KR101092987B1 - Fpcb having bending part and methode the same - Google Patents

Abstract

PURPOSE: A flexible printed circuit board which includes a bending part and a manufacturing method thereof are provided to arrange two cover lays separated from each other while being placing the bending part between the two cover lays, thereby arranging an ink print layer between the two cover lays and maintaining a bent state by the ink print layer. CONSTITUTION: A circuit pattern layer(24) is arranged in a copper foil lamination plate. The copper foil lamination plate is comprised by laminating a polyimide layer and copper layer. A first cover lay(32) and second cover lay(34) are separated by placing a blank part without an adhesive layer between the first cover lay and second cover lay. An ink print layer(50) is heat hardened by applying ink in the blank part.

Description

FPCB having bending part and methode the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed circuit board (FPCB) having a bent portion and a method of manufacturing the same, and particularly, to be optimal for bending and using a flexible printed circuit board adjacent to an anisotropic conductive film (ACF) bonding portion connected to a liquid crystal display panel. The present invention relates to a flexible circuit board having a bent portion characterized by the technology and a method of manufacturing the same.

In general, LCD modules, which are essentially used for personal portable devices, are equipped with a printed circuit board that mounts an integrated circuit device and its peripheral devices as driving circuits necessary for driving LCDs. It is a trend.

 The flexible circuit board of the LCD module is connected to the LCD panel through an electrical connection means using an anisotropic conductive film-ACF (ACF) bonding to transmit the LCD driving signal.

However, in order to connect the flexible printed circuit board of the LCD module and the LCD panel, it is often necessary to bend the flexible printed circuit board of the LCD module according to the shape or structure of the manufactured product case. This is because the connection direction between the flexible circuit board of the LCD module and the main circuit board of the user set is often not aligned in a straight line.

Accordingly, in the case of bending a flexible circuit board having an ACF bonding portion (hereinafter, referred to as an 'ACF circuit pattern layer' for explaining a layer structure when expressed on a layered cross section), the flexible circuit board 100 shown in FIG. 1A is illustrated. It is bent to have a structure as shown in FIG.

In the drawing, reference numeral 100 denotes a flexible circuit board. A circuit pattern layer 24 is formed on the flexible circuit board 100, and a part of the circuit pattern layer 24 is an ACF circuit pattern layer as a circuit pattern at an end of the flexible circuit board. It is electrically connected as 24a, and the coverlay 132 is attached to the upper portion of the circuit pattern layer 24 through the adhesive layer 128.

Reference numeral 10 denotes a general copper clad laminate laminated with a polyimide layer 12 and copper-coated copper layers 14 and 14 '.

The bent portion is selected to a proper position adjacent to the ACF circuit pattern layer 24a to bend the flexible circuit board as shown in FIG. 1B, and at this time, due to the multilayer structure laminated with the coverlay 132 and the adhesive layer 128, different tensile ratios are obtained. This action and due to the inherent properties of the coverlay and the adhesive layer itself, the action of the force to return to the original direction in the direction that the bent portion is unfolded, that is, spring back characteristics appear. This acts as a cause that the connection work is not easy even when the ACF circuit pattern layer 24a is in contact with the other circuit so that the ACF circuit pattern layer 24a is electrically contacted, and causes a problem such as poor electrical contact even after connecting.

Therefore, in the conventional flexible circuit board, a technical means for maintaining the bent state of the bent portion is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a technical means of partially replacing a coverlay to maintain a bent state of a flexible circuit board, and in particular, adjacent to an ACF portion of a flexible circuit board. It is an object of the present invention to provide a flexible circuit board having a bent portion and a method of manufacturing the same, which can be very usefully used when applied thereto.

A flexible circuit board having a bent portion of the present invention for achieving the above object,

In a flexible circuit board in which a circuit pattern layer is provided on a general copper-clad laminate in which a polyimide layer and a copper layer are laminated, and a coverlay is attached by an adhesive layer thereon.

The first coverlay and the second coverlay, which are separated from each other, are formed in the bent portion requiring bending of the flexible circuit board to form a blank without the coverlay and the adhesive layer so that the circuit pattern layer is exposed. Forming a thermosetting ink print layer by applying ink to the blank area, the ink print layer is characterized in that the structure covering a portion of the upper portion of the first coverlay and the second coverlay located on both sides of the blank portion.

In the above-described configuration, the second coverlay is formed to have a narrow width, and the flexible circuit board is connected to another circuit device from an ink print layer to a position beyond the narrow width of the second coverlay. Characterized in that the pattern layer is formed to be exposed.

On the other hand, the method of manufacturing a flexible circuit board having a bent portion of the present invention, one step of forming a circuit pattern layer on the copper-clad laminate (10);

A second step of cutting the coverlay to provide a 'B' shaped blank portion (BLANK) in consideration of a position corresponding to the bent portion of the copper-clad laminate;

Attaching the coverlay provided with the blank to the upper portion of the circuit pattern layer;

Four steps of printing, applying, and curing the ink to a degree that slightly covers a portion of the side end portion of the coverlay adjacent to the blank portion to form an ink print layer;

A fifth step of cutting the flexible circuit board including the copper foil laminated plate to the coverlay having the four steps to a desired shape;

A sixth step of bending the ink print layer; It is characterized by the above.

Here, the coverlay after being cut at the time of cutting the coverlay in the fifth step is separated from each other as the first coverlay and the second coverlay, the coverlay before the cutting in the second step The second coverlay may be formed to have a narrow width so as to arrange and cut the position of the space portion, thereby providing a space portion and attaching the coverlay with the space portion in the third step.

An ACF circuit pattern layer for connecting to another circuit device is formed at an end of the flexible circuit board in the second coverlay side direction.

The ink used in the fourth step,

15-30% by weight of anhydride, 15-30% by weight of epoxy resin, 15-30% by weight of barium sulfate, 15-30% by weight of silicate compound, phenolic resin (Phenol Resin) 15 wt% or less, Organic Pigment (Organic Pigment) 15 wt% or less, Silicon Polymer (Silicon Polymer) 15 wt% or less.

The flexible circuit board having the bent portion of the present invention configured as described above has two coverlays separated from each other with the bent portion formed therebetween, and the ink print layer is formed between the two coverlays to form the coverlay by the ink print layer. It has the effect of maintaining the bent state while functioning.

The ink print layer may employ a material having a significantly less spring back phenomenon than the conventional coverlay itself and the adhesive layer itself, and an ink print layer having excellent bending retention is formed on the circuit pattern layer between two coverlays. Direct application can eliminate the effects due to the spring back properties of existing coverlays and adhesive layers, with the exception of the relatively small spring back properties of the ink print layer. Therefore, the bent state has excellent bending retention characteristics that are maintained as it is. At the same time, it is of course possible to maintain the insulation protection function as a replacement for the coverlay function.

On the other hand, in the method step of manufacturing the flexible circuit board, the present invention has a process technology for separating the coverlay into two separate stars and a technique for restricting the ink from being applied onto the ACF circuit pattern layer during ink application. do.

The second coverlay serves as a dam that prevents ink from flowing to the ACF circuit pattern layer when the ink is applied to form the ink print layer.

That is, the present invention provides a step groove formed by a step in which the liquid ink liquid applied to form the liquid ink printing layer before curing is present between the second coverlay and the copper clad laminate (CCL). In 3d, the ink liquid does not pass the second coverlay due to the surface tension (interface tension) at the portion indicated by 'B'.

In general interfacial phenomena, liquids that are free to move molecules form spheres to minimize the number of molecules located at the corners, and the combination of surface tension and solid-liquid adhesion forces that move along the edge structure. Will be used. The surface tension (interface tension) is a theory and phenomenon in the natural law defined as a force acting to minimize the area generated at the interface when a substance of different states such as a liquid and a gas or a liquid and a solid are in contact with each other.

In addition, the flexible printed circuit board manufactured as described above has a characteristic that the bending portion is maintained in the bent state by the ink print layer, which is several times better than when using the conventional coverlay. By maintaining the effect of preventing contact failure even after a long time.

Figure 1a is a cross-sectional view illustrating a flexible circuit board having a conventional bent portion,
Figure 1b is a cross-sectional view showing the bent state of Figure 1a,
2 is a plan view showing a flexible circuit board according to an embodiment of the present invention;
3A to 3F are layer cross-sectional views showing the layer structure of the flexible circuit board according to the manufacturing procedure of the present invention;
4 is a plan view of a coverlay illustrating a shape in which a blank portion is formed in advance in the coverlay itself to make two coverlays attached to the flexible circuit board and spaced apart from each other in the method of manufacturing a flexible circuit board of the present invention;

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 3A to FIG. 3F, the circuit pattern layer 24 is provided on the copper-clad laminate 10 formed by laminating the polyimide layer 12 and the copper layer 14, and has an adhesive layer formed thereon. 28 is limited to the flexible circuit board to which the coverlay 30 is attached. The coverlay 30 is a coverlay of the upper surface according to the features of the present invention, reference numeral 42 is a coverlay of the lower surface, the coverlay of the lower surface in the bent portion (A) is not necessary because its attachment If there is a circuit on the bottom surface, it may be partially taken as needed for protection. The present invention is based on the premise that there is no coverlay on the lower surface of the bent portion and will not be referred to in the claims for the coverlay of the unnecessary lower surface.

Referring to FIGS. 2 and 3A to 3F, the coverlay 30 and the adhesive layer may be exposed so that the circuit pattern layer 24 is exposed to the bent portion A that requires bending of the flexible circuit board 1. The first coverlay 32 and the second coverlay 34 are separated from each other by having a blank (C) without (28). 3A to 3C, the blank portion corresponds to a portion without a coverlay and an adhesive layer between the first coverlay and the second coverlay, and is indicated by a reference numeral 'C' in FIG. 4.

In addition to the above-described structure, the present invention forms an ink print layer 50 which is thermally cured by applying ink to the blank portion C. The ink print layer 50 is shown in FIGS. 2, 3E and 3F. As described above, the first coverlay 32 and the second coverlay 34 positioned on both sides of the blank portion partially cover the upper portion.

If the structure is partially covered in this way, the ink print layer 50 at the time of bending serves to prevent the peeling off the coverlays (32, 34) easily.

In addition, in the present invention, the liquid ink liquid applied to form the liquid ink printing layer 50 before curing is present between the second coverlay 32 and the copper clad laminate 10 (CCL). The ink liquid does not easily cross the second coverlay 34 by the surface tension (interface tension) in the step groove formed due to the step (a portion indicated by reference numeral 'B' in FIG. 3D). The liquid ink flows vertically along the stepped grooves B and does not easily cross the stepped grooves B, so that a partially covering structure can be maintained.

The thickness of the ink print layer may be determined based on the thickness of the coverlay, and the thinner the thickness of the coverlay and the ink print layer will be advantageous to the flexibility of the flexible printed circuit board.

2, 3D, and 4, the width P34 of the second coverlay 34 is narrower than the width P32 of the first coverlay 32, and the flexible circuit board 1 is fixed. The ACF circuit pattern layer 24a for connecting to other circuit devices from the ink print layer 50 to a position beyond the width P34 of the second coverlay 34 is formed to be exposed to the outside. That is, the present invention may be applied to all flexible circuit boards requiring bending as in claim 1 of the present application, or may be applied to the ACF adjacent portions of the flexible circuit board having an ACF as in claim 2.

The flexible circuit board of the present invention having such a structure can be produced by the following process.

3A to 3F, a step of forming a circuit pattern layer 24 on a copper clad laminate 10; A step 2 of cutting the coverlay 30 by providing a blank portion (C, see FIG. 4 of the drawing) having a 'ㅁ' shape to a position corresponding to the bent portion A of the copper-clad laminate 10; Attaching the coverlay 30 provided with the blank portion C to the upper portion of the circuit pattern layer 24 through an adhesive layer 28; Forming an ink print layer (50) by printing, applying and curing ink to partially cover the upper surface of the side end portion of the coverlay (30) adjacent to the blank portion (C); After cutting the flexible circuit board 1 having finished the four steps in a predetermined shape, the first coverlay 32 and the second coverlay (by cutting both sides of the 'ㅁ' shape of the coverlay 30 are removed). A fifth step to separate from each other in 34); And a sixth step of bending the flexible printed circuit board at a portion of the ink print layer 50. It is done by. In FIG. 3A to FIG. 3F, reference numeral 22 denotes a via hole, and reference numeral 26 denotes an etched portion.

Cutting both sides of the 'ㅁ' shape of the fifth step corresponds to cutting a portion of the cutting line of 'D' in FIG. 4, wherein the copper-clad laminate 10 and the ink printing layer 50 are also Cut together, the coverlay 30 is separated into a first coverlay 32 and a second coverlay 34 sandwiching the ink print layer 50 as shown in FIG. 2.

Conventional coverlay (C / L) is usually about 27 ~ 37um thick.

In the case of the ink print layer, it is preferable to form a thickness of 10 to 20 μm, and in forming the thickness, the characteristics of the ink composition and the composition ratio are affected.

In the fourth step, the liquid ink for forming the ink print layer preferably contains the following compositional components.

Table 1 below shows ink compositions and ratios.

[Table 1]

The anhydride (Acid anhydride) is used for promoting the curing and if the amount is a large amount to act to cure at a low temperature, and in the present invention in the cured state is useful in maintaining the spring back properties, that is, bent state .

The epoxy resin is used for adhesiveness and retention of bending state. The epoxy resin has an epoxy group in the molecule. This epoxy group reacts with phenol resin, which is a curing agent, to form a three-dimensional polymer structure that is crosslinked.

The barium sulfate is used to disperse the pigment.

The silicate compound is used to increase the insulation properties of the ink print layer.

The phenol resin (Phenol Resin) is used to heat the ink.

The organic pigment (Organic Pigment) is used as a pigment added to implement the color of the ink printing layer.

The silicon polymer is used for adhesiveness and gas permeability, and is also used for bending property and bending retention of the flexible circuit board in accordance with the present invention due to ductility.

The present invention manufactured by the above method is applied to the flexible circuit board having the bent portion, but is particularly preferably applied to the ACF adjacent portion in the flexible circuit board having the ACF.

To this end, an ACF circuit pattern layer 24a for connecting with other circuit devices in the first step of the manufacturing method is formed at an end of the flexible circuit board 1 in the direction of the second coverlay 34. To the rights of the claims.

In this case, the ACF circuit pattern layer 24a may raise an anisotropic conductive film (ACF) on the upper portion of the circuit pattern, which is performed in a later step of the manufacturing method of the present invention. In general, this may be done immediately after the first step process or immediately after another step.

As described above, the flexible circuit board manufactured by applying all the structures and methods provided by the present invention was tested for the bending state retention performance of the present invention. This is a test of the spring back characteristic of returning to the original state when the flexible circuit board is unfolded in a bent state.

Table 2 below shows the data of the spring back characteristics and the original coverlay when the applicant.

TABLE 2

The samples were tested by comparing the coverlay and ink on the same flexible printed circuit board base (CCL).

It is an experiment to measure the force received in the right direction when the right plate is pushed to the left by rolling the sample in a circular shape as shown in the photograph in Table 2 above. In other words, the force to be unfolded in a bent state is measured in grams (g).

In the sample, the thickness of the ink print layer was about 10 to 20 um and about 27 to 37 um for the coverlay (C / L).

In the experiments of Table 2, when the spring back characteristics of the samples 1 to 5 of the flexible circuit board manufactured by the coverlay and the ink print layer were tested, the spring back characteristics were compared when the ink print layer was used as compared with the conventional coverlay. In the problem to which the present invention aims, it was confirmed that the performance was nearly 4 to 5 times better.

Therefore, when the ink printed layer is formed in the flexible circuit board as in the present invention, the bending state can be easily maintained, and thus it can be seen that it is very useful when applied to a bent portion such as an ACF portion.

1-Flexible Circuit Board 10-Copper Clad Laminate
12-polyimide layer 14-copper layer
24-Circuit Pattern Layer 24a- ACF Circuit Pattern Layer
28-Adhesive Layer 30-Coverlay
32-1st coverlay 34-2nd coverlay
42-Bottom Coverlay 50-Ink Printing Layer
A-Bend B-Stepway
C-blank D-cutting line

Claims (5)

The circuit pattern layer 24 is provided on the copper-clad laminate 10 in which the polyimide layer 12 and the copper layer 14 are laminated, and the flexible circuit having the coverlay 30 attached thereto by the adhesive layer 28 thereon. In the substrate,
The bending portion A which needs to be bent in the flexible circuit board 1 is provided with a blank portion C (blank) without the coverlay 30 and the adhesive layer 28 so that the circuit pattern layer 24 is exposed. The coverlay 32 and the second coverlay 34 are separated, and an ink print layer 50 formed by heat-curing by applying ink to the blank portion is formed, and the ink print layer 50 is formed on both sides of the blank portion. The flexible circuit board having a bent portion, characterized in that the structure is a part covering the upper portion of the first coverlay (32) and the second coverlay (34) located in the.
The width P34 of the second coverlay 34 is narrower than the width P32 of the first coverlay 32. The ink printed layer is formed on the spiritual printed circuit board 1. Flexible structure having a bent portion, characterized in that the ACF circuit pattern layer (24a) for connecting to other circuit devices from the 50 to the position beyond the width (P34) of the second coverlay 34 is exposed Circuit board.
Forming a circuit pattern layer 24 on the copper-clad laminate 10;
2 steps of cutting the coverlay 30 by providing a blank portion C having a 'ㅁ' shape to a position corresponding to the bent portion A of the copper-clad laminate 10;
Attaching the coverlay 30 provided with the blank portion C to the upper portion of the circuit pattern layer 24 through an adhesive layer 28;
Forming an ink print layer (50) by printing, applying and curing ink to partially cover the upper surface of the side end portion of the coverlay (30) adjacent to the blank portion (C);
After cutting the flexible circuit board 1 having completed the four steps, by cutting off both sides of the 'ㅁ' shape of the coverlay 30 to be separated from each other by the first coverlay 32 and the second coverlay 34. A fifth step of causing;
And a sixth step of bending the flexible printed circuit board manufactured through the fifth step at the ink print layer 50. A method of manufacturing a flexible circuit board having a bent portion, characterized in that performed by.
4. The ACF circuit pattern layer 24a of claim 3, wherein an ACF circuit pattern layer 24a is formed at an end portion of the flexible circuit board 1 in the direction of the second coverlay 34 to connect with another circuit device in the first step. A method of manufacturing a flexible circuit board having a bent portion.
The ink according to claim 3, wherein the ink used in the fourth step is
15-30% by weight of anhydride, 15-30% by weight of epoxy resin, 15-30% by weight of barium sulfate, 15-30% by weight of silicate compound, phenolic resin (Phenol Resin) 15 wt% or less, Organic Pigment (Organic Pigment) 15 wt% or less, Silicon Polymer (Silicone Polymer) The manufacturing method of a flexible circuit board comprising a component component of 15 wt% or less.

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