Abstract:
A high speed, high density electrical connector for use with printed circuit boards is described. The connector is in two pieces, each piece including columns of signal contacts and shield plates which interconnect when the two pieces are mated. The shield plates are disposed in each piece of the connector such that, when mated, the shield plates are substantially perpendicular to the shield plates in the other piece of the connector. The shields have a grounding arrangement that is adapted to control the electromagnetic fields for various system architectures, simultaneous switching configurations and signal speeds. Additionally, at least one piece of the connector is manufactured from wafers, with each ground plane and signal column injection molded into components which, when combined, form a wafer.

Description:
RELATED APPLICATION INFORMATION  
       [0001]    This application claims priority to U.S. Application 60/179,722 filed Feb. 3, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Electrical connectors are used in many electronic systems. It is generally easier and more cost effective to manufacture a system on several printed circuit boards that are then joined together with electrical connectors. A traditional arrangement for joining several printed circuit boards is to have one printed circuit board serve as a backplane. Other printed circuit boards, called daughter boards, are connected through the backplane.  
           [0003]    A traditional backplane is a printed circuit board with many connectors. Conducting traces in the printed circuit board connect to signal pins in the connectors so signals may be routed between the connectors. Daughter boards also contain connectors that are plugged into the connectors on the backplane. In this way, signals are routed among the daughter boards through the backplane. The daughter cards often plug into the backplane at a right angle. The connectors used for these applications contain a right angle bend and are often called “right angle connectors.” 
           [0004]    Connectors are also used in other configurations for interconnecting printed circuit boards, and even for connecting cables to printed circuit boards. Sometimes, one or more small printed circuit boards are connected to another larger printed circuit board. The larger printed circuit board is called a “mother board” and the printed circuit boards plugged into it are called daughter boards. Also, boards of the same size are sometimes aligned in parallel. Connectors used in these applications are sometimes called “stacking connectors” or “mezzanine connectors.” 
           [0005]    Regardless of the exact application, electrical connector designs have generally needed to mirror trends in the electronics industry. Electronic systems generally have gotten smaller and faster. They also handle much more data than systems built just a few years ago. These trends mean that electrical connectors must carry more and faster data signals in a smaller space without degrading the signal.  
           [0006]    Connectors can be made to carry more signals in less space by placing the signal contacts in the connector closer together. Such connectors are called “high density connectors.” The difficulty with placing signal contacts closer together is that there is electromagnetic coupling between the signal contacts. As the signal contacts are placed closer together, the electromagnetic coupling increases. Electromagnetic coupling also increases as the speed of the signals increase.  
           [0007]    In a conductor, electromagnetic coupling is indicated by measuring the “cross talk” of the connector. Cross talk is generally measured by placing a signal on one or more signal contacts and measuring the amount of signal coupled to the contact from other neighboring signal contacts. In a traditional pin in box connector mating in which a grid of pin in box matings are provided, the cross talk is generally recognized as a sum total of signal coupling contributions from each of the four sides of the pin in box mating as well as those located diagonally from the mating.  
           [0008]    A traditional method of reducing cross talk is to ground signal pins within the field of the signal pins. The disadvantage of this approach is that it reduces the effective signal density of the connector.  
           [0009]    To make both a high speed and high density connector, connector designers have inserted shield members in proximity to signal contacts. The shields reduce the electromagnetic coupling between signal contacts, thus countering the effect of closer spacing or higher frequency signals. Shielding, if appropriately configured, can also control the impedance of the signal paths through the connector, which can also improve the integrity of signals carried by the connector.  
           [0010]    An early use of shielding is shown in Japanese patent disclosure 49-6543 by Fujitsu, Ltd. dated Feb. 15, 1974. U.S. Pat. Nos. 4,632,476 and 4,806,107, both assigned to AT&amp;T Bell Laboratories, show connector designs in which shields are used between columns of signal contacts. These patents describe connectors in which the shields run parallel to the signal contacts through both the daughter board and the backplane connectors. Cantilevered beams are used to make electrical contact between the shield and the backplane connectors. Patents 5,433,617; 5,429,521; 5,429,520 and 5,433,618, all assigned to Framatome Connectors International, show a similar arrangement. The electrical connection between the backplane and shield is, however, made with a spring type contact.  
           [0011]    Other connectors have the shield plate within only the daughter card connector. Examples of such connector designs can be found in patents 4,846,727, 4,975,084, 5,496,183 and 5,066,236, all assigned to AMP, Inc. Another connector with shields only within the daughter board connector is shown in U.S. Pat. No. 5,484,310, assigned to Teradyne, Inc.  
           [0012]    A modular approach to connector systems was introduced by Teradyne Connection Systems, of Nashua, New Hampshire. In a connector system called HD+®, multiple modules or columns of signal contacts are arranged on a metal stiffener. Typically, 15 to 20 such columns are provided in each module. A more flexible configuration results from the modularity of the connector such that connectors “customized” for a particular application do not require specialized tooling or machinery to create. In addition, many tolerance issues that occur in larger non-modular connectors may be avoided.  
           [0013]    A more recent development in such modular connectors was introduced by Teradyne, Inc. and is shown in U.S. Pat. Nos. 5,980,321 and 5,993,259 which are hereby incorporated by reference. Teradyne, Inc., assignee of the above-identified patents, sells a commercial embodiment under the trade name VHDM™.  
           [0014]    The patents show a two piece connector. A daughter card portion of the connector includes a plurality of modules held on a metal stiffener. Here, each module is assembled from two wafers, a ground wafer and a signal wafer. The backplane connector, or pin header, includes columns of signal pins with a plurality of backplane shields located between adjacent columns of signal pins.  
           [0015]    Yet another variation of a modular connector is disclosed in patent application Ser. No. 09/199,126 which is hereby incorporated by reference. Teradyne Inc., assignee of the patent application, sells a commercial embodiment of the connector under the trade name VHDM - HSD. The application shows a connector similar to the VHDM™ connector, a modular connector held together on a metal stiffener, each module being assembled from two wafers. The wafers shown in the patent application, however, have signal contacts arranged in pairs. These contact pairs are configured to provide a differential signal. Signal contacts that comprise a pair are spaced closer to each other than either contact is to an adjacent signal contact that is a member of a different signal pair.  
         SUMMARY OF THE INVENTION  
         [0016]    As discussed in the background, higher speed and higher density connectors are required to keep pace with the current trends in the electronic systems industry. With these higher densities and higher speeds however electromagnetic coupling or cross talk between the signal contacts becomes more problematic.  
           [0017]    An electrical connector having mating pieces with shields in one piece oriented transversely to the shields in a second piece is therefore provided. In a preferred embodiment, one piece of the connector is assembled from wafers with shields positioned between the wafers. The shields in one piece have contact portions associated therewith for making electrical connection to shield in the other piece. With such an arrangement, a connector is provided that is easily manufactured and possesses improved shielding characteristics.  
           [0018]    In other embodiments, the second piece of the connector is manufactured from a metal and includes slots into which signal contacts surrounded by an insulative material are inserted. With such an arrangement, the signal contacts are provided an additional four-walled shield against cross talk.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a Connector with Egg-Crate Shielding, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. For clarity and ease of description, the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0020]    [0020]FIG. 1 is an exploded view of a connector assembly made according to one embodiment of the invention.  
         [0021]    [0021]FIG. 2 is the backplane connector of FIG. 1.  
         [0022]    [0022]FIG. 3 is the backplane shield plate  130  of FIG. 1.  
         [0023]    [0023]FIG. 4 is an alternate view of a representative signal wafer of FIG. 1.  
         [0024]    [0024]FIG. 5 is a view of the daughter card shield plate  140  of FIG. 1 prior to molding.  
         [0025]    [0025]FIG. 6 is a top sectional view of a shielding pattern that results when the two pieces of the connector of FIG. 1 are mated.  
         [0026]    [0026]FIG. 7 is an alternate embodiment of the connector  100  of FIG. 1.  
         [0027]    [0027]FIG. 8 is an alternate embodiment of the wafer of FIG. 4.  
         [0028]    [0028]FIG. 9 is an alternate embodiment of the backplane connector of FIG. 2.  
         [0029]    [0029]FIG. 10 is an alternate embodiment of the backplane shield plate of FIG. 3.  
         [0030]    [0030]FIG. 11 is an alternate embodiment of the daughter card shield plate of FIG. 5.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0031]    [0031]FIG. 1 is an exploded view of a connector assembly  100  made in accordance with one embodiment of the invention. The connector assembly  100  includes two pieces. The first piece is connected to a daughter card  102  and may be referred to as a daughter card connector  120 . The second piece is connected to a backplane  104  and may be referred to as a backplane connector  110 . The daughter card connector  120  and backplane connector  110  are intermatable and together form a substrate-to-substrate connector. Here, the connector is shown and will be described as connecting a backplane and daughter card. However, the techniques described herein may also be implemented in other substrate to substrate connectors and also in cable to substrate connectors.  
         [0032]    Generally, multiple backplane connectors are connected to a backplane and are aligned side by side. Correspondingly, multiple daughter card connectors are provided on a daughter card to mate with the multiple backplane connectors. Here, for purposes of illustration and ease of description, only a single backplane connector  110  and daughter card connector  120  are shown.  
         [0033]    Referring also to FIG. 2, the support for the backplane connector  110  is a shroud  122  that is preferably formed by an injection molding process using an insulative material. Suitable insulative materials are a plastic such as a liquid crystal polymer (LCP), a polyphenyline sulfide (PPS), or a high temperature nylon. The shroud  122  includes sidewall grooves  124  in opposing sides of the shroud  122 . As will be discussed below, these sidewall grooves  124  are used to align elements of the daughter card connector  120  when the two connectors  110 ,  120  are mated. Running along a floor of the shroud  122 , perpendicular to the sidewall grooves are a plurality of narrow grooves or trenches  125  which receive a backplane shield  130 .  
         [0034]    The backplane connector  110  includes an array of signal conductors that transfer signals between the backplane  104  and the daughter card  102  when the backplane connector  110  is mated with the daughter card connector  120 . Disposed at a first end of the signal conductors are mating contacts  126 . In a preferred embodiment, the mating contacts  126  take the form of signal blades  126  and are configured to provide a path to transfer a differential signal. A differential signal is provided by a pair of conduction paths  126   a ,  126   b  which is typically referred to as a differential pair. The voltage difference between the two paths represents the differential signal pair. In a preferred embodiment, there are eight rows of signal blades  126  in each column. These eight signal blades may be configured to provide eight single ended signals or as mentioned above, four differential signal pairs.  
         [0035]    The signal blades  126  extend through the shroud  122  and terminate in tail elements  128 , which in the preferred embodiment, are adapted for being press fit into signal holes  112  in the backplane  104 . Signal holes  112  are plated through holes that connect to signal traces in the backplane  104 . FIG. 1 shows the tail elements as “eye of the needle” tails however, the tail elements  128  may take various forms, such as surface mount elements, spring contacts, solderable pins, etc.  
         [0036]    Referring also to FIG. 3, a plurality of shield plates  130  is provided between the columns of signal blades  126 , each disposed within one of the plurality of trenches  125 . The shield plates  126  may be formed from a copper alloy such as beryllium copper or, more typically, a brass or phosphor bronze. The shield plates  130  are also formed in an appropriate thickness in the range of 8-12 mils to provide additional stability to the structure.  
         [0037]    In a single-ended embodiment, the shield plates are disposed between the columns of signal blades  126 . In the preferred embodiment, the shield plates  130  are disposed between pairs of signal blades  126 . The shield plates  130  are substantially planar in form and terminate at a base end in tail elements  132  adapted for being press fit into ground holes  114  in the backplane  104 . In the preferred embodiment, the tail elements  132  take the form of “eye of the needle” contacts. Ground holes  114  are plated through holes that connect to ground planes on the backplane  104 . In a preferred embodiment, the shield plate  130  includes ten tail elements  132 . A beveled edge (not labeled) is provided at the top end of the shield plate  130 . In one embodiment, the shield plates  130  include strengthening ribs  134  on a first face of the shield plate  130 .  
         [0038]    Referring again to FIG. 1, the daughter card connector  120  is a modular connector. That is, it includes a plurality of modules or wafers  136 . The plurality of wafers are supported by a metal stiffener  142 . Here, a representative section of the metal stiffener  142  is shown. Also shown, is an exemplary wafer  136 . In a preferred embodiment, the daughter card connector  120  includes a plurality of wafers stacked side-by-side, each wafer being supported by the metal stiffener  142 .  
         [0039]    The metal stiffener  142  is generally formed from a metal strip, typically a stainless steel or an extruded aluminum, and is stamped with a plurality of apertures  162 . The plurality of apertures  162  are adapted to accept features  158  from each of the plurality of wafers  136  that combine to retain the wafers  136  in position. Here, the metal stiffener  142  includes three apertures  162  to retain the wafer&#39;s position; a first  162   a  located at a first end, the second  162   b  located within a substantially ninety degree bend in the metal stiffener and the third  162   c  located at a second end of the metal stiffener  142 . When attached, the metal stiffener  142  engages each of two edges on the wafers  136 .  
         [0040]    Each wafer  136  includes a signal portion  148  and a shielding portion  140 . Both the signal portion  148  and shielding portion  140  include an insulative housing  138 ,  139  which is insert molded from an insulative material. Typical materials used to form the housings  138 ,  139  include a liquid crystal polymer (LCP), a polyphenyline sulfide (PPS) or other suitable high temperature resistant insulative material.  
         [0041]    Disposed within the insulative housing  138  of the signal portion  148  are conductive elements that extend outward from the insulative housing  138  through each of two ends. The conductive elements are formed from a copper alloy such as beryllium copper and are stamped from a roll of material approximately eight mils thick.  
         [0042]    At a first end, each conductive element terminates in a tail element  146  adapted to be press fit into a signal hole  116  in the daughter card  102 . Signal holes  116  are plated through holes that connect to signal traces in the daughter card  102 . At a second end, each conductive element terminates in a mating contact  144 . In a preferred embodiment, the mating contact takes the form of a beam structure  144  adapted to receive the signal blades  126  from the backplane connector  110 . For each signal blade  126  included in the backplane connector  110 , there is provided a corresponding beam structure  144  in the daughter card connector  120 .  
         [0043]    In a preferred embodiment, eight rows, or four differential pairs, of beam structures are provided in each wafer  136 . The spacing between differential pairs as measured across the wafer is 1.6 mm to 1.8 mm. The group to group spacing, also measured across the wafer, is approximately 5 mm. That is, the spacing between repeating, identical features such as between the left signal blade  126  in a first pair and the left signal blade  126  in an adjacent pair is 5 mm.  
         [0044]    Included on a third and fourth end of the insulative housing  138  are multiple features  158   a -  158   c  that are inserted into the stiffener apertures  162  to fasten the wafer  136  to the stiffener  142 . The features  158   a ,  158   b  on the fourth end take the form of tabs formed in the insulative housing while the feature  158   c  on the third end is a hub which is adapted to provide an interference fit in the third aperture  162   c  in the metal stiffener  142 .  
         [0045]    The shielding portion of the wafer  136 , also referred to as the shield  140 , is formed of a copper alloy, typically a beryllium copper, and is stamped from a roll of material approximately eight mils thick. As described above, the shield is also partially disposed in insulative material.  
         [0046]    The insulative material on the shield  140  defines a plurality of cavities  166  in which the signal beams  144  reside. Adjacent to these defined cavities  166  on the first and third ends of the wafer  136  are shroud guides  160   a ,  160   b  which engage the sidewall grooves  124  of the backplane connector  110  when the daughter card  120  and backplane  110  connectors are mated, thus aiding the alignment process. The combination of the sidewall grooves  124  and the shroud guides  160   a ,  160   b  prevent unwanted rotation of the wafers  136  and support uniform spacing between the wafers  136  when the backplane connector  110  and the daughter card connector  120  are mated. The wafer pitch, or spacing between the wafers is within the range of 1.75 mm to 2 mm, with a preferred wafer pitch being 1.85 mm.  
         [0047]    The sidewall grooves  124  also provide additional stability to the wafers by balancing the forces of the mating contacts. In the preferred embodiment, the signal blades  126  of the backplane connector  110  mate with the signal beams  144  of the daughter card connector  120 . The nature of this mating interface is that the forces from the beams are all applied to a single side, or surface of the blades. As a result, the forces provided by this mating interface are all in a single direction with no opposing force available equalize the pressure. The sidewall grooves  124  provided in the backplane shroud  122  equalize this force thus providing stability to the connector  100 .  
         [0048]    Disposed at a first end of the shield  140  are a plurality of tail elements. Each tail element is adapted to be press fit into a ground hole  118  in the daughter card  102 . Ground holes  118  are plated through holes that connect to ground traces in the daughter card  102 . In the illustrated embodiment, the shield  140  includes three tail elements  152  however, in a preferred embodiment four tail elements  152  are included. In a preferred embodiment, the tail elements take the form of “eye of the needle” elements.  
         [0049]    At a second end of the shield  140  are mating contacts  150 . In the illustrated embodiment, the mating contacts  150  take the form of beams that are adapted to receive the beveled edge of the backplane connector shield  130 . The resulting connection between the shields  130 ,  140  provides a ground path between the daughter card  102  and the backplane  104  through the connectors  110 ,  120 .  
         [0050]    Referring now to FIG. 4, an assembled wafer is shown. When the signal  148  and ground portions  140  of the wafer  136  are assembled, the signal tail elements  146  and the ground tail elements  152  are disposed in a line defining a single plane. As shown, a single ground tail element  152  is disposed between each pair of signal tail elements  146 .  
         [0051]    Referring now to FIG. 5, the shield  140 , as shown before the molding process, includes wings  154   a ,  154   b  disposed on opposing sides of the shield  140 . In the finished wafer  136 , these wings  154   a ,  154   b  are disposed within the insulative material that forms the shroud guides  160   a ,  160   b.    
         [0052]    Generally, to form the wings  154   a ,  154   b , the shield  140  is first stamped from a roll of metal, typically a copper alloy such as beryllium copper. The wings  154   a ,  154   b  are bent out of the plane of the shield  140  to form a substantially 90° angle with the shield  140 . The resulting wings  154   a ,  154   b  thus form new planes which are substantially perpendicular to the plane of the shield  140 .  
         [0053]    The shield  140  also includes the tail elements  152   a - 152   c  previously described, the shield termination beams  150   a - 150   c  and a plurality of shield fingers  170   a - 170   d . The shield fingers  170   a - 170   d  are disposed adjacent to the mating contacts  150   a - 150   c  and between the wings  154   a ,  154   b . Strengthening ribs  172  are provided on the face of the shield fingers  170   a - 170   d . In a preferred embodiment, four shield fingers  170   a - 170   d  are provided with two strengthening ribs  172   aa - 172   db  disposed on each shield finger  170   a - 170   d  to oppose the forces exerted by the opposing mating contacts.  
         [0054]    Also included on the face of the shield  140  is a plurality of protruding openings or eyelets  156  that serve to hold the shield  140  and signal portion  148  of the wafer  136  together. The signal portion  148  includes apertures or eyelet receptors  164  (FIG. 4) through which these eyelets  156  may be inserted. After insertion, a forward edge (not labeled) of the eyelets  156  may be rolled back to engage the face of the signal portion surrounding the eyelet receptors  164 , consequently locking the shield  140  and signal portion  148  together.  
         [0055]    The shield  140  is further shown to include flow-through holes  168 . Flow-through holes  168  accept the insulative material applied to the shield  140  during the insertion molding process. The insulative material deposits within the flow-through holes  168  thus creating a stronger bond between the insulative material and the shield  140 . In a preferred embodiment, a single flow-through hole  168  is provided on the face of each shield finger  170   a - 170   d  and within the bend of each wings  154   a ,  154   b.    
         [0056]    In the illustrated embodiment, mating contacts  150   a - 150   c  are arc shaped beams attached at either end to an edge of one of the shield fingers  170   b - 170   d . Like the wings  154   a ,  154   b , the mating contacts  150   a - 150   c  are typically bent out of the plane of the shield  140  after the shield has been stamped. In a preferred embodiment, at least two bends are formed in the shield termination beams  150   a - 150   c  to provide a sufficient spring force.  
         [0057]    The gaps (not labeled), which are formed when the mating contacts  150   a - 150   c  are bent into position, receive the beveled edge of the backplane shield  130  when the two connectors  110 ,  120  are mated. The gaps, however, are not of sufficient width to freely accept the beveled edge of the backplane shield  130 . Accordingly, the mating contacts  150   a - 150   c  are displaced by the backplane shield  130 . The displacement generates a spring force in the mating contacts  150   a - 150   c  thus providing an effective electrical contact between the shields  130 ,  140  and completing the ground path between the connectors  110 ,  120 .  
         [0058]    [0058]FIG. 6 is a top sectional view of a shielding pattern that results when the two pieces of the connector  100  of FIG. 1 are mated. Only certain of the elements of the backplane connector  110  and the daughter card connector  120  are represented in the diagram.  
         [0059]    Specifically, the backplane  130  and daughter card  140  shields, the signal blades  126 , and the sidewall grooves  124  of the shroud  122  are included. Further shown with respect to a representative daughter card shield  140   a  are an outline representing the insulative material formed around the shield  140   a , the corresponding beam structures  144  from the daughter card connector  120  and the mating contacts  150 .  
         [0060]    When mated, the shield plates  130 ,  140  in each connector  110 ,  120  form a grid pattern. Located within each cell of the grid is a signal contact. Here, the signal contact is a differential pair comprised of two signal blades  126  from the backplane connector  110  and two beam structures  144  from the daughter card connector  120 . In a single-ended embodiment, a single signal blade  126  and a single beam structure  144  comprise the signal contact.  
         [0061]    The shield configuration represented in FIG. 6 isolates each signal contact from each neighboring signal contact by providing a combination of one or more of the backplane shields  130  and one or more of the daughter card shields  140  between a signal contact and its abutting contact. In addition, it should also be noted that the wings  154   a ,  154   b , located on either side of the daughter card shield  140 , further inhibit cross talk between signal contacts that are located adjacent to the shroud  122  sidewalls and additionally form a symmetric ground configuration to provide for a balanced differential pair.  
         [0062]    Referring now to FIG. 7, an alternate embodiment of the connector  100 ′ is shown. Connector  100 ′ is shown to include a backplane connector  200 , and a daughter card connector  210 . The daughter card connector  210  includes a plurality of wafers  236  held on a metal stiffener  242 . Two representative wafers  236  are shown. The wafers  236  include a plurality of contact tails  246 ,  252  that are adapted to attach to the first circuit board  102 . The wafers further include a plurality of signal beams  244  that are adapted to mate with the signal blades  226  extending from the backplane connector  200 .  
         [0063]    Disposed between the signal beams  244  is a plurality of mating contacts  250 . The mating contacts  250  are adapted to receive a beveled edge of a backplane shield  230  included in the backplane connector  200 . The backplane shield  230  is also shown to include a plurality of tail elements  232  adapted to be press fit into the second circuit board  104 .  
         [0064]    Referring now to FIG. 8, a wafer  236  is shown to include a signal portion  248  and a shield portion  240 . The signal portion  248  includes an insulative housing  238  which is preferably insert injection molded. A high temperature, insulative material such as LCP or PPS are suitable to form the insulative housing  238 .  
         [0065]    The signal portion  248  is shown to include contact tails  246  and signal beams  244 . Here the contact tails  246  and signal beams  244  are configured as differential pairs providing a differential signal therefrom, however, a single ended configuration may also be provided. The signal portion  248  also includes eyelet receptors  264  that receive eyelets  256  from the shield portion  240  of the wafer  236 . The eyelets  256  are inserted into the eyelet receptors  264  and are rolled radially outward against the surface of the signal portion  248 , thus locking the two portions together.  
         [0066]    A lower section of the shield portion  240 , or shield  240 , is insert molded using an insulative material such as LCP or PPS. The insulative housing forms a plurality of cavities  266  that receive the signal beams from the signal portion  248 . A floor of each cavity  266  includes an aperture  340  through which the signal blades  226  from the backplane connector  200  access the signal beams  244  of the daughter card connector  210 .  
         [0067]    The shield  240  is further shown to include contact tails  252  and mating contacts  250 . The mating contacts will be described in more detail in conjunction with FIG. 11.  
         [0068]    Referring now to FIG. 9, the backplane connector  200  is shown to include a shroud  222 . The shroud  222  is formed from a metal, preferably a die cast zinc. The shroud includes sidewall grooves  224  that are used, inter alia, to guide the wafers  236  into proper position within the shroud  222 . The sidewall grooves  224  are located on opposing walls of the shroud  222 .  
         [0069]    Located on the floor of the shroud  222  are a plurality of apertures  234  and a plurality of narrow trenches  225 . The plurality of apertures  234 , here rectangular-shaped, are adapted to receive a block of insulative material  300 , preferably molded from an LCP, a PPS or other temperature resistant, insulative material. The insulative block  300  is press fit into the apertures  234  after the shroud has been cast. In a preferred embodiment the plurality of insulative blocks  300  are affixed to a sheet of insulative material to make handling and insertion more convenient.  
         [0070]    Each insulative block  300  includes at least one channel  310  that is adapted to receive a signal blade  226 . In a preferred embodiment in which connector  100 ′ is configured to transfer differential signals, the insulative block  300  includes two channels  310  to receive a pair of signal blades  226 . The signal blades  226  are pressed into the insulative block  300  which, in turn, is pressed into the metal shroud  222 . Extending from the bottom of the insulative block  300  are contact tails  228  which are adapted to be press fit into the second circuit board  104 .  
         [0071]    Here, the rectangular-shaped apertures  234  provide additional shielding from cross talk for signals travelling through the backplane connector  200 . The insulative block  300  insulates the signal blades  226  from the metal shroud  222 .  
         [0072]    The backplane connector  200  is further shown to include a plurality of backplane shields  230  that are inserted into the narrow trenches  225  located on the floor of the metal shroud  222 . Extending from the bottom of the metal shroud  222  are the contact tails  232 . The backplane shield  230  is shown to include a plurality of shield beams  320 . Also included on the backplane shield are means for commoning the grounds or, more specifically, means for electrically connecting the backplane shield  320  to the metal shroud  222 . Here the means for commoning the grounds are shown as a plurality of light press fit contacts  231   
         [0073]    The shield beams  320  work in concert with the mating contacts  250  of the wafer  236  to provide a complete ground path through the connector  100 ′. The interplay of these features as well as additional details regarding the backplane shield  230  and a shield  240  included in the daughter connector  210  wafer  236  will be described more fully in conjunction with FIGS. 10 and 11 below.  
         [0074]    Referring now to FIG. 10 the backplane shield  230  is formed from a copper alloy such as beryllium copper, brass or phosphor bronze. The shield beams  230  are stamped from the backplane shield  230 , and are bent out of the plane of the backplane shield. The shield beams are further fashioned to include a curved or arced region  322  at a distal end of the beam  320 .  
         [0075]    Referring also to FIG. 11, the shield  240  of the daughter card connector  210  is shown to include a plurality of mating contacts  250 . Each mating contact  250  includes a slot (not numbered) and a daughter card shield beam  251 . The daughter card shield beams  251  are stamped from the daughter card shield  240  and bent out of the plane of the shield  240 . A distal end of the shield beam  251  is bent to provide a short tab  249  extending from the bottom of the beam  251  at an angle.  
         [0076]    When mated, the beveled edge of the backplane shield  230  is inserted into the mating contact  250  of the daughter card shield  240 , specifically lodging in the slot of the mating contact  250 . An electrical contact is further established as the backplane shield beam  320  engages the daughter card shield beam  251 . In a preferred embodiment, the curved region  322  of the backplane shield beam  320  resiliently engages the short tab  249  of the daughter card shield beam  251 .  
         [0077]    The daughter card shield  240  further includes shield wings  254  disposed at opposite sides of the shield  240  adjacent to the mating contacts  250  and daughter card shield beams  251 . The shield wings provide additional protection against cross talk introduced along the edges of the connector proximate to the sidewall grooves  224 .  
         [0078]    Further included on a face of the daughter card shield  240  are strengthening ribs  272 . The strengthening ribs provide additional stability and support to the daughter card shield  240  in view of the forces provided by the mating interface between the two shields  230 ,  240 .  
         [0079]    Having described multiple embodiments, numerous alternative embodiments or variations might also be made. For example, the type of contact described for connecting the backplane  110  or daughter card  120  connectors to their respective circuit board  104 ,  102  are primarily shown and described as being eye of the needle connectors. Other similar connector types may also be used. Specific examples include, surface mount elements, spring contacts, solderable pins etc.  
         [0080]    In addition, the shield termination beam contact  150  is described as an arc shaped beam. Other structures may also be conceived to provide the required function such as cantilever beams.  
         [0081]    As another example, a differential connector is described in that signal conductors are provided in pairs. Each pair is intended in a preferred embodiment to carry one differential signal. The connector can also be used to carry single ended signals. Alternatively, the connector might be manufactured using the same techniques but with a single signal conductor in place of each pair. The spacing between ground contacts might be reduced in this configuration to make a denser connector.  
         [0082]    Also, the connector is described in connection with a right angle daughter card to backplane assembly application. The invention need not be so limited. Similar structures could be used for cable connectors, mezzanine connectors or connectors with other shapes.  
         [0083]    Further, the wafers are described as being supported by a metal stiffener. Alternatively, the wafers could be supported by a plastic stiffener or may be glued together.  
         [0084]    Variations might also be made to the structure or construction of the insulative housing. While the preferred embodiment is described in conjunction with an insert molding process, the connector might be formed by first molding a housing and then inserting conductive members into the housing.  
         [0085]    In addition, other contact structures may be used. For example, opposed beam receptacles may be used instead of the blade and beam mating structures recited. Alternatively, the location of the blades and beams may be reversed. Other variations include changes to the shape of the tails. Solder tails for through-hole attachment might be used or leads for surface mount soldering might be used. Pressure mount tails may be used as well as other forms of attachment.  
         [0086]    While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.