Patent Publication Number: US-6655966-B2

Title: Modular connector with grounding interconnect

Description:
BACKGROUND OF THE INVENTION 
     Certain embodiments of the present invention generally relate to electrical connectors, and more particularly to high-speed high-density board-to-board connectors. 
     Modular connectors exist for connecting various types of circuit boards, such as daughter cards, mother boards, back planes and the like. The modular connectors convey a densely packed number of signal lines between the circuit boards. The modular connectors each include multiple wafers or signal modules stacked in parallel. The wafers have two sides that have ground planes and signal lines formed thereon. The signal lines carry data between mating ends of the wafers, and the ground planes control impedance. The signal lines may be arranged on adjacent wafers to form differential pairs. In differential pair applications, a signal is divided and transmitted in a first direction over a pair of conductors (and hence through a pair of pins or contacts). A return signal is similarly divided and transmitted in an opposite direction over the same pair of conductors (and hence through the same pair of pins or contacts). For example, two signal lines on adjacent wafers may form a differential pair and carry a divided signal along the two signal lines. 
     There is a trend in board-to-board connectors toward increased data rates and line densities. Line density is a measure of differential pairs per linear inch measured along the direction perpendicular to the wafers. Generally, increasing the data rates and line density increases insertion loss and cross talk between signal lines. Ground planes reduce interference between signal lines and therefore decrease insertion loss and cross talk. 
     However, existing modular connectors have experienced difficulty in conveying extremely high speed data signals without severely attenuating the output signal. In particular, as data rates rise into the giga-hertz range, the signals output by the modular connectors are increasingly attenuated, such as by over 1 dB. This attenuation is also referred to as insertion loss. Attenuation is due in part to the fact that the ground planes within the connector housing develop local potentials with respect to one another during use. The buildup of the potentials between the ground planes causes the ground planes to resonate at certain frequencies, resulting in degraded throughput signals (insertion loss) and increased cross talk between signal lines on the wafers. 
     A need remains for an improved connector that can more adequately handle high-speed high-density data rates. 
     BRIEF SUMMARY OF THE INVENTION 
     An embodiment of the present invention provides an electrical connector having a connector housing with signal modules and grounding members therein. Each signal module has a ground plane on at least one side thereof. The ground planes have contact pads formed at opposite ends thereof proximate mating ends of the signal modules. The grounding members interconnect the ground planes on adjacent signal modules to one another at a point along the ground planes or the contact pads. Optionally, the signal modules may be printed circuit boards. Alternatively, the signal modules may be pieces of molded plastic with metal traces mounted thereon. 
     Optionally, the signal modules may include vias having conductive liners therethrough that electrically connect ground planes on opposite sides of a signal module. The signal modules may be arranged parallel to one another within the housing. Each signal module may have one or more ground planes and one or more signal lines. Optionally, adjacent signal modules may have signal lines facing one another and forming differential pairs. 
     The grounding member may include pins adjoining two or more vias on two or more signal modules to one another. Alternatively, the grounding member may be a conductive rod that extends through a plurality of vias in a plurality of signal modules. The grounding member may be a metal object interposed between adjacent signal modules and may have one of spring members, dimples and beams that contact ground planes on the adjacent modules. Alternatively, the grounding member may be a metal rack having slots cut therein for receiving signal modules, where the signal modules include projections contacting ground planes on the signal modules. 
     An advantage of certain embodiments of the present invention is that the connector can carry large amounts of data quickly and in a very high line density with reduced insertion loss and cross talk. Because the ground planes are electrically interconnected within the connector housing by the conductive liners of the vias and the grounding members, the development of local potentials on the ground planes is minimized, thereby reducing insertion loss rates and cross talk between signal lines. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 illustrates a top front perspective view of a connector assembly formed in accordance with an embodiment of the present invention. 
     FIG. 2 illustrates a bottom rear perspective view of a connector assembly formed in accordance with an alternative embodiment of the present invention. 
     FIG. 3 illustrates a top rear perspective view of a connector assembly formed in accordance with an alternative embodiment of the present invention. 
     FIG. 4 illustrates a top rear perspective view of a connector assembly formed in accordance with an alternative embodiment of the present invention. 
     FIG. 5 illustrates a top rear perspective view of a signal module and a grounding bracket formed in accordance with an embodiment of the present invention. 
     FIG. 6 illustrates a bottom front perspective view of a grounding plate formed in accordance with an embodiment of the present invention. 
     FIG. 7 illustrates a top front perspective view of the grounding plate of FIG. 6 joined with a signal module in accordance with an embodiment of the present invention. 
     FIG. 8 illustrates a right side plan view of a signal module formed in accordance with an embodiment of the present invention 
     FIG. 9 illustrates a left side plan view of a signal module formed in accordance with an embodiment of the present invention. 
     FIG. 10 illustrates a bottom front perspective view of a grounding plate formed in accordance with an embodiment of the present invention. 
     FIG. 11 illustrates a bottom front perspective view of a grounding plate formed in accordance with an embodiment of the present invention. 
     FIG. 12 illustrates a top rear perspective view of a connector assembly with an inter-connector assembly grounding clip formed in accordance with an embodiment of the resent invention. 
     FIG. 13 illustrates a top rear perspective view of a connector assembly with an inter-connector assembly grounding clip formed in accordance with an alternative embodiment of the present invention. 
     FIG. 14 illustrates a graph of insertion loss performance of a right angle connector assembly not formed in accordance with an embodiment of the present invention. 
     FIG. 15 illustrates a graph of insertion loss performance of a right angle connector assembly formed in accordance with an embodiment of the present invention. 
    
    
     The foregoing summary, as well as the following detailed description of certain 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, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a plug  2  formed in accordance with an embodiment of the present invention. The plug  2  is configured to mate with a receptacle (not shown) to form a right angle connector assembly (not shown). The plug  2  includes a connector housing  4  and a plurality of signal modules  6  mounted therein. The signal modules  6  are arranged parallel to one another and spaced apart by gaps  8 . The signal modules  6  include mating ends  10  and  12  formed at right angles to one another. The mating end  10  includes pads  14  for mating with a contact (not visible) that has a pin  16  extending downward therefrom. The pin  16  is configured to be inserted into a via in a daughter printed circuit board (PCB) (not shown). The mating end  12  includes pads  18  that are configured to mate with a back plane PCB (not shown). The signal modules include side surfaces  20  and  22  that have ground planes  24  and signal lines  28 . For example, each of the signal modules  6  includes six ground planes  24  and four signal lines  28 . 
     Each of the signal modules  6  also includes a drill hole  32  for location purposes during manufacturing and a plurality of holes or vias  34 . The vias  34  include conductive liners  36  that electrically connect the ground planes  24  on the side surfaces  20  and  22  of each signal module  6  to one another. In the embodiment of FIG. 1, grounding rods  38  are inserted through selected vias  34  in at least two signal modules  6 . The grounding rods  38  electrically inter-connect the ground planes  24  of different signal modules  6  to one another. 
     FIG. 2 illustrates a plug  42  formed in accordance with an alternative embodiment of the present invention. The plug  42  includes connector housings  44  and  46  (unmated in FIG.  2 ). The connector housing  44  includes top and rear walls  48  and  50  that hold a plurality of signal modules  52  arranged parallel to one another and spaced apart at gaps  54 . The signal modules  52  include ground planes  56  and signal lines  58  arranged on both sides  60 ,  62  of the signal modules  52 . The ground planes  56  include pads  64  that are located proximate mating ends  66  of the signal modules  52 . The signal modules  52  also include vias  68  having conductive liners therethrough that electrically connect the ground planes  56  on opposite sides  60  and  62  of the signal modules  52  to one another. 
     The connector housing  46  includes front and bottom walls  70  and  72  that join with the top and rear walls  48  and  50 . The bottom wall  72  includes channels  74  extending along a length thereof for receiving bottom edges  76  of the signal modules  52 . The front wall  70  includes slots  78  for receiving mating ends  66  of the signal modules  52 . 
     The front wall  70  includes plastic rails  80  located between, and along, the slots  78  and having contact brackets  82  clasped thereto. The contact brackets  82  include a flat body section  84  having flat legs  86  that clasp the rails  80 . When the connector housings  44  and  46  are mated, the slots  78  receive the mating ends  66  of the signal modules  52 , and the flat legs  86  of the contact brackets  82  engage the ground planes  56 . For example, when the connector housings  44  and  46  are mated, each of the contact brackets  82  is electrically connected to the ground planes  56  of two adjacent of the signal modules  52 . 
     FIG. 3 illustrates a plug  90  formed in accordance with an alternative embodiment of the present invention. The plug  90  includes connector housings  92  and  94 . The connector housing  92  includes signal modules  96  therein. The signal modules  96  include side surfaces  98  having ground planes  100  and signal lines  102  formed thereon. The signal modules  96  are held within a conductive plate  104  having flat parallel bars  106  separated by parallel slots  108  cut therebetween. The slots  108  receive the signal modules  96  so that the planes of the signal modules  96  are perpendicular to the plane of the conductive plate  104 . The bars  106  include compliant fingers  110  extending horizontally therefrom and bending towards mating ends  112  of the signal modules  96 . The compliant fingers  110  engage, and electrically interconnect, the ground planes  100  of the signal modules  96 . Thus all of the ground planes  100  are electrically connected to one another. 
     FIG. 4 illustrates a plug  114  formed in accordance with an alternative embodiment of the present invention. The plug  114  includes connector housings  116  and  118 . The connector housing  116  includes signal modules  120  and a U-shaped grounding jacket  122  therein. The connector housing  116  includes front and bottom walls  124  and  126  that are aligned perpendicular to one another. The front and bottom walls  124  and  126  include L-shaped channels  128  (only partially visible) for receiving the signal modules  120 . The channels  128  turn 90 degrees at a juncture  130  between the front and bottom walls  124  and  126 . The signal modules  120  include side surfaces  132  having ground planes  134  and signal lines  136  formed thereon. The grounding jacket  122  includes front and back walls  138  and  140  that are aligned parallel to one another and spaced apart. The front and back walls  138  and  140  are joined together by a bottom wall  139 . The walls  138 - 140  include parallel slots  142  cut therethrough and spaced apart by flat bars  144 . The slots  142  are aligned with the channels  128  and receive the signal modules  120 . The flat bars  144  include semicircular projections  146  protruding into the slots  142  and engaging, and electrically interconnecting, the ground planes  134  on the signal modules  120 . 
     FIG. 5 illustrates a signal module  150  adjacent to and engaged with a U-shaped grounding bracket  152  formed in accordance with an embodiment of the present invention. The signal module  150  includes vias  154  having conductive liners  156  therethrough. The signal module  150  also includes side surfaces  158 ,  160  having ground planes  162  and signal lines  164  formed thereon. The grounding bracket  152  includes planar sidewalls  166  and  168  aligned parallel to, and separated from, one another, and joined by a bottom wall  170 . The sidewalls  166  and  168  include extruded dimples  172  protruding outward in a direction perpendicular to, and away from, both of the sidewalls  166  and  168 . The dimples  172  engage the ground planes  162  of the signal module  150 , thereby electrically interconnecting the ground planes  162  on the side surface  158 . 
     The ground planes  162  on the side surface  160  (not visible) are electrically connected to the ground planes  162  on the side surface  158  through the conductive liners  156  of the vias  154 . Thus, all of the ground planes  162  of the signal module  150  are electrically connected to one another. Alternatively, the signal module  150  and grounding bracket  152  can be stacked into a connector housing (not shown) in an alternating arrangement of signal modules  150  and metal brackets  152  so that all of the ground planes  162  of several signal modules  150  are electrically interconnected with one another. In such an arrangement, friction between the dimples  172  and the ground planes  162  retains the metal brackets  152  in position. 
     FIG. 6 illustrates a grounding plate  174  formed in accordance with an embodiment of the present invention. The grounding plate  174  is for insertion between parallel signal modules (not shown) and can be mounted on a signal module. The grounding plate  174  includes a flat body section  176 . The flat body section  176  includes via-engaging beams  178  extending therefrom in a direction perpendicular to the plane of the flat body section  176 . The flat body section  176  also includes ground-plane engaging beams  180  extending therefrom at acute angles to the plane of the flat body section  176 . The ground-plane engaging beams  180  bend away from the flat body section  176  in a direction opposite to a direction in which the via-engaging beams  178  extend. 
     FIG. 7 illustrates a signal module  182  with the metal plate  174  mounted thereon. The signal module  182  includes a drill hole  184  for location purposes during manufacturing. The signal module  182  also has side surfaces  186  and  188  that have ground planes  190  and signal lines  192  formed thereon. The ground planes  190  include vias  194  that extend through the signal module  182 . The vias  194  have conductive liners  196  therethrough that electrically connect the ground planes  190  on the side surface  186  to the ground planes  190  on the side surface  188 . The via-engaging beams  178  of the metal plate  174  are inserted into selected vias  194  on the side surface  186 , thereby electrically connecting and physically attaching the metal plate  174  to the ground planes  190 . Thus, all of the ground planes  190  of the signal module  182  are electrically connected to one another. 
     Optionally, additional metal plates  174  and signal modules  182  can be stacked into a connector housing (not shown) in an alternating arrangement so that all of the ground planes  190  of the multiple signal modules  182  are electrically interconnected with one another. In such an arrangement, the ground plane-engaging beams  180  of the metal plates  174  contact the ground planes  190  on the side surfaces  188  of the signal modules  182 . The ground plane-engaging beams  180  of each of the metal plates  174  would be electrically connected, but not physically attached, to the ground planes  190  of the side surface  188 , while the via-engaging beams  178  of each of the metal plates  174  would be electrically connected, and physically attached, to the ground planes  190  of the side surface  186 . 
     FIG. 8 illustrates a right side plan view of a signal module  200  formed in accordance with an embodiment of the present invention. The signal module  200  includes mating ends  202  and  204  that are aligned perpendicular to one another and have pads  206  for mating with contacts (not shown). The signal module  200  includes a drill hole  207  for location purposes during manufacturing. The signal module  200  also includes a side surface  208  that has ground planes  210 - 212  and signal lines  214  and  216 . The signal line  214  is located between the ground planes  210  and  211 , and the signal line  216  is located between the ground planes  211  and  212 . The ground planes  210 - 212  include vias  218  that have conductive lining extending through the vias  218 . 
     FIG. 9 illustrates a left side plan view of the signal module  200 . The signal module  200  includes a side surface  222  opposite to the side surface  208 . The side surface  222  includes ground planes  224 - 226  and signal lines  228  and  230 . The signal line  228  is located between the ground planes  224  and  225 , and the signal line  230  is located between the ground planes  225  and  226 . The conductive lining that extends through the vias  218  electrically connects the ground planes  210 - 212  of the side surface  208  to the ground planes  224 - 226  of the side surface  222 . For example, the ground plane  210  is electrically connected to the ground plane  224 , the ground plane  211  is electrically connected to the ground planes  224  and  225 , and the ground plane  212  is electrically connected to the ground planes  225  and  226 . 
     FIG. 10 illustrates a grounding contact  232 , for insertion between signal modules  200  stacked in a parallel arrangement (not shown), formed in accordance with an embodiment of the present invention. The grounding contact  232  is a stamped strip of metal having rectangular ends  234  and  236  configured to be inserted into slots in a connector housing (not shown). The grounding contact  232  includes a height  238 , width  240 , and thickness  242 . The grounding contact  232  includes spring elements  244  having rounded ends  246  that extend outward beyond the width  240  of the grounding contact  232 . When the grounding contact  232  is installed between the signal modules  200  in a connector housing (not shown), the rounded ends  246  of the spring elements  244  engage the ground planes  210 - 212  and  224 - 226  of the signal modules  200 , thereby electrically connecting the ground planes  210 - 212  on the side surfaces  208  of the signal modules  200  to the ground planes  224 - 226  on the side surfaces  222  of adjacent signal modules  200 . 
     FIG. 11 illustrates a bottom front view of a grounding contact  248 , for insertion between signal modules  200  stacked in a parallel arrangement (not shown), formed in accordance with an embodiment of the present invention. The grounding contact  248  is a stamped strip of metal having a planar body section  250  and rectangular ends  252  and  254  configured to be inserted into slots in a connector housing (not shown). The grounding contact  248  includes edges  256  and  258  extending vertically from the end  252  to the end  254 . The edges  256  and  258  include compliant beams  260 - 265  extending outward horizontally therefrom and at angles to the planar body section  250  of the grounding contact  248 . The compliant beams  260 - 265  include curved ends  268  for engaging the ground planes  210 - 212  and  224 - 226  of the signal modules  200 . When the grounding contact  248  is installed between the signal modules  200  in a connector housing, the curved ends  268  of the compliant beams  260 - 265  engage the ground planes  210 - 212  and  224 - 226  of the signal modules  200 , thereby electrically connecting the ground planes  210 - 212  on the side surfaces  208  of the signal modules  200  to the ground planes  224 - 226  on the side surfaces  222  of adjacent signal modules  200 . 
     FIG. 12 illustrates a plug  270  formed in accordance with an alternative embodiment of the present invention. The plug  270  includes mated connector housings  272  and  274  having a plurality of signal modules  276  aligned parallel to one another therein. The plug  270  includes sides  278  and  280 . The side  278  includes an inter-connector assembly grounding clip  282 . The grounding clip  282  includes two zigzagged bars  284  and  286 . The bar  284  includes corners  288 - 290  protruding inward toward, and contacting, ground planes  292  on the signal module  276  that is most closely located to the side  278 . The bar  286  includes corners  294 - 296  protruding outward away from the corners  288 - 290  and configured to the contact ground planes  292  on a signal module  276  in an adjacent plug  270 , thereby electrically interconnecting the ground planes  292  of signal modules  276  on adjacent plugs  270 . 
     FIG. 13 illustrates a plug  300  formed in accordance with an embodiment of the present invention. The plug  300  includes mated connector housings  302  and  304  having a plurality of signal modules  306  aligned parallel to one another therein. The plug  300  includes sides  308  and  310 . The side  308  includes an inter-connector assembly grounding clip  312 . The grounding clip  312  includes three flat beams  314 - 316 .  316 . The beams  314  and  316  include buckles  318  protruding inward toward, and contacting, the ground planes  320  on the signal module  306  that is most closely located to the side  308 . The middle beam  315  is bent outward away from the connector assembly  300  and is configured to contact a middle beam  315  of a grounding clip  312  on a side  310  of an adjacent plug  300 , thereby electrically interconnecting the ground planes  320  of adjacent plugs  300 . 
     FIG. 14 illustrates a graph of insertion loss performance of a right angle connector assembly not formed in accordance with an embodiment of the present invention. The graph depicts insertion loss measured in dB along a y-axis versus fundamental frequency of a transmitted signal measured in GHz along an x-axis. The insertion loss is equal to 20 times the log base  10  of (voltage output/voltage input). Voltage input is the measure in volts of the signal input at one end of a signal line, and voltage output is the measure in volts of the signal output at an opposite end of the signal line. As the fundamental frequency increases from 0.00 to 5.00 GHz, the absolute value of insertion loss increases. As the fundamental frequency increases from 5.00 to 6.00 GHz, the absolute value of insertion loss generally increases, but along ranges  322  and  324 , the absolute value of insertion loss decreases. At a fundamental frequency of 4.00 GHz, the absolute value of insertion loss is greater than 1.00 dB  326 . At a fundamental frequency of 5.00 GHz, the absolute value of insertion loss is about 2.50 dB  328 . At a fundamental frequency of 6.00 GHz, the absolute value of insertion loss is about 4.00 dB  330 . 
     FIG. 15 illustrates a graph of insertion loss performance of a right angle connector assembly formed in accordance with an embodiment of the present invention. The graph depicts insertion loss measured in dB along a y-axis versus fundamental frequency measured in GHz along an x-axis. As the fundamental frequency increases from 0.00 to 6.00 GHz, the absolute value of insertion loss increases. At a fundamental frequency of 4.00 GHz, the absolute value of insertion loss is less than 1.00 dB  332 . At a fundamental frequency of 5.00 GHz, the absolute value of insertion loss is less than 1.50 dB  334 . At a fundamental frequency of 6.00 GHz, the absolute value of insertion loss is still less than 1.50 dB  336 . 
     While certain embodiments of the present invention employ plugs for right angle connector assemblies, other embodiments may include plugs for straight or orthogonal connector assemblies. 
     While certain embodiments of the present invention employ plugs for connector assemblies, other embodiments may include receptacles for connector assemblies. 
     While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. 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. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.