Rapid bonding resin composition, adhesive film and application

Abstract

The invention belongs to the technical field of printed circuit boards, and discloses a rapid bonding resin composition, an adhesive film and application. The rapid bonding resin composition is prepared from the following raw materials in parts by mass: 15 to 25 parts of carboxyl-containing benzoxazine resin, 5 to 10 parts of epoxy resin, 17 to 26 parts of solid carboxy nitrile rubber, 0.25 to 0.5 part of cross-linking agent and 3 to 8 parts of inorganic filler. The adhesive film prepared from the resin composition can be quickly adhered, has high peel strength and good acid and alkali resistance and thermal shock resistance, and meets the production and adhesion requirements of flexible printed circuit boards.

Description

Technical Field

[0001] The invention belongs to the technical field of printed circuit boards, and in particular relates to a quick bonding resin composition, an adhesive film and applications thereof. Background Art

[0002] In the production process of flexible printed circuit boards, a large amount of adhesive film is needed to bond materials together. For example, the bonding between flexible printed circuit boards and reinforcing materials, and the bonding between multi-layer circuit boards. With the development of electronic products towards miniaturization and thinness, flexible printed circuit boards are continuously updated and applied, and their application areas are becoming wider and wider. With the expansion of product terminal application areas and the requirement for short product processing cycles, there is an urgent need for adhesive films that can achieve rapid bonding applications.

[0003] In the current production and application of flexible printed circuit boards, the types of adhesive films used are mainly acrylate and epoxy. After rapid lamination, the curing conditions for acrylate adhesive films are 150-160℃, 1-2h, and the curing conditions for epoxy adhesive films are 170-180℃, 1-2h.

[0004] CN109679511A provides an epoxy type fast curing adhesive film and a preparation method thereof. The curing adhesive film uses an accelerator to accelerate the reaction rate, and the curing conditions are 150°C and 5 minutes of curing. The curing adhesive film is applied in the surface protection of parts and components. After rapid curing, it has stable corrosion resistance, good adhesion, and good flexural resistance, which can reduce the cost of later use and improve efficiency. The adhesive film of the invention is quite different from the adhesive film used in the production of flexible printed circuit boards. The adhesive film for flexible printed circuit boards is used for structural bonding, and has clear requirements for bonding strength, heat resistance, etc.

[0005] CN1580171A discloses a heat-curing adhesive film for flexible circuit assembly and its preparation method, which is obtained by coating an adhesive solution formed by epoxy resin, nitrile rubber toughening agent, aromatic amine curing agent, imidazole derivative curing agent and ketone solvent, and can be completely cured within tens of seconds at 180°C by using aromatic polyamine and imidazole derivative composite curing agent. The composition uses brominated bisphenol A epoxy resin, which does not meet the current environmental protection requirements.

[0006] CN115895541A discloses a fast curing epoxy adhesive film and its preparation method. The patent adds amino-terminated isocyanate to obtain isocyanate at high temperature, thereby reducing the reaction temperature time, so that the epoxy adhesive film can be cured within 10 minutes at 150°C. Since the adhesive film generates a large amount of polyurethane after curing, the heat resistance of the composition is reduced and the heat shock resistance requirements of the flexible printed circuit board cannot be met. Summary of the invention

[0007] The purpose of the present invention is to provide a quick bonding resin composition, adhesive film and application. The adhesive film prepared by the resin composition can quickly complete bonding, has high peel strength, good heat shock resistance, and meets the production bonding requirements of flexible printed circuit boards.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A quick bonding resin composition is provided, wherein the mass fractions of the components are as follows:

[0010]

[0011] According to the above scheme, the carboxyl-containing benzoxazine monomer is at least one of the following structural formulas:

[0012]

[0013] According to the above scheme, the epoxy resin is a bisphenol A type epoxy resin, one or a mixture of which the epoxy equivalent is 530 to 1000 g / eq.

[0014] According to the above scheme, the solid carboxyl nitrile rubber is one or a mixture of NITRICLEAN-3350X and NITRICLEAN-3330X.

[0015] According to the above scheme, the carboxyl content of the solid carboxyl nitrile rubber is 6-8%.

[0016] According to the above scheme, the cross-linking agent is one or a combination of two or more of 2-methylimidazole, 2-ethyl-4-methylimidazole and 2-phenylimidazole.

[0017] According to the above scheme, the inorganic filler is selected from one or a combination of two or more of silicon dioxide, aluminum oxide, aluminum hydroxide, magnesium oxide, magnesium hydroxide, calcium carbonate and kaolin.

[0018] Provided is an adhesive film comprising a coating layer prepared from the above-mentioned rapid bonding resin composition.

[0019] According to the above scheme, the adhesive film comprises a release film carrier, a coating layer prepared from the above rapid bonding resin composition and a release film in sequence.

[0020] Provided is a method for preparing the above-mentioned adhesive film, comprising the steps of: adding the components of the above-mentioned quick bonding resin composition except the inorganic filler into an organic solvent to dissolve to obtain a uniformly dispersed mixed liquid, and then adding the inorganic filler to disperse evenly to obtain an adhesive solution; coating the adhesive solution on a release film cloth, and then baking it, and then compounding it with another release film, and finally performing a heat treatment to obtain an adhesive film.

[0021] According to the above scheme, the organic solvent is a mixed solvent of butanone, ethyl acetate and dimethylformamide. Preferably, the mass ratio of butanone, ethyl acetate and dimethylformamide is 5-6:4-5:1.

[0022] According to the above scheme, the solid content of the glue solution is 45-60%.

[0023] According to the above scheme, the baking temperature is 90-150° C. and the baking time is 4-10 minutes.

[0024] According to the above scheme, the heat treatment process is: 60-80°C, 8-24 hours.

[0025] According to the above solution, the release film is a polyester release film with a release agent covered on the surface.

[0026] Provided is an application of the adhesive film in bonding a reinforcing plate to a flexible circuit board.

[0027] According to the above scheme, the application is: remove the release film on the surface of the film, bond it to a flexible circuit board and a polyimide reinforcement plate, and press it at 170-180°C, 9-11MPa, and 90-150s to prepare a locally reinforced flexible circuit board.

[0028] The present invention provides a fast bonding resin composition, which is mainly composed of carboxyl-containing benzoxazine monomers and solid carboxyl nitrile rubber, with appropriate amounts of epoxy resin and imidazole crosslinking agent, and inorganic filler. The obtained composition can quickly complete bonding and also has high peel strength and good heat shock resistance; wherein:

[0029] Epoxy resin undergoes cross-linking polymerization reaction under the action of imidazole cross-linking agent to generate macromolecules with three-dimensional network structure. The molecule itself has strong cohesive force. At the same time, because epoxy resin itself contains polar groups such as hydroxyl group and ether bond, the epoxy resin and the bonded interface produce dipole force. Therefore, the epoxy resin has high bonding strength after curing. However, the cured product of epoxy resin and imidazole cross-linking agent has poor heat resistance. Adding too much will cause the heat resistance of the entire resin combination to decrease.

[0030] The carboxyl-containing benzoxazine monomer can be ring-opened under the catalysis of imidazole crosslinking agents. After ring-opening, it has excellent heat resistance whether it is homopolymerized or copolymerized with epoxy resin. At the same time, the carboxyl group in the carboxyl benzoxazine monomer and the solid carboxyl nitrile rubber can accelerate the ring-opening of the oxazine ring and reduce the curing temperature of the benzoxazine monomer, so that the carboxyl benzoxazine monomer and the epoxy resin are in the early stage of the crosslinking reaction after heat treatment, laying a good foundation for the subsequent rapid bonding.

[0031] In addition, the amount of imidazole crosslinking agent in the resin composition of the present invention must be controlled within a certain range. If the amount of imidazole crosslinking agent is insufficient, the ring-opening degree of epoxy resin and carboxylbenzoxazine monomer is insufficient, the prepared adhesive film is not sufficiently cured after heat treatment and lamination, the crosslinking density is insufficient, and both the bonding strength and heat resistance are reduced. If the amount of imidazole crosslinking agent is too much, the epoxy resin will be completely crosslinked before lamination, resulting in a decrease in heat resistance and adhesion of the resin composition.

[0032] Combined with an appropriate amount of solid carboxy nitrile rubber, solid carboxy nitrile rubber has excellent heat resistance, has a certain pressure sensitivity, can be quickly bonded after lamination, and synergizes with carboxy benzoxazine resin and epoxy resin to have stable bonding performance. However, solid carboxy nitrile rubber needs to be in an appropriate amount. After the film is heat-treated, the carboxy benzoxazine monomer and epoxy resin are already in the initial stage of the cross-linking reaction (the "gel" stage), and the wettability of the film during lamination decreases. The decrease in wettability will directly affect the surface bonding with the adherend. In this case, if there is not enough solid carboxy nitrile rubber to give the film pressure sensitivity, the bonding force of the film after lamination will be insufficient; and if the amount of solid carboxy nitrile rubber added is too large, the "thermosetting" characteristics of the resin composition decrease, the "high elastic state" characteristics dominate, the overall cross-linking density of the system decreases, and the cohesion is insufficient, resulting in insufficient stability of the bonding strength at room temperature after the film is pressed, a sharp decrease in bonding strength at high temperature, and unqualified solder resistance.

[0033] The present invention has the following technical effects:

[0034] The present invention uses a carboxyl-containing benzoxazine monomer as a main resin, cooperates with an appropriate amount of epoxy resin, an imidazole crosslinking agent and a solid carboxyl nitrile rubber, and is further combined with an inorganic filler, so that the curing temperature of the resin composition can be effectively reduced, the crosslinking reaction rate can be increased, and when the adhesive film is prepared, the heat treatment, such as under the conditions of 60-80° C. and 8-24 hours, can be carried out through the ring-opening reaction of the epoxy resin, and the carboxyl-containing benzoxazine monomer can partially undergo a ring-opening crosslinking reaction, so that the epoxy resin and the carboxyl-containing benzoxazine monomer are in the "gel" stage of the thermosetting resin. When used for subsequent bonding of a reinforcing plate of a flexible printed circuit board, the adhesive film can be quickly crosslinked and cured in 90-150 seconds under the conditions of 170-180° C. and 9-11 MPa, and has the characteristics of good bonding performance, high peel strength, acid and alkali resistance, good heat resistance, and low water absorption, and can meet the production bonding requirements of the flexible printed circuit board. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is described in detail below with reference to embodiments, but the protection scope of the present invention is not limited thereto.

[0036] Example 1

[0037] Carboxyl benzoxazine, epoxy resin, solid carboxyl nitrile rubber, crosslinking agent, etc. are prepared according to the formula in Table 1, and then dissolved in butanone, ethyl acetate and dimethylformamide in a mass ratio of 5:4:1 as an organic solvent. After the dissolution is completed, inorganic fillers are added and quickly dispersed evenly to prepare a glue solution.

[0038] The adhesive liquid was coated on the polyester release film by a coating machine, and then passed through a drying oven with an average temperature of 100°C for 5 minutes to form a 25μm dry adhesive, which was then compounded with the release film and treated at 60°C for 24 hours to form an adhesive film. The release film of the adhesive film was torn off, and it was bonded to a flexible circuit board and a polyimide reinforcement board, and then pressed at 170°C, 10MPa, and 2 minutes to prepare a partially reinforced flexible circuit board sample.

[0039] According to the IPC-TM650 test method, the peel strength, heat resistance, water absorption, acid and alkali resistance of the samples were tested. The specific test results are shown in Table 2.

[0040] Example 2

[0041] Carboxyl benzoxazine, epoxy resin, solid carboxyl nitrile rubber, crosslinking agent, etc. are prepared according to the formula in Table 1, and then dissolved in butanone, ethyl acetate and dimethylformamide in a mass ratio of 5:4:1 as an organic solvent. After the dissolution is completed, inorganic fillers are added and quickly dispersed evenly to prepare a glue solution.

[0042] The adhesive liquid was coated onto the polyester release film by a coating machine, and then passed through a drying oven at an average temperature of 100°C for 5 minutes to form a 25μm dry adhesive, which was then compounded with the release film and treated at 70°C for 12 hours to form an adhesive film. The release film of the adhesive film was torn off, and it was bonded to a flexible circuit board and a polyimide reinforcement board, and then pressed at 170°C, 10MPa, and 2 minutes to prepare a partially reinforced flexible circuit board sample.

[0043] According to the IPC-TM650 test method, the peel strength, heat resistance, water absorption, acid and alkali resistance of the samples were tested. The specific test results are shown in Table 2.

[0044] Example 3

[0045] Carboxyl benzoxazine, epoxy resin, solid carboxyl nitrile rubber, crosslinking agent, etc. are prepared according to the formula in Table 1, and then dissolved in butanone, ethyl acetate and dimethylformamide in a mass ratio of 5:4:1 as an organic solvent. After the dissolution is completed, inorganic fillers are added and quickly dispersed evenly to prepare a glue solution.

[0046] The adhesive liquid was coated onto the polyester release film by a coating machine, and then passed through a drying oven at an average temperature of 100°C for 5 minutes to form a 25μm dry adhesive, which was then compounded with the release film and treated at 80°C for 8 hours to form an adhesive film. The release film of the adhesive film was torn off, and it was bonded to a flexible circuit board and a polyimide reinforcement board, and then pressed at 170°C, 10MPa, and 2 minutes to prepare a partially reinforced flexible circuit board sample.

[0047] According to the IPC-TM650 test method, the peel strength, heat resistance, water absorption, acid and alkali resistance of the samples were tested. The specific test results are shown in Table 2.

[0048] Embodiment 4-5

[0049] The preparation methods of the resin composition, adhesive solution and adhesive film of Examples 4-5 are the same as that of Example 1. The specific component proportions are shown in Table 1, and the test results are shown in Table 2.

[0050] Comparative Example 1-2

[0051] The preparation methods of the resin composition, adhesive solution and adhesive film of Comparative Examples 1-2 are the same as those of Example 1. The specific component proportions are shown in Table 1, and the test results are shown in Table 2.

[0052] Table 1. Ratio of components of the resin composition obtained in Examples 1-5 and Comparative Examples 1-2 (in parts by mass)

[0053]

[0054]

[0055] Raw materials used in the examples:

[0056] Carboxyl-containing benzoxazine monomer: The structural formula is as follows:

[0057]

[0058] Epoxy resin: CYD-013, epoxy equivalent 700~800g / eq.

[0059] Solid carboxyl nitrile rubber: NITRICLEAN-3350X, carboxyl content is 7%.

[0060] Cross-linking agent: 2-ethyl-4-methylimidazole.

[0061] Inorganic filler: aluminum hydroxide.

[0062] Organic solvent: a mixture of butanone, ethyl acetate and dimethylformamide in a mass ratio of 5:4:1.

[0063] Table 2

[0064]

[0065] Note:

[0066] Acid and alkali resistance: tested in accordance with GB / T 13357-2017 8.1.3.

[0067] Table 2 shows that after lamination at 170°C, 10MPa, and 2 minutes, the peel strength of the adhesive film obtained in Examples 1-5 is ≧1.39N / mm, which meets the bonding requirements of the flexible circuit board. At the same time, it can pass the solder resistance test at 288°C, 10s, and 3 times, meeting the thermal shock resistance requirements of the flexible circuit board. The TGA test shows that the decomposition temperature (Td, 2%) of the adhesive film after curing is not less than 324°C, which once again shows that the adhesive film has good heat resistance.

[0068] Compared with Example 1, in Comparative Example 1, too much cross-linking agent was added, and both the peel strength and solder resistance were reduced, indicating that the increase in the amount of cross-linking agent will cause the epoxy resin to cross-link and cure during heat treatment to form an epoxy resin imidazole cured product, which will lead to insufficient heat resistance and adhesion.

[0069] Compared with Example 1, in Comparative Example 2, the amount of solid carboxyl nitrile rubber added was too little, the peel strength decreased significantly, and the soldering resistance was qualified. This indicates that insufficient addition of solid carboxyl nitrile rubber directly leads to a decrease in bonding performance, but does not affect the cross-linking and curing of the resin composition, so the soldering resistance can still pass the test.

[0070] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A quick bonding resin composition, characterized in that The following raw materials are included by weight:

2. The resin composition according to claim 1, characterized in that The carboxyl-containing benzoxazine monomer is at least one of the following structural formulas:

3. The resin composition according to claim 1, characterized in that The epoxy resin is a bisphenol A epoxy resin, one or a mixture of which the epoxy equivalent is 530 to 1000 g / eq; the carboxyl content of the solid carboxyl nitrile rubber is 6 to 8%.

4. The resin composition according to claim 1, characterized in that The imidazole crosslinking agent is one or a combination of two or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole; the inorganic filler is one or a combination of two or more selected from silicon dioxide, aluminum oxide, aluminum hydroxide, magnesium oxide, magnesium hydroxide, calcium carbonate, and kaolin.

5. A film, characterized in that: The invention comprises a coating layer prepared from the rapid bonding resin composition according to any one of claims 1 to 4.

6. A method for preparing the adhesive film according to claim 5, characterized in that: The following steps are involved: The components except the inorganic filler in the quick bonding resin composition according to any one of claims 1 to 4 are added to an organic solvent to dissolve to obtain a uniformly dispersed mixed liquid, and then the inorganic filler is added and dispersed evenly to obtain a glue solution; the glue solution is coated on a release film cloth, and then baked, and then compounded with another release film, and finally heat-treated to obtain a glue film.

7. The preparation method according to claim 6, characterized in that: The organic solvent is a mixed solvent of butanone, ethyl acetate and dimethylformamide; and the release film is a polyester release film with a release agent covered on the surface.

8. The preparation method according to claim 6, characterized in that: The baking temperature is 90-150° C., and the baking time is 4-10 minutes; the heat treatment process is 60-80° C., and the time is 8-24 hours.

9. Use of the adhesive film according to claim 5 in bonding reinforcing plates to flexible circuit boards.

10. The use according to claim 9, characterized in that: The application is: the adhesive film is bonded to a flexible circuit board and a polyimide reinforcement plate, and pressed at 170-180° C., 9-11 MPa, and 1.5-2.5 minutes to prepare a partially reinforced flexible circuit board.

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