Patent Publication Number: US-9413112-B2

Title: Electrical connector having contact modules

Description:
BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to electrical connectors that have contact modules. 
     Some electrical systems utilize an electrical connector, such as a receptacle or header connector, to interconnect a circuit board and at least one pluggable module. The electrical connector is mounted to the circuit board. For example, the electrical connector includes electrical terminals with tails that terminate to conductive vias on the circuit board. The circuit board has signal traces routed from the conductive vias. An opposite end of the electrical terminals may extend into a mating interface of the electrical connector for electrical connection to a circuit card or electrical contacts of a corresponding pluggable module mated to the electrical connector. A conductive signal pathway is formed that includes the circuit card or an electrical contact of the pluggable module, the electrical terminal of the electrical connector that engages the circuit card or electrical contact, and the signal trace routed from the conductive via that engages the electrical terminal. 
     Due to size constraints of electrical connectors, increasing density of electrical terminals in electrical connectors, and the desire for smaller connector footprints, the signal traces on the circuit board are routed away from the footprint of the electrical connector in close proximity to one another and often in multiple layers of the circuit board. As the density of electrical terminals in the electrical connector increases, there is less space between corresponding vias of the circuit board to route the signal traces away from the connector footprint. Signal trace routing is further complicated when the electrical terminal tails at the connector footprint are arranged in various groupings or arrays that do not provide designated routes for signal traces between the corresponding vias that engage the electrical terminal tails. One known way to accommodate additional electrical terminal tails is to increase the number of layers of the circuit board used to route the signal traces away from the connector footprint. However, thick circuit boards are undesirable and more expensive to manufacture than thinner boards having fewer layers. 
     A need remains for an electrical connector that facilitates routing of signal traces in a circuit board on which the connector is mounted. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, an electrical connector is provided that includes a housing having a mounting face and a mating face, a plurality of contact modules held by the housing, and a plurality of ground plates also held by the housing. Each contact module includes a left signal wafer and a right signal wafer stacked next to each other along a stack axis. Each of the signal wafers extends parallel to a contact module plane. The signal wafers include electrical terminals held by a dielectric body. The electrical terminals have mounting contacts protruding from the dielectric body at the mounting face of the housing. The electrical terminals of at least one of the signal wafers in each contact module are jogged toward the other signal wafer in the contact module. The mounting contacts of each contact module align in a column that extends parallel to the contact module plane. Each of the ground plates extends parallel to the contact module plane and is disposed along an outer side of a corresponding contact module. 
     In another embodiment, an electrical connector is provided that includes a housing, a plurality of contact modules, a plurality of ground plates, and a plurality of ground cross connects. The housing has a mounting face and a mating face. The contact modules and the ground plates are held by the housing. The ground cross connects are at the mounting face of the housing. Each contact module includes a left signal wafer and a right signal wafer stacked next to each other along a stack axis. Each of the signal wafers extends parallel to a contact module plane. The signal wafers include electrical terminals held by a dielectric body. The electrical terminals have mounting contacts protruding from the dielectric body at the mounting face of the housing. Each of the ground plates extends parallel to the contact module plane and is disposed along an outer side of a corresponding contact module. The mounting contacts and the ground contacts are arranged in an array at the mounting face of the housing. The array includes plural columns extending parallel to the contact module plane. Each column has a ground contact disposed between mounting contacts to provide shielding therebetween. Adjacent columns in the array are separated by a column void. Each ground cross connect extends across at least one contact module and electrically and mechanically engages corresponding ground plates at opposite sides of the at least one contact module. The ground cross connects each have at least one ground contact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an electrical system in accordance with an exemplary embodiment. 
         FIG. 2  is a perspective view of a module stack of an electrical connector according to an exemplary embodiment. 
         FIG. 3  is a front exploded view of a contact module of the electrical connector according to an embodiment. 
         FIG. 4  is a front assembled view of the contact module of  FIG. 3 . 
         FIG. 5  is a bottom perspective view of a portion of the module stack of  FIG. 2  according to an exemplary embodiment. 
         FIG. 6  illustrates a footprint of the electrical connector in accordance with an exemplary embodiment. 
         FIG. 7  illustrates a circuit board showing a footprint of signal vias and ground vias that corresponds to the layout of the contacts of the electrical connector. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments set forth herein include electrical connectors that mount to circuit boards. The electrical connectors provide spaces for signal trace routes along the circuit boards away from the footprints of the electrical connectors. The electrical connectors described herein reduce the need to add additional layers to and/or increase the area of the circuit boards upon which the electrical connectors are mounted. 
       FIG. 1  is a perspective view of an electrical system  100  in accordance with an exemplary embodiment. The electrical system  100  includes an electrical connector  102  that is mounted on a host circuit board  104 . The electrical system  100  further includes pluggable modules  106  that are configured to mate with the electrical connector  102  to electrically connect the pluggable modules  106  to the electrical connector  102 . Signals are transmitted between the pluggable modules  106  and the circuit board  104  through the electrical connector  102 . Two pluggable modules  106  are shown in  FIG. 1 , although the electrical connector  102  may be configured to engage more or less than two pluggable modules in alternative embodiments. The electrical system  100  is oriented with respect to a longitudinal axis  191 , an elevation axis  192 , and a lateral axis  193 . The axes  191 - 193  are mutually perpendicular. Although the elevation axis  192  appears to extend in a vertical direction parallel to gravity in  FIG. 1 , it is understood that the axes  191 - 193  are not required to have any particular orientation with respect to gravity. 
     The electrical connector  102  has a connector housing  108 . A plurality of contact modules  204  (shown in  FIG. 2 ) and ground plates  206  ( FIG. 2 ) are held by the housing  108 . The contact modules  204  and/or the ground plates  206  are held at least partially within the housing  108 . The housing  108  has a mating face  110  and a mounting face  111 . The mating face  110  is configured to engage the pluggable modules  106 . The mounting face  111  is configured to engage the circuit board  104 . The mating face  110  includes a front wall  112  and at least one mating interface  114  extending forward from the front wall  112  along the longitudinal axis  191 . In the illustrated embodiment, the mating face  110  includes first and second mating interfaces  114 A,  114 B, respectively. The first mating interface  114 A is stacked over the second mating interface  114 B along the elevation axis  192  such that the second mating interface  114 B is positioned between the first mating interface  114 A and the circuit board  104 . The electrical connector  102  may include other than two mating interfaces  114  and/or different relative arrangements of mating interfaces  114  in other embodiments. 
     The front wall  112  of the housing  108  is joined to other walls to define a module cavity (not shown) that receives the contact modules  204  (shown in  FIG. 2 ) and ground plates  206  ( FIG. 2 ). For example, the housing  108  has a top wall  116 , opposing side walls  118 , and a back wall (not shown) that is opposite the front wall  112 . As used herein, relative or spatial terms such as “top,” “bottom,” “upper,” “lower,” “left,” and “right” are only used to distinguish the referenced elements and do not necessarily require particular positions or orientations in the electrical system  100  or in the surrounding environment of the electrical system  100 . The mounting face  111  of the housing  108  may be at least partially open to allow the contact modules  204  and ground plates  206  protrude from the module cavity to mount and electrically connect to the circuit board  104 . 
     The circuit board  104  may be a daughter card or a mother board in the electrical system  100 . The circuit board  104  may include multiple insulating layers and conductive layers stacked on each other. The circuit board  104  includes conductive elements, such as pads and/or vias, arranged in an array at a top surface  144  of the circuit board  104 . The conductive elements may be positioned to align with mounting contacts of the electrical connector  102  at the mounting face  111 , such that the conductive elements engage the contacts when the electrical connector  102  is mounted to the circuit board  104 . Conductive traces  146  extend from each of the conductive elements away from the footprint of the electrical connector  102 . The footprint is defined by the layout of contacts at the mounting face  111  of the housing  108 . The conductive traces  146  may be disposed on different conductive layers of the circuit board  104 . In an exemplary embodiment, the footprint of the electrical connector  102  defines column voids that provide corresponding spaces on the circuit board  104  for routing traces to/from the contacts at the mounting face  111 . The circuit board  104  may thus be thinner or use fewer layers for routing the traces  146  from the electrical connector  102 . Any additional layers of the circuit board  104  not used for routing traces  146  from the electrical connector  102  may be used to route other traces for other electrical components mounted to the circuit board  104 . 
     The pluggable modules  106  optionally may be input/output (I/O) transceivers configured to transmit data signals in the form of electrical signals and/or optical signals. Each pluggable module  106  has a shell  130  and is connected to a cable  132 . The shell  130  houses and at least partially surrounds an internal circuit board  126 . In an embodiment, the cable  132  may be directly attached to the internal circuit board  126  within the shell  130 . In an alternative embodiment, the pluggable module  106  may have a receptacle (not shown) that receives a plug connector (not shown) at an end of the cable  132  to allow for selective mating between different modules and cables. An edge  128  of the internal circuit board  126  is disposed within a socket  140  of the shell  130 . The socket  140  is configured to receive therein a corresponding mating interface  114  of the electrical connector  102  when the pluggable module  106  mates to the electrical connector  102 . To mate with the electrical connector  102 , the pluggable module  106  is advanced along the longitudinal axis  191  in a mating direction  142  towards the mating interface  114 . 
     The at least one mating interface  114  of the electrical connector  102  includes a port or opening  120  at a front end  123 . The port  120  is open to a mating cavity  122  within the mating interface  114 . A plurality of mating contacts  124  of the contact modules  204  (shown in  FIG. 2 ) and the ground plates  206  ( FIG. 2 ) are disposed within the mating cavity  122 . The mating contacts  124  may be contact beams that are configured to electrically connect to the internal circuit board  126  of a corresponding mating pluggable module  106 . The port  120  is sized and shaped to receive the internal circuit board  126  therethrough. For example, the edge  128  of the internal circuit board  126  is loaded through the port  120  of the mating interface  114  when the pluggable module  106  mates with the mating interface  114 . The edge  128  of the internal circuit board  126  is received within the mating cavity  122 , where conductors on the circuit board  126  electrically connect to the mating contacts  124  of the electrical connector  102 . 
       FIG. 2  is a perspective view of a module stack  202  of the electrical connector  102  (shown in  FIG. 1 ) in accordance with an embodiment. The module stack  202  includes the components of the electrical connector  102  within the connector housing  108  (shown in  FIG. 1 ). The module stack  202  includes a plurality of contact modules  204  and ground plates  206  stacked side-by-side along a stack axis  208 . For example, in the illustrated embodiment the contact modules  204  and ground plates  206  are arranged in an alternating sequence such that adjacent contact modules  204  are separated by a ground plate  206 . Likewise, adjacent ground plates  206  are separated by a contact module  204 . The contact modules  204  have a left outer side  212  and a right outer side  214 . Each ground plate  206  is disposed along the left outer side  212  or the right outer side  214  of a corresponding contact module  204 . The ground plates  206  may abut the outer sides  212 ,  214  of the contact modules  204 . 
     Each contact module  204  extends along a contact module plane  210 . The contact module planes  210  of the contact modules  204  may be parallel to each other. The contact module planes  210  may be perpendicular to the stack axis  208 . Each contact module  204  includes a left signal wafer  216  and a right signal wafer  218  stacked next to each other along the stack axis  208 . The signal wafers  216 ,  218  each extend parallel to the contact module plane  210 . The left and right signal wafers  216 ,  218  abut each other at an interface or seam  224 . In an embodiment, at least part of the interface  224  defines the contact module plane  210 . 
     The left and right signal wafers  216 ,  218  each include electrical terminals  220  held by a dielectric body  222 . For example, the electrical terminals  220  may be over-molded with a dielectric material to form the signal wafers  216 ,  218 . In  FIG. 2 , the electrical terminals  220  of the left signal wafer  216  are shown in phantom. Each signal wafer  216 ,  218  includes four electrical terminals  220 . In alternative embodiments, the signal wafers  216 ,  218  may include more or less than four electrical terminals  220 . The electrical terminals  220  have mounting contacts  226  protruding from the dielectric body  222  at a mounting edge  228  of the dielectric body  222 . The mounting contacts  226  are configured to be electrically terminated to the host circuit board  104  (shown in  FIG. 1 ). For example, the mounting contacts  226  may extend downward (for example, towards the circuit board  104 ) from the mounting edge  228 . In an exemplary embodiment, the mounting contacts  226  are pin contacts, such as compliant eye-of-the-needle-type contacts. Pin contacts facilitate press-fit termination of the electrical connector  102  (shown in  FIG. 1 ) to the host circuit board  104  via thru-hole mounting. The mounting contacts  226  may be terminated to the circuit board  104  by other methods in alternative embodiments, such as via soldering to contact pads on the circuit board  104 . 
     In an exemplary embodiment, all of the mounting contacts  226  of the left and right signal wafers  216 ,  218  of each contact module  204  align in a column  230 . The column  230  extends parallel to the contact module plane  210 , and optionally is co-planar with the contact module plane  210 . The column  230  of one contact module  204  is separated from an adjacent column  230  of an adjacent contact module  204  by a column void  232 . The column void  232  extends the length of the module stack  202  along the longitudinal axis  191 . The column void  232  is devoid of electrical contacts. When the electrical connector  102  (shown in  FIG. 2 ) is mounted to the circuit board  104  ( FIG. 1 ), the column voids  232  between columns  230  of mounting contacts  226  provide spaces on the circuit board  104  for routing signal traces  146  ( FIG. 1 ) away from the footprint of the electrical connector  102 , as described further herein. 
     The electrical terminals  220  of the left and right signal wafers  216 ,  218  further include the mating contacts  124 . The mating contacts  124  protrude from the dielectric body  222  at a mating edge  234  of the dielectric body  222 . For example, the mating contacts  124  extend forward from the corresponding dielectric bodies  222  along the longitudinal axis  191 . The mating contacts  124  are configured to electrically and mechanically engage contact pads  138  of the internal circuit board  126  of a corresponding pluggable module  106 . The mating contacts  124  of each wafer  216 ,  218  may be oriented in a column  236  that extends along the elevation axis  192 . Each wafer  216 ,  218  in  FIG. 2  includes four mating contacts  124 , with one mating contact  124  extending from each of the four electrical terminals  220 . The mating contacts  124  of the contact modules  204  align in rows  238  parallel to the stack axis  208 . For example, the mating contacts  124  of each signal wafer  216 ,  218  may align in multiple different rows  238 . In an embodiment, each mating interface  114  (shown in  FIG. 1 ) of the housing  108  ( FIG. 1 ) houses two rows  238  of mating contacts  124 . One row  238  defines an upper row that is configured to engage a top surface of the corresponding internal circuit board  126  of the mating pluggable module  106  ( FIG. 1 ), and the other row  238  defines a lower row that engages a bottom surface of the internal circuit board  126 . 
     In an embodiment, the mating contacts  124  include an elongated arm  240  and a mating tip  242 . The arm  240  extends from the mating edge  234  of the dielectric body  222  to the mating tip  242 . The mating tip  242  is configured to mechanically and electrically engage a corresponding contact pad  138  on the internal circuit board  126  of one of the pluggable modules  106  (shown in  FIG. 1 ). The arm  240  may be configured to deflect as the mating tip  242  engages the contact pad  138  to provide a biasing force that retains the mechanical connection between the mating tip  242  and the contact pad  138 . In an embodiment, adjacent mating contacts  124  (in the same row) of the left and right signal wafers  216 ,  218  in each contact module  204  are arranged as differential pairs  244  that transmit differential signals. For example, the mating contact  124  of the left signal wafer  216  may be a positive contact, and the mating contact  124  of the right signal wafer  218  in the differential pair  244  may be a negative contact, or vice-versa. In an embodiment, each differential pair  244  is further arranged as adjacent mounting contacts  226  in the same column  230 . As such, each differential pair  244  is formed of one electrical terminal  220  of the left signal wafer  216  and one electrical terminal  220  of the right signal wafer  218  in one contact module  204 . At the mating edges  234 , the mating contacts  124  of one differential pair  244  are aligned side-by-side along the stack axis  208 , but at the mounting edges  228 , the mounting contacts  226  of the same differential pair  244  are aligned front-to-back parallel to the contact module plane  210 . 
     The ground plates  206  extend parallel to the contact module planes  210 . The ground plates  206  are formed of a thin conductive material that is not over-molded or otherwise encapsulated with a dielectric material. The ground plates  206  each include ground mating contacts  246  that align laterally with the mating contacts  124  of the contact modules  204  in the rows  238 . For example, each ground plate  206  may include four ground mating contacts  246  that each align in a different one of the rows  238 . For the ground plates  206  disposed between two contact modules  204  (for example, located away from the edges of the module stack  202 ), each ground mating contact  246  is disposed between two mating contacts  124 . The ground mating contacts  246  provide shielding between the mating contacts  124  of the adjacent contact modules  204 , to reduce crosstalk that degrades electrical performance. 
     The module stack  202  may include ground tie bars  248  that extend across a width of the module stack  202  along the stack axis  208  and provide shielding and/or a reference ground plane between the electrical terminals  220  of each signal wafer  216 ,  218 . The ground tie bars  248  extend through slots (not shown) in the contact modules  204  and the ground plates  206 . The slots in the ground plates  206  may be sized and shaped such that the ground plates  206  mechanically and electrically connect to the ground tie bars  248  to electrically common the plural ground plates  206  in the module stack  202 . The module stack  202  optionally may include mating ground tie bars  249  that extend across the width of the module stack  202  and engage the ground mating contacts  246 . The mating ground tie bars  249  electrically common the ground mating contacts  246  of a corresponding row  238  external of the dielectric bodies  222 . The ground mating contacts  246  optionally may have retention fingers  251  that engage the mating ground tie bars  249  and secure the ground tie bars  249  in place. 
     In an exemplary embodiment, the module stack  202  includes ground cross connects  250 . The ground cross connects  250  are disposed at the mounting edges  228  of the signal wafers  216 ,  218  at or near the mounting face  111  (shown in  FIG. 1 ) of the housing  108  ( FIG. 1 ). Each ground cross connect  250  extends across at least one contact module  204  transverse to the contact module plane  210 . The ground cross connect  250  is configured to mechanically and electrically engage the corresponding ground plates  206  at opposite sides of the at least one contact module  204 . Like the ground tie bars  248 , the ground cross connects  250  provide shielding between electrical terminals  220  and also electrically common the corresponding ground plates  206 . Four ground cross connects  250  are shown in  FIG. 2 , although the module stack  202  may include additional ground cross connects  250  that are not visible in the illustrated embodiment. 
     In an exemplary embodiment, the ground cross connects  250  include at least one ground mounting contact  252 , referred to herein as ground contact  252 , that is configured to mount to the host circuit board  104  (shown in  FIG. 1 ). Each ground contact  252  aligns with the mounting contacts  226  of the electrical terminals  220  in one of the columns  230 . For example, as described further below, at least some of the ground contacts  252  are each disposed between two mounting contacts  226  in the same column  230 , such that the ground contact  252  provides shielding between the mounting contacts  226 . One ground contact  252  may extend between mounting contacts  226  of two different differential pairs  244 . In an embodiment, the ground plates  206  do not include ground contacts that mount to the circuit board  104 , but the ground cross connects  250 , which engage and extend between the ground plates  206 , do include ground contacts  252 . By aligning the ground contacts  252  with the mounting contacts  226  in the columns  230 , the column voids  232  defined between adjacent columns  230  may be wider along the stack axis  208  than if the ground contacts  252  did not align with the mounting contacts  226 . Increased width of the column voids  232  increases the space along the circuit board  104  to accommodate routing of signal traces  146  (shown in  FIG. 1 ). 
       FIG. 3  is a front exploded view of a contact module  204  of the electrical connector  102  (shown in  FIG. 1 ) according to an embodiment.  FIG. 4  is a front assembled view of the contact module  204  of  FIG. 3 . The left signal wafer  216  and the right signal wafer  218  each have an inner side  260  and an outer side  262 . The inner sides  260  of the left and right signal wafers  216 ,  218  face each other. The inner sides  260  may abut each other in the assembled contact module  204  to define the interface  224 . The outer side  262  of the left signal wafer  216  defines the left outer side  212  of the contact module  204 , and the outer side  262  of the right signal wafer  218  defines the right outer side  214  of the contact module  204 .  FIG. 3  shows the mating contacts  124  and mounting contacts  226  of the left and right signal wafers  216 ,  218 . Only one of the four mounting contacts  226  in each signal wafer  216 ,  218  is visible because the mounting contacts  226  are aligned in a column  230  (shown in  FIG. 2 ) and the other three contacts  226  are behind the visible contact  226 . The portion of the electrical terminals  220  within the dielectric bodies  222  between the mating contacts  124  and the mounting contacts  226  is shown in phantom in  FIG. 3 . 
     In an embodiment, the electrical terminals  220  of at least one of the signal wafers  216 ,  218  in the contact module  204  are jogged in a jogged segment  268  proximate to the mounting edge  228  of the respective dielectric body  222 . The electrical terminals  220  of at least one signal wafer are jogged towards the other signal wafer in the contact module  204 . The terminals  220  are “jogged” such that the terminals  220  are bent or curved out of plane from another segment of the terminals  220 . For example, the mating contacts  124  of the electrical terminals  220  extend in a first signal plane  264 . The mounting contacts  226  of the electrical terminals  220  are offset from the first signal plane  264  by the jogged segment  268  such that the mounting contacts  226  extend in a second signal plane  266  that is different from the first signal plane  264 . The electrical terminals  220  in the jogged segment  268  may have an S-curve such that the first and second signal planes  264 ,  266  are parallel to each other but spaced apart by a distance  270 . In an exemplary embodiment, the electrical terminals  220  of both the left and the right signal wafers  216 ,  218  are jogged towards each other, as shown in  FIG. 3 . 
     As shown in  FIG. 4 , the left and right signal wafers  216 ,  218  are pressed against each other to form the assembled contact module  204 . As the signal wafers  216 ,  218  are joined, the mounting contacts  226  of both the signal wafers  216 ,  218  align in a single column  230 . The jogged segment  268  of the right signal wafer  218  is received in a recessed area  269  of the left signal wafer  216 , as shown in  FIG. 3 . Likewise, the jogged segment  268  of the left signal wafer  216  may be received in a corresponding recessed area (not shown) of the right signal wafer  218 . In an exemplary embodiment, the column  230  is a single file column having a width of only a single contact such that only one mounting contact  226  is visible from the front as shown in  FIG. 4 . The column  230  of mounting contacts  226  is parallel with the contact module plane  210 . The column  230  in  FIG. 4  is co-planar with the contact module plane  210 . The contact module plane  210  may extend along and be co-planar with the interface  224  between the left and right signal wafers  216 ,  218 , at least until the jogged segment  268  where the interface  224  is no longer co-planar with the contact module plane  210 . As such, the column  230  may be co-planar with the portion of the interface  224  excluding the jogged segment  268 . 
       FIG. 5  is a bottom perspective view of a portion of the module stack  202  of  FIG. 2  according to an exemplary embodiment. A bottom side  271  of the module stack  202  includes the mounting edges  228  of the dielectric bodies  222  of the contact modules  204 . The mounting contacts  226  protrude from the mounting edges  228 . The bottom side  271  of the module stack  202  is positioned at the mounting face  111  (shown in  FIG. 1 ) of the housing  108  ( FIG. 1 ). 
     The mounting contacts  226  of the contact modules  204  are aligned in the columns  230 . Each column  230  is defined by the mounting contacts  226  of one of the contact modules  204 . The columns  230  are parallel to each other. The columns  230  may each be co-planar with the contact module plane  210  of the respective contact module  204 . In an exemplary embodiment, both the electrical terminals  220  (shown in  FIG. 3 ) of the left and right signal wafers  216 ,  218  in each contact module  204  are jogged towards each other. As shown in  FIG. 5 , the mounting edges  228  of the left and right signal wafers  216 ,  218 , due to the jogged segments  268  (shown in  FIG. 3 ) of the electrical terminals  220  and the recessed areas  269  ( FIG. 3 ) of the signal wafers  216 ,  218  that receive the jogged segments  268 , define an undulating or snaking interface  224  between the mating edge  234  of the contact modules  204  and an opposite, rear edge  272  of the contact modules  204 . The mounting contacts  226  of the left and right signal wafers  216 ,  218  are aligned in the contact module plane  210  and are disposed in an alternating sequence at respective different distances from the mating edge  234 . When the signal wafers  216 ,  218  are aligned to form a contact module  204 , the jogged segments  268  of the left signal wafer  216  intermesh with the jogged segments  268  of the right signal wafer  218 . As such, the mounting contacts  226  of the left signal wafer  216  alternate with the mounting contacts  226  of the right signal wafer  218  along the length of the contact module  204  between the mating edge  234  and the rear edge  272 . 
     The mounting contacts  226  may be arranged in pairs  244 . The pairs  244  may be differential pairs configured to convey differential signals. Each column  230  includes multiple pairs  244  along the length of the column  230 . In an exemplary embodiment, a respective ground cross connect  250  extends between corresponding adjacent pairs  244  of mounting contacts  226  in each column  230 . The contact modules  204  may define slots  274  in the dielectric bodies  222  at the mounting edge  228  to receive the ground cross connects  250 . A ground contact  252  of each ground cross connect  250  aligns with the mounting contacts  226  in a corresponding column  230 . The mounting contacts  226  and ground contacts  252  in each column  230  may be aligned in a single file line between the mating edge  234  and the rear edge  272 . In an embodiment, a ground contact  252  is disposed between two mounting contacts  226  in the same column  230  to provide shielding therebetween. For example, the two mounting contacts  226  on either side of the ground contact  252  may be parts of different differential pairs  244  of mounting contacts  226 . The ground contact  252  thus provides shielding between adjacent differential pairs  244  within the same column  230 . 
     The ground cross connects  250  include a body  276  from which the at least one ground contact  252  extends. In an embodiment, the body  276  of the ground cross connect  250  is received in a corresponding slot  274 . The ground plates  206  may also include slots  278  that receive the bodies  276  of the ground cross connects  250 . The ground cross connects  250  may be slid into the slots  274 ,  278  from the bottom  271  of the module stack  202 . The bodies  276  of the ground cross connects  250  extend across at least one contact module  204  and the ground plates  206  on either side of the contact module  204 . The slots  278  in the ground plates  206  may be sized and/or the bodies  276  of the ground cross connects  250  may be shaped such that the bodies  276  mechanically engage the corresponding ground plates  206  that the respective ground cross connects  250  extend across. The ground cross connects  250  are formed of a conductive material, such as metal, to electrically engage the ground plates  206  that the ground cross connects  250  mechanically engage, thereby forming a ground path between ground plates  206  to electrically common adjacent ground plates  206  in the module stack  202 . The combination of the ground plates  206  at sides of the contact modules  204  and the ground cross connects  250  extending across the contact modules  204  may define conductive boxes around the pairs  244  of mounting contacts  226  at or near the mounting edge  228 . The conductive boxes provide electrical shielding along all sides of the corresponding pairs  244 . 
     In the illustrated embodiment, each of the ground cross connects  250  extend across two contact modules  204  and three ground plates  206  disposed on the sides of the contact modules  204 . The three ground plates  206  may be electrically commoned to each other at multiple locations along the length of the ground plates  206  by the ground cross connects  250 . The ground cross connects  250  each extend across a corresponding column void  232  defined by the columns  230  of mounting contacts  226  and ground contacts  252 . In addition, the ground cross connects  250  in the illustrated embodiment each include two ground contacts  252 . The two ground contacts  252  are disposed within respective different columns  230  of mounting contacts  226 . In other embodiments, at least some of the ground cross connects  250  may extend across more than two contact modules  204  and/or may include more than two ground contacts  252 . Optionally, ground cross connects  250  may not extend across at least some of the contact modules  204  of the module stack  202 . For example, ground cross connects  250  do not extend across contact modules  204 A and  204 B in  FIG. 5 , and the contact modules  204 A,  204 B are not separated by a ground plate  206 . Optionally, the mounting contacts  226  of the contact modules  204 A,  204 B may be low speed contacts, such as single ended contacts, that do not require the shielding provided by the ground plates  206  and ground cross connects  250 . The mounting contacts  226  of the other contact modules  204  (other than the contact modules  204 A,  204 B) may be high speed contacts. 
     In an embodiment, the mounting contacts  226  and the ground contacts  252  in adjacent columns  230  are staggered such that the mounting contacts  226  and the ground contacts  252  of the adjacent columns  230  are offset at respective different distances from the mating edges  234  of the respective contact modules  204 . The mating edges  234  of the contact modules  204  in the module stack  202  are used as reference points because the mating edges  234  are linearly aligned, such that each mating edge  234  is at the same relative position along the longitudinal axis  191  (shown in  FIG. 1 ) of the electrical connector  102  ( FIG. 1 ). For example, mounting contact  226 A in column  230 A is adjacent to mounting contact  226 B in column  230 B. Mounting contact  226 A is separated from the mating edge  234  by a first distance  280 . Mounting contact  226 B is separated from the mating edge  234  by a second distance  282  that is greater than the first distance  280 . Furthermore, the ground contacts  252  of adjacent columns  230  may also be offset. For example, ground contact  252 A in column  230 A is adjacent to ground contact  252 B in column  230 B. Ground contact  252 A is separated from the mating edge  234  by a third distance  284 . Ground contact  252 B is separated from the mating edge  234  by a fourth distance  286  that is greater than the third distance  284 . Because ground contacts  252 A and  252 B are coupled to the body  276  of the same ground cross connect  250 , the body  276  includes an offset segment  288  that is jogged out of plane from the rest of the body  276 . The ground contact  252 B extends from the offset segment  288  of the body  276 . The ground contact  252 A, however, extends from the body  276  at a location spaced apart from the offset segment  288 . The offset segment  288  is optionally jogged in a direction away from the mating edge  234 , which causes the ground contact  252 B to be disposed further from the mating edge  234  than the ground contact  252 A. 
       FIG. 6  illustrates a footprint  300  of the electrical connector  102  (shown in  FIG. 1 ) in accordance with an exemplary embodiment. The footprint  300  is at the mounting face  111  (shown in  FIG. 1 ) of the housing  108  ( FIG. 1 ). The footprint  300  is defined by the layout of the mounting contacts  226  and the ground contacts  252 . The mounting contacts  226  and the ground contacts  252  are arranged in an array at the mounting face  111 . The array includes plural columns  230  that extend parallel to the contact module plane  210  of at least one contact module  204 . The outlines of the contact modules  204  and ground plates  206  are shown in phantom. The ground contacts  252  extend from the ground cross connects  250  (shown in  FIG. 5 ). 
     Adjacent columns  230  are separated by column voids  232 . The column voids  232  extend parallel to the contact module plane  210 . The column voids  232  extend from the mating edge  234  to the rear edge  272 . The column voids  232  provide space within the footprint  300  of the electrical connector  102  (shown in  FIG. 1 ) for routing electrically conductive traces  146  (shown in  FIG. 1 ) along the circuit board  104  ( FIG. 1 ) away from the footprint  300 . For example, the column voids  232  allow for more conductive traces  146  to be routed under the footprint  300  on the same layer of the circuit board  104  than in other known electrical systems, which allows the circuit board  104  to have fewer layers, reducing cost and complexity. In addition, the column voids  232  may reduce cross-talk between mounting contacts  226  of adjacent contact modules  204 . 
     The mounting contacts  226  are arranged as pairs  244 . The pairs  244  of mounting contacts  226  may be differential pairs. The mounting contacts  226  of each pair  244  are disposed in the same column  230  and separated from each other by a pitch  302 , wherein pitch is defined as a dimension between centerpoints of the contacts  226 . In an embodiment, the mounting contacts  226  in adjacent columns  230  are staggered such that the mounting contacts  226  in one column  230  are disposed at a distance from the mating edge  234  that is a half-pitch  304  (for example, half of the pitch  302 ) further than the mounting contacts  226  in an adjacent column  230 . In other embodiments, the mounting contacts  226  of adjacent columns  230  may be staggered by distances other than half of the pitch  302  between pairs  244  of mounting contacts  226 . 
       FIG. 7  illustrates the circuit board  104  showing a footprint  310  of signal vias  312  and ground vias  314  that corresponds to the layout of the mounting contacts  226  (shown in  FIG. 6 ) and the ground contacts  252  ( FIG. 6 ) of the electrical connector  102  (shown in  FIG. 1 ). For example, the signal vias  312  are configured to receive the mounting contacts  226 , and the ground vias  314  are configured to receive the ground contacts  252 . The mounting contacts  226  mechanically engage the corresponding signal vias  312  to electrically connect the electrical terminals  220  (shown in  FIG. 2 ) to the vias  312 . The signal vias  312  are each coupled to a conductive trace  146  that extends from the corresponding signal via  312  and is routed through the footprint  310  on the circuit board  104 .  FIG. 7  illustrates an embodiment where the conductive traces  146  from all of the signal vias  312  are routed out from under the electrical connector  102  on one layer. Other layers of the circuit board  104  may be used for routing traces from other components, which may allow for a reduction in the overall size of the circuit board  104 . 
     The signal vias  312  and ground vias  314  are arranged in columns  316  that correspond to the columns  230  (shown in  FIG. 6 ) of the mounting contacts  226  ( FIG. 6 ) and ground contacts  252  ( FIG. 6 ). In an exemplary embodiment, at least some of the conductive traces  146  extend along and within routes  318  defined between adjacent columns  316  of vias  312 ,  314 . When the electrical connector  102  (shown in  FIG. 1 ) is mounted to the circuit board  104 , the routes  318  align with the column voids  232  (shown in  FIG. 6 ). The routes  318  are wide enough to support multiple conductive traces  146  side-by-side. For example, although a maximum of four traces  146  are shown side-by-side in the routes  318  in  FIG. 7 , the routes  318  may provide enough space for more than four traces  146 , such as six, eight, or ten traces  146 ). 
     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.