Flexible flat cables, flexible flat cables with connectors, and electronic devices.

Abstract

We provide technology that can effectively reduce crosstalk. [Solution] The flexible flat cable according to the embodiment comprises a plurality of conductor lines arranged parallel to each other, and an insulating layer provided around the plurality of conductor lines, wherein the plurality of conductor lines include a plurality of transmission lines arranged in a row in a cross section perpendicular to the longitudinal direction of the plurality of conductor lines, and at least one open line with both ends electrically open, wherein the plurality of transmission lines include a plurality of ground lines, and a pair of first signal lines and a pair of second signal lines located between the plurality of ground lines in the cross section, wherein the open line is located in the cross section on the first direction side of the pair of first signal lines perpendicular to the arrangement direction of the plurality of transmission lines.

Description

[[Technical Field]]

[0001] The present disclosure relates to a flexible flat cable, a flexible flat cable with a connector, and an electronic device. [[Background Art]]

[0002] Patent Document 1 discloses a shielded flexible flat cable. This flexible flat cable has a plurality of conductors arranged parallel to each other. The plurality of conductors include two pairs of signal lines for differential transmission, a ground line arranged between the two pairs of signal lines, an insulating layer, and a shield layer. The insulating layer is provided around the two pairs of signal lines and the ground line. The shield layer covers the outer peripheral surface of the insulating layer. The shield layer and the ground line are electrically connected to each other. Therefore, the shield layer and the ground line surround each of the two pairs of signal lines. This suppresses crosstalk between the two pairs of signal lines. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] International Publication No. 2019 / 208247 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] In the above-described conventional flexible flat cable, the shield layer and the ground line are bonded to each other by a conductive adhesive and electrically connected. In recent years, amid growing demands for cost reduction, the above conventional example has a relatively complicated configuration in which the shield layer and the ground line are bonded with a conductive adhesive. From the perspective of cost reduction, a technology that can effectively reduce crosstalk with a simpler configuration is desired.

[0005] This disclosure aims to provide a technology that can effectively reduce crosstalk. [Means for solving the problem]

[0006] The flexible flat cable embodiment comprises a plurality of conductor lines arranged parallel to each other, and an insulating layer provided around the plurality of conductor lines. The plurality of conductor lines include a plurality of transmission lines arranged in a row in a cross section perpendicular to the longitudinal direction of the plurality of conductor lines, and at least one open line with both ends electrically open. The plurality of transmission lines include a plurality of ground lines, and a pair of first signal lines and a pair of second signal lines located between the plurality of ground lines in the cross section. The open line is located in the cross section on the first direction side of the pair of first signal lines, perpendicular to the arrangement direction of the plurality of transmission lines. [Effects of the Invention]

[0007] According to this disclosure, crosstalk can be effectively reduced. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of an electronic device according to an embodiment. [Figure 2] Figure 2 is a perspective view showing an example of a flexible flat cable according to the embodiment. [Figure 3] Figure 3 is a cross-sectional view taken along the line III-III in Figure 2. [Figure 4] Figure 4 is a plan view showing the end of a flexible flat cable according to the embodiment. [Figure 5] Figure 5 is a cross-sectional view of a flexible flat cable according to the first modified example. [Figure 6] Figure 6 is a cross-sectional view of a flexible flat cable according to the second modified example. [Figure 7] Figure 7 is a cross-sectional view of a flexible flat cable according to the third modified example. [Figure 8] Figure 8 is a graph showing the frequency characteristics of the insertion loss for the examples and comparative examples. [Figure 9] Figure 9 is a graph showing the frequency characteristics of the reflection loss for the examples and comparative examples. [Figure 10] Figure 10 is a graph showing the frequency characteristics of near-end crosstalk in the examples and comparative examples. [Figure 11] Figure 11 is a graph showing the frequency characteristics of far-end crosstalk in the examples and comparative examples. [Modes for carrying out the invention]

[0009] First, the details of the embodiment will be listed and explained. [Summary of the Embodiment]

[0010] (1) The flexible flat cable according to the embodiment comprises a plurality of conductor lines arranged parallel to each other, and an insulating layer provided around the plurality of conductor lines. The plurality of conductor lines include a plurality of transmission lines arranged in a row in a cross section perpendicular to the longitudinal direction of the plurality of conductor lines, and at least one open line with both ends electrically open. The plurality of transmission lines include a plurality of ground lines, and a pair of first signal lines and a pair of second signal lines located between the plurality of ground lines in the cross section. The open line is located in the cross section on the first direction side of the pair of first signal lines, perpendicular to the arrangement direction of the plurality of transmission lines. According to the above configuration, the open line reflects and absorbs the crosstalk components radiated from the pair of first signal lines and the pair of second signal lines. As a result, the mutual propagation of crosstalk components between the pair of first signal lines and the pair of second signal lines can be suppressed. As a result, crosstalk between the pair of first signal lines and the pair of second signal lines is effectively reduced.

[0011] (2) The flexible flat cable described in (1) above may further include a shield layer provided on the outer surface of the insulating layer. In this case, noise from the pair of first signal lines and the pair of second signal lines can be shielded, and the pair of first signal lines and the pair of second signal lines can be shielded from external noise.

[0012] (3) In the flexible flat cable according to (1) or (2) above, the position in the arrangement direction of at least one of the pair of first signal lines and the position in the arrangement direction of the open line may overlap each other. In this case, an open line can be arranged at a position that can serve as a path for crosstalk components. This makes it possible to effectively suppress mutual transmission of crosstalk components between the pair of first signal lines and the pair of second signal lines.

[0013] (4) In the flexible flat cable according to any one of (1) to (3) above, when there are a plurality of the open lines, the plurality of open lines may include a pair of first open lines located on the first direction side of the pair of first signal lines in the cross section. In this case, an open line is arranged for each of the pair of first signal lines. This makes it possible to more effectively suppress mutual transmission of crosstalk components between the pair of first signal lines and the pair of second signal lines.

[0014] (5) Further, in the flexible flat cable according to (4) above, the plurality of open lines may further include a pair of second open lines located on a second direction side, which is the direction opposite to the first direction, of the pair of first signal lines in the cross section. In this case, the pair of first open lines can reflect and absorb crosstalk components on the first direction side of the pair of first signal lines, and the pair of second open lines can reflect and absorb crosstalk components on the second direction side of the pair of first signal lines.

[0015] (6) In the flexible flat cable described in (5) above, the plurality of open lines may further include a pair of third open lines located on the first direction side of the pair of second signal lines in the cross-section, and a pair of fourth open lines located on the second direction side of the pair of second signal lines in the cross-section. In this case, open lines are provided on the first and second direction sides of each signal line included in the pair of first signal lines and the pair of second signal lines. This makes it possible to more effectively suppress the transmission of crosstalk components between the pair of first signal lines and the pair of second signal lines.

[0016] (7) In the flexible flat cable described in (6) above, the pair of first open lines and the pair of third open lines may be arranged in a row along the arrangement direction in the cross-section, and the pair of second open lines and the pair of fourth open lines may be arranged in a row along the arrangement direction in the cross-section. In this case, if the insulating layer is made up in multiple layers along the arrangement lines of multiple transmission lines and the arrangement lines of multiple open lines in the cross-section, it becomes easy to provide multiple conductor lines aligned along each arrangement line.

[0017] (8) In any one of the flexible flat cables described in (1) to (7) above, each of the plurality of transmission lines may have extensions at both ends that extend beyond the ends of the open line. In this case, if connectors are provided at both ends of multiple transmission lines, the terminals of the connectors are connected to the extensions, and the open lines are not connected to the terminals of the connectors. Therefore, the open lines can be kept electrically isolated.

[0018] (9) In any one of the flexible flat cables described in (1) to (8) above, the pair of first signal lines may have first connection ends connected to a first differential transmission line, and the pair of second signal lines may have second connection ends connected to a second differential transmission line. In this case, a differential signal is transmitted through the pair of first signal lines, and another differential signal is transmitted through the pair of second signal lines.

[0019] (10) A flexible flat cable with a connector, which is an embodiment from another viewpoint, comprises a flexible flat cable and connectors provided at both ends of the flexible flat cable. The flexible flat cable comprises a plurality of conductor lines arranged parallel to each other and an insulating layer provided around the plurality of conductor lines. The plurality of conductor lines include a plurality of transmission lines arranged in a row in a cross section perpendicular to the longitudinal direction of the plurality of conductor lines and at least one open line which is an unconnected portion whose ends are not connected to the terminals of the connector. The plurality of transmission lines include a plurality of ground lines and a pair of first signal lines and a pair of second signal lines whose ends are connected to the terminals of the connector and which are located between the plurality of ground lines in the cross section. The open line is located in the cross section on the first direction side of the pair of first signal lines which is perpendicular to the arrangement direction of the plurality of transmission lines.

[0020] (11) Another embodiment of the electronic device from another viewpoint comprises a first electronic device, a second electronic device that exchanges a first differential signal and a second differential signal with the first electronic device, and a flexible flat cable connecting the first electronic device and the second electronic device. The flexible flat cable comprises a plurality of conductor lines arranged parallel to each other, and an insulating layer provided around the plurality of conductor lines. The plurality of conductor lines include a plurality of transmission lines arranged in a row in a cross section perpendicular to the longitudinal direction of the plurality of conductor lines, and at least one open line with both ends electrically open. The plurality of transmission lines include a plurality of ground lines, and a pair of first signal lines and a pair of second signal lines located between the plurality of ground lines in the cross section. The pair of first signal lines are lines for the first differential signal. The pair of second signal lines are lines for the second differential signal. The open line is located in the cross-section on the side of the pair of first signal lines that is perpendicular to the arrangement direction of the plurality of transmission lines.

[0021] [Details of the embodiment] Preferred embodiments will be described below with reference to the drawings. Furthermore, at least some of the embodiments described below may be combined in any way.

[0022] [Regarding the configuration of electronic equipment] Figure 1 shows an example of an electronic device according to an embodiment. In Figure 1, the electronic device 100 comprises a first electronic device 101, a second electronic device 102, and a flexible flat cable 103 with a connector. The flexible flat cable 103 with a connector connects the first electronic device 101 and the second electronic device 102. The first electronic device 101 and the second electronic device 102 exchange a first differential signal and a second operating signal with each other.

[0023] The first electronic device 101 includes a first differential transmission line 101a and a second differential transmission line 101b. The second electronic device 102 includes a third differential transmission line 102a and a fourth differential transmission line 102b. The first differential transmission line 101a and the third differential transmission line 102a are connected via a flexible flat cable 103 with a connector. The first differential signal is exchanged between the first differential transmission line 101a and the third differential transmission line 102a. The second differential transmission line 101b and the fourth differential transmission line 102b are connected via a flexible flat cable 103 with a connector. The second differential signal is exchanged between the second differential transmission line 101b and the fourth differential transmission line 102b.

[0024] The flexible flat cable 103 with connectors comprises a flexible flat cable 1, a first connector 111, and a second connector 112. The first connector 111 and the second connector 112 are provided at the ends of the flexible flat cable 1.

[0025] The first connector 111 has a plurality of first terminals 111a. The plurality of first terminals 111a are electrically connected to the transmission lines included in the flexible flat cable 1. When the first connector 111 is plugged into the first electronic device 101, the plurality of first terminals 111a electrically connect the transmission lines of the flexible flat cable 1 to the differential transmission lines 101a and 101b of the first electronic device 101.

[0026] The second connector 112 has a plurality of second terminals 112a. The plurality of second terminals 112a are electrically connected to the transmission lines contained in the flexible flat cable 1. When the second connector 112 is plugged into the second electronic device 102, the plurality of second terminals 112a electrically connect the transmission lines of the flexible flat cable 1 to the differential transmission lines 102a and 102b of the second electronic device 102. As a result, the first differential transmission line 101a and the third differential transmission line 102a are connected, and the second differential transmission line 101b and the fourth differential transmission line 102b are connected.

[0027] [Regarding the configuration of flexible flat cables] Figure 2 is a perspective view showing an example of a flexible flat cable according to the embodiment. Figure 3 is a cross-sectional view taken along the line III-III in Figure 2. The flexible flat cable 1 according to this embodiment is a cable that electrically connects a first electronic device 101 and a second electronic device 102 inside the electronic device 100.

[0028] In the following explanation, the three mutually orthogonal directions in each figure will be referred to as the X, Y, and Z directions. Also, as shown in Figure 2, one direction of the X direction will be referred to as the X1 direction, and the opposite direction of the X1 direction will be referred to as the X2 direction. One direction of the Y direction will be referred to as the Y1 direction, and the opposite direction of the Y1 direction will be referred to as the Y2 direction. One direction of the Z direction will be referred to as the Z1 direction, and the opposite direction of the Z1 direction will be referred to as the Z2 direction. Figure 3 shows a cross-section of the flexible flat cable 1 along the XZ plane as viewed from the Y2 direction.

[0029] In Figure 2, the longitudinal direction of the flexible flat cable 1 (hereinafter also referred to as FFC1) is along the Y direction. The width direction of FFC1 is along the X direction. In the following explanation, it will be assumed that FFC1 is positioned in an extended state in the Y direction, as shown in Figure 2.

[0030] FFC1 includes multiple conductor lines 2, an insulating layer 4, and a shielding layer 6. In other words, FFC1 is a shielded flexible flat cable. The multiple conductor lines 2 are flat rectangular conductors made of copper or the like. The width dimension of the multiple conductor lines 2 along the X direction is the same for all of them. The multiple conductor lines 2 extend along the Y direction and are arranged parallel to each other. The multiple conductor lines 2 extend over almost the entire length (Y direction) of the FFC1.

[0031] Multiple conductor lines 2 include multiple transmission lines 8 and multiple open lines 14. As shown in Figure 3, the multiple transmission lines 8 are arranged in a line along the X direction in a cross-section perpendicular to the longitudinal direction of the multiple conductor lines 2. The multiple transmission lines 8 are arranged along the first arrangement line P1. The first arrangement line P1 is a straight line that aligns with the arrangement of the multiple transmission lines 8 in a cross-section perpendicular to the longitudinal direction. The first arrangement line P1 is a line that aligns with the X direction and is located approximately in the center of the Z direction of FFC1. The multiple transmission lines 8 include multiple ground lines 10, a pair of first signal lines 11, and a pair of second signal lines 12.

[0032] Multiple ground lines 10 are arranged in a line along the first alignment line P1 in a cross section perpendicular to the longitudinal direction. The multiple ground lines 10 include a first ground line 10a, a second ground line 10b, a third ground line 10c, and a fourth ground line 10d. The first ground line 10a, the second ground line 10b, the third ground line 10c, and the fourth ground line 10d are arranged in order along the X1 direction. Each of the multiple ground lines 10, on the Y2 direction side, is electrically connected to the first terminal 111a (Figure 1) of the first connector 111. Each of the multiple ground lines 10, on the Y1 direction side, is electrically connected to the second terminal 112a (Figure 1) of the second connector 112. The terminals connected to the multiple ground lines 10 are connected to the ground lines of the first electronic device 101 and the second electronic device 102.

[0033] As shown in Figure 3, the pair of first signal lines 11 and the pair of second signal lines 12 are located between the multiple ground lines 10 in a cross section perpendicular to the longitudinal direction of the multiple conductor lines 2. The pair of first signal lines 11 are used as transmission lines for the first differential signal. The Y2 direction end of each of the pair of first signal lines 11 is electrically connected to the first terminal 111a (Figure 1) of the first connector 111. The Y1 direction end of each of the pair of first signal lines 11 is electrically connected to the second terminal 112a (Figure 1) of the second connector 112. The pair of second signal lines 12 are used as transmission lines for the second differential signal. The Y2 direction end of each pair of second signal lines 12 is electrically connected to the first terminal 111a (Figure 1) of the first connector 111. The Y1 direction end of each pair of second signal lines 12 is electrically connected to the second terminal 112a (Figure 1) of the second connector 112.

[0034] The pair of first signal lines 11 are located between the first ground line 10a and the second ground line 10b, as shown in Figure 3. The pair of first signal lines 11 are aligned along the first array line P1. The pair of second signal lines 12 are located between the third ground line 10c and the fourth ground line 10d, as shown in Figure 3. The pair of second signal lines 12 are aligned along the first array line P1. Between the pair of first signal lines 11 and the pair of second signal lines 12, there are two ground lines 10 (second ground line 10b and third ground line 10c).

[0035] Thus, the multiple ground lines 10, the pair of first signal lines 11, and the pair of second signal lines 12 are arranged in a line along the first arrangement line P1. Furthermore, the multiple ground lines 10, the pair of first signal lines 11, and the pair of second signal lines 12 are arranged at equal intervals in the X direction.

[0036] Each of the multiple open tracks 14 has an electrically open end. Furthermore, each of the multiple open tracks 14 is not grounded. In other words, when a pair of first signal lines 11 and a pair of second signal lines 12 are used as transmission lines, both ends of the multiple open lines 14 are electrically open without being connected to connectors or the like. As a result, the multiple open lines 14 are not connected to equipment or the like, and are not grounded. Therefore, the multiple open lines 14 are electrically floating. In this embodiment, the thickness of the multiple open lines 14 is thinner than the thickness of the multiple transmission lines 8. However, the thickness of the multiple open lines 14 may be the same as the thickness of the multiple transmission lines 8, or it may be thicker than the thickness of the multiple transmission lines 8.

[0037] The multiple open tracks 14 include a pair of first open tracks 14a, a pair of second open tracks 14b, a pair of third open tracks 14c, and a pair of fourth open tracks 14d. As shown in Figure 3, the pair of first open lines 14a are located on the first direction side (Z1 direction side) of the pair of first signal lines 11 in a cross section perpendicular to the longitudinal direction. The first direction is the direction perpendicular to the arrangement direction (X direction) of the multiple transmission lines 8. The position of the pair of first open lines 14a in the X direction coincides with the position of the pair of first signal lines 11 in the X direction. The pair of second open lines 14b are located on the second direction side (Z2 direction side) of the pair of first signal lines 11 in a cross section perpendicular to the longitudinal direction. The second direction is the opposite direction to the first direction. The position of the pair of second open lines 14b in the X direction coincides with the position of the pair of first signal lines 11 in the X direction.

[0038] The pair of third open lines 14c are located on the first direction side (Z1 direction side) of the pair of second signal lines 12 in a cross section perpendicular to the longitudinal direction. The positions of the pair of third open lines 14c in the X direction coincide with the positions of the pair of second signal lines 12 in the X direction. The pair of fourth open lines 14d are located on the second direction side (Z2 direction side) of the pair of second signal lines 12 in a cross section perpendicular to the longitudinal direction. The position of the pair of fourth open lines 14d in the X direction coincides with the position of the pair of second signal lines 12 in the X direction.

[0039] As shown in Figure 3, the pair of first open lines 14a and the pair of third open lines 14c are arranged in a line along the arrangement direction (X direction) of the multiple transmission lines 8. The pair of first open lines 14a and the pair of third open lines 14c are arranged along the second arrangement line P2. The second arrangement line P2 is a straight line along the arrangement of the pair of first open lines 14a and the pair of third open lines 14c in a cross section perpendicular to the longitudinal direction. The second arrangement line P2 is parallel to the first arrangement line P1 and is located on the Z1 direction side of the first arrangement line P1. The pair of second open lines 14b and the pair of fourth open lines 14d are arranged in a line along the arrangement direction (X direction) of the multiple transmission lines 8, as shown in Figure 3. The pair of second open lines 14b and the pair of fourth open lines 14d are arranged along the third arrangement line P3. The third arrangement line P3 is a straight line along the arrangement of the pair of second open lines 14b and the pair of fourth open lines 14d in a cross section perpendicular to the longitudinal direction. The third arrangement line P3 is parallel to the first arrangement line P1 and is located on the Z2 direction side of the first arrangement line P1. Note that the distance in the Z direction between the first alignment line P1 and the second alignment line P2 is the same as the distance in the Z direction between the first alignment line P1 and the third alignment line P3.

[0040] The insulating layer 4 is provided around the multiple conductor lines 2. The insulating layer 4 covers the sides of the multiple conductor lines 2 and is interposed between the multiple conductor lines 2. In this way, the insulating layer 4 insulates the multiple conductor lines 2 from each other. The insulating layer 4 also maintains the arrangement of the multiple conductor lines 2. The insulating layer 4 is formed by laminating multiple sublayers. For example, the insulating layer 4 is formed by laminating at least four sublayers separated along the first arrangement line P1, the second arrangement line P2, and the third arrangement line P3. As the multiple sublayers to be laminated, for example, a flexible resin film is used. As the material of the film, polyester resin, polyphenylene sulfide resin, and polyimide resin are used. Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, and polybutylene naphthalate resin. In addition, an adhesive layer made of an insulating material may be interposed between the multiple sublayers.

[0041] In this embodiment, multiple conductor lines 2 are arranged along a first arrangement line P1, a second arrangement line P2, and a third arrangement line P3. Therefore, when stacking multiple sublayers, multiple conductor lines 2 can be arranged, and it becomes easy to provide multiple conductor lines arranged along each plane.

[0042] The shield layer 6 is laminated on the outer surface of the insulating layer 4. The shield layer 6 includes a pair of shield films 16. The pair of shield films 16 cover the insulating layer 4 from the Z1 direction and the Z2 direction. The X-direction ends of the pair of shield films 16 are bonded to the X-direction end face of the insulating layer 4. This constitutes the shield layer 6. The shield layer 6 (a pair of shield films 16) is, for example, a resin film on which a conductor such as aluminum has been vapor-deposited. The shielding layer 6 shields against noise generated when signals are applied to the pair of first signal lines 11 and the pair of second signal lines 12, and also shields the pair of first signal lines 11 and the pair of second signal lines 12 from external noise.

[0043] According to the FFC1 configuration described above, when a pair of first signal lines 11 and a pair of second signal lines 12 are used as transmission lines, the multiple open lines 14 reflect and absorb the crosstalk components radiated from the pair of first signal lines 11 and the pair of second signal lines 12. This makes it possible to suppress the mutual propagation of crosstalk components between the pair of first signal lines 11 and the pair of second signal lines 12. As a result, crosstalk between the pair of first signal lines 11 and the pair of second signal lines 12 is effectively reduced.

[0044] In other words, according to the FFC1 of this embodiment, there is no configuration in which the shield layer and the ground wire are bonded with a conductive adhesive, as in the conventional flexible flat cable described above, so crosstalk can be reduced with a simpler configuration.

[0045] The effect of reducing crosstalk may vary depending on the distance d1 (Figure 3) between the multiple open lines 14 and the pair of first signal lines 11 (pair of second signal lines 12). Reducing the interval d1 increases the crosstalk reduction effect, but also increases the insertion loss in the pair of first signal lines 11. Increasing the spacing d1 reduces the insertion loss in the pair of first signal lines 11, but also reduces the effect of reducing crosstalk. Therefore, the interval d1 is determined by considering the balance between the crosstalk reduction effect and the insertion loss.

[0046] Figure 4 is a plan view showing the end of the FFC1 according to the embodiment. In Figure 4, parts of the insulating layer 4 and the shielding layer 6 of the FFC1 are omitted. As shown in Figure 4, the pair of first open lines 14a overlap with the pair of first signal lines 11 in a plan view. Also, the pair of third open lines 14c overlap with the pair of second signal lines 12 in a plan view. In other words, the positions of the pair of first signal lines 11 in the direction of arrangement (X direction) and the positions of the pair of first open lines 14a in the direction of arrangement (X direction) overlap with each other. Also, the positions of the pair of second signal lines 12 in the direction of arrangement (X direction) and the positions of the pair of third open lines 14c in the direction of arrangement (X direction) overlap with each other. Furthermore, the positions of the pair of first signal lines 11 in the X direction and the positions of the pair of second open lines 14b in the X direction also overlap with each other, and similarly, the positions of the pair of second signal lines 12 in the X direction and the positions of the pair of fourth open lines 14d in the X direction also overlap with each other.

[0047] In this way, the positions of the signal lines 11 and 12 in the X direction and the position of the open line 14 in the X direction overlap, so that the open line 14 is positioned in a location where it can become a path for crosstalk components. As a result, the multiple open lines 14 can effectively suppress the mutual transmission of crosstalk components between the pair of first signal lines 11 and the pair of second signal lines 12.

[0048] Furthermore, as shown in Figures 4 and 2, the lengths of the multiple open lines 14 in the Y direction are shorter than the length of the transmission line 8. The lengths of the multiple open lines 14 in the Y direction are the same as each other. The positions of both ends of each of the multiple transmission lines 8 in the Y direction coincide with the positions of the end faces 1a of FFC1 in the Y direction. The ends of each of the multiple open tracks 14 in the Y direction are located away from the end face 1a in the Y direction.

[0049] As shown in Figure 4, the pair of end edges 14a1 of the pair of first open tracks 14a are located on the Y1 side relative to the end face 1a. Similarly, the pair of end edges 14c1 of the pair of third open tracks 14c are also located on the Y1 side relative to the end face 1a. Note that the pair of end edges 14a1 are the Y2 side end edges of the pair of first open tracks 14a, and the pair of end edges 14c1 are the Y2 side end edges of the pair of third open tracks 14c. Furthermore, the pair of end edges of the pair of second open tracks 14b, and the pair of end edges of the pair of fourth open tracks 14d, are also located on the Y1 side of the end face 1a. In other words, each of the multiple transmission lines 8 has multiple extensions 8a that extend beyond the edges of the multiple open lines 14.

[0050] Therefore, there are no open tracks 14 in the Y-direction region E between the end face 1a and the edges of the multiple open tracks 14. Figure 4 shows the Y2-direction end of FFC1, but the Y1-direction end of FFC1 has the same configuration as the Y2-direction end of FFC1. Therefore, multiple transmission lines 8 also have multiple extensions 8a at the Y1-direction end, and region E also exists at the Y1-direction end of FFC1 (Figure 2). Thus, FFC1 has a region E at both ends where there are no open tracks 14. The first connector 111 is provided in the region E at the Y2 direction end of the FFC1. Therefore, the first terminal 111a of the first connector 111 is connected to multiple extensions 8a and is not electrically connected to multiple open lines 14. Furthermore, the second connector 112 is provided in the region E at the Y1 direction end of the FFC1. Therefore, the second terminal 112a of the second connector 112 is connected to multiple extensions 8a and is not electrically connected to multiple open lines 14. In this way, the ends of each of the multiple open lines 14 are not electrically connected to the connectors 111 and 112, and the multiple open lines 14 remain electrically open. In other words, both ends of the open track 14 are unconnected sections that are not connected to terminals 111a and 112a of connectors 111 and 112.

[0051] As described above, the pair of first signal lines 11 are used as transmission lines for the first differential signal, and the pair of second signal lines 12 are used as transmission lines for the second differential signal. Therefore, in Figure 4, the extensions 8a of the pair of first signal lines 11 are connected to the first differential transmission line 101a of the first electronic device 101 via the first connector 111. The extensions 8a of the pair of first signal lines 11 on the Y1 direction side are connected to the third differential transmission line 102a of the second electronic device 102 via the second connector 112. In other words, the extensions 8a of the pair of first signal lines 11 constitute the first connection end connected to the first differential transmission line 101a. As a result, the first differential signal is transmitted to the pair of first signal lines 11.

[0052] Furthermore, in Figure 4, the extensions 8a of the pair of second signal lines 12 are connected to the second differential transmission line 101b of the first electronic device 101 via the first connector 111. The extensions 8a of the pair of second signal lines 12 on the Y1 direction side are connected to the fourth differential transmission line 102b of the second electronic device 102 via the second connector 112. In other words, the extensions 8a of the pair of second signal lines 12 constitute a second connection end that is connected to the second differential transmission line 101b. As a result, the second differential signal is transmitted to the pair of second signal lines 12.

[0053] [Regarding variations] Figure 5 is a cross-sectional view of FFC1 according to the first modified example. This modified example differs from the above embodiment in that a ground line 10e is interposed between the pair of first signal lines 11 and the pair of second signal lines 12. The configuration is otherwise the same.

[0054] As in this modified example, even when there is only one ground line 10 between the pair of first signal lines 11 and the pair of second signal lines 12, there are multiple open lines 14, so that crosstalk between the pair of first signal lines 11 and the pair of second signal lines 12 is effectively reduced.

[0055] Figure 6 is a cross-sectional view of FFC1 according to the second modified example. This modified example differs from the above embodiment in that the width dimension in the X direction of the multiple open lines 14 is greater than the width dimension in the X direction of the multiple transmission lines 8. In this case as well, crosstalk between the pair of first signal lines 11 and the pair of second signal lines 12 is effectively reduced.

[0056] In this modified example, the case where the width dimension in the X direction of the multiple open lines 14 is larger than the width dimension in the X direction of the multiple transmission lines 8 is illustrated, but the width dimension in the X direction of the multiple open lines 14 may be smaller than the width dimension in the X direction of the multiple transmission lines 8.

[0057] Figure 7 is a cross-sectional view of FFC1 according to the third modified example. This modified example differs from the above embodiment in that the positions of the multiple open lines 14 in the X direction are offset from the positions of the pair of first signal lines 11 and the pair of second signal lines 12.

[0058] In this modified example, the pair of first open lines 14a and the pair of second open lines 14b are offset in the X1 direction relative to the pair of first signal lines 11. The positions of the pair of first signal lines 11 in the X direction and the positions of the pair of first open lines 14a in the X direction overlap with each other, and similarly the positions of the pair of first signal lines 11 in the X direction and the positions of the pair of second open lines 14b in the X direction also overlap with each other. The pair of third open lines 14c and the pair of fourth open lines 14d are offset in the X2 direction relative to the pair of second signal lines 12. The positions of the pair of second signal lines 12 in the X direction and the positions of the pair of third open lines 14c in the X direction overlap with each other, and the positions of the pair of second signal lines 12 in the X direction and the positions of the pair of fourth open lines 14d in the X direction also overlap with each other. Therefore, the pair of first signal lines 11 and the pair of open lines 14a and 14b overlap each other in a plan view. Similarly, the pair of second signal lines 12 and the pair of open lines 14c and 14d also overlap each other in a plan view. In this case as well, crosstalk between the pair of first signal lines 11 and the pair of second signal lines 12 is effectively reduced.

[0059] 〔others〕 It should be noted that the embodiments disclosed herein are illustrative in all respects and not restrictive. For example, the above embodiments and modifications illustrate a case where four open lines 14 are provided for a pair of first signal lines 11 and a pair of second signal lines 12. However, it is sufficient to have at least one open line 14. In this case, the open line 14 is located on at least one side of either the pair of first signal lines 11 or the pair of second signal lines 12 in either the Z1 direction or the Z2 direction. In this case, it is sufficient that the position of the open track 14 in the X direction coincides with the position of the pair of signal tracks in the X direction.

[0060] Furthermore, a pair of open lines 14 may be provided for only one pair of signal lines among the pair of first signal lines 11 and the pair of second signal lines 12, or two pairs of open lines 14 may be provided. When a pair of open lines 14 are provided in the signal line pair, the pair of open lines 14 are provided in only one of the Z1 and Z2 directions. When two pairs of open lines 14 are provided in the signal line pair, one pair of open lines 14 is provided in each of the Z1 and Z2 directions.

[0061] Furthermore, the above embodiments and modifications illustrate a case where the FFC1 comprises a pair of first signal lines 11 and a pair of second signal lines 12. However, the FFC1 may also comprise one or more pairs of third signal lines. In this case, the pair of third signal lines are arranged between multiple ground lines 10, similar to the pair of first signal lines 11 and the pair of second signal lines 12.

[0062] Furthermore, in the above embodiments and modifications, the example given is that each of the multiple open lines 14 is composed of a single line extending over almost the entire longitudinal area of ​​the FFC 1. However, the open lines 14 may be provided in only a part of the entire longitudinal area of ​​the FFC 1, as long as they have a length corresponding to the frequency (wavelength) of the signal transmitted through the multiple transmission lines 8. Alternatively, the open lines 14 may be composed of multiple divided lines arranged in a single line over the entire longitudinal area of ​​the FFC 1. In other words, the open lines 14 may be fragmented in the longitudinal direction. In this case, the length of each of the multiple divided lines is determined according to the frequency (wavelength) of the signal transmitted through the multiple transmission lines 8.

[0063] The scope of the present invention is indicated by the claims, not in the sense described above, and is intended to include the meaning and scope of equivalents of the claims, and all modifications within that scope.

[0064] [Regarding verification tests] Next, we will describe the verification tests conducted on the flexible flat cable mentioned above. In the verification tests, models were constructed for the examples and comparative examples shown below, and the characteristics of each example and comparative example were determined by computer simulation using these models.

[0065] Examples The FFC1 used in the flexible flat cable 103 with connector shown in the embodiment was constructed as a model for the example. The dimensions of each part in the embodiment were set as follows. Length L1 (Figure 2: Length in the Y direction of FFC1, ground line 10, and signal lines 11, 12): 50 mm Length L2 (Figure 2: Length in the Y direction of multiple open tracks 14): 45 mm Width W1 (Figure 3: Width of insulating layer 4 in the Z direction): 0.7 mm Spacing d1 (Figure 3: Spacing between open track 14 and signal tracks 11 and 12): 0.21 mm Width W2 (Figure 3: width in the X direction of open track 14, signal tracks 11 and 12): 0.28 mm Spacing d2 (Figure 3: Pitch of adjacent conductor lines 2): 0.52 mm Thickness of ground track 10, signal tracks 11 and 12: 0.05 mm Thickness of open track 14: 0.03mm

[0066] Furthermore, the impedance of the pair of first signal lines 11 and the pair of second signal lines 12 in FFC1 was set to 102Ω. Furthermore, polyethylene was assumed as the material for the insulating layer 4, with a relative permittivity of εr = 2.25 and a dielectric loss tangent of tanδ = 0.001.

[0067] • Comparative Example A comparative example model was constructed by removing several open tracks 14 from the example.

[0068] Comparison of Examples and Comparative Examples The S-parameter S21 was determined as the insertion loss when the Y1 direction end of the pair of first signal lines 11 was designated as port 1, the Y2 direction end of the pair of first signal lines 11 was designated as port 2, the Y1 direction end of the pair of second signal lines 12 was designated as port 3, and the Y2 direction end of the pair of second signal lines 12 was designated as port 4. Similarly, S11 was determined as the return loss, S31 as the near-end crosstalk (NEXT), and S41 as the far-end crosstalk (FEXT).

[0069] Figure 8 is a graph showing the frequency characteristics of insertion loss for the example and comparative example. In Figure 8, the horizontal axis represents the frequency of the transmitted signal, and the vertical axis represents the insertion loss (S21). Also, in Figure 8, the solid line represents the graph for the example, and the dashed line represents the graph for the comparative example. As shown in Figure 8, there is no significant difference between the insertion loss of the embodiment and the insertion loss of the comparative example. Therefore, this result confirms that the open line 14 does not affect the passage characteristics of the signal lines 11 and 12.

[0070] Figure 9 is a graph showing the frequency characteristics of the reflection loss for the example and comparative example. In Figure 9, the horizontal axis represents the frequency of the transmitted signal, and the vertical axis represents the reflection loss (S11). Also, in Figure 9, the solid line represents the graph for the example, and the dashed line represents the graph for the comparative example. As shown in Figure 9, there is no significant difference between the reflection loss of the embodiment and the reflection loss of the comparative example. Therefore, this result confirms that the open line 14 does not affect the reflection characteristics of the signal lines 11 and 12.

[0071] Figure 10 is a graph showing the frequency characteristics of near-end crosstalk for the example and comparative example. In Figure 10, the horizontal axis represents the frequency of the transmitted signal, and the vertical axis represents the near-end crosstalk (S31). Also, in Figure 10, the solid line represents the graph for the example, and the dashed line represents the graph for the comparative example. As shown in Figure 10, the near-end crosstalk in the embodiment is reduced across the entire frequency band of 0-20 GHz, which is the measurement range, compared to the near-end crosstalk in the comparative example.

[0072] Figure 11 is a graph showing the frequency characteristics of far-end crosstalk for the example and comparative example. In Figure 11, the horizontal axis represents the frequency of the transmitted signal, and the vertical axis represents the far-end crosstalk (S41). Also, in Figure 11, the solid line represents the graph for the example, and the dashed line represents the graph for the comparative example. As shown in Figure 11, the far-end crosstalk in the embodiment is reduced across the entire frequency band of 0-20 GHz, which is the measurement range, compared to the far-end crosstalk in the comparative example.

[0073] As described above, the verification test results confirm that the flexible flat cable according to the embodiment can effectively reduce crosstalk. The effects of the embodiments described herein are not limited to those described above. [Explanation of Symbols]

[0074] 1 Flexible flat cable 1a End face 2 Conductor lines 4. Insulating layer 6 Shield Layer 8. Transmission lines 8a extension 10 Grand Railway 10a First Ground Track 10b Second Ground Track 10c Third Ground Track 10d 4th Ground Track 10e Grand Track 11. First signal line 12. Second signal line 14 Open track 14a 1st open track 14a1 edge 14b 2nd open track 14c 3rd open track 14c1 edge 14d 4th open track 16 Shield film 100 Electronic equipment 101 1st electronic device 101a First differential transmission line 101b Second differential transmission line 102 Second electronic device 102a Third differential transmission line 102b Fourth differential transmission line 103 Flexible flat cable with connector 111 First Connector 111a 1st terminal 112 Second connector 112a 2nd terminal E area P1 1st plane P2 2nd plane P3 3rd plane W1 width W2 width d1 interval d2 interval

Claims

1. Multiple conductor lines arranged parallel to each other, The system comprises an insulating layer provided around the plurality of conductor lines, The aforementioned plurality of conductor lines are Multiple transmission lines arranged in a line in a cross-section perpendicular to the longitudinal direction of the aforementioned multiple conductor lines, It includes at least one open line with both ends electrically open, The aforementioned plurality of transmission lines are Multiple ground tracks and The cross-section includes a pair of first signal lines and a pair of second signal lines located between the plurality of ground lines, The open line is located in the cross-section on the first direction side of the pair of first signal lines, which is perpendicular to the arrangement direction of the plurality of transmission lines. Flexible flat cable.

2. The insulating layer further comprises a shielding layer provided on the outer surface of the insulating layer. The flexible flat cable according to claim 1.

3. The position in the arrangement direction of at least one of the pair of first signal lines and the position in the arrangement direction of the open line overlap with each other. The flexible flat cable according to claim 1.

4. The aforementioned open tracks are numerous, The plurality of open lines include a pair of first open lines located on the first direction side of the pair of first signal lines in the cross-section. The flexible flat cable according to claim 1.

5. The plurality of open lines further include a pair of second open lines located in the cross-section on the second direction side, which is the opposite direction to the first direction of the pair of first signal lines. The flexible flat cable according to claim 4.

6. The multiple open tracks are, In the cross-section, a pair of third open lines located on the first direction side of the pair of second signal lines, The cross-section further includes a pair of fourth open lines located on the second direction side of the pair of second signal lines. The flexible flat cable according to claim 5.

7. The pair of first open lines and the pair of third open lines are arranged in a line along the direction of arrangement in the cross-section. The pair of second open lines and the pair of fourth open lines are arranged in a line along the direction of arrangement in the cross-section. The flexible flat cable according to claim 6.

8. Each of the aforementioned plurality of transmission lines has an extension at both ends that extends beyond both ends of the open line. The flexible flat cable according to claim 1.

9. The pair of first signal lines each have a first connection end connected to a first differential transmission line. The pair of second signal lines have second connection ends connected to the second differential transmission line. The flexible flat cable according to claim 1.

10. Flexible flat cable and The flexible flat cable comprises connectors provided at both ends, The aforementioned flexible flat cable is Multiple conductor lines arranged parallel to each other, The system comprises an insulating layer provided around the plurality of conductor lines, The aforementioned plurality of conductor lines are Multiple transmission lines arranged in a line in a cross-section perpendicular to the longitudinal direction of the aforementioned multiple conductor lines, It includes at least one open line, the ends of which are unconnected portions not connected to the terminals of the connector, The aforementioned plurality of transmission lines are Multiple ground tracks and It includes a pair of first signal lines and a pair of second signal lines, both of which are connected to the terminals of the connector and located between the plurality of ground lines in the cross-section, The open line is located in the cross-section on the first direction side of the pair of first signal lines, which is perpendicular to the arrangement direction of the plurality of transmission lines. Flexible flat cable with connector.

11. The first electronic device and, A second electronic device that exchanges a first differential signal and a second differential signal with the first electronic device, The device comprises a flexible flat cable connecting the first electronic device and the second electronic device, The aforementioned flexible flat cable is Multiple conductor lines arranged parallel to each other, The system comprises an insulating layer provided around the plurality of conductor lines, The aforementioned plurality of conductor lines are Multiple transmission lines arranged in a line in a cross-section perpendicular to the longitudinal direction of the aforementioned multiple conductor lines, It includes at least one open line with both ends electrically open, The aforementioned plurality of transmission lines are Multiple ground tracks and The cross-section includes a pair of first signal lines and a pair of second signal lines located between the plurality of ground lines, The pair of first signal lines are lines for the first differential signal, The pair of second signal lines are lines for the second differential signal, The open line is located in the cross-section on the first direction side of the pair of first signal lines, which is perpendicular to the arrangement direction of the plurality of transmission lines. electronic equipment.

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