A novel halogen-free copper clad laminate and its preparation method

Abstract

The present invention provides a halogen-free copper clad laminate, which comprises, by mass parts of raw materials, 90 to 110 parts by weight of epoxy resin, 100 to 300 parts by weight of a nitrogen- and phosphorus-containing epoxy curing agent, 0.5 to 5 parts by weight of an accelerator, 300 to 700 parts by weight of a solvent, and 150 to 400 parts by weight of an inorganic filler. The halogen-free copper clad laminate provided by the present invention has a specific formulation and composition, and contains a nitrogen- and phosphorus-containing epoxy curing agent with a specific structure and composition. The curing agent has an amino group as an active group, a high nitrogen element content, and better synergistic flame retardant effect with phosphorus. Moreover, the nitrogen element is on the main chain of the long-chain curing agent, having better compatibility and stability. The present invention is further combined with other simple raw material formulations and a specific pressing process, thereby obtaining a halogen-free copper clad laminate with more excellent flame retardant performance and comprehensive performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of halogen-free copper clad laminates, and relates to a halogen-free copper clad laminate and a preparation method thereof, and particularly relates to a novel halogen-free copper clad laminate and a preparation method thereof. Background Art

[0002] Copper Clad Laminate (CCL) is a plate-like material made by impregnating electronic glass fiber cloth or other reinforcing materials with resin, and covering one or both sides with copper foil and then hot-pressing. It is simply called copper clad laminate. Various printed circuit boards with different forms and functions are processed, etched, drilled, and copper-plated on the copper clad laminate selectively to make different printed circuits. It mainly plays the roles of interconnecting conduction, insulation, and support in the printed circuit board, and has a great influence on the signal transmission speed, energy loss, characteristic impedance, etc. in the circuit. Therefore, the performance, quality, processability, manufacturing level, manufacturing cost, long-term reliability, and stability of the printed circuit board largely depend on the copper clad laminate.

[0003] Copper clad laminates can be divided into two major categories: rigid copper clad laminates and flexible copper clad laminates. Among them, rigid copper clad laminates can be divided into organic resin copper clad laminates, metal-based (core) copper clad laminates, and ceramic-based copper clad laminates according to the insulating material and its structure. Among these, according to the insulating resin used, it can be divided into epoxy resin copper clad laminates, polyester resin copper clad laminates, cyanate ester resin copper clad laminates, etc., and epoxy resin copper clad laminates are an important part of copper clad laminates. Epoxy copper clad laminate is a hard copper clad laminate made by impregnating glass fiber cloth or wood pulp paper with epoxy resin, and covering one or both sides with copper foil and then hot-pressing. It is the main base material for producing printed circuit boards in household appliances, and usually has strict requirements for flame retardancy.

[0004] In the traditional epoxy resin flame retardant technology, halogen compounds (tetrabromobisphenol A) have been widely used in electronic materials that require flame retardant properties due to their excellent flame retardancy. However, during the combustion of halogen flame retardants, corrosive and toxic carcinogenic substances such as hydrogen bromide, tetrabromodibenzodioxin, and tetrabromodibenzofuran are released, and they have gradually been prohibited by environmental protection regulations. From the perspective of environmental protection, currently, phosphorus-based flame retardants are a better choice in the flame retardant system.

[0005] In the current existing technology, phosphorus-based flame retardants are mostly phosphoric acid esters or phosphoric acid esters or 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) compounds. As a curing agent for epoxy resin copper clad laminates, when used comprehensively, it is necessary to supplement with dicyandiamide (Dicy) curing agent to prepare epoxy resin adhesive, and a phosphorus-containing flame retardant epoxy resin copper clad laminate system is obtained. Moreover, phenolic or modified phenolic resins are mostly reacted with DOPO or DOPO compounds to obtain hydroxyl-containing compounds, and during curing, the hydroxyl groups act as active groups to react with epoxy resin to obtain a network cross-linked resin. However, this method will affect the comprehensive performance of the prepared epoxy resin copper clad laminate.

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

[0007] In view of this, the present invention provides a halogen-free copper clad laminate and a preparation method thereof, especially a novel halogen-free copper clad laminate. The halogen-free copper clad laminate provided by the present invention contains a specific nitrogen and phosphorus-containing epoxy curing agent, which has an amino group as an active group, a high nitrogen element content, a good synergistic flame retardant effect with phosphorus, better compatibility and stability, and further improves the comprehensive performance of epoxy resin copper clad laminates; moreover, the preparation method is simple, the conditions are mild, the controllability is good, and it is more conducive to industrial scale production and popularization and application.

[0008] The present invention provides a halogen-free copper clad laminate, calculated by mass parts of raw materials, including:

[0009]

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

[0011]

[0012] Wherein, the R is selected from

[0013] The R1 is selected from

[0014] The epoxy resin includes one or more of bisphenol A epoxy resin, phenol novolac epoxy resin, o-cresol novolac epoxy resin, bisphenol A novolac epoxy resin and bisphenol F epoxy resin;

[0015] The accelerator includes one or more of 2-methylimidazole, imidazole, 2-ethyl-4-methylimidazole and 2,4-dimethylimidazole.

[0016] Preferably, the solvent includes one or more of DMF, cyclohexanone, acetone, methyl ethyl ketone, and propylene glycol methyl ether;

[0017] The inorganic filler includes one or more of silica, silica powder, mica powder, magnesium hydroxide, aluminum hydroxide, and magnesium hydroxide;

[0018] The nitrogen- and phosphorus-containing epoxy curing agent includes a nitrogen- and phosphorus-containing phenolic curing agent;

[0019] The active group of the nitrogen- and phosphorus-containing epoxy curing agent includes an amino group.

[0020] Preferably, the raw materials further include fiberglass cloth;

[0021] The nitrogen- and phosphorus-containing epoxy curing agent is a curing agent for epoxy resin;

[0022] The raw materials do not contain other amine curing agents;

[0023] The nitrogen- and phosphorus-containing epoxy curing agent is a nitrogen- and phosphorus-containing epoxy curing agent with a flame retardant effect;

[0024] The flame retardant effect is specifically a nitrogen-phosphorus synergistic flame retardant effect.

[0025] Preferably, the preparation method of the nitrogen- and phosphorus-containing epoxy curing agent includes the following steps:

[0026] 1) Mix a DOPO organic solution, a catalyst, an isocyanate, and an organic solvent, and then react to obtain an intermediate solution;

[0027] 2) React the intermediate solution obtained in the above step with a diamine again to obtain a nitrogen- and phosphorus-containing epoxy curing agent.

[0028] 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;

[0029] The catalyst includes one or more of imidazole compounds, quaternary ammonium salt compounds, and triphenylphosphine compounds;

[0030] The isocyanate includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phthalic diisocyanate, and isophorone diisocyanate;

[0031] The organic solvent includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone;

[0032] The catalyst includes tetrabutylammonium bromide.

[0033] The proportion of the catalyst in the total mass of the DOPO and the isocyanate is 0.05 wt% to 0.2 wt%;

[0034] The molar ratio of the DOPO to the isocyanate is (0.8 to 1.2):1.

[0035] Preferably, the temperature of the reaction is 150 to 190 °C;

[0036] The time of the reaction is 2 to 3 h;

[0037] The specific mixing method is as follows: after pre-mixing the catalyst and the isocyanate to obtain a solution, then dropping the DOPO organic solution into the solution for mixing;

[0038] The dropping time is 1 to 3 h;

[0039] The molar ratio of the DOPO to the diamine is (0.8 to 1.2):1;

[0040] The diamine includes one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenylsulfone, bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane;

[0041] The temperature of the re-reaction is 110 to 130 °C;

[0042] The time of the re-reaction is 4 to 6 h.

[0043] The present invention also provides a preparation method of a halogen-free copper clad laminate, comprising the following steps:

[0044] A) Mix epoxy resin, a nitrogen and phosphorus-containing epoxy curing agent, a promoter and a solvent, and then add an inorganic filler and continue to mix to obtain a glue solution;

[0045] B) Immerse a glass fiber cloth in the glue solution obtained in the above step, and then dry it to obtain a semi-cured sheet;

[0046] C) Stack multiple layers of the semi-cured sheets obtained in the above step, and then laminate them with copper foil, and then press them to obtain a halogen-free copper clad laminate.

[0047] Preferably, the rotation speed of the mixing is 400 to 1000 revolutions per minute;

[0048] The rotation speed of the continuous mixing is 400 to 1000 revolutions per minute;

[0049] The time of the continuous mixing is 1 to 4 h;

[0050] The drying temperature is 100 to 250 °C.

[0051] Preferably, the pressure of the pressing is 20 - 30 kg / cm 2 ;

[0052] The pressing is gradient pressing;

[0053] For the gradient pressing, the first gradient is to increase the temperature from 85°C to 220°C, and the time of the first gradient is 30 min;

[0054] For the second gradient of the gradient pressing, the heat preservation temperature is 220°C, and the heat preservation time of the second gradient is 120 min;

[0055] For the third gradient of the gradient pressing, the temperature is decreased from 220°C to 130°C, and the time of the third gradient is 30 min.

[0056] The present invention provides a halogen - free copper - clad laminate. Calculated by mass parts of raw materials, it includes 90 - 110 parts by weight of epoxy resin, 100 - 300 parts by weight of a nitrogen - and - phosphorus - containing epoxy curing agent, 0.5 - 5 parts by weight of an accelerator, 300 - 700 parts by weight of a solvent, and 150 - 400 parts by weight of an inorganic filler. Compared with the prior art, for the problem that the use of a phosphorus - based flame - retardant curing agent in the existing epoxy resin halogen - free copper - clad laminate affects the comprehensive performance of the epoxy resin system, it is considered in the research that although through the nitrogen - phosphorus synergistic effect, while improving the flame - retardant effect, the comprehensive performance of the epoxy resin system can also be ensured and enhanced. For example, adding Dicy, and another example is in Patent CN103755925, a phosphorus - containing phenolic curing agent is obtained by etherifying phenolic resin and reacting with DOPO, and a nitrogen - containing additive such as melamine or acetoguanamine is added during the reaction process to introduce nitrogen element. However, the present invention believes that this way of introducing nitrogen by adding nitrogen - containing compounds additionally not only has the problem of cumbersome process, but also the addition amount of this addition method is limited, the proportion of nitrogen element is not high, the comprehensive effect improvement is limited, and there are also defects in terms of compatibility and stability of such small - molecule nitrogen - containing compounds.

[0057] Based on this, the present invention particularly designs a halogen - free copper - clad laminate with a specific formula and composition, which contains a nitrogen - and - phosphorus - containing epoxy curing agent with a specific structure and composition. This is a new type of long - chain nitrogen - and - phosphorus - containing epoxy curing agent. The synthesized curing agent uses an amino group as the active group, has a high nitrogen element content, has a better synergistic flame - retardant effect with phosphorus, and the nitrogen element is on the main chain of the long - chain curing agent, having better compatibility and stability. At the same time, the comprehensive performance of the epoxy resin halogen - free copper - clad laminate is further improved, thereby obtaining a halogen - free copper - clad laminate with excellent flame - retardant performance and comprehensive performance.

[0058] The present invention uses a novel nitrogen and phosphorus-containing resin as an epoxy resin curing agent to obtain a halogen-free flame-retardant copper clad laminate material on the premise of simplifying the resin formula, and further improves the comprehensive performance of the copper clad laminate while ensuring the excellent flame-retardant effect of the existing flame-retardant copper clad laminate formula. The present invention reacts isocyanate as the initial raw material with DOPO to make DOPO more easily incorporated into the resin, obtaining a phosphorus-containing aldehyde compound, and then reacting with diamine to obtain a nitrogen and phosphorus-containing epoxy curing agent. The present invention introduces nitrogen element through the assistance of isocyanate group after the reaction of DOPO with isocyanate, obtaining a nitrogen and phosphorus-containing epoxy curing agent with amino group as the active group, changing the existing phosphorus-containing curing agents which all have hydroxyl group as the active group, but introducing amino group as the epoxy curing group; moreover, the phosphorus in this curing agent is not easily precipitated and has excellent compatibility with epoxy resin; at the same time, this curing agent contains amino group, and when curing with epoxy resin, no additional amine curing agent needs to be added, and the nitrogen element is fixed on the long chain, which is more stable and has better compatibility. The present invention increases the proportion of nitrogen element in the nitrogen and phosphorus curing agent, has a good nitrogen and phosphorus synergistic effect in flame retardancy, and better realizes the effect of nitrogen and phosphorus co-blending flame retardancy in the epoxy curing system. More importantly, the prepared epoxy resin system has excellent performance in main properties such as solder resistance, glass transition temperature, peel strength and thermal weight loss.

[0059] The nitrogen and phosphorus-containing epoxy curing agent provided by the present invention has amino group as the active group, high nitrogen element content, good synergistic flame-retardant effect with phosphorus, and the halogen-free flame-retardant copper clad laminate has excellent comprehensive properties such as solder resistance, glass transition temperature, peel strength and thermal weight loss; moreover, the preparation method is simple, the conditions are mild, the controllability is good, and it is more conducive to industrial scale production and popularization and application. The novel halogen-free copper clad laminate provided by the present invention directly uses this phosphorus-containing amine curing agent, simplifies the resin glue formula, and then combines with other simple raw material formulas and specific pressing processes, thereby obtaining a halogen-free copper clad laminate with more excellent flame-retardant performance and comprehensive performance.

[0060] The experimental results show that the halogen-free flame-retardant copper clad laminate using the nitrogen and phosphorus-containing epoxy curing agent provided by the present invention has a flame-retardant effect reaching the UL-94V-0 level, and the comprehensive properties such as the solder resistance, glass transition temperature, peel strength and thermal weight loss of the board all reach or exceed the level of commercially available products. Detailed Embodiments

[0061] In order to further understand the present invention, the technical solutions 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 a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0062] For all raw materials of the present invention, there are no special restrictions on their sources, and they can be purchased on the market or prepared according to conventional methods well-known to those skilled in the art.

[0063] For all raw materials of the present invention, there are no special restrictions on their purities. The present invention preferably uses analytical pure or conventional purities in the field of copper clad laminate preparation.

[0064] The present invention provides a halogen-free copper clad laminate, which includes, by mass parts of raw materials:

[0065]

[0066] In the present invention, the addition amount of the epoxy resin is 90 to 110 parts by weight, can be 94 to 106 parts by weight, and is preferably 98 to 102 parts by weight.

[0067] In the present invention, the addition amount of the nitrogen and phosphorus-containing epoxy curing agent is 100 to 300 parts by weight, can be 140 to 260 parts by weight, and is preferably 180 to 220 parts by weight.

[0068] In the present invention, the addition amount of the accelerator is 0.5 to 5 parts by weight, can be 1.5 to 4 parts by weight, and is preferably 2.5 to 3 parts by weight.

[0069] In the present invention, the addition amount of the solvent is 300 to 700 parts by weight, can be 350 to 650 parts by weight, is preferably 400 to 600 parts by weight, and more preferably 450 to 550 parts by weight.

[0070] In the present invention, the addition amount of the inorganic filler is 150 to 400 parts by weight, can be 200 to 350 parts by weight, and is preferably 250 to 300 parts by weight.

[0071] In the present invention, the molar ratio of active hydrogen (hydrogen atoms connected to N) to epoxy groups on the nitrogen and phosphorus-containing epoxy curing agent is preferably (0.95 to 1.2):1, more preferably (1.00 to 1.15):1, and even more preferably (1.05 to 1.10):1.

[0072] In the present invention, the dosage of the accelerator is preferably 0.05 wt% to 0.2 wt% of the total weight of the resin system, more preferably 0.07 wt% to 0.18 wt%, and even more preferably 0.1 wt% to 0.15 wt%.

[0073] In the present invention, the mass ratio of the inorganic filler to the resin system is preferably (0.2 to 0.4):1, more preferably (0.23 to 0.38):1, and even more preferably (0.25 to 0.35):1.

[0074] In the present invention, the amount of the solvent is preferably such that the solid content of the raw material slurry is between 55% and 65%, more preferably between 57% and 63%, and even more preferably between 59% and 61%.

[0075] In the present invention, the resin system preferably refers to a system including epoxy resin, additives (curing agent and accelerator), and filler, excluding the solvent. For the final epoxy copper clad laminate, it does not include fibers, and the raw material slurry is the sum of the resin system and the solvent.

[0076] In the present invention, the epoxy resin preferably includes one or more of bisphenol A epoxy resin, phenol novolac epoxy resin, o-cresol novolac epoxy resin, bisphenol A novolac epoxy resin, and bisphenol F epoxy resin, more preferably bisphenol A epoxy resin, phenol novolac epoxy resin, o-cresol novolac epoxy resin, bisphenol A novolac epoxy resin, or bisphenol F epoxy resin. Specifically, the epoxy resin in the present invention can be phenol novolac epoxy resin.

[0077] In the present 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.

[0078] In the present invention, the solvent preferably includes one or more of DMF, cyclohexanone, acetone, methyl ethyl ketone, and propylene glycol methyl ether, more preferably DMF, cyclohexanone, acetone, methyl ethyl ketone, or propylene glycol methyl ether.

[0079] In the present invention, the inorganic filler preferably includes one or more of silica, silica powder, mica powder, magnesium hydroxide, aluminum hydroxide, and magnesium hydroxide, more preferably silica, silica powder, mica powder, magnesium hydroxide, aluminum hydroxide, or magnesium hydroxide.

[0080] In the present invention, the nitrogen- and phosphorus-containing epoxy curing agent preferably includes a nitrogen- and phosphorus-containing phenol novolac curing agent.

[0081] In the present invention, the active group of the nitrogen- and phosphorus-containing epoxy curing agent preferably includes an amino group.

[0082] In the present invention, the raw materials preferably further include a glass fiber cloth.

[0083] In the present invention, the nitrogen- and phosphorus-containing epoxy curing agent is preferably a curing agent for epoxy resin.

[0084] In the present invention, the raw materials preferably do not contain other amine curing agents.

[0085] In the present invention, the nitrogen- and phosphorus-containing epoxy curing agent is preferably a nitrogen- and phosphorus-containing epoxy curing agent with a flame retardant effect.

[0086] In the present invention, the flame retardant effect is specifically preferably the synergistic nitrogen-phosphorus flame retardant effect.

[0087] In the present invention, the nitrogen and phosphorus-containing epoxy curing agent preferably has a structure as shown in formula (I):

[0088]

[0089] Wherein, R preferably is selected from

[0090] In the present invention, R1 preferably is selected from

[0091] In the present invention, the preparation method of the nitrogen and phosphorus-containing epoxy curing agent preferably comprises the following steps:

[0092] 1) Mix a DOPO organic solution, a catalyst, an isocyanate and an organic solvent, and then carry out a reaction to obtain an intermediate solution;

[0093] 2) React the intermediate solution obtained in the above step with a diamine again to obtain a nitrogen and phosphorus-containing epoxy curing agent.

[0094] In the present invention, first, a DOPO organic solution, a catalyst, an isocyanate and an organic solvent are mixed and then reacted to obtain an intermediate solution.

[0095] In the present invention, the solvent of the DOPO organic solution preferably comprises one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether and cyclohexanone, and more preferably is toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether or cyclohexanone.

[0096] In the present invention, the catalyst preferably comprises one or more of imidazole compounds, quaternary ammonium salt compounds and triphenylphosphine compounds, and more preferably is an imidazole compound, a quaternary ammonium salt compound or a triphenylphosphine compound. Specifically, the catalyst preferably comprises tetrabutylammonium bromide.

[0097] In the present invention, the isocyanate preferably comprises one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate and isophorone diisocyanate, and more preferably is diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI) or isophorone diisocyanate (IPDI).

[0098] In the present 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, and more preferably is toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, or cyclohexanone.

[0099] In the present invention, the proportion of the catalyst in the total mass of DOPO and isocyanate is preferably 0.05 wt% to 0.2 wt%, more preferably 0.08 wt% to 0.17 wt%, and even more preferably 0.11 wt% to 0.14 wt%.

[0100] In the present invention, the molar ratio of DOPO to isocyanate is preferably (0.8 to 1.2):1, more preferably (0.85 to 1.15):1, even more preferably (0.9 to 1.1):1, and even more preferably (0.95 to 1.05):1.

[0101] In the present invention, the temperature of the reaction is preferably 150 to 190 °C, more preferably 155 to 185 °C, even more preferably 160 to 180 °C, and even more preferably 165 to 175 °C, so as to better inhibit the self-polymerization of isocyanate.

[0102] In the present invention, the reaction time is preferably 2 to 3 h, more preferably 2.2 to 2.8 h, and even more preferably 2.4 to 2.6 h.

[0103] In the present invention, the mixing method is specifically preferably that after pre-mixing the catalyst and isocyanate to obtain a solution, the DOPO organic solution is then dropwise added to the solution for mixing.

[0104] In the present invention, the dropping time is preferably 1 to 3 h, more preferably 1.4 to 2.6 h, and even more preferably 1.8 to 2.2 h.

[0105] In the present invention, the dropping is preferably carried out at the reaction temperature. That is, the dropping temperature is preferably 150 to 190 °C, more preferably 155 to 185 °C, even more preferably 160 to 180 °C, and even more preferably 165 to 175 °C.

[0106] Finally, in the present invention, the intermediate solution obtained in the above steps is reacted with diamine again to obtain a nitrogen and phosphorus-containing epoxy curing agent.

[0107] In the present invention, the molar ratio of DOPO to diamine is preferably (0.8 to 1.2):1, more preferably (0.85 to 1.15):1, even more preferably (0.9 to 1.1):1, and even more preferably (0.95 to 1.05):1.

[0108] In the present invention, the diamine preferably includes one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenylsulfone, 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), diaminodiphenylsulfone (DDS), bisphenol A type diether diamine, or 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane.

[0109] In the present invention, the temperature of the re-reaction is preferably 110 - 130 °C, more preferably 115 - 125 °C, and even more preferably 119 - 121 °C.

[0110] In the present invention, the time of the re-reaction is preferably 4 - 6 h, more preferably 4.4 - 5.6 h, and even more preferably 4.8 - 5.2 h.

[0111] To complete and refine the overall technical solution of the present invention, further ensure the structure and composition of the nitrogen and phosphorus-containing epoxy curing agent, and better improve the flame retardancy, curing effect, and system stability of the nitrogen and phosphorus-containing epoxy curing agent, the above-mentioned nitrogen and phosphorus-containing epoxy curing agent and its preparation method preferably can be the following:

[0112] 1. React DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) with isocyanate to obtain DOPO-R-CHO.

[0113] Drop the DOPO / toluene solution into the isocyanate (or isocyanate solution) containing a catalyst at a certain temperature.

[0114] Specifically, the isocyanate includes but is not limited to diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), m-xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), and preferably MDI.

[0115] Specifically, the commonly used catalysts include imidazole-based, quaternary ammonium salt-based, and triphenylphosphine-based compounds, and preferably the quaternary ammonium salt-based compound - tetrabutylammonium bromide.

[0116] The reaction formula of the above steps is as follows:

[0117]

[0118] 2. React DOPO-R-CHO with diamine to synthesize a nitrogen and phosphorus-containing amine curing agent.

[0119] Specifically, the diamine includes but is not limited to phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane (DDM), diaminodiphenylsulfone (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 them, amines with a methyl or ethyl group on the benzene ring contribute to improving the dielectric properties of the resin..

[0120] The reaction formula of the above steps is as follows:

[0121]

[0122] The nitrogen-phosphorus-containing epoxy curing agent with a specific structure and composition specially designed in the present invention is a novel nitrogen-phosphorus-containing epoxy curing agent. It has an amino group as the active group, a high nitrogen element content, and a better synergistic flame retardant effect with phosphorus. Moreover, the nitrogen element is on the main chain of the long-chain curing agent, having better compatibility and stability, and further improving the comprehensive performance of the epoxy resin halogen-free copper clad laminate at the same time.

[0123] In the present invention, DOPO reacts with isocyanate, and then nitrogen element is introduced with the assistance of isocyanate group to obtain a nitrogen-phosphorus-containing epoxy curing agent with an amino group as the active group, changing the existing phosphorus-containing curing agents that all have a hydroxyl group as the active group and introducing an amino group as the epoxy curing group; moreover, the phosphorus in this curing agent is not easy to precipitate, and it has excellent compatibility with epoxy resin; at the same time, this curing agent contains an amino group, and no additional amine curing agent needs to be added when curing with epoxy resin, and the nitrogen element is fixed on the long chain, which is more stable and has better compatibility. The present invention increases the proportion of nitrogen element in the nitrogen-phosphorus curing agent, improves the nitrogen-phosphorus synergistic effect in flame retardancy, and better realizes the nitrogen-phosphorus co-blended flame retardant effect of the epoxy curing system.

[0124] The present invention provides a preparation method of a halogen-free copper clad laminate, including the following steps:

[0125] A) Mix epoxy resin, nitrogen-phosphorus-containing epoxy curing agent, accelerator, and solvent, and then add inorganic filler and continue to mix to obtain a glue solution;

[0126] B) Immerse a glass fiber cloth in the glue solution obtained in the above step, and then dry it to obtain a prepreg;

[0127] C) Stack multiple layers of the prepreg obtained in the above step, then laminate it with copper foil, and after pressing, obtain a halogen-free copper clad laminate.

[0128] In the present invention, epoxy resin, nitrogen-phosphorus-containing epoxy curing agent, accelerator, and solvent are first mixed, and then inorganic filler is added and continued to mix to obtain a glue solution.

[0129] In the present invention, the rotation speed of the mixing is preferably 400 to 1000 revolutions per minute, more preferably 500 to 900 revolutions per minute, and even more preferably 600 to 800 revolutions per minute.

[0130] In the present invention, the mixing is specifically preferably carried out until a uniform suspension is obtained to obtain the adhesive solution for impregnating the copper clad laminate.

[0131] In the present invention, the rotation speed of the continued mixing is preferably 400 to 1000 revolutions per minute, more preferably 500 to 900 revolutions per minute, and even more preferably 600 to 800 revolutions per minute.

[0132] In the present invention, the time of the continued mixing is preferably 1 to 4 h, more preferably 1.5 to 3.5 h, and even more preferably 2 to 3 h.

[0133] In the present invention, the glass fiber cloth is impregnated in the adhesive solution obtained in the above step and then dried to obtain a prepreg.

[0134] In the present invention, the drying temperature is preferably 100 to 250 °C, more preferably 130 to 220 °C, and even more preferably 160 to 190 °C.

[0135] Finally, in the present invention, the prepregs obtained in the above steps are stacked in multiple layers, and then laminated with copper foil, and after pressing, a halogen-free copper clad laminate is obtained.

[0136] In the present invention, the pressure of the pressing is preferably 20 to 30 kg / cm 2 , more preferably 22 to 28 kg / cm 2 , more preferably 24 to 26 kg / cm 2 .

[0137] In the present invention, the pressing is preferably gradient pressing.

[0138] In the present invention, the first gradient of the gradient pressing is preferably from 85 °C to 220 °C, and the time of the first gradient is preferably 30 min.

[0139] In the present invention, the holding temperature of the second gradient of the gradient pressing is preferably 220 °C, and the holding time of the second gradient is preferably 120 min.

[0140] In the present invention, the third gradient of the gradient pressing is preferably from 220 °C to 130 °C, and the time of the third gradient is preferably 30 min.

[0141] In order to complete and refine the overall technical solution of the present invention, further ensure the flame retardant performance, curing effect and system stability of the nitrogen and phosphorus-containing epoxy curing agent, and better improve the flame retardant performance and stability of the copper clad laminate, the preparation method of the above-mentioned novel halogen-free copper clad laminate preferably may be the following steps:

[0142] The epoxy resin, a novel nitrogen- and phosphorus-containing epoxy curing agent, a promoter and a solvent are stirred and dissolved at a high speed of 400 - 1000 revolutions per minute, and then inorganic fillers are added and stirring continues for 2 h. The glass fiber cloth is impregnated in the above-mentioned adhesive solution and dried at 100 - 250 °C to obtain a prepreg. After the obtained prepreg is cut, eight pieces are grouped and laminated with copper foil for pressing.

[0143] The pressing conditions are: the pressure is 25 kg / cm 2 , and the heating program is 85 °C → 220 °C → 220 °C → 130 °C, and the heating times are 30 min, 120 min, and 30 min.

[0144] The above content of the present invention provides a novel halogen-free copper clad laminate and its preparation method. The halogen-free copper clad laminate with a specific formulation and composition contains a nitrogen- and phosphorus-containing epoxy curing agent with a specific structure and composition, which is a novel long-chain nitrogen- and phosphorus-containing epoxy curing agent. The synthesized curing agent uses an amino group as the active group, has a high nitrogen element content, and has a better synergistic flame retardant effect with phosphorus. Moreover, the nitrogen element is on the main chain of the long-chain curing agent, having better compatibility and stability, and further improving the comprehensive performance of the epoxy resin halogen-free copper clad laminate, thereby obtaining a halogen-free copper clad laminate with excellent flame retardant performance and comprehensive performance.

[0145] The present invention uses a novel nitrogen- and phosphorus-containing resin as the epoxy resin curing agent to obtain a halogen-free flame retardant copper clad laminate material on the premise of simplifying the resin formulation, and further improves the comprehensive performance of the copper clad laminate on the basis of ensuring the excellent flame retardant effect of the existing flame retardant copper clad laminate formulation. The present invention uses isocyanate as the initial raw material to react with DOPO, making DOPO more easily incorporated into the resin to obtain a phosphorus-containing aldehyde compound, and then reacting with diamine to obtain a nitrogen- and phosphorus-containing epoxy curing agent. The present invention uses the reaction of DOPO and isocyanate to assist in introducing nitrogen element through the isocyanate group, obtaining a nitrogen- and phosphorus-containing epoxy curing agent with an amino group as the active group, changing the existing phosphorus-containing curing agents that all use a hydroxyl group as the active group, but introducing an amino group as the epoxy curing group; moreover, the phosphorus in this curing agent is not easily precipitated and has excellent compatibility with epoxy resin; at the same time, this curing agent contains an amino group, and no additional amine curing agent needs to be added when curing with epoxy resin, and the nitrogen element is fixed on the long chain, which is more stable and has better compatibility. The present invention increases the proportion of nitrogen element in the nitrogen- and phosphorus-containing curing agent, has a good nitrogen-phosphorus synergistic effect in flame retardancy, better realizes the effect of nitrogen-phosphorus co-blending flame retardancy in the epoxy curing system. More importantly, the prepared epoxy resin system has excellent performance in main properties such as solder resistance, glass transition temperature, peel strength and thermal weight loss.

[0146] The nitrogen and phosphorus-containing epoxy curing agent provided by the present invention uses amino groups as active groups, has a high nitrogen element content, has a good synergistic flame retardant effect with phosphorus, and is a halogen-free flame retardant copper clad laminate, having excellent comprehensive properties such as solder resistance, glass transition temperature, peel strength, and thermal weight loss; moreover, the preparation method is simple, the conditions are mild, and the controllability is good, which is more conducive to industrial scale production and popularization and application. The novel halogen-free copper clad laminate provided by the present invention directly uses this phosphorus-containing amine curing agent, simplifies the resin glue formula, and then combines with other simple raw material formulas and a specific pressing process to obtain a halogen-free copper clad laminate with more excellent flame retardant properties and comprehensive properties.

[0147] The experimental results show that the halogen-free flame retardant copper clad laminate using the nitrogen and phosphorus-containing epoxy curing agent provided by the present invention has a flame retardant effect reaching the UL-94V-0 level, and the comprehensive properties such as the solder resistance, glass transition temperature, peel strength, and thermal weight loss of the board all reach or exceed the level of commercially available products.

[0148] In order 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 in conjunction with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and give the detailed implementation methods and specific operation processes, only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments.

[0149] Embodiment

[0150] The epoxy resin, nitrogen and phosphorus-containing epoxy curing agent, accelerator and solvent are stirred and dissolved at a high speed of 400-1000 revolutions per minute, and then inorganic fillers are added and stirred for another 2 h. The glass fiber cloth is impregnated in the above glue solution and dried at 100-250 °C to obtain a prepreg. The obtained prepreg is cut into groups of 8 sheets and laminated with copper foil for pressing.

[0151] The pressing conditions are: the pressure is 25 kg / cm 2 , the heating program is 85 °C → 220 °C → 220 °C → 130 °C, and the heating times are 30 min, 120 min, and 30 min.

[0152] The resin glue solution is prepared according to the proportions in Table 1, and finally the copper clad laminate material is obtained and its performance is tested. The halogen-free curing agent in the control group is the XZ-92741 product produced by Dow.

[0153] The structure of the curing agent used in the embodiment is shown in the figure.

[0154]

[0155] Referring to Table 1, Table 1 shows the raw material formulas, process parameters, and performance test results of the copper clad laminate materials prepared in the embodiments and comparative examples of the present invention.

[0156] Table 1

[0157]

[0158] The nitrogen and phosphorus-containing epoxy curing agent synthesized by the method of the present invention has the same excellent flame retardancy as the commercially available phosphorus-containing curing agent, and both can reach the UL-94 V-0 level.

[0159] 1. Gel time: Weigh 0.2 mg of the pre-impregnated powder and place it on a hot plate at a temperature of 170 °C, and record the time required to gel.

[0160] 2. Interlaminar bonding strength: Test according to the IPC-TM-650-2.4.8C method.

[0161] 3. Thermal weight loss Td5%: Use TGA to test, and measure according to the TGA test method specified in IPC-TM-650 2.4.24.6.

[0162] 4. Solder heat resistance at 288 °C (after 2 hours in a PCT pressure cooker)

[0163] The test method is to immerse the above-mentioned test piece after the pressure cooker test into a 288 °C soldering furnace, and record the time required for the test piece to burst and delaminate; when the substrate does not show blistering or delamination in the tin furnace for more than 5 minutes, the evaluation can be ended.

[0164] 5. Glass transition temperature (Temperature of glass transition) test:

[0165] Use a differential scanning calorimeter (abbreviated as DSC), with a heating rate of 20 °C / min.

[0166] 6. Flame retardancy test:

[0167] According to the UL-94 standard method, test the flame retardancy of the sample.

[0168] The above has introduced in detail a novel halogen-free copper clad laminate and its preparation method provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in the technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention 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 the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A halogen-free copper clad laminate, characterized in that, By parts by mass of the raw materials, it includes: 90 - 110 parts by weight of epoxy resin; 100 - 300 parts by weight of nitrogen - and - phosphorus - containing epoxy curing agent; 0.5 - 5 parts by weight of accelerator; 300 - 700 parts by weight of solvent; 150 - 400 parts by weight of inorganic filler; The nitrogen - and - phosphorus - containing epoxy curing agent has the structure shown in formula (I): , or .

2. The halogen-free copper clad laminate according to claim 1, characterized in that, The epoxy resin includes one or more of bisphenol A epoxy resin, phenol - formaldehyde epoxy resin, o - cresol - formaldehyde epoxy resin, bisphenol A - phenol - formaldehyde epoxy resin, and bisphenol F epoxy resin; The accelerator includes one or more of 2 - methylimidazole, imidazole, 2 - ethyl - 4 - methylimidazole, and 2,4 - dimethylimidazole.

3. The halogen-free copper clad laminate according to claim 1, characterized in that, The solvent includes one or more of DMF, cyclohexanone, acetone, methyl ethyl ketone, and propylene glycol methyl ether; The inorganic filler includes one or more of silica, silica powder, mica powder, magnesium hydroxide, aluminum hydroxide, and magnesium hydroxide; 4. The halogen-free copper clad laminate according to claim 1, characterized in that, The raw materials further include fiberglass cloth; The nitrogen - and - phosphorus - containing epoxy curing agent is a curing agent for epoxy resin; The raw materials do not contain other amine - based curing agents; The nitrogen - and - phosphorus - containing epoxy curing agent is a nitrogen - and - phosphorus - containing epoxy curing agent with flame - retardant effect; The flame - retardant effect is specifically a nitrogen - phosphorus synergistic flame - retardant effect.

5. The halogen-free copper clad laminate according to claim 1, characterized in that, The preparation method of the nitrogen - and - phosphorus - containing epoxy curing agent includes the following steps: 1) Mix the DOPO organic solution, catalyst, isocyanate, and organic solvent, and then carry out a reaction to obtain an intermediate solution; 2) React the intermediate solution obtained in the above step with diamine again to obtain the nitrogen - and - phosphorus - containing epoxy curing agent.

6. The halogen-free copper clad laminate according to claim 5, characterized in that, 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; The catalyst includes one or more of imidazole - based compounds, quaternary ammonium salt - based compounds, and triphenylphosphine - based compounds; The isocyanate includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and isophorone diisocyanate; The organic solvent includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone; The catalyst includes tetrabutylammonium bromide; The proportion of the catalyst in the total mass of DOPO and isocyanate is 0.05wt% - 0.2wt%; The molar ratio of DOPO to isocyanate is (0.8 - 1.2):1; 7. The halogen-free copper clad laminate according to claim 5, characterized in that, The temperature of the reaction is 150 - 190°C; The time of the reaction is 2 - 3h; The specific mixing method is to pre - mix the catalyst and isocyanate to obtain a solution, and then drop - add the DOPO organic solution into the solution for mixing; The dropping time is 1 - 3h; The molar ratio of DOPO to diamine is (0.8 - 1.2):1; The diamine includes one or more of phenylenediamine, 4,4’ - diamino - 3,3’ - dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenylsulfone, bisphenol A - type diether diamine, and 3,3’ - dimethyl - 5,5’ - diethyl - 4,4’ - diaminodiphenylmethane. The temperature of the re-reaction is 110~130°C; The time of the re-reaction is 4~6 h.

8. A method for preparing a halogen-free copper clad laminate according to any one of claims 1 to 7, characterized in that, It includes the following steps: A) Mix epoxy resin, nitrogen and phosphorus-containing epoxy curing agent, accelerator and solvent, and then add inorganic filler and continue to mix to obtain a glue solution; B) Immerse the glass fiber cloth in the glue solution obtained in the above step, and then dry it to obtain a semi-cured sheet; C) Stack multiple layers of the semi-cured sheets obtained in the above step, and then laminate them with copper foil, and then press them to obtain a halogen-free copper clad laminate.

9. According to the preparation method described in claim 8, characterized in that, The rotation speed of the mixing is 400~1000 revolutions per minute; The rotation speed of the continued mixing is 400~1000 revolutions per minute; The time of the continued mixing is 1~4 h; The temperature of the drying is 100~250°C.

10. According to the preparation method described in claim 8, characterized in that, The pressure of the pressing is 20~30 kg / cm 2 ; The pressing is gradient pressing; The first gradient of the gradient pressing is to raise the temperature from 85°C to 220°C, and the time of the first gradient is 30 min; The holding temperature of the second gradient of the gradient pressing is 220°C, and the holding time of the second gradient is 120 min; The third gradient of the gradient pressing is to lower the temperature from 220°C to 130°C, and the time of the third gradient is 30 min.

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