Halogen-free resin composition and high-Tg low-loss copper-clad plate prepared from same

Abstract

The invention discloses a halogen-free resin composition and a high-Tg low-loss copper-clad plate prepared from the halogen-free resin composition. The halogen-free resin composition comprises the following raw materials: a bismaleimide polymer, aromatic diamine, benzoxazine resin, a phosphorus flame retardant, an inorganic filler, an imidazole catalyst and a solvent. According to the invention, through prepolymerization of the bismaleimide polymer, especially the oligomer and the aromatic diamine, the brittleness problem of common bismaleimide is solved, the modified bismaleimide has excellent toughness, and the problems of bismaleimide precipitation and board resin agglomeration when a large amount of bismaleimide resin is used are solved.

Description

Technical Field

[0001] The present invention belongs to the field of high-frequency and high-speed copper-clad laminates, and particularly relates to a halogen-free resin composition and a high-Tg low-loss copper-clad laminate prepared therefrom. The copper-clad laminate has high Tg, high heat resistance, low dielectric loss, excellent copper foil peel strength and modulus retention rate, and can be applied to the field of packaging substrates. Background Art

[0002] The packaging substrate is a key component connecting the chip and the external circuit board, and its performance directly affects the overall performance of electronic products. With the rapid development of the electronics industry towards miniaturization, high performance and high reliability, low-loss and low coefficient of thermal expansion packaging substrates have emerged as the times require.

[0003] In high-speed and high-frequency circuits, the integrity of signal transmission is crucial. Due to the material or structural characteristics of traditional packaging substrates, signals will encounter significant losses during transmission, resulting in a decline in signal quality, which severely limits the performance improvement of devices such as 5G communication base stations and high-end servers. To meet the application requirements of high-speed signal transmission of the new generation of IC chips, it is required that the packaging substrate has an excellent low dielectric loss coefficient (Df) to achieve higher frequencies and lower losses, improve the bandwidth and signal-to-noise ratio of the PCB, and at the same time, it also needs to have good heat resistance, excellent mechanical properties and high-temperature dimensional stability.

[0004] Currently, using bismaleimide triazine resin (i.e., BT resin, prepared by combining bismaleimide and cyanate ester) as the main body and adding other blends such as epoxy resin and polyphenylene ether resin is the mainstream resin system for preparing packaging substrates, but the laminated sheets of this system cannot simultaneously achieve low loss (Low loss, Df between 0.005 - 0.01), low coefficient of thermal expansion, high peel strength, high flexural modulus, etc.

[0005] Patent CN113004856A provides a high-Tg thermosetting resin composition, its preparation method and application. This patent uses bismaleimide resin, various cyanate ester resins and biphenyl-type epoxy resin as the main body, and is formulated with an imidazole-type catalyst, a phosphorus-based or nitrogen-based flame retardant, inorganic fillers and organic solvents to form a glue solution, and then prepares a prepreg by a conventional method, and finally presses it into a copper-clad laminate. The glass transition temperature (Tg) of the obtained copper-clad laminate can reach 280 °C, Df is 0.008, but the peel strength of 6.6 lb / in (i.e., 1.16 N / mm) and the Z-axis coefficient of thermal expansion (Z-CTE) of 1.61% still cannot meet the high-reliability requirements of high-speed packaging substrates.

[0006] The resin system of Patent CN117924932A is a modified bismaleimide prepolymer, cyanate ester resin and other functional resins, and the functional resins include one or more of benzoxazine resin, modified polyphenylene ether resin and hydrocarbon resin. The laminate prepared from this adhesive solution has a Tg of 275 °C, a Z-CTE of 0.7%, and a Df of 0.0031, reaching the very low loss level, which has exceeded the low loss level.

[0007] The resin compositions described in the above patents respectively use BT resin in combination with epoxy resin or benzoxazine / modified polyphenylene ether / hydrocarbon resin. The structural polarity of BT resin is relatively low, resulting in unsatisfactory peel strength. Introducing epoxy resin will increase the Z-CTE and reduce the reliability of the carrier board. Using polyphenylene ether resin and hydrocarbon resin will greatly increase the cost of the solution and the Df exceeds the standard.

[0008] In summary, it is necessary to develop a copper clad laminate that can maintain the Df at the low loss level while ensuring high Tg, low Z-CTE, and high modulus retention rate of the board, and at the same time increase the peel strength to 1.5 N / mm to meet the requirements of high-speed packaging carrier boards. Summary of the Invention

[0009] The purpose of the present invention is to provide a halogen-free resin composition and a prepreg and a copper clad laminate prepared using the same to solve the above technical problems.

[0010] To solve the above technical problems, the present invention adopts the following technical solutions: A halogen-free resin composition, comprising the following raw materials: bismaleimide polymer, aromatic diamine, benzoxazine resin, phosphorus-based flame retardant, inorganic filler, imidazole catalyst, solvent.

[0011] Preferably, the bismaleimide polymer includes one or more of the compounds having the following general formula: (1)

[0012] (2)

[0013] (3) .

[0014] Preferably, in the general formula of the compound, the value range of n includes 2 to 100.

[0015] Preferably, it includes the following raw materials in parts by solid weight: The bismaleimide polymer: 50 to 200 parts; The aromatic diamine: 5 to 35 parts; The benzoxazine resin: 10 to 40 parts; The phosphorus-based flame retardant: 5 to 60 parts; The inorganic filler: 100 to 200 parts; The imidazole catalyst: 0.01 to 3 parts; The solvent: 120 to 200 parts.

[0016] Preferably, the aromatic diamine includes one or more of 4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether, and 4,4-diaminodiphenyl sulfone; the benzoxazine resin includes one or more of bisphenol A-type benzoxazine, bisphenol F-type benzoxazine, dicyclopentadiene benzoxazine, phenolphthalein-type benzoxazine, MDA (4,4'-diaminodiphenylmethane)-type benzoxazine, ODA (4,4'-diaminodiphenyl ether)-type benzoxazine, allylamine-type benzoxazine, and allyl bisphenol A-type benzoxazine; the phosphorus-based flame retardant includes one or more of inorganic phosphorus, condensed phosphate esters, phosphoric acid, hypophosphites, phosphorus oxides, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-phenyl-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, tris(2,6-dimethylphenyl)phosphine, and phosphazene; the inorganic filler includes one or more of silica, alumina, titanium oxide, mica, aluminum hydroxide, magnesium hydroxide, talc, aluminum borate, barium sulfate, and calcium carbonate; the imidazole catalyst includes one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole; the solvent includes one or more of acetone, butanone, methyl isobutyl ketone, N,N-dimethylformamide, propylene glycol methyl ether, toluene, and cyclohexanone A preparation method of the above-mentioned halogen-free resin composition includes: A. Adding the bismaleimide polymer and the aromatic diamine into the solvent, mixing and clarifying to obtain a clarified liquid; B. Heating the clarified liquid and stirring for a prepolymerization reaction to obtain a prepolymer precursor liquid; C. After cooling the prepolymer precursor liquid, adding the benzoxazine resin, mixing and dissolving, then adding the phosphorus-based flame retardant and the inorganic filler, and mixing evenly to obtain a mixture; D. Adding the imidazole catalyst to the mixture to adjust the gelation time to obtain the halogen-free resin composition.

[0017] The flame retardant and inorganic filler are insoluble in the liquid and can only be dispersed evenly by stirring. If added simultaneously with the benzoxazine resin, it may cause problems such as incomplete dissolution and slow dissolution rate of the benzoxazine resin. Therefore, it is necessary to first add the benzoxazine resin to the prepolymer precursor solution to dissolve it completely, then add the flame retardant and inorganic filler and stir and mix them, and finally add the imidazole catalyst to condition the gelation time to obtain a halogen-free resin composition based on bismaleimide resin.

[0018] Preferably, in step A, the temperature of the mixing and clarification includes room temperature; in step B, the reaction temperature of the prepolymerization reaction includes 80-130 °C, and the reaction time includes 30-300 minutes; in step C, the temperature of the cooling includes room temperature, and the way of mixing evenly includes stirring for 60-200 minutes; in step D, the operation of conditioning the gelation time includes: conditioning the gelation time for 150-400 s at a test temperature of 150-180 °C.

[0019] When conditioning the gelation time, if the gelation time is greater than 400 s, additional imidazole catalyst needs to be added until the gelation time is 150-400 s.

[0020] Conditioning the gelation time for 150-400 s at a test temperature of 150-180 °C facilitates the adjustment of the baking time and temperature during the subsequent production of the prepreg; if the gelation time is too long, both the baking time and temperature will become longer and higher, which is not conducive to operation.

[0021] An application of the above halogen-free resin composition, used for one or more of prepregs and copper clad laminates.

[0022] A prepreg obtained by the above application.

[0023] Preferably, the preparation method of the prepreg is as follows: Immerse the fiberglass cloth in the halogen-free resin composition, and after immersion, bake it at a temperature of 150-200 °C for 2-9 minutes to obtain a prepreg.

[0024] A copper clad laminate obtained by the above application.

[0025] Preferably, the preparation method of the copper clad laminate is as follows: Take 4-10 sheets of the prepreg, stack them, cover copper foils on the upper and lower surfaces respectively, and then perform hot pressing to obtain a copper clad laminate.

[0026] Implementing the present invention has the following beneficial effects: 1. In the present invention, through the prepolymerization of bismaleimide polymers, especially oligomers and aromatic diamines, the brittleness problem of ordinary bismaleimide is solved. After modification, it has excellent toughness, and the problems of bismaleimide precipitation and resin agglomeration in the plate when a large amount of bismaleimide resin is used are also solved.

[0027] 2. In the present invention, a network structure is formed after the prepolymerization of bismaleimide oligomers and aromatic diamines. Based on this network structure, the curing crosslinking density of the system is increased, and the Tg, modulus retention rate, and peel strength of the substrate are all improved. In contrast, using bismaleimide monomers and aromatic diamines for prepolymerization can only achieve a chain extension effect and form a linear structure, which cannot increase the curing crosslinking density and cannot reach the effect of the present invention.

[0028] 3. In the present invention, by controlling the addition ratio of bismaleimide oligomers and aromatic diamines, as well as the prepolymerization temperature and time, network structures with different crosslinking densities can be obtained, and substrates with different Tg, moduli, and peel strengths can be obtained in subsequent preparation steps.

[0029] 4. The prepolymer prepared in the present invention has poor wettability on fiberglass cloth, which is also a problem existing in all bismaleimide resins. By adding benzoxazine resin and blending it with the prepolymer, the problem of poor wetting can be solved; and the added benzoxazine will react with the remaining maleimide groups in the prepolymer, bridging the original network structure and maintaining its toughness, avoiding the mutual polymerization of maleimide groups to form a larger, lower-fluidity, and poorer-toughness network structure. Specific Embodiments

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments.

[0031] Example 1: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane (DDM), and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, and 60 g of N,N-dimethylformamide) are placed in a flask and stirred to dissolve. Then, a condensing reflux device is installed, and the temperature is raised to 110 °C and reacted for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A type benzoxazine and 0.5 g of 2-methylimidazole are added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino-modified spherical silica are added, and stirred for 30 - 60 min until a uniform glue solution is obtained.

[0032] Example 2: 100 g of bismaleimide oligomer MIR-3000, 15 g of 4,4-diaminodiphenylmethane, and a total of 150 g of solvents (30 g of methyl ethyl ketone, 60 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condenser reflux device was installed, and the temperature was raised to 110 °C for reaction for 90 min to obtain a prepolymer precursor solution. After cooling, 25 g of allyl bisphenol A benzoxazine and 0.3 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 140 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous adhesive solution was obtained.

[0033] Example 3: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenyl sulfone (DDS), and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condenser reflux device was installed, and the temperature was raised to 110 °C for reaction for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous adhesive solution was obtained.

[0034] Example 4: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condenser reflux device was installed, and the temperature was raised to 110 °C for reaction for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of ODA type benzoxazine and 0.4 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous adhesive solution was obtained.

[0035] Example 5: 100 g of bismaleimide oligomer BMI-2300, 10 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condenser reflux device was installed, and the temperature was raised to 110 °C for reaction for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous adhesive solution was obtained.

[0036] Example 6: 100 g of bismaleimide oligomer BMI-2300, 30 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condensation reflux device was installed, and the temperature was raised to 110 °C for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a uniform colloidal solution was obtained.

[0037] Example 7: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condensation reflux device was installed, and the temperature was raised to 90 °C for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a uniform colloidal solution was obtained.

[0038] Example 8: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condensation reflux device was installed, and the temperature was raised to 130 °C for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a uniform colloidal solution was obtained.

[0039] Example 9: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred until dissolved. Then, a condensation reflux device was installed, and the temperature was raised to 130 °C for 30 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a uniform colloidal solution was obtained.

[0040] Comparative Example 1 100 g of bismaleimide monomer BMI-70, 20 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvents (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred to dissolve. Then, a condensing reflux device was installed, and the temperature was raised to 110 °C and reacted for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous glue solution was obtained.

[0041] Comparative Example 2: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane, and a total of 140 g of solvents (30 g of methyl ethyl ketone, 50 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred to dissolve. Then, a condensing reflux device was installed, and the temperature was raised to 110 °C and reacted for 90 min to obtain a prepolymer precursor solution. After cooling, 0.5 g of 2-methylimidazole, 20 g of phosphazene, and 120 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous glue solution was obtained.

[0042] Comparative Example 3: 100 g of bismaleimide oligomer BMI-2300, 30 g of allyl bisphenol A benzoxazine, 0.5 g of 2-methylimidazole, and a total of 150 g of solvents (30 g of methyl ethyl ketone, 60 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred to dissolve, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous glue solution was obtained.

[0043] Comparative Example 4: 100 g of bismaleimide oligomer BMI-2300, 40 g of 4,4-diaminodiphenylmethane, and a total of 170 g of solvents (30 g of methyl ethyl ketone, 80 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask and stirred to dissolve. Then, a condensing reflux device was installed, and the temperature was raised to 110 °C and reacted for 90 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous glue solution was obtained.

[0044] Comparative Example 5: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane, 30 g of allyl bisphenol A benzoxazine, 0.5 g of 2-methylimidazole, and a total of 160 g of solvent (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask, stirred and dissolved, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous glue solution was obtained.

[0045] Comparative Example 6: 100 g of bismaleimide oligomer BMI-2300, 20 g of 4,4-diaminodiphenylmethane, and a total of 160 g of solvent (30 g of methyl ethyl ketone, 70 g of cyclohexanone, 60 g of N,N-dimethylformamide) were placed in a flask, stirred and dissolved, then a condensation reflux device was installed, heated to 60 °C and reacted for 180 min to obtain a prepolymer precursor solution. After cooling, 30 g of allyl bisphenol A benzoxazine and 0.5 g of 2-methylimidazole were added, stirred evenly, and 20 g of phosphazene and 150 g of phenylamino modified spherical silica were added, and stirred for 30 - 60 min until a homogeneous glue solution was obtained.

[0046] Effect Example 1 The halogen-free resin compositions prepared in Examples 1 - 9 and Comparative Examples 1 - 6 were coated on the reinforcing material, ordinary electronic grade 2116 glass fiber cloth, and baked in an oven at 171 °C for 3 - 6 min to obtain prepregs.

[0047] Six pieces of the above prepregs were stacked, and one piece of 1 oz HTE copper foil was covered on each of the upper and lower surfaces, and placed in a vacuum hot press for lamination. The initial hot plate temperature was 130 °C, and the heating rate was maintained at 2.5 °C / min to 220 °C, and then held at a constant temperature for 120 min to obtain a copper clad laminate, and the properties of this copper clad laminate were evaluated.

[0048] The property evaluations of the above Examples 1 - 9 and Comparative Examples 1 - 6 were tested according to the following methods: (1) Tg and flexural modulus: A dynamic mechanical property tester (DMA850) was used, with a heating rate of 5 °C / min and a nitrogen atmosphere.

[0049] (2) Z-CTE: A thermomechanical analyzer (Q400 TMA System) was used, with a heating rate of 10 °C / min and a test temperature range of 50 - 260 °C.

[0050] (3) Peel strength: Tested according to the IPC-TM-650 2.4.9 standard.

[0051] (4) PCT: Four 100 mm × 100 mm copper-free samples were taken and cooked in a pressure cooker at 121 °C and 105 KPa for 12 h, then immersed in a 288 °C tin bath, and the time of board explosion and delamination was recorded.

[0052] (5) Dielectric loss: A separated dielectric resonant cavity was used to test copper-free samples at a frequency of 10 GHz.

[0053] (6) Sub-surface condition: Take 4 samples for sectioning and observe the dispersion of resin and filler under an electron microscope. If there is uneven dispersion, it is judged as resin agglomeration.

[0054] (7) Plate toughness: Use a paint film impactor to perform an impact test at a fixed height and compare the cross grain. Use ☆ to indicate the toughness of the plate. The more ☆, the better the toughness.

[0055] The raw material manufacturers and brands of each component used in Examples 1 to 9 and Comparative Examples 1 to 6 are shown in Table 1: Table 1

[0056] According to the variables of the embodiments and comparative examples, they were divided into the following groups for analysis.

[0057] (1) Different resin combinations. The solid components and addition amounts are shown in Table 2: Table 2

[0058] Note: In the above case, the prepolymerization conditions of bismaleimide and aromatic diamine were 110℃ and 90min.

[0059] The characteristics of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 3: Table 3

[0060] Note: Plate toughness ☆☆☆ indicates the best toughness and is easy to process, ☆☆ indicates moderate toughness, and ☆ indicates the worst toughness and is difficult to process.

[0061] As can be seen from Table 3, compared with Comparative Example 1, Example 1 uses bismaleimide oligomer and aromatic diamine for prepolymerization. Since each maleimide group can react with an amino group, it is unexpectedly found that it can generate a network structure (such as Formula 1) during the prepolymerization process; Comparative Example 1 uses bismaleimide monomer and aromatic diamine for prepolymerization as a conventional process, and only a chain structure (such as Formula 2) is generated during the prepolymerization process. It can be seen from the characteristic evaluation table that Example 1 after the resin generates a network structure has better Tg, bending modulus and its retention rate, Z-CTE and peel strength for preparing copper clad laminate products, and the toughness of the board does not decrease due to the formation of a network structure after prepolymerization.

[0062] Formula 1:

[0063] Formula II:

[0064] In Example 1 compared with Comparative Example 2, benzoxazine resin was added after prepolymerization in Example 1. It can be seen from the property evaluation table that after adding benzoxazine resin, various properties and subsurface conditions of the substrate have been improved.

[0065] In Examples 2 - 4 compared with Example 1, replacements were made in terms of the types of bismaleimide oligomer, aromatic diamine, and benzoxazine resin respectively, and substrates with different properties can be obtained. In Example 3, when DDM was replaced with DDS, a substrate with a dielectric loss of 0.0076 can be obtained; in Example 4, when allyl bisphenol A type benzoxazine was replaced with OD type benzoxazine, a substrate with a dielectric loss of 0.0083 can be obtained.

[0066] (2) Different ratios of bismaleimide oligomer and aromatic diamine. The solid components and addition amounts are shown in Table 4: Table 4

[0067] Note: The prepolymerization conditions for bismaleimide and aromatic diamine in the above cases are 110°C and 90 min, and Comparative Example 3 does not require prepolymerization.

[0068] The property evaluations of Examples 1, 5, 6 and Comparative Examples 3, 4 are shown in Table 5: Table 5:

[0069] Note: The toughness of the plate ☆☆☆ indicates the best toughness and easy to process, ☆☆ indicates moderate toughness, and ☆ indicates the worst toughness and difficult to process.

[0070] It can be seen from Table 5 that Examples 1, 5, 6 and Comparative Examples 3, 4 studied the addition amount of aromatic diamine. It can be seen from the property evaluation table that when no aromatic diamine is added (Comparative Example 3), the properties such as the Tg and modulus retention rate of the substrate are not ideal; when 10 - 30 parts of DDM are added (Examples 5, 1, 6 respectively), the Tg and flexural modulus retention rate of the substrate gradually increase and the Z - CTE gradually decreases with the increase of the DDM addition amount; but when the DDM addition amount is increased to 40 parts (Comparative Example 4), although the Tg and Z - CTE properties of the substrate are better, the PCT representing the heat resistance drops to 2 min, and the subsurface of the substrate is difficult to process due to excessive cross - linking degree, decreased toughness, and decreased fluidity, resulting in resin agglomeration.

[0071] (3) Different prepolymerization conditions. The solid components and addition amounts of the following examples and comparative examples are the same as those in Example 1. The prepolymerization temperature and time are shown in Table 6: Table 6

[0072] Examples 1, 7 - 9, and Comparative Examples 5 and 6 were evaluated for their properties as shown in Table 7: Table 7

[0073] Note: For the toughness of the sheet material, ☆☆☆ indicates the best toughness and easy to process, ☆☆ indicates moderate toughness, and ☆ indicates the worst toughness and difficult to process.

[0074] As can be seen from Table 7, compared with Comparative Examples 5 and 6, in Example 7, from the property evaluation table, when there is no prepolymerization and the prepolymerization temperature is 60 °C (Comparative Examples 5 and 6), there is no obvious difference in their properties, and there is resin agglomeration on the subsurface, indicating that when the prepolymerization temperature is low, the reaction between the bismaleimide oligomer and the aromatic diamine cannot be activated, and the two still exist in the system separately before sizing and baking, resulting in the blending reaction of the bismaleimide oligomer, aromatic diamine, and benzoxazine, and the performance of the substrate deteriorates. When the prepolymerization temperature is increased to 90 °C (Example 7), all indicators return to normal and there is no abnormality on the subsurface, indicating that pre - polymerizing the bismaleimide oligomer and the aromatic diamine in advance can adjust the reaction sequence of the system and improve the performance of the substrate.

[0075] Examples 7, 1, and 8 are substrates prepared by prepolymerizing the bismaleimide oligomer and the aromatic diamine at 90 °C, 110 °C, and 130 °C respectively. From the property evaluation table, it can be seen that as the prepolymerization temperature increases, the degree of cross - linking formed increases, and the Tg of the substrate increases. However, due to the higher prepolymerization temperature in Example 8, the toughness of the sheet material is inferior to that of Examples 1 and 7.

[0076] Compared with Example 7, in Example 9, prepolymerization was carried out only for 30 min at 130 °C, and the performance is similar to that of Example 7 prepolymerized at 90 °C for 90 min. However, due to the higher prepolymerization temperature in Example 9, the toughness of the sheet material is inferior to that of Example 7.

[0077] In summary, the present invention uses prepolymerization of the bismaleimide oligomer and the aromatic diamine to adjust the reaction sequence. By reasonably controlling the ratio, prepolymerization time, and temperature of the two, a low - dielectric - loss substrate with high Tg, low Z - CTE, high modulus retention rate, and high peel strength can be obtained. Especially, the formulation ratio of Example 1 is the best, which can meet the requirements of high - speed packaging substrates.

[0078] The above - mentioned is only the preferred embodiment of the present invention, and it does not impose any limitation on the technical scope of the present invention. Therefore, any minor modification, equivalent change, and modification made to the above - mentioned embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A halogen-free resin composition, characterized in that The invention comprises the following raw materials: bismaleimide polymer, aromatic diamine, benzoxazine resin, phosphorus flame retardant, inorganic filler, imidazole catalyst and solvent.

2. The halogen-free resin composition according to claim 1, characterized in that: The bismaleimide polymer includes one or more compounds having the following general formula: （1） （2） （3） 。 3. The halogen-free resin composition according to claim 2, characterized in that: In the general formula of the compound, the value of n ranges from 2 to 100.

4. The halogen-free resin composition according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: The bismaleimide polymer: 50-200 parts; The aromatic diamine: 5 to 35 parts; The benzoxazine resin: 10-40 parts; The phosphorus flame retardant: 5-60 parts; The inorganic filler: 100-200 parts; The imidazole catalyst: 0.01-3 parts; The solvent: 120-200 parts.

5. The halogen-free resin composition according to claim 1, characterized in that: The aromatic diamine includes one or more of 4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether, and 4,4-diaminodiphenyl sulfone; the benzoxazine resin includes one or more of bisphenol A benzoxazine, bisphenol F benzoxazine, dicyclopentadiene benzoxazine, phenolphthalein benzoxazine, MDA benzoxazine, ODA benzoxazine, allylamine benzoxazine, and allyl bisphenol A benzoxazine; the phosphorus-based flame retardant includes inorganic phosphorus, condensed phosphate, phosphoric acid, hypophosphite, phosphorus oxide, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa- One or more of 10-phosphaphenanthrene-10-oxide, 10-phenyl-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, tri(2,6-dimethylphenyl)phosphine, and phosphazene; the inorganic filler includes one or more of silicon dioxide, aluminum oxide, titanium oxide, mica, aluminum hydroxide, magnesium hydroxide, talc, aluminum borate, barium sulfate, and calcium carbonate; the imidazole catalyst includes one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole; the solvent includes one or more of acetone, butanone, methyl isobutyl ketone, N,N-dimethylformamide, propylene glycol methyl ether, toluene, and cyclohexanone.

6. A method for preparing the halogen-free resin composition according to claim 1, characterized in that: include: A. adding the bismaleimide polymer and the aromatic diamine into the solvent, mixing and clarifying to obtain a clarified solution; B. heating the clarified liquid and stirring it to carry out a prepolymerization reaction to obtain a prepolymerization precursor liquid; C. After cooling the prepolymer precursor solution, adding the benzoxazine resin, mixing and dissolving, adding the phosphorus flame retardant and the inorganic filler, mixing evenly, and obtaining a mixture; D. adding the imidazole catalyst to the mixture, adjusting the gelation time, and obtaining the halogen-free resin composition.

7. The method for preparing the halogen-free resin composition according to claim 6, characterized in that: In step A, the temperature of the mixing and clarifying includes room temperature; in step B, the reaction temperature of the prepolymerization reaction includes 80 to 130° C., and the reaction time includes 30 to 300 minutes; in step C, the cooling temperature includes room temperature, and the uniform mixing method includes stirring for 60 to 200 minutes; In step D, the operation of adjusting the gelation time includes: adjusting the gelation time to 150-400 s at a test temperature of 150-180° C.

8. An application of the halogen-free resin composition according to claim 1, characterized in that: Used for one or more of prepreg and copper clad laminate.

9. A prepreg obtained according to the use of claim 8.

10. A copper clad laminate obtained according to claim 8.

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