Abstract:
A terminator assembly for a twinax wire. According to this embodiment, a PCB is provided which receives the twinax wire and provides a positive connection between a grounding bar of the PCB and the drain wide of the twinax pair. The drain wire is extended in an orthogonal direction to the twinax pair, and is engaged using an interference fit with the grounding bar. The grounding bar assembly also provides improved shielding for the twinax pair, where the integral shielding of the twinax wire has been removed to provide the connection. In an alternate embodiment, the terminating end of the twinax wire itself is encased in a termination clip. This clip provides shielding for the twinax pair, while electrically connecting with the twinax drain wire. The twinax wire, with the terminating clip, can then be easily attached to a connector PCB adapted to receive the terminator clip.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention generally relates to wire termination techniques for twinax and shielded parallel pair wires used for high performance cables and in particular to methods that provide a low inductance path for the drain wire and shield of the twinax wire. 
     2. Description of the Related Art 
     Copper cables for digital communications use many different types of connectors, bulk wire, and wire termination techniques. While copper cables are used in a wide variety of applications, performance requirements for cables continue to increase to keep pace with integrated circuit technology performance increases. In order to meet the performance increases, many copper cables interfaces use low voltage differential signals that require a low skew and low cross-talk connector, bulk wire, and cable assembly construction. 
     The basic types of bulk wire used in I/O (input/output) cables includes ribbon, twisted pair, coax, twinax, and quad constructions. The preferred bulk wire construction for high speed differential cables is a “twinax” or shielded parallel pair wire. The parallel pair construction is optimized to provide low signal skew performance and the shielding surrounding the wire pair ensure low cross-talk between wire pairs, The shield of the twinax wire is stripped back to expose the insulated signal wires and the drain wire for termination processing. The length of shielding removed from the twinax wire has a significant effect on the shielding performance of the wire. 
     I/O connectors that are used in copper cables come in many shapes, sizes, and number of contacts. The number of contacts used in the connector is determined by the signal interface requirements. A differential serial interface would typically use a total of 4 signal contacts while a differential parallel interface would typically use a minimum of 36 signal contacts. Many of the current generation of I/O connectors use additional contacts connected to ground to enhance the performance of the connector interface. Ground blades or plates can be used instead of dedicated ground contacts to further enhance the performance of the connector. Most I/O connectors also include a metal shell that provides a connection from the braid shielding in the bulk wire and continuous 360 degree shield around the connector housing to minimize EMI radiation problems. 
     Typical wire termination techniques for copper cables include bare wire crimping, soldering, welding, and insulation displacement (IDC). Another wire termination technique that is often used for high speed cables includes a small printed circuit card or paddle card attached to the connector with the conductors in the bulk wire soldered to the paddle card. This type of wire termination provides a simple way to incorporate equalization in the cable assembly by adding chip capacitors and resistors to the circuitry on the paddle card. 
     FIG. 7 shows an isometric view of an I/O cable connector  700  attached to a small printed circuit card  704 , in a conventional manner. The I/O cable connector  700  is comprised of an insulating plastic housing  702 , a metal shell  703 , and multiple conductive contacts  701 . The ends of the contacts  701  in the connector  700  are soldered to the corresponding terminal pads  707  on the printed circuit card  704 . The printed circuit card  704  also has multiple terminal pads  706  on the top  705  and bottom surfaces for wire terminations. 
     FIG. 8 shows an isometric view of multiple twinax wires  810  terminated to the printed circuit card  804  attached to the I/O cable connector  800 , in a conventional manner. The twinax wires  810  are comprised of two parallel copper signal wires  812 ,  813  that are covered with insulating dielectric material  814 ,  815  and surrounded by a thin metallized shield  816 . A third bare copper wire  811  or drain wire is located between the two insulated signal conductors  812 ,  813  and soldered to corresponding terminal pads  806  on the surface  805  of the printed circuit card  804 . A portion of the metallized shield  816  is removed to expose the drain wire  811  and the insulation  814 ,  815  covering each of the signal conductors  812 ,  813  to allow soldering to the terminal pads  806  on the printed circuit card  804 . A portion of the insulation  814 , 815  covering each of the signal wires  812 ,  813  is removed to allow soldering to the terminal pads  806  on the printed circuit card  804 . 
     Impedance variations in the cable assembly can cause reflections in a high speed signal interface and result in data errors. Uniform geometry and materials in the bulk wire along with a gradual transition in geometry from the bulk wire to the wire termination and connector interface is essential to minimize impedance variations. Repeatability and consistency of the wire termination process has a similar effect. 
     Cross-talk from one signal to an adjacent signal or excessive skew between the two conductors of a differential signal can also result in data errors. It would therefore be desirable to provide individually shielded twinax construction, which would minimize cross-talk in the bulk wire and consistent dielectric material properties ensure low signal skew. Further, it would be desirable to provide dedicated ground pins, blades, or plates in the connector along with equal length differential signal wiring and a ground plane paddle card construction to further minimize the effects of cross-talk and skew in the connector and wire termination area. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of the present invention to provide a technique for terminating multiple twinax wires with individual shields and drain wires. 
     It is another object of the present invention to provide a technique for minimizing the impedance discontinuity of the wire terminations. 
     It is yet another object of the present invention to provide a technique for minimizing the cross-talk in the wire termination area. 
     It is yet another object of the present invention to provide a low inductance connection from the drain wires on the individually shielded twinax wires to the ground connections in the cable connector. 
     It is yet an additional object of the present invention to provide a technique for terminating the twinax signal conductors directly to the terminals on the cable connector for applications that do not require equalization circuitry in the cable assembly. 
     The foregoing objects are achieved as is now described. The preferred embodiment provides a terminator assembly for a twinax wire. According to this embodiment, a PCB is provided which receives the twinax wire and provides a positive connection between a grounding bar of the PCB and the drain wide of the twinax pair. The drain wire is extended in an orthogonal direction to the twinax pair, and is engaged using an interference fit with the grounding bar. The grounding bar assembly also provides improved shielding for the twinax pair, where the integral shielding of the twinax wire has been removed to provide the connection. In an alternate embodiment, the terminating end of the twinax wire itself is encased in a termination clip. This clip provides shielding for the twinax pair, while electrically connecting with the twinax drain wire. The twinax wire, with the terminating clip, can then be easily attached to a connector PCB adapted to receive the terminator clip. 
     The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 shows an isometric view of a twinax wire; 
     FIG. 2 shows an isometric view of a first embodiment of multiple twinax wires terminated to a small printed circuit card; 
     FIG. 3 shows an isometric view of a twinax wire with a first embodiment of a terminated clip attached to the drain wire; 
     FIG. 4 shows an isometric view of a second embodiment of multiple twinax wires terminated to a small printed circuit card; 
     FIG. 5 shows an isometric view of a twinax wire with a second embodiment of a termination clip attached tot he drain wire; 
     FIG. 6 shows an isometric view of a third embodiment of multiple twinax wires terminated to a small printed circuit card; 
     FIG. 7 shows an isometric view of an I/O cable connector attached to a small printed circuit card; 
     FIG. 8 shows an isometric view of multiple twinax wires terminated to the printed circuit card attached to the I/O cable connector; 
     FIG. 9 shows an isometric view of a twinax wire with an third embodiment of a termination clip attached to the drain wire; and 
     FIG. 10 shows an isometric view of a first embodiment of direct termination of multiple twinax wires to the I/O connector contacts. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference now to the figures, and in particular with reference to FIG. 1, an isometric view of a twinax wire  10  is shown. The twinax wire  10  in FIG. 1 is similar to the twinax wire  810  shown in FIG.  8  and is comprised of two parallel copper signal wires  11 ,  12  that are covered with insulating dielectric material  13 ,  14  and surrounded by a thin metallized shield  16 . A third bare copper wire  15  or drain wire is located between the two insulated signal conductors  11 ,  12  and is used to make contact with the conductive surface of the thin metallized shield  16 . A portion of the metallized shield  16  is removed to expose the drain wire  15  and the insulation  13 ,  14  covering the two signal wires  11 ,  12 . The drain wire  15  is formed at right angle to the axis of the signal wires  11 ,  12 . The portion of the insulation  13 ,  14  covering each of the signal wires  11 ,  12  is removed in preparation of termination. 
     FIG. 2 shows an isometric view of a first embodiment of the present invention, wherein multiple twinax wires  10  are terminated to a small printed circuit card  90 . A grounding bar  95  with multiple apertures  96  and slots  97  is used to align the twinax wires  10  to the terminal pads  93  on printed circuit card  90  and provide a low inductance connection to the drain wires  15  for each of the twinax wires  10 . The size and shape of the apertures  96  in the grounding bar  95  corresponds to the size and shape of the twinax wires  10 . The location of the apertures  96  in the grounding bar  95  correspond to the location of the terminal pads  95  on the printed circuit card  90 . The slots  97  in the grounding bar  95  are sized to provide an interference fit with the drain wires  15  in the twinax wires  10 . The apertures  96  in the grounding bar  95  also provide additional shielding for the twinax wires  10  where the thin metallized shield  16  has been removed. 
     FIG. 3 shows an isometric view of a twinax wire  40  with a first embodiment of a termination clip  50  attached to the drain wire  46 . The twinax wire  40  in FIG. 3 is similar to the twinax wire  10  shown in FIG.  1  and is comprised of two parallel copper signal wires  41 ,  42  that are covered with insulating dielectric material  43 ,  44  and surrounded by a thin metallized shield  45 . A third bare copper wire  46  or drain wire is located between the two insulated signal conductors  41 ,  42  and is used to make contact with the conductive surface of the thin metallized shield  45 . A portion of the metallized shield  45  is removed to expose the drain wire  46  and the insulation  43 ,  44  covering the two signal wires  41 ,  42 . The drain wire  46  is formed at the right angle to the axis of the signal wires  41 ,  42 . A portion of the insulation  43 ,  44  covering each of the signal wires  41 ,  42  is removed in preparation for termination. A metal termination clip  50  is attached to the twinax wire  40 . The size and shape of the metal clip  50  corresponds to the size and shape of the twinax wire  40 . The slot  51  in the metal clip  50  corresponds to the size and shape of the drain wire  46 . The slot  51  in the metal clip  50  is connected to the drain wire  46  in the twinax wire  40  using an interference fit. The right angle portion of the drain wire  46  is trimmed to be almost flush with the other surface  52  of the metal clip  50 . 
     FIG. 4 shows an isometric view of a second embodiment of the present invention, wherein multiple twinax wires  40  are terminated to a small printed circuit card  70 . A grounding bar  80  with multiple apertures  81  is used to align the twinax wires  40  to the terminal pads  75  on printed circuit card  70  and provide a low inductance connection to the drain wire  46  for each of the twinax wires  40 . The size and shape of the apertures  81  in the grounding bar  80  corresponds to the size and shape of the metal ground clip  50  attached to each of the twinax wires  40 . The location of the apertures  81  in the grounding bar  80  correspond to the location of the terminal pads  75  on the printed circuit card  70 . The metal termination clips  50  attached to each of the twinax wires  40  provide a low inductance connection between the drain wires  46  and the grounding bar  80 . The apertures  81  in the grounding bar  80  also provide addition shielding for the twinax wires  40  where the thin metallized shield  45  has been removed. 
     FIG. 5 shows an isometric view of a twinax wire  20  according to a third embodiment of the present invention, wherein a termination clip  30  is attached to the drain wire  25 . The twinax wire  20  in FIG. 5 is similar to the twinax wire  40  shown in FIG.  3  and is comprised of two parallel copper signal wires  21 ,  21  that are covered with insulating dielectric material  23 ,  24  and surrounded by a thin metallized shield  26 . A third bare copper wire  25  or drain wire is located between the two insulated signal conductors  21 ,  22  and is used to make contact with the conductive surface of the thin metallized shield  26 . A portion of the metallized shield  26  is removed to expose the drain wire  25  and the insulation  23 ,  24  covering the two signal wires  21 ,  22 . The drain wire  25  is formed at right angle to the axis of the signal wires  21 ,  22 . A portion of the insulation  23 ,  24  covering each of the signal wires  21 ,  22  is removed in preparation for termination. A metal termination clip  30  is attached to the twinax wire  20  using an interference fit. The right angle portion of the drain wire  25  is trimmed to be almost flush with the outer surface  32  of the metal clip  30 . An elongated portion  33  of the termination clip  30  extends beyond the end of the signal wires  21 ,  22  and has a slotted end  34 . 
     FIG. 6 shows an isometric view of a third embodiment of multiple twinax wires  20  terminated to a small printed circuit card  60 . Multiple slots  66  in the printed circuit card  60  are used to align the twinax wires  20  to the terminal pads  65  on printed circuit card  60  corresponds to the length of the elongated portion  33  of the metal termination clip  30  attached to each of the twinax wires  20 . The slots  66  in the printed circuit card  60  are located between the terminal pads  65 . The metal termination clips  30  attached to each of the twinax wires  20  provide a low inductance connection between the drain wires  25  and the grounding pads  67  on the printed circuit card  60 . The metal termination clip  30  also provide addition shielding between the twinax wires  20  and the circuitry lines  64  on the printed circuit card  60 . 
     FIG. 9 shows an isometric view of a twinax wire  120  with an third embodiment of a termination clip  130  attached to the drain wire  125 . The twinax wire  120  in FIG. 9 is similar to the twinax wire  40  shown in FIG.  5  and is comprised of two parallel copper signal wires  121 ,  122  that are covered with insulating dielectric material  123 ,  124  and surrounded by a thin metallized shield  126 . A third bare copper wire  125  or drain wire is located between the two insulated signal conductors  121 ,  122  and is used to make contact with the conductive surface of the thin metallized shield  126 . A portion of the metallized shield  126  is removed to expose the drain wire  125  and the insulation  123 ,  124  covering the two signal wires  121 ,  122 . The drain wire  125  is formed at right angle to the axis of the signal wires  121 ,  122 . A portion of the insulation  123 ,  124  covering each of the signal wires  121 ,  122  is removed in preparation for termination. A metal termination clip  130  is attached to the twinax wire  120 . The size and shape of the curved portion of the metal clip  132  corresponds to the size and shape of the twinax wire  120 . The narrow slot  131  in the base of the metal clip  130  is connected to the drain wire  125  in the twinax wire  120  using an interference fit. The right angle portion of the drain wire  125  is trimmed to be almost flush with the outer surface of the metal clip  130 . The geometry of the opposite end  133  of the termination clip is designed to match the multiple cavities  154  in the I/O connector housing  152  shown in FIG.  10 . 
     FIG. 10 shows an isometric view of a first embodiment of a direct termination of multiple twinax wires  120  to the I/O connector contacts  153 . A thin metal tube  140  is attached to each of the signal wires  121 ,  122  on each of the multiple twinax wires  120 . The thin metal tube  140  is attached to the ends of the signal wires  121 ,  122  by mechanical crimping techniques. The metal tube  140  is positioned with the ends of the signal wires  121 ,  122  inserted half way through the length of the tube  140 . The open half of the metal tube  140  is filled with a solder paste material. The multiple twinax wires  120  with the metal termination clips  130  and metal tubes  140  attached are assembled to the I/O connector  150  by aligning the metal tubes  140  with the ends of the contacts  153  in the connector  150  and inserting the termination clips  130  into the multiple cavities  154  in the connector housing  152 . Additional features  134  on the termination clip  130  are used to locate and retain the clips  130  in the connector housing  152 . Localized heating and reflowing of the solder paste in the ends of the metal tubes  140  provides a direct connection between the signal wires  121 ,  122  in the twinax wires  120  and the signal contacts  153  in the I/O connector  150 . The blade shaped end  133  of the termination clip  130  provides a means of directly connecting the drain wire  125  and shield  126  on the twinax wires  120  to the ground contacts on the mating I/O connector. 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.