JP2005135839A - Differential cable, and mounting method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a differential cable and a mounting method of the same capable of reducing cross-talk between signal cables. <P>SOLUTION: The differential cable comprises a pair of signal wires 11 connected to differential wirings 17 formed on front and back surfaces of a base plate 16; a pair of drain wires 12 arranged between the signal wires 11 to be connected with the grounds 18 formed on the front and back surfaces of the base plate 16; and a shield 13 collectively covering the signal wires 11 and the drain wires 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a differential cable used for a board built-in connector and a mounting method thereof.

  The differential cable is used for a board built-in connector or the like (see, for example, Patent Documents 1 and 2). As shown in FIG. 5A, the differential cable 30 includes a pair of signal lines 31, a single drain line 32, and a shield 33 that collectively covers the signal line 31 and the drain line 32.

  As shown in FIG. 5B, the differential wiring 35 and the ground 36 are arranged so that the board 34 built in the board built-in connector is paired on both the front and back sides. When mounting the plurality of differential cables 30 on the substrate 34, one signal line 31 is connected to the differential wiring 35 on the surface of the substrate 34 and the other signal line 31 is connected to the substrate 34. Are connected to the differential wiring 35 on the back surface. Further, the drain line 32 is connected to the ground 36 between the signal lines 31 connected to the surface of the substrate 34. That is, the drain line 32 is disposed only on one side of the front and back surfaces of the substrate 34.

JP 2002-304917 A JP 2003-141944 A

  However, although the crosstalk generated on the surface of the substrate 34 on which the drain line 32 is disposed is small, there is a problem that the crosstalk generated on the back surface of the substrate 34 on which the drain line 32 is not disposed is very large. In addition, the crosstalk that should be removed by the differential wiring 35 paired on the front and back surfaces of the substrate 34 is also good because the arrangement of the drain lines 32 is not symmetrical on the front and back surfaces of the substrate 34. There was a problem that it could not be removed and remained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a differential cable that can reduce crosstalk between signal lines and a mounting method thereof.

  In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that a pair of signal lines respectively connected to differential wirings formed on both the front and back surfaces of the substrate, and the front and back surfaces of the substrate disposed between these signal lines. A differential cable comprising a pair of drain lines respectively connected to a formed ground, and a shield that collectively covers the signal lines and the drain lines.

  The invention of claim 2 is a mounting method of a differential cable in which a plurality of differential cables having a pair of signal lines and a pair of drain lines are mounted on a substrate having differential wiring and ground on both front and back surfaces. In the differential cable, one signal line is connected to the differential wiring on the surface of the substrate, the other signal line is connected to the differential wiring on the back surface of the substrate, and one drain line is connected to the surface of the substrate. Connect to the ground, connect the other drain line to the ground on the back side of the substrate, and place a drain line between the signal lines on the front and back sides of the substrate for the signal line and drain line of each differential cable. This is a method for mounting a differential cable.

  The invention of claim 3 is the differential cable mounting method according to claim 2, wherein the signal line and the drain line are arranged symmetrically on the front and back surfaces of the substrate.

  According to the present invention, there is an excellent effect that crosstalk between signal lines can be reduced.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a differential cable according to the present embodiment.

  As shown in FIG. 1, the differential cable 10 includes a pair of signal lines 11, a pair of drain lines 12 disposed between the signal lines 11, and a shield 13 that collectively covers the signal lines 11 and the drain lines 12. Is provided. Each signal line 11 includes a central conductor 14 and an insulator 15 that covers the central conductor 14.

  In the present embodiment, two signal lines 11 are arranged in parallel, and two drain lines 12 are arranged in parallel substantially perpendicularly to the center between these signal lines 11, and each signal line 11 and drain line are arranged in parallel. Lines 12 are arranged symmetrically.

  In the differential cable 10 according to the present embodiment, the signal line 11 and the drain line 12 are symmetrically arranged, so that the occurrence of crosstalk between the signal lines 11 can be reduced over the entire length of the differential cable 10. it can. Furthermore, according to the present embodiment, in the conventional differential cable 30, the drain line 12 is added to a place where it was a dead space. Therefore, the cross-sectional area of the differential cable 10 does not increase compared to the conventional case.

  Next, a method for mounting the differential cable 10 will be described with reference to FIG.

  FIG. 2A is a cross-sectional view of a substrate to which a differential cable is connected. FIG. 2B is a cross-sectional view showing a state where the differential cable is mounted on the substrate.

  As shown in FIG. 2A, the substrate 16 is arranged on both the front and back surfaces of the substrate 16, the differential wiring 17 connected to the signal line 11 of the differential cable 10, and the drain line 12 of the differential cable 10. Are connected to each other, and a differential wiring 17 and an insulating layer 19 provided between the grounds 18. The ground 18 is connected to the front and back surfaces of the substrate 16 through a through hole 19 a provided in the insulating layer 19.

  As shown in FIG. 2B, when the differential cable 10 is mounted on the substrate 16, for one differential cable 10, the central conductor 14 of one signal line 11 is connected to the differential wiring 17 on the surface of the substrate 16. , The central conductor 14 of the other signal line 11 is connected to the differential wiring 17 on the back surface of the substrate 16, one drain line 12 is connected to the ground 18 on the surface of the substrate 16, and the other drain line 12 is connected Connected to the ground 18 on the back surface of the substrate 16. The connection of the central conductor 14 of the signal line 11 to the differential wiring 17 and the connection of the drain line 12 to the ground 18 are performed by soldering. Further, with respect to the center conductor 14 and the drain line 12 of the signal line 11 of each differential cable 10, the drain line 12 is disposed between the center conductors 14 of the signal lines 11 on the front and back surfaces of the substrate 16.

  That is, the central conductor 14 and the drain line 12 of the signal line 11 are arranged so as to be symmetrical on the front and back surfaces of the substrate 16. In the present embodiment, the central conductor 14 and the drain line 12 of the signal line 11 are arranged symmetrically with respect to the center C in the thickness direction and the width direction of the substrate 16.

  Next, the crosstalk reduction effect by the mounting method of the differential cable 10 of this Embodiment is demonstrated.

  FIG. 3 is a graph showing the measurement result of crosstalk.

  In FIG. 3, the solid line 20 shows the measurement result of the mounting method of the differential cable 10 of this embodiment, and the broken line 21 shows the measurement result of the conventional differential cable mounting method. Here, a conventional differential cable mounting method is shown in FIG.

  As shown in FIG. 3, in the mounting method of the differential cable 10 of the present embodiment, the crosstalk (near-end crosstalk; NXT) was substantially zero during the measurement, whereas the conventional differential cable In the mounting method, the maximum crosstalk was 1.14%.

  In the mounting method of the differential cable 10 of the present embodiment, the drain line 12 is necessarily arranged between the central conductors 14 of the adjacent signal lines 11 on the front surface or the back surface of the substrate 16. Therefore, according to the present embodiment, the electric field coupling between the center conductors 14 of the signal line 11 can be suppressed and the crosstalk can be reduced as compared with the conventional case.

  Further, since the signal line 11 and the drain line 12 of the differential cable 10 are arranged so as to be symmetrical on the front and back surfaces of the substrate 16, the crosstalk generated on the front and back surfaces of the substrate 16 cancels each other.

  In the differential cable 10, the drain line 12 is not necessarily arranged in the shield 13. For example, as shown in FIGS. 4A and 4B, the drain line 22 may be disposed outside the shield 13. In this way, the number of drain lines 12 (22) can be increased without considering the symmetry of the differential cable 10. As a result, various structures of the differential cable 10 can be considered. In any structure, the mounting method on the substrate 16 may be the same as that of the above-described embodiment.

  Further, instead of the drain line 12 (22) of the differential cable 10, a drain body (not shown) made of a metal or the like instead of the drain line 12 (22) may be provided on the substrate 16. In this case, the drain body may be connected to the ground 18 of the substrate 16 at once.

It is sectional drawing of the differential cable which concerns on this Embodiment. (A) is sectional drawing of the board | substrate with which a differential cable is connected. (B) is sectional drawing which shows the state which mounted the differential cable in the board | substrate. It is a graph which shows the measurement result of crosstalk. (A) is sectional drawing of the differential cable which shows the modification of a drain wire. (B) is sectional drawing of the differential cable which shows the modification of a drain wire. (A) is sectional drawing of the conventional differential cable. (B) is sectional drawing which shows the state which mounted the conventional differential cable in the board | substrate.

Explanation of symbols

10 Differential Cable 11 Signal Line 12 Drain Line 13 Shield 14 Center Conductor 16 Board 17 Differential Wiring 18 Ground

Claims (3)

  A pair of signal lines respectively connected to the differential wiring formed on the front and back surfaces of the substrate; a pair of drain lines respectively disposed between these signal lines and connected to the ground formed on the front and back surfaces of the substrate; A differential cable comprising: a shield that collectively covers the signal line and the drain line.   A differential cable mounting method in which a plurality of differential cables having a pair of signal lines and a pair of drain lines are mounted on a substrate having differential wiring and ground on both front and back surfaces. Are connected to the differential wiring on the surface of the substrate, the other signal line is connected to the differential wiring on the back surface of the substrate, one drain line is connected to the ground on the surface of the substrate, and the other The differential line is characterized in that the drain line is connected to the ground on the back surface of the substrate, and the signal line and the drain line of each differential cable are respectively arranged between the signal lines on the front and back surfaces of the substrate. Cable mounting method. The differential cable mounting method according to claim 2, wherein the signal lines and the drain lines are arranged symmetrically on the front and back surfaces of the substrate.

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