A resin composition and a flexible copper clad plate prepared therefrom

Abstract

The present application relates to a kind of resin composition and the flexible copper-clad plate prepared by it, the resin composition includes the following weight parts of component: carboxyl saturated polyester resin 40-50 parts, phenolic oxygen resin 15-20 parts, liquid epoxy resin 5-10 parts and 1-cyanoethyl-2-ethyl-4-methyl imidazole 0.05-0.15 parts.The present application uses carboxyl saturated polyester resin and phenolic oxygen resin blend as main resin, introduces liquid epoxy resin, effectively improves the wettability and filling of copper foil;1-cyanoethyl-2-ethyl-4-methyl imidazole is used simultaneously, avoids the problem that the peeling strength of plate is caused by the solvent residue due to the use of high boiling point solvent, the obtained resin composition is prepared copper-clad plate sub apparent no bubble is generated, peeling strength is high, and the aging resistance is excellent, very suitable for high reliability application field such as vehicle-mounted power battery.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit substrate technology, and more particularly to a resin composition and the flexible copper-clad laminate prepared therefrom. Background Technology

[0002] Flexible copper-clad laminates (CCLs) are characterized by their lightness, thinness, and flexibility, and are used to manufacture flexible printed circuit boards (PCBs). Based on manufacturing processes or product structures, flexible CCLs can be classified into two-layer flexible CCLs (also known as adhesive-free flexible CCLs) and three-layer flexible CCLs (also known as adhesive-coated flexible CCLs). Adhesive-free flexible CCLs have only two layers: copper foil and polyimide. They possess high reliability characteristics such as high heat resistance, high aging resistance, and resistance to ion migration. Adhesive-coated flexible CCLs, on the other hand, have an additional adhesive layer between the copper foil and the polyimide film. The performance of this adhesive plays a decisive role in the performance of adhesive-coated flexible CCLs. Currently, the epoxy adhesives commonly used in flexible copper clad laminates are made of carboxylated nitrile rubber toughened epoxy resin. The unsaturated double bond energy and covalent bond dissociation energy of the carboxylated nitrile rubber molecular chain are low, making it prone to chemical reactions or breakage under the influence of heat, oxygen, and light. In addition, the carboxylated nitrile rubber has a high content of impurity ions such as chloride ions, which makes the aging resistance and ion migration resistance of epoxy adhesive flexible copper clad laminates poor.

[0003] CN107674388A discloses a resin composition comprising a carboxyl-containing polyester resin, a multifunctional epoxy resin, a nitrogen-containing epoxy compound, a flame retardant, and a solvent. Films, cover films, and copper-clad laminates prepared using this resin composition exhibit advantages such as halogen-free properties, high temperature resistance, aging resistance, excellent flexibility, and high peel strength. However, this patent uses a high amount of carboxyl-containing polyester resin, and the multifunctional epoxy resins used are all solid, resulting in a high overall melting temperature of the resin composition. It neglects issues related to continuous production, low rolling temperatures, and poor wettability and filling properties of the resin composition on rough copper foil surfaces.

[0004] CN103483586A discloses a modified polyimide resin as a toughening agent for epoxy resin; CN107793702A discloses a resin composition for adhesive films and cover films, which comprises polyamide-imide resin, epoxy resin, and phosphorus-containing phenolic resin. Both of these resin compositions, with polyamide-imide resin as the main component, do not contain carboxyl-based nitrile rubber and exhibit excellent heat aging resistance. Adhesive films or cover films made from them possess high Tg, high heat resistance, and good flame retardancy. However, the high material cost of polyimide resin compositions and polyamide-imide resin compositions limits their widespread application.

[0005] CN116410684A discloses a resin composition and a cover film prepared therefrom, comprising a carboxyl-containing polyester resin, a phenolic resin, a multifunctional epoxy resin (all solid), and a 2,4-diamino-6-[2-(2-methyl-1-imidazolium)ethyl]-s-triazine curing agent. The cover film prepared therefrom still has high peel strength, excellent heat aging resistance and chemical resistance after high temperature and long-term treatment. However, when it is applied to flexible copper-clad laminates and cured, micro-bubbles appear on the board surface, and the peel strength of the copper foil is low.

[0006] With the increasing demands on the reliability of flexible printed circuit boards in electronic product applications, high reliability requirements are also being placed on flexible copper clad laminates. Therefore, improving the reliability of adhesive-bonded flexible copper clad laminates, and thus enhancing the safety and reliability of electronic products, is of practical significance. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a resin composition and a flexible copper-clad laminate prepared therefrom. This invention uses a blend of carboxyl-saturated polyester resin and phenolic resin as the main resin, and introduces liquid epoxy resin, effectively improving the wettability and filling properties of the copper foil. Simultaneously, the use of 1-cyanoethyl-2-ethyl-4-methylimidazole avoids the problem of reduced peel strength caused by solvent residue due to the use of high-boiling-point solvents. The resulting copper-clad laminate prepared from this resin composition exhibits no apparent bubble formation, high peel strength, and excellent aging resistance, making it highly suitable for high-reliability applications such as automotive power batteries.

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

[0009] In a first aspect, the present invention provides a resin composition comprising the following components in parts by weight:

[0010] 40-50 parts of carboxyl-saturated polyester resin, 15-20 parts of phenolic resin, 5-10 parts of liquid epoxy resin, and 0.05-0.15 parts of 1-cyanoethyl-2-ethyl-4-methylimidazolium.

[0011] The "parts" and "parts by weight" used in this invention are calculated based on solid content and do not include solvents, dispersants, etc.

[0012] In this invention, the carboxyl-saturated polyester resin can be, for example, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, etc.; the phenolic resin can be, for example, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc.; the liquid epoxy resin can be, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.; and the imidazole curing agent can be, for example, 0.05 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.12 parts, 0.14 parts, 0.15 parts, etc.

[0013] This invention uses a blend of carboxyl-saturated polyester resin and phenolic resin as the main resin, giving the resin composition excellent aging resistance. By introducing a small-molecule epoxy resin that is liquid at room temperature (i.e., liquid epoxy resin), the wettability and filling properties of the copper foil are effectively improved. This overcomes the defects of carboxyl-saturated polyester resin and phenolic resin, which have poor wettability and filling properties on the rough surface of the copper foil under low rolling temperature during continuous production of adhesive flexible copper clad laminates due to their high melt viscosity, as well as the defects of insufficient board compaction and low peel strength. At the same time, 1-cyanoethyl-2-ethyl-4-methylimidazolium is used as a specific imidazole curing agent. This substance is soluble in low-boiling-point solvents, effectively avoiding the problem of reduced board peel strength and sub-surface microbubbles caused by the use of high-boiling-point solvents and incomplete evaporation during coating, which result in the resin composition remaining in the adhesive layer.

[0014] In this invention, the carboxyl-saturated polyester resin exhibits excellent heat aging resistance and heat resistance, and because it contains carboxyl groups, it can react with liquid epoxy resin. If too much carboxyl-saturated polyester resin is used, the glass transition temperature of the resin composition will be low, resulting in poor bending resistance of the flexible copper-clad laminate prepared from it; if too little carboxyl-saturated polyester resin is used, the flexibility and adhesion of the resin composition will decrease.

[0015] In this invention, the phenolic resin is an ultra-high molecular weight epoxy resin with a high glass transition temperature, which can improve the flexibility, modulus, and glass transition temperature of the resin composition. Too much phenolic resin reduces the adhesiveness of the resin composition; too little phenolic resin results in a lower modulus and glass transition temperature, and reduces the bending resistance of the flexible copper-clad laminate.

[0016] In this invention, the liquid epoxy resin refers to a low molecular weight epoxy resin that is liquid at room temperature. It not only reacts with carboxyl-saturated polyester resin but also helps improve the wetting and filling properties of the resin composition on the rough surface of the copper foil during roll lamination. If too much liquid epoxy resin is used, the amount of corresponding large molecular weight resins such as carboxyl-saturated polyester resin and phenolic resin decreases, thus reducing the flexibility of the resin composition. Conversely, if too little liquid epoxy resin is used, the amount of corresponding large molecular weight resins such as carboxyl-saturated polyester resin and phenolic resin increases, thus reducing the wettability and filling properties of the resin composition on the rough surface of the copper foil.

[0017] In this invention, the 1-cyanoethyl-2-ethyl-4-methylimidazole can be used as a curing agent for liquid epoxy resin and as an accelerator for the reaction between carboxyl saturated polyester resin and epoxy resin. Using this substance effectively avoids the defects of reduced peel strength of the board caused by the use of high-boiling-point solvents and incomplete evaporation during coating, which leave residues in the adhesive layer.

[0018] Preferably, the resin composition further includes an organic solvent.

[0019] Preferably, the organic solvent added to the resin composition has a solid content of 35-45%, for example, 35%, 36%, 38%, 40%, 42%, 44%, 46%, etc.

[0020] Preferably, the boiling point of the organic solvent is ≤100℃, for example, it can be 10℃, 20℃, 50℃, 80℃ or 90℃.

[0021] Preferably, the organic solvent includes any one or a combination of at least two of butanone, acetone, or ethyl acetate.

[0022] Preferably, the solvent residue content of the semi-cured resin composition obtained after partial cross-linking and curing of the resin composition by heating is ≤0.5%, for example, it can be 0.45%, 0.4%, 0.35%, 0.3%, 0.25%, 0.2%, 0.15%, 0.1%, 0.05%, etc.

[0023] The heating described in this invention is performed at 80-160℃ (e.g., 80℃, 100℃, 120℃, 140℃, 160℃, etc.) for 2-5 minutes (e.g., 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, etc.) to partially crosslink and cure the resin composition, thereby obtaining a semi-cured resin composition, and then the solvent residue content is tested.

[0024] In this invention, by selecting a low-boiling-point solvent, the solvent residue of the volatile components after the resin composition is partially cross-linked and cured by heating is low. When applied to copper-clad laminates, no bubbles are generated on the first appearance, and the resulting copper-clad laminate has high peel strength.

[0025] While increasing the oven drying temperature can reduce solvent residue, high temperatures also accelerate the cross-linking reaction of the resin composition, increasing its melt viscosity. This results in poorer wetting and filling properties on the rough surface of the copper foil, leading to a decrease in the peel strength of the board. In cover film products, high-boiling-point solvents remaining in the resin layer can be expelled during baking through the micropores in the polymer base film and release paper protective layer. However, in flexible copper-clad laminates, the aforementioned venting micropores are absent in the dense structure of the copper foil, making solvent residue more likely to cause microbubble defects on the subsurface of the board.

[0026] Preferably, the acid value of the carboxyl-saturated polyester resin is 10-25 mgKOH / g, for example, it can be 10 mgKOH / g, 14 mgKOH / g, 18 mgKOH / g, 22 mgKOH / g, 25 mgKOH / g, etc.

[0027] In this invention, the carboxyl-saturated polyester resin contains carboxyl groups and has a high acid value and high reactivity, and can react with liquid epoxy resin.

[0028] Preferably, the number average molecular weight of the carboxyl-saturated polyester resin is 5,000-20,000, for example, it can be 5,000, 8,000, 10,000, 14,000, 16,000, 20,000, etc.

[0029] Preferably, the weight-average molecular weight of the phenolic resin is 45,000-65,000, for example, it can be 45,000, 48,000, 54,000, 58,000, 62,000, 65,000, etc.

[0030] For example, number-average molecular weight and weight-average molecular weight can be determined by GB / T 21863-2008, based on polystyrene calibration, by gel permeation chromatography (GPC).

[0031] Preferably, the liquid epoxy resin includes any one or a combination of at least two of bisphenol A type epoxy resin, bisphenol F type epoxy resin, glycidyl ester epoxy resin, or glycidylamine epoxy resin.

[0032] Preferably, the epoxy equivalent of the liquid epoxy resin is 80-200 g / eq, for example, it can be 80 g / eq, 100 g / eq, 120 g / eq, 140 g / eq, 160 g / eq, 180 g / eq, 200 g / eq, etc.

[0033] In this invention, the liquid epoxy resin refers to an epoxy resin that is liquid at a temperature of 20°C. For example, the determination of whether an epoxy resin is liquid or solid can be performed according to Appendix 2, "Method for Confirmation of Liquid State," of the Ministry Ordinance on Testing and Properties of Hazardous Materials (Ordinance No. 1 of the Ministry of Housing and Urban-Rural Development, Heisei 1). For details, please refer to the specific determination method in CN118325282A.

[0034] Preferably, the resin composition further includes 10-20 parts of a phosphorus-containing flame retardant, for example, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, etc.

[0035] Preferably, the phosphorus-containing flame retardant includes any one or a combination of at least two of aluminum diethylphosphonate, melamine polyphosphate, or hexaphenoxycyclotriphosphazene.

[0036] Preferably, the resin composition further includes 5-10 parts of inorganic filler, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc.

[0037] Preferably, the inorganic filler includes any one or a combination of at least two of aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, kaolin, or alumina.

[0038] Preferably, the resin composition further includes 0.2-0.5 parts of an antioxidant, such as 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc.

[0039] Preferably, the antioxidant includes hindered phenolic antioxidants and / or hindered amine antioxidants.

[0040] In this invention, the antioxidant can delay the oxidation of the epoxy resin composition during high-temperature curing and subsequent processing. The antioxidants used include, but are not limited to, any one or a combination of at least two of the hindered phenolic antioxidants CHINOX 1010, CHINOX 1076, CHINOX 1098, CHINOX 1325 (all manufactured by Double Bond Chemical Co., Ltd.) or hindered amine antioxidants DNP (manufactured by Kaiyuan Fine Chemical Co., Ltd.).

[0041] In a second aspect, the present invention provides a resin film, the material of which comprises the resin composition as described in the first aspect.

[0042] Preferably, the resin film is obtained by coating the resin composition onto a release material and then drying and / or semi-curing it.

[0043] Thirdly, the present invention provides a flexible copper-clad laminate, the flexible copper-clad laminate comprising a base film and a resin layer located on one or both sides of the base film, wherein a copper foil is disposed on the surface of the resin layer; the resin layer is a coating of the resin composition as described in the first aspect.

[0044] Preferably, the base film comprises a polyimide film.

[0045] Preferably, the thickness of the base film is 12.5-50 μm, for example, it can be 12.5 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc.

[0046] Preferably, the thickness of the resin layer is 10-50 μm, for example, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc.

[0047] Preferably, the thickness of the copper foil is 12-70 μm, for example, it can be 12 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, etc.

[0048] For example, the preparation method of the flexible copper-clad laminate of the present invention includes: coating the resin composition on one or both sides of the base film and drying it; then rolling copper foil onto the surface of the resin composition and curing it to obtain the flexible copper-clad laminate.

[0049] Preferably, the drying temperature is 80-160℃, for example, it can be 80℃, 100℃, 120℃, 140℃, 160℃, etc.

[0050] Preferably, the drying time is 2-5 minutes, for example, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, etc.

[0051] Preferably, the temperature of the roller pressing is 70-90℃, for example, it can be 70℃, 75℃, 80℃, 85℃, 90℃, etc.

[0052] Preferably, the curing temperature is 160-180℃, for example, it can be 160℃, 165℃, 170℃, 175℃, 180℃, etc.

[0053] Preferably, the curing time is 1.5-2.5 hours, for example, 1.5 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.5 hours, etc.

[0054] Compared with the prior art, the present invention has at least the following beneficial effects:

[0055] This invention uses a blend of carboxyl-saturated polyester resin and phenolic resin as the main resin, giving the resin composition excellent aging resistance. By introducing a small-molecule epoxy resin that is liquid at room temperature (i.e., liquid epoxy resin), the wettability and filling properties of the copper foil are effectively improved. At the same time, 1-cyanoethyl-2-ethyl-4-methylimidazolium is used as a specific imidazolium curing agent, which effectively avoids the problem of the resin composition remaining in the adhesive layer due to the use of high-boiling-point solvents and incomplete evaporation during coating, resulting in a decrease in the peel strength or heat resistance of the board.

[0056] The resin composition provided by this invention has low residual solvent after heating and curing, and good wettability to copper foil. When applied to copper-clad laminates, no bubbles are generated on the subsurface. At the same time, the peel strength of the copper-clad laminate obtained reaches 1.61-1.68 N / mm, and it can still reach more than 1.46 N / mm after being treated at 125°C for 1000 hours. It has excellent aging resistance and is suitable for high-reliability applications such as automotive power batteries. Detailed Implementation

[0057] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0058] The materials used in the following embodiments are from the following sources:

[0059] Carboxyl-saturated polyester resin, brand name RV-74SS, Toyobo Co., Ltd., acid value 17mgKOH / g, number average molecular weight 16000;

[0060] Carboxyl-saturated polyester resin, brand name AL-148, Suzhou Hanhai New Material Co., Ltd., acid value 15mgKOH / g, number average molecular weight 15000;

[0061] Phenoxy resin, grade 1276, Mitsubishi Chemical Corporation, with a weight-average molecular weight of 51,000.

[0062] Phenoxy resin, brand name PKHJ, InChem Corporation, weight average molecular weight is 57,000;

[0063] Bisphenol A type epoxy resin 1, liquid, grade GELR128E, epoxy equivalent 185g / eq, Hongchang Electronic Materials Co., Ltd.

[0064] Bisphenol A type epoxy resin 2, solid, grade GESR901, epoxy equivalent 465g / eq, Hongchang Electronic Materials Co., Ltd.

[0065] Bisphenol F type epoxy resin 1, liquid, grade KF-8100, epoxy equivalent 170g / eq, KOLON INDUSTRIES;

[0066] 1-Cyanoethyl-2-ethyl-4-methylimidazole, Shikoku Kasei Corporation;

[0067] Aluminum diethylphosphinate, grade OP-935, Clariant;

[0068] Boehmite, grade APYRAL AOH 60, Nabaltec AG;

[0069] Antioxidant 1010, brand name CHINOX 1010, manufactured by Double Bond Chemical Company;

[0070] 2,4-Diamino-6-[2-(2-methyl-1-imidazolium)ethyl]-S-triazine, Shanghai Haodeng Materials Co., Ltd.;

[0071] 2-Undecylimidazole, Shikoku Chemical Co., Ltd.

[0072] Examples 1-3, Comparative Examples 1-3

[0073] The above embodiments and comparative examples each provide a resin composition, the components and amounts (parts by weight of solids) of which are shown in Table 1 and Table 2. The solid components are dissolved and dispersed in an organic solvent according to the proportions in Table 1 and Table 2 to obtain resin compositions with a solid content of 40%.

[0074] The resin compositions provided in Examples 1-3 and Comparative Examples 1-3 were coated onto a 25 μm thick polyimide film (GF05, PI Advanced Materials Co., Ltd.) using a coating machine, with the resin composition layer thickness controlled at 38 μm. The layers were then baked in an oven at 140°C for 3 minutes to form a partially cross-linked and cured resin composition layer on the polyimide film. This layer was then rolled and laminated with a 35 μm rolled copper foil (BHYX, Nikko Metals Co., Ltd.) at a rolling temperature of 80°C to form a single-sided flexible copper clad laminate semi-finished product. The above coating, baking, and rolling lamination process was then repeated on the PI film surface of the single-sided flexible copper clad laminate semi-finished product to form a double-sided flexible copper clad laminate semi-finished product. Finally, the product was cured at 170°C for 2 hours to obtain the finished flexible copper clad laminate.

[0075] Test case

[0076] The solvent residue content of the semi-cured resin obtained after heating and semi-curing of the resin compositions provided in Examples 1-3 and Comparative Examples 1-3, and the performance of the prepared flexible copper-clad laminates were tested. The results are shown in Tables 1 and 2.

[0077] Table 1

[0078]

[0079] Table 2

[0080]

[0081]

[0082] The above performance testing methods are as follows:

[0083] (1) Solvent residual content:

[0084] The resin composition is coated onto the surface of a polyimide film base using a coating machine, dried in an oven, and heated at 140°C for 3 minutes to remove the organic solvent and partially crosslink and cure the resin composition, forming a semi-cured resin composition layer on the surface of the polyimide film base.

[0085] The polyimide film base was cut into 10cm×10cm pieces, and the weight was measured using an electronic balance. The weight of the three samples was measured, and the average value was taken as the mass of the polyimide film base.

[0086] The carrier resin film (polyimide film base film + semi-cured resin composition layer) was cut into 10cm × 10cm pieces, and its initial mass was determined using an electronic balance. Next, the carrier resin film was placed on a metal mesh and heated in an oven pre-set to 200℃ for 15 minutes, then transferred to a desiccator and allowed to stand for 30 minutes to cool to room temperature. Then, the mass of the carrier resin film after baking was determined using an electronic balance. The initial mass and the mass after baking of all three samples were measured, and the average value was used to calculate the amount of solvent contained in the semi-cured resin layer (residual solvent content):

[0087] Residual solvent content (mass%) = 100 × (initial mass of carrier resin film - mass of carrier resin film after baking) / (initial mass of carrier resin film - mass of polyimide film base film).

[0088] (2) Peel strength: Tested according to IPC-TM-650 2.4.9 method, in the receiving state (A state).

[0089] (3) Heat aging resistance: After baking the sample in an oven at 125℃ for 1000h, take it out and test the peel strength. The test conditions are E-1000 / 125.

[0090] (4) Secondary appearance: After etching the copper foil of the flexible copper-clad laminate, the secondary surface of the board should be free of defects such as microbubbles, missing glue, white spots, and foreign matter.

[0091] As can be seen from Examples 1-3, the resin composition provided by the present invention has low residual solvent after heating and curing, and good wettability to copper foil. When applied to copper-clad laminates, no bubbles are generated on the subsurface. At the same time, the peel strength of the copper-clad laminate obtained reaches 1.61-1.68 N / mm, and can still reach more than 1.46 N / mm after being treated at 125°C for 1000 hours, showing excellent aging resistance.

[0092] A comparison of Example 1 and Comparative Examples 1-3 shows that in Comparative Example 1, solid bisphenol A epoxy resin was used, resulting in poor wettability of the resin composition on the copper foil during rolling, leading to low peel strength of the board. In Comparative Example 2, 2,4-diamino-6-[2-(2-methyl-1-imidazolium)ethyl]-s-triazine was used instead of 1-cyanoethyl-2-ethyl-4-methylimidazolium. Since 2,4-diamino-6-[2-(2-methyl-1-imidazolium)ethyl]-s-triazine is poorly soluble in butanone and requires the use of the high-boiling-point solvent dimethyl sulfoxide for dissolution, during the preparation of double-sided flexible copper-clad laminates, the high-boiling-point solvent did not completely evaporate and remained in the adhesive layer, causing problems such as microbubbling and decreased peel strength during curing, resulting in poor aging resistance of the board. In Comparative Example 3, 2-undecylimidazolium was used instead of 1-cyanoethyl-2-ethyl-4-methylimidazolium, resulting in a decrease in peel strength and heat aging resistance of the board.

[0093] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A resin composition, characterized in that, The resin composition comprises the following components in parts by weight: 40-50 parts of carboxyl-saturated polyester resin, 15-20 parts of phenolic resin, 5-10 parts of liquid epoxy resin and 0.05-0.15 parts of 1-cyanoethyl-2-ethyl-4-methylimidazolium; The resin composition further includes an organic solvent; The boiling point of the organic solvent is ≤100℃.

2. The resin composition according to claim 1, characterized in that, The organic solvent added to the resin composition has a solid content of 35-45%.

3. The resin composition according to claim 1, characterized in that, The organic solvent includes any one or a combination of at least two of butanone, acetone, or ethyl acetate.

4. The resin composition according to claim 1, characterized in that, The solvent residue content of the semi-cured resin composition obtained after the resin composition is partially cross-linked and cured by heating is ≤0.5%.

5. The resin composition according to claim 1, characterized in that, The acid value of the carboxyl-saturated polyester resin is 10-25 mgKOH / g.

6. The resin composition according to claim 1, characterized in that, The number average molecular weight of the carboxyl-saturated polyester resin is 5000-20000.

7. The resin composition according to claim 1, characterized in that, The weight-average molecular weight of the phenolic resin is 45,000-65,000.

8. The resin composition according to claim 1, characterized in that, The liquid epoxy resin includes any one or a combination of at least two of bisphenol A type epoxy resin, bisphenol F type epoxy resin, glycidyl ester epoxy resin, or glycidylamine epoxy resin.

9. The resin composition according to claim 1, characterized in that, The epoxy equivalent of the liquid epoxy resin is 80-200 g / eq.

10. The resin composition according to claim 1, characterized in that, The resin composition also includes 10-20 parts of a phosphorus-containing flame retardant.

11. The resin composition according to claim 10, characterized in that, The phosphorus-containing flame retardant includes any one or a combination of at least two of aluminum diethylphosphonate, melamine polyphosphate, or hexaphenoxycyclotriphosphazene.

12. The resin composition according to claim 1, characterized in that, The resin composition further includes 5-10 parts of inorganic filler.

13. The resin composition according to claim 12, characterized in that, The inorganic filler includes any one or a combination of at least two of aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, kaolin, or alumina.

14. The resin composition according to claim 1, characterized in that, The resin composition further includes 0.2-0.5 parts of an antioxidant.

15. The resin composition according to claim 14, characterized in that, The antioxidants include hindered phenolic antioxidants and / or hindered amine antioxidants.

16. A resin film, characterized in that, The resin film is made of the resin composition as described in any one of claims 1-15.

17. The resin film according to claim 16, characterized in that, The resin film is obtained by coating the resin composition onto a release material and then drying and / or semi-curing it.

18. A flexible copper-clad laminate, characterized in that, The flexible copper-clad laminate includes a base film and a resin layer located on one or both sides of the base film, wherein a copper foil is disposed on the surface of the resin layer; the resin layer is a coating of the resin composition as described in any one of claims 1-15.

19. The flexible copper-clad laminate according to claim 18, characterized in that, The base film includes a polyimide film.

20. The flexible copper-clad laminate according to claim 18, characterized in that, The thickness of the base film is 12.5-50 μm.

21. The flexible copper-clad laminate according to claim 18, characterized in that, The thickness of the resin layer is 10-50 μm.

22. The flexible copper-clad laminate according to claim 18, characterized in that, The thickness of the copper foil is 12-70 μm.

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