JP5928242B2 - Differential signal transmission cable and connection method thereof to circuit board - Google Patents

Description

  The present invention relates to a differential signal transmission cable that includes a pair of signal line conductors and transmits a differential signal whose phase is inverted by 180 degrees and a method for connecting the same to a circuit board.

  Conventionally, in devices such as servers, routers, and storage products that handle high-speed digital signals of several Gbit / s or more, differential interface standards such as LVDS (Low Voltage Differential Signal) have been adopted. Differential signals are transmitted between the circuit boards using a differential signal transmission cable. The differential signal has a feature of high resistance to external noise while realizing a low system power supply voltage.

  The differential signal transmission cable has a pair of signal line conductors, and each signal line conductor transmits a positive side signal (positive) and a negative side signal (negative) with the phase inverted by 180 degrees. ing. The potential difference between these two signals (plus signal and minus signal) becomes a signal level. For example, if the potential difference is plus, the signal level is “High”, and if it is minus, the signal level is received as “Low”. It is designed to be recognized on the side.

  As a differential signal transmission cable for transmitting such a differential signal, for example, a technique described in Patent Document 1 is known. The differential signal transmission cable described in Patent Document 1 includes a pair of signal line conductors arranged in parallel at predetermined intervals, and each of these signal line conductors is covered with an insulator. That is, the signal line conductors are held in parallel at predetermined intervals by the insulator. The periphery of the insulator is covered with a sheet-like outer conductor, and the periphery of the outer conductor is covered with a sheath (protective skin).

  Then, by sequentially stripping one end side of the differential signal transmission cable, each signal line conductor and a part of the outer conductor are exposed to the outside. A metal shield connection terminal (ground conductor) is connected to the exposed portion of the external conductor by caulking. The shield terminal includes a plate-like metal and a solder connection pin integrally formed with the plate-like metal, and the plate-like metal is plastically deformed following the shape of the external conductor when caulking. Thereby, the external conductor and the shield terminal are electrically connected, and the external conductor can be electrically connected to the ground pad of the circuit board via the shield terminal (plate metal and solder connection pin).

  Here, in the differential signal transmission cable described in the cited reference 1, the lengths of the exposed portions of the signal line conductors and the solder connection pins are set to substantially the same length, and further from the pad surface of the circuit board. The height position is set to substantially the same height position. This suppresses deterioration of electrical characteristics in the high frequency range (Ghz band), that is, deterioration of characteristic impedance, skew characteristics, and the like. Further, the forming (shape forming) between the exposed portion of each signal line conductor and the solder connection pin is facilitated, and the workability of solder connection to the signal pad and ground pad of the circuit board is improved.

JP 2012-099434 A (FIGS. 1 and 2)

  However, according to the differential signal transmission cable described in Patent Document 1 described above, when the shield connection terminal is plastically deformed (clamped) along the shape of the outer conductor, the cable is placed inside the outer conductor. A certain insulator may be elastically deformed by a caulking force, and as a result, the distance between the signal line conductors further inside the insulator may change, resulting in a manufacturing problem that does not conform to the design dimensions. This may cause a problem that the electrical characteristics of the differential signal transmission cable vary from product to product.

  An object of the present invention is to provide a differential signal transmission cable capable of obtaining stable electrical characteristics for each product and a method for connecting the same to a circuit board.

The differential signal transmission cable of the present invention is formed at a pair of signal line conductors arranged at predetermined intervals via an insulator and at the end of the signal line conductor, and is electrically connected to a signal pad on a circuit board. Electrically connected to a signal pad connecting portion, an outer conductor provided around the insulator, a body portion provided around the outer conductor and electrically connected to the outer conductor, and a ground pad of the circuit board and the ground conductor having a ground pad connection portion connected to said provided around the main body portion, and a heat-shrinkable tube for crimping the outer conductor of the main body portion to contract by heating, said body portion Rukoto is formed into a plate shape, wherein the opposite side coating and the circuit board side of the outer conductor, the heat shrinkable tube to coat the both end portions in the longitudinal direction of the signal line conductors of said main body portion Features To.

  The differential signal transmission cable according to the present invention is characterized in that the main body portion extends to the circuit board side of the outer conductor.

  The differential signal transmission cable according to the present invention is characterized in that a base end side of the ground pad connection portion is formed thicker than a tip end side of the ground pad connection portion.

  The differential signal transmission cable according to the present invention is characterized in that a rough surface portion having a rough surface is provided on at least one of the outer conductor side and the heat shrinkable tube side of the main body portion.

The differential signal transmission cable of the present invention is formed at a pair of signal line conductors arranged at predetermined intervals via an insulator and at the end of the signal line conductor, and is electrically connected to a signal pad on a circuit board. Electrically connected to a signal pad connecting portion, an outer conductor provided around the insulator, a body portion provided around the outer conductor and electrically connected to the outer conductor, and a ground pad of the circuit board A ground conductor having a ground pad connection portion connected to the main body portion, and a heat shrinkable tube provided around the main body portion and shrinking by heating to crimp the main body portion to the outer conductor, and the outer conductor A metal foil that is electrically connected to both the outer conductor and the main body is provided on the uncovered portion that is not covered by the main body .

In the differential signal transmission cable of the present invention, the ground conductor is formed in a rod shape so that the cross-sectional shape is uniform along the longitudinal direction, and the one side along the longitudinal direction is the main body portion, The other side along the longitudinal direction is the ground pad connecting portion .

  In the differential signal transmission cable of the present invention, the insulator side along the longitudinal direction of the signal pad connecting portion and the main body portion side along the longitudinal direction of the ground pad connecting portion are arranged on the pad surfaces of the circuit board. It arrange | positions with respect to the same height position with respect to it.

  The differential signal transmission cable according to the present invention is characterized in that a cross-sectional shape of the ground pad connecting portion is formed in a polygonal shape.

Differential signal transmission cable of the present invention, the surface of the ground pad connections, tin plating process is characterized in that it into effect.

The differential signal transmission cable of the present invention is formed at a pair of signal line conductors arranged at predetermined intervals via an insulator and at the end of the signal line conductor, and is electrically connected to a signal pad on a circuit board. Electrically connected to a signal pad connecting portion, an outer conductor provided around the insulator, a body portion provided around the outer conductor and electrically connected to the outer conductor, and a ground pad of the circuit board A ground conductor having a ground pad connection portion connected to the main body portion, and a heat shrinkable tube that is provided around the main body portion and contracts by heating to crimp the main body portion to the outer conductor . A conductor is formed of a metal tape, a portion wound around the outer conductor is the main body portion, and a portion drawn in the longitudinal direction of the signal line conductor is the ground pad connection portion. And wherein the door.

  The differential signal transmission cable according to the present invention is characterized in that a pair of the ground pad connection portions are provided so as to be mirror-image symmetric with respect to each signal line conductor.

A method for connecting a differential signal transmission cable to a circuit board according to the present invention provides a cable assembly including a pair of signal line conductors arranged at predetermined intervals via an insulator and an outer conductor provided around the insulator. A grounding conductor provided with a plate-like main body provided around the outer conductor and electrically connected to the outer conductor, and a ground pad connecting portion electrically connected to the ground pad of the circuit board. Preparing a heat shrinkable tube that shrinks by heating, preparing a circuit board on which a signal pad and the ground pad are formed, and exposing the signal line conductor from an end of the cable assembly A connection portion forming step for forming a signal pad connection portion electrically connected to the signal pad, and the signal pad of the outer conductor. A vicinity of de connecting portion the main body portion so as to cover the opposite side positioning said circuit board side of the outer conductor, in the longitudinal direction of the signal line conductors of the main body under the state A positioning step of positioning the heat-shrinkable tube so as to cover both ends along the line, and heating and shrinking the heat-shrinkable tube to crimp the main body to the outer conductor to complete a differential signal transmission cable. A tube heating step, and a solder connection step of soldering the signal pad connection portion and the ground pad connection portion of the differential signal transmission cable so as to face the signal pad and the ground pad, respectively. Features.

  According to the differential signal transmission cable of the present invention and the connection method thereof to the circuit board, the main body portion of the ground conductor is attached by the contraction force of the heat-shrinkable tube that is smaller than the crimping force by the conventional crimping process. Since the outer conductor is pressure-bonded, the elastic deformation of the insulator inside the outer conductor can be suppressed while firmly connecting the ground conductor and the outer conductor. Accordingly, the distance between the signal line conductors can be made as designed, and thus stable electrical characteristics can be obtained for each product.

It is a perspective view which shows the connection structure of the cable for differential signal transmission which concerns on 1st Embodiment of this invention, and a circuit board. It is A arrow directional view of FIG. (A) is sectional drawing which follows the BB line of FIG. 2, (b) is sectional drawing which follows the CC line of FIG. 2, (c) is sectional drawing which shows the modification of a heat-shrinkable tube. It is. (A) is a perspective view showing the details of the ground conductor of FIG. 2, (b) is a perspective view showing a first modification of the ground conductor, (c) is a second modification of the ground conductor. FIG. It is a flowchart figure which shows the connection procedure to the circuit board of the cable for differential signal transmission of FIG. It is explanatory drawing explaining the assembly procedure of the cable for differential signal transmission of FIG. FIG. 2 is a perspective view showing a case where a plurality of differential signal transmission cables in FIG. 1 are connected to a circuit board. It is a top view corresponding to Drawing 2 showing the cable for differential signal transmission concerning a 2nd embodiment of the present invention. It is a cross-sectional view showing a differential signal transmission cable according to a third embodiment of the present invention. (A) is a perspective view which shows the detail of the conductor for grounds of the cable for differential signal transmission which concerns on 4th Embodiment of this invention, (b) is a modification of the conductor for grounds of Fig.10 (a). It is sectional drawing shown. (A) is a perspective view which shows the detail of the conductor for grounds of the cable for differential signal transmission which concerns on 5th Embodiment of this invention, (b) is a modification of the conductor for grounds of Fig.11 (a). It is a perspective view shown. It is a perspective view which shows the cable for differential signal transmission which concerns on 6th Embodiment of this invention.

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

  FIG. 1 is a perspective view showing a connection structure between a differential signal transmission cable and a circuit board according to the first embodiment of the present invention, and FIG. 2 is a view taken in the direction of arrow A in FIG.

  As shown in FIGS. 1 and 2, the differential signal transmission cable 10 according to the first embodiment includes a pair of signal line conductors 11. A positive signal (positive) as a differential signal is transmitted to one of the signal line conductors 11, and a negative signal (negative) as a differential signal is transmitted to the other of the signal line conductors 11. ) The signal is transmitted. Each signal line conductor 11 is formed of, for example, an annealed copper wire (Tinned Annealed Copper Wire) whose surface is tin-plated, and each signal line conductor 11 is covered with an insulator 12.

  The insulator 12 is made of, for example, expanded polyethylene (Expanded Poly-Ethylene) in order to give the differential signal transmission cable 10 flexibility, and has a substantially elliptical cross section. The insulator 12 holds the signal line conductors 11 so as to be arranged at a predetermined interval, and the insulators 12 are arranged around the signal line conductors 11 so as to have substantially the same thickness. Here, the melting temperature of the foamed polyethylene which is the material of the insulator 12 is set to [110 ° C. to 120 ° C.]. However, the insulator 12 is not limited to a substantially elliptical cross section as shown in the figure. For example, the insulator 12 is an insulator having a circular cross section so as to cover each signal line conductor 11 separately. May be. Further, as shown in the drawing, the insulator is not limited to a substantially elliptical insulator having straight portions on the upper and lower sides, but may be a substantially elliptical insulator having an arc shape on each of the upper and lower straight portions.

  3A is a cross-sectional view taken along line BB in FIG. 2, FIG. 3B is a cross-sectional view taken along line CC in FIG. 2, and FIG. 3C is a cross-sectional view showing a modification of the heat-shrinkable tube. Represents.

  As shown in FIG. 3A, most of the signal line conductors 11 along the longitudinal direction are disposed inside the insulator 12, and the end portions (left side in the figure) of the signal line conductors 11 are insulated. It is exposed outside the body 12. The exposed portion of each signal line conductor 11 is a signal pad connection portion 11a, and the signal pad connection portion 11a is electrically connected to the signal pad 22 of the circuit board 20 by solder connection. The length dimension of each signal pad connecting portion 11a is set to approximately L1. Here, since the surface of each signal pad connecting portion 11a has been subjected to tin plating as described above, the solder wettability is improved, so that high quality solder connection (molding of solder fillet) is achieved. This is possible (see the shaded area in FIG. 2).

  Each signal pad connecting portion 11 a is formed in advance into a stepped shape before connecting the differential signal transmission cable 10 to the circuit board 20. Here, since the cross-sectional shape of each signal pad connecting portion 11a is circular, stress concentration does not occur during forming. Therefore, each signal pad connecting portion 11a can be easily formed without breaking. Further, the height difference between the distal end side and the proximal end side of each signal pad connection portion 11a, that is, the height dimension from the pad surface on the circuit board 20 on the insulator 12 side along the longitudinal direction of each signal pad connection portion 11a is: As shown in FIG. 2, both are set to substantially h1.

  An outer conductor 13 for suppressing the influence of external noise is provided around the insulator 12. The outer conductor 13 is formed of, for example, a sheet-like copper foil and covers the entire periphery of the insulator 12. However, the external conductor 13 is not limited to a copper foil, and may be another metal foil, or may be a braided sheet in which a thin metal wire such as an annealed copper wire is knitted.

  As shown in FIGS. 1 and 3 (a) and 3 (b), most of the outer conductor 13 along the longitudinal direction is covered with a sheath 14, and the end of the outer conductor 13 (the left side in the figure) is a sheath. 14 is exposed to the outside. Here, the sheath 14 is formed of, for example, heat-resistant PVC (Heat Resistant Polyvinyl Chloride), and functions as an outer skin that protects the differential signal transmission cable 10.

  4A is a perspective view showing details of the ground conductor in FIG. 2, FIG. 4B is a perspective view showing a first modification of the ground conductor, and FIG. 4C is a second modification of the ground conductor. A perspective view is shown.

  A ground conductor 15 is provided at a portion exposed to the outside of the outer conductor 13, that is, at an end portion of the outer conductor 13. As shown in FIG. 4A, the ground conductor 15 is formed of a metal plate material such as copper having excellent conductivity, and is formed into a substantially rectangular plate shape, and is integrated with the main body portion 15a. It has a pair of molded ground pad connection portions 15b.

  As shown in FIG. 2, the main body portion 15 a is provided around the outer conductor 13, and is curved following the peripheral shape of the outer conductor 13. The main body 15 a covers the opposite side (upper half in the drawing) of the outer conductor 13 along the short direction (thickness direction) of the outer conductor 13 and is electrically connected to the outer conductor 13. As a result, the main body 15a can be easily attached to the outer conductor 13, and the assembly workability of the differential signal transmission cable 10 is improved (see arrow (1) in FIG. 6).

  As shown in FIG. 3B, each ground pad connecting portion 15b has a circular shape with the same cross-sectional shape as each signal line conductor 11 and a length of about L2 (L2>). L1). Here, by making the cross-sectional shape of each ground pad connection portion 15b circular, stress concentration is prevented during forming as with each signal pad connection portion 11a.

  The base end portion of each ground pad connecting portion 15b is connected to both end sides (left and right end sides in FIG. 2) along the longitudinal direction of the main body portion 15a. That is, the pair of ground pad connection portions 15b are provided so as to be mirror-image symmetric with respect to each signal line conductor 11.

  The tip of each ground pad connection portion 15b is electrically connected to the ground pad 23 of the circuit board 20 by solder connection. Here, the surface of each ground pad connection portion 15b is subjected to tin plating in the same manner as each signal pad connection portion 11a. Therefore, solder wettability is improved, and high-quality solder connection (forming of solder fillets) is possible (see the shaded portion in FIG. 2).

  Each ground pad connection portion 15b is formed in a stepped shape in advance before connecting the differential signal transmission cable 10 to the circuit board 20, and the difference in height between the distal end side and the proximal end side of each ground pad connection portion 15b, That is, as shown in FIG. 2, the height dimension from the pad surface of the circuit board 20 on the connection side with the main body portion 15a along the longitudinal direction of each ground pad connection portion 15b is set to substantially h2. h2 = h1). Thus, the base end sides of the signal pad connection portions 11a and the ground pad connection portions 15b are arranged at the same height position with respect to the pad surface of the circuit board 20, respectively.

  As shown in FIGS. 3A and 3B, each of the signal pad connection portions 11 a and each of the ground pad connection portions 15 b is viewed from the side of the differential signal transmission cable 10. It is attached to the outer conductor 13 so that it sometimes overlaps. This suppresses deterioration of electrical characteristics in the high frequency range (Ghz band), that is, deterioration of characteristic impedance and skew characteristics.

  In addition, the formation of each signal pad connecting portion 11a and each ground pad connecting portion 15b can be easily performed simultaneously, and the workability of solder connection to the signal pad 22 and the ground pad 23 of the circuit board 20 is improved. .

  The ground conductor 15 may have a shape as shown in FIG. 4B (first modification). The ground conductor 15 of the first modification is different from the ground conductor 15 of FIG. 4A in that one ground pad connection portion 15b is omitted. Thus, by omitting one ground pad connecting portion 15b, the ground conductor 15 can be reduced in size and weight, and the connection work (solder connection) of the differential signal transmission cable 10 to the circuit board 20 is simplified. can do.

  Further, the ground conductor 15 may have a shape (second modified example) as shown in FIG. The ground conductor 15 of the second modification is different from the ground conductor 15 of FIG. 4B in that the cross-sectional shape of the ground pad connection portion 15b is a square shape (polygonal shape). . Further, the difference is that an arcuate wide portion 15c is provided in which the proximal end side of the ground pad connecting portion 15b is thicker than the distal end side.

  Thus, by making the cross-sectional shape of the ground pad connection portion 15b square, the ground conductor 15 can be easily formed by only one step of punching, and thus the manufacturing cost can be reduced. . Furthermore, since the ground pad connecting portion 15b and the ground pad 23 can be brought into surface contact, a more suitable solder connection can be made and the reliability of the product can be improved. Further, since the arc-shaped wide portion 15c can increase the rigidity of the base of the ground pad connecting portion 15b and reduce the stress concentration acting on the root, the ground pad connecting portion 15b is damaged when the ground pad connecting portion 15b is formed. Can be surely prevented.

  However, both of the ground pad connection portions 15b in FIG. 4A may have a square cross-sectional shape, and each of the ground pad connection portions 15b has an arcuate wide width at the roots of both. The part 15c may be provided. Further, the cross-sectional shape of each ground pad connection portion 15b is not limited to a circular shape or a square shape (quadrangle), but may be a triangular shape or a polygonal shape that is a pentagon or more. In this case, it is preferable to form one polygonal surface so as to be in surface contact with the ground pad 23.

  As shown in FIGS. 3A and 3B, a heat shrinkable tube 16 that shrinks by heating is provided around the main body portion 15 a of the ground conductor 15. The heat shrinkable tube 16 is formed of, for example, polyolefin, and is covered with a margin (gap) around the outer conductor 13 and the ground conductor 15 before heat shrinkage as shown in FIG. It has become.

  The shrinkage temperature of the heat shrinkable tube 16 is set to [80 ° C. to 100 ° C.]. Therefore, when the heat shrinkable tube 16 is shrunk, the insulator 12 (melting temperature [110 ° C. to 120 ° C.]) is melted. There is nothing wrong. The shrinkage ratio of the heat shrinkable tube 16 is set to 2: 1 or more.

  The heat-shrinkable tube 16 is located on the side opposite to the ground pad connecting portion 15b side, that is, on the sheath 14 side (right side in FIGS. 3A and 3B) along the short direction of the main body portion 15a of the ground conductor 15. It is provided so that the edge part of this may be coat | covered. Thereby, the main body 15 a can be electrically connected to the external conductor 13 while positioning the ground conductor 15 at a predetermined position of the external conductor 13. Here, the contraction force by the heat shrinkable tube 16 can be adjusted by the heating temperature and the heating time. In the present embodiment, the contraction force is set to a force that does not cause the insulator 12 to be elastically deformed while the main body portion 15a is pressure-bonded to the outer conductor 13 and electrically connected so that both can be sufficiently conducted. Yes. That is, the distance between the signal line conductors 11 is not changed by the contraction force of the heat shrinkable tube 16.

  Here, the heat-shrinkable tube 16 may have a shape (modified example) as shown in FIG. The heat-shrinkable tube 16 according to this modification includes the ground pad connecting portion 15b side along the short direction of the main body portion 15a of the ground conductor 15, that is, the longitudinal direction of each signal line conductor 11 of the main body portion 15a, and the opposite side. And both ends (the left and right sides in FIG. 3C) are covered. As described above, the heat-shrinkable tube 16 covers both ends along the short direction of the main body portion 15a, so that the number of heating points increases. Compared to the heat-shrinkable tube 16 shown in FIGS. 3 (a) and 3 (b). Thus, the pull-out strength of the ground conductor 15 can be improved.

  As shown in FIGS. 1 to 3, the circuit board 20 to which the differential signal transmission cable 10 is electrically connected includes a resin board body 21. The signal pad 22 and a pair of ground pads 23 are formed. Each signal pad 22 and each ground pad 23 are arranged in a line corresponding to each signal pad connection portion 11 a and each ground pad connection portion 15 b of the differential signal transmission cable 10.

  Each signal pad 22 is electrically connected to a pair of signal lines 24 formed on the surface portion 21 a of the substrate body 21, and a differential signal is transmitted through each signal line 24.

  On the other hand, each ground pad 23 is electrically connected to one end portion of a through hole 25 penetrating from the front surface portion 21a of the substrate body 21 toward the back surface portion 21b. The other end of each through-hole 25 is electrically connected to the entire ground 26 formed on the back surface 21b.

  Here, each signal pad 22, each ground pad 23, each signal line 24, and the entire surface ground 26 are simultaneously formed on the front surface portion 21a and the back surface portion 21b of the substrate body 21 together with other circuit patterns (not shown). It has become so.

  Next, a method for connecting the differential signal transmission cable 10 formed as described above to the circuit board 20 will be described in detail with reference to the drawings.

  5 is a flowchart showing a procedure for connecting the differential signal transmission cable of FIG. 1 to the circuit board, and FIG. 6 is an explanatory diagram for explaining an assembly procedure of the differential signal transmission cable of FIG. .

[Part preparation process]
First, in step S1 of FIG. 5, as shown in FIG. 6, a cable assembly CA manufactured in another manufacturing process is prepared. Here, the cable assembly CA includes a pair of signal line conductors 11 arranged at predetermined intervals via the insulator 12, an external conductor 13 provided around the insulator 12, and a sheath 14 provided around the external conductor 13. , Indicates a state of the sub-assembly where the ground conductor 15 is not connected.

  In step S1, the main body 15a provided around the outer conductor 13 and electrically connected to the outer conductor 13 and the ground electrically connected to the ground pad 23 of the circuit board 20 (see FIG. 1). While preparing the grounding conductor 15 provided with the pad connection part 15b, the heat contraction tube 16 which shrinks by heating is prepared.

  Further, in step S1, the circuit board 20 manufactured in another manufacturing process, that is, each signal pad 22, each ground pad 23, each signal line 24, each through hole 25, the entire ground 26 and other circuit patterns are formed. The prepared circuit board 20 is prepared. Thereby, the parts preparation process is completed.

[Connection part forming process]
Next, in step S2 of FIG. 5, as shown in FIG. 6, a process of sequentially stripping the end portions of the cable assembly CA is performed. Specifically, the insulator 12 and the external conductor 13 are removed by a predetermined length from the end of the cable assembly CA to expose the end of each signal line conductor 11, and thereby each signal pad 22 of the circuit board 20. Each signal pad connection part 11a electrically connected to (refer FIG. 1) is formed. In step S2, the sheath 14 is removed from the end of the outer conductor 13 by a predetermined length to expose the outer conductor 13. Thereby, a connection part formation process is completed.

[Positioning process]
Thereafter, in step S3 of FIG. 5, the main body portion 15a of the ground conductor 15 is positioned in the vicinity of each signal pad connection portion 11a of the external conductor 13 as indicated by an arrow (1) in FIG. Next, in this state, as shown by an arrow (2) in FIG. 6, the heat shrinkable tube 16 is covered and positioned so as to cover the main body portion 15a. Here, when positioning the main body 15a, the direction of each ground pad connection portion 15b is directed toward each signal pad connection portion 11a, and the positions of these tip portions (the left end portion in the figure) are set in the longitudinal direction of the cable assembly CA. To match. Thereby, the positioning process is completed.

[Tube heating process]
Thereafter, in step S4 of FIG. 5, the heat shrinkable tube 16 is contracted by heating the periphery of the heat shrinkable tube 16 evenly using a heating jig (not shown) (not shown). Then, the main body portion 15a is pressure-bonded to the outer conductor 13 by the contraction force of the heat-shrinkable tube 16, and the differential signal transmission cable 10 is completed. Thereby, the tube heating process is completed.

[Solder connection process]
Thereafter, in step S5 of FIG. 5, first, as shown in FIGS. 1 to 3, each signal pad connection portion 11a and each ground pad connection portion 15b of the differential signal transmission cable 10 are collectively formed in a stepped shape. To form. Next, the tip ends of the formed signal pad connection portions 11a and the ground pad connection portions 15b face the signal pads 22 and the ground pads 23 of the circuit board 20, respectively, and a total of four places are connected to a connecting jig (solder). Solder with a trowel etc. Thereby, the solder connection process is completed, and the connection work of the differential signal transmission cable 10 to the circuit board 20 is completed.

  Here, since the tip portions of the signal pad connecting portions 11a and the ground pad connecting portions 15b are soldered, the heat (for example, 200 ° C. to 400 ° C.) of the connecting jig is used for the insulator 12 or the heat shrinkable tube. 16 is difficult to transmit. Therefore, the insulator 12 and the heat shrinkable tube 16 are not melted by heat at the time of solder connection.

  FIG. 7 is a perspective view showing a case where a plurality of differential signal transmission cables of FIG. 1 are connected to a circuit board. As shown in FIG. 7, a plurality of (four in the figure) differential signal transmission cables are used. When the cable 10 is connected to the predetermined circuit board 20, the adjacent differential signal transmission cables 10 are not brought into contact with each other in order to prevent crosstalk between the differential signal transmission cables 10. Arrange so that.

  As described above in detail, according to the differential signal transmission cable 10 and the connection method thereof to the circuit board 20 according to the first embodiment, the thermal contraction is smaller than the conventional caulking force by caulking. The main body portion 15a of the ground conductor 15 is crimped to the external conductor 13 by the contraction force of the tube 16, so that the ground conductor 15 and the external conductor 13 are electrically connected to each other and the insulation inside the external conductor 13 is provided. Elastic deformation of the body 12 can be suppressed. Therefore, the distance between the signal line conductors 11 can be set according to the design dimension, and stable electrical characteristics can be obtained for each product.

  Next, a second embodiment of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 8 is a plan view corresponding to FIG. 2 showing a differential signal transmission cable according to the second embodiment of the present invention.

  As shown in FIG. 8, the differential signal transmission cable 30 according to the second embodiment is different in structure of the ground conductor 31 from the first embodiment. As shown in FIG. 8, the ground conductor 31 includes a main body 31 a, and the short side direction (thickness direction) of the external conductor 13 is disposed at both ends (left and right ends in the figure) along the longitudinal direction of the main body 31 a. Arm portions 31b extending to the side of the circuit board 20 are provided. Each arm portion 31b is also curved following the peripheral shape of the outer conductor 13 like the main body portion 31a.

  In addition, by providing each arm part 31b, the space | interval between the cable 30 for differential signal transmission and the circuit board 20 is made wide compared with 1st Embodiment. Here, when the ground conductor 31 is connected to the external conductor 13, the main body 31a and each arm 31b are faced from the longitudinal direction of the external conductor 13 (each signal line conductor 11), and the main body 31a and each arm 31b are faced. The external conductor 13 is inserted and connected to the inside of the arm portion 31b.

  Also in the second embodiment formed as described above, the same effects as those in the first embodiment described above can be achieved. In addition, in the second embodiment, since the ground conductor 31 is connected so as to hold the periphery of the external conductor 13, the contact portion between the external conductor 13 and the ground conductor 31 can be increased, Positioning work before fixing with the heat-shrinkable tube 16 can be performed accurately and reliably. Therefore, stable electrical characteristics can be obtained for each product, and the reliability of the product can be further improved.

  Next, a third embodiment of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 9 is a cross-sectional view showing a differential signal transmission cable according to the third embodiment of the present invention.

  As shown in FIG. 9, the differential signal transmission cable 40 according to the third embodiment has a metal foil on the circuit board 20 side (lower side in the figure) along the short direction (thickness direction) of the outer conductor 13. The conductor sheet 41 is provided. That is, the conductor sheet 41 is provided so as to cover the non-covered portion 13 a that is not covered by the main body portion 15 a of the outer conductor 13. The conductor sheet 41 is made of a metal material having excellent conductivity such as copper, is thinner than the main body portion 15a of the ground conductor 15, and is freely deformable. The conductor sheet 41 is formed in a substantially rectangular shape similar to the main body portion 15a, and is electrically connected to both the external conductor 13 and the main body portion 15a.

  The conductor sheet 41 is positioned at a predetermined position around the outer conductor 13 by the contraction force of the heat contraction tube 16 together with the main body portion 15a. However, as the conductor sheet 41, a braided sheet in which fine metal wires such as an annealed copper wire are knitted can also be used.

  In the third embodiment formed as described above, the same operational effects as those of the first embodiment described above can be obtained. In addition to this, in the third embodiment, the electrical connection between the external conductor 13 and the ground conductor 15 can be made more reliable, so that more stable electrical characteristics can be obtained. Reliability can be further improved.

  Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 10A is a perspective view showing details of the ground conductor of the differential signal transmission cable according to the fourth embodiment of the present invention, and FIG. 10B is a modified example of the ground conductor of FIG. FIG.

  As shown in FIGS. 10A and 10B, the differential signal transmission cable 50 according to the fourth embodiment is different in the structure of the ground conductor 51 from the first embodiment. . As shown in FIG. 10A, the ground conductor 51 includes a main body 51a, and the surface of the main body 51a on the heat-shrinkable tube 16 side (upper side in the drawing) is more surface than other portions of the ground conductor 51. A rough surface portion 51b having a rough surface is formed. The rough surface portion 51b is formed, for example, by rubbing with rough sand paper or the like. However, the rough surface portion 51b is not limited to the heat shrinkable tube 16 side of the main body portion 51a, but may be provided on the outer conductor 13 side (lower side in the drawing) of the main body portion 51a, or the outer conductor 13 side of the main body portion 51a. You may provide only.

  Moreover, you may make it provide the rough surface part 51c (modification) of a shape as shown in FIG.10 (b) in the main-body part 51a of the conductor 51 for grounds. That is, the rough surface portion 51c shown in FIG. 10 (b) is formed by providing a plurality of through holes 51d penetrating in the thickness direction of the main body portion 51a, and this also reduces the surface roughness of the main body portion 51a. 51 can be rougher than the other parts. In this case, all of the plurality of through holes 51d can be formed by a single punching process, and the rough surface portion 51c can be formed at a time on both sides (upper and lower sides in the figure) of the main body 51a.

  Also in the fourth embodiment formed as described above, the same operational effects as those of the first embodiment described above can be achieved. In addition, in the fourth embodiment, the connection strength between the external conductor 13 and the ground conductor 51 or the connection strength between the ground conductor 51 and the heat shrinkable tube 16 is improved. The pull-out strength with respect to the conductor 13 or the heat shrinkable tube 16 can be improved. Further, by providing the rough surface portions 51b and 51c on the outer conductor 13 side of the main body portion 51a, the electrical connection between the ground conductor 51 and the outer conductor 13 can be made more reliable, thereby improving the reliability of the product. Further improvement is possible.

  Next, a fifth embodiment of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 11A is a perspective view showing details of the ground conductor of the differential signal transmission cable according to the fifth embodiment of the present invention, and FIG. 11B is a modified example of the ground conductor of FIG. The perspective view shown is represented.

  As shown in FIGS. 11A and 11B, the differential signal transmission cable 60 according to the fifth embodiment is different in the structure of the ground conductor 61 from the first embodiment. . Specifically, the ground conductor 61 is formed of a pair of rod-shaped conductors 61a having the same diameter as each signal line conductor 11 using a metal material such as copper, and each rod-shaped conductor 61a is connected to each signal pad connecting portion 11a. It is provided so as to be mirror image symmetric with respect to each other. Each bar-shaped conductor 61a has a uniform cross-sectional shape along its longitudinal direction, and the sheath 14 side (one side) along the longitudinal direction becomes the main body portion 61b, and each signal pad connecting portion 11a along the longitudinal direction. The side (the other side) is a ground pad connecting portion 61c. However, the cross-sectional shape of the ground conductor 61 may be a square shape as shown in FIG.

  Then, under the state where each main body 61b is temporarily fixed with the temporary fixing tape 62, each main body 61b is covered with the heat-shrinkable tube 16, and the heat-shrinkable tube 16 is contracted. Thereby, the ground conductor 61 can be positioned and fixed at a predetermined position around the outer conductor 13. However, the material of the temporary fixing tape 62 is preferably made of metal so that the electrical connection between the external conductor 13 and the ground conductor 61 is more reliable. Here, by making the temporary fixing tape 62 made of metal, the temporary fixing tape 62 has the same function as the conductor sheet 41 (see FIG. 9) in the differential signal transmission cable 40 according to the third embodiment. Will have.

  The ground conductor 61 may have a shape (modified example) as shown in FIG. That is, the ground conductor 61 shown in FIG. 11B has a step shape between the main body portion 61b and the ground pad connection portion 61c, and the signal pad connection portion 11a and the ground pad connection portion 61c are adjacent to each other. The distance between is wide. Accordingly, it is possible to cope with a wide space between the signal pad 22 and the ground pad 23 (see FIG. 1) of the circuit board 20.

  Also in the fifth embodiment formed as described above, the same operational effects as those of the above-described first embodiment can be obtained. In addition, in the fifth embodiment, since the shape of the ground conductor 61 can be simplified to a rod shape, the manufacturing cost is further reduced while the end portion of the differential signal transmission cable 60 is reduced in size and weight. can do.

  Next, a sixth embodiment of the present invention will be described in detail with reference to the drawings. Note that portions having the same functions as those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 12 is a perspective view showing a differential signal transmission cable according to the sixth embodiment of the present invention.

  As shown in FIG. 12, the differential signal transmission cable 70 according to the sixth embodiment is different in the structure of the ground conductor 71 from the first embodiment. Specifically, the ground conductor 71 is formed of a metal tape 71a made of a metal material such as copper. The portion of the metal tape 71a wound around the outer conductor 13 becomes the main body portion 71b, and is pulled out in the longitudinal direction of each signal line conductor 11 of the metal tape 71a, that is, pulled out to each signal pad connecting portion 11a side. This portion is the ground pad connection portion 71c. Here, each ground pad connection portion 71c is also provided to be mirror-image symmetric with respect to each signal pad connection portion 11a. It should be noted that the drawing amount of each ground pad connection portion 71c is adjusted to the length dimension of each signal pad connection portion 11a.

  Then, the metal tape 71a is wound around the outer conductor 13, and the main pad 71b is covered with the heat shrinkable tube 16 under the state where each ground pad connecting portion 71c is pulled out (the state shown in the figure). 16 is shrunk. Thereby, the ground conductor 71 can be positioned and fixed at a predetermined position around the outer conductor 13.

  In the sixth embodiment formed as described above, the same operational effects as those of the first embodiment described above can be obtained. In addition, in the sixth embodiment, since the ground conductor 71 can be thinned as a metal tape, the end of the differential signal transmission cable 70 is further reduced in size and weight, and the manufacturing cost is further reduced. can do.

  It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, in the first to fifth embodiments, when each signal pad connecting portion 11a and each ground pad connecting portion 15b, 61c are solder-connected to each signal pad 22 and each ground pad 23, each step is performed in advance. Although what was formed in the attached shape was shown, this invention is not limited to this. For example, when each signal pad and each ground pad are formed at the end of the circuit board, the forming operation can be omitted. As a result, the manufacturing process can be simplified and the manufacturing cost can be reduced. In addition, since each signal pad connection portion and each ground pad connection portion can be made straight, it is possible to obtain more stable electrical characteristics.

  Further, in each of the above embodiments, the differential signal transmission cables 10, 30, 40, 50, 60, 70 are electrically connected to the circuit board 20, and the connection work is completed under this state. Although shown, the present invention is not limited to this. For example, the connection portion between the circuit board and the differential signal transmission cable may be covered with a resin mold. In this case, since the metal portion can be protected from dust, moisture, etc., it becomes possible to maintain predetermined electrical characteristics over a long period of time.

DESCRIPTION OF SYMBOLS 10 Differential signal transmission cable 11 Signal line conductor 11a Signal pad connection part 12 Insulator 13 Outer conductor 13a Uncovered part 15 Ground conductor 15a Body part 15b Ground pad connection part 16 Heat shrinkable tube 20 Circuit board 22 Signal pad 23 Ground Pad 41 Conductor sheet (metal foil)
51b Rough surface 71a Metal tape CA cable assembly

Claims (12)

A pair of signal line conductors arranged at predetermined intervals via an insulator;
A signal pad connection part formed at an end of the signal line conductor and electrically connected to a signal pad of a circuit board;
An outer conductor provided around the insulator;
A main body provided around the outer conductor and electrically connected to the outer conductor; and a ground conductor having a ground pad connecting portion electrically connected to a ground pad of the circuit board;
A heat-shrinkable tube that is provided around the main body portion and contracts by heating to crimp the main body portion to the outer conductor;
Equipped with a,
The main body is formed in a plate shape and covers the side of the outer conductor opposite to the circuit board side,
The heat shrinkable tube, a differential signal transmission cable which is characterized that you cover the both end portions in the longitudinal direction of the signal line conductors of the main body portion. The differential signal transmission cable according to claim 1 , wherein the main body portion extends to the circuit board side of the outer conductor. 3. The differential signal transmission cable according to claim 1 , wherein a proximal end side of the ground pad connection portion is formed thicker than a distal end side of the ground pad connection portion. . 4. The differential signal transmission cable according to claim 1, wherein at least one of the outer conductor side and the heat shrinkable tube side of the main body portion is roughened. A differential signal transmission cable characterized by providing a rough surface portion. A pair of signal line conductors arranged at predetermined intervals via an insulator;
A signal pad connection part formed at an end of the signal line conductor and electrically connected to a signal pad of a circuit board;
An outer conductor provided around the insulator;
A main body provided around the outer conductor and electrically connected to the outer conductor; and a ground conductor having a ground pad connecting portion electrically connected to a ground pad of the circuit board;
A heat-shrinkable tube that is provided around the main body portion and contracts by heating to crimp the main body portion to the outer conductor;
With
A differential signal transmission cable, wherein a metal foil electrically connected to both the outer conductor and the main body is provided on an uncovered portion of the outer conductor that is not covered by the main body. 6. The differential signal transmission cable according to claim 5 , wherein the ground conductor is formed in a rod shape so that a cross-sectional shape is uniform along a longitudinal direction thereof, and the main body portion is disposed on one side along the longitudinal direction. And the other side along the longitudinal direction is the ground pad connecting portion. The differential signal transmission cable according to any one of claims 1 to 6 , wherein the insulator side along the longitudinal direction of the signal pad connecting portion and the main body portion side along the longitudinal direction of the ground pad connecting portion are arranged. The differential signal transmission cable is arranged at the same height position with respect to the pad surfaces of the circuit board. In the differential signal transmission cable according to any one of claims 1 to 7, the differential signal transmission cable, characterized in that the cross-sectional shape of the ground pad connections are formed in a polygonal shape. In differential signal transmission cable according to any one of claims 1 to 8, the surface of the ground pad connections, differential signal transmission cable which tin plating process is characterized in that it into effect. A pair of signal line conductors arranged at predetermined intervals via an insulator;
A signal pad connection part formed at an end of the signal line conductor and electrically connected to a signal pad of a circuit board;
An outer conductor provided around the insulator;
A main body provided around the outer conductor and electrically connected to the outer conductor; and a ground conductor having a ground pad connecting portion electrically connected to a ground pad of the circuit board;
A heat-shrinkable tube that is provided around the main body portion and contracts by heating to crimp the main body portion to the outer conductor;
With
The ground conductor is formed of a metal tape, a portion wound around the outer conductor is used as the main body portion, and a portion drawn out in the longitudinal direction of the signal line conductor is used as the ground pad connection portion. Cable for differential signal transmission. In the differential signal transmission cable according to any one of claims 1 to 10, the difference, characterized in that the ground pad connections, provided the pair so as to be mirror symmetrical with respect to the each signal line conductors Dynamic signal transmission cable. A cable assembly including a pair of signal line conductors arranged at predetermined intervals via an insulator and an outer conductor provided around the insulator is prepared, and is provided around the outer conductor and electrically connected to the outer conductor. Preparing a ground conductor having a plate-like main body portion to be connected and a ground pad connection portion electrically connected to a ground pad of a circuit board, preparing a heat-shrinkable tube that shrinks by heating, A parts preparation step of preparing the circuit board on which a ground pad is formed;
A connecting portion forming step of forming a signal pad connecting portion electrically connected to the signal pad by exposing the signal line conductor from an end portion of the cable assembly;
The main body is positioned so as to cover the outer conductor in the vicinity of the signal pad connecting portion and opposite the circuit board side of the outer conductor, and the signal of the main body under the state is positioned. A positioning step for positioning the heat-shrinkable tube so as to cover both ends along the longitudinal direction of the wire conductor ;
A tube heating step for heating the heat shrinkable tube to shrink the main body portion to the outer conductor to complete a differential signal transmission cable,
A solder connection step of solder connecting the signal pad connection portion and the ground pad connection portion of the differential signal transmission cable so as to face the signal pad and the ground pad, respectively;
A method for connecting a differential signal transmission cable to a circuit board.

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