Flexible flat cable

Abstract

The utility model discloses a flexible flat cable. The flexible flat cable comprises a plurality of metal wires which are arranged in parallel; a first insulating layer covering the first surface of the metal wire; a first shielding layer covering the first insulating layer; the tail end of the metal wire exceeds the first insulating layer and the first shielding layer to form a contact part; a second insulating layer covering a second surface of the metal wire; a second shielding layer covering the second insulating layer; a metal layer and a reinforcing plate are arranged between the second insulating layer and the second shielding layer, the metal layer continuously extends along the arrangement direction of the plurality of contact parts, the reinforcing plate is positioned between the metal layer and the second shielding layer, and the projections of the plurality of contact parts and the metal layer in the thickness direction of the flexible flat cable are overlapped. And the metal layer is closer to the contact part, so that the capacitance at the contact part is increased, the impedance at the contact part is further reduced, and the overall impedance of the flexible flat cable is maintained within the impedance specification limit of a product during high-frequency signal transmission, so that the high-frequency transmission effect is ensured.

Description

[Technical field]

[0001] The utility model relates to a flexible flat cable, in particular to a flexible flat cable capable of transmitting high-frequency signals. [Background technology]

[0002] The flexible flat cable includes a metal conductor and an insulating layer covering the upper and lower sides of the metal conductor. The end of the metal conductor is exposed relative to the insulating layer on one side to form a contact portion, and the contact portion contacts the terminal of the docking connector to form an electrical connection. Since the contact portion is exposed to the air outside the insulating layer, when transmitting high-frequency signals, the AC impedance at the contact portion is significantly increased compared to the AC impedance at the unexposed portion of the metal conductor, which is easy to exceed the impedance specification limit of the product and may also increase the transmission loss. In view of this, a new flexible flat cable is needed to solve the above problems. [Contents of the utility model]

[0003] In view of the background technology, the applicant has found that by providing a metal layer between the insulating layer and the reinforcing plate at the contact portion of the flexible flat cable, the impedance at the contact portion can be reduced when transmitting high-frequency (eg, 10 GHz) signals, thereby achieving a high-frequency transmission effect.

[0004] In order to achieve the above purpose, the utility model adopts the following technical means:

[0005] A flexible flat cable comprises: a plurality of metal conductors arranged in parallel; a first insulating layer covering a first surface of the metal conductors; a first shielding layer covering the first insulating layer; the ends of the metal conductors extend beyond the first insulating layer and the first shielding layer to form contact portions; a second insulating layer covering a second surface of the metal conductors; a second shielding layer covering the second insulating layer; a metal layer and a reinforcing plate arranged between the second insulating layer and the second shielding layer, the metal layer extending continuously along the arrangement direction of the plurality of contact portions, the reinforcing plate being located between the metal layer and the second shielding layer, and the plurality of contact portions overlapping with the projection of the metal layer in the thickness direction of the flexible flat cable.

[0006] Furthermore, in the extension direction of the metal wire, the length of the metal layer is not less than the length of the contact portion.

[0007] Furthermore, the second insulating layer includes a film and a gasket made of different materials, the gasket covers the second surface of the contact part and is located between the contact part and the metal layer, and in the extension direction of the metal wire, the film continuously covers the second surface of the metal wire and ends between the contact part and the reinforcement plate, and the contact part is isolated from the film.

[0008] Furthermore, in the extension direction of the metal wire, the length of the gasket is not less than the length of the contact portion, and the length of the metal layer is equal to the length of the gasket.

[0009] Furthermore, the length of the gasket is greater than the length of the contact portion, and the portion of the gasket that exceeds the length of the contact portion overlaps with the film in a thickness direction and sandwiches a portion of the metal layer.

[0010] Furthermore, in the extension direction of the metal wire, the length of the reinforcement plate is greater than the length of the gasket, and the hardness of the reinforcement plate is greater than the hardness of the gasket.

[0011] Furthermore, the metal conductor includes a grounding conductor, and the flexible flat cable also has a through hole that penetrates the second insulating layer, the metal layer, and the reinforcement plate at the grounding conductor, and a conductive glue filling the through hole, and the conductive glue electrically connects the grounding conductor, the metal layer, and the second shielding layer.

[0012] Furthermore, the metal layer is copper foil or aluminum foil.

[0013] Furthermore, the thickness of the metal layer is at least 0.01 mm, and the thickness of the metal layer is smaller than the thickness of each of the first shielding layer and the second shielding layer.

[0014] Furthermore, in the arrangement direction of the metal wires, the width of the metal layer is greater than the distance between the two metal wires that are farthest apart, and in the thickness direction of the flexible flat cable, the distance between the contact portion and the metal layer is less than or equal to the distance between the contact portion and the first shielding layer.

[0015] The above-mentioned technical means has the following technical effects: the metal layer is arranged closer to the contact part than the second shielding layer, the capacitance of the flexible flat cable at the contact part is increased, and then the impedance at the contact part is reduced, and the high-frequency signal transmission loss at the contact part is reduced to ensure the effect of high-frequency transmission.

Brief Description of the Drawings

[0016] Figure 1 It is a three-dimensional schematic diagram of a first embodiment of the flexible flat cable of the utility model;

[0017] Figure 2 for Figure 1 A partial cross-sectional view observed along the thickness direction;

[0018] Figure 3 for Figure 2 Section view along line AA;

[0019] Figure 4for Figure 2 Section view taken along line BB;

[0020] Figure 5 Impedance curve diagrams of the first embodiment and the comparative example;

[0021] Figure 6 It is a schematic diagram of a second embodiment of the flexible flat cable of the present invention.

[0022] Description of Figure Numbers:

[0023] Flexible flat cable 1 Metal conductor 11 Contact portion 111

[0024] Signal conductor 11s Ground conductor 11g First insulating layer 12

[0025] First shielding layer 13 Second insulating layer 14 Gasket 141

[0026] Film 142 Second shielding layer 15 Metal layer 16

[0027] Reinforcement plate 17 Through hole 18 Conductive adhesive 19 [Specific implementation method]

[0028] In order to facilitate a better understanding of the purpose, structure, features and functions of the present invention, the present invention is further described in conjunction with the accompanying drawings and specific implementation methods.

[0029] Figures 1 to 4 The present invention is a schematic diagram of a first embodiment of a flexible flat cable 1, wherein the flexible flat cable 1 comprises a plurality of metal wires 11 arranged in parallel; a first insulating layer 12 covering a first surface of the metal wire 11; a first shielding layer 13 covering the first insulating layer 12; an end of the metal wire 11 exceeds the first insulating layer 12 and the first shielding layer 13 to form a contact portion 111; a second insulating layer 14 covering a second surface of the metal wire 11; a second shielding layer 15 covering the second insulating layer 14; a metal layer 16 and a reinforcing plate 17 are arranged between the second insulating layer 14 and the second shielding layer 15, the metal layer 16 continuously extends along the arrangement direction of the plurality of contact portions 111, the plurality of contact portions 111 overlap with the projection of the metal layer 16 in the thickness direction of the flexible flat cable 1, and the reinforcing plate 17 is located between the metal layer 16 and the second shielding layer 15.

[0030] refer to Figure 1 The plurality of metal wires 11 include a plurality of signal wires 11s and a plurality of ground wires 11g.

[0031] refer to Figure 2The metal layer 16 extends continuously along the arrangement direction of the multiple contact portions 111. In the arrangement direction of the metal wires 11, the width of the metal layer 16 is greater than the distance between the two metal wires 11 that are farthest apart. The multiple contact portions 111 overlap with the projection of the metal layer 16 in the thickness direction of the flexible flat cable 1.

[0032] like Figure 3 and Figure 4 As shown, in the thickness direction of the flexible flat cable 1 , the first surface is the upper surface of the metal wire 11 , and the second surface is the lower surface of the metal wire 11 , but the present invention is not limited thereto.

[0033] refer to Figure 3 In the thickness direction of the flexible flat cable 1, in the present embodiment, the distance between the contact portion 111 and the metal layer 16 is substantially equal to the distance between the contact portion 111 and the first shielding layer 13; in other embodiments, the distance between the contact portion 111 and the metal layer 16 may be smaller than the distance between the contact portion 111 and the first shielding layer 13.

[0034] refer to Figure 3 and Figure 4 In this embodiment, in the extension direction of the metal wire 11, the length of the metal layer 16 is greater than the length of the contact portion 111; the metal layer 16 is copper foil or aluminum foil, the thickness of the metal layer 16 is at least 0.01 mm, and in order to control the overall thickness of the flexible flat cable 1 at the contact portion 111, the thickness of the metal layer 16 is less than the thickness of each of the first shielding layer 13 and the second shielding layer 15. In other embodiments, the length of the metal layer 16 can be equal to the length of the contact portion 111, so in the present utility model, the length of the metal layer 16 is not less than the length of the contact portion 111.

[0035] refer to Figure 3 and Figure 4In this embodiment, the second insulating layer 14 includes a film 142 and a gasket 141 made of different materials. The gasket 141 covers the second surface of the contact portion 111 and is located between the contact portion 111 and the metal layer 16. In the extension direction of the metal wire 11, the gasket 141 and the metal layer 16 are of equal length, so the length of the gasket 141 is greater than the length of the contact portion 111. In the extension direction of the metal wire 11, the film 142 continuously covers the second surface not covered by the gasket 141 and ends between the contact portion 111 and the reinforcing plate 17, and the contact portion 111 is isolated from the film 142. In the embodiment where the length of the metal layer 16 is equal to the length of the contact portion 111, the length of the gasket 141 is also equal to the length of the contact portion 111. Therefore, in the present utility model, the length of the gasket 141 is not less than the length of the contact portion 111.

[0036] Generally speaking, the dielectric constant of the film 142 is not the same as the dielectric constant of the gasket 141. The dielectric constant and dielectric damage of the film 142 are required to be as low as possible to reduce signal transmission loss; and the gasket 141 can adjust the impedance of the flexible flat cable 1 at the contact portion 111 together with the metal layer 16, so the dielectric constant requirement of the gasket 141 needs to consider the thickness of the metal layer 16 and the impedance specification limit of the flexible flat cable 1. In addition, in this embodiment, the material of the first insulating layer 12 is the same as that of the film 142.

[0037] refer to Figure 3 and Figure 4 In the extension direction of the metal wire 11, the length of the reinforcing plate 17 is greater than the length of the gasket 141, and the hardness of the reinforcing plate 17 is greater than the hardness of the gasket 141, so that the flexible flat cable 1 reaches a sufficiently large hardness at the contact portion 111, which is convenient for insertion into the docking electrical connector.

[0038] refer to Figure 4 The flexible flat cable 1 also has a through hole 18 penetrating the first insulating layer 12, the second insulating layer 14, the metal layer 16, and the reinforcing plate 17 on both sides of the grounding wire 11g in the thickness direction, and a conductive glue 19 filling the through hole 18. The conductive glue 19 electrically connects the grounding wire 11g and the first shielding layer 13, the second shielding layer 15, and the metal layer 16 to reduce the crosstalk between the signal wires 11s.

[0039] Figure 5The time domain impedance curve of the first embodiment and the time domain impedance curve of the comparative example without the metal layer 16 are shown. The unit of the horizontal axis value is picosecond (ps), and the unit of the vertical axis value is ohm (Ω). The impedance value of the contact portion roughly corresponds to the impedance value in the range of 70ps to 100ps. Figure 5 , wherein the dotted line is the time domain impedance curve of the first embodiment, and the solid line is the time domain impedance curve of the comparative example without the metal layer 16. Obviously, at the contact portion 111, the impedance value of the first embodiment is lower than that of the comparative example, wherein point M1 is lower than point M2, i.e., the impedance value of the contact portion 111 of the first embodiment when transmitting a 10 GHz signal is reduced by about 5Ω at most compared to the impedance value of the contact portion of the comparative example when transmitting a 10 GHz signal. Except for the contact portion 111, the impedance curve of the first embodiment is similar to the impedance curve of the comparative example.

[0040] Figure 6 FIG. 1 is a schematic diagram of a second embodiment of the flexible flat cable 1 of the present invention. Figure 5 The length of the gasket 141 is greater than the length of the contact portion 111. The difference between the second embodiment and the first embodiment is that the portion of the gasket 141 that exceeds the length of the contact portion 111 overlaps with a portion of the membrane 142 in the thickness direction and sandwiches a portion of the metal layer 16.

[0041] The flexible flat cable of the utility model has the following beneficial effects:

[0042] (1) The metal layer 16 is arranged closer to the contact portion 111 than the second shielding layer 15, so as to increase the capacitance of the flexible flat cable 1 at the contact portion 111, thereby reducing the impedance at the contact portion 111, and reducing the high-frequency signal transmission loss at the contact portion 111, thereby ensuring that the flexible flat cable 1 can transmit high-frequency signals.

[0043] (2) In the extension direction of the metal wire 11, the length of the metal layer 16 is not less than the length of the contact portion 111, so that the metal layer 16 can overlap with the complete contact portion 111 up and down, thereby achieving a more significant impedance adjustment effect.

[0044] (3) The gasket 141 is equal in length to the metal layer 16 and is made of a material different from that of the film 142 . The gasket 141 can cooperate with the metal layer 16 to further adjust the impedance at the contact portion 111 .

[0045] (4) The length of the reinforcing plate 17 is greater than the length of the gasket 141 , and the hardness of the reinforcing plate 17 is greater than the hardness of the gasket 141 , so that the flexible flat cable 1 has a sufficiently large hardness at the contact portion 111 , which is convenient for insertion into the docking electrical connector.

[0046] (5) The thickness of the metal layer 16 is smaller than the thickness of the first shielding layer 13 and the second shielding layer 15 to control the overall thickness of the flexible flat cable 1 at the contact portion 111 so that the flexible flat cable 1 can be smoothly inserted into the mating electrical connector.

[0047] (6) In the arrangement direction of the metal wires 11, the width of the metal layer 16 is greater than the distance between the two metal wires 11 that are farthest apart, so that the metal layer 16 can simultaneously adjust the impedance of multiple metal wires 11. In the thickness direction of the flexible flat cable 1, the distance between the contact portion 111 and the metal layer 16 is less than or equal to the distance between the contact portion 111 and the first shielding layer 13, that is, the thickness at the contact portion 111 is controlled, and the impedance at the contact portion 111 can be reduced by a sufficient value to meet the performance requirements of the flexible flat cable.

[0048] (7) The conductive adhesive 19 electrically connects the grounding wire 11g and the first shielding layer 13, the second shielding layer 15, and the metal layer 16 to reduce the crosstalk between the signal wires 11s.

[0049] The above detailed description is only an explanation of the preferred embodiment of the present utility model, and does not limit the patent scope of the present utility model. Therefore, all equivalent technical changes made by using the description and illustrations of the present utility model are included in the patent scope of the present utility model.

Claims

1. A flexible flat cable, characterized in that: include: Multiple metal wires arranged in parallel; a first insulating layer covering a first surface of the metal wire; a first shielding layer covering the first insulating layer; The end of the metal wire exceeds the first insulating layer and the first shielding layer to form a contact portion; a second insulating layer covering a second surface of the metal wire; a second shielding layer covering the second insulating layer; A metal layer and a reinforcement plate are arranged between the second insulating layer and the second shielding layer, the metal layer extends continuously along the arrangement direction of the multiple contact parts, the reinforcement plate is located between the metal layer and the second shielding layer, and the multiple contact parts overlap with the projection of the metal layer in the thickness direction of the flexible flat cable.

2. The flexible flat cable according to claim 1, characterized in that: In the extending direction of the metal wire, the length of the metal layer is not less than the length of the contact portion.

3. The flexible flat cable according to claim 1, wherein: The second insulating layer includes a film and a gasket made of different materials. The gasket covers the second surface of the contact part and is located between the contact part and the metal layer. In the extension direction of the metal wire, the film continuously covers the second surface of the metal wire and ends between the contact part and the reinforcement plate. The contact part is isolated from the film.

4. The flexible flat cable according to claim 3, characterized in that: In the extending direction of the metal wire, the length of the gasket is not less than the length of the contact portion, and the length of the metal layer is equal to the length of the gasket.

5. The flexible flat cable according to claim 4, characterized in that: The length of the gasket is greater than the length of the contact portion, and a portion of the gasket exceeding the length of the contact portion overlaps with the film in a thickness direction and sandwiches a portion of the metal layer.

6. The flexible flat cable according to claim 3, characterized in that: In the extending direction of the metal wire, the length of the reinforcing plate is greater than the length of the gasket, and the hardness of the reinforcing plate is greater than the hardness of the gasket.

7. The flexible flat cable according to claim 1, wherein: The metal conductor includes a grounding conductor, and the flexible flat cable also has a through hole penetrating the second insulating layer, the metal layer, and the reinforcing plate at the grounding conductor and a conductive glue filling the through hole, and the conductive glue electrically connects the grounding conductor, the metal layer, and the second shielding layer.

8. The flexible flat cable according to claim 1, wherein: The metal layer is copper foil or aluminum foil.

9. The flexible flat cable according to claim 1, wherein: The thickness of the metal layer is at least 0.01 mm, and the thickness of the metal layer is smaller than the thickness of the first shielding layer and the second shielding layer.

10. The flexible flat cable according to claim 1, wherein: In the arrangement direction of the metal wires, the width of the metal layer is greater than the distance between the two metal wires that are farthest apart, and in the thickness direction of the flexible flat cable, the distance between the contact portion and the metal layer is less than or equal to the distance between the contact portion and the first shielding layer.

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