Method for manufacturing flexible printed circuit board and flexible printed circuit board manufactured by same

A method for manufacturing a flexible printed circuit board in which base sheets composed of Teflon film having heat resistance and low dielectric constant are stacked to prevent loss of a high frequency signal while minimizing dielectric loss due to the high frequency signal and a flexible printed circuit board manufactured by the same are disclosed. The proposed method for manufacturing a flexible printed circuit board comprises a step of preparing a base sheet which is a Teflon film having a thin film pattern formed on one surface thereof, a step of preparing an adhesive sheet, a step of stacking a plurality of base sheets and adhesive sheets, and a step of heating, pressing, and adhering a stacked body in which the plurality of base sheets and adhesive sheets are stacked.

TECHNICAL FIELD

The present disclosure relates to a method for manufacturing a flexible printed circuit board and the flexible printed circuit board manufactured by the same, and more particularly, to a method for manufacturing a flexible printed circuit board having heat resistance and flexibility and the flexible printed circuit board manufactured by the same.

BACKGROUND ART

In general, a printed circuit board is a board that may be flexibly bent by forming a circuit pattern on a thin insulating film, and is widely used in a portable electronic device and an automation device or a display product requiring bending and flexibility when mounted and used.

In general, the printed circuit board is manufactured by bonding or die-casting a copper foil to a polyimide (PI) film. At this time, since the polyimide film has characteristics such as high mechanical strength, heat resistance, insulation, and solvent resistance, it is much used as a base material of a printed circuit board.

Meanwhile, as the use of services for transmitting large amounts of information in real time, such as a video call, movie watching, and real-time relay, increases, a portable terminal is mounted with circuits for transmitting large amounts of information by using a high frequency band (for example, GHz).

However, in the case of transmitting a high frequency signal by using a printed circuit board made of a polyimide film, there is a problem in that a signal loss of the high frequency signal occurs due to the dielectric loss inherent in the material.

In other words, there is a problem in that the polyimide film has a high dielectric constant, dielectric loss occurs at transmission and reception of the high frequency signal, such that loss of the high frequency signal occurs, thereby occurring disconnection when using services such as a video call, movie watching, and real-time relay.

Further, there is a problem in that a printed circuit board made of a film having low dielectric constant may minimize the loss of the high frequency signal, but has a low melting temperature to degrade heat resistance, such that a surface is melted by a high temperature of about 250° C. generated in a Surface Mount Technology (SMT) process for mounting a device for a high frequency, thereby causing defects.

Further, there is a problem in that the low dielectric constant and the high heat resistance film are formed at a high price, such that the manufacturing cost of the printed circuit board increases, thereby losing the competitiveness in the market.

DISCLOSURE

Technical Problem

The present disclosure is intended to solve the above conventional problems, and an object of the present disclosure is to provide a method for manufacturing a flexible printed circuit board and the flexible printed circuit board manufactured by the same, which stacks base sheets made of a Teflon film of heat resistance and low dielectric constant, thereby preventing loss of a high frequency signal while minimizing dielectric loss caused by the high frequency signal.

In other words, an object of the present disclosure is to provide a method for manufacturing a flexible printed circuit board and the flexible printed circuit board manufactured by the same, which constitutes a base sheet by forming a circuit pattern on a Teflon base material having excellent heat resistance and dielectric properties, and stacking a plurality of base sheets, thereby forming high heat resistance and low dielectric constant properties.

Further, another object of the present disclosure is to provide a method for manufacturing a flexible printed circuit board and the flexible printed circuit board manufactured by the same, which may reform the surface of a Teflon film, thereby manufacturing a multi-layer flexible printed circuit board by using the Teflon film.

Further, still another object of the present disclosure is to provide a method for manufacturing a flexible printed circuit board and the flexible printed circuit board manufactured by the same, which may form an adhesive layer of a Teflon material on a base sheet, which is a Teflon film, thereby manufacturing a multi-layer flexible printed circuit board.

In other words, still another object of the present disclosure is to provide a method for manufacturing a flexible printed circuit board and the flexible printed circuit board manufactured by the same, which may form a coating adhesive layer on a surface of a Teflon film in an impregnation coating or printing method, and heat, press, and adhere the stacked Teflon films, thereby manufacturing a multi-layer flexible printed circuit board.

Technical Solution

For achieving the objects, a method for manufacturing a flexible printed circuit board according to an embodiment of the present disclosure includes preparing a base sheet, which is a Teflon film having a thin film pattern formed thereon, stacking a plurality of base sheets, and heating, pressing, and adhering a stacked body in which the plurality of base sheets have been stacked. At this time, the preparing the base sheet may prepare the Teflon film having a surface reformed layer or an adhesive layer of a Teflon material formed thereon as the base sheet.

For achieving the objects, a flexible printed circuit board according to an embodiment of the present disclosure includes a stacked body in which a plurality of base sheets have been stacked and a circuit pattern formed on the stacked body, and the base sheet includes a Teflon film having a thin film pattern formed thereon. At this time, the Teflon film may have an adhesive layer or a surface reformed layer formed thereon.

Advantageous Effects

According to the present disclosure, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may stack the plurality of base sheets having high heat resistance and low dielectric constant, thereby minimizing the dielectric loss due to the high frequency signal, and preventing the loss of the high frequency signal.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may stack the base sheets made of the Teflon film having the heat resistant and the low dielectric constant to form the dielectric constant lower than the conventional flexible printed circuit board constituting the base sheet by using the polyimide or polypropylene film, thereby manufacturing the flexible printed circuit board that has minimized the dielectric loss.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may constitute the base sheet with the Teflon sheet to improve reliability, thereby preventing deformation and breakage of the flexible printed circuit board due to the heat (about 250° C.) applied in the reflow process.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may constitute the base sheet with the Teflon sheet, thereby manufacturing the flexible printed circuit board having high heat resistance and low dielectric constant properties.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may form the base sheet by adhering the guide film to the Teflon film, thereby preventing the shape of the Teflon film from being deformed or broken in the manufacturing process to prevent the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may stack the plurality of base sheets and adhesive sheets by forming the guide hole in the base sheet and the adhesive sheet and disposing so that the guide pin formed on the jig penetrates the guide hole formed in the base sheet and the adhesive sheet and then moving them downwards not to perform the alignment process of the stacked base materials (in other words, the base sheet and the adhesive sheet) in the stacking process, thereby simplifying the manufacturing process.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may stack the plurality of base sheets and adhesive sheets by disposing so that the guide pin formed on the jig penetrates the guide hole formed in the base sheet and the adhesive sheet and then moving them downwards to align the thin film patterns formed on the stacked base sheets at accurate locations, thereby preventing the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may form the surface reformed layer, which is ceramic or oxide, on the surface of the Teflon film to improve the adhesive property of the surface of the Teflon film, thereby manufacturing the multi-layer flexible printed circuit board by using the Teflon film having a difficult-to-adhere property.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may form the surface reformed layer, which is ceramic or oxide, on the surface of the Teflon film to improve the adhesive property of the Teflon film, thereby adhering the Teflon film with the adhesive sheets of various materials.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may form the surface reformed layer, which is ceramic or oxide, on the surface of the Teflon film to use the adhesive sheets of various materials, thereby minimizing the manufacturing cost of the flexible printed circuit board.

Further, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may form the adhesive layer including the Teflon slurry on the surface of the Teflon film to improve the adhesive property of the surface of the Teflon film, thereby manufacturing the multi-layer flexible printed circuit board by using the Teflon film having a difficult-to-adhere property.

BEST MODE

Hereinafter, the most preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present disclosure pertains may easily carry out the technical spirit of the present disclosure. First, in adding reference numerals to the components of each drawing, it should be noted that the same components have the same reference numerals as much as possible even if they are displayed on different drawings. In addition, in describing the present disclosure, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present disclosure, the detailed description thereof will be omitted.

Referring toFIGS. 1 and 2, a method for manufacturing a flexible printed circuit board according to a first embodiment of the present disclosure includes preparing a base sheet (S110), preparing an adhesive sheet (S120), stacking (S130), adhering (S140), forming a via hole (S150), and forming a connection pattern (S160).

The preparing the base sheet (S110) prepares the base sheet110on which a guide film112, a Teflon film111, and a thin film pattern116are sequentially stacked, and in which a guide hole penetrating the guide film112and the Teflon film111is formed. At this time, a guide pin220of a jig200is inserted into the guide hole in order to easily perform the stacking (S130) to be described later.

Referring toFIGS. 3 and 4, the preparing the base sheet (S110) includes adhering the Teflon film and the guide film (S111), forming a seed layer (S113), forming a plating layer (S115), forming a thin film pattern (S117), and forming a first guide hole (S119).

The adhering the Teflon film and the guide film (S111) prepares the Teflon film111of heat resistance and low dielectric constant. In other words, a flexible printed circuit board has been completely manufactured and then is mounted with a semiconductor element through a surface mount technology process (in other words, an SMT process).

At this time, there is a problem in that a flexible printed circuit board for a high frequency under development constitutes the base sheet110by using the polypropylene having heat resistance of about 160° C. to 180° C., such that the base sheet110is deformed or broken due to the heat (about 250° C.) applied in a reflow process of the surface mount technology process.

In order to prevent the reliability of the flexible printed circuit board from being degraded if the base sheet110is deformed or broken, the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure constitutes the base sheet110by using the Teflon film111.

At this time, since the Teflon film111is not deformed even in the heat of about 300° C., deformation and breakage of the base sheet due to the heat applied in the reflow process may be prevented.

Accordingly, the adhering the Teflon film and the guide film (S111) constitutes the base sheet110by using the Teflon film111.

As a result, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may prevent deformation and breakage of the flexible printed circuit board due to the heat (about 250° C.) applied in the reflow process, thereby improving reliability.

The Teflon is mainly used as lubricant, release material, and insulation material. Since the Teflon has the best heat resistance and dielectric properties (in other words, low dielectric constant) among polymer materials, it is used as a base material of a printed circuit board for a high frequency requiring low dielectric constant and heat resistance.

However, since the Teflon is soft-melting and thermoplastic, the base material is deformed by heat and pressure applied in the manufacturing process, thereby causing a high defective rate. Accordingly, the Teflon is mainly used as a thick hard-type single-sided or double-sided base material.

In an embodiment of the present disclosure, the Teflon film111of a thin film is used as the base sheet110in order to manufacture the flexible printed circuit board. The Teflon film111is deformed or broken in a shape even at a small pressure applied in the manufacturing process due to the soft-melting property, thereby degrading the manufacturing yield and reliability of the flexible printed circuit board.

Accordingly, the adhering the Teflon film and the guide film (S111) adheres the guide film112to one surface of the Teflon film111in order to prevent deformation and breakage of the Teflon film111in the manufacturing process.

At this time, the guide film112is, for example, a hard polyethylene terephthalate (PET) film.

The adhering the Teflon film and the guide film (S111) adheres the Teflon film111and the guide film112by interposing an adhesive sheet113between the Teflon film111and the guide film112. In other words, since the guide film112should be removed in the stacking (S130) to be described later, the adhering the Teflon film and the guide film (S111) couples the Teflon film111and the guide film112in an adhering state (in other words, the adhesive sheet113) capable of being easily removed while supporting the Teflon film111. Here, the adhesive sheet113is, for example, a silicone (Si)-based adhesive agent.

As described above, the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure may form the base sheet110by adhering the guide film112to the Teflon film111, thereby preventing the shape of the Teflon film111from being deformed or broken in the manufacturing process to prevent the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The forming the seed layer (S113) forms a seed layer114of a thin film on one surface of the Teflon film111. The forming the seed layer (S113) forms the seed layer114on the other surface (in other words, the surface opposite to one surface on which the guide film112has been adhered) of the Teflon film111through a deposition process or a sputtering process. Here, the forming the seed layer (S113) forms the seed layer114of a mixed material of mixing nickel copper (NiCu) and copper (Cu) or a nickel copper (NiCu) material on the other surface of the Teflon film111.

The forming the plating layer (S115) forms a plating layer115on the seed layer114. At this time, the forming the plating layer (S115) forms the plating layer115on the seed layer114by electroplating copper (Cu).

Here, the seed layer114and the plating layer115are elements constituting a circuit pattern, and are formed at a thickness of about 5 μm.

The forming the thin film pattern (S117) forms a thin film pattern116on the other surface of the Teflon film111. In other words, the forming the thin film pattern (S117) forms the thin film pattern116of a predetermined shape by removing parts of the seed layer114and the plating layer115formed on the other surface of the Teflon film111through an etching process.

The forming the first guide hole (S119) forms a plurality of first guide holes117penetrating the Teflon film111and the guide film112. In other words, the forming the first guide hole (S119) forms the plurality of first guide holes117in order to align the base sheets110at accurate locations while firmly fixing the base sheet110to the jig200in the stacking (S130) to be described later. Here, the forming the first guide hole (S119) forms the first guide hole117in the base sheet110through a punching process, a laser drill process, or the like.

The preparing the adhesive sheet (S120) prepares an adhesive sheet120in which a plurality of second guide holes122have been formed. At this time, the preparing the adhesive sheet (S120) forms the second guide hole122at a location corresponding to the first guide hole117at the time of stacking the base sheet110and the adhesive sheet120.

The preparing the adhesive sheet (S120) may prepare the adhesive sheet120of a multi-layer structure having an adhesive layer formed on one surface or both surfaces of the film base material.

For example, the adhesive sheet120may be a Casted polypropylene (CPP) film of low dielectric constant having a low dielectric loss. At this time, the CPP film is formed in a multi-layer structure having the adhesive layer formed on one surface or both surfaces of a polypropylene (PP) film (hereinafter, a PP film).

Here, the adhesive layer may be made of a composite material of mixing the same material as the CPP film (for example, a material of polyethylene (PE), polypropylene (PP), polyimide, or the like) and an additive (for example, acrylate, or the like) in order to increase an adhesive force between polymer (in other words, the Teflon film111of the base sheet110) and the metal (in other words, the thin film pattern116).

The preparing the adhesive sheet (S120) may also prepare the adhesive sheet120of a single layer structure.

At this time, the preparing the adhesive sheet (S120) is, for example, to prepare the adhesive sheet120made of a composite material of mixing a material such as polyethylene, polypropylene, or polyimide with an additive, which has an excellent adhesive property with polymer and metal.

The preparing the adhesive sheet (S120) may also prepare the adhesive sheet120of a Teflon material.

The stacking (S130) stacks the plurality of base sheets110and the adhesive sheet120. At this time, the stacking (S130) interposes the adhesive sheet120between the base sheets110by alternately stacking the base sheet110and the adhesive sheet120.

The stacking (S130) stacks the plurality of base sheets110and the adhesive sheet120by using the jig200. In other words, the stacking (S130) may provide reliability of the flexible printed circuit board only when the thin film patterns116of the base sheet110are stacked to be aligned at accurate locations.

Accordingly, the stacking (S130) stacks the plurality of base sheets110and the adhesive sheet120by using the jig200including the guide pin220.

An example of the stacking (S130) that stacks two base sheets110(in other words, a first base sheet110aand a second base sheet110b) and the adhesive sheet120will be explained with reference toFIGS. 5 and 6as follows.

The stacking (S130) includes stacking the first base sheet110a(S131), removing the guide film112aof the first base sheet110a(S133), stacking the adhesive sheet120(S135), stacking the second base sheet110b(S137), and removing a guide film112bof the second base sheet110b(S139).

The stacking the first base sheet110a(S131) stacks the first base sheet110aon the jig200. In other words, the stacking the first base sheet110a(S131) stacks the first base sheet110aon the jig200by disposing so that the guide pins220of the jig200penetrate first guide holes117aof the first base sheet110a, respectively and then moving them downwards.

At this time, the stacking the first base sheet110a(S131) stacks the first base sheet110aso that a thin film pattern116aformed on the first base sheet110ais positioned downwards in order to easily remove the guide film112a. In other words, the stacking the first base sheet110a(S131) disposes the guide film112aon the top by stacking the first base sheet110aso that the thin film pattern116ais positioned downwards.

The removing the guide film112aof the first base sheet110a(S133) removes the guide film112afrom the first base sheet110astacked on the jig200. In other words, the removing the guide film112aof the first base sheet110a(S133) removes the guide film112aof the first base sheet110adisposed on the top and the adhesive film113a.

The stacking the adhesive sheet120(S135) stacks the adhesive sheet120on the jig200. In other words, the stacking the adhesive sheet120(S135) stacks the adhesive sheet120on the jig200by disposing so that the guide pins220of the jig200penetrate the second guide holes122of the adhesive sheet120, respectively and then moving them downwards. At this time, the stacking the adhesive sheet120(S135) stacks the adhesive sheet120above the first base sheet110astacked on the jig200.

The stacking the second base sheet110b(S137) stacks the second base sheet110bon the jig200. In other words, the stacking the second base sheet110b(S137) stacks the second base sheet110bon the jig200by disposing so that the guide pins220of the jig200penetrate the first guide holes117bof the second base sheet110b, respectively and then moving them downwards.

At this time, the stacking the second base sheet110b(S137) stacks the second base sheet110babove the adhesive sheet120stacked on the jig200. The stacking the second base sheet110b(S137) stacks the second base sheet110bso that one surface, on which the thin film pattern116bhas been formed, is disposed above the adhesive sheet120.

The removing the guide film112bof the second base sheet110b(S139) removes the guide film112bfrom the second base sheet110bstacked on the jig200. In other words, the removing the guide film112bof the second base sheet110b(S139) removes the guide film112bof the second base sheet110bdisposed on the top and an adhesive film113b.

As described above, the method for manufacturing the flexible printed circuit board may stack the plurality of base sheets110and the adhesive sheet120by disposing so that the guide pin220formed on the jig200penetrates the guide holes (in other words, the first guide hole117and the second guide hole122) formed in the base sheet110and the adhesive sheet120and then moving them downwards in the stacking (S130) not to perform the alignment process of the stacked base materials (in other words, the base sheet110and the adhesive sheet120) in the stacking process, thereby simplifying the manufacturing process.

Further, the method for manufacturing the flexible printed circuit board may stack the plurality of base sheets110and the adhesive sheet120by disposing so that the guide pin220formed on the jig200penetrates the guide holes (in other words, the first guide hole117and the second guide hole122) formed in the base sheet110and the adhesive sheet120and then moving them downwards in the stacking (S130) to align the thin film patterns116formed on the stacked base sheets110at accurate locations, thereby preventing the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The adhering (S140) constitutes a stacked body by adhering the plurality of base sheets110and the adhesive sheet120stacked on the jig200.

The adhering (S140) is, for example, to constitute the stacked body by compressing and preliminarily adhering the plurality of base sheets110and the adhesive sheet120and then mainly adhering the plurality of base sheets110and the adhesive sheet120.

Here, the preliminary adhering is, for example, to compress the plurality of base sheets110and the adhesive sheet120stacked on the jig200through a Water Injection Molding (WIM) process that compresses it by applying a high water pressure.

The main adhering is, for example, to adhere the plurality of base sheets110and the adhesive sheet120preliminarily adhered through a hot press process applying a predetermined pressure and heat. At this time, the main adhering (in other words, the hot press process) adheres the plurality of base sheets110and the adhesive sheet120by applying a lower pressure than that in the preliminary adhering (in other words, the water injection molding process).

If the adhesive sheet120has been made of a Teflon material, the main adhering applies a pressure with a high temperature of about 300° C. or more.

The adhering (S140) constitutes the stacked body by completing the adhering of the plurality of base sheets110and the adhesive sheet120, and separates the stacked body from the jig200.

The forming the via hole (S150) forms one or more via holes130penetrating the stacked body. In other words, the forming the via hole (S150) forms the via hole130in the stacked body separated from the jig200through a punching process, a laser drill process, or the like.

Here, although it has been illustrated inFIGS. 1 and 2that the plurality of base sheets110and the adhesive sheet120have been stacked and adhered to each other and then the via hole130is formed therein, it is not limited thereto and the respective base sheets110and the adhesive sheet120may also be stacked and adhered to each other after the via hole130has been formed therein.

The forming the connection pattern (S160) forms a connection pattern140in the via hole130in order to electrically connect (in other words, electrically conduct) the thin film patterns116formed on the plurality of base sheets110, respectively. At this time, the forming the connection pattern (S160) forms the connection pattern140by filling a conductive material in the via hole130. Here, the forming the connection pattern (S160) may also form the connection pattern140by electroplating a conductive material on the inner wall surface of the via hole130and the thin film pattern116exposed to the outside of the stacked body.

Meanwhile, the method for manufacturing the flexible printed circuit board may further include forming a protective layer on the upper surface of the stacked body configured by stacking the plurality of base sheets110and the adhesive sheets120.

The forming the protective layer forms a protective layer covering the surfaces of the thin film pattern116and the base sheet110by applying and then curing a coating liquid on the surfaces of the base material and the thin film pattern116stacked on the uppermost portion of the stacked body. At this time, the protective layer may be made of a composite material containing a resin such as polypropylene and polyimide.

Further, the method for manufacturing the flexible printed circuit board may further include forming an electrode part. At this time, the forming the electrode part may form the electrode part by removing a part of the protective layer and then electroplating a conductive material such as copper on the corresponding area. Here, the electrode part may be formed on at least one of the plurality of thin film patterns116disposed on the upper surface of the stacked body.

Referring toFIG. 7, a printed circuit board manufactured by the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure is configured to include a stacked body in which the plurality of base sheets110and the adhesive sheet120have been alternately stacked and then adhered to each other, and a circuit pattern formed in the stacked body and on the upper surface thereof.

As the stacked body is configured by alternately stacking the plurality of base sheets110and the adhesive sheet120, the stacked body is configured by repeatedly stacking the Teflon film111and the adhesive sheet120. At this time, the stacked body has the adhesive sheet120interposed between the Teflon films111.

At this time, although it has been illustrated inFIG. 7that the adhesive sheet120is configured in a single layer, it is not limited thereto and may also be configured in a multi-layer structure.

The circuit pattern is composed of the thin film pattern116exposed to the upper surface of the stacked body, the thin film pattern116interposed in the stacked body, and the connection pattern140electrically connecting them.

In other words, as the base sheets110are stacked, the circuit pattern has the thin film pattern116, which has been formed on the base sheet110stacked on the uppermost portion thereof, exposed to the upper surface of the stacked body, and has the thin film patterns116, which have been formed on other base sheets110, interposed in the stacked body. At this time, the thin film patterns116are electrically connected (in other words, electrically conducted) through the connection pattern140formed in the via hole130.

Here, although it has been illustrated inFIG. 7that the connection pattern140is formed by being filled in the via hole130, it is not limited thereto and may also be formed by being plated on the inner wall surface of the via hole130.

Referring toFIGS. 8 and 9, a method for manufacturing a flexible printed circuit board according to a second embodiment of the present disclosure includes preparing a base sheet (S210), preparing an adhesive sheet (S230), stacking (S240), adhering (S250), forming a via hole (S260), and forming a connection pattern (S270).

The preparing the base sheet (S210) prepares a base sheet310on which a guide film312, a Teflon film311, and a thin film pattern316are sequentially stacked, and in which a guide hole penetrating the guide film312and the Teflon film311is formed. At this time, the guide pin220of the jig200is inserted into the guide hole in order to easily perform the stacking (S240) to be described later.

The preparing the base sheet (S210) forms a surface reformed layer318on both surfaces (in other words, the upper surface and the lower surface) of the Teflon film in order to improve the adhesive property of the Teflon film. At this time, the preparing the base sheet (S210) may form the surface reformed layer318only on one surface, to which the adhesive sheet320is adhered, of the upper surface and the lower surface of the Teflon film. Here, the surface reformed layer318may be, for example, ceramic (for example, titanium dioxide (TiO2)) or oxide having excellent adhesive property with the adhesive sheet320of various materials.

Referring toFIGS. 10 and 11, the preparing the base sheet (S210) forms the surface reformed layer318on one surface of the Teflon film311. To this end, the preparing the base sheet (S210) includes adhering a Teflon film and a guide film (S211), forming a seed layer (S212), forming a plating layer (S213), forming a thin film pattern (S214), forming a surface reformed layer (S215), and forming a first guide hole (S216).

The adhering the Teflon film and the guide film (S211) prepares the Teflon film311of heat resistance and low dielectric constant. In other words, the flexible printed circuit board has been completely manufactured and then is mounted with a semiconductor element through a surface mount technology process (in other words, an SMT process).

At this time, there is a problem in that a flexible printed circuit board for a high frequency under development constitutes the base sheet310by using polypropylene having heat resistance of about 160° C. to 180° C., such that the base sheet310is deformed or broken due to the heat (about 250° C.) applied in the reflow process of the surface mount technology process.

In order to prevent the reliability of the flexible printed circuit board from being degraded if the base sheet310is deformed or broken, the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure constitutes the base sheet310by using the Teflon film311.

At this time, since the Teflon film311is not deformed even in the heat of about 300° C., deformation and breakage of the base sheet due to the heat applied in the reflow process may be prevented.

Accordingly, the adhering the Teflon film and the guide film (S211) constitutes the base sheet310by using the Teflon film311.

As a result, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may prevent deformation and breakage of the flexible printed circuit board due to the heat (about 250° C.) applied in the reflow process, thereby improving reliability.

The Teflon is mainly used as lubricant, release material, and insulation material. Since the Teflon has the best heat resistance and dielectric properties (in other words, low dielectric constant) among polymer materials, it is used as a base material of a flexible printed circuit board for a high frequency requiring low dielectric constant and heat resistance.

However, since the Teflon is soft-melting and thermoplastic, the base material is deformed by heat and pressure applied in the manufacturing process, thereby causing a high defective rate. Accordingly, the Teflon is mainly used as a thick hard-type single-sided or double-sided base material.

An embodiment of the present disclosure uses the Teflon film311of a thin film as the base sheet310in order to manufacture the flexible printed circuit board. The Teflon film311is deformed or broken in a shape even at a small pressure applied in the manufacturing process due to the soft-melting property, thereby degrading the manufacturing yield and reliability of the flexible printed circuit board.

Accordingly, the adhering the Teflon film and the guide film (S211) adheres the guide film312to one surface of the Teflon film311in order to prevent deformation and breakage of the Teflon film311in the manufacturing process.

At this time, the guide film312is, for example, a hard polyethylene terephthalate (PET) film.

The adhering the Teflon film and the guide film (S211) adheres the Teflon film311and the guide film312by interposing an adhesive sheet313between the Teflon film311and the guide film312. In other words, since the guide film312should be removed in the stacking (S240) to be described later, the adhering the Teflon film and the guide film (S211) couples the Teflon film311and the guide film312in an adhering state (in other words, the adhesive sheet313) capable of being easily removed while supporting the Teflon film311. Here, the adhesive sheet313is, for example, a silicone (Si)-based adhesive agent.

As described above, the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure may form the base sheet310by adhering the guide film312to the Teflon film311, thereby preventing the shape of the Teflon film311from being deformed or broken in the manufacturing process to prevent the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The forming the seed layer (S212) forms a seed layer314of a thin film on one surface of the Teflon film311. The forming the seed layer (S212) forms the seed layer314on the other surface (in other words, the surface opposite to one surface to which the guide film312has been adhered) of the Teflon film311through a deposition process or a sputtering process. Here, the forming the seed layer (S212) forms the seed layer314of a mixed material of mixing nickel copper (NiCu) and copper (Cu) or a nickel copper (NiCu) material on the other surface of the Teflon film311.

The forming the plating layer (S213) forms a plating layer315on the seed layer314. At this time, the forming the plating layer (S213) forms the plating layer315on the seed layer314by electroplating copper (Cu).

Here, the seed layer314and the plating layer315are elements constituting a circuit pattern, and are formed at a thickness of about 5 μm.

The forming the thin film pattern (S214) forms a thin film pattern316on the other surface of the Teflon film311. In other words, the forming the thin film pattern (S214) forms the thin film pattern316of a predetermined shape by removing parts of the seed layer314and the plating layer315formed on the other surface of the Teflon film311through an etching process.

The forming the surface reformed layer (S215) forms a surface reformed layer318on one surface of the Teflon film311. In other words, the forming the surface reformed layer (S215) forms the surface reformed layer318on one surface, on which the thin film pattern316has been formed, of both surfaces (in other words, the upper surface and the lower surface) of the Teflon film311. At this time, the surface reformed layer318is formed on the upper surface and the periphery of the thin film pattern316, and the upper surface of the Teflon film311exposed to the space between the thin film patterns316.

The forming the surface reformed layer (S215) forms the surface reformed layer318by depositing ceramic or oxide on one surface of the Teflon film311through a sputter process, which is a vacuum deposition method. At this time, the surface reformed layer318is a material selected from ceramic, oxide, nitride, and carbonate having excellent adhesive property with the adhesive sheet320, and the sputter process is, for example, an oxide sputtering process.

As described above, the method for manufacturing the flexible printed circuit board may form the surface reformed layer318, which is ceramic or oxide, on the surface of the Teflon film to improve the adhesive property of the surface of the Teflon film, thereby manufacturing a multi-layer flexible printed circuit board by using the Teflon film having a difficult-to-adhere property, and to adhere the Teflon film with the adhesive sheet of various materials, thereby minimizing the manufacturing cost of the flexible printed circuit board.

The forming the first guide hole (S216) forms a plurality of first guide holes317penetrating the surface reformed layer318, the Teflon film311, and the guide film312. In other words, the forming the first guide hole (S216) forms the plurality of first guide holes317in order to align the base sheets310at accurate locations while firmly fixing the base sheet310to the jig200in the stacking (S240) to be described later. Here, the forming the first guide hole (S216) forms the first guide hole317in the base sheet310through a punching process, a laser drill process, or the like.

Referring toFIGS. 12 and 13, the forming the surface reformed layer (S215) may include forming a first surface reformed layer (S217), removing a guide film (S218), and forming a second surface reformed layer (S219).

The forming the first surface reformed layer (S217) forms a first surface reformed layer318aon one surface of the Teflon film311. In other words, the forming the first surface reformed layer (S217) forms the first surface reformed layer318aon one surface, on which the thin film pattern316has been formed, of both surfaces (in other words, the upper surface and the lower surface) of the Teflon film311. At this time, the first surface reformed layer318ais formed on the upper surface and the periphery of the thin film pattern316, and the upper surface of the Teflon film311exposed to the space between the thin film patterns316.

The forming the first surface reformed layer (S217) forms the first surface reformed layer318aby depositing ceramic or oxide on one surface of the Teflon film311through a sputter process, which is a vacuum deposition method. At this time, the first surface reformed layer318ais a material selected from ceramic, oxide, nitride, and carbonate having excellent adhesive property with the adhesive sheet320, and the sputter process is, for example, an oxide sputtering process.

The removing the guide film (S218) removes the guide film312adhered to the other surface of the Teflon film311. In other words, the removing the guide film (S218) is a previous operation for forming the second surface reformed layer318bon the other surface of the Teflon film311, and removes the guide film312adhered to the other surface of the Teflon film311and the adhesive film313.

The forming the second surface reformed layer (S219) forms the second surface reformed layer318bon the other surface of the Teflon film311. In other words, the forming the second surface reformed layer (S219) forms the second surface reformed layer318bby depositing ceramic or oxide on the other surface of the Teflon film311(in other words, the lower surface on which the guide film312has been removed) through a sputter process, which is a vacuum deposition method. At this time, the second surface reformed layer318bis a material selected from ceramic, oxide, nitride, and carbonate having excellent adhesive property with the adhesive sheet320, and the sputter process is, for example, an oxide sputtering process.

The forming the first guide hole (S216) forms the plurality of first guide holes317penetrating the first surface reformed layer318a, the Teflon film311, and the second surface reformed layer318b. In other words, the forming the first guide hole (S216) forms the plurality of first guide holes317in order to align the base sheets310at accurate locations while firmly fixing the base sheet310to the jig200in the stacking (S240) to be described later. Here, the forming the first guide hole (S216) forms the first guide hole317in the base sheet310through a punching process, a laser drill process, or the like.

Referring toFIGS. 14 and 15, the preparing the base sheet (S210) forms the surface reformed layer318on at least one surface of both surfaces of the Teflon film311. To this end, the preparing the base sheet (S210) includes forming a surface reformed layer (S221), adhering a Teflon film and a guide film (S222), forming a seed layer (S223), forming a plating layer (S224), forming a thin film pattern (S225), and forming a first guide hole (S226).

The forming the surface reformed layer (S221) forms the surface reformed layer318on the surface of the Teflon film311. At this time, although it has been illustrated inFIG. 15that the surface reformed layer318is formed on both surfaces (in other words, the upper surface and the lower surface) of the Teflon film311, it is not limited thereto and the surface reformed layer318may be formed only on one surface of both surfaces of the Teflon film311.

In other words, the forming the surface reformed layer (S221) may form the surface reformed layer318only on one surface, on which the thin film pattern316will be formed, of both surfaces of the Teflon film311, or form the surface reformed layer318only on the other surface, to which the guide film will be adhered, of both surfaces of the Teflon film311.

The forming the surface reformed layer (S221) forms the surface reformed layer318by depositing ceramic or oxide on the surface of the Teflon film311through a sputter process, which is a vacuum deposition method. At this time, the surface reformed layer318is a material selected from ceramic, oxide, nitride, and carbonate having excellent adhesive property with the adhesive sheet320, and the sputter process is, for example, an oxide sputtering process.

As described above, the method for manufacturing the flexible printed circuit board may form the surface reformed layer318, which is ceramic or oxide, on the surface of the Teflon film to improve the adhesive property of the surface of the Teflon film, thereby manufacturing the multi-layer flexible printed circuit board by using the Teflon film having a difficult-to-adhere property, and to adhere the Teflon film with the adhesive sheet of various materials, thereby minimizing the manufacturing cost of the flexible printed circuit board.

The adhering the Teflon film and the guide film (S222) adheres the guide film312to one surface of the Teflon film311in order to prevent deformation or breakage of the Teflon film311in the manufacturing process of the flexible printed circuit board. At this time, the guide film312is, for example, a hard polyethylene terephthalate (PET) film.

The adhering the Teflon film and the guide film (S222) adheres the Teflon film311and the guide film312by interposing the adhesive sheet313between the surface reformed layer318and the guide film312formed on one surface (in other words, the lower surface) of the Teflon film311. In other words, since the guide film312should be removed in the stacking (S240) to be described later, the adhering the Teflon film and the guide film (S222) couples the Teflon film311and the guide film312in an adhering state (in other words, the adhesive sheet313) capable of being easily removed while supporting the Teflon film311. Here, the adhesive sheet313is, for example, a silicone (Si)-based adhesive agent.

Meanwhile, the adhering the Teflon film and the guide film (S222) may be omitted if the hard surface reformed layer is formed in the S221.

As described above, the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure may form the base sheet310by adhering the guide film312to the Teflon film311, thereby preventing the shape of the Teflon film311from being deformed or broken in the manufacturing process to prevent the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The forming the seed layer (S223) forms the seed layer314of a thin film on one surface of the Teflon film311. The forming the seed layer (S223) forms the seed layer314on the upper surface of the surface reformed layer318formed on the other surface (in other words, the upper surface) of the Teflon film311through a deposition process or a sputtering process. Here, the forming the seed layer (S223) forms the seed layer314of a mixed material of mixing nickel copper (NiCu) and copper (Cu) or a nickel copper (NiCu) material on the other surface of the Teflon film311.

The forming the plating layer (S224) forms the plating layer315on the seed layer314. At this time, the forming the plating layer (S224) forms the plating layer315on the seed layer314by electroplating copper (Cu).

Here, the seed layer314and the plating layer315are elements constituting a circuit pattern, and are formed at a thickness of about 5 μm.

The forming the thin film pattern (S225) forms the thin film pattern316on the other surface of the Teflon film311. In other words, the forming the thin film pattern (S225) forms the thin film pattern316of a predetermined shape by removing parts of the seed layer314and the plating layer315formed on the other surface of the Teflon film311through an etching process.

The forming the first guide hole317(S226) forms the plurality of first guide holes317penetrating the surface reformed layer318, the Teflon film311, and the guide film312. In other words, the forming the first guide hole317(S226) forms the plurality of first guide holes317in order to align the base sheets310at accurate locations while firmly fixing the base sheet310to the jig200in the stacking (S240) to be described later. Here, the forming the first guide hole317(S226) forms the first guide hole317in the base sheet310through a punching process, a laser drill process, or the like.

The preparing the adhesive sheet (S230) prepares the adhesive sheet320in which the plurality of second guide holes322have been formed. At this time, the preparing the adhesive sheet (S230) forms the second guide hole322at a location corresponding to the first guide hole317at the time of stacking the base sheet310and the adhesive sheet320.

The preparing the adhesive sheet (S230) may prepare the adhesive sheet320of a multi-layer structure on which an adhesive layer has been formed on one surface or both surfaces of a film base material.

For example, the adhesive sheet320may be a Casted polypropylene (CPP) film of low dielectric constant having a low dielectric loss. At this time, the CPP film is formed in a multi-layer structure in which an adhesive layer has been formed on one surface or both surfaces of a polypropylene (PP) film (hereinafter, PP film).

Here, the adhesive layer is made of a composite material of mixing the same material as the CPP film (for example, a material of polyethylene (PE), polypropylene (PP), polyimide, or the like) and an additive (for example, acrylate, or the like) in order to increase the adhesive force with polymer (in other words, the Teflon film311of the base sheet310) and metal (in other words, the thin film pattern316).

The preparing the adhesive sheet (S230) may also prepare the adhesive sheet320of a single layer structure. At this time, the preparing the adhesive sheet (S230) is, for example, to prepare the adhesive sheet320made of a composite material of mixing a material such as polyethylene, polypropylene, or polyimide and an additive, which has excellent adhesive property with polymer and metal.

The stacking (S240) stacks the plurality of base sheets310and the adhesive sheet320. At this time, the stacking (S240) interposes the adhesive sheet320between the base sheets310by alternately stacking the base sheet310and the adhesive sheet320.

The stacking (S240) stacks the plurality of base sheets310and the adhesive sheet320by using the jig200. In other words, the stacking (S240) may provide reliability of the flexible printed circuit board only when the thin film patterns316of the base sheet310are stacked to be aligned at accurate locations.

Accordingly, the stacking (S240) stacks the plurality of base sheets310and the adhesive sheet320by using the jig200including the guide pin220.

An example of the stacking (S240) that stacks two base sheets310(in other words, the first base sheet310aand the second base sheet310b) and the adhesive sheet320will be explained with reference toFIGS. 16 and 17as follows.

The stacking (S240) includes stacking the first base sheet310a(S241), removing the guide film312aof the first base sheet310a(S243), stacking the adhesive sheet320(S245), stacking the second base sheet310b(S247), and removing the guide film312bof the second base sheet310b(S249).

The stacking the first base sheet310a(S241) stacks the first base sheet310aon the jig200. In other words, the stacking the first base sheet310a(S241) stacks the first base sheet310aon the jig200by disposing so that the guide pins220of the jig200penetrate the first guide holes317aof the first base sheet310a, respectively and then moving them downwards.

At this time, the stacking the first base sheet310a(S241) stacks the first base sheet310aso that the thin film pattern316aformed on the first base sheet310ais positioned downwards in order to easily remove the guide film312a. In other words, the stacking the first base sheet310a(S241) disposes the guide film312aon the top by stacking the first base sheet310aso that the thin film pattern316ais positioned downwards.

The removing the guide film312aof the first base sheet310a(S243) removes the guide film312afrom the first base sheet310astacked on the jig200. In other words, the removing the guide film312aof the first base sheet310a(S243) removes the guide film312aof the first base sheet310adisposed on the top and an adhesive film313a.

The stacking the adhesive sheet320(S245) stacks the adhesive sheet320on the jig200. In other words, the stacking the adhesive sheet320(S245) stacks the adhesive sheet320on the jig200by disposing so that the guide pins220of the jig200penetrate the second guide holes322of the adhesive sheet320, respectively and then moving them downwards. At this time, the stacking the adhesive sheet320(S245) stacks the adhesive sheet320above the first base sheet310astacked on the jig200.

The stacking the second base sheet310b(S247) stacks the second base sheet310bon the jig200. In other words, the stacking the second base sheet310b(S247) stacks the second base sheet310bon the jig200by disposing so that the guide pins220of the jig200penetrate the first guide holes317bof the second base sheet310b, respectively and then moving them downwards.

At this time, the stacking the second base sheet310b(S247) stacks the second base sheet310babove the adhesive sheet320stacked on the jig200. The stacking the second base sheet310b(S247) stacks the second base sheet310bso that one surface, on which the thin film pattern316bhas been formed, is disposed above the adhesive sheet320.

The removing the guide film312bof the second base sheet310b(S249) removes the guide film312bfrom the second base sheet310bstacked on the jig200. In other words, the removing the guide film312bof the second base sheet310b(S249) removes the guide film312bof the second base sheet310bdisposed on the top and an adhesive film313b.

Here, in the case of a state where the surface reformed layer318has been formed on the lower surface of the base sheet310and the guide film has been removed, the operations S243and S249may be omitted.

As described above, the method for manufacturing the flexible printed circuit board may stack the plurality of base sheets310and the adhesive sheet320by disposing so that the guide pin220formed on the jig200penetrates the guide hole (in other words, the first guide hole317and the second guide hole322) formed in the base sheet310and the adhesive sheet320and then moving them downwards in the stacking (S240) not to perform the alignment process of the stacked base materials (in other words, the base sheet310and the adhesive sheet320) in the stacking process, thereby simplifying the manufacturing process.

Further, the method for manufacturing the flexible printed circuit board may stack the plurality of base sheets310and the adhesive sheet320by disposing so that the guide pin220formed on the jig200penetrates the guide hole (in other words, the first guide hole317and the second guide hole322) formed in the base sheet310and the adhesive sheet320and then moving them downwards in the stacking (S240) to align the thin film patterns316formed on the stacked base sheets310at accurate locations, thereby preventing the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The adhering (S250) constitutes a stacked body by adhering the plurality of base sheets310and the adhesive sheets320stacked on the jig200.

The adhering (S250) is, for example, to constitute the stacked body by compressing and preliminarily adhering the plurality of base sheets310and the adhesive sheets320and then mainly adhering the plurality of base sheets310and the adhesive sheets320.

Here, the preliminary adhering is, for example, to compress the plurality of base sheets310and the adhesive sheet320stacked on the jig200through a Water Injection Molding (WIM) process that compresses it by applying a high water pressure.

The main adhering is, for example, to adhere the plurality of base sheets310and the adhesive sheet320preliminarily adhered through a hot press process applying a predetermined pressure and heat. At this time, the main adhering (in other words, the hot press process) adheres the plurality of base sheets310and the adhesive sheet320by applying a lower pressure than that in the preliminary adhering (in other words, the water injection molding process).

The adhering (S250) constitutes the stacked body by completing the adhering of the plurality of base sheets310and the adhesive sheet320, and separates the stacked body from the jig200.

The forming the via hole (S260) forms one or more via holes330penetrating the stacked body. In other words, the forming the via hole (S260) forms the via hole330in the stacked body separated from the jig200through a punching process, a laser drill process, or the like.

Here, although it has been illustrated inFIGS. 8 and 9that the plurality of base sheets310and the adhesive sheet320are stacked and adhered to each other and then the via hole330is formed, it is not limited thereto and the respective base sheets310and the adhesive sheet320may also be stacked and adhered to each other after the via hole330is formed.

The forming the connection pattern (S270) forms a connection pattern340in the via hole330in order to electrically connect (in other words, electrically conduct) the thin film patterns316formed on the plurality of base sheets310, respectively. At this time, the forming the connection pattern (S270) forms the connection pattern340by filling a conductive material in the via hole330. Here, the forming the connection pattern (S270) may also form the connection pattern340by electroplating the conductive material on the inner wall surface of the via hole330and the thin film pattern316exposed to the outside of the stacked body.

Meanwhile, the method for manufacturing the flexible printed circuit board may further include forming a protective layer on the upper surface of the stacked body configured by stacking the plurality of base sheets310and the adhesive sheet320.

The forming the protective layer forms a protective layer covering the surfaces of the thin film pattern316and the base sheet310by applying and then curing a coating liquid on the surfaces of the base material and the thin film pattern316stacked on the uppermost portion of the stacked body. At this time, the protective layer may be made of a composite material containing a resin such as polypropylene and polyimide.

Further, the method for manufacturing the flexible printed circuit board may further include forming an electrode part. At this time, the forming the electrode part may form the electrode part by removing a part of the protective layer and then electroplating a conductive material such as copper on the corresponding area. Here, the electrode part may be formed on at least one of the plurality of thin film patterns316disposed on the upper surface of the stacked body.

Referring toFIGS. 18 and 19, a flexible printed circuit board according to the second embodiment of the present disclosure may be configured to include the stacked body in which the plurality of base sheets310and the adhesive sheet320have been alternately stacked and then adhered to each other, and a circuit pattern formed in the stacked body and on the upper surface thereof. Here, although it has been illustrated inFIGS. 18 and 19that the flexible printed circuit board has two base sheets310and one adhesive sheet320stacked thereon for convenience of description, the flexible printed circuit board may have three or more base sheets310and two or more adhesive sheets320stacked thereon, which may be configured variously according to the required thickness.

The stacked body is configured by alternately stacking the plurality of base sheets310and the adhesive sheet320. In other words, the stacked body is configured by repeatedly stacking the plurality of base sheets310, and the adhesive sheet320is interposed between the base sheets310to adhere the base sheets310.

At this time, the base sheet310has the surface reformed layer318disposed on at least one surface of both surfaces (in other words, the upper surface and the lower surface) thereof in order to resolve a difficult-to-adhere property of the Teflon film311.

In other words, as illustrated inFIG. 18, the surface reformed layer318is formed on one surface (in other words, the upper surface), on which the thin film pattern316has been formed, of both surfaces of the base sheet310. At this time, the surface reformed layer318is formed on the upper surface and the periphery of the thin film pattern316, and the upper surface of the Teflon film311exposed to the space between the thin film patterns316.

Meanwhile, as illustrated inFIG. 19, the surface reformed layer318may also be formed on both surfaces (in other words, the upper surface and the lower surface) of the base sheet310. In other words, the surface reformed layer may also be formed on the upper surface and the periphery of the thin film pattern316, a part of the upper surface of the Teflon film311exposed to the space between the thin film patterns316, and the entire lower surface of the Teflon film311.

On the other hand, the stacked body may also be configured by interchangeably using the Teflon film311having the surface reformed layer318formed only on the upper surface thereof, the Teflon film311having the surface reformed layer318formed only on the lower surface thereof, and the Teflon film311having the surface reformed layer318formed on both surfaces thereof.

For example, as illustrated inFIG. 20, the base sheet310, which has been stacked on the uppermost portion, of the base sheets310constituting the stacked body may have the surface reformed layer318formed only on the lower surface thereof, and the base sheet310stacked on the lowermost portion thereof may have the surface reformed layer318formed only on the upper surface thereof. At this time, other base sheets310interposed between the base sheets310stacked on the uppermost portion and the lowermost portion thereof have the surface reformed layer318formed on both surfaces (in other words, the upper surface and the lower surface) thereof.

The circuit pattern is composed of the thin film pattern316exposed to the upper surface of the stacked body, the thin film pattern316interposed in the stacked body, and the connection pattern340electrically connecting them.

In other words, as the base sheets310are stacked, the circuit pattern has the thin film pattern316, which has been formed on the base sheet310stacked on the uppermost portion thereof, exposed to the upper surface of the stacked body, and has the thin film patterns316formed on other base sheets310interposed in the stacked body. At this time, the thin film patterns316are electrically connected (in other words, electrically conducted) through the connection pattern340formed in the via hole330.

Referring toFIGS. 21 and 22, the flexible printed circuit board according to the second embodiment of the present disclosure is configured to include the stacked body in which the plurality of base sheets310and the adhesive sheet320have been alternately stacked and then adhered to each other, and the circuit pattern formed in the stacked body and on the upper surface thereof. Here, although it has been illustrated inFIGS. 21 and 22that the flexible printed circuit board has two base sheets310and one adhesive sheet320stacked thereon for convenience of description, the flexible printed circuit board may have three or more base sheets310and two or more adhesive sheets320stacked thereon, which may be configured variously according to the required thickness.

The stacked body is configured by alternately stacking the plurality of base sheets310and the adhesive sheet320. In other words, the stacked body is configured by repeatedly stacking the plurality of base sheets310, and the adhesive sheet320is interposed between the base sheets310to adhere the base sheets310.

At this time, the base sheet310has the surface reformed layer318disposed on at least one surface of both surfaces (in other words, the upper surface and the lower surface) thereof in order to resolve a difficult-to-adhere property of the Teflon film311.

In other words, as illustrated inFIG. 21, the surface reformed layer318is formed on one surface (in other words, the upper surface), on which the thin film pattern316has been formed, of both surfaces of the base sheet310. At this time, the surface reformed layer318is formed at a predetermined thickness on the upper surface of the Teflon film311, and the thin film patterns316are formed on the upper surface of the surface reformed layer318.

Meanwhile, as illustrated inFIG. 22, the surface reformed layer318may also be formed on both surfaces (in other words, the upper surface and the lower surface) of the base sheet310.

On the other hand, the stacked body may also be configured by interchangeably using the Teflon film311having the surface reformed layer318formed only on the upper surface thereof, the Teflon film311having the surface reformed layer318formed only on the lower surface thereof, and the Teflon film311having the surface reformed layer318formed on both surfaces thereof.

For example, as illustrated inFIG. 23, the base sheet310, which has been stacked on the uppermost portion, of the base sheets310constituting the stacked body may have the surface reformed layer318formed only on the lower surface thereof, and the base sheet310stacked on the lowermost portion thereof may have the surface reformed layer318formed only on the upper surface thereof. At this time, other base sheets310interposed between the base sheets310stacked on the uppermost portion and the lowermost portion thereof have the surface reformed layer318formed on both surfaces (in other words, the upper surface and the lower surface) thereof.

The circuit pattern is composed of the thin film pattern316exposed to the upper surface of the stacked body, the thin film pattern316interposed in the stacked body, and the connection pattern340electrically connecting them.

In other words, as the base sheets310are stacked, the circuit pattern has the thin film pattern316, which has been formed on the base sheet310stacked on the uppermost portion thereof, exposed to the upper surface of the stacked body, and has the thin film patterns316formed on other base sheets310interposed in the stacked body. At this time, the thin film patterns316are electrically connected (in other words, electrically conducted) through the connection pattern340formed in the via hole330.

Here, although it has been illustrated inFIGS. 18 to 23that the adhesive sheet320is configured in a single layer, it is not limited thereto and may also be configured in a multi-layer structure.

Further, although it has been illustrated inFIGS. 18 to 23that the connection pattern340is formed by being filled in the via hole330, it is not limited thereto and may also be formed by being plated on the inner wall surface of the via hole330.

Referring toFIGS. 24 and 25, a method for manufacturing a flexible printed circuit board according to a third embodiment of the present disclosure includes preparing a base sheet (S310), stacking (S330), adhering (S350), forming a via hole (S370), and forming a connection pattern (S390).

The preparing the base sheet (S310) prepares a base sheet410on which a guide film412, a Teflon film411, and a thin film pattern416are sequentially stacked, and in which a guide hole418penetrating the guide film412and the Teflon film411is formed. At this time, the guide hole418is a hole into which the guide pin220of the jig200is inserted in order to easily perform the stacking (S330) to be described later.

The preparing the base sheet (S310) forms an adhesive layer417on the Teflon film411in order to improve the adhesive property of the Teflon film411. The preparing the base sheet (S310) forms the adhesive layer417only on one surface, which is adhered to another base sheet410, of the upper surface and the lower surface of the Teflon film411. At this time, the preparing the base sheet (S310) forms the adhesive layer417on the upper surface and the lower surface of the Teflon film411. Here, the adhesive layer417is a Teflon material, for example.

Referring toFIGS. 26 and 27, the preparing the base sheet (S310) includes adhering a Teflon film and a guide film (S311), forming a seed layer (S312), forming a plating layer (S313), forming a thin film pattern (S314), forming an adhesive layer (S315), and forming a guide hole (S316).

The adhering the Teflon film and the guide film (S311) prepares the Teflon film411of heat resistance and low dielectric constant.

In general, the flexible printed circuit board has been completely manufactured, and then is mounted with a semiconductor element through a surface mount technology process (in other words, an SMT process).

At this time, since the conventional flexible printed circuit board constitutes the base sheet410by using polypropylene (PP) having heat resistance of about 160° C. to 180° C., the base sheet410is deformed or broken by the heat (about 250° C.) applied in the reflow process of the surface mount technology process, thereby degrading reliability of the flexible printed circuit board.

The method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure constitutes the base sheet410by using the Teflon film411in order to prevent reliability of the flexible printed circuit board from being degraded.

In other words, since the Teflon film411is not deformed even in the heat of about 300° C., deformation and breakage of the base sheet due to the heat applied in the reflow process may be prevented.

Accordingly, the adhering the Teflon film and the guide film (S311) constitutes the base sheet410by using the Teflon film411.

As a result, the method for manufacturing the flexible printed circuit board and the flexible printed circuit board manufactured by the same may prevent deformation and breakage of the flexible printed circuit board due to the heat applied in the reflow process, thereby improving reliability.

The Teflon is mainly used as lubricant, release material, and insulation material. Since the Teflon has the best heat resistance and dielectric properties (in other words, low dielectric constant) among polymer materials, it is used as a base material of a printed circuit board for a high frequency requiring low dielectric constant and heat resistance.

However, since the Teflon is soft-melting and thermoplastic, the base material is deformed by heat and pressure applied in the manufacturing process, thereby causing a high defective rate. Accordingly, the Teflon is mainly used as a thick hard-type single-sided or double-sided base material.

In an embodiment of the present disclosure, the Teflon film411of a thin film is used as the base sheet410in order to manufacture a flexible printed circuit board. The Teflon film411is deformed or broken in a shape even at a small pressure applied in the manufacturing process due to the soft-melting property, thereby degrading the manufacturing yield and reliability of the flexible printed circuit board.

Accordingly, the adhering the Teflon film and the guide film (S311) adheres the guide film412to one surface of the Teflon film411in order to prevent deformation and breakage of the Teflon film411in the manufacturing process. At this time, the guide film412is, for example, a hard polyethylene terephthalate (PET) film.

The adhering the Teflon film and the guide film (S311) adheres the Teflon film411and the guide film412by interposing an adhesive sheet413between the Teflon film411and the guide film412. In other words, since the guide film412should be removed in the stacking (S330) to be described later, the adhering the Teflon film and the guide film (S311) couples the Teflon film411and the guide film412in an adhering state (in other words, the adhesive sheet413) capable of being easily removed while supporting the Teflon film411. Here, the adhesive sheet413is, for example, a silicone (Si)-based adhesive agent.

As described above, the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure may form the base sheet410by adhering the guide film412to the Teflon film411, thereby preventing the shape of the Teflon film411from being deformed or broken in the manufacturing process to prevent the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The forming the seed layer (S312) forms a seed layer414of a thin film on one surface of the Teflon film411. The forming the seed layer (S312) forms the seed layer414on the other surface (in other words, the surface opposite to one surface to which the guide film412has been adhered) of the Teflon film411through a deposition process or a sputtering process.

Here, the forming the seed layer (S312) forms the seed layer414of a mixed material of mixing nickel copper (NiCu) and copper (Cu) or a nickel copper (NiCu) material on the other surface of the Teflon film411.

The forming the plating layer (S313) forms a plating layer415on the seed layer414. At this time, the forming the plating layer (S313) forms the plating layer415on the seed layer414by electroplating copper (Cu).

Here, the seed layer414and the plating layer415are elements constituting the circuit pattern, and are formed at a thickness of about 5 μm.

The forming the thin film pattern (S314) forms a thin film pattern416on the other surface of the Teflon film411. In other words, the forming the thin film pattern (S314) forms the thin film pattern416of a predetermined shape by removing parts of the seed layer414and the plating layer415formed on the other surface of the Teflon film411through an etching process.

The forming the adhesive layer (S315) forms an adhesive layer417on one surface of the Teflon film411. In other words, the forming the adhesive layer (S315) forms the adhesive layer417on one surface, on which the thin film pattern416has been formed, of both surfaces (in other words, the upper surface and lower surface) of the Teflon film411. At this time, the adhesive layer417is formed on the upper surface and the periphery of the thin film pattern416, and the upper surface of the Teflon film411exposed to the space between the thin film patterns416.

Here, although it has been illustrated inFIG. 27that the surface of the adhesive layer417is flat, the adhesive layer417may be actually formed so that a portion formed above the thin film pattern416is higher than the other portions, thereby forming unevenness.

The forming the adhesive layer (S315) forms the adhesive layer417on one surface of the Teflon film411through an impregnation coating process. In other words, the forming the adhesive layer (S315) inserts the Teflon film411into a solvent (for example, water) in a state where a Teflon slurry (grains) has been dispersed and then presses it at high heat. Accordingly, the Teflon slurry is impregnation-coated on the surface of the Teflon film411to form the adhesive layer417.

The forming the adhesive layer (S315) may also form the adhesive layer417on one surface of the Teflon film411through a printing process. In other words, the forming the adhesive layer (S315) forms the adhesive layer417by printing (for example, gravuring, spraying) the Teflon slurry on one surface of the Teflon film411.

The forming the guide hole (S316) forms the plurality of guide holes418penetrating the adhesive layer417, the Teflon film411, and the guide film412. In other words, the forming the guide hole (S316) forms the plurality of guide holes418in order to align the base sheets410at accurate locations while firmly fixing the base sheet410to the jig200in the stacking (S330) to be described later. Here, the forming the guide hole (S316) forms the guide hole418in the base sheet410through a punching process, a laser drill process, or the like.

Meanwhile, the preparing the base sheet (S310) may also form the adhesive layer417(in other words, a first adhesive layer417aand a second adhesive layer417b) on both surfaces of the Teflon film411.

To this end, referring toFIGS. 28 and 29, the forming the adhesive layer (S315) may include forming a first adhesive layer (S317), removing a guide film (S318), and forming a second adhesive layer (S319).

The adhering the Teflon film and the guide film (S311) adheres the guide film412to one surface of the Teflon film411of heat resistance and low dielectric constant. At this time, the guide film412is, for example, a hard polyethylene terephthalate (PET) film.

The adhering the Teflon film and the guide film (S311) adheres the Teflon film411and the guide film412by interposing the adhesive sheet413between the Teflon film411and the guide film412.

At this time, in order to easily remove the guide film412in the stacking (S330) to be described later, the adhering the Teflon film and the guide film (S311) couples the Teflon film411and the guide film412in an adhering state (in other words, the adhesive sheet413) capable of being easily removed while supporting the Teflon film411. Here, the adhesive sheet413is, for example, a silicone (Si)-based adhesive agent.

The forming the first adhesive layer (S317) forms the first adhesive layer417aon one surface of the Teflon film411. In other words, the forming the first adhesive layer (S317) forms the first adhesive layer417aon one surface, on which the thin film pattern416has been formed, of both surfaces (in other words, the upper surface and the lower surface) of the Teflon film411.

The forming the first adhesive layer (S317) forms the first adhesive layer417aof a Teflon material on one surface of the Teflon film411through an impregnation coating process or a printing process (for example, gravure printing, spray printing, or the like).

The removing the guide film (S318) removes the guide film412adhered to the other surface of the Teflon film411. In other words, the removing the guide film (S318) is a previous operation for forming the second adhesive layer417bon the other surface of the Teflon film411, and removes the guide film412adhered to the other surface of the Teflon film411and the adhesive film413.

The forming the second adhesive layer (S319) forms the second adhesive layer417bon the other surface of the Teflon film411. In other words, the forming the second adhesive layer (S319) forms the second adhesive layer417bof a Teflon material on the other surface (in other words, the lower surface on which the guide film412has been removed) of the Teflon film411through an impregnation coating process or a printing process.

As described above, the method for manufacturing the flexible printed circuit board may form the adhesive layer417of a Teflon material on the surface of the Teflon film411to improve the adhesive property of the surface of the Teflon film411, thereby manufacturing the multi-layer flexible printed circuit board by using the Teflon film411having a difficult-to-adhere property.

The forming the guide hole (S316) forms the plurality of guide holes418penetrating the first adhesive layer417a, the Teflon film411, and the second adhesive layer417b. In other words, the forming the guide hole (S316) forms the plurality of guide holes418in order to align the base sheets410at accurate locations while firmly fixing the base sheet410to the jig200in the stacking (S330) to be described later. Here, the forming the guide hole (S316) forms the guide hole418in the base sheet410through a punching process, a laser drill process, or the like.

Referring toFIGS. 30 and 31, the preparing the base sheet (S310) forms the thin film pattern416after forming the adhesive layer417on at least one surface of both surfaces of the Teflon film411.

To this end, the preparing the base sheet (S310) includes forming an adhesive layer (S321), adhering the Teflon film411and the guide film412(S322), forming a seed layer (S323), forming a plating layer (S324), forming a thin film pattern (S325), and forming a guide hole (S326).

The forming the adhesive layer (S321) forms the adhesive layer417on the surface of the Teflon film411through an impregnation coating process or a printing process. At this time, the forming the adhesive layer (S321) is, for example, to form the adhesive layer417of a Teflon material on the surface of the Teflon film411.

The forming the adhesive layer (S321) may form the adhesive layer417only on one surface, on which the thin film pattern416will be formed, of the both surfaces of the Teflon film411, or form the adhesive layer417only on the other surface, to which the guide film412will be adhered, of both surfaces of the Teflon film411.

Here, although it has been illustrated inFIG. 31that the adhesive layer417is formed only on one surface (in other words, the lower surface) of the Teflon film411, it is not limited thereto and the adhesive layer417may also be formed on both surfaces (in other words, the upper surface and the lower surface) of the Teflon film411.

As described above, the method for manufacturing the flexible printed circuit board may form the adhesive layer417of a Teflon material on the surface of the Teflon film411to improve the adhesive property of the surface of the Teflon film411, thereby manufacturing the multi-layer flexible printed circuit board by using the Teflon film411having a difficult-to-adhere property.

As described above, the method for manufacturing the flexible printed circuit board according to an embodiment of the present disclosure may form the base sheet410by adhering the guide film412to the Teflon film411, thereby preventing the shape of the Teflon film411from being deformed or broken in the manufacturing process to prevent the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The forming the seed layer (S323) forms the seed layer414of a thin film on one surface of the Teflon film411. The forming the seed layer (S323) forms the seed layer414on the upper surface of the adhesive layer417formed on the other surface (in other words, the upper surface) of the Teflon film411through a deposition process or a sputtering process. Here, the forming the seed layer (S323) forms the seed layer414of a mixed material of mixing nickel copper (NiCu) and copper (Cu) or a nickel copper (NiCu) material on the other surface of the Teflon film411.

The forming the plating layer (S324) forms the plating layer415on the seed layer414. At this time, the forming the plating layer (S324) forms the plating layer415on the seed layer414by electroplating copper (Cu).

Here, the seed layer414and the plating layer415are elements constituting the circuit pattern, and are formed at a thickness of about 5 μm.

The forming the thin film pattern (S325) forms a thin film pattern416on the other surface of the Teflon film411. In other words, the forming the thin film pattern (S325) forms the thin film pattern416of a predetermined shape by removing parts of the seed layer414and the plating layer415formed on the other surface of the Teflon film411through an etching process.

The forming the guide hole (S326) forms the plurality of guide holes418penetrating the adhesive layer417, the Teflon film411, and the guide film412. In other words, the forming the guide hole (S326) forms the plurality of guide holes418in order to align the base sheets410at accurate locations while firmly fixing the base sheet410to the jig200in the stacking (S330) to be described later. Here, the forming the guide hole (S326) forms the guide hole418in the base sheet410through a punching process, a laser drill process, or the like.

The stacking (S330) stacks the plurality of base sheets410. The stacking (S330) stacks the plurality of base sheets410by using the jig200.

At this time, the stacking (S330) may provide reliability of the flexible printed circuit board only when the thin film patterns416of the base sheet410are stacked to be aligned at accurate locations.

Accordingly, the stacking (S330) stacks the plurality of base sheets410and the adhesive sheet by using the jig200including the guide pin220.

An example of the stacking (S330) that stacks two base sheets410(in other words, the first base sheet410aand the second base sheet410b) will be explained with reference toFIGS. 32 and 33as follows.

The stacking (S330) may include stacking the first base sheet410a(S331), removing the guide film412aof the first base sheet410a(S333), stacking the second base sheet410b(S335), and removing the guide film412bof the second base sheet410b(S337).

The stacking the first base sheet410a(S310) stacks the first base sheet410aon the jig200. In other words, the stacking the first base sheet410a(S310) stacks the first base sheet410aon the jig200by disposing so that the guide pins220of the jig200penetrate the guide holes418aof the first base sheet410a, respectively and then moving them downwards.

At this time, the stacking the first base sheet410a(S310) stacks the first base sheet410aso that the thin film pattern416aformed on the first base sheet410ais positioned downwards in order to easily remove the guide film412a. In other words, the stacking the first base sheet410a(S310) disposes the guide film412aon the top by stacking the first base sheet410aso that the thin film pattern416ais positioned downwards.

The removing the guide film412aof the first base sheet410a(S333) removes the guide film412afrom the first base sheet410astacked on the jig200. In other words, the removing the guide film412aof the first base sheet410a(S333) removes the guide film412aof the first base sheet410adisposed on the top and the adhesive film413a.

The stacking the second base sheet410b(S335) stacks the second base sheet410bon the jig200. In other words, the stacking the second base sheet410b(S335) stacks the second base sheet410bon the jig200by disposing so that the guide pins220of the jig200penetrate the guide holes418bof the second base sheet410b, respectively and then moving them downwards.

At this time, the stacking the second base sheet410b(S335) stacks the second base sheet410babove the first base sheet410astacked on the jig200. The stacking the second base sheet410b(S335) stacks the second base sheet410bso that one surface, on which the thin film pattern416bhas been formed, is disposed above the adhesive sheet.

The removing the guide film412bof the second base sheet410b(S337) removes the guide film412bfrom the second base sheet410bstacked on the jig200. In other words, the removing the guide film412bof the second base sheet410b(S337) removes the guide film412bof the second base sheet410bdisposed on the top and the adhesive film413b.

Here, in the case of a state where the adhesive layer417has been formed on the lower surface of the base sheet410and the guide film412has been removed, the operations S230and S270may be omitted.

As described above, the method for manufacturing the flexible printed circuit board may stack the plurality of base sheets410by disposing so that the guide pin220formed on the jig200penetrates the guide hole418formed in the base sheets410and then moving them downwards in the stacking (S330) not to perform the alignment process of the adhesive sheet in the stacking process, thereby simplifying the manufacturing process.

Further, the method for manufacturing the flexible printed circuit board may stack the plurality of base sheets410by disposing so that the guide pin220formed on the jig200penetrates the guide hole418formed in the base sheet410and then moving them downwards in the stacking (S330) to align the thin film patterns416formed on the stacked base sheets410at accurate locations, thereby preventing the manufacturing yield and reliability of the flexible printed circuit board from being degraded.

The adhering (S350) constitutes the stacked body by adhering the plurality of base sheets410and the adhesive sheet stacked on the jig200. At this time, the adhering (S350) is, for example, to adhere the plurality of base sheets410included in the stacked body through a hot press process that simultaneously applies a predetermined pressure and heat. Here, since the adhesive layer417is made of a Teflon material, the adhering (S350) heats the stacked body at a temperature of about 300° C. or more.

The adhering (S350) separates the stacked body from the jig200when the plurality of base sheets410are completely adhered to constitute the stacked body.

The forming the via hole (S370) forms one or more via holes420penetrating the stacked body. In other words, the forming the via hole (S370) forms the via hole420in the stacked body separated from the jig200through a punching process, a laser drill process, or the like.

Here, although it has been illustrated inFIGS. 24 and 25that the plurality of base sheets410and the adhesive sheet are stacked and adhered to each other and then the via hole420is formed, it is not limited thereto and the respective base sheets410and adhesive sheet may also be stacked and adhered to each other after the via hole420is formed.

The forming the connection pattern (S390) forms the connection pattern430in the via hole420in order to electrically connect (in other words, electrically conduct) the thin film patterns416formed on the plurality of base sheets410, respectively. At this time, the forming the connection pattern (S390) forms the connection pattern430by filling a conductive material in the via hole420. Here, the forming the connection pattern (S390) may also form the connection pattern430by electroplating the conductive material on the inner wall surface of the via hole420and the thin film pattern416exposed to the outside of the stacked body.

Meanwhile, the method for manufacturing the flexible printed circuit board may further include forming a protective layer on the upper surface of the stacked body configured by stacking the plurality of base sheets410.

The forming the protective layer forms a protective layer covering the surfaces of the thin film pattern416and the base sheet410by applying and then curing a coating liquid to the surfaces of the base sheet410stacked on the uppermost portion of the stacked body and the thin film pattern416. At this time, the protective layer may be made of a composite material containing a resin such as polypropylene and polyimide.

Further, the method for manufacturing the flexible printed circuit board may further include forming an electrode part. At this time, the forming the electrode part may form the electrode part by removing a part of the protective layer and then plating a conductive material such as copper on the corresponding area. Here, the electrode part may be formed on at least one of the plurality of thin film patterns416disposed on the upper surface of the stacked body.

Referring toFIG. 34, the flexible printed circuit board according to the third embodiment of the present disclosure is configured to include a stacked body in which the plurality of base sheets410are stacked and then adhered to each other, and a circuit pattern formed in the stacked body and on the upper surface thereof.

The base sheet410is composed of the Teflon film411having the thin film pattern416formed on one surface thereof. At this time, the thin film pattern416is composed of the seed layer414formed on the surface of the Teflon film411and the plating layer415formed on the upper surface of the seed layer414.

The base sheet410includes the adhesive layer417formed on at least one surface of the upper surface and the lower surface of the Teflon film411. At this time, the adhesive layer417may be formed only on one surface of the Teflon film411adhered to another base sheet410, or formed on both surfaces of the Teflon film411.

The adhesive layer417is, for example, a Teflon material, and is formed on the surface of the Teflon film411through an impregnation coating or printing (for example, gravure, spray, or the like) process.

As the plurality of base sheets410is configured by being stacked, some areas of the stacked body are formed in a structure in which the Teflon film411and the adhesive layer417have been alternately stacked, and the remaining areas are formed in a structure in which the Teflon film411, the thin film pattern416, and the adhesive layer417have been alternately stacked.

The circuit pattern is composed of the thin film pattern416exposed to the upper surface of the stacked body, the thin film pattern416interposed in the stacked body, and the connection pattern430electrically connecting the thin film patterns416.

In other words, as the base sheets410are stacked, the circuit pattern has the thin film pattern416, which has been formed on the base sheet410stacked on the uppermost portion thereof, exposed to the upper surface of the stacked body, and has the thin film patterns416formed on the other base sheets410interposed in the stacked body. At this time, the thin film patterns416are electrically connected (in other words, electrically conducted) through the connection pattern430formed in the via hole420.

Here, although it has been illustrated inFIG. 34that the connection pattern430is formed by being filled in the via hole420, it is not limited thereto and may also be formed by being plated on the inner wall surface of the via hole420.

As described above, although preferred embodiments according to the present disclosure has been described, it may be modified in various forms, and it is understood by those skilled in the art that various modified examples and changed examples may be practiced without departing from the claims of the present disclosure.