A flame-retardant PCB copper-clad substrate and its preparation method

Abstract

The present invention relates to the technical field of circuit boards, and specifically discloses a flame-retardant PCB copper-clad substrate and a preparation method thereof, with fluorine-containing pyridine-type benzoxazine and epoxy resin as a resin matrix, adding 4,4-diaminodiphenylmethane, KH-550 modified nano-silica hollow spheres and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as additives, preparing a copper-clad substrate resin glue, and stacking the KH-560 modified glass fiber cloth with copper-clad substrate resin glue together and hot-pressing together with copper foil to form a flame-retardant PCB copper-clad substrate. The flame-retardant PCB copper-clad substrate not only has good heat resistance and good flame retardancy, but also has low dielectric constant and dielectric loss, meeting the needs of high-frequency and high-speed high-performance PCB boards.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and in particular to a flame-retardant PCB copper-clad substrate and a preparation method thereof. Background Art

[0002] A printed circuit board (PCB) is an electronic component manufactured by printing a conductive metal coating onto an insulating substrate, thereby reducing wiring between electronic parts and lowering production costs. It is a product of the development of electronic information technology towards smaller, lighter, and more multifunctional components. As a carrier for electrical connections between electronic components, PCBs are widely used, ranging from remote controls, radios, and flashlights to televisions, computers, and aircraft. PCBs are currently developing towards high precision, high density, high performance, microporous, thinner, and higher-rise designs. As the primary substrate material for PCB manufacturing, the quality of copper-clad laminates (CCLs) influences the performance, quality, and quality of the PCB. Therefore, CCLs should exhibit superior performance. However, the flame retardancy, heat resistance, and dielectric properties of current CCLs do not meet the requirements for high-performance PCB development. Summary of the Invention

[0003] The purpose of the present invention is to provide a flame-retardant PCB copper-clad substrate and a preparation method thereof, so as to solve the problems of insufficient flame retardancy, insufficient heat resistance and insufficient dielectric properties of the copper-clad substrate.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] A method for preparing a flame-retardant PCB copper-clad substrate, the preparation method comprising:

[0006] After cutting the glass fiber cloth into a suitable size, modifying it with KH-560, fully impregnating the modified glass fiber cloth in the resin glue for the copper clad substrate, taking it out, drying it at 25-30°C, and drying it at 110-120°C for 10-20 minutes to obtain a prepreg;

[0007] The semi-cured sheets are stacked up, and a layer of copper foil is placed on the stacked cured sheets. The temperature is raised and cured in stages at 3-5 MPa according to (95-105)°C / (0.8-1.2)h, (135-145)°C / (0.8-1.2)h, (155-165)°C / (1.8-2.2)h, (175-185)°C / (1.8-2.2)h, and (195-205)°C / (1.8-2.2)h. After curing, the sheet is cooled and the burrs are trimmed to obtain a flame-retardant PCB copper-clad substrate.

[0008] As a limitation of the present invention, the preparation method of the resin glue for copper clad substrate is:

[0009] Fluorine-containing pyridine benzoxazine, epoxy resin, 4,4-diaminodiphenylmethane and acetone were mixed and stirred at 50-70° C. and 500-700 rpm for 20-30 min. KH-550 modified nano-silica hollow spheres and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added. The temperature was lowered to 20-30° C. and stirring was continued for 0.5-1.5 h to obtain a resin adhesive for copper clad substrate.

[0010] As a limitation of the present invention, the resin adhesive for the film-faced board includes, by mass, 23 to 27 parts of fluorine-containing pyridine-type benzoxazine, 63 to 67 parts of epoxy resin, 1 to 3 parts of 4,4-diaminodiphenylmethane, 13 to 15 parts of KH-550 modified nano-silica hollow spheres, 15 to 17 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 145 to 155 parts of acetone.

[0011] As a limitation of the present invention, the preparation method of the fluorinated pyridine-type benzoxazine is:

[0012] Toluene, ethyl acetate, and paraformaldehyde are mixed, and stirred at 150-250 rpm for 5-15 minutes under nitrogen as a protective gas to obtain a paraformaldehyde solution. 3,5-difluoro-2,6-diaminopyridine, phenol, toluene, and ethyl acetate are mixed and stirred uniformly to obtain an aminopyridine / phenol solution. The aminopyridine / phenol solution is slowly added to the paraformaldehyde solution and stirred uniformly. The mixture is reacted at 80-100° C. and 200-400 rpm under nitrogen as a protective gas for 8-12 hours. After the reaction is completed, the mixture is allowed to stand and separate into layers. The organic solvent layer is taken, rotary evaporated, and vacuum dried to remove the solvent to obtain a fluorine-containing pyridine-type benzoxazine.

[0013] As a limitation of the present invention, the paraformaldehyde solution includes, by mass, 48.70 to 48.74 parts of toluene, 25.24 to 25.28 parts of ethyl acetate, and 7.42 to 7.46 parts of paraformaldehyde.

[0014] As a limitation of the present invention, the aminopyridine / phenol solution includes, by mass, 4.34 to 4.38 parts of 3,5-difluoro-2,6-diaminopyridine, 11.64 to 11.68 parts of phenol, 97.42 to 97.46 parts of toluene, and 50.50 to 50.54 parts of ethyl acetate.

[0015] As a limitation of the present invention, the preparation method of the KH-550 modified nano-silica hollow spheres is:

[0016] Cetyltrimethylammonium bromide, ammonia water, ethanol, and deionized water are mixed, stirred at 25-30° C. and 400-600 rpm for 5-15 minutes to obtain a cetyltrimethylammonium bromide solution, ethyl orthosilicate is added to the cetyltrimethylammonium bromide solution, reacted at 25-30° C. and 400-600 rpm for 0.5-1.5 hours, centrifuged after completion of the reaction, washed with deionized water, and dried at 450-550° C. for 4-6 hours to obtain hollow nano-silica spheres;

[0017] Mix KH-550, deionized water, and ethanol, stir evenly, adjust the pH with acetic acid to obtain a KH-550 ethanol solution, mix the nano-silica hollow spheres and the KH-550 ethanol solution, ultrasonically disperse for 10 to 20 minutes, and react at 70 to 90° C. for 3 to 5 hours to obtain KH-550 modified nano-silica hollow spheres.

[0018] As a limitation of the present invention, the preparation of nano-silica hollow spheres includes 0.38-0.42 parts of hexadecyltrimethylammonium bromide, 0.64-0.68 parts of ammonia water, and 0.26-0.30 parts of ethyl orthosilicate, calculated by mass.

[0019] As a limitation of the present invention, the preparation of KH-550 modified nano-silica hollow spheres includes 46-50 parts of nano-silica hollow spheres, 1.98-2.02 parts of KH-550, 9-11 parts of deionized water, and 86-90 parts of ethanol, calculated by mass.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Fluorine-containing pyridine-type benzoxazine, prepared from paraformaldehyde, phenol, and 3,5-difluoro-2,6-diaminopyridine, introduces fluorine atoms to form C—F bonds, which are less polar than C—H bonds. This reduces the molecular polarity and increases the free volume of the molecule, thereby lowering the dielectric constant of the sheet. Furthermore, the pyridine functional groups within the resin not only increase the nitrogen content within the polymer, improving the flame retardancy of the resin matrix, but also, due to the presence of negatively charged nitrogen atoms in the pyridine ring, increase intra- and intermolecular hydrogen bonding in the resin, enhancing its heat resistance.

[0022] Nanosilica microspheres, synthesized using tetraethyl orthosilicate as the silicon source and cetyltrimethylammonium bromide as the template, have internal cavities. When mixed with resin, they increase the resin's porosity, reducing the number of polarized molecules per unit volume, thereby effectively lowering the resin's dielectric constant. Furthermore, silica itself exhibits high-temperature resistance, a low thermal expansion coefficient, and stable chemical properties, which, when mixed with resin, also enhances the resin's heat resistance and thermal stability.

[0023] Silane coupling agents KH-550 and KH-560 were used to modify nano-silica hollow spheres and glass fiber cloth respectively, which improved the compatibility between nano-silica microspheres and glass fiber cloth and the resin, made the materials more tightly combined, and reduced the occurrence of nano-silica microsphere agglomeration in the resin. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] Paraformaldehyde (95%) and epoxy resin (0.48 mol / 100 g) were provided by Shanghai MacLean, and glass fiber cloth (200 g / cm 3 ) provided by Jiangxi Yanhu Fiberglass, copper foil (128g / cm 2 ) provided by Huizhou United Copper Foil.

[0026] Example 1: A method for preparing a flame-retardant copper-clad PCB substrate, specifically:

[0027] Step 1: Preparation of fluorinated pyridine-type benzoxazine

[0028] By mass, 48.72 parts of toluene, 25.26 parts of ethyl acetate, and 7.44 parts of paraformaldehyde were mixed, and stirred at 200 rpm for 10 minutes under nitrogen as a protective gas to obtain a paraformaldehyde solution. 4.36 parts of 3,5-difluoro-2,6-diaminopyridine, 11.66 parts of phenol, 97.44 parts of toluene, and 50.52 parts of ethyl acetate were mixed and stirred uniformly to obtain an aminopyridine / phenol solution. 163.98 parts of the aminopyridine / phenol solution were slowly added to 81.42 parts of the paraformaldehyde solution and stirred uniformly. The mixture was reacted at 90° C. and 300 rpm under nitrogen as a protective gas for 10 hours. After the reaction was completed, the mixture was allowed to stand and separate, and the organic solvent layer was taken, rotary evaporated, and vacuum dried to remove the solvent to obtain a fluorine-containing pyridine-type benzoxazine.

[0029] Step 2: Preparation of hollow silica nanospheres

[0030] 0.4 parts of hexadecyltrimethylammonium bromide, 0.66 parts of ammonia water, 36.58 parts of ethanol, and 63.42 parts of deionized water were mixed, and the mixture was stirred at 27°C and 500 rpm for 10 minutes to obtain a hexadecyltrimethylammonium bromide solution. 0.28 parts of ethyl orthosilicate were added to 101.06 parts of the hexadecyltrimethylammonium bromide solution, and the mixture was reacted at 27°C and 500 rpm for 1 hour. After the reaction, the mixture was centrifuged, washed with deionized water, and dried at 500°C for 5 hours to obtain nano-silica hollow spheres.

[0031] Step 3: Preparation of KH-550 modified nano-silica hollow spheres

[0032] 2 parts of KH-550, 10 parts of deionized water, and 88 parts of ethanol were mixed by mass, stirred evenly, and the pH was adjusted to 4 with acetic acid to obtain a KH-550 ethanol solution. 48 parts of nano-silica hollow spheres and 100 parts of the KH-550 ethanol solution were mixed, ultrasonically dispersed for 15 minutes, and reacted at 80°C for 6 hours to obtain KH-550 modified nano-silica hollow spheres.

[0033] Step 4: Prepare the copper clad substrate resin glue

[0034] By mass, 25 parts of fluorine-containing pyridine benzoxazine, 65 parts of epoxy resin, 2 parts of 4,4-diaminodiphenylmethane, and 150 parts of acetone were mixed and stirred at 60°C and 600rpm for 30min. 14 parts of KH-550 modified nano-silica hollow spheres and 16 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added. The temperature was lowered to 25°C and stirring was continued for 1h to obtain a resin glue for copper clad substrate.

[0035] Step 5: Prepare the prepreg

[0036] Mix 15 parts of KH-560, 50 parts of deionized water, and 1.6 parts of methanol, stir evenly, adjust the pH of the solution to 4 with acetic acid, and hydrolyze at 27°C for 2 hours to obtain a KH-560 solution. Cut the glass fiber cloth into 200mm×200mm sizes and soak it in the KH-560 solution for 30 minutes to obtain a modified glass fiber cloth. The modified glass fiber cloth is fully immersed in the resin glue for the film-coated board and then taken out, dried at 27°C, and dried at 115°C for 15 minutes to obtain a semi-cured sheet.

[0037] Step 6: Prepare flame-retardant copper-clad PCB substrate

[0038] Eight prepregs were stacked up, and a layer of copper foil was placed on the stacked prepregs. The materials were cured at 4 MPa at a temperature of 100°C / 1h, 140°C / 1h, 160°C / 2h, 180°C / 2h, and 200°C / 2h. After curing, the materials were cooled and the burrs were trimmed to obtain a flame-retardant copper-clad PCB substrate.

[0039] Example 2: A method for preparing a flame-retardant copper-clad PCB substrate, specifically:

[0040] Step 1: Preparation of fluorinated pyridine-type benzoxazine

[0041] By mass, 48.72 parts of toluene, 25.26 parts of ethyl acetate, and 7.44 parts of paraformaldehyde were mixed, and stirred at 200 rpm for 10 minutes under nitrogen as a protective gas to obtain a paraformaldehyde solution. 4.36 parts of 3,5-difluoro-2,6-diaminopyridine, 11.66 parts of phenol, 97.44 parts of toluene, and 50.52 parts of ethyl acetate were mixed and stirred uniformly to obtain an aminopyridine / phenol solution. 163.98 parts of the aminopyridine / phenol solution were slowly added to 81.42 parts of the paraformaldehyde solution and stirred uniformly. The mixture was reacted at 90° C. and 300 rpm under nitrogen as a protective gas for 10 hours. After the reaction was completed, the mixture was allowed to stand and separate, and the organic solvent layer was taken, rotary evaporated, and vacuum dried to remove the solvent to obtain a fluorine-containing pyridine-type benzoxazine.

[0042] Step 2: Preparation of hollow silica nanospheres

[0043] 0.4 parts of hexadecyltrimethylammonium bromide, 0.66 parts of ammonia water, 36.58 parts of ethanol, and 63.42 parts of deionized water were mixed, and the mixture was stirred at 27°C and 500 rpm for 10 minutes to obtain a hexadecyltrimethylammonium bromide solution. 0.28 parts of ethyl orthosilicate were added to 101.06 parts of the hexadecyltrimethylammonium bromide solution, and the mixture was reacted at 27°C and 500 rpm for 1 hour. After the reaction, the mixture was centrifuged, washed with deionized water, and dried at 500°C for 5 hours to obtain nano-silica hollow spheres.

[0044] Step 3: Preparation of KH-550 modified nano-silica hollow spheres

[0045] 2 parts of KH-550, 10 parts of deionized water, and 88 parts of ethanol were mixed by mass, stirred evenly, and the pH was adjusted to 4 with acetic acid to obtain a KH-550 ethanol solution. 48 parts of nano-silica hollow spheres and 100 parts of the KH-550 ethanol solution were mixed, ultrasonically dispersed for 15 minutes, and reacted at 80°C for 6 hours to obtain KH-550 modified nano-silica hollow spheres.

[0046] Step 4: Prepare the copper clad substrate resin glue

[0047] By mass, 23 parts of fluorine-containing pyridine benzoxazine, 63 parts of epoxy resin, 1 part of 4,4-diaminodiphenylmethane, and 145 parts of acetone were mixed and stirred at 60°C and 600rpm for 30min. 13 parts of KH-550 modified nano-silica hollow spheres and 15 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added. The temperature was lowered to 25°C and stirring was continued for 1h to obtain a resin glue for copper-clad substrates.

[0048] Step 5: Prepare the prepreg

[0049] Mix 15 parts of KH-560, 50 parts of deionized water, and 1.6 parts of methanol, stir evenly, adjust the pH of the solution to 4 with acetic acid, and hydrolyze at 27°C for 2 hours to obtain a KH-560 solution. Cut the glass fiber cloth into 200mm×200mm sizes and soak it in the KH-560 solution for 30 minutes to obtain a modified glass fiber cloth. The modified glass fiber cloth is fully immersed in the resin glue for the film-coated board and then taken out, dried at 27°C, and dried at 115°C for 15 minutes to obtain a semi-cured sheet.

[0050] Step 6: Prepare flame-retardant copper-clad PCB substrate

[0051] Eight prepregs were stacked up, and a layer of copper foil was placed on the stacked prepregs. The materials were cured at 4 MPa at a temperature of 100°C / 1h, 140°C / 1h, 160°C / 2h, 180°C / 2h, and 200°C / 2h. After curing, the materials were cooled and the burrs were trimmed to obtain a flame-retardant copper-clad PCB substrate.

[0052] Example 3: A method for preparing a flame-retardant copper-clad PCB substrate, specifically comprising:

[0053] Step 1: Preparation of fluorinated pyridine-type benzoxazine

[0054] By mass, 48.72 parts of toluene, 25.26 parts of ethyl acetate, and 7.44 parts of paraformaldehyde were mixed and stirred at 200 rpm for 10 min under nitrogen as a protective gas to obtain a paraformaldehyde solution. 4.36 parts of 3,5-difluoro-2,6-diaminopyridine, 11.66 parts of phenol, 97.44 parts of toluene, and 50.52 parts of ethyl acetate were mixed and stirred uniformly to obtain an aminopyridine / phenol solution. 163.98 parts of the aminopyridine / phenol solution were slowly added to 81.42 parts of the paraformaldehyde solution and stirred uniformly. The mixture was reacted at 90° C. and 300 rpm under nitrogen as a protective gas for 10 h. After the reaction was completed, the mixture was allowed to stand and separate, and the organic solvent layer was taken, rotary evaporated, and dried in vacuo to remove the solvent to obtain a fluorine-containing pyridine-type benzoxazine.

[0055] Step 2: Preparation of hollow silica nanospheres

[0056] 0.4 parts of hexadecyltrimethylammonium bromide, 0.66 parts of ammonia water, 36.58 parts of ethanol, and 63.42 parts of deionized water were mixed, and the mixture was stirred at 27°C and 500 rpm for 10 minutes to obtain a hexadecyltrimethylammonium bromide solution. 0.28 parts of ethyl orthosilicate were added to 101.06 parts of the hexadecyltrimethylammonium bromide solution, and the mixture was reacted at 27°C and 500 rpm for 1 hour. After the reaction, the mixture was centrifuged, washed with deionized water, and dried at 500°C for 5 hours to obtain nano-silica hollow spheres.

[0057] Step 3: Preparation of KH-550 modified nano-silica hollow spheres

[0058] 2 parts of KH-550, 10 parts of deionized water, and 88 parts of ethanol were mixed by mass, stirred evenly, and the pH was adjusted to 4 with acetic acid to obtain a KH-550 ethanol solution. 48 parts of nano-silica hollow spheres and 100 parts of the KH-550 ethanol solution were mixed, ultrasonically dispersed for 15 minutes, and reacted at 80°C for 6 hours to obtain KH-550 modified nano-silica hollow spheres.

[0059] Step 4: Prepare the copper clad substrate resin glue

[0060] By mass, 27 parts of fluorine-containing pyridine benzoxazine, 67 parts of epoxy resin, 3 parts of 4,4-diaminodiphenylmethane, and 155 parts of acetone were mixed and stirred at 60°C and 600rpm for 30min. 15 parts of KH-550 modified nano-silica hollow spheres and 17 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added. The temperature was lowered to 25°C and stirring was continued for 1h to obtain a resin glue for copper-clad substrates.

[0061] Step 5: Prepare the prepreg

[0062] Mix 15 parts of KH-560, 50 parts of deionized water, and 1.6 parts of methanol, stir evenly, adjust the pH of the solution to 4 with acetic acid, and hydrolyze at 27°C for 2 hours to obtain a KH-560 solution. Cut the glass fiber cloth into 200mm×200mm sizes and soak it in the KH-560 solution for 30 minutes to obtain a modified glass fiber cloth. The modified glass fiber cloth is fully immersed in the resin glue for the film-coated board and then taken out, dried at 27°C, and dried at 115°C for 15 minutes to obtain a semi-cured sheet.

[0063] Step 6: Prepare flame-retardant copper-clad PCB substrate

[0064] Eight prepregs were stacked up, and a layer of copper foil was placed on the stacked prepregs. The materials were cured at 4 MPa at a temperature of 100°C / 1h, 140°C / 1h, 160°C / 2h, 180°C / 2h, and 200°C / 2h. After curing, the materials were cooled and the burrs were trimmed to obtain a flame-retardant copper-clad PCB substrate.

[0065] Based on Example 1, control experiments were conducted, specifically Comparative Example 1, Comparative Example 2 and Comparative Example 3, as described below:

[0066] Comparative Example 1: The nano-silica hollow spheres were not modified with KH-550, and the other conditions were the same as those in Example 1.

[0067] A method for preparing a flame-retardant PCB copper-clad substrate, specifically comprising:

[0068] Step 1: Preparation of fluorinated pyridine-type benzoxazine

[0069] By mass, 48.72 parts of toluene, 25.26 parts of ethyl acetate, and 7.44 parts of paraformaldehyde were mixed, and stirred at 200 rpm for 10 minutes under nitrogen as a protective gas to obtain a paraformaldehyde solution. 4.36 parts of 3,5-difluoro-2,6-diaminopyridine, 11.66 parts of phenol, 97.44 parts of toluene, and 50.52 parts of ethyl acetate were mixed and stirred uniformly to obtain an aminopyridine / phenol solution. 163.98 parts of the aminopyridine / phenol solution were slowly added to 81.42 parts of the paraformaldehyde solution and stirred uniformly. The mixture was reacted at 90° C. and 300 rpm under nitrogen as a protective gas for 10 hours. After the reaction was completed, the mixture was allowed to stand and separate, and the organic solvent layer was taken, rotary evaporated, and vacuum dried to remove the solvent to obtain a fluorine-containing pyridine-type benzoxazine.

[0070] Step 2: Preparation of hollow silica nanospheres

[0071] 0.4 parts of hexadecyltrimethylammonium bromide, 0.66 parts of ammonia water, 36.58 parts of ethanol, and 63.42 parts of deionized water were mixed, and the mixture was stirred at 27°C and 500 rpm for 10 minutes to obtain a hexadecyltrimethylammonium bromide solution. 0.28 parts of ethyl orthosilicate were added to 101.06 parts of the hexadecyltrimethylammonium bromide solution, and the mixture was reacted at 27°C and 500 rpm for 1 hour. After the reaction, the mixture was centrifuged, washed with deionized water, and dried at 500°C for 5 hours to obtain nano-silica hollow spheres.

[0072] Step 3: Prepare the copper clad substrate resin glue

[0073] By mass, 25 parts of fluorine-containing pyridine benzoxazine, 65 parts of epoxy resin, 2 parts of 4,4-diaminodiphenylmethane, and 150 parts of acetone were mixed, stirred at 60°C and 600rpm for 30min, 14 parts of nano-silica hollow spheres and 16 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added, the temperature was lowered to 25°C, and stirring was continued for 1h to obtain a resin glue for copper clad substrate.

[0074] Step 4: Prepare the prepreg

[0075] Mix 15 parts of KH-560, 50 parts of deionized water, and 1.6 parts of methanol, stir evenly, adjust the pH of the solution to 4 with acetic acid, and hydrolyze at 27°C for 2 hours to obtain a KH-560 solution. Cut the glass fiber cloth into 200mm×200mm sizes and soak it in the KH-560 solution for 30 minutes to obtain a modified glass fiber cloth. The modified glass fiber cloth is fully immersed in the resin glue for the film-coated board and then taken out, dried at 27°C, and dried at 115°C for 15 minutes to obtain a semi-cured sheet.

[0076] Step 5: Prepare flame-retardant copper-clad PCB substrate

[0077] Eight prepregs were stacked up, and a layer of copper foil was placed on the stacked prepregs. The materials were cured at 4 MPa at a temperature of 100°C / 1h, 140°C / 1h, 160°C / 2h, 180°C / 2h, and 200°C / 2h. After curing, the materials were cooled and the burrs were trimmed to obtain a flame-retardant copper-clad PCB substrate.

[0078] Comparative Example 2: Nano-silica particles were used instead of nano-silica hollow spheres, and the remaining conditions were the same as those in Example 1.

[0079] A method for preparing a flame-retardant PCB copper-clad substrate, specifically comprising:

[0080] Step 1: Preparation of fluorinated pyridine-type benzoxazine

[0081] By mass, 48.72 parts of toluene, 25.26 parts of ethyl acetate, and 7.44 parts of paraformaldehyde were mixed, and stirred at 200 rpm for 10 minutes under nitrogen as a protective gas to obtain a paraformaldehyde solution. 4.36 parts of 3,5-difluoro-2,6-diaminopyridine, 11.66 parts of phenol, 97.44 parts of toluene, and 50.52 parts of ethyl acetate were mixed and stirred uniformly to obtain an aminopyridine / phenol solution. 163.98 parts of the aminopyridine / phenol solution were slowly added to 81.42 parts of the paraformaldehyde solution and stirred uniformly. The mixture was reacted at 90° C. and 300 rpm under nitrogen as a protective gas for 10 hours. After the reaction was completed, the mixture was allowed to stand and separate, and the organic solvent layer was taken, rotary evaporated, and vacuum dried to remove the solvent to obtain a fluorine-containing pyridine-type benzoxazine.

[0082] Step 2: Preparation of KH-550 modified nanosilica

[0083] By mass, 2 parts of KH-550, 10 parts of deionized water, and 88 parts of ethanol were mixed and stirred evenly. The pH was adjusted to 4 with acetic acid to obtain a KH-550 ethanol solution. 48 parts of nano-silica and 100 parts of the KH-550 ethanol solution were mixed, ultrasonically dispersed for 15 minutes, and reacted at 80°C for 6 hours to obtain KH-550 modified nano-silica.

[0084] Step 3: Prepare the copper clad substrate resin glue

[0085] By mass, 25 parts of fluorine-containing pyridine benzoxazine, 65 parts of epoxy resin, 2 parts of 4,4-diaminodiphenylmethane, and 150 parts of acetone were mixed, stirred at 60°C and 600rpm for 30min, 14 parts of nano-silica and 16 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added, the temperature was lowered to 25°C, and stirring was continued for 1h to obtain a resin glue for copper clad substrate.

[0086] Step: Preparing prepreg

[0087] Mix 15 parts of KH-560, 50 parts of deionized water, and 1.6 parts of methanol, stir evenly, adjust the pH of the solution to 4 with acetic acid, and hydrolyze at 27°C for 2 hours to obtain a KH-560 solution. Cut the glass fiber cloth into 200mm×200mm sizes and soak it in the KH-560 solution for 30 minutes to obtain a modified glass fiber cloth. The modified glass fiber cloth is fully immersed in the resin glue for the film-coated board and then taken out, dried at 27°C, and dried at 115°C for 15 minutes to obtain a semi-cured sheet.

[0088] Step 5: Prepare flame-retardant copper-clad PCB substrate

[0089] Eight prepregs were stacked up, and a layer of copper foil was placed on the stacked prepregs. The materials were cured at 4 MPa at a temperature of 100°C / 1h, 140°C / 1h, 160°C / 2h, 180°C / 2h, and 200°C / 2h. After curing, the materials were cooled and the burrs were trimmed to obtain a flame-retardant copper-clad PCB substrate.

[0090] Comparative Example 3: 3,5-difluoro-2,6-diaminopyridine was replaced with p-fluoroaniline to prepare fluorinated benzoxazine. The remaining conditions were the same as those in Example 1.

[0091] A method for preparing a flame-retardant PCB copper-clad substrate, specifically comprising:

[0092] Step 1: Preparation of Fluorinated Benzoxazine

[0093] By mass, 48.72 parts of toluene, 25.26 parts of ethyl acetate and 7.44 parts of paraformaldehyde were mixed and stirred at 200 rpm for 10 min under nitrogen as a protective gas to obtain a paraformaldehyde solution. 4.36 parts of p-fluoroaniline, 11.66 parts of phenol, 97.44 parts of toluene and 50.52 parts of ethyl acetate were mixed and stirred to obtain a p-fluoroaniline / phenol solution. 163.98 parts of p-fluoroaniline / phenol solution were slowly added to 81.42 parts of paraformaldehyde solution and stirred to obtain a fluorinated benzoxazine. The mixture was reacted at 90°C and 300 rpm under nitrogen as a protective gas for 10 h. After the reaction was completed, the mixture was allowed to stand and separate, and the organic solvent layer was taken, rotary evaporated, and vacuum dried to remove the solvent to obtain a fluorinated benzoxazine.

[0094] Step 2: Preparation of hollow silica nanospheres

[0095] 0.4 parts of hexadecyltrimethylammonium bromide, 0.66 parts of ammonia water, 36.58 parts of ethanol, and 63.42 parts of deionized water were mixed, and the mixture was stirred at 27°C and 500 rpm for 10 minutes to obtain a hexadecyltrimethylammonium bromide solution. 0.28 parts of ethyl orthosilicate were added to 101.06 parts of the hexadecyltrimethylammonium bromide solution, and the mixture was reacted at 27°C and 500 rpm for 1 hour. After the reaction, the mixture was centrifuged, washed with deionized water, and dried at 500°C for 5 hours to obtain nano-silica hollow spheres.

[0096] Step 3: Preparation of KH-550 modified nano-silica hollow spheres

[0097] 2 parts of KH-550, 10 parts of deionized water, and 88 parts of ethanol were mixed by mass, stirred evenly, and the pH was adjusted to 4 with acetic acid to obtain a KH-550 ethanol solution. 48 parts of nano-silica hollow spheres and 100 parts of the KH-550 ethanol solution were mixed, ultrasonically dispersed for 15 minutes, and reacted at 80°C for 6 hours to obtain KH-550 modified nano-silica hollow spheres.

[0098] Step 4: Prepare the copper clad substrate resin glue

[0099] By mass, 25 parts of fluorinated benzoxazine, 65 parts of epoxy resin, 2 parts of 4,4-diaminodiphenylmethane, and 150 parts of acetone were mixed, stirred at 60°C and 600rpm for 30min, 14 parts of KH-550 modified nano-silica hollow spheres and 16 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added, the temperature was lowered to 25°C, and stirring was continued for 1h to obtain a resin glue for copper clad substrate.

[0100] Step 5: Prepare the prepreg

[0101] Mix 15 parts of KH-560, 50 parts of deionized water, and 1.6 parts of methanol, stir evenly, adjust the pH of the solution to 4 with acetic acid, and hydrolyze at 27°C for 2 hours to obtain a KH-560 solution. Cut the glass fiber cloth into 200mm×200mm sizes and soak it in the KH-560 solution for 30 minutes to obtain a modified glass fiber cloth. The modified glass fiber cloth is fully immersed in the resin glue for the film-coated board and then taken out, dried at 27°C, and dried at 115°C for 15 minutes to obtain a semi-cured sheet.

[0102] Step 6: Prepare flame-retardant copper-clad PCB substrate

[0103] Eight prepregs were stacked up, and a layer of copper foil was placed on the stacked prepregs. The materials were cured at 4 MPa at a temperature of 100°C / 1h, 140°C / 1h, 160°C / 2h, 180°C / 2h, and 200°C / 2h. After curing, the materials were cooled and the burrs were trimmed to obtain a flame-retardant copper-clad PCB substrate.

[0104] Detection experiment:

[0105] The flame-retardant PCB copper-clad substrates required for the test were prepared according to the preparation methods in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively.

[0106] Heat resistance test: Dynamic mechanical analysis (DMA) was used to test each sample with a sample size of 5 mm × 5 mm × 1 mm to measure the glass transition temperature Tg of the resin material.

[0107] Flame retardancy testing: Based on the UL94 V0 vertical combustion standard, a CZF-2 comprehensive vertical combustion tester was used to test the flame. Five specimens, each measuring 125mm x 13mm x 3mm, were collected. The flame height of the vertical combustion tester was adjusted to approximately 2cm. One end of the specimen was held perpendicular to the flame and ignited for 1 second. The flame was then removed, and the time it took for the specimen to continue burning until it self-extinguished was recorded. Each specimen was ignited twice, and the afterburn time after 10 ignitions was recorded. A maximum afterburn time of no more than 10 seconds, an average afterburn time of no more than 5 seconds over 10 ignitions, and no dripping ignited the cotton ball were considered UL94 V-0. A maximum burning time of no more than 30 seconds, an average burning time of no more than 25 seconds, and no dripping ignited the cotton ball were considered UL94 V-1. A maximum burning time of no more than 30 seconds, an average burning time of no more than 25 seconds, and no dripping ignited the cotton ball were considered UL94 V-2.

[0108] Dielectric performance test: Based on the flat plate capacitance method, a TZDM-RT-300 dielectric measuring instrument is used. A sample with a diameter of 50 mm is placed in the resonant circuit of the measuring instrument at a frequency of 1 to 100 MHz to test the dielectric constant and dielectric loss of the sample.

[0109]

[0110] Conclusion: From the experiment, it can be seen that the heat resistance, solder immersion resistance, flame retardancy and dielectric properties of the flame-retardant PCB copper-clad substrate prepared by the preparation method of Example 1 are superior to those of the flame-retardant PCB copper-clad substrate prepared by the preparation methods of Comparative Examples 1, 2 and 3, effectively solving the problems of insufficient heat resistance and flame retardancy of PCB copper-clad substrates. In addition, the dielectric constant and dielectric loss of the sample of Example 1 are lower than those of the samples of Comparative Examples 1, 2 and 3, which is conducive to the development of high-frequency, high-speed, high-performance PCB boards.

[0111] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a flame-retardant copper-clad PCB substrate, characterized by: The preparation method is: Step 1: Toluene, ethyl acetate, and paraformaldehyde are mixed, and stirred at 150-250 rpm for 5-15 minutes under nitrogen as a protective gas to obtain a paraformaldehyde solution. 3,5-difluoro-2,6-diaminopyridine, phenol, toluene, and ethyl acetate are mixed and stirred uniformly to obtain an aminopyridine / phenol solution. The aminopyridine / phenol solution is slowly added to the paraformaldehyde solution and stirred uniformly. The mixture is reacted at 80-100° C. and 200-400 rpm under nitrogen as a protective gas for 8-12 hours. After the reaction is completed, the mixture is allowed to stand and separate, and the organic solvent layer is taken, rotary evaporated, and vacuum dried to remove the solvent to obtain a fluorine-containing pyridine-type benzoxazine; Step 2: Mix fluorinated pyridine benzoxazine, epoxy resin, 4,4-diaminodiphenylmethane, and acetone, stir at 50-70° C. and 500-700 rpm for 20-30 minutes, add KH-550 modified nano-silica hollow spheres and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, cool to 20-30° C., and continue stirring for 0.5-1.5 hours to obtain a resin glue for copper clad substrates; Step 3: After cutting the glass fiber cloth into a suitable size, modify it with KH-560, fully immerse the modified glass fiber cloth in the resin glue for the copper clad substrate, take it out, dry it at 25-30°C, and dry it at 110-120°C for 10-20 minutes to obtain a prepreg; Step 4: Stack the prepregs and place a layer of copper foil on the stacked prepregs. Curing is carried out in stages at 3-5 MPa. After curing, cool the prepregs and trim the burrs to obtain a flame-retardant copper-clad PCB substrate.

2. The method for preparing a flame-retardant copper-clad PCB substrate according to claim 1, wherein: Calculated by mass, the resin adhesive for the film-faced board includes 23 to 27 parts of fluorine-containing pyridine-type benzoxazine, 63 to 67 parts of epoxy resin, 1 to 3 parts of 4,4-diaminodiphenylmethane, 13 to 15 parts of KH-550 modified nano-silica hollow spheres, 15 to 17 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 145 to 155 parts of acetone.

3. The method for preparing a flame-retardant copper-clad PCB substrate according to claim 1, wherein: The paraformaldehyde solution includes 48.70 to 48.74 parts of toluene, 25.24 to 25.28 parts of ethyl acetate, and 7.42 to 7.46 parts of paraformaldehyde in parts by mass.

4. The method for preparing a flame-retardant copper-clad PCB substrate according to claim 1, wherein: In parts by mass, the aminopyridine / phenol solution includes 4.34 to 4.38 parts of 3,5-difluoro-2,6-diaminopyridine, 11.64 to 11.68 parts of phenol, 97.42 to 97.46 parts of toluene, and 50.50 to 50.54 parts of ethyl acetate.

5. The method for preparing a flame-retardant copper-clad PCB substrate according to claim 1, wherein: The preparation method of KH-550 modified nano-silica hollow spheres is as follows: Cetyltrimethylammonium bromide, ammonia water, ethanol, and deionized water are mixed, stirred at 25-30° C. and 400-600 rpm for 5-15 minutes to obtain a cetyltrimethylammonium bromide solution, ethyl orthosilicate is added to the cetyltrimethylammonium bromide solution, reacted at 25-30° C. and 400-600 rpm for 0.5-1.5 hours, centrifuged after completion of the reaction, washed with deionized water, and dried at 450-550° C. for 4-6 hours to obtain hollow nano-silica spheres; Mix KH-550, deionized water, and ethanol, stir evenly, adjust the pH with acetic acid to obtain a KH-550 ethanol solution, mix the nano-silica hollow spheres and the KH-550 ethanol solution, ultrasonically disperse for 10 to 20 minutes, and react at 70 to 90° C. for 3 to 5 hours to obtain KH-550 modified nano-silica hollow spheres.

6. The method for preparing a flame-retardant copper-clad PCB substrate according to claim 5, wherein: The preparation of nano-silica hollow spheres includes 0.38-0.42 parts of hexadecyltrimethylammonium bromide, 0.64-0.68 parts of ammonia water, and 0.26-0.30 parts of ethyl orthosilicate, calculated by mass.

7. The method for preparing a flame-retardant copper-clad PCB substrate according to claim 5, wherein: The preparation method of KH-550 modified nano-silica hollow spheres includes 46 to 50 parts of nano-silica hollow spheres, 1.98 to 2.02 parts of KH-550, 9 to 11 parts of deionized water, and 86 to 90 parts of ethanol, based on parts by mass.

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