JP2003142786A - Flexible printed circuit board - Google Patents

Abstract

(57) [Problem] To provide a flexible printed wiring board which can make mounting of a capacitor for noise component bypass unnecessary. SOLUTION: This is a wiring board 1 having at least a power supply line 3 and a ground line 4 formed on a surface of a flexible base material 2. The power supply line 3 and the ground line 4 are mutually attached at a mounting portion A of an IC 7. Along with being laminated,
Ferroelectric layer 8 between power supply line 3 and ground line 4
Is formed. According to this configuration, it is possible to reduce a noise component emitted from the electronic component to the power supply line or the like without mounting the discrete type capacitor on the wiring board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed wiring board in which at least a power line and a ground line are formed on the surface of a flexible base material.

[0002]

2. Description of the Related Art This type of flexible printed wiring board (hereinafter also referred to as "wiring board") is becoming smaller with the miniaturization of home appliances, information equipment such as personal computers, and office automation equipment.
Widely used in recent years. This wiring board 51 is shown in FIG.
As shown in FIG. 7, a power source line 3 and a ground line 4 (collectively referred to as a “power feeding line”) are formed on the surface of a base material 2 formed of a flexible resin material such as polyester. Are formed together with a plurality of signal lines 5. The surfaces of the base material 2, the power supply line 3, the ground line 4, and the signal line 5 are covered with a cover layer 6 except for the lands for mounting electronic components provided on the lines 3, 4, and 5. Also, the wiring board 5
An IC 7 that operates by receiving power from the power supply line 3 and the ground line 4 is mounted on the circuit 1, and a bypass capacitor 52 is mounted on the circuit 1. In this case, the capacitor 52 is connected to the power supply line 3 in the portion B near the electronic component (for example, IC7) mounted in the mounting portion A.
Is connected and arranged between the IC and the ground line 4, and the IC7
By bypassing the generated noise component, the propagation of the noise component to other electronic components is reduced.

[0003]

However, the wiring board 51 has the following problems. That is, in this wiring board 51, in order to prevent the propagation of the noise component to other electronic components, each electronic component that is the source of the noise component is
A bypass capacitor 52 is arranged in the vicinity thereof. Therefore, the wiring board 51 has a problem that the mounting space for the other electronic components is reduced by the mounting space of the capacitor 52, which makes it difficult to achieve high-density mounting. In addition, when the number of capacitors for bypassing the noise component is increased, the space between the electronic components is reduced, so that the wiring board 5 does not interfere with each other.
As a result of the decrease in the amount of bending that can bend 1 there is also a problem that the advantageous characteristics inherent in the wiring board 51, such as flexibility, can not be effectively used.

The present invention has been made in view of the above problems, and a main object of the present invention is to provide a flexible printed wiring board which makes it unnecessary to mount a capacitor for bypassing a noise component.

[0005]

In order to achieve the above object, the flexible printed wiring board according to claim 1 is a flexible printed wiring board in which at least a power supply line and a ground line are formed on the surface of a flexible base material. The power supply line and the ground line are stacked on each other at a mounting site of an electronic component, and a ferroelectric layer is formed between the power supply line and the ground line.

A flexible printed wiring board according to a second aspect is the flexible printed wiring board according to the first aspect, wherein the power supply line and the ground line in the mounting portion of the electronic component are equivalent to the outer shape of the electronic component. Each is formed in a shape.

According to a third aspect of the present invention, there is provided a flexible printed wiring board according to the first or second aspect, wherein the flexible printed wiring board has an input side portion to the flexible printed wiring board in at least one of the power supply line and the ground line. A magnetic layer is formed between the electronic component mounting portion and the at least one line. In this case, a magnetic material layer is formed adjacent to both the power source line and the ground line between each input side portion to the flexible printed wiring board and the electronic component mounting portion. preferable.

A flexible printed wiring board according to a fourth aspect of the present invention is the flexible printed wiring board according to the third aspect, wherein the magnetic layer is formed so as to sandwich the at least one line.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the flexible printed wiring board according to the present invention will be described below with reference to the accompanying drawings.

First, the structure of a flexible printed wiring board (hereinafter also referred to as a wiring board) 1 will be described with reference to FIG. The same components as those of the conventional wiring board 51 are designated by the same reference numerals, and duplicate description will be omitted.

As shown in FIGS. 1 and 2, the wiring board 1 has a power source line 3 and a ground line 4 formed together with a plurality of signal lines 5 on a surface of a flexible substrate 2. It is configured. The surfaces of the base material 2, the power supply line 3, the ground line 4, and the signal line 5 are
It is covered with a cover layer 6 except for the lands described below provided in each of the lines 3, 4, and 5. In this case, each of the lines 3, 4, and 5 is formed of a conductive metal material such as copper or aluminum (metal foil formed by pressing using a mold or vapor deposition), and as an example, an adhesive (not shown). No. 2) is attached and integrated with the base material 2.

At the mounting portion A of this wiring board 1, a power source P
An electronic component (for example, IC 7) that can be a source of a noise component in an operating state in which power is supplied from S is mounted. Further, in the mounting portion A, the power supply line 3, the ground line 4, and the signal line 5 are laminated on each other via an insulating layer. In this case, the power supply line 3 and the ground line 4 are partly formed in a planar shape having the same shape as the IC7 at the mounting portion A of the IC7, and are also formed in the planar shape having the same shape as the IC7. Layer 8
As an example, the power supply line 3 and the ground line 4 are laminated in this order from the side of the base material 2 via (also having electrical insulation). Here, the ferroelectric layer 8 is formed of a ferroelectric material or a high dielectric constant material such as barium titanate, titanium oxide, high dielectric constant glass, polyimide, and ferroelectric constant resin. In this configuration, the power supply line 3, the ferroelectric layer 8 and the ground line 4 which are formed in the same plane shape and are laminated on each other are equivalently equivalent to a capacitor using the power supply line 3 and the ground line 4 as electrodes. 9 is formed, and this capacitor 9 is
It is locally formed inside the wiring substrate 1 located immediately below.

In this wiring board 1, the capacitor 9
The insulating layer 10 is laminated on the ground line 4 constituting the. Further, on the insulating layer 10, a land 5a to which the signal lines 5, 5 ... Are connected and each signal terminal 7a of the IC 7 is connected, and a power supply land 11 to which a power supply terminal 7b of the IC 7 is connected. , And the ground terminal 7 of IC7
A power feeding land 12 (see FIG. 1) to which c (see FIG. 3) is connected is formed. In this case, each power feeding land 1
Reference numerals 1 and 12 are respectively connected to the power line 3 and the ground line 4 formed in a planar shape via via holes 13. With this configuration, as shown in FIG. 3, each end of the capacitor 9 is connected to the power supply terminal 7b and the ground terminal 7c of the IC 7, respectively.

As described above, in this wiring board 1, the power supply line 3, the ferroelectric layer 8 and the ground line 4 each formed in a planar shape are provided immediately below the mounting portion A of the IC 7 which can be a source of noise components. By stacking, the capacitor 9 is locally formed, and this capacitor 9 is I
It is directly connected between the power supply terminal 7b of C7 and the ground terminal. Therefore, according to this wiring board 1,
Unlike the conventional wiring board 51, the IC 7 can be mounted without mounting a discrete type capacitor on the wiring board 1.
It is possible to reduce the noise component emitted from the power supply line to the ground line 4 by bypassing it. Further, since it is not necessary to mount a discrete type noise component bypass capacitor on the wiring board 1, the mounting space can be efficiently used as a space for mounting electronic components. Further, since a sufficient space can be secured between the electronic components, it is possible to secure a sufficient amount of bending that allows the wiring board 1 to be bent without causing the mounted electronic components to interfere with each other. As a result, it is possible to effectively use the advantageous characteristics inherent in the wiring board 1, such as flexibility.

Further, in this wiring board 1, the capacitor 9
Power supply line 3 formed in a planar shape that functions as each electrode of
And between the power supply terminal 7b of the IC 7 and the ground line 4
And the ground terminals 7c of the IC 7 are directly connected by the via holes 13 without using wiring lines. For this reason, the loop length (wiring line) of the current loop C (see element 3) through which the noise component passes can be made extremely short, and as a result, the noise component removal performance of the capacitor 9 due to the inductance of the wiring line can be reduced. Can be effectively prevented.

Further, in this wiring board 1, the power supply line 3 and the ground line 4 are provided in the mounting portion A of the IC 7.
Are locally formed in a planar shape, and the parts other than the mounting part A are formed in a linear shape similarly to the wiring board 51. Therefore, with respect to the noise component generated inside the IC 7, the impedance at the portion between the power supply line 3 and the ground line 4 (the portion where the capacitor 9 is formed) immediately below the mounting portion A is low, and Impedance is formed to be high in the parts other than the mounting part A in the line 3 and the ground line 4. That is,
Wiring board 1 for solid power supply line and solid ground pattern
It is possible to locally form a portion with high impedance and a portion with low impedance with respect to the power supply line 3 and the ground line 4 as compared with the configuration formed in FIG. Therefore, the generated noise component is mainly bypassed to the power supply line 3 or the ground line 4 via the low-impedance capacitor 9. As a result, the power line 3
It is possible to sufficiently reduce the noise component that propagates to other mounted components via the or ground line 4.

Further, since the capacitor 9 is formed immediately below the electronic component such as the IC 7, the power source line 3 and the ground line 4 functioning as the respective electrodes of the capacitor 9 can be provided without reducing the mounting space for other electronic components. It is possible to expand the area of the portion formed in a planar shape to the same size as the planar shape of the IC 7. Therefore, the capacitance of the capacitor 9 can be increased.
Therefore, as compared with the conventional wiring board 51 on which the discrete type capacitor for bypassing the noise component is mounted, even when the number of mounted parts is large, the capacitor 9
As a result, a relatively large capacity can be secured,
The noise component can be reliably removed.

The present invention is not limited to the configurations shown in the above embodiments, and can be modified as appropriate.
For example, as in the wiring board 21 shown in FIGS. 1 and 4, between the input terminal T2 (input side portion) of the wiring board 1 and the mounting portion A of the IC 7 in the ground line 4, the magnetic line is adjacent to the ground line 4. A configuration of forming the body layer 22 can also be adopted. In both figures, the same components as those of the wiring board 1 are designated by the same reference numerals, and the duplicated description will be omitted.

In this wiring board 21, the magnetic layer 22 is
It is formed by attaching the magnetic body to the base material 2 by a technique such as coating or pasting. Therefore, in this wiring board 21, the loss in the high frequency region in the vicinity of the magnetic layer 22 increases with respect to the current flowing through the ground line 4. Therefore, the magnetic layer 22 causes the ground line 4 to act as an inductance with respect to the noise component that is superimposed on the current flowing through the ground line 4. As a result, as shown in FIG.
Has a circuit configuration in which the inductor L is equivalently provided. Therefore, the impedance of the current loop D reaching the IC 7 via the ground line 4, the power supply PS, and the power supply line 3 can be increased, so that the leakage of the noise component generated in the IC 7 to the current loop D can be sufficiently reduced. As a result, power line 3 and ground line 4
It is possible to further reduce the amount of propagation of the noise component that propagates to other mounted components via the. It should be noted that the power supply line 3 can be made to act as an inductance with the same configuration.

In the wiring board 21, the magnetic layer 22 is formed only on one side (the lower side in FIG. 4) of the ground line 4, but both sides (the upper side and the lower side in the figure) of the ground line 4 are adopted. It is also possible to adopt a configuration in which the magnetic layer 22 is formed on the side) and the ground line 4 is sandwiched between the magnetic layers 22 and 22. With this configuration, it is possible to further increase the inductance of the inductor L and enhance the effect of removing the noise component. Further, instead of the ground line 4, a configuration is adopted in which the magnetic layer 22 is formed adjacent to a portion of the power supply line 3 between the input terminal (input side portion) T1 of the wiring board 1 and the mounting portion A of the IC 7. Even if it is, the same effect can be obtained. In addition, the magnetic layer 22 is provided adjacent to both the power supply line 3 and the ground line 4.
It is also possible to adopt a configuration for forming Further, the magnetic layer 2 is disposed adjacent to the ground line 4 (or the power supply line 3) in the substrate surface direction (horizontal direction) of the substrate 2.
It is also possible to adopt a configuration that forms 2.

[0021]

As described above, according to the flexible printed wiring board of the first aspect, the power supply line and the ground line are laminated at the mounting site of the electronic component, and the power supply line and the ground line are strongly interposed between the power supply line and the ground line. By forming the dielectric layer, it is possible to locally form a capacitor for bypassing the noise component directly under the electronic component,
Unlike the conventional wiring board 51, it is possible to bypass and reduce a noise component emitted from an electronic component to a power supply line or the like without mounting a discrete type capacitor on the wiring board. Further, since it is not necessary to mount a discrete type noise component bypass capacitor on the wiring board 1, the mounting space can be efficiently used as a space for mounting electronic components. Further, since a sufficient space can be secured between the electronic components, it is possible to secure a sufficient amount of bending of the wiring board without causing the mounted electronic components to interfere with each other. As a result, it is possible to effectively use the advantageous properties inherent in the wiring board, such as flexibility. Further, since the capacitor for bypassing the noise component is formed immediately below the electronic component, this capacitor can be connected to the power supply terminal and the ground terminal of the electronic component in the shortest distance. Therefore, since the loop length of the current loop for bypassing the noise component can be formed extremely short, it is possible to effectively prevent the deterioration of the noise component removal performance due to the inductance of the wiring line in the current loop. As a result, high frequency noise components can be effectively removed.

According to another aspect of the flexible printed wiring board of the present invention, the power supply line and the ground line in the mounting portion of the electronic component are formed in the same shape as the outer shape of the electronic component, so The capacitance of the noise component bypass capacitor can be made larger without reducing the mounting space. Therefore, the conventional wiring board 5 mounting the discrete type capacitor for bypassing the noise component
Compared to 1, even when the number of mounted components is large, a relatively large capacity can be secured as a capacitor for bypassing noise components, and as a result, noise components can be reliably removed.

According to the flexible printed wiring board of the third aspect, at least one of the power source line and the ground line is provided between the input side portion of the flexible printed wiring board and the electronic component mounting portion. By forming the magnetic layer adjacent to the line, the magnetic layer causes at least one line to act as an inductance, and as a result, it is possible to equivalently configure a circuit in which an inductor is interposed in the line,
It is possible to further reduce the propagation amount of the noise component that propagates to other mounted components via the line.

Further, according to the flexible printed wiring board of the fourth aspect, since the magnetic layer is formed so as to sandwich at least one line, the inductance of the inductor equivalently interposed in the line is further increased. Since it can be formed, the effect of removing noise components can be further improved.

[Brief description of drawings]

FIG. 1 is a plan view for explaining the configuration of a flexible printed wiring board 1 according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a cross-sectional structure of a wiring board 1 in the vicinity of a mounting portion A of an IC 7.

FIG. 3 is a circuit diagram showing an equivalent circuit of a power supply line on the wiring board 1.

FIG. 4 is a wiring board 21 near the mounting portion A of the IC 7.
FIG. 3 is a schematic diagram for explaining the cross-sectional structure of FIG.

5 is a circuit diagram showing an equivalent circuit of a power supply line on the wiring board 21. FIG.

FIG. 6 is a plan view for explaining the configuration of a conventional wiring board 51.

FIG. 7 is a wiring board 51 near the mounting portion A of the IC 7.
FIG. 3 is a schematic diagram for explaining the cross-sectional structure of FIG.

[Explanation of symbols]

1,21 wiring board 2 base materials 3 power lines 4 ground lines 5 signal lines 6 cover layers 7 IC 8 Ferroelectric layer 9 capacitors 10 Insulation layer 22 Magnetic layer A mounting area T1, T2 input terminals

Claims (4)

[Claims] 1. A flexible printed wiring board in which at least a power supply line and a ground line are formed on a surface of a flexible substrate, wherein the power supply line and the ground line are laminated at a mounting site of an electronic component. A flexible printed wiring board having a ferroelectric layer formed between the power supply line and the ground line. 2. The flexible printed wiring board according to claim 1, wherein the power supply line and the ground line in the mounting portion of the electronic component are formed in the same shape as the outer shape of the electronic component. 3. A magnetic layer between at least one of the power supply line and the ground line between an input side portion to the flexible printed wiring board and a mounting portion of the electronic component adjacent to the at least one line. The flexible printed wiring board according to claim 1, wherein the flexible printed wiring board is formed. 4. The flexible printed wiring board according to claim 3, wherein the magnetic layer is formed so as to sandwich the at least one line.