Folding-resistant flexible flat cable

Abstract

The invention discloses a folding-resistant flexible flat cable. The folding-resistant flexible flat cable comprises a single low-dielectric mixed material layer, a plurality of wires, two metal material layers and two insulating protective layers, the leads are located in the single low dielectric mixed material layer and are arranged side by side at intervals. The two metal material layers are respectively and directly overlapped on the upper surface and the lower surface of the single low-dielectric mixed material layer. The two insulation protection layers are respectively laminated on the two metal material layers.

Description

TECHNICAL FIELD

[0001] The present invention relates to a cable, and more particularly to a flexible flat cable with folding resistance. BACKGROUND

[0002] According to the characteristic impedance formula of a strip line, the dielectric constant (Dk) of a dielectric material layer between two conductive metal layers and the thickness of the dielectric material layer and the size of a strip line inside the dielectric material layer all affect the characteristic impedance of the strip line. Based on this, if a row of signal lines (i.e. strip lines) of a flexible flat cable (FFC) is to have uniform characteristic impedance to avoid or reduce the reflection loss and insertion loss caused by uneven impedance distribution, the spacing and dielectric constant between the signal lines and the shielding layers (i.e. conductive metal layers) of the flexible flat cable must be kept as uniform as possible. In other words, no matter what state the flexible flat cable is in, the dielectric material layer between the signal lines and the shielding layers must have good enough adhesion to keep the spacing and dielectric constant between the signal lines and the shielding layers of the flexible flat cable as consistent as possible.

[0003] However, the signal lines and the shielding layers of the flexible flat cable are usually bonded to the dielectric material layer by an adhesive layer respectively, and when the flexible flat cable is folded, the folded part may cause partial peeling between the shielding layers and the dielectric material layer due to uneven adhesion or insufficient adhesion of the two adhesive layers, etc., thereby causing the spacing between the two shielding layers to be inconsistent, affecting the thickness uniformity of the dielectric material layer therebetween. In addition, the insufficient flexibility of the dielectric material layer itself causes cracks or cracks to occur in the folded part of the dielectric material layer, causing the dielectric constant between the row of signal lines and the two shielding layers to change locally. This means that the characteristic impedance of the row of signal lines of the flexible flat cable at the folded part will lose its original uniformity, and thus cause a certain degree of reflection loss in the row of signal lines, thereby causing the insertion loss to increase and affecting the transmission characteristics of the row of signal lines. In other words, the row of signal lines originally has uniform characteristic impedance when the flexible flat cable is not folded, but once it is folded, the characteristic impedance of the row of signal lines becomes unevenly distributed and it is difficult to maintain good transmission characteristics.

[0004] Therefore, it is urgent to provide a flexible flat cable that can maintain good transmission characteristics of its signal lines when it is folded. SUMMARY

[0005] The present invention provides a flexible flat cable with folding resistance, which can maintain good transmission characteristics after being folded.

[0006] More specifically, the flexible flat cable of the present invention comprises a single low dielectric hybrid material layer, a plurality of conductive wires spaced and arranged within the single low dielectric hybrid material layer, two metal material layers laminated to the single low dielectric hybrid material layer, and two insulating protective layers respectively laminated to each of the metal material layers. The single low dielectric hybrid material layer comprises a mixture of maleic anhydride grafted polyolefin elastomer and polyolefin elastomer, and there is no other material layer between each of the conductive wires and the single low dielectric hybrid material layer. The two metal material layers are each made of conductive material. An inner surface of each of the metal material layers is directly laminated to an upper surface and a lower surface of the single low dielectric hybrid material layer, respectively. There is no other material layer between the inner surface of each of the metal material layers and the upper and lower surfaces of the single low dielectric hybrid material layer, so that there is only the single low dielectric hybrid material layer and the conductive wires between the two metal material layers.

[0007] In one embodiment, the content of maleic anhydride (MAH) in the maleic anhydride grafted polyolefin elastomer of the flexible flat cable of the present invention is 0.01-2%.

[0008] In one embodiment, the single low dielectric hybrid material layer of the flexible flat cable of the present invention is composed of 0-70 wt% of low dielectric constant polyolefin elastomer and 30-100 wt% of maleic anhydride grafted polyolefin elastomer.

[0009] In one embodiment, the adhesion between the single low dielectric hybrid material layer and each of the metal material layers of the flexible flat cable of the present invention is greater than or equal to 20 N / mm.

[0010] In one embodiment, the melt flow index of the single low dielectric hybrid material layer of the flexible flat cable of the present invention is 10-40 g / 10 min.

[0011] In one embodiment, the melting point temperature of the single low dielectric hybrid material layer of the flexible flat cable of the present invention is 95-180°C.

[0012] In one embodiment, the specific gravity of the single low dielectric hybrid material layer of the flexible flat cable of the present invention is 0.85-0.9.

[0013] In one embodiment, the upper limit of the working temperature tolerance of the single low dielectric hybrid material layer of the flexible flat cable of the present invention is -50-150°C.

[0014] In one embodiment, the Shore A hardness of the single low dielectric hybrid material layer of the flexible flat cable of the present invention is 50-90.

[0015] In one embodiment, the water absorption of the single low dielectric hybrid material layer of the flexible flat cable of the present application is 0.001 to 1%.

[0016] In one embodiment, the thickness of the single low dielectric hybrid material layer of the flexible flat cable of the present application is 100 to 450 μm.

[0017] In one embodiment, the cross-sectional shape of each of the conductive wires of the flexible flat cable of the present application is circular, and the diameter thereof is 25 to 40 AWG, the internal impedance thereof is 65 to 110 ohms, and the center-to-center distance between two adjacent conductive wires is 0.3 to 0.8 mm. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a partial cross-sectional enlarged view of a preferred embodiment of the flexible flat cable of the present application.

[0019] Figure 2 is a plan view of the preferred embodiment of the present application.

[0020] Figure 3 is a plan view of the preferred embodiment of the present application being folded into an N shape.

[0021] Figure 4 is a manufacturing view of the preferred embodiment of the present application.

[0022] Figure 5 is a partial cross-sectional enlarged view of the polyester insulation tape of the preferred embodiment of the present application.

[0023] Figure 6 is a graph showing the relationship between the insertion loss and the frequency of the preferred embodiment of the present application when not folded and when folded into an N shape.

[0024] Figure 7 is a graph showing the relationship between the characteristic impedance and the frequency of the preferred embodiment of the present application when not folded and when folded into an N shape.

[0025] MAIN REFERENCE NUMERALS:

[0026] Flexible flat cable 1 Conductive wire 11

[0027] Single low dielectric hybrid material layer 12 Low dielectric adhesive material 121

[0028] Metal material layer 13 Insulation protective layer 14

[0029] Polyester insulation tape 100 Electrical connector 2

[0030] Center-to-center distance Dc Diameter Dd

[0031] Heat press roller R1

[0032] First fold 10a Second fold 10b Detailed Implementation

[0033] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0034] Figure 1 and Figure 2 This is a schematic diagram of a preferred embodiment of the flexible flat cable 1 of the present invention. Each end of the cable has an electrical connector 2, which are respectively used to connect to two electronic devices (not shown) to enable signal transmission between the two electronic devices via the flexible flat cable 1. Either of the aforementioned electrical connectors 2 can also be connected to a corresponding mating electrical connector to form an electrical connection. Furthermore, Figure 3 This illustrates a possible usage state of the flexible flat cable 1, in which the flexible flat cable 1 is folded into an N-shape, thereby forming a first fold 10a and a second fold 10b.

[0035] like Figure 1 As shown, the layered structure of the flexible flat cable 1 of the present invention includes a single low-dielectric composite material layer 12, a plurality of conductors 11 located inside the single low-dielectric composite material layer 12 and spaced apart and arranged side by side, two metal material layers 13 respectively directly superimposed on the upper and lower surfaces of the single low-dielectric composite material layer 12, and two insulating protective layers 14 respectively superimposed on the two metal material layers 13. The conductors 11 form a row of signal lines for transmitting differential signals.

[0036] The single low-dielectric hybrid material layer 12 is a single layer, that is, the entire layer is made of the same hybrid material. There are no other material layers between each conductor 11 and the single low-dielectric hybrid material layer 12.

[0037] The single low dielectric hybrid material layer 12 is insulating, and has adhesiveness, elasticity and low dielectric constant. In one embodiment, the single low dielectric hybrid material layer 12 comprises one or more of low dielectric constant polyolefin elastomer (POE) and maleic anhydride grafted polyolefin elastomer (MAH-g-POE). The low dielectric constant polyolefin elastomer and the maleic anhydride grafted polyolefin elastomer are mixed uniformly to form the single low dielectric hybrid material layer 12. The low dielectric constant polyolefin elastomer has high crystallinity, and thus has the characteristics of being hard, brittle and having low flowability. The maleic anhydride grafted polyolefin elastomer has high dielectric constant, but has the characteristics of being non-crystalline, and thus has high elasticity and low crystallinity. In other words, compared with the low dielectric constant polyolefin elastomer, the maleic anhydride grafted polyolefin elastomer has higher dielectric constant, but is less hard and less brittle due to its high elasticity, and has higher adhesiveness than the low dielectric constant polyolefin elastomer. Therefore, the single low dielectric hybrid material layer 12 formed by mixing the low dielectric constant polyolefin elastomer and the maleic anhydride grafted polyolefin elastomer not only has low dielectric constant and low overall crystallinity, but also has good adhesiveness and excellent elasticity.

[0038] In one embodiment, the content of the maleic anhydride (MAH) in the maleic anhydride grafted polyolefin elastomer is 0.01-2%. That is, the grafting ratio of the maleic anhydride (MAH) to the polyolefin in the material is 0.01-2%.

[0039] In one embodiment, the content of the low dielectric constant polyolefin elastomer in the single low dielectric hybrid material layer 12 is preferably 0-70wt%, and the content of the maleic anhydride grafted polyolefin elastomer in the single low dielectric hybrid material layer 12 is preferably 30-100wt%. In other words, the single low dielectric hybrid material layer 12 is formed by mixing 0-70wt% of the low dielectric constant polyolefin elastomer and 30-100wt% of the maleic anhydride grafted polyolefin elastomer, so that the single low dielectric hybrid material layer 12 has good adhesiveness, good insulating property, high elasticity, low crystallinity and low dielectric constant.

[0040] Furthermore, by adding the maleic anhydride grafted polyolefin elastomer and achieving the above-mentioned ratio, the adhesion (or peel force) between the single low dielectric hybrid material layer 12 and the metal material layer 13 can be increased from less than 0.5 N / mm to greater than or equal to 20 N / mm, and the heat of fusion of the single low dielectric hybrid material layer 12 can be reduced. This means that the crystallinity of the polyolefin elastomer as a high molecular material is reduced due to the addition of the maleic anhydride grafted polyolefin elastomer, so that the single low dielectric hybrid material layer 12 composed of the former two has better flexibility (i.e., better softness and extensibility) due to the increase in the non-crystalline region.

[0041] In addition, the single low dielectric hybrid material layer 12 has at least one or more or all of the following properties:

[0042] a dielectric constant Dk = 1.5 to 3;

[0043] an adhesion N = 20 N / mm or more;

[0044] a flow rate (or melt flow index) MI = 10 to 40 g / 10 min (under a measurement condition of a material weight of 2.16 Kg and a melting temperature of 190°C);

[0045] a melting point temperature = 95 to 180°C;

[0046] a specific gravity = 0.85 to 0.9;

[0047] a Shore A hardness = 50 to 90;

[0048] a dielectric loss (Df) = 0.0001 to 0.01; and

[0049] a water absorption = 0.001 to 1%.

[0050] In addition, the single low dielectric hybrid material layer 12 can withstand a working temperature of up to -50 to 150°C.

[0051] In addition, the thickness of the single low dielectric hybrid material layer 12 is preferably 100 to 450 μm ± 10 μm, but is not limited thereto.

[0052] The cross-sectional shape of each of the conductive wires 11 can be circular, rectangular, square, or other shapes. In the preferred embodiment, the cross-sectional shape of each of the conductive wires 11 is circular, and the diameter Dd is preferably 25 to 40 AWG, the internal impedance is preferably 65 to 110 ohms, and the center-to-center distance between adjacent two of the conductive wires 11 is preferably 0.3 to 0.8 mm.

[0053] Each of these metallic material layers 13 serves to provide electromagnetic shielding, and its thickness is preferably 0.003–0.020 mm.

[0054] Each of the conductors 11 and each of the metal material layers 13 is made of a conductive material, such as copper, silver, aluminum, gold, or their alloys, but is not limited thereto. An inner surface of each metal material layer 13 is directly laminated to an upper surface and a lower surface of a single low-dielectric hybrid material layer 12, and there are no other material layers between the inner surface of each metal material layer 13 and the upper and lower surfaces of the single low-dielectric hybrid material layer 12, such that only the single low-dielectric hybrid material layer 12 and the conductors 11 exist between the two metal material layers 13.

[0055] The thickness of each insulating protective layer 14 is preferably 0.005 to 0.05 mm, and the material is preferably a thermoplastic or thermosetting insulating material. In addition, each insulating protective layer 14 can be bonded to the adjacent metal material layer 13 by an adhesive layer (not shown).

[0056] Figure 4 The diagram shows how the conductors 11 are inserted between two pre-made polyester insulation tapes 100, and then the two polyester insulation tapes 100 are clamped together with two hot-pressing rollers R1 to obtain the flexible flat cable 1 of the present invention. Figure 5 As shown, each of the polyester insulating tapes 100 comprises an insulating protective layer 14, a metal material layer 13, and a low-dielectric composite material layer 121. The metal material layer 13 is sandwiched between the other two. Preferably, the metal material layer 13 is directly laminated to an inner surface of the low-dielectric composite material layer 121, the insulating protective layer 14 is laminated to an outer surface of the metal material layer 13, and there are no other material layers between the metal material layer 13 and the low-dielectric composite material layer 121.

[0057] When the spaced-apart wires 11 are introduced between the two polyester insulating tapes 100, the low-dielectric composite material layer 121 of one polyester insulating tape 100 faces the upper surface of each wire 11, while the low-dielectric composite material layer 121 of the other polyester insulating tape 100 faces the lower surface of each wire 11. Therefore, when the two polyester insulating tapes 100 are clamped by the two hot-pressing rollers R1, the low-dielectric composite material layer 121 of one polyester insulating tape 100 will bond together with the low-dielectric composite material layer 121 of the other polyester insulating tape 100, such that the wires 11 are wrapped by the two low-dielectric composite material layers 121. In other words, the wires 11 are located inside the single low-dielectric composite material layer 12 formed by the two low-dielectric composite material layers 121. The two low-dielectric hybrid material layers 121 use the same material as the single low-dielectric hybrid material layer 12, which will not be described in detail.

[0058] As described above, the single low-dielectric hybrid material layer 12 of the present invention is directly bonded to each of the metal material layers 13, without any other material layers between them. Furthermore, the single low-dielectric hybrid material layer 12 of the present invention not only possesses a low dielectric constant but also exhibits good adhesion, high elasticity, and low crystallinity. This makes it difficult for the low-dielectric hybrid material layer 12 and the metal material layer 13 to peel off due to folding, and also makes it less prone to cracks or fissures due to folding. Therefore, the flexible flat cable 1 of the present invention has good flexibility and is quite resistant to folding. This can also be seen from... Figure 6 and Figure 7 The curve confirms this, in more detail:

[0059] Figure 6 This invention illustrates the wires 11 of the present invention both before and after the flexible flat cable 1 is folded into an N-shape (see [reference]). Figure 3 The graph shows the relationship between insertion loss and frequency. As can be seen from the graph, the two curves almost overlap. This indicates that compared with the insertion loss when it is not folded, the insertion loss of the conductors 11 of the present invention does not decrease significantly when the flexible flat cable 1 is folded into an N-shape. It is evident that even if the flexible flat cable 1 is folded, it does not affect the insertion loss of its conductors 11, regardless of the frequency.

[0060] Figure 7 This invention illustrates the wires 11 of the present invention both before and after the flexible flat cable 1 is folded into an N-shape (see [reference]). Figure 3The characteristic impedance versus time curves of the two curves show that the maximum change in characteristic impedance at positions P1 and P2 corresponding to the first fold 10a and the second fold 10b is only about 1 ohm. This demonstrates that even if the flexible flat cable 1 of the present invention is folded, it will not cause too much impedance change on these conductors 11.

[0061] In summary, the insertion loss and characteristic impedance of the flexible flat cable 1 of the present invention did not change significantly before and after being folded. Therefore, it can still maintain its original good transmission characteristics after being folded.

Claims

1. A flexible flat cable, comprising: A single low-dielectric hybrid material layer comprising a mixture of maleic anhydride-grafted polyolefin elastomer and polyolefin elastomer. Multiple conductors are spaced apart and arranged side by side inside the single low-dielectric hybrid material layer, and there are no other material layers between each conductor and the single low-dielectric hybrid material layer; Two metal material layers are made of conductive material. The inner surface of each metal material layer is directly stacked on the upper and lower surfaces of the single low-dielectric hybrid material layer. There are no other material layers between the inner surface of each metal material layer and the upper and lower surfaces of the single low-dielectric hybrid material layer, so that only the single low-dielectric hybrid material layer and the conductor exist between the two metal material layers. and Two insulating protective layers are respectively stacked on one outer surface of each metal material layer.

2. The flexible flat cable as described in claim 1, wherein, The maleic anhydride content in the maleic anhydride-grafted polyolefin elastomer is 0.01-2%.

3. The flexible flat cable as described in claim 2, wherein, The single low-dielectric hybrid material layer is composed of 0-70 wt% low-dielectric-constant polyolefin elastomer and 30-100 wt% maleic anhydride-grafted polyolefin elastomer.

4. The flexible flat cable as described in claim 2, wherein, The adhesion between the single low-dielectric hybrid material layer and each of the metal material layers is greater than or equal to 20 N / mm.

5. The flexible flat cable as described in claim 2, wherein, The melt flow index of the single low-dielectric hybrid material layer is 10–40 g / 10 min.

6. The flexible flat cable as described in claim 2, wherein, The melting point temperature of the single low-dielectric hybrid material layer is 95–180°C.

7. The flexible flat cable as described in claim 2, wherein, The specific gravity of the single low-dielectric hybrid material layer is 0.85-0.

9.

8. The flexible flat cable as described in claim 2, wherein, The upper limit of the operating temperature that the single low-dielectric hybrid material layer can withstand is -50 to 150°C.

9. The flexible flat cable of claim 2, wherein the Shore A hardness of the single low-dielectric hybrid material layer is 50 to 90.

10. The flexible flat cable of claim 2, wherein the water absorption rate of the single low-dielectric composite material layer is 0.001 to 1%.

11. The flexible flat cable of claim 2, wherein the thickness of the single low-dielectric hybrid material layer is 100–450 μm.

12. The flexible flat cable as claimed in claim 2, wherein each of the conductors has a circular cross-sectional shape and a diameter of 25 to 40 AWG, an internal impedance of 65 to 110 ohms, and a center-to-center distance of 0.3 to 0.8 mm between two adjacent conductors.

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