TWI591088B - Flexible printed circuit board - Google Patents

Description

Flexible printed circuit board

The present invention provides a resin composition, a cover film, and a flexible printed circuit board, and more particularly, a resin composition which can produce a cover film having a single layer structure. The cover film having a single layer structure can be directly disposed on the copper circuit wiring layer of the flexible printed circuit board.

Flexible printed circuit boards are indispensable components in electronic products. Under the current trend of light, thin, short and small in the technology industry, the research and development direction of various components in flexible printed circuit boards has also tended to the above objectives.

In general, the currently known flexible printed circuit board may comprise at least a polyimide substrate, a copper circuit wiring layer provided on the surface of the polyimide substrate, and a cover film provided on the copper circuit wiring layer. The conventional cover film is composed of a double layer structure of a polymer layer and an adhesive layer, and the polymer layer is usually a thermosetting resin (for example, a polyimide resin) to protect the copper circuit wiring layer from being easily damaged. The adhesive layer is used to help the polymer layer adhere to the copper circuit wiring layer.

The thickness of the above two-layer structure is relatively thick, which does not conform to the current development trend of the light and thin electronics industry.

In order to improve the disadvantages of the above two-layer structure, there is a technique which proposes a resin composition comprising an epoxy resin, a hardening accelerator, a crosslinking agent, and a phosphorus-containing phenol resin. The semi-cured film formed using the above resin composition can be directly disposed on the copper foil. However, the above-mentioned semi-cured film has poor adhesion to the copper foil, and its filling property, solder heat resistance, flexibility, flame resistance, and ion mobility resistance cannot satisfy the industrial demand.

Another technique is to provide a resin composition comprising a halogen-free epoxy resin, a thermoplastic resin and/or a synthetic rubber, a curing agent, and a nitrogen-containing flame retardant. However, the film layer obtained by the above resin composition has poor peeling strength, filling property, and ion migration resistance.

Therefore, there is a need to provide a resin composition which can produce a cover film which has good peeling resistance, filling property, solder heat resistance, flexibility, flame resistance and ion migration resistance, and the above cover film is single The layer structure can be directly disposed on the copper circuit wiring layer without the need to help the bonding through the adhesive layer.

Therefore, an aspect of the present invention is to provide a resin composition comprising a specific epoxy resin and a toughening agent, which can increase the peeling strength, the filling property, the solder heat resistance, and the bending property of the obtained cover film. , flame resistance and ion mobility.

Another aspect of the present invention is to provide a cover film which is obtained by using the above resin composition, which may have a single layer structure.

Another aspect of the present invention is to propose a flexible printed circuit A plate, which may have the cover film described above.

According to the above aspect of the invention, a resin composition is first proposed. In an embodiment, the resin composition may include an epoxy resin (A), a hardener (B), a catalyst (C), a flame retardant (D), a toughening agent (E), and a solvent (F). Wherein the epoxy resin (A) comprises a first epoxy resin (a-1) and a second epoxy resin (a-2), and the first epoxy resin (a-1) may have the following formula (I) Structure:

In the formula (I), R ¹ is , R ² is or , a is an integer from 0 to 2, and * represents a bond.

The above toughening agent (E) may comprise a polyester resin. The amount of the first epoxy resin (a-1) used is 100 parts by weight based on the epoxy resin (A). 30 parts by weight to 50 parts by weight, the second epoxy resin (a-2) is used in an amount of 50 parts by weight to 70 parts by weight, and the hardener (B) is used in an amount of 16 parts by weight to 20 parts by weight, based on the catalyst (C) The amount used is from 0.8 part by weight to 1 part by weight, the flame retardant (D) is used in an amount of from 50 parts by weight to 60 parts by weight, the toughening agent (E) is used in an amount of from 70 parts by weight to 90 parts by weight, and the solvent (F) is used in an amount of from 75 parts by weight to 85 parts by weight.

According to an embodiment of the present invention, the first epoxy resin (a-1) is at least one selected from the group consisting of the structures represented by the following formula (I-1) to formula (I-3).

According to an embodiment of the present invention, the second epoxy resin (a-2) comprises a novolac epoxy resin, a bisphenol A epoxy resin, an alicyclic epoxy resin, a heterocyclic epoxy resin, and a propylene oxide A glycol ester type epoxy resin or any combination of the above.

According to an embodiment of the present invention, the hardener (B) may comprise a polyamine-based compound, an phthalic anhydride compound, or any combination thereof.

According to an embodiment of the invention, the catalyst (C) may comprise an imidazole compound, a tertiary phosphine, a boron fluoride complex or any combination of the above.

According to an embodiment of the present invention, the flame retardant (D) may be composed of a phosphorus-containing compound and a metal-containing compound, wherein the metal-containing compound may comprise a metal oxide or a metal hydroxide.

According to an embodiment of the present invention, the metal-containing compound has an average particle diameter ranging from 1 μm to 5 μm.

According to an embodiment of the invention, the polyester resin may be a polyurethane.

According to the above aspect of the invention, there is further provided a cover film formed on the surface of the substrate by the coating step, the baking step, and the aging step by the above resin composition.

According to the above aspect of the invention, a soft printing method is further proposed. The circuit board comprises a substrate, a copper circuit wiring layer provided on the substrate, and the above-mentioned cover film, wherein the cover film is disposed on the copper circuit wiring layer, and the cover film has a single layer structure and does not have an adhesive layer.

By applying the resin composition of the present invention, the obtained cover film can have a single layer structure, and the cover film can be directly disposed on the copper circuit wiring layer, thereby reducing the overall thickness of the flexible printed circuit board. Further, the cover film can have good peeling resistance, filling property, solder heat resistance, bendability, flame resistance, and ion mobility resistance.

100,200‧‧‧Package

110, 210‧‧ ‧ cover film

120, 220‧‧‧ plastic substrate

130, 230‧‧‧ release paper

200F‧‧‧Soft printed circuit board

241‧‧‧ copper circuit wiring layer

243‧‧‧ Polyimine substrate

240‧‧‧Soft printed circuit board semi-finished products

250‧‧‧buffering material release film

310A, 310B, 310C, 310D, 310E, 310F‧‧‧ cover film

320A, 320B, 320C, 320D, 320E, 320F‧‧‧ copper circuit wiring layer

DI, D2, D3, D4, D5, D6‧‧‧ spacing

The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; 2A] to [FIG. 2F] are cross-sectional views showing the intermediate process of the method for manufacturing the flexible printed circuit board of the present invention; [FIG. 3] showing the softness of the cover film formed by applying the resin composition of Example 3 of the present invention. A variation diagram of the insulation resistance of the printed circuit board; and [Fig. 4] is a cross-sectional electron micrograph showing a cover film formed by the resin composition of the embodiment 3 of the present invention applied to a flexible printed circuit board.

One aspect of the present invention provides a resin composition comprising an epoxy resin (A), a hardener (B), a catalyst (C), a flame retardant (D), Toughener (E) and solvent (F). The cover film obtained by the above resin composition has a single layer structure and can be directly provided on the copper circuit wiring layer to reduce the thickness of the obtained flexible printed circuit board. Further, the cover film has good peeling resistance, filling property, solder heat resistance, bendability, flame resistance, and ion mobility resistance.

The single layer structure referred to in the present invention means that the cover film does not need to use an adhesive (that is, the cover film does not include an adhesive layer), and can be directly disposed on the copper circuit wiring layer.

Hereinafter, each component of the resin composition of the present invention will be specifically described.

Resin composition Epoxy resin (A)

The epoxy resin (A) referred to herein as the first epoxy resin (a-1) and the second epoxy resin (a-2).

First epoxy resin (a-1)

The first epoxy resin (a-1) referred to herein as the present invention may comprise the structure represented by the following formula (I):

In the above formula (I), R ¹ is , R ² is or , a is an integer from 0 to 2, and * represents a bond.

Specifically, the first epoxy resin (a-1) may be a compound having a structure represented by the following formula (I-1) to formula (I-3) or any combination of the above compounds.

In an example, the first epoxy resin (a-1) may be a product of the model number NC-513, NC-514, NC-547 manufactured by Cardolite Corporation or any combination of the above.

The first epoxy resin (a-1) may be used in an amount of 30 parts by weight to 50 parts by weight based on 100 parts by weight of the epoxy resin (A). If the epoxy resin (A) does not contain the first epoxy resin (a-1), or the amount thereof is too small, the resulting cover film is inferior in peeling strength, flame resistance, and solder heat resistance. On the other hand, if the amount of the first epoxy resin (a-1) is too large, since the first epoxy resin (a-1) is a low-viscosity epoxy resin, the resin composition is used in the process of covering the film. There will be problems with poor formability.

Second epoxy resin (a-2)

The second epoxy resin (a-2) described herein may comprise A novolac epoxy resin, a bisphenol A epoxy resin, an alicyclic epoxy resin, a heterocyclic epoxy resin, a glycidyl ester epoxy resin, or any combination thereof.

The phenolic epoxy resin may be, for example, a product of the product type NPPN-431A70 or NPEB-454A80 manufactured by Nanya Plastics Co., Ltd., a product of the CNE-200EL series manufactured by Changchun Synthetic Resin Co., Ltd., Dow. The product model of the company manufactured by Chemical Co., Ltd. is a product of DEN 438 or any combination of the above, but the invention is not limited thereto.

The bisphenol A type epoxy resin described above may be, for example, a product of the product type BE-188 manufactured by Changchun Synthetic Resin Co., Ltd., a product of the product type DER671 manufactured by The Dow Chemical Co., Ltd., manufactured by Huntsman. The product of the trade name of GT-7071 or GT-7072, the product of Kukdo Chemical Co., Ltd. of the product type KD-211G, or any combination of the above, is not limited thereto.

As the aforementioned alicyclic epoxy resin, for example, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexylmethyl-3' can be used. , a dimer adduct of 4'-epoxycyclohexane carboxylate and caprolactone, 1,2,8,9-diepoxylimene or any combination thereof. Specifically, it can be, for example, a product of the type of CELLOXIDE 2021, 2081 or 3000 manufactured by DAICEL Co., Ltd., but the present invention is not limited thereto.

The above heterocyclic epoxy resin may be, for example, a product of the trade name of Araldite PT810 manufactured by Huntsman Advanced Materials, a product of the trade name TEPIC manufactured by Nissan Chemical Industries, Ltd., or a combination thereof, but the present invention is not limited thereto.

The above-mentioned epoxy propyl ester type epoxy resin may comprise a copolymerized epoxy resin of a glycidyl methacrylate copolymer copolymer, a cyclohexylmaleimide and a glycidyl methacrylate or the above Combinations of the invention are not limited thereto.

In a preferred embodiment, the first epoxy resin (a-1) can be used, for example, with a novolac epoxy resin and a bisphenol A type epoxy resin.

The second epoxy resin (a-2) may be used in an amount of 50 parts by weight to 70 parts by weight based on 100 parts by weight of the epoxy resin (A). When the second epoxy resin (a-2) is not used in the resin composition, the moldability of the resin composition is not good, and it is difficult to form a cover film.

Hardener (B)

The hardener (B) referred to herein as the present invention may comprise a polyamine-based compound, an phthalic anhydride compound, or any combination thereof.

Specifically, the above polyamine compound may be, for example, diethylenetriamine, diaminodiphenylmethane, 3,3'-diaminodiphenylphosphonium, 4,4'-diaminodiphenyl Base, dinitramine or any combination of the above.

Specifically, the above phthalic anhydride compound may be, for example, phthalic anhydride, tetrahydrophthalic anhydride or any combination of the above.

In a preferred embodiment, a hardener having different operating temperatures can be selectively used in the resin composition, for example, using both diaminodiphenylphosphonium and dinitrileamine to make the resin composition at different temperatures. Under, have different degrees of thermal cure.

Based on the above epoxy resin (A), the amount used is 100 weight. The curing agent (B) may be used in an amount of from 16 parts by weight to 20 parts by weight. If the amount of the curing agent (B) used does not fall within the above-mentioned range, the cover film may have a problem of poor flame resistance, solder heat resistance, and/or peel strength.

Catalyst (C)

The catalyst (C) referred to herein as the invention may comprise an imidazole compound, a tertiary phosphine, a boron fluoride complex or any combination of the above.

In a specific example, the imidazole compound described above may include, but is not limited to, 1-methylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, or a combination thereof.

In a specific example, the above tertiary phosphine may be triphenylphosphine, tributylphosphine or a combination thereof.

In a specific example, the boron fluoride complex may be, for example, a complex of boron trifluoride and monoethylamine, a complex of boron trifluoride and n-butylamine, and boron trifluoride. An aniline complex, zinc borohydride or a combination thereof.

In a preferred embodiment, the catalyst (C) can be a combination of a boron fluoride complex and an imidazole compound.

The catalyst (C) may be used in an amount of from 0.8 part by weight to 1 part by weight based on 100 parts by weight of the epoxy resin (A). The catalyst of the present invention is used as a hardening accelerator which contributes to the curing of the resin composition. When the amount of the catalyst (C) used is too small, the flame retardancy and solder heat resistance of the cover film obtained from the resin composition are not good.

Flame retardant (D)

The flame retardant (D) referred to herein as being composed of a phosphorus-containing compound and a metal-containing compound. The above metal-containing compound contains a metal oxide or a metal hydroxide. Preferably, the metal-containing compound has an average particle diameter of from 1 μm to 5 μm.

Specifically, the above phosphorus-containing compound includes, but is not limited to, bisphenol biphenyl phosphate, ammonium polyphosphate, hydroquinone-bis-(biphenyl phosphate), potassium phosphite, sodium phosphite, diethyl phosphate Aluminum or any combination of the above.

Specifically, the above metal oxide may contain antimony trioxide.

Specifically, the above metal hydroxide may be, for example, aluminum hydroxide, magnesium hydroxide or a combination thereof.

The flame retardant (D) may be used in an amount of 50 parts by weight to 60 parts by weight based on 100 parts by weight of the epoxy resin (A). In a preferred example, the amount of the metal-containing compound used is from 30 parts by weight to 50 parts by weight based on 100 parts by weight of the flame retardant (D).

In addition, when the average particle diameter of the metal-containing compound is not less than 5 μm, the flame retardant (D) cannot be uniformly dispersed in the resin composition, so that the resin composition cannot be uniformly applied to the substrate.

Toughener (E)

The toughening agent (E) referred to herein as at least comprises a polyester resin. In one example, the above polyester resin may preferably be a polyaminomethyl ester.

In an embodiment, the toughening agent (E) may further comprise other toughening agents, such as: nitrile rubber, phenoxy resin, polyamidoximine resin, or any combination thereof.

In one example, the nitrile rubber can be, for example, a carboxyacrylonitrile butadiene rubber, a butadiene-acrylonitrile copolymer, an epoxy modified butadiene rubber, or any combination thereof.

The toughening agent (E) can further improve the flame resistance of the cover film in addition to the flexibility of the cover film obtained by reinforcing the resin composition, based on the use amount of the epoxy resin (A) of 100 parts by weight. The amount used may be from 70 parts by weight to 90 parts by weight. In the present invention, a polyester resin is used as the toughening agent (E). Therefore, if the polyester resin is not used as the toughening agent (E) or the toughening agent (E) is too small, the flame resistance of the cover film is not good. . However, if too much toughening agent (E) is added, the flexibility of the cover film is also poor.

Solvent (F)

The solvent (F) referred to herein as the solvent is not particularly limited, and is only soluble in the epoxy resin (A), and the hardener (B), the catalyst (C), the flame retardant (D), and the toughening agent (E) are dispersed. ), but it is not suitable for the reaction with the above components.

In a specific example, the solvent (F) may include, but is not limited to, acetone, methyl ethyl ketone, toluene, xylene, dimethylformamide, ethylene glycol monomethyl ether, propylene glycol methyl ether, or any combination thereof.

The solvent (F) may be used in an amount of from 75 to 85 parts by weight based on 100 parts by weight of the epoxy resin (A).

Additive (G)

The resin composition of the present invention may further contain an additive (G). The above additive (G) may include, but is not limited to, an antioxidant, a cation scavenger, and a yin Ion trapping agent, dispersing agent, leveling agent or any combination of the above.

The above antioxidant may be, for example, distearyl pentaerythritol diphosphite, phenyl diisononyl phosphite, and a carbon alkyl-4,4 diisoprene-fatty alcohol-phosphite chelate compound or the above random combination. Specifically, as the antioxidant, a product of the type STAB PEP-8T (AR-2) manufactured by ADEKA Corporation can be used.

The above dispersing agent may, for example, be a polyester-modified polydimethyldecane. Specifically, the dispersant may be a product of the type BYK-310 manufactured by BYK Chemical Additives and Instruments. The above leveling agent can be, for example, a product of the type BYK-W903 manufactured by BYK Chemical Additives and Instruments.

In particular, although a cation scavenger and/or an anionic scavenger may be additionally added to the resin composition of the present invention to increase the ion mobility. However, in the present invention, the cation scavenger and/or the anion scavenger are not necessarily added, and the resin composition of the present invention has good ion mobility resistance which satisfies the current market demand.

Method for producing resin composition

The method for producing a resin composition of the present invention is to first add a curing agent (B), a catalyst (C), a selectively added additive (G), and a solvent (F) to a reactor for mixing. Thereafter, an epoxy resin (A) and a flame retardant (D) were added to the above reactor and mixed. Next, a toughening agent (E) is added to the above reactor, and stirred and stirred at room temperature to obtain a resin composition of the present invention. Among them, the viscosity of the resin composition at 25 ° C is preferably from 1000 cps to 2000 cps.

Cover film manufacturing method

In the method for producing a cover film according to the present invention, after the resin composition is subjected to a coating step, a baking step, and a aging step, a cover film is formed on the surface of the substrate.

Alternatively, a release paper may be provided on the other surface of the cover film (the side not in contact with the substrate) to facilitate the transport and storage of the prepared cover film.

Specifically, in the above production method, the resin composition is first applied onto the surface of the substrate. In one example, the substrate may be, for example, a plastic substrate of polyethylene terephthalate (PET). The coated substrate is subjected to a baking step to remove the solvent in the resin composition. Thereafter, press-bonding was carried out at a temperature of 70 ° C and a pressure of 1.6 kgf / cm ² to obtain a package 100 as shown in FIG. Figure 1 illustrates a package 100 comprising a cover film of the present invention. In FIG. 1, the cover film 110 is disposed between the plastic substrate 120 and the release paper 130 to protect the cover film 110 from being easily damaged during transportation. In order to control the amount of overflow, the cover film is aged at a temperature of 50 ° C to 70 ° C to obtain the cover film of the present invention.

It should be noted that the package 100 shown in FIG. 1 has a three-layer film (cover film 110, plastic substrate 120, and release paper 130), but when applied to manufacture a flexible printed circuit board, only the cover film 110 is used for protection. Copper circuit wiring layer. In other words, the cover film 110 of the present invention has a single-layer structure when it is used to manufacture a flexible printed circuit board, and can be directly disposed on the copper circuit wiring layer of the flexible printed circuit board without passing through the adhesive layer.

Flexible printed circuit board manufacturing method

2A to 2F, which are cross-sectional views showing an intermediate process of the method of manufacturing the flexible printed circuit board of the present invention. First, as shown in FIG. 2A, a package 200 comprising a cover film of the present invention is provided, which comprises a cover film 210, a plastic substrate 220, and a release paper 230. Next, as shown in FIG. 2B, the release paper 230 is peeled off to expose the cover film 210. Thereafter, as shown in FIG. 2C, the cover film 210 is placed on the copper circuit wiring layer 241 of the flexible printed circuit board blank 240, and pre-adhered for 10 seconds, wherein the copper circuit wiring layer 241 is attached to the substrate 243. In an embodiment, the substrate 243 can be a polyimide substrate. Then, as shown in FIG. 2D, the substrate 220 overlying the cover film 210 is peeled off. Thereafter, as shown in FIG. 2E, the high temperature is subjected to thermocompression, wherein the buffer film release film 250 may be used to separate the cover film 210 from the press to prevent the cover film 210 from being damaged. Next, the flexible printed circuit board 200F of the present invention can be obtained by heating to the curing temperature of the curing agent (B) to perform a hardening step.

Specifically, as shown in FIG. 2F, the cover film 210 of the present invention can be directly pressed against the copper circuit wiring layer 241 and the substrate 243 without using an adhesive, so that the cover film 210 of the present invention is a single layer. structure.

In one embodiment, the package 200 may be subjected to a hole opening step so that the cover film 210 may have a through hole to facilitate exposure of a specific portion of the copper circuit wiring layer (not shown), adding a flexible printed circuit board and Other plug-ins combine the applicability.

Next, the resin group of the present invention will be specifically described in several embodiments. The substance and the effect it achieves.

Example 1

First, 15.2 parts by weight of 4,4'-diaminodiphenylphosphonium (B-1), 3.0 parts by weight of diethylenetriamine (B-2), 0.5 parts by weight of boron trifluoride and a single Ethylamine complex (C-1), 0.4 parts by weight of 2-methylimidazole (C-2), 1.6 parts by weight of distearyl pentaerythritol diphosphite (G-1), 0.04 parts by weight Dispersant (by BYK Chemical Additives and Instruments, model number BYK-310; G-2), 0.22 parts by weight of leveling agent (by BYK Chemical Additives and Instruments, model number BYK-W903; G-3 69 parts by weight of methyl ethyl ketone (F-1) and 9 parts by weight of toluene (F-2) were added to the reactor for mixing. Thereafter, 40 parts by weight of the first epoxy resin (a-1-1) represented by the formula (I-2) and 40 parts by weight of a bisphenol A type epoxy resin (Changchun Synthetic Resin Co., Ltd.) were added to the above reactor. Co., Ltd., model BE-188; a-2-2), 20 parts by weight of phenolic epoxy resin (manufactured by Changchun Synthetic Resin Co., Ltd., model: CNE-200ELB; a-2-1), 33 parts by weight The aluminum diethyl phosphate (D-1) and 27 parts by weight of aluminum hydroxide (D-2) having an average particle diameter of 3 μm were mixed. Next, 80 parts by weight of polyaminomethyl ester (manufactured by TOYOBO, model: SD-5000; E-1) was added and mixed at room temperature to obtain a resin composition of Example 1. Here, the viscosity of the resin composition of Example 1 at 14 ° C was 1450 cps.

Next, the resin composition of Example 1 was applied to a plastic substrate. Then, a baking step is performed to remove the solvent in the resin composition. After that, the hot pressing and the aging step are performed to control the amount of overflow, and then the first embodiment can be obtained. Cover film. The evaluation results of the cover film of Example 1 are shown in Table 1.

Examples 2 to 3 and Comparative Examples 2 to 3

Examples 2 to 3 and Comparative Examples 2 to 3 were carried out in the same manner as in Example 1, except that Examples 2 to 3 and Comparative Examples 2 to 3 were used to change the kind or amount of each component in the resin composition. . The specific component types, usage amounts, and evaluation results of Examples 2 to 3 and Comparative Examples 2 to 3 are shown in Table 1, and are not described herein.

Comparative example 1

In Comparative Example 1, a cover film was obtained by the same method as in Example 1, except that the cover film of Comparative Example 1 was further provided with a polyimide layer. In other words, Comparative Example 1 belongs to a two-layer structure. The components and evaluation results of the resin coating film of Comparative Example 1 are shown in Table 1. It is to be noted that, in the case of Comparative Example 1, the polyimide layer was not used, and the evaluation result was similar to that of Comparative Example 2.

Evaluation method Structure

The structure referred to herein as a single layer is preferred. Specifically, the single layer means that the obtained cover film can be directly disposed on the copper circuit wiring layer, and the cover film and the copper circuit wiring layer are not bonded via the adhesive layer. On the other hand, the double layer means that the cover film is bonded to the copper circuit wiring layer via the adhesive layer. The present invention is preferably a single layer structure.

2. Cover film thickness

The thinner the thickness of the cover film herein, the better. It is additionally noted that in the above-mentioned two-layer structure, the thickness of the cover film is the total thickness of the adhesive layer and the cover film.

3. The amount of glue overflow

The semi-finished product is filled in a circular overflow tank, and is thermocompression-bonded at a high temperature, and then heated to a hardening temperature of the hardener (B) to perform a hardening step to harden it into a film. The width of the above-mentioned film overflow circular overflow tank is examined, which is the so-called overflow amount. In general, the above width is preferably from 0.1 mm to 0.2 mm. If the amount of overflow does not fall within the above range, the coating film formed using the resin composition may have a disadvantage of excessive insulation resistance or poor adhesion to the substrate.

4. Peel strength (for copper or p-polyimine resin)

The peeling strength referred to herein is a cover film formed of the resin compositions of Examples 1 to 3 and Comparative Examples 1 to 3, respectively, formed on a copper substrate or a polyimide substrate to be tested. The adhesion of the cover film of the present invention to the above two substrates.

Specifically, first, the resin compositions of the above-described Examples 1 to 3 and Comparative Examples 1 to 3 were applied onto a substrate (a copper substrate or a polyimide substrate). Next, the coated substrate is thermocompression bonded. Thereafter, hardening is further performed to form a cover film on the surface of the substrate. Then, the cover film was cut into test pieces having a width of 1 cm and a length of 10 cm. Take the above test piece at 180 degrees The direction and the peeling force of the speed of 50 mm/min were pulled, and the pressure applied to the cover film when the substrate was peeled off was examined.

5. Solder heat resistance

The test for solder heat resistance is first to form the cover film of the present invention on a copper substrate, and the specific formation method is as described above for the evaluation of the peel strength, and therefore, it will not be described here.

The substrate on which the cover film was formed was cut into test pieces of 5 cm × 5 cm. Thereafter, the test piece was immersed in a tin liquid at 288 ° C for 30 seconds. After the test piece was taken out, it was observed whether the test piece had delamination or discoloration. The evaluation criteria of the solder heat resistance of the present invention are as follows:

○: No delamination and no discoloration.

X: delamination or discoloration.

6. Flexibility

The test of the bendability is first to form the cover film of the present invention on a copper substrate, and the method of forming the same is shown in the test method for the peel strength described above, and is not described here. Thereafter, the copper substrate provided with the cover film was cut into a test piece of 30 mm × 5 mm. The bending property referred to in the present invention is carried out in accordance with the MIT method, and as the MIT folding device, a grooved film folding fatigue tester (model: 549) manufactured by Toyo Seiki Co., Ltd. is used, with a bending radius of 0.38 mm and a load of 500 g. The test piece was repeatedly bent until the circuit could not be turned on. The more the number of bends, the better the bendability.

7. Flame resistance

The flame resistance referred to in the present invention is carried out in accordance with the regulations of UL94-V0. Specifically, the cover film of the present invention was subjected to a burning test of 10 seconds each, and if the flame was extinguished within 30 seconds and no burning matter fell, it represented good flame resistance. On the contrary, the flame resistance is not good. The specific evaluation criteria are as follows:

○: The flame was extinguished within 30 seconds and no burning matter fell, and the flame resistance was good.

X: The flame is not extinguished within 30 seconds, or there is no burning matter falling, and the flame resistance is not good.

8. Resistance to ion mobility

In the present invention, the resin composition of Example 3 was further formed into a cover film to carry out a test for resistance to ion mobility. First, the cover film is attached to the copper circuit wiring layer of the flexible printed circuit board, and the above-mentioned bonding step is performed in a fast press manner. Next, the above flexible printed circuit board was subjected to a hardening process to obtain a test piece required for the test for resistance to ion mobility. Next, a voltage of 100 V was applied to the test piece for 1000 hours in an environment of 85 ° C and a relative humidity of 85%, and the change in the insulation resistance was recorded. In general, after 1000 hours of testing, the insulation resistance is maintained above 10 ⁹ Ω, and the insulation resistance difference before and after the test is less than 1 order of magnitude (10 ¹ ), that is, the specifications are met (O stands for pass; X stands for no Qualified), which represents good ion mobility, and the evaluation results are shown in Figure 3. The above difference in insulation resistance is calculated as shown in the following formula (II).

Insulation resistance difference = insulation resistance before test / insulation resistance after test (II)

9. Coverage

In the present invention, the resin composition of Example 3 was further formed into a cover film for the test of the filling property. The above test was a test piece prepared by the same manufacturing method as the ion mobility resistance test, except that the test for the filling property was a copper circuit wiring layer having different pitches (25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm). The cross section of the test piece was observed by an electron microscope, and the gap between the circuit wirings was filled with the cover film of the present invention, indicating that the filling property was good. The results of the evaluation of the filling are shown in Figure 4.

According to the examples 1 to 3 of Table 1, the cover film obtained by using the resin composition of the present invention may have a single layer structure and further have a relatively thin thickness. In addition, the cover film of the present invention has good peeling strength (or adhesion) and solder heat resistance to the copper substrate and the polyimide substrate, and the cover film has better bendability and flame resistance. Resistance to ion mobility.

In addition, according to FIG. 3, the cover film formed by the resin composition of the present invention has an overall insulation resistance of 10 ⁹ Ω after 1000 hours of voltage measurement for 1000 hours, and the difference in insulation resistance before and after the test is less than one order of magnitude. , representing that the prepared cover film has good resistance to ion mobility. 4, the cover film of the present invention (for example, the cover film 310A to the cover film 310F) has a pitch of 25 μm to 50 μm (pitch D1 of 50 μm, pitch D2 of 45 μm, pitch D3 of 40 μm, and pitch D4 of 35 μm). The flexible printed circuit board of the copper circuit wiring layer (for example, the copper circuit wiring layer 320A to the copper circuit wiring layer 320F) having a pitch D5 of 30 μm and a pitch D6 of 25 μm can have good filling property.

On the other hand, according to the comparative example of Table 1, it is understood that when the respective components in the resin composition or the amount thereof used do not conform to the range claimed by the present invention, the predetermined thickness, the amount of overflow, the peel strength, and the bending of the present invention cannot be attained. Properties, flame resistance and/or solder heat resistance. In particular, according to Comparative Example 1 of Table 1, it is understood that, in the case where the first epoxy resin (a-1) of the present invention is not used, coverage by a conventional two-layer structure (polyimine layer plus adhesive layer) is used. Although the film can improve the peeling strength and increase the flexibility by the covered polyimide layer, the thickness of the cover film of Comparative Example 1 is thick, which does not meet the current goal of thinning. Further, if the cover film of Comparative Example 1 did not form a two-layer structure and its composition was similar to that of Comparative Example 2, the evaluation result was also similar to that of Comparative Example 2, and the intended properties of the present invention could not be attained.

The resin composition, the cover film, and the flexible printed circuit board of the present invention are applied by a specific composition of the resin composition (for example, specific use of the first epoxy resin (a-1) and the second epoxy resin (a-2) The ratio of the amount, and the specific type of toughening agent, can be directly disposed on the copper circuit wiring layer without the adhesive layer, in other words, the cover film has a single layer structure and the thickness is relatively small. thin. In addition, the cover film has good peel strength, solder heat resistance, bendability, flame resistance, ion mobility resistance, and filling properties.

While the invention has been described above in terms of several embodiments, it is not intended to limit the scope of the invention, and the invention may be practiced in various embodiments without departing from the spirit and scope of the invention. The scope of protection of the present invention is defined by the scope of the appended claims.

Compound of formula (1-1) (a-2) (made by Cardolite Co., Ltd.; NC-514)

A-2-1 phenolic epoxy resin (manufactured by Changchun Synthetic Resin Co., Ltd.; model: CNE-200ELB; epoxy equivalent: 200g/eq)

A-2-2 bisphenol A epoxy resin (manufactured by Changchun Synthetic Resin Co., Ltd.; model BE-188; epoxy equivalent: 187g/eq)

A-3-1 bisphenol A epoxy resin (manufactured by Changchun Synthetic Resin Co., Ltd.; model: BE-150X-75; epoxy equivalent: 500g/eq)

B-1 4,4'-diaminodiphenyl hydrazine (manufactured by Atul; trade name AtulSulpho 44DDS)

B-2 Diethylenetriamine (made by Qinyu Enterprise)

C-1 Complex of boron trifluoride and monoethylamine (manufactured by Toshin Chemical Co., Ltd.)

C-2 2-methylimidazole (four countries)

D-1 diethylaluminum phosphate (manufactured by Clariant Chemical Co., Ltd.; model OP935)

D-2 aluminum hydroxide (manufactured by Showa Chemical; model H-42M (FAL): average particle size 3 μ m)

E-1 Polyaminomethyl ester (TOYOBO; model SD-5000)

E-2 Acrylonitrile-butadiene rubber (made by Nandi Chemical; model is Hycarl042)

F-1 butanone

F-2 toluene

G-1 distearyl pentaerythritol diphosphite (antioxidant; manufactured by ADEKA; model STAB PEP-8T (AR-2))

G-2 dispersant (BYK chemical additives and instruments; model BYK-310)

G-3 leveling agent (by BYK Chemical Additives and Instruments; model number BYK-W903)

200F‧‧‧Soft printed circuit board

210‧‧‧ Cover film

241‧‧‧ copper circuit wiring layer

243‧‧‧ Polyimine substrate

Claims (9)

A flexible printed circuit board comprising: a substrate; a copper circuit wiring layer disposed on a surface of the substrate; and a cover film disposed on the copper circuit wiring layer, wherein the cover film is a single layer The structure does not have an adhesive layer, the cover film comprises a resin composition, and the resin composition comprises: an epoxy resin (A) comprising: a first epoxy resin (a-1), wherein the first ring The oxygen resin (a-1) has a structure represented by the following formula (I): In the formula (I), the R ¹ is , the R ² is or a is an integer from 0 to 2, and the * is a bond; and a second epoxy resin (a-2); a hardener (B); a catalyst (C); a flame retardant (D) a toughening agent (E), wherein the toughening agent (E) comprises a polyester resin; and a solvent (F), wherein the first ring is used based on the epoxy resin (A) used in an amount of 100 parts by weight The oxygen resin (a-1) is used in an amount of 30 parts by weight to 50 parts by weight, and the second epoxy resin (a-2) is used in an amount of 50 parts by weight to 70 parts by weight, and the curing agent (B) is used. The amount of the catalyst (C) is from 0.8 part by weight to 1 part by weight, the amount of the flame retardant (D) used is from 50 parts by weight to 60 parts by weight, the toughening agent (for the amount of from 16 parts by weight to 20 parts by weight) E) is used in an amount of from 70 parts by weight to 90 parts by weight, and the solvent (F) is used in an amount of from 75 parts by weight to 85 parts by weight. The flexible printed circuit board according to claim 1, wherein the first epoxy resin (a-1) is selected from the structures represented by the following formulas (I-1) to (I-3) Forming at least one of a group. The flexible printed circuit board according to claim 1, wherein the second epoxy resin (a-2) comprises a novolac epoxy resin, a bisphenol A epoxy resin, an alicyclic epoxy resin, and a heterocyclic ring. Type epoxy resin, epoxy propyl ester type epoxy resin or any combination of the above. The flexible printed circuit board of claim 1, wherein the hardener (B) comprises a polyamine compound, an phthalic anhydride compound, or any combination thereof. Soft printing as described in item 1 of the patent application A circuit board in which the catalyst (C) comprises an imidazole compound, a tertiary phosphine, a boron fluoride complex or any combination of the above. The flexible printed circuit board of claim 1, wherein the flame retardant (D) is composed of a phosphorus-containing compound and a metal-containing compound, and the metal-containing compound comprises a metal oxide or a metal hydroxide. . The flexible printed circuit board of claim 6, wherein one of the metal-containing compounds has an average particle diameter ranging from 1 μm to 5 μm. The flexible printed circuit board of claim 1, wherein the polyester resin is a polyurethane. The flexible printed circuit board of claim 1, wherein the cover film is provided on the copper circuit wiring layer by a coating step, a baking step, and a curing step by the resin composition. .