JPH07302955A - Double-sided flexible printed board - Google Patents

Abstract

PURPOSE:To provide a double-sided flexible printed board which can be easily handled by preventing the board from warping and improves the yield of parts mounting. CONSTITUTION:In a double-sided flexible printed board (FPC) 1 which is curved at least partly, at least curved sections are employed as single-sided wiring sections 10, 11 and 12. On the opposite surface of the single-sided wiring section, a reinforcing conductive pattern 3 and a photosensitive cover lay (PIC) layer are formed only in the part other than the curved sections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided flexible printed circuit board, and more particularly to a double-sided flexible printed circuit board at least a part of which is curved.

[0002]

2. Description of the Related Art Recently, a double-sided flexible printed circuit (FPC) using a cover lay having a photosensitive adhesive layer.
Is being developed. The above-mentioned photosensitive coverlay (PIC: Photo Imageable Coverlay) is available at DUPON, USA at the 1993 JPA show.
There is a photosensitive cover lay (PIC) for flexible wiring boards (FPC), which was exhibited as a reference by T.

PI for this flexible wiring board (FPC)
C is an insulating film having the folding resistance and flexibility required on FPC, and according to the reference material ("Technical Information Bulletin circuit board material") at the JPA show above, it is a conventional polyimide film. It has various advantages as compared with a double-sided FPC that uses a cover lay having an adhesive layer.

That is, in the conventional FPC manufacturing process, there is a possibility that dimensional accuracy of the coverlay or the FPC circuit side, positional deviation when the coverlay is attached to the FPC circuit, and the like may occur. Is becoming the limit. However, in the above-mentioned FIC PIC, since the cover lay itself is made photosensitive so that the cover lay can be aligned with the photo tool (photographic film) after being attached to the FPC circuit, The positional accuracy between the FPC circuit and the FPC circuit can be improved.

Further, in the conventional coverlay, it was necessary to provide a clearance of ± 0.3 mm for the pad portion, but in the above PIC, the clearance is ± 0 by making the coverlay itself photosensitive. .1m
can be reduced from m to ± 0.05 mm,
As a result, the pad portion can be miniaturized.

Since the solder dam can be formed between the QFP pads by using the PIC, solder bridges between the lead frames can be prevented and the yield can be improved and the mounting can be easily performed.

Further, in the present situation, the cost for the die is very high because the die for coverlay punching is changed many times from the trial production to the mass production. According to this, since it is possible to perform imaging with a photo tool, a mold for a coverlay is not necessary, and it is possible to reduce the cost related to the mold at the trial production stage.

Further, as described above, since the mold is unnecessary, the lead time required for manufacturing the mold is also unnecessary, and the development lead time can be shortened. Further, the storage management of the photo tools and the like does not require a space as compared with the conventional mold management, and the management can be simplified.
The cost can be reduced.

On the other hand, since the above-mentioned PIC has a three-layer structure in which it is a dry film and is sandwiched by protective films from both sides, it can be used in a dry film production line which is usually used, and both sides can be processed simultaneously. Etc., excellent workability is possible and insulation coating (lamination)
The imaging can be done later, opening up more automation possibilities like the ideal manufacturing method reel-to-reel process.

[0010]

However, the above-mentioned PIC
According to the above, as compared with the FPC using the coverlay having the adhesive layer in the conventional polymide film, the coverlay itself does not have elasticity, so that the substrate warps during the manufacturing of the substrate, and the handling is easy. There is a problem that it is difficult. Especially in the case of a double-sided flexible printed circuit board, the one-sided wiring part is bent back and the boards are entangled with each other. It may cause it.

Also, in the conventional FPC using a cover lay having an adhesive layer on a polymide film, if the thickness of the base film is thin, the whole substrate is not elastic, and therefore the same problem occurs. There is a point.

In order to solve the above-mentioned problems, an object of the present invention is to secure elasticity of a curved portion of a double-sided flexible printed circuit board (FPC) which is a single-sided wiring so that the board itself does not warp. Another object of the present invention is to provide a double-sided flexible printed circuit board that facilitates the handling of the board and improves the yield of mounting components.

[0013]

A double-sided flexible printed circuit board according to the present invention is a double-sided flexible printed circuit board, at least a part of which is curved, wherein at least the curved portion is a single-sided wiring portion and the opposite side of the single-sided wiring portion. The surface is characterized in that a conductive pattern for reinforcement and a coverlay are formed only in the areas other than the curved portion, and the coverlay is made of a photosensitive coverlay. Further, in the double-sided flexible printed circuit board, the curved portion of the flexible printed circuit board is a one-sided wiring portion, and the surface opposite to the one-sided wiring portion is in the vicinity of the curved portion.
It is characterized in that a conductive pattern and a coverlay for reinforcement are formed.

[0014]

In the double-sided flexible printed circuit board, at least the curved portion is the one-sided wiring portion, and the surface opposite to the one-sided wiring portion is provided with the conductive pattern for reinforcement and the photosensitive coverlay only in the portion other than the curved portion. , Give flexibility to the flexible printed circuit board itself. Further, in the double-sided flexible printed circuit board, the curved portion of the flexible printed circuit board is a one-sided wiring portion, and a conductive pattern and a coverlay for reinforcement are formed on the surface opposite to the one-sided wiring portion in the vicinity of the curved portion. The flexible printed circuit board itself has elasticity.

[0015]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a perspective view showing the appearance of a double-sided flexible printed circuit board (FPC) according to an embodiment of the present invention.

The double-sided flexible printed circuit board (FPC) 1 of this embodiment is coated with a photosensitive coverlay (PIC) layer for insulation.
The portions indicated by reference numerals 10, 11, and 12 indicate the single-sided wiring portion of the FPC 1. This single-sided wiring section 10, 11, 1
In No. 2, it is designed to be curved at the curve center line L.

Conductive patterns 2 of an FPC circuit made of, for example, copper or the like are provided on both sides of the FPC 1 to electrically connect respective members such as ICs arranged at various places on the FPC 1. It is like this. Also,
The conductive pattern 3 is a pseudo (dummy) reinforcing conductive pattern provided on the surface opposite to the one-sided wiring portion 12, that is, on the back surface side. In addition, also in the one-sided wiring portions 10 and 11, the reinforcing conductive pattern 3 is provided on the opposite surface (not shown).

FIG. 2 shows the single-sided wiring portions 10, 11, 12 described above.
FIG. 3 is an enlarged view of an essential part showing a schematic plan view of FIG.
FIG. 3 is a cross-sectional view showing an outline of the single-sided wiring parts 10, 11 and 12. As shown in FIGS. 2 and 3, the single-sided wiring portions 10, 11, 12 of the FPC 1 are configured to be curved at the center line L of curvature, and the A-side (front side) of the base film 6 of the FPC 1 is described. Is provided with the conductive pattern 2, and a PIC layer 4 that insulates the conductive pattern 2 is covered (laminated) on the conductive pattern 2. Then, by the conductive pattern 2, as shown in FIG.
The components on the PC 1 are connected (see FIG. 1).
In the curved portion 11).

On the other hand, on the B side (rear side), a pseudo reinforcing conductive pattern 3 is provided in a portion other than the vicinity of the curved center line L, and the conductive pattern 3 is insulated on the upper layer thereof. The PIC layer 5 is covered (laminated).

Then, the single-sided wiring portion 10 of the FPC 1,
On the B surface side of 11 and 12, the reinforcing conductive pattern 3 and the PIC layer 5 are not disposed between MM, that is, in the vicinity of the curved center line L, and on the A surface side. Only the conductive pattern 2 and the PIC layer 4 are provided.

With such a structure, according to the above-described embodiment, the surface of the double-sided flexible printed circuit board 1 opposite to the single-sided wiring portions 10, 11, 12 is different, that is, other than the curved portion on the B-side. By disposing the conductive pattern 3 for reinforcement and the PIC layer 5 only on the back side, elasticity can be given to the double-sided flexible printed circuit board (FPC) 1 itself and the board itself can be prevented from warping. .

At the same time, the single-sided wiring portions 10, 11,
On the B surface side of 12, the reinforcing conductive pattern 3 and the PIC layer 5 are not disposed in the vicinity of the curved center line L.
Since only the conductive pattern 2 and the PIC layer 4 are provided on the surface side, flexibility (flexibility) is provided in the vicinity of the curved center line L of the single-sided wiring portions 10, 11, and 12.
Can be provided. Therefore, the above FPC
Since the board itself does not warp when components are mounted on the device 1, the mounting yield can be improved. On the other hand, when the FPC 1 is mounted on the device side, the single-sided wiring parts 10, 11, 12 are used. FP near the curved center line L of
Since the C1 can be freely curved due to its flexibility, the FPC1 can be freely arranged in a device.

In a conventional FPC using a coverlay having an adhesive layer on a polymide film, even if the base film has a small thickness, the same structure is used to impart elasticity to the substrate. Therefore, it is possible to obtain exactly the same effect.

[0024]

As described above, according to the present invention, in the double-sided flexible printed board having the photosensitive coverlay layer, the curved portion is the one-sided wiring portion, and the surface on the opposite side of the one-sided wiring portion is the curved portion. Besides, by forming the conductive pattern for reinforcement and the photosensitive coverlay only, the elasticity of the substrate itself can be secured and the warp of the substrate can be prevented. As a result, it is possible to provide a double-sided flexible printed circuit board that facilitates the handling of the board and improves the yield of mounting components.

[Brief description of drawings]

FIG. 1 is a perspective view showing the appearance of a double-sided flexible printed circuit board (FPC) according to an embodiment of the present invention.

2 is a double-sided flexible printed circuit board (F
The principal part enlarged view which developed the one-sided wiring part of PC) planarly.

3 is a double-sided flexible printed circuit board (F
Sectional drawing of the single-sided wiring part of PC).

[Explanation of symbols]

 1 ... Double-sided flexible printed circuit board (FPC) 2 ... Conductive pattern 3 ... Conductive pattern for reinforcement 4, 5 ... Photosensitive coverlay (PIC) layer 6 ... Base film 10, 11, 12 ... Single-sided wiring Part L ... Curved center line

Claims (3)

[Claims] 1. A double-sided flexible printed circuit board, at least a part of which is curved, wherein at least the curved portion is a single-sided wiring portion, and a surface on the opposite side of the single-sided wiring portion is a conductive conductive material for reinforcement other than the curved portion. A double-sided flexible printed circuit board, characterized in that a pattern and a coverlay are formed. 2. The double-sided flexible printed circuit board according to claim 1, wherein the coverlay is a photosensitive coverlay. 3. A double-sided flexible printed circuit board, wherein a curved portion of the flexible printed circuit board is a one-sided wiring portion, and a conductive pattern and a coverlay for reinforcement are provided in the vicinity of the curved portion on a surface opposite to the one-sided wiring portion. A double-sided flexible printed board characterized by being formed.