Resin composition and cover film

Abstract

The present application provides a kind of resin composition and covering film, the resin composition includes the following weight parts of component: epoxy resin 35-45 parts, carboxyl-terminated butyl nitrile rubber 18-28 parts, copolyamide resin 5-7 parts, polyvinyl butyral resin 2-4 parts, amine curing agent 2.8-4.2 parts.In the epoxy resin system in the present application, copolyamide resin, polyvinyl butyral resin and carboxyl-terminated butyl nitrile rubber are combined to improve the toughening and blocking performance together, solve the problem of covering film overflow, overflow edge is neat when pressing, there is no small molecule overflow, and the heat resistance, adhesion of resin composition can be considered.

Description

Technical Field

[0001] This invention belongs to the field of flexible copper clad laminate technology, and relates to a resin composition and a covering film. Background Technology

[0002] Flexible printed circuit boards (FPCBs) use polyimide film-type cover films, which are made by coating a resin composition (adhesive) onto one side of a polyimide film (PI film), followed by drying and partial cross-linking. Commonly used adhesives include epoxy adhesives and acrylic adhesives. Acrylic adhesives have a high-molecular-weight acrylic resin as their main resin, and there is no problem with small-molecule overflow during cover film lamination. However, epoxy adhesives have a low-molecular-weight epoxy resin as their main resin, and due to the very low melt viscosity of epoxy resin, small-molecule overflow quality problems such as sawtooth overflow, secondary overflow, spraying, and skipping often occur during cover film lamination.

[0003] When small-molecule adhesive overflow occurs in the cover film, the overflowed adhesive will leave residues on the pads and circuits, reducing the effective conductor area. Therefore, improving the quality of adhesive overflow in epoxy cover films has become an important research topic in the industry.

[0004] Therefore, there is a desire to develop epoxy adhesive cover films that can improve the quality of adhesive overflow. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a resin composition and a cover film. The resin composition of the present invention can significantly improve the problem of adhesive overflow in the cover film, resulting in neat overflow edges during lamination, absence of small-molecule overflow, and simultaneously maintaining the flexibility, heat resistance, and adhesiveness of the resin composition.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a resin composition comprising the following components in parts by weight:

[0008] 35-45 parts epoxy resin, 18-28 parts carboxyl-terminated nitrile butadiene rubber, 5-7 parts copolyamide resin, 2-4 parts polyvinyl butyral resin, and 2.8-4.2 parts amine curing agent.

[0009] In the epoxy resin system of this invention, a combination of copolyamide resin, polyvinyl butyral resin, and carboxyl-terminated nitrile rubber is used to jointly improve toughening and adhesive resistance. The carboxyl-terminated nitrile rubber is the main toughening and adhesive resistance component, and copolyamide resin and polyvinyl butyral resin are introduced as auxiliary toughening and adhesive resistance components. The cover film prepared with this resin composition has excellent adhesive overflow characteristics. The adhesive overflow edge of the cover film is neat when pressed, there is no small molecule adhesive overflow, and it can take into account the flexibility, heat resistance and adhesion of the resin composition.

[0010] In this invention, the copolyamide resin and polyvinyl butyral resin have high molecular weight and melt viscosity, and their molecular weight and melt viscosity are designed in a gradient manner. When added to the resin composition, the melt viscosity of the resin composition at different melting stages is increased. This can synergistically supplement the adhesive-blocking voids left by the phase separation of the carboxyl-terminated nitrile rubber and epoxy resin during the curing process due to the formation of the "island" structure, effectively preventing small molecule adhesive overflow from the cover film.

[0011] In the resin composition of the present invention, the content of the epoxy resin can be 35 parts, 38 parts, 40 parts, 42 parts or 45 parts, the content of the carboxyl-terminated butadiene-acrylonitrile rubber can be 18 parts, 21 parts, 23 parts, 25 parts or 28 parts, the content of the copolyamide resin can be 5 parts, 5.5 parts, 6 parts, 6.5 parts or 7 parts, the content of the polyvinyl butyral resin can be 2 parts, 2.5 parts, 3 parts, 3.5 parts or 4 parts, and the content of the amine curing agent can be 2.8 parts, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts or 4.2 parts.

[0012] Preferably, the epoxy resin is selected from one or a mixture of at least two of the following: bisphenol A type epoxy resin, dicyclopentadiene phenol type epoxy resin, phenolic epoxy resin, o-cresol type phenolic epoxy resin, bisphenol A type phenolic epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, phosphorus-containing epoxy resin, nitrogen-containing epoxy resin, and tetrafunctional epoxy resin. Excessive epoxy resin content reduces the flexibility of the resin composition and increases the amount of adhesive overflow in the cover film; insufficient epoxy resin content reduces the curing crosslinking density and heat resistance of the resin composition.

[0013] Preferably, the carboxyl-terminated nitrile butadiene rubber is a terpolymer of butadiene, acrylonitrile, and organic acids (e.g., acrylic acid, methacrylic acid, etc.), wherein the acrylonitrile content is 18-50% by mass (e.g., 18% by mass, 20% by mass, 25% by mass, 30% by mass, 40% by mass, or 50% by mass). Commercially available products can be used, including but not limited to: Nipol 1072CGX and Nipol 1072CGJ (Zeon Corporation), NANCAR 1072CG (Nan Tei Chemical Co., Ltd.), XER-32 (JSR Corporation), KRYNAC X740 and KRYNAC X750 (ARLANXEO Corporation). Insufficient use of carboxyl-terminated nitrile butadiene rubber results in insignificant toughening and adhesive resistance; excessive use leads to stickiness in the cover film adhesive layer, and a decrease in peel strength and heat resistance.

[0014] In this invention, the copolyamide resin has a high melting temperature and high melt viscosity, which can impede the flow of the resin composition under high temperature and high pressure. If too much copolyamide resin is used, the crosslinking density of the resin composition is low, and the heat resistance decreases; if too little is used, the synergistic adhesive-blocking effect is not obvious, and the overflow edge of the cover film is uneven. Preferably, the amine value of the copolyamide resin is 3-5 mgKOH / g, for example, 3 mgKOH / g, 3.5 mgKOH / g, 4 mgKOH / g, 4.5 mgKOH / g, or 5 mgKOH / g. Preferably, the number average molecular weight of the copolyamide resin is 10,000-25,000 (e.g., 10,000, 15,000, 18,000, 20,000, 22,000, or 25,000, etc.), and preferably, the melting point of the copolyamide resin is 100-160℃ (e.g., 110℃, 120℃, 130℃, 140℃, 150℃, or 160℃). The copolyamide resin may be a commercially available product, including, but not limited to, M1276F (glass transition temperature 32°C, amine value 3.3 mg KOH / g, melting point 112°C) or M995F (glass transition temperature 25°C, amine value 4.8 mg KOH / g, melting point 148°C) from Arkema, France.

[0015] Preferably, the number-average molecular weight of the polyvinyl butyral resin is 100,000-130,000 (e.g., 100,000, 110,000, 120,000, or 130,000). Higher molecular weight polyvinyl butyral resins have higher glass transition temperatures and melt viscosities, resulting in better flexibility, film-forming properties, and adhesive resistance. If the amount of polyvinyl butyral resin used is too small, the synergistic adhesive resistance effect is not significant; if the amount used is too large, the heat resistance of the resin composition will decrease. The polyvinyl butyral resin can be a commercially available product, exemplarily including but not limited to KS-5Z and KS-6Z from Sekisui Chemicals Co., Ltd. The number-average molecular weight of this invention can be determined by gel permeation chromatography based on polystyrene calibration, referring to GB / T21863-2008.

[0016] Preferably, the amine curing agent is selected from one or more of dicyandiamide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, or aliphatic amines.

[0017] Preferably, the amine curing agent is a combination of 4,4'-diaminodiphenyl sulfone and dicyandiamide. Preferably, the amount of 4,4'-diaminodiphenyl sulfone in the combination is 2.5-4.0 parts by weight, and the amount of dicyandiamide is 0.1-0.3 parts by weight. As a preferred embodiment of the present invention, by combining the high-temperature resistant curing agent 4,4'-diaminodiphenyl sulfone and the latent curing agent dicyandiamide to form a composite curing agent, the resin composition and the prepared cover film can possess high heat resistance and peel strength.

[0018] In this invention, if too much amine curing agent is used, the crosslinking density of the resin composition is high and the flexibility decreases; if too little curing agent is used, the crosslinking density of the resin composition is insufficient and the heat resistance decreases.

[0019] Preferably, the resin composition further contains 18-28 parts of filler, for example 18, 19, 20, 21, 22, 25, or 28 parts. If the amount of filler is too small, it will affect the flame retardancy of the resin composition; if the amount of filler is too large, it will affect the heat resistance and flexibility of the resin composition.

[0020] Preferably, the filler is an inorganic filler or an organic filler.

[0021] Preferably, the inorganic filler is at least one of aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, kaolin, or alumina.

[0022] Preferably, the organic filler is at least one of aluminum diethylphosphinate, melamine, or cyanuric acid.

[0023] Preferably, the average particle size D50 of the filler is 0.5-5μm (0.5μm, 1μm, 2μm, 3μm, 4μm or 5μm). If the filler particle size is too large, the coating appearance will be poor; if the particle size is too small, the dispersion effect will be poor.

[0024] Preferably, the resin composition further contains 0.05-0.15 parts of an antioxidant, such as 0.06 parts, 0.08 parts, 0.10 parts, 0.12 parts, 0.14 parts, or 0.15 parts. Preferably, the antioxidant is a hindered phenolic antioxidant or a hindered amine antioxidant. The antioxidant can delay the oxidation of the resin composition during high-temperature curing and subsequent processing applications. The antioxidant can be a hindered phenolic antioxidant such as CHINOX 1010, CHINOX 1076, CHINOX 1098, CHINOX 1325 (all from Shuangjian Chemical Co., Ltd.), or a hindered amine antioxidant such as DNP (from Kaiyuan Fine Chemicals).

[0025] On the other hand, the present invention provides a resin solution obtained by dissolving or dispersing the resin composition described above in an organic solvent.

[0026] 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, etc.

[0027] The organic solvent is used to dissolve the curing agent, disperse the filler, and adjust the viscosity of the resin solution. The prepared resin solution preferably has a solid content of 35%-45%, such as 35%, 38%, 40%, 42%, or 45%, and the viscosity is suitable to provide good processability and prevent surface defects during coating.

[0028] On the other hand, the present invention provides a cover film comprising a polymer base film, an adhesive layer coated on the polymer base film, and a release paper layer adhered to the adhesive layer, the adhesive layer being formed of the resin composition described above.

[0029] Preferably, the polymer base film is a polyimide film.

[0030] 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.

[0031] 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.

[0032] Preferably, the thickness of the release paper layer is 110-130μm, for example, 110μm, 112μm, 115μm, 118μm, 120μm, 122μm, 125μm, 128μm or 130μm.

[0033] In this invention, the covering film can be prepared using the following method:

[0034] First, a bead mill, in conjunction with a high-shear stirring and dispersing device, is used to mix the various components of the present invention together to prepare a resin composition. Then, a coating machine is used to coat this resin composition onto one surface of a polyimide film. After drying in an oven, the film is heated at 160°C for 5 minutes to remove the organic solvent and partially cross-link and cure the resin composition, forming a semi-cured resin composition layer on the polyimide film. Next, the film is rolled and laminated with release paper at a pressing temperature of 80°C, and then wound up to obtain the cover film.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] In the epoxy resin system of this invention, a combination of copolyamide resin, polyvinyl butyral resin and carboxyl-terminated nitrile rubber is used to jointly improve toughening and adhesive resistance, thus synergistically solving the problem of adhesive overflow in the cover film. During pressing, the overflow edge is neat, there is no small molecule overflow, and the heat resistance and adhesion of the resin composition are also taken into account. Attached Figure Description

[0037] Figure 1 A schematic diagram of the optical morphology of the adhesive overflow edge of the cover film;

[0038] Figure 2 A schematic diagram of the optical morphology of the serrated adhesive overflow of the cover film;

[0039] Figure 3 This is a schematic diagram of the optical morphology of the adhesive sprayed onto the cover film. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0041] Example 1

[0042] A resin composition comprising: 40 parts by weight of bisphenol A type epoxy resin (GESN901, Hongchang Electronic Materials Co., Ltd.), 23 parts by weight of carboxyl-terminated butadiene-acrylonitrile rubber (NANCAR 1072CG, Nandi Chemical Industry Co., Ltd.), 6 parts by weight of copolyamide resin (M1276F, Arkema), 3 parts by weight of polyvinyl butyral resin (KS-5Z, Sekisui Chemicals Co., Ltd., molecular weight 130,000), 3.5 parts by weight of 4,4'-diaminodiphenyl sulfone (Atul Corporation, India), 0.2 parts by weight of dicyandiamide (Ningxia Darong Chemical Metallurgy Co., Ltd.), 13 parts by weight of aluminum hydroxide (H-42M, Showa Denko Co., Ltd., D50 particle size 1.1 μm), 14 parts by weight of aluminum diethylphosphinate (OP-935, Clariant, D50 particle size 3.5 μm), and antioxidant 1010 (CHINOX). 1010, Double Bond Chemical Company) 0.1 parts by weight.

[0043] First, dissolve the carboxyl-terminated butadiene-acrylonitrile rubber, resin, and curing agent separately with methyl ethyl ketone and ethylene glycol monomethyl ether, then mix them with the remaining components. Adjust the solid content of the resin solution to 40% with methyl ethyl ketone to prepare the resin solution.

[0044] Examples 2-4, Comparative Examples 1-11

[0045] A resin composition, the components and their contents are shown in Tables 1 and 2. The units of each component in Tables 1 and 2 are parts by weight (i.e., solid parts by weight excluding solvent).

[0046] The resin solutions of Examples 1-4 and Comparative Examples 1-11 were coated onto a 12.5 μm thick polyimide film (TL-012, Damai Technology Co., Ltd.) using a coating machine. The thickness of the resin composition layer was controlled to be 15 μm. The film was then placed in an oven at 160°C and baked for 5 minutes to form a partially cross-linked and cured resin composition layer on the polyimide film. The film was then rolled and laminated with a 120 μm release paper at a pressing temperature of 80°C to obtain a cover film.

[0047] The performance of the cover film in Examples 1-4 and Comparative Examples 1-11 was tested, and the results are shown in Tables 1 and 2.

[0048] Table 1

[0049]

[0050]

[0051] [Note] NC-3000-H: Biphenyl type epoxy resin, manufactured by Nippon Kayaku Co., Ltd.; 4,4'-Diaminodiphenyl ether: manufactured by Wakayama Seika Kogyo Co., Ltd.

[0052] Table 2

[0053]

[0054]

[0055]

[0056] [Note] Polyamide-imide: manufactured by Toyobo Co., Ltd.; BH-6: manufactured by Sekisui Chemical Co., Ltd.

[0057] The test methods for the performance of the covering film are as follows:

[0058] (1) Excess adhesive amount and morphology: The excess adhesive amount was tested according to IPC-TM-650 2.3.17.1 method; the morphology of the excess adhesive on the cover film was observed, and the criteria for judging the morphology of the excess adhesive were as follows. Figures 1-3 As shown, where Figure 1 To ensure the excess glue is smooth, Figure 2 The excess glue is in a serrated pattern. Figure 3 It is for spraying adhesive.

[0059] (2) Peel strength: According to the IPC-TM-650 2.4.9 method, the cover film was first pressed with the smooth surface of 18μm rolled copper foil (BHYX-92F-T, Nikko Metals Co., Ltd.), and then baked at 160°C for 1 hour before the peel strength was tested.

[0060] (3) Solderability: The test was conducted according to the method of IPC-TM-650 2.4.13. The sample was completely immersed in the solder bath for 20 seconds, and the highest test temperature at which the sample did not blister or separate was recorded.

[0061] As can be seen from the data in Table 1, the cover film prepared by the resin composition of the present invention has good heat resistance and adhesion, the adhesive overflow edge of the cover film is smooth, the peel strength is above 0.85 N / mm, and the immersion soldering temperature is above 330°C; among them, Example 1 uses a composite curing agent compared with Example 6, and its heat resistance and peel strength are better.

[0062] In Comparative Examples 1 and 2, only polyvinyl butyral resin or copolyamide resin was used alone. In Comparative Example 3, neither polyvinyl butyral resin nor copolyamide resin was used. The overflow edges of the cover film showed varying degrees of serrated overflow, with Comparative Example 3 showing more serrated overflow.

[0063] Comparative Example 4: The amount of carboxyl-terminated nitrile rubber was too small. Even with the addition of polyvinyl butyral resin and copolyamide resin, the adhesive blocking effect was poor, and the overflow edge of the cover film showed a lot of serrated overflow. Comparative Example 5: The amount of carboxyl-terminated nitrile rubber was too large, and the peel strength and heat resistance of the cover film decreased.

[0064] In Comparative Example 6, the amount of copolyamide resin was too small, resulting in less serrated overflow on the cover film. In Comparative Example 7, the amount of copolyamide resin was too large, resulting in smooth overflow on the cover film, but reduced heat resistance and peel strength.

[0065] In Comparative Example 8, the amount of polyvinyl butyral resin was too small, resulting in less serrated overflow edges on the cover film; in Comparative Example 9, the amount of polyvinyl butyral resin was too large, resulting in smooth overflow edges on the cover film, but reduced heat resistance.

[0066] Comparative Example 10 shows that using a lower molecular weight polyvinyl butyral resin (number average molecular weight 92,000) resulted in fewer serrated overflows at the edge of the cover film.

[0067] Comparative Example 11 illustrates that using polyamide-imide instead of copolyamide resin results in poor compatibility with carboxyl-terminated butadiene-acrylonitrile rubber and polyvinyl butyral resin, failing to achieve the synergistic adhesive inhibition purpose, and leading to a decrease in the peel strength and heat resistance of the cover film.

[0068] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope 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: 35-45 parts epoxy resin, 18-28 parts carboxyl-terminated butadiene-acrylonitrile rubber, 5-7 parts copolyamide resin, 2-4 parts polyvinyl butyral resin, and 2.8-4.2 parts amine curing agent; The carboxyl-terminated nitrile rubber is a ternary copolymer of butadiene, acrylonitrile, and organic acid, wherein the acrylonitrile content is 18-50% by mass. The number average molecular weight of the copolyamide resin is 10,000-25,000; The number average molecular weight of the polyvinyl butyral resin is 100,000-130,000. The amine value of the copolyamide resin is 3-5 mg KOH / g; The melting point of the copolyamide resin is 100-160℃.

2. The resin composition according to claim 1, characterized in that, The epoxy resin is selected from one or a mixture of at least two of the following: bisphenol A type epoxy resin, dicyclopentadiene phenol type epoxy resin, phenolic epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, phosphorus-containing epoxy resin, nitrogen-containing epoxy resin, and tetrafunctional epoxy resin.

3. The resin composition according to claim 1, characterized in that, The amine curing agent is selected from one or more of dicyandiamide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, or aliphatic amines.

4. The resin composition according to claim 3, characterized in that, The amine curing agent is a combination of 4,4'-diaminodiphenyl sulfone and dicyandiamide.

5. The resin composition according to claim 4, characterized in that, The amount of 4,4'-diaminodiphenyl sulfone in the combination is 2.5-4.0 parts by weight, and the amount of dicyandiamide is 0.1-0.3 parts by weight.

6. The resin composition according to claim 1, characterized in that, The resin composition also contains 18-28 parts of filler.

7. The resin composition according to claim 6, characterized in that, The packing material can be inorganic or organic.

8. The resin composition according to claim 7, characterized in that, The inorganic filler is at least one of aluminum hydroxide, magnesium hydroxide, boehmite, talc, silica, kaolin, or alumina.

9. The resin composition according to claim 7, characterized in that, The organic filler is at least one of aluminum diethylphosphinate, melamine, or cyanuric acid.

10. The resin composition according to claim 6, characterized in that, The average particle size D50 of the filler is 0.5-5 μm.

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

12. The resin composition according to claim 11, characterized in that, The antioxidant is a hindered phenolic antioxidant or a hindered amine antioxidant.

13. A resin adhesive, characterized in that, It is obtained by dissolving or dispersing the resin composition as described in any one of claims 1-12 in an organic solvent.

14. The resin adhesive according to claim 13, 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, and butyl acetate.

15. The resin adhesive according to claim 13, characterized in that, The solid content of the resin solution is 35%-45%.

16. A covering film, characterized in that, The cover film includes a polymer base film, an adhesive layer coated on the polymer base film, and a release paper layer adhered to the adhesive layer, wherein the adhesive layer is formed of a resin composition as described in any one of claims 1-12.

17. The covering film according to claim 16, characterized in that, The polymer base film is a polyimide film.

18. The covering film according to claim 16, characterized in that, The thickness of the polymer base film is 7.5-50 μm.

19. The covering film according to claim 16, characterized in that, The thickness of the adhesive layer is 5-50 μm.

20. The covering film according to claim 16, characterized in that, The thickness of the release paper layer is 110-130 μm.

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