JP2001189533A - Flexible printed board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible printed board (an FPC) in which adhesives need not be used. SOLUTION: Adhesives need not be used and a manufacturing process is simplified by the flexible printed board 100 in which copper circuit sheets 110 are buried directly between extrusion-molded resin films 120, 130, to which the sheets 110 are thermocompression-bonded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed circuit (FPC) which does not require the use of an adhesive and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, an FPC is, as shown in FIG.
A pattern circuit of a metal foil layer 3 is formed on a base film side adhesive layer 2 of a base film 1, and a cover lay film 5 on which a cover lay side adhesive layer 4 is applied is attached thereon.

The base film 1 is usually made of a flexible film such as a polyimide resin or a polyethylene terephthalate (PET) resin. Usually, the base film 1 is coated on the entire surface of the film with a base film-side adhesive layer 2 in advance. A film (CCL = Copper Composite Laminate) with a metal (copper) foil to which the foil layer 3 is attached is used.

Then, as shown in FIG. 6, this CCL1
For No. 0, a desired pattern circuit is formed in the metal foil layer portion by applying a technique such as a lithography technique. That is, a dry film (DF) is temporarily laminated on the CCL, and thereafter, a pattern circuit is formed through each of the steps of exposure, development, and etching, and unnecessary DF is removed.

Thereafter, the CCL on which the pattern circuit is formed is formed.
10, a coverlay (CL = Cover) made of a flexible film such as a polyimide resin or a PET resin.
Layer) film 5 is adhered by the cover lay side adhesive layer 4 applied to one side of the film 5 as described above, and the FPC 20 is obtained through the pressing and curing steps.

[0006]

However, in the case of the FPC according to such a conventional manufacturing method, an adhesive layer is provided on the CCL side or the CL side, and this adhesive may adversely affect the global environment and the human body. May be contained, such as halogenated compounds or antimony.

Further, in the conventional manufacturing method shown in FIG. 6, the process is complicated, and at the same time, usually an epoxy-based thermosetting type adhesive is often used as an adhesive. After the treatment, a curing step is required. Since this process cure takes a relatively long time, it is rate-limiting, and there is a problem that the productivity of the entire manufacturing process is largely affected.

The present invention has been made in view of such a conventional problem. Basically, by eliminating the need for an adhesive, an excellent FPC and an FPC having solved the above-mentioned conventional problems have been solved. It does not provide a manufacturing method.

[0009]

According to the present invention, there is provided a flexible printed circuit board characterized in that a copper circuit sheet is directly embedded between heat-pressed and extruded resin films.

According to a second aspect of the present invention, after extruding a resin film on one side of a copper circuit sheet, the two are thermocompression bonded together.
Subsequently, after extruding a resin film on the copper circuit sheet side of the resin film to which the copper circuit sheet is attached, the two are thermocompression bonded, and cut into appropriate lengths. It is in.

According to a third aspect of the present invention, there is provided the method for manufacturing a flexible printed circuit board according to the second aspect, wherein the resin film is a thermoplastic resin film.

[0012]

FIG. 1 shows an embodiment of an FPC according to the present invention. In the FPC 100, the copper circuit sheet 110 is directly embedded between the extruded resin films 120 and 130 which are thermocompression-bonded. As the resin films 120 and 130, a thermoplastic resin film such as polyimide or polyester is used.

[0013] This FPC 100 does not have an adhesive layer and does not use an adhesive as in the prior art. Therefore, the FPC 100 has no effect on the global environment or the human body caused by a halide or antimony which may be contained in the adhesive. Problems such as adverse effects are fundamentally eliminated.

The FPC 100 having such a structure is shown in FIGS.
It can be manufactured by the manufacturing method according to the present invention as shown in FIG. First, in forming the copper circuit sheet 110, there is no particular limitation. For example, as shown in FIG. 2, a method of preparing a copper foil 111 and directly punching it out to form a desired pattern circuit, or a method of forming the copper foil 111 And a method of applying the same lithography technology as in the past.

According to the lithography technique,
After once attaching the copper foil 111 to the carrier film, a dry film (DF) is further laminated, and thereafter, a pattern circuit is formed through each of the steps of exposure, development, and etching. It may be removed.

Next, the thermoplastic resin films 120 and 130 are sequentially extruded on both sides of the copper circuit sheet 110, and then thermocompression-bonded to obtain the FPC 100 of the present invention.

More specifically, first, as shown in FIG. 3, a thermoplastic resin film 120 is extruded on one side of a copper circuit sheet 110 by an extruder 210 and passed between a pair of rollers 220, 220 to be overlaid. At the same time, it is formed into a predetermined thickness. Thereafter, the two parts are continuously bonded to each other in a thermocompression bonding section 230 in a high temperature state of 200 ° C. or more in a nitrogen atmosphere.
Is led through a pair of pressure rollers 231 and 231 to be integrally thermocompression-bonded, and wound on a drum or the like by the winder 240 as the FPC intermediate body 100a.

Thereafter, as shown in FIG. 4, the drum in which the FPC intermediate 100a is wound is set on the delivery unit 250, and the FPC intermediate 100a is sent out.
The thermoplastic resin film 130 is extruded by the extruder 210 toward the copper circuit sheet 110 side of the PC intermediate body 100a, passed through a pair of rollers 220, 220 and superposed, and formed into a predetermined thickness. Thereafter, the two are successively guided by the thermocompression bonding unit 230 which is in a high temperature state of 200 ° C. or more in a nitrogen atmosphere, and a plurality of the pair of pressure
If the thermocompression bonding is performed integrally through the
An FPC continuous body 100b in which the PCs 100 are continuously connected is obtained. This may be once taken up by a winder on a drum or the like as shown in FIG. 2, but is guided to a cutting device 270 by a pair of pinch rollers 260 as shown in FIG. Then, the desired FPC 100 is obtained.

Example 1 A 50 μm thick thermoplastic polyimide film was extruded on one side of a copper circuit sheet made of 36 μm copper foil, and then guided to a thermocompression bonding section as described above.
Both are integrally thermocompressed, and subsequently, a 50 μm-thick thermoplastic polyimide film is extruded on the other side of the copper circuit sheet, and then guided to the thermocompression bonding section in the same manner as above, and the upper and lower sides of the copper circuit sheet embedded therein Both thermoplastic polyimide films were thermocompression bonded together to obtain a sample FPC. Then, the peel strength between the polyimide film layer of the FPC and the copper circuit sheet was measured.

Example 2 A 50 μm-thick thermoplastic polyester film was extruded on one side of a copper circuit sheet made of 36 μm copper foil, and then guided to the thermocompression bonding section as described above, and both were integrally thermocompression bonded. Then, after extruding a thermoplastic polyester film having a thickness of 50 μm on the other side of the copper circuit sheet, it was guided to the thermocompression bonding section in the same manner as above, and the upper and lower thermoplastic polyester films in which the copper circuit sheet was embedded were integrated. Thermocompression bonding, and the sample F
PC was obtained. Then, the peel strength between the polyester film layer and the copper circuit sheet was measured.

Comparative Example 1 A copper circuit sheet made of a 36 μm copper foil was put between two thermoplastic polyimide films having a thickness of 25 μm, and these were pressed by a hot press to form a gap between both upper and lower thermoplastic polyimide films. To obtain a sample FPC in which a copper circuit sheet was embedded. And this FPC
The peel strength between the polyimide film layer and the copper circuit sheet was measured.

Comparative Example 2 A copper circuit sheet made of a 36 μm copper foil was placed between two thermoplastic polyester films having a thickness of 25 μm, and these were pressed by a hot press to form a sheet between both upper and lower thermoplastic polyester films. To obtain a sample FPC in which a copper circuit sheet was embedded. And this F
The peel strength between the polyester film layer of the PC and the copper circuit sheet was measured.

Comparative Example 3 Normal CCL (copper foil thickness 36
A sample FPC was obtained by a conventional method using μm, adhesive layer thickness 20 μm, polyimide base film thickness 25 μm) and CL (adhesive layer thickness 30 μm, polyimide cover film thickness 25 μm). The peel strength between the polyimide film layer of this FPC and the copper circuit sheet was measured.

FP of Examples 1 and 2 and Comparative Examples 1 to 3
The peel strength determined for C was as shown in Table 1. From Table 1, it can be seen that the FPCs according to the first and second embodiments of the present invention are shown.
Although the peel strength is slightly inferior to the FPCs of Comparative Examples 1 to 3, this type of FPC usually needs only to have a strength of about 0.30 kg / cm. Even in Examples 1 and 2 of the present invention, it can be seen that the strength (numerical value) is practically any problem.

[0025]

[Table 1]

In the above embodiment, the single-sided FP is used.
However, in the present invention, a double-sided FPC can be manufactured by repeating the same manufacturing process.
Furthermore, if this manufacturing process is repeated a plurality of times, a multilayer FPC having three or more layers can be manufactured relatively easily.

[0027]

As is apparent from the above description, according to the FPC and the method of manufacturing the same according to the present invention, the conventional FPC
Since there is no adhesive layer and no adhesive is used, problems such as adverse effects on the global environment and the human body caused by halides and antimony that may be contained in the adhesive are fundamental. Will be resolved.

Further, in the manufacturing method of the present invention, since the steps are simplified and the curing step is not required, the productivity is high and the cost can be reduced significantly. Furthermore, by repeating the manufacturing process of the present invention, a multilayer FPC having three or more layers can be appropriately manufactured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of an FPC according to the present invention.

FIG. 2 is a process chart schematically showing an FPC manufacturing method according to the present invention.

FIG. 3 is a schematic explanatory view showing an example of specific steps in a method of manufacturing an FPC according to the present invention.

FIG. 4 is a schematic explanatory view showing an example of another specific process in the method of manufacturing an FPC according to the present invention.

FIG. 5 is a longitudinal sectional view showing a conventional FPC.

FIG. 6 is a process chart showing an outline of a conventional method of manufacturing an FPC.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 FPC 100 a FPC intermediate 100 b FPC continuous body 110 copper circuit sheet 111 copper foil 120 resin film (base film) 130 resin film (cover film) 210 extruder 230 thermocompression bonding section 231 pressure bonding roller 240 winder 250 feeding machine 270 cutting apparatus

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takayuki Imai 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd. (72) Inventor Sadamitsu Sadamitsu 1-5-1, Kiba, Koto-ku, Tokyo Stock Company F term in Fujikura (reference) 5E338 AA01 AA12 AA16 CC01 CD01 EE32 EE60 5E343 AA16 AA33 BB24 BB67 DD54 DD56 ER33 ER39 GG20

Claims (3)

[Claims] 1. A flexible printed circuit board in which a copper circuit sheet is directly embedded between thermocompression-bonded extruded resin films. 2. After extruding a resin film on one side of a copper circuit sheet, the two are thermocompression bonded. Subsequently, after extruding the resin film on the copper circuit sheet side of the resin film to which the copper circuit sheet is adhered, both are extruded. A method for producing a flexible printed circuit board, which comprises thermocompression bonding and cutting this into an appropriate length. 3. The method according to claim 2, wherein the resin film is a thermoplastic resin film.