WO2016086404A1

WO2016086404A1 - Flat cable

Info

Publication number: WO2016086404A1
Application number: PCT/CN2014/093110
Authority: WO
Inventors: Nobuyuki Yamazaki; Hiroyuki Semba; Keiichiro Fukuda; Takayoshi Koinuma
Original assignee: Sumitomo Electric Industries, Ltd.
Priority date: 2014-12-05
Filing date: 2014-12-05
Publication date: 2016-06-09
Also published as: CN106030725A; JP2017536681A

Abstract

A flat cable includes a plurality of coaxial cables mutually arranged in parallel, the coaxial cable in which a cross-sectional area of a central conductor is 0.006 mm² or less, and an insulating film having a base material, and a thermoplastic adhesive layer formed on the base material. The insulating film is stuck on only one side of a parallel plane of the plurality of coaxial cables, and the plural coaxial cables are fixed to the thermoplastic adhesive layer.

Description

FLAT CABLE

Technical Field

The present invention relates to a flat cable having a coaxial cable.

Background Art

There are cases where a flat cable must be bent and wired according to a wiring path of the flat cable. Normally, wiring is carried out using an FPC (flexible printed circuit board) , but there is a limit of a communication speed or a distance in the case of transmitting a high-speed electrical signal. As solution means, it is contemplated to use a coaxial cable with good high-speed transmission. For example, in Patent Reference 1, in order to bundle each coaxial cable constructing a flat cable, plural coaxial cables are first arranged on the same plane and a flexible adhesive is applied to the vicinity of its center and is cured. Then, the end of each coaxial cable is folded and the folded portion is fixed by an adhesive tape and a desired folded part is formed.

Citation ListPatentliterature

[Patent Document 1] JP-A-2010-218832

Summary of Invention

Technical Problem

In the method forbeing fixed by the adhesive as described in Patent Reference 1, while the adhesive is solidified, a part of the adhesive may flow to cause a positional deviation of the arranged coaxial cables. In this case, a distance between each of the coaxial cables varies and it may become difficult to do work of connection to a terminal of a substrate or a connector. Also, in the case of differential transmission by two coaxial cables, a length difference between the coaxial cables may be caused to decrease skew characteristics.

Also, in the case of using this technique, it is difficult to stabilize the amount of application of the adhesive and also, the time necessary for curing is one day or more, with the result that it is not suitable for mass production and it remains in small production use.

Solution means includes, for example, a configuration of sticking base materials with gluing agents from both surfaces of coaxial cables arranged in parallel. However, in that configuration, the stuck portion of the base material becomes thick and also hard, and it may become difficult to arrange the coaxial cables according to a wiring path. For example, when the stuck portions of the base materials are folded, the folded and stacked portions including the thickness of the base materials of both surfaces become thick, with the result that a folded state tends to be released by the restoring forces of the base materials of both surfaces and the coaxial cables.

In order to obtain flexibility, it is necessary to stick only the side of one surface, but in this case, the gluing agent is exposed to the outside. In this case, secondary demerits such as adhesion of a foreign substance happen.

An object of the invention is to provide a thin and soft flat cable without exposing a gluing agent while preventing occurrence of a deviation of a distance between each of the coaxial cables.

Solution to Problem

A flat cable according to the invention, comprises:

a plurality of coaxial cables mutually arranged in parallel, the coaxial cable in which a cross-sectional area of a central conductor is 0.006 mm² or less； and

an insulating film having a base material, and a thermoplastic adhesive layer formed on the base material,

wherein the insulating film is stuck on only one side of a parallel plane of the plurality of coaxial cables, and the plural coaxial cables are fixed to the thermoplastic adhesive layer.

Advantageous Effects of Invention

According to the invention, it is possible to provide a thin and soft flat cable without exposing a gluing agent while preventing occurrence of a deviation of a distance between each of the coaxial cables.

Brief Description of the Drawings

Fig. 1 is a plan view of a flat cable according to an embodiment of the invention.

Fig. 2 is a sectional view taken on line E-E of the flat cable shown in Fig. 1.

Fig. 3 is a plan view showing a modified example 1 of a flat cable.

Fig. 4 is a schematic configuration diagram of a manufacturing apparatus of the flat cable shown in Fig. 3.

Figs. 5A and 5B are diagrams describing operation of a block structural body formed in a flat cable processing part.

Fig. 6 is a plan view showing a modified example 2 of a flat cable.

Description of Embodiments

Firstly, thesummary of embodiments of the invention will be explained.

(1)A flat cable according to an exemplary embodiment of the invention comprises:

According to the configuration of (1) , the insulating film is stuck on only one side of the parallel plane of the coaxial cables with the coaxial cables arranged in parallel, the coaxial cable in which the cross-sectional area of the central conductor is 0.006 mm² or less. As a result, an increase in thickness of the flat cable is prevented and the flat cable thinner and softer than a conventional flat cable can be obtained. Accordingly, for example, wiring can be carried out with the whole flat cable arched according to a wiring path. Also, since each of the coaxial cables can be fixed so as to stick the insulating film on the parallel plane of the plural coaxial cables arranged in parallel, a deviation of a distance between each of the coaxial cables can be prevented from occurring in the case of a fixing step. Also, since the flat cable of the invention has the thermoplastic adhesive layer, the adhesive layer exposed to the side of the coaxial cable or between the coaxial cables maintains a state without having adhesion properties at the usual time of use except at the time of heating and melting to the cable. As a result, secondary demerits such as adhesion of a foreign substance are not caused.

(2) The insulating film may be stuck on only one side of the parallel plane in a state in which each of the coaxial cables is bent in the same direction while being mutually arranged in parallel in the parallel plane.

According to the configuration of (2) , a bent portion of each of the coaxial cables can be thinned in thickness and also be softened as compared with a configuration of folding the portion in which each of the coaxial cables is fixed in a straight state.

(3) A part of the coaxial cable may make contact with a base material and the other part of the coaxial cable may be exposed from a thermoplastic adhesive layer.

According to the configuration of (3) , the thinner and softer flat cable can be obtained. There is no fear that the molten or softened thermoplastic adhesive layer adheres to other members in the case of sticking the insulating film.

(4) A sheath of the coaxial cable may be formed by winding a polyester tape.

The sheath of the coaxial cable requires a material which has a good affinity for the thermoplastic adhesive layer and is tightly fixed. For example, for the sheath formed by spirally winding the polyester tape two or more turns, in the case of heating and again molding the thermoplastic adhesive layer of the insulating film, the sheath is tightly fixed to the adhesive layer and also the thermoplastic adhesive enters a gap between spiral winds of the sheath to thereby improve more adhesion.

Thus, the sheath formed by the polyester tape is tightly fixed to the thermoplastic adhesive layer of the insulating film. As a result, the deviation of the distance between each of the coaxial cables can further be prevented from occurring.

(5) The base material of the insulating film may be polyester, and the thermoplastic adhesive layer may be a polyester adhesive.

According to the configuration of (5) , since the thermoplastic adhesive layer of the insulating film and the sheath of the coaxial cable are formed of the same kind of material, the thermoplastic adhesive layer easily adheres to the sheath mutually. As a result, each of the coaxial cables is tightly fixed by the insulating film, and the deviation of the distance can be prevented from occurring.

An example of an embodiment of a flat cable according to the invention will hereinafter be described with reference to the drawings.

As shown in Figs. 1 and 2, a flat cable 1 includes plural (five in the present example) coaxial cables 10 arranged in parallel in a plane state, and an insulating film 20 covering the five coaxial cables 10 arranged in parallel. In the flat cable 1, each of the coaxial cables 10 is extended while maintaining, for example, a state equally spaced in parallel and is formed in a straight line shape inside an area arranged in parallel. In each of the coaxial cables 10, one distal end 11Aand the other distal end 11B are exposed from the insulating film 20. These distal ends 11A, 11B are soldered to a substrate to form terminal parts connected. In addition, connectors may be attached to these

distal ends

11A, 11B.

The coaxial cable 10 includes a central conductor 11, an inner insulator 12, an outer conductor 13 and a sheath 14. The inner insulator 12 is formed on an outer periphery of the central conductor 11. The outer conductor 13 is formed on an outer periphery of the inner insulator 12. The sheath 14 is formed on an outer periphery of the outer conductor 13.

The central conductor 11 is constructed of, for example, a metal wire such as copper. As the central conductor 11, for example, a conductor thinner than that of AWG (American Wire Gauge) 40 is used. That is, as the central conductor 11, a conductor having a cross-sectional area of 0.006 mm² or less is used.

The inner insulator 12 and the sheath 14 are constructed of an insulating resin. The sheath 14 is formed by winding, for example, a polyester tape. The sheath 14 requires a material making close contact with a thermoplastic material, and may be formed by extrusion molding of fluorine rubber such as THV. The sheath 14 has an outside diameter of, for example, 0.30 mm or less.

The insulating film 20 includes a base material 21 and a thermoplastic adhesive layer 22. The insulating film 20 is a film in which the thermoplastic adhesive layer 22 is integrally formed on a surface of one side of the base material 21, and its thickness is formed in, for example, 50 to 75 μm. The insulating film 20 is stuck on only one side of a parallel plane 10a formed by the five coaxial cables 10. The insulating film 20 is heated and pressurized by, for example, a hot stamp or a pair of rollers, and is stuck on the parallel plane 10a of the coaxial cables 10.

The base material 21 of the insulating film 20 is constructed of a resin having insulation, for example, polyester. A thickness of the base material 21 is formed in, for example, 8 to 20 μm. The thermoplastic adhesive layer 22 is constructed of an adhesive of, for example, epoxy resin, acrylic resin or polyamide. A thickness of the thermoplastic adhesive layer 22 is formed in, for example, 30 to 67 μm. Each of the coaxial cables 10 is fixed to the thermoplastic adhesive layer 22 with a part of the coaxial cable 10 buried in the thermoplastic adhesive layer 22. The thermoplastic adhesive layer is preferably set in the thickness thinner than a diameter of the coaxial cable 10 with the coaxial cables stuck as shown in Fig. 2. In other words, preferably, a part of the coaxial cable makes contact with the base material and also the other part of the coaxial cable is exposed from the thermoplastic adhesive layer.

In the case of fixing plural coaxial cables arranged in parallel in a flat cable conventionally, base materials were stuckand fixed so as to sandwich a parallel plane of the coaxial cables from both vertical sides of the parallel plane. However, in this configuration, the flat cable often became thick and also hard since the base materials were stuck on the vertical sides of the parallel plane. In such a flat cable, it may become difficult to arrange the coaxial cables according to a wiring path. For example, when the stuck portions of the base materials are folded in a direction intersecting with the parallel plane, the folded and stacked portions including the thickness of the base materials stuck on both surfaces become thick, with the result that it becomes difficult to maintain a folded state by the restoring forces of the base materials.

On the other hand, according to the flat cable 1 of the embodiment, the insulating film 20 is stuck on only one side of the parallel plane 10a of the coaxial cables with the coaxial cables 10 arranged in parallel, the coaxial cable 10 in which a cross-sectional area of the central conductor 11 is 0.006 mm² or less. As a result, an increase in thickness of the flat cable 1 is prevented and the flat cable 1 thinner and softer than a conventional flat cable can be obtained. Accordingly, flexibility of bending according to a wiring path can be improved and, for example, wiring can easily be carried out with the whole flat cable 1 arched.

Also, according to the flat cable 1 of the embodiment, the sheath 14 of the coaxial cable 10 and the thermoplastic adhesive layer 22 of the insulating film 20 are formed of the same kind of material to enhance adhesion properties. As a result, for example, by sticking the insulating film 20 while heating using a hot stamp, a roller, etc. , each of the coaxial cables 10 can tightly be fixed to the insulating film 20 of only one surface while ensuring softness and thinness.

Also as described above, by sticking the insulating film 20 and fixing each of the coaxial cables 10, a deviation of a distance (for example, a deviation of the coaxial cables due to meandering) can be prevented from occurring in each of the coaxial cables 10 arranged in parallel in the case of a step of fixing the coaxial cables 10. Consequently, for example, work in the case of soldering the distal ends 11A, 11B of each of the coaxial cables 10 to a substrate or work in the case of attaching connectors to the distal ends 11A, 11B can be done easily. Also, when an edge part (rest portion) of the insulating film 20 in a width direction is cut and removed after the insulating film 20 is stuck on the coaxial cables 10, there is no meandering portion caused by the deviation of the distance, with the result that the coaxial cables 10 can be prevented from being damaged in the case of cutting the edge part. Also, a decrease in skew characteristics in the case of differential transmission, caused by a length difference between each of the coaxial cables 10 can be prevented.

Also, each of the coaxial cables 10 can be fixed to the insulating film 20 in a short time by using the thermoplastic adhesive layer 22 with short solidification time. As a result, after the coaxial cables 10 are fixed, adhesion properties are not left on an exposed surface of the thermoplastic adhesive layer 22. Hence, a foreign substance can be prevented from adhering to the periphery of the coaxial cables 10 on the side which is not covered with the base material 21.

Thus, the insulating film 20 is stuck on only one surface side of the coaxial cables 10 arranged in parallel, but the thermoplastic adhesive layer 22 is tightly fixed to the sheath 14 and gaps between the coaxial cables are filled with the thermoplastic adhesive layer 22, with the result that the five coaxial cables 10 can surely be fixed while maintaining thinness and softness.

(Modified example 1)

Next, a modified example 1 (a flat cable 2) of the flat cable 1 will be described with reference to each drawing.

As shown in Fig. 3, in the flat cable 2 of the modified example 1, each coaxial cable 10 is bent in

bent parts

30a, 30b oftwo places and is formed in a crank shape in a plane arranged in parallel. In the present example, a direction X shown in Fig. 3 is a direction in which each coaxial cable 10 extends, and is called a longitudinal direction X of the coaxial cable 10. Each of the coaxial cables 10 of the flat cable 2 is bent in the same direction in substantially the same position mutually in the longitudinal direction X while maintaining an equal distance without changing an arrangement order in a parallel plane of the coaxial cables 10 arranged in parallel in a plane state. Bending angles of the coaxial cable 10 in the

bent parts

30a, 30b are set at any angles. In the present example, each of the coaxial cables 10 is bent at an angle of about 60°in respectively opposite directions in the

bent parts

30a, 30b of two places.

An insulating film 20 is formed in a crank shape along an external shape of arrangement of the coaxial cables 10 so as to cover the whole five coaxial cables 10 bent. The insulating film 20 is stuck on only one side of a parallel plane 10a of the coaxial cables 10 (see Fig. 2) .

Next, a manufacturing method of the flat cable 2 will be described with reference to each drawing.

The flat cable 2 is manufactured using a manufacturing apparatus 40 shown in Fig. 4. In Fig. 4, each of the coaxial cables 10 reeled out of each supply reel 51 of a coaxial cable supply part 41 is aligned in a parallel state by a coaxial cable aligning part 42 and then is fed to a processing part 43.

In the processing part 43, the coaxial cables 10 are bent in a parallel plane by a block structural body 60 shown in Figs. 5A and 5B. Specifically, as shown in Figs. 5A and 5B, a first alignment block 61 is moved in a direction (downward direction of the drawing) intersecting with a longitudinal direction of

groove parts

61a, 62a with respect to a second alignment block 62 in a state in which each of the coaxial cables 10 is received inside the

groove parts

61a, 62a. Accordingly, the coaxial cables 10 received inside the

groove parts

61a, 62a are pulled laterally by the first alignment block 61 and are bent at an angle of about 60°.

Subsequently, the insulating film 20 is supplied to the upward side of the parallel plane 10a of the coaxial cables 10. The insulating film 20 is pressed and heated on the coaxial cables 10 by a heater plate downwardly moved from the upward side. Accordingly, the insulating film 20 is stuck on only one side of the parallel plane 10a of the coaxial cables 10, and the coaxial cables 10 are fixed by a thermoplastic adhesive layer 22.

A flat cable processed by the processing part 43 is wound on a reel 52 of a winding part 44 (see Fig. 4) . The flat cable 2 (see Fig. 3) having the

bent parts

30a, 30b of two places bent at an angle of about 60°in opposite directions is obtained by cutting the strip-shaped flat cable wound on the reel 52 in a predetermined length.

According to the flat cable 2 of the modified example 1, it is unnecessary to bend the coaxial cables 10 again in the case of bending wiring paths of the coaxial cables 10 since each of the coaxial cables 10 is formed in the shape in which the wiring path is previously bent by the

bent parts

30a, 30b. As a result, the bent part can be softened and thinned in thickness since the coaxial cable is not stacked on the other coaxial cables so as to run on as compared with a flat cable constructed so that a part of the wiring path must be bent so as to be folded in the case of bending the wiring path.

(Modified example 2)

Next, a modified example 2 (a flat cable 3) of the flat cable 1 will be described with reference to each drawing.

As shown in Fig. 6, in the flat cable 3, coaxial cables 10 are bent in a bent part 30c of one place and are formed in an L shape in a plane arranged in parallel. Each of the coaxial cables 10 of the flat cable 3 is bent in the same direction while maintaining the same positional relation mutually and maintaining an equal distance without changing an arrangement order in a parallel plane of the coaxial cables 10. A bending angle of the coaxial cable 10 in the bent part 30c is bent at any angle (about 90°in the present example) . As shown in Fig. 6, the coaxial cable 10 may be bent in a circular arc shape and the straight portion may have an angle of about 90°. In a manner similar to the example described above, an insulating film 20 is formed in an L shape along an external shape of arrangement of the coaxial cables 10 and is stuck on only one side of a parallel plane 10a. In the flat cable of the present example, the coaxial cables are fitted into predetermined grooves and the insulating film 20 is stuck while heating using a hot stamp, a roller, etc. and thereby, manufacturing variations in any shape do not occur and the flat cables are mass-produced at low cost. The coaxial cables 10 may be bent and also be aligned and directly stuck on a thermoplastic adhesive on a base material.

Also in the flat cable 3 with the shape as shown in modified example 2, the bent part can be softened and thinned in thickness in a manner similar to the example described above.

[Example]

Constant-temperature tests and distalend processing evaluations were made on each of the flat cables 1 to 3 described above.

(Test specimen and evaluation specimen)

The flat cables 1 to 3 described above are set as target specimens.

As a coaxial cable 10, a cable with 44AWG and an outside diameter of 0.26 mm is used. As an insulating film 20, a film having a base material 21 with a thickness of 20 μm and a thermoplastic adhesive layer 22 with a thickness of 55 μm is used. Athickness of each of the flat cables 1 to 3 is 0.28 mm.

(Constant-temperature test)

After the flat cables 1 to 3 are left for 96 hours in each of the constant-temperature chambers of -40℃, 65℃and 95℃, a state of each of the members is observed.

(Test result)

In all of the flat cables 1 to 3, cracks in the thermoplastic adhesive layer 22 and peeling of the base material 21 did not occur, and each of the coaxial cables 10 was fixed by the insulating film 20 and had no abnormality.

(Distal end processing evaluation)

In the ends of the flat cables 1 to 3, a width direction which is a parallel direction of the coaxial cables 10 is irradiated with a laser, and the insulating film 20 and sheaths 14 of the coaxial cables 10 are burned off and the distal ends are removed.

Outer conductors 13 of the coaxial cables 10 exposed by removing the insulating film 20 and the sheaths 14 are immersed in a solder bath, and each of the outer conductors 13 is soldered.

(Evaluation result)

The insulating film 20 and the sheaths 14 could be burned off collectively with laser. Also, the insulating film 20 and the sheaths 14 burned off could be removed collectively.

The insulating film 20 and the sheaths 14 which were not removed in the coaxial cables 10 had no damage from cutting, and the outer conductors 13 could be soldered.

In addition, the invention is not limited to the embodiment described above, and modifications, improvements, etc. can properly be made freely. Moreover, materials, shapes, dimensions, numerical values, forms, the number of components, arrangement places, etc. of each of the components in the embodiment described above are freely selected and are not limited as long as the invention can be achieved.

Reference Signs List

1, 2, 3: FLAT CABLE

10: COAXIAL CABLE

10a: PARALLEL PLANE

11: CENTRAL CONDUCTOR

14: SHEATH

20: INSULATING FILM

21: BASE MATERIAL

22: THERMOPLASTIC ADHESIVE LAYER

30a, 30b, 30c: BENT PART

X: LONGITUDINAL DIRECTION OF COAXIAL CABLE

Claims

A flat cable comprising:

a plurality of coaxial cables mutually arranged in parallel, the coaxial cable in which a cross-sectional area of a central conductor is 0.006mm² or less； and

an insulating film having a base material, and a thermoplastic adhesive layer formed on the base material,

wherein the insulating film is stuck on only one side of a parallel plane of the plurality of coaxial cables, and the plural coaxial cables are fixed to the thermoplastic adhesive layer.
The flat cable as claimed in claim 1, wherein the insulating film is stuck on only one side of the parallel plane in a state in which each of the coaxial cables is bent in the same direction while being mutually arranged in parallel in the parallel plane.
The flat cable as claimed in claim 1 or 2, wherein a part of the coaxial cable makes contact with a base material and the other part of the coaxial cable is exposed from a thermoplastic adhesive layer.
The flat cable as in any one of claims 1 to 3, wherein a sheath of the coaxial cable is formed by winding a polyester tape.
The flat cable as claimed in claim 4, wherein the base material of the insulating film is polyester, and the thermoplastic adhesive layer is a polyester adhesive.