JP6645364B2 - Flexible flat cable with shield and manufacturing method thereof - Google Patents

Description

  The present invention relates to a shielded flexible flat cable and a method for manufacturing the same.

  2. Description of the Related Art As electronic devices become smaller and lighter, electrical wiring members between electronic components mounted on the electronic devices are required to be small and highly flexible so that wiring can be performed in a limited space. As such an electric wiring member, for example, there is a flexible flat cable using a flexible rectangular conductor. In particular, a shielded flexible flat cable having a shield function is used for wiring of an electronic device that requires noise countermeasures.

  In the flexible flat cable, a plurality of conductors including a ground line are arranged in parallel, and an insulating layer is provided around the plurality of conductors. In the flexible flat cable with a shield, a shield layer such as a metal foil is further provided so as to cover the insulating layer, and the ground line and the shield layer are electrically connected.

  As an electrical connection structure between the ground line of the shielded flexible flat cable and the shield layer, a structure in which the ground line is exposed on the surface side of the insulating layer and the exposed ground line and the shield layer are electrically connected has been proposed. (See JP-A-2009-123563). Specifically, in this conventional shielded flexible flat cable, a ground wire is cut at a portion other than the end in the longitudinal direction, and the cut ground wire is folded back to the surface side of the insulating layer to be exposed. , A shield layer is provided via a conductive adhesive layer. In the above-mentioned conventional shielded flexible flat cable, the ground line folded back to the surface side of the insulating layer and the shield layer are electrically connected by the conductive adhesive layer.

JP 2009-123563 A

  In the above-mentioned conventional structure, the ground line and the shield layer are bonded via a conductive adhesive layer. The conductive adhesive contains, for example, a conductive filler and the like, and the ground line and the shield layer are electrically connected via the conductive filler. Therefore, in order to electrically stably connect the ground line and the shield line, it is necessary to apply a relatively thick conductive adhesive to increase the density of the conductive filler. Further, in the above-described conventional structure, the conductive adhesive layer also plays a role of bonding the shield layer and the insulating layer. Therefore, the conductive adhesive is applied to a portion other than the portion where the ground line and the shield layer are connected. Therefore, the conventional structure requires a relatively large amount of conductive adhesive. Further, since the cost per unit amount of this conductive adhesive is higher than that of the non-conductive adhesive, the above-mentioned conventional shielded flexible flat cable is likely to increase in manufacturing cost and has room for improvement.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a shielded flexible flat cable excellent in manufacturing cost and a method for manufacturing the same.

  A shielded flexible flat cable according to one aspect of the present invention is a flat cable main body having a plurality of conductors arranged in parallel and including one or more ground wires and an insulating layer provided around the plurality of conductors. And a shielded flexible flat cable comprising a shield tape disposed so as to cover the flat cable body, wherein the shield tape is a non-conductive layer laminated on the shield layer and the flat cable body side of the shield layer. The flat cable main body, wherein one or more ground lines of the flat cable main body are exposed on a surface of the flat cable main body at a part of a shield tape covering area. Laminated between the exposed portion of the ground line and the shield tape, and Further comprising a conductive sheet for electrically connecting the lines and the shield layer.

  A method for manufacturing a shielded flexible flat cable according to another aspect of the present invention includes a plurality of conductors including one or more ground wires arranged in parallel, and an insulating layer disposed around the plurality of conductors. A method for manufacturing a shielded flexible flat cable, comprising: a flat cable main body having: and a shield tape disposed to cover the flat cable main body, wherein the shield tape is laminated on the shield layer and the shield layer. A step of partially exposing the ground wire of the flat cable main body to the surface of the flat cable main body, and a step of electrically exposing the ground wire exposed portion of the flat cable main body. Laminating a conductive sheet, and covering the conductive sheet on the surface side of the flat cable main body. And a step of arranging the shield tape so that the adhesive layer is on the flat cable main body side, and a step of thermocompression bonding the flat cable main body, the conductive sheet and the shield tape, wherein the conductive sheet is formed of the ground wire. And the shield layer are electrically connected.

  The shielded flexible flat cable of the present invention and the method of manufacturing the same are excellent in manufacturing cost.

It is a top view of a shielded flexible flat cable of one embodiment of the present invention. It is sectional drawing in the AA line of the flexible flat cable with a shield of FIG. It is sectional drawing in the BB line of the flexible flat cable with a shield of FIG. It is sectional drawing in CC line of the flexible flat cable with a shield of FIG. It is sectional drawing of the flexible flat cable with a shield which concerns on embodiment different from the flexible flat cable with a shield of FIG.

[Description of Embodiment of the Present Invention]
A shielded flexible flat cable according to one aspect of the present invention is a flat cable main body having a plurality of conductors arranged in parallel and including one or more ground wires and an insulating layer provided around the plurality of conductors. And a shielded flexible flat cable comprising a shield tape disposed so as to cover the flat cable body, wherein the shield tape is a non-conductive layer laminated on the shield layer and the flat cable body side of the shield layer. The flat cable main body, wherein one or more ground lines of the flat cable main body are exposed on a surface of the flat cable main body at a part of a shield tape covering area. Laminated between the exposed portion of the ground line and the shield tape, and Further comprising a conductive sheet for electrically connecting the lines and the shield layer.

  In the flexible flat cable with a shield, the ground line exposed on the surface of the flat cable main body and the shield layer are electrically connected by a conductive sheet. Therefore, in the flexible flat cable with a shield, there is no need to conduct the ground line and the shield layer by the adhesive layer, and the adhesive layer can be made non-conductive. For this reason, in the shielded flexible flat cable, it is not necessary to consider the conductivity of the adhesive layer, so that the amount of the applied adhesive can be relatively reduced. Therefore, coupled with the fact that the cost per unit amount of the non-conductive adhesive is lower than the cost of the conductive adhesive, the flexible flat cable with the shield reduces the manufacturing cost as compared with the case where the conductive adhesive layer is used. Can be reduced.

  Preferably, the conductive sheet has a porous core material and a conductive adhesive. Since the conductive sheet has the porous core material as described above, the conductive adhesive can be impregnated inside the porous core material. The electrical connection between the ground line and the shield layer can be more reliably obtained by the impregnated conductive adhesive.

  Preferably, the core is a non-conductive nonwoven fabric. Since the nonwoven fabric rebounds resiliently, by making the core material a nonwoven fabric, the contact between the conductive sheet and the ground wire and the shield layer can be obtained more reliably. In addition, since the non-conductive non-woven fabric is less expensive than the conductive non-woven fabric, the manufacturing cost of the shielded flexible flat cable can be reduced by using the non-conductive non-woven fabric as the core material.

  It is preferable that the conductive sheet has a conductive and porous core material. By making the core material of the conductive sheet conductive and porous in this way, during the production of the shielded flexible flat cable, between the conductive sheet and the ground wire, or between the conductive sheet and the shield layer. Even if a non-conductive adhesive invades between them, the invading adhesive can be absorbed by the conductive sheet. Therefore, the electrical connection between the ground line and the shield layer can be obtained more reliably.

  The core is preferably a conductive nonwoven fabric. Since the nonwoven fabric is elastically repelled, the contact resistance between the ground wire and the shield layer can be relatively reduced by using the conductive material as the core material. Further, since the nonwoven fabric has a relatively high fiber density, it has relatively high conductivity. For this reason, by making the core material a conductive nonwoven fabric, the electrical connectivity is improved.

  A method for manufacturing a shielded flexible flat cable according to another aspect of the present invention includes a plurality of conductors arranged in parallel and including one or more ground wires, and an insulating layer disposed around the plurality of conductors. A method of manufacturing a shielded flexible flat cable, comprising: a flat cable main body having: A step of partially exposing the ground wire of the flat cable main body to the surface of the flat cable main body, and a step of electrically exposing the ground wire exposed portion of the flat cable main body. Laminating a conductive sheet, and covering the conductive sheet on the surface side of the flat cable main body. And a step of arranging the shield tape so that the adhesive layer is on the flat cable main body side, and a step of thermocompression bonding the flat cable main body, the conductive sheet and the shield tape, wherein the conductive sheet is provided with the ground wire And the shield layer are electrically connected.

  The manufacturing method of the shielded flexible flat cable includes a step of thermocompression bonding the flat cable main body, the conductive sheet, and the shield tape. The adhesive layer is melted by this thermocompression bonding and is extruded from between the conductive sheet and the shield layer of the shield tape, so that the conductive sheet and the shield layer are electrically connected. Therefore, there is no need to conduct the ground line and the shield layer by the adhesive layer, and the adhesive layer can be made non-conductive. For this reason, in the method for manufacturing the shielded flexible flat cable, since the adhesive layer for bonding the shield layer and the insulating layer is non-conductive, the adhesive layer is more conductive than the conductive adhesive layer. The cost of the adhesive used can be reduced. Therefore, the method for manufacturing the shielded flexible flat cable is excellent in manufacturing cost.

[Details of Embodiment of the Present Invention]
Hereinafter, a shielded flexible flat cable and a method for manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the drawings.

[First embodiment]
[Flexible flat cable with shield]
The flexible flat cable 1 with a shield shown in FIGS. 1 to 4 includes a flat cable main body 2, a shield tape 3 disposed so as to cover the flat cable main body 2, and the flat cable main body 2 and the shield tape 3. And a conductive sheet 4 laminated therebetween.

<Flat cable body>
The flat cable main body 2 has a plurality of conductors 20 arranged in parallel and an insulating layer 21 provided around the plurality of conductors 20. The plurality of conductors 20 include a plurality of ground lines 20G. The flat cable main body 2 has a rectangular shape in which the length in the arrangement direction of the plurality of conductors 20 is larger than the length in the thickness direction in a cross-sectional view perpendicular to the length direction.

  The flat cable main body 2 has a folded structure of a plurality of ground wires 20G on one surface side. Hereinafter, as shown in FIG. 2, the side of the flat cable main body 2 having the folded structure of the ground line 20G will be described as an upper surface side, and the opposite surface side will be described as a lower surface side.

  The folded structure of the ground line 20G is configured such that the ground line 20G and the insulating layer 21 laminated on the upper surface side of the ground line 20G before the folding are folded back to the upper surface side. Therefore, the folded insulating layer 21 is located on the lower surface side of the folded ground line 20G, and the folded ground line 20G is exposed on the surface of the flat cable main body 2. In addition, a part of the exposed ground line 20 </ b> G is connected to the conductive sheet 4.

(conductor)
The conductor 20 is not particularly limited. For example, a general conductor such as an element wire such as copper, a copper alloy, and tin-plated copper, or a stranded wire can be used. Further, acicular crystals (whiskers) may be generated on the surface of the conductor 20 due to the application of compressive stress at a portion connected to an electronic component or the like. May be subjected to gold plating or the like. By applying gold plating in this way, even when the conductors 20 are arranged at a narrow pitch, a short circuit between the conductors 20 due to whiskers can be suppressed.

  The cross-sectional shape of the conductor 20 is not particularly limited, but may be, for example, a rectangular shape from the viewpoint that the average thickness of the flat cable main body 2 can be reduced.

  The lower limit of the average thickness of the conductor 20 is preferably 10 μm, more preferably 20 μm. On the other hand, the upper limit of the average thickness of the conductor 20 is preferably 100 μm, more preferably 70 μm. If the average thickness of the conductor 20 is less than the above lower limit, the mechanical strength of the conductor 20 may be insufficient. Conversely, if the average thickness of the conductor 20 exceeds the upper limit, the shielded flexible flat cable 1 may be unnecessarily thick.

  The lower limit of the average width of the conductor 20 is preferably 0.1 mm, more preferably 0.3 mm. On the other hand, the upper limit of the average width of the conductor 20 is preferably 3 mm, more preferably 2 mm. When the average width of the conductor 20 is less than the above lower limit, the conductivity may be insufficient. Conversely, when the average width of the conductor 20 exceeds the upper limit, the width of the shielded flexible flat cable 1 may be unnecessarily large.

  The lower limit of the average interval (average width of the gap) between the conductors 20 is preferably 0.1 mm, more preferably 0.2 mm. On the other hand, the upper limit of the average interval between the conductors 20 is preferably 0.7 mm, more preferably 0.5 mm. If the average interval between the conductors 20 is less than the above lower limit, there is a possibility that adjacent conductors 20 may contact each other. Conversely, if the average interval of the conductors 20 exceeds the upper limit, the width of the shielded flexible flat cable 1 may be unnecessarily large.

  The number of conductors 20 in the shielded flexible flat cable 1 can be increased or decreased as necessary and is not particularly limited, but may be, for example, 10 or more and 100 or less.

(Ground line)
The ground lines 20G are arranged in parallel with the other conductors 20. The ground line 20G is cut in the middle, and one cut side is folded back to the upper surface side of the flat cable main body 2 together with the insulating layer 21 laminated on the upper surface side of the ground line 20G before being folded. For this reason, the flat cable main body 2 has a gap at a position before the ground line 20G and the insulating layer 21 are folded back.

  Further, since the folded ground line 20G is electrically connected to the shield tape 3 via the conductive sheet 4, it is folded so as to be located at a part of the shield tape covering area of the flat cable main body 2. I have.

  The lower limit of the average length in plan view of the portion where the ground line 20G is folded and exposed on the upper surface of the flat cable main body 2 (ground line exposed portion) is preferably 5 mm, more preferably 7 mm. On the other hand, the upper limit of the average length of the exposed portion of the ground line is preferably 15 mm, more preferably 13 mm. If the average length of the exposed portion of the ground line is less than the lower limit, the connection resistance between the ground line 20G and the shield layer 30 may increase. Since the average length of the gap substantially coincides with the average length of the exposed portion of the ground line, the volume of the gap increases as the average length of the exposed portion of the ground line increases. Therefore, when the average length of the exposed portion of the ground line exceeds the upper limit, the strength of the flat cable main body 2 may be insufficient due to an increase in the volume of the gap.

(Insulating layer)
The insulating layer 21 is disposed between the pair of insulating films 21 a and the pair of insulating films 21 a disposed so as to sandwich the plurality of conductors 20 and is disposed so as to cover the periphery of the conductor 20. And a conductor holding adhesive layer 21b.

  The insulating film 21a is formed of a sheet member having flexibility and electrical insulation. Specifically, a resin film can be used as the insulating film 21a. As a main component of the resin film, for example, polyimide, polyester (eg, polyethylene terephthalate), polyphenylene sulfide, or the like is suitably used.

  As a minimum of average thickness of insulating film 21a, 9 micrometers is preferred and 12 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the insulating film 21a is preferably 75 μm, and more preferably 50 μm. If the average thickness of the insulating film 21a is less than the lower limit, the strength of the insulating film 21a may be insufficient. Conversely, when the average thickness of the insulating film 21a exceeds the upper limit, the shielded flexible flat cable 1 may be unnecessarily thick or the shielded flexible flat cable 1 may have insufficient flexibility. There is.

  The material of the conductor holding adhesive layer 21b is not particularly limited as long as it is non-conductive and can be bonded to the pair of insulating films 21a. For example, epoxy resin, polyimide, polyester, phenol resin, polyurethane, acrylic Examples include various resin-based adhesives such as resins, melamine resins, and polyamideimides. Above all, a thermoplastic resin which can be firmly bonded to the insulating film 21a by re-melting is preferable, and among these thermoplastic resins, polyester having excellent moldability, insulating properties, and the like is preferable.

  The lower limit of the average thickness of the conductor holding adhesive layer 21b (the average distance between the conductor 20 and the insulating film 21a) in a region overlapping with the conductor 20 in plan view is preferably 5 μm, and more preferably 10 μm. On the other hand, the upper limit of the average thickness is preferably 100 μm, more preferably 50 μm. If the average thickness is less than the lower limit, the bonding strength between the plurality of conductors 20 and the insulating film 21a may be insufficient. Conversely, if the average thickness exceeds the upper limit, the shielded flexible flat cable 1 may be unnecessarily thick.

(Opening)
The flat cable main body 2 has an opening 22 for forming a folded structure of the ground line 20G. The opening 22 includes a gap 22a at a position before the ground line 20G and the insulating layer 21 are folded back, and a cavity 22b located on the lower surface side of the gap 22a. The cavity 22 b of the opening 22 has a rectangular shape whose one side is substantially parallel to the longitudinal direction of the flat cable main body 2 in plan view. The upper surface of the cavity 22b of the opening 22 is constituted by an insulating layer 21 on the upper surface side of the conductor 20 excluding the ground line 20G, and the lower surface of the cavity 22b of the opening 22 is An opening in the surface.

  The length of one side of the cavity 22b of the opening 22 in the longitudinal direction of the flat cable body 2 is substantially equal to the average length of the gap 22a. The length of one side of the cavity 22b of the opening 22 in the width direction of the flat cable main body 2 is not particularly limited, and for example, is substantially equal to the entire width of the arrangement region of the plurality of conductors 20, as shown in FIG. be able to. Preferably, the conductor 20 and the shield layer 30 are insulated by an insulating member. For example, by using an insulating adhesive tape as an insulating member and closing the cavity 22b of the opening 22, the conductor 20 and the shield layer 30 can be insulated.

<Shield tape>
The shield tape 3 covers the flat cable main body 2. The shield tape 3 may be wound and disposed so as to cover the entire circumference of the flat cable main body 2 in a sectional view perpendicular to the length direction of the flat cable main body 2 as shown in FIG. You may arrange | position so that the flat cable main body 2 may be pinched by the shield tape 3. FIG. The shield tape 3 may cover the entire surface of the flat cable main body 2 or may cover a part of the surface.

  The shield tape 3 has a shield layer 30 and an adhesive layer 31 laminated on the flat cable main body 2 side of the shield layer 30.

(Shield layer)
The shield layer 30 of the shield tape 3 is formed from a conductive material. As a material of the shield layer 30, for example, a metal foil, a metal deposition film, a conductive woven fabric, a conductive nonwoven fabric, or the like can be used. In addition, examples of the component that expresses conductivity in the shield layer 30 include aluminum, copper, nickel, silver, and iron. When a metal deposition film is used as the shield layer 30, a base layer formed of, for example, a resin film or the like is provided on the outer surface side of the shield layer 30. As a specific example of the shield layer 30, a silver vapor-deposited film formed on the surface of an aluminum foil or a resin film is particularly preferably used.

  The lower limit of the average thickness of the shield layer 30 is preferably 0.05 μm, and more preferably 0.08 μm. On the other hand, the upper limit of the average thickness of the shield layer 30 is preferably 0.2 mm, more preferably 0.1 mm. If the average thickness of the shield layer 30 is less than the above lower limit, the electric resistance of the shield layer 30 may increase, and the shielding capability may be insufficient. Conversely, if the average thickness of the shield layer 30 exceeds the above upper limit, the thickness of the shielded flexible flat cable 1 may become unnecessarily large, or the flexibility of the shielded flexible flat cable 1 may be insufficient. There is a possibility that.

(Adhesive layer)
The adhesive layer 31 is laminated on the flat cable main body 2 side of the shield layer 30. The adhesive layer 31 may be laminated on the entire surface of the shield layer 30 in contact with the insulating layer 21 as shown in FIG. It may be laminated on the part.

  The adhesive layer 31 is non-conductive. The adhesive constituting the adhesive layer 31 is not particularly limited as long as it is non-conductive, but may be made of the same material as the conductor holding adhesive layer 21b.

  The lower limit of the average thickness of the adhesive layer 31 is preferably 1 μm, more preferably 3 μm. On the other hand, the upper limit of the average thickness of the adhesive layer 31 is preferably 20 μm, more preferably 10 μm. If the average thickness of the adhesive layer 31 is less than the lower limit, the adhesive strength between the insulating layer 21 and the shield layer 30 may be insufficient. On the other hand, if the average thickness of the adhesive layer 31 exceeds the upper limit, the flexible flat cable with shield 1 may be manufactured between the conductive sheet 4 and the ground line 20G or between the conductive sheet 4 and the shield layer 30 at the time of manufacturing the shielded flexible flat cable 1. And the non-conductive adhesive may easily enter between them, and the ground line 20G and the shield layer 30 may not be sufficiently electrically connected.

<Conductive sheet>
The conductive sheet 4 is laminated between the ground cable exposed portion of the flat cable main body 2 and the shield tape 3. The conductive sheet 4 includes a conductive core material 40 for electrically connecting the ground line 20G and the shield layer 30 to each other, a sheet adhesive layer 41 laminated on the flat cable body 2 side of the core material 40, Having.

  The core material 40 of the conductive sheet 4 is not particularly limited as long as it has conductivity, but the core material 40 is preferably porous. By making the core material 40 porous, a non-conductive material is provided between the conductive sheet 4 and the ground wire 20G or between the conductive sheet 4 and the shield layer 30 at the time of manufacturing the shielded flexible flat cable 1. Even when the conductive adhesive has entered, the entered adhesive can be absorbed by the conductive sheet 4. Therefore, the electrical connection between the ground line 20G and the shield layer 30 can be obtained more reliably.

  When the core material 40 is porous, the core material 40 is preferably in a mesh shape or a sponge shape. Since the ground line 20G connected to the conductive sheet 4 is exposed on the surface of the insulating layer 21, the shield layer 30 covering the ground line 20G rises above the surface of the insulating layer 21 at the exposed portion of the ground line. For this reason, in the exposed portion of the ground line, the shield layer 30 easily applies a pressing force for pressing the ground line 20G toward the insulating layer 21 side. Therefore, by forming the core material 40 into a mesh shape, the total area receiving the pressure is reduced, so that the pressure applied to the core material 40 is increased, and the electrical connection between the ground wire 20G and the shield layer 30 is improved. Is improved. In addition, since the core member 40 is made of a sponge, the core member 40 is elastically repelled by the pressing, so that the electrical connection between the ground line 20G and the shield layer 30 is improved.

  When the core material 40 has a mesh shape, examples of the core material 40 include a wire formed by coating a surface of polyethylene terephthalate (PET) or polyester with a metal such as copper or nickel in a mesh shape. Can be. When the core material 40 is in the form of a sponge, the core material 40 may include, for example, conductive urethane foam. Further, a conductive nonwoven fabric or the like can be used as the core material 40.

  Among them, as the core material 40, a conductive nonwoven fabric is preferable, and a conductive nonwoven fabric impregnated with a conductive adhesive is particularly preferable. Since the nonwoven fabric is elastically repelled by the pressing, the contact resistance between the ground line 20G and the shield layer 30 can be relatively reduced by using the conductive material as the core material 40. Further, since the nonwoven fabric has a relatively high fiber density, it has relatively high conductivity. For this reason, by making the core material 40 a conductive nonwoven fabric, the electrical connectivity is improved. Examples of such a conductive nonwoven fabric include a carbon nonwoven fabric, an organic fiber nonwoven fabric having a conductive fiber surface, and a metal nonwoven fabric using a metal fiber mainly containing Fe, Ni, or the like. Examples of the conductive adhesive include an adhesive in which a conductive filler such as metal particles is dispersed, a solder paste in which metal powder is kneaded with a flux, and the like.

  The conductive sheet 4 includes a sheet adhesive layer 41 laminated on the core material 40 on the flat cable main body 2 side. Since the conductive sheet 4 includes the sheet adhesive layer 41 as described above, the conductive sheet 4 can be relatively easily fixed to the flat cable main body 2 by the sheet adhesive layer 41. For this reason, when disposing the shield layer 30 in the manufacture of the shielded flexible flat cable 1, the conductive sheet 4 is less likely to be displaced. Therefore, the electrical connection between the ground line 20G and the shield layer 30 can be obtained more reliably.

  Examples of the material of the sheet adhesive layer 41 include a conductive adhesive and an adhesive. When the core member 40 is formed in a mesh shape, a non-conductive adhesive or pressure-sensitive adhesive may be used. When the core material 40 is in a mesh shape, for example, when the conductive sheet 4 is fixed to the flat cable main body 2 side, the conductive sheet 4 and the flat cable main body 2 are overlapped and pressed, so that the adhesive is applied. Moves to the grid portion of the mesh, and the conductive sheet 4 and the flat cable main body 2 can be electrically connected. Examples of such an adhesive include an acrylic adhesive and a polyurethane adhesive. In order to make the adhesive conductive, for example, a conductive filler of a metal such as silver, copper, or gold may be contained.

  The size of the conductive sheet 4 in plan view may be a size that can cover a part of the ground line exposed portion, but is preferably a size that covers the entire ground line exposed portion from the viewpoint of conductivity. .

  The lower limit of the average thickness of the core material 40 is preferably 10 μm, and more preferably 20 μm. On the other hand, the upper limit of the average thickness of the core material 40 is preferably 500 μm, more preferably 400 μm. When the average thickness of the core member 40 is less than the lower limit, the pressing by the shield layer 30 is insufficient, and the ground line 20 </ b> G and the shield layer 30 may not be sufficiently electrically connected. Conversely, if the average thickness of the core member 40 exceeds the upper limit, there is a possibility that the demand for downsizing the electronic device may be violated.

  The lower limit of the average thickness of the sheet adhesive layer 41 is preferably 1 μm, more preferably 2 μm. On the other hand, the upper limit of the average thickness of the sheet adhesive layer 41 is preferably 50 μm, and more preferably 30 μm. If the average thickness of the sheet adhesive layer 41 is less than the lower limit, the adhesive strength may be insufficient. Conversely, when the average thickness of the sheet adhesive layer 41 exceeds the upper limit, the conductive sheet 4 becomes unnecessarily thick, which may be against the demand for downsizing of the electronic device.

[Method of manufacturing flexible flat cable with shield]
The method for manufacturing the shielded flexible flat cable includes a flat cable main body forming step, a ground line exposing step, a conductive sheet laminating step, a shield tape arranging step, and a thermocompression bonding step. A flat cable main body 2 having a plurality of conductors 20 arranged in parallel and including a ground line 20G and an insulating layer 21 disposed around the plurality of conductors 20 by the method for manufacturing the shielded flexible flat cable; The shielded flexible flat cable 1 is provided so as to cover the flat cable main body 2 and includes a shield layer 30 and a shield tape 3 having an adhesive layer 31 laminated on the flat cable main body side of the shield layer 30. Can be manufactured.

<Flat cable body forming process>
In the flat cable main body forming step, the flat cable main body 2 is formed.

  In this step, a plurality of conductors 20 arranged in parallel are sandwiched between a pair of insulating films 21a having an adhesive layer laminated on opposing surfaces and heated. By this heating, the adhesive layers laminated on the respective insulating films 21a are melted and integrated to form a conductor holding adhesive layer 21b, and the pair of insulating films 21a and the conductors 20 are fixed, and the flat cable body 2 is fixed. To form

  Here, an opening corresponding to the hollow portion of the opening 22 is formed in advance on one of the pair of insulating films 21a. Thereby, together with the formation of the flat cable main body 2, a concave portion corresponding to the hollow portion of the opening 22 is formed, and the conductor 20 including the ground line 20G is exposed in the concave portion.

  The heating in the flat cable main body forming step can be performed, for example, by a heat roll at a temperature of 80 ° C to 200 ° C and a speed of 0.5 m / min to 10 m / min.

<Ground wire exposure process>
In the ground wire exposing step, the ground wire 20G of the flat cable main body 2 is partially exposed on the surface of the flat cable main body 2.

  This step can be performed, for example, by the following procedure. First, the ground line 20G exposed in the concave portion is cut from the lower surface side of the flat cable main body 2 to the upper surface side at one end thereof together with the insulating layer 21 laminated on the upper surface side of the ground line 20G. Further, the insulating layer 21 laminated on the upper surface side of the exposed ground line 20G is cut along the longitudinal direction of the flat cable main body 2 so as to be flush with the side surface of the ground line 20G. The cutting of the insulating layer 21 is performed on each of the two side surfaces of the ground line 20G. Next, the cut ground line 20G and the insulating layer 21 laminated on the upper surface side of the ground line 20G are folded back to the upper surface side. By folding back in this way, the ground wire 20G is partially exposed on the surface of the flat cable main body 2.

<Conductive sheet lamination process>
In the conductive sheet laminating step, the conductive sheet 4 is laminated so as to cover the exposed portion of the ground line of the flat cable main body 2.

  Specifically, since the conductive sheet 4 includes the core material 40 and the sheet adhesive layer 41, the conductive sheet 4 is laminated so that the sheet adhesive layer 41 of the conductive sheet 4 is on the flat cable main body 2 side. The conductive sheet 4 is fixed while covering the exposed portion of the ground line.

<Shield tape placement process>
In the shield tape arranging step, the shield tape 3 is arranged on the surface side of the flat cable main body 2 so as to cover the exposed portion of the ground line. The shield tape 3 is arranged such that the shield adhesive layer 31 is on the flat cable main body 2 side. The shield adhesive layer 31 is non-conductive.

<Thermo-compression bonding process>
In the thermocompression bonding step, the flat cable main body 2, the conductive sheet 4, and the shield tape 3 are thermocompression bonded.

  The thermocompression bonding can be performed using, for example, a heating laminator provided with a heating roller, a heating press, or the like. A specific heating temperature in the thermocompression bonding step can be, for example, 50 ° C. or more and 200 ° C. or less. In addition, the pressing load in the thermocompression bonding step can be, for example, 0.1 MPa to 5 MPa, and the pressing time can be, for example, 1 second to 60 seconds.

  The adhesive layer 31 is melted by the thermocompression bonding and is extruded from between the conductive sheet 4 and the shield layer 30 of the shield tape 3, so that the conductive sheet 4 and the shield layer 30 are electrically connected. Thereby, the ground line 20 </ b> G and the shield layer 30 are electrically connected via the conductive sheet 4.

〔advantage〕
In the shielded flexible flat cable 1, the ground wire 20 </ b> G exposed on the surface of the flat cable main body 2 and the shield layer 30 are electrically connected by the conductive sheet 4. Therefore, in the shielded flexible flat cable 1, there is no need to conduct the ground line 20G and the shield layer 30 by the adhesive layer 31, and the adhesive layer 31 can be made non-conductive. For this reason, in the shielded flexible flat cable 1, it is not necessary to consider the conductivity of the adhesive layer 31, so that the applied amount of the adhesive can be relatively reduced. Therefore, coupled with the fact that the cost per unit amount of the non-conductive adhesive is lower than the cost of the conductive adhesive, the flexible flat cable with shield 1 has a higher manufacturing cost than the case where the conductive adhesive layer is used. Can be reduced.

  In addition, the method for manufacturing the shielded flexible flat cable is excellent in manufacturing cost.

[Second embodiment]
[Flexible flat cable with shield]
The shielded flexible flat cable 5 shown in FIG. 5 has a flat cable main body 2, a shield tape 3 disposed to cover the flat cable main body 2, and a laminate between the flat cable main body 2 and the shield tape 3. And a conductive sheet 6 to be formed. The flexible flat cable with shield 5 has the same configuration as the flexible flat cable with shield 1 in FIG. 2 except for the configuration of the conductive sheet 6. Therefore, only the conductive sheet 6 will be described below.

<Conductive sheet>
The conductive sheet 6 is laminated between the ground line exposed portion of the flat cable main body 2 and the shield tape 3. The conductive sheet 6 has a porous core material and a conductive adhesive.

  The core material is not particularly limited as long as it is porous, and examples thereof include urethane foam and nonwoven fabric. The core material may be conductive, but is preferably non-conductive, and particularly preferably non-conductive nonwoven fabric. Since the ground line 20G connected to the conductive sheet 6 is exposed on the surface of the insulating layer 21, the shield layer 30 covering the ground line 20G rises above the surface of the insulating layer 21 at the exposed portion of the ground line. For this reason, in the exposed portion of the ground line, the shield layer 30 is likely to press the ground line 20G toward the insulating layer. Since the nonwoven fabric resiliently repels by this pressing, by making the core material a nonwoven fabric, the contact between the conductive sheet 6 and the ground wire 20G and the shield layer 30 can be obtained more reliably. Further, since the conductive sheet 6 obtains an electrical connection between the ground line 20G and the shield layer 30 by a conductive adhesive, the core material can be made non-conductive. Since the nonconductive nonwoven fabric is less expensive than the conductive nonwoven fabric, the manufacturing cost of the shielded flexible flat cable 5 can be reduced by using the nonconductive nonwoven fabric as the core material.

  The conductive adhesive impregnates the core material to electrically connect the ground line 20G and the shield layer 30. Examples of the conductive adhesive include an adhesive in which a conductive filler such as metal particles is dispersed, a solder paste in which metal powder is kneaded with a flux, and the like.

  The size of the conductive sheet 6 in plan view may be a size that can cover a part of the ground line exposed portion, but is preferably a size that covers the entire ground line exposed portion from the viewpoint of conductivity.

  The lower limit of the average thickness of the conductive sheet 6 is preferably 10 μm, and more preferably 20 μm. On the other hand, the upper limit of the average thickness of the conductive sheet 6 is preferably 500 μm, more preferably 400 μm. If the average thickness of the conductive sheet 6 is less than the lower limit, the pressing by the shield layer 30 may be insufficient, and the ground line 20G and the shield layer 30 may not be electrically connected sufficiently. Conversely, if the average thickness of the conductive sheet 6 exceeds the upper limit, there is a possibility that the demand for downsizing the electronic device may be violated.

[Method of manufacturing flexible flat cable with shield]
The method for manufacturing the shielded flexible flat cable includes a flat cable main body forming step, a ground line exposing step, a conductive sheet laminating step, a shield tape arranging step, and a thermocompression bonding step.

<Flat cable body forming process>
Since the flat cable main body forming step is the same as the flat cable main body forming step of the first embodiment, the description is omitted.

<Ground wire exposure process>
The ground line exposing step is the same as the ground line exposing step of the first embodiment, and a description thereof will be omitted.

<Conductive sheet lamination process>
In the conductive sheet laminating step, the conductive sheet 6 is laminated so as to cover the exposed portion of the ground line of the flat cable main body 2.

  Specifically, for example, a conductive sheet 6 in which a non-conductive nonwoven fabric is impregnated with a conductive adhesive in advance is prepared, and the conductive sheet 6 is fixed while covering the exposed portion of the ground line. Also, the conductive sheet 6 is laminated by first applying a conductive adhesive to the exposed portion of the ground wire of the flat cable main body 2, disposing a core material on the applied surface, and then thermocompression bonding the conductive adhesive. An agent may be impregnated into the core material. This thermocompression bonding may be performed by thermocompression bonding in a thermocompression bonding step described later.

<Shield tape placement process>
Since the shield tape arranging step is the same as the shield tape arranging step of the first embodiment, the description is omitted.

<Thermo-compression bonding process>
In the thermocompression bonding step, the flat cable main body 2, the conductive sheet 6, and the shield tape 3 are thermocompression bonded. The thermocompression bonding can be performed similarly to the thermocompression bonding of the first embodiment. The adhesive layer 31 is melted and extruded from between the conductive sheet 6 and the shield layer 30 of the shield tape 3. Further, the exposed portion of the ground wire of the flat cable main body 2 and the shield layer 30 are electrically connected by the conductive adhesive impregnating the core material of the conductive sheet 6 by the thermocompression bonding.

〔advantage〕
In the flexible flat cable 5 with a shield, since the conductive sheet 6 has a porous core material, a conductive adhesive can be impregnated inside the porous core material. The electrical connection between the ground line 20G and the shield layer 30 can be more reliably obtained by the impregnated conductive adhesive.

[Other Embodiments]
The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is not limited to the configuration of the above-described embodiment, but is indicated by the appended claims, and is intended to include all modifications within the scope and meaning equivalent to the appended claims. You.

  In the above embodiment, the case where the insulating layer of the flat cable main body has a pair of insulating films and the conductor holding adhesive layer disposed between the pair of insulating films has been described. The configuration of the layers is not limited to this. Examples of other configurations of the insulating layer include a configuration in which a plurality of conductors are sandwiched between a pair of insulating films, a configuration in which a plurality of conductors are covered only with a conductor holding adhesive layer, and the like.

  Further, the shield tape may further include a resin layer on a surface of the shield layer opposite to the adhesive layer. Since the shield tape has the resin layer, peeling and corrosion of the shield layer can be prevented. As the material of the resin layer, for example, the same material as the insulating film of the insulating layer can be used.

  In the above-described embodiment, the case where the folded structure of the ground line is provided on one side of the flat cable main body is described, but the folded structure of the ground line may be provided on both sides.

  Further, the flat cable main body may have an aperture insulating layer that covers an exposed conductor other than the ground line in the aperture. Since the flat cable main body has the opening insulating layer, the dent of the opening of the flat cable main body is reduced, and the flatness of the surface of the flat cable main body is increased, so that the adhesion to the shield tape is improved.

  Further, in the above-described embodiment, the configuration in which the ground wire is folded to be exposed on the surface of the flat cable main body has been described. However, the ground wire may be exposed to the surface in another configuration. As such a configuration, for example, a configuration in which a filling layer is provided on the lower surface side of a ground line cut in a tongue shape and the ground line is lifted to the upper surface side by the filling layer can be cited.

  In the first embodiment, the case where the conductive sheet has the sheet adhesive layer on the surface of the core material on the flat cable main body side has been described, but this sheet adhesive layer may be omitted. Conversely, the sheet adhesive layer may be provided on both sides of the core of the conductive sheet.

  In the above-described embodiment, the case where a plurality of exposed portions of the ground line is covered with one conductive sheet has been described. However, each exposed portion of the ground line may be covered with a conductive sheet.

  In the above embodiment, the case where the flat cable main body has a plurality of ground lines has been described, but the number of ground lines may be one.

  In the above embodiment, in the method for manufacturing a shielded flexible flat cable, a method in which a concave portion is provided in advance in a flat cable main body forming step, and a ground wire exposed in the concave portion in the ground line exposing step is folded back to the surface side, has been described. The ground wire may be exposed on the surface of the flat cable body by a method. As such a method, for example, a method of cutting the ground wire together with the insulating layer in a tongue shape except for one end in the longitudinal direction of the flat cable main body, peeling off the insulating layer on the lower surface side, and then turning it back to the upper surface side may be mentioned. it can.

  Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.

[No. 1]
A flat cable main body was prepared in which 20 rectangular conductors (average width 0.3 mm, average thickness 35 μm) arranged in parallel were fixed by an insulating film and an adhesive layer. The flat cable body used had an opening (average length: 10 mm × average width: 15 mm) corresponding to the hollow portion of the opening previously formed on one insulating film.

  The seventh and fourteenth conductors of the twenty conductors of the flat cable main body were used as ground lines. The portions of the ground wires exposed at the openings were cut off at one end thereof, and were then turned back to partially expose the ground wires to the surface of the flat cable main body.

  Next, a conductive mesh (“MST30” manufactured by Seiren Co., Ltd.) was prepared as a conductive sheet. The conductive mesh mainly includes Cu-Ni-plated polyester fibers, and has an average thickness of 0.03 mm.

  This conductive sheet was cut into a size of 10 mm × 10 mm and arranged so as to cover the ground line exposed on the surface of the flat cable main body.

  Next, a shield tape was wound so as to wrap the flat cable body, and thermocompression-bonded by a hot press at 100 ° C. and 0.3 MPa. As the above-mentioned shield tape, silver was deposited on PET having an average thickness of 25 μm with an average thickness of 0.1 μm, and an antioxidant layer was formed on this silver-deposited surface with a resin (“Nipporan 5199” and “Coronate 2023” manufactured by Tosoh Corporation). (A mixture having a weight ratio of 10: 1) was applied to form an average thickness of 0.3 μm, and a non-conductive adhesive (“Vylon 55ss” manufactured by Toyobo Co., Ltd.) was applied to the surface of the antioxidant layer. One coated at 3 μm was used.

  In this way, No. Thus, a shielded flexible flat cable was obtained.

[No. 2]
A conductive sponge (“Si-5007AMS” manufactured by Seiren Co., Ltd.) was prepared as a conductive sheet. This conductive sponge contains conductive urethane foam as a main component.

  No. 3 except that the conductive sheet was used. No. 1 in the same manner as the shielded flexible flat cable. A flexible flat cable with shield No. 2 was obtained.

[No. 3]
A conductive nonwoven fabric (“CN4490” manufactured by 3M) was prepared as a conductive sheet. This conductive non-woven fabric is mainly composed of Cu-Ni plated fibers, and has an average thickness of 0.05 mm.

  No. 3 except that the conductive sheet was used. No. 1 in the same manner as the shielded flexible flat cable. A flexible flat cable with shield No. 3 was obtained.

[No. 4]
A non-conductive nonwoven fabric ("JH-30015" manufactured by Japan Vilene Co., Ltd.) impregnated with a conductive adhesive was prepared as a conductive sheet. As the conductive adhesive, an adhesive diluted with toluene and methyl ethyl ketone to a concentration of 35% by weight (“Byron 55ss” of Toyobo Co., Ltd.) and a conductive filler (“TFM-L10F” of Toyo Aluminum Co., Ltd.) )) At a weight ratio of 100: 70.

  No. 3 except that the conductive sheet was used. No. 1 in the same manner as the shielded flexible flat cable. 4 was obtained.

[Measurement]
No. 1 to No. For the flexible flat cable with shield No. 4, the resistance between two ground wires was measured by a four-terminal method. Table 1 shows the results.

  From the results in Table 1, No. 1 to No. In the flexible flat cable with a shield of No. 4, the ground line exposed on the surface of the flat cable main body and the shield layer can be electrically connected by the conductive sheet. Therefore, No. 1 to No. It can be seen that the flexible flat cable with shield of No. 4 does not need to conduct the ground line and the shield layer by the adhesive layer, and can reduce the manufacturing cost as compared with the case of using the conductive adhesive layer.

  In addition, different conductive sheet Nos. 1 to No. Comparing the flexible flat cable with shield of No. 4 with No. 4 using a non-conductive nonwoven fabric impregnated with a conductive adhesive as a conductive sheet. 4 has a particularly low resistance value between the two ground lines. It can be seen that by using a non-conductive nonwoven fabric impregnated with a conductive adhesive as the conductive sheet, the electrical connection between the ground wire and the shield layer can be more reliably obtained by the impregnated conductive adhesive.

  The shielded flexible flat cable of the present invention and the method of manufacturing the same are excellent in manufacturing cost.

1, 5 Flexible flat cable with shield 2 Flat cable main body 3 Shield tape 4, 6 Conductive sheet 20 Conductor 20G Ground wire 21 Insulating layer 21a Insulating film 21b Conductor holding adhesive layer 22 Opening 22a Void 22b Cavity 30 Shield layer 31 Adhesion Agent layer 40 Core material 41 Sheet adhesive layer

Claims (6)

A flat cable body having a plurality of conductors arranged in parallel and including one or more ground lines, and an insulating layer provided around the plurality of conductors, and provided so as to cover the flat cable body. A flexible flat cable with a shield comprising a shield tape and
The shield tape has a shield layer and a non-conductive adhesive layer laminated on the flat cable body side of the shield layer,
At least one of the ground lines has a cut end,
A portion of the ground line including the cut end and an insulating layer portion disposed around a portion of the ground line have a folded portion that is folded,
It is configured such that a part of the ground line including the cut end is exposed at the folded portion ,
Further provided is a conductive sheet laminated between the folded portion and the shield tape, and electrically connecting a part of the exposed ground line and the shield layer ,
The average length of the exposed portion of the ground line in plan view is 5 mm or more and 15 mm or less,
Flexible flat cable shielded that have a hole adjacent to the ground line and the insulating layer folded back above.
  The flexible flat cable with a shield according to claim 1, wherein the conductive sheet has a porous core material and a conductive adhesive.   The flexible flat cable with a shield according to claim 2, wherein the core material is a non-conductive nonwoven fabric.   The flexible flat cable with a shield according to claim 1, wherein the conductive sheet has a conductive and porous core material.   The flexible flat cable with a shield according to claim 4, wherein the core material is a conductive nonwoven fabric. A flat cable body having a plurality of conductors arranged in parallel and including one or more ground lines and an insulating layer provided around the plurality of conductors, and provided to cover the flat cable body. A method for manufacturing a shielded flexible flat cable comprising a shield tape and
The shield tape has a shield layer and a non-conductive adhesive layer laminated on the shield layer,
Cutting at least one of the ground lines,
And a ground line having the cut off ends, a step of partially exposing wrap and an insulating layer disposed around the ground line on one surface of the flat cable body,
Laminating a conductive sheet so as to cover the folded ground line exposed portion of the flat cable body,
A step of covering the conductive sheet on the surface side of the flat cable main body, and arranging the shield tape such that the adhesive layer is on the flat cable main body side,
Thermocompression bonding of the flat cable body, conductive sheet and shield tape,
The conductive sheet electrically connects the folded ground line and the shield layer ,
The average length of the exposed portion of the ground line in plan view is 5 mm or more and 15 mm or less,
Method for manufacturing a shielded flexible flat cable with which have the apertures adjacent to the ground line and the insulating layer folded back above.

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