Patent Publication Number: US-8992252-B2

Title: Receptacle assembly for a midplane connector system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/638,897 filed Apr. 26, 2012, the subject matter of which is herein incorporated by reference in its entirety. 
     This application relates to U.S. Provisional Application No. 61/638,920 filed Apr. 26, 2012 and to U.S. Provisional Application No. 61/638,942 filed Apr. 26, 2012, the subject matter of both of which are herein incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to receptacle assemblies for use in midplane connector systems. 
     Some electrical systems, such as network switches and computer servers with switching capability, include receptacle connectors that are oriented orthogonally on opposite sides of a midplane in a cross-connect application. Switch cards may be connected on one side of the midplane and line cards may be connected on the other side of the midplane. The line card and switch card are joined through header connectors that are mounted on opposite sides of the midplane board. Typically, traces are provided on the sides and/or the layers of the midplane board to route the signals between the header connectors. Sometimes the line card and switch card are joined through header connectors that are mounted on the midplane in an orthogonal relation to one another. The connectors include patterns of signal and ground contacts that extend through a pattern of vias in the midplane. 
     However, conventional orthogonal connectors have experienced certain limitations. For example, it is desirable to increase the density of the signal and ground contacts within the connectors. Heretofore, the contact density has been limited in orthogonal connectors, due to the contact and via patterns. Conventional systems provide the needed 90° rotation within the midplane assembly, such as having each header providing 45° of rotation of the signal paths. In such systems, identical receptacle assemblies are used. However, the routing of the signals through the header connectors and midplane circuit board is complex, expensive and may lead to signal degradation. 
     Some connector systems avoid the 90° rotation in the midplane assembly by using a receptacle assembly on one side that is oriented 90° with respect to the receptacle assembly on the other side. Such connector systems have encountered problems with contact density and signal integrity. 
     A need remains for an improved orthogonal midplane connector system that has high contact density and improved signal integrity in differential pair applications. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a receptacle assembly is provided having a receptacle housing having a mating end and a contact module received in the housing. The contact module includes a conductive holder and a frame assembly received in the conductive holder and electrically shielded by the conductive holder. The frame assembly has a plurality of receptacle signal contacts having mating portions extending from the conductive holder. The receptacle signal contacts are arranged in differential pairs carrying differential signals. Ground shields are received in the conductive holder between the frame assembly and the conductive holder. The ground shields have grounding beams extending along the mating portions of the receptacle signal contacts. The grounding beams are arranged on four sides of each differential pair of the receptacle signal contacts. 
     In a further embodiment, a receptacle assembly is provided including a receptacle housing having a mating end and a plurality of contact modules received in the housing. Each contact module includes a conductive holder and a frame assembly received in the conductive holder and electrically shielded by the conductive holder. The frame assembly has a plurality of receptacle signal contacts. The receptacle signal contacts have mating portions extending from the conductive holder. The receptacle signal contacts are arranged in differential pairs carrying differential signals. Ground shields are coupled to the conductive holder. The ground shields have grounding beams extending along the mating portions of the receptacle signal contacts. The grounding beams are configured to engage header ground shields of a header assembly. The grounding beams are arranged as beam sets with each beam set surrounding a different differential pair of receptacle signal contacts. The grounding beams of each beam set are configured to engage more than one header ground shield. 
     In a further embodiment, a receptacle assembly is provided including a receptacle housing having a mating end and a contact module received in the housing. The contact module includes a conductive holder having a mating end and a frame assembly received in the conductive holder and electrically shielded by the conductive holder. The frame assembly has a plurality of receptacle signal contacts having mating portions extending from the conductive holder beyond the mating end. The receptacle signal contacts are arranged in differential pairs carrying differential signals. The receptacle signal contacts have a lateral width measured from an outside edge of one receptacle signal contact of each pair to an opposite outside edge of the other receptacle signal contact of each pair. Ground shields are coupled to the conductive holder. The ground shields have grounding beams extending longitudinally beyond the mating end of the conductive holder along the mating portions of the receptacle signal contacts. Each grounding beam has a base portion proximal the mating end of the conductive holder and a tail portion distal of the mating end of the conductive holder. The base portion has a base width at least as wide as the lateral width. The tail portion is narrower than the base portion. The base portion extends at least half of a longitudinal length of the grounding beam. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a midplane connector system formed in accordance with an exemplary embodiment. 
         FIG. 2  is an exploded view of a midplane assembly showing first and second header assemblies poised for mounting to a midplane circuit board. 
         FIG. 3  is a front, exploded perspective view of a first receptacle assembly formed in accordance with an exemplary embodiment. 
         FIG. 4  is a front perspective view of a portion of a second receptacle assembly. 
         FIG. 5  is an exploded view of a contact module for the second receptacle assembly shown in  FIG. 4 . 
         FIG. 6  is a side perspective view of a frame for the contact module formed in accordance with an exemplary embodiment. 
         FIG. 7  illustrates a leadframe of the frame. 
         FIG. 8  is a side perspective view of another frame for the contact module formed in accordance with an exemplary embodiment. 
         FIG. 9  is a side perspective view of a frame assembly showing the frame shown in  FIG. 6  and the frame shown in  FIG. 8  coupled together. 
         FIG. 10  illustrates portions of frame assemblies. 
         FIG. 11  illustrates a portion of the second receptacle assembly showing a plurality of contact modules arranged in a stacked configuration. 
         FIG. 12  is a side perspective view of a ground shield for the contact module shown in  FIG. 5  and formed in accordance with an exemplary embodiment. 
         FIG. 13  is a side perspective view of a ground shield for the contact module shown in  FIG. 5  and formed in accordance with an exemplary embodiment. 
         FIG. 14  is a side perspective view of a portion of the second receptacle assembly. 
         FIG. 15  is a front perspective view of a portion of the contact module shown in  FIG. 5 . 
         FIG. 16  is a front view of a portion of the second receptacle assembly showing a plurality of contact modules arranged in a stacked configuration. 
         FIG. 17  is a side view of a portion of the contact module shown in  FIG. 5 . 
         FIG. 18  illustrates a portion of the ground shield shown in  FIG. 12 . 
         FIG. 19  illustrates a portion of the contact module shown in  FIG. 5 . 
         FIG. 20  is a cross-sectional view of the contact module shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a perspective view of a midplane connector system  100  formed in accordance with an exemplary embodiment. The midplane connector system  100  includes a midplane assembly  102 , a first connector assembly  104  configured to be coupled to one side of the midplane assembly  102  and a second connector assembly  106  configured to be connected to a second side the midplane assembly  102 . The midplane assembly  102  is used to electrically connect the first and second connector assemblies  104 ,  106 . Optionally, the first connector assembly  104  may be part of a daughter card and the second connector assembly  106  may be part of a backplane, or vice versa. The first and second connector assemblies  104 ,  106  may be line cards or switch cards. 
     The midplane assembly  102  includes a midplane circuit board  110  having a first side  112  and second side  114 . The midplane assembly  102  includes a first header assembly  116  mounted to and extending from the first side  112  of the midplane circuit board  110 . The midplane assembly  102  includes a second header assembly  118  mounted to and extending from the second side  114  of the midplane circuit board  110 . The first and second header assemblies  116 ,  118  each include header signal contacts  120  (shown in  FIG. 2 ) electrically connected to one another through the midplane circuit board  110 . 
     The midplane assembly  102  includes a plurality of signal paths therethrough defined by the header signal contacts  120  and conductive vias that extend through the midplane circuit board  110 . The header signal contacts  120  of the first and second header assemblies  116 ,  118  are received in the same conductive via to define a signal path through the midplane assembly  102 . In an exemplary embodiment, the signal paths pass straight through the midplane assembly  102  along linear paths. Such a design of the midplane circuit board  110  is less complex and less expensive to manufacture than a circuit board that routes traces between different vias to connect the first and second header assemblies  116 ,  118 . 
     In an exemplary embodiment, the first and second header assemblies  116 ,  118  may be identical to one another. Having the first and second header assemblies  116 ,  118  identical to one another reduces the overall number of different parts that are needed for the midplane connector system  100 . The first and second header assemblies  116 ,  118  may have an identical pinout allowing the first and second header assemblies  116 ,  118  to be mounted to the midplane circuit board  110  using conductive vias that pass straight through the midplane circuit board  110  between the first side  112  and the second side  114 . The first and second header assemblies  116 ,  118  are not rotated 90° relative to one another as is typical of conventional connector systems, and thus do not suffer from a loss in density or a loss in performance as is typical of such connector systems. The header assemblies  116 ,  118  may be rotated 180° relative to one another to facilitate different card positions. 
     The first and second header assemblies  116 ,  118  include header ground shields  122  that provide electrical shielding around corresponding header signal contacts  120 . In an exemplary embodiment, the header signal contacts  120  are arranged in pairs configured to convey differential signals. The header ground shields  122  peripherally surround a corresponding pair of the header signal contacts  120 . In an exemplary embodiment, the header ground shields  122  are C-shaped, covering three sides of the pair of header signal contacts  120 . One side of the header ground shield  122  is open. In the illustrated embodiment, the header ground shields  122  have an open bottom, but the header ground shield  122  below the open bottom provides shielding across the open bottom. Each pair of header signal contacts  120  is therefore surrounded on all four sides thereof using the C-shaped header ground shield  122  and the header ground shield  122  below the pair of header signal contacts  120 . 
     The first and second header assemblies  116 ,  118  each include a header housing  124  that holds the header signal contacts  120  and the header ground shields  122 . The header housing  124  is manufactured from a dielectric material, such as a plastic material. The header housing  124  includes a base  126  configured to be mounted to the midplane circuit board  110 . The header housing  124  includes shroud walls  128  extending from the base  126 . The shroud walls  128  cover portions of the header signal contacts  120  and header ground shields  122 . The connector assemblies  104 ,  106  are coupled to the shroud walls  128 . The shroud walls  128  may guide the connector assemblies  104 ,  106  during mating with the header assemblies  116 ,  118  respectively. 
     In alternative embodiments, the first and second header assemblies  116 ,  118  may include contact modules loaded into a housing, similar to the connector assemblies  104 ,  106 . Optionally, the first and second header assemblies  116 ,  118  may be mounted to cables rather than the midplane circuit board  110 . 
     The first connector assembly  104  includes a first circuit board  130  and a first receptacle assembly  132  coupled to the first circuit board  130 . The first receptacle assembly  132  is configured to be coupled to the first header assembly  116 . The first receptacle assembly  132  has a header interface  134  configured to be mated with the first header assembly  116 . The first receptacle assembly  132  has a board interface  136  configured to be mated with the first circuit board  130 . In an exemplary embodiment, the board interface  136  is orientated perpendicular with respect to the header interface  134 . When the first receptacle assembly  132  is coupled to the first header assembly  116 , the first circuit board  130  is orientated perpendicular with respect to the midplane circuit board  110 . 
     The first receptacle assembly  132  includes a receptacle housing  138  that holds a plurality of contact modules  140 . The contact modules  140  are held in a stacked configuration generally parallel to one another. The contact modules  140  hold a plurality of receptacle signal contacts  142  (shown in  FIG. 3 ) that are electrically connected to the first circuit board  130  and define signal paths through the first receptacle assembly  132 . The receptacle signal contacts  142  are configured to be electrically connected to the header signal contacts  120  of the first header assembly  116 . In an exemplary embodiment, the contact modules  140  provide electrical shielding for the receptacle signal contacts  142 . Optionally, the receptacle signal contacts  142  may be arranged in pairs carrying differential signals. In an exemplary embodiment, the contact modules  140  generally provide 360° shielding for each pair of receptacle signal contacts  142  along substantially the entire length of the receptacle signal contacts  142  between the board interface  136  and the header interface  134 . The shield structure of the contact modules  140  that provides the electrical shielding for the pairs of receptacle signal contacts  142  is electrically connected to the header ground shields  122  of the first header assembly  116  and is electrically connected to a ground plane of the first circuit board  130 . 
     The second connector assembly  106  includes a second circuit board  150  and a second receptacle assembly  152  coupled to the second circuit board  150 . The second receptacle assembly  152  is configured to be coupled to the second header assembly  118 . The second receptacle assembly  152  has a header interface  154  configured to be mated with the second header assembly  118 . The second receptacle assembly  152  has a board interface  156  configured to be mated with the second circuit board  150 . In an exemplary embodiment, the board interface  156  is oriented perpendicular with respect to the header interface  154 . When the second receptacle assembly  152  is coupled to the second header assembly  118 , the second circuit board  150  is oriented perpendicular with respect to the midplane circuit board  110 . The second circuit board  150  is oriented perpendicular to the first circuit board  130 . 
     The second receptacle assembly  152  includes a receptacle housing  158  that holds a plurality of contact modules  160 . The contact modules  160  are held in a stacked configuration generally parallel to one another. The contact modules  160  hold a plurality of receptacle signal contacts  162  (shown in  FIG. 4 ) that are electrically connected to the second circuit board  150  and define signal paths through the second receptacle assembly  152 . The receptacle signal contacts  162  are configured to be electrically connected to the header signal contacts  120  of the second header assembly  118 . In an exemplary embodiment, the contact modules  160  provide electrical shielding for the receptacle signal contacts  162 . Optionally, the receptacle signal contacts  162  may be arranged in pairs carrying differential signals. In an exemplary embodiment, the contact modules  160  generally provide 360° shielding for each pair of receptacle signal contacts  162  along substantially the entire length of the receptacle signal contacts  162  between the board interface  156  and the header interface  154 . The shield structure of the contact modules  160  that provides the electrical shielding for the pairs of receptacle signal contacts  162  is electrically connected to the header ground shields  122  of the second header assembly  118  and is electrically connected to a ground plane of the second circuit board  150 . 
     In the illustrated embodiment, the first circuit board  130  is oriented generally horizontally. The contact modules  140  of the first receptacle assembly  132  are orientated generally vertically. The second circuit board  150  is oriented generally vertically. The contact modules  160  of the second receptacle assembly  152  are oriented generally horizontally. The first connector assembly  104  and the second connector assembly  106  have an orthogonal orientation with respect to one another. The signal contacts within each differential pair, including the receptacle signal contacts  142  of the first receptacle assembly  132 , the receptacle signal contacts  162  of the second receptacle assembly  152 , and the header signal contacts  120 , are all oriented generally horizontally. Optionally, the first and/or second receptacle assemblies  132 ,  152  may be mounted to cables rather than the circuit boards  130 ,  150 . 
       FIG. 2  is an exploded view of the midplane assembly  102  showing the first and second header assemblies  116 ,  118  poised for mounting to the midplane circuit board  110 . A plurality of conductive vias  170  extend through the midplane circuit board  110  between the first and second sides  112 ,  114 . The vias  170  extend straight through the midplane circuit board  110 . No traces are needed along the midplane circuit board  110  to interconnect vias on one side of the midplane circuit board  110  with vias on the other side of the midplane circuit board  110  as is typical with conventional midplane circuit boards that have the header assemblies rotated 90°. Having the vias  170  pass straight through the midplane circuit board  110  and eliminating traces between the vias allows for better performance and reduces the cost of the midplane circuit board  110 . The conductive vias  170  receive the header signal contacts  120  of the first and second header assemblies  116 ,  118 . Some of the conductive vias  170  are configured to receive the header ground shields  122 . The conductive vias  170  that receive the header ground shields  122  may surround the pair of conductive vias  170  that receive the corresponding pair of header signal contacts  120 . The same conductive vias  170  receive header ground shields  122  of both header assemblies  116 ,  118  to directly connect such header ground shields  122 . The same conductive vias  170  receive header signal contacts  120  of both header assemblies  116 ,  118  to directly connect such header signal contacts  120 . 
     In an exemplary embodiment, the header signal contacts  120  include compliant pins  172  that are configured to be loaded into corresponding conductive vias  170 . The compliant pins  172  are mechanically and electrically connected to the conductive vias  170 . The header signal contacts  120  may be pins at the mating end, or may have other types of mating interfaces in alternative embodiments, such as sockets, blades, spring beams and the like. In an exemplary embodiment, the header ground shields  122  include compliant pins  174  that are configured to be received in corresponding conductive vias  170 . The compliant pins  174  are mechanically and electrically connected to the conductive vias  170 . 
     The header ground shields  122  are C-shaped and provide shielding on three sides of the pair of header signal contacts  120 . The header ground shields  122  have a plurality of walls, such as three planar walls  176 ,  178 ,  180 . The walls  176 ,  178 ,  180  may be integrally formed or alternatively, may be separate pieces. The compliant pins  174  extend from each of the walls  176 ,  178 ,  180  to electrically connect the walls  176 ,  178 ,  180  to the midplane circuit board  110 . The wall  178  defines a center wall or top wall of the header ground shield  122 . The walls  176 ,  180  define side walls that extend from the center wall  178 . The side walls  176 ,  180  may be generally perpendicular with respect to the center wall  178 . The bottom of each header ground shield  122  is open between the side walls  176 ,  180 . The header ground shield  122  associated with another pair of header signal contacts  120  provides shielding along the open, fourth side thereof such that each of the pairs of header signal contacts  120  is shielded from each adjacent pair in the same column and the same row. For example, the top wall  178  of a first header ground shield  122  which is below a second header ground shield  122  provides shielding across the open bottom of the C-shaped second header shield  122 . 
     Other configurations or shapes for the header ground shields  122  are possible in alternative embodiments. More or less walls may be provided in alternative embodiments. The walls may be bent or angled rather than being planar. In other alternative embodiments, the header ground shields  122  may provide shielding for individual header signal contacts  120  or sets of contacts having more than two header signal contacts  120 . 
       FIG. 3  is a front, exploded perspective view of the first receptacle assembly  132  formed in accordance with an exemplary embodiment.  FIG. 3  illustrates one of the contact modules  140  in an exploded state and poised for assembly and loading into the receptacle housing  138 . The receptacle housing  138  includes a plurality of signal contact openings  200  and a plurality of ground contacts openings  202  at a mating end  204  of the receptacle housing  138 . The mating end  204  defines the header interface  134  of the first receptacle assembly  132 . 
     The contact modules  140  are coupled to the receptacle housing  138  such that the receptacle signal contacts  142  are received in corresponding signal contact openings  200 . Optionally, a single receptacle signal contact  142  is received in each signal contact opening  200 . The signal contact openings  200  may also receive corresponding header signal contacts  120  (shown in  FIG. 2 ) therein when the receptacle and header assemblies  132 ,  116  are mated. The ground contact openings  202  receive corresponding header ground shields  122  (shown in  FIG. 2 ) therein when the receptacle and header assemblies  132 ,  116  are mated. The ground contact openings  202  receive grounding members, such as grounding beams of the contact modules  140  that mate with the header ground shields  122  to electrically common the receptacle and header assemblies  132 ,  116 . 
     The receptacle housing  138  is manufactured from a dielectric material, such as a plastic material, and provides isolation between the signal contact openings  200  and the ground contact openings  202 . The receptacle housing  138  isolates the receptacle signal contacts  142  and the header signal contacts  120  from the header ground shields  122 . The receptacle housing  138  isolates each set of receptacle and header signal contacts  142 ,  120  from other sets of receptacle and header signal contacts  142 ,  120 . 
     The ground contact openings  202  are C-shaped in the illustrated embodiment to receive the C-shaped header ground shields  122 . Other shapes are possible in alternative embodiments, such as when other shaped header ground shields  122  are used. The signal contact openings  200  are chamfered at the mating end  204  to guide the header signal contacts  120  into the signal contact openings  200  during mating. 
     The contact module  140  includes a conductive holder  210 , which in the illustrated embodiment includes a first holder member  212  and a second holder member  214  that are coupled together to form the holder  210 . The holder members  212 ,  214  are fabricated from a conductive material. For example, the holder members  212 ,  214  may be die cast from a metal material. Alternatively, the holder members  212 ,  214  may be stamped and formed or may be fabricated from a plastic material that has been metalized or coated with a metallic layer. By having the holder members  212 ,  214  fabricated from a conductive material, the holder members  212 ,  214  may provide electrical shielding for the first receptacle assembly  132 . When the holder members  212 ,  214  are coupled together, the holder members  212 ,  214  define at least a portion of a shield structure to provide electrical shielding for the receptacle signal contacts  142 . 
     The conductive holder  210  holds a frame assembly  220 , which includes the receptacle signal contacts  142 . The holder members  212 ,  214  provide shielding around the frame assembly  220  and receptacle signal contacts  142 . The holder members  212 ,  214  include tabs  222 ,  224  that extend inward toward one another to define discrete channels  226 ,  228 , respectively. The tabs  222 ,  224  define at least a portion of a shield structure that provides electrical shielding around the receptacle signal contacts  142 . The tabs  222 ,  224  are configured to extend into the frame assembly  220  such that the tabs  222 ,  224  are positioned between receptacle signal contacts  142  to provide shielding between corresponding receptacle signal contacts  142 . In alternative embodiments, one holder member  212  or  214  could have a tab that accommodates the entire frame assembly  220  and the other holder member  212  or  214  acts as a lid. 
     The frame assembly  220  includes a pair of dielectric frames  230 ,  232  surrounding the receptacle signal contacts  142 . In an exemplary embodiment, the receptacle signal contacts  142  are initially held together as leadframes (not shown), which, are overmolded with dielectric material to form the dielectric frames  230 ,  232 . Other manufacturing processes may be utilized to form the dielectric frames  230 ,  232  other than overmolding a leadframe, such as loading receptacle signal contacts  142  into a formed dielectric body. The dielectric frames  230 ,  232  include openings  234  that receive the tabs  222 ,  224 . The openings  234  are located between adjacent receptacle signal contacts  142  such that when the tabs  222 ,  224  are loaded into the openings  234 , the tabs  222 ,  224  are positioned between adjacent receptacle signal contacts  142  to provide shielding between such receptacle signal contacts  142 . 
     The receptacle signal contacts  142  have mating portions  236  extending from the front walls of the dielectric frames  230 ,  232  and mounting portions  238  extending from the bottom walls of the dielectric frames  230 ,  232 . Other configurations are possible in alternative embodiments. The mating portions  236  and mounting portions  238  are the portions of the receptacle signal contacts  142  that extend from the dielectric frames  230 ,  232 . In an exemplary embodiment, the mating portions  236  extend generally perpendicular with respect to the mounting portions  238 . Inner portions or encased portions of the receptacle signal contacts  142  transition between the mating portions  236  and the mounting portions  238  within the dielectric frames  230 ,  232 . The mating portions  236  are configured to be mated with, and electrically connected to, corresponding header signal contacts  120  (shown in  FIG. 2 ). The mating portions  236  may have a split-beam type of connection, or may have other types of mating interfaces in alternative embodiments, such as pins, sockets, blades, and the like. The mounting portions  238  are configured to be electrically connected to the first circuit board  130 . For example, the mounting portions  238  may include compliant pins that extend into conductive vias  240  in the first circuit board  130 . 
     In an exemplary embodiment, the receptacle signal contacts  142  are arranged as differential pairs. In an exemplary embodiment, one of the receptacle signal contacts  142  of each pair is held by the dielectric frame  230  while the other receptacle signal contact  142  of the differential pair is held by the other dielectric frame  232 . The receptacle signal contacts  142  of each pair extend through the frame assembly  220  generally along parallel paths such that the receptacle signal contacts  142  are skewless between the mating portions  236  and the mounting portions  238 . Each contact module  140  holds both receptacle signal contacts  142  of each pair. The receptacle signal contacts  142  of the pairs are held in different columns. Each contact module  140  has two columns of receptacle signal contacts  142 . One column is defined by the receptacle signal contacts  142  held by the dielectric frame  230  and another column is defined by the receptacle signal contacts  142  held by the dielectric frame  232 . The receptacle signal contacts  142  of each pair are arranged in a row extending generally perpendicular with respect to the columns. 
     The holder members  212 ,  214  provide electrical shielding between and around respective pairs of the receptacle signal contacts  142 . The holder members  212 ,  214  provide shielding from electromagnetic interference (EMI) and/or radio frequency interference (RFI). The holder members  212 ,  214  may provide shielding from other types of interference as well. The holder members  212 ,  214  prevent crosstalk between different pairs of receptacle signal contacts  142 . The holder members  212 ,  214  provide electrical shielding around the outside of the frames  230 ,  232 , and thus around the outside of all of the receptacle signal contacts  142 , as well as between the receptacle signal contacts  142 , such as between pairs of receptacle signal contacts  142  using the tabs  222 ,  224 . The holder members  212 ,  214  control electrical characteristics, such as impedance control, crosstalk control, and the like, of the receptacle signal contacts  142 . 
     In an exemplary embodiment, the contact module  140  includes a ground shield  250  coupled to one side of the conductive holder  210 . The ground shield  250  includes a main body  252  that is generally planar and extends alongside of the second holder member  214 . The ground shield  250  includes grounding beams  254  extending from a front  256  of the main body  252 . The grounding beams  254  are configured to extend into the ground contact openings  202 . The grounding beams  254  are configured to engage and be electrically connected to the header ground shields  122  (shown in  FIG. 2 ) when the contact modules  140  are loaded into the receptacle housing  138  and when the first receptacle assembly  132  is coupled to the first header assembly  116 . The grounding beams  254  may be deflectable. The grounding beams  254  are configured to be positioned between pairs of the receptacle signal contacts  142 . For example, one grounding beam  254  is configured to be positioned above each pair of receptacle signal contacts  142  and another grounding beam  254  is configured to be positioned below each pair of receptacle signal contacts  142 . The grounding beams  254  provide shielding along the mating portions  236  of the receptacle signal contacts  142 . Optionally, other grounding beams may be provided along the sides of the mating portions  236  in addition to, or in the alternative to, the grounding beams  254  above and below the receptacle signal contacts  142 . In alternative embodiments, two ground shields may be used, one on each side with each ground shield providing grounding beams. 
     The ground shield  250  includes ground pins  258  extending from a bottom  260  of the ground shield  250 . The ground pins  258  may be compliant pins. The ground pins  258  are configured to be received in corresponding conductive vias  262  in the first circuit board  130 . In the illustrated embodiment, the ground pins  258  are all arranged in a single column generally aligned with the main body  252 . The ground pins  258  may be arranged in different locations in alternative embodiments. For example, at least some of the ground pins  258  may be bent inward into the conductive holder  210  such that the ground pins  258  are aligned with and positioned between the mounting portions  238  of corresponding receptacle signal contacts  142 . In other embodiments, ground bars may be used that extend across all of the contact modules  140 . 
     During assembly, the frame assembly  220  is loaded into the conductive holder  210 . The first and second holder members  212 ,  214  are coupled together around the frame assembly  220 . The ground shield  250  is coupled to the second holder member  214 . The contact module  140  is then loaded into the rear of the receptacle housing  138 . Once all of the contact modules  140  are loaded into the receptacle housing  138 , the first receptacle assembly  132  may be mounted to the first circuit board  130  by loading the mounting portions  238  and the ground pins  258  into the conductive vias  240 ,  262 , respectively. 
       FIG. 4  is a front perspective view of the second receptacle assembly  152  showing one of the contact modules  160  poised for loading into the receptacle housing  158 . The receptacle housing  158  includes a plurality of signal contact openings  300  and a plurality of ground contacts openings  302  at a mating end  304  of the receptacle housing  158 . The mating end  304  defines the header interface  154  of the second receptacle assembly  152 . 
     The contact modules  160  are coupled to the receptacle housing  158  such that the receptacle signal contacts  162  are received in corresponding signal contact openings  300 . Optionally, a single receptacle signal contact  162  is received in each signal contact opening  300 . The signal contact openings  300  may also receive corresponding header signal contacts  120  (shown in  FIG. 2 ) therein when the receptacle and header assemblies  152 ,  118  are mated. The ground contact openings  302  receive corresponding header ground shields  122  (shown in  FIG. 2 ) therein when the receptacle and header assemblies  152 ,  118  are mated. The ground contact openings  302  receive grounding members, such as grounding beams of the contact modules  160 , which mate with the header ground shields  122  to electrically common the receptacle and header assemblies  152 ,  118 . 
     The receptacle housing  158  is manufactured from a dielectric material, such as a plastic material, and provides isolation between the signal contact openings  300  and the ground contact openings  302 . The receptacle housing  158  isolates the receptacle signal contacts  162  and the header signal contacts  120  from the header ground shields  122 . The receptacle housing  158  isolates each set of receptacle and header signal contacts  162 ,  120  from other sets of receptacle and header signal contacts  162 ,  120 . 
     The ground contact openings  302  are C-shaped in the illustrated embodiment to receive the C-shaped header ground shields  122 . Other shapes are possible in alternative embodiments, such as when other shaped header ground shields  122  are used. The ground contact openings  302  are chamfered at the mating end  304  to guide the header ground shields  122  into the ground contact openings  302  during mating. The signal contact openings  300  are chamfered at the mating end  304  to guide the header signal contacts  120  into the signal contact openings  300  during mating. 
       FIG. 5  is an exploded view of the contact module  160 . The contact module  160  includes a conductive holder  310 , which in the illustrated embodiment includes a first holder member  312  and a second holder member  314  that are coupled together to form the holder  310 . The conductive holder  310  has a mating end  316  and a mounting end  318 . 
     The holder members  312 ,  314  are fabricated from a conductive material. For example, the holder members  312 ,  314  may be die cast from a metal material. Alternatively, the holder members  312 ,  314  may be stamped and formed or may be fabricated from a plastic material that has been metalized or coated with a metallic layer. By having the holder members  312 ,  314  fabricated from a conductive material, the holder members  312 ,  314  may provide electrical shielding for the second receptacle assembly  152 . When the holder members  312 ,  314  are coupled together, the holder members  312 ,  314  define at least a portion of a shield structure to provide electrical shielding for the receptacle signal contacts  162 . 
     The conductive holder  310  holds a frame assembly  320 , which includes the receptacle signal contacts  162 . The holder members  312 ,  314  provide shielding around the frame assembly  320  and receptacle signal contacts  162 . The holder members  312 ,  314  include tabs  322 ,  324  that extend inward toward one another to define discrete, shielded channels  326 ,  328 , respectively. Optionally, tabs may be provided on only the holder member  312  or the holder member  314  rather than on both holder members  312 ,  314 . The tabs  322 ,  324  define at least a portion of a shield structure that provides electrical shielding around the receptacle signal contacts  162 . The tabs  322 ,  324  are configured to extend into the frame assembly  320  such that the tabs  322 ,  324  are positioned between pairs of the receptacle signal contacts  162  to provide shielding between the corresponding pairs of the receptacle signal contacts  162 . 
     The frame assembly  320  includes a first frame  330  and a second frame  332  that surround corresponding receptacle signal contacts  162 . Optionally, the first frame  330  may be manufactured from a dielectric material overmolded over the corresponding receptacle signal contacts  162 . The second frame  332  may be manufactured from a dielectric material overmolded over the corresponding receptacle signal contacts  162 . The first and second frames  330 ,  332  are coupled together to form the frame assembly  320 . 
     In an exemplary embodiment, the receptacle signal contacts  162  of the first frame  330  form part of a common leadframe that is overmolded to encase the receptacle signal contacts  162 . The receptacle signal contacts  162  of the second frame  332  form part of a common leadframe, separate from the leadframe of the first frame  330 , that is separately overmolded to encase the corresponding receptacle signal contacts  162 . Other manufacturing processes may be utilized to form the dielectric frames  330 ,  332  other than overmolding leadframes. 
     The first and second frames  330 ,  332  are assembled such that the tabs  322 ,  324  extend therethrough between corresponding differential pairs of the receptacle signal contacts  162 . The holder members  312 ,  314  provide electrical shielding between and around respective pairs of the receptacle signal contacts  162 . The holder members  312 ,  314  provide shielding from electromagnetic interference (EMI) and/or radio frequency interference (RFI). The holder members  312 ,  314  may provide shielding from other types of interference as well. The holder members  312 ,  314  prevent crosstalk between different pairs of receptacle signal contacts  162 . The holder members  312 ,  314  provide electrical shielding around the outside of the first and second frames  330 ,  332 , and thus around the outside of all of the receptacle signal contacts  162 , as well as between the receptacle signal contacts  162 , such as between pairs of receptacle signal contacts  162  separated by the tabs  322 ,  324 . The holder members  312 ,  314  control electrical characteristics, such as impedance control, crosstalk control, and the like, of the receptacle signal contacts  162 . 
     The contact module  160  includes a first ground shield  350  and a second ground shield  352  that provide shielding for the receptacle signal contacts  162 . The ground shields  350 ,  352  make ground terminations to the header ground shields  122  (shown in  FIG. 1 ) and the second circuit board  150  (shown in  FIG. 1 ). In an exemplary embodiment, the ground shields  350 ,  352  are internal ground shields positioned within the conductive holder  310 . The ground shields  350 ,  352  are inlaid within the conductive holder  310 . For example, the first ground shield  350  is laid in the first holder member  312  and positioned between the first holder member  312  and the frame assembly  320 . The second ground shield  352  is laid in the second holder member  314  and positioned between the second holder member  314  and the frame assembly  320 . 
     The first ground shield  350  includes flanking grounding beams  354  and in-column grounding beams  356  extending from a front thereof. The grounding beams  354 ,  356  are oriented generally perpendicular to each other. The grounding beams  354 ,  356  extend along different sides of the receptacle signal contacts  162 . For example, the flanking grounding beams  354  may extend along a side of both receptacle signal contacts  162  out of column with respect to the receptacle signal contacts  162 , while the in-column grounding beams  356  are in-column with the receptacle signal contacts  162 . The grounding beams  354 ,  356  are configured to extend into the ground contact openings  302  (shown in  FIG. 4 ). The grounding beams  354 ,  356  are configured to engage and be electrically connected to the header ground shields  122  (shown in  FIG. 1 ) when the contact modules  160  are loaded into the receptacle housing  158  and when the second receptacle assembly  152  is coupled to the second header assembly  118 . The grounding beams  354 ,  356  may be deflectable. 
     The first ground shield  350  includes ground pins  358  extending from a bottom of the ground shield  350 . The ground pins  358  may be compliant pins. The ground pins  358  are configured to be received in corresponding conductive vias in the second circuit board  150 . 
     The second ground shield  352  includes flanking grounding beams  364  and in-column grounding beams  366  extending from a front thereof. The grounding beams  364 ,  366  are oriented generally perpendicular to each other. The grounding beams  364 ,  366  extend along different sides of the receptacle signal contacts  162 . For example, the flanking grounding beams  364  may extend along a side of both receptacle signal contacts  162  out of column with respect to the receptacle signal contacts  162  while the in-column grounding beams  366  are aligned in-column with the receptacle signal contacts  162  generally opposite the grounding beam  356 . When assembled, the grounding beams  354 ,  356 ,  364 ,  366  are located on all four sides of the mating portions of the pair of receptacle signal contacts  162 . The grounding beams  364 ,  366  are configured to extend into the ground contact openings  302 . The grounding beams  364 ,  366  are configured to engage and be electrically connected to the header ground shields  122  (shown in  FIG. 1 ) when the contact modules  160  are loaded into the receptacle housing  158  and when the second receptacle assembly  152  is coupled to the second header assembly  118 . The grounding beams  364 ,  366  may be deflectable. 
     The second ground shield  352  includes ground pins  368  extending from a bottom of the second ground shield  352 . The ground pins  368  may be compliant pins. The ground pins  368  are configured to be received in corresponding conductive vias in the second circuit board  150 . 
     In an exemplary embodiment, the header assemblies  116 ,  118  (shown in  FIG. 2 ) may be manufactured in a similar manner as the receptacle assemblies  132 ,  152 , such as including contact modules received in a housing. The contact modules of the header assemblies may include inlaid ground shields that define the C-shaped ground shields or that have grounding beams on three or more sides of the header signal contacts. 
       FIG. 6  is a side perspective view of the first frame  330  formed in accordance with an exemplary embodiment. The first frame  330  includes a plurality of frame members  400  each supporting different differential pairs of receptacle signal contacts  162 . The frame members  400  are separated by gaps  402 . Any number of frame members  400  may be provided. In the illustrated embodiment, three frame members  400  are used corresponding to three differential pairs of receptacle signal contacts  162  of the first frame  330 . 
     The frame members  400  extend between a mating end  404  of the first frame  330  and a mounting end  406  of the first frame  330 . In the illustrated embodiment, the mating end  404  is generally perpendicular with respect to the mounting end  406 , however other orientations are possible in alternative embodiments. The receptacle signal contacts  162  have mating portions  420  that extend from the frame members  400  beyond the mating end  404 , and mounting portions  422  that extend from the frame members  400  beyond the mounting end  406 , for electrical termination to other components such as the second header assembly  118  and the second circuit board  150  (both shown in  FIG. 1 ). 
     The frame members  400  are connected by bridges  408  that span the gaps  402 . The bridges  408  position the frame members  400  with respect to one another. The bridges  408  are co-molded with the frame members  400 . 
       FIG. 7  illustrates a leadframe  410  of the frame assembly  320 . The receptacle signal contacts  162  are formed as part of the leadframe  410 . The leadframe  410  is a stamped and funned structure and is initially held together by a carrier  412  with connecting portions between each of the conductors defining the receptacle signal contacts  162 . The carrier  412  is later removed after the receptacle signal contacts  162  are held by the frame members  400 . 
     As illustrated in  FIG. 7 , the leadframe  410  is generally planar and defines a leadframe plane. The mating and mounting portions  420 ,  422  are integrally formed with the conductors of the leadframe  410 . The conductors extend along predetermined paths between each mating portion  420  and corresponding mounting portion  422 . The mating portions  420  are configured to be mated with and electrically connected to corresponding header signal contacts  120  (shown in  FIG. 2 ). The mounting portions  422  are configured to be electrically connected to the second circuit board  150 . For example, the mounting portions  420  may include compliant pins that extend into conductive vias in the second circuit board  150 . 
     With reference back to  FIG. 6 , portions of the leadframe  410  are enclosed within the frame members  400 . In an exemplary embodiment, portions of the leadframe  410  are exposed through the frame members  400  in certain areas. In some embodiments, the frame members  400  are manufactured using an overmolding process. During the overmolding process, a majority of the leadframe  410  is encased in a dielectric material which forms the frame members  400 . The mating portions  420  extend from the mating end  404  along an edge of the frame members  400  (e.g. a front edge), and the mounting portions  422  extend from the mounting end  406  along another edge of the frame members  400  (e.g. a side edge). 
     The receptacle signal contacts  162  are arranged in pairs. One of the receptacle signal contacts  162  in each pair defines a radially inner receptacle signal contact (measured from the intersection between the mating and mounting ends of the contact module  160 ), while the other receptacle signal contact  162  in each pair defines a radially outer receptacle signal contact. The inner and outer receptacle signal contacts  162  have different lengths between the mating portions  420  and the mounting portions  422 . In an exemplary embodiment, the radially outer receptacle signal contacts  162  are exposed to air through the frame members  400  for electrical compensation, such as to reduce electrical skew. 
     The frame members  400  include locating posts  430  extending therefrom. The locating posts  430  are configured to be received in corresponding openings in the conductive holder  310  (shown in  FIG. 5 ) to locate and/or secure the first frame  330  within the conductive holder  310 . In an exemplary embodiment, the bridges  408  near the mounting end  406  include locating channels  432  formed therethrough. The locating channels  432  receive tabs or other features of the conductive holder  310  to position and or secure the first frame  330  with respect to the conductive holder  310 . 
     In an exemplary embodiment, at least some of the frame members  400  include troughs  434 . The troughs  434  are recessed areas that are configured to receive portions of the second frame  332  (shown in  FIG. 5 ). Optionally, the troughs  434  may be generally aligned with the bridges  408 . Optionally, at least one frame coupling member (not shown) is located within each trough  434 . The frame coupling member is configured to extend into the second frame  332  to position the first frame  330  with respect to the second frame  332 . 
     In an exemplary embodiment, the bridges  408  include coupling members  438  that interact with corresponding coupling members of the second frame  332  to secure the first frame  330  with respect to the second frame  332 . In the illustrated embodiment, the coupling members  438  constitute openings extending through the bridges  408 . The openings receive posts or other types of coupling members therein. Other types of coupling members  438  may be provided on the bridges  408 , such as post, slots, latches, or other types of fasteners. 
       FIG. 8  is a side perspective view of the second frame  332  formed in accordance with an exemplary embodiment. The second frame  332  includes a plurality of frame members  450  each supporting different differential pairs of receptacle signal contacts  162 . The frame members  450  are separated by gaps  452 . Any number of frame members  450  may be provided. In the illustrated embodiment, three frame members  450  are used corresponding to three differential pairs of receptacle signal contacts  162  of the second frame  332 . 
     The frame members  450  extend between a mating end  454  of the second frame  332  and a mounting end  456  of the second frame  332 . In the illustrated embodiment, the mating end  454  is generally perpendicular with respect to the mounting end  456 , however other orientations are possible in alternative embodiments. The receptacle signal contacts  162  extend from the frame members  450  beyond the mating end  454  and beyond the mounting end  456  for electrical termination to other components, such as the second header assembly  118  and the second circuit board  150  (both shown in  FIG. 1 ). 
     The frame members  450  are connected by bridges  458  that span the gaps  452 . The bridges  458  position the frame members  450  with respect to one another. The bridges  458  are co-molded with the frame members  450 . 
     In an exemplary embodiment, the second frame  332  includes a leadframe, similar to the leadframe  410  (shown in  FIG. 7 ), where like components are identified by like reference numerals. The frame members  450  are overmolded over the receptacle signal contacts  162  defined by the leadframe. The receptacle signal contacts  162  are arranged in pairs. The mating portions  420  extend from the mating end  454  along an edge of the frame members  450  (e.g. a front edge), and the mounting portions  422  extend from the mounting end  456  along another edge of the frame members  450  (e.g. a side edge). 
     The frame members  450  include locating posts  480  extending therefrom. The locating posts  480  are configured to be received in corresponding openings in the conductive holder  310  (shown in  FIG. 5 ) to locate and/or secure the second frame  332  within the conductive holder  310 . In an exemplary embodiment, the bridges  458  near the mounting end  456  include locating channels  482  formed therethrough. The locating channels  482  receive tabs or other features of the conductive holder  310  to position and or secure the second frame  332  with respect to the conductive holder  310 . 
     In an exemplary embodiment, at least some of the frame members  450  include troughs  484 . The troughs  484  are recessed areas that are configured to receive portions of the first frame  330  (shown in  FIG. 6 ). Optionally, the troughs  484  may be generally aligned with the bridges  458 . Optionally, at least one frame coupling member  486  is located within each trough  484 . The frame coupling member  486  is configured to extend into the first frame  330  to position the first frame  330  with respect to the second frame  332 . Optionally, the frame coupling members  486  may also be used as locating posts, such as when the frame coupling members  486  are longer and are configured to extend into the conductive holder  310  in addition to extending through the coupling member  438  (shown in  FIG. 6 ) of the first frame  330 . 
     In an exemplary embodiment, the bridges  458  include coupling members  488  that interact with corresponding coupling members of the first frame  330  to secure the first frame  330  with respect to the second frame  332 . In the illustrated embodiment, the coupling members  488  constitute openings extending through the bridges  458 . The openings receive posts or other types of coupling members therein. Other types of coupling members  488  may be provided on the bridges  458 , such as post, slots, latches, or other types of fasteners. 
       FIG. 9  is a side perspective view of the frame assembly  320  showing the first frame  330  and the second frame  332  coupled together. The first and second frames  330 ,  332  are internested such that the frame members  400  of the first frame  330  are received in corresponding gaps  452  of the second frame  332  between frame members  450  of the second frame  332 . The first and second frames  330 ,  332  are interested such that the frame members  450  of the second frame  332  are received in corresponding gaps  402  of the first frame  330  between frame members  400  of the first frame  330 . The first and second frames  330 ,  332  are internested such that the frame members  400 ,  450  of the first and second frames  330 ,  332  are generally co-planar. The frame members  400 ,  450  are arranged in an alternating sequence (e.g. frame member  400 , frame member  450 , frame member  400 , frame member  450 ). Internesting the frame members  400 ,  450  positions the differential pairs of receptacle signal contacts  162  of the first frame  330  interspersed between corresponding differential pairs of receptacle signal contacts  162  of the second frame  332 , and vice versa. 
     When the first and second frames  330 ,  332  are coupled together, the bridges  408  span across and engage corresponding frame members  450  of the second frame  332 . For example, the bridges  408  are received in corresponding troughs  484 . Similarly, the bridges  458  (also shown in  FIG. 8 ) of the second frame  332  span across and engage corresponding frame members  400  of the first frame  330 . For example, the bridges  458  are received in corresponding troughs  434  in the frame members  400 . The coupling members  438  engage corresponding frame coupling members  486  to secure the first frame  330  with respect to the second frame  332 . 
     In an exemplary embodiment, the gaps  402 ,  452  are sufficiently wide to accommodate the corresponding frame members  450 ,  400 . For example, a width of the gaps  402  is wider than a width  490  of the frame members  450 . Similarly, a width of the gaps  452  is wider than a width  492  of the frame members  400 . In an exemplary embodiment, the widths,  490 ,  492  are dimensioned such that windows  494  are defined between the frame members  400 ,  450 . A width  496  of the windows  494  may vary depending on the widths of the gaps  402 ,  452  and the widths  490 ,  492  of the frame members  450 ,  400 . In an exemplary embodiment, the windows  494  are sized and shaped to receive the tabs  322 ,  324  (shown in  FIG. 5 ) of the conductive holder  310  (shown in  FIG. 5 ). Having the tabs  322 ,  324  in the windows  494  provides electrical shielding between each of the differential pairs of receptacle signal contacts  162 . 
     Having the first frame  330  manufactured separately from the second frame  332  allows adequate spacing between the receptacle signal contacts  162  for stamping and forming the mating portions  420  of the receptacle signal contacts  162 . For example, a dimension of material that is required to form the mating portions  420  may be greater than the desired spacing. In order to have the tight spacing between the receptacle signal contacts  162 , the two frames  330 ,  332  are separately manufactured and coupled together. 
       FIG. 10  illustrates portions of frame assemblies  320  illustrating the mating portions  420  of the receptacle signal contacts  162  extending from corresponding frame members  400 . In the illustrated embodiment, the mating portions  420  define a wish bone type of contact having twin beams configured to receive a header signal contact  120  (shown in  FIG. 2 ) therebetween. The mating portions  420  each have a primary beam  424  and a secondary beam  426  that is generally parallel to the primary beam  424  and spaced apart from the primary beam  424  across a gap  428 . The beams  424 ,  426  are deflectable during mating with the header signal contact  120 . The secondary beam  426  is folded over to oppose the primary beam  424 . The folded over portion has a generally U-shaped configuration. In an exemplary embodiment, the secondary beams  426  of the receptacle signal contacts  162  of each differential pair are folded over in respective opposite directions. For example, one of the secondary beams  426  of each differential pair is folded over in a clockwise direction (when viewed from the front) while the other secondary beam  426  of the differential pair is folded over in a counter-clockwise direction (when viewed from the front). 
       FIG. 11  illustrates a portion of the second receptacle assembly  152  showing a plurality of the contact modules  160  arranged in a stacked configuration. The contact module  160  at the near end is shown with the holder member  314  (shown in  FIG. 5 ) removed for clarity to illustrate the frame assembly  320 . The frame assembly  320  is loaded into the conductive holder  310  such that the tabs  322  extend into the windows  494  between the frame members  400 ,  450  and thus between the differential pairs of receptacle signal contact  162 . The locating posts  430 ,  480  serve to position the frame assembly  320  within the conductive holder  310 . 
       FIG. 12  is a side perspective view of the second ground shield  352  formed in accordance with an exemplary embodiment. The second ground shield  352  includes a main body  600  that is configured to be received within the conductive holder  310  (shown in  FIG. 5 ). The main body  600  includes a plurality of arms  602  separated by gaps  604 . The main body  600  extends between a mating end  606  and a mounting end  608 . The grounding beams  364 ,  366  extend from the main body  600  at the mating end  606 . The ground pins  368  are provided at the mounting end  608 . In the illustrated embodiment, the mating and mounting ends  606 ,  608  are oriented generally perpendicular to one another, however other orientations are possible in alternative embodiments. 
     The arms  602  extend between the grounding beams  364 ,  366 , and the ground pins  368 . The arms  602  are generally the portions of the second ground shield  352  housed within the conductive holder  310 , while the grounding beams  364 ,  366  and ground pins  368  are the portions of the second ground shield  352  extending exterior of the conductive holder  310 . The arms  602  are configured to extend along the frame members  400 ,  450  (shown in  FIG. 9 ) transitioning within the conductive holder  310 . Each arm  602  is sized and shaped to transition along the corresponding differential pair of receptacle signal contacts  162  (shown in  FIG. 5 ). The arms  602  are wide enough to cover both receptacle signal contacts  162  of the corresponding differential pair. 
     The arms  602  are connected by cross beams  610  that extend across the gaps  604 . The cross beams  610  hold the arms  602  in position relative to each other. The gaps  604  are sized and shaped to receive corresponding tabs  322  and/or  324  (shown in  FIG. 5 ) of the conductive holder  310 . 
     The arms  602  include openings  612  extending therethrough. The openings  612  are configured to receive locating posts  430 ,  480  (shown in  FIG. 9 ) extending from the frames  330 ,  332  (shown in  FIG. 9 ) to position the second ground shield  352  with respect to the frame assembly  320  (shown in  FIG. 9 ). The openings  612  may receive posts extending from the conductive holder  310  rather than the frames  330 ,  332 . Optionally, each arm  602  may include an opening  612  proximate to the grounding beams  364 ,  366  and another opening  612  proximate to the ground pins  368 . As such, the anus  602  are supported near the mating and mounting ends  306 ,  308  of the second ground shield  352 . 
     In an exemplary embodiment, the second ground shield  352  is stamped and formed. The arms  602  are defined by a stamping process where material is removed to form the gaps  604  between the arms  602 . The grounding beams  364  and/or  366  are bent and formed to define spring beams that are configured to engage the header ground shields  122  (shown in  FIG. 1 ). The ground pins  368  are stamped and may be bent to a certain position for coupling with the second circuit board  150  (shown in  FIG. 1 ). 
     In an exemplary embodiment, the ground shield  352  includes a jogged section  614  at the mounting end  608 . The jogged section  614  transitions between a mounting edge  616  and the main body  600 . The jogged section  614  transitions out of plane with respect to a ground shield plane defined by the main body  600 . For example, the ground shield  352  is bent at a bend line  618  out of the ground shield plane to define the jogged section  614 . The jogged section  614  may have a curved transition or may be an angular transition at the bend line  618 . The jogged section  614  transitions the mounting edge  616 , and thus the ground pins  368  that extend from the mounting edge  616 , out of the ground shield plane. In an exemplary embodiment, the jogged section  614  transitions in such a way that the ground pins  368  are parallel to the ground shield plane, but are non-coplanar with the ground shield plane. The transition is used to position the ground pins  368  for mounting to the circuit board  150  (shown in  FIG. 1 ). For example, the ground pins  368  may need to be spaced at a certain distance from the mounting portions  422  (shown in  FIG. 7 ) of the receptacle signal contacts  162 . 
     Having the ground pins  368  offset from the main body  600  may cause damage to the ground pins  368  during mounting to the circuit board  150 . For example, forces exerted on the ground pins  368  may cause the ground pins  368  to buckle and/or shear due to being offset from the main body  600 . In an exemplary embodiment, features are provided to mitigate the buckling forces on the ground pins  368 . For example, in an exemplary embodiment, the ground shield  352  includes bearing surfaces  620  proximate to the ground pins  368 . The bearing surfaces  620  are provided at the mounting end  608 . The bearing surface  620  serve to transfer the forces imparted on the ground pins  368  during mounting to the second circuit board  150  from the second ground shield  352  to the conductive holder  310  and/or the frame assembly  320 . Having the bearing surfaces  620  close to the ground pins  368  mitigates buckling of the ground pins  368 . 
       FIG. 13  is a side perspective view of the first ground shield  350  formed in accordance with an exemplary embodiment. The first ground shield  350  includes a main body  630  that is configured to be received within the conductive holder  310  (shown in  FIG. 5 ). The main body  630  includes a plurality of arms  632  separated by gaps  634 . The main body  630  extends between a mating end  636  and a mounting end  638 . The grounding beams  354 ,  356  extend from the main body  630  at the mating end  636 . The ground pins  358  are provided at the mounting end  638 . In the illustrated embodiment, the mating and mounting ends  636 ,  638  are oriented generally perpendicular to one another, however other orientations are possible in alternative embodiments. 
     The arms  632  extend between the grounding beams  354 ,  356 , and the ground pins  358 . The arms  632  are generally the portions of the first ground shield  350  housed within the conductive holder  310 , while the grounding beams  354 ,  356  and ground pins  358  are the portions of the first ground shield  350  extending exterior of the conductive holder  310 . The arms  632  are configured to extend along the frame members  400 ,  450  (shown in  FIG. 9 ) transitioning within the conductive holder  310 . Each arm  632  is sized and shaped to transition along the corresponding differential pair of receptacle signal contacts  162  (shown in  FIG. 5 ). The arms  632  are wide enough to cover both receptacle signal contacts  162  of the corresponding differential pair. 
     The arms  632  are connected by cross beams  640  that extend across the gaps  634 . The cross beams  640  hold the arms  632  in position relative to each other. The gaps  634  are sized and shaped to receive corresponding tabs  322  and/or  324  (shown in  FIG. 5 ) of the conductive holder  310 . Optionally, the cross beams  640  may be offset with respect to the cross beams  610  (shown in  FIG. 12 ) when the contact module  160  is assembled, such as to improve crosstalk. 
     The arms  632  include openings  642  extending therethrough. The openings  642  are configured to receive locating posts  430 ,  480  (shown in  FIG. 9 ) extending from the frames  330 ,  332  (shown in  FIG. 9 ) to position the first ground shield  350  with respect to the frame assembly  320  (shown in  FIG. 9 ). The openings  642  may receive posts extending from the conductive holder  310  rather than the frames  330 ,  332 . Optionally, each arm  632  may include an opening  642  proximate to the grounding beams  354 ,  356  and another opening  642  proximate to the ground pins  358 . As such, the arms  632  are supported near the mating and mounting ends  636 ,  638  of the first ground shield  350 . 
     In an exemplary embodiment, the first ground shield  350  is stamped and formed. The arms  632  are defined by a stamping process where material is removed to form the gaps  634  between the arms  632 . The grounding beams  354  and/or  356  are bent and formed to define spring beams that are configured to engage the header ground shields  122  (shown in  FIG. 1 ). The ground pins  358  are stamped and may be bent to a position for coupling with the second circuit board  150  (shown in  FIG. 1 ). 
     In an exemplary embodiment, the first ground shield  350  includes bearing surfaces  644  proximate to the ground pins  358 . The bearing surfaces  644  are provided at the mounting end  638 . The bearing surfaces  644  serve to transfer the forces imparted on the ground pins  358  during mounting to the circuit board  150  from the first ground shield  350  to the conductive holder  310  and/or the frame assembly  320 . In the illustrated embodiment, the bearing surfaces  644  are defined by the openings  642 . 
       FIG. 14  is a side perspective view of a portion of the second receptacle assembly  152  with the second holder member  314  (shown in  FIG. 5 ) of the near end contact module  160  removed to illustrated the frame assembly  320  and the second ground shield  352 . When assembled, the first ground shield  350  is loaded into the first holder member  312  and abuts against an interior wall surface  650  of the first holder member  312 . The frame assembly  320  is positioned within the conductive holder  310  against the first ground shield  350 . The second ground shield  352  is coupled to the frame assembly  320 . The locating posts  430 ,  480  are received in the openings  612  to secure the second ground shield  352  to the frame assembly  320 . The bearing surfaces  620  defined by the openings  612  bear against the locating posts  430 ,  480  to transfer forces between the second ground shield  352  and the frame assembly  320 . The second holder member  314  (not shown) may be coupled to the first holder member  312  over the frame assembly  320  and the second ground shield  352 . Other assembly methods are possible in alternative embodiments. 
     An organizer  652  is provided at the mounting end. The organizer  652  includes openings  654  that receive the ground pins  358 ,  368 . The organizer  652  holds the true positions of the ground pins  358 ,  368  for mounting to the second circuit board  150  (shown in  FIG. 1 ). The organizer  652  may be pressed onto the ground pins  358  during mounting of the second receptacle assembly  152  to the second circuit board  150 . 
       FIG. 15  is a front perspective view of a portion of one of the contact modules  160 . The mating portions  420  of the receptacle signal contacts  162  extend forward from a mating end  822  of the conductive holder  310 . The grounding beams  354 ,  356 ,  364 ,  366  extend forward from the mating end  822  of the conductive holder  310  along the mating portions  420  of the receptacle signal contacts  162 . In an exemplary embodiment, the grounding beams  354 ,  356 ,  364 ,  366  are arranged in beam sets  824 . Each beam set  824  surrounds a different differential pair of receptacle signal contacts  162 . In an exemplary embodiment, each beam set  824  surrounds the differential pair of receptacle signal contacts on four sides thereof. 
     The receptacle signal contacts  162  of each pair are arranged in a single column with the other receptacle signal contacts  162  of the other differential pairs of the contact module  160 . For example, all of the receptacle signal contacts  162  of the contact module  160  are aligned along a column axis  826 . The in-column grounding beams  356 ,  366  are also arranged in column with the receptacle signal contacts  162  along the column axis  826 . The in-column grounding beams  356 ,  366  provide shielding between adjacent differential pairs of receptacle signal contacts  162  that are held in the same contact module  160 . In an exemplary embodiment, because each differential pair of receptacle signal contacts  162  includes grounding beams on all four sides, two grounding beams  356 ,  366  (of different beam sets  824 ) are provided between each differential pair of receptacle signal contacts  162 . For example, the in-column grounding beam  366  of one beam set  824  and the in-column grounding beam  356  of another beam set  824  are both positioned between adjacent differential pairs of the receptacle signal contacts  162 . Such in column grounding beams  356 ,  366  of the different beam sets  824  are configured to engage different header ground shields  122  (shown in  FIG. 1 ). 
     The flanking grounding beams  354 ,  364  are offset with respect to the receptacle signal contacts  162  and the column axis  826 . The flanking grounding beams  354 ,  364  flank the corresponding differential pairs of receptacle signal contacts  162  on opposite sides thereof. Row axes  828  extend through each of the receptacle signal contacts  162  perpendicular to the column axis  826 . For each differential pair of receptacle signal contacts  162 , each of the flanking ground beams  354 ,  364  of the corresponding beam set  824  is aligned with the row axis  828  of a corresponding one of the receptacle signal contacts  162 , at least along a portion of the length of such receptacle signal contact  162 . The flanking grounding beams  354 ,  364  are sufficiently wide to provide electrical shielding along both receptacle signal contacts  162  of the corresponding differential pair. 
     The flanking grounding beam  354  includes a base portion  830  proximal the mating end  822  of the conductive holder  310 . The flanking grounding beam  354  includes a tail portion  832  distal of the mating end  822  of the conductive holder  310 . The base portion  830  has a base width  834  extending between a first side edge  836  and a second side edge  838  of the base portion  830 . The tail portion  832  is narrower than the base portion  830 . Optionally the tail portion  832  may taper to a tip  839 . The tip  839  generally defines a mating interface for the flanking grounding beam  354 . In an exemplary embodiment, the tail portion  832  is offset toward the second side edge  838  rather than being centered between the first and second side edges  836 ,  838 . Having the tail portion  832  offset allows the tail portion  832  to be aligned with one of the receptacle signal contacts  162  of the corresponding differential pair and to be non-aligned with the other receptacle signal contact  162  of such differential pair. The tail portion  832  is aligned with the row axis  828  of the corresponding receptacle signal contact  162 . 
     The flanking grounding beam  364  includes a base portion  840  proximal to the mating end  822  of the conductive holder  310 . The flanking grounding beam  364  includes a tail portion  842  distal of the mating end  822  of the conductive holder  310 . The base portion  840  has a base width extending between a first side edge and a second side edge of the base portion  840 , similar to the flanking grounding beam  354 . The tail portion  842  is narrower than the base portion  840 . Optionally the tail portion  842  may taper to a tip  849 . The tip  849  generally defines a mating interface for the flanking grounding beam  364 . In an exemplary embodiment, the tail portion  842  is offset toward the first side edge rather than being centered between the first and second side edges. The tail portion  842  is offset with respect to the tail portion  832  of the flanking grounding beam  364  such that the tail portion  842  extends along one of the receptacle signal contacts  162  while the tail portion  832  of the flanking ground beam  354  extends along the other receptacle signal contact  162  of the differential pair. The tail portion  842  is aligned with the row axis  828  of the corresponding receptacle signal contact  162 . 
     The in-column grounding beam  356  includes a base portion  850  proximal the mating end  822  of the conductive  310 . The in-column grounding beam  356  includes a tail portion  852  distal of the mating end  822  of the conductive holder  310 . The base portion  850  has a base width extending between a first side edge and a second side edge of the base portion  850 . The tail portion  852  is narrower than the base portion  850 . Optionally the tail portion  852  may taper to a tip  859 . The tip  859  generally defines a mating interface for the in-column grounding beam  356 . The tail portion  852  is aligned in-column with the receptacle signal contacts  162 . 
     The in-column grounding beam  366  includes a base portion  860  proximal the mating end  822  of the conductive  310 . The in-column grounding beam  366  includes a tail portion  862  distal of the mating end  822  of the conductive holder  310 . The base portion  860  has a base width  864  extending between a first side edge  866  and a second side edge  868  of the base portion  860 , similar to the in-column grounding beam  356 . The tail portion  862  is narrower than the base portion  860 . Optionally the tail portion  862  may taper to a tip  869 . The tip  869  generally defines a mating interface for the in-column grounding beam  366 . The tail portion  862  is aligned in-column with the receptacle signal contacts  162 . 
     The wider base portions,  830 ,  840 ,  850 ,  860  provide electrical shielding around all sides of the differential pairs of receptacle signal contacts near the mating end  822  of the conductive holder  310 . When the header ground shields  122  are not fully mated, and thus are spaced apart from the mating end  822 , the base portions,  830 ,  840 ,  850 ,  860  provide full shielding on all four sides of the receptacle signal contacts  162 . The narrower tail portions  832 ,  842 ,  852 ,  862  provide mechanical spring characteristics for the grounding beams  354 ,  356 ,  364 ,  366 . The size and shapes of the grounding beams  354 ,  356 ,  364 ,  366  are designed to balance the electrical shielding characteristics with the mechanical spring characteristics. 
       FIG. 16  is a front view of a portion of the second receptacle assembly  152  showing a plurality of contact modules  160  arranged in a stacked configuration. The beam sets  824  are illustrated surrounding all four sides of the corresponding differential pairs of receptacle signal contacts  162 . A header ground shield  122  is shown in phantom in  FIG. 16  to illustrate the position of the header ground shields  122  with respect to the beam sets  824  and the receptacle signal contacts  162 . The header ground shields  122  are C-shaped and extend along three sides of the differential pair of receptacle signal contacts  162 . 
     The in-column grounding beam  356  engages an interior side of the side wall  180  of the header ground shield  122 . The in-column grounding beam  366  engages the interior side of the sidewall  176  of the header ground shield  122 . The flanking grounding beam  364  engages an interior side  870  of the center wall  178  of the header ground shield  122 . The flanking grounding beam  354  of an adjacent beam set  824  engages an exterior side  872  of the center wall  178  of the header ground shield  122 . As such, three of the grounding beams  356 ,  364 ,  366  engage a common header ground shield  122  while the other grounding beam  354  engages a different header ground shield  122 . As such, each beam set  824  is configured to engage two different header ground shields  122 . Having the flanking grounding beams  354 ,  364  allows the first ground shield  350  of one contact module  160  to be electrically commoned with the second ground shield  352  of the adjacent contact module  160 . It also allows the header ground shields  122  to be electrically commoned to ground shields  350 ,  352  of different contact modules  160 . The ground energy is referenced to both contact modules  160 . Well referenced return paths are thus provided by the beam sets  824 . The electrical performance of the second receptacle assembly  152  is enhanced by having the beam sets  824  electrically connected to more than one header ground shield  122 . 
     In an exemplary embodiment, the offset of the tail portions  832 ,  842  of the adjacent flanking grounding beams  354 ,  364  (in different beam sets  824 ) allows interesting of such grounding beams  354 ,  364 , such as when the grounding beams  354 ,  364  are in an undeflected state. The grounding beams  354 ,  364  are staggered to fit in the limited space between the contact modules  160 .  FIG. 16  also illustrates that the flanking ground beams  354  of different beam sets  824  are aligned along a common row axis  828  while the flanking grounding beams  364  of different beam sets  824  are aligned with a different row axis  828 . 
     The receptacle signal contacts  162  have a transverse width  874  measured in a transverse direction, which is parallel to the row axes  828 . The transverse width  874  is measured from an outside edge  876  of the receptacle signal contacts  162  to an opposite outside edge  878  of the receptacle signal contacts  162 . Base widths  854 ,  864  of the base portions  850 ,  860 , respectively, are approximately equal to the transverse widths  874  of the receptacle signal contacts  162 . The base widths  854 ,  864  may be slightly greater than the transverse width  874  or slightly narrower than the transverse width  874 . The base widths  854 ,  864  are wide enough to cover the majority of the transverse width  874  of the receptacle signal contacts  162 . 
       FIG. 17  is a side view of a portion of one of the contact modules  160 . A pair of the receptacle signal contacts  162  is shown with the corresponding beam set  824  surrounding four sides of the pair of receptacle signal contacts  162 . The receptacle signal contacts  162  have a lateral width  880  measured in a lateral direction, which is parallel to the column axis  826 . The lateral width  880  is measured from an outside edge  882  of one of the receptacle signal contacts  162  to an opposite edge  884  of the other receptacle signal contact  162  of the pair. The base width  834  of the base portion  830  is approximately equal to the lateral width  880 . The base width  834  may be slightly greater than the lateral width  880  or slightly narrower than the lateral width  880 . The base width  834  is wide enough to cover the majority of both of the receptacle signal contacts  162 . 
     The mating portions  420  (shown in  FIGS. 6 and 7 ) of the receptacle signal contacts  162  have longitudinal lengths  886  measured from the mating end  822  of the conductive holder  310  to the distal ends of the receptacle signal contacts  162 . The longitudinal lengths  886  are measured longitudinally along the receptacle signal contacts  162 . The flanking grounding beam  354  has a beam length  888  measured from the mating end  822  of the conductive holder  310  to the tip  839 . The base portion  830  has a base portion length  890  and the tail portion  832  has a tail portion length  892 . Optionally, the base portion length  890  may be at least half of the beam length  888 . The flanking grounding beam  364  has similar dimensions as the flanking grounding beam  354 . 
     The in-column grounding beams  356 ,  366  have beam lengths  894  measured from the mating end  822  of the conductive holder  310  to the tips  859 ,  869 . The base portions  850 ,  860  have base portion lengths  896  and the tail portions  852 ,  862  have tail portion lengths  898 . Optionally, the base portion lengths  896  may be at least half of the beam lengths  894 . 
       FIG. 18  illustrates a portion of the first ground shield  350 . The first ground shield  350  includes a locating tab  900 . In the illustrated embodiment, the locating tab  900  extends from a portion of the first ground shield  350  interior of the grounding beam  356 . The locating tab  900  is configured to be positioned interior of the conductive holder  310  (shown in  FIG. 5 ). The locating tab  900  is used to position the first ground shield  350  within the conductive holder  310 . 
     The first ground shield  350  includes a shunt tab  902 . The shunt tab  902  is configured to be spring biased against the conductive holder  310  to ensure an electrical connection is made between the first ground shield  350  and the conductive holder  310 . The shunt tab  902  may be deflectable. 
       FIG. 19  illustrates a portion of the contact module  160  with the first holder member  312  (shown in  FIG. 5 ) removed to illustrate the frame assembly  320  and the ground shields  350 ,  352 . The second ground shield  352 , similar to the first ground shield  350 , includes a locating tab  900  and a shunt tab  902 . The conductive holder  310  includes recesses that receive the locating tabs  900  and shunt tabs  902  of the first and second ground shields  350 ,  352 . The shunt tabs  902  are biased against surfaces of the conductive holder  310  to ensure an electrical connection between the ground shields  350 ,  352  and the conductive holder  310 . The shunt tabs  902  are located near the mating end  822  of the conductive holder  310  to electrically connect the ground shields  350 ,  352  to the conductive holder  310  proximate to the mating end  822 . As such, the ground energy from the header ground shield  122  (shown in  FIG. 1 ) is transferred to the conductive holder  310  proximate to the grounding beams  356 ,  366 . 
       FIG. 20  is a cross-sectional view of the contact module  160 . The locating tabs  900  of the first and second ground shields  350 ,  352  are shown received in corresponding locating slots  904  in the conductive holder  310 . The locating tabs  900  are used to locate the ground shields  350 ,  352  with respect to the conductive holder  310 , and thus, the frame assembly  320 . 
     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, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.