KR102564878B1 - Method for manufacturing flexible circuit board and flexible circuit board manufactured by the method - Google Patents

Abstract

In order to be applied to a touch pressure sensor using low current, a method for manufacturing a flexible printed circuit board to minimize the thickness of the board by forming a circuit pattern through electroless plating is proposed. The proposed flexible printed circuit board manufacturing method includes preparing a flexible base substrate, forming seed layers on both sides of the base substrate, etching a portion of the seed layer formed on both sides of the base substrate to form a thin film pattern, and base substrate. and forming a thin film circuit pattern by forming an electroless plating layer on the thin film pattern on both sides of the substrate.

Description

Flexible printed circuit board manufacturing method and flexible printed circuit board manufactured thereby

The present invention relates to a method for manufacturing a flexible printed circuit board, and more particularly, to a method for manufacturing a flexible printed circuit board used as a circuit using low current, such as a touch pressure sensor (or force touch sensor).

In general, a flexible printed circuit board is a board that can be flexibly bent by forming a circuit pattern on a thin insulating film.

Flexible printed circuit boards are widely used in portable electronic devices and automation devices or display products that require bending and flexibility when used.

In particular, flexible printed circuit boards are widely used in mobile terminals such as smartphones, for which demand has exploded in recent years. For example, the flexible printed circuit board is used for a near field communication (NFC) antenna of a portable terminal, a digitizer, a touch pressure sensor (or force touch sensor), and the like.

The touch pressure sensor detects touch pressure and is used to classify and execute an installed program or application according to the touch pressure.

At this time, the flexible printed circuit board for the touch pressure sensor is required to have a relatively thin thickness compared to the flexible printed circuit board used for antennas, digitizers, etc. in order to secure visibility and thin the touch screen panel.

Korean Patent Publication No. 10-2014-0158617 (Name: Flexible printed circuit board and its manufacturing method)

The present invention has been proposed in view of the above circumstances, and a method for manufacturing a flexible printed circuit board to minimize the thickness of the board by forming a circuit pattern through electroless plating for application to a touch pressure sensor using low current, and thereby It is an object of the present invention to provide a flexible printed circuit board manufactured by

In addition, another object of the present invention is to provide a flexible printed circuit board manufacturing method to reduce manufacturing cost by simplifying the manufacturing process.

In order to achieve the above object, a method for manufacturing a flexible printed circuit board according to an embodiment of the present invention includes preparing a flexible base material, forming seed layers on both sides of the base material, and seed layers formed on both sides of the base material. Forming a thin film pattern by etching a part of the base substrate and forming a thin film circuit pattern by forming an electroless plating layer on the thin film pattern on both sides of the base substrate.

Preparing the base substrate may include forming a via hole penetrating the base substrate.

In the step of forming the seed layer, the seed layer may also be formed on the inner wall of the via hole.

Forming the seed layer may include depositing a first thin film seed layer on both sides of the base substrate. In this case, the first thin film seed layer may be formed of an alloy including nickel and copper.

Forming the seed layer may further include depositing a second thin film seed layer on the first thin film seed layer. In this case, the second thin film seed layer may be formed of copper.

Forming the thin film pattern may include disposing a mask having a shape corresponding to the thin film pattern on the seed layer and etching a portion of the seed layer exposed through the mask to form the thin film pattern.

In the forming of the thin film circuit pattern, an electroless plating layer may be formed on the top surface and around the thin film pattern.

In the forming of the thin film circuit pattern, an electroless plating layer may be formed by directly electroless plating copper on the thin film pattern formed from the seed layer.

The method may further include forming a protective coating layer on the base substrate on which the thin film circuit pattern is formed and forming a terminal unit for connecting the thin film circuit pattern to an external circuit.

In order to achieve the above object, the flexible printed circuit board manufactured by the flexible printed circuit board manufacturing method according to the embodiment of the present invention is a flexible printed circuit board manufactured by the above-described flexible printed circuit board manufacturing method, and includes a flexible base. It includes a substrate, a thin film pattern formed on both sides of the base substrate, and an electroless plating layer formed directly on the upper surface and circumference of the thin film pattern.

According to the present invention, a flexible printed circuit board manufacturing method and a flexible printed circuit board manufactured thereby form a thin film pattern using a seed layer, and form an electroless plating layer through electroless plating, thereby forming a photoresist layer on the seed layer. After forming, there is an effect of minimizing the thickness of the flexible printed circuit board by forming a thin film circuit pattern with a relatively thin thickness compared to the prior art of forming a circuit pattern through etching.

In addition, the flexible printed circuit board manufacturing method and the flexible printed circuit board manufactured by the method do not perform pretreatment, catalyst, nickel plating, etc. during electroless plating, and copper is directly plated on the thin film pattern, such as pretreatment, catalyst, nickel plating, etc. There is an effect of minimizing the thickness of the flexible printed circuit board by forming a thin film circuit pattern of relatively thin thickness compared to the conventional electroless plating to perform.

In addition, the flexible printed circuit board manufacturing method and the flexible printed circuit board manufactured by the method reduce manufacturing cost by simplifying the manufacturing process by directly plating copper on the thin film pattern without performing pretreatment, catalyst, nickel plating, etc. during electroless plating. There is an effect of improving the marketability of flexible printed circuit boards by reducing and improving productivity to secure economic feasibility.

1 and 2 are views for explaining a method of manufacturing a flexible printed circuit board according to an embodiment of the present invention.
3 and 4 are views for explaining the seed layer forming step of FIG. 1;
5 and 6 are views for explaining the thin film pattern forming step of FIG. 1;
7 and 8 are views for explaining a modified example of a method for manufacturing a flexible printed circuit board according to an embodiment of the present invention.
9 is a view for explaining another modified example of a method for manufacturing a flexible printed circuit board according to an embodiment of the present invention.
10 is a view for explaining an application example of a flexible printed circuit board manufactured by a method for manufacturing a flexible printed circuit board according to an embodiment of the present invention.

Hereinafter, the most preferred embodiment of the present invention will be described with reference to the accompanying drawings in order to explain in detail to the extent that those skilled in the art can easily practice the technical idea of the present invention. . First, in adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description will be omitted.

1 and 2, the flexible printed circuit board manufacturing method includes preparing a base substrate 100 (S100), forming a seed layer 200 on the base substrate 100 (S200), seed layer Process (200) to form the thin film pattern 300 (S300) and form the thin film circuit pattern 500 (S400). Hereinafter, in order to easily explain the flexible printed circuit board manufacturing method, the formation of the thin film circuit pattern 500 on both sides of the base substrate 100 has been described as an example, but it is not limited thereto and only on one side of the base substrate 100. The thin film circuit pattern 500 may be formed.

In the step of preparing the base substrate 100 ( S100 ), one or more via holes 120 penetrating the base substrate 100 are formed. That is, in the step of preparing the base substrate 100 (S100), the thin film circuit pattern 500 formed on one side of the base substrate 100 and the other side formed on the other side of the base substrate 100 through punching One or more via holes 120 for connecting the thin film circuit patterns 500 are formed.

At this time, the base substrate 100 is composed of an insulating film having flexibility. The base substrate 100 is composed of a transparent or translucent insulating film having a very thin and flexible property to maintain the shape of the flexible printed circuit board.

For example, the base substrate 100 may be composed of an insulating film such as a PET film or a PI film. Here, the PI film is thin and flexible, has excellent heat resistance and bending resistance, has little dimensional change and is resistant to heat, so it is suitable as an insulating film when transferring punched metal foil using heat, and PET film is relatively cheaper than PI film. It has the advantage of being cheap.

Forming the seed layer 200 on the base substrate 100 ( S200 ) forms thin seed layers 200 on both sides of the base substrate 100 through a deposition process. That is, in the step of forming the seed layer 200 on the base substrate 100 ( S200 ), thin seed layers 200 are formed on both sides of the base substrate 100 through a deposition process. At this time, in the step of forming the seed layer 200 on the base substrate 100 (S200), the thin seed layer 200 is also formed on the inner wall of the via hole 120 formed on the base substrate 100.

In the step of forming the seed layer 200 on the base substrate 100 (S200), when the chamber for performing the deposition process is composed of one, a thin seed layer ( 200), and after turning the base substrate 100 over, a thin seed layer 200 is formed on the other side of the base substrate 100 through a secondary deposition process. At this time, the thin seed layer 200 is formed on the inner wall of the via hole 120 through at least one of the first deposition process and the second deposition process.

Forming the seed layer 200 on the base substrate 100 (S200) is to form a thin seed layer 200 on one surface of the base substrate 100 in the chamber when two chambers are used to perform the deposition process. After that, the thin seed layer 200 may be formed on the other side of the base substrate 100 in another chamber.

In the step of forming the seed layer 200 on the base substrate 100 (S200), the metal substrate is heated and evaporated in a vacuum, and the evaporated metal molecules are condensed on the surface of the base substrate 100 at a temperature lower than the vapor temperature to form a thin film. The seed layer 200 of a thin film is formed by a vacuum deposition method to form a. For example, in the step of forming the seed layer 200 on the base substrate 100 (S200), the thin seed layer 200 may be formed on the base substrate 100 through a sputtering process, which is a vacuum deposition method. there is.

The seed layer 200 of the thin film formed through the step of forming the seed layer 200 on the base substrate 100 (S200) is formed on the base substrate 100 by vacuum deposition and has strong adhesive strength with the base substrate 100, Even when the base substrate 100 is bent, it can remain firmly attached to the base substrate 100 without being separated from the base substrate 100 .

The seed layer 200 of the thin film formed through the step of forming the seed layer 200 on the base substrate 100 (S200) is formed to have a thickness of about 10 nm to 35 nm, and the seed layer 200 of the thin film is copper. , It may be formed of one of silver, gold, nickel, chromium, tungsten, molybdenum, and aluminum, or an alloy in which at least one of copper, silver, gold, nickel, chromium, tungsten, molybdenum, and aluminum is mixed, which will be described later. It is formed of a metal having excellent adhesion to the plating layer 400 .

Meanwhile, as shown in FIGS. 3 and 4 , the step of forming the seed layer 200 on the base substrate 100 (S200) is the step of forming the first thin film seed layer 220 (S220) and the second A step of forming a thin seed layer 240 (S240) may be included.

In the step of forming the first thin film seed layer 220 (S220), the first thin film seed layer 220 is formed on both sides of the base substrate 100 through vacuum deposition (eg, a sputtering process). At this time, in the step of forming the first thin film seed layer 220 (S220), it is made of an alloy containing nickel (Ni) and copper (Cu) through vacuum deposition in order to increase the adhesive strength (bonding strength) with the base substrate 100. A one-thin film seed layer 220 may be formed.

In the step of forming the second thin film seed layer 240 ( S240 ), the second thin film seed layer 240 is formed on the first thin film seed layer 220 through vacuum deposition (eg, a sputtering process). At this time, in the step of forming the second thin film seed layer 240 (S240), copper having excellent adhesion to the electroless plating layer 400 described later is vacuum-deposited on the first thin film seed layer 220 to form the second thin film seed layer 220. A thin seed layer 240 is formed. That is, in the step of forming the second thin film seed layer 240 (S240), copper ( A second thin film seed layer 240 is formed of Cu).

Forming the thin film pattern 300 (S300) forms the thin film pattern 300 by etching a portion of the seed layer 200 formed in step S200. At this time, in the step of forming the thin film pattern 300 (S300), the thin film pattern 300 having a thickness of about 30 nm is formed. Here, since the thin film pattern 300 is formed by etching the seed layer 200, it is indicated in the drawing with the same material as the seed layer 200.

To this end, as shown in FIGS. 5 and 6 , forming the thin film pattern 300 ( S300 ) may include a masking step ( S320 ) and an etching step ( S340 ).

In the masking step ( S320 ), a mask 600 for forming the thin film pattern 300 is disposed on the seed layer 200 . That is, in the masking step (S320), a mask 600 having a shape corresponding to the shape of the thin film pattern 300 is disposed on both sides of the base substrate 100 on which the seed layer 200 is formed.

At this time, the mask 600 is a coating material in which photoresist films are stacked, and dry-film resists made of materials that can withstand various electroplating solutions or corrosive solutions can be used. In the mask 600 , an etching groove 620 is formed to expose a portion to be etched in the seed layer 200 .

Here, the masking step (S320) has been described as simultaneously processing the seed layer 200 formed on both sides of the base substrate 100, but each side may be masked individually, or may be performed through a photolithography process.

In the etching step ( S340 ), a portion of the seed layer 200 excluding the thin film pattern 300 is etched by spraying an etchant while the mask 600 is disposed on the seed layer 200 . That is, in the etching step (S340), a portion of the seed layer 200 exposed by the mask 500 (ie, a region excluding the shape of the thin film pattern 300 in the seed layer 200) is etched to form the thin film pattern 300. form

Here, since the thin film pattern 300 is formed using only the seed layer 200 in the etching step (S340), the prior art of forming the thin film pattern 300 after forming a photoresist layer on the seed layer 200 Etching should be slowed down compared to That is, in the etching step (S340), since the thickness of the layer to be etched (ie, the seed layer 200) is relatively thin compared to the prior art, it is preferable to relatively slow down the etching rate.

Therefore, in the etching step (S340), it is preferable to relatively slow down the etching rate by diluting the etchant or adjusting or changing the amount of additives added to the etchant.

In the step of forming the thin film circuit pattern 500 (S400), an electroless plating layer 400 made of copper (Cu) is plated on the surface of the thin film pattern 300 through electroless plating to form the thin film circuit pattern 500. do.

In the step of forming the thin film pattern 300 (S300), since the thin film pattern is formed by etching the seed layer 200, the thin film pattern 300 has low conductivity.

Accordingly, in the step of forming the thin film circuit pattern 500 (S400), in order to increase the conductivity of the thin film pattern 300, the electroless plating layer 400 is formed on the thin film pattern 300 through electroless plating to form the thin film pattern 300. Increase the thickness of (300).

Here, in the step of forming the thin film circuit pattern 500 (S400), the electroless plating layer 400 having a thickness of approximately 1 μm to 2 μm is formed on the thin film pattern 300. In the step of forming the thin film circuit pattern 500 (S400), the electroless plating layer 400 is formed on the surface of the thin film pattern 300 (ie, the upper surface and the circumference of the thin film pattern 300) through electroless plating. At this time, in the step of forming the thin film circuit pattern 500 (S400), the electroless plating layer 400 may be formed by directly electroless plating copper on the thin film pattern 300.

Also, in the step of forming the thin film pattern 300 (S300), since the thin film pattern is formed, an island phenomenon in which the thin film patterns 300 are spaced apart from each other may occur.

Therefore, in the step of forming the thin film circuit pattern 500 (S400), the electroless plating layer 400 is formed on the thin film pattern 300 through electroless plating, so that the electroless plating layer 400 is formed even when the island phenomenon occurs. allow it to form.

Electroless plating is cheaper than electrolytic plating, but has disadvantages in that the electroless plating layer 400 cannot be formed thicker than electrolytic plating and the plating time is relatively long.

However, electroless plating is equivalent to electrolytic plating and plating time when forming a thin electroless plating layer 400, so in the step of forming the thin film circuit pattern 500 through electroless plating (S400), electroless plating An electroless plating layer 400 is formed on the thin film pattern 300 through gold.

At this time, the step of forming the thin film circuit pattern 500 through electroless plating (S400) is performed directly on the thin film pattern 300 without performing a generally used electroless plating pretreatment, catalyst, nickel plating, or the like. Electroless plating is performed to form the electroless plating layer 400 . Here, the electroless plating layer 400 may be formed of copper.

Meanwhile, as shown in FIGS. 7 and 8 , the method of manufacturing a flexible printed circuit board may further include forming a protective coating layer 700 covering the thin film circuit pattern 500 (S500).

In the step of forming the protective coating layer 700 (S500), a liquid coating solution is applied to the base substrate 100 and cured to form the protective coating layer 700 that covers and protects the thin film circuit pattern 500.

At this time, it is preferable that the protective coating layer 700 is formed of a synthetic resin coating layer using the same type of coating liquid as the base substrate 100 to have excellent adhesion to the base substrate 100 and to be more firmly integrated with the base substrate 100. do. For example, the base substrate 100 is a PI film, and the protective coating layer 700 is a PI coating layer or a PAI coating layer.

Meanwhile, as shown in FIG. 9 , the method of manufacturing the flexible printed circuit board may further include forming a terminal part (S600).

In the step of forming the terminal unit (S600), a portion of the protective coating layer 700 is removed, and then a conductive material such as copper is plated on the corresponding region to form the terminal unit.

10 shows a touch pressure sensor 800 to which a flexible printed circuit board manufactured by a method for manufacturing a flexible printed circuit board according to an embodiment of the present invention is applied.

The touch pressure sensor 800 is a sensor for detecting touch pressure and distinguishing and executing an installed program or application according to the touch pressure.

The touch pressure sensor 800 is disposed on the rear side of the touch screen panel separately from the touch sensor disposed on the front side of the display panel such as an LCD to detect a touch and detects the touch pressure.

To this end, the touch pressure sensor 800 includes an elastic membrane member 820, a first electrode member 840 disposed on an upper surface of the elastic membrane member 820, and a second electrode disposed on a lower surface of the elastic membrane member 820. member 860.

At this time, the first electrode member 840 and the second electrode member 860 are substrates that sense touch pressure and may be composed of a flexible printed circuit board manufactured by the method for manufacturing a flexible printed circuit board according to an embodiment of the present invention. there is. Here, in FIG. 10, a flexible printed circuit board in which the thin film circuit pattern 500 is formed only on one surface of the base member 100 is shown as an example.

As described above, the flexible printed circuit board manufacturing method and the flexible printed circuit board manufactured thereby form a thin film pattern using a seed layer and form an electroless plating layer through electroless plating, thereby forming a photoresist layer on the seed layer. After forming, there is an effect of minimizing the thickness of the flexible printed circuit board by forming a thin film circuit pattern with a relatively thin thickness compared to the prior art of forming a circuit pattern through etching.

In addition, the flexible printed circuit board manufacturing method is based on the conventional electroless plating in which pretreatment, catalyst, nickel plating, etc. are performed by directly plating copper on a thin film pattern without performing pretreatment, catalyst, nickel plating, etc. during electroless plating. There is an effect of minimizing the thickness of the flexible printed circuit board by forming a thin film circuit pattern having a relatively thin thickness compared to the present invention.

In addition, the flexible printed circuit board manufacturing method does not perform pretreatment, catalyst, nickel plating, etc. during electroless plating, and copper is directly plated on the thin film pattern, thereby simplifying the manufacturing process to reduce manufacturing cost and improving productivity to increase economic feasibility. By securing it, there is an effect of improving the marketability of the flexible printed circuit board.

Although the preferred embodiment according to the present invention has been described above, it can be modified in various forms, and those skilled in the art can make various modifications and variations without departing from the scope of the claims of the present invention. It is understood that this can be done.

100: base material 120: via hole
200: seed layer 220: first thin film seed layer
240: second thin film seed layer 300: thin film pattern
400: electroless plating layer 500: thin film circuit pattern
600: mask 620: etching groove
700: protective coating layer 800: touch pressure sensor
820: elastic membrane member 840: first electrode member
860: second electrode member

Claims (13)

Preparing a flexible base substrate having one or more via holes formed thereon;
forming a seed layer having a thickness of 10 nm to 35 nm on both surfaces of the base substrate and on inner walls of the via hole;
Forming a thin film pattern by etching a portion of the seed layer formed on the entire surface of both surfaces of the base substrate; and
Forming a thin film circuit pattern by forming an electroless plating layer having a thickness of 1 μm to 2 μm to cover an upper surface and a circumference of the thin film pattern formed by etching a portion of the seed layer; As a method for manufacturing a circuit board,
The flexible printed circuit board is laminated on the upper and lower portions of the elastic membrane member to form a touch pressure sensor. delete delete According to claim 1,
Forming the seed layer,
depositing a first thin seed layer on both surfaces of the base substrate and on the inner wall of the via hole; and
Method for manufacturing a flexible printed circuit board for a touch pressure sensor comprising the step of depositing a second thin film seed layer on the first thin film seed layer. According to claim 4,
The first thin film seed layer is formed of an alloy containing nickel and copper,
The second thin film seed layer is a method of manufacturing a flexible printed circuit board for a touch pressure sensor formed of copper. According to claim 1,
Forming the thin film pattern,
disposing a mask having a shape corresponding to the thin film pattern on the seed layer; and
Forming a thin film pattern by etching a portion of the seed layer exposed through the mask. According to claim 1,
Forming the thin film circuit pattern,
A method for manufacturing a flexible printed circuit board for a touch pressure sensor, characterized in that forming an electroless plating layer by directly electroless plating copper on the upper surface and circumference of the thin film pattern. According to claim 1,
The method of manufacturing a flexible printed circuit board for a touch pressure sensor, further comprising forming a protective coating layer on the base substrate on which the thin film circuit pattern is formed. According to claim 1,
The method of manufacturing a flexible printed circuit board for a touch pressure sensor, further comprising forming a terminal unit for connecting the thin film circuit pattern to an external circuit. delete delete delete delete

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