A halogen-free flame-retardant FR-4 copper clad plate based on a benzoxazine resin and a preparation method thereof

Abstract

The application discloses a kind of benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad plate and its preparation method, including benzoxazine-epoxy resin impregnation glue solution, glass fiber cloth and copper foil, the raw materials of the benzoxazine-epoxy resin impregnation glue solution include the following mass fraction of raw materials: epoxy resin 100 parts, modified nitrogen-containing benzoxazine resin 40~60 parts, metal hydroxide 20~40 parts, epoxy resin curing agent 0.4~0.6 parts, composite solvent 70~80 parts, the modified nitrogen-containing benzoxazine resin molecular chain is also grafted with polyethylene glycol segment.The modified nitrogen-containing benzoxazine resin can act as an epoxy resin curing agent while also acting as a reactive flame retardant for epoxy resin, can significantly improve the flame retardancy of the epoxy resin itself, and in the process of promoting the curing of the epoxy resin, no by-product small molecules are produced, which can reduce the occurrence of defects, thereby improving the mechanical properties of the obtained copper-clad plate.

Description

Technical Field

[0001] This application relates to the field of copper clad laminates, and in particular to a benzoxazine resin-based halogen-free flame-retardant FR-4 copper clad laminate and its preparation method. Background Technology

[0002] During the use of electronic devices, the printed circuit boards (PCBs) they contain often pose a fire hazard due to heat accumulation. To prevent this, the flame-retardant properties of the PCBs are of paramount importance. As a fundamental material in the manufacturing process of PCBs, improving the flame-retardant properties of copper-clad laminates (CCLs) is crucial for enhancing the overall flame-retardant performance of PCBs.

[0003] In the preparation of flame-retardant copper clad laminates, flame-retardant compounds containing environmentally harmful elements such as halogens or antimony are often introduced to improve the flame retardancy of the board. However, with the increasing awareness of environmental protection, the demand for halogen-free flame-retardant copper clad laminates is increasing. However, in order to maintain flame retardancy, the heat resistance and mechanical properties, including toughness and strength, of commonly used halogen-free flame-retardant copper clad laminates are lower than those of general halogen flame-retardant copper clad laminates. Summary of the Invention

[0004] To address the issues of poor flame retardant performance, reduced heat resistance, and decreased mechanical properties of halogen-free flame-retardant copper-clad laminates, this application provides a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate and its preparation method.

[0005] In a first aspect, this application provides a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, comprising a benzoxazine-epoxy resin impregnating solution, fiberglass cloth, and copper foil, wherein the raw materials of the benzoxazine-epoxy resin impregnating solution include the following parts by weight:

[0006] 100 parts epoxy resin;

[0007] 40-60 parts of modified nitrogen-containing benzoxazine resin;

[0008] 20-40 parts of metal hydroxide;

[0009] 0.4 to 0.6 parts of epoxy resin curing agent;

[0010] 70-80 parts of composite solvent;

[0011] The modified nitrogen-containing benzoxazine resin molecular chain is further grafted with polyethylene glycol segments.

[0012] More preferably, the epoxy resin is a bisphenol A type epoxy resin.

[0013] Preferably, the metal hydroxide includes one or a combination of magnesium hydroxide and aluminum hydroxide.

[0014] Preferably, the composite solvent is a mixed solution of acetone, butanone and toluene in a mass ratio of 1:(0.6-1):(0.8-1.2).

[0015] By adopting the above technical solution, a modified nitrogen-containing benzoxazine resin is added to epoxy resin. This modified nitrogen-containing benzoxazine resin acts as both a curing agent and a reactive flame retardant for epoxy resin, significantly improving the flame retardancy of the epoxy resin itself. Furthermore, during the epoxy resin curing process, no small byproduct molecules are generated, and there is no significant volume change. This eliminates residual stress within the epoxy resin after curing, reduces defects, and thus improves the mechanical properties of the resulting copper-clad laminate. This modified nitrogen-containing benzoxazine resin introduces nitrogen into the benzoxazine resin base. On one hand, benzoxazine resin itself has certain flame retardancy, and its reaction with epoxy resin during curing improves the flame retardant performance of the epoxy resin. On the other hand, its thermal decomposition products are non-combustible gases such as ammonia and carbon dioxide. These gases dilute the oxygen concentration in the air and absorb most of the heat during decomposition, thus achieving a flame retardant effect. Moreover, this modified nitrogen-containing benzoxazine resin flame retardant has low toxicity, low smoke density, and low corrosivity, and will not cause significant corrosion to electronic equipment. Meanwhile, conventional nitrogen-containing flame retardants are difficult to react with the matrix resin due to their supramolecular structure. However, this modified nitrogen-containing benzoxazine resin is a reactive flame retardant that reacts chemically with epoxy resin in the form of reactive monomers. Compared with conventional nitrogen-containing flame retardants, it can significantly enhance the flame retardancy of epoxy resin and has a long-lasting flame retardant effect. There will be no phenomenon such as the flame retardant precipitating out of the system and losing its flame retardant properties due to long-term exposure.

[0016] Meanwhile, the benzoxazine-epoxy resin impregnation solution contains a large number of benzene ring structures, resulting in high material rigidity and enhanced heat resistance. This manifests as high strength and good thermal stability in the copper-clad laminate formed by the benzoxazine-epoxy resin impregnation solution, but poor toughness. Polyethylene glycol segments are also grafted onto the molecular chains of this modified nitrogen-containing benzoxazine resin. As a flexible group, polyethylene glycol can interpenetrate between the molecular chains of the epoxy resin after the modified nitrogen-containing benzoxazine resin reacts with the epoxy resin, reducing the interaction forces between the molecular chains and improving the toughness of the material. Furthermore, the hydroxyl groups contained in polyethylene glycol can react with the polar groups in the epoxy resin during the curing process, increasing the crosslinking density between the modified nitrogen-containing benzoxazine resin and the epoxy resin, thereby improving the mechanical properties of the formed copper-clad laminate.

[0017] Meanwhile, the benzoxazine-epoxy resin impregnation system also contains metal hydroxides and composite solvents. Compared with other similar inorganic flame retardants, the metal hydroxides not only have a good synergistic effect on the flame retardant effect of the modified nitrogen-containing benzoxazine resin, but also can inhibit the generation of smoke and harmful gases. In the system, it has a triple effect of flame retardancy, smoke suppression and filling. The modified nitrogen-containing benzoxazine resin has good dispersibility and compatibility with epoxy resin in the composite solution, which can better play the role of curing epoxy resin.

[0018] Preferably, the raw materials for the modified nitrogen-containing benzoxazine resin include formaldehyde, melamine, bisphenol A, and polyethylene glycol in a mass ratio of 1:(0.4-0.5):(0.45-0.55):(0.3-0.5).

[0019] Preferably, the polyethylene glycol is one or a combination of polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400.

[0020] By adopting the above technical solution, this application uses a solvent-free method to prepare modified nitrogen-containing benzoxazine resin. Formaldehyde acts as both a reactant and a solvent during the reaction process, and no other organic solvents are introduced during the preparation process, ensuring the purity of the finished product. At the same time, melamine is added during the preparation process, and its triazine ring introduces nitrogen elements into the benzoxazine resin, enhancing the flame retardancy of the benzoxazine resin. Polyethylene glycol has a low molecular weight, which increases the toughness of epoxy resin without affecting the curing efficiency of epoxy resin, and plays a good promoting role in epoxy resin.

[0021] Preferably, the modified nitrogen-containing benzoxazine resin is prepared according to the following method:

[0022] Adjust the pH of the formaldehyde solution to 8-9, add melamine, raise the temperature to 65-75℃, stir until the solution is clear, then add bisphenol A, stir to dissolve, raise the temperature to 80-90℃, and continue stirring to obtain a mixed solution; adjust the temperature of the obtained mixed solution to 40-50℃, add polyethylene glycol, stir to dissolve, add a catalyst, raise the temperature to 120-130℃, stir to react for 2-3 hours, and then filter, let stand, and dehydrate under reduced pressure to obtain the modified nitrogen-containing benzoxazine resin.

[0023] More preferably, the catalyst includes one or a combination of manganese dioxide and copper dioxide.

[0024] By employing the above technical solution, under weakly alkaline conditions, formaldehyde first reacts with the amino groups contained in melamine. After the introduction of bisphenol A propane, a dehydration and ring-closing reaction occurs, gradually forming an oxazine ring structure. Then, under the action of a catalyst, it is compounded with polyethylene glycol, allowing polyethylene glycol segments to be grafted onto the molecular chain of the benzoxazine resin. The resulting modified nitrogen-containing benzoxazine resin not only improves the flame retardancy of epoxy resin but also increases the curing efficiency and mechanical properties of epoxy resin.

[0025] Preferably, the epoxy resin is modified with siloxane.

[0026] Preferably, the raw materials used in the epoxy resin modification treatment include epoxy resin and hydroxyl-terminated polydimethylsiloxane in a mass ratio of 100:(30-40).

[0027] More preferably, the epoxy resin is modified with siloxane according to the following method:

[0028] After uniformly mixing epoxy resin with hydroxyl-terminated polydimethylsiloxane, the temperature is raised to 120-140℃, and then an organotin catalyst is added. The mixture is stirred and reacted for 2-3 hours under a pressure of 0.1-0.2 MPa to obtain epoxy resin modified with siloxane.

[0029] By employing the above technical solution, under the catalytic action of an organotin catalyst, the hydroxyl groups in the epoxy resin, or the hydroxyl groups formed after ring opening of the epoxy groups, can undergo a dehydration condensation reaction with the hydroxyl groups in the terminal hydroxyl polydimethylsiloxane, resulting in siloxane segments on the epoxy resin molecular chain. The addition of these siloxane segments can increase the glass transition temperature of the epoxy resin, thereby improving its thermal stability, and consequently enhancing its flame retardant effect and stability. Simultaneously, the silanol groups can react with the hydroxyl groups on the surface of the glass fiber cloth; therefore, the introduction of silanol groups can also increase the bonding strength between the epoxy resin and the glass fiber cloth, improve the adhesion between the benzoxazine-epoxy resin impregnation solution and the glass fiber cloth, and enhance the peel strength of the copper-clad laminate.

[0030] Preferably, the benzoxazine-epoxy resin impregnation solution is prepared according to the following method:

[0031] After mixing epoxy resin and modified nitrogen-containing benzoxazine resin, a composite solvent is added and stirred for 10-20 minutes. Then, epoxy resin curing agent is added, the temperature is raised to 80-90℃ and the reaction is continued for 2-3 hours. Then, metal hydroxide is added and stirred for another 2-3 hours to obtain benzoxazine-epoxy resin impregnation solution.

[0032] Preferably, the epoxy resin curing agent includes one or a combination of several of 1,2,4,6-tris(dimethylaminomethyl)phenol, benzyl dimethylamine, triethylamine, triethanolamine, and o-hydroxybenzyl dimethylamine.

[0033] Secondly, this application also provides a method for preparing a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, comprising the following methods:

[0034] S1. Impregnate glass fiber cloth with benzoxazine-epoxy resin impregnation solution, and then perform semi-curing treatment, wherein the semi-curing temperature is 140-180℃ and the semi-curing time is 6-8h to obtain a semi-cured sheet.

[0035] S2. Cut the obtained prepreg and place a copper foil on the top and bottom of the prepreg. Press it under a pressure of 0.6-1 MPa and a temperature of 150-180℃. After post-processing, obtain benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate.

[0036] Preferably, the fiberglass cloth is alkali-free fiberglass cloth.

[0037] Preferably, the post-treatment temperature is 200–210℃ and the post-treatment time is 1.5–2.5 h.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. In the benzoxazine-epoxy resin impregnation solution of this application, a modified nitrogen-containing benzoxazine resin is added to the epoxy resin. This modified nitrogen-containing benzoxazine resin acts as both an epoxy resin curing agent and a reactive flame retardant for the epoxy resin, which can significantly improve the flame retardancy of the epoxy resin itself. Furthermore, during the process of promoting epoxy resin curing, no by-product small molecules are generated, and there is no significant volume change. This can eliminate the residual stress inside the epoxy resin after curing, reduce the generation of defects, and thus improve the mechanical properties of the obtained copper-clad laminate. Furthermore, the modified nitrogen-containing benzoxazine resin also has polyethylene glycol segments grafted onto its molecular chains. As a flexible group, polyethylene glycol can interpenetrate between the molecular chains of the epoxy resin after the modified nitrogen-containing benzoxazine resin reacts with the epoxy resin, reducing the interaction forces between the molecular chains and improving the toughness of the material. In addition, the hydroxyl groups contained in polyethylene glycol can react with the polar groups in the epoxy resin during the curing process, increasing the crosslinking density between the modified nitrogen-containing benzoxazine resin and the epoxy resin, thereby improving the mechanical properties of the formed copper-clad laminate.

[0040] 2. The epoxy resin used in this application has also undergone siloxane modification. The addition of siloxane segments can increase the glass transition temperature of the epoxy resin, thereby improving its thermal stability, and thus enhancing its flame retardant effect and stability. Simultaneously, the silanol groups can react with the hydroxyl groups on the surface of the glass fiber cloth. Therefore, the introduction of silanol groups can also increase the bonding strength between the epoxy resin and the glass fiber cloth, improve the adhesion between the benzoxazine-epoxy resin impregnation solution and the glass fiber cloth, and improve the peel strength of the copper-clad laminate. Detailed Implementation

[0041] Preparation example of modified nitrogen-containing benzoxazine resin

[0042] Preparation Example 1-1: A modified nitrogen-containing benzoxazine resin was prepared according to the following method:

[0043] Take 300 ml of 30% formaldehyde solution and adjust the pH of the formaldehyde solution to 8. Add 45 g of melamine, raise the temperature to 70°C, and stir until the solution is clear. Then add 50 g of bisphenol A propane, stir to dissolve, raise the temperature to 80°C, and continue stirring to obtain a mixed solution. Adjust the temperature of the obtained mixed solution to 40°C, add 40 g of polyethylene glycol 400, stir to dissolve, add 2 g of manganese dioxide, raise the temperature to 130°C, and stir to react for 2 hours. After filtration, standing, and dehydration under reduced pressure, the modified nitrogen-containing benzoxazine resin is obtained.

[0044] Preparation Example 1-2 is a modified nitrogen-containing benzoxazine resin, which differs from Preparation Example 1-1 only in that the amount of melamine added is 40g and the amount of bisphenol A added is 45g.

[0045] Preparation Examples 1-3: A modified nitrogen-containing benzoxazine resin, differing from Preparation Example 1-1 only in that the amount of melamine added is 50g and the amount of bisphenol A added is 55g.

[0046] Preparation Examples 1-4: A modified nitrogen-containing benzoxazine resin, differing from Preparation Example 1-1 only in that the amount of polyethylene glycol 400 added is 30g.

[0047] Preparation Examples 1-5: A modified nitrogen-containing benzoxazine resin, differing from Preparation Example 1-1 only in that the amount of polyethylene glycol 400 added is 50g.

[0048] Preparation Examples 1-6: A modified nitrogen-containing benzoxazine resin, differing from Preparation Example 1-1 only in that the amount of polyethylene glycol 400 added is 20g.

[0049] Preparation Examples 1-7: A modified nitrogen-containing benzoxazine resin, differing from Preparation Example 1-1 only in that the amount of polyethylene glycol 400 added is 60g.

[0050] Preparation Examples 1-8: A modified nitrogen-containing benzoxazine resin, differing from Preparation Example 1-1 only in that an equal amount of polyethylene glycol 800 is used instead of polyethylene glycol 400.

[0051] Preparation Examples 1-9: A modified nitrogen-containing benzoxazine resin was prepared according to the following method:

[0052] Take 300 ml of 30% formaldehyde solution and adjust the pH of the formaldehyde solution to 8. Add 45 g of melamine, raise the temperature to 70°C, stir the reaction until the solution is clear, then add 50 g of bisphenol A propane, stir to dissolve, raise the temperature to 80°C, continue stirring the reaction, and after standing and dehydration under reduced pressure, obtain the modified nitrogen-containing benzoxazine resin.

[0053] Preparation example of benzoxazine-epoxy resin impregnation solution

[0054] 2-1, a benzoxazine-epoxy resin impregnation solution, was prepared according to the following method:

[0055] 100g of epoxy resin E-51 was mixed with 50g of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1, and then 75g of a composite solvent of acetone, butanone and toluene in a mass ratio of 1:1:1 was added. After stirring and mixing for 10min, 0.5g of benzyl dimethylamine was added, the temperature was raised to 80℃ and the reaction was continued for 3h. Then, 30g of magnesium hydroxide (average particle size ≤2μm) was added and stirred for another 2h to obtain the benzoxazine-epoxy resin impregnation solution.

[0056] Preparation Examples 2-2 to 2-7 are benzoxazine-epoxy resin impregnation solutions, which differ from Preparation Example 2-1 only in the proportions of the raw materials used, as shown in Table 1:

[0057] Table 1 Formulations of Preparation Examples 2-1 to 2-7

[0058]

[0059] The modified nitrogen-containing benzoxazine resin used in all of these preparations was the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1; the composite solvent used in Preparation Examples 2-4 was a composite solvent of acetone, butanone and toluene with a mass ratio of 1:0.8:1.2, and the composite solvent used in Preparation Examples 2-5 was a composite solvent of acetone, butanone and toluene with a mass ratio of 1:1:0.8.

[0060] Preparation Examples 2-8: A benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-2 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0061] Preparation Examples 2-9: A benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-3 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0062] Preparation Example 2-10 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-4 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0063] Preparation Example 2-11 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-5 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0064] Preparation Example 2-12: A benzoxazine resin-epoxy resin impregnating solution was prepared according to the following method:

[0065] Take 100g of epoxy resin E-51 and 35g of hydroxyl-terminated polydimethylsiloxane (average number average molecular weight of 1000) and mix them evenly. Raise the temperature to 120℃, then add 5g of dibutyltin dilaurate. Stir and react for 2h under a pressure of 0.1MPa to obtain epoxy resin modified with siloxane.

[0066] Take 100g of epoxy resin modified with siloxane and mix it with 50g of modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1. Then add 75g of a composite solvent of acetone, butanone and toluene in a mass ratio of 1:1:1. After stirring and mixing for 10min, add 0.5g of benzyl dimethylamine, raise the temperature to 80℃ and continue stirring for 3h. Then add 30g of magnesium hydroxide and stir for another 2h to obtain benzoxazine-epoxy resin impregnation solution.

[0067] Preparation Example 2-13 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-6 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0068] Preparation Example 2-14 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-7 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0069] Preparation Example 2-15 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-8 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0070] Preparation Example 2-16, a benzoxazine-epoxy resin impregnation solution, differs from Preparation Example 2-1 only in that the amount of modified nitrogen-containing benzoxazine resin added in Preparation Example 1-1 is 30g.

[0071] Preparation Example 2-17 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that the amount of modified nitrogen-containing benzoxazine resin added in Preparation Example 1-1 is 70g.

[0072] Preparation Example 2-18 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that an equal amount of the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-9 is used to replace the modified nitrogen-containing benzoxazine resin prepared in Preparation Example 1-1.

[0073] Preparation Example 2-19 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that the modified nitrogen-containing benzoxazine resin obtained in Preparation Example 1-1 is replaced with melamine, and the amount of melamine added is 20g.

[0074] Preparation Example 2-20 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that the amount of magnesium hydroxide added is 10g.

[0075] Preparation Example 2-21 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that the amount of magnesium hydroxide added is 50g.

[0076] Preparation Example 2-22 is a benzoxazine-epoxy resin impregnation solution, which differs from Preparation Example 2-1 only in that magnesium hydroxide is not added.

[0077] Example

[0078] Example 1: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate was prepared according to the following method:

[0079] S1. The benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 was used to impregnate alkali-free glass fiber cloth (model 7628 glass fiber cloth), and then semi-curing treatment was performed. During the semi-curing process, the temperature was first cured at 140°C for 2 hours, then the temperature was increased to 160°C and cured for 2 hours, and then the temperature was increased again to 180°C and cured for 2 hours to obtain a semi-cured sheet.

[0080] S2. The obtained prepreg is cut and a copper foil is placed on top and bottom of the prepreg. It is then pressed at a pressure of 0.6 MPa and a temperature of 180°C, and then post-processed to obtain benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate. The specific post-processing process is as follows: temperature 200°C, processing time 2 hours.

[0081] Example 2: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Example 2-2 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Example 2-1 to impregnate alkali-free glass fiber cloth.

[0082] Example 3: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, which differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-3 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate the alkali-free glass fiber cloth.

[0083] Example 4: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-4 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0084] Example 5: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Examples 2-5 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Example 2-1 to impregnate alkali-free glass fiber cloth.

[0085] Example 6: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Examples 2-6 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Example 2-1 to impregnate alkali-free glass fiber cloth.

[0086] Example 7: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Examples 2-7 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Example 2-1 to impregnate alkali-free glass fiber cloth.

[0087] Example 8: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Examples 2-8 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Example 2-1 to impregnate alkali-free glass fiber cloth.

[0088] Example 9: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Examples 2-9 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Example 2-1 to impregnate alkali-free glass fiber cloth.

[0089] Example 10: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-10 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0090] Example 11: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-11 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0091] Example 12, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-12 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0092] Example 13, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-13 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0093] Example 14: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-14 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0094] Example 15: A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differing from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-15 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0095] Comparative Example

[0096] Comparative Example 1 is a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, which differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-16 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate the alkali-free glass fiber cloth.

[0097] Comparative Example 2, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-17 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate the alkali-free glass fiber cloth.

[0098] Comparative Example 3, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-18 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate the alkali-free glass fiber cloth.

[0099] Comparative Example 4, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-19 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate the alkali-free glass fiber cloth.

[0100] Comparative Example 5, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-20 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate alkali-free glass fiber cloth.

[0101] Comparative Example 6, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-21 is used to impregnate the alkali-free glass fiber cloth.

[0102] Comparative Example 7, a benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, differs from Example 1 only in that an equal amount of the benzoxazine-epoxy resin impregnating solution prepared in Preparation Examples 2-22 is used to replace the benzoxazine-epoxy resin impregnating solution prepared in Preparation Example 2-1 to impregnate the alkali-free glass fiber cloth.

[0103] Performance testing

[0104] 1. Thermal stability test: The glass transition temperature of the prepregs obtained in the examples and comparative examples was tested by differential scanning calorimetry.

[0105] 2. Peel strength test: The peel strength of the benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminates obtained in the examples and comparative examples was tested according to IPC-TM-650 2.4.8.1 "Peel strength and metal foil (reference target hole of thin plate)".

[0106] 3. Flame retardant performance test: The flame retardant performance of the benzoxazine resin-based halogen-free flame retardant FR-4 copper clad laminates obtained in the examples and comparative examples was tested according to the UL94 safety standard "Tests on the flammability of plastic materials in equipment and appliances".

[0107] 4. Electrical performance testing: The breakdown voltage of the benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminates obtained in the examples and comparative examples was tested according to the relevant records in GJB 1651A-2017 "Test Methods for Metal Foil Laminates for Printed Circuits".

[0108] The results of the above experiments are shown in Table 2;

[0109] Table 1 Test Results of Dibenzoxazine Resin-Based Halogen-Free Flame-Retardant FR-4 Copper Clad Laminates

[0110]

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[0112] According to Table 2, and in conjunction with Examples 1 and 2-7, it can be seen that the glass transition temperature, peel strength, flame retardant rating, and breakdown voltage of Examples 2-7 are not significantly different from those of Example 1. This indicates that the thermal stability, mechanical properties, flame retardant properties, and electrical properties of Examples 2-7 are not significantly different from those of Example 1. This may be because Examples 2-7 are simply variations on the raw material ratios within the required range in the preparation process of the benzoxazine-epoxy resin impregnation solution, based on Example 1. This suggests that changing the raw material ratios within the required range has no significant impact on the performance of the final copper-clad laminate.

[0113] Combining Examples 1 and 8-11, it can be seen that the glass transition temperature, peel strength, flame retardant rating, and breakdown voltage of Examples 8-11 are not significantly different from those of Example 1. This indicates that the thermal stability, mechanical properties, flame retardant properties, and electrical properties of Examples 8-11 are not significantly different from those of Example 1. This may be because the modified nitrogen-containing benzoxazine resin used in Examples 8-11 for the benzoxazine-epoxy resin impregnation solution only changed the raw materials used within the required range during preparation. This suggests that within the required range, changing the proportion of the modified nitrogen-containing benzoxazine resin raw materials has little impact on the performance of the final copper-clad laminate.

[0114] Combining Examples 1 and 12, it can be seen that the peel strength and breakdown voltage of Example 12 are slightly improved compared to Example 1, indicating that the mechanical and electrical properties of Example 12 are improved compared to Example 1. This may be because the epoxy resin in the benzoxazine-epoxy resin impregnation solution used in Example 12 is modified with siloxane. The modified epoxy resin exhibits improved flame retardancy and electrical properties, and the silanol groups it contains can react with the hydroxyl groups on the substrate surface, increasing the peel strength of the copper-clad laminate.

[0115] Combining Examples 1, 13, and 14, it can be seen that the glass transition temperature, peel strength, and breakdown voltage of Examples 13 and 14 are slightly lower than those of Example 1, indicating a decrease in the thermal stability, mechanical properties, and electrical properties of Examples 13 and 14. This may be because, in Example 13, the amount of polyethylene glycol added to the modified nitrogen-containing benzoxazine resin in the benzoxazine-epoxy resin impregnation solution was reduced during preparation. This resulted in reduced cross-linking with the epoxy resin, decreased thermal stability, and reduced toughness enhancement. Furthermore, the reduced bonding between the polar groups in the polyethylene glycol and the substrate led to a decrease in the peel strength of the copper-clad laminate. In Example 14, the amount of polyethylene glycol added to the modified nitrogen-containing benzoxazine resin in the benzoxazine-epoxy resin impregnation solution was increased during preparation. The large amount of polyethylene glycol added affects the curing efficiency of the epoxy resin and reduces its thermal stability, thus lowering the material's electrical properties.

[0116] Combining Examples 1 and 15, it can be seen that the glass transition temperature, peel strength, and breakdown voltage of Example 15 are slightly lower than those of Example 1, indicating that the thermal stability, mechanical properties, and electrical properties of Example 15 are somewhat reduced. This may be because the modified nitrogen-containing benzoxazine resin in the benzoxazine-epoxy resin impregnation solution raw material of Example 15 has a large molecular weight of polyethylene glycol during the preparation process. Increased molecular weight makes it difficult to achieve interlocking between molecular chains, reducing the strengthening effect on the toughness of the epoxy resin. Furthermore, the large molecular weight of polyethylene glycol lowers the glass transition temperature of the epoxy resin, resulting in decreased thermal stability of the obtained copper-clad laminate.

[0117] Based on Examples 1, 1, and 2, it can be seen that the flame retardancy of Comparative Example 1 is lower than that of Example 1. The glass transition temperature, peel strength, and breakdown voltage of Comparative Examples 1 and 2 are also lower than those of Example 1, indicating that the thermal stability, mechanical properties, and electrical properties of Comparative Examples 1 and 2 are lower than those of Example 1. Furthermore, the flame retardancy of Comparative Example 1 is lower than that of Example 1. This may be because the amount of modified nitrogen-containing benzoxazine resin added to the benzoxazine-epoxy resin impregnation solution used in Comparative Example 1 is reduced, resulting in a decrease in overall nitrogen content and thus a decrease in flame retardancy. Secondly, without the reinforcing effect of benzoxazine resin and epoxy resin, the thermal stability of the material is lower. In Comparative Example 2, the amount of modified nitrogen-containing benzoxazine resin added to the benzoxazine-epoxy resin impregnation solution was increased, so the flame retardancy did not change significantly. However, the addition of a large amount of modified nitrogen-containing benzoxazine resin and rigid groups such as benzene rings will reduce the adhesion between the resin and the substrate and reduce the peel strength of the copper clad laminate. On the other hand, it will also reduce the thermal stability of the material.

[0118] Combining Example 1 and Comparative Example 3, it can be seen that the glass transition temperature, peel strength, and breakdown voltage of Comparative Example 3 are slightly lower than those of Example 1, indicating that the thermal stability, mechanical properties, and electrical properties of Comparative Example 3 are somewhat reduced. This may be because the modified nitrogen-containing benzoxazine resin in the benzoxazine-epoxy resin impregnation solution used in Comparative Example 3 does not contain polyethylene glycol during preparation, leading to a decrease in the crosslinking density between the modified nitrogen-containing benzoxazine resin and the epoxy resin, resulting in a decrease in the thermal stability of the material. Secondly, the lack of polyethylene glycol results in poor toughness of the epoxy resin, poor peel strength with the substrate, and a decrease in electrical properties.

[0119] Combining Example 1 and Comparative Example 4, it can be seen that the glass transition temperature, peel strength, flame retardancy rating, and breakdown voltage of Comparative Example 4 are lower than those of Example 1, indicating that the thermal stability, mechanical properties, flame retardancy, and electrical properties of Comparative Example 4 are lower than those of Example 1. This may be because the modified nitrogen-containing benzoxazine resin was replaced with the nitrogen-based flame retardant melamine in Comparative Example 4. On the one hand, melamine is a non-reactive flame retardant with generally poor compatibility with epoxy resin, and it is prone to precipitating out during use, losing its flame-retardant synergistic effect, and it does not improve the stability and mechanical properties of the epoxy resin.

[0120] Based on Examples 1, 5, 6, and 7, it can be seen that the glass transition temperature, peel strength, flame retardancy rating, and breakdown voltage of Comparative Examples 5 to 7 are lower than those of Example 1, indicating that the thermal stability, mechanical properties, flame retardancy, and electrical properties of Comparative Examples 5 to 7 are lower than those of Example 1. This may be because the amount of magnesium hydroxide added to the benzoxazine-epoxy resin impregnating solution used in Comparative Example 5 is reduced, while no magnesium hydroxide is added in Comparative Example 7, thus reducing the flame retardancy and reinforcing effect on the epoxy resin. In Comparative Example 6, the amount of magnesium hydroxide added to the benzoxazine-epoxy resin impregnating solution is increased; however, the excessive addition of magnesium hydroxide as a filler can actually reduce the various properties of the epoxy resin.

[0121] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate, comprising a benzoxazine-epoxy resin impregnation solution, fiberglass cloth, and copper foil, characterized in that, The raw materials for the benzoxazine-epoxy resin impregnation solution include the following parts by weight: 100 parts epoxy resin; 40-60 parts of modified nitrogen-containing benzoxazine resin; 20-40 parts of metal hydroxide; 0.4 to 0.6 parts of epoxy resin curing agent; 70-80 parts of composite solvent; The modified nitrogen-containing benzoxazine resin molecular chain is further grafted with polyethylene glycol segments, and the raw materials of the modified nitrogen-containing benzoxazine resin include formaldehyde, melamine, bisphenol A and polyethylene glycol in a mass ratio of 1:(0.4-0.5):(0.45-0.55):(0.3-0.5). The metal hydroxide includes one or a combination of magnesium hydroxide and aluminum hydroxide; The polyethylene glycol is one or a combination of polyethylene glycol 200, polyethylene glycol 300, and polyethylene glycol 400.

2. The benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate according to claim 1, characterized in that, The composite solvent is a mixed solution of acetone, butanone and toluene in a mass ratio of 1:(0.6~1):(0.8~1.2).

3. The benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate according to claim 1, characterized in that, The modified nitrogen-containing benzoxazine resin was prepared according to the following method: Adjust the pH of the formaldehyde solution to 8-9, add melamine, raise the temperature to 65-75℃, stir until the solution is clear, then add bisphenol A, stir to dissolve, raise the temperature to 80-90℃, and continue stirring to obtain a mixed solution; adjust the temperature of the obtained mixed solution to 40-50℃, add polyethylene glycol, stir to dissolve, add a catalyst, raise the temperature to 120-130℃, stir to react for 2-3 hours, and then filter, let stand, and dehydrate under reduced pressure to obtain the modified nitrogen-containing benzoxazine resin.

4. The benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate according to claim 1, characterized in that, The epoxy resin is modified with siloxane.

5. The benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate according to claim 4, characterized in that, The raw materials used in the epoxy resin siloxane modification treatment include epoxy resin and hydroxyl-terminated polydimethylsiloxane in a mass ratio of 100:(30-40).

6. The benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate according to claim 1, characterized in that, The benzoxazine-epoxy resin impregnation solution was prepared according to the following method: After mixing epoxy resin and modified nitrogen-containing benzoxazine resin, a composite solvent is added and stirred for 10-20 minutes. Then, epoxy resin curing agent is added, the temperature is raised to 80-90℃ and the reaction is continued for 2-3 hours. Then, metal hydroxide is added and stirred for another 2-3 hours to obtain benzoxazine-epoxy resin impregnation solution.

7. The method for preparing benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate according to any one of claims 1 to 6, characterized in that, It is prepared by the following methods: S1. Impregnate glass fiber cloth with benzoxazine-epoxy resin impregnation solution, and then perform semi-curing treatment, wherein the semi-curing temperature is 140-180℃ and the semi-curing time is 6-8h to obtain a semi-cured sheet. S2. Cut the obtained prepreg and place a copper foil on the top and bottom of the prepreg. Press it under a pressure of 0.6-1 MPa and a temperature of 150-180℃. After post-processing, obtain benzoxazine resin-based halogen-free flame-retardant FR-4 copper-clad laminate.

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