Abstract:
An electrical connector assembly is provided for that includes two groups of circuit boards that mate with, or connect to, one another in an orthogonal, or non-parallel manner. The electrical connector includes a plurality of circuit boards; a first connector housing including channels adapted to retain the first group of the circuit boards; a second connector housing also including channels adapted to retain the second group of the circuit boards; and a board interface located between the first and second connector housing. The board interface is formed as part of one of the first and second connector housings. The board interface includes opposing mating faces of the first and second groups of circuit boards that join the first group of circuit boards in a non-parallel relationship to the second group of circuit boards. Preferably, the circuit boards are joined orthogonally. The first connector housing may be a header, while the second connector housing may be a plug, or vice versa. Each circuit board includes signal and ground contacts along an edge joining the board interface. The signal contacts on one circuit board in the first group of circuit boards electrically engage the signal contacts on at least two circuit boards in the second group of circuit boards, and vice versa.

Description:
BACKGROUND OF THE INVENTION 
     A preferred embodiment of the present invention generally relates to improvements in electrical connectors that connect printed circuit boards to one another and more particularly relates to electrical connectors that orthogonally connect, or mate, printed circuit boards. 
     Various electronic systems, such as computers, comprise a wide array of components mounted on printed circuit boards, such as daughterboards and motherboards that are interconnected to transfer signals and power throughout the systems. The transfer of signals and power between the circuit boards requires electrical connectors between the circuit boards that are typically through a backplane. The backplane supports part of an electrical connector that joins the two circuit boards. 
     Typically, a backplane is a printed circuit board that mounts into a server and communication switches. Multiple daughter cards are plugged into the backplane. One circuit board connects to another circuit board via connectors held in the backplane. Hence, in the past, in order for one circuit board to connect to another circuit board, a backplane was required as a conduit there between. As more circuit boards are required, more connections are required with the backplane. Generally, the circuit boards are aligned in parallel, such as a common plane or in parallel planes. The common parallel or planar alignment of multiple circuit boards is, in part, due to the need to afford a space-efficient and good signal quality connection with the backplane. 
     However, connecting circuit boards via a backplane leads to the potential for signal interference. Because the circuit boards are all connected via the backplane, signals from the various circuit boards may interfere with each other, especially as the signals travel through the common backplane. Additionally, signal strength may be attenuated as signals travel through the backplane. In general, signals passing between two daughterboards pass through at least one connector when input to the backplane and one connector when output from the backplane. The signal is attenuated at each connector. 
     Thus a need has existed for an electrical connector that directly connects circuit boards. Specifically, a need has existed for an electrical connector that connects circuit boards without a backplane, thereby improving system performance while reducing signal interference and signal attenuation. 
     SUMMARY OF THE INVENTION 
     At least one embodiment of the present invention relates to an electrical connector assembly that includes two groups of circuit boards, or wafers, that mate with, or connect to, one another in an orthogonal, or non-parallel manner. The electrical connector includes a plurality of circuit boards; a first connector housing including channels adapted to retain the first group of the circuit boards; a second connector housing also including channels adapted to retain the second group of the circuit boards; and a board interface located between the first and second connector housing. The first connector housing may be a receptacle connector, while the second connector housing may be a plug connector, or vice versa. 
     The channels in the first and second connector housings, are aligned parallel to, and retain, the first and second groups of circuit boards parallel to the first and second circuit board planes, respectively. In at least one embodiment of the present invention, the first circuit board plane intersects the second circuit board plane along a line extending along a length of the first and second connector housings. The first connector housing, such as a plug connector housing, and the second connector housing, such as a receptacle connector housing, have mating faces that mate with each other in a non-planar interconnection. The non-planar interconnection joins the plug mating edges at an angle to the receptacle mating edges. 
     The board interface is formed as part of one of the first and second connector housings. The board interface includes opposing mating faces of the first and second groups of circuit boards that join the first group of circuit boards in a non-parallel relationship to the second group of circuit boards. Preferably, the circuit boards are joined orthogonally. The opposing faces include first and second sets of slots that receive the first and second groups of circuit boards, respectively. The first set of slots are aligned transverse to the second set of slots. Additionally, the opposing faces of the board interface may include first and second sets of passages orthogonally joining said first group of circuit boards to the second group of circuit boards. 
     Each circuit board includes signal and ground contacts along an edge joining the board interface. The signal contacts on one circuit board in the first group of circuit boards electrically engage the signal contacts on at least two circuit boards in the second group of circuit boards, and vice versa. 
     The electrical connector also includes card-edge terminals that electrically interconnect the first and second groups of circuit boards. The card-edge terminals include a first contact surface on one end arranged to engage a first circuit board and a second contact surface on an opposite end arranged to engage a second circuit board. The first and second contact surfaces orthogonally face one another. 
     Each circuit board includes signal and ground contacts along an edge joining the board interface. The signal contacts on one circuit board in the first group of circuit boards electrically engage signal contacts on at least two circuit boards in the second group of circuit boards, and vice versa. 
     One embodiment of the present invention includes a plug connector that includes plug slots defining a plug plane and, a receptacle connector that includes receptacle slots defining a receptacle plane. The plug slots and said receptacle slots receive plug circuit boards and receptacle circuit boards, respectively, along the plug plane aligned in a non-parallel, transverse, or otherwise non-parallel relation to the header plane. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, embodiments which are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentality shown in the attached drawings. 
     FIG. 1 illustrates an exploded view of a plug connector formed in accordance with an embodiment of the present invention. 
     FIG. 2 illustrates an exploded view of a receptacle connector formed in accordance with an embodiment of the present invention. 
     FIG. 3 illustrates a first side of the plug circuit board, or plug wafer, formed in accordance with an embodiment of the present invention. 
     FIG. 4 illustrates a second side of the plug circuit board, or plug wafer with the header mating edge including a plurality of mating signal contact pads and vias. 
     FIG. 5 illustrates a first side of the receptacle circuit board, or receptacle wafer, formed in accordance with an embodiment of the present invention. 
     FIG. 6 illustrates a second side of the receptacle circuit board, or receptacle wafer. 
     FIG. 7 illustrates an assembled plug connector formed in accordance with an embodiment of the present invention. 
     FIG. 8 illustrates an assembled receptacle connector formed in accordance with an embodiment of the present invention. 
     FIG. 9 illustrates the receptacle connector and the plug connector prior to mating according to an embodiment of the present invention. 
     FIG. 10 illustrates a ground terminal formed in accordance with an embodiment of the present invention. 
     FIG. 11 illustrates a signal terminal formed in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates an exploded view of a plug connector  100  formed in accordance with an embodiment of the present invention. The plug connector  100  includes an interface housing  110 , a base  120 , a plurality of plug circuit boards  130  (also known as plug wafers), and a cover  140 . The interface housing  110  includes top, bottom and side walls,  111 ,  113 , and  115 , and a face plate  119 . The face plate  119  includes a plurality of board slots  114 , and the bottom wall  113  and top wall  111  include a plurality of lower guide slots  117  and upper guide slots (not shown), respectively. Notches  116  are formed on one side of the interface housing  110 , for example, the top wall  111 . The base  120  includes a front end  121  and a rear end  123 , with a plurality of channels  122  extending along a length thereof. Each channel  122  includes a series of receptacles  125 . Each receptacle  125  retains a compliant contact  127 . Each compliant contact  127  includes a single prong  128  that extends down through the bottom of the base  120 . Additionally, each compliant contact  127  includes a double prong  129  that extends up through the top of the base  120 . Each plug circuit board  130  includes a plug mating edge  132 , a base contact edge  133 , and an interface guide edge  134 . The plug mating edge  132  includes contact pads  310  along one end as further describe below with respect to FIGS. 3 and 4. The base contact edge  133  includes a plurality of signal and ground contact pads  322  and  326  on either side of the base contact edge  133 . The cover  140  includes tabs  144  and slots  142  along a back wall. 
     Each plug circuit board  130  is positioned within a channel  122  of the base  120 . The channels  122  are aligned parallel to one another, and retain the plug circuit boards  130 . The double prong  129  of the compliant contact  127  that extends up through the base  120  contacts a plug circuit board  130  at signal or ground contact pads  322  or  326  located on either side of the plug circuit board  130  along the base contact edge  133 . The base contact edge  133  is held between the prongs of the double prong  129  of the compliant contact  127  so that each prong of the double prong  129  contacts a signal or ground contact pad  322  or  326  located on opposite sides of the base contact edge  133 . The single prong  128  of the compliant contact  127  extending down through the base  120  may be connected to a receptacle on a printed circuit board (not shown) or another circuit board (not shown). The number of compliant contacts  127  equals the number of signal or ground contact pads  322  and  326  along one side of the base contact edge  133 . 
     The plug mating edges  132  of the plug circuit boards  130  pass through the board slots  114  of the interface housing  110 . The plug circuit boards  130  are further retained by the lower guide slots  117  of the interface housing  110 . The lower guide slots  117  are parallel to one another and securely retain, the interface guide edges  134  of the plug circuit boards  130 . A plug mating face  137 , shown below with respect to FIG. 7, is formed once the plug mating edges  132  are positioned within a cavity formed within the interface housing  110 . The interface housing  110  connects or fastens to the base  120  to provide more stability to the plug connector  100 . 
     After the plug circuit boards  130  are positioned within the base  120  and the interface housing  110 , the cover  140  is mounted onto the base  120  and the interface housing  110 . The plug circuit boards  130  are further retained by the cover slots  142  formed in the cover  140 . The cover  140  connects to the base  120 . Additionally, the cover  140  connects to the interface housing  110  via the tabs  144  that fit into the corresponding notches  116  formed within the interface housing  110 . Therefore, the plug connector  100  forms a housing that retains a group of plug circuit boards  130 . Alternatively, the cover  140  may connect to the interface housing  110  via a different number of tabs  144 , or via a variety of fastening agents, such as screws, glue and the like. 
     FIG. 2 illustrates an exploded view of a receptacle connector  200  formed in accordance with an embodiment of the present invention. The receptacle connector  200  includes an interface housing  205 , a base  220 , a plurality of receptacle circuit boards  230  and a cover  240 . The interface housing  205  includes plug circuit board slots  206 , a receptacle mating face  210 , a terminal passage  211 , guide barriers  215  formed between the receptacle mating face  210  and the terminal passage  211 , and notches  207 . The interface housing  205  allows the passage of rows of card-edge terminals  212 . Each card-edge terminal  212  includes a plug interconnect  214 , a receptacle interconnect  216  and an intermediate portion  217  connecting the plug interconnect  214  to the receptacle interconnect  216 . As further described below with respect to FIGS. 10 and 11, the card edge terminal  212  may be a signal terminal or a ground terminal. The base  220  includes a plurality of parallel channels  222 . Each channel  222  includes a series of receptacles  225 . Each receptacle  225  retains one compliant contact  227 . Each compliant contact  227  includes a single prong  228  that extends down through the bottom of the base  220 . Additionally, each compliant contact  227  includes a double prong  229  that extends up through top of the base  220 . Each receptacle circuit board  230  includes a receptacle mating edge  232  and a base contact edge  233 . The receptacle mating edge  232  and the base contact edge  233  include contact pads  510 ,  512 ,  522  and  524 , as further described below with respect to FIGS. 5 and 6. The base contact edge  233  includes a plurality of contact pads  522 ,  524  on either side. The cover  240  includes tabs  244  and slots  242 . 
     Each receptacle circuit board  230  is positioned within a channel  222  of the base  220 . The channels  222  are aligned parallel to one another, and retain the receptacle circuit boards  230 . The double prong  229  of the compliant contact  227  extends up through the base  220  and contacts a receptacle circuit board  230  at signal or ground contact pads  522  or  524  located on either side of the receptacle circuit board  230  on the base contact edge  233 . The base contact edge  233  is held between the prongs of the double prong  229  of the compliant contact  227  so that each prong of the double prong  229  contacts a signal or ground contact pad  522  or  524  located on either side of the base contact edge  233 . The single prong  228  of the compliant contact  227  extends down through the base  220  and may be connected to a receptacle on a printed circuit board (not shown) or another circuit board (not shown). The number of compliant contacts  227  equals the number of contact pads  522  and  524  located on one side of the base contact edge  233 . 
     Each receptacle circuit board  230  connects to a card-edge terminal  212  via the receptacle interconnect  216  of the card-edge terminal  212 . The receptacle interconnect  216  connects to the receptacle mating edge  232  at ground and signal contact pads  510  and  512 . The receptacle interconnect  216  may be shaped like a tuning fork with one prong of the receptacle interconnect  216  contacting a ground and signal contact pad  510  or  512  on one side of the receptacle circuit board  230  while the other prong of the receptacle interconnect  216  contacts a ground and signal contact pad  510  or  512  located on the opposite side of the same receptacle circuit board  230 . As additional receptacle circuit boards  230  are positioned within the base  220  and connected to the card-edge terminals  212 , straight rows of card-edge terminals  212  are formed due to the coplanar positioning of the ground and signal contact pads  510  and  512  of the receptacle circuit boards  230 . Preferably, as further described below with respect to FIGS. 10 and 11, the plug interconnect  214  includes a single beam if the card-edge terminal  212  is a ground terminal, or a double beam if the card-edge terminal  212  is a signal terminal. 
     FIG. 10 illustrates a ground terminal  12  formed in accordance with an embodiment of the present invention. The ground terminal  12  includes a single beam plug interconnect  14  on one end of an intermediate portion  16  and a receptacle ground interconnect  18  shaped like a tuning fork on the opposite end. The receptacle ground interconnect  18  includes two prongs  2  and  4 . The receptacle ground interconnect  18  may have the same shape as the receptacle interconnect  216  of the general card-edge terminal  212 . Therefore one prong  2  of the receptacle ground interconnect  18  contacts a ground contact pad  510  on one side of the receptacle circuit board  230  while the other prong  4  of the receptacle ground interconnect  18  contacts a ground contact pad  510  on the other side of the receptacle circuit board  230 . That is, the receptacle circuit board  230  is straddled by the receptacle ground interconnect  18 . The single beam plug interconnect  14  contacts a ground contact pad  310  located on one side of the plug circuit board  130 . 
     FIG. 11 illustrates a signal terminal  22  formed in accordance with an embodiment of the present invention. The signal terminal  22  includes a double beam plug interconnect  24  on one side of an intermediate portion  26  and a receptacle signal interconnect  28  shaped like a tuning fork on the opposite end. The receptacle signal interconnect  28  includes two prongs  3  and  5 . The receptacle signal interconnect  28  may have the same shape as the receptacle interconnect  216  of the general card-edge terminal  212  and the receptacle ground interconnect  18  of the ground terminal  12 . Therefore one prong  3  of the receptacle signal interconnect  28  contacts a signal contact pad  512  on one side of the receptacle circuit board  230  while the other prong of the receptacle signal interconnect  28  contacts a signal contact pad  512  on the other side of the receptacle circuit board  230 . That is, the receptacle circuit board  230  is straddled by the receptacle signal interconnect  28 . The double beam plug interconnect  24  contacts a signal contact pad  410  located on one side of the plug circuit board  130 . That is, both beams of the plug interconnect  24  contact one signal contact pad  410  located on one side of the plug circuit board  130 . 
     The signal contact pads  512  are connected to the receptacle signal interconnects  28  of the signal terminals  22 . Additionally, the aligned ground contact pads  510  are then connected to the receptacle ground interconnects  18  of the ground terminals  12 . Therefore a plurality of parallel rows of ground terminals  12  and signal terminals  22  are formed. 
     Referring again to FIG. 2, the terminal passage  211  includes a plurality of openings (not shown) that allow each row of card-edge terminals  212 , including signal terminals  22  and ground terminals  12 , to pass. Preferably, the openings of the terminal passage  211  form cavities that extend from the terminal passage  211  to the receptacle mating face  210 . The solid structure formed between the terminal passage  211  and the receptacle mating face  210  forms guide barriers  215  that support the card-edge terminals  212  and the plug mating edges  132  of the plug circuit boards  130 . Additionally, the guide barriers  215  guide the plug mating edges  132  into the plug interconnects  214  of the card-edge terminals  212 . Each plug interconnect  214  of each card-edge terminal  212  is positioned within the interface housing  205  of the receptacle connector  200 . Additionally, the interface housing  205  connects to the base  220  to provide additional stability for the receptacle connector  200 . 
     After the receptacle circuit boards  230  are positioned within the base  220  and the rows of card-edge terminals  212  are positioned within the interface housing  205  and connected to the receptacle circuit boards  230 , the cover  240  is positioned onto the base  220  and the interface housing  205  (FIG.  8 ). The receptacle circuit boards  230  are further retained by slots (not shown) formed in the cover  240 . The cover  240  connects to the base  220 . Additionally, the cover  240  connects to the interface housing  205  via three tabs  244  that fit into three corresponding notches  207  formed within the interface housing  205 . Therefore, the receptacle connector  200  forms a housing that retains a group of receptacle circuit boards  230 . Alternatively, the cover  240  may connect to the interface housing  205  via a different number of tabs  244 , or via a variety of fastening agents, such as screws, glue and the like. 
     FIG. 3 illustrates a first side of the plug circuit board  130 , or plug wafer, formed in accordance with an embodiment of the present invention. FIG. 3 illustrates one exemplary configuration of signal and ground traces  316  and a plurality of mating ground contact pads  310  and vias  314 . The base contact edge  133  includes a plurality of base signal contact pads  322 , base ground contact pads  326  and vias  314 . Traces  316  and vias  314  on the plug mating edge  132  connect the base signal contact pads  322  to mating signal contact pads, shown below with respect to FIG. 4, located on a second side of the plug circuit board  130 . Preferably, the base ground contact pads  326  and base signal contact pads  322  are arranged so that two base ground contact pads  326  are separated by two base signal contact pads  322 . The vias  314  provide an electrical connection between the first side of the plug circuit board  130  and the second side of the plug circuit board  130 . 
     FIG. 4 illustrates a second side of the plug circuit board  130 , or plug wafer with the plug mating edge  132  including a plurality of mating signal contact pads  410  and vias  314 . The base contact edge  133  includes a plurality of base signal contact pads  322  and base ground contact pads  326 . Traces  316  connect the mating signal contact pads  410  to base signal contact pads  322 . Preferably, the base ground contact pads  326  and base signal contact pads  322  are arranged so that two base ground contact pads  326  are separated by two base signal contact pads  322 . The vias  314  provide an electrical connection between the second side of the header circuit board  130  and a first side of the header circuit board  130 . 
     FIG. 5 illustrates a first side of the receptacle circuit board  230 , or receptacle wafer, formed in accordance with an embodiment of the present invention. The receptacle mating edge  232  includes a plurality of mating ground contact pads  510 , mating signal contact pads  512  and vias  514 . Preferably, the mating ground contact pads  510  and mating signal contact pads  512  are arranged on the receptacle mating edge  232  in an alternating fashion. That is, two mating ground contact pads  510  are separated by one mating signal contact pad  512 , and vice versa. The base contact edge  233  includes a plurality of base signal contact pads  522 , base ground contact pads  524  and vias  514 . Traces  516  connect the mating signal contact pads  512  to base signal contact pads  522 . Preferably, the base ground contact pads  524  and base signal pads  522  are arranged so that two base ground contact pads  524  are separated by two base signal pads  522 . The vias  514  provide an electrical connection between the first side of the receptacle circuit board  230  and a second side of the receptacle circuit board  230 . 
     FIG. 5 illustrates a first side of the receptacle circuit board  230 , or receptacle wafer, formed in accordance with an embodiment of the present invention. The receptacle mating edge  232  includes a plurality of mating ground contact pads  510 , mating signal contact pads  512  and vias  514 . Preferably, the mating ground contact pads  510  and mating signal contact pads are arranged on the receptacle mating edge  232  in an alternating fashion. That is, two mating ground contact pads  510  are separated by one mating signal contact pad  512 , and vice versa. The base contact edge  233  includes a plurality of base signal contact pads  522 , base ground contact pads  524  and vias  514 . Traces  516  connect the mating signal contact pads  512  to base signal contact pads  522 . Preferably, the base ground contact pads  524  and base signal pads  522  are arranged so that two base ground contact pads  524  are separated by two base signal pads  522 . The vias  514  provide an electrical connection between the first side of the receptacle circuit board  230  and a second side of the receptacle circuit board  230 . 
     FIG. 6 illustrates a second side of the receptacle circuit board  230 , or receptacle wafer. The receptacle mating edge  232  includes a plurality of mating ground contact pads  510 , mating signal contact pads  512  and vias  514 . Preferably, the mating ground contact pads  510  and mating signal contact pads are arranged on the receptacle mating edge  232  in an alternating fashion. That is, two mating ground contact pads  510  are separated by one mating signal contact pad  512 , and vice versa. The base contact edge  233  includes a plurality of base signal contact pads  522 , base ground contact pads  524  and vias  514 . Traces  516  connect the mating signal contact pads  512  to base signal contact pads  522 . Preferably, the base ground contact pads  524  and base signal pads  522  are arranged so that two base ground contact pads  524  are separated by two base signal pads  522 . The vias  514  provide an electrical connection between the second side of the receptacle circuit board  230  and the first side of the receptacle circuit board  230 . 
     FIG. 7 illustrates an assembled plug connector  100  formed in accordance with an embodiment of the present invention. As further described above with respect to FIG. 1, the plug connector  100 , as shown in FIG. 7, includes the interface housing  110  connected to the base  120  and the cover  140 . The outermost plug circuit boards  130  form side walls (only one side wall shown) of the plug connector  100 . The cover  140  is fastened onto the interface housing via the notches  116  of the interface housing receiving the tabs  144  of the cover  140 . 
     The plug mating face  137  is formed via the alignment and positioning of the plug circuit boards  130  on the lower guide slots  117 . The plug mating face  137  is formed within the cavity formed within the interface housing  110 . 
     The single prongs  128  of the compliant contacts  127  are connected to the base contact edges  133  of the plug circuit boards  130  via the double prongs  129 . Because the plug circuit boards  130  are aligned parallel to each other, the compliant contacts  127  are aligned in parallel rows. Therefore, the single prongs  128  of the compliant contacts  127  extend through the bottom of the base  120  thereby forming parallel rows of single prongs  128 . The single prongs  128  of the compliant contacts  127  may be positioned within receptacles (not shown) formed in a printed circuit board (not shown). 
     FIG. 8 illustrates an assembled receptacle connector  200  formed in accordance with an embodiment of the present invention. As further described above with respect to FIG. 2, the receptacle connector  200  includes the interface housing  205  connected to the base  220 . The outermost receptacle circuit boards  230  form side walls (only one shown) of the receptacle connector  200 . The interface housing  205  and the base  220  are both connected to the cover  240 . The cover  240  is connected to the interface housing  205  via the receipt of the tabs  244  by the notches  207 . 
     The plug circuit board receptacle slots  206  are formed in the interface housing  205 . The plug circuit board receptacle slots  206  follow the contour of the interface housing  205  starting from one side of the interface housing  205  and extending over the surface of the receptacle mating face  210 . The plug circuit board receptacle slots  206  are parallel with each other and correspond directly to the plug circuit boards  130  positioned within the plug connector  100 . The plug circuit boards  130  positioned within the plug mating face  137  are mated into the receptacle connector  200  via the plug circuit board receptacle slots  206 . 
     The receptacle mating face  210  includes a plurality of guide barriers  215  formed within the receptacle mating face  210 . The guide barriers  215  support the plug circuit boards  130  after the plug circuit boards  130  are connected to the receptacle connector  200  via the mating of the plug mating face  137  with the receptacle mating face  210 . Additionally, the guide barriers  215  guide the plug mating edges  132  to the plug interconnects  214  of the card-edge terminals  212  that are located within the interface housing  205 . Additionally, the card-edge terminals  212  are also supported by the guide barriers  215  that extend from the receptacle mating face  210  to the terminal passage  211 . 
     The single prongs  228  of the compliant contacts  227  are connected to the base contact edges  233  of the receptacle circuit boards  230  via the double prongs  229 . Because the receptacle circuit boards  230  are aligned parallel to each other, the compliant contacts  227  are aligned in parallel rows. Therefore, the single prongs  228  of the compliant contacts  227  extend through the bottom of the base  220  thereby forming parallel rows of single prongs  228 . The single prongs  228  of the compliant contacts  227  may be positioned within receptacles (not shown) formed in a printed circuit board (not shown). 
     FIG. 9 illustrates the plug connector  100  and the receptacle connector  200  prior to mating according to an embodiment of the present invention. The plug connector  100  is connected to a printed circuit board  910  via the single prongs  128  of the compliant contacts  127 . The receptacle connector  200  is connected to a printed circuit board  920  via the single prongs  228  of the compliant contacts  227 . 
     In operation, the plug circuit boards  130  mate with the receptacle circuit boards  230  via the mating of the receptacle mating face  210  and the plug mating face  137  in an orthogonal manner. That is, when the receptacle connector  200  is mated with the plug connector  100 , the receptacle circuit boards  230  are transverse to, or rotated  900  in relation to, the plug circuit boards  130 . Therefore, if the plug connector  100  is positioned in an orientation such that the plug circuit boards  130  are arranged in horizontal rows, the receptacle circuit boards  230  are thereby arranged in vertical columns when the plug connector  100  is mated to the receptacle connector  200 . Conversely, if the plug connector  100  is positioned in an orientation such that the plug circuit boards are arranged in vertical columns, the receptacle circuit boards  230  are thereby arranged in horizontal rows when the plug connector  100  is mated to the receptacle connector  200 . That is, the plug mating face  137  opposes the receptacle mating face  210  when the plug mating face  137  interfaces with the receptacle mating face  210 . A board interface is formed as the receptacle connector  200  is mated with the plug connector  100 . 
     As the plug mating face  137  is mated with the receptacle mating face  210 , the plug circuit boards  130  are moved into the interface housing  205  of the receptacle connector  200  via the plug circuit board receptacle slots  206  until the plug mating edges  132  contact the plug interconnects  214  of the card-edge terminals  212 . As the plug mating edges  132  move into the interface housing  205 , the receptacle mating face  210  is mated with the plug mating face  137  located within the cavity formed within the interface housing  110  of the plug connector  100 . Preferably, once the plug connector  100  and the receptacle connector  200  are fully mated, the interface housing  205  of the receptacle connector  200  is fastened into the interface housing  110  of the plug connector  100 . 
     The plug mating edges  132  of the plug circuit boards  130  connect to the plug interconnects  214  once the plug connector  100  is fully mated with the receptacle connector  200 . Once mated, horizontal rows of the plug circuit boards  130  are connected to vertical columns of the receptacle circuit boards  230 . Conversely, the plug connector  100  may be mated to the receptacle connector  200  in such a manner that vertical columns of the plug circuit boards  130  are connected to horizontal rows of the receptacle circuit boards  230 . That is, the plug circuit boards  130  are connected to the receptacle circuit boards  230  in an orthogonal fashion. Therefore, the plug connector  100  orthogonally connects to the receptacle connector  200 . The orthogonal connection of the plug connector  100  to the receptacle connector  200  forms a board interface between the plug connector  100  and the receptacle connector  200 . Thus, the printed circuit boards  910 ,  920  are physically and electrically connected via the union of the plug connector  100  and the receptacle connector  200  without the need of a back plane. 
     As stated above with respect to FIG. 2, the plug interconnect  214  may be a ground terminal  12  or a signal terminal  22 . If the card-edge terminal  212  is a signal terminal  22 , the double beam plug interconnect  24  contacts one mating signal contact pad  410  of the plug mating edge  132 . Because the mating signal contact pads  410  of a particular plug circuit board  130  are located on only one side of the plug circuit board  130  as shown in FIG. 4, only one side of the plug circuit board  130  contacts the double beam plug interconnects  24 . The plug circuit board  130  connects to a particular receptacle circuit board  230  via the signal terminal  22 . That is, because the double beam plug interconnect  24  and the receptacle signal interconnect  28  are connected via the intermediate portion  26 , the signal terminal  22  forms a physical and electrical connection between the plug circuit board  130  and the receptacle circuit board  230 . If, however, the card-edge terminal  212  is a ground terminal  12 , the single beam plug interconnect  14  contacts one mating ground contact pad  310  of the plug mating edge  132 . Because the mating ground contact pads  310  are located on the opposite side of the plug circuit board  130  as the mating signal contact pads  410 , only one side of the plug circuit board  130  contacts the single beam plug interconnects  14 . The plug circuit board  130  connects to a particular plug circuit board via the ground terminal  12 . That is, because the single beam plug interconnect  14  and the receptacle ground interconnect  18  are connected via the intermediate portion  16 , the ground terminal  12  forms a physical link between the plug circuit board  130  and the receptacle circuit board  230 . 
     The card-edge terminals  212  extend into the interface housing  205  of the receptacle connector  200  via the terminal passage  211 . As stated above with respect to FIG. 2, the receptacle interconnect  216  of each card-edge terminal  212  may be shaped like a tuning fork. The receptacle mating edge  232  of the receptacle circuit board  230  is positioned between the two tuning fork prongs of the receptacle interconnect  216 . Each prong of the receptacle interconnect  216  contacts either a signal contact pad  512 , or a ground signal contact pad  510  located on either side of the receptacle mating edge  232 . That is, the receptacle signal interconnect  28  of the signal terminal  22  contacts a signal contact pad  512  on one side of the receptacle circuit board  230  while simultaneously contacting a signal contact pad  512  on the other side of the receptacle circuit board  230 . Similarly, a receptacle ground interconnect  18  of the ground terminal  12  contacts a ground contact pad  510  on one side of the receptacle circuit board  230  while simultaneously contacting a ground contact pad on the other side of the receptacle circuit board  230 . 
     As discussed above, each plug circuit board  130  includes multiple, or a plurality of, mating ground and signal contact pads  310 ,  410  located on opposite sides of each plug mating edge  132 . Each mating ground or signal contact pad  310 ,  410  connects to a plug interconnect  214  of a card-edge terminal  212  when the plug connector  100  is mated to the receptacle connector  200 . Each card-edge  212  connects to either two mating signal contact pads  512 , or two mating ground contact pads  510  located on either side of a receptacle circuit board  230  via the receptacle interconnect  216 . Therefore, each plug circuit board  130  is physically and electrically connected to multiple receptacle circuit boards  230 . 
     Similarly, each receptacle circuit board  230  includes multiple, or a plurality of, mating ground and signal contact pads  510 ,  512 . A pair of mating ground or signal contact pads  510 ,  512  connect to a receptacle connector  216  of a card-edge terminal  212  when the receptacle connector  200  is mated to the plug connector  100 . Each card-edge terminal  212  connects to a mating ground or signal contact pad  310  or  410  located on one side of a plug circuit board  130  via the plug interconnect  214 . Therefore, each receptacle circuit board  230  is physically and electrically connected to multiple plug circuit boards  130 . 
     Alternatively, the plug circuit boards  130  may be configured similar to the receptacle circuit boards  230 . That is, the plug circuit boards  130  may have mating ground and signal contact pads  310 ,  410  on both sides of the plug circuit board. In that case, the card-edge terminal  212  may include a tuning fork plug interconnect and a tuning fork receptacle interconnect. Thus, the tuning fork receptacle interconnect may be positioned in an orientation that is rotated 90° from that of the tuning fork plug interconnect. 
     Thus, at least some of the above embodiments provide an improved electrical connector for edge mating circuit boards. The electrical connectors connect printed circuit boards without a back plane. At least some of the above embodiments provide a more direct connection between the printed circuit boards thereby improving system performance by reducing signal interference and attenuation. 
     While the embodiments discussed above primarily concern configurations in which the plug connector  100  and the receptacle connector  200  are oriented orthogonal to one another, alternative angular orientations may be provided. For example, the rows of header and plug circuit boards  130  and  230  may be arranged at other non-parallel configurations, such as obtuse or acute angles with respect to one another. 
     While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore contemplated by the appended claims to cover such modifications that incorporate those features coming within the scope of the invention.