Patent Publication Number: US-2023137275-A1

Title: Electrical connector having contact modules

Description:
BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to communication systems. 
     Communication systems use electrical connectors to electrically connect various components to allow data communication between the components. For example, in a backplane system, circuit board assemblies having electrical connectors mounted to circuit boards are mated to electrically connect the circuit boards. The system may include an equipment rack used to support the circuit board assemblies relative to each other. The circuit board assemblies may be mated at angles relative to each other leading to the mating interface being slightly offset or skewed, which can lead to improper mating of some of the contacts. Additionally, known rack mount circuit board backplane connectors typically need to absorb large dimensional tolerance accumulation of the relative distance between the circuit boards inserted from both sides of the equipment rack. Typical tolerance distances may be 1.5 mm or more. The contacts of the backplane connectors at the mating zone are sized to accommodate the circuit board mating tolerance distances. For example, the lengths of the contacts include the lengths required for mechanical mating and any designed contact wipe length plus the additional circuit board mating tolerance distance. The contacts have such length to accommodate the possible range of circuit board mating conditions. The additional length of the contacts is typically provided as an extension of the stub of the contact, which is the portion of the contact that extends past the mating point, to ensure that the contacts remain mated regardless of the circuit board positions. In high speed connectors, the stubs can significantly degrade the signal integrity performance of the connector. The electrical stub acts as a reflective element for energy that travels along the stub. When the energy travels back at certain combinations of signal wavelength (for example, frequency) and physical stub length, the stub can generate a null in transmitted energy at a specific frequency. When the stub is long enough, and the respective frequency low enough, the null is detrimental to the transmitted energy of the signal that reaches the receiver. 
     A need remains for electrical connectors of a communication system having improved mating for improved signal integrity performance. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, an electrical connector is provided and includes a connector housing having a mating end at a front of the connector housing configured to be mating with a mating electrical connector. The connector housing includes a contact module chamber. An electrical connector includes a stack of contact modules received in the contact module chamber. Each contact module includes a module body holding a plurality of contacts. The contacts have mating ends at the mating end of the connector housing for mating with the mating electrical connector; and an electrical connector includes a contact module biasing members between the contact modules and the connector housing to forward bias the contact modules in the contact module chamber, wherein the contact module biasing members are compressible to allow the contact modules to move independent from each other relative to the connector housing in the contact module chamber when mating with the mating electrical connector. 
     In another embodiment, a circuit board assembly includes a circuit board having a mounting surface. The circuit board has a mating edge and side edges extending from the mating edge to a rear edge. The circuit board has a board guide feature for locating the circuit board in an equipment rack; and a circuit board assembly includes an electrical connector mounted to the mounting surface of the circuit board at the mating edge. The electrical connector includes a connector housing having a mating end at a front of the connector housing configured to be mated with a mating electrical connector The connector housing includes a contact module chamber. The electrical connector includes a stack of contact modules received in the contact module chamber. Each contact module includes a module body holding a plurality of contacts. The contacts have mating ends at the mating end of the connector housing for mating with the mating electrical connector, and the electrical connector includes contact module biasing members between the contact modules and the connector housing to forward bias the contact modules in the contact module chamber, wherein the contact module biasing members are compressible to allow the contact modules to move independent from each other relative to the connector housing and the circuit board in the contact module chamber when mated with the mating electrical connector. 
     In a further embodiment, a communication system includes a first circuit board assembly including a first circuit board and a first electrical connector coupled to the first circuit board. The first electrical connector includes a first connector housing having a mating end at a front of the first connector housing, the first connector housing includes a first contact module chamber. The first electrical connector includes a stack of first contact modules received in the first contact module chamber. Each first contact module includes a first module body holding a plurality of first contacts. The first contacts have mating ends at the mating end of the first connector housing, and the first electrical connector include first contact module biasing members between the first contact modules and the first connector housing to forward bias the first contact modules in the first contact module chamber; and communication system includes a second circuit board assembly including a second circuit board and a second electrical connector coupled to the second circuit board. The second electrical connector has a second connector housing holding second contacts in a contact array. The second connector housing has a mating end coupled to the mating end of the first connector housing along a mating axis; communication system includes wherein the first contact module biasing members are compressible to allow the first module body and the first contacts of each first contact module to float independent from each other relative to the first connector housing in the first contact module chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of a communication system in accordance with an exemplary embodiment. 
         FIG.  2    is a top perspective view of the communication system in accordance with an exemplary embodiment. 
         FIG.  3    is a rear perspective view of the communication system in accordance with an exemplary embodiment. 
         FIG.  4    is a perspective view of a portion of the communication system showing the mating interface of the first circuit board assembly in accordance with an exemplary embodiment. 
         FIG.  5    is a perspective view of a portion of the communication system showing the mating interface of the second circuit board assembly in accordance with an exemplary embodiment. 
         FIG.  6    is a partial sectional view of the second electrical connector in accordance with an exemplary embodiment. 
         FIG.  7    is a schematic view of the first electrical connector mated with the second electrical connector in accordance with an exemplary embodiment. 
         FIG.  8    is a schematic view of the first electrical connector mated with the second electrical connector in accordance with an exemplary embodiment 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG.  1    is a schematic view of a communication system  100  in accordance with an exemplary embodiment. The communication system  100  includes a first circuit board assembly  200  and a second circuit board assembly  300  electrically coupled together. In various embodiments, the communication system  100  may be a server or network switch. In other various embodiments, the communication system  100  may be a backplane system. The first circuit board assembly  200  and/or the second circuit board assembly  300  may be a backplane assembly. The first circuit board assembly  200  and/or the second circuit board assembly  300  may be a daughtercard assembly. The first circuit board assembly  200  and/or the second circuit board assembly  300  may be a motherboard assembly. 
     In an exemplary embodiment, the first circuit board assembly  200  and/or the second circuit board assembly  300  includes a compressible mating interface to take up mating tolerance for the communication system  100 . For example, portions of the connectors of the first circuit board assembly  200  and/or the second circuit board assembly  300  may be spring loaded or otherwise compressible. Optionally, the first circuit board assembly  200  and/or the second circuit board assembly  300  may include a spring loaded connector configured to be compressed in the mating direction. 
     In an exemplary embodiment, the communication system  100  includes an equipment rack  110  used to hold the first circuit board assembly  200  and/or the second circuit board assembly  300 . The equipment rack  110  includes frame members  112  forming one or more chambers for the first circuit board assembly  200  and/or the second circuit board assembly  300 . In the illustrated embodiment, the equipment rack  110  includes a front chamber  120  configured to receive the first circuit board assembly  200  and a rear chamber  130  configured to receive the second circuit board assembly  300 . Optionally, multiple circuit board assemblies may be received in the front chamber  120  and/or the rear chamber  130 . The equipment rack  110  may be open at the front and/or the rear and/or the sides. Alternatively, the equipment rack  110  may include walls or panels (not shown) that close the chambers  120 ,  130  at the front and/or the rear and/or the sides. The equipment rack  110  may include horizontally oriented trays or platforms that divide the chambers  120 ,  130  into stacked sub-chambers each receiving a corresponding circuit board assembly. The equipment rack  110  may include vertically oriented divider walls that divide the chambers  120 ,  130  into adjacent sub-chambers each receive a corresponding circuit board assembly. 
     In an exemplary embodiment, the equipment rack  110  includes front guide elements  122  in the front chamber  120 . The front guide elements  122  are used to guide the first circuit board assembly  200  into the front chamber  120 . The front guide elements  122  may locate the first circuit board assembly  200  relative to the equipment rack  110 , such as for mating with the second circuit board assembly  200 . In an exemplary embodiment, the front guide elements  122  are rails or tracks having a slot or groove that receive the first circuit board assembly  200 . Other types of guide elements may be used in alternative embodiments, such as tabs, pins, posts, openings, sockets, and the like. 
     In an exemplary embodiment, the equipment rack  110  includes rear guide elements  132  in the rear chamber  130 . The rear guide elements  132  are used to guide the second circuit board assembly  300  into the rear chamber  130 . The rear guide elements  132  may locate the second circuit board assembly  300  relative to the equipment rack  110 , such as for mating with the first circuit board assembly  200 . In an exemplary embodiment, the rear guide elements  132  are rails or tracks having a slot or groove that receive the second circuit board assembly  300 . Other types of guide elements may be used in alternative embodiments, such as tabs, pins, posts, openings, sockets, and the like. 
     During assembly, the first circuit board assembly  200  is loaded into the front chamber  120  through the front end and the second circuit board assembly  300  is loaded into the rear chamber  130  through the rear end. The first and second circuit board assemblies  200 ,  300  are mated within the equipment rack  110 , such as at the center of the equipment rack  110 . The first and second circuit board assemblies  200 ,  300  slide into and out of the equipment rack  110 , such as along the guide elements  122 ,  132 . In the illustrated embodiment, the first and second circuit board assemblies  200 ,  300  are oriented perpendicular to each other. For example, the first circuit board assembly  200  is oriented vertically and the second circuit board assembly  300  is oriented horizontally, or vice versa. In other various embodiments, the first and second circuit board assemblies  200 ,  300  are oriented parallel to each other. For example, the first and second circuit board assemblies  200 ,  300  may both be oriented vertically. Alternatively, the first and second circuit board assemblies  200 ,  300  may both be oriented horizontally. 
     The first circuit board assembly  200  includes a first circuit board  210  and a first electrical connector  250  coupled to the first circuit board  210 . The first electrical connector  250  is configured to be mated with the second circuit board assembly  300 . Optionally, the first electrical connector  250  is a floating connector, wherein the first electrical connector  250  is movable relative to the first circuit board  210 . The first electrical connector  250  may be moved when mated with the second circuit board assembly  300 . For example, the housing of the first electrical connector  250  may be compressible and movable relative to the first circuit board  210  and/or the contact modules of the first electrical connector  250  may be compressible and movable within the housing to define a compressible mating interface. In various embodiments, the first electrical connector  250  may be a fixed connector, wherein the first electrical connector  250  is fixed relative to the first circuit board  210 , but the contact modules may be movable and compressed when mated with the second circuit board assembly  300 . The movable contact modules may accommodate angled or offset mating. 
     The second circuit board assembly  300  includes a second circuit board  310  and a second electrical connector  350  coupled to the second circuit board  310 . The second electrical connector  350  is configured to be mated with the first electrical connector  250  of the first circuit board assembly  200 . Optionally, the second electrical connector  350  may be a floating connector, wherein the second electrical connector  350  is movable relative to the second circuit board  310 . The second electrical connector  350  may be moved when mated with the second circuit board assembly  300 . For example, the housing of the second electrical connector  350  may be compressible and/or the contact modules of the second electrical connector  350  may be compressible and movable within the housing to define a compressible mating interface. In various embodiments, the second electrical connector  350  may be a fixed connector, wherein the second electrical connector  350  is fixed relative to the second circuit board  310 , but the contact modules may be movable and compressed when mated with the first electrical connector  250 . The movable contact modules may accommodate angled or offset mating. 
       FIG.  2    is a top perspective view of the communication system  100  in accordance with an exemplary embodiment.  FIG.  3    is a rear perspective view of the communication system  100  in accordance with an exemplary embodiment.  FIG.  2    shows the first electrical connector  250  as a cable connector and the second electrical connector  350  as a board connector. The first electrical connector  250  is a floating connector and the second electrical connector  350  is a fixed connector.  FIG.  3    shows the first electrical connector  250  as a cable connector and the second electrical connector  350  as a cable connector. The first electrical connector  250  is a floating connector and the second electrical connector  350  is a fixed connector. In alternative embodiments, the second electrical connector  350  may be a floating connector. 
     In the illustrated embodiments, the communication system  100  includes multiple front circuit board assemblies  200  and multiple rear circuit board assemblies  300 ; however, the communication system  100  may include a single front circuit board assembly  200  and/or a single rear circuit board assembly  300 . In the illustrated embodiment, the circuit board  210  has a single electrical connector  250  and the circuit board  310  has a single electrical connector  350 ; however, the circuit board  210  may include multiple electrical connectors  250  and/or the circuit board  310  may include multiple electrical connectors  350 . 
     The first circuit board  210  includes a mating edge  212  at a front of the first circuit board  210  and side edges  214 ,  216  extending between the mating edge  212  and a rear edge  218 . The first circuit board  210  is rectangular in the illustrated embodiment. The first circuit board  210  may have other shapes in alternative embodiments. The circuit board  210  includes first and second surfaces  220 ,  222  (for example, upper and lower surfaces). The first electrical connector  250  is mounted to the first surface  220  of the circuit board  210  at a mounting area  224 . Optionally, the mounting area  224  may be located proximate to the mating edge  212 . One or more electrical connectors may additionally or alternatively be located at the second surface  222 . 
     In an exemplary embodiment, the first circuit board  210  includes one or more electrical components  226  coupled to the first circuit board  210 . The electrical components  226  may be chips, integrated circuits, processors, memory modules, electrical connectors or other components. The electrical components  226  may be electrically connected to the circuit board  210 , such as through traces, pads, vias or other circuits. In an exemplary embodiment, the electrical components  226  are electrically connected to the first electrical connector  250 , such as through the first circuit board  210  or by direct connection through the cables. 
     The first circuit board  210  includes one or more board guide features  230  for locating the circuit board  210  in the equipment rack  110  (shown in  FIG.  1   ). The board guide features  230  are configured to be coupled to the corresponding guide elements  122  (shown in  FIG.  1   ). In the illustrated embodiment, the board guide features  230  are defined by the edges of the circuit board  210  along the side edges  214 ,  216 , which are configured to slide into grooves of the track defining the guide elements  122 . Other types of guide features may be used in alternative embodiments, such as rails, slots tabs, pins, and the like. 
     In an exemplary embodiment, the first circuit board assembly  200  includes latching features  232  at the rear edge  218 . The latching features  232  are used to secure the first circuit board assembly  200  to the equipment rack  110 . The latching features  232  may be used to press the circuit board  210  forward (toward the second circuit board  310 ) during mating or may be used to pull the circuit board  210  rearward during unmating. 
     In an exemplary embodiment, the first circuit board assembly  200  includes a first connector mount  240 . The first connector mount  240  includes a bracket  242  and one or more biasing members  244  coupled to the bracket  242  and the electrical connector  250 . The biasing members  244  forward bias the electrical connector  250  for mating with the second electrical connector  350 . In an exemplary embodiment, the biasing members  244  are springs, such as coil springs. Other types of biasing members may be used in alternative embodiments, such as compressible foam members. The biasing members  244  allow the electrical connector  250  to move relative to the circuit board  210 , such as during mating with the second electrical connector  350 . The biasing members  244  provide compressive forces for maintaining mechanical and electrical connection between the first and second electrical connectors  250 ,  350 . The biasing members  244  accommodate the mating tolerances between the circuit board assemblies  200 ,  300  within the equipment rack  110 . For example, the circuit board  210  may have a positional range within the equipment rack  110  (for example, position of the mating edge  212  within the equipment rack  110  may vary by approximately 1.5 mm). The biasing members  244  may accommodate some or all of the mating dimensional tolerance distance (for example, approximately 1.5 mm) of the circuit board  210  in the equipment rack  110 . In an exemplary embodiment, the electrical connector  250  may include compliance features to allow further floating movement at the mating interface to accommodate the mating tolerances. For example, the contact modules of the electrical connector  250  may be movable relative to the connector housing, such as in the mating direction, to accommodate the mating tolerances. The contact modules of the electrical connector  250  may be movable relative to the connector housing to accommodate angular tolerance, such as a situation where the circuit boards  210 ,  310  are mated askew (for example, at an angle). 
     The second circuit board  310  includes a mating edge  312  at a front of the second circuit board  310  and side edges  314 ,  316  extending between the mating edge  312  and a rear edge  318 . The mating edge  312  faces the mating edge  212  of the first circuit board  210 . The circuit board  310  includes first and second surfaces  320 ,  322  (for example, left side and right side). The second electrical connector  350  is mounted to the first surface  320  of the circuit board  310  at a mounting area  324 . Optionally, the mounting area  324  may be located proximate to the mating edge  312 . One or more electrical connectors may additionally or alternatively be located at the second surface  322 . 
     In an exemplary embodiment, the second circuit board  310  includes one or more electrical components  326  coupled to the second circuit board  310 . The electrical components  326  may be chips, integrated circuits, processors, memory modules, electrical connectors or other components. The electrical components  326  may be electrically connected to the circuit board  310 , such as through traces, pads, vias or other circuits. In an exemplary embodiment, the electrical components  326  are electrically connected to the second electrical connector  350 , such as through the second circuit board  310  or by direct connection through cables. 
     The second circuit board  310  includes one or more board guide features  330  for locating the circuit board  310  in the equipment rack  110  (shown in  FIG.  1   ). The board guide features  330  are configured to be coupled to the corresponding guide elements  132  (shown in  FIG.  1   ). In the illustrated embodiment, the board guide features  330  are defined by the edges of the circuit board  310  along the side edges  314 ,  316 , which are configured to slide into grooves of the track defining the guide elements  132 . Other types of guide features may be used in alternative embodiments, such as rails, slots tabs, pins, and the like. In an exemplary embodiment, the electrical connector  350  may include compliance features to allow floating movement at the mating interface to accommodate mating tolerances. For example, the contact modules of the electrical connector  350  may be movable relative to the connector housing, such as in the mating direction, to accommodate the mating tolerances. The contact modules of the electrical connector  350  may be movable relative to the connector housing to accommodate angular tolerance, such as a situation where the circuit boards  210 ,  310  are mated askew (for example, at an angle). 
     In an exemplary embodiment, the second circuit board assembly  300  includes latching features  332  at the rear edge  318 . The latching features  332  are used to secure the second circuit board assembly  300  to the equipment rack  110 . The latching features  332  may be used to press the circuit board  310  forward (toward the first circuit board  210 ) during mating or may be used to pull the circuit board  310  rearward during unmating. 
       FIG.  4    is a perspective view of a portion of the communication system  100  showing the mating interface of the first circuit board assembly  200  in accordance with an exemplary embodiment.  FIG.  5    is a perspective view of a portion of the communication system  100  showing the mating interface of the second circuit board assembly  300  in accordance with an exemplary embodiment. In an exemplary embodiment, the first electrical connector  250  is a receptacle connector and the second electrical connector  350  is a header connector. However, in an alternative embodiment, the first electrical connector  250  is a header connector and the second electrical connector  350  is a receptacle connector. Other types of connectors may be used in alternative embodiments. In an exemplary embodiment, the first circuit board assembly  200  has a compressible mating interface in the illustrated embodiment (for example, the contacts are movable relative to the housing during mating). The second circuit board assembly  300  has a fixed mating interface in the illustrated embodiment (for example, the contacts are fixed relative to the housing during mating). However, the second circuit board assembly  300  may have a compressible mating interface (for example, the contacts are movable relative to the housing during mating). 
     The first electrical connector  250  includes a connector housing  252  holding first contacts  254  ( FIG.  4   ) in a contact array. In various embodiments, the contacts  254  may be arranged together in first contact modules  256 , also known as chicklets, which may be overmolded leadframes. In an exemplary embodiment, the first contact modules  256  are movably coupled to the connector housing  252 . For example, the contact modules  256  may be movable independently from each other relative to the connector housing  252  to form a flexible mating interface. In an exemplary embodiment, contact module biasing members are provided between the contact modules  256  and the connector housing  252  to allow independent movement of the contact modules  256 . The connector housing  252  includes a mating end  258  configured to be mated with the second electrical connector  350 . The mating end  258  is at the front of the connector housing  252 . The contacts  254  are exposed at the mating end  258  for mating with corresponding contacts of the second electrical connector  350 . 
     In the illustrated embodiment, the first electrical connector  250  is a cable connector having a plurality of first cables  260  extending from the connector housing  252 . The connector housing  252  includes a cable end  262 . The cables  260  extend from the cable end  262 . In the illustrated embodiment, the cable end  262  is opposite the mating end  258 ; however, other orientations are possible in alternative embodiments, such as being a right angle connector with the cable end  262  perpendicular to the mating end  258 . The cables  260  may be individual cables  260 , such as coaxial cables or twin axial cables. In other embodiments, the cables  260  may be flat, flexible cables, such as flex circuits. The cables  260  are electrically connected to corresponding contacts  254 . For example, the cables  260  form parts of the contact modules  256  and are connected to the contacts  254  within the contact modules  256 . The cables  260  extend from the contact modules  256 . The cables  260  are flexible to allow movement of the first electrical connector  250  relative to the connector housing  252  and the first circuit board  210 . 
     The first electrical connector  250  is configured to be mated with the second electrical connector  350  in a mating direction (along a mating axis  264 ). The mating end  258  may be perpendicular to the mating axis  264 . In an exemplary embodiment, the first electrical connector  250  is movable in a direction parallel to the mating axis  264 . For example, the first electrical connector  250  may be pressed rearward during mating. In an exemplary embodiment, the contact modules  256  are movable within the connector housing  252  in the mating direction (for example, along the mating axis  264 ). For example, the contact modules  256  may be spring biased relative to the connector housing  252 . 
     In an exemplary embodiment, the connector housing  252  includes one or more mounting features  266 . The mounting features  266  may be tabs or ears extending from one or more sides of the connector housing  252 . The mounting features  266  may be coupled to the connector mount  240 , such as to the bracket  242 . In an exemplary embodiment, the biasing members  244  are coupled to the mounting features  266 . The biasing members  244  may press the mounting features  266  forward against the bracket  242 . The bracket  242  operates as a forward stop for the connector housing  252 . The bracket  242  positions the first electrical connector  250  for mating with the second electrical connector  350 . 
     The contacts  254  are provided at the mating end  258  for mating with the second electrical connector  350 . In an exemplary embodiment, the connector housing  252  includes contact channels  257  at the mating end  258 , including both signal channels and ground channels. The ground channels hold ground contacts or ground shields, which provide electrical shielding for the contacts  254 . In the illustrated embodiment, the ground channels are C-shaped. 
     In an exemplary embodiment, the contacts  254  are stamped and formed contacts. The contacts  254  have a metal body extending between a mating end  272  and a terminating end (not shown) opposite the mating end. In an exemplary embodiment, conductors of the cables  260  are terminated to the terminating end of the corresponding contacts  254 . For example, the terminating end may include a solder pad, a crimp barrel, an insulation displacement termination, or another type of electrical termination. The contacts  254  may be movable relative to the connector housing  252 , such as when the contact modules  256  are moved relative to the connector housing  252 . In alternative embodiments, rather than being terminated to the cables  260 , the terminating ends of the contacts  254  may be terminated directly to the circuit board  210 , such as being soldered or press fit into plated vias of the circuit board  210 . In such embodiment, the first electrical connector  250  may be fixed relative to the circuit board  210 . 
     The mating end  272  of each contact  254  includes a mating interface configured to be electrically connected to the corresponding contact of the second electrical connector  350 . The mating ends  272  of the contacts  254  are arranged in the contact channels for mating with the second electrical connector  350 . In an exemplary embodiment, the mating ends  272  include sockets (such as split beam contacts). Other contact types can be used in alternative embodiments, such as pads, pins, sockets, and the like. In an exemplary embodiment, the mating end  272  has a short electrical length downstream of the mating interface (for example, the curved ends of the beams forming stubs beyond the mating interfaces), leading to a short electrical stub. In an exemplary embodiment, because the first electrical connector  250  is able to float relative to the first circuit board  210 , the mating ends  272  of the contacts  254  may have short mechanical stubs. For example the lengths of the mechanical stubs beyond the mating interfaces may be very short (for example, less than 1.0 mm) as the mating ends  272  do not need to accommodate for the tolerance of the circuit board mating. In an exemplary embodiment, because the contact modules  256  are able to float relative to the connector housing  252 , the mating ends  272  of the contacts  254  may be very short as the mating ends  272  can accommodate at least some of the tolerance of the circuit board mating as such tolerance is accommodated by the spring loaded, floating movement of the electrical connector  250  (for example, as provided by the biasing members  244 ). The length of the stub at the mating end  272  may be short enough to just accommodate mechanical mating plus any contact wipe, but does not need to accommodate any circuit board mating tolerance. 
     The second electrical connector  350  includes a connector housing  352  holding second contacts  354  ( FIG.  5   ) in a contact array. In various embodiments, the contacts  354  may be arranged together in second contact modules  356 , also known as chicklets, which may be overmolded leadframes. The connector housing  352  includes a mating end  358  configured to be mated with the first electrical connector  250 . The mating end  358  is at the front of the connector housing  352  (facing the mating end  258  of the first electrical connector  250 ). The second contacts  354  are exposed at the mating end  358  for mating with the first contacts  254 . 
     In various embodiments, the second electrical connector  350  is a cable connector having cables (not shown) extending from the contact modules  356 . The contact modules  356  may be movable within the connector housing  352  in the mating direction (for example, along the mating axis  264 ). For example, the contact modules  356  may be spring biased relative to the connector housing  352 . In other various embodiments, the second electrical connector  350  is a board connector configured to be mounted directly to the second circuit board  310 . The connector housing  352  includes a mounting end mounted to the second circuit board  310 . In the illustrated embodiment, the second electrical connector  350  is a right-angle connector having the mounting end perpendicular to the mating end  358 ; however, other orientations are possible in alternative embodiments. The connector housing  352  may include mounting features for mounting the connector housing  352  to the circuit board  310 , such as mounting lugs that receive threaded fasteners, press tabs, solder tabs, and the like. Alternatively, the contacts  354  may be used to mount the second electrical connector  350  to the circuit board  310 , such as using press fit pins. 
     The second electrical connector  350  is configured to be mated with the first electrical connector  250  in the mating direction along the mating axis  264 . In an exemplary embodiment, the second electrical connector  350  is a header connector. The second electrical connector  350  includes shroud walls forming a reception space for the first electrical connector  250 . In an exemplary embodiment, the first electrical connector  250  (and/or the second electrical connector  350 ) may be pressed rearward during mating as the second circuit board assembly  300  is loaded into the equipment rack  110 . The first contact modules  256  (and/or the second contact modules  356 ) may be pressed rearward during mating as the second circuit board assembly  300  is loaded into the equipment rack  110 . The movement of the electrical connectors  250 ,  350  and/or the movement of the contact modules  256 ,  356  allows the contacts  254 ,  354  to be relatively short as the contacts  254 ,  354  do not need to accommodate for the circuit board mating tolerance, which may be approximately 1.5 mm, meaning that the first contacts  254  and/or the second contacts  354  may be shortened, such as by approximately 1.5 mm, compared to other systems. 
     The contacts  354  are provided at the mating end  358  for mating with the first electrical connector  250 . In an exemplary embodiment, the contacts  354  are stamped and formed contacts. The contacts  354  have a metal body extending between a mating end  372  and a terminating end (not shown) opposite the mating end  372 . In an exemplary embodiment, the terminating ends of the contacts  354  may be terminated directly to the circuit board  310 , such as being soldered or press fit into plated vias of the circuit board  310 . Alternatively, the contacts  354  may be terminated to cables rather than directly to the circuit board  310 . The contacts  354  may be movable relative to the connector housing  352 , such as when the contact modules  356  are moved relative to the connector housing  352 . 
     The mating end  372  of each second contact  354  includes a mating interface configured to be electrically connected to the first contact  254 . In the illustrated embodiment, the mating ends  372  include pins. The pins may be arranged in pairs. Other contact types can be used in alternative embodiments, such as pads, spring beams, sockets, and the like. In an exemplary embodiment, the second electrical connector  350  includes ground contacts  374  providing electrical shielding for the pins. The ground contacts  374  are C-shaped in the illustrated embodiment. 
     In an exemplary embodiment, the mating end  372  has a short electrical length downstream of the mating interface, leading to a short electrical stub. In an exemplary embodiment, because the first electrical connector  250  is able to float (press rearward) when mated with the first electrical connector  250 , the mating ends  372  of the contacts  354  are very short as the mating ends  372  do not need to accommodate the tolerance of the circuit board mating as such tolerance is accommodated by the spring loaded, floating movement of the first electrical connector  250 . In an exemplary embodiment, when the contact modules  356  are able to float (press rearward) when mated with the first electrical connector  250 , the mating ends  372  of the contacts  354  are very short as the mating ends  372  do not need to accommodate the tolerance of the circuit board mating as such tolerance is accommodated by the floating movement of the contact modules  356 . The length of the stub at the mating end  372  may be short enough to just accommodate mechanical mating plus any contact wipe, but does not need to accommodate any circuit board mating tolerance. 
     The floating mating interface provided by the connector mounts and/or the contact modules  256 ,  356  absorbs the circuit board mating tolerance (for example, absorbs 1.5 mm mating tolerance or more). The floating mating interface eliminates the need for the contact interface to be able to absorb the large rack mating tolerances allowing the use of contacts having short stubs. The stubs at the ends of the contacts  254  and/or  354  may be shortened (for example, less than 1.0 mm), which improves the performance of the communication system  100  by improving the signal integrity along the signal paths. The performance, particularly at high speeds (for example, above 100 Gbps and more particularly, above 200 Gbps) is improved compared to contacts having long electrical stubs. 
       FIG.  6    is a partial sectional view of the second electrical connector  350  in accordance with an exemplary embodiment.  FIG.  6    shows one of the contact modules  356  coupled to the connector housing  352 . In the illustrated embodiment, the second electrical connector  350  is a cable connector having cables  360  coupled to the contacts  354  and extending from the contact modules  356 . In the illustrated embodiment, the contact modules  356  are movable relative to the connector housing  352 . The contact modules  356  may float within the connector housing  352  when mated with the first electrical connector  250  (shown in  FIG.  4   ) independently from each other. 
     The connector housing  352  has a plurality of walls  380  forming a contact module chamber  382 . For example, the walls  380  may include side walls, an upper wall, a lower wall, a front wall, a rear wall, or other walls. The contact module chamber  382  receives the stack of contact modules  356 . Optionally, the front portion of the contact module chamber  382  may receive the first electrical connector  250  (shown in  FIG.  4   ). In various embodiments, the walls  380  may include internal walls, such as divider walls that divide the contact module chamber  382  into channels receiving corresponding contact modules  356 . The connector housing  352  may include latching features  384  for securing the contact modules  356  in the contact module chamber  382 . In an exemplary embodiment, the connector housing  352  includes one or more locating feature  386  for locating the contact modules  356  in the chamber  382 . The locating features  386  are located in the chamber  382 . In the illustrated embodiment, the locating features  386  are tabs extending from the upper and lower walls into the chamber  382 . The locating features  386  may be located proximate to the rear of the connector housing  352 . The locating features  386  may be parts of the divider walls defining the channels. 
     In an exemplary embodiment, the second contact module  356  is an overmolded leadframe. For example, a leadframe having a plurality of signal conductors is overmolded by a dielectric module body  390 . The signal conductors form the contacts  354 . The contacts  354  may be arranged in pairs. 
     In an exemplary embodiment, the second contact module  356  includes one or more ground shields  392  coupled to the side(s) of the second contact module  356 . The ground shield  392  may be a stamped and formed shield. The ground shield  392  provides electrical shielding for the second contact module  356 . The ground shield  392  includes the ground contacts  374  at the front. The ground contacts  374  may be integral with the ground shield  392 . Alternatively, the ground contacts  374  may be separate and coupled to the ground shield  392 . 
     In an exemplary embodiment, the electrical connector  350  includes contact module biasing members  400  between the contact modules  356  and the connector housing  352 . The contact module biasing members  400  forward bias the contact modules  356  in the contact module chamber  382 . The contact module biasing members  400  are compressible to allow the contact modules  356  to move independent from each other relative to the connector housing  352 . For example, when the first electrical connector  250  is coupled to the second electrical connector  350  the contact modules  356  may be pressed rearward against the spring forces of the contact module biasing members  400 . In an exemplary embodiment, the contact modules  356  are slidable in a sliding direction parallel to the mating direction with the first electrical connector  250  against the spring forces of the contact module biasing members  400 . 
     In various embodiments, the contact module biasing members  400  extend along one or both sides of the contact module  356  such that the contact module biasing members  400  are located between adjacent contact modules  356 . In other various embodiments, the contact module biasing members extend along tops and/or bottoms of the contact modules  356  to engage the upper wall or the lower wall, respectively, of the connector housing  352 . 
     In an exemplary embodiment, the contact module biasing members  400  are integral with the contact modules  356 . For example, the contact module biasing members  400  are stamped and formed with the ground shields  392 . In an exemplary embodiment, the contact module biasing members  400  include deflectable springs. Each contact module biasing member  400  includes a fixed end  402  and a free end  404  at the distal end of the contact module biasing member  400  opposite the fixed end  402 . The fixed end  402  defines a base  406  of the contact module biasing member  400 . The base  406  extends from the ground shield  392 . For example, the base  406  may be bent or folded from the ground shield  392 , such as perpendicular to the ground shield  392 . The contact module biasing member  400  includes a spring arm  408  between the ends  402 ,  404 . The spring arm  408  is cantilevered from the base  406 . The spring arm  408  extends from the ground shield  392  to the free end  404 . The free end  404  is configured to engage the connector housing  352 , such as the corresponding locating feature  386 . The free end  404  engages the connector housing  352  to position the contact modules  356  relative to the connector housing  352 . In an exemplary embodiment, the contact module  356  includes multiple contact module biasing members  400 . For example, the contact module  356  includes an upper spring arm  408   a  and a lower spring arm  408   b.  The upper spring arm  408   a  engages the upper locating feature  386   a  and the lower spring arm  408   b  engages the lower locating feature  386   b.    
     When assembled, the contact modules  356  are held in the connector housing  352 . The contact module biasing members  400  forward bias the contact modules  356  in the chamber  382 . During mating, the contact modules  356  are slidable in the sliding direction (for example, rearward). As the contact modules  356  are moved rearward, the spring arms  408  are flexed creating spring forces that tend to press the contact modules  356  forward. The spring force may be based on the size of the spring arm  404  (for example, height, width, thickness). In an exemplary embodiment, the spring force may be greater than a mating force (for example, wiping contact force) between the first and second contacts  254 ,  354  such that the contact modules  356  do not move during mating. In such embodiments, the contact modules  356  move relative to the connector housing  352  during an over-mating condition. For example, the over-mating may occur during the final loading or locking of the first and second circuit boards  210 ,  310  in the equipment rack  110 . The contact modules  356  may be compressible in the rearward sliding direction to accommodate the final travel of the first and second circuit boards  210 ,  310 , such as the 1.5 mm mating tolerance. 
       FIG.  7    is a schematic view of the first electrical connector  250  mated with the second electrical connector  350  in accordance with an exemplary embodiment.  FIG.  7    illustrates the first and second electrical connectors  250 ,  350  mated at a skew angle  364  relative to the mating axis  264 . The skew angle  364  is non-perpendicular to the mating axis  264 . When mated at the skew angle, the contact modules  356  are movable within the connector housing  352  to accommodate the angled mating interface. For example, the contact modules  356  are independently movable relative to the connector housing  352  such that the contact modules  356  may be compressed different distances when mated with the first electrical connector  250 . In the illustrated embodiment, the contact modules  356  on the left side are compressed further than the contact modules  356  on the right side. For example, the front of the module body  390  of the left side contact module  356   a  is located a first distance  410  from the front of the connector housing  352  and the front of the module body  390  of the right side contact module  356   b  is located a second distance  412  from the front of the connector housing  352 . The second distance  412  is different than the first distance  410 . 
       FIG.  8    is a schematic view of the first electrical connector  250  mated with the second electrical connector  350  in accordance with an exemplary embodiment.  FIG.  8    illustrates the first electrical connector  250  having movable contact modules  256  and the second electrical connector  350  having movable contact modules  356 . In the illustrated embodiment, the first electrical connector  250  includes a biasing device  420  coupled to the connector housing  252 . The biasing device  420  includes contact module biasing members  422  extending from a base  424 . The contact module biasing members  422  engage the corresponding contact modules  256  to forward bias the contact modules  256 . The contact module biasing members  422  have spring arms  426  with distal ends  428  configured to engage the contact modules  256 . The contact module biasing members  422  may engage the sides of the contact modules  256 . Alternatively, the contact module biasing members  422  may engage the tops and/or the bottoms of the contact modules  256 . In the illustrated embodiment, the second electrical connector  350  includes a biasing device  430  coupled to the connector housing  352 . The biasing device  430  includes contact module biasing members  432  extending from a base  434 . The contact module biasing members  432  engage the corresponding contact modules  356  to forward bias the contact modules  356 . The contact module biasing members  432  have spring arms  436  with distal ends  438  configured to engage the contact modules  356 . The contact module biasing members  432  may engage the sides of the contact modules  356 . Alternatively, the contact module biasing members  432  may engage the tops and/or the bottoms of the contact modules  356 . 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.