Abstract:
An electrical connector is provided having a conductive receptacle assembly with walls including grounding contacts, and a conductive plug member for connection to the receptacle assembly. The plug member includes peripheral surfaces that electrically engage grounding contacts on the receptacle assembly. A latch assembly is mounted to the plug member and includes a spring biasing face place that lockably engages one wall of the receptacle assembly. The latch assembly is conductive to afford a grounding correction between the plug member and receptacle assembly along one peripheral wall therebetween. The plug is formed with upper and lower shells, each of which is formed as a unitary structure, such as during a diecast molding procedure. The upper and lower shells are conductive and formed with substantially no openings therein to define a chamber therebetween offering significant EMI shielding characteristics. A PC equalization board is enclosed within the upper and lower shells. The PC equalization board is maintained in a fixed position and orientation by directly contacting shelves and keying protrusions formed integrally on the interior surfaces of the sides of one of the upper and lower shells.

Description:
BACKGROUND OF THE INVENTION 
     The preferred embodiments of the present invention generally relate to electrical connectors for use with high speed serial data, and more particularly, to connector assemblies for transferring high speed serial data from a cable to a circuit board. 
     In the past, electrical cable assemblies have been proposed for connecting electrical cable to circuit boards. Conventional cable assemblies have been provided with an equalizer circuit board within the connector for performing signal conditioning. Performing signal conditioning within a circuit in the connector assembly, reduces the time required to incorporate signal conditioning circuit elements with a cable assembly and reduces the time required for connection of the circuit elements with the electrical contacts and the cable conductors. One example of a conventional cable assembly with an equalizer board is described in U.S. Pat. No. 5,766,027, commonly owned with the present application. 
     Conventional high speed serial data connectors (HSSDC) comprise a plug and receptacle combination interconnected through contact fingers. The plug receives an insulated holder that, in turn, receives an equalizer card. The equalizer card includes signal conditioning circuitry. 
     HSSDC connectors form a grounding plane surrounding the adjoining surfaces of the receptacle and plug in order to afford electromagnetic interference (EMI) shielding around the contact fingers forming the high speed serial data connection between the plug and receptacle. In conventional HSSDC connectors, the grounding plane has been maintained by locating a plurality of grounding beams on the top, bottom and side walls of the receptacle and engaging the top, bottom and side surfaces of the plug. Conventional grounding beams are J-shaped integral extensions of the walls and are bent to project forward, upward and into the opening of the receptacle. The J-shaped ground beams are biased inward to maintain an electrical connection with the plug once inserted. 
     However, J-shaped grounding beams take up an operation region inside the receptacle between the receptacle and plug walls. The region thickness substantially equals the radius of the J-shaped portion of the grounding beam. Consequently, the height and width of the opening in the receptacle must be greater than the height and width of the plug by an amount at least equal to the curved radius of the grounding beams. When grounding beams are located above, below and on either side of the plug, they undesirably increase the height and width of the receptacle. Certain applications for HSSDC connectors have significant space constraints. 
     In addition, the distance between the grounding beams should be maintained less than a predetermined maximum spacing. Otherwise, energy due to high speed signals radiates from the connection of the plug and receptacle. The spacing between grounding beams controls the frequency range at which signals may be carried through the connection. As the frequency of the transmitted signal increases, the maximum acceptable distance between the grounding beams decreases. The maximum distance is calculated between the two grounding beams that are furthest from one another (e.g., top to bottom, side to side, top to side or side to bottom). The connector assembly is preferably operable with frequencies having a wavelength range between six and twenty-four times greater than the largest distance between any two grounding beams. 
     The need for a large portion of the perimeter to be covered with grounding contacts is balanced with other design considerations, such as physical constraints, material cost, complexity and the forces needed to connect the plug and receptacle. As additional grounding beams or contacts are added, the plug becomes harder to insert into the receptacle since each contact presents a contact force to the plug that must be overcome to bend the contact open. A compromise is reached between the cost, complexity, physical size, forces needed to insert the plug and the EMI shielding characteristics of the connector. 
     Conventional HSSDC assemblies have used sheet metal to construct the plug and receptacle. Sheet metal is folded into a desired configuration. When protrusions, shelves and other features are desired to be added to the plug, holes must be punched through the sheet metal shell, or separate components must be fitted in the sheet metal to offer the features. Components, separate and apart from the metal shell, are also provided to latch the plug in the receptacle. It is undesirable to punch holes through the metal shell since the openings permit leakage of electromagnetic radiation. Conventional HSSDC connectors provide a plastic insert into the plug metal shell. The plastic insert includes the desired features for holding the PC equalizing board. 
     A need exists for an improved HSSDC connection assembly that simplifies the number of parts needed to construct the connector and reduces the physical dimensions of the connector without sacrificing electrical performance, latching performance or connection forces. It is an object of the preferred embodiments of the present invention to meet one or more of these needs and other objectives that will become apparent from the description and drawings set forth below. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with at least one preferred embodiment of the present invention, an electrical connector is provided having a conductive receptacle assembly with walls defining a connector opening. At least one of the walls includes grounding contacts. The electrical connector further includes a conductive plug member for connection to the receptacle assembly through the connector opening. The plug member includes peripheral surfaces that are electrically engaged by the ground contacts on the walls of the receptacle assembly. A latch assembly is mounted to the plug member. The latch assembly includes a spring bias facing plate that lockably engages one of the side walls of the receptacle when the plug is inserted into the receptacle. The latch assembly is conductive and maintains a grounding connection between the plug member and a wall of the receptacle to which the latch is secured. The grounding contacts maintain grounding connections between the remaining walls of the receptacle and the walls of the plug member in order that the latch assembly and grounding contact form a grounding plane that surround the periphery of the plug. 
     In accordance with one embodiment, the latch assembly includes a principal body extending laterally to be formed integrally with side flanges. The principal body extends in a longitudinal direction to be formed integral with the facing plate. A locking projection is formed on the facing plate and arranged to align with and directly engage a hole in the receptacle assembly. The facing plate remains bias against the receptacle assembly to maintain the latch and grounding connections. The latch assembly further includes a leading section having a hole and lower lip portion directly engaging a knob and a U-shaped recess in a front face of the plug member. The leading section of the latch is sandwiched between a front face of the upper shell and a cross bar of the lower shell of the plug member when the shells are combined. 
     In one embodiment, the latch assembly is comprised of a T-shaped body integrally molded with side flanges, the facing plate and a leading edge. The side flanges and leading edge include holes that snapably engage knobs projecting from the exterior of the plug member. The holes and knobs secure the latch assembly to the plug member. 
     In another embodiment, the receptacle includes multiple J-shaped ground beams provided along at least one wall of the receptacle proximate the opening thereto through which the plug is received. The J-shaped grounding beams are formed integral with lead edges of the walls of the receptacle and extend forward, upward and into the receptacle opening to form grounding connections with the plug. 
     In yet another embodiment, an electrical connector is provided having a plug assembly matingly connected with a receptacle for carrying high speed serial data from a serial cable. The connector includes an upper shell having a top, sides, a back end and front face all formed integrally with one another. A lower shell is provided with a bottom, sides, a back end and a front face all formed integrally with one another. The upper and lower shells sealably join one another along mating edges of the sides, back ends and front faces to form an EMI shielded chamber therein. A PC equalization board having signal conditioning circuitry is enclosed within the upper and lower shells. The PC equalization board includes side edges having a contour that conforms to an interior contour of the side walls. The PC equalization board directly contacts and is supported by the interior surfaces of the side walls of the upper and lower shells to maintain the PC board in a desired horizontal and vertical orientation and relation to the plug. The mating edges of the sides, front face and back end of the lower shell include a skirt. Corresponding edges of the sides, front face and back end of the upper shell include a recess configured to mate with the skirt on the lower shell in order to provide an EMI shielded connection therebetween. 
     In one embodiment of the plug, the front face of the upper shell includes pens extending forward therefrom. The front face of the lower shell includes a cross bar connecting the sides thereof. The pins on the upper shell are inserted under the crossbar of the lower shell to retain the front faces of the upper and lower shells securely engaged with one another. 
     In another embodiment of the plug, the back ends of the upper and lower shells includes integral upper and lower tubular sections, respectively. When the upper and lower shells are combined, the upper and lower tubular sections mate with one another to form a circular opening to receive the cable. A ferrule is inserted over the upper and lower tubular sections and crimped thereon to secure the back ends of the shells to one another. 
     In another embodiment of the plug, the interior surfaces of the lower shell include integral protrusions defining shells directly support the PC equalization board in a desired vertical position and orientation. The interior surfaces of the lower shell also include integral protrusions defining keys that are received within recesses in either side of the PC board to maintain the PC board in a desired horizontal position and orientation with respect to the plug. 
     In yet another embodiment of the plug, the bottom of the shell is provided with a notch, while the receptacle is provided with a polarizing key. The notch and polarizing key are configured to align with one another only when the plug is properly oriented relative to the receptacle. The plug may not be inserted into the receptacle until the polarizing key is aligned with a notch, thereby preventing incorrect connection. 
     In one embodiment, the upper and lower shells are formed of diecast injection molded conductive material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentality shown in the attached drawings. 
     FIG. 1 illustrates a perspective view of a plug formed in accordance with a preferred embodiment of the present invention. 
     FIG. 2 illustrates a perspective view of a receptacle shell formed in accordance with a preferred embodiment of the present invention. 
     FIG. 3 illustrates a perspective view of an insulated housing and contact fingers formed in accordance with a preferred embodiment of the present invention. 
     FIG. 4 illustrates a perspective view of upper and lower shells included within a plug formed in accordance with a preferred embodiment of the present invention. 
     FIG. 5 illustrates a perspective view of a latch assembly mounted to the upper and lower shells in accordance with a preferred embodiment of the present invention. 
     FIG. 6 illustrates a portion of a quad cable and wire organizer received within a plug in accordance with the preferred embodiment of the present invention. 
     FIG. 7 illustrates a perspective view of a ferrule and strain relief mounted to a plug in accordance with a preferred embodiment of the present invention. 
     FIG. 8 illustrates a top perspective view of a PC equalizer board formed in accordance with a preferred embodiment of the present invention. 
     FIG. 9 illustrates a bottom perspective view of a PC equalizer board formed in accordance with a preferred embodiment of the present invention. 
     FIG. 10 illustrates a top plan view of a plug formed in accordance with a preferred embodiment of the present invention. 
     FIG. 11 illustrates a side plan view of a plug formed in accordance with a preferred embodiment the present invention. 
     FIG. 12 illustrates a bottom plan view of a plug formed in accordance with a preferred embodiment of the present invention. 
     FIG. 13 is a top plan view of a receptacle formed in accordance with a preferred embodiment of the present invention. 
     FIG. 14 is a side plan view of a receptacle formed in accordance with a preferred embodiment of the present invention. 
     FIG. 15 is a bottom plan view of a receptacle formed in accordance with a preferred embodiment of the present invention. 
     FIG. 16 is a front plan view of a receptacle formed in accordance with a preferred embodiment of the present invention. 
     FIG. 17 is a perspective view of a receptacle formed in accordance with a preferred embodiment of the present invention. 
     FIG. 18 is a front plan view of a plug formed in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a perspective view of a plug assembly  10  configured in accordance to one preferred embodiment of the present invention. The plug assembly  10  includes an upper shell  12  and a lower shell  14  enclosing a PC equalization board  16 . The plug assembly  10  also includes a latch assembly  18  removably mounted to the upper and lower shells  12  and  14 . The plug assembly  10  is securely mounted to the end of a cable  30  capable of transmitting high speed serial data, such as a quad cable and the like. A strain relief  20  is secured to the back end of the upper and lower shells  12  and  14  to protect the interconnection between the plug assembly  10  and the cable  30 . The strain relief  20  includes multiple notches  22  cut therein to afford flexibility to the strain relief  20 . The upper and lower shells  12  and  14  are formed through diecast molding of a conductive material, such as zinc, magnesium and the like. The latch assembly  18  is stamped and formed of phosphorous bronze, brass and the like. 
     FIG. 2 illustrates a perspective view of a socket or receptacle shield  50  formed in accordance with one preferred embodiment of the present invention. The receptacle shield  50  snappingly receives and is secured to the plug  10  to form a mating electrical connection therebetween. The receptacle shield  50  includes a top  52 , sides  54  and bottom  56  forming four walls that define a front face  62  to receive the plug  10 . A rear face  58  is closed with a back wall  57 . The receptacle shield  50  may be formed of sheet material folded around an insulated housing  60  (FIG.  3 ). 
     FIG. 3 illustrates the insulated housing  60  and a plurality of contact fingers  64  to be mounted therein. Each contact finger  64  is formed in an L-shape with horizontal and vertical legs  66  and  68 . The horizontal legs  66  include a spoon-shaped contact region  70  on an outer end, while vertical legs  68  include an elbow-shaped contact region  72  on the outer end. The spoon-shaped contact regions  70  frictionally engage contact pads  24  on the PC board  16 . The elbow-shaped contact regions  72  are soldered to surface mount, contact pads on a motherboard (not shown), to which the receptacle shield  50  is securely mounted. The housing  60  includes a plug receiving opening  74  therein that accepts the front edge of the PC board  16 . The opening  74  includes a plurality of projections  76  extending downward from an upper edge of the opening  74  to define recessed slots  78  therebetween. The slots  78  receive the horizontal legs  66  of the contact fingers  64 . The housing  60  maintains the contact fingers  64  in a predetermined position and orientation by frictionally mounting the horizontal legs  66  of the contact fingers  64  in the slots  78  between the projections  76 . The bottom of the housing  60  includes pins  80  and  82  that are received through holes in the receptacle shield  50  and motherboard to align, and secure in place, the housing  60 . The housing  60  includes upper and lower ledges  81  and  83  projecting forward from a body. The lower ledge  83  includes grooves  85 , and a polarizing key  84 . The upper and lower ledges  81  and  83  cooperate to guide the plug  10  into the opening  74 . Opposite sides of the housing  60  include recessed notches  86  to receive the guide wings  26  on the plug  10 . 
     The receptacle shield  50  includes J-shaped grounding beams  90  formed integral with the bottom  56  and projecting forward, upward and into the front face  62 . The grounding beams  90  are biased inward to contact the bottom surface of the lower shell  14  to form grounding connections between the bottom surface of the plug  10  and the receptacle shield  50 . The sides  54  of the receptacle shield  50  include inwardly projecting contact guide wings  92  located near the rear end of the sides  54 . The contact guide wings  92  include base sections punched out of sides  54 . Outer ends of the guide wings  92  are bent to form ramped surfaces  94  projecting inward into the interior of the receptacle shield  50 . The ramped surfaces  94  engage the guide wings  26  on either side of the plug  10  as the guide wings  26  enter notches  86  to form grounding connections therewith. The sides  54 , top  52  and bottom  56  of the receptacle shield  50  further include chassis ground contacts  96 ,  98  and  99 , respectively, that project outward. The chassis ground contacts  96 ,  98  and  99  form grounding connections with the metal chassis of the computer (not shown). The front edges of the sides  54  and top  52  include guide flanges  100  and  102 , respectively, that are flared outward to form a lead-in area to guide the face of the plug  10  into the receptacle. The bottom  56  includes tabs  104  projecting downward to be received within the motherboard and securely soldered thereto. The back wall  57  includes tabs  106  projecting outward from either side thereof that are folded over and along the sides  56  to cover the seams formed between the back wall  57  and sides  54  when the walls of the receptacle are folded into a desired shape. The top  52  includes a hole  108  near the guide flange  102  to receive a locking member  139  on the plug  10 . 
     FIGS. 4-8 illustrate perspective views of the components forming the plug  10  and connecting the plug  10  to an end of a cable  30 . The upper and lower shells  12  and  14  (FIG. 4) enclose the PC equalization board  16  (FIG. 8) and a wire organizer  32  (FIG.  6 ). The wire organizer  32  includes upper and lower recesses  34  and  35  which receive corresponding differential pairs  36  and  37 , respectively, of transmit and receive insulated conductive lines. The wire organizer  32  maintains the differential pairs  36  and  37  in a desired arrangement with respect to one another to minimize interference and cross talk caused by high speed signals being carried through the cable  30  at the region within which the cable  30  presents signals onto the PC equalization board  16 . The upper and lower shells  12  and  14  include upper and lower tubular sections  38  and  39  that combine to form a tubular opening through which the cable  30  enters the plug  10 . The shield of the cable is received over the upper and lower tubular sections  38  and  39  and the ferrule is slid over the shield and crimped to secure the upper and lower shells  12  and  14  and shield to one another. The strain relief  20  is then placed over the ferrule  40  to provide additional support to the point of connection between the cable  30  and plug  10 . 
     The plug  10  is described in more detail hereafter in connection with FIGS.  4  and  10 - 12 . FIGS. 10-12 illustrate top, side and bottom views, respectively, of the plug  10 . The upper shell  12  includes a top  120 , sides  122 , a front face  124  and a back wall  126  formed integrally with one another. The back wall  126  is also integrally formed with the upper tubular section  38  to form a unitary upper shell  12 . The sides  122  include opposed knobs  128  projecting outward therefrom. 
     The latch assembly  18  (FIG. 5) includes a T-shaped principle section  132 , integrally formed with side flanges  134 , a front or facing plate  136  and a leading section  138 . The front plate  136  includes a locking member  139  extending upward. The guide flange  102  contacts the locking member  139  and biases the front plate downward as the plug  10  is inserted into the receptacle shield  50 . The locking member  139  latchably engages hole  108  (FIG. 13) in the top  52  of the receptacle shield  50  when the plug  10  is inserted in the receptacle shield  50 . The side flanges  134  include holes  140  that are snapped over knobs  128  to secure the latch assembly  18  onto the upper shell  12 . The side flanges  134  also include tabs  142  extending downward that are received within recesses  164  in either side  160  of the lower shell  14  when the upper and lower shells  12  and  14  are combined. The leading section  138  includes a hole  144  that receives a knob  146  projecting from the front face  124  of the upper shell  12 . The front face  124  further includes pins  148  and a U-shaped recess  150 . The U-shaped recess  150  receives a lower lip portion  152  of the leading section  138  of the latch assembly  18 . 
     A travel limiting projection  130  extends upward from the top  120  and is located below the key-shaped principle section  132  proximate the intersection of the T-shaped principle section  132  and front plate  136 . The projection  130  is spaced below the principle section  132  by a distance sufficient to permit the latch assembly  18  to bend downward when the plug  10  is moved into a mating connection with the receptacle shield  50 . The projection  130  is constructed to limit the amount by which the latch assembly  18  is permitted to bend to prevent over straining the connection between the front plate  136  and principle section  132 . 
     The lower shell  14  is constructed of a unitary diecast molded member including sides  160 , bottom  161 , a front face  162 , and a rear wall  163 . The rear wall  163  is formed integrally with the lower tubular section  39 . The sides  160  include slotted recesses  164  that receive tabs  142  on the latch assembly  18  once assembled. The front edges of the sides  160  form the guide wings  26 . The guide wings  26  are interconnected via a crossbar  166 . The lower shell  14  further includes shelves  168  formed integrally upon the interior surface of the sides  160  to support the PC board  16 . Keys  170  are also formed integrally with the sides  160  to properly orient and align the PC board  16 . A skirt  172  is molded along the upper edge of the sides  160  to be received in a mating relation with the lower edges of the sides  122  of the upper shell  12 . The skirts  172  form a sealed connection between the sides  160  and  122  of the upper and lower shells  12  and  14 . The bottom  161  includes a slot  174  (FIG. 12) configured to receive a polarizing key  84  (FIG. 3) mounted on the top of the lower ledge  83  of the housing  60 . 
     During construction, the latch assembly  18  is mounted upon the upper shell  12  by locating the knob  146  in the hole  144  and the lower lip  152  in the U-shaped recess  150 . The side flanges  134  are snapped downward over the sides  122  until the holes  140  receive the knobs  128 . Once the PC board  16 , wire organizer  32  and cable  30  are properly mounted within the plug  10 , the upper shell  12  and latch assembly  18  are combined with the lower shell  14 . To mount the upper and lower shells  12  and  14  to one another, the front face  124  of the upper shell  12  is inserted with the pins  148  located below the crossbar  166 . The upper shell  12  is then rotated downward until tabs  142  are received within recesses  164  and the lower edge of the sides  122  securely mates with the skirt  172  on the upper edge of the sides  160 . Once the tabs  142  are received within recesses  164 , the side flanges  134  are held firmly against the sides  122  of the upper shell  12 , thereby retaining the knobs  128  securely within the holes  140 . The shield of the cable is slid over the upper and lower tubular sections  38  and  39 , the ferrule  40  is slid over the shield and crimped in a frictional manner. The strain relief  20  is then pulled up over the ferrule  40 . 
     The latch assembly  18  securely locks the plug  10  within the receptacle shield  50 , while the front plate  136  provides a grounding connection along a width of the front plate  136  between the top  120  and top  52 . The width of the latch assembly  18  may be varied to provide adequate grounding characteristics for EMI shielding and to provide a desired biasing force upward against to top  52  of the receptacle shield  50 . By way of example only, the front plate  136  may be as wide as the leading edge of the PC equalizer board  16 . 
     FIGS. 8 and 9 illustrate the PC equalization board  16  in accordance with at least one preferred embodiment of the present invention. The PC board  16  includes circuit components that perform signal conditioning upon high speed serial data received from cable  30 . The PC board  16  includes front face  182 , back end  186 , top surface  188 , bottom surface  190  and opposed side edges  191 . The front face  182  includes chamfered edges  184  to facilitate insertion of the PC board  16  into the opening  74  of the housing  60 . The top surface  188  includes multiple contact pads  180  and  181 , and ground pads  204  aligned adjacent one another and located proximate the front face  182 . The contact pads  180 ,  181  and ground pads  204  electrically and frictionally engage the spoon-shaped contact regions  70  upon contact fingers  64 . 
     In the example of FIGS. 8 and 9, the contact pads  180  on the top surface  188  correspond to a differential pair of either transmit or receive insulated conductors. The differential pair of contact pads  180  are connected to a differential pair of solder pads  194  via linear electrical traces  192 . The differential pair of solder pads  194  are connected to a corresponding differential pair  36  of the cable  30  via a soldering connection. A second differential pair of contact pads  181  are connected through vias  196  to linear traces  198  (FIG. 9) on the bottom surface  190  of the PC board  16 . The linear traces  198  expand at the rear end to form equalizing component receiving regions  200  (FIG.  8 ). The bottom surface  190  of the PC board  16  also includes a differential pair of solder pads  202  adapted to be electrically connected to differential pair  37  of the cable  30 . The solder pads  202  and regions  200  are separated by non-conductive gaps  212 . 
     The solder pads.  202  and component receiving regions  200  are spaced apart from one another and configured to receive electrical equalization components  210  spanning the gap  212  therebetween. The equalization components  210  may be varied to afford different desired electrical characteristics to the PC board  16 . For instance, the components  210  may comprise one resistor and one capacitor, the values for which are based upon various signal characteristics of the cable  30 . By way of example only, a cable  30  having an impedance of  100  ohms is operated with a first PC board  16  having one combination of values for components  210 , while a cable  30  having an impedance of  150  ohms is operable with a different PC board  16  having a separate combination of values for components  210 . 
     The PC board  16  includes an internal grounding plane extending from the back end  186  to the front face  182  and entirely enclosed within the PC board  16 . An edge of the grounding plane is designated by reference numeral  220 . Grounding pads  204  are provided on the top surface  188  proximate the front face  182 . The ground pads  204  are connected to a grounding plane imbedded within and extending along the length of the PC board  16 . The ground pads  204  are connected to the grounding plane through ground vias  206 . Ground solder pads  208  are provided on the top and bottom surfaces  188  and  190  of the PC board  16 . The ground soldering pads  208  are connected to the grounding plane through ground vias  206 . The grounding plane  220  enables interconnection of grounding pads  204  and grounding solder pads  208 . Interconnects  196  do not electrically communicate with the grounding plane  220 . 
     The configuration of contact pads  180 ,  181 , and ground pads  204  along the top surface  188  may be varied, provided that the configuration of contact and grounding pads does not afford undue reflection, signal interference or cross talk. According to at least one preferred embodiment of the present invention, the contact pads  180 ,  181  and ground pads  204  are arranged to include ground pads  204  proximate opposite sides  191  while contact pads  181  and contact pads  180  are separated by a third grounding pad  204 . Hence, the contact and ground pad configuration includes one ground pad, two contact pads, one ground pad, two contact pads, and one ground pad. Adjacent contact pads in the preferred embodiment of FIGS. 8 and 9 include contact pads adjacent one another that are associated with a single differential pair to minimize cross talk. 
     The PC board  16  includes a configuration of keying projections  214 - 217  and notches  218 - 219  configured to fit between keys  170  and sides  160  of the lower shell  14 . The keying projections  214 - 217 , notches  218 - 219  and keys  170  cooperate to insure that the PC board  16  is placed with the top surface  188  pointed upward and is located at a desired longitudinal and vertical position within the plug  10 . The keys  170  are received by notches  218 - 219 , while the keying projections  214  and  215  rest upon shelves  168  (FIG.  4 ). The projections  216  and  217  rest upon shelves  169 . 
     FIGS. 13-16 illustrate top, side, bottom and front views, respectively, of the receptacle shield  50 . FIG. 13 illustrates the top  52  including ground contacts  98  to afford grounding connections with the chassis. Grounding contacts  96  project outward from the sides  54  to also provide grounding contacts with the chassis. FIG. 13 also provides a clear view of the guide flanges  100  and  102 . FIG. 14 illustrates a plurality of tabs  104  extending downward from the bottom of the receptacle shield  50  that are received in the motherboard and soldered thereto. 
     FIG. 15 illustrates the bottom  56  in more detail including ground contacts  99  and standoffs  101 . The pins  80  and  82  are formed integral with the standoffs  101 . The pins  80  and  82  also are inserted through holes in the motherboard. Optionally, pin  82  may be constructed with a diamond cross-section to permit easier installation on the motherboard, while maintaining proper alignment. The bottom  56  receives the contact regions  72  of the contact fingers  64  near the back  57 . The contact regions  72  are surface mounted upon contacts on the motherboard in order to provide electrical connections between the motherboard and the differential pairs of cable  30  via the PC board  16 , contact fingers  64 . 
     FIG. 16 illustrates a front view of the receptacle shield  50  showing grounding beams  90 , polarizing key  84 , opening  70  and projections  76 . 
     During construction, the housing  60  is inserted within the receptacle shield  50  and mounted on the motherboard. The plug  10  is assembled as explained above and mounted to the end of a cable  30 , such as a quad cable capable of carrying high speed serial data. The plug  10  is connected to the receptacle shield  50  by inserting the front face  182  of the PC board  16  into the opening  74  until contacts  180 ,  181  and  204  engage contact fingers  64 . The locking member  139  engages the hole  108  in the top  52  of the receptacle shield  50  in order to maintain the plug  10  within the receptacle shield  50 . The biasing forces applied by the latch assembly  18  maintain the locking member  139  within the hole  108 . The latch assembly  18  maintains a grounding connection between the top  120  of the plug  10  and the top  52  of the receptacle shield  50 . Contact guide wings  92  maintain a grounding connection between the guide wings  26  of the plug  10  and the sides  54  of the receptacle shield  50 . Grounding beams  90  maintain grounding connections between the bottom  161  of the plug  10  and the bottom  56  of the receptacle shield  50 . Contact guide wings  92  enable the width of the receptacle to be minimized. Optionally, the grounding beams  90  may be removed and contact guide wings (such as guide wings  92 ) may be provided in the bottom  56  of the receptacle shield  50  in order to further reduce the height of the receptacle shield  50 . Contact guide wings  92  afford a lesser profile than needed for grounding beams  90 . Thus, receptacles using grounding beams along either side of the receptacle would require a wider receptacle. Contact guide wings  92  reduce the overall width of the receptacle. The receptacle shield  50  is substantially void of any specific structure in the top  52  for providing a grounding contact with the plug  10 . Instead, the latch assembly  18  is constructed in a manner that performs the dual functions of locking the plug and receptacle together, while simultaneously affording a grounding connection between the top of the plug and the surface of the top  52  of the receptacle shield  50 . In the foregoing manner, the latch assembly  18  reduces the complexity of the receptacle shield  50  and the height of the receptacle. 
     The upper and lower shells  12  and  14  of the plug  10  are substantially void of any openings in the bottom  161 , sides  160  and  122 , and top  120 , thereby affording EMI shielding characteristics without the need for additional shielding structure therearound. The upper and lower shells  12  and  14  are formed of diecast molded conductive material, thereby affording the ability to include integral features (e.g., shelves  168 , keys  170 , recesses  164 ) without forming holes in the shells or adding separate components thereto. 
     In accordance with at least one alternative embodiment, the contour of the PC board  16  is configured to be loosely received within the lower shell  14 . The sides  191  of the PC board  16  are permitted to float laterally, from side to side between the sides  161  of the lower shell  14 . The lateral float between the sides  191  and  161  permits the face  182  to be properly guided into the opening  74  in the holder  60 . 
     While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore contemplated by the appended claims to cover such modifications as incorporate those features which come within the spirit and scope of the invention.