Abstract:
This invention relates generally to an electrical connector assembly for interconnecting printed circuit boards. More specifically, this invention relates to a high speed, high density electrical connector and connector assembly having wafers with an improved pin conductor. The connector contains a shield plate having at least one contact end that is bent in a direction perpendicular to the plane of the shield plate.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to an electrical connector assembly for interconnecting printed circuit boards. More specifically, this invention relates to a high speed, high density electrical connector and connector assembly having wafers with an improved pin conductor. 
     BACKGROUND OF THE INVENTION 
     Electrical connectors are used in many electronic systems. It is generally easier and more cost effective to manufacture a system on several printed circuit boards (“PCBs”) which are then connected to one another by electrical connectors. A traditional arrangement for connecting several PCBs is to have one PCB serve as a backplane. Other PCBs, which are called daughter boards or daughter cards, are then connected through the backplane by electrical connectors. 
     Electrical connectors can be designed for single-ended signals, as well as for differential signals. A single-ended signal is carried on a single signal conducting path, with the voltage relative to a common ground reference set of conductors being the signal. For this reason, single-ended signal paths are very sensitive to noise present on the common reference conductors. It has thus been recognized that this presents a significant limitation on single-ended signal use for systems with growing numbers of higher frequency signal paths. 
     Differential signals are signals represented by a pair of conducting paths, called a “differential pair.” The voltage difference between the conductive paths represents the signal. In general, the two conducing paths of a differential pair are arranged to run near each other. If any other source of electrical noise is electromagnetically coupled to the differential pair, the effect on each conducting path of the pair should be similar. Because the signal on the differential pair is treated as the difference between the voltages on the two conducting paths, a common noise voltage that is coupled to both conducting paths in the differential pair does not affect the signal. This renders a differential pair less sensitive to cross-talk noise, as compared with a single-ended signal path. One example of a differential pair electrical connector is the GBX™ connector manufactured and sold by the assignee of the present application. 
     While presently available differential pair electrical connector designs provide generally satisfactory performance, the inventors of the present invention have noted that current high density connectors contain very small pins that are weak and sometime break when inserted into vias on the circuit board. This problem is especially apparent on the pins, particularly the press-fit tails, on the shield plate. 
     Therefore, there remains a need for a high speed, high density electrical connector and connector assembly design that provides stronger pins on the shield plate of the connector. 
     SUMMARY OF THE INVENTION 
     The present invention relates an electrical connector including a plurality of wafers, with each wafer having an insulative housing, a plurality of signal conductors and a shield plate. A portion of the shield plate is exposed so that a conductive member can electrically connect the shield plates of the wafers at the exposed portion of the shield plate. The exposed portion preferably contains press-fit contact tails aligned in a row. At least one of the contact tails is bent in a direction substantially perpendicular to the plane of the shield plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of this invention, as well as the invention itself, may be more fully understood from the following description of the drawings in which: 
         FIG. 1  is a perspective view of an embodiment of the electrical connector assembly of the present invention showing one of the wafers of a first electrical connector about to mate with a second electrical connector; 
         FIG. 2  is an exploded view of the wafer of the electrical connector utilizing single ended signals; 
         FIG. 3  is a perspective view of a shield plate of the wafer of  FIG. 2 ; 
         FIG. 4  is a perspective view of the first contact ends of the shield plate of the wafer of  FIG. 2   
         FIG. 5  is an exploded view of the wafer of the electrical connector utilizing differential pair signals; 
         FIG. 6  is a perspective view of a shield plate of the wafer of  FIG. 2 ; 
         FIG. 7  is a perspective view of the wafer assembly at the first contact ends. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is shown an electrical connector assembly in accordance with an embodiment of the present invention. The electrical connector assembly  10  includes a first electrical connector mateable to a second electrical connector  100 . The first electrical connector includes a plurality of wafers  20 , only one of which is shown in  FIG. 1 , with the plurality of wafers  20  preferably held together by a stiffener, such as that disclosed in U.S. Pat. No. 6,872,085, which is incorporated herein by reference. If needed each of the wafers  20  can be provided with an attachment feature  21  for engaging the stiffener. For exemplary purposes only, the first electrical connector has ten wafers  20 , with each wafer  20  having six single-ended signal conductors  24  and a corresponding shield plate  26  (see  FIG. 2 ). However, as will be apparent a person skilled in the art, the number of wafers, the number of signal conductors and the number of shield plates may vary as desired. 
       FIG. 2  is an exploded view of the wafer  20  which includes an insulative housing  22 , formed around the signal conductors  24  and the shield plate  26 , usually by a molding process. The signal conductors  24  are preferably disposed in the housing  22  over the shield plate  26 . The signal conductors  24 , for example, may be pressed into channels provided in the second housing portion  22   b . The first housing  22  is then preferably molded over the assembly to form the wafer  20 . The wafer assembly is more fully described in U.S. Pat. No. 6,409,543, which is incorporated herein by reference. 
     Each signal conductor  24  has a first contact end  30  connectable to a printed circuit board (not shown), a second contact end  32  connectable to the second electrical connector  100 , and an intermediate portion  31  therebetween. Each shield plate  26  has a first contact end  40  connectable to the printed circuit board, a second contact end  42  connectable to the second electrical connector  100 , and an intermediate plate portion  41  therebetween. The shield plate  26  is shown in greater detail in  FIG. 3 . 
     In an embodiment of the present invention, the first contact end  30  of the signal conductors  24  is preferably a press-fit contact tail; and the second contact end  32  of the signal conductors  24  is preferably a dual beam structure configured to mate to a corresponding mating structure of the second electrical connector  100 . The first contact end  40  of the shield plate  26  also includes press-fit contact tails similar to the press-fit contact tails of the signal conductors  24 . The second contact end  42  of the shield plate  26  includes opposing contacting members that are configured to provide a predetermined amount of flexibility when mating to a corresponding structure of the second electrical connector  100 . While the drawings show contact tails adapted for press-fit, it should be apparent to one of ordinary skill in the art that the first contact end  30  of the signal conductors  24  and the first contact end  40  of the shield plate  26  may take any known form (e.g., pressure-mount contact tail, paste-in-hole solder attachment, contact pad adapted for soldering) for connecting to a printed circuit board. 
     Referring to  FIG. 4 , each of the first contact ends  40  of the shield plate  26  contains a neck portion  49  that brings the first contact end  40  out of the plane of the intermediate plate portion  41  and, when assembled in the wafer  20 , toward a respective one of the signal conductors  24 . The neck portion  49  aligns the first contact ends  40  of the shield plate  26  and the first contact ends  30  of the signal conductors  24  in a manner to achieve a desired electrical performance. In the non-limiting embodiment shown, the first contact ends  30  of the signal conductors  24  and the first contact ends  40  of the shield plate  26  are aligned in approximately a straight line when the wafer is assembled. 
     The neck portion  49  has a double bend so that the first contact end  40  extends outward from the intermediate plate portion  41 , in a plane which is substantially parallel to the plane of the shield plate  26 , as shown. The double bent neck portion  49 , however, can operate as a spring when the first contact end  40  is inserted into the via of the PCB, where the insertion force pushes the first contact end  30  back against the double bend. The double bend neck portion  49  extends from the leading edge  48  of the intermediate plate portion  41  so that the connection between the neck portion  49  and the intermediate plate portion  41  is perpendicular to the direction of insertion. The bend is susceptible to being deformed and lose its spring force over time or if there is a slight misalignment during insertion of the first contact end  40  into the via. This can result in a weak first contact end  40  of the shield plate  26 , and the possibility of breakage when inserted into the vias on the PCB. To relieve this weakness, a support member or rib can be positioned on the top or bottom surface of the neck portion  49 . 
     At least one of the first contact ends  40  is formed by bending the contact end upward so that a body portion  43  is approximately perpendicular to the plane of the shield plate, and toward the signal conductors when assembled.  FIG. 4  shows first contact end  40   b , at one edge of the shield plate  26 , being bent in this manner; however, other contact ends can also be bent in the same way. That first contact end  40   b  is bent upward toward the signal conductors  24  for the body portion  43  in a plane approximately perpendicular to the plane of the shield plate  26 . The perpendicular contact end  40   b  can be formed by stamping a tab at the end of the shield plate, then folding the tab upward toward the signal conductors  24 . The fold forms an elongated connection  51  between the first contact end  40   b  and a side edge of the intermediate plate portion  41  and is preferably substantially parallel to the central longitudinal axis of the first contact end  40   b  and perpendicular to the leading edge  48  of the shield plate  26 . Due to the bend in the body portion  43  toward the signal conductors  24 , the first contact end  40   b  is aligned with the first contact ends  30  of the signal conductors  24  and the other first contact ends  40  of the shield plate  26  to form a substantially linear line. 
     The bent first contact end  40   b  need not be at an edge of the shield plate  26 , as illustrated in  FIG. 4 . Rather, the bent contact end  40   b  can be positioned along the leading edge  48  of the shield plate  26 , as shown in  FIG. 3 . Here, the body  43  of the contact  40   b  is punched out of the intermediate plate portion  41  along the leading edge  48 , which forms an opening  46  in the intermediate plate portion  41 . The bent contact end  40   b  has a body portion  43  that attaches to and is integral with the intermediate plate portion  41  along one side to form the connection  51 , and has an opposing side and rear side that are unattached to and free from the intermediate plate portion  41 . The bent contact end  40   b  is a single piece of material that contains a body portion  43  and a contact pin portion  44 . The body portion  43  is integral with the shield plate  26  and shares an elongated side edge with the shield plate  26 . The contact pin portion  44  projects forward from the body portion  43 . In effect, the contact pin portion  44  is supported by the body portion  43  which, in turn, is supported by the shield plate  26 . That results in a strong contact end  40   b , which produces a more reliable, rigid connection with the PCB. 
     Both the leading edge contact  40   b  ( FIG. 3 ) and the side edge contact  40   b  ( FIG. 4 ) provide a strong contact  40   b . Each of those has a connection  51  to the intermediate portion  41  that is parallel to the direction of the insertion force. That provides a strong and durable connection that is better able to oppose the insertion force. Although the body portion  43  is illustrated as supporting only one contact pin portion  44 , more than one contact pin portion  44  can be provided on a single body portion  43 . 
       FIGS. 1-4  show embodiments of the present invention as applied to a connector having single ended signals. The same concept, however, is also applicable to connectors having differential pairs, as shown in  FIGS. 5-6 .  FIG. 5  shows an enlarged view of a wafer  520  for a connector utilizing differential pairs. This wafer is similar to the wafer  20  shown in  FIG. 2 , but with the signal conductors  524  being grouped in pairs  524   a  and  524   b ,  524   c  and  524   d . The wafer  520  includes an insulative housing  522 , formed around the signal conductors  524  and the shield plate  526 , usually by a molding process. The wafer  520  is formed as previously noted for the wafer  20 . 
     Each signal conductor  524  has a first contact end connectable to a printed circuit board (not shown), a second contact end connectable to the second electrical connector, and an intermediate portion therebetween. Each shield plate  526  has a first contact end  540  connectable to the printed circuit board, a second contact end  542  connectable to the second electrical connector, and an intermediate plate portion  541  therebetween. The shield plate  526  is shown in greater detail in  FIG. 6 . Overall, because the signal conductors  524  are grouped in pairs, the relative positioning of the first contact ends of the signal conductors  524  and the first contact ends  540  of the shield plate  526  are slightly different than the shield plate  26  of the wafer  20  (shown in  FIGS. 1-4 ). For the single ended signal wafer  20 , the first contact ends alternate between signal conductor and shield plate, while for the signal pair wafer  500 , the first contact ends of each pair are separated by a first contact end of the shield plate. Thus, for the single ended signal wafer  20 , the pattern of the first end is G-S-G-S-G-S-G, where G signifies a first contact end of the shield plate (a ground signal), and S signifies a first contact end of a signal conductor (a positive or negative signal); for the signal pair wafer  520 , the pattern is G-S-S-G-S-S-G. 
     Referring to  FIG. 6 , each of the first contact ends  540  of the shield plate  526  contains a neck portion  549  that brings the first contact end  540  out of the plane of the shield plate  526  and, when assembled in the wafer  520 , toward the signal conductor  24 . As previously explained for the wafer  20 , the neck portion  549  aligns the first contact ends  540  of the shield plate  526  and the first contact ends  530  of the signal conductors  524  in approximately a straight line when the wafer is assembled. Further, at least one of the first contact ends  540  is formed by bending the contact end so that it is approximately perpendicular to the plane of the shield plate, and toward the signal conductors when assembled.  FIG. 6  shows first contact end  540   b , at the edge of the shield plate  526 , being bent in this manner. That first contact end  540   b  is bent toward the signal conductors  524  in a plane approximately perpendicular to the plane of the shield plate  526 . Due to the bend toward the signal conductors  524 , the first contact end  540   b  also aligns with the first contact ends  530  of the signal conductors and the other first contact ends  40   b  of the shield plate  26  to form a substantially linear line. In doing so, however, there is no bends in the neck portion of the first contact end  540   b.    
     In certain embodiments the neck portion  49  or  549  can include a rib  660  to strengthen the neck portion  49  of  549 . This rib  660  provides reinforcement in the neck portion  49  or  549  to provide strength. However, a rib is not needed in the bent first contact end  40   b  or  540   b  because it does not require the reinforcement. 
       FIG. 7  shows the assembly of the bent first contact end  40   b  or  540   b  in the wafer  20  or  520 . Essentially, the perpendicular first contact end  40   b  or  540   b  of the shield plate  26  or  526  fits in to a notch  700  in the in the insulated housing  22  or  522 . While the remaining parts of the shield plate  26  or  526  lays flat on a surface of the insulated housing  22  or  522 . 
     Although certain presently preferred embodiments of the invention have been specifically described herein, it will be apparent to those skilled in the art to which the invention pertains that variations and modifications of the various embodiments shown and described herein may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention be limited only to the extent required by the appended claims and the applicable rules of law.