Communication Cable

Abstract

In a communication cable having a multi-core cable with a plurality of core cables in which a pair of signal lines are covered with an insulator, in which the insulator is covered with a shield tape, and in which the shield tape is covered with a wrapping tape, and having a connector formed on an end portion of the multi-core cable, the communication cable further has a substrate to which each core cable is connected; a first joint portion at which the signal line and the substrate are solder-joined to each other; a second joint portion at which the shield tape and the substrate are solder-joined to each other; and a resin portion which molds a connection portion between the core cable and the substrate, and the connection portion excluding the first joint portion and the second joint portion is molded by the resin portion.

Claims

1. A communication cable including a cable and a connector formed on an end portion of the cable, the cable including a signal line, an insulator covering the signal line, a shield member covering the insulator, and an insulating member covering the shield member, the communication cable comprising: a case which is inserted/removed to/from a slot formed on a communication device to which the communication cable is connected; a substrate housed in the case and to which the cable is connected; a first joint portion at which the signal line and the substrate are solder-joined to each other; a second joint portion at which the shield member and the substrate are solder-joined to each other; and a resin portion molding a connection portion between the cable and the substrate, wherein the connection portion excluding the first joint portion and the second joint portion is molded by the resin portion.

2. A communication cable including a cable and a connector formed on an end portion of the cable, the cable including a signal line, an insulator covering the signal line, a shield member covering the insulator, and an insulating member covering the shield member, the communication cable comprising: a case which is inserted/removed to/from a slot formed on a communication device to which the communication cable is connected; a substrate housed in the case and to which the cable is connected; a first joint portion at which the signal line and the substrate are solder-joined to each other; a second joint portion at which the shield member and the substrate are solder-joined to each other; and a resin portion molding a connection portion between the cable and the substrate, wherein the connection portion including the second joint portion is molded by the resin portion.

3. The communication cable according to claim 1, wherein the cable is a multi-core cable obtained by collectively bundling a plurality of core cables into one cable, each including the signal line, the insulator, the shield member and the insulating member.

4. The communication cable according to claim 2, wherein the cable is a multi-core cable obtained by collectively bundling a plurality of core cables into one cable, each including the signal line, the insulator, the shield member and the insulating member.

5. The communication cable according to claim 1, further comprising: a plurality of connection pad groups formed along one side of the substrate and in each of which the signal line and the shield member are solder-joined to each other; and a placing portion formed between the one side of the substrate and the plurality of connection pad groups and on which an end portion of the cable is placed.

6. The communication cable according to claim 2, further comprising: a plurality of connection pad groups formed along one side of the substrate and in each of which the signal line and the shield member are solder-joined to each other; and a placing portion formed between the one side of the substrate and the plurality of connection pad groups and on which an end portion of the cable is placed.

7. The communication cable according to claim 5, wherein, when a dimension of the placing portion along a longitudinal direction of the substrate is assumed to be a width of the placing portion, the width of the placing portion is 1 mm or more and 7 mm or less.

8. The communication cable according to claim 6, wherein, when a dimension of the placing portion along a longitudinal direction of the substrate is assumed to be a width of the placing portion, the width of the placing portion is 1 mm or more and 7 mm or less.

9. The communication cable according to claim 5, wherein an end portion of the cable and the placing portion are fixed to each other through an adhesive layer formed between the end portion of the cable and the placing portion.

10. The communication cable according to claim 6, wherein an end portion of the cable and the placing portion are fixed to each other through an adhesive layer formed between the end portion of the cable and the placing portion.

11. The communication cable according to claim 9, wherein the adhesive layer is formed by an adhesive applied onto a solder resist layer formed on a front surface of the placing portion and cured between the solder resist layer and the end portion of the cable.

12. The communication cable according to claim 10, wherein the adhesive layer is formed by an adhesive applied onto a solder resist layer formed on a front surface of the placing portion and cured between the solder resist layer and the end portion of the cable.

13. The communication cable according to claim 11, wherein the adhesive is a cyanoacrylate-based adhesive.

14. The communication cable according to claim 12, wherein the adhesive is a cyanoacrylate-based adhesive.

15. The communication cable according to claim 1, wherein the resin portion is made of a resin material with a tensile shear adhesive strength of 4.8 Mpa or more.

16. The communication cable according to claim 1, wherein the resin portion is made of polyamide, polypropylene or ethylene-vinyl acetate copolymer resin.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0016] FIG. 1 is a perspective view showing an appearance of a communication cable;

[0017] FIG. 2 is a perspective view showing an inner structure of a connector;

[0018] FIG. 3A is a cross-sectional view showing a structure of a multi-core cable;

[0019] FIG. 3B is a perspective view showing a structure of a core cable;

[0020] FIG. 4 is a plan view showing a layout of a pad and a placing portion on a substrate;

[0021] FIG. 5 is an explanatory view showing a connection structure between a multi-core cable and the substrate;

[0022] FIG. 6 is another explanatory view showing the connection structure between the multi-core cable and the substrate; and

[0023] FIG. 7 is still another explanatory view showing the connection structure between the multi-core cable and the substrate.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, one example of an embodiment of a communication cable of the present invention will be described in detail with reference to the drawings. In the following explanation, note that the same or substantially the same components are denoted with the same reference character in each reference drawing.

[0025] A communication cable 1 shown in FIG. 1 is provided with a multi-core cable 2 serving as a cable, and a connector 3 formed on an end portion of the multi-core cable 2. The communication cable is a multi-channel communication cable for transmitting differential signals, and is used for high-speed signal transmission of several tens of Gbit/sec or higher per channel. Specifically, the communication cable 1 is used for 4 channels. Therefore, as shown in FIG. 3A, the multi-core cable 2 includes 8 (2 cables/1 channel) core cables 10. More specifically, two core cables 10 are arranged in the center of the multi-core cable 2, and six core cables 10 are arranged outside the two core cables 10 so as to surround the two core cables 10. A buffer tape 11 is wound around the two center core cables 10, and another buffer tape 12 is wound around the six outer core cables 10. In other words, the buffer tape 11 is interposed between the two inner core cables 10 and the six outer core cables 10. Moreover, a metal foil tape (aluminum tape 13) is wound around the buffer tape 12, the aluminum tape 13 is covered with a copper wire (braid wire 14) braided into a net shape, and the braid wire 14 is covered with a sheath (jacket) 15. Note that the aluminum tape 13 and the braid wire 14 form a shield layer for shielding noises. That is, a plurality of (8 in the present embodiment) core cables 10 included in the multi-core cable 2 are covered with the shield layer. Note that the buffer tape 11 is configured by an insulating tape made of, for example, heat resistant PVC.

[0026] As shown in FIG. 3B, each of the core cables 10 included in the multi-core cable 2 has a pair of signal lines 20a and 20b through which phase-reversal signals are transmitted, an insulator 21 covering these signal lines 20a and 20b, a shield member (shield tape 22) covering the insulator 21, and an insulating member (wrapping tape 23) covering the shield tape 22. In this manner, the multi-core cable 2 has the plurality of core cables 10, and each of the core cables 10 has the signal lines 20a and 20b, the insulator 21, the shield tape 22 serving as a shield member and the wrapping tape 23 serving as an insulating member. Of course, the shield member is not limited to the shield tape 22, and the insulting member is not limited to the wrapping tape 23. In the following explanation, when the signal lines 20a and 20b included in each of the core cables 10 are not particularly distinct from each other, note that the two lines are collectively referred to as “signal line 20” in some cases.

[0027] The shield tape 22 is a laminate body formed of a resin film and a metal film, and is longitudinally wrapped around the insulator 21 so that the resin film is placed inside. The wrapping tape 23 is a tape for preventing loosening of the shield tape 22, and is laterally wrapped (helically wrapped) around the shield tape 22. Note that the shield tape 22 of the present embodiment is a laminate body formed of a PET film and a copper film. However, a material for each film configuring the shield tape 22 is not limited to such a specific material. Moreover, the number of the laminating films configuring the shield tape 22 is not limited to such a specific number of laminating films, either.

[0028] With reference to FIG. 1 again, the connector 3 has a case 30 configured by a lower case 31 and an upper case 32 made of metal. As shown in FIG. 2, the substrate 40 is housed in the case 30, and the substrate 40 housed in the case 30 is fixed inside the case 30. Moreover, the end portion of the multi-core cable 2 is drawn into the case 30, and the end portion of the multi-core cable 2 is connected to the substrate 40. Furthermore, the connection portion between the end portion of the multi-core cable 2 and the substrate 40 is molded by a resin portion 50. The details of the resin portion 50 and the connection portion between the substrate 40 and the end portion of the multi-core cable 2 molded by the resin portion 50 will be described later.

[0029] As shown in FIG. 1 and FIG. 2, a latch 33 which slides in the longitudinal direction of the case 30 is formed on both side surfaces of the case 30. Respective ends of the latches 33 are coupled to each other through a coupling portion 34, and a pull tab 35 is attached to the coupling portion 34. The pull tab 35 extends toward a rear side of the case 30 along the multi-core cable 2 extending from the case 30.

[0030] The connector 3 (case 30) has a shape and a dimension that are insertable/removable to/from the slot (cage) formed in the communication device. When the connector 3 is inserted into the cage, a locking piece formed on the cage is engaged with the connector 3. Meanwhile, when the pull tab 35 is pulled rearward to slide the latch 33 in the same direction, the engagement of the locking piece with the connector 3 is released. Specifically, the above-described locking piece is formed on each of both sidewalls of the cage, which face with each other. When the connector 3 is inserted into the cage, each locking piece is fitted to an engaging portion formed on each of both side surfaces of the connector 3. As a result, the locking pieces are engaged with the connector 3, so that the connector 3 is not pulled out of the cage. On the other hand, when the pull tab 35 is pulled to slide the latches 33 rearward, the locking pieces engaged with the engaging portions are pushed outward from the engaging portions by the tips of the latches 33. As a result, the engagement of the locking pieces with the connector 3 is released, so that the connector 3 can be pulled out of the cage.

[0031] Next, mainly with reference to FIG. 4 to FIG. 6, the details of the resin portion 50 shown in FIG. 2 and the connection portion between the substrate 40 and the end portion of the multi-core cable 2 molded by the resin portion 50 will be described. FIG. 4 is an enlarged plan view of the substrate 40. The substrate 40 shown in the drawing is a glass epoxy substrate, and has a rectangular plane shape as a whole. A plurality of connector pads 41 are formed along one side (short side 40a) of a front surface of the substrate 40, and a plurality of ground pads 42 and signal pads 43 are formed along the other side (short side 40b). The connector pads 41 and the signal pads 43 are electrically connected to each other through a wiring pattern formed on the substrate 40 although not shown. Note that a signal processing IC is formed on the wiring pattern for use in connecting the connector pads 41 and the signal pads 43 in some cases. The following explanation defines a side on which the connector pads 41 are formed among both sides of the substrate 40 in the longitudinal direction as a front side or a forward end side, and defines a side on which the ground pads 42 and the signal pads 43 are formed as a rear side or a rearward end side. Of course, these definitions are only definitions for convenience of explanation.

[0032] As shown in FIG. 4, four ground pads 42 are formed on the rear side of the front surface of the substrate 40. Each of the ground pads 42 has a U-shaped plane shape, and two signal pads 43 are formed inside each ground pad 42. These three pads (one ground pad 42 and two signal pads 43 inside the ground pad) are formed as a set so as to form one connection pad group 44. Moreover, one connection pad group 44 corresponds to one core cable 10 (FIG. 3A). That is, on the front surface of the substrate 40, four connection pad groups 44 corresponding to four core cables 10 are formed along the one side (short side 40b) of the substrate 40.

[0033] Further, on the front surface of the substrate 40, a placing portion 46 is formed between the short side 40b and the connection pad group 44. In other words, a region between the short side 40b and the connection pad group 44 is the placing portion 46. This placing portion 46 is a region where an end portion of the core cable 10 connected to the substrate 40 is placed, and a width (W) of the placing portion 46 is 5 mm. Here, the width (W) of the placing portion 46 is a dimension of the placing portion 46 along a longitudinal direction of the substrate 40.

[0034] Although not shown in the drawings, the same four connection pad groups 44 are also formed on the rear surface of the substrate 40. That is, eight connection pad groups 44 in total are formed on the substrate 40. And, the same connector pads and placing portions as the connector pads 41 and the placing portions 46 shown in FIG. 4 are also formed on the rear surface of the substrate 40.

[0035] As shown in FIG. 2, the forward end side of the substrate 40 protrudes forward from the case 30, and the connector pads 41 formed on the substrate 40 are exposed out of the case 30. The forward end side of the substrate 40 including the connector pads 41 exposed out of the case 30 forms a plug connector of a card edge type.

[0036] As shown in FIG. 4, a plurality of cut-out portions 45 are formed on each long side of the substrate 40. These cut-out portions 45 are used for positioning the substrate 40 while being engaged with protrusions formed inside the lower case 31 (FIG. 2).

[0037] As shown in FIG. 5, the sheath 15, the braid wire 14, the aluminum tape 13, the buffer tape 12 and the buffer tape 11 shown in FIG. 3A are removed in the end portion of the multi-core cable 2 drawn into the case 30 (FIG. 2), so that the end portions of the respective core cables 10 are exposed. At the same time, the end portions of the respective core cables 10 are released from the bonding by the sheath 15, the braid wire 14, the aluminum tape 13, the buffer tape 12 and buffer tape 11, so as to be separated from each other. That is, the multi-core cable 2 is branched into eight lines inside the connector 3 (FIG. 2). Therefore, in the following explanation, each end portion of the core cables 10 that are released from the bonding by the sheath 15 and others and are separated from each other is referred to as “branch wire 10a” to be distinct from other portions of the multi-core cables 10 in some cases. That is, inside the connector 3 (FIG. 2), eight branch wires 10a extend from the end portion of the multi-core cable 2. Of course, the above-described distinction is only distinction for convenience of explanation, and each branch wire 10a is a part of each core cable 10, and is continuously formed from the other portions. Therefore, each branch wire 10a has substantially the same cross-sectional structure as the cross-sectional structure shown in FIG. 3B.

[0038] Note that a ring-shaped shield connection member 2a shown in FIG. 5 is made of a metallic material. From the outer periphery, the shield connection member 2a swages the aluminum tape 13 and the braid wire 14 that are folded back at the end portion of the sheath 15 onto the sheath 15, so that the shield connection member 2a is electrically connected to these members. Moreover, the shield connection member 2a is made in contact with the metallic case 30 (FIG. 2). That is, the aluminum tape 13 and the braid wire 14 are electrically connected to the case 30 through the shield connection member 2a.

[0039] As shown in FIG. 5, each of the end portions of the respective core cables 10 (branch wires 10a) has a region where the wrapping tape 23 shown in FIG. 3B is removed so that the shield tape 22 is exposed, and a portion beyond the region has another region where not only the wrapping tape 23 but also the shield tape 22 and the insulator 21 are removed so that the signal line 20 is exposed. An end portion of each branch wire 10a including the above-described two regions is placed in the placing portion 46 of the substrate 40, and is fixed to the placing portion 46 by an adhesive. Specifically, between the end portion of each branch wire 10a and the placing portion 46, an adhesive layer 47 (FIG. 7) is formed by an adhesive applied onto a solder resist layer which is formed on a front surface of the placing portion 46 and which is cured between the solder resist layer and the end portion of the branch wire 10a, so that the end portion of the branch wire 10a and the placing portion 46 are fixed to each other through the adhesive layer 47.

[0040] The signal line 20 and the shield tape 22 that are exposed at the end portion of each of the branch wires 10a are connected to the connection pad group 44 corresponding to each of the branch wires 10a. More specifically, the signal lines 20a and 20b of one branch wire 10a are solder-joined to the signal pads 43 and 43 belonging to the corresponding connection pad group 44, respectively, and the shield tape 22 of the branch wire 10a is solder-joined to the ground pad 42 belonging to the same connection pad group 44 as the connection pad group 44 to which the signal pads 43 belong, the signal pads 43 being solder-joined with the signal lines 20a and 20b of the corresponding branch wire 10a.

[0041] Therefore, the substrate 40 has eight joint portions at each of which the corresponding core cable 10 (branch wire 10a) and the connection pad group 44 are solder-joined to each other. Specifically, the front surface of the substrate has four joint portions, and the rear surface of the substrate has four joint portions. Moreover, as shown in FIG. 6, the joint portions include a first joint portion at which the signal line 20 and the signal pad 43 (FIG. 4, FIG. 5) are solder-joined to each other and a second joint portion at which the shield tape 22 and the ground pad 42 (FIG. 4, FIG. 5) are solder-joined to each other.

[0042] As shown in FIG. 5 and FIG. 6, the connection portion between each core cable 10 (branch wire 10a) and the substrate 40 is molded by a resin portion 50. More specifically, the connection portion excluding the first joint portion and the second joint portion is molded by the resin portion 50. In other words, the first joint portion and the second joint portion are not molded by the resin portion 50 but exposed. In still other words, the signal line 20 solder-joined to the substrate 40 and the shield tape 22 are not molded by the resin portion 50 but exposed.

[0043] On the other hand, as shown in FIGS. 6 and 7, the resin portion 50 extends to the base or its vicinity of the base of each of the branch wires 10a beyond the rearward end of the substrate 40. That is, the resin portion 50 molds substantially the entire length of each of the branch wires 10a excluding the joint portion to the substrate 40. As a result, the eight branch wires 10a are integrated by the resin portion 50.

[0044] As described above, in the present embodiment, the plurality of core cables 10 included in the multi-core cable 2 are solder-joined to the substrate 40. At the same time, portions of the ends of the respective core cables 10, the portions being not solder-joined to the substrate 40, are collectively molded by the resin portion 50. Further, portions of the ends of the respective core cables 10, the portions being molded by the resin portion 50 (the portions being not solder-joined), are fixed to the placing portion 46 of the substrate 40 by the adhesive. Therefore, even when a bending force and a tensile force are applied to the multi-core cable 2 extending from the connector 3 (case 30), the connection portion between each core cable 10 and the substrate 40, that is, the first joint portion and second joint portion, are difficult to be damaged. For example, the solder joint between the signal line 20 and signal pad 43 at the first joint portion is difficult to be broken, and the signal pad 43 is difficult to be peeled off from the front surface of the substrate. Note that the adhesive for fixing the end portion of the core cable 10 to the placing portion 46 of the substrate 40 also plays a role of temporarily fixing the end portion of the core cable 10 to the substrate 40 in the process of forming the resin portion 50.

[0045] Meanwhile, the first joint portion and the second joint portion of the connection portion between the core cable 10 and the substrate 40 are not molded by the resin portion 50. Therefore, impedances of the first joint portion and the second joint portion are not lowered by a dielectric constant of the resin portion 50. Therefore, even when a high-speed signal of several tens of Gbit/sec or higher is transmitted, reflection of the signal due to impedance mismatching does not occur.

[0046] Of course, the present invention has an embodiment in which the second joint portion is molded by the resin portion 50. In other words, the present invention has an embodiment in which the shield tape 22 is molded by the resin portion 50. This embodiment is inferior to the embodiment in which the first joint portion and the second joint portion are not molded in the impedance matching, but superior thereto in the connection strength. Further, even when the shield tape 22 is molded by the resin portion 50, the influence on the signal transmission is small.

[0047] The present invention is not limited to the above-described embodiments, and can be variously modified within a scope of the invention. For example, the resin portion 50 in the above-described embodiments is made of polyamide. However, the resin material for forming the resin portion 50 is not particularly limited to this material. In place of polyamide, the resin portion 50 may be made of, for example, polypropylene or ethylene-vinyl acetate copolymer resin.

[0048] Furthermore, from the viewpoint of suppressing the damage on the connection portion due to an external force, it is preferable to form the resin portion 50 by a resin material having a tensile shear adhesive strength of 4.8 Mpa or more.

[0049] Further, the adhesive layer 47 according to the above-described embodiments is made of a cyanoacrylate-based adhesive. Of course, the adhesive forming the adhesive layer 47 is not limited to a specific adhesive. Of course, when the adhesive layer 47 is made by an adhesive applied to be overlapped onto the solder resist layer formed on the front surface of the placing portion 46, it is required to select an adhesive which is not prevented from being cured by the solder resist layer.

[0050] The width (W) of the placing portion 46 shown in FIG. 4 is not limited to 5 mm. The width (W) of the placing portion 46 can be appropriately changed under conditions and others that can house the substrate 40 inside the case 30 whose dimension and shape are standardized and that can provide a strength large enough to fix the end portion of the core cable 10 to the substrate 40. When the above-described conditions are considered, note that the width (W) of the placing portion 46 is preferably 1 mm or more and 7 mm or less.

[0051] The communication cable of the present invention includes a communication cable having a connector formed on an end portion of one cable in which a signal line is covered with an insulator, in which the insulator is covered with a shield member, and in which the shield member is covered with an insulating member. Moreover, the cable configuring the communication cable of the present invention includes a multi-core cable obtained by collectively bundling a plurality of core cables into one cable, each of which includes one signal line. That is, the multi-core cable including a plurality of core cables that are not used for transmission of differential signals is also included in the cable configuring the communication cable of the present invention.