Patent Publication Number: US-8123560-B2

Title: Modular connector system

Description:
BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to connector systems, and more particularly, to header connectors and receptacle connectors of a connector system. 
     Some connector systems, such as backplane connector systems, utilize electrical connectors to interconnect two circuit boards, such as a motherboard and daughtercard. Electrical connectors, such as a header connector and a receptacle connector, are mounted on the circuit boards and mated together. 
     However, known backplane connector systems are not without disadvantages. For instance, typically, the connector systems are designed for operation in relatively benign office environments. The header and receptacle connectors are limited in terms of ruggedness with respect to performance demands in environments outside of a controlled office environment, such as high shock and vibration environments common in particular industries, such as aerospace and defense industries. For example, the signal contacts of one of the connectors typically only provides mating spring contact to one or two sides of the mating contact of the other connector at the separable interface. Additionally, the interface between the connectors and the circuit boards is typically not capable of withstanding high shock and vibration environments. 
     Furthermore, the header and receptacle connectors of known backplane connector systems have unique connector features that maintain connector signal integrity, which require a specific connector orientation on the circuit board. For example, special keying features are typically provided that limit orientation of the connector on the board and/or with the complementary connector. Keying features are provided to key the connector contacts within the connector housing. Typically, left and right modules are provided to complete a connector offering, resulting in multiple connector housings and assemblies. 
     Moreover, typical header and receptacle connectors have a primarily plastic housing construction, which has limited shielding benefits and does not provide protection from electrostatic discharge. As such, the connectors leave the digital signals susceptible to security breaches as well as electrostatic discharges during field repair and maintenance. 
     A need remains for a connector system that provides high speed signal integrity while offering adequate physical protection of the connectors. A need remains for a connector system that can withstand increased shock and vibration levels, while maintaining high speed signal integrity. A need remains for a connector system that is unconstrained with limitations of connector orientation. A need remains for a connector system that provides protection from interferences and/or electrostatic discharge. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a connector system is provided including a first connector comprising a housing holding a plurality of contacts, a second connector comprising a housing holding a plurality of contacts, and a metal shield having walls defining a shielded chamber. The first and second connectors are configured to be mounted to a circuit board in a stacked arrangement next to one another. The first and second connectors are configured to be arranged in a shielded configuration in which the first and second connectors are positioned within the shielded chamber and mounted to the circuit board with the metal shield. The first and second connectors are also configured to be arranged in an unshielded configuration in which the first and second connectors are mounted to the circuit board without the metal shield. 
     In a further embodiment, a connector system is provided that includes a receptacle connector having a receptacle cavity and a plurality of receptacle contacts held within the receptacle cavity. The connector system also includes a plastic header connector, a shielded header connector and a rugged header connector. The plastic header connector has a housing defining a plastic outer perimeter holding a plurality of header contacts and defining a mating interface. The shielded header connector has a housing and a metal shield surrounding the housing defining a shielded outer perimeter. The housing of the shielded header connector holds a plurality of header contacts, and the header contacts and the shielded outer perimeter defining a mating interface. The rugged header connector has a housing and a rugged metal shell surrounding the housing defining a rugged outer perimeter. The housing of the rugged header connector holds a plurality of header contacts, and the header contacts and the rugged outer perimeter defining a mating interface. The mating interfaces are substantially the same such that the plastic header connector, shielded header connector, and rugged header connector are intermatable with the receptacle connector. 
     In a further embodiment, a connector system is provided including a header connector holding a plurality of header contacts and having an outer perimeter. The connector system also includes a plastic receptacle connector, a shielded receptacle connector and a rugged receptacle connector. The plastic receptacle connector has a housing defining a plastic outer perimeter and a receptacle cavity. The housing of the plastic header connector holds a plurality of contact modules holding a plurality of receptacle contacts extending into the receptacle cavity. The receptacle contacts and the housing define a mating interlace. The shielded receptacle connector has a housing and a metal shield surrounding the housing and defining a shielded outer perimeter. The housing of the shielded receptacle connector has a receptacle cavity and holds a plurality of contact modules holding a plurality of receptacle contacts extending into the receptacle cavity. The receptacle contacts and the housing define a mating interface. The rugged receptacle connector has a housing and a rugged metal shell surrounding the housing defining a rugged outer perimeter and having a receptacle cavity. The housing of the rugged header connector holds a plurality of contact modules holding a plurality of receptacle contacts extending into the receptacle cavity. The receptacle contacts and the housing define a mating interface. The mating interfaces are substantially the same such that the plastic receptacle connector, shielded receptacle connector, and rugged receptacle connector are intermatable with the header connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a plastic connector system formed in accordance with an exemplary embodiment. 
         FIG. 2  illustrates a shielded connector system formed in accordance with an alternative embodiment. 
         FIG. 3  illustrates a rugged connector system formed in accordance with a further embodiment. 
         FIG. 4  is an exploded view of a header connector and corresponding receptacle connector of the plastic connector system. 
         FIG. 5  is a perspective view of a contact module for the receptacle connector shown in  FIG. 4 . 
         FIG. 6  is a perspective view of a header contact for the header connector shown in  FIG. 4 . 
         FIG. 7  is a perspective view of an alternative header contact for the header connector shown in  FIG. 4 . 
         FIG. 8  is a cross sectional view of the header connector taken along line  8 - 8  shown in  FIG. 4 . 
         FIG. 9  is a cross sectional view of the plastic connector system taken along line  9 - 9  shown in  FIG. 4  with the header connector and the receptacle connector in an assembled state. 
         FIG. 10  is a cross sectional view of a mating interface of a header contact and a receptacle contact. 
         FIG. 11  is a front perspective view of a receptacle assembly for the shielded connector system shown in  FIG. 2 . 
         FIG. 12  is a front perspective, partially exploded view of a header assembly for the shielded connector system. 
         FIG. 13  is a front perspective, assembled view of the header assembly for the shielded connector system. 
         FIG. 14  is a rear perspective, partially exploded view of a receptacle assembly for the rugged connector system shown in  FIG. 3 . 
         FIG. 15  is a rear perspective, partially exploded view of a header assembly for the rugged connector system. 
         FIG. 16  illustrates a plastic header assembly poised for mating with a shielded receptacle assembly. 
         FIG. 17  illustrates a plastic header assembly poised for mating with a rugged receptacle assembly. 
         FIG. 18  illustrates a shielded header assembly poised for mating with a plastic receptacle assembly. 
         FIG. 19  illustrates a shielded header assembly poised for mating with a rugged receptacle assembly. 
         FIG. 20  illustrates a rugged header assembly poised for mating with a plastic receptacle assembly. 
         FIG. 21  illustrates a rugged header assembly poised for mating with a shielded receptacle assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Connector systems are illustrated and described herein having different parts and components. The parts and components have common features, sizes and shapes such that the parts and components are interchangeable. For example, the various connectors described herein are intermatable and backwards compatible with other connectors from other systems. The various connectors have common mating interfaces such that the various connectors are mating compatible with corresponding mating halves. The various connectors define interchangeable modules that have different degrees of ruggedness or robustness and/or different degrees of electrical performance, such as bandwidth or data rate. 
     The various connectors of the connector systems illustrated and described herein are generally one of three types of connectors, namely plastic connectors, shielded connectors or rugged connectors. The shielded connectors and the rugged connectors generally define higher performance connectors as compared to the plastic connectors, because such connectors have electrical shielding surrounding the connectors. The shielded connectors generally define more robust connectors as compared to the plastic connectors, as the shielded connectors have a metal casing surrounding the connectors. The rugged connectors generally define more robust connectors as compared to the shielded connectors, as the rugged connectors have a machined metal frame, a diecast frame or another rugged type of frame surrounding the connectors, which is more durable than the metal casing surrounding the shielded connectors. 
     The various connectors of the connector systems illustrated and described herein generally represent connector assemblies, which include more than one individual connector. The connector assemblies are grouped together as a unit for simultaneously mating with corresponding connector assemblies. The individual connectors may be ganged together and mounted to a circuit board as a unit, or alternatively, may be individually mounted to the circuit board, and then the assembly and circuit board mounted to the corresponding connector assembly as a unit. In exemplary embodiments, the individual connectors are symmetrically designed such that the connectors may be utilized in more than one orientation, such as in 180° orientations. The connectors may be designed to have mechanical and/or electrical reversibility to the circuit board and/or to the corresponding mating half. As such, manufacturing may be simplified. Additionally, assembly may be simplified. Furthermore, part count may be reduced and total product count may be reduced. Optionally, the various connectors may represent end modules that may be provided at one end or the other end of the connector assembly. In exemplary embodiments, the connector may be used at either end. Alternatively, the connector may be designed to be either a right-end or a left-end module. Optionally, the various connectors may represent interior modules that may be used between designated end modules. In exemplary embodiments, the connector systems are expandable such that any number of connectors may be utilized, such as by adding additional interior modules, to achieve a desired configuration and number of contacts. Optionally, the various connectors may be useable as either end modules or interior modules. 
     The various connectors of the connector systems illustrated and described herein generally represent either header connectors or receptacle connectors. The connectors are board mounted connectors, however one or both of the mating halves of the connectors may be cable mounted rather than board mounted. Optionally, one mating half, such as the header connector, is mounted to a backplane, while the other mating half, such as the receptacle connector, is mounted to a daughtercard. Optionally, one mating half, such as the header connector, may constitute a vertical connector, where the contacts thereof pass straight through the connector, while the other mating half, such as the receptacle connector, may constitute a right-angle connector, where the contacts thereof are bent at 90° within the connector. Having one of the connectors as a right angle connector orients the circuit boards perpendicular to one another. Alternatively, both of the connectors may be right angle connectors such that the circuit boards are oriented parallel and/or coplanar with one another. 
       FIG. 1  illustrates a connector system  100  formed in accordance with an exemplary embodiment. The connector system  100  includes a header assembly  102  and a receptacle assembly  104 . The header assembly  102  is coupled to the receptacle assembly  104 . The header assembly  102  is mounted to a circuit board  106 . The receptacle assembly  104  is mounted to a circuit board  108 . The circuit board  106  may represent a backplane and the circuit board  108  may represent a daughter card. 
     The header assembly  102  includes a plurality of header connectors  110  mounted to the circuit board  106 . In the illustrated embodiment, three header connectors  110  are provided, including opposite end connectors and an interior connector. The header assembly  102  has a mating face  112  configured to be mated to the receptacle assembly  104 . The header assembly  102  has a mounting face  114  configured to be mounted the circuit board  106 . The mating face  112  and the mounting face  114  are generally parallel to one another. Alternative configurations are possible in alternative embodiments. The header assembly  102  constitutes a vertical connector assembly having contacts that pass straight through the header connectors  110 . 
     In an exemplary embodiment, guide pins  116  extend from the circuit board  106  for guiding mating of the header assembly  102  and the receptacle assembly  104 . Alternatively, guide sockets may be provided rather than guide pins. Other types of components, such as power modules, fiber-optic connectors, RF coaxial connectors, keying hardware, and the like may be coupled to the circuit board  106  for mating with corresponding components on the circuit board  108 . 
     Each header connector  110  includes a housing  120  extending between the mating and mounting faces  112 ,  114 . The housing  120  holds a plurality of header contacts  122 . The housing  120  is fabricated from a dielectric material, such as a plastic material. The header connector  110  constitutes a plastic connector. The header connector  110  does not include any metal shield surrounding the housing  120  or any protective shell surrounding the housing  120 . The ruggedness of the header connector  110  is relatively low as compared to other types of connectors described herein. Additionally, the header connector  110  is unshielded. 
     The header contacts  122  may be arranged in differential pairs. Alternatively, the header contacts  122  may be single ended signal contacts. The header contacts  122  may be signal contacts, ground contacts, power contacts or other types of contacts. The header contacts  122  may be arranged in any pattern and orientation with respect to one another. In an exemplary embodiment, the header contacts  122  are arranged in a matrix of rows and columns. 
     The receptacle assembly  104  includes a plurality of receptacle connectors  150  mounted to the circuit board  108 . In the illustrated embodiment, three receptacle connectors  150  are provided, including opposite end connectors and an interior connector. The receptacle assembly  104  has a mating face  152  configured to be mated to the header assembly  102 . The receptacle assembly  104  has a mounting face  154  configured to be mounted the circuit board  108 . The mating face  152  and the mounting face  154  are generally perpendicular to one another. Alternative configurations are possible in alternative embodiments. The receptacle assembly  104  constitutes a right angle connector assembly having right angle contacts that extend from perpendicular sides of the receptacle connectors  150 . 
     In an exemplary embodiment, guide sockets  156  extend from the circuit board  108  for guiding mating of the header assembly  102  and the receptacle assembly  104 . Alternatively, guide pins may be provided rather than guide sockets. Other types of components, such as power modules, fiber-optic connectors, RF coaxial connectors, keying hardware, and the like may be coupled to the circuit board  108  for mating with corresponding components on the circuit board  106 . 
     Each receptacle connector  150  includes a housing  160  extending between the mating and mounting faces  152 ,  154 . The housing  160  holds a plurality of receptacle contacts  162 . The housing  160  is fabricated from a dielectric material, such as a plastic material. The receptacle connector  150  constitutes a plastic connector. The receptacle connector  150  does not include any metal shield surrounding the housing  160  or any protective shell surrounding the housing  160 . The ruggedness of the receptacle connector  150  is relatively low as compared to other types of connectors described herein. Additionally, the receptacle connector  150  is unshielded. 
     The receptacle contacts  162  may be arranged in differential pairs. Alternatively, the receptacle contacts  162  may be single ended signal contacts. The receptacle contacts  162  may be signal contacts, ground contacts, power contacts or other types of contacts. The receptacle contacts  162  may be arranged in any pattern and orientation with respect to one another. In an exemplary embodiment, the receptacle contacts  162  are arranged in a matrix of rows and columns. 
       FIG. 2  illustrates a connector system  200  formed in accordance with an exemplary embodiment. The connector system  200  includes a header assembly  202  and a receptacle assembly  204 . The header assembly  202  is matable with the receptacle assembly  204 . The header assembly  202  and the receptacle assembly  204  are similar to the header assembly  102  and the receptacle assembly  104  (both shown in  FIG. 1 ) in some respects, however the header assembly  202  and the receptacle assembly  204  constitute shielded connector assemblies having metal shields that provide electrical shielding. The header assembly  202  is mounted to a circuit board  206 . The receptacle assembly  204  is mounted to a circuit board  208 . The circuit board  206  may represent a backplane and the circuit board  208  may represent a daughter card. 
     The header assembly  202  includes a plurality of header connectors  210  mounted to the circuit board  206 . In the illustrated embodiment, three header connectors  210  are provided, including opposite end connectors and an interior connector. The header assembly  202  has a mating face  212  configured to be mated to the receptacle assembly  204 . The header assembly  202  has a mounting face  214  configured to be mounted the circuit board  206 . The mating face  212  and the mounting face  214  are generally parallel to one another. Alternative configurations are possible in alternative embodiments. The header assembly  202  constitutes a vertical connector assembly having contacts that pass straight through the header connectors  210 . 
     In an exemplary embodiment, a metal shield  216  surrounds the header connectors  210 . The metal shield  216  may be a stamped and formed metal piece that surrounds the header connectors  210 . Optionally, the metal shield  216  may be mounted over the header connectors  210  after the header connectors  210  are coupled to the circuit board  206 . Alternatively, the header connectors  210  may be loaded into the metal shield  216 , and then the entire unit (header connectors  210  and metal shield  216 ) mounted to the circuit board  206 . In other alternative embodiments, the metal shield  216  may be mounted to the circuit board  206  and then the header connectors  210  loaded therein. The metal shield  216  may include ground pins  218  (shown in  FIG. 12 ) that extend into the circuit board  206 , such as into ground vias of the circuit board  206 , to electrically ground the metal shield  216 . The metal shield  216  provides shielding from interference, such as electromagnetic interference (EMI), electrostatic discharge (ESD), cross-talk, and the like. 
     Each header connector  210  includes a housing  220  extending between the mating and mounting faces  212 ,  214 . The housing  220  holds a plurality of header contacts  222 . The housing  220  is fabricated from a dielectric material, such as a plastic material. The metal shield  216  surrounds the housings  220 . When assembled, the header assembly  202  constitutes a shielded connector assembly. The metal shield  216  provides some mechanical protection to the header connectors  210 , such as protection from impact, as well as adding stability to the header assembly  202  by holding the individual header connectors  210  together. The metal shield  216  may be secured to the circuit board  206 , such as by the ground pins  218 , to help hold the header assembly  202  on the circuit board  206 , which may make the header assembly  202  more rugged, such as by resisting shock or vibration. The ruggedness of the header assembly  202  is higher than the plastic version, namely the header assembly  102  (shown in  FIG. 1 ). 
     The header contacts  222  may be arranged in differential pairs. Alternatively, the header contacts  222  may be single ended signal contacts. The header contacts  222  may be signal contacts, ground contacts, power contacts or other types of contacts. The header contacts  222  may be arranged in any pattern and orientation with respect to one another. In an exemplary embodiment, the header contacts  222  are arranged in a matrix of rows and columns. 
     In an exemplary embodiment, the header connectors  210  and the header contacts  222  are substantially identical to the header connectors  110  and the header contacts  122 , respectively (shown in  FIG. 1 ). The difference is that the metal shield  216  is utilized with the header assembly  202 . The header connectors  210  and the header contacts  222  are interchangeable with the header connectors  110  and the header contacts  122 . A reduced part count is thus achieved by not needing different header connectors and different header contacts with the shielded version as compared to the plastic version. Additionally, because the header connectors  210  and the header contacts  222  are substantially identical to the header connectors  110  and the header contacts  122 , the header connectors  210  and the header contacts  222  may be mated with the receptacle connectors  150  and the receptacle contacts  162  (both shown in  FIG. 1 ). The header assembly  202  is backward compatible with the receptacle assembly  104  (shown in  FIG. 1 ). 
     The receptacle assembly  204  includes a plurality of receptacle connectors  250  mounted to the circuit board  208 . In the illustrated embodiment, three receptacle connectors  250  are provided, including opposite end connectors and an interior connector. The receptacle assembly  204  has a mating face  252  configured to be mated to the header assembly  202 . The receptacle assembly  204  has a mounting face  254  configured to be mounted the circuit board  208 . The mating face  252  and the mounting face  254  are generally perpendicular to one another. Alternative configurations are possible in alternative embodiments. The receptacle assembly  204  constitutes a right angle connector assembly having right angle contacts that extend from perpendicular sides of the receptacle connectors  250 . 
     In an exemplary embodiment, a metal shield  256  surrounds the receptacle connectors  250 . The metal shield  256  may be a stamped and formed metal piece that surrounds the receptacle connectors  250 . Optionally, the receptacle connectors  250  may be loaded into the metal shield  256 , and then the entire unit (receptacle connectors  250  and metal shield  256 ) mounted to the circuit board  208 . Alternatively, the metal shield  256  may be mounted over the receptacle connectors  250  after the receptacle connectors  250  are coupled to the circuit board  208 . The metal shield  256  may include ground pins that extend into the circuit board  208 , such as into ground vias of the circuit board  208 , to electrically ground the metal shield  256 . The metal shield  256  provides shielding from interference, such as EMI, ESD, cross-talk, and the like. 
     Each receptacle connector  250  includes a housing  260  extending between the mating and mounting faces  252 ,  254 . The housing  260  holds a plurality of receptacle contacts  262 . The housing  260  is fabricated from a dielectric material, such as a plastic material. The metal shield  256  surrounds the housings  260 . When assembled, the receptacle assembly  204  constitutes a shielded connector assembly. The metal shield  256  provides some mechanical protection to the receptacle connectors  250 , such as protection from impact, as well as adding stability to the receptacle assembly  204  by holding the individual receptacle connectors  250  together. The metal shield  256  may be secured to the circuit board  208 , such as by the ground pins, to help hold the receptacle assembly  204  on the circuit board  208 , which may make the receptacle assembly  204  more rugged, such as by resisting shock or vibration. The ruggedness of the receptacle assembly  204  is higher than the plastic version, namely the receptacle assembly  104  (shown in  FIG. 1 ). 
     The receptacle contacts  262  may be arranged in differential pairs. Alternatively, the receptacle contacts  262  may be single ended signal contacts. The receptacle contacts  262  may be signal contacts, ground contacts, power contacts or other types of contacts. The receptacle contacts  262  may be arranged in any pattern and orientation with respect to one another. In an exemplary embodiment, the receptacle contacts  262  are arranged in a matrix of rows and columns. 
     In an exemplary embodiment, the receptacle connectors  250  and the receptacle contacts  262  are substantially identical to the receptacle connectors  150  and the receptacle contacts  162 , respectively (shown in  FIG. 1 ). The difference is that the metal shield  256  is utilized with the receptacle assembly  204 . The receptacle connectors  250  and the receptacle contacts  262  are interchangeable with the receptacle connectors  150  and the receptacle contacts  162 . A reduced part count is thus achieved by not needing different receptacle connectors and different receptacle contacts with the shielded version as compared to the plastic version. Additionally, because the receptacle connectors  250  and the receptacle contacts  262  are substantially identical to the receptacle connectors  150  and the receptacle contacts  162 , the receptacle connectors  250  and the receptacle contacts  262  may be mated with the header connectors  110  and the header contacts  122  (both shown in  FIG. 1 ). The receptacle assembly  204  is backward compatible with the header assembly  102  (shown in  FIG. 1 ). 
       FIG. 3  illustrates a connector system  300  formed in accordance with an exemplary embodiment. The connector system  300  includes a header assembly  302  and a receptacle assembly  304 . The header assembly  302  is matable with the receptacle assembly  304 . The header assembly  302  and the receptacle assembly  304  are similar to the header assembly  102  and the receptacle assembly  104  (both shown in  FIG. 1 ) in some respects, however the header assembly  302  and the receptacle assembly  304  constitute rugged connector assemblies having rugged shells, such as machined metal or diecast shells, which provide rugged protection and securing as well as electrical shielding. 
     The header assembly  302  is mounted to a circuit board  306 . The receptacle assembly  304  is mounted to a circuit board  308 . The circuit board  306  may represent a backplane and the circuit board  308  may represent a daughter card. 
     The header assembly  302  includes a plurality of header connectors  310  mounted to the circuit board  306 . In the illustrated embodiment, three header connectors  310  are provided, including opposite end connectors and an interior connector. The header assembly  302  has a mating face  312  configured to be mated to the receptacle assembly  304 . The header assembly  302  has a mounting face  314  configured to be mounted the circuit board  306 . The mating face  312  and the mounting face  314  are generally parallel to one another. Alternative configurations are possible in alternative embodiments. The header assembly  302  constitutes a vertical connector assembly having contacts that pass straight through the header connectors  310 . 
     In an exemplary embodiment, a shell  316  surrounds the header connectors  310 . The shell  316  may he a machined metal piece or diecast metal piece that surrounds the header connectors  310 . Other forming operations or processes may be used in alternative embodiments. Other types of materials, such as synthetic materials like rubber, may be used in alternative embodiments. The synthetic materials may be metalized, such as by being impregnated with metal particles or flakes, or by coating or plating the shell. Optionally, the header connectors  310  may be loaded into the shell  316 , and then the entire unit (header connectors  310  and shell  316 ) mounted to the circuit board  306 . Alternatively, the shell  316  may be mounted over the header connectors  310  after the header connectors  310  are coupled to the circuit board  306 . The shell  316  may be electrically grounded to the circuit board  306 . The shell  316  may provide shielding from interference, such as EMI, ESD, cross-talk, and the like. The shell  316  may be secured to the circuit board  306  by board locks. 
     Each header connector  310  includes a housing  320  extending between the mating and mounting faces  312 ,  314 . The housing  320  holds a plurality of header contacts  322 . The housing  320  is fabricated from a dielectric material, such as a plastic material. The shell  316  surrounds the housings  320 . When assembled, the header assembly  302  constitutes a rugged connector assembly. The shell  316  provides mechanical protection to the header connectors  310 , such as protection from impact. The shell  316  adds stability to the header assembly  302  by holding the individual header connectors  310  together as well as by being secured to the circuit board  306  by board locks, which may make the header assembly  302  more rugged, such as by resisting shock or vibration. The ruggedness of the header assembly  302  is higher than the plastic version, namely the header assembly  102  (shown in  FIG. 1 ), and the shielded version, namely the header assembly  202  (shown in  FIG. 2 ). 
     The header contacts  322  may be arranged in differential pairs. Alternatively, the header contacts  322  may be single ended signal contacts. The header contacts  322  may be signal contacts, ground contacts, power contacts or other types of contacts. The header contacts  322  may be arranged in any pattern and orientation with respect to one another. In an exemplary embodiment, the header contacts  322  are arranged in a matrix of rows and columns. 
     In an exemplary embodiment, the header connectors  310  and the header contacts  322  are substantially identical to the header connectors  110  and the header contacts  122 , respectively (shown in  FIG. 1 ). The difference is that the shell  316  is utilized with the header assembly  302 . The header connectors  310  and the header contacts  322  are interchangeable with the header connectors  110  and the header contacts  122 . A reduced part count is thus achieved by not needing different header connectors and different header contacts with the shielded version as compared to the plastic version. Alternatively, the header connectors  310  may have a different shaped housing  320  configured to fit into the shell  316 . Additionally, the header assembly  302  may have a substantially identical mating interface as the header assemblies  102 ,  202  (shown in  FIGS. 1 and 2 , respectively) for mating with the receptacle assemblies  104 ,  204  (shown in  FIGS. 1 and 2 , respectively). The header assembly  302  is backward compatible with the receptacle assemblies  104 ,  204 . 
     The receptacle assembly  304  includes a plurality of receptacle connectors  350  mounted to the circuit board  308 . In the illustrated embodiment, three receptacle connectors  350  are provided, including opposite end connectors and an interior connector. Optionally, the end connectors and interior connectors may be substantially identical to one another, such that the connectors are interchangeable. The receptacle assembly  304  has a mating face  352  configured to be mated to the header assembly  302 . The receptacle assembly  304  has a mounting face  354  configured to be mounted the circuit board  308 . The mating face  352  and the mounting face  354  are generally perpendicular to one another. Alternative configurations are possible in alternative embodiments. The receptacle assembly  304  constitutes a right angle connector assembly having right angle contacts that extend from perpendicular sides of the receptacle connectors  350 . 
     In an exemplary embodiment, a shell  356  surrounds the receptacle connectors  350 . The shell  356  may be a machined metal piece or diecast metal piece that surrounds the receptacle connectors  350 . Other forming operations or processes may be used in alternative embodiments. Other types of materials, such as synthetic materials like rubber, may be used in alternative embodiments. The synthetic materials may be metalized, such as by being impregnated with metal particles or flakes, or by coating or plating the shell. Optionally, the receptacle connectors  350  may be loaded into the shell  356 , and then the entire unit (receptacle connectors  350  and shell  356 ) mounted to the circuit board  308 . Alternatively, the shell  356  may be mounted over the receptacle connectors  350  after the receptacle connectors  350  are coupled to the circuit board  308 . The shell  356  may be electrically grounded to the circuit board  308 . The shell  356  may provide shielding from interference, such as EMI, ESD, cross-talk, and the like. The shell  356  may be secured to the circuit board  308  by board locks. 
     Each receptacle connector  350  includes a housing  360  extending between the mating and mounting faces  352 ,  354 . The housing  360  holds a plurality of receptacle contacts  362 . The housing  360  is fabricated from a dielectric material, such as a plastic material. The shell  356  surrounds the housings  360 . When assembled, the receptacle assembly  304  constitutes a rugged connector assembly. The shell  356  provides mechanical protection to the receptacle connectors  350 , such as protection from impact. The shell  356  adds stability to the receptacle assembly  304  by holding the individual receptacle connectors  350  together as well as by being secured to the circuit board  308  by board locks, which may make the receptacle assembly  304  more rugged, such as by resisting shock or vibration. The ruggedness of the receptacle assembly  304  is higher than the plastic version, namely the receptacle assembly  104  (shown in  FIG. 1 ), and the shielded version, namely the receptacle assembly  204  (shown in  FIG. 2 ). 
     The receptacle contacts  362  may be arranged in differential pairs. Alternatively, the receptacle contacts  362  may be single ended signal contacts. The receptacle contacts  362  may be signal contacts, ground contacts, power contacts or other types of contacts. The receptacle contacts  362  may be arranged in any pattern and orientation with respect to one another. In an exemplary embodiment, the receptacle contacts  362  are arranged in a matrix of rows and columns. 
     In an exemplary embodiment, the receptacle connectors  350  and the receptacle contacts  362  are substantially identical to the receptacle connectors  150  and the receptacle contacts  162 , respectively (shown in  FIG. 1 ). The difference is that the shell  356  is utilized with the receptacle assembly  304 . The receptacle connectors  350  and the receptacle contacts  362  are interchangeable with the receptacle connectors  150  and the receptacle contacts  162 . A reduced part count is thus achieved by not needing different receptacle connectors and different receptacle contacts with the shielded version as compared to the plastic version. Alternatively, the receptacle connectors  350  may have a different shaped housing  360  configured to fit into the shell  356 . Additionally, the receptacle assembly  304  may have a substantially identical mating interface as the receptacle assemblies  104 ,  204  (shown in  FIGS. 1 and 2 , respectively) for mating with the header assemblies  102 ,  202  (shown in  FIGS. 1 and 2 , respectively). The receptacle assembly  304  is backward compatible with the header assemblies  102 ,  202 . 
       FIG. 4  is an exploded view of one of the header connectors  110  and one of the receptacle connectors  150 . The header connector  110  is generally box shaped having opposite top and bottom ends and opposite sides extending between the top and bottom ends. Optionally, the top and bottom ends and the sides may have approximately equal lengths such that the header connector  110  has a square cross section. Alternatively, the sides may be longer or shorter than the top and bottom ends. 
     The housing  120  includes contact channels  124  extending entirely between the mating face  112  and the mounting face  114 . The header contacts  122  are received in corresponding channels  124 . Optionally, the header contacts  122  may be loaded through the mounting face  114 . Portions of the header contacts  122  extend from the mounting face  114  for mounting to the circuit board  106  (shown in  FIG. 1 ). The contact channels  124  are arranged in rows and columns. 
     In an exemplary embodiment, air pockets  126  are provided between the contact channels  124  in different columns. Optionally, air pockets may be provided between the rows of contact channels  124  in addition to, or in the alternative to, the air pockets  126  between the columns. The air pockets  126  extend entirely between the mating face  112  and the mounting face  114 . The air pockets  126  may be sized and shaped, and positioned, in proximity to the contact channels  124  to control an impedance of the header contacts  122  of the header connector  110 . For example, providing the air pockets  126  and/or providing larger air pockets may raise an impedance of the header connectors  122 . In an exemplary embodiment, the housing  120  includes a plurality of outer air pockets  128  arranged along the sides of the housing  120 . The outer air pockets  128  are open along the sides of the housing  120 . When the header connector  110  is stacked next to an adjacent header connector  110 , the outer air pockets  128  are aligned with one another and form a common air pocket that is sized and shaped substantially similar to the air pockets  126  that are internal to the housing  120 . 
     The housing  120  includes lips  130  at the top and bottom ends proximate to the mating face  112 . The lips  130  may be configured to receive a metal shield in some embodiments, as described in further detail below. The housing  120  includes alignment lugs  132  extending from the top and bottom ends proximate to the mating face  112 . The alignment lugs  132  help align the header connector  110  when mated with the receptacle connector  150 . 
     The receptacle connector  150  is generally box shaped having opposite top and bottom ends and opposite sides extending between the top and bottom ends. Optionally, the top and bottom ends and the sides may have approximately equal lengths such that the receptacle connector  150  has a square cross section. Alternatively, the sides may be longer or shorter than the top and bottom ends. 
     The housing  160  includes contact channels  164  extending therethrough proximate to the mating face  152 . The contact modules  158  are loaded into the housing  160  such that the receptacle contacts  162  are received in corresponding channels  164 . Optionally, the receptacle contacts  162  may be loaded through a rear end of the housing  160 . Portions of the receptacle contacts  162  extend from the mating face  152  for mating with the header contacts  122 . The contact channels  164  are arranged in rows and columns. 
     In an exemplary embodiment, air pockets  166  are provided between the contact channels  164  in different columns. Optionally, air pockets may be provided between the rows of contact channels  164  in addition to, or in the alternative to, the air pockets  166  between the columns. The air pockets  166  extend entirely between the front and the rear ends of the housing  160 . The air pockets  166  may be sized and shaped, and positioned, in proximity to the contact channels  164  to control an impedance of the receptacle contacts  162  of the receptacle connector  150 . For example, providing the air pockets  166  and/or providing larger air pockets may raise an impedance of the receptacle connectors  162 . In an exemplary embodiment, the housing  160  includes a plurality of outer air pockets  168  arranged along the sides of the housing  160 . The outer air pockets  168  are open along the sides of the housing  160 . When the receptacle connector  150  is stacked next to an adjacent receptacle connector  150 , the outer air pockets  168  are aligned with one another and form a common air pocket that is sized and shaped substantially similar to the air pockets  166  that are internal to the housing  160 . 
     The housing  160  includes a hood  170  at the top and bottom ends proximate to the mating face  152 . The housing  160  includes alignment slots  172  extending through the hood  170 . The alignment slots  172  receive the alignment lugs  132  to help align the receptacle connector  150  when mated with the header connector  110 . The housing  160  includes a receptacle cavity  174  defined between the hoods  170 . The receptacle cavity  174  receives the header connector  110  therein. 
       FIG. 5  is a partially exploded side perspective view of one of the contact modules  158 . The contact module  158  includes a dielectric body  180  holding the receptacle contacts  162 . In an exemplary embodiment, the receptacle contacts  162  are manufactured as part of a lead frame held by a carrier, and the dielectric body  180  is overmolded over the receptacle contacts  162 . Alternative assembly processes or manufacturing processes may be used in alternative embodiments. The dielectric body  180  has a mating face  182  and a mounting face  184 , which are generally perpendicular to one another. The contact module  158  defines a right angle contact module with portions of the receptacle contacts  162  being at right angles with one another. 
     The receptacle contacts  162  include mating pins  186  extending from the mating face  182 . The receptacle contacts  162  include mounting tails  188  extending from the mounting face  184 . The mating pins  186  are configured to be mated with the header contacts  122 . The mounting tails  188  are configured to be loaded into plated vias on the circuit board  108  (shown in  FIG. 1 ). In the illustrated embodiment, the mounting tails  188  constitute press-fit tails, such as eye-of-the-needle tails, that are loaded into the vias and electrically and mechanically secured thereto by an interference fit. 
     The dielectric body  180  includes a plurality of openings  190  through a side of the dielectric body  180 . A ground shield  192  is configured to be mounted to the side of the dielectric body  180 . The ground shield  192  provides electrical shielding from an adjacent contact module  158 . The ground shield  192  is generally planar and includes barbs  194  extending inward from the ground shield  192 . The barbs  194  are received in corresponding openings  190  to contact corresponding receptacle contacts  162 . Optionally, the barbs  194  may have opposed fingers similar to insulation displacement contacts that clamp onto opposite sides of the receptacle contacts  162 . The barbs  194  are configured to engage the receptacle contacts  162  that define ground contacts, generally referenced as ground receptacle contacts  162 ′. Each of the ground receptacle contacts  162 ′ is electrically commoned with one another via the ground shield  192 . In an exemplary embodiment, the ground receptacle contacts  162 ′ have mating pins  186 ′ that are longer than mating pins  186  of the signal contacts. The receptacle connector  150  is configured for sequence mating with the header connector  110 . Optionally, the dielectric body  180  may include more openings  190  than the ground shield  192  includes barbs  194 . Less than all of the openings  190  receive barbs  194 . 
     Optionally, different types of contacts modules  158  may be provided. For example, A-type contact modules and B-type contact modules  158  may be used together within the receptacle connector  150 . The A and B type contact modules  158  are positioned adjacent to one another such that B-type contact modules  158  are provided between each of the A-type contact modules  158 , and vice versa. 
     The A and B type contact modules  158  may have an identical dielectric body  180  with identical openings  190 . The A and B type contact modules  158  may have different ground shields  192  having barbs  194  that are positioned at different locations. When an A-type ground shield  192  is coupled to an A-type contact module  158 , the ground shield  192  engages predetermined ones of the receptacle contacts  162 . When a B-type ground shield  192  is coupled to a B-type contact module  158 , the barbs  194  extend into different openings  190  and engage different ones of the receptacle contacts  162 .  FIG. 4  illustrates both A and B type contact modules  158 . As can be seen in  FIG. 4 , the ground receptacle contacts  162 ′ (e.g., the longer receptacle contacts  162 ) have different patterns. When the A and B type contact modules  158  are loaded into the housing  160 , the ground receptacle contacts  162 ′ of adjacent contact modules  158  are not aligned with one another. 
       FIG. 6  is a side perspective view the header contact  122 . The header contact  122  includes a contact body  400  extending between a mating end  401  and a mounting end  402  along a longitudinal axis  404 . The header contact  122  generally extends along a primary plane  406  and secondary plane  408  that is perpendicular to the primary plane  406  and that intersect along the longitudinal axis  404 . In an exemplary embodiment, the header contact  122  is symmetric about the primary plane  406 . The header contact  122  is also symmetric about the secondary plane  408 . 
     The header contact  122  includes a base  410 , a contact tail  412  extending from the base  410  to the mounting end  402 , and a box-shaped socket  414  that extends from the base  410  to the mating end  401 . The base  410  is a generally flat, generally rectangular portion of the header contact  122 . The base  410  lies within the primary plane  406 . The header contact  122  is stamped and formed from a blank sheet of material to form the base  410 , contact tail  412 , and box-shaped socket  414 . The base  410 , contact tail  412 , and box-shaped socket  414  are integrally formed with one another as a unitary one-piece structure. The base  410 , contact tail  412 , and box-shaped socket  414  are formed to provide symmetry along both the primary plane  406  and the secondary plane  408 . For example, the base  410  and the contact tail  412  are aligned with the central axis of the box-shaped socket  414 . 
     The base  410  includes front shoulders  416  and rear shoulders  418 . The header contact  122  is configured to be loaded into the contact channels  124  (shown in  FIG. 4 ) until the front shoulders  416  engage stops within the contact channels  124 . The rear shoulders  418  define a bearing surface for pushing the header contact  122  into the contact channel  124 . Optionally, the base  410  may include bumps  420  along the outer edges thereof that engage the contact channel  124  to provide an interference fit to hold the header contact  122  within the contact channel  124 . When loaded into the contact channel  124 , the contact tail  412  extends outward from the contact channel  124  for mounting to the circuit board  106  (shown in  FIG. 1 ). 
     The box-shaped socket  414  defines a reception area  422  configured to receive the receptacle contact  162  (shown in  FIG. 4 ). The box-shaped socket  414  includes an inner ring  424  and an outer ring  426 . The inner and outer rings  424 ,  426  extend circumferentially around the reception area  422 . Optionally, the inner and outer rings  424 ,  426  enclose the reception area  422  along the corresponding segment of the longitudinal axis  404 . The box-shaped socket  414  includes opposed primary springs  428  extending between the inner and outer rings  424 .  426 . The box-shaped socket  414  includes opposed secondary springs  430  that extend between the inner and outer rings  424 ,  426 . 
     In an exemplary embodiment, the primary springs  428  extend entirely between the inner and outer rings  424 ,  426 . The secondary springs  430  extend partially between the inner and outer rings  424 ,  426 . For example, the secondary springs  430  may extend from the outer ring  426  towards the inner ring  424 , but stop short of the inner ring  424  such that the secondary springs  430  do not engage the inner ring  424 . The secondary springs  430  are cantilevered beams that are configured to be deflected when engaging the receptacle contact  162 . The primary and secondary springs  428 ,  430  generally have a concave shape between the inner and outer rings  424 ,  426 . The primary and secondary springs  428 ,  430  extend at least partially into the reception area  422 . The cross-sectional area of the reception area  422 , within the inner and outer rings  424 ,  426 , is larger than the cross-sectional area of the reception area  422  along the primary and secondary springs  428 ,  430 . 
     When the receptacle contact  162  is loaded into the reception area  422 , the receptacle contact  162  engages the primary and secondary springs  428 ,  430 . The primary and secondary springs  428 ,  430  are at least partially deflected outward by the receptacle contact  162  and are held against the receptacle contact  162  by a biasing force or spring force acting on the receptacle contact  162 . The primary springs  428  and secondary springs  430  provide four points of contact on the receptacle contact  162 . For example, the primary springs  428  engage opposite sides of the receptacle contact  162 . Similarly, the secondary springs  430  engage opposite sides of the receptacle contact  162 , which are generally perpendicular to the points of contact of the primary springs  428 . Having four points of contacts acting in four different directions provides a robust mating interface between the header contact  122  and the receptacle contact  162 . The mating interface withstands demanding environments, such as high shock environments and/or vibration. Additionally, having four points of contact provides multiple points of contact, even if one or more should fail and/or be degraded. 
     The box-shaped socket  414  includes first and second longitudinal extensions  432 ,  434  extending along opposite, primary sides of the reception area  422 . The longitudinal extensions  432 ,  434  extend between the inner ring  424  and the base  410 . The first longitudinal extension  432  is a continuous extension that transitions from the base  410 . The second longitudinal extension  434  is separate from, and engages the first longitudinal extension  432  and/or the base  410  proximate to the transition from the first longitudinal extension  432  and the base  410 . In an exemplary embodiment, the longitudinal extensions  432 ,  434  merge toward one another, and engage one another, proximate to the base  410 . The first and second longitudinal extensions  432 ,  434  provide symmetry about the primary plane  406 . For example, the first and second longitudinal extensions  432 ,  434  have complementary shapes and distances from the primary plane  406  along the longitudinal axis  404 . 
     Optionally, the secondary sides of the box-shaped socket  414  between the inner ring  424  and the base  410  are open. Alternatively, such portions of the box-shaped socket  414  may be closed. 
       FIG. 7  is a perspective view of an alternative header contact  460 . The header contact  460  is similar to the header contact  122  (shown in  FIG. 6 ), however the header contact  460  does not include a second longitudinal extension. The header contact  460  is not symmetric along the entire length thereof. For example, between a base  462  and a box-shaped socket  464 , the header contact  460  is not symmetric, rather, the header contact  460  includes a single longitudinal extension along one side. The box-shaped socket  464  and the base  462  are aligned with one another along the central axis, such that when the header contact  460  is loaded into the header connector  110  (shown in  FIG. 1 ) the mating end and mounting end of the header contact  460  are aligned with one another. 
       FIG. 8  is a cross-sectional view of the header connector  110  taken along line  8 - 8  shown in  FIG. 4 . The header contacts  122  are shown loaded into the contact channels  124 . The header connector  110  is symmetric about a central axis  470  of the header connector  110 . For example, an equal number of header contacts  122  are provided on both sides of the central axis  470 . Additionally, the spacing between each of the header contacts  122  is the same between each adjacent header contact  122 . The air pockets  126  are the same size across the entire housing  120 . 
     As shown in  FIG. 8 , the header contacts  122  are symmetric about the longitudinal axis  404 . For example, the box-shaped socket  414  is substantially identical on both sides of the longitudinal axis  404 . Additionally, the base  410  and the contact tail  412  extend along the longitudinal axis  404 . 
       FIG. 9  is a cross-sectional view of the connector system  100  showing the receptacle connector  150  coupled to the header connector  110 . When mated, the receptacle contacts  162  are loaded into the box-shaped socket  414  of the corresponding header contacts  122 . The secondary springs  430  engage opposite sides of the receptacle contacts  162 . 
     When assembled, the ground receptacle contacts  162 ′ (e.g., the longer receptacle contacts  162 ) extend further into the box-shaped socket  414  than the signal contacts  162  (e.g. the shorter receptacle contacts  162 ). The header contacts  122  define either ground header contacts or signal header contacts, depending on which type of receptacle contact  162 ′ or  162  to which the header contact  122  is mated. In an exemplary embodiment, because the receptacle contacts  162  are arranged as differential pairs, within each column, the header contacts  122  are arranged in a ground-signal-signal-ground pattern, with grounds between each pair of signals. The grounds provide electrical shielding between the signals, which increases the performance of the connector system. The air pockets  126  (shown in  FIG. 8 ) are provided between adjacent columns of header and receptacle contacts  122 ,  162 . Having the grounds between the differential pairs of signals allows the header and receptacle contacts  122 ,  162  to be packaged more densely within the header and receptacle connectors  110 ,  150 . For example, the grounds affect the cross-talk of the header and receptacle contacts  122 ,  162 . Having the air pockets  126 ,  156  between the columns of header and receptacle contacts  122 ,  162  allows the header and receptacle contacts  122 ,  162  to be packaged more densely within the header and receptacle connectors  110 ,  150 . For example, the air pockets  126 ,  156  affect the impedance of the header and receptacle contacts  122 ,  162 . 
     The box-shaped sockets  414  are configured to accommodate both the shorter length signal receptacle contacts  162  and the longer length ground receptacle contacts  162 ′. Different signal and ground header contacts do not need to be provided. Rather, each header contact  122  is substantially identical to one another and can accommodate either a signal receptacle contact  162  or a ground receptacle contact  162 ′ of the receptacle connector  150 . The longitudinal extensions  432 ,  434  extend along the ground receptacle contacts  162 . The longitudinal extensions  432 ,  434  extend along both sides of the ground receptacle contacts  162 , and engage each other beyond the end of the ground receptacle contacts  162 , to prevent an electrical stub. 
     When assembled, the header connector  110  is received in the receptacle cavity  174  of the receptacle connector  150 . The hood  170  extends along the top and the bottom of the header connector  110 . Optionally, a metal shield (shown in phantom) may be coupled to the header connector  110  and a metal shield (shown in phantom) may be coupled to the receptacle connector  150 , thus defining shielded versions of the connectors (e.g. defining the header connector  210  and receptacle connector  250 , both shown in  FIG. 2 ). Optionally, the metal shield of the receptacle connector  150  may extend along an inner surface of the hood  170  such that the metal shield of the receptacle connector  150  engages the metal shield of the header connector  110 . The metal shields may be electrically commoned and grounded to one another. Such electrical commoning may occur prior to the ground receptacle contact  162  being mated with the corresponding header contacts  122 . 
       FIG. 10  illustrates one of the receptacle contacts  162  mated to one of the header contacts  122 . The receptacle contact  162  includes a generally rectangular outer surface  480 . When loaded into the reception area  422 , the outer surfaces  480  engage the primary and secondary springs  428 ,  430 . The primary springs  428  press inward on the outer surfaces  480  in generally opposite directions represented by the arrows P 1  and P 2 . Similarly, the secondary springs  430  press inward on the outer surfaces  480  in generally opposite directions represented by the arrows S 1  and S 2 , which are generally perpendicular to the arrows P 1  and P 2  representing the spring force exerted by the primary springs  428 . As such, the springs  428 ,  430  press against the receptacle contact  162  in four orthogonal directions (e.g. north, south, east and west). 
       FIG. 11  is a front perspective view of the receptacle assembly  204 . The receptacle assembly  204  constitutes a shielded receptacle assembly  204 . The metal shield  256  is included to provide the shielding. As shown in  FIG. 11 , the receptacle connectors  250  are received within the metal shield  256 . The metal shield  256  entirely circumferentially surrounds the receptacle connectors  250 . For example, the metal shield  256  may extend along the tops, the bottoms, the sides, and the back of the receptacle connector  250 . Optionally, a portion of the bottom of the receptacle connector  250  may be open, wherein the metal shield  256  does not extend across such open portion. The mounting ends of the contact modules  158  (shown in  FIG. 5 ) are allowed to extend through the metal shield  256  for mating to the circuit board  208  (shown in  FIG. 2 ). Optionally, the metal shield  256  may extend across a portion of the bottom of the receptacle connectors  250 . For example, the portion below the housing  260  may have the metal shield  256  extending there along. 
     The metal shield  256  includes a front edge  280  having clips  282  extending therefrom. The clips  282  have spring fingers  284  that are received in the receptacle cavity  274 . The clips  282  wrap around hoods  270  of the housing  260 . The clips  282  hold the position of the receptacle connector  250  within the metal shield  256 . The metal shield  256  includes a back wall  286  (only a portion of which is illustrated in  FIG. 11 ) that extends across the back of the receptacle connector  250 . The receptacle connectors  250  are captured between the clips  282  and the back wall  286 . 
     The spring fingers  284  are exposed within the receptacle cavity  274 . When the header assembly  202  (shown in  FIG. 2 ) is loaded into the receptacle cavity  274 , the spring fingers  284  engage the metal shield  216  (shown in  FIG. 2 ). 
     The spring fingers  284  are electrically connected to the metal shield  216  of the header assembly  202 . The receptacle assembly  204  may be electrically commoned with the header assembly  202  via the spring fingers  284 . Optionally, the spring fingers  284  may be at least partially deflected when the header assembly  202  is loaded into a receptacle cavity  274  such that the spring fingers  284  are biased against the metal shield  216 , thus ensuring electrical connection therebetween. Any number of spring fingers  284  may be provided. The spring fingers  284  may be located anywhere along the perimeter of the receptacle cavity  274 . In an exemplary embodiment, the spring fingers  284  are provided along the top, the bottom, and both sides of the receptacle cavity  274 . 
     The metal shield  256  includes a plurality of ground pins  288  extending from the bottom proximate to the sides and/or the back of the metal shield  256 . The ground pins  288  are configured to be received in plated vias in the circuit board  208  (shown in  FIG. 2 ). The ground pins  288  provide electrical continuity between the circuit board  208  and the metal shield  256 . The ground pins  288  provide mechanical securing of the metal shield  256  to the circuit board  208 , which may increase ruggedness of the receptacle assembly  204 . 
       FIG. 12  is an exploded perspective view of the header assembly  202 .  FIG. 13  is an assembled view of the header assembly  202 . The header connectors  210  are illustrated poised for loading into the metal shield  216 . The header connectors  210  may be substantially identical to the header connectors  110  (shown in  FIG. 1 ), such that the header connectors  210 ,  110  are interchangeable. 
     The housing  220  includes contact channels  224  extending entirely between the mating face  212  and the mounting face  214 . The header contacts  222  are received in corresponding channels  224 . Optionally, the header contacts  222  may be loaded through the mounting face  214 . Portions of the header contacts  222  extend from the mounting face  214  for mounting to the circuit board  206  (shown in  FIG. 2 ). The contact channels  224  are arranged in rows and columns. 
     In an exemplary embodiment, air pockets  226  are provided between the contact channels  224  in different columns. Optionally, air pockets may be provided between the rows of contact channels  224  in addition to, or in the alternative to, the air pockets  226  between the columns. The air pockets  226  extend entirely between the mating face  212  and the mounting face  214 . The air pockets  226  may be sized and shaped, and positioned, in proximity to the contact channels  224  to control an impedance of the header contacts  222  of the header connector  210 . 
     In an exemplary embodiment, the housing  220  includes a plurality of outer air pockets  228  arranged along the sides of the housing  220 . The outer air pockets  228  are open along the sides of the housing  220 . When the header connector  210  is stacked next to an adjacent header connector  210 , the outer air pockets  228  are aligned with one another and form a common air pocket that is sized and shaped substantially similar to the air pockets  226  that are internal to the housing  220 . 
     The housing  220  includes lips  230  at the top and bottom ends proximate to the mating face  212 . The lips  230  engage the metal shield  216 . The housing  220  include recesses  231  formed in the top and bottom ends thereof. The recesses  231  are open along the sides of the housing  220 . Additionally, the recesses  231  are open along the top or the bottom ends of the housing  220 . 
     The housing  220  includes alignment lugs  232  extending from the top and bottom ends proximate to the mating face  212 . The alignment lugs  232  help align the header connector  210  when mated with the receptacle connector  250  (shown in  FIG. 11 ). The alignment lugs  232  engage the metal shield  216 , which may secure the housings  220  within the metal shield  216 . The alignment lug  232  includes slots  233  formed within the sides of the alignment lug  232  between the alignment lug  232  and the top and bottom ends of the housing  220 . 
     Two different types of header connectors  210  are illustrated in  FIG. 12 , namely an end connector  234  and an interior connector  236 . Two end connectors  234  are loaded into the metal shield  216  to form the header assembly  202 . The end connectors  234  are rotated 180° with respect to one another. One or more interior connectors  236  may be provided between the end connectors  234 . The number of interior connectors  236  may be selected depending on particular application and the particular number of header contacts  222  that are needed for the particular application. Optionally, the header assembly  202  may not include any interior connectors  236 , but rather only include the two end connectors  234 . 
     The end connectors  234  have the lip  230  extending along three sides of the housing  220 , whereas the interior connectors  236  have the lip  230  extending only along the top and the bottom ends thereof. Additionally, the interior connectors  236  include outer air pockets  228  on both sides thereof, whereas the end connectors  234  include outer air pockets  228  only on one side thereof. The opposite side is generally flat. 
     The end connectors  234  include one recess  231  on the top end proximate to an interior side thereof and one recess  231  on the bottom end proximate to the interior side thereof. In contrast, the interior connectors  236  include two recesses  231  on the top end proximate to both sides thereof and two recesses  231  on the bottom end proximate to both sides thereof. 
     The metal shield  216  includes a plurality of walls  240  that define a shield chamber  242 . The ground pins  218  extend downwardly from the bottoms of the walls  240 . Any number of ground pins  218  may be provided. Optionally, the positioning of the ground pins  218  may be selected to correspond to a position of the header connectors  210  within the shield chamber  242 . For example, ground pins  218  may be aligned with certain ones of the header contacts  222 . For example, the ground pins  218  may be aligned with header contacts  222  that constitute signal contacts. Optionally, the header contacts  122  may be arranged within the housing  220  in a ground signal-signal ground pattern. However, because the housing  220  holds nine header contacts  222  within each column, the header contacts  222  may have a pattern that ends with a signal contact at the outermost row. In such cases, the ground pins  218  may be provided aligned within such column either below or above the header contact  222  ending as a signal contact. The ground pins  218  may he provided a predetermined distance from the header contact  222 . Optionally, the distance may be the same as the distances between each adjacent header contact  222  such that the contact pitch is maintained. 
     The metal shield  216  includes a plurality of tabs  244  extending therefrom. The tabs  244  are received in the space defined between the lip  230  and the housing  220 . The tabs  244  have a convex shape such that the tabs  244  bulge outward. When the header assembly  202  is loaded into the receptacle cavity  274  (shown in  FIG. 11 ) of the receptacle assembly  204  (shown in  FIG. 11 ) the tabs  244  engage the metal shield  256  (shown in  FIG. 11 ) of the receptacle assembly  204 . The tabs  244  may help hold the header connectors  210  within the shield chamber  242 . 
     The metal shield  216  includes a plurality of channels  246  formed therein. Protrusions  248  extend into each of the channels  246 . When the header connectors  210  are loaded into the shield chamber  242 , the alignment lugs  232  are received in the channels  246 . The protrusions  248  are received in the slots  233  defined between the alignment lugs  232  and the walls of the housing  220 . The protrusions  248  engage the housing  220  and/or the alignment lug  232  to secure the header connector  210  within the shield chamber  242 . For example, the protrusions  248  may engage the alignment lugs  232  in an interference fit. Other securing means and features may be provided in alternative embodiments to secure the header connectors  210  within the shield chamber  242 . 
     As shown in  FIG. 13 , when the header connectors  210  are loaded into the shield chamber  242 , the housings  220  abut against one another. The outer air pockets  128  of adjacent header connectors  210  are aligned with one another and cooperate to define a common air pocket. 
       FIG. 14  is an exploded rear perspective view of the receptacle assembly  304 . The receptacle assembly  304  constitutes a rugged receptacle assembly  304 . The shell  356  is included to provide the mechanical protection and/or electrical shielding. The shell  356  provides mechanical protection to the receptacle connectors  350 , such as protection from impact. The shell  356  adds stability to the receptacle assembly  304  by holding the individual receptacle connectors  350  together as well as by being secured to the circuit board  308  (shown in  FIG. 3 ) by board locks (e.g. fasteners through the circuit board  308  that engage the shell  356  to secure the shell  356  to the circuit board  308 ), which may make the receptacle assembly  304  more rugged, such as by resisting shock or vibration. 
     The receptacle connectors  350  are received within the shell  356 . Each receptacle connector  350  includes a plurality of contact modules  358  received in the housing  360 . The contact modules  358  may be substantially similar to the contact modules  158  (shown in  FIG. 4 ). The contact modules  358 ,  158  may be interchangeable, which reduces the overall part count of the connector family. 
     The shell  356  may be a machined metal piece or diecast metal piece that entirely circumferentially surrounds the receptacle connectors  350 . For example, the shell  356  may extend along the tops, the bottoms, the sides, and the back of the receptacle connectors  350 . In an exemplary embodiment, the shell  356  includes a back cover  380  that extends along the back of the receptacle connectors  350  once the receptacle connectors  350  are loaded into the receptacle cavity  374 . The back cover  380  holds the receptacle connectors  350  in the receptacle cavity  374 , which may add to the ruggedness of the receptacle assembly  304 . The back cover  380  may be secured using fasteners  382 , or other securing means or features in alternative embodiments. 
     Optionally, a portion of the bottom of the receptacle connector  350  may be open, wherein the shell  356  does not extend across such open portion. The mounting ends of the contact modules  358  are allowed to extend through the shell  356  for mating to the circuit board  308  (shown in  FIG. 3 ). Optionally, the shell  356  may extend across a portion of the bottom of the receptacle connectors  350 . For example, the portion below the housings  360  may have the shell  356  extending there along. 
     In the illustrated embodiment, three receptacle connectors  350  are provided, including opposite end connectors and an interior connector. Optionally, the end connectors and the interior connector may be substantially identical to one another, as such, different end connectors and interior connectors do not need to be provided, which reduces the overall part count. Alternatively, the end connectors may have different features than the interior connector. 
       FIG. 15  is a rear perspective view of the header assembly  302 , with one of the header connectors  310  poised for loading into the shell  316 . Optionally, each of the header connectors  310  may be identical to one another, as such, different end connectors and interior connectors do not need to be provided, which reduces the overall part count. The header connectors  310  may be substantially identical to the header connectors  110  (shown in  FIG. 1 ) or the header connectors  210  (shown in  FIG. 2 ), such that the header connectors  310  are interchangeable with the header connectors  110  or  210 . Alternatively, the header connectors  310  may have different features than the header connectors  110 ,  210 ; however the header assembly  302  may provide a substantially similar mating interface for intermatability. 
     The housing  320  includes contact channels  324  extending entirely between the mating face  312  and the mounting face  314 . The header contacts  322  are received in corresponding channels  324 . Optionally, the header contacts  322  may be loaded through the mounting face  314 . Portions of the header contacts  322  extend from the mounting face  314  for mounting to the circuit board  306  (shown in  FIG. 3 ). The contact channels  324  are arranged in rows and columns. 
     In an exemplary embodiment, air pockets  326  are provided between the contact channels  324  in different columns. Optionally, air pockets may be provided between the rows of contact channels  324  in addition to, or in the alternative to, the air pockets  326  between the columns. The air pockets  326  extend entirely between the mating face  312  and the mounting face  314 . The air pockets  326  may be sized and shaped, and positioned, in proximity to the contact channels  324  to control an impedance of the header contacts  322  of the header connector  310 . 
     In an exemplary embodiment, the housing  320  includes a plurality of outer air pockets  328  arranged along the sides of the housing  320 . The outer air pockets  328  are open along the sides of the housing  320 . When the header connector  310  is stacked next to an adjacent header connector  310 , the outer air pockets  328  are aligned with one another and form a common air pocket that is sized and shaped substantially similar to the air pockets  326  that are internal to the housing  320 . 
     The housing  320  includes shoulders  330  at the top and bottom ends proximate to the mounting face  314 . The shoulders  330  engage the shell  316  to position the housings  320  within the shell  316 . The housing  320  includes ribs  332  extending from the top and bottom ends. The ribs  332  help align the header connector  310  within the shell  316 . 
     The shell  316  includes a plurality of walls  340  that define a shell chamber  342 . The shell  316  includes a ledge  344  proximate to the mounting face  314 . The shoulders  330  rest on the ledge  344  to position the housing  320  within the shell chamber  342 . The shell  316  includes a plurality of outwardly extending alignment lugs  346  that are oriented and positioned similar to the alignment lugs  132  or  232  (shown in  FIGS. 1 and 2 , respectively), allowing intermatability of the header assembly  302  with the receptacle assemblies  104 ,  204  (shown in  FIGS. 1 and 2 , respectively). The alignment lugs  346  include board locks (e.g. threaded openings that receive threaded fasteners) to secure the shell  316  to the circuit board  306  (shown in  FIG. 3 ). 
       FIG. 16  illustrates a plastic header assembly  102  poised for mating with a shielded receptacle assembly  204 . When the receptacle assembly  204  is mated to the header assembly  102 , the header assembly  102  is received in the receptacle cavity  274 . The box-shaped header contacts  122  receive the receptacle contacts  262 . 
     The plastic header assembly  102  fits within the shielded receptacle assembly  204  in the same manner as the plastic header assembly  102  fits within the plastic receptacle assembly  104  (shown in  FIG. 1 ). The mating interfaces are substantially identical such that the plastic receptacle assembly  104  and the shielded receptacle assembly  204  are both configured to receive the plastic header assembly  102 . The metal shield  256  of the shielded receptacle assembly  204  provides shielding around the interfaces between the header contacts  122  and the receptacle contacts  262 . 
       FIG. 17  illustrates a plastic header assembly  102  poised for mating with a rugged receptacle assembly  304 . When the receptacle assembly  304  is mated to the header assembly  102 , the header assembly  102  is received in the receptacle cavity  374 . The box-shaped header contacts  122  receive the receptacle contacts  362 . 
     The plastic header assembly  102  fits within the rugged receptacle assembly  304  in the same manner as the plastic header assembly  102  fits within the plastic receptacle assembly  104  (shown in  FIG. 1 ). The mating interfaces are substantially identical such that the plastic receptacle assembly  104  and the rugged receptacle assembly  304  are both configured to receive the plastic header assembly  102 . The shell  356  of the rugged receptacle assembly  304  provides shielding around the interfaces between the header contacts  122  and the receptacle contacts  362 . 
       FIG. 18  illustrates a shielded header assembly  202  poised for mating with a plastic receptacle assembly  104 . When the receptacle assembly  104  is mated to the header assembly  202 , the header assembly  202  is received in the receptacle cavity  174 . The box-shaped header contacts  222  receive the receptacle contacts  162 . 
     The shielded header assembly  202  fits within the plastic receptacle assembly  104  in the same manner as the shielded header assembly  202  fits within the shielded receptacle assembly  204  (shown in  FIG. 2 ). The mating interfaces are substantially identical such that the plastic receptacle assembly  104  and the shielded receptacle assembly  204  are both configured to receive the shielded header assembly  202 . The metal shield  216  of the shielded header assembly  202  provides shielding around the interfaces between the header contacts  222  and the receptacle contacts  162 . 
       FIG. 19  illustrates a shielded header assembly  202  poised for mating with a rugged receptacle assembly  304 . When the receptacle assembly  304  is mated to the header assembly  202 , the header assembly  202  is received in the receptacle cavity  374 . The box-shaped header contacts  222  receive the receptacle contacts  362 . 
     The shielded header assembly  202  fits within the rugged receptacle assembly  304  in the same manner as the shielded header assembly  202  fits within the shielded receptacle assembly  204  (shown in  FIG. 2 ). The mating interfaces are substantially identical such that the rugged receptacle assembly  304  and the shielded receptacle assembly  204  are both configured to receive the shielded header assembly  202 . The metal shield  216  of the shielded header assembly  202 , as well as the metal shell  356  of the rugged receptacle assembly  304 , provides shielding around the interfaces between the header contacts  222  and the receptacle contacts  362 . 
       FIG. 20  illustrates a rugged header assembly  302  poised for mating with a plastic receptacle assembly  104 . When the receptacle assembly  104  is mated to the header assembly  302 , the header assembly  302  is received in the receptacle cavity  174 . The box-shaped header contacts  322  receive the receptacle contacts  162 . 
     The rugged header assembly  302  fits within the plastic receptacle assembly  104  in the same manner as the rugged header assembly  302  fits within the rugged receptacle assembly  304  (shown in  FIG. 3 ). The mating interfaces are substantially identical such that the plastic receptacle assembly  104  and the rugged receptacle assembly  304  are both configured to receive the rugged header assembly  302 . The shell  316  of the rugged header assembly  302  provides shielding around the interfaces between the header contacts  322  and the receptacle contacts  162 . 
       FIG. 21  illustrates a rugged header assembly  302  poised for mating with a shielded receptacle assembly  204 . When the receptacle assembly  204  is mated to the header assembly  302 , the header assembly  302  is received in the receptacle cavity  274 . The box-shaped header contacts  322  receive the receptacle contacts  262 . 
     The rugged header assembly  302  fits within the shielded receptacle assembly  204  in the same manner as the rugged header assembly  302  fits within the rugged receptacle assembly  304  (shown in  FIG. 3 ). The mating interfaces are substantially identical such that the shielded receptacle assembly  204  and the rugged receptacle assembly  304  are both configured to receive the rugged header assembly  302 . The shell  316  of the rugged header assembly  302 , as well as the metal shield  216  of the shielded receptacle assembly  204 , provides shielding around the interfaces between the header contacts  322  and the receptacle contacts  262 . 
     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.