Shielded flat cable

Abstract

In the present invention, a shielded flat cable comprises a plurality of conductors that are arranged in parallel with one another, a first dielectric layer that covers the plurality of conductors and is formed by a first dielectric substance, and a shield layer that covers an outer surface of the first dielectric layer, wherein the shield layer is composed of a second dielectric layer that is formed by a second dielectric substance, a metal layer, an anchor coat layer, and a base material layer, said layers being layered in that order, the second dielectric layer including a flame retardant, the dielectric tangent of the second dielectric substance being greater than the dielectric tangent of the first dielectric substance, and the first dielectric layer and the second dielectric layer being bonded to each other.

Description

Technical Field

[0001] The present disclosure relates to a shielded flat cable.

Background Art

[0002] Patent Document 1 discloses a shielded flat cable having a plurality of conductors arranged in parallel with each other, a resin insulation layer covering the conductors, a shield layer covering the outer surface of the resin insulation layer, and a pair of flame-retardant resin films covering the outer surface of the shield layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The shielded flat cable of the present disclosure has a plurality of conductors arranged in parallel with each other, a first dielectric layer covering the plurality of conductors and formed of a first dielectric, and a shield layer covering the outer surface of the first dielectric layer. The shield layer is formed by laminating a second dielectric layer formed of a second dielectric, a metal layer, an anchor coat layer, and a base material layer in this order. The second dielectric layer contains a flame retardant, the dielectric tangent of the second dielectric is larger than the dielectric tangent of the first dielectric, and the first dielectric layer and the second dielectric layer are adhered to each other.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a cross-sectional view showing a shielded flat cable according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a shielded flat cable according to a second embodiment. [Figure 3] FIG. 3 is a cross-sectional view showing a modified example of the shielded flat cable according to the second embodiment. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] Shielded flat cables used for transmitting high-frequency signals require both excellent transmission characteristics and flame retardancy.

[0007] [Effects of this disclosure] According to this disclosure, shielded flat cables can achieve both transmission characteristics and flame retardancy.

[0008] The implementation methods are described below.

[0009] [Description of Embodiments in this Disclosure] The embodiments of this disclosure are first listed and described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description of them is not repeated.

[0010] [1] A shielded flat cable according to one aspect of the present disclosure comprises a plurality of conductors arranged in parallel with each other, a first dielectric layer formed of a first dielectric material covering the plurality of conductors, and a shield layer covering the outer surface of the first dielectric layer, wherein the shield layer is formed by laminating a second dielectric layer formed of a second dielectric material, a metal layer, an anchor coat layer, and a substrate layer in this order, the second dielectric layer contains a flame retardant, the dielectric loss tangent of the second dielectric is greater than the dielectric loss tangent of the first dielectric, and the first dielectric layer and the second dielectric layer are bonded together.

[0011] According to one aspect of this disclosure, a shielded flat cable can achieve both transmission characteristics and flame retardancy.

[0012] [2] In [1], the metal layer exposed at the widthwise end of the shield flat cable of the shield layer is covered along the direction in which the plurality of conductors extend, and an insulating layer formed of an insulator is provided. By providing the insulating layer, the dielectric strength can be improved.

[0013] [3] In [2], the exposed metal layer is covered with an insulating film. By covering the exposed metal layer with an insulating film, the dielectric strength can be improved.

[0014] [4] In [2], the exposed metal layer is covered with a single resin layer that seamlessly surrounds the shield layer. layer By covering the exposed metal layer with a single resin layer that seamlessly surrounds it, the dielectric strength can be improved.

[0015] [5] In any of [1] to [4], the dielectric loss tangent of the first dielectric is 0.001 or less. By making the dielectric loss tangent of the first dielectric 0.001 or less, the electrical characteristics of the signal propagating through the conductor can be improved.

[0016] [6] In any of [1] to [5], the thickness of the first dielectric layer is 120 μm or more. By making the thickness of the first dielectric layer 120 μm or more, the transmission characteristics of signals propagating through the conductor can be improved.

[0017] [7] In any of [1] to [6], the thickness of the second dielectric layer is 100 μm or less. By making the thickness of the second dielectric layer 100 μm or less, the influence of the second dielectric layer on the transmission characteristics of signals propagating through the conductor can be reduced.

[0018] [8] In any of [1] to [7], in a cross section perpendicular to the direction in which the plurality of conductors extend, the end of the shield layer is on the outer surface of the first dielectric layer. By having the end of the shield layer on the outer surface of the first dielectric layer in a cross section perpendicular to the direction in which the plurality of conductors extend, airtightness can be improved.

[0019] 〔9〕 The shielded flat cable according to one aspect of the present disclosure includes a plurality of conductors arranged in parallel with each other, a first dielectric layer covering the plurality of conductors and formed of a first dielectric, and a shield layer covering the outer surface of the first dielectric layer. The shield layer is formed by laminating a second dielectric layer formed of a second dielectric and a metal layer. The second dielectric layer contains a flame retardant, the dielectric tangent of the second dielectric is larger than the dielectric tangent of the first dielectric, the first dielectric layer and the second dielectric layer are adhered to each other, and the shield layer is surrounded by a protective layer made of resin.

[0020] According to the shielded flat cable according to one aspect of the present disclosure, the transmission characteristics and flame retardancy of the shielded flat cable can be achieved simultaneously.

[0021] [Details of Embodiments of the Present Disclosure] Hereinafter, embodiments of the present disclosure will be described in detail, but the present embodiments are not limited thereto. In the present specification and drawings, components having substantially the same functional configuration may be denoted by the same reference numerals to omit redundant descriptions. In each figure, an XYZ orthogonal coordinate system may be set for convenience of explanation.

[0022] (First Embodiment) The shielded flat cable according to the first embodiment will be described. FIG. 1 is a cross-sectional view showing a shielded flat cable 100 which is an example of the shielded flat cable according to the first embodiment. FIG. 1 shows a cross-section perpendicular to the longitudinal direction of the shielded flat cable 100.

[0023] The shielded flat cable 100 is a cable used for electrically connecting devices or for internal wiring of devices.

[0024] The shielded flat cable 100 includes a plurality of conductors 10, a dielectric layer 20, a shield layer 30, and an insulator layer 40.

[0025] As shown in Figure 1, the shielded flat cable 100 has a plurality of conductors 10 arranged along a plane 101 parallel to the XY plane. The plurality of conductors 10 are arranged in parallel with each other along the plane 101. Although four conductors 10 are explicitly shown in Figure 1, the number of conductors 10 is arbitrary. The shielded flat cable 100 only needs to have two or more conductors 10. The plurality of conductors 10 are arranged in a planar shape. The plurality of conductors 10 extend in the X-axis direction and are arranged in parallel in the Y-axis direction. The X-axis direction is the longitudinal direction of the shielded flat cable 100, and the Y-axis direction is the width direction of the shielded flat cable 100.

[0026] The conductor 10 is, for example, a round conductor. The conductor 10 is formed from a metal wire, such as copper wire, tin-plated soft copper wire, or silver-plated copper wire. The conductor 10 is formed in a circular shape in the YZ cross-section. Note that the conductor 10 is not limited to a round conductor; it may also be a rectangular conductor or an irregularly shaped conductor.

[0027] The shielded flat cable 100 has a dielectric layer 20 that covers multiple conductors 10, sandwiching a surface 101. For example, the dielectric layer 20 has a dielectric layer 21 on the -Z side of the surface 101 and a dielectric layer 22 on the +Z side of the surface 101. The dielectric layer 20 is a layer that ensures the dielectric breakdown voltage or high-frequency characteristics of the shielded flat cable 100.

[0028] The dielectric layer 20 is formed from a dielectric material. The dielectric material forming the dielectric layer 20 is, for example, made from polyolefin. The dielectric loss tangent of the dielectric layer 20 is 0.001 or less. The thickness of the dielectric layer 20 is, for example, 200 μm. In other words, the thickness of the dielectric layer 21 and dielectric layer 22 that constitute the dielectric layer 20 is 100 μm each.

[0029] The dielectric layer 20 may be formed from a single dielectric layer, or it may be formed from multiple dielectric layers, for example, five dielectric layers.

[0030] Note that dielectric layer 20 is an example of a first dielectric layer, and the dielectric forming dielectric layer 20 is an example of a first dielectric.

[0031] The dielectric material forming the dielectric layer 20 may be made from, for example, polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyester, and polyphenylene sulfide. Furthermore, the thickness of the dielectric layer 20 is not limited to 200 μm, but may be 120 μm or more. For example, the thickness of the dielectric layer 20 may be appropriately determined within the range of 120 μm to 2000 μm. In other words, the thicknesses of the dielectric layers 21 and 22 constituting the dielectric layer 20 may be appropriately determined within the range of 60 μm to 1000 μm. layer 20 The transmission characteristics of the shielded flat cable 100 can be improved by setting the dielectric loss tangent value (at 60Hz) to 0.001 or less. For even better transmission characteristics, it is preferable that the dielectric loss tangent of the dielectric material be 0.0005 or less.

[0032] The shielded flat cable 100 has a shielding layer 30 that covers the outer surface of the dielectric layer 20. The shielding layer 30 includes a shielding layer 30a that covers the outer surface 20A on the +Z side of the dielectric layer 20, The dielectric layer 20 has a shield layer 30b that covers the outer surface 20B on the +Y side, the outer surface 20C on the -Z side, and the outer surface 20D on the -Y side. Each of the shield layers 30a and 30b is an adhesive shield layer that includes a metal layer as a shield. Each of the shield layers 30a and 30b includes an adhesive layer 31 and a metal layer 32 that serves as a shield. Furthermore, each of the shield layers 30a and 30b has an anchor coat layer 33 and a base layer 34 in order outside the metal layer 32.

[0033] The shield layer 30 has a laminated portion 30F on its outer surface 20A side, at the +Y end of the shield layer 30a, where the shield layer 30b is laminated and bonded onto the shield layer 30a. The shield layer 30b has an end portion 30S where the metal layer 32 of the shield layer 30b is exposed. The shield layer 30 also has a laminated portion 30G on its outer surface 20A side, at the -Y end of the shield layer 30a, where the shield layer 30b is laminated and bonded onto the shield layer 30a. The shield layer 30b has an end portion 30T where the metal layer 32 of the shield layer 30b is exposed. The ends 30S and 30T are located above the outer surface 20A of the dielectric layer 20. The shield layer 30 has a central portion 30H on its upper side where the shield layer 30a is exposed. In the shielded flat cable 100, the adhesive layer 31 of the shield layer 30b is bonded to the base material layer 34 of the shield layer 30a in the laminated sections 30F and 30G, thereby improving airtightness.

[0034] The adhesive layer 31 is provided between the dielectric layer 20 and the metal layer 32, and adheres the dielectric layer 20 and the metal layer 32. The dielectric layer 20 and the adhesive layer 31 are bonded together. The adhesive layer 31 is a flame retardant-containing adhesive. The material of the adhesive layer 31 can be, for example, polyester resin or polyolefin resin. The adhesive layer 31 contains brominated flame retardants, nitrogen-based flame retardants, phosphorus-based flame retardants, or antimony trioxide as flame retardants. The dielectric loss tangent of the adhesive layer 31 is greater than 0.001. The thickness of the adhesive layer 31 is, for example, several μm. The thickness of the adhesive layer 31 is thinner than the respective thicknesses of the dielectric layer 21 and dielectric layer 22 in the dielectric layer 20.

[0035] Since the dielectric layer 20 is provided in contact with the conductor 10, the characteristics of the dielectric layer 20 greatly affect the transmission characteristics of the signal propagating through the conductor 10. For example, to improve flame retardancy, it is conceivable to add a flame retardant to the dielectric that makes up the dielectric layer 20, but adding a flame retardant to the dielectric that makes up the dielectric layer 20 will worsen the transmission characteristics (insertion loss) of the signal propagating through the conductor 10.

[0036] Therefore, in the shielded flat cable 100, in order to improve flame retardancy while suppressing deterioration of the transmission characteristics of the signal propagating through the conductor 10, no flame retardant is added to the dielectric layer, and the dielectric loss tangent value is set to 0.001 or less, while the adhesive layer 31 located inside the metal layer 32 of the shield layer 30 contains a flame retardant. The shielded flat cable 100 can suppress deterioration of the transmission characteristics of the signal propagating through the conductor 10 by providing a dielectric layer 20 and an adhesive layer 31 as dielectrics inside the metal layer 32 of the shield layer 30. Specifically, the insertion loss at 16 GHz can be reduced to 6 dB / m or less.

[0037] Furthermore, by providing the shielded flat cable 100 with an adhesive layer 31 containing a flame retardant inside the metal layer 32 of the shield layer 30, the flame retardancy of the shielded flat cable 100 can be improved.

[0038] In the shielded flat cable 100, both the dielectric layer 20 and the adhesive layer 31 are dielectrics, so the dielectric beneath the shielding metal layer 32 consists of multiple layers with different dielectric properties. In other words, the shielded flat cable 100 has two or more layers with different dielectric loss tangents beneath the shielding metal layer 32.

[0039] The dielectric material closest to the conductor 10 significantly affects the signal transmission characteristics. Therefore, the shielded flat cable 100 can maintain signal transmission characteristics by providing a thick layer with good dielectric properties in the dielectric layer 20. Furthermore, since the thickness of the adhesive layer 31, which acts as the dielectric on the underside of the shielding metal layer 32, is 100 μm or less, the shielded flat cable 100 can suppress the impact on signal transmission characteristics even if the dielectric properties of the adhesive layer 31 deteriorate slightly.

[0040] Because the adhesive layer 31 contains a flame retardant, a flame retardant is not required in the base layer 34 and the base layer 42. Therefore, since a flexible material without a flame retardant can be applied to each of the base layer 34 and the base layer 42, the shielded flat cable 100 can be made more flexible. In addition, since there is no need to provide an additional flame retardant layer on the outside of the shielded flat cable 100 to improve flame retardancy, the shielded flat cable 100 can be made thinner.

[0041] As described above, the shielded flat cable 100 achieves a balance between thinness, flexibility, transmission characteristics, and flame retardancy. The transmission characteristics are improved by reducing insertion loss.

[0042] The thickness of the adhesive layer 31 may be appropriately determined within the range of 1 μm to 100 μm.

[0043] Note that the adhesive layer 31 is an example of a second dielectric layer, and the dielectric forming the adhesive layer 31 is an example of a second dielectric.

[0044] The metal layer 32 is a layer that provides shielding functionality for noise reduction or ensuring high-frequency characteristics of the shielded flat cable 100. The metal layer 32 is formed from, for example, a metal foil such as copper foil or aluminum foil. The thickness of the metal layer 32 is, for example, 10 μm.

[0045] The anchor coat layer 33 is provided between the metal layer 32 and the base material layer 34, and adheres the metal layer 32 and the base material layer 34. The material of the anchor coat layer 33 is not limited. For example, a urethane-based anchor coat material can be used as the material of the anchor coat layer 33, which is a polyurethane main component mixed with an isocyanate-based curing agent. The anchor coat layer 33 is an example of an adhesive. The anchor coat layer 33 contains a brominated flame retardant, a nitrogen-based flame retardant, a phosphorus-based flame retardant, or antimony trioxide as a flame retardant.

[0046] The base layer 34 is a layer that mechanically and electrically protects the metal layer 32. The base layer 34 is formed of, for example, polyethylene terephthalate. The thickness of the base layer 34 is, for example, 5 to 25 μm.

[0047] The shielded flat cable 100 has an insulating layer 40 (insulating film) that covers each of the ends 30S and 30T where the metal layer 32 of the shield layer 30b is exposed. The insulating layer 40 covers each of the ends 30S and 30T along the direction in which the multiple conductors 10 extend. The insulating layer 40 is laminated on the upper part 40F of the laminated portion 30F of the shield layer 30. The insulating layer 40 is also laminated on the upper part 40G of the laminated portion 30G of the shield layer 30 G It is laminated on top of the other layer. Furthermore, the insulating layer 40 is laminated on the shield layer 30a in the central part 30H of the shield layer 30.

[0048] As described above, the insulating layer 40 is laminated on top of the shield layer 30, so that the ends 30S and 30T of the shield layer 30b, where the metal layer 32 is exposed, are covered by the insulating layer 40. By covering the ends 30S and 30T with the insulating layer 40, the shielded flat cable 100 can have a higher dielectric strength.

[0049] The structure of the insulating layer 40 will now be described. The insulating layer 40 includes an adhesive layer 41 and a base material layer 42.

[0050] The adhesive layer 41 is provided between the shield layer 30 and the base material layer 42, and adheres the shield layer 30 and the base material layer 42 together. The adhesive layer 41 is a flame retardant-containing adhesive.

[0051] The base layer 42 is a layer that protects the ends 30S and 30T of the shield layer 30. The base layer 42 is formed of, for example, polyethylene terephthalate.

[0052] The base material layer 42 may be a single-layer base material layer or a multi-layer base material layer.

[0053] The insulating layer 40 can improve dielectric strength by covering the ends 30S and 30T of the shielding layer 30b where the metal layer 32 is exposed. By improving dielectric strength, it is possible to meet the dielectric strength standards (AC1000V) specified in standards such as UL (UNDERWRITERS LABORATORIES).

[0054] Furthermore, if the shielded flat cable 100 meets the required specifications even without the insulating layer 40, the shielded flat cable 100 does not need to include the insulating layer 40.

[0055] (Second Embodiment) A shielded flat cable according to the second embodiment will now be described. Figure 2 is a cross-sectional view showing a shielded flat cable 200, which is an example of a shielded flat cable according to the second embodiment. Figure 2 shows a cross-section perpendicular to the longitudinal direction of the shielded flat cable 200. The shielded flat cable 200, which is an example of a shielded flat cable according to the second embodiment, has a protective layer 50 instead of the insulating layer 40 of the shielded flat cable 100.

[0056] The protective layer 50 is a layer that covers the entire perimeter of the shield layer 30 and protects the shield layer 30. The protective layer 50 is formed of an insulating material. The protective layer 50 is formed, for example, by wrapping tape, coating, or extrusion molding. The protective layer 50 may also be a jacket. The protective layer 50 is, for example, a single resin layer that seamlessly surrounds the shield layer 30. The protective layer 50 covers the exposed metal layer 32.

[0057] Similar to the shielded flat cable 100, the shielded flat cable 200 achieves a balance between thinness, flexibility, transmission characteristics, and flame retardancy.

[0058] Furthermore, if the shielded flat cable 200 has dielectric strength due to the protective layer 50 being made of an insulating material, the base material layer 34 in the shield layer 30 does not need to be included.

[0059] As a modification of the shielded flat cable according to the second embodiment, a shielded flat cable without the base material layer 34 will be described. Figure 3 is a cross-sectional view showing a shielded flat cable 210, which is an example of a modification of the shielded flat cable according to the second embodiment. Figure 3 shows a cross-section of the shielded flat cable 210 perpendicular to the longitudinal direction.

[0060] The shielded flat cable 210 has a shielding layer 130 in place of the shielding layer 30 of the shielded flat cable 200. The shielding layer 130 has shielding layers 130a and 130b in place of shielding layers 30a and 30b of the shielding layer 30. Each of the shielding layers 130a and 130b has an adhesive layer 31 and a metal layer 32 that serves as a shield.

[0061] Although embodiments have been described in detail above, the invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope described in the claims. [Explanation of Symbols]

[0062] 10 Conductors 20, 21, 22 Dielectric layers 20A, 20B, 20C, 20D Exterior Shield layers 30, 30a, 30b, 130, 130a, 130b 30F, 30G laminated section 30S, 30T end 30H central part 31 Adhesive layer 32 Metal layer 33 Anchor Coat Layer 34 Base material layer 40 Insulator layer 40F, 40G upper 41 Adhesive layer 42 Base material layer 50 protective layer 100, 200, 210 Shielded Flat Cable 101 sides

Claims

1. A plurality of conductors extending in a first direction and arranged in parallel with each other in a second direction intersecting the first direction, A first dielectric layer covering the plurality of conductors, formed of a first dielectric, having a first outer surface on the first side in the second direction, a second outer surface on the second side in a third direction intersecting the first and second directions, a third outer surface on the third side opposite to the first side in the second direction, and a fourth outer surface on the fourth side opposite to the second side in the third direction. A first shield layer covering the first outer surface, A second shield layer covering the second outer surface, the third outer surface, and the fourth outer surface, It has, Each of the first and second shield layers is formed by laminating a second dielectric layer made of a second dielectric, a metal layer, an anchor coat layer, and a substrate layer in this order. The second dielectric layer contains a flame retardant, and the dielectric loss tangent of the second dielectric is greater than the dielectric loss tangent of the first dielectric. The first shield layer has a first end in the second direction and a second end located opposite to the first end in the second direction. The second shield layer has a third end that is laminated and bonded on the first end, and a fourth end that is laminated and bonded on the second end, The first dielectric layer and the second dielectric layer of the first shield layer are bonded together, and the first dielectric layer and the second dielectric layer of the second shield layer are bonded together. Shielded flat cable.

2. The metal layer exposed at each of the third and fourth ends is covered along the first direction and has an insulating layer formed of an insulator, The shielded flat cable according to claim 1.

3. The exposed metal layer is covered with an insulating film. The shielded flat cable according to claim 2.

4. The exposed metal layer is covered with a single resin layer that seamlessly surrounds the first shield layer and the second shield layer. The shielded flat cable according to claim 2.

5. The dielectric loss tangent of the first dielectric is 0.001 or less. A shielded flat cable according to any one of claims 1 to 4.

6. The thickness of the first dielectric layer is 120 μm or more. A shielded flat cable according to any one of claims 1 to 4.

7. The thickness of the second dielectric layer is 100 μm or less. A shielded flat cable according to any one of claims 1 to 4.

8. In a cross-section perpendicular to the direction in which the plurality of conductors extend, the third end and the fourth end are located on the first outer surface, A shielded flat cable according to any one of claims 1 to 4.

9. A plurality of conductors extending in a first direction and arranged in parallel with each other in a second direction intersecting the first direction, A first dielectric layer covering the plurality of conductors, formed of a first dielectric, having a first outer surface on the first side in the second direction, a second outer surface on the second side in a third direction intersecting the first and second directions, a third outer surface on the third side opposite to the first side in the second direction, and a fourth outer surface on the fourth side opposite to the second side in the third direction. A first shield layer covering the first outer surface, A second shield layer covering the second outer surface, the third outer surface, and the fourth outer surface, It has, Each of the first and second shield layers is formed by laminating a second dielectric layer made of a second dielectric material and a metal layer. The second dielectric layer contains a flame retardant, and the dielectric loss tangent of the second dielectric is greater than the dielectric loss tangent of the first dielectric. The first shield layer has a first end that coincides with the edge of the first dielectric layer in the second direction, and a second end that is located opposite to the first end in the second direction and coincides with the edge of the first dielectric layer. The second shield layer has a third end that is laminated and bonded on the first end, and a fourth end that is laminated and bonded on the second end, The first dielectric layer and the second dielectric layer of the first shield layer are bonded together, and the first dielectric layer and the second dielectric layer of the second shield layer are bonded together. The first shield layer and the second shield layer are surrounded by a protective layer made of resin. Shielded flat cable.

Images