomer with a number average molecular weight of 250 - 350 in the benzoxazine resin ≤ 51% and the content of the high polymer with a number average molecular weight above 1500 < 32%, the compatibility of the benzoxazine resin in the halogen-free low dielectric formula can be improved, the apparent defect of resin deficiency in the adhesive sheet caused by benzoxazine can be solved, and at the same time, the copper clad laminate prepared from the halogen-free low dielectric formula has good Tg, dielectric properties, water absorption rate, heat resistance and flame retardant properties.

[0014] In the present invention, the epoxy resin is selected from any one or a combination of at least two of trifunctional epoxy resins or tetrafunctional epoxy resins.

[0015] In the present invention, the epoxy resin is selected from any one or a combination of at least two of dicyclopentadiene type epoxy resin, dimethylphenol type phenolic epoxy resin, tetramethylbiphenyl epoxy resin, biphenyl epoxy resin, phenolic epoxy resin, bisphenol A phenolic epoxy resin, bisphenol F phenolic epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, epoxy resin containing C1 - C6 alkyl, MDI modified epoxy resin, epoxy resin containing naphthalene ring or epoxidized polybutadiene.

[0016] Preferably, the epoxy equivalent of the epoxy resin is 150-600 g / eq, such as 150 g / eq, 200 g / eq, 250 g / eq, 300 g / eq, 350 g / eq, 400 g / eq, 450 g / eq, 500 g / eq, 550 g / eq or 600 g / eq.

[0017] Preferably, the content of dicyclopentadiene-type epoxy resin in the epoxy resin is 20-40 parts by weight, such as 20 parts by weight, 23 parts by weight, 25 parts by weight, 28 parts by weight, 30 parts by weight, 35 parts by weight, 38 parts by weight or 40 parts by weight. Dicyclopentadiene has a low dielectric constant, which can improve the dielectric properties of the resin composition.

[0018] In the present invention, the content of the low-dielectric curing agent in the halogen-free flame-retardant resin composition can be 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 40 parts by weight, 50 parts by weight, 60 parts by weight, 70 parts by weight or 75 parts by weight.

[0019] Preferably, the low-dielectric curing agent includes an acid anhydride curing agent and / or an active ester curing agent.

[0020] Preferably, the acid anhydride curing agent is selected from any one or a combination of at least two of the following B11 or B12:

[0021]

[0022]

[0023] Wherein, n:x = 1:1 to 8:1.

[0024] B12 is a copolymer resin having a structural unit derived from an aromatic vinyl compound and a structural unit derived from maleic anhydride.

[0025] Preferably, the content of the acid anhydride curing agent in the low-dielectric curing agent is 1-50 parts by weight, and can be, for example, 1 part by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight or 50 parts by weight.

[0026] Preferably, the active ester curing agent is selected from any one or a combination of at least two of the active esters having the following B21 or B22 structure:

[0027]

[0028] In B21, X is phenyl or naphthyl, j is 0 or 1, k is 0 or 1, and n represents that the repeating unit is 0.25 to 1.25 (for example, 0.25, 0.50, 0.80, 1.0, 1.1, 1.2, or 1.25);

[0029]

[0030] In B21, m, n, and q are independently integers from 1 to 6 (for example, 1, 2, 3, 4, 5, or 6), X is phenyl or naphthyl, and Y is the following group:

[0031]

[0032] where K is 0 or 1.

[0033] Preferably, the benzoxazine resin is selected from any one or a combination of at least two of bisphenol A type benzoxazine resin, bisphenol F type benzoxazine resin, bisphenol S type benzoxazine resin, DDM type benzoxazine resin, ODA type benzoxazine resin, phenolphthalein type benzoxazine resin, or DCPD type benzoxazine resin.

[0034] In the halogen-free flame-retardant resin composition of the present invention, the amount of the benzoxazine resin can be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, or 40 parts by weight.

[0035] Preferably, the phosphorus-containing flame retardant is selected from inorganic phosphorus-based flame retardants and / or organic phosphorus-based flame retardants.

[0036] Preferably, the inorganic phosphorus-based flame retardant is selected from any one or a combination of at least two of red phosphorus, ammonium phosphate, phosphoric acid amide, phosphoric acid, or phosphine oxide.

[0037] Preferably, the ammonium phosphate includes any one or a combination of at least two of monoammonium phosphate, diammonium phosphate, or triammonium phosphate.

[0038] Preferably, the organic phosphorus-based flame retardant is selected from any one or a combination of at least two of aromatic phosphate esters, monosubstituted phosphonic acid diesters, disubstituted phosphinic acid esters, metal salts of disubstituted phosphinic acids, cyclic organic phosphorus compounds, or phosphorus-containing phenolic resins. Preferably, any one or a combination of at least two of aromatic phosphate esters, metal salts of disubstituted phosphinic acids, or phosphorus-containing phenolic resins, and further preferably phosphorus-containing phenolic resins.

[0039] In the halogen-free flame-retardant resin composition of the present invention, the amount of the phosphorus-containing flame retardant can be 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, or 50 parts by weight.

[0040] Preferably, the halogen-free flame retardant resin composition further comprises a filler.

[0041] Preferably, the filler is selected from any one or a combination of at least two of aluminum hydroxide, silica, talcum powder, boehmite, zeolite, wollastonite, magnesium oxide, calcium silicate, calcium carbonate, clay or mica.

[0042] Preferably, the median particle size D50 of the filler is 1.8 - 3.2 μm (such as 1.8 μm, 2.0 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3.0 μm or 3.2 μm), and the maximum particle size D100 is 5.0 - 15.0 μm (such as 5.0 μm, 7.0 μm, 10.0 μm, 12.0 μm, 14.0 μm or 15.0 μm).

[0043] Preferably, the physical form of the filler can be flaky, rod-shaped, spherical, hollow spherical, granular, fibrous or plate-shaped, etc.

[0044] In the present invention, the filler can be selectively treated with a silane coupling agent.

[0045] Preferably, the content of the filler in the halogen-free flame retardant resin composition is 40 to 400 parts by weight, and can be, for example, 40 parts by weight, 50 parts by weight, 80 parts by weight, 100 parts by weight, 130 parts by weight, 150 parts by weight, 180 parts by weight, 200 parts by weight, 250 parts by weight, 300 parts by weight, 350 parts by weight or 400 parts by weight.

[0046] Preferably, the halogen-free flame retardant resin composition further comprises a curing accelerator.

[0047] Preferably, the curing accelerator is selected from any one or a combination of at least two of imidazole-based accelerators, pyridine-based curing agents, Lewis acid-based curing agents, amine-based curing agents, phenolic curing agents, cyanate ester compounds or active ester compounds.

[0048] On the other hand, the present invention provides a prepreg, which comprises the halogen-free flame retardant resin composition as described above.

[0049] Preferably, the prepreg comprises a base material and the halogen-free flame retardant resin composition attached to the base material;

[0050] Preferably, the prepreg comprises a base material and the halogen-free flame retardant resin composition attached to the base material after impregnation and drying treatment.

[0051] On the other hand, the present invention provides a metal foil-clad laminate, which comprises at least one prepreg as described above and metal foils covered on one side or both sides of the stacked prepregs.

[0052] On the other hand, the present invention provides a printed circuit board, which includes at least one of the prepreg or the metal foil clad laminate as described above.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] By selecting the content ranges of the low molecular weight and high molecular weight components in the benzoxazine resin, the present invention can improve the compatibility of the benzoxazine in the resin composition, achieve the effect of eliminating the resin deficiency defect of the bonding sheet, and at the same time maintain the good viscosity of the bonding sheet, ensuring that the Tg, dielectric properties, heat resistance, water absorption rate and flame retardancy of the copper clad laminate do not deteriorate. Specific Embodiments

[0055] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0056] The materials and grade information involved in the following examples and comparative examples are as follows:

[0057] A1: CNE type epoxy resin (o-cresol novolac epoxy resin): NPCN-704, epoxy equivalent: 200-220 g / eq, Nan Ya Resins;

[0058] A2: HP-7200HHH, DCPD type epoxy resin, epoxy equivalent: 280-290 g / eq, DIC of Japan;

[0059] A3: Phenol novolac epoxy resin, BNE-200, equivalent: 200 g / eq, Chang Chun Resins of Chinese Taiwan;

[0060] B1: Styrene maleic anhydride copolymer: SMA-EF40, Cray Valley of the United States;

[0061] B2: Active ester curing agent: DFE-617L, Dongcai of Sichuan;

[0062] C: Benzoxazine resin, self-made, information is as follows:

[0063]

[0064]

[0065] D1: Phosphorus-containing phenol formaldehyde resin: XZ92741, Dow of the United States;

[0066] D2: Phosphate ester flame retardant: PX200, Daihachi of Japan;

[0067] E: Spherical silica: Q099, D100 is 5 μm, JinYi of Chongqing

[0068] F: Catalyst: 2-ethyl-4-methylimidazole, Shikoku Kasei

[0069] Preparation Example

[0070] Taking the synthesis of ODA-type benzoxazine resin as an example, other types of benzoxazine resins can be prepared with reference to the following synthesis steps:

[0071] (1) Synthesis of benzoxazine resin C1

[0072] In a 500 mL three-necked flask equipped with a stirrer, a condenser and a thermometer, add 81 g (1 mol) of formaldehyde solution (37%), then add 100 mL of N,N-dimethylformamide (DMF) and stir well. Add 47.1 g (0.25 mol) of diaminodiphenylmethane in batches, controlling the reaction temperature not to exceed 30 °C. After the addition in batches is completed, maintain the reaction for 10 min, then add 75 g (0.5 mol) of phenol. Heat to bring the reaction solution to the reflux temperature, maintain the reaction for 0.5 hour, and stop heating. Take the resin layer and remove the solvent with a rotary evaporator to obtain a yellowish-brown viscous benzoxazine resin C1. Molecular weight distribution of C1: Proportion of low molecular weight with 250 ≤ Mn ≤ 350: 80%, Proportion of high molecular weight component with Mn ≥ 1500: 10%, Average number-average molecular weight Mn: 285, 190 °C GT: 600 s

[0073] (2) Synthesis of benzoxazine resin C2

[0074] In a 500 mL three-necked flask equipped with a stirrer, a condenser and a thermometer, add 81 g (1 mol) of formaldehyde solution (37%), then add 100 mL of N,N-dimethylformamide (DMF) and stir well. Add 47.1 g (0.25 mol) of diaminodiphenylmethane in batches, controlling the reaction temperature not to exceed 30 °C. After the addition in batches is completed, maintain the reaction for 10 min, then add 75 g (0.5 mol) of phenol. Heat to bring the reaction solution to the reflux temperature, maintain the reaction for 1 hour, and stop heating. Take the resin layer and remove the solvent with a rotary evaporator to obtain a yellowish-brown viscous benzoxazine resin C2. Molecular weight distribution of C2: Proportion of low molecular weight component with 250 ≤ Mn ≤ 350: 70%, Proportion of high molecular weight component with Mn ≥ 1500: 15%, Average number-average molecular weight Mn: 480, 190 °C GT: 501 s

[0075] (3) Synthesis of benzoxazine resin C3

[0076] In a 500 mL three-necked flask equipped with a stirrer, a condenser and a thermometer, 81 g (1 mol) of formaldehyde solution (37%) was added, and then 100 mL of N,N-dimethylformamide (DMF) was added and stirred evenly. 47.1 g (0.25 mol) of diaminodiphenylmethane was added in batches, and the reaction temperature was controlled not to exceed 30 °C. After the addition in batches was completed, the reaction was maintained for 10 min, and then 75 g (0.5 mol) of phenol was added. The mixture was heated to the reflux temperature and the reaction was maintained for 2 hours, then the heating was stopped. The resin layer was taken and the solvent was removed by a rotary evaporator to obtain a yellowish-brown viscous benzoxazine resin C3. Molecular weight distribution of C3: Proportion of low molecular weight components with 250 ≤ Mn ≤ 350: 50%, Proportion of high molecular weight components with Mn ≥ 1500: 30%, Average number-average molecular weight Mn: 550, GT at 190 °C: 405 s.

[0077] (4) Synthesis of benzoxazine resin C4

[0078] In a 500 mL three-necked flask equipped with a stirrer, a condenser and a thermometer, 81 g (1 mol) of formaldehyde solution (37%) was added, and then 100 mL of N,N-dimethylformamide (DMF) was added and stirred evenly. 47.1 g (0.25 mol) of diaminodiphenylmethane was added in batches, and the reaction temperature was controlled not to exceed 30 °C. After the addition in batches was completed, the reaction was maintained for 10 min, and then 75 g (0.5 mol) of phenol was added. The mixture was heated to the reflux temperature and the reaction was maintained for 3 hours, then the heating was stopped. The resin layer was taken and the solvent was removed by a rotary evaporator to obtain a yellowish-brown viscous benzoxazine resin C4. Molecular weight distribution of C4: Proportion of low molecular weight components with 250 ≤ Mn ≤ 350: 40%, Proportion of high molecular weight components with Mn ≥ 1500: 31%, Average number-average molecular weight Mn: 890, GT at 190 °C: 320 s.

[0079] (5) Synthesis of benzoxazine resin C5

[0080] In a 500 mL three-necked flask equipped with a stirrer, a condenser and a thermometer, 81 g (1 mol) of formaldehyde solution (37%) was added, and then 100 mL of N,N-dimethylformamide (DMF) was added and stirred evenly. 47.1 g (0.25 mol) of diaminodiphenylmethane was added in batches, and the reaction temperature was controlled not to exceed 30 °C. After the addition in batches was completed, the reaction was maintained for 10 min, and then 75 g (0.5 mol) of phenol was added. The mixture was heated to reach the reflux temperature, and the reaction was maintained for 4 hours, and then the heating was stopped. The resin layer was taken, and the solvent was removed by a rotary evaporator to obtain a yellowish-brown viscous benzoxazine resin C5. Molecular weight distribution of C5: Proportion of low molecular weight components with 250 ≤ Mn ≤ 350: 30%, Proportion of high molecular weight components with Mn ≥ 1500: 50%, Average number average molecular weight Mn: 1480, GT at 190 °C: 280 s.

[0081] (6) Synthesis of benzoxazine resin C6

[0082] In a 500 mL three-necked flask equipped with a stirrer, a condenser and a thermometer, 81 g (1 mol) of formaldehyde solution (37%) was added, and then 100 mL of N,N-dimethylformamide (DMF) was added and stirred evenly. 47.1 g (0.25 mol) of diaminodiphenylmethane was added in batches, and the reaction temperature was controlled not to exceed 30 °C. After the addition in batches was completed, the reaction was maintained for 10 min, and then 75 g (0.5 mol) of phenol was added. The mixture was heated to reach the reflux temperature, and the reaction was maintained for 5 hours, and then the heating was stopped. The resin layer was taken, and the solvent was removed by a rotary evaporator to obtain a yellowish-brown viscous benzoxazine resin C6. Molecular weight distribution of C6: Proportion of low molecular weight components with 250 ≤ Mn ≤ 350: 0, Proportion of high molecular weight components with Mn ≥ 1500: 95%, Average number average molecular weight Mn: 1680, GT at 190 °C: 98 s.

[0083] The formulation compositions and physical property data of each example are shown in Table 1, and the formulation compositions and physical property data of the comparative examples are shown in Table 2.

[0084] Table 1

[0085]

[0086] Table 2

[0087]

[0088]

[0089] Note: In Table 2,

[0090] "O" indicates no resin defect / fisheye defect,

[0091] "X" indicates having resin defect / fisheye defect,

[0092] "NG" indicates that the T288 test fails.

[0093] "OK" indicates that the 288 test passes.

[0094] The above performance test methods are as follows:

[0095] (1) Viscosity: Tested using a rotational viscometer, test temperature: 174 °C, gear: IV.

[0096] (2) Glass transition temperature: Differential scanning calorimetry (DSC), determined according to the DSC method specified in IPC-TM-650 2.4.25.

[0097] (3) Dielectric constant (1 GHz): Measured according to the parallel plate capacitance method, in accordance with the method specified in IPC-TM-650 2.5.5.9.

[0098] (4) Water absorption rate: After etching the copper foil on the surface of the copper clad laminate, dry the substrate and weigh the original weight. Then place the substrate in a pressure cooker and process it at 120 °C and 150 KPa for two hours. Take it out, dry it with a dry cloth, and weigh the weight of the sample after water absorption. The PCT water absorption rate is (weight after cooking - weight before cooking) / weight before cooking.

[0099] (5) CTE-Z: Measured using a thermomechanical analyzer, in accordance with the method specified in IPC-TM-650 2.4.24.

[0100] (6) T288: Measured using a thermomechanical analyzer, in accordance with the method specified in IPC-TM-650 2.4.24.1.

[0101] (7) Flammability: Determined according to the vertical burning method of the UL-94 standard.

[0102] From the appearance of the prepreg: Compared with Examples 1-8, due to the use of benzoxazine C1 and C2 with a low molecular content exceeding 51%, resin deficiency defects appear in the appearance of the prepregs of Comparative Examples 1, 2, and 7. In Comparative Examples 3 and 4, due to the use of benzoxazine C5 and C6 with a high molecular weight (Mn≥1500) accounting for more than 32%, the problem of excessive viscosity of the prepreg appears, which is not conducive to lamination and filling with glue.

[0103] In terms of the performance of the board: Compared with Example 7, in Comparative Example 5, due to the lower amount of benzoxazine used, the Tg of the board decreased significantly. In Comparative Example 7, the higher amount of benzoxazine used led to a significant increase in the viscosity of the prepreg. In Comparative Example 6, the amount of the low-dielectric curing agent used was too low, resulting in a significant increase in the dielectric constant and deterioration of the dielectric properties. In Comparative Example 8, the excessive amount of the phosphorus-containing flame retardant used led to an increase in the water absorption rate of the board and the failure of T288, indicating a decrease in heat resistance. In Comparative Example 7, the too low amount of the phosphorus-containing flame retardant used led to a decrease in the flame retardancy of the board, failing to meet the requirements of V-0 level.

[0104] The applicant declares that the present invention uses the above embodiments to illustrate the halogen-free flame-retardant resin composition, prepreg, laminate and printed circuit board of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A halogen-free flame-retardant resin composition, characterized in that, Comprising the following components in parts by weight: (A) Epoxy resin: 100 parts by weight; (B) Low-dielectric curing agent: 10 - 75 parts by weight; (C) Benzoxazine resin: 5 - 40 parts by weight; (D) Phosphorus-containing flame retardant: 20 - 50 parts by weight; In the said benzoxazine resin, the weight percentage of the component with a number-average molecular weight of 250 - 350 is ≤ 51%, and the weight percentage of the component with a number-average molecular weight above 1500 is < 32%; The said epoxy resin comprises o-cresol novolac epoxy resin and dicyclopentadiene-type epoxy resin; The said low-dielectric curing agent includes acid anhydride curing agent and / or active ester curing agent.

2. The halogen-free flame-retardant resin composition according to claim 1, wherein The epoxy equivalent of the said epoxy resin is 150 - 600 g / eq.

3. The halogen-free flame retardant resin composition according to claim 1, characterized in that, The content of dicyclopentadiene-type epoxy resin in the said epoxy resin is 20 - 40 parts by weight.

4. The halogen-free flame retardant resin composition according to claim 1, wherein The said acid anhydride curing agent is selected from any one or a combination of at least two of the following B11 or B12: wherein, n:x = 1:1 - 8:

1.

5. The halogen-free flame retardant resin composition according to claim 1, wherein The content of acid anhydride curing agent in the said low-dielectric curing agent is 1 - 50 parts by weight.

6. The halogen-free flame retardant resin composition according to claim 1, wherein The said active ester curing agent is selected from any one or a combination of at least two of the active esters having the following B21 or B22 structure: In B21, X is phenyl or naphthyl, j is 0 or 1, k is 0 or 1, and n represents the repeating unit is 1; In B22, m, n, q are independently integers from 1 to 6, X is phenyl or naphthyl, and Y is the following group: where K is 0 or 1.

7. The halogen-free flame retardant resin composition according to claim 1, characterized in that, The said benzoxazine resin is selected from any one or a combination of at least two of bisphenol A-type benzoxazine resin, bisphenol F-type benzoxazine resin, bisphenol S-type benzoxazine resin, DDM-type benzoxazine resin, ODA-type benzoxazine resin, phenolphthalein-type benzoxazine resin or DCPD-type benzoxazine resin.

8. The halogen-free flame retardant resin composition according to claim 1, characterized in that, The said phosphorus-containing flame retardant is selected from inorganic phosphorus-based flame retardants and / or organic phosphorus-based flame retardants.

9. The halogen-free flame retardant resin composition according to claim 8, wherein The said inorganic phosphorus-based flame retardants are selected from any one or a combination of at least two of red phosphorus, ammonium phosphate, phosphoric acid amide, phosphoric acid or phosphine oxide.

10. The halogen-free flame retardant resin composition according to claim 9, wherein, The said ammonium phosphate includes any one or a combination of at least two of monoammonium phosphate, diammonium phosphate or triammonium phosphate.

11. The halogen-free flame retardant resin composition according to claim 8, wherein The said organic phosphorus-based flame retardants are selected from any one or a combination of at least two of aromatic phosphates, monosubstituted phosphonic acid diesters, disubstituted phosphinic acid esters, metal salts of disubstituted phosphinic acids, cyclic organic phosphorus compounds or phosphorus-containing phenolic resins.

12. The halogen-free flame-retardant resin composition according to claim 11, wherein The said organic phosphorus-based flame retardants are selected from any one or a combination of at least two of aromatic phosphates, metal salts of disubstituted phosphinic acids or phosphorus-containing phenolic resins.

13. The halogen-free flame retardant resin composition according to claim 12, wherein, The said organic phosphorus-based flame retardants are selected from phosphorus-containing phenolic resins.

14. The halogen-free flame retardant resin composition according to claim 1, characterized in that, The said halogen-free flame-retardant resin composition further includes a filler.

15. The halogen-free flame retardant resin composition according to claim 14, wherein The said filler is selected from any one or a combination of at least two of aluminum hydroxide, silica, talc powder, boehmite, zeolite, wollastonite, magnesium oxide, calcium silicate, calcium carbonate, clay or mica.

16. The halogen-free flame retardant resin composition according to claim 14, characterized in that, The median particle size D50 of the said filler is 1.8 - 3.2 μm, and the maximum particle size D100 is 5.0 - 15.0 μm.

17. The halogen-free flame-retardant resin composition according to claim 14, wherein The physical form of the said filler can be flaky, rod-shaped, spherical, hollow spherical, granular, fibrous or plate-shaped.

18. The halogen-free flame retardant resin composition according to claim 14, wherein, The content of the filler in the halogen-free flame retardant resin composition is 40 to 400 parts by weight.

19. The halogen-free flame retardant resin composition according to claim 1, characterized in that, The halogen-free flame retardant resin composition further includes a curing accelerator.

20. The halogen-free flame retardant resin composition according to claim 19, wherein, The curing accelerator is selected from any one or a combination of at least two of imidazole-based accelerators, pyridine-based curing agents, Lewis acid-based curing agents, amine-based curing agents, phenolic curing agents, cyanate ester compounds or active ester compounds.

21. A prepreg, characterized in that, The prepreg includes the halogen-free flame retardant resin composition according to any one of claims 1-20.

22. A metal-clad laminate, characterized in that, The metal foil-clad laminate includes at least one prepreg according to claim 21 and metal foils coated on one or both sides of the stacked prepregs.

23. A printed circuit board, characterized in that, The printed circuit board includes at least one of the prepreg according to claim 21 or the metal foil-clad laminate according to claim 22.

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