A bonding sheet, a method for preparing the same, and a copper-clad plate including the same

Abstract

This invention provides an adhesive sheet and its preparation method, as well as a copper-clad laminate containing the same. The adhesive sheet includes a reinforcing material and a resin material attached to the reinforcing material after two impregnation and drying processes. The resin material comprises a first resin composition attached after a first impregnation and drying and a second resin composition attached after a second impregnation and drying. The first resin composition comprises a combination of phenolic resin, a nitrogen-containing flame retardant, and a phosphorus-containing flame retardant. The second resin composition comprises a combination of biphenyl-type epoxy resin, a curing agent, a halogenated flame retardant, and an antimony-containing flame retardant. Through the design of the first and second resin compositions and their synergistic interaction, the adhesive sheet achieves significant improvements in flame retardancy, heat resistance, and processability, enabling the copper-clad laminate containing it to possess excellent flame retardancy, heat resistance, and punching processability, resulting in a significant improvement in overall performance.

Description

Technical Field

[0001] This invention belongs to the field of copper clad laminate technology, specifically relating to an adhesive sheet and its preparation method, and a copper clad laminate containing the same. Background Technology

[0002] Copper clad laminates (CCLs) serve multiple functions, including supporting electronic components, forming conductive circuit patterns, and providing insulation between layers / circuits. As a fundamental electronic material, its technological level directly restricts and influences the manufacturing level, performance, quality, and reliability of electronic products. CEM-1 CCLs use electronic-grade fiberglass cloth and bleached wood pulp paper as reinforcing materials, impregnated with a resin composition specifically for CCLs to create the outer and core materials, which are then covered with copper foil and hot-pressed. CEM-1 CCLs exhibit superior performance compared to paper-based CCLs and are less expensive than fiberglass cloth CCLs, demonstrating strong competitiveness in mechanical properties, processability, electrical performance, and cost. In recent years, with the increasing lead-free and functional integration of end products, the corresponding circuits have become increasingly complex, placing higher demands on the heat resistance, flame retardancy, and perforation properties of CEM-1 CCLs. Therefore, improving the flame retardancy and heat resistance of CEM-1 CCLs is a key research focus in the industry.

[0003] CN111572131A discloses a method for preparing CEM-1 copper clad laminate, comprising the following steps: Preparing the surface resin: mixing 10-70 parts of solvent-based epoxy resin, 0.1-2 parts of curing agent and curing accelerator, 10-40 parts of solvent, and 0.1-30 parts of flame retardant, wherein the flame retardant is one or more of magnesium hydroxide, antimony trioxide, and aluminum hydroxide; Preparing the inner resin for the first impregnation: mixing 30-45 parts of water-soluble phenolic resin, 150-200 parts of methanol, 30-50 parts of acetone, and 100-150 parts of water; Preparing the inner resin for the second impregnation: mixing 40-50 parts of polyvinyl alcohol formaldehyde-polyvinyl alcohol-polyacrylic acid copolymer, 10-40 parts of epoxy resin, 125-130 parts of solvent-based phenolic resin, 0-50 parts of cyanate ester resin, and 10-50 parts of cyanate ester modified resin. The resin, 10-50 parts of electronic-grade filler, and 10-60 parts of flame retardant are mixed evenly. The flame retardant is one or a mixture of two of magnesium hydroxide and antimony trioxide. Electronic-grade glass fiber cloth is impregnated with surface resin and then coated with a glue machine at 100-200℃ to obtain a surface prepreg. Wood pulp fiber paper is impregnated with resin for the first and second impregnations of the inner material and then coated with a glue machine at 100-200℃ to obtain an inner material prepreg. Several inner material prepregs are stacked together, and a surface prepreg is applied to each side. Finally, copper foil is applied to the single-sided or double-sided surface prepreg and hot-pressed to obtain a CEM-1 copper clad laminate. Although the heat resistance of this copper clad laminate is improved compared with ordinary boards, its resistance to immersion soldering at 288℃ is <70s, which is still significantly insufficient. Furthermore, its flame retardant and punching performance cannot meet the performance requirements of high-performance circuit boards.

[0004] CN109233209A discloses a halogenated antimony-free resin composition, comprising the following components: 25-70 parts by weight of flame-retardant epoxy resin, 10-40 parts by weight of non-flame-retardant epoxy resin, 20-60 parts by weight of composite curing agent, and 0.05-1.0 parts by weight of curing accelerator; wherein the flame-retardant epoxy resin includes a composition of phosphorus-containing epoxy resin, brominated epoxy resin, and nitrogen-containing epoxy resin, which, when combined with the non-flame-retardant epoxy resin, can enhance the flame retardancy, solderability, and heat resistance of CEM-1 copper-clad laminate. However, due to the addition of a large amount of flame-retardant components to the resin system, the perforation properties of the copper-clad laminate deteriorate, and the heat resistance also needs further improvement.

[0005] CN111806001A discloses a method for preparing CEM-1 copper clad laminate, including steps such as preparing surface prepreg adhesive, preparing inner material first impregnation resin adhesive, preparing inner material second impregnation resin adhesive, preparing prepreg, and hot pressing molding; wherein, a phosphorus-containing flame retardant is added to the inner material first impregnation resin adhesive, and a phosphorus-containing epoxy, a nitrogen-containing phenolic, and a phosphorus- and nitrogen-containing flame retardant are added to the inner material second impregnation resin adhesive, so that the copper clad laminate has an FV0 flame retardancy rating; however, the large amount of flame retardant added to the board results in poor heat resistance and punching performance, and the 288℃ dip soldering resistance is only 24-26s.

[0006] Currently, the main way to improve the flame retardancy of CEM-1 copper clad laminates in the industry is to add a large amount of flame retardant. However, a large amount of flame retardant will lead to a decrease in the heat resistance and punching ability of CEM-1 copper clad laminates, making it difficult to improve their overall performance. Therefore, developing copper clad laminates that combine excellent flame retardancy, heat resistance, and punching processability is an urgent problem to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an adhesive sheet and its preparation method, as well as a copper-clad laminate containing the adhesive sheet. Through the design and synergy of the first resin composition and the second resin composition, the adhesive sheet achieves significant improvements in flame retardancy, heat resistance, and processability, enabling the copper-clad laminate containing the adhesive sheet to possess excellent flame retardancy, heat resistance, and punching processability, resulting in a significant improvement in overall performance.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides an adhesive sheet comprising a reinforcing material and a resin material attached to the reinforcing material after being impregnated and dried twice;

[0010] The resin material comprises a combination of a first resin composition that adheres after a first impregnation and drying and a second resin composition that adheres after a second impregnation and drying;

[0011] The first resin composition comprises a combination of phenolic resin, a nitrogen-containing flame retardant, and a phosphorus-containing flame retardant;

[0012] The second resin composition comprises a combination of biphenyl-type epoxy resin, a curing agent, a halogenated flame retardant, and an antimony-containing flame retardant.

[0013] In the adhesive sheet provided by the present invention, the resin material is attached to the reinforcing material through two impregnation and drying processes. The first impregnation and drying process attaches a first resin composition containing phenolic resin, nitrogen-containing flame retardant and phosphorus-containing flame retardant to the reinforcing material. Then, the second impregnation and drying process is carried out to achieve the attachment of a second resin composition. Specifically, this invention is based on the principle of selecting different flame retardant systems for CEM-1 copper clad laminates during different combustion processes. A halogenated antimony flame retardant system is selected for the first combustion stage, and a phosphorus-nitrogen flame retardant system is selected for the second combustion stage, achieving highly efficient flame retardancy at different combustion stages. This significantly reduces the amount of halogenated antimony flame retardant used. Furthermore, through the synergistic compounding of biphenyl-type epoxy resin, curing agent, halogenated antimony flame retardant, and the first resin composition, it solves the problem in the prior art where adding large amounts of flame retardants (e.g., large amounts of halogenated antimony flame retardants) results in poor heat resistance and punching performance of CEM-1 copper clad laminates. This allows the copper clad laminate containing the adhesive sheet to possess excellent flame retardancy while also significantly improving heat resistance and punching performance, effectively improving the overall performance of the copper clad laminate and fully meeting the application requirements of high-performance circuit boards.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0015] Preferably, the first resin composition comprises, by weight, the following components:

[0016] 100 parts of phenolic resin

[0017] 5-10 parts of nitrogen-containing flame retardant

[0018] 10-20 parts of phosphorus-containing flame retardant.

[0019] Specifically, the nitrogen-containing flame retardant has a mass fraction of 5-10 parts, for example, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts or 9.5 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0020] The phosphorus-containing flame retardant is in the range of 10-20 parts by weight, for example, 11, 12, 13, 14, 15, 16, 17, 18 or 19 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0021] Preferably, the phenolic resin is an aqueous phenolic resin, and more preferably a small-molecule water-soluble phenolic resin.

[0022] Preferably, the number average molecular weight of the phenolic resin is 100-2000 g / mol, for example, it can be 200 g / mol, 500 g / mol, 800 g / mol, 1000 g / mol, 1200 g / mol, 1500 g / mol or 1800 g / mol, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0023] Preferably, the nitrogen-containing flame retardant includes any one or a combination of at least two of vinyl isocyanate, melamine-glyoxal resin, melamine-formaldehyde resin, methylated melamine resin, butylated melamine resin, triisocyanurate-modified melamine resin, and organosilicon-modified melamine resin.

[0024] Preferably, the phosphorus-containing flame retardant is a water-based phosphorus-containing flame retardant.

[0025] Preferably, the phosphorus-containing flame retardant includes any one or a combination of at least two of alkoxycyclotriphosphazene, phenoxycyclotriphosphazene, hexa-p-aldehyde phenoxycyclotriphosphazene, hexa(4-DOPO hydroxymethylphenoxy)cyclotriphosphazene, (2-allylphenoxy)pentaphenoxycyclotriphosphazene, and hexa(4-nitrophenoxy)cyclotriphosphazene.

[0026] Preferably, the second resin composition comprises, by weight, the following components:

[0027]

[0028] Specifically, the curing agent has a mass fraction of 20-80 parts, for example, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts or 75 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0029] The halogenated flame retardant is present in parts by weight of 2-10, for example, 3, 4, 5, 6, 7, 8 or 9 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0030] The antimony-containing flame retardant is in the range of 1-5 parts by weight, for example, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts or 4.5 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0031] Preferably, the epoxy equivalent of the biphenyl-type epoxy resin is 120-270 g / eq, for example, it can be 130 g / eq, 150 g / eq, 160 g / eq, 170 g / eq, 180 g / eq, 190 g / eq, 200 g / eq, 220 g / eq or 250 g / eq, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, and 150-250 g / eq is further preferred.

[0032] As a preferred embodiment of the present invention, the biphenyl-type epoxy resin has an epoxy equivalent of 150-250 g / eq. As the main resin of the second resin composition, it works synergistically with other components to further improve the heat resistance of the adhesive sheet.

[0033] Preferably, the curing agent includes any one or a combination of at least two of vegetable oil-modified phenolic resin, linear phenolic resin, and thermosetting phenolic resin.

[0034] Preferably, the halogenated flame retardant includes a brominated flame retardant.

[0035] Preferably, the halogenated flame retardant includes any one or a combination of at least two of tetrabromobisphenol A, tribromophenol, decabromodiphenyl ethane, and octabromodiphenyl ethane.

[0036] Preferably, the antimony-containing flame retardant includes any one or a combination of at least two of antimony oxide, antimony halide, and antimonate.

[0037] Preferably, the second resin composition further includes a curing accelerator.

[0038] Preferably, based on 100 parts by weight of the biphenyl epoxy resin, the curing accelerator has a mass of ≤1 part, for example, it can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9 parts, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0039] Preferably, the curing accelerator comprises any one or a combination of at least two of the following: tertiary amines, quaternary ammonium salts, imidazole compounds, organometallic complexes, and tertiary phosphine.

[0040] Preferably, the imidazole compound includes any one or a combination of at least two of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 2-dodecylimidazole, 2-heptadecanylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4-methylimidazole, and 1-cyanoethyl-2-methylimidazole.

[0041] Preferably, the reinforcing material includes at least one of wood pulp paper, cotton pulp paper, or nonwoven fabric, and more preferably wood pulp paper and / or cotton pulp paper.

[0042] Preferably, the mass ratio of the first resin composition to the second resin composition is 1:(8-12), for example, it can be 1:8.5, 1:9, 1:9.5, 1:10, 1:10.5, 1:11 or 1:11.5, and more preferably 1:10.

[0043] In a second aspect, the present invention provides a method for preparing an adhesive sheet as described in the first aspect, the method comprising:

[0044] The reinforcing material is first impregnated in a resin solution of a first resin composition, and then first dried to obtain a prepreg.

[0045] The prepreg is placed in a resin solution of a second resin composition for a second impregnation, followed by a second drying, to obtain the adhesive sheet.

[0046] Preferably, the solvent of the resin liquid in the first resin composition includes water.

[0047] Preferably, the solid content of the resin liquid in the first resin composition is 10%-30%, for example, it can be 12%, 15%, 18%, 20%, 22%, 25% or 28%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0048] Preferably, the solvent of the resin liquid of the second resin composition includes any one or a combination of at least two of ketone solvents, aromatic hydrocarbon solvents, and ester solvents, and more preferably ketone solvents and / or aromatic hydrocarbon solvents.

[0049] Preferably, the ketone solvent includes any one or a combination of at least two of acetone, butanone, and cyclohexanone.

[0050] Preferably, the aromatic hydrocarbon solvent includes any one or a combination of at least two of toluene, xylene, and trimethylbenzene.

[0051] Preferably, the ester solvent includes ethyl acetate and / or butyl acetate.

[0052] Preferably, the solid content of the resin liquid in the second resin composition is 50%-70%, for example, it can be 52%, 55%, 58%, 60%, 62%, 65% or 68%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0053] Preferably, the first immersion time and the second immersion time are each independently 5-60s, for example, 6s, 8s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s or 55s, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0054] Preferably, the temperatures of the first drying and the second drying are each independently between 100-220°C, for example, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or 210°C, as well as specific values ​​between the above-mentioned values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0055] Preferably, the drying time for the first drying and the drying time for the second drying are each independently 1-30 min, for example, 2 min, 5 min, 8 min, 10 min, 15 min, 20 min or 25 min, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 1-10 min is further preferred.

[0056] Preferably, the first drying time is 3-5 minutes.

[0057] Preferably, the second drying time is 2-4 minutes.

[0058] Thirdly, the present invention provides a copper-clad laminate, the copper-clad laminate comprising copper foil and at least one adhesive sheet as described in the first aspect.

[0059] Preferably, the copper clad laminate is a CEM-1 copper clad laminate, which includes a laminate and copper foil disposed on one or both sides of the laminate; the laminate includes a face material and a core material, and the core material includes at least one adhesive sheet as described in the first aspect.

[0060] Preferably, the number of adhesive sheets in the core material is 1-20, for example, 2, 3, 5, 6, 8, 10, 12, 15 or 18 sheets.

[0061] For example, the method for preparing the copper-clad laminate includes: bonding fabric to both sides of a core material to obtain a laminate, then pressing copper foil onto one or both sides of the laminate and curing it to obtain the copper-clad laminate.

[0062] Preferably, the curing temperature is 130-190℃, for example 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃ or 185℃, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0063] Preferably, the curing pressure is 4-8 MPa, for example, it can be 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa or 7.5 MPa, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0064] Preferably, the curing time is 30-300 min, for example, it can be 40 min, 60 min, 80 min, 100 min, 120 min, 140 min, 150 min, 160 min, 180 min, 200 min, 220 min, 240 min, 260 min or 280 min, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0065] Thirdly, the present invention provides a printed circuit board, the printed circuit board comprising at least one of the adhesive sheet as described in the first aspect and the copper clad laminate as described in the third aspect.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] (1) In the adhesive sheet provided by the present invention, through the design of the first resin composition and the second resin composition and their synergy, the adhesive sheet achieves significant improvement in flame retardancy, heat resistance and processability, which solves the problem that the CEM-1 copper clad laminate has poor heat resistance and punching performance due to the addition of a large amount of flame retardant in the prior art. The copper clad laminate containing the adhesive sheet has excellent flame retardancy as well as significantly improved heat resistance and punching performance, low water absorption, good resistance to damp heat and excellent comprehensive performance.

[0068] (2) Through the design and further optimization of the first resin composition and the second resin composition in the adhesive sheet, the present invention enables the CEM-1 copper clad laminate containing it to have a flame retardancy of UL-94V-0, thermal stress (288℃, floating solder) ≥173s, thermal stress (288℃, immersion solder) ≥115s, T260 ≥95min, and punching processability of level 5. It has excellent flame retardancy, heat resistance and punching processability, and low water absorption, which fully meets the application requirements of high-performance circuit boards. Detailed Implementation

[0069] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0070] In the following specific embodiments of the present invention, the materials involved are as follows:

[0071] (1) Phenolic resin

[0072] The water-based phenolic resin, brand name SQ-9322, with a number average molecular weight of 300-500 g / mol, was purchased from Jinan Shengquan Group Co., Ltd.

[0073] (2) Nitrogen-containing flame retardants

[0074] B1: Melamine-formaldehyde resin, JX-2533, purchased from Dalian Jinxin Chemical Co., Ltd.

[0075] B2: Vinyl isocyanate, JS-5634, purchased from Hubei Jusheng Technology Co., Ltd.;

[0076] B3: Methyl etherified melamine resin, CYMEL 303LF, purchased from Foshan Weng Kai'er.

[0077] (3) Phosphorus-containing flame retardants

[0078] C1: Phenoxycyclotriphosphazene, SPB-100, purchased from Hubei Yuancheng Saichuang Technology Co., Ltd.;

[0079] C2: Hexa-p-aldehyde phenoxycyclotriphosphazene, TC-130, purchased from Jiangsu Tiancheng Chemical Co., Ltd.;

[0080] C3: Hexa(4-DOPOhydroxymethylphenoxy)cyclotriphosphazene, GC-PNP, purchased from Wuhan Haishan Technology Co., Ltd.

[0081] (4) Biphenyl type epoxy resin

[0082] D1: Epoxy equivalent is 171g / eq, grade is YL6121L, purchased from Shanghai Zhongsi Industrial Co., Ltd.;

[0083] D2: Epoxy equivalent is 190g / eq, grade is JX9000H, purchased from Hunan Jiashengde Materials Co., Ltd.;

[0084] D3: Epoxy equivalent of 230g / eq, grade SQXN-321, manufactured by Jinan Shengquan Group Co., Ltd.

[0085] D4: Epoxy equivalent of 300g / eq, grade BPNE3501, purchased from Hunan Jiashengde Materials Co., Ltd.

[0086] (5) Other epoxy resins

[0087] Bisphenol A epoxy resin, epoxy equivalent of 180 g / eq, grade GELR127, was purchased from Hongchang Electronic Materials Co., Ltd.

[0088] (5) Curing agent

[0089] Linear phenolic resin, ZP150, purchased from Zhangjiagang Yarui Chemical Co., Ltd.

[0090] (6) Halogenated flame retardants

[0091] F1: Decabromodiphenyl ethane, ZK-500, purchased from Chengdu Jiaye Biotechnology Co., Ltd.;

[0092] F2: Tetrabromobisphenol A, BC-52, purchased from Laizhou Dilong Chemical Co., Ltd.;

[0093] F3: Tribromophenol, ZX-45, purchased from Qianyan Chemical Technology (Wuhan) Co., Ltd.;

[0094] (7) Antimony-containing flame retardants

[0095] G1: Antimony pentoxide, SD-405, purchased from Wuhan Xinghe Chemical Co., Ltd.;

[0096] G2: Antimony pentoxide, ZP530, purchased from Zhangjiagang Yarui Chemical Co., Ltd.;

[0097] G3: Sodium antimonate, YC-278, purchased from Hubei Yongcheng Industrial Co., Ltd.

[0098] (8) Curing accelerator

[0099] 2-Methylimidazole, TD-230, was purchased from Hubei Xingyinhe Chemical Co., Ltd.

[0100] Example 1

[0101] An adhesive sheet includes a reinforcing material and a resin material attached to the reinforcing material after two impregnation-drying processes; the resin material comprises a combination of a first resin composition attached after a first impregnation-drying and a second resin composition attached after a second impregnation-drying; the first resin composition comprises, by weight, 100 parts of waterborne phenolic resin, 8 parts of nitrogen-containing flame retardant B1, and 15 parts of phosphorus-containing flame retardant C1; the second resin composition comprises, by weight, 100 parts of biphenyl-type epoxy resin D1, 50 parts of linear phenolic resin, 6 parts of halogenated flame retardant F1, 3 parts of antimony-containing flame retardant G1, and 0.1 parts of curing accelerator.

[0102] The adhesive sheet is prepared as follows:

[0103] (1) According to the above formula, add water-based phenolic resin, nitrogen-containing flame retardant, phosphorus-containing flame retardant and water into a container, stir to mix evenly, and finally adjust the solid content with water to 20% to obtain the first adhesive solution; use wood pulp fiber paper to impregnate the first adhesive solution for 10s, and then dry at 220℃ for 4min to obtain the prepreg.

[0104] (2) According to the above formula, add biphenyl epoxy resin, linear phenolic resin, halogenated flame retardant, antimony-containing flame retardant, curing accelerator and acetone into a container, stir to mix evenly, and finally adjust the solid content to 60% with acetone to obtain the second adhesive liquid; use the prepreg obtained in step (1) to impregnate the second adhesive liquid for 15s, and then dry at 180℃ for 3min to obtain the adhesive sheet.

[0105] A CEM-1 copper clad laminate includes a laminate and copper foil disposed on both sides of the laminate. The laminate includes a face sheet and a core material, wherein the core material is an adhesive sheet provided in this embodiment. The specific preparation method is as follows: five adhesive sheets provided in this embodiment are stacked to form the core material. A face sheet (glass fiber cloth-based prepreg) is placed on both sides of the core material stack. Copper foil is then covered on both sides of the outer side of the face sheet. The core material is then hot-pressed at 160°C and 5MPa for 120 minutes in a press to produce a 1.6mm CEM-1 copper clad laminate.

[0106] Examples 2-12, Comparative Examples 1-3

[0107] An adhesive sheet differs from Example 1 only in that the components of the first resin composition and / or the second resin composition are different, and the specific formulations are shown in Tables 1 and 2; the amount of each component in Tables 1 and 2 is in "parts"; the preparation method of the adhesive sheet is the same as that of Example 1.

[0108] The bonding sheets provided in Examples 2-12 and Comparative Examples 1-3 were prepared into CEM-1 copper-clad laminates using the method described in Example 1, and the following physical property evaluation tests were performed:

[0109] (1) Thermal stress: The thermal stress test method specified in GB / T 4722-2017 was used to determine the floating weld and dip weld under 288℃ conditions respectively;

[0110] (2) Punching performance: The punching performance shall be determined in accordance with the punching performance test method specified in GB / T 4722-2017; and tested in accordance with UL-94 standard.

[0111] (3) Flame retardancy: Tested according to UL94 “50W (20mm) vertical burning test: V-0, V-1 and V-2” test method;

[0112] (4) Thermal delamination time T260: refers to the time before the delamination phenomenon occurs when the board is at a set temperature of 260℃ due to heat.

[0113] (5) Water absorption rate: determined according to IPC-TM-6502.6.2.1 method.

[0114] The test results are shown in Tables 1 and 2 below.

[0115] Table 1

[0116]

[0117]

[0118] Table 2

[0119]

[0120]

[0121]

[0122] Comparative Example 5

[0123] An adhesive sheet differs from Example 1 only in that the first resin composition comprises, by weight, 100 parts of waterborne phenolic resin; and the second resin composition comprises, by weight, 100 parts of biphenyl-type epoxy resin D1, 50 parts of linear phenolic resin, 6 parts of halogenated flame retardant F1, 3 parts of antimony-containing flame retardant G1, 0.1 parts of curing accelerator, 8 parts of nitrogen-containing flame retardant B1, and 15 parts of phosphorus-containing flame retardant C1.

[0124] The adhesive sheet is prepared as follows:

[0125] (1) Add water-based phenolic resin and water to a container according to the above formula amount, stir to mix evenly, and finally adjust the solid content to 20% with water to obtain the first adhesive solution; use wood pulp fiber paper to impregnate the first adhesive solution for 10s, and then dry at 220℃ for 4min to obtain the prepreg.

[0126] (2) According to the aforementioned formula, add biphenyl-type epoxy resin, linear phenolic resin, halogenated flame retardant, antimony-containing flame retardant, curing accelerator, nitrogen-containing flame retardant, phosphorus-containing flame retardant and acetone into a container, stir to mix evenly, and finally adjust the solid content to 60% with acetone to obtain the second adhesive liquid; use the prepreg obtained in step (1) to impregnate the second adhesive liquid for 16s, and then dry at 180℃ for 3min to obtain the adhesive sheet.

[0127] Comparative Example 6

[0128] An adhesive sheet differs from Example 1 only in that the first resin composition comprises, by weight, 100 parts of waterborne phenolic resin, 6 parts of halogenated flame retardant F1, and 3 parts of antimony-containing flame retardant G1; and the second resin composition comprises, by weight, 100 parts of biphenyl-type epoxy resin D1, 50 parts of linear phenolic resin, 0.1 parts of curing accelerator, 8 parts of nitrogen-containing flame retardant B1, and 15 parts of phosphorus-containing flame retardant C1.

[0129] The adhesive sheet is prepared as follows:

[0130] (1) According to the above formula, add water-based phenolic resin, halogenated flame retardant, antimony-containing flame retardant and water into a container, stir to mix evenly, and finally adjust the solid content with water to 20% to obtain the first adhesive solution; use wood pulp fiber paper to impregnate the first adhesive solution for 15s, and then dry at 220℃ for 4min to obtain the prepreg.

[0131] (2) According to the above formula, add biphenyl epoxy resin, linear phenolic resin, curing accelerator, nitrogen-containing flame retardant, phosphorus-containing flame retardant and acetone into a container, stir to mix evenly, and finally adjust the solid content to 60% with acetone to obtain the second adhesive liquid; use the prepreg obtained in step (1) to impregnate the second adhesive liquid for 12s, and then dry at 180℃ for 3min to obtain the adhesive sheet.

[0132] Comparative Example 7

[0133] An adhesive sheet differs from Example 1 only in that the first resin composition comprises, by weight, 100 parts of waterborne phenolic resin, 8 parts of nitrogen-containing flame retardant B1, 15 parts of phosphorus-containing flame retardant C1, 6 parts of halogenated flame retardant F1, and 3 parts of antimony-containing flame retardant G1; and the second resin composition comprises, by weight, 100 parts of biphenyl-type epoxy resin D1, 50 parts of linear phenolic resin, and 0.1 parts of curing accelerator.

[0134] The adhesive sheet is prepared as follows:

[0135] (1) According to the above formula, add water-based phenolic resin, nitrogen-containing flame retardant, phosphorus-containing flame retardant, halogenated flame retardant, antimony-containing flame retardant and water into a container, stir to mix evenly, and finally adjust the solid content with water to 20% to obtain the first adhesive solution; use wood pulp fiber paper to impregnate the first adhesive solution for 18s, and then dry at 220℃ for 4min to obtain the prepreg.

[0136] (2) According to the above formula, add biphenyl epoxy resin, linear phenolic resin, curing accelerator and acetone into a container, stir to mix evenly, and finally adjust the solid content to 60% with acetone to obtain the second adhesive liquid; use the prepreg obtained in step (1) to impregnate the second adhesive liquid for 12s, and then dry at 180℃ for 3min to obtain the adhesive sheet.

[0137] The bonding sheets provided in Comparative Examples 5-7 were prepared into CEM-1 copper-clad laminates using the method described in Example 1, and their performance was tested using the same method. The test results are shown in Table 3.

[0138] Table 3

[0139]

[0140] Based on the performance data in Tables 1, 2, and 3, it can be seen that the present invention, through the design and compounding of the first resin composition and the second resin composition, significantly improves the flame retardancy, heat resistance, and processability of the adhesive sheet. The CEM-1 copper clad laminate containing it has a flame retardancy rating of V-0, a punching processability rating of 5, a thermal stress (288℃, floating solder) of 173-220s, a thermal stress (288℃, immersion solder) of 115-147s, a T260 of 95-100min, and a water absorption rate of 0.07-0.10%, resulting in better overall performance.

[0141] Furthermore, analysis of Examples 1-3 and Example 10 shows that the heat resistance of Example 10 is slightly inferior to that of Examples 1-3, indicating that when the epoxy equivalent of the biphenyl-type epoxy resin in the second resin composition is 150-250 g / eq, it can enable the bonding sheet and copper-clad laminate to have better heat resistance.

[0142] Analysis of Example 1 and Comparative Examples 1-3 shows that the flame retardancy of Comparative Example 1 is significantly reduced, the heat resistance and flame retardancy of Comparative Example 2 are both reduced, and the heat resistance and perforation properties of Comparative Example 3 are drastically reduced. This indicates that in the second resin composition of the present invention, when using biphenyl epoxy resin, the amount of halogenated flame retardant and antimony-containing flame retardant is significantly reduced, enabling the copper-clad laminate to simultaneously possess excellent heat resistance, flame retardancy and perforation properties.

[0143] Analysis of Examples 1-3, Example 11, and Comparative Example 4 shows that the flame retardancy of Examples 11 and Comparative Example 4 is reduced. This indicates that when the amount of nitrogen-containing flame retardant in the first resin composition of the present invention is 5-10 parts and the amount of phosphorus-containing flame retardant is 10-20 parts, nitrogen and phosphorus synergistically retard the flame and work together with the second resin composition to enable the copper-clad laminate to have excellent heat resistance and flame retardancy.

[0144] Analysis of Examples 6-9 and Example 12 shows that the flame retardancy of Example 12 is reduced, indicating that when the halogenated flame retardant in the second resin composition of the present invention is 2-10 parts and the antimony-containing flame retardant is 1-5 parts, the copper-clad laminate can have excellent heat resistance and flame retardancy.

[0145] Analysis of Example 1 and Comparative Examples 5-7 shows that the heat resistance, flame retardancy, and perforation properties of Comparative Examples 5-7 decreased to varying degrees, while the water absorption rate increased. This indicates that the present invention uses a first resin combined with a nitrogen-containing flame retardant and a phosphorus-containing flame retardant, and a second resin combined with a halogenated flame retardant and an antimony-containing flame retardant, respectively, and impregnates the copper-clad laminate with adhesive solution once and twice in a specific order, which enables the copper-clad laminate to simultaneously possess excellent heat resistance, flame retardancy, perforation properties, and low water absorption rate.

[0146] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the adhesive sheet and its preparation method, as well as the copper-clad laminate containing it. However, the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An adhesive sheet, characterized in that, The adhesive sheet includes a reinforcing material and a resin material attached to the reinforcing material after two impregnations and drying. The resin material comprises a combination of a first resin composition that adheres after a first impregnation and drying and a second resin composition that adheres after a second impregnation and drying; The first resin composition comprises, by weight, the following components: 100 parts of phenolic resin 5-10 parts of nitrogen-containing flame retardant 10-20 parts of phosphorus-containing flame retardant; The phenolic resin is an aqueous phenolic resin; The number-average molecular weight of the phenolic resin is 100-2000 g / mol; The second resin composition comprises, by weight, the following components: 100 parts of biphenyl-type epoxy resin 20-80 parts of curing agent 2-10 parts of halogenated flame retardant 1-5 parts antimony flame retardant; The epoxy equivalent of the biphenyl-type epoxy resin is 120-270 g / eq.

2. The adhesive sheet according to claim 1, characterized in that, The nitrogen-containing flame retardant includes any one or a combination of at least two of the following: vinyl isocyanate, melamine-glyoxal resin, melamine-formaldehyde resin, methylated melamine resin, butylated melamine resin, triisocyanurate-modified melamine resin, and organosilicon-modified melamine resin.

3. The adhesive sheet according to claim 1, characterized in that, The phosphorus-containing flame retardant includes any one or a combination of at least two of the following: alkoxycyclotriphosphazene, phenoxycyclotriphosphazene, hexa-p-aldehyde phenoxycyclotriphosphazene, hexa(4-DOPO hydroxymethylphenoxy)cyclotriphosphazene, (2-allylphenoxy)pentaphenoxycyclotriphosphazene, and hexa(4-nitrophenoxy)cyclotriphosphazene.

4. The adhesive sheet according to claim 1, characterized in that, The epoxy equivalent of the biphenyl-type epoxy resin is 150-250 g / eq.

5. The adhesive sheet according to claim 1, characterized in that, The curing agent includes any one or a combination of at least two of the following: vegetable oil modified phenolic resin, linear phenolic resin, and thermosetting phenolic resin.

6. The adhesive sheet according to claim 1, characterized in that, The halogenated flame retardant includes any one or a combination of at least two of tetrabromobisphenol A, tribromophenol, decabromodiphenyl ethane, and octabromodiphenyl ethane.

7. The adhesive sheet according to claim 1, characterized in that, The antimony-containing flame retardant includes any one or a combination of at least two of antimony oxide, antimony halide, and antimonates.

8. The adhesive sheet according to claim 1, characterized in that, The second resin composition also includes a curing accelerator.

9. The adhesive sheet according to claim 8, characterized in that, Based on 100 parts by weight of the biphenyl-type epoxy resin, the curing accelerator has a mass fraction of ≤1 part.

10. The adhesive sheet according to claim 8, characterized in that, The curing accelerator includes any one or a combination of at least two of the following: tertiary amines, quaternary ammonium salts, imidazole compounds, organometallic complexes, and tertiary phosphine.

11. The adhesive sheet according to claim 1, characterized in that, The reinforcing material includes at least one of wood pulp paper, cotton pulp paper, or nonwoven fabric.

12. A method for preparing an adhesive sheet as described in any one of claims 1-11, characterized in that, The preparation method includes: The reinforcing material is first impregnated in a resin solution of a first resin composition, and then first dried to obtain a prepreg. The prepreg is placed in a resin solution of a second resin composition for a second impregnation, followed by a second drying, to obtain the adhesive sheet.

13. A copper-clad laminate, characterized in that, The copper-clad laminate includes copper foil and at least one adhesive sheet as described in any one of claims 1-11.

14. The copper-clad laminate according to claim 13, characterized in that, The copper clad laminate is a CEM-1 copper clad laminate, which includes a laminate and copper foil disposed on one or both sides of the laminate; the laminate includes a face material and a core material, and the core material includes at least one adhesive sheet as described in any one of claims 1-11.

15. A printed circuit board, characterized in that, The printed circuit board includes at least one of the bonding sheet as described in any one of claims 1-11 and the copper-clad laminate as described in claim 13 or 14.

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