JPH08116140A - Flexible printed wiring board - Google Patents

Abstract

PURPOSE: To acquire a flexible printed wiring board by making a part to be bent softer than a periphery thereof or by hardening a part not to be bent and partially providing a difference in hardness to enable easy bending at a soft part. CONSTITUTION: A 25μm-thick base polyimide film 2, a 25μm-thick cover-lay polyimide film 1 and a 20μm-thick epoxy adhesive layer 3 at a position 5 to be bent are removed and modified polyimide insulation resin paint 5 provided with flexibility is applied to the part 5. As for strength of each material layer, a base polyimide film of 300kg/mm<2> , a cover-lay polyimide film of 300kg/mm<2> an epoxy adhesive layer of 120kg/mm<2> and a deformed polyimide insulation resin layer of 50kg/mm<2> are used. Therefore, if bending stress is applied from both sides of an FPC under such FPC constitution, the insulation resin part 5 bends accurately as specified to fall into a bending habit readily, and processing is made easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel structure of an FPC that needs to be bent at a certain place.

[0002]

2. Description of the Related Art Conventionally, when an FPC that needs to be bent at a certain position is required, the part of the FPC to be bent is fixed, and a heat bar is applied to the part to bend it gradually or bend it in advance. I had adopted the technique of bending at once without putting on.

[0003]

The conventional FPC has the same structure and / or the same hardness in all parts, and if it is attempted to bend it at a certain position, it will be R as a whole unless it is bent by a heat bar. There was a risk of making a club.

[0004]

As a result of various studies on such a problem, the inventors made the FPC part to be bent softer than the surrounding structure or hardened the part which is not bent to be partially hardened. It has been found that it is possible to easily bend the FPC that needs to be bent only at a desired portion by providing the difference in height, and thus the present invention has been completed.

That is, according to the present invention: In an FPC, a portion (place) to be bent is made softer than the surroundings, or a portion which is not bent is made hard so as to have a partial hardness difference, and an FPC which is easily bent at a soft portion is provided. provide. Further, in the FPC in which a predetermined circuit is formed, the coverlay film, the base film, or both of the portions (locations) to be bent are removed, and an FPC in which a flexible insulating resin is applied to the portion is provided. Also, in an FPC that has the required circuit formed on one side,
A solid copper foil was left on the back surface via the base film, and the copper foil was left only on the portion (location) where the bending was desired.
Provide a PC.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a cross-sectional structure of an FPC in which a highly flexible insulating resin is provided only in a portion (location) to be bent. Figure 2
[Fig. 2] is a schematic diagram showing a cross-sectional structure of an FPC in a state where bending stress is applied to both sides of the FPC in Fig. 1.

In FIGS. 1 and 2, reference numerals 1 and 2 are a cover lay film and a base film made of polyimide resin, polyester resin, etc., and 3 is an adhesive agent for joining the copper foil 4 to the cover lay film 1 and the base film 2. An epoxy adhesive or a modified polyimide adhesive modified to give flexibility is preferable. Reference numeral 5 is a highly flexible insulating resin applied to a portion removed by an appropriate means such as peeling off the cover lay film 1 and / or the base film 2 and the adhesive 3 at a portion to be bent.

The highly flexible insulating resin is not particularly limited as long as it is softer than the coverlay film and the base film, but relatively flexible insulating resin such as epoxy, acrylic and polyester resins. Resin is desirable. Further, a modified polyimide resin modified to give flexibility can also be used. The mode of use is not particularly limited as long as the resin can be applied to the removed portion, but it is preferable to use a liquid such as an insulating paint in view of the ease of construction (corresponding to claim 2).

Therefore, bending stress 6 is applied from both sides of the FPC.
When applied, the high-flexibility insulating resin portion 5 can be easily bent as shown in FIG. Figure 3 shows the FP with the solid copper foil on the back of only the part (location) to be bent removed.
It is a schematic diagram which shows the cross-section of C. FIG. 4 shows the FPC of FIG.
FIG. 3 is a schematic diagram showing a cross-sectional structure of the FPC in a state where bending stress is applied to both sides of the FPC.

In FIGS. 3 and 4, 11 and 12 are cover lay films made of polyimide resin, polyester resin or the like,
Reference numeral 13 is a base film, and 13 is an adhesive for joining the copper foil 14 and the coverlay film 11, preferably an epoxy adhesive. In this case, the base film 12 employs a substrate that is directly bonded to the copper foils 14 and 15. However, as shown in FIGS. Is also good.

Reference numeral 15 denotes a solid copper foil applied to the entire back surface of the FPC, which is the remaining solid copper foil obtained by removing the solid copper foil only at the portion (location) to be bent. F for the solid copper foil 15
The same material as the copper foil portion 14 forming the conductive portion of the PC may be used and is not particularly limited (corresponding to claim 3). Therefore, if bending stress 16 is applied from both sides of the FPC, it can be easily bent at a place where there is no solid copper foil, as shown in FIG.

[0012]

The present invention will be described in detail with reference to the following examples, which do not limit the scope of the present invention. (Example 1) According to the configuration of the FPC of FIG. 1, a base polyimide film 2 having a thickness of 25 μm, a coverlay polyimide film 1 having a thickness of 25 μm, and an epoxy adhesive layer 3, 3 having a thickness of 20 μm at a portion 5 to be bent are provided. Removed,
A modified polyimide insulating resin coating having flexibility was applied to the portion 5.

It can be seen that each material layer has the following strengths: base polyimide film 300 kg / mm ² coverlay polyimide film 300 kg / mm ² epoxy adhesive layer 120 kg / mm ² modified polyimide insulating resin layer 50 kg / mm ² When a bending stress was applied from both sides of the FPC under such an FPC structure, the insulating resin portion 5 was bent accurately as shown in FIG.

(Embodiment 2) A coverlay polyimide film 1 having a thickness of 25 μm according to the structure of the FPC shown in FIG.
1,20 μm thick epoxy adhesive layer 13,35 μm
FPC made of the copper foil 14, the 25 μm thick base polyimide film 12 and the solid copper foil 15
The structure was obtained by removing the solid copper foil on the backside where it was desired to bend. Then, as shown in FIG. 4, F is applied to the portion without the solid copper foil.
When stress was applied from both sides of the PC, it bent exactly as specified.

[0015]

EFFECTS OF THE INVENTION With the above FPC structure, the bending portion is partially flexible as compared with the surroundings.
When bending stress is applied to both sides of the PC, the bending can be easily performed at that portion. In addition, in the conventional heat bar, since the bending habit is not attached, it is difficult to process, but according to the present invention, the bending habit can be attached easily, and there is an advantage that the processing is easy.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an FPC in which a highly flexible insulating resin is provided only in a portion (location) to be bent.

FIG. 2 is a schematic view showing a cross-sectional structure of the FPC in a state where stress is applied to both sides of the FPC shown in FIG.

FIG. 3 is a schematic diagram showing a cross-sectional structure of the FPC in a state where the solid copper foil on the back surface of only the portion (location) to be bent is removed.

4 is a schematic diagram showing a cross-sectional structure of the FPC in a state where stress is applied to both sides of the FPC of FIG. 3 to bend the FPC.

[Explanation of symbols]

 1 Coverlay film 2 Base film 3 Adhesive 4 Copper foil 5 Highly flexible insulating resin 7 Bending stress 11 Coverlay film 12 Base film 13 Adhesive 14 Copper foil 15 Solid copper foil 16 Bending stress

[Procedure amendment]

[Submission date] November 25, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Conventionally, when an FPC that needs to be bent at a certain position is required, the part of the FPC to be bent is fixed, and a heat bar is applied to the part to bend it gradually or bend it in advance. We used a method of carefully bending all at once without attaching.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

[0015]

EFFECTS OF THE INVENTION With the above FPC structure, the bent portion is partially flexible as compared with the surroundings, so that the FP
When bending stress is applied to both sides of C, it is possible to easily bend at that portion. In addition, it is difficult to process because there is no bending habit in the past.
According to the present invention, it is possible to easily bend and bend, and there is an advantage in that it is easy to process, as compared with the case where it takes a lot of time to hit it.

Claims (3)

[Claims] 1. In a flexible printed wiring board (abbreviated as FPC), a portion to be bent (portion) is made softer than the surroundings, or a portion which is not bent is made hard so as to partially provide a difference in hardness. FPC characterized by being easy to bend. 2. In an FPC having a predetermined circuit formed therein, the coverlay film, the base film, or both of the portions (locations) to be bent are removed, and a flexible insulating resin is applied to the portions. Characteristic FPC. 3. An FPC having a required circuit formed on one side.
In the FPC, the solid copper foil is left on the back surface through the base film, and the copper foil is not left only on the portion (location) to be bent.