KR20090020203A - Flexible printed circuit board - Google Patents

Abstract

A flexible printed circuit board is provided to prevent the size of impedance of data transmission line path from being smaller even if the conductor thickness thins down and to suppress all kinds of the EMI(Electromagnetic interference) or the crosstalk generated when using the various signal in data transmission line path. The flexible printed circuit board(300) comprises a dielectric layer(302), a data circuit layer(304), the first ground layer(310) and the second ground layer. The data circuit layer is formed on the upper side of the dielectric layer and includes the data transmission path part. The first ground layer is formed in the lower side of the dielectric layer and consists of the beehive shape pattern. The second ground layer is formed on the upper side of the dielectric layer and is separated from the data transmission path part with the predetermined interval. The second ground layer consists of the beehive shape pattern.

Description

Flexible Printed Circuit Board

1A is a top view for explaining a flexible printed circuit board according to the prior art.

1B is a cross-sectional view taken along line AA ′ of a flexible printed circuit board according to the prior art.

1C is a side view of the flexible printed circuit board W side according to the prior art.

Figure 1d is a bottom view showing a ground layer patterned in a square shape in a flexible printed circuit board according to the prior art.

Figure 2 is a bottom view showing a ground layer patterned in a rhombus shape in the flexible printed circuit board according to the prior art.

3A is a top view for explaining the flexible printed circuit board of the first embodiment according to the present invention;

3B is a cross-sectional view taken along line B-B 'of the flexible printed circuit board of the first embodiment according to the present invention;

3C is a side view of the flexible printed circuit board X side in a first embodiment according to the present invention;

3D is a bottom view of a ground layer patterned in a honeycomb pattern in the flexible printed circuit board of the first embodiment according to the present invention;

4A is a top view of a flexible printed circuit board including a honeycomb ground layer in a first embodiment according to the present invention;

4B is a cross-sectional view taken along line C-C 'of the flexible printed circuit board including the honeycomb ground layer in the first embodiment according to the present invention;

Fig. 5A is a top view for explaining the flexible printed circuit board of the second embodiment according to the present invention.

Fig. 5B is a sectional view taken along line D-D 'of the flexible printed circuit board of the second embodiment according to the present invention;

Fig. 5C is a side view of the flexible printed circuit board Y side in the second embodiment according to the present invention.

6 is a graph illustrating characteristic impedance of a data transmission line according to a change in position of the data transmission line in a flexible printed circuit board.

FIG. 7A is a graph illustrating a coupling phenomenon (near-end cross-talk) occurring in another data transmission line of a signal input terminal in a data transmission line unit. FIG.

7B is a graph illustrating a coupling phenomenon (far-end cross-talk) occurring in another data transmission line of a signal output terminal in the data transmission line unit.

FIG. 8A is a graph showing an eye pattern when using a differential mode signal of a flexible printed circuit board of a ground layer formed in a square pattern in the prior art. FIG.

8B is a graph showing an eye pattern when using a differential mode signal of a flexible printed circuit board of a ground layer formed in a honeycomb pattern in the present invention.

*** Explanation of symbols for the main parts of the drawing ***

300: flexible printed circuit board 302: dielectric layer

304: data transmission line portion 306: hexagonal first opening

308: honeycomb pattern 310: first ground layer

The present invention relates to a flexible printed circuit board (FPCB).

Digital devices such as mobile communication devices, LCDs (Liquid Crystal Displays), and camcorders require the bending of circuit boards due to the narrow mounting space of components due to the characteristics of devices becoming thinner, and function as a substrate even in the part requiring folding. As a necessity of a product capable of fulfilling the need arises, a flexible printed circuit board (FPCB) using a flexible polymer film such as polyimide or polyester is used.

Such flexible printed circuit boards do not increase in thickness even when stacked in a plurality of layers, and thus are widely used for the purpose of forming a multilayer circuit board by stacking a plurality of substrates.

In addition, the dielectric thickness of the flexible printed circuit board is manufactured to 25㎛, and is currently manufactured to 12.5㎛ or less in the manufacturing process, the dielectric thickness of the flexible printed circuit board is getting thinner as the wireless communication system becomes smaller and lighter.

1A is a top view illustrating a flexible printed circuit board according to the prior art, FIG. 1B is a cross-sectional view taken along line AA ′ of the flexible printed circuit board according to the prior art, and FIG. 1C is a side view of the flexible printed circuit board W according to the prior art. 1D is a bottom view of a ground layer patterned in a square shape in a flexible printed circuit board according to the prior art.

As shown in FIGS. 1A to 1D, the flexible printed circuit board 100 includes an insulating polymer film 102, a data transmission line part 104 formed on an upper surface of the insulating polymer film 102, and The ground layer 110 is formed on the lower surface of the insulating polymer film 102.

The data transmission line part 104 is formed by applying a copper film to the upper surface of the insulating polymer film 102 and then patterning the copper foil film, and the ground layer 110 is formed on the lower surface of the insulating polymer film 102. After the copper foil film is applied, a plurality of square openings 106 are formed on the copper foil film to form a square pattern 108 patterned in a square shape.

In addition, as shown in FIG. 2, the ground layer 110 may be formed of a rhombus-shaped pattern 114 patterned into a rhombus by forming a plurality of rhombus-shaped openings 112 in the copper foil film.

2 is a bottom view showing a ground layer patterned in a rhombus shape in a flexible printed circuit board according to the related art.

In addition, the flexibility of the data transmission line 104 in the flexible printed circuit board 100 (which may be bent and twisted without physical damage) is an important factor related to the reliability of the flexible printed circuit board 100.

However, in the flexible printed circuit board 100 according to the related art, the data transmission line part 104 or the ground layer 110 uses a large number of conductors such as copper, and the copper conductors are used in the flexible printed circuit board 100. It is one of the inhibitors.

In addition, as the thickness of the conductor becomes thinner, the characteristic impedance of the data transmission line unit 104 becomes very small due to the increase in the capacitors of the data transmission line unit 104 and the ground layer 110, and is generally used in communication. 50 Ω or more impedance matching becomes impossible.

In addition, when the ground layer 110 is patterned in a square or rhombus shape as described above, the position change of the data transmission line portion 102, for example, (a) (see (Fig. 1a) described above) up or down. Due to the large impedance change of the data transmission line unit 104 due to the change in position, electromagnetic interference (EMI) problem occurs when various signals are used for the data transmission line unit 104.

In addition, when the data transmission line unit 104 is used as one or more combined data transmission lines, crosstalk of each data transmission line is large, and when the differential mode signal is used, the eye pattern area is small. Signal processing may cause system malfunction.

An object of the present invention is to improve the problem that the impedance size of a data transmission line decreases as the conductor thickness of a flexible printed circuit board (FPCB) becomes thinner.

In addition, an object of the present invention is to suppress a crosstalk phenomenon or various electromagnetic interference (EMI) generated when various signals are used in a data transmission line.

The present invention includes a dielectric layer, a data circuit layer including a data transmission line portion formed on an upper surface of the dielectric layer, and a first ground layer formed on a lower surface of the dielectric layer and patterned in a honeycomb shape.

The semiconductor device may further include a second ground layer formed on the upper surface of the dielectric layer and spaced apart from the data transmission line by a predetermined interval and patterned in a honeycomb shape.

In the present invention, the data transmission line portion or the ground layer is formed of a copper conductor.

In the present invention, the data transmission line unit includes at least one data transmission line.

In the present invention, the dielectric layer is formed of a flexible polymer film.

In the present invention, the flexible polymer film is formed of polyimide or polyester.

The present invention also provides a data circuit layer including a dielectric layer, a data transmission line portion formed on an upper surface of the dielectric layer, and a ground layer formed on an upper surface of the dielectric layer and spaced apart from the data circuit layer by a predetermined distance and patterned in a honeycomb shape. Include.

In the present invention, the data transmission line portion or the ground layer is formed of a copper conductor.

In the present invention, the data transmission line unit includes at least one data transmission line.

In the present invention, the dielectric layer is formed of a flexible polymer film.

In the present invention, the flexible polymer film is formed of polyimide or polyester.

Hereinafter, a flexible printed circuit board according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3A is a top view illustrating the flexible printed circuit board of the first embodiment according to the present invention, FIG. 3B is a cross-sectional view taken along line BB ′ of the flexible printed circuit board of the first embodiment according to the present invention, and FIG. FIG. 3D is a bottom view of a ground layer patterned in a honeycomb shape in the flexible printed circuit board of the first embodiment according to the present invention.

As shown in FIGS. 3A to 3D, the flexible printed circuit board 300 may include a dielectric layer 302, a data transmission line portion 304 formed on an upper surface of the dielectric layer 302, and a lower surface of the dielectric layer 302. One ground layer 310 is included.

Here, the dielectric layer 302 may be formed of polyimide or polyester of a flexible polymer film.

First, after coating a copper conductor on the lower surface of the dielectric layer 302, a first opening 306 having a hexagon shape is formed on the copper conductor to form a honeycomb pattern 308 patterned in a honeycomb shape. The ground layer 310 is formed.

Next, after the copper conductor is coated on the top surface of the dielectric layer 302, the copper conductor is patterned to form the data transmission line part 304 to complete the flexible printed circuit board 300.

In addition, as illustrated in FIGS. 4A and 4B, the flexible printed circuit board 300 is formed on the upper surface of the dielectric layer 302 and has a honeycomb-shaped second spaced apart from the data transmission line unit 304 at predetermined intervals. The ground layer 316 may be further included.

Here, the second ground layer 316 may be formed as a honeycomb pattern 314 patterned in a honeycomb form by forming a plurality of hexagonal second openings 312 on the copper conductor.

The second ground layer 316 may be formed at the same time as the data transmission line unit 34 so as to be spaced apart from the data transmission line unit 304 by a predetermined distance from both sides.

In addition, the data transmission line unit 304 may include at least one data transmission line.

4A is a top view of a flexible printed circuit board including a honeycomb ground layer in the first embodiment according to the present invention, and FIG. 4B includes a honeycomb ground layer in the first embodiment according to the present invention. CC 'is sectional drawing of a flexible printed circuit board.

5A is a top view illustrating the flexible printed circuit board of the second embodiment according to the present invention, and FIG. 5B is a DD ′ cross-sectional view of the flexible printed circuit board of the second embodiment according to the present invention, and FIG. In the second embodiment according to the present invention, there is shown a side view of the flexible printed circuit board Y side.

As shown in FIGS. 5A to 5C, the flexible printed circuit board 500 is formed on the upper surface of the dielectric layer 502 and the dielectric layer 502 and the upper surface of the data transmission line portion 503 and the dielectric layer 502. A ground layer 508 spaced apart from the furnace part 510 by a predetermined interval and patterned in a honeycomb shape is included.

Here, the dielectric layer 502 may be formed of polyimide or polyester of a flexible polymer film.

In the flexible printed circuit board 500, after applying a copper conductor to the upper surface of the dielectric layer 502, the copper conductor is patterned to form a data transmission line portion 503, and a hexagonal opening 504 is formed on the copper conductor. The ground layer 508 is formed by forming a honeycomb pattern 506 patterned to form a honeycomb.

Here, the ground layer 508 is formed on the upper surface of the dielectric layer 502, and is spaced apart from the data transmission line portion 503 by a predetermined distance on both sides.

6 is a graph illustrating characteristic impedance of a data transmission line according to a change in position of the data transmission line of a flexible printed circuit board.

As shown in FIG. 6, the impedance of the data transmission line in the flexible printed circuit board 100 using the ground layer 110 formed in the square or rhombus-shaped pattern 114 in the related art is represented by (a). It can be seen that there is a change in the characteristic impedance of the data transmission line as it changes from (see FIG. 1A) to an upper or lower position (for example, 100 to 300).

However, in the present invention, the flexible printed circuit board 300 using the ground layers 310, 316, 508 (see (FIG. 3B), (FIG. 4B), (FIG. 5B)) formed in a honeycomb pattern. The characteristic impedance of the data transmission line at 500 is the position above or below the data transmission line at (b), (c), (d) (see (Fig. 3a), (Fig. 4a), (Fig. 5a) above). It can be seen that there is no change in characteristic impedance of the data transmission line due to the change from (100 to 300).

That is, the ground layers 310, 316, 508 ((FIG. 3B), (FIG. 4B), (FIG. 5B) to have characteristic impedance of the data transmission line in the flexible printed circuit board 300, 500 of the present invention. By designing a honeycomb pattern, there is almost no change in characteristic impedance of the data transmission line due to the change of the position of the data transmission line, and it is possible to effectively cope with the EMI problem caused by the change of the position of the data transmission line.

In addition, the characteristic impedance of the data transmission line may implement characteristic impedances of various data transmission lines by adjusting the length of one side in the hexagonal honeycomb shape.

7A is a graph illustrating a near-end cross-talk occurring in another data transmission line of a pulse signal input terminal in a data transmission line part, and FIG. 7B is a pulse signal in the data transmission line part. This graph shows the coupling phenomenon (Far-end Cross-talk) in other data transmission line of output terminal.

As shown in FIGS. 7A and 7B, in the prior art, the flexible printed circuit board of the present invention is formed by forming the ground layer 110 of the flexible printed circuit board 100 in a pattern of a square shape (A) (C). By forming the ground layers 310, 316, and 508 of the 300 and 500 in a honeycomb (B) and (D) pattern, the crosstalk phenomenon at the pulse signal input or output terminal of the data transmission line is conventional flexible printing. It can be seen that in the flexible printed circuit board 300, 500 of the present invention is significantly reduced than in the circuit board 100.

8A is a graph illustrating an eye pattern when using a differential mode signal of a flexible printed circuit board of a ground layer formed in a square pattern in the prior art, and FIG. 8B is a ground layer formed in a honeycomb pattern in the present invention. This is a graph showing the eye pattern when using differential mode signal of flexible printed circuit board.

As shown in FIGS. 8A and 8B, the flexible printed circuit board 300 and 500 according to the present invention are formed in the prior art, rather than the ground layer 110 of the flexible printed circuit board 100 having a square pattern. By forming the ground layers 310, 316, and 508 in a honeycomb pattern, the (g) of the eye pattern in the present invention, rather than the (f) spacing of the eye pattern in the related art. It can be seen that the spacing becomes smaller and the eye pattern area G of the present invention is wider than the conventional eye pattern area F. FIG.

Here, the eye-pattern area is an area of a hexagonal shape when an arbitrary digital signal, for example, a digital signal such as 0110110101010111001101 .. is applied to an input terminal of a data transmission line and the graphs appearing at the output terminal of the data transmission line overlap each other. This is called the eye-pattern area.

8A and 8B, eye0 on the y-axis represents a voltage level, and the unit is [V], and represents the voltage level of the digital signal output from the output terminal of the data transmission line.

That is, by having the eye pattern area G of the present invention larger than the eye pattern area F of the prior art, it is possible to prevent malfunction of the system during signal processing in the system.

In addition, the present invention forms the copper conductors of the ground layers 310, 316, and 508 in a honeycomb pattern to reduce the area of the copper conductors, thereby improving the ductility of the flexible printed circuit boards 300 and 500. Can be.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited to the above-described embodiments, and those skilled in the art to which the present invention pertains can make various modifications and Modifications are possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

According to the present invention, the ground layer of the flexible printed circuit board is formed in a honeycomb pattern, thereby improving the problem that the impedance of the data transmission line becomes smaller as the thickness of the copper conductor of the flexible printed circuit board becomes thinner. There is.

In addition, the present invention has the effect of reducing the cross-talk phenomenon of the flexible printed circuit board.

In addition, the present invention has an effect that can suppress various electromagnetic interference (EMI) problem caused by the change in the position of the data transmission line of the flexible printed circuit board.

In addition, the present invention can improve the ductility of the flexible printed circuit board by forming the dielectric of the ground layer in a honeycomb pattern to reduce the area of the copper conductor.

Claims (11)

A dielectric layer, A data circuit layer including a data transmission line part formed on an upper surface of the dielectric layer; And a first ground layer formed on a bottom surface of the dielectric layer and patterned in a honeycomb shape. The method of claim 1, And a second ground layer formed on the upper surface of the dielectric layer and spaced apart from the data transmission line by a predetermined interval and patterned in a honeycomb shape. The method according to claim 1 or 2, And the data transmission line portion or the ground layer is formed of a copper conductor. The method of claim 1 The data transmission line unit flexible printed circuit board including at least one data transmission line. The method of claim 1, The dielectric layer is a flexible printed circuit board formed of a flexible polymer film. The method of claim 1,  The flexible polymer film is a flexible printed circuit board formed of polyimide (polyimide) or polyester. A dielectric layer, And a data circuit layer including a data transmission line part formed on an upper surface of the dielectric layer and a ground layer formed on an upper surface of the dielectric layer and spaced apart from the data circuit layer by a predetermined distance and patterned in a honeycomb shape. The method of claim 7, wherein  And the data transmission line portion or ground layer is formed of a copper conductor. The method of claim 7, wherein The data transmission line unit flexible printed circuit board including at least one data transmission line. The method of claim 7, wherein The dielectric layer is a flexible printed circuit board formed of a flexible polymer film. The method of claim 7, wherein  The flexible polymer film is a flexible printed circuit board formed of polyimide (polyimide) or polyester.

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