Halogen-free copper-clad plate and preparation method thereof

Abstract

The invention provides a halogen-free copper-clad plate and a preparation method thereof, and belongs to the technical field of materials. Hollow silicon dioxide microspheres with inner layers containing fluorine are prepared, the surfaces of the hollow silicon dioxide microspheres are modified through phytic acid and coated with nano AlN powder to form a composite material, the composite material is modified through a silane coupling agent KH560 and reacts with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, the prepared flame-retardant modified composite material is mixed with urea resin and 4, 4 '-diaminodiphenyl ether type benzoxazine to react, and the flame-retardant modified composite material is prepared. Uniformly coating the mixture on glass fiber cloth, and drying to obtain a fiber cloth layer; and laminating the fiber cloth, pasting copper foils on the two surfaces of the fiber cloth, and pressing to obtain the halogen-free copper-clad plate. The halogen-free copper-clad plate prepared by the invention has the advantages of excellent dielectric property, low water absorption rate, good mechanical property and heat dissipation performance, better heat resistance, better flame retardance, stable processing size and wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of materials, and in particular to a halogen-free copper clad laminate and a preparation method thereof. Background Art

[0002] The full name of copper clad laminate is copper clad laminate, which is a product made of glass fiber cloth impregnated with resin, covered with copper foil on one or both sides, and hot pressed. It is a printed circuit board material widely used in the electronics industry.

[0003] Copper clad laminate is the basic material of the electronic information industry. It often causes fire and damages objects due to its low flame retardancy. Therefore, its flame retardancy is particularly important. Halogen flame retardants are commonly used in copper clad laminates. The most commonly used halogen flame retardant is bromine flame retardant, which has high flame retardant efficiency and is widely used. It can enhance flame retardancy and thermal stability when used in conjunction with phosphorus flame retardants. However, halogen flame retardants will produce a large amount of corrosive gases, which are easy to pollute the environment and its application is limited. The existing copper clad laminates have good performance in various aspects, but lack flame retardancy. In addition, the high-speed transmission of high-frequency signals in printed circuit boards will be affected by electrical loss and series interference. If these effects are to be eliminated, the copper clad laminate must have a low dielectric constant and dielectric loss. As a signal transmission material, its dielectric material and copper foil should have excellent bonding properties to prevent interlayer damage during processing. At the same time, since moisture will also increase dielectric loss and affect product performance, the copper clad laminate dielectric material should have a low water absorption rate.

[0004] Therefore, it is of great significance to develop a copper clad laminate with high flame retardancy, low dielectric constant and low water absorption. Summary of the invention

[0005] The object of the present invention is to provide a halogen-free copper clad laminate and a preparation method thereof, which has excellent dielectric properties, low water absorption, good mechanical properties and heat dissipation properties, good heat resistance, good flame retardancy, stable processing dimensions, and broad application prospects.

[0006] The technical solution of the present invention is achieved in this way: The invention provides a method for preparing a halogen-free copper clad laminate. The method comprises the following steps: preparing hollow silica microspheres containing fluorine in an inner layer, modifying the surface of the hollow silica microspheres with phytic acid, coating the microspheres with nano AlN powder to form a composite material, modifying the microspheres with a silane coupling agent KH560, reacting the microspheres with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, mixing the prepared flame-retardant modified composite material with urea-formaldehyde resin and 4,4'-diaminodiphenyl ether type benzoxazine, uniformly coating the microspheres on glass fiber cloth, drying the microspheres to obtain a fiber cloth layer; stacking the fiber cloths, pasting copper foils on both sides of the microspheres, pressing the microspheres to obtain a halogen-free copper clad laminate.

[0007] As a further improvement of the present invention, the following steps are included: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: adding fluorine-containing silane to water, adjusting the pH value of the solution, stirring the reaction, centrifuging, washing, spray drying, and obtaining hollow silica microspheres containing fluorine in the inner layer; S2. Preparation of phytic acid-modified silica microspheres: adding the inner layer of fluorine-containing hollow silica microspheres, phytic acid, and dipotassium hydrogen phosphate to water, stirring and mixing, hydrothermal reaction, centrifugation, washing, and drying to obtain phytic acid-modified silica microspheres; S3. Preparation of nano AlN powder: Aluminum powder and melamine were mixed, ball-milled under inert gas protection, and calcined to obtain nano AlN powder; S4. Preparation of modified composite material: mixing nano-AlN powder and phytic acid-modified silica microspheres to obtain a composite material, adding the composite material to ethanol, adding silane coupling agent KH560, heating and stirring to react, centrifuging, washing, and drying to obtain a modified composite material; S5. Flame retardant modification: The modified composite material and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to toluene, triphenylphosphine was added, the reaction was heated under reflux with stirring, filtered, washed, aged with ethanol, and dried to obtain a flame retardant modified composite material; S6. Preparation of modified benzoxazine resin; urea-formaldehyde resin and 4,4'-diaminodiphenyl ether type benzoxazine were uniformly mixed, butanone was added to adjust the solid content, a flame retardant modified composite material was added, the reaction was stirred, and a accelerator was added to obtain a modified benzoxazine resin; S7. Preparation of halogen-free copper clad laminate: uniformly coating the modified benzoxazine resin on glass fiber cloth, drying, and obtaining a fiber cloth layer; stacking the fiber cloth layers, pasting copper foil on both sides, and pressing to obtain a halogen-free copper clad laminate.

[0008] As a further improvement of the present invention, the ratio of fluorine-containing silane and water in step S1 is 10-12:70-80, the pH value of the adjusted solution is 10-11, and the stirring reaction time is 55-65°C for 8-10h.

[0009] Preferably, the fluorine-containing silane is selected from at least one of dodecafluoroheptylpropyltrimethoxysilane, dodecafluoroheptylpropylmethyldimethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane or 1H,1H,2H,2H-perfluorooctyltrimethoxysilane.

[0010] As a further improvement of the present invention, in step S2, the mass ratio of the inner layer fluorine-containing hollow silica microspheres, phytic acid, and dipotassium hydrogen phosphate is 10-15:4-6:0.5-1, the temperature of the hydrothermal reaction is 120-140° C., and the time is 5-7 hours.

[0011] As a further improvement of the present invention, the molar ratio of aluminum powder to melamine in step S3 is 1:1, the calcination temperature is 550-650° C., the time is 1-2 h, and the ball milling time is 5-7 h.

[0012] As a further improvement of the present invention, in step S4, the mass ratio of the nano-AlN powder, phytic acid-modified silica microspheres and silane coupling agent KH560 is 5-7:10:3-5, and the temperature of the heating and stirring reaction is 40-50° C. and the time is 2-4 hours.

[0013] As a further improvement of the present invention, the mass ratio of the modified composite material, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triphenylphosphine in step S5 is 10-12:1-2:0.01-0.012, the heating reflux stirring reaction time is 4-6h, and the ethanol aging time is 24-27h.

[0014] As a further improvement of the present invention, in step S6, the mass ratio of the urea-formaldehyde resin, 4,4'-diaminodiphenyl ether type benzoxazine, the flame retardant modified composite material and the accelerator is 15-25:65-70:7-10:0.5-1, the stirring reaction time is 10-12h, the adjusted solid content is 55-65%, and the accelerator is dicyandiamide.

[0015] As a further improvement of the present invention, the drying temperature in step S7 is 150-160°C, the time is 1-2h, the number of fiber cloth layers is 8-10, the copper foil is 35μm, and the pressing conditions are to increase the temperature to 130-140°C at 5°C / min under a pressure of 0.8-1MPa, increase the pressure to 4-5MPa and maintain the pressure for 10-15min, then increase the temperature to 210-230°C at 5°C / min and maintain the temperature for 60-80min, then reduce to room temperature and release the pressure.

[0016] The present invention further protects a halogen-free copper clad laminate prepared by the above preparation method.

[0017] The present invention has the following beneficial effects: In the preparation process of the hollow silica microspheres with fluorine in the inner layer of the present invention, the fluorine-containing silane is initially insoluble in water, and disperses into small droplets during the stirring process. At this time, the fluorine-containing group will spontaneously face the inside of the shell due to hydrophobicity, and the silane part is exposed to the outside. Under alkaline conditions, the silane part is hydrolyzed to form a silica layer, thereby forming hollow spherical nanoparticles. In addition to the air inside the cavity that can reduce the dielectric constant, the introduction of the fluorine-containing group on the inner surface further reduces the dielectric constant. And the fluorine-containing group does not directly contact the resin, avoiding the problem of poor compatibility.

[0018] The prepared inner layer of fluorine-containing hollow silica microspheres is reacted with phytic acid through the hydroxyl groups on the surface to prepare phytic acid-modified silica microspheres, which increases the phosphorus content in the resin and has a good synergistic flame retardant effect. However, since phytic acid contains abundant oxygen atoms and has good affinity for water, the water absorption of the prepared material is improved. Therefore, in the present invention, the prepared phytic acid-modified silica microspheres and the prepared nano-AlN powder can form a complex bond with Al through phosphate to fix the AlN powder, and the prepared composite material wraps the phytic acid-modified silica microspheres, thereby effectively isolating water. In addition, the thermal conductivity of the resin is significantly improved, so that the prepared halogen-free copper clad laminate has good heat dissipation, and at the same time, it has no obvious effect on the water absorption of the resin material.

[0019] The present invention further modifies the surface of the prepared composite material by a silane coupling agent with an epoxy group, so that part of the epoxy group can be coupled with DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) under the catalysis of triphenylphosphine, so that the prepared flame-retardant modified composite material has a high content of nitrogen, phosphorus and silicon, thereby greatly improving its flame retardant performance and mechanical modification effect on the resin material, and at the same time, having a lower dielectric constant and low water absorption.

[0020] Benzoxazine resin (BOZ) is a new type of thermosetting resin made by condensation of phenol, primary amine and formaldehyde, and its molecule contains a six-membered heterocyclic chair structure of C, N and O. The cured product of benzoxazine has the characteristics of low dielectric constant, low water absorption, high heat resistance, stable processing dimensions and flame retardancy, but has disadvantages such as large linear expansion coefficient, insufficient heat resistance and poor strength. Urea-formaldehyde resin reacts with the remaining epoxy groups on the flame-retardant modified composite material, so that the flame-retardant modified composite material can be well dispersed in the resin material, thereby greatly avoiding the influence of inorganic particles on the mechanical properties of the resin due to uneven dispersion, greatly improving its compatibility, and thus having good flame retardant and mechanical improvement effects, and further reducing the dielectric constant and water absorption.

[0021] The halogen-free copper clad laminate prepared by the present invention has excellent dielectric properties, low water absorption, good mechanical properties and heat dissipation properties, good heat resistance, good flame retardancy, stable processing dimensions, and broad application prospects. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0023] This embodiment provides a method for preparing a halogen-free copper clad laminate, comprising the following steps: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: 10 g of dodecafluoroheptylpropyltrimethoxysilane was added to 70 mL of water, the pH value of the solution was adjusted to 10, the reaction was stirred at 55° C. for 8 h, centrifuged, washed, and spray-dried to obtain hollow silica microspheres containing fluorine in the inner layer; S2. Preparation of phytic acid-modified silica microspheres: 10 g of hollow silica microspheres containing fluorine in the inner layer, 4 g of phytic acid, and 0.5 g of dipotassium hydrogen phosphate were added to 200 mL of water, stirred for 10 min, subjected to hydrothermal reaction at 120° C. for 5 h, centrifuged, washed, and dried to obtain phytic acid-modified silica microspheres; S3. Preparation of nano AlN powder: Aluminum powder and melamine were mixed in a molar ratio of 1:1, ball-milled for 5 h under nitrogen protection, and calcined at 550 ° C for 1 h to obtain nano AlN powder; S4. Preparation of modified composite material: 5 g of nano-AlN powder and 10 g of phytic acid-modified silica microspheres were stirred and mixed for 15 min to obtain a composite material, the composite material was added to 200 mL of ethanol, 3 g of silane coupling agent KH560 was added, heated to 40° C., stirred for reaction for 2 h, centrifuged, washed, and dried to obtain a modified composite material; S5 flame retardant modification: 10g of the modified composite material and 1g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to 200mL of toluene, 0.01g of triphenylphosphine was added, the reaction was heated under reflux with stirring for 4h, filtered, washed, aged with ethanol for 24h, and dried to obtain a flame retardant modified composite material; S6. Preparation of modified benzoxazine resin; 15 g of urea-formaldehyde resin and 65 g of 4,4'-diaminodiphenyl ether type benzoxazine were stirred and mixed for 15 min, butanone was added to adjust the solid content to 55%, 7 g of flame retardant modified composite material was added, the reaction was stirred for 10 h, 0.5 g of dicyandiamide was added to obtain a modified benzoxazine resin; S7. Preparation of halogen-free copper clad laminate: The modified benzoxazine resin is uniformly coated on 2116 glass fiber cloth, and dried at 150°C for 1h to obtain a fiber cloth layer; 8 layers of fiber cloth are stacked, and 35μm copper foil is pasted on both sides. The temperature is increased to 130°C at 5°C / min under a pressure of 0.8MPa, and the pressure is increased to 4MPa and maintained at the pressure for 10min, then the temperature is increased to 210°C at 5°C / min and maintained at the pressure for 60min, then the temperature is reduced to room temperature, and the pressure is released to obtain a halogen-free copper clad laminate. Example 2

[0024] This embodiment provides a method for preparing a halogen-free copper clad laminate, comprising the following steps: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: 12 g of 3,3,3-trifluoropropyltrimethoxysilane was added to 80 mL of water, the pH value of the solution was adjusted to 11, the reaction was stirred at 65°C for 10 h, centrifuged, washed, and spray-dried to obtain hollow silica microspheres containing fluorine in the inner layer; S2. Preparation of phytic acid-modified silica microspheres: 15 g of hollow silica microspheres containing fluorine in the inner layer, 6 g of phytic acid, and 1 g of dipotassium hydrogen phosphate were added to 200 mL of water, stirred for 10 min, subjected to hydrothermal reaction at 140° C. for 7 h, centrifuged, washed, and dried to obtain phytic acid-modified silica microspheres; S3. Preparation of nano AlN powder: Aluminum powder and melamine were mixed in a molar ratio of 1:1, ball milled for 7 h under nitrogen protection, and calcined at 650 ° C for 2 h to obtain nano AlN powder; S4. Preparation of modified composite material: 7 g of nano-AlN powder and 10 g of phytic acid-modified silica microspheres were stirred and mixed for 15 min to obtain a composite material, the composite material was added to 200 mL of ethanol, 5 g of silane coupling agent KH560 was added, heated to 50° C., stirred for reaction for 4 h, centrifuged, washed, and dried to obtain a modified composite material; S5 flame retardant modification: 12g of the modified composite material and 2g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to 200mL of toluene, 0.012g of triphenylphosphine was added, the reaction was heated under reflux with stirring for 6h, filtered, washed, aged with ethanol for 27h, and dried to obtain a flame retardant modified composite material; S6. Preparation of modified benzoxazine resin; 25 g of urea-formaldehyde resin and 70 g of 4,4'-diaminodiphenyl ether type benzoxazine were stirred and mixed for 15 min, butanone was added to adjust the solid content to 65%, 10 g of flame retardant modified composite material was added, the reaction was stirred for 12 h, 1 g of dicyandiamide was added to obtain a modified benzoxazine resin; S7. Preparation of halogen-free copper clad laminate: The modified benzoxazine resin is uniformly coated on 2116 glass fiber cloth, and dried at 160°C for 2h to obtain a fiber cloth layer; 10 layers of fiber cloth are stacked, and 35μm copper foil is pasted on both sides, and the temperature is increased to 140°C at 5°C / min under a pressure of 1MPa, and the pressure is increased to 5MPa and maintained for 15min, and then the temperature is increased to 230°C at 5°C / min and maintained for 80min, and then the temperature is reduced to room temperature and the pressure is released to obtain a halogen-free copper clad laminate. Example 3

[0025] This embodiment provides a method for preparing a halogen-free copper clad laminate, comprising the following steps: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: 11 g of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane was added to 75 mL of water, the pH value of the solution was adjusted to 10.5, the reaction was stirred at 60°C for 9 hours, centrifuged, washed, and spray-dried to obtain hollow silica microspheres containing fluorine in the inner layer; S2. Preparation of phytic acid-modified silica microspheres: 12 g of hollow silica microspheres containing fluorine in the inner layer, 5 g of phytic acid, and 0.7 g of dipotassium hydrogen phosphate were added to 200 mL of water, stirred for 10 min, subjected to hydrothermal reaction at 130° C. for 6 h, centrifuged, washed, and dried to obtain phytic acid-modified silica microspheres; S3. Preparation of nano AlN powder: Aluminum powder and melamine were mixed in a molar ratio of 1:1, ball-milled for 6 h under nitrogen protection, and calcined at 600 ° C for 1.5 h to obtain nano AlN powder; S4. Preparation of modified composite material: 6 g of nano-AlN powder and 10 g of phytic acid-modified silica microspheres were stirred and mixed for 15 min to obtain a composite material, the composite material was added to 200 mL of ethanol, 4 g of silane coupling agent KH560 was added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain a modified composite material; S5 flame retardant modification: 11g of the modified composite material and 1.5g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to 200mL of toluene, 0.011g of triphenylphosphine was added, the reaction was heated to reflux with stirring for 5h, filtered, washed, aged with ethanol for 26h, and dried to obtain a flame retardant modified composite material; S6. Preparation of modified benzoxazine resin; 20 g of urea-formaldehyde resin and 67 g of 4,4'-diaminodiphenyl ether type benzoxazine were stirred and mixed for 15 min, butanone was added to adjust the solid content to 60%, 8.5 g of flame retardant modified composite material was added, the reaction was stirred for 11 h, 0.7 g of dicyandiamide was added to obtain a modified benzoxazine resin; S7. Preparation of halogen-free copper clad laminate: The modified benzoxazine resin is uniformly coated on 2116 glass fiber cloth, and dried at 155°C for 1.5h to obtain a fiber cloth layer; 9 layers of fiber cloth are stacked, and 35μm copper foil is pasted on both sides. The temperature is increased to 135°C at 5°C / min under a pressure of 0.9MPa, and the pressure is increased to 4.5MPa and maintained at pressure for 12min, and then the temperature is increased to 220°C at 5°C / min and maintained at pressure for 70min, and then the temperature is reduced to room temperature and the pressure is released to obtain a halogen-free copper clad laminate.

[0026] Comparative Example 1 Compared with Example 3, the difference is that ethyl orthosilicate is used instead of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane.

[0027] The details are as follows: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: 11 g of tetraethyl orthosilicate was added to 75 mL of water, the pH value of the solution was adjusted to 10.5, the reaction was stirred at 60° C. for 9 h, centrifuged, washed, and spray-dried to obtain hollow silica microspheres containing fluorine in the inner layer.

[0028] Comparative Example 2 Compared with Example 3, the difference is that step S2 is not performed.

[0029] The details are as follows: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: 11 g of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane was added to 75 mL of water, the pH value of the solution was adjusted to 10.5, the reaction was stirred at 60°C for 9 hours, centrifuged, washed, and spray-dried to obtain hollow silica microspheres containing fluorine in the inner layer; S2. Preparation of nano AlN powder: Aluminum powder and melamine were mixed in a molar ratio of 1:1, ball-milled for 6 h under nitrogen protection, and calcined at 600 ° C for 1.5 h to obtain nano AlN powder; S3. Preparation of modified composite material: 6 g of nano-AlN powder and 10 g of hollow silica microspheres containing fluorine in the inner layer were stirred and mixed for 15 min to obtain a composite material, the composite material was added to 200 mL of ethanol, 4 g of silane coupling agent KH560 was added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain a modified composite material; S4 flame retardant modification: 11g of the modified composite material and 1.5g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to 200mL of toluene, 0.011g of triphenylphosphine was added, the reaction was heated under reflux with stirring for 5h, filtered, washed, aged for 26h with ethanol, and dried to obtain a flame retardant modified composite material; S5. Preparation of modified benzoxazine resin; 20 g of urea-formaldehyde resin and 67 g of 4,4'-diaminodiphenyl ether type benzoxazine were stirred and mixed for 15 min, butanone was added to adjust the solid content to 60%, 8.5 g of flame retardant modified composite material was added, the reaction was stirred for 11 h, 0.7 g of dicyandiamide was added to obtain a modified benzoxazine resin; S6. Preparation of halogen-free copper clad laminate: The modified benzoxazine resin is uniformly coated on 2116 glass fiber cloth, and dried at 155°C for 1.5h to obtain a fiber cloth layer; 9 layers of fiber cloth are stacked, and 35μm copper foil is pasted on both sides. The temperature is increased to 135°C at 5°C / min under a pressure of 0.9MPa, and the pressure is increased to 4.5MPa and maintained at pressure for 12min, and then the temperature is increased to 220°C at 5°C / min and maintained at pressure for 70min, and then the temperature is reduced to room temperature and the pressure is released to obtain a halogen-free copper clad laminate.

[0030] Comparative Example 3 Compared with Example 3, the difference is that no nano AlN powder is added in step S4.

[0031] The details are as follows: S4. Preparation of modified composite materials: 16 g of phytic acid-modified silica microspheres were added to 200 mL of ethanol, and 4 g of silane coupling agent KH560 was added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain a modified composite material.

[0032] Comparative Example 4 Compared with Example 3, the difference is that the silane coupling agent KH560 modification is not performed in step S4.

[0033] The details are as follows: S4. Preparation of modified composite material: 6 g of nano-AlN powder and 10 g of phytic acid-modified silica microspheres were stirred and mixed for 15 min to prepare a composite material.

[0034] Comparative Example 5 Compared with Embodiment 3, the difference is that step S5 is not performed.

[0035] The details are as follows: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: 11 g of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane was added to 75 mL of water, the pH value of the solution was adjusted to 10.5, the reaction was stirred at 60°C for 9 hours, centrifuged, washed, and spray-dried to obtain hollow silica microspheres containing fluorine in the inner layer; S2. Preparation of phytic acid-modified silica microspheres: 12 g of hollow silica microspheres containing fluorine in the inner layer, 5 g of phytic acid, and 0.7 g of dipotassium hydrogen phosphate were added to 200 mL of water, stirred for 10 min, subjected to hydrothermal reaction at 130° C. for 6 h, centrifuged, washed, and dried to obtain phytic acid-modified silica microspheres; S3. Preparation of nano AlN powder: Aluminum powder and melamine were mixed in a molar ratio of 1:1, ball-milled for 6 h under nitrogen protection, and calcined at 600 ° C for 1.5 h to obtain nano AlN powder; S4. Preparation of modified composite material: 6 g of nano-AlN powder and 10 g of phytic acid-modified silica microspheres were stirred and mixed for 15 min to obtain a composite material, the composite material was added to 200 mL of ethanol, 4 g of silane coupling agent KH560 was added, heated to 45° C., stirred for reaction for 3 h, centrifuged, washed, and dried to obtain a modified composite material; S5. Preparation of modified benzoxazine resin; 20 g of urea-formaldehyde resin and 67 g of 4,4'-diaminodiphenyl ether type benzoxazine were stirred and mixed for 15 min, butanone was added to adjust the solid content to 60%, 8.5 g of the modified composite material was added, the reaction was stirred for 11 h, 0.7 g of dicyandiamide was added to obtain a modified benzoxazine resin; S6. Preparation of halogen-free copper clad laminate: The modified benzoxazine resin is uniformly coated on 2116 glass fiber cloth, and dried at 155°C for 1.5h to obtain a fiber cloth layer; 9 layers of fiber cloth are stacked, and 35μm copper foil is pasted on both sides. The temperature is increased to 135°C at 5°C / min under a pressure of 0.9MPa, and the pressure is increased to 4.5MPa and maintained at pressure for 12min, and then the temperature is increased to 220°C at 5°C / min and maintained at pressure for 70min, and then the temperature is reduced to room temperature and the pressure is released to obtain a halogen-free copper clad laminate.

[0036] Test Example 1 The halogen-free copper clad laminates prepared in Examples 1-3 of the present invention and Comparative Examples 1-5 were subjected to performance tests. The results are shown in Table 1.

[0037] The dielectric constant and dielectric loss of the copper clad laminate were measured using the SPDR type separated dielectric resonant cavity test method, and the average of the three results was taken. The test frequency was 5GHz. The water absorption of the copper clad laminate was measured according to IPC-TM-650 2.6. The test surface size was 50.8mm×50.8mm, the test temperature was 25℃, the test time was 24h, and the average of the three results was taken. The bending strength and peeling strength tests were carried out according to IPC-TM-6502.4 (Test Method Manual Mechanical Test Method). The peeling area was 80mm×10mm. The front and back sides of the copper clad laminate were tested 6 times to take the average value. The size of the bending specimen was 63.5mm×25.4mm×0.79mm, and the average value was taken after 3 measurements.

[0038] Table 1

[0039] It can be seen from the above table that the halogen-free copper clad laminates prepared in Examples 1-3 of the present invention have lower dielectric constants and dielectric losses, better mechanical properties, and lower water absorption.

[0040] Test Example 2 The halogen-free copper clad laminates prepared in Examples 1-3 of the present invention and Comparative Examples 1-5 were subjected to performance tests. The results are shown in Table 2.

[0041] Thermal conductivity: Thermal resistance meter, tested according to ASTM D5470 standard. Flammability: Flammability test chamber (flammability rating is UL94).

[0042] Table 2

[0043] It can be seen from the above table that the halogen-free copper clad laminates prepared in Examples 1-3 of the present invention have higher thermal conductivity and flame retardancy.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a halogen-free copper clad laminate, characterized in that: Hollow silica microspheres with fluorine in the inner layer are prepared, the surface is modified with phytic acid, coated with nano-AlN powder to form a composite material, modified with silane coupling agent KH560, reacted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, the flame-retardant modified composite material is mixed with urea-formaldehyde resin and 4,4'-diaminodiphenyl ether type benzoxazine, uniformly coated on glass fiber cloth, dried to obtain a fiber cloth layer; the fiber cloth is stacked, copper foil is pasted on both sides, and pressed to obtain a halogen-free copper clad laminate.

2. The preparation method according to claim 1, characterized in that: The following steps are involved: S1. Preparation of hollow silica microspheres containing fluorine in the inner layer: adding fluorine-containing silane to water, adjusting the pH value of the solution, stirring the reaction, centrifuging, washing, spray drying, and obtaining hollow silica microspheres containing fluorine in the inner layer; S2. Preparation of phytic acid-modified silica microspheres: adding the inner layer of fluorine-containing hollow silica microspheres, phytic acid, and dipotassium hydrogen phosphate to water, stirring and mixing, hydrothermal reaction, centrifugation, washing, and drying to obtain phytic acid-modified silica microspheres; S3. Preparation of nano AlN powder: Aluminum powder and melamine were mixed, ball-milled under inert gas protection, and calcined to obtain nano AlN powder; S4. Preparation of modified composite material: mixing nano-AlN powder and phytic acid-modified silica microspheres to obtain a composite material, adding the composite material to ethanol, adding silane coupling agent KH560, heating and stirring to react, centrifuging, washing, and drying to obtain a modified composite material; S5. Flame retardant modification: The modified composite material and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to toluene, triphenylphosphine was added, the reaction was heated under reflux with stirring, filtered, washed, aged with ethanol, and dried to obtain a flame retardant modified composite material; S6. Preparation of modified benzoxazine resin; urea-formaldehyde resin and 4,4'-diaminodiphenyl ether type benzoxazine were uniformly mixed, butanone was added to adjust the solid content, a flame retardant modified composite material was added, the reaction was stirred, and a accelerator was added to obtain a modified benzoxazine resin; S7. Preparation of halogen-free copper clad laminate: uniformly coating the modified benzoxazine resin on glass fiber cloth, drying, and obtaining a fiber cloth layer; stacking the fiber cloth layers, pasting copper foil on both sides, and pressing to obtain a halogen-free copper clad laminate.

3. The preparation method according to claim 2, characterized in that: In step S1, the ratio of fluorinated silane to water is 10-12:70-80, the pH value of the solution is adjusted to 10-11, and the stirring reaction time is 55-65° C. for 8-10 hours.

4. The preparation method according to claim 2, characterized in that: In step S2, the mass ratio of the inner layer fluorine-containing hollow silica microspheres, phytic acid, and dipotassium hydrogen phosphate is 10-15:4-6:0.5-1, and the temperature of the hydrothermal reaction is 120-140° C. and the time is 5-7 hours.

5. The preparation method according to claim 2, characterized in that: In step S3, the molar ratio of aluminum powder to melamine is 1:1, the calcination temperature is 550-650° C., the time is 1-2 h, and the ball milling time is 5-7 h.

6. The preparation method according to claim 2, characterized in that: In step S4, the mass ratio of the nano-AlN powder, the phytic acid-modified silica microspheres and the silane coupling agent KH560 is 5-7:10:3-5, and the temperature of the heating and stirring reaction is 40-50° C. and the time is 2-4 hours.

7. The preparation method according to claim 2, characterized in that: In step S5, the mass ratio of the modified composite material, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triphenylphosphine is 10-12:1-2:0.01-0.012, the heating reflux stirring reaction time is 4-6h, and the ethanol aging time is 24-27h.

8. The preparation method according to claim 2, characterized in that: In step S6, the mass ratio of urea-formaldehyde resin, 4,4'-diaminodiphenyl ether type benzoxazine, flame retardant modified composite material and accelerator is 15-25:65-70:7-10:0.5-1, the stirring reaction time is 10-12h, the adjusted solid content is 55-65%, and the accelerator is dicyandiamide.

9. The preparation method according to claim 2, characterized in that: The drying temperature in step S7 is 150-160°C, the time is 1-2h, the number of layers of the fiber cloth is 8-10, the copper foil is 35μm, and the pressing conditions are to increase the temperature to 130-140°C at 5°C / min under a pressure of 0.8-1MPa, increase the pressure to 4-5MPa and maintain the pressure for 10-15min, then increase the temperature to 210-230°C at 5°C / min and maintain the temperature for 60-80min, then reduce to room temperature and release the pressure.

10. A halogen-free copper clad laminate prepared by the preparation method according to any one of claims 1 to 9.

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