KR20160064466A - Method for manufacturing flexible printed circuit board, and flexible printed circuit board manufactured thereby - Google Patents

Abstract

The present invention relates to a method for manufacturing a flexible printed circuit board. More particularly, the present invention relates to a method for manufacturing a flexible printed circuit board which includes a process of hardening a composite for an adhesive layer through two steps. The method for manufacturing a flexible printed circuit board improves adhesion to provide a flexible printed circuit board having superior flexibility and durability and the reliability of a circuit. Also, it can be used to various kinds of small and medium electronic devices such as a smart phone, a display, a solar cell, and electronic paper.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a flexible printed circuit board and a flexible printed circuit board manufactured thereby,

The present invention relates to a method of manufacturing a flexible printed circuit board having excellent interfacial adhesion and a flexible printed circuit board manufactured thereby.

The printed circuit board connects or supports various parts to the printed circuit board according to the circuit design of the electric wiring. The printed circuit board may include a rigid printed circuit board, a flexible printed circuit board, a rigid-flexible printed circuit board coupled to the rigid printed circuit board, and a rigid-flexible printed circuit board similar to a multi- It is divided into printed circuit board.

Among these, a flexible printed circuit board (FPCB) is advantageous in that the flexible printed circuit board (FPCB) has a thin thickness and excellent bendability because a component or a copper foil circuit is mounted on a flexible insulating film such as polyimide. For this reason, the flexible printed circuit board is widely used in core substrates for small and medium-sized electronic devices such as mobile phones, digital cameras, notebook computers, tablet PCs, electronic books, and electronic notebooks. Further, in the future, the importance of a flexible printed circuit board in increasing the degree of integration, miniaturization, light weight, and flexibility of communication and electronic devices is increasing.

As a method for producing such a flexible printed circuit board, there is a method of bonding a film-like substrate to a thin metal film layer by using an adhesive such as an acrylic resin or an epoxy resin or a method of directly bonding an aqueous solution of a substrate material on a metal layer And the like.

However, since the adhesive used in the production method using an adhesive is an epoxy, phenol, acrylonitrile, butadiene resin or the like and its heat resistance is inferior to that of the polyimide used for the substrate, There is a concern. In general, the bonding with the circuit is performed at a temperature of 300 to 400 DEG C, and a pressure of 0.2 to 0.3 N per bump is applied. When bonding is performed under such a condition, heat and pressure are applied directly to the adhesive layer to cause thermal decomposition of the adhesive layer, and the wiring is largely submerged in the adhesive layer, resulting in disconnection.

On the other hand, since the manufacturing method using no adhesive does not directly form the metal layer on the substrate, the kind of the substrate and the thickness of the metal layer can be freely changed, but the adhesion with the metal layer is low. In addition, pinholes and the like are apt to occur, and the productivity is difficult to increase, which is also a problem of high cost. Further, when the metal layer is thin, there are problems such as generation of curl in the metal layer, generation of wrinkles in the metal layer, foaming of the resin layer and oxidation deterioration of the copper foil due to volumetric contraction or heat shrinkage during drying or curing.

In recent years, in order to improve the interfacial adhesion between the substrate and the metal in the flexible printed circuit board manufacturing method regardless of whether or not an adhesive is used, an interfacial adhesion improving layer is formed between the metal layer and the substrate after dry pretreatment using a plasma or an ion beam A method of modifying the surface of the substrate by wet pretreatment of the surface of the substrate with an alkali solution or a fluorine-based solvent, a method of changing the type of the adhesive used on the substrate, or a method using an adhesion promoter have been actively studied.

Korean Patent Registration No. 10-0764300 discloses a method in which a surface of a polymer film as a substrate is subjected to a dry pretreatment with a plasma and then a dissimilar metal layer made of nickel, chromium, or an alloy thereof is formed and then a metal layer is formed to form a dissimilar metal layer And a method of enhancing the adhesion between the substrate and the metal layer by acting as a set organization.

In Korean Patent Registration No. 10-0679072, the surface of a substrate is treated with a surfactant containing a silane-based coupling agent in a fluorine-based solvent, thereby lowering the surface energy of the substrate and stably forming a bond between the substrate and the metal layer. And the like.

Korean Patent Registration No. 10-0593741 proposes a method of improving adhesion by forming a tie layer of a copper tin compound containing Zn-V or Zn-Ta between a polyimide film as a substrate and a copper conductive layer as a metal layer have.

These patents show that although the adhesive strength is improved, the effects are not sufficient and problems caused by poor circuitry or insufficient durability can not be solved.

Korean Patent Registration No. 10-064300 Korean Patent Registration No. 10-0679072 Korean Patent Registration No. 10-0593741

As a result of various studies on the material and the manufacturing method so that an excellent adhesive force can be sufficiently maintained, the Applicant has confirmed that the above problems can be solved through the step of curing the adhesive layer composition in two steps, Respectively.

Accordingly, it is an object of the present invention to provide a method of manufacturing a flexible printed circuit board that improves the interfacial adhesion between a substrate and a metal layer through two heat treatments at a different temperature of a composition for an adhesive layer.

Another object of the present invention is to provide a flexible printed circuit board having excellent interfacial adhesion by the above-described manufacturing method, excellent chemical resistance and heat resistance, and high reliability and bending durability even under frequent bending or severe conditions.

In order to achieve the above object,

Applying a composition for an adhesive layer to a substrate;

Heat treating at a first temperature to form a semi-cured adhesive layer;

Forming a seed layer on the semi-cured adhesive layer;

Forming a metal layer on the seed layer; And

And a step of heat-treating at a second temperature to cure the flexible printed circuit board.

The first temperature may range from 50 to 250 ° C.

The second temperature may be in the range of 100 to 350 占. At this time, the difference between the first temperature and the second temperature may be 30 to 150 °.

The present invention is also a flexible printed circuit board manufactured through the above steps.

The method of manufacturing a flexible printed circuit board according to the present invention can maintain the reliability of the bending durability and circuit performance of the entire substrate while improving the interfacial adhesion between the substrate and the metal layer through two-step curing of the adhesive layer composition.

The flexible printed circuit board obtained through such a manufacturing method can be applied to various small and medium electronic apparatuses such as a smart phone, a display, a solar cell, and an electronic paper.

1 is a flowchart illustrating a method of manufacturing a flexible printed circuit board according to an embodiment of the present invention.
2 is a cross-sectional view showing a flexible printed circuit board according to this embodiment.

The present invention proposes a method of manufacturing a flexible printed circuit board in which the adhesive strength between the substrate and the metal layer is improved by curing the adhesive layer composition in two steps.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

1 is a flowchart illustrating a method of manufacturing a flexible printed circuit board according to an aspect of the present invention.

As shown in FIG. 1, a method of manufacturing a flexible printed circuit board according to the present invention includes:

(S1) applying a composition for an adhesive layer to a substrate;

(S2) heat-treating at a first temperature to form a semi-cured adhesive layer;

(S3) forming a seed layer on the semi-cured adhesive layer;

Forming a metal layer on the seed layer (S4); And

And a step (S5) of curing by heat treatment at a second temperature.

Each step will be described in more detail below.

First, in step S1, a composition for an adhesive layer is applied to a substrate.

The substrate of the present invention is that the space and supports the conductor circuits are arranged to to be connected to each other receive various electric and electronic components to power and therefore less dimensional change even in a severe condition a high glass transition temperature (T _g), It should be superior in heat resistance and also superior in flexibility and insulation. In addition, the chemical resistance and moisture resistance must also be excellent.

The material of the substrate is selected from the group consisting of polystyrene (PS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), polytetrafluoroethylene (LCP), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), ethylene-chlorotrifluoroethylene copolymer ), Polychlorotrifluoroethylene (PCTFE), and combinations thereof. Polyethylene terephthalate (PET) or polyimide (PI) is preferably used because polyethylene terephthalate and polyimide are excellent in insulation, heat resistance and bending resistance, flexible, less deformed in dimension and strong in heat.

At this time, the thickness of the substrate varies depending on the application and is not particularly limited, but is preferably 10 to 150 mu m, more preferably 25 to 50 mu m. At this time, if it is less than the above range, it is difficult to support or handle the conductor circuit, and conversely, if it exceeds the range, the flexibility becomes poor.

 The composition for an adhesive layer of the present invention is a composition for forming an adhesive layer for bonding a substrate and a seed layer, and includes an adhesive. These adhesive layers are most affected when exposed to thermal shocks in the manufacture and use of flexible printed circuit boards.

The adhesive layer composition may be one selected from the group consisting of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), and combinations thereof. Preferably, polyimide (PI) is used.

The composition for the adhesive layer may be applied in the form of a monomer mixture, an oligomer or a precursor solution, preferably a polyamic acid precursor solution in the case of polyimide.

The resins mentioned above may be prepared directly or purchased commercially. The preparation can be carried out according to any conventionally known method.

In the case of polyimide, it can be obtained by reacting a carboxylic acid anhydride with a diamine compound.

The carboxylic acid anhydride is not particularly limited in the present invention, and examples thereof include 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 1,4-hydroquinone dibenzoate- 3 ', 4,4'-tetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic acid Bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4- (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2- , 3,3-hexafluoropropane dianhydride, and 2,2-bis [(3,4-dicarboxyphenoxy) phenyl] propane dianhydride, and combinations thereof.

Also, in the case of the diamine compound, p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenylsulfide, 3,4'-diaminodiphenyl Sulfide, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'- 3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, Diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, ), 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, and combinations thereof.

Commercially available polyimide resins include POLYZEN 150P, a product of PICOMAX, and FinePI-100, a product of Fine Polymer Co.,

Polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are polyester resins, which can be prepared by the reaction of a dicarboxylic acid with an alcohol compound.

The dicarboxylic acid compound is an aliphatic or aromatic organic compound having two carboxyl groups, including aliphatic dicarboxylic acids and anhydrides thereof; Aromatic dicarboxylic acids and their anhydrides; And derivatives thereof can be used. Specifically, substituted or unsubstituted aliphatic dicarboxylic acids having 2 to 17 carbon atoms such as substituted or unsubstituted oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid and the like; Substituted or unsubstituted aromatic dicarboxylic acids having 6 to 18 carbon atoms such as substituted or unsubstituted phthalic acid, isophthalic acid, terephthalic acid and the like; Aliphatic dicarboxylic acids or their anhydrides or derivatives thereof having 2 to 6 carbon atoms such as oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid may be used, It is not necessarily limited. The dicarboxylic compound may be used singly or in combination of two or more.

The alcohol compound is an aliphatic or aromatic organic compound having one hydroxyl group, and includes aliphatic monoalcohols; Aromatic monoalcohols; And monohydroxy compounds containing at least one etheric oxygen may be used. Specific examples thereof include substituted or unsubstituted alcohols having 2 to 15 carbon atoms such as substituted or unsubstituted alcohols such as ethanol, propanol, butanol, pentanol, hexanol, heptanol, 2-ethylhexanol, octanol, decanol, Aliphatic monoalcohols; Substituted or unsubstituted aromatic monoalcohols having 6 to 18 carbon atoms such as substituted or unsubstituted phenol; Ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl Propylene glycol monomethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol Substituted or unsubstituted monohydroxy compounds having 2 to 15 carbon atoms containing at least one etheric oxygen such as monobutyl ether and the like. Preferably, the use of a substituted or unsubstituted monohydroxy compound having 2 to 15 carbon atoms, which contains at least one etheric oxygen, maximizes the pinhole effect and can exhibit stable dispersibility in an aqueous medium, It is not. The monohydroxy compound may be used singly or in combination of two or more.

Commercially available polyester resins include DVB-2318, DVB-2319, Polycoat, Aekyung Chemical Co., Ltd., which are products of Noru Paint Co., Ltd.

At this time, the solvent for forming the adhesive layer composition is not particularly limited and may be suitably selected in accordance with the intended purpose. Specific examples thereof include ketone solvents such as water, acetone, methyl, ethyl ketone and cyclohexanone, acetates such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate and carbitol acetate, Carbitol and the like, and cyclic ester compounds such as ? -Butyrolactone, aromatic hydrocarbons such as toluene, xylene and petroleum naphtha, dimethylformamide, dimethylacetamide, N -methylpyrrolidone and combinations thereof One selected species can be used.

The content of the above-mentioned solvent is preferably in the range of 10 to 40% by weight so as to have an appropriate viscosity for ease of work.

A curing agent may further be added to the adhesive layer composition according to the present invention. As the curing agent usually used, there are a heat curing agent and a photo-curing agent, and mainly amines, imidazoles, tertiary amines, quick-curing mercaptans, acid anhydrides and the like are used.

If necessary, the adhesive composition of the present invention may further contain less than 5% by weight of a curing assistant, a diluent, a thickener, a filler, a softener, an accelerator, a colorant, a flame retarder, a light stabilizer, a coupling agent and a polymerization inhibitor. These additives are selectively added depending on the intended use, application, processing conditions, and the like of the adhesive.

The composition for the adhesive layer has a rotational viscosity of about 1 to 500 cP, particularly 5 to 100 cP, more preferably about 10 to 50 cP for proper handleability of the solution.

The thickness of the adhesive layer composition varies depending on the use. When used in the manufacture of a flexible printed circuit board, it is preferable that the thickness of the adhesive layer is in the range of 1 to 10 mu m since the thickness of the metal layer serving as a circuit is generally 5 to 70 mu m. If the thickness is too thin, the interfacial adhesion is insufficient. On the other hand, if the thickness is too thick, the curing time becomes long and the product quality becomes problematic.

The coating can be carried out by a conventional wet coating method. Typically, one of dip coating, spray coating, spin coating, knife coating, roller coating, gravure coating and rod coating is possible, Spray coating is performed.

Next, in step S2, heat treatment is performed at a first temperature to form a semi-cured adhesive layer.

Particularly, the first temperature is in the range of 50 to 250 ° C. The temperature range can be appropriately adjusted according to the composition for the adhesive layer. For example, when the polyimide resin is used as the composition for the adhesive layer, it is preferably in the range of 150 to 200 占 폚, and in the case of the polyester resin, it is preferably in the range of 100 to 120 占 폚.

At this time, the heat treatment time at the first temperature may be adjusted depending on the substrate or solvent used so that a part of the organic solvent contained in the adhesive layer composition is removed and becomes semi-hardened. The heat treatment time is preferably about 10 to 20 minutes.

In addition, the heat treatment method at the first temperature is not particularly limited, and can be carried out by selecting a conventional heat treatment method in the technical field. For example, heat can be applied using an electric oven or a drying oven, IR drying, UV drying, and the like.

Here, the semi-cured adhesive layer is characterized in that the degree of polymerization of the adhesive layer composition ranges from 50 to 80% after the first heat treatment at room temperature (25 to 30 占 폚). At this time, the semi-cured state is formed by using a property that stickiness remains on the surface when the adhesive layer composition is semi-cured. That is, this stickiness plays a role of enhancing the adhesive force with the metal layer formed thereon. Therefore, when the curing is sufficiently performed to eliminate the stickiness, that is, to have a degree of polymerization of 95% or more, adherence to the metal layer formed on the surface is disadvantageously deteriorated due to disappearance of surface stickiness. If the degree of polymerization is less than 50%, the adhesion to the metal layer formed thereon is improved, but the stickiness is too strong, which may adversely affect the relative surface, or the adhesive layer may be too slanted to form a metal layer.

Next, in step S3, a seed layer is formed on the adhesive layer through step S2.

The seed layer may include at least one of aluminum (Al), titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Pd), silver (Ag), tin (Sn), neodymium (Nd), tungsten (W), platinum (Pt), gold (Au) and combinations thereof. Preferably, one kind selected from aluminum (Al), Ti (titanium), Cr (chromium), nickel (Ni), copper (Cu), neodymium (Nd), tungsten (W) and combinations thereof is used.

At this time, the seed layer is formed by a conventional vacuum deposition method. The vacuum deposition method includes chemical vapor deposition (CVD) and physical vapor deposition (PVD) using a physical method. CVD includes MOCVD (Metal-Organic Chemical Vapor Deposition) and HVPE (Hydride Vapor Phase Epitaxy). PVD includes thermal evaporation, E-Beam deposition, laser deposition, sputtering, and ion plating.

CVD using a chemical method is a method in which a substance to be deposited on a substrate is injected as a gas in a gaseous state rather than a solid state, and is deposited on the substrate in a reaction chamber through high temperature decomposition or high temperature chemical reaction. This method is excellent in adhesion and can be uniformly deposited on a complex substrate, and deposition of a high purity substance is easy. In addition, localized deposition can be performed by selecting a desired region on a substrate of a specific type. However, since a high temperature of 500 ° C or more is required for a smooth reaction, there may be a problem in the physical properties of the substrate and the metal.

The evaporation method of the evaporation material includes resistance heating, electron beam heating, ion beam heating, laser heating, and high frequency induction heating, and resistance heating and electron beam heating Is mainly used. Vacuum deposition is the most excellent method in terms of high-speed film formation, but it has a problem that adhesion is too low.

Sputtering is a technique of depositing a thin film on the surface of a substrate by bombarding a metal plate with an inert element such as argon and causing metal molecules to protrude therefrom. Sputtering is superior to other vacuum evaporation techniques in terms of adhesion to a thin film, but there is a problem in forming a high-speed film by a technique of the lowest deposition rate.

Ion plating is a method in which a gas such as argon is injected into a vacuum chamber to cause a plasma in a vacuum state to ionize a deposition material and a gas to deposit the material to be deposited with a high energy. Since the evaporated particles are deposited with high energy, the deposition rate is high and adhesion is good. In general, a film formed by ion plating has an adhesion of 50 to 100 times higher than that of conventional vacuum deposition or wet plating, and a uniform compound film can be easily obtained due to the activation effect by discharge.

In the present invention, the sputtering method is preferable in consideration of the adhesion and uniformity of the seed layer.

The seed layer is intended to further increase the adhesion with the metal layer. The thickness of the seed layer is preferably in the range of 0.01 to 1 占 퐉 in consideration of circuit formation. It is advantageous that the thickness is low considering the mass productivity and more preferably in the range of 0.03 to 0.2 탆.

Next, in step S4, a metal layer is formed on the seed layer after step S3.

The metal layer may be at least one of aluminum (Al), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), palladium (Pd) Sn), platinum (Pt), gold (Au), and combinations thereof. Preferably, one species selected from copper (Cu), silver (Ag), and combinations thereof is used.

At this time, the metal layer is formed by a conventional vacuum deposition method. The vacuum deposition method is as described in the above-mentioned seed layer.

In the present invention, the sputtering method is preferable when the adhesion and uniformity of the metal layer are considered.

At this time, the metal layer has a thickness of 5 to 70 μm, preferably 10 to 50 μm, more preferably 5 to 20 μm. At this time, in consideration of formation of a thick circuit, it is generally preferable to be in the range of 5 to 70 mu m, and it is more preferable that it is in the range of 5 to 20 mu m in consideration of the fine wiring formation. The thickness of the metal layer may vary depending on the apparatus to which the flexible printed circuit board of the present invention is applied, and is not particularly limited in the present invention.

Next, in step S5, a flexible printed circuit board can be manufactured by heat-treating at a second temperature to be cured.

The step S5 of the present invention is performed not only to fix the metal layer to the substrate by completely curing the semi-cured adhesive layer composition but also to form a bond between the metal particles in the metal layer to have excellent electrical conductivity.

And the second temperature is 100 to 350 ° C. The temperature range may be determined depending on the characteristics of the substrate, the composition for the adhesive layer, and the metal layer. Specifically, when the composition for the adhesive layer is polyimide, it is preferably in the range of 250 to 300 占 폚, and in the case of the polyester-based resin, it is in the range of 150 to 200 占 폚.

The polyethylene terephthalate or polyimide used in the present invention or in the composition for the adhesive layer is a material developed for high temperature. However, when the process is performed at a temperature higher than a set temperature, shrinkage occurs, and defects such as dents and carbonization are caused . Conversely, if the curing temperature is not sufficient, problems may occur in adhesion and durability. If the metal layer is treated at an excessively high temperature, the metals are adhered to each other, and the material for increasing electrical conductivity such as polymer resin and solvent is removed to increase the resistance.

At this time, the heat treatment time at the second temperature may be controlled according to a substrate, a solvent, a metal, or the like, which is contained in the composition for the adhesive layer so that the organic solvent is completely removed and is completely cured. Generally, it is preferably about 10 to 60 minutes.

In addition, the heat treatment method at the second temperature is not particularly limited, and can be carried out by selecting a conventional heat treatment method in the technical field. For example, heat treatment can be performed using an electric oven, a drying oven, IR drying, UV drying, or the like.

In particular, the difference between the first temperature and the second temperature is 30 to 150 ° C. Such a temperature difference is related to the aforementioned degree of curing, and curing can be performed at different temperatures, thereby firmly bonding the substrate and the metal layer and improving the reliability of the entire flexible printed circuit board. At this time, if the temperature difference is too large or small, there is a problem that the adhesive strength improving effect is not exhibited. Therefore, it is preferable that the adhesive layer composition has a difference between the first temperature and the second temperature of about 50 to 150 DEG C when the polyimide is used and about 30 to 100 DEG C when the polyester is used.

A flexible printed circuit board made by the method of manufacturing a flexible printed circuit board according to the present invention may be added with an appropriate additional process.

Concretely, after the flexible printed circuit board obtained through steps S1 to S5 is pressed by a hot press, a circuit can be formed through a photolithography process such as exposure, development, and etching process.

The soft brace circuit board manufactured through the above steps is as shown in Fig. 2, the flexible printed circuit board 10 has a structure in which an adhesive layer 3 is formed so as to surround the entire surface of the substrate 1, and a seed layer 5 and a metal layer 7 are sequentially stacked on the adhesive layer 3 .

The flexible printed circuit board 10 having such a structure can be manufactured in a manufacturing process of the adhesive layer 3

By performing the step of two-step curing the composition for the adhesive layer, the adhesive force between the substrate and the metal layer can be effectively improved. As a result, the flexible printed circuit board according to the manufacturing method of the present invention exhibits excellent interfacial adhesion, and is excellent in flexibility, chemical resistance, and heat resistance, so that high reliability can be secured without a circuit defect rate or malfunction under frequent bending or severe operating conditions .

The method for manufacturing a flexible printed circuit board according to the present invention is a method for manufacturing a flexible printed circuit board by maintaining a good adhesive force between a substrate and a metal layer, Or display products.

Hereinafter, preferred embodiments and experimental examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited by these examples.

Examples 1 to 2 and Comparative Examples 1 to 3: Flexible printed circuit board fabrication

[Example 1]

A coating composition (PLC300SPI - PicoMAX Co., Ltd.) containing polyimide was spray-coated on one side of a polyimide film having a thickness of 25 占 퐉 as a substrate so as to have a thickness of 3 占 퐉. Subsequently, after heat treatment at 180 占 폚 for 10 minutes, a seed layer and a copper metal layer were formed on the semi-cured adhesive layer to a thickness of 0.2 占 퐉 by sputtering. Next, the substrate was subjected to heat treatment at 290 占 폚 for 30 minutes to form a pattern and a plating process to produce a flexible printed circuit board.

[Example 2]

On one side of a polyimide film having a thickness of 25 占 퐉 as a substrate, a polyester-containing adhesive composition (Polycoat-Akei Chemical) was spin-coated to a thickness of 3 占 퐉. Subsequently, after heat treatment at 105 占 폚 for 10 minutes, a seed layer and a copper metal layer were formed on the semi-cured adhesive layer to a thickness of 0.2 占 퐉 by sputtering. Next, the substrate was heat-treated at 175 캜 for 30 minutes to produce a flexible printed circuit board.

[Comparative Example 1]

A flexible printed circuit board was fabricated in the same manner as in Example 1 except that the composition for an adhesive layer was used as an acrylic adhesive.

[Comparative Example 2]

A flexible printed circuit board was fabricated in the same manner as in Example 1 except that the first temperature was maintained at 100 캜 for 10 minutes by heat treatment.

[Comparative Example 3]

A flexible printed circuit board was fabricated in the same manner as in Example 2 except that the second temperature was 130 ° C for 30 minutes.

Experimental Example 1: Peel strength evaluation

The peel strength was a value measured by a 90 ° angle peeling test (pulling rate: 50 mm / min) by applying a copper plating having a thickness of 12 μm on the sputter layer and applying IPC-650PM 2.4.9.D standard.

Experimental Example 2: Flexural durability evaluation

A single-sided circuit board was produced by screen-printing the flexible printed circuit boards prepared in Examples 1 to 2 and Comparative Examples 1 to 3 using a 200-mesh plate. The produced single-sided circuit board was bent at 180 °. The bending durability evaluation is as follows.

≪ Evaluation of bending durability &

Good: Flexibility

X: Insufficient flexing

The polymerization degree after the first temperature heat treatment Degree of polymerization after the second temperature heat treatment Peel strength
[Kgf / cm2] Bending durability Example 1 70% 95% 1.0 ○ Example 2 60% 90% 0.8 ○ Comparative Example 1 - - 0.4 X Comparative Example 2 40% 95% 0.5 X Comparative Example 3 80% 95% 0.3 X

Referring to Table 1, when the heat treatment process was carried out at the first temperature and the second temperature according to the production method of the present invention, Comparative Example 1 in which the semi-cured state was not changed and Comparative Examples 2 to 3, 3, it was confirmed that the resin had excellent flexural durability because no whitening occurred at the bent portion.

The method of manufacturing a flexible printed circuit board according to the present invention has excellent interfacial adhesion and bending durability, and the obtained flexible printed circuit board can be used for various small and medium sized electronic devices such as a smart phone, a display, a solar cell, and an electronic paper.

1: substrate 3: adhesive layer
5: seed layer 7: metal layer
10: Flexible printed circuit board

Claims (10)

Applying a composition for an adhesive layer to a substrate;
Heat treating at a first temperature to form a semi-cured adhesive layer;
Forming a seed layer on the semi-cured adhesive layer;
Forming a metal layer on the seed layer; And
And heat-treating at a second temperature to harden the flexible printed circuit board. The method of claim 1, wherein the first temperature is between 50 and 250 ° C. [4] The method of claim 1, wherein the second temperature is 100 to 350 [deg.] C. The method of claim 1, wherein the difference between the first temperature and the second temperature is between 30 and 150 ° C. The method of claim 1, wherein the substrate is selected from the group consisting of polystyrene (PS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), polytetrafluoroethylene , Liquid crystal polymer (LCP), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), ethylene- chlorotrifluoroethylene (ECTFE), polychlorotrifluoroethylene (PCTFE), and a combination thereof. [4] The composition for an adhesive layer according to claim 1, wherein the composition for the adhesive layer is one selected from the group consisting of polyethylene terephthalide (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide A method of manufacturing a flexible printed circuit board. The method of claim 1, wherein the seed layer is selected from the group consisting of aluminum (Al), titanium (Ti), chromium (Cr)
(Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), palladium (Pd), silver (Ag), tin (Sn), neodymium , Tungsten (W), platinum (Pt), gold (Au), and combinations thereof. The method of claim 1, wherein the metal layer comprises at least one of aluminum (Al), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), palladium (Ag), tin (Sn), platinum (Pt), gold (Au), and a combination thereof. [4] The method of claim 1, wherein the seed layer and the metal layer are formed using a material selected from the group consisting of MOCVD (Metal Organic Chemical Vapor Deposition), HVPE (Thermal Vapor Phase Epitaxy), thermal deposition, E-Beam deposition, laser deposition, sputtering, Wherein the step of forming the flexible printed circuit board comprises the steps of: A flexible printed circuit board produced by the method of any one of claims 1 to 9.

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