Multilayer printed circuit board and preparation method thereof

Abstract

The invention relates to the technical field of electronic base materials, in particular to a multilayer printed circuit board and a preparation method thereof. A resin adhesive is prepared from modified boehmite, bisphenol A epoxy vinyl resin, branched epoxy resin, a curing agent and an accelerant, and then the resin prepreg is prepared by impregnating glass fabric in the resin adhesive. The surface of the printed circuit board is coated with an imidazole compound treating fluid, and then the resin prepreg and the printed circuit board are overlapped to obtain the multi-layer printed circuit board. According to the present invention, the imidazole compound and the copper have strong coordination activity and can be adsorbed on the surface of the printed circuit board to form the compact film, the gamma-isocyanate propyl triethoxy silane and the vinyl trimethoxy silane are added to make the generated silane film more compact, and the modified boehmite is added to improve the stripping resistance of the printed circuit board.

Description

Technical Field

[0001] The invention relates to the technical field of electronic substrates, in particular to a multilayer printed circuit board and a preparation method thereof. Background Art

[0002] With the rapid development of global information technology, digitalization and networking have become global trends, and electronic products are developing towards thinness, lightness and high density. As a key component of electronic products, printed circuit boards are required to have low dielectric constant, low dielectric loss, good thermal stability and reliability in high-frequency and high-speed transmission applications.

[0003] Epoxy resin materials are an important component of printed circuit boards. Traditional epoxy resin materials are gradually losing their advantages in high-performance substrate materials due to the limitation of dielectric properties. The prior art discloses the use of materials such as polytetrafluoroethylene, cyanate esters, polyphenylene oxide, and styrene-maleic anhydride to modify epoxy resins. Although polytetrafluoroethylene, cyanate esters, and polyphenylene oxides have excellent dielectric properties to a certain extent, they also have many disadvantages, such as complex manufacturing processes, environmental pollution, and high prices. Epoxy resins modified with styrene-maleic anhydride have problems such as poor adhesion and unstable dielectric constant values.

[0004] In order to solve the above problems and improve the peeling resistance and dielectric properties of the printed circuit board, the present invention provides a multilayer printed circuit board and a preparation method thereof. Summary of the invention

[0005] The object of the present invention is to provide a multilayer printed circuit board and a method for preparing the same, so as to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: A method for preparing a multilayer printed circuit board comprises the following steps: Step 1: uniformly mix the modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator to obtain resin glue; immerse the glass fiber cloth in the resin glue, take it out and dry it to obtain a resin semi-cured sheet; Step 2: Take the circuit board, drill and etch, and form an electroplated copper layer on the surface of the circuit board and the inner wall of the hole to obtain a printed circuit board; Step 3: Clean five printed circuit boards, and then apply imidazole compound treatment liquid on their surfaces respectively, place a resin semi-cured sheet between adjacent single-piece printed circuit boards, a total of five printed circuit boards and four resin semi-cured sheets, after stacking, press at 120-135°C for 70-80 minutes, irradiate under ultraviolet light for 40-50 minutes, demold, pin, and trim to obtain a multi-layer printed circuit board.

[0007] More optimally, the preparation method of the modified boehmite is: take boehmite and toluene, stir evenly, add 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane dropwise, react at 115-120°C for 5-7h, add vinyltrimethoxysilane, react for 5-7h, filter and dry to obtain modified boehmite.

[0008] More optimally, the mass ratio of the 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is (1.5-1.8):(0.7-0.8).

[0009] Preferably, the preparation method of the branched epoxy resin comprises the following steps: S1: Take potassium carbonate, resveratrol and N,N-dimethylformamide, stir at 75-85°C for 30-40 min, add 1,6-dibromohexane, react for 22-26 h, cool to 25-35°C, centrifuge to obtain the supernatant, add hydrochloric acid, rotary evaporate, precipitate and dry to obtain compound A; S2: Take compound A, tetrabutylammonium bromide, N,N-dimethylformamide and epichlorohydrin, react at 75-85°C for 7-9h, cool to 25-30°C, add sodium hydroxide solution dropwise, react for 10-14h, centrifuge, rotary evaporate, precipitate and dry to obtain a branched epoxy resin.

[0010] More optimally, the preparation method of the imidazole compound treatment liquid is: take imidazole and tetrahydrofuran, stir evenly, heat to 50-55°C, add γ-isocyanatepropyltriethoxysilane and 3-mercaptopropyltriethoxysilane, stir for 3-4 hours, evaporate the solvent, separate through a column, and obtain an imidazole compound; take an imidazole compound, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and deionized water, stir evenly, and obtain an imidazole compound treatment liquid.

[0011] Preferably, the particle size of the boehmite is 1-10 μm.

[0012] More optimally, the resin glue comprises the following components, by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 10-20 parts of branched epoxy resin, 20-30 parts of curing agent benzoxazine resin, 0.5-0.7 parts of accelerator, and 70-80 parts of modified boehmite.

[0013] More optimally, the promoter is any one or more of 1-methylimidazole and 2-methylimidazole.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) The present invention uses modified boehmite, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent, and accelerator to prepare a resin glue, and then prepares a resin semi-cured sheet by impregnating glass fiber cloth with the resin glue. An imidazole compound treatment liquid is coated on the surface of a printed circuit board, and then the resin semi-cured sheet and the printed circuit board are superimposed to obtain a multi-layer printed circuit board.

[0015] (2) Imidazole compounds and copper have strong coordination activity and can be adsorbed on the surface of printed circuit boards to form a tight film. Adding γ-isocyanate propyl triethoxysilane and 3-mercaptopropyl triethoxysilane can make the generated silane film tighter and enhance the surface corrosion resistance of the printed circuit board. When the printed circuit board is treated with imidazole compound treatment liquid, 3-mercaptopropyl triethoxysilane can form a chemical bond with the metal surface of the circuit board through the mercapto group, thereby increasing the surface roughness of the printed circuit board and improving the peeling resistance of the printed circuit board.

[0016] (3) The present invention uses resveratrol to synthesize compound A through nucleophilic substitution polycondensation reaction, and then adds epichlorohydrin to prepare a branched epoxy resin. The resin has a large number of epoxy groups and many active sites. At the same time, the rigid stilbene structure in resveratrol helps to improve the mechanical properties of the branched epoxy resin, thereby improving the service life of the printed circuit board.

[0017] The present invention uses boehmite with a particle size of 1-10 μm. The boehmite has a small particle size and a larger specific surface area, and can react with more 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane. First, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane is added to connect amino groups to the surface of the boehmite. The amino groups react with a large number of epoxy groups in the branched epoxy resin, thereby improving the poor compatibility of the boehmite due to the large specific surface area and improving the dielectric properties of the printed circuit board. Then, vinyltrimethoxysilane is used for further reaction, and the mass of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is controlled to be (1.5-1.8): (0.7-0.8). At this time, under the action of the photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone, a mercapto-vinyl reaction can be generated to increase the interfacial force between the printed circuit board and the resin semi-cured sheet, thereby improving the peeling resistance of the printed circuit board. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] There is no special restriction on the purchase manufacturers of all raw materials involved in the present invention, and illustratively include: boehmite: particle size: 1-10µm; epoxy resin: tetramethyl bisphenol F epoxy resin: model: A1-DPE-265, which can be purchased from Sichuan Dongcai Technology Group Co., Ltd.; bisphenol A epoxy vinyl resin: model: 3301, which can be purchased from Langfang Yongda Anticorrosion Materials Co., Ltd.; benzoxazine resin: model: B1-D125, which can be purchased from Sichuan Dongcai Technology Group Co., Ltd.; 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane: item number: 413348, which can be purchased from Sigma-Aldrich Shanghai Trading Co., Ltd.; glass fiber cloth: 2116 electronic grade glass fiber cloth, thickness 0.05mm, which can be purchased from Langfang Anlang Sealing Materials Co., Ltd.

[0020] Embodiment 1: A method for preparing a multilayer printed circuit board comprises the following steps: Step 1: Preparation of imidazole compounds: Take 3.6g of imidazole and 50mL of tetrahydrofuran, stir evenly, heat to 53°C, add 13g of γ-isocyanatepropyltriethoxysilane and 6g of 3-mercaptopropyltriethoxysilane, stir for 3.5h, evaporate the solvent, separate through a column to obtain an imidazole compound; take 30g of the imidazole compound, 1mL of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 100mL of deionized water, stir evenly to obtain an imidazole compound treatment solution; Step 2: Preparation of branched epoxy resin: Take 30g potassium carbonate, 24g resveratrol, and 250mL N,N-dimethylformamide, stir at 80°C for 35min, add 23g 1,6-dibromohexane, react for 24h, cool to 30°C, centrifuge to take the supernatant, add 10mL hydrochloric acid, rotary evaporate, precipitate, and dry to obtain compound A; Take 25g of compound A, 0.35g of tetrabutylammonium bromide, 130mL of N,N-dimethylformamide, and 235g of epichlorohydrin, react at 80°C for 8h, cool to 27°C, dropwise add 100mL of sodium hydroxide solution, react for 12h, centrifuge, rotary evaporate, precipitate, and dry to obtain a branched epoxy resin; Step 3: Preparation of modified boehmite: Take 5 g of boehmite and 200 mL of toluene, stir evenly, add 1.8 mL of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane dropwise, react at 117°C for 6 h, add 0.75 mL of vinyltrimethoxysilane, react for 6 h, filter and dry to obtain modified boehmite; The mass ratio of the 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is 1.8:0.75; Step 4: Preparation of resin prepreg: The modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator are mixed uniformly to obtain resin glue; the glass fiber cloth is immersed in the resin glue, taken out and dried to obtain a resin semi-cured sheet; The resin glue includes the following components, measured by weight: The resin glue includes the following components, measured by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 15 parts of branched epoxy resin, 25 parts of curing agent benzoxazine resin, 0.6 parts of accelerator 2-methylimidazole, and 75 parts of modified boehmite.

[0021] Step 5: Preparation of multilayer printed circuit boards: Taking the circuit board, drilling and etching, forming an electroplated copper layer on the surface of the circuit board and the inner wall of the hole, and obtaining a printed circuit board; Take five printed circuit boards, clean them, and then coat a layer of imidazole compound treatment liquid with a thickness of 0.2µm on their surfaces. Place a resin semi-cured sheet between adjacent single printed circuit boards. There are five printed circuit boards and four resin semi-cured sheets in total. After stacking, press them at 125°C for 75 minutes, irradiate them under an 800W ultraviolet lamp for 45 minutes, demold, pin, and trim to obtain a multilayer printed circuit board.

[0022] Embodiment 2: A method for preparing a multilayer printed circuit board comprises the following steps: Step 1: Preparation of imidazole compounds: Take 3.6g of imidazole and 50mL of tetrahydrofuran, stir evenly, heat to 50°C, add 13g of γ-isocyanatepropyltriethoxysilane and 6g of 3-mercaptopropyltriethoxysilane, stir for 3h, evaporate the solvent, separate through a column to obtain an imidazole compound; take 30g of the imidazole compound, 1mL of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 100mL of deionized water, stir evenly to obtain an imidazole compound treatment solution; Step 2: Preparation of branched epoxy resin: Take 30g potassium carbonate, 24g resveratrol, and 250mL N,N-dimethylformamide, stir at 75°C for 30min, add 23g 1,6-dibromohexane, react for 22h, cool to 25°C, centrifuge to take the supernatant, add 10mL hydrochloric acid, rotary evaporate, precipitate, and dry to obtain compound A; Take 25g of compound A, 0.35g of tetrabutylammonium bromide, 130mL of N,N-dimethylformamide, and 235g of epichlorohydrin, react at 75°C for 7h, cool to 25°C, add 100mL of sodium hydroxide solution dropwise, react for 10h, centrifuge, rotary evaporate, precipitate, and dry to obtain a branched epoxy resin; Step 3: Preparation of modified boehmite: Take 5 g of boehmite and 200 mL of toluene, stir evenly, add 1.8 mL of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane dropwise, react at 115°C for 5 h, add 0.7 mL of vinyltrimethoxysilane, react for 5 h, filter and dry to obtain modified boehmite; The mass ratio of the 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is 1.8:0.7; Step 4: Preparation of resin prepreg: The modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator are mixed uniformly to obtain resin glue; the glass fiber cloth is immersed in the resin glue, taken out and dried to obtain a resin semi-cured sheet; The resin glue includes the following components, measured by weight: The resin glue includes the following components, measured by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 10 parts of branched epoxy resin, 20 parts of curing agent benzoxazine resin, 0.5 parts of accelerator 2-methylimidazole, and 70 parts of modified boehmite.

[0023] Step 5: Preparation of multilayer printed circuit boards: Taking the circuit board, drilling and etching, forming an electroplated copper layer on the surface of the circuit board and the inner wall of the hole, and obtaining a printed circuit board; Take five printed circuit boards, clean them, and then coat a layer of imidazole compound treatment liquid with a thickness of 0.2µm on their surfaces. Place a resin semi-cured sheet between adjacent single-piece printed circuit boards. There are five printed circuit boards and four resin semi-cured sheets in total. After stacking, press them at 120°C for 70 minutes, irradiate them under an 800W ultraviolet lamp for 40 minutes, demold, pin, and trim to obtain a multilayer printed circuit board.

[0024] Embodiment 3: A method for preparing a multilayer printed circuit board, comprising the following steps: Step 1: Preparation of imidazole compounds: Take 3.6g of imidazole and 50mL of tetrahydrofuran, stir evenly, heat to 55°C, add 13g of γ-isocyanatepropyltriethoxysilane and 6g of 3-mercaptopropyltriethoxysilane, stir for 4h, evaporate the solvent, separate through a column to obtain an imidazole compound; take 30g of the imidazole compound, 1mL of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 100mL of deionized water, stir evenly to obtain an imidazole compound treatment solution; Step 2: Preparation of branched epoxy resin: Take 30g potassium carbonate, 24g resveratrol, and 250mL N,N-dimethylformamide, stir at 85°C for 40min, add 23g 1,6-dibromohexane, react for 26h, cool to 35°C, centrifuge to take the supernatant, add 10mL hydrochloric acid, rotary evaporate, precipitate, and dry to obtain compound A; Take 25g of compound A, 0.35g of tetrabutylammonium bromide, 130mL of N,N-dimethylformamide, and 235g of epichlorohydrin, react at 85°C for 9h, cool to 30°C, dropwise add 100mL of sodium hydroxide solution, react for 14h, centrifuge, rotary evaporate, precipitate, and dry to obtain a branched epoxy resin; Step 3: Preparation of modified boehmite: Take 5 g of boehmite and 200 mL of toluene, stir evenly, add 1.8 mL of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane dropwise, react at 120°C for 7 h, add 0.8 mL of vinyltrimethoxysilane, react for 7 h, filter and dry to obtain modified boehmite; The mass ratio of the 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is 1.8:0.8; Step 4: Preparation of resin prepreg: The modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator are mixed uniformly to obtain resin glue; the glass fiber cloth is immersed in the resin glue, taken out and dried to obtain a resin semi-cured sheet; The resin glue includes the following components, measured by weight: The resin glue includes the following components, measured by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 20 parts of branched epoxy resin, 30 parts of curing agent benzoxazine resin, 0.7 parts of accelerator 2-methylimidazole, and 80 parts of modified boehmite.

[0025] Step 5: Preparation of multilayer printed circuit boards: Taking the circuit board, drilling and etching, forming an electroplated copper layer on the surface of the circuit board and the inner wall of the hole, and obtaining a printed circuit board; Take five printed circuit boards, clean them, and then coat a layer of imidazole compound treatment liquid with a thickness of 0.2µm on their surfaces. Place a resin semi-cured sheet between adjacent single printed circuit boards. There are five printed circuit boards and four resin semi-cured sheets in total. After stacking, press them at 135°C for 80 minutes, irradiate them under an 800W ultraviolet lamp for 50 minutes, demold, pin, and trim to obtain a multilayer printed circuit board.

[0026] Comparative Example 1: The mass ratio of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is 1.8:0.5, and the rest is the same as Example 1: Step 1: Preparation of imidazole compounds: Take 3.6g of imidazole and 50mL of tetrahydrofuran, stir evenly, heat to 53°C, add 13g of γ-isocyanatepropyltriethoxysilane and 6g of 3-mercaptopropyltriethoxysilane, stir for 3.5h, evaporate the solvent, separate through a column to obtain an imidazole compound; take 30g of the imidazole compound, 1mL of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 100mL of deionized water, stir evenly to obtain an imidazole compound treatment solution; Step 2: Preparation of branched epoxy resin: Take 30g potassium carbonate, 24g resveratrol, and 250mL N,N-dimethylformamide, stir at 80°C for 35min, add 23g 1,6-dibromohexane, react for 24h, cool to 30°C, centrifuge to take the supernatant, add 10mL hydrochloric acid, rotary evaporate, precipitate, and dry to obtain compound A; Take 25g of compound A, 0.35g of tetrabutylammonium bromide, 130mL of N,N-dimethylformamide, and 235g of epichlorohydrin, react at 80°C for 8h, cool to 27°C, dropwise add 100mL of sodium hydroxide solution, react for 12h, centrifuge, rotary evaporate, precipitate, and dry to obtain a branched epoxy resin; Step 3: Preparation of modified boehmite: Take 5 g of boehmite and 200 mL of toluene, stir evenly, add 1.8 mL of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane dropwise, react at 117°C for 6 h, add 0.5 mL of vinyltrimethoxysilane, react for 6 h, filter and dry to obtain modified boehmite; The mass ratio of the 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is 1.8:0.5; Step 4: Preparation of resin prepreg: The modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator are mixed uniformly to obtain resin glue; the glass fiber cloth is immersed in the resin glue, taken out and dried to obtain a resin semi-cured sheet; The resin glue includes the following components, measured by weight: The resin glue includes the following components, measured by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 15 parts of branched epoxy resin, 25 parts of curing agent benzoxazine resin, 0.6 parts of accelerator 2-methylimidazole, and 75 parts of modified boehmite.

[0027] Step 5: Preparation of multilayer printed circuit boards: Taking the circuit board, drilling and etching, forming an electroplated copper layer on the surface of the circuit board and the inner wall of the hole, and obtaining a printed circuit board; Take five printed circuit boards, clean them, and then coat a layer of imidazole compound treatment liquid with a thickness of 0.2µm on their surfaces. Place a resin semi-cured sheet between adjacent single printed circuit boards. There are five printed circuit boards and four resin semi-cured sheets in total. After stacking, press them at 125°C for 75 minutes, irradiate them under an 800W ultraviolet lamp for 45 minutes, demold, pin, and trim to obtain a multilayer printed circuit board.

[0028] Comparative Example 2: The boehmite was treated without adding 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, and the rest was the same as Example 1: Step 1: Preparation of imidazole compounds: Take 3.6g of imidazole and 50mL of tetrahydrofuran, stir evenly, heat to 53°C, add 13g of γ-isocyanatepropyltriethoxysilane and 6g of 3-mercaptopropyltriethoxysilane, stir for 3.5h, evaporate the solvent, separate through a column to obtain an imidazole compound; take 30g of the imidazole compound, 1mL of 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 100mL of deionized water, stir evenly to obtain an imidazole compound treatment solution; Step 2: Preparation of branched epoxy resin: Take 30g potassium carbonate, 24g resveratrol, and 250mL N,N-dimethylformamide, stir at 80°C for 35min, add 23g 1,6-dibromohexane, react for 24h, cool to 30°C, centrifuge to take the supernatant, add 10mL hydrochloric acid, rotary evaporate, precipitate, and dry to obtain compound A; Take 25g of compound A, 0.35g of tetrabutylammonium bromide, 130mL of N,N-dimethylformamide, and 235g of epichlorohydrin, react at 80°C for 8h, cool to 27°C, dropwise add 100mL of sodium hydroxide solution, react for 12h, centrifuge, rotary evaporate, precipitate, and dry to obtain a branched epoxy resin; Step 3: Preparation of modified boehmite: Take 5 g of boehmite and 200 mL of toluene, stir evenly, add 1.8 mL of vinyltrimethoxysilane dropwise, react at 117 ° C for 12 h, filter and dry to obtain modified boehmite; Step 4: Preparation of resin prepreg: The modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator are mixed uniformly to obtain resin glue; the glass fiber cloth is immersed in the resin glue, taken out and dried to obtain a resin semi-cured sheet; The resin glue includes the following components, measured by weight: The resin glue includes the following components, measured by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 15 parts of branched epoxy resin, 25 parts of curing agent benzoxazine resin, 0.6 parts of accelerator 2-methylimidazole, and 75 parts of modified boehmite.

[0029] Step 5: Preparation of multilayer printed circuit boards: Taking the circuit board, drilling and etching, forming an electroplated copper layer on the surface of the circuit board and the inner wall of the hole, and obtaining a printed circuit board; Take five printed circuit boards, clean them, and then coat a layer of imidazole compound treatment liquid with a thickness of 0.2µm on their surfaces. Place a resin semi-cured sheet between adjacent single printed circuit boards. There are five printed circuit boards and four resin semi-cured sheets in total. After stacking, press them at 125°C for 75 minutes, irradiate them under an 800W ultraviolet lamp for 45 minutes, demold, pin, and trim to obtain a multilayer printed circuit board.

[0030] Comparative Example 3: The imidazole compound treatment solution is not coated on the surface of the printed circuit board, and the rest is the same as Example 1: Step 1: Preparation of branched epoxy resin: Take 30g potassium carbonate, 24g resveratrol, and 250mL N,N-dimethylformamide, stir at 80°C for 35min, add 23g 1,6-dibromohexane, react for 24h, cool to 30°C, centrifuge to take the supernatant, add 10mL hydrochloric acid, rotary evaporate, precipitate, and dry to obtain compound A; Take 25g of compound A, 0.35g of tetrabutylammonium bromide, 130mL of N,N-dimethylformamide, and 235g of epichlorohydrin, react at 80°C for 8h, cool to 27°C, dropwise add 100mL of sodium hydroxide solution, react for 12h, centrifuge, rotary evaporate, precipitate, and dry to obtain a branched epoxy resin; Step 2: Preparation of modified boehmite: Take 5 g of boehmite and 200 mL of toluene, stir evenly, add 1.8 mL of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane dropwise, react at 117°C for 6 h, add 0.75 mL of vinyltrimethoxysilane, react for 6 h, filter and dry to obtain modified boehmite; The mass ratio of the 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is 1.8:0.75; Step 3: Preparation of resin prepreg: The modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator are mixed uniformly to obtain resin glue; the glass fiber cloth is immersed in the resin glue, taken out and dried to obtain a resin semi-cured sheet; The resin glue includes the following components, measured by weight: The resin glue includes the following components, measured by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 15 parts of branched epoxy resin, 25 parts of curing agent benzoxazine resin, 0.6 parts of accelerator 2-methylimidazole, and 75 parts of modified boehmite.

[0031] Step 4: Preparation of multilayer printed circuit boards: Taking the circuit board, drilling and etching, forming an electroplated copper layer on the surface of the circuit board and the inner wall of the hole, and obtaining a printed circuit board; Take five printed circuit boards, clean them, place a resin semi-cured sheet between adjacent single-piece printed circuit boards, a total of five printed circuit boards and four resin semi-cured sheets, after stacking, press them at 125°C for 75 minutes, irradiate them under an 800W ultraviolet lamp for 45 minutes, demold, pin, and trim to obtain a multi-layer printed circuit board.

[0032] experiment: The multilayer printed circuit boards prepared in Examples 1-3 and Comparative Examples 1-3 were used for performance testing, and the dielectric loss factor at 10 GHz and the peel strength between the single-layer printed circuit board and the resin prepreg were tested with reference to IPC-TM650. The obtained data are shown in the following table:

[0033] Conclusion: From the comparison of the data in the table, it can be seen that in Comparative Example 1, the mass ratio of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane and vinyltrimethoxysilane is 1.8:0.5, the amount of vinyltrimethoxysilane added is reduced, the vinyl grafted on the modified boehmite is reduced, the interfacial force between the printed circuit board and the resin semi-cured sheet is reduced, and the peeling resistance of the printed circuit board is reduced. Comparative Example 2 does not add 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane to treat boehmite, the compatibility of boehmite in epoxy resin is deteriorated, and the peeling resistance and dielectric properties of the printed circuit board are reduced. Comparative Example 3 does not coat the surface of the printed circuit board with an imidazole compound treatment solution, and the peeling resistance of the printed circuit board is reduced.

[0034] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a multilayer printed circuit board, characterized in that: The following steps are involved: Step 1: uniformly mix the modified boehmite, epoxy resin, bisphenol A epoxy vinyl resin, branched epoxy resin, curing agent and accelerator to obtain resin glue; immerse the glass fiber cloth in the resin glue, take it out and dry it to obtain a resin semi-cured sheet; Step 2: Take the circuit board, drill and etch, and form an electroplated copper layer on the surface of the circuit board and the inner wall of the hole to obtain a printed circuit board; Step 3: Clean five printed circuit boards, and then apply imidazole compound treatment liquid on their surfaces respectively, place a resin semi-cured sheet between adjacent single-piece printed circuit boards, a total of five printed circuit boards and four resin semi-cured sheets, after stacking, press at 120-135°C for 70-80 minutes, irradiate under ultraviolet light for 40-50 minutes, demold, pin, and trim to obtain a multi-layer printed circuit board.

2. The method for preparing a multilayer printed circuit board according to claim 1, characterized in that: The preparation method of the modified boehmite is as follows: taking boehmite and toluene, stirring evenly, dropping 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, reacting at 115-120° C. for 5-7 hours, adding vinyltrimethoxysilane, reacting for 5-7 hours, filtering, and drying to obtain the modified boehmite.

3. The method for preparing a multilayer printed circuit board according to claim 2, characterized in that: The mass ratio of the 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane to vinyltrimethoxysilane is (1.5-1.8):(0.7-0.8).

4. The method for preparing a multilayer printed circuit board according to claim 1, characterized in that: The preparation method of the branched epoxy resin is: The following steps are involved: S1: Take potassium carbonate, resveratrol and N,N-dimethylformamide, stir at 75-85°C for 30-40 min, add 1,6-dibromohexane, react for 22-26 h, cool to 25-35°C, centrifuge to obtain the supernatant, add hydrochloric acid, rotary evaporate, precipitate and dry to obtain compound A; S2: Take compound A, tetrabutylammonium bromide, N,N-dimethylformamide and epichlorohydrin, react at 75-85°C for 7-9h, cool to 25-30°C, add sodium hydroxide solution dropwise, react for 10-14h, centrifuge, rotary evaporate, precipitate and dry to obtain a branched epoxy resin.

5. The method for preparing a multilayer printed circuit board according to claim 1, characterized in that: The preparation method of the imidazole compound treatment liquid is as follows: take imidazole and tetrahydrofuran, stir evenly, heat to 50-55° C., add γ-isocyanatepropyltriethoxysilane and 3-mercaptopropyltriethoxysilane, stir for 3-4 hours, evaporate the solvent, separate through a column to obtain an imidazole compound; take an imidazole compound, 2-hydroxy-2-methyl-1-phenyl-1-propanone and deionized water, stir evenly to obtain an imidazole compound treatment liquid.

6. The method for preparing a multilayer printed circuit board according to claim 2, characterized in that: The particle size of the boehmite is 1-10 μm.

7. The method for preparing a multilayer printed circuit board according to claim 1, characterized in that: The resin glue comprises the following components, by weight: 65 parts of epoxy resin, 35 parts of bisphenol A epoxy vinyl resin, 10-20 parts of branched epoxy resin, 20-30 parts of curing agent benzoxazine resin, 0.5-0.7 parts of accelerator, and 70-80 parts of modified boehmite.

8. The method for preparing a multilayer printed circuit board according to claim 7, characterized in that: The accelerator is any one or more of 1-methylimidazole and 2-methylimidazole.

9. A multilayer printed circuit board prepared according to the method for preparing a multilayer printed circuit board according to any one of claims 1 to 8.

Images