A novel halogen-free copper clad plate and a preparation method thereof

Abstract

The application provides a halogen-free copper-clad plate, which comprises 90-110 parts by weight of epoxy resin, 100-300 parts by weight of phosphorus-containing amine bismaleimide curing agent, 0.5-5 parts by weight of accelerator, 300-700 parts by weight of solvent and 150-400 parts by weight of inorganic filler according to the mass parts of raw materials. The halogen-free copper-clad plate provided by the application has a specific formula and composition, and the phosphorus-containing amine bismaleimide curing agent with a specific structure and composition has an amine group as an active group, high nitrogen content, better synergistic flame-retardant effect with phosphorus, better compatibility and stability of nitrogen elements on the main chain of the long-chain curing agent. Further, the curing agent contains a maleimide group, so that the cured product has excellent heat resistance. The halogen-free copper-clad plate with more excellent heat resistance and comprehensive performance is obtained by the combination of the other simple raw material formula and the specific pressing process.

Description

Technical Field

[0001] This invention belongs to the technical field of halogen-free copper clad laminates, and relates to a halogen-free copper clad laminate and its preparation method, particularly to a novel halogen-free copper clad laminate and its preparation method. Background Technology

[0002] Copper-clad laminate (CCL) is a sheet material made by impregnating electronic fiberglass cloth or other reinforcing materials with resin, covering one or both sides with copper foil, and then hot-pressing it. Various types and functions of printed circuit boards (PCBs) are manufactured by selectively processing, etching, drilling, and copper plating on CCLs to create different printed circuits. CCLs primarily serve to interconnect, insulate, and support PCBs, significantly influencing signal transmission speed, energy loss, and characteristic impedance. Therefore, the performance, quality, manufacturability, manufacturing level, manufacturing cost, and long-term reliability and stability of PCBs largely depend on CCLs.

[0003] Copper clad laminates (CCLs) can be broadly classified into rigid CCLs and flexible CCLs. Rigid CCLs, based on their insulating materials and structure, can be further divided into organic resin CCLs, metal-based (core) CCLs, and ceramic-based CCLs. Within these, the insulating resins used can be categorized into epoxy resin CCLs, polyester resin CCLs, and cyanate ester resin CCLs, among others. Epoxy resin CCLs are a crucial component of CCLs. Epoxy CCLs are rigid CCLs made by impregnating fiberglass cloth or wood pulp paper with epoxy resin, covering one or both sides with copper foil, and then hot-pressing them. They are a primary substrate for printed circuit boards (PCBs) in the production of consumer electronics and typically have strict requirements for flame retardancy.

[0004] In traditional epoxy resin flame retardant technology, halogen compounds (tetrabromobisphenol A) are widely used in electronic materials requiring flame retardant properties due to their excellent flame retardancy. However, halogen flame retardants release corrosive, toxic, and carcinogenic substances such as hydrogen bromide, tetrabromodiphenyl dioxin, and tetrabromodiphenyl benzofuran during combustion, and have been gradually banned by environmental regulations. From an environmental perspective, phosphorus-based flame retardants are now the better choice in flame retardant systems.

[0005] Currently, phosphorus-based flame retardants mostly use phosphate esters or 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) compounds. When used as curing agents for epoxy resin copper-clad laminates, dicyandiamide curing agents are often added to the epoxy resin solution to obtain a phosphorus-containing flame-retardant epoxy resin copper-clad laminate system. Furthermore, phenolic or modified phenolic resins are often reacted with DOPO or DOPO-like compounds to obtain hydroxyl-containing compounds. During curing, the hydroxyl groups act as active groups, reacting with the epoxy resin to form a network cross-linked resin. However, this approach can negatively impact the overall performance of the prepared epoxy resin copper-clad laminate.

[0006] Therefore, finding a more suitable flame-retardant curing agent to further guarantee or improve the overall performance of epoxy resin copper clad laminates has become one of the urgent problems to be solved by many leading researchers and scientific research enterprises in this field. Summary of the Invention

[0007] This invention provides a halogen-free copper clad laminate and its preparation method, particularly a novel halogen-free copper clad laminate. The halogen-free copper clad laminate provided by this invention contains a specific phosphorus-amine heat-resistant epoxy curing agent, which uses amine groups as active groups, has a high nitrogen content, exhibits good synergistic flame-retardant effect with phosphorus, and possesses better compatibility and stability. Furthermore, it effectively improves heat resistance, further enhancing the overall performance of the epoxy resin copper clad laminate. Moreover, the preparation method is simple, the conditions are mild, and the controllability is good, making it more conducive to industrial-scale production and widespread application.

[0008] This invention provides a halogen-free copper-clad laminate, comprising, by weight of raw materials:

[0009]

[0010] Preferably, the phosphorus-containing bismaleimide curing agent has the structure shown in formula (I):

[0011]

[0012] Wherein, R is selected from

[0013] R1 is selected from

[0014] R2 is selected from

[0015] The epoxy resin includes one or more of bisphenol A type epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, bisphenol A phenolic epoxy resin, and bisphenol F epoxy resin.

[0016] The accelerator includes one or more of 2-methylimidazole, imidazole, 2-ethyl-4-methylimidazole and 2,4-dimethylimidazole;

[0017] The solvent includes one or more of DMF, cyclohexanone, acetone, butanone, and propylene glycol methyl ether;

[0018] The inorganic filler includes one or more of silicon dioxide, silica powder, mica powder, magnesium hydroxide, aluminum hydroxide, and magnesium hydroxide.

[0019] The phosphorus-containing bismaleimide curing agent includes a phosphorus-containing phenolic curing agent.

[0020] Preferably, the active groups of the phosphorus-containing bismaleimide curing agent include amine groups;

[0021] The phosphorus-containing bismaleimide curing agent comprises a bismaleimide structure;

[0022] The raw materials also include glass fiber cloth;

[0023] The phosphorus-containing bismaleimide curing agent is a curing agent used for epoxy resins;

[0024] The Tg of the epoxy resin cured product prepared by the phosphorus-containing bismaleimide curing agent is greater than 200℃.

[0025] The raw materials do not contain other amine curing agents;

[0026] The phosphorus-containing bismaleimide curing agent is a phosphorus-containing bismaleimide curing agent with flame retardant effect;

[0027] The flame retardant effect is specifically a nitrogen-phosphorus synergistic flame retardant effect.

[0028] Preferably, the preparation method of the phosphorus-containing bismaleimide curing agent includes the following steps:

[0029] 1) After mixing DOPO organic solution, catalyst, isocyanate and organic solvent, the reaction is carried out to obtain intermediate solution;

[0030] 2) The intermediate solution obtained in the above steps is reacted with diamine again to obtain the reaction solution;

[0031] 3) After refluxing the reaction solution obtained in the above steps with bismaleimide compounds, a phosphorus-amine bismaleimide curing agent is obtained.

[0032] Preferably, the solvent of the DOPO organic solution includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone;

[0033] The catalyst includes one or more of imidazole compounds, quaternary ammonium salt compounds, and triphenylphosphine compounds;

[0034] The isocyanate includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl diisocyanate, and isophorone diisocyanate;

[0035] The organic solvent includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone;

[0036] The catalyst accounts for 0.05 wt% to 0.2 wt% of the total mass of the DOPO and isocyanate;

[0037] The molar ratio of DOPO to isocyanate is (0.8–1.2):1.

[0038] Preferably, the catalyst comprises tetrabutylammonium bromide;

[0039] The reaction temperature is 150–190°C;

[0040] The reaction time is 2-3 hours;

[0041] The specific mixing method involves premixing the catalyst and isocyanate to obtain a solution, and then adding the DOPO organic solution dropwise into the solution for mixing.

[0042] The dripping time is 1–3 hours;

[0043] The temperature at which the drop is added is 150–190°C;

[0044] The molar ratio of DOPO to diamine is (0.8–1.2):1;

[0045] The diamine includes one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenyl sulfone, bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane.

[0046] Preferably, the temperature of the second reaction is 110–130°C;

[0047] The time for the second reaction is 4 to 6 hours;

[0048] The molar ratio of DOPO to bismaleimide compounds is (0.8–1.2):1;

[0049] The bismaleimide compounds include one or more of the following: DDM-modified bismaleimide, DDS-modified bismaleimide, 4,4'-diamino-3,3'-dimethylbiphenyl-modified bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane-modified bismaleimide, and bisphenol A type diether diamine-modified bismaleimide.

[0050] The reflux reaction temperature is 110–140°C;

[0051] The reflux reaction time is 1–4 hours;

[0052] The reflux reaction is followed by a process of heating to remove the solvent and / or dissolving the solvent.

[0053] This invention provides a method for preparing halogen-free copper-clad laminate, comprising the following steps:

[0054] A) Mix epoxy resin, phosphoamine bismaleimide curing agent, accelerator and solvent, then add inorganic filler and continue mixing to obtain adhesive solution;

[0055] B) After impregnating the fiberglass cloth with the adhesive solution obtained in the above steps, dry it to obtain a semi-cured sheet;

[0056] C) The prepreg obtained in the above steps is stacked in multiple layers, then stacked with copper foil, and pressed to obtain halogen-free copper-clad laminate.

[0057] Preferably, the mixing speed is 400-1000 rpm;

[0058] The mixing speed is 400-1000 rpm.

[0059] The mixing time is 1 to 4 hours;

[0060] The drying temperature is 100–250°C.

[0061] Preferably, the pressing pressure is 20-30 kg / cm². 2 ;

[0062] The suppression is gradient suppression;

[0063] The first gradient of the gradient suppression is a temperature increase from 85℃ to 220℃, and the time for the first gradient is 30 minutes.

[0064] The holding temperature of the second gradient of the gradient pressing is 220℃, and the holding time of the second gradient is 120min.

[0065] The third gradient of the gradient suppression is a temperature drop from 220℃ to 130℃, and the time for the third gradient is 30 minutes.

[0066] This invention provides a halogen-free copper-clad laminate, comprising, by weight, 90-110 parts epoxy resin, 100-300 parts phosphorus-containing bismaleimide curing agent, 0.5-5 parts accelerator, 300-700 parts solvent, and 150-400 parts inorganic filler. Compared with existing technologies, this invention addresses the problem of phosphorus-based flame-retardant curing agents affecting the overall performance of the epoxy resin system in existing halogen-free epoxy resin copper-clad laminates. The research suggests that while using a nitrogen-phosphorus synergistic effect can improve the flame-retardant effect, it is also possible to maintain and enhance the overall performance of the epoxy resin system. For example, adding Dicy, or as described in patent CN103755925, a phosphorus-containing phenolic curing agent is obtained by reacting phenolic resin with DOPO after etherification, with nitrogen-containing additives such as melamine or acetylguanidine added during the reaction to introduce nitrogen. However, this invention believes that this method of introducing additional nitrogen-containing compounds not only has the problem of complicated process, but also the addition amount is limited, the proportion of nitrogen element is not high, the overall effect is limited, and this small molecule nitrogen-containing compound also has defects in terms of compatibility and stability.

[0067] Based on this, the present invention specifically designs a halogen-free copper-clad laminate with a specific formula and composition, containing a phosphorus-amine bismaleimide curing agent with a specific structure and composition. This is a novel long-chain phosphorus-amine and bismaleimide epoxy curing agent. The synthesized curing agent uses amine groups as active groups, has a high nitrogen content, and exhibits better synergistic flame-retardant effect with phosphorus. Moreover, nitrogen is located on the main chain of the long-chain curing agent, demonstrating better compatibility and stability. Simultaneously, the presence of maleimide groups gives the cured product excellent heat resistance, further improving the overall performance of the epoxy resin during application, resulting in a halogen-free copper-clad laminate with excellent flame-retardant and comprehensive performance.

[0068] This invention uses a novel phosphorus-amine bismaleimide resin as an epoxy resin curing agent to obtain a halogen-free flame-retardant copper clad laminate material while simplifying the resin formulation. Moreover, while ensuring the excellent flame-retardant effect of existing flame-retardant copper clad laminate formulations, it further improves the overall performance of the copper clad laminate, especially its heat resistance.

[0069] This invention reacts isocyanate as an initial raw material with DOPO, making it easier for DOPO to bind within the resin to obtain a phosphorus-containing aldehyde compound. This compound then reacts with a diamine to obtain a phosphorus-containing amine curing agent. Finally, it reacts again with modified bismaleimide to obtain a heat-resistant curing agent containing phosphorus-amine and modified bismaleimide groups. This invention introduces nitrogen through isocyanate facilitation after the reaction of DOPO with isocyanate, and further introduces a bismaleimide structure, resulting in a phosphorus-containing amine heat-resistant epoxy curing agent with amine groups as active groups and excellent heat resistance. This invention changes the existing phosphorus-containing curing agents, which all use hydroxyl groups as active groups, by introducing amine groups as epoxy curing groups. Furthermore, the phosphorus in this curing agent is less prone to precipitation and has excellent compatibility with epoxy resins. Simultaneously, the presence of amine groups eliminates the need for additional amine curing agents during epoxy resin curing, and the nitrogen element is fixed on a long chain, making it more stable and improving compatibility. Furthermore, the presence of maleimide groups in this curing agent gives the cured product excellent heat resistance. This invention increases the proportion of nitrogen in nitrogen-phosphorus curing agents, resulting in a better synergistic effect of nitrogen and phosphorus in flame retardancy. It also better achieves the flame retardant effect of nitrogen-phosphorus blending in epoxy curing systems. More importantly, the prepared halogen-free flame-retardant copper-clad laminate exhibits excellent performance in key properties such as solder resistance, glass transition temperature, peel strength, and thermal weight loss, especially in heat resistance, with a high glass transition temperature.

[0070] The phosphorus-amine bismaleimide heat-resistant epoxy curing agent provided by this invention uses amine groups as active groups, has a high nitrogen content, and exhibits good synergistic flame-retardant effect with phosphorus. The halogen-free flame-retardant copper-clad laminate prepared with this agent significantly improves the system's heat resistance and also possesses excellent solder resistance, peel strength, and thermal weight loss. Furthermore, the preparation method is simple, the conditions are mild, and the controllability is good, making it more conducive to industrial-scale production and widespread application. The novel halogen-free copper-clad laminate provided by this invention directly uses this phosphorus-amine curing agent, simplifying the resin formulation. Combined with other simple raw material formulations and a specific pressing process, a halogen-free copper-clad laminate with superior flame-retardant and overall performance is obtained.

[0071] Experimental results show that the halogen-free flame-retardant copper-clad laminate provided by this invention, using a phosphamide-containing bismaleimide heat-resistant epoxy curing agent, achieves a flame-retardant effect reaching the UL-94V-0 level. Furthermore, the laminate's main properties, such as solder resistance, peel strength, and thermal weight loss, all meet or exceed the levels of commercially available products, especially the glass transition temperature T0. g ≥210℃. Detailed Implementation

[0072] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0073] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0074] There are no particular restrictions on the purity of any raw materials used in this invention. However, it is preferred to use analytical grade or conventional purity in the field of copper clad laminate preparation.

[0075] This invention provides a halogen-free copper-clad laminate, comprising, by weight of raw materials:

[0076]

[0077] In this invention, the amount of epoxy resin added is 90 to 110 parts by weight, which can be 94 to 106 parts by weight, and preferably 98 to 102 parts by weight.

[0078] In this invention, the amount of the phosphorus-containing bismaleimide curing agent added is 100-300 parts by weight, which can be 140-260 parts by weight, and preferably 180-220 parts by weight.

[0079] In this invention, the amount of the accelerator added is 0.5 to 5 parts by weight, which can be 1.5 to 4 parts by weight, and preferably 2.5 to 3 parts by weight.

[0080] In this invention, the amount of solvent added is 300-700 parts by weight, which can be 350-650 parts by weight, preferably 400-600 parts by weight, and more preferably 450-550 parts by weight.

[0081] In this invention, the amount of inorganic filler added is 150-400 parts by weight, which can be 200-350 parts by weight, and preferably 250-300 parts by weight.

[0082] In this invention, the molar ratio of active hydrogen (hydrogen atoms connected to N) to epoxy groups on the phosphorus-amine bismaleimide curing agent is preferably (0.95-1.2):1, more preferably (1.00-1.15):1, and even more preferably (1.05-1.10):1.

[0083] In this invention, the amount of accelerator is preferably 0.05wt% to 0.2wt% of the total weight of the resin system, more preferably 0.07wt% to 0.18wt%, and even more preferably 0.1wt% to 0.15wt%.

[0084] In this invention, the mass ratio of the inorganic filler to the resin system is preferably (0.2-0.4):1, more preferably (0.23-0.38):1, and even more preferably (0.25-0.35):1.

[0085] In this invention, the amount of solvent used is preferably such that the solid content of the raw material slurry is between 55% and 65%, more preferably 57% to 63%, and even more preferably 59% to 61%.

[0086] In this invention, the resin system preferably includes epoxy resin, additives (curing agent and accelerator) and filler, but excludes solvent. The final epoxy resin copper clad laminate does not include fibers, and the raw material slurry is the sum of the resin system and solvent.

[0087] In this invention, the epoxy resin preferably includes one or more of bisphenol A type epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, bisphenol A phenolic epoxy resin, and bisphenol F epoxy resin, more preferably bisphenol A type epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, bisphenol A phenolic epoxy resin, or bisphenol F epoxy resin. Specifically, the epoxy resin in this invention can be a phenolic epoxy resin.

[0088] In this invention, the accelerator preferably includes one or more of 2-methylimidazole, imidazole, 2-ethyl-4-methylimidazole and 2,4-dimethylimidazole, more preferably 2-methylimidazole, imidazole, 2-ethyl-4-methylimidazole or 2,4-dimethylimidazole.

[0089] In this invention, the solvent preferably includes one or more of DMF, cyclohexanone, acetone, butanone, and propylene glycol methyl ether, more preferably DMF, cyclohexanone, acetone, butanone, or propylene glycol methyl ether.

[0090] In this invention, the inorganic filler preferably includes one or more of silicon dioxide, silicon micro powder, mica powder, magnesium hydroxide, aluminum hydroxide, and magnesium hydroxide, and more preferably silicon dioxide, silicon micro powder, mica powder, magnesium hydroxide, aluminum hydroxide, or magnesium hydroxide.

[0091] In this invention, the phosphorus-containing bismaleimide curing agent preferably includes a phosphorus-containing phenolic curing agent.

[0092] In this invention, the active group of the phosphorus-containing bismaleimide curing agent preferably includes an amine group.

[0093] In this invention, the raw materials preferably also include glass fiber cloth.

[0094] In this invention, the phosphorus-containing bismaleimide curing agent preferably contains a bismaleimide structure.

[0095] In this invention, the phosphorus-containing bismaleimide curing agent is preferably a curing agent for epoxy resins.

[0096] In this invention, the raw materials preferably do not contain other amine curing agents.

[0097] In this invention, the Tg of the epoxy resin cured product prepared by the phosphorus-amine bismaleimide curing agent is preferably greater than 200°C, more preferably greater than 210°C, and even more preferably greater than 220°C.

[0098] In this invention, the phosphorus-containing bismaleimide curing agent is preferably a phosphorus-containing bismaleimide curing agent with flame retardant effect.

[0099] In this invention, the flame retardant effect is preferably a nitrogen-phosphorus synergistic flame retardant effect.

[0100] In this invention, the curing agent preferably has a structure as shown in formula (I):

[0101]

[0102] Wherein, R is selected from

[0103] R1 is selected from

[0104] R2 is selected from

[0105] In this invention, the preparation method of the phosphorus-containing bismaleimide curing agent preferably includes the following steps:

[0106] 1) After mixing DOPO organic solution, catalyst, isocyanate and organic solvent, the reaction is carried out to obtain intermediate solution;

[0107] 2) The intermediate solution obtained in the above steps is reacted with diamine again to obtain the reaction solution;

[0108] 3) After refluxing the reaction solution obtained in the above steps with bismaleimide compounds, a phosphorus-amine curing agent is obtained.

[0109] The present invention first mixes DOPO organic solution, catalyst, isocyanate and organic solvent and then reacts them to obtain intermediate solution.

[0110] In this invention, the solvent of the DOPO organic solution preferably includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone, more preferably toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, or cyclohexanone.

[0111] In this invention, the catalyst preferably includes one or more of imidazole compounds, quaternary ammonium salt compounds, and triphenylphosphine compounds, more preferably imidazole compounds, quaternary ammonium salt compounds, or triphenylphosphine compounds.

[0112] In this invention, the isocyanate preferably includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl dimethyl diisocyanate, and isophorone diisocyanate, more preferably diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl dimethyl diisocyanate, or isophorone diisocyanate.

[0113] In this invention, the organic solvent preferably includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone, more preferably toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, or cyclohexanone.

[0114] In this invention, the catalyst accounts for 0.05 wt% to 0.2 wt% of the total mass of DOPO and isocyanate, more preferably 0.08 wt% to 0.17 wt%, and even more preferably 0.11 wt% to 0.14 wt%.

[0115] In this invention, the molar ratio of DOPO to isocyanate is preferably (0.8-1.2):1, more preferably (0.85-1.15):1, more preferably (0.9-1.1):1, and even more preferably (0.95-1.05):1.

[0116] In this invention, the reaction temperature is preferably 150-190°C, more preferably 155-185°C, even more preferably 160-180°C, and even more preferably 165-175°C, thereby better suppressing isocyanate self-polymerization.

[0117] In this invention, the reaction time is preferably 2 to 3 hours, more preferably 2.2 to 2.8 hours, and even more preferably 2.4 to 2.6 hours.

[0118] In this invention, the preferred mixing method is to premix the catalyst and isocyanate to obtain a solution, and then add the DOPO organic solution dropwise to the solution for mixing.

[0119] In this invention, the dripping time is preferably 1 to 3 hours, more preferably 1.4 to 2.6 hours, and even more preferably 1.8 to 2.2 hours.

[0120] In this invention, the dropping is preferably performed at the reaction temperature. That is, the dropping temperature is preferably 150-190°C, more preferably 155-185°C, even more preferably 160-180°C, and even more preferably 165-175°C.

[0121] In this invention, the intermediate solution obtained in the above steps is reacted again with diamine to obtain a reaction solution.

[0122] In this invention, the diamine preferably includes one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenyl sulfone, bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, more preferably phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane (DDM), diaminodiphenyl sulfone (DDS), bisphenol A type diether diamine, or 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane.

[0123] In this invention, the molar ratio of DOPO to diamine is preferably (0.8-1.2):1, more preferably (0.85-1.15):1, even more preferably (0.9-1.1):1, and even more preferably (0.95-1.05):1.

[0124] In this invention, the temperature of the second reaction is preferably 110-130°C, more preferably 115-125°C, and even more preferably 119-121°C.

[0125] In this invention, the time for the second reaction is preferably 4 to 6 hours, more preferably 4.4 to 5.6 hours, and even more preferably 4.8 to 5.2 hours.

[0126] Finally, the reaction solution obtained in the above steps is refluxed with a bismaleimide compound to obtain a phosphorus-amine curing agent.

[0127] In this invention, the molar ratio of DOPO to the bismaleimide compound is preferably (0.8–1.2):1, more preferably (0.85–1.15):1, even more preferably (0.9–1.1):1, and even more preferably (0.95–1.05):1.

[0128] In this invention, the bismaleimide compounds preferably include one or more of the following: DDM-modified bismaleimide (DDM-BMI), DDS-modified bismaleimide (DDS-BMI), 4,4'-diamino-3,3'-dimethylbiphenyl-modified bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane-modified bismaleimide, and bisphenol A type diether diamine-modified bismaleimide; more preferably, they are DDM-modified bismaleimide, DDS-modified bismaleimide, 4,4'-diamino-3,3'-dimethylbiphenyl-modified bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane-modified bismaleimide, or bisphenol A type diether diamine-modified bismaleimide.

[0129] In this invention, the temperature of the reflux reaction is preferably 110-140°C, more preferably 115-135°C, and even more preferably 120-130°C.

[0130] In this invention, the reflux reaction time is preferably 1 to 4 hours, more preferably 1.5 to 3.5 hours, and even more preferably 2 to 3 hours.

[0131] In this invention, the reflux reaction preferably includes a step of heating to remove the solvent and / or dissolving, more preferably a step of heating to remove the solvent or dissolving.

[0132] To complete and refine the overall technical solution, this invention further ensures the structure and composition of the phosphoamine-containing curing agent, better improves its flame retardant properties, curing effect, and system stability, and further enhances the overall performance of the subsequent epoxy resin system, including its heat resistance. The preferred methods for preparing the aforementioned phosphoamine-containing curing agent and its preparation method are as follows:

[0133] The novel phosphorus-amine phenolic curing agent synthesized in this invention has an active group of amine and contains a bismaleimide structure.

[0134] 1. DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) reacts with isocyanate to give DOPO-R-CHO.

[0135] At a certain temperature, a DOPO / toluene solution is dropped into an isocyanate (or isocyanate solution) containing a catalyst.

[0136] Specifically, isocyanates include, but are not limited to, diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), m-phenylenedimethyl isocyanate (XDI), and isophorone diisocyanate (IPDI), with MDI being preferred.

[0137] Specifically, catalysts commonly used include imidazole compounds, quaternary ammonium salts, and triphenylphosphine compounds, with tetrabutylammonium bromide being a preferred quaternary ammonium salt.

[0138] The reaction formulas for the above steps are shown below:

[0139]

[0140] 2. DOPO-R-CHO reacts with diamine to synthesize phosphorus-containing amine curing agents.

[0141] Specifically, the diamines include, but are not limited to, phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane (DDM), diaminodiphenyl sulfone (DDS), bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, more preferably 4,4'-diamino-3,3'-dimethylbiphenyl. Among these, amines with a methyl or ethyl group on the benzene ring contribute to improving the dielectric properties of the resin.

[0142] The reaction formulas for the above steps are shown below:

[0143]

[0144] 3. The introduction of bismaleimide (BMI) further increases the glass transition temperature of the cured resin, improving the heat resistance of the board. Bismaleimide can be DDM-BMI, DDS-BMI, or other bismaleimide compounds containing benzene rings or heterocycles.

[0145] The reaction formulas for the above steps are shown below:

[0146]

[0147] This invention presents a novel phosphorus-amine bismaleimide curing agent with a specific structure and composition. It features amine groups as active groups, a high nitrogen content, and a better synergistic flame-retardant effect with phosphorus. Furthermore, the nitrogen element, located on the main chain of the long-chain curing agent, exhibits better compatibility and stability. The presence of maleimide groups further enhances the heat resistance of the cured product, thus improving the overall performance of halogen-free epoxy resin copper clad laminates. This effectively solves the problem that existing copper clad laminates typically use a combination of special epoxy resins with high heat-resistant groups and phosphorus-containing curing agents to achieve halogen-free flame retardancy and high Tg.

[0148] This invention involves reacting DOPO with isocyanate to introduce nitrogen via isocyanate ion, and further introducing a bismaleimide structure to obtain a phosphorus-amine heat-resistant epoxy curing agent with amine groups as active groups, exhibiting excellent heat resistance. This invention differs from existing phosphorus-containing curing agents that use hydroxyl groups as active groups; instead, it introduces amine groups as epoxy curing groups. Furthermore, this curing agent does not readily precipitate phosphorus and exhibits excellent compatibility with epoxy resins. Simultaneously, the presence of amine groups eliminates the need for additional amine curing agents during epoxy resin curing, and the nitrogen element is fixed on a long chain, resulting in greater stability and better compatibility. Moreover, the presence of bismaleimide groups in this compound endows the cured product with excellent heat resistance. This invention increases the proportion of nitrogen in the nitrogen-phosphorus curing agent, resulting in a better nitrogen-phosphorus synergistic effect in flame retardancy. This better achieves the flame retardant effect of nitrogen-phosphorus blending in epoxy resin halogen-free copper clad laminate. More importantly, the prepared epoxy resin halogen-free copper clad laminate exhibits excellent performance in key properties such as solder resistance, peel strength, and thermal weight loss, especially in heat resistance, with a high glass transition temperature.

[0149] This invention provides a method for preparing halogen-free copper-clad laminate, comprising the following steps:

[0150] A) Mix epoxy resin, phosphoamine bismaleimide curing agent, accelerator and solvent, then add inorganic filler and continue mixing to obtain adhesive solution;

[0151] B) After impregnating the fiberglass cloth with the adhesive solution obtained in the above steps, dry it to obtain a semi-cured sheet;

[0152] C) The prepreg obtained in the above steps is stacked in multiple layers, then stacked with copper foil, and pressed to obtain halogen-free copper-clad laminate.

[0153] The present invention first mixes epoxy resin, phosphoamine bismaleimide curing agent, accelerator and solvent, and then adds inorganic filler and continues mixing to obtain adhesive solution.

[0154] In this invention, the mixing speed is preferably 400-1000 rpm, more preferably 500-900 rpm, and even more preferably 600-800 rpm.

[0155] In this invention, the rotational speed for continued mixing is preferably 400-1000 rpm, more preferably 500-900 rpm, and even more preferably 600-800 rpm.

[0156] In this invention, the mixing time is preferably 1 to 4 hours, more preferably 1.5 to 3.5 hours, and even more preferably 2 to 3 hours.

[0157] In this invention, the glass fiber cloth is impregnated in the adhesive solution obtained in the above steps and then dried to obtain a semi-cured sheet.

[0158] In this invention, the drying temperature is preferably 100-250°C, more preferably 130-220°C, and even more preferably 160-190°C.

[0159] Finally, the present invention stacks multiple layers of the prepreg obtained in the above steps, then stacks them with copper foil, and then presses them to obtain a halogen-free copper-clad laminate.

[0160] In this invention, the pressing pressure is preferably 20-30 kg / cm². 2 More preferably, it is 22–28 kg / cm². 2 More preferably, it is 24–26 kg / cm². 2 .

[0161] In this invention, the suppression is preferably gradient suppression.

[0162] In this invention, the first gradient of the gradient pressing is preferably a temperature increase from 85°C to 220°C, and the first gradient time is preferably 30 min.

[0163] In this invention, the heat preservation temperature of the second gradient of the gradient pressing is preferably 220°C, and the heat preservation time of the second gradient is preferably 120 min.

[0164] In this invention, the third gradient of the gradient suppression is preferably a temperature drop from 220°C to 130°C, and the time for the third gradient is preferably 30 minutes.

[0165] To complete and refine the overall technical solution, this invention further ensures the flame retardant properties, curing effect, and system stability of the phosphorus-amine bismaleimide curing agent, and better improves the flame retardant properties, stability, and heat resistance of copper-clad laminates. The preferred preparation method for the aforementioned novel halogen-free copper-clad laminate can be the following steps:

[0166] Epoxy resin, a novel phosphorus-amine bismaleimide curing agent, an accelerator, and a solvent were dissolved by high-speed stirring at 400–1000 rpm. Inorganic fillers were then added, and stirring continued for 2 hours. Glass fiber cloth was impregnated in the above adhesive solution and dried at 100–250°C to obtain a prepreg. The obtained prepreg was cut into groups of eight and stacked with copper foil for pressing.

[0167] The pressing conditions are: pressure of 25 kg / cm². 2 The heating program is 85℃→220℃→220℃→130℃, with heating times of 30min, 120min, and 30min.

[0168] The present invention provides a novel halogen-free copper clad laminate and its preparation method. This halogen-free copper clad laminate, with its specific formulation and composition, contains a phosphorus-amine bismaleimide curing agent with a specific structure and composition. This is a novel long-chain phosphorus-amine and bismaleimide epoxy curing agent. The synthesized curing agent uses amine groups as active groups, has a high nitrogen content, and exhibits better synergistic flame-retardant effect with phosphorus. Furthermore, the nitrogen element, located on the main chain of the long-chain curing agent, demonstrates better compatibility and stability. Simultaneously, the presence of maleimide groups gives the cured product excellent heat resistance, further enhancing the overall performance of the epoxy resin during application, resulting in a halogen-free copper clad laminate with excellent flame-retardant and comprehensive properties.

[0169] This invention uses a novel phosphorus-amine bismaleimide resin as an epoxy resin curing agent to obtain a halogen-free flame-retardant copper clad laminate material while simplifying the resin formulation. Moreover, while ensuring the excellent flame-retardant effect of existing flame-retardant copper clad laminate formulations, it further improves the overall performance of the copper clad laminate, especially its heat resistance.

[0170] This invention reacts isocyanate as an initial raw material with DOPO, making it easier for DOPO to bind within the resin to obtain a phosphorus-containing aldehyde compound. This compound then reacts with a diamine to obtain a phosphorus-containing amine curing agent. Finally, it reacts again with modified bismaleimide to obtain a heat-resistant curing agent containing phosphorus-amine and modified bismaleimide groups. This invention introduces nitrogen through isocyanate facilitation after the reaction of DOPO with isocyanate, and further introduces a bismaleimide structure, resulting in a phosphorus-containing amine heat-resistant epoxy curing agent with amine groups as active groups and excellent heat resistance. This invention changes the existing phosphorus-containing curing agents, which all use hydroxyl groups as active groups, by introducing amine groups as epoxy curing groups. Furthermore, the phosphorus in this curing agent is less prone to precipitation and has excellent compatibility with epoxy resins. Simultaneously, the presence of amine groups eliminates the need for additional amine curing agents during epoxy resin curing, and the nitrogen element is fixed on a long chain, making it more stable and improving compatibility. Furthermore, the presence of maleimide groups in this curing agent gives the cured product excellent heat resistance. This invention increases the proportion of nitrogen in nitrogen-phosphorus curing agents, resulting in a better synergistic effect of nitrogen and phosphorus in flame retardancy. It also better achieves the flame retardant effect of nitrogen-phosphorus blending in epoxy curing systems. More importantly, the prepared halogen-free flame-retardant copper-clad laminate exhibits excellent performance in key properties such as solder resistance, glass transition temperature, peel strength, and thermal weight loss, especially in heat resistance, with a high glass transition temperature.

[0171] The phosphorus-amine bismaleimide heat-resistant epoxy curing agent provided by this invention uses amine groups as active groups, has a high nitrogen content, and exhibits good synergistic flame-retardant effect with phosphorus. The halogen-free flame-retardant copper-clad laminate prepared with this agent significantly improves the system's heat resistance and also possesses excellent solder resistance, peel strength, and thermal weight loss. Furthermore, the preparation method is simple, the conditions are mild, and the controllability is good, making it more conducive to industrial-scale production and widespread application. The novel halogen-free copper-clad laminate provided by this invention directly uses this phosphorus-amine curing agent, simplifying the resin formulation. Combined with other simple raw material formulations and a specific pressing process, a halogen-free copper-clad laminate with superior flame-retardant and overall performance is obtained.

[0172] Experimental results show that the halogen-free flame-retardant copper-clad laminate provided by this invention, using a phosphamide-containing bismaleimide heat-resistant epoxy curing agent, achieves a flame-retardant effect reaching the UL-94V-0 level. Furthermore, the laminate's main properties, such as solder resistance, peel strength, and thermal weight loss, all meet or exceed the levels of commercially available products, especially the glass transition temperature T0. g ≥210℃.

[0173] To further illustrate the present invention, the following describes in detail a halogen-free copper-clad laminate and its preparation method provided by the present invention with reference to embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0174] Example

[0175] Epoxy resin, phosphamide-containing bismaleimide curing agent, accelerator, and solvent were dissolved by high-speed stirring at 400–1000 rpm. Inorganic filler was then added, and stirring continued for 2 hours. Glass fiber cloth was impregnated in the above adhesive solution and dried at 100–250°C to obtain a prepreg. The obtained prepreg was cut into groups of eight and stacked with copper foil for pressing.

[0176] The pressing conditions are: pressure of 25 kg / cm². 2 The heating program is 85℃→220℃→220℃→130℃, with heating times of 30min, 120min, and 30min.

[0177] The resin solution was prepared according to the proportions in Table 1, and the copper-clad laminate material was finally obtained and its performance was tested. The control group used Dow's XZ-92741 product as the halogen-free curing agent.

[0178] The curing agent used in the example has the following structure:

[0179]

[0180] See Table 1, which shows the raw material formulation, process parameters, and performance test results of the copper-clad laminate materials prepared in the embodiments and comparative examples of the present invention.

[0181] Table 1

[0182]

[0183]

[0184] As shown in Table 1, the phosphorus-containing bismaleimide curing agent synthesized according to the method of this invention has the same excellent flame retardancy as commercially available phosphorus-containing curing agents, and both can reach the UL-94V-0 level. Moreover, the phosphorus-containing bismaleimide phenolic curing agent containing the bismaleimide structure has a much higher Tg after curing than conventional high Tg products, which can greatly improve the heat resistance of copper-clad laminates.

[0185] 1. Gelation time: Weigh 0.2 mg of pre-impregnated powder and place it on a hot plate. The hot plate temperature is 170℃. Record the time required for gelation.

[0186] 2. Interlayer bonding strength: Tested according to IPC-TM-650-2.4.8C method.

[0187] 3. Thermogravimetric analysis (Td5%): The TGA test was performed according to the TGA test method specified in IPC-TM-650 2.4.24.6.

[0188] 4.288℃ solder resistance (after 2 hours in a PCT pressure cooker)

[0189] The testing method involves immersing the pressure cooker-tested sample in a 288°C soldering furnace and recording the time required for the sample to blister and delaminate. The evaluation can be concluded when the substrate has been in the soldering furnace for more than 5 minutes without blistering or delamination.

[0190] 5. Glass transition temperature test:

[0191] A differential scanning calorimeter (DSC) was used, with a heating rate of 20 °C / min.

[0192] 6. Flame retardancy test:

[0193] The flame retardancy of the sample was tested according to the UL-94 standard method.

[0194] The present invention provides a novel halogen-free copper-clad laminate and its preparation method, which has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A halogen-free copper clad plate characterized by, According to the mass fraction of raw materials, including: Epoxy resin 90~110 parts by weight; Phosphorus-containing amine bismaleimide curing agent 100~300 parts by weight; Accelerator 0.5~5 parts by weight; Solvent 300~700 parts by weight; Inorganic filler 150~400 parts by weight; The phosphorus-containing amine bismaleimide curing agent has a structure as shown in formula (I): （I）； wherein R is selected from , , , , or ; said R1 is selected from , , , , or ; The R2is selected from , , , or .

2. The halogen-free copper clad plate according to claim 1, wherein The epoxy resin is one or more of bisphenol A type epoxy resin, phenol novolac epoxy resin, o-cresol novolac epoxy resin, bisphenol A novolac epoxy resin and bisphenol F epoxy resin; The accelerator is one or more of 2-methyl imidazole, imidazole, 2-ethyl-4-methyl imidazole and 2,4-dimethyl imidazole.

3. The halogen-free copper clad plate according to claim 1, wherein The solvent is one or more of DMF, cyclohexanone, acetone, butanone and propylene glycol methyl ether; The inorganic filler is one or more of silicon dioxide, silicon powder, mica powder, magnesium hydroxide, aluminum hydroxide and magnesium hydroxide; The phosphorus-containing amine bismaleimide curing agent is a phosphorus-containing amine phenolic curing agent.

4. The halogen-free copper clad plate according to claim 1, wherein The preparation method of the phosphorus-containing amine bismaleimide curing agent comprises the following steps: 1) After mixing DOPO organic solution, catalyst, isocyanate and organic solvent, reaction is carried out to obtain an intermediate solution; 2) After the intermediate solution obtained in the above step is reacted with diamine again, a reaction liquid is obtained; 3) After refluxing the reaction liquid obtained in the above step with bismaleimide compound, a phosphorus-containing amine bismaleimide curing agent is obtained.

5. The halogen-free copper clad plate according to claim 4, wherein The solvent of the DOPO organic solution is one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether and cyclohexanone; The catalyst is one or more of imidazole compound, quaternary ammonium salt compound and triphenylphosphine compound; The isocyanate is one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl dimethyl diisocyanate and isophorone diisocyanate; The organic solvent is one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether and cyclohexanone; The proportion of the catalyst in the total mass of the DOPO and isocyanate is 0.05wt%-0.2wt%; The molar ratio of the DOPO to isocyanate is (0.8-1.2):

1.

6. The halogen-free copper clad plate according to claim 4, wherein The catalyst is tetrabutylammonium bromide; The reaction temperature is 150-190℃; The reaction time is 2-3h; The mixing mode is specifically that the catalyst and isocyanate are premixed to obtain a solution, and then the DOPO organic solution is added dropwise into the solution for mixing; The dropping time is 1-3h; The dropping temperature is 150-190℃; The molar ratio of the DOPO to diamine is (0.8-1.2):1; The diamine is one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethyl diphenyl, diaminodiphenylmethane, diaminodiphenyl sulfone, bisphenol A type diether diamine and 3,3'-dimethyl-5,5'-diethyl-4,4'-diamino diphenylmethane.

7. The halogen-free copper clad plate according to claim 4, wherein The re-reaction temperature is 110-130℃; The re-reaction time is 4-6h; The molar ratio of the DOPO to the bismaleimide compound is (0.8-1.2):1; The temperature of the reflux reaction is 110-140℃; The time of the reflux reaction is 1-4h; The reflux reaction is further followed by a step of heating to remove solvent and / or a step of dissolving.

8. A method for producing the halogen-free copper clad plate according to any one of claims 1 to 7, characterized by, The method comprises the following steps: A) mixing an epoxy resin, a phosphorus-containing amine bismaleimide curing agent, an accelerator and a solvent, and then adding an inorganic filler to continue mixing to obtain a glue solution; B) impregnating a glass fiber cloth in the glue solution obtained in the above step, and then drying to obtain a prepreg; C) laminating the prepreg obtained in the above step in multiple layers, and then laminating with a copper foil, and then pressing to obtain a halogen-free copper-clad plate.

9. The production method according to claim 8, characterized by, The rotating speed of the mixing is 400-1000rpm; The rotating speed of the continued mixing is 400-1000rpm; The time of the continued mixing is 1-4h; The temperature of the drying is 100-250℃.

10. The method of claim 8, wherein, The pressing pressure is 20-30 kg / cm 2 ; The pressing is gradient pressing; The first gradient of the gradient pressing is 85℃ to 220℃, and the time of the first gradient is 30min; The holding temperature of the second gradient of the gradient pressing is 220℃, and the holding time of the second gradient is 120min; The third gradient of the gradient pressing is 220℃ to 130℃, and the time of the third gradient is 30min.

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