Patent Publication Number: US-2011070753-A1

Title: Electrical connector module with contacts of a differential pair held in separate chicklets

Description:
BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to electrical connectors, and more particularly, to high density electrical connectors. 
     Some electrical systems, such as network switches or computer servers with switching capabilities, include large backplanes with several daughter cards, such as switch cards or line cards, plugged into the backplane. The electrical systems utilize electrical connectors to interconnect the circuit boards defining the cards to the circuit board defining the backplane. Typically, the electrical connector is a right angle connector mounted to an edge of the backplane or one of the cards. The electrical connector is mated with a header connector mounted to a midplane. 
     Known electrical systems that utilize right angle connectors and header connectors mounted to a midplane are not without disadvantages. For instance, a large number of switch cards and line cards are typically connected to the backplane, which increases the overall size of the backplane. The density of the electrical connectors has an impact on the overall size of the electrical connectors, and thus the overall size of the backplane. The density may be expressed in terms of the number of signal contacts or pairs of signal contacts per linear inch of the electrical connector. While decreasing the spacing between the signal contacts is one way of increasing the density, decreasing the spacing may negatively affect the electrical performance of the electrical connector. The amount of undesirable coupling between adjacent signal contacts is based at least in part on the distance between the signal contacts. As such, merely changing the spacing between the signal contacts may not be an effective way to increase the density of the electrical connector, as the electrical connector may not perform adequately. 
     One method of reducing undesirable coupling and corresponding signal degradation between adjacent signals may be achieved by surrounding particular signal contacts or pairs of signal contacts with ground contacts. However, adding ground contacts reduces the overall density of the electrical connector by taking up space, thus increasing the spacing between the signal contacts or pairs of signal contacts. 
     Thus, providing a high density electrical connector with minimal signal loss remains a challenge. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, an electrical connector is provided that includes a housing and contact modules held in the housing. Each of the contact modules has a first chicklet and a second chicklet coupled together to form a corresponding one of the contact modules. Contacts are held in the contact modules and arranged in differential pairs. A first contact in each of the differential pairs is held by the first chicklet and a second contact in each of the differential pairs is held by the second chicklet. 
     In another embodiment, an electrical connector is provided including contact modules each having a first chicklet and a second chicklet separate and distinct from one another. The first chicklet has a first body holding first contacts and the second chicklet has a second body holding second contacts. The first body and the second body are coupled together along a contact module plane. The first contacts and the second contacts being arranged in differential pairs with each of the first contacts being oriented on an opposite side of the contact module plane as a corresponding one of the second contacts to define the differential pair. The electrical connector also includes a housing holding the contact modules such that the contact module planes are parallel to one another. 
     In a further embodiment, an electrical connector is provided that includes a housing holding a plurality of contact modules. The contact modules each include a first chicklet having a first body holding first contacts and first ground contact fingers being electrically grounded. The contact modules each include a second chicklet having a second body holding second contacts and having second ground contact fingers being electrically grounded. The second chicklet is separate and distinct from the first chicklet, and the second chicklet is coupled to the first chicklet to form each contact module. The contact modules have the first and second contacts arranged in differential pairs with one of the contacts of each differential pair being one of the first contacts and the other of the contacts of each differential pair being one of the second contacts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a connector system formed in accordance with an exemplary embodiment illustrating a receptacle connector and a header connector in unmated positions. 
         FIG. 2  is a front view of the header connector. 
         FIG. 3  is a front view of the receptacle connector. 
         FIG. 4  is a front perspective view a contact module for the receptacle connector shown in  FIG. 1 . 
         FIG. 5  is a front perspective view of a first chicklet forming part of the contact module shown in  FIG. 4 . 
         FIG. 6  illustrates a ground shield being coupled to the first chicklet shown in  FIG. 5 . 
         FIG. 7  illustrates the ground shield coupled to the first chicklet. 
         FIG. 8  is a front perspective view of a second chicklet forming part of the contact module shown in  FIG. 4 . 
         FIG. 9  illustrates the second chicklet shown in  FIG. 8  being coupled to the first chicklet shown in  FIG. 5 . 
         FIG. 10  is a front perspective view of an alternative contact module for the receptacle connector shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a perspective view of a connector system  100  formed in accordance with an exemplary embodiment illustrating two electrical connectors  102 ,  104  in an unmated position prior to mating with one another. The electrical connectors  102 ,  104  are each configured to be board mounted to circuit boards, such as backplanes, daughter cards, midplanes, or other circuit boards that are configured to be coupled together. The electrical connectors  102 ,  104  are utilized to electrically connect the circuit boards to one another. The electrical connectors  102 ,  104  may be cable mounted rather than board mounted in an alternative embodiment. 
     In the illustrated embodiment, the first electrical connector  102  constitutes a receptacle connector, and may be referred to hereinafter as receptacle connector  102 . The second electrical connector  104  constitutes a header connector, and may be referred to hereinafter as header connector  104 . The receptacle connector  102  is configured for mating with the header connector  104 . A mating axis  106  extends through both the first and second electrical connectors  102 ,  104  and the first and second electrical connectors  102 ,  104  are mated with one another in a direction parallel to and along the mating axis  106 . 
     It is realized that in alternative embodiments different types of electrical connectors may be utilized to electrically connect the circuit boards. The different types of electrical connectors may have different shapes, form factors, mating interfaces, contact arrangements, contact types and the like in alternative embodiments. The receptacle connector  102  and header connector  104  are merely illustrative of an exemplary embodiment of the connector system  100 . 
     The receptacle connector  102  includes a housing  112  having a mating face  114  at a front  116  of the housing  112 . The front  116  is perpendicular to the mating axis  106 . The housing  112  includes a plurality of contact channels  118  open at the front  116 . A plurality of contact modules  120  are held by the housing  112 . The contact modules  120  have a plurality of first and second signal contacts  122 ,  123  (shown in  FIG. 4 ) (only the tails of which are illustrated in  FIG. 1 ) that extend into the contact channels  118 . The contact modules  120  are loaded through a rear  124  of the housing  112  such that the contact modules  120  are arranged vertically within the housing  112 . In the illustrated embodiment, the receptacle connector  102  includes two different types of contact modules  120 , namely an A type and a B type (identified by the reference numeral  420 ) of contact module. The A and B types of contact modules  120  differ in their arrangement of signal and ground contacts, as will be described in further detail below. 
     The contact modules  120  are configured to be electrically connected to one of the circuit boards along a mounting face  126 . The mating face  114  is oriented perpendicular with respect to the mounting face  126  and the mating axis  106 . The mounting face  126 , as well as the circuit board, are arranged horizontally. Different, non-horizontal orientations are possible in alternative embodiments. 
     The header connector  104  includes a housing  128  having a mating face  130  at a front  132  of the housing  128 . The front  132  is perpendicular to the mating axis  106 . The housing  128  includes a chamber  134  that receives at least a portion of the receptacle connector  102 . An array of signal contacts  136  is arranged within the chamber  134  for mating with corresponding signal contacts  122 ,  123  of the receptacle connector  102 . The signal contacts  136  are held by the housing  128  and extend along the mating axis  106  into the chamber  134 . The signal contacts  136  are electrically connected to the corresponding circuit board. The signal contacts  136  are blade-type contacts having a generally rectangular cross-section. The housing  128  also holds a plurality of ground contacts  138 . The ground contacts  138  are configured to mate with ground contacts  140  (shown in  FIG. 4 ) of the receptacle connector  102 . 
     The signal contacts  136  include mating portions  142  at one end thereof and mounting portions  144  at the opposite end thereof. In the illustrated embodiment, the mounting portions  144  are eye-of-the-needle type contacts, however other types are possible in alternative embodiments. The mounting portions  144  are configured to be mounted to the circuit board. 
       FIG. 2  is a front view of the header connector  104  illustrating the signal contacts  136  and the ground contacts  138 . The signal contacts  136  and the ground contacts  138  are arranged in a matrix of columns  500  and rows  502 . The signal contacts  136  are arranged in differential pairs  504 , with adjacent differential pairs  504  being separated by ground contacts  138 . The signal contacts  136  within each differential pair  504  are aligned with one another within the corresponding row  502 . As a result, the overall density of the header connector  104  is increased as the number of signal contacts  136  provided over a given vertical height of the housing  128  is increased by aligning the signal contacts in a row  502 , as compared to a situation in which the signal contacts  136  of each differential pair  504  are staggered vertically along the column  500 . 
     Within each row  502 , adjacent differential pairs  504  are separated by a ground contact  138 . Similarly, within each column  500 , adjacent differential pairs  504  are separated by a ground contact  138 . The pattern of signal contacts  136  and ground contacts  138  in adjacent columns  500  alternates. For example, in the right-most column, the column  500  has a differential pair  504  of signal contacts  136  at the top-most position, followed by a ground contact  138  vertically below that. The pattern continues with alternating signal contacts  136  and ground contacts  138 . In the second column from the right, the pattern is different, with a ground contact  138  at the top-most position, followed by a differential pair  504  of signal contacts  136 . 
     In the illustrated embodiment, the signal contacts  136  and the ground contacts  138  are oriented differently. The signal contacts  136  include broadside surfaces  510  and edgeside surfaces  512  extending between the broadside surfaces  510 . The edgeside surfaces  512  may be narrower than the broadside surfaces  510 . The broadside surfaces  510  are oriented parallel to the rows  502  and the edgeside surfaces  512  are oriented parallel to the columns  500 . Alternatively, the ground contacts  138  include broadside surfaces  514  and edgeside surfaces  516  extending between the broadside surfaces  514 . The broadside surfaces  514  are oriented parallel to the columns  500  and the edgeside surfaces  516  are oriented parallel to the rows  502 . In alternative embodiments, the signal contacts  136  and/or the ground contacts  138  may have an angular orientation with respect to the columns  500  and the rows  502 . For example, the signal contacts  136  and/or the ground contacts  138  may be turned approximately 45° with respect to the columns  500  and the rows  502 . Such an arrangement may affect the broadside and/or edgeside coupling between signal contacts  136 . 
       FIG. 3  is a front view of the receptacle connector  102  illustrating mating portions of the signal contacts  122 ,  123  and the ground contacts  140 .  FIG. 3  also illustrates the housing  112  and contact channels  118 . In an exemplary embodiment, the contact channels  118  include both signal contact channels  520  and ground contact channels  522 . 
     The signal contact channels  520  are configured to receive the signal contacts  122 ,  123  as well as the signal contacts  136  (shown in  FIGS. 1 and 2 ) of the header connector  104 . The signal contact channels  520  are arranged in a pattern that complements the pattern of signal contacts  122 ,  123 ,  136 . The signal contact channels  520  are defined by channel walls  524 . In the illustrated embodiment, the channel walls  524  define signal contact channels  520  that have a rectangular cross-section. 
     The ground contact channels  522  are configured to receive the ground contacts  140  as well as the ground contacts  138  (shown in  FIGS. 1 and 2 ) of the header connector  104 . The ground contact channels  522  are arranged in a pattern that complements the pattern of ground contacts  138 ,  140 . The ground contact channels  522  are defined by channel walls  526 . In the illustrated embodiment, the channel walls  526  define ground contact channels  522  that have a rectangular cross-section. 
     The signal contacts  122 ,  123  and the ground contacts  142  are received in corresponding contact channels  520 ,  522 . The signal contacts  122 ,  123  and the ground contacts  140  are arranged in a matrix of columns  530  and rows  532 . The first and second signal contacts  122 ,  123  are arranged in differential pairs  534 , with adjacent differential pairs  534  being separated by ground contacts  140 . The signal contacts  122 ,  123  within each differential pair  534  are aligned with one another within one of the rows  532 . As a result, the overall density of the receptacle connector  102  is increased as the number of signal contacts  122 ,  123  provided over a given vertical height of the housing  112  is increased by aligning the signal contacts  122 ,  123  of a differential pair in the same row  532 , as compared to a situation in which the signal contacts of a differential pair are staggered vertically along a column. 
     Within each row  532 , adjacent differential pairs  534  are separated by a ground contact  140 . Similarly, within each column  530 , adjacent differential pairs  534  are separated by a ground contact  140 . The pattern of signal contacts  122 ,  123  and ground contacts  140  in adjacent columns  530  alternates. In the illustrated embodiment, the signal contacts  122 ,  123  and ground contacts  140  are generally aligned with one another along the contact module column  530 . However, because the signal contacts  122 ,  123  are staggered with respect to the central plane of the contact module  120 , it may be understood that the first contacts  122  are aligned in a first column and the second contacts  123  are aligned in a second column that is parallel to the first column. 
       FIG. 4  is a front perspective view a contact module  120  for the receptacle connector  102  (shown in  FIG. 1 ). The contact module  120  includes a first chicklet  152  and a second chicklet  154 . The first and second chicklets  152 ,  154  are separate and distinct from one another. The first and second chicklets  152 ,  154  are coupled together along a contact module plane  156  to form the contact module  120 . The contact module plane  156  may be centered along the contact module  120 . Optionally, the first and second chicklets  152 ,  154  are generally mirrored halves that are coupled together to form the contact module  120 , but that include complementary mating features that hold the mirrored halves together. Once the first and second chicklets  152 ,  154  are coupled together, the contact module  120  may be loaded into the housing  112  (shown in  FIG. 1 ). 
     The first chicklet  152  includes a body  160  that holds the first signal contacts  122 . A first ground shield  162  is coupled to the body  160 . The ground shield  162  includes first ground contact fingers  164  extending forward from the ground shield  162 . 
     The second chicklet  154  includes a body  170  that holds the second signal contacts  123 . A second ground shield  172  is coupled to the body  170 . The ground shield  172  includes second ground contact fingers  174  extending forward from the ground shield  172 . 
     When assembled, the signal contacts  122 ,  123  of both the first and second chicklets  152 ,  154  are aligned with one another on opposite sides of the contact module plane  156 . The signal contacts  122 ,  123  are arranged in differential pairs  534 , with the first signal contact  122  of the differential pair  534  being held by the first chicklet  152  on one side of the contact module plane  156  and the second signal contact  123  of the differential pair  534  being held by the second chicklet  154  on the opposite side of the contact module plane  156 . When assembled, the ground contact fingers  164 ,  174  are aligned with one another on opposite sides of the contact module plane  156  and form a ground contact set. Each ground contact set of ground contact fingers  164 ,  174  defines one of the ground contacts  140 . Each ground contact  140  includes two beams that engage opposite sides of the ground contact  138  (shown in  FIG. 2 ) when the ground contact  138  is loaded therebetween. The two beams are comprised of the two ground contact fingers  164 ,  174 , which represent spring fingers that engage opposite sides of the corresponding ground contact  138 . Optionally, the ground fingers  164 ,  174  may have different lengths to sequence the mating of the ground contact set with the corresponding ground contact  138 . As such, the mating forces may be reduced and/or the stub effect may be reduced. The ground shields  162 ,  172  may be electrically commoned via the ground contact  138  disposed between, and directly engaged by, the ground contact fingers  164 ,  174 . 
       FIG. 5  is a front perspective view of the first chicklet  152  forming part of the contact module  120  (shown in  FIG. 4 ). In an exemplary embodiment, the first chicklet  152  is formed with an overmolded lead frame type of structure, however the first chicklet  152  is not limited to such structure. The body  160  is formed by the dielectric material of the overmold, which encases a lead frame  180 . 
     The lead frame  180  includes a plurality of stamped and formed metal conductors initially held together by a frame or carrier (not shown) that is ultimately removed. The metal conductors define the signal contacts  122 . The signal contacts  122  are configured to carry data signals. In alternative embodiments, other types of contacts may be provided in addition to, or in the alternative to, the signal contacts  122 , such as ground contacts, power contacts, and the like. In the illustrated embodiment, the signal contacts  122  of the first chicklet  152  are not arranged to carry differential pair signals with other signal contacts  122  of the first chicklet  152 , but rather are configured to carry data signals that are independent from one another. However, the first signal contacts  122  cooperate with corresponding second signal contacts  123  of the second chicklet  154  (shown in  FIG. 4 ) to carry differential pair signals with such corresponding second signal contacts  123 . Hence, the signal contacts  122  in the first chicklet  152  that are arranged adjacent one another and in a common vertical column are associated with different differential pairs. 
     The signal contacts  122  have a mating portion  182  and a mounting portion  184  that are both exposed beyond edges of the body  160 . In the illustrated embodiment, the mounting portion  184  constitutes an eye of the needle type contact that is configured to be received within a via of the circuit board. The mating portion  182  extends forwardly from a front end of the body  160 . In the illustrated embodiment, the mating portion  182  constitutes a tuning fork style of contact that is configured to receive and mate with the blade type of signal contact  136  (shown in  FIG. 1 ). Other types of contacts may be used in alternative embodiments for mating with the blade type of signal contact  136  or other types of signal contacts. In an exemplary embodiment, the mating portion  182  includes a jogged section  186  that transitions the mating portion  182  out of plane with respect to other portions of the signal contact  122 . 
     The signal contacts  122  transition between the mating and mounting portions  182 ,  184  within the body  160 . In an exemplary embodiment, the first chicklet  152  is a right angle chicklet with the mating portion  182  being oriented generally perpendicular with respect to the mounting portion  184 . The signal contacts  122  are generally coplanar with one another along a lead frame plane  188 . The lead frame plane  188  may be substantially centered within the body  160 . The jogged section  186  may transition the mating portion  182  out of the lead frame plane  188 . 
     The body  160  has opposed inner and outer sides  190 ,  192 . The inner and outer sides  190 ,  192  are generally parallel to the lead frame plane  188 . The signal contacts  122  may be generally centered between the inner and outer sides  190 ,  192 . Optionally, the inner side  190  may be planar. The outer side  192  may include a recess that receives the first ground shield  162  (shown in  FIG. 4 ). In an exemplary embodiment, the body  160  includes securing features  194  for securing the first chicklet  152  together with second chicklet  154  (shown in  FIG. 4 ). In the illustrated embodiment, the securing features  194  are represented by pegs that extend inwardly from the inner side  190 , and may be referred to hereinafter as pegs  194 . The pegs  194  may be cylindrical in shape or have other shapes. Other types of securing features may be used in alternative embodiments, such as an opening, a fastener, a latch, an adhesive, and the like. Any number of securing features  194  may be used. More than one type of securing features  194  may be provided. In an exemplary embodiment, the body  160  includes grooves  196  at the corner of the front edge and outer side  192  that are configured to receive portions of the first ground shield  162 . 
       FIG. 6  illustrates the first ground shield  162  being coupled to the first chicklet  152 . The first ground shield  162  is coupled to the outer side  192  of the body  160 . The body  160  includes slots  198 . The ground shield  162  includes first grounding tabs  200  extending inward therefrom. The first grounding tabs  200  are configured to be received in the slots  198 . 
     The first ground shield  162  includes a forward mating edge  202  and a bottom mounting edge  204  that is perpendicular to the mating edge  202 . The ground shield  162  also includes a rear edge  206  opposite the mating edge  202  and a top edge  208  opposite the mounting edge  204 . The ground shield  162  has an inner side  210  and an outer side  212 . When mounted to the contact module  120 , the inner side  210  generally faces the body  160  and the outer side  212  generally faces away from the body  160 . 
     In an exemplary embodiment, the ground shield  162  includes the first ground contact fingers  164  that extend forward from the mating edge  202 . The first ground contact fingers  164  may extend inward from the inner side  210 . The first ground contact fingers  164  are arranged along the mating edge  202  in a predetermined pattern. The first ground contact fingers  164  are aligned with the grooves  196 . The first ground contact fingers  164  represent spring fingers that are deflectable. A mating interface  214  is provided proximate to a distal end of the first ground contact fingers  164 . The mating interface  214  is configured for mating with the ground contact  138  (shown in  FIG. 1 ). 
     The ground shield  162  includes shield tails  216  that extend downward and inward from the mounting edge  204 . The shield tails  216  may include one or more eye-of-the-needle type contacts that fit into vias in the circuit board. Other types of contacts may be used for through hole mounting or surface mounting to the circuit board. The bulk of each shield tail  216  is positioned inward with respect to the ground shield  162 , which is generally towards the contact module  120  when the ground shield  162  is coupled to the contact module  120 . The shield tails  216  are configured to fit in slots  218  formed in the body  160 . The shield tails  216  may be stamped from a ground plate  220  defining the ground shield  162  and then bent inward with respect to the ground plate  220 . The shield tails  216  are electrically commoned with one another by the ground plate  220 . Similarly, the first ground contact fingers  164  are electrically commoned with one another by the ground plate  220 . 
       FIG. 7  illustrates the ground shield  162  coupled to the first chicklet  152 . When assembled, the ground shield  162  is coupled to the outer side  192  of the body  160 . The first grounding tabs  200  are received in the slots  198 . Optionally, the first grounding tabs  202  may extend beyond the inner side  190  such that the first grounding tabs  202  engage the second chicklet  154  (shown in  FIG. 4 ). 
     The first ground contact fingers  164  extend forward of the ground shield  162  and the body  160 . The first ground contact fingers  164  may be aligned with, and extend along, the lead frame plane  188 . The first ground contact fingers  164  are interspersed between each of the signal contacts  122 . 
     The shield tails  216  extend into the slots  218  of the body  160 . The shield tails  216  may be aligned with, and extend along, the lead frame plane  188 . The shield tails  216  are interspersed between each of the mounting portions  184  of the signal contacts  122 . 
       FIG. 8  is a front perspective view of the second chicklet  154  forming part of the contact module  120  (shown in  FIG. 4 ). The second chicklet  154  represents an overmolded lead frame type of structure. The body  170  is formed by the dielectric material of the overmold, which encases a lead frame (not shown) similar to the lead frame  180  (shown in  FIG. 5 ). The lead frame includes metal conductors that define the signal contacts  123 . The second signal contacts  123  cooperate with corresponding first signal contacts  122  of the first chicklet  152  (shown in  FIG. 4 ) to carry differential pair signals with such corresponding first signal contacts  122 . 
     Each signal contact  123  has a mating portion  282  and a mounting portion  284  that are both exposed beyond edges of the body  170 . In the illustrated embodiment, the mounting portion  284  constitutes an eye of the needle type contact that is configured to be received within a via of the circuit board. The mating portion  282  extends forwardly from a front end of the body  170 . In the illustrated embodiment, the mating portion  282  constitutes a tuning fork style of contact that is configured to receive and mate with the blade type of signal contact  136  (shown in  FIG. 1 ) of the header connector  104 . Other types of contacts may be used in alternative embodiments. In an exemplary embodiment, the mating portion  282  includes a jogged section  286 . The signal contacts  123  are generally coplanar with one another along a lead frame plane  288 . The lead frame plane  288  may be substantially centered within the body  170 . The jogged section  286  may transition the mating portion  282  out of the lead frame plane  288 . 
     The body  170  has opposed inner and outer sides  290 ,  292 . The inner and outer sides  290 ,  292  are generally parallel to the lead frame plane  288 . The signal contacts  123  may be generally centered between the inner and outer sides  290 ,  292 . Optionally, the inner side  290  may be planar. The outer side  292  may include a recess that receives the second ground shield  172 . In an exemplary embodiment, the body  170  includes securing features  294  for securing the first chicklet  152  together with second chicklet  154 . In the illustrated embodiment, the securing features  294  are represented by openings, and may be referred to hereinafter as openings  294 . The openings  294  are hexagon shaped to provide an interference fit with the securing features  194  (shown in  FIG. 5 ), however other shapes are possible. Other types of securing features may be used in alternative embodiments, such as a pin, a peg, a fastener, a latch, and adhesive, and the like. Any number of securing features  294  may be used. More than one type of securing features  294  may be provided. In an exemplary embodiment, the body  170  includes grooves  296  at the corner of the front edge and outer side  292  that are configured to receive portions of the second ground shield  172 . 
     The second ground shield  172  is coupled to the outer side  292  of the body  170 . The body  170  includes slots  298 . The ground shield  172  includes second grounding tabs  300  extending inward therefrom. The second grounding tabs  300  are configured to be received in the slots  298 . 
     The second ground shield  172  includes a forward mating edge  302  and a bottom mounting edge  304  that is perpendicular to the mating edge  302 . In an exemplary embodiment, the second ground shield  172  includes the second ground contact fingers  174  that extend forward from the mating edge  302 . The second ground contact fingers  174  may extend inward from the inner side  290 . The second ground contact fingers  174  are arranged along the mating edge  302  in a predetermined pattern and are aligned with the grooves  296 . The second ground contact fingers  174  represent spring fingers that are deflectable. A mating interface  314  is positioned proximate to a distal end of the second ground contact fingers  174 . The mating interface  314  is configured for mating with the ground contact  138  (shown in  FIG. 1 ). 
     The ground shield  172  includes shield tails  316  that extend downward and inward from the mounting edge  304 . The shield tails  316  may include one or more eye-of-the-needle type contacts that fit into vias in the circuit board. Other types of contacts may be used for through hole mounting or surface mounting to the circuit board. The bulk of each shield tail  316  is positioned inward with respect to the ground shield  172 , which is generally towards the contact module  120  when the ground shield  162  is coupled to the contact module  120 . The shield tails  316  are configured to fit in slots  318  formed in the body  170 . The shield tails  316  may be stamped from a ground plate  320  defining the ground shield  172  and then bent inward with respect to the ground plate  320 . The shield tails  316  are electrically commoned with one another by the ground plate  320 . Similarly, the second ground contact fingers  174  are electrically commoned with one another by the ground plate  320 . 
     When assembled, the ground shield  172  is coupled to the outer side  292  of the body  170 . The second grounding tabs  300  are received in the slots  298 . Optionally, the second grounding tabs  300  may extend beyond the inner side  290  such that the second grounding tabs  300  engage the first chicklet  152 . The second ground contact fingers  174  are interspersed between each of the signal contacts  123 . The shield tails  316  extend into the slots  318  of the body  160 . The shield tails  316  may be aligned with, and extend along, the lead frame plane  288 . The shield tails  316  are interspersed between each of the mounting portions  284  of the signal contacts  123 . 
       FIG. 9  illustrates the second chicklet  154  being coupled to the first chicklet  152 . The first and second chicklets  152 ,  154  are aligned with one another and mated together to form the contact module  120 . When mated, the pegs  194  are received in the openings  294 . The pegs  194  may be held by an interference fit within the openings  294  to securely hold the first and second chicklets  152 ,  154  together. 
     When mated, the first grounding tabs  200  are received within the slots  298  of the second chicklet  154 . For example, the slots  298  may be wide enough to accommodate both grounding tabs  200 ,  300 . The first grounding tabs  200  include barbs  340  that engage the slots  298  to secure the first and second chicklets  152 ,  154  together. The first grounding tabs  200  engage the second grounding tabs  300  within the slots  298  to electrically common the first and second ground shields  162 ,  172 . Similarly, when mated, the second grounding tabs  300  are received within the slots  198  of the first chicklet  152 . For example, the slots  198  may be wide enough to accommodate both grounding tabs  200 ,  300 . The second grounding tabs  300  include barbs (not shown), which may be similar to the barbs  340 , that engage the slots  198  to secure the first and second chicklets  152 ,  154  together. The second grounding tabs  300  engage the first grounding tabs  200  within the slots  198  to electrically common the first and second ground shields  162 ,  172 . 
     Referring back to  FIG. 4 , the contact module  120  is illustrated in the assembled state with the first and second chicklets  152 ,  154  coupled together. The signal contacts  122 ,  123  of both the first and second chicklets  152 ,  154  are vertically aligned directly across from one another on either side of the contact module plane  156 . The first and second ground contact fingers  164 ,  174  are also vertically aligned directly across from one another on either side of the contact module plane  156 . The signal contacts  122 ,  123  receive a corresponding signal contact  136  (shown in  FIG. 1 ) of the header connector  104  (shown in  FIG. 1 ). The first and second ground contact fingers  164 ,  174  cooperate to both engage the same ground contact  138  (shown in  FIG. 1 ) of the header connector  104 . 
       FIG. 10  is a front perspective view of an alternative contact module  420  for the receptacle connector  102  (shown in  FIG. 1 ). The contact module  420  is substantially similar to the contact module  120 , however the contact module  420  has a different arrangement of signal and ground contacts. 
     The contact module  420  includes first and second chicklets  422 ,  424 . The first and second chicklets  422 ,  424  both have signal contacts  426 ,  427 , respectively, that are arranged as differential pairs, with one of the signal contacts  426 ,  427  of each differential pair being held by the first chicklet  422 , and with the other of the signal contacts  426 ,  427  of each differential pair being held by the second chicklet  424 . A contact module plane  428  is defined along the line of intersection between the first and second chicklets  422 ,  424 . The first and second signal contacts  426 ,  427  are disposed on respective opposite sides of the contact module plane  428  to define the differential pair. As such, neither the first chicklet  422  nor the second chicklet  424  holds signal contacts  426 ,  427  that carry differential pair signals within a single chicklet  422 ,  424 . Rather, each of the signal contacts  426  in the first chicklet  422  cooperates with a corresponding signal contact  427  in the second chicklet  424  to form a differential pair that carries differential signals. 
     Each of the first and second chicklets  422 ,  424  has a ground shield  430 . The ground shields  430  have first and second ground contact fingers  432 ,  434  that are aligned directly across from one another on either side of the contact module plane  428 . The aligned first and second ground contact fingers  432 ,  434  cooperate to define a ground contact  436  that mates with one of the ground contacts  138  (shown in  FIG. 1 ). The ground shields  430  are electrically commoned by grounding tabs  438  that extend through the bodies of the chicklets  422 ,  424 . The ground shields  430  are also electrically commoned when mated with the header connector  104  by the first and second ground contact fingers  432 ,  434  engaging the same ground contacts  138 . 
     The ground contacts  436  are interspersed between each of the differential pairs of signal contacts  426 ,  427 . The pattern of ground contacts  436  and signal contacts  426 ,  427  differs from the pattern of ground contacts  140  and signal contacts  122  (shown in  FIG. 4 ). For example, with the contact module  420 , the signal contacts  426 ,  427  are at an upper-most position along the front edge, followed by a ground contact  436 , then signal contacts  426 ,  427  and so on vertically down the front edge. Alternatively, the contact module  120  (shown in  FIG. 4 ) has the opposite pattern, beginning with the ground contact  140  at the uppermost position, followed by the signal contacts  122 , and so on. 
     Referring back to  FIG. 1 , when the contact modules  120 ,  420  are loaded into the housing  112 , the pattern of signal and ground contacts may be altered by alternating the contact modules  120 ,  420 . As such, the vertical position of the signal contacts may be changed in adjacent rows by sandwiching the contact modules  120  between two of the contact modules  420 , and vice versa. The contact modules  120 ,  420  are loaded into the housing  112  in an assembled state with the first and second chicklets  152 ,  154  coupled together prior to loading the contact modules  120  into the housing  112  and with the first and second chicklets  422 ,  424  coupled together prior to loading the contact modules  420  into the housing  112 . 
     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.