JP2002100846A - Printed wiring board and optical disc device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board and an optical disc device which easily suppress a noise caused by contact with flexible wiring members. SOLUTION: A flexible wiring member 12 contacts the surface of a printed wiring board 11, an insulation film 15 is applied to regions of the board 11 surface other than wiring patterns, such as through-holes 16, wirings 17, etc., and an air layer 18 is formed between the wiring patterns 16, 17 and the wiring member 12, thereby reducing the capacitance between a conductive layer 12B of the wiring member 12 and the wiring patterns 16, 17 and increasing the impedance between them. This suppresses crosstalks, i.e., noise signal generation between the conductor layer 12B and the wiring patterns 16, 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FFC (Flexible
Flat Cable) / Flexible Printed Circuitboard (FPC)
The present invention relates to a printed wiring board and an optical disk device that can suppress noise generated by contact between a flexible wiring member such as a flexible wiring member and a wiring pattern on the printed wiring board.

[0002]

2. Description of the Related Art In an optical disk apparatus, an optical head (optical pickup) for performing at least one of recording and reproduction with respect to an optical disk includes a flexible wiring member (FFC).
Alternatively, it is electrically connected to the wiring pattern of the printed wiring board via the FPC.

For example, as shown in FIG. 5, a flexible wiring member 2 is formed by forming a conductor layer on an insulating film.
One end is connected to the surface of the printed wiring board 1 on which the wiring pattern is to be formed via the connector 3, and is configured to be able to reciprocate along the radial direction (tracking direction) of the optical disk indicated by the arrow in the figure. It constitutes a part of a transmission path of an input / output signal such as a read signal (reproduction signal) from the optical head 4 to the printed wiring board 1 or a write signal (recording signal) from the printed wiring board 1 to the optical head 4. Then, by the movement of the optical head 4, as shown in FIG.
It may come in contact with the wiring pattern on the substrate surface.

[0004]

As shown in FIG. 6, for a flexible wiring member 2, a conductor layer 2B is formed on a polyester-based or polyimide-based insulating film 2A. It is composed by covering with. Therefore, when the insulating film 2A and the wiring pattern (through-holes are shown in the drawing) 6 on the substrate surface are in contact with each other, a capacitor is formed between the conductor layer 2B and the through-hole 6. For this reason, a digital electric signal appears as noise via the capacitance of the capacitor, which may deteriorate the jitter and error rate of the optical disc device.

As is well known, a capacitor passes an alternating current,
As the frequency becomes higher and the capacitance becomes larger, the impedance becomes smaller. Therefore, under the clock frequency of the digital signal, the impedance (resistance value) of the capacitor between the wiring pattern on the substrate 1 and the flexible wiring member 2 becomes smaller. )
Can be considered connected. Since a digital signal is a signal whose voltage rapidly changes between 0 and 5 V, for example, when this digital signal is connected via the above-mentioned capacitance, crosstalk due to a jump of a pulse-like noise waveform, that is, deterioration of signal quality, occurs. It becomes a problem.

In order to prevent this, some shield plate is additionally arranged between the wiring pattern on the substrate surface and the flexible wiring member 2, or the wiring pattern and the flexible wiring member 2 are prevented from contacting each other. Although various methods such as adoption of a mechanical structure are conceivable, all of these methods complicate the equipment.

An object of the present invention is to provide a printed wiring board and an optical disk device which can easily suppress noise generation due to contact with a flexible wiring member.

[0008]

The above-mentioned noise signal is easily generated due to the static electricity between the conductor layer of the flexible wiring member and the wiring pattern on the printed wiring board in contact with the insulating film. It is related to the size of the capacity. That is, the capacitance C can be represented by the following equation in a pseudo manner. C = 8.855 × 10 ⁻¹² × εS / D Here, ε represents the relative permittivity of the dielectric (here, the insulating film), S represents the surface area of the dielectric, and D represents the thickness of the dielectric. ε
Has a specific value depending on the material, and is usually about 4 to 5 for a polyester insulating material used for FPC, and about 3.5 for a low dielectric constant polyimide insulating material. Further, the ease with which the noise signal is generated is related to the magnitude of the impedance between the conductor layer of the flexible wiring member and the wiring pattern on the printed wiring board with which the insulating film contacts. That is, the impedance between them, 1 / ωC (Ω), is
Since the lower the capacitance C and the higher the signal frequency, the lower the capacitance, the more likely noise is generated. That is, as the impedance increases, the generation of noise is suppressed.

In view of the above, the present invention is directed to an area on a printed wiring board with which an insulating film of a flexible wiring member comes in contact, and an air layer is provided between the wiring pattern in the area and the flexible wiring member. Characterized in that an air layer forming means for forming is provided.

That is, by interposing an air (ε = 1) layer having a small relative dielectric constant between the insulating film of the flexible wiring member and the wiring pattern on the printed wiring board, the capacitance C By decreasing ε and increasing D to increase the impedance between the two, the generation of noise signals due to the contact between the insulating film and the wiring pattern is reduced.

The air layer forming means prints an insulating film applied to a region between the wiring patterns on the printed wiring board, for example, a part number or a symbol indicating the type of the board on the board by a method such as a silk screen. It can be formed at the same time as the printing step using a printing material (silk).
Further, since the non-woven fabric made of insulating fiber forms an air layer inside, the non-woven fabric may be provided in a region on the printed wiring board in contact with the flexible wiring member.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show a first embodiment of the present invention. A wiring pattern 1 on which various element groups (not shown) for processing input / output signals such as a reproduction signal from an optical head (optical pickup) 14 or a recording signal to be sent to the optical head 14 is mounted on the printed wiring board 11.
6, 17 are formed.

On the surface of the printed wiring board 11 on which the wiring patterns 16 and 17 are formed,
One end of a flexible wiring member 12 such as FC or FPC is connected, and the optical head 14 is connected to the other end. As shown in FIG. 3, the flexible wiring member 12 has a structure in which a conductor layer 12B is formed on a polyester-based or polyimide-based insulating film 12A and is covered with an insulating cover film 12C as shown in FIG. Then, an electric signal is communicated between the printed wiring board 11 and the optical head 14. The optical head 14 is configured to be able to reciprocate along a radial direction (an arrow direction in the figure) of an optical disk (not shown).

In this embodiment, as shown in FIGS. 1 and 2, the movement of the optical head 14 causes the flexible wiring member 12 to move.
An insulating film 15 is applied to a part of the printed wiring board 11 where a part of the printed wiring board 11 contacts. This insulating film 15
In the present embodiment, it is constituted as a printing material (silk material) which is configured as an air layer forming means according to the present invention and is printed on the printed wiring board 11 as a symbol such as a part number or a type of the board. Coated simultaneously with these symbols.

At this time, as shown in FIG.
Reference numeral 5 is applied to a region between the wiring patterns such as the through hole 16 and the wiring 17 of the printed wiring board 11, that is, an insulating region where the wiring patterns 16 and 17 are not formed.

Next, the operation of the present embodiment will be described.

As the optical head 14 moves, a part of the insulating film 12 A of the flexible wiring member 12 comes into surface contact with the surface of the printed wiring board 11. At this time, as shown in FIG. 3, the insulating film 12A comes into contact with the upper surface of the insulating film 15 applied on the printed wiring board 11, and the air layer 18 is formed between the insulating film 12A and the wiring pattern (the through hole 16 is shown in the figure). To face each other. That is, the insulating film 15 prevents the insulating film 12A of the flexible wiring member 12 from contacting the wiring pattern (the through hole 16 and the wiring 17).

According to the present embodiment, the flexible wiring member 12 is provided on the printed wiring board 11.
When the flexible wiring member 12 and the wiring pattern 1
Since the insulating film 15 for forming the air layer 18 is applied between the conductive layer 12 and the conductive layer 12B of the flexible wiring member 12 and the wiring patterns 16 and 17, as compared with the case where the insulating film 15 is not applied. Can be reduced. Therefore, the impedance between the two is increased, and the conductor layer 12
The signal crosstalk between B and the wiring patterns 16 and 17, that is, the generation of a noise signal can be suppressed, and as a result, in the optical disk device, the influence that directly affects the performance of the device such as the deterioration of the jitter and the error rate is reduced. .

Further, an insulating film 15 as an air layer forming means is provided.
However, since it is formed by a silk printing process on the printed wiring board 11, the generation of a noise signal can be easily suppressed only by changing the pattern of the screen.

Next, FIG. 4 shows a second embodiment of the present invention. In the drawings, the same reference numerals are given to portions corresponding to the above-described first embodiment, and a detailed description thereof will be omitted.

In the present embodiment, as the air layer forming means, a nonwoven fabric 25 made of electrically insulating fibers is arranged in a region on the printed wiring board 11 where the flexible wiring member 12 contacts. is there. Since the nonwoven fabric 25 has a low fiber density, an air layer 28 is formed between the wiring pattern such as the through-hole 16 and the wiring 17 and the flexible wiring member 12 depending on the arrangement of the nonwoven fabric 25.

As a result, similarly to the first embodiment, the capacitance between the wiring patterns 16, 17 and the flexible wiring member 12 can be reduced, and the impedance can be increased. Conductive layer 12B and wiring pattern 1
Generation of a noise signal between 6 and 17 can be suppressed, and as a result, in the optical disk device, the influence directly affecting the performance of the device such as jitter and deterioration of the error rate is reduced.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited to these embodiments.
Various modifications are possible based on the technical idea of the present invention.

For example, in the above-described embodiment, the multilayer wiring board having the through holes 16 has been described as an example of the printed wiring board 11, but the printed wiring board 11 does not have the through holes 16.
The present invention is applicable to a so-called single-sided substrate.

In the first embodiment described above,
The insulating film 15 as an air layer forming means applied to the area between the wiring patterns 16 and 17 is not applied to the entire area between the wiring patterns 16 and 17 as shown in FIG. 17 and flexible wiring member 12
Within the minimum range that can form a layer of air between
It is also possible to apply the insulating film 15 partially.

In each of the above embodiments, the optical disk device has been described as an example. However, the present invention is also applicable to a printer device in which a print head is connected by a flexible wiring member.

[0028]

As described above, according to the printed wiring board of the present invention, the generation of a noise signal due to the contact between the wiring pattern on the surface and the flexible wiring member can be suppressed with a simple configuration. .

According to the optical disk device of the present invention,
It is possible to prevent deterioration of the performance of the device by preventing jitter and error rate from deteriorating.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically illustrating a relationship between a printed wiring board according to a first embodiment of the present invention and an optical head connected to the printed wiring board via a flexible wiring member.

FIG. 2 shows a wiring pattern on the surface of the printed wiring board;
FIG. 3 is a partial plan view for explaining a relationship with an insulating film constituting an air layer forming unit according to the present invention.

FIG. 3 is a side sectional view of a main part showing an air space forming unit according to the first embodiment of the present invention.

FIG. 4 is a side sectional view of a main part showing an air space forming unit according to a second embodiment of the present invention.

FIG. 5 is a perspective view schematically illustrating a relationship between a conventional printed wiring board and an optical head connected to the printed wiring board via a flexible wiring member.

FIG. 6 is a side sectional view of a main part for explaining a problem of the related art.

[Explanation of symbols]

11: Printed wiring board, 12: Flexible wiring member, 12
B: insulating film, 12B: conductor layer, 14: optical head,
15: insulating film (air layer forming means), 16: through hole (wiring pattern), 17: wiring (wiring pattern), 1
8, 28: air layer, 25: non-woven fabric (air layer forming means).

Claims (6)

[Claims] 1. A printed wiring board having a wiring pattern on a surface and a flexible wiring member having a conductor layer formed on an insulating film connected to the surface, wherein a region of the surface where the insulating film contacts is provided. A printed wiring board provided with air layer forming means for forming an air layer between the wiring pattern and the insulating film. 2. The printed wiring board according to claim 1, wherein said air layer forming means is an insulating film applied to a region between said wiring patterns. 3. The printed wiring board according to claim 1, wherein the air layer forming means is a non-woven fabric made of insulating fibers. 4. An optical head for performing at least one of recording and reproduction on an optical disk, a printed wiring board on which a wiring pattern is formed on a surface, and an optical head connected between the optical head and the printed wiring board. An optical disc device comprising: a flexible wiring member formed by forming a conductor layer on an insulating film; wherein an area between the wiring pattern and the insulating film with respect to a region on the printed wiring board with which the insulating film contacts. An optical disk device, further comprising an air layer forming means for forming an air layer. 5. The optical disk device according to claim 4, wherein said air layer forming means is an insulating film applied to a region between said wiring patterns. 6. The optical disk device according to claim 4, wherein said air layer forming means is a non-woven fabric made of insulating fibers.