A polyimide composite-based back adhesive copper foil and a preparation method thereof

Abstract

The application discloses a kind of based on polyimide composite back glue copper foil and its preparation method, it is related to back glue copper foil technical field.The application uses p-phenylenediamine, 2,2'-bis (trifluoromethyl) -4,4' diamino diphenyl, 1,3-bis (4-aminophenoxy) benzene, biphenyl tetraacid anhydride preparation polyimide resin, the introduction of fluoromethyl group improves the dielectric property of polyimide matrix;Meanwhile, epoxy resin blending is also added, the high reactivity of epoxy group is used, the interfacial adhesion between polyimide layer and copper foil is improved.In the adhesive modified epoxy resin, silicon sol coated nano cerium-boron nitride composite is added, the dielectric loss of epoxy resin is reduced, while the compatibility with polyimide resin is excellent, the interlayer adhesion is enhanced, and the peel strength and bending resistance of back glue copper foil are improved.

Description

Technical Field

[0001] This invention relates to the field of adhesive-backed copper foil technology, specifically to an adhesive-backed copper foil based on polyimide composite material and its preparation method. Background Technology

[0002] Adhesive-backed copper foil is a key material used in the manufacture of flexible circuits. For flexible circuit boards, high flexural strength is a pressing issue, involving the matching of copper foil, adhesive, and polyimide layer. With the increasing prevalence of displays in foldable phones, computers, and other electronic products, a core requirement is excellent dynamic flexural strength, ensuring the screen can withstand long-term bending without damage. Optimized rolled copper foil flexible circuit boards can typically pass tens to hundreds of thousands of bending tests. Polyimide possesses a variety of superior properties, including heat resistance, chemical resistance, excellent mechanical properties, superior electrical insulation, and good dimensional stability. These combined advantages make polyimide an irreplaceable key material in many cutting-edge fields. However, further improvements are needed to enhance the flexural strength of adhesive-backed copper foil to meet its applications in aerospace, microelectronics and semiconductors, high-end robotics, sensor substrates, and other precision instruments.

[0003] To address the aforementioned issues and further improve the bending resistance of adhesive-backed copper foil, this application provides an adhesive-backed copper foil based on polyimide composite material and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a solution to the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing adhesive-backed copper foil based on polyimide composite material includes the following steps: Step 1: Take polyvinylpyrrolidone and anhydrous ethanol, stir evenly, add nano-cerium-boron nitride composite, deionized water and ammonia monohydrate, stir evenly, add modified silica sol, stir evenly, add silane coupling agent KH560, react for 2-3 hours, filter, wash and dry to obtain silica sol-coated nano-cerium-boron nitride composite. Step 2: Coat the nano-cerium-boron nitride composite with polyimide resin, epoxy resin, and silica sol, and stir until homogeneous to obtain the polyimide composite material; Step 3: Coat one side of the copper foil with polyimide composite material and bake to obtain a single-sided panel; coat the side of the single-sided panel with modified epoxy resin and bake to obtain an adhesive-backed copper foil.

[0006] A more optimized method for preparing the modified silica sol is as follows: tetraethyl orthosilicate is added to a mixture of anhydrous ethanol, deionized water, and silane coupling agent KH560, stirred until homogeneous, and hydrochloric acid is added to adjust the pH to 2-3. The mixture is stirred until homogeneous at 60-65°C and cooled to room temperature to obtain silica sol. Chitosan powder is added to an acetic acid solution and stirred until homogeneous to obtain a chitosan solution. Silica sol is added, stirred until homogeneous, and the mixture is heated to 45-50°C and reacted for 4-5 hours to obtain the modified silica sol.

[0007] A more optimized method for preparing the nano-cerium-boron nitride composite includes the following steps: S1: Add boric acid and melamine to deionized water, heat in a water bath to 88-92℃, stir evenly, then react at 80℃ for 2-3 hours, cool, filter and dry to obtain the precursor; calcine the precursor under a nitrogen atmosphere to obtain porous boron nitride. S2: Porous boron nitride and cerium chloride aqueous solution are stirred and heated to 65-67℃, then sodium carbonate aqueous solution is added dropwise, and the mixture is kept at this temperature and stirred for 50-70 min. After centrifugation, drying and calcination, nano-cerium-boron nitride composite is obtained.

[0008] In a more optimized manner, the mass ratio of the polyimide resin, epoxy resin, and silica sol-coated nano-cerium-boron nitride composite is (89-92):(5-6):(5-6).

[0009] In a more optimized manner, the preparation method of the modified epoxy resin includes the following steps: A: Take nano-alumina and anhydrous ethanol, ultrasonically disperse for 1-2 hours, add polyvinylpyrrolidone, ultrasonically disperse, wash, filter, add anhydrous ethanol, disperse to obtain alumina dispersion; take anhydrous ethanol, ammonia, and deionized water, stir evenly to obtain solution A; take anhydrous ethanol and tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 10-15 minutes, add solution B dropwise, stir for 11-13 hours, centrifuge, wash, dry, calcine, cool to obtain alumina-silica particles; B: Add alumina-silica particles to epoxy resin and stir for 1-2 hours; add curing agent and stir for 1-2 hours to obtain modified epoxy resin.

[0010] More preferably, the polyimide resin is synthesized from an acid dianhydride compound and a diamine compound, wherein the acid dianhydride compound is any one or more of the following: pyromellitic dianhydride, biphenyl dianhydride, 3,3',4,4'-diphenyl ether dianhydride, 3,3',4,4'-benzophenone dianhydride, bisphenol A type diether dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride, and 4,4-(p-phenylene dioxy)diphthalic dianhydride.

[0011] More preferably, the diamine compound is: p-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenylhexafluoropropane, 4,4-bis(4-aminophenoxy)biphenyl, 4,4'-diaminobenzoylaniline, 4-aminophenyl-4-aminobenzylaniline. The ester, bis(4-aminophenyl) terephthalate, bis(4-(4-aminophenoxy)phenyl) sulfone, bis(4-amino-3-carboxyphenyl)methane, 4,4'-diaminobenzophenone, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 9,9-bis(4-aminophenyl)fluorene, 3,3'-dimethyl-4,4'-diaminobiphenyl, and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, are all one or more of these compounds.

[0012] In a more optimized manner, the preparation method of the polyimide resin is as follows: take p-phenylenediamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1,3-bis(4-aminophenoxy)benzene, add N,N-dimethylacetamide, stir evenly, add biphenyl tetracarboxylic anhydride, stir for 3-4 hours, and obtain polyimide resin.

[0013] More optimally, in step two, the epoxy resin is any one or more of the following: aromatic glycidyl ether epoxy resin, aromatic glycidyl amine epoxy resin, alicyclic glycidyl ester epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and fluorene epoxy resin.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This application adds a silica sol-coated nano-cerium-boron nitride composite to a polyimide composite material, which improves the peel strength and folding strength between the polyimide composite material and the copper foil of the adhesive-backed copper foil. First, a porous boron nitride is prepared, and then cerium doping is performed on it to enhance the chemical bonding with the resin, thereby improving the folding strength, aging resistance and dielectric properties of the adhesive-backed copper foil.

[0015] 2. Coating the surface of the nano-cerium-boron nitride composite with amino-containing silica sol solves the agglomeration problem of the nano-cerium-boron nitride composite, improves its dispersibility in the polyimide composite material, and enhances its mechanical properties. On the other hand, the hydroxyl and amino groups introduced by chitosan form hydrogen bonds with the epoxy and carboxyl groups of the resin, further improving the interfacial bonding force of the adhesive copper foil.

[0016] 3. In the embodiments of this application, p-phenylenediamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 1,3-bis(4-aminophenoxy)benzene, and biphenyl tetracarboxylic anhydride are used to prepare polyimide resin. The introduction of fluoromethyl groups improves the dielectric properties of the polyimide matrix. At the same time, epoxy resin is also added for blending. The high reactivity of epoxy groups is used to improve the interfacial adhesion between the polyimide layer and the copper foil.

[0017] 4. The addition of silica sol-coated nano-cerium-boron nitride composite to the adhesive-modified epoxy resin reduces the dielectric loss of the epoxy resin, while exhibiting excellent compatibility with polyimide resin, enhancing interlayer bonding, and improving the peel strength and bending resistance of the adhesive-backed copper foil. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an adhesive-backed copper foil based on polyimide composite material according to Embodiment 1 of the present invention.

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The sources and types of substances involved in this application are not particularly limited, and exemplary ones include: nano alumina: 1-50nm; curing agent: methyltetrahydrophthalic anhydride; epoxy resin: type: E51.

[0021] Example 1: A method for preparing adhesive-backed copper foil based on polyimide composite material, comprising the following steps: Step 1: Preparation of adhesive-backed copper foil: A polyimide resin, epoxy resin, and silica sol-coated nano-cerium-boron nitride composite were weighed in a mass ratio of 90:5.5:5.5 and stirred evenly to obtain a polyimide composite material. Polyimide composite material was coated on one side of copper foil with a coating thickness of 6 μm. After coating, the foil was placed in an oven and baked at 220℃ for 3 min to obtain a single-sided panel. Modified epoxy resin was coated onto the polyimide composite material side of a single-sided panel with a coating thickness of 10 μm. After coating, the panel was placed in an oven and baked at 160°C for 3 minutes to obtain an adhesive-backed copper foil. Step 2: Preparation of modified epoxy resin: Take 1g of nano-alumina and 100mL of anhydrous ethanol, sonicate for 1.5h, add 3g of polyvinylpyrrolidone, sonicate again, wash, filter, add 100mL of anhydrous ethanol, disperse again to obtain alumina dispersion; take 35mL of anhydrous ethanol, 11.25mL of ammonia, and 3.5mL of deionized water, stir evenly to obtain solution A; take 50mL of anhydrous ethanol and 1.25mL of tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 12min, add solution B dropwise, stir for 12h, centrifuge, wash, dry, then calcine at 600℃ for 4h, cool to obtain alumina-silica particles; Add 1g of alumina-silica particles to 100g of epoxy resin and stir in a 50℃ constant temperature water bath for 1.5h; add 33g of curing agent and stir for 1.5h to obtain modified epoxy resin. Step 3: Preparation of polyimide resin: Take 4.6g of p-phenylenediamine, 3.1g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1.3g of 1,3-bis(4-aminophenoxy)benzene, add 170g of N,N-dimethylacetamide, stir evenly, add 17.2g of biphenyl tetracarboxylic anhydride, stir for 3.5h to obtain polyimide resin; Step 4: Preparation of porous boron nitride: 25g of boric acid and 25.5g of melamine were added to 500mL of deionized water, heated in a water bath to 90℃, stirred evenly, and then reacted at 80℃ for 2.5h. The mixture was then cooled to 28℃, filtered, and dried to obtain the precursor. The precursor was calcined at 980℃ for 3.5h under a nitrogen atmosphere to obtain porous boron nitride. 5g of porous boron nitride, 100g of 0.15mol / L cerium chloride aqueous solution were stirred and heated to 65℃, and then 100g of 0.225mol / L sodium carbonate aqueous solution was added dropwise. The mixture was kept warm and stirred for 60min, centrifuged, dried, and calcined at 850℃ for 3h to obtain nano-cerium-boron nitride composite. Step 5: Preparation of modified silica sol: 10g of tetraethyl orthosilicate was added to a mixture of 17.7g of anhydrous ethanol, 4.6g of deionized water and 8g of silane coupling agent KH560, stirred evenly, and hydrochloric acid was added to adjust the pH to 3. The mixture was stirred evenly at 62℃ and cooled to room temperature to obtain silica sol. 1g of chitosan powder was added to 30mL of 2% acetic acid solution and stirred until homogeneous to obtain a chitosan solution; silica sol was added, stirred until homogeneous, and the mixture was heated to 47℃ and reacted for 4.5h to obtain a modified silica sol. Step Six: Preparation of silica sol-coated nano-cerium-boron nitride composite: Take 0.5g of polyvinylpyrrolidone and 100mL of anhydrous ethanol, stir well, add 5g of nano-cerium-boron nitride composite, 1mL of deionized water and 2mL of ammonia monohydrate, stir for 3.5min, add 1.5mL of modified silica sol, stir for 3.5h, add 0.2mL of silane coupling agent KH560, react for 2.5h, filter, wash and dry to obtain silica sol-coated nano-cerium-boron nitride composite.

[0022] Example 2: A method for preparing adhesive-backed copper foil based on polyimide composite material, comprising the following steps: Step 1: Preparation of adhesive-backed copper foil: A polyimide resin, epoxy resin, and silica sol-coated nano-cerium-boron nitride composite were weighed in a mass ratio of 89:6:5 and stirred evenly to obtain a polyimide composite material. Polyimide composite material was coated on one side of copper foil with a coating thickness of 6 μm. After coating, the foil was placed in an oven and baked at 220℃ for 3 min to obtain a single-sided panel. Modified epoxy resin was coated onto the polyimide composite material side of a single-sided panel with a coating thickness of 10 μm. After coating, the panel was placed in an oven and baked at 160°C for 3 minutes to obtain an adhesive-backed copper foil. Step 2: Preparation of modified epoxy resin: Take 1g of nano-alumina and 100mL of anhydrous ethanol, sonicate for 1.5h, add 3g of polyvinylpyrrolidone, sonicate again, wash, filter, add 100mL of anhydrous ethanol, disperse to obtain alumina dispersion; take 35mL of anhydrous ethanol, 11.25mL of ammonia, and 3.5mL of deionized water, stir evenly to obtain solution A; take 50mL of anhydrous ethanol and 1.25mL of tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 10min, add solution B dropwise, stir for 11h, centrifuge, wash, dry, then calcine at 600℃ for 4h, cool to obtain alumina-silica particles; Add 1g of alumina-silica particles to 100g of epoxy resin and stir in a 50℃ constant temperature water bath for 1h; add 33g of curing agent and stir for 1h to obtain modified epoxy resin. Step 3: Preparation of polyimide resin: Take 4.6g of p-phenylenediamine, 3.1g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1.3g of 1,3-bis(4-aminophenoxy)benzene, add 170g of N,N-dimethylacetamide, stir until uniform, add 17.2g of biphenyl tetracarboxylic anhydride, stir for 3h to obtain polyimide resin; Step 4: Preparation of porous boron nitride: 25g of boric acid and 25.5g of melamine were added to 500mL of deionized water, heated in a water bath to 88℃, stirred evenly, and then reacted at 80℃ for 2h. The mixture was then cooled to 25℃, filtered, and dried to obtain the precursor. The precursor was calcined at 950℃ for 3h under a nitrogen atmosphere to obtain porous boron nitride. 5g of porous boron nitride, 100g of 0.15mol / L cerium chloride aqueous solution were stirred and heated to 65℃, and then 100g of 0.225mol / L sodium carbonate aqueous solution was added dropwise. The mixture was kept warm and stirred for 50min, centrifuged, dried, and calcined at 850℃ for 3h to obtain nano-cerium-boron nitride composite. Step 5: Preparation of modified silica sol: 10g of tetraethyl orthosilicate was added to a mixture of 17.7g of anhydrous ethanol, 4.6g of deionized water and 8g of silane coupling agent KH560, stirred evenly, and hydrochloric acid was added to adjust the pH to 2. The mixture was stirred evenly at 60℃ and cooled to room temperature to obtain silica sol. 1g of chitosan powder was added to 30mL of 2% acetic acid solution and stirred until homogeneous to obtain a chitosan solution; silica sol was added, stirred until homogeneous, and the mixture was heated to 45℃ and reacted for 4h to obtain a modified silica sol. Step Six: Preparation of silica sol-coated nano-cerium-boron nitride composite: Take 0.5g of polyvinylpyrrolidone and 100mL of anhydrous ethanol, stir well, add 5g of nano-cerium-boron nitride composite, 1mL of deionized water and 2mL of ammonia monohydrate, stir for 3min, add 1.5mL of modified silica sol, stir for 3h, add 0.2mL of silane coupling agent KH560, react for 2h, filter, wash and dry to obtain silica sol-coated nano-cerium-boron nitride composite.

[0023] Example 3: A method for preparing adhesive-backed copper foil based on polyimide composite material, comprising the following steps: Step 1: Preparation of adhesive-backed copper foil: A polyimide resin, epoxy resin, and silica sol-coated nano-cerium-boron nitride composite were weighed in a mass ratio of 92:6:6 and stirred evenly to obtain a polyimide composite material. Polyimide composite material was coated on one side of copper foil with a coating thickness of 6 μm. After coating, the foil was placed in an oven and baked at 220℃ for 3 min to obtain a single-sided panel. Modified epoxy resin was coated onto the polyimide composite material side of a single-sided panel with a coating thickness of 10 μm. After coating, the panel was placed in an oven and baked at 160°C for 3 minutes to obtain an adhesive-backed copper foil. Step 2: Preparation of modified epoxy resin: Take 1g of nano-alumina and 100mL of anhydrous ethanol, sonicate for 2h, add 3g of polyvinylpyrrolidone, sonicate again, wash, filter, add 100mL of anhydrous ethanol, disperse again to obtain alumina dispersion; take 35mL of anhydrous ethanol, 11.25mL of ammonia, and 3.5mL of deionized water, stir evenly to obtain solution A; take 50mL of anhydrous ethanol and 1.25mL of tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 15min, add solution B dropwise, stir for 13h, centrifuge, wash, dry, then calcine at 600℃ for 4h, cool to obtain alumina-silica particles; Add 1g of alumina-silica particles to 100g of epoxy resin and stir in a 50℃ constant temperature water bath for 2h; add 33g of curing agent and stir for 2h to obtain modified epoxy resin. Step 3: Preparation of polyimide resin: Take 4.6g of p-phenylenediamine, 3.1g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1.3g of 1,3-bis(4-aminophenoxy)benzene, add 170g of N,N-dimethylacetamide, stir evenly, add 17.2g of biphenyl tetracarboxylic anhydride, stir for 4h to obtain polyimide resin; Step 4: Preparation of porous boron nitride: 25g of boric acid and 25.5g of melamine were added to 500mL of deionized water, heated to 92℃ in a water bath, stirred evenly, and then reacted at 80℃ for 3h. The mixture was then cooled to 30℃, filtered, and dried to obtain the precursor. The precursor was calcined at 1000℃ for 4h under a nitrogen atmosphere to obtain porous boron nitride. 5g of porous boron nitride and 100g of 0.15mol / L cerium chloride aqueous solution were stirred and heated to 65℃, and then 100g of 0.225mol / L sodium carbonate aqueous solution was added dropwise. The mixture was kept warm and stirred for 70min, centrifuged, dried, and calcined at 850℃ for 3.5h to obtain nano-cerium-boron nitride composite. Step 5: Preparation of modified silica sol: 10g of tetraethyl orthosilicate was added to a mixture of 17.7g of anhydrous ethanol, 4.6g of deionized water and 8g of silane coupling agent KH560, stirred evenly, and hydrochloric acid was added to adjust the pH to 3. The mixture was stirred evenly at 65℃ and cooled to room temperature to obtain silica sol. 1g of chitosan powder was added to 30mL of 2% acetic acid solution and stirred until homogeneous to obtain a chitosan solution; silica sol was added, stirred until homogeneous, and heated to 50℃ for 5h to obtain a modified silica sol. Step Six: Preparation of silica sol-coated nano-cerium-boron nitride composite: Take 0.5g of polyvinylpyrrolidone and 100mL of anhydrous ethanol, stir well, add 5g of nano-cerium-boron nitride composite, 1mL of deionized water and 2mL of ammonia monohydrate, stir for 4min, add 1.5mL of modified silica sol, stir for 4h, add 0.2mL of silane coupling agent KH560, react for 3h, filter, wash and dry to obtain silica sol-coated nano-cerium-boron nitride composite.

[0024] Comparative Example 1: No nano-cerium added, otherwise the same as Example 1: Step 1: Preparation of adhesive-backed copper foil: A polyimide resin, epoxy resin, and silica sol-coated boron nitride composite were weighed in a mass ratio of 90:5.5:5.5 and stirred evenly to obtain a polyimide composite material. Polyimide composite material was coated on one side of copper foil with a coating thickness of 6 μm. After coating, the foil was placed in an oven and baked at 220℃ for 3 min to obtain a single-sided panel. Modified epoxy resin was coated onto the polyimide composite material side of a single-sided panel with a coating thickness of 10 μm. After coating, the panel was placed in an oven and baked at 160°C for 3 minutes to obtain an adhesive-backed copper foil. Step 2: Preparation of modified epoxy resin: Take 1g of nano-alumina and 100mL of anhydrous ethanol, sonicate for 1.5h, add 3g of polyvinylpyrrolidone, sonicate again, wash, filter, add 100mL of anhydrous ethanol, disperse again to obtain alumina dispersion; take 35mL of anhydrous ethanol, 11.25mL of ammonia, and 3.5mL of deionized water, stir evenly to obtain solution A; take 50mL of anhydrous ethanol and 1.25mL of tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 12min, add solution B dropwise, stir for 12h, centrifuge, wash, dry, then calcine at 600℃ for 4h, cool to obtain alumina-silica particles; Add 1g of alumina-silica particles to 100g of epoxy resin and stir in a 50℃ constant temperature water bath for 1.5h; add 33g of curing agent and stir for 1.5h to obtain modified epoxy resin. Step 3: Preparation of polyimide resin: Take 4.6g of p-phenylenediamine, 3.1g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1.3g of 1,3-bis(4-aminophenoxy)benzene, add 170g of N,N-dimethylacetamide, stir evenly, add 17.2g of biphenyl tetracarboxylic anhydride, stir for 3.5h to obtain polyimide resin; Step 4: Preparation of porous boron nitride: 25g of boric acid and 25.5g of melamine were added to 500mL of deionized water, heated in a water bath to 90℃, stirred evenly, and then reacted at 80℃ for 2.5h. The mixture was then cooled to 28℃, filtered, and dried to obtain the precursor. The precursor was calcined at 980℃ for 3.5h under a nitrogen atmosphere to obtain porous boron nitride. Step 5: Preparation of modified silica sol: 10g of tetraethyl orthosilicate was added to a mixture of 17.7g of anhydrous ethanol, 4.6g of deionized water and 8g of silane coupling agent KH560, stirred evenly, and hydrochloric acid was added to adjust the pH to 3. The mixture was stirred evenly at 62℃ and cooled to room temperature to obtain silica sol. 1g of chitosan powder was added to 30mL of 2% acetic acid solution and stirred until homogeneous to obtain a chitosan solution; silica sol was added, stirred until homogeneous, and the mixture was heated to 47℃ and reacted for 4.5h to obtain a modified silica sol. Step Six: Preparation of the silica sol-coated boron nitride composite: Take 0.5g of polyvinylpyrrolidone and 100mL of anhydrous ethanol, stir well, add 5g of porous boron nitride, 1mL of deionized water and 2mL of ammonia monohydrate, stir for 3.5min, add 1.5mL of modified silica sol, stir for 3.5h, add 0.2mL of silane coupling agent KH560, react for 2.5h, filter, wash and dry to obtain silica sol-coated boron nitride composite.

[0025] Comparative Example 2: No silica sol coating, otherwise the same as Example 1: Step 1: Preparation of adhesive-backed copper foil: Polyimide resin, epoxy resin, and nano-cerium-boron nitride composite were weighed in a mass ratio of 90:5.5:5.5 and stirred evenly to obtain a polyimide composite material. Polyimide composite material was coated on one side of copper foil with a coating thickness of 6 μm. After coating, the foil was placed in an oven and baked at 220℃ for 3 min to obtain a single-sided panel. Modified epoxy resin was coated onto the polyimide composite material side of a single-sided panel with a coating thickness of 10 μm. After coating, the panel was placed in an oven and baked at 160°C for 3 minutes to obtain an adhesive-backed copper foil. Step 2: Preparation of modified epoxy resin: Take 1g of nano-alumina and 100mL of anhydrous ethanol, sonicate for 1.5h, add 3g of polyvinylpyrrolidone, sonicate again, wash, filter, add 100mL of anhydrous ethanol, disperse again to obtain alumina dispersion; take 35mL of anhydrous ethanol, 11.25mL of ammonia, and 3.5mL of deionized water, stir evenly to obtain solution A; take 50mL of anhydrous ethanol and 1.25mL of tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 12min, add solution B dropwise, stir for 12h, centrifuge, wash, dry, then calcine at 600℃ for 4h, cool to obtain alumina-silica particles; Add 1g of alumina-silica particles to 100g of epoxy resin and stir in a 50℃ constant temperature water bath for 1.5h; add 33g of curing agent and stir for 1.5h to obtain modified epoxy resin. Step 3: Preparation of polyimide resin: Take 4.6g of p-phenylenediamine, 3.1g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1.3g of 1,3-bis(4-aminophenoxy)benzene, add 170g of N,N-dimethylacetamide, stir evenly, add 17.2g of biphenyl tetracarboxylic anhydride, stir for 3.5h to obtain polyimide resin; Step 4: Preparation of porous boron nitride: 25g of boric acid and 25.5g of melamine were added to 500mL of deionized water, heated in a water bath to 90℃, stirred evenly, and then reacted at 80℃ for 2.5h. The mixture was then cooled to 28℃, filtered, and dried to obtain the precursor. The precursor was calcined at 980℃ for 3.5h under a nitrogen atmosphere to obtain porous boron nitride. 5g of porous boron nitride and 100g of 0.15mol / L cerium chloride aqueous solution were stirred and heated to 65℃, and then 100g of 0.225mol / L sodium carbonate aqueous solution was added dropwise. The mixture was kept warm and stirred for 60min, centrifuged, dried, and calcined at 850℃ for 3h to obtain nano-cerium-boron nitride composite.

[0026] Comparative Example 3: No modification to the silica sol, otherwise the same as Example 1: Step 1: Preparation of adhesive-backed copper foil: A polyimide resin, epoxy resin, and silica sol-coated nano-cerium-boron nitride composite were weighed in a mass ratio of 90:5.5:5.5 and stirred evenly to obtain a polyimide composite material. Polyimide composite material was coated on one side of copper foil with a coating thickness of 6 μm. After coating, the foil was placed in an oven and baked at 220℃ for 3 min to obtain a single-sided panel. Modified epoxy resin was coated onto the polyimide composite material side of a single-sided panel with a coating thickness of 10 μm. After coating, the panel was placed in an oven and baked at 160°C for 3 minutes to obtain an adhesive-backed copper foil. Step 2: Preparation of modified epoxy resin: Take 1g of nano-alumina and 100mL of anhydrous ethanol, sonicate for 1.5h, add 3g of polyvinylpyrrolidone, sonicate again, wash, filter, add 100mL of anhydrous ethanol, disperse again to obtain alumina dispersion; take 35mL of anhydrous ethanol, 11.25mL of ammonia, and 3.5mL of deionized water, stir evenly to obtain solution A; take 50mL of anhydrous ethanol and 1.25mL of tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 12min, add solution B dropwise, stir for 12h, centrifuge, wash, dry, then calcine at 600℃ for 4h, cool to obtain alumina-silica particles; Add 1g of alumina-silica particles to 100g of epoxy resin and stir in a 50℃ constant temperature water bath for 1.5h; add 33g of curing agent and stir for 1.5h to obtain modified epoxy resin. Step 3: Preparation of polyimide resin: Take 4.6g of p-phenylenediamine, 3.1g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1.3g of 1,3-bis(4-aminophenoxy)benzene, add 170g of N,N-dimethylacetamide, stir evenly, add 17.2g of biphenyl tetracarboxylic anhydride, stir for 3.5h to obtain polyimide resin; Step 4: Preparation of porous boron nitride: 25g of boric acid and 25.5g of melamine were added to 500mL of deionized water, heated in a water bath to 90℃, stirred evenly, and then reacted at 80℃ for 2.5h. The mixture was then cooled to 28℃, filtered, and dried to obtain the precursor. The precursor was calcined at 980℃ for 3.5h under a nitrogen atmosphere to obtain porous boron nitride. 5g of porous boron nitride, 100g of 0.15mol / L cerium chloride aqueous solution were stirred and heated to 65℃, and then 100g of 0.225mol / L sodium carbonate aqueous solution was added dropwise. The mixture was kept warm and stirred for 60min, centrifuged, dried, and calcined at 850℃ for 3h to obtain nano-cerium-boron nitride composite. Step 5: Preparation of modified silica sol: 10g of tetraethyl orthosilicate was added to a mixture of 17.7g of anhydrous ethanol, 4.6g of deionized water and 8g of silane coupling agent KH560, stirred evenly, and hydrochloric acid was added to adjust the pH to 3. The mixture was stirred evenly at 62℃ and cooled to room temperature to obtain silica sol. Step Six: Preparation of silica sol-coated nano-cerium-boron nitride composite: Take 0.5g of polyvinylpyrrolidone and 100mL of anhydrous ethanol, stir well, add 5g of nano-cerium-boron nitride composite, 1mL of deionized water and 2mL of ammonia monohydrate, stir for 3.5min, add 1.5mL of silica sol, stir for 3.5h, add 0.2mL of silane coupling agent KH560, react for 2.5h, filter, wash and dry to obtain silica sol-coated nano-cerium-boron nitride composite.

[0027] Comparative Example 4: Ordinary boron nitride was selected, and the rest was the same as in Example 1: 5g of boron nitride (particle size: 100nm, available from Brofos Nanotechnology (Ningbo) Co., Ltd., model: Brofos-BN-100), 100g of 0.15mol / L cerium chloride aqueous solution were stirred and heated to 65℃. Then, 100g of 0.225mol / L sodium carbonate aqueous solution was added dropwise. The mixture was kept warm and stirred for 60min, centrifuged, dried, and calcined at 850℃ for 3h to obtain nano-cerium-boron nitride composite.

[0028] experiment: The adhesive-backed copper foils prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. Referring to IPC-TM650.2.4.9, samples cut to 20mm × 0.3175mm were stretched to a length of 30mm using a universal testing machine at a tensile speed of 50mm / min to obtain the peel strength. Samples were then cut to 30mm × 5mm and their bending properties were tested using a grooved film flexural fatigue testing machine with a bending radius of 0.8mm and a load of 500g. The samples were repeatedly bent until the circuit could no longer conduct. A higher number of bends indicates better bending properties. The data obtained are shown in Table 1 below. Table 1 Conclusion: The data comparison in the table shows that in Comparative Example 1, without the addition of nano-cerium, the flexural strength of the adhesive-backed copper foil decreased, and the peel strength slightly decreased. In Comparative Example 2, without silica sol coating, the dispersibility of the nano-cerium-boron nitride composite decreased, leading to a decrease in the flexural strength of the adhesive-backed copper foil and the bonding strength between the copper foil and the polyimide composite layer. In Comparative Example 3, without silica sol modification or the addition of chitosan, the peel strength of the adhesive-backed copper foil decreased. In Comparative Example 4, using ordinary boron nitride, the specific surface area was small, resulting in fewer substances that could be loaded, thus reducing performance. The embodiments of this application, by adding silica sol to coat the nano-cerium-boron nitride composite with the polyimide composite material, improved the peel strength and flexural strength between the polyimide composite surface and the copper foil of the adhesive-backed copper foil. Coating the surface of the nano-cerium-boron nitride composite with amino-containing silica sol solves the agglomeration problem of the nano-cerium-boron nitride composite, improves its dispersibility in polyimide composites, and enhances its mechanical properties. On the other hand, the introduction of chitosan in this application can form hydrogen bonds with the epoxy and carboxyl groups of the resin, further improving the agglomeration problem of the nano-cerium-boron nitride composite in polyimide composites.

[0029] 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 implemented 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 exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing adhesive-backed copper foil based on polyimide composite material, characterized in that: Includes the following steps: Step 1: Take polyvinylpyrrolidone and anhydrous ethanol, stir evenly, add nano-cerium-boron nitride composite, deionized water and ammonia monohydrate, stir evenly, add modified silica sol, stir evenly, add silane coupling agent KH560, react for 2-3 hours, filter, wash and dry to obtain silica sol-coated nano-cerium-boron nitride composite. Step 2: Coat the nano-cerium-boron nitride composite with polyimide resin, epoxy resin, and silica sol, and stir until homogeneous to obtain the polyimide composite material; Step 3: Coat one side of the copper foil with polyimide composite material and bake to obtain a single-sided panel; coat the side of the single-sided panel with modified epoxy resin and bake to obtain an adhesive-backed copper foil.

2. The method for preparing adhesive-backed copper foil based on polyimide composite material according to claim 1, characterized in that: The modified silica sol is prepared as follows: tetraethyl orthosilicate is added to a mixture of anhydrous ethanol, deionized water and silane coupling agent KH560, stirred evenly, hydrochloric acid is added to adjust the pH to 2-3, stirred evenly at 60-65℃, and cooled to room temperature to obtain silica sol; chitosan powder is added to acetic acid solution and stirred evenly to obtain chitosan solution; silica sol is added, stirred evenly, and heated to 45-50℃ for 4-5 hours to obtain modified silica sol.

3. The method for preparing adhesive-backed copper foil based on polyimide composite material according to claim 1, characterized in that: The preparation method of the nano-cerium-boron nitride composite includes the following steps: S1: Add boric acid and melamine to deionized water, heat in a water bath to 88-92℃, stir evenly, then react at 80℃ for 2-3 hours, cool, filter and dry to obtain the precursor; calcine the precursor under a nitrogen atmosphere to obtain porous boron nitride. S2: Porous boron nitride and cerium chloride aqueous solution are stirred and heated to 65-67℃, then sodium carbonate aqueous solution is added dropwise, and the mixture is kept at this temperature and stirred for 50-70 min. After centrifugation, drying and calcination, nano-cerium-boron nitride composite is obtained.

4. The method for preparing adhesive-backed copper foil based on polyimide composite material according to claim 1, characterized in that: The mass ratio of the polyimide resin, epoxy resin, and silica sol-coated nano-cerium-boron nitride composite is (89-92):(5-6):(5-6).

5. The method for preparing adhesive-backed copper foil based on polyimide composite material according to claim 1, characterized in that: The method for preparing the modified epoxy resin is as follows: Includes the following steps: A: Take nano-alumina and anhydrous ethanol, ultrasonically disperse for 1-2 hours, add polyvinylpyrrolidone, ultrasonically disperse, wash, filter, add anhydrous ethanol, disperse to obtain alumina dispersion; take anhydrous ethanol, ammonia, and deionized water, stir evenly to obtain solution A; take anhydrous ethanol and tetraethyl orthosilicate, stir evenly to obtain solution B; add solution A to the alumina dispersion, stir for 10-15 minutes, add solution B dropwise, stir for 11-13 hours, centrifuge, wash, dry, calcine, cool to obtain alumina-silica particles; B: Add alumina-silica particles to epoxy resin and stir for 1-2 hours; add curing agent and stir for 1-2 hours to obtain modified epoxy resin.

6. The method for preparing adhesive-backed copper foil based on polyimide composite material according to claim 1, characterized in that: The polyimide resin is synthesized from an acid dianhydride compound and a diamine compound. The acid dianhydride compound is any one or more of the following: pyromellitic dianhydride, biphenyl dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, bisphenol A type diether dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride, and 4,4-(p-phenylene dioxy)diphthalic dianhydride.

7. The method for preparing a polyimide composite-based adhesive copper foil according to claim 6, characterized in that: The diamine compounds are: p-phenylenediamine, 4,4'-diaminodiphenyl ether, 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenylhexafluoropropane, 4,4-bis(4-aminophenoxy)biphenyl, 4,4'-diaminobenzoylaniline, 4-aminophenyl-4-aminobenzoic acid ester, Any one or more of the following: di(4-aminophenyl) terephthalate, di(4-(4-aminophenoxy)phenyl) sulfone, di(4-amino-3-carboxyphenyl)methane, 4,4'-diaminobenzophenone, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 9,9-bis(4-aminophenyl)fluorene, 3,3'-dimethyl-4,4'-diaminobiphenyl, and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene.

8. The method for preparing adhesive-backed copper foil based on polyimide composite material according to claim 1, characterized in that: The polyimide resin is prepared by taking p-phenylenediamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and 1,3-bis(4-aminophenoxy)benzene, adding N,N-dimethylacetamide, stirring evenly, adding biphenyl tetracarboxylic anhydride, and stirring for 3-4 hours to obtain the polyimide resin.

9. The method for preparing adhesive-backed copper foil based on polyimide composite material according to claim 1, characterized in that: In step two, the epoxy resin is any one or more of the following: aromatic glycidyl ether epoxy resin, aromatic glycidyl amine epoxy resin, alicyclic glycidyl ester epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and fluorene epoxy resin.

10. The adhesive-backed copper foil prepared by the method for preparing a polyimide composite material-based adhesive-backed copper foil according to any one of claims 1-9.

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