Barrier adhesive film for flexible circuit board and production method thereof

Abstract

The present invention discloses a barrier adhesive film for flexible circuit boards and a production method thereof, which belongs to the technical field of barrier adhesive films, including a copperplate paper layer, a circuit board is arranged below the copperplate paper layer, the copperplate paper layer and the circuit board are connected by an adhesive layer, a glue assembly layer is arranged above the copperplate paper layer, and a protective layer is arranged above the glue assembly layer. The present invention discloses a barrier adhesive film for flexible circuit boards and a production method thereof, wherein the transparent hardened layer has good hardness and scratch resistance, and the white reflective shielding layer has the characteristics of high reflectivity, high temperature yellowing resistance, low penetration, high surface roughness, high flexibility, low rebound force, good reliability, good flame resistance, etc. The protective layer is arranged to effectively protect the flexible circuit board and prevent the flexible circuit board from being damaged. The high temperature resistant silica gel is used as the middle layer of the barrier adhesive film, which can play a good adhesive resistance and avoid the problem of epoxy adhesive overflowing and remaining on the surface of the metal copper block.

Description

Technical Field

[0001] The present invention relates to the technical field of barrier films, and in particular to a barrier film for a flexible circuit board and a production method thereof. Background Technology

[0002] With the development of information and communication industries, the microelectronics industry has developed rapidly. Flexible printed circuit boards have emerged and developed rapidly, and have been widely used in many fields such as mobile phones, liquid crystal displays, and tablets. The biggest difference between flexible printed circuit boards and PCBs (Printed Circuit Boards, rigid printed circuit boards) is that the function of the cover film used in the former exceeds the solder mask ink used for PCBs. It not only acts as a solder mask to protect the FPC from dust, moisture, and chemical corrosion, but also reduces the impact of stress during the bending process. In addition, with the development of the FPC market, the cover film has been given more functions. Among them, the white cover film has the characteristics of high reflectivity, low penetration, high temperature resistance, and weather resistance, which can achieve a shielding effect. With the mass production of electronic products or electrical products, the application scope of circuit boards has gradually expanded, and the output of circuit boards has also been increasing. In the prior art, adhesive film is often used in the production process of circuit boards.

[0003] However, in the process of molding and pressing, there are often the following defects:

[0004] 1. The existing flexible circuit board has no protective layer, which makes the flexible circuit board easy to be damaged and affects the service life of the flexible circuit board;

[0005] 2. Secondly, the existing adhesive barrier films still have many disadvantages. Some low-cost adhesive barrier films have poor performance and easily cause the epoxy adhesive to overflow and remain on the surface of the metal copper block. SUMMARY OF THE INVENTION

[0006] The purpose of the present invention is to provide a barrier film for flexible circuit boards and a production method thereof. The transparent hardened layer has good hardness and scratch resistance, and the white reflective shielding layer has the characteristics of high reflectivity, high temperature yellowing resistance, low penetration, high surface roughness, high flexibility, low rebound force, good reliability, good flame resistance, etc. The protective layer is set to effectively protect the flexible circuit board to prevent damage to the flexible circuit board. The high temperature resistant silicone is used as the middle layer of the barrier film, which can play a good role in adhesive resistance and avoid the problem of epoxy glue overflowing and remaining on the surface of the metal copper block, so as to solve the problems raised in the above background technology.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A barrier film for a flexible circuit board, comprising a copperplate paper layer, a circuit board is arranged below the copperplate paper layer, and the copperplate paper layer and the circuit board are connected by an adhesive layer;

[0009] Above the coated paper layer, there is a glue group layer, and above the glue group layer, there is a protective layer;

[0010] The protective layer includes a transparent hardening layer, a white reflective shielding layer, an insulating layer, and a waterproof layer. Above the transparent hardening layer, there is a connected white reflective shielding layer. Above the white reflective shielding layer, there is a connected insulating layer. Above the insulating layer, there is a connected waterproof layer.

[0011] Furthermore, the glue group layer includes a PET substrate layer, a release coating layer, a softening layer, and an inner glue layer. Above the PET substrate layer, there is an inner glue layer coated. Above the inner glue layer, there is a release coating layer coated. Above the release coating layer, there is a softening layer coated.

[0012] Furthermore, the raw materials for the glue group layer include polyethylene terephthalate, modified polyurethane acrylate, acrylate monomer, silicone resin, silicon dioxide, silicone raw rubber, diluting solvent, silicone crosslinking agent, anchoring agent, silicone catalyst, and cast polypropylene film. The raw material ratio is as follows: polyethylene terephthalate 25 - 48 parts, modified polyurethane acrylate 15 - 33 parts, acrylate monomer 27 - 46 parts, silicone resin 2.5 - 6.7 parts, silicon dioxide 2.5 - 6.7 parts, silicone raw rubber 4 - 18 parts, diluting solvent 36 - 58 parts, silicone crosslinking agent 0.3 - 1.8 parts, anchoring agent 0.5 - 2.3 parts, silicone catalyst 0.1 - 2.4 parts, and cast polypropylene film 11 - 28 parts.

[0013] Furthermore, the raw materials for the protective layer include polyurethane acrylate prepolymer, reactive diluent, photoinitiator, leveling agent, inorganic pigment, organic pigment, and biaxially oriented polypropylene. The raw material ratio is as follows: polyurethane acrylate prepolymer 12 - 39 parts, reactive diluent 22 - 56 parts, photoinitiator 1.2 - 3.2 parts, leveling agent 0.8 - 2.9 parts.

[0014] Furthermore, the modified polyurethane acrylate uses isophorone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and their trimers as raw materials;

[0015] Furthermore, the silicone resin is one or more of acrylated products of silicone oil, epoxy modified silicone resin, ammonia modified silicone resin, polyurethane modified silicone resin, fatty acid modified silicone resin, silicone rubber resin, and silicone oil.

[0016] The present invention provides another technical solution: a production method of a barrier adhesive film for a flexible printed circuit board, including the following steps:

[0017] S1: Mix polyurethane acrylate prepolymer, reactive diluent, photoinitiator and leveling agent to form a transparent hardening layer, and mix inorganic pigment and organic pigment to form a white reflective shielding layer;

[0018] S2: Take biaxially oriented polypropylene to make an insulating layer, laminate the transparent hardening layer, white reflective shielding layer and insulating layer, and press them to form a protective film, and coat a waterproof coating on the surface of the protective film to form a waterproof layer;

[0019] S3: Mix a certain amount of modified polyurethane acrylate, acrylate monomer, silicone resin and silica to form a release coating, and make a PET substrate layer from polyethylene terephthalate;

[0020] S4: Mix silicone raw rubber, diluting solvent, silicone crosslinking agent, anchoring agent and silicone catalyst, and stir and fuse them, and make the liquid after mixing into an inner glue layer, and take a cast polypropylene film to make a softening layer;

[0021] S5: Laminate the PET substrate layer, inner glue layer, release coating and softening layer in sequence, and press the laminated substrates to form a combined glue layer;

[0022] S6: Attach the combined glue layer to the circuit board through an adhesive layer, laminate the protective layer on the combined glue layer, place the circuit board, combined glue layer and protective layer on a hot press, and press the barrier adhesive film onto the circuit board.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. For the barrier adhesive film for flexible circuit boards and its production method proposed by the present invention, the release coating has good comprehensive performance in terms of hardness, solvent resistance and release stability. Polyurethane acrylate can provide a higher crosslinking density for the release coating, thereby effectively preventing the strong penetration of isocyanate in the new binder component at high temperature into the release coating, resulting in abnormal peeling of the release paper. The transparent hardening layer has good hardness and scratch resistance. The white reflective shielding layer has characteristics such as high reflectivity, high temperature resistance to yellowing, low penetration rate, high surface roughness, high flexibility, low rebound force, good reliability, and good flame retardancy. By setting it in the protective layer, it can effectively protect the flexible circuit board and prevent the flexible circuit board from being damaged;

[0025] 2. The barrier adhesive film for flexible printed circuit boards and its production method proposed by the present invention. The silicone resin is one or more of acrylic ester products of silicone oil, epoxy-modified silicone resin, ammonia-modified silicone resin, polyurethane-modified silicone resin, fatty acid-modified silicone resin, silicone rubber resin, and silicone oil. Applying high-temperature-resistant silica gel to the intermediate layer of the resist film can achieve good resist properties and avoid the problem of epoxy adhesive overflowing and remaining on the surface of the metal copper block. The release coating uses a special formula of silicone oil, which is very beneficial for the press molding of printed circuit boards with embedded metal copper blocks. In addition to having good resist properties, it also has moderate fluidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0027] Figure 2 It is a schematic diagram of the resist layer structure of the present invention;

[0028] Figure 3 It is a schematic diagram of the protective layer structure of the present invention;

[0029] Figure 4 It is a flowchart of the present invention.

[0030] In the figure: 1. Copper paper layer; 11. Adhesive layer; 2. Resist layer; 21. PET substrate layer; 22. Release coating; 23. Softening layer; 24. Inner adhesive layer; 3. Protective layer; 31. Clear hardening layer; 32. White reflective shielding layer; 33. Insulating layer; 34. Waterproof layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Embodiment 1:

[0033] In order to solve the problem that the existing flexible printed circuit boards have no protective layer, resulting in easy damage to the flexible printed circuit boards and affecting the service life of the flexible printed circuit boards, and there are still many drawbacks in the existing resist films. Some resist films with low cost have poor performance and are prone to the problem of epoxy adhesive overflowing and remaining on the surface of the metal copper block. Please refer to Figures 1 - 4 , the following technical solutions are provided in this embodiment:

[0034] A barrier adhesive film for a flexible printed circuit board and its production method, including a copperplate paper layer 1, a printed circuit board is arranged below the copperplate paper layer 1, and the copperplate paper layer 1 and the printed circuit board are connected by an adhesive layer 11;

[0035] Above the copperplate paper layer 1, a glue group layer 2 is arranged, and a protective layer 3 is arranged above the glue group layer 2;

[0036] The protective layer 3 includes a transparent hardening layer 31, a white reflective shielding layer 32, an insulating layer 33 and a waterproof layer 34. The white reflective shielding layer 32 is connected above the transparent hardening layer 31, the insulating layer 33 is connected above the white reflective shielding layer 32, and the waterproof layer 34 is connected above the insulating layer 33.

[0037] The glue group layer 2 includes a PET substrate layer 21, a release coating 22, a softening layer 23 and an inner glue layer 24. The inner glue layer 24 is coated above the PET substrate layer 21, the release coating 22 is coated above the inner glue layer 24, and the softening layer 23 is coated above the release coating 22.

[0038] The raw materials for the glue group layer 2 include polyethylene terephthalate, modified polyurethane acrylate, acrylate monomer, silicone resin, silica, silicone raw rubber, diluting solvent, silicone crosslinking agent, anchoring agent, silicone catalyst and cast polypropylene film. The raw material ratio is as follows: 25 parts of polyethylene terephthalate, 15 parts of modified polyurethane acrylate, 27 parts of acrylate monomer, 2.5 parts of silicone resin, 2.5 parts of silica, 4 parts of silicone raw rubber, 36 parts of diluting solvent, 0.3 part of silicone crosslinking agent, 0.5 part of anchoring agent, 0.1 part of silicone catalyst and 11 parts of cast polypropylene film;

[0039] The modified polyurethane acrylate uses isophorone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and their trimers as raw materials;

[0040] The silicone resin is one or more of acrylated products of silicone oil, epoxy modified silicone resin, ammonia modified silicone resin, polyurethane modified silicone resin, fatty acid modified silicone resin, silicone rubber resin and silicone oil. Applying high-temperature resistant silica gel to the intermediate layer of the resist film can achieve good resist glue property and avoid the problem of epoxy glue overflowing and remaining on the surface of the metal copper block. The release coating adopts a special formula of silicone oil, which is very beneficial to the pressing and forming of printed circuit boards with embedded metal copper blocks. In addition to having good resist glue property, it also has moderate fluidity.

[0041] The raw materials for the preparation of the protective layer 3 include polyurethane acrylate prepolymer, reactive diluent, photoinitiator, leveling agent, inorganic pigment, organic pigment and biaxially oriented polypropylene, and the raw material ratio is as follows: 12 parts of polyurethane acrylate prepolymer, 22 parts of reactive diluent, 1.2 parts of photoinitiator, and 0.8 parts of leveling agent.

[0042] The release coating 22 has good comprehensive properties in terms of hardness, solvent resistance and release stability. Polyurethane acrylate can provide a higher crosslinking density for the release coating, thus effectively preventing the strong penetration of isocyanate in the new binder component at high temperature into the release coating, resulting in abnormal peeling of the release paper. The transparent hardening layer has good hardness and scratch resistance. The white reflective shielding layer has characteristics such as high reflectivity, high temperature yellowing resistance, low penetration rate, high surface roughness, high flexibility, low rebound force, good reliability and good flame retardancy. By arranging the protective layer 3, the flexible printed circuit board is effectively protected to prevent damage to the flexible printed circuit board.

[0043] The present invention provides another technical solution: a production method of a barrier adhesive film for a flexible printed circuit board, comprising the following steps:

[0044] S1: Mix the polyurethane acrylate prepolymer, reactive diluent, photoinitiator and leveling agent to form a transparent hardening layer 31, and then mix the inorganic pigment and organic pigment to form a white reflective shielding layer 32;

[0045] S2: Use biaxially oriented polypropylene to form an insulating layer 33, laminate the transparent hardening layer 31, the white reflective shielding layer 32 and the insulating layer 33, and press them to form a protective film, and coat a waterproof coating on the surface of the protective film to form a waterproof layer 34;

[0046] S3: Mix a certain amount of modified polyurethane acrylate, acrylate monomer, silicone resin and silica to form a release coating 22, and use polyethylene terephthalate to form a PET substrate layer 21;

[0047] S4: Mix organosilicon raw rubber, diluting solvent, silicone crosslinking agent, anchoring agent and silicone catalyst and stir and fuse them, and make the liquid after mixing into an inner glue layer 24, and use cast polypropylene film to form a softening layer 23;

[0048] S5: Laminate the PET substrate layer 21, the inner glue layer 24, the release coating 22 and the softening layer 23 in sequence, and press the laminated substrates to form a composite glue layer 2;

[0049] S6: The composite glue layer 2 is adhered to the circuit board through the adhesive layer 11, and the protective layer 3 is laminated on the composite glue layer 2. The circuit board, the composite glue layer 2 and the protective layer 3 are placed on a hot press, and the barrier adhesive film is pressed onto the circuit board.

[0050] Example Two:

[0051] A barrier adhesive film for flexible printed circuit boards and its production method, including a copperplate paper layer 1, a printed circuit board is arranged below the copperplate paper layer 1, and the copperplate paper layer 1 and the printed circuit board are connected by an adhesive layer 11;

[0052] Above the copperplate paper layer 1, there is a glue group layer 2, and above the glue group layer 2, there is a protective layer 3;

[0053] The protective layer 3 includes a transparent hardening layer 31, a white reflective shielding layer 32, an insulating layer 33 and a waterproof layer 34. The white reflective shielding layer 32 is connected above the transparent hardening layer 31, the insulating layer 33 is connected above the white reflective shielding layer 32, and the waterproof layer 34 is connected above the insulating layer 33.

[0054] The glue group layer 2 includes a PET base material layer 21, a release coating 22, a softening layer 23 and an inner glue layer 24. The inner glue layer 24 is coated above the PET base material layer 21, the release coating 22 is coated above the inner glue layer 24, and the softening layer 23 is coated above the release coating 22.

[0055] The raw materials for the glue group layer 2 include polyethylene terephthalate, modified polyurethane acrylate, acrylate monomer, silicone resin, silica, silicone raw rubber, diluting solvent, silicone crosslinking agent, anchoring agent, silicone catalyst and cast polypropylene film. The raw material ratio is as follows: 48 parts of polyethylene terephthalate, 33 parts of modified polyurethane acrylate, 46 parts of acrylate monomer, 6.7 parts of silicone resin, 6.7 parts of silica, 18 parts of silicone raw rubber, 58 parts of diluting solvent, 1.8 parts of silicone crosslinking agent, 2.3 parts of anchoring agent, 2.4 parts of silicone catalyst and 28 parts of cast polypropylene film;

[0056] The modified polyurethane acrylate uses isophorone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and their trimers as raw materials;

[0057] The silicone resin is one or more of acrylated products of silicone oil, epoxy modified silicone resin, ammonia modified silicone resin, polyurethane modified silicone resin, fatty acid modified silicone resin, silicone rubber resin and silicone oil. Applying high-temperature resistant silica gel to the intermediate layer of the resist film can achieve good resist glue property and avoid the problem of epoxy glue overflowing and remaining on the surface of the metal copper block. The release coating adopts a special formula of silicone oil, which is very beneficial to the pressing and forming of printed circuit boards with embedded metal copper blocks. In addition to having good resist glue property, it also has moderate fluidity.

[0058] The raw materials for the preparation of the protective layer 3 include polyurethane acrylate prepolymer, reactive diluent, photoinitiator, leveling agent, inorganic pigment, organic pigment and biaxially oriented polypropylene, and the raw material ratio is as follows: 39 parts of polyurethane acrylate prepolymer, 56 parts of reactive diluent, 3.2 parts of photoinitiator, and 2.9 parts of leveling agent.

[0059] The release coating 22 has good comprehensive properties in terms of hardness, solvent resistance and release stability. Polyurethane acrylate can provide a higher crosslinking density for the release coating, thus effectively preventing the strong penetration of isocyanate in the new binder component to the release coating at high temperature, resulting in abnormal peeling of the release paper. The transparent hardening layer has good hardness and scratch resistance. The white reflective shielding layer has characteristics such as high reflectivity, high temperature resistance to yellowing, low penetration rate, high surface roughness, high flexibility, low rebound force, good reliability and good flame retardancy. By being arranged on the protective layer 3, it can effectively protect the flexible printed circuit board and prevent the flexible printed circuit board from being damaged.

[0060] In summary, for the barrier adhesive film for flexible printed circuit boards and its production method proposed by the present invention, the raw materials for the preparation of the protective layer 3 include polyurethane acrylate prepolymer, reactive diluent, photoinitiator, leveling agent, inorganic pigment, organic pigment and biaxially oriented polypropylene, and the raw material ratio is as follows: 12 - 39 parts of polyurethane acrylate prepolymer, 22 - 56 parts of reactive diluent, 1.2 - 3.2 parts of photoinitiator, 0.8 - 2.9 parts of leveling agent. The release coating 22 has good comprehensive properties in terms of hardness, solvent resistance and release stability. Polyurethane acrylate can provide a higher crosslinking density for the release coating, thus effectively preventing the strong penetration of isocyanate in the new binder component to the release coating at high temperature, resulting in abnormal peeling of the release paper. The transparent hardening layer has good hardness and scratch resistance. The white reflective shielding layer has characteristics such as high reflectivity, high temperature resistance to yellowing, low penetration rate, high surface roughness, high flexibility, low rebound force, good reliability and good flame retardancy. By being arranged on the protective layer 3, it can effectively protect the flexible printed circuit board and prevent the flexible printed circuit board from being damaged. The organosilicon resin is one or more of acrylated products of organosilicon oil, epoxy modified organosilicon resin, ammonia modified organosilicon resin, polyurethane modified organosilicon resin, fatty acid modified organosilicon resin, silicone rubber resin and organosilicon oil. Applying high temperature resistant silica gel to the intermediate layer of the resist film can achieve good resist performance and avoid the problem of epoxy glue overflowing and remaining on the surface of the metal copper block. The release coating adopts a special formula of organosilicon oil, which is very beneficial to the press molding of printed circuit boards with embedded metal copper blocks. In addition to having good resist performance, it also has moderate fluidity.

[0061] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A barrier film for a flexible circuit board, characterized in that: It comprises a copper paper layer (1), a circuit board is arranged below the copper paper layer (1), and the copper paper layer (1) and the circuit board are connected by an adhesive layer (11); A glue blocking layer (2) is arranged above the coated paper layer (1), and a protective layer (3) is arranged above the glue blocking layer (2); The protective layer (3) comprises a transparent hardened layer (31), a white reflective shielding layer (32), an insulating layer (33) and a waterproof layer (34); the transparent hardened layer (31) is connected to the white reflective shielding layer (32); the white reflective shielding layer (32) is connected to the insulating layer (33); the waterproof layer (34) is connected to the insulating layer (33); the protective layer (3) is prepared from raw materials comprising polyurethane acrylate prepolymer, reactive diluent, photoinitiator, leveling agent, inorganic pigment, organic pigment and biaxially oriented polypropylene, wherein the raw material ratio is as follows: 12 to 39 parts of polyurethane acrylate prepolymer, 22 to 56 parts of reactive diluent, 1.2 to 3.2 parts of photoinitiator and 0.8 to 2.9 parts of leveling agent.

2. The barrier film for a flexible circuit board according to claim 1, characterized in that: The adhesive barrier layer (2) comprises a PET base material layer (21), a release coating (22), a softening layer (23) and an inner adhesive layer (24); the inner adhesive layer (24) is coated on the upper side of the PET base material layer (21); the release coating (22) is coated on the upper side of the inner adhesive layer (24); and the softening layer (23) is coated on the upper side of the release coating (22).

3. The barrier film for a flexible circuit board according to claim 1, characterized in that: The raw materials of the adhesive barrier layer (2) include polyethylene terephthalate, modified polyurethane acrylate, acrylate monomer, silicone resin, silicon dioxide, silicone rubber, diluent solvent, silicone crosslinking agent, anchoring agent, silicone catalyst and cast polypropylene film, wherein the raw material ratio is as follows: 25-48 parts of polyethylene terephthalate, 15-33 parts of modified polyurethane acrylate, 27-46 parts of acrylate monomer, 2.5-6.7 parts of silicone resin, 2.5-6.7 parts of silicon dioxide, 4-18 parts of silicone rubber, 36-58 parts of diluent solvent, 0.3-1.8 parts of silicone crosslinking agent, 0.5-2.3 parts of anchoring agent, 0.1-2.4 parts of silicone catalyst and 11-28 parts of cast polypropylene film.

4. The barrier film for a flexible circuit board according to claim 3, characterized in that: The modified polyurethane acrylate takes isophorone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and trimer thereof as raw materials.

5. The barrier film for a flexible circuit board according to claim 3, characterized in that: The silicone resin is one or more of an acrylic ester product of silicone oil, an epoxy-modified silicone resin, an ammonia-modified silicone resin, a polyurethane-modified silicone resin, a fatty acid-modified silicone resin, a silicone rubber resin and silicone oil.

6. A method for producing a barrier film for a flexible circuit board according to any one of claims 1 to 5, characterized in that: The steps include: S1: a polyurethane acrylate prepolymer, a reactive diluent, a photoinitiator and a leveling agent are mixed to form a transparent hardened layer (31), and an inorganic pigment and an organic pigment are mixed to form a white reflective shielding layer (32); S2: biaxially oriented polypropylene is used to form an insulating layer (33), and a transparent hardened layer (31), a white reflective shielding layer (32) and an insulating layer (33) are superimposed and pressed to form a protective film, and a waterproof coating is coated on the surface of the protective film to form a waterproof layer (34); S3: taking a certain amount of modified polyurethane acrylate, acrylate monomer, silicone resin and silicon dioxide and fusing them to form a release coating (22), and preparing a PET substrate layer (21) with polyethylene terephthalate; S4: mixing organic silicone rubber, diluent solvent, silicone cross-linking agent, anchoring agent and silicone catalyst, stirring and fusing them, and making the mixed liquid into an inner rubber layer (24), and taking a cast polypropylene film into a softening layer (23); S5: stacking the PET substrate layer (21), the inner rubber layer (24), the release coating layer (22) and the softening layer (23) in sequence, and pressing the stacked substrates to form a rubber barrier layer (2); S6: The barrier layer (2) is adhered to the circuit board via the adhesive layer (11), and the protective layer (3) is laminated on the barrier layer (2). The circuit board, the barrier layer (2) and the protective layer (3) are placed on a hot press, and the barrier film is pressed onto the circuit board.

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