High-frequency characteristic impedance FFC (flexible flat cable)

Abstract

The utility model relates to the technical field of flexible flat cable manufacturing, in particular to a high-frequency characteristic impedance flexible flat cable (FFC). The conductor layer is composed of a plurality of wires arranged in parallel. The number of the insulating layers is two, and the insulating layers cooperatively wrap the conductor layer. And the non-metal reinforcing plates are arranged at the two ends of the FFC, and are attached and bonded with the insulating layer or the conductor layer. The characteristic impedance layer wraps the periphery of the insulating layer. And a certain lead is folded back and grounded. The non-metal reinforcing plate is of a multi-layer composite structure and comprises an aluminum oxide layer; alternatively, the length of the characteristic impedance layer is prolonged, and the characteristic impedance layer abuts against the non-metal reinforcing plate and partially / completely covers the length S of the wire port. Thus, on one hand, discontinuous conductive points existing on the surface of the FFC are eliminated, and electromagnetism cannot penetrate through the insulating layer, so that the phenomenon that signal electromagnetic waves interact with other electronic elements in a mainboard due to the fact that the electromagnetism penetrates through non-conductive gaps and leaks is effectively avoided; and on the other hand, the impedance high point and the return loss are obviously reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of flexible flat cable manufacturing, in particular to a high-frequency characteristic impedance FFC cable. Background Art

[0002] FFC cable, also known as Flexible Flat Cable, can arbitrarily select the number of wires and the spacing, making the connection more convenient and greatly reducing the volume of electronic products. FFC cables are suitable for use as data transmission cables between moving parts and motherboards, between PCB boards, and in miniaturized electrical equipment, and are widely used in mobile phones, tablet computers, cameras, medical equipment, automotive electronics and other fields.

[0003] In the prior art, as Figure 1 shown, the main structure of the FFC cable is that two layers of hot-melt PET film or PI film up and down press a group of flat copper wires arranged at a specific spacing at high temperature, and reinforcing plates exist at both ends of the FFC cable. The main function is to adjust the thickness of both ends of the FFC flexible cable and improve the plugging and unplugging convenience. The FFC cable not only plays a role in guiding current and conducting, but also plays a role in signal transmission. In practical applications, it is found that the FFC cable has the following problems, specifically: 1) There are a large number of non-conductive gaps on the FFC cable, which will inevitably lead to electromagnetic leakage. The signal electromagnetic waves on the FFC cable will interact with other electronic components in the motherboard, resulting in signal transmission interference; 2) The impedance high points (indirectly reflecting the high-frequency characteristic impedance performance) of the FFC cable are too high, and signals are extremely likely to be reflected during transmission, resulting in incomplete and distorted received signals from time to time (as Figure 2 、 3 shown). The reason is that during the signal transmission process through the FFC cable, at a point where the signal arrives, an electric field will be formed between the FFC cable and the reference plane. Due to the existence of the electric field, a momentary small current will be generated, and this small current exists at every point in the FFC cable. At the same time, the signal also has a certain voltage. In this way, during the signal transmission process through the FFC cable, each point of the FFC cable will be equivalent to a resistor. Therefore, it is urgent for those skilled in the art to solve the above problems. Summary of the Utility Model

[0004] Therefore, in view of the above existing problems and defects, the R & D and design team of the present utility model collected relevant materials, through multi-party evaluation and consideration, and through continuous experiments and modifications by the R & D and design team members, finally led to the emergence of this high-frequency characteristic impedance FFC cable.

[0005] To solve the above technical problems, the present utility model relates to a high-frequency characteristic impedance FFC flexible cable, which includes a conductor layer, an insulating layer, and a non-metallic reinforcing plate. The conductor layer is composed of multiple parallel wires. The number of insulating layers is 2, which cooperate to wrap the conductor layer to insulate it from the outside. The number of non-metallic reinforcing plates is 2, and they are attached and bonded to the insulating layer or the conductor layer. Furthermore, the high-frequency characteristic impedance FFC flexible cable also includes a characteristic impedance layer. The characteristic impedance layer is used to eliminate the discontinuous conductive points existing in the conductor layer, and it is wrapped around the periphery of the insulating layer. And a certain wire is folded back to ground.

[0006] Along its thickness direction, the non-metallic reinforcing plate is sequentially composed of an external PET layer, an alumina layer, a middle PET layer, an internal PET layer, and a hot melt adhesive layer.

[0007] Alternatively, the length of the characteristic impedance layer is extended, leaning against the non-metallic reinforcing plate, and partially / entirely covering the length S of the wire opening.

[0008] As a further improvement of the technical solution disclosed by the present utility model, the wire is preferably a tinned flat copper wire, and the spacing P is 0.3, 0.5, 0.8, 1.0, 1.25, 2.0 or 2.54 mm.

[0009] As a further improvement of the technical solution disclosed by the present utility model, the insulating layer is a layered structure, which is composed of a PET substrate and a flame retardant resin layer. The thickness value range of the insulating layer is 0.043 - 0.1 mm, the thickness value range of the PET substrate is 0.019 - 0.05 mm, and the thickness value range of the flame retardant resin layer is 0.024 - 0.05 mm.

[0010] As a further improvement of the technical solution disclosed by the present utility model, after the insulating layer is formed, the adhesive-to-adhesive peel strength and the adhesive-to-wire peel strength are both not less than 1 Kg / in, and it is not broken down under the environment of AC 500 V / min, and the DC 500 V impedance is greater than 1000 mΩ·m.

[0011] As a further improvement of the technical solution disclosed by the present utility model, after the non-metallic reinforcing plate is formed, the thickness value of the hot melt adhesive layer is not greater than 0.03 mm, and the total thickness value tolerance is controlled within 0.005 mm.

[0012] As a further improvement of the technical solution disclosed by the present utility model, the characteristic impedance layer includes a conductive layer, an adhesive layer, and conductive powder. The adhesive layer is brushed and formed on the inner side of the conductive layer. A large amount of conductive powder is scattered on the adhesive layer.

[0013] As a further improvement of the technical solution disclosed by the present utility model, the conductive layer is preferably aluminum foil, copper foil, silver paste-coated mesh, or black electromagnetic film.

[0014] As a further improvement of the technical solution disclosed by the present utility model, the characteristic impedance layer is in contact with the non-metallic reinforcement plate and is electrically connected to the alumina layer.

[0015] In practical applications, the high-frequency characteristic impedance FFC flexible cable disclosed by the present utility model has at least achieved the following beneficial technical effects: specifically:

[0016] 1) By adding a characteristic impedance layer, the discontinuous conductive points existing on the surface of the FFC flexible cable are eliminated, ensuring that the entire surface is electrically continuous, and the conductor layer is cooperatively wrapped by two opposing insulating layers, and electromagnetic waves cannot penetrate the insulating layer, thereby effectively avoiding the occurrence of the interaction between the signal electromagnetic wave and other electronic components in the main board caused by the leakage of electromagnetic waves through non-conductive gaps, and further preventing the signal during the transmission process from being interfered.

[0017] 2) By adding a characteristic impedance layer and using it to achieve the grounding of the conductor layer, both the impedance high point and the return loss are significantly reduced. In this way, not only can the interference of external electromagnetic waves and external signals to the transmitted signal be effectively prevented, but also the anti-interference ability and the reliability and stability of transmitting data of the FFC flexible cable can be improved, ensuring that the signal is transmitted completely and faithfully. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 is a schematic structural diagram of an FFC flexible cable in the prior art.

[0020] Figure 2 is a test result diagram of the impedance high point of an FFC flexible cable in the prior art.

[0021] Figure 3 is a test result diagram of the return loss of an FFC flexible cable in the prior art.

[0022] Figure 4 is a top view of the first embodiment of the high-frequency characteristic impedance FFC flexible cable in the present utility model.

[0023] Figure 5 is a front view of the first embodiment of the high-frequency characteristic impedance FFC flexible cable in the present utility model.

[0024] Figure 6 is Figure 5 the partial enlarged view I of

[0025] Figure 7 It is a schematic structural diagram of the upper insulating layer in the first embodiment of the high-frequency characteristic impedance FFC cable of the present utility model.

[0026] Figure 8 It is a schematic structural diagram of the upper characteristic impedance layer in the first embodiment of the high-frequency characteristic impedance FFC cable of the present utility model.

[0027] Figure 9 is Figure 8 bottom view of.

[0028] Figure 10 It is a schematic diagram of the state of the first embodiment of the high-frequency characteristic impedance FFC cable of the present utility model after being assembled with the electrical connector.

[0029] Figure 11 It is a test result diagram of the impedance high point of the first embodiment of the high-frequency characteristic impedance FFC cable of the present utility model.

[0030] Figure 12 It is a test result diagram of the return loss of the first embodiment of the high-frequency characteristic impedance FFC cable of the present utility model.

[0031] Figure 13 It is a schematic structural diagram of the second embodiment of the high-frequency characteristic impedance FFC cable in the present utility model.

[0032] Figure 14 is Figure 13 partial enlarged view of II.

[0033] Figure 15 It is a schematic diagram of the state of the second embodiment of the high-frequency characteristic impedance FFC cable of the present utility model after being assembled with the electrical connector.

[0034] Figure 16 It is a test result diagram of the impedance high point of the second embodiment of the high-frequency characteristic impedance FFC cable of the present utility model.

[0035] Figure 17 It is a test result diagram of the return loss of the second embodiment of the high-frequency characteristic impedance FFC cable of the present utility model.

[0036] Figure 18 It is a schematic structural diagram of the third embodiment of the high-frequency characteristic impedance FFC cable in the present utility model.

[0037] Figure 19 is Figure 18 partial enlarged view of III.

[0038] Figure 20This is a schematic diagram of the third implementation mode of the high-frequency characteristic impedance FFC flexible cable of the present utility model with respect to the state after the electrical connector is assembled.

[0039] 1 - Conductor layer; 11 - Conducting wire; 2 - Insulating layer; 21 - Upper insulating layer; 211 - PET substrate; 212 - Flame-retardant resin layer; 22 - Lower insulating layer; 3 - Non-metallic reinforcement plate; 31 - Left non-metallic reinforcement plate; 311 - External PET layer; 312 - Alumina layer; 313 - Middle PET layer; 314 - Inner PET layer; 315 - Hot melt adhesive layer; 32 - Right non-metallic reinforcement plate; 4 - Characteristic impedance layer; 41 - Upper characteristic impedance layer; 411 - Conductive layer; 412 - Adhesive layer; 413 - Conductive powder; 42 - Lower characteristic impedance layer. Specific implementation mode

[0040] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by terms such as "left", "right", "upper", "lower", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0041] The following will further elaborate on the content disclosed in the present utility model in conjunction with specific embodiments. Figure 4 、 Figure 5 The top view and front view of the first implementation mode of the high-frequency characteristic impedance FFC flexible cable in the present utility model are respectively shown. It can be seen that it mainly consists of several parts such as a conductor layer 1, an insulating layer 2, a non-metallic reinforcement plate 3, and a characteristic impedance layer 4. Among them, the conductor layer 1 is composed of multiple parallel arranged conducting wires 11, and a certain conducting wire 11 is folded back to be grounded. The electrical performance exhibited by the FFC flexible cable is closely related to the quality of the conducting wire 11. Therefore, the conducting wire 11 is preferably a tinned flat angle copper wire with relatively excellent conductivity and corrosion resistance. The number of insulating layers 2 is 2, namely the upper insulating layer 21 and the lower insulating layer 22, which cooperate to wrap the conductor layer 1 to insulate it from the outside. The number of non-metallic reinforcement plates 3 is 2, namely the left non-metallic reinforcement plate 31 and the right non-metallic reinforcement plate 32. The left non-metallic reinforcement plate 31 and the right non-metallic reinforcement plate 32 are respectively arranged at the left and right ends of the FFC flexible cable, and are attached and bonded to the upper insulating layer 21 and the lower insulating layer 22 according to the process requirements. The number of characteristic impedance layers 4 is also 2, namely the upper characteristic impedance layer 41 and the lower characteristic impedance layer 42, which cooperate to eliminate the discontinuous conductive points existing in the conductor layer 1. The length of the lower characteristic impedance layer 42 is extended, leaning on the left non-metallic reinforcement plate 31 and the right non-metallic reinforcement plate 32, and partially / entirely covering the length S of the wire port (as shown in Figure 6 ).

[0042] By adopting the above technical solution for setting, the discontinuous conductive points existing on the surface of the FFC flexible cable are eliminated, ensuring that the entire surface is electrically conductive and continuous. Moreover, the conductor layer 1 is cooperatively wrapped by two opposing upper insulating layers 21 and lower insulating layers 22, and electromagnetic waves cannot penetrate through the upper insulating layer 21 or the lower insulating layer 22. Thus, the phenomenon that the signal electromagnetic waves interact with other electronic components within the main board due to electromagnetic leakage through non-conductive gaps is effectively avoided, and the signal during the transmission process is thus protected from interference.

[0043] Furthermore, it should also be noted that by adding an upper characteristic impedance layer 41 and a lower characteristic impedance layer 42 and using them to ground the conductor layer 1, both the impedance high point and the return loss are significantly reduced. In this way, not only can the interference of external electromagnetic waves and external signals to the transmitted signal be effectively prevented, but also the anti-interference ability of the FFC flexible cable and the reliability and stability of data transmission can be improved, ensuring that the signal is transmitted completely and faithfully (as shown in Figure 11 、 12 .

[0044] For a single FFC flexible cable, the number of wires 11 is not limited, and the length is unrestricted, resulting in products of various specifications and models.

[0045] Furthermore, the pitch P between the wires is a key parameter in the design of the FFC flexible cable, and the specific value needs to be determined according to the specific application scenario and design requirements to ensure the stability and efficiency of signal transmission. To be applicable to different electronic devices and application requirements, the pitch P between adjacent wires 11 is preferably 0.3, 0.5, 0.8, 1.0, 1.25, 2.0 or 2.54 mm.

[0046] As shown in Figure 7 , the upper insulating layer 21 is a layered structure, which is composed of a PET substrate 211 and a flame-retardant resin layer 212. The thickness value range of the upper insulating layer 21 is 0.043 - 0.1 mm, the thickness value range of the PET substrate 211 is 0.019 - 0.05 mm, and the thickness value range of the flame-retardant resin layer 212 is 0.024 - 0.05 mm. After the upper insulating layer 21 is formed, both the adhesive-to-adhesive peel strength and the adhesive-to-wire peel strength are not less than 1 Kg / in, and it is not broken down under the environment of AC 500 V / min, and the DC 500 V impedance is greater than 1000 mΩ·m. In this way, without significantly increasing the complexity of the process and the production cost, the upper insulating layer 21 simultaneously has characteristics such as good heat resistance stability, oil resistance, high voltage resistance, acid resistance, water resistance, and flame retardancy. Compared with the upper insulating layer 21, the lower insulating layer 22 has the same design structure, which will not be elaborated here.

[0047] As shown in Figure 8 、 9As shown in the figure, the upper characteristic impedance layer 41 is composed of a conductive layer 411, an adhesive layer 412, and conductive powder 413. Among them, the conductive layer 41 is preferably an aluminum foil, a copper foil, a silver paste-coated mesh, or a black electromagnetic film. The adhesive layer 412 is brushed and formed on the inner side of the conductive layer 411. A large amount of conductive powder 413 is scattered on the adhesive layer 412. Compared with the upper characteristic impedance layer 41, the lower characteristic impedance layer 42 has the same design structure, which will not be elaborated here. In this way, after the FFC flexible cable is formed, a large amount of conductive powder 413 is evenly distributed between the upper characteristic impedance layer 41 and the upper insulating layer 21, and between the lower characteristic impedance layer 42 and the lower insulating layer 22, so as to effectively eliminate the discontinuous conductive points existing on the surface of the FFC flexible cable, and thus facilitate the improvement of the EMI shielding and anti-interference performance of the FFC flexible cable.

[0048] Figure 10 Fig. shows a schematic diagram of the state of the first embodiment of the high-frequency characteristic impedance FFC flexible cable of the present invention after being assembled with an electrical connector.

[0049] It is known that conventional non-metallic reinforcing plates 31 are generally classified into phenolic resin plates, PET plates, PI plates, or fiberglass cloths, etc. However, they only play the role of thickening the FFC flexible cable and improving the structural strength of the plug-in part, and do not have the ability to improve the characteristic impedance performance of the line port length S area. In view of this, Figure 13 Fig. shows a schematic structural diagram of the second embodiment of the high-frequency characteristic impedance FFC flexible cable in the present invention. The difference from the above first embodiment is that the upper characteristic impedance layer 41 and the lower characteristic impedance layer 42 are not extended, and only the design structures of the left non-metallic reinforcing plate 31 and the right non-metallic reinforcing plate 32 are optimized. Since the left non-metallic reinforcing plate 31 and the right non-metallic reinforcing plate 32 have the same design structure and the same action mechanism, only the left non-metallic reinforcing plate 31 will be taken as an example for illustration here. Specifically, as Figure 14 shown in the figure, along its thickness direction, the left non-metallic reinforcing plate 31 is sequentially composed of an external PET layer 311, an alumina layer 312, a middle PET layer 313, an internal PET layer 314, and a hot melt adhesive layer 315. After the non-metallic reinforcing plate is formed, the thickness value of the hot melt adhesive layer is not greater than 0.03 mm, and the total thickness value tolerance is controlled within 0.005 mm. A planar conductor alumina layer 312 is provided in the left non-metallic reinforcing plate 31. As Figure 16 、 17 shown in the figure, the impedance high point and return loss of the FFC flexible cable are both significantly reduced, which can not only effectively prevent the interference of external electromagnetic waves and external signals on the transmitted signal, but also improve the anti-interference ability and the reliability and stability of transmitting data of the FFC flexible cable, ensuring that the signal is transmitted completely and faithfully.

[0050] Figure 15The figure shows a schematic diagram of the state of the second embodiment of the high-frequency characteristic impedance FFC cable of the present utility model after being assembled with the electrical connector.

[0051] Figure 18 , Figure 19 The figure respectively shows a schematic diagram of the structure of the third embodiment of the high-frequency characteristic impedance FFC cable of the present utility model and its partial enlarged view III. It can be seen that, compared with the above-mentioned first embodiment and second embodiment, the difference lies in that the designed lengths of the left non-metallic reinforcement plate 31 and the right non-metallic reinforcement plate 32 are both appropriately extended, and the extended sections are in a semi-peeled state after being attached and fixed. In this way, not only can the characteristic impedance performance of the S area of the FFC cable wire port be further improved, but also the mechanical protection of the upper characteristic impedance layer 41 and the lower characteristic impedance layer 42 is strengthened, preventing the occurrence of phenomena such as wrinkling or even damage to the upper characteristic impedance layer 41 and the lower characteristic impedance layer 42 due to mechanical external forces during the plugging and unplugging process.

[0052] Figure 20 The figure shows a schematic diagram of the state of the third embodiment of the high-frequency characteristic impedance FFC cable of the present utility model after being assembled with the electrical connector.

[0053] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-frequency characteristic impedance FFC cable, comprising a conductor layer, an insulating layer and a non-metallic reinforcing plate; the conductor layer is composed of a plurality of wires arranged in parallel; the number of the insulating layers is 2, which cooperate to wrap the conductor layer to insulate it from the outside; the number of the non-metallic reinforcing plates is 2, and they are attached to or bonded to the insulating layer or the conductor layer, characterized in that: It also includes a characteristic impedance layer; the characteristic impedance layer is used to eliminate the discontinuous conductive points in the conductor layer, and is wrapped around the outer periphery of the insulating layer; and one of the conductors is folded back and grounded; Along the thickness direction, the non-metallic reinforcing plate is compounded in sequence by an outer PET layer, an aluminum oxide layer, a middle PET layer, an inner PET layer and a hot melt adhesive layer; Alternatively, the characteristic impedance layer is extended in length, overlapped with the non-metallic reinforcing plate, and partially / completely covers the line opening length S.

2. The high frequency characteristic impedance FFC cable according to claim 1, characterized in that: The conductors are tinned rectangular copper wires, and the spacing P is 0.3, 0.5, 0.8, 1.0, 1.25, 2.0 or 2.54 mm.

3. The high frequency characteristic impedance FFC cable according to claim 1, characterized in that: The insulating layer is a layered structure, which is composed of a PET substrate and a flame retardant resin layer; the thickness of the insulating layer ranges from 0.043 to 0.1 mm, the thickness of the PET substrate ranges from 0.019 to 0.05 mm, and the thickness of the flame retardant resin layer ranges from 0.024 to 0.05 mm.

4. The high frequency characteristic impedance FFC cable according to claim 3, characterized in that: After the insulating layer is formed, the adhesive-to-adhesive peeling strength and the adhesive-to-wire peeling strength are not less than 1Kg / in, and there is no breakdown in an AC500V / min environment, and the DC500V impedance is greater than 1000mΩ.m.

5. The high frequency characteristic impedance FFC cable according to claim 1, characterized in that: After the non-metallic reinforcing plate is formed, the thickness of the hot melt adhesive layer is no more than 0.03 mm, and the total thickness tolerance is controlled within 0.005 mm.

6. The high frequency characteristic impedance FFC cable according to claim 1, characterized in that: The characteristic impedance layer includes a conductive layer, an adhesive layer and conductive powder; the adhesive layer is brushed and formed on the inner side of the conductive layer; a large amount of the conductive powder is sprinkled on the adhesive layer.

7. The high frequency characteristic impedance FFC cable according to claim 6, characterized in that: The conductive layer is aluminum foil, copper foil, silver paste coated mesh or black electromagnetic film.

8. The high frequency characteristic impedance FFC cable according to any one of claims 1 to 7, characterized in that: The characteristic impedance layer is in contact with the non-metallic reinforcing plate and is electrically connected to the aluminum oxide layer.

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