A resin composition and a cover film prepared therefrom

Abstract

The present application provides a resin composition and a cover film prepared therefrom, the resin composition comprising the following components by weight: carboxyl-containing polyester resin 45-55 parts, phenolic oxygen resin 18-25 parts, multifunctional epoxy resin 10-15 parts, curing agent 0.2-0.6 parts, the curing agent being 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-s-triazine. The cover film prepared from the resin composition of the present application still has high peel strength, excellent heat aging resistance and chemical resistance after long-time treatment at high temperature, and is very suitable for multilayer flexible printed circuit boards, capable of meeting the processing requirements of multiple pressing and multiple SMT of rigid-flex combined circuit boards, and long-term use at high temperature.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electronic circuit substrate, and relates to a resin composition and a cover film prepared therefrom, in particular to a high heat-aging-resistant resin composition and a cover film prepared therefrom. BACKGROUND

[0002] As a surface protective layer of flexible printed circuit board (FPCB), the cover film protects the circuit from contamination by dust, moisture and chemicals and other forms of damage, plays an insulating and soldering role, and has certain flexibility and reinforcing effect, which can reduce the stress of the conductor in the bending process and improve the bending resistance of the flexible printed circuit board. The most widely used cover film for FPCB is a polyimide film type cover film, which is formed by coating an adhesive (resin composition) on one side of a polyimide film (PI film) and then drying and partially cross-linking. In the past two decades, the cover film for FPCB mainly uses epoxy adhesive, which uses epoxy resin as the main resin and carboxyl nitrile rubber as the toughening agent. However, due to the presence of a large number of unsaturated double bonds in the carboxyl nitrile rubber, it is easy to oxidize and break at high temperatures, and the heat-aging resistance is poor. Therefore, the peel strength of the epoxy adhesive cover film decreases greatly after long-time baking, heat treatment or multiple pressing, which leads to a decrease in adhesion reliability and cannot meet the processing requirements of multiple high-temperature pressing, multiple SMT and long-time use in high-temperature environment of multi-layer flexible circuit boards and rigid-flex combined circuit boards.

[0003] CN102010569A discloses a halogen-free flame-retardant epoxy resin composition and a high-flexibility cover film prepared therefrom, and CN102010567A discloses a halogen-free and phosphorus-free epoxy resin composition and a cover film prepared therefrom. Both of them are epoxy resin compositions with different properties, and both of them use carboxyl nitrile rubber. However, due to the poor heat-aging resistance of carboxyl nitrile rubber, the heat-aging resistance of the cover film prepared from these epoxy resin compositions is also poor.

[0004] Therefore, in the field, it is desirable to develop a material that can solve the problem of heat-aging resistance of epoxy adhesive cover film, and also has high peel strength, chemical resistance and good processability. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims to provide a resin composition and a cover film prepared therefrom, in particular to provide a high heat-aging-resistant resin composition and a cover film prepared therefrom. The resin composition of the present application has good heat-aging resistance, and the cover film prepared therefrom still has high peel strength, excellent heat-aging resistance and chemical resistance after long-time treatment at high temperature, and is very suitable for multilayer flexible printed circuit boards, and can meet the processing requirements of rigid-flexible combined circuit boards for multiple pressing and multiple SMT, and can be used in long-term high-temperature applications.

[0006] To achieve this purpose, the present application adopts the following technical solutions:

[0007] In one aspect, the present application provides a resin composition comprising the following components by weight:

[0008] The carboxyl-containing polyester resin is 45-55 parts, the phenolic oxygen resin is 18-25 parts, the multifunctional epoxy resin is 10-15 parts, the curing agent is 0.2-0.6 parts, the filler is 15-25 parts, and the antioxidant is 0.05-0.15 parts, and the curing agent is 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-s-triazine.

[0009] The resin composition of the present application takes the carboxyl-containing polyester resin as the main resin, cooperates with the phenolic oxygen resin and the multifunctional epoxy resin to improve the flexibility and heat resistance of the resin composition, and endows the resin composition with high heat-aging resistance, adhesion and flexibility. The 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-s-triazine is used as a curing agent to improve the crosslinking density and chemical resistance of the resin composition.

[0010] In the resin composition of the present application, the content of the carboxyl-containing polyester resin can be 45 parts, 48 parts, 50 parts, 52 parts or 55 parts, the content of the phenolic oxygen resin can be 18 parts, 20 parts, 23 parts or 25 parts, the content of the multifunctional epoxy resin can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts or 15 parts, and the content of the curing agent can be 0.2 parts, 0.4 parts, 0.5 parts or 0.6 parts.

[0011] The carboxyl-containing polyester resin has excellent heat-aging resistance and heat resistance, and has high reactivity due to its high acid value and carboxyl content, and can react with epoxy resin. The carboxyl-containing polyester resin can use commercially available products, and exemplary ones include but are not limited to BX-39SS from Toyobo Co., Ltd. or H204 from Hyperbranched Resin Technology.

[0012] If the carboxyl group-containing polyester resin is used in too large an amount in the present application, the glass transition temperature of the resin composition is low, the cover film prepared therefrom is highly tacky, and the FPCB to which the cover film is bonded is likely to be wrinkled when bent. If the carboxyl group-containing polyester resin is too small in amount, the flexibility and adhesiveness of the resin composition are likely to be reduced.

[0013] In the present application, the phenolic oxygen resin has a high glass transition temperature, and thus the flexibility, modulus, glass transition temperature of the resin composition can be improved, and the tackiness of the cover film can be improved. If the phenolic oxygen resin is used in too large an amount in the present application, the adhesiveness of the resin composition is reduced. If the phenolic oxygen resin is used in too small an amount, the modulus and glass transition temperature of the resin composition are low, and the cover film is likely to be wrinkled when the FPCB to which the cover film is bonded is bent. The phenolic oxygen resin can be a commercially available product, and exemplary examples thereof include, but are not limited to, 1276 of Mitsubishi Chemical Corporation, EPONOL Resin 53-BH-35 of Momentive, or PKHH of Inchem.

[0014] Preferably, the acid value of the carboxyl group-containing polyester resin is 25 to 65 mgKOH / g, for example, 25 mgKOH / g, 28 mgKOH / g, 30 mgKOH / g, 32 mgKOH / g, 35 mgKOH / g, 38 mgKOH / g, 40 mgKOH / g, 42 mgKOH / g, 45 mgKOH / g, 48 mgKOH / g, 50 mgKOH / g, 52 mgKOH / g, 55 mgKOH / g, 58 mgKOH / g, 60 mgKOH / g, 62 mgKOH / g, or 65 mgKOH / g. The carboxyl group-containing polyester resin in the present application can be in the form of a solid or a resin solution, and the acid value of the carboxyl group-containing polyester resin is the acid value corresponding to the solid state.

[0015] Preferably, the number average molecular weight of the carboxyl group-containing saturated polyester resin is 5,000 to 20,000, for example, 5,000, 8,000, 10,000, 12,000, 15,000, 18,000, or 20,000.

[0016] Preferably, the glass transition temperature of the carboxyl group-containing saturated polyester resin is -10 to 50°C, for example, -10°C, -8°C, -5°C, -3°C, 0°C, 3°C, 5°C, 8°C, 10°C, 13°C, 15°C, 18°C, 20°C, 25°C, 28°C, 30°C, 35°C, 38°C, 40°C, 43°C, 45°C, 48°C, or 50°C.

[0017] In the present application, the multifunctional epoxy resin can increase the curing crosslinking density of the resin composition, and thus the heat resistance and chemical resistance of the resin cured product can be improved. Preferably, the multifunctional epoxy resin is selected from one or a combination of at least two of a biphenyl type epoxy resin, a phenol type novolac epoxy resin, an o-cresol type novolac epoxy resin, a bisphenol A type novolac epoxy resin, and a dicyclopentadiene phenol type epoxy resin.

[0018] In the present application, the curing agent is 2,4-diamino-6-[2-(2-methyl-1-imidazole) ethyl]-s-triazine, CAS No.: 38668-46-1.

[0019] In the present application, 2,4-diamino-6-[2-(2-methyl-1-imidazole) ethyl]-s-triazine acts as a latent curing agent in the resin composition, and makes the solution and the cover film of the resin composition have a longer pot life. It reacts with the epoxy resin to increase the crosslinking density, heat resistance and chemical resistance of the resin composition. If the amount of 2,4-diamino-6-[2-(2-methyl-1-imidazole) ethyl]-s-triazine is too small, the chemical resistance of the resin composition is poor; if 2,4-diamino-6-[2-(2-methyl-1-imidazole) ethyl]-s-triazine is too much, the gelation time of the resin composition is shortened, which is not conducive to the storage of the resin composition solution. It is found that the commonly used imidazole compounds such as 2-methyl imidazole, 2-undecyl imidazole, isocyanide-2-ethyl-4-methyl imidazole (2E4MZ-CN) and amine curing agents such as dicyandiamide are not suitable for the curing agent of the resin composition of the present application. The commonly used imidazole compounds can reduce the chemical resistance and storage period of the cover film, and dicyandiamide can reduce the heat resistance and moisture resistance of the cover film.

[0020] Preferably, the resin composition further contains 15-25 parts of a filler, and the content of the filler can be 15 parts, 18 parts, 20 parts, 22 parts or 25 parts.

[0021] The filler is an inorganic filler or an organic filler, wherein the inorganic filler is at least one of aluminum hydroxide, magnesium hydroxide, boehmite, talc, silicon dioxide, kaolin, aluminum oxide, and the organic filler is at least one of aluminum diethylphosphinate, melamine cyanamide and other organic fillers.

[0022] Preferably, the resin composition further contains 0.05-0.15 parts of an antioxidant, and the content of the antioxidant can be 0.05 parts, 0.08 parts, 0.1 parts, 0.12 parts or 0.15 parts.

[0023] The antioxidant is a hindered phenol antioxidant or a hindered amine antioxidant. The antioxidant can delay the oxidation of the epoxy resin composition during high temperature curing and subsequent processing applications. The antioxidant can be a hindered phenol antioxidant CHINOX 1010, CHINOX 1076, CHINOX 1098, CHINOZ 1325 (all from Double Bond Chemical Industry Co., Ltd.), and the like. The hindered amine antioxidant can be DNP (Kaiyuan Fine Chemicals), and the like.

[0024] In another aspect, the present application provides a resin adhesive solution, which is obtained by dissolving or dispersing the resin composition as described above in an organic solvent.

[0025] Preferably, the organic solvent is selected from one or a combination of at least two of acetone, butanone, cyclohexanone, ethylene glycol monomethyl ether, propylene glycol methyl ether, propylene glycol methyl ether acetate, ethyl acetate, butyl acetate, dimethyl sulfoxide.

[0026] In the present application, the organic solvent is used to dissolve the curing agent and the resin, disperse the filler, and adjust the viscosity of the resin composition solution. The prepared resin composition solution has a solid content of 35%-45% and a suitable solution viscosity, which can provide good processability.

[0027] In another aspect, the present application provides a cover film, which comprises a polymer base film, an adhesive layer on the polymer base film, and a release paper layer on the adhesive layer, wherein the adhesive layer is formed of the resin composition as described above.

[0028] Preferably, the polymer base film is a polyimide film.

[0029] Preferably, the thickness of the polymer base film is 7.5-50 μm, for example, 7.5 μm, 9 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0030] Preferably, the thickness of the adhesive layer is 5-50 μm, for example, 5 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0031] Preferably, the thickness of the release paper layer is 110-130 μm, for example, 110 μm, 112 μm, 115 μm, 118 μm, 120 μm, 122 μm, 125 μm, 128 μm, or 130 μm.

[0032] The resin composition of the present application is prepared by mixing the components of the present application together using a bead mill and a high shear stirring dispersing device. The resin composition is then coated on one surface of a polyimide film using a coater and dried in an oven at 140°C for 5 minutes to remove the organic solvent and partially cross-link the resin composition, thereby forming a semi-cured resin composition layer on the polyimide film. The resin composition layer is then laminated with a release paper at a lamination temperature of 80°C and wound to obtain a coverlay film.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] The resin composition of the present application uses a carboxyl-containing polyester resin as the main resin, and a phenolic oxygen-containing resin and a multifunctional epoxy resin are used to improve the flexibility and heat resistance of the resin composition, and to impart high heat aging resistance, adhesion and flexibility to the resin composition. The use of 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-s-triazine as a curing agent improves the cross-linking density and chemical resistance of the resin composition, so that the coverlay film prepared therefrom still has high peel strength, excellent heat aging resistance and chemical resistance after long-term treatment at high temperature, and is very suitable for multi-layer flexible printed circuit boards, can meet the processing requirements of multiple lamination and multiple SMT of rigid-flexible combined circuit boards, and can be used for long-term use at high temperature. DETAILED DESCRIPTION

[0035] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0036] Example 1

[0037] A resin composition comprising: carboxyl-containing polyester resin (BX-39SS, Toyo Rika Co., Ltd.) 50 parts by weight, phenolic oxygen-containing resin (1276, Mitsubishi Chemical Corporation) 21 parts by weight, biphenyl-type epoxy resin (NC-3000H, Japan Chemical Industry Co., Ltd.) 12 parts by weight, 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-s-triazine (2MZ-A, Shikoku Chemicals Corporation) 0.4 parts by weight, aluminum diethyl phosphinate (OP-935, Clariant) 20 parts by weight, and antioxidant 1010 (CHINOX 1010, Shuangjian Chemical Industry Co., Ltd.) 0.1 parts by weight.

[0038] The solid components are dissolved and dispersed in an organic solvent according to the above proportions, and butanone is used to adjust the resin composition glue to have a solid content of 40%.

[0039] Examples 2-3, Comparative Examples 1-12

[0040] A resin composition, components and their contents as shown in Table 1, Table 2; the amount of each component in Table 1-2 is in parts by weight (i.e. parts by weight of solid without solvent).

[0041] The resin composition glue of Examples 1-3, Comparative Examples 1-12 were respectively coated onto a polyimide film (TL-012, Dymax Technology Co., Ltd.) with a coating machine to a thickness of 12.5 μm, the thickness of the resin composition layer was controlled to be 15 μm, and then placed in an oven at 160°C for 5 minutes to form a partially cross-linked and cured resin composition layer on the polyimide film, and then the resin composition layer was laminated with 120 μm release paper at a lamination temperature of 75°C to obtain a cover film.

[0042] The performance of the cover film of Examples 1-3, Comparative Examples 1-12 was tested, and the results are shown in Table 1, Table 2.

[0043] Table 1

[0044]

[0045]

[0046] Table 2

[0047]

[0048] The test method for the performance of the above cover film is as follows:

[0049] (1) Peel strength: tested according to IPC-TM-650 2.4.9 method, the cover film was first laminated with 18 μm rolled copper foil (BHYX-92F-T, Nikkan Kogyo Co., Ltd.) smooth surface, and then the peel strength was tested after baking at 160°C for 1 hour.

[0050] (2) Heat aging resistance: the cover film was first laminated with 18 μm rolled copper foil (BHYX-92F-T, Nikkan Kogyo Co., Ltd.) smooth surface, and then the peel strength was tested after baking at 200°C for 6 hours.

[0051] (3) Chemical resistance: tested according to IPC-TM-650 2.3.2 method. The chemical resistance of the cover film was characterized by the peel strength retention rate, i.e. the peel strength of the sample after chemical treatment / the peel strength before treatment x 100%. The higher the peel strength retention rate, the better the chemical resistance, and vice versa, which will cause the FPCB to drop during the wet process.

[0052] (4) Bending wrinkle: The cover film was pressed on both sides of flexible copper clad plate SF305 10H20DE (a product commercially available from Shengyi Science and Technology Co., Ltd.), and baked at 160°C for 1 hour. The cured material was cut into a test sample with a width of 10 mm and a length of not less than 50 mm. A 1.0 mm thick plug gauge was selected, and the sample was manually bent 5 times. The sample after bending was sliced and analyzed, and the wrinkle height was measured. The cover film wrinkle at the bending position was observed, and the wrinkle degree (wrinkle height) was classified into no wrinkle (the bending surface was smooth, and the wrinkle height was 0 μm), slight wrinkle (0 μm < wrinkle height ≤ 15 μm), and severe wrinkle (wrinkle height > 15 μm).

[0053] As shown in Table 1, the resin composition in the present application enables the cover film to have a peel strength of 1.12 N / mm or more, a heat aging resistance of 0.73 N / mm or more, a chemical resistance of 95% or more, and no bending wrinkle.

[0054] Comparative Example 1 did not use a phenolic oxygen resin, and the cover film had severe wrinkle. In Comparative Examples 2-4, the curing agent was replaced by 2-undecylimidazole, 2E4MZ-A, and blocked isocyanate, respectively, and the corresponding cover film had a significantly reduced chemical resistance. In Comparative Example 5, the amount of phenolic oxygen resin was too small, and the cover film had slight wrinkle. In Comparative Example 6, the amount of phenolic oxygen resin was too large, and the cover film had a reduced peel strength and poor heat aging resistance. In Comparative Example 7, the amount of multifunctional epoxy resin was too small, and the cover film had poor heat aging resistance and poor chemical resistance. In Comparative Example 8, the amount of multifunctional epoxy resin was too large, and the cover film had a reduced peel strength and poor heat aging resistance. In Comparative Example 9, the amount of curing agent 2,4-diamino-6-[2-(2-methyl-1-imidazole) ethyl]-S-triazine was too small, and the cover film had poor heat aging resistance and poor chemical resistance. In Comparative Example 10, the amount of curing agent 2,4-diamino-6-[2-(2-methyl-1-imidazole) ethyl]-S-triazine was too large, and the cover film had a reduced peel strength and poor heat aging resistance. In Comparative Example 11, the amount of carboxyl-containing polyester resin was too large, and the cover film had a reduced chemical resistance and slight wrinkle. In Comparative Example 12, the amount of carboxyl-containing polyester resin was too small, and the cover film had a reduced peel strength and poor heat aging resistance.

[0055] The applicant states that the high heat aging resistant resin composition of the present application and the cover film prepared therefrom are illustrated by the above examples, but the present application is not limited to the above examples, i.e., it does not mean that the present application must rely on the above examples to be implemented. It should be understood by those skilled in the art that any improvement on the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific modes, etc. all fall within the protection scope and disclosure scope of the present application.

Claims

1. A resin composition, characterized in that, The resin composition comprises the following components in parts by weight: The mixture contains 45-55 parts of carboxyl polyester resin, 18-25 parts of phenolic resin, 10-15 parts of multifunctional epoxy resin, and 0.2-0.6 parts of curing agent, wherein the curing agent is 2,4-diamino-6-[2-(2-methyl-1-imidazolium)ethyl]-s-triazine; The acid value of the carboxyl-containing polyester resin is 25-65 mg KOH / g; The multifunctional epoxy resin is a biphenyl-type epoxy resin.

2. The resin composition according to claim 1, characterized in that, The resin composition also contains 15-25 parts of filler.

3. The resin composition according to claim 2, characterized in that, The packing material can be inorganic or organic.

4. The resin composition according to claim 3, characterized in that, The inorganic filler is at least one of aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, kaolin, or alumina.

5. The resin composition according to claim 3, characterized in that, The organic filler is at least one of aluminum diethylphosphinate, melamine, or cyanuric acid.

6. The resin composition according to claim 1, characterized in that, The resin composition also contains 0.05-0.15 parts of antioxidant.

7. The resin composition according to claim 6, characterized in that, The antioxidant is a hindered phenolic antioxidant or a hindered amine antioxidant.

8. A resin adhesive, characterized in that, It is obtained by dissolving or dispersing the resin composition as described in any one of claims 1-7 in an organic solvent.

9. The resin adhesive according to claim 8, characterized in that, The organic solvent is selected from one or a combination of at least two of acetone, butanone, cyclohexanone, ethylene glycol monomethyl ether, propylene glycol methyl ether, propylene glycol methyl ether acetate, ethyl acetate, butyl acetate, and dimethyl sulfoxide.

10. The resin adhesive according to claim 8, characterized in that, The solid content of the resin solution is 35%-45%.

11. A covering film, characterized in that, The cover film comprises a polymer base film, an adhesive layer on the polymer base film, and a release paper layer on the adhesive layer, wherein the adhesive layer is formed of a resin composition as described in any one of claims 1-7.

12. The covering film according to claim 11, characterized in that, The polymer base film is a polyimide film.

13. The covering film according to claim 11, characterized in that, The thickness of the polymer base film is 7.5-50 μm.

14. The covering film according to claim 11, characterized in that, The thickness of the adhesive layer is 5-50 μm.

15. The covering film according to claim 11, characterized in that, The thickness of the release paper layer is 110-130 μm.

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