Patent Publication Number: US-10790618-B2

Title: Electrical connector system having a header connector

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit to U.S. Provisional Application No. 62/623,935, filed Jan. 30, 2018, titled “ELECTRICAL CONNECTOR SYSTEM HAVING A HEADER CONNECTOR”, the subject matter of which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to header connectors for electrical connector systems. 
     Some electrical systems utilize electrical connectors, such as header assemblies and receptacle assemblies, to interconnect two circuit boards, such as a motherboard and daughtercard. Some known electrical connectors include a housing holding signal contacts and ground shields providing electrical shielding for the signal contacts. The signal contacts and the ground shields include mounting portions, such as eye of the needle pins, terminated to the circuit board. The circuit board includes signal vias and ground vias to receive the mounting portions. The mounting interface between the signal contacts and the ground shields with the circuit board is electrically noisy and an area of signal degradation. 
     A need remains for an electrical connector system providing electrical shielding for the signal contacts for terminating high speed, high density electrical connectors to circuit boards. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a header connector is provided including signal contacts, header shields and a header housing holding the signal contacts and the header shields. The signal contacts are arranged in pairs each having a base, a mating pin extending from a front of the base and a mounting portion extending from a rear of the base for termination to a circuit board. The header shields have walls defining shield pockets receiving corresponding pairs of the signal contacts to provide electrical shielding for the pairs of signal contacts. Each header shield has a base and a mounting portion extending from a rear of the base for termination to the circuit board. The header housing has a front shell and a rear shell. The front shell is dielectric and the rear shell is conductive and providing electrical shielding for the signal contacts. The front shell holds the signal contacts. The rear shell holds the header shields and is electrically connected to each of the header shields. 
     In another embodiment, a header connector is provided having signal contacts, header shields and a header housing holding the signal contacts and the header shields. The signal contacts are arranged in pairs each having a base, a mating pin extending from a front of the base and a mounting portion extending from a rear of the base for termination to a circuit board. The header shields have walls defining shield pockets receiving corresponding pairs of the signal contacts to provide electrical shielding for the pairs of signal contacts. Each header shield has a base and a mounting portion extending from a rear of the base for termination to the circuit board. The header housing has a front shell and a rear shell. The front shell is dielectric and the rear shell is conductive and providing electrical shielding for the signal contacts. The front shell has a front plate and shroud walls extending from the front plate to define a mating cavity configured to receive a mating electrical connector. The front plate has contact hubs including contact channels arranged in pairs receiving corresponding signal contacts. The front housing has shield channels partially surrounding each contact hub. Each shield channel receives a corresponding header shield. The rear shell includes pockets receiving corresponding header shields and contact hubs. The header shields are electrically connected to the rear shell in the corresponding pocket. 
     In a further embodiment, an electrical connector system is provided including a printed circuit board having a substrate having a connector surface, signal vias and ground vias with a ground plane electrically connected to the ground vias. The electrical connector system includes a header connector having signal contacts, header shields and a header housing holding the signal contacts and the header shields. The signal contacts are arranged in pairs each having a base, a mating pin extending from a front of the base and a mounting portion extending from a rear of the base received in corresponding signal vias. The header shields have walls defining shield pockets receiving corresponding pairs of the signal contacts to provide electrical shielding for the pairs of signal contacts. Each header shield has a base and a mounting portion extending from a rear of the base received in corresponding ground vias. The header housing has a front shell and a rear shell. The front shell is dielectric and the rear shell is conductive and providing electrical shielding for the signal contacts. The front shell has a front plate and shroud walls extending from the front plate to define a mating cavity configured to receive a mating electrical connector. The front plate has contact hubs including contact channels arranged in pairs receiving corresponding signal contacts. The front housing has shield channels partially surrounding each contact hub. Each shield channel receives a corresponding header shield. The rear shell includes pockets receiving corresponding header shields and contact hubs. The header shields are electrically connected to the rear shell in the corresponding pocket. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of an electrical connector system formed in accordance with an exemplary embodiment. 
         FIG. 2  is an exploded view of a header connector of the electrical connector system in accordance with an exemplary embodiment. 
         FIG. 3  is a side view of the header connector in accordance with an exemplary embodiment. 
         FIG. 4  is a front view of one of the signal contact in accordance with an exemplary embodiment. 
         FIG. 5  is a side view of one of the signal contacts in accordance with an exemplary embodiment. 
         FIG. 6  is a side view of a portion of the header connector showing a header shield and signal contacts. 
         FIG. 7  is a rear perspective view of a portion of the header connector showing signal contacts and header shields. 
         FIG. 8  is a rear perspective view of a portion of the header connector in accordance with an exemplary embodiment with a rear shell removed to illustrate header shields relative to a front shell. 
         FIG. 9  is a rear perspective view of a portion of the header connector in accordance with an exemplary embodiment with a front shell removed to illustrate the rear shell relative to the header shields and the signal contacts. 
         FIG. 10  is a front view of a portion of the header connector in accordance with an exemplary embodiment with the front shell removed to illustrate the rear shell relative to the header shields and the signal contacts. 
         FIG. 11  is a rear view of the header connector in accordance with an exemplary embodiment. 
         FIG. 12  is an enlarged view of the rear of the header connector in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a front perspective view of an electrical connector system  100  formed in accordance with an exemplary embodiment. The connector system  100  includes a first electrical connector  102  configured to be mounted to a printed circuit board (PCB)  104  and a second electrical connector  106  configured to be mounted to a printed circuit board (PCB)  108 . In the illustrated embodiment, the electrical connector  106  is a header connector and may be referred to hereinafter as header connector  106 . The header connector  106  may be mounted to a backplane circuit board. In the illustrated embodiment, the electrical connector  102  is a receptacle connector and may be mounted to a daughtercard circuit board; however, various other types of connectors may be used in various embodiments. The receptacle connector may be a right angle connector, a vertical connector or another type of connector. 
     The header connector  106  includes a housing  110  holding a plurality of signal contacts  112  and header shields  114 . In an exemplary embodiment, the housing  110  is a multi-piece housing having a dielectric portion at the front that holds the signal contacts  112  and a conductive portion at the rear that is electrically connected to the header shields  114 . The conductive portion may be electrically connected to the PCB  108 , such as a ground plane at the surface of the PCB  108 . The signal contacts  112  may be arranged in pairs  116 . Optionally, the signal contacts  112  may be arranged in pairs carrying differential signals; however other signal arrangements are possible in alternative embodiments, such as single-ended applications. Optionally, the pairs  116  of signal contacts  112  may be arranged in columns (pair-in-column signal contacts). Alternatively, the pairs  116  of signal contacts  112  may be arranged in rows (pair-in-row signal contacts). 
     Each header shield  114  extends around corresponding signal contacts  112 , such as around corresponding pairs  116  of signal contacts  112 . The header shields  114  provide shielding for each pair  116  of signal contacts  112  along substantially the entire lengths of the signal contacts  112 . The header shields  114  may be electrically grounded at the circuit board  108 . The header shields  114  may be electrically grounded at the electrical connector  102 . In the illustrated embodiment, the header shields  114  are C-shaped having three walls extending along three sides of each pair of signal contacts  112 . The header shield  114  adjacent to the pair  116  provides electrical shielding along the fourth, open side of the pair  116 . As such, the pairs  116  of signal contacts  112  are circumferentially surrounded on all four sides by the header shields  114 . 
     The electrical connector  102  includes a housing  120  that holds a plurality of contact modules  122 . The contact modules  122  are held in a stacked configuration generally parallel to one another. The contact modules  122  may be loaded into the housing  120  side-by-side in the stacked configuration as a unit or group. Any number of contact modules  122  may be provided in the electrical connector  102 . The contact modules  122  each include a plurality of signal contacts (not shown) that define signal paths through the electrical connector  102 . The signal contacts are configured to be electrically connected to corresponding signal contacts  112  of the header connector  106 . 
     The electrical connector  102  includes a mating end  128 , such as at a front of the electrical connector  102 , and a mounting end  130 , such as at a bottom of the electrical connector  102 . In the illustrated embodiment, the mounting end  130  is oriented substantially perpendicular to the mating end  128 . The mating and mounting ends  128 ,  130  may be at different locations other than the front and bottom in alternative embodiments. The signal contacts extend through the electrical connector  102  from the mating end  128  to the mounting end  130  for mounting to the PCB  104 . 
     In an exemplary embodiment, each contact module  122  has a shield structure  126  for providing electrical shielding for the signal contacts. The shield structure is configured to be electrically connected to the header shields  114  of the header connector  106 . The shields structure may be ground shields coupled to sides of the contact modules  122 . The shield structure  126  may provide shielding from electromagnetic interference (EMI) and/or radio frequency interference (RFI), and may provide shielding from other types of interference as well to better control electrical characteristics, such as impedance, cross-talk, and the like, of the signal contacts. The contact modules  122  provide shielding for each pair of signal contacts along substantially the entire length of the signal contacts between the mating end  128  and the mounting end  130 . In an exemplary embodiment, the shield structure  126  is configured to be electrically connected to the mating electrical connector and/or the PCB  104 . The shield structure  126  may be electrically connected to the PCB  104  by features, such as grounding pins and/or surface tabs. 
     The housing  120  includes a plurality of signal contact openings  132  and a plurality of ground contact openings  134  at the mating end  128 . The signal contacts are received in corresponding signal contact openings  132 . The signal contact openings  132  receive corresponding signal contacts  112  of the header connector  106 . In the illustrated embodiment, the ground contact openings  134  are C-shaped extending along three sides of the corresponding pair of signal contact openings  132 . The ground contact openings  134  receive header shields  114  of the header connector  106 . The ground contact openings  134  also receive portions of the shield structure  126  (for example, beams and/or fingers) of the contact modules  122  that mate with the mating header shields  114  to electrically common the shield structure  126  with the mating header connector  106 . 
       FIG. 2  is an exploded view of the header connector  106  in accordance with an exemplary embodiment.  FIG. 3  is a side view of the header connector  106  in accordance with an exemplary embodiment. The header connector  106  includes the housing  110  holding the signal contacts  112  and the header shields  114 . In an exemplary embodiment, the housing  110  includes a front shell  136  and a rear shell  138 . The front shell  136  is manufactured from a dielectric material. The rear shell  138  is manufactured from a conductive material. For example, the rear shell  138  may be plated or coated, such as a plated plastic shell. The rear shell  138  may be molded with conductive particles and nonconductive particles, such as a binder material. The rear shell  138  may be die cast from a metal material. The rear shell  138  provides electrical shielding through at least part of the housing  110 . The rear shell  138  electrically commons the header shields  114 . The rear shell  138  provides electrical shielding in the mounting zone where the signal contacts  112  and the header shields  114  are mounted to the PCB  108  (shown in  FIG. 1 ). 
     The housing  110  extends between a mating end  140  and a mounting end  142  configured to be mounted to the PCB  108  (shown in  FIG. 1 ). The front shell  136  is provided at the mating end  140  and the rear shell  138  is provided at the mounting end  142 . The front shell  136  includes a front plate  144  at the rear of the front shell  136  and shroud walls  146  extending from the front plate  144  to the mating end  140 . The front plate  144  extends between a front surface  145  and a rear surface  147 . The front plate  144  has a thickness between the front surface  145  and the rear surface  147 . In an exemplary embodiment, the thickness of the front plate  144  is less than the thickness of the rear shell  138 . For example, the rear shell  138  has significant thickness to provide rigid structural support for the header shields  114  and/or to provide electrical shielding along a significant depth of the housing  110 . The front plate  144  and the shroud walls  146  define a mating cavity  148  configured to receive the electrical connector  102  (shown in  FIG. 1 ). The front plate  144  includes contact channels  150  that receive corresponding signal contacts  112  and shield channels  152  that receive corresponding header shields  114 . The signal contacts  112  and the header shields  114  are configured to extend from the front plate  144  into the cavity  148  for mating with the electrical connector  102 . The signal contacts  112  and the header shields  114  are configured to extend from the front plate  144  into the rear shell  138  for termination to the PCB  108 . 
     In an exemplary embodiment, the signal contacts  112  are stamped and formed from a metal sheet or blank. Optionally, each of the signal contacts  112  may be identical; however, different signal contacts  112 , such as signal contacts within each pair  116  may have different features, such as mirrored features). With additional reference to  FIGS. 4 and 5 , which are front and side views, respectively, of the signal contacts  112 , each signal contact  112  includes a base  160 , a mating pin  162  extending from a front of the base  160  and a signal mounting portion  164  extending from a rear of the base  160  opposite the mating pin  162 . The base  160  may be held in the contact channel  150  by an interference fit. For example, the base  160  may include dimples, tabs or barbs that interfere with the plastic material of the front shell  136  to hold the signal contact  112  in the front shell  136 . 
     The signal contact  112  extends between a mating end  166  and a mounting end  168 . The mating pin  162  is provided at the mating end  166 . The signal mounting portion  164  is provided at the mounting end  168  and configured to be terminated to the PCB  108 , such as in the signal vias of the PCB  108 . The base  160  includes a first edge  170  and a second edge  172  opposite the first edge  170  extending between a top  174  and a bottom  176 . The mating pin  162  extends from the top  174  of the base  160 . The signal mounting portion  164  extends from the bottom  176  of the base  160 . The base  160  has a first side  178  and a second side  180  opposite the first side  178  extending between the top  174  and the bottom  176 . In an exemplary embodiment, the signal contacts  112  within each pair  116  are received in corresponding contact channels  150  such that the first sides  178  of the bases  160  face each other and the second sides  180  face away from each other. For example, the signal contacts  112  within each pair  116  are inverted 180° relative to each other. Other orientations are possible in alternative embodiments. 
     The mating pin  162  extends along a mating pin axis  182 . In an exemplary embodiment, the mating pin  162  is oriented relative to the base  160  such that the mating pin axis  182  is approximately centered between the first and second edges  170 ,  172 . In an exemplary embodiment, the mating pin  162  is rolled or formed into a pin shape. For example, edges of the mating pin  162  may be folded inward to form a U-shaped pin. In the illustrated embodiment, the mating pin  162  includes a first rail  184  and a second rail  186  with a folded portion  188  between the first rail  184  and the second rail  186 . Optionally, the first and second rails  184 ,  186  may be separated by a gap. The gap may be open at the second side  180 . The folded portion  188  may be provided at the first side  178 . Optionally, the first and second rails  184 ,  186  may extend generally parallel to each other with the folded portion  188  connecting therebetween. The folded portion  188  may be curved between the first and second rails  184 ,  186 . In an exemplary embodiment, the mating pin  162  is offset out of the plane of the base  160 , such that the mating pin axis  182  is offset relative to the base  160 , such as offset from the second side  180 . For example, the base  160  may be directly below the folded portion  188  while the first and second rails  184 ,  186  are offset relative to the base  160 . 
     The signal mounting portion  164  may be stamped and formed with the base  160 . In an exemplary embodiment, the signal mounting portion  164  is a compliant pin, such as an eye of the needle pin. The signal mounting portion  164  includes a compliant portion  190 , which may be a bulged portion that is wider than other portions of the signal mounting portion  164 . The compliant portion  190  may have an opening  192  therethrough allowing the compliant portion  190  to be flexed or squeezed inward when mating to the PCB  108 . In an exemplary embodiment, the signal mounting portion  164  is offset from the mating pin axis  182 . For example, the mating pin  162  may be approximately centered between the first and second edges  170 ,  172 , whereas the signal mounting portion  164  is positioned closer to the first edge  170  than the second edge  172 . Optionally, the signal mounting portion  164  may be positioned at the first edge  170 . When the signal contacts  112  within the pair  116  are coupled to the front shell  136 , the signal contacts  112  are inverted 180° relative to each other such that the signal mounting portions  164  are offset in opposite directions from each other, such as on opposite sides of the mating pin axes  182 . In an exemplary embodiment, the compliant portion  190  is in plane with the base  160 , such as directly below the bottom  176 . In alternative embodiments, the signal mounting portion  164  may be offset out of the plane of the base  160 . 
     The signal contact  112  includes barbs  194  along the first and second edges  170 ,  172  used to secure the signal contact  112  in the front shell  136 . For example, the base  160  is received in the contact channel  150  and the barbs  194  dig into the plastic material of the front shell  136  to mechanically hold the signal contact  112  in the front shell  136 . Other attachment means may be used in alternative embodiments. 
     With reference back to  FIGS. 2 and 3 , the header shield  114  includes a base  200  defined by a plurality of walls  202 . The header shield  114  includes ground mounting portions  204  extending from the base  200 . The header shield  114  extends between a mating end  206  and a mounting end  208 . The base  200  is provided at or near the mounting end  208 . The ground mounting portions  204  are provided at the mounting end  208  and configured to be terminated to the PCB  108 . For example, the ground mounting portions  204  are configured to be received in the ground vias of the PCB  108 . The base  200  is configured to be received in the shield channel  152  in the front plate  144  of the front shell  136 . The base  200  is configured to be mechanically and electrically connected to the rear shell  138 . The base  200  may be held in the shield channel  152  by an interference fit. The base  200  may be held in the rear shell  138  by an interference fit. For example, the base  200  may include securing features  240 , such as dimples, tabs or barbs, which interfere with the plastic material of the front shell  136  and/or the conductive material of the rear shell  138  to mechanically hold the header shield  114  in the front shell  136  and/or the rear shell  138 . In the illustrated embodiment, the securing features  240  are dimples and may be referred to hereinafter as dimples  240 . In alternative embodiments, the dimples  240  may be provided on the front shell  136  and/or the rear shell  138  to provide the mechanical and/or electrical connection. For example, the dimples may be crush ribs or other types of dimples. Optionally, the header shield  114  may be captured between the front shell  136  and the rear shell  138  and held therebetween. 
     In an exemplary embodiment, the header shield  114  is C-shaped with the walls  202  including an end wall  210 , a first side wall  212  and a second side wall  214 . The first side wall  212  extends from a first edge  216  of the end wall  210  and the second side wall  214  extends from a second edge  218  of the end wall  210  opposite the first edge  216 . The end wall  210 , the first side wall  212  and the second side wall  214  form a shield pocket  220  configured to receive a corresponding pair  116  of the signal contacts  112 . The walls  202  surround three sides of the corresponding pair  116  of the signal contacts  112  to provide electrical shielding for the pair  116  of signal contacts  112 . The header shield  114  may have other shapes in alternative embodiments. The header shield  114  has an open side  222  opposite the end wall  210  between the first and second side walls  212 ,  214 . The open side  222  is configured to be closed and shielded by the adjacent header shield  114  and/or part of the rear shell  138  to provide circumferential shielding for the shield pocket  220 . 
     The end wall  210  includes one or more of the ground mounting portions  204 . The first side wall  212  includes one or more of the ground mounting portions  204 . The second side wall  214  includes one or more of the ground mounting portions  204 . Each ground mounting portion  204  may be stamped and formed with the base  200 . In an exemplary embodiment, the ground mounting portion  204  is a compliant pin, such as an eye of the needle pin. The ground mounting portion  204  includes a compliant portion  230 , which may be a bulged portion that is wider than other portions of the ground mounting portion  204 . The compliant portion  230  may have an opening  232  therethrough allowing the compliant portion  230  to be flexed and squeezed inward when mating to the PCB  108 . In an exemplary embodiment, the end wall  210  includes a pair of the ground mounting portions  204 , which are configured to be arranged in line with the signal contacts  112  of the corresponding pair  116 . 
     The end wall  210  includes one or more of the dimples  240 . The first side wall  212  includes one or more of the dimples  240 . The second side wall  214  includes one or more of the dimples  240 . Optionally, the dimples  240  may include front dimples  242  configured to interface with the front shell  136  and rear dimples  244  configured to interface with the rear shell  138 . The front dimples  242  and the rear dimples  244  are provided along the base  200 . The front dimples  242  are axially offset forward of the rear dimples  244 . Optionally, the front dimples  242  may extend from and stand proud of an inner surface  246  of the corresponding walls  210 ,  212 ,  214  and the rear dimples  244  may extend from and stand proud of an outer surface  248  of the corresponding walls  210 ,  212 ,  214 . 
     In an exemplary embodiment, the first side wall  212  includes a wing  234  configured to be bent out of plane with the first side wall  212 . The ground mounting portion  204  extends from the wing  234  and the wing  234  is used to position the ground mounting portion  204  out of the plane of the first side wall  212 . Optionally, the wing  234  includes one of the dimples  240  to electrically connect the wing  234  to the rear shell  138 . In an exemplary embodiment, the second side wall  214  includes a wing  236  configured to be bent out of plane with the second side wall  214 . The ground mounting portion  204  extends from the wing  236  and the wing  236  is used to position the ground mounting portion  204  out of the plane of the second side wall  214 . Optionally, the wing  236  includes one of the dimples  240  to electrically connect the wing  236  to the rear shell  138 . Optionally, the wings  234 ,  236  are shaped differently to offset the ground mounting portions  204  relative to each other. For example, the wing  236  may position the corresponding ground mounting portion  204  further from the end wall  210  and the wing  234  may position the corresponding ground mounting portion  204  closer to the end wall  210 . 
       FIG. 6  is a side view of a portion of the header connector  106  showing one of the header shields  114  and the corresponding signal contacts  112 .  FIG. 7  is a rear perspective view of a portion of the header connector  106  showing pairs  116  of signal contacts  112  and the corresponding header shields  114 . The signal contacts  112  are arranged in the shield pocket  220  and surrounded by the end wall  210 , the first side wall  212  and the second side wall  214 . The signal contacts  112  are shown inverted relative to each other with the mating pins  162  facing in opposite directions. In the illustrated embodiment, the signal mounting portions  164  are provided at the first edges  170  of the corresponding bases  160 . Because the signal contacts  112  are inverted 180° with respect to each other, the signal mounting portions  164  are offset on opposite sides of the corresponding mating pins  162 . 
     The header shield  114  surrounds the signal contacts  112 . The ground mounting portions  204  extend from the base  200  for termination to the PCB  108 . In the illustrated embodiment, the end walls  210  includes two ground mounting portions  204  that are generally aligned with the bases  160  of the pair  116  of signal contacts  112 . The wing  234  includes one of the ground mounting portions  204  and the wing  236  includes one of the ground mounting portions  204 . Optionally, other portions of the sidewalls  212 ,  214  may include ground mounting portions  204 . 
     In an exemplary embodiment, the end wall  210  includes one of the front dimples  242 , the first side wall  212  includes one of the front dimples  242 , and the second side wall  214  includes one of the front dimples  242 . In an exemplary embodiment, the end wall  210  includes multiple rear dimples  244 , the first side wall  212  includes one the rear dimples  244 , the wing  234  includes one of the rear dimples  244 , the second side wall  214  includes one of the rear dimples  244 , and the wing  236  includes one of the rear dimples  244 . Other arrangements of the dimples  240  are possible in alternative embodiments. In alternative embodiments, the dimples or interference features may be provided on the front shell  136  and/or the rear shell  138  rather than the header shields  114 . 
       FIG. 8  is a rear perspective view of a portion of the header connector  106  in accordance with an exemplary embodiment with the rear shell  138  removed to illustrate the header shields  114  relative to the front shell  136 . In an exemplary embodiment, the front shell  136  includes a chamber  300  at the rear surface  147 . The chamber  300  is defined by mounting rails  302  extending rearward from opposite sides of the front shell  136 . The mounting rails  302  may be used for mounting the header connector  106  to the PCB  108  (shown in  FIG. 1 ). 
     In an exemplary embodiment, the front shell  136  includes contact hubs  310  that hold the signal contacts  112 . Optionally, each contact hubs  310  has a pair of the contact channels  150  that receive corresponding signal contacts  112 . In an exemplary embodiment, the bases  160  of the signal contacts  112  are held in the contact hubs  310 . For example, the barbs dig into the dielectric material of the contact hubs  310  to mechanically secure the signal contacts  112  in the contact channels  150 . The contact hubs  310  electrically isolate the signal contacts  112  from the header shields  114 . In an exemplary embodiment, the contact hubs  310  have hub extensions  312  that extend rearward from the rear surface  147  of the front shell  136 . The hub extensions  312  are configured to extend into the rear shell  138 . The hub extensions  312  are positioned between the signal contacts  112  and the rear shell  138 . The contact channels  150  extend through the hub extensions  312 . 
     In an exemplary embodiment, the front plate  144  of the front shell  136  includes separating walls  320  between columns of contact hubs  310  and cross beams  322  between rows of contact hubs  310 . The separating walls  320  and the cross beams  322  are integral with each other and with the contact hubs  310 . For example, the separating walls  320 , the cross beams  322  and the contact hubs  310  may be co-molded, such as during an injection molding process. In an exemplary embodiment, the separating walls  320  extend longitudinally between the opposite sides of the front shell  136 . The cross beams  322  extend laterally between the separating walls  320 . The contact hubs  310  are located between adjacent separating walls  320 . The contact hubs  310  are located between adjacent cross beams  322 . In an exemplary embodiment, the contact hubs  310  extend from corresponding cross beams  322 . 
     The contact hubs  310  are surrounded by the shield channels  152 . For example, the shield channels  152  have C-shapes partially surrounding the contact hubs  310 . The separating walls  320  are separated from the contact hubs  310  by the shield channels  152 . The cross beams  322  are separated from adjacent contact hubs  310  by the shield channels  152 . In an exemplary embodiment, the shield channels  152  extend along 3 sides of the contact hubs  310 , with the fourth side being connected to the corresponding cross beam  322 . The header shields  114  are received in the shield channels  152  and partially surround the contact hubs  310 , and the hub extensions  312 , through the front shell  136 . For example, the contact hubs  310  and the hub extensions  312  are received in the shield pockets  220  of the header shields  114 . When the header shields  114  are loaded in the front plate  144 , the front dimples  242  (shown in  FIG. 6 ) mechanically engage the front shell  136  to hold the header shields  114  in the front shell  136  by an interference fit. For example, the front dimples  242  may directly engage the contact hubs  310 . Alternatively or additionally, the front dimples  242  may directly engage the inner surfaces of the separating walls  320  and/or the cross beams  322 . In an exemplary embodiment, the header shields  114  extend forward of the contact hubs  310  and rearward of the contact extensions  312  of the contact hubs  310 . 
       FIG. 9  is a rear perspective view of a portion of the header connector  106  in accordance with an exemplary embodiment with the front shell  136  removed to illustrate the rear shell  138  relative to the header shields  114  and the signal contacts  112 . In an exemplary embodiment, the rear shell  138  includes a rear plate  350  extending between a front surface  352  and a rear surface  354 . The front surface  352  is configured to face and/or abut against the front shell  136  (shown in  FIG. 8 ). The rear surface  354  is configured to face and/or abut against the PCB  108  (shown in  FIG. 1 ). 
     In an exemplary embodiment, the rear shell  138  includes separating walls  360  and cross beams  362  between the separating walls  360 . The separating walls  360  and the cross beams  360  to form pockets  364  that receive corresponding header shields  114  and the signal contacts  112 . The pockets  364  are configured to receive the hub extensions  312  (shown in  FIG. 8 ). The separating walls  360  are located between columns of the pockets  364  and the cross beams  362  are located between rows of the pockets  364 . The separating walls  360  and the cross beams  362  are integral with each other. For example, the separating walls  360  and the cross beams  362  may be co-molded or cast. The separating walls  360  and the cross beams  362  may be plated or coated such that the separating walls  360  and the cross beams  362  are conductive. In an exemplary embodiment, the separating walls  360  extend longitudinally between the opposite sides of the rear shell  138 . The cross beams  362  extend laterally between the separating walls  360  and may be oriented perpendicular to the separating walls  360  defining generally rectangular shaped pockets  364 . The pockets  364  may have other shapes in alternative embodiments. 
     In an exemplary embodiment, the separating walls  360  and/or the cross beams  362  include slots  366  that receive corresponding wings  234 ,  236  of the header shields  114 . The slots  366  may be angled relative to the separating walls  360  and/or the cross beams  362 . The slots  366  are open at the rear surface  354  for receiving the wings  234 ,  236 . For example, the header shields  114  may be rear loaded into the rear shell  138 . 
     The header shields  114  are received in the pockets  364  and extend partially around the perimeter of the pockets  364 . When the header shields  114  are loaded in the rear plate  350 , the rear dimples  244  mechanically engage the rear shell  138  to hold the header shields  114  in the rear shell  138  by an interference fit. The engagement of the rear dimples  244  with the rear plate  350  electrically connects the header shields  114  to the rear shell  138 . In alternative embodiments, the dimples or interference features may be provided on the rear shell  138  rather than the header shields  114 . In an exemplary embodiment, the header shields  114  have multiple points of contacts with the rear plate  350  using multiple rear dimples  244 . For example, the rear dimples  244  may be provided along the end wall  210 , the first side wall  212  and the second side wall  214 . The rear dimples  244  may be provided along the first wing  234  and the second wing  236 . In an exemplary embodiment, the rear dimples  244  are located close to the ground mounting portions  204  to create natural paths for the ground energy between the header shields  114  and the rear plate  350 . In an exemplary embodiment, the header shields  114  extend forward of the rear plate  350  for mating with the electrical connector  104  and extend rearward of the rear plate  350  for termination to the PCB  108 . 
     In an exemplary embodiment, the cross beams  362  include grooves  368  formed therein. The grooves  368  thin portions of the cross beams  362  in select areas. For example, the grooves  368  may be provided immediately below the signal contacts  112 . The grooves  368  separate or distance the cross beams  322  from the signal contacts  112  for signal integrity. For example, the shape and/or location of the grooves  368  may be selected for impedance control, such as to position the conductive material of the cross beams  362  a predetermined distance from the signal contacts  112 . The grooves  368  may receive portions of the hub extensions  312  (shown in  FIG. 6 ). The grooves  368  may be formed in the cross beams  362  to provide spacing for the material of the hub extensions  312 , such as for impedance control and or manufacturability of the hub extensions  312 . 
       FIG. 10  is a front view of a portion of the header connector  106  in accordance with an exemplary embodiment with the front shell  136  removed to illustrate the rear shell  138  relative to the header shields  114  and the signal contacts  112 . The header shields  114  and corresponding signal contacts  112  are arranged in columns and in rows. The separating walls  360  are arranged between the columns and the cross beams are arranged between the rows. 
     In an exemplary embodiment, the rear shell  138  includes mounting features  370  for mounting the rear shell  138  to the front shell  136 . The mounting features  370 , in the illustrated embodiment, are openings configured to receive posts or tabs of the front shell  136 . Other types of mounting features may be used in alternative embodiments. In an exemplary embodiment, the mounting features  370  are keyed for keyed mating with the front shell  136 . For example, the shape of the mounting features  370  and/or the locations of the mounting features  370  may be used for keyed mating to ensure proper orientation of the rear shell  138  relative to the front shell  136 . 
       FIG. 11  is a rear view of the header connector  106  in accordance with an exemplary embodiment.  FIG. 12  is an enlarged view of the rear of the header connector  106  in accordance with an exemplary embodiment. The rear shell  138  is loaded into the chamber  300  of the front shell  136 . The front shell  136  includes mounting features  372  that interact with the mounting features  370  of the rear shell  138 . In the illustrated embodiment, the mounting features  372  are posts received in the mounting features  370 . In an exemplary embodiment, the mounting rails  302  include pockets  374  that receive the mounting features  370 . 
     When assembled, the signal contacts  112  are received in corresponding contact channels  150  of the contact hubs  310 . The contact hubs  310  are received in corresponding pockets  364  in the rear shell  136 . The header shields  114  are received in corresponding pockets  364  and the rear shell  136 . The header shields  114  surround the contact hubs  310  to provide electrical shielding for the signal contacts  112 . In an exemplary embodiment, the header shields  114  are positioned between the contact hubs  310  and the inner surfaces of the separating walls  360  and the cross beams  362  defining the pockets  364 . The header shields  114  are pressed into mechanical and electrical contact with the rear shell  136  by the contact hubs  310 . For example, the sidewalls  212 ,  214  engage the separating walls  360  and the end walls  210  engage the cross beams  362 . The C-shaped header shields  114  and the cross beams  362  provide circumferential shielding around the signal contacts  112 . For example, the cross beams  362  close off the open side of the C-shaped header shields  114 . The wings  234 ,  236  are angled into the corresponding slots  366  and are electrically connected to the rear shell  138  in the slots  366 . 
     In an exemplary embodiment, the rear shell  138  includes a mounting interface  380  for mounting to the printed circuit board  108  (shown in  FIG. 1 ). The mounting interface  380  may be at the rear surface of the rear shell  138 . The mounting interface  380  may extend from the rear surface of the rear shell  138 . The mounting interface  380  may be a separate component extending from the rear shell  138 . The mating interface  380  may be a spring beam or other mating component. The printed circuit board  108  may include a similar or complementary mating interface. The mating interface of the PCB  108  may be a ground pad or a ground plane or a ground via. Optionally, the mounting interface  380  may be soldered to the PCB  108 . The mounting interface  380  may be press-fit to the PCB  108 . The mounting interface  380  may be a compressing connection, such as a spring beam therebetween. 
     In an exemplary embodiment, a header connector is provided including signal contacts arranged in pairs, each signal contact having a base, a mating pin extending from a front of the base and a mounting portion extending from a rear of the base for termination to a circuit board; header shields having walls defining shield pockets receiving corresponding pairs of the signal contacts to provide electrical shielding for the pairs of signal contacts, each header shield having a base and a mounting portion extending from a rear of the base for termination to the circuit board; and a header housing holding the signal contacts and the header shields, the header housing having a front shell and a rear shell, the front shell being dielectric, the rear shell being conductive and providing electrical shielding for the signal contacts, the front shell holding the signal contacts, the rear shell holding the header shields and being electrically connected to each of the header shields. 
     In various embodiments, the front shell includes a front plate having a front surface and a rear surface, the rear shell includes a rear plate having a front surface and a rear surface, the front surface of the rear plate abuts against the rear surface of the front plate. In various embodiments, the front plate has a first thickness and the rear plate has a second thickness greater than the first thickness. 
     In various embodiments, the front shell includes contact hubs, each contact hub having a pair of contact channels receiving corresponding signal contacts, the contact hub electrically isolating the signal contacts from the header shield. In various embodiments, the contact hubs include hub extensions extending into pockets in the rear shell, the hub extensions being positioned between the signal contacts and the rear shell. In various embodiments, the hub extensions extend beyond a rear surface of the rear shell. In various embodiments, the front shell includes shield channels partially surrounding each contact hub, each shield channel receiving a corresponding header shield, the header shield extending forward of the contact hub and rearward of the contact hub. In various embodiments, the contact hubs include hub extensions extending into pockets in the rear shell, the header shields extending along the hub extensions into the pockets between the rear shell and the hub extensions. In various embodiments, the front shell includes separating walls between columns of hub extensions and cross beams between rows of hub extensions. In various embodiments, the hub extensions extend from corresponding cross beams, the hub extensions being separated from the separating walls by shield channels receiving corresponding header shields. 
     In various embodiments, the header shield includes dimples at the base, the dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. 
     In various embodiments, the header shield includes front dimples and rear dimples at the base, the front dimples engaging the front shell by an interference fit to mechanically connect the header shield to the front shell, the rear dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. 
     In various embodiments, each header shield includes an end wall, a first side wall extending from a first edge of the end wall and a second side wall extending from a second edge of the end wall, the end wall, the first side wall and the second side wall being C-shaped and forming the shield pocket. In various embodiments, the end wall, the first side wall and the second side wall each include dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. In various embodiments, the first side wall includes a wing extending therefrom at an angle, the wing being received in a slot in the rear shell to electrically connect the header shield to the rear shell. 
     In various embodiments, the rear shell includes a mounting feature, the front shell includes a mounting feature interacting with the mounting feature of the rear shell to secure the front shell to the rear shell. In various embodiments, the mounting feature of the rear shell is keyed for keyed mating with the front shell. 
     In various embodiments, the rear shell includes separating walls and cross beams between the separating walls forming pockets receiving corresponding header shields and the signal contacts, each header shield engaging and being directly electrically coupled to at least one separating wall and at least one cross beam. In various embodiments, the cross beams include grooves therein to separate the cross beams from the signal contacts for impedance control. In various embodiments, the walls of the header shields are C-shaped having an open side, the cross beams spanning the open side of the corresponding header shield to provide electrical shielding for the corresponding signal contacts. 
     In various embodiments, the rear shell includes a mounting interface for mounting to the printed circuit board. In various embodiments, the mounting interface is electrically connected to a ground plane of the printed circuit board. In various embodiments, the mounting interface is soldered to the printed circuit board. In various embodiments, the mounting interface is press-fit against an interface of the printed circuit board. In various embodiments, the mounting interface includes a spring beam between the rear shell and a ground conductor of the printed circuit board. 
     In an exemplary embodiment, a header connector is provided including signal contacts arranged in pairs, each signal contact having a base, a mating pin extending from a front of the base and a mounting portion extending from a rear of the base for termination to a circuit board; header shields having walls defining shield pockets receiving corresponding pairs of the signal contacts to provide electrical shielding for the pairs of signal contacts, each header shield having a base and a mounting portion extending from a rear of the base for termination to the circuit board; and a header housing holding the signal contacts and the header shields, the header housing having a front shell and a rear shell, the front shell being dielectric, the rear shell being conductive and providing electrical shielding for the signal contacts, the front shell having a front plate and shroud walls extending from the front plate to define a mating cavity configured to receive a mating electrical connector, the front plate having contact hubs including contact channels arranged in pairs receiving corresponding signal contacts, the front housing having shield channels partially surrounding each contact hub, each shield channel receiving a corresponding header shield, the rear shell including pockets receiving corresponding header shields and contact hubs, the header shields being electrically connected to the rear shell in the corresponding pocket. 
     In various embodiments, the front shell includes a front plate having a front surface and a rear surface, the rear shell includes a rear plate having a front surface and a rear surface, the front surface of the rear plate abuts against the rear surface of the front plate. In various embodiments, the front plate has a first thickness and the rear plate has a second thickness greater than the first thickness. 
     In various embodiments, the contact hubs include hub extensions extending into the pockets in the rear shell, the hub extensions being positioned between the signal contacts and the rear shell. In various embodiments, the hub extensions extend beyond a rear surface of the rear shell. 
     In various embodiments, the header shield extends forward of the contact hub and rearward of the contact hub. 
     In various embodiments, the contact hubs include hub extensions extending into the pockets in the rear shell, the header shields extending along the hub extensions into the pockets between the rear shell and the hub extensions. 
     In various embodiments, the front shell includes separating walls between columns of hub extensions and cross beams between rows of hub extensions. 
     In various embodiments, the hub extensions extend from corresponding cross beams, the hub extensions being separated from the separating walls by shield channels receiving corresponding header shields. 
     In various embodiments, the header shield includes dimples at the base, the dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. 
     In various embodiments, the header shield includes front dimples and rear dimples at the base, the front dimples engaging the front shell by an interference fit to mechanically connect the header shield to the front shell, the rear dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. 
     In various embodiments, each header shield includes an end wall, a first side wall extending from a first edge of the end wall and a second side wall extending from a second edge of the end wall, the end wall, the first side wall and the second side wall being C-shaped and forming the shield pocket. In various embodiments, the end wall, the first side wall and the second side wall each include dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. In various embodiments, the first side wall includes a wing extending therefrom at an angle, the wing being received in a slot in the rear shell to electrically connect the header shield to the rear shell. 
     In various embodiments, the rear shell includes a mounting feature, the front shell includes a mounting feature interacting with the mounting feature of the rear shell to secure the front shell to the rear shell. In various embodiments, the mounting feature of the rear shell is keyed for keyed mating with the front shell. 
     In various embodiments, the rear shell includes separating walls and cross beams between the separating walls forming the pockets, each header shield engaging and being directly electrically coupled to at least one separating wall and at least one cross beam. In various embodiments, the cross beams include grooves therein to separate the cross beams from the signal contacts for impedance control. In various embodiments, the walls of the header shields are C-shaped having an open side, the cross beams spanning the open side of the corresponding header shield to provide electrical shielding for the corresponding signal contacts. 
     In an exemplary embodiment, an electrical connector system is provided including a printed circuit board (PCB) comprising a substrate having a connector surface, the substrate having signal vias and ground vias, the substrate having a ground plane electrically connected to the ground vias; and a header connector including signal contacts arranged in pairs, each signal contact having a base, a mating pin extending from a front of the base and a mounting portion extending from a rear of the base, the mounting portion being received in a corresponding signal via; header shields having walls defining shield pockets receiving corresponding pairs of the signal contacts to provide electrical shielding for the pairs of signal contacts, each header shield having a base and a mounting portion extending from a rear of the base, the mounting portion being received in a corresponding ground via and being electrically connected to the ground plane of the substrate; and a header housing holding the signal contacts and the header shields, the header housing having a front shell and a rear shell, the front shell being dielectric, the rear shell being conductive and providing electrical shielding for the signal contacts, the front shell having a front plate and shroud walls extending from the front plate to define a mating cavity configured to receive a mating electrical connector, the front plate all having contact hubs including contact channels arranged in pairs receiving corresponding signal contacts, the front housing having shield channels partially surrounding each contact hub, each shield channel receiving a corresponding header shield, the rear shell including pockets receiving corresponding header shields and contact hubs, the header shields being electrically connected to the rear shell in the corresponding pocket. 
     In various embodiments, the front shell includes a front plate having a front surface and a rear surface, the rear shell includes a rear plate having a front surface and a rear surface, the front surface of the rear plate abuts against the rear surface of the front plate. In various embodiments, the front plate has a first thickness and the rear plate has a second thickness greater than the first thickness. 
     In various embodiments, the contact hubs include hub extensions extending into the pockets in the rear shell, the hub extensions being positioned between the signal contacts and the rear shell. In various embodiments, the hub extensions extend beyond a rear surface of the rear shell. 
     In various embodiments, the header shield extends forward of the contact hub and rearward of the contact hub. 
     In various embodiments, the contact hubs include hub extensions extending into the pockets in the rear shell, the header shields extending along the hub extensions into the pockets between the rear shell and the hub extensions. 
     In various embodiments, the front shell includes separating walls between columns of hub extensions and cross beams between rows of hub extensions. In various embodiments, the hub extensions extend from corresponding cross beams, the hub extensions being separated from the separating walls by shield channels receiving corresponding header shields. 
     In various embodiments, the header shield includes dimples at the base, the dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. 
     In various embodiments, the header shield includes front dimples and rear dimples at the base, the front dimples engaging the front shell by an interference fit to mechanically connect the header shield to the front shell, the rear dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. 
     In various embodiments, each header shield includes an end wall, a first side wall extending from a first edge of the end wall and a second side wall extending from a second edge of the end wall, the end wall, the first side wall and the second side wall being C-shaped and forming the shield pocket. In various embodiments, the end wall, the first side wall and the second side wall each include dimples engaging the rear shell by an interference fit to mechanically and electrically connect the header shield to the rear shell. In various embodiments, the first side wall includes a wing extending therefrom at an angle, the wing being received in a slot in the rear shell to electrically connect the header shield to the rear shell. 
     In various embodiments, the rear shell includes a mounting feature, the front shell includes a mounting feature interacting with the mounting feature of the rear shell to secure the front shell to the rear shell. In various embodiments, the mounting feature of the rear shell is keyed for keyed mating with the front shell. 
     In various embodiments, the rear shell includes separating walls and cross beams between the separating walls forming the pockets, each header shield engaging and being directly electrically coupled to at least one separating wall and at least one cross beam. In various embodiments, the cross beams include grooves therein to separate the cross beams from the signal contacts for impedance control. In various embodiments, the walls of the header shields are C-shaped having an open side, the cross beams spanning the open side of the corresponding header shield to provide electrical shielding for the corresponding signal contacts. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f) unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.