KR102279623B1 - Manufacturing Method of Flexible Circuit Board Using Master Mold with Fine Pattern - Google Patents

Abstract

The present invention relates to a method for manufacturing a flexible printed circuit board, wherein the manufacturing method includes electroplating of a master mold having a fine engraved pattern on a first surface and a coating layer made of an insulating material in an area where the fine engraving pattern is not formed. Since the metal circuit pattern of the flexible printed circuit board is implemented by performing it, there is no restriction on the shape or size of the pattern, the shape and dimensional reproducibility are excellent, and the process is very simple, so there is an economic advantage.

Description

Manufacturing Method of Flexible Circuit Board Using Master Mold with Fine Pattern

The present invention relates to a method of manufacturing a flexible printed circuit board by performing plating on one surface of a master mold having a fine pattern.

In general, a printed circuit board (PCB) is a flexible printed circuit board (FPCB), a rigid printed circuit board (Rigid PCB), and a combination of the two (Rigid-flexible PCB). ), and are currently used in various industrial fields according to their respective uses.

The most commonly used patterning method for such a printed circuit board is to use a photolithography process, which is the entire surface of the board in order to compose a circuit with metal (usually copper) on the surface of the circuit board base. After a copper coating is applied to the copper surface, a photoresist or solder resist is applied on the surface of the coated copper, the photoresist is selectively reacted through exposure using a film in which the circuit pattern to be constructed is developed, and then the printed copper is thus printed. By selectively removing the photoresist and copper of the substrate, a patterned PCB is obtained.

However, the photolithography process has limitations in pattern precision due to the wavelength band of light used, the cost of the production process according to the exposure and etching process is high, and disadvantageous in producing a large product. In addition, since all of the metal except for the portion of the conductive wire made of copper or gold constituting the circuit is removed by wet or dry etching, there is a problem in that the metal is wasted heavily and causes environmental pollution.

In order to solve this problem, a technology of designing a circuit pattern on a base substrate during patterning of a circuit board, manufacturing a press mold according to the designed pattern, and punching it with a thin copper plate or a thin stainless plate, etc. have been developed.

However, the technologies developed so far have limitations in that the shape and dimensional reproducibility are low when the size of the micro-pattern is reduced to several to tens of micrometers. Therefore, the development of a circuit board having excellent fairness and economic feasibility and few restrictions on the circuit pattern is difficult. is being demanded

Republic of Korea Patent Publication No. 10-2009-0013424

It is an object of the present invention to provide a method of manufacturing a flexible circuit board that is not only capable of realizing a fine circuit pattern structure through a simple process, has no restrictions on the shape or size of the implemented pattern, has excellent reproducibility, and is economical.

In order to solve the above problems, the present invention in one embodiment,

Forming a copper layer having a fine embossed pattern corresponding to the fine engraved pattern of the master mold on the surface in contact with the first surface of the master mold by electroplating copper or a copper alloy on the first surface of the master mold on which the fine engraved pattern is formed ;

Forming a flexible circuit board including a copper layer and a nickel layer on one surface of the master mold by forming a nickel layer by electrolytic plating or electroless plating of nickel or a nickel alloy on the other surface of the copper layer having a surface on which a fine embossed pattern is formed step; and

Detaching the master mold from the formed flexible circuit board to obtain a flexible printed circuit board in which a copper layer having a fine embossed pattern structure is laminated on a nickel layer,
The master mold in which a fine engraving pattern is formed on the first surface,
forming a coating layer made of an insulating material on the first surface of the master mold; and
It is manufactured by performing the step of forming a fine engraved pattern by etching the surface of the master mold on which the coating layer is formed with a laser.

At this time, the master mold may form a copper layer having an embossed cross-sectional structure having an average height of 10 μm to 300 μm through a fine engraved pattern formed on the first surface, and the cross-sectional structure is polygonal, hemispherical, oval and prism. It may have any one of the types or a combination thereof.

In addition, the micro-embossed pattern includes a linear surface structure having an average width and an interval between the patterns of 3 μm to 500 μm, respectively, and the surface structure extends in different directions to form a serpentine, a lattice Alternatively, it may have the shape of a circle.

In addition, the first surface of the master mold includes a coating layer made of an insulating material in an area where the fine engraving pattern is not formed, and between the first surface of the master mold and the coating layer, from the group consisting of chromium (Cr) and chromium oxide. A functional layer including one or more selected metal compounds may be further included.

In addition, the total thickness of the copper layer and the nickel layer may be 5㎛ to 300㎛.

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Here, the laser etching may be performed by irradiating a laser beam having a power of 1.0KW to 8.0KW and a frequency of 70kH to 80kH at 1500 mm/s to 1600 mm/s.

The method for manufacturing a flexible printed circuit board according to the present invention is performed by electrolytic plating of a master mold having a fine engraved pattern on a first surface, but having a coating layer made of an insulating material in an area where the fine engraved pattern is not formed, thereby forming the metal of the flexible circuit board. Since the circuit pattern is implemented, there is no restriction on the shape or size of the pattern, and the shape and dimensional reproducibility for a pattern with a size of several to tens of micrometers is excellent, and the process is very simple, so there is an economic advantage.

1 is a flowchart illustrating a process of manufacturing a flexible printed circuit board according to the present invention.
2 is a conceptual diagram illustrating the principle of forming a fine embossed pattern of a copper layer using a master mold prepared according to the present invention.
3 is a flowchart illustrating a manufacturing process of a master mold according to the present invention.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, the present invention will be described in more detail.

The present invention in one embodiment,

Forming a copper layer having a fine embossed pattern corresponding to the fine engraved pattern of the master mold on the surface in contact with the first surface of the master mold by electroplating copper or a copper alloy on the first surface of the master mold on which the fine engraved pattern is formed ;

Forming a flexible circuit board including a copper layer and a nickel layer on one surface of the master mold by forming a nickel layer by electrolytic plating or electroless plating of nickel or a nickel alloy on the other surface of the copper layer having a surface on which a fine embossed pattern is formed step; and

There is provided a method of manufacturing a flexible printed circuit board, comprising the step of removing a master mold from the formed flexible circuit board to obtain a flexible printed circuit board in which a copper layer having a fine embossed pattern structure is laminated on a nickel layer.

The method of manufacturing a flexible circuit board according to the present invention implements a metal wiring structure by plating and molding a circuit pattern using a master mold having a fine intaglio pattern, so there is no restriction on the shape or size of the pattern, and the shape and dimensional reproducibility are excellent. There is this.

1 is a flowchart showing a manufacturing process of a flexible printed circuit board according to the present invention.

Referring to FIG. 1 , a method of manufacturing a flexible circuit board according to the present invention includes forming a copper layer through electrolytic plating on a first surface of a master mold on which a fine engraving pattern is formed; forming a nickel layer on the formed copper layer through electrolytic plating or electroless plating; and separating the formed copper layer and the nickel layer from the master mold.

Specifically, the step of forming the copper layer is a step of introducing the circuit pattern of the flexible circuit board, and the surface foreign substances are removed through electrolytic degreasing of the master mold having the fine engraved pattern on the first surface, and the copper precursor, such as A copper layer having a fine embossed pattern corresponding to the fine engraved pattern of the master mold through electrolytic plating by applying electricity after immersion in a plating solution containing a copper salt such as copper sulfate, copper chloride, copper cyanide (opening): 10 µm≤, specifically 15 µm to 50 µm) can be formed.

Here, in the present invention, the thickness of the copper layer is easier to control compared to the case where electroless plating is performed by performing electroplating when forming the copper layer, and plating is possible regardless of the type of material of the master mold, and has a constant diameter. In addition to being able to form a copper layer having an opening, there is an advantage in that the performance and/or physical properties of the copper layer can be controlled by using an additive in the plating solution.

In addition, the fine embossed pattern of the copper layer thus formed may have an average height, average width, and inter-pattern spacing within a certain range, which may be the same as the fine embossed pattern formed on the first surface of the master mold.

For example, the fine embossed pattern formed on the copper layer according to the present invention has an average height of 10 μm to 300 μm, specifically 10 μm to 200 μm, 10 μm to 100 μm, 10 μm to 50 μm, 50 μm to 250 μm. , 100 μm to 200 μm, 150 μm to 300 μm, 20 μm to 60 μm, 30 μm to 50 μm, 10 μm to 30 μm or 15 μm to 25 μm; The cross-sectional structure may have any one of polygonal, hemispherical, elliptical, and prismatic, or a combination thereof.

In addition, the micro-embossed pattern may be introduced into the substrate in the form of a line having an average width and a pattern interval of 3 μm to 500 μm, respectively. More specifically, the fine embossed pattern has an average width and pattern spacing of 3 μm to 400 μm, 3 μm to 350 μm, 3 μm to 300 μm, 3 μm to 250 μm, 3 μm to 200 μm, and 3 μm to 100, respectively. μm, 5 μm to 100 μm, 100 μm to 200 μm, 80 μm to 150 μm, 50 μm to 100 μm, 10 μm to 50 μm, 25 μm to 50 μm, 20 μm to 40 μm, 25 μm to 35 μm, It may be provided on the substrate in a linear structure of 10 μm to 20 μm, 5 μm to 15 μm, 3 μm to 8 μm, or 3 μm to 50 μm.

In addition, the fine embossed pattern is not particularly limited in its form, but may be patterned in a linear structure so that the pattern can be concentrated in a narrow area, and the embossed pattern of the linear structure is extended in a single direction or in different directions It may be an extended circle, or it may be patterned in the form of a serpentine or a lattice.

As an example, the micro-embossed pattern may have a line structure in the form of a circle having a plurality of regions each extending in different directions, and the line structure has an average height of the micro-embossed pattern of 20 μm to 25 μm, The average width may be 20 μm to 50 μm, the average length may be 50 mm to 110 mm, and the distance between patterns extending in different directions (ie, pattern spacing) may be 50 μm to 100 μm.

As another example, the micro-embossed pattern may have a line structure in the form of a circle having a plurality of regions each extending in different directions, and the line structure has an average height of the micro-embossed pattern of 15 μm to 20 μm, , may have an average width of 5 μm to 9 μm, an average length of 10,000 μm to 11,000 μm, and a distance between patterns extending in different directions (ie, pattern spacing) from 5 μm to 10 μm.

The present invention can increase the intensity of the fine pattern in the circuit board by adjusting the average width and the pattern interval of the fine embossed pattern within the above range, and can reduce the damage of the fine embossed pattern when detaching the flexible circuit board from the master mold. there is.

In addition, in the step of forming the nickel layer on the formed copper layer, the master mold immersed in the copper plating solution is taken out, washed so that the plating solution does not remain, and is continuously immersed in the plating solution containing the nickel precursor and then applied to electrolytic plating or The nickel layer may be formed through electroless plating. Here, the electrolytic plating or electroless plating conditions used in the art may be appropriately applied to the counter electrode corresponding to the electrolyte or the master mold used during plating.

In addition, the step of obtaining the flexible circuit board from the master mold may be performed by detaching the laminate including the formed copper layer and the nickel layer from the master mold.

Here, the copper layer and the nickel layer act as conductive layers of the flexible circuit board, and their total thickness may be 5 μm to 300 μm, and in this case, the thickness of the nickel layer may be smaller than the thickness of the copper layer. Specifically, the total thickness of the copper layer and the nickel layer is 5 μm to 300 μm, 5 μm to 200 μm, 5 μm to 150 μm, 5 μm to 100 μm, 40 μm to 100 μm, 100 μm to 200 μm, 150 μm to 220 μm, 5 μm to 10 μm, 5 μm to 15 μm, 5 μm to 20 μm, 10 μm to 50 μm, 15 μm to 25 μm, 30 μm to 90 μm, 50 μm to 100 μm, 90 μm to 140 μm, may be 120 μm to 150 μm.

As an example, the total thickness of the copper layer and the nickel layer may be 15 μm to 50 μm, and in this case, the thickness of the nickel layer may be 3 μm to 10 μm.

On the other hand, the method of manufacturing a flexible circuit board according to the present invention includes the steps of laminating a transparent film on the nickel layer before or after the step of obtaining the flexible circuit board by detaching the master mold from the flexible circuit board including the copper layer and the nickel layer may further include.

At this time, the transparent film is at this time, the transparent film 30 is polyethylene terephthalate (Polyethylene terephthalate, PET), polypropylene (Polypropylene, PP), polyimide (Polyimide, PI), polycarbonate (Polycarbonate, PC), poly Methyl methacrylate (Poly (methylmethacrylate), PMMA), polyethylene naphthalate (polyethylenenaphthalate, PEN), polyether ether ketone (Polyetheretherketone, PEEK), polyethersulfone (Polyethersulfone, PES) or polyarylite (Polyarylite) selected from It may be any one or more types.

까지 승온시킨 후, 150

에서 10분 ~ 100분 동안 유지하여 수행될 수 있다.In addition, the lamination may be performed by conventional means for bonding the metal layer and the transparent film in the art. For example, in the lamination, a transparent film is placed on a nickel layer, and 150 at a pressure of 30 to 60 kg/cm 2

After raising the temperature to 150

It can be carried out by holding for 10 to 100 minutes at

Furthermore, the flexible printed circuit board thus formed has a structure in which a nickel layer and a copper layer are sequentially stacked on a transparent film, and the copper layer located on the uppermost layer may have a fine embossed pattern induced by the master mold on the surface.

On the other hand, the master mold used in the present invention is not particularly limited as long as it is a material through which electricity can flow when electricity is applied, and may be used. For example, the master mold may include a conductive polymer such as PEDOT:PSS and polyaniline having electrical conductivity; It may include a metal such as aluminum (Al) and titanium (Ti), a metal alloy thereof, a carbon material such as carbon fiber, or stainless steel (SUS). In the present invention, stainless steel (SUS) with good durability may be used for repeated use of the master mold.

In addition, the master mold,

forming a coating layer made of an insulating material on the first surface of the master mold; and

It may be manufactured by performing the step of forming a fine engraved pattern by etching the surface of the master mold on which the coating layer is formed with a laser.

Accordingly, the first surface of the master mold may include a coating layer made of an insulating material in a region where the fine engraving pattern is not formed.

Specifically, in the master mold used in the present invention, as shown in FIG. 3 , a coating layer composed of an insulating material is applied to the first surface of the master mold before forming a fine engraved pattern of several to tens of micrometers in size on the first surface. and etched by irradiating a laser beam on the surface of the master mold on which the coating layer is formed to form a fine engraved pattern on the first surface. Here, since the surface of the master mold is etched at the same time as the coating layer is removed by the laser beam in the area where the fine engraving pattern is formed, the surface of the master mold is exposed, but the coating layer may remain in the area where the fine engraving pattern is not formed. During electroplating to form a copper layer, the copper layer is formed only on the exposed area of the surface of the master mold through which current flows, so the coating layer remains in the area where the fine intaglio pattern is not formed as described above, and the area in which the fine intaglio pattern is formed is exposed. In this case, the copper layer may be formed at a higher density in the fine engraved pattern area, and thus the performance of the flexible printed circuit board may be further improved.

On the other hand, if the coating layer is made of an insulating material, it can be used without being particularly limited. For example, the coating layer may include at least one selected from the group consisting of polyimide, Teflon, and ceramic, and is commonly used in the art to form a coating layer including a polymer or a coating layer including a ceramic. It can be formed by any method.

As an example, in the present invention, the coating layer may be formed by spin coating Teflon on the first surface of the master mold, and the thickness thereof is 0.5 μm to 30 μm, 0.5 μm to 20 μm, 0.5 μm to 10 μm, 10 μm to 30 μm, 10 μm to 20 μm, 20 μm to 30 μm, or 15 μm to 25 μm.

In addition, the master mold includes at least one metal compound selected from the group consisting of chromium (Cr) and chromium oxide between the first surface and the coating layer, and is 0.5 µm to 2 µm, specifically 0.8 µm to 1.8 µm or 1.0 It may further include a functional layer having a thickness of ㎛ to 1.5㎛. The functional layer is a black permeable film electrolyzed onto ultra-fine ceramics, and has a high degree of corrosion protection due to the intermediate diffusion layer created inside the first surface of the master mold and a crack group magnetic to the ceramic-based ultra-fine particle laminate. Since the energy density of intermetallic corrosion is lowered and dispersed, excellent corrosion resistance can be realized. In addition, when the master mold is a metal material such as stainless steel (SUS) and the coating layer is an organic material such as Teflon, it is possible to improve the durability of the master mold by increasing adhesion between the master mold and the coating layer.

In addition, the laser etching can be performed using a fiber laser, a nanosecond laser, a Ya laser, a CO2 laser, etc., and removes the coating layer, as well as several to tens of micrometers on the surface without penetrating the master mold. Laser irradiation conditions can be precisely controlled in order to form a meter-level engraved pattern.

Specifically, the laser etching may be performed by irradiating a laser beam having a power of 1.0KW to 8.0KW and a frequency of 70kH to 80kH at 1500 mm/s to 1600 mm/s.

As an example, the laser etching may be performed by irradiating a laser beam having a power of 5.0KW to 6.0KW and a frequency of 74kH to 76kH at about 1550 mm/s to 1560 mm/s.

Claims (6)

Forming a copper layer having a fine embossed pattern corresponding to the fine engraved pattern of the master mold on the surface in contact with the first surface of the master mold by electrolytic plating copper or copper alloy on the first surface of the master mold on which the fine engraved pattern is formed ;
Forming a flexible circuit board including a copper layer and a nickel layer on one surface of the master mold by forming a nickel layer by electrolytic plating or electroless plating of nickel or a nickel alloy on the other surface of the copper layer having a surface on which a fine embossed pattern is formed step; and
Detaching the master mold from the formed flexible circuit board to obtain a flexible printed circuit board in which a copper layer having a fine embossed pattern structure is laminated on a nickel layer,
The master mold in which a fine engraving pattern is formed on the first surface,
forming a coating layer made of an insulating material on the first surface of the master mold; and
It is manufactured by irradiating a laser beam on the surface of the master mold on which the coating layer is formed to form a fine engraved pattern in which the coating layer and the master mold surface are etched,
The laser etching is performed by irradiating a laser beam having a power of 1.0 kW to 8.0 kW and a frequency of 70 kHz to 80 kHz at 1500 mm/s to 1600 mm/s,
The fine engraved pattern formed on the master mold has an average height of 10 μm to 300 μm, an average width of 3 μm to 500 μm, and an interval between the patterns of 3 μm to 500 μm.
According to claim 1,
The fine embossed pattern is,
It includes an embossed cross-sectional structure with an average height of 10 μm to 300 μm,
The cross-sectional structure is a method of manufacturing a flexible printed circuit board having any one or a combination of polygonal, hemispherical, elliptical, and prismatic.
According to claim 1,
The method of manufacturing a flexible printed circuit board, the first surface of the master mold further comprising a coating layer made of an insulating material in a region where the fine engraved pattern is not formed.
According to claim 1,
The method of manufacturing a flexible circuit board, wherein the master mold further comprises a functional layer comprising at least one metal compound selected from the group consisting of chromium (Cr) and chromium oxide between the first surface and the coating layer.
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