Patent Publication Number: US-7713088-B2

Title: Broadside-coupled signal pair configurations for electrical connectors

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit under 35 U.S.C. § 119(e) of provisional U.S. patent application Ser. No. 60/849,535, filed Oct. 5, 2006, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     An electrical connector may provide signal connections between electronic devices using signal contacts. The electrical connector may include a leadframe assembly that has a dielectric leadframe housing and a plurality of electrical contacts extending therethrough. Typically, the electrical contacts within a leadframe assembly are arranged into a linear array that extends along a direction along which the leadframe housing is elongated. The contacts may be arranged edge-to-edge along the direction along which the linear array extends. The electrical contacts in one or more leadframe assemblies may form differential signal pairs. A differential signal pair may consist of two contacts that carry a differential signal. The value, or amplitude, of the differential signal may be the difference between the individual voltages on each contact. The contacts that form the pair may be broadside-coupled (i.e., arranged such that the broadside of one contact faces the broadside of the other contact with which it forms the pair). Broadside or microstrip coupling is often desirable as a mechanism to control (e.g., minimize or eliminate) skew between the contacts that form the differential signal pair. 
     When designing a printed circuit board (PCB), circuit designers typically establish a desired differential impedance for the traces on the PCB that form differential signal pairs. Thus, it is usually desirable to maintain the same desired impedance between the differential signal contacts in the electrical connector, and to maintain a constant differential impedance profile along the lengths of the differential signal contacts from their mating ends to their mounting ends. It may further be desirable to minimize or eliminate insertion loss (i.e., a decrease in signal amplitude resulting from the insertion of the electrical connector into the signal&#39;s path). Insertion loss may be a function of the electrical connector&#39;s operating frequency. That is, insertion loss may be a greater at higher operating frequencies. 
     Therefore, a need exists for a high-speed electrical connector that minimizes insertion loss at higher operating frequencies while maintaining a desired differential impedance between differential signal contacts. 
     SUMMARY 
     The disclosed embodiments include an electrical connector having a first electrical contact and a second electrical contact adjacent to the first electrical contact. The first electrical contact may define a first broadside and a second broadside opposite the first broadside. The second electrical contact may define a third broadside and a fourth broadside opposite the third broadside. The electrical connector may further include a non-air dielectric and a commoned ground plate. The non-air dielectric may be disposed between the second broadside of the first electrical contact and the fourth broadside of the second electrical contact. The commoned ground plate and the first electrical contact may be adjacent to one another and may be separated by an air dielectric. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  depict a portion of a prior-art connector system, in isometric and side views, respectively. 
         FIG. 1C  depicts a contact arrangement of the prior-art connector system shown in  FIGS. 1A and 1B . 
         FIGS. 2A and 2B  depict a portion of a connector system, in isometric and side views, respectively, according to an embodiment. 
         FIG. 2C  depicts an example dielectric material that may be disposed between leadframe assemblies of a plug connector shown in  FIGS. 2A and 2B . 
         FIG. 2D  depicts an example contact arrangement of the plug connector shown in  FIGS. 2A and 2B . 
         FIGS. 3A and 3B  depict a portion of a connector system, in isometric and side views, respectively, according to another embodiment. 
         FIG. 3C  depicts an example contact arrangement of a plug connector shown in  FIGS. 3A and 3B . 
         FIGS. 4A and 4B  depict a portion of a connector system, in isometric and side views, respectively, according to yet another embodiment. 
         FIG. 4C  depict an example contact arrangement of a plug connector shown in  FIGS. 4A and 4B . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1A and 1B  depict isometric and side views, respectively, of a prior art connector system  100 . The connector system  100  includes a plug connector  102  mated to a receptacle connector  104 . The plug connector  102  may be mounted to a first substrate, such as a printed circuit board  106 . The receptacle connector  104  may be mounted to a second substrate, such as a printed circuit board  108 . The plug connector  102  and the receptacle connector  104  are shown as vertical connectors. That is, the plug connector  102  and the receptacle connector  104  each define mating planes that are generally parallel to their respective mounting planes. 
     The plug connector  102  may include a connector housing, a base  110 , leadframe assemblies  126 , and electrical contacts  114 . The connector housing of the plug connector  102  may include an interface portion  105  that defines one or more grooves  107 . As will be further discussed below, the grooves  107  may receive a portion of the receptacle connector  104  and, therefore, may help provide mechanical rigidity and support to the connector system  100 . 
     Each of the leadframe assemblies  126  of the plug connector  102  may include a first leadframe housing  128  and a second leadframe housing  130 . The first leadframe housing  128  and the second leadframe housing  130  may be made of a dielectric material, such as plastic, for example. The leadframe assemblies  126  may be insert molded leadframe assemblies (IMLAs) and may house a linear array of electrical contacts  114 . For example, as will be further discussed below, the array of electrical contacts  114  may be arranged edge-to-edge in each lead frame assembly  126 , i.e., the edges of adjacent electrical contacts  114  may face one another. 
     The electrical contacts  114  of the plug connector  102  may each have a cross-section that defines two opposing edges and two opposing broadsides. Each electrical contact  114  may also define at least three portions along its length. For example, as shown in  FIG. 1B , each electrical contact  114  may define a mating end  116 , a lead portion  118 , and a terminal end  121 . The mating end  116  may be blade-shaped, and may be received by a respective electrical contact  136  of the receptacle connector  104 . The terminal end  121  may be “compliant” and, therefore, may be press-fit into an aperture  124  of the base  110 . The terminal end  121  may electrically connect with a ball grid array (BGA)  125  on a substrate face  122  of the base  110 . The lead portion  118  of the electrical contact  114  may extend from the terminal end  121  to the mating end  116 . 
     The base  110  of the plug connector  102  may be made of a dielectric material, such as plastic, for example. The base  110  may define a plane having a connector face  120  and the substrate face  122 . The plane defined by the base  110  may be generally parallel to a plane defined by the printed circuit board  106 . As shown in  FIG. 1A , the connector face  120  of the base  110  may define the apertures  124  that receive the terminal ends  121  of the electrical contacts  114 . The substrate face  122  of the base  110  may include the BGA  125 , which may electrically connect the electrical contacts  114  to the printed circuit board  106 . 
     The receptacle connector  104  may include a connector housing, a base  112 , leadframe assemblies  132 , and electrical contacts  136 . The connector housing of the receptacle connector  104  may include an interface portion  109  that defines one or more ridges  111 . Upon mating the plug connector  102  and the receptacle connector  104 , the ridges  111  on the connector housing of the receptacle connector  104  may engage with the grooves  107  on the connector housing of the plug connector  102 . Thus, as noted above, the grooves  107  and the ridges  111  may provide mechanical rigidity and support to the connector system  100 . 
     Each of the leadframe assemblies  132  of the receptacle connector  104  may include a leadframe housing  133 . The leadframe housing  133  may be made of a dielectric material, such as plastic, for example. Each of the leadframe assemblies  132  may be an insert molded leadframe assembly (IMLAs) and may house a linear array of electrical contacts  136 . For example, the array of electrical contacts  136  may be arranged edge-to-edge in the leadframe assembly  132 , i.e., the edges of adjacent electrical contacts  136  may face one another. 
     Like the electrical contacts  114 , the electrical contacts  136  of the receptacle connector  104  may have a cross-section that defines two opposing edges and two opposing broadsides. Each electrical contact  136  may define at least three portions along its length. For example, as shown in  FIG. 1B , each electrical contact  136  may define a mating end  141 , a lead portion  144 , and a terminal end  146 . The mating end  141  of the electrical contact  136  may be any receptacle for receiving a male contact, such as the blade-shaped mating end  116  of the electrical contact  114 . For example, the mating end  141  may include at least two-opposing tines  148  that define a slot therebetween. The slot of the mating end  141  may receive the blade-shaped mating end  116  of the electrical contacts  114 . The width of the slot (i.e., the distance between the opposing tines  148 ) may be smaller than the thickness of the blade-shaped mating end  116 . Thus, the opposing tines  148  may exert a force on each side of the blade-shaped mating end  116 , thereby retaining the mating end  116  of the of the electrical contact  114  in the mating end  142  of the electrical contact  136 . Alternatively, as shown in  FIG. 1A , the mating end  141  may include a single tine  148  that is configured to make contact with one side of the blade-shaped mating end  116 . 
     The terminal end  146  of the electrical contact  136  may be “compliant” and, therefore, may be press-fit into an aperture (not shown) of the base  112 . The terminal end  146  may electrically connect with a ball grid array (BGA)  142  on a substrate face  140  of the base  112 . The lead portion  144  of each electrical contact  136  may extend from the terminal end  146  to the mating end  141 . 
     The base  112  of the receptacle connector  104  may be made of a dielectric material, such as plastic, for example. The base  112  may define a plane having a connector face  138  and the substrate face  140 . The plane defined by the base  112  may be generally parallel to a plane defined by the printed circuit board  108 . The connector face  138  may define apertures (not shown) for receiving the terminal ends  146  of electrical contacts  136 . Although the apertures of the base  112  are not shown in  FIGS. 1A and 1B , the apertures in the connector face  138  of the base  112  may be the same or similar to the apertures  124  in the connector face  120  of the base  110 . The substrate face  140  may include the BGA  142 , which may electrically connect the electrical contacts  136  to the printed circuit board  108 . 
       FIG. 1C  depicts a contact arrangement  190 , viewed from the face of the plug connector  102 , in which the electrical contacts  114  are arranged in linear arrays. As shown in  FIG. 1C , the electrical contacts  114  may be arranged in a 5×4 array, though it will be appreciated that the plug connector  102  may include any number of the electrical contacts  114  arranged in various configurations. As shown, the plug connector  102  may include contact rows  150 ,  152 ,  154 ,  156 ,  158  and contact columns  160 ,  162 ,  164 ,  166 . 
     As noted above, each of the electrical contacts  114  may have a cross-section that defines two opposing edges and two opposing broadsides. The electrical contacts  114  may be arranged edge-to-edge along each of the columns  160 ,  162 ,  164 ,  166 . In addition, the electrical contacts  114  maybe arranged broadside-to-broadside along each of the rows  150 ,  152 ,  154 ,  156 ,  158 . As shown in  FIG. 1C , the broadsides of the electrical contacts  114  in the rows  150 ,  154 ,  158  may be smaller than the broadsides of the electrical contacts  114  in the rows  152 ,  156 . Each of the electrical contacts  114  may be surrounded on all sides by a dielectric  176 , which may be air. 
     The electrical contacts  114  in the plug connector  102  may include ground contacts G and signal contacts S. As shown in  FIG. 1C , the rows  150 ,  154 ,  158  of the plug connector  102  may include all ground contacts G. The rows  152 ,  156  of the plug connector  102  may include both ground contacts G and signal contacts S. For example, the electrical contacts  114  in the rows  152 ,  156  may be arranged in a G-S-S-G pattern. As noted above, the electrical contacts  114  may be arranged broadside-to-broadside along each of the rows  150 ,  152 ,  154 ,  156 ,  158 . Accordingly, adjacent signal contacts S in rows  152 ,  156  may form broadside coupled differential signal pairs, such as the differential signal pairs  174  shown in  FIG. 1C . 
       FIGS. 2A and 2B  depict isometric and side views, respectively, of a connector system  200  according to an embodiment. The connector system  200  may include a plug connector  202  mated to the receptacle connector  104 . The plug connector  202  may be mounted to the printed circuit board  106 . The receptacle connector  104  may be mounted to the printed circuit board  108 . The plug connector  202  and the receptacle connector  104  are shown as vertical connectors. However, it will be appreciated that either or both of the plug connector  202  and the receptacle connector  104  may be right-angle connectors in alternative embodiments. 
     The plug connector  202  may include the base  110 , leadframe assemblies  126 , and electrical contacts  114 . As shown in  FIG. 2B , the plug connector  202  may further include a non-air dielectric, such as a dielectric material  204 , positioned between adjacent leadframe assemblies  126 . In particular, the dielectric material  204  may be positioned between the adjacent leadframe assemblies that house one or more signal contacts S. The dielectric material  204  may be made from any suitable material, such as plastic, for example. The dielectric material  204  may be molded as part of the leadframe assemblies  126 . Alternatively, the dielectric material  204  may be molded independent of the leadframe assemblies  126  and subsequently inserted therebetween. 
       FIG. 2C  depicts a side view of the dielectric material  204 . As shown in  FIG. 2C , the dielectric material  204  may include header portions  205   a ,  205   b , that extend substantially parallel to one another. The dielectric material may further include interconnecting portions  206   a ,  206   b  that extend substantially parallel to one another and substantially perpendicular to the header portions  205   a ,  205   b . The interconnecting portions  206   a ,  206   b  may connect the header portion  205   a  to the header portion  205   b.    
     As noted above with respect to  FIGS. 2A and 2B , the dielectric material  204  may be disposed between adjacent leadframe assemblies  126  having signal contacts S (i.e., the inner leadframe assemblies  126  shown in  FIGS. 2A and 2B ). More specifically, the header portion  205   a  of the dielectric material  204  may be adjacent to the first leadframe housing  128  and may extend along a length thereof. The header portion  205   b  of the dielectric material  204  may be adjacent to the second leadframe housing  130  and may extend along a length thereof. Thus, the header portions  205   a ,  205   b  may be disposed adjacent to at least a portion of each electrical contact  114  in the inner leadframe assemblies  126 . The interconnecting portions  206   a ,  206   b  of the dielectric material  204  may extend substantially parallel to the electrical contacts  114  in the inner leadframe assemblies  126 . In particular, as will be further discussed below, the interconnecting portions  206   a ,  206   b  may extend along the lengths of each signal contact housed in the inner leadframe assemblies  126 . 
       FIG. 2D  depicts a contact arrangement  290 , viewed from the face of the plug connector  202 , that includes the linear arrays of electrical contacts  114  and a portion of the dielectric material  204 . Like the contact arrangement depicted in  FIG. 1C , the electrical contacts  114  may be arranged in a 5×4 array and may define contact rows  150 ,  152 ,  154 ,  156 ,  158  and contact columns  160 ,  162 ,  164 ,  166 . The electrical contacts  114  in the plug connector  202  may have a cross-section that defines two opposing edges and two opposing broadsides. The electrical contacts  114  may be arranged edge-to-edge along each of the columns  160 ,  162 ,  164 ,  166 . In addition, the electrical contacts  114  may be arranged broadside-to-broadside along each of the rows  150 ,  152 ,  154 ,  156 ,  158 . The broadsides of the electrical contacts  114  in the rows  150 ,  154 ,  158  may be smaller than the broadsides of the electrical contacts  114  in the rows  152 ,  156 . 
     The electrical contacts  114  in the plug connector  202  may also include ground contacts G and signal contacts S. The rows  150 ,  154 ,  158  of the plug connector  202  may include all ground contacts G, and the rows  152 ,  156  may include both ground contacts G and signal contacts S. For example, the electrical contacts  114  in the rows  152 ,  156  may be arranged in a G-S-S-G pattern. The electrical contacts  114  may be arranged broadside-to-broadside along each of the rows  150 ,  152 ,  154 ,  156 ,  158 . Accordingly, adjacent signal contacts S in rows  152 ,  156  may form broadside coupled differential signal pairs  174 . 
     As shown in  FIG. 2D , the interconnecting portions  206   a ,  206   b  of the dielectric material  204  may define a generally rectangular cross-section and may be positioned between adjacent signal contacts S in the columns  162 ,  164 . That is, the interconnecting portions  206   a ,  206   b  may be positioned between the signal contacts S of each broadside-coupled differential signal pair  174  in the plug connector  202 . In addition, each of the electrical contacts  114  may be surrounded on all sides by the dielectric  176 , which may be different than the dielectric material  204  disposed between the broadside-coupled differential signal pairs  174 . 
     As further shown in  FIG. 2D , the interconnecting portions  206   a ,  206   b  may extend a greater distance than each of the electrical contacts  114  in the direction of the rows  150 ,  152 ,  154 ,  156 ,  158  (i.e., the interconnecting portions  206   a ,  206   b  may be wider than the electrical contacts  114 ), though it will be appreciated that the widths of the interconnecting portions  206   a ,  206   b  may be equal to or less than the widths of the electrical contacts  114  in other embodiments. In addition, the interconnecting portions  206   a ,  206   b  may extend substantially the same distance as each of the electrical contacts  114  in the direction of the contact columns  160 ,  162 ,  164 ,  166  (i.e., the height of each of the interconnecting portions  206   a ,  206   b  may be substantially the same as the heights of the electrical contacts  114  in the contact rows  152 ,  156 ), though it will be appreciated that the heights of the interconnecting portions  206   a ,  206   b  may be greater than or less than the heights of the electrical contacts  114  in other embodiments. 
       FIGS. 3A and 3B  depict isometric and side views, respectively, of a connector system  300  according to another embodiment. The connector system  300  includes a plug connector  302  mated to the receptacle connector  104 . The plug connector  302  may be mounted to the printed circuit board  106 . The receptacle connector  104  may be mounted to the printed circuit board  108 . The plug connector  302  and the receptacle connector  104  are shown as vertical connectors. However, it will be appreciated that either or both of the plug connector  302  and the receptacle connector  104  may be right-angle connectors in alternative embodiments. 
     The plug connector  302  may include the base  110 , leadframe assemblies  126 , and electrical contacts  114 . As shown in  FIG. 3A , the plug connector  302  may further include a commoned ground plate  178  housed in at least one of the leadframe assemblies  126 . The commoned ground plate  178  may be a continuous, electrically conductive sheet that extends along an entire contact column and that is brought to ground, thereby shielding all electrical contacts  114  adjacent to the commoned ground plate  178 . The commoned ground plate  178  may include a plate portion  180 , terminal ends  182 , and mating interfaces  184 . 
     More specifically, the plate portion  180  of the commoned ground plate  178  may be housed within the leadframe assembly  126 , and may extend from the terminal ends  182  to the mating interfaces  184 . As shown in  FIG. 3A , the commoned ground plate  178  may include terminal ends  182  extending from the plate portion  180 , and extending from the second leadframe housing  130  of the leadframe assembly  126 . The terminal ends  182  may be compliant and may, therefore, be press-fit into the apertures  124  of the base  110 . The terminal ends  182  of the commoned ground plate  178  may electrically connect with the BGA  125  on the bottom side  122  of the base  110 . 
     The commoned ground plate  178  may also include mating interfaces  184  extending from the plate portion  180 , and extending above the first leadframe housing  128  of the lead frame assembly  126 . The mating interfaces  184  may be blade-shaped, and may be received by the respective mating ends  141  of the electrical contacts  136 . 
       FIG. 3C  depicts a contact arrangement  390 , viewed from the face of the plug connector  302 , that includes linear arrays of electrical contacts  114  and commoned ground plates  178   a ,  178   b . The electrical contacts  114  and the commoned ground plates  178   a ,  178   b  may be arranged in a 5×4 array and may define contact rows  150 ,  152 ,  154 ,  156 ,  158  and contact columns  160 ,  162 ,  164 ,  166 . Like the contact arrangement depicted in  FIG. 1C , the electrical contacts  114  in the plug connector  302  may have a cross-section that defines two opposing edges and two opposing broadsides. The electrical contacts  114  may be arranged edge-to-edge along each of the columns  162 ,  164 . In addition, the electrical contacts  114  may be arranged broadside-to-broadside along each of the rows  150 ,  152 ,  154 ,  156 ,  158 . The broadsides of the electrical contacts  114  in the rows  150 ,  154 ,  158  may be smaller than the broadsides of the electrical contacts  114  in the rows  152 ,  156 . 
     The commoned ground plates  178   a ,  178   b  may be positioned adjacent to the contact columns  162 ,  164 , respectively. Thus, as shown in  FIG. 3C , the commoned ground plates  178   a ,  178   c  may replace the ground contacts G in the contact columns  160 ,  166  shown in  FIG. 1C . 
     The electrical contacts  114  in the plug connector  302  may include ground contacts G and signal contacts S. The rows  150 ,  154 ,  158  of the plug connector  302  may include all ground contacts G, and the rows  152 ,  156  may include both ground contacts G and signal contacts S. For example, the commoned ground plates  178   a ,  178   b  and the electrical contacts  114  in the rows  152 ,  156  may be arranged in a G-S-S-G pattern. The electrical contacts  114  may be arranged broadside-to-broadside along each of the rows  150 ,  152 ,  154 ,  156 ,  158 . Accordingly, adjacent signal contacts S in rows  152 ,  156  may form broadside coupled differential signal pairs  174 . 
     The commoned ground plates  178   a ,  178   b  may each have a cross-section that is generally rectangular in shape. As shown in  FIG. 3C , the commoned ground plates  178   a ,  178   b  may each extend substantially the entire length of the contact columns  160 ,  162 ,  164 ,  166 . The commoned ground plates  178   a ,  178   b  may also extend substantially the same distance as each of the electrical contacts  114  in the direction of the contact rows (i.e., each of the commoned ground plates  178   a ,  178   b  may have substantially the same width as the electrical contacts  114 ), though it will be appreciated that the widths of the commoned ground plates  178   a ,  178   b  may be less than or greater than the widths of the electrical contacts  114  in other embodiments. The electrical contacts  114  and the commoned ground plates  178   a ,  178   b  may be surrounded on all sides by the dielectric  176 . 
       FIGS. 4A and 4B  depict isometric and side views, respectively, of a connector system  400  according to yet another embodiment. The connector system  400  may include a plug connector  402  mated to the receptacle connector  104 . The plug connector  402  may be mounted to the printed circuit board  106 . The receptacle connector  104  may be mounted to the printed circuit board  108 . The plug connector  402  and the receptacle connector  104  are shown as vertical connectors. However, either or both of the plug connector  402  and the receptacle connector  104  may be right-angle connectors in alternative embodiments. The plug connector  402  may include the base  110 , the leadframe assemblies  126 , the electrical contacts  114 , the commoned ground plates  178   a ,  178   b , and the dielectric material  204 . 
       FIG. 4C  depicts a contact arrangement  490 , viewed from the face of the plug connector  402 , that includes linear arrays of electrical contacts  114 , the commoned ground plates  178   a ,  178   b  and the dielectric material  204 . As shown in  FIG. 4C , the interconnecting portions  206   a ,  206   b  of the dielectric material  204  may define a generally rectangular cross-section and may be positioned between the signal contacts S in the contact columns  162 ,  164 . That is, the interconnecting portions  206   a ,  206   b  may be positioned between the broadside-coupled differential signal pairs  174  in the contact columns  162 ,  164 . In addition, each of the electrical contacts  114  and the commoned ground plates  178   a ,  178   b  may be surrounded on all sides by the dielectric  176 , which may be different than the dielectric material  204  disposed between the broadside-coupled differential signal pairs  174 . 
     As further shown in  FIG. 4C , the commoned ground plates  178   a ,  178   b  may be positioned adjacent to the contact columns  162 ,  164 , respectively. Thus, the commoned ground plates  178   a ,  178   b  may replace the ground contacts G in the contact columns  160 ,  166  shown in  FIG. 1C . The commoned ground plates  178   a ,  178   b  may each have a cross-section that is generally rectangular in shape. As shown in  FIG. 4C , the commoned ground plates  178   a ,  178   b  may each extend substantially the entire length of the contact columns  160 ,  162 ,  164 ,  166 . The commoned ground plates  178   a ,  178   b  may also extend substantially the same distance as each of the electrical contacts  114  in the direction of the contact rows (i.e., each of the commoned ground plates  178   a ,  178   b  may have the same width as the electrical contacts  114 ), though it will be appreciated that the widths of the of the commoned ground plates  178   a ,  178   b  may be less than or greater than the widths of the electrical contacts  114  in other embodiments. 
     It has also been found that embodiments as described herein break up the coupling wave that moves up the connector causing an insertion loss “suck out” about the 4 GHz region. An object of the dielectric material  204  is to change the impedance slightly between signal and ground to minimize the coupling wave and the insertion loss suck out associated therewith. The ground plane is to minimize the signal pair coupling to the ground individual pin edge and to provide a continuous ground plane.