Shielded flat cable

Abstract

A shielded flat cable is provided with: a plurality of conductors parallel to each other; a first dielectric layer covering the plurality of conductors and formed of a first dielectric; and a shield layer covering an outer surface of the first dielectric layer, the shield layer being formed by laminating a second dielectric layer comprising a second dielectric, a metal layer, a tackifying coating layer, and a base material layer in this order, the second dielectric layer containing a flame retardant, the metal layer containing a flame retardant, the tackifying coating layer containing a flame retardant, and the base material layer containing a flame retardant. The dielectric loss tangent of the second dielectric medium is larger than that of the first dielectric medium, and the first dielectric medium layer is bonded with the second dielectric medium layer.

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; a resin insulating layer covering the conductors; a shielding layer having an adhesive covering the outer surface of the resin insulating layer; and a pair of flame-retardant resin films covering the outer surface of the shielding layer.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2022 / 003895 Summary of the Invention

[0006] The shielded flat cable disclosed herein comprises: a plurality of conductors arranged in parallel with one another; a first dielectric layer covering the plurality of conductors and formed of a first dielectric; and a shielding layer covering the outer surface of the first dielectric layer, the shielding layer being formed by stacking, in that order, a second dielectric layer formed of a second dielectric, a metal layer, an adhesion-promoting coating, and a base material layer, the second dielectric layer containing a flame retardant, the second dielectric having a dielectric loss tangent greater than that of the first dielectric, and the first dielectric layer and the second dielectric layer being bonded to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a cross-sectional view showing the shielded flat cable according to the first embodiment.

[0008] Figure 2 It is a cross-sectional view showing a shielded flat cable according to a second embodiment.

[0009] Figure 3 It is a cross-sectional view showing a modified example of the shielded flat cable according to the second embodiment. DETAILED DESCRIPTION

[0010] [Problems to be Solved by the Present Disclosure]

[0011] Shielded flat cables used for transmitting high-frequency signals are required to have both transmission characteristics and flame retardancy.

[0012] [Effects of the Present Disclosure]

[0013] According to the present disclosure, it is possible to achieve both transmission characteristics and flame retardancy of a shielded flat cable.

[0014] Hereinafter, a method for implementing the invention will be described.

[0015] [Description of Embodiments of the Present Disclosure]

[0016] First, the embodiments of the present disclosure will be described below. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0017] [1] A shielded flat cable according to one embodiment of the present disclosure includes: a plurality of conductors arranged in parallel; a first dielectric layer covering the plurality of conductors and formed of the first dielectric; and a shield layer covering the outer surface of the first dielectric layer, the shield layer being formed by laminating, in this order, a second dielectric layer formed of a second dielectric, a metal layer, an adhesion-promoting coating layer, and a base material layer, the second dielectric layer containing a flame retardant, the second dielectric layer having a dielectric loss tangent greater than that of the first dielectric, and the first dielectric layer and the second dielectric layer being bonded to each other.

[0018] According to the shielded flat cable of one aspect of the present disclosure, both transmission characteristics and flame retardancy of the shielded flat cable can be achieved.

[0019] [2] In [1], the shielded flat cable includes an insulating layer covering the metal layer exposed at the end portion of the shielded flat cable in the width direction of the shielded flat cable, along the direction in which the plurality of conductors extend, the insulating layer being formed of an insulator. The insulating layer can improve the dielectric strength.

[0020] [3] In [2], the exposed metal layer is covered with an insulating film. By covering the exposed metal layer with the insulating film, the dielectric strength can be improved.

[0021] [4] In [2], the exposed metal layer is covered with a single resin layer that surrounds the shield layer without interruption. By covering the exposed metal layer with a single resin layer that surrounds the shield layer without interruption, the dielectric strength can be improved.

[0022] [5] In any one of [1] to [4], the dielectric loss tangent of the first dielectric is less than or equal to 0.001. By setting the dielectric loss tangent of the first dielectric to be less than or equal to 0.001, the electrical characteristics of the signal propagating through the conductor can be improved.

[0023] [6] In any one 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 the signal propagating through the conductor can be improved.

[0024] [7] In any one 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 the signal propagating through the conductor can be reduced.

[0025] [8] In any one 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 located above the outer surface of the first dielectric layer. By having the end of the shield layer located above 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.

[0026] [9] A shielded flat cable according to one embodiment of the present disclosure includes: a plurality of conductors arranged in parallel with one another; 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 being formed by laminating a second dielectric layer formed of a second dielectric and a metal layer, the second dielectric layer containing a flame retardant, the second dielectric having a dielectric loss tangent greater than that of the first dielectric, the first dielectric layer and the second dielectric layer being bonded to each other, and the shield layer being surrounded by a protective layer formed of a resin.

[0027] According to the shielded flat cable of one aspect of the present disclosure, both transmission characteristics and flame retardancy of the shielded flat cable can be achieved.

[0028] [Details of the embodiments of the present disclosure]

[0029] The following describes the embodiments of the present disclosure in detail, but the embodiments are not limited to these. It should be noted that in this specification and the accompanying drawings, components with substantially the same functional configuration are sometimes denoted by the same reference numerals to omit duplicate descriptions. For ease of description, an XYZ orthogonal coordinate system is set in each figure.

[0030] (First embodiment)

[0031] A shielded flat cable according to a first embodiment will be described. Figure 1 1 is a cross-sectional view showing a shielded flat cable 100 as an example of the shielded flat cable according to the first embodiment. Figure 1 A cross section perpendicular to the longitudinal direction of the shielded flat cable 100 is shown.

[0032] The shielded flat cable 100 is a cable used for electrically connecting devices or for wiring within devices.

[0033] The shielded flat cable 100 includes a plurality of conductors 10 , a dielectric layer 20 , a shield layer 30 , and an insulator layer 40 .

[0034] like Figure 1 As shown in FIG. 1 , the shielded flat cable 100 includes a plurality of conductors 10 arranged along a surface 101 parallel to the XY plane. The plurality of conductors 10 are arranged in parallel along the surface 101. Figure 1 Although four conductors 10 are explicitly shown, the number of conductors 10 is arbitrary. The shielded flat cable 100 only needs to have two or more conductors 10. The multiple conductors 10 are arranged in a planar shape. For example, the multiple 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.

[0035] Conductor 10 is, for example, a circular conductor. Conductor 10 is formed from a metal wire such as copper wire, tinned annealed copper wire, or silver-plated copper wire. Conductor 10 is formed into a circular shape in the YZ cross-section. It should be noted that conductor 10 is not limited to a circular conductor and may also be a flat conductor or a special-shaped conductor.

[0036] The shielded flat cable 100 includes dielectric layers 20 covering a plurality of conductors 10 across a surface 101. For example, the dielectric layers 20 include 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 layers 20 are used to ensure the insulation withstand voltage and high-frequency characteristics of the shielded flat cable 100.

[0037] Dielectric layer 20 is formed of a dielectric. The dielectric forming dielectric layer 20 is formed, for example, from polyolefin. The dielectric loss tangent of dielectric layer 20 is equal to or less than 0.001. The thickness of dielectric layer 20 is, for example, 200 μm. In other words, dielectric layer 21 and dielectric layer 22 constituting dielectric layer 20 each have a thickness of 100 μm.

[0038] The dielectric layer 20 may be formed of a single dielectric layer or a plurality of dielectric layers, for example, five dielectric layers.

[0039] It should be noted that the dielectric layer 20 is an example of a first dielectric layer, and the dielectric forming the dielectric layer 20 is an example of a first dielectric.

[0040] It should be noted that the dielectric forming the dielectric layer 20 can also be formed of any resin selected from the group consisting of polyethylene, polypropylene, polyimide, polyethylene terephthalate, polyester, and polyphenylene sulfide. In addition, the thickness of the dielectric layer 20 is not limited to 200 μm, as long as it is greater than or equal to 120 μm. For example, the thickness of the dielectric layer 20 can also be appropriately determined within the range of 120 μm to 2000 μm. In other words, the thickness of each of the dielectric layer 21 and the dielectric layer 22 constituting the dielectric layer 20 can also be appropriately determined within the range of 60 μm to 1000 μm. By making the value of the dielectric loss tangent of the dielectric (value at 60 Hz) less than or equal to 0.001, the transmission characteristics of the shielded flat cable 100 can be improved. In order to make the transmission characteristics better, the dielectric loss tangent of the dielectric is preferably less than or equal to 0.0005.

[0041] The shielded flat cable 100 includes a shield layer 30 covering the outer surface of the dielectric layer 20. The shield layer 30 includes a shield layer 30a covering the outer surface 20A on the +Z side of the dielectric layer 20; and a shield layer 30b covering the outer surface 20B on the +Y side of the dielectric layer 20, the outer surface 20C on the -Z side of the dielectric layer 20, and the outer surface 20D on the -Y side of the dielectric layer 20. The shield layers 30a and 30b are adhesive-attached shield layers that include a metal layer as a shielding portion. The shield layers 30a and 30b each include an adhesive layer 31 and a metal layer 32 serving as a shielding portion. Furthermore, the shield layers 30a and 30b each have an adhesion promoter coating 33 and a base material layer 34 in this order on the outer sides of the metal layer 32.

[0042] The shield layer 30 has a laminated portion 30F formed by laminating and bonding the shield layer 30b on the shield layer 30a at the end on the +Y side of the shield layer 30a on the outer surface 20A side. The shield layer 30b has an end 30S where the metal layer 32 of the shield layer 30b is exposed. In addition, the shield layer 30 has a laminated portion 30G formed by laminating and bonding the shield layer 30b on the shield layer 30a at the end on the -Y side of the shield layer 30a on the outer surface 20A side. The shield layer 30b has an end 30T where the metal layer 32 of the shield layer 30b is exposed. The end 30S and the end 30T are located above the outer surface 20A of the dielectric layer 20. The shield layer 30 has a central portion 30H on the upper side where the shield layer 30a is exposed. In the shielded flat cable 100 , the adhesive layer 31 of the shield layer 30 b is bonded to the base material layer 34 of the shield layer 30 a in the laminated portion 30F and the laminated portion 30G, thereby improving airtightness.

[0043] Adhesive layer 31 is provided between dielectric layer 20 and metal layer 32 to bond dielectric layer 20 and metal layer 32. Dielectric layer 20 is bonded to adhesive layer 31. Adhesive layer 31 is an adhesive to which a flame retardant is added. Adhesive layer 31 may be made of, for example, polyester resin or polyolefin resin. Adhesive layer 31 may include, as flame retardants, brominated flame retardants, nitrogen flame retardants, phosphorus flame retardants, or antimony trioxide. The dielectric loss tangent of adhesive layer 31 is greater than 0.001. The thickness of adhesive layer 31 is, for example, several μm. The thickness of adhesive layer 31 is thinner than the thickness of each of dielectric layer 21 and dielectric layer 22 in dielectric layer 20.

[0044] Since the dielectric layer 20 is provided in contact with the conductor 10, the properties of the dielectric layer 20 significantly affect the transmission characteristics of the signal propagating through the conductor 10. For example, to improve flame retardancy, one approach is to add a flame retardant to the dielectric material constituting the dielectric layer 20. However, adding a flame retardant to the dielectric material constituting the dielectric layer 20 deteriorates the transmission characteristics (insertion loss) of the signal propagating through the conductor 10.

[0045] Therefore, in order to suppress degradation of the transmission characteristics of signals propagating through the conductor 10 and improve flame retardancy, the shielded flat cable 100 maintains a dielectric loss tangent of 0.001 or less. The adhesive layer 31 of the shield layer 30, located inside the metal layer 32, contains a flame retardant, rather than adding a flame retardant to the dielectric layer. By including the dielectric layer 20 and the adhesive layer 31 inside the metal layer 32 of the shield layer 30 as dielectrics, the shielded flat cable 100 suppresses degradation of the transmission characteristics of signals propagating through the conductor 10. Specifically, the insertion loss at 16 GHz can be reduced to 6 dB / m or less.

[0046] Furthermore, the shielded flat cable 100 includes the adhesive layer 31 to which the flame retardant is added on the inner side of the metal layer 32 of the shield layer 30 , thereby improving the flame retardancy of the shielded flat cable 100 .

[0047] In the shielded flat cable 100, both the dielectric layer 20 and the adhesive layer 31 are dielectric. Therefore, the dielectric layer beneath the metal layer 32, which forms the shield, 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 metal layer 32, which forms the shield.

[0048] The dielectric material close to the conductor 10 significantly affects signal transmission characteristics. Therefore, the shielded flat cable 100 maintains signal transmission characteristics by including a relatively thick layer with excellent dielectric properties in the dielectric layer 20. Furthermore, the thickness of the adhesive layer 31, which serves as a dielectric material below the metal layer 32 that forms the shield, is 100 μm or less. Therefore, even if the dielectric properties of the adhesive layer 31 deteriorate slightly, the effect on signal transmission characteristics is minimized in the shielded flat cable 100.

[0049] The adhesive layer 31 contains a flame retardant, eliminating the need for flame retardants in the base material layers 34 and 42. Consequently, the base material layers 34 and 42 can each be made of a flexible material that does not contain a flame retardant, thereby making the shielded flat cable 100 more flexible. Furthermore, since there is no need to provide a separate 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.

[0050] As described above, the shielded flat cable 100 aims to achieve a balance between thinness and flexibility, transmission characteristics, and flame retardancy. Regarding transmission characteristics, the improvement is in insertion loss.

[0051] It should be noted that the thickness of the adhesive layer 31 may be appropriately determined within the range of 1 μm to 100 μm.

[0052] It should be noted 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.

[0053] The metal layer 32 is a layer having a shielding function for noise suppression and ensuring high-frequency characteristics of the shielded flat cable 100. The metal layer 32 is formed of metal foil such as copper foil or aluminum foil, for example. The thickness of the metal layer 32 is, for example, 10 μm.

[0054] The adhesion coating 33 is provided between the metal layer 32 and the base material layer 34 to bond the metal layer 32 to the base material layer 34. The material of the adhesion coating 33 is not limited. For example, as the material of the adhesion coating 33, a urethane-based adhesion coating material can be used, which is formed by mixing an isocyanate-based curing agent with polyurethane as a main agent. The adhesion coating 33 is an example of an adhesive. The adhesion coating 33 includes a brominated flame retardant, a nitrogen-based flame retardant, a phosphorus-based flame retardant, and antimony trioxide as flame retardants.

[0055] The base material layer 34 is a layer that mechanically and electrically protects the metal layer 32. The base material layer 34 is formed of, for example, polyethylene terephthalate and has a thickness of, for example, 5 μm to 25 μm.

[0056] The shielded flat cable 100 includes an insulator layer 40 (insulating film) that covers the exposed ends 30S and 30T of the metal layer 32 of the shield layer 30b. The insulator layer 40 covers the ends 30S and 30T along the direction in which the plurality of conductors 10 extend. The insulator layer 40 is laminated on the laminated portion 30F of the shield layer 30 at an upper portion 40F. Furthermore, the insulator layer 40 is laminated on the laminated portion 30F at an upper portion 40G of the laminated portion 30G of the shield layer 30. Furthermore, the insulator layer 40 is laminated on the shield layer 30a at a central portion 30H of the shield layer 30.

[0057] The insulating layer 40 is stacked on the shield layer 30 as described above, so that the exposed ends 30S and 30T of the metal layer 32 of the shield layer 30b are covered by the insulating layer 40. Covering the ends 30S and 30T with the insulating layer 40 increases the dielectric strength of the shielded flat cable 100.

[0058] The structure of the insulating layer 40 will be described. The insulating layer 40 includes an adhesive layer 41 and a base material layer 42 .

[0059] The adhesive layer 41 is provided between the shielding layer 30 and the base material layer 42 to bond the shielding layer 30 to the base material layer 42. The adhesive layer 41 is an adhesive to which a flame retardant is added.

[0060] The base material layer 42 is a layer that protects the end portion 30S and the end portion 30T of the shield layer 30. The base material layer 42 is formed of, for example, polyethylene terephthalate.

[0061] It should be noted that the base material layer 42 may be a single-layer base material layer or a multi-layer base material layer.

[0062] The insulating layer 40 covers the exposed ends 30S and 30T of the metal layer 32 of the shield layer 30b, thereby improving the dielectric strength. This improved dielectric strength allows the device to meet the dielectric strength (AC1000V) standards specified in, for example, UL (Underwriters Laboratories) standards.

[0063] Note that, if the shielded flat cable 100 satisfies the required specifications even without the insulating layer 40 , the shielded flat cable 100 may not include the insulating layer 40 .

[0064] (Second embodiment)

[0065] A shielded flat cable according to a second embodiment will be described. Figure 2 1 is a cross-sectional view showing a shielded flat cable 200 as an example of a shielded flat cable according to the second embodiment. Figure 2 1 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 the shielded flat cable according to the second embodiment, includes a protective layer 50 instead of the insulating layer 40 of the shielded flat cable 100 .

[0066] The protective layer 50 is a layer that covers the entire periphery of the shielding layer 30 to protect the shielding layer 30. The protective layer 50 is formed from an insulating material. The protective layer 50 is formed, for example, by winding a 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 continuously surrounds the shielding layer 30. The protective layer 50 covers the exposed metal layer 32.

[0067] Similar to the shielded flat cable 100 , the shielded flat cable 200 aims to achieve a balance between thinness and flexibility, transmission characteristics, and flame retardancy.

[0068] Note that, when the protective layer 50 is formed of an insulating material, the shielded flat cable 200 has dielectric strength due to the protective layer 50 , and therefore may not include the base material layer 34 in the shield layer 30 .

[0069] As a modification of the shielded flat cable of the second embodiment, a shielded flat cable that does not include the base material layer 34 will be described. Figure 3 1 is a cross-sectional view showing a shielded flat cable 210 as a modified example of the shielded flat cable according to the second embodiment. Figure 3 A cross section perpendicular to the longitudinal direction of the shielded flat cable 210 is shown.

[0070] The shielded flat cable 210 includes a shield layer 130 instead of the shield layer 30 of the shielded flat cable 200. The shield layer 130 includes shield layers 130a and 130b instead of the shield layers 30a and 30b of the shield layer 30. The shield layers 130a and 130b each include an adhesive layer 31 and a metal layer 32 serving as a shield portion.

[0071] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the claims.

[0072] Description of Reference Numerals

[0073] 10: conductor;

[0074] 20, 21, 22: dielectric layer;

[0075] 20A, 20B, 20C, 20D: outer surface;

[0076] 30, 30a, 30b, 130, 130a, 130b: shielding layer;

[0077] 30F, 30G: laminated portion;

[0078] 30S, 30T: end;

[0079] 30H: Central part;

[0080] 31: adhesive layer;

[0081] 32: Metal layer;

[0082] 33: adhesion-enhancing coating;

[0083] 34: base material layer;

[0084] 40: insulator layer;

[0085] 40F, 40G: upper part;

[0086] 41: adhesive layer;

[0087] 42: base material layer;

[0088] 50: protective layer;

[0089] 100, 200, 210: shielded flat cable;

[0090] 101: Noodles.

Claims

1. A shielded flat cable having: a plurality of conductors, the plurality of conductors being arranged in parallel with each other; a first dielectric layer covering the plurality of conductors and formed of a first dielectric; and a shielding layer covering an outer surface of the first dielectric layer, The shielding layer is formed by stacking a second dielectric layer formed of a second dielectric, a metal layer, an adhesion-promoting coating layer, and a base material 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, The first dielectric layer is bonded to the second dielectric layer.

2. The shielded flat cable according to claim 1, comprising: The insulating layer covers the metal layer exposed at an end portion of the shield layer in the width direction of the shielded flat cable along a direction in which the plurality of conductors extend, and the insulating layer is formed of an insulator.

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

4. The shielded flat cable according to claim 2, wherein The exposed metal layer is covered with a single resin layer that surrounds the shielding layer without interruption.

5. The shielded flat cable according to any one of claims 1 to 4, wherein The dielectric loss tangent of the first dielectric is less than or equal to 0.

001.

6. The shielded flat cable according to any one of claims 1 to 5, wherein The thickness of the first dielectric layer is greater than or equal to 120 μm.

7. The shielded flat cable according to any one of claims 1 to 6, wherein The thickness of the second dielectric layer is less than or equal to 100 μm.

8. The shielded flat cable according to any one of claims 1 to 7, wherein In a cross section perpendicular to a direction in which the plurality of conductors extend, an end portion of the shielding layer is located above an outer surface of the first dielectric layer.

9. A shielded flat cable comprising: a plurality of conductors, the plurality of conductors being arranged in parallel with each other; a first dielectric layer covering the plurality of conductors and formed of a first dielectric; and a shielding layer covering an outer surface of the first dielectric layer, The shielding layer is formed by laminating a second dielectric layer formed by a second dielectric and a metal layer. 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, The first dielectric layer is bonded to the second dielectric layer, A protective layer formed of resin surrounds the shielding layer.

Images